13,297 research outputs found
Quantum Melting of the Charge Density Wave State in 1T-TiSe2
We report a Raman scattering study of low-temperature, pressure-induced
melting of the CDW phase of 1T-TiSe2. Our Raman scattering measurements reveal
that the collapse of the CDW state occurs in three stages: (i) For P<5 kbar,
the pressure dependence of the CDW amplitude mode energies and intensities are
indicative of a ``crystalline'' CDW regime; (ii) for 5 < P < 25 kbar, there is
a decrease in the CDW amplitude mode energies and intensities with increasing
pressure that suggests a regime in which the CDW softens, and may decouple from
the lattice; and (iii) for P>25 kbar, the absence of amplitude modes reveals a
melted CDW regime.Comment: 5 pages, 4 figure
A family of thermostable fungal cellulases created by structure-guided recombination
SCHEMA structure-guided recombination of 3 fungal class II cellobiohydrolases (CBH II cellulases) has yielded a collection of highly thermostable CBH II chimeras. Twenty-three of 48 genes sampled from the 6,561 possible chimeric sequences were secreted by the Saccharomyces cerevisiae heterologous host in catalytically active form. Five of these chimeras have half-lives of thermal inactivation at 63°C that are greater than the most stable parent, CBH II enzyme from the thermophilic fungus Humicola insolens, which suggests that this chimera collection contains hundreds of highly stable cellulases. Twenty-five new sequences were designed based on mathematical modeling of the thermostabilities for the first set of chimeras. Ten of these sequences were expressed in active form; all 10 retained more activity than H. insolens CBH II after incubation at 63°C. The total of 15 validated thermostable CBH II enzymes have high sequence diversity, differing from their closest natural homologs at up to 63 amino acid positions. Selected purified thermostable chimeras hydrolyzed phosphoric acid swollen cellulose at temperatures 7 to 15°C higher than the parent enzymes. These chimeras also hydrolyzed as much or more cellulose than the parent CBH II enzymes in long-time cellulose hydrolysis assays and had pH/activity profiles as broad, or broader than, the parent enzymes. Generating this group of diverse, thermostable fungal CBH II chimeras is the first step in building an inventory of stable cellulases from which optimized enzyme mixtures for biomass conversion can be formulated
Summary of the Very Large Hadron Collider Physics and Detector Workshop
One of the options for an accelerator beyond the LHC is a hadron collider
with higher energy. Work is going on to explore accelerator technologies that
would make such a machine feasible. This workshop concentrated on the physics
and detector issues associated with a hadron collider with an energy in the
center of mass of the order of 100 to 200 TeV
Stable dietary isotopes and mtDNA from Woodland period southern Ontario people: results from a tooth sampling protocol
AbstractBioarchaeological research must balance scholarly commitment to the generation of new knowledge, descendants' interests in their collective past, and the now common practice of rapid re-interment of excavated human remains. This paper documents the first results of a negotiated protocol built on the retention of one tooth per archaeologically derived skeleton, teeth that can then be used for destructive testing associated with ancient DNA and stable isotope investigations. Seven archaeological sites dating from the 13th to 16th centuries provided 53 teeth, 10 of which were subdivided between DNA and isotope labs. All tooth roots yielded haplogroup results, and five provided more detailed sequence results. Stable isotopes of carbon and nitrogen document heavy reliance on maize among all individuals, as well as reliance on a diverse range of fish. This work establishes baseline mtDNA information for Northern Iroquoians, and confirms the value of using dental tissues for dietary reconstruction. Particularly when human remains are fragmentary or co-mingled, this approach holds promise for ongoing incorporation of bioarchaeology into reconstructions of past peoples' lives
A Benchmark Study on Sentiment Analysis for Software Engineering Research
A recent research trend has emerged to identify developers' emotions, by
applying sentiment analysis to the content of communication traces left in
collaborative development environments. Trying to overcome the limitations
posed by using off-the-shelf sentiment analysis tools, researchers recently
started to develop their own tools for the software engineering domain. In this
paper, we report a benchmark study to assess the performance and reliability of
three sentiment analysis tools specifically customized for software
engineering. Furthermore, we offer a reflection on the open challenges, as they
emerge from a qualitative analysis of misclassified texts.Comment: Proceedings of 15th International Conference on Mining Software
Repositories (MSR 2018
Skeletal Muscle Sorbitol Levels in Diabetic Rats with and without Insulin Therapy and Endurance Exercise Training
Sorbitol accumulation
is postulated to play a role in skeletal muscle
dysfunction associated with diabetes. The
purpose of this study was to determine the
effects of insulin and of endurance exercise on
skeletal muscle sorbitol levels in
streptozotocin-induced diabetic rats. Rats were
assigned to one experimental group (control
sedentary, control exercise, diabetic sedentary,
diabetic exercise, diabetic sedentary
no-insulin). Diabetic rats received daily
subcutaneous insulin. The exercise-trained rats
ran on a treadmill (1 hour, 5X/wk, for
12 weeks). Skeletal muscle sorbitol levels
were the highest in the diabetic sedentary
no-insulin group. Diabetic sedentary rats
receiving insulin had similar sorbitol levels to
control sedentary rats. Endurance exercise did
not significantly affect sorbitol levels. These
results indicate that insulin treatment lowers
sorbitol in skeletal muscle; therefore sorbitol
accumulation is probably not related to muscle
dysfunction in insulin-treated diabetic
individuals. Endurance exercise did not
influence intramuscular sorbitol values as
strongly as insulin
Profile: The Kilifi Health and Demographic Surveillance System (KHDSS).
The Kilifi Health and Demographic Surveillance System (KHDSS), located on the Indian Ocean coast of Kenya, was established in 2000 as a record of births, pregnancies, migration events and deaths and is maintained by 4-monthly household visits. The study area was selected to capture the majority of patients admitted to Kilifi District Hospital. The KHDSS has 260 000 residents and the hospital admits 4400 paediatric patients and 3400 adult patients per year. At the hospital, morbidity events are linked in real time by a computer search of the population register. Linked surveillance was extended to KHDSS vaccine clinics in 2008. KHDSS data have been used to define the incidence of hospital presentation with childhood infectious diseases (e.g. rotavirus diarrhoea, pneumococcal disease), to test the association between genetic risk factors (e.g. thalassaemia and sickle cell disease) and infectious diseases, to define the community prevalence of chronic diseases (e.g. epilepsy), to evaluate access to health care and to calculate the operational effectiveness of major public health interventions (e.g. conjugate Haemophilus influenzae type b vaccine). Rapport with residents is maintained through an active programme of community engagement. A system of collaborative engagement exists for sharing data on survival, morbidity, socio-economic status and vaccine coverage
Topological transitions in carbon nanotube networks via nanoscale confinement
Efforts aimed at large-scale integration of nanoelectronic devices that
exploit the superior electronic and mechanical properties of single-walled
carbon nanotubes (SWCNTs) remain limited by the difficulties associated with
manipulation and packaging of individual SWNTs. Alternative approaches based on
ultra-thin carbon nanotube networks (CNNs) have enjoyed success of late with
the realization of several scalable device applications. However, precise
control over the network electronic transport is challenging due to i) an often
uncontrollable interplay between network coverage and its topology and ii) the
inherent electrical heterogeneity of the constituent SWNTs. In this letter, we
use template-assisted fluidic assembly of SWCNT networks to explore the effect
of geometric confinement on the network topology. Heterogeneous SWCNT networks
dip-coated onto sub-micron wide ultra-thin polymer channels exhibit a topology
that becomes increasingly aligned with decreasing channel width and thickness.
Experimental scale coarse-grained computations of interacting SWCNTs show that
the effect is a reflection of an aligned topology that is no longer dependent
on the network density, which in turn emerges as a robust knob that can induce
semiconductor-to-metallic transitions in the network response. Our study
demonstrates the effectiveness of directed assembly on channels with varying
degrees of confinement as a simple tool to tailor the conductance of the
otherwise heterogeneous network, opening up the possibility of robust
large-scale CNN-based devices.Comment: 4 pages, 3 figure
The Role of Polycyclic Aromatic Hydrocarbons in Ultraviolet Extinction. I. Probing small molecular PAHs
We have obtained new STIS/HST spectra to search for structure in the
ultraviolet interstellar extinction curve, with particular emphasis on a search
for absorption features produced by polycyclic aromatic hydrocarbons (PAHs).
The presence of these molecules in the interstellar medium has been postulated
to explain the infrared emission features seen in the 3-13 m spectra of
numerous sources. UV spectra are uniquely capable of identifying specific PAH
molecules. We obtained high S/N UV spectra of stars which are significantly
more reddened than those observed in previous studies. These data put limits on
the role of small (30-50 carbon atoms) PAHs in UV extinction and call for
further observations to probe the role of larger PAHs. PAHs are of importance
because of their ubiquity and high abundance inferred from the infrared data
and also because they may link the molecular and dust phases of the
interstellar medium. A presence or absence of ultraviolet absorption bands due
to PAHs could be a definitive test of this hypothesis. We should be able to
detect a 20 \AA wide feature down to a 3 limit of 0.02 A. No
such absorption features are seen other than the well-known 2175 \AA bump.Comment: 16 pages, 3 figure, ApJ in pres
VLT/UVES Observations of Interstellar Molecules and Diffuse Bands in the Magellanic Clouds
We discuss the abundances of interstellar CH, CH+, and CN in the Magellanic
Clouds (MC), derived from spectra of 7 SMC and 13 LMC stars obtained (mostly)
with the VLT/UVES. CH and/or CH+ are detected toward 3 SMC and 9 LMC stars; CN
is detected toward 2 stars. In the MC, the CH/H2 ratio is comparable to that
found for diffuse Galactic molecular clouds in some sight lines, but is lower
by factors up to 10-15 in others. The abundance of CH in the MC thus appears to
depend on local physical conditions -- and not just on metallicity. The
observed relationships between the column density of CH and those of CN, CH+,
Na I, and K I in the MC are generally consistent with the trends observed in
our Galaxy. Using existing data for the rotational populations of H2, we
estimate temperatures, radiation field strengths, and local hydrogen densities
for the diffuse molecular gas. Densities estimated from N(CH), assuming that CH
is produced via steady-state gas-phase reactions, are considerably higher; much
better agreement is found by assuming that the CH is made via the (still
undetermined) process(es) responsible for the observed CH+. The UVES spectra
also reveal absorption from the diffuse interstellar bands at 5780, 5797, and
6284 A in the MC. On average, the three DIBs are weaker by factors of 7-9 (LMC)
and about 20 (SMC), compared to those observed in Galactic sight lines with
similar N(H I), and by factors of order 2-6, relative to E(B-V), N(Na I), and
N(K I). The detection of several of the ``C2 DIBs'', with strengths similar to
those in comparable Galactic sight lines, however, indicates that no single,
uniform scaling factor (e.g., one related to metallicity) applies to all DIBs
(or all sight lines) in the MC. (abstract abridged)Comment: 59 pages, 15 figures, 10 tables; aastex; accepted to ApJ
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