1,165 research outputs found
Neuroanatomical Asymmetry, Handedness, and Family History of Handedness : A Study of the Markers of Structural and Functional Lateralization
This study investigated the associations between (1) handedness (demonstrated preference of one hand for the performance of most unimanual tasks) and neuroanatomical asymmetry (measurable differences in width between the cerebral hemispheres) and (2) familial history of handedness (the presence of a left-handed sibling or parent of a right-handed subject) as an intervening factor in the relation between handedness and neuroanatomical asymmetry. Width measurements of the brain were derived from computerized tomographic ( CT) films and grouped in to categories by hand preference (measured by the Edinburgh Handedness Inventory) and family history. The measurements of right (n=68), right with left-· handed relatives (n=24), and left-handed (n=16) groups were then compared by width and other transformations of the brain measurements. Subjects were adults of both sexes who had been referred for neurologic examination and were diagnosed as free of major distorting brain pathology. Hemispheric widths were compared by group, as ratios (left÷right) and as differences (left-right).
Analysis of variance revealed significant differences between right-hemisphere widths at three percentages of brain length in the posterior occipital and temporal-parietal portion of the right hemisphere. The two right-handed groups had significantly smaller right-hemisphere measurements than the left group at 80% (p=.03), 75% (p= .012), and 60% (p= .029) of brain length. There were no significant left-hemisphere differences between the groups. In terms of ratios of sides and differences between sides in the same brain region, the left - handed group was different from the right-handed group at the p
Handedness appears to be moderately associated with neuroanatomical asymmetry. The differences in sizes of brain structures and their relation to functionally lateralized abilities may shed light on the processes by which each hemisphere becomes specialized to perform specific tasks and other aspects of individual differences
Prototyping Operational Autonomy for Space Traffic Management
Current state of the art in Space Traffic Management (STM) relies on a handful of providers for surveillance and collision prediction, and manual coordination between operators. Neither is scalable to support the expected 10x increase in spacecraft population in less than 10 years, nor does it support automated manuever planning. We present a software prototype of an STM architecture based on open Application Programming Interfaces (APIs), drawing on previous work by NASA to develop an architecture for low-altitude Unmanned Aerial System Traffic Management. The STM architecture is designed to provide structure to the interactions between spacecraft operators, various regulatory bodies, and service suppliers, while maintaining flexibility of these interactions and the ability for new market participants to enter easily. Autonomy is an indispensable part of the proposed architecture in enabling efficient data sharing, coordination between STM participants and safe flight operations. Examples of autonomy within STM include syncing multiple non-authoritative catalogs of resident space objects, or determining which spacecraft maneuvers when preventing impending conjunctions between multiple spacecraft. The STM prototype is based on modern micro-service architecture adhering to OpenAPI standards and deployed in industry standard Docker containers, facilitating easy communication between different participants or services. The system architecture is designed to facilitate adding and replacing services with minimal disruption. We have implemented some example participant services (e.g. a space situational awareness provider/SSA, a conjunction assessment supplier/CAS, an automated maneuver advisor/AMA) within the prototype. Different services, with creative algorithms folded into then, can fulfil similar functional roles within the STM architecture by flexibly connecting to it using pre-defined APIs and data models, thereby lowering the barrier to entry of new players in the STM marketplace. We demonstrate the STM prototype on a multiple conjunction scenario with multiple maneuverable spacecraft, where an example CAS and AMA can recommend optimal maneuvers to the spacecraft operators, based on a predefined reward function. Such tools can intelligently search the space of potential collision avoidance maneuvers with varying parameters like lead time and propellant usage, optimize a customized reward function, and be implemented as a scheduling service within the STM architecture. The case study shows an example of autonomous maneuver planning is possible using the API-based framework. As satellite populations and predicted conjunctions increase, an STM architecture can facilitate seamless information exchange related to collision prediction and mitigation among various service applications on different platforms and servers. The availability of such an STM network also opens up new research topics on satellite maneuver planning, scheduling and negotiation across disjoint entities
Alpha helix-coil phase transition: analysis of ab initio theory predictions
In the present paper we present results of calculations obtained with the use
of the theoretical method described in our preceding paper [1] and perform
detail analysis of alpha helix-random coil transition in alanine polypeptides
of different length. We have calculated the potential energy surfaces of
polypeptides with respect to their twisting degrees of freedom and construct a
parameter-free partition function of the polypeptide using the suggested method
[1]. From the build up partition function we derive various thermodynamical
characteristics for alanine polypeptides of different length as a function of
temperature. Thus, we analyze the temperature dependence of the heat capacity,
latent heat and helicity for alanine polypeptides consisting of 21, 30, 40, 50
and 100 amino acids. Alternatively, we have obtained same thermodynamical
characteristics from the use of molecular dynamics simulations and compared
them with the results of the new statistical mechanics approach. The comparison
proves the validity of the statistical mechanic approach and establishes its
accuracy.Comment: 34 pages, 12 figure
Ab initio theory of helix-coil phase transition
In this paper we suggest a theoretical method based on the statistical
mechanics for treating the alpha-helix-random coil transition in alanine
polypeptides. We consider this process as a first-order phase transition and
develop a theory which is free of model parameters and is based solely on
fundamental physical principles. It describes essential thermodynamical
properties of the system such as heat capacity, the phase transition
temperature and others from the analysis of the polypeptide potential energy
surface calculated as a function of two dihedral angles, responsible for the
polypeptide twisting. The suggested theory is general and with some
modification can be applied for the description of phase transitions in other
complex molecular systems (e.g. proteins, DNA, nanotubes, atomic clusters,
fullerenes).Comment: 24 pages, 3 figure
Dynamical scaling of the DNA unzipping transition
We report studies of the equilibrium and the dynamics of a general set of
lattice models which capture the essence of the force-induced or mechanical DNA
unzipping transition. Besides yielding the whole equilibrium phase diagram in
the force vs temperature plane, which reveals the presence of an interesting
re-entrant unzipping transition for low T, these models enable us to
characterize the dynamics of the process starting from a non-equilibrium
initial condition. The thermal melting of the DNA strands displays a model
dependent time evolution. On the contrary, our results suggest that the
dynamical mechanism for the unzipping by force is very robust and the scaling
behaviour does not depend on the details of the description we adopt.Comment: 6 pages, 4 figures, A shorter version of this paper appeared in Phys.
Rev. Lett. 88, 028102 (2002
Mapping the complete glycoproteome of virion-derived HIV-1 gp120 provides insights into broadly neutralizing antibody binding
The surface envelope glycoprotein (SU) of Human immunodeficiency virus type 1 (HIV-1), gp120SU plays an essential role in virus binding to target CD4+ T-cells and is a major vaccine target. Gp120 has remarkably high levels of N-linked glycosylation and there is considerable evidence that this “glycan shield” can help protect the virus from antibody-mediated neutralization. In recent years, however, it has become clear that gp120 glycosylation can also be included in the targets of recognition by some of the most potent broadly neutralizing antibodies. Knowing the site-specific glycosylation of gp120 can facilitate the rational design of glycopeptide antigens for HIV vaccine development. While most prior studies have focused on glycan analysis of recombinant forms of gp120, here we report the first systematic glycosylation site analysis of gp120 derived from virions produced by infected T lymphoid cells and show that a single site is exclusively substituted with complex glycans. These results should help guide the design of vaccine immunogens
P16-52. HIV-activated human plasmacytoid DCs induce Tregs through an indoleamine 2,3-dioxygenase-dependent mechanism
International audiencen.
Theory of Chiral Order in Random Copolymers
Recent experiments have found that polyisocyanates composed of a mixture of
opposite enantiomers follow a chiral ``majority rule:'' the chiral order of the
copolymer, measured by optical activity, is dominated by whichever enantiomer
is in the majority. We explain this majority rule theoretically by mapping the
random copolymer onto the random-field Ising model. Using this model, we
predict the chiral order as a function of enantiomer concentration, in
quantitative agreement with the experiments, and show how the sharpness of the
majority-rule curve can be controlled.Comment: 13 pages, including 4 postscript figures, uses REVTeX 3.0 and
epsf.st
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