1,884 research outputs found
Neutrino Mass Sum-rules in Flavor Symmetry Models
Four different neutrino mass sum-rules have been analyzed: these frequently
arise in flavor symmetry models based on the groups A_4, S_4 or T', which are
often constructed to generate tri-bimaximal mixing. In general, neutrino mass
can be probed in three different ways, using beta decay, neutrino-less double
beta decay and cosmology. The general relations between the corresponding three
neutrino mass observables are well known. The sum-rules lead to relations
between the observables that are different from the general case and therefore
only certain regions in parameter space are allowed. Plots of the neutrino mass
observables are given for the sum-rules, and analytical expressions for the
observables are provided. The case of deviations from the exact sum-rules is
also discussed, which can introduce new features. The sum-rules could be used
to distinguish some of the many models in the literature, which all lead to the
same neutrino oscillation results.Comment: 22 pages, 10 figures; matches the version published in Nuclear
Physics
Spin States of Homochiral and Heterochiral Isomers of [Fe(PyBox)2]2+ Derivatives
The following iron(II) complexes of 2,6-bis(oxazolinyl)pyridine (PyBox; LH) derivatives are reported: [Fe(LH)2][ClO4]2 (1); [Fe((R)-LMe)2][ClO4]2 ((R)-2; LMe=2,6-bis{4-methyloxazolinyl}pyridine); [Fe((R)-LPh)2][ClO4]2 ((R)-3) and [Fe((R)-LPh)((S)-LPh)][ClO4]2 ((RS)-3; LPh=2,6-bis{4-phenyloxazolinyl}pyridine); and [Fe((R)-LiPr)2][ClO4]2 ((R)-4) and [Fe((R)-LiPr)((S)-LiPr)][ClO4]2 ((RS)-4; LiPr=2,6-bis{4-isopropyloxazolinyl}pyridine). Solid (R)-3⋅MeNO2 exhibits an unusual very gradual, but discontinuous thermal spin-crossover with an approximate Tmath formula of 350 K. The discontinuity around 240 K lies well below Tmath formula , and is unconnected to a crystallographic phase change occurring at 170 K. Rather, it can be correlated with a gradual ordering of the ligand conformation as the temperature is raised. The other solid compounds either exhibit spin-crossover above room temperature (1 and (RS)-3), or remain high-spin between 5–300 K [(R)-2, (R)-4 and (RS)-4]. Homochiral (R)-3 and (R)-4 exhibit more twisted ligand conformations and coordination geometries than their heterochiral isomers, which can be attributed to steric clashes between ligand substituents [(R)-3]; or, between the isopropyl substituents of one ligand and the backbone of the other ((R)-4). In solution, (RS)-3 retains its structural integrity but (RS)-4 undergoes significant racemization through ligand redistribution by 1H NMR. (R)-4 and (RS)-4 remain high-spin in solution, whereas the other compounds all undergo spin-crossover equilibria. Importantly, Tmath formula for (R)-3 (244 K) is 34 K lower than for (RS)-3 (278 K) in CD3CN, which is the first demonstration of chiral discrimination between metal ion spin states in a molecular complex
New WHO Violence Prevention Information System, an interactive knowledge platform of scientific findings on violence.
Scientific information on violence can be difficult to compile and understand. It is scattered across websites, databases, technical reports and academic journals, and rarely addresses all types of violence. In response, in October 2017 WHO released the Violence Prevention Information System or Violence Info, an online interactive collection of scientific information about the prevalence, consequences, risk factors and preventability of all forms of interpersonal violence. It covers homicide, child maltreatment, youth violence, intimate partner violence, elder abuse and sexual violence
Di-μ-thioÂsemicarbazide-κ4 S:S-bisÂ[bisÂ(thioÂsemicarbazide-κS)copper(I)] diiodide
The title compound, [Cu2{SC(NH2)NHNH2}6]I2, was obtained by the reaction of CuI and thioÂsemicarbazide (TSCZ) in acetonitrile. Each CuI ion is coordinated by four S atoms of the TSCZ ligands, forming a tetraÂhedral geometry. Centrosymmetric dimers are formed by two coordination tetraÂhedra sharing a common edge, with a Cu⋯Cu distance of 2.8236 (14) Å. The I− ion does not have any direct interÂaction with the metal. The crystal structure is stabilized by weak N—H⋯N, N—H⋯S and N—H⋯I hydrogen bonds, forming a three-dimensional network structure
Violence Info methodology
The Violence Prevention Information System (Violence Info) aims to improve access to scientific information about all types of interpersonal violence, including findings on prevalence rates, risk factors, consequences, and prevention and response strategies, through creating a data repository and displaying the information in a user-friendly format on a website. This document details the methodology used to develop the Violence Info data repository and website
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Dermoscopy for melanoma detection and triage in primary care: a systematic review.
OBJECTIVE: Most skin lesions first present in primary care, where distinguishing rare melanomas from benign lesions can be challenging. Dermoscopy improves diagnostic accuracy among specialists and is promoted for use by primary care physicians (PCPs). However, when used by untrained clinicians, accuracy may be no better than visual inspection. This study aimed to undertake a systematic review of literature reporting use of dermoscopy to triage suspicious skin lesions in primary care settings, and challenges for implementation. DESIGN: A systematic literature review and narrative synthesis. DATA SOURCES: We searched MEDLINE, Cochrane Central, EMBASE, Cumulative Index to Nursing and Allied Health Literature, and SCOPUS bibliographic databases from 1 January 1990 to 31 December 2017, without language restrictions. INCLUSION CRITERIA: Studies including assessment of dermoscopy accuracy, acceptability to patients and PCPs, training requirements, and cost-effectiveness of dermoscopy modes in primary care, including trials, diagnostic accuracy and acceptability studies. RESULTS: 23 studies met the review criteria, representing 49 769 lesions and 3708 PCPs, all from high-income countries. There was a paucity of studies set truly in primary care and the outcomes measured were diverse. The heterogeneity therefore made meta-analysis unfeasible; the data were synthesised through narrative review. Dermoscopy, with appropriate training, was associated with improved diagnostic accuracy for melanoma and benign lesions, and reduced unnecessary excisions and referrals. Teledermoscopy-based referral systems improved triage accuracy. Only three studies examined cost-effectiveness; hence, there was insufficient evidence to draw conclusions. Costs, training and time requirements were considered important implementation barriers. Patient satisfaction was seldom assessed. Computer-aided dermoscopy and other technological advances have not yet been tested in primary care. CONCLUSIONS: Dermoscopy could help PCPs triage suspicious lesions for biopsy, urgent referral or reassurance. However, it will be important to establish further evidence on minimum training requirements to reach competence, as well as the cost-effectiveness and patient acceptability of implementing dermoscopy in primary care. TRIAL REGISTRATION NUMBER: CRD42018091395.CRU
Brevinin-2GHk from Sylvirana guentheri and the design of truncated analogs exhibiting the enhancement of antimicrobial activity
Brevinins are an important antimicrobial peptide (AMP) family discovered in the skin secretions of Ranidae frogs. The members demonstrate a typical C-terminal ranabox, as well as a diverse range of other structural characteristics. In this study, we identified a novel brevinin-2 peptide from the skin secretion of Sylvirana guentheri, via cloning transcripts, and identifying the expressed mature peptide, in the skin secretion. The confirmed amino acid sequence of the mature peptide was designated brevinin-2GHk (BR2GK). Moreover, as a previous study had demonstrated that the N-terminus of brevinin-2 is responsible for exerting antimicrobial activity, we also designed a series of truncated derivatives of BR2GK. The results show that the truncated derivatives exhibit significantly improved antimicrobial activity and cytotoxicity compared to the parent peptide, except a Pro14 substituted analog. The circular dichroism (CD) analysis of this analog revealed that it did not fold into a helical conformation in the presence of either lipopolysaccharides (LPS) or TFE, indicating that position 14 is involved in the formation of the α-helix. Furthermore, three more analogs with the substitutions of Ala, Lys and Arg at the position 14, respectively, revealed the influence on the membrane disruption potency on bacteria and mammalian cells by the structural changes at this position. Overall, the N-terminal 25-mer truncates demonstrated the potent antimicrobial activity with low cytotoxicity
The Speciation of Homochiral and Heterochiral Diastereomers of Homoleptic Cobalt(II) and Zinc(II) PyBox Complexes
Homochiral [M((R)-LR)2]2+ and heterochiral [M((R)-LR)((S)-LR)]2+ isomers of [Zn(LPh)2][BF4]2, [Zn(LiPr)2][BF4]2, [Co(LPh)2][BF4]2, and [Co(LiPr)2][BF4]2 (LPh = 2,6-bis(4-phenyloxazolinyl)pyridine; LiPr = 2,6-bis(4-isopropyloxazolinyl)pyridine) have been prepared and characterised. Six of the eight compounds were crystallographically characterised, showing that steric repulsions between ligand substituents lead to more distorted coordination geometries in the homochiral isomers, especially in the LiPr complexes. Heterochiral [M((R)-LiPr)((S)-LiPr)]2+ (M = Zn or Co) undergoes partial racemisation in CD3CN through ligand redistribution reactions, whereas [M((R)-LPh)((S)-LPh)]2+ does not (in agreement with previous reports). This may be a consequence of intramolecular π... π - interactions in [M((R)-LPh)((S)-LPh)]2+, whereby each pyridyl group is sandwiched between two phenyl substituents from the other LPh ligand. These π... π -interactions are disrupted in homochiral [M((R)-LR)2]2+, owing to the aforementioned steric clash between phenyl substituents in that isomer
Neutrino - nucleon reaction rates in the supernova core in the relativistic random phase approximation
In view of the application to supernova simulations, we calculate neutrino
reaction rates with nucleons via the neutral and charged currents in the
supernova core in the relativistic random phase approximation (RPA) and study
their effects on the opacity of the supernova core. The formulation is based on
the Lagrangian employed in the calculation of nuclear equation of state (EOS)
in the relativistic mean field theory (RMF). The nonlinear meson terms are
treated appropriately so that the consistency of the density correlation
derived in RPA with the thermodynamic derivative obtained from EOS by RMF is
satisfied in the static and long wave length limit. We employ pion and rho
meson exchange interactions together with the phenomenological Landau-Migdal
parameters for the isospin-dependent nuclear interactions. We find that both
the charged and neutral current reaction rates are suppressed from the standard
Bruenn's approximate formula considerably in the high density regime. In the
low density regime, on the other hand, the vector current contribution to the
neutrino-nucleon scattering rate is enhanced in the vicinity of the boundary of
the liquid-gas phase transition, while the other contributions are moderately
suppressed there also. In the high temperature regime or in the regime where
electrons have a large chemical potential, the latter of which is important
only for the electron capture process and its inverse process, the recoil of
nucleons cannot be neglected and further reduces the reaction rates with
respect to the standard approximate formula which discards any energy transfer
in the processes. These issues could have a great impact on the neutrino
heating mechanism of collapse-driven supernovae.Comment: 16pages, 19figures, submitted to PR
Brevinin-2GHk from Sylvirana guentheri and the design of truncated analogs exhibiting the enhancement of antimicrobial activity
Brevinins are an important antimicrobial peptide (AMP) family discovered in the skin secretions of Ranidae frogs. The members demonstrate a typical C-terminal ranabox, as well as a diverse range of other structural characteristics. In this study, we identified a novel brevinin-2 peptide from the skin secretion of Sylvirana guentheri, via cloning transcripts, and identifying the expressed mature peptide, in the skin secretion. The confirmed amino acid sequence of the mature peptide was designated brevinin-2GHk (BR2GK). Moreover, as a previous study had demonstrated that the N-terminus of brevinin-2 is responsible for exerting antimicrobial activity, we also designed a series of truncated derivatives of BR2GK. The results show that the truncated derivatives exhibit significantly improved antimicrobial activity and cytotoxicity compared to the parent peptide, except a Pro14 substituted analog. The circular dichroism (CD) analysis of this analog revealed that it did not fold into a helical conformation in the presence of either lipopolysaccharides (LPS) or TFE, indicating that position 14 is involved in the formation of the α-helix. Furthermore, three more analogs with the substitutions of Ala, Lys and Arg at the position 14, respectively, revealed the influence on the membrane disruption potency on bacteria and mammalian cells by the structural changes at this position. Overall, the N-terminal 25-mer truncates demonstrated the potent antimicrobial activity with low cytotoxicity
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