cssi/SciSciGPT-SciSciNet huggingface dataset:
On the small cycle transversal of planar graphs

We consider the problem of finding a k-edge transversal set that intersects all (simple) cycles of length at most s in a planar graph, where s>=3 is a constant. This problem, referred to as Small Cycle Transversal, is known to be NP-complete. We present a polynomial-time algorithm that computes a kernel of size 36s^3k for Small Cycle Transversal. In order to achieve this kernel, we extend the region decomposition technique of Alber et al. (2004) [1] by considering a unique region decomposition that is defined by shortest paths. Our kernel size is a significant improvement in terms of s over the kernel size obtained under the meta-kernelization framework by Bodlaender et al. (2009) [7].
Mediterranean Summer Climate and the Importance of Middle East Topography

AbstractIn summer, the atmospheric circulation over the Mediterranean is characterized by localized intense subsidence and low-level northerlies over the central to eastern portion of the basin. Here, simulations with the Community Atmosphere Model, version 5 are used to investigate the influence of the elevated terrain of North Africa and the Middle East on this summertime circulation. This builds on previous work that recognized a role for North African topography in localizing the Mediterranean subsidence.By flattening the two regions of elevated terrain in the model, it is demonstrated that, while they both conspire to produce about 30% of the summertime subsidence, contrary to previous work, the mountains of the Middle East dominate in this topographic contribution by far. This topography, consisting primarily of the Zagros mountain range, alters the circulation throughout the depth of the troposphere over the Mediterranean and farther east. The model results suggest that about 20% of the Mediterrane...
Effect of side chain length on biotransformation, hepatic transport, and choleretic properties of chenodeoxycholyl homologues in the rodent: Studies with dinorchenodeoxycholic acid, norchenodeoxycholic acid, and chenodeoxycholic acid

To assess the effect of side chain length on the metabolism and physiological effects of homologues of chenodeoxycholic acid (CDCA), dinorCDCA, the C22 homologue, was synthesized and its hepatic biotransformation, transport kinetics, and choleretic properties were defined in rat and hamster biliary fistula and in isolated perfused rat liver. Results were compared with those of norCDCA, the C23 homologue, and of CDCA, the natural C24 homologue. In the rat, dinorCDCA was secreted mostly in unconjugated form (the majority as dinor-alpha-muricholic acid); the remainder was glucuronidated. In the hamster, glucuronidation was greater, and the unconjugated fraction contained equal parts of dinorCDCA and 5beta-hydroxy-dinorCDCA. NorCDCA was glucuronidated extensively (70%, rat; 40%, hamster). CDCA, in contrast, was efficiently amidated with taurine or glycine. In the perfused liver, the initial uptake rate of all three homologues was identical; later, regurgitation and/or cholehepatic shunting of dinorCDCA and norCDCA, but not of CDCA, occurred. In rats and hamsters with biliary fistulas, dinorCDCA and norCDCA, but not CDCA, induced a bicarbonate-rich hypercholeresis of canalicular origin. Hypercholeresis was not induced by the taurine conjugate of dinorCDCA. Hepatobiliary retention of both dinorCDCA and norCDCA occurred, consistent with efficient ductular absorption (calculated to be 94%) and cholehepatic cycling of the unmetabolized bile acids. It is concluded that dinorCDCA, as norCDCA, is inefficiently amidated, is metabolized as a xenobiotic, and induces hypercholeresis. DinorCDCA is the first dihydroxy bile acid to be identified that is secreted largely in unconjugated form in bile.
Hall-Littlewood polynomials and fixed point enumeration

We resolve affirmatively some conjectures of Reiner, Stanton, and White (2004) [12] regarding enumeration of transportation matrices which are invariant under certain cyclic row and column rotations. Our results are phrased in terms of the bicyclic sieving phenomenon introduced by Barcelo, Reiner, and Stanton (2009) [1]. The proofs of our results use various tools from symmetric function theory such as the Stanton-White rim hook correspondence (Stanton and White (1985) [18]) and results concerning the specialization of Hall-Littlewood polynomials due to Lascoux, Leclerc, and Thibon (1994, 1997) [5,6].
A Poincaré-Birkhoff-Witt theorem for quadratic algebras with group actions

Braverman, Gaitsgory, Polishchuk, and Positselski gave necessary and sufficient conditions for a nonhomogeneous quadratic algebra to satisfy the Poincare-Birkhoff-Witt property when its homogeneous version is Koszul. We widen their viewpoint and consider a quotient of an algebra that is free over some (not necessarily semisimple) subalgebra. We show that their theorem holds under a weaker hypothesis: We require the homogeneous version of the nonhomogeneous quadratic algebra to be the skew group algebra (semidirect product algebra) of a finite group acting on a Koszul algebra, obtaining conditions for the Poincare-Birkhoff-Witt property over (nonsemisimple) group algebras. We prove our main results by exploiting a double complex adapted from Guccione, Guccione, and Valqui (formed from a Koszul complex and a resolution of the group), giving a practical way to analyze Hochschild cohomology and deformations of skew group algebras in positive characteristic. We apply these conditions to graded Hecke algebras and Drinfeld orbifold algebras (including rational Cherednik algebras and symplectic reflection algebras) in arbitrary characteristic, with special interest in the case when the characteristic of the underlying field divides the order of the acting group.
Two-Dimensional Modeling of Lithium Deposition during Cell Charging

Empirical observations have shown that lithium deposition occurs preferentially at electrode edges and that extending the negative electrode beyond the edge of the positive by approximately 1 mm can prevent deposition from occurring. In this work, we use a simplified COMSOL Multiphysics model to explain this behavior and to investigate the conditions under which deposition occurs, paying particular attention to the magnitude of edge effects. Model results show that geometric effects generate overpotential at the edge of the electrode and create conditions which favor plating, despite unused capacity in the center of the electrode. Extending the negative electrode beyond the edge of the positive provides excess capacity where it is needed and prevents deposition from occurring before the cutoff potential is reached. Under the assumptions of this model, an extension of 0.4 mm is sufficient to prevent the onset of lithium deposition until after the cutoff potential is reached.
Asymmetric dihydroxylation route to a dipeptide isostere of a protease inhibitor: enantioselective synthesis of the core unit of ritonavir.

An enantioselective synthesis of the dipeptide isostere of ritonavir has been accomplished utilizing Sharpless asymmetric hydroxylation as the key step.
Quantifying the Value of Open Source Hardware Development

With the maturation of digital manufacturing technologies like 3-D printing, a new paradigm is emerging of distributed manufacturing in both scientific equipment and consumer goods. Hardware released under free licenses is known as free and open source hardware (FOSH). The availability of these FOSH designs has a large value to those with access to digital manufacturing methods and particularly for scientists with needs for highly-customized low-volume production products. It is challenging to use traditional funding models to support the necessary investment of resources in FOSH development because of the difficulty in quantifying the value of the result. In order to overcome that challenge and harvest the current opportunity in both low-cost scientific equipment and consumer products, this article evaluates the following methods to quantify the value of FOSH design including: 1) downloaded substitution valuation; 2) avoided reproduction valuation and 3) market savings valuation along with additional benefits related to market expansion, scientific innovation acceleration, educational enhancement and medical care improvement. The strengths and weaknesses of these methods are analyzed and the results show that the methods are relatively straight-forward to institute, based on reliable freely-available data, and that they minimize assumptions. A case study of a syringe pump with numerous scientific and medical applications is presented. The results found millions of dollars of economic value from a relatively simple scientific device being released under open-licenses representing orders of magnitude increase in value from conventional proprietary development. The inescapable conclusion of this study is that FOSH development should be funded by organizations interested in maximizing return on public investments particularly in technologies associated with science, medicine and education.
Semiclassical second microlocal propagation of regularity and integrable systems

We develop a second-microlocal calculus of pseudodifferential operators in the semiclassical setting. These operators test for Lagrangian regularity of semiclassical families of distributions on a manifold X with respect to a Lagrangian submanifold of T*X. The construction of the calculus, closely analogous to one performed by Bony in the setting of homogeneous Lagrangians, proceeds via the consideration of a model case, that of the zero section of T*ℝn, and conjugation by appropriate Fourier integral operators. We prove a propagation theorem for the associated wavefront set analogous to Hormander’s theorem for operators of real principal type. As an application, we consider the propagation of Lagrangian regularity on invariant tori for quasimodes (e.g., eigenfunctions) of an operator with completely integrable classical hamiltonian. We prove a secondary propagation result for second wavefront set which implies that even in the (extreme) case of Lagrangian tori with all frequencies rational, provided a nondegeneracy assumption holds, Lagrangian regularity either spreads to fill out a whole torus or holds nowhere locally on it.
Kinetic Products Under Thermal Conditions: Rapid Entry into α/β-D-Galactofuranosides Using Microwave Irradiation and Selective Lewis Acids

A modified Fischer-Lubineau reaction, employing microwave irradiation and selected Lewis acids such as Mn(ClO4)2, Mn(C2H3O2)3, FeCl3, CoCl2, and AgF as independent additives, induces rapid entry into α/β-d-galactofuranosides in very good yield and purity.
On Parabolicity and Area Growth of Minimal Surfaces

We establish parabolicity and quadratic area growth for minimal surfaces-with-boundary contained in regions of ℝ3 which are within a sub-logarithmic factor of the exterior of a cone. Unlike previous work showing that these two properties hold for minimal surfaces-with-boundary contained between two catenoids, we do not make use of universal superharmonic functions. Instead, we use stochastic methods, which have the additional feature of giving a type of parabolicity in a more general context than Brownian motion on a minimal surface.
Fast planning through planning graph analysis

Abstract We introduce a new approach to planning in STRIPS-like domains based on constructing and analyzing a compact structure we call a planning graph. We describe a new planner, Graphplan, that uses this paradigm. Graphplan always returns a shortest possible partial-order plan, or states that no valid plan exists. We provide empirical evidence in favor of this approach, showing that Graphplan outperforms the total-order planner, Prodigy and the partial-order planner, UCPOP, on a variety of interesting natural and artificial planning problems. We also give empirical evidence that the plans produced by Graphplan are quite sensible. Since searches made by this approach are fundamentally different from the searches of other common planning methods, they provide a new perspective on the planning problem.
Femtochemistry: Recent Progress in Studies of Dynamics and Control of Reactions and Their Transition States

This Centennial Issue of The Journal of Physical Chemistry marks not only its achievements since birth in 1896 but also an era of great scientific contributions to the field of chemical dynamics. Pioneering work in the studies of molecular reaction dynamics, which continued over a century, led to new methods of experimentation and to new concepts. Letokhov [1] has identified “three waves” in the development of molecular dynamics, depending on the time scale. In this account we focus on the third wave characterized by femtosecond time resolution. Chemistry occurring on this time scale, femtochemistry, is microscopic, on the length scale of a bond, allowing us to address the nature of transition states and their control, a subject also started in the first part of this century.
Ab-initio Electronic and Structural Properties of Rutile Titanium Dioxide

Ab-initio, self-consistent electronic energy bands of rutile TiO2 are reported within the local density functional approximation (LDA). Our first principle, non-relativistic and ground state calculations employed a local density functional approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). Within the framework of the Bagayoko–Zhao–Williams (BZW) method, we solved self-consistently both the Kohn–Sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states. Our calculated band structure shows that there is significant O 2p–Ti 3d hybridization in the valence bands. These bands are well separated from the conduction bands by an indirect band gap of 2.95 eV, from Γ to R. Consequently, this work predicts that rutile TiO2 is an indirect band gap material, as all other gaps from our calculations are larger than 2.95 eV. We found a slightly larger, direct band gap of 3.05 eV, at the Γ point, in excellent agreement with experiment. Our calculations reproduced the peaks in the measured conduction and valence bands densities of states, within experimental uncertainties. We also calculated electron effective mass. Our structural optimization led to lattice parameters of 4.65 and 2.97 A for a0 and c0, respectively with a u parameter of 0.3051 and a bulk modulus of 215 GPa.
Dietary supplementation with methylseleninic acid, but not selenomethionine, reduces spontaneous metastasis of Lewis lung carcinoma in mice

The present study investigated the effects of dietary supplementation with methylseleninic acid (MSeA), in comparison with selenomethionine (SeMet), on spontaneous metastasis of Lewis lung carcinoma (LLC) in male C57BL/6 mice using intramuscular and subcutaneous injection models. Mice were fed AIN93G control diet or that diet supplemented with MSeA or SeMet at 2.5 mg selenium/kg for 4 weeks at which time they were injected intramuscularly or subcutaneously with 2.5 × 105 viable LLC cells. Experiments were terminated 2 weeks later for mice injected intramuscularly or 2 weeks after surgical removal of primary tumors from mice subcutaneously injected with cancer cells. Dietary supplementation with MSeA significantly reduced pulmonary metastatic yield when compared with the controls (p < 0.05) in both models; however, SeMet did not have such an effect. Supplementation with MSeA significantly decreased plasma concentrations of urokinase-type plasminogen activator (p < 0.05) and plasminogen activator inhibitor-1 (p < 0.05). Furthermore, MSeA significantly reduced plasma concentrations of vascular endothelial growth factor (p < 0.05), fibroblast growth factor basic (p < 0.05) and platelet-derived growth factor-BB (p < 0.05) when compared with the controls. Selenomethionine did not affect any of the aforementioned measurements. These results demonstrate that MSeA reduces spontaneous metastasis of LLC in mice, perhaps through inhibition of the urokinase plasminogen activator system and reducing angiogenesis.
Phase engineering of transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) represent a family of materials with versatile electronic, optical, and chemical properties. Most TMD bulk crystals are van der Waals solids with strong bonding within the plane but weak interlayer bonding. The individual layers can be readily isolated. Single layer TMDs possess intriguing properties that are ideal for both fundamental and technologically relevant research studies. We review the structure and phases of single and few layered TMDs. We also describe recent progress in phase engineering in TMDs. The ability to tune the chemistry by choosing a unique combination of transition metals and chalcogen atoms along with controlling their properties by phase engineering allows new functionalities to be realized with TMDs.
Early kinetic studies on CO substitution reactions of metal carbonyls

Abstract Research done in our laboratory, spanning the period 1956–1970, on CO substitution kinetics and mechanisms of metal carbonyls is highlighted. In today's language of organometallic chemistry, it was shown that (1) 18-electron binary metal carbonyls react by a dissociative ( S N 1) process, while 16-electron systems react by associative ( S N 2) mechanisms, (2) metal carbonyls of 18-electrons with certain ligands (NO, η 5 -C 5 H 5 ) react by an associative process via a pair of electrons localized on the ligand in the reaction pathway, e.g. for η 5 -C 5 H 5 , ring slippage of η 5 → η 3 → η 5 (3), insertion of CO in an alkyl metal bond was described mechanistically as alkyl migration, and (4) the ligand substitution lability of organometallic complexes of the 2nd row transition metal of a given triad was discovered.
Transition from activated to diffusive behavior in the vortex-liquid state in YBa2Cu3O7

Abstract In the vortex-liquid state in YBa 2 Cu 3 O 7 , there exist two distinct dissipative states separated by a field H > k . Below H k , the resistivity is strongly field-activated, with a prefactor that is anomalously enhanced over the normal-state resistivity ϱ N by ≈12 orders of magnitude. At H k , the prefactor collapses to a temperature-independent value equal to ϱ N , and the vortex motion becomes diffusive. The existence of the H k boundary is also reflected in the anomalous behavior of the Hall resistivity.
An empirically based simulation model for heavy-duty gas turbine engines using treated residual fuel

An empirically based engine simulation model was developed to analyze the operation of a heavy-duty gas turbine on ash-bearing fuel. The effect of the ash in the combustion products on turbine efficiency was determined employing field data. The model was applied to the prediction of the performance of an advanced cooled turbine engine with a water-cooled first-stage nozzle, when operated with ash-bearing fuels. Experimental data from a turbine simulator rig were used to estimate the expected rates of ash deposit formation in the advanced-cooled turbine engine, so that the results could be compared with those for current engines. The results of the simulations indicate that the rate of decrease in engine power would be 32 percent less in the advanced-cooled engine with water cooling. An improvement in predicted specific fuel consumption performance was also noted, with a rate of increase of 38 percent for the advanced-cooled engine.
On Ramsey's Conjecture: Efficient Allocations in the Neoclassical Growth Model with Private Information

Abstract In his seminal paper of 1928, Ramsey conjectured that if agents discounted the future differently, in the long run all agents except the most patient would live at the subsistence level. The validity of this conjecture was investigated in different environments. In particular, it has been confirmed in the neoclassical growth model with dynamically complete markets. This paper studies this conjecture in a version of this model that includes private information and heterogeneous agents. A version of Bayesian implementation is introduced and a recursive formulation of the original allocation problem is established. Efficient allocations are renegotiation-proof and the expected utility of any agent cannot go to zero with positive probability if the economy does not collapse. If the economy collapses all agents will get zero consumption forever. Thus, including any degree of private information in the neoclassical growth model will deny Ramsey's conjecture, if efficient allocations are considered.
Adventures in Crystal Growth: Synthesis and Characterization of Single Crystals of Complex Intermetallic Compounds

The central motivation of this manuscript is to highlight the discovery of novel, highly correlated electron systems. Ternary phases with unusual ground states composed of lanthanides, transition metals, and main group elements exhibit competing behavior leading to potentially novel physical properties. These systems are known to exhibit exotic properties such as unconventional superconductivity, heavy fermion behavior, and unusual forms of magnetism. The flux-growth method provides an avenue to discover and grow large single crystalline materials so that structure–physical property relationships may be determined. The growth of high quality single crystals is necessary to elucidate the intrinsic magnetic, electronic, and thermodynamic properties and has played a significant role in advancing basic and applied materials research. In this manuscript, we review the crystal structures, physical properties, and structure–property correlations of a select group of intermetallic compounds to demonstrate the pot...
A Method of Generating Functions of Several Variables Using Analog Diode Logic

A diode-resistor network technique for simulating functions of any number of variables is described. The function is approximated by a polyhedron, or its N-dimensional equivalent, and this polyhedral model is generated directly by the circuit. The circuit is formed of two cascaded sections: the first, using resistive networks, generates voltages representing each of the faces of the polyhedron; the second section, using analog diode logic, selects the appro priate voltage as the output.The analog diode logic uses basic circuits similar to those used in digital logic. It is shown that the analog logic can be described by a distributive lattice, closely related to Boolean algebra. Methods of logic synthesis are developed. Circuit design is discussed, and it is shown how the effect on the logic section of the finite source impedance of the resistive net works which feed it can be turned to practical ad vantage.The specific example of the multiplication of two variables is studied in some detail, providing a ...
Simulation Evaluation of Equivalent Vision Technologies for Aerospace Operations

A fixed-based simulation experiment was conducted in NASA Langley Research Center s Integration Flight Deck simulator to investigate enabling technologies for equivalent visual operations (EVO) in the emerging Next Generation Air Transportation System operating environment. EVO implies the capability to achieve or even improve on the safety of current-day Visual Flight Rules (VFR) operations, maintain the operational tempos of VFR, and perhaps even retain VFR procedures - all independent of the actual weather and visibility conditions. Twenty-four air transport-rated pilots evaluated the use of Synthetic/Enhanced Vision Systems (S/EVS) and eXternal Vision Systems (XVS) technologies as enabling technologies for future all-weather operations. The experimental objectives were to determine the feasibility of XVS/SVS/EVS to provide for all weather (visibility) landing capability without the need (or ability) for a visual approach segment and to determine the interaction of XVS/EVS and peripheral vision cues for terminal area and surface operations. Another key element of the testing investigated the pilot's awareness and reaction to non-normal events (i.e., failure conditions) that were unexpectedly introduced into the experiment. These non-normal runs served as critical determinants in the underlying safety of all-weather operations. Experimental data from this test are cast into performance-based approach and landing standards which might establish a basis for future all-weather landing operations. Glideslope tracking performance appears to have improved with the elimination of the approach visual segment. This improvement can most likely be attributed to the fact that the pilots didn't have to simultaneously perform glideslope corrections and find required visual landing references in order to continue a landing. Lateral tracking performance was excellent regardless of the display concept being evaluated or whether or not there were peripheral cues in the side window. Although workload ratings were significantly less when peripheral cues were present compared to when there were none, these differences appear to be operationally inconsequential. Larger display concepts tested in this experiment showed significant situation awareness (SA) improvements and workload reductions compared to smaller display concepts. With a fixed display size, a color display was more influential in SA and workload ratings than a collimated display.
Dynamic Analysis of a Buckling-Type Amplification Mechanism to Maximize the Power Output by Varying the Load Impedance and Control Timing

Due to the limited displacement of piezoelectric stack actuators, common practice is to use some form of displacement amplification mechanism. This paper focuses on an externally leveraged mechanism that utilized a buckling motion to achieve large amplification ratios within a single stage. This mechanism interfaces with a sinusoidal gear track that acts as the load. The dynamics of the system are derived and are shown to be fifth order. Due to the significantly nonlinear amplification caused by the buckling phenomenon and the gear, the dynamics are run in simulation to gain insight into the performance of the actuator. There is shown to be an optimal speed at which to run the actuator to maximize the possible power output. Furthermore, due to the simple binary control significant benefits are achieved by varying the control timing based on the velocity to ensure the force and velocity of the output are in phase.Copyright © 2012 by ASME
Oxidative Coupling of Enolates, Enol Silanes, and Enamines: Methods and Natural Product Synthesis

Oxidative coupling of enolates, enol silanes, and enamines provides a direct method for the construction of useful 1,4-dicarbonyl synthons. Despite its first being reported in 1935, with subsequent important advances beginning in the 1970s, the development of this powerful reaction into a reliable methodology was somewhat limited. In recent years, though, there have been a number of reports from several research groups demonstrating advances in several neglected areas of oxidative coupling. This microreview summarizes these new advances in methodology and provides an overview of recent natural product syntheses that showcase the power of these transformations.
Weights on the rise: where and for whom?

Using over 70 nationally representative surveys, I find evidence of a dramatic increase in the share of women who are overweight in developing and transition economies, especially in Latin America and the Middle East. Urban rates of the overweight, measured by the body mass index (BMI), are also far higher than those in rural areas. In examining the inter-temporal changes in the entire standardized weight distribution, there are nonetheless many instances where it is not possible to reject the null of non-dominance, especially in rural areas. It is also clear that the distribution of women’s BMIs in most countries is becoming markedly less equitable, and that this increase in univariate inequality is driven largely by the increase in BMIs among overweight and obese women. This is somewhat analogous to the oft discussed “rich get richer” story. That is, the increasing concentration of weight, standardized by heights, among the overweight is driving a significant share of the overall increase in BMI inequality. A related finding is that when I decompose the changes in the prevalence of overweight into the effect of shifts in the mean versus changes in the distribution, in many countries, even holding mean BMI constant, there would be a marked increase in the prevalence of clinically overweight women due to changes in the shape of the BMI distribution.
The Black Hole Mass-Galaxy Luminosity Relationship For Sloan Digital Sky Survey Quasars

We investigate the relationship between the mass of the central supermassive black hole, M BH, and the host galaxy luminosity, L gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M BH-L gal relationship by examining the redshift dependence of Δ log M BH, the offset in M BH from the local M BH-L gal relationship. There is little systematic trend in Δ log M BH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ*, we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ* in statistical studies.
Absolute Continuity of Brownian Bridges Under Certain Gauge Transformations

We prove absolute continuity of Gaussian measures associated to complex Brownian bridges under certain gauge transformations. As an application we prove that the invariant measure for the periodic derivative nonlinear Schr¨ odinger equation obtained by Nahmod, Oh, Rey-Bellet and Staffilani in (20), and with respect to which they proved almost surely global well-posedness, coincides with the weighted Wiener measure con- structed by Thomann and Tzvetkov (24). Thus, in particular we prove the invariance of the measure constructed in (24).
The speed of cooling fronts and the functional form of the dimensionless viscosity in accretion disks

We examine the speed of inward-traveling cooling fronts in accretion disks. We show that their speed is determined by the rarefaction wave that precedes them and is approximately αFcF(H/r)q, where αF is the dimensionless viscosity, cF is the sound speed, r is the radial coordinate, H is the disk thickness, and all quantities are evaluated at the cooling front. The scaling exponent q lies in the interval [0, 1], depending on the slope of the (T, Σ) relation in the hot state. For a Kramer's law opacity and α ∝ (H/r)n, where n is of order unity, we find that q ~ 1/2. This supports the numerical work of Cannizzo, Chen, & Livio and their conclusion that n ≈ 3/2 is necessary to reproduce the exponential decay of luminosity in black hole X-ray binary systems. Our results are insensitive to the structure of the disk outside of the radius where rapid cooling sets in. In particular, the width of the rapid cooling zone is a consequence of the cooling front speed rather than its cause. We conclude that the exponential luminosity decay of cooling disks is probably compatible with the wave-driven dynamo model. It is not compatible with models with separate, constant values of α for the hot and cold states.
Concept formation vs. logistic regression: predicting death in trauma patients

This study compares two classification models used to predict survival of injured patients entering the emergency department. Concept formation is a machine learning technique that summarizes known examples/cases in the form of a tree. After the tree is constructed, it can then be used to predict the classification of new cases. Logistic regression, on the other hand, is a statistical model that allows for a quantitative relationship for a dichotomous event with several independent variables. The outcome (dependent) variable must have only two choices, e.g. does or does not occur, alive or dead. etc. The result of this model is an equation which is then used to predict the probability of class membership of a new case. The two models were evaluated on a trauma registry database composed of information on all trauma patients admitted in 1992 to a Level I trauma center. A total of 2155 records, representing all trauma patients admitted for more than 24 h or who died in the Emergency Department, were grouped into two databases as follows: (1) discharge status of 'died' (containing 151 records), and (2) any discharge status other than 'died' (containing 2004 records). Both databases contained the same variables.
Tungsten carbide (WC) synthesis from novel precursors

Abstract This paper deals with the production and properties of tungsten carbide (WC) powders from novel carbon coated precursors. The process has two steps in which the oxide powders were first coated with carbon by cracking of a hydrocarbon gas, propylene (C 3 H 6 ), secondly mixed with a substantial amount of carbon black, and finally treated at temperatures in the range of 600-1400°C for 2 h in flowing Ar or 10% H 2 -Ar atmosphere to synthesize WC. The produced powders were characterized using TEM, BET surface area analyzer, X-ray diffraction and chemical analysis (oxygen and carbon). The results obtained for various types of precursors treated in different atmospheres indicated that the coated precursors produced high quality powders. Single phase, submicron WC powders were synthesized at temperatures as low as 1100°C. WC powders produced at 1400°C for 2 h in flowing 10%H 2 -Ar gas mixture were submicron (3–5 m 2 /g), single phase, and had low oxygen content (0.2–0.5 wt%). The sintering tests demonstrated that these powders can be densified to near theoretical density using 20 wt% Co binder at 1500°C for 2 h in flowing 10%H 2 -Ar atmosphere.
Synthesis of a New MAX Compound (Cr0.5V0.5)2GeC and its Compressive Behavior up to 49 GPa

Abstract In this paper we report for the first time the synthesis of a new ternary layered ceramic (Cr 0.5 V 0.5 ) 2 GeC, a 211 M n +1 AX n compound by hot-pressing. Scanning electron microscopy and X-ray diffraction were used to characterize and confirm the hexagonal crystal structure of this ternary layered ceramic. The calculated lattice parameters are a = 2.9773 A and c = 12.1619 A. Using a diamond anvil cell and synchrotron radiation we also report the pressure dependencies of the lattice parameters. No phase transformation was observed and the phase is stable up to 49 GPa. The bulk modulus of (Cr 0.5 V 0.5 ) 2 GeC calculated using the Birch–Murnaghan equation of state is 219 ± 5 GPa with K ′ = 4.1 ± 0.3, which is higher than the end members V 2 GeC and Cr 2 GeC.
Many sparse cuts via higher eigenvalues

Cheeger's fundamental inequality states that any edge-weighted graph has a vertex subset S such that its expansion (a.k.a. conductance) is bounded as follows: [ φ(S) def= (w(S,bar{S}))/(min set(w(S), w(bar(S)))) ≤ √(2 λ2) ] where w is the total edge weight of a subset or a cut and λ2 is the second smallest eigenvalue of the normalized Laplacian of the graph. Here we prove the following natural generalization: for any integer k ∈ [n], there exist ck disjoint subsets S1, ..., Sck, such that [ maxi φ(Si) ≤ C √(λk log k) ] where λk is the kth smallest eigenvalue of the normalized Laplacian and c0 are suitable absolute constants. Our proof is via a polynomial-time algorithm to find such subsets, consisting of a spectral projection and a randomized rounding. As a consequence, we get the same upper bound for the small set expansion problem, namely for any k, there is a subset S whose weight is at most a O(1/k) fraction of the total weight and φ(S) ≤ C √(λk log k). Both results are the best possible up to constant factors. The underlying algorithmic problem, namely finding k subsets such that the maximum expansion is minimized, besides extending sparse cuts to more than one subset, appears to be a natural clustering problem in its own right.
The minimum period of the Ehrhart quasi-polynomial of a rational polytope

If P ⊆ Rd is a rational polytope, then ip(n) := #(nP ∩ Zd) is a quasi-polynomial in n, called the Ehrhart quasi-polynomial of P. The minimum period of ip(n) must divide D(P) = min{n ∈ Z >0:nP is an integral polytope}. Few examples are known where the minimum period is not exactly D(P). We show that for any D, there is a 2-dimensional triangle P such that D(P) = D but such that the minimum period of ip(n) is 1, that is, ip(n) is a polynomial in n. We also characterize all polygons P such that ip(n) is a polynomial. In addition, we provide a counterexample to a conjecture by T. Zaslavsky about the periods of the coefficients of the Ehrhart quasi-polynomial.
Synthesis of 7-membered cyclic hydroxyguanidines: Novel HIV-1 protease inhibitors

Abstract Novel cyclic 7-membered hydroxyguanidine based HIV-1 protease inhibitors have been synthesized from 7-membered cyclic thiourea.
Nematic Lyotropic Liquid Crystals as Media for Chemical Reactions

Abstract An old theme in liquid crystal research, first introduced by Svedberg in 1916, is the examination of how chemical reactivity is modulated by the anisotropy of the medium to result in changes in rates of reaction or structures of product. We have recently returned to this problem by examining reactions in aqueous lyotropic nematic media. One can identify systems in which phase transitions occur from rod to disc to spherical aggregates of amphiphiles as functions of either temperature or concentration of surfactant, cosurfactant, or electrolyte, and study model reactions occurring through these phase transitions. One can orient the lyotropic medium in a magnetic field and assess the degree of ordering of reactant and product and their penetration into the micellar media by spectroscopic methods.
A diastereo-and enantioselective synthesis of α-substituted anti-α,β-diaminophosphonic acid derivatives

Highly diastereo- and enantioselective additions of α-nitrophosphonates to imines catalyzed by a chiral Bronsted acid are described.
Multiplex de novo sequencing of peptide antibiotics

Proliferation of drug-resistant diseases raises the challenge of searching for new, more efficient antibiotics. Currently, some of the most effective antibiotics (i.e., Vancomycin and Daptomycin) are cyclic peptides produced by non-ribosomal biosynthetic pathways. The isolation and sequencing of cyclic peptide antibiotics, unlike the same activity with linear peptides, is time-consuming and error-prone. The dominant technique for sequencing cyclic peptides is NMR-based and requires large amounts (milligrams) of purified materials that, for most compounds, are not possible to obtain. Given these facts, there is a need for new tools to sequence cyclic NRPs using picograms of material. Since nearly all cyclic NRPs are produced along with related analogs, we develop a mass spectrometry approach for sequencing all related peptides at once (in contrast to the existing approach that analyzes individual peptides). Our results suggest that instead of attempting to isolate and NMR-sequence the most abundant compound, one should acquire spectra of many related compounds and sequence all of them simultaneously using tandem mass spectrometry. We illustrate applications of this approach by sequencing new variants of cyclic peptide antibiotics from Bacillus brevis, as well as sequencing a previously unknown familiy of cyclic NRPs produced by marine bacteria.
Agmon-kato-kuroda theorems for a large class of perturbations

We prove asymptotic completeness for operators of the form H=-Δ+L on L2(Rd), d≥2, where L is an admissible perturbation. Our class of admissible perturbations contains multiplication operators defined by real-valued potentials V∈Lq(Rd), q∈[d/2,(d+1)/2] (if d=2, then we require q∈(1,3/2]), as well as real-valued potentials V satisfying a global Kato condition. The class of admissible perturbations also contains first-order differential operators of the form a→·∇-∇·a→ for suitable vector potentials a. Our main technical statement is a new limiting absorption principle, which we prove using techniques from harmonic analysis related to the Stein-Tomas restriction theorem
Cationic Pd(II)-Catalyzed Fujiwara-Moritani Reactions at Room Temperature in Water

PdII-catalyzed Fujiwara−Moritani reactions can be carried out without external acid at room temperature and in water as the only medium. A highly active cationic PdII catalyst, [Pd(MeCN)4](BF4)2, easily activates aromatic C−H bonds to produce electron-rich cinnamates in good yields.
New N-heterocyclic carbene ligand and its application in asymmetric nickel-catalyzed aldehyde/alkyne reductive couplings.

A new chiral N-heterocyclic carbene ligand has been prepared and examined in nickel-catalyzed, asymmetric reductive couplings of aldehydes and alkynes. In comparison with related structures that have been largely examined in asymmetric ring-closing metathesis reactions, the new ligand provides superior yields and enantioselectivities in the nickel-catalyzed reductive couplings. The scope of asymmetric couplings in intermolecular variants as well as a 14-membered macrocyclization is illustrated.
FRAMEWORK FOR CONTROL OF DYNAMIC ICE BREAKUP BY RIVER REGULATION

Abstract : This report describes and classifies the entire range of ice breakup behavior, from the thermal to dynamic, to provide order to this complex process. The theory and model of the authors are refined, building on the concept of an intrinsic relationship between river waves and dynamic ice breakup. A force balance is developed for a common dynamic breakup behavior. Empirical criteria that quantify the resistance to breakup of an ice cover are obtained from a case study and compared with published values. Sensitivity studies of ice breakup with the completed model demonstrate insights that follow from the theory presented and the intuitive nature of the results. This framework for understanding river ice processes provides the option for ice management by river regulation, and we focus on the potential for control of ice breakup. The concept of controlled breakup involves a release of water from a dam that moves the ice downstream of locations with a high potential for damage during uncontrolled breakup. The abrupt, short-duration characteristics of the controlled release, patterned after those of unregulated river breakup, minimize both the volume of water required to cause breakup and the water levels at breakup. The open water created by the breakup collects heat that increases the rate of melting of the ice. The benefits of successful regulation include flooding prevention, minimum erosion, and decreased potential for ice damage to structures during breakup, with out adverse effects on the environment. keywords: Flood control; Ice jams; Ice management; River ice; Unsteady flow.
Particulate Matter Associated with Vehicles on the Road

Experiments at the Allegheny and Tuscarora Mountain Tunnels of the Pennsylvania Turnpike in 1975–1979 have resulted in a comprehensive description of the airborne particulate matter associated with highway traffic. Because of strong variations of traffic composition with time, emission rates of most species were resolvable into emission rates for each of the two vehicle categories: gasoline-powered vehicles and heavy-duty diesels. Thirty-four elements were identified, accounting for all of the vehicle-derived airborne particulate mass. The principal component was carbon (elemental and organic) from exhausts of heavy-duty diesels, which comprised on the average 10%–15% of the traffic. Per vehicle-kilometer, diesels were the preponderant source of most of the other species as well. Other emissions resulted from oxidation of diesel-fuel sulfur to H2SO4 (5% of the particulate mass total for traffic overall), inorganic additives and adventitious components of fuels and motor oils (10% of the overall mass total...
Planning and control for microassembly of structures composed of stress-engineered MEMS microrobots

We present control strategies that implement planar microassembly using groups of stress-engineered MEMS microrobots (MicroStressBots) controlled through a single global control signal. The global control signal couples the motion of the devices, causing the system to be highly underactuated. In order for the robots to assemble into arbitrary planar shapes despite the high degree of underactuation, it is desirable that each robot be independently maneuverable (independently controllable). To achieve independent control, we fabricated robots that behave (move) differently from one another in response to the same global control signal. We harnessed this differentiation to develop assembly control strategies, where the assembly goal is a desired geometric shape that can be obtained by connecting the chassis of individual robots. We derived and experimentally tested assembly plans that command some of the robots to make progress toward the goal, while other robots are constrained to remain in small circular trajectories (orbits) until it is their turn to move into the goal shape. Our control strategies were tested on systems of fabricated MicroStressBots. The robots are 240-280 Âµm A 60 Âµm A 7-20 Âµm in size and move simultaneously within a single operating environment. We demonstrated the feasibility of our control scheme by accurately assembling five different types of planar microstructures.
Reassessing the role of constituency in congressional voting

Poole and Rosenthal (1997) argue that mostcongressional voting can be understood in terms of alow-dimensional spatial model. This paper uses their model toassess the importance of the two mechanisms that couldcontribute to the vote-predicting power of constituencyvariables: (i) constituency variables may predict wherelegislators fall along one or two dimensions in thevote-predicting spatial model and (ii) constituency variablesmay account for errors in the spatial model's predictions. Thepaper compares different methods of using a basicset of constituency variables to generate out-of-sample predictionsfor representatives' votes. The analysis covers a large numberof recent House roll call votes, considering Democrats andRepublicans separately and using Poole and Rosenthal'sW-NOMINATE scores to measure legislators' locations invote-predicting space. The results show that the predictivepower of a basic set of constituency variables arisesprincipally from its ability to predict representatives'locations in Poole and Rosenthal's space, not from its abilityto explain errors in the predictions based on that space. Thisholds true to a remarkable extent, consistent with Poole andRosenthal's argument that the influence of constituentinterests occurs largely through logrolling mechanismsreflected in their spatial model.
Differential contraction of subducted lithosphere layers generates deep earthquakes

Abstract The origin of forces for generating deep earthquakes remains elusive. We propose a new mechanical model that involves constant release of shear strain accumulated between the crust and mantle lithosphere caused by differential volume changes during phase transformations as a slab sinks. This generates increasing down-dip compression inside the slab with depth, consistent with the global distribution of deep earthquake focal mechanisms. Using experimentally calibrated slab rheology, we show that the estimated distribution of slab internal stress agrees well with the depth–frequency relationship of deep earthquakes in both cold and warm slabs, with the peak in seismicity at ∼600 km depth corresponding to an induced stress maximum. This mechanism of residual stress within a cold slab also provides a solution to deep earthquakes occurring beneath former subduction zones such as western Tonga and Spain. We further suggest that this model may reconcile existing geodynamic paradoxes concerning the absolute strength of slabs, discrepancies on mantle rock strength between laboratory and geophysical inversions, as well as the competition between earthquake-generating stresses and slab-pull forces.