A Supersymmetric U(1)' Model with Multiple Dark Matters

We consider a scenario where a supersymmetric model has multiple dark matter particles. Adding a U(1)' gauge symmetry is a well-motivated extension of the Minimal Supersymmetric Standard Model (MSSM). It can cure the problems of the MSSM such as the mu-problem or the proton decay problem with high-dimensional lepton number and baryon number violating operators which R-parity allows. An extra parity (U-parity) may arise as a residual discrete symmetry after U(1)' gauge symmetry is spontaneously broken. The Lightest U-parity Particle (LUP) is stable under the new parity becoming a new dark matter candidate. Up to three massive particles can be stable in the presence of the R-parity and the U-parity. We numerically illustrate that multiple stable particles in our model can satisfy both constraints from the relic density and the direct detection, thus providing a specific scenario where a supersymmetric model has well-motivated multiple dark matters consistent with experimental constraints. The scenario provides new possibilities in the present and upcoming dark matter searches in the direct detection and collider experiments.Comment: 25 pages, 5 figure

Effect of temperature and litter quality on decomposition rate of Pinus patula needle litter

AbstractThis study examined the mass loss and CO2 production from Pinus patula (Schlecht et Cham) leaf litter collected from fertilized plots in the Mpumalanga Province. Litter decomposition increased with increasing temperature. Warming between 15 and 18°C significantly increased the amount of CO2 emissions from the litter. Mass loss positively correlated with temperature levels. Nitrogen fertilizer applications had significant effects on litter decomposition rate but a minor effect on litter nitrogen quality. Litter quality was not a strong predictor of decomposition rates implying temperature is the major factor influencing the decomposition rate of Pinus patula needle litter. Results of this study are consistent with the hypothesis that the rate of nutrient cycling in non-limiting environments will increase, due primarily to an increase in litter decomposition as a result of increased temperatures

Experimental study on the performance of superfinish hard turned surfaces in rolling contact

In this study, specimens of AISI 52100 with hardness of 62-63 Rc were hard turned using different cutting parameters. Surface roughness, residual stress, and micro-hardness were measured. The workpieces were then tested for the rolling contact fatigue life under several maximum Hertzian contact stresses. Results indicate that the choice of the cutting parameters greatly affects the surface integrity aspects of the hard turned parts and consequently, the fatigue life. For the range of experiments performed, it is found that varying the cutting parameters largely changes the fatigue life by a factor up to 40 times. The repeatability of the fatigue life of hard turned workpieces under the same loading is found to be much more consistent than that of ground workpieces

The Sensitivity of First Generation Epoch of Reionization Observatories and Their Potential for Differentiating Theoretical Power Spectra

Statistical observations of the epoch of reionization (EOR) power spectrum provide a rich data set for understanding the transition from the cosmic "dark ages" to the ionized universe we see today. EOR observations have become an active area of experimental cosmology, and three first generation observatories--MWA, PAST, and LOFAR--are currently under development. In this paper we provide the first quantitative calculation of the three dimensional power spectrum sensitivity, incorporating the design parameters of a planned array. This calculation is then used to explore the constraints these first generation observations can place on the EOR power spectrum. The results demonstrate the potential of upcoming power spectrum observations to constrain theories of structure formation and reionization.Comment: 7 pages with 5 figures. Submitted to Ap

Structure and age-dependent development of the turkey liver: a comparative study of a highly selected meat-type and a wild-type turkey line

In this study the macroscopic and microscopic structure of the liver of a fast growing, meat-type turkey line (British United turkeys BUT Big 6, n = 25) and a wild-type turkey line (Wild Canadian turkey, n = 48) were compared at the age of 4, 8, 12, 16, and 20 wk. Because the growth plates of long bones were still detectable in the 20-week-old wild-type turkeys, indicating immaturity, a group of 8 wild-type turkeys at the age of 24 wk was included in the original scope of the study. Over the term of the study, the body and liver weights of birds from the meat-type turkey line increased at a faster rate than those of the wild-type turkey line. However, the relative liver weight of the meat-type turkeys declined (from 2.7 to 0.9%) to a greater extent than that of the wild-type turkeys (from 2.8 to 1.9%), suggesting a mismatch in development between muscle weights and liver weights of the meat-type turkeys. Signs of high levels of fat storage in the liver were detected in both lines but were greater in the wild-type turkey line, suggesting a better feed conversion by the extreme-genotype birds i.e., meat-type birds. For the first time, this study presents morphologic data on the structure and arrangement of the lymphatic tissue within the healthy turkey liver, describing two different types of lymphatic aggregations within the liver parenchyma, i.e., aggregations with and without fibrous capsules. Despite differences during development, both adult meat-type and adult wild-type turkeys had similar numbers of lymphatic aggregations

Geometric synthesis of a hybrid limit cycle for the stabilizing control of a class of nonlinear switched dynamical systems

International audienceThis paper proposes a new constructive method for synthesizing a hybrid limit cycle for the stabilizing control of a class of switched dynamical systems in IR 2 , switching between two discrete modes and without state discontinuity. For each mode, the system is continuous, linear or nonlinear. This method is based on a geometric approach. The first part of this paper demonstrates a necessary and sufficient condition of the existence and stability of a hybrid limit cycle consisting of a sequence of two operating modes in IR 2 which respects the technological constraints (minimum duration between two successive switchings, boundedness of the real valued state variables). It outlines the established method for reaching this hybrid limit cycle from an initial state, and then stablizing it, taking into account the constraints on the continuous variables. This is then illustrated on a Buck electrical energy converter and a nonlinear switched system in IR 2. The second part of the paper proposes and demonstrates an extension to IR n for a class of systems, which is then illustrated on a nonlinear switched system in IR 3

A CFD-DEM Eulerian-Lagrangian solver for particle-laden viscoelastic flows (for oral presentation)

The ability to simulate the behavior of dense suspensions using computationally-efficient Eulerian-Lagrangian techniques requires accurate particulate-phase drag models that are valid for a wide range of material parameters. The present work aims at developing appropriate drag models for moderately-dense suspensions, in which the continuous phase also has viscoelastic characteristics. To this end, we parametrize the suspension properties through the Deborah number and the particle volume fraction, and compute the evolution in the drag coefficient of spheres translating through a viscoelastic fluid that is described by the Oldroyd-B model. To calculate the drag coefficient, we resort to 3D direct numerical simulations (DNS) of unconfined viscoelastic creeping flows (Re < 0.1) past random arrays of stationary spheres, over a wide range of Deborah numbers (De < 5), volume fractions (φ < 20%) and particle configurations. From these calculations we obtain a closure law F(De, φ) for the drag force in the viscoelastic fluid (with fixed retardation ratio = 0.5), which is on average within 4.7% of the DNS results. Subsequently, this closure law was incorporated into a CFD-DEM Eulerian-Lagrangian solver to handle particle-laden viscoelastic flow calculations, and two case studies were simulated to assess the accuracy and robustness of our numerical approach. These tests consisted of simulating the settling process in Newtonian and viscoelastic fluids within eccentric annular pipes and rectangular channels; configurations commonly employed in hydraulic fracturing operations. The numerical results obtained were found to be in good agreement with experimental data available for suspensions in Newtonian matrix fluids. For the case of viscoelastic fluids, the resulting particle distribution is presented for different elasticity numbers (i.e., El = De/Re) and particle volume fractions, and the results provide insight into the pronounced effects of viscoelastic matrix fluids in hydraulic fracturing operationsMIT-EXPL/TDI/0038/2019. FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020 and MIT-EXPL/TDI/0038/2019 – APROVA – Aprendizagem PROfunda na modelação de escoamentos com fluidos de matriz Viscoelástica Aditivados com partículas (POCI-01-0145-FEDER-016665). The authors would like to acknowledge the Minho University cluster under the project NORTE-07-0162-FEDER-000086 (URL: http://search6.di.uminho.pt), the Minho Advanced Computing Center (MACC) (URL: https:// macc.fccn.pt), the Texas Advanced Computing Center (TACC) at The University of Texas at Austin (URL:http://www.tacc .utexas.edu), the Gompute HPC Cloud Platform (URL: https://www.gompute.com) for providing HPC resources that have contributed to the research results reported within this work

CFD-DEM modeling of particle-laden viscoelastic flows in hydraulic fracturing operations

The ability to simulate the behavior of dense suspensions, using computationally-efficient Eulerian-Lagrangian techniques, requires accurate particulate-phase drag models that are valid for a wide range of process fluids and material parameters. The currently available closed-form drag models – which enable rapid calculation of the momentum exchange between the continuous and dispersed phases – are only valid for dilute suspensions with inelastic base fluids. The present work aims at developing appropriate drag models for moderately-dense suspensions (particle volume fractions < 20%), in which the continuous phase has viscoelastic characteristics. To this end, we parametrize the suspension properties through the Deborah number and the particle volume fraction, and compute the evolution in the drag coefficient of spheres translating through a viscoelastic fluid that is described by the Oldroyd-B model. To calculate the drag coefficient, we resort to three-dimensional direct numerical simulations (DNS) of unconfined viscoelastic creeping flows (Re < 0.1) past random arrays of stationary spheres, over a wide range of Deborah numbers (De < 5), volume fractions (φ < 20%) and particle configurations. From these calculations we obtain a closure law F(De, φ) for the drag force in a fluid described by the quasi-linear Oldroyd-B viscoelastic fluid model (with fixed retardation ratio β=0.5), which is, on average, within 4.7% of the DNS results. Subsequently, this closure law was incorporated into a CFD-DEM Eulerian-Lagrangian solver to handle particle-laden viscoelastic flow calculations, and two case studies were simulated to assess the accuracy and robustness of our numerical approach. These tests consisted of simulating the settling process in Newtonian and viscoelastic fluids within eccentric annular pipes and rectangular channels; configurations commonly employed in hydraulic fracturing operations. The numerical results obtained were found to be in good agreement with experimental data available for suspensions in Newtonian matrix fluids. For the case of viscoelastic fluids, the resulting particle distribution is presented for different elasticity numbers (i.e., El = De/Re) and particle volume fractions, and the results provide additional insights into the pronounced effects of viscoelastic matrix fluids in hydraulic fracturing operationsMIT-EXPL/TDI/0038/2019. y FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020 and MIT-EXPL/TDI/0038/2019 – APROVA – Aprendizagem PROfunda na modelação de escoamentos com fluidos de matriz Viscoelástica Aditivados com partículas (POCI-01-0145-FEDER-016665). The authors would like to acknowledge the Minho University cluster under the project NORTE-07-0162-FEDER-000086 (URL: http://search6.di.uminho.pt), the Minho Advanced Computing Center (MACC) (URL: https:// macc.fccn.pt), the Texas Advanced Computing Center (TACC) at The University of Texas at Austin (URL:http://www.tacc.utexas.edu), the Gompute HPC Cloud Platform (URL: https://www.gompute.com) for providing HPC resources that have contributed to the research results reported within this work

The role and value of nurses in care provision: Views and expectations of Emirati Nationals in the western region of Abu Dhabi, United Arab Emirates

Background: Reliable health user information is needed to effectively organize nursing services and deliver quality patientcentered care. Nurse leaders of Al Gharbia Health Services (AGHS) noted that although budget data and general workforce information were readily available, detailed information about patient experiences, views, and expectations was lacking. Objective: This study aimed to obtain preliminary data regarding health and nursing service expectations of Emirati nationals in the remote western region of Abu Dhabi, United Arab Emirates (UAE). Methods: This study used qualitative descriptive methodology. Semi-structured interviews were conducted with a sample of Emirati families who had recently accessed AGHS. Interviews focused on service user understanding and expectations of the role of nurses, nursing services, and the health service overall. Results: Emirati nationals’ views and expectations regarding nurses’ role and function in the healthcare team were highlighted. Participants’ expectations and the attributes they valued were distributed across two distinct areas: clinical competence and the “softer” skills of compassion, caring, and respect. Conclusions: These findings facilitate understanding of the expectations of Emirati health service users. Importantly, the results counter regional perceptions of nursing under-valued as a servant role across the UAE and broader Gulf Cooperation Council region. The findings may inform a range of activities including: a large-scale survey regarding the views and expectations of Emirati health service users; pre-service nursing education and nursing in service development; and the recruitment of Emirati nationals to the nursing profession. Further investigation regarding perceptions and valuing of nursing within the Emirati community is warranted