cssi/SciSciGPT-SciSciNet huggingface dataset:
Determinación de variables predictivas de deserción inicial para generar un sistema de alerta temprana. Análisis sobre una muestra de estudiantes beneficiarios de la beca de nivelación académica en una universidad pública en Chile

The quantitative results of the program “Academic Leveling Scholarship” from year 2016 were analyzed, from a sample of 250 beneficiaries. Statistic datasets were checked using Decision Tree and Clustering techniques in the search of information in institutional data bases that will be relevant to develop an Early Dropout Prediction Model. This model will allow for selecting students with a higher risk of dropping out to receive a timely focused accompaniment. It concluded that there exists, at least, one characterization variable upon the first-year students that allows for identifying the dropout risk in the selected sample regarding the score obtained in the specific math test of the university selection process. The relevance of this research is its contribution to predictive evidence to align efforts that different universities are making to improve their permanence indexes, especially regarding the recent diversification of the population that has been admitted to higher education due to universal access policy, free education, equity and inclusion.
Use of virtual reality in the inpatient rehabilitation of COVID-19 patients.

Abstract Introduction Use of virtual reality (VR) in healthcare has expanded in recent years. The challenges faced by patients with prolonged COVID-19-related hospitalizations – social isolation, disability, neurologic sequelae, adjustment-related anxiety, depression, and stress – may be mitigated by the novel use of VR as one modality of a comprehensive rehabilitation plan. This descriptive study aimed to understand patient satisfaction and perceived benefit of virtual reality on a COVID-19 recovery unit, as well as the logistical and operational feasibility of providing VR content for patients and staff. Materials and methods During the COVID-19 surge in New York City in 2020, the COVID-19 Recovery Unit (CRU) of a large academic hospital invited patients and staff to participate in VR sessions with three categories of experience: (1) Guided meditation, (2) Exploration of natural environments, (3) Cognitive stimulation games. Patients and staff were surveyed about satisfaction and perceived benefit. Results 13 patients and 11 staff were surveyed, with median patient satisfaction scores of 9 out of 10, with ten representing “extremely satisfied,” and median staff satisfaction scores of 10. 13/13 patients answered “yes” to recommending the therapy to others, and 12/13 answered “yes” to perceived enhancement of their treatment. 11/11 staff answered “yes” to recommending the therapy to others, and 11/11 answered “yes” to perceived enhancement of their wellbeing. Discussion A VR program implemented on a COVID-19 rehabilitation unit for patients and healthcare providers was rated as highly satisfactory with perceived benefit by survey respondents. Participants commented that the use of VR was useful in coping with isolation and loneliness, and could be implemented within the context of clinical care for COVID-19 patients as part of a comprehensive rehabilitation model. The use of VR was also logistically and operationally feasible on the CRU. Future work to compare benefits of VR to standard neuropsychological rehabilitation is needed.
The degree of astrocyte activation is predictive of the incubation time to prion disease.

In neurodegenerative diseases including Alzheimer’s, Parkinson’s and prion diseases, astrocytes acquire disease-associated reactive phenotypes. With growing appreciation of their role in chronic neurodegeneration, the questions whether astrocytes lose their ability to perform homeostatic functions in the reactive states and whether the reactive phenotypes are neurotoxic or neuroprotective remain unsettled. The current work examined region-specific changes in expression of genes, which report on astrocyte physiological functions and their reactive states, in C57Black/6J mice challenged with four prion strains via two inoculation routes. Unexpectedly, strong reverse correlation between the incubation time to the diseases and the degree of astrocyte activation along with disturbance in functional pathways was observed. The animal groups with the most severe astrocyte response and degree of activation showed the most rapid disease progression. The degree of activation tightly intertwined with the global transformation of the homeostatic state, characterized by disturbances in multiple gene sets responsible for normal physiological functions producing a neurotoxic, reactive phenotype as a net result. The neurotoxic reactive phenotype exhibited a universal gene signature regardless of the prion strain. The current work suggests that the degree of astrocyte activation along with the disturbance in their physiological pathways contribute to the faster progression of disease and perhaps even drive prion pathogenesis.
Beyond Local or Distant Search:Co-evolution of Cognition Representation and Behavioral Capabilities

Organizational search is indispensable to organizational learning and adaptation. But organizations often search in the vicinity of their existing routines and capabilities due to bounded rationali...
Performance Metrics for Fluidic Soft Robot Rotational Actuators.

The field of soft robotics is continuing to grow as more researchers see the potential for robots3that can safely interact in unmodeled, unstructured, and uncertain environments. However,4in order for the design, integration, and control of soft robotic actuators to develop into a full5engineering methodology, a set of metrics and standards need to be established. This paper6attempts to lay the groundwork for that process by proposing six soft robot actuator metrics that7can be used to evaluate and compare characteristics and performance of soft robot actuators.8Data from eight different soft robot rotational actuators (five distinct designs) was used to evaluate9these soft robot actuator metrics and show their utility. Additionally we provide a simple case10study as an example of how these metrics can be used to evaluate soft robot actuators for a11designated task. While this paper does not claim to present a comprehensive list of all possible12soft robot actuator metrics, the metrics presented can 1) be used to initiate the development and13comparison of soft robot actuators in an engineering framework and 2) start a broader discussion14of which metrics should be standardized in future soft robot actuator research.
Endogenous Labor Supply, Rigid Factor Prices And A Second Best Solution

The conventional wisdom asserts that distortions due to factor price rigidities should be eliminated by subsidies. However, we argue that the success of this policy rests upon the fact that the return to the factor is a pure rent. If factor supply is endogenous, then subsidies to employers and taxes on factor owners are needed to support the optimal solution. Since we believe this policy combination works only by assuming away the problem, we then devise a model to study the optimal policies in a second best world. Our results show that, in general, both factor subsidies (or taxes) and export subsidies (or taxes) are needed to achieve this constrained optimum.
Peristomal varices after proctocolectomy in patients with primary sclerosing cholangitis.

Abstract Primary sclerosing cholangitis is a chronic cholestatic liver disease that is commonly associated with chronic ulcerative colitis. We observed the development of varices in the abdominal wall surrounding the ileostomy stoma of patients with primary sclerosing cholangitis who underwent proctocolectomy and ileostomy for chronic ulcerative colitis. In 10 of 19 patients, the development of peristomal varices was documented 12–133 mo after operation. Risk factors for the development of peristomal varices included splenomegaly, esophageal varices, advanced histologic stage at liver biopsy, low serum albumin, thrombocytopenia, and an increased prothrombin time. Recurrent bleeding from peristomal varices was a major problem; 7 of 10 patients required repeated blood transfusions. The only therapy of long-term benefit was surgical decompression of the portal venous system in 1 patient and liver transplantation in a second patient. In contrast, there was no perirectal bleeding in 4 patients with primary sclerosing cholangitis who underwent proctocolectomy with an ileoanal anastomosis.
The Epidemiology of Hepatitis C Virus in the Fertile Crescent: Systematic Review and Meta-Analysis

To characterize hepatitis C virus (HCV) epidemiology in countries of the Fertile Crescent region of the Middle East and North Africa (MENA), namely Iraq, Jordan, Lebanon, Palestine, and Syria.We systematically reviewed and synthesized available records of HCV incidence and prevalence following PRISMA guidelines. Meta-analyses were implemented using a DerSimonian-Laird random effects model with inverse weighting to estimate the country-specific HCV prevalence among the various at risk population groups.We identified eight HCV incidence and 240 HCV prevalence measures in the Fertile Crescent. HCV sero-conversion risk among hemodialysis patients was 9.2% in Jordan and 40.3% in Iraq, and ranged between 0% and 3.5% among other populations in Iraq over different follow-up times. Our meta-analyses estimated HCV prevalence among the general population at 0.2% in Iraq (range: 0-7.2%; 95% CI: 0.1-0.3%), 0.3% in Jordan (range: 0-2.0%; 95% CI: 0.1-0.5%), 0.2% in Lebanon (range: 0-3.4%; 95% CI: 0.1-0.3%), 0.2% in Palestine (range: 0-9.0%; 95% CI: 0.2-0.3%), and 0.4% in Syria (range: 0.3-0.9%; 95% CI: 0.4-0.5%). Among populations at high risk, HCV prevalence was estimated at 19.5% in Iraq (range: 0-67.3%; 95% CI: 14.9-24.5%), 37.0% in Jordan (range: 21-59.5%; 95% CI: 29.3-45.0%), 14.5% in Lebanon (range: 0-52.8%; 95% CI: 5.6-26.5%), and 47.4% in Syria (range: 21.0-75.0%; 95% CI: 32.5-62.5%). Genotypes 4 and 1 appear to be the dominant circulating strains.HCV prevalence in the population at large appears to be below 1%, lower than that in other MENA sub-regions, and tending towards the lower end of the global range. However, there is evidence for ongoing HCV transmission within medical facilities and among people who inject drugs (PWID). Migration dynamics appear to have played a role in determining the circulating genotypes. HCV prevention efforts should be targeted, and focus on infection control in clinical settings and harm reduction among PWID.
Temperature dependence of the growth-induced anisotropy of Ge-substituted garnet films by resonance techniques

Ferromagnetic resonance techniques have been used to measure the growth-and stress-induced uniaxial magnetic anisotropy of LPE grown garnet films of the nominal composition Y1.64Eu0.10Lu0.30Ca0.96Ge0.96Fe4.04O12 from 130°K to near the Curie temperature, 455°K. The longitudinal and transverse resonance fields were measured prior and subsequent to an anneal at 1453°K. The growth-induced anisotropy, KGu ∼−0.03 × 104 ergs/cm3 at 300°K, was found to be approximately 10% of the stress-induced anisotropy, and of opposite sign for these tensile films. The associated anisotropy field, 2KGuM exhibited a reversal of slope, with a maximum occurring at 310°K. A model which assumes the existence of a surface anisotropy is proposed to explain these observations. The temperature dependence of the cubic anisotropy, the magnetization, the linewidth, and the exchange constant have been measured also.
A group of related surface glycoproteins distinguish sets and subsets of sensory afferents in the leech nervous system

The distribution of 4 surface glycoproteins on axons of peripheral neurons was studied in the leechHirudo medicinalis through monoclonal antibodies. All 4 glycoproteins have a similar molecular weight of 130 kDa. Immunohistochemical localization of these glycoproteins on tissue sections of nerves and neuropil reveals tracts of afferent axons organized as nested sets. Their distribution suggests a possible role for these molecules in mediating axon fasciculation.
Effects of dietary factors on iron uptake from ferritin by Caco-2 cells

Biofortification of staple foods with iron (Fe) in the form of ferritin (Ft) is now possible, both by conventional plant breeding methods and transgenic approaches. Ft-Fe from plants and animals is absorbed well (25-30%) by human subjects, but little is known about dietary factors affecting its absorption. We used human intestinal Caco-2 cells and compared Fe absorption from animal Ft and FeSO4 to determine the effects of inhibitors and enhancers, such as phytic acid, ascorbic acid, tannic acid, calcium and heme. When postconfluent cells were coincubated with 59Fe-labeled (1 microM) FeSO4 and dietary factors, at different molar ratios of dietary factor to Fe (phytic acid:Fe, 10:1; ascorbic acid:Fe, 50:1; tannic acid:Fe, 50:1; calcium:Fe, 10:1 and hemin:Fe, 10:1), all inhibited uptake from FeSO4, except ascorbate, confirming earlier studies. In contrast, these dietary factors had little or no effect on Fe uptake from undigested Ft or Ft digested in vitro at pH 4, except tannins. However, results after in vitro digestion of Ft at pH 2 were similar to those obtained for FeSO4. These results suggest that Fe uptake occurs from both undigested as well as digested Ft but, possibly, via different mechanisms. The Fe-Ft stability shown here could minimize Fe-induced oxidation of Fe-supplemented food products.
Pathogenesis of chronic obstructive pulmonary disease (COPD)

Abstract Chronic obstructive pulmonary disease (COPD) could develop following long-term exposure of individuals to cigarette smoke, toxic gases, and particulate matter, resulting in airway flow limitation, pulmonary failure, multiple systemic effects, and, eventually, death. The disease is associated with pulmonary inflammation with its own specific characteristics, and could be exacerbated by multiple factors such as microbial infection. COPD is chronic and progressive in nature, and multiple pulmonary inflammatory cells are detected at different stages of the disease, with a possible network of interactions with parenchymal cells. The pathological changes in the lung of COPD patients are characterized by an excess of extracellular matrix deposition, yet, loss of extracellular matrix in alveoli, increased thickness of airway walls, mucus hypersecretions, and destruction of alveolar septae, resulting in narrowing of airway diameters, reduced functional lung parenchyma, and decreased elastic tethering forces to maintain airway patency. Multiple factors, such as inflammatory cytokines, proteolytic proteinases, and oxidative stress molecules are suspected to be responsible, each at some degree, for these structural changes leading to airway obstruction. Because not everyone exposed to cigarette smoke will develop the disease, it is reasonable to think that multiple risk factors are involved and that COPD could be developed along a variety of pathways. Our current understanding of pulmonary changes associated with COPD, its similarity and differences with asthma, the nature of inflammatory cells associated with the disease, and the capacity of different molecules to induce a variety of these structural alterations are discussed to advance a cellular and molecular look at the pathogenesis of COPD.
Simple numerical system for scoring the cosmetic effects of radiation and surgery post‐conservation therapy for breast cancer

To improve the documentation of cosmetic outcome in women with breast cancer treated by conservative surgery and radiation, we developed a simple numerical scoring system. Cosmetic scores are based on the effects of surgery and radiation and also include a comparison of breast symmetry. The scoring system ranges from a minimum score of 2 to a maximum of 10. Between June 1978 and June 1992, 226 patients were treated at the University of Wisconsin by tumorectomy and breast irradiation. Of these, 209 patients were evaluable after a minimum period of 2 years. Blind tests of interobserver agreement gave a correlation coefficient of 0.74 between faculty and resident scores. Scores tended to be slightly lower for larger or node-positive cancer, but they were not adversely affected by tumor location or by the type of prior chemotherapy. At 2, 5, and 10 years post-treatment, mean cosmetic scores were 8.1, 7.3, and 6.2, while local recurrence rates were 2, 8, and 16%, respectively. This numerical system for assessing breast cosmesis is easy to use and is more amenable to statistical analysis than qualitative descriptors such as “excellent, good, fair, or poor.” © Wiley-Liss, Inc.
Photon interferometry of quark-gluon dynamics

Abstract Two-photon intensity interferometry is used as a probe of the dynamics of quarks and gluons in a high energy nucleus-nucleus collision. Under the assumption that transverse expansion of hadrons in the final state is not important, we show that the correlation of high transverse-momentum photons is sensitive to the details of the space-time evolution of the high density QCD plasma. This is in contrast to hadron interferometry, which is sensitive mainly to the later dilute stage of the reaction.
Frequency, characteristics, and clinical significance of transient ST segment elevation in patients with acute coronary syndromes.

Background Prior investigations of transient myocardial ischaemia have focused on ST depression events. Therefore, the purpose of this analysis was to determine the frequency, characteristics, and clinical significance of transient ST segment elevation in patients with acute coronary syndromes. Methods A secondary analysis from two prospective studies utilizing 12-lead ST segment monitoring was used to compare ST elevation vs ST depression events. Results Of 868 patients, 177 (20%) had 574 events (242, ST elevation; 332, ST depression). Patients with ST elevation were more likely to have single vessel coronary artery disease, whereas patients with ST depression were more likely to have triple vessel coronary artery disease. ST elevation events were of shorter duration, more often associated with chest pain, and had greater ST changes than ST depression events. There was no difference in clinical outcome between patients with ST elevation vs depression; however, those with ST events were more likely to have adverse hospital outcomes (OR, 3·67) or death (OR, 2·03) than patients without ST events. After controlling for clinical prognostic factors, transient ST events observed with continuous ST monitoring predicted hospital death independently from signs of ischaemia on the initial standard 12-lead ECG. Conclusions Transient ST elevation is nearly as prevalent as transient ST depression in patients with acute coronary syndromes. Since the vast majority of ST events are brief and otherwise clinically silent, ST segment monitoring is more efficacious in detecting ischaemic events and in predicting adverse clinical outcomes than patients' symptoms or the initial standard 12-lead ECG.
Incorporation of anti-angiogenesis therapy in the management of advanced ovarian carcinoma—Mechanistics, review of phase III randomized clinical trials, and regulatory implications

Despite survival gains achieved nearly two decades ago with combination platinum- and taxane-based intravenous chemotherapy, overall survival curves have remained relatively unchanged during the 21st century using newer cytotoxic agents. Although combined intravenous-intraperitoneal (IV-IP) chemotherapy is promising, tolerability remains a significant issue. An emphasis has been placed on exploring dose dense schedules and targeted agents. Vascular endothelial growth factor (VEGF) has emerged as an important therapeutic target in several solid tumors including ovarian carcinoma. The monoclonal antibody, bevacizumab, binds VEGF, thus preventing activation of the VEGF receptor (VEGFR) leading to inhibition of tumor angiogenesis. To date eight phase 3 randomized controlled trials incorporating anti-angiogenesis therapy in the treatment of newly diagnosed and recurrent ovarian carcinoma have met their primary endpoints. Four of these trials included bevacizumab and were reported from 2010 to 2012. During 2013, the other four studies were reported, each studying one of the following novel anti-angiogenesis agents: pazopanib, cediranib, trebananib, and nintedanib. Importantly, none of these drugs have been approved by the United States Food and Drug Administration (US FDA) for the treatment of ovarian cancer. The purpose of this review will be to highlight both VEGF-dependent and non-VEGF dependent angiogenic pathways in ovarian cancer and discuss the phase 3 experiences and regulatory implications of targeting the tumor microenviroment with anti-angiogenesis therapy.
Guest Editorial: Special Section on Multimedia Systems

This PDF file contains the editorial “Guest Editorial: Multimedia Systems” for JEI Vol. 5 Issue 02
Mutational analysis of 23S ribosomal RNA structure and function in Escherichia coli.

Publisher Summary The Escherichia coli ( E. Coli ) ribosome is the best-characterized system in which translation has been investigated at the molecular level. The E. coli ribosome is a (70s) complex of RNA and protein composed of two subunits, the large (50s) subunit and the small (30s) subunit. This chapter reviews the structure and the function of 16s ribosomal RNA in E. coli. The chapter investigates the effects of mutations introduced into rRNA genes. Expression of rRNA genes is essential and there are seven copies of the rRNA genes in the E. coli genome. Mutational analysis of 16s ribosomal RNA structure and function is a powerful approach to the study of the role of this RNA in the process of translation. There is also great promise in two novel genetic approaches to the study of 16s rRNA—inactivation of as many as four chromosomal rrn operons in E. coli by insertion–deletion mutagenesis using antibiotic resistance cassettes and the introduction of antibiotic resistance mutations into the single chromosomal rRNA operon of Halobacterium halobium .
Thermal instability of a horizontal layer of liquid with maximum density

An investigation is carried out to determine the onset of convection of a horizontal layer of liquid subject to temperature of T1 and T2 at lower and upper surfaces, respectively. The liquid is assumed to possess a maximum density value at Tmax with Tmax between T1 and T2. The temperature-density relationship within the temperature range |T1 — T2| can be expressed as ρ = ρmax [1 — γ1 (T — Tmax)2 — γ2 (T — Tmax)3]. Both rigid-rigid and rigid-free surface conditions were considered. The critical Rayleigh number defined in Equations (20) and (24) is found to be dependent upon two parameters. Experimental observations on the onset of convection were made and compared with the theoretical results. The experimental work consists of the measurement of the melting rate of a block of ice with melting from both below and above. In all cases, excellent agreement between experimental and theoretical results were obtained.
Fourier transform infrared microspectroscopic observation of the migration of water in individual grain kernels with tempering using D 2 O

Discrimination of added water (D 2 O) applied at the surface of grain from naturally occurring water already present before the moisture `tempering' process is possible. Cross sections of grain were examined by FT-IR microspectroscopic techniques to measure the inward migration of the D 2 O applied at the surface of the grain kernel prior to sectioning. The relative ability for uptake and retention of water by localized morphologically distinct regions of the kernel were observed and mapped from moving stage data accumulations.
Quantitation of megakaryocytopoiesis in liquid culture by enzymatic determination of acetylcholinesterase

A method has been developed to quantitate megakaryocytopoiesis in culture by measuring acetylcholinesterase synthesized in vitro. Murine marrow cells, treated with diisopropylfluorosphosphate (DFP) to inactivate initial acetylcholinesterase (AchE) present in megakaryocytes and contaminating blood, were set up in Iscove's medium supplemented with 15% DFP-treated horse serum +/- pokeweed mitogen-stimulated spleen cell conditioned medium (PWM-SCM) in 96-well microplates. Following the culture period, Triton X-100, dithiobisnitrobenzoic acid (DTNB), and acetylthiocholine iodide were added to each well. AchE synthesized in culture cleaved acetylthiocholine to thiocholine, which stochiometrically reduced the colorless indicator DTNB to a highly colored product. Thirty minutes following the addition of substrate, the plates were assayed for activity with a vertical recording photometer. When platelets, freshly prepared bone marrow cells, or cultured marrow were assayed by this method, a linear relationship was observed between optical density (OD) and the number of cells assayed. Moreover, a linear relationship between the number of AchE-positive megakaryocytes determined histochemically and AchE activity determined spectrophotometrically was observed. Red cells exhibited no activity. Inhibitor studies demonstrated that the activity measured was true AchE. Separation of marrow by density gradient centrifugation showed that the megakaryocyte enriched fraction contained all the AchE while the megakaryocyte depleted fraction contained none. From the data we conclude that this rapid, semiautomated method quantitates megakaryocytic AchE synthesis in culture, and that this method will be a useful assay system for the detection of factors that influence megakaryocytopoiesis.
Mathematics Culture Clash: Negotiating New Classroom Norms with Prospective Teachers

Abstract As part of an investigation of the mathematical and pedagogical development of prospective teachers, the second author taught mathematics to a group of undergraduate teacher candidates in a way that is compatible with current mathematics education reform principles. Initially, the lack of a shared basis for communication was evident when these students, acculturated to the practices of school mathematics, interacted with a teacher who was trying to promote inquiry mathematics. Our analysis of the data indicates that by the latter stages of the course, a classroom microculture characterized by inquiry mathematics had evolved. In this article, we examine the processes by which the participants in this classroom community negotiated norms and practices. The result of this analysis was an identification and elaboration of four categories of interaction central to the ongoing negotiation. This article illustrates how each of these categories of interaction contributed to the negotiation of new norms and practices.
Mixing length in low Reynolds number compressible turbulent boundary layers

The paper studies the effect of low Reynolds number in high-speed turbulent boundary layers on variations of mixing length. Boundary layers downstream of natural transition on plates, cones and cylinders, and boundary layers on nozzle walls without laminarization-retransition are considered. The problem of whether low Reynolds number amplification of shear stress is a result of transitional flow structure is considered. It is concluded that a knowledge of low Reynolds number boundary layer transition may be relevant to the design of high-speed vehicles.
Mean and fluctuating velocity contours and acoustic characteristics of subsonic and supersonic jets

Mean and fluctuating velocity contours were determined for a convergent nozzle from surveys with impact pressure and piezoelectric pressure gauge probes, at Mach numbers of 0.6 to 1.4. For supersonic Mach numbers of 1.2 and 1.4, the length of the supersonic region increased as the square of the Mach number, and the peak pressure fluctuations occurred close to the sonic velocity contour. For subsonic Mach numbers of 0.6 to 1.0, the peak pressure fluctuations occurred in a toroidal region located approximately 4 to 6 diameters from the nozzle. The normalized sound power spectra for subsonic Mach numbers were similar, and for supersonic Mach numbers the power spectra shifted to the higher frequencies.
A simple plant-location model for quantity-setting firms subject to price uncertainty

Abstract The uncapacitated plant location problem under uncertainty is formulated in a mean-variance framework with prices in various markets correlated via their response to a common random factor. This formulation results in a mixed-integer quadratic programming problem. However, for a given integer solution, the resulting quadratic programming problem is amenable to a very simple solution procedure. The simplicity of this algorithm means that reasonably large problems should be solvable using existing branch-and-bound techniques.
Lifetime distributions for unidirectional fibrous composites under creep-rupture loading

Monte-Carlo simulations and theoretical modeling are used to study the statistical failure modes and associated lifetime distribution of unidirectional 2D and 3D fiber-matrix composites under constant load. Within the composite the fibers weaken over time and break randomly, and the matrix undergoes linear viscoelastic creep in shear. The statistics of fiber failure are governed by the breakdown model of Coleman (1958a), which embodies a Weibull hazard functional of fiber load history imparting power-law sensitivity to fiber load with exponent ρ, and Weibull lifetime characteristics with shape parameter β. The matrix has a power-law creep compliance in shear with exponent α. Fiber load redistribution at breaks is calculated using a shear-lag mechanics model, which is much more realistic than idealized rules based on equal, global or local load-sharing. The present study is concerned only with the `avalanche' failure regime discussed by Curtin and Scher (1997) which occurs for sufficiently large ρ, and whereby the composite lifetime distribution follows weakest-link scaling. The present Monte-Carlo failure simulations reveal two distinct failure modes within the avalanche regime: For larger ρ, where fiber failure is very sensitive to load level, the weakest link volume fails in a `brittle' manner by the gradual growth of a cluster of mostly contiguous fiber breaks, which then abruptly transitions into a catastrophic crack. For smaller ρ, where this load sensitivity is much less, the weakest link volume shows `tough' behavior, i.e., distributed damage in terms of random fiber failures until the failure of a critical volume and its catastrophic extension. The transition from brittle to tough failure mode for each ρ within the avalanche regime is gradual and depends on the matrix creep exponent α and Weibull exponent β. Also, as α increases above zero the sensitivity of median composite lifetime to load level increasingly deviates from power-law scaling known to occur in the elastic matrix case, α=0. By probabilistic modeling of the dominant failure modes in each regime we obtain distribution forms and various scalings for damage growth, and for carefully chosen sets of parameter values we analytically extend simulation results on small composites (limited by current computer power) to more realistic sizes. Our analytical strength distributions are applicable for ρ>2 in 2D, and ρ≳4 in 3D. The 2D bound coincides with the avalanche-percolation threshold derived by Curtin and Scher (1997) using entirely different arguments.
Interrupted aortic arch in an active, asymptomatic adult.

A 32-year-old male football player with no significant past medical history was hospitalized and treated for a Staphylococcus aureus psoas abscess. Though the patient had no cardiac symptoms, physical exam incidentally revealed a machine-like murmur over the right scapula and a soft, systolic murmur over the left second intercostal space. Blood pressure was noted to be 165/90 …
Adatom coalescence and cluster motion on amorphous surfaces via a molecular dynamics computer simulation

Abstract A molecular dynamics computer simulation technique of model systems was used to (a) determine the extent of coalescence of a dispersion of adatoms on the amorphous surface as a function of the adatom-substrate interaction energy, and (b) evaluate the effect of the adatom-substrate interaction energy on the mobility of a 10 atom cluster on amorphous and crystalline surfaces. Results show that at low temperatures the diffusion of adatoms on the amorphous surface is limited by the high density of sites from which adatoms require a significant amount of thermal energy in order to escape. At higher temperatures, the amorphous surface can relax and accommodate adatoms and clusters more readily than a low index crystalline surface, again inhibiting diffusion. Such results help explain the experimentally observed high sticking coefficients and higher densities of small clusters experimentally observed in depositions on amorphous surfaces as compared to crystalline surfaces.
Testing a stability conjecture with plane-wave Cauchy horizons

Plane-wave Cauchy horizons serve as an important testing ground for a previously developed Cauchy horizon stability conjecture. The conjecture uses test fields to predict the stability of Cauchy horizons in general relativistic spacetimes. Three cases are considered: single plane waves with (a) aligned test fields and (b) colliding test fields; and (c) non-singular interaction regions in colliding-wave spacetimes. A restricted form of the stability conjecture is proven for case (a). The conjecture is shown to agree with arbitrary exact back-reaction solutions in this case, as long as no Weyl-tensor singularities are introduced on an initial Cauchy surface. Four examples of case (b) are analysed; in three the conjecture agrees with exact back-reaction solutions, and in the fourth the conjecture correctly indicates instability, but misjudges the type of singularity formed. A possible reason for the disagreement is discussed. Two examples of case (c) are analysed, in which test null dust is added to the interaction regions of a colliding electromagnetic spacetime (Bell-Szekeres) and a colliding gravitational wave spacetime (Chandrasekhar-Xanthopoulos). The conjecture is shown to agree with known exact back-reaction solutions.
Bile acid enhancement of reserpine‐induced blepharoptosis

A more rapid onset of blepharoptotic activity in mice as well as a significantly increased oral potency relative to reserpine base was noted for reserpine coprecipitates with deoxycholic, cholic, and lithocholic acids. Some enhancement of potency was seen for a reserpine–trihydroxycholane combination, while a reserpine-cholanic acid coprecipitate was about equivalent to reserpine base. The use of water-soluble reserpine acetate increases both the apparent relative potency and the duration of activity, while the relatively water-insoluble reserpine hydrochloride only increases the duration of reserpine-like activity.
A new measure of ifra-ness and its application to two sample test

A continuous life distribution function f with f(x)=0 for x ≶ is said to be increasing failure rate average (IFRA) if and only if and all x For testing the null hypothesis that f is an exponentia distribution versus the alternative hypothesis that f is a nonexponential IFRA distribution DESHPANDE [BIometrika 70 (1983): 514:518] proposed a class of testing which depends on b the choice of b has been crucial since than In this paper we propose a new measure of IFRA ness that is independent of b and we use it to test whether one destribution is more IFRA than other. The Properties of the test such as unbiasedness, consistency and asymptotic normality are dscussed.Monte Carolo estimates of power are obtained for small sample sizes. Large sample performance is measured in terms of Asymptotic relative efficiency with respect to Tiwri and ZALKIAr,s (1988) test.
Clinical and surgical considerations for cerebellopontine angle meningiomas.

Abstract We retrospectively reviewed 24 patients with cerebellopontine angle (CPA) meningioma from our institution to describe the clinical and surgical significance of extensions into the internal auditory canal (IAC). Of these patients, 62% had invasion of the IAC, which was associated with high rates of unilateral hearing loss at presentation (67% versus [vs.] 22%, p
Planning for disaster: who gets the doctors?

Dr Snipes and colleagues1 recently explored factors influencing faculty and resident physicians' willingness and ability to report for duty during disaster events. Training program directors and hospital emergency planners using these data should consider an additional problem: several different hospitals and programs may lay claim to physicians, particularly physicians in training, who may “belong” to the medical school, to the host department and hospital, and to the department and hospital to which they are assigned on rotation. As each of these institutions does their own planning, 2 or more may be counting on the same physician and neglecting the chance the physician may be willing and able to respond but would choose to respond elsewhere. Those seeking to replicate the work of Dr Snipes et al1 are encouraged to add a new question: “If the medical school, the host hospital/program, and the hospital/program of your current rotation all need your help now, to which site would you report?” Program directors should decide the hierarchy, inform their trainees, and notify hospital and regional emergency planners. Trainees, faculty, and indeed each of us should have a personal and family emergency plan2 and a basic supply kit to enable us to be useful contributors to our institutions' and communities' response to disaster.
Isotopic, chemical and textural relations during the experimental alteration of biogenic high-magnesian calcite

Abstract Dissolution runs with four biogenic high magnesian calcites (HMC) of different magnesium content were conducted in distilled water saturated with 100% CO2 and 3% CO2 at 70°C and 35°C in order to study the mechanism of alteration of HMC to low magnesian calcite (LMC). The isotopic composition (δ13C and δ18O) of the solutions (−30%. relative to PDB and +40%. relative to SMOW, respectively) was maintained far from isotopic equilibrium with respect to the dissolving carbonate. The isotopic composition and Mg content of the residual solid phase was monitored throughout the approach to stoichiometric saturation. For the coralline algae Goniolithon, heterogeneous and possibly incongruent dissolution occurred which reduced the Mg Ca mole ratio in the solid from 0.44 to 0.26. The alteration was accompanied by an apparent isotopic equilibration of up to 20% of the solid. Runs with two littoral foraminifera, Archaias and Sorites showed a decrease in the Mg Ca mole ratio from 0.18 to 0.14 in the solid and an apparent isotopic equilibration of up to 10%. These changes began to occur before the bulk solution became saturated with respect to LMC. On the other hand the echinoid Clypeaster dissolved homogeneously and congruently with much smaller changes in magnesium and stable isotope composition: from 0.16 to 0.14 in Mg Ca mole ratio and less than 5% apparent isotopic equilibration. All isotopic shifts were in the direction of equilibrium with the solution isotopic composition. No isotopic shifts were observed in runs with Iceland spar under identical conditions. Textural differences in microstructure discovered by SEM examination of the HMC materials used suggest the possibility of an overall textural control over the observed differences in isotopic and chemical behaviour during the dissolution runs.
Traffic density and stationary sources of air pollution associated with wheeze, asthma, and immunoglobulin E from birth to age 5 years among New York City children

Exposures to ambient air traffic-related pollutants and their sources have been associated with respiratory and asthma morbidity in children. However, longitudinal investigation of the effects of traffic-related exposures during early childhood is limited. We examined associations of residential proximity and density of traffic and stationary sources of air pollution with wheeze, asthma, and immunoglobulin (Ig) E among New York City children between birth and age 5 years. Subjects included 593 Dominican and African American participants from the Columbia Center for Children's Environmental Health cohort. Prenatally, through age 5 years, residential and respiratory health data were collected every 3-6 months. At ages 2, 3, and 5 years, serum IgE was measured. Spatial data on the proximity and density of roadways and built environment were collected for a 250 m buffer around subjects' homes. Associations of wheeze, asthma, total IgE, and allergen-specific IgE with prenatal, earlier childhood, and concurrent exposures to air pollution sources were analyzed using generalized estimating equations or logistic regression. In repeated measures analyses, concurrent residential density of four-way intersections was associated significantly with wheeze (odds ratio: 1.26; 95% confidence interval [CI]: 1.01, 1.57). Age 1 exposures also were associated with wheeze at subsequent ages. Concurrent proximity to highway was associated more strongly with total IgE (ratio of the geometric mean levels: 1.25; 95% CI: 1.09, 1.42) than were prenatal or earlier childhood exposures. Positive associations also were observed between percent commercial building area and asthma, wheeze, and IgE and between proximity to stationary sources of air pollution and asthma. Longitudinal investigation suggests that among Dominican and African American children living in Northern Manhattan and South Bronx during ages 0-5 years, residence in neighborhoods with high density of traffic and industrial facilities may contribute to chronic respiratory morbidity, and concurrent, prenatal, and earlier childhood exposures may be important. These findings may have broad implications for other urban populations that commonly have high asthma prevalence and exposure to a high density of traffic and stationary air pollution sources.
Isolation and biochemical characterization of the PilA protein of Neisseria meningitidis.

Abstract PilA is the response regulator of a two-component regulatory system that controls a number of genes in the pathogenic Neisseria. Previous work has shown that Neisseria gonorrhoeae (GC) PilA binds DNA and also hydrolyzes GTP. Here, we report the cloning, sequencing, purification, and biochemical characterization of PilA from N. meningitidis (MC) strain 8013. MC pilA is 94% identical to GC pilA at the nucleotide level. Of the 78 nucleotide changes, 52 are silent, while 26 result in a total of 20 amino acid changes. Additionally, the MC homolog has a 4-amino-acid insertion between the putative DNA-binding and GTP-binding domains. Purified MC PilA binds to the same DNA fragment we have previously shown to be bound by GC PilA specifically and also hydrolyzes GTP. The K m of MC PilA for GTP is 8.6 μM, similar to that determined for the GC protein. However, the maximum velocity ( V max ) is ∼35-fold greater than the GC PilA activity. Additionally, the nucleotide specificity of MC PilA differs from that of GC PilA. While GC PilA hydrolyzes only GTP, MC PilA hydrolyzes GTP and ATP equally well, and CTP and UTP also compete for this activity.
High school seniors' social network and other ICT use preferences and concerns

The study develops an in-depth picture of teens' thoughts and opinions related to social networks and ICT's, particularly preferences towards, and concerns related to, their use. Using a series of six semi-structured focus group interviews, data were gathered from 45 high school seniors attending a highly technological public high school. Focus group questions included 1) preferred methods for communicating with friends and family; 2) reasons for engaging or not engaging in online social networking; 3) how ICT's for social networking and other communication purposes were selected; and 4) decisions related to accepting online "friends." Findings contradicted earlier "digital natives" literature, which suggests that teens are avid users of technology for technology's sake. Instead, the teens viewed ICTs and social networks from a more pragmatic view, using them as tools for quick and easy communication and for relationship building and maintenance. General findings indicated that 1) communication media were selected based on the closeness of the relationship with the message receiver(s) and the number of intended receivers; 2) social networks, such as Facebook, were used for less frequent contact with wider range of friends and relatives; 3) teens used ICTs differently for communication with adults than with peers; and 4) teens preferred to use email for interactions with teachers. An eight-category typology of four ICT capability preferences (Simplicity of interface design/Ease of use, Speed of use, Constant contact/Ubiquitous communication, and Multitasking) and four ICT use concerns (Information privacy, Information security, Communication overload; and Reduced face-to-face communication and interaction) is proposed.
Adenocarcinoma of the colon with choriocarcinoma in its metastases.

A 49-year-old woman died from metastases from a colon carcinoma. This was predominantly an ordinary tubular adenocarcinoma but it included areas of much less differentiated appearance with giant cells, while the hepatic and pulmonary metastases were poorly differentiated and contained choriocarcinoma, as established by means of morphologic and immunocytochemical examination. The choriocarcinoma appeared to be due to metaplasia within the carcinomatous tissue. This and other similar cases of mixed tumors suggest that unexpected trophoblastic differentiation may result from aberrant differentiation of locally proliferating cells, rather than originating in ectopic germ cells or in foci of embryonic totipotent cells. Implications for possible origin and for classification of tumors are briefly discussed. Cancer 46:570–575, 1980.
IS THE 3.5 μm INFRARED FEATURE ON ENCELADUS DUE TO HYDROGEN PEROXIDE

We use new and previously published measurements from our laboratory to examine the assignment of a 3.5 μm feature in the infrared spectrum of Enceladus. The spectral feature, taken with Cassini's VIMS Spectrometer, has recently been interpreted as an absorption band from hydrogen peroxide on the surface. Such identification is important because it would imply an intense flux of magnetospheric particles, which are thought to be required to produce H2O2 from surface water ice. We compare the position and width of this feature with measurements of infrared spectra of water-hydrogen peroxide mixtures. We conclude that the reported feature from Enceladus does not correspond to hydrogen peroxide.
Endohedral complexes of C58 cage with H2 and CO

Abstract Ab initio Hartree–Fock (HF) calculations were carried out to determine the structures and energies of the endohedral complexes of C 58 cage with H 2 or CO. It was demonstrated that the formation of these complexes is endothermic with destabilization energies of 3.3 kcal/mol for H 2 and 18.6 kcal/mol for CO. Furthermore, the H 2 and CO molecules have different orientations in the C 58 cage, namely, the orientation of the molecular axis of the former is normal to the face of the 7-member ring, while that of the latter is parallel to that face. In addition, the H–H bond of the H 2 molecule is shortened inside the cage, whereas the length of the C–O bond remains unchanged.
Free agents’ impact on the labor market for baseball players

This paper evaluates the 1976 free agent rule’s impact on the labor market for baseball players. Free agency has specific consequences for monopsonistic exploitation and racial discrimination in salary determination. It reduces monopsonistic exploitation for all players and increases salary opportunities for black and Latino players. However, this change in a player’s status vis-a-vis a team has generated salary disparities among players based, not on race, but bargaining position.