Dark Matter Annihilation and the PAMELA, FERMI and ATIC Anomalies

If dark matter (DM) annihilation accounts for the tantalizing excess of cosmic ray electron/positrons, as reported by the PAMELA, ATIC, HESS and FERMI observatories, then the implied annihilation cross section must be relatively large. This results, in the context of standard cosmological models, in very small relic DM abundances that are incompatible with astrophysical observations. We explore possible resolutions to this apparent conflict in terms of non-standard cosmological scenarios; plausibly allowing for large cross sections, while maintaining relic abundances in accord with current observations.Comment: 13 pages, 3 figures; published for publication in Physical Review

Maternal haemodynamic function differs in pre‐eclampsia when it is associated with a small‐for‐gestational‐age newborn: a prospective cohort study

Objective To describe maternal haemodynamic differences in gestational hypertension with small‐for‐gestational‐age babies (HDP + SGA), gestational hypertension with appropriate‐for‐gestational‐age babies (HDP‐only) and control pregnancies. Design Prospective cohort study. Setting Tertiary Hospital, UK. Population Women with gestational hypertension and healthy pregnant women. Methods Maternal haemodynamic indices were measured using a non‐invasive Ultrasound Cardiac Output Monitor (USCOM‐1A®) and corrected for gestational age and maternal characteristics using device‐specific reference ranges. Main outcome measures Maternal cardiac output, stroke volume, systemic vascular resistance. Results We included 114 HDP + SGA, 202 HDP‐only and 401 control pregnancies at 26–41 weeks of gestation. There was no significant difference in the mean arterial blood pressure (110 versus 107 mmHg, P = 0.445) between the two HDP groups at presentation. Pregnancies complicated by HDP + SGA had significantly lower median heart rate (76 versus 85 bpm versus 83 bpm), lower cardiac output (0.85 versus 0.98 versus 0.97 MoM) and higher systemic vascular resistance (1.4 versus 1.0 versus 1.2 MoM) compared with control and HDP‐only pregnancies, respectively (all P < 0.05). Conclusion Women with HDP + SGA present with more severe haemodynamic dysfunction than HDP‐only. Even HDP‐only pregnancies exhibit impaired haemodynamic indices compared with normal pregnancies, supporting a role of the maternal cardiovascular system in gestational hypertension irrespective of fetal size. Central haemodynamic changes may play a role in the pathogenesis of pre‐eclampsia and should be considered alongside placental aetiology

The Enigma of the Dark Matter

One of the great scientific enigmas still unsolved, the existence of dark matter, is reviewed. Simple gravitational arguments imply that most of the mass in the Universe, at least 90%, is some (unknown) non-luminous matter. Some particle candidates for dark matter are discussed with particular emphasis on the neutralino, a particle predicted by the supersymmetric extension of the Standard Model of particle physics. Experiments searching for these relic particles, carried out by many groups around the world, are also discussed. These experiments are becoming more sensitive every year and in fact one of the collaborations claims that the first direct evidence for dark matter has already been observed.Comment: Invited review article for the journal Contemporary Physics. The level is suitable for researchers which are non-specialists in the subject, and also for students. Latex, 20 pages, 5 figure

A Hybrid Graphical User Authentication Scheme in Mobile Cloud Computing Environments

User authentication is a critical security requirement for accessing resources in cloud computing systems. A text-based password is a standard user authentication way and it is still extensively used so far. However, textual passwords are difficult to remember, which forces users to write it down and compromise security. In recent years, graphical user authentication methods have been proposed as an alternative way used to verify the identity of users. The most critical challenges cloud-computing users face is to post their sensitive data on external servers that are not directly under their control and that can be used or managed by other people. This paper proposes a question-based hybrid graphical user authentication scheme for portable cloud-computing environments. The proposed scheme comprises advantages over both recognition- and recall-based techniques without storing any sensitive information on cloud servers. The experimental study and survey have been conducted to investigate the user satisfaction about the performance and usability aspects of the proposed scheme. The study results show that the proposed scheme is secure, easy to use, and immune to potential password attacks such as brute force password guessing attacks and shoulder surfing attack

B -> K pi Puzzle and New Sources of CP Violation in Supersymmetry

The difference between the CP asymmetries of the $B^0 \to K^+ \pi^-$ and $B^+ \to K^+ \pi^0$ decays has been recently confirmed with an evidence larger than $5\sigma$'s. We discuss it as a possible signal of new physics associated with new (large) CP violation in the electroweak penguin contributions. We propose a supersymmetry breaking scheme where such new sources of CP violation occur in the flavor non-universal trilinear scalar couplings.Comment: 4 pages, 2 figure

Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-is(neopentyloxy)-3-(neopentyloxycarbonyl)- 1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO2 NWs) and subsequent squeegee method to apply TiO2 NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm2. The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO2 NWs/TiO2 NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually

BEHAVIOR OF REINFORCED CONCRETE CONTINUOUS BEAMS STRENGHENED WITH NEAR SURFACE MOUNTED REINFORCEMENT

Using Near Surface Mounted (NSM) technique for flexural strengthening of reinforced concrete continuous beams became particularly attractive for researchers and applicators. Due to the existence of carbon fiber reinforced polymer (CFRP)laminates as external strengthening it is subjected to severe damage resulting from mechanical and environmental conditions. There is limited experimental work investigating the behavior of reinforced concrete continuous beams strengthened using NSM technique.This paper presents an experimental investigation of the behavior of reinforced concrete continuous beams strengthened with near surface mounted (NSM) technique in the hogging and sagging moment region. The main variable was changing the lengths of the NSM strips within the negative and positive moment region. The effect of the change in lengths of the NSM strips on the failure load, mid-span deflection, strain on reinforcement, slippage of CFRP strips and crack widths were investigated. The study revealed that the NSM technique can enhance crack and failure loads and controls crack widths

Properties of Carbon Black From Jatropha Seed Shell as a Potential Source of Filler Enhancement in Biocomposites

The use of biomass as filler in biocomposites are becoming widespread in the present decade because its variety of advantages. Jatropha (jatropha curcas L) seed shell after separated from kernel can be used to produce carbon black because of its higher carbon content, and have the potentiality to use as reinforcement in composites. In this study, carbon black was produced from jatropha seed shell by carbonization in furnace method for 1 hour at 600oC. Thermo gravimetric analysis to analyze seed shell of jatropha as raw material. The morphological properties of the carbon black were analyzed by elemental analysis by X-ray (EDX), SEM, TEM, XRD, SEM, and TEM. It was found that the yield of carbon black was 40% which included 4 different sizes ranging from 70 – 300 mesh in distribution of particle size analysis. Carbon black suggested that it could be a good filler or reinforcement in biocomposite

Comparison of Ising magnet on directed versus undirected Erdos-Renyi and scale-free network

Scale-free networks are a recently developed approach to model the interactions found in complex natural and man-made systems. Such networks exhibit a power-law distribution of node link (degree) frequencies n(k) in which a small number of highly connected nodes predominate over a much greater number of sparsely connected ones. In contrast, in an Erdos-Renyi network each of N sites is connected to every site with a low probability p (of the orde r of 1/N). Then the number k of neighbors will fluctuate according to a Poisson distribution. One can instead assume that each site selects exactly k neighbors among the other sites. Here we compare in both cases the usual network with the directed network, when site A selects site B as a neighbor, and then B influences A but A does not influence B. As we change from undirected to directed scale-free networks, the spontaneous magnetization vanishes after an equilibration time following an Arrhenius law, while the directed ER networks have a positive Curie temperature.Comment: 10 pages including all figures, for Int. J, Mod. Phys. C 1