Speech Communication

Contains reports on three research projects.U.S. Air Force (Air Force Cambridge Research Center, Air Research and Development Command) under Contract AF 19(604)-2061National Science Foundatio

Realfast: Real-Time, Commensal Fast Transient Surveys with the Very Large Array

Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. Realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hours of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways real-time analysis can help in other fields of astrophysics.Comment: Accepted to ApJS Special Issue on Data; 11 pages, 4 figure

Modelling of the Mechanical Behaviour of Ultra-Fine Grained Titanium Alloys at High Strain Rates

Results of numerical simulations of the mechanical behaviour of coarse grained and UFG titanium alloys under quasi-static uniaxial compression and plane shock wave loading are presented in this paper. Constitutive equations predict the strain hardening behaviour, the strain rate sensitivity of the flow stress and the temperature softening of titanium alloys with a range of grain sizes from 20 µm to 100 nm. Characteristics of the mechanical behaviour of UFG a and a+ß titanium alloys in wide range of strain rates are discussed

The Mechanical Behaviour of Ultra Fine Grained Titanium Alloys at High Strain Rates

Within this study the mechanical behaviour of ultra-fine grained Ti-6-22-22S titanium alloy was investigated and compared to coarse grained material. By severe plastic deformation using the cyclic channel die compression process, grain sizes between 300 and 500 nm were obtained. The mechanical behaviour was studied over a wide range of strain rates from 10^(-3) - 107 s^(-1) under compressive loading using different experimental techniques. A significant increase of flow stress with decreasing grain size compared to the coarse grain state was found. An evaluation of the strain hardening behaviour of the UFG material shows a significant increase of the strain hardening coefficient at high strain rates for low plastic deformation. The strain rate sensitivity of the material is found to be constant within a range of strain rates from 10^(-3) to 106 s^(-1) but increases at higher plastic strains. However, compressive deformability is nearly constant up to 102 s-1 and decreased disproportionately at higher rates of strain. With decreasing grain size a significant decrease of compressive deformability was found. The strength at failure is increased with increasing strain rate

Prévalence du VIH chez la Femme Enceinte et Transmission Mère-Enfant du VIH à la Maternité de l’Hôpital Général de Douala, Cameroun

Nous rapportons ici une évaluation sommaire de nos activités de prévention transmission mère-enfant du VIH sur 6 ans (2002 à 2007). Il s’agissait d’une étude descriptive et rétrospective effectuée à l’Hôpital Général de Douala. Les enfants inclus étaient âgés d’au moins 18 mois. La technique d’ELISA GENSCREEN 3ème génération pour le VIH a été utilisée. Sur 5261 accouchements effectués pendant cette période, 138 étaient de mères VIH positifs (prévalence : 2,62%). Quatre de nos patientes étaient testées négatives au premier trimestre de gestation. Des 138 bébés, 87 seulement ont pu être testés (63%), dont 4 contaminés (prévalence de transmission : 4,6%). Des 4 enfants contaminés, un seul a reçu la prévention adéquate en grossesse, soit un taux de transmission sous prévention de 1,19%. Une meilleure organisation des stratégies de réduction de la transmission mèreenfant du VIH/SIDA, même dans un environnement à ressources limitées, peut conduire à des résultats similaires à ceux des pays du Nord. A la lumière de cette étude, nous recommandons fortement un deuxième test du VIH au 3ème rimestre de la grossesse afin de réduire davantage le risque de sa transmission périnatale.Mots Clés prévalence du VIH ; femme enceinte ; transmission mère-enfant du VI

Trend in admissions, clinical features and outcome of preeclampsia and eclampsia as seen from the intensive care unit of the Douala General Hospital, Cameroon

Introduction: Hypertensive disorders in pregnancy (HDP) are a major cause of maternal morbidity and mortality. We aimed at determining the trends in admission, profiles and outcomes of women admitted for preeclampsia and eclampsia to an intensive care unit (ICU) in Cameroon. Methods: A retrospective study involving 74 women admitted to the ICU of the Douala General Hospital for severe preeclampsia and eclampsia from January 2007 to December 2014. Clinical profiles and outcome data were obtained from patient records. Statistical analysis was performed using SPSS version 20. Results: Of the 74 women admitted to ICU (72.5% for eclampsia), mean age was 30.2years and the majority (90.5%) were aged 20-39 years. While overall trend in admission for HDP increased over the years, mortality remained stable. Mean gestational age (GA) on admission was 34.0 weeks (33.5 for preeclampsia vs 35.4 for eclampsia). Most patients presented with complications of which acute kidney injury was most frequent (66.7%). Visual problems were more common in patients with eclampsia compared to preeclampsia (p=0.01). HELLP syndrome and acute pulmonary oedema (APO) were predominant in patients with preeclampsia, while cerebrovascular accidents (CVA) occurred more in patients with eclampsia. Overall mortality was 24.3%. Presence of APO was associated with mortality in multivariable analysis (O.R.= 0.03, p=0,01). Conclusion: Trends in admission for HDP were increasing with high but stable mortality rate. Patients presented late most of whom with complications. Interventions improving antenatal care services and multidisciplinary management approach may improve maternal outcome in patients with HDP

Water Dynamics at Protein Interfaces: Ultrafast Optical Kerr Effect Study

The behavior of water molecules surrounding a protein can have an important bearing on its structure and function. Consequently, a great deal of attention has been focused on changes in the relaxation dynamics of water when it is located at the protein surface. Here we use the ultrafast optical Kerr effect to study the H-bond structure and dynamics of aqueous solutions of proteins. Measurements are made for three proteins as a function of concentration. We find that the water dynamics in the first solvation layer of the proteins are slowed by up to a factor of 8 in comparison to those in bulk water. The most marked slowdown was observed for the most hydrophilic protein studied, bovine serum albumin, whereas the most hydrophobic protein, trypsin, had a slightly smaller effect. The terahertz Raman spectra of these protein solutions resemble those of pure water up to 5 wt % of protein, above which a new feature appears at 80 cm–1, which is assigned to a bending of the protein amide chain

Reconciling MOND and dark matter?

Observations of galaxies suggest a one-to-one analytic relation between the inferred gravity of dark matter at any radius and the enclosed baryonic mass, a relation summarized by Milgrom's law of modified Newtonian dynamics (MOND). However, present-day covariant versions of MOND usually require some additional fields contributing to the geometry, as well as an additional hot dark matter component to explain cluster dynamics and cosmology. Here, we envisage a slightly more mundane explanation, suggesting that dark matter does exist but is the source of MOND-like phenomenology in galaxies. We assume a canonical action for dark matter, but also add an interaction term between baryonic matter, gravity, and dark matter, such that standard matter effectively obeys the MOND field equation in galaxies. We show that even the simplest realization of the framework leads to a model which reproduces some phenomenological predictions of cold dark matter (CDM) and MOND at those scales where these are most successful. We also devise a more general form of the interaction term, introducing the medium density as a new order parameter. This allows for new physical effects which should be amenable to observational tests in the near future. Hence, this very general framework, which can be furthermore related to a generalized scalar-tensor theory, opens the way to a possible unification of the successes of CDM and MOND at different scales.Comment: 9 page

The Tensor-Vector-Scalar theory and its cosmology

Over the last few decades, astronomers and cosmologists have accumulated vast amounts of data clearly demonstrating that our current theories of fundamental particles and of gravity are inadequate to explain the observed discrepancy between the dynamics and the distribution of the visible matter in the Universe. The Modified Newtonian Dynamics (MOND) proposal aims at solving the problem by postulating that Newton's second law of motion is modified for accelerations smaller than ~10^{-10}m/s^2. This simple amendment, has had tremendous success in explaining galactic rotation curves. However, being non-relativistic, it cannot make firm predictions for cosmology. A relativistic theory called Tensor-Vector-Scalar (TeVeS) has been proposed by Bekenstein building on earlier work of Sanders which has a MOND limit for non-relativistic systems. In this article I give a short introduction to TeVeS theory and focus on its predictions for cosmology as well as some non-cosmological studies.Comment: 44 pages, topical review for Classical and Quantum Gravit

The impact of the COVID-19 pandemic upon pancreatic cancer treatment (CONTACT Study): a UK national observational cohort study.

INTRODUCTION: CONTACT is a national multidisciplinary study assessing the impact of the COVID-19 pandemic upon diagnostic and treatment pathways among patients with pancreatic ductal adenocarcinoma (PDAC). METHODS: The treatment of consecutive patients with newly diagnosed PDAC from a pre-COVID-19 pandemic cohort (07/01/2019-03/03/2019) were compared to a cohort diagnosed during the first wave of the UK pandemic ('COVID' cohort, 16/03/2020-10/05/2020), with 12-month follow-up. RESULTS: Among 984 patients (pre-COVID: n = 483, COVID: n = 501), the COVID cohort was less likely to receive staging investigations other than CT scanning (29.5% vs. 37.2%, p = 0.010). Among patients treated with curative intent, there was a reduction in the proportion of patients recommended surgery (54.5% vs. 76.6%, p = 0.001) and increase in the proportion recommended upfront chemotherapy (45.5% vs. 23.4%, p = 0.002). Among patients on a non-curative pathway, fewer patients were recommended (47.4% vs. 57.3%, p = 0.004) or received palliative anti-cancer therapy (20.5% vs. 26.5%, p = 0.045). Ultimately, fewer patients in the COVID cohort underwent surgical resection (6.4% vs. 9.3%, p = 0.036), whilst more patients received no anti-cancer treatment (69.3% vs. 59.2% p = 0.009). Despite these differences, there was no difference in median overall survival between the COVID and pre-COVID cohorts, (3.5 (IQR 2.8-4.1) vs. 4.4 (IQR 3.6-5.2) months, p = 0.093). CONCLUSION: Pathways for patients with PDAC were significantly disrupted during the first wave of the COVID-19 pandemic, with fewer patients receiving standard treatments. However, no significant impact on survival was discerned