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  • 1
    Electronic Resource
    Electronic Resource
    Flow structure and heat transfer in a horizontal converging channel heated from below (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 2128-2136 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed experimental study is carried out to investigate the flow structure and heat transfer in a converging horizontal channel with localized heating on the bottom surface. This configuration arises in typical chemical vapor deposition (CVD) systems and the impact of the transport mechanisms on the deposition process is of particular interest. Experimental observations of various flow circumstances indicate the appearance of longitudinal and transverse roll structures. These flow structures have direct implications with respect to CVD processing where deposition rates and film quality are critically dependent on reactive species and byproduct transport onto the deposition surface. Different flow regimes are observed for typical operating conditions, and their existence is described using regime maps. Regime boundaries are correlated in terms of important parameters that describe the flow rate, heating rate, and tilt angle. A regime transition from longitudinal rolls to transverse rolls occurs at around Gr/Re2=6000, while the critical Rayleigh number is found to be dependent on the flow. Heat transfer correlations are also derived and it is seen that the heating rate is the dominant effect on the susceptor temperature, while the effects of flow rate and tilt angle are small. The implication of heat transfer results on mass transfer are discussed for horizontal CVD reactors. The flow structure and heat transfer phenomena observed in this study yield valuable insight into the basic buoyancy and forced-flow-induced transport in horizontal channels as well as guidelines for the modeling and design of CVD systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870458
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclo-oxygenase-2 over-expression in sporadic colorectal carcinoma without lymph node involvement (2003)
    Oxford, UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 18 (2003), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background : Cyclo-oxygenase-2 over-expression has been reported in most advanced human colorectal cancers.Aims : To assess the prevalence of cyclo-oxygenase-2 over-expression in non-advanced colorectal cancers, to investigate the correlation between cyclo-oxygenase-2 status and tumour clinicopathological features and molecular phenotype, and to determine the impact of cyclo-oxygenase-2 status on long-term clinical outcome.Methods : Sixty-one patients who had undergone surgery for colorectal cancer without lymph node involvement were evaluated retrospectively. Cyclo-oxygenase-2 expression was determined by immunohistochemistry. The tumour replication error phenotype was assessed by amplification of the two microsatellites, BAT-25 and BAT-26.Results : Thirty-six tumours were classified as cyclo-oxygenase-2 positive and 25 as cyclo-oxygenase-2 negative. No correlation was found between cyclo-oxygenase-2 over-expression and clinicopathological features or molecular phenotype. Cyclo-oxygenase-2 over-expression was an independent predictor of a poor prognosis. Indeed, the relative risk of tumour recurrence or death for patients with cyclo-oxygenase-2-positive tumours was 2.13 times that of patients with cyclo-oxygenase-2-negative tumours (P = 0.008; 95% confidence interval, 1.22–3.73). This difference remained significant when post-operative deaths were censored in the multivariate analysis (P = 0.014).Conclusion : Cyclo-oxygenase-2 over-expression is not associated with tumour phenotype, but is indicative of a poorer clinical outcome in patients with non-advanced colorectal carcinoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.2003.01758.x
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  • 3
    Electronic Resource
    Electronic Resource
    A randomised, controlled, crossover trial of oral midazolam and nitrous oxide for paediatric dental sedation (2002)
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 57 (2002), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary A randomised, controlled, crossover trial was designed to assess the safety and effectiveness of oral midazolam sedation for orthodontic extractions. Forty-six ASA physical status I children aged 10–16 years were recruited. Each child required two treatment sessions. Sedation with either oral midazolam 0.5 mg.kg−1 or nitrous oxide in oxygen was used at the first visit, the alternative being used at the second visit. Blood pressure, heart rate, arterial oxygen saturation, and sedation and behavioural scores were recorded every 5 min. Anxiety levels and postoperative satisfaction were also recorded. Blood pressure, heart rate and arterial oxygen saturation in both groups were similar and within acceptable clinical limits. The median [range] lowest arterial oxygen saturation levels for subjects in the midazolam and nitrous oxide groups were 95 [90–100]% and 98 [93–100]%, respectively. The median [range] time to the maximum level of sedation in the midazolam group was 20 [5–65] min compared with 5 [5–10] min in the nitrous oxide group (p 〈 0.001). The median [range] duration of treatment was similar in both groups (midazolam group: 10 [5–30] min, nitrous oxide group: 10 [5−25] min). Seventy-four per cent of subjects were prepared to have oral midazolam sedation again, 54% preferring it. Oral midazolam appears to be a safe and acceptable form of sedation for 10–16-year-old paediatric dental patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2044.2002.02784.x
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  • 4
    Electronic Resource
    Electronic Resource
    A prospective randomised controlled study of patient-controlled propofol sedation in phobic dental patients (2000)
    Oxford : Blackwell Science Ltd
    Anaesthesia 55 (2000), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The safety and effectiveness of patient-controlled propofol sedation was prospectively assessed in 18 healthy, phobic dental patients. Using a randomised, crossover design each patient received two sessions of equivalent dental treatment under patient-controlled or clinician-controlled propofol sedation. The patient-controlled technique used 29.8% less drug (time-weighted dose) than the clinician-controlled method (p = 0.011). There was a high correlation between number of demands and number of doses actually infused during the patient-controlled technique (r = 0.99, p 〈 0.001). Clinically, the level of sedation was lighter and the degree of operator satisfaction was higher with patient-controlled sedation. Blood pressure and arterial oxygen saturation showed minimal changes and remained within normal ranges during both techniques. Patient-controlled sedation produced a greater reduction in dental and general anxiety compared with clinician-controlled sedation, but the difference did not reach statistical significance. Three times the number of patients expressed a preference for the patient-controlled, compared with the clinician-controlled, technique. Patient-controlled sedation provides safe and acceptable intra-operative anxiolysis for phobic dental patients, but with reduced propofol dosage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2044.2000.01279.x
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  • 5
    Electronic Resource
    Electronic Resource
    Leaf age affects the seasonal pattern of photosynthetic capacityand net ecosystem exchange of carbon in a deciduous forest (2001)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Temporal trends in photosynthetic capacity are a critical factorin determining the seasonality and magnitude of ecosystem carbonfluxes. At a mixed deciduous forest in the south-eastern United States (Walker Branch Watershed, Oak Ridge, TN, USA), we independently measured seasonal trends in photosynthetic capacity (using single-leaf gas exchange techniques) and the whole-canopycarbon flux (using the eddy covariance method). Soil respiration was also measured using chambers and an eddy covariance system beneath the canopy. These independent chamber and eddy covariance measurements, along with a biophysical model (CANOAK), areused to examine how leaf age affects the seasonal pattern of carbon uptake during the growing season. When the measured seasonality in photosynthetic capacity is representedin the CANOAK simulations, there is good agreement with the eddy covariance data on the seasonal trends in carbon uptake. Removing the temporal trends in the simulations by using the early season maximum value of photosynthetic capacity over the entire growing season over estimates the annual carbon uptake by about 300 g C m−2 year−1– halfthe total estimated annual net ecosystem exchange. Alternatively, use of the mean value of photosynthetic capacity incorrectly simulates the seasonality in carbon uptake by the forest. In addition to changes related to leaf development and senescence, photosynthetic capacitydecreased in the middle and late summer, even when leaf nitrogenwas essentially constant. When only these middle and late summer reductions were neglected in the model simulations, CANOAK still overestimated the carbon uptake by an amount comparable to 25% ofthe total annual net ecosystem exchange.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0016-8025.2001.00706.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of phenotypic plasticity on pathogen transmission in the field in a Lepidoptera-NPV system (2000)
    Springer
    Oecologia 124 (2000), S. 373-380 
    Details
    ISSN: 1432-1939
    Keywords: Key words Transmission ; Mass action assumption ; Phase polyphenism ; Spodoptera exempta ; Baculoviruses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In models of insect–pathogen interactions, the transmission parameter (ν) is the term that describes the efficiency with which pathogens are transmitted between hosts. There are two components to the transmission parameter, namely the rate at which the host encounters pathogens (contact rate) and the rate at which contact between host and pathogen results in infection (host susceptibility). Here it is shown that in larvae of Spodoptera exempta (Lepidoptera: Noctuidae), in which rearing density triggers the expression of one of two alternative phenotypes, the high-density morph is associated with an increase in larval activity. This response is likely to result in an increase in the contact rate between hosts and pathogens. Rearing density is also known to affect susceptibility of S. exempta to pathogens, with the high-density morph showing increased resistance to a baculovirus. In order to determine whether density-dependent differences observed in the laboratory might affect transmission in the wild, a field trial was carried out to estimate the transmission parameter for S. exempta and its nuclear polyhedrosis virus (NPV). The transmission parameter was found to be significantly higher among larvae reared in isolation than among those reared in crowds. Models of insect–pathogen interactions, in which the transmission parameter is assumed to be constant, will therefore not fully describe the S. exempta-NPV system. The finding that crowding can influence transmission in this way has major implications for both the long-term population dynamics and the invasion dynamics of insect–pathogen systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420000397
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  • 7
    Electronic Resource
    Electronic Resource
    A flexible and efficient procedure for the solution and phase refinement of protein structures (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 1137-1147 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: An ab initio method is described for solving protein structures for which atomic resolution (better than 1.2 Å) data are available. The problem is divided into two stages. Firstly, a substructure composed of a small percentage (∼5%) of the scattering matter of the unit cell is positioned. This is used to generate a starting set of phases that are slightly better than random. Secondly, the full structure is developed from this phase set. The substructure can be a constellation of atoms that scatter anomalously, such as metal or S atoms. Alternatively, a structural fragment such as an idealized α-helix or a motif from some distantly related protein can be orientated and sometimes positioned by an extensive molecular-replacement search, checking the correlation coefficient between observed and calculated structure factors for the highest normalized structure-factor amplitudes |E|. The top solutions are further ranked on the correlation coefficient for all E values. The phases generated from such fragments are improved using Patterson superposition maps and Sayre-equation refinement carried out with fast Fourier transforms. Phase refinement is completed using a novel density-modification process referred to as dynamic density modification (DDM). The method is illustrated by the solution of a number of known proteins. It has proved fast and very effective, able in these tests to solve proteins of up to 5000 atoms. The resulting electron-density maps show the major part of the structures at atomic resolution and can readily be interpreted by automated procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090744490000932X
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  • 8
    Electronic Resource
    Electronic Resource
    reply: Nonlinearity and the Moran effect (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 406 (2000), S. 847-847 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Grenfell et al. reply — The Moran effect refers to systems of population dynamics that are linear: under these circumstances, the long-term correlation between population densities will be the same as the correlation between the random environmental perturbations. The Soay sheep ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35022649
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  • 9
    Electronic Resource
    Electronic Resource
    Selective control of flow coherence in triangular jets (2004)
    Springer
    Experiments in fluids 6 (2004), S. 129-135 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The triangular jet was investigated for use as a passive device to enhance fine-scale mixing and to reduce the coherence of large-scale structures in the flow. The suppression of the structures is vital to the enhancement of molecular mixing, which is important for efficient chemical reactions including combustion. The sharp corners in the jet injector introduced high instability modes into the flow via the non-symmetric mean velocity and pressure distribution around the nozzle. Both aerodynamic and hydrodynamic flows showed the difference between the flow at the corner (vertex) and at the flat side. While highly coherent structures could be generated at the flat side, the corner flow was dominated by highly turbulent small-scale eddies. The flow characteristics were tested using hotwire anemometry for mean flow and turbulence analysis, and flow visualization in air and water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196464
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  • 10
    Electronic Resource
    Electronic Resource
    Intercomparison of Formaldehyde Measurements in Clean and Polluted Atmospheres (2000)
    Springer
    Journal of atmospheric chemistry 37 (2000), S. 53-80 
    Details
    ISSN: 1573-0662
    Keywords: fluorescence ; spectroscopy ; tunable diode laser ; differential optical absorption ; intercomparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Three different techniques used tomeasure atmospheric formaldehyde were compared duringa field campaign carried out at a clean maritime siteon the West coast of Ireland. Two spectroscopictechniques Differential Optical AbsorptionSpectroscopy (DOAS) and Tunable Diode Laser AbsorptionSpectroscopy (TDLAS), together with a glass coil/Hantzschreaction/fluorescence technique, wereemployed for measurements of atmospheric formaldehydeof the order of a few hundred pptv. The betteragreement was observed between the fluorescence andDOAS instruments.Two DOAS instruments were compared to the glasscoil/Hantzsch reaction/fluorescence technique at asemi-polluted site on the North Norfolk coast, U.K.,where concentrations of formaldehyde were observed atlevels up to 4 ppbv. A very good agreement wasobserved between the two instruments.The glass coil/Hantzsch reaction/fluorescence and theTDLAS instruments were also deployed simultaneously inorder to measure indoor air inside a mobile laboratorylocated at the Imperial College Silwood Park site nearAscot, U.K. The doors of the mobile laboratory wereleft open in order to obtain the backgroundformaldehyde concentrations. Closing them afterwardsallowed us to observe the increase in concentrationsas a result of indoor emissions. The agreement betweenthe two instruments was outstanding (correlationcoefficient was 99%).The results from this study showed that of the fourinstruments included in this intercomparison the glasscoil/Hantzsch reaction/fluorescence technique provedthe most suitable for continuous measurements offormaldehyde in the background atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006383520819
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