cssi/SciSciGPT-SciSciNet huggingface dataset:
Affine Motion of 2d Incompressible Fluids Surrounded by Vacuum and Flows in SL (2 ,R )

The affine motion of two-dimensional (2d) incompressible fluids surrounded by vacuum can be reduced to a completely integrable and globally solvable Hamiltonian system of ordinary differential equations for the deformation gradient in $$\mathrm{SL}(2,\mathbb {R})$$. In the case of perfect fluids, the motion is given by geodesic flow in $$\mathrm{SL}(2,\mathbb {R})$$ with the Euclidean metric, while for magnetically conducting fluids (MHD), the motion is governed by a harmonic oscillator in $$\mathrm{SL}(2,\mathbb {R})$$. A complete classification of the dynamics is given including rigid motions, rotating eddies with stable and unstable manifolds, and solutions with vanishing pressure. For perfect fluids, the displacement generically becomes unbounded, as $$t\rightarrow \pm \infty $$. For MHD, solutions are bounded and generically quasi-periodic and recurrent.
Retroperitoneal approach for the treatment of diaphragmatic crus syndrome: technical note

Objective Myelopathy selectively involving the lower extremities can occur secondary to spondylotic changes, tumor, vascular malformations, or thoracolumbar cord ischemia. Vascular causes of myelopathy are rarely described. An uncommon etiology within this category is diaphragmatic crus syndrome, in which compression of an intersegmental artery supplying the cord leads to myelopathy. The authors present the operative technique for treating this syndrome, describing their experience with 3 patients treated for acute-onset lower-extremity myelopathy secondary to hypoperfusion of the anterior spinal artery. Methods All patients had compression of a lumbar intersegmental artery supplying the cord; the compression was caused by the diaphragmatic crus. Compression of the intersegmental artery was probably producing the patients' symptoms by decreasing blood flow through the artery of Adamkiewicz, causing lumbosacral ischemia. Results All patients underwent surgery to transect the offending diaphragmatic crus. Each patient experienced substantial symptom improvement, and 2 patients made a full neurological recovery before discharge. Conclusions Diaphragmatic crus syndrome is a rare or under-recognized cause of ischemic myelopathy. Patients present with episodic acute-on-chronic lower-extremity paraparesis, gait instability, and numbness. Angiography confirms compression of an intersegmental artery that gives rise to a dominant radiculomedullary artery. Transecting the offending diaphragmatic crus can produce complete resolution of neurological symptoms.
Three-Phase Interleaved LLC Resonant Converter with Integrated Planar Magnetics for Telecom and Server Application

The LLC converter is considered the most efficient topology in server and telecom applications. And, it has been demonstrated that three interleaved LLC converters can achieve further efficiency improvement at the 3KW power level. However, the magnetic components for multiphase LLC are complex, bulky, and difficult to manufacture in a cost-effective manner. In this paper, a high-frequency GaN based three-phase LLC converter is utilized to attempt to address these challenges. With GaN operating at 1 megahertz, all magnetic components, namely three inductors and three transformers, can be integrated in one common structure while all magnetic windings are contained in a compact 4-layer PCB with 3 oz. copper. The proposed structure can be easily and cost effectively manufactured in high quantities. Furthermore, up to a 20db reduction of common-mode noise, from 150KHz up to 30MHz, can be realized if 2 additional PCB layers are employed for proposed CM noise shielding. A 3kW 400V/48V 3-phase prototype is demonstrated, with an expected peak efficiency of 97.4% and a power density of 450W/in3 (28 kW/L).
Unravelling high-temperature stability of lithium-ion battery with lithium-rich oxide cathode in localized high-concentration electrolyte

Abstract Lithium (Li)-rich manganese (Mn)-rich oxide (LMR) cathode materials, despite of the high specific capacity up to 250 mAh g−1 suffer from instability of cathode/electrolyte interfacial layer at high working voltages, causing continuous voltage decay and capacity fading, especially at elevated temperatures. In various battery systems, localized high-concentration electrolytes (LHCEs) have been widely reported as a promising candidate to form effective electrode/electrolyte interphases. Here, an optimized LHCE is studied in graphite (Gr)-based full cells containing LMR cathode, being cycled at 25, 45 and 60 °C with the reference of a conventional LiPF6-based electrolyte. It is revealed that the LHCE can effectively suppress continuous electrolyte decompositions and mitigate the dissolution of Mn ions due to the formation of more protective electrode/electrolyte interphases on both anode and cathode, which, in turn, lead to significantly improved cycling stability and enhanced rate capability under the selected temperatures. The mechanistic understanding on the failure of the conventional LiPF6-containing electrolyte and the function of the LHCE in Gr||LMR cells under high temperatures provides valuable perspectives of electrolyte development for practical applications of LMR cathodes in high energy density batteries over a wide temperature range.
A Balanced Power Amplifier with Asymmetric Coupled-Line Couplers and Wilkinson Baluns in a 90 nm SiGe BiCMOS Technology

This work presents the design of a high power, two-stage, wideband, balanced power amplifier (PA) implemented in a 90 nm SiGe BiCMOS technology. Asymmetric coupled-line couplers were employed at the input and output of the circuit for impedance transformation and quadrature signal splitting and combining. The design achieves 17.3 dB small-signal gain with 41.8 GHz 3-dB bandwidth from 28.1 GHz to 69.9 GHz. To obtain high output power, two novel Wilkinson baluns were included, together with the output coupler, to achieve an overall 4-way differential power combining. A 24.4 dBm saturated output power (P SAT ) is achieved with a 22.0 GHz 1-dB P SAT bandwidth covering from 45.0 GHz to 67.0 GHz. The circuit shows a peak power added efficiency (PAE) of 14.2% at 60 GHz and the peak PAE is above 11.50% across the 1-dB P SAT bandwidth. The two stages adopt common-emitter power cells with the first stage biased at 2.0 V and second stage at 1.8 V. The chip size is 1.22 mm2 including bondpads.
Exploring the Multidimensional Nature of Resilience in Pain and Function among Aging Adults with Chronic Low Back Pain

Evidence supports the adaptive benefits of resilience among older adults with chronic pain. However, previous investigations have largely examined resilience factors in isolation with a predominant focus on psychological mechanisms, thereby overlooking other factors (e.g., health, social) that may attenuate pain burden. To address this gap, the current study used a multisystem approach in the examination of resilience by exploring the association of a range of protective factors with pain and physical functioning among older adults with chronic low back pain (cLBP). Community-dwelling adults (N=60) ages 60+ with cLBP completed measures of psychological (positive affect, hope, wellbeing, optimism), health (waist-hip ratio, body mass index, medical comorbidities), and social (emotional, instrumental, informational support) functioning. Principal component analysis (PCA) was then conducted to create composite domains for these measures. Participants also completed self-report measures of low back pain intensity and physical function (PROMIS), as well as a performance-based measure assessing lower-extremity function and movement-evoked pain (SPPB). Hierarchical linear regression analyses were used to assess the contribution of each multisystem resilience composite to pain intensity and physical function, after controlling for sociodemographic characteristics. PCA resulted in a three-factor solution (Component 1: positive, psychological factors; Component 2: health-related functioning; Component 3: social support) that accounted for 72.4% of the variance in the set of items. The three composite measures explained an additional 14% and 18% of the variance in SPPB function (p=.004) and PROMIS self-reported function (p=.02), respectively. Specifically, higher levels of psychological and health-related resilience were associated with greater physical function (all ps
Memory consolidation as an adaptive process

We rely on our long-term memories to guide future behaviors, making it adaptive to prioritize the retention of goal-relevant, salient information in memory. In this review, we discuss findings from rodent and human research to demonstrate that active processes during post-encoding consolidation support the selective stabilization of recent experience into adaptive, long-term memories. Building upon literatures focused on dynamics at the cellular level, we highlight that consolidation also transforms memories at the systems level to support future goal-relevant behavior, resulting in more generalized memory traces in the brain and behavior. We synthesize previous literatures spanning animal research, human cognitive neuroscience, and cognitive psychology to propose an integrative framework for adaptive consolidation by which goal-relevant memoranda are "tagged" for subsequent consolidation, resulting in selective transformations to the structure of memories that support flexible, goal-relevant behaviors.
Nonlinear flight physics of the Lie Bracket roll mechanism

In this paper, we review the concept of Lie brackets and how it can be exploited in generating motion in unactuated directions through nonlinear interactions between two or more control inputs. Applying this technique to the airplane flight dynamics near stall, a new rolling mechanism is discovered through nonlinear interactions between the elevator and the aileron control inputs. This mechanism, referred to as the Lie Bracket Roll Augmentation (LIBRA) mechanism, possesses a significantly higher roll control authority near stall compared to the conventional roll mechanism using ailerons only; it produces more than an order-of-magnitude stronger roll motion over the first second. The main contribution of this paper is to study the nonlinear flight physics that lead to this superior performance of the LIBRA mechanism. In fact, the LIBRA performance in free flight (six DOF) is double that in a confined environment of two-DOF roll-pitch dynamics. The natural feedback from the airplane motion (roll, yaw, and sideslip) into the LIBRA mechanism boosts its performance through interesting nonlinear interplay between roll and yaw, while exploiting some of the changes in the airplane characteristics near stall.
Transforming Traditional Labs into Virtual Computing Labs for Distance Education

Abstract---The demand for on-line courses continues to rise in academia because (1) on-line courses remove time barriers that would otherwise restrict a student from pursuing academic endeavors, (2) they remove the distance barriers for academia in reaching potential students and (3) they can to some extent alleviate budgetary and physical constraints on the academia in imparting education to students. The on-line instruction mode rather easily accommodates courses in some disciplines such as history, sociology, and political science. However, it posits significant adoption challenges for courses that require hands-on computing experimentation such as computer networking, system administration, web application development and database administration. Nevertheless, given the demand for on-line courses, there is a need to devise strategies that would allow students to conduct computing experiments through remote access. This paper presents an approach to transform traditional computer labs into a virtual lab environment. Such transformation allows students to remotely conduct experiments that involve software and hardware interaction. The methodology presented here can be applied to a large number of computing courses encountered in Management Information Systems and Computer Sciences disciplines.
Respiratory Mechanisms in the Flexibacteriaceae: Terminal Oxidase Systems of Saprospira grandis and Vitreoscilla Species

Particles from both Saprospira grandis and Vitreoscilla species, obtained by high-pressure extrusion and sonic treatment, respectively, actively catalyze the oxidation of reduced nicotinamide adenine dinucleotide (NADH) and succinate with O2. These activities are inhibited by cyanide but not by antimycin; Saprospira is also amytal- and rotenone-insensitive. Vitreoscilla preparations were unable to oxidize mammalian ferrocytochrome c and reduced tetramethyl-p-phenylenediamine, whereas the Saprospira preparations did so actively. Low-temperature (77 K) difference spectroscopy of Vitreoscilla cells and particles indicates the presence of three maxima in the cytochrome alpha-region at 554, 558, and 562 nm. All three cytochromes are active in NADH and succinate oxidation, but none is ascorbate reducible. Cytochrome o is the only CO-binding pigment present and is probably the terminal oxidase; it has properties similar to the cytochrome o isolated in solubilized form from this organism. Saprospira cells and membranes exhibit four cytochrome absorption bands whose maxima are at 550, 554, 558, and 603 nm at 77 K. The latter component has not been noted previously. NADH and succinate reduce all four cytochromes, but ascorbate reduces only the 550- and 603-nm pigments. CO spectra indicate the presence of cytochrome a,a3 which is probably the oxidase. A second CO-binding pigment is present which is not a peroxidase but may be a cytochrome.
Emotion Discourse, Social Cognition, and Social Skills in Children With and Without Developmental Delays

This study examined parent-child emotion discourse, children's independent social information processing, and social skills outcomes in 146 families of 8-year-olds with and without developmental delays. Children's emergent social-cognitive understanding (internal state understanding, perspective taking, and causal reasoning and problem solving) was coded in the context of parent-child conversations about emotion, and children were interviewed separately to assess social problem solving. Mothers, fathers, and teachers reported on children's social skills. The proposed strengths-based model partially accounted for social skills differences between typically developing children and children with delays. A multigroup analysis of the model linking emotion discourse to social skills through children's prosocial problem solving suggested that processes operated similarly for the two groups. Implications for ecologically focused prevention and intervention are discussed.
A Comparison of Experimental Observations and Numerical Predictions for the Initiation of Fiber Microbuckling in Notched Composite Laminates

The results of the present experimental study of fiber microbuckling indicates that free surfaces, ply orientations, and resin-rich regions affect the strain level for the initiation of in-plane fiber microbuckling. Nonlinear matrix constitutive behavior, in conjunction with initial fiber waviness, cause significant reductions of fiber microbuckling initiation strain level; these two factors generate nonlinear global stress-strain responses in the models. The fiber microbuckling initiation strains correlate well with the applied strain associated with asymptotic local shear strains.
An extended radix-based digital calibration technique for multi-stage ADC

A radix-based digital self-calibration technique for multi-stage analog-to-digital converter (ADC) is presented. This technique can correct errors due to capacitor mismatch and finite opamp gain. The equivalent radix of each stage is extracted by measuring the discontinuity on the ADC transfer curve and iteratively adjusting the equivalent radix to minimize this discontinuity. A much more accurate analog to digital conversion can be achieved by calculating the digital output based on these equivalent radices. While the principle is very similar to a method described previously, this technique can be applied to those ADCs having multiplying-digital-to-analog-converter (MDAC) with more widely used "capacitor-flip-over" structure. This can be seen as an extension to the previous method.
Quorum sensing: the explanation of a curious phenomenon reveals a common characteristic of bacteria.

In the 1960s bacterial bioluminescence attracted increasing interest among microbiologists and biochemists. Plating seawater samples taken from virtually any place on the globe revealed the presence of bioluminescent bacteria, but at a rather low level of abundance, not more than a few cells per milliliter. A question frequently raised was what function the light emission might have in such “free-living” planktonic bioluminescent bacteria. The question was even more compelling because the maximum light emission of these bacteria under ideal conditions in the laboratory is about 103 to 104 photons s−1 cell−1. Even at this level of luminescence, populations found free in seawater would produce nowhere near enough light to have physiological or ecological significance.
Information Theory of Stochastic Processes

The sections in this article are 1 Asymptotic Equipartition Property 2 Information Stability Property 3 Application to Source Coding Theory 4 Application to Channel Coding Theory 5 Final Remarks
Measurement Invariance, Factor Analysis and Factorial Invariance.

Several concepts are introduced and defined: measurement invariance, structural bias, weak measurement invariance, strong factorial invariance, and strict factorial invariance. It is shown that factorial invariance has implications for (weak) measurement invariance. Definitions of fairness in employment/admissions testing and salary equity are provided and it is argued that strict factorial invariance is required for fairness/equity to exist. Implications for item and test bias are developed and it is argued that item or test bias probably depends on the existence of latent variables that are irrelevant to the primary goal of test constructers.
Factors Affecting Sorghum and Corn Seed Predation by Foraging Red Imported Fire Ants (Hymenoptera: Formicidae)

A description of red imported fire ant, Solenopsis invicta (Buren), damage to corn, Zea mays L., and sorghum, Sorghum bicolor (L.), seeds is presented with results of laboratory experiments. Worker ants damaged seeds by rasping through the pericarp at the germ portion of seed and removing the embryo (germ). Occasionally, the pericarp was removed and/or the leaflet and root tissue were damaged. Only rarely was the endosperm consumed. Ants damaged dry seeds, but water-soaked or germinating seeds were damaged at a higher rate. When ants were offered flour of ground embryo and ground endosperm, the embryo portion was consumed more quickly. In simulated plantings, seeds with the embryo portion inaccessible to foraging S. invicta were rarely damaged. Numbers of seeds damaged during a limited exposure period were correlated with colony size in laboratory colonies. Colonies initially unresponsive to sorghum seeds and deprived of food or water increased their consumption of sorghum seeds relative to colonies receiving a normal schedule of artificial diet. Results confirm observations of fire ant damage in field situations.
Electron crystallography of the scrapie prion protein complexed with heavy metals.

The insolubility of the disease-causing isoform of the prion protein (PrPSc) has prevented studies of its three-dimensional structure at atomic resolution. Electron crystallography of two-dimensional crystals of N-terminally truncated PrPSc (PrP 27–30) and a miniprion (PrPSc106) provided the first insights at intermediate resolution on the molecular architecture of the prion. Here, we report on the structure of PrP 27–30 and PrPSc106 negatively stained with heavy metals. The interactions of the heavy metals with the crystal lattice were governed by tertiary and quaternary structural elements of the protein as well as the charge and size of the heavy metal salts. Staining with molybdate anions revealed three prominent densities near the center of the trimer that forms the unit cell, coinciding with the location of the β-helix that was proposed for the structure of PrPSc. Differential staining also confirmed the location of the internal deletion of PrPSc106 at or near these densities.
Strain-rate sensitivity index of thermoplastics

Strain-rate sensitivity index, m, values of several thermoplastics (HDPE, PP, PMMA, PS, PVC, PC, and PA) were determined at ambient temperature by both variable strain-rate and stressrelaxation methods. Specimens were loaded in tension in the elastic portion of the stress-strain curve at various strain rates and the load was recorded as a function of elongation. Index values were determined from the relation \(m = [\partial \ln (\sigma )]/[\partial \ln (\dot e)]_{e, T} \). Specimens were also loaded in tension at constant strain rate to the proportional limit, loading was halted, and the load was recorded as a function of time at constant strain. A numerical algorithm was implemented to minimize the root-mean-square difference between an empirical equation and the experimental data, i.e. $$\Phi (n, \tau ) = \left( {1/N\sum\limits_i {\{ P_o \exp [ - (t_i /\tau )^n ] - P(t_i )\} } ^2 } \right)^{1/2} $$
Characterization of PRMT1 from Plasmodium falciparum

3 during parasite development, suggesting that histone- arginine methylation may play a conserved role in chromatin- mediated gene regulation. Consistent with the presence of potential substrates in both the cytoplasm and nucleus, green fluorescent protein-tagged PfPRMT1 and untagged PfPRMT1 were localized in both cellular compartments, with the majority in the cytoplasm. In vitro assays showed that PfPRMT1 could be inhibited by several small-molecule inhibitors, with IC50- values in the sub-micromolar range. Most of these compounds also effectively inhibited parasite growth, suggesting that parasite PRMTs are promising targets for developing antiparasitic drugs.
Pressure Dependence of Ionic Conductivity in KCl, NaCl, KBr, and NaBr

The pressure dependence of the ionic conductivity of KCl, NaCl, KBr, and NaBr has been measured to 6 kbar in the intrinsic and extrinsic temperature regions. In the intrinsic region the conductivity deviates markedly from a simple exponential decrease with pressure. A detailed analysis, including contributions from anions and extrinsic cation vacancies, shows that pressure can suppress the intrinsic vacancies sufficiently to cause such a deviation. The analysis also shows that the uncertainties in the estimated activation volumes are greater than those determined in previous work. For KCl, NaCl, KBr, and NaBr crystals, respectively, the estimated activation volumes for motion of cation vacancies are 8 \ifmmode\pm\else\textpm\fi{} 1, 7 \ifmmode\pm\else\textpm\fi{} 1, 11 \ifmmode\pm\else\textpm\fi{} 1, and 8 \ifmmode\pm\else\textpm\fi{} 1 ${\mathrm{cm}}^{3}$/mole, and the activation volumes for formation of Schottky defects are 61 \ifmmode\pm\else\textpm\fi{} 9, 55 \ifmmode\pm\else\textpm\fi{} 9, 54 \ifmmode\pm\else\textpm\fi{} 9, and 44 \ifmmode\pm\else\textpm\fi{} 9 ${\mathrm{cm}}^{3}$/mole. The values for activation volumes of motion agree with predictions of the strain-energy model of Keyes. Schottky-defect-formation volumes are substantially larger than the molar volumes in KCl and NaCl, but in KBr and NaBr they are approximately equal.
Characterization and purification of bacteriophages using chromatofocusing

The technique of chromatofocusing was applied to the characterization and purification of three bacteriophages that are routinely used for testing virus filters: φX174, PR772, and PP7. Chemically well-defined eluent buffers were used, instead of the more commonly used chromatofocusing polyampholyte buffers. Chromatographic column packings were selected to minimize band broadening by confining bacteriophage adsorption solely to the exterior particle surface. Under the conditions used it was determined that bacteriophages could be made to focus into narrow bands in a retained pH gradient with recoveries of live phage that ranged from 15 to nearly 100% as determined by a plaque-forming assay. Retention times and apparent isoelectric point data were obtained for samples consisting either of purified bacteriophage, or samples consisting of crude preparations of bacteriophages containing host cell impurities. Isoelectric point estimates were obtained using modified, previously described models. The results obtained suggest that chromatofocusing is a simple and rapid method for obtaining approximate isoelectric points for bacteriophages and probably other types of viruses. It is also likely a useful method for purifying these materials.
CO2 dialysis in one chemoreceptor site, the RTN: stimulus intensity and sensitivity in the awake rat.

Abstract We stimulate single central chemoreceptor sites in the unanesthetized rat by focal microdialysis of artificial cerebrospinal fluid (aCSF) equilibrated with 25% CO2. Here, in the retrotrapezoid nucleus (RTN) we measured the focal stimulus intensity with a pH electrode adjacent to the dialysis probe. During 25% CO2 dialysis, RTN pH decreased by 0.069 (0.013, SEM) pH units (N=5), 44% of the change observed during 7% CO2 breathing, −0.157 (0.019) pH units (N=4). During 7% CO2 breathing, PaCO2 increased by 15 Torr (N=5). We calculate the ΔPaCO2 that would produce a ΔpH at the RTN approximately like that observed during 25% CO2 dialysis as 44% of 15 Torr, or 6.6 Torr ΔPaCO2. Using ventilatory response data from our lab, we estimate overall chemoreceptor sensitivity as 13% Δ V e /Torr ΔPaCO2 and RTN sensitivity as 3% Δ V e /Torr ΔPaCO2. The RTN provides 23% of the overall response. This may be an underestimate. During RTN stimulation PaCO2 decreases by 4.9 (0.7) Torr (N=5), which may inhibit other chemoreceptor sites. Multiple chemoreceptor sites may interact to provide high sensitivity in systemic hypercapnia and stability during heterogeneous stimulation and inhibition.
The Relative Merits of Average Cost Pricing, Marginal Cost Pricing and Price Discrimination

Introduction, 342. — I. Theoretical development, 343; constant cost, 344; decreasing cost, 345; increasing cost, 353. — II. Electric light and power industry, 355. — III. The railroads, 363. — IV. The telephone industry, 369. — V. Conclusion, 371.
Confirmatory Factor Structure of the Kaufman Assessment Battery for Children-Second Edition: Consistency with Cattell-Horn-Carroll Theory.

The Kaufman Assessment Battery for Children-Second Edition (KABC-II) is a departure from the original KABC in that it allows for interpretation via two theoretical models of intelligence. This study had two purposes: to determine whether the KABC-II measures the same constructs across ages and to investigate whether those constructs are consistent with Cattell-Horn-Carroll (CHC) theory. Multiple-sample analyses were used to test for equality of the variancecovariance matrices across the 3- to 18-year-old sample. Higher-order confirmatory factor analyses were used to compare the KABC-II model with rival CHC models for children ages 6 to 18. Results show that the KABC-II measures the same constructs across all ages. The KABC-II factor structure for school-age children is aligned closely with five broad abilities from CHC theory, although some inconsistencies were found. Models without time bonuses fit better than those with time bonuses. The results provide support for the construct validity of the KABC-II. Additional research is needed to more completely understand the measurement of fluid reasoning and the role of time bonuses on some tasks.
Effects of Constant and Fluctuating Temperatures on Developmental Rates and Demographic Statistics for the Corn Leaf Aphid (Homoptera: Aphididae)

Relationships between temperature and developmental rate of immature apterous and alate corn leaf aphids, Rhopalosiphum maidis (Fitch), were studied in the laboratory at constant and fluctuating temperatures. Estimates of lower (6.1°C) and upper (26.3°C) thresholds for development were determined from studies done at constant temperatures. Developmental rates were determined and demographic statistics estimated for cohorts of corn leaf aphids exposed to fluctuating temperature regimes that simulated average and extreme low and high temperature conditions during late spring in eastern South Dakota. For cohorts exposed to fluctuating temperatures, degree-day (DD) summations using lower and upper developmental thresholds were consistent with expected DD requirements derived from constant temperature studies of development. Demographic statistics expressed on a DD time scale differed among cohorts of apterous and alate corn leaf aphids exposed to identical temperature regimes. For each temperature regime, the intrinsic rate of increase of apterae exceeded that of alatae. However, temperature had a negligible effect on potential population growth rates of either morph. Stable in star distributions for apterous corn leaf aphid cohorts were only slightly affected by temperature; approximately 57, 19, 10, 6, and 8%of each cohort were first, second, third, and fourth instars and adults, respectively.
Cloning, characterization, and engineering of fungal L-arabinitol dehydrogenases

L-Arabinitol 4-dehydrogenase (LAD) catalyzes the conversion of L-arabinitol to L-xylulose with concomitant NAD+ reduction in fungal L-arabinose catabolism. It is an important enzyme in the development of recombinant organisms that convert L-arabinose to fuels and chemicals. Here, we report the cloning, characterization, and engineering of four fungal LADs from Penicillium chrysogenum, Pichia guilliermondii, Aspergillus niger, and Trichoderma longibrachiatum, respectively. The LAD from P. guilliermondii was inactive, while the other three LADs were NAD+-dependent and showed high catalytic activities, with P. chrysogenum LAD being the most active. T. longibrachiatum LAD was the most thermally stable and showed the maximum activity in the temperature range of 55–65°C with the other LADs showed the maximum activity in the temperature range of 40–50°C. These LADs were active from pH 7 to 11 with an optimal pH of 9.4. Site-directed mutagenesis was used to alter the cofactor specificity of these LADs. In a T. longibrachiatum LAD mutant, the cofactor preference toward NADP+ was increased by 2.5 × 104-fold, whereas the cofactor preference toward NADP+ of the P. chrysogenum and A. niger LAD mutants was also drastically improved, albeit at the expense of significantly reduced catalytic efficiencies. The wild-type LADs and their mutants with altered cofactor specificity could be used to investigate the functionality of the fungal L-arabinose pathways in the development of recombinant organisms for efficient microbial L-arabinose utilization.
Concanavalin A binding to rod outer segment membranes: Usefulness for preparation of intact disks

Abstract Centrifugation of bovine rod outer segments in a continuous metrizamide [2-(3-acetamido-5-N-methylacetamido-2,4,6-triiodobenzamido)-2-deoxy- d -glucose] gradient resulted in the separation of two outer segment bands. The lower (higher-density) band was stained very extensively with the fluorescent marker didansyl- l -cystine but the upper (lower-density) band was stained only weakly. This was interpreted to indicate that the outer segments in the upper band are closed, while those in the lower band are open or leaky. The closed outer segments were found to bind to concanavalin A Sepharose beads. The binding was inhibited by α-methylmannoside. The disks were released from closed outer segments by incubation in 5% Ficoll and chromatographed on a concanavalin A Sepharose column. Essentially all disks were collected in the void volume of the column; less than 10% of the disks loaded were eluted with α-methylmannoside. If the disks were freeze-thawed and placed on the column, however, a considerable fraction of the disks became capable of binding to the column. We interpreted the results to indicate that the concanavalin A binding sites of intact disks are located on the internal surface and are exposed by freezethawing. This was confirmed by the binding of concanavalin A-ferritin to freeze-thawed disks but not to intact disks. Photic bleaching of rhodopsin did not alter the binding properties of outer segment and disks. Sonication or hypotonic disruption of disks would produce a heterogeneous population of membrane vesicles with respect to size and sidedness. However, most of the vesicles eluted from a concanavalin A Sepharose column were collected in the void volume. The purified vesicles would have the same membrane sidedness as intact disks. The procedure described in this paper therefore provides a simple method for the preparation of intact disks and the membrane vesicles with the concanavalin A binding sites on the internal surface.
Novel microfabricated device to measure hormone/neurotransmitter release with millisecond temporal resolution

We are developing a novel readout for secretion of hormones and neurotransmitter on micro/nanofabricated chips. Traditional biochemical assays of signaling molecules secreted from cells are slow, cumbersome and have at best, a temporal resolution of several seconds. On the other hand, electrochemical measurement of hormone or transmitter secretion can obtain millisecond temporal resolution if the diffusion distance between the release site on the cell and the working electrode is within 1 micron. Carbon fiber microelectrodes can have millisecond time resolution, but can only measure release form a small fraction of the cell surface. We have fabricated arrays of Au electrodes in wells micromachined on the surface of silicon microchips. Each well/microelectrode roughly conforms to the shape of a single cell in order to capture release forma large fraction of the surface area of each cell with minimal diffusional delays. This paper will present details of the microfabrication process flow as well a initial results demonstrating millisecond-resolution measurement of catecholamine secretion form adrenal chromaffin cells. Our goal for this project is to develop enabling technology for massively parallel systems on a chip such as cell-based biosensors to detect neurotoxins and high-throughput assays of drugs that affect neurotransmitter release.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Characterizing link connectivity for opportunistic mobile networking: Does mobility suffice?

With recent drastic growth in the number of users carrying smart mobile devices, it is not hard to envision opportunistic ad-hoc communications taking place with such devices carried by humans. This leads to, however, a new challenge to the conventional link-level metrics, solely defined based on user mobility, such as inter-contact time, since there are many constraints including limited battery power that prevent the wireless interface of each user from being always `on' for communication. By taking into account the process of each user's availability jointly with mobility-induced contact/inter-contact process, we investigate how each of them affects the link-level connectivity depending on their relative operating time scales. We then identify three distinct regimes in each of which (1) the so-called impact of mobility on network performance prevails; (2) such impact of mobility disappears or its extent is not that significant; (3) the user availability process becomes dominant. Our findings not only caution that mobility alone is not sufficient to characterize the link-level dynamics, which in turn can lead to highly misleading results, but also suggest the presence of many uncharted research territories for further exploration.
Regulation of ethylene biosynthesis in climacteric apple fruit by elevated CO2 and reduced O2 atmospheres

Abstract Autocatalytic (System II) C 2 H 4 biosynthesis in climacteric ‘Golden Delicious’ apples ( Malus domestica Borkh) was effectively inhibited at 20°C by atmospheres of 20% CO 2 -enriched air (17% O 2 + 63% N 2 ) or 0.25% O 2 (balance N 2 ). In vitro 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACC-S) activity of apples held in atmospheres of air + 20% CO 2 or 0.25% O 2 was significantly inhibited when compared to apples kept in air, and correlated well with fruit C 2 H 4 production rates. In vivo and in vitro ACC oxidase (ACC-O) activity of fruit held in atmospheres of air, air + 20% CO 2 or 0.25% O 2 were similar when the assays were performed under standard assay conditions (i.e., in vivo assay performed in air, in vitro assay performed in air + 6% CO 2 ). However, if the in vivo or in vitro ACC-O enzyme activity assays were performed in an atmosphere of 0.25% O 2 , ACC-O catalytic competency and activity were significantly reduced. When the in vivo or in vitro ACC-O enzyme activity assays were performed in an atmosphere of air + 20% CO 2 , ACC-O enzyme activity was actually stimulated. These data indicate that elevated levels of CO 2 do not inhibit ACC-O catalytic competency. Western blot analysis revealed that ACC-O protein abundance was not significantly affected by any of the treatments tested, and only the 0.25% O 2 atmosphere significantly inhibited ACC-O activity. ACC-S activity was significantly reduced by atmospheres of air + 20% CO 2 or 0.25% O 2 but not via direct inhibition of ACC-S catalytic competency.
The bacterial origin of rat breath pentane.

Abstract Vitamin E-deficient rats or rats subjected to other conditions thought to lead to peroxidation of tissue lipids produce pentane and other hydrocarbon gases in the breath. However, pentane production is found to depend on the linoleate content of the recent diet. It is decreased or eliminated by inclusion of ascorbic acid in the food or water, by removal of linoleate from the diet, by starvation and by the antibiotic, clindamycin. It is enhanced by feeding linoleate hydroperoxide or by removal of vitamin E from the diet for a short period. These findings lead to the conclusion that the major source of pentane is not membrane lipid peroxidation but is from the action of intestinal bacteria on linoleate hydroperoxide.
Large scale underwater FDTD ELF simulations using Acceleware and MPI parallel processing

Very large FDTD simulations are being developed to determine the underwater propagation of EM signals at ELF frequencies. Two different approaches are being use to handle the large computation spaces, the use of hardware and software by Acceleware, and the use of the Message Passing Interface (MPI) for parallelization.
Structural Dynamic Considerations for a Hydrocode Analysis of Hypervelocity Test Sled Impacts

Numerical analysis of a hypervelocity test sled configuration has been accomplished with structural dynamic analysis and hydrocode analysis for investigating hypervelocity gouging. Previous studies have considered these two aspects of the system primarily apart from each other. It is desired to obtain numerical analysis of hypervelocity gouging that applies directly to a given test sled configuration. An improved analysis may be obtained for this purpose by applying structural dynamic considerations to the hydrocode analysis of slipper impacts on a rail. The primary objective of improving the input model for the hydrocode analysis is to simulate actual field conditions, such as sliding impacts with rail misalignments and on coated rails. The CTH hydrocode input model is adjusted by the addition of an artificial mass to simulate the test sled mass. Three-dimensional impacts are considered in the context of two-dimensional plane strain conditions. Shock reflections are also considered, and the results for sliding impact with a rail misalignment are discussed. The numerical results indicate characteristics seen in field gouges such as jetting and high-temperature effects.
Unusual infectious complications of dermatologic procedures

Because dermatologic procedures disrupt skin integrity, they alter the body's protective barrier and predispose individuals to cutaneous infection. Postoperative wound infections--even with common pathogens such as S. aureus--seldom complicate dermatologic procedures; however, unusual infections have been reported to complicate excisions, biopsies, skin grafts, chemical peels, dermabrasion, laser resurfacing, liposuction, blepharoplasty, and injections (eg, with anesthetic solutions or botulinum toxin). Numerous environmental and patient risk factors increase the rate of postoperative wound infections, but otherwise healthy individuals undergoing relatively simple procedures are sometimes affected. Obtaining a thorough patient, history (including history of prior HSV infection or any immunocompromising factors) is crucial. Patients should be warned of potential complications, particularly when they are undergoing cosmetic procedures. It is important to maintain a high index of suspicion for possible wound infection in all patients that extends several months postoperatively. Manifestations of unusual postoperative infections are highly variable, and they might be secondary to bacterial, fungal, viral, or parasitic pathogens. Bacterial lesions are often polymicrobial, and bacterial superinfection can exacerbate other wound complications such as HSV reactivation. Most wound infections remain localized, but occasionally systemic disease occurs. For example, cutaneous diphtheria or rapidly growing mycobacteria rarely disseminate, whereas TSS results in systemic disease caused by toxin release. Some unusual postsurgical infections are self-limited, but they can still be potentially life threatening or disfiguring. Antimicrobial prophylaxis might reduce the risk of wound infection in some cases. Clinicians can better care for patients by becoming familiar with the causes and clinical manifestations of unusual dermatologic postoperative wound infections (Table 1). Following the recognition of an infectious process, appropriate diagnostic procedures allow for pathogen identification and the prompt institution of indicated therapy.
Spectroelectrochemical evidence for imine-alcohol intermediate formed upon electrochemical oxidation of uric acid

Abstract Electrochemical oxidation of uric acid in phosphate-containing supporting electrolytes between pH 3–9 at a reticulated vitreous carbon electrode in a thin-layer spectroelectrochemical cell leads to formation of U.V.-absorbing intermediate species. Electrochemical reduction of the intermediate-containing solution leads to the partial regeneration of uric acid. This behavior provides compelling evidence that an imine-alcohol is one of the U.V.-absorbing intermediate species since only this compound may be expected to be reduced to a species which can regenerate uric acid.
Mother, Child, Race, Nation: The Visual Iconography of Rescue and the Politics of Transnational and Transracial Adoption

‘Third World’ poverty and hunger conjures up certain conventionalised images: thin children, with or without their mothers. This paper explores the genealogy of such images in the mid-twentieth century, and shows how they mobilise ideologies of ‘rescue’ while pointing away from structural (political, military and economic) explanations for poverty, famine and other disasters. These images had a counterpart in practices of transnational and transracial adoption, which became the subject of debate in the USA during the 1940s, 1950s and 1960s, and were at least as much about symbolic debates over race as the fate of particular children. Together, these visual and familial practices made US foreign and domestic poverty policy intelligible as a debate over whether to save women and children. When they cast the USA as rescuer, they made it all but impossible to understand what US political, military or economic power had to do with creating the problem.
Invariants in auditory frequency relations.

A group theoretic description of auditory frequency is shown to have important implications for understanding invariants in sound patterns. Frequency can be mathematically conceived in terms of a logarithmic spiral which involves two generative group parameters. The spiral representation not only underlies the logarithmic relationship between the frequency of a tone and its stated musical pitch but it affords an objective basis for invariants that summarize other well-known auditory relationships including distinctions which involve different tuning systems. The spiral analysis represents a new and potentially useful tool for describing auditory invariants with important implications for emerging theories of music perception and issues in psychophysical scaling of tonal patterns.
The impact of bone size on broadband ultrasound attenuation.

Abstract Quantitative ultrasound (QUS) is a simple, inexpensive and radiation-free technique to study skeletal status in osteoporosis. Broadband ultrasound attenuation (BUA) is typically used without normalizing for bone thickness. We investigated the impact of bone thickness on BUA, both in in vitro and in vivo , using commercially available ultrasound scanners (Walker Sonix UBA 575 and 575+). For the study in vitro , we analyzed 12 paired cubes (12 × 12 × 12 mm 3 ) of bovine trabecular bone cut from six “parent” blocks (24 × 12 × 12 mm 3 ). These “parent” blocks showed a fairly homogeneous structure as assessed by conventional radiography. BUA and dual x-ray absorptiometry (DXA) measurements of bone mineral density (BMD) were obtained. The difference between the paired cubes was significant for BUA ( p p > 0.05). The BUA of the “parent” blocks was larger by 32–92% than the average BUA of the corresponding paired cubes, and always less than the sum of the paired cubes (5–34%). BUA thus added up in a complex and nonlinear fashion. Measurements in vivo of the calcaneal bone width demonstrated on radiographs (study in vivo I, 28 postmenopausal women) and CT images (study in vivo II, 17 women) showed a small, positive but not significant correlation with BUA ( r 2 = 0.13 and r 2 = 0.007, p > 0.05). The magnitude of this effect provides further evidence that BUA does not scale linearly with bone size. Our results indicate that simple normalization of BUA data by specifying the results in decibels per megahertz per millimeter units may not be appropriate. The impact of bone size on BUA in vivo is relatively small, introducing errors of less than 1–10% for typical variability of calcaneal width of 2.8–3.0 mm. Unless marked variability of calcaneal bone width is encountered (e.g., in pediatric units) bone thickness represents only a minor source of accuracy errors for BUA.
Fourier Transform Infrared Absorption Study of Hexa(hexylthio)triphenylene: A Discotic Liquid Crystal

Abstract We have used Fourier transform infrared absorption spectroscopy to study the molecular motions of hexa(hexylthio)triphenylene as a function of temperature. Our measurements show pronounced changes in the CH3 stretching mode frequencies at the K → H transition. (The H phase displays long range incommensurate helical order). However, the CH2 stretching mode frequencies show much less variation with temperature, suggesting that only the ends of the alkyl tails undergo much change in the different phases. The CH bending and benzene stretching vibrations show a change in the frequency-temperature dependence at both the K → H and the H → Dhd transitions. There is no observable change in the spectrum in going from the Dnd to the 1 phase. We also present detailed syntheses for hexa(hexyl-thio)triphenylene and its C5 and C7 homologs. Physics Abstracts Classification: 64.70.M, 61.30.E, 33.20.E, 78.30.