Trace-gas detection in ambient air with a thermoelectrically cooled, pulsed quantum-cascade distributed feedback laser

A pulsed quantum-cascade distributed feedback laser operating at near room temperature was used for sensitive high-resolution IR absorption spectroscopy of ambient air at a wavelength of ~8 mum. Near-transform-limited laser pulses were obtained owing to short (~5-ns) current pulse excitation and optimized electrical coupling. Fast and slow computer-controlled frequency scanning techniques were implemented and characterized. Fast computer-controlled laser wavelength switching was used to acquire second-derivative absorption spectra. The minimum detectable absorption was found to be 3 x 10(-4) with 10(5) laser pulses (20-kHz repetition rate), and 1.7 x 10(-4) for 5 x 10(5) pulses, based on the standard deviation of the linear regression analysis.     

Structural rearrangements near the chromophore influence the maturation speed and brightness of DsRed variants

The red fluorescent protein DsRed has been extensively engineered for use as an in vivo research tool. In fast maturing DsRed variants, the chromophore maturation half-time is approximately 40 min, compared to approximately 12 h for wild-type DsRed. Further, DsRed has been converted from a tetramer into a monomer, a task that entailed mutating approximately 20% of the amino acids. These engineered variants of DsRed have proven extremely valuable for biomedical research, but the structural basis for the improved characteristics has not been thoroughly investigated. Here we present a 1.7 A crystal structure of the fast maturing tetrameric variant DsRed.T4. We also present a biochemical characterization and 1.6 A crystal structure of the monomeric variant DsRed.M1, also known as DsRed-Monomer. Analysis of the crystal structures suggests that rearrangements of Ser69 and Glu215 contribute to fast maturation, and that positioning of the Lys70 side chain modulates fluorescence quantum yield. Despite the 45 mutations in DsRed.M1 relative to wild-type DsRed, there is a root-mean-square deviation of only 0.3 A between the two structures. We propose that novel intramolecular interactions in DsRed.M1 partially compensate for the loss of intermolecular interactions found in the tetramer.     

Anticipating market effects of new uses for whey and evaluating returns to research and development

As U.S. dairy farms continue to become more productive, increasing demand is a key to improved economic prospects for the dairy industry. One way to expand demand for dairy products is to find new, economically viable uses for milk. Ex ante economic analysis of new uses for agricultural products anticipates the potential market effects of innovations, and provides a basis for evaluating investment in research and development and setting research priorities. This study evaluated potential economic effects of new applications of films and coatings made from whey protein. An economic simulation model was used to predict the likely effects of the innovations on dairy markets. Cost comparisons with existing technologies and interviews with industry officials were the basis for evaluating potential for commercial adoption of the innovations. The economic simulation model traces the projected increased demand for whey through the markets for dairy products and milk. The associated increased demand for milk could result in benefits to U.S. milk producers of $123.0 million in present value terms, compared to a research cost of $ 4.9 million, with the dairy industry, consumers, and taxpayers all contributing. Interpreting the cost of the research program as an investment on behalf of milk producers, the benefits to producers from development of new whey uses represent an annual rate of return between 28 and 33%. These results are useful for evaluating further investment in the whey research program. The methods illustrated here are applicable to the evaluation of a wide range of research and promotion efforts.     

Effects of lipid-encapsulated conjugated linoleic acid supplementation on milk production, bioenergetic status and indicators of reproductive performance in lactating dairy cows

Conjugated linoleic acid (CLA) reduces mammary milk fat synthesis in a dose-dependent manner. Our objective was to determine the effects of lipid-encapsulated CLA (LE-CLA) supplementation on milk production, reproductive performance and metabolic responses in lactating dairy cows fed a grass silage-based diet. Seventy-two Holstein-Friesian cows (32 primiparous and 40 multiparous) were used in a completely randomized block design. Cows received either 80 g of LE-CLA daily or 60 g of calcium salts of palm fatty acids daily (control) from parturition until 60 days in milk. LE-CLA contained a 50:50 mix of cis-9,trans-11 CLA and trans-10,cis-12 CLA, resulting in a daily intake of 6 g of each isomer. Milk production and dry matter intake were recorded daily, and blood samples were collected 3-times a week. Blood samples were analysed for circulating concentrations of glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), insulin and insulin-like growth factor-I (IGF-I). Progesterone was measured in blood samples collected after the first post-partum insemination. Ovarian ultrasound examinations commenced at 8-10 d post partum and were carried out 3-times a week until first ovulation. LE-CLA treatment resulted in decreased milk fat concentration, with consequent improvements in energy balance and body condition score (BCS). The peak concentration of NEFA in blood was reduced by LE-CLA, but circulating concentrations of insulin, glucose, IGF-I, BHBA and progesterone were not affected. There was no effect of LE-CLA supplementation on the post-partum interval to first ovulation. Services per conception tended to be reduced. The reduction in milk energy output and improvement in energy status and BCS in LE-CLA-supplemented cows provides a strong rationale for further studies with greater cow numbers to test effects on reproductive performance.     

Evaluation of lean meat quality in pigs using two electronic probes

The Danish Fat-O-Meater grading probe (FOM) and the Fibre Optic Probe (FOP) developed at IFR, Bristol, were evaluated for their potential ability to predict lean meat quality in a sample of 76 pig carcasses showing a wide range of quality in the M. longissimus dorsi. When probings were made after chilling at about 20 h post mortem the correlations between probe value (FOP_u and FOM_u) and reflectance (EEL value), drip loss during storage and subjective assessment score for colour-structure were high (FOP_u and reflectance, r = 0·89; drip loss, r = 0·78; subjective assessment, r = 0·90. FOM_u and reflectance, r = 0·88; drip loss, r = 0·73; subjective assessment r = 0·81). Nevertheless, probe values could not be used to unambiguously group samples into normal, pale, soft, exudative (PSE) or dark, firm, dry (DFD) classes. Correlations between probe values at 45 min post mortem and measures of ultimate meat quality were much lower. Neither probe could potentially differentiate between normal and DFD meat at this time and differentiation between normal and PSE meat was also poorer.     

The influence of non‐structural components on tall building stiffness

The lateral load resisting system of a multi‐storey building is considered to be an assembly of structural components, such as the structural frame, shear walls, concrete cores, etc. However, in reality, some so‐called ‘non‐structural components (NSCs)’ also play important roles in adding stiffness to the building. To evaluate the contributions from those NSCs and to quantify some of their contributions to the stiffness of the structure under service level loads, this paper reports on the analysis of a lateral load resisting system with different components so that the stiffness contribution from each individual component may be evaluated. Results from finite element analyses are verified by other theoretical calculations. Discussions and conclusions on the performance of both single components and the building system are also provided. Copyright © 2009 John Wiley & Sons, Ltd.     

Serological methods and selective agars to enumerate Campylobacter from broiler carcasses: data from inter- and intralaboratory analyses

Routine analytical means to estimate Campylobacter numbers per milliliter of carcass rinses are needed in high-sample-throughput poultry laboratories. We compared three serological confirmatory tests that were amenable to such a setting when used in conjunction with Campy-Line and Campy-Cefex Campylobacter selective agars. Pre- and post-chlorinated chiller carcass rinse samples were obtained and held on ice, then analyzed 24 h later in two separate laboratories. Presumptive counts on both pre- and postchiller samples from between laboratories on individual agars and between both agars were highly correlated. Agreement among the three serological tests was nearly complete. The use of a premeasured and dried latex anti-Campylobacter antibody agglutination test format was superior to that of either a liquid latex agglutination format or a direct phosphate-buffer microscopic technique in terms of practicality as was the inclusion of an unarmed latex control to detect auto agglutination. A routine procedure for Campylobacter level estimation was suggested. This procedure, when used in conjunction with a serological confirmatory step, should provide processors with a means to assess reductions in numbers per milliliter of carcass rinses versus strictly presence-absence testing.     

A systematic study of tert-butylacrylamide-methyl acrylate-acrylic acid radical solution terpolymerization

Multi-functional polymers used for personal care products can be synthesized by radical polymerization of acrylic acid (AA) in alcohol/water solutions with non-functional monomers such as methyl acrylate (MA) and N-tert-butylacrylamide (t-BuAAm). However, solvents capable of forming or disrupting hydrogen bonds cause the polymerization kinetics of these monomers to deviate from their polymerization behaviour in bulk and non-polar solvents. In this work, a previous mechanistic model developed for MA/t-BuAAm copolymerization is extended to represent the terpolymerization system MA/t-BuAAm/AA. The additional kinetic coefficients required for the system are estimated from fitting to AA homopolymerizations and AA/MA and AA/t-BuAAm copolymerizations conducted in an ethanol/water solution. In-situ nuclear magnetic resonance (NMR) spectroscopy is used to follow monomer conversions and composition drift behaviour, with the molar mass distributions of the polymer products characterized by size-exclusion chromatography. Although AA is more reactive than MA in non-polar solvents, the reactivities of the two monomers equalize under the experimental conditions examined. Thus, the batch and semi-batch terpolymerization data collected are represented equally well by a reduced acrylate/t-BuAAm copolymerization model and the full terpolymerization implementation.