cssi/SciSciGPT-SciSciNet huggingface dataset:
TU‐E‐213A‐01: Quality Assurance for the Leksell Gamma Knife Perfexion™

The Leksell Gamma Knife_ Perfexion_ is the latest gamma stereotactic radiosurgery (GSR) unit manufactured by Elekta (Elekta Instrument, AB, Sweden). Introduced in 2006, it is substantially different in design and operation from previous Gamma Knife (GK) models. The major differences are in the collimation system, the configuration of the radioactive 60Co sources, and in the patient positioning system. The Perfexion_ has one fixed tungstencollimator containing 576 different collimating channels, whereas older GK models have one primary collimator, located inside the unit, and 4 interchangeable secondary collimators that are mounted manually. In the Perfexion_, 192 60Co sources are situated on 8 moveable sectors (24 sources per sector), that slide over the collimator placing the sources over the planned collimating channels to deliver the desired radiation shot size. In older GK models, by contrast, 201 60Co sources are fixed in space and arranged in a pseudo‐hemispherical configuration. Finally, for the Perfexion™ the treatment table, which moves with sub‐millimeter accuracy in three orthogonal directions, is the patient positioning system. For older model GK units, patient positioning is accomplished by attaching the Leksell stereotactic frame to the secondary collimator via specialized hardware called trunnions or via the automatic‐patient‐positioner (APS). The specific goals of quality assurance (QA) for gamma stereotactic radiosurgery include determining the dose rate for the largest available collimator, measuring the relative output factors and beam profiles for each collimator size and comparing the results to those used in or calculated by the treatment‐planning program, and verifying that the radiation focal point coincides with the center of the patient positioning system. Although these QA tasks for GSR units have remained essentially unchanged over the years, new tools and protocols designed for linear accelerator QA have become available that can be applied to QA for GSR devices. With this in mind, a new AAPM Task Group (TG‐178) has recently been formed and charged with updating QA procedures for older GSR devices that have static sources, creating new QA protocols for GSR devices that are characterized by moving sources, and suggesting a protocol for ionization chamber calibration specific to GSR devices. This lecture will describe the operation of the Leksell Gamma Knife_ Perfexion_ and the unique features of QA for GSR units, with emphasis on the Perfexion_. Some of the questions faced by TG‐178 will be discussed, old QA procedures will be reviewed and possible new QA tests will be suggested. Learning Objectives: 1. Review QA requirements for GSR units 2. Understand the design differences between older GK models and the Perfexion_ and the implications of these differences on routine QA 3. Become familiar with tools provided by the manufacturer to facilitate GK QA 4. Understand the difficulties associated with dosimetriccalibration of GSR units 5. Review the use of radiochromic film for GK QA
Measurement of rates of grazing of the ostracod Cyprinotus carolinensis on blue-green algae

Measurements were made of the rates of grazing of the ostracod Cyprinotus carolinensis fed 14C-labelled filamentous blue-green algae (cyanobacteria). The grazing rate was a linear function of food concentration at densities below 1.1 µg dry weight of algae · ml-1 and independent of concentration at densities above 11.5 µg algae · ml-1. Starvation affected grazing rates significantly, but light vs. dark feeding, animal density, and the volume of feeding container did not. Grazing on Nostoc sp. was a linear function of ostracod size. Respiration of C. carolinensis and the blue-green algae was not a significant factor in the tests of grazing.
Interactions between particulate inclusions in a smectic-A liquid crystal

We study theoretically the smectic mediated interactions between pointlike inclusions in a lamellar phase. The two-body interaction is derived and we discuss the virial expansion in the limits of weak and strong interactions. The leading order finite density corrections to the interaction potential are calculated using a mean field theory, which allows the particle density, potential, and effective smectic moduli to be calculated self-consistently. The effective bending modulus of the membranes is found to increase linearly with the particle density. We also give the structure factor S(q) for small but finite particle density.
Calcium effects on gap junction structure and cell coupling

PROTOPLASMIC molecules of low molecular weight are known to travel freely across the boundaries between most neighbouring cells through small intercellular channels generally thought to be at the intramembranous particles of gap junctions1–3. The permeability of the channels can be decreased to a complete interruption of cell communication by a variety of treatments2–10. Most of these treatments raise the concentration of ionised calcium, [Ca2+], in the cytoplasm8, suggesting that calcium may be the uncoupling agent in both vertebrate9 and invertebrate cells2,8. In some systems glutaraldehyde fixation has also been shown to produce uncoupling3; however, this type of uncoupling does not seem to be triggered by calcium10. In parallel with functional uncoupling reversible structural changes have been described in gap junctions of crayfish characterised by an increase in tightness and regularity of particle aggregation and a decrease in junctional thickness and particle size10. These changes, interpreted as reflecting conformational rearrangements in the protein framework of the channels resulting in channel obliteration, were recently confirmed in the rat11 although in the latter, functional uncoupling was not measured electrophysiologically, but only presumed on the basis of reasonable comparative arguments. It remains uncertain whether or not the changes in both the gap junction structure and the cell coupling are due to a direct action of calcium on the junctional membranes. We show here that the junctional change is indeed a calcium effect, triggered by [Ca2+] as low as 5×10−7 M.
Theory of multiphase mixtures—A thermomechanical formulation

The paper presents a theory of mixtures with the nonzero interfacial area between the constituents of the mixture. The conservation laws are physically motivated by utilizing a volume averaging procedure and by the definition of a mapping transformation. It is shown that the theory constructed in this manner is consistent with the theory of mixtures with a vanishingly small interfacial area and that a second law of thermodynamics can be assigned for each phase of the mixture. The conservation laws are examined for invariance properties with the principle of the material frame indifference, and a particular constitutive assumption is discussed. Also presented in the paper are the conservation laws in the integral form and the jump conditions for the singular surfaces in the multiphase mixture.
Deep lamellar endothelial keratoplasty: histopathology of complications in initial cases.

Purpose: To report complications encountered after 2 initial cases of deep lamellar endothelial keratoplasty. Methods: Review of clinical findings of 2 initial cases in which intraoperative and postoperative complications were encountered. Comeal buttons from the 2 cases were evaluated by light microscopy and transmission electron microscopy. Results: Complications encountered were related to the graft-recipient interface and the lamellar dissection of the recipient and donor corneas. Conclusion: Deep lamellar endothelial keratoplasty is an evolving procedure that shows much promise. These 2 cases show that the procedure entails a separate skill set from penetrating keratoplasty and requires significant surgeon practice before being introduced into the individual's transplant practice.
Rational DuRability Design of HeteRogeneous functional MateRials: soMe fiRst PRinciPles

The present paper proposes a rational approach to the design of constituents, their morphology, and their multiscale arrangement in heterogeneous functional material systems to control the evolution of their properties, morphology, and performance as they interact over specified histories of applied mechanical, electrical, chemical, and thermal fields. The principal thrust of the paper is the postulate of a “first law” for such an approach, which states that “only 100 percent efficient systems are 100 percent durable; the durability is controlled by non-conservative changes in the material state, which are uniquely reflected in changes in the material compliance to applied fields.” The application of the “first law of rational durability design” is discussed for mechanical and electrical applied fields acting upon primarily two-phase heterogeneous material systems. A rational design analysis is demonstrated, and the results are compared with experimental data for fiber-reinforced control materials. The application of the concepts to heterogeneous functional materials (HeteroFoaM) used in fuel cells, batteries, membranes, and electrolyzers is also discussed.
Design of a Coded-Aperture Imaging System for simulated reactor-accident experiments

AbstractThe application of coded aperture imaging to the measurement of fuel location in nuclearfuel pins undergoing simulated reactor accident conditions is described. Modifications tonormal coded aperture techniques, including the use of a one- dimensional, thick (1.5 cm)aperture, are described. The predicted and experimentally measured performance of theaperture is compared, and results of steady state imaging tests using trie duneu ApertureIhaging System (CAIS) are shown.IntroductionA new type of high resolution diagnostic system has been developed to determine thelocation and movement of nuclear fuel undergoing simulated accident conditions in experi-ments performed in Sandia's Annular Core Research Reactor (ACRR). The nature of theexperiments required that either the radiation emitted from the fissioning fuel under testor a separate source of penetrating radiation be used for imaging. The resultant systemutilizes the gamma radiation emitted by the test fuel as the method of imaging the fuelmotion. Furthermore, because of the need to obtain statistically meaningful high resolu-tion images on a short time scale (< 1 cosec) a coded aperture imaging system was imple-mented instead of a conventional pinhole configuration.A mi)rq detailed description of the system and its operation has been published else-
Complete heart block complicating retrograde left ventricular catheterization : case report and review

Complete heart block (CHB) following retrograde left ventricular catheterization is uncommon. We report a case of transient CHB in a patient with severe aortic stenosis and bifascicular block on the baseline surface electrocardiogram during retrograde left ventricular catheterization. The block resolved spontaneously without sequelae. A review of the literature using MedLine was performed and recommendations for temporary and permanent pacing are outlined.
Comparative Performance of Color-Measuring Instruments; Second Report

The comparative performance of twelve different late-model color-measuring instruments was studied for precision (short-term repeatability) and conformance of color measurement and color-difference measurement. The instruments tested included four true and two abridged spectrophotometers and six colorimeters, all being integrating-sphere instruments except three 45°/0° colorimeters. All the colorimeters were individually calibrated for close conformance to CIE coordinates. Forty-four samples taken from the group studied in the previous paper were measured three times on each instrument, by three different well-trained operators. Again, a GE spectrophotometer was considered the reference instrument for conformance studies. Overall, the GE spectrophotometer, the Hunterlab D25D colorimeter, and the Koll-morgen KCS-18 and KCS-40 abridged spectrophotometers demonstrated the best performance. Statistical treatment of the data has been improved vastly since the earlier paper, and some recalculated results are included.
Rate-control and multi-channel scheduling for wireless live streaming with stringent deadlines

SVC-based live video-streaming in multi-channel wireless networks leads to a challenging joint rate-control and scheduling problem with stringent deadline constraints. Tradi- tional utility-based approaches often did not explicitly account for deadlines. In this paper, we explicitly account for deadlines and study the problem of optimizing the total reward from packets meeting their deadlines in a modern 4G OFDM system. Motivat- ed by a heuristic utility-based approach, we propose a class of threshold-based rate-control and wireless scheduling policies that can respect the deadline constraints and approach the optimal system reward asymptotically as the system size increases. We also propose a distributed realization of our threshold-based policies that can be easily implemented in practical scenarios. We substantiate the result via both analysis and simulation. I. INTRODUCTION
The Use of Protonation Induced Changes in Carbon-13 NMR Chemical Shifts to Investigate the Solution Microscopic Structure of Partially Protonated Polybasic Molecules

Abstract Changes in the NMR chemical shift of carbon-13 nuclei upon protonation of a nearby basic center are shown to be a useful method of probing the microscopic site of protonation of molecules containing multiple basic centers, such as diethylenetriaminepenta-acetic acid (DTPA). This approach is also shown to support the predominance of the pyridine amine protonated tautomer in the 4-pyridone ↔ 4-hydroxypyridine equilibrium.
1.3.1 An Integrated Problem Reporting and Resolution System

With few exceptions, all system development projects have a need to identify, track, and resolve issues, action items, problems and changes. Within an organization, many different mechanisms may be used to perform this function across projects. Indeed, on a single project, a number of different systems may be in place to track the various types of ‘problems‘. This paper describes an integrated approach for establishing a project problem reporting and resolution system which handles all categories of items, from identification through closure. This approach, which includes a process description and automation support, was successfully implemented and used on a $30M project over a two year period with the described results.
Supercuspidal L-packets of positive depth and twisted Coxeter elements

The local Langlands correspondence is a conjectural connection between representations of groups G(k) for connected reductive groups G over a padic field k and certain homomorphisms (Langlands parameters) from the Galois (or Weil-Deligne group) of k into a complex Lie group G which is dual, in a certain sense, to G and which encodes the splitting structure of G over k. More introductory remarks on the local Langlands correspondence can be found in [21]. WhenG = GL1 this correspondence should reduce to local abelian class field theory. For G = GLn, the Langlands correspondence is uniquely determined by local factors [24] and was shown to exist in [23] and [25]. So far this correspondence is not completely explicit, but much progress has been made in this direction; see [9], [10], for example. For groups other than GLn or PGLn, the theory is much less advanced; new phenomena appear, arising on the arithmetic side from the difference between conjugacy and stable conjugacy and on the dual side from nontrivial monodromy of Langlands parameters. This means that a single Langlands parameter φ should determine not just one, but a finite set of representations Π(φ); these are the “L-packets” of the title. However, since local factors have not been defined in general, there is no precise characterization of an L-packet for general groups. One can, at present, only hope to define finite sets of representations Π(φ) attached to Langlands parameters φ, and show that they have properties expected (or perhaps unexpected) of L-packets. (See [14, chap. 3] for some of these properties.) One is thereby proposing a definition of local factors for the representations in the sets Π(φ) (cf. [4, chap.3]). This paper is a sequel to [14]. The aim of both papers is to verify, in an explicit and natural way, the local Langlands correspondence for the simplest kinds of non-abelian extensions of k, and the simplest kinds of
High negative interference and heterozygosis: A study of the mechanism of recombination in bacteriophage T4☆☆☆

Abstract In the progeny from crosses of bacteriophage T4B involving closely linked r II markers, there exist particles which upon growth are capable of producing r + recombinant progeny, but which themselves are neither genetically nor phenotypically r + . Evidence is presented that these particles are partial heterozygotes, which are structurally biparental (nonrecombinant heterozygotes) and which give as primary segregants the two parental types. A comparison of recombinant formation in bacteria infected with nonrecombinant heterozygotes and in bacteria infected with the two parental types is described. Cells infected with nonrecombinant heterozygotes produce a higher frequency of recombinant clones and larger clones of recombinants. These differences are ascribed to different mechanisms of recombinant formation in the two types of cells. It is suggested that nonrecombinant heterozygotes form recombinant segregants by some process inherent in their mode of reproduction. This property of the nonrecombinant heterozygote may account for the apparent positive correlation of neighboring exchanges characteristic of recombination over short segments of the phage genome.
Effect of L-arginine or nitroglycerine during deep hypothermic circulatory arrest in neonatal lambs.

Abstract Background The role of nitric oxide (NO) in ischemia-reperfusion injury remains controversial. This study evaluated the effects of l-arginine (NO precursor) or nitroglycerine (NO donor) on cardiac and lung function after deep hypothermic circulatory arrest in neonatal lambs. Methods Three groups of anesthetized lambs underwent cardiopulmonary bypass, deep hypothermic circulatory arrest (120 minutes at 18°C), and rewarming (40 minutes). During reperfusion, l-arginine (5 mg/kg per minute), nitroglycerine (2 μg/kg per minute), or saline (control group) was infused for 100 minutes. All animals were separated from cardiopulmonary bypass and observed for 3 additional hours. Preload recruitable stroke work, cardiac index, pulmonary vascular resistance, alveolar-arterial oxygen difference, and lung compliance plasma nitrate/nitrite levels (NO metabolites) were measured before and after cardiopulmonary bypass. Malondialdehyde in heart tissue and lung tissue was measured 3 hours after cardiopulmonary bypass. Results Recovery of preload recruitable stroke work and cardiac index were significantly higher in the l-arginine and nitroglycerine groups than in the control group ( p p Conclusions l-arginine and nitroglycerine improved recovery of left ventricular function and reduced pulmonary vascular resistance after deep hypothermic circulatory arrest. The mechanism of beneficial action could involve increased NO levels, but we did not find higher levels of NO metabolites compared with controls. Tissue malondialdehyde levels were not affected by l-arginine or nitroglycerine. These results show that, at these dosage levels, provision of substrate for NO production or provision of an NO donor were beneficial to the recovery of myocardial and pulmonary vascular function.
Inhibition of Glutathione Peroxidase Mediates the Collateral Sensitivity of Multidrug-resistant Cells to Tiopronin

Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is often the result of overexpression of ATP-binding cassette transporters following chemotherapy. A common ATP-binding cassette transporter that is overexpressed in MDR cancer cells is P-glycoprotein, which actively effluxes drugs against a concentration gradient, producing an MDR phenotype. Collateral sensitivity (CS), a phenomenon of drug hypersensitivity, is defined as the ability of certain compounds to selectively target MDR cells, but not the drug-sensitive parent cells from which they were derived. The drug tiopronin has been previously shown to elicit CS. However, unlike other CS agents, the mechanism of action was not dependent on the expression of P-glycoprotein in MDR cells. We have determined that the CS activity of tiopronin is mediated by the generation of reactive oxygen species (ROS) and that CS can be reversed by a variety of ROS-scavenging compounds. Specifically, selective toxicity of tiopronin toward MDR cells is achieved by inhibition of glutathione peroxidase (GPx), and the mode of inhibition of GPx1 by tiopronin is shown in this report. Why MDR cells are particularly sensitive to ROS is discussed, as is the difficulty in exploiting this hypersensitivity to tiopronin in the clinic.
β-Carotene Attenuates Peroxide-Induced Vasoconstriction in the Human Placenta

Objective:Placental lipid peroxides and thromboxane are abnormally increased in preeclampsia. Peroxides stimulate thromboxane to increase placental vasoconstriction. antioxidants, such as β-carotene, control lipid peroxidation. Reduced levels of βcarotene (0.25 μmol/L) have been found in preeclamptic women. We hypothesized that normal (0.5 μmol/L) or elevated (1.0 μmol/L) levels of β-carotene would attenuate peroxide-induced vasoconstriction in the human placenta, whereas low levels would not.Methods:Isolated human placental cotyledons (n = 8) were sequentially perfused with control Krebs-Ringer-bicarbonate buffer, 200 μmol/L t-butyl hydroperoxide, and then with progressively increasing concentrations of β-carotene (0.25, 0.5, and 1 μmol/L) plus t-butyl hydroperoxide. Fetal perfusion pressure was monitored continuously, and maternal and fetal effluent samples were collected for each treatment. Samples were analyzed for lipid peroxides and for thromboxane and prostacyclin by their stable metabolites thromb...
Production and Cycling of Calcium Carbonate in a Shelf-Edge Reef System (St. Croix, U.S. Virgin Islands): Applications to the Nature of Reef Systems in the Fossil Record

ABSTRACT Geologic reefs are the end-products of not only constructive processes that produce calcium carbonate, but also of destructive processes (e.g., bioerosion and wave action) that reduce solid substrate to sediment, and of physical processes that rework the reef fabric and transport sediment. A study was conducted at Cane Bay on the island of St. Croix, U.S. Virgin Islands to quantify the suite of processes that have influenced Holocene reef development. Data on carbonate production, reef accretion, bioerosion, and sediment transport were used to construct a detailed "carbonate budget" and to apply the findings of this study to the character of reefs observed in the fossil record. Total carbonate production on the reef ranged from 0 to 5.78 kg/m2 per year, with a reef-wide average of 1.21 kg/m2 per year (1.13 by corals; 0.02 by coralline algae; 0.06 by primarily molluscs, forams and echinoderms). Based on 7 cores, only 0.91 kg/m2 per year of this have been retained within the reef interior. The remaining 0.24 kg/m2 per year of sediment, along with the 0.06 kg/m2 per year contributed directly by molluscs, etc., are deposited within reef channels and are probably flushed from the reef by major storms. Of the material recovered in the cores, 58% was either loose sediment and rubble or open void space. Much of the recognizable coral material was demonstrably reworked and out of place. Accretion rates across the shelf generally increased with water depth, as a result of active slumping along the steepening reef face over the past 2,000-3,000 years. The importance of detrital material in the reef fabric and the major role played by secondary processes that constantly rework the substrate have resulted in a reef whose interior is more of a "garbage pile" than an in-place assemblage of corals cemented together into a rigid "framework." The physical similarities between the detrital fabric of the reef at Cane Bay and those found in many ancient deposits imply that the general processes operating along the Cane Bay shelf have persisted during much of the evolution of ancient reefs. It is proposed that our modern models overemphasize the importance of in-place framework as a criterion for an "ecologic reef."
Wanted-Central Tendency and Variability of Test Norm Tables: How to Recover them?

An algorithm for estimation of means and standard deviations or raw scores underlying table values of standard test scores is presented. An application of a computer program, operationalizing the suggested algorithm, is discussed within the framework of a comparison of estimated and known table values for sample MMPI subscales.
Phenology of Shorebird Migration in Western Kentucky

Abstract Staging areas along the coasts provide reliable food resources, and shorebirds may use the same stopover locations every year. However, shorebirds use sites opportunistically in the interior of North America because of the transient nature of many habitats. Little is known, however, about the use of wetlands by migrating shorebirds in many areas of the Mississippi Alluvial Valley (MAV), including Kentucky. During 2004 and 2005, we examined the phenology of migration by shorebirds using stopover habitats in Kentucky. From March to October, we surveyed shorebirds in each moist soil unit as well as at other natural and man-made wetlands at each wildlife management area. Species abundance was recorded a minimum of once every 10-day period. We observed 25 species and 12,307 individual shorebirds during our study, with Charadrius vociferous (Killdeer; n = 4134), Calidris melanotos (Pectoral Sandpiper; n = 2912), Calidris minutilla (Least Sandpiper; n = 1138), Tringa melanoleuca (Gmelin) (Greater Yellow...
The anatomy of asthma care visits in community family practice.

Background: We know little about the activities that occur during asthma-related visits with primary care physicians. A better understanding of how time is spent during visits for asthma may facilitate the design of programs to enhance asthma disease management.Objective: To describe the content of asthma visits made to family physicians.Methods: Research nurses directly observed consecutive outpatient visits during two separate days in the offices of 138 community family physicians. Time was classified into 20 different behavioral categories using the Davis Observation Code, and compared for visits for asthma, visits for other chronic conditions, and visits for non-asthma-related acute illnesses during 3035 visits by patients of all ages. Results: Visits for asthma shared several characteristics with visits for other chronic conditions but were longer than visits for other chronic illnesses or for acute illness. Asthma visits were distinguished from both acute care and other chronic care visits by a grea...
Interfacial Segregation in Perovskites: I, Theory

Based on thermodynamic principles a theory for equilibrium interfacial segregation is proposed for perovskite materials, and this theory is applied to BaTiO3. An approach developed by Frenkel and refined by Kliewer and Koehler is extended to undoped ternary oxide materials such as BaTiO3. The approach uses regular solution approximations and considers space charge effects as the major driving force for segregation. The analysis based on this model indicates the presence of a negative space charge potential (−0.1 V at 800°C) at the surface of pure BaTiO3. The model also predicts cation enrichment at the interface. The thickness of the space charge layer decreases with increasing temperature, and calculated values agree well with experimental results. Since both elastic and electrostatic driving forces are important for dopant/impurity segregation, an approach where the grain boundary is considered to be a two-dimensional phase, in equilibrium with the three-dimensional phase of the grain, proves useful. Solving for the impurity/dopant segregation ratio is case specific and requires knowledge of the charge neutrality conditions as well as the strain energy contribution.
Getting precise and pragmatic about the assessment of bullying: the development of the California Bullying Victimization Scale

Accurate assessment of bullying is essential to intervention planning and evaluation. Limitations to many currently available self-report measures of bullying victimization include a lack of psychometric information, use of the emotionally laden term "bullying" in definition-first approaches to self-report surveys, and not assessing all components of the definition of bullying (chronicity, intentionality, and imbalance of power) in behavioral-based self-report methods. To address these limitations, we developed the California Bullying Victimization Scale (CBVS), which is a self-report scale that measures the three-part definition of bullying without the use of the term bully. We examined test-retest reliability and the concurrent and predictive validity of the CBVS across students in Grades 5-12 in four central California schools. Concurrent validity was assessed by comparing the CBVS with a common, definition-based bullying victimization measure. Predictive validity was examined through the co-administration of measures of psychological well-being. Analysis by grade and gender are included. Results support the test-retest reliability of the CBVS over a 2-week period. The CBVS was significantly, positively correlated with another bullying assessment and was related in expected directions to measures of well-being. Implications for differentiating peer victimization and bullying victimization via self-report measures are discussed.
The Rotational Dispersion of Sound in Hydrogen

The development of the interferometric method originally due to Pierce has definitely established the existence of an acoustic dispersion phenomenon in gases at supersonic frequencies. The experimental investigations of Abello, Kneser, Richards and Reid and others have shown this dispersion to exist in CO2, C2H4, CS2 and SO2. An explanation of the mechanism of the effect was advanced by Rice and Herzfeld; and on the basis of this mechanism the dispersion formula has been derived by Kneser, Rutgers and Bourgin. The density variations produced in the gas by the sound wave result in a disturbance of the equilibrium distribution of energy between the various degrees of freedom of the molecule, there being excess of translational energy in the compressional phase for example. This equilibrium is then re-established, after a certain length of time which is characteristic of the gas, by inelastic collisions. When the period of the wave is of the order of this characteristic time, this exchange becomes incomplete and the specific heat of the gas diminishes, the sound velocity therefore increases until, as the frequency increases further, there is no time during a cycle for energy to be transferred. The sound velocity then approaches a constant value. In the case of all gases previously investigated it is quite certain that the dispersion is to be attributed to the failure of the vibrational energy exchanges to follow the acoustic cycle. However, recently Richards and Reid have reported certain effects which, they assert, indicate a dispersion region in hydrogen due to rotational energy lag and lying at least partly in frequency range 94—451 kc. However, on the basis of the classical kinetic theory of Jeans one would expect to find such a dispersion only at frequencies of the order 106 kc. Further, Richards states that the experimental accuracy in the case of the hydrogen measurements was not very great. For these reasons it was considered advisable to investigate this problem further.
Mobile Robot Navigation: The CMU System

ocusing primarily on system architecture, this article describes the current status of autonomous land vehicle (ALV) research at F Carnegie Mellon University’s Robotics Institute. We will (1) discuss issues concerning outdoor navigation; (2) describe our system’s perception, planning, and control components that address these issues; (3) examine Codger, the software system that integrates these components into a single system, synchronizing the dataflow between them (thereby rnaximizing parallelism); and (4) present the results of our experiments, problems uncovered in the process, and plans for addressing those problems. Carnegie Mellon’s ALV group has created an autonomous mobile robot system capable of operating in outdoor environments. Using two sensors-a color camera and a laser range finder-our system can drive a robot vehicle continuously on a network of sidewalks, up a bicycle slope, and over a curved road through an area populated with trees. The complexity of real-world domains and requirements for continuous and real-time motion require that such robot systems provide architectural support for multiple sensors and parallel processing-capabilities not found in simpler robot systems. At CMU, we are studying mobile robot system architecture and have developed a navigation system working at two test sites and on two experimental vehicles.
Betaine Aldehyde Dehydrogenase in Sorghum (Molecular Cloning and Expression of Two Related Genes)

The ability to synthesize and accumulate glycine betaine is wide-spread among angiosperms and is thought to contribute to salt and drought tolerance. In plants glycine betaine is synthesized by the two-step oxidation of choline via the intermediate betaine aldehyde, catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase (BADH). Two sorghum (Sorghum bicolor) cDNA clones, BADH1 and BADH15, putatively encoding betaine aldehyde dehydrogenase were isolated and characterized. BADH1 is a truncated cDNA of 1391 bp. BADH15 is a full-length cDNA clone, 1812 bp in length, predicted to encode a protein of 53.6 kD. The predicted amino acid sequences of BADH1 and BADH15 share significant homology with other plant BADHs. The effects of water deficit on BADH mRNA expression, leaf water relations, and glycine betaine accumulation were investigated in leaves of preflowering sorghum plants. BADH1 and BADH15 mRNA were both induced by water deficit and their expression coincided with the observed glycine betaine accumulation. During the course of 17 d, the leaf water potential in stressed sorghum plants reached -2.3 MPa. In response to water deficit, glycine betaine levels increased 26-fold and proline levels increased 108-fold. In severely stressed plants, proline accounted for >60% of the total free amino acid pool. Accumulation of these compatible solutes significantly contributed to osmotic potential and allowed a maximal osmotic adjustment of 0.405 MPa.
Imaging Mimics of Primary Malignant Tumors of the Central Nervous System (CNS)

Imaging has become a central part of the evaluation of lesions of the central nervous system. Despite patterns of the appearances of several types of central nervous system malignancies and improving resolution of imaging techniques, there are other processes that can display similar characteristics. Time and again, vascular, inflammatory, and vascular lesions will mimic a neoplastic process, requiring tissue diagnosis. With the introduction of advanced magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging in the evaluation of the brain tumor, there has been improvement in determining whether a lesion is neoplastic, and further advances may lead to noninvasive pathological and molecular diagnoses.
Estimating the magnitude of data asymmetry in palaeozoological biogeography

Palaeozoological data are asymmetrical because they indicate the presence of a species in the area in which its remains are recovered, but the absence of remains is not necessarily evidence for the absence of a species. It is impossible to measure the magnitude of data asymmetry with respect to biogeography, but the magnitude can be estimated. The proportion of sites in an area where a species is known to occur that have not produced remains of that species is an estimate of counter-ubiquity. The proportion of identified faunal remains in an area where a species is known to occur that do not represent that species is another estimate of data asymmetry. Bivariate plots of the number of sites in an area that have produced remains of a taxon against the total number of faunal remains identified in the area indicate that data asymmetry can be estimated as the inverse of sample size. More sites and more identified faunal remains tend to produce more occurrences of a species, so more sites and more identified faunal remains will tend to provide a database that is not only more accurate but also less asymmetrical with respect to the geographical range of a species. Copyright © 2007 John Wiley & Sons, Ltd.
Late neuropathological consequences of strangulation

A case of a young man who was a victim of strangulation is presented. He arrived at the hospital in refractory status epilepticus, controlled only with intravenous pentobarbital. The initial CT scan showed mild cortical edema. Two days later, a CT scan showed diffuse cortical swelling and bilateral basal ganglia infarcts. Upon discontinuation of pentobarbital therapy, his neurological examination revealed spontaneous ventilation and a gag reflex. A CT scan 4 weeks after the insult demonstrated hypodensities in both cerebral hemispheres and hydrocephalus. EEG was isoelectric throughout his hospitalization. He survived nearly 5 months and succumbed to pneumonia. Neuropathological examination demonstrated severe encephalomalacia, multiple cystic infarcts and generalized compensatory ventriculomegaly. Microscopic examination was particularly remarkable for a pronounced gemistocytic astrocyte proliferation in the white matter. This case illustrates the long-term neuropathological consequences of severe, global hypoxia/ischemia and the paucity of intact brain required to maintain a persistent vegetative state.
Stationary transversal hot zones in adiabatic packed‐bed reactors

A pseudo-homogeneous model predicts that a stationary, stable, transversal nonuniform temperature pattern cannot form in any cross section of an adiabatic packed-bed reactor used to conduct a single reaction, if its dynamics depends only on the concentration of a limiting reactant and temperature. This is due to the fact that the transversal heat dispersion in the reactor is larger than that of the limiting reactant. This conclusion is proved for a shallow packed-bed reactor described by a pseudo-homogeneous model. Extensive numerical simulations showed that a two-phase model of an adiabatic packed-bed reactor exhibits the same behavioral features. A stable, stationary hot zone can form in the cross section of the reactor only under the unrealistic assumption that the transversal species dispersion exceeded that of the temperature. © 2005 American Institute of Chemical Engineers AIChE J, 2005
Social technology restriction alters state-anxiety but not autonomic activity in humans

Social technology is extensively used by young adults throughout the world, and it has been suggested that interrupting access to this technology induces anxiety. However, the influence of social technology restriction on anxiety and autonomic activity in young adults has not been formally examined. Therefore, we hypothesized that restriction of social technology would increase state-anxiety and alter neural cardiovascular regulation of arterial blood pressure. Twenty-one college students (age 18–23 yr) were examined during two consecutive weeks in which social technology use was normal or restricted (randomized crossover design). Mean arterial pressure (MAP), heart rate, and muscle sympathetic nerve activity (MSNA) were measured at rest and during several classic autonomic stressors, including isometric handgrip, postexercise muscle ischemia, cold pressor test, and mental stress. Tertile analysis revealed that restriction of social technology was associated with increases (12 ± 2 au; range 5 to 21; n = 7), decreases (−6 ± 2 au; range −2 to −11; n = 6), or no change (0 ± 0 au; range −1 to 3; n = 8) in state-anxiety. Social technology restriction did not alter MAP (74 ± 1 vs. 73 ± 1 mmHg), heart rate (62 ± 2 vs. 61 ± 2 beats/min), or MSNA (9 ± 1 vs. 9 ± 1 bursts/min) at rest, and it did not alter neural or cardiovascular responses to acute stressors. In conclusion, social technology restriction appears to have an interindividual influence on anxiety, but not autonomic activity. It remains unclear how repeated bouts, or chronic restriction of social technology, influence long-term psychological and cardiovascular health.
High beta ion driven microinstabilities in the large experiment on instabilities and anisotropies

Summary form only given, as follows. Construction of the West Virginia University (WVU) Large Experiment on Instabilities and Anisotropies (LEIA) is now complete. LEIA is designed to investigate a wide variety of high beta, space relevant plasma phenomena. Of particular interest are electromagnetic instabilities driven by the free energy associated with non-isotropic ion distributions, i.e., different parallel and perpendicular ion temperatures. These instabilities occur at plasma betas (/spl beta/=8/spl pi/kT/B/sup 2/) of order unity and ion temperature anisotropies, perpendicular divided by parallel, over the range 0.25 to 4.0. The plasma for LEIA is generated with a steady-state helicon plasma source. By varying the source magnetic field and the magnetic field in LEIA, the ion temperature anisotropy in LEIA can be controlled. Initial measurements of the magnetic fluctuation spectra as a function of plasma parameters, e.g., plasma beta and ion temperature anisotropy, will be presented.
Depletion of brain serotonin by 5,7-DHT modifies hamster circadian rhythm response to light

The midbrain raphe complex innervates the circadian rhythm regulating system by direct projections to the suprachiasmatic nucleus (SCN) and the intergeniculate leaflet (IGL). The present experiments examined the changes in circadian rhythm regulation consequent to the depletion of brain serotonin by central 5,7-dihydroxytryptamine (DHT) application. Adult male hamsters with access to running wheels were entrained to a light-dark cycle 14:10 (LD) of photoperiod, pre-treated with desmethylimipramine and given bilateral lateral ventricle infusions of 75 micrograms DHT/2.5 microliters 0.5% ascorbic acid in saline or vehicle only. Two separate experiments were performed. Four weeks after surgery, animals were transferred to either constant light (LL; Experiment 1) or constant dark (DD; Experiment 2). Animals remained in LL for 85 days, then were transferred to DD for 50 days, followed by a return to LD 14:10 for 14 days. Animals in Expt. 2 remained in DD for 55 days, were given 3 days food deprivation, then, beginning 35 days later, were periodically exposed to 30 min light pulses as a phase response curve (PRC) to light was generated. DHT treatment induced rapid appearance of advanced activity onset, delayed offset and longer duration of the nocturnal activity phase. DHT animals in LL had circadian locomotor rhythms much longer than control animals (24.43 +/- 0.04 vs 24.19 +/- 0.05 h) and normal circadian rhythmicity was rapidly lost by DHT animals in LL. There was no effect of DHT on circadian period in DD, but the DHT treated animals in DD had a larger phase delay region of the PRC than did controls and this was associated with an overall change in the temporal properties of the PRC. Serotonin immunohistochemistry showed an approximate 90% loss of cells from the dorsal raphe nucleus and decreased density of the serotonergic terminal field in the SCN and IGL. The results support the view that the serotonergic system modulates the phasic actions of light on the hamster circadian rhythm system. The data also indicate that hamsters can have a Type 0 PRC.
Parsing activity into meaningful events

People segment ongoing activity into meaningful events, which has important implications for memory and planning. Movement is one basis for segmentation. Perceptual experiments show that movement features are correlated with participants' segmentation of simple events. Neuroimaging data show that regions motion processing regions transiently increase activity at natural event boundaries. The strong relationships between movement and event segmentation may prove helpful for human-robot interaction. It may be possible for computational vision systems to automatically segment ongoing activity into meaningful units, such that those units can be used as the input to algorithms for recognizing the significance of a partner's actions.
Optimization of Interference Alignment Beamforming Vectors

The K user interference alignment scheme proposed by Cadambe and Jafar (CJ) achieves K/2 degrees of freedom for networks with frequency selective channels. In this paper, we provide two new algorithms that optimize the precoding subspaces which maximize the data rate performance of the CJ scheme while maintaining the achievable degrees of freedom. One design is obtained as a global solution of a constrained convex (concave) optimization problem that maximizes the sum rate. The other design provides a low complexity closed-form solution to a constrained maximization problem with a suboptimal sum rate objective function. We also show that both designs can be combined with Shen, Host-Madsen and Vidal orthonormalization that achieves further gains in sum rate by optimizing the precoding vectors generated by the proposed algorithms.
A Note on the Eigenvalues of Saddle Point Matrices

The spectral properties of saddle point matrices arising from saddle point problems are discussed. The relations of the eigenvalues and the determinants between the saddle point matrices and their sub blocks are investigated. An appropriate estimate on the maximum eigenvalue of saddle point matrix is given. In the numerical experiment the saddle point matrices derived from the mixed finite element discretizations on Stokes equation are observed. Numerical results confirm the theoretical analysis and demonstrate that the estimate on the maximum eigenvalue of saddle point matrix is proper.
The Effect of Abnormal Chromosome 10 on Transposition of Modulator from the R Locus in Maize

Transposition of the non-specific repressor element, Modulator, from the R locus on chromosome 10 in maize, is enhanced by coupling with the K10 segment at a distance of at least 35 map units from R . There is no detectable interaction in the repulsion phase. The K10 effect appears to be relatively greater in the earlier somatic cell generations during ear development. The transposition rate also is affected by the direction of crosses, being somewhat higher on the ears of F1 plants which received the compound mutable R allele from the pollen parent. The significance of the behavior of Modulator and other instability phenomena of higher plants is discussed in relation to chromosome organization.
Aggressive Transmission with ARQ in Quasi-Static Fading Channels

The problem of efficient communication over a quasi-static wireless fading channel is considered in this paper. The disadvantages of two well-known schemes, single-layer transmission (SLT) and multi-layer transmission (MLT), are pointed out. A new scheme named aggressive transmission with ARQ (AT-ARQ) is developed and optimized to provide better performance, at the expense of requiring ARQ feedback. Optimal power allocation among (re)transmissions is derived. A comprehensive performance comparison of the three schemes, under different performance metrics such as throughput, outage probability, and the combination of two, is reported via numerical simulations. Substantial performance improvement is observed with even 1-bit ARQ feedback in Rayleigh fading.