cssi/SciSciGPT-SciSciNet huggingface dataset:
Spectroscopic characterization of heme iron-nitrosyl species and their role in NO reductase mechanisms in diiron proteins.

Covering: up to November 2006Nitric oxide (NO) plays an important role in cell signalling and in the mammalian immune response to infection. On its own, NO is a relatively inert radical, and when it is used as a signalling molecule, its concentration remains within the picomolar range. However, at infection sites, the NO concentration can reach the micromolar range, and reactions with other radical species and transition metals lead to a broad toxicity. Under aerobic conditions, microorganisms cope with this nitrosative stress by oxidizing NO to nitrate (NO3−). Microbial hemoglobins play an essential role in this NO-detoxifying process. Under anaerobic conditions, detoxification occurs via a 2-electron reduction of two NO molecules to N2O. In many bacteria and archaea, this NO-reductase reaction is catalyzed by diiron proteins. Despite the importance of this reaction in providing microorganisms with a resistance to the mammalian immune response, its mechanism remains ill-defined. Because NO is an obligatory intermediate of the denitrification pathway, respiratory NO reductases also provide resistance to toxic concentrations of NO. This family of enzymes is the focus of this review. Respiratory NO reductases are integral membrane protein complexes that contain a norB subunit evolutionarily related to subunit I of cytochrome c oxidase (CcO). NorB anchors one high-spin heme b3 and one non-heme iron known as FeB, i.e., analogous to CuB in CcO. A second group of diiron proteins with NO-reductase activity is comprised of the large family of soluble flavoprotein A found in strict and facultative anaerobic bacteria and archaea. These soluble detoxifying NO reductases contain a non-heme diiron cluster with a Fe–Fe distance of 3.4 A and are only briefly mentioned here as a promising field of research. This article describes possible mechanisms of NO reduction to N2O in denitrifying NO-reductase (NOR) proteins and critically reviews recent experimental results. Relevant theoretical model calculations and spectroscopic studies of the NO-reductase reaction in heme/copper terminal oxidases are also overviewed.
The Synthesis of Carboxylic Acids via an Aldol-Grob Reaction Sequence

Abstract Ketones react with aromatic aldehydes via a tandem Aldol-Grob reaction sequence. The reaction, initiated by boron trifluoride, produces a carboxylic acid fragment and can serve as an alternative to the Baeyer-Villiger reaction.
Structural and mechanistic insights into methane oxidation by particulate methane monooxygenase.

Particulate methane monooxygense (pMMO) is an integral membrane copper-containing enzyme that converts methane to methanol. Knowledge of how pMMO selectively oxidizes methane under ambient conditions could impact the development of new catalysts. The crystal structure of Methylococcus capsulatus (Bath) pMMO reveals the composition and location of three metal centers. Spectroscopic data provide insight into the coordination environments and oxidation states of these metal centers. These results, combined with computational studies and comparisons to relevant systems, are discussed in the context of identifying the most likely site for O2 activation.
Which spatial partition trees are adaptive to intrinsic dimension

Recent theory work has found that a special type of spatial partition tree -- called a random projection tree -- is adaptive to the intrinsic dimension of the data from which it is built. Here we examine this same question, with a combination of theory and experiments, for a broader class of trees that includes k-d trees, dyadic trees, and PCA trees. Our motivation is to get a feel for (i) the kind of intrinsic low dimensional structure that can be empirically verified, (ii) the extent to which a spatial partition can exploit such structure, and (iii) the implications for standard statistical tasks such as regression, vector quantization, and nearest neighbor search.
Synthesis of flavonol derivatives as probes of biological processes

Abstract Two synthetic derivatives of the flavonol kaempferol were prepared in order to probe the biological mechanism of action of this natural product. Efficient synthetic routes to both a benzophenone-containing derivative and an amine-containing derivative are reported herein.
Halogenated catechols from cycloaddition reactions of η4-(2-ethoxyvinylketene)iron(0) complexes with 1-haloalkynes

1-chloroalkynes and 1-bromohexyne undergo cycloaddition reactions with ethoxyvinylketeneiron(0) complexes to form chloro and bromocatechols. With most substituents, the halogen is incorporated ortho to the phenolic hydroxyl group regioselectively. With chloroethyne, chlorohexyne, and methyl chloropropiolate, the reverse regioselection is observed. Ab initio calculations reveal that the products are, in most cases, nearly isoenergetic, which indicates that the intermediate ketene-alkyne adduct geometry must be important in determining the product distribution.
Intensity-modulated radiation therapy (IMRT) for prostate cancer with the use of a rectal balloon for prostate immobilization: acute toxicity and dose-volume analysis.

Abstract Purpose: To report acute toxicity and to evaluate the relationship between dose–volume effects and acute toxicity in patients with localized prostate cancer, treated with intensity-modulated radiation therapy (IMRT). Methods and Materials: Acute toxicity (both lower gastrointestinal [GI] and genito-urinary [GU]) in 100 patients treated with IMRT definitively to a prescribed dose of 70 Gy were assessed using RTOG scoring criteria. A rectal balloon was used for prostate immobilization. Mean doses to seminal vesicles, prostate, bladder, and rectum were recorded. Average irradiated bladder and rectal volumes above 65, 70, and 75 Gy were assessed. A relationship between dose volume and clinical toxicity was evaluated. All patients completed the full duration of acute toxicity assessment. Results: Mean doses to the prostate and seminal vesicles were 75.8 and 73.9 Gy. This represents a moderate dose escalation. Acute GI toxicity profile was very favorable. Eleven percent and 6% of the patients had grade 1 and 2 GI toxicity, respectively, while 83% had no GI complaint. For GU complaints, 38% and 35% had grade 1 and 2 toxicity, respectively, while 27% had no complaints. There was no grade 3 or higher acute GI or GU toxicity. Mean doses to the bladder were 22.8, 23.4, and 26.1 Gy for grade 0, 1, and 2 GU toxicity, respectively ( p = 0.132). There is no statistically significant relationship between acute GU toxicity and the bladder volume receiving > 65 Gy, > 70 Gy, or > 75 Gy. In evaluating acute GI toxicity, there are very few grade 1 and 2 events. No relationship was found between acute rectal toxicity and mean rectal dose or irradiated rectal volumes receiving more than 65, 70, and 75 Gy. Conclusion: The findings are important with regard to the safety of IMRT, especially in reducing acute GI toxicity. Dose escalation with IMRT using a prostate immobilization technique is feasible. The findings are also important because they contribute to the clinical and dosimetric correlation aspect in the use of IMRT to treat prostate cancer. A larger cohort may be needed to determine if there is a relationship between acute GU toxicity and (a) mean bladder dose and (b) irradiated bladder volume receiving > 65 Gy, > 70 Gy, or > 75 Gy. A larger cohort of patients treated to a higher dose may be needed to show a relationship between dose volume and acute GI toxicity.
RESPONDING TO SURPRISE

▪ Abstract This essay explores governmental and scholarly responses to the December 7, 1941 attack on Pearl Harbor and the September 11, 2001 attacks on the United States. Both events caught intelligence analysts, military officers, and elected officials by surprise. This essay describes the differences between the two events, especially in the ways official inquiries have helped shape our understanding of why the surprise occurred. Before both events, data suggesting that attacks were possible or even probable were available within the “intelligence pipeline.” The essay focuses on how scholars and official investigations reported and explained that finding. It also identifies continuities between the investigations that followed the Japanese and al Qaeda attacks on the United States.
The Red Edge Shift: An Explanation Of Its Relationship To Stress And The Concentration Of Chlorophyll A

The wavelength of the first derivative maxima of the red edge of vegetation reflectance spectra (675 to 760 nm.) was found to be function of chlorophyll concentration. This was observed in corn and soybeans where the chlorophyll content changed as a function of nitrogen deficiency stress. It was seen in the transmittance spectra of pure chlorophyll in DMSO, It was also observed when the chlorophyll changed as a function of percent canopy cover. It has been concluded that the first derivative maximum is a manifestation of the point of maximal slope change as the absorption of chlorophyll asymptoticly approaches zero. The wavelength of maximum slope is directly related to the chlorophyll concentration, shifting from the blue to the red as the chlorophyll concentration increases.
Squareness in the special L-value and special L-values of twists

Let N be a prime and let A be a quotient of J0(N) over Q associated to a newform such that the special L-value of A (at s = 1) is non-zero. Suppose that the algebraic part of the special L-value of A is divisible by an odd prime q such that q does not divide the numerator of . Then the Birch and Swinnerton-Dyer conjecture predicts that the q-adic valuations of the algebraic part of the special L-value of A and of the order of the Shafarevich–Tate group are both positive even numbers. Under a certain mod q non-vanishing hypothesis on special L-values of twists of A, we show that the q-adic valuations of the algebraic part of the special L-value of A and of the Birch and Swinnerton-Dyer conjectural order of the Shafarevich–Tate group of A are both positive even numbers. We also give a formula for the algebraic part of the special L-value of A over quadratic imaginary fields K in terms of the free abelian group on isomorphism classes of supersingular elliptic curves in characteristic N (equivalently, over conjugacy classes of maximal orders in the definite quaternion algebra over Q ramified at N and ∞) which shows that this algebraic part is a perfect square up to powers of the prime two and of primes dividing the discriminant of K. Finally, for an optimal elliptic curve of arbitrary conductor E, we give a formula for the special L-value of the twist E-D of E by a negative fundamental discriminant -D, which shows that this special L-value is an integer up to a power of 2, under some hypotheses. In view of the second part of the Birch and Swinnerton-Dyer conjecture, this leads us to the surprising conjecture that the square of the order of the torsion subgroup of E-D divides the product of the order of the Shafarevich–Tate group of E-D and the orders of the arithmetic component groups of E-D, under certain mild hypotheses.
Understanding partitions and the 'no partition' assumption

Discusses partitions in asynchronous message-passing systems. In such systems, slow processes and slow links can lead to virtual partitions that are indistinguishable from real ones. To overcome the impossibility of detecting crashed processes in an asynchronous system, the system model incorporates a failure suspector to detect (possibly erroneously) process failures. Based on failure suspicions, the authors give a definition of partitions that accounts for real partitions as well as virtual ones. It is shown that under certain assumptions about the process behavior, any incorrect failure suspicion inevitably partitions the system. It is then shown how to interpret the absence-of-partition assumption. >
Observations of Herbig Ae Disks with Nulling Interferometry

We present the results of 10 � m nulling interferometric observations of 13 Herbig Ae stars using the Magellan I (Baade) and the MMT 6.5 m telescopes. A portion of the observations was completed with the adaptive secondary at the MMT. We have conclusively spatially resolved 3 of the 13 stars, HD 100546, AB Aur, and HD 179218, the latter two recently resolved using adaptive optics in combination with nulling interferometry. For the resolved objects we find that the 10 � m emitting regions have a spatial extent of 15Y30 AU in diameter. We also have some evidence for resolved emission surrounding an additional two stars (V892 Tau and R CrA). For those objects in our study with mid-IR SEDs in the classification of Meeus and coworkers, we find that the group I objects (those with constant to increasing mid-IR flux) are more likely to be resolved, within our limited sample. This trend is evident in correlations in the inferred disksizes versus the submillimeter SED slope and disk sizeversus fractional infrared luminosity of the systems. We explore the spatial distribution and orientation of the warm dust in the resolved systems and constrain physical models that are consistent with their observational signatures.
Target assignment for robotic networks: Asymptotic performance under limited communication

We are given an equal number of mobile robotic agents, and distinct target locations. Each agent has simple integrator dynamics, a limited communication range, and knowledge of the position of every target. We address the problem of designing a distributed algorithm that allows the group of agents to divide the targets among themselves and, simultaneously, leads each agent to reach its unique target. We do not require connectivity of the communication graph at any time. We introduce a novel assignment-based algorithm with the following features: initial assignments and robot motions follow a greedy rule, and distributed refinements of the assignment exploit an implicit circular ordering of the targets. We prove correctness of the algorithm, and give worst-case asymptotic bounds on the time to complete the assignment as the environment grows with the number of agents. We show that among a certain class of distributed algorithms, our algorithm is asymptotically optimal. The analysis utilizes results on the Euclidean traveling salesperson problem.
How to construct random functions

A constructive theory of randomness for functions, based on computational complexity, is developed, and a pseudorandom function generator is presented. This generator is a deterministic polynomial-time algorithm that transforms pairs (g, r), where g is any one-way function and r is a random k-bit string, to polynomial-time computable functions ƒr: {1, … , 2k} → {1, … , 2k}. These ƒr's cannot be distinguished from random functions by any probabilistic polynomial-time algorithm that asks and receives the value of a function at arguments of its choice. The result has applications in cryptography, random constructions, and complexity theory.
Radiation Curable Conductive Ink

A radiation curable, screen printable conductive ink has been developed for use on thermoplastic circuit boards. The fast application and cure of this solventless material allow mass production of low cost circuits suitable for use with systems that can tolerate higher resistance. In one application, a photoflash array, Flipflash, utilizes a piezoelectric crystal to provide the high voltage necessary to overcome the resistance of the system. The conductive medium in this ink was identified from a wide range of available materials. It allows a rapid radiation cure of the binder which provides excellent adhesion and circuit stability.
Are we there yet? when to stop a markov chain while generating random graphs

Markov chains are convenient means of generating realizations of networks with a given (joint or otherwise) degree distribution, since they simply require a procedure for rewiring edges. The major challenge is to find the right number of steps to run such a chain, so that we generate truly independent samples. Theoretical bounds for mixing times of these Markov chains are too large to be practically useful. Practitioners have no useful guide for choosing the length, and tend to pick numbers fairly arbitrarily. We give a principled mathematical argument showing that it suffices for the length to be proportional to the number of desired number of edges. We also prescribe a method for choosing this proportionality constant. We run a series of experiments showing that the distributions of common graph properties converge in this time, providing empirical evidence for our claims.
Inspiratory resistance, cerebral blood flow velocity, and symptoms of acute hypotension.

INTRODUCTION Symptoms of orthostatic intolerance, e.g., following prolonged bed rest and microgravity exposure, are associated with reductions in cerebral blood flow. We tested the hypothesis that spontaneously breathing through an impedance threshold device (ITD) would attenuate the fall in cerebral blood flow velocity (CBFV) during a hypotensive orthostatic challenge and reduce the severity of reported symptoms. METHODS While breathing through either an active ITD (-7 cm H2O inspiratory impedance) or a sham ITD (no impedance), 19 subjects performed a squat stand test (SST). Symptoms upon stand were recorded on a 5-point scale (1 = normal; 5 = faint) of subject-perceived rating (SPR). To address our hypothesis, only data from symptomatic subjects (SPR > 1 during the sham trial) were analyzed (N = 9). Mean arterial blood pressure (MAP) and mean CBFV were measured continuously throughout the SST and analyzed in time and frequency domains. RESULTS Breathing with the active ITD during the SST reduced the severity of orthostatic symptoms in eight of the nine symptomatic subjects (sham ITD SPR, 1.9 +/- 0.1; active ITD SPR, 1.1 +/- 0.1), but there was no statistically distinguishable difference in the reduction of mean CBFV between the two trials (sham ITD, -39 +/- 3% vs. active ITD, -44 +/- 3%). High frequency oscillations in mean CBFV, however, were greater during the active ITD trial (7.8 +/- 2.6 cm x s(-2)) compared with the sham ITD trial (2.5 +/- 0.9 cm x s(-2)). CONCLUSIONS Higher oscillations in CBFV while breathing with the active ITD may account for the reduction in symptom severity during orthostatic hypotension despite the same fall in absolute CBFV.
Inference of gene predictor set using Boolean satisfiability

The inference of gene predictors in the gene regulatory network (GRN) has become an important research area in the genomics and medical disciplines. Accurate predicators are necessary for constructing the GRN model and to enable targeted biological experiments that attempt to validate or control the regulation process. In this paper, we implement a SAT-based algorithm to determine the gene predictor set from steady state gene expression data (attractor states). Using the attractor states as input, the states are ordered into attractor cycles. For each attractor cycle ordering, all possible predictors are enumerated and a conjunctive normal form (CNF) expression is generated which encodes these predictors and their biological constraints. Each CNF is solved using a SAT solver to find candidate predictor sets. Statistical analysis of the resulting predictor sets selects the most likely predictor set of the GRN, corresponding to the attractor data. We demonstrate our algorithm on attractor state data from a melanoma study [1] and present our predictor set results.
On the role of variable infectivity in the dynamics of the human immunodeficiency virus epidemic

In this paper, we study the effects of variable infectivity in combination with a variable incubation period on the dynamics of HIV (the human immunodeficiency virus, the etiological agent for AIDS, the acquired immunodeficiency syndrome) in a homogeneously mixing population. In the model discussed here, the functional relationship between mean sexual activity and size of the population is assumed to be nonlinear and to saturate at high population sizes. We identify a basic reproductive number R0 and show that the disease dies out if R0 1 the incidence rate converges to or oscillates around a uniquely determined nonzero equilibrium, the stability of which is studied. Our findings provide the analytical basis for exploring the parameter range in which the equilibrium is locally asymptotically stable. Oscillations cannot be excluded in general, and may occur in particular, if the variable infectivity is concentrated at an earlier part of the incubation period. Whether they can also occur for the reported two peaks of infectivity observed in HIV-infected individuals has to be the subject of future numerical investigations.
Synthesis and anti-Pneumocystis carinii activity of conformationally restricted analogues of pentamidine

Abstract Aseries of conformationally restricted analogues of pentamidine in which the flexible central bridge has been replaced by trans-cyclopropyl, phenyl, pyridinyl, piperazinyl or homopiperazinyl groups as conformationally restricted linkers have been synthesized. The anti-Pneumocystis carinii activity of these compounds was evaluated in a cell culture model and the DNA binding affinity was determined by thermal denaturation measurements. At 1 μM, compounds 2, 3, 5, 7, 9 and pentamidine were highly effective and caused total inhibition of P. carinii growth in culture. At 0.1 μM, compounds 2, 5, 7 and 10 were more active than pentamidine with N, N′-bis(4-amidinophenyl)piperazine 7 being approximately 15-fold more effective than pentamidine. The most active compounds, 7 and 10, showed strong binding affinities for calf thymus DNA and poly(dA-dT); however, a clear correlation between DNA binding affinity and the in vitro anti-P. carinii activity of these compounds was not observed. The results suggest that the nature of the central linker influences the biological actions of these compounds.
Lansce fail-safe radiation shutter design for isotope production facility

Dose rate modeling and post irradiation measurements of the Isotope Production Facility (IPF) beamline, at the Los Alamos Neutron Science Center (LANSCE) accelerator have determined that a radiation shielding shutter is required to protect personnel from shine from irradiated targets for routine beam tunnel entries. This paper will describe radiation dose modeling, shielding calculations, and the fail-safe mechanical shutter design.
Nonlinear evolution of interacting oblique waves on two-dimensional shear layers

The effects of critical layer nonlinearity are considered on spatially growing oblique instability waves on nominally two-dimensional shear layers between parallel streams. The analysis shows that three-dimensional effects cause nonlinearity to occur at much smaller amplitudes than it does in two-dimensional flows. The nonlinear instability wave amplitude is determined by an integro-differential equation with cubic type nonlinearity. The numerical solutions to this equation are worked out and discussed in some detail. The numerical solutions always end in a singularity at a finite downstream distance.
Valuation of the Debt Tax Shield

In this study, we use cross-sectional regressions to estimate the value of the debt tax shield. Recognizing that debt is correlated with the value of operations along nontax dimensions, we estimate reverse regressions in which we regress future profitability on firm value and debt rather than regressing firm value on debt and profitability. Reversing the regressions mitigates bias and facilitates the use of market information to control for differences in risk and expected growth. Our estimated value for the debt tax shield is approximately 40 percent ~10 percent! of debt balances ~firm value!, net of the personal tax disadvantage of debt. THE DEBT TAX SHIELD HAS STIMULATED decades of debate regarding firm valuation and the cost of capital. In 1963, Modigliani and Miller ~hereafter MM! first hypothesized that the tax benefits of debt increase firm value and decrease the cost of using debt capital. In 1977, Miller countered that firms pass out the tax benefits of debt to creditors through high interest rates to compensate them for the personal tax disadvantage of debt. Others have proposed that the financial distress costs of debt offset at least some of the tax benefits ~see, e.g., DeAngelo and Masulis, 1980!. A priori, therefore, the firm valuation and capital structure implications of the debt tax shield are unclear, so empirical investigation is required. Empirical investigation of the debt tax shield has followed three primary lines of inquiry. First, many studies investigate the MM prediction that the debt tax shield promotes the use of debt versus equity financing. For example, Bradley, Jarrell, and Kim ~1984!, Long and Malitz ~1985!, Titman and Wessels ~1988!, and Fischer, Heinkel, and Zechner ~1989! use various forms of debt0equity ratios to test whether nondebt tax shields, such as depreciation or investment tax credits, reduce the propensity to use debt tax shields. None of these studies find significant tax effects. In contrast, certain recent
Long trend dynamics in social media

A main characteristic of social media is that its diverse content, copiously generated by both standard outlets and general users, constantly competes for the scarce attention of large audiences. Out of this flood of information some topics manage to get enough attention to become the most popular ones and thus to be prominently displayed as trends. Equally important, some of these trends persist long enough so as to shape part of the social agenda. How this happens is the focus of this paper. By introducing a stochastic dynamical model that takes into account the user’s repeated involvement with given topics, we can predict the distribution of trend durations as well as the thresholds in popularity that lead to their emergence within social media. Detailed measurements of datasets from Twitter confirm the validity of the model and its predictions.
ILC RF system R&D

The ILC linac group at SLAC is actively pursuing a broad range of R&D to improve the reliability and reduce the cost of the L-band (1.3 GHz) rf system. Current activities include the development of a Marx-style modulator and a 10 MW sheet-beam klystron, construction of an rf distribution system with adjustable power tap- offs and custom hybrids, tests of cavity coupler components to understand rf processing limitations, simulations of multipacting in the couplers and optimization of the cavity fill parameters for operation with a large spread of sustainable cavity gradients. Also, a prototype positron capture cavity is being developed for the ILC injectors. This paper surveys the results from the past year and notes related L-band R&D at other labs, in particular, that at DESY for the XFEL project.
Evolving Discretionary Practices of U.S Antidumping Activity

Using data on U.S. dumping margin calculations by the U.S. Department of Commerce (USDOC), we first document the rapid rise in U.S. dumping margins from around 15% in the early 1980s to over 60% by 2000. Second, statistical analysis finds that USDOC discretionary practices have played the major role in rising U.S. dumping margins over this period. Importantly, the evolving effect of discretionary practices is due not only to increasing use of these practices over time, but to apparent changes in implementation of these practices that mean a higher increase in the dumping margin whenever they are applied. Utilisant des donnees sur le calcul de l'ecart entre les prix aux Etats-Unis et les prix de ces biens dans leur marche national d'origine (dumping margin) calcules par le U.S. Department of Commerce (USDOC), on montre que ces marges sont passees d'environ 15% au debut des annees 80 a plus de 60% en l'an 2000. Une analyse statistique suggere que les pratiques discretionnaires du USDOC ont joue un role important dans l'accroissement de ces marges au cours de la periode. Cela n'est pas attribuable seulement a l'accroissement de ces pratiques dans le temps, mais aux changements apparents dans la mise en application de ces pratiques qui se sont traduits par un accroissement de la marge quand on choisit de l'appliquer.
Structure of Water and Electron Beam Damaged High Temperature Superconductors

High Resolution electron microscope observations of the effect of water vapour and the electron beam on high temperature superconductors indicate that the effects are very similar. Water vapour leads to the decomposition into a barium compound which in the microscope is barium oxide (presumably barium carbonate in air) which takes the form of whiskers on the surface and the green and brown phases. The electron beam first produces a true surface amorphous phase which on prelonged irradiation develops a barium oxide surface coating. Different from the results of ion beam damage, we have not seen any evidence for preferential formation of the amorphous phase at grain boundaries. These results indicate that as the oxygen content of the material is reduced, the barium cations become more mobile and can therefore diffuse out to the surface.
On Fast and Accurate Detection of Unauthorized Wireless Access Points Using Clock Skews

We explore the use of clock skew of a wireless local area network access point (AP) as its fingerprint to detect unauthorized APs quickly and accurately. The main goal behind using clock skews is to overcome one of the major limitations of existing solutions - the inability to effectively detect Medium Access Control (MAC) address spoofing. We calculate the clock skew of an AP from the IEEE 802.11 Time Synchronization Function (TSF) time stamps sent out in the beacon/probe response frames. We use two different methods for this purpose - one based on linear programming and the other based on least-square fit. We supplement these methods with a heuristic for differentiating original packets from those sent by the fake APs. We collect TSF time stamp data from several APs in three different residential settings. Using our measurement data as well as data obtained from a large conference setting, we find that clock skews remain consistent over time for the same AP but vary significantly across APs. Furthermore, we improve the resolution of received time stamp of the frames and show that with this enhancement, our methodology can find clock skews very quickly, using 50-100 packets in most of the cases. We also discuss and quantify the impact of various external factors including temperature variation, virtualization, clock source selection, and NTP synchronization on clock skews. Our results indicate that the use of clock skews appears to be an efficient and robust method for detecting fake APs in wireless local area networks.
Experimental search for pentaquarks

Abstract The experimental evidence for pentaquarks, both old and new, is discussed. Constraints due to K + N scattering data from previous decades are first reviewed, and then experiments with positive evidence and those with null results. Finally, the problem of the narrow width of the Θ + pentaquark is discussed, along with theoretical implications.
Cosmological Recombination of Lithium and Its Effect on the Microwave Background Anisotropies

The cosmological recombination history of lithium, produced during big bang nucleosynthesis, is presented using updated chemistry and cosmological parameters consistent with recent cosmic microwave background (CMB) measurements. For the popular set of cosmological parameters, about a fifth of the lithium ions recombine into neutral atoms by a redshift z ~ 400. The neutral lithium atoms scatter resonantly the CMB at 6708 A and distort its intensity and polarization anisotropies at observed wavelengths around ~300 μm, as originally suggested by Loeb. The modified anisotropies resulting from the lithium recombination history are calculated for a variety of cosmological models and found to result primarily in a suppression of the power spectrum amplitude. Significant modification of the power spectrum occurs for models that assume a large primordial abundance of lithium. While detection of the lithium signal might prove difficult, it offers the possibility of inferring the lithium primordial abundance and is the only probe proposed to date of the large-scale structure of the universe for z ~ 500-100.
Enantioselective synthesis of β-amino esters and its application to the synthesis of the enantiomers of the antidepressant Venlafaxine

β-Amino esters are readily formed from the rhodium(II) prolinate-catalyzed intermolecular C–H insertion between methyl aryldiazoacetates and a bis-silyl protected methylamine.
Expansion of an Ion Sheath into a Collision-Dominated Plasma

If a large negative voltage is applied to an insulated disc inserted in a collision-dominated plasma, the electrons are expelled from the region near the disc leaving a bare cloud of ions. This "transient sheath" is well documented in ion acoustic wave experiments. This paper examines the evolution of the ions in this sheath into a collision-dominated plasma. A new sheath whose dimension is of the order of twice the transient sheath dimension if found.
Understanding the acceptability of a computer decision support system in pediatric primary care.

Objective Individual users' attitudes and opinions help predict successful adoption of health information technology (HIT) into practice; however, little is known about pediatric users' acceptance of HIT for medical decision-making at the point of care. Materials and methods We wished to examine the attitudes and opinions of pediatric users' toward the Child Health Improvement through Computer Automation (CHICA) system, a computer decision support system linked to an electronic health record in four community pediatric clinics. Surveys were administered in 2011 and 2012 to all users to measure CHICA's acceptability and users' satisfaction with it. Free text comments were analyzed for themes to understand areas of potential technical refinement. Results 70 participants completed the survey in 2011 (100% response rate) and 64 of 66 (97% response rate) in 2012. Initially, satisfaction with CHICA was mixed. In general, users felt the system held promise; however various critiques reflected difficulties understanding integrated technical aspects of how CHICA worked, as well as concern with the format and wording on generated forms for families and users. In the subsequent year, users' ratings reflected improved satisfaction and acceptance. Comments also reflected a deeper understanding of the system's logic, often accompanied by suggestions on potential refinements to make CHICA more useful at the point of care. Conclusions Pediatric users appreciate the system's automation and enhancements that allow relevant and meaningful clinical data to be accessible at point of care. Understanding users' acceptability and satisfaction is critical for ongoing refinement of HIT to ensure successful adoption into practice.
On fractionally spaced blind adaptive equalization under symbol timing offsets using Godard and related equalizers

The problem of fractionally spaced (FS) blind adaptive equalization under symbol-timing-phase offsets is considered. In the case of trained (nonblind) equalizers, the performance of FS equalizers is known to be independent of the timing-phase unlike that of baud-rate equalizers. Moreover, trained FS equalizers synthesize optimal filters in the minimum mean-square error sense, and hence are superior to baud-rate trained equalizers. It is an open question whether such properties hold true for FS Godard blind equalizers. We present a simulation example where such advantages do not materialize. We also present a solution based upon a parallel multimodel Godard baud-rate filter bank approach which yields a performance almost invariant w.r.t. symbol-timing-phase and superior to that of baud-rate equalizers.
TASI Lectures on the Cosmological Constant

The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision experiments. Absent overwhelming evidence to the contrary, dark energy can only be interpreted as vacuum energy, so the venerable assumption that Lambda=0 conflicts with observation. The possibility remains that Lambda is fundamentally variable, though constant over large spacetime regions. This can explain the observed value, but only in a theory satisfying a number of restrictive kinematic and dynamical conditions. String theory offers a concrete realization through its landscape of metastable vacua.
Application of detailed fission-product decay gamma spectra in the calculation of photoneutron spectra from D(. gamma. ,n) reactions in PWR fuel

Abstract The magnitude, average neutron energy, and spectrum of the photoneutron source in a PWR fuel is calculated for shutdown times to 100 y using CINDER radionuclide inventory calculations, ENDF/B-V γ line decay spectra, MCNP γ transport calculations, and PHONEX D(γ, n) reaction physics calculations.
Molecular memory with atomically smooth graphene contacts

We report the use of bilayer graphene as an atomically smooth contact for nanoscale devices. A two-terminal bucky-ball (C60) based molecular memory is fabricated with bilayer graphene as a contact on the polycrystalline nickel electrode. Graphene provides an atomically smooth covering over an otherwise rough metal surface. The use of graphene additionally prohibits the electromigration of nickel into the C60 layer. The devices exhibit a low-resistance state in the first sweep cycle and irreversibly switch to a high-resistance state at 0.8 to 1.2 V bias. In the subsequent cycles, the devices retain the high-resistance state, thus making it write-once read-many memory.
The topological classification of minimal surfaces in R^3

We give a complete topological classification of properly embedded minimal surfaces in Euclidian three-space
The Copper-Catalyzed N-Arylation of Indoles

A general method for the N-arylation of indoles using catalysts derived from CuI and trans-1,2-cyclohexanediamine (1a), trans-N,N'-dimethyl-1,2-cyclohexanediamine (2a), or N,N'-dimethyl-ethylenediamine (3) is reported. N-Arylindoles can be produced in high yield from the coupling of an aryl iodide or aryl bromide with a variety of indoles.
Instantaneous Liquid Interfaces

We describe and illustrate a simple procedure for identifying a liquid interface from atomic coordinates. In particular, a coarse-grained density field is constructed, and the interface is defined as a constant density surface for this coarse-grained field. In applications to a molecular dynamics simulation of liquid water, it is shown that this procedure provides instructive and useful pictures of liquid-vapor interfaces and of liquid-protein interfaces.
Effect of Shaft Frequency on Cavitation in a Journal Bearing for Noncentered Circular Whirl

This paper deals with the effect of shaft frequency on the performance of a submerged journal undergoing noncentered circular whirl. The main emphasis of the paper is on the behavior of the vapor cavitation bubble and its effect on the bearing performance as a function of frequency. A cavitation algorithm due to Elrod was implemented in a computer program which solves a time-dependent Reynolds equation. This algorithm automatically handles the boundary conditions by using a switch function and a control volume approach which conserves mass throughout the entire flow. The shaft frequencies in this investigation ranged from 0 rad/s (squeeze-film damper) to −104 rad/s (a case in which oil-whip condition was produced momentarily). For the particular vibration amplitude chosen in this investigation it was observed that vapor cavitation had an effect on the load components for the full range of shaft frequencies investigated. Presented at the 42nd Annual Meeting in Anaheim, California May 11–14, 1987
Environmental Impacts of Distributed Manufacturing from 3-D Printing of Polymer Components and Products

Although additive layer manufacturing is well established for rapid prototyping the low throughput and historic costs have prevented mass-scale adoption. The recent development of the RepRap, an open source self-replicating rapid prototyper, has made low-cost 3-D printers readily available to the public at reasonable prices (<$1,000). The RepRap (Prusa Mendell variant) currently prints 3-D objects in a 200x200x140 square millimeters build envelope from acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). ABS and PLA are both thermoplastics that can be injection-molded, each with their own benefits, as ABS is rigid and durable, while PLA is plant-based and can be recycled and composted. The melting temperature of ABS and PLA enable use in low-cost 3-D printers, as these temperature are low enough to use in melt extrusion in the home, while high enough for prints to retain their shape at average use temperatures. Using 3-D printers to manufacture provides the ability to both change the fill composition by printing voids and fabricate shapes that are impossible to make using tradition methods like injection molding. This allows more complicated shapes to be created while using less material, which could reduce environmental impact. As the open source 3-D printers continue to evolve and improve in both cost and performance, the potential for economically-viable distributed manufacturing of products increases. Thus, products and components could be customized and printed on-site by individual consumers as needed, reversing the historical trend towards centrally mass-manufactured and shipped products. Distributed manufacturing reduces embodied transportation energy from the distribution of conventional centralized manufacturing, but questions remain concerning the potential for increases in the overall embodied energy of the manufacturing due to reduction in scale. In order to quantify the environmental impact of distributed manufacturing using 3-D printers, a life cycle analysis was performed on a plastic juicer. The energy consumed and emissions produced from conventional large-scale production overseas are compared to experimental measurements on a RepRap producing identical products with ABS and PLA. The results of this LCA are discussed in relation to the environmental impact of distributed manufacturing with 3-D printers and polymer selection for 3-D printing to reduce this impact. The results of this study show that distributed manufacturing uses less energy than conventional manufacturing due to the RepRap's unique ability to reduce fill composition. Distributed manufacturing also has less emissions than conventional manufacturing when using PLA and when using ABS with solar photovoltaic power. The results of this study indicate that open-source additive layer distributed manufacturing is both technically viable and beneficial from an ecological perspective.
A framework to support managerial activities using office information systems

A broad discussion is presented of the problems and issues involved in the development of integrated office systems to support higher-level tasks of managers. The authors provide conceptual integration by establishing a framework for the office activities of managers. They discuss the technological integration of disparate office systems through architecture and design of an integrated office information system (IOIS). The IOIS described was developed from the integration of four IOISs at the University of Arizona: the integrated spreadsheet-based inferencing systems (ISBIS); Plexsys planning software (Plexware); the Resource Management Expert (RME); and an intelligent mail system (AIMAIL). >
Type Ia Supernovae and Cosmology

I discuss the use of Type Ia supernovae (SNe Ia) for cosmological distance determinations. Low-redshift SNe Ia (z ≲ 0.1) demonstrate that the Hubble expansion is linear with H 0 = 72±8 km s−1 Mpc−1, and that the properties of dust in other galaxies are generally similar to those of dust in the Milky Way. The light curves of high-redshift (z = 0.3–1) SNe Ia are stretched in a manner consistent with the expansion of space; similarly, their spectra exhibit slower temporal evolution (by a factor of 1 + z) than those of nearby SNe Ia. The measured luminosity distances of SNe Ia as a function of redshift have shown that the expansion of the Universe is currently accelerating, probably due to the presence of repulsive dark energy such as Einstein’s cosmological constant (Λ). From about 200 SNe Ia, we find that H 0 t 0 = 0.96±0.04, and ΩΛ − 1.4ΩM = 0.35±0.14. Combining our data with the results of large-scale structure surveys, we find a best fit for ΩM and ΩΛ of 0.28 and 0.72, respectively — essentially identical to the recent WMAP results (and having comparable precision). The sum of the densities, ∼ 1.0, agrees with extensive measurements of the cosmic microwave background radiation, including WMAP, and coincides with the value predicted by most inflationary models for the early Universe: the Universe is flat on large scales. A number of possible systematic effects (dust, supernova evolution) thus far do not seem to eliminate the need for ΩΛ > 0. However, during the past few years some very peculiar low-redshift SNe Ia have been discovered, and we must be mindful of possible systematic effects if such objects are more abundant at high redshifts. Recently, analyses of SNe Ia at z = 1.0–1.7 provide further support for current acceleration, and give tentative evidence for an early epoch of deceleration. The dynamical age of the Universe is estimated to be 13.1±1.5 Gyr, consistent with the ages of globular star clusters and with the WMAP result of 13.7±0.2 Gyr. According to the most recent data sets, the SN Ia rate at z > 1 is several times greater than that at low redshifts, presumably because of higher star formation rates long ago. Moreover, the typical delay time from progenitor star formation to SN Ia explosion appears to be substantial, ∼ 3 Gyr. Current projects include the search for additional SNe Ia at z > 1 to confirm the early deceleration, and the measurement of a few hundred SNe Ia at z = 0.2–0.8 to more accurately determine the equation-of-state parameter of the dark energy, w = {tiP}/(ρ c 2), whose value is now constrained by SNe Ia to be in the range −1.48 ≲ w ≲ – 0.72 at 95% confidence.
Tunable Ligands for Asymmetric Catalysis: Readily Available Carbohydrate-Derived Diarylphosphinites Induce High Selectivity in the Hydrovinylation of Styrene Derivatives

Only a limited number of ligands have been successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphonites prepared from readily available carbohydrates in conjunction with a highly dissociated counterion ([3,5-(CF3)2-C6H3)4B]- or SbF6-) effect the hydrovinylation of 4-bromostyrene or 4-isobutylstyrene under ambient pressure of ethylene with the best overall selectivities reported to date for these important substrates. In a prototypical synthesis of a 2-arylpropionic acid, 3-(4-bromophenyl)-1-butene (prepared in 98% isolated yield and 89% ee from 4-bromostyrene) has been transformed into (R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, ozonolysis, and subsequent oxidation of the resulting aldehyde.
Wealth Effects, Distribution, and the Theory of Organization☆

Abstract We construct a general equilibrium model of firm formation in which organization is endogenous. Firms are coalitions of agents providing effort and investment capital. Effort is unobservable unless a fixed monitoring cost is paid, and borrowing is subject to a costly state verification problem. Because incentives vary with an agent's wealth, different types of agents become attractive firm members under different circumstances. When borrowing is not costly, firms essentially consist of one type of agent and are organized efficiently. But when the costly state verification problem is sufficiently severe, firm organization will depend on the distribution of wealth: with enough inequality, it will tend to be dictated by incentives of rich agents to earn high returns to wealth, even if the chosen organizational form is not a technically efficient way to provide incentives.Journal of Economic LiteratureClassification Numbers: D2, D31, J41, L2.