cssi/SciSciGPT-SciSciNet huggingface dataset:
A comparison of heuristics for a school bus scheduling problem

The study was carried out in North carolina to identify which procedure gave good bus schedules for realistically sized problems using a reasonable amount of computer time, so that multiple runs with parameter changes were economically possible. The main objective is to combine trips to minimise the size of the required fleet and travel costs. The three heuristics used were 'assmt', 'orl', and 'ilp' and were used on a group of 30 sample problems from actual bus data gathered from 113 routes and 15 schools with 10 distinct opening times. Results suggested that each of the heuristics could provide good schedules. However, although significantly faster, assmt appeared to produce some combinations needing manual adjustment. Although icp provided consistently good solutions, it required a large linear programming package, and could give non integer solutions. Feasible combinations were generated by orl, but it required the largest amount of computer time and often gave inferior solutions. It is suggested that for trips of 200 or more the potential savings in capital costs could not justify the use of ilp and orl, at the same time, the manual adjustments required by assmt could be excessive. (TRRL)
Kinetics of intersubband optical excitation and photoinduced electron transfer in an asymmetric double quantum well

Optical excitation of electrons in an asymmetric double quantum well is theoretically examined. The well is biased to align the excited levels and permit resonant electron tunneling. Emphasis is made on the photoinduced transfer of electrons counter to the bias electric-field force. Systems with a weak polarization relaxation (dephasing) are studied with use of the conventional Schr\"odinger-equation technique. A density-matrix approach is developed to describe optical excitations in the presence of an arbitrary dephasing. Quantum beats, which follow a short-pulse excitation of the double well, are shown to depend crucially on the dephasing. The excitation profiles obtained for cases of different dephasing reveal the full range of tunneling coupling between the wells from completely coherent to incoherent (stepwise).
Regional variations of the Caribbean mid-summer drought

Pentad satellite-based precipitation estimates were input into a wavelet analysis to quantify the length, timing, and strength of the mid-summer drought (MSD) for the Caribbean Sea and surrounding regions. For most of the Caribbean the time between the first and second summer precipitation maxima is 98 to 117 days (∼3 to 4 months). The MSD appears in early-June over Puerto Rico and Hispaniola, and develops progressively later in the summer season towards the west, finally occurring in early-October over the Gulf of Mexico. The MSD is most intense in the eastern Pacific, strong and significant in the western Caribbean, and almost nonexistent in the eastern Caribbean. Forcing mechanisms are examined to help explain the regional variability in the Caribbean. A July increase in surface pressure and surface divergence, caused by the changing wind field, appears to contribute to a strong concurrent MSD over the waters bounded by Jamaica, Cuba, and the Yucatan peninsula. Finally, the island of Jamaica itself appears to block the flow of the tradewinds as they migrate northward and intensify into mid-summer, thus enhancing the divergence, and in turn MSD, immediately to the west.
Geometry of the Prytz planimeter

Abstract The Prytz planimeter is a simple example of a system governed by a nonholonomic constraint. It is unique among planimeters in that it measures something more subtle than area, combining the area, centroid and other moments of the region being measured, with weights depending on the length of the planimeter. As a tool for measuring area, it is most accurate for regions that are small relative to its length. The configuration space of the planimeter is a non-principal circle bundle acted on by SU (1,1) (≈ SL(2, R)). The motion of the planimeter is realized as parallel translation for a connection on this bundle and for a connection on a principal SU(1, 1)-bundle. The holonomy group is SU(1,1). As a consequence, the planimeter is an example of a system with a phase shift on the circle that is not a simple rotation. There is a qualitative difference in the holonomy when tracing large regions as opposed to small ones. Generic elements of SU(1,1) act on S1 with two fixed points or with no fixed points. When tracing small regions, the holonomy acts without fixed points. Menzin's conjecture states (roughly) that if a planimeter of length l traces the boundary of a region with area A > πl2, then it exhibits an asymptotic behaviour and the holonomy acts with two fixed points, one attracting and one repelling. This is obvious if the region is a disk, and intuitively plausible if the region is convex and A > πl2. A proof of this conjecture is given for a special case, and the conjecture is shown to imply the isoperimetric inequality.
Dynamics of an A-DNA homopolymer crystal with sodium ions: A Green-function approach

We apply lattice dynamics to calculate the vibrational modes of a perfect A-DNA homopolymer crystal with sodium ions. A Green-function method is used to reduce the dimension of the matrix to be diagonalized. We concentrate on the biologically significant crystal modes with frequencies less than 100 wave numbers. 94% of the crystal modes were likely to be located in this frequency range. Characteristics of the crystal modes are analyzed. We find that the interhelical modes dominate in the frequency range 25--30 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and the intrahelical modes dominate for frequencies greater than 80 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The infrared absorption peaks at 35, 50, and 83 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in our model. The former two bands are not counterion dependent and the latter one is. Our Raman scattering spectrum peaks around 30 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and it is strongly counterion dependent. The counterion-dependency trend of this band is the same as that of the experimental 25-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ feature, extrapolated to 0 relative humidity, observed in both DNA and RNA crystals. The characteristics of the experimental Raman scattering features at 25 and 35 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ are consistent with our results.
Molecular and Immunopathology Studies of Oncogenes and Tumor-Suppressor Genes in Bladder Cancer

Target genes implicated in cellular transformation and tumor progression have been divided into two categories: proto-oncogenes (that when activated become dominant events characterized by gain of function) and tumor-suppressor genes (recessive events characterized by the loss of function). Alterations in proto-oncogenes and tumor-suppressor genes seem equally prevalent among human cancers. Multiple mutations appear to be required to conform the malignant phenotype. It is therefore conceivable that cancer be viewed fundamentally as a genetic disease entailing inherited (also calledgerm-line) and/or acquired (also termedsomatic) mutations of genes in these two categories. Molecular studies of bladder neoplasms have identified a series of nonrandom genetic alterations affecting a particular set of oncogenes and tumor-suppressor genes. Because the modality of therapy for patients with bladder neoplasms primarily depends onmorphological evaluation and clinical staging, the diagnosis carries significant consequences. However, it is well known that morphologically similar tumors presenting in any assigned stage may behave in radically different fashions, which seriously hampers the physician's ability accurately to predict clinical behavior in a given case. Recent studies have shown that inactivation of certain tumor-suppressor genes, such as RB andTP53, occur in bladder tumors that have a more aggressive clinical outcome and poor prognosis. In the present paper we review the molecular abnormalities associated with these dominant and recessive genes in bladder cancer and discuss the potential clinical use of their detection. The implementation of objective predictive assays to identify these alterations in clinical material will enhance our ability to assess tumor biological activities and to design effective treatment regimens. The need now is to translate this newly developed scientific knowledge into diagnostic and therapeutic strategies, which in turn will enhance the quality of life and prolong the survival of patients with bladder cancer.
The dusty starburst nucleus of M33

We have thoroughly characterized the ultraviolet to near-infrared (0.15-2.2 μm) spectral energy distribution (SED) of the central parsec of the M33 nucleus through new infrared photometry and optical/near-infrared spectroscopy, combined with ultraviolet/optical observations from the literature and the Hubble Space Telescope archive. The SED shows evidence for a significant level of attenuation, which we model through a Monte Carlo radiative transfer code as a shell of clumpy Milky Way-type dust (τV ~ 2 ± 1). The discovery of Milky Way-type dust (with a strong 2175 A bump) internal to the M33 nucleus is different from previous work, which has found SMC-like dust (no bump) near starburst regions. The amount by which dust can be processed may be related to the mass and age of the starburst as well as the extent to which the dust can shield itself. Our starburst models include the effects of this dust and can fit the SED if the nucleus was the site of a moderate (~108 L☉ at 10 Myr) episode of coeval star formation about 70 Myr ago. This result is quite different from previous studies, which resorted to multiple stellar populations (between two and seven) attenuated by either no or very little internal dust. The M33 nuclear starburst is remarkably similar to an older version (70 versus 10 Myr) of the ultracompact starburst in the center of the Milky Way.
A Death-Defying Attempt to Articulate a Coherent Definition of Environmental History

В первой части статьи содержится обзор становления дисциплины истории окружающей среды, начиная с представлений о том, что люди являются биологическими субъектами, чье поведение можно объяснить с помощью моделей, заимствованных из зоологии, экологии и прочих наук о природе, до утверждения представлений о сложной культурной обусловленности человеческой деятельности. Дуглас Уинер показывает, к каким изменениям в дисциплине привел отказ от эссенциализированных и стабильных понятий природы и культуры (размежевание с собственно экологами, эпистемологический постструктурализм и даже утеря дисциплиной четкого объекта изучения). Автор приводит примеры из собственного исследования, посвященного истории природозащиты в СССР начиная со сталинских времен для иллюстрации тезиса о том, что история окружающей среды есть всегда история властных отношений, и не только власти и общества, но и конкуренции элит внутри общества и пр. С этой точки зрения во второй части статьи рассматриваются советская и нацистская политики преобразования природы и общества, а также имперская логика захвата и колонизации (на примере Британской империи в Индии) и идеологическая обусловленность представлений о прогрессивном освоении среды модерным национализмом (на примере сионистской риторики освоения Палестины). В заключительной части статьи автор позиционирует историю окружающей среды в системе более устоявшихся исторических дисциплин, подчеркивая присущую ей высокую методологическую рефлексивность, новаторский характер проблематизации истории “природы” и “культуры”, а также ее общественно-политическую значимость.
Natural and engineered biosynthesis of fluorinated natural products

Both natural products and synthetic organofluorines play important roles in the discovery and design of pharmaceuticals. The combination of these two classes of molecules has the potential to be useful in the ongoing search for new bioactive compounds but our ability to produce site-selectively fluorinated natural products remains limited by challenges in compatibility between their high structural complexity and current methods for fluorination. Living systems provide an alternative route to chemical fluorination and could enable the production of organofluorine natural products through synthetic biology approaches. While the identification of biogenic organofluorines has been limited, the study of the native organisms and enzymes that utilize these compounds can help to guide efforts to engineer the incorporation of this unusual element into complex pharmacologically active natural products. This review covers recent advances in understanding both natural and engineered production of organofluorine natural products.
Spitzer IRAC Observations of White Dwarfs. II. Massive Planetary and Cold Brown Dwarf Companions to Young and Old Degenerates

This paper presents a sensitive and comprehensive IRAC 3-8 μm photometric survey of white dwarfs for companions in the planetary-mass regime with temperatures cooler than the known T dwarfs. The search focuses on descendents of intermediate-mass stars with M 3 M☉ whose inner, few hundred AU regions cannot be probed effectively for massive planets and brown dwarfs by any alternative existing method. Furthermore, examination for mid-infrared excess explores an extensive range of orbital semimajor axes, including the intermediate 5-50 AU range, poorly covered and incompletely accessible by other techniques at main-sequence or evolved stars. Three samples of white dwarfs are chosen which together represent relatively young as well as older populations of stars: nine open cluster white dwarfs, 22 high-mass field white dwarfs, and 17 metal-rich field white dwarfs. In particular, these targets include: seven Hyades and four field white dwarfs of similar age, one Pleiades and 19 field white dwarfs of similar age, and van Maanen 2 and 16 similarly metal-rich white dwarfs with ages between 1 and 7 Gyr. No substellar companion candidates were identified at any star. By demanding a 15% minimum photometric excess at 4.5 μm to indicate a companion detection, upper limits in the planetary-mass regime are established at 34 of the sample white dwarfs, 20 of which have limits below 10 MJ according to substellar cooling models. Specifically, limits below the minimum mass for deuterium burning are established at all Pleiades and Hyades white dwarfs, as well as similarly young field white dwarfs, half a dozen of which receive limits at or below 5 MJ. Two IRAC epochs at vMa 2 rule out T 200 K proper-motion companions within 1200 AU.
The implications of hydrogen emission line ratios in quasi-stellar objects

The results of multilevel, depth-dependent, fully interlocked radiative transfer calculations for hydrogen emission line strengths in a single QSO emission line cloud (ELC) are summarized. The hydrogen-line forming region of the ELC is found to be quite thick (tau sub el between 1,000 and 100,000), which is consistent with heating of a pure hydrogen cloud by photoionization. Results indicate that the volume-averaged escape probability approach introduces large errors by assuming, in effect, that a single point in the ELC is representative of the emergent radiation; that the influence of frequency redistribution on the photon escape probability in resonance and subordinate lines must be explicitly recognized, and that full consistency between excitation and ionization processes must be maintained.
Allowances for Corporate Equity in Practice

This article provides an overview of full and partial allowance for corporate equity (ACE) tax systems in practice. In the recent past, ACE systems existed in Austria, Croatia and Italy. Brazil still applies a variant of such a system and Belgium introduced one in 2006. This article summarizes the empirical literature on past ACE systems, and provides a theoretical and empirical assessment of the Brazilian ACE variant. The main finding is that the Brazilian reform introduced an ACE system for a minority of firms only, with the majority instead having a system of dividend deductibility. Despite the reduction in the tax preference for debt finance, capital structures have not changed much, but dividends have increased. Investment appears to have benefited from the reform, although the extent to which this was due to the new structure rather than the tax cut is unclear. (JEL codes: H25, H21, C33) Copyright , Oxford University Press.
Integration and conventional systems at STAR

At the beginning of the design and construction of the STAR Detector, the collaboration assigned a team of physicists and engineers the responsibility of coordinating the construction of the detector. This group managed the general space assignments for each sub-system and coordinated the assembly and planning for the detector. Furthermore, as this group was the only STAR group with the responsibility of looking at the system as a whole, the collaboration assigned it several tasks that spanned the different sub-detectors. These items included grounding, rack layout, cable distribution, electrical, power and water, and safety systems. This paper describes these systems and their performance.
Zodiacal dust bands - Their relation to asteroid families

The zodiacal dust band phenomenon is presently reproduced by a mathematical model of orbitally evolved collisional debris spatial distributions whose torus exhibits particle-density maxima at heliocentric latitudes near its constituent particles' mean proper orbital inclinations, as well as near the loci of the particle orbits' perihelia and aphelia. Models of dust toruses for seven asteroid families are generated and compared with observations of the principal dust bands. Nonequilibrium models of dust band production and evolution furnish a framework within which all dust band observations can be understood.
The Coronal X-ray Spectrum of the Multiple Weak-Lined T Tauri Star System HD 98800

We present high-resolution X-ray spectra of the multiple (hierarchical quadruple) weak-lined T Tauri star system HD 98800, obtained with the High Energy Transmission Grating Spectrograph (HETGS) on board the Chandra X-Ray Observatory. In the zeroth-order Chandra/HETGS X-ray image, both principle binary components of HD 98800 (A and B, separation 08) are detected; component A was observed to flare during the observation. The infrared excess (dust disk) component, HD 98800B, is a factor of ~4 fainter in X-rays than the apparently "diskless" HD 98800A in quiescence. The line ratios of He-like species (e.g., Ne IX and O VII) in the HD 98800A spectrum indicate that the X-ray-emitting plasma around HD 98800 is in a typical coronal density regime (log n 11). We conclude that the dominant X-ray-emitting component(s) of HD 98800 is (are) coronally active. The sharp spectral differences between HD 98800 and the classical T Tauri star TW Hya demonstrate the potential utility of high-resolution X-ray spectroscopy in providing diagnostics of pre-main-sequence accretion processes.
The Combinatorics of Biased Riffle Shuffles

This paper studies biased riffle shuffles, first defined by Diaconis, Fill, and Pitman. These shuffles generalize the well-studied Gilbert-Shannon-Reeds shuffle and convolve nicely. An upper bound is given for the time for these shuffles to converge to the uniform distribution; this matches lower bounds of Lalley. A careful version of a bijection of Gessel leads to a generating function for cycle structure after one of these shuffles and gives new results about descents in random permutations. Results are also obtained about the inversion and descent structure of a permutation after one of these shuffles.
Using hybrid alignment for iterative sequence database searches

Progressive sequence model refinement by means of iterative searches is an effective technique for high sensitivity database searches and is currently employed in popular tools such as PSI-BLAST and SAM. Recently, a novel alignment algorithm has been proposed that offers features expected to improve the sensitivity of such iterative approaches, specifically a well-characterized theory of its statistics even in the presence of position-specific gap costs. Here, we demonstrate that the new hybrid alignment algorithm is ready to be used as the alignment core of PSI-BLAST. In addition, we evaluate the accuracy of two proposed approaches to edge effect correction in short sequence alignment statistics that turns out to be one of the crucial issues in developing a hybrid-alignment based version of PSI-BLAST. Copyright © 2004 John Wiley & Sons, Ltd.
Instrumental Variable Estimation of Nonlinear Errors-in-Variables Models

This paper establishes that instruments enable the identification of nonparametric regression models in the presence of measurement error by providing a closed form solution for the regression function in terms of Fourier transforms of conditional expectations of observable variables. For parametrically specified regression functions, we propose a root n consistent and asymptotically normal estimator that takes the familiar form of a generalized method of moments estimator with a plugged-in nonparametric kernel density estimate. Both the identification and the estimation methodologies rely on Fourier analysis and on the theory of generalized functions. The finite-sample properties of the estimator are investigated through Monte Carlo simulations.
The federal depository library system: A descriptive analysis

Abstract It is the intention of the investigators to provide an overall panoramic view of the U.S. Federal Documents Depository system. Basic characteristics of the depository libraries in the system are provided and an attempt made to determine significant relationships among these descriptive variables. Certain sub-populations of the depository libraries are singled out for special attention. These are depository libraries in academic institutions, depositories subscribing to less than 25% of depository item categories, and libraries which had given up their depository status between 1970 and 1976. Perhaps the most significant finding of the study is the relatively low priority given in many depositories to documents as witnessed by the small number of staff assigned to work in this area.
Toric stacks I: The theory of stacky fans

The purpose of this paper and its sequel is to introduce and develop a theory of toric stacks which encompasses and extends several notions of toric stacks defined in the literature, as well as classical toric varieties. In this paper, we define a toric stack as the stack quotient of a toric variety by a subgroup of its torus (we also define a generically stacky version). Any toric stack arises from a combinatorial gadget called a stacky fan. We develop a dictionary between the combinatorics of stacky fans and the geometry of toric stacks, stressing stacky phenomena such as canonical stacks and good moduli space morphisms. We also show that smooth toric stacks carry a moduli interpretation extending the usual moduli interpretations of P^n and [A^1/G_m]. Indeed, smooth toric stacks precisely solve moduli problems specified by (generalized) effective Cartier divisors with given linear relations and given intersection relations. Smooth toric stacks therefore form a natural closure to the class of moduli problems introduced for smooth toric varieties and smooth toric DM stacks in papers by Cox and Perroni, respectively. We include a plethora of examples to illustrate the general theory. We hope that this theory of toric stacks can serve as a companion to an introduction to stacks, in much the same way that toric varieties can serve as a companion to an introduction to schemes.
Synthesis of a 28-mer oligosaccharide core of Mycobacterial lipoarabinomannan (LAM) requires only two n-pentenyl orthoester progenitors

Regioselective glycosidation of acceptor polyols greatly reduces the number of orthogonal protecting groups that are normally required for conventional syntheses of highly branched oligosaccharides. The MATCH between a donor and one of the many-OHs is the basis of a simple, ready synthesis of the 28-mer oligosaccharide described in this manuscript. The strategy relies heavily upon the unique interplay between n-pentenyl orthoesters (NPOEs), n-pentenyl glycosides, ytterbium triflate, and N-iodosuccinimide which allows exquisite, high-yielding regio- and chemoselective glycosylations. The NPOEs, effective as mannose or arabinose donors, are the sole sources of all saccharide components of the lipoarabinomannan oligosaccharide. Once considerable systematic research had been invested, the 12-mer mannan, 92, and 16-mer capped arabinan, 91, domains can be rapidly assembled in 300 mg and 1 g quantities, respectively, using conventional laboratory equipment. The 28-mer, 93 (MW = 11122.54) is, as far as we are aware of, the largest hetero-oligosaccharide that has been synthesized.
Identifiable reparametrizations of linear compartment models

Structural identifiability concerns finding which unknown parameters of a model can be quantified from given input-output data. Many linear ODE models, used in systems biology and pharmacokinetics, are unidentifiable, which means that parameters can take on an infinite number of values and yet yield the same input-output data. We use commutative algebra and graph theory to study a particular class of unidentifiable models and find conditions to obtain identifiable scaling reparametrizations of these models. Our main result is that the existence of an identifiable scaling reparametrization is equivalent to the existence of a scaling reparametrization by monomial functions. We provide an algorithm for finding these reparametrizations when they exist and partial results beginning to classify graphs which possess an identifiable scaling reparametrization.
Anomaly matching conditions and the moduli space of supersymmetric gauge theories

Abstract The structure of the moduli space of N = 1 supersymmetric gauge theories is analyzed from an algebraic geometric viewpoint. The connection between the fundamental fields of the ultraviolet theory, and the gauge-invariant composite fields of the infrared theory is explained in detail. The results are then used to prove an anomaly matching theorem. The theorem is used to study anomaly matching for supersymmetric QCD, and can explain all the known anomaly matching results for this case.
Numerical studies of the photoluminescence spectrum of quantum Hall systems

Abstract The eigenfunctions and eigenvalues of a system consisting of a finite number of electrons on a two-dimensional plane together with a few holes on a neighboring plane are obtained by numerical diagonalization within the subspace of the lowest Landau level. The energy spectrum and ground state energy per particle are studied as a function of the Landau level degeneracy and the interlayer separation. By evaluating the square of the matrix element of the luminescence operator between the initial state with N e electrons and one hole and various final states with N e − 1 electrons and no hole, and multiplying by a delta function which conserves energy, the luminescence intensity I (Ω) is obtained.
The Phenomenological Status of Late Time Phase Transition Models after Cosmic Background Radiation Anisotropy Measurements

Some relatively model-independent results for structure formation via late time phase transitions (LTPT) are discussed. In particular, generic LTPT power spectra are presented. The implication of the recent Cosmic Background Explorer (COBE) detection of the cosmic background radiation (CBR) anisotropy at large angular scales (greater than or approximately equal to 7 deg) and the tight upper limits from small angular scales (approximately 1 deg) to LTPT models are discussed. Special attention is focused on the observational constraints and possible non-Gaussian signatures of CBR temperature anisotropies from LTPT and other non-Gaussian models. It is shown that while LTPT have been seriously constrained by the recent data, viable models do remain which provide more power on the 100-200 Mpc scales than do more traditional primordial Gaussian density fluctuation models. Tests for such models are presented, including possible anisotropies on angular scales less than 8 min.
Accuracy of Least Squares Solutions

I HAVE recently obtained the solution of this problem: Given n linear equations of condition in m unknowns, and that (1) the set of errors of the equations of condition are a sample drawn at random from a normal population of unknown standard deviation, and that (2) nothing more is known about the values of the unknowns or of than that which can be inferred from the equations of condition, then (A) what are the values of the unknowns—By rigorous, direct methods, and with no further assumptions, I have obtained the distribution functions in answer to question (A). They are the same as those which Jeffreys1 obtained in semi-intuitive fashion, by making the somewhat arbitrary assumption that the “prior probability” that lies in a certain range d is proportional simply to d/.
Between the penthouse and the outhouse: the sorting of economics professors

Oyer (2007, 2008) considered the turnover of economics professors early in their careers. He found professors are more likely to move down from higher ranked schools than up from lower ranked schools. An asymmetric information model suggests this phenomenon is explained by imperfect screening at one's initial hiring. The smaller the fraction of more able individuals, and the more accurate the screening, the greater the chance downward movement exceeds upward movement.
Finite temperature correlations in the one-dimensional quantum Ising model.

Abstract We extend the form-factors approach to the quantum Ising model at finite temperature. The two-point function of the energy is obtained in closed form, while the two-point function of the spin is written as a Fredholm determinant. Using the approach of Korepin et al., we obtain, starting directly from the continuum formulation, a set of six differential equations satisfied by this two-point function. Four of these equations involve only space-time derivatives, of which three are equivalent to the equations obtained earlier. In addition, we obtain two new equations involving a temperature derivative. Some of these results are generalized to the Ising model on the half line with a magnetic field at the origin.
Dynamic performance measurement with intangible assets

The increasing importance of intangible assets in modern economies is driving companies to include measures of intangible assets in managerial performance evaluations. For the multiperiod principal-agent model analyzed in this paper, a manager must be motivated to invest in intangible assets like customer satisfaction or product quality. The intangible asset is not verifiable for contracting purposes, but the parties can rely on a noisy indicator of the current asset value. I derive a class of value added performance measures, which effectively aggregate the current cash flow and consecutive realizations of the noisy indicator of the intangible asset. This class of performance measures is shown to be optimal for different scenarios regarding contract commitment and observability of the actual investment decisions. Long-term contracts are examined as a baseline. However, in practice firms usually adopt shorter medium-term contracts that are periodically renegotiated. I show that this more realistic contracting scenario yields the same investment patterns and efficiency levels as those obtained under long-term commitment.
On q-Gaussians and exchangeability

The q-Gaussian distributions introduced by Tsallis are discussed from the point of view of variance mixtures of normals and exchangeability. For each , there is a q-Gaussian distribution that maximizes the Tsallis entropy under suitable constraints. This paper shows that q-Gaussian random variables can be represented as variance mixtures of normals when q > 1. These variance mixtures of normals are the attractors in central limit theorems for sequences of exchangeable random variables, thereby providing a possible model that has been extensively studied in probability theory. The formulation provided has the additional advantage of yielding, for each q, a process which is naturally the q-analog of the Brownian motion. Explicit mixing distributions for q-Gaussians should facilitate applications to areas such as option pricing. The model might provide insight into the study of superstatistics.
Optimum Skewed Redundant Inertial Navigators

The problem of proper placement of the inertial sensors to optimize system performance is important to system designers. This is especially true of redundant strapdown systems that employ more sensors than the conventional, mutually orthogonal sets of three. In systems designed for a free fall environment and with no preferred direction, such as for spacecraft attitude reference, the sensor input axes should divide the three-space equally, and can thus be viewed as being normal to the faces of regular polyhedra.' In Earth-bound inertial navigators, the effect of gravity-dependent sensor errors and the generally reduced effect of azimuth errors on navigation accuracy significantly alter the situation. Both effects tend to decrease sensor elevation angles in an optimized system. Formulas are derived and curves are drawn for optimum sensor elevation and azimuth angles vs a 0-sensitive sensor error parameter, and a mission relative azimuth error parameter. Tetrad, pentad, and hexad arrays are analyzed, affording a dramatic improvement in accuracy as well as autonomous fault isolation and/or detection capability.
Flow insensitive points-to sets

Abstract Pointer analysis is an important part of source code analysis. Many programs that manipulate source code take points-to sets as part of their input. Points-to related data collected from 27 mid-sized C programs (ranging in size from 1168 to 87,579 lines of code) is presented. The data shows the relative sizes and the complexities of computing points-to sets. Such data is useful in improving algorithms for the computation of points-to sets as well as algorithms that make use of this information in other operations.
New Proofs for NMAC and HMAC: Security without Collision Resistance

HMAC was proved in Bellare et al. (Advances in Cryptology---CRYPTO'96, Springer, Berlin, Heidelberg, 1996) to be a PRF assuming that (1) the underlying compression function is a PRF, and (2) the iterated hash function is weakly collision resistant. However, subsequent attacks showed that assumption (2) is false for MD5 and SHA-1, removing the proof-based support for HMAC in these cases. This paper proves that HMAC is a PRF under the sole assumption that the compression function is a PRF. This recovers a proof-based guarantee since no known attacks compromise the pseudorandomness of the compression function, and it also helps explain the resistance to attack that HMAC has shown even when implemented with hash functions whose (weak) collision resistance is compromised. We also show that an even weaker than PRF condition on the compression function, namely that it is a privacy-preserving MAC, suffices to establish HMAC is a secure MAC as long as the hash function meets the very weak requirement of being computationally almost universal, where again the value lies in the fact that known attacks do not invalidate the assumptions made.
Synthesis and Biological Activities of Flavonoid Derivatives as A3 Adenosine Receptor Antagonists

A broad screening of phytochemicals has demonstrated that certain flavone and flavonol derivatives have a relatively high affinity at A3 adenosine receptors, with Ki values of > or = 1 microM (Ji et al. J. Med. Chem. 1996, 39, 781-788). We have further modified the flavone structure to achieve a degree of selectivity for cloned human brain A3 receptors, determined in competitive binding assays versus [125I]AB-MECA[N6-(4-amino-3-iodobenzyl)adenosine-5'-(N-methylur onamide)]. Affinity was determined in radioligand binding assays at rat brain A1 and A2a receptors using [3H]-N6-PIA ([3H]-(R)-N6-phenylisopropyladenosine) and [3H]CGS21680 [[3H]-2-[[4-(2-carboxyethyl)phenyl]ethylamino]-5'-(N-ethylcarbamoyl++ +)adenosine], respectively. The triethyl and tripropyl ether derivatives of the flavonol galangin, 4, had Ki values of 0.3 - 0.4 microM at human A3 receptors. The presence of a 5-hydroxyl group increased selectivity of flavonols for human A3 receptors. The 2',3,4',7-tetraethyl ether derivative of the flavonol morin, 7, displayed a Ki value of 4.8 microM at human A3 receptors and was inactive at rat A1/A2a receptors. 3,6-Dichloro-2'-(isopropyloxy)-4'-methylflavone, 11e, was both potent and highly selective (approximately 200-fold) for human A3 receptors (Ki = 0.56 microM). Among dihydroflavonol analogues, the 2-styryl instead of the 2-aryl substituent, in 15, afforded selectivity for human A3 vs rat A1 or A2A receptors. The 2-styryl-6-propoxy derivative, 20, of the furanochromone visnagin was 30-fold selective for human A3 receptors vs either rat A1 or A2A receptors. Several of the more potent derivatives effectively antagonized the effects of an agonist in a functional A3 receptor assay, i.e. inhibition of adenylyl cyclase in CHO cells expressing cloned rat A3 receptors. In conclusion, these series of flavonoids provide leads for the development of novel potent and subtype selective A3 antagonists.
Robotic mitral valve surgery

The first robotic mitral valve repair was performed in May 1998 by Dr. Carpentier using an early prototype of the da Vinci® articulated intracardiac »wrist« robotic device. A week later, Dr. Mohr performed the first coronary anastomosis and repaired five mitral valves with the device. Grossi et al. of New York University partially repaired a mitral valve using the Zeus™ system (Computer Motion, Inc.) but no annuloplasty ring was inserted. Four days later, in May 2000, our group performed the first complete da Vinci® mitral repair in North America. Subsequently, we performed 20 other mitral repairs as part of a phase I safety and efficacy Food and Drug Administration (FDA) trial. These initial results were encouraging and prompted a phase II multicenter FDA trial that was completed in 2002. A total of 112 patients were enrolled at 10 different institutions and all types of repair were performed. The excellent results of these studies prompted FDA approval of the da Vinci® system for mitral valve (MV) surgery in November 2002. Just 8 years later, robotic assisted MV repair surgery became standard at many centers across the world with excellent results. All types of repairs, including complex bileaflet repairs, are currently performed routinely using only ports and a 2- to 4-cm mini-incision. Still further technological developments will eventually lead to better total endoscopic mitral valve repairs. To this end, we are on the cusp of developing a closed-chest operation that can be reproduced by many surgeons.
Chemistry of carbonyl-derived ligands. Nucleophilic attack on anionic acetylide clusters

The broad range of reactions of anionic ketenylidene clusters is reviewed. We then describe some chemistry of the triiron nonacarbonyl acetylide clusters (PPN)[Fe3(CO)9CCOR] (Ia,Ib), (a: R = CH2CH3; b: R = C(O)CH3; PPN = bis(triphenylphosphine)iminium (1 +), (Ph3P)2N+), which are derived from the iron ketenylidene (PPN)2[Fe3(CO)9CCO]. The ethoxyacetylide cluster Ia adds a single phosphine to form a phosphonium alkyne (PPN)[Fe3(CO)9PMePh2CCOEt] (II). In contrast, Ib reacts with loss of acetate anion to form an unusual phosphonium acetylide cluster [Fe3(CO)9CCPMePh2] (III), which is also formed cleanly by protonation of II with one equivalent of triflic acid, HSO3CF3. Implications of the formation of these products on bonding and mechanism are considered. Clusters II and III are spectroscopically characterized, and a single crystal X-ray structure determination of II and III are reported. (PPN)[Fe3(CO)9PMePh2CCOEt] (II) crystallizes in the triclinic space group P1; a 9.910(1); b 16.920(2); c 17.372(2) A; α 74.83(1)°; β 84.65(1)°; γ 86.07(1)°; V 2796(1) A3; Z = 2. [Fe3(CO)9CCPMePh2] (III) crystallizes with an orthorhombic lattice; space group Pbca; a 7.898(1); b 19.885(2); c 31.906(5) A; V 5011(2) A3; Z = 8.
The growth of silicon nitride crystalline films using microwave plasma enhanced chemical vapor deposition

Crystalline thin films of silicon nitride have been grown on a variety of substrates by microwave plasma-enhanced chemical vapor deposition using N2, O2, and CH4 gases at a temperature of 800 °C. X-ray diffraction and Rutherford backscattering measurements indicate the deposits are stoichiometric silicon nitride with varying amounts of the α and β phases. Scanning electron microscopy imaging indicates β-Si3N4 possesses sixfold symmetry with particle sizes in the submicron range. In one experiment, the silicon necessary for growth comes from the single crystal silicon substrate due to etching/sputtering by the nitrogen plasma. The dependence of the grain size on the methane concentration is investigated. In another experiment, an organo-silicon source, methoxytrimethylsilane, is used to grow silicon nitride with controlled introduction of the silicon necessary for growth. Thin crystalline films are deposited at rates of 0.1 μm/h as determined by profilometry. A growth mechanism for both cases is proposed.
A Pelvic Muscle Precontraction Can Reduce Cough-Related Urine Loss in Selected Women With Mild SUI

OBJECTIVES: To test the hypothesis that selected older women with mild-to-moderate stress urinary incontinence (SUI) can learn to demonstrate significantly reduced urine loss in 1 week by intentionally contracting the pelvic floor muscles before and during a cough (a skill we have termed “The Knack”). DESIGN: A prospective, randomized, single-blind interventional study. SETTING: The Older American Independence Center, a federally sponsored research program affiliated with the University of Michigan in Ann Arbor, Michigan. PARTICIPANTS: Twenty-seven women with a mean (SD) age of 68.0 (5.5) years, self-reported SUI, and demonstrable urine loss during a deep cough. INTERVENTION: Women were randomized to an immediate intervention group (Group I: n = 13) who were taught the Knack after their first clinic visit, or a wait-listed control group (Group II: n = 14) who were taught the Knack after 1 month. MEASUREMENTS: At 1 week after instruction, we tested the efficacy of the Knack in a standing stress test by (1) comparing the volumes of cough-related urine loss leaked by all subjects, with and without use of the Knack, and (2) comparing the volumes of cough-related urine loss leaked by Group I, using the Knack, with Group II, which had not yet been taught the Knack. RESULTS: Intra-individual results showed that at 1-week follow-up, the Knack was used to reduce urine loss resulting from a medium cough by an average of 98.2%, compared with that of a similar cough performed 1 minute before without the Knack (P =.009); likewise urine loss was reduced by an average of 73.3% (P =.003) in a deep cough. Reduction in urine loss was not significantly correlated with a digital measure of pelvic floor muscle strength. CONCLUSION: Within 1 week, selected older women with mild-to-moderate SUI can acquire the skill of using a properly-timed pelvic floor muscle contraction to significantly reduce urine leakage during a cough.
D-branes on the null-brane

We study D-branes in the null-brane background. Using the covariant formalism of the worldsheet theory, we construct the boundary states describing D-branes on the null-brane. From the cylinder amplitudes, we find that the D-branes with codimension zero or two have time-dependent effective tensions.
AN/APS-137 inverse synthetic aperture radar system enhancement through gallium arsenide IC insertion

The use of bipolar GaAs ICs is evaluated with respect to the AN/APS-137 Inverse Synthetic Aperture Radar (ISAR) system on the basis of power and size requirements and resolution quality. System upgrades include a software change and other modifications in the receiver weapon-replaceable assembly (WRA). A block diagram of the receiver WRA is given which describes the modified circuitry after the insertion of GaAs ICs. A 250-MHz technology is required to achieve a 200 MHz sampling rate with 80-percent reliability derating, and the GaAs satisfies this requirement. The IC designs are described with particular attention given to the data buffer and delay generator and related operational requirements. It is shown that the two GaAs ASICs using the Standard Gate structure can provide the resolution improvements required for the AN/APS-137 radar ISAR range.
A decision support system and a heuristic interactive approach for solving discrete multiple criteria problems

The paper consists of two parts: (1) a decision-support system (DSS) for discrete multiple criteria decision-making (MCDM) problems; and (2) a heuristic interactive approach when the decision-maker (DM) responds to paired comparisons of alternatives. In the DSS, the DM is provided with flexibility in terms of using different approaches, different assumptions, and manipulating and controlling the solution procedure in a very simple and convenient way. In the interactive approach it is assumed that the DM wishes to maximize an unknown quasiconcave utility function for discrete MCDM problems. Several heuristic procedures are developed for ranking and eliminating alternatives, assuming that the DM can make paired comparisons and indicate strength of preference. An interactive paired comparison method is developed using these heuristics and a gradient-based procedure. Heuristic approaches for finding local adjacent discrete points to approximate the gradient and for identifying discrete points for the one-dimensional search are discussed. >
THE ROBUSTNESS OF ABNORMAL RETURNS FROM THE EARNINGS YIELD CONTRARIAN INVESTMENT STRATEGY

We examine the sensitivity of the abnormal profitability of the earnings' yield (E/P)-based contrarian investment strategy to the following two risk measurement issues: (a) return-measurement interval over which systematic risk is estimated and (b) time variation in systematic risk. We conduct our analysis using the capital asset pricing model to parameterize risk. We find that the estimates of systematic risk of E/P-ranked portfolios are not sensitive to the return-measurement interval. Consequently the abnormal profits to the E/P-based contrarian investment strategy observed in prior studies are not artifacts of the return-measurement interval. Furthermore, although both the raw and abnormal returns to E/P-ranked portfolios exhibit mean reversion, time variation in systematic risk ensuing from this mean-reverting behavior does not substantially affect abnormal profits to E/P-ranked portfolios. JEL classification: G11, G12, G14
Materials Chemistry in 3D Templates for Functional Photonics

This Perspective overviews many of the developments in templated porous three-dimensional photonics, with a particular focus on functional architectures, and provides suggestions for future opportunities for research. A significant diversity of 3D structures is available today with characteristic dimensions appropriate for providing strong light–matter interactions, in no small part due to recent advances in 3D patterning techniques. However, the optical functionality of these structures has generally remained limited. Advances in materials chemistry have the opportunity to dramatically increase the function of templated 3D photonics, and a few examples of highly functional templated 3D photonics for sensing, solar energy harvesting, optical metamaterials, and light emission are presented as first examples of success.