3,984 research outputs found
Implications of the Little Higgs Dark Matter and T-odd Fermions
We study the phenomenology of dark matter in the Littlest Higgs model with
T-parity after the discovery of Higgs boson. We analyze the relic abundance of
dark matter, focusing on the effects of coannihilaitons with T-odd fermions.
After determining the parameter space that predicts the correct relic abundance
measured by WMAP and Planck collaborations, we evaluate the elastic scattering
cross section between dark matter and nucleon. In comparison with experimental
results, we find that the lower mass of dark matter is constrained mildly by
LUX 2013 while the future XENON experiment has potential to explore most of the
parameter space for both T-odd lepton and T-odd quark coannihilation scenarios.
We also study the collider signatures of T-odd fermion pair production at the
LHC. Even though the production cross sections are large, it turns out very
challenging to search for these T-odd fermions directly at the collider because
the visible charged leptons or jets are very soft. Furthermore, we show that,
with an extra hard jet radiated out from the initial state, the T-odd quark
pair production can contribute significantly to mono-jet plus missing energy
search at the LHC
Constraints on Unparticle Interactions from Invisible Decays of Z, Quarkonia and Neutrinos
Unparticles (\U) interact weakly with particles. The direct signature of
unparticles will be in the form of missing energy. We study constraints on
unparticle interactions using totally invisible decay modes of , vector
quarkonia and neutrinos. The constraints on the unparticle interaction
scale \Lambda_\U are very sensitive to the dimension d_\U of the
unparticles. From invisible and decays, we find that with d_\U close
to 1 for vector \U, the unparticle scale \Lambda_\U can be more than
TeV, and for d_\U around 2, the scale can be lower than one TeV. From
invisible neutrino decays, we find that if d_\U is close to 3/2, the scale
can be more than the Planck mass, but with d_\U around 2 the scale can be as
low as a few hundred GeV. We also study the possibility of using V (Z)\to
\gamma + \U to constrain unparticle interactions, and find that present data
give weak constraints.Comment: 12 pages, 4 figures, version to appear in JHEP
ALMA Nutator Design and Preliminary Performance
We report the past two years of collaboration between the different actors on
the ALMA nutator. Building on previous developments, the nutator has seen
changes in much of the design. A high-modulus carbon fiber structure has been
added on the back of the mirror in order to transfer the voice coils forces
with less deformation, thus reducing delay problems due to flexing. The
controller is now an off-the-shelf National Instrument NI-cRIO, and the
amplifier a class D servo drive from Advanced Motion Controls, with high peak
power able to drive the coils at 300 Volts DC. The stow mechanism has been
totally redesigned to improve on the repeatability and precision of the stow
position, which is also the reference for the 26 bits Heidenhain encoders. This
also improves on the accuracy of the stow position with wind loading. Finally,
the software, written largely with National Instrument's LabView, has been
developed. We will discuss these changes and the preliminary performances
achieved to date. Keywords: ALMA, nutator, class D, high-modulus carbon fiber.Comment: Published: 23 August 2012; 12 page
Assembling a cellulase cocktail and a cellodextrin transporter into a yeast host for CBP ethanol production
Background: Many microorganisms possess enzymes that can efficiently degrade lignocellulosic materials, but donot have the capability to produce a large amount of ethanol. Thus, attempts have been made to transform suchenzymes into fermentative microbes to serve as hosts for ethanol production. However, an efficient host for aconsolidated bioprocess (CBP) remains to be found. For this purpose, a synthetic biology technique that cantransform multiple genes into a genome is instrumental. Moreover, a strategy to select cellulases that interactsynergistically is needed.Results: To engineer a yeast for CBP bio-ethanol production, a synthetic biology technique, called “promoter-basedgene assembly and simultaneous overexpression” (PGASO), that can simultaneously transform and express multiplegenes in a kefir yeast, Kluyveromyces marxianus KY3, was recently developed. To formulate an efficient cellulasecocktail, a filter-paper-activity assay for selecting heterologous cellulolytic enzymes was established in this study andused to select five cellulase genes, including two cellobiohydrolases, two endo-β-1,4-glucanases and onebeta-glucosidase genes from different fungi. In addition, a fungal cellodextrin transporter gene was chosen totransport cellodextrin into the cytoplasm. These six genes plus a selection marker gene were one-step assembledinto the KY3 genome using PGASO. Our experimental data showed that the recombinant strain KR7 could expressthe five heterologous cellulase genes and that KR7 could convert crystalline cellulose into ethanol.Conclusion: Seven heterologous genes, including five cellulases, a cellodextrin transporter and a selection marker,were simultaneously transformed into the KY3 genome to derive a new strain, KR7, which could directly convertcellulose to ethanol. The present study demonstrates the potential of our strategy of combining a cocktailformulation protocol and a synthetic biology technique to develop a designer yeast host
Finding a Fair Land Dispute Settlement Mechanism Between Adat Law Community Vs. Investor
Land utilization for investment in local areas raises various land related problems that ends with conflicts within the community. A conflict that occurs, usually begins with the management of communal land “tanah ulayat” within the adat law community environment, and in this case, land utilization that is managed by the third party (investors). The basic problem is the difference of perception and expectations toward the company that exists in the land which is claimed by the community. Both parties have their own claim on the land based on each legal systems, in this situation adat law or local law faced with state law which is used by investors. So far, the Indonesian government has yet to have legal grounds in giving a directions for land dispute/conflict settlement mechanism. This paper attempts to give an input regarding a land dispute settlement mechanism that can be accepted for all disputing parties. The paper features critical analysis using legal pluralism approach towards related government policies and technical regulations in the ministerial level. These regulations, among others are, Minister of Agrarian Regulation No. 5 of 1999 on the Guidance for Dispute Settlement of Communal Land Rights, and Ministry of Agrarian and Spatial Affairs Regulation No. 9 of 2015 on Procedures of Appointment of Communal Land Rights for Adat Law Community and Communities Located in certain regions, also the draft of Law regarding Recognition and Protection of Adat Law Community
Exploring quantum criticality based on ultracold atoms in optical lattices
Critical behavior developed near a quantum phase transition, interesting in
its own right, offers exciting opportunities to explore the universality of
strongly-correlated systems near the ground state. Cold atoms in optical
lattices, in particular, represent a paradigmatic system, for which the quantum
phase transition between the superfluid and Mott insulator states can be
externally induced by tuning the microscopic parameters. In this paper, we
describe our approach to study quantum criticality of cesium atoms in a
two-dimensional lattice based on in situ density measurements. Our research
agenda involves testing critical scaling of thermodynamic observables and
extracting transport properties in the quantum critical regime. We present and
discuss experimental progress on both fronts. In particular, the thermodynamic
measurement suggests that the equation of state near the critical point follows
the predicted scaling law at low temperatures.Comment: 15 pages, 6 figure
Susceptibility of Human Embryonic Stem Cell-Derived Neural Cells to Japanese Encephalitis Virus Infection
Pluripotent human embryonic stem cells (hESCs) can be efficiently directed to become immature neuroepithelial precursor cells (NPCs) and functional mature neural cells, including neurotransmitter-secreting neurons and glial cells. Investigating the susceptibility of these hESCs-derived neural cells to neurotrophic viruses, such as Japanese encephalitis virus (JEV), provides insight into the viral cell tropism in the infected human brain. We demonstrate that hESC-derived NPCs are highly vulnerable to JEV infection at a low multiplicity of infection (MOI). In addition, glial fibrillary acid protein (GFAP)-expressing glial cells are also susceptible to JEV infection. In contrast, only a few mature neurons were infected at MOI 10 or higher on the third day post-infection. In addition, functional neurotransmitter-secreting neurons are also resistant to JEV infection at high MOI. Moreover, we discover that vimentin intermediate filament, reported as a putative neurovirulent JEV receptor, is highly expressed in NPCs and glial cells, but not mature neurons. These results indicate that the expression of vimentin in neural cells correlates to the cell tropism of JEV. Finally, we further demonstrate that membranous vimentin is necessary for the susceptibility of hESC-derived NPCs to JEV infection
All-electric all-semiconductor spin field-effect transistors.
The spin field-effect transistor envisioned by Datta and Das opens a gateway to spin information processing. Although the coherent manipulation of electron spins in semiconductors is now possible, the realization of a functional spin field-effect transistor for information processing has yet to be achieved, owing to several fundamental challenges such as the low spin-injection efficiency due to resistance mismatch, spin relaxation and the spread of spin precession angles. Alternative spin transistor designs have therefore been proposed, but these differ from the field-effect transistor concept and require the use of optical or magnetic elements, which pose difficulties for incorporation into integrated circuits. Here, we present an all-electric and all-semiconductor spin field-effect transistor in which these obstacles are overcome by using two quantum point contacts as spin injectors and detectors. Distinct engineering architectures of spin-orbit coupling are exploited for the quantum point contacts and the central semiconductor channel to achieve complete control of the electron spins (spin injection, manipulation and detection) in a purely electrical manner. Such a device is compatible with large-scale integration and holds promise for future spintronic devices for information processing.We thank C.-W. Chang, C.-C. Cheng, M. Fletcher, S. N. Holmes, C.-T. Liang, S.-T. Lo and
J. R. Petta for discussion and/or technical assistance on device fabrication and measurements.
This work was supported by the Ministry of Science and Technology (Taiwan), the Headquarters
of University Advancement at the National Cheng Kung University, and the Engineering and
Physical Sciences Research Council (UK).This is the accepted manuscript. The final version is available at http://www.nature.com/nnano/journal/v10/n1/full/nnano.2014.296.htm
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