Single stage and double absorption heat transformers used to recover energy in a distillation column of butane and pentane

This paper presents the theoretical analysis of the use of single stage and double absorption heat transformers operating with the water–lithium bromide mixture coupled to a butane and pentane distillation column in a Mexican refinery. A mathematical model of the heat transformers was developed in FORTRAN and integrated as a user model to the Aspen Plus simulation code. Both components coupled to the column were modelled on steady-state conditions. The results show that it is theoretically possible to reduce the energy consumed in the reboiler between 26 and 43% by the use of single stage heat transformer at specific conditions, and between 28 and 33% with double absorption heat transformers for a wide range of operating conditions. Copyright © 2003 John Wiley & Sons, Ltd.     

Proteomic Biomarkers of the Apnea Hypopnea Index and Obstructive Sleep Apnea: Insights into the Pathophysiology of Presence,Severity, and Treatment Response

Obstructive sleep apnea (OSA), a disease associated with excessive sleepiness and increased cardiovascular risk, affects an estimated 1 billion people worldwide. The present study examined proteomic biomarkers indicative of presence, severity, and treatment response in OSA. Participants (n = 1391) of the Stanford Technology Analytics and Genomics in Sleep study had blood collected and completed an overnight polysomnography for scoring the apnea–hypopnea index (AHI). A highly multiplexed aptamer-based array (SomaScan) was used to quantify 5000 proteins in all plasma samples. Two separate intervention-based cohorts with sleep apnea (n = 41) provided samples pre- and post-continuous/positive airway pressure (CPAP/PAP). Multivariate analyses identified 84 proteins (47 positively, 37 negatively) associated with AHI after correction for multiple testing. Of the top 15 features from a machine learning classifier for AHI ≥ 15 vs. AHI < 15 (Area Under the Curve (AUC) = 0.74), 8 were significant markers of both AHI and OSA from multivariate analyses. Exploration of pre- and post-intervention analysis identified 5 of the 84 proteins to be significantly decreased following CPAP/PAP treatment, with pathways involving endothelial function, blood coagulation, and inflammatory response. The present study identified PAI-1, tPA, and sE-Selectin as key biomarkers and suggests that endothelial dysfunction and increased coagulopathy are important consequences of OSA, which may explain the association with cardiovascular disease and stroke.     

Wet shells and dry tales: the evolutionary ‘Just-So’ stories behind the structure–function of biominerals

The ability of evolution to shape organic form involves the interactions of multiple systems of constraints, including fabrication, phylogeny and function. The tendency to place function above everything else has characterized some of the historical biological literature as a series of ‘Just-So’ stories that provided untested explanations for individual features of an organism. A similar tendency occurs in biomaterials research, where features for which a mechanical function can be postulated are treated as an adaptation. Moreover, functional adaptation of an entire structure is often discussed based on the local characterization of specimens kept in conditions that are far from those in which they evolved. In this work, environmental- and frequency-dependent mechanical characterization of the shells of two cephalopods, Nautilus pompilius and Argonauta argo, is used to demonstrate the importance of multi-scale environmentally controlled characterization of biogenic materials. We uncover two mechanistically independent strategies to achieve deformable, stiff, strong and tough highly mineralized structures. These results are then used to critique interpretations of adaptation in the literature. By integrating the hierarchical nature of biological structures and the environment in which they exist, biomaterials testing can be a powerful tool for generating functional hypotheses that should be informed by how these structures are fabricated and their evolutionary history.     

"国家点火装置"开始运转

“国家点火装置”计划约在15年前提出设想,现在这个装置正在建造,其初始运转十分成功,超出每个人的预计。在第一批四束激光运转中,激光系统的各个方面,从光束质量到能量结构,都符合设计规格。最终它将有192个光束．其已完成的2％的光束发射．已产生世界最高的激光能量。     

The performance properties of electrically small resonant multiple-arm folded wire antennas

In this tutorial article, the resonant radiation properties of electrically small, multiple-arm, folded wire antennas are considered and compared as a function of the antenna's height, the cylindrical diameter occupied, the geometry, and the number of folded arms within the antenna structure. The radiation properties considered include resonant resistance, efficiency, radiation patterns, and the operating bandwidth, which is characterized using the antenna's quality factor (Q). It is shown that electrically small, multiple-arm, folded wire antenna designs offer significant performance improvements relative to simple open-ended wire antennas, in terms of increased resonant resistance, bandwidth, and efficiency. However, when multiple-arm, folded wire antennas of the same height and cylindrical diameter, but having significantly different geometries, are made to be self-resonant at the same frequency, they exhibit similar resonant performance properties. This illustrates that the resonant performance properties of these antennas are primarily established by their height and the physical volume occupied relative to the resonant wavelength. Various design parameters are considered and described for achieving self-resonance and a reasonable impedance match with an electrically small, multiple-arm folded wire antenna. Finally, the performance properties of the multiple-arm folded wire configurations are compared with those of an impedance-matched, non-folded, open-ended wire configuration. It is shown that the multiple-arm folded wire configurations exhibit a lower Q than the impedance-matched, non-folded wire configuration.     

Low Q electrically small linear and elliptical polarized spherical dipole antennas

Electrically small antennas are generally presumed to exhibit high impedance mismatch (high VSWR), low efficiency, high quality factor (Q); and, therefore, narrow operating bandwidth. For an electric or magnetic dipole antenna, there is a fundamental lower bound for the quality factor that is determined as a function of the antenna's occupied physical volume. In this paper, the quality factor of a resonant, electrically small electric dipole is minimized by allowing the antenna geometry to utilize the occupied spherical volume to the greatest extent possible. A self-resonant, electrically small electric dipole antenna is presented that exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and a quality factor that is within 1.5 times the fundamental lower bound at a value of ka less than 0.27. Through an arrangement of the antenna's wire geometry, the electrically small dipole's polarization is converted from linear to elliptical (with an axial ratio of 3 dB), resulting in a further reduction in the quality factor. The elliptically polarized, electrically small antenna exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and it has an omnidirectional, figure-eight radiation pattern.     

Modelling methodology for thermal analysis of hot solder dip process

The shift of electronics industry towards the use of lead-free solders in components manufacturing brought also the challenge of addressing the problem of tin whiskers. Manufacturers of high reliability and safety critical equipment in sectors such as defence and aerospace rely increasingly on the use of commercial-of-the-shelf (COTS) electronic components for their products and systems. The use of COTS components with lead-free solder plated terminations comes with the risks for their long term reliability associated with tin whisker growth related failures. In the case of leaded type electronic components such as Quad Flat Package (QFP) and Small Outline Package (SOP), one of the promising solutions to this problem is to “re-finish” the package terminations by replacing the lead-free solder coatings on the leads with conventional tin–lead solder. This involves subjecting the electronic components to a post-manufacturing process known as Hot Solder Dip (HSD). One of the main concerns for adopting HSD (refinishing) as a strategy to the tin whisker problem is the potential risk for thermally induced damage in the components when subjected to this process.     

Determining the Dielectric Constants of Organic Photovoltaic Materials Using Impedance Spectroscopy

The photovoltaic and electrical properties of organic semiconductors are characterized by their low dielectric constant, which leads to the formation of polarons and Frenkel excitons. The low dielectric constant of organic semiconductors has been suggested to be significantly influential in geminate and bimolecular recombination losses in organic photovoltaics (OPVs). However, despite the critical attention that the dielectric constant has received in literature discussions, there has not yet been a thorough study of the dielectric constant in common organic semiconductors and how it changes when blended. In fact, there have been some inconsistent and contradictory reports on such dielectric constants, making it difficult to identify trends. Herein, at first a detailed explanation of a specific methodology to determine the dielectric constant in OPV materials with impedance spectroscopy is provided, including guidelines for possible experimental pitfalls. Using this methodology, the analysis for the dielectric constant of 17 common neat organic semiconductors is carried out. Furthermore, the relationship between the dielectric constant and blend morphology are studied and determined. It is found that the dielectric constant of a blend system can be very accurately predicted solely based on the dielectric constants of the neat materials, scaled by their respective weight ratios in the blend film.     

Polydipsia-induced alcohol dependency in rats: a reexamination

Seven Holtzman rats were kept on a polydipsia-induced schedule of alcohol consumption for 3 months in a replication of a 1972 study by Falk and colleagues. Contrary to their results, there was no evidence of alcoholism.