cssi/SciSciGPT-SciSciNet huggingface dataset:
Diffusionally accommodated interfacial sliding in metal-silicon systems

The kinetics and mechanism of diffusionally accommodated interfacial sliding (interfacial creep) under far-field shear and normal stresses was studied, based on diffusion-bonded Al-Si-Al sandwich specimens. A previously developed interfacial creep law [Funn and Dutta, Acta Mater 1999; 47: 149], which proposed that interfaces may slide via interface-diffusion controlled diffusional creep, was experimentally validated by carrying out a systematic parametric study. In agreement with the model, the Si-Al interfaces slid via diffusional creep (n = 1) under the influence of an effective shear stress, which depends on the far-field shear and normal stresses, as well as the interfacial topography. Compressive stresses acting normal to the interface lowered the effective shear stress, resulting in a threshold effect, thus reducing the sliding rate. The rate of sliding was controlled by diffusional mass transport through a thin amorphous, O-rich interfacial layer, under the influence of local interfacial stress gradients, which arose due to the topological features of the interface. Instances of interfacial sliding in the absence of interfacial de-cohesion, which have been noted in composites, thin-film systems, etc., may be explained by the present mechanism, which also offers an alternative rationalization of threshold behavior during diffusional flow (besides interface-reaction control).
Late Results of Homotransplantation of the Lung in Dogs

SUMMARY Of 37 animals subjected to one of four treatment programs to alter immunologic mechanism, nine survived longer than three months. Four animals remain alive 15 to 29 months after transplantation. No animal now has significant function of the homotransplanted lung.
Computational study of the chair–chair interconversion and stereoelectronic interactions in 1,2,3‐trithiacyclo‐hexane (1,2,3‐trithiane)

Ab initio theory, density functional theory (DFT) and Moller–Plesset perturbation theory (MP2) with the 6–31G(d), 6–31++G(d), 6–31G(d,p), 6–31+G(d,p), 6–31++G(d,p), 6–311G(d,p) and 6–311+G(d,p) basis sets were used to study stereoelectronic hyperconjugative interactions and the mechanism of the chair–chair conformational interconversion in 1,2,3-trithiacyclohexane (1,2,3-trithiane). The relative energies, enthalpies, entropies, free energies and structural parameters of the chair, 1,4-twist and 2,5-twist conformers, a distorted 1,4-boat transition state and a 2,5-boat transition state were calculated. The HF calculated energy difference (ΔE) between the chair conformer of 1,2,3-trithiane and the distorted 1,4-boat transition state was 10.59 kcal mol−1 (1 kcal=4.184 kJ). The 1,4-twist conformer and the 2,5-boat transition state are close in energy, as are the 2,5-twist conformer and the distorted 1,4-boat transition state. B3LYP/6–311+G(d,p) calculated the chair conformer of 1,2,3-trithiane to be 5.83, 10.09, and 5.96 kcal mol−1, respectively, lower in energy than the 1,4-twist conformer, 2,5-twist conformer and 2,5-boat transition state. Intrinsic reaction coordinate (IRC) calculations were used to connect the transition state between the chair conformer and the 1,4-twist conformer. B3LYP/6–31+G(d,p) and B3LYP/6–311+G(d,p) calculated this transition state to be 14.25 kcal mol−1 higher in energy than the chair conformer. In the chair conformer, the respective C4—H and C6—H bond lengths are equal, but the C5—Heq bond is longer than the C5—Hax bond. In the 1,4-twist conformer, the C4—Hiso bond lengths are equal, the C5—Hψeq bond is longer than the C5—Hψax bond and the C6—H bond lengths are equal. In the 2,5-twist conformer, equal C—H bond lengths are found at C4 and at C5, but the C6—Hψeq bond is longer than the C6—Hψax bond. Copyright © 2003 John Wiley & Sons, Ltd. Additional material for this paper is available in Wiley Intersciene
A Test of the Efficacy of an Information Literacy Lesson in an Introductory Biology Laboratory Course with a Strong Science-Writing Component

Competency in science information literacy is an objective of most undergraduate biology programs and increasingly important in freshman introductory courses. We implemented a controlled study to test the efficacy of a single, information literacy lesson at the beginning of the semester in an introductory biology laboratory course with embedded writing components. We examined effects of this pedagogical manipulation by comparing laboratory sections that received the lesson with those that did not. We found that skills related to the identification of primary or secondary sources and use of proper citation format were higher in those sections that received a single literacy lesson in the semester-long course. Additionally, one year after the course, students who completed the course showed better mastery of information literacy skills compared to students who did not take the laboratory course. We used results from this controlled study to inform curriculum content decisions in our introductory biology cou...
Arrhythmias during Intracardiac Catheterization

This paper summarizes the incidence of various arrhythmias in an unselected series of cardiac catheterizations and presents evidence for their reflex origin in some instances. The hazards are discussed and comments made about prophylaxis and treatment.
Organization of the photosynthetic membrane in maize mesophyll and bundle sheath chloroplasts

The freeze-fracturing technique has been used to investigate membrane architecture in the mesophyll and bundle sheath chloroplasts of Zea mays. The structural organization of mesophyll chloroplasts is virtually identical to that of other species of higher plants which have been investigated with this technique. Characteristic distributions of particles of various sizes are seen on each fracture face after membrane splitting during the fracturing process, and these distributions indicate the differentiation of the membrane system into sacked (grana) and unstacked (stroma) regions, typical of grana-containing chloroplasts. Bundle sheath chloroplasts contain very few grana, and the thylakoids of these plastids are therefore largely unstacked. Analysis of artificially unstacked mesophyll chloroplasts indicates that this difference is not merely related to the presence or absence of adhesion between adjacent thylakoids, but reflects a substantial difference in membrane substructure between mesophyll and bundle sheath photosynthetic membranes. Bundle sheath thylakoids contain virtually the same number of small (P fracture face) particles as mesophyll thylakoids, but contain only 40% as many of the larger (E fracture face) tetrameric particles. These differences, together with biochemical data indicating the comparative deficiency of bundle sheath chloroplasts in Photosystem II activity, suggest that the E face particles are related to the presence or absence of Photosystem II activity.
The Influence of Symbols and Equations on Understanding Mathematical Equivalence

Students with mathematics difficulty demonstrate lower mathematics performance than typical-performing peers. One contributing factor to lower mathematics performance may be misunderstanding of mat...
Formation of a single base mismatch impedes spontaneous DNA branch migration.

Abstract DNA branch migration, a process whereby two homologous DNA duplexes exchange strands, is an essential component of genetic recombination. Models for homologous recombination have invoked spontaneous branch migration as one mechanism for the generation of large regions of heteroduplex DNA. During recombination, two homologous parental duplexes that contain similar, but not identical, sequences are paired and undergo strand exchange. An important issue is whether spontaneous branch migration is capable of traversing sequence heterology such as mismatches, insertions and deletions. We use a model four strand system to examine the effect of mispaired or unpaired bases on branch migration. The assay consists of annealing two short duplexes having defined sequence heterologies. Following annealing, a Holliday junction is formed that is free to branch migrate. Our results demonstrate that a single base mismatch, insertion or deletion is sufficient to pose a substantial barrier to spontaneous branch migration. In the presence of magnesium, branch migration through such sequence heterologies is almost completely blocked. Others have shown that non-mobile four-way junctions undergo a dramatic shift in conformation in the presence of magnesium. Our data suggest that a similar transition occurs for the mobile Holliday junction. We also discuss how proteins may facilitate branch migration through sequence heterologies in vivo.
Towards quantitative prediction of aerosol deposition from turbulent flows

Abstract Predictions of aerosol deposition rates from turbulent flow using computational fluid dynamics simulations have been compared with experimental data. The influence of turbulence model choice has been assessed. The use of isotropic turbulence models resulted in over-prediction of V + by more than 3 orders of magnitude for τ + ∼ 0.2 , whilst the anisotropic RSM gave results in good agreement with experiment. For τ + > 10 ( d p ∼ 10 μ m for Re = 9894 ) there was little difference between the turbulence models. Simulations for both Re = 9894 and 50,000 were carried out and good performance was seen for both. The effect of drag model was assessed and resulted in little difference in predicted deposition velocity. The influence of grid resolution was also investigated and it was seen that the cell centre of the wall-adjacent cell should be at a distance of y + = 2 or less for quantitative prediction of deposition. Coarser grids resulted in over-prediction for low τ + .
Anti-viral effector T cell responses and trafficking are not dependent upon DRAK2 signaling following viral infection of the central nervous system.

The signaling events involved in T cell trafficking into the central nervous system (CNS) following viral infection are not fully understood. Intracerebral infection of mice with mouse hepatitis virus (MHV) results in an acute encephalomyelitis followed by an immune-mediated demyelinating disease. Although chemokine signaling is critical in promoting T cell infiltration into the CNS and control of viral replication, additional signaling pathways have not been completely explored. DRAK2, a lymphoid-restricted serine/threonine kinase, prevents spurious T cell activation. Yet Drak2− / − mice are resistant to MOG-induced experimental autoimmune encephalomyelitis (EAE), suggesting that DRAK2 may influence T cell trafficking into the CNS. In order to further characterize the molecular mechanisms governing T cell activation and accumulation within the CNS in response to viral infection, MHV was instilled into the CNS of Drak2− / − mice. Drak2-deficient T cells possessed no obvious defects in trafficking into the...
Factors affecting the shelf stability of sunflower nuts

Dehulled, raw, whole sunflower kernels of high-oleic acid (HOA) and high-linoleic acid (HLA) types were shelf-stable at 23 and 37°C for over one year. Dry-roasted HOA kernels were more stable than dry-roasted HLA kernels. Oilroasted HLA kernels were more stable than dry-roasted ones. Stability of roasting oil and storage temperature had no appreciable effect on shelf stability of kernels.
Empirical agent based models of cooperation in public goods games

Agent-based models are a popular way to explore the dynamics of human interactions, but rarely are these models based on empirical observations of actual human behavior. Here we exploit data collected in an experimental setting where over 150 human players played in a series of almost a hundred public goods games. First, we fit a series of deterministic models to the data, finding that a reasonably parsimonious model with just three parameters performs extremely well on the standard test of predicting average contributions. This same model, however, performs extremely poorly when predicting the full distribution of contributions, which is strongly bimodal. In response, we introduce and test a corresponding series of stochastic models, thus identifying a model that both predicts average contribution and also the full distribution. Finally, we deploy this model to explore hypotheses about regions of the parameter space outside of what was experimentally accessible. In particular, we investigate (a) whether a previous conclusion that network topology does not impact contribution levels holds for much larger networks than could be studied in a lab; (b) to what extent observed contributions depend on average network degree and variance in the degree distribution, and (c) the dependency of contributions on degree assortativity as well as the correlation between the generosity of players and the degree of the nodes to which they are assigned.
Kinetics of Oily Soil Release

The kinetics of detergency of liquid and mixed (liquid-solid) oily soil from cellulosic and synthetic fabrics has been investigated. A three-step soil-release mechanism is postulated involving (a) an induction period during which soil re moval is slow, (b) a rapid soil-removal period during which the amount of soil retained decreases linearly with the loga rithm of washing time, and (c) a final period during which soil retention is essentially constant. The soil-release rate is related to the diffusion rate of water into the soiled fabric. The ability of a fabric to release soil is not related to the rate at which the liquid front of a hydrophilic liquid (water, an aqueous detergent, ethylene glycol, etc) advances on the unsoiled fabric, but to the diffusion of water into the entire capillary system of the fabric. Diffusion of water into the fiber bundle facilitates soil release. Studies were made of the release of oily soil as affected by amount of soil (0.7-87% owf), wash temperature, agitation, and vis...
Children's attitudes toward the mentally ill: a developmental analysis.

For 577 children, Grades K through 8, attitudes toward mental illness and mentally ill persons relative to other stigmatized groups were measured on a projective measure of social distance. Attitudes toward deviant groups were evidenced by kindergarten and did not change appreciably with increasing age/grade. Across the grades assessed, four distinct and consistent concept groupings emerged. From the most to least preferred they were (1) normal, (2) physically handicapped, (3) mentally ill, mentally retarded, and emotionally disturbed, and (4) convict and crazy. Attitudes of kindergarten children were strikingly similar to those of peers in Grade 8. Crazy people (synonymous with the professional-technical term mental illness) are apparently regarded with the same fear, distrust, digust, and aversion by children and adults alike.
Ages of travertine deposits in eastern Grand Canyon National Park, Arizona

Travertine deposits in eastern Grand Canyon National Park, Arizona, are inferred to have formed under conditions of effective wetness that were greater than present. Uranium-series dating of 17 samples indicates that the deposits formed at about 15,000, 71,000, 111,000, 171,000, and 338,000 yr B.P. Intervals of travertine deposition are essentially contemporaneous with dated high paleolake levels, montane glacial maxima, and high paleowater-table levels from several Great Basin localities.
Designability of Graphitic Cones

Abstract : We show that, with topologically flexible seeds which are allowed to explore different growth modes, graphitic cones are inherently more "designable" than flat graphitic disks. The designability of a structure is the number of seed topologies encoding that structure. We illustrate designability with a simple model, where graphite grows onto C(n) (5<n<3O) ring seeds. For a wide range of ring sizes, cones are the most likely topological outcome. Results from the model agree well with data from special cone-rich carbon black samples. The concept of designability allows entropy to be incorporated into the "pentagon road" model of the formation of curved graphitic structures.
Pharmacokinetic comparison of 5 g of azlocillin every 8 h and 4 g every 6 h in healthy volunteers.

To compare the multiple-dose pharmacokinetics of two dosage regimens of azlocillin, we studied 12 healthy volunteers via a randomized, crossover design with a 2-week washout phase between regimens. Serum and urine samples were collected for 8 h following the fifth dose of a regimen of 4 g every 6 h and the fourth dose of a regimen of 5 g every 8 h. Data for concentrations in serum were fitted to a two-compartment open model by nonlinear regression. Statistically significant differences (P less than 0.05) were observed in the following parameters (mean +/- standard deviation) for the 4- and 5-g regimens, respectively: area under the serum concentration-time curve during the dosing interval, 592 +/- 140 versus 772 +/- 151 micrograms.h/ml; terminal elimination rate constant, 0.5364 +/- 0.0912 versus 0.4758 +/- 0.0486 h-1; renal clearance, 87.6 +/- 16.1 versus 76.1 +/- 13.5 ml/min; maximum drug concentration in serum, 381 +/- 89 versus 473 +/- 90 micrograms/ml; and minimum drug concentration in serum, 19 +/- 10 versus 8 +/- 4 micrograms/ml. No significant differences were seen in the following parameters: V1, V beta, k10, k12, k21, total systemic clearance, and nonrenal clearance. These data support the presence of saturable renal elimination of azlocillin, as well as the feasibility of an 8-h dosing interval.
Gαo and Gαq regulate the expression of daf-7, a TGFβ-like gene, in Caenorhabditis elegans.

Caenorhabditis elegans enter an alternate developmental stage called dauer in unfavorable conditions such as starvation, overcrowding, or high temperature. Several evolutionarily conserved signaling pathways control dauer formation. DAF-7/TGFβ and serotonin, important ligands in these signaling pathways, affect not only dauer formation, but also the expression of one another. The heterotrimeric G proteins GOA-1 (Gαo) and EGL-30 (Gαq) mediate serotonin signaling as well as serotonin biosynthesis in C. elegans. It is not known whether GOA-1 or EGL-30 also affect dauer formation and/or daf-7 expression, which are both modulated in part by serotonin. The purpose of this study is to better understand the relationship between proteins important for neuronal signaling and developmental plasticity in both C. elegans and humans. Using promoter-GFP transgenic worms, it was determined that both goa-1 and egl-30 regulate daf-7 expression during larval development. In addition, the normal daf-7 response to high temperature or starvation was altered in goa-1 and egl-30 mutants. Despite the effect of goa-1 and egl-30 mutations on daf-7 expression in various environmental conditions, there was no effect of the mutations on dauer formation. This paper provides evidence that while goa-1 and egl-30 are important for normal daf-7 expression, mutations in these genes are not sufficient to disrupt dauer formation.
A Modified Diffusion Method for the Determination of Urinary Fluoride

Abstract A modified diffusion method for the determination of urinary fluoride is described. Recovery of added fluoride is accurate to ±0.5 μg/ml within the range of 2 to 12 μg/ml of urine. The method is simple to use and is suggested for trial as a screening test in industry.
Solid state fermentation of broiler litter for production of biocontrol agents.

Abstract Several varieties of heat-sterilized broiler litter with 60% (wet basis, wb) moisture content were substrate in solid-state fermentations to produce biocontrol agents. Litter varieties included litter produced by one flock of broilers from medicated and non-medicated controlled rations, and litter produced by two flocks and four flocks on a single application of bedding material from medicated commercial sources. Litter preparations were inoculated with monocultures of Bacillus thuringiensis serovar japonensis strain Buibui, a pathogen of Japanese beetle larvae (Popillia japonica), or Pseudomonas fluorescens 2-79. B. thuringiensis did not grow in unextracted 1-flock litter nor in water extracted litter, but grew in methanol extracted litter to 5×1010 cell forming units (CFU)/g litter (dry weight, dw) and a spore count of 1×10 10 CFU / g litter (dw). B. thuringiensis also grew in unprocessed 2-flock and 4-flock litter, achieving cell counts of 3×109 and 1×10 9 CFU / g litter (dw), respectively, and spore counts of 1×10 9 CFU / g litter (dw). P. fluorescens grew in medicated 1-flock litter with no extraction to a cell density greater than 4×10 11 CFU / g litter (dw). Bioassays in soil containing over 0.5% (db) litter fermented with B. thuringiensis resulted in over 90% mortality in 21 days for first instars of Japanese beetle when compared to a control treatment using compost without fermented litter. The investigations demonstrate that bacterial biocontrol agents produced via solid substrate fermentations using broiler poultry litter have potential in biocontrol applications in the soil environment.
From Representative Democracy to Participatory Competitive Authoritarianism: Hugo Chávez and Venezuelan Politics

The study of Latin American politics has always generated great new research questions, and within Latin America, no country's experience has generated more interesting questions than Venezuela since the election of Hugo Chavez in 1998. Contemporary Venezuela raises fascinating questions about the collapse of a highly institutionalized party system and the erosion or breakdown of what had been the third-oldest democracy outside of the advanced industrial democracies. What accounts for these stunning developments? What can we learn from them? These issues go to the core of important developments in Latin American politics, and they are major issues for comparative political scientists beyond Latin America.
Structural characterization of human histidine triad nucleotide‐binding protein 2, a member of the histidine triad superfamily

The histidine triad proteins (HITs) constitute a large and ubiquitous superfamily of nucleotide hydrolases. The human histidine triad nucleotide-binding proteins (hHints) are a distinct class of HITs noted for their acyl-AMP hydrolase and phosphoramidase activity. The first high-resolution crystal structures of hHint2 with and without bound AMP are described. The differences between hHint2 and previously known HIT family protein structures are discussed. HIT family enzymes have historically been divided into five classes based on their catalytic specificity: Hint, fragile HIT protein, galactose-1-phosphate uridylyltransferase, DcpS and aprataxin. However, although several structures exist for the enzymes in these classes, the endogenous substrates of many of these enzymes have not been identified or biochemically characterized. To better understand the structural relationships of the HIT enzymes, a structure-based phylogeny was constructed that resulted in the identification of several new putative HIT clades with potential acyl-AMP hydrolase and phosphoramidase activity. Database Atomic coordinates have been deposited in the Protein Data Bank under accession numbers 4INC and 4INI Structured digital abstract hHint2 and hHint2 bind by x-ray crystallography (View interaction)
The Art of Cerebral Aneurysms—3 Decades of Postoperative Drawings: Review, Classification, and Efficacy for Training

Objective To focus on postoperative drawings of aneurysms, which serve as visual records and teaching tools for neurosurgeons and reinforce three-dimensional vascular configurations that are specific for different cerebral aneurysms, and examine experience with this technique, particularly in regard to the training of neurosurgical residents. Methods After performing craniotomy for aneurysm treatment, formal postoperative drawings were created and reviewed. Microsurgical issues graphically highlighted included the totality of aneurysmal dome anatomy, position of visible and hidden branch vessels, rupture points, clipping techniques, and location of adjacent cranial nerves. Drawings were cataloged and categorized according to location. Results Over a 28-year period, during a continuous series of 1480 microsurgically treated aneurysms, 619 drawings (221 of anterior cerebral artery, 154 of middle cerebral artery, 214 of internal carotid artery, 30 of posterior circulation) were created. Postoperative drawings in each location were presented and reviewed. Drawings demonstrated site-specific microsurgical approaches, morphologies, and points of obscuration and rupture. Conclusions Creation and review of postoperative drawings are important adjuncts for the development of three-dimensional understanding of aneurysmal anatomy. This classic art has impact in the digital age and allows patterns of morphology, projection, and anatomy to be reinforced. Surgical atlases created from postoperative drawings function as reference and teaching tools. The creation of postoperative drawings should be a routine part of the training and methodology of vascular neurosurgeons.
Near field microwave brain imaging

A procedure for near field microwave imaging of biological tissues is presented. A two-port microstrip test fixture mounted on a 2D translation stage is employed to capture the transmission images of 1 mm thick slices of rat brain. Spatial resolution and contrast of such images are discussed in terms of insertion loss and extracted tissue permittivity.
The Determination of Trace Elements in Natural Waters Using the Stabilized Temperature Platform Furnace

We have developed procedures to determine 12 trace elements, Al, As, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, and V, in natural water using the stabilized temperature platform furnace. Suitable matrix modifiers were tested. Confirmation of the techniques was obtained by recovery experiments at four different concentration levels. Only simple aqueous standards were required and the method of additions was not used. A simple recovery experiment was satisfactory confirmation of freedom from chemical interferences. The detection limits in the natural waters were less than 1 μg/liter, closer to 0.1 μg/liter for most of the elements. The precision was 10 to 15%. The work did not require clean-room facilities.
TESTING THE UNTESTABLE ASSUMPTIONS OF THE CHAIN AND POSTSTRATIFICATION EQUATING METHODS FOR THE NEAT DESIGN

This paper focuses on the Non-Equivalent Groups with Anchor Test (NEAT) design for test equating and on two classes of observed—score equating (OSE) methods—chain equating (CE) and poststratification equating (PSE). These two classes of methods reflect two distinctly different ways of using the information provided by the anchor test for computing OSE functions. Each of the two classes includes linear and nonlinear equating methods. In practical situations, it is known that the PSE and CE methods tend to give different results when the two groups of examinees differ in ability. However, given that both methods are justified by making untestable assumptions, it is difficult to conclude which, if either, of the two equating approaches is more correct. This study compares predictions from both the PSE and the CE assumptions that can be tested in a comparable way with the data from a special study. Results indicate that both CE and PSE make very similar predictions but that those of CE are slightly more accurate than those of PSE.
Evaluation of the sensory irritation potential of volatile organic chemicals from carpets--alone and in combination.

Abstract Some individuals have reported burning or painful sensations in the eyes or upper respiratory tract when they enter certain indoor environments. Recently, carpets have been suggested as a potential source of organic chemicals that could contribute to this irritation. The sensations are generally termed ‘sensory irritation’ or ‘pungency’, and result from stimulation of trigeminal nerve endings. Indoor air quality is typically evaluated based on the concentrations of individual airborne materials, and rarely do concentrations of potentially offending materials exceed levels expected to cause adverse human health effects. In particular, volatile organic chemicals are measured at low levels (ppb) in the indoor environment. Sources of these organics vary considerably, but concentrations of the individual chemicals do not ordinarily exceed irritating levels. It is possible that the chemical mixture may cause effects not predicted by the present data available on individual chemicals. A list of approximately 50 chemicals identified in carpet emissions was developed for the study. Chemicals were selected from over 200, based on the highest frequency of occurrence and/or highest rate of emission. A mouse model of sensory irritation was used to examine the individual chemicals. In this model, mice are exposed to airborne chemicals by inhalation and evaluated for changes in respiratory function parameters. The model relies on chemical stimulation of the trigeminal nerve endings to elicit a response identified by a decrease in respiratory frequency and an alteration in the breathing pattern. Chemicals are compared quantitatively by measuring the airborne concentration required to elicit a 50% depression in respiratory rate (RD50). Some of the chemicals were previously evaluated by this method, while others were recently examined. The emission chemicals tested individually to date have had RD50 values that generally range from 100 ppm to more than 1000 ppm, indicating that human respiratory irritation would not be expected from the individual chemicals at levels measured in the indoor environment. Differences observed in timing of response from one chemical to another and experimental variability will be important considerations for mixtures testing. The potential for combinations of these emission chemicals to cause sensory irritation at low concentrations, resulting in additivity, synergy, or antagonism of the response, will be addressed. These results should have general application for assessing the risk of causing respiratory irritation in humans exposed to combinations of organic chemicals.
Random Colonic Mucosal Biopsies During Colonoscopy Performed for Chronic Diarrhea: Differences in Practice Patterns Between Gastroenterologists and Surgeons in a Study of 300 Patients

Random Colonic Mucosal Biopsies During Colonoscopy Performed for Chronic Diarrhea: Differences in Practice Patterns Between Gastroenterologists and Surgeons in a Study of 300 Patients
A Semantic Field Approach to Passive Vocabulary Acquisition for Reading Comprehension.

Traditionally, vocabulary study has been based on a word-by-word approach and, as such, has often been criticized as a component in ESL curricula. This study compares a traditional approach to vocabulary instruction with an approach based on the semantic fields of words that appeared in college-level reading texts. Half of the words presented to experimental groups (semantic field approach) were randomly selected and presented to control groups (traditional approach), according to the format used in current vocabulary texts. The semantic field approach was based on the association between five related words and a keyword that could be mentally substituted in context. Testing revealed some short-term advantage for the control groups, but no significant differences were revealed on long-term testing. Since experimental groups were exposed to twice as many words in the same amount of time, the findings lend support to the use of the semantic field approach. In addition, long-term testing revealed, for the words in this study, a highly significant difference favoring vocabulary taught experimentally over incidental learning that may occur during exposure to academic English.
Enzymatic syntheses of DNA-silicas using DNA polymerase.

Abstract Oligothymidylic acids couple to an activated ester silica (N-hydroxysuccinimidyl-silica) only when they contain an added aminoalkyl group. Heteropolymeric oligomers containing other nucleotide bases were shown to also couple by way of the nucleotide base (adenine, cytosine, or guanine); however, when a heteropolymeric oligonucleotide also contains a 5′-aminoalkyl moiety, coupling by way of the latter is the favored reaction. When duplex hybrids of oligonucleotides are formed, the nucleotide bases are protected from chemical coupling. Coupling by way of nucleotide bases would be detrimental to some chromatography experiments. On the basis of these observations, two different procedures were developed to produce DNA-silicas in which a single strand of the DNA is coupled by only its 5′-terminus. In the first of these, the polymerase chain reaction was used with a 5′-aminoalkyl primer to make a duplex DNA with one strand containing the 5′-aminoalkyl group and the duplex DNA is then coupled to the activated ester silica. This yielded a silica containing about 0.17 nmol of a 242-mer per gram silica which bound only probes seecific for the coupled strand. In the other procedure, a template DNA strand was poly(A) tailed and hybridized to (dT)18-silica. DNA polymerase I (Klenow large fragments) was then used to copy the template-specified sequence directly onto the 3′-terminus of the (dT)18. This procedure yielded about 1.2 to 2.7 nmol DNA copied/g of silica of a specific 21-mer sequence. The DNA-silica produced selectively hybridized only with complementary sequences and not with DNA lacking that sequence. Either of these procedures thus produces DNA-silicas from heteropolymeric DNA sequences with a predetermined, specific 5′-terminal site of attachment.
Protonation Sites in Pyrimidine and Pyrimidinamines in the Gas Phase

Protonation sites in gaseous pyrimidine (1), 2-pyrimidinamine (2), and 4-pyrimidinamine (3) were elucidated by neutralization−reionization mass spectrometry and MP2/6-311G(2d,p) ab initio calculations. Pyrimidine was protonated with NH4+ and t-C4H9+ exclusively at the nitrogen atoms whose proton affinity (PA) was calculated at 879 kJ mol-1 in excellent agreement with the experimental datum. The C-2 and C-5 positions in 1 had PA = 573 and 645 kJ mol-1, respectively. 2 was protonated with t-C4H9+ at N-1 and/or N-3 and the amine group in a statistical 2:1 ratio, consistent with the calculated PA = 909 and 864 kJ mol-1, respectively. 3 was protonated at N-1, N-3, and the amine group, which had PA = 943, 905, and 835 kJ mol-1, respectively. The C-5 positions in 2 and 3 were less basic, PA = 807 and 781 kJ mol-1, respectively, and were not attacked by the gas-phase acids used. The thermodynamic proton affinities of gaseous 1, 2, and 3 followed the order of their basicities in solution. The substituent electroni...
A short synthesis of several gambir alkaloids

Abstract A high-yield, one-step synthesis of dl -dihydrogambirtannine (II) is described in which a novel tetrahydro-β-carboline synthesis by reductive cyclization plays a key role. Ourouparine (III) has been oxidized with peroxide in dioxane solution to form oxogambirtannine (IV). Some improvements on the synthesis of 5-carbomethoxyisoquinoline are presented.
Mechanisms of Antioxidants in the Oxidation of Foods

ABSTRACT: Antioxidants delay or inhibit lipid oxidation at low concentration. Tocopherols, ascorbic acid, carotenoids, flavonoids, amino acids, phospholipids, and sterols are natural antioxidants in foods. Antioxidants inhibit the oxidation of foods by scavenging free radicals, chelating prooxidative metals, quenching singlet oxygen and photosensitizers, and inactivating lipoxygenase. Antioxidants show interactions, such as synergism (tocopherols and ascorbic acids), antagonism (α-tocopherol and caffeic acid), and simple addition. Synergism occurs when one antioxidant is regenerated by others, when one antioxidant protects another antioxidant by its sacrificial oxidation, and when 2 or more antioxidants show different antioxidant mechanisms.
Incorporating density dependence into the oviposition preference–offspring performance hypothesis

1. Although theory predicts a positive relationship between oviposition preferences and the developmental performance of offspring, the strength of this relationship may depend not only on breeding site quality, but also on the complex interactions between environmental heterogeneity and density-dependent processes. Environmental heterogeneity may not only alter the strength of density dependence, but may also fundamentally alter density-dependent relationships and the preference-performance relationship. 2. Here I present results from a series of field experiments testing the effects of environmental heterogeneity and density-dependent feedback on offspring performance in tree-hole mosquitoes. Specifically, I asked: (i) how do oviposition activity, patterns of colonization and larval density differ among habitats and among oviposition sites with different resources; and (ii) how is performance influenced by the density of conspecifics, the type of resource in the oviposition site, and the type of habitat in which the oviposition site is located? 3. Performance did not differ among habitats at low offspring densities, but was higher in deciduous forest habitats than in evergreen forest habitats at high densities. Oviposition activity and larval densities were also higher in deciduous forests, suggesting a weak preference for these habitats. 4. The observed divergence of fitness among habitats with increasing density may select for consistent but weak preferences for deciduous habitats if regional abundances vary temporally. This would generate a negative preference-performance relationship when population densities are low, but a positive relationship when population densities are high. 5. This study demonstrates that failure to recognize that fitness differences among habitats may themselves be density-dependent may bias our assumptions about the ecological and evolutionary processes determining oviposition preferences in natural systems.
Nicotinic receptor assembly requires multiple regions throughout the gamma subunit.

Assembly of ionotropic neurotransmitter receptors typified by acetylcholine receptors (AChRs) is thought to be directed by an N-terminal extracellular domain of a subunit. Consistent with this hypothesis, chimeras with the δ subunit N-terminal domain fused to the rest of the γ subunit can substitute for δ, but not γ, subunits during AChR assembly. However, chimeras with the γ subunit N-terminal domain fused to the rest of the δ subunit cannot substitute for γ or δ subunits during assembly. Furthermore, expression of this chimera with the four wild-type subunits prevents the formation of α-bungarotoxin (Bgt) binding sites. Instead of AChR pentamers, complexes are assembled containing only the chimera and either α or β subunits. Based on the results of additional γ-δ chimeras, there are at least two different regions within the C-terminal half of the chimera required for the dominant-negative effect. Our results indicate that the N-terminal domain of the γ subunit mediates the initial subunit associations, whereas signals in the C-terminal half of the subunit are required for subsequent subunit interactions.
An optimization‐based domain decomposition method for the Boussinesq equations

We study an optimization based domain decomposition method for the Boussinesq equations governing natural convection problems. Domain decomposition is cast into a constrained minimization problem for which the objective functional measures the jump in the dependent variables across the interface between solid and fluid subdomains. We showthat solutions of the minimization problem exist and derive an optimality system from which these solutions may be determined. Finite element approximations of the solutions of the optimality system are examined. The domain decomposition method is also reformulated as a nonlinear least-squares problem and the results of some numerical experiments are given. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 1–25, 2002
Regulatory Reforms in the Telecommunications Sector in Developing Countries: The Role of Democracy and Private Interests

We investigate the determinants of regulatory reforms between 1990 and 1998 in 50 developing countries. We find that the reforms are attributable to differences in the configurations of interest groups and in the political structure - in particular, the decision-making mechanisms and the ideology of the legislature. Regulatory reforms are more likely in countries with strong pro-reform interest groups (a larger financial sector and a greater proportion of urban consumers) and less likely in countries where incumbent operators have already made large investments and hence have strong incentives to oppose the reforms. Democracy facilitates the actions of interest groups.
Surgical management of brachial plexus region tumors.

BACKGROUND Brachial plexus region tumors are uncommon and often present a challenge to neurosurgeons. METHODS Provide a brief historical overview, a description of the anatomy, and contribute information that provides management guidelines and improves surgical outcomes for tumors of the brachial plexus region. We also review different surgical approaches followed by surgical outcome from recent studies, as well as our own experience of treating 42 patients with tumors of the brachial plexus region at the University of Pennsylvania Medical Center between 1990 and 2001. RESULTS A thorough understanding of the anatomy, the clinical presentation, imaging techniques, and the various surgical approaches for brachial plexus tumor resection is necessary to ensure the best possible treatment outcome. CONCLUSION We conclude that with proper patient selection and appropriate perioperative and intraoperative management, neurologic deficits from brachial plexus tumor surgery can be minimized.
Parallel factor analysis of spider fluorophores.

Fluorophores from the hemolymph of yellow sac spiders (Cheiracanthium mildei) have been characterized using excitation emission matrix (EEM) fluorescence spectroscopy. This approach provides characterization of fluorophores present in the organism without having to isolate pure samples. Minimal variation occurs between individual samples and each EEM has two distinct peaks, suggesting two fluorophores may be present in the hemolymph. Parallel factor analysis reveals that three fluorophores (with excitation and emission maxima at 270/319, 330/389, and 350/465 nm) best explains the sample to sample variation. By comparing the spectra of the three individual components to fluorophores found in scorpions it is shown that these spiders possess different fluorophores than scorpions. Furthermore, the fluorescence observed is not consistent with β-carboline or 4-methyl-7-hydroxycoumarin, two compounds previously described in scorpions.
Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release

Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future.
RORα Augments Thyroid Hormone Receptor-Mediated Transcriptional Activation1

This study is designed to clarify the role of an orphan nuclear hormone receptor, RORα, on thyroid hormone (TH) receptor (TR)-mediated transcription on a TH-response element (TRE). A transient transfection study using various TREs [i.e., F2 (chick lysozyme TRE), DR4 (direct repeat), and palindrome TRE] and TR and RORα1 was performed. When RORα1 and TR were cotransfected into CV1 cells, RORα1 enhanced the transactivation by liganded-TR on all TREs tested without an effect on basal repression by unliganded TR. By electrophoretic mobility shift assay, on the other hand, although RORα bound to all TREs tested as a monomer, no (or weak) TR and RORα1 heterodimer formation was observed on various TREs except when a putative ROR-response element was present. The transactivation by RORα1 on a ROR-response element, which does not contain a TRE, was not enhanced by TR. The effect of RORα1 on the TREs is unique, because, whereas other nuclear hormone receptors (such as vitamin D receptor) may competitively bind to TR...
Side Chain-dependent Stacking Modulates Tau Filament Structure

The misfolding of proteins into highly ordered fibrils with similar physical properties is a hallmark of many degenerative diseases. Here, we use the microtubule associated protein tau as a model system to investigate the role of amino acid side chains in the formation of such fibrils. We identify a region (positions 272-289) in the tau protein that, in the fibrillar state, either forms part of a core of parallel, in-register, β-strands, or remains unfolded. Single point mutations are sufficient to control this conformational switch with disease mutants G272V and ΔK280 (found in familial forms of dementia) inducing a folded state. Through systematic mutagenesis we derive a propensity scale for individual amino acids to form fibrils with parallel, in-register, β-strands. This scale should not only apply to tau fibrils but generally to all fibrils with same strand arrangement.
Patterns of neuronal differentiation in developing cultures of neonatal mouse cerebellum: a living and silver impregnation study.

Organotypic explants of neonatal mouse cerebellum were cultured for periods up to 56 days in vitro. Living cultures were compared to those fixed and stained by the Holmes' reduced silver nitrate method. The explants consist of a heterologous neuronal population comparable to that found in situ. Since the differentiation of the cerebellum is actively in progress during the neonatal and postnatal periods, cultures derived from such tissue demonstrate the developmental phases that are present at the time of explantation. The in vitro. maintenance of neonatal mouse cerebellum allows the expression of those aspects of neuronal development which are intrinsic to the cell proper and primarily concerned with type-specific differentiation, e.g., neurofibrillary development; axonal growth; myelination; and the acquiring of basic dendritic patterns. The secondary aspects of differentiation, which determine the adult state and which are characterized primarily by the increasing complexity of dendritic formation and of synaptic interactions, occur to a much lesser extent in vitro. The importance of recognizing transitional forms as normal and not peculiar to the in vitro situation is emphasized.
Homotopy invariance of 4-manifold decompositions: Connected sums

Abstract Given any homotopy equivalence f : M → X 1 # ⋯ # X n of closed orientable 4-manifolds, where each fundamental group π 1 ( X i ) satisfies Freedmanʼs Null Disc Lemma, we show that M is topologically h-cobordant to a connected sum M ′ = M 1 ′ # ⋯ # M n ′ such that f is h-bordant to some f 1 ′ # ⋯ # f n ′ with each f i ′ : M i ′ → X i a homotopy equivalence. Moreover, such a replacement M ′ of M is unique up to a connected sum of h-cobordisms. In summary, the existence and uniqueness, up to h-cobordism, of connected sum decompositions of such orientable 4-manifolds M is an invariant of homotopy equivalence. Also we establish that the Borel Conjecture is true in dimension 4, up to s-cobordism, if the fundamental group satisfies the Farrell–Jones Conjecture.