334 research outputs found
The PMS project: Poor Man's Supercomputer
We briefly describe the Poor Man's Supercomputer (PMS) project carried out at
Eotvos University, Budapest. The goal was to develop a cost effective,
scalable, fast parallel computer to perform numerical calculations of physical
problems that can be implemented on a lattice with nearest neighbour
interactions. To this end we developed the PMS architecture using PC components
and designed a special, low cost communication hardware and the driver software
for Linux OS. Our first implementation of PMS includes 32 nodes (PMS1). The
performance of PMS1 was tested by Lattice Gauge Theory simulations. Using SU(3)
pure gauge theory or bosonic MSSM on PMS1 we obtained 3Mflop
price-to-sustained performance for double and single precision operations,
respectively. The design of the special hardware and the communication driver
are freely available upon request for non-profit organizations.Comment: Latex, 13 pages, 6 figures included, minor additions, typos correcte
On Linear Codes with Random Multiplier Vectors and the Maximum Trace Dimension Property
Let be a linear code of length and dimension over the finite
field . The trace code is a linear code of
the same length over the subfield . The obvious upper bound
for the dimension of the trace code over is . If equality
holds, then we say that has maximum trace dimension. The problem of finding
the true dimension of trace codes and their duals is relevant for the size of
the public key of various code-based cryptographic protocols. Let
denote the code obtained from and a multiplier vector
. In this paper, we give a lower bound for
the probability that a random multiplier vector produces a code
of maximum trace dimension. We give an interpretation of the
bound for the class of algebraic geometry codes in terms of the degree of the
defining divisor. The bound explains the experimental fact that random
alternant codes have minimal dimension. Our bound holds whenever , where is the Singleton defect of . For the extremal case
, numerical experiments reveal a closed connection between the
probability of having maximum trace dimension and the probability that a random
matrix has full rank
Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study.
Objectives Decreased thyroid volume has been related to increased prevalence of thyroid cancer.Subjects and methods One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63).Results Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%).Conclusions Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects
Synaptic and cellular changes induced by the schizophrenia susceptibility gene G72 are rescued by N-acetylcysteine treatment
Genetic studies have linked the primate-specific gene locus G72 to the development of schizophrenia and bipolar disorder. Transgenic mice carrying the entire gene locus express G72 mRNA in dentate gyrus (DG) and entorhinal cortex, causing altered electrophysiological properties of their connections. These transgenic mice exhibit behavioral alterations related to psychiatric diseases, including cognitive deficits that can be reversed by treatment with N-acetylcysteine, which was also found to be effective in human patients. Here, we show that G72 transgenic mice have larger excitatory synapses with an increased amount of N-methyl-d-aspartate (NMDA) receptors in the molecular layer of DG, compared with wild-type littermates. Furthermore, transgenic animals have lower number of dentate granule cells with a parallel, but an even stronger decrease in the number of excitatory synapses in the molecular layer. Importantly, we also show that treatment with N-acetylcysteine can effectively normalize all these changes in transgenic animals, resulting in a state similar to wild-type mice. Our results show that G72 transcripts induce robust alterations in the glutamatergic system at the synaptic level that can be rescued with N-acetylcysteine treatment
The Bajnok-Janik formula and wrapping corrections
We write down the simplified TBA equations of the string
sigma-model for minimal energy twist-two operators in the sl(2) sector of the
model. By using the linearized version of these TBA equations it is shown that
the wrapping corrected Bethe equations for these states are identical, up to
O(g^8), to the Bethe equations calculated in the generalized L\"uscher approach
(Bajnok-Janik formula). Applications of the Bajnok-Janik formula to
relativistic integrable models, the nonlinear O(n) sigma models for n=2,3,4 and
the SU(n) principal sigma models, are also discussed.Comment: Latex, 22 pages, published versio
Recognition of ASF1 Using Hydrocarbon Constrained Peptides
Inhibition of the histone H3-ASF1 (anti-silencing function 1) protein-protein interaction (PPI) represents a potential approach for treatment of numerous cancers. As an α-helix mediated PPI, constraint of the key histone H3 helix (residues 118-135) represents a strategy through which chemical probes might be elaborated to test this hypothesis. In this work variant H3118-135 peptides bearing pentenyl glycine residues at i and i + 4 positions were constrained by olefin metathesis. Biophysical analyses revealed that promotion of a bioactive helical conformation depends on the position at which the constraint is introduced, but that potency of binding towards ASF1 is unaffected by the constraint and instead that enthalpy-entropy compensation occurs
Testing SNe Ia distance measurement methods with SN 2011fe
The nearby, bright, almost completely unreddened Type Ia supernova 2011fe in
M101 provides a unique opportunity to test both the precision and the accuracy
of the extragalactic distances derived from SNe Ia light curve fitters. We
apply the current, public versions of the independent light curve fitting codes
MLCS2k2 and SALT2 to compute the distance modulus of SN 2011fe from
high-precision, multi-color (BVRI) light curves. The results from the two
fitting codes confirm that 2011fe is a "normal" (not peculiar) and only
slightly reddened SN Ia. New unreddened distance moduli are derived as 29.21
+/- 0.07 mag (D ~ 6.95 +/- 0.23$ Mpc, MLCS2k2), and 29.05 +/- 0.07 mag (6.46
+/- 0.21 Mpc, SALT2). Despite the very good fitting quality achieved with both
light curve fitters, the resulting distance moduli are inconsistent by 2 sigma.
Both are marginally consistent (at ~1 sigma) with the HST Key Project distance
modulus for M101. The SALT2 distance is in good agreement with the recently
revised Cepheid- and TRGB-distance to M101. Averaging all SN- and Cepheid-based
estimates, the absolute distance to M101 is ~6.6 +/- 0.5 Mpc.Comment: 8 pages, 7 figures, accepted for publication in A&
V456 Ophiuchi and V490 Cygni: Systems with the shortest apsidal-motion periods
Our main aim is the first detailed analysis of the two eclipsing binaries
V456 Oph and V490 Cyg. The system V456 Oph has been studied both
photometrically via an analysis of its light curve observed by the INTEGRAL/OMC
and by the period analysis of all available times of minima. V490 Cyg has been
studied by means of a period analysis only. Many new times of minima for both
systems have recently been observed and derived. This allows us for the first
time to study in detail the processes that affect both binaries. The main
result is the discovery that both systems have eccentric orbits. For V456 Oph
we deal with the eccentric eclipsing binary system with the shortest orbital
period known (about 1.016 day), while the apsidal motion period is about 23
years. V490 Cyg represents the eclipsing system with the shortest apsidal
motion period (about 18.8 years only). The two components of V456 Oph are
probably of spectral type F. We compare and discuss the V456 Oph results from
the light curve and the period analysis, but a more detailed spectroscopy is
needed to confirm the physical parameters of the components more precisely.Comment: 4 pages, 3 figures, published in A&A: 2011A&A...527A..43
The continuing story of SN IIb 2013df: new optical and IR observations and analysis
This work has been supported by the Hungarian Scientific Research Fund (OTKA) Grants NN107637, K104607, K83790, and K113117. TS is supported by the OTKA Postdoctoral Fellowship PD112325. JCW’s Supernova group at the UT Austin is supported by NSF Grant AST 11-09881 grant. JMS is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. KS and AP are supported by the ‘Lend¨ulet-2009’ Young Researchers Program and the LP2012-31 grant of the Hungarian Academy of Sciences, respectively; KS is also supported by the ESA PECS Contract no. 4000110889/14/NL/NDe.SN 2013df is a nearby Type IIb supernova that seems to be the spectroscopic twin of the well-known SN 1993J. Previous studies revealed many, but not all interesting properties of this event. Our goal was to add new understanding of both the early- and late-time phases of SN 2013df. Our spectral analysis is based on six optical spectra obtained with the 9.2 m Hobby-Eberly Telescope during the first month after explosion, complemented by a near-infrared spectrum. We applied the SYNAPPS spectral synthesis code to constrain the chemical composition and physical properties of the ejecta. A principal result is the identification of 'high-velocity' He i lines in the early spectra of SN 2013df, manifest as the blue component of the double-troughed profile at ~5650 Å. This finding, together with the lack of clear separation of H and He lines in velocity space, indicates that both H and He features form at the outer envelope during the early phases. We also obtained ground-based BVRI and g'r'i'z' photometric data up to +45 d and unfiltered measurements with the ROTSE-IIIb telescope up to +168 d. From the modelling of the early-time quasi-bolometric light curve, we find Mej ~ 3.2-4.6 M⊙ and Ekin ~ 2.6-2.8 × 1051 erg for the initial ejecta mass and the initial kinetic energy, respectively, which agree well with the values derived from the separate modelling of the light-curve tail. Late-time mid-infrared excess indicates circumstellar interaction starting ~1 yr after explosion, in accordance with previously published optical, X-ray, and radio data.Publisher PDFPeer reviewe
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