HAPS Gateway Link in the 5850-7075 MHz and Coexistence with Fixed Satellite Service

Gateway link is essential to connect HAPS platform to terrestrial based networks. This crucial link is incorporated in HAPS fixed service spectrum allocation in considerably high frequencies, renders the link for more attenuations by atmospheric gases, and rain effects, especially when the regional climate is not favorable. However, under the agenda item 1.20 of World Radio Conference-2012 (WRC-12) new HAPS allocation in the 5850-7075 MHz band is proposed. Although, spectrum features are incomparably reliable, on the contrary, Fixed Satellite Service (FSS) uplink transmissions will have signal levels much higher than those in HAPS systems and have the potential for causing interference at the HAPS gateway receiver. In this article a key aspect of co-channel interference phenomena is investigated to facilitate optimum frequency sharing in the band in question. By proposing mitigation techniques and statistical method this generic prediction model enhances the capability of the HAPS spectrum sharing and provides flexibility in spectrum planning for different fixed services

Fourth-generation SM imprints in B -> K^*l^+l^- decays with polarized K^*

The implication of the fourth-generation quarks in the B -> K^*l^+l^- (l=mu,tau) decays, when K^* meson is longitudinally or transversely polarized, is presented. In this context, the dependence of the branching ratio with polarized K^* and the helicity fractions (f_{L,T}) of K^* meson are studied. It is observed that the polarized branching ratios as well as helicity fractions are sensitive to the NP parameters, especially when the final state leptons are tauons. Hence the measurements of these observables at LHC can serve as a good tool to investigate the indirect searches of new physics beyond the Standard Model.Comment: 13 pages, 10 figures, V2: some of the graphs are modified according to the new data from recent experiments. arXiv admin note: substantial text overlap with arXiv:1107.569

Coulomb blockade in silicon based structures at temperatures up to 50 K

Coulomb blockade has been observed in the current-voltage characteristics of structures fabricated in silicon germanium delta-doped material at temperatures up to 50 K. This is consistent with the estimated effective tunnel capacitance of 10 aF which is significantly smaller than the reported capacitances of tunnel junctions made from Al or GaAs/AlGaAs heterostructures

Unlocking the mergers and acquisitions puzzle in the United Arab Emirates: investigating the impact of corporate leverage on target selection and payment methods

Following a long stream of literature on the drivers of Mergers and Acquisition (M&A) activities, this study examines the effect of corporate leverage on several decisions of M&A deals in the context of the United Arab Emirates (UAE). Using M&A data from the Thomson One database for the period between 2005 and 2022, we find that corporate leverage significantly influences the type of M&A target. This study further adds to the prior literature on the contradictory behaviours of high- and low-leverage firms by examining whether acquisition decisions differ amongst them in M&A deals in the UAE context. Results indicate that high (low) leverage firms are less (more) likely to acquire private targets and more (less) inclined to acquire a target from a different (same) industry. Furthermore, our results show that the relationship between the method of payment used in M&A deals and corporate leverage is insignificant. We control for endogeneity using Heckman’s two-stage method. In brief, this paper extends the literature with conclusive evidence that considerations of capital structure can significantly anticipate and explain firms’ behaviour toward M&A choices. The implication of findings may include a call to reform some aspects of the Competition Law in the UAE by requiring private firms to enhance their disclosure practices similar to their public counterparts

Optical Properties of Organometallic Perovskite: An ab initio Study using Relativistic GW Correction and Bethe-Salpeter Equation

In the development of highly efficient photovoltaic cells, solid perovskite systems have demonstrated unprecedented promise, with the figure of merit exceeding nineteen percent of efficiency. In this paper, we investigate the optical and vibrational properties of organometallic cubic perovskite CH3NH3PbI3 using first-principles calculations. For accurate theoretical description, we go beyond conventional density functional theory (DFT), and calculated optical conductivity using relativist quasi-particle (GW) correction. Incorporating these many-body effects, we further solve Bethe-Salpeter equations (BSE) for excitons, and found enhanced optical conductivity near the gap edge. Due to the presence of organic methylammonium cations near the center of the perovskite cell, the system is sensitive to low energy vibrational modes. We estimate the phonon modes of CH3NH3PbI3 using small displacement approach, and further calculate the infrared absorption (IR) spectra. Qualitatively, our calculations of low-energy phonon frequencies are in good agreement with our terahertz measurements. Therefore, for both energy scales (around 2 eV and 0-20 meV), our calculations reveal the importance of many-body effects and their contributions to the desirable optical properties in the cubic organometallic perovskites system.Comment: 5 pages, 4 figure

Emergency peripartum hysterectomy in a tertiary hospital in Upper Egypt: six years analysis

Background: Emergency peripartum hysterectomy (EPH) is often performed for life-threatening obstetric conditions especially when conservative treatment approach fails to stop postpartum hemorrhage. The aim of the study is to detect the incidence, indications, and complications of EPH over 6 years in Assiut Women Health Hospital in Upper Egypt.Methods: A historical cohort study conducted between January 2009 and December 2014. Detailed review of all files of cases of EPH including maternal age, parity, gestational age, type of delivery, indications for EPH and outcome of the hysterectomy.Results: The overall incidence of EPH was 1.30 per 1,000 deliveries. The main indications for hysterectomies were uterine atony 60 (48.78 %), abnormal placentation 27 (21.95 %) and rupture uterus 25 (20.32 %). There were 48 (39.02%) maternal deaths, while the perinatal mortality was 20.32% (25 cases). Using multivariate logistic regression analysis, we found that woman’s age ≥ 40 years and parity ≥ 5 were the most significant independent predictors for maternal mortality in cases of EPH (OR 5.49; 95% CI 2.16 - 13.96) and (OR 0.34; 95% CI 0.15 - 0.77) respectively.Conclusions: The incidence of EPH in Upper Egypt is high. Uterine atony is the major indication for EPH in our hospital. Late referral and delayed decisions to perform hysterectomy contributes in the high mortality rate

Neutrino Experiments: Status, Recent Progress, and Prospects

Neutrino physics has seen an explosion of activity and new results in the last decade. In this report the current state of the field is summarized, with a particular focus on progress in the last two years. Prospects for the near term (roughly 5 years) are also described.Comment: 14 pages, 10 figures, proceedings of plenary talk at EPS HEP 2007 Conference, Manchester, UK. Updated with citation added to Figure 1