cssi/SciSciGPT-SciSciNet huggingface dataset:
Comparison of Linear and Nonlinear Forms of Isotherm Models for Strontium Sorption on a Sodium Bentonite

Sorption on bentonite will play an important role in retarding the migration of radionuclides from a waste repository. Bentonite is characterized by low permeability, water swelling capability and excellent sorption potential for cationic radionuclides. To correctly assess the sorption potential of radionuclides on bentonite is essential for the development of predictive migration models. The sorption isotherm model is usually used to describe the sorption behavior and assess the sorption potential of radionuclides on bentonite. However, there are few studies to investigate the feasibility of isotherm models for the sorption of radionuclides on bentonite. Thus, in this study, we compared the goodness-of-fit of linear and nonlinear forms of two common isotherm models, Langmuir and Freundlich equations. The experimental sorption isotherms of strontium (Sr) on Wyoming bentonite, MX-80, were used for illustration. The results showed that the nonlinear forms of Langmuir and Freundlich isotherm models are more suitable for fitting the experimental sorption isotherms of Sr on MX-80 than are the linear forms. Thus, the nonlinear forms of isotherm models should be primarily adopted to fit experimental isotherms. On the other hand, we also found that the goodness-of-fit of Langmuir model is better than that of Freundlich model. Moreover, based on the theoretical assumptions of Langmuir isotherm model, the parameters M and K L represent the sorption capacity and affinity, respectively. One can use the values of M and K L , obtained from fitting the experimental isotherms, to assess the sorption potential of radionuclides in bentonite. Thus, we suggested that the Langmuir isotherm model is more useful for investigating the sorption behavior of radionuclides on bentonite.
Influence of a Chemically Defined Diet on the Composition of Serum and Urine

We have studied the effects of ingestion of a chemically defined diet on the constituents of serum and urine of five normal volunteers. The diet, believed to meet all human nutritional requirements, caused a decrease in serum cholesterol and urea nitrogen and an increase in serum phosphate, uric acid, and creatinine. Urinary creatinine is unchanged from that of a random diet but urinary electrolytes, urea, and uric acid decrease to a new stable value, which is achieved after four days. High-resolution techniques have been used to measure the carbohydrate-containing constituents of urine and those that can be detected by their ultraviolet absorbance or their reaction with ninhydrin. A considerable decrease in the number of these urinary constituents is effected by the chemical diet within four days, but even by this time all compounds attributable to the random diet may not have been completely eliminated. Many urinary components that persist while the subjects are on the simplified diet have been tentatively identified.
Molecular dynamics simulations of ion-irradiation induced deflection of 2D graphene films

Abstract Ion-irradiation induced surface stress generation and the resulting deflection of 2D cantilever graphene films is studied using molecular dynamics (MD) simulations. The simulation results show that the free-end deflection is strongly dependent on the kinetic energy of the incident ions. At low incident energies (≪10 eV), the graphene film bends towards the irradiated side (upward deflection in our simulations); a transition from bending towards the irradiated side (upward deflection) to bending away from the irradiated side (downward deflection) occurs when the incident energy is ∼10 eV; the downward deflection peaks at ∼50 eV. Further increases of the incident energy cause the magnitude of downward deflection to decrease. The evolution of free-end deflection with respect to the number of incidences is also dependent on the incident energy. The dependence of the deflection behavior of the graphene films on the incident energy revealed by our atomistic simulations suggests the generation of intrinsic stress of different levels in the growing films. Such behavior may be attributed to competing mechanisms of production and annihilation of interstitial- and vacancy-like defects in the growing film. Understanding the dependence of thin film deflection on the incident energy provides guidelines for controlling thin film shapes at the nanometer scale using ion-beam machining.
Spectroscopic ellipsometry data analysis : measured versus calculated quantities

Abstract Spectroscopic ellipsometry is a very powerful technique for optical characterization of thin-film and bulk materials, but the technique measures functions of complex reflection coefficients, which are usually not of interest per se. The interesting characteristics, such as film thickness, surface roughness thickness and optical functions can be determined only by modeling the near-surface region of the sample Jones matrix. However, the measured quantities are not equivalent to those determined from the modeling. Ellipsometry measurements determine elements of the sample Mueller matrix, but the usual result of modeling calculations are elements of the sample. Often this difference is academic, but if the sample depolarizes the light, it is not. Ellipsometry calculations also include methods for determining the optical functions of materials. Data for bulk materials are usually accurate for substrates, but are not appropriate for most thin films. Therefore, reasonable parameterizations are quite useful in performing spectroscopic ellipsometry data analysis. Recently, there has been an increased interest in anisotropic materials, both in thin-film and bulk form. A generalized procedure will be presented for calculating the elements of the Jones matrix for any number of layers, any one of which may or may not be uniaxial.
Wave‐vector‐ and frequency‐dependent dielectric functions in the hartree‐fock‐slater approximation

The time-dependent Hartree-Fock-Slater equation was used to derive an expression for the wave-vector- and frequency-dependent dielectric function ϵ(q, ω). The effect of including the Xα exchange in the derivation is to subtract a term from the Coulomb contribution to the dielectric function in the random phase approximation. Self-consistent LCAO Hartree-Fock-Slater energy bands were used to compute (q, ω) at several points q along the [100], [110], and [111] axes in the first Brillouin zone. The real and imaginary parts of the dielectric function were computed independently. It was found that for wave vectors in the first Brillouin zone, there is little difference between the random phase and Hartree-Fock-Slater dielectric functions.
Unitarizable scalar multipoles

We show that the scalar multipole (□ +m2)n φ = 0 forn odd and all massesm⩾0 allows a Gupta-Bleuler-type quantization with a unitary space of physical states.
Selective activation of Ia afferents by transient muscle stretch

1. This report extends the work of Lundberg and Winsbury (1960a and 1960b) in emphasizing the usefulness of brief muscle stretch for selective activation of the primary endings of muscle spindles. 2. In 36 experiments on anesthetized cats a distribution of rhomboid stretch (20 msec duration) thresholds was obtained for activation of 393 stretch receptors from de-efferented soleus muscles maintained at comparable degrees of initial tension by setting length to give a peak of active tension during an isometric twitch. These receptors included 153 Ia afferents with conduction velocities greater than 75 m/sec, 127 Ib afferents and 97 group II afferents with conduction velocities below 65 m/sec. A pull of 60 μ or less activated 95% of the Ia fibers in contrast to 41% of the group II fibers and only 3% of the Ib fibers. At threshold the mean latency (normalized) between the onset of stretch and impulse arrival at the spinal cord (recording electrodes) was 5.4 msec for the Ia fibers (S.D.±1.7 msec), 10.6 (± 3.9) msec for the group II fibers, and 9.1 (± 3.3) msec for the Ib afferents. In all cases only one impulse was initiated by the test stretch and no significant differences were encountered in the responses of receptors located in proximal, middle and distal portions of the muscle. 3. In 7 experiments soleus nerve volleys were recorded at nerve-muscle and spinal cord-dorsal root levels during similar stretching procedures. A stretch of 5 μ amplitude was sufficient to generate a group I volley. As stretch amplitude was raised to 60 μ this volley grew progressively in size and decreased in duration as well as in latency from stretch onset to volley formation. A second volley, 1.5 to 2.0 msec after the first, developed with a 30 μ stretch. At 60 μ stretch its size was approximately 30–50% that of the first volley. Conduction velocity for the first volley was 90–110 m/sec and was faster than the second volley by 5–10 m/sec. Our data on isolated afferents suggest that the first volley is of Ia origin while the second volley represents predominantly a second discharge from some Ia afferents plus a minor group II input. Significant Ib contribution is excluded since only 4 of the 127 Ib fibers responded within this stretch range and then at latencies beyond formation of either volley.
Communication apprehension as temperamental expression: A Communibiological paradigm

Over the past two decades, a large amount of research focusing on correlates and consequences of communication apprehension has accumulated. Despite this massive research effort, few viable models of the development of the trait have been proffered. Also during the past twenty years, psychobiologists have made impressive strides toward the explanation of human behavior by identifying underlying neurological processes, especially in affective domains. In this essay, we propose a theory of communication apprehension, anchored in the trait‐oriented work of psychobiology as articulated in the temperament literature. Drawing from the extensive work of both psychobiologists and communication apprehension, researchers in our field, we contend that communication apprehension represents individuals’ expression of inborn, biological functioning, which has been shown to be antecedent to social experience and, therefore, independent of social learning processes. In formulating our theoretical framework, we (1) presen...
Structural Studies Of Islet Amyloid Polypeptide In The Presence Of Insulin And Lipid Membranes

Previous work by others has shown that insulin inhibits the formation of fibrils from islet amyloid polypeptide. The mechanism for the inhibition is not known. To address this issue, we are studying IAPP in the presence of lipid membranes, with or without insulin. Circular dichroism spectra of IAPP alone in phospholipid membranes show that it undergoes a structural rearrangement from α-helix to a β-sheet conformation. In the presence of insulin, this transition is not observed, that is, IAPP remained a-helical. To explain this, we are using other biophysical methods including solution-state NMR, electron microscopy, SDS-PAGE and limited proteolysis monitored by mass spectrometry. Results from these studies will be presented and discussed in this poster.
Aggregation of polyoxyethylene in dilute solutions

Light scattering as a function of scattering angle, concentration, and temperature reveals that polyoxyethylene (POE) forms large aggregates in benzene and chloroform, while in methanol and dioxane almost complete molecular dispersion occurs. Although the solutions containing large aggregates contain a distribution of molecular weights, the angular envelopes of c/R (θ) versus sin2θ/2 exhibit pronounced upward curvature, indicating that the aggregates are dense structures such as spheres or highly branched coils. In methanol, the angular envelopes exhibit moderate downward curvature, reflecting the essentially molecularly dispersed character of the solution and the breadth of the molecular weight distribution. In filtered solutions of dioxane, a tendency exists for minima to occur in the angular envelopes; this can be rationalized in terms of the anisotropy of the scattering. The polarized components of the scattered intensity VV, HV, VH, and HH were studied in the scattering plane. For the large aggregates HV is angular dependent, while in methanol and dioxane HV is independent of angle. Heating or cooling a POE solution in benzene followed by a study of the angular envelope, shows that the aggregates are stable. Hydrodynamic measurements fail to detect the existence of the aggregates. Taking all the data into consideration, the large aggregates appear to be compact, extensively branched, anisotropic, and stable.
Exposure to Violence and Achievement Motivation Beliefs: Moderating Roles of Cultural-Ecological Factors

This study conceptualized individual-level cultural-ecological factors (racial identity and religious coping) as adolescent assets that would promote achievement motivation and reduce negative associations between community violence exposure and motivation. Our examination of African American adolescents (N = 380) from urban contexts indicated a negative association between community violence exposure and motivation beliefs (academic self-efficacy and academic importance). Accounting for socioeconomic factors and parental support, higher racial pride (private regard), and higher use of religion to cope with difficult times predicted higher motivation beliefs. Religious coping reduced the negative association of violence exposure with motivation beliefs. Among boys, however, there was a stronger, negative relationship between community violence and academic self-efficacy for those higher in private regard. Boys reporting higher private regard had more positive motivation beliefs when experiencing lower community violence. Results suggest cultural-ecological factors can support academic motivation but also may not fully protect youth exposed to high ecological risk.
ESL students' use of concordance in the transfer of academic word knowledge: An exploratory study

Concordancing in the classroom is fairly a new approach that has emerged with the use of corpora in language learning. In a concordance, language is presented in an authentic context; learners are able to examine a key word in the context of a string of sentences which can exemplify the use of that particular word. This exploratory study examined whether the use of an online concordance program together with an online dictionary by 18 intermediate ESL undergraduates aided in the transfer of word knowledge to an academic writing task. The results indicate that there was statistically significant transfer of vocabulary knowledge to the writing task.
The Zeeman effect in astrophysics

Abstract George E. Hale discovered the Zeeman effect in sunspot spectra in 1908, and derived the laws of sunspot polarity. Recent observations of the much weaker (1 to 50 gauss) magnetic fields of the solar photosphere, made with the solar magnetograph, are described. The bearing of these results on circulation in the sun and their consequences for the topology of the sun's magnetic field are mentioned, with reference to the solar cycle and to reversal of the sun's polar field. The problem of measuring the magnetic field of stars is outlined, with reference to instrumental requirements. Spectrographs and crystals are described, together with techniques of measurement of magnetic fields in sharp-line stellar spectra. Results of a systematic program of observations with the 100-inch and 200-inch telescopes are reviewed. All stellar magnetic fields are variable; some are periodic. The strongest yet measured is 34 000 gauss. The magnetic variations are usually related to variations in light, color, line width, and line intensity. Chemical abundance anomalies are common in magnetic stars, and this has led to much work on nuclear reactions in stellar atmospheres, but the phenomena have not been satisfactorily explained. The possible importance of element concentration through paramagnetic migration in strong magnetic field gradients, enhanced by optical pumping, is pointed out.
Flow cytometry: An aid in monitoring lymphocyte transformation in whole blood cultures☆

Abstract A combination of whole blood cultures, hypotonic fluorescent staining of nucleated cells, and flow cytometry resulted in a greatly improved technique for measuring lymphocyte blastogenesis. Sample preparation was reduced to two steps with no centrifugation. The technique was successfully used to analyze blood cultures derived from experimentally and naturally infected cows. The technique was also shown to be ideally suited for analyzing lymphocytes cultured in whole blood cultures and (1) avoids the problems of tritiated thymidine analysis and (2) provides a direct analysis of the number of cells responding to antigenic stimulation.
AIDS on the wards: a residency in medical ethics.

AIDS is well on its way to becoming a medically orthodox disease pathogenesis determined and etiology defined; in the next 5 years the technology of AIDS diagnosis and treatment will become increasingly sure and sophisticated. But the ethical tangles surrounding the disease have only grown an will continue to do so. The purpose of this essay is not to review the ethical issues that commonly occur in the care of patients with AIDS. Most of these "patient-oriented" decisions difficult though they are stay on familiar ground. Other issues though have been largely ignored in these discussions. These are the "physician-oriented" ethical issues--more difficult than the others perhaps only because physicians are less accustomed to discussing them or admitting they exist. But by now probably no physician in the US can honestly deny considering them. Is a physician ethically obliged to care for a patient with AIDS? What does the care of these patients do to the physicians training practice and quality of life? The tendency has been to ascribe physicians reluctance to care for patients with AIDS exclusively to fear of infection with the AIDS virus. In fact this fear is only one and possibly the least important of the difficulties that have confounded medical residents in caring for these patients. These needy time-consuming patients are all to frequently patients that many physicians have inherent difficulty in accepting. Dislike of homosexuals--still the largest category of patients--is as common in hospitals as anywhere else. Drug addicts--the other large category of patients--are notoriously unpopular patients on hospital wards. What determines how residents will react to an onslaught of patients with AIDS is very hard to say. Whether they will be weakened or strengthened probably depends more on individual makeup than anything else.
Significant characteristics of democratic presidential nomination acceptance speeches

Democratic presidential nomination acceptance speeches have become part of American tradition. Beginning as relatively unimportant supplements to letters of acceptance, the speeches have evolved into major political addresses. After conducting both an historical review of the period involved—1832‐1972—and a content analysis of the speeches, the author identifies some of the principal rhetorical traditions surrounding such speeches.
The semiconductor silicon industry roadmap: Epochs driven by the dynamics between disruptive technologies and core competencies

Abstract The resource-based perspective has done much to identify idiosyncratic firm attributes that may be a principal source of competitive advantages. Unfortunately, there has been little systematic industry evidence to support the strategic importance of core competence, nor has there been much work on the temporal or cumulative nature of core capabilities within an industrial setting. Further, little or no research has been performed demonstrating how the advent of technological discontinuities or disruptive technologies plays a part in creating epochs in technology competency development and the roadmap of an industry. In this study, we analyze the evolutionary and cumulative nature of core capabilities and their interactions with technological discontinuities from a market-driven perspective. We have studied the evolution of 167 firms through the 50-year history of the semiconductor silicon industry. Over time, there were several structural shifts in the necessary competencies through the advent of disruptive technologies. In the last 30 years, however, the change in the required competencies has been more cumulative in nature. We summarize this in a roadmap detailing the epochs in the semiconductor silicon industry.
Return to sport following hip injury

Returning to both recreational and competitive sport requires the patient demonstrate the ability to perform their activity without pain, without compensation and without apprehension. The primary focus of this article will be to provide progressive weight bearing phased treatment solutions and both objective and empirical return to play testing suggestions. In addition to satisfactorily completing the test battery with maximum effort, the patient must demonstrate the ability to meet the demands for competing within their respective sport specific environment. Returning to competition will most likely include early phase movement screening and clinical clearance followed by late phase athletic and field testing. Hip structure will and must influence training program design. It is therefore important to recognize that indications for return to play must not focus on a single rehabilitation or exercise variable, but rather a combination of clinical, functional and sport specific demands.
Diffuse optical tomography based on a WKB approximation.

An image reconstruction algorithm based on a Wentzel–Kramers–Brillouin (WKB) approximation in the frequency domain in terms of path integration is tested with both simulated and experimental data. The algorithm can be used with full frequency domain data (amplitude modulation and phase shift), or partial data (amplitude or phase shift). This algorithm reconstructs an image of photon density wave propagation factor k without knowing the optical parameters of the background medium. Reconstruction was performed for data sets of different modulation frequencies and different detector geometries. The reconstruction time on a SUN-SPARC 5 station was about 5 min for images with a 128×128 pixel size.
Design and verification for transportation system security

Cyber-security has emerged as a pressing issue for transportation systems. Studies have shown that attackers can attack modern vehicles from a variety of interfaces and gain access to the most safety-critical components. Such threats become even broader and more challenging with the emergence of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication technologies. Addressing the security issues in transportation systems requires comprehensive approaches that encompass considerations of security mechanisms, safety properties, resource constraints, and other related system metrics. In this work, we propose an integrated framework that combines hybrid modeling, formal verification, and automated synthesis techniques for analyzing the security and safety of transportation systems and carrying out design space exploration of both in-vehicle electronic control systems and vehicle-to-vehicle communications. We demonstrate the ideas of our framework through a case study of cooperative adaptive cruise control.
Tracking progress: predictors of students' weekly achievement during a circuits and electronics MOOC

Massive open online courses (MOOCs) provide learning materials and automated assessments for large numbers of virtual users. Because every interaction is recorded, we can longitudinally model performance over the course of the class. We create a panel model of achievement in an early MOOC to estimate within- and between-user differences. In this study, we hope to contribute to HCI literature by, first, applying quasi-experimental methods to identify behaviors that may support student learning in a virtual environment, and, second, by using a panel model that takes into account the longitudinal, dynamic nature of a multiple-week class.
Heterogeneity of hypogammaglobulinemia.

In 1952, Ogden Bruton described the first patient with recurrent infections and hypogammaglobulinemia [1]. For many years thereafter, hypogammaglobulinemia (or agammaglobulinemia) was believed to result from a deficiency (or absence) of the antibody-producing cells, or “B” cell line of the lymphoid system. With increased recognition of functional subpopulations of the lymphoid system, however, it has become apparent that a variety of mechanisms may result in the phenotype of hypogammaglobulinemia. Since these entities may be clinically indistinguishable, it is important to understand the various categories of disease which may be involved. In this concise review, these areas are briefly summarized, More complete reviews of the subject (including acquired forms of immunodeficiency) are available [2, 3].
Microbial degradation of phosmet on blueberry fruit and in aqueous systems by indigenous bacterial flora on lowbush blueberries (Vaccinium angustifolium)

Phosmet-adapted bacteria isolated from lowbush blueberries (Vaccinium angustifolium) were evaluated for their ability to degrade phosmet on blueberry fruit and in minimal salt solutions. Microbial metabolism of phosmet by isolates of Enterobacter agglomerans and Pseudomonas fluorescens resulted in significant reductions (P < 0.05; 33.8%) in phosmet residues on blueberry fruit. Degradation was accompanied by microbial proliferation of phosmet-adapted bacteria. Preferential utilization of phosmet as a carbon source was investigated in minimal salt solutions inoculated with either E. agglomerans or P. fluorescens and supplemented with phosmet or phosmet and glucose. Microbial degradation concurrent with the proliferation of P. fluorescens was similar in both liquid systems, indicative of preferential utilization of phosmet as an energy substrate. E. agglomerans exhibited the ability to degrade phosmet as a carbon source, yet in the presence of added glucose, phosmet degradation occurred within the 1st 24 h only followed by total population mortality resulting in no appreciable degradation. Characteristic utilization of glucose by this isolate suggests a possible switch in carbon substrate utilization away from phosmet, which resulted in toxicity from the remaining phosmet. Overall, microbial metabolism of phosmet as an energy source resulted in significant degradation of residues on blueberries and in minimal salt solutions. Thus, the role of adapted strains of E. agglomerans and P. fluorescens in degrading phosmet on blueberries represents an extensive plant-microorganism relationship, which is essential to determination of phosmet persistence under pre- and postharvest conditions.
Self-Assembled Monolayers as Models for Studying Protein Adsorption to Polymer Surfaces

Self-assembled monolayers (SAMs) of functionalized alkanethiolates on gold are a well-characterized system for studying the interfacial properties of organic materials. We have used SAMs as models for the surfaces of organic polymers and used mem to study the adsorption of proteins onto organic materials. We have formed SAMs from mixtures of alkanethiols in which one alkanethiol is hydrophobic and the other is terminated by a short (2 ≤ n ≤ 17) oligomer of poly(ethylene oxide). These “mixed” SAMs effectively resist the adsorption of fibrinogen from moderately concentrated (1 mg/mL) solutions. Protein adsorption begins when ≤ 5% of the accessible area of the surface consists of hydrophobic groups. These findings suggest that real protein-resistant monolayers must present an almost defect-free surface of oligo(ethylene oxide) groups in order to eliminate adsorption.
Chandra automated point source processing

We have implemented a system to automatically analyze Chandra x-ray observations of point sources for use in monitoring telescope parameters such as point spread function, spectral resolution, and pointing accuracy, as well as for use in scientific studies. The Chandra archive currently contains at least 50 observations of star cluster-like objects, yielding 5,000+ sources of all spectral types well-suited for cataloging. The system incorporates off-the-shelf tools to perform the steps from source detection to temporal and spectral analyses. Our software contribution comes from wrapper scripts to autonomously run each step in turn, verify intermediate results, apply any logic required to set parameters, decide best-fit results, merge in data from other catalogs and to format convenient text and web-based output. We will outline this processing pipeline design and challenges, discuss the scientific applications, and focus on its role in monitoring on-orbit observatory performance.
TU-C-BRB-05: Development of a Software Framework for Quality Control and Optimization of a Paperless Radiation Therapy Process

Purpose: To implement a software framework for quality control and optimization of a paperless radiation therapy process. Methods: After analyzing the radiation therapy process as implemented using a conventional paper chart, we re‐implemented it in a paperless environment using workflow mechanisms available in Radiation OncologyInformation System (ARIA, Varian Medical Systems), such as on‐line Appointments, Tasks, Dynamic Word Documents, and Checklists. In order to ensure that the software‐based procedure steps of the paperless process were being adhered to, we have developed a collection of software modules which queries the SQL‐compliant database that underlies ARIA, analyses the results, and alerts users, mainly via emails, of the existence of any procedures or documentation they may not have completed.Results: All treatment plans for our conventional accelerators are now developed in a paperless environment. Currently, there are a total of 10 software modules, written in perl and SQL and comprising around 17,000 lines of code, reporting on specific aspects of the paperless process, such as treatment consent presence, prescription approval, target volume approval, plan approval, pre‐treatment check execution and others. The use of softwarecontrol modules, which execute daily, weekly or monthly, has resulted in a several‐fold decrease in the number of process errors. The email alerts from the reporting software have become an essential part of the workflow environment in the department. These have contributed to the general acceptance of the paperless process, despite the added computer‐based effort it involves. Conclusions: A paperless radiation therapy process opens up the possibility for automated monitoring and control of workflow steps essential for maintaining and improving patient safety. We have demonstrated that the implementation of software tools to perform this function results in significant, quantifiable process improvement.
Does UML make the grade? Insights from the software development community

The Unified Modeling Language (UML) has become the de facto standard for systems development and has been promoted as a technology that will help solve some of the longstanding problems in the software industry. However, there is still little empirical evidence supporting the claim that UML is an effective approach to modeling software systems. Indeed, there is much anecdotal evidence suggesting the contrary, i.e. that UML is overly complex, inconsistent, incomplete and difficult to learn. This paper describes an investigation into the adoption and use of UML in the software development community. A web-based survey was conducted eliciting responses from users of UML worldwide. Results indicate a wide diversity of opinion regarding UML, reflecting the relative immaturity of the technology as well as the controversy over its effectiveness. This paper discusses the results of the survey and charts of the course for future research in UML usage.
On the estimation of distributed systems with uncertain parameters

This paper formulates the basic state estimation procedures for a class of distributed systems with uncertain parameters. The parameters are not assumed to be random but believed to be arbitrary time functions known to be in a closed and bounded region. The developed estimation scheme provides an assured accuracy and a "guaranteed" error estimator which gives an upper bound of the estimation error for any allowed variation of uncertain parameters. The estimation algorithm will be much simpler and easier to implement than any adaptive estimation scheme, since the parameter estimation procedure is not required and is therefore bypassed.
Donepezil Treatment and Alzheimer Disease: Can the Results of Randomized Clinical Trials Be Applied to Alzheimer Disease Patients in Clinical Practice?

Objective: To determine if results from randomized clinical trials of donepezil in Alzheimer disease (AD) patients can be applied to AD patients in clinical practice by comparing the findings from a Nordic one-year randomized AD donepezil trial with data from a one-year prospective, observational study of AD patients. Methods: AD patients from a consortium of California sites were systematically followed for at least one year. Their treatment regimens, including prescription of donepezil, were determined by their individual physician according to his or her usual criteria. Results: The 148 California patients treated with donepezil had a one-year decline of 1.3 (3.5 SD) points on the Mini-Mental State Exam compared to a decline of 3.3 (4.4 SD) in the 158 AD patients who received no anti-Alzheimer drugs. The Mini-Mental State Exam decline in Nordic sample was 0.25 points for the 91 patients receiving donepezil and 2.2 for the 98 placebo patients. The overall effect sizes were estimated at about 0.49 in both studies. The California data were further analyzed using propensity methods; after taking into account differences that could bias prescribing decisions, benefits associated with taking donepezil remained. Conclusion: A comparison of a randomized clinical trial of donepezil in AD patients and this observational study indicates that if appropriate methodological and statistical precautions are undertaken, then results from randomized clinical trials can be predictive with AD patients in clinical practice. This California study supports the modest effectiveness of donepezil in AD patients having clinical characteristics similar to those of the Nordic study. (Am J Geriatr Psychiatry 2007; 15:953–960)
PORTFOLIO INSURANCE AND VOLATILITY REGIME SWITCHING

A new equilibrium model of portfolio insurance is presented in order to study the volatility effects of dynamic insurance strategies. While prior research has focused on the relationship between portfolio insurance and the overall level of market volatility, this article shows that the salient feature of portfolio insurance is volatility regime switching. Regime switching is shown to be a necessary condition for portfolio insurance, which provides a new explanation for the pervasive volatility clustering effect that is found in most equity markets. The equilibrium involves a free boundary and the local time of the equilibrium price process at the free boundary plays an important role in solving the model.
Dynamics of silica cell wall morphogenesis in the diatom Cyclotella cryptica: Substructure formation and the role of microfilaments

Diatoms are unicellular algae that make cell walls out of silica with highly ornate features on the nano- to microscale. The complexity and variety of diatom cell wall structures exceeds those possible with synthetic materials chemistry approaches. Understanding the design and assembly processes involved in diatom silicification should provide insight into patterning on the unicellular level, and information for biomimetic approaches for materials synthesis. In this report we examine the formation of distinct cell wall structures (valves and girdle bands) in the diatom Cyclotella cryptica by high resolution imaging using SEM, AFM, and fluorescence microscopy. Special attention was paid to imaging structural intermediates, which provided insight into the underlying design and assembly principles involved. Distinct stages in valve formation were identified, indicating a transition from a fractally organized structure to a dynamic pathway-dependent process. Substructures in the valves appeared to be pre-positioned prior to complete silicification, suggesting that organics responsible for these structures were pre-assembled and put in place. Microtubules and microfilamentous actin play significant roles in the positioning process, and actin is also important in the pathway-dependent expansion of the front of silicification. Our results indicate that even though all silica structures in C. cryptica are made of assemblies of nanoparticulate silica, control of meso- and microscale structure occurs on a higher order. It is apparent that diatoms integrate bottom up and top down control and synthesis mechanisms to form the diversity of structures possible.
Methyaluminoxane (MAO) Polymerization Mechanism and Kinetic Model from Ab Initio Molecular Dynamics and Electronic Structure Calculations

MAO is the co-catalyst in metallocene catalytic systems, which are widely used in single-site olefin polymerization due to their high stereoselectivity. To date, the structures of the catalytically active compound or compounds in MAO have eluded researchers. Although many structural models have been proposed, none are generally accepted. In this study, aspects of the formation mechanism of MAO are addressed. Molecular dynamics simulations at the MP2 level of theory were carried out for presumed elementary steps in MAO formation via hydrolysis of trimethylaluminum (TMA). Methane production was observed, in agreement with experiment, as well as intermediate species that are consistent with the known structural features of MAO and similar to isolated and structurally characterized aluminoxanes. A (CH3)3Al-OH2 species, which we denote as TMA-OH2, containing a stable Al-O single bond emerged as the building block molecule. From this species, a hexameric cage was formed and activation barriers for the various reactions were calculated. Three distinct channels were identified for growth beyond the hexameric cage. It was concluded that MAO formation is a step polymerization through a bifunctional monomer, with [(CH3)Al-O] as the structural unit and a kinetic model was proposed. The structures that emerged were in agreement with the crystallographic evidence for aluminoxanes and support the experimental data regarding the MAO chemical composition.
Structural freedom, topological disorder, and the irradiation-induced amorphization of ceramic structures

Abstract The susceptibility to irradiation-induced loss of long-range translational and orientational order during amorphization of crystalline solids, a process which usually amounts to topological disordering, can be understood on the basis of available structural freedom which depends on the redundancies present in structural connectivity. A surprisingly good correlation has been established between the critical accumulated energy deposited per atom — or displacements per atom (dpa) — required for amorphization during ion irradiation and the calculated structural freedom for the structure type irradiated over a wide range of non-metal structural types. These include AO, AO2, A2O3, ABO3, ABO4, A2B2O7 and A2BO4 compact structure types, in which weakest links can often be identified, as well as less-compact network structures. The present contribution specifically compares the order of susceptibility to amorphization — in these more complex oxide structures and in the simpler network structures Si3N4, SiC, Be2SiO4, AlPO4, Si, SiO2, P2O5 and graphite — on the basis of structural connectivity and discusses the anomalous susceptibility of SiC.
Crosscurrents in HIV-1 evolution

Substitutions in CD8+ T cell epitopes in viral proteins can alter the complex interaction between viruses and host immunity. Reduced viral fitness and recognition of altered and subdominant epitopes are possible outcomes.
M-learning: a new wave of learning

The mobile revolution is finally here. The evidence of mobile penetration and adoption is irrefutable. Mobile devices are getting smaller and more powerful. They have the ability to deliver learning objects and provide access to online systems and services. M-learning is a natural extension of e-learning. It has the potential to further expand where, how and when we learn and perform in all the aspects of our life. M-learning will not replace traditional learning. It fulfils the growing demands for lifelong learning opportunities that enable learners to 'learn while you earn on the go'.
Reproductive cycle-associated mood symptoms in women with major depression and bipolar disorder

Background: We sought to determine the prevalence of, and association between, reproductive cycle-associated mood symptoms in women with affective disorders. We hypothesized that symptoms would correlate with each other across a woman's reproductive life span in both major depression (MDD) and bipolar I disorder (BP). Methods: 2412 women with, MDD or BP were asked standardized questions about mood symptoms prior to menstruation, within a month of childbirth and during perimenopause. Lifetime rates for each of these symptom types were determined and an odds ratio was calculated correlating each of the types with the others. Results: Of 2524 women with mood disorders, 67.7% reported premenstrual symptoms. Of those at risk, 20.9% reported postpartum symptoms and 26.4% reported perimenopausal symptoms. The rates did not differ between women with MDD and BP but were significantly different from women who were never ill. The symptoms were significantly correlated in women with MDD with odds ratios from 1.66 to 1.82, but were not in women with BP. Limitations: This is a secondary analysis of a sample that was collected for other purposes and is based upon retrospecitve reporting. Conclusions: Reproductive cycle-associated mood symptoms were commonly reported in women with mood disorders and did not differ based on diagnosis. In MDD, but not BP, the occurrence of these symptoms was trait-like as the presence of one predicted the occurrence of the others. Further prospective study is required to clarify the determinants of this trait.
Effect of orotic acid upon serum bilirubin in newborn infants with erythrocyte G-6-PD deficiency.

Summary Fifty mature male newborns with erythrocyte G-6-PD deficiency were used for a study con cerning the effectiveness of orotic acid in preventing severe hyperbilirubinemia. Twentyfive randomly selected neonates were given orotic acid (100 mg/kg/day) orally in two daily doses from their 1st to their 5th day of life. Twenty-five newborns were not treated According to these results orotic acid does not seem to be effective in preventing severe hyperbilirubinemia, which frequently occurs in newborn babies' with erythrocyte G-6-PD deficiency. and served as controls. Six exchange transfusions were performed in the test group and six in the controls.
Evidence that hematopoiesis may be a stochastic process in vivo

To study the behavior of hematopoietic stem cells in vivo, hematopoiesis was simulated by assuming that all stem cell decisions (that is, replication, apoptosis, initiation of a differentiation/maturation program) were determined by chance. Predicted outcomes from simulated experiments were compared with data obtained in autologous marrow transplantation studies of glucose 6-phosphate dehydrogenase (G6PD) heterozygous female Safari cats. With this approach, we prove that stochastic differentiation can result in the wide spectrum of discrete outcomes observed in vivo, and that clonal dominance can occur by chance. As the analyses also suggest that the frequency of feline hematopoietic stem cells is only 6 per 10(7) nucleated marrow cells, and that sem cells do not replicate on average more frequently than once every three weeks, these large-animal data challenge clinical strategies for marrow transplantation and gene therapy.
Assessing how people change

Traditional assessments of behavior change relied on discrete measures based on assumptions that changes occur quickly, dichotomously, and without relapse. People were expected to shift dramatically from smokers to nonsmokers or from unhealthy to healthy lifestyles. A stage model of change has greater potential to assess the dynamics of change with some people progressing linearly from contemplation to maintenance, others relapsing back to contemplation, and others remaining in a stage like contemplation for long periods. Stage measures provide differential predictions for the amount of progress people in different stages will make after treatment. Assessing processes of change that people apply to progress from one stage to the next can also help to explain the dynamics of behavior change.
Oxygen-carrying iridium complexes: kinetics, mechanism, and thermodynamics.

The rates of oxygenation and deoxygenation of a series of iridium complexes increase and decrease, respectively, with increasing electron-releasing tendency of the anionic ligands (A) attached to the metal atom in the oxygencarrying compounds, [IrA(CO)(Ph3P)2]. Calculated heats of oxygenation (—ΔH2), related to Ir-O2 bond energies, are proportional to the previously reported O-O bond lengths in the oxygen adducts, [O2IrA(CO)(Ph3P)2].
A value function arising in the economics of information

Abstract The value function for a problem in the economics of the optimal accumulation of information is calculated as a fixed point of a contraction mapping by direct numerical iteration. The optimal policy function is obtained as is the function defined as the sum of current expected reward and the discounted expected value of following the optimal policy in the future. The optimal policy function is shown to be sensitive to the discount factor; indeed for large values of the discount factor (weighting the future heavily) the policy function has a break and the value function is apparently not differentiable.
Student Views of Effective Online Teaching in Higher Education

This study investigated student views of online instruction in higher education courses. Data were collected from 199 online students using a Web-based instrument. The instrument consisted of items...
First principles simulation of liquid silicon

Abstract We present a simulation method based on ab initio pseudopotentials and quantum forces to examine the properties of liquid silicon. Our simulation does not use fictitious electron dynamics. We employ Langevin dynamics to thermalize the liquid. Once the desired temperature has been achieved, the Langevin “viscosity” term is turned off to examine dynamical properties. No “ad hoc” dynamics need be employed to equilibrate the system to the desired temperature. Results for liquid silicon including the pair correlation function, electronic structure and self-diffusion parameters are presented and compared to previous calculations, and to experiment.
Improving on Darwin

Evolutionary Processes and Metaphors. Edited by Mae-Wan Ho and Sidney W. Fox. Wiley:1988. Pp.333. £35.95, $85.