503 research outputs found
Signals of Unconventional E Models at Colliders
Generation dependent discrete symmetries often appear in models derived from
superstring theories. In particular, in the framework of E models the
presence of such symmetries is required in order to allow for the radiative
generation of naturally small neutrino masses. Recently it was shown that by
imposing suitable generation dependent discrete symmetries, a class of models
can be consistently constructed in which the three sets of known fermions in
each generation do not have the same assignments with respect to the {\bf 27}
representation of E. In this scenario, the different embedding in the gauge
group of the three generations implies in particular that the known charged
leptons couple in a non--universal way to the new neutral gauge bosons
present in these models. We exploit this fact to study the
signature of this class of models at present and future colliders. We
show that some signals of deviation from lepton universality as well as some
other discrepancies with the standard model predictions which have been
observed at the TRISTAN collider in the production rate of and ,
can be accounted for if the mass is not much heavier than 300 GeV. We
also study the discovery limits for lepton universality violation of this type
at LEP-2 and at the 500 GeV Next Linear Collider (NLC). We show that
models predicting unconventional assignments for the leptons will give an
unmistakable signature, when the mass is as heavy as GeV
(LEP-2) and TeV (NLC).Comment: Plain Tex, 20 pages. 4 PostScript figures (uses `epsf.tex'). Modified
file-format. No changes in the tex
Unconventional superstring derived E models and neutrino phenomenology
Conventional superstring derived E models can accommodate small neutrino
masses if a discrete symmetry is imposed which forbids tree level Dirac
neutrino masses but allows for radiative mass generation. Since the only
possible symmetries of this kind are known to be generation dependent, we
explore the possibility that the three sets of light states in each generation
do not have the same assignments with respect to the 27 of , leading to
non universal gauge interactions under the additional factors for the
known fermions. We argue that models realising such a scenario are viable, with
their structure being constrained mainly by the requirement of the absence of
flavor changing neutral currents in the Higgs sector. Moreover, in contrast to
the standard case, rank 6 models are not disfavoured with respect to rank 5. By
requiring the number of light neutral states to be minimal, these models have
an almost unique pattern of neutrino masses and mixings. We construct a model
based on the unconventional assignment scenario in which (with a natural choice
of the parameters) m_{\nut}\sim O(10)eV is generated at one loop, m_{\num}
is generated at two loops and lies in a range interesting for the solar
neutrino problem, and \nue remains massless. In addition, since baryon and
lepton number are conserved, there is no proton decay in the model. To
illustrate the non-standard phenomenology implied by our scheme we also discuss
a second scenario in which an attempt for solving the solar neutrino puzzle
with matter enhanced oscillations and practically massless neutrinos can be
formulated, and in which peculiar effects for the \num --> \nut conversion
of the upward-going atmospheric neutrinos could arise as well.Comment: Plain Tex, 33 pages, 3 PostScript figures (uses epsf.tex). Modified
file-format. No changes in the tex
Metastatic eccrine porocarcinoma: report of a case and review of the literature
Eccrine porocarcinoma (EPC) is a rare type of skin cancer arising from the intraepidermal portion of eccrine sweat glands or acrosyringium, representing 0.005-0.01% of all cutaneous tumors. About 20% of EPC will recur and about 20% will metastasize to regional lymph nodes. There is a mortality rate of 67% in patients with lymph node metastases. Although rare, the occurrence of distant metastases has been reported
Mortality profiles in a country facing epidemiological transition: An analysis of registered data
BACKGROUND: Sub-national analyses of causes of death and time-trends help to define public health policy priorities. They are particularly important in countries undergoing epidemiological transition like Peru. There are no studies exploring Peruvian national and regional characteristics of such epidemiological transition. We aimed to describe Peru's national and regional mortality profiles between 1996 and 2000. METHODS: Registered mortality data for the study period were corrected for under-registration following standardized methods. Main causes of death by age group and by geographical region were determined. Departmental mortality profiles were constructed to evaluate mortality transition, using 1996 data as baseline. Annual cumulative slopes for the period 1996-2000 were estimated for each department and region. RESULTS: For the study period non-communicable diseases explained more than half of all causes of death, communicable diseases more than one third, and injuries 10.8% of all deaths. Lima accounted for 32% of total population and 20% of total deaths. The Andean region, with 38% of Peru's population, accounted for half of all country deaths. Departmental mortality predominance shifted from communicable diseases in 1996 towards non-communicable diseases and injuries in 2000. Maternal and perinatal conditions, and nutritional deficiencies and nutritional anaemia declined markedly in all departments and regions. Infectious diseases decreased in all regions except Lima. In all regions acute respiratory infections are a leading cause of death, but their proportion ranged from 9.3% in Lima and Callao to 15.3% in the Andean region. Tuberculosis and injuries ranked high in Lima and the Andean region. CONCLUSION: Peruvian mortality shows a double burden of communicable and non-communicable, with increasing importance of non-communicable diseases and injuries. This challenges national and sub-national health system performance and policy making
Replication of the association of chromosomal region 9p21.3 with generalized aggressive periodontitis (gAgP) using an independent case-control cohort
Background: The human chromosomal region 9p21.3 has been shown to be strongly associated with Coronary Heart Disease (CHD) in several Genome-wide Association Studies (GWAS). Recently, this region has also been shown to be associated with Aggressive Periodontitis (AgP), strengthening the hypothesis that the established epidemiological association between periodontitis and CHD is caused by a shared genetic background, in addition to common environmental and behavioural risk factors. However, the size of the analyzed cohorts in this primary analysis was small compared to other association studies on complex diseases. Using our own AgP cohort, we attempted to confirm the described associations for the chromosomal region 9p21.3. Methods: We analyzed our cohort consisting of patients suffering from the most severe form of AgP, generalized AgP (gAgP) (n = 130) and appropriate periodontally healthy control individuals (n = 339) by genotyping four tagging SNPs (rs2891168, rs1333042, rs1333048 and rs496892), located in the chromosomal region 9p21.3, that have been associated with AgP. Results: The results confirmed significant associations between three of the four SNPs and gAgP. The combination of our results with those from the study which described this association for the first time in a meta-analysis of the four tagging SNPs produced clearly lower p-values compared with the results of each individual study. According to these results, the most plausible genetic model for the association of all four tested SNPs with gAgP seems to be the multiplicative one. Conclusion: We positively replicated the finding of an association between the chromosomal region 9p21.3 and gAgP. This result strengthens support for the hypothesis that shared susceptibility genes within this chromosomal locus might be involved in the pathogenesis of both CHD and gAgP
Venezuelan Equine Encephalitis Virus, Southern Mexico
Evidence of enzootic and endemic Venezuelan equine encephalitis virus circulation in southern Mexico since the 1996 epizootic was obtained from serosurveys and virus isolations
K2-291b:A rocky super-Earth in a 2.2 day orbit
K2-291 (EPIC 247418783) is a solar-type star with a radius of R_star = 0.899
0.034 R_sun and mass of M_star=0.934 0.038 M_sun. From K2 C13 data,
we found one super-Earth planet (R_p = 1.589+0.095-0.072 R_Earth) transiting
this star on a short period orbit (P = 2.225177 +6.6e-5 -6.8e-5 days). We
followed this system up with adaptive-optic imaging and spectroscopy to derive
stellar parameters, search for stellar companions, and determine a planet mass.
From our 75 radial velocity measurements using HIRES on Keck I and HARPS-N on
Telescopio Nazionale Galileo, we constrained the mass of EPIC 247418783b to M_p
= 6.49 1.16 M_Earth. We found it necessary to model correlated stellar
activity radial velocity signals with a Gaussian process in order to more
accurately model the effect of stellar noise on our data; the addition of the
Gaussian process also improved the precision of this mass measurement. With a
bulk density of 8.84+2.50-2.03 g cm-3, the planet is consistent with an
Earth-like rock/iron composition and no substantial gaseous envelope. Such an
envelope, if it existed in the past, was likely eroded away by
photo-evaporation during the first billion years of the star's lifetime.Comment: Accepted to AJ, 15 pages, 8 figure
Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis
BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London
TOI-1235 b: A Keystone Super-Earth For Testing Radius Valley Emergence Models Around Early M Dwarfs
Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, ), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R s = 0.630 ± 0.015 , M s = 0.640 ± 0.016 ). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of , which implies an iron core mass fraction of % in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be \u3c0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin ( days, ) that cannot be firmly ruled out by our data
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