Future DCS objectives in communication network timing and synchronization

The Defense Communication System will be moving rapidly toward providing switched digital service to it's users within the next ten years. The principal driving force in the transition to a digital system is the requirement for high performance secure voice service. Additionally, the anticipated data requirements in this time frame can be handled most effectively by a digital network. The characteristics of a switched digital network which impose timing and synchronization requirements on the system design are presented. Several alternative approaches to implementing a timing subsystem suitable for a switched digital communications system have been considered. These include pulse stuffing, independent stable clocks, and clock correction techniques. The advantages and disadvantages of each approach are discussed relative to both the strategic and tactical communication system requirements

The effect of protein backbone hydration on the amide vibrations in Raman and Raman optical activity spectra

Raman and specifically Raman optical activity (ROA) spectroscopy are very sensitive to the solution structure and conformation of biomolecules. Because of this strong conformational sensitivity, density functional theory (DFT) calculations are often used to get a better understanding of the experimentally observed spectral patterns. While e.g. for carbohydrate structure the water molecules that surround the solute have been demonstrated to be of vital importance to get accurate modelled ROA spectra, the effect of explicit water molecules on the calculated ROA patterns of peptides and proteins is less well studied. Here, the effect of protein backbone hydration was studied using DFT calculations of HCO-(l-Ala)(5)-NH2 in specific secondary structure conformations with different treatments of the solvation. The effect of the explicit water molecules on the calculated spectra mainly arises from the formation of hydrogen bonds with the amide C?O and N-H groups. Hydrogen bonding of water with the C?O group determines the shape and position of the amide I band. The C?O bond length increases upon formation of C?OH2O hydrogen bonds. The effect of the explicit water molecules on the amide III vibrations arises from hydrogen bonding of the solvent with both the C?O and N-H group, but their contributions to this spectral region differ: geometrically, the formation of a C?OH2O bond decreases the C-N bond length, while upon forming a N-HH2O hydrogen bond, the N-H bond length increases

Compressed Online Dictionary Learning for Fast fMRI Decomposition

We present a method for fast resting-state fMRI spatial decomposi-tions of very large datasets, based on the reduction of the temporal dimension before applying dictionary learning on concatenated individual records from groups of subjects. Introducing a measure of correspondence between spatial decompositions of rest fMRI, we demonstrates that time-reduced dictionary learning produces result as reliable as non-reduced decompositions. We also show that this reduction significantly improves computational scalability

Ramachandran mapping of peptide conformation using a large database of computed Raman and Raman optical activity spectra

In the past few decades, Raman optical activity (ROA) spectroscopy has been shown to be very sensitive to the solution structure of peptides and proteins. A major and urgent challenge remains the need to make detailed assignments of experimental ROA patterns and relate those to the solution structure adopted by the protein. In the past few years, theoretical developments and implementations of ROA theory have made it possible to use quantum chemical methods to compute the ROA spectra of peptides. In this work, a large database of ROA spectra of peptide model structures describing the allowed backbone conformations of proteins was systematically calculated and used to make unprecedented detailed assignments of experimental ROA patterns to the conformational elements of the peptide in solution. By using a similarity index to compare an experimental spectrum to the database spectra (2902 theoretical spectra), the conformational preference of the peptide in solution can be assigned to a very specific region in the Ramachandran space. For six (poly)peptides this approach was validated and gives excellent agreement between experiment and theory. Additionally, hydrogen/deuterium exchanged structures and the conformational dependence of the amide modes in Raman spectra can be analysed using the new database. The excellent agreement between experiment and theory demonstrates the power of the newly developed database as a tool to study Raman and ROA patterns of peptides and proteins. The interpretation of experimental ROA patterns of different proteins published in the scientific literature is discussed based on the spectral trends observed in the database

Combats between humans and animals on Mycenaean seals

One class of representation on Mycenaean seals, the combats between humans and animals, is the subject of this thesis. It is hoped that the study of this uniform group of 42 seals may illustrate aesthetic and other criteria for dating seals as a whole as well as shed some light on the interactions between the Aegean and the Orient and Egypt through the type (form) and meaning (content) of elemental motifs employed. After a definition of actual and possible combat scenes which shall be included in our survey, we proceed to distinguish Mycenaean from Cretan and modern gems and, on the basis of aesthetics, shape, dimensions, material and technique, to order the Helladic sealstones chronologically. Such a chronological arrangement is prerequisite to an analysis of the elements of human and animal positions, weapon, landscape, dress, hair, miscellaneous objects and composition, as they appear in human-lion, human-boar, human-non-bovine ruminant, human-bull and human-fantastic animal scenes. Once we know when such elements entered the Mycenaean repertoire, we may look to the arts of Crete, Egypt and the Near East for their contemporary or previous appearance, and thereby observe native initiative or foreign intrusions in the depiction of the combat theme in Greece. It is seen that, aside from some accessories of dress and hair, the mode of combating animals from a chariot with a bow and arrow, some miscellaneous objects, antithetic and Group V bull composition, and the subject of human-fantastic animal encounters, the theme and manner of expression of human-animal combats developed largely in the Aegean. Although there was great interaction between Crete and Greece, which may have provided the themes of ruminant and possibly bull combat, yet the subject matter of lion and boar combats and the idea of confronting the beast with short range weapons was a Helladic contribution. The interpretation of underlying significance of human-animal combat scenes is shown to be quite uncertain and although there may exist possible hints of religious or mythological connotation, no general conclusions can be drawn about any particular combat theme or about man-animal combats as a whole.<p

Impacts Of Vertical Grid Resolution On The Representation Of A Convective Environment

In a pre-convective environment, modeled atmospheric conditions can be presented as discrete parameters, which serve as valuable resources both in forecasting potential severe weather events and also in assessing changes in convective potential over time. However, the value of these parameters may depend on the vertical resolution of the simulation that is used to do the calculation. Upper-air radiosonde sounding data from various research campaigns (e.g., PECAN, DC3, TRMM-LBA, etc.) in both midlatitude and tropical convective regimes are analyzed and later interpolated to the pressure levels in a range of atmospheric reanalysis and operational models. Indices such as CAPE, CIN, bulk shear, and strength of capping inversion are then calculated using both the raw sounding and the interpolated soundings. Interpolated soundings consistently underestimated CAPE, although models with a larger number of vertical levels underestimated CAPE less (e.g., ERA5). Kinematic parameters; however, were well correlated to the observed. The accurate representation of the capping inversion was found to be sensitive to both the number and distribution of levels in the first several kilometers. Increasing vertical resolution from previous model versions, may improve accuracy of parameters (e.g., ERA5, GFSv16). Based on vertical resolution alone, this study shows that decreased vertical resolution can impact the ability of convective parameters to represent a potentially convective environment