1,316 research outputs found
Pauli blocking effects and Cooper triples in three-component Fermi gases
We investigate the effect of Pauli blocking on universal two- and three-body
states in the medium. Their corresponding energies are extracted from the poles
of two- and three-body in-medium scattering amplitudes. Compared to the vacuum,
the binding of dimer and trimer states is reduced by the medium effects. In
two-body scattering, the well-known physics of Cooper pairs is recovered. In
the three-body sector, we find a new class of positive energy poles which can
be interpreted as Cooper triples.Comment: 19 pages, 9 figures, discussion expanded, final versio
Towards Understanding Spontaneous Speech: Word Accuracy vs. Concept Accuracy
In this paper we describe an approach to automatic evaluation of both the
speech recognition and understanding capabilities of a spoken dialogue system
for train time table information. We use word accuracy for recognition and
concept accuracy for understanding performance judgement. Both measures are
calculated by comparing these modules' output with a correct reference answer.
We report evaluation results for a spontaneous speech corpus with about 10000
utterances. We observed a nearly linear relationship between word accuracy and
concept accuracy.Comment: 4 pages PS, Latex2e source importing 2 eps figures, uses icslp.cls,
caption.sty, psfig.sty; to appear in the Proceedings of the Fourth
International Conference on Spoken Language Processing (ICSLP 96
Fluctuations of noise and the low frequency cutoff paradox
Recent experiments on blinking quantum dots and weak turbulence in liquid
crystals reveal the fundamental connection between noise and power law
intermittency. The non-stationarity of the process implies that the power
spectrum is random -- a manifestation of weak ergodicity breaking. Here we
obtain the universal distribution of the power spectrum, which can be used to
identify intermittency as the source of the noise. We solve an outstanding
paradox on the non integrability of noise and the violation of Parseval's
theorem. We explain why there is no physical low frequency cutoff and therefore
cannot be found in experiments.Comment: 5 pages, 2 figures, supplementary material (4 pages
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge
We report a rare observation of a mini-fracture in near-surface
sediments (30 cm below the seafloor) visualized using a rotational scanning
X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of
Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker
signatures revealed clear differences in the geochemical and biogeochemical
regimes of this core compared with two additional unfractured cores
recovered from pockmark sites at Vestnesa Ridge, which we attribute to
differential methane transport mechanisms. In the sediment core featuring
the shallow mini-fracture at pockmark Lomvi, we observed high concentrations
of both methane and sulfate throughout the core in tandem with moderately
elevated values for total alkalinity, 13C-depleted dissolved inorganic
carbon (DIC), and 13C-depleted lipid biomarkers (diagnostic for the
slow-growing microbial communities mediating the anaerobic oxidation of
methane with sulfate – AOM). In a separate unfractured core, recovered from
the same pockmark about 80 m away from the fractured core, we observed
complete sulfate depletion in the top centimeters of the sediment and much
more pronounced signatures of AOM than in the fractured core. Our data
indicate a gas advection-dominated transport mode in both cores, facilitating
methane migration into sulfate-rich surface sediments. However, the moderate
expression of AOM signals suggest a rather recent onset of gas migration at
the site of the fractured core, while the geochemical evidence for a
well-established AOM community at the second coring site suggest that gas
migration has been going on for a longer period of time. A third core
recovered from another pockmark along the Vestnesa Ridge Lunde pockmark
was dominated by diffusive transport with only weak geochemical and
biogeochemical evidence for AOM. Our study highlights that advective fluid
and gas transport supported by mini-fractures can be important in modulating
methane dynamics in surface sediments.</p
A Comparison of Hybrid and End-to-End Models for Syllable Recognition
This paper presents a comparison of a traditional hybrid speech recognition
system (kaldi using WFST and TDNN with lattice-free MMI) and a lexicon-free
end-to-end (TensorFlow implementation of multi-layer LSTM with CTC training)
models for German syllable recognition on the Verbmobil corpus. The results
show that explicitly modeling prior knowledge is still valuable in building
recognition systems. With a strong language model (LM) based on syllables, the
structured approach significantly outperforms the end-to-end model. The best
word error rate (WER) regarding syllables was achieved using kaldi with a
4-gram LM, modeling all syllables observed in the training set. It achieved
10.0% WER w.r.t. the syllables, compared to the end-to-end approach where the
best WER was 27.53%. The work presented here has implications for building
future recognition systems that operate independent of a large vocabulary, as
typically used in a tasks such as recognition of syllabic or agglutinative
languages, out-of-vocabulary techniques, keyword search indexing and medical
speech processing.Comment: 22th International Conference of Text, Speech and Dialogue TSD201
Reconstitution of mammary gland development in vitro: Requirement of c-met and c-erbB2 signaling for branching and alveolar morphogenesis
We have established a cell culture system that reproduces morphogenic processes in the developing mammary gland. EpH4 mouse mammary epithelial cells cultured in matrigel form branched tubules in the presence of hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the c-met tyrosine kinase receptor. In contrast, alveolar structures are formed in the presence of neuregulin, a ligand of c-erbB tyrosine kinase receptors. These distinct morphogenic responses can also be observed with selected human mammary carcinoma tissue in explant culture. HGF/SF-induced branching was abrogated by the PI3 kinase inhibitors wortmannin and LY294002. In contrast, neuregulin- induced alveolar morphogenesis was inhibited by the MAPK kinase inhibitor PD98059. The c-met-mediated response could also be evoked by transfection of a c-met specific substrate, Gab1, which can activate the PI3 kinase pathway. An activated hybrid receptor that contained the intracellular domain of c-erbB2 receptor suffices to induce alveolar morphogenesis, and was observed in the presence of tyrosine residues Y1028, Y1144, Y1201, and Y1226/27 in the substrate-binding domain of c-erbB2. Our data demonstrate that c-met and c-erbB2 signaling elicit distinct morphogenic programs in mammary epithelial cells: formation of branched tubules relies on a pathway involving PI3 kinase, whereas alveolar morphogenesis requires MAPK kinase
Treatment of tuberculosis in a region with high drug resistance: Outcomes, drug resistance amplification and re-infection
Introduction: Emerging antituberculosis drug resistance is a serious threat for tuberculosis (TB) control, especially in Eastern
European countries.
Methods: We combined drug susceptibility results and molecular strain typing data with treatment outcome reports to
assess the influence of drug resistance on TB treatment outcomes in a prospective cohort of patients from Abkhazia
(Georgia). Patients received individualized treatment regimens based on drug susceptibility testing (DST) results. Definitions
for antituberculosis drug resistance and treatment outcomes were in line with current WHO recommendations. First and
second line DST, and molecular typing were performed in a supranational laboratory for Mycobacterium tuberculosis (MTB)
strains from consecutive sputum smear-positive TB patients at baseline and during treatment.
Results: At baseline, MTB strains were fully drug-susceptible in 189/326 (58.0%) of patients. Resistance to at least H or R
(PDR-TB) and multidrug-resistance (MDR-TB) were found in 69/326 (21.2%) and 68/326 (20.9%) of strains, respectively. Three
MDR-TB strains were also extensively resistant (XDR-TB). During treatment, 3/189 (1.6%) fully susceptible patients at baseline
were re-infected with a MDR-TB strain and 2/58 (3.4%) PDR-TB patients became MDR-TB due to resistance amplification. 5/
47 (10.6%) MDR- patients became XDR-TB during treatment. Treatment success was observed in 161/189 (85.2%), 54/69
(78.3%) and 22/68 (32.3%) of patients with fully drug susceptible, PDR- and MDR-TB, respectively. Development of ofloxacin
resistance was significantly associated with a negative treatment outcome.
Conclusion: In Abkhazia, a region with high prevalence of drug resistant TB, the use of individualized MDR-TB treatment
regimens resulted in poor treatment outcomes and XDR-TB amplification. Nosocomial transmission of MDR-TB emphasizes
the importance of infection control in hospitals
Laboratory Simulations of the Titan Surface to Elucidate the Huygens Probe GCMS Observations
The Cassini/Huygens mission has vastly increased the information we have available to stndy Satnro's moon Titan. The complete mission has included an array of observational methods including remote sensing techniques, upper atmosphere in-situ saropling, and the descent of the Huygens probe directly through the atmosphere to the surface [1,2]. The instruments on the Huygens probe remain the ouly source of in-situ measurements at the surface of Titan, and work evaluating these measurements to create a pict.rre of the surface environment is ongoing. In particular, the Gas Chromatograph Mass Spectrometer (GCMS) experiment on Huygens found that although there were no heavy hydrocarbons detected in the lower atmosphere, a rich spectrum of mass peaks arose once the probe landed on the surface [3,4], However, to date it has not been possible to extract the identity and abundances of the many minor components of the spectra due to a lack of temperatnre- and instrumentappropriate data for the relevant species. We are performing laboratory stndies designed to elucidate the spectrum collected on Titan's surface, utilizing a cryogenic charober maintained at appropriate temperature and pressure conditions. The experiments will simulate the temperatnre rise experienced by the surface, which led to an enhanced signal of volatiles detected by the Huygens GCMS. The objective of this study is to exaroine the characteristics of various surface analogs as measured by the Huygens GCMS flight spare instrument, which is currently housed in our laboratory at NASA Goddard Space Flight Center (GSFC). This identification cannot be adequately accomplished through theoretical work alone since the thermodynamic properties of many species at these temperatnres (94 K, HASI measurement [5]) are not known
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