17 research outputs found
String compactification, QCD axion and axion-photon-photon coupling
It is pointed out that there exist a few problems to be overcome toward an
observable sub-eV QCD axion in superstring compactification. We give a general
expression for the axion decay constant. For a large domain wall number
, the axion decay constant can be substantially lowered from a generic
value of a scalar singlet VEV. The Yukawa coupling structure in the recent
model is studied completely, including the needed nonrenormalizable
terms toward realistic quark and lepton masses. In this model we find an
approximate global symmetry and vacuum so that a QCD axion results but its
decay constant is at the GUT scale. The axion-photon-photon coupling is
calculated for a realistic vacuum satisfying the quark and lepton mass matrix
conditions. It is the first time calculation of in
realistic string compactifications: .Comment: 33 pages, 2 figures, JHEP format, some errors in the superpotential
couplings are corrected and the following discussions are changed
correspondingl
Higgs Boson Bounds in Three and Four Generation Scenarios
In light of recent experimental results, we present updated bounds on the
lightest Higgs boson mass in the Standard Model (SM) and in the Minimal
Supersymmetric extension of the Standard Model (MSSM). The vacuum stability
lower bound on the pure SM Higgs boson mass when the SM is taken to be valid up
to the Planck scale lies above the MSSM lightest Higgs boson mass upper bound
for a large amount of SUSY parameter space. If the lightest Higgs boson is
detected with a mass M_{H} < 134 GeV (150 GeV) for a top quark mass M_{top} =
172 GeV (179 GeV), it may indicate the existence of a fourth generation of
fermions. The region of inconsistency is removed and the MSSM is salvagable for
such values of M_{H} if one postulates the existence of a fourth generation of
leptons and quarks with isodoublet degenerate masses M_{L} and M_{Q} such that
60 GeV 170 GeV.Comment: 7 pages, 4 figures. To be published in Physical Review
Fecal Viral Concentration and Diarrhea in Norovirus Gastroenteritis
Fecal viral concentrations of 40 patients infected with norovirus genogroup GII.4 correlated with diarrhea duration and frequency of vomiting. Higher viral concentration and older age were independently associated with prolonged diarrhea (>4 days). These findings provide information on the pathogenesis and transmission of norovirus infections
Socialâenvironmental drivers inform strategic management of coral reefs in the Anthropocene
Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblagesâthe foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014â2017 global coral bleaching event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse
Simulation and Activated Sludge Model-Based Iterative Learning Control for a Sequencing Batch Reactor
Medicating the coast in a metropolitan city: Enantiomeric profiles and joint probabilistic risk assessment of antidepressants and antihistamines
Pharmaceuticals are receiving increasing attention as emerging contaminants in the aquatic environment. Herein, we investigated the occurrence of 11 antidepressants, 6 antihistamines and 4 metabolites in treated wastewater effluents, rivers, stormwater, and seawater in Hong Kong, with special focus on chirality. The average levels of âpharmaceuticals ranged from 0.525 to 1070 ng/L in all samples and the total annual mass load of target pharmaceuticals in the marine environment of Hong Kong was 756 kg/y. Antihistamines accounted for >80 % of âpharmaceuticals, with diphenhydramine and fexofenadine being predominant. The occurrence and enantiomeric profiles of brompheniramine and promethazine sulfoxide were reported in global natural waters for the first time. Among chiral pharmaceuticals, mirtazapine and fexofenadine exhibited R-preference, while others mostly exhibited S-preference, implying that the ecological risks derived from achiral data for chiral pharmaceuticals may be biased. The joint probabilistic risk assessment of fluoxetine revealed that R-fluoxetine and rac-fluoxetine presented different ecological risks from that of S-fluoxetine; Such assessment also revealed that target pharmaceuticals posed only minimal to low risks, except that diphenhydramine posed an intermediate risk. As estimated, 10 % aquatic species will be affected when the environmental level of diphenhydramine exceeds 7.40 ng/L, which was seen in 46.9 % samples. Collectively, this study highlights further investigations on the enantioselectivity of chiral pharmaceuticals, particularly on environmental behavior and ecotoxicity using local aquatic species as target organisms