cssi/SciSciGPT-SciSciNet huggingface dataset:
Stability and stiffness characteristics of the national x-ray mask standard

Finite element analyses have been performed to investigate the stability and stiffness characteristics of the ARPA-NIST National X-ray Mask Standard. The use of different materials (such as silicon carbide and Pyrex) for the support ring has been studied to identify the effects on the maximum in-plane mounting distortions (within a 50 mm by 50 mm patterned area). Additional finite element calculations have been completed to determine the out-of-plane distortions (or bowing) of the mask due to the fabrication process. Parametric studies have been performed to identify the stiffness characteristics of the mask as the overall ring thickness is reduced while the wafer thickness is increased. Results show how various design parameters can be controlled to repeatedly fabricate masks that fulfill requirements for sub-0.13 micrometer technology.
Hypervelocity collisions of binary stars at the Galactic Centre

Recent surveys have identified seven hypervelocity stars (HVSs) in the halo of the Milky Way. Most of these stars may have originated from the breakup of binary star systems by the nuclear black hole SgrA*. In some instances, the breakup of the binary may lead to a collision between its member stars. We examine the dynamical properties of these collisions by simulating thousands of different binary orbits around SgrA* with a direct N-body integration code. For some orbital parameters, the two stars collide with an impact velocity lower than their escape velocity and may therefore coalesce. It is possible for a coalescing binary to have sufficient velocity to escape the galaxy. Furthermore, some of the massive S-stars near Sgr A* might be the merger remnants of binary systems, however this production method can not account for most of the S-stars.
Tropical Polytopes and Cellular Resolutions

Tropical polytopes are images of polytopes in an affine space over the Puiseux series field under the degree map. This viewpoint gives rise to a family of cellular resolutions of monomial ideals that generalize the hull complex of Bayer and Sturmfels [Bayer and Sturmfels 98], instances of which improve upon the hull resolution in the sense of being smaller. We also suggest a new definition of a face of a tropical polytope, which has nicer properties than previous definitions; we give examples and provide many conjectures and directions for further research in this area.
Radiative Efficiency of Collisionless Accretion

The radiative efficiency, η ≡ L/c2, of a slowly accreting black hole is estimated using a two-temperature model of accretion. The radiative efficiency depends on the magnetic field strength near the Schwarzschild radius. For weak magnetic fields, i.e., β-1 ≡ B2/8πp 10-3, the low efficiency η ~ 10-4 that is assumed in some theoretical models is achieved. For β-1 > 10-3, a significant fraction of viscous heat is dissipated by electrons and radiated away resulting in η > 10-4. At equipartition magnetic fields, β-1 ~ 1, we estimate η ~ 10-1.
A Formal Model of Berezin-Toeplitz Quantization

We give a new construction of symbols of the differential operators on the sections of a quantum line bundle L over a Kahler manifold M using the natural contravariant connection on L. These symbols are the functions on the tangent bundle TM polynomial on fibres. For high tensor powers of L, the asymptotics of the composition of these symbols leads to the star product of a deformation quantization with separation of variables on TM corresponding to some pseudo-Kahler structure on TM. Surprisingly, this star product is intimately related to the formal symplectic groupoid with separation of variables over M. We extend the star product on TM to generalized functions supported on the zero section of TM. The resulting algebra of generalized functions contains an idempotent element which can be thought of as a natural counterpart of the Bergman projection operator. Using this idempotent, we define an algebra of Toeplitz elements and show that it is naturally isomorphic to the algebra of Berezin-Toeplitz deformation quantization on M.
Determination of compressive residual stress in a doubly-clamped microbeam according to its buckled shape

In this work, an analytical relationship is derived for a doubly-clamped microbeam when it buckles after release from the substrate. In terms of the relationship, compressive residual stress in the doubly-clamped microbeam can be determined according to its buckled shape, allowing one to find the compressive residual stress directly without much experimental effort. This relationship has been used to determine compressive residual stresses in four types of doubly-clamped SiO"2 microbeams. In addition, four methods have been applied to find the elongations of these SiO"2 microbeams, and the corresponding results are compared. Finally, the residual stresses in doubly-clamped SiO"2 microbeams predicted according to the derived relationship are compared with those found in SiO"2 microcantilevers, and the results have a good match.
High-Redshift Candidates and the Nature of Small Galaxies in the Hubble Deep Field*

We present results on two related topics: (1) a discussion of high-redshift candidates (z > 4.5) and (2) a study of very small galaxies at intermediate redshifts, both sets being detected in the region of the northern Hubble Deep Field (HDF) covered by the deep NICMOS observations at 1.6 and 1.1 μm. The high-redshift candidates are just those with redshift z > 4.5 as given in the recent catalog of Thompson, Weymann, and Storrie-Lombardi, while the "small galaxy" sample is defined to be those objects with isophotal area ≤0.2 arcsec^2 and with photometric redshift 1 ≤ z ≤ 4.5. Of the 19 possible high-redshift candidates listed in the Thompson et al. catalog, 11 have (nominal) photometric redshifts less than 5.0. Of these, however, only four are "robust" in the sense of yielding high redshifts when the fluxes are randomly perturbed with errors comparable to the estimated measuring error in each wave band. For the eight other objects with nominal photometric redshifts greater than 5.0, one (WFPC2 4-473) has a published spectroscopic redshift. Of the remaining seven, four are robust in the sense indicated above. Two of these form a close pair (NIC 586 and NIC 107). The redshift of the object having formally the highest redshift, at 6.56 (NIC 118 = WFPC2 4-601), is problematic, since F606W and F814W flux are clearly present, and the nature of this object poses a dilemma. Previous work by Colley et al. has suggested that compact sources in the WFPC2 HDF images are subgalactic components at redshifts z > 0.5 since they are correlated on scales less than 1'', corresponding to physical scales of less than 8 kpc (H_0 = 65 km s^(-1) Mpc^(-1), q_0 = 0.125). We confirm these correlations in the WFPC2 data. However, we do not detect the correlation of close pairs of galaxies on small scales in the ~0.65 arcmin^2 region of the HDF that we surveyed with NICMOS. The smaller area surveyed and lower resolution will make any real correlation more difficult to measure in these data. We have examined averaged images of these faint (V_(606) ~ 27-29), compact objects to search for extended, surrounding flux from older, fainter populations of stars. We find no evidence from the averaged images that isolated, compact objects in the Hubble Deep Field are embedded in fainter, more extended galaxies. For three different assumptions about possible star formation histories in these objects we set limits on the total amount of stars that could have been formed in an annulus corresponding to radii between ~ 6 and 10 kpc, which is typically a few times 10^8 M_☉. We suggest that some of these objects may be protogalactic fragments.
A continuum mixture theory with an application to turbulent snow, air flows and sedimentation

Abstract A continuum mixture theory is specialized for the case of turbulent snow, air transport and sedimentation. To facilitate closure a constitutive assumption is made for the turbulent variables of the snow phase in terms of the mean velocities or shear gradients of the airflow. The resulting turbulent equations of motion for the snow phase contain a set of terms which could be characterized as apparent or turbulent buoyancies. The magnitude of these terms is large where shear gradients of the airflow are large. The system of non-linear partial differential equations resulting from the turbulent equations of motion are approximated by finite difference techniques. Solutions for the snow phase velocity and density fields are investigated for a variety of one and two dimensional airflow regimes. The model snow phase velocity and density field solutions are compared with observed snow and air mixture flows over flat surfaces and over the crest of a triangular barrier. Lastly, the accumulation rate of deposited snow on the immediate lee of the two dimensional barrier is compared with observation.
Chemistry of 4,6-O-Benzylidene-d-glycopyranosyl Triflates: Contrasting Behavior between the Gluco and Manno Series

Activation of either anomer of S-phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-deoxy-1-thia-D-glucopyranoside with triflic anhydride in dichloromethane at -78 degrees C in the presence of 2,6-di-tert-butyl-4-methylpyridine affords a highly active glycosylating species which, on addition of alcohols, provides alpha-glucosides with high selectivity. This selectivity stands in stark contrast to the analogous mannopyranoside series, which affords the beta-mannosides with excellent selectivity under the same conditions. Low-temperature NMR experiments support the notion that a glucosyl triflate is formed in the initial activation step. Possible reasons for the diverging stereoselectivity in the gluco and manno series are discussed.
New open-framework in the uranyl vanadates A3(UO2)7(VO4)5O (A=Li, Ag) with intergrowth structure between A(UO2)4(VO4)3 and A2(UO2)3(VO4)2O

Abstract New uranyl vanadates A3(UO2)7(VO4)5O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for ∞2[UO2(VO4)2]4− and D for ∞2[(UO2)2(VO4)3]5− built from UO6 square bipyramids and connected through VO4 tetrahedra to ∞1[U(3)O5-U(4)O5]8− infinite chains of edge-shared U(3)O7 and U(4)O7 pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar ∞[UO5]4− chains are connected only by S-type sheets in A2(UO2)3(VO4)2O and by D-type sheets in A(UO2)4(VO4)3, thus A3(UO2)7(VO4)5O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 A, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F2; 1, a=7.2794(9) A, c=14.514(4) A, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I⩾2σ(I); 3, a=7.2373(3) A, c=14.7973(15) A, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I⩾2σ(I).
Dephasing of Quantum Bits by a Quasi-Static Mesoscopic Environment

We examine coherent processes in a two-state quantum system that is strongly coupled to a mesoscopic spin bath and weakly coupled to other environmental degrees of freedom. Our analysis is specifically aimed at understanding the quantum dynamics of solid-state quantum bits such as electron spins in semiconductor structures and superconducting islands. The role of mesoscopic degrees of freedom with long correlation times (local degrees of freedom such as nuclear spins and charge traps) in qubit-related dephasing is discussed in terms of a quasi-static bath. A mathematical framework simultaneously describing coupling to the slow mesoscopic bath and a Markovian environment is developed and the dephasing and decoherence properties of the total system are investigated. The model is applied to several specific examples with direct relevance to current experiments. Comparisons to experiments suggests that such quasi-static degrees of freedom play an important role in current qubit implementations. Several methods of mitigating the bath-induced error are considered.
Baryonic coherent state formation from small domain disoriented chiral condensates

Abstract Rare hyperon yields such as the Ω and Ω ¯ in heavy ion collision experiments are hard to be reproduced by numerical models. This, in combination with the thermal fit to SPS data, seems to call for a new production mechanism beyond the usual ones. Small domain disoriented chiral condensates (DCC) were proposed to be such a source of rare hyperons through skyrmion formation at the chiral phase transition. Here skyrmions are treated as coherent states of baryons on a compact manifold so that the distribution of baryons produced from a skyrmion can be known. From this more refined treatment, the number of topological defects produced are more than doubled to 30 or more and the domain size at the SPS is found to be even smaller than before at 1.1–1.5 fm. It is imperative therefore not to use only pion distribution but other means for observing DCC .
Global‐scale P wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 1. Data set development

[1] We extend the Bayesloc seismic multiple-event location algorithm for application to global arrival time data sets. Bayesloc is a formulation of the joint probability distribution spanning multiple-event location parameters, including hypocenters, travel time corrections, pick precision, and phase labels. Stochastic priors may be used to constrain any of the Bayesloc parameters. Markov Chain Monte Carlo sampling is used to draw samples from the joint probability distribution, and the posteriori samples are summarized to infer conventional location parameters such as the hypocenter. The first application of the broad area Bayesloc algorithm is to a data set consisting of all well-recorded events in the Middle East and the most well-recorded events with 5° spatial sampling globally. This sampling strategy is designed to provide the ray coverage needed to determine lithospheric-scale P wave velocity structure in the Middle East using the complementary ray geometry provided by regional (subhorizontal) and teleseismic (subvertical) raypaths and to determine a consistent, albeit lower-resolution, image of global mantle structure. The data set consists of 5401 events and 878,535 P, Pn, pP, sP, and PcP arrivals recorded at 4606 stations. Relocated epicenters are an average of 16 km from bulletin locations. The data set included events that are known to an accuracy of 1 km (a.k.a. GT1) based on nonseismic information. The average distance between GT1 epicenters and our relocated epicenters is 5.6 km. For arrivals labeled P, Pn, and PcP, ∼92%, ∼90%, and 96% are properly labeled with probability >0.9, respectively. Incorrect phase labels are found to be erroneous at rates of 0.6%, 0.2%, 1.6%, and 2.5% for P, Pn, PcP, and depth phases (pP and sP), respectively. Labels found to be incorrect, but not erroneous, were reassigned to another phase label. P and Pn residual standard deviation with respect to ak135 travel times are dramatically reduced from 3.45 s to 1.01 s. The differences between travel time residuals for nearly reciprocal raypaths are significantly reduced from the input event locations, suggesting that Bayesloc relocation improves data set consistency. The reciprocity tests suggest that the dominant contribution to travel time residuals calculated from information provided in global bulletins is location and picks errors, not travel time prediction errors due to 3-D structure. Modeling the whole multiple-event system results in accurate locations and an internally consistent data set that is ideal for tomography and other travel time calibration studies. Simmons et al. (2011) (companion paper) use the Bayesloc-processed data set to develop a 3-D tomographic image, which further reduces residual standard deviation to 0.50 s.
Role of sintering in snow construction

BECAUSE of the almost complete lack of roads in the polar regions, the ability to land aircraft on snow has always been of great importance in polar operations. In Greenland the first operation that utilized aircraft landings on snow was that of Ellsworth and Amundsen with Riiser-Larsen and Dietrichson as pilots in 1925. The following year Byrd flew his ski-equipped Fokker trimotor to the North Pole with Floyd Bennett as pilot. In 1928-29 the skiplane was introduced to the Antarctic by Byrd [1]. Since then landing on skis in Greenland and the Antarctic has gradually become a routine matter. Since World War II, prepared runways where large aircraft without skis can operate have predominated. The demand for prepared runways increased with the construction of the early warning sites in Greenland and the Antarctic phase of IGY in 1956. Presently, the large aircraft being used in polar operations are the C-124 (Globemaster) and the C-130 (Hercules), both with wheeled landing gear. The latter is also equipped with a ski-wheeled type modification for Greenland and Antarctic use; however, this reduces the load-carrying capacity. Since not all aircraft are equipped with skis the capability of landing wheeled aircraft on snow runways has become of considerable interest. In addition wheels are much lighter than skis, cause less drag on take off, and have no air drag. For ski-equipped aircraft longer runways are needed to lift the same amount of weight and air speed is lowered appreciably by air drag. A snow runway was constructed at Site II, Greenland, in 1955 and was successfully used for landing wheeled aircraft with cargo (C-124, C-47) and personnel (C-54) [2]. Similar attempts have been made in the Antarctic, but without success. It is the purpose of this paper to theoretically and experimentally analyze the problem of snow runways and establish criteria permitting adequate site evaluation and effective construction of landing strips. The results are applicable not only to polar regions but also to temperate areas with a heavy annual snow accumulation.
Dural arteriovenous malformations of the skull base

AbstractDural arteriovenous malformations (AVMs) are interesting lesions, which can present as diagnostic and therapeutic challenges. Such AVMs were initially described as located solely in the dural venous sinuses, but during the last decade researchers have discovered them in other locations such as the tentorium and foramen magnum. It is understandable that they can develop in other locations because numerous arteriovenous shunts normally occur all over the dura. Early reports emphasize that they are congenital; however, some investigators have proposed that they are acquired lesions arising after sinus thrombosis and trauma. They also have variable clinical features. From 1975 to 2000 we treated 400 AVMs, of which 46 were dural. Of these 46 dural AVMs, 18 could be classified as skull base AVMs. We restricted the designation of skull base AVMs to those AVMs located in the tentorium or adjacent to bones of the skull base. Two of these AVMs actually had their vascular nidus located in the bone. The commo...
Place-based programs and the geographic dispersion of employment

Abstract Government efforts to improve local economic conditions by encouraging private investment in targeted communities could affect the broader geographic distribution of employment in a region, especially to the extent that subsidized businesses face few constraints on whom they hire. This paper examines the labor market impacts of investment subsidized by the U.S. federal government's New Markets Tax Credit (NMTC) program, which provides tax incentives to promote business investment in low-income neighborhoods. To identify the program's effects, I exploit a discontinuity in the rule determining the eligibility of census tracts for NMTC-subsidized investment. Using rich administrative data on workers' residence and workplace locations, I find evidence that many of the new jobs created in areas that receive subsidized investment do not go to residents of targeted neighborhoods. The results suggest that the local economic benefits of place-based programs may be diluted when subsidized businesses have scope to hire from broader regional labor markets.
The reformers’ dilemma: media, policy ownership, and reform

Current proposals for strengthening policy ownership in reforming economies are fundamentally flawed. Modeling the reform process as a prisoners’ dilemma demonstrates that political agents must overcome this conflict of interests before present proposals for bolstering ownership will work. A politically autonomous mass media is one important mechanism enabling political agents to do this. Reforming countries without free media face an uphill battle overcoming the problems associated with transition. We test our theory by investigating the relationship between media freedom, foreign aid, and economic development in 26 post-socialist transition countries. The results of this analysis support our theory.
Testing scientific software: A systematic literature review

Context: Scientific software plays an important role in critical decision making, for example making weather predictions based on climate models, and computation of evidence for research publications. Recently, scientists have had to retract publications due to errors caused by software faults. Systematic testing can identify such faults in code. Objective: This study aims to identify specific challenges, proposed solutions, and unsolved problems faced when testing scientific software. Method: We conducted a systematic literature survey to identify and analyze relevant literature. We identified 62 studies that provided relevant information about testing scientific software. Results: We found that challenges faced when testing scientific software fall into two main categories: (1) testing challenges that occur due to characteristics of scientific software such as oracle problems and (2) testing challenges that occur due to cultural differences between scientists and the software engineering community such as viewing the code and the model that it implements as inseparable entities. In addition, we identified methods to potentially overcome these challenges and their limitations. Finally we describe unsolved challenges and how software engineering researchers and practitioners can help to overcome them. Conclusions: Scientific software presents special challenges for testing. Specifically, cultural differences between scientist developers and software engineers, along with the characteristics of the scientific software make testing more difficult. Existing techniques such as code clone detection can help to improve the testing process. Software engineers should consider special challenges posed by scientific software such as oracle problems when developing testing techniques.
Dynamics of wide bandwidth semiconductor lasers

In this paper we summarize the most important recent advances and results in high speed diode lasers. These advances have primarily come about as a result of physical understanding of the properties that affect the dynamic performance of these lasers. A great deal of progress has been made in understanding the active region properties of such devices, including the electron and hole transport dynamics as well as the effect of active region doping and strain. At the very high frequencies characteristic of the highest speed lasers reported to date the microwave signal propagation becomes an important issue that can limit the laser bandwidth. The distribution of signals along the laser length due to these effects are discussed, analyzed, and measured, and conclusions about bandwidth and device operation are drawn from the analysis. All of these different issues are summarized in this paper from both a theoretical and experimental perspective. The laser structures that address and overcome the problems caused by such factors are presented along with the best results obtained to date.
MEASURING THE EFFECT OF RESTRUCTURING ON CORPORATE PERFORMANCE: THE CASE OF MANAGEMENT BUYOUTS

Recent research has attempted to document that the financial gains associated with takeovers, LBOs, and other types of restructuring are attributable to subsequent improvements in operating performance. In this paper, the authors develop a more general framework for measuring the effect of corporate restructuring on performance and apply the framework to a sample of firms taken private by their management. They demonstrate that the estimation approaches employed in the literature embody restrictions on the general framework which the data can reject. However, the authors' best estimates provide evidence that management buyouts improve corporate performance, and the magnitudes of these improvements are similar to existing estimates. Copyright 1994 by MIT Press.
Value conflicts and social choice in electronic funds transfer system developments

During the last few years, computer-based systems which automate the transfer and recording of debits and credits have begun to be implemented on a large scale. These systems promise both financial benefits for the institutions that use them and potential conveniences to their customers. However, they also raise significant social, legal, and technical questions that must be resolved if full scale systems for Electronic Funds Transfer (EFT) are not to cause more problems for the larger public than they solve. This paper examines the incentives for EFT developments and the social problems they raise in the context of conflicts between five different value positions that are often implicit in analyses of proposed EFT arrangements. These conflicts reflect the relative importance of certain problems for specific groups. The value positions implicit in EFT proposals help to organize analyses of market arrangements, system reliability, and privacy of transactions. These topics are analyzed in this article and related to the value positions held by concerned parties. Last, the ways in which the public can learn about the social qualities of different EFT arrangements and the pace of EFT developments are both discussed in the context of social choice.
Matrix Equations and Normal Forms for Context-Free Grammars

The relationship between the set of productions of a context-free grammar and the corresponding set of defining equations is first pointed out. The closure operation on a matrix of strings is defined and this concept is used to formalize the solution to a set of linear equations. A procedure is then given for rewriting a context-free grammar in Greibach normal form, where the replacements string of each production begins with a terminal symbol. An additional procedure is given for rewriting the grammar so that each replacement string both begins and ends with a terminal symbol. Neither procedure requires the evaluation of regular begins and ends with a terminal symbol. Neither procedure requires the evaluation of regular expressions over the total vocabulary of the grammar, as is required by Greibach's procedure.
Robust, compact, and inexpensive analog controllers for cabin noise control

Active Noise Control has been an area of research interest in the recent decades with the goal of providing reduced noise levels in automobile and aircraft enclosures. Although digital controllers are adaptable and efficient, they lack the simplicity of analog controllers due to the requirement of a computer, D/A and A/D boards. Analog controllers on the other hand can be designed to be compact using current IC technology and hence are relatively very cheap. The following paper studies the application of an analog robust controller to abate the noise radiated into a non-reverberant wooden enclosure by a clamped aluminum plate. Since only the odd-odd modes radiate efficiently, a SISO robust analog controller was designed and built inexpensively for a piezoelectric actuator and accelerometer sensor placed at the center of the plate. A reduction of 17 dB is observed when the panel is excited at its fundamental frequency, the dominant radiating mode. When the plate is excited with narrowband noise (40 - 316 Hz), the controller reduces the noise levels in the enclosure by 9 dB. The experimental results agree well with the controller simulation carried out using MATLAB.
Copper-Catalyzed Synthesis of 2,4-Disubstituted Allenoates from α-Diazoesters

A Cu-catalyzed method for coupling α-substituted-α-diazoesters with terminal alkynes to give substituted allenoates is described. Key to the development of a selective method was the recognition that an adventitous base catalyzes the isomerization to form the allenoate product. A plausible mechanism is proposed, based in part on evidence against a mechanism that involves a Cu(I)-acetylide as a low-valent intermediate.
Institutions and national development in Latin America: a comparative study

We review the theoretical and empirical literatures on the role of institutions on national development as a prelude to present a more rigorous and measurable definition of the concept and a methodology to study this relationship at the national and subnational levels. The existing research literature features conflicting definitions of the concept of "institutions" and empirical tests based mostly on reputational indices, with countries as units of analysis. The present study's methodology is based on a set of five strategic organizations studied comparatively in five Latin American countries. These include key federal agencies, public administrative organizations, and stock exchanges. Systematic analysis of results show a pattern of differences between economically-oriented institutions and those entrusted with providing basic services to the general population. Consistent differences in institutional quality also emerge across countries, despite similar levels of economic development. Using the algebraic methods developed by Ragin, we test six hypotheses about factors determining the developmental character of particular institutions. Implications of results for theory and for methodological practices of future studies in this field are discussed.
Characterization of the coronary vascular capacitance, resistance, and flow in endocardium and epicardium based on a nonlinear dynamic analog model

Abstract An electrical analog model consisting of capacitors, diodes, linear, and nonlinear resistors was used to characterize the coronary pressure-flow relationships from the arterial side of the coronary circulation. Based on this analog model, an identifiable system was formulated whereby the coronary vascular capacitance and resistance in the endocardial and epicardial layer of the heart were estimated. This was done by solving a constrained least-squares problem using a non-linear programming technique. Experimental data were obtained from 28 animal studies using swine with an artificially induced coronary stenosis. The analog model showed a very consistent representation of the coronary hemodynamics. The model also generated accurate estimates of the endocardial to epicardial blood flow ratios compared to those independently measured by the radioactive microsphere technique. The model-predicted epicardial capacitance had a mean of 4.2 × 10-3ml/mmHg per 100 g tissue; while the endocardial capacitance was negligible in most cases. The result indicated that, in the stenosed coronary circulation of swine, capacitive flow contributes 20% in root-mean-square value to the total flow activity in epicardium; while flow in the endocardium is dominated by a resistive, vascular waterfall effect.
The kinetic Sunyaev-Zel'dovich effect due to the electrons of our galaxy

We compute the effect of local electrons on the CMB temperature anisotropies. The number density and distribution of free electrons in our Galaxy has been accurately measured from pulsar dispersion measurements. Because of their distribution, the dynamics of our Galaxy, and the Galaxy peculiar velocity with respect to the Hubble flow, these free electrons leave a frequency-independent imprint on the cosmic microwave background (CMB). In particular, the coherent motion of the free electrons with respect to us and to the CMB rest frame produce a kinetic Sunyaev-Zel'dovich signal. We compute this effect and we note that the large-scale antisymmetry of the signal gives it an angular power spectrum with a sawtooth pattern, where even multipoles are suppressed with respect to the odd ones. We find the signal to be small (~2 μK) and subdominant compared to the primary CMB and other foreground signals. However, since the parameters of this model are constrained by other independent astrophysical observations, it can be taken into account if more precise measurements of the primordial signal are required.
The conformational states of Mg.ATP in water.

The conformational equilibria of MgAEATP in solution is studied using molecular dynamics (MD) augmented with umbrella sampling methods. Free en- ergy comparisons show that the Mg 2+ ion is equally likely to coordinate the oxygens of the two end phos- phates, or of all three phosphates. The MD trajectories reveal two major degrees of freedom of the MgAEATP molecule in solution, and we compute the free energy as a function of these variables, and determine its elastic properties. Comparing the free energy function with several crystallographic structures of ATP analogs, we find that the crystal structures correspond to states where ATP would be elastically strained. The average water density around MgAEATP is investigated to show the average number of hydrogen bonds and the hydro- phobicity.
Some physical considerations governing the choice of internally administered radioisotopes for therapy.

Calculations are presented for the determination of radiation dose delivered by internally administered radioisotopes to specific tumour sites and to critical areas in the body. Some of the variables included in these calculations are: the metabolizing function of the isotope in the various sites, the half life, the beta and gamma ray energies of the isotope, and the tumour size. From this, an expression has been obtained for the ratio of dose in the critical volume and the tumour, and the effect of the various parameters on this ratio. The derived expressions are used to calculate the relative advantage of various iodine isotopes from data on nine patients who received therapeutic doses of 131I. The calculatiosn indicate that for most patients the iodine isotopes having a higher beta to gamma ray energy ratio are more advantageous to use, as long as their half life is of the order of one day or more. It appears that 131I is probably not always the most desirable of the iodine isotopes for maximal tumour and minimal critical volume irradiation.
Moisture sensing in transformer oil using thin-film microdielectrometry

In-situ moisture sensing in transformer oil by measuring the change in dielectric properties of 1- to 7- mu m-thick layers of plasma-deposited bromobenzene coated on interdigitated 50- mu m-wavelength electrodes of a microdielectrometer chip is demonstrated. Gain-phase measurements in the frequency range of 0.0005 to 10000 Hz, normalized to the frequency of peak phase shift, are found to be universal. Evidence is presented that the coatings act as semipermeable membranes serving as barriers to the transformer oil, but absorbing moisture in proportion to its absolute content in the oil. Sensitivity to moisture from less than 5 to about 50 p.p.m. is found with a transient response of less than a few minutes. Although the method is well suited to following the dynamics of water in paper-oil systems over periods of days or perhaps weeks, a long-term loss of sensitivity must be overcome if the sensor is to be used without recalibration for extended periods of time. Its use for discerning abnormal behavior in a pilot transformer monitoring system is described. >
Fabrication and characterization of dual phase magnesia–zirconia ceramics doped with plutonia

Abstract Dual phase magnesia–zirconia ceramics doped with plutonia are being studied as an inert matrix fuel (IMF) for light water reactors. The motivation of this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on yttria stabilized zirconia. The concept uses the MgO phase as an efficient heat conductor to increase thermal conductivity of the composite. In this paper ceramic fabrication and characterization by scanning electron microscopy, energy and wavelength dispersive X-ray spectroscopy is discussed. Characterization shows that the ceramics consist of the two-phase matrix and PuO2-rich inclusions. The matrix is comprised of pure MgO phase and MgO–ZrO2–PuO2 solid solution. The PuO2-rich inclusion contained dissolved MgO and ZrO2.
Solar and Stellar Magnetic Fields and Structures: Observations

This review of stellar magnetic field measurements is both a critique of recent spectral diagnostic techniques and a summary of important trends now appearing in the data. I will discuss both the Zeeman broadening techniques that have evolved from Robinson’s original approach and techniques based on circular and linear polarization data. I conclude with an ambitious agenda for developing self-consistent models of the magnetic atmospheres of active stars.
Brain-Derived Neurotrophic Factor and Collagen Tubulization Enhance Functional Recovery After Peripheral Nerve Transection and Repair

Objective: To investigate the effect of brain-derived neurotrophic factor (BDNF) and collagen tubulization (CT) on the regeneration of transected peripheral nerves. Methods and Design: The left sciatic nerve of 40 SpragueDawley rats was transected then repaired using one of four techniques: epineurial coaptation, CT, CT with BDNF delivered by an osmotic pump to the repair site, or CT with BDNF covalently cross-linked to the collagen matrix (CT/linked-BDNF). Sciatic functional indices were measured preoperatively and then postoperatively at 10-day intervals for 90 days. Segments of the sciatic nerves proximal and distal to the repair site were harvested at 90 days for histologic and morphometric evaluation. Results: Animals repaired by CT/linked-BDNF (n=10) demonstrated the most favorable functional recovery of all groups, with statistically significant differences seen compared with animals repaired by CT (n=10, P =.05) and epineurial coaptation (n=9, P P =.005 and P =.02, respectively). Nerves repaired by CT/linked-BDNF had the largest mean axon diameters proximal and distal to the repair site. Conclusions: Brain-derived neurotrophic factor and CT improve the rate and the degree to which recovery of sciatic function occurs after nerve transection and repair. Animals repaired by CT/BDNF-linked demonstrated the most favorable functional recovery of all groups. Animals whose repair technique included BDNF had the largest mean axon diameters of all groups. (Arch Otolaryngol Head Neck Surg. 1996;122:407-413)
Spatial Training Improves Children's Mathematics Ability

We tested whether mental rotation training improved math performance in 6- to 8-year-olds. Children were pretested on a range of number and math skills. Then one group received a single session of mental rotation training using an object completion task that had previously improved spatial ability in children this age (Ehrlich, Levine, & Goldin-Meadow, 2006). The remaining children completed crossword puzzles instead. Children's posttest scores revealed that those in the spatial training group improved significantly on calculation problems. In contrast, children in the control group did not improve on any math tasks. Further analyses revealed that the spatial training group's improvement was largely due to better performance on missing term problems (e.g., 4 + ____ = 11).
An Empirically Based Model for Predicting Infrared Luminosity Functions, Deep Infrared Galaxy Counts, and the Diffuse Infrared Background

We predict luminosity functions and number counts for extragalactic infrared sources at various wavelengths using the framework of our empirically based model. Comparisons of our galaxy count results with existing data indicate that either galaxy luminosity evolution is not much stronger than Q = 3.1, where L ∝ (1 + z)Q, or that this evolution does not continue beyond a redshift of 2. However, a derivation of the far-infrared background from COBE Diffuse Infrared Background Experiment data suggests a stronger evolution for the far-infrared emission, with Q > 4 in the redshift range between 0 and 1. We discuss several interpretations of these results and also discuss how future observations can reconcile this apparent conflict. We also make predictions of the redshift distributions of extragalactic infrared sources at selected flux levels, which can be tested by planned detectors. Finally, we predict the fluxes at which various future surveys will become confusion-limited.
Sharp metastability threshold for two-dimensional bootstrap percolation

In the bootstrap percolation model, sites in an L by L square are initially independently declared active with probability p. At each time step, an inactive site becomes active if at least two of its four neighbours are active. We study the behaviour as p→0 and L→∞ simultaneously of the probability I(L,p) that the entire square is eventually active. We prove that I(L,p)→1 if \(\), and I(L,p)→0 if \(\), where λ=π2/18. We prove the same behaviour, with the same threshold λ, for the probability J(L,p) that a site is active by time L in the process on the infinite lattice. The same results hold for the so-called modified bootstrap percolation model, but with threshold λ′=π2/6. The existence of the thresholds λ,λ′ settles a conjecture of Aizenman and Lebowitz [3], while the determination of their values corrects numerical predictions of Adler, Stauffer and Aharony [2].
FACILE FORMATION OF N-ALKYL-OXAZOLIDIN-2-ONES FROM N-ALKYL-NITROXYETHYLAMINES AND CARBONATE ANION IN BIPHASIC MEDIA

Abstract Nitration of N-alkyl ethanolamines ( 1 ) followed by treatment of their corresponding N-alkyl-N-(2-nitroxyethyl)amine salts ( 2 ) in a biphasic CH 2 Cl 2 /aqueous Na 2 CO 3 or NaHCO 3 mixture at 25 °C gives N-alkyl-oxazolidin-2-ones ( 3 ). This represents a new method that allows the preparation of oxazolidinones at ambient temperature with the use of aqueous carbonate.
The Role of Sign in Students' Modeling of Scalar Equations

Helping students set up equations is one of the major goals of teaching a course in physics that contains elements of problem solving. Students must take the stories we present, interpret them, and turn them into physics; from there, they must turn that physical, idealized story into mathematics. How they do so and what problems lie along the way are a major source of difficulty for us as instructors. In this paper, we consider just one such difficulty, getting the plus and minus signs correct when setting a net force equal to mass times acceleration. Even in such simple equations, we find that students make common errors in how they connect the mathematics and the physics. Specifically, we have seen college physics students use physical and mathematical reasoning inconsistently when determining signs of terms in equations. The problem seems to lie in how a vector equation gets interpreted into a scalar equation (whose form depends on one's choice of coordinate system).
Simulation of random packing of spherical particles with different size distributions

A numerical model for a loose packing process of spherical particles is presented. The simulation model starts with randomly choosing a sphere according to a pregenerated continuous particle-size distribution, and then dropping the sphere into a dimension-specified box, and obtaining its final position by using dropping and rolling rules which are derived from a similar physical process of spheres dropping in the gravitational field to minimize its gravity potential. Effects of three different particle-size distributions on the packing structure were investigated. Analysis on the physical background of the powder-based manufacturing process is additionally applied to produce optimal packing parameters of bimodal and Gaussian distributions to improve the quality of the fabricated parts. The results showed that higher packing density can be obtained using bimodal size distribution with a particle-size ratio from 1.5 to 2.0 and the mixture composition around n2:n1=6:4. For particle size with a Gaussian distribution, the particle radii should be limited in a narrow range around 0.67 to 1.5.
Perfect sampling using bounding chains

In Monte Carlo simulation, samples are drawn from a distribution to estimate properties of the distribution that are too difficult to compute analytically. This has applications in numerous fields, including optimization, statistics, statistical mechanics, genetics, and the design of approximation algorithms. In the Monte Carlo Markov chain method, a Markov chain is constructed which has the target distribution as its stationary distribution. After running the Markov chain “long enough”, the distribution of the final state will be close to the stationary distribution of the chain. Unfortunately, for most Markov chains, the time needed to converge to the stationary distribution (the mixing time) is completely unknown. Here we develop several new techniques for dealing with unknown mixing times. First we introduce the idea of a bounding chain, which delivers a wealth of information about the chain. Once a bounding chain is created for a particular chain, it is possible to empirically estimate the mixing time of the chain. Using ideas such as coupling from the past and the Fill-Murdoch-Rosenthal algorithm, bounding chains can also become the basis of perfect sampling algorithms. Unlike traditional Monte Carlo Markov chain methods, these algorithms draw samples which are exactly distributed according to the stationary distribution. We develop bounding chains for several Markov chains of practical interest, chains from statistical mechanics like the Swendsen-Wang chain for the Ising model, the Dyer-Greenhill chain for the discrete hard core gas model, and the continuous Widom-Rowlinson mixture model with more than three components in the mixture. We also give techniques for sampling from weighted permutations which have applications in database access and nonparametric statistical tests. In addition, we present here bounding chains for a variety of Markov chains of theoretical interest, such as the k coloring chain, the sink free orientation chain, and the antiferromagnetic Potts model with more than three colors. Finally we develop new Markov chains (and bounding chains) for the continuous hard core gas model and the Widom-Rowlinson model which are provably faster in practice.
Efficient Palladium-Catalyzed N-Arylation of Indoles

The N-arylation of indoles, including a variety of substituted ones, has been carried out using bulky, electron-rich phosphines as the supporting ligand in combination with Pd2(dba)3. Using this catalyst system, the efficient coupling of indole and a variety of substituted indoles with aryl iodides, bromides, chlorides, and triflates can be achieved.