50,292 research outputs found
A consistent model for leptogenesis, dark matter and the IceCube signal
We discuss a left-right symmetric extension of the Standard Model in which
the three additional right-handed neutrinos play a central role in explaining
the baryon asymmetry of the Universe, the dark matter abundance and the ultra
energetic signal detected by the IceCube experiment. The energy spectrum and
neutrino flux measured by IceCube are ascribed to the decays of the lightest
right-handed neutrino , thus fixing its mass and lifetime, while the
production of in the primordial thermal bath occurs via a freeze-in
mechanism driven by the additional interactions. The constraints
imposed by IceCube and the dark matter abundance allow nonetheless the heavier
right-handed neutrinos to realize a standard type-I seesaw leptogenesis, with
the asymmetry dominantly produced by the next-to-lightest neutrino .
Further consequences and predictions of the model are that: the
production implies a specific power-law relation between the reheating
temperature of the Universe and the vacuum expectation value of the
triplet; leptogenesis imposes a lower bound on the reheating temperature of the
Universe at 7\times10^9\,\mbox{GeV}. Additionally, the model requires a
vanishing absolute neutrino mass scale .Comment: 19 pages, 4 figures. Constraints from cosmic-ray antiprotons and
gamma rays added, with hadrophobic assignment of the matter multiplets to
satisfy bounds. References added. Matches version published in JHE
A novel synthetic chemistry approach to linkage-specific ubiquitin conjugation.
Ubiquitination is of great importance as the post-translational modification of proteins with ubiquitin, or ubiquitin chains, facilitates a number of vital cellular processes. Herein we present a facile method of preparing various ubiquitin conjugates under mild conditions using michael acceptors based on dibromo-maleimides and dibromo-pyridazinediones
Prospects for intermediate mass black hole binary searches with advanced gravitational-wave detectors
We estimated the sensitivity of the upcoming advanced, ground-based
gravitational-wave observatories (the upgraded LIGO and Virgo and the KAGRA
interferometers) to coalescing intermediate mass black hole binaries (IMBHB).
We added waveforms modeling the gravitational radiation emitted by IMBHBs to
detectors' simulated data and searched for the injected signals with the
coherent WaveBurst algorithm. The tested binary's parameter space covers
non-spinning IMBHBs with source-frame total masses between 50 and 1050
and mass ratios between and 1. We found that
advanced detectors could be sensitive to these systems up to a range of a few
Gpc. A theoretical model was adopted to estimate the expected observation
rates, yielding up to a few tens of events per year. Thus, our results indicate
that advanced detectors will have a reasonable chance to collect the first
direct evidence for intermediate mass black holes and open a new, intriguing
channel for probing the Universe over cosmological scales.Comment: 9 pages, 4 figures, corrected the name of one author (previously
misspelled
On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films
The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces
New Forms of Employer-Worker Relationships in Australian Universities
This paper aims to investigate if the 'high-performance paradigm' and a Unitary Strategic HRM approach of WorkChoices has brought about new forms of employer-worker relationships within Australian universities. In the context of these developments, this paper will first set out to examine the literature to help explain the transition of Australiaâs industrial relations system. The paper will then proceed to outline the qualitative research design before reporting and discussing the results gathered through the undertaking of semi-structured interviews with Human Resource Managers/Directors and/or representatives from Australian universities as well as acclaimed academics within the field. The results highlight that whilst WorkChoices did bring forth a new form of work practice, the new practice did not necessarily promote innovative HRM practices nor did it encourage or cultivate new forms of employer-worker relationships within Australian universitie
The role of controllability in optimizing quantum dynamics
This paper discusses the important role of controllability played on the
complexity of optimizing quantum mechanical control systems. The study is based
on a topology analysis of the corresponding quantum control landscape, which is
referred to as the optimization objective as a functional of control fields. We
find that the degree of controllability is closely relevant with the ruggedness
of the landscape, which determines the search efficiency for global optima.
This effect is demonstrated via the gate fidelity control landscape of a system
whose controllability is restricted on a SU(2) dynamic symmetry group. We show
that multiple local false traps (i.e., non-global suboptima) exist even if the
target gate is realizable and that the number of these traps is increased by
the loss of controllability, while the controllable systems are always devoid
of false traps.Comment: 13 pages, 3 figure
Subsquares Approach - Simple Scheme for Solving Overdetermined Interval Linear Systems
In this work we present a new simple but efficient scheme - Subsquares
approach - for development of algorithms for enclosing the solution set of
overdetermined interval linear systems. We are going to show two algorithms
based on this scheme and discuss their features. We start with a simple
algorithm as a motivation, then we continue with a sequential algorithm. Both
algorithms can be easily parallelized. The features of both algorithms will be
discussed and numerically tested.Comment: submitted to PPAM 201
Towards Verifying Nonlinear Integer Arithmetic
We eliminate a key roadblock to efficient verification of nonlinear integer
arithmetic using CDCL SAT solvers, by showing how to construct short resolution
proofs for many properties of the most widely used multiplier circuits. Such
short proofs were conjectured not to exist. More precisely, we give n^{O(1)}
size regular resolution proofs for arbitrary degree 2 identities on array,
diagonal, and Booth multipliers and quasipolynomial- n^{O(\log n)} size proofs
for these identities on Wallace tree multipliers.Comment: Expanded and simplified with improved result
Elasto-plastic damage modelling of beams and columns with mechanical degradation
© 2017 Techno-Press, Ltd. Within the context of continuum mechanics, inelastic behaviours of constitutive responses are usually modelled by using phenomenological approaches. Elasto-plastic damage modelling is extensively used for concrete material in the case of progressive strength and stiffness deterioration. In this paper, a review of the main features of elasto-plastic damage modelling is presented for uniaxial stress-strain relationship. It has been reported in literature that the influence of Alkali-Silica Reaction (ASR) can lead to severe degradations in the modulus of elasticity and compression strength of the concrete material. In order to incorporate the effects of ASR related degradation, in this paper the constitutive model of concrete is based on the coupled damage-plasticity approach where degradation in concrete properties can be captured by adjusting the yield and damage criteria as well as the hardening moduli related parameters within the model. These parameters are adjusted according to results of concrete behaviour from the literature. The effect of ASR on the dynamic behaviour of a beam and a column are illustrated under moving load and cyclic load cases
Low-noise design issues for analog front-end electronics in 130 nm and 90 nm CMOS technologies
Deep sub-micron CMOS technologies provide wellestablished solutions to the implementation of low-noise front-end electronics in various detector applications. The IC designers’ effort is presently shifting to 130 nm CMOS technologies, or even to the next technology node, to implement readout integrated circuits for silicon strip and pixel detectors, in view of future HEP applications. In this work the results of noise measurements carried out on CMOS devices in 130 nm and 90 nm commercial processes are presented. The behavior of the 1/f and white noise terms is studied as a function of the device polarity and of the gate length and width. The study is focused on low current density applications where devices are biased in weak or moderate inversion. Data obtained from the measurements provide a powerful tool to establish design criteria in nanoscale CMOS processes for detector front-ends in LHC upgrades
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