cssi/SciSciGPT-SciSciNet huggingface dataset:
Solid Motor Aft Closure Insulation Erosion

The erosion rate of aft closure insulation in a number of large solid propellant motors was empirically analyzed by correlating the average ablation rate with a number of variables that had previously been demonstrated to affect heat flux. The main correlating parameter was a heat flux based on the simplified Bartz heat transfer coefficient corrected for two-dimensional effects. A multiplying group contained terms related to port-to-throat ratio, local wall angle, grain geometry and nozzle cant angle. The resulting equation gave a good correlation and is a useful design tool.
On the level sets of the Takagi-van der Waerden functions

Abstract This paper examines the level sets of the continuous but nowhere differentiable functions f r ( x ) = ∑ n = 0 ∞ r − n ϕ ( r n x ) , where ϕ ( x ) is the distance from x to the nearest integer, and r is an integer with r ≥ 2 . It is shown, by using properties of a symmetric correlated random walk, that almost all level sets of f r are finite (with respect to Lebesgue measure on the range of f), but that for an abscissa x chosen at random from [ 0 , 1 ) , the level set at level y = f r ( x ) is uncountable almost surely. As a result, the occupation measure of f r is singular.
The War on Poverty's Experiment in Public Medicine: Community Health Centers and the Mortality of Older Americans

This paper uses the rollout of the first Community Health Centers (CHCs) to study the longer-term health effects of increasing access to primary care. Within ten years, CHCs are associated with a reduction in age-adjusted mortality rates of 2 percent among those 50 and older. The implied 7 to 13 percent decrease in one-year mortality risk among beneficiaries amounts to 20 to 40 percent of the 1966 poor/non-poor mortality gap for this age group. Large effects for those 65 and older suggest that increased access to primary care has longer-term benefits, even for populations with near universal health insurance. (JEL H75, I12, I13, I18, I32, I38, J14).
PROJECTED THREE-POINT CORRELATION FUNCTIONS AND GALAXY BIAS

The three-point correlation function (3PCF) can now be measured in large galaxy redshift surveys, but in three dimensions its interpretation is complicated by the presence of redshift-space distortions. I investigate the projected 3PCF, where these distortions are eliminated by integrating over the redshift dimension, as is commonly done for the two-point correlation function. The calculation of the projected 3PCF from the real-space, three-dimensional bispectrum is greatly simplified by expanding both quantities in Fourier components, analogous to Szapudi's expansion of the three-dimensional quantities in multipole components. In the weakly nonlinear regime, the bispectrum can be well represented by the first few Fourier components. There is a well-known relation between the reduced 3PCFs of matter and galaxies in the weakly nonlinear regime, which can be used to infer galaxy bias factors if the real-space three-dimensional galaxy correlation functions (two-point and three-point) can be measured. I show that the same relation holds for the reduced projected 3PCFs if these are properly defined. These results should aid determinations of galaxy bias from large redshift surveys by eliminating the complication of redshift-space distortions.
Approximately optimal mechanism design: motivation, examples, and lessons learned

This survey describes the approximately optimal mechanism design paradigm and uses it to investigate two basic questions in auction theory. First, when is complexity --- in the sense of detailed distributional knowledge --- an essential feature of revenue-maximizing single-item auctions? Second, do combinatorial auctions require high-dimensional bid spaces to achieve good social welfare?
Correcting velocity dispersions of dwarf spheroidal galaxies for binary orbital motion

We show that the measured velocity dispersions of dwarf spheroidal galaxies from about 4 to 10 km s^(–1) are unlikely to be inflated by more than 30% due to the orbital motion of binary stars and demonstrate that the intrinsic velocity dispersions can be determined to within a few percent accuracy using two-epoch observations with 1-2 yr as the optimal time interval. The crucial observable is the threshold fraction—the fraction of stars that show velocity changes larger than a given threshold between measurements. The threshold fraction is tightly correlated with the dispersion introduced by binaries, independent of the underlying binary fraction and distribution of orbital parameters. We outline a simple procedure to correct the velocity dispersion to within a few percent accuracy by using the threshold fraction and provide fitting functions for this method. We also develop a methodology for constraining properties of binary populations from both single- and two-epoch velocity measurements by including the binary velocity distribution in a Bayesian analysis.
Complex Polycyclic Scaffolds by Metathesis Rearrangement of Himbert Arene/Allene Cycloadducts

The intramolecular arene/allene cycloaddition first described 30 years ago by Himbert and Henn permits rapid access to strained polycyclic compounds. Alkene metathesis processes cleanly rearrange appropriately substituted cycloadducts into complex, functional-group-rich polycyclic lactams of potential utility for natural product synthesis and medicinal chemistry.
Noise analysis of phase-locked loops

This work addresses the problem of noise analysis of phase-locked loops (PLLs). The problem is formulated as a stochastic differential equation and is solved in the presence of circuit white noise sources yielding the spectrum of the PLL output. Specifically, the effect of loop filter characteristics, phase-frequency detector, and phase noise of the open-loop voltage-controlled oscillator (VCO) on the PLL output spectrum is quantified. These results are derived using a full nonlinear analysis of the VCO in the feedback loop and cannot be predicted using traditional linear analyses or the phase noise analysis of open-loop oscillators. The computed spectrum matches well with measured results; specifically, the shape of the output spectrum matches very well with measured PLL output spectra reported in the literature for different kinds of loop filters and phase detectors. The PLL output spectrum computation only requires the phase noise of the VCO, loop filter and phase detector noise, phase detector gain, and loop filter transfer function and does not require the transient simulation of the entire PLL which can be very expensive. The noise analysis technique is illustrated with some examples.
A Transect of 200 Shallow Shear-Velocity Profiles across the Los Angeles Basin

This study assesses a 60 km north-northeast–south-southwest transect along the San Gabriel River for shallow shear velocities, in San Gabriel Valley and the Los Angeles Basin of southern California. We assessed a total of 214 sites, 199 along the transect at 300-m spacing, during a one-week field campaign with the refraction microtremor (ReMi) technique. The transect9s maximum 30-m shear velocity (Vs30) occurs in coarse alluvium of San Gabriel Valley where the San Gabriel River exits the San Gabriel Mountains, at 730 m/sec, upper National Earthquake Hazards Reduction Program (nehrp) site class C. Much of the northeast section of the transect (in San Gabriel Valley) is also nehrp class C, or near the CD class boundary. The section of the transect south from Whittier Narrows to Seal Beach shows nehrp-D velocities in active alluvium. The transect9s lowest Vs30, 230 m/ sec at the Alamitos Bay estuary, is also classed as nehrp-D. An increase toward the nehrp CD class boundary occurs at the shoreline beach outside Alamitos Bay, confirmed by additional measurements on Seal Beach. Our measured Vs30 values generally show good correlation with published site-classification maps and existing borehole data sets. There is no evidence in our data for an increase in velocity predicted by Wills et al. (2000) at their CD to BC site classification boundary at the San Gabriel Mountains front, nor for any decrease at their D to DE class boundary at Alamitos Bay. Very large Vs30 variations exist in soil and geologic units sampled by our survey. The Vs30 variations we measured are smaller than Vs30 variations of 30% or more we found between closely spaced (
A 13-b 10-Msample/s ADC digitally calibrated with oversampling delta-sigma converter

Two key techniques necessary to digitally calibrate multistep or pipelined converters are demonstrated in a differential 5-V, 13-b, 10-Msample/s analog-to-digital converter (ADC). One technique, called code-error calibration, is to linearize the transfer characteristic of digital-to-analog converters (DAC's) while the other, called gain-error proration, is to evenly distribute interstage gain errors over the full conversion range. The core of the former technique is an oversampling delta-sigma ratio calibrator working synchronously with the converter. This digital calibration process constantly tracks and updates the code errors without interfering with the normal operation. The prototype converter fabricated using a 1.4-/spl mu/m BiCMOS process consumes 360 mW with a 5-V single supply and exhibits a signal-to-noise ratio of 71 dB and a maximum end-point integral nonlinearity of 1.8 LSB at a 13-b level. The proposed techniques can be incorporated into general multistep or pipelined ADC's without sacrificing the conversion speed. >
Unexpected formation of glycals upon attempted C-alkylation of protected glycosylacetylenes.

Abstract Treatment of 3,7-anhydro-4,5,6,8-tetra- O -benzyl-1,2-dideoxy- d - glycero - d - galacto- oct-1-ynitol (β- d -mannosyl acetylene, 1 ) with 5 equivalents of n -butyllithium at either 0 or −78 °C resulted in the elimination of benzyl alcohol to yield 3,7-anhydro-5,6,8-tri- O -benzyl-1,2,4-trideoxy- d - arabino- oct-3-en-1-ynitol (glycal acetylene, 3 ) as the major product. Additional studies showed that 3 is also produced from two isomers of 1 with α- d -mannosyl and β- d -glucosyl stereochemistry, but in lower yields. Furthermore, substrates in which the acetylene moiety is replaced by either a methyl or phenyl group do not produce a glycal product under these conditions. Finally, treatment of 1 with phenyllithium provides 3 in low yield. Deuterium labeling studies suggest that the reaction proceeds through an E2, rather than an E1cB, mechanism.
Data augmentation for non-Gaussian regression models using variance-mean mixtures

We use the theory of normal variance-mean mixtures to derive a data-augmentation scheme that unies a wide class of statistical models under a single framework. This generalizes existing theory on normal variance mixtures for priors in regression and classication. It also allows variants of the expectation-maximization algorithm to be brought to bear on a much wider range of models than previously appreciated. We demonstate the resulting gains in accuracy and stability on several examples, including sparse quantile regression and binary logistic regression.
Policies for a better-fed world

A wide range of interventions, from subsidized grains all the way to conditions on nutrition in conditional cash transfers, have either been tried or put in place in different countries in order to fight under-nutrition. A number of important policy experiments in recent years, directly or indirectly, offer important insights into how best to design these interventions. This essay is an attempt to pull together some of those insights, with the aim of saying something about what the optimal design should look like.
A wavenumber partitioning scheme for two-dimensional statistical closures

A technique of wavenumber partitioning that conserves both energy and enstrophy is developed for two-dimensional statistical closures. This advance facilitates the computation of energy spectra over seven wavenumber decades, a task that will clearly remain outside the realm of conventional numerical simulations for the foreseeable future. Within the context of the test-field model, the method is used to demonstrate Kraichnan's logarithmically-corrected scaling for the enstrophy inertial range and to make a quantitative assessment of the effect of replacing the physical Laplacian viscosity with an enhanced hyperviscosity.
Advance Provision of Emergency Contraception in an Urban Pediatric Emergency Department

Abstract Study Objective To assess whether a policy and educational intervention in an urban, pediatric emergency department (ED) increases advance provision of emergency contraception (EC) to patients. Design/Setting/Participants A pre- and post-intervention, retrospective chart review was conducted in an urban, pediatric ED assessing provider care of sexually active female adolescents and young adults. Intervention/Main Outcome Measures A policy was instituted recommending that ED providers prescribe EC and provide an educational handout to all sexually active female adolescents and young adults. ED providers were educated about EC and this policy. Charts, subsequently reviewed, included sexually active female patients, age 13–21 years, presenting to the ED status post sexual assault, seeking EC, or with an abdominal, gynecologic, or urologic complaint. Student’s t-tests, Pearson’s chi-square and Fisher’s Exact tests compared pre- and post-intervention provider and patient characteristics and outcomes. Results The mean age of the patient sample was 18.8 years (SD=1.7), 83% were Black or Hispanic, 43% were previously pregnant, 25% reported not using birth control. Last unprotected sexual intercourse was not documented for 87% of patients presenting with medical complaints. There was no difference in the advance prescribing of EC or the provision of the educational handout to patients pre- (3.3%) or post- (5.6%) intervention (P = 0.73). Conclusions Despite a policy and an educational intervention for providers, little change occurred in advance EC prescribing in an urban, pediatric ED. Additionally, many providers were not documenting last unprotected sexual intercourse, potentially missing an opportunity to treat patients with EC at the time of their visit.
Currency Choice and Exchange Rate Pass-Through

In the open economy macro literature with nominal rigidities, the currency in which goods are priced has important implications for optimal monetary and exchange rate policy and for exchange rate pass-through. We show, using novel data on currency and prices for U.S. imports, that even conditional on a price change, there is a large difierence in the pass-through of the average good priced in dollars (25%) versus non-dollars (95%). We document this to be the case across countries and within disaggregated sectors. This flnding contradicts the assumption in an important class of models that the currency of pricing is exogenous. We present a model of endogenous currency choice in a dynamic price setting environment and show that the predictions of the model are strongly supported by the data.
Atomic deuterium/hydrogen in the Galaxy

An accurate value of the D/H ratio in the local interstellar medium (LISM) and a better understanding of the D/H variations with position in the Galactic disk and halo are vitally important questions as they provide information on the primordial D/H ratio in the Galaxy at the time of the protosolar nebula, and the amount of astration and mixing in the Galaxy over time. Recent measurements have been obtained with UV spectrographs on FUSE, HST, and IMAPS using hot white dwarfs, OB stars, and late-type stars as background light sources against which to measure absorption by D and H in the interstellar medium along the lines of sight. Recent analyses of FUSE observations of seven white dwarfs and subdwarfs provide a weighted mean value of DIR = (1.52 ± 0.08) x 10—5(15.2 ± 0.8 ppm), consistent with the value of (1.50 ± 0.10) x 10-5(15.0 + 1.0 ppm) obtained from analysis of lines of sight toward nearby late-type stars. Both numbers refer to the ISM within about 100 pc of the Sun, which samples warm clouds located within the Local Bubble. Outside of the Local Bubble at distances of 200 to 500 pc, analyses of far-UV spectra obtained with the IMAPS instrument indicate a much wider range of D/H ratios between 0.8 to 2.2 ppm. This portion of the Galactic disk provides information on inhomogeneous astration in the Galaxy.
Accounting education, research and practice: After Enron, where do we go?

Abstract Recent accounting scandals have brought into question the efficacy of accounting education and research and the relationship of accounting educators to the profession. This paper calls for a comprehensive reassessment of accounting education, especially in terms of: undergraduate accounting programs; the development of an approach to accounting research and scholarship that is more closely focused on impact rather than purely methodological rigor; and the establishment of significantly more interaction between the profession and accounting educators. These changes, some of which could be painful and disruptive to the current structure of accounting departments, must begin to occur or we as accounting educators run the risk of being marginalized as the accounting profession tries to respond to the needs of society.
Alignable Deposition of Thin Film Semiconductor Materials for Integrated Micro-Opto-Electronic Systems

The selective and alienable deposition of patterned thin film epitaxial GaAs/GaAlAs and InP/InGaAsP devices onto host substrates such as silicon for low cost hybrid integrated micro-opto-electronic systems is reported. Using a combination of semiconductor etch layers and selective etches, the epilayers can be separated from the growth substrate. We use a thin polyimide diaphragm as the transparent transfer medium for these epitaxial materials and devices. Each of these thin film devices or a group of these devices on the polyimide is optically aligned and selectively deposited onto the host substrate. Using this technique, GaAs and InP-based light emitting diodes and optical detectors which are microns thick were grown on lattice matched GaAs and InP substrates, lifted off, aligned and selectively deposited onto a silicon host substrate. The devices were then electrically contacted and tested using standard microelectronic fabrication and testing techniques. This method also enables the manufacturable, sparse distribution of costly photonic devices or the deposition of aligned arrays of devices to fabricate larger arrays. The integration of these light weight devices with microsensors and microactuators will foster micro-opto-electro-mechanical integration.
The dilated chiral quark model

Abstract It is argued that constituent quarks live in an effective theory that possesses an approximate conformal invariance. An effective lagrangian is constructed which in the large- N c approximation incorporates Regge asymptotic constraints. The resulting picture explains why linear-sigma models provide successful constituent quark descriptions, both at zero and finite temperature. Our analysis suggests an interesting relation between non-linearly realized conformal invariance and the completion of chiral multiplets in the broken symmetry phase.
Stochastic wobble of accretion discs and jets from turbulent rocket torques

Models of accretion discs and their associated outflows often incorporate assumptions of axisymmetry and symmetry across the disc plane. However, for turbulent discs these symmetries only apply to averaged quantities and do not apply locally. The local asymmetries can induce local imbalances in outflow power across the disc mid-plane, which can in turn induce local tilting torques. Here we calculate the effect of the resulting stochastic torques on disc annuli that are a consequence of standard mean field accretion disc models. The torques induce a random walk of the vector perpendicular to the plane of each averaged annulus. This random walk is characterized by a radially dependent diffusion coefficient which we calculate for small angle tilt. We use the coefficient to calculate a radially dependent time-scale for annular tilt and associated jet wobble. The wobble time depends on the square of the wander angle so the age of a given system determines the maximum wobble angle. We apply this to examples of blazars, young stellar objects and binary engines of pre-planetary nebulae and microquasars. It is noteworthy that for an averaging time t_w ∼ 3d , we estimate a wobble angle for jets in SS 433 of θ∼ 0.8° , not inconsistent with observational data. In general the non-periodic nature of the stochastic wobble could distinguish it from faster periodic jet precession.
Thinking about development

Preface Introduction 1. The evolution of development thought 2. Global institutions for an interdependent world 3. The judo trick: the role of direct foreign investment in developing countries 4. Markets and states: against minimalism and dichotomy 5. The political economy of reform Discussion Bibliography.
Metropolitan Area Networks

A metropolitan area network (MAN) is a shared network that covers the distances in most cities. The applications of MANs and the techniques that are used for communications is rapidly changing. MANs were originally used to interconnect the users in a single organization, and several specialized networks were developed. However, the Internet has increased the demand for high-speed communications to individual consumers. In consumer applications, cost is particularly important. The networks use existing infrastructure or infrastructure that can be deployed with minimal investment and use access devices that are popular in other applications and therefore cost less than new devices. The first generation of MANs used protocols and network topologies that are similar to local area networks but are specifically designed to span the greater distances and operate at the higher transmission rates that occur in a MAN. We describe three of these protocols: the American National Standards Institute (ANSI) X3T9 standard, fiber distributed data interface, (FDDI), the IEEE 802.6 standard, dual bus distributed queue protocol, (DQDB), and an experimental network, the Manhattan Street Network, (MSN). Currently, the most widely used MANs use the existing cable TV (CATV) network and easily deployed wireless networks. The CATV standards are not keeping pace with the applications. We describe the common characteristics of the applications and describe in detail an application that is based on Ethernet technology and that can be extended to carry packet voice communications. The IEEE 802.11 standard, wireless fidelity (WiFi), is the most widely used wireless access technology. This standard is described in detail, along with a competing access technique, Bluetooth, and the IEEE 802.16 standard that can be used to extend the range of wireless access techniques to the metropolitan area. In the conclusion we predict future changes. These changes are fueled by the need for improved reliability, the emergence of IP-voice, the increased use of wireless technologies, the overuse of the cellular bands, the eventual deployment of fiber to the home, and a resurgence of ATM-like, cell-based transmission. Keywords: metropolitan area networks; MAN; ethernet; IEEE 802.11; IEEE 802.16
The Price of Disclosure in the Thoroughbred Yearling Market

In this article, we examine disclosure as a tool to mitigate the effects of asymmetric information in a Thoroughbred yearling market. If disclosures influence market price, information contained therein must be valuable to buyers and hence diminish asymmetric information. Using public auction data, we find that disclosures do not influence price in a segment of the auction in which an implicit quality certification is available. However, in the other segment, we find evidence that some disclosures may provide valuable information to buyers.
Market equilibrium under separable, piecewise-linear, concave utilities

We consider Fisher and Arrow--Debreu markets under additively separable, piecewise-linear, concave utility functions and obtain the following results. For both market models, if an equilibrium exists, there is one that is rational and can be written using polynomially many bits. There is no simple necessary and sufficient condition for the existence of an equilibrium: The problem of checking for existence of an equilibrium is NP-complete for both market models; the same holds for existence of an e-approximate equilibrium, for e = O(n−5). Under standard (mild) sufficient conditions, the problem of finding an exact equilibrium is in PPAD for both market models. Finally, building on the techniques of Chen et al. [2009a] we prove that under these sufficient conditions, finding an equilibrium for Fisher markets is PPAD-hard.
Information and the Operation of Markets: Tests Based on a General Equilibrium Model of Land Leasing in India

Abstract This paper develops an estimable general equilibrium model of land leasing to test the extent to which information is commonly held in a village and whether village markets are efficient. Information regarding the relative farming skill of households is found to be widespread, but the assumption of perfectly efficient markets within the village is rejected. These results have ramifications for the estimation of agricultural household models and for our understanding of rural institutions. The model is derived from the primitives of the production technology, the extent of information and the distributions of assets and several household unobservables. Simultaneity and selection issues are dealt with explicitly in a two-stage maximum likelihood estimation procedure using panel data from India.
Preparation of C70-Doped Solid Silica Gel via Sol–Gel Process

We reported the first preparation of C70-doped solid gel. Its UV-visible spectrum was recorded.
Solution-Phase Synthesis of Highly Conductive Tungsten Diselenide Nanosheets

WSe2 nanosheets are prepared by injecting tBu2Se2 into a solution of WCl4 in dodecylamine at 150 °C (N2 atmosphere, heating to 225 °C, 6 h, quenching).
Strings on a cone and black hole entropy

Abstract String propagation on a cone with deficit angle 2 π (1 − 1/ N ) is described by constructing a non-compact orbifold of a plane by a Z N subgroup of rotations. It is modular invariant and has tachyons in the twisted sectors that are localized at the tip of the cone. A possible connection with the quantum corrections to the black hole entropy is outlined. The entropy computed by analytically continuing in N would receive contribution only from the twisted sectors and be naturally proportional to the area of the event horizon. Evidence is presented for a new duality for these orbifolds similar to the R → 1/ R duality.
Implementing a Prolog machine with multiple functional units

This paper describes the microarchitecture of the PLUM, a high performance Prolog machine. Multiple specialized functional units, each with a port to memory, operate in parallel using data driven control. Instructions are dynamically scheduled by a Prefetch Unit to execute on several specialized functional units. Out of order execution is allowed, and instructions execute when their operands are available. Special synchronization techniques that ensure correct parallel unification and pipelined operation are discussed. The performance of the PLUM is limited by unification, since almost all other operations execute in parallel with unification. Unification time is reduced by parallel unification, resulting in an overall speedup of approximately a factor of 4 over the Berkeley PLM.
Myopic Solutions of Homogeneous Sequential Decision Processes

An optimum of a Markov decision process (MDP) is myopic if it can be obtained by solving a series of static problems. Myopic optima are desirable because they can be computed relatively easily. We identify new classes of MDPs with myopic optima and sequential games with myopic equilibrium points. In one of the classes, the single-period reward is homogeneous with respect to the state variable. We illustrate the results with models of revenue management and investment.
Intramolecular cycloaddition of azomethine ylides in the preparation of pyrrolidino[2',3':3,4]pyrrolidino[1,2- a]benzimidazoles.

The parent pyrrolidino[2‘,3‘:3,4]pyrrolidino[1,2-a]benzimidazole heterocycle as well as a series of novel analogues have been synthesized utilizing a microwave-assisted intramolecular cycloaddition of azomethine ylides as the key transformation. A variety of diversity groups were added to explore the scope of this reaction and to provide a number of new compounds for biological screening.
Compressed sensing for practical optical imaging systems: A tutorial

The emerging field of compressed sensing (CS, also referred to as compressive sampling)1, 2 has potentially powerful implications for the design of optical imaging devices. In particular, compressed sensing theory suggests that one can recover a scene at a higher resolution than is dictated by the pitch of the focal plane array. This rather remarkable result comes with some important caveats however, especially when practical issues associated with physical implementation are taken into account. This tutorial discusses compressed sensing in the context of optical imaging devices, emphasizing the practical hurdles related to building such devices and offering suggestions for overcoming these hurdles. Examples and analysis specifically related to infrared imaging highlight the challenges associated with large format focal plane arrays and how these challenges can be mitigated using compressed sensing ideas.
Invariant distributions and collisionless equilibria

This paper discusses the possibility of constructing time-independent solutions to the collisionless Boltzmann equation which depend on quantities other than global isolating integrals such as energy and angular momentum. The key point is that, at least in principle, a self-consistent equilibrium can be constructed from any set of time-independent phase-space building blocks which, when combined, generate the mass distribution associated with an assumed time-independent potential. This approach provides a way to justify Schwarzschild’s method for the numerical construction of self-consistent equilibria with arbitrary time-independent potentials, generalizing thereby an approach developed by Vandervoort for integrable potentials. As a simple illustration, Schwarzschild’s method is reformulated to allow for a straightforward computation of equilibria which depend only on one or two global integrals and no other quantities, as is reasonable, for example, for modelling axisymmetric configurations characterized by a non-integrable potential.
Distortion cancellation performance of miniature delay filters for feed-forward linear power amplifiers

The technique of feed-forward amplitude control has been widely used in the linearization of power amplifiers for wireless communication systems. In this technique, an error signal due to third order intermodulation distortion (IMD) is extracted, amplified, and used to correct the delayed main line distorted signal. For example, a miniature prototype base station for the Global System for Mobile Communications/Code Division Multiple Access (GSM/CDMA) cellular system uses feed-forward amplifiers with bulky and expensive coaxial cables, about 20 feet in length, to provide about 25 ns of delay. This paper shows alternate space-saving approaches of achieving these delays using three different types of delay filters: electromagnetic interdigital/lumped (<2.5"), ceramic (<1.8"), and ladder-type surface acoustic wave (SAW) (0.15"). The delay lines introduce phase and amplitude imbalance and delay mismatch in the linearization loop due to fabrication tolerances. These adversely affect the IMD cancellation. Using an RF system simulation tool, this paper critically compares the IMD cancellation performance achieved using the three technologies. Simulation results show that the optimization of delay mismatch can achieve the desired cancellation more easily than other parameters. It is shown that, if the critical system parameter (phase deviation from linearity), is maintained at <2.5/spl deg/ peak-to-peak over a 20 MHz bandwidth in the frequency range 855 MHz to 875 MHz, one can achieve 25 dB of IMD cancellation performance. This paper concludes with the suggestion of a set of realistic specifications for a miniature delay filter for the low power loop of the feed-forward amplifier.
Large-Scale Learning with Less RAM via Randomization

We reduce the memory footprint of popular large-scale online learning methods by projecting our weight vector onto a coarse discrete set using randomized rounding. Compared to standard 32-bit float encodings, this reduces RAM usage by more than 50% during training and by up to 95% when making predictions from a fixed model, with almost no loss in accuracy. We also show that randomized counting can be used to implement percoordinate learning rates, improving model quality with little additional RAM. We prove these memory-saving methods achieve regret guarantees similar to their exact variants. Empirical evaluation confirms excellent performance, dominating standard approaches across memory versus accuracy tradeoffs.
Visions: The coming revolutions in particle physics

Wonderful opportunities await particle physics over the next decade, with the coming of the Large Hadron Collider to explore the 1-TeV scale (extending efforts at LEP and the Tevatron to unravel the nature of electroweak symmetry breaking) and many initiatives to develop our understanding of the problem of identity and the dimensionality of spacetime.
A unifying model for lookahead LR parsing

Abstract We present a construction method for lookahead LR parsers that unifies several of the construction algorithms available in the literature. The model allows single, multiple and arbitrary symbol lookahead, each only when required. Three user-supplied parameters are used by the construction method; specific settings of these parameters yield well-known grammar classes such as LALR(k), SLR(k), and several subsets of the LR-Regular class, among others. Thus, rather than using several severely incompatible parser generators, or making unnatural changes to the grammar to accommodate the parsing technique, one may manipulate these parameters to obtain a suitable parser. The model captures the essence of the problem of computing lookahead for LR parsers, and provides a better understanding of the relationships among the corresponding classes of context-free grammars.
Distances and absolute magnitudes of dwarf novae: murmurs of period bounce

We redetermine the relationship between absolute magnitude and orbital period for dwarf novae, based on 46 stars with good distance estimates. This improves upon Warner's previous relation, building upon today's improved estimates of distance and binary inclination, and greater wavelength coverage. Together with other distance and dynamical constraints, this calibration is then applied to a set of ∼300 known or likely dwarf novae of short orbital period, to study the dependence of quiescent M υ , time-averaged M υ , mass ratio q and white-dwarf temperature T WD , on P or b. These distributions show that stars become much fainter as they approach the minimum P orb , and appear to show evolutionary tracks as the secondary is whittled down by mass-loss. Stars on the lower branch have the expected properties of 'period bouncers' - with a feeble secondary, faint accretion light, cool white dwarf and long recurrence time between eruptions. Period bounce seems to occur at a mass of 0.058 ± 0.008 M o . Stars on the lower branch may also have higher velocities and heights above the Galactic plane, consistent with a greater age. Some are very nearby, despite strong selection effects discriminating against the discovery of these faint binaries accreting at very low rates. Period bouncers appear to be very common, and probably would dominate a complete census of cataclysmic variables.
Branes intersecting at angles

Abstract We show that configurations of multiple D-branes related by SU(N) rotations will preserve unbroken supersymmetry. This includes cases in which two D-branes are related by a rotation of arbitrarily small angle, and we discuss some of the physics of this. In particular, we discuss a way of obtaining 4D chiral fermions on the intersection of D-branes. We also rephrase the condition for unbroken supersymmetry as the condition that a ‘generalized holonomy group’ associated with the brane configuration and manifold is reduced, and relate this condition (in type IIA string theory) to a condition in eleven dimensions.
NEUTRON IRRADIATION AND SURFACE HOMOGENEITY OF GRAPHITIC MATERIALS

Abstract The possibility of assessing by means of sorption techniques the surface damage due to neutron irradiation of graphitic materials has been investigated. Samples of a graphitized carbon-black (S6-D3) were subjected to an integrated neutron flux of 2.6×1019n/cm2 and 4.7×1020n/cm2 of both thermal and fast neutrons. In each case the form of the argon isotherms determined at 77°K indicated that the homogeneity of the surface remained essentially unchanged. For the more extensive irradiation a significant reduction in the surface area was observed. A sample of a non-graphitized carbon-black (S6) was also exposed to a thermal and fast-neutron flux of 5.0×1020n/cm2, but showed little or no tendency to form a more homogeneous surface. These observations may be explained by the ease of migration of displaced atoms to either previously vacated sites or the edges of crystallites.
Effects of frequency spreads on beam breakup instabilities in linear accelerators

Structure mode frequency spreads are shown to have a rather different influence on beam breakup growths than betatron frequency spreads. Analytic and numerical studies show that a finite spread in the breakup mode frequency leads to an algebraic decay of the beam breakup instabilities even if the quality factor Q to infinity . Asymptotic formulas and the time scale for this phase mixing to occur are presented. Effects of stagger tuning are examined numerically. >
A combinatorial algorithm for visualizing representatives with minimal self-intersection

Given an orientable surface with boundary and a free homotopy class of a closed curve on this surface, we present a purely combinatorial algorithm which produces a representative of that homotopy class with minimal self-intersection.
Ethics in Research

Abstract Unethical conduct in research can be divided into five categories: 1) falsification of data, in which the researcher manipulates results, provides data without experimentation, or biases the results to give a false impression of their value; 2) failure to credit others (former colleagues, students, associates) for research results or ideas; 3) plagiarism, use of other's published material (ideas, graphs, or tabular data) without permission or credit; 4) conflicts of commitment or interest in which work or ownership in a private firm in some way conflicts or detracts from the duties to the institution they represent or allows private gain through the individual's employment at the institution; 5) biased experimental design or interpretation of data to support public or private groups that have provided financial support for research. Although none of these should be condoned or tolerated by the scientific community, the latter two are probably more serious, because they are insidious, hard to prove, and, in the long run, result in the loss of public confidence in science.
Interstellar Carbodiimide (HNCNH): A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features

In this work, we identify carbodiimide (HNCNH), which is an isomer of the well-known interstellar species cyanamide (NH_(2)CN), in weak maser emission, using data from the Green Bank Telescope PRIMOS survey toward Sgr B2(N). All spectral lines observed are in emission and have energy levels in excess of 170 K, indicating that the molecule likely resides in relatively hot gas that characterizes the denser regions of this star-forming region. The anticipated abundance of this molecule from ice mantle experiments is ~10% of the abundance of NH_(2)CN, which in Sgr B2(N) corresponds to ~2 × 10^(13) cm^(–2). Such an abundance results in transition intensities well below the detection limit of any current astronomical facility and, as such, HNCNH could only be detected by those transitions which are amplified by masing.
PROTECTING OUR HOMELAND: INCORPORATING VULNERABILITY TO TERRORISM IN STATE HOMELAND SECURITY GRANTS

Vulnerabilities realized following the terrorist attacks of September 11, 2001 highlight the need for the Federal government to allocate funding for the prevention and response to terrorist events based on vulnerability to terrorism. However, the funding formula used by the State Homeland Security Program (SHSP) is based on a lump sum to all states plus an incremental amount distributed by population. Therein the formula does not explicitly address varying risks across States. The objective of this paper is to theoretically formulate an alternative formula to distribute grant funding based on vulnerability to terrorism across States. Empirical techniques are used to test three hypotheses regarding grant funding. State government data are used to infer the optimal funding levels to cover expected damages associated with various targets: population density, hazardous material sources, federal courts, hospitals, interstates, pipelines, power generation, public water use, airports, universities, port capacity, and confined feeding operations. State allocations for the SHSP and the larger Homeland Security Grant Program (HSGP) are compared to allocations based on vulnerability to terrorism. Vulnerability-based allocations are calculated for all states. The difference between vulnerability-based allocations and the SHSP allocations indicate that the SHSP program over-compensates for population-based vulnerabilities and under-compensates for other vulnerabilities. The results suggest that the HSGP does not eliminate the population-bias of the SHSP.
Topological defects and structure formation

Topological defects are produced during phase transitions in the very early Universe. They arise in most unified theories of strong, weak and electromagnetic interactions. This article focuses on the role of topological defects in cosmology, with particular emphasis on the models of structure formation based on defects. The role of topological defects in baryogenesis is also reviewed.
Asymmetric Synthesis of Aziridine 2-Phosphonates from Enantiopure Sulfinimines (N-Sulfinyl Imines). Synthesis of α-Amino Phosphonates

An aza-Darzens reaction, involving the addition of chloromethylphosphonate anions to enantiopure sulfinimines, has been developed for the asymmetric synthesis of aziridine 2-phosphonates. Best results involve cyclization of the syn and anti diastereomerically pure α-chloro-β-amino phosphonates to cis- and trans-N-sulfinyl aziridine 2-phosphonates, respectively, with n-BuLi. A transition-state hypothesis is proposed wherein the chloromethylphosphonate anion adds to the C−N bond on the side that is opposite the bulky p-tolyl sulfinyl group. The N-sulfinyl group is easily removed by treatment with MeMgBr or TFA/MeOH, which affords the NH-aziridines in good yield. Using transfer hydrogenation conditions, the NH-aziridines were regioselectively opened to the corresponding enantiopure α-amino phosphonates without N-activation and in excellent yield.
DIRECT PHOTON PRODUCTION IN d+A AND A+A COLLISIONS AT RHIC

Direct photon production in minimum bias d+Cu and d+Au and central Cu+Cu and Au+Au collisions at center-of-mass energies and 200 GeV at RHIC is systematically investigated. We study the jet quenching effect, the medium-induced photon bremsstrahlung and jet-photon conversion in the hot QGP. We account for known cold nuclear matter effects, such as the isospin effect,the Cronin effect, shadowing and cold nuclear matter energy loss. It is shown that at high pT the nuclear modification factor for direct photons is dominated by cold nuclear matter effects and there is no evidence for large cross-section amplification due to medium-induced photon bremsstrahlung and jet-photon conversion in the medium. Comparison of numerical simulations to experimental data also rules out large Cronin enhancement and incoherent photon emission in the QGP but the error bars in the current experimental data cannot provide further constraints on the magnitudes of other nuclear matter effects.
Modular architectures for adaptive multichannel lattice algorithms

A modular architecture for adaptive multichannel lattice algorithms is presented. This architecture requires no matrix computations and has a regular structure, which significantly simplifies its implementation as compared to the multichannel (matrix) version of the same algorithms. Because the suggested architecture exhibits a high degree of parallelism and local communication, it is well suited for implementation in dedicated (VLSI) hardware. The derivation of this modular architecture demonstrates a powerful principle for modular decomposition of multichannel recursions into systolic-arraylike architectures. The scope of applicability of this principle extends beyond multichannel lattice (and related least-squares) algorithms to other algorithms involving matrix computations, such as multiplication; factorization, and inversion.
Separated covariance filtering

A separated covariance filter (SCF) for estimating position and velocity given noisy measurements is discussed. The SCF calculates the state errors due to measurement errors and those due to target acceleration separately. The SCF overcomes two difficulties with the standard Kalman filter technique: (1) selection of the process noise covariance; and (2) interpreting the Kalman state covariance. The SCF is adaptable to a stream of unsequenced measurements. >
Transscleral diffusion of ethacrynic acid and sodium fluorescein

Transscleral drug delivery is an effective method for treatment of eye diseases in posterior segment. Therefore, we investigated transscleral permeability of ethacrynic acid (ECA), a potential drug for treating glaucoma. To determine the ex vivo permeability of ECA across the sclera, we quantified the diffusion coefficients of two molecules, ECA and sodium fluorescein, in fresh porcine sclera mounted in a two-chamber diffusion apparatus. All experiments were conducted with phosphate-buffered solution (PBS) at 4/spl deg/C for a period ranging from 2 to 14 hours. The concentrations of ECA and sodium fluorescein were measured at room temperature (25/spl deg/C) with UV and fluorescence spectrophotometers, respectively. The results showed that the permeability of ECA (303 Da) was 4.21/spl plusmn/0.82/spl times/10/sup -5/ cm/sec (n=9), whereas the permeability of sodium fluorescein (376 Da) was 1.06/spl plusmn/0.88/spl times/10/sup -6/ cm/sec (n=12). These results suggest that the sclera tissue is more permeable to ECA than sodium fluorescein.
A Look at the Generalized Heron Problem through the Lens of Majorization-Minimization

In a recent issue of this MONTHLY, Mordukhovich, Nam, and Salinas pose and solve an interesting non-differentiable generalization of the Heron problem in the framework of modern convex analysis. In the generalized Heron problem, we are given kC 1 closed con- vex sets in R d equipped with its Euclidean norm and asked to find the point in the last set such that the sum of the distances to the first k sets is minimal. In later work, the authors gen- eralize the Heron problem even further, relax its convexity assumptions, study its theoretical properties, and pursue subgradient algorithms for solving the convex case. Here, we revisit the original problem solely from the numerical perspective. By exploiting the majorization- minimization (MM) principle of computational statistics and rudimentary techniques from differential calculus, we are able to construct a very fast algorithm for solving the Euclidean version of the generalized Heron problem.