cssi/SciSciGPT-SciSciNet huggingface dataset:
Polychlorinated biphenyls (PCBs): mutagenicity and carcinogenicity.

The potential mutagenicity and carcinogenicity of commercial PCBs has been investigated in both in vivo and in vitro systems and several conclusions can be drawn from these studies. (1) PCBs can covalently adduct DNA both in vivo and in vitro (using a source of metabolic activation); the more highly chlorinated biphenyls are poorly metabolized and these compounds tend to exhibit very low binding to DNA. Based on the structure-activity relationships for PCBs (Safe, 1984) it is unlikely that the more toxic compounds such as 3,3',4,4',5-penta- and 3,3',4,4',5,5'-hexachlorobiphenyl, would form covalent adducts with DNA. (2) PCB mixtures and individual compounds exhibit minimal mutagenic activity in most assay systems. (3) The more highly chlorinated PCB mixtures (i.e. greater than 50% Cl by weight) are hepatocarcinogens in rodents whereas data from a limited number of studies suggest that the lower chlorinated mixtures are not carcinogenic. (4) In some model systems, the higher chlorinated PCB mixtures act as promoters of preneoplastic lesions and hepatocellular carcinomas in rodents treated with a variety of initiators. (5) Aroclor 1254 acts as a promoter of skin papilloma formation in HRS/J hairless mice and structure-activity and genetic studies suggest that the Ah receptor is necessary but not sufficient for the activity of halogenated aryl hydrocarbons as promoters in hairless mice. (6) Individual PCB congeners and higher chlorinated commercial mixtures also exhibit anti-carcinogenic activity in the CD-1 mouse skin cancer model. (7) Results from occupational studies suggest that individuals exposed to PCBs may have an excess of cancer at some sites, however, the most comprehensive study (Brown, 1987) suggests that there are no significant increases in the overall cancer rate in workers exposed to PCBs. Follow-up and continuing epidemiological studies on the PCB-exposed workers are required to further clarify the potential carcinogenic effects of PCBs on humans. In several strains of rats and mice, there is a high incidence of hepatic preneoplastic lesions and carcinomas and these lesions can be induced by diverse promoting agents (Schulte-Hermann et al., 1983; Weinstein, 1984). Since PCBs are not mutagenic and do not readily form covalent adducts with cellular DNA, it is likely that the higher chlorinated biphenyls are not genotoxic and act as promoters of carcinogenesis in rodents. A comparable mechanism has been suggested for 2,3,7,8-TCDD (Shu et al., 1987; Weinstein, 1984). For PCBs, the role of the Ah receptor in mediating their activity as promoters has not been delineated.(ABSTRACT TRUNCATED AT 400 WORDS)
Translational control and the unfolded protein response.

Cellular stresses that disrupt the processing of proteins slated for the secretory pathway induce the unfolded protein response (UPR), a regulatory network involving both translational and transcriptional control mechanisms that is designed to expand the secretory pathway and alleviate cellular injury. PERK (PEK/EIF2AK3) mediates the translational control arm of the UPR by enhancing phosphorylation of eIF2. Phosphorylation of eIF2 reduces global protein synthesis, preventing further overload of the secretory pathway and allowing the cell to direct a new pattern of mRNA synthesis that enhances the processing capacity of the endoplasmic reticulum (ER). PERK also directs preferential translation of stress-related transcripts, including that encoding ATF4, a transcriptional activator that contributes to the UPR. Reduced global translation also leads to reduced levels of key regulatory proteins that are subject to rapid turnover, facilitating activation of transcription factors such as NF-B during cellular str...
An application of the single specimen technique to a double cantilever beam specimen to determine GIC from a single test record

Abstract The single specimen technique is effectively used in classical fracture mechanics for evaluating the J -integral from a single test record. It was previously shown using a cracked lap shear specimen that the technique can be applied to composite structures and the energy release rate of composite laminates can be determined from a single test specimen. The objective of this investigation is to determine the η el form of a double cantilever beam (DCB) specimen, and to compare it with that of a compact tension (CT) specimen. The result showed that while η el is linearly related to crack length for the CT specimen, it is proportional to the reciprocal of the crack length for the DCB composite specimen. Also, G Ic determined from the compliance method was compared with that determined from the η el approach. The result showed that the η el form determined from a single beam analysis can be used to determine G Ic from a single test record.
Motivation as a Multifactor Trait

Abstract In looking at motivation as a multifactored trait rather than as a singular trait, a larger portion of the variance in academic achievement is explained. Sixty college students were administered five motivation instruments, each having two components. When the total instruments were used, they explained 23% of the variance, but when they were broken into their component parts, they explained 36%; thus, a schema for approaching motivation as a multifactor trait is presented.
The Prereflective Cogito as Contaminated Opacity

The “I think” that accompanies all my intentional acts is the prereflective cogito. It can be declined in the nominative, genitive, dative, and accusative cases: nominative because I am given to myself as a subject, genitive because each experiential awareness is mine, dative because the content of each awareness is given to me, and accusative because even as subject I am always given to myself as the object of the look and address of another. But it is a mistake to think of consciousness as “pure” by virtue of the formality of this structure. Even at the transcendental level, consciousness is contaminated by contingency and particularly in ways that render it opaque to itself in its relation to nature, society, and God.
A nonparametric procedure for analyzing repeated measures of spatially correlated data

Many agricultural, biological, and environmental studies involve detecting temporal changes of a response variable, based on data observed at sampling sites in a spatial region and repeatedly over several time points. That is, data are repeated measures over time and are potentially correlated across space. The traditional repeated-measures analysis allows for time dependence but assumes that the observations at different sampling sites are mutually independent, which may not be suitable for field data that are correlated across space. In this paper, a nonparametric large-sample inference procedure is developed to assess the time effects while accounting for the spatial dependence using a block bootstrap. For illustration, the methodology is applied to describe the population changes of root-lesion nematodes over time in a production field in Wisconsin.
Edge detection and thinning in time-varying image sequences using spatio-temporal templates

Abstract A new computational paradigm for the extraction of spatio-temporal edge information in a sequence of images is presented. Extracted edge information consists of an edge type, orientation, and motion class. A set of three-dimensional (two-dimensional spatial and one-dimensional temporal) templates is developed. The extracted edge features facilitate efficient thinning of edge data. Sample experimental results are shown. The proposed approach forms the preprocessing stage of an image motion understanding system.
Enhanced thermoelectric properties of (Bi0.5Sb1.5Te3)1−x−y (PbTe)x(Zn4Sb3)y by combinatorial screening

Abstract The effects of doping Bi 0.5 Sb 1.5 Te 3 thin films with PbTe and Zn 4 Sb 3 were studied using a combinatorial approach. We demonstrate the structural and thermoelectric properties of (Bi 0.5 Sb 1.5 Te 3 ) 1 − x − y (PbTe) x (Zn 4 Sb 3 ) y thin films grown with varying concentrations of PbTe and Zn 4 Sb 3 , for 0.012 x y x = 0.036 and y = 0.011. The lowest electrical resistivity was 1.17 (m-Ω-cm) at x = 0.0254 and y = 0.006. The compound with x = 0.0254 and y = 0.006 showed the highest power factor (12.57 μW/K 2 -cm). The effects on the thermoelectric properties of these materials are extremely important for understanding the fundamental characteristics of (Bi 0.5 Sb 1.5 Te 3 ) 1 − x − y (PbTe) x (Zn 4 Sb 3 ) y embedded thermoelectric composites.
Mode- and complexation-specific singlet-triplet coupling in jet-cooled perylene studied by time-resolved fluorescence spectroscopy

Abstract Fluorescence spectral data for jet-cooled perylene indicate little or no vibrational coupling for most levels up to 1057 cm −1 . Fluorescence time profiles have been measured for several levels, and evidence presented for several cases of coupling to the triplet manifold. The principal Franck-Condon-active mode 353 1 exhibits a single-exponential decay, although the emission spectrum indicates little or no singlet vibrational level mixing. The (CH 4 ) 1 complex of perylene, also excited into 353 1 , exhibits a single-exponential profile with a fast decay, again indicating strong singlet-triplet coupling, while the 2 : 1 and 3 : 1 complexes at the same energy are strongly fluorescent. These results imply that singlet-triplet coupling is level-selective, and can be induced by complexation.
Rapid FPGA design prototyping through preservation of system logic: A case study

FPGA designs often contain significant amounts of logic such as a board support package that remains unaltered throughout the design process. However, during normal operation, standard FPGA implementation tools re-implement the entire system, including the unchanged logic, adding to the turn around time of design iterations. Recently, FPGA implementation flows have appeared that allow preserving parts of a previously implemented design. In this study, we evaluate the potential speedups in implementation time achievable through preserving the unchanging portion of a design's implementation. We perform these evaluations using Xilinx Partitions, Xilinx SmartGuide, and the HMFlow rapid implementation tool.
The Self Consistent Field and the Structure of Atoms

The method proposed by Hartree for the solution of problems in atomic structure is examined as to its accuracy as a method of solving Schr\"odinger's equation. A wave function is set up at once from his method, and the matrix of the energy computed with respect to it. The non-diagonal terms are shown to be small, indicating that the function is a good approximation to a real solution. The energy levels are found by perturbation theory from this matrix, and are compared with the term values as found by Hartree. His values should be corrected for three reasons: he has neglected the fact that electron distributions are not really spherical; he has not considered the resonant interactions between electrons; and he has made an approximation which amounts to neglecting the polarization energy. The sizes of these corrections are estimated, and they are found to be of the order of the errors actually present in the numerical cases he has worked out.
Photoreceptor degeneration in the eyes of an amphisbaenian in response to constant light or constant darkness

Eye morphology and behavioral responses were studied in Bipes biporus (Cope) exposed to normal photoperiods, constant light, and constant darkness. Control animals had retinas with a reduced number of outer segments relative to the typical vertebrate retina. In addition, many of these outer segments were poorly formed, suggesting a capability for light detection but not for image formation. Constant light led to detached retinas and eventual degeneration of outer segments. Earliest signs of detachment appeared in younger animals, but no subsequent age differences were found. Constant dark-induced changes were similar to light-induced changes except that dark-induced changes were not so severe, did not depend on age, and included loss of pigment from cells in the pigmented epithelium. Retinal damage in constant dark animals suggests that free-living Bipes biporus are occasionally exposed to light. Dark-seeking behavior of normal animals diminishes after exposure to constant light.
Multiple Penalty Mechanisms in a Principal–Agent Model under Different Institutional Arrangements☆

Abstract This paper develops a principal–agent model that involves a multiple penalty mechanism, containing both monetary- and resource-based penalties, and analyzes it in two institutional settings: a market economy and a centrally planned economy. In the latter economy, the agent's wealth dep*ends mostly on real resources and only to a limited degree on monetary resources; therefore, monetary-based penalties have less penalizing power than resource-based penalties. Based on this premise, the model generates testable hypotheses regarding the differences in optimal penalty imposition between the two economic systems.J. Comp. Econom.,March 1999, 27(1), pp. 168–189. University of Kansas, 213 Summerfield Hall, Lawrence, Kansas 66045.
Effects of Seeding Reservoir Fluctuation Zones on Young-of-the-Year Black Bass and Associated Species

Abstract Fertilized rye grew well in the fluctuation zone of Lake Nottely, a tributary reservoir in northern Georgia, during fall and winter drawdown providing cover at a materials cost of $38/hectare. Considering the three species of black bass (Micropterus salmoides, Micropterus punctulatus, and Micropterus dolomleui) in Lake Nottely together, young-of-the-year (y-o-y) bass were consistently more abundant in the flooded, seeded areas than in the unseeded control areas from the middle of June to the middle of July; however, in late summer the number of y-o-y black bass in both areas was similar. Seeded areas had a slight but positive effect on growth of the bass in that they were 8% larger and 13% heavier than y-o-y bass in the control area by the end of the summer. Numbers of aquatic insects and small sunfish were more abundant in the seeded areas. Y-o-y black bass were more piscivorous in the seeded areas, and there was no apparent negative effect on y-o-y bass due to sunfish (Lepomis spp.), y-o-y whit...
Viscous-fingering experiments with periodic boundary conditions

Experimental realization of a Hele-Shaw cell with periodic boundary conditions (PBC's) is achieved by building an azimuthal cell with two coaxial cylinders separated by a small gap. The development of viscous-fingering patterns formed by a critical binary liquid mixture at very low viscosity contrast has been observed and recorded from the onset of instability to very late stages. Comparison with the experimental results measured in cells which have sidewalls shows that PBC's yield few differences of results. At the early stage there is no sidewall disturbance so the Fourier transforms show less noise in the low-wave-number modes. Because the annular cell is larger than the earlier cells, it was possible to follow the flow to a very late nonlinear stage where, instead of showing steadily lengthening and broadening fingers, the necks of the longer fingers, crowded by fattening bulbs of the tips of the less-long fingers, constrict until their width is no longer negligible in comparison to the cell gap, at which point the pattern breaks up into a rich variety of bubbles.
Attention strongly increases oxygen metabolic response to stimulus in primary visual cortex

Top-down attention enhances neural processing, but its effect on metabolic activity in primary visual cortex (V1) is unclear. Combined blood flow and oxygenation measurements provide the best tool for investigating modulations of oxidative metabolism. We measured the human V1 response to a peripheral low contrast stimulus using fMRI and found a larger fractional modulation of blood flow with attention compared to the blood oxygenation level dependent (BOLD) response, thus indicating a much larger modulation of oxygen metabolism than was previously thought. These findings point to different aspects of neural activity driving flow and metabolic changes to different degrees. We propose that V1 flow is driven strongly but not exclusively by the initial sensory-driven neural activity, which dominates the response in the unattended condition, while V1 oxygen metabolism is driven strongly by the overall neural activity, which is modulated by top-down signals related to attention.
Spatial Patterns of Soil Surface C Flux in Experimental Canopy Gaps

To explore within-gap spatial patterns of soil surface CO2 flux, we measured instantaneous soil surface CO2 flux, soil surface temperature, and soil moisture in north–south transects across canopy gaps and in adjacent contiguous forest from April to November 2010 in a second-growth northern hardwood forest in Wisconsin, USA. Throughout the growing season, soil surface CO2 flux was higher in the northern 1/3 and northern edge of gaps compared to the central and southern portions. These patterns were driven primarily by within-gap variation in soil temperature, which was itself driven by within-gap patterns of insolation. Most locations in the northern 1/3 and northern edge of gaps had significantly higher modeled total growing season C flux (mean 725 g C m−2) compared to the contiguous forest (mean 706 g C m−2), whereas C flux in the central and southern portions of gaps (mean 555 g C m−2) was significantly lower than both the contiguous forest and the northern portions of gaps.
In vitro synthesis of vitamin D-3 by cultured human keratinocytes and fibroblasts: action spectrum and effect of AY-9944.

Abstract With delineation of the photochemical events occurring in the skin after ultraviolet exposure, there has been increased interest in the skin's role in the vitamin D-3-endocrine system. We provide here in vitro conditions for the generation of both labelled (from [ 3 H]acetate) and unlabelled vitamin D-3 in cultures of human ke keratinocytes and fibroblasts. Sterol precursors and photoproducts in irradiated and non-irradiated cultures are identified by co-chromatography, ultraviolet absorbance spectra, thermal conversion characteristics of previtamin D-3 and mass spectrometry. Because the conversion of 7-dehydrocholesterol to cholesterol is more efficient in vitro than in vivo, the specific Δ 7 inhibitor, AY-9944, was added in non-toxic doses to modulate 7-dehydrocholesterol content. Both cell types were equally capable of generating photoproducts, 3epending on the amount of 7-dehydrocholesterol present. The 290 ± 5 and 295 nm filters were much more efficient than the 305 nm filter for generating previtamin D-3 and vitamin D-3 in fibroblasts. In contrast, the 305 nm filter was as efficient as the 290 ± 5 and 295 nm filters in keratinocytes, where it yielded previtamin D-3, with much less lumisterol and tachysterol than appeared with the shorter-wavelength filters. The amount of lumisterol and tachysterol versus previtamin D-3 formed in both cell types was dependent on the total energy applied, with lower energies (less then 1 J/cm 2 ) favoring previtamin D-3 over the other photoproducts. The use of cultured cells provides a system whereby regulation of vitamin D-3 synthesis by extracutaneous factors can be studied in a homogeneous setting.
Leveraging avatars in 3D virtual environments (Second Life) for interactive learning: the moderating role of the behavioral activation system vs. behavioral inhibition system and the mediating role of enjoyment

Within the Entertainment-Education (E-E) framework, two experiments examined the effects of avatar-based e-health education targeting college students. Study 1 (between-subjects factorial design experiment: N = 94) tested the effects of message framing in e-learning and the moderating role of students' motivational systems on their enjoyment of the e-learning experience. The results indicated a significant interaction between message framing and students' motivational systems on their enjoyment of the e-learning experience, as well as the significant impact of avatar-based e-health education on the students' knowledge acquisition and condom use/safe sex self-efficacy improvements. Study 2 (within-subjects design: N = 88) examined the influence of students' parasocial interaction (PSI) with a pedagogical avatar on the cognitive (evaluation of educational value), affective (enjoyment), and behavioral (willingness to take part in Human Papillomavirus awareness campaigns) dimensions of the E-E process. The re...
Aircraft observations of rapid meridional transport from the tropical tropopause layer into the lowermost stratosphere: Implications for midlatitude ozone

[1] Meridional transport from the tropics redistributes ozone and water vapor at middle and high latitudes. In situ measurements of water vapor, CH4, and N2O, acquired aboard the NASA ER-2 aircraft during January−March 2000 in a campaign to survey the Arctic vortex, are used to examine transport into the lowermost stratosphere in the context of middle- and high-latitude ozone declines observed over the last several decades. Analysis of tracer-tracer correlations of H2O + 2*CH4 and N2O indicates that rapid, poleward isentropic transport from the lower tropical stratosphere coupled with diabatic descent between the subtropical and polar jet streams delivers very young air to the high-latitude lowermost stratosphere during winter, while descent of older air from the vortex and subsequent transport to lower latitudes is very limited. From middle to late winter, mixing ratios of H2O + 2*CH4 decrease by about 1 ppmv immediately outside the vortex, consistent with rapid transport of the winter phase of the seasonal cycle in water vapor to high latitudes from the lower tropical stratosphere. No evidence of isentropic mixing from the upper tropical troposphere survives in the high-latitude lowermost stratosphere except below 350 K, where markedly higher water vapor mixing ratios indicate mixing from the extratropical troposphere. All of these transport processes pose dynamical and chemical consequences for ozone. Transport from the lower tropical stratosphere (1) exports ozone-poor air to midlatitudes and the subvortex region and (2) distributes elevated water vapor to high latitudes, potentially enhancing halogen-catalyzed ozone destruction through heterogeneous processing in the polar vortex.
Shared Governance and Punctuated Equilibrium in Higher Education: The Case for Student Recruitment, Retention, and Graduation

No longer can higher education institutions rely on passive approaches to recruiting students, retaining those students through graduation, and reaping the benefits of alumni support. Each institution must aggressively engage in marketing and customer relationship management techniques to maintain an adequate student body and sufficient alumni support. The ever quickening pace of societal and technological change creates intense competitive pressure for quality students, which in turn requires unprecedented attention to the business of recruiting and retention. These and other challenges have led to the “punctuated equilibrium” in higher education. For higher education institutions to survive and thrive during this paradigm shift, they must practice and embrace the principles of shared governance.
Overlapping identities in the American South

Abstract Despite the extensive literature on southern identity, we know surprisingly little about how regional identity competes with potential loyalties toward other groups in the South. We investigate the prevalence and predictors of four overlapping identifies—Appalachian, Southern, North Carolinian, and American. We find that people identify primarily as Americans, followed by North Carolinians, Southerners, and finally Appalachians. We also examine the correlation between these overlapping identities and test multivariate models to explain each identity using a common set of predictors: age, education, time in region, sex, political ideology, and race. Identity correlates shift depending on the group under consideration and that time in the region is the most consistent predictor, followed by age, and political ideology.
Educational Equity Policies and the Centralization of American Public Education: The Case of Bilingual Education

Sixty years ago, federal guidelines regarding the instruction of special populations in American public schools were nonexistent. Racial minorities, language minorities, women, the poor, and those with physical and mental disabilities had not been identified as groups that needed special protections. Much has changed since then. Federal legislation that is designed to ensure that all of these groups have access to equal educational opportunities in the United States is now in place. This article examines the evolution of policies surrounding bilingual education to illustrate that the need to ensure the educational opportunities of certain student populations compelled the federal government to become more involved in the governance and oversight of American public education. The implementation of such federal “protection policies” designed to expand educational opportunities for traditionally underserved groups of students ultimately fortified and solidified the federal government's more pronounced role i...
Iliac Vein Approach to Permanent Pacemaker Implantation

Since July 1980, 90 patients have had 95 permanent pacemakers implanted via an iliac vein approach. An incision is made superior to the inguinal ligament and the iliac vein is cannulated with a single lead for the ventricle or two leads for the atrium and ventricle. The pulse generator is placed in the subcutaneous tissue of the abdomen lateral to the umbilicus via a second incision. Overall 28 pacemaker implants were for atrial pacing, 53 for ventricular pacing and 14 were dual chamber. Nine (21%) of the atrial leads displaced and required repositioning and 5 (7%) of the ventricular leads dislodged and required revision. Lead dislodgement, especially in the atrium, remains a major weakness of the approach, and decreases its utility. Eleven percent of the last 19 atrial leads have dislodged. Nevertheless, the method is simple to perform and is presented as an alternative to the usual pectoral implantation site.
Separation of intramolecular NOE and exchange peaks in water exchange spectroscopy using spin-echo filters

A technique for separating intramolecular NOE and solvent-proton exchange peaks in exchange spectroscopy is demonstrated. This method utilizes the large differences in relaxation and coupling properties of water and macromolecules to separate the two effects. The spin-echo filter consists of a water-frequency selective 90° pulse followed by a spin-echo sequence. If the echo time is sufficiently long, protein resonances (e.g. CαH protons) excited by the selective pulse are removed due to their much shorter T2 values and J-coupling evolution. By combining the filter with exchange spectroscopy (EXSY) or water exchange (WEX) filter experiments, exchange peaks can be selectively observed. In this paper the filter is combined with a modified version of the WEX filter (WEX II filter) with 1D and 2D detection and applied to a zinc finger peptide and to staphylococcal nuclease, allowing estimation of the contribution of intramolecular NOEs to the exchange spectra.
Active Control of Supersonic Jets Operating in Various Flow Regimes

Localized arc filament plasma actuators were used to control a supersonic jet from an axisymmetric nozzle of design Mach number of 1.3 operating from overexpanded to underexpanded flow regimes with the fully expanded jet Mach number (MJ) from 1.1 to 1.5. The Reynolds number based on the 2.54 cm nozzle exit diameter was from 1.0x10 6 to 1.4x10 6 . Laser based planar flow visualizations, schlieren imaging, and particle imaging velocimetry measurements were used to evaluate the effects of control. Eight actuators, distributed azimuthally approximately 1 mm upstream of the nozzle exit, were used to force various azimuthal modes over a large frequency range (StDF of 0.07 to 2.70). The preliminary results in the underexpanded jets (MJ = 1.4 and 1.5) were quite similar to our previous results in the ideally expanded jet (MJ = 1.3). The jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.33 (f = 5 kHz). The jet also responded to forcing with various azimuthal modes (m=0 to 3 and m= ±1, ±2, ±4). Forcing the jet with the azimuthal mode m= ±1 at the jet preferred mode frequency provided the maximum mixing enhancement. Conversely, the preliminary results showed that the overexpanded jets (MJ = 1.1 and 1.2) did not respond at all or the response was relatively small. Detailed experiments are underway to further explore this issue.
Stein Quotients of Connected Complex Lie Groups

Various algebraic and geometric conditions on connected complex Lie groups G and H are shown to characterize the quotient G/H as a Stein manifold. Among these conditions are analytic analogues of the algebraic notions of observable or strongly observable subgroups and cohomological conditions expressed in terms of equivariant maps. A specific group theoretic condition on H, generalizing Matsushima's criterion for reductive groups, is shown to be necessary for G/H to be Stein and the sufficiency of this condition is proven when G is solvable or when H satisfies a dimension restriction. Also included is a geometric description of a Stein quotient G/H as a bundle space over an orbit of a maximal reductive subgroup of G, and a theorem on the orbits of solvable groups In ℂn.
On polynomial monosplines with fixed point evaluations

Abstract This paper discusses quadrature formulae for polynomial splines which include known values of even multiplicities. The formula is written as a sum of derivative values as opposed to divided differences, allowing for spline functions of lower degree. Free nodes are allowed odd multiplicities. It is shown that a feasibility condition similar to the fundamental theorem of determinants for splines is required.
Parametric Analysis of Parasitic Pressure Drop and Heat Losses for a Parabolic Trough With Considerations of Varying Aperture Sizes and Receiver Sizes

The collector aperture and diameter of the receiver of a parabolic trough were studied to investigate the relative impacts of parasitic pressure drop, heat losses, and heat flux intercepted by the receiver tube. The configuration of an LS-2 parabolic trough was used as the baseline, and the size of the HCE and collector aperture were parametrically varied using values between the baseline and twice their original size. A Matlab computer model was created to determine the flux on the receiver, heat loss from the HCE, and pressure drop within the heat transfer fluid (HTF) at each combination of aperture size and receiver diameter. Flux on the receiver is calculated for each geometry assuming a Gaussian flux distribution. Based on pressure data from SEGS VII, the standard Darcy-Weisbach equation for the pressure drop was modified to include the contribution that connective joints of varying quantities and types have on the pressure drop within the HTF. The model employs the Sandia thermal resistive network and iteratively solves for the temperatures accounting for various heat transfer modes that contribute to the heat lost by the HCE. The Matlab model expresses pressure drop and heat losses in terms of electric power. It does this by calculating both the power required to pump the HTF for varying pressure drops and the power that could have been produced if heat was not lost to the environment. The Matlab model displays the results in the form of surface plots that represent the values of heat loss, efficiency, pumping power, etc. as a function of aperture size and receiver diameter. The combined effects of pressure drop, heat loss, and heat flux intercepted by the receiver tube were evaluated, and results show that configurations with receiver diameters ranging from 85–90 millimeters and large (up to 10 meter) aperture sizes minimize the overall power consumption and maximize the efficiency of a single loop. Structural effects, wind and gravity loads, and factors associated with the balance of plant were not considered.Copyright © 2011 by ASME
Thematic evolution of ISTRO: transition in scientific issues and research focus from 1955 to 2000

Abstract The International Soil and Tillage Research Organization (ISTRO) was initiated in 1955 as an activity of the World Ploughing Organization holding the world ploughing contests. The membership of ISTRO has grown from a dozen agricultural engineers and soil scientists in western Europe in the 1950s to 450 members from around the world in 2000. Thematic evolution of ISTRO has addressed four distinct but inter-related issues: (i) ploughing, mechanization and energy/power requirements during the 1950s and 1960s; (ii) reduced or conservation tillage and mulch farming during the 1970s, and soil compaction, soil strength and soil tilth during the 1980s; (iii) agricultural sustainability and soil quality in the 1990s; (iv) greenhouse effect, environment quality and modeling in the year 2000 and beyond. The ISTRO and its members will continue to play an important role in meeting the ever-increasing food demand of the growing human population of the world without jeopardizing soil and water resources that are already under great stress. A possible future strategy lies in understanding the processes and establishing the cause–effect relationship which create synergistic effects in enhancing productivity per unit input of land, labor, energy and time.
Decentralized production planning and choice of organizational structure

Abstract The possibilities of decentralizing production planning tasks depend on the organizational structure oft he product ion system. If process organization is used, a local unit is naturally responsible for the planning of similar operations. In case of line organization, a local unit is instead in charge of most of the planning for a certain family of items. This paper illustrates and discusses how the production organization affects the overall results of the planning efforts, A simple production situation is analysed in detail.
Surface mapping brain function on 3D models

A flexible graphics system for displaying functional and anatomic data on arbitrary collections of surfaces on or within the brain is presented. The system makes it possible to show complex, convoluted surfaces with the shading cues necessary to understand their shapes; to vary viewpoint, object position, illumination, and perspective easily; to show multiple-objects in one view, with or without transparency, in order to examine internal surfaces and intersecting objects in relation to each other; and to superimpose quantitative information on biological or otherwise defined surfaces anywhere within the volume, thus furthering understanding of both quantitative and positional information in its global context. These display techniques are applied to a new form of biological surface model, the removed surface. The surface-removal method creates a set of surfaces internal to a given object, so that, given a specified distance, every point on the created surfaces is equidistant from the surface of the enclosing object. The method is based on thresholding a derived scalar field, the minimum distance field. Models made by this method have applications in 3-D neurobiology and provide an alternative to cutaways for viewing patterns of internal functional activity. >
Velocity-selective magnetic-resonance laser cooling

We describe a new sub-Doppler cooling scheme that cools atoms to nonzero velocity ${\mathit{v}}_{\mathit{r}}$. The atomic motion in a combined optical standing wave and constant magnetic field induces a velocity-selective magnetic resonance that produces strong cooling for negative laser detuning to ${\mathit{v}}_{\mathit{r}}$=${\mathrm{\ensuremath{\omega}}}_{\mathit{Z}}$/2k, with ${\mathrm{\ensuremath{\omega}}}_{\mathit{Z}}$ the Larmor frequency. In a one-dimensinal optical molasses transverse to a thermal Rb beam we observe the bunching of the atoms into two peaks corresponding to \ifmmode\pm\else\textpm\fi{}${\mathit{v}}_{\mathit{r}}$. We present a quantitative comparison between our theory and experiment and suggest some applications.
American and Soviet Children's Attitudes toward Computers

For a decade significant resources in the United States have been expended to put computers in the schools. Many school districts are now taking stock of the effects of this computerization as they prepare strategic plans for the school reform of the next decade. Similarly, recent events in Eastern Europe are bringing about massive school reform, and the role that the computer could play in reform efforts is being carefully considered. As plans for increased use of computer technology are made, it is important for policy makers, educators and researchers to understand how children relate to the new technologies. In this study the attitudes of eight to twelve year old American and Soviet children toward computers were examined by comparing their responses to attitude statements and their drawings of computer users. Although some significant differences by country and gender were found, the attitudes of the children from both countries were found to be very similar and mostly positive. One of the greatest d...
A model of vertebrate resting metabolic rate: balancing energetics and O2 transport in system design.

Abstract In vertebrates, maximal rates of oxygen consumption ( V O 2 , max ) exceed resting rates ( V O 2 , rest ) by an average factor of ten. This pattern of factorial scope has led to the hypothesis that V O 2 , rest and V O 2 , max are causally linked in vertebrates (aerobic capacity model, Bennett and Ruben, Science 206, 649–654, 1979). We propose an alternate theory that vertebrate resting metabolic rates are regulated at levels to optimize metabolic performance during activity, by reducing cardiovascular response times for O2 transport. First, we argue that circulatory convection has the potential to be rate-limiting to vertebrate aerobic adjustment. We then show mathematically that incremental changes in convection requirements exhibit a nonlinear dependence on initial values. From this, a cost–benefit model is constructed, using energetics and blood-convection requirements, to predict the optimal fractional allocation to V O 2 , rest in vertebrates as 11% of V O 2 , max . The implications of our results to vertebrate metabolic design and the evolution of endothermy are discussed.
General methods for the derivation of sampling theorems

This paper presents an integral representation for the derivation of sampling expansions. The representation uses the theory of self-adjoint differential equations. Different methods of evaluating the resulting triple integral have different physical significances and yield the commonly used approaches to the derivation of sampling expansions. The first- and second-order differential operators are discussed, and the physical interpretation of the first-order case is emphasized.
Obstacle avoidance with perturbation/correlation method

We propose a novel technique for acquiring effective information for obstacle avoidance in mobile robot navigation. Instead of simply receiving data at a single point, we actively give perturbations to the system and measure the response from the system. Correlating the input and the output, we can formulate the correlation function and useful information to guide the mobile robot such as gradient can be obtained from this function. This algorithm is applied to the obstacle avoidance in mobile robot navigation and the experimental results are provided.
The One Woman Director Mandate: History and Trajectory

In 2013, India passed historic legislation mandating that boards of publicly listed and certain other large companies must include one woman director. The mandate, which came into effect on April 1, 2015, has the potential to vastly change the profile of Indian boards and board members. This chapter examines the history and trajectory of India’s board diversity requirement. It seeks to understand the genesis and goals of this requirement, and explores some of the challenges that India has already faced and may continue to face with respect to the possible effectiveness of this requirement. The chapter then considers for the Indian context the implications of business and social science literature on gender diversity on corporate boards.
Effect of water availability and genetic diversity on flowering phenology, synchrony and reproductive investment in summer squash

Current agricultural practices rely on crops with developmental phenologies adapted to local climate, photoperiods and soils; however, global climate change will alter some abiotic factors (e.g. temperature and precipitation). Previously adapted varieties may be poorly prepared for these changing conditions, if such conditions induce mismatched phenologies. Crops that depend on cross-pollination and synchronous flowering may be most susceptible, e.g. monoecious plants have separate male and female flowers, and changes in flowering synchrony may alter yield. Using genetically diverse (open-pollinated (OP)) and genetically homogeneous (hybrid) varieties of a monoecious crop, courgette, also known as zuchinni (Cucurbita pepo), phenological responses to experimentally manipulated moisture conditions were explored in an agricultural context. Under drier and wetter conditions, the hybrid courgette plants shifted towards a male-biased floral sex ratio due to the reduced production of female flowers. However, flowering synchrony and fruit production were unaffected by moisture treatment in both varieties. The hybrid and OP varieties differed in many traits related to floral sex ratios, phenology, synchrony and fruit production. Further, the OP variety displayed more phenotypic variation than the hybrid in many traits. Being in a population context rather than relying on self-pollination increased the availability of potential mates for a given female flower in both the hybrid and, particularly, the OP variety. Thus, the increased genetic diversity found in OP v. hybrid varieties may buffer the possible environmental effects on flowering synchrony within a cropping context. Finally, the likelihood of female flowers setting fruit increased with the number of male flowers within a population, and the rate of increase was higher in the hybrid variety. In summary, climate change is predicted to reduce investment in female function in some monoecious crops and genetically diverse varieties may play an important role in maintaining reproductive synchrony in altered environments.
Novel thermosets prepared by cationic copolymerization of various vegetable oils- : synthesis and their structure-property relationships

A range of thermoset plastics have been prepared by the cationic copolymerization of olive, peanut, sesame, canola, corn, soybean, grapeseed, sunflower, low saturation soy, safflower, walnut, and linseed oils with divinylbenzene or a combination of styrene and divinylbenzene comonomers catalyzed by boron trifluoride diethyl etherate. The chemical, physical, thermal, and mechanical properties of these new polymers have been investigated as a function of the vegetable oil composition. The vegetable oil reactivity has a direct effect on most of the polymers' properties, which can be reasonably predicted by careful choice of the vegetable oil. Coupled with variations in the comonomer and stoichiometry, the choice of vegetable oil allows one to tailor the polymer's properties for specific applications.
Influence of strain on space-charge distribution at ferroelectric thin-film free surfaces

Abstract Ferroelectric perovskites are wide-bandgap semiconductors and therefore are often modeled as perfect dielectrics. However, space charges can play an important role in regions with large electric fields, such as at domain walls, free surfaces, near electrodes, etc. In this paper, we apply a mesoscale model to examine the space-charge distribution at free-surface closure domain patterns in a ferroelectric thin film. The model uses a conventional electromechanical phase-field approach for ferroelectric domain patterns in combination with drift–diffusion based equations to model space-charge distribution. We additionally apply a boundary element method to compute the stray electric fields outside the ferroelectric free surface. We probe the influence of mechanical strain, such as would be applied through a substrate, on the distribution of space charge. We find an indirect, but strong, coupling between mechanics and space-charge distribution. The physical mechanism of this coupling is as follows: the mechanical strain induces changes in the domain patterns and polarization distribution; this in turn changes the local electric fields sufficiently that space charges are redistributed on the free surface rather than moving towards the bottom electrode. We note two interesting features of this coupling: first, the coupling mechanism is operative only at free surfaces due to the complex domain patterns in these regions, and would not occur in the bulk; second, although domain patterns are visually only marginally changed by the presence of space charges, the changes in electric field due to these seemingly small changes is significant and this provides the coupling with space charge.
Noninvasive prenatal testing goes global.

Noninvasive prenatal genetic testing is becoming available worldwide—particularly in low- and middle-income countries—but practical and ethical challenges must be overcome.
Analytical Throughput Evaluation of Wireless Networks Using Multibeam Antennas

In a wireless network, concurrent communications between a node and multiple neighboring nodes through the use of multibeam antenna (MBA) has been shown effective to utilize the spatial dimensionality. As a result, the network throughput and quality-of-service (QoS) can be improved. MBAs can be implemented using multiple fixed-beam antennas (MFBAs) or multi-channel smart antennas (MCSAs). In this paper, the one-hop throughput performance of a node equipped with MBA is evaluated in an analytical framework. Both MFBA and MCSA are considered by using an equivalent antenna beam model. It becomes clear that the use of MFBA is the pessimistic case of MCSA as the normalized beamwidth reaches the maximum value. The upper bound of throughput is achieved in the presence of idealized collision avoidance schemes, whereas the lower bound is reached in the absence of collision avoidance schemes.
A synthetic utilization bound for aperiodic tasks with resource requirements

Utilization bounds for schedulability of aperiodic tasks are new in real-time scheduling literature. All aperiodic bounds known to date apply only to independent tasks. They either assume a liquid task model (one with infinitely many infinitesimal tasks) or are limited to deadline-monotonic and earliest-deadline first scheduling. In this paper, the authors make two important contributions. First, they derive the first aperiodic utilization bound that considers a task model with resource requirements. Second, the new bound is a function of a parameter called preemptable deadline ratio that depends on the scheduling policy. We show that many scheduling policies can be classified by this parameter allowing per-policy bounds to be derived. Simulation results demonstrating the applicability of aperiodic utilization bounds are presented.
Impact of melanin on microbial virulence and clinical resistance to antimicrobial compounds

Melanins are negatively charged, hydrophobic pigments of high molecular weight ([54][1], [88][2], [95][3], [139][4]) that are composed of polymerized phenolic and/or indolic compounds (Fig. [1][5]) ([45][6], [128][7]). Melanins are produced by organisms in all biological kingdoms, including a wide