Cosmological Constant, Dark Matter, and Electroweak Phase Transition

Accepting the fine tuned cosmological constant hypothesis, we have recently proposed that this hypothesis can be tested if the dark matter freeze out occurs at the electroweak scale and if one were to measure an anomalous shift in the dark matter relic abundance. In this paper, we numerically compute this relic abundance shift in the context of explicit singlet extensions of the Standard Model and explore the properties of the phase transition which would lead to the observationally most favorable scenario. Through the numerical exploration, we explicitly identify a parameter space in a singlet extension of the standard model which gives order unity observable effects. We also clarify the notion of a temperature dependence in the vacuum energy.Comment: 58 pages, 10 figure

Performance of the star‐shaped flyer in the study of brittle materials: Three dimensional computer simulations and experimental observations

A three dimensional finite element computer simulation has been performed to assess the effects of release waves in normal impact soft‐recovery experiments when a star‐shaped flyer plate is used. Their effects on the monitored velocity‐time profiles have been identified and their implications in the interpretation of wave spreading and spall signal events highlighted. The calculation shows that the star‐shaped flyer plate indeed minimizes the magnitude of edge effects. The major perturbation to the one‐dimensional response within the central region of the target plate results from spherical waves emanating from the corners of the star‐shaped plate. Experimental evidence of the development of a damage ring located in coincidence with the eight entrant corners of the flyer plate is reported. Microscopy studies performed in the intact recovered samples revealed that this damage ring eliminates undesired boundary release waves within the central region of the specimen. Consequently, the observed damage in compression and tension within this region can be attributed primarily to the conditions arising from a state of uniaxial strain.

Resummation Methods at Finite Temperature: The Tadpole Way

We examine several resummation methods for computing higher order corrections to the finite temperature effective potential, in the context of a scalar $\phi^4$ theory. We show by explicit calculation to four loops that dressing the propagator, not the vertex, of the one-loop tadpole correctly counts ``daisy'' and ``super-daisy'' diagrams.Comment: 18 pages, LaTeX, CALT-68-1858, HUTP-93-A011, EFI-93-2

Heat damage, Maillard reactions, and measurement of reactive lysine in feed ingredients and diets

Feed cost represents 70% of the total cost of poultry and pork production (Patience et al., 2015); therefore, a number of processing techniques have been developed to maximize utilization of nutrients in feed ingredients and diets for optimum animal growth performance. Oilseed meals are commonly exposed to varying degrees of heat to remove solvents used during oil extraction, increase nutrient digestibility, improve storage life, and to reduce anti-nutritional factors (Liener, 1994; Rehman and Shah, 2005; Goebel and Stein, 2011). Heat is also applied in the production of distillers dried grains with solubles (DDGS) from dry grind ethanol facilities during the liquefaction and drying stages (Bothast and Schlicher, 2005). Thus, heat treatment of many processed feed ingredients is a necessity. However, excessive heat results in reduced nutrient digestibility due to formation of Maillard reaction products (González-Vega et al., 2011; Pahm et al., 2008). Maillard reaction involves the reaction of reducing sugars with the terminal/Ɛ-amino group of amino acids (AA; particularly Lys), and products of the Maillard reaction can render AA in diets and/or feed ingredients unavailable (Finot and Magnenat, 1981). Factors affecting the rate of formation of Maillard reaction products include temperature, pH, substrate, and water activity, and each of these factors may affect the kinetics of the reactions in specific ways. Caramelization, which involves the oxidation of sugars and is another form of heat damage may also take place (Pahm et al., 2008). Formation of enzymatically resistant bonds between ε-amino groups of Lys and carboxyl groups of Glu and Asp can also occur, and these indigestible peptides can reduce protein digestibility and block AA transport across the intestinal wall (Dworschák, 1980). Other consequences of heat damage include conversion of some of the L-forms of AA into D-forms (racemization) and formation of lysinoalanine (Hirano et al., 1973; Meade et al., 2005). The objective of this contribution is to review the current understanding about heat damage, stages and products of Maillard reaction, and measurement of reactive Lys in diets and feed ingredients. Effects of heat damage in feed ingredients and diets on nutrient digestibility and growth performance of pigs will also be discussed

Self-pulsing dynamics of ultrasound in a magnetoacoustic resonator

A theoretical model of parametric magnetostrictive generator of ultrasound is considered, taking into account magnetic and magnetoacoustic nonlinearities. The stability and temporal dynamics of the system is analized with standard techniques revealing that, for a given set of parameters, the model presents a homoclinic or saddle--loop bifurcation, which predicts that the ultrasound is emitted in the form of pulses or spikes with arbitrarily low frequency.Comment: 5 pages, 5 figure

Design of Intervention Program for Preventing of Alcohol Misuse in University Students

In the Universidad de Oriente of Santiago de Cuba, recent diagnoses showed there is currently an increase in the rate of young people who consume alcoholic beverages. Therefore, the present research has like General Objective: To design a psychoeducational intervention program to prevent the undue consumption of alcohol in the Student Residence of the University of the East of Santiago de Cuba. Techniques such as Composition, Risk Perception Questionnaire on Alcohol Consumption, Social Skills Questionnaire and Preference Questionnaire for leisure time have used. The main results were that 94% of these young people had a low perception of risk on alcohol consumption and only 15% were able to identify the main negative consequences associated with consumption. 96% had insufficient development of social skills, which is associated with the poor ability to resist the pressure of the group

Reduced graphene oxides as carbocatalysts in acceptorless dehydrogenation of N-heterocycles

The catalytic properties of graphene-derived materials are evaluated in acceptorless dehydrogenation of N-heterocycles. Among them, reduced graphene oxides (rGOs) are active (quantitative yields in 23 h) under mild conditions (130 °C) and act as efficient heterogeneous carbocatalysts. rGO exhibits reusability and stability at least during eight consecutive runs. Mechanistic investigations supported by experimental evidence (i.e., organic molecules as model compounds, purposely addition of metal impurities and selective functional group masking experiments) suggest a preferential contribution of ketone carbonyl groups as active sites for this transformation.

A No-Lose Theorem for Higgs Searches at a Future Linear Collider

Assuming perturbativity up to a high energy scale $\sim 10^{16}$ GeV, we demonstrate that a future $e^+e^-$ linear collider operating at $\sqrt{s} =$ 500 GeV with $\int{\cal L}=$ 500 fb$^{-1}$ per year (such as the recently proposed TESLA facility) will detect a Higgs boson signal regardless of the complexity of the Higgs sector and of how the Higgs bosons decay.Comment: 4 pages, LaTe

Calculable Upper Limit on the Mass of the Lightest Higgs Boson in Any Perturbatively Valid Supersymmetric Theory

We show that there is a calculable upper limit on the mass of the lightest Higgs boson in any supersymmetric theory that remains perturbative up to a high scale . There are no restrictions on the Higgs sector, or the gauge group or particle content. We estimate the value of the upper limit to be m_{\hcirc} < 146 GeV for 100 GeV < $M_t$ < 145 GeV, from all effects except possibly additional heavy fermions beyond top (which could increase the limit by 0-20 GeV if any existed); for $M_t$ > 145 GeV the limit decreases monotonically. We expect to be able to decrease the value of the upper limit by at least a few percent by very careful analysis of the conditions. It is not normal in models for the actual mass to saturate the upper limit.Comment: 8 pages, UM-TH-92-24, Plain TeX. (One table available by fax on request to [email protected]

Two-Higgs doublet models from TeV-scale supersymmetric extra U(1) models

We investigate the reduction of a general TeV-scale supersymmetric extra U(1) model to a 2HDM below the TeV- scale through the tree level non-decoupling. Portions of the parameter space of the extra U(1) model appropriate for obtaining a 2HDM are identified. Various properties of the resulting 2HDM are connected to the parameter space of the underlying model. PACS: 12.60.Jv, 12.60.Cn, 12.60.FrComment: 12 pages, 4 postscript figures, to appear in Phys. Rev.