4,718 research outputs found
Shuttle Ku-band and S-band communications implementation study
Various aspects of the shuttle orbiter S-band network communication system, the S-band payload communication system, and the Ku-band communication system are considered. A method is proposed for obtaining more accurate S-band antenna patterns of the actual shuttle orbiter vehicle during flight because the preliminary antenna patterns using mock-ups are not realistic that they do not include the effects of additional appendages such as wings and tail structures. The Ku-band communication system is discussed especially the TDRS antenna pointing accuracy with respect to the orbiter and the modifications required and resulting performance characteristics of the convolutionally encoded high data rate return link to maintain bit synchronizer lock on the ground. The TDRS user constraints on data bit clock jitter and data asymmetry on unbalanced QPSK with noisy phase references are included. The S-band payload communication system study is outlined including the advantages and experimental results of a peak regulator design built and evaluated by Axiomatrix for the bent-pipe link versus the existing RMS-type regulator. The nominal sweep rate for the deep-space transponder of 250 Hz/s, and effects of phase noise on the performance of a communication system are analyzed
Mechanisms of Aminoglycoside Ototoxicity and Targets of Hair Cell Protection
Aminoglycosides are commonly prescribed antibiotics with deleterious side effects to the inner ear. Due to their popular application as a result of their potent antimicrobial activities, many efforts have been undertaken to prevent aminoglycoside ototoxicity. Over the years, understanding of the antimicrobial as well as ototoxic mechanisms of aminoglycosides has increased. These mechanisms are reviewed in regard to established and potential future targets of hair cell protection
Correlated percolation models of structured habitat in ecology
Percolation offers acknowledged models of random media when the relevant
medium characteristics can be described as a binary feature. However, when
considering habitat modeling in ecology, a natural constraint comes from
nearest-neighbor correlations between the suitable/unsuitable states of the
spatial units forming the habitat. Such constraints are also relevant in the
physics of aggregation where underlying processes may lead to a form of
correlated percolation. However, in ecology, the processes leading to habitat
correlations are in general not known or very complex. As proposed by Hiebeler
[Ecology {\bf 81}, 1629 (2000)], these correlations can be captured in a
lattice model by an observable aggregation parameter , supplementing the
density of suitable sites. We investigate this model as an instance of
correlated percolation. We analyze the phase diagram of the percolation
transition and compute the cluster size distribution, the pair-connectedness
function and the correlation function . We find that while
displays a power-law decrease associated with long-range correlations in a wide
domain of parameter values, critical properties are compatible with the
universality class of uncorrelated percolation. We contrast the correlation
structures obtained respectively for the correlated percolation model and for
the Ising model, and show that the diversity of habitat configurations
generated by the Hiebeler model is richer than the archetypal Ising model. We
also find that emergent structural properties are peculiar to the implemented
algorithm, leading to questioning the notion of a well-defined model of
aggregated habitat. We conclude that the choice of model and algorithm have
strong consequences on what insights ecological studies can get using such
models of species habitat
Shuttle orbiter Ku-band radar/communications system design evaluation
Tasks performed in an examination and critique of a Ku-band radar communications system for the shuttle orbiter are reported. Topics cover: (1) Ku-band high gain antenna/widebeam horn design evaluation; (2) evaluation of the Ku-band SPA and EA-1 LRU software; (3) system test evaluation; (4) critical design review and development test evaluation; (5) Ku-band bent pipe channel performance evaluation; (6) Ku-band LRU interchangeability analysis; and (7) deliverable test equipment evaluation. Where discrepancies were found, modifications and improvements to the Ku-band system and the associated test procedures are suggested
Functional Subdomains within Human FFA
Cataloged from PDF version of article.The fusiform face area (FFA) is a well-studied human brain region that shows strong activation for faces. In functional MRI studies, FFA is often assumed to be a homogeneous collection of voxels with similar visual tuning. To test this assumption, we used natural movies and a quantitative voxelwise modeling and decoding framework to estimate category tuning profiles for individual voxels within FFA. We find that the responses in most FFA voxels are strongly enhanced by faces, as reported in previous studies. However, we also find that responses of individual voxels are selectively enhanced or suppressed by a wide variety of other categories and that these broader tuning profiles differ across FFA voxels. Cluster analysis of category tuning profiles across voxels reveals three spatially segregated functional subdomains within FFA. These subdomains differ primarily in their responses for nonface categories, such as animals, vehicles, and communication verbs. Furthermore, this segregation does not depend on the statistical threshold used to define FFA from responses to functional localizers. These results suggest that voxels within FFA represent more diverse information about object and action categories than generally assumed. © 2013 the authors
Vertical Variability and Lateral Distribution of Late Wisconsinan Sediments Parallel to theAxis of the Buried Valley of Mud Brook North of Akron, Summit County, Ohio
Author Institution: Department of Geology & Environmental Science, University of AkronThe buried valley of Mud Brook in northern Summit County, OH, contains sediments associated with the late
Wisconsinan glaciation. The vertical variability and lateral distribution of these sediments can be ascertained from information
derived from logs from highway borings and water wells along a 15-km north-south transect parallel to the axis of the buried
valley. Textural, carbonate, clay mineral, and lithologic analyses of samples from roadcuts, geological borings, and some highway
department borings provide additional information to assign lithofacies units to specific glaciations. Cross sections show that
nearly similar depositional environments existed before each late Wisconsinan glacial advance. The proglacial sediments consist
of outwash and lacustrine deposits overridden by ice that deposited an overlying till. Sediments associated with the Lavery and
Hiram advances overlie a Kent-aged kame plateau within the Summit County Morainic Complex at the southern end of the study
area. Farther north meltwater accumulated and drowned ground moraine to form post-glacial lakes that were eventually drained
as the drainage network of Mud Brook became better integrated
On Linear Information Systems
Scott's information systems provide a categorically equivalent, intensional
description of Scott domains and continuous functions. Following a well
established pattern in denotational semantics, we define a linear version of
information systems, providing a model of intuitionistic linear logic (a
new-Seely category), with a "set-theoretic" interpretation of exponentials that
recovers Scott continuous functions via the co-Kleisli construction. From a
domain theoretic point of view, linear information systems are equivalent to
prime algebraic Scott domains, which in turn generalize prime algebraic
lattices, already known to provide a model of classical linear logic
Space Shuttle program communication and tracking systems interface analysis
The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis
Quantum Number Density Asymmetries Within QCD Jets Correlated With Lambda Polarization
The observation of jets in a variety of hard-scattering processes has allowed
the quantitative study of perturbative quantum chromodynamics (PQCD) by
comparing detailed theoretical predictions with a wide range of experimental
data. This paper examines how some important, nonperturbative, facets of QCD
involving the internal dynamical structure of jets can be studied by measuring
the spin orientation of Lambda particles produced in these jets. The
measurement of the transverse polarization for an individual Lambda within a
QCD jet permits the definition of spin-directed asymmetries in local quantum
number densities in rapidity space (such as charge, strangeness and baryon
number densities) involving neighboring hadrons in the jet. These asymmetries
can only be generated by soft, nonperturbative dynamical mechanisms and such
measurements can provide insight not otherwise accessible into the color
rearrangement that occurs during the hadronization stage of the fragmentation
process.Comment: The replacement manuscript contains a new abstract, five pages of
additional material and a revised version of Fig.
Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth
We have prepared iron microwires in a combination of focused electron beam
induced deposition (FEBID) and autocatalytic growth from the iron
pentacarbonyl, Fe(CO)5, precursor gas under UHV conditions. The electrical
transport properties of the microwires were investigated and it was found that
the temperature dependence of the longitudinal resistivity (rhoxx) shows a
typical metallic behaviour with a room temperature value of about 88
micro{\Omega} cm. In order to investigate the magnetotransport properties we
have measured the isothermal Hall-resistivities in the range between 4.2 K and
260 K. From these measurements positive values for the ordinary and the
anomalous Hall coefficients were derived. The relation between anomalous Hall
resistivity (rhoAN) and longitudinal resistivity is quadratic, rhoAN rho^2 xx,
revealing an intrinsic origin of the anomalous Hall effect. Finally, at low
temperature in the transversal geometry a negative magnetoresistance of about
0.2 % was measured
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