An Efficient Method for online Detection of Polychronous Patterns in Spiking Neural Network

Polychronous neural groups are effective structures for the recognition of precise spike-timing patterns but the detection method is an inefficient multi-stage brute force process that works off-line on pre-recorded simulation data. This work presents a new model of polychronous patterns that can capture precise sequences of spikes directly in the neural simulation. In this scheme, each neuron is assigned a randomized code that is used to tag the post-synaptic neurons whenever a spike is transmitted. This creates a polychronous code that preserves the order of pre-synaptic activity and can be registered in a hash table when the post-synaptic neuron spikes. A polychronous code is a sub-component of a polychronous group that will occur, along with others, when the group is active. We demonstrate the representational and pattern recognition ability of polychronous codes on a direction selective visual task involving moving bars that is typical of a computation performed by simple cells in the cortex. The computational efficiency of the proposed algorithm far exceeds existing polychronous group detection methods and is well suited for online detection.Comment: 17 pages, 8 figure

Chasing μ

Conducting and semiconducting, π-conjugated polymers are promising materials for micro- and nano-optoelectronic applications because of their widely tunable physical, electrical, and optical properties. These polymers have been used to fabricate a number of electronic devices including field-effect transistors, light-emitting diodes, and photovoltaic cells. However, widespread commercial application of these devices has yet to be realized, due in part to poor electronic transport characteristics and device degradation. Nanostructuring of conjugated polymers by various methods has demonstrated marked improvements in molecular ordering and electronic transport. In this research, nanoscale, tubular structures of semiconducting polymers fabricated by template wetting nanofabrication procedures are explored. In particular, confinement-induced effects on the electronic carrier transport property mobility, μ, were investigated for both highly ordered and amorphous polymers. Analysis of space-charge-limited currents provided the key means of monitoring transport characteristics and molecular order. The effects of chemical filtration, nanotube diameter, solvent selection, and temperature are examined in detail

Toward a methodology for the system integration of adaptive resilience in armor

17 USC 105 interim-entered record; under temporary embargo.This article introduces a novel augmentation to systems engineering methodology based on the integration of adaptive capacity, which produces enhanced resilience in technological systems that operate in complex operating environments. The implementation of this methodology enhances system resistance to top-level function failure or accelerates the system's functional recovery in the event of a top-level function failure due to functional requirement shift, evolutions, or perturbations. The research expands system engineering, design, and integration methodologies, which currently do not explicitly address system adaptation and resilience, through the definition and demonstration of a methodology to integrate adaptive resilience and demonstrates its implementation in a relevant armor system case study. The methodology accomplishes this objective by defining adaptive design considerations, identifying controllable adaptive performance factors, characterizing adaptive performance factors and configurations, mapping and integrating adaptive components, and verifying and validating the adaptive components and configurations that achieve system requirements and adaptive design considerations. The utility of this research is demonstrated through development of an adaptive resilient armor system called the mechanically adaptive armor linkage (MAAL), which was designed, developed, and validated using the methodology for the system integration of adaptive resilience (MSIAR). The conceptual validity of the methodology is proven through a physical comparative test and evaluation of the system described in the case study. The research and resulting methodology supplements and enhances traditional systems engineering processes by offering systems designers the opportunity to integrate adaptive capacity into systems, enhancing their resilient resistance, or recovery to top-level function failure in complex operating environments.U.S. Government affiliation is unstated in article text

Small Ring Analogs of Acetylcholine. Synthesis and Absolute Configurations of Cyclopropane Derivatives.

Conformational rigidity has been conferred upon the OCCN portion of acetylcholine by incorporation of the C atoms into a cyclopropane ring. trans-2-Acetoxycyclopropyltrimethylammonium iodide has been prepared from an olefinic starting material, 2-vinyloxytetrahydropyran; assignment of the trans configuration to the 1,2-disubstituted cyclopropane systems was based upon literature precedent and upon nmr data, and was confirmed by X-ray crystallographic analysis. Resolution of one of the racemic intermediates in the reaction sequence was achieved, which permitted preparation of both enantiomers of the final product. X-Ray crystallographic analysis has demonstrated that the muscarinically active (+)-trans-2-acetoxycyclopropyltrimethylammonium iodide possesses the same absolute configuration as the muscarinically active enantiomers of Acetyl-β-methylcholine and muscarine

Small Ring Analogs of Acetylcholine. Synthesis and Absolute Configurations of Cyclopropane Derivatives.

Conformational rigidity has been conferred upon the OCCN portion of acetylcholine by incorporation of the C atoms into a cyclopropane ring. trans-2-Acetoxycyclopropyltrimethylammonium iodide has been prepared from an olefinic starting material, 2-vinyloxytetrahydropyran; assignment of the trans configuration to the 1,2-disubstituted cyclopropane systems was based upon literature precedent and upon nmr data, and was confirmed by X-ray crystallographic analysis. Resolution of one of the racemic intermediates in the reaction sequence was achieved, which permitted preparation of both enantiomers of the final product. X-Ray crystallographic analysis has demonstrated that the muscarinically active (+)-trans-2-acetoxycyclopropyltrimethylammonium iodide possesses the same absolute configuration as the muscarinically active enantiomers of Acetyl-β-methylcholine and muscarine

Governance mechanisms in transnational business relationships

Empirical research on buyer-supplier relationships has almost exclusively examined domestic (both firms from the same country) exchange. The growing importance of international marketing and global sourcing suggest a need to understand relationships across national boundaries -- transnational business relationships. Drawing on theories of governance, the authors hypothesize differences in governance between domestic and transnational business relationships. They examine the use of three specific governance mechanisms (market governance, trust, and formal contracts) commonly employed in buyer-supplier relationships. Hypotheses are tested with data from 511 purchasing professionals in the United States and Germany (201 reporting on transnational relationships). Results indicate that market governance and trust are used less in transnational than in domestic relationships. No differences are found in the use of contracts. Implications for theory and practice are discussed

Follicle-Stimulating Hormone Promotes RANK Expression on Human Monocytes

Elevated serum concentrations of follicle-stimulating hormone (FSH) are associated with diminished bone density in women, beginning years before menopause and the decline in estradiol. We hypothesized that FSH promotes development of myeloid cells toward the bone-resorbing osteoclast phenotype. This was tested by isolating peripheral blood mononuclear cells from nine healthy adults, incubating them in the presence of FSH at three different concentrations spanning the physiological range, and then measuring the expression of receptor activator for NF-κB (RANK, a surface marker for osteoclasts) on CD14+ cells by flow cytometry. In the absence of FSH, 3.3±0.5% of the cells expressed high levels of the receptor (RANKhigh). Increasing concentrations of FSH caused a biphasic dose-response, with a maximal (1.5-fold) increase in RANKhigh cells achieved with 50mIU/ml FSH (P=0.02). Cytokines that influence development of osteoclasts were also measured in culture supernatants: macrophage colony stimulating factor (M-CSF), osteoprotegerin (OPG) and tumor necrosis factor-α (TNFα) concentrations were not significantly influenced by FSH, whereas RANK-ligand was undetectable. This study supports the concept that the elevated circulating concentrations of FSH during perimenopause may contribute to the increased rate of bone loss by promoting the development of osteoclast precursor cells