Stress-induced suppression of natural killer cell cytotoxicity in the rat: A naltrexone-insensitive paradigm.

The suppression of natural killer (NK) cell cytotoxicity by footshock stress can be attenuated by opioid antagonists, implicating endogenous opioids in its mediation. A stress paradigm that includes NK suppression that is not blocked by the opioid antagonist naltrexone is reported. This stress paradigm is also shown to cause analgesia and elevated plasma corticosterone levels that are not attenuated by naltrexone. In the first experiment, a significant suppression of NK cell cytotoxicity after forced swimming was demonstrated in Fischer 344 rats treated with either saline or naltrexone, compared with nonstressed controls. Significantly higher corticosterone levels were evident in both stressed groups. In the second experiment, the same stress paradigm was shown to cause significant analgesia in the tail-flick test. It is concluded that opioids need not always be involved in the suppression of NK cell cytotoxicity by stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling study of the light stimulation of a neuron cell with channelrhodopsin-2 mutants

Channelrhodopsin-2 (ChR2) has become a widely used tool for stimulating neurons with light. Nevertheless, the underlying dynamics of the ChR2-evoked spikes are still not yet fully understood. Here, we develop a model that describes the response of ChR2-expressing neurons to light stimuli and use the model to explore the light-to-spike process. We show that an optimal stimulation yield is achieved when the optical energies are delivered in short pulses. The model allows us to theoretically examine the effects of using various types of ChR2 mutants. We show that while increasing the lifetime and shuttering speed of ChR2 have limited effect, reducing the threshold irradiance by increased conductance will eliminate adaptation and allow constant dynamic range. The model and the conclusion presented in this study can help to interpret experimental results, design illumination protocols, and seek improvement strategies in the nascent optogenetic field.     

Tuning energetic levels in nanocrystal quantum dots through surface manipulations

We demonstrate tuning of the electronic level positions with respect to the vacuum level in colloidal InAs nanocrystals using surface ligand exchange. Electrochemical as well as scanning tunneling spectroscopy measurements reveal that the tuning is largely dependent on the nanocrystal size and the surface linking group, while the polarity of the ligand molecules has a lesser effect. The implications of affecting the electronic system of nanocrystal through its capping are illustrated through prototype devices.     

Environmentally friendly slow release formulations of alachlor based on clay-phosphatidylcholine

A new clay-liposome complex was developed for reducing leaching of herbicides and contamination of groundwater. The liposomes were composed of the neutral and Environmental Protection Agency approved phospholipid phosphatidylcholine (PC). Adsorption of PC liposomes on the clay mineral montmorillonite could exceed the cation exchange capacity of the clay, and was well simulated by the Langmuir equation. X-ray diffraction results for 6 mM PC and 1.6 g/L clay (3 day incubation) yielded a basal spacing of 7.49 nm, which was interpreted as the formation of a supported planar bilayer on montmorillonite platelets. Fluorescence methods demonstrated structural changes which reflected adsorption of PC followed by loss of vesicle integrity as measured by the penetration of dithionite into the internal monolayer of fluorescently labeled liposomes, resulting in a decrease in fluorescence intensity to 18% of initial after 4 h. Energy transfer was demonstrated after 1 h from labeled liposomes to montmorillonite labeled by an acceptor. The neutral herbicide alachlor adsorbed on the liposome-clay complex, yielding a formulation of up to 40% active ingredient, and 1.6-fold reduction in herbicide release in comparison to the commercial formulation. Hence, the PC-montmorillonite complex can form a basis for environmentally friendly formulations of herbicides, which would yield reduced leaching.     

The relative growth of internal organs in light and heavy breeds

The relative weights of the gastro-intestinal segments and of some other internal organs from light and heavy breed chicks from hatching to 21 days of age were compared. 2. The relative weight of the duodenum and jejunum was higher in the light breed than in the heavy one, the reverse relationship was found for the ileum and caecum. 3. The relative growth of the pancreas, heart, cerebrum and cerebellum was greater in the light breed.     

Property-Preserving Data Reconstruction

We initiate a new line of investigation into online property-preserving data reconstruction. Consider a dataset which is assumed to satisfy various (known) structural properties; e.g., it may consist of sorted numbers, or points on a manifold, or vectors in a polyhedral cone, or codewords from an error-correcting code. Because of noise and errors, however, an (unknown) fraction of the data is deemed unsound, i.e., in violation with the expected structural properties. Can one still query into the dataset in an online fashion and be provided data that is always sound? In other words, can one design a filter which, when given a query to any item I in the dataset, returns a sound item J that, although not necessarily in the dataset, differs from I as infrequently as possible. No preprocessing should be allowed and queries should be answered online.We consider the case of a monotone function. Specifically, the dataset encodes a function f:{1,…,n}?? R that is at (unknown) distance ε from monotone, meaning that f can—and must—be modified at ε n places to become monotone.Our main result is a randomized filter that can answer any query in O(log?² nlog? log?n) time while modifying the function f at only O(ε n) places. The amortized time over n function evaluations is O(log?n). The filter works as stated with probability arbitrarily close to 1. We provide an alternative filter with O(log?n) worst case query time and O(ε nlog?n) function modifications. For reconstructing d-dimensional monotone functions of the form f:{1,…,n} ^d ? ? R, we present a filter that takes (2 ^O(d)(log?n)^4d?2log?log?n) time per query and modifies at most O(ε n ^d ) function values (for constant d).     

Solo-valency and the cost of coordination

This paper introduces solo-valency, a variation on the valency proof technique originated by Fischer, Lynch, and Paterson. The new technique focuses on critical events that influence the responses of solo runs by individual operations, rather than on critical events that influence a protocol’s single decision value. It allows us to derive lower bounds on the time to perform an operation for lock-free implementations of concurrent objects such as linearizable queues, stacks, sets, hash tables, counters, approximate agreement, and more. Time is measured as the number of distinct base objects accessed and the number of stalls caused by contention in accessing memory, incurred by a process as it performs a single operation. We introduce the influence level metric that quantifies the extent to which the response of a solo execution of one process can be changed by other processes. We then prove the existence of a relationship between the space complexity, latency, contention and influence level of all lock-free object implementations. Our results are broad in that they hold for implementations that may use any collection of read-modify-write operations in addition to read and write, and in that they apply even if base objects have unbounded size. Part of this work was done while the first author was a graduate student in the Department of Computer Science, Tel-Aviv University. This work was supported in part by a grant from Sun Microsystems.     

On the Discrete Maximum Principle for the Beltrami Color Flow

We analyze the discrete maximum principle for the Beltrami color flow. The Beltrami flow can display linear as well as nonlinear behavior according to the values of a parameter β, which represents the ratio between spatial and color distances. In general, the standard schemes fail to satisfy the discrete maximum principle. In this work we show that a nonnegative second order difference scheme can be built for this flow only for small β, i.e. linear-like diffusion. Since this limitation is too severe, we construct a novel finite difference scheme, which is not nonnegative and satisfies the discrete maximum principle for all values of β. Numerical results support the analysis.

Characterization of forward scattering parameters from anarbitrarily shaped cylinder by near-field probing

The forward scattering from an arbitrarily shaped cylinder is characterized by its scattering pattern and the induced field ratio (IFR). Accurate calculation of these parameters for arbitrarily shaped and composite beams is in many cases time consuming, therefore analytical approximations are used. A combined experimental and numerical procedure for evaluation of these parameters based on near-field probing is presented as an alternative. This procedure is shown to be far more accurate than the analytical approximations presently used in calculations of the total scattering effect of tuned sandwich radomes. The results obtained by this method verify well with the scattering characteristics computed analytically or numerically by the method of moments     

Elimination Trees and the Construction of Pools and Stacks

Shared pools and stacks are two coordination structures with a history of applications ranging from simple producer/consumer buffers to job-schedulers and procedure stacks. This paper introduces elimination trees, a novel form of diffracting trees that offer pool and stack implementations with superior response (on average constant) under high loads, while guaranteeing logarithmic time ``deterministic' termination under sparse request patterns. Received February 28, 1996, and in final form January 23, 1997.