A study of longitudinal curvature effects on the hypersonic laminar boundary layer

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Comparative Density Functional Theory Study of Magnetic Exchange Coupling in Di-nuclear Transition Metal Complexes

Multi-center transition metal complexes (MCTMs) with magnetically interacting ions have been proposed as components for information processing devices and storage units. For any practical application of MCTMs as magnetic units, it is crucial to characterize their magnetic behavior, and in particular the isotropic magnetic exchange coupling, J, between its magnetic centers. Due to the large size of typical MCTMs, density functional theory (DFT) is the only practical electronic structure method for evaluating the J coupling. Here we assess the accuracy of different density functional approximations for predicting the magnetic couplings of seven di-metal transition metal complexes with known reliable experimental J couplings spanning from ferromagnetic to strong antiferromagnetic. The density functionals considered include global hybrid functionals which mix semilocal density functional approximations and exact exchange with a fixed admixing parameter, six local hybrid functionals where the admixing parameters are extended to be spatially dependent, the SCAN and r$^2$SCAN meta-generalized gradient approximations (GGAs), and two widely used GGAs. We found that global hybrids have a tendency to over-correct the error in magnetic coupling parameters from the Perdew-Burke-Ernzerhof (PBE) GGA, while the performance of local hybrid density functionals is scattered without a clear trend, suggesting that more efforts are needed for the extension from global to local hybrid density functionals for this particular property. The SCAN and r$^2$SCAN meta-GGAs are found to perform as well or better than the global and local hybrids on most tested complexes. We further analyze the charge density redistribution of meta-GGAs as well as global and local hybrid density functionals with respect to that of PBE, in connection to the self-interaction error (SIE) or delocalization error

Scroll waves in isotropic excitable media : linear instabilities, bifurcations and restabilized states

Scroll waves are three-dimensional analogs of spiral waves. The linear stability spectrum of untwisted and twisted scroll waves is computed for a two-variable reaction-diffusion model of an excitable medium. Different bands of modes are seen to be unstable in different regions of parameter space. The corresponding bifurcations and bifurcated states are characterized by performing direct numerical simulations. In addition, computations of the adjoint linear stability operator eigenmodes are also performed and serve to obtain a number of matrix elements characterizing the long-wavelength deformations of scroll waves.Comment: 30 pages 16 figures, submitted to Phys. Rev.

DNA evidence of bowhead whale exploitation by Greenlandic Paleo-Inuit 4,000 years ago

The demographic history of Greenland is characterized by recurrent migrations and extinctions since the first humans arrived 4,500 years ago. Our current understanding of these extinct cultures relies primarily on preserved fossils found in their archaeological deposits, which hold valuable information on past subsistence practices. However, some exploited taxa, though economically important, comprise only a small fraction of these sub-fossil assemblages. Here we reconstruct a comprehensive record of past subsistence economies in Greenland by sequencing ancient DNA from four well-described midden deposits. Our results confirm that the species found in the fossil record, like harp seal and ringed seal, were a vital part of Inuit subsistence, but also add a new dimension with evidence that caribou, walrus and whale species played a more prominent role for the survival of Paleo-Inuit cultures than previously reported. Most notably, we report evidence of bowhead whale exploitation by the Saqqaq culture 4,000 years ago.Full Tex

Analytical, Optimal, and Sparse Optimal Control of Traveling Wave Solutions to Reaction-Diffusion Systems

This work deals with the position control of selected patterns in reaction-diffusion systems. Exemplarily, the Schl\"{o}gl and FitzHugh-Nagumo model are discussed using three different approaches. First, an analytical solution is proposed. Second, the standard optimal control procedure is applied. The third approach extends standard optimal control to so-called sparse optimal control that results in very localized control signals and allows the analysis of second order optimality conditions.Comment: 22 pages, 3 figures, 2 table

Thalamic neuron models encode stimulus information by burst-size modulation

Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons

Methods of predicting the weight of carcass roast and steak meat from easily obtainable carcass measurements

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Not availabl

A biometrical evaluation of weight of beef cows and performance of their progeny

Data from Experimental Station herds in Alabama, Florida, Georgia, Louisiana, North Carolina, South Carolina and Texas were included in this cooperative Southern Regional Beef Cattle Breeding Project (S-10) study. Records form straightbred Angus, Brahman, Brangus, Herefords and Santa Gertrudis were studied. Analytical methods included the least-squares method of fitting constants and auxiliary methods for estimation of various parameters. Computer programs were written for these methods. Primary objectives of this study were to partition variance in cow weight and to evaluate linear and quadratic relationships between cow weight and progeny preweaning performance. Two measures of cow weight were available: weight after parturition (PCW) and weight at weaning (WCW). Progeny traits were birth weight (BW), weaning weight (WW) and average daily gain from birth to weaning (ADG). Sources of variation evaluated for cow weight included location, breed, sire, year of record, age in years, previous parity and calving month. Paternal half-sib estimates of heritability determined from combined location data were 0.96 for PCW and 0.74 for WCW. Combined location estimates of heritability from the regression of daughter's average record on dam's average record were 0.42 for PCW and 0.44 for WCW. Repeatability estimates indicateed that temporary environmental effects accounted for less than forty percent of the variation in PCW or WCW. The sources of variation evaluated for the progeny traits were location, breed, sire, year, sex, birth month and age, wright and previous parity of dam. Age of calf in days was included in the model for WW. Age and weight of dam tended to account for similar sources of variation in the progeny traits. Dam weight appeared more closely related to variation in BW than did dam age; however, dam age appeared more closely related to variation in ADG and WW than did dam weight. The quadratic relationships between the two weights of dam and the three progeny traits were calculated and plotted for each location. Even though the degree of curvilinearity of the dam weight-progeny trait regression relationship varied considerable across locations, they were generally positive. Sex of calf consistently accounted for an important portion of variation in the progeny traits. Males were heavier at birth and weaning and had higher ADG's than females. Calves raised by dams parous the previous year were lighter at birth and weaning and had lower ADG's. Estimates of heritability for the progeny traits ranged from low to moderate and phenotypic, genetic and environmental correlations among these traits were generally high