cssi/SciSciGPT-SciSciNet huggingface dataset:
Modeling, Stability Analysis and Simulation of Buck Converter in a DC Microgrid

Rapid reduction of non-renewable sources of energy is driving development toward sustainability. Increased integration of distributed generation units, including renewable sources of energy and energy storage systems (ESS), has simulated research in new techniques of power generation. At the same time, integration of these distributed generation units in the conventional power generation setup has become challenging. To counteract these challenges, the concept of DC microgrid (DCMG) has been introduced. DCMG incorporates several power converters at the source-side and the load-side. There are certain stability issues related to these power converters that need to be investigated to ensure the overall stability of the DCMG. This paper deals with the design of a simulation platform of a buck converter at the source side of the DCMG. Such a simulation platform will be beneficial to study the stability of the DCMG. The paper also shows the stability analysis of the developed simulation platform and calculation of its sensitivity function for robustness.
Crystalline: Fast and Memory Efficient Wait-Free Reclamation.

Historically, memory management based on lock-free reference counting was very inefficient, especially for read-dominated workloads. Thus, approaches such as epoch-based reclamation (EBR), hazard pointers (HP), or a combination thereof have received significant attention. EBR exhibits excellent performance but is blocking due to potentially unbounded memory usage. In contrast, HP are non-blocking and achieve good memory efficiency but are much slower. Moreover, HP are only lock-free in the general case. Recently, several new memory reclamation approaches such as WFE and Hyaline have been proposed. WFE achieves wait-freedom, but is less memory efficient and suffers from suboptimal performance in oversubscribed scenarios; Hyaline achieves higher performance and memory efficiency, but lacks wait-freedom. We present a new wait-free memory reclamation scheme, Crystalline, that simultaneously addresses the challenges of high performance, high memory efficiency, and wait-freedom. Crystalline guarantees complete wait-freedom even when threads are dynamically recycled, asynchronously reclaims memory in the sense that any thread can reclaim memory retired by any other thread, and ensures (an almost) balanced reclamation workload across all threads. The latter two properties result in Crystalline's high performance and high memory efficiency. Simultaneously ensuring all three properties require overcoming unique challenges which we discuss in the paper. Crystalline's implementation relies on specialized instructions which are widely available on commodity hardware such as x86-64 or ARM64. Our experimental evaluations show that Crystalline exhibits outstanding scalability and memory efficiency, and achieves superior throughput than typical reclamation schemes such as EBR as the number of threads grows.
A Discussion of Multiplicative Decompositions and Strain Measures

In the context of a purely mechanical development for materials that possess some degree of elasticity, two-factor and three-factor multiplicative decompositions of the deformation gradient, as well as related strain measures, are discussed in detail. Different factors in the decompositions (and their polar subfactors) have different degrees of rotational non-uniqueness. Moreover, different deformation measures generally behave differently under superposed rigid motions, which has important implications for the roles that they are allowed to play in constitutive equations. A certain unique right stretch tensor emerges, which yields strain measures suitable for describing anisotropic elastic responses of solids that have evolving stress-free local configurations.
Isometric training effects upon central facilitation.

Abstract Two matched groups of 10 subjects each were employed to assess possible central facilitation effects over 4 weeks of training. Each of the 12 training sessions consisted of 20 trials of maximum isometric wrist flexion for 5 sec. with a 30-sec. rest period between trials. Two experimental conditions were used. On alternate sessions condition one consisted of 20 trials with odd-numbered trials being unilateral and even-numbered trials being simultaneous bilateral efforts. Condition two consisted of the first 15 trials being unilateral and the last 5 trials simultaneous bilateral. The right limb in Group I and the left limb in Group II constituted the criterion measures. Central facilitation effects due to simultaneous bilateral isometric wrist contractions were: (a) not present initially and (b) not elicited through the 4 weeks of training. The finding held for both dominant and nondominant limbs and for fatigued and nonfatigued states.
Zinc Sulfide (ZnS)

Publisher Summary In the context of natural zinc sulfide (ZnS), the natural crystal forms of ZnS include—zinc blende and wurtzite. Zinc blende is the prototype of the B-3 structure. Wurtzite is the prototype of the B-4 structure. Other crystal modifications of the natural zinc sulfide are also known. It is noted that substantial amounts of impurities are usually found in zinc sulfide minerals, primarily iron. Other common impurities include—Cu, Ag, Pb, K, Na, Ga, Hg, Cd, and rare earths. These impurities affect the body color of the minerals. The purest crystals are rarely colorless, usually having a light yellow body color. Natural ZnS crystals usually have hydrothermal or metamorphic origin. In the context of synthetic ZnS, a variety of techniques have been developed to obtain large, well-formed, high-purity crystals. These include different evaporation or sublimation techniques, the high-pressure growth from molten ZnS, hydrothermal techniques, and growth from solution. In addition, thin layer ZnS coatings on a variety of substrates and sintered hot-pressed polycrystalline ZnS windows are routinely produced for a variety of applications.
Two crystal forms of bovine superoxide dismutase.

Abstract In the course of x-ray crystallographic investigation of superoxide dismutase, two suitable crystal forms of the bovine enzyme have been obtained. A monoclinic form grown from 58% 2-methyl-2,4-pentanediol has space group C2 and the following cell dimensions: a = 93.4 A, b = 90.4 A, c = 71.6 A, β = 95.1°, with 4 subunits (2 molecules) per asymmetric unit. An orthorhombic form grown from concentrated protein solution at 4° has space group P212121, and a = 51 A, b = 61 A, and c = 147 A, probably with 4 subunits per asymmetric unit.
Citrate Cleavage Enzyme and Fatty Acid Synthesis

A series of experiments was performed to test the proposal of others that citrate cleavage enzyme (EC 4.1.3.8) regulates the rate of fatty acid synthesis in rat liver. The results show that, in recovery from fasting, fatty acid synthesis increased markedly without change in citrate cleavage enzyme activity. After the administration of alloxan, fatty acid synthesis decreased prior to any change in citrate cleavage enzyme. Substitution of a high carbohydrate, low fat diet resulted in large increases in citrate cleavage enzyme activity without concomitant change in lipogenesis. The addition of purified citrate cleavage enzyme from rat liver to the fatty acid-synthesizing system from fasted animals did not restore fatty acid synthesis. It was concluded that citrate cleavage enzyme does not play a primary regulatory role in fatty acid synthesis.
Computer simulation of a novel technique for radio-frequency ablation of ventricular arrhythmias

Ventricular Tachycardia (VT) is a rapid arrhythmia, most commonly due to reentrant electrical activity in the heart. A common treatment for VT is Radio-Frequency Ablation (RFA), which is minimally invasive, but requires maintenance of VT until the target site for ablation is determined. Most patients with VT cannot tolerate this maintenance phase due to hemodynamic instability and for those who are hemodynamically stable, the RFA procedure is successful in permanently terminating the VT in only approximately half of the cases. Therefore, the need for an RFA procedure that accurately localizes the site for ablation, or exit site of the reentry circuit, and is safe for unstable patients is evident. We believe utilization of the Single Equivalent Moving Dipole model and inverse problem in cardiology will prove to be efficient in localizing the exit site of the reentry circuit and guiding the ablation catheter to that localized site during the RFA procedure. In principle, our RFA technique only requires a single beat of VT to localize the exit site of the reentry circuit. The objective of this thesis is to determine in a simulation model if one can guide a catheter to the exit site of the reentry circuit using body surface potentials in order to ablate that site with radio-frequency energy. In our new approach to RFA, we sought to design a finite element model to simulate VT due to reentry, develop an algorithm to localize the exit site of the reentry circuit through analysis of body surface potentials, localize the ablation catheter in both slow and fast VT, and advance the ablation catheter to the localized exit site of the reentry circuit. The proposed new RFA procedure promises to provide a new rapid and effective means for treatment of VT.
Brain and Perception: Holonomy and Structure in Figural Processing

Contents: Preface. Acknowledgments. Viewpoint. Prolegomenon.Aims and Origins. Outlines of a Holonomic Brain Theory. Part I: Configural Aspects. Transformational Realism: The Optic Array, the Optical Image and the Retinal Process. Imaging: Cooperativity in Primary Sensory Systems. Object-Forms and Object Spaces: Sensory-Motor Reciprocity. Images of Achievement and Action Spaces: Somatic Processes in the Control of Action. Part II: Cognitive Aspects. Comprehension: Contributions of the Posterior Cerebral Convexity in Enhancing Processing Span. Familiarization and Valuation: The Contributions of the Amygdala System to the Demarcation of an Episode. Irrelevance and Innovation: The Contributions of the Hippocampus and Limbic Forebrain to the Processing of Context. Envisioning Proprieties and Priorities Practical Inference: The Far Frontal Cortex as Executive Processor. Epilogue. Appendices: Neurodynamics: A Theory of Nonlocal Cortical Processing. Symmetry, Invariance and Group Theory in Object Perception. The Definition of Context. Familiarization as Transfer Among Contexts. The Formation of Prototypes. Neurodynamics and Innovation. The Neurodynamics of Covariation and Inference.
Complexity, Accountability, and School Improvement

In this article, Jennifer O'Day builds on her earlier work defining and examining the standards-based reform movement in the United States. Here, O'Day explores accountability mechanisms currently associated with standards-based reform efforts that "take the school as the unit of accountability and seek to improve student learning by improving the functioning of the school organization." She examines such accountability mechanisms using the theoretical framework of complexity theory and focuses on how information travels through complex systems, with the understanding that information, its existence and usage, is key to improving schools. Drawing on work conducted with researchers at the Consortium for Policy Research in Education (CPRE), she contrasts the Chicago Public Schools' outcomes-based bureaucratic accountability approach with the combination of administrative and professional accountability found in the Baltimore City Schools. She argues that the combination of administrative and professional ac...
Origin of Life

The Stardust Revolution: The New Story of Our Origin in the Stars. By Jacob Berkowitz. 2012. Prometheus Books. (ISBN 9781616145491). 376 pp. Hardback. $27.00. Whether you think of it as a revolution story, an evolution story, or even, simply, a history tale, reading this book by the science writer Jacob Berkowitz is like going on a discovery walk through the annals of who’s-who in astrobiology, a budding new field that studies the origin, evolution, and distribution of life on earth, in the universe, and more. It is filled with name-dropping, anecdotes (a bit of an overload of them), birthing analogies, and puns. NASA’s 1999 Stardust mission spent 200 million dollars to bring back stardust material that weighs less than a grain of salt, and now, we have a “catalog of more than ten thousand pre-solar grains” (5–7 billion years old). Hoagy Carmichael wrote and recorded it, Bing Crosby, Louis Armstrong, Nat King Cole, Frank Sinatra, Doris Day, Ringo Starr, and Rod Stewart (to name a few) sang about the “Stardust …
In vivo two-photon microscopy for imaging leukocytes in atherosclerotic plaques (547.16)

Atherosclerosis is characterized by chronic inflammation of the walls of large and medium arteries that have been infiltrated by macrophages, dendritic cells (DCs), T cells, and other leukocytes. Disease progression is determined in part by a variety of cell functions that are regulated by the cell’s motility, including recruitment, transmigration, egress, phagocytosis, and interaction between multiple cell types. In vivo imaging is necessary to better understand leukocyte activity during atherosclerosis within the native plaque microenvironment. Two-photon microscopy is emerging as a valuable tool to image live, fluorescent cells in explants or certain organs in vivo. However, new technical challenges are introduced when imaging tissues that move within the body, such as arteries, which expand with every heart beat. In-frame and between-frame motion cause still images to be distorted and movies to appear unsteady, making cell tracking infeasible. We engineered an integrated hardware and software system f...
Electrophysiological behavior of an endogenously active neurosecretory cell.

Summary An identified neurosecretory cell in the snail, cell 11 in Otala lactea , has been shown to have patterned impulse activity of endogenous origin. Several lines of evidence supporting this view are: hyperpolarization of the cell revealed no EPSPs driving the cell, the cell continued to act as a bursting pacemaker in concentrations of magnesium ion sufficient to block all synaptic activity, and the isolated soma of the cell exhibited spontaneous bursting behavior. While the action potential was due to increases in sodium and calcium conductances, the pacemaker potential was dependent only on the sodium ions in the medium. Stimulation of peripheral nerves evoked only IPSPs in cell 11 and, therefore, it was suggested that the cell's secretory activity was modulated primarily by inhibitory processes. The axon of cell 11 runs in the visceral nerve and terminates specifically in the auricle of the snail's heart. The activity of cell 11 did not appear to effect the rate or strength of the heartbeat, which suggested that this neurohemal location of termination was specifically related to the cell's secretory activity.
Treatment of chronic bacterial prostatitis with temafloxacin.

In an open multicenter study [corrected], 112 male patients (mean age 47.1 years) with documented symptomatic chronic bacterial prostatitis were treated with oral temafloxacin 400 mg b.i.d. for 28 days. Urine and prostatic secretions were obtained for culture and susceptibility testing, and clinical signs and symptoms were evaluated at day 14 as well as 5-9 days and 26-30 days post-treatment. The most frequently isolated pretreatment pathogens (n = 97) were 36 strains (38%) of Escherichia coli and 16 strains (17%) of Enterococcus. Clinical success (cure plus improvement) was demonstrated in 74 of 81 (91%) patients at visit 4, 5-9 days post-treatment and at visit 5, 26-30 days post-treatment in 61 of 71 (86%) patients. At visit 4, 94% of patients had eradication of pretreatment pathogens. At visit 5, 92% had continued eradication of their original pathogens. Improvement was observed in the severity of signs and symptoms that existed pretreatment at visit 4 (visit 5): dysuria, 92% (93%); perineal pain, 95% (93%); lower abdominal pain, 93% (100%); lower back pain, 88% (93%); scrotal/penile pain, 91% (83%). Digestive system (6.3%) and nervous system (4.5%) adverse events were observed most frequently. Temafloxacin 400 mg b.i.d. administered orally for 28 days represents a safe and effective treatment for chronic bacterial prostatitis.
Umklapp surface scattering in a tight-binding model

The calculations exhibit general features of the Umklapp process in a simple context. It is shown that the Umklapp rate is not limited by any small parameter and that special behaviour (independent of the boundary conditions) occurs at extremal points of the bands. It is also shown that interband surface scattering has only small probability for electrons in small pocket states.
Methodologies and tools for intelligent agents in distributed control

Agent technology also provides an appropriate framework to integrate knowledge with production actions. Knowledge integration depends on balanced information in and across organizations. So, replacing the central models with distributed intelligent agents make it possible to cope with demands more efficiently. In this, each agent represents a specific activity to support overall operations. With agents, maintaining the overall system is easier because instead of changes occurring to a colossal program, changes take place on a small scale without disrupting overall operations. We've developed a set of tools and methodologies to help design, build, test, and verify such systems. Using these tools and methodologies, we've devised an agent architecture that we've applied to a US Navy shipboard chilled-water system.
Large-scale and small-scale methods for the preparation of 5,10-methylenetetrahydrofolate.

Abstract Two procedures have been developed for the synthesis and isolation of 5,10-methylenetetrahydrofolate, the cofactor for the reaction catalyzed by thymidylate synthesize, one of which can be used for large-scale preparations of the cofactor and the other for small-scale syntheses especially suitable for obtaining the radio labeled cofactor. The large-scale procedure involves treatment of folic acid with dithionite to give dihydrofolate, which is then converted to tetrahydrofolate by dihydrofolate reductase (L. casei). The small-scale method involves a direct enzymatic reduction of folic acid to tetrahydrofolate by dihydrofolate reductase, and has been used to prepare the double-labeled 5,10-[14C]methylene[3′,5′,7,9-3H]tetrahydrofolate. In both procedures, after the reduction steps have been performed, the tetrahydrofolate is treated in situ with formaldehyde prior to purification by DEAE-cellulose chromatography, thus allowing the isolation of 5,10-methylenetetrahydrofolate as a dry powder after ly...
Discussion of Presentation by Dr Barrett G. Haik, Et Al

HEMANGIOMAS have been classified in a variety of ways. The concepts governing taxonomy of hemangiomas are being reevaluated in the light of present thinking about angiogenesis and recent ultrastructural studies of vascular tumors. The classification of hemangiomas of the eyelids that recently has been developed by Ashton, Zimmerman, and co-workers on behalf of the World Health Organization is given in the Table.
The effect of over-the-counter ranitidine 75 mg on night-time heartburn in patients with erosive oesophagitis on daily proton pump inhibitor maintenance therapy

Summary Background H2-receptor antagonists are widely used with proton pump inhibitors. Aim To determine if H2-receptor antagonists used in conjunction with proton pump inhibitors were effective for nocturnal heartburn in patients taking proton pump inhibitors. Methods We evaluated 386 patients with erosive oesophagitis documented at endoscopy who were receiving single daily maintenance proton pump inhibitor therapy to determine if they had symptoms of nocturnal heartburn. Patients with two or more episodes of night-time a week were invited to participate in the study. Patients were randomly assigned to a single dose of an over-the-counter preparation of ranitidine 75 mg at bedtime or matching placebo for 14 days. Results The prevalence of nocturnal symptoms was 10.6%. Mean symptom scores on the first day of the trial (baseline) were similar between the treatment group (1.1 ± 0.9) and the placebo group (1.1 ± 1.1). On day 3, symptom scores were significantly lower in the ranitidine group (0.71 ± 0.69) compared with the control group (1.4 ± 1.2; P = 0.045). On day 14, mean symptom scores were similar in the ranitidine group (0.82 ± 0.95) and the control group (1 ± 0.84). Conclusions Nocturnal heartburn is uncommon on proton pump inhibitor therapy; the addition of ranitidine at bedtime resulted in a decrease in symptom scores on day 3 but there were no differences on day 14.
A qualitative analysis of pulmonary hypertension: a role for accelerative forces.

The systolic, diastolic, and pulse pressures of patients with elevated left atrial pressures (ELAP) were compared to those of patients before and after balloon occlusion of one pulmonary artery. Balloon occlusion was observed to effect primarily a systolic pressure increase both at rest and during exercise. The most striking pressure rise in the ELAP group was of the diastolic levels. An hydraulic analogy supports the concept that, if stroke volume is maintained, in addition to a change in resistance produced by balloon occlusion the post-occlusive acceleration requirements are significantly elevated and probably account for much of the systolic pressure rise.
Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

Abstract LaGaO3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol–gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa1−yMgyO3−δ (LGM), La1−xSrxGa1−yMgyO3−δ (LSGM), and La1−xBaxGa1−yMgyO3−δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.
Arrangement and identification of simple isometric viruses according to their dominating stabilizing interactions

Capsid-stabilized turnip yellow mosaic virus (TYMV) and protein-RNA linkage-stabilized cucumber mosaic virus (CMV) possess totally different stability characteristics which can serve as distinguishing characteristics to arrange and identify other simple isometric viruses according to their dominating stabilizing interactions.
Poverty and Economic Morphology of Ohio Central-City Neighborhoods:

The authors examine the relationship between poverty and economic activities in 24 selected industries in more than 100 neighborhoods in Ohio central cities. As expected, local economies deteriorated as poverty levels increased. However, the economic deterioration began much earlier, and was much more serious, than has been suggested in earlier ghetto studies. Furthermore, the decline in neighborhood jobs associated with the economic deterioration was massive. If neighborhood jobs are seen as a road to economic and social recovery for ghetto residents, the findings are very bleak indeed.
Quantum 1/f noise in spintronics and the future of downscaling

Spintronics is a new direction in electronics. It contains many applications, including spin valves, GMR devices, “spin batteries,” spin-controlled electronic devices, and even spin-controlled wide-bandgap compound semiconductors due to the development of rare-earth-doped nitrides with ferromagnetic properties. Spintronics allows for manipulation of both the spin transport and the charge transported by the electrons. It allows the downscaling to lower device sizes and extension of Moore's law to higher device densities, because it requires less energy to just control the spin of the electron, and the quantum 1/f noise associated with spin control is several orders of magnitude below that associated with conventional electronics. However, the injected spin-polarized current is subject to spin-flip due to various causes. The rate of each of these spin-flip currents is affected by quantum 1/f noise, because of the low-frequency photon emission amplitude that is associated with the elementary spin flip process, no matter what causes the spin flip. As a result, in a spin valve, the leakage current will show 1/f noise. In devices with injection and subsequent control of spin-polarized electrons, the effects obtained will also show this spintronic quantum 1/f noise. For instance, the light output of a spin-controlled LED will exhibit quantum 1/f intensity fluctuations. The present paper calculates the 1/f noise expected in spintronic currents. The spectral density of this fundamental 1/f noise is inherently proportional to the square of the current that is affected by it, but is also inversely proportional to the number of carriers defining this current. The latter dependence can cause the spectrum to be proportional to the first power of the current.
A note on the distribution of ectopic thyroid tissue in five species of poeciliid fishes

The intraperitoneal injection of polycyclic aromatic hydrocarbons in young Amazon mollies induces proliferation of ectopic thyroid tissue in the spleen. We have surveyed untreated mollies, Poecilia formosa, and four closely related poeciliid fishes to see if ectopic thyroid tissue occurs normally in the spleen. If this were the case, it is possible that the tissue may have been stimulated to proliferate by the injected compounds. We found no instances of ectopic thyroid at any site in 50 untreated Amazon mollies examined nor in some 50 spleens dissected from other untreated fish. Splenic thyroid tissue was found in five guppies from 50 surveyed, but did not occur in other species.
Comparative Ability of Various PCBs, PCDFs, and TCDD to Induce Cytochrome P450 1A1 and 1A2 Activity Following 4 Weeks of Treatment

Abstract Comparative Ability of Various PCBs, PCDFs, and TCDD to Induce Cytochrome P450 1A1 and 1A2 Activity Following 4 Weeks of Treatment. De Vito, M. J., Maier, W. E., Diliberto, J. J., and Birnbaum, L. S. (1993). Fundam. Appl. Toxicol. 20, 125-130. Toxic equivalency factors (TEFs) have been proposed for dibenzo-p-dioxins, dibenzofurans, and polyhalogenated biphenyls. The proposed toxic equivalency factors (TEFs), which are presently being evaluated in our laboratory, are currently used to estimate the potential health risk associated with exposure to complex mixtures containing these chemicals. In preliminary studies, equally potent doses, based on the published TEFs and relative enzyme-inducing potency, of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran, 1,2,3,7,8-pentachlorodibenzofuran, 1,2,3,4,6,7,8,9-octachlorodibenzofuran, 3,4,3′,4′-tetrachlorobiphenyl, 2,3,4,3′,4′-pentachlorobipbenyl, 3,4,5,3′,4′-pentachlorobiphenyl, 2,3,4,3′,4′,5′-hexachlorobiphenyl, 2,3,4,5,3′,4′-hexachlorobiphenyl, and 3,4,5,3′,4′,5′-hexachlorobiphenyl were administered to female B6C3F1 mice 5 days a week over a 4-week period. Hepatic, skin, and lung cytochrome P450 1A1 and hepatic 1A2 activities were determined for all chemicals tested and compared to those from TCDD-treated mice. These initial studies indicate that the present TEFs do not reliably predict induction potency for many of the chemicals. Furthermore, our data suggest that the relative inductive potency of these chemicals may be tissue specific and that estimates of TEFs based on hepatic ethoxyresorufin O-deethylase activity may not accurately reflect the potency of these chemicals in nonhepatic tissue. The TEFs proposed for the "dioxin-like" polychlorinated biphenyls (PCBs) overestimate the potency of these compounds by factors of 10-1000. The present study indicates that more experimental data are required before TEFs for PCBs should be used in regulatory decision making.
The Value of Mechanistic Biophysical Information for Systems-Level Understanding of Complex Biological Processes Such as Cytokinesis

This review illustrates the value of quantitative information including concentrations, kinetic constants and equilibrium constants in modeling and simulating complex biological processes. Although much has been learned about some biological systems without these parameter values, they greatly strengthen mechanistic accounts of dynamical systems. The analysis of muscle contraction is a classic example of the value of combining an inventory of the molecules, atomic structures of the molecules, kinetic constants for the reactions, reconstitutions with purified proteins and theoretical modeling to account for the contraction of whole muscles. A similar strategy is now being used to understand the mechanism of cytokinesis using fission yeast as a favorable model system.
Optical spectra of the intermediate oxides of titanium, vanadium, molybdenum, and tungsten

Abstract Optical absorption spectra have been measured for 25 transition metal oxides in systems TiO, VO, MoO, and WO by a diffuse reflectance technique. Each spectrum shows one or more maxima above an intense background absorption. The transition energies of the maxima vary logarithmically with the carrier concentration in accordance with Meyer's rule.
IBF: An Integrated Business Framework for Virtual Communities

The paper provides an integrated business framework for Business-to-Business, Business-to-Consumer and Consumer-to-Consumer Virtual Communities. The framework involves internal and external factors. Internal factors that include: market analysis; products/services promotion; development of trust; social influence and Knowledge sharing, differ from the different orientations of the framework, while the external factors involve competitors and technological aspects that, while differing from the framework business orientation, have an important impact on the design and development of the business activities.
Extensions of Kronecker product algebra with applications in continuum and computational mechanics

Kronecker product algebra is widely applied in control theory. However, it does not appear to have been commonly applied to continuum and computational mechanics (CCM). In broad terms the goal of the current investigation is to extend Kronecker product algebra so that it can be broadly applied to CCM. Many CCM quantities, such as the tangent compliance tensor in finite strain plasticity, are very elaborate or difficult to derive when expressed in terms of tensor indicial or conventional matrix notation. However, as shown in the current article, with some extensions Kronecker product algebra can be used to derive compact expressions for such quantities. In the following, Kronecker product algebra is reviewed and there are given several extensions, and applications of the extensions are presented in continuum mechanics, computational mechanics and dynamics. In particular, Kronecker counterparts of quadratic products and of tensor outer products are presented. Kronecker operations on block matrices are introduced. Kronecker product algebra is extended to third and fourth order tensors. The tensorial nature of Kronecker products of tensors is established. A compact expression is given for the differential of an isotropic function of a second-order tensor. The extensions are used to derive compact expressions in continuum mechanics, for example the transformation relating the tangent compliance tensor in finite strain plasticity in undeformed to that in deformed coordinates. A compact expression is obtained in the nonlinear finite element method for the tangent stiffness matrix in undeformed coordinates, including the effect of boundary conditions prescribed in the current configuration. The aforementioned differential is used to derive the tangent modulus tensor in hyperelastic materials whose strain energy density is a function of stretch ratios. Finally, block operations are used to derive a simple asymptotic stability criterion for a damped linear mechanical system in which the constituent matrices appear explicitly.
Cortical localization patterns in the somatic sensory cortex of the opossum

Abstract Primary evoked responses and single neuron activity were recorded from the cerebral cortex of the virginian opossum following stimulation of the appendages, particularly a contralateral forepaw and its digits. The electrical activity and discharge patterns of single neurons were comparable to those in higher mammals; both inhibitory and occlusive interactions were observed. Primary evoked responses also resembled those in higher mammals. The areas of the cerebral cortex which responded to stimulation of the palm and the five digits were coextensive, comprising about one-third of the dorsal surface of the cerebral hemisphere. Topographic maps for the contralateral palm and digits constructed on the bases of peak-to-peak voltage and latency of primary evoked response differed in both location and arrangement. Latency-based maps were more medially displaced than amplitude-based maps obtained from the same data although these were usually a mirror image of the amplitude maps. Two possible explanations of this differing topographic arrangement are tendered, and it is suggested that the cortical map based upon minimal latency of the primary evoked response is the primary representation of the periphery at the cerebral cortex.
REGIONAL ANESTHESIA IN PEDIATRICS

The use of regional anesthetic techniques in infants and children has become increasingly accepted as standard care. The most commonly performed regional anesthetic techniques used in pediatric patients are the caudal and lumbar approaches to the epidural space, ilioinguinal/iliohypogastric, and penile nerve blockade. These and other techniques are reviewed, along with specific issues such as risks, benefits, drug dosage, and local anesthetic toxicity. The safety of regional anesthetic techniques in pediatric patients is addressed, with recommendations for prevention and treatment of complications.
Use of surface-enhanced laser desorption ionization protein chip system to analyze streptococcal exotoxin B activity secreted by Streptococcus pyogenes.

Abstract Ciphergen surface-enhanced laser desorption ionization (SELDI) protein chip technology was used to analyze the secretion and autoactivation of the Streptococcus pyogenes cysteine protease SpeB. This method allowed rapid identification of both the zymogen form of the protein Mr∼41,000 and the fully active enzyme Mr∼28,500. SpeB production in culture supernatants was demonstrated to be growth-phase regulated and SpeB positive and negative variants of a blood passaged S. pyogenes isolate could readily be distinguished. In kinetic studies of the autoactivation of the zymogen form of SpeB, the sequential generation of four intermediates was detected before the accumulation of the fully active enzyme. The methods described enabled enhanced speed, use of lower sample volumes and concentrations, and a more complete molecular characterization of SpeB than allowed by existing methods of analysis using SDS-PAGE and Western immunoblotting.
Agrammatic verb errors in Spanish speakers and their normal discourse correlates

Abstract Agrammatic verb errors are characterized by a reliance on simple verb forms without elaborated inflectional markings. Yet agrammatism studies on verbs have not addressed the possible correlations that might exist between pre-morbid verb use patterns and agrammatic verb production, especially frequency in oral discourse. Spanish, a language with a highly inflected verb system, is a useful context to explore this interaction. This study investigated agrammatic and normal verb use for those Spanish verb tenses found in daily conversation (Silva-Corvalan, 1983; Bentivoglio and Sedano, 1992). We analyzed agrammatic verb performance in spoken discourse and a sentence repetition task, and compared it with verb use in normal spoken and printed narratives. Findings suggested that the present was the most frequently used tense by both agrammatics and normals. The preterit, the second most frequent tense in normals, was similarly employed correctly by agrammatic subjects in the repetition task but was not present in their discourse. All other verb tenses, minimally found in normal texts, were similarly never produced in agrammatic discourse or minimally produced correctly in agrammatic sentence repetition. These results suggest that daily verb use patterns have a facilitating effect on verb use by Spanish-speaking agrammatic subjects. They agree with earlier arguments supporting the resistance of high-frequency words to errors in normal and aphasic speakers (Hall, 1954; Howes, 1964; Rochford & Williams, 1984), possibly a reflection of an automatic, routinized, and overlearned nature due to their early acquisition (Schnitzer, 1989), and a significant degree of lexical strength (Bybee, 1985; 1995; Stemberger & MacWhinney, 1986).
Volume conservation in the liquid drop model

Abstract Although the L = 0 (breathing) mode does not conserve volume and the L = 2 (quadropole) mode conserves volume only to first order, both modes together can conserve volume to second order when a certain interference relation among the six mode amplitudes is satisfied. The quantized versions of the liquid drop model with volume conservation imposed to first and to second order have different dynamical groups [IU(5), U(6), respectively], different Hilbert spaces [infinite dimensional, finite dimensional, respectively], and different rotationally invariant operators from which hamiltonians can be constructed.
The volcanic geology and petrology of Isla Pinta, Galapagos archipelago

Pinta, one of the northern islands in the Galapagos archipelago, is the top of a shield volcano which became emergent ∼0.7 m.y. ago. A regional north-north west-trending fracture system influenced the locus of volcanism. Pinta9s geologic development can be divided into an older, shield stage and a younger, fissure stage. Each stage produced a similar, yet distinct, series of evolved olivine tholeiites (magnesium number = 52). The shield series underwent some additional shallow-level fractionation in a periodically replenished chamber. Rare-earth-element data indicate that the mantle source for both of the series has residual garnet. Higher concentrations of incompatible trace elements iri the fissure series imply a lower degree of partial melting. 143 Nd/ 144 Nd and 87 Sr/ 86 Sr ratios suggest that both series have an enriched, hotspot-type source. Despite close proximity to the Galapagos spreading ridge, Pinta9s lavas lack features characteristic of mid-ocean ridge basalts. The isotopic and rare-earth-element data from Pinta and the other northern islands are consistent with previous models for the Galapagos spreading ridge, which require north-south axially directed transfer of enriched asthenosphere and/or melts from the Galapagos hotspot to the Galapagos Ridge.
Multifocal ERG in subjects with a history of retinopathy of prematurity.

Purpose: Investigate the function of the central retina in subjects with a history of retinopathy of prematurity (ROP). Methods: Multifocal electroretinogram (mfERG) responses to a scaled array of 103 hexagons were recorded in subjects, aged 11–23 years (N = 11), with a documented history of mild ROP. The amplitude and implicit time of the components (N1, P1, N2) of the first order kernel for six concentric rings were compared to those of control subjects (N = 9). Results: The amplitude of each component varied significantly with eccentricity in both ROP and control subjects and was significantly smaller in the ROP subjects. The discrepancy between ROP and control subjects was greatest for central rings (1–3) and smaller for peripheral rings (4–6). The slopes of the functions summarizing log response density as a function of log eccentricity (degrees visual angle) were significantly shallower in ROP subjects. The implicit time of each component was longer in ROP subjects at all eccentricities. Conclusions: ROP associated alterations in neural retinal development may underlie the subtle macular dysfunction disclosed by the mfERG.
Parallel computing forty years ago

Abstract The author’s initiation into computing 40 years ago, and the early development of parallel computing paradigms within hardware and software systems which evolved at that time, are recounted in a personal trace. It was an optimal time to learn computing and the intuition gained has been of great value to the author ever since. It is hoped that the following account of one segment of early computing will be of interest especially to the younger readers.
MIXOTROPHY AND NITROGEN UPTAKE BY PFIESTERIA PISCICIDA (DINOPHYCEAE)

The nutritional versatility of dinoflagellates is a complicating factor in identifying potential links between nutrient enrichment and the proliferation of harmful algal blooms. For example, although dinoflagellates associated with harmful algal blooms (e.g. red tides) are generally considered to be phototrophic and use inorganic nutrients such as nitrate or phosphate, many of these species also have pronounced heterotrophic capabilities either as osmotrophs or phagotrophs. Recently, the widespread occurrence of the heterotrophic toxic dinoflagellate, Pfiesteria piscicida Steidinger et Burkholder, has been documented in turbid estuarine waters. Pfiesteria piscicida has a relatively proficient grazing ability, but also has an ability to function as a phototroph by acquiring chloroplasts from algal prey, a process termed kleptoplastidy. We tested the ability of kleptoplastidic P. piscicida to take up 15N-labeled NH, NO, urea, or glutamate. The photosynthetic activity of these cultures was verified, in part, by use of the fluorochrome, primulin, which indicated a positive relationship between photosynthetic starch production and growth irradiance. All four N substrates were taken up by P. piscicida, and the highest uptake rates were in the range cited for phytoplankton and were similar to N uptake estimates for phagotrophic P. piscicida. The demonstration of direct nutrient acquisition by kleptoplastidic P. piscicida suggests that the response of the dinoflagellate to nutrient enrichment is complex, and that the specific pathway of nutrient stimulation (e.g. indirect stimulation through enhancement of phytoplankton prey abundance vs. direct stimulation by saprotrophic nutrient uptake) may depend on P. piscicida’s nutritional state (phagotrophy vs. phototrophy).
Black smokers on the Mid‐Atlantic Ridge

Evidence for a variety of active hydrothermal venting phenomena, including black smokers, was discovered at a site on the Mid-Atlantic Ridge by a research team of government and university scientists. The work was accomplished on a cruise of the National Oceanic and Atmospheric Administration (NOAA) ship Researcher during July 1985 as part of the NOAA Vents Program. The site of the venting phenomena is the Trans-Atlantic Geotraverse (TAG) Hydrothermal Field on the east wall of the rift valley of the Mid-Atlantic Ridge at 26°N. The TAG Hydrothermal Field was the first hydrothermal field to be found on an oceanic ridge; it was discovered 12 years ago in 1973. However, until the present cruise, only low-temperature hydrothermal activity had been documented, and the existence of higher-temperature hydrothermal activity along slow spreading oceanic ridges (half rate 2 cm/yr), such as the Mid-Atlantic Ridge, was in question.
Imperfect lubricated squeezing flow viscometry for foods

Commercial mayonnaise and mustard samples placed in a wide, shallow Teflon container were compressed by a wide Teflon plate to induce an ‘imperfect’ lubricated squeezing flow. A dominant squeezing flow regime could be clearly identified as a linear region in the log F(t) vs log H(t) relationship, F(t) and H(t) being the momentary force and specimen height respectively. The slope of the relationship enabled the estimation of the flow index, n, and the consistency coefficient K. The n values of the mayonnaise were on the order of 0.6–0.85 and those of the mustard about 0.7. The corresponding K values were on the order of 6–13 and 4–5 kPasn respectively. Considering the crudeness of the array the measurements were highly reproducible and sensitive enough to detect differences (mayonnaise) or establish similarities (mustard) in products of different brands. The calculated flow index was practically independent of the plate's radius and of the consistency coefficient, which had a weak dependency on the latter. The calculated elongational viscosity vs biaxial strain rate relationship could also be used to compare the different products and brands. At 0.01 s−1 the elongational viscosity of the maynonnaise was on the order of 150 kPas, and of the mustard 60 kPas.
HYPERCALCÆMIA AFTER ORAL CALCIUM-CARBONATE THERAPY IN PATIENTS ON CHRONIC HÆMODIALYSIS

Abstract Oral calcium carbonate is widely used in chronic renal failure as a phosphate- binding antacid. Unexpectedly, severe hypercalcaemia developed in three out of ten haemodialysis patients treated with 3·2-6·4 g. calcium carbonate per day for 4-8 weeks. In one patient the serum-calcium reached 15·8 mg. per 100 ml., and he had nausea, vomiting, muscular weakness, personality changes, and subconjunctival calcifications. Two other patients were symptom-free with serum-calcium levels of 13·2 and 12·7 mg. per 100 ml. Hyperparathyroidism, raised dialysate calcium concentrations, and vitamin-D intoxication were excluded as causes of this complication. When calcium carbonate was discontinued, serum-calcium promptly returned to normal, and in the first patient all signs and symptoms disappeared. It is concluded that the hypercalcaemia resulted from intestinal absorption of calcium, probably by passive diffusion not dependent upon vitamin D. Calcium carbonate should be used with caution in patients maintained on chronic haemodialysis.
Alkoxycyclooctatetraene Anion Radicals: An Unusual Spin Density Perturbation Due to 1,3-Carbon/Carbon Interactions

A series of new alkoxycyclooctatetraene ethers was synthesized and their anion radicals generated in hexamethylphosphoramide. The EPR measured spin densities can be explained in terms of the odd electron occupying MOs, ae4′ ) [1/2x(n 2 + 1)](na1 + a2 - na3 - a4 + na5 + a6 - na7 - a8) and ae5′ ) [1/2x(n 2 + 1)](na1 - a2 - na3 + a4 + na5 - a6 - na7 + a8), where n increases with the electronreleasing nature of the alkoxy group. The anion radicals of n-propoxycyclooctatetraene and ibuprofoxycyclooctatetraene exhibit a small (ca. 0.35 G) splitting for the A proton on the sp 3 hybridized carbon. Further, the EPR pattern for the tert-butoxycyclooctatetraene anion radical is consistent with a relatively smaller value for n (in ae4′ and ae5′). These observations are consistent with a rather unusual homohyperconjugative interaction involving overlap of the U-bond to the A-hydrogen and the ﷿-system of the conjugated COT ring.
Indications for Radiofrequency Ablation in the Pediatric Population

Pediatric radiofrequency ablation procedures have become commonplace since their introduction to clinical practice 6 years ago. Excellent success rates coupled with low complication rates have allowed these procedures to be offered as first-line therapy to many children. This review focuses on the current indications for radiofrequency ablation in children. These indications are not the same as for adults. They are based on the natural history of various forms of arrhythmias, the risks of the procedure, and the current success rates of the procedures, all of which are dependent upon the age of the patient.