1,650 research outputs found
Extragalactic and galactic gamma-rays and neutrinos from annihilating dark matter
We describe cosmic gamma-ray and neutrino signals of dark matter
annihilation, explaining how the complementarity of these signals provides
additional information that, if observable, can enlighten the particle nature
of dark matter. This is discussed in the context of exploiting the separate
galactic and extragalactic components of the signal, using the spherical halo
model distribution of dark matter. We motivate the discussion with
supersymmetric extensions of the standard model of particle physics. We
consider the minimal supersymmetric standard model (MSSM) where both neutrinos
and gamma-rays are produced from annihilations. We also consider a gauged B-L,
baryon number minus lepton number, extension of the MSSM, where annihilation
can be purely to heavy right-handed neutrinos. We compare the galactic and
extragalactic components of these signals, and conclude that it is not yet
clear which may dominate when looking out of the galactic plane. To answer this
question, we must have an understanding of the contribution of halo
substructure to the annihilation signals. We find that different theories with
indistinguishable gamma-ray signals can be distinguished in the neutrino
signal. Gamma-ray annihilation signals are difficult to observe from the
galactic center, due to abundant astrophysical sources; but annihilation
neutrinos from there would not be so hidden, if they can be observed over the
atmospheric neutrinos produced by cosmic rays.Comment: 15 pages, 11 figure
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Where constructionism and critical realism converge: interrogating the domain of epistemological relativism
The paper interrogates the status, nature and significance of epistemological relativism as a key element of constructionism and critical realism. It finds that epistemological relativism is espoused by authorities in critical realism and marginalized or displaced in the field of management and organization studies, resulting in forms of analysis that are empirically, but not fully critically, realist. This evaluation prompts reflection on the question of whether, how and with what implications epistemological relativism might be recast at the heart of critical realist studies of management and organization
Fast pyrolysis of halogenated plastics recovered from waste computers
The disposal of waste computers is an issue that is gaining increasing interest around the world. In this paper, results from the fast pyrolysis in a fluidized bed reactor of three different waste computer monitor casings composed of mainly acrylonitrile-butadiene-styrene (ABS) copolymer and two different waste computer body casings composed of mostly poly(vinyl chloride) (PVC) type polymers are presented. Preliminary characterization of the waste plastics was investigated using coupled thermogravimetric analysis-Fourier transform infrared spectrometry (TGA-FT-IR). The results showed that the plastics decomposed in two stages. For the ABS-containing monitor casings, aromatic and aliphatic material were released in the first and second stages. The PVC-containing computer body casing samples showed a first-stage evolution of HCl and a second stage evolution of aromatic and aliphatic material and further HCl. In addition, each of the five plastics was fast-pyrolyzed in a laboratory-scale fluidized bed reactor at 500 °C. The fluidized bed pyrolysis led to the conversion of most of the plastics to pyrolysis oil, although the two PVC computer body cases produced large quantities of HCl. The pyrolysis oils were characterized by GC-MS and it was found that they were chemically very heterogeneous and contained a wide range of aliphatic, aromatic, halogenated, oxygenated, and nitrogenated compounds
Observable Neutron Antineutron Oscillation in High Scale Seesaw Models
We discuss a realistic high scale ( GeV) supersymmetric
seesaw model based on the gauge group
where neutron-anti-neutron oscillation can occur at an observable rate. This is
contrary to the naive dimensional arguments which say that
and is therefore unobservable if the seesaw
scale GeV. Two reasons for the enhanced rate in our model
are: (i) accidental global symmetries which keep some of the diquark Higgs
masses at the weak scale and (ii) a new supersymmetric contribution from a
lower dimensional operator. The net result is that rather than , causing the enhancement. The model
can also explain the origin of matter via leptogenesis and is testable at LHC
where the light diquark states can be produced.Comment: 4 pages and one figure; minor changes; final result unchange
Spin Relaxation Resonances Due to the Spin-Axis Interaction in Dense Rubidium and Cesium Vapor
Resonances in the magnetic decoupling curves for the spin relaxation of dense
alkali-metal vapors prove that much of the relaxation is due to the spin-axis
interaction in triplet dimers. Initial estimates of the spin-axis coupling
coefficients for the dimers are 290 MHz for Rb; 2500 MHz for Cs.Comment: submitted to Physical Review Letters, text + 3 figure
Real-Gas Effects and Phase Separation in Underexpanded Jets at Engine-Relevant Conditions
A numerical framework implemented in the open-source tool OpenFOAM is
presented in this work combining a hybrid, pressure-based solver with a
vapor-liquid equilibrium model based on the cubic equation of state. This
framework is used in the present work to investigate underexpanded jets at
engine-relevant conditions where real-gas effects and mixture induced phase
separation are probable to occur. A thorough validation and discussion of the
applied vapor-liquid equilibrium model is conducted by means of general
thermodynamic relations and measurement data available in the literature.
Engine-relevant simulation cases for two different fuels were defined. Analyses
of the flow field show that the used fuel has a first order effect on the
occurrence of phase separation. In the case of phase separation two different
effects could be revealed causing the single-phase instability, namely the
strong expansion and the mixing of the fuel with the chamber gas. A comparison
of single-phase and two-phase jets disclosed that the phase separation leads to
a completely different penetration depth in contrast to single-phase injection
and therefore commonly used analytical approaches fail to predict the
penetration depth.Comment: Preprint submitted to AIAA Scitech 2018, Kissimmee, Florid
The Non-linear Dynamics of Meaning-Processing in Social Systems
Social order cannot be considered as a stable phenomenon because it contains
an order of reproduced expectations. When the expectations operate upon one
another, they generate a non-linear dynamics that processes meaning. Specific
meaning can be stabilized, for example, in social institutions, but all meaning
arises from a horizon of possible meanings. Using Luhmann's (1984) social
systems theory and Rosen's (1985) theory of anticipatory systems, I submit
equations for modeling the processing of meaning in inter-human communication.
First, a self-referential system can use a model of itself for the
anticipation. Under the condition of functional differentiation, the social
system can be expected to entertain a set of models; each model can also
contain a model of the other models. Two anticipatory mechanisms are then
possible: one transversal between the models, and a longitudinal one providing
the modeled systems with meaning from the perspective of hindsight. A system
containing two anticipatory mechanisms can become hyper-incursive. Without
making decisions, however, a hyper-incursive system would be overloaded with
uncertainty. Under this pressure, informed decisions tend to replace the
"natural preferences" of agents and an order of cultural expectations can
increasingly be shaped
Sleptogenesis
We propose that the observed baryon asymmetry of the Universe can naturally
arise from a net asymmetry generated in the sleptonic sector at fairly low
reheat temperatures. The best candidate is indeed the right-handed sneutrino.
The initial asymmetry in the sneutrino sector can be produced from the decay of
the inflaton, and is subsequently transferred into the Standard Model (s)lepton
doublet via the decay of the sneutrino. The active sphalerons then reprocess
the leptonic asymmetry into the baryonic asymmetry. The marked feature of this
scenario is that the lepton asymmetry is decoupled from the neutrino Yukawa
sector. We exhibit that our scenario can be embedded within models which seek
the origin of a tiny mass for neutrinos.Comment: 7 revtex pages, 2 figures (uses axodraw). Minor changes for better
clarification and updated references. Final version to appear in Phys. Rev.
Processfolio: uniting Academic Literacies and Critical Emancipatory Action Research for practitioner-led inquiry into EAP writing assessment
This paper reports on the design and implementation of an alternative form of writing assessment on a UK English for Academic Purposes (EAP) presessional course. The assessment, termed processfolio, was a response to research inquiry into how writing assessment in a local context negated student agency and inculcated disempowering models of teaching and learning academic writing. The project merged an Academic Literacies approach to writing (Lea and Street, 1998) with a Critical Emancipatory Action Research (Carr and Kemmis, 1986) framework and a Critical Realist(Bhaskar, 1989) perspective. Data collected from the folios and interviews with students and teachers on their experiences of the processfolio found that a small scale intervention has potential for agency to be exercised within the highly constrained context of a UK EAP pre-sessional. New directions in research are proposed which can engage students and teachers to work for change in UK EAP assessment within their internal and external constraints
A holistic multi-methodology for sustainable renovation
A review of the barriers for building renovation has revealed a lack of methodologies, which can promote sustainability objectives and assist various stakeholders during the design stage of building renovation/retrofitting projects. The purpose of this paper is to develop a Holistic Multi-methodology for Sustainable Renovation, which aims to deal with complexity of renovation projects. It provides a framework through which to involve the different stakeholders in the design process to improve group learning and group decision-making, and hence make the building renovation design process more robust and efficient. Therefore, the paper discusses the essence of multifaceted barriers in building renovation regarding cultural changes and technological/physical changes. The outcome is a proposal for a multi-methodology framework, which is developed by introducing, evaluating and mixing methods from Soft Systems Methodologies (SSM) with Multiple Criteria Decision Making (MCDM). The potential of applying the proposed methodology in renovation projects is demonstrated through a case study
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