3,530 research outputs found
Stable isotope relationships between apatite phosphate (δ18O), structural carbonate (δ18O, δ13C), and collagen (δ2H, δ13C, δ15N, δ34S) in modern human dentine
Rationale
The use of multiâisotopic analysis (δ2H, δ13C, δ15N, δ18O, and δ34S values) of modern human body tissues for provenancing of unknown individuals in forensics is increasing. Tooth dentine develops during childhood and adolescence, therefore providing geographical information from that period of life. Tooth apatite δ18O values are commonly used for the reconstruction of drinking water values, and HâCâNâS isotope ratios in collagen supply additional information about the composition of diet. We tested if dentine collagen δ2H values provide similar information to apatite δ18O values with a proofâofâconcept study.
Methods
Tooth samples were taken from modernâday individuals born in different regions of the world. Apatite and collagen were prepared from dentine. Stable isotope analyses were performed on apatite phosphate oxygen (δ18Ophos); oxygen and carbon of the structural carbonate (δ18Ocarb, δ13Ccarb); and hydrogen, carbon, nitrogen, and sulfur of the collagen (δ2Hcoll, δ13Ccoll, δ15N, δ34S).
Results
δ18Ophos, δ18Ocarb, and δ2Hcoll values are highly correlated in modern human dentine. There are significant relationships of δ18O values in the apatite fraction and δ2H values in the collagen fraction with local δ18O and δ2H precipitation values, respectively. Pearson correlation coefficients indicate no direct relationship between δ15N values and the isotope ratios of any other element. Weak relationships exist between collagen δ34S values and δ18Ocarb or δ18Ophos values.
Conclusions
The highly significant correlation of δ18Ophos, δ18Ocarb, and δ2Hcoll values in the modern human dentine implies that measurement of δ2H values in collagen or δ18O values in bioapatite will provide reliable information about the climate at the person's whereabouts
Over-the-fiber Digital Predistortion Using Reinforcement Learning
We demonstrate, for the first time, experimental over-the-fiber training of
transmitter neural networks (NNs) using reinforcement learning. Optical
back-to-back training of a novel NN-based digital predistorter outperforms
arcsine-based predistortion with up to 60\% bit-error-rate reduction
Adenosine-5â˛-phosphosulfate - a multifaceted modulator of bifunctional 3â˛-phospho-adenosine-5â˛-phosphosulfate synthases and related enzymes
All sulfation reactions rely on active sulfate in the form of 3â˛-phosphoadenosine-5â˛-phosphosulfate (PAPS). In fungi, bacteria, and plants, the enzymes responsible for PAPS synthesis, ATP sulfurylase and adenosine-5â˛-phosphosulfate (APS) kinase, reside on separate polypeptide chains. In metazoans, however, bifunctional PAPS synthases catalyze the consecutive steps of sulfate activation by converting sulfate to PAPS via the intermediate APS. This intricate molecule and the related nucleotides PAPS and 3â˛-phospho-adenosine-5â˛-phosphate modulate the function of various enzymes from sulfation pathways, and these effects are summarized in this review. On the ATP sulfurylase domain that initially produces APS from sulfate and ATP, APS acts as a potent product inhibitor, being competitive with both ATP and sulfate. For the APS kinase domain that phosphorylates APS to PAPS, APS is an uncompetitive substrate inhibitor that can bind both at the ATP/ADP binding site and the PAPS/APS-binding site. For human PAPS synthase 1, the steady-state concentration of APS has been modelled to be 1.6 lM, but this may increase up to 60 lM under conditions of sulfate excess. It is noteworthy that the APS concentration for maximal APS kinase activity is 15 lM. Finally, we recognized APS as a highly specific stabilizer of bifunctional PAPS synthases. APS most likely stabilizes the APS kinase part of these proteins by forming a dead-end enzymeâADPâAPS complex at APS concentrations between 0.5 and 5 lM; at higher concentrations, APS may bind to the catalytic centers of ATP sulfurylase. Based on the assumption that cellular concentrations of APS fluctuate within this range, APS can therefore be regarded as a key modulator of PAPS synthase functions
Studies on grain boundaries in nanocrystalline silicon grown by Hot-Wire CVD
The use of a tantalum wire in hot-wire chemical vapour deposition (HWCVD) has allowed the deposition of dense nanocrystalline silicon at low filament temperatures (1550 °C). A transition in the crystalline preferential orientation from (2 2 0) to (1 1 1) was observed around 1700 °C. Transmission electron microscopy (TEM) images, together with secondary ion mass spectrometry (SIMS) measurements, suggested that no oxidation occurred in materials obtained at low filament temperature due to the high density of the tissue surrounding grain boundaries. A greater concentration of SiH 3 radicals formed at these temperatures seemed to be responsible for the higher density
Non-Fermi liquid behavior and scaling of low frequency suppression in optical conductivity spectra of CaRuO
Optical conductivity spectra of paramagnetic CaRuO are
investigated at various temperatures. At T=10 K, it shows a non-Fermi liquid
behavior of , similar to the case
of a ferromagnet SrRuO. As the temperature () is increased, on the other
hand, in the low frequency region is progressively
suppressed, deviating from the 1/{\omega}^{\frac 12%}-dependence.
Interestingly, the suppression of is found to scale with
at all temperatures. The origin of the scaling
behavior coupled with the non-Fermi liquid behavior is discussed.Comment: 4 pages, 3 figure
Light MSSM Higgs boson mass to three-loop accuracy
The light CP even Higgs boson mass, Mh, is calculated to three-loop accuracy
within the Minimal Supersymmetric Standard Model (MSSM). The result is
expressed in terms of DRbar parameters and implemented in the computer program
H3m. The calculation is based on the proper approximations and their
combination in various regions of the parameter space. The three-loop effects
to Mh are typically of the order of a few hundred MeV and opposite in sign to
the two-loop corrections. The remaining theory uncertainty due to higher order
perturbative corrections is estimated to be less than 1 GeV.Comment: 39 pages, 13 figures. v2: minor changes, typos fixe
Exceptional capture of methane at low pressure by an ironâbased metalâorganic framework
The selective capture of methane (CH4) at low concentrations and its separation from N2 are extremely challenging owing to the weak host-guest interactions between CH4 molecules and any sorbent material. Here, we report the exceptional adsorption of CH4 at low pressure and efficient separation of CH4/N2 by MFM-300(Fe). MFM-300(Fe) shows a very high uptake for CH4 of 0.85 mmol gâ1 at 1 mbar and 298 K and a record CH4/N2 selectivity of 45 for porous solids, representing a new benchmark for CH4 capture and CH4/N2 separation. The excellent separation of CH4/N2 by MFM-300(Fe) has been confirmed by dynamic breakthrough experiments. In situ neutron powder diffraction, and solid-state nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modelling, reveal a unique and strong binding of CH4 molecules involving Fe-OH¡¡¡CH4 and C¡¡¡phenyl ring interactions within the pores of MFM-300(Fe), thus promoting the exceptional adsorption of CH4 at low pressure
Evolution of lysine acetylation in the RNA polymerase II C-terminal domain
Š 2015 Simonti et al.; licensee BioMed Central.Background: RPB1, the largest subunit of RNA polymerase II, contains a highly modifiable C-terminal domain (CTD) that consists of variations of a consensus heptad repeat sequence (Y1S2
Dietary factors related to hypertension risk in Korean adults-data from the Korean national health and nutrition examination survey III
Regional differences between large cities and rural areas are observed in the Korean National Health and Nutrition Examination Survey (KNHANES). This present study was conducted to evaluate the effect of dietary factors on hypertension risk in Korean populations, especially residents of the Chungcheong province which was not in metropolitan area, using KNHANES III. A total of 544 adults aged ⼠19 years were placed into either the normotensive or the hypertensive group. Subject characteristics, BMI, blood pressure, and nutrient intakes were compared between the two groups using a chi-square test and t-test. We estimated odds ratios (ORs) using multiple logistic regression, adjusted for energy intake and selected covariates. There were significant differences in age, education level, alcohol consumption, and BMI between the normotensive and hypertensive groups. We found decreased ORs for the medium versus lowest tertile of calcium intake (multivariate OR = 0.43, 95% CI: 0.21-0.88), for the highest versus lowest tertile of calcium intake (multivariate OR = 0.43, 95% CI: 0.20-0.90) with significant trends in risk (P = 0.040), and for the medium versus lowest tertile of potassium intake (multivariate OR = 0.43, 95% CI: 0.20-0.89). Subjects with the highest sodium/calcium ratio had a 2.10-fold greater risk of hypertension compared to the subject with the lowest, with significant trends in risk (P = 0.002). Adequate calcium and potassium intake should be encouraged and regional differences should be considered in making a healthy plan for hypertension management
Thermodynamics of quantum systems under dynamical control
In this review the debated rapport between thermodynamics and quantum
mechanics is addressed in the framework of the theory of
periodically-driven/controlled quantum-thermodynamic machines. The basic model
studied here is that of a two-level system (TLS), whose energy is periodically
modulated while the system is coupled to thermal baths. When the modulation
interval is short compared to the bath memory time, the system-bath
correlations are affected, thereby causing cooling or heating of the TLS,
depending on the interval. In steady state, a periodically-modulated TLS
coupled to two distinct baths constitutes the simplest quantum heat machine
(QHM) that may operate as either an engine or a refrigerator, depending on the
modulation rate. We find their efficiency and power-output bounds and the
conditions for attaining these bounds. An extension of this model to multilevel
systems shows that the QHM power output can be boosted by the multilevel
degeneracy.
These results are used to scrutinize basic thermodynamic principles: (i)
Externally-driven/modulated QHMs may attain the Carnot efficiency bound, but
when the driving is done by a quantum device ("piston"), the efficiency
strongly depends on its initial quantum state. Such dependence has been unknown
thus far. (ii) The refrigeration rate effected by QHMs does not vanish as the
temperature approaches absolute zero for certain quantized baths, e.g.,
magnons, thous challenging Nernst's unattainability principle. (iii)
System-bath correlations allow more work extraction under periodic control than
that expected from the Szilard-Landauer principle, provided the period is in
the non-Markovian domain. Thus, dynamically-controlled QHMs may benefit from
hitherto unexploited thermodynamic resources
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