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Notes: We report the growth, fabrication, and characterization of AlxGa1−xN (0≤x≤0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates. The group III-nitride heteroepitaxial layers are grown by low-pressure metalorganic chemical vapor deposition on double polished sapphire substrates using various growth conditions. The back-illuminated devices exhibit very low dark current densities. Furthermore, they exhibit external quantum efficiencies up to 35% at the peak of the photoresponse (λ∼280 nm). Improvements were made to the growth technique in order to achieve crack-free Al0.4Ga0.6N active regions on a thick Al0.6Ga0.4N window layer and to obtain activated p-type Al0.4Ga0.6N layers. © 2000 American Institute of Physics.

Notes: We report on the device performance of selective-area regrown Al0.30Ga0.70N p–i–n photodiodes. Tensile strain, induced by the lattice mismatch between AlxGa1−xN and GaN, leads to cracking above the critical thickness in layers with high aluminum concentration. Selective-area regrown devices with ≤70 μm diameters were fabricated without signs of cracking. These devices show low dark current densities with flat photoresponse and a forward turn-on current of ∼25 A/cm2 at 7 V. A quantum efficiency greater than 20% was achieved at zero bias with a peak wavelength of λ=315 nm. A differential resistance of R0=3.46×1014 Ω and a detectivity of D*=4.85×1013 cm Hz1/2 W−1 was demonstrated. © 2000 American Institute of Physics.

Notes: Forest development following stand-replacing disturbance influences a variety of ecosystem processes including carbon exchange with the atmosphere. On a series of ponderosa pine (Pinius ponderosa var. Laws.) stands ranging from 9 to〉 300 years in central Oregon, USA, we used biological measurements to estimate carbon storage in vegetation and soil pools, net primary productivity (NPP) and net ecosystem productivity (NEP) to examine variation with stand age. Measurements were made on plots representing four age classes with three replications: initiation (I, 9–23 years), young (Y, 56–89 years), mature (M, 95–106 years), and old (O, 190–316 years) stands typical of the forest type in the region. Net ecosystem productivity was lowest in the I stands (−124 g C m−2 yr−1), moderate in Y stands (118 g C m−2 yr−1), highest in M stands (170 g C m−2 yr−1), and low in the O stands (35 g C m−2 yr−1). Net primary productivity followed similar trends, but did not decline as much in the O stands. The ratio of fine root to foliage carbon was highest in the I stands, which is likely necessary for establishment in the semiarid environment, where forests are subject to drought during the growing season (300–800 mm precipitation per year). Carbon storage in live mass was the highest in the O stands (mean 17.6 kg C m−2). Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass increased rapidly until 150–200 years, and did not decline in older stands. Forest inventory data on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands ∼ 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggests that NEP averages ∼ 70 g C m−2 year−1 for ponderosa pine forests in Oregon. About 85% of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration. To investigate variation in carbon storage and fluxes with disturbance, simulation with process models requires a dynamic parameterization for biomass allocation that depends on stand age, and should include a representation of competition between multiple plant functional types for space, water, and nutrients.

Notes: Asthma and atopic disorders are the most common chronic diseases in the developed countries. Knowledge of the risk factors for these disorders may facilitate the development of preventive strategies aimed at reducing prevalence rates.To investigate the risk factors for asthma and allergic diseases in a large number of adults who are the parents of children in the National Asthma Campaign Manchester Asthma and Allergy Study.All pregnant women and their partners attending ‘Booking’ antenatal clinics were invited to take part in the study. Questionnaire data were collected including the history of asthma and other atopic diseases, pet ownership and smoking habits, and skin prick tests were performed. The prevalence of atopy and the risk factors for asthma and allergic disorders were investigated in all subjects who completed the questionnaire and underwent skin testing. Statistical analysis was carried out using logistic regression. Initially, risk factors were assessed by univariate analysis to see how each potential explanatory variable affected the probability of having allergic disease. Variables were then tested in a forward stepwise multivariate analysis.In 5687 adult subjects there was a very high (48.2%) prevalence of atopy, and 9.7% of subjects had a diagnosis of asthma. In a multivariate regression analysis sensitization to dust mite, cat, dog and mixed grasses were all independently associated with asthma. The odds ratios for current asthma increased with the increasing number of positive skin tests (any two allergens – OR 4.3, 95% CI 3.3–5.5; any three allergens – OR 7.0 95% CI 5.3–9.3; all four allergens – OR 10.4, 95% CI 7.7–14; P 〈 0.00001). Dog ownership (OR 1.31, 95% CI 1.10–1.57; P = 0.003) and current smoking (OR 1.36, 95% CI 1.15–1.62; P = 0.0004) were significantly and directly associated with ’asthma ever’. Thirteen per cent of participants reported a history of eczema. In the multivariate analysis the strongest independent associate of eczema was sensitization to dog (OR 1.37, 95% CI 1.14–1.63, P 〈 0.0001). Apart from dog, the strength of the association between sensitization to common allergens and eczema appeared to be much lower than in the case of asthma. The prevalence of hay fever was high (20.6%), and in the multivariate analysis the association between sensitization to pollen and hay fever was extremely strong (OR 13.6, 95% CI 11.3–16.3; P 〈 0.0001).The results of the current study emphasize the importance of sensitization to indoor allergens in asthma. However, evidence of a possible direct role of allergen exposure in asthma causation remains unclear.

Notes: Considerable research has been conducted in recent years on the accelerated method of pork processing, the processing of pork without carcass chilling. A limited amount of information exists regarding the emulsion properties of tissues handled in this manner. Alternate sides from 48 pork carcasses were processed in either an accelerated or conventional manner. Lean and fat tissue from the sides was incorporated in a standard frankfurter emulsion. Proximate analyses of the frankfurters prepared from the two forms of processed pork revealed no significant differences. Similarly, no differences were found for normal or severe cookout of finished frankfurters. Differences in emulsion stability values were not significant for total ml of loss per 100g emulsion (6.35 and 5.69, respectively, for accelerated and conventional). Accelerated processed frankfurters possessed greater (P 〈 0.01) gel/water loss (4.89 ml/g). than conventionally processed pork frankfurters (4.61 ml/g). The accelerated processed pork resulted in less fat loss (P 〈 0.05) than did the conventionally processed franks; and the accelerated pork emulsion percent solids (0.84 ml/g) was higher (P 〈 0.01) than the conventionally processed pork frankfurters (0.38 ml/g). No significant difference was obtained for emulsification capacity of the lean pork tissue that had undergone accelerated or conventional processing prior to use in frankfurter production.

Notes: Eighty steers, forty each of two biological types (large, late maturing, and small, early maturing) were placed on nutritional regimes containing four levels of roughage. After slaughter, 40 top loins were press/cleave portioned and mechanically tenderized, 40 top loins were press/cleave portioned only, 40 top loins were mechanically tenderized only and 40 top loins remained untreated to serve as controls. Each nutritional regime and biological type was equally represented in each of the processing treatments. Taste panel evaluations indicated a preference for tenderized steaks (P 〈 0.05) over those not tenderized. Press/cleave portioning had very little effect on the steaks. The combination of press/cleave portioning and mechanical tenderization appeared to be an acceptable industry practice.

Notes: The upstream spawning migrations of brown trout and sea trout were studied using stationary traps placed in Kirk Burn, a tributary of the upper Tweed. The sea trout spawning period extended from early November to the first week of December, while that of brown trout occurred from the middle of October to the third week of December. Sea trout were predominantly maiden spawners of ages 2.1+ and 3.1+ while brown trout were mostly age 2+ and 3+. Male-female sex ratios approximated 1:1.4 in sea trout but 6 : 1 in brown trout. Brown trout males participated in the spawning activities of sea trout. Low water conditions in Kirk Burn hindered the upstream movement of spawning sea trout, while sudden increases in water level appeared to stimulate the upstream migration of both brown trout and sea trout. The suggestion is advanced that the freshwater resident brown trout of the Tweed which migrate upstream into the smaller tributaries to spawn is wholly, or at least partially, the progeny of anadromous parents.

Notes: The effects of cooking method, reheating method and frozen storage on physical, chemical and palatability factors of restructured pork patties were evaluated over a period of 6 wk. Frozen restructured pork patties (25% fat) were cooked using a convection oven or an electric grill. Cooked patties were vacuum packaged and refrozen for subsequent reheating and evaluation initially and following storage periods of 2, 4 and 6 wk. Reheating devices employed were a microwave oven, a convection oven and an infrared oven. Samples cooked using the convection oven had greater moisture contents and higher 2-thiobarbituric acid (TBA) values than those patties cooked using the electric grill. Percent protein, fat, ash and cooking loss were greater for the electric grill treatment due to greater moisture loss. The TBA values increased to 2 wk of storage and then remained relatively stable. Cooked color was more acceptable initially than after 6 wk of storage. The control treatment, which was not reheated, had the lowest cooking loss and the infrared oven reheating treatment had the highest cooking loss. Taste panel evaluations were in the acceptable range both initially and after 6 wk of storage. Both cooking methods and all reheating methods also yielded acceptable products as evaluated by the taste panel. Cooking and reheating with convection ovens should be recommended if precooking and reheating of restructured pork is deemed necessary for fast food and institutional establishments. This procedure will yield an acceptable product with a lower cooking loss than any of the other cooking/reheating combinations studied. However, if time is of importance, reheating with microwave ovens may be considered although this method will yield a less juicy product with higher cooking losses.

Notes: Effect of microstructure on mixed-mode (mode I + II), high-cycle fatigue thresholds in a Ti-6Al-4V alloy is reported over a range of crack sizes from tens of micrometers to in excess of several millimeters. Specifically, two microstructural conditions were examined—a fine-grained equiaxed bimodal structure (grain size ∼20 µm) and a coarser lamellar structure (colony size ∼500 µm). Studies were conducted over a range of mode-mixities, from pure mode I (ΔKII/ΔKI = 0) to nearly pure mode II (ΔKII/ΔKI ∼ 7.1), at load ratios (minimum load/maximum load) between 0.1 and 0.8, with thresholds characterized in terms of the strain-energy release rate (ΔG) incorporating both tensile and shear-loading components. In the presence of through-thickness cracks—large (〉 4 mm) compared to microstructural dimensions—significant effects of mode-mixity and load ratio were observed for both microstructures, with the lamellar alloy generally displaying the better resistance. However, these effects were substantially reduced if allowance was made for crack-tip shielding. Additionally, when thresholds were measured in the presence of cracks comparable to microstructural dimensions, specifically short (∼200 µm) through-thickness cracks and microstructurally small (〈 50 µm) surface cracks, where the influence of crack-tip shielding would be minimal, such effects were similarly markedly reduced. Moreover, small-crack ΔGTH thresholds were some 50–90 times smaller than corresponding large crack values. Such effects are discussed in terms of the dominant role of mode I behaviour and the effects of microstructure (in relation to crack size) in promoting crack-tip shielding that arises from significant changes in the crack path in the two structures.