2,523 research outputs found
Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun
We search for persistent and quasi-periodic release events of streamer blobs
during 2007 with the Large Angle Spectrometric Coronagraph on the \textit{Solar
and Heliospheric Observatory} and assess the velocity of the slow solar wind
along the plasma sheet above the corresponding streamer by measuring the
dynamic parameters of blobs. We find 10 quasi-periodic release events of
streamer blobs lasting for three to four days. In each day of these events, we
observe three-five blobs. The results are in line with previous studies using
data observed near the last solar minimum. Using the measured blob velocity as
a proxy for that of the mean flow, we suggest that the velocity of the
background slow solar wind near the Sun can vary significantly within a few
hours. This provides an observational manifestation of the large velocity
variability of the slow solar wind near the Sun.Comment: 14 pages, 5 figures, accepted by Soalr Physic
Superconductivity in MgB_2 doped with Ti and C
Measurements of the superconducting upper critical field, H_{c2}, and
critical current density, J_c, have been carried out for MgB_2 doped with Ti
and/or C in order to explore the problems encountered if these dopants are used
to enhance the superconducting performance. Carbon replaces boron in the MgB_2
lattice and apparently shortens the electronic mean free path thereby raising
H_c2. Titanium forms precipitates of either TiB or TiB_2 that enhance the flux
pinning and raise J_c. Most of these precipitates are intra-granular in the
MgB_2 phase. If approximately 0.5% Ti and approximately 2% C are co-deposited
with B to form doped boron fibers and these fibers are in turn reacted in Mg
vapor to form MgB_2, the resulting superconductor has H_{c2}(T=0) ~ 25 T and
J_c ~ 10,000 A/cm**2 at 5 K and 2.2 T.Comment: 11 pages, 10 figure
SMYD3 tandem repeats polymorphism is not associated with the occurrence and metastasis of hepatocellular carcinoma in a Chinese population
A variable number of tandem repeats (VNTR) polymorphism in regulatory region of SMYD3 coding for histone methyltransferase has been shown to be associated with colorectal cancer, hepatocellular carcinoma (HCC), and breast cancer in Japanese population. Aim of the study is to investigate the potential association between the functional SMYD3 tandem repeats polymorphism and HCC in Chinese population. Material and Methods: The case-control study included 200 HCC patients and 261 healthy controls. The VNTR polymorphism in the promoter of SMDY3 was genotyped by PCR and direct-sequencing analysis. Odds ratio and 95% confidence interval were used to estimate the association between the polymorphisms and risk of HCC. Results: The allele frequencies for SMYD3 2 and 3 repeats were 15.71% and 84.29% among controls; and 12.75%, and 87.25% among cases (P = 0.22). The odds ratio for 3/3 versus 2/2 and 2/3 genotypes was 1.30 (P = 0.18). The frequencies of 3 alleles were not increased with HCC stage increased (trend test, P = 0.45). Conclusion: SMYD3 polymorphism is not associated with the occurrence and metastasis of HCC in Chinese population.Известно, что полиморфизм тандемных повторов (VNTR) в регуляторном участке гена SMYD3,кодирующем метилтрансферазу
гистонов, ассоциирован с развитием рака прямой кишки, карциномы печени (HCC) и рака молочной железы и является популяционно-зависимой
характеристикой. Цель работы состояла в исследовании возможной связи междуVNTR Геном SMYD3 и развитием
HCC у населения Китая. Материалы и методы: исследование типа “случай-контроль” проводили с участием 200 пациентов с
HCC и 261 здорового донора. Полиморфизм VNTR в промоторной области гена SMDY3генотипировали методами PCR. Для оценки связи между полиморфизмом и риском развитияHCC использовали отношение шансов (OR) и 95%
доверительные интервалы. Результаты: частота аллелей для повторов SMYD3 2 и 3 составила 15,71 и 84,29% в контрольной
группе и 12,75 и 87,25% — в группе больных (P = 0,22). OR Генотипов 3/3 versus 2/2 и 2/3 составило 1,30 (P = 0.18). Частота
3 аллелей не возрастала при повышении стадии заболевания (P = 0,45). Выводы: полиморфизм гена SMYD3 не ассоциирован
с развитием и метастазированием HCC у населения Китая
Effective Dynamic Range in Measurements with Flash Analog-to-Digital Convertor
Flash Analog to Digital Convertor (FADC) is frequently used in nuclear and
particle physics experiments, often as the major component in big multi-channel
systems. The large data volume makes the optimization of operating parameters
necessary. This article reports a study of a method to extend the dynamic range
of an 8-bit FADC from the nominal value. By comparing the integrated
pulse area with that of a reference profile, good energy reconstruction and
event identification can be achieved on saturated events from CsI(Tl) crystal
scintillators. The effective dynamic range can be extended by at least 4 more
bits. The algorithm is generic and is expected to be applicable to other
detector systems with FADC readout.Comment: 19 pages, 1 table, 10 figure
Metallic liquid hydrogen and likely Al2O3 metallic glass
Dynamic compression has been used to synthesize liquid metallic hydrogen at
140 GPa (1.4 million bar) and experimental data and theory predict Al2O3 might
be a metallic glass at ~300 GPa. The mechanism of metallization in both cases
is probably a Mott-like transition. The strength of sapphire causes shock
dissipation to be split differently in the strong solid and soft fluid. Once
the 4.5-eV H-H and Al-O bonds are broken at sufficiently high pressures in
liquid H2 and in sapphire (single-crystal Al2O3), electrons are delocalized,
which leads to formation of energy bands in fluid H and probably in amorphous
Al2O3. The high strength of sapphire causes shock dissipation to be absorbed
primarily in entropy up to ~400 GPa, which also causes the 300-K isotherm and
Hugoniot to be virtually coincident in this pressure range. Above ~400 GPa
shock dissipation must go primarily into temperature, which is observed
experimentally as a rapid increase in shock pressure above ~400 GPa. The
metallization of glassy Al2O3, if verified, is expected to be general in strong
oxide insulators. Implications for Super Earths are discussed.Comment: 8 pages, 5 figures, 14th Liquid and Amorphous Metals Conference, Rome
201
Optimal packetisation of MPEG-4 using RTP over mobile networks
The introduction of third-generation wireless networks should result in real-time mobile
video communications becoming a reality. Delivery of such video is likely to be facilitated by the realtime
transport protocol (RTP). Careful packetisation of the video data is necessary to ensure the
optimal trade-off between channel utilisation and error robustness. Theoretical analyses for two basic
schemes of MPEG-4 data encapsulation within RTP packets are presented. Simulations over a GPRS
(general packet radio service) network are used to validate the analysis of the most efficient scheme.
Finally, a motion adaptive system for deriving MPEG-4 video packet sizes is presented. Further
simulations demonstrate the benefits of the adaptive system
Structural results on convexity relative to cost functions
Mass transportation problems appear in various areas of mathematics, their
solutions involving cost convex potentials. Fenchel duality also represents an
important concept for a wide variety of optimization problems, both from the
theoretical and the computational viewpoints. We drew a parallel to the
classical theory of convex functions by investigating the cost convexity and
its connections with the usual convexity. We give a generalization of Jensen's
inequality for cost convex functions.Comment: 10 page
Remote sensing of fuel moisture content from ratios of narrow-band vegetation water and dry-matter indices
Fuel moisture content (FMC) is an important variable for predicting the occurrence and spread of wildfire. Because FMC is calculated from the ratio of canopy water content to dry-matter content, we hypothesized that FMC may be estimated by remote sensing with a ratio of a vegetation water index to a vegetation dry-matter index. Four vegetation water indices, six dry-matter indices, and the resulting water/dry-matter index ratios were calculated using simulated leaf reflectances from the PROSPECT model. Two water indices, the Normalized Difference Infrared Index (NDII) and the Normalized Difference Water Index (NDWI), were more correlated with leaf water content than with FMC, and were not correlated with leaf dry-matter content. Two dry-matter indices, the Normalized Dry Matter Index (NDMI) and a recent index (unnamed) were correlated to leaf dry matter content, were inversely correlated with FMC, and were not correlated with water content. Ratios of these water indices and these dry-matter indices were highly and consistently correlated with FMC. Ratios of other water indices with other dry-matter indices were not consistently correlated with FMC. The ratio of NDII with NDMI was strongly related to FMC by a quadratic polynomial equation with an R2 of 0.947. Spectral reflectance data were acquired for single leaves and leaf stacks of Quercus alba, Acer rubrum, and Zea mays; the relationship between FMC and NDII/NDMI had an R2 of 0.853 and was almost identical to the equation from the PROSPECT model simulations. For the SAIL model simulations, the relationship between NDII/NDMI and FMC at the canopy scale had an R2 of 0.900, but the quadratic polynomial equation differed from the equations determined from the PROSPECT simulations and spectral reflectance data. NDMI requires narrow-band sensors to measure the effect of dry matter on reflectance at 1722 nm whereas NDII may be determined with many different sensors. Therefore, monitoring FMC with NDII/NDMI requires either a new sensor or a combination of two sensors, one with high temporal resolution for monitoring water content and one with high spectral resolution for estimating dry-matter content
Persistent global power fluctuations near a dynamic transition in electroconvection
This is a study of the global fluctuations in power dissipation and light
transmission through a liquid crystal just above the onset of
electroconvection.
The source of the fluctuations is found to be the creation and annihilation
of defects. They are spatially uncorrelated and yet temporally correlated. The
temporal correlation is seen to persist for extremely long times. There seems
to be an especially close relation between defect creation/annihilat ion in
electroconvection and thermal plumes in Rayleigh-B\'enard convection
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