1,154 research outputs found
On the Munn-Silbey approach to polaron transport with off-diagonal coupling
Improved results using a method similar to the Munn-Silbey approach have been
obtained on the temperature dependence of transport properties of an extended
Holstein model incorporating simultaneous diagonal and off-diagonal
exciton-phonon coupling. The Hamiltonian is partially diagonalized by a
canonical transformation, and optimal transformation coefficients are
determined in a self-consistent manner. Calculated transport properties exhibit
substantial corrections on those obtained previously by Munn and Silbey for a
wide range of temperatures thanks to a numerically exact evaluation and an
added momentum-dependence of the transformation matrix. Results on the
diffusion coefficient in the moderate and weak coupling regime show distinct
band-like and hopping-like transport features as a function of temperature.Comment: 12 pages, 6 figures, accpeted in Journal of Physical Chemistry B:
Shaul Mukamel Festschrift (2011
Characterisation of a pucBA deletion mutant from Rhodopseudomonas palustris lacking all but the pucBAd genes
Rhodopseudomonas palustris is a species of purple photosynthetic bacteria that has a multigene family of puc genes that encode the alpha and beta apoproteins, which form the LH2 complexes. A genetic dissection strategy has been adopted in order to try and understand which spectroscopic form of LH2 these different genes produce. This paper presents a characterisation of one of the deletion mutants generated in this program, the pucBAd only mutant. This mutant produces an unusual spectroscopic form of LH2 that only has a single large NIR absorption band at 800 nm. Spectroscopic and pigment analyses on this complex suggest that it has basically a similar overall structure as that of the wild-type HL LH2 complex. The mutant has the unique phenotype where the mutant LH2 complex is only produced when cells are grown at LL. At HL the mutant only produces the LH1-RC core complex
Analysis of Iophenoxic Acid Analogues in Small Indian Mongoose (\u3ci\u3eHerpestes Auropunctatus\u3c/i\u3e) Sera for Use as an Oral Rabies Vaccination Biological Marker
The small Indian mongoose (Herpestes auropunctatus) is a reservoir of rabies virus (RABV) in Puerto Rico and comprises over 70% of animal rabies cases reported annually. The control of RABV circulation in wildlife reservoirs is typically accomplished by a strategy of oral rabies vaccination (ORV). Currently no wildlife ORV program exists in Puerto Rico. Research into oral rabies vaccines and various bait types for mongooses has been conducted with promising results. Monitoring the success of ORV relies on estimating bait uptake by target species, which typically involves evaluating a change in RABV neutralizing antibodies (RVNA) post vaccination. This strategy may be difficult to interpret in areas with an active wildlife ORV program or in areas where RABV is enzootic and background levels of RVNA are present in reservoir species. In such situations, a biomarker incorporated with the vaccine or the bait matrix may be useful. We offered 16 captive mongooses placebo ORV baits containing ethyl-iophenoxic acid (et-IPA) in concentrations of 0.4% and 1% inside the bait and 0.14% in the external bait matrix. We also offered 12 captive mongooses ORV baits containing methyl-iophenoxic acid (me-IPA) in concentrations of 0.035%, 0.07% and 0.14% in the external bait matrix. We collected a serum sample prior to bait offering and then weekly for up to eight weeks post offering. We extracted Iophenoxic acids from sera into acetonitrile and quantified using liquid chromatography/mass spectrometry. We analyzed sera for et-IPA or me-IPA by liquid chromatography-mass spectrometry. We found adequate marking ability for at least eight and four weeks for et- and me-IPA, respectively. Both IPA derivatives could be suitable for field evaluation of ORV bait uptake in mongooses. Due to the longevity of the marker in mongoose sera, care must be taken to not confound results by using the same IPA derivative during consecutive evaluations
Analysis of Iophenoxic Acid Analogues in Small Indian Mongoose (\u3ci\u3eHerpestes Auropunctatus\u3c/i\u3e) Sera for Use as an Oral Rabies Vaccination Biological Marker
The small Indian mongoose (Herpestes auropunctatus) is a reservoir of rabies virus (RABV) in Puerto Rico and comprises over 70% of animal rabies cases reported annually. The control of RABV circulation in wildlife reservoirs is typically accomplished by a strategy of oral rabies vaccination (ORV). Currently no wildlife ORV program exists in Puerto Rico. Research into oral rabies vaccines and various bait types for mongooses has been conducted with promising results. Monitoring the success of ORV relies on estimating bait uptake by target species, which typically involves evaluating a change in RABV neutralizing antibodies (RVNA) post vaccination. This strategy may be difficult to interpret in areas with an active wildlife ORV program or in areas where RABV is enzootic and background levels of RVNA are present in reservoir species. In such situations, a biomarker incorporated with the vaccine or the bait matrix may be useful. We offered 16 captive mongooses placebo ORV baits containing ethyl-iophenoxic acid (et-IPA) in concentrations of 0.4% and 1% inside the bait and 0.14% in the external bait matrix. We also offered 12 captive mongooses ORV baits containing methyl-iophenoxic acid (me-IPA) in concentrations of 0.035%, 0.07% and 0.14% in the external bait matrix. We collected a serum sample prior to bait offering and then weekly for up to eight weeks post offering. We extracted Iophenoxic acids from sera into acetonitrile and quantified using liquid chromatography/mass spectrometry. We analyzed sera for et-IPA or me-IPA by liquid chromatography-mass spectrometry. We found adequate marking ability for at least eight and four weeks for et- and me-IPA, respectively. Both IPA derivatives could be suitable for field evaluation of ORV bait uptake in mongooses. Due to the longevity of the marker in mongoose sera, care must be taken to not confound results by using the same IPA derivative during consecutive evaluations
Fishing for iodine: What aquatic foraging by bonobos tells us about human evolution
Background: Expansion of brain tissue and development of advanced cognitive skills are characteristic traits of human evolution. Their emergence has been causally linked to the intake of nutrients that promote brain development and iodine is considered a critical resource. Rich sources of iodine exist in coastal areas and evolutionary scenarios associate the progressive development of brain size and cognitive skills to such landscapes. This raises the question of how early hominins living in continental areas could have met their iodine requirements. One way to explore this question is to use information from hominoid primates as a proxy for the nutritional ecology of early hominins. Bonobos are particularly interesting in this context as they are restricted to the central part of the Congo basin, an area considered to be iodine deficient based on human standards.
Methods: Pooled samples of fruit, terrestrial and aquatic herbs were used to assess mineral content with an inductively coupled plasma optical emission spectrometer. Iodine content was measured with the catalytic technique of Sandell-Kolthoff and two separate inductively coupled plasma mass spectrometry methods.
Results: Nutritional analyses revealed that the mineral content of aquatic herbs is higher than in other plant foods. Moreover, two species of aquatic herbs consumed by bonobos contain iodine concentrations that are almost equivalent to marine algae.
Conclusions: These data challenge the general notion that the Congo basin is iodine deficient and demonstrate that its lowland forest offers natural sources of iodine in concentrations high enough to prevent iodine deficiency in hominoids and humans
Multidrug- and extensively drug-resistant tuberculosis
We evaluated risk factors and treatment outcomes associated with multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) in Germany in 2004–2006. In 177 (4%) of 4,557 culture-positive TB cases, Mycobacterium tuberculosis isolates were identified as MDR TB; an additional 7 (0.15%) met criteria for XDR TB. Of these 184 patients, 148 (80%) were born in countries of the former Soviet Union. In patients with XDR TB, hospitalization was longer (mean ± SD 202 ± 130 vs. 123 ± 81 days; p = 0.015) and resistance to all first-line drugs was more frequent (36% vs. 86%; p = 0.013) than in patients with MDR TB. Seventy-four (40%) of these 184 patients received treatment with linezolid. Treatment success rates ranged from 59% for the entire cohort (59% for MDR TB and 57% for XDR TB) to 87% for those with a definitive outcome (n = 125; 89% for MDR TB and 80% for XDR TB). Extensive drug susceptibility testing and availability of second- and third-line drugs under inpatient management conditions permit relatively high treatment success rates in MDR- and XDR TB
Exploring CEvNS with NUCLEUS at the Chooz Nuclear Power Plant
Coherent elastic neutrino-nucleus scattering (CENS) offers a unique way
to study neutrino properties and to search for new physics beyond the Standard
Model. Nuclear reactors are promising sources to explore this process at low
energies since they deliver large fluxes of (anti-)neutrinos with typical
energies of a few MeV. In this paper, a new-generation experiment to study
CENS is described. The NUCLEUS experiment will use cryogenic detectors
which feature an unprecedentedly low energy threshold and a time response fast
enough to be operated in above-ground conditions. Both sensitivity to
low-energy nuclear recoils and a high event rate tolerance are stringent
requirements to measure CENS of reactor antineutrinos. A new experimental
site, denoted the Very-Near-Site (VNS) at the Chooz nuclear power plant in
France is described. The VNS is located between the two 4.25 GW
reactor cores and matches the requirements of NUCLEUS. First results of on-site
measurements of neutron and muon backgrounds, the expected dominant background
contributions, are given. In this paper a preliminary experimental setup with
dedicated active and passive background reduction techniques is presented.
Furthermore, the feasibility to operate the NUCLEUS detectors in coincidence
with an active muon-veto at shallow overburden is studied. The paper concludes
with a sensitivity study pointing out the promising physics potential of
NUCLEUS at the Chooz nuclear power plant
Recommended from our members
Enzymatic degradation of polyethylene terephthalate nanoplastics analyzed in real time by isothermal titration calorimetry
Plastics are globally used for a variety of benefits. As a consequence of poor recycling or reuse, improperly disposed plastic waste accumulates in terrestrial and aquatic ecosystems to a considerable extent. Large plastic waste items become fragmented to small particles through mechanical and (photo)chemical processes. Particles with sizes ranging from millimeter (microplastics, <5 mm) to nanometer (nanoplastics, NP, <100 nm) are apparently persistent and have adverse effects on ecosystems and human health. Current research therefore focuses on whether and to what extent microorganisms or enzymes can degrade these NP. In this study, we addressed the question of what information isothermal titration calorimetry, which tracks the heat of reaction of the chain scission of a polyester, can provide about the kinetics and completeness of the degradation process. The majority of the heat represents the cleavage energy of the ester bonds in polymer backbones providing real-time kinetic information. Calorimetry operates even in complex matrices. Using the example of the cutinase-catalyzed degradation of polyethylene terephthalate (PET) nanoparticles, we found that calorimetry (isothermal titration calorimetry-ITC) in combination with thermokinetic models is excellently suited for an in-depth analysis of the degradation processes of NP. For instance, we can separately quantify i) the enthalpy of surface adsorption ∆AdsH = 129 ± 2 kJ mol−1, ii) the enthalpy of the cleavage of the ester bonds ∆EBH = −58 ± 1.9 kJ mol−1 and the apparent equilibrium constant of the enzyme substrate complex K = 0.046 ± 0.015 g L−1. It could be determined that the heat production of PET NP degradation depends to 95% on the reaction heat and only to 5% on the adsorption heat. The fact that the percentage of cleaved ester bonds (η = 12.9 ± 2.4%) is quantifiable with the new method is of particular practical importance. The new method promises a quantification of enzymatic and microbial adsorption to NP and their degradation in mimicked real-world aquatic conditions
- …