184 research outputs found
Conicoid Mirrors
The first order equation relating object and image location for a mirror of
arbitrary conic-sectional shape is derived. It is also shown that the parabolic
reflecting surface is the only one free of aberration and only in the limiting
case of distant sources.Comment: 9 page
Measures of fine tuning
Fine-tuning criteria are frequently used to place upper limits on the masses
of superpartners in supersymmetric extensions of the standard model. However,
commonly used prescriptions for quantifying naturalness have some important
shortcomings. Motivated by this, we propose new criteria for quantifying fine
tuning that can be used to place upper limits on superpartner masses with
greater fidelity. In addition, our analysis attempts to make explicit the
assumptions implicit in quantifications of naturalness. We apply our criteria
to the minimal supersymmetric extension of the standard model, and we find that
the scale of supersymmetry breaking can be larger than previous methods
indicate.Comment: 15 pages, LaTex, 5 figures uuencoded, gz-compressed file. Minor
revisions bring the archived manuscript into agreement with published versio
Discrete symmetries and isosinglet quarks in low-energy supersymmetry
Many extensions of the minimal supersymmetric standard model contain
superfields for quarks which are singlets under weak isospin with electric
charge -1/3. We explore the possibility that such isosinglet quarks have low or
intermediate scale masses, but do not mediate rapid proton decay because of a
discrete symmetry. By imposing the discrete gauge anomaly cancellation
conditions, we show that the simplest way to achieve this is to extend the Z_3
"baryon parity" of Ibanez and Ross to the isosinglet quark superfields. This
can be done in three distinct ways. This strategy is not consistent with grand
unification with a simple gauge group, but may find a natural place in
superstring-inspired models, for example. An interesting feature of this
scenario is that proton decay is absolutely forbidden.Comment: 13 pages, MIT-CTP-2345, NUB-3097-94T
Circulating microRNA signature in non-alcoholic fatty liver disease: from serum non-coding RNAs to liver histology and disease pathogenesis
OBJECTIVES: We used a screening strategy of global serum microRNA (miRNA) profiling, followed by a second stage of independent replication and exploration of liver expression of selected miRNAs to study: (1) the circulating miRNA signature associated with non-alcoholic fatty liver disease (NAFLD) progression and predictive power, (2) the role of miRNAs in disease biology and (3) the association between circulating miRNAs and features of the metabolic syndrome. METHODS: The study used a case-control design and included patients with NAFLD proven through biopsy and healthy controls. RESULTS: Among 84 circulating miRNAs analysed, miR-122, miR-192, miR-19a and miR-19b, miR-125b, and miR-375 were upregulated >2-fold (p<0.05) either in simple steatosis (SS) or non-alcoholic steatohepatitis (NASH). The most dramatic and significant fold changes were observed in the serum levels of miR-122 (7.2-fold change in NASH vs controls and 3.1-fold change in NASH vs SS) and miR-192 (4.4-fold change in NASH vs controls); these results were replicated in the validation set. The majority of serum miR-122 circulate in argonaute2-free forms. Circulating miR-19a/b and miR-125b were correlated with biomarkers of atherosclerosis. Liver miR-122 expression was 10-fold (p<0.03) downregulated in NASH compared with SS and was preferentially expressed at the edge of lipid-laden hepatocytes. In vitro exploration showed that overexpression of miR-122 enhances alanine aminotransferase activity. CONCLUSIONS: miR-122 plays a role of physiological significance in the biology of NAFLD; circulating miRNAs mirror the histological and molecular events occurring in the liver. NAFLD has a distinguishing circulating miRNA profile associated with a global dysmetabolic disease state and cardiovascular risk.Fil: Pirola, Carlos Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Fernandez Gianotti, Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Castaño, Gustavo Osvaldo. Gobierno de la Ciudad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mallardi, Pablo. Hospital Diego Thompson; ArgentinaFil: San Martino, Julio. Hospital Diego Thompson; ArgentinaFil: González López Ledesma, María Mora. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Flichman, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; ArgentinaFil: Mirshahi, Faridodin. Virginia Commonwealth University; Estados UnidosFil: Sanyal, Arun J.. Virginia Commonwealth University; ArgentinaFil: Sookoian, Silvia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital "Dr. Abel Zubizarreta"; Argentin
eIMRT: a web platform for the verification and optimization of radiation treatment plans
The eIMRT platform is a remote distributed computing tool that provides users with Internet access to three different services: Monte Carlo optimization of treatment plans, CRT & IMRT treatment optimization, and a database of relevant radiation treatments/clinical cases. These services are accessible through a user-friendly and platform independent web page. Its flexible and scalable design focuses on providing the final users with services rather than a collection of software pieces. All input and output data (CT, contours, treatment plans and dose distributions) are handled using the DICOM format. The design, implementation, and support of the verification and optimization algorithms are hidden to the user. This allows a unified, robust handling of the software and hardware that enables these computation-intensive services. The eIMRT platform is currently hosted by the Galician Supercomputing Center (CESGA) and may be accessible upon request (there is a demo version at http://eimrt.cesga.es:8080/ eIMRT2/demo; request access in http://eimrt.cesga.es/signup.html). This paper describes all aspects of the eIMRT algorithms in depth, its user interface, and its services. Due to the flexible design of the platform, it has numerous applications including the intercenter comparison of treatment planning, the quality assurance of radiation treatments, the design and implementation of new approaches to certain types of treatments, and the sharing of information on radiation treatment techniques. In addition, the web platform and software tools developed for treatment verification and optimization have a modular design that allows the user to extend them with new algorithms. This software is not a commercial product. It is the result of the collaborative effort of different public research institutions and is planned to be distributed as an open source project. In this way, it will be available to any user; new releases will be generated with the new implemented codes or upgradesThis work was financed by Xunta de Galicia of Spain through grant PGIDT05SIN00101CT and by the European Community through the BeInGrid projectS
Constraints on the Minimal Supergravity Model with Large
In the minimal supergravity model (mSUGRA), as the parameter
increases, the charged Higgs boson and light bottom squark masses decrease,
which can potentially increase contributions from , \tg\tb_j and
\tz_i\tb_j loops in the decay . We update a previous QCD
improved decay calculation to include in addition the effects of
gluino and neutralino loops. We find that in the mSUGRA model, loops involving
charginos also increase, and dominate over , , \tg\tq and
\tz_i\tq contributions for \tan\beta\agt 5-10. We find for large values of
that most of the parameter space of the mSUGRA model for
is ruled out due to too large a value of branching ratio . For and large , most of parameter space is
allowed, although the regions with the least fine-tuning (low and
) are ruled out due to too low a value of . We
compare the constraints from to constraints from the neutralino
relic density, and to expectations for sparticle discovery at LEP2 and the
Fermilab Tevatron colliders. Finally, we show that non-universal GUT
scale soft breaking squark mass terms can enhance gluino loop contributions to
decay rate even if these are diagonal.Comment: 14 page REVTEX file plus 6 PS figure
Naturalness Lowers the Upper Bound on the Lightest Higgs Boson Mass in Supersymmetry
We quantify the extent to which naturalness is lost as experimental lower
bounds on the Higgs boson mass increase, and we compute the natural upper bound
on the lightest supersymmetric Higgs boson mass. We find that it would be
unnatural for the mass of the lightest supersymmetric Higgs boson to saturate
it's maximal upper bound. In the absence of significant fine-tuning, the
lightest Higgs boson mass should lie below GeV, and in the most natural
cases it should be lighter than GeV. For modest , these bounds
are significantly lower. Our results imply that a failure to observe a light
Higgs boson in pre-LHC experiments could provide a serious challenge to the
principal motivation for weak-scale supersymmetry.Comment: 11 pages, LaTex, 3 ps.figure
An 8-mm diameter fibre robot positioner for massive spectroscopy surveys
This article has been accepted for publication in Monthly Notices of Royal Astronomical Society © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reservedMassive spectroscopic survey are becoming trendy in astrophysics and cosmology, as they can address new fundamental knowledge such as understanding the formation of the Milky Way and probing the nature of the mysterious dark energy. To enable massive spectroscopic surveys, new technology has been developed to place thousands of optical fibres at a given position on a focal plane. This technology needs to be: (1) accurate, with micrometer positional accuracy; (2) fast to minimize overhead; (3) robust to minimize failure; and (4) low cost. In this paper, we present the development, properties, and performance of a new single 8-mm in diameter fibre positioner robot, using two 4-mm DC-brushless gearmotors, that allows us to achieve accuracies up to 0.07 arcsec (5 μm). This device has been developed in the context of the Dark Energy Spectroscopic InstrumentWe acknowledge support from the Spanish MICINNs Consolider-Ingenio 2010 Program me under grant MultiDark CSD2009-00064, HEPHACOS S2009/ESP-1473, and MINECO Centro de Excelencia Severo Ochoa Programme under grant SEV-2012-0249. We also thank the support from a CSIC-AVS contract through MICINN grant AYA2010-21231-C02- 01, and CDTI grant IDC-20101033; and support from the Spanish MINECO research grants AYA2012-31101 and FPA2012-34694. JPK, PH and LM acknowledge support from the ERC advanced grant LIDA and from an SNF Interdisciplinary grant
Naturalness and superpartner masses or when to give up on weak scale supersymmetry
Superpartner masses cannot be arbitrarily heavy if supersymmetric extensions
of the standard model explain the stability of the gauge hierarchy. This
ancient and hallowed motivation for weak scale supersymmetry is often quoted,
yet no reliable determination of this upper limit on superpartner masses
exists. In this paper we compute upper bounds on superpartner masses in the
minimal supersymmetric model, and we identify which values of the superpartner
masses correspond to the most natural explanation of the hierarchy stability.
We compare the most natural value of these masses and their upper limits to the
physics reach of current and future colliders. As a result, we find that
supersymmetry could explain weak scale stability naturally even if no
superpartners are discovered at LEP II or the Tevatron (even with the Main
Injector upgrade). However, we find that supersymmetry cannot provide a
complete explanation of weak scale stability, if squarks and gluinos have
masses beyond the physics reach of the LHC. Moreover, in the most natural
scenarios, many sparticles, for example, charginos, squarks, and gluinos, lie
within the physics reach of either LEP II or the Tevatron. Our analysis
determines the most natural value of the chargino (squark) ((gluino)) mass
consistent with current experimental constraints is 50 (250) ((250)) GeV
and the corresponding theoretical upper bound is 250 (700) ((800)) GeV.Comment: 14 pages, LaTex, 17 figures uuencoded, gz-compressed file. Minor
revisions bring archived manuscript in line with the published versio
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