cssi/SciSciGPT-SciSciNet huggingface dataset:
Impostorism in American medical students during early clinical training: gender differences and intercorrelating factors.

Objectives This study examined the incidence and severity of impostorism in third-year medical students as they transitioned from the preclinical to clinical phases of training. Methods A cross-sectional study was conducted in third-year medical students (N=215). Respondents completed a voluntary, anonymous, 60-item survey that included the Clance Impostor Phenomenon Scale and the Perceived Stress Scale. Student's-t, Mann-Whitney, and Chi-Square tests and Pearson correlation were used to determine differences between subgroups of students and relationships between instruments scores and demographic parameters. Results Fifty-nine percent of students responded with N=112 (59% female) completing at least one instrument. The mean impostor score was 63.0 ± 14.6 (moderate-to-frequent impostor feelings) and was 9% higher in females (U=1181, p = .046). Perceived Stress scores for females were 17% higher than males (t(109)=2.87, p=.005). Females had lower United States Medical Licensing Examination (USMLE) Step 1 scores (t(107)= 3.06, p=.003). Impostor and perceived stress scores were correlated for males (r(46)=.47, p=.002) and females (r(64)=.54,p<.0001). Impostor and USMLE Step 1 scores were negatively correlated for males (r(45) =-.32, p= .034) but not females (r(63) = -.11, p=.40). Conclusions These findings demonstrate the intercorrelation between impostorism and stress in male and female medical students and raise interesting questions regarding the contributions of gender and other factors involved with medical training.
Randomized Robust matrix Completion for the Community Detection Problem

This paper focuses on the unsupervised clustering of large partially observed graphs. We propose a provable randomized framework in which a clustering algorithm is applied to a graph’s adjacency matrix generated from a stochastic block model. A sub-matrix is constructed using random sampling, and the low rank component is found using a convex-optimization-based matrix completion algorithm. The clusters are then identified based on this low rank component using a correlation-based retrieval step. Additionally, a new random node sampling algorithm is presented which significantly improves upon the performance of the clustering algorithm with unbalanced data. Given a partially observed graph with adjacency matrix $\mathrm{A} \in \mathbb{R}^{N\times N},$ the proposed approach can reduce the computational complexity from $\mathrm{O}(N^{2})$ to $\mathrm{O}(N)$.
Stereoscopic television system

Abstract A high-resolution stereoscopic television system has been developed for remote viewing applications requiring depth perception. Two camera chains are used, their video outputs being displayed on two miniature kinescope. The kinescope are viewed as binoculars to provide the separate perspective images for the two eyes. Many of the difficults problems encountered in the development of stereoscopic television have been overcome In particular, it avoids the requirement of closely matched components. The resolution obtained is 500 lines for each perspective image. A lower resolution multiple-observer system used in conjunction with the binocular device is suggested.
Referral, Learning and Inventory Decisions in Social Networks

With the proliferation of digital social networks and social media like Facebook, Twitter, and Instagram, businesses increasingly used referral programs to increase market exposure and sales. We study the interactions between social learning and referral programs and examine their impact on demand uncertainty and firms' inventory decisions. We characterize customers' purchasing strategies based on their knowledge of their own preference types and their observation of others' purchasing decisions and then derive the demand distributions when customers are involved in social learning in a referral program. While customers who lack knowledge of their own preferences introduce bias to the demand expectation, social learning reduces the bias at the expense of increasing demand variance. We examine two effects of stock-outs: (i) the \emph{market exposure effect} is the negative effect of stock-out of one product on the sales of another product due to the structure of referral program, and (ii) the \emph{demand substitution effect} on customer's choices when one product goes out of stock. We characterize the optimal inventory levels for a different number of referrals. We find that the optimal inventory levels are governed by different combinations of the two effects under different ranges of the number of referrals. For a low number of referrals, the market exposure effect is dominant because the stock-out of one product can end the referral chains while for a high number of referrals the substitution effect is dominant because the referral chains do not end until either both products are out of stock or all customers are reached through referral chains. In the middle range of values for the number of referrals, both effects become important because the stock-out of the more popular product can lead to the end of referral chains while the stock-out of the less popular product may not end referral chains and cause substitution by customers. These effects are not observed in traditional inventory problems and are present due to the rich interaction between social learning and referral program structure.
Nonparametric scoring rules

A scoring rule is a device for eliciting and assessing probabilistic forecasts from an agent. When dealing with continuous outcome spaces, and absent any prior insights into the structure of the agent's beliefs, the rule should allow for a flexible reporting interface that can accurately represent complicated, multi-modal distributions. In this paper, we provide such a scoring rule based on a nonparametric approach of eliciting a set of samples from the agent and efficiently evaluating the score using kernel methods. We prove that sampled reports of increasing size converge rapidly to the true score, and that sampled reports are approximately optimal. We also demonstrate a connection between the scoring rule and the maximum mean discrepancy divergence. Experimental results are provided that confirm rapid convergence and that the expected score correlates well with standard notions of divergence, both important considerations for ensuring that agents are incentivized to report accurate information.
Is it agriculture yet? Intensified maize-use at 1000 cal BC in the Soconusco and Mesoamerica

Abstract The development of food production in Mesoamerica was a complex and protracted process. We argue that while maize had been cultivated for many millennia, this cereal grain assumed a markedly more important role in the political economy of the Soconusco (and elsewhere in Mexico, Guatemala and Belize) only after 1000 cal BC. Macrobotanical data from the long-occupied village of Cuauhtemoc document low-level maize production from 1900 to 1400 cal BC with a significant increase during the final centuries of the site’s occupation after 1000 cal BC. Botanical evidence of increased maize consumption at this time occurred with evidence for changing groundstone use, intensified exploitation of dog and deer as well as iconography linking maize with rulership. This was also when monumental architecture was first built to mark a regional hierarchy of political centers. Changes evident in the Soconusco at 1000 cal BC parallel transformations in both highland and lowland regions of Mesoamerica when ceramic-using villagers expanded into new environments, farther away from the permanent water sources favored by Late Archaic and Early Formative peoples. We interpret the changes evident at 1000 cal BC in terms of both proximate historical factors as well as ultimate adaptive causes to produce a fuller understanding of changing Mesoamerican food production practices.
Characterization of mammary-derived growth factor 1 receptors and response in human mammary epithelial cell lines

Mammary-derived growth factor 1 (MDGF1, with a molecular mass of 62 kDa and pI of 4.8) has been purified from human milk (Bano, M., Salomon, D. S., and Kidwell, W. R. (1985) J. Biol. Chem. 260, 5745-5752). N-terminal sequence of 18 amino acids showed no homology to any known growth promoting peptides. The present study was carried out to evaluate the biological effects of and binding sites for MDGF1 on normal human and breast cancer cell lines. At a concentration of 10-25 ng/ml the factor stimulated the growth of estrogen receptor-positive MCF-7 human breast cancer cells by 50% and also stimulated the synthesis of collagen IV by 40%. It did not have any effect on ZR75-1, T47-D, and MDA-MB 231 cells. The factor showed a biphasic effect on the estrogen receptor-negative MDA-MB 468 cells at concentrations above 5 ng/ml. The growth of normal human mammary epithelial cells (184 strain) was enhanced by 35%, whereas immortalized non-tumorigenic 184A1N4 human mammary epithelial cells were stimulated by about 60-70%. However, transformation of these cells by SV40-T, v-Ha-ras, or v-mos desensitized them to MDGF1. Iodinated MDGF1 binds to moderate affinity sites on the responsive MCF-7, MDA-MB 468, and 184A1N4 cell lines (KD = 6 x 10(-9) M). Cross-linking of 125I-MDGF1 to binding sites revealed the presence of a major band of molecular mass of approximately 180-200 kDa in MCF-7 and MDA-MB 468 cell lines. Labeling of this band was inhibited by excess unlabeled MDGF1. These data suggest that human mammary epithelial cell lines possess receptors for MDGF1.
Regulation of adenosine 3':5'-monophosphate content in human astrocytoma cells by adenosine and the adenine nucleotides.

Abstract Adenosine and the adenine nucleotides AMP, ADP, and ATP (but not adenine) cause a rapid increase in the concentration of adenosine 3':5'-monophosphate (cAMP) in cultured human astrocytoma cells. Adenosine and AMP are equi-potent, causing a half-maximal rise in cAMP content at a concentration of about 10 µm. The time course of a rise in cAMP content to the maximal level effected by adenosine or AMP is the same (t1/2 ≃ 1 min). AMP is converted to adenosine in the incubation medium but not to an extent sufficient to account for its effect. The rate of uptake of adenosine into the cells is markedly faster than that of AMP, even though the t1/2 of their effects is the same. During a 10-min exposure of cells to 100 µm [3H]adenosine, the intracellular concentration of cAMP rises to 600 to 800 pmoles per mg of protein, of which only 30 to 40 pmoles per mg of protein are contributed by exogenous adenosine. The uptake of adenosine can be inhibited to greater than 95% by dipyridamole without any inhibition of the effect of adenosine on cAMP content. Such observations suggest that nucleotides act directly and need not be converted to adenosine to cause a rise in intracellular cAMP and that adenosine need not enter the cell to increase cAMP content. Theophylline is a rapidly acting, competitive inhibitor of the effect of adenosine. The inhibitory effect of theophylline is presumed to occur at the proposed extracellular site of action of adenosine and could not be related by our experiments to its well known action as an inhibitor of phosphodiesterase activity. On the other hand, papaverine potentiates the effect of adenosine, presumably as a result of the inhibition of phosphodiesterase. In contrast to theophylline, papaverine is a potent inhibitor (I50 = 17 µm) of the soluble, low Km phosphodiesterase from the astrocytoma cells. Catecholamines, which potentiate the effect of adenosine in brain slices, cause only additive increases in cAMP content in the astrocytoma cells when present with adenosine. Neither α- nor β-adrenergic receptor antagonists (phentolamine and propranolol) have any inhibitory action on the effect of adenosine. The results suggest that adenosine increases intracellular cAMP content as a result of its interaction with a specific plasma membrane surface receptor which results in the activation of adenylate cyclase.
Stoichiometry of Photosynthetic Phosphorylation

Abstract The P/2e- ratio of noncyclic photophosphorylation was investigated in the light of recent reports that it is greater than one and may reflect the existence of two types of electron transport, a phosphorylating and a nonphosphorylating type, superimposed on each other. Our results, obtained under experimental conditions that included those reported to be conducive to high ratios, are consistent with the operation in noncyclic photophosphorylation of only one type of electron transport which, in the presence of ADP, orthophosphate, and Mg++, leads to ATP formation with a P/2e- of 1. The reported P/2e- ratios approaching 4 when electron acceptors such as ferricyanide are added at slow rates were not confirmed.
Linear and non-linear disturbance evolution in a compressible boundary-layer with localized roughness

A numerical investigation of disturbance amplification in a laminar compressible flat-plate boundary layer with a localized two-dimensional roughness is carried out. Both linear and weakly non-linear disturbance evolution are considered. The non-linear case exhibits a secondary subharmonic resonance. In addition to deterministic simulations, a stochastic approach is applied. The random parameter is chosen to be the height of the roughness in the linear case, while in the non-linear case the amplitude of the primary disturbance is considered a random parameter.
Platelet Composite Coatings for Tin Whisker Mitigation

Reliable methods for tin whisker mitigation are needed for applications that utilize tin-plated commercial components. Tin can grow whiskers that can lead to electrical shorting, possibly causing critical systems to fail catastrophically. The mechanisms of tin whisker growth are unclear and this makes prediction of the lifetimes of critical components uncertain. The development of robust methods for tin whisker mitigation is currently the best approach to eliminating the risk of shorting. Current mitigation methods are based on unfilled polymer coatings that are not impenetrable to tin whiskers. In this paper we report tin whisker mitigation results for several filled polymer coatings. The whisker-penetration resistance of the coatings was evaluated at elevated temperature and high humidity and under temperature cycling conditions. The composite coatings comprised Ni and MgF2-coated Al/Ni/Al platelets in epoxy resin or silicone rubber. In addition to improved whisker mitigation, these platelet composites have enhanced thermal conductivity and dielectric constant compared with unfilled polymers.
Kinetic Method Analysis of the Effect of cis- and trans-Hydroxylation on the Proton Affinity of Proline

Proton affinities of proline and hydroxyproline were measured using the Cooks’ kinetic method. The measurements show that hydroxylation increases the proton affinity, which is consistent with X3LYP computation results. This work supports findings from a previous study (S. Mezzache et al., Rapid Commun. Mass Spectrom. 2005, 19, 2279) that modification of proline increases its proton affinity, but it does not provide compelling evidence for the prediction in the same study that proton affinity of the molecule is substantially influenced by intramolecular interactions involving the proton. PBE1PBE calculations suggest that isotropic polarizability rather than intramolecular hydrogen-bonding interactions provides a more suitable diagnosis for trends in proton affinity changes associated with modifications.
Predicted Risk of Mortality, Transfusion, and Postoperative Outcomes in Isolated Primary Valve Operations

Background Transfusion has been linked with increased postoperative morbidity and death after cardiac operations. The purpose of this study was to determine the associations among The Society of Thoracic Surgeons Predicted Risk of Mortality (PROM), transfusion, and postoperative outcomes in patients who underwent isolated primary valve operations. Methods A retrospective review of the local Society of Thoracic Surgeons database of 1,575 adults undergoing isolated primary valve operations from 2003 to 2013 at a United States academic center was performed. Patients were compared by their postoperative transfusion status (NONE vs TRANS) and by PROM. Taking into account procedure type and preoperative hemoglobin, three-step multiple linear or logistic regression analyses were performed to assess (1) the influence of PROM on postoperative outcomes, (2) influence of PROM on transfusion, and (3) influence of PROM and transfusion on postoperative outcomes. Results Of 1,575 patients studied, 1,245 (79%) received transfusions. The mean PROM was 1.2% (95% confidence interval [CI], 1.1 to 1.3) for patients in the NONE group, and was 2.7% (95% CI, 2.6 to 2.9) for the TRANS group. The correlation between PROM and total red blood cell units transfused was r = 0.31 ( p Conclusions Increased PROM yielded higher risks of transfusion. Postoperative outcomes were worse in patients who received a transfusion. This study suggests that the association between transfusion and clinical outcomes may be partly explained by the higher PROM among patients who ultimately received transfusions.
TGF-β type II receptor in rat renal vascular development: Localization to juxtaglomerular cells

TGF-γ type II receptor in rat renal vascular development: Localization to juxtaglomerular cells. To further define the role of transforming growth factor-beta (TGF-γ) receptors in renal vascular development, detailed immunohistochemical studies of TGF-γ receptor expression were performed from gestational day 15 through adulthood. On gestational day 15, TGF-γ type II receptor immunoreactivity was restricted to perirenal stromal and vascular cells. On gestational day 17 TGF-γ type II receptor immunoreactive stromal cells were observed within the kidney, with the same distribution as stromal α-smooth muscle actin and renin immunoreactive cells, and intense stromal TGF-γ type II receptor immunoreactivity continued through postnatal day 5. As vascular development progressed, TGF-γ type II receptor, α-smooth muscle actin and renin immunoreactivity became progressively restricted to small renal arteries and arterioles. Expression of TGF-γ type II receptors and renin was very intense in afferent glomerular arterioles during postnatal days 5 to 15, and then became progressively restricted only to juxtaglomerular cells in the mature kidney. TGF-γ type I receptor (ALK-5, ALK-1 and ALK-2) immunoreactivity was not detected in stromal or vascular elements during development or in the mature kidney. Intense TGF-γ type II receptor expression in renal stromal vascular smooth muscle cell precursors and developing blood vessels suggests a role for the TGF-γ type II receptors in the formation of the renal vascular smooth muscle compartment. The continued intense expression in juxtaglomerular cells argues for a role in renin synthesis and/or release. The absence of ALK-5, ALK-1, and ALK-2 in developing vascular smooth muscle and mature juxtaglomerular cells indicates that the canonical view of TGF-γ signaling may not hold in these locations.
Expression of vascular endothelial growth factor and Flk-1 in developing and glucocorticoid-treated mouse lung.

Although the endothelial cell is the most abundant cell type in the differentiated lung, little is known about regulation of lung developmental vasculogenesis. Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen and angiogenic factor that has putative roles in vascular development. Mitogenic actions of VEGF are mediated by the tyrosine kinase receptor KDR/murine homologue fetal liver kinase Flk-1. HLF (hypoxia-inducible factor-like factor) is a transcription factor that increases VEGF gene transcription. Dexamethasone augments lung maturation in fetal and postnatal animals. However, in vitro studies suggest that dexamethasone blocks induction of VEGF. The objectives for the current study were to measure VEGF mRNA and Flk-1 mRNA in developing mouse lung and to measure the effects of dexamethasone treatment in vivo on VEGF and Flk-1 in newborn mouse lung. Our results show that VEGF and Flk-1 messages increase in parallel during normal lung development (d 13 embryonic to adult) and that the distal epithelium expresses VEGF mRNA at all ages examined. Dexamethasone (0.1–5.0 mg·kg−1·d−1) treatment of 6-d-old mice resulted in significantly increased VEGF, HLF, and Flk-1 mRNA. Dexamethasone did not affect cell-specific expression of VEGF, VEGF protein, or proportions of VEGF mRNA splice variants. These data suggest that the developing alveolar epithelium has an important role in regulating alveolar capillary development. In addition, unlike effects on cultured cells, dexamethasone, even in relatively high doses, did not adversely affect VEGF expression in vivo. The relatively high levels of VEGF and Flk-1 mRNA in adult lung imply a role for pulmonary VEGF in endothelial cell maintenance or capillary permeability.
"It's better to be smart than dumb" or the clinical importance of ignorance.

I n the course of clinical teaching, it is not unusual to preserve and propagate maxims: pithy, usually practical guides for intellectual, medical, and personal conduct. We know them as “pearls.” We joke about pearls. We drop them. We covet them the way a poet relishes a succinct sonorous rhyme. They are the haiku of medicine. Their influence is sometimes in excess of their validity. It is usually true that “you never see a fat pheo,” but “never” is a word too precise for clinical medicine. Medical pearls may be misapplied to circumstances outside the clinical arena. “The patient always comes first” is turning out not to be a totally supportable political or economic principle. After 20 years of rounding and lecturing, I have accumulated some of my own pearls. I would like to examine one of these maxims in the light of some of medicine’s contemporary dilemmas. Lee’s first rule states that it is better to be smart than dumb. This scholiurn used to be infrequently required, but lately I find myself using it more and more. And I find myself increasingly curious about the need to repetitively emphasize what seems to be so obviously pertinent to medicine. The answer is to be found, in part, in two ancient, seemingly inimical notions that have reentered a cycle of popularity and influence during the past few years: economic realism and mystical medicine. Ever since bipedal primates became self-conscious and aware of their individual aloneness, humankind has had to deal with illness, pain, and death as more than a fact of life. Explanations and remedies had to be explored and constructed, as much for social solace as for individual restoration. The idea that the quality of life determines the course of individual human existence is the fundamental concern of mystical medicine: disease and damnation are the inexorable consequence of debauchery and deviation. Illness can be produced by social and spiritual malfeasance as well as by biologic malfunction. Dietary, dialectic, and devotional rules and rituals have been created to prevent and to repair the baleful effects of bad thoughts, bad living, bad spirits, and bad biology. The liturgies and rites of the world’s religions contain elements of mystical medicine.
Validation of fractal-like kinetic models by time-resolved binding kinetics of dansylamide and carbonic anhydrase in crowded media.

Kinetic studies of biochemical reactions are typically carried out in a dilute solution that rarely contains anything more than reactants, products, and buffers. In such studies, mass-action-based kinetic models are used to analyze the progress curves. However, intracellular compartments are crowded by macromolecules. Therefore, we investigated the adequacy of the proposed generalizations of the mass-action model, which are meant to describe reactions in crowded media. To validate these models, we measured time-resolved kinetics for dansylamide binding to carbonic anhydrase in solutions crowded with polyethylene glycol and Ficoll. The measured progress curves clearly show the effects of crowding. The fractal-like model proposed by Savageau was used to fit these curves. In this model, the association rate coefficient ka allometrically depends on concentrations of reactants. We also considered the fractal kinetic model proposed by Schnell and Turner, in which ka depends on time according to a Zipf-Mandelbrot distribution, and some generalizations of these models. We found that the generalization of the mass-action model, in which association and dissociation rate coefficients are concentration-dependent, represents the preferred model. Other models based on time-dependent rate coefficients were inadequate or not preferred by model selection criteria.
On the numerical solution of differential equations for renal counterflow systems.

The mathematical models of the renal concentrating mechanism contribute toward an increased understanding of renal function. These models involve the solution of a system of differential equations for the renal counterflow systems. Analytic solutions of these differential equations, except for very simple models, cannot be obtained. Therefore numerical methods have to be used. One of the principal considerations, in the selection of a numerical method, is to strike a proper balance between the total computational effort and the minimization of discretization (truncation) errors, so that the resulting numerical solution is a reasonably close approximation to the correct solution of the differential equations. There are two ways in which the discretization error can be decreased. The first is to decrease the size of the discretization step-usually called the space chop or step size. Naturally, this leads to an increase in the total amount of storage and computation and often also an increase in the computer round-off errors. The second alternative is to select a numerical method which, for a given space chop, has a small discretization error. This also leads to an increase in the computational effort, particularly in the number of function evaluations. In a recent paper in this Journal (I) we described how the physiological connectivity and flow directions in the various tubules constituting a nephron can be exploited to develop sparse matrix methods which lead to a decrease in the
On steady state uniqueness and multiplicity in gas-liquid continuous stirred tank reactors with fast reactions

Abstract The steady state behavior of a non-adiabatic gas-liquid continuous stirred tank reactor with fast pseudo-first-order reactions is analyzed via two models. Both models explicitly account for the nature of the gas feed, and one also accounts for possible variations in the interfacial area a with conversion and temperature. Steady state uniqueness and multiplicity criteria are obtained for diverse conditions of the gas feed, both when a is variable and when it is assumed to be invariant. It is shown that the occurrence of steady state multiplicity in such reacting systems is strongly dependent on the nature of the gas feed. It is also shown that large differences in the predictions of uniqueness and multiplicity can arise if variation in a is not taken into consideration, especially for solute-rich gas feeds.
Synthesis of some organotins containing the cyclopentane ring

Abstract The synthesis of the cis and trans isomers of 2-hydroxymethylcyclopentyltrimethylstannane and of cis -2-hydroxycyclopentylmethyltrimethylstannane are described, with 2-carbethoxycyclopentanone used as the common source of the carbon skeleton.
Thrombolysis versus primary percutaneous transluminal coronary angioplasty for acute myocardial infarction

For the patient with acute myocardial infarction (MI), both primary percutaneous transluminal coronary angioplasty (PTCA) and intravenous thrombolytic therapy are effective in restoring antegrade coronary blood flow, improving left ventricular systolic function, and reducing mortality. Primary PTCA is effective when performed quickly by experienced operators. It is the preferred therapy in the patient a) with a contraindication to thrombolytic therapy, b) aged 70 years or older, and c) in whom thrombolytic therapy is likely to be ineffective (ie, the patient with cardiogenic shock). Thrombolytic therapy is widely available and can be given quickly and easily. As a result, it remains the treatment of choice for most patients with acute MI. The goal of therapy for the patient with acute MI is the rapid and sustained restoration of coronary blood flow. For the individual patient, the better therapy-primary PTCA or thrombolytic therapy-is the one that can be given more safely and expeditiously.
Reduction of N-oxides and sulfoxide by the same terminal reductase inProteus mirabilis

Proteus mirabilis can grow anaerobically on the fermentable substrate, glucose. When the glucose medium was supplemented with an electron acceptor, growth doubled. However, the organism failed to grow anaerobically on the oxidizable substrate glycerol unless the medium was supplemented with an external electron acceptor. Dimethyl sulfoxide (DMSO), trimethylamine N-oxide (TMAO), nicotinamide N-oxide (NAMO), and nitrate (NO3) can serve this function. Cell-free extracts ofP. mirabilis can reduce these compounds in the presence of various electron donors. In order to determine whether the same or different terminal reductase(s) are involved in the reduction of these compounds, we isolated mutants unable to grow on glycerol/DMSO medium. When these mutants were tested on glycerol medium containing TMAO, NAMO, and NO3 as electron acceptors, it was found that there were two groups. Group I mutants were unable to grow with DMSO, TMAO, and NAMO, while their growth was unaffected with NO3. Group II mutants were unable to grow on any electron acceptor including NO3. Enzyme assays using reduced benzyl viologen with both groups of mutants were in agreement with growth studies. On the basis of these results, we conclude that the same terminal reductase is involved in the reduction of DMSO, TMAO, and NAMO (group I) and that the additional loss of NO3 reductase in group II mutants is probably owing to a defect in the synthesis or insertion of molybdenum cofactor.
Efficient xerographic photoreceptors from conjugated polymers and polymer blends

Bilayer xerographic photoreceptors in which (pi)-conjugated polymers and binary conjugated polymer blends are used as the charge generation layer have been fabricated, evaluated, and shown to be highly efficient. Devices incorporating poly(1,4-phenylene benzobisthiazole), poly(2,5-pyridylene benzobisthiazole), poly(l ,4-phenylenebisvinylene benzobisthiazole), poly(1 ,4-(2-hydroxy)phenylene benzobisthiazole), and poly(benzimidazobenzophenanthroline ladder) as the charge generation layer and a layer of tris(p-tolyl)amine (TTA) dispersed in polycarbonate as the charge-transport layer showed good photosensitivities (6-18 ergs/cm 2 ), good dark decay characteristics (2-10 V/s at surface potentials of 400- 600 V), and high charge generation quantum efficiencies (20-50% at ~10 6 V/cm). Photoreceptors using binary blends of conjugated polymers had enhanced spectral range of photosensitivity (300-700 nm) and significantly enhanced quantum yield for charge photogeneration relative to the component conjugated polymers. Photocarrier generation in these bilayer photoreceptors is extrinsic in nature and is mediated by exciplex formation between the conjugated polymer and TTA at the bilayer interface. Observed nanoscale size effects, in which the photoreceptor performance (quantum efficiency, photosensitivity) is enhanced with decreasing size of the charge generation layer, provide a means of tuning the photoconductive properties of optoelectronic devices based on conjugated polymers. A model derived from Onsager's 1934 theory was used to estimate the primary quantum yield of ion-pairs and ion-pair separation distance in the bilayer photoreceptors to be 0.21-0.62, and 4-6 angstroms, respectively.
Bridging the gap between stewards and creators

Many technology-intensive companies today depend on employees with specialized technical skills, and managers may not fully understand the work these employees do. Moreover, managers and technical employees may have very different worldviews, and their worldviews may conflict during the process of business innovation. After researching the movement of Internet and computing pioneers among various organizations during a period between the early 1960s and the mid-1990s, the authors identified two distinct personality types that are both vital to successful technological innovation ? but whose mindsets often clash. The authors dub these two types stewards and creators. An organization?s stewards are usually managers; their goal is the careful allocation of the organization?s resources, with an aim of achieving an optimal return on investment. Creators, on the other hand, are often skilled, specialized employees, and their focus is on a grand vision and mission; they frequently view business concerns as secondary. According to the authors, conflict between stewards and creators is, to some extent, inevitable. However, when such conflict is managed poorly, the organization?s capacity to innovate effectively may be impaired. The authors suggest eight guidelines for managing steward-creator conflict more successfully. These guidelines include (1) Keep talented creators around, although they can be difficult to manage; (2) balance the influence of stewards and creators in the organization, so neither group always wins; (3) cultivate people who have credibility with both creators and stewards and can help resolve conflicts; (4) use peer review to more accurately evaluate creators? specialized technical work; (5) structure the innovation process so that creators produce tangible artifacts regularly; (6) realize that there will always be some conflict between an organizations? creators and its stewards; (7) avoid overly prescriptive control mechanisms that may alienate creators; and (8) ensure that closure on projects is achieved neither too quickly nor too slowly.
NMR studies of equilibria between lewis bases and tetrabenzylzirconium or tetrabenzylhafnium

Abstract Equilibrium quotients (Q) for the reaction (M = Zr, B = pyridine, 4-picoline, 3,5-lutidine; M = Hf, B = tetrahydrofuran) have been obtained in chlorobenzene solvent. The value has also baeen obtained in 1,4-dioxane for the system (C6H5CH2)4Zr/4·picoline. Equilibrium quitients increase with a change of base in the order tetrahydrofuran
Electrochemical features of platelet interactions

Abstract Platelets participate in hemostasis and thrombus formation. The physicochemical basis at the molecular level for platelet adhesion, cohesion to form aggregates and the resultant viscous metamorphosis is not well understood. Under physiological conditions, blood platelets possess a net negative charge and decreases or changes in this charge have been implicated in both their adhesion and aggregation. The peripheral zone of the platelet contains glycoproteins and glycolipids. A variety of charged groups are present including positively charged amino groups and at least three types of negatively charged groups. The carboxyl group of terminal sialic acid residues is considered to be a major contributor to the negative charge of platelets. Removal of as little as 10 percent of the peripheral zone sialic acid by neuraminidase results in a shortened platelet lifespan in vivo . The electrokinetic properties of blood platelets are changed by interaction with a great variety of agents. In those cases where specific adsorption occurs it is possible to study the relationship between adsorption, change in surface charge, and the process of aggregation. It should be noted that in physiological media only those charge groups within about 8 A of the electrophoretic surface of the platelet will contribute to a significant extent to the electrophoretic properties. The electrophoretic mobility of platelets has been determined for a variety of animal species and in humans for a wide spectrum of disease situations. The measurement of platelet electrophoretic mobilities before and after treatment with adenosine diphosphate and norepinephrine has been introduced as a test of platelet function. However, so many variables may influence the surface properties of blood platelets including method of preparation, time, temperature, pH, contact phenomena, shear conditions, ionic strength and composition of suspending media, conditions for mobility measurements, etc., that considerable apparent disagreement exists in the literature regarding platelet electrokinetics.
Intraoperative radiation therapy for locally advanced recurrent rectal or rectosigmoid cancer

Abstract Background and purpose : To update and summarize the experience at the Massachusetts General Hospital of a treatment program of high-dose preoperative irradiation, surgical re-resection, and intraoperative radiation therapy (IORT) as a salvage treatment for patients with recurrent rectal or rectosigmoid carcinoma. Patients and methods : From June 1978 to February 1997, the records of 69 patients with locally recurrent rectal carcinomas or rectosigmoid carcinomas without metastases referred for consideration of IORT were reviewed. Forty-nine patients received IORT and local control and disease-free survival curves were calculated using the actuarial method of Kaplan–Meier. Results : The 5-year overall survival, local control and disease-free survival rates of 49 patients receiving IORT were 27, 35, and 20%, respectively. Thirty-four patients who underwent a macroscopic complete resection had a significantly better 5-year overall survival than the remaining 15 patients with gross residual disease (33 vs. 13%, P =0.05, log rank). For those patients, local control and disease-free survival rates were 46 and 27%, respectively. Patients with a microscopic complete resection had a superior 5-year overall survival than partially resected patients (40 vs. 14%, P =0.0001, log rank). Chemotherapy had no significant influence on overall or disease-free survival. Conclusion : The current analysis shows the importance of a microscopic complete resection in a multi-modality approach with IORT for survival and local control. Salvage is rare for patients undergoing subtotal resection.
Methylmercury movements across the perfused guinea pig placenta in late gestation

Abstract Placentas from guinea pigs between 61 and 63 days gestation were perfused from the fetal side in situ at rates ranging from 0.35 to 4.54 ml/min. The dam was injected intravenously with tracer quantities of tritiated water and radiolabeled mercury in the form of methylmercuric chloride. Maternal plasma and the perfusate samples were analyzed for radiolabeled mercury and tritiated water, and corrections were made for net water flows by using radioiodinated serum albumin. Radiomercury and tritium clearances were therefore measured concurrently. The clearance of tritiated water was a linear function of perfusion rate. The relationship between tritium clearance and perfusion rate for all experiments combined was described by the equation: y = 0.16 + 0.54 x , where y is tritium clearance and x is perfusion rate. Clearance of radiolabeled mercury measured 0.15 ± 0.01 ml/min (mean ± SE). No significant relationship between radiomercury and tritium clearance was detected. It appears that calcium and low concentrations of methylmercury may move across the placenta by the same or similar mechanisms.
Reliability of myocardial perfusion quantification in angiography using a digital flat panel cardiac system

Discordance between lesion severity from angiocardiography and physiological effects has been reported elsewhere. Quantification of myocardial perfusion during the angiography procedure may supply additional information about short- and long-term outcomes and may be helpful for clinical decision making. In previous works, myocardial perfusion has been assessed using time density curves (TDC), which represent the contrast medium dilution over time in the myocardium. The mean transit time (MTT), derived from the TDC, has been reported as a good indicator of the regional myocardial perfusion. Our objective is to estimate the accuracy and reproducibility of MTT estimation on digital flat panel (DFP) images. We have simulated typical myocardium TDC obtained with a DFP cardiac system (Innova 2000, GE), taking into account scatter and noise. Logarithmic or linear subtractions have been applied to derive a contrast medium concentration proportional quantity from image intensity. A non-linear minimisation realises the model curve fitting. MTT estimates are more stable with linear subtraction in presence of scatter. However logarithmic subtraction presents smaller bias when scatter level is small. Both approaches are equally sensible to image noise. Linear subtraction should be preferred. Image noise has a high influence on MTT accuracy and we may reduce.
XOR performance of a quantum dot semiconductor optical amplifier based Mach-Zehnder interferometer.

The performance of all-optical XOR gate based on quantum-dot (QD) SOA MZI has been simulated. The saturation power, optical gain and phase response of a QD SOA has been analyzed numerically using a rate equation model of quantum dots embedded in a wetting layer. The calculated response is used to model the XOR performance. For the parameters used here, XOR operation at ~250 Gb/s is feasible using QD based Mach-Zehnder interferometers. The speed is limited by the relaxation time from wetting layer to the quantum dots.
Kinetics of DCE and VC mineralization under methanogenic and Fe(III)- reducing conditions

The kinetics of anaerobic mineralization of DCE and VC under methanogenic and Fe(III)-reducing conditions as a function of dissolved contaminant concentration were evaluated. Microorganisms indigenous to creek bed sedi ments, where groundwater contaminated with chlorinated ethenes continuously discharges, demonstrated significant mineralization of DCE and VC under methanogenic and Fe(III)-reducing conditions. Over 37 days, the recovery of [1,2-14C]VC radioactivity as 14CO2 ranged from 5% to 44% and from 8% to 100% under methanogenic and Fe(III)-reducing conditions, respectively. The recovery of [1,2-14C]DCE radioactivity as 14CO2 ranged from 4% to 14% and did not vary significantly between methanogenic and Fe(III)-reducing conditions. VC mineralization was described by Michaelis−Menten kinetics. Under methanogenic condi tions, Vmax was 0.19 ± 0.01 μmol L-1 d-1 and the half-saturation constant, km, was 7.6 ± 1.7 μM. Under Fe(III)-reducing conditions, Vmax was 0.76 ± 0.07 μmol L-1 d-1 and km was 1.3 ± 0.5 μ...
Behavioral and subjective effects of ethanol: relationship to cerebral metabolism using PET.

This study examined the effects of ethanol on regional cerebral metabolic rate using positron emission tomography (PET). The study explored the relationship between the mood-altering effects of ethanol and its effects on regional cerebral glucose utilization (CMRglu) in eight healthy male volunteers. In the first phase of the study, the subjects participated in a behavioral preference procedure conducted in a recreational environment to determine their responses to ethanol (0.5 g/kg) in a naturalistic setting. They then participated in three PET sessions, receiving at three to seven day intervals, in counterbalanced order, placebo, 0.5 g/kg or 0.8 g/kg ethanol. PET scans were conducted using a PETT-VI scanner with F-18-2-fluoro-2-deoxyglucose (FDG) as the tracer. The mood-altering effects of ethanol were measured in both the naturalistic and the PET phases of the study. Ethanol produced comparable effects on mood in the naturalistic and the PET settings (i.e., increases in positive mood). The lower dose of ethanol produced variable effects on whole brain and regional CMRglu across subjects. There was some suggestion that certain regional metabolic changes after ethanol were correlated with subjective responses to the drug. The higher dose of ethanol decreased whole brain CMRglu in most subjects. All regions were affected about equally. It was concluded that the mood-altering effects of ethanol are not related in a simple manner to regional changes in CMRglu.
General M.G. Vallejo and the advent of the Americans : a biography

The gifts of fortune -- The pivotal year: 1841 -- The advent of the Americans -- A new governor brings crisis -- A small war heats up -- "Ojal a que lo tomen los americanos ("I hope the Americans take it") -- Prelude to revolt -- "Men with nothing to lose" -- The revolt begins -- Ordeal on the Sacramento -- Murder and misdirection -- What friend Larkin will do -- A changed man -- The Californians retake the South -- The slip and slide transition -- Consequences.
An exploratory study of pressure ulcers after spinal cord injury: relationship to protective behaviors and risk factors.

Abstract Krause JS, Vines CL, Farley TL, Sniezek J, Coker J. An exploratory study of pressure ulcers after spinal cord injury: relationship to protective behaviors and risk factors. Arch Phys Med Rehabil 2001;82:107-13. Objectives: To identify protective behaviors and risk factors associated with the development of pressure ulcers (PUs) after spinal cord injury (SCI). Design: A cross-sectional study to evaluate the relationship between protective behaviors and risk factors and 3 PU outcomes: a current PU, PUs within the past year, and ever hospitalized for a PU. Logistic regression was then used to identify the variables most strongly associated with PU outcomes. Setting: Data were collected by case managers employed by the Arkansas Spinal Cord Commission, an agency that provides services to persons with SCI. Participants: A total of 650 of 991 eligible individuals with SCI from a statewide population-based SCI registry participated. All ambulatory participants were eliminated, leaving 560 patients. Average age of the respondents was 27.2 years at injury (median age, 25yr) and 43.6 years at the time of the survey (median age, 42yr). Main Outcome Measures: A 200-item interview was developed to measure a broad range of outcomes associated with SCI (including secondary conditions such as PUs), as well as risk and protective behaviors related to these outcomes. Results: Several characteristics and behaviors were related to PU outcomes. Being underweight (odds ratio [OR] = 2.18), having used medications to treat pain (OR = 1.33) or spasticity (OR = 1.31), having smoked at least 100 cigarettes over a lifetime (OR = 1.31), and being a current smoker (OR = 1.21) were associated with having a PU in the past year. Having completed a college degree (OR = 0.23), being married (OR = 0.49), and being currently employed (OR = 0.54) were associated with a lower risk of having a PU in the past year. Being underweight (OR = 1.94), having a history of incarceration (OR = 1.78), having attempted suicide (OR = 1.71), and reporting alcohol or drug treatment (OR = 1.65) were associated with having been hospitalized for a PU since injury. This study was unable to evaluate the efficacy of traditional health maintenance or protective behaviors for PUs, such as weight shifts or skin checks. Conclusions: PUs are least likely to occur among individuals who maintain normal weight, return to a work and family role, and who do not have a history of tobacco use, suicidal behaviors, or self-reported incarcerations, or alcohol or drug abuse. Additional research is needed to identify better the risk factors for the occurrence of PUs. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
The effects of apomorphine and haldol on PCP induced behavioral and motor abnormalities in the rat

Abstract Behavioral abnormalities and motor dysfunctions induced by the administration of PCP to rats is antagonized by both the dopamine agonist apomorphite and the dopamine antagonist haloperidol. In the test situation used, however, the antagonistic effects of apomorphine were much more rapid than those of haloperidol. These results suggest that PCP may be acting on specific presynaptic dopamine receptors and that this reaction is effectively antagonized by low doses of apomorphine in a manner similar to its effects in reducing schizophrenic symptoms and choreiform movement disorders.