cssi/SciSciGPT-SciSciNet huggingface dataset:
Experimental and numerical simulation of dissolution and precipitation: implications for fracture sealing at Yucca Mountain, Nevada.

Abstract Plugging of flow paths caused by mineral precipitation in fractures above the potential repository at Yucca Mountain, Nevada could reduce the probability of water seeping into the repository. As part of an ongoing effort to evaluate thermal-hydrological-chemical (THC) effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation under anticipated temperature and pressure conditions in the repository. To replicate mineral dissolution by vapor condensate in fractured tuff, water was flowed through crushed Yucca Mountain tuff at 94 °C. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/l; silica was the dominant dissolved constituent. A portion of the steady-state mineralized water was flowed into a vertically oriented planar fracture in a block of welded Topopah Spring Tuff that was maintained at 80 °C at the top and 130 °C at the bottom. The fracture began to seal with amorphous silica within 5 days. A 1-D plug-flow numerical model was used to simulate mineral dissolution, and a similar model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The mineral precipitation simulations predicted the precipitation of amorphous silica at the base of the boiling front, leading to a greater than 50-fold decrease in fracture permeability in 5 days, consistent with the laboratory experiment. These results help validate the use of a numerical model to simulate THC processes at Yucca Mountain. The experiment and simulations indicated that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. However, differences in fluid flow rates and thermal gradients between the experimental setup and anticipated conditions at Yucca Mountain need to be factored into scaling the results of the dissolution/precipitation experiments and associated simulations to THC models for the potential Yucca Mountain repository.
Synthesis of furans and pyrroles via migratory and double migratory cycloisomerization reactions of homopropargylic aldehydes and imines.

A novel gold-catalyzed divergent synthesis of furans and pyrroles employing readily available homopropargylic aldehydes and imines has been developed. The regiochemical outcome of this reaction is dependent on the substituent on the terminal alkyne of substrate. Thus, substrates possessing alkyl and aryl substituent at the alkyne moiety produce 2,3,5-substituted furans and pyrroles via a migratory cycloisomerization reaction. Whereas, their silicon analogues are capable of undergoing a double migratory process leading to 2,3,4-substituted heterocycles.
[1+4] Cycloaddition of vinyl isocyanates with isocyanides. Construction of functionally elaborate pyrrolinone derivatives

Abstract Reaction of alkyl isocyanides with vinyl isocyanates affords highly functionalized pyrrolinone and hydroindolone products via a novel [1+4] cyclization process.
On the complexity of LR(k) testing

In this paper we derive upper bounds on the complexity of LR(k) testing both when k is considered to be a fixed integer and also when k is considered to be a parameter of the problem. In the latter case, we show that the lower bounds on the running time of such algorithms depend very strongly on the representation chosen for k. Thus LR(k) testing is NP-complete when k is expressed in unary and complete for nondeterministic exponential time when k is expressed in binary.These results carry over to many other parameterized classes of grammars, such as the LL(k), strong LL(k), SLR(k), LC(k), strong LC(k), BRC(l,k), BC(l,k) and extended precedence (l,k) grammars.
Is the CO adduct of myoglobin bent, and does it matter?

Early reports of a severely bent CO adduct in myoglobin inspired the idea that heme proteins discriminate against CO, relative to O2, via steric hindrance imposed by a distal histidine residue. Recent results showing that the bound CO is only slightly distorted do not by themselves overthrow the steric hypothesis, because the steric energy could be stored in displacements of the protein. However, experimental data on site-directed mutants show that the main determinant of ligand affinity changes is the polarity of the binding pocket and that H-bonding by the distal histidine accounts for about 85% of the O2/CO discrimination while steric hindrance accounts for the remaining 15%.
Taking, giving, and impure altruism in dictator games

We show that, if giving is equivalent to not taking, impure altruism could account for List’s (in Journal of Political Economy 115(3):482–493, 2007) finding that the payoff to recipients in a dictator game decreases when the dictator has the option to take. We examine behavior in dictator games with different taking options but equivalent final payoff possibilities. We find that recipients tend to earn more as the amount the dictator must take to achieve a given final payoff increases, a result consistent with the hypothesis that the cold prickle of taking is stronger than the warm glow of giving. We conclude that not taking is not equivalent to giving and agree with List (in Journal of Political Economy 115(3):482–493, 2007) that the current social preference models fail to rationalize the observed data.
SDSSJ092712.65+294344.0: NGC 1275 at z = 0.7?

SDSSJ092712.65+294344.0 was identified by the Sloan Digital Sky Survey as a quasar, but has the unusual property of having two emission-line systems offset by 2650 km s–1. One of these contains the usual combination of broad and narrow lines; the other contains only narrow lines. In the first paper commenting on this system, it was interpreted as a galaxy in which a pair of black holes had merged, imparting a several thousand km s–1 recoil to the new, larger black hole. In two other papers, it was interpreted as a small-separation binary black hole. We propose a new interpretation: that this system is a more distant analog of NGC 1275, a large and small galaxy interacting near the center of a rich cluster.
A geometrical approach to N = 2 super Yang-Mills theory on the two dimensional lattice

We propose a discretization of two dimensional Euclidean Yang-Mills theories with N = 2 supersymmetry which preserves exactly both gauge invariance and an element of supersymmetry. The approach starts from the twisted form of the continuum super Yang Mills action which we show may be written in terms of two real Kahler-Dirac fields whose components transform into each other under the twisted supersymmetry. Once the theory is written in this geometrical language it is straightforward to discretize by mapping the component tensor fields to appropriate geometrical structures in the lattice and by replacing the continuum exterior derivative and its adjoint by appropriate lattice covariant difference operators. The lattice action is local and possesses a unique vacuum state while the use of Kahler-Dirac fermions ensures the model does not exhibit spectrum doubling.
Cochleosacculotomy Revisited: Long-term Results Poorer Than Expected

• Cochleosacculotomy has been described as a simple, efficacious treatment for relief of vertigo in patients with Meniere's disease in whom medical therapy has failed. We reviewed records of 11 elderly patients with good vestibular function who were thought to be ideal candidates for this procedure. Average follow-up was 17 months. Contrary to previous reports, long-term control of vertigo was poor, and more than 80% of the patients suffered a significant hearing loss from this procedure. Four of 11 patients required a second surgical procedure to control their vertigo. Audiometric measures revealed statistically significant postoperative increases in puretone thresholds at all frequencies and speech reception threshold, and a decrease in discrimination scores. Based on the results of this study, we no longer plan to use cochleosacculotomy for the treatment of elderly patients with Meniere's disease. (Arch Otolaryngol Head Neck Surg. 1991;117:1150-1152)
Damage to solids caused by cavitation

This paper describes the early stages of cavitation damage observed in cavitating venturi tunnels. The cavitating fluids were water and mercury, and a wide range of specimen materials were used. The damage was found to consist of single-event symmetical craters and irregular fatigue-type failures. The degree of damage was highly sensitive to minor flow perturbations, and this is discussed. The effect of stress level in the specimen before testing, and relations between cavitation resistance and the mechanical properties of the materials are considered.
Tidal breakup of binary stars at the Galactic Center. II. Hydrodynamic simulations

In Paper I, we followed the evolution of binary stars as they orbited near the supermassive black hole (SMBH) at the Galactic center, noting the cases in which the two stars would come close enough together to collide. In this paper, we replace the point-mass stars by fluid realizations, and use a smoothed-particle hydrodynamics code to follow the close interactions. We model the binary components as main-sequence stars with initial masses of 1, 3, and 6 solar masses, and with chemical composition profiles taken from stellar evolution codes. Outcomes of the close interactions include mergers, collisions that leave both stars intact, and ejection of one star at high velocity accompanied by capture of the other star into a tight orbit around the SMBH. For the first time, we follow the evolution of the collision products for many ( 100) orbits around the SMBH. Stars that are initially too small to be tidally disrupted by the SMBH can be puffed up by close encounters or collisions, with the result that tidal stripping occurs in subsequent periapse passages. In these cases, mass loss occurs episodically, sometimes for hundreds of orbits before the star is completely disrupted. Repeated tidal flares, of either increasing or decreasing intensity, are a predicted consequence. In collisions involving a low-mass and a high-mass star, the merger product acquires a high core hydrogen abundance from the smaller star, effectively resetting the nuclear evolution clock to a younger age. Elements like Li, Be, and B that can exist only in the outermost envelope of a star are severely depleted due to envelope ejection during collisions and due to tidal forces from the SMBH. Tidal spin-up can occur due to either a collision or tidal torque by the SMBH at periapsis. However, in the absence of collisions, tidal spin-up of stars is only important in a narrow range of periapse distances, r t/2 r per r t, with r t the tidal disruption radius. We discuss the implications of these results for the formation of the S-stars and the hypervelocity stars.
Use of open source distribution for a machine tool controller

In recent years a growing number of government and university las, non-profit organizations and even a few for- profit corporations have found that making their source code public is good for both developers and users. In machine tool control, a growing number of users are demanding that the controllers they buy be `open architecture,' which would allow third parties and end-users at least limited ability to modify, extend or replace the components of that controller. This paper examines the advantages and dangers of going one step further, and providing `open source' controllers by relating the experiences of users and developers of the Enhanced Machine Controller. We also examine some implications for the development of standards for open-architecture but closed-source controllers. Some of the questions we hope to answer include: How can the quality be maintained after the source code has been modified? Can the code be trusted to run on expensive machines and parts, or when the safety of the operator is an issue? Can `open- architecture' but closed-source controllers ever achieve the level of flexibility or extensibility that open-source controllers can?© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Bayesian linking of geosynchronous orbital debris tracks as seen by the Large Synoptic Survey Telescope

Abstract We describe a Bayesian sampling model for linking and constraining orbit models from angular observations of “streaks” in optical telescope images. Our algorithm is particularly suited to situations where the observation times are small fractions of the orbital periods of the observed objects or when there is significant confusion of objects in the observation field. We use Markov Chain Monte Carlo to sample from the joint posterior distribution of the parameters of multiple orbit models (up to the number of observed tracks) and parameters describing which tracks are linked with which orbit models. Using this algorithm, we forecast the constraints on geosynchronous (GEO) debris orbits achievable with the planned Large Synoptic Survey Telescope (LSST). Because of the short 15 s exposure times, preliminary orbit determinations of GEO objects from LSST will have large and degenerate errors on the orbital elements. Combined with the expected crowded fields of GEO debris it will be challenging to reliably link orbital tracks in LSST observations given the currently planned observing cadence.
Overtwisted energy-minimizing curl eigenfields

This paper concerns topological and geometric properties of energy-minimizing solutions to the steady Euler equations for a fluid on a three-dimensional manifold. Specifically, we consider energy-minimizing divergence-free eigenfields of the curl operator in dimension three from the perspective of contact topology. We give a negative answer to a question of Etnyre and the first author by constructing curl eigenfields which minimize L2 energy on their co-adjoint orbit, yet are orthogonal to an overtwisted contact structure. We then show progress towards the conjecture that K-contact structures on Seifert fibred manifolds always define tight minimizers.
Proving Theorems about LISP Functions

We describe some simple heuristics combining evaluation and mathematical induction which we have implemented in a program that automatically proves a wide variety of theorems about recursive LISP functions. The method the program uses to generate induction formulas is described at length. The theorems proved by the program include that REVERSE is its own inverse and that a particular SORT program is correct. Appendix B contains a list of the theorems proved by the program.
EFFICIENCY OF MAGNETIC TO KINETIC ENERGY CONVERSION IN A MONOPOLE MAGNETOSPHERE

Unconfined relativistic outflows from rotating, magnetized compact objects are often well modeled by assuming that the field geometry is approximately a split-monopole at large radii. Earlier work has indicated that such an unconfined flow has an inefficient conversion of magnetic energy to kinetic energy. This has led to the conclusion that ideal magnetohydrodynamical (MHD) processes fail to explain observations of, e.g., the Crab pulsar wind at large radii where energy conversion appears efficient. In addition, as a model for astrophysical jets, the monopole field geometry has been abandoned in favor of externally confined jets since the latter appeared to be generically more efficient jet accelerators. We perform time-dependent axisymmetric relativistic MHD simulations in order to find steady-state solutions for a wind from a compact object endowed with a monopole field geometry. Our simulations follow the outflow for 10 orders of magnitude in distance from the compact object, which is large enough to study both the initial 'acceleration zone' of the magnetized wind as well as the asymptotic 'coasting zone'. We obtain the surprising result that acceleration is actually efficient in the polar region, which develops a jet despite not being confined by an external medium. Our models contain jets thatmore » have sufficient energy to account for moderately energetic long and short gamma-ray burst (GRB) events ({approx}10{sup 51}-10{sup 52} erg), collimate into narrow opening angles (opening half-angle {theta} {sub j} {approx} 0.03 rad), become matter-dominated at large radii (electromagnetic energy flux per unit matter energy flux {sigma} < 1), and move at ultrarelativistic Lorentz factors ({gamma} {sub j} {approx} 200 for our fiducial model). The simulated jets have {gamma} {sub j}{theta} {sub j} {approx} 5-15, so they are in principle capable of generating 'achromatic jet breaks' in GRB afterglow light curves. By defining a 'causality surface' beyond which the jet cannot communicate with a generalized 'magnetic nozzle' near the axis of rotation, we obtain approximate analytical solutions for the Lorentz factor that fit the numerical solutions well. This allows us to extend our results to monopole wind models with arbitrary magnetization. Overall, our results demonstrate that the production of ultrarelativistic jets is a more robust process than previously thought.« less
Experimental and theoretical study of a solar thermochemical receiver module

Abstract A prototype test module of a solar thermochemical receiver using an reaction system is designed, built, and tested to establish a technical data base for future subsystem design efforts. Emphasis is placed on experimental verification of the computer simulation to establish a reliable design tool to predict the thermochemical performance of the receiver with a reasonable degree of confidence. The computational results are compared with experimental results obtained from the module tested at New Mexico State University. Reasonable agreement is found over a range of test conditions. It is concluded that the present design offers satisfactory conversion performance and operational flexibility for the construction of a complete reactor/receiver unit for use in a 10- to 15-kW dish collector system. However, further development works are required to resolve the problems associated with the catalyst contamination and the reactor construction material compatibility.
Frequency shifts of colliding fermions in optical lattice clocks

We discuss the novel frequency shift due to inhomogeneous excitations, particularly in the context of optical frequency lattice clocks. We analyze in detail the frequency shifts due to scattering-induced tunneling. These shifts have terms that are linear and non-linear in the atomic density. We show that they are small at moderate to high lattice depths.
Integrated Anomaly Detection for cyber security of the substations

Cyber intrusions to substations of a power grid are a source of vulnerability since most substations are unmanned and with limited protection of the physical security. In the worst case, simultaneous intrusions into multiple substations can lead to severe cascading events, causing catastrophic power outages. In this paper, an integrated Anomaly Detection System (ADS) is proposed which contains host- and network-based anomaly detection systems for the substations, and simultaneous anomaly detection for multiple substations. Potential scenarios of simultaneous intrusions into the substations have been simulated using a substation automation testbed. The host-based anomaly detection considers temporal anomalies in the substation facilities, e.g., userinterfaces, Intelligent Electronic Devices (IEDs) and circuit breakers. The malicious behaviors of substation automation based on multicast messages, e.g., Generic Object Oriented Substation Event (GOOSE) and Sampled Measured Value (SMV), are incorporated in the proposed network-based anomaly detection. The proposed simultaneous intrusion detection method is able to identify the same type of attacks at multiple substations and their locations. The result is a new integrated tool for detection and mitigation of cyber intrusions at a single substation or multiple substations of a power grid.
Synthesis of diazadibenzo-18-crown-6 ligands with appended chromophoric and fluorophoric groups as potential metal ion chemosensors

Six new diazadibenzo-18-crown-6 ligands substituted with two each of 8-hydroxyquinoline (7), 8-amino-quinoline (attached through its C-2 or C-7 position) (12 and 13), 8-methoxyquinoline (18), 5-chloro-8-methoxyquinoline (19), and dansylamidoethyl (21) side arms were synthesized as potential metal ion chemosensors and potential reagents for the selective extraction of certain metal ions from aqueous solutions. Ligands 7, 12, 13, 18, and 19 were synthesized by reductive amination of diazadibenzo-18-crown-6 (5) and the appropriate quinolinecarboxaldehydes. Bis(dansylamidoethyl)-substituted ligand 21 was synthesized by treating diazacrown ether 5 with N-dansylaziridine (20).
Energy aware algorithm design via probabilistic computing: from algorithms and models to Moore's law and novel (semiconductor) devices

The energy consumed by computations is becoming an increasing concern both within the context of high-performance systems well as embedded systems, on par with the past focus on raw speed or its derivative performance. In this talk, we will outline a novel framework for designing and analyzing algorithms wherein the figure of merit is the energy complexity – a measure of the (physical) energy consumed. Using the formulation of an energy-aware switch, and a network of such switches, fundamental limits will be established for the energy needed for switching deterministically, as well as energy savings derived from probabilistic switching, with a probability of being correct, p. Specifically, it is shown that a single deterministic switching step for computing a BIT consumes at least (.(κ.T ln(2))) Joules of energy, whereas the energy consumed by a single probabilistic switching step to compute a PBIT can be as low as (.(κ.T ln(2p))) Joules. These results are developed within the context of an idealized switching device introduced here, constrained by the laws of classical (statistical) thermodynamics (of Maxwell, Boltzmann and Gibbs), as well as by the constraints of idealized semiconductor devices. Based on this notion of switching, models for algorithm analysis and design, as well as upper- and lower- bounds on energy complexity and hence, for the first time, asymptotic energy savings via the use of probabilistic computing will be established. Possible approaches to realizing these probabilistic switches using conventional CMOS technology, as well as their potential for accelerating the current semiconductor roadmap that is based on deterministic computing, including the projections implied by Moore’s law, will be outlined. This work draws upon basic concepts from computer science, microelectronics and classical thermodynamics, and in the interest of being self-contained, the presentation will include a brief survey of the relevant thermodynamics.
Triple asymmetric synthesis for fragment assembly: Validity of approximate multiplicativity of the three diastereofacial selectivities

Abstract A strategy of triple asymmetric synthesis is illustrated to be effective for stereochemical control in fragment assembly, a task often encountered in convergent natural product synthesis. The stereochemical outcome of aldol reactions involving three chiral components supports a rule of approximate multiplicativity of facial selectivities intrinsic to the chiral reactants involved in each reaction.
Lithium Production in Hot Advection-dominated Accretion Flows in Soft X-Ray Transients

High Li abundances have been reported in the late-type secondaries of five soft X-ray transients (SXTs): V404 Cyg, A0620-00, GS 2000+25, Nova Mus 1991, and Cen X-4. Since Li is likely to be depleted in stars of this type, the origin of the Li is puzzling. Li has not been seen in similar secondaries of cataclysmic variables, which suggests that the high Li abundance is not due to an anomalous suppression of Li depletion in close binaries. SXTs in the quiescent state have been modeled in terms of hot advection-dominated accretion flows (ADAFs), in which the ions are essentially at virial temperature. At such temperatures, Li production via α-α spallation is possible. We show that ADAFs can produce sufficient Li via spallation to explain the observations in the black hole SXTs V404 Cyg, A0620-00, GS 2000+25, and Nova Mus 1991. If this explanation is correct, it is the first independent confirmation that accretion flows in quiescent SXTs have a two-temperature plasma with ion temperature much higher than electron temperature. Depending on the Li depletion timescale in the secondary, which may range between 107-109 yr, the model requires ~10-4 to 10-6 of the accreted mass to be intercepted by the secondary after undergoing Li production and being ejected. In the case of the neutron star SXT, Cen X-4, we can explain the observed Li only if the mass-accretion rate is ~10-3 times the Eddington rate and if there is enhanced ejection due to a propeller effect. We discuss possible observational tests of this proposal. Li production during outbursts could be quite important and may even dominate over the production during quiescence, but the estimate of the Li yield is uncertain. We calculate the expected luminosity in gamma-ray lines due to the production of excited Li and Be nuclei, but conclude that the line cannot be detected with current instruments.
Equation-of-State Parameters for Poly(dimethylsiloxane)

Abstract The thermal expansivity α=V−1(∂V/∂T)p and thermal pressure coefficient γ=(∂p/∂T)v for poly(dimethylsiloxane) (PDMS), mol wt ≈ 105, have been determined accurately over the temperature ranges 20–207 and 24–161°, respectively. Characteristic parameters ν*, T*, and p* calculated from these results are compared with those for other polymers and for low molecular weight liquids. For PDMS, α is much larger and γ much smaller than for any other polymer. The characteristic pressure p* appears to be a more reliable index of the intermolecular energy than the cohesive energy density for this purpose. It is approximately the same for a polymer as for corresponding low molecular weight liquids. For PDMS and HMDS (hexamethyldisiloxane) p* assumes exceptionally low values of 341 and 358 J cm−3, respectively, which are duplicated only by the fluorocarbons (p* ≈ 360 J cm−3).
The ice pond—production and seasonal storage of ice for cooling

Abstract The ice pond is a scheme of making ice in winter and storing it for cooling in summer. During winter a large excavated reservoir is filled with a snow/ice mixture produced by a snow machine of the type used in ski resorts. At the end of the cold season the ice is covered with insulation. When cooling is needed, chilled water is pumped from the pond, and, after being warmed by the load, the water is returned to the pond. Since the ice in the ice pond is porous, it forms a very effective heat exchanger. Water can be extracted at temperatures between 0 and 1°C, thus providing excellent potential for dehumidification. Experimental ice ponds have been built and operated from 1980 to 1982, and a full scale ice pond (with 10,000 m3 capacity) has been built to supply cooling for a 12,000 m2 office building. This paper describes the operating experience gained so far. The basic processes of ice making, ice preservation and ice utilization are described, and the economic prospects for ice ponds are analysed.
Constructions of Kähler–Einstein metrics with negative scalar curvature

We show that on Kahler manifolds with negative first Chern class, the sequence of algebraic metrics introduced by Tsuji converges uniformly to the Kahler–Einstein metric. For algebraic surfaces of general type and orbifolds with isolated singularities, we prove a convergence result for a modified version of Tsuji’s iterative construction.
STABILITY OF MOTIONS OF THERMOELASTIC FLUIDS

It is shown that the second law of thermodynamics induces uniqueness and continuous dependence upon initial-state and supply terms of smooth thermodynamic processes of thermoelastic fluids within the broader class of thermodynamic processes with shock waves.
Optimization of ARQ Protocols in Interference Networks with QoS Constraints

We study optimal transmission strategies in interfering wireless networks, under Quality of Service constraints. A buffered, dynamic network with multiple sources is considered, and sources use a retransmission strategy in order to improve packet delivery probability. The optimization problem is formulated as a Markov Decision Process, where constraints and objective functions are ratios of time-averaged cost functions. The optimal strategy is found as the solution of a Linear Fractional Program, where the optimization variables are the steady-state probability of state-action pairs. Numerical results illustrate the dependence of optimal transmission/interference strategies on the constraints imposed on the network.
Spontaneous Self-Embedding of Three-Dimensional SiGe Islands

It is shown that. under appropriate conditions, high-Ge-concentration coherent 3D SiGe islands grown on Si(100) self-embed in a matrix of low-Ge-concentration alloy. The process may be more generally useful for preserving the shape of self-assembled “quantum dot” islands during embedding in a matrix material.
Free radical 4‐nitrophenylation of thieno[2,3‐b]pyridine. Part 1: General experimental procedure and prediction of isomeric ratios of products

Thieno[2,3-b]pyridine (1) was warmed at 45 ± 7° with diazotized 4-nitroaniline (2) (molar ratio 1:2 = 3.6:1) in buffered (sodium acetate-acetic acid) aqueous solution until gas evolution ceased. The reaction mixture was separated into these fractions: (a) water-soluble (discarded), (b) acetone-soluble (tars), (c) ether-soluble, and (d) ether- and chloroform-soluble, but acetone-insoluble (rust-colored solids, Y, 12% yield as 4-nitrophenyl-1 isomers, 3). Fractional evaporative distillations of (b) and (c) gave recovered 1 (69%) and yellow-red sublimates (Z, 20% yield as 3). Y and Z were handled separately for isolation and identification of isomers [2]. Three general methods for predicting the isomeric ratios of 3 which one should obtain are presented, viz. (1) an amalgamation of reported free-radical phenylation results for quinoline and benzo[b]thiophene, (2) calculations of Frontier Radical Densities for positions 2-6 only, and (3) Molecular Orbital calculations for electron densities and superdelocalizabilities for free-radical attack at positions 1-7, as modified by a proposed rearrangement of the attacking group from the heteroatomic N and S positions to adjacent alpha positions.
Vinylboranes as trans-dihydroxyethylene equivalents for diels-alder reactions

Abstract Several vinylboranes were explored as trans -1,2-dihydroxyethylene equivalents for Diels-Alder reactions. Use of the 1,2-bis(boryl)ethylene 4 allows the direct formation of 1,2-dihydroxycyclohexenes in high yield. The 2-phenyldimethylsilylvinylborane 8 is a good alternative that allows for hydroxyl-group differentiation.
Experiences teaching operating systems using virtual platforms and Linux

Operating system courses teach students much more when they provide hands-on kernel-level project experience with a real operating system. However, enabling a large class of students to do kernel development can be difficult. To address this problem, we created a virtual kernel development environment in which operating systems can be developed, debugged, and rebooted in a shared computer facility without affecting other users. Using virtual machines and remote display technology, our virtual kernel development laboratory enables even distance learning students at remote locations to participate in kernel development projects with on-campus students. We have successfully deployed and used our virtual kernel development environment together with the open-source Linux kernel to provide kernel-level project experiences for over nine hundred students in the introductory operating system course at Columbia University.
Dynamic changes and processes in the Mississippi River delta

Research in the modern delta of the Mississippi River has revealed short-term changes and processes that are of significant magnitude. Deltaic lobes, each lobe covering an area of 30,000 sq km and having an average thickness of 35 km, switch sites of deposition on an average of every 1,500 yr. Through short periods of geologic time, this process results in a relatively thick accumulation of stacked deltaic cycles covering extremely large areas. Within a single delta lobe, and operating on an even higher frequency, are bay fills and overbank splays. Bay fills, having areas of 250 sq km and thickness of 15 m, require only 150 yr to accumulate. Four major events have taken place in the modern Balize delta since 1838. Overbank splays are much smaller, covering areas of less than 2 sq km and having thicknesses of 3 m, but are associated with high floods on the river. At the river mouth, continued progradation of the distributary channel can form distributary mouth sand bodies that have dimensions of 17 km long, 8 km wide, and a thickness of 80 m in a period of only 200 yr. Differential sedimentary loading at the river mouth results in formation of diapirs that display vertical movements in excess of 100 m in a period of 20 yr. On the subaqueous delta platform, sediment instabilities operate nearly continuously, mass-moving large quantities of shallow-water deposits to deeper-water environments via arcuate rotational slides and mudflow gullies and depositional lobes. All of these changes and processes operate at differing spatial and temporal scales, but all result in deposition of large volumes of sediment over extremely short periods of time.
Oxidant-induced Endothelial Leak Correlates with Decreased Cellular Energy Levels

A common finding in oxidant-induced organ injury is loss of vascular endothelial cell (EC) integrity and subsequent leak. The mechanisms involved are unclear, but maintenance of EC structure and functional integrity is highly dependent on the EC energy level. This study investigates whether oxidant-induced EC injury and concomitant increased monolayer permeability correlate with decreased energy levels. Rabbit pulmonary microvascular EC in vitro were exposed to varying levels of glucose oxidase as an oxidant-generating source for 2 h. Permeability changes were determined by albumin-Evans blue dye exclusion by monolayers of EC. ATP (nm/10(6) cells) and energy charge [ATP + 1/2ADP/(ATP + ADP + AMP)] were determined by HPLC. ATP and energy charge were found to decrease as permeability increased in response to increasing glucose oxidase concentration. ATP levels were a significantly more sensitive predictor of increased permeability than was energy charge. At 24 h, both permeability and ATP levels returned toward baseline. It appears that cell energy charge is preserved despite significant increases in monolayer permeability.
Temperature and pressure measurements using oxygen fluorescence

Abstract A method for the measurement of temperature and pressure using oxygen fluorescence for eventual use aboard an aircraft is presented. A xenon flashlamp is used to excite oxygen molecules with photons of wavelengths from 185 to 200 nm. Large windows of detection (100 nm and 65 nm) are used to reduce the fluctuations in the total measured fluorescence caused by predissociation and quantum noise. Temperature and pressure are correlated with fluorescence ratio. The resulting error in temperature and pressure is found to depend on the number of averaged samples. A typical error for a flash rate of 60 Hz is ±3 °C for temperatures from −22 to 44 °C and ±0.06 atm for pressures from 0.5 to 2.0 atm.
Information and Distinguishability of Ensembles of Identical Quantum States

We consider a fixed quantum measurement performed over n identical copies of quantum states. Using a rigorous notion of distinguishability based on Shannon’s 12th theorem, we show that in the case of a single qubit, the number of distinguishable states is \(W(\alpha_1,\alpha_2,n)=|\alpha_1-\alpha_2|{\sqrt{\frac{2n}{\pi e}}}\), where (α1,α2) is the angle interval from which the states are chosen. In the general case of an N-dimensional Hilbert space and an area Ω of the domain on the unit sphere from which the states are chosen, the number of distinguishable states is \(W(N,n,\Omega)=\Omega(\frac{2n}{\pi e})^{\frac{N-1}{2}}\). The optimal distribution is uniform over the domain in Cartesian coordinates.
The Factorial Function and Generalizations

(2000). The Factorial Function and Generalizations. The American Mathematical Monthly: Vol. 107, No. 9, pp. 783-799.
Incentives, downsizing, and value creation at General Dynamics

In 1991, defense contractor General Dynamics engaged a new management team which adopted an explicit corporate objective of creating shareholder value. The company tied executive compensation to shareholder wealth creation, and subsequently implemented a strategy that included downsizing, restructuring, and exit. Paying large executive cash bonuses amid layoffs ignited controversy. However, by 1993 shareholders realized gains approaching $4.5 billion, representing a dividend-reinvested return of 553%. The study shows how incentives assist in shaping strategy, illustrates the political costs and economic benefits of downsizing and demonstrates that even firms in declining industries have substantial opportunities for value creation.
Predictions from three-generation Calabi-Yau string theory.

Superstring models are considered where there is ${\mathrm{E}}_{6}$ flux breaking to [SU(3)${]}^{3}$ at compactification and dynamical breaking of [SU(3)${]}^{3}$ to SU(3${)}_{\mathit{C}}$\ifmmode\times\else\texttimes\fi{}SU(2${)}_{\mathit{L}}$\ifmmode\times\else\texttimes\fi{}U(1${)}_{\mathit{Y}}$ at an intermediate scale ${\mathit{M}}_{\mathit{I}}$. If the intermediate scale breaking preserves matter parity (to stabilize the proton) and is triggered by supersymmetry breaking, then it is shown that there will always be at least two, and often four, new light SU(3${)}_{\mathit{C}}$\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}U(1) neutral chiral multiplets (in addition to the usual standard-model states). The interactions of these new particles with the standard-model particles are deduced and are expected to produce \ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma} decay and, in some cases, neutrino masses and oscillations in a range that may be accessible to experiment.
Separation and Surface Nuclei Effects in a Cavitation Susceptibility Meter

This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM's with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.
Representations of modular skew group algebras

In this paper we study representations of skew group algebras $\Lambda G$, where $\Lambda$ is a connected, basic, finite-dimensional algebra (or a locally finite graded algebra) over an algebraically closed field $k$ with characteristic $p \geqslant 0$, and $G$ is an arbitrary finite group each element of which acts as an algebra automorphism on $\Lambda$. We characterize skew group algebras with finite global dimension or finite representation type, and classify the representation types of transporter categories for $p \neq 2,3$. When $\Lambda$ is a locally finite graded algebra and the action of $G$ on $\Lambda$ preserves grading, we show that $\Lambda G$ is a generalized Koszul algebra if and only if so is $\Lambda$.
Integrated robust identification and control of large-scale processes

We propose the use of pseudo-singular values, which are closely related to singular values but are allowed to have sign, as a convenient approach for developing techniques for the identification and control of large-scale processes. Steady-state controllability can be assessed directly in terms of the pseudo-singular values. It is shown that to control an output disturbance direction with zero steady-state error it is necessary to correctly identify the sign of the corresponding pseudo-singular value. At the identification stage, this motivates the estimation of confidence intervals for the pseudo-singular values from input-output data. A controller with integral action should not attempt to manipulate in process input directions corresponding to output disturbance directions that cannot be controlled with confidence. These principles motivate a controller structure appropriate for providing the robust control of poorly conditioned large-scale processes. Any controller design technique can be applied to produce a controller with the proposed controller structure. The controllability results and the integrated identification/controller design procedure are illustrated using an industrial paper machine example.
Optically sectioned fluorescence endomicroscopy with hybrid-illumination imaging through a flexible fiber bundle

We present an endomicroscope apparatus that exhibits out-of-focus background rejection based on wide-field illumination through a flexible imaging fiber bundle. Our technique, called HiLo microscopy, involves acquiring two images, one with grid-pattern illumination and another with standard uniform illumination. An evaluation of the image contrast with grid-pattern illumination provides an optically sectioned image with low resolution. This is complemented with high-resolution information from the uniform illumination image, leading to a full-resolution image that is optically sectioned. HiLo endomicroscope movies are presented of fluorescently labeled rat colonic mucosa.
Laguerre-Gaussian modes and the Wigner transform

Recent developments in laser physics have called renewed attention to Laguerre–Gaussian (LG) beams of paraxial light. In this paper we consider the corresponding LG modes for the two-dimensional harmonic oscillator, which appear in the transversal plane at the laser beam's waist. We see how they arise as Wigner transforms of Hermite–Gaussian modes, and we proceed to find a closed form for their own Wigner transforms, providing an alternative to the methods of Simon and Agarwal. Our main observation is that the Wigner transform intertwines the creation and annihilation operators for the two classes of modes.
State gun policy and cross-state externalities: evidence from crime gun tracing

This paper provides a theoretical and empirical analysis of cross-state externalities associated with gun regulations that impact gun trafficking. Using tracing data, which identify the source state for crime guns recovered in destination states, we find that firearms tend to flow from states with weak laws to states with strict laws, satisfying a key theoretical condition for the existence of externalities. We also find that gun flows are more significant between nearby states, suggesting that externalities are spatial in nature. Finally, we present evidence that criminal possession of guns is higher in states exposed to weak laws in nearby states. Language: en
Spacecraft Formation Dynamics and Design

Previous research on the solutions of two-point boundary value problems is applied to spacecraft formation dynamics and design. The underlying idea is to model the motion of a spacecraft formation as a Hamiltonian dynamic system in the vicinity of a reference solution. Then the nonlinear phase flow can be analytically described using generating functions found by solving the Hamilton‐Jacobi equation. Such an approach is very powerful and allows the study of any Hamiltonian dynamical systems independent of the complexity of its vector field and the solution of any two-point boundary value problem to be solved using only simple function evaluations. The details of the approach are presented through the study of a nontrivial example, the design of a formation in Earth orbit. For the analysis, the effect of the J2 and J3 gravity coefficients are taken into account. The reference trajectory is chosen to be an orbit with high inclination, i = π/3, and eccentricity, e = 0.3. Two missions are considered. First, given several tasks over a one-month period modeled as configurations at given times, the optimal sequence of reconfigurations to achieve these tasks with minimum fuel expenditure is found. Next, the theory is used to find stable configurations such that the spacecraft stay close to each other for an arbitrary but finite period of time. Both of these tasks are extremely difficult using conventional approaches, yet are simple to solve with the presented approach.
Some Constraints on the Formation of Globular Clusters

We explore the constraints on globular cluster formation provided by the observed conditions in starbursts in which globular clusters are currently forming and by the observed properties of young and old globular clusters. We note that the pressure in the interstellar medium of starbursts and mergers implies that molecular clouds in these environments have radii similar to those of globular clusters. Such molecular clouds are therefore viable precursors to globular clusters if the star formation efficiency in the clouds is high. A high star formation efficiency may be a consequence of the high density and associated high binding energy and short dynamical timescale of molecular clouds in such environments. We also note that the apparent lack of a mass-radius relationship in young and old globular cluster systems places important constraints on globular cluster formation models. This is because molecular clouds are observed to follow a virial scaling relation between mass and radius. We suggest that a variable star formation efficiency may weaken or eliminate the mass-radius relation of molecular clouds as they fragment to form globular clusters. We attribute the absence of young globular clusters in the disks of ordinary galaxies such as the Milky Way to the relatively low ambient pressures in such systems.
Location decision of heterogeneous multinational firms

Abstract We examine how multinational firms with heterogeneous total factor productivity (TFP) self-select into different host countries. Both aggregate- and firm-level estimates suggest that more productive French firms are more likely than their less efficient competitors to invest in relatively tough host countries. Countries with a smaller market potential, higher fixed costs of investment or lower import tariffs tend to have higher cutoff productivities and attract a greater proportion of productive multinationals. This self-selection mechanism remains largely robust when we control for unobserved firm and country heterogeneity and address potential TFP endogeneity.
AN ACCOUNT OF RECENT INVESTIGATIONS RELATING TO THE LUNEBURG THEORY OF BINOCULAR SPACE PERCEPTION

(1955). An Account of Recent Investigations Relating to the Luneburg Theory of Binocular Space Perception. Clinical and Experimental Optometry: Vol. 38, No. 5, pp. 226-229.