cssi/SciSciGPT-SciSciNet huggingface dataset:
Effects of gas hydrates on the chemical and physical properties of seawater

Abstract Huge deposits of oceanic methane hydrate (MH) exist on the seafloor on continental margins. MH transforms into water and methane (CH 4 ) gas in bubbles when it dissociates in seawater. That CH 4 may be oxidized (via bacteria) into carbon dioxide (CO 2 ) before the bubbles rise to the sea surface or dissolve into seawater again. Similarly, nitrogen hydrate is expected to exist in seawater. The nitrogen coming out of nitrogen hydrate can be fixed and oxidized into nitrate. Analysis of the relationship among seawater temperature, “apparent oxygen utilization” (AOU) and the concentration of CO 2, , based on WOCE ocean observations, reveals some characteristics that are not part of a stoichiometry relation. Analysis of individual profiles implies that the dissociation of gas hydrates occurs according to temperature and pressure (depth) at hydrate phase boundary. A quantity, named as virtual oxygen utilization (VOU), is calculated to account for the depletion of dissolved oxygen in seawater due to biochemical oxidation processes. The results show a good agreement between AOU and VOU at depth greater than the level where hydrates dissociate. The VOU is less than AOU in the layer of seawater beneath the euphotic zone. That is attributed to the escape of CO 2 into the atmosphere. The oceanic MH provides a huge biochemical fuel source to generate heat internal to world oceans. This may explain the observed ocean warming at the intermediate depth during last several decades. The role of microbes in altering the chemical and physical properties of seawater and the course of climate change cannot be ignored.
The Dynamic Effects of Firm-Level Borrowing Constraints

In this paper, I develop a detailed dynamic model of firm behavior in order to see whether financial constraints and endogenous exit are important propagation mechanisms.To do this, I construct an economy where firms face financial constraints, fixed costs, and persistent idiosyncratic shocks. Using numerical methods, I analyzehowa large collection of these firmsresponds to aggregate productivity shocks. A common result is that financial constraints tend to dampen the economy's initial response to aggregate productivity shocks but equity accumulation and exit dynamics amplify the longer-term response. The relative sizes of these two effects, however, are sensitive to firms' environments.
Trade facilitation in ASEAN member countries: Measuring progress and assessing priorities

This paper reviews recent progress and indicators of trade facilitation in member countries of the Association of Southeast Asian Nations. The findings show that import and export costs vary considerably in the member countries, from very low to moderately high levels. Tariff and non-tariff barriers are generally low to moderate. Infrastructure quality and services sector competitiveness range from fair to excellent. Using a standard gravity model, the authors find that trade flows in Southeast Asia are particularly sensitive to transport infrastructure and information and communications technology. The results suggest that the region stands to make significant economic gains from trade facilitation reform. These gains could be considerably larger than those from comparable tariff reforms. Estimates suggest that improving port facilities in the region, for example, could expand trade by up to 7.5 percent or $22 billion. The authors interpret this as an indication of the vital role that transport infrastructure can play in enhancing intra-regional trade.
The Dark Side of Rapport: Agent Misbehavior Face-to-Face and Online

A considerable body of research has extolled the virtues of establishing rapport in negotiations. Negotiators who are high in rapport tend to be more likely to reach an agreement and more satisfied with the outcome. Although rapport generally has been found to have positive effects in standard negotiation settings, we investigate the effects of rapport in impasse settings, where conflict between negotiators' core needs means that a successful deal can only be reached when one or both parties acts unethically or “misbehaves,” for example, by lying to the negotiation partner. In a series of three experiments, we find that negotiators who have a high level of rapport are more likely to behave unethically than are negotiators who have a low level of rapport. We find this effect holds both when high rapport results from the way in which negotiations are conducted (face-to-face versus computer mediated) and also when rapport is established through a brief rapport-building exercise before negotiations begin. Finally, we find that the negative effects (unethical behavior)---but not the positive effects (satisfaction with the negotiation, trust, and willingness to work in the future with the negotiation partner)---of high rapport are reduced when negotiators are given a simple reminder before negotiations begin that one's actions can have long-term repercussions for one's reputation. Taken together, this research supports the idea that, despite its several advantages, in certain situations rapport has a dark side, of which negotiators must be wary. This paper was accepted by Pradeep Chintagunta and Preyas Desai, special issue editors. This paper was accepted by Pradeep Chintagunta and Preyas Desai, special issue editors.
Multi-scale 3D scene flow from binocular stereo sequences

Scene flow methods estimate the three-dimensional motion field for points in the world, using multi-camera video data. Such methods combine multi-view reconstruction with motion estimation. This paper describes an alternative formulation for dense scene flow estimation that provides reliable results using only two cameras by fusing stereo and optical flow estimation into a single coherent framework. Internally, the proposed algorithm generates probability distributions for optical flow and disparity. Taking into account the uncertainty in the intermediate stages allows for more reliable estimation of the 3D scene flow than previous methods allow. To handle the aperture problems inherent in the estimation of optical flow and disparity, a multi-scale method along with a novel region-based technique is used within a regularized solution. This combined approach both preserves discontinuities and prevents over-regularization-two problems commonly associated with the basic multi-scale approaches. Experiments with synthetic and real test data demonstrate the strength of the proposed approach.
The Effect of Short Selling on Market Reactions to Earnings Announcements

This paper examines the effect of the inherent demand implied by short interest by studying how stock price reactions to earnings announcements depend on the level of short interest. We find that, for extreme good and bad news events, the inherent demand increases stock prices around the earnings announcement date, with the effect being stronger for good news relative to bad news. Specifically, the initial market reaction to an extreme positive earnings surprise is larger for firms with high levels of short interest. On the other hand, for an extreme negative earnings surprise event, the initial market reaction is less negative for heavily shorted firms. Furthermore, we find that the post-earnings-announcement drift is smaller (larger) in magnitude for extreme positive (negative) earnings surprises for the heavily shorted firms.
Vassiliev invariants and the cubical knot complex

Abstract We construct a cubical CW-complex CK(M) whose rational cohomology algebra contains Vassiliev invariants of knots in the 3-manifold M. We construct CK ( R 3 ) by attaching cells to CK( R 3 ) for every degenerate 1-singular and 2-singular knot, and we show that π 1 ( CK ( R 3 ))=1 and π 2 ( CK ( R 3 ))= Z . We give conditions for Vassiliev invariants to be nontrivial in cohomology. In particular, for R 3 we show that v2 uniquely generates H2(CK,D), where D is the subcomplex of degenerate singular knots. More generally, we show that any Vassiliev invariant coming from the Conway polynomial is nontrivial in cohomology. The cup product in H ∗ (CK) provides a new graded commutative algebra of Vassiliev invariants evaluated on ordered singular knots. We show how the cup product arises naturally from a cocommutative differential graded Hopf algebra of ordered chord diagrams.
Central Convection and Solar Neutrinos

Mixing in a convective core on a time scale that is short compared with the lifetime of ${\mathrm{Be}}^{7}$ against electron capture would reduce the flux of neutrinos resulting from ${\mathrm{B}}^{8}$ decay near the solar center.
On the extreme points of moments sets

Necessary and sufficient conditions for a measure to be an extreme point of the set of measures on a given measurable space with prescribed generalized moments are given, as well as an application to extremal problems over such moment sets; these conditions are expressed in terms of atomic partitions of the measurable space. It is also shown that every such extreme measure can be adequately represented by a linear combination of k Dirac probability measures with nonnegative coefficients, where k is the number of restrictions on moments; moreover, when the measurable space has appropriate topological properties, the phrase “can be adequately represented by” here can be replaced simply by “is”. Applications to specific extremal problems are also given, including an exact lower bound on the exponential moments of truncated random variables, exact lower bounds on generalized moments of the interarrival distribution in queuing systems, and probability measures on product spaces with prescribed generalized marginal moments.
Resolving three-dimensional anisotropic structure with shear wave splitting tomography

SUMMARY Shear wave splitting observations are a commonly used tool for inferring anisotropy and flow within the Earth's interior. Here we present the development and validation of a new technique for imaging anisotropy in the upper mantle using local events—shear wave splitting tomography (SWST). The mantle is parametrized as a 3-D block model of crystallographic orientations with the elastic properties of olivine and orthopyroxene, and both orthorhombic and hexagonal symmetries are tested. To efficiently forward calculate splitting, the Christoffel equation is used to progressively split the horizontal components of a synthetic wavelet in each block of the model, and predicted shear wave splitting parameters are obtained with an eigenvalue minimization technique. Numerically calculated partial derivatives are utilized in a linearized, damped least-squares inversion to solve for a best-fitting model of crystallographic orientations. To account for the non-linear properties of shear wave splitting, the inversion is applied iteratively and partial derivatives are recalculated after each iteration. A starting model that incorporates information from predicted splitting parameters is found by spatially averaging fast directions and the ratio of observed-to-predicted splitting times. Models from inversions utilizing this average starting model reach lower misfit levels than do inversions with a random or uniform starting model. Modelling results using synthetic data from several anisotropic structures (i.e. sharp lateral and vertical variations in anisotropy) both within an idealized and a real (Nicaragua–Costa Rica) subduction zone illustrate the capabilities and limitations of SWST. With a station spacing of 25 km in an idealized subduction zone containing uniformly spaced events down to 225 km, both the azimuth and dip of crystallographic axes are resolvable to a depth of 100–150 km and lateral heterogeneities in anisotropy on a scale of 50 km at arc and forearc distances from the trench are retrieved. Spatial resolution of anisotropy at scales of 75 km is possible further into the backarc above 150 km depth. The geometry of stations and observed seismicity in the Nicaragua–Costa Rica subduction zone yields partial to good resolution at scales of 50–75 km beneath the forearc, arc and limited regions of the backarc down to 100 km, and resolution at coarser scales is possible in wider regions beneath the backarc. Given the distributions of seismic sources within many subduction zones and the advances in broad-band seismic array deployments, this new method offers a powerful means with which to constrain the orientation of anisotropic fabric in the upper mantle.
STATE-DEPENDENT NOMINAL RIGIDITIES & DISINFLATION PROGRAMS IN SMALL OPEN ECONOMIES

Experiences of high-inflation economies suggest that exchange rate-based (ERB) and money-based (MB) disinflations induce sharply different dynamics in consumption and GDP. I study the role of nominal rigidities to explain such dynamics. I build on Calvo pricing to introduce elements of state-dependent into an otherwise standard small open economy. This new feature delivers state-dependent nominal rigidities (SDNR). Nonlinear simulations show that the model with SDNR generates a dynamic behavior consistent with both ERB and MB disinflations; however the model’s special case with constant nominal rigidities is not successful rationalizing ERB disinflations.
TGF-β inhibits Akt-induced transformation in intestinal epithelial cells

Background During the early stages of colorectal carcinogenesis, the phosphatidylinositol 3-kinase (PI3K)/Akt pathway is activated, enabling the transformed cells to survive and grow in the absence of anchorage to extracellular matrix. Transforming growth factor β (TGF-β) is an important tumor suppressor in the colon, and it is inactivated during later stages of colorectal carcinogenesis. The purpose of this study was to determine whether TGF-β inhibits Akt-induced anchorage-independent growth and resistance to anoikis in gut epithelial cells. Methods Rat intestinal epithelial cells (RIE-1) were infected with a retrovirus containing pLXSN-mAkt, and three independent clones were selected. Anchorage-independent growth was examined by colony formation in soft agar and cell counting in ultralow attachment plates. Anoikis was analyzed with the use of Annexin V staining. Results All three clones of RIE-1/mAkt formed colonies in soft agar, which were decreased by TGF-β. TGF-β induced anoikis and treatment with a general caspase inhibitor, zVAD-fluoromethyl ketone, blocked TGF-β–mediated decrease in colony formation. Conclusions TGF-β attenuated Akt-induced anchorage-independent growth in RIE-1 cells in part by enhancing anoikis. Our data demonstrate a novel tumor-suppressor activity of TGF-β and provide the molecular justification for the required activation of the PI3K/Akt pathway and the subsequent inactivation of TGF-β signaling during colorectal carcinogenesis.
Pipelining: the generalized concept and sequencing strategies

In this paper, we generalize the concept of pipelining to increase throughput, processing speed, resource utilization and reliability. Its wide application spectrum is demonstrated and major design problems such as sequencing, reconfiguration, etc., are indicated. A scheme called the dynamic sequencing and segmentation model (DSSM) is proposed as a solution for providing efficient sequencing with very low overhead. The model is analyzed under various realistic environments and its performance is evaluated.
A pocket-size broadband electric field detection and storage device

The radio-frequency (RF) dosimeter developed by the Oak Ridge National Laboratory is described. It is a portable, pocket-sized, cumulative-dose recording device designed to detect and record the strengths and durations of electric fields present in the work areas of naval vessels. The device measures an integrated dose and records the electric fields that exceed the permissible levels set by the American National Standards Institute. Features of the RF dosimeter include a frequency range of 30 MHz to 10 GHz and a three-dimensional sensor. Data obtained with the RF dosimeter will be used to determine the ambient field-strength profile for shipboard personnel over an extended time. Readings are acquired and averaged over a 6-min period corresponding to the rise time of the core body temperature. These values are stored for up to 6 months, after which the data are transferred to a computer by means on the dosimeter's serial port. >
Effects of Multiple Clients on the Reliability of Audit Reports

This paper demonstrates the existence of two different kinds of externalities induced by an auditor servicing multiple clients at the same time. First, we show that the capital market price for a client can increase in the number of qualified reports that his auditor issues to his other clients, thus producing a stock price externality. Second, when the audit firm has limited wealth, an additional client can actually decrease the audit quality and increase the average likelihood of audit failure relative to a single-client setting because of reporting externalities. Our analysis also demonstrates how requiring a more effective audit oversight mechanism can actually produce unintended consequences such as an increased likelihood of audit failures.
Information-Flow Control for Programming on Encrypted Data

Using homomorphic encryption and secure multiparty computation, cloud servers may perform regularly structured computation on encrypted data, without access to decryption keys. However, prior approaches for programming on encrypted data involve restrictive models such as boolean circuits, or standard languages that do not guarantee secure execution of all expressible programs. We present an expressive core language for secure cloud computing, with primitive types, conditionals, standard functional features, mutable state, and a secrecy preserving form of general recursion. This language, which uses an augmented information-flow type system to prevent control-flow leakage, allows programs to be developed and tested using conventional means, then exported to a variety of secure cloud execution platforms, dramatically reducing the amount of specialized knowledge needed to write secure code. We present a Haskell-based implementation and prove that cloud implementations based on secret sharing, homomorphic encryption, or other alternatives satisfying our general definition meet precise security requirements.
Writing up qualitative research … better

The article contains the conference given by professor Harry Wolcott in May 2003 in Medellin for the presentation of the second edition in Spanish of his book Writing Up Qualitative Research. He asks why is always the second chapter of a written report the ";Revision of Literature"; and could it be something else instead? He proposes for chapter two to be ";Linking Up"; of literature, theory and method as an alternative to the traditional literature review, on demand, as necessary, instead of treating this activities as independent exercises. With respect to literature review readers want to be engaged immediately with the problem being addressed. References are critical in helping to analyse and to situate the problem and the research in a broad context. Making the link to theory should be next, but until it is quite clear what is the research interest and how it relates to the report. Finally, linking up through method, what readers want to know is how data was obtained or what are the bases for making inferences. In this manner the researcher may inform the reader since the beginning with enough detail about the problem, its context, the theory it t articulates to and the method. Key words: qualitative research, writing research reports, report structure
Communication optimizations for fine-grained UPC applications

Global address space languages like UPC exhibit high performance and portability on a broad class of shared and distributed memory parallel architectures. The most scalable applications use bulk memory copies rather than individual reads and writes to the shared space, but finer-grained sharing can be useful for scenarios such as dynamic load balancing, event signaling, and distributed hash tables. In this paper we present three optimization techniques for global address space programs with fine-grained communication: redundancy elimination, use of split-phase communication, and communication coalescing. Parallel UPC programs are analyzed using static single assignment form and a dataflow graph, which are extended to handle the various shared and private pointer types that are available in UPC. The optimizations also take advantage of UPC's relaxed memory consistency model, which reduces the need for cross thread analysis. We demonstrate the effectiveness of the analysis and optimizations using several benchmarks, which were chosen to reflect the kinds of finegrained, communication-intensive phases that exist in some larger applications. The optimizations show speedups of up to 70% on three parallel systems, which represent three different types of cluster network technologies.
Optical Processors For Scene Analysis

Optical processors can perform the required operations for the various levels of a hierarchical/ inference computer vision system for scene analysis (detection, enhancement, recognition, feature extraction, and classification) on a multifunctional programmable optical architecture.
Switchable low-loss RF MEMS Ka-band frequency-selective surface

A switchable frequency-selective surface (FSS) was developed at 30 GHz using RF microelectromechanical systems (MEMS) switches on a 500-/spl mu/m-thick glass substrate. The 3-in-diameter FSS is composed of 909 unit cells and 3636 MEMS bridges with a yield of 99.5%. The single-pole FSS shows a transmission loss of 2.0 dB and a -3-dB bandwidth of 3.2 GHz at a resonant frequency of 30.2 GHz with the MEMS bridges in the up-state position. The -1-dB bandwidth is 1.6 GHz. When the MEMS bridges are actuated to the down-state position, an insertion loss of 27.5 dB is measured. Theory and experiment agree quite well. The power handling is limited to approximately 25 W with passive air cooling and >150 W with active air cooling due to the increased temperature of the overall circuit resulting from the transmission loss (for continuous-wave operation with the assumed maximum allowable temperature of 80/spl deg/C), or 370 W-3.5 kW due to self-actuation of the RF MEMS bridges (for pulsed incident power). Experimental results validate that 20 W of continuous-wave power can be transferred by the RF MEMS FSS with no change in the frequency response. This is the first demonstration of a switched low-loss FSS at Ka-band frequencies.
Racial Discrimination Among NBA Referees

The NBA provides an intriguing place to assess discrimination: referees and players are involved in repeated interactions in a high-pressure setting, with referees making split-second decisions that might allow implicit racial biases to become evident. We find that more personal fouls are awarded against players when they are officiated by an opposite-race officiating crew than when they are officiated by an own-race refereeing crew. These biases are sufficiently large so that they affect the outcome of an appreciable number of games. Our results do not distinguish whether the bias stems from the actions of white or black referees.
Lithium MAS NMR studies of cathode materials for lithium-ion batteries

The application of NMR spectroscopy to study the cathode materials used in lithium-ion rechargeable batteries is described. The research described in this review article clearly demonstrates that it is now possible to obtain a wealth of information from the spectra of these materials, even in the paramagnetic or metallic state, both prior and following electrochemical cycling of a battery. First, we review the work performed at Stony Brook and elsewhere, initially to develop a detailed understanding of the shift mechanisms that result in the large shifts in the spectra of paramagnetic lithium manganates, and then, to apply this knowledge to probe local structure and electronic properties in a range of materials. NMR of a wider range of cathode materials is then briefly discussed. Finally, the experimental methods typically used in this field are briefly described.
Corruption in Developing Countries

Recent years have seen a remarkable expansion in economists' ability to measure corruption. This in turn has led to a new generation of well-identified, microeconomic studies. We review the evidence on corruption in developing countries in light of these recent advances, focusing on three questions: how much corruption is there, what are the efficiency consequences of corruption, and what determines the level of corruption? We find robust evidence that corruption responds to standard economic incentive theory but also that the effects of anticorruption policies often attenuate as officials find alternate strategies to pursue rents.
O-minimal residue fields of o-minimal fields

Abstract Let R be an o-minimal field with a proper convex subring V . We axiomatize the class of all structures ( R , V ) such that k ind , the corresponding residue field with structure induced from R via the residue map, is o-minimal. More precisely, in Mařikova (2010) [8] it was shown that certain first-order conditions on ( R , V ) are sufficient for the o-minimality of k ind . Here we prove that these conditions are also necessary.
A Flared, Orbiting, Dusty Disk around HD 233517

We find that the infrared excess around HD 233517, a first-ascent red giant, can be explained naturally if the star possesses an orbiting, flared, dusty disk. We estimate that the outer radius of this disk is ~45 AU and the total mass within the disk is ~0.01 M☉. We speculate that this disk is the result of the engulfment of a low-mass companion star that occurred when HD 233517 became a red giant.
The index of a numerical semigroup ring

Abstract Let R = k [ ∣ t a , t b , t c ∣ ] be a complete intersection numerical semigroup ring over an infinite field k , where a , b , c ∈ N . The generalized Loewy length, which is Auslander’s index in this case, is computed in terms of the minimal generators of the semigroup: a , b and c . Examples provided show that the left hand side of Ding’s inequality mult ( R ) − index ( R ) − codim ( R ) + 1 ≥ 0 can be made arbitrarily large for rings R with edim ( R ) = 3 . The index of a complete intersection numerical semigroup ring with embedding dimension greater than three is also computed.
A novel electrode array for diameter-dependent control of axonal excitability: a Simulation study

Electrical extracellular stimulation of peripheral nerve activates the large-diameter motor fibers before the small ones, a recruitment order opposite the physiological recruitment of myelinated motor fibers during voluntary muscle contraction. Current methods to solve this problem require a long-duration stimulus pulse which could lead to electrode corrosion and nerve damage. The hypothesis that the excitability of specific diameter fibers can be suppressed by reshaping the profile of extracellular potential along the axon using multiple electrodes is tested using computer simulations in two different volume conductors. Simulations in a homogenous medium with a nine-contact electrode array show that the current excitation threshold (I/sub th/) of large diameter axons (13-17 /spl mu/m) (0.6-3.0 mA) is higher than that of small-diameter axons (2-7 /spl mu/m) (0.4-0.7 mA) with 200-/spl mu/m axon-electrode distance and 10-/spl mu/s stimulus pulse. The electrode array is also tested in a three-dimensional finite-element model of the sacral root model of dog (ventral root of S3). A single cathode activates large-diameter axons before activating small axons. However, a nine-electrode array activates 50% of small axons while recruiting only 10% of large ones and activates 90% of small axons while recruiting only 50% of large ones. The simulations suggest that the near-physiological recruitment order can be achieved with an electrode array. The diameter selectivity of the electrode array can be controlled by the electrode separation and the method is independent of pulse width.
Stereo Matching with Transparency and Matting

This paper formulates and solves a new variant of the stereo correspondence problem: simultaneously recovering the disparities, true colors, and opacities of visible surface elements. This problem arises in newer applications of stereo reconstruction, such as view interpolation and the layering of real imagery with synthetic graphics for special effects and virtual studio applications. While this problem is intrinsically more difficult than traditional stereo correspondence, where only the disparities are being recovered, it provides a principled way of dealing with commonly occurring problems such as occlusions and the handling of mixed (foreground/background) pixels near depth discontinuities. It also provides a novel means for separating foreground and background objects (matting), without the use of a special blue screen. We formulate the problem as the recovery of colors and opacities in a generalized 3D (x, y, d) disparity space, and solve the problem using a combination of initial evidence aggregation followed by iterative energy minimization.
Simulating the Effects of Gravitational Field and Atmosphere on Behavior of Granular Media

Designs for structures, vehicles, and equipment to be used on the surfaces of the moon and Mars cannot be optimized without a knowledge of how soils in various gravitational fields and atmospheric conditions behave when subjected to static and dynamic loading. Strengths of the lunar and Martian gravitational fields (0.17 and 0.38 times terrestrial, respectively) can be simulated for approximately 30 sec by flying the KC-135 aircraft through appropriate parabolas. Effects of gravitational field on explosion crater formation and projectile penetration have been investigated. Techniques devised for use in these tests are discussed. Diameters of explosion craters and depths of projectile penetration in sand were found to increase as the gravitational field strength decreased. Atmospheric pressure variations down to ultra-high vacuum are significant in the behavior of rock powders. Approaches used in ultra-high vacuum tests on adhesion and compressibility of basalt powders are discussed. The forces of adhesion between rock powders and metal alloy surfaces were noted to be greater in ultra-high vacuum than in air. The forces required to compress slowly a basalt powder are greater after bakeout and exposure to ultra-high vacuum than when this rock powder is tested at atmospheric pressure.
Physical design refinement: The ‘merge-reduce’ approach

Physical database design tools rely on a DBA-provided workload to pick an “optimal” set of indexes and materialized views. Such tools allow either creating a new such configuration or adding new structures to existing ones. However, these tools do not provide adequate support for the incremental and flexible refinement of existing physical structures. Although such refinements are often very valuable for DBAs, a completely manual approach to refinement can lead to infeasible solutions (e.g., excessive use of space). In this article, we focus on the important problem of physical design refinement and propose a transformational architecture that is based upon two novel primitive operations, called merging and reduction. These operators help refine a configuration, treating indexes and materialized views in a unified way, as well as succinctly explain the refinement process to DBAs.
Carcinogenicity of N′-Nitrosonornicotine in Sprague-Dawley Rats

N'-Nitrosonornicotine was added to the drinking water of outbred Sprague-Dawley rats. Adenocarcinomas of the olfactory epithelium occurred in all 15 rats, squamous papillomas o- the esophagus in 1, squamous papillomas of the nonglandular stomach in 1, and a hepatacellular tumor in 1. The possible ingestion and subsequent in vivo nitrosation of nicotine and/or nornicotine could create a serious carcinogenic hazard to cigarette smokers.
On Variational Principles for Gravitating Perfect Fluids

Abstract The connection is established between two different action principles for perfect fluids in the context of general relativity. For one of these actions,S, the fluid four–velocity is expressed as a sum of products of scalar fields and their gradients (the velocity–potential representation). For the other action,S, the fluid four–velocity is proportional to the totally antisymmetric product of gradients of the fluid Lagrangian coordinates. The relationship betweenSandSis established by expressingSin Hamiltonian form and identifying certain canonical coordinates as ignorable. Elimination of these coordinates and their conjugates yields the actionS. The key step in the analysis is a point canonical transformation in which all tensor fields on space are expressed in terms of the Lagrangian coordinate system supplied by the fluid. The canonical transformation is of interest in its own right. It can be applied to any physical system that includes a material medium described by Lagrangian coordinates. The result is a Hamiltonian description of the system in which the momentum constraint is trivial.
High-Frequency VLBI Imaging of the Jet Base of M87

VLBA and Global VLBI observations of M87 at 43 GHz, some new and some previously published, are used to study the structural evolution of the jet with a spatial resolution of under 100 Schwarzschild radii. The images, taken between 1999 and 2004, have an angular resolution of 0.00043'' × 0.00021''. An edge-brightened jet structure and an indication of a large opening angle at the jet base are seen in all five epochs. In addition, a probable counterjet is seen in the latter three epochs. A 22 GHz VLBA image also confirms many of the structures seen at the higher frequency, including the counterjet. A comparison of the counterjet flux density at 22 and 43 GHz reveals that it is not free-free absorbed at these frequencies. Attempts to obtain speeds from the proper motions of jet and counterjet components indicate that these observations are undersampled. The closest pair of images gives apparent speeds of (0.25-0.40)c for the jet and 0.17c for the counterjet. These speeds should be treated as lower limits because of possible errors in associating components between epochs. If they are real, they indicate that the jet is oriented 30°-45° from the line of sight and that the component speeds along the jet are (0.3-0.5)c. Using the jet orientation derived from proper motions, the spectral index of the counterjet, and a jet-to-counterjet brightness ratio of 14.4, the inferred bulk flow is (0.6-0.7)c, which, given the considerable uncertainties in how to measure the brightness ratio, is not significantly larger than the component speed.
Nanostructured electrochromic smart windows: traditional materials and NIR-selective plasmonic nanocrystals

Electrochromic devices, which dynamically change colour under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterials, which can provide electrochromic devices with improved colouration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. In an effort to demonstrate a new type of electrochromic device that goes beyond the capabilities of commonly used electrochromic materials, researchers have turned to plasmonic transparent conductive oxide (TCO) nanocrystals. Electrochemical injection of electrons into plasmonic TCO nanocrystal films induces a shift in the plasmon frequency and gives rise to the new functionality of selective optical modulation in the near-infrared region of the solar spectrum. These nanocrystals can be used as building blocks to enable creation of advanced electrochromic devices containing mesoporous electrodes or nanocrystal-in-glass composites. Such devices have been important in advancing the field towards achieving the ideal smart window with independent control over visible and NIR transmittance.
Direct Enantioselective Organocatalytic Hydroxymethylation of Aldehydes Catalyzed by α,α-Diphenylprolinol Trimethylsilyl Ether

The direct enantioselective hydroxymethylation of aldehydes utilizing α,α-diphenylprolinol trimethylsilyl ether as an organocatalyst is described. The intermediate α-substituted β-hydroxyaldehydes were not isolated but converted to the more readily isolable derivatives. For example, the derived hydroxy acids were isolated in up to 94% yield with excellent enantioselectivity.
Preorthodontic Uncovering and Autonomous Eruption of Palatally Impacted Maxillary Canines

Palatally impacted maxillary canines are a challenge for any orthodontist. Often the surgeon will perform an incorrect uncovering technique, the orthodontic mechanics to erupt the tooth could be inappropriate, and as a result the periodontal and esthetic outcome could be disastrous. However, in the adolescent patient, the management of palatally impacted maxillary canines can be predictable, stable, and esthetic. However, to accomplish these results, the orthodontist and surgeon must select the appropriate method of surgical uncovering. This article discusses the advantages of preorthodontic uncovering and autonomous eruption of palatally impacted maxillary canines. The surgical technique will be described and illustrated, and consecutively treated cases will be displayed. An evidence-based discussion will feature the benefits of preorthodontic uncovering and autonomous eruption of palatally impacted maxillary canines.
Degradation in performance of adaptive null-steering antennas

The degradation in the overall main beam gain performance capability of a phased array, which necessarily accompanies the required formation of pattern nulls, is quantified in a simple way. A simulation illustrates the formulation.
A primogenitary linked quad tree approach for solution storage and retrieval in heuristic binary optimization

Abstract A data structure, called the primogenitary linked quad tree (PLQT), is used to store and retrieve solutions in heuristic solution procedures for binary optimization problems. Two ways are proposed to use integer vectors to represent solutions represented by binary vectors. One way is to encode binary vectors into integer vectors in a much lower dimension and the other is to use the sorted indices of binary variables with values equal to 0 or equal to 1. The integer vectors are used as composite keys to store and retrieve solutions in the PLQT. An algorithm processing trial solutions for insertion into or retrieval from the PLQT is developed. Examples are provided to demonstrate the way the algorithm works. Another algorithm traversing the PLQT is also developed. Computational results show that the PLQT approach takes only a very tiny portion of the CPU time taken by a linear list approach for the same purpose for any reasonable application. The CPU time taken by the PLQT managing trial solutions is negligible as compared to that taken by a heuristic procedure for any reasonably hard to solve binary optimization problem, as shown in a tabu search heuristic procedure for the capacitated facility location problem. Compared to the hashing approach, the PLQT approach takes the same or less amount of CPU time but much less memory space while completely eliminating collision.
Interaction between directional epistasis and average mutational effects.

We investigate the relationship between the average fitness decay due to single mutations and the strength of epistatic interactions in genetic sequences. We observe that epistatic interactions between mutations are correlated to the average fitness decay, both in RNA secondary structure prediction as well as in digital organisms replicating in silico . This correlation implies that, during adaptation, epistasis and average mutational effect cannot be optimized independently. In experiments with RNA sequences evolving on a neutral network, the selective pressure to decrease the mutational load then leads to a reduction in the amount of sequences with strong antagonistic interactions between deleterious mutations in the population.
TOTAL SYNTHESIS OF (+)-CURACIN A, A MARINE CYTOTOXIC AGENT

Abstract The total synthesis of curacin A, a cytotoxic agent that interacts with the colchicine binding site on tubulin, is described. The convergent synthesis utilizes natural product and chiral pool starting materials (geraniol, serine) and asymmetric synthesis (chiral allylborane addition, Charette cyclopropanation) to procure the various chiral fragments in enantiomerically pure form. The assembly of the natural product involves carbon-carbon bond formation (Julia coupling) and heterocycle preparation (Wipf thiazoline synthesis).
Magnesium halide-catalyzed anti-aldol reactions of chiral N-acylthiazolidinethiones.

Diastereoselective direct aldol reactions of chiral N-acylthiazolidinethiones occur in high yield with preference for the illustrated anti diastereomer. This reaction is catalyzed by 10% MgBr2·OEt2 in the presence of triethylamine and chlorotrimethylsilane. Yields range from 56 to 93% with diastereoselectivity up to 19:1 for a variety of N-acylthiazolidinethiones and unsaturated aldehydes.
Piercing Translates and Homothets of a Convex Body

According to a classical result of Grunbaum, the transversal number τ(ℱ) of any family ℱ of pairwise-intersecting translates or homothets of a convex body C in ℝd is bounded by a function of d. Denote by α(C) (resp. β(C)) the supremum of the ratio of the transversal number τ(ℱ) to the packing number ν(ℱ) over all finite families ℱ of translates (resp. homothets) of a convex body C in ℝd . Kim et al. recently showed that α(C) is bounded by a function of d for any convex body C in ℝd , and gave the first bounds on α(C) for convex bodies C in ℝd and on β(C) for convex bodies C in the plane. Here we show that β(C) is also bounded by a function of d for any convex body C in ℝd , and present new or improved bounds on both α(C) and β(C) for various convex bodies C in ℝd for all dimensions d. Our techniques explore interesting inequalities linking the covering and packing densities of a convex body. Our methods for obtaining upper bounds are constructive and lead to efficient constant-factor approximation algorithms for finding a minimum-cardinality point set that pierces a set of translates or homothets of a convex body.
Prediction of the flowfield in laser propulsion devices

The difficulties encountered in modeling laser heating in a propulsive nozzle are discussed. Two basic formulations, an approximate low Mach number analysis or the complete Navier-Stokes equations, can be used. The former reduces to a single ordinary differential equation for which the mass flow is an eigenvalue. This representation has been considered by several researchers, but the precision with which the eigenvalue must be determined makes it impractical to obtain solutions for some values of the parameters. The present paper contains the first reported solutions to the complete Navier-Stokes equations for this problem. These results, which were obtained with an implicit time-marching method, no longer contain an eigenvalue, but the complex, rapidly developing physics in the flowfield prevent convergence in some regimes. Solutions for laser absorption in hydrogen-seedant mixtures demonstrate that the position of the heat absorption region is controlled by the incoming beam intensity while the mass flux is determined by the nozzle throat area. These two methods are related to each other by showing that the eigenvalue analysis is a rational approximation to the Navier-Stokes equations.
Helicopter Blade Response and Aeromechanical Stability with a Magnetorheological Fluid Based Lag Damper

This paper explores the feasibility of using Magnetorheological (MR) fluid-based dampers for lag damping augmentation in helicopters. An MR damper model is integrated with a rotor aeromechanical model. Two different control schemes are presented-namely the On-Off scheme and the Feedback Linearization scheme. In the On-Off scheme, two criteria are used to obtain equivalent linear damping for the nonlinear MR damper as a function of the size of perturbation and the applied field. The Feedback Linearization scheme uses a feedback controller to linearize the force output of the MR damper. The two control schemes are compared for lag transient response in ground resonance and their ability to reduce periodic damper loads in forward flight. It is shown that an MR damper of a size comparable to an elastomeric damper can provide sufficient damping for ground resonance stabilization and can significantly reduce periodic damper loads with ajudicious choice of operation scheme.
A framework for studying synaptic plasticity with neural spike train data

Learning and memory in the brain are implemented by complex, time-varying changes in neural circuitry. The computational rules according to which synaptic weights change over time are the subject of much research, and are not precisely understood. Until recently, limitations in experimental methods have made it challenging to test hypotheses about synaptic plasticity on a large scale. However, as such data become available and these barriers are lifted, it becomes necessary to develop analysis techniques to validate plasticity models. Here, we present a highly extensible framework for modeling arbitrary synaptic plasticity rules on spike train data in populations of interconnected neurons. We treat synaptic weights as a (potentially nonlinear) dynamical system embedded in a fully-Bayesian generalized linear model (GLM). In addition, we provide an algorithm for inferring synaptic weight trajectories alongside the parameters of the GLM and of the learning rules. Using this method, we perform model comparison of two proposed variants of the well-known spike-timing-dependent plasticity (STDP) rule, where nonlinear effects play a substantial role. On synthetic data generated from the biophysical simulator NEURON, we show that we can recover the weight trajectories, the pattern of connectivity, and the underlying learning rules.
Comparison of supercritical airfoil flow calculations with wind tunnel results

Navier-Stokes calculations have been performed for a supercritical airfoil at a transonic design condition and at a subsonic condition. Wind-tunnel pressure-rail measurements were employed as boundary data in the calculations to account for wall-interference effects. A fine mesh was used so that most details of the flows were resolved, particular attention having been given to the trailing-edge region. Detailed comparisons are made with the experimental data. Good agreement was obtained on the airfoil except at the trailing edge where separation occurred. Flow details in the trailing-edge region are examined and differences are shown to be attributable to the turbulence model employed.
Instrumentation for the Gamma-ray Large Area Space Telescope (GLAST) mission

The Gamma-ray Large Area Space Telescope (GLAST) is the next orbiting high-energy gamma-ray mission, scheduled for launch by NASA in 2006. The GLAST Observatory will have two scientific instruments: (1) the Large Area Telescope (LAT), an imaging, wide field-of-view telescope sensitive to radiation over the energy range from ~20 MeV to more than 300 GeV, and (2) the GLAST Burst Monitor (GBM), sensitive to transient bursts from 10 keV to 25 MeV. The GBM is described elsewhere in this proceedings by Lichti, et al. The LAT, a pair-conversion telescope, is being developed by an international collaboration from the United States, France, Italy, Japan, and Sweden. It will have sensitivity more than 40 times better than that of EGRET. In this paper the LAT instrument, its expected performance, and the current state of its development are described.