cssi/SciSciGPT-SciSciNet huggingface dataset:
Direct in situ measurement of dissolved zinc in the presence of zinc oxide nanoparticles using anodic stripping voltammetry

The wide use of metal-based nanomaterials such as zinc oxide (ZnO) nanoparticles (NPs) has generated concerns regarding their environmental and health risks. For ZnO NPs, their toxicity in aquatic systems often depends on the release of dissolved zinc species, and the rate of dissolution is influenced by water chemistry, including the presence of zinc-chelating ligands. A challenge, however, remains in quantifying the dissolution of ZnO NPs, particularly for time scales that are short enough to determine rates. This paper reports the application of anodic stripping voltammetry (ASV) with a hanging mercury drop electrode to directly measure the concentration of dissolved zinc in ZnO NP suspensions, without separation of the ZnO NPs from the aqueous phase. The effects of the deposition time and the electrochemical potential scan rate on the ASV measurement were consistent with expectations for dissolved phase measurements. The dissolved zinc concentration measured by ASV ([Zn]ASV) was compared with that measured by inductively coupled plasma mass spectrometry (ICP-MS) after ultracentrifugation ([Zn]ICP-MS), for four types of ZnO NPs with different coatings and primary particle diameters. For small ZnO NPs (4–5 nm), [Zn]ASV was 20% higher than [Zn]ICP-MS, suggesting that these small NPs contributed to the voltammetric measurement. For larger ZnO NPs (approximately 20 nm), [Zn]ASV was (79 ± 19)% of [Zn]ICP-MS, despite the high concentrations of ZnO NPs in suspension. Using ASV, the dissolution of ZnO NPs was studied, with or without Suwannee River Fulvic Acid (SRFA). Although SRFA diminished the ASV stripping current, dissolution of 20 nm ZnO NPs was significantly promoted at high fulvic acid to ZnO NP ratios. The ASV method described in this paper provides a useful tool for studying the dissolution kinetics of ZnO NPs in complex environmental matrices.
Characterization of the rat oral microbiome and the effects of dietary nitrate

The nitrate–nitrite–NO pathway to nitric oxide (NO) production is a symbiotic pathway in mammals that is dependent on nitrate reducing oral commensal bacteria. Studies suggest that by contributing NO to the mammalian host, the oral microbiome helps maintain cardiovascular health. To begin to understand how changes in oral microbiota affect physiological functions such as blood pressure, we have characterized the Wistar rat nitrate reducing oral microbiome. Using 16S rRNA gene sequencing and analysis we compare the native Wistar rat tongue microbiome to that of healthy humans and to that of rats with sodium nitrate and chlorhexidine mouthwash treatments. We demonstrate that the rat tongue microbiome is less diverse than the human tongue microbiome, but that the physiological activity is comparable, as sodium nitrate supplementation significantly lowered diastolic blood pressure in Wistar rats and also lowers blood pressure (diastolic and systolic) in humans. We also show for the first time that sodium nitrate supplementation alters the abundance of specific bacterial species on the tongue. Our results suggest that the changes in oral nitrate reducing bacteria may affect nitric oxide availability and physiological functions such as blood pressure. Understanding individual changes in human oral microbiome may offer novel dietary approaches to restore NO availability and blood pressure.
Heat transfer between horizontal tubes and freeboard region of a low-rank coal fluidized bed combustor

Experiments are conducted to measure the heat transfer rates to air-cooled horizontal tubes of diameter 38.1mm in the freeboard region of a pilot-scale fluidized-bed combustor burning North Dakota lignite- Silica sand with diameter ranging from 883 to 973 μim is used as bed material. The tests are carried out without limestone addition and ash recycle, at average bed temperatures ranging from 698 to 1117K, freeboard temperatures of 700 to 1139 K and superficial velocities of 1.74 to 1.86 m/s. Among the existing correlations, those proposed by George and Grace (1982), and Byam et al. (1981) are found to predict the experimental results quite well and their root-mean-square deviations are found to be 15.8 and 18.4 percent respectively. @KEYWORDS: Heat transfer, Fluidized bed Coal combustor
Transformation electromagnetics devices based on tensor impedance surfaces

Since its introduction, the transformation electromagnetics design method (J. B. Pendry, et. al, Science, 23, 1780-1782, 2006) has been used to devise innovative microwave and optical devices such as beam-benders, beam-shifters, collimators, and invisibility cloaks. Transformation electromagnetics allows an initial field configuration to be transformed to a desired one via a change in material parameters prescribed by a coordinate transformation. The transformed materials are generally anisotropic and inhomogeneous. Along with volumetric designs, planar transformation-based devices using transmission-line networks have also been pursued. In this work, we present a method to implement planar transformation electromagnetics devices using tensor impedance surfaces.
The first structurally characterized nitrosyl heme thiolate model complex

The NO ligand in the formally {FeNO}6 compound [Fe(oep)(NO)(thiolate)] is bent, and does not impart a significant structural trans effect to the Fe–S bond.
Radionuclidic standardization by primary methods: An overview

Primary methods of radionuclidic standardization serve as the underlying basis of the physical measurement standards of activity that are needed in virtually every sub-discipline of radioanalytical and nuclear chemistry. Primary methods refer to the direct measurement of the number of nuclear transformations that occur per unit time, without recourse to other calibrations or standards. Such measurements, leading to the development and dissemination of radioactivity standards, are primarily performed under the purview of national metrology laboratories, like the National Institute of Standards and Technology (NIST) in the USA. This paper briefly reviews some of the various primary methods that have been developed by many such laboratories over many years. Their features and their role in ensuring the quality of radioactivity measurements are highlighted by several primary standardizations that have been recently performed at NIST.
Morphological and Rheological Responses to Shear Start-up and Flow Reversal of Thermotropic Liquid-Crystalline Polymers

Novel rheo-optical methods have been used to directly observe morphology evolution, during shear start-up and reversal flow, in semiflexible main-chain thermotropic liquid-crystalline polymers (TLCPs). Using a specially designed microrheometer allowing for simultaneous transient optical and mechanical observations, we observed band formation upon reversal of flow direction. It was seen that this band formation causes asymmetric light diffraction in HV small-angle light scattering mode, indicating a tilted arrangement of the regularly spaced bands. Also conducted were shear start-up and flow reversal experiments using a cone-and-plate rheometer under the same thermal and deformation histories as those in rheo-optical experiments for polymers of differing spacer lengths at equal temperature difference below the nematic-to-isotropic transition temperature (TNI). It was observed that, during both shear start- up and flow reversal, the first normal stress difference N1 + (A o , t) exhibits a large overshoot followed by an oscillatory decay, while shear stress U + (A o , t) exhibits a large overshoot followed by a monotonic decay. It was found that the higher the applied shear rate, the larger the overshoot of N1 + (A o , t) and U + (A o , t), and the longer the persistence of oscillations in N1 + (A o , t). Similarity was found between the ratio N1 + (A o , t)/ U + (A o , t) and flow birefringence ¢n + (A o , t) during shear start-up and flow reversal of the TLCPs investigated in this study. Further, we found that the ratio U + (t,A o )/U scales with A o t but the ratio N1 + (A o , t )/ N1 does not, where U denotes shear stress at steady state and N1 denotes first normal stress difference at steady state.
An electron microscopic study of degenerative changes in the cat cerebellum after intrinsic and extrinsic lesions.

Degenerative changes in the cerebellum of the cat have been observed electron microscopically 2 to 30 days after surgical lesions were placed in the inferior or middle cerebellar peduncles or after undercutting or isolating cerebellar folia. The changes were confined to the mossy fibers of the white matter and granular layer except when Purkinje cells were damaged buy undercutting. Mossy fiber terminals in the glomeruli underwent two kinds of change. Either the synaptic vesicles and mitochondria coalesced into dense clumps with loss of mitochondrial outer membranes and proliferation of cristae, or the vesicles and miotochondria disappeared leaving a swollen terminal containing only a few large pleomorphic vesicles and small dense polygonal bodies. Neurofilaments proliferated and filled a few terminals but most of the neurofilamentous hypertrophy and proliferation was confined to myelinated axons. Some phagocytosis of degenerated endings was observed and mild fibrous gliosis occurred in the glomeruli. All of the changes observed in the present study have been reported in degenerating synapses and axons elsewhere in the central and peripheral nervous system, but there appeared to be more pleomorphism and less predictability of changes in the cerebellar cortex than have been noted in other single areas of the central nervous system.
Thermal structure of the atmosphere of Venus from Pioneer Venus radio occultations

The processing and analysis results from 87 radio occultation experiments performed with the Pioneer Venus Orbiter are detailed. Atmospheric structure data were obtained with S-band (2293 MHz) and X-band (8407 MHz) signals transmitted through the 40 and 85 km levels of the Venus atmosphere. Latitudes of -68 to 88 deg at solar zenith angles of 8-166 deg were explored. The conversion of the data into acceptable form for the barometric equation to use the perfect gas law to obtain the temperature profiles is described. The temperature structures were more dependent on latitude than solar illumination conditions, with the greatest changes occurring in the circumpolar region. The polar tropopause altitude was about 4.8 km above its value at lower altitudes, with a temperature drop of 60 K and a pressure drop of 240 mb.
RRKM reaction rate theory for transition states of any looseness

Unimolecular rate theory for various types of reactions is implemented for any looseness of transition state. Quantum states are counted for all but the “transitional” modes, their phase space being counted via Monte Carlo sampling. The rate constant k_(EJ) is then weighted with the initial E and J distributions.
Bayesian analysis of linear models with two random components with special reference to the balanced incomplete block design.

Abstract : The paper considers linear models which contain two random components and enable representation of general designs with block effects random. It shows how, within a Bayesian framework, to combine the intra- and inter-block information about the location parameters. The balanced incomplete block design, an important special case, is considered in detail and illustrated by an example. A simple approximation to the marginal distribution of an individual contrast is also presented and illustrated.
Pathophysiology of Pelvic Floor Hypertonic Disorders

The pelvic floor represents the neuromuscular unit that provides support and functional control for the pelvic viscera. Its integrity, both anatomic and functional, is the key in some of the basic functions of life: storage of urine and feces, evacuation of urine and feces, support of pelvic organs, and sexual function. When this integrity is compromised, the results lead to many of the problems seen by clinicians. Pelvic floor dysfunction can involve weakness and result in stress incontinence, fecal incontinence, and pelvic organ prolapse. Pelvic floor dysfunction can also involve the development of hypertonic, dysfunctional muscles. This article discusses the pathophysiology of hypertonic disorders that often result in elimination problems, chronic pelvic pain, and bladder disorders that include bladder pain syndromes, retention, and incontinence. The hypertonic disorders are very common and are often not considered in the evaluation and management of patients with these problems.
Outcomes of symptomatic abdominal aortic aneurysm repair.

Objective Operative mortality of patients undergoing symptomatic abdominal aortic aneurysm (Sx-AAA) repair has been reported at 6% to 30% during the past 25 years. We used a multicenter regional database to describe the contemporary outcomes of patients undergoing repair of Sx-AAA. Methods All patients undergoing infrarenal AAA repair in 11 hospitals comprising the Vascular Study Group of Northern New England (VSGNNE) between 2003 and 2009 were studied. Sx-AAA was prospectively defined as an AAA accompanied by abdominal or back pain or tenderness, but without rupture. The primary study end point was in-hospital mortality. Secondary end points included in-hospital postoperative major adverse events (MAE) and late survival. These outcomes were compared between symptomatic patients and contemporary VSGNNE cohorts of elective (E-AAA) and ruptured AAAs (R-AAAs) treated within the same study period. Results During the study period, 2386 AAA repairs were performed, comprising 1959 (82%) E-AAAs, 156 (7%) Sx-AAAs, and 271 (11%) R-AAAs. Repair was endovascular in 945 (48%) E-AAAs, 60 (38%) Sx-AAAs, and 33 (12%) R-AAAs. Hospital mortality was 1.7% for E-AAA repair and 1.3% for Sx-AAA repair, but was 34.7% for R-AAA repair (P 85. Kaplan-Meier analysis demonstrated that at 1 and 4 years, Sx-AAA repair was associated with intermediate survival (83% and 68%) compared with E-AAA repair (89% and 73%) and R-AAA repair (49% and 35%; P Conclusion The operative mortality of patients with Sx-AAA in contemporary practice appears better than that previously reported in the literature. Despite low operative mortality, MAE and late survival are intermediate compared with E-AAA and R-AAA repair. Review of previous series shows a trend for lower operative mortality after Sx-AAA repair in more recent series, which likely reflects improved perioperative care and more use of endovascular aneurysm repair.
Trolox and 6,7-dinitroquinoxaline-2,3-dione prevent necrosis but not apoptosis in cultured neurons subjected to oxygen deprivation

There is a growing body of evidence suggesting that apoptosis is involved in ischemic brain injury. Recent studies suggest that a rapid necrosis masked a more subtle apoptotic death in neurons subjected to oxygen deprivation in culture. To test this hypothesis, we treated cultured neurons with potential antinecrotic drugs during and after oxygen deprivation. The results show that 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), which interfered with kainate receptor activation and lipid peroxidation respectively, prevented necrosis but allowed neurons to undergo apoptosis. Flow cytometric analysis of DNA degradation and hydrogen peroxide generation, as well as fluorescent microscopy of nuclear fragmentation revealed that apoptotic activity was higher in DNXQ-treated cells than in Trolox-treated cells. This difference in occurrence of apoptosis may be due to the difference in oxidative stress generated from these two different agents.
Effect of Stacking Sequence on the Mechanical Properties of Glass-Carbon Hybrid Composites Before and After Impact

Hybrid composites are susceptible to accidental low energy impacts from hazards such as tools dropping during maintenance, transportation debris and hailstones. These impacts can cause significant strength reduction and localized damage which is potentially a source of mechanical weakness especially for graphite composites. The effect of stacking sequence on mechanical properties of stitched composites is studied for low velocity impact damages. Tests were performed for the same volume fraction (Vf) with different hybrid sequence and ply angle. The incorporation of glass fibers in carbon reinforced structures improved impact properties and increased the strain to failure. The addition of carbon fibers to the surface of glass-reinforced composites increases the flexural modulus for undamaged samples. Tensile failure mechanism of damaged plies seems to be affected by the interaction of reinforcement property, hybrid order and ply angle.
The changing landscape of American Banking: The impact of Riegle-Neal

The Riegle-Neal Interstate Banking and Branching Efficiency Act of 1994, which became fully operative on June 1, 1997, eliminated virtually all interstate banking and branching restrictions in the U.S. It was assumed that banks and bank holding companies would use their new geographic freedom to expand across state lines through mergers, acquisitions, and the establishment of de novo facilities. There was considerable concern that there would be fewer but more sizable banks that would abandon or increase fees for smaller customers including individuals, businesses, and rural communities. This paper provides an early glimpse at the accuracy of these predictions by studying the changes in the number and size of banks serving the Seventh Federal Reserve District since the enforcement of Riegle-Neal.
A physical difference between the fast- and slow-refolding forms of nitrotyrosyl ribonuclease A: the pK values of the nitrotyrosyl groups.

Abstract In the preceding paper we present kinetic evidence for a slow equilibrium between two conformational forms of heat-unfolded ribonuclease A whose rates of refolding differ 100-fold. In a search for physical differences between these two forms, we undertook a study of the p K changes during refolding of a specific set of freely ionizing surface groups. By use of a standard procedure the three freely ionizing tyrosine groups (p K ∼- 10) have been nitrated by tetranitromethane, yielding three nitrotyrosine groups (p K ∼- 6.8). Nitrotyrosyl ribonuclease A closely resembles the unmodified enzyme as regards: (1) enzymatic activity; (2) thermal unfolding transition at neutral pH; and (3) kinetics of refolding. In particular, stopped-flow measurements of 2′CMP binding during refolding show that the fast-refolding reaction is unchanged by nitration and yields fully folded enzyme able to bind 2′CMP. The p K change of the nitrotyrosyl groups upon refolding is quite different in the fast- and slow-refolding reactions. In the slow reaction it is small (− 0.046 ± 0.006 pH unit) but easily measureable, whereas in the fast-reaction it is too small to be detected (− Δp K less than 0.02 pH unit). This difference in p K change upon refolding can be attributed to different p K values of the nitrotyrosyl groups in the slow-refolding and fast-refolding forms of the heat-unfolded protein. Presumably the same structural differences between these two heat-unfolded forms are responsible both for the p K difference and for the 100-fold difference in rates of refolding. These results support the simple three-species mechanism for refolding discussed in the preceding paper. (a) They demonstrate a physical difference between the fast- and slow-refolding species. (b) They do not show any additional kinetic complexity when refolding is measured by a property that distinguishes between the fast- and slow-refolding species.
Science in Suzhou: establishment and function of neural circuits

The Cold Spring Harbour Asia conference on ‘Assembly, Plasticity, Dysfunction and Repair of Neural Circuits’ took place in Suzhou, China, in October 2011. Developmental, cell, molecular and systems neuroscientists convened to discuss the establishment, function and plasticity of neural circuits in diverse organisms.
Aging of erythrocytes results in altered red cell surface properties in the rat, but not in the human. Studies by partitioning in two-polymer aqueous phase systems

Aqueous solutions of dextran and of poly(ethylene glycol) when mixed give rise to two-phase systems useful in separating cells, on the basis of their surface properties, by partitioning. Depending on whether salts with unequal or equal affinity for the two phases are chosen, phases with or without an electrostatic potential difference between the phases are obtained. At appropriate polymer concentrations the former yield cell partition coefficients (i.e., the quantity of cells in the top phase as a percentage of total cells added) based on charge-associated surface properties while the latter reflect membrane lipid-related parameters. With increasing cell age, rat erythrocytes have diminishing partition coefficients in both charged and uncharged phases. Using the elevated aspartate aminotransferase levels of younger red cells as a marker, we have not found that young mature erythrocytes of human do not have the highest partition coefficient in the red cell population as they do in rat. Experiments with isotopically labeled dog red cells yield results similar to those found with human erythrocytes. Furthermore, density-separated young and old red cells from human give overlapping countercurrent distribution curves. Finally, countercurrent distribution of human red blood cells followed by pooling of cells from the left and right ends of the distribution and subjection of these cells to a redistribution gives curves that overlap with each other and with the original countercurrent distribution. This indicates that not only are human red cells not subfractionated based on possible age-related surface alterations, but also that they are not subfractionated by partitioning based on any surface parameter. These results are consistent with our previous findings that membrane sialic acid/hemoglobin absorbance is essentially constant through the extraction train after countercurrent distribution of human erythrocytes in a charged phase system; and with the recent reports of others that there is no difference in electrophoretic mobility between human young and old red cells.
Theory of paramagnetic singlet-doublet excitations in double-hexagonal close-packed praseodymium

The magnetic excitation spectrum of the singlet-doublet magnet double-hexagonal close-packed praseodymium, which has been measured by means of inelastic neutron scattering, is analyzed using a diagrammatic high-density expansion technique. The lowest-order random-phase-approximation diagrams give a detailed description of the wave-vector and temperature dependence of the four modes in terms of a Hamiltonian including isotropic Heisenberg interatomic exchange interactions and anisotropic, dipolarlike exchange interactions. In general, the modes are linearly or elliptically polarized. The leading contributions to the line shapes of the excitations are obtained by extending the $\frac{1}{Z}$ expansion of the generalized susceptibility propagators one order beyond the random-phase approximation. This damping corresponds to spin-wave scattering on single-site fluctuations. The propagators are calculated self-consistently by including internally renormalized Green's functions. The theoretical spectral functions are in detailed agreement with experiment.
Painkilling Drugs in Collegiate Athletics: Knowledge, Attitudes, and Use of Student Athletes:

This study was designed to examine the attitudes of student athletes toward the use of painkilling drugs. A total of 563 student athletes at two Division One NCAA universities were surveyed in this study. Twenty-nine percent of the student athletes (n = 165) reported that they felt there is nothing wrong with using painkilling drugs on the day of competition (when injured) to cope with pain. These student athletes reported that they would use painkilling drugs to mask injury in order to continue to participate in their sport. Student athletes' perceptions of societal norms and expectations related to competition, and the degree of control student athletes perceive that they have when deciding to use painkillers, may be important determinants governing the extent to which they may be at risk for abusing these substances. Research on planned behavior and reasoned action against suggests that salient beliefs affect intentions and subsequent behaviors, either through attitudes or subjective norms, or the degree of (perceived) control that an individual feels he/she has over the behavior [1, 2]. This theoretical model was used as a guiding framework for analyzing the attitudes of college athletes toward painkilling drugs. Recommendations are included in this article for coaches, educators, team physicians, team trainers, and administrators who are concerned about controlling the use and abuse of painkilling drugs by student athletes.
The functions of multiple singing modes: experimental tests in yellow warblers, Dendroica petechia

Abstract In several groups of songbirds, including the North American wood warblers (Parulidae), males subdivide their song repertoires into two different categories, or ‘modes’, of singing. Previous studies of wood warblers suggest that the two singing modes in this group are each specialized for interacting with one of the two sexes: Type 1 singing for interacting with females and Type 2 for interacting with other males. Here I examine the responses of male and female yellow warblers to the two singing modes produced by males. Using song playback experiments, I found that male yellow warblers responded to potential intruders with Type 1 singing, rather than Type 2 singing, as predicted. In tests using the copulation solicitation assay, females implanted with oestradiol responded equally strongly to both Type 1 and Type 2 singing. These results suggest that male wood warblers use both singing modes to interact with males and females, and that the singing modes do not have distinct, sex-specific functions as previously thought. Factors other than intra- and intersexual selection are therefore likely to have helped shape the evolution of distinct singing modes.
Sulfide remobilization during low temperature alteration of seafloor basalt

Abstract The behavior of sulfide minerals during the physical and chemical changes accompanying seafloor alteration was studied in three basalt flows from the bottom of D.S.D.P. Hole 418A, Leg 53. The rocks are mildly altered, and contain primary, authigenic, and vein sulfide minerals. Sulfide habit, mineralogy, and trace element content are inter-related and are correlated with the extent and type of silicate and oxide alteration. Incipient alteration at > 90°–100°C was accompanied by low temperature reequilibration of pyrrhotite, and locally, by the oxidation of pyrrhotite to pyrite plus magnetite. The dominant stage of alteration, at ≤90°C, is characterized by dissolution and local redistribution of pyrite and chalcopyrite, whose precipitation appears to be controlled by the water/rock ratio and the extent to which the water has been modified by reaction with the basalt. Chalcopyrite was concentrated relative to pyrite by slight changes in fluid composition caused by reaction with other minerals. Concurrent precipitation of smectite causes a net increase in rock volume, tending to restrict seawater access. Calculations of rock cooling rate through time suggest that the most prolonged hydrothermal circulation occurs at low temperatures, giving rise to pervasive low temperature alteration assemblages.
Subacute myeloid leukemia: A clinical review

The data on 31 patients who fit into the clinical spectrum of subacute myeloid leukemia have been reviewed. The majority of patients were male with a median age of 61 years. The interval from onset of symptoms to actual diagnosis was extremely variable, with a mean of 16 months and a median of six months. Most patients presented with anemia and thrombocytopenia, although the white blood cell count varied from striking leukopenia to marked leukocytosis. Examination of the bone marrow invariably revealed abnormalities of all cell lines with megaloblastoid erythrogenesis and dysplastic megakaryocytopoiesis. Although the white cell line showed prominence of immature forms, there was more maturation than is seen in acute myeloid leukemia. Survival from diagnosis was variable, from less than one month to greater than 68 months, with a median of only six months. Anemia and hepatosplenomegaly were prognosticators of a poor outlook; patients with hepatosplenomegaly in association with either leukocytosis or thrombocytopenia had a particularly poor outlook, with a median survival of only one and a half months. Approximately half the patients received chemotherapy with no demonstrated effect on survival.
Hydrogen ion changes of rhodopsin I. Proton uptake during the metarhodopsin I478 metarhodopsin II308 reaction

The hydrogen ion changes resulting from the photolysis of the rod visual pigment, rhodopsin, have been investigated. Low temperature was used to isolate the metarhodopsin I478 to II380 reaction of rhodopsin and indicator dye was used to simultaneously measure the hydrogen ion changes of the rhodopsin solution. The results indicate that illuminated rhodopsin takes up a proton during the metarhodopsin I478 to II380 reaction and releases protons at later intermediate stages. The results are consistent with data indicating pK changes of rhodopsin as the basis for the R2 phase of the early receptor potential and hydrogen ion changes of the medium or pK changes of rhodopsin as having effects on the late receptor potential.
TU-C-T-6C-01: Introduction: ``How much complexity is necessary for IMRT?

IMRTtreatment planning and delivery systems have developed rapidly over the past 5 years. Every manufacturer of linear accelerators now offers IMRT delivery systems using multileaf collimators and some sort of automated delivery scheme. Most treatment planning systems now offer “inverse” planning algorithms that optimize fluence and dose distributions given a set of dose constraints for tumors and normal tissues. For some accelerator manufacturers, the output of the planning system is a set of multileaf shapes, or “segments” with associated intensities, which combine to give a variable intensity distribution for each beam angle. This delivery system is referred to as static multileaf IMRT (or SMLC). For others, the intensity distribution is continuous and the leaves move with variable speed across the field with the beam remaining on. This is called dynamic multileaf IMRT, or DMLC. SMLC tends to be somewhat time consuming relative to conventional delivery, as there is overhead due to communication between the MLC controller and the accelerator. For DMLC, very little time is lost relative to conventional beam delivery times. Most IMRT planning systems have a mechanism for controlling the complexity of the resulting plan, which is determined by the number of beam angles and the number of intensity levels specified in the plan. Highly complex plans are those that end up with large numbers of beam segments and small monitor units per segment, translating into rapid dose gradients within the patient. These are presumably desirable when a tumor is immediately adjacent to a very sensitive normal tissue and the dose falloff must be rapid outside the tumor border. On the other hand, dose delivery errors are expected to be greater with highly complex plans, since the dosimetry of small fields and the linearity of the dose at small numbers of monitor units, are rather uncertain. This fact drives us to limit the complexity as much as reasonably possible. Since DMLC does not have a significant time penalty for high complexity, there is a tendency to plan highly complex IMRT for these delivery systems. For SMLC, the constraints of treatment time tend to drive the planner to choose less complex solutions. The question to be addressed in this Symposium is how much complexity is necessary for IMRT. Clearly, the answer is site‐dependent, but even at a given site, the answer is not clear. Today's speakers will describe the incentives for simplicity (time and dose accuracy), methods of controlling the complexity and the tradeoffs between complexity and conformality.
The reparative phenomena at the site of balloon angioplasty in humans and experimental models

Abstract We have previously described the healing phenomena after PTCA in humans and developed a swine model of balloon angioplasty that closely mimics the vascular responses seen in humans. Our data from clinical, autopsy, and animal studies strongly indicate that thrombus formation at the site of balloon angioplasty is a rare event in both humans and experimental animals. Restenosis is a reactive proliferative response to the arterial wall injury characterized predominantly, but not exclusively, by smooth muscle cell proliferation and excessive synthesis of connective tissue matrix. Luminal phenomena such as adhesion and activation of platelets and leukocytes contribute to the proliferative processes.
Time dependence of transmembrane potential changes and intracellular calcium flux in stimulated human monocytes.

An important characteristic of the functional differentiation of the blood monocyte is the development of its capacity to recognize and respond to stimuli. This ability is mediated to a large extent by specific receptor glyco-proteins located on the cell surface. Stimulation of mononuclear phagocytes via these receptors results in a rapid rise in intracellular Ca+ + concentration, accompanied or followed by a change in membrane potential, generation of oxidative products, degranulation, and effector functions such as phagocytosis, aggregation, or locomotion. While the development of these characteristics is difficult to characterize in vivo, several investigators have demonstrated in vitro changes in these cells that correlate with the development of effector function. To examine the mechanisms of specific membrane-stimulus interactions of monocytes as they differentiate into macrophage-like cells, we studied the responses of human monocytes and of monocytes incubated in serum-containing medium for up to 96 hr to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP). Freshly isolated monocytes exhibited little change in transmembrane potential following stimulation with an optimal concentration of peptide and underwent a significant increase only after 48 hr in culture. While constant resting intracellular Ca+ + concentrations were maintained during the culture period, intracellular Ca+ + levels following fMLP stimulation increased with with incubation in serum, for up to 96 hr. In contrast, fMLP-induced respiratory burst activity increased from 0 to 24 hr in culture; it remained elevated at 48 hr but declined again by 96 hr. Incubation of the cells for 24 hr increased their random (unstimulated) motility in modified Boyden chambers but did not alter the cells' directed (chemotactic) response to fMLP in comparison to the response of freshly isolated monocytes. Peptide binding to the cells did not increase during the incubation period, indicating that an increase in receptor number or in affinity for fMLP was not responsible for the enhanced responsiveness to fMLP as incubation time increased. These studies indicate that incubation of monocytes in serum-containing medium leads to a complex, altered series of responses to fMLP that correlate with the differentiation of the original monocytes in vitro and may relate to the in vivo differentiation of monocytes to macrophages.
The size, composition and function of wild bottlenose dolphin (Tursiops sp.) mother–calf groups in Shark Bay, Australia

The fission–fusion society of bottlenose dolphins seems particularly well suited to balancing the costs and benefits of grouping. Here, we examined four nonmutually exclusive hypotheses regarding the causes and/or functions of calf grouping patterns when with and away from the mother: maternal influence, same-sex bond formation, protection and social skill development. We evaluated the role of calf (calf sex, age and separation from their mothers) and maternal characteristics (foraging time and sociality) in shaping the size and composition of mother–calf groups using focal observations of 49 mothers and 89 calves. Mother–calf groups were biased towards association with females of all ages and with male calves, but contained relatively few juvenile and adult males. Although there was some support for all of the hypotheses, the social skills hypothesis best explained male calf social patterns, and maternal influence better explained female calf social patterns. While maternal sociality influenced calves of both sexes, daughters mirrored the mother during separations, whereas sons did the opposite, seeking more social contact if their mothers were solitary and seeking less social contact if their mothers were sociable. During mother–calf separations, calves of both sexes preferentially associated with immatures over adults, but male calves preferred juvenile and adult male associates, which female calves, like their mothers, avoided. Calf social patterns illustrate the specific social and ecological challenges that they face in relation to and independent of their mothers.
Correlating Coronal Temperature and Gravitational Potential: A Test of the Nonthermal Boundary Hypothesis

It has been suggested that a nonthermal boundary condition can account for the existence of a coronal temperature inversion in stars. The nonthermal hypothesis makes falsifiable predictions of the maximum coronal temperature obtainable. This maximum temperature corresponds to the depth of the potential well at the boundary, which is effectively R*, and so varies as M*/R*. Here, we compare this prediction with one-temperature fits to single stars in Einstein data. We find that the coronal temperatures in dwarfs are consistent with a nonthermal boundary condition, but the nonthermal hypothesis cannot readily account for the coronal temperatures of class III giants. However, interpreting the emission from the noncompliant giants in alternate terms suggests that a dwarf companion may be the source of the X-rays. More generally, gravitational potential is found to be a useful quantity to ordering coronal observations: (1) the "dividing line" near K4, beyond which giant star coronae are not observed, corresponds to a rather precipitous factor of 10 drop in the strength of the stellar gravitational potential; and (2) M dwarfs and A stars of class III-V, whose coronae have been somewhat of a puzzle, all have relatively deep gravitational potentials.
Crystallization of copolymers of ethylene glycol and diethylene glycol terephthalate

Rates of crystallization of polyethylene terephthalate and copolymers of ethylene glycol and diethylene glycol terephthalate were measured in the temperature range of 110 to 240°C.; this is the region of temperature in which the crystallization takes place at a measurable rate. It was found that the rate is defined by a modified Avrami type of equation over the entire temperature range of crystallization. Molecular motion, which limits crystallization at lower temperatures, was found to be a relaxation mechanism rather than simple viscous flow; to account for this, a modification of the Avrami type of equation was made. Data on copolymers of ethylene glycol and diethylene glycol terephthalate have shown that introduction of the longer chain yields a more flexible structure; hence at lower temperatures, where molecular motion is rate-determining, the rate is increased. At higher temperatures introduction of the copolymer decreases the crystallization rate in the manner one would expect from the depression of the crystalline melting point.
KINETIC AND SPECTROSCOPIC FEATURES OF SOME CAROTENOID TRIPLET STATES: SENSITIZATION BY SINGLET OXYGEN

— Triplet-triplet absorption spectra of a series of carotenoid pigments in benzene solution have been determined by pulse radiolysis experiments. The natural lifetimes in deaerated solution have also been measured. They fall in the range 2–10 µs as found for other carotenoids under similar conditions. Pulsed laser (337 nm) excitation of benzene solutions containing oxygen, carotenoid and a photosensitized molecule (anthracene) showed the generation of absorption spectra of the triplet states. These absorptions decayed by first order kinetics in such a way as to indicate that they were formed in reactions with singlet oxygen, itself generated by interaction with the anthracene triplet state. Bimolecular rate constants for energy transfer from O*2 (1△g), to carotenoid have been evaluated.
Measurement of the neutron electric form factor G E n in $\mathop{d}\limits^{\scriptstyle\to}(\mathop{e}\limits^{\scriptstyle\to},e'n)p$ quasielastic scattering

We have measured the electric form factor of the neutron, G E n , at two momentum transfers (Q 2= 0.5 and Q 2= 1.0 GeV/c 2) through $\mathop{d}\limits^{\scriptstyle\to}(\mathop{e}\limits^{\scriptstyle\to},e'n)p$ quasielastic scattering in Jefferson Lab's Hall C. Longitudinally polarized electrons scattered from polarized deuterated ammonia and G E n was extracted from the beam-target asymmetry A V ed which, in quasielastic kinematics, is particularly sensitive to G E n and insensitive to MEC and FSI.
The thickness distortion of 57Fe backscatter Mössbauer spectra

Abstract The thickness distortion of a backscatter 14.41 keV γ-ray Mossbauer spectrum is calculated for the case of isotropic γ-ray re-emission in the absorber, and a method of extracting the true absorber material resonant scattering cross section from experimental data is suggested and demonstrated. Some other features of backscatter and transmission 57Fe Mossbauer spectra are compared.
How available is positron emission tomography in the United States

Positron emission tomography (PET) has become a major clinical diagnostic and prognostic tool for oncology and multiple other arenas. To some, however, the perception exists that PET is not available as a resource in their community. Our goal with this project was to determine how available clinical PET was in the United States. We used existing lists of PET centers, websites from PET scanner manufacturers, as well as a common Internet search engine to find clinical PET facilities. A mapping program was then used to determine area coverage with a 75-mile radius for each PET scanner found, and the United States Census website was utilized as a source of population data for covered and not covered areas. We found that 97% of the US population lives within 75 miles of a clinical PET facility. Thus, it appears that the idea of clinical PET being unavailable to many is a misconception, which may be limiting its use by some physicians who are unaware of how common it has become.
THE ECONOMIC WELFARE OF THE AGED AND INCOME SECURITY PROGRAMS

This paper examines several nonmoney components of economic welfare in both a theoretical and an empirical framework, computes the distributional ranking of aged families arising from such a measure, and subsequently examines the target effectiveness of eleven programs of the U.S. federal government aimed at the aged. While the theoretical discussion attempts to cover all factors contributing to the economic welfare of the aged, the empirical measure is somewhat less comprehensive, excluding the value of nonmarket productive activities and leisure time as well as benefits derived from direct government expenditures and some in-kind transfers and taxes. The study makes use of a subsample of the 1967 Survey of Economic Opportunity data composed of all families with at least one aged member. Specific attention is devoted to dissaving from net worth, in-kind transfers, incidence of taxes, and intrafamily transfers. Government cash and in-kind transfers are found to constitute a third of the total measured economic welfare of the aged, and the impact of each of these programs is examined individually. As might be expected, public assistance and public housing are the programs of most benefit to the aged poor. Medicaid and Medicare are substantially less so, and Social Security is distributionally neutral. Such programs as unemployment insurance are of little benefit to the aged. Tax expenditures, finally, provide no benefits to even the lower half of the distribution.
Nonoscillatory Solutions of Second-Order Differential Equations without Monotonicity Assumptions

The continuability, boundedness, monotonicity, and asymptotic properties of nonoscillatory solutions for a class of second-order nonlinear differential equations [𝑝(𝑡)ℎ(𝑥(𝑡))𝑓(𝑥(𝑡))]=𝑞(𝑡)𝑔(𝑥(𝑡)) are discussed without monotonicity assumption for function g. It is proved that all solutions can be extended to infinity, are eventually monotonic, and can be classified into disjoint classes that are fully characterized in terms of several integral conditions. Moreover, necessary and sufficient conditions for the existence of solutions in each class and for the boundedness of all solutions are established.
Effects of partitioning allochthonous and autochthonous resources on food web stability

The flux of energetic and nutrient resources across habitat boundaries can exert major impacts on the dynamics of the recipient food web. Competition for these resources can be a key factor structuring many ecological communities. Competition theory suggests that competing species should exhibit some partitioning to minimize competitive interactions. Species should partition both in situ (autochthonous) resources and (allochthonous) resources that enter the food web from outside sources. Allochthonous resources are important sources of energy and nutrients in many low productivity systems and can significantly influence community structure. The focus of this paper is on: (i) the influence of resource partitioning on food web stability, but concurrently we examine the compound effects of; (ii) the trophic level(s) that has access to allochthonous resources; (iii) the amount of allochthonous resource input; and (iv) the strength of the consumer–resource interactions. We start with a three trophic level food chain model (resource–consumer–predator) and separate the higher two trophic levels into two trophospecies. In the model, allochthonous resources are either one type available to both consumers and predators or two distinct types, one for consumers and one for predators. The feeding preferences of the consumer and predator trophospecies were varied so that they could either be generalists or specialists on allochthonous and/or autochthonous resources. The degree of specialization influenced system persistence by altering the structure and, therefore, the indirect effects of the food web. With regard to the trophic level(s) that has access to allochthonous resources, we found that a single allochthonous resource available to both consumers and predators is more unstable than two allochthonous resources. The results demonstrate that species populating food webs that experience low to moderate allochthonous resources are more persistent. The results also support the notion that strong links destabilize food web dynamics, but that weak to moderate strength links stabilize food web dynamics. These results are consistent with the idea that the particular structure, resource availability, and relative strength of links of food webs (such as degree of specialization) can influence the stability of communities. Given that allochthonous resources are important resources in many ecosystems, we argue that the influence of such resources on species’ and community persistence needs to be examined more thoroughly to provide a clearer understanding of food web dynamics.