Multimode Dynamics and Emergence of a Characteristic Length Scale in a One-Dimensional Quantum System

We study the nonequilibrium dynamics of a coherently split one-dimensional Bose gas by measuring the full probability distribution functions of matter-wave interference. Observing the system on different length scales allows us to probe the dynamics of excitations on different energy scales, revealing two distinct length-scale-dependent regimes of relaxation. We measure the crossover length scale separating these two regimes and identify it with the prethermalized phase-correlation length of the system. Our approach enables a direct observation of the multimode dynamics characterizing one-dimensional quantum systems.Physic

Prethermalization Revealed by the Relaxation Dynamics of Full Distribution Functions

We detail the experimental observation of the non-equilibrium many-body phenomenon prethermalization. We study the dynamics of a rapidly and coherently split one-dimensional Bose gas. An analysis based on the use of full quantum mechanical probability distributions of matter wave interference contrast reveals that the system evolves toward a quasi-steady state. This state, which can be characterized by an effective temperature, is not the final thermal equilibrium state. We compare the evolution of the system to an integrable Tomonaga–Luttinger liquid model, and show that the system dephases to a prethermalized state rather than undergoing thermalization toward a final thermal equilibrium state.Physic

High risk of coagulopathy among Type-2 Diabetes Mellitus clients at a municipal hospital in Ghana

Background: Persistent hyperglycaemia in diabetes mellitus causes coagulopathies due to glycation of haemoglobin, prothrombin, fibrinogen and other proteins involved in the clotting mechanism. Shortened activated partial thromboplastin time (APTT) and prothrombin time (PT) reflect hypercoagulable state, which is associated with an increased thrombotic risk and adverse cardiovascular effects. This study assessed the coagulation profile of type 2diabetes mellitus (T2DM) clients at a municipal hospital in Ghana.Methods: A hospital-based case-control study was conducted from January to April 2015 at the Agona Swedru Municipal Hospital. Sixty (60) persons with T2DM and 40 without were recruited and screened using appropriate protocols. Blood samples were collected for coagulation and biochemical tests. Demographic and clinical information were collected using pre-tested questionnaire. Data was analyzed with GraphPad Prism version 5.Results: APTT and PT were significantly shorter among patients with T2DM compared to those without (20.88 ± 5.19 v 31.23 ± 5.41, P=0.0001; and 11.03 ± 2.06sec v 14.46 ± 1.86, P=0.0001 respectively). INR was decreased among patients with T2DM compared to those without (0.83 ± 0.18 v 1.13 ± 0.17, P=0.0001). No significant difference was found in platelet count between T2DM and non-diabetics (179.85 ± 66.15×103 /mm3 v 168.55 ± 35.77×103 /mm3, P=0.326). Serum magnesium was lower among the T2DM patients compared to the non-diabetics, while serum ionized calcium was significantly higher among the T2DM patients (P<0.05).Conclusion: Clients with T2DM may have a high coagulation risk evidenced by shortened APTT, PT and a high ionized calcium compared with controls.Funding: Study was funded by Lord Ampomah and Solomon PanfordKeywords: Type 2 Diabetes Mellitus, coagulation, prothrombin time, activated partial thromboplastin time, ionized calciu

Variability in modern pollen rain from moist and wet tropical forest plots in Ghana, West Africa

How pollen moves within and between ecosystems affects factors such as the genetic structure of populations, how resilient they are to environmental change, and the amount and nature of pollen preserved in the sedimentary record. We set artificial pollen traps in two 100 m by 100 m vegetation plots, one in a wet evergreen forest, and one in a moist semi-deciduous forest in Ghana, West Africa. Five traps from each plot were counted annually from 2011 to 2014, to examine spatial and temporal variation in the pollen rain of the most abundant taxa shared between pollen and vegetation assemblages. Samples from the wet evergreen plot exhibited high variability within years, with the dominant pollen types changing between samples, and many pollen taxa being over-represented relative to their parent plant abundance in some traps whilst being entirely absent from others. The most abundant plant taxa of the wet evergreen plot (Drypetes and Cynometra) do, however, constitute major components of the pollen rain. There is less variation between samples from the moist semi-deciduous plot spatially, as it is dominated by Celtis, which typically comprises >70% of the pollen assemblages. We conclude that pollen rain in these tropical ecosystems is highly heterogeneous, and suggest that pollen assemblages obtained by trapping are susceptible to small-scale variations in forest structure. Conversely, this may mean that current recommendations of more than three years of trapping in tropical systems may be too high, and that space could substitute for time in modern tropical pollen trapping

Challenges in Nigeria’s education sector and the migration of Nigerian postgraduate students to South African universities

Education remains the weapon for upward stratification, social and economic development of any nation but the Nigerian government has not shown enough commitment to the educational sector. The manifestation could be seen in the shrinking government funding on education, decaying and lack of infrastructure in Nigeria’s universities which have led to demoralization of the academia. A major consequence of this is the frustration experienced by postgraduate students who are pursuing higher education and having to spend longer period than expected record time. This frustration in pursuing higher educational qualification often leads to stunted career progression. This has led to an alternative decision to migrate in search of higher education abroad. Consequently, in recent times, Nigerian postgraduate students have migrated more than ever before to South African Universities that are believed to have modern facilities for training and ensuring completion of programmes in record time. This study employed the use of structured questionnaire to investigate the determinants of this form of migration. Among other findings, this study found that the decision to migrate and pursue postgraduate student abroad is informed by the demoralization and frustration suffered in attaining postgraduate education in Nigeria. The study also found that many Nigerian postgraduate migrant students that desired to stay back in South Africa after the programme were discouraged from doing so because of the frequent hostilities between the bulging South African youths. Their hostility is associated with the shrinking capacity of the host government (South Africa) to create new jobs for them. In addition, the belief of the agitating South African youth that the migrant postgraduates are responsible for their unemployed status, by taking up their jobs especially in those areas where required skills among the South African are lacking further gingers hostilities. This study, therefore, suggests among others that the home country should increase budgetary allocation to improve the education sector as well as monitor such allocation to ensure that it is prudently utilized. It is also recommended that institutional processes and procedures to monitor and evaluate postgraduate studies in Nigerian universities be institutionalized

The modern pollen-vegetation relationship of a tropical forest-savannah mosaic landscape, Ghana, West Africa

Transitions between forest and savannah vegetation types in fossil pollen records are often poorly understood due to over-production by taxa such as Poaceae and a lack of modern pollen-vegetation studies. Here, modern pollen assemblages from within a forest-savannah transition in West Africa are presented and compared, their characteristic taxa discussed, and implications for the fossil record considered. Fifteen artificial pollen traps were deployed for 1 year, to collect pollen rain from three vegetation plots within the forest-savannah transition in Ghana. High percentages of Poaceae and Melastomataceae/Combretaceae were recorded in all three plots. Erythrophleum suaveolens characterised the forest plot, Manilkara obovata the transition plot and Terminalia the savannah plot. The results indicate that Poaceae pollen influx rates provide the best representation of the forest-savannah gradient, and that a Poaceae abundance of >40% should be considered as indicative of savannah-type vegetation in the fossil record

Heat conductance is strongly anisotropic for pristine silicon nanowires

We compute atomistically the heat conductance for ultra-thin pristine silicon nanowires (SiNWs) with diameters ranging from 1 to 5 nm. The room temperature thermal conductance is found to be highly anisotropic: wires oriented along the direction have 50-75% larger conductance than wires oriented along the and directions. We show that the anisotropies can be qualitatively understood and reproduced from the bulk phonon band structure. Ab initio density functional theory (DFT) is used to study the thinnest wires, but becomes computationally prohibitive for larger diameters, where we instead use the Tersoff empirical potential model (TEP). For the smallest wires, the thermal conductances obtained from DFT- and TEP calculations agree within 10%. The presented results could be relevant for future phonon-engineering of nanowire devices.Comment: 7 pages, 5 figure

Spectrophotometric analysis of gamma-ray burst afterglow extinction curves with X-shooter

In this work we use gamma-ray burst (GRB) afterglow spectra observed with the VLT/X-shooter spectrograph to measure rest-frame extinction in GRB lines-of-sight by modeling the broadband near-infrared (NIR) to X-ray afterglow spectral energy distributions (SEDs). Our sample consists of nine Swift GRBs, eight of them belonging to the long-duration and one to the short-duration class. Dust is modeled using the average extinction curves of the Milky Way and the two Magellanic Clouds. We derive the rest-frame extinction of the entire sample, which fall in the range $0 \lesssim {\it A}_{\rm V} \lesssim 1.2$. Moreover, the SMC extinction curve is the preferred extinction curve template for the majority of our sample, a result which is in agreement with those commonly observed in GRB lines-of-sights. In one analysed case (GRB 120119A), the common extinction curve templates fail to reproduce the observed extinction. To illustrate the advantage of using the high-quality X-shooter afterglow SEDs over the photometric SEDs, we repeat the modeling using the broadband SEDs with the NIR-to-UV photometric measurements instead of the spectra. The main result is that the spectroscopic data, thanks to a combination of excellent resolution and coverage of the blue part of the SED, are more successful in constraining the extinction curves and therefore the dust properties in GRB hosts with respect to photometric measurements. In all cases but one the extinction curve of one template is preferred over the others. We show that the modeled values of the extinction and the spectral slope, obtained through spectroscopic and photometric SED analysis, can differ significantly for individual events. Finally we stress that, regardless of the resolution of the optical-to-NIR data, the SED modeling gives reliable results only when the fit is performed on a SED covering a broader spectral region