The thermodynamics and roughening of solid-solid interfaces

The dynamics of sharp interfaces separating two non-hydrostatically stressed solids is analyzed using the idea that the rate of mass transport across the interface is proportional to the thermodynamic potential difference across the interface. The solids are allowed to exchange mass by transforming one solid into the other, thermodynamic relations for the transformation of a mass element are derived and a linear stability analysis of the interface is carried out. The stability is shown to depend on the order of the phase transition occurring at the interface. Numerical simulations are performed in the non-linear regime to investigate the evolution and roughening of the interface. It is shown that even small contrasts in the referential densities of the solids may lead to the formation of finger like structures aligned with the principal direction of the far field stress.Comment: (24 pages, 8 figures; V2: added figures, text revisions

Controlled Synchronization of One Class of Nonlinear Systems under Information Constraints

Output feedback controlled synchronization problems for a class of nonlinear unstable systems under information constraints imposed by limited capacity of the communication channel are analyzed. A binary time-varying coder-decoder scheme is described and a theoretical analysis for multi-dimensional master-slave systems represented in Lurie form (linear part plus nonlinearity depending only on measurable outputs) is provided. An output feedback control law is proposed based on the Passification Theorem. It is shown that the synchronization error exponentially tends to zero for sufficiantly high transmission rate (channel capacity). The results obtained for synchronization problem can be extended to tracking problems in a straightforward manner, if the reference signal is described by an {external} ({exogenious}) state space model. The results are applied to controlled synchronization of two chaotic Chua systems via a communication channel with limited capacity.Comment: 8 pages, 2 figure

The Effect of Early vs. Normal Calf Weaning on Feedlot Performance and Herd Management: A Cross-Discipline Case Study

A study of early vs. normal weaning of calves concludes that early weaning improves feedlot production efficiency, reducing per day and per pound feedlot production costs. Early weaned steers finished higher thus feedlot profitability was not affected. Early weaning has a positive affect on cow health and pasture utilization rates.Livestock Production/Industries,

Host cell invasion by Staphylococcus aureus stimulates the shedding of microvesicles

During severe sepsis, microvesicles that are positive for tissue factor (TF) are at increased levels within blood and in pulmonary lavage. These microvesicles potentially disperse TF, the major initiator of the coagulation cascade, throughout multiple organ systems, initiating fibrin deposition and resultant ischemia. The source of these microvesicles has remained incompletely defined. Although TF+ microvesicles are shed from cells that express nascent TF transcript in response to injury, recent findings revealed that circulating, full-length TF protein is detectable prior to these nascent transcripts. This finding suggested that the protein is released from constitutive sources as an acute response. We examined whether Staphylococcus aureus, the Gram-positive bacteria that is emerging as one of the most common etiologic agents in sepsis, is capable of stimulating the release of TF+ microvesicles from a pulmonary cell line that constitutively expresses TF protein. We found that host cell invasion stimulated an acute release of TF+ microvesicles and that these microvesicles mediated the transfer of the protein to TF-negative endothelial cells. We also found that transfer was inhibited by cholesterol-lowering simvastatin. Taken together, our findings reveal that S. aureus pathogenesis extends to the acute release of TF+ microvesicles and that inhibiting dispersal by this mechanism may provide a therapeutic target

A target-cell limited model can reproduce influenza infection dynamics in hosts with differing immune responses

We consider a hierarchy of ordinary differential equation models that describe the within-host viral kinetics of influenza infections: the IR model explicitly accounts for an immune response to the virus, while the simpler, target-cell limited TEIV and TV models do not. We show that when the IR model is fitted to pooled experimental murine data of the viral load, fraction of dead cells, and immune response levels, its parameters values can be determined. However, if, as is common, only viral load data are available, we can estimate parameters of the TEIV and TV models but not the IR model. These results are substantiated by a structural and practical identifiability analysis. We then use the IR model to generate synthetic data representing infections in hosts whose immune responses differ. We fit the TV model to these synthetic datasets and show that it can reproduce the characteristic exponential increase and decay of viral load generated by the IR model. Furthermore, the values of the fitted parameters of the TV model can be mapped from the immune response parameters in the IR model. We conclude that, if only viral load data are available, a simple target-cell limited model can reproduce influenza infection dynamics and distinguish between hosts with differing immune responses

ExELS: an exoplanet legacy science proposal for the ESA Euclid mission. II. Hot exoplanets and sub-stellar systems

The Exoplanet Euclid Legacy Survey (ExELS) proposes to determine the frequency of cold exoplanets down to Earth mass from host separations of ~1 AU out to the free-floating regime by detecting microlensing events in Galactic Bulge. We show that ExELS can also detect large numbers of hot, transiting exoplanets in the same population. The combined microlensing+transit survey would allow the first self-consistent estimate of the relative frequencies of hot and cold sub-stellar companions, reducing biases in comparing "near-field" radial velocity and transiting exoplanets with "far-field" microlensing exoplanets. The age of the Bulge and its spread in metallicity further allows ExELS to better constrain both the variation of companion frequency with metallicity and statistically explore the strength of star-planet tides. We conservatively estimate that ExELS will detect ~4100 sub-stellar objects, with sensitivity typically reaching down to Neptune-mass planets. Of these, ~600 will be detectable in both Euclid's VIS (optical) channel and NISP H-band imager, with ~90% of detections being hot Jupiters. Likely scenarios predict a range of 2900-7000 for VIS and 400-1600 for H-band. Twice as many can be expected in VIS if the cadence can be increased to match the 20-minute H-band cadence. The separation of planets from brown dwarfs via Doppler boosting or ellipsoidal variability will be possible in a handful of cases. Radial velocity confirmation should be possible in some cases, using 30-metre-class telescopes. We expect secondary eclipses, and reflection and emission from planets to be detectable in up to ~100 systems in both VIS and NISP-H. Transits of ~500 planetary-radius companions will be characterised with two-colour photometry and ~40 with four-colour photometry (VIS,YJH), and the albedo of (and emission from) a large sample of hot Jupiters in the H-band can be explored statistically.Comment: 18 pages, 16 figures, accepted MNRA

The Use of Gamma-ray Bursts as Direction and Time Markers in SETI Strategies

When transmitting a signal over a large distance it is more efficient to send a brief beamed signal than a continuous omni-directional transmission but this requires that the receiver knows where and when to look for the transmission. For SETI, the use of various natural phenomena has previously been suggested to achieve the desired synchronization. Here it is proposed that gamma-ray bursts may well the best ``synchronizers'' of all currently known phenomena due to their large intrinsic luminosities, high occurrence rate, isotropic sky distribution, large distance from the Galaxy, short duration, and easy detectability. For targeted searches, precise positions for gamma-ray bursts are required together with precise distance measurements to a target star. The required burst position determinations are now starting to be obtained, aided in large part by the discovery of optical afterglows. Good distance measurements are currently available from Hipparcos and even better measurements should be provided by spacecraft now being developed. For non-targeted searches, positional accuracies simply better than a detector's field of view may suffice but the time delay between the detection of a gamma-ray burst and the reception of the transmitted signal cannot be predicted in an obvious way.Comment: 8 pages, accepted for publication in PAS

Large Deformation Effects in the N = Z 44Ti Compound Nucleus

The N = Z 44Ti* nucleus has been populated in Fusion Evaporation process at very high excitation energies and angular momenta using two entrance channels with different mass-asymmetry. The deformation effects in the rapidly rotating nuclei have been investigated through the energy distribution of the alpha-particle combined to statistical-model calculations. In the case of low-multiplicity events, the ratio between first particle emitted has been measured and shows significant disagreement with the predictions of the statistical-model. This may explain The large discrepancies observed in proton energy spectra measured in previous experiments performed in the same mass region.Comment: Proceeding of the 10th International Conference on Nuclear Reaction Mechanisms, Varenna Italy, June 9-13 2003. 10 pages, 6 figures, 1 tabl

ExELS: an exoplanet legacy science proposal for the ESA Euclid mission. II. Hot exoplanets and sub-stellar systems

The Exoplanet Euclid Legacy Survey (ExELS) proposes to determine the frequency of cold exoplanets down to Earth mass from host separations of ~1 AU out to the free-floating regime by detecting microlensing events in Galactic Bulge. We show that ExELS can also detect large numbers of hot, transiting exoplanets in the same population. The combined microlensing+transit survey would allow the first self-consistent estimate of the relative frequencies of hot and cold sub-stellar companions, reducing biases in comparing "near-field" radial velocity and transiting exoplanets with "far-field" microlensing exoplanets. The age of the Bulge and its spread in metallicity further allows ExELS to better constrain both the variation of companion frequency with metallicity and statistically explore the strength of star-planet tides. We conservatively estimate that ExELS will detect ~4100 sub-stellar objects, with sensitivity typically reaching down to Neptune-mass planets. Of these, ~600 will be detectable in both Euclid's VIS (optical) channel and NISP H-band imager, with ~90% of detections being hot Jupiters. Likely scenarios predict a range of 2900-7000 for VIS and 400-1600 for H-band. Twice as many can be expected in VIS if the cadence can be increased to match the 20-minute H-band cadence. The separation of planets from brown dwarfs via Doppler boosting or ellipsoidal variability will be possible in a handful of cases. Radial velocity confirmation should be possible in some cases, using 30-metre-class telescopes. We expect secondary eclipses, and reflection and emission from planets to be detectable in up to ~100 systems in both VIS and NISP-H. Transits of ~500 planetary-radius companions will be characterised with two-colour photometry and ~40 with four-colour photometry (VIS,YJH), and the albedo of (and emission from) a large sample of hot Jupiters in the H-band can be explored statistically.Comment: 18 pages, 16 figures, accepted MNRA

On the Possibility of Observing the Shapiro Effect for Pulsars in Globular Clusters

For pulsars in globular clusters, we suggest using observations of the relativistic time delay of their radiation in the gravitational eld of a massive body (the Shapiro effect) located close to the line of sight to detect and identify invisible compact objects and to study the distribution of both visible and dark matter in globular clusters and various components of the Galaxy. We have derived the dependences of the event probability on the Galactic latitude and longitude of sources for two models of the mass distribution in the Galaxy: the classical Bahcall-Soneira model and the more recent Dehnen-Binney model. Using three globular clusters (M15, 47 Tuc, Terzan 5) as an example, we show that the ratios of the probability of the events due to the passages of massive Galactic objects close to the line of sight to the parameter f2 for pulsars in the globular clusters 47 Tuc and M15 are comparable to those for close passages of massive objects in the clusters themselves and are considerably higher than those for the cluster Terzan 5. We have estimated the rates of such events. We have determined the number of objects near the line of sight toward the pulsar that can produce a modulation of its pulse arrival times characteristic of the effect under consideration; the population of brown dwarfs in the Galactic disk, whose concentration is comparable to that of the disk stars, has been taken into account for the first time.Comment: 26 pages, 9 figure