501 research outputs found
Calculation of the Density of States Using Discrete Variable Representation and Toeplitz Matrices
A direct and exact method for calculating the density of states for systems
with localized potentials is presented. The method is based on explicit
inversion of the operator . The operator is written in the discrete
variable representation of the Hamiltonian, and the Toeplitz property of the
asymptotic part of the obtained {\it infinite} matrix is used. Thus, the
problem is reduced to the inversion of a {\it finite} matrix
Flight control systems research
Theoretical development is reported for the parameter optimization design technique needed for digital flight control system design. The results of an example case study applying the optimization technique for continuous systems to an F-8 aircraft feedback control system are presented. The concept of evolving the simplest system configuration that is capable of meeting a specified set of performance requirements is illustrated in this work
Antioxidant activity, total phenolic content and antimicrobial activity of two medicinal plants from Sulaimani City, Iraqi Kurdistan Region
Malabar spinach fruit with dark blue skin and deep red violet flesh is a potential source of natural colorant. Nasturtium officinal (watercress) of family Brassica ceae has been long used as a home remedy or a medical plant by the people Iraq- Sulaimaini City .The aim of this study was to investigate the antioxidant , antimicrobial activity of Malabar spinach &Nasturtium official (water cress) extracts using various in vitro assay systems including ferric reducing antioxidant power (FRAP),1,1-dipheny-2-picrylhydrazyl (DPPH), and 2,2-azinobis -3- ethylbenzothiozoline sulphonate (ABTS ).Antibacterial activity were tested against five gram-positive ,three gram –negative bacteria and two fungi by disc diffusion method for different extract and determining their minimum inhibitory concentration (MIC)values . Total phenolic content was determined by folin ciocalteu reagent for the extract (mg Gallic acid /g extract ). From the result highest total phenol content was shown by Malabar spinach & Nastartium officinale in methanol extracts. Elemental analysis have been done element by inductive couple plasma (ICP) techniques for each this two medicinal plants high amount of Na ,K Ca, Mn ,Zn ,Mg, Fe, Cu ,and se elements have been detected in ppb. Key words: Malabar spinach , Nasturtium officinal, antioxidant  , antimicrobial ,phenolic
Entorhinal and ventromedial prefrontal cortices abstract and generalize the structure of reinforcement learning problems
Knowledge of the structure of a problem, such as relationships between stimuli, enables rapid learning and flexible inference. Humans and other animals can abstract this structural knowledge and generalize it to solve new problems. For example, in spatial reasoning, shortest-path inferences are immediate in new environments. Spatial structural transfer is mediated by cells in entorhinal and (in humans) medial prefrontal cortices, which maintain their co-activation structure across different environments and behavioral states. Here, using fMRI, we show that entorhinal and ventromedial prefrontal cortex (vmPFC) representations perform a much broader role in generalizing the structure of problems. We introduce a task-remapping paradigm, where subjects solve multiple reinforcement learning (RL) problems differing in structural or sensory properties. We show that, as with space, entorhinal representations are preserved across different RL problems only if task structure is preserved. In vmPFC and ventral striatum, representations of prediction error also depend on task structure
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SURROGATE MARKERS IN ANIMAL MODELS OF ACQUIRED EPILEPSY: THE GOOD, THE BAD AND THE UGLY
Superdiffusion of massive particles induced by multi-scale velocity fields
We study drag-induced diffusion of massive particles in scale-free velocity
fields, where superdiffusive behavior emerges due to the scale-free size
distribution of the vortices of the underlying velocity field. The results show
qualitative resemblance to what is observed in fluid systems, namely the
diffusive exponent for the mean square separation of pairs of particles and the
preferential concentration of the particles, both as a function of the response
time.Comment: 5 pages, 5 figures. Accepted for publication in EP
Investigation of the Multiple Method Adaptive Control (MMAC) method for flight control systems
The stochastic adaptive control of the NASA F-8C digital-fly-by-wire aircraft using the multiple model adaptive control (MMAC) method is presented. The selection of the performance criteria for the lateral and the longitudinal dynamics, the design of the Kalman filters for different operating conditions, the identification algorithm associated with the MMAC method, the control system design, and simulation results obtained using the real time simulator of the F-8 aircraft at the NASA Langley Research Center are discussed
Forebrain CRF<sub>1</sub> modulates early-life stress-programmed cognitive deficits
Childhood traumatic events hamper the development of the hippocampus and impair declarative memory in susceptible individuals. Persistent elevations of hippocampal corticotropin-releasing factor (CRF), acting through CRF receptor 1 (CRF1), in experimental models of early-life stress have suggested a role for this endogenous stress hormone in the resulting structural modifications and cognitive dysfunction. However, direct testing of this possibility has been difficult. In the current study, we subjected conditional forebrain CRF1 knock-out (CRF1-CKO) mice to an impoverished postnatal environment and examined the role of forebrain CRF1 in the long-lasting effects of early-life stress on learning and memory. Early-life stress impaired spatial learning and memory in wild-type mice, and postnatal forebrain CRF overexpression reproduced these deleterious effects. Cognitive deficits in stressed wild-type mice were associated with disrupted long-term potentiation (LTP) and a reduced number of dendritic spines in area CA3 but not in CA1. Forebrain CRF1 deficiency restored cognitive function, LTP and spine density in area CA3, and augmented CA1 LTP and spine density in stressed mice. In addition, early-life stress differentially regulated the amount of hippocampal excitatory and inhibitory synapses in wild-type and CRF1-CKO mice, accompanied by alterations in the neurexin-neuroligin complex. These data suggest that the functional, structural and molecular changes evoked by early-life stress are at least partly dependent on persistent forebrain CRF1 signaling, providing a molecular target for the prevention of cognitive deficits in adults with a history of early-life adversity
Dimensional Reduction for Directed Branched Polymers
Dimensional reduction occurs when the critical behavior of one system can be
related to that of another system in a lower dimension. We show that this
occurs for directed branched polymers (DBP) by giving an exact relationship
between DBP models in D+1 dimensions and repulsive gases at negative activity
in D dimensions. This implies relations between exponents of the two models:
(the exponent describing the singularity of the
pressure), and (the correlation length exponent of
the repulsive gas). It also leads to the relation ,
where is the Yang-Lee edge exponent. We derive exact expressions
for the number of DBP of size N in two dimensions.Comment: 7 pages, 1 eps figure, ref 24 correcte
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