Bibliothek

Notizen: Student clinical practice is a significant and essential part of nursing education. Accordingly, clinical placements need to be positive and valuable. The purpose of this study was to describe newly-graduated nurses' perceptions of their student clinical intersession placements and how these placements impacted their functioning as graduate nurses. Inductive semantic analysis of the data revealed four themes: developing nursing skills and knowledge; preparing for future employment; experiencing supportive relationships; and experiencing realities of work-life. Educators must ensure that clinical placements are in an environment that is conducive to learning and promotes the personal and professional development of nursing students. Positive clinical experiences are more likely related to how valued and supported students feel than the physical aspects of a placement; thus, it is imperative educators assess and focus on providing placements that offer a supportive learning environment.

Notizen: Understanding the genetic underpinnings to complex diseases requires consideration of sophisticated analytical methods designed to uncover intricate associations across multiple predictor variables. At the same time, knowledge of whether single nucleotide polymorphisms within a gene are on the same (in cis) or on different (in trans) chromosomal copies, may provide crucial information about measures of disease progression. In association studies of unrelated individuals, allelic phase is generally unobservable, generating an additional analytical challenge. In this manuscript, we describe a novel approach that combines multiple imputation and random forests for this high-dimensional, unobservable data setting. An application to a cohort of HIV-1 infected individuals receiving anti-retroviral therapies is presented. A simulation study is also presented to characterize method performance.

Notizen: Child growth is characterised by increases in height, and increases in maturational status. Functional data analysis provides a tool to separate these two sources of variation (registration) and differentiates between the variation in maturational tempo (temporal, or "phase" variation) and the variation in height (amplitude variation). We extended this concept by combining Principal Component Analysis (PCA) and the Maximum Likelihood Principle. Longitudinal data on height were obtained from two large growth studies from Lublin, Poland, and Zurich, Switzerland, with altogether 361 children. Variation in amplitude monotonically rises with age; variation in phase peaks during puberty. During mid-puberty, phase variation is large and explains up to 40 percent of total height variance in girls, and up to 50 percent in boys. Eight amplitude and 4 phase components appeared biologically significant. The largest amplitude component explained 91% of the amplitude variance and is characterised by an almost horizontal pattern. The largest phase component explained 66% (boys) and 63% (girls) of phase variance, rises throughout childhood and reaches up to 0.85 years in adolescent boys, and up to 0.75 years in adolescent girls. Phase components significantly correlated with the clinical signs of puberty. The combination of PCA and the Maximum Likelihood Principle provides a new, powerful and automatic tool for growth modelling that includes estimates of future growth, adult stature and developmental tempo. Preliminary results indicate that this approach can be used for automatised screening purposes.

Notizen: Analyses of individual disease-exposure data within a population are useful when exposure of interest varies sufficiently within the population. When the within-population variance of exposure is limited, however, power of the individual-data analysis is reduced. In such situations, aggregated-data analyses of disease data across populations, with a sample of individual exposure data from each population, can be powerful in estimating the exposure effect if between-population variation of exposure is large. In this paper, we consider a new analytical framework that is a combination of the individual- and aggregated-data analyses, based on an estimating equation approach. The proposed analysis utilizes strengths from individual data and aggregated data in the estimation of the exposure effect of interest, depending on which of the exposure variations (within- versus between-population) dominates. Simulation studies under various different scenarios were performed to show the strengths of the proposed approach in the estimation of the exposure effects of interest.

Notizen: Human Patient Simulators (HPS), electronically controlled mannequins as patient models, are increasingly being used in nursing education. However, no studies have validated the influence of systematic practice with HPS on clinical performance of nursing students. This pilot study attempted to identify the nursing clinical practice parameters influenced by HPS by evaluating the clinical performance of 12 senior second degree BSN students in five categories: safety, basic assessment skills, prioritization, problem-focused assessment, ensuing interventions, delegation and communication in a complex two-patient, simulated assignment. Students who practiced with the HPS in addition to their usual clinical training had significantly higher scores than the control group (usual clinical training alone) on Patient Identification (a subcategory of the safety category; p = 0.001), and on Assessing Vital Signs (a subcategory of the basic assessment category; p = 0.009). The control and intervention groups' performances were similar in every other category. Replication of this pilot with a larger sample is recommended.

Notizen: The purpose of this study was to explore American student perceptions of caring for Korean patients during a 2 week exchange program. Perceptions of Korea/Koreans focused on five areas: respect, hospitality and gift giving, ability to speak English, hierarchal relationships, and being protective. Their perceptions of personal change focused in four areas: valuing personal cultural experiences, increasing cultural awareness and compassion, seeing people from other ethnic groups as individuals and developing interest in oriental medicine. Four areas of importance identified when caring for Korean patients included showing respect, importance of family, food, and care for post-partum mothers. Differences were experienced between an individualistic, low-context society (United States) and a collectivistic, high context society (Korea) where the influence of Confucianism is pervasive.

Notizen: Carper's (1978) seminal work has been used in nursing education for many years as a method for introducing students to the multitude of ways of knowing that support nursing practice. This manuscript focuses on the aesthetic pattern of knowing and the ongoing debate in nursing literature surrounding aesthetics, evidence and nursing practice. Writers will describe and critique a strategy used to introduce first year undergraduate nursing students to this pattern of knowing. The implications of the critique of the project and the ongoing debate in relation to Carper's (1978) work, evidenced based practice and nursing praxis are discussed.

Notizen: There is a growing literature on the statistical analysis of data from association-football/soccer games, seasons or groups of seasons. In contrast this paper is concerned with a single play, that is a sequence of successful passes. The play studied contained 25 passes and ended in a goal for Argentina in World Cup 2006. One question addressed is how to describe analytically the spatial-temporal movement of such a particular sequence of passes. The basic data are points in the plane, successively joined by straight lines. The resulting figure represents the trajectory of the moving soccer ball. The approach of this study is to develop a useful potential function, a concept arising from physics and engineering. In particular the potential function leads to a regression model that may be fit directly by linear least squares. The resulting potential function may be used for simple description, summary, comparison, simulation, prediction, model appraisal, bootstrapping, and employed for estimating quantities of interest. The purpose illustrated here is to simulate play in a game where the ball goes back and forth between two teams each having their own potential function.

Notizen: Previous studies have attempted to model goal scoring in sports such as ice hockey as simple Poisson processes. Others (Thomas, 2006) have shown that events within the game of ice hockey are better modelled as a Semi-Markov process determined by puck possession and location. I demonstrate that a similarly defined Semi-Markov process model is well-suited to describe the times between goals scored in NHL hockey, and use this to demonstrate that the scoring of a goal has the effect of shortening the remainder of the game by roughly 20 seconds. This is used to improve previous estimates of the value of a goal scored, calculated as a difference in win probabilities at specific time points during the game.

Notizen: In the 2004 Ryder Cup Matches, US Captain Hal Sutton decided to pair his two best players, Tiger Woods and Phil Mickelson, in the opening four-ball match. The popular press characterized this pairing with the adjectives ``bold" and ``risky" since it is generally thought that balanced teams are preferable to unbalanced. In this paper I compare a Balanced strategy (matching stronger players with weaker players so that the resulting pairs are balanced) against an Unbalanced strategy (matching stronger players with stronger players and weaker players with weaker players) and find the Balanced strategy to be superior, but only slightly so.

Notizen: We present a quantitative analysis of throwing ability for major league outfielders and catchers. We use detailed game event data to tabulate success and failure events in outfielder and catcher throwing opportunities. We attribute a run contribution to each success or failure which is tabulated for each player in each season. We use four seasons of data to estimate the overall throwing ability of each player using a Bayesian hierarchical model. This model allows us to shrink individual player estimates towards an overall population mean depending on the number of opportunities for each player. We use the posterior distribution of player abilities from this model to identify players with significant positive and negative throwing contributions. Our results for both outfielders and catchers are publicly available.

Notizen: Student evaluations of teaching provide administrators an overall picture of the effectiveness of personnel and contribute data for promotion and merit decisions. These evaluations must be assessed for their relevance, validity, and reliability. This paper describes the development process and psychometric testing for clinical (n = 149) and didactic (n = 148) student evaluation of teaching forms for undergraduate and graduate courses in one college of nursing. Validity and reliability results were quite strong for the instruments, both of which evidenced a one-factor solution with factor loadings ranging from .68-.88 and Cronbach's alphas of .96 (Classroom) and .95 (Clinical). The clinical and classroom evaluation tools are relatively short, decreasing the burden on students who need to complete the instruments for multiple instructors in any one semester. Initial testing of the psychometric properties of the tools supports their continued use in colleges of nursing.

Notizen: For at least the last 50 years two ways of looking at tort law have struggled for dominance. One characterized by system-builders, as Izhak Englard so felicitously termed us; the other by those who have seen in tort law the highest manifestation of the common law tradition of responding to breaches in non-criminal, often non-contractual interpersonal relationships. In this paper, I would like to explore the relationship between these two approaches, which I will suggest, find their common law antecedents, where else but, in the forms of actions, from which so much of modern Anglo-American private law derives. I will suggest that both approaches have always been there and that they have affected and shaped each other over the centuries and continue to do so today.

Notizen: In this article I argue that the noble cause of comparative law as an intellectual activity is undermined by those who focus on its forensic utility. Specifically, I examine the practical value to practitioners and judges in the court of final appeal in an English-speaking jurisdiction of paying attention to how tort issues are analysed in a different jurisdiction when the subject matter of the domestic case at hand does not positively require it. Part I argues that the benefits of resorting to ``comparative tort reasoning" vary greatly according to the focus of the legal analysis in issue: outcomes, arguments, principle, or conceptual arrangement; and that by far the potential for enrichment is greatest in the context of comparative tort argumentation. Part II addresses the study of law across not just jurisdictional but language barriers: ``comparative foreign-language law." My argument here is that the practitioner and judge in an English-speaking jurisdiction should exercise extreme caution in using comparative materials from foreign language systems. Part III considers ``coordinated" tort materials: materials that seek to expound tort law across multiple intra-national tort jurisdictions, such as restatements of law by the American Law Institute, or across multiple national tort jurisdictions such as Helmut Koziol's ``Principles of European Tort Law" published in 2005.

Notizen: The "idea of private law" has occupied a prominent place in tort theorizing over the past twenty years. To American ears, the idea has a libertarian ring, implying a realm of private freedom beyond the reach of public power. But the idea of "private law" pursued in recent tort theory is different. This strand of tort theory takes an essentially formal view of "private law" as a form of adjudication through which one member of civil society invokes the public power of the state to call another member of civil society to account for breach of an obligation, owed by the latter to the former. In a number of recent, elegant essays, Arthur Ripstein has advanced a particular version of this view, a version distinguished in important part by its enlistment of the political philosophy of John Rawls in support of this project. Tort Law in a Liberal State is a further contribution to this project, summarizing Professor Ripstein's view and arguing for both the interpretive and the philosophical plausibility of his project.Personal Inviolability and Private Law raises objections to both aspects of Ripstein's project, and briefly explains why "public law" conceptions of tort are at least as plausible as "private law" ones, both philosophically and interpretively. Interpretively, Professor Ripstein's conception is open to three serious objections. First, by placing the calling of one member of civil society to account by another at the center of their view, "private law" theorists threaten to place the remedial cart before the substantive horse. Prior to the late nineteenth century, tort existed--to the extent that it existed at all--as an essentially remedial body of law. Our modern law of torts comes into existence with (and by the recognition of) tort as a freestanding law of primary obligation. By placing such great weight both on Kant's property-centered account of private law and on "private law" theory's heavily remedial conception of tort, Professor Ripstein's conception cuts against the fundamental thrust of modern tort law. That thrust is to make obligation central and to treat right and remedy as separable. Ripstein, by contrast, places enormous weight on remedy and takes right and remedy to be indivisible.Second, Tort Law in a Liberal State is, in important part, a brief for the fault principle. Professor Ripstein is right to distinguish between "harm-based" torts such as liability for accidental injury, negligently inflicted and right-based" torts such as trespass, but wrong to claim that "harm-based" liability in tort is always fault-based. This claim leads Professor Ripstein both to a distorted account of tort law's various strict liabilities and to a fundamental mischaracterization of much of the conduct subject to liability in tort. Professor Ripstein's recasting of strict liabilities as fault ones commits him to the unfortunate idea that there is something intrinsically wrong with valuable, productive activities, blamelessly conducted. Both the recasting of particular strict liabilities in fault terms, and the righteous condemnation of risk to which this recasting leads, are mistaken. Rylands conduct in the famous case of Rylands v. Fletcher was not wrongful; Atlantic Cement's conduct in Boomer was not wrongful; and Lake Erie's conduct in Vincent was not wrongful. In all of these cases, defendant's only "fault" lay in (unreasonably) failing to make reparation for harm (reasonably) inflicted. More generally and more importantly, risk, like pollution, is not wrongful in itself, and harm is a matter of moral concern even when it issues from blameless conduct. Strict liability is a morally significant and instructive form of liability because it registers the perception that serious harm must sometimes be repaired, even though it has been faultlessly inflicted. Third and last, it is an interpretive mistake to insist that "public" and "private" forms of tort and accident law express fundamentally different values and moral conceptions. "Public law" schemes frequently complement or perfect "private law" ones, and threads of political morality tie private and public accident law institutions together. Zoning law's relation to nuisance is only one of many cases in point. Professor Ripstein's philosophical claims are likewise open to objection. For starters, Professor Ripstein's attachment to the form of "private law" transforms Kant's preoccupation with the inviolability of persons into a preoccupation with the formal purity of legal institutions. This is a path to avoid. An accident law faithful to the power of Kant's philosophy must be give pride of place to the inviolability of our persons, not to the inviolability of our legal forms. That latter path leads to endowing legal rules with the intrinsic value held only by persons. Second, Ripstein's assertion that Rawls' theory of justice commits him to the particular institutional form of "private law" is unpersuasive. Famously and explicitly, Rawls' theory leaves open the choice between capitalism and market socialism. The most natural and plausible reading of his theory of justice shows that it also leaves open the far more modest institutional choice between "private" and "public" law institutions. The final part of Personal Inviolability and "Private Law" briefly suggests that some form of enterprise liability constructed around a conception of commutative justice may, in fact, express the independence, equality and inviolability of democratic citizens more adequately than a "private law" constructed around a conception of corrective justice does. Free and equal citizens have ample reason not to place their rights against one another at the mercy of a "private law" negligence lottery, and to seek surer reparation for serious injury.

Notizen: This paper extends the Fractionally integrated GARCH (FIGARCH) model by incorporating Normal Inverse Gaussian Distribution (NIG). The proposed model is flexible and allows one to model time-variation, long memory, fat tails as well as asymmetry and skewness in the distribution of financial returns. GARCH and FIGARCH models for daily log exchange rate returns with Normal, Student's t and NIG error distributions as well as GARCH/FIGARCH-in-mean models with t errors are estimated and compared both in terms of sample fit as well as out-of-the-sample predictive ability in several dimensions. The FIGARCH model with symmetric and asymmetric NIG errors outperform alternatives both in-sample fit and 1-day and 5-day ahead predictions of the quartiles of the exchange rate return distributions.

Notizen: We present a novel specification of a dynamic multinomial ordered choice model, where the latent variable is a function of strictly stationary exogenous variables and lags of the choice variable. We prove that such a model with weakly dependent errors will have a strictly stationary solution which is L-2 near epoch dependent. We also derive consistency and asymptotic normality of the maximum likelihood estimator for a probit specification of the model. We illustrate a possible application of the model by estimating a discrete version of a robust ``difference" monetary policy rule for the period 1990:2006 at a monthly frequency.

Notizen: One of the most familiar empirical stylized facts about output dynamics in the United States is the positive autocorrelation of output growth. This paper shows that positive autocorrelation can be better captured by shifts between business cycle states rather than by the standard view of autoregressive coefficients. The result is extremely robust to different nonlinear alternative models and applies not only to output but also to the most relevant macroeconomic variables.

Notizen: We propose a simple computational method in the context of generalized method of moments for improving the efficiency of regression coefficient estimates. The gains in efficiency arise by incorporating additional moment conditions in the estimation framework based on maximal overlap wavelet packet transforms of the continuous explanatory variables. A major advantage of the proposed method is that it does not require additional exogenous auxiliary information but relies on wavelet packet transforms of the existing continuous explanatory variables. Based on existing theory, we provide theoretical arguments for the proposed methodology, for both linear and non-linear models, and demonstrate its advantages with both an empirical application concerning two brand demand models and a Monte Carlo simulation study.

Notizen: As a growing economic sector in many Muslim countries, Islamic banking has its roots in the application of the Shari'a. This is because Islamic banking is, in principle, based on legally recognized financial contracts and transactions that should be free of riba and gharar, both of which are interpreted somewhat differently by major Sunni and Shi'i schools of law. The objective of this study is (a) to shed light on the development of the debate on riba among Sunni and Shi'i scholars and the position of governments on the problem of interest-free banking in the twentieth century in Egypt, Iran and Pakistan; and (b) to study the implications of this debate for Islamic financial contracts. It is concluded that the expansion of a modern and viable internationally orientated Islamic banking and finance depends mainly on the development of financial capital markets, more independent and transparent central banking in Muslim countries, and a more innovative and flexible approach to Shari'a by different schools of law in Muslim countries.

Notizen: This paper presents an empirical analysis of Wagner's law in the case of Turkey over the period 1960-2000. The paper uses modern time-series econometric techniques to test the law's proposition that in the course of economic development, government expenditures increase. The results of this study do not support the empirical validity of Wagner's law for Turkey for the period 1960-2000. However, the paper finds statistical evidence for an augmented version of Wagner's law.

Notizen: This study tests the validity of the purchasing power parity (PPP) theory using a panel of ten Arab countries. It also measures the speed of convergence for the panel and for the Gulf Cooperation Council (GCC), including Bahrain, Kuwait, Qatar, Saudi Arabia and United Arab Emirates which follow a hard dollar peg. The test is conducted using nine base currencies. The main findings are first on the validity of PPP. (1) The null of unit root is rejected using each of the nine currencies as a numeraire--the result appears to be invariant to the choice of the base currency. (2) The result appears to be stronger when the estimation is based on heterogeneous rather than homogeneous serial correlations among panel units. Secondly, on persistence. (3) The estimated average half-life of a shock to the real exchange rate in the full panel is 2.19 years. (4) The study reveals that for the GCC economies deviation from PPP will be more persistent due to the hard peg, the dollar volatility and the weak goods market arbitrage. Clearly, the GCC countries will need to move to a more stable peg to be able to achieve the benefits they hope by engaging in a monetary union by 2010.

Notizen: Lebanon's Second Republic: Prospects for the Twenty-first Century, edited by Kail C. Ellis (Gainesville: University Press of Florida, 2002). 236 pp., $59.95, ISBN 0813025397

Notizen: We consider long horizon regression models where the disturbance and the predictor are possibly fractionally integrated. Asymptotic distributions of the OLS estimator and of the test statistic are given. It is found that the t-statistic diverges at the rate of square root of T, where T is the sample size. Thus, it is desirable to use the scaled test statistic, as it converges to a well-defined limit, which depends on the memory parameters through the functionals on the fractional Wiener processes. Simulation studies present some empirical distributions of the scaled test statistic according to different values of the memory parameters. The proposed model with fractional processes is empirically more tractable than the model with local to unity processes, since memory parameters are consistently estimable unlike localizing parameters in the latter model.

Notizen: There is a large literature that examines purchasing power parity (PPP). The growth in this literature is mainly due to the absence of a consensus view on whether or not PPP holds. This paper considers PPP for 11 Middle Eastern countries using a number of tests: the one-break test unit root, the two-breaks unit root test, and the panel Lagrange multiplier (LM) unit root test with structural breaks. The main finding from univariate tests is that there is evidence for PPP in only seven countries (Lebanon, Saudi Arabia, Egypt, Iran, Syria, Tunisia and Sudan). However, when the panel LM test is applied with two structural breaks, strong evidence is found in favor of PPP for the Middle Eastern countries.

Notizen: Over the last several decades, the economic performance of the Middle East and North Africa (MENA) has lagged behind many other parts of the world. While a number of factors have been cited as the cause of the region's malaise, the lack of globalization is increasingly mentioned as a possible source of difficulty. Focusing on the factors responsible for increased levels of globalization, it appears that internal policy reforms rather than external constraints are primarily responsible for the relative integration of the MENA countries into the world economy. Of the areas of policy under the direct control of MENA governments, improvements in several categories of governance, rather than further economic reforms, appear most effective in the attainment of increased levels of globalization.

Notizen: The aim of this paper is to empirically investigate the sources of inflation in Egypt. For this, price dynamics is herein represented by a vector error-correction model, which we use to test for the existence of a long-run relationship between the consumer price index, real gross domestic product (GDP), the exchange rate, interest rate, money supply and world prices. Then using the augmented VAR approach, we test for Granger non-causality between the different variables and inflation. The main results that are of interest to monetary policy in Egypt suggest that structural reforms based on improving the country's productive capacity, shrinking the budget deficit and credit to the government, are crucial for controlling inflation.

Notizen: In this paper we use household survey data to study the evolution of income distribution in Mexico over the last decade, a period of rapid integration to the global and North American economies -- "globalization" for short. We measure differences in income inequality, over time and across Mexican states, and relate them to regional differences in the degree of globalization, controlling for the potential endogenous relationship between the two. We use the percent of state employment in exporting firms or in firms with foreign capital participation, as well as data on state trade, as proxies for integration to the world economy. Our findings strongly indicate that globalization has not raised income inequality in Mexico. On the contrary, we present compelling evidence showing that income distribution is more equitable in states that are more closely linked to the world economy and that those states exhibit larger declines in inequality. We also find some statistical evidence suggesting that deepening globalization results in reduced inequality, although our results are sketchier on this point, perhaps because such effect is only observable in the long run. As a potential explanation of why globalization might improve the distribution of income among Mexican households, we show that states that are more integrated to the world economy offer better work opportunities for low-skilled women relative to more educated female workers.

Notizen: The exchange rate pass-through for Nigeria imports is estimated by applying an econometric procedure to sectoral data which avoids the pit-falls in previous studies. We use the mark-up approach, which implies setting export prices as a mark-up on production costs. So, the price facing importers is the exchange rate adjusted production costs where mark-up depends on the competitive pressures in the import's market and the nominal exchange rate. Our results indicate incomplete pass-through at varying degrees across sectors, which implies that the foreign exporters passed on only part of the increase in their costs of production to import prices. Also, it reveals that the effort of the Nigerian government in encouraging companies to use local inputs where possible instead of relying on imported intermediate inputs is gradually yielding positive results. Important policy implications that follow from our results of incomplete pass-through to domestic prices could influence CBN forecasts of future path of inflation, a key element in the conduct of monetary policy. Indeed, the successful implementation of monetary policy presupposes that CBN has not only a good understanding of inflation dynamics but is also relatively successful at predicting the future path of inflation. Also, our results imply that the exchange rate policy may be a blunt instrument when used to restore external balance since relative price adjustments will be limited. Furthermore, the incomplete pass-through suggests that exchange rate changes are likely to lead to smaller real effects on the economy through lower changes in both the terms of trade and import volumes and finally, the extent of inflation (deflation) effects of exchange rate depreciation (appreciation) operating through changes in the prices of imported goods will be moderated.

Notizen: The economic effects of NAFTA on Mexico have been discussed and measured mostly in terms of its effect on employment on both sides of the border and by the increase in Mexico-US trade and investments before and after NAFTA. These are the wrong ways to measure the effects of a free trade area on a member state. In this paper, I will first discuss the theoretically correct method of evaluating the economic effects of the formation of a free trade area in general and then apply this method to correctly measure the effects of NAFTA on Mexico.

Notizen: This study evaluates structural changes over time in the cross-country relationship between growth and volatility. Using a GMM 2SLS method to control for endogenous variables, and a time-series based rolling window estimation procedure, this study adds to the current literature in two significant ways. The first is that to assume the cross-country growth/volatility correlation is constant over time, or differs across ad hoc predetermined intervals of time is inappropriate. Instead, the early to mid 1990's seems to be the primary area whereby there are significant changes in the relationship across countries. Specifically, volatility negatively impacted growth for developed nations around this time, while it positively impacted growth for developing nations--the latter happening a few years later than the former. The second finding is that the positive impact that trade had on the growth/volatility relationship for developing countries during this period is outweighed by the negative impact of gross capital flows. Among developed nations, globalization reduces a negative effect that gross capital flows has on the relationship. For policy and constituency appeasement purposes the former is an argument for caution when entering into the global economy, and the latter an argument to embrace it.

Notizen: In this article the changes in trade patterns introduced by the ASEAN Free Trade Area (AFTA) are examined. Variation in growth trends and the shift-and-share methodology are used to identify the impact of trade liberalization under AFTA on intra- and extra-regional commodity trade. Data at the commodity level are used and the results indicate that AFTA had trade creation effects, with little evidence of trade diversion.

Notizen: This paper examines the relationships between the aggregate R&D activities of the EU and the US using multivariate Granger-causality tests. Our estimation results indicate that the EU reacts positively to increases in R&D productivity in the US. On the other hand, R&D activity in the EU is a direct Granger-cause of both R&D and labour productivity in the US, and the effects are negative. It was shown in the literature that the US reacts submissively to successful Japanese R&D. We extend the literature by demonstrating that the US also reacts submissively to increased R&D effort in the EU.

Notizen: Cell phone use is increasing worldwide, leading to a concern that cell phone use while driving increases accidents. Several countries, three states and Washington, D.C. have banned the use of hand-held cell phones while driving. In this paper, we develop a new approach for estimating the relationship between cell phone use while driving and accidents. Our approach is the first to allow for the direct estimation of the impact of a cell phone ban while driving. It is based on new survey data from over 7,000 individuals.This paper differs from previous research in two significant ways: first, we use a larger sample of individual-level data; and second, we test for selection effects, such as whether drivers who use cell phones are inherently less safe drivers, even when not on the phone.The paper has two key findings. First, the impact of cell phone use on accidents varies across the population. This result implies that previous estimates of the impact of cell phone use on risk for the population, based on accident-only samples, may be overstated by about one-third. Second, once we correct for endogeneity, there is no significant effect of hands-free or hand-held cell phone use on accidents.

Notizen: When the city of New Orleans was flooded after Hurricane Katrina in August of 2005, coverage of the beleaguered city was soon dominated by horrifying tales of violent crime. These stories, carried in all the major media, and verified by top officials of the City, turned out to be completely false. The major emphasis on violent crime, however, had immediate and dire consequences. Rescuers and victims of the flood lost precious time hunkering down instead of rescuing themselves or others. Escapees from the city faced stigma and sometimes armed resistance to their seeking refuge. Politicians responsible for one of the worst failures of government in American history found crucial political traction by railing against lawlessness. Now a year later, the most significant long term consequences of this "false memory" of criminal violence in the wake of the flood, may be in shaping America's "risk imaginary." For a long time American personal and governmental attitudes toward risk were shaped by the work accident as a model of modern risk and insurance as an exemplary tool of risk governance. In recent decades, those models and the images, narratives, and discourses supporting them, have been replaced by ominous images of grave technological disasters and fearsome violent crimes. These new figures haunting our risk imaginary have undercut support for broad measures of social risk spreading and encouraged privatization, isolation, and heavy reliance on police and prisons as tools of government. Now, the false memory of post-Katrina violence may reinforce those tendencies by condensing the disaster and crime fears of recent decades into a memorable and racially coded image of terror.

Notizen: Why do heat waves, which annually cause far more death, on average, than any other natural disaster, provoke little public reaction? Heat waves will become more common place and heat wave deaths more frequent as temperatures increase from climate change. Models predict that annual heat wave deaths in the U.S. by 2050 will easily surpass the death toll from Hurricane Katrina. This Article analyzes extensive data about heat waves, evaluates why heat waves seem not to raise widespread public concern and suggests that mechanisms already exist -- though widely ignored -- to mitigate the worst effects of excess heat. These mechanisms include careful emergency planning, the provision of air conditioning availability and funding, and larger structural changes in the delivery of electricity, energy efficiency and land use planning. Yet the nature of the victims of heat waves combined with cognitive mechanisms that cause individuals to systematically underestimate risk from heat waves and the fact that heat waves cause little property damage all contribute to a failure by many jurisdictions to adopt policies and programs that can mitigate heat wave deaths.

Notizen: This paper begins by exploring the impact of the 2006 midterm elections on the distribution of policy preferences within the U.S. House and Senate during the 110th Congress. We then consider the consequences of the new political configuration in Washington for the distribution of power between party leaders and the committee systems in both chambers, the patterns of bargaining that will occur between congressional Democrats and the Bush White House, and the likely contents of legislative outcomes during 2007-08.

Notizen: The author contends that Michael Bloomberg's 2005 re-election signalled the collapse of Democratic Party dominance in New York mayoral elections. The author discusses the campaign, and suggests that the collapse of Democratic hegemony is due to the decline of the party organizations, the willingness of organized labor to support Republicans, and the city's changing economics and demographics.

Notizen: This brief essay assesses the resources and liabilities that Fred Thompson brings to 2008 Republican presidential nomination politics. It examines facets of Thompson's Senate career, as well as his work as a lobbyist and actor. Although Thompson benefits from a political context in which social and religious conservatives find flaws in the first tier candidates and from national visibility, his relatively centrist voting record among Republican senators, reputed, but largely, untested campaign skills, lobbying activities, and late entry in the contest present significant obstacles for him.

Notizen: The author discusses Rudolph Giuliani and Michael Bloomberg, the two most recent Mayors of New York City, and their prospects for the Presidency. While the New York mayoralty has historically been a ``political dead end," Giuliani is a front-runner for the Republican nomination and Bloomberg is being discussed as a potential independent candidate. The author briefly examines their leadership styles and offers some ideas about how they might deal with aspects of the Presidency. Finally, the author notes the possibility that two other ``New Yorkers" also are serious candidates: Senator Hillary Clinton, who was elected to the Senate while still First Lady, and Fred Dalton Thompson, the unannounced candidate for the Republican nomination. Thompson, who served in the U.S. Senate for eight years (1995-2003), and before that had come to national prominence as the Minority Counsel during the Senate's Watergate Hearings (1973), is known to many voters as ``Arthur Branch," the fictional Manhattan District Attorney, a character that he has played for the last five seasons (2002-2007) on the NBC television program, ``Law and Order."

Notizen: A book review of Gary Jacobson's A Divider, Not a Uniter.

Notizen: Research indicates that large biorefineries capable of handling 5000-10000MT of biomass per day are necessary to achieve process economies. However, such large biorefineries also entail increased costs of biomass transportation and storage, high transaction costs of contracting with a large number of farmers for biomass supply, potential market power issues, and local environmental impacts. We propose a network of regional biomass preprocessing centers (RBPC) that form an extended biomass supply chain feeding into a biorefinery, as a way to address these issues. The RBPC, in its mature form, is conceptualized as a flexible processing facility capable of pre-treating and converting biomass into appropriate feedstocks for a variety of final products such as fuels, chemicals, electricity, and animal feeds. We evaluate the technical and financial feasibility of a simple RBPC that uses ammonia fiber expansion pretreatment process and produces animal feed along with biorefinery feedstock.

Notizen: The goal of this paper is to develop a nonlinear observer-based control strategy for a jacketed continuous stirred tank reactor (CSTR). The nonlinear adaptive state estimator/observer (ASE/ASO) is designed based on a model structure that mainly consists of an energy balance equation. In this observation approach, reactor concentration is considered as an imprecisely known extra state (augmented state) with no dynamics. Despite significant process/model discrepancy, the proposed state observer estimated adequately the states of the simulated reactor. Mainly due to the design simplicity, negligible computational effort and fast convergence, the observer is recommended for online implementation. The generic model controller (GMC) has also been synthesized for the example reactor. The nonlinear GMC scheme receives the required information about the reactor concentration from the ASE for calculating the controller responses. Simulation experiments have been carried out to investigate the superior performance provided by the proposed GMC-ASE algorithm compared to the conventional proportional integral (PI) controller.

Notizen: One of the main uses given to ferrous sulphate in the pharmaceutical industry is that of iron supplement. The objectives of this work were to recycle a Cuban metallurgical solid waste with high iron concentration in its two oxidation forms, as well as the finding of optimal conditions for the leaching reaction of this solid waste with sulfuric acid. These results will allow defining a technology for the synthesis of iron inorganic salt for the pharmaceutical industry. A complete factorial experimental design was made, which included three Independent variables on three different levels (3^3) in order to optimize extraction of iron (II) and iron (III). These variables were: sulfuric acid concentration, reaction temperature and molar relation between sulfuric acid and both iron species. The goal of multiple optimizations was to maximize conversions of both iron species and their concentrations in the final liquor, favouring the first.

Notizen: An industrial steam reformer of a methanol plant was modeled at a dynamic condition in which a one dimensional homogeneous model was coupled with a verified kinetics from the literature. A close agreement was observed between the results of the model and industrial data from a real plant at steady state conditions. The open loop response of the system to switching between two operating conditions was investigated and shown that the produced synthesis gas during the transition period would be unsuitable for the downstream methanol converter. The genetic algorithm was then employed to perform a multi-objective dynamic optimization on the reactor performance in case of switching the feed and operating conditions. Maximization of methane conversion and minimization of a stoichiometric parameter, were considered as the two objectives' functions that were optimized for a fixed feed rate of methane to the existing unit. The results of the dynamic optimization for the specified reformer configuration were achieved after switching the operating condition. Results of the optimization showed that the produced synthesis gas would stay in its acceptable limits in terms of quality of the feed of the methanol converter and also, the final conversion of the reformer would be improved compared to the steady state condition. This procedure could be applied to the advanced process control of the methanol plant.

Notizen: Due to varied flow behavior, the demarcation of hydrodynamic flow regimes is an important task in the design and scale-up of bubble column reactors. This article reviews most hydrodynamic studies performed for flow regime identification in bubble columns. It begins with a brief introduction to various flow regimes. The second section examines experimental methods for measurement of flow regime transition. A few experimental studies are presented in detail, followed by the effect of operating and design conditions on flow regime transition. A table summarizes the reported experimental studies, along with their operating and design conditions and significant conclusions. The next section deals with the current state of transition prediction, and includes purely empirical correlations, semi-empirical models, linear stability theory, and Computational Fluid Dynamics (CFD) based studies.

Notizen: A tangential flow two colliding streams cyclone reactor (TFTCSCR) was employed as a chemical reactor in the implementation of a solid-liquid reaction. The reaction between barium sulfide particles and a sodium carbonate solution as a typical example of such reactions was considered. Higher conversions of BaS obtained in this reactor may indicate the better performance capability of TFTCSCR relative to those of conventional reaction systems. A stochastic model, based on the Markov chain discrete formulation has been developed for the TFTCSCR, which describes the flow pattern and the residence time distribution (RTD) within the reactor. The predicted values for BaS conversion have been compared with those determined experimentally. The degree of agreement was between 80-85%.

Notizen: A mathematical model is developed to optimize the performance of the radial flow reactors of styrene production through an oxidative reheat process. The model integrates the hydrodynamic configuration of the reactors with the underlying chemical reactions where the kinetic expressions were found in the literature. The predictions of the model were compared with the actual plant data and satisfactory results were obtained. In order to optimize the performance of the plant, a combination of yield and selectivity styrene was adopted as the objective function. The global criterion multi-objective method using Levenberg-Marquardt algorithm was used in order to search for the optimal solution of the process. Three main process variables, i.e., the flow rate of steam injected to the second and third reactor and the fraction of oxygen injected to the secondary injection port of the second reactor, were determined in the optimization. The results show that the optimal operating conditions may lead to 2.6 % increase in the styrene yield and 1.5% increase in styrene selectivity, which significantly improves the profitability of the whole styrene production process.

Notizen: The past attempts of Arrhenius plots of carbon nanotube (CNT) yield (or CNT length) to obtain the overall activation energy for CNT formation under changing reaction temperature conditions have created substantial errors. Here we propose an inverse method to accurately account for the effect of temperature on gas-phase reactions and species composition. The overall activation energy of soot formation for a xylene-based CVD reactor was calculated and successfully compared with the measured gas-phase concentration data. Our proposed inverse method is expected to help improve the performance of CVD reactors and optimize its design.

Notizen: Amorphous natural silicoaluminates, such as expanded perlite, transform themselves in three-dimensional crystalline species, exhibiting effects of the alkaline solutions with NaCl. In this paper the kinetics and the effect of the reaction conditions over the crystallization process are studied.Na(OH) solutions 15%, 18%, and 20 % w/v, and NaCl solutions from 0 % up to 30 % w/v were used. Temperature range was from 80ºC to 95 ºC. The effect of the solid/liquid relationship and the fluid dynamic conditions were studied. The rate of the zeolite formation process depends on the concentration of Na(OH) / NaCl solutions and on the reaction temperatures.The fluid dynamic conditions and the solid/liquid relationships have no effect over the crystallization process in the studied range. The effect of the NaCl is to increase the reaction rate independently of the kind of obtained zeolite, which is associated with the relationship Si/Al.Powder X - ray diffraction (XRD) analysis and scanning electron microscopic (SEM) were employed to study the zeolite formation process in order to elucidate the mode of zeolite crystallization.The mechanism implies the formation of units of nuclei of growth, and the population of these units is controlled by NaCl concentrations. The nucleation and growth Avrami model properly describes the process of formation of the crystalline species. It is found that the parameters k and n are linked respectively with the conditions and the reaction mechanism.

Notizen: A generalized modeling approach is used to develop a systematic algorithm for formulating and solving chemical/biochemical reaction engineering problems. This systematic approach is general enough that it can treat different systems with varying degrees of complexity utilizing the same methodology. The procedure can be used in both introductory and advanced chemical/biochemical reaction engineering courses. This will provide the students with a powerful "toolkit" to tackle a wide range of academic and industrial engineering problems as well as a solid starting point for developing research projects in this field. This may also allow the students to have a better understanding of the multiple phenomena encountered in chemical/biochemical engineering systems and encourage them to prepare models at an optimum level of sophistication for design, optimization, and exploration of novel ideas.

Notizen: Supercritical fluid extraction solubility data for monoolein, diolein and triolein in carbon dioxide were measured using a phase equilibrium re-circulation high-pressure type apparatus at 60° C and at various pressures. In order to examine the supercritical fluid extraction operation effects at high-pressures, detailed experimental determination were made on the compositions of the equilibrium vapor and liquid phases in the system (carbon dioxide/monoolein, carbon dioxide/diolein and carbon dioxide/triolein) at various conditions. It was found that weight fractions of up to 1% of monoolein could be obtained in the vapor phase. This might be sufficient to make supercritical fluid extraction using carbon dioxide solvent a possibility for this component. This renders a separation by simple distillation impossible. These systems were modeled based on the Redlich-Kowng equation of state. The experimental data was found to agree well with the data obtained by the model.

Notizen: An experimental investigation of the combined influence of flow pulsation and modified duct surface on cross-flow transport and convective heat transfer intensification in laminar flow was carried out. The experiments were performed with a fluid with a kinematic viscosity of 1.8x10-6 m2/s and Prandtl number of Pr = 15. The active length L of the channel is 900 mm and lateral extension is W = 90 mm. Pulsation amplitude (A range of 0.28 mm - 0.53 mm) was used together with pulsation frequency (range of 16 Hz ? f ? 54 Hz). A steady flow Reynolds number range of 100 〈 Re 〈 600 was studied. All the geometric parameters of the device such as the relative fin spacing and relative fin thickness were constant. The results of the flow visualization showed recirculation eddies formation when flow pulsation and fins are combined. This enhances the mixing of the fluid within the channel. The intensification of the heat transfer coefficient due to pulsation and use of fins becomes more significant with increasing pulsation amplitude. The combined influence of flow pulsation and modified surface geometry on the heat transfer coefficient was found to be significant at moderately low but non-zero net flow rates or Peclet number Pe. Maximum heat transfer intensification of 2.4 was obtained. In general, no significant heat transfer was obtained at very low and very high flow rates.

Notizen: The concepts of green chemistry and sustainable development are being considered more and more due to the evolution of regulations and mentalities. In this context, the development of supercritical fluid technologies should go on to evolve in the right direction. Since the nineteen fifties, studies and development efforts have been focused on new ways of separating substances using the specific properties of supercritical fluids. In this context, a mention must be made about the use of carbon dioxide as an extracting agent in many industrial processes (decaffeination of coffee and tea, extraction of hops, spice, aromatic substances, fragrances, pharmaceuticals, etc). Processes using these fluids are particularly attractive at the industrial scale in many fields such as impregnation, analytical and preparative separations, organic synthesis, waste management and material recycling. The industrial development of the supercritical fluid technology is accompanied by numerous research activities, in particular, in the field of inorganic Materials Science for the synthesis of multifunctional nanomaterials.Today, supercritical fluid technology allows the production, with a reduction of the environmental impact, of well designed nanomaterials with controlled properties for applications in many interesting fields, such as catalysis, electronics, energy, optics, pharmacology, etc. This paper is focused on the interest of using supercritical fluids to overcome the drawbacks of solution chemistry approaches for designing multifunctional nanomaterials in term of chemical engineering, sustainable chemistry and control of size, morphology, composition and the structure of nanomaterials.

Notizen: The performances of a semi-industrial-scale membrane bioreactor to treat dilute swine wastewater were investigated on a 3 month running period. The treated water was directly reused in the piggery for flushing purposes. The pilot was proved to have good performances in terms of ammonium removal (99%), and COD removal (86%), despite an accumulation of heavy metals in the biological tanks (up to 17 mg/L for zinc and up to 115 mg/L for copper). 79% of the total phosphorus was eliminated through the process, 61% via centrifugation and 18% by biological uptake. The pilot showed a good adaptability to the variations of the loading rates of dilute swine wastewater's major components (COD, TN, TP, heavy metals).

Notizen: This work deals with the multicriteria cost-environment design of multiproduct batch plants, where the design variables are the equipment item sizes as well as the operating conditions. The case study is a multiproduct batch plant for the production of four recombinant proteins. Given the important combinatorial aspect of the problem, the approach used consists in coupling a stochastic algorithm, indeed a Genetic Algorithm (GA) with a Discrete Event Simulator (DES). To take into account the conflicting situations that may be encountered at the earliest stage of batch plant design, i.e. compromise situations between cost and environmental consideration, a Multicriteria Genetic Algorithm (MUGA) was developed with a Pareto optimal ranking method. The results show how the methodology can be used to find a range of trade-off solutions for optimizing batch plant design.

Notizen: Microstructured reactors with their benefits especially concerning enhanced mass and heat transfer represent a means for process intensification. A broadly used microstructured lab tool in the area of gas/liquid contacting is the Falling Film Microreactor (FFMR) developed by IMM in which liquid films of a few tens of micrometer thickness and interfacial areas of up to 20,000 m2/m3 combined with an effective heat exchange can be obtained. Now the concept of the Falling Film Microreactor has been developed further with regard to increasing throughput in order to reach pilot production level and as a basis for future production scale throughput. Therefore, two different prototypes with a tenfold larger structured surface area have been developed and realized. The feasibility of a corresponding increase of throughput has been demonstrated for the oxidation of an organic compound using oxygen which is closely linked to an industrial relevant reaction and additionally by the absorption of CO2 in an aqueous sodium hydroxide solution. Naturally, process optimisation itself also contributes to the efforts to increase throughput. Therefore, the oxidation reaction has been optimised in both varying process parameters (temperature, flow rates, pressure) and reactor parameters (microchannel width and depth) in the original, standard Falling Film Microreactor. Conducting experiments at 10 bar instead of ambient pressure and using a reaction plate with 1200 µm x 400 µm channels instead of 600 µm x 200 µm channels lead to an increase in conversion. These investigations also encourage exploring more challenging process conditions and thereby following the concept of "novel chemistry."

Notizen: This work is related to the tracking of sulfate concentration trajectories in a continuous anaerobic bioreactor, where Desulfovibrio alaskensis is considered for different operation purposes. A new design of a class of nonlinear proportional control law with an adaptive gain was proposed. The proposed controller was applied to the mathematical bioreactor's model with the kinetics experimentally corroborated; this describes the dynamics of biomass, sulfate and sulfide concentrations. The open-loop stability conditions of the optimum set points and the corresponding closed-loop performances were analyzed. The proposed control law is able to track trajectories, despite sustained disturbances. An Internal Model Control (IMC) Proportional-Integral Controller was implemented for comparison purposes and the corresponding performances were illustrated via numerical experiments.

Notizen: Sulphate-reducing bacteria (SRB) are anaerobic bacteria that couple the oxidation of simple organic compounds to the reduction of sulphate to sulphide. SRB have become important components of bioremediation systems. In this work, a natural SRB sludge was collected in the coastal mud flat of Colindres (Cantabria, Spain) and the removal of soluble cadmium as cadmium sulphide from a synthetic feeding was studied. Discontinuous experiments were performed at room temperature, using four 600 ml reactors. In stage 1, a 250 mL biomass solution (18.16 g/L of volatile matter) was introduced in each reactor and was fed with a solution of cadmium sulphate, sodium sulphate and sucrose as carbon and energy source. The Chemical Oxygen Demand (COD) to SO4-2 ratio (this SO4-2 coming from Na2SO4) was 10 in all the stages of the four reactors, and the different cadmium content tested in each reactor varied from 4 to 12 mg/L. Stages 2, 3, 4 and 5 were performed with the same biomass but with higher initial cadmium amount, from 16 to 300 mg/L, in order to determine the amount of metal causing inhibition of the bacterial activity. Soluble cadmium was analyzed by Atomic Absorption Spectrometry. Additionally in stage 4, the evolution of pH and COD was studied. Results indicated that inhibition of biomass was not found up to a Cd concentration of 300 mg/L. Continuous experiments were performed in an UASB reactor of 1 litter of useful capacity, being the hydraulic residence time 0.833 days and 720 mg of COD/day the organic matter in the influent. After a period of acclimation, biomass was fed with increasing amounts of soluble Cadmium and the specific rate of cadmium elimination was determined.

Notizen: This article examines the propagation of kefir grains in fresh HTP whole fat cows' milk, with some additions (glucose and bakers yeast). The objective of our work was an experimental determination of the various process parameters relative influence on the propagation and daily kefir grain increase mass, using the Taguchi method for experimental design. The effects of medium temperature, glucose mass concentration, bakers yeast mass concentration and the rotational frequency of the stirrer at four levels were studied. Orthogonal array layout of L16 was selected for the proposed experimental design. All experiments were performed in an automated laboratory reaction calorimeter RC1 (Mettler-Toledo) with the same milk (3.5 % fat). The gravimetric method was used to determine daily kefir grain mass increases. Relative contributions of the proposed influencing process parameters on the daily kefir grains increase mass were estimated by analysis of the variance (ANOVA). The highest increase (51.5 %) was found at the rotational frequency of the stirrer 90 (1/min), at glucose mass concentration 20 g/L, and at medium temperature 24 °C. Within the observed range of yeast mass concentration this process parameter was found to be insignificant compared to others. The rotational frequency of the stirrer has the highest relative influence on the daily kefir grains increase mass (37.3 %) while glucose mass concentration and medium temperature have lower ones, 18.8 % and 9.9 %, respectively. The remaining fraction represents error influence. The main reason for its relatively high value (34.0 %) is that kefir grains are bulky and awkward to handle. This fact confirms the importance of optimal kefir grains production management.

Notizen: A gas-solid fluidized bed bioreactor has been successfully used for the bioremediation of ethanol (a model volatile organic compound, VOC) contaminated air. A key objective of this fluidized bioreactor study was to compare the performance of fluid bed operation to packed bed operation. A fluid bed system increased homogeneity and improved upon operating problems such as plugging and channelling normally associated with packed bed bioreactors. The bioreactor bed was comprised of a mixture of moist sawdust particles and glass spheres. Depending on the superficial velocity of the waste gas stream, the bioreactor could be operated in either packed or fluidized mode. During fluid bed operation, the sawdust and glass sphere mixture was maintained in a bubbling/slugging regime. As expected, fluid bed operation demonstrated significantly higher mass transfer rates but the maximum elimination capacity was 75 g m-3sawdust h-1 as compared to 225 g m-3sawdust h-1 for packed bed operation. In packed bed mode, higher ethanol concentrations were used in order to have comparable ethanol loadings and this may have contributed to faster growth rates and thus faster bioremediation rates.

Notizen: Fixed-bed columns containing solid catalysts and adsorbents were employed for simultaneous reaction and separation. The models developed for propene metathesis were validated with experimental data for configurations with and without the effect of pressure swing reaction. The models for the mass and momentum transfer in the catalyst bed and adsorber were solved using orthogonal collocation within the method of lines. The reactor/separator performances were tested for beds with varying numbers of layers of catalysts and adsorbents which were arranged sequentially. The pressure reaction columns behaved as reactor/separators in series. As the number of layers increased, a homogeneous distribution of the catalyst and adsorbent was approached in the limit. These configurations with variable catalyst/adsorbent distributions were investigated for propene metathesis reaction, in terms of product purity, selectivity, conversion, recovery, yield and productivity. Improved reactor performance was observed with a pressure swing separation system and in particular with close to well-mixed reactor/separator configurations.

Notizen: There is not much known about the reactivity of hydrocarbon soot to oxygen and NO. According to the chemical and structural properties of one soot obtained from acetylene pyrolysis, SEVACARB MT and CABOT carbon blacks were selected to perform a reactivity study. The properties of the materials were determined through ultimate and proximate analysis as well as SEM, TEM and XRD techniques. A study of the oxidation of the three materials is performed for different oxidation conditions of temperature (1123-1273 K) and oxygen concentration (100-1000 ppmv). The reaction of acetylene soot with NO and SEVACARB MT carbon black is carried out at 1373 K with 1800-3000 ppmv NO. Results are compared to analyze their reactivity similarities and the possibility of using carbon blacks as acetylene soot substitutes in laboratory work.

Notizen: Fischer-Tropsch synthesis (FTS) offers the potential to produce high-value transportation fuels or petrochemicals from biomass (``2nd generation biofuels"). Primary synthesis products contain mainly n-alkanes and n-alkenes, ranging from methane to high molecular weight waxes. Bifunctional catalysts, as used in petroleum refining, are capable of modifying hydrocarbon molecules. They are characterized by the presence of acidic sites, which provide the hydrocracking and isomerization functions, as well as metal sites, which provide hydro-/dehydrogenation functions, and thus avoid the formation of carbon. The present study addresses the combination of FT synthesis (with Co or Fe catalysts) and hydrocarbon modification reactions. Experimental results obtained in a dual layer configuration with Fe and Co catalysts and Pt/ZSM-5 indicate i) an increase of branched hydrocarbons in the gasoline range (C5-C10), ii) a decrease of alkene and alcohol yields, iii) partial hydrocracking of long chain hydrocarbon molecules leading to higher yields of gasoline and distillates, iv) nearly constant methane selectivity in comparison with the FT catalyst alone, and v) no significant catalyst deactivation. In addition, studies with 1-octene as the model compound were carried out, being mixed with synthesis gas H2/CO or with H2/Ar. The presence of CO decreases reaction rates of hydrogenation and hydrocracking, although all reactions still occur to a significant extent. For the conditions used in this study (1 MPa, 200-300 °C, 4000 kg s/m3), a significant change of hydrocarbon product composition with hydroprocessing catalyst functions added can be observed.

Notizen: Hydrogenation of vegetable oils using stable catalysts with satisfactory activity and selectivity as well as very low trans fatty acid (TFA) and saturated fatty acid (SFA) production is a challenging task. It is known that unhealthy TFA formation is the result of positional and conjugative isomerization side-reactions occurring during hydrogenation. From this standpoint, it is possible to formulate active, selective and stable catalysts which would minimize the production of TFA and SFA. Monometallic Pd and bimetallic Pd-Me (Me=Mo, Ni, Co, Ru, and Sr,) highly dispersed on mesostructured SBA-silica material with pore size ranging from 6 to 7 nm, BET-specific surface of 800-900 m²/g, and metal nominal total loading up to 1.0 % w/w, were comparatively investigated as catalysts for lowering the unhealthy trans (TFA) and saturated (SFA) fatty acids and maximizing the highly health-beneficial cis-monoenes production during the hydrogenation of sunflower oil at 110 oC under hydrogen pressure of 5 atm. The Pd-catalyst at nominal metal loading of 0.8 % supported on nanostructured support was active and selective for the hydrogenation of sunflower oil under mild process conditions. It produced less saturated acid and reached a good selectivity towards monoenes. In all cases, the consecutive impregnations of Pd and a second metal on the mesoporous silica support preserved the mesoporous structure of the support with slight modification of the textural characteristics in terms of BET surface area, pore size distribution and total pore volume. The addition of nominal 0.2 % Co, Sr or Ru to 0.8% Pd-catalyst enhanced its activity. However, the addition of nominal 0.2 % Ni or Mo dropped the activity of monometallic Pd-catalyst significantly. It is clearly shown that Ru had some promoting effect to inhibit further the formation of trans fatty acids. The addition of a second metal to Pd-catalyst had no significant effect on the formation of C18:0. High degree of metal-metal, metal-support as well as metal-oil interactions would greatly influence the reaction mechanisms of the vegetable oil hydrogenation.

Notizen: The technological development of catalytic processes under rapid deactivation requires the rigorous calculation of the deactivation kinetic equation in order to be useful in the simulation and optimization of industrial processes. Accordingly, suitable equipment for reaction and product analysis and a rigorous methodology for kinetic data analysis are required. These aspects are approached in this paper using the transformation of methanol into olefins on a SAPO-18 as the model reaction. In this reaction, deactivation is rapid and there is also an initiation period depending on process conditions. The correct use of gas chromatography allows for improving the collection of experimental data of composition with time-on-stream, given that, on the one hand, it minimizes the time required for analysis (4 min), and on the other, a better homogenization of the reaction product sample is achieved, which allows for a more accurate determination of the composition corresponding to a given time-on-stream. Furthermore, the rigorous kinetic modelling of deactivation requires a data analysis methodology that considers the past history of the catalyst and an activity to be defined based on a rigorous physical meaning. Accordingly, the concept of the integrated kinetic model has been used in this paper, whose basis is the calculation of kinetic parameters by simultaneously solving the zero time-on-stream kinetic model and the kinetic equation for deactivation.

Notizen: Producing hydrogen from natural gas for a mini scale fuel cell is a new challenge for researchers. Therefore, modeling of hydrogen production microreactors should be helpful for designing and developing new microreactors. Experimental sensing of velocity, concentration, temperature and reaction rates in numerous points of the microreactor is impracticable. A microreactor in special geometry was considered for hydrogen production and a CFD model was developed in order to incorporate the mechanism of autothermal reforming. This mechanism includes three main reactions and Langmuir-Hinshelwood type kinetic rates. A three dimensional reformer model was developed to simulate the reactive laminar flow model of this microreactor. Effects of styles of feed entrance, air to fuel ratio and adding water to methane were studied. This model shows that there are hot spots near the entrance of the microreactor where the total oxidation of methane occurs and air distribution along the microreactor is a good solution for hot spot problems. The model shows that air distribution is good for fuel cell application because of high hydrogen production and low CO content in the outlet.

Notizen: A set of TiO2 samples with different anatase/rutile ratios was prepared by calcinations at different temperatures from commercial photocatalyst Degussa P25. The effects of the two crystalline phases of titanium (IV) oxide on the photocatalytic activity in gaseous phase through oxidation of light hydrocarbons were studied. Crystalline phase transformation from anatase to rutile occurred at 700°C for P25. Results indicate that samples with higher anatase/rutile ratios presented higher intrinsic activities for the photodegradation of a propane/isobutane/butane (40/35/25 %V) mixture. However, the activity did not totally disappear after complete crystalline transformation from anatase to rutile, indicating that the pure rutile phase also presents photoactivity. During the photocatalytic reaction of TiO2 samples, a linear dependence was found between the inverse of the intrinsic reaction rate constant (k intrinsic) and the water adsorption capacity in the surface (WAPS) of the synthesized TiO2 catalyst. The thermal treatment used to induce the formation of rutile by calcination would presumably reduce water adsorption capacity and surface area, leading to a decrease in photocatalytic activity.

Notizen: Within the context of reducing the green house gas emissions, substituting hydrogen for natural gas could have a great environmental impact, but hydrogen has different combustion characteristics than natural gas. This paper reports results of experimental tests of premixed combustion of natural gas-hydrogen mixtures in a porous burner made of open cell metallic foam. The technology of porous radiant burners shows environmental and economical advantages compared to traditional diffusion flame burners. The tests showed that substituting natural gas for hydrogen in a porous burner reduces the pollutant emissions of CO and NOx and the quantity of CO2 produced. For specific powers below 500 kW/m2, the emissions were below the "Blue Angel" label values. But working conditions are limited by hydrogen addition and the equivalence ratio has to be lowered to prevent flashback. The radiant combustion mode is more difficult to obtain with mixtures containing hydrogen and it disappears completely for mixtures with more than 80% vol. hydrogen.

Notizen: Used tyres pose a serious environmental problem and pyrolysis is considered one of the more feasible solutions that may be economically profitable on a large scale. In this study the pyrolysis of tyres has been carried out in a conical spouted bed reactor at 500 °C and the liquid product has been characterized taking into account composition, heat value and simulated distillation. The tyre mass feed in each run was 2 g and the bed was made up of 15 g of sand. Pyrolysis of scrap tyre at the 500 °C gives way to a yield of 3.1% of gases, 37.6% of liquid fraction (C5-C10 range hydrocarbons), 25.6% of tar (C11+) and 33.7% of char. The liquid fraction is of suitable quality for its use as fuel but the char requires activation for its upgrading.

Notizen: The specific surface area of ground perovskites is strongly dependent on the synthesis and pretreatment conditions. Calcining the ground LaCo1-xCuxO3-? perovskites at 5000C causes a decrease of their specific surface, but the further reductive pretreatment of the calcined sample in hydrogen leads to only a minor change in the specific surface area. The introduction of extra- and intra-perovskite lattice copper has different effects on the structure stability, reducibility and catalytic properties of LaCoO3 perovskites. Under the same pretreatment conditions the basic structure of both LaCoO3 and Cu2O/LaCoO3 samples is retained at the reduction temperature of 5000C (90 min) while that of Co-Cu based perovskites is completely collapsed producing a high dispersion of bimetallic metals and Co-Cu alloys supported on amorphous La2O3. For a series of LaCo1-xCuxO3 samples, increasing the copper content in the perovskite structure leads to an increase in the metal surface area of the reduced phase. The pretreated catalysts were tested for CO dissociation and for alcohol synthesis from syngas. The results indicated that the copper sites neighboring with cobalt atoms in the reduced perovskites decrease the activity in CO dissociation and increase the rate of higher alcohol synthesis while extra-perovkite lattice copper tends to produce methanol, methane and CO2. The overall activity in syngas conversion and higher alcohol productivity are proportional to the Co-Cu metal surface. The role of dual sites of Co and Cu for the synthesis of higher alcohols is discussed. The catalytic activity and alcohol productivity as well as product distribution depend strongly on reaction temperature and pretreatment conditions. The highest productivity of alcohols in the present study is about 73 mg/gcat/h for sample LaCo0.7Cu0.3O3.

Notizen: Heterogeneous photocatalysis with titanium dioxide TiO2 is an advanced oxidation processes that uses ultraviolet radiation to carry out reactions leading to the degradation of polluting agents in water. For the development and scaling up of efficient photocatalytic processes it is important to model the transport of radiation in the reactor volume, because it affects the photo reaction. In the present work we have used the P1 approximation of radiative transfer theory to evaluate radiation distributions inside a specific annular photocatalytic reactor known as Photo CREC-Water II. The reactor consists of two concentric tubes with a TiO2/water suspension flowing axially in the annular space between them, and a lamp at the center of the inner tube. The theoretical results are compared with experimental data from measurements of radiation transmission through several observation windows in the external reactor wall. In general the model describes the observed experimental results well. Due to the nature of the employed approximation a good quantitative agreement is possible only for suspensions with a large optical depth. For small optical depths the agreement is adequate only for the central portion of the reactor length.

Notizen: In this study, the dissolution kinetics of tincal in phosphoric acid solutions was investigated. The effects of reaction temperature, acid concentration, solid to liquid ratio, particle size and stirring speed were determined in the experiments. The results showed that the dissolution rate increased with increasing acid concentration, reaction temperature, stirring speed and increased with decreasing particle size and solid to liquid ratio. The dissolution rate was found to be based on the first order pseudo homogenous reaction model. The activation energy of the tincal in phosphoric acid solution was determined as 42.28 kJ.mol-1.

Notizen: Stevia rebaudiana is a plant native of South America, and its active constituents are considered, by Food Science researchers, the "sweeteners of the future." Therefore, research on this plant has been increased. Stevia is a source of natural diet sweetening, without calories and safe for health. Its crude extract, however, is foul-smelling, bitter tasting, and dark brown; subsequent purification is essential to obtain a product of commercial quality. In this work, adsorption in modified zeolites associated with the filtration with membranes was applied in order to purify stevia crude extract. For the adsorption process, 40 g of CaX modified zeolites were used. In the ultrafiltration process, membranes with porosities of 0.05, 0.1 and 0.2 ?m were used. The transmembrane pressure was fixed at 2, 4 and 6 bar for each membrane. The best conditions of flux were obtained with the 0.2 ?m membrane and 6 bar, resulting in high clarification and recuperation of stevioside (91.75%). This work shows that the adsorption in modified zeolites associated with the membrane filtration is promising for stevia extract purification.

Notizen: Air gasification of dried sewage sludge (DSS) in a fluidized bed has been studied as an effective alternative for the management of this material in a usable way. Nevertheless, one of the major issues in this technology is to deal with the tar formed during the process. To minimize the tar production, it is very important to optimize the operating conditions. In a previous work (Many et al., Energy Fuels, Vol. 19, 629-636, 2005) some unexpected results, in which tar production increases with the equivalence ratio, have been obtained. As it has been mentioned in that work, tar production could present unexpected trends while the bed composition changes from sand to a mixture of char and sand. Ashes contained in char have catalytic active metals which could promote gasification reactions. As the char content in the bed increases, the catalytic activity in the reactor could increase too, until the steady state is achieved. The aim of this work is to characterize the non-stationary period and its influence on the overall results obtained from gasification tests. Experiments have been carried out in a laboratory-scale BFB reactor at atmospheric pressure and at a reactor temperature of 1123 K with an equivalent ratio of 30%. Results show that at the beginning of the experiments the tar production was higher, until the steady state is reached. The gasification study has been enhanced with an analysis of tar composition by means of GC/MS and GC/FID. An effect of the transition period has been observed in tar composition also. The nitrogen aromatics percent increased with time whereas the polycyclic aromatic hydrocarbon decreased.

Notizen: Previous nonparametric statistical methods on constructing the test and null statistics require having at least 4 arrays under each condition. In this paper, we provide an improved method of constructing the test and null statistics which only requires 2 arrays under one condition if the number of arrays under the other condition is at least 3. The conventional testing method defines the rejection region by controlling the probability of Type I error. In this paper, we propose to determine the critical values (or the cut-off points) of the rejection region by directly controlling the false discovery rate. Simulations were carried out to compare the performance of our proposed method with several existing methods. Finally, our proposed method is applied to the rat data of Pan et al. (2003). It is seen from both simulations and the rat data that our method has lower false discovery rates than those from the significance analysis of microarray (SAM) method of Tusher et al. (2001) and the mixture model method (MMM) of Pan et al. (2003).

Notizen: Microarrays are a tool for measuring the expression levels of a large number of genes simultaneously. In the microarray experiment, however, many undesirable systematic variations are observed. Correct identification and removal of these variations is essential to allow the comparison of expression levels across experiments. We describe the use of linear mixed models for the normalization of two-color spotted microarrays for various sources of variation including printtip variation. Normalization with linear mixed models provides a parametric model of which results compare favorably to intensity dependent normalization LOWESS methods. We illustrate the use of this technique on two datasets. The first dataset contains 24 arrays, each with approximately 600 genes, replicated 3 times per array. A second dataset, coming from the apo AI experiment, was used to further illustrate the methods. Finally, a simulation study was done to compare between methods.

Notizen: In genetic association studies, there is increasing interest in understanding the joint effects of genetic and nongenetic factors. For rare diseases, the case-control study is a practical design, and logistic regression is the standard method of inference. However, the power to detect statistical interaction is a concern, even with relatively large samples. Under independence of genetic and nongenetic covariates, improved precision of interaction estimators is possible, but logistic regression does not make use of this assumption and consequently is not statistically efficient. In recent work to improve efficiency, profile likelihood methods have been used to develop semi-parametric inference that incorporates the independence assumption. We describe an alternate derivation of these estimators for rare diseases that is based on classic arguments from case-control inference. These arguments lead to a simplification in the variance estimator. We also describe a strategy for relaxing the independence assumption. Under either independence or the proposed dependence model, inference for association parameters is conveniently obtained by fitting a conditional logistic regression. The statistical properties of the proposed methodology are investigated by simulation.

Notizen: Dose-response studies are commonly used in experiments in pharmaceutical research in order to investigate the dependence of the response on dose, i.e., a trend of the response level toxicity with respect to dose. In this paper we focus on dose-response experiments within a microarray setting in which several microarrays are available for a sequence of increasing dose levels. A gene is called differentially expressed if there is a monotonic trend (with respect to dose) in the gene expression. We review several testing procedures which can be used in order to test equality among the gene expression means against ordered alternatives with respect to dose, namely Williams' (Williams 1971 and 1972), Marcus' (Marcus 1976), global likelihood ratio test (Bartholomew 1961, Barlow et al. 1972, and Robertson et al. 1988), and M (Hu et al. 2005) statistics. Additionally we introduce a modification to the standard error of the M statistic. We compare the performance of these five test statistics. Moreover, we discuss the issue of one-sided versus two-sided testing procedures. False Discovery Rate (Benjamni and Hochberg 1995, Ge et al. 2003), and resampling-based Familywise Error Rate (Westfall and Young 1993) are used to handle the multiple testing issue. The methods above are applied to a data set with 4 doses (3 arrays per dose) and 16,998 genes. Results on the number of significant genes from each statistic are discussed. A simulation study is conducted to investigate the power of each statistic. A R library IsoGene implementing the methods is available from the first author.

Notizen: Liquid Chromatography - Mass Spectrometry (LC-MS) is a powerful method for sensitive detection and quantification of proteins and peptides in complex biological fluids like serum. LC-MS produces complex data sets, consisting of some hundreds of millions of data points per sample at a resolution of 0.1 amu in the m/z domain and 7000 data points in the time domain. However, the detection of the lower abundance proteins from this data is hampered by the presence of artefacts, such as high frequency noise and spikes. Moreover, not all of the tens of thousands of the chromatograms produced per sample are relevant for the pursuit of the biomarkers. Thus in analysing the LC-MS data, two critical pre-processing issues arise. Which of the thousands of the: 1. chromatograms per sample are relevant for the detection of the biomarkers?, and 2. signals per chromatogram are truly compound-related? Each of these issues involves assessing the significance (deviation from noise) of multiple observations and the issue of multiple comparisons arises. Current methods disregard the multiplicity and provide no concrete threshold for significance. However, with such procedures, the probability of one or more false-positives is high as the number of tests to be performed is large, and must be controlled. Realizing that the cut-offs for declaring a chromatogram (or a signal) to be compound-related can hugely influence which proteins are detected, it seems natural to define thresholds that are neither arbitrary nor subjective. We suggest the choice of thresholds guided by the critical aim of controlling the False Discovery Rate (FDR) in multiple hypotheses testing for significance over a large set of features produced per sample. This involves the use of the regression diagnostics to characterize the signals of a chromatogram (e.g. as outliers or influential) and to suggest suitable tests statistics for the multiple testing procedures (MTP) for discriminating noise and spikes from true signals. The role of the Generalized Linear Models (GLM) in this MTP is investigated. The method is applied to LC-MS datasets from trypsin-digested serum spiked with varying levels of horse heart cytochrome C (cytoc).

Notizen: When trying to learn a model for the prediction of an outcome given a set of covariates, a statistician has many estimation procedures in their toolbox. A few examples of these candidate learners are: least squares, least angle regression, random forests, and spline regression. Previous articles (van der Laan and Dudoit (2003); van der Laan et al. (2006); Sinisi et al. (2007)) theoretically validated the use of cross validation to select an optimal learner among many candidate learners. Motivated by this use of cross validation, we propose a new prediction method for creating a weighted combination of many candidate learners to build the super learner. This article proposes a fast algorithm for constructing a super learner in prediction which uses V-fold cross-validation to select weights to combine an initial set of candidate learners. In addition, this paper contains a practical demonstration of the adaptivity of this so called super learner to various true data generating distributions. This approach for construction of a super learner generalizes to any parameter which can be defined as a minimizer of a loss function.

Notizen: We investigate an important issue of a meta-algorithm for selecting variables in the framework of microarray data. This wrapper method starts from any classification algorithm and weights each variable (i.e. gene) relative to its efficiency for classification. An optimization procedure is then inferred which exhibits important genes for the studied biological process. Theory and application with the SVM classifier were presented in Gadat and Younes, 2007 and we extend this method with CART. The classification error rates are computed on three famous public databases (Leukemia, Colon and Prostate) and compared with those from other wrapper methods (RFE, lo norm SVM, Random Forests). This allows the assessment of the statistical relevance of the proposed algorithm. Furthermore, a biological interpretation with the Ingenuity Pathway Analysis software outputs clearly shows that the gene selections from the different wrapper methods raise very relevant biological information, compared to a classical filter gene selection with T-test.

Notizen: Microarray applications for the study of gene expression are becoming accessible for researchers in more and more systems. Applications from field or laboratory experiments are often complicated by the need to superimpose sample pairing for two-color arrays on experimental designs that may already be complex. For example, split-plot designs are commonly used in biological systems where experiments involve two types of treatments that are not readily applied at the same scale. We demonstrate how effects that are confounded with arrays can still be estimated when there is sufficient replication. To illustrate, we evaluate three methods of sample pairing superimposed on a split-plot design with two treatments, deriving the variance associated with parameter estimates for each. Design A has levels of the whole plot treatment paired on the same microarray within a level of the subplot treatment. Design B has crossed levels paired on the same microarray. Design C has levels of the treatment applied to subplots paired on the same microarray within a whole plot. Designs A and B have lower variance than design C for comparing the levels of the whole plot treatment. Designs B and C have lower variance for comparing the levels of the subplot treatment and design C has lower variance for comparing the levels of the subplot treatment within each level of the whole plot treatment. We provide SAS code for the analyses of variance discussed.

Notizen: Although researchers use duplicate genotyped data to calculate an inconsistency rate, there is no power analysis to assess the value of the duplicate data. In this paper, we present a model in which the genotyping error rate is related to the inconsistency rate. We extend the g genotype by h phenotype chi-squared test to incorporate the duplicate genotyped data. When a subject is inconsistently genotyped (that is, has two observed genotypes), our procedure is to allocate 0.5 units to each of the two genotypes. We specify the multivariate analysis of variance (MANOVA) test comparing these extended counts. We provide freely available software for this test and also for a permutation test used on small samples. A simulation study shows that the asymptotic null distribution of the MANOVA test holds when the total number of subjects, N, is at least 300. We also document with a simulation study that the asymptotic distribution of this test under various alternative hypotheses is a satisfactory approximation to the simulated power. In all cases, the power of the MANOVA test using the duplicate genotyped data is greater than the power of the chi-squared test ignoring the duplicate data. Power increases ranged from 0.776% to 4.652% for 80% powered tests and 0.292% to 2.028% for 95% powered tests. Researchers now can compute the value of the duplicate genotyped data as part of the design of the study.

Notizen: A number of computational methods have been proposed for identifying transcription factor binding sites from a set of unaligned sequences that are thought to share the motif in question. We here introduce an algorithm, called cosmo, that allows this search to be supervised by specifying a set of constraints that the position weight matrix of the unknown motif must satisfy. Such constraints may be formulated, for example, on the basis of prior knowledge about the structure of the transcription factor in question. The algorithm is based on the same two-component multinomial mixture model used by MEME, with stronger reliance, however, on the likelihood principle instead of more ad-hoc criteria like the E-value. The intensity parameter in the ZOOPS and TCM models, for instance, is estimated based on a profile-likelihood approach, and the width of the unknown motif is selected based on BIC. These changes allow cosmo to outperform MEME even in the absence of any constraints, as evidenced by 2- to 3-fold greater sensitivity in some simulation studies. Additional improvements in performance can be achieved by selecting the model type (OOPS, ZOOPS, or TCM) data-adaptively or by supplying correctly specified constraints, especially if the motif appears only as a weak signal in the data. The algorithm can data-adaptively choose between working in a given constrained model or in the completely unconstrained model, guarding against the risk of supplying mis-specified constraints. Simulation studies suggest that this approach can offer 3 to 3.5 times greater sensitivity than MEME. The algorithm has been implemented in the form of a stand-alone C program as well as a web application that can be accessed at http://cosmoweb.berkeley.edu. An R package is available through Bioconductor (http://bioconductor.org).

Notizen: There have been various attempts to reconstruct gene regulatory networks from microarray expression data in the past. However, owing to the limited amount of independent experimental conditions and noise inherent in the measurements, the results have been rather modest so far. For this reason it seems advisable to include biological prior knowledge, related, for instance, to transcription factor binding locations in promoter regions or partially known signalling pathways from the literature. In the present paper, we consider a Bayesian approach to systematically integrate expression data with multiple sources of prior knowledge. Each source is encoded via a separate energy function, from which a prior distribution over network structures in the form of a Gibbs distribution is constructed. The hyperparameters associated with the different sources of prior knowledge, which measure the influence of the respective prior relative to the data, are sampled from the posterior distribution with MCMC. We have evaluated the proposed scheme on the yeast cell cycle and the Raf signalling pathway. Our findings quantify to what extent the inclusion of independent prior knowledge improves the network reconstruction accuracy, and the values of the hyperparameters inferred with the proposed scheme were found to be close to optimal with respect to minimizing the reconstruction error.

Notizen: In a hidden Markov model, one "estimates" the state of the hidden Markov chain at t by computing via the forwards-backwards algorithm the conditional distribution of the state vector given the observed data. The covariance matrix of this conditional distribution measures the information lost by failure to observe directly the state of the hidden process. In the case where changes of state occur slowly relative to the speed at which information about the underlying state accumulates in the observed data, we compute approximately these covariances in terms of functionals of Brownian motion that arise in change-point analysis. Applications in gene mapping, where these covariances play a role in standardizing the score statistic and in evaluating the loss of noncentrality due to incomplete information, are discussed. Numerical examples illustrate the range of validity and limitations of our results.

Notizen: Digital images obtained by the laser scanning of spotted microarrays often include saturated pixel values. These arise when the scan settings are sufficiently high and some pixels exceed the limit L=65535 and are instead set to L. Failure to adjust for this censoring leads to biased estimates of gene expression levels. To impute censored values, we propose a linear model based on the principal components of uncensored spots on the same array. This is computationally fast, flexible to adapt to distinctive spot shapes and profiles on different arrays, and is shown to be more effective than the polynomial-hyperbolic model in correcting for the bias. The application to biological data demonstrates the potential for enhancing the dynamic range of detection. Fortran90 subroutines implementing these methods are available at http://www.bioss.ac.uk/~chris.

Notizen: In this paper, we propose a novel method for sparse logistic regression with non-convex regularization Lp (p 〈1). Based on smooth approximation, we develop several fast algorithms for learning the classifier that is applicable to high dimensional dataset such as gene expression. To the best of our knowledge, these are the first algorithms to perform sparse logistic regression with an Lp and elastic net (Le) penalty. The regularization parameters are decided through maximizing the area under the ROC curve (AUC) of the test data. Experimental results on methylation and microarray data attest the accuracy, sparsity, and efficiency of the proposed algorithms. Biomarkers identified with our methods are compared with that in the literature. Our computational results show that Lp Logistic regression (p 〈1) outperforms the L1 logistic regression and SCAD SVM. Software is available upon request from the first author.

Notizen: Quantitative Polymerase Chain Reaction (Q-PCR) aims at determining the initial quantity of specific nucleic acids from the observation of the number of amplified DNA molecules. The most widely used technology to monitor the number of DNA molecules as they replicate is based on fluorescence chemistry. Considering this measurement technique, the observation of DNA amplification by PCR contains intrinsically two kinds of variability. On the one hand, the number of replicated DNA molecules is random, and on the other hand, the measurement of the fluorescence emitted by the DNA molecules is collected with some random error. Relying on a stochastic model of these two types of variability, we aim at providing estimators of the parameters arising in the proposed model, and, more specifically, of the initial amount of molecules. The theory of branching processes is classically used to model the evolution of the number of DNA molecules at each replication cycle. The model is a binary splitting Galton-Watson branching process. Its unknown parameters are the initial number of DNA molecules and the reaction efficiency of PCR, which is defined as the probability of replication of a DNA molecule. The number of DNA molecules is indirectly observed through noisy fluorescence measurements resulting in a so-called Hidden Markov Model. We aim at inference of the parameters of the underlying branching process, and the parameters of the noise from the fluorescence measurements in a Bayesian framework. Using simulations and experimental data, we investigate the performance of the Bayesian estimators obtained by Markov Chain Monte Carlo methods.

Notizen: Multi-color optical mapping is a new technique being developed to obtain detailed physical maps (indicating relative positions of various recognition sites) of DNA molecules. We consider a study design in which the data consist of noisy observations of multiple copies of a DNA molecule marked with colors at recognition sites. The primary goal is to estimate a physical map. A secondary goal is to estimate error rates associated with the experiment, which are potentially useful for analysis and refinement of the biochemical steps in the mapping procedure. We propose statistical models for various sources of error and use maximum likelihood estimation (MLE) to construct a physical map and estimate error rates. To overcome difficulties arising in the maximization process, a latent-variable Markov chain version of the model is proposed, and the EM algorithm is used for maximization. In addition, a simulated annealing procedure is applied to maximize the profile likelihood over the discrete space of sequences of colors. We apply the methods to simulated data on the bacteriophage lambda genome.

Notizen: We propose here a simple and robust approach for meta-analysis of molecular association studies. Making use of the binary structure of the data, and by treating the genotypes as independent variables in a logistic regression, we apply a simple and commonly used methodology that performs satisfactorily, being at the same time very flexible. We present simple tests for detecting heterogeneity and we describe a random effects extension of the method in order to allow for between studies heterogeneity. We derive also simple tests for assessing the most plausible genetic model of inheritance, and its between-studies heterogeneity as well as adjusting for covariates. The methodology introduced here is easily extended in cases with polytomous or continuous outcomes as well as in cases with more than two alleles. We apply the methodology in several published meta-analyses of genetic association studies with very encouraging results. The main advantages of the proposed methodology is its flexibility and the ease of use, while at the same time covers almost every aspect of a meta-analysis providing overall estimates without the need of multiple comparisons. We anticipate that this simple method would be used in the future in meta-analyses of genetic association studies. A STATA command performing all the available computations is available at http://bioinformatics.biol.uoa.gr/~pbagos/metagen/.