cssi/SciSciGPT-SciSciNet huggingface dataset:
Fractal generation in a two-dimensional active-nematic fluid.

Active fluids, composed of individual self-propelled agents, can generate complex large-scale coherent flows. A particularly important laboratory realization of such an active fluid is a system composed of microtubules, aligned in a quasi-two-dimensional (2D) nematic phase and driven by adenosine-triphosphate-fueled kinesin motor proteins. This system exhibits robust chaotic advection and gives rise to a pronounced fractal structure in the nematic contours. We characterize such experimentally derived fractals using the power spectrum and discover that the power spectrum decays as k − β for large wavenumbers k. The parameter β is measured for several experimental realizations. Though β is effectively constant in time, it does vary with experimental parameters, indicating differences in the scale-free behavior of the microtubule-based active nematic. Though the fractal patterns generated in this active system are reminiscent of passively advected dye in 2D chaotic flows, the underlying mechanism for fractal generation is more subtle. We provide a simple, physically inspired mathematical model of fractal generation in this system that relies on the material being locally compressible, though the total area of the material is conserved globally. The model also requires that large-scale density variations are injected into the material periodically. The model reproduces the power-spectrum decay k − β seen in experiments. Linearizing the model of fractal generation about the equilibrium density, we derive an analytic relationship between β and a single dimensionless quantity r, which characterizes the compressibility.
Quantifying the contribution of Neanderthal introgression to the heritability of complex traits

Eurasians have ~2% Neanderthal ancestry, but we lack a comprehensive understanding of the genome-wide influence of Neanderthal introgression on modern human diseases and traits. Here, we quantify the contribution of introgressed alleles to the heritability of more than 400 diverse traits. We show that genomic regions in which detectable Neanderthal ancestry remains are depleted of heritability for all traits considered, except those related to skin and hair. Introgressed variants themselves are also depleted for contributions to the heritability of most traits. However, introgressed variants shared across multiple Neanderthal populations are enriched for heritability and have consistent directions of effect on several traits with potential relevance to human adaptation to non-African environments, including hair and skin traits, autoimmunity, chronotype, bone density, lung capacity, and menopause age. Integrating our results, we propose a model in which selection against introgressed functional variation was the dominant trend (especially for cognitive traits); however, for a few traits, introgressed variants provided beneficial variation via uni-directional (e.g., lightening skin color) or bi-directional (e.g., modulating immune response) effects.
An average John theorem

We prove that the 12–snowflake of any finite-dimensional normed space X embeds into a Hilbert space with quadratic average distortion O(log dim(X)). We deduce from this (optimal) statement that if an n–vertex expander embeds with average distortion D⩾1 into X, then necessarily dim(X)⩾nΩ(1∕D), which is sharp by the work of Johnson, Lindenstrauss and Schechtman (1987). This improves over the previously best-known bound dim(X)≳(logn)2∕D2 of Linial, London and Rabinovich (1995), strengthens a theorem of Matousek (1996) which resolved questions of Johnson and Lindenstrauss (1982), Bourgain (1985) and Arias-de-Reyna and Rodriguez-Piazza (1992), and answers negatively a question that was posed (for algorithmic purposes) by Andoni, Nguyen, Nikolov, Razenshteyn and Waingarten (2016).
Distributed Algorithms for Matching in Hypergraphs

We study the d-Uniform Hypergraph Matching (d-UHM) problem: given an n-vertex hypergraph G where every hyperedge is of size d, find a maximum cardinality set of disjoint hyperedges. For \(d\ge 3\), the problem of finding the maximum matching is NP-complete, and was one of Karp’s 21 NP-complete problems. In this paper we are interested in the problem of finding matchings in hypergraphs in the massively parallel computation (MPC) model that is a common abstraction of MapReduce-style computation. In this model, we present the first three parallel algorithms for d-Uniform Hypergraph Matching, and we analyse them in terms of resources such as memory usage, rounds of communication needed, and approximation ratio. The highlights include:
Right-angled Artin groups as normal subgroups of mapping class groups

We construct the first examples of normal subgroups of mapping class groups that are isomorphic to non-free right-angled Artin groups. Our construction also gives normal, non-free right-angled Artin subgroups of other groups, such as braid groups and pure braid groups, as well as many subgroups of the mapping class group, such as the Torelli subgroup. Our work recovers and generalizes the seminal result of Dahmani–Guirardel–Osin, which gives free, purely pseudo-Anosov normal subgroups of mapping class groups. We give two applications of our methods: (1) we produce an explicit proper normal subgroup of the mapping class group that is not contained in any level congruence subgroup and (2) we produce an explicit example of a pseudo-Anosov mapping class with the property that all of its even powers have free normal closure and its odd powers normally generate the entire mapping class group. The technical theorem at the heart of our work is a new version of the windmill apparatus of Dahmani–Guirardel–Osin, which is tailored to the setting of group actions on the projection complexes of Bestvina–Bromberg–Fujiwara.
Gluing equations for real projective structures on 3-manifolds

Given an orientable ideally triangulated 3-manifold M, we define a system of real valued equations and inequalities whose solutions can be used to construct projective structures on M. These equations represent a unifying framework for the classical Thurston gluing equations in hyperbolic geometry and their more recent counterparts in Anti-de Sitter and half-pipe geometry. Moreover, these equations can be used to detect properly convex structures on M. The paper also includes explicit examples where the equations are used to construct properly convex structures.
Graph Universal Adversarial Attacks: A Few Bad Actors Ruin Graph Learning Models

Deep neural networks, while generalize well, are known to be sensitive to small adversarial perturbations. This phenomenon poses severe security threat and calls for in-depth investigation of the robustness of deep learning models. With the emergence of neural networks for graph structured data, similar investigations are urged to understand their robustness. It has been found that adversarially perturbing the graph structure and/or node features may result in a significant degradation of the model performance. In this work, we show from a different angle that such fragility similarly occurs if the graph contains a few bad-actor nodes, which compromise a trained graph neural network through flipping the connections to any targeted victim. Worse, the bad actors found for one graph model severely compromise other models as well. We call the bad actors ``anchor nodes'' and propose an algorithm, named GUA, to identify them. Thorough empirical investigations suggest an interesting finding that the anchor nodes often belong to the same class; and they also corroborate the intuitive trade-off between the number of anchor nodes and the attack success rate. For the dataset Cora which contains 2708 nodes, as few as six anchor nodes will result in an attack success rate higher than 80\% for GCN and other three models.
MADLens, a python package for fast and differentiable non-Gaussian lensing simulations

Abstract We present MADLens a python package for producing non-Gaussian lensing convergence maps at arbitrary source redshifts with unprecedented precision. MADLens is designed to achieve high accuracy while keeping computational costs as low as possible. A MADLens simulation with only 25 6 3 particles produces convergence maps whose power agrees with theoretical lensing power spectra up to L = 10000 within the accuracy limits of HaloFit. This is made possible by a combination of a highly parallelizable particle-mesh algorithm, a sub-evolution scheme in the lensing projection, and a machine-learning inspired sharpening step. Further, MADLens is fully differentiable with respect to the initial conditions of the underlying particle-mesh simulations and a number of cosmological parameters. These properties allow MADLens to be used as a forward model in Bayesian inference algorithms that require optimization or derivative-aided sampling. Another use case for MADLens is the production of large, high resolution simulation sets as they are required for training novel deep-learning-based lensing analysis tools. We make the MADLens package publicly available under a Creative Commons License .
Channel Estimation via Successive Denoising in MIMO OFDM Systems: A Reinforcement Learning Approach

In general, reliable communication via multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) requires accurate channel estimation at the receiver. The existing literature largely focuses on denoising methods for channel estimation that depend on either (i) channel analysis in the time-domain with prior channel knowledge or (ii) supervised learning techniques which require large prelabeled datasets for training. To address these limitations, we present a frequency-domain denoising method based on a reinforcement learning framework that does not need a priori channel knowledge and pre-labeled data. Our methodology includes a new successive channel denoising process based on channel curvature computation, for which we obtain a channel curvature magnitude threshold to identify unreliable channel estimates. Based on this process, we formulate the denoising mechanism as a Markov decision process, where we define the actions through a geometry-based channel estimation update, and the reward function based on a policy that reduces mean squared error (MSE). We then resort to Q-learning to update the channel estimates. Numerical results verify that our denoising algorithm can successfully mitigate noise in channel estimates. In particular, our algorithm provides a significant improvement over the practical least squares (LS) estimation method and provides performance that approaches that of the ideal linear minimum mean square error (LMMSE) estimation with perfect knowledge of channel statistics.
Acceleration by Pulsar Winds in Binary Systems

In the absence of accretion torques, a pulsar in a binary system will spin down due to electromagnetic dipole radiation, and the spin-down power will drive a wind of relativistic electron-position pairs. Winds from pulsars with short periods will prevent any subsequent accretion but may be confined by the companion star atmosphere, wind, or magnetosphere to form a standing shock. This paper investigates the possibility of particle acceleration at such a pulsar wind shock and the production of VHE and UHE gamma-rays from interactions of accelerated protons in the companion star's wind or atmosphere. It is found that, in close binaries containing active pulsars, protons will be shock accelerated to a maximum energy dependent on the pulsar spin-down luminosity. If a significant fraction of the spin-down power goes into particle acceleration, these systems should be sources of VHE and possibly UHE gamma-rays. The application of the pulsar wind model to binary sources such as Cygnus X-3 is discussed, as well as the possibility of observing VHE gamma-rays from known binary radio pulsar systems. 62 refs.
Real-Time Speaker Counting in a Cocktail Party Scenario Using Attention-Guided Convolutional Neural Network

Most current speech technology systems are designed to operate well even in the presence of multiple active speakers. However, most solutions assume that the number of co-current speakers is known. Unfortunately, this information might not always be available in real-world applications. In this study, we propose a real-time, single-channel attention-guided Convolutional Neural Network (CNN) to estimate the number of active speakers in overlapping speech. The proposed system extracts higher-level information from the speech spectral content using a CNN model. Next, the attention mechanism summarizes the extracted information into a compact feature vector without losing critical information. Finally, the active speakers are classified using a fully connected network. Experiments on simulated overlapping speech using WSJ corpus show that the attention solution is shown to improve the performance by almost 3% absolute over conventional temporal average pooling. The proposed Attention-guided CNN achieves 76.15% for both Weighted Accuracy and average Recall, and 75.80% Precision on speech segments as short as 20 frames (i.e., 200 ms). All the classification metrics exceed 92% for the attention-guided model in offline scenarios where the input signal is more than 100 frames long (i.e., 1s).
Care and Liberation in Creating a Student-Led Public Interest Technology Clinic

Engineers disengage from public welfare concerns during undergraduate engineering education [1] . In her widely cited study, Erin Cech argued that this arises from a culture of depoliticization in engineering that dismisses “nontechnical” concerns and competencies, reifying a false technical/social dichotomy and meritocratic ideology that justifies existing social structures. Our college, Olin College of Engineering, was part of that study, displaying similar patterns to more traditional schools. We are resisting that trend by embracing “public interest technology” (PIT) [2] , which we believe offers a response to the culture of disengagement. In our application, PIT represents a community of practice that encourages engineers to fully engage with context, inequity, and uncertainty; to connect technical work to their own lives and environment; and to prioritize the common good while minimizing public harms.
Learning reward functions from diverse sources of human feedback: Optimally integrating demonstrations and preferences:

Reward functions are a common way to specify the objective of a robot. As designing reward functions can be extremely challenging, a more promising approach is to directly learn reward functions fr...
Cover Combinatorial Filters and Their Minimization Problem

Recent research has examined algorithms to minimize robots’ resource footprints. The class of combinatorial filters (discrete variants of widely-used probabilistic estimators) has been studied and methods for reducing their space requirements introduced. This paper extends existing combinatorial filters by introducing a natural generalization: cover combinatorial filters. In addressing the new —but still NP-complete— problem of minimization of cover filters, we show that multiple concepts previously believed about combinatorial filters (and actually conjectured, claimed, or assumed to be) are in fact false. For instance, minimization does not induce an equivalence relation. We give an exact algorithm for the cover filter minimization problem. Unlike prior work (based on graph coloring) we consider a type of clique-cover problem, involving a new conditional constraint, from which we can find more general relations. In addition to solving the more general problem, the algorithm also corrects flaws present in all prior filter reduction methods. In employing SAT, the algorithm provides a promising basis for future practical development.
Design of Vehicle Power Transmission Systems

The power transmission system is a critical component of any machine. Accordingly, the detailed analysis of this system is essential for both design purposes and the detailed assessment of machine performance. Due to the large number of possible power transmission system components and the nature of these systems, general power transmission system analysis methods have been difficult to develop. However, such analysis methods could meet a wide variety of needs for system design. This paper discusses the general power transmission system analysis approach developed by the authors over the last several years based on their study of vehicle powertrains. The formulation and solution of the governing equations are discussed, and the ability of the approach in addressing critical design related issues is demonstrated through an example system simulation.
The Size-Power Tradeoff in HAR Inference

Heteroskedasticity and autocorrelation-robust (HAR) inference in time series regression typically involves kernel estimation of the long-run variance. Conventional wisdom holds that, for a given kernel, the choice of truncation parameter trades off a test’s null rejection rate and power, and that this tradeoff differs across kernels. We formalize this intuition: using higher-order expansions, we provide a unified size-power frontier for both kernel and weighted orthonormal series tests using nonstandard “fixed-b” critical values. We also provide a frontier for the subset of these tests for which the fixed-b distribution is t or F. These frontiers are respectively achieved by the QS kernel and equal-weighted periodogram. The frontiers have simple closed-form expressions, which upon evaluation show that the price paid for restricting attention to tests with t and F critical values is small. The frontiers are derived for the Gaussian multivariate location model, but simulations suggest the qualitative findings extend to stochastic regressors.
Assumption-Lean Analysis of Cluster Randomized Trials in Infectious Diseases for Intent-to-Treat Effects and Network Effects

Cluster randomized trials (CRTs) are a popular design to study the effect of interventions in infectious disease settings. However, standard analysis of CRTs primarily relies on strong parametric m...
Ultrafast and Nonlinear Semiconductor Metasurfaces

Resonant dielectric metasurfaces offer unparalleled degrees of freedom to design flat-optics and study fundamental aspects of light mater interaction due to the freedom to use optical resonances of electrical and magnetic character and different symmetries, extremely low loss when operating below the semiconductor band gap, and controlled coupling and interactions between the meta-atoms. Additionally, transient sub-picosecond behavior can be imparted to the metasurface using pulsed pumping and controlling of carrier dynamics and decay. In this talk I will overview some of our work based on such metasurfaces made from III-V semiconductors. 1 In particular, I will focus on harmonic generation, 2 - 5 ultrafast switching and diffraction, 6 - 8 transient frequency conversion 9 and perfect absorbing metasurfaces for THz emission and detection. 10 - 15
High-oxygen-affinity hemoglobinopathy-associated erythrocytosis: Clinical outcomes and impact of therapy in 41 cases.

We describe presenting features, treatment strategies, and follow-up events involving 41 patients (median age 39 years, range 1-81; 54% males) with high oxygen affinity (HOA) hemoglobinopathy-associated erythrocytosis, seen at our institution (1973-2020). Thirty-four (83%) patients carried β-chain (13 Malmo, 4 Olympia, 3 San Diego, 2 Wood) and 7 (17%) α-chain (4 Dallas and one each Columbia-Missouri, Jackson, and Wayne) variants. Median (range) hemoglobin (Hgb)/hematocrit (Hct), serum erythropoietin and p50 were 18 g/dL/52.9% (16-21.9/48-66), 10.4 mIU (4-36.3), and 20 mmHg (12-25), respectively. Family history was documented in 24 patients and history of thrombosis in two (5%). Treatment included phlebotomy in 23 and antiplatelet therapy in 21 patients. At a median follow-up of 10 years, 23 (56%) patients reported one or more symptoms that were thought to be related to their increased Hct while thrombosis was documented in 10 (24%) patients. Neither Hgb/Hct level nor active phlebotomy showed a significant correlation with either thrombotic or nonthrombotic symptoms (p > .1 in all instances). Among 23 pregnancies recorded, 78% resulted in live births and no fetal loss was attributed to erythrocytosis. The current study does not implicate Hgb/Hct level as a major contributor of morbidity in HOA hemoglobinopathy-associated erythrocytosis and suggests limited therapeutic value for phlebotomy.
Reconstructing Interactive 3D Scenes by Panoptic Mapping and CAD Model Alignments

In this paper, we rethink the problem of scene reconstruction from an embodied agent’s perspective: While the classic view focuses on the reconstruction accuracy, our new perspective emphasizes the underlying functions and constraints such that the reconstructed scenes provide actionable information for simulating interactions with agents. Here, we address this challenging problem by reconstructing an interactive scene using RGB-D data stream, which captures (i) the semantics and geometry of objects and layouts by a 3D volumetric panoptic mapping module, and (ii) object affordance and contextual relations by reasoning over physical common sense among objects, organized by a graph-based scene representation. Crucially, this reconstructed scene replaces the object meshes in the dense panoptic map with part-based articulated CAD models for finer-grained robot interactions. In the experiments, we demonstrate that (i) our panoptic mapping module outperforms previous state-of-the-art methods, (ii) a high-performant physical reasoning procedure that matches, aligns, and replaces objects’ meshes with best-fitted CAD models, and (iii) reconstructed scenes are physically plausible and naturally afford actionable interactions; without any manual labeling, they are seamlessly imported to ROS-based simulators and virtual environments for complex robot task executions.1
SCARE: Side Channel Attack on In-Memory Computing for Reverse Engineering

In-memory computing (IMC) architectures provide a much needed solution to energy-efficiency barriers posed by Von-Neumann computing. The functions implemented in such in-memory architectures are often proprietary and constitute confidential intellectual property (IP). Our studies indicate that IMC architectures implemented using resistive RAM (RRAM) are susceptible to side channel attack (SCA). Unlike the conventional SCAs that are aimed to leak private keys from cryptographic implementations, SCA on IMC for reverse engineering (SCARE) can reveal the sensitive IP implemented within the memory through power/timing side channels. Therefore, the adversary does not need to perform invasive reverse engineering (RE) to unlock the functionality. We demonstrate SCARE by taking recent IMC architectures, such as dynamic computing in memory (DCIM) and memristor-aided logic (MAGIC) as test cases. Simulation results indicate that AND, OR, and NOR gates (which are the building blocks of complex functions) yield distinct power and timing signatures based on the number of inputs, making them vulnerable to SCA. We show that adversary can use templates (using foundry-calibrated simulations or fabricating known functions in test chips) and analysis to identify the structure of the implemented function by testing a limited number of patterns. We also propose countermeasures, such as redundant inputs and expansion of literals. Redundant inputs can mask the IP with 25% area and 20% power overhead. However, functions can be found at higher RE effort. Expansion of literals incurs 36% power overhead. However, it imposes a brute force search increasing the adversarial RE effort by $3.04\times $ .
Reactive navigation in partially familiar planar environments using semantic perceptual feedback

This article solves the planar navigation problem by recourse to an online reactive scheme that exploits recent advances in simultaneous localization and mapping (SLAM) and visual object recognitio...
Numerical transfer matrix study of frustrated next-nearest-neighbor Ising models on square lattices

Ising models with frustrated next-nearest-neighbor interactions present a rich array of modulated phases. These phases, however, assemble and relax slowly, which hinders their computational study. In two dimensions, strong fluctuations further hamper determining their equilibrium phase behavior from theoretical approximations. The exact numerical transfer matrix (TM) method, which bypasses both difficulties, can serve as a benchmark method once its own numerical challenges are surmounted. Building on our recent study [Hu and Charbonneau, Phys. Rev. B 103, 094441 (2021)], in which we evaluated the two-dimensional axial next-nearest-neighbor Ising model with transfer matrices, we here extend the effective usage of the TM method to Ising models with biaxial, diagonal, and third-nearest-neighbor frustration models. The high-accuracy TM numerics help resolve various physical ambiguities about these reference models, thus providing a clearer overview of modulated phase formation in two dimensions.
Inductive construction of stable envelopes

We revisit the construction of stable envelopes in equivariant elliptic cohomology (Aganagic and Okounkov in Elliptic stable envelopes. arXiv:1604.00423 ) and give a direct inductive proof of their existence and uniqueness in a rather general situation. We also discuss the specialization of this construction to equivariant K-theory.
Who Invented the Trinity Nuclear Test’s Christy Gadget? Patents and Evidence from the Archives

The Christy Gadget is the informal name for the plutonium device detonated in the Trinity test on July 16, 1945. In September 1944, Robert Christy, working in the theoretical implosion group, propo...
Analytic Study of Families of Spurious Minima in Two-Layer ReLU Neural Networks: A Tale of Symmetry II

We study the optimization problem associated with fitting two-layer ReLU neural networks with respect to the squared loss, where labels are generated by a target network. We make use of the rich symmetry structure to develop a novel set of tools for studying families of spurious minima. In contrast to existing approaches which operate in limiting regimes, our technique directly addresses the nonconvex loss landscape for a finite number of inputs $d$ and neurons $k$, and provides analytic, rather than heuristic, information. In particular, we derive analytic estimates for the loss at different minima, and prove that modulo $O(d^{-1/2})$-terms the Hessian spectrum concentrates near small positive constants, with the exception of $\Theta(d)$ eigenvalues which grow linearly with~$d$. We further show that the Hessian spectrum at global and spurious minima coincide to $O(d^{-1/2})$-order, thus challenging our ability to argue about statistical generalization through local curvature. Lastly, our technique provides the exact \emph{fractional} dimensionality at which families of critical points turn from saddles into spurious minima. This makes possible the study of the creation and the annihilation of spurious minima using powerful tools from equivariant bifurcation theory.
Learning with Different Amounts of Annotation: From Zero to Many Labels

Training NLP systems typically assumes access to annotated data that has a single human label per example. Given imperfect labeling from annotators and inherent ambiguity of language, we hypothesize that single label is not sufficient to learn the spectrum of language interpretation. We explore new annotation distribution schemes, assigning multiple labels per example for a small subset of training examples. Introducing such multi label examples at the cost of annotating fewer examples brings clear gains on natural language inference task and entity typing task, even when we simply first train with a single label data and then fine tune with multi label examples. Extending a MixUp data augmentation framework, we propose a learning algorithm that can learn from training examples with different amount of annotation (with zero, one, or multiple labels). This algorithm efficiently combines signals from uneven training data and brings additional gains in low annotation budget and cross domain settings. Together, our method achieves consistent gains in two tasks, suggesting distributing labels unevenly among training examples can be beneficial for many NLP tasks.
Pointwise normality and Fourier decay for self-conformal measures

Abstract Let Φ be a C 1 + γ smooth IFS on R , where γ > 0 . We provide mild conditions on the derivative cocycle that ensure that every self conformal measure is supported on points x that are absolutely normal. That is, for every integer p ≥ 2 the sequence { p k x } k ∈ N equidistributes modulo 1. We thus extend several state of the art results of Hochman and Shmerkin [29] about the prevalence of normal numbers in fractals. When Φ is self-similar we show that the set of absolutely normal numbers has full Hausdorff dimension in its attractor, unless Φ has an explicit structure that is associated with some integer n ≥ 2 . These conditions on the derivative cocycle are also shown to imply that every self conformal measure is a Rajchman measure, that is, its Fourier transform decays to 0 at infinity. When Φ is self similar and satisfies a certain Diophantine condition, we establish a logarithmic rate of decay.
Design and Realization of Ohmic and Schottky Interfaces for Oxide Electronics

Understanding band alignment and charge transfer at complex oxide interfaces is critical to tailoring and utilizing their diverse functionality. Towards this goal, we design and experimentally validate both Ohmic- and Schottky-like charge transfers at oxide/oxide semiconductor/metal interfaces. We utilize a method for predicting band alignment and charge transfer in ABO3 perovskites, where previously established rules for simple semiconductors fail. The prototypical systems chosen are the rare class of oxide metals, SrBO3 with B=V-Ta, when interfaced with the multifaceted semiconducting oxide, SrTiO3. For B=Nb and Ta, we confirm that a large accumulation of charge occurs in SrTiO3 due to higher energy Nb and Ta d-states relative to Ti; this gives rise to a high mobility metallic interface, which is an ideal epitaxial oxide/oxide Ohmic contact. On the other hand, for B=V, there is no charge transfer into the SrTiO3 interface, which serves as a highly conductive epitaxial gate metal. Going beyond these specific cases, this work opens the door to integrating the vast phenomena of ABO3 perovskites into a wide range of practical devices.
Association of socioeconomic status with long-term outcomes in 1-year survivors of allogeneic hematopoietic cell transplantation

Association of socioeconomic status with long-term outcomes in 1-year survivors of allogeneic hematopoietic cell transplantation
Enantioselectivity on Naturally Chiral Metal Surfaces

Enantioselective heterogeneous catalysis requires surfaces with structures that are chiral at the atomic level. It is possible to obtain naturally chiral surfaces from crystalline inorganic materials with chiral bulk structures. It is also possible to create naturally chiral surfaces from achiral materials by exposing surfaces that have atomic structures with no mirror symmetry planes oriented perpendicular to the surface. Over the past decade there have been a number of experimental and theoretical demonstrations of the enantiospecific physical phenomena and surface chemistry that arise from the adsorption of chiral organic compounds on the naturally chiral, high Miller index places of metals.
Extending Formal Cryptographic Protocol Analysis Techniques for Group Protocols and Low-Level Cryptographic Primitives

Abstract : We have recently seen the development of a number of new tools for the analysis of cryptographic protocols. Many of them are based on state exploration, that is, they try to find as many paths through the protocol as possible, in the hope that, if there is an error, it will be discovered. But, since the search space offered by a cryptographic protocol is infinite, this search alone cannot guarantee security if no attack is found. However, some state exploration tools do offer the ability to prove security results as well as find flaws by the use of theoretical results about the system that they are examining. In particular, the NRL Protocol Analyzer [4] allows its user to interactively prove lemmas that limit the size of its search space. If the resulting search space is finite, then it too can guarantee that a protocol is secure by performing an exhaustive search. However, the ability to make such guarantees brings with it certain limitations. In particular, most of the systems developed so far model only a very limited set of cryptographic primitives, often only encryption (public and shared key) and concatenation. They also avoid low-level features of cryptographic algorithms, such as the commutativity and distributivity properties of RSA.
Instrumentation and techniques for acoustic research in wind tunnels

Several methods for aiding acoustic measurements inside wind tunnels are described; these include: placing acoustic material in the test section, using low tip-speed drive fans for reducing background noise, using proper microphone strut design for low wind noise, using directional receivers, and simulating the reverberant noise fields. The instrumentation and techniques were developed for acoustic research in both a small and a large closed-test-section wind tunnel at NASA Ames Research Center, and may be applicable to many different types of aeroacoustic wind tunnels.
Acetate metabolism by Escherichia coli in high-cell-density fermentation.

Little is known about the cellular physiology of Escherichia coli at high cell densities (e.g., greater than 50 g [dry cell weight] per liter), particularly in relation to the cellular response to different growth conditions. E. coli W3100 cultures were grown under identical physical and nutritional conditions, by using a computer-controlled fermentation system which maintains the glucose concentration at 0.5 g/liter, to high cell densities at pH values of 6.0, 6.5, 7.0, and 7.5. The data suggest a relationship between the pH of the environment and the amount of acetate excreted by the organism during growth. At pH values of 6.0 and 6.5, the acetate reached a concentration of 6 g/liter, whereas at pH 7.5, the acetate reached a concentration of 12 g/liter. Furthermore, at pH values of 6.0 to 7.0, the E. coli culture undergoes a dramatic metabolic switch in which oxygen and glucose consumption and CO2 evolution all temporarily decreased by 50 to 80%, with a concomitant initiation of acetate utilization. After a 30-min pause in which approximately 50% of the available acetate is consumed, the culture recovers and resumes consuming glucose and oxygen and producing acetate and CO2 at preswitch levels. During the switch period, the specific activity of isocitrate lyase typically increases approximately fourfold.
Spatiotemporally modulated antennas

Antennas are the basic tool we use to bridge structural modes into free-space radiation. The properties of an antenna depend on its geometry, materials, and electric size, as well as on its environment. These are the degrees of freedom that one typically has in an antenna design, which determine its characteristics such as directivity, gain, input impedance, radiation efficiency etc. However, one may ask what about the time variable? Can it be used as an additional degree of freedom, namely, would it be possible to increase the variety of properties of a given antenna by modulating its materials, or by loading its terminals by a time dependent resonant tanks?
THE ROLE OF LATVIAN PORTS WITHIN BALTIC SEA REGION

Latvian ports play an important role in the national economy. Latvia has established itself as a transit country (mainly for the Russian, Central Asia and Belarus cargoes). Transit cargoes account for approximately 85% of the total volume of cargoes in the Latvian ports. The Latvian ports handle on average 60 million tons per year. The transportation and storage account for approximately 13% of the Latvian GDP, and the total revenues from transit cargoes account for approximately 4.4% of the GDP and are equal to 27.7% of the total volume of the export of services. Traditional competitors of the Latvian ports include Klaipeda, Tallinn, St. Petersburg and Primorsk ports. Also Ust-luga has joined the above list as it is developed rapidly by Russia. Thus, there is a threat that Russia might direct its cargoes to the ports of its own region by providing the sufficient capacity of its own ports. Therefore, it is necessary to pay special attention to the requalification of cargoes on the Latvian ports into the cargoes with high value added. The topicality of the issue of this research is determined by the current increased attention to the operation of the Latvian large ports, the efficiency of their operations and the competitiveness in comparison to other ports of the Baltic sea region, as well as the initiative of the European Commission regarding the review of the ports policy and their further operation on the European Union level. The article will be focused on Latvian large ports freight volume proportion in comparison to the Baltic Sea ports: Tallinn, Klaipeda, Ust-Luga. Calculations will be made using HHI index (Herfindahl-Hirschman Index), which describes „market power” division between all the subjects in the current market. Particular attention will be focused on cargo structure analysis of Baltic ports and restructuring of cargo circulation in the Baltic Sea region. DOI: http://dx.doi.org/10.5755/j01.eis.0.7.5145
Dense array EEG: Methodology and new hypothesis on epilepsy syndromes

Dense array EEG is a method of recording electroencephalography (EEG) with many more electrodes (up to 256) than is utilized with standard techniques that typically employ 19-21 scalp electrodes. The rationale for this approach is to enhance the spatial resolution of scalp EEG. In our research, dense array EEG is used in conjunction with a realistic model of head tissue conductivity and methods of electrographic source analysis to determine cerebral cortical localization of epileptiform discharges. In studies of patients with absence seizures, only localized cortical regions are involved during the attack. Typically, absences are accompanied by "wave-spike" complexes that show, both at the beginning and throughout the ictus, repetitive cycles of stereotyped, localized involvement of mainly mesial and orbital frontal cortex. Dense array EEG can also be used for long-term EEG video monitoring (LTM). We have used dense array EEG LTM to capture seizures in over 40 patients with medically refractory localization-related epilepsy, including both temporal and extra temporal cases, where standard LTM failed to reveal reliable ictal localization. One research goal is to test the validity of dense array LTM findings by comparison with invasive LTM and surgical outcome. Collection of a prospective series of surgical candidates who undergo both procedures is currently underway. Analysis of subjects with either generalized or localization-related seizures suggest that all seizures, including those traditionally classified as "generalized," propagate through discrete cortical networks. Furthermore, based on initial review of propagation patterns, we hypothesize that all epileptic seizures may be fundamentally corticothalamic or corticolimbic in nature. Dense array EEG may prove useful in noninvasive ictal localization, when standard methods fail. Future research will determine if the method will reduce the need for invasive EEG recordings, or assist in the appropriate placement of novel treatment devices.
Effects of different packaging atmospheres and injection-enhancement on beef tenderness, sensory attributes, desmin degradation, and display color.

The objectives were to determine the effects of packaging atmosphere and injection-enhancement on tenderness, sensory traits, desmin degradation, and display color of different beef muscles. Longissimus lumborum (LL; n = 12 pairs), semitendinosus (ST; n = 12 pairs), and triceps brachii (TB; n = 24 pairs; 12 from the same carcasses as the LL and ST and 12 additional pairs) were obtained from the same USDA Select, A-maturity carcasses. On d 7 postmortem, each muscle from one side of the carcass was injection-enhanced, and each muscle from the other side was nonenhanced. Steaks 2.54-cm thick were cut from the muscles and packaged in vacuum packaging (VP), ultra-low oxygen with CO (ULO(2)CO; 0.4% CO/35% CO(2)/69.6% N(2)) modified atmosphere packaging (MAP), or high-oxygen MAP (HiO(2); 80% O(2)/20% CO(2)) and assigned to 14-d tenderness or display followed by 18- or 28-d tenderness measurement. Steaks packaged in HiO(2) MAP were in dark storage (2 degrees C) for 4 d and all other steaks for 14 d. Steaks for Warner-Bratzler shear force, sensory panel (n = 8 trained panelists), and desmin degradation were cooked to 70 degrees C. Steaks were displayed under fluorescent lighting (2,153 lx, 3,000 K) for 7 d. Trained color panelists (n = 10) assigned display color scores. Enhanced steaks had lower (P 0.05) by packaging or enhancement. Enhanced steaks were darker (P < 0.05) initially than nonenhanced steaks. Steaks packaged in HiO(2) MAP discolored faster (P < 0.05) and to a greater extent (P < 0.05) than steaks packaged in VP or ULO(2)CO MAP. Nonenhanced muscles packaged in VP and ULO(2)CO MAP had more stable display color and very desirable tenderness and flavor compared with those packaged in HiO(2) MAP.
Evidence on the stochastic structure of exchange rates in the inter-war period

Investigations of the behaviour of exchange rates during the recent period of float have uncovered a number of robust results such as a random walk in spot rates, the presence of ARCH effects and the existence of common stochastic trends. Data on six exchange rates during the inter-war float are examined. These appear to be non-stationary and are characterized by conditional heteroscedasticity though there is little evidence of cointegration. Evidence of the transmission of volatility between markets is uncovered.
Investigation into three-dimensional effects of finite contact width on fretting fatigue

Three-dimensional effects due to finite contact width on the contact characteristics and fretting fatigue behavior were investigated. Two contact configurations were considered: cylinder-on-flat and flat with rounded edge-on flat. Three-dimensional finite element methodology was developed based on the submodeling technique. Stress components and relative displacement converged well with ease in both contact configurations; however, the flat pad configuration provided a slightly better and faster convergence. The contact region affected by the free edge boundary was dependent on the contact geometry, i.e. it was slightly more in the cylindrical pad than the flat pad, however the affected region was less than 7% of the total contact surface in the case of cylindrical-on-flat configuration. The contact pressure and stick region decreased at the free edge, which were in agreement with their experimental counterparts, hence a localized gross slip condition can develop near the free edge even though stick-slip condition prevails over most of the contact area. Analysis using a critical plane based multi-axial fatigue parameter showed that there is a very small effect due to free edge boundary on fletting fatigue crack initiation, which was confined near the edge. Two-dimensional plane strain analysis provided the contact characteristics and fretting fatigue behavior that were in agreement with their counterparts from three-dimensional analysis over most of the contact area. Therefore, two-dimensional plane strain methodology can be used for the analysis of fretting fatigue tests involving finite width.
β-adrenergic responsiveness in cultured aorta smooth muscle cells Effects of subculture and aging

Abstract β-Adrenoceptor-mediated vasorelaxation is diminished in vessels from a variety of aged species including humans. This phenomenon was studied for the first time in cultured aorta smooth muscle cells (ASMC) from young (4- to 6-month) and old (24- to 26-month) F-344 rats. Cyclic AMP (cAMP) accumulation was assessed following isoproterenol and forskolin stimulations in primary cultures and after 1–4 passages of aorta smooth muscle cells. Isoproterenol and forskolin increased cAMP accumulation 6- and 10-fold, respectively, in primary cultures from young rats. Isoproterenol stimulation was reduced markedly in passaged cells. Forskolin stimulation was unaffected, indicating passage-related phenotypic changes in receptor-mediated stimulation, but not in post-receptor adenylate cyclase activation. The response to isoproterenol was diminished in old animals, but that to forksolin was unaltered. Thus, cultured ASMC from F-344 rats are highly responsive toβ-adrenoceptor stimulation and demonstrate age-related changes, but undergo phenotypic modulation during passage.
The infrared spectra of some aliphatic monocarboxylic acids in the 700-350 cm -1 region

Abstract The infrared spectra of 28 aliphatic monocarboxylic acids of varying structure are recorded in the 700-350 cm −1 region. It is shown that the structural configuration adjacent to the carbonyl group affects the spectra in a specific manner. It is therefore possible to differentiate α-alkyl branched acids from straight-chain acids. Striking differences in the spectra of liquid and solid forms of the straight-chain acids were observed. The spectra of the solids below about 510 cm −1 are quite characteristic of the individual acids and may be used for differentiation of these compounds.