2,529 research outputs found

    Higgs boson production via vector-like top-partner decays: diphoton or multilepton plus multijets channels at the LHC

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    We first build a minimal model of vector-like quarks where the dominant Higgs boson production process at LHC -- the gluon fusion -- can be significantly suppressed, being motivated by the recent stringent constraints from the search for direct Higgs production over a wide Higgs mass range. Within this model, compatible with the present experimental constraints on direct Higgs searches, we demonstrate that the Higgs (hh) production via a heavy vector-like top-partner (t2t_2) decay, pp→t2tˉ2pp \to t_2 \bar t_2, t2→tht_2\to t h, allows to discover a Higgs boson at the LHC and measure its mass, through the decay channels h→γγh\to \gamma\gamma or h→ZZh\to ZZ. We also comment on the recent hint in LHC data from a possible ∼125\sim 125 GeV Higgs scalar, in the presence of heavy vector-like top quarks.Comment: 14 pages, 8 figure

    SWIRP (Submm-Wave and Long Wave InfraRed Polarimeter); Development and Characterization of a Sub-Mm Polarimeter for Ice Cloud Investigations

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    A major source of uncertainty in climate models is the presence, shape and distribution of ice particles in the uppermost layers of the clouds. The effects of this component are poorly constrained, turning ice particles into an almost-free variable in many climate models.NASA-GSFC is developing a new instrument aimed at measuring the size and shape of ice particles. The instrument consists of two sub-mm polarimeters (at 220 and 670 GHz) coupled with a long-wave infrared polarimeter at 10 micron. Each polarimeter has identical V-pol and H-pol channels; the axes of polarization are defined geometrically by the orientation of the waveguide elements, and the purity has been measured in the lab. The instrument is configured as a conical scanner, suitable for deployment as a payload on a small satellite or on a high-altitude sub-orbital platform. From a 400 km orbit, the instrument has a 3dB spatial resolution of 20 (10) km at 220 (670) GHz and a swath of 600 km over 180 degrees of view.The BAPTA (Bearing And Power Transfer Assembly) carries heritage from the SSMIS design, now in its 22nd year of on-orbit operation, but with a much reduced SWaP (Size Weight and Power) footprint, suitable for a small satellite.The main components of the instrument have been fabricated and are undergoing final testing prior to their integration as a single unit. The sub-mm channels have dedicated secondary reflectors which illuminate a shared primary reflector. The receiving units are placed behind the focal point of the optical arrangement, so that all beams equally illuminate the primary reflector and are almost co-located on the ground (within a single 220 GHz footprint). Primary and secondary beam patterns have been measured and verified to match the as-designed expectations. A Zytex (TM) window is deployed to protect the secondary reflectors and the feed horns from debris and other contaminants, and to reduce the heat load from the active (hot) IR calibration unit. The insertion loss of Zytex has been measured and is accounted in the calibration equation of the sub-mm channels.The radiometric performance of the sub-mm receivers has been characterized in the lab and under operational conditions of temperature and pressure.This paper discusses the design constraints on the sub-mm components, details of the scientific goals and their flowdown, and describes the characterization of the polarimeters. Options to optimize the layout and distribution of the masses within the assembly, with the goal of making the instrument even more compact and fully-compatible with cubesat-class satellites will be presented

    Four Years of Airborne Measurements of Wildfire Emissions in California, with a Focus on the Evolution of Emissions During the Soberanes Megafire

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    Biomass burning is an important source of trace gases and particles which can influence air quality on local, regional, and global scales. With wildfire events increasing due to changes in land use, increasing population, and climate change, characterizing wildfire emissions and their evolution is vital. In this work we report in situ airborne measurements of carbon dioxide (CO2), methane (CH4), water vapor (H2O), ozone (O3), and formaldehyde (HCHO) from nine wildfire events in California between 2013 and 2016, which were sampled as part of the Alpha Jet Atmospheric eXperiment (AJAX) based at NASA Ames Research Center. One of those fires, the Soberanes Megafire, began on 22 July 2016 and burned for three months. During that time, five flights were executed to sample emissions near and downwind of the Soberanes wildfire. In situ data are used to determine enhancement ratios (ERs), or excess mixing ratio relative to CO2, as well as assess O3 production from the fire. Changes in the emissions as a function of fire evolution are explored. Air quality impacts downwind of the fire are addressed using ground-based monitoring site data, satellite smoke products, and the Community Multiscale Air Quality (CMAQ) photochemical grid model

    Carriers of human mitochondrial DNA macrohaplogroup M colonized India from southeastern Asia

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    Background: From a mtDNA dominant perspective, the exit from Africa of modern humans to colonize Eurasia occurred once, around 60 kya, following a southern coastal route across Arabia and India to reach Australia short after. These pioneers carried with them the currently dominant Eurasian lineages M and N. Based also on mtDNA phylogenetic and phylogeographic grounds, some authors have proposed the coeval existence of a northern route across the Levant that brought mtDNA macrohaplogroup N to Australia. To contrast both hypothesis, here we reanalyzed the phylogeography and respective ages of mtDNA haplogroups belonging to macrohaplogroup M in different regions of Eurasia and Australasia.  Results: The macrohaplogroup M has a historical implantation in West Eurasia, including the Arabian Peninsula. Founder ages of M lineages in India are significantly younger than those in East Asia, Southeast Asia and Near Oceania. Moreover, there is a significant positive correlation between the age of the M haplogroups and its longitudinal geographical distribution. These results point to a colonization of the Indian subcontinent by modern humans carrying M lineages from the east instead the west side.  Conclusions: The existence of a northern route, previously proposed for the mtDNA macrohaplogroup N, is confirmed here for the macrohaplogroup M. Both mtDNA macrolineages seem to have differentiated in South East Asia from ancestral L3 lineages. Taking this genetic evidence and those reported by other disciplines we have constructed a new and more conciliatory model to explain the history of modern humans out of Africa

    Time-dependent Mechanics and Lagrangian submanifolds of Dirac manifolds

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    A description of time-dependent Mechanics in terms of Lagrangian submanifolds of Dirac manifolds (in particular, presymplectic and Poisson manifolds) is presented. Two new Tulczyjew triples are discussed. The first one is adapted to the restricted Hamiltonian formalism and the second one is adapted to the extended Hamiltonian formalism

    The Effects of Static and Dynamic Stretching on Postural Stability, Hip Flexibility, and Power

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    Getting Under the Skin of Clinical Inertia in Insulin Initiation: The Translating Research Into Action for Diabetes (TRIAD) Insulin Starts Project

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    Purpose The purpose of this cross-sectional study is to explore primary care providers’ (PCPs) perceptions about barriers to initiating insulin among patients. Studies suggest that many patients with poorly controlled type 2 diabetes do not receive insulin initiation by PCPs. Methods As part of the Translating Research Into Action for Diabetes study, the authors conducted structured interviews in health systems in Indiana, New Jersey, and California, asking PCPs about the importance of insulin initiation and factors affecting this decision. The authors calculated proportions choosing each multiple-choice response option and listed the most frequently offered open-ended response categories. Results Among 83 PCPs, 45% were women; 60% were white; and they averaged 13.4 years in practice. Four-fifths of PCPs endorsed guideline-concordant glycemic targets, but 54% individualized targets based on patient age, life expectancy, medical comorbidities, self-management capacity, and willingness. Most (64%) reported that many patients were resistant to new oral or insulin therapies due to fears about the therapy and what it meant about their disease progression. Two-thirds (64%) cited patient resistance as a barrier to insulin initiation, and 43% cited problems with patient self-management, including cognitive or mental health issues, dexterity, or ability to adhere. Eighty percent felt that patient nonadherence would dissuade them from initiating insulin at least some of the time. Conclusions PCPs perceived that patient resistance and poor self- management skills were significant barriers to initiating insulin. Future studies should investigate whether systems-level interventions to improve patient-provider communication about insulin and enhance providers’ perceptions of patient self-management capacity can increase guideline-concordant, patient-centered insulin initiation

    Rationale and Design of a Comparative Effectiveness Trial to Prevent Type 2 Diabetes in Mothers and Children: The ENCOURAGE Healthy Families Study

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    The number of youth with type 2 diabetes (T2D) is expected to quadruple over 4 decades. Gestational diabetes mellitus (GDM) is also increasing and is linked with development of T2D in women, and greater risk for T2D in adolescents exposed to GDM. Despite the increasing prevalence of T2D, approaches to prevent diabetes in high-risk youth and families are rare. To address this, we are conducting the Encourage Health Families Study (ENCOURAGE). This is a randomized trial evaluating the comparative effectiveness and costs of an adaptation of the Diabetes Prevention Program (DPP) directed at mothers who had GDM or prediabetes and their children. The intervention is a group-based lifestyle program which we developed and implemented in partnership with the YMCA. We are comparing the ENCOURAGE intervention targeted to 1) mothers who have had GDM or prediabetes, and 2) mothers who have had GDM or prediabetes along with their school-aged children. This manuscript provides 1) the rationale for a targeted approach to preventing T2D and the interventions, 2) description of the translation of the DPP curriculum, and 3) the study design and methodology. The primary aims are to determine if participation leads to 1) weight loss in high-risk mothers, and 2) youth having healthier weights and lifestyle habits. We will also evaluate costs associated with each approach. These data are essential to build a translation model of T2D prevention that is both realistic and feasible to address this growing problem in both youth and adults

    On the Hamilton-Jacobi Theory for Singular Lagrangian Systems

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    We develop a Hamilton-Jacobi theory for singular lagrangian systems using the Gotay-Nester-Hinds constraint algorithm. The procedure works even if the system has secondary constraints.Comment: 36 page

    Hamiltonian dynamics and constrained variational calculus: continuous and discrete settings

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    The aim of this paper is to study the relationship between Hamiltonian dynamics and constrained variational calculus. We describe both using the notion of Lagrangian submanifolds of convenient symplectic manifolds and using the so-called Tulczyjew's triples. The results are also extended to the case of discrete dynamics and nonholonomic mechanics. Interesting applications to geometrical integration of Hamiltonian systems are obtained.Comment: 33 page
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