52,117 research outputs found
Studying Intermediate pT Hadron Production with Fluctuations
Mechanisms for particle production at intermediate pT in nuclear collisions
at RHIC are discussed, emphasizing the differences in associated jet-like
correlations between color-neutral and colored production. An alternative
production mechanism involving both recombination and fragmentation is
suggested, which might simultaneously lead to an enhancement of baryons and to
jet-like correlations. To gain more insight into the relative importance of
different mechanisms a study of constrained distributions of associated
multiplicity is proposed. In a simple model it is shown that these multiplicity
distributions may change significantly, if the nature of the production
mechanism fluctuates from event to event.Comment: 7 pages, 4 figures, talk at Hot Quarks 2004 conferenc
Empirical comparison of diffusion kurtosis imaging and diffusion basis spectrum imaging using the same acquisition in healthy young adults
As diffusion tensor imaging gains widespread use, many researchers have been motivated to go beyond the tensor model and fit more complex diffusion models, to gain a more complete description of white matter microstructure and associated pathology. Two such models are diffusion kurtosis imaging (DKI) and diffusion basis spectrum imaging (DBSI). It is not clear which DKI parameters are most closely related to DBSI parameters, so in the interest of enabling comparisons between DKI and DBSI studies, we conducted an empirical survey of the interrelation of these models in 12 healthy volunteers using the same diffusion acquisition. We found that mean kurtosis is positively associated with the DBSI fiber ratio and negatively associated with the hindered ratio. This was primarily driven by the radial component of kurtosis. The axial component of kurtosis was strongly and specifically correlated with the restricted ratio. The joint spatial distributions of DBSI and DKI parameters are tissue-dependent and stable across healthy individuals. Our contribution is a better understanding of the biological interpretability of the parameters generated by the two models in healthy individuals
Nonplanar Chiral Metamaterials with Negative Index
We demonstrate experimentally and numerically that nonplanar chiral
metamaterials give giant optical activity, circular dichroism, and negative
refractive index. The transmission, reflection, and the retrieval results of
the experiments agree pretty well with the simulations. This is an important
step toward the design and fabrication of three-dimensional isotropic chiral
metamaterials.Comment: 3 pages 4 figure
Marketing Channel and Technology Adoption: Chinese Villages in the Local Horticulture Market
China has been experiencing the substantial changes in agricultural sectors in the past decades. Interaction between diversified channels for marketing agricultural products and modern technology adoption are important for restructuring agriculture and improving productivity, but fewer researches have been done in this field in China. With the village - level data collected a round Beijing, the capital of China, this study attempts to find out the major market channel(s) in rural China and its (their) linkage with technology innovation in the horticulture sector. The study finds that small brokers still dominate horticultural product distribution in rural area because of their cheap labor costs; however, the modern supply chain components such as supermarkets are penetrating the rural area and competing with small brokers. Modern market channels stimulate the adoptions of new technology, whereas technology adoption had few effects on modern market channel selection. In addition, shares of crop such as vegetables and fruits are soaring; surprisingly villages farther away from Beijing experienced faster crop restructuring with higher specialization. In the future we try to incorporate wholesalers or supermarkets into the analysis, which can depict a more complete picture of rural market development.Crop Production/Industries,
Time-dependent versus static quantum transport simulations beyond linear response
To explore whether the density-functional theory non-equilibrium Green's
function formalism (DFT-NEGF) provides a rigorous framework for quantum
transport, we carried out time-dependent density functional theory (TDDFT)
calculations of the transient current through two realistic molecular devices,
a carbon chain and a benzenediol molecule inbetween two aluminum electrodes.
The TDDFT simulations for the steady state current exactly reproduce the
results of fully self-consistent DFT-NEGF calculations even beyond linear
response. In contrast, sizable differences are found with respect to an
equilibrium, non-self-consistent treatment which are related here to
differences in the Kohn-Sham and fully interacting susceptibility of the device
region. Moreover, earlier analytical conjectures on the equivalence of static
and time-dependent approaches in the low bias regime are confirmed with high
numerical precision.Comment: 4 pages, 4 figure
Production and state-selective detection of ultracold, ground state RbCs molecules
Using resonance-enhanced two-photon ionization, we detect ultracold,
ground-state RbCs molecules formed via photoassociation in a laser-cooled
mixture of 85Rb and 133Cs atoms. We obtain extensive bound-bound excitation
spectra of these molecules, which provide detailed information about their
vibrational distribution, as well as spectroscopic data on the RbCs ground
a^3\Sigma^+ and excited (2)^3\Sigma^+, (1)^1\Pi states. Analysis of this data
allows us to predict strong transitions from observed excited levels to the
absolute vibronic ground state of RbCs, potentially allowing the production of
stable, ultracold polar molecules at rates as large as 10^7 s^{-1}
Genome-wide association study of electrocardiographic and heart rate variability traits: the Framingham Heart Study
BACKGROUND: Heritable electrocardiographic (ECG) and heart rate variability (HRV) measures, reflecting pacemaking, conduction, repolarization and autonomic function in the heart have been associated with risks for cardiac arrhythmias. Whereas several rare monogenic conditions with extreme phenotypes have been noted, few common genetic factors contributing to interindividual variability in ECG and HRV measures have been identified. We report the results of a community-based genomewide association study of six ECG and HRV intermediate traits. METHODS: Genotyping using Affymetrix 100K GeneChip was conducted on 1345 related Framingham Heart Study Original and Offspring cohort participants. We analyzed 1175 Original and Offspring participants with ECG data (mean age 52 years, 52% women) and 548 Offspring participants with HRV data (mean age 48 years, 51% women), in relation to 70,987 SNPs with minor allele frequency â„ 0.10, call rate â„ 80%, Hardy-Weinberg p-value â„ 0.001. We used generalized estimating equations to test association of SNP alleles with multivariable-adjusted residuals for QT, RR, and PR intervals, the ratio of low frequency to high frequency power (LF/HFP), total power (TP) and the standard deviation of normal RR intervals (SDNN). RESULTS: Associations at p < 10-3 were found for 117 (QT), 105 (RR), 111 (PR), 102 (LF/HF), 121 (TP), and 102 (SDNN) SNPs. Several common variants in NOS1AP (4 SNPs with p-values < 10-3; lowest p-value, rs6683968, p = 1 Ă 10-4) were associated with adjusted QT residuals, consistent with our previously reported finding for NOS1AP in an unrelated sample of FHS Offspring and other cohorts. All results are publicly available at NCBI's dbGaP at. CONCLUSION: In the community-based Framingham Heart Study none of the ECG and HRV results individually attained genomewide significance. However, the presence of bona fide QT-associated SNPs among the top 117 results for QT duration supports the importance of efforts to validate top results from the reported scans. Finding genetic variants associated with ECG and HRV quantitative traits may identify novel genes and pathways implicated in arrhythmogenesis and allow for improved recognition of individuals at high risk for arrhythmias in the general population.National Institutes of Health (K23 N01-HC25195); Doris Duke Charitable Foundation Clinical Scientist Developement Award; Pfizer; National Institutes of Health National Center for Research Resources Shared Instrumentation grant (1S10RR163736-01A1
A frequency-response-based method of sound velocity measurement in an impedance tube
A stable and accurate new method for the measurement of the velocity of sound is proposed. The method is based on the characteristics of the frequency response measured at different positions in an impedance tube and it eliminates adverse effects caused by reflections from the transmitting transducer at the bottom of the impedance tube. A series of experiments is conducted, at different water temperatures, different positions in the impedance tube and under constant pressure, to validate the feasibility and stability of the new method. The new technique is also extended to hydrostatic pressure conditions with stable sound velocity. Our method generates an accurate measurement result in comparison to the estimated or average value obtained with currently existing methods. The novel method is suitable to be widely used in underwater acoustics
Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground
(Abridged) We observed one transit and one occultation of the hot Jupiter
WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on
the MPG/ESO 2.2-meter telescope. From the transit event, we have independently
derived WASP-43's system parameters with high precision, and improved the
period to be 0.81347437(13) days. No significant variation in transit depths is
detected, with the largest deviations coming from the i', H, and K bands. Given
the observational uncertainties, the broad-band transmission spectrum can be
explained by either a flat featureless straight line that indicates thick
clouds, synthetic spectra with absorption signatures of atomic Na/K or
molecular TiO/VO that indicate cloud-free atmosphere, or a Rayleigh scattering
profile that indicates high-altitude hazes. From the occultation event, we have
detected planetary dayside thermal emission in the K-band with a flux ratio of
0.197 +/- 0.042%, which confirms previous detections obtained in the 2.09
micron narrow band and Ks-band. The K-band brightness temperature 1878
+108/-116 K favors an atmosphere with poor day- to night-side heat
redistribution. We also have a marginal detection in the i'-band (0.037
+0.023/-0.021%), which is either a false positive, a signature of non-blackbody
radiation at this wavelength, or an indication of reflective hazes at high
altitude.Comment: 14 pages, 9 figures, accepted for publication in A&
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