2,602 research outputs found
Preliminary study of 10Be/7Be in rainwater from Xi'an by Accelerator Mass Spectrometry
The 10Be/7Be ratio is a sensitive tracer for the study of atmospheric
transport, particularly with regard to stratosphere-troposphere exchange.
Measurements with high accuracy and efficiency are crucial to 7Be and 10Be
tracer studies. This article describes sample preparation procedures and
analytical benchmarks for 7Be and 10Be measurements at the Xian Accelerator
Mass Spectrometry (Xian-AMS) laboratory for the study of rainwater samples. We
describe a sample preparation procedure to fabricate beryllium oxide (BeO) AMS
targets that includes co-precipitation, anion exchange column separation and
purification. We then provide details for the AMS measurement of 7Be and 10Be
following the sequence BeO- -> Be2+ -> Be4+ in the Xian- AMS. The 10Be/7Be
ratio of rainwater collected in Xian is shown to be about 1.3 at the time of
rainfall. The virtue of the method described here is that both 7Be and 10Be are
measured in the same sample, and is suitable for routine analysis of large
numbers of rainwater samples by AMS
su(2) and su(1,1) displaced number states and their nonclassical properties
We study su(2) and su(1,1) displaced number states. Those states are
eigenstates of density-dependent interaction systems of quantized radiation
field with classical current. Those states are intermediate states
interpolating between number and displaced number states. Their photon number
distribution, statistical and squeezing properties are studied in detail. It is
show that these states exhibit strong nonclassical properties.Comment: 10 pages, 3 figure
Towards a Fisher-information description of complexity in de Sitter universe
Recent developments on holography and quantum information physics suggest
that quantum information theory come to play a fundamental role in
understanding quantum gravity. Cosmology, on the other hand, plays a
significant role in testing quantum gravity effects. How to apply this idea to
a realistic universe is still missing. Here we show some concepts in quantum
information theory have their cosmological descriptions. Particularly, we show
complexity of a tensor network can be regarded as a Fisher information
measure(FIM) of a dS universe, followed by several observations: (i) the
holographic entanglement entropy has a tensor-network description and admits a
information-theoretical interpretation, (ii) on-shell action of dS spacetime
has a same description of FIM, (iii) complexity/action(CA) duality holds for dS
spacetime. Our result is also valid for gravity, whose FIM exhibits the
same features of a recent proposed norm complexity.Comment: 18 pages, 3 figures. v2: improvements to presentation, fixes typos
and matches published versio
Calibration of the Pulsed Electroacoustic Technique in the Presence of Trapped Charge
The influence of pulse voltage on the accuracy of charge density distribution in the pulsed electroacoustic technique (PEA) is discussed. It is shown that significant error can be introduced if a low dc voltage and high pulse voltage are used to calibrate charge density. However, our main focus in the present paper is to deal with one of the practical situations where space charge exists in the material prior to any measurements. The conventional calibration method can no longer be used to calibrate charge density due to the interference by the charge on the electrode induced by space charge. A method has been proposed which is based on two measurements. Firstly, the sample containing charge is measured without any applied voltage. The second measurement is carried out with a small external applied voltage. The applied voltage should be small enough so there is no disturbance of the existing charge in the sample. The difference of the two measurements can be used for calibration. An additional advantage of the proposed method avoids the influence of the pulse voltage on calibration and therefore gives a more accurate representation of space charge. The proposed method has been validated
Graphene oxide-Au nano particle coated quartz crystal microbalance biosensor for the real time analysis of carcinoembryonic antigen
A label-free quartz crystal microbalance (QCM) biosensor was developed for the selective and real-time estimation of carcinoembryonic antigen (CEA) through the present study. Graphene oxide-Au nanoparticles (GO-AuNPs) was in situ synthesised on the surface of the QCM electrode and the antibody of CEA (monoclonal anti-CEA from mouse) was covalently immobilized on this layer as the bioreceptor for CEA. Mercaptoacetic acidâEDCâNHS reaction mechanism was used for anti-CEA immobilization. The effect of oxygen plasma treatment of the QCM electrode surface before bioreceptor preparation on the performance of the biosensor was tested and was found promising. CEA solutions with various concentrations were analysed using the bioreceptors to estimate the sensitivity and detection limit of the biosensor. The biosensors selectively recognized and captured CEA biomolecules with a detection limit of 0.06 and 0.09 ng mLâ1 of CEA for oxygen plasma-treated (E2) and untreated (E1) bioreceptors, respectively. The sensitivity was estimated at 102 and 79 Hz, respectively, for E2 and E1. Clinical serum samples were analysed and the results were found in good agreement with the ELISA analysis. Long term stability was also found to be excellent. Langmuir adsorption isotherm was also conducted using the experimental results
Genetic insights on sleep schedules: this time, it's PERsonal.
The study of circadian rhythms is emerging as a fruitful opportunity for understanding cellular mechanisms that govern human physiology and behavior, fueled by evidence directly linking sleep disorders to genetic mutations affecting circadian molecular pathways. Familial advanced sleep-phase disorder (FASPD) is the first recognized Mendelian circadian rhythm trait, and affected individuals exhibit exceptionally early sleep-wake onset due to altered post-translational regulation of period homolog 2 (PER2). Behavioral and cellular circadian rhythms are analogously affected because the circadian period length of behavior is reduced in the absence of environmental time cues, and cycle duration of the molecular clock is likewise shortened. In light of these findings, we review the PER2 dynamics in the context of circadian regulation to reveal the mechanism of sleep-schedule modulation. Understanding PER2 regulation and functionality may shed new light on how our genetic composition can influence our sleep-wake behaviors
Vibrational frequencies and structural properties of transition metals via total-energy calculations
We have used a self-consistent pseudopotential method within local-density-functional theory to calculate the equilibrium ground state properties of transition metals Mo, Nb, and Zr. From our calculations, we obtain equilibrium lattice constants, cohesive energies, and bulk moduli which are in excellent agreement with the experiments;First principles frozen phonon calculations are then performed for the longitudinal (2/3,2/3,2/3) phonon in Mo, Nb, and bcc Zr as well as the H-point phonon in Mo and Nb. These calculations involve the precise evaluation of the total crystalline energy as a function of lattice displacement and yield phonon frequencies to within a few percent of the experimental values. Anharmonic terms are obtained with little additional effort and are found to be very important for causing the tendency toward the (omega)-phase instability in bcc Zr. These calculations allow a detailed analysis of the mechanisms causing phonon anomalies. They also provide first principle benchmarks at a few wavevectors where phenomenological models can be tested or their parameters determined;The validity of the adiabatic approximation is investigated for the Mo H-point phonon. Non-adiabatic effects are found to be small, while effects caused by the many-body renormalization of electronic states near the Fermi energy are found to be of the same order of magnitude as the discrepancy between experiment and the frozen phonon results;The microscopic interactions responsible for the vast frequency differences of the longitudinal (2/3,2/3,2/3) phonon in Mo, Nb, and Zr are analyzed by making use of the Hellmann-Feynman theorem. The stiffening of this mode as the electron per atom ratio increases from Nb to Mo is shown to arise from a development of directional bonding. The precipitous dip in this mode for the high temperature bcc phase of Zr is related to the d-electron screening, and the;tendency for this mode to go soft and cause a transformation to the (omega)-phase is also associated with details of the electronic structure; (\u271)DOE Report IS-T-1065. This work was performed under Contract No. W-7405-Eng-82 with the U.S. Department of Energy
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