cssi/SciSciGPT-SciSciNet huggingface dataset:
Productive Capacity of Periphyton as a Determinant of Plant-Herbivore Interactions in Streams

To investigate the influence of plant productivity on plant-herbivore inter- actions in stream ecosystems, we varied the productive capacity of algal assemblages by exposing periphyton to three levels of irradiance and two levels of grazing. We studied interactions between algal assemblages (grown from algae obtained from four Oregon streams) and herbivorous snails (Juga silicula) in 15 laboratory streams containing either 250 snails/m2 or no snails. Biomass, production, export, and taxonomic structure of the algal community were measured at intervals throughout the 75-d study. Ingestion rate and assimilation efficiency of snails also were measured on six different dates using dual-isotope labeling, and snail growth was measured at the end of the experiment. Rates of primary production, algal biomass accumulation, and dominance by chloro- phytes generally increased with higher irradiance, although these patterns were modified by herbivores. Ungrazed periphyton at low irradiance (photon flux density: 20 ,umol-m-2- s-1) accumulated little biomass, which was further reduced by grazing snails. At inter- mediate (100 ,umol.m-2 s-) and high (400 ,Lmol.m-2-s-1) irradiance, snails delayed the accumulation of algal biomass but did not affect the final biomass attained. After 43 d, net primary production (NPP) at high irradiance was unaffected by grazing, whereas grazing increased NPP at both low and intermediate irradiance. Algal export increased with both irradiance and the presence of grazers and constituted a significant loss of plant biomass from the streams. Grazing by Juga delayed algal succession and altered algal taxonomic structure and assemblage physiognomy by reducing the relative abundance of erect and non-attached algae, while increasing the abundance of adnate diatoms. Snails grew slowly at low irradiance, due to scant food resources, but had high growth rates at intermediate and high irradiance, probably because food was not limiting. Assim- ilation efficiencies for snails generally varied from 40 to 70% and were highest at low irradiance. At low irradiance, 90% ofbenthic production was harvested by grazers, whereas only 10% accumulated as attached biomass or was exported. At higher irradiances, 85% persisted as attached algae or was exported. In these stream ecosystems, the biomass and production of grazers were influenced by abiotic constraints placed on algal productive capacity (i.e., the ability of a plant assemblage to generate biomass). The structure and metabolism of algal assemblages were affected, in turn, by consumptive demand of herbivores. The productive capacity of periphyton mod- ified the nature and outcome of plant-herbivore interactions. This capacity therefore has important implications for the operation of stream ecosystems.
"The physical significance and application of L, B 0, and R 0 to geomagnetically trapped particles""

In a dipole field, many different invariant shells (I, Bm) share exactly the same lines of force. These invariant shells are therefore members of a degenerate system. In the geomagnetic field, which is assumed static and without electric field, these degenerate systems are split by azimuthal asymmetry. A distinction is made, therefore, between the use of parameters as invariants of charged particle motion (invariant representation) and their use as constants for all particles on a line of force (degenerate representation). We find that McIlwain's L value associates nondegenerate geomagnetic shells with dipole degenerate systems if L at a point in space is redefined to apply only to particles mirroring at that point. Emphasis is placed on the redefined L as an invariant parameter of particle motion and on the near equality of the L value of a particle and the equatorial radius R0 of the line of force on which the particle is mirroring. Although the original definition of L resulted in a very useful parameter, the present definition allows a physical interpretation of L as originally applied and extends its usefulness beyond that allowed by the original definition. With the present definition, the different values of L along a line of force can be identified with the radial separation of particles mirroring on that line as they drift in longitude. This separation is ≈2 per cent of the shell radius and represents the accuracy with which a single magnetic field parameter, such as the minimum field intensity B0 of a line, describes all particles on the line (a degenerate representation). Beyond 3 earth radii, it is found that R0 gives a representation of comparable accuracy. However, an invariant representation (L, Bm) or (I, Bm) is limited only by the accuracy of the determination of the mirror field Bm and the longitudinal invariant I, both of which depend on the accuracy of the magnetic field representation.
A Process Model for the Production of Hydrogen Using High Temperature Electrolysis

High temperature electrolysis (HTE) involves the splitting of steam into hydrogen and oxygen at high temperatures. The primary advantage of HTE over conventional low temperature electrolysis is that considerably higher hydrogen production efficiencies can be achieved. Performing the electrolysis process at high temperatures results in more favorable thermodynamics for electrolysis, more efficient production of electricity, and allows direct use of process heat to generate steam. This paper presents the results of process analyses performed to evaluate the hydrogen production efficiencies of an HTE plant coupled to a 600 MWt Modular Helium Reactor (MHR) that supplies both the electricity and process heat needed to drive the process. The MHR operates with a coolant outlet temperature of 950 C. Approximately 87% of the high-temperature heat is used to generate electricity at high efficiency using a direct, Brayton-cycle power conversion system. The remaining high-temperature heat is used to generate a superheated steam / hydrogen mixture that is supplied to the electrolyzers. The analyses were performed using the HYSYS process modeling software. The model used to perform the analyses consisted of three loops; a primary high temperature helium loop, a secondary helium loop and the HTE process loop. The detailed model included realistic representations of all major components in the system, including pumps, compressors, heat exchange equipment, and the electrolysis stack. The design of the hydrogen production process loop also included a steam-sweep gas system to remove oxygen from the electrolysis stack so that it can be recovered and used for other applications. Results of the process analyses showed that hydrogen production efficiencies in the range of 45% to 50% are achievable with this system.Copyright © 2006 by ASME
Apo and Nickel-Bound Forms of the Pyrococcus horikoshii Species of the Metalloregulatory Protein: NikR Characterized by Molecular Dynamics Simulations

The understanding of metal ion homeostasis at the molecular-level is critical to our understanding of how toxic metal ions are delivered safely and specifically to the appropriate location within cells.1–3 There is a significant structural, biochemical and medical literature on the homeostasis of Cu, for example, due to its role in several neurodegenerative disorders (Alzheimer’s and amyotrophic lateral sclerosis (Lou Gehrig’ disease), for example).1, 2, 4–8 Despite its inherent toxicity, many microorganisms require cellular nickel as an enzyme co-factor.9, 10 Escherichia coli and Heliobacter pylori, for example, utilize nickel for [NiFe]-hydrogenases and urease, which are important for microbial energy metabolism and creation of ammonia as nitrogen source, respectively.10, 11 NikR is a DNA-binding metalloregulatory protein that utilizes nickel-responsive allostery to modulate cellular nickel concentrations in various ways.3, 12, 13 In E. coli, NikR detects cellular nickel levels and selectively binds and represses the operon which encodes NikABCDE, an ABC-type membrane transporter12, 14 effectively reducing nickel import. In H. pylori, NikR, activated by high nickel levels, represses expression of nickel-dependent proteins, such as the HoxN type permease (NixA) which imports nickel, while stimulating activation of other proteins.15 Hence, NikR senses intracellular levels of Ni and shuts downs the production of the transporter when the level of Ni is appropriate for the cell to function.12
Patient outcomes after peripheral revascularization surgery.

Acquired peripheral vascular disease (PVD) is a significant problem in the United States, resulting in both morbidity and mortality. The purpose of the pilot study was to determine patient outcomes after peripheral revascularization surgery. The specific aims of the pilot study were to examine peripheral revascularization surgical patient outcomes (PVD-related clinical symptoms, functioning, atherosclerotic disease risk factor reduction, and patient satisfaction) and to determine the influence of selected patient demographic characteristics (gender, age) on selected patient outcomes (PVD-related clinical symptoms, functioning, atherosclerotic disease risk factor reduction, and patient satisfaction). A prospective, repeated measures design was used for the study. A total of 39 patients, 18 women and 21 men, participated in the study, with a mean age of 68.86 years (SD = 13.61). The average length of hospitalization after surgery was 4.05 days. At 1 month after discharge, the majority of patients had relief from claudication and paresthesia. In regard to outcomes related to atherosclerotic risk factor modification, patients reported that they exercised on a routine basis, an average of 5.31 +/- 1.97 times per week. Before surgery, 21 patients reported that they smoked; 6 patients reported that they continued to smoke at follow-up. There were no significant differences in mean total scores of atherosclerotic risk modification by either gender or age groups ( or =65 years) with the use of one-way analyses of variance (ANOVAs). By using a Likert scale (ie, 0 to 10), the mean level of functioning was 8.18 +/- 2.76, with women having significantly higher mean levels of functioning (F = 4.26, P <.05). Comparing baseline scores of functioning on the Medical Outcomes Study Short-Form 36 (MOS SF-36), there was a significant improvement (F = 2.11, P <.05) in general health subscale scores at 1 month after surgery. Subjects' mean overall satisfaction with the results of surgery, with a 0 to 10 scale, was 7.33 +/- 2.84. Again, by using one-way ANOVAs, females had significantly higher mean satisfaction rating than males (F = 4.52, P <.05). Although findings from this pilot study are limited in their generalizability, clinicians need to continue to evaluate opportunities to further reduce variability in clinical practice patterns for optimal patient outcomes. Study findings also indicated that additional interventions are warranted to educate and provide rehabilitation for patients regarding an exercise program and overall behavior modification strategies to reduce risk for atherosclerotic disease.
Rethinking Professional Development: Building a Culture of Teacher Learning

This article describes a case study of an educational organization, the Big Picture Company, trying to implement a highly unusual school design. It offers a close look at its professional development strategies and how its comprehensive program helps create a culture where teachers can, and do, learn. I detail five professional development strategies Big Picture employs to build communities of practice: Mentoring: The buddy system; Networking: Extending the community; Observation days: Two-way feedback in action; Case studies: Group learning to tap into the collective knowledge base; and Workshops: Learning from experienced teachers and honing individual skills.
Distinct human papillomavirus type 16 methylomes in cervical cells at different stages of premalignancy

Human papillomavirus (HPV) gene expression is dramatically altered during cervical carcinogenesis. Because dysregulated genes frequently show abnormal patterns of DNA methylation, we hypothesized that comprehensive mapping of the HPV methylomes in cervical samples at different stages of progression would reveal patterns of clinical significance. To test this hypothesis, thirteen HPV16-positive samples were obtained from women undergoing routine cervical cancer screening. Complete methylation data were obtained for 98.7% of the HPV16 CpGs in all samples by bisulfite-sequencing. Most HPV16 CpGs were unmethylated or methylated in only one sample. The other CpGs were methylated at levels ranging from 11% to 100% of the HPV16 copies per sample. The results showed three major patterns and two variants of one pattern. The patterns showed minimal or no methylation (A), low level methylation in the E1 and E6 genes (B), and high level methylation at many CpGs in the E5/L2/L1 region (C). Generally, pattern A was associated with negative cytology, pattern B with low-grade lesions, and pattern C with high-grade lesions. The severity of the cervical lesions was then ranked by the HPV16 DNA methylation patterns and, independently, by the pathologic diagnoses. Statistical analysis of the two rating methods showed highly significant agreement. In conclusion, analysis of the HPV16 DNA methylomes in clinical samples of cervical cells led to the identification of distinct methylation patterns which, after validation in larger studies, could have potential utility as biomarkers of neoplastic cervical progression.
ELECTROOSMOSIS THROUGH PORES WITH NONUNIFORMLY CHARGED WALLS

The movement of fluid through a charged capillary by the action of an electric field is analyzed in the case where the charge density on the capillary wall varies with axial position. The capillary's radius is assumed much greater than the Debye screening length of the fluid. Our results show that the mean fluid velocity within the capillary is given exactly by the classical Helmholtz equation with the local zeta potential replaced by the average zeta potential, determined by integrating the local value over the length of the capillary. If the magnitude of the local zeta potential exceeds the thermal potential (kT/e), the relationship between zeta potential and wall charge is nonlinear, so that the Helmholtz equation cannot be used to calculate the average charge from a measured electroosmotic flow or streaming potential. Although the mean electroosmotic velocity depends only on the average zeta potential, the fluid velocity field within the capillary is a strong function of the distribution of zeta poten...
On accuracy, stability and efficiency of the Newmark method with incomplete solution by multilevel methods

The use of an incomplete iterative solver aimed at approximating solution of equilibrium equation resulting from the finite element semidiscretization in space is studied. Our approach is motivated by the fact that: (i) the effective stiffness matrix is well conditioned because of the stabilizing effect of the diagonally dominated mass matrix, (ii) the dominance of the temporal error in implicit computations with large step size, and (iii) the utilization of a class of iterative methods where the primary computational cost is associated with a construction of the preconditioner rather than with an iterative process. One of the primary goals of the present manuscript is to control the temporal and the equilibrium solution errors and to give their a posteriori estimates. Numerical experiments reveal that the computational cost of three cycles conducted with the Generalized Aggregation Multilevel solver [1–4] is comparable to a single back substitution on the source grid, while the resulting equilibrium solution error is negligible compared with the local temporal error. Copyright © 1999 John Wiley & Sons, Ltd.
Practice of pediatric pulmonology: results of the Future of Pediatric Education Project (FOPE)

In 1996, the Future of Pediatric Education (FOPE) Project of the American Academy of Pediatrics (AAP) developed surveys to describe the nature of pediatric practices, recent trends in clinical practice, and anticipated workforce needs for both pediatric generalists and pediatric sub-specialists. A survey was specifically developed to describe the features of pediatric pulmonology as self-reported by pediatric pulmonologists. The survey was distributed to members of the AAP Pulmonology Section, the Pediatric Assembly of the American Thoracic Society, and certified pediatric pulmonologists recognized by the American Board of Pediatrics. Of the 535 respondents (67% of those invited to respond), the responses of 388 certified and 94 trained but not board-certified pulmonologists were included in the results. The characteristics of certified and non-certified respondents were the same for most survey questions. Clinical activities occupy 73 +/- 29% of professional time. Most pulmonologists work in urban, inner city, or suburban settings and 85% are affiliated with a medical school. One third are in private practice. As a group, research activities occupy less than 15% of their time. Most pediatric pulmonologists maintain a referral practice and use physician extenders to provide care. Patients with asthma and cystic fibrosis comprise 60-70% of patient volume. Both the volume and complexity of patients are increasing, as is competition for pediatric sub-specialty services. Pediatric pulmonary practices vary in size and in volume of patients that they manage in various settings. Forty percent of respondents identify allergists and other pediatric pulmonologists as sources of competition. Sixty-nine percent of respondents do not believe that there is a current need for additional pediatric pulmonologists in their respective communities. Only 15% of respondents plan to retire in the next decade.
A screen for yeast mutants with defects in the dolichol-mediated pathway for N-glycosylation

Abstract Dolichol in the form of dolichyl phosphate participates in the synthesis of N- and O-linked glycoproteins and phosphatidylinositol-linked proteins in the yeast Saccharomyces cerevisiae. In this organism, as well as in higher eukaryotes, a number of the enzymes in the polyisoprenoid and glycoprotein biosynthetic pathways have not been identified. In this study, we have developed a convenient, highly sensitive assay that uses one of the end products of the dolichylphosphate synthetic pathway, oligosaccharide-diphosphodolichol, and a 125I-labeled peptide substrate for N-linked glycosylation to screen a collection of temperature-sensitive yeast mutants for defects in protein glycosylation. By using a combination of biochemical and genetic procedures, the defective mutants were grouped into three categories: those containing defects in dolichyl-phosphate synthesis (class 1), lipid-linked oligosaccharide assembly (class 2), or oligosaccharide transferase activity (class 3). Among the mutants identified by this screen were sec59 (which encodes dolichol kinase) and a mutant that affects the activity of the ALG1-encoded mannosyltransferase that forms dolichol-PP-(GlcNAc)2Man1. Of particular interest was a mutant that exhibits a temperature-sensitive defect in oligosaccharide transferase activity. This mutant, meg1 (microsomal protein essential for glycosylation 1) assembles a complete oligosaccharide chain and, therefore, is likely to be a class 3 mutant. We report the cloning of MEG1, the gene that rescues the oligosaccharide transferase activity defect in this mutant. A number of criteria distinguish this gene from previously described genes in this pathway.
Notch signaling activates Yorkie non-cell autonomously in Drosophila

In Drosophila imaginal epithelia, cells mutant for the endocytic neoplastic tumor suppressor gene vps25 stimulate nearby untransformed cells to express Drosophila Inhibitor-of-Apoptosis-Protein-1 (DIAP-1), conferring resistance to apoptosis non-cell autonomously. Here, we show that the non-cell autonomous induction of DIAP-1 is mediated by Yorkie, the conserved downstream effector of Hippo signaling. The non-cell autonomous induction of Yorkie is due to Notch signaling from vps25 mutant cells. Moreover, activated Notch in normal cells is sufficient to induce non-cell autonomous Yorkie activity in wing imaginal discs. Our data identify a novel mechanism by which Notch promotes cell survival non-cell autonomously and by which neoplastic tumor cells generate a supportive microenvironment for tumor growth.
Southeast Pacific Stratocumulus in the Community Atmosphere Model

AbstractForecasts of October 2006 are used to investigate southeast Pacific stratocumulus in the Community Atmosphere Model, versions 4 and 5 (CAM4 and CAM5). Both models quickly develop biases similar to their climatic biases, suggesting that parameterized physics are the root of the climate errors. An extensive cloud deck is produced in CAM4, but the cloud structure is unrealistic because the boundary layer is too shallow and moist. The boundary layer structure is improved in CAM5, but during the daytime the boundary layer decouples from the cloud layer, causing the cloud layer to break up and transition toward a more trade wind cumulus structure in the afternoon. The cloud liquid water budget shows how different parameterizations contribute to maintaining these different expressions of stratocumulus. Sensitivity experiments help elucidate the origins of the errors. The importance of the diurnal cycle of these clouds for climate simulations is emphasized.
Temporal relationships of blood pressure, heart rate, baroreflex function, and body temperature change over a hibernation bout in Syrian hamsters

Hibernating mammals undergo torpor during which blood pressure (BP), heart rate (HR), metabolic rate, and core temperature (TC) dramatically decrease, conserving energy. While the cardiovascular system remains functional, temporal changes in BP, HR, and baroreceptor-HR reflex sensitivity (BRS) over complete hibernation bouts and their relation to TC are unknown. We implanted BP/temperature telemetry transmitters into Syrian hamsters to test three hypotheses: H-1) BP, HR, and BRS decrease concurrently during entry into hibernation and increase concurrently during arousal; H-2) these changes occur before changes in TC; and H-3) the pattern of changes is consistent over successive bouts. We found: 1) upon hibernation entry, BP and HR declined before TC and BRS, suggesting baroreflex control of HR continues to regulate BP as the BP set point decreases; 2) during the later phase of entry, BRS decreased rapidly whereas BP and TC fell gradually, suggesting the importance of TC in further BP declines; 3) during torpor, BP slowly increased (but remained relatively low) without changes in HR or BRS or increased TC, suggesting minimal baroreflex or temperature influence; 4) during arousal, increased TC and BRS significantly lagged increases in BP and HR, consistent with establishment of tissue perfusion before increased TC/metabolism; and 5) the temporal pattern of these changes was similar over successive bouts in all hamsters. These results negate H-1, support H-2 with respect to BP and HR, support H-3, and indicate that the baroreflex contributes to cardiovascular regulation over a hibernation bout, albeit operating in a fundamentally different manner during entry vs. arousal.
Enterococci Concentrations in Diverse Coastal Environments Exhibit Extreme Variability

Fecal indicator bacteria (FIB) concentrations in a single grab sample of water are used to notify the public about the safety of swimming in coastal waters. If concentrations are over a single-sample standard, waters are closed or placed under an advisory. Previous work has shown that notification errors occur often because FIB vary more quickly than monitoring results can be obtained (typically 24 h). Rapid detection technologies (such as quantitative polymerase chain reaction) that allow FIB quantification in hours have been suggested as a solution to notification errors. In the present study, I explore variability of enterococci (ENT) over time scales less than a day that might affect interpretation of FIB concentrations from a single grab sample, even if obtained rapidly. Five new data sets of ENT collected at 10 and 1 min periodicities for 24 and 1 h, respectively, are presented. Data sets are collected in diverse marine environments from a turbulent surf zone to a quiescent bay. ENT vary with solar and tidal cycles, as has been observed in previous studies. Over short time scales, ENT are extremely variable in each environment even the quiescent bay. Changes in ENT concentrations between consecutive samples (1 or 10 min apart) greater than the single-sample standard (104 most probable number per 100 mL) are not unusual. Variability, defined as the change in concentration between consecutive samples, is not distinct between environments. ENT change by 60% on average between consecutive samples, and by as much as 700%. Spectral analyses reveal no spectral peaks, but power-law decline of spectral density with frequency. Power-law exponents are close to 1 suggesting ENT time series share properties with 1/f noise and are fractal in nature. Since fractal time series have no characteristic time scale associated with them, it is not obvious how the fractal nature of ENT can be exploited for adaptive sampling or management. Policy makers, as well as scientists designing field campaigns for microbial source tracking and epidemiology studies, are cautioned that a single sample of water reveals little about the true water quality at a beach. Multiple samples must be taken to gain a snapshot into the patchy structure of microbial water quality and associated human health risk.
Proteomic biomarkers of adverse pregnancy outcome in preterm birth: a theranostics opportunity

Biomedical research is evolving rapidly to address biological systems, such as molecular pathways integrated into complex networks. Tools for molecular discoveries are evolving to address old challenges and create new opportunities. Despite considerable financial and research effort combined with a variety of interventions, the rate of preterm birth has steadily increased to reach a high of 12.7%. Disappointingly, each year, 4.5 million premature infants are born in the USA alone. Although the etiology of most preterm births remains unknown, several distinct pathophysiological pathways are involved in triggering the syndrome, such as myometrial stretching, oxidative stress, decidual hemorrhage and infection. Novel research and diagnostic applications stemming from opportunities presented by the advances of genomics and proteomics begin to impact on clinical diagnosis, vaccine development, drug discovery and unique therapies in a modern diagnostic–therapeutic framework – part of the new scientific field of...
Oil Seal Quality Control—Important or Imperative

In 1957, a research program was initiated for the study of radial lip seals. Results of this study indicated that there was a lack of seal technology concerning the seal lip characteristics and a lack of equipment to measure various design parameters necessary to good sealing practice. From a program of planned experimentation, there emerged a series of controls which, when put into practice, resulted in vastly improved seals being available for assembly and an inherent reduction in the sealing problems.
Small business support of youth physical activity opportunities

Abstract Purpose. Describe small business support for youth physical activity opportunities (YPAO) and identify factors associated with this support. Design. Cross-sectional analysis of quantitative data relating business characteristics and support for YPAO. Setting. Eight demographically heterogeneous, urban neighborhoods in a Midwest metropolitan area. Subjects. Adult small business owners (n = 90; 65% response rate; mean age 48.4 years; 73.3% male; 45.2% minority). Measures. Neighborhood demographics from the 2000 U.S. Census and self-reported business and owner characteristics. Analysis. Multivariate analysis of variance was used to contrast business and owner characteristics between businesses that did and did not support YPAO. Results. Businesses supporting YPAO had larger annual operating (F = 7.6; p = .018) and advertising budgets (F = 8.5; p = .009) and had younger owners (F = 6.1; p = .034), with sports backgrounds (χ2 = 5.6; p = .018) and who felt businesses should support YP...
A novel intensity modulator for photonic ADCs using an injection-locked mode-locked laser

A novel intensity modulator for pulsed light is proposed and demonstrated here for the first time. This has been realized by introducing an injection-locked AlGaInAs mode-locked laser into one arm of a Mach-Zehnder interferometer.
Patient-Reported Outcomes in the Practice-based Opportunities for Weight Reduction (POWER) Trial

To evaluate effects of two behavioral weight-loss interventions (in-person, remote) on health-related quality of life (HRQOL) compared to a control intervention. Four hundred and fifty-one obese US adults with at least one cardiovascular risk factor completed five measures of HRQOL and depression: MOS SF-12 physical component summary (PCS) and mental component summary; EuroQoL-5 dimensions single index and visual analog scale; PHQ-8 depression symptoms; and PSQI sleep quality scores at baseline and 6 and 24 months after randomization. Change in each outcome was analyzed using outcome-specific mixed-effects models controlling for participant demographic characteristics. PCS-12 scores over 24 months improved more among participants in the in-person active intervention arm than among control arm participants (P < 0.05, ES = 0.21); there were no other statistically significant treatment arm differences in HRQOL change. Greater weight loss was associated with improvements in most outcomes (P < 0.05 to < 0.0001). Participants in the in-person active intervention improved more in physical function HRQOL than participants in the control arm did. Greater weight loss during the study was associated with greater improvement in all PRO except for sleep quality, suggesting that weight loss is a key factor in improving HRQOL.
Optical enantiomorphs of homoserine and homocystine.

Abstract Chloroacetyl- dl -homoserine lactone was synthesized. After opening the ring at pH 8, and treating with hog kidney acylase I, dl -homoserine ([α]D = −8.8 ° in water and +18.3 ° in 2 N HCl) was obtained in 72% yield. From the mother liquor, chloroacetyl- d -homoserine was separated, yielding on HCl hydrolysis the lactone of d -homoserine · HCl ([α]D = +26.7 ° in water). Refluxing of the lactone at pH 8 resulted in d -homoserine in 60% yield ([α]D = +8.6 ° in water and −18.2 ° in 2 N HCl). A sample of the lactone of l -homoserine · HCl prepared by refluxing l -homoserine with HCl yielded [α]D = −27.0 ° in water. N-Acetyl-S-benzyl- dl -homocysteine was subjected at pH 7.5 to the action of acylase I, yielding S-benzyl- l -homocysteine in 85% yield ([α]D = +27.2 ° in 2 N HCl) and N-acetyl-S-benzyl- d -homocysteine. The latter compound after refluxing with HCl followed by neutralization yielded S-benzyl- d -homocysteine in 65% yield with [α]D = −27.3 °. From the S-benzyl derivatives, l - and d -homocystine were prepared by du Vigneaud's procedure, with [α]D respectively of +77.5 ° and −77.5 °. The l -enantiomorphs of homoserine and S-benzylhomocysteine are readily oxidized by Crotolus adamanteus venom l -amino acid oxidase, and the corresponding d -enantiomorphs by hog kidney d -amino acid oxidase. By means of these preparations it was determined that the l -and d -enantiomorphs of the two amino acids were more than 99.9% optically pure.
Ionic Interconversion of Pacemaker and Nonpacemaker Cultured Chick Heart Cells

Trypsin-dispersed cells from hearts (ventricles) of 7 to 8 day chick embryos were cultured 3 to 21 days. The cells became attached to the culture dish and assembled into monolayer communities. By means of a bridge circuit, one microelectrode was used for simultaneously passing current and recording membrane potentials (Vm). The input resistance, calculated by the measured AV,~ for a known step of current, averaged I0 Mg. Electrotonic depolarization of nonpacemaker ceils had no effect on frequency of firing. Within 2 min after addition of Ba ++ (5 to 10 re_M) to the Tyrode bath, the cells became partially depolarized and quiescent nonpacemaker cells developed oscillations in Vm which led to action potentials. With time, the depolarization became nearly complete and the input resistance increased 2 to I0 times. During such sus- tained depolarizations, action potentials were no longer produced and often tiny oscillations were observed; however, large action potentials developed during hyperpolarizing pulses. Thus, the automaticity of the depolarized cell became apparent during artificial repolarization. Sr ++ (5 to I0 raM) initially produced hyperpolarization and induced automaticity in quiescent nonpace- maker cells. Elevated (K +) o (20 to 30 mM) suppressed automaticity of pacemaker cells and decreased Rm concomitantly. Thus, Ba ++ probably converts nonpace- maker cells into pacemaker ceils independently of its depolarizing action. Ba ++ may induce automaticity and depolarization by decreasing gK, and elevated (K+)o may depress automaticity by increasing gK. The data support the hy- pothesis that the level of gK determines whether a cell shall function as a pace- maker. Cultured heart cells represent a useful tool in the investigation of the electro- physiological properties of cardiac muscle because the cells may be grown as monolayers and the impalement of cells may be visually observed. In addition, since the ceils in culture are aneural, the effects of various chemical agents can be determined independently of nerves. That is, the preparation can help determine whether the site of action of an agent in intact cardiac muscle is directly on the muscle ceils. For example, we have recently reported (24) that cultured chick ventricular cells are insensitive to several autonomic 867
Ethanol downregulates transcription of the PAI-1 gene in cultured human endothelial cells.

Abstract Human endothelial cells are a major site of synthesis for plasminogen activator inhibitor type-1. Elevated plasminogen activator inhibitor type-1 levels in young survivors of myocardial infarction [1] suggest that plasminogen activator inhibitor type-1 may have an important pathologic role in the development of coronary artery disease. Epidemiological studies indicate that moderate alcohol consumption (1–2 drinks/day) reduces the risk for cardiovascular mortality. This cardioprotective benefit has been attributed in part to an increase in fibrinolysis, which decreases fibrin-based thrombosis. The studies described herein were performed to determine whether moderate levels of ethanol affect plasminogen activator inhibitor type-1 gene expression. Cultured human endothelial cells were exposed to 0.1% v/v ethanol for 1 hour. Following incubation in the absence of ethanol plasminogen activator inhibitor type-1, mRNA levels were decreased in a time- and dose-dependent manner, reaching a maximum decrease of 3- to 4-fold at 2 to 4 hours following ethanol challenge. This decline in mRNA occurs at the transcription level; therefore, nuclear transcription run-on assays were performed. A 2.5- to 5-fold decrease in the rate of plasminogen activator inhibitor type-1 gene transcription was measured at 2 and 4 hours following ethanol challenge. Next, a 3.4- and a 1.1-kb fragment from the plasminogen activator inhibitor type-1 promoter region were linked to a luciferase reporter gene, and these constructs were transfected into human endothelial cells. Treatment of these transiently transfected human endothelial cells with ethanol showed a 2- to 3.5-fold decrease in promoter activity, respectively. These results indicate that low doses of ethanol downregulate transcription of the plasminogen activator inhibitor type-1 gene in cultured human endothelial cells. However, the mechanism(s) for this transcriptional decrease is currently unknown.
Maternal lifestyle and environmental risk factors for autism spectrum disorders

Background: Over the past 10 years, research into environmental risk factors for autism has grown dramatically, bringing evidence that an array of non-genetic factors acting during the prenatal period may influence neurodevelopment. Methods: This paper reviews the evidence on modifiable preconception and/or prenatal factors that have been associated, in some studies, with autism spectrum disorder (ASD), including nutrition, substance use and exposure to environmental agents. This review is restricted to human studies with at least 50 cases of ASD, having a valid comparison group, conducted within the past decade and focusing on maternal lifestyle or environmental chemicals. Results: Higher maternal intake of certain nutrients and supplements has been associated with reduction in ASD risk, with the strongest evidence for periconceptional folic acid supplements. Although many investigations have suggested no impact of maternal smoking and alcohol use on ASD, more rigorous exposure assessment is needed. A number of studies have demonstrated significant increases in ASD risk with estimated exposure to air pollution during the prenatal period, particularly for heavy metals and particulate matter. Little research has assessed other persistent and non-persistent organic pollutants in association with ASD specifically. Conclusions: More work is needed to examine fats, vitamins and other maternal nutrients, as well as endocrine-disrupting chemicals and pesticides, in association with ASD, given sound biological plausibility and evidence regarding other neurodevelopmental deficits. The field can be advanced by large-scale epidemiological studies, attention to critical aetiological windows and how these vary by exposure, and use of biomarkers and other means to understand underlying mechanisms.
Stem/progenitor cells derived from adult tissues: potential for the treatment of diabetes mellitus

In view of the recent success in pancreatic islet transplantation, interest in treating diabetes by the delivery of insulin-producing β-cells has been renewed. Because differentiated pancreatic β-c...
Numerically stable iterative method for the inversion of wave-front aberrations from measured point-spread-function data

This paper outlines a method for the determination of the unknown wave-front aberration function of an optical system from noisy measurements of the corresponding point-spread function. The problem is cast as a nonlinear least-squares estimation problem for the values of the wave-front aberration function at N points over the slit aperture, from measurements of the point-spread function at M points with M⩾N. Newton’s method is used to replace the nonlinear minimization problem with a sequence of linear problems. Each such problem requires the inversion of the Hessian matrix of the error metric that is shown to be both singular (with rank ⩽N−1) and ill-conditioned. To overcome singularity, the pseudoinverse is used; to overcome ill-conditioning the pseudoinverse is calculated using singular value decomposition and the singular values then filtered. Attention is drawn to difficulties such as nonuniqueness, sensitivity of algorithms to initial guess, etc.; the ancillary mathematical details being set out in appendices. Some illustrative numerical results are presented and analyzed.
Possible roles for the membrane cytoskeleton in regulating red cell stability and deformability

Several observations suggest the presence of a membrane cytoskeleton in the red cell. Some of these imply possible roles for that cytoskeleton in regulating red cell shape and deformability. One of the most striking examples of this role is that of the spectrin-free spherocyte mouse. In this condition, spectrin is virtually absent from the membranes of erythrocyte cells and osmotic fragility and survival is markedly affected. The mice are afflicted with an extreme haemolytic anaemia which is barely compatible with life. An unequivocal role for the cytoskeleton in being responsible for this disorder has been shown through experiments in which the cytoskeleton has been reconstituted by specific rebinding of normal mouse spectrin to these defective cell membranes. Marked improvement in membrane fragmentation, membrane, membrane fusion, and osmotic stability following reconstitution indicated that these functions are partially regulated through the membrane cytoskeleton, and its predominant protein, spectrin.
Neurological morbidity and mortality associated with the endovascular treatment of cerebral arteriovenous malformations before and during the Onyx era

OBJECT The widespread implementation of the embolic agent Onyx has changed the endovascular management of cerebral arteriovenous malformations (AVMs). Recent data suggest that outcomes following embolization and resection may have worsened in the Onyx era. It has been hypothesized that there may be increased complications with Onyx embolization and increased surgical aggressiveness in patients treated with Onyx. In this study the authors analyzed their institutional experience with the endovascular treatment of cerebral AVMs prior to and after the introduction of Onyx to determine factors associated with periprocedural neurological morbidity and mortality. METHODS A retrospective review was performed of all patients with cerebral AVMs undergoing embolization at the Barrow Neurological Institute from 1995 to 2012. RESULTS Endovascular treatment of 342 cerebral AVMs was performed over 446 treatment sessions (mean age 37.8 years, range 1–83 years). Clinical presentation included hemorrhage in 47.6%, seizures...
Expanded Genetic Map of Gibberella moniliformis (Fusarium verticillioides)

Gibberella moniliformis (Fusarium verticillioides) is primarily a pathogen of maize, but it can also cause disease in other crop species. This pathogenicity, as well as the contamination of food- and feedstuffs with the fumonisin mycotoxins, results in economically significant losses to both farmers and food processors. The dissection of important biological characters in this fungus has been hampered by the lack of a uniformly dense genetic map. The existing restriction fragment length polymorphism-based map contains significant gaps, making it difficult to routinely locate biologically important genes, such as those involved in pathogenicity or mycotoxin production, with precision. We utilized amplified fragment length polymorphisms (AFLPs) to saturate the existing genetic map and added 486 AFLP markers to the 150 markers on the existing map. The resulting map has an average marker interval of 3.9 map units and averages 21 kb/map unit. The additional markers expanded the map from 1,452 to 2,188 map units distributed across 12 chromosomes. The maximum distance between adjacent markers is 29 map units. We identified AFLP markers less than 1 map unit from the mating type (MAT) locus and 2.5 map units from the spore killer (SK) locus; eight AFLP markers map within 8.5 units of the FUM1 (fumonisin biosynthetic) locus. The increased saturation of this map will facilitate further development of G. moniliformis as a model system for the genetic and population genetic studies of related, but less genetically tractable, plant pathogenic fungi.
Application of on-line nano-liquid chromatography/mass spectrometry in metabolite identification studies.

Metabolite identification is an important part of the drug discovery and development process. High sensitivity is necessary to identify metabolic products in vitro and in vivo. The most common method utilizes standard high-performance liquid chromatography (4.6 mm i.d. column and 1 mL/min flow rate) coupled to tandem mass spectrometry (HPLC/MS/MS). We have developed a method that utilizes a nano-LC system coupled to a high-resolution tandem mass spectrometer to identify metabolites from in vitro and in vivo samples. Using this approach, we were able to increase the sensitivity of analysis by approximately 1000-fold over HPLC/MS. In vitro samples were analyzed after simple acetonitrile precipitation, centrifugation, and dilution. The significant improvement in sensitivity enabled us to conduct experiments at very low substrate concentrations (0.01 μM), and very low incubation volumes (20 μL). In vivo samples were injected after simple dilution without any pre-purification. All the metabolites identified by conventional HPLC/MS/MS were also identified using the nano-LC method. This study demonstrates a very sensitive approach to identifying phase I and II metabolites with throughput and separation equivalent to the standard HPLC/MS/MS method. Copyright © 2012 John Wiley & Sons, Ltd.
The effect of punishment shock intensity upon responding under multiple schedules

In the first of two experiments, responses of two pigeons were maintained by multiple variable-interval, variable-ratio schedules of food reinforcement. Concurrent punishment was introduced, which consisted of a brief electric shock after each tenth response. The initial punishment intensities had no lasting effect upon responding. Then, as shock intensity increased, variable-ratio response rates were suppressed more quickly than variable-interval response rates. When shock intensity decreased, variable-interval responding recovered more quickly, but the rates under both schedules eventually returned to their pre-punishment levels. In the second experiment, the following conditions were studied in three additional pigeons: (1) With each shock intensity in effect for a number of sessions, punishment shock intensity was gradually increased and decreased and responding was maintained by multiple variable-ratio, fixed-ratio schedules of food reinforcement; (2) Changes in punishment shock intensity as described above with responding maintained by either a variable-ratio or a fixed-ratio schedule, which were presented on alternate days; (3) Session-to-session changes in shock intensity with responding maintained by multiple variable-ratio, fixed-ratio schedules. Responding under the two schedules was suppressed to approximately the same extent by a particular shock intensity. Also, post-reinforcement pauses under the fixed-ratio schedule increased as response suppression increased.
Improved staining procedures for semithin epoxy sections of plant tissues.

Improved and reliable methods are described for staining semithin sections of plant materials fixed in glutaraldehyde-osmium and embedded in epoxy resins. One-micron sections are fixed to slides, s...
Comparative high voltage impulse measurement

A facility has been developed for the determination of the ratio of pulse high voltage dividers over the range from 10 kV to 300 kV using comparative techniques with Kerr electro-optic voltage measurement systems and reference resistive voltage dividers. Pulse voltage ratios of test dividers can be determined with relative expanded uncertainties of 0.4 % (coverage factor k = 2 and thus a two standard deviation estimate) or less using the complementary resistive divider/Kerr cell reference systems. This paper describes the facility and specialized procedures used at NIST for the determination of test voltage divider ratios through comparative techniques. The error sources and special considerations in the construction and use of reference voltage dividers to minimize errors are discussed, and estimates of the measurement uncertainties are presented.