Mean Field Theory of the Morphology Transition in Stochastic Diffusion Limited Growth

We propose a mean-field model for describing the averaged properties of a class of stochastic diffusion-limited growth systems. We then show that this model exhibits a morphology transition from a dense-branching structure with a convex envelope to a dendritic one with an overall concave morphology. We have also constructed an order parameter which describes the transition quantitatively. The transition is shown to be continuous, which can be verified by noting the non-existence of any hysteresis.Comment: 16 pages, 5 figure

Front Stability in Mean Field Models of Diffusion Limited Growth

We present calculations of the stability of planar fronts in two mean field models of diffusion limited growth. The steady state solution for the front can exist for a continuous family of velocities, we show that the selected velocity is given by marginal stability theory. We find that naive mean field theory has no instability to transverse perturbations, while a threshold mean field theory has such a Mullins-Sekerka instability. These results place on firm theoretical ground the observed lack of the dendritic morphology in naive mean field theory and its presence in threshold models. The existence of a Mullins-Sekerka instability is related to the behavior of the mean field theories in the zero-undercooling limit.Comment: 26 pp. revtex, 7 uuencoded ps figures. submitted to PR

Aggregation Patterns in Stressed Bacteria

We study the formation of spot patterns seen in a variety of bacterial species when the bacteria are subjected to oxidative stress due to hazardous byproducts of respiration. Our approach consists of coupling the cell density field to a chemoattractant concentration as well as to nutrient and waste fields. The latter serves as a triggering field for emission of chemoattractant. Important elements in the proposed model include the propagation of a front of motile bacteria radially outward form an initial site, a Turing instability of the uniformly dense state and a reduction of motility for cells sufficiently far behind the front. The wide variety of patterns seen in the experiments is explained as being due the variation of the details of the initiation of the chemoattractant emission as well as the transition to a non-motile phase.Comment: 4 pages, REVTeX with 4 postscript figures (uuencoded) Figures 1a and 1b are available from the authors; paper submitted to PRL

Novel type of phase transition in a system of self-driven particles

A simple model with a novel type of dynamics is introduced in order to investigate the emergence of self-ordered motion in systems of particles with biologically motivated interaction. In our model particles are driven with a constant absolute velocity and at each time step assume the average direction of motion of the particles in their neighborhood with some random perturbation ($\eta$) added. We present numerical evidence that this model results in a kinetic phase transition from no transport (zero average velocity, $| {\bf v}_a | =0$) to finite net transport through spontaneous symmetry breaking of the rotational symmetry. The transition is continuous since $| {\bf v}_a |$ is found to scale as $(\eta_c-\eta)^\beta$ with $\beta\simeq 0.45$

Ageing enhances cellular immunity to myeloperoxidase and experimental anti-myeloperoxidase glomerulonephritis

OBJECTIVES: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease characterised by small blood vessel inflammation, commonly affecting the kidneys and respiratory tract. It is unclear why the incidence of this condition increases with age. Previous studies in a passive antibody transfer system in aged mice have implicated innate effectors. To test the hypothesis that autoimmunity to myeloperoxidase, an autoantigen responsible for ANCA-associated vasculitis, increases with age, anti-myeloperoxidase autoimmunity was studied in murine models of active autoimmunity and disease induced by cellular immunity. METHODS: Young (8 weeks) and aged (either 15 or 22 month) mice were immunised with whole proteins or peptides from ovalbumin, as a model foreign antigen, or myeloperoxidase protein or peptides. Mice were subjected to a model of active anti-myeloperoxidase glomerulonephritis. Cellular and humoral immune responses and tissue inflammation were assessed. RESULTS: While cellular immunity to ovalbumin was diminished in aged mice, cellular autoimmunity to myeloperoxidase and its immunodominant CD4+ and CD8+ T cell epitopes was increased after immunization with either MPO peptides or whole MPO protein, assessed by peptide and antigen specific production of the pro-inflammatory cytokines interferon-γ and interleukin-17A. MPO-ANCA titres were not increased in aged mice compared with young mice. In experimental anti-MPO glomerulonephritis, cell mediated injury was increased, likely due to CD4+ and CD8+ T cells, innate immunity and the increased vulnerability of aged kidneys. CONCLUSION: Heightened cellular immunity to MPO develops with ageing in mice and may contribute to the increased incidence and severity of ANCA-associated vasculitis in older people

The Evolution of FTK, a Real-Time Tracker for Hadron Collider Experiments

We describe the architecture evolution of the highly-parallel dedicated processor FTK, which is driven by the simulation of LHC events at high luminosity (1034 cm-2 s-1). FTK is able to provide precise on-line track reconstruction for future hadronic collider experiments. The processor, organized in a two-tiered pipelined architecture, execute very fast algorithms based on the use of a large bank of pre-stored patterns of trajectory points (first tier) in combination with full resolution track fitting to refine pattern recognition and to determine off-line quality track parameters. We describe here how the high luminosity simulation results have produced a new organization of the hardware inside the FTK processor core.Comment: 11th ICATPP conferenc

Results of a Pilot Study in the U.S. and Vietnam to Assess the Utility and Acceptability of a Multi-Level Pregnancy Test (MLPT) for Home Monitoring of hCG Trends After Assisted Reproduction.

Background To evaluate the utility and acceptability of using multi-level pregnancy tests (MLPTs) at home to monitor hCG trends following assisted reproductive technology (ART). Methods One hundred and four women presenting for ART at either Stanford Medicine Fertility and Reproductive Health Clinic (Stanford, CA) or Hung Vuong Hospital (Ho Chi Minh City, Vietnam) participated in this pilot study. Women were asked to perform the MLPT at home, primarily on days when they were also scheduled to receive standard clinic-based serum hCG testing. These tests were administered up to 6 times over the 6-week period following embryo transfer or intrauterine insemination (IUI). Concordance of serial hCG readings for each time point was assessed by comparing trends in urine MLPT results with trends in serum hCG. Stable or increasing hCG level was interpreted as an indication of a progressing pregnancy, while a declining hCG was interpreted as a lack of established or progressing pregnancy. At study end, all participants were asked about the acceptability and convenience of using the MLPT at home for monitoring hCG trends following ART. Results Data from both urine and serum testing are available for 156 of 179 clinic visits (87.2%). There was high concordance of serial trend results between the two types of tests: among the 156 sets of serum and urine hCG data points, 150 (96.2%) showed a matching trend in hCG pattern and 6 (3.8%) resulted in a discordant trend. Seventy-three percent of women reported being satisfied or very satisfied with using the MLPTs at home. Almost all (96.6%) said that the MLPT was easy or very easy to use. Conclusion The MLPT offers women and health care providers a client-friendly diagnostic tool to detect very early pregnancy and monitor its progress. Trial registration This study was registered on clinicaltrials.gov as NCT01846403 (May 1, 2013), and NCT01919502 (August 5, 2013)

Determination of the Jet Energy Scale at the Collider Detector at Fermilab

A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron $p\bar{p}$ collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3% systematic uncertainty

A search for direct muon production in the forward direction

We propose to search for direct muon production in the forward direction from 300 GeV protons incident on a heavy nuclear target. By using the first stage of the Ml beam as a source of a diffracted proton beam and the second and third stages of Ml as a spectrometer, one can make a measurement of the direct muon to pion ratio at values of x between 0.3 and 0.75. If this ratio is on the order of 10{sup -4}, the event rates are on the order of 800 direct muons/hr. at an x of .5. The modifications to the Ml beam are minor

Protocol for a randomised controlled trial of a school based cognitive behaviour therapy (CBT) intervention to prevent depression in high risk adolescents (PROMISE)

<p>Abstract</p> <p>Background</p> <p>Depression in adolescents is a significant problem that impairs everyday functioning and increases the risk of severe mental health disorders in adulthood. Relatively few adolescents with depression are identified and referred for treatment indicating the need to investigate alternative preventive approaches.</p> <p>Study Design</p> <p>A pragmatic cluster randomised controlled trial evaluating the effectiveness of a school based prevention programme on symptoms of depression in "high risk" adolescents (aged 12-16). The unit of allocation is year groups (n = 28) which are assigned to one of three conditions: an active intervention based upon cognitive behaviour therapy, attention control or treatment as usual. Assessments will be undertaken at screening, baseline, 6 months and 12 months. The primary outcome measure is change on the Short Mood and Feeling Questionnaire at 12 months. Secondary outcome measures will assess changes in negative thoughts, self esteem, anxiety, school connectedness, peer attachment, alcohol and substance misuse, bullying and self harm.</p> <p>Discussion</p> <p>As of August 2010, all 28 year groups (n = 5023) had been recruited and the assigned interventions delivered. Final 12 month assessments are scheduled to be completed by March 2011.</p> <p>Trial Registration</p> <p>ISRCTN19083628</p