Gamma flashes from relativistic electron-positron plasma droplets

Ultra-intense lasers are expected to produce, in near future, relativistic electron-positron plasma droplets. Considering the local photon production rate in complete leading order in quantum electrodynamics (QED), we point out that these droplets are interesting sources of gamma ray flashesComment: 4 pages, 6 figures; Text has been revised and new refs. are adde

Comparison of Compressive Strength and Flexural Capacity between Engineered Cementitious Composites (Bendable Concrete) and Conventional Concrete used in Bangladesh

The Engineered Cementitious Composites (ECC) is made of the same ingredients as in regular concrete. The coarse aggregate is replaced with tiny Polyvinyl Alcohol fibres. This structure offers maximum flexibility and it is expected to cost less. It looks exactly like normal concrete, but under excessive strain, the ECC concrete allows, the specially coated network of fibre in the cement to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage. As this is a special type of concrete there are no defined codes for it, thus for these reasons, the parameters needed are to be obtained using trial and error method. During the composite preparation, sieve analysis was carried out. Composites were reinforced with Polyvinyl Alcohol (PVA) at the following ratios: 0 % (control), 0.5 %, 1 % and 1.5 %. The cylindrical specimens were subjected to compression and the slab specimens were subjected to flexural test using a Universal Testing Machine, while acquiring data with GOM Correlation Software. Test results reveal that fibre ratio 1% is most acceptable for attaining best compressive strength along with high flexural value. Even though 1% fibre content concrete in the flexural strength test showed 33% less strength of what 1.5% fibre content concrete gained, in the long run, for having the highest compressive strength value (almost 62% more than of 0% fibre content concrete and 15% more than of 1.5% fibre content concrete), 1% fibre content concrete is most suited for constructions

Conserved Density Fluctuation and Temporal Correlation Function in HTL Perturbation Theory

Considering recently developed Hard Thermal Loop perturbation theory that takes into account the effect of the variation of the external field through the fluctuations of a conserved quantity we calculate the temporal component of the Euclidian correlation function in the vector channel. The results are found to be in good agreement with the very recent results obtained within the quenched approximation of QCD and small values of the quark mass ($\sim 0.1T$) on improved lattices of size $128^3\times N_\tau$ at ($N_\tau=40, \ T=1.2T_C$), ($N_\tau=48, \ T=1.45T_C$), and ($N_\tau=16, \ T=2.98T_C$), where $N_\tau$ is the temporal extent of the lattice. This suggests that the results from lattice QCD and Hard Thermal Loop perturbation theory are in close proximity for a quantity associated with the conserved density fluctuation.Comment: 16 pages, 4 figures; One para added in introduction, Fig 1 modified; Accepted in Phys. Rev.

Low Mass Dilepton Rate from the Deconfined Phase

We discuss low mass dilepton rates ($\le 1$ GeV) from the deconfined phase of QCD using both perturbative and non-perturbative models and compare with those from lattice gauge theory and in-medium hadron gas. Our analysis suggests that the rate at very low invariant mass ($M\le 200$ MeV) using the nonperturbative gluon condensate in a semiempirical way within the Green function dominates over the Born-rate and independent of any uncertainty associated with the choice of the strong coupling in perturbation theory. On the other hand the rate from $\rho-q$ interaction in the deconfined phase is important between 200 MeV $\le M \le 1 GeV as it is almost of same order of the Born-rate as well as in-medium hadron gas rate. Also the higher order perturbative rate, leaving aside its various uncertainties, from HTL approximation becomes reliable at$M\ge 200$MeV and also becomes comparable with the Born-rate and the lattice-rate for$M\ge 500$ MeV, constraining on the broad resonance structures in the dilepton rate at large invariant mass. We also discuss the lattice constraints on the low mass dilepton rate. Furthermore, we discuss a more realistic way to advocate the quark-hadron duality hypothesis based on the dilepton rates from QGP and hadron gas than it is done in the literature.Comment: 24 pages, 9 figures; Discussion added, Accepted in Phys. Rev.

Comparative cost of ART and conventional treatment within a dental school clinic

PKBACKGROUND: The changing oral health needs in South Africa require that both the teaching and clinical techniques of atraumatic restorative treatment (ART) form a part of the restorative undergraduate curriculum. OBJECTIVE: This study was undertaken to establish and compare the estimated costing of an amalgam, composite resin and ART restoration within the Board of Health Funders (BHF) recommended scale of benefits at the School of Oral Health Sciences Oral and Dental Hospital, University of the Witwatersrand (SOHS). METHODS: Fixed and variable costs were calculated by pricing items and equipment used in each procedure. The output values were established according to the recommended scale of benefits (BHF, 1999). This enabled the calculation of contribution margins and net income for each of the three restorations. RESULTS: The annual capital cost for the ART approach is approximately 50% of the other two options (e.g. per multiple surface restoration ART = R1.58; amalgam and composite resin restorative procedures: R3.12 and R3.10 respectively), despite the fact that ART restorations are rendered in a modern dental setting. CONCLUSIONS: Our study shows that implementation of the ART approach within the clinic setting of the SOHS can be accomplished without additional cost. Furthermore ART can be performed as an economically viable alternative to conventional treatment procedures within the clinic setting. The study represents a first step towards determining the cost efficiency of implementing ART as a pragmatic and cost-effective restorative option within the SOHS, University of the Witwatersrand

Towards the implementation of a sustainable cold chain for the livestock value chain in Bangladesh

The cold chain is essential for food quality and safety. Good management of the postharvest cold chain can reduce food losses. The International Institute of Refrigeration (IIR) estimated that the lack of a cold chain causes significant global food losses of up to 20% of the global food supply (IIR, 2009). Besides economic and health considerations, the environmental sustainability of the food cold supply chain should be considered to prevent further increases in emissions that could potentially increase global warming. This paper presents an assessment of the livestock cold chain related gaps in Bangladesh which is one of the initiative within the World Bank LDDP (Livestock and Dairy Development Project) project (LDDP, P161246). Information on technological and non-technological issues which can be tackled are presented. Practical recommendations to develop the cold chain in Bangladesh for milk and meat are provided

Colour-singlet clustering of partons and recombination model for hadronization of quark-gluon plasma

$SU(N_c)$ colour-singlet restriction, along with flavour and spin symmetry, on thermal partonic ensemble is shown to recombine the partons with internal colour structure into colour-singlet multi-quark clusters which can be identified with various hadronic modes at a given temperature. This provides a possible basis for recombination model for hadronization of quark-gluon plasma. This also leads to a natural explanation for the ratio of (anti)protons to pions and the quark number scaling of the elliptic flow coefficient in relativistic heavy-ion collisions.Comment: 5 pages; version accepted as a Rapid Communication in Phys. Rev.

Radiative and Collisional Jet Energy Loss in the Quark-Gluon Plasma at RHIC

We calculate and compare bremsstrahlung and collisional energy loss of hard partons traversing a quark-gluon plasma. Our treatment of both processes is complete at leading order in the coupling and accounts for the probabilistic nature of the jet energy loss. We find that the nuclear modification factor $R_{AA}$ for neutral $\pi^0$ production in heavy ion collisions is sensitive to the inclusion of collisional and radiative energy loss contributions while the averaged energy loss only slightly increases if collisional energy loss is included for parent parton energies $E\gg T$. These results are important for the understanding of jet quenching in Au+Au collisions at $200 {\rm AGeV}$ at RHIC. Comparison with data is performed applying the energy loss calculation to a relativistic ideal (3+1)-dimensional hydrodynamic description of the thermalized medium formed at RHIC.Comment: 4 pages, 3 figure

Comparison of Compressive Strength and Flexural Capacity between Engineered Cementitious Composites (Bendable Concrete) and Conventional Concrete used in Bangladesh

The Engineered Cementitious Composites (ECC) is made of the same ingredients as in regular concrete. The coarse aggregate is replaced with tiny Polyvinyl Alcohol fibres. This structure offers maximum flexibility and it is expected to cost less. It looks exactly like normal concrete, but under excessive strain, the ECC concrete allows, the specially coated network of fibre in the cement to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage. As this is a special type of concrete there are no defined codes for it, thus for these reasons, the parameters needed are to be obtained using trial and error method. During the composite preparation, sieve analysis was carried out. Composites were reinforced with Polyvinyl Alcohol (PVA) at the following ratios: 0 % (control), 0.5 %, 1 % and 1.5 %. The cylindrical specimens were subjected to compression and the slab specimens were subjected to flexural test using a Universal Testing Machine, while acquiring data with GOM Correlation Software. Test results reveal that fibre ratio 1% is most acceptable for attaining best compressive strength along with high flexural value. Even though 1% fibre content concrete in the flexural strength test showed 33% less strength of what 1.5% fibre content concrete gained, in the long run, for having the highest compressive strength value (almost 62% more than of 0% fibre content concrete and 15% more than of 1.5% fibre content concrete), 1% fibre content concrete is most suited for constructions

Screening of a Moving Parton in the Quark-Gluon Plasma

The screening potential of a parton moving through a quark-gluon plasma is calculated using the semi-classical transport theory. An anisotropic potential showing a minimum in the direction of the parton velocity is found. As consequences possible new bound states and J/psi dissociation are discussed.Comment: 4 pages, 2 figures, final, extended version, to be published in Phys.Rev.