A comparison between models based on equations of state and density-based models for describing the solubility of solutes in CO2

The poor dissolution behaviour of solid drugs in biological environment leads to a low bioavailability. However, the dissolution rate of such drugs can be enhanced dramatically by reduction of the particle size. At present, supercritical fluid based particle size reduction processes are gaining in importance in pharmaceutical technology. For the design of such particle formation processes and the determination of their best operating conditions the knowledge of phase equilibrium and solute solubility in a supercritical fluid is essential. Today, models based on equations of state, together with different mixing rules, are most widely used to correlate and predict the solubility in supercritical fluids. Therefore the accurate knowledge of the required solute data, such as critical parameters, acentric factor, solid molar volume, and sublimation pressure of the solutes is essential. However, the common, non-equation of state based group-contribution methods are mostly empirical and often lead to inconsistent and unreliable results. Thus, due to the lack of information on these data, density-based models are often used for the correlation of experimental solubility data. In this investigation, the solubility of Salicylic acid, of S-Naproxen, of RS-Ibuprofen and of Phytosterol in CO₂ is correlated by different methods: two methods for the pressure-solubility correlation and two methods for the density-solubility correlation. In addition, the influence of solute data predicted by different group-contribution methods is investigated. With the exception of S-Naproxen all systems investigated can be modelled sufficient well with a non-cubic equation of state while a cubic equation of state gives less accurate results. In addition, it is shown that for the solutes investigated, the equation of state based method is very sensitive to the values of the sublimation pressure.     

Investigating the cow skin and teat canal microbiomes of the bovine udder using different sampling and sequencing approaches

There is a need for standardized, efficient, and practical sampling methods to support large population-based studies of the internal and external epithelial microbiomes of the bovine udder. The primary objective of this study was to evaluate different sampling devices for the isolation of microbial DNA originating from the internal and external teat epithelium. Secondary objectives were to survey and compare the microbial diversity of external and teat canal epithelial microbiomes using amplicon and shotgun metagenomic sequencing approaches. To address these objectives, we enrolled a convenience sample of 24 Holstein dairy cows and collected samples from the external epithelium at the base of udder, the external teat barrel epithelium, the external teat apex epithelium, and the teat canal epithelium. Extracted DNA was quantified and subjected to PCR amplification of the V4 hypervariable region of the 16S rRNA gene and sequenced on the Illumina MiSeq platform (Illumina Inc., San Diego, CA). A subset of samples was subjected to a shallow shotgun metagenomic assay on the Illumina HiSeq platform. For samples collected from the external teat epithelium, we found that gauze squares consistently yielded more DNA than swabs, and Simpson's reciprocal index of diversity was higher for gauze than for swabs. The teat canal epithelial samples exhibited significantly lower diversity than the external sampling locations, but there were no significant differences in diversity between teat apex, teat barrel, and base of the udder samples. There were, however, differences in the microbial distribution and abundances of specific bacteria across external epithelial surfaces. The proportion of shotgun sequence reads classified as Bos taurus was highly variable between sampling locations, ranging from 0.33% in teat apex samples to 99.91% in teat canal samples. These results indicate that gauze squares should be considered for studying the microbiome of the external epithelium of the bovine udder, particularly if DNA yield must be maximized. Further, the relative proportion of host to non-host DNA present in samples collected from the internal and external teat epithelium should be considered when designing studies that utilize shotgun metagenomic sequencing.     

ProMeKreis设计指南：用于有利于回用的产品开发的辅助方法

 在BMBF联合计划的ProMeKreis范围内，制订了有利于回用的产品开发方法，它可作为“有利于回用的产品开发的指南”，这一“指南”是一个综合性的辅助方法，有利于产品的整修、改进和使用，其中与给料有关的使用过程的系统研究和优化导致设计过程中的处理方法有显著的改进。     

ASYRIO: Antenna SYstem Reconfiguration in Orbit

ASYRIO is a development program, carried out at CASA's facilities under an ESA (ESTEC) contract. The objective is the technological development of reconfigurable microwave devices, and their application to an antenna system for communications satellites with flexible-coverage illumination and reconfigurable missions. The associated hardware consists of an antenna-feed demonstration model, and a set of space-qualified reconfigurable components. These are to be capable of operation in space conditions, and reconfigurable through software control from an earth master station. A scenario has been tried for the second generation of Spanish-telecommunication satellites. This scenario is the fundamental input for antenna-system requirements. It presents supranational-coverage characteristics. It is for use where a flexible mission is needed or desired; detailed analysis of each particular case shows the more-appropriate reconfiguration implementation. A multibeam-reflector antenna has been accepted as the baseline for a high-gain-antenna definition, with a fixed-parabolic reflector, and a reconfigurable multibeam-feed subsystem. Reconfigurability is accomplished by the variable components assembled in the feed beam-forming network. The feed-demonstration model that supports the Spanish mission has been designed, manufactured, and tested, both electrically and thermomechanically, to verify its compliance with space geostationary environmental conditions during and after launch     

Comparison of numerical computations of optical-waveguide transmission parameters

Two numerical techniques for the computation of the phase and group velocities of an inhomogeneous optical waveguide are compared. It is concluded that direct solution of the original differential equation is the most effective method.     

Equilibrium swelling and kinetics of pH-responsive hydrogels: models, experiments, and simulations

The widespread application of ionic hydrogels in a number of applications like control of microfluidic flow, development of muscle-like actuators, filtration/separation and drug delivery makes it important to properly understand these materials. Understanding hydrogel properties is also important from the standpoint of their similarity to many biological tissues. Typically, gel size is sensitive to outer solution pH and salt concentration. In this paper, we develop models to predict the swelling/deswelling of hydrogels in buffered pH solutions. An equilibrium model has been developed to predict the degree of swelling of the hydrogel at a given pH and salt concentration in the solution. A kinetic model has been developed to predict the rate of swelling of the hydrogel when the solution pH is changed. Experiments are performed to characterize the mechanical properties of the hydrogel in different pH solutions. The degree of swelling as well as the rate of swelling of the hydrogel are also studied through experiments. The simulations are compared with experimental results and the models are found to predict the swelling/deswelling processes accurately.     

A single amino acid change in human O6-alkylguanine-DNA alkyltransferase decreasing sensitivity to inactivation by O6-benzylguanine

Mammalian O6-alkylguanine-DNA alkyltransferases (AGTs) are readily inactivated by incubation with the pseudosubstrate, O6-benzylguanine, but the equivalent protein from the Escherichia coli ogt gene is much less sensitive and the Saccharomyces cerevisiae and E. coli ada gene product AGTs are completely resistant to this compound. We have expressed the normal human AGT and various point mutations (C145A, W100A, and P140A) in an ada- ogt- strain of E. coli and tested these proteins against DNA substrates containing O6-methylguanine, for inactivation by O6-benzylguanine and for the ability to produce guanine from O6-benzylguanine. The C145A mutation was inactive as expected since this residue forms the methyl acceptor site. Mutants W100A and P140A were fully active against methylated DNA substrates but the P140A mutant was much less sensitive to inactivation by O6-benzylguanine and failed to form significant amounts of [3H]guanine when incubated with O6-benzyl[8-3H]-guanine. The proline at position 140 in mammalian AGTs is replaced by alanine in the Ada and yeast AGTs and by serine in the Ogt AGT. These results suggest that this proline residue affects the configuration of the active site allowing the O6-benzylguanine to enter and react with the mammalian AGT. The production of resistance to O6-benzylguanine by a single base change raises the possibility that such resistance may arise quite readily in cells of tumors treated therapeutically with the combination of O6-benzylguanine and an alkylating agent.     

Critical Operating Conditions For A Novel Flying Tester

Increased recording densities are often achieved through a reduction in the flying height over a thin film disk possessing diminishing surface roughness. Flying heights will continue to decrease until the head-disk interface (HDI) operates under quasi-contact conditions, i.e., ultra-low flying with intermittent slider-disk collisions. The failure mechanisms that occur in such quasi-contact devices may differ from those experienced in current, higher flying hard drive assemblies. In this paper, the authors will present the experimental, numerical, and theoretical tools that have been developed to study the behavior of the HDI under ultra-low flying conditions. These tools include an accelerated flyability tester and a numerical algorithm applicable to highly rarefied air bearings that possess large pressure gradients. Air bearing simulation results, as well as the results from a simple flying height scaling analysis, will be compared to flying test results in both air and helium to obtain insight into the stability of the HDI under accelerated testing conditions. A new concept introduced in this paper is that of critical conditions, i.e., the band of operating conditions which mark the transition from stable to erratic behavior, which can be determined both experimentally and theoretically. Such insight should provide design criteria for both quasi-contact storage devices, as well as novel accelerated wear testers.     

The Dynamics of Carbon–Nutrient Balance: Effects of Cottonwood Acclimation to Short- and Long-Term Shade on Beetle Feeding Preferences

The carbon–nutrient balance hypothesis (CNBH) predicts that shading should increase leaf palatability to herbivores by decreasing concentrations of carbon (C) -based chemical defenses and increasing nitrogen (N). We measured cottonwood (Populus deltoids) growth, leaf chemistry, and beetle (Plagiodera versicolora) feeding preferences on saplings grown in either continuous high (HH) or low (LL) light, and saplings switched from high to low (HL) or low to high (LH) light for nine days. As expected, based on the CNBH, shading increased total N and decreased total phenol glycoside (C-based secondary metabolites) concentrations in plants from all shade treatments (LL, HL, and LH), relative to HH plants, with plant growth and gross leaf chemistry being affected by initial and final light regime. In contrast, while specific phenol glycoside concentrations were affected by the initial and final light regime, they also showed an initial × final light interaction. Beetles tended to prefer LL to HH plants. Beetles unexpectedly preferred HH to either HL or LH switched plants, most likely because high concentrations of a specific phenol glycoside – salicin – occurred in both switched treatments and inhibited beetle feeding. Plant chemical allocation during light acclimation led to unpredictable changes in specific C-based compounds, even though plant growth and gross chemistry conformed to expectations for shading effects and the CNBH. The response of this herbivore to altered concentrations of a specific compound confounded predictions based on average dynamics of suites of chemicals. Our findings may help explain why relationships between light availability and herbivory in field studies, where light varies on many time scales, can differ from those predicted by the CNBH. Understanding both dynamic plant chemical responses to altered resource availability and controls over allocation to specific compounds would likely enhance future predictability of specific environment-plant-herbivore interactions.