Effects of a Periodic Decay Rate on the Statistics of Radioactive Decay: New Methods to Search for Violations of the Law of Radioactive Change

It is a long-held tenet of nuclear physics, from the early work of Rutherford and Soddy up to present times that the disintegration of each species of radioactive nuclide occurs randomly at a constant rate unaffected by interactions with the external environment. During the past 15 years or so, reports have been published of some 10 or more unstable nuclides with non-exponential, periodic decay rates claimed to be of geophysical, astrophysical, or cosmological origin. Deviations from standard exponential decay are weak, and the claims are controversial. This paper examines the effects of a periodic decay rate on the statistical distributions of 1) nuclear activity measurements and 2) nuclear lifetime measurements. It is demonstrated that the modifications to these distributions are approximately 100 times more sensitive to non-standard radioactive decay than measurements of the decay curve, power spectrum, or autocorrelation function for corresponding system parameters.

A New Yellow Long Lasting Phosphor Y_2O_2S∶Ti

A new kind of doped rare earth free phosphor Y 2O 2S∶xTi (0<x≤0.10) with doped Ti as activative center was synthesized by solid state reaction and sintered at 1200 ℃ for 2.5 h under reducing atmosphere. XRD patterns, photoluminescence spectra, time-resolved phosphorescence spectra and decay curves of the phosphor were investigated. XRD results reveal that a single Y 2O 2S phase exists with Ti content up to 6% (mol fraction). Yellow long lasting phosphorescence for present materials was observed in the dark with naked eye after the removal of the excitation light. From the time-resolved phosphorescence spectra the broad emission band centered at 565 nm was confirmed to be responsible for the long lasting phosphorescence which could maintain above 1 h. The possible mechanism responsible for the long lasting phosphorescence of the Y 2O 2S∶Ti phosphor was proposed.

Virtual neighborhood technique for moduli spaces of holomorphic curves

We use the technique of Ruan(1999)and Li and Ruan(2001)to construct the virtual neighborhoods and show that the Gromov-Witten invariants can be defined as integrals over the top strata of the virtual neighborhoods.We prove that the invariants defined in this way satisfy all the axioms of Gromov-Witten invariants summarized by Kontsevich and Manin(1994).

Lifetime measurements in 138Nd

Lifetimes of the 2_(1)^(+),4_(1)^(+),7_(2)^(-),10_(2)^(+),12_(2)^(+),and 14_(1)^(+) states in 138 Nd populated via the 123 Sb(19 F,4n)138 Nd fusion–evaporation reaction were measured with the recoil distance Doppler shift technique in combination with the differential decay curve method.The B(E2;2_(1)^(+)→0_(1)^(+))value fit well with the systematic trend in the Nd isotope chain and Grodzins rule,which proved that 138Nd is a transitional nucleus.

Self-Similarities of Pulmonary Arterial Tree and a New Integrated Model of Pulmonary Circulation with the Name of Fractal Phasic Perfusion (FPP) Model

Pulmonary arterial hypertension (PAH) has become an important topic of basic and clinical research in recent years. Morphologic researches have shown that specific PAH-lesions are located in the lobular small muscular arteries and correlate with hemodynamic measurements. However, it still remains to be shown how pathological changes of the small arteries in the lobule develop to PAH. Based on both fractal properties of pulmonary arterial tree and asynchronous phasic contractions of lobular arterial muscles under the evenness of the pulmonary capillary pressure (PCP) in the lung, the author has constructed an integrated model of pulmonary circulation which has produced a mathematical relationship between the mean pulmonary arterial pressure (MPAP) and the cardiac output (CO). By use of the expression between MPAP and CO, it has been able to explain the pathogenesis of PAH in terms of statistical changes among regional and temporal perfusions in the lung. In order to detect clinically the early stage of PAH, the author has suggested that it is important to establish the pulmonary functional imaging of regional and temporal perfusions.

Enhancement of red to orange emission ratio of YPO_4:Eu^(3+),Ce^(3+) and its dependence on Ce^(3+) concentration

Eu3＋ and Ce3＋ co-doped YPO4 microspheres were synthesized by hydrothermal method without template. The emission spectra showed that the red emission centered at 618nm could be readily increased relatively to the orange emission centered at 590nm by controlling the doping concentration of Ce3＋ ion. The investigation based on excitation spectra and decay curves demonstrated that the doped Ce3＋ ions took two efficient energy transfers to Eu3＋ ions and affected the lifetime of the emission states of Eu3＋ ions so that the emission spectra of Eu3＋ ion were accordingly tuned with the Ce3＋ content increasing. This controllable red （5D0→7F2） to orange （ 5D0→7F1） emission ratio of YPO4：Eu3＋,Ce3＋ made it very promising for encoded anti-fake labels and bio-labels.

Investigation of the temperature characteristic in SrB4O7：Sm2＋ phosphor-in-glass by analyzing the lifetime of 684 nm

The SrB4O7：Sm2＋ phosphor was synthesized by high temperature solid state reaction method. The phosphor-in-glass was prepared by mixing and firing the phosphor and TeO2-ZnO glass precursor. The XRD results showed that the phosphor-in-glass was in amorphous phase because of the tiny mass fraction of phosphor in glass. The emission spectrum under the 355 nm excitation was measured, and it exhibited the same characteristic emission peaks as the phosphor sample. The temperature characteristic of the SrB4O7：Sm2＋ phosphor-in-glass was discussed by analyzing the lifetime of 684 nm emission at various temperatures. The relative temperature sensitivity of 5%/K around 573 K was obtained for the temperature dependent lifetime, suggesting that the material in this study is a promising candidate for temperature sensor application.

Kinetics of fluorescence properties of Eu^(3+) ion in strontium-aluminiumbismuth-borate glasses

Eu3＋ doped strontium-aluminium-bismuth-borate glasses with the chemical composition（50–x）B2O3＋20Bi2O3＋7Al F3＋ 8Sr O＋15Sr F2＋x Eu2O3（where x=0.1 mol.%, 0.5 mol.%, 1.0 mol.% and 1.5 mol.%） were prepared by the conventional melt quenching technique.Structural properties of the prepared glasses were analysed through X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS） and Raman spectral techniques.Thermal stability of glass was analysed by differential thermal analysis（DTA） curve.Photoluminescence characteristics were studied using excitation, emission spectra and decay curves of Eu3＋ doped strontium-aluminium-bismuth-borate glasses.The Judd-Ofelt（J-O） intensity parameters, Ωλ（λ=2, 4 and 6） were obtained using emission spectra and was used to identify the nature of Eu3＋ ions with their surrounding ligands.Using J-O parameters the transition probabilities（A）, stimulated emission cross-sections σE p, branching ratios（βR） and radiative lifetimes（τmeas and τcal） were evaluated for the 5D0→7F J（J=0, 1, 2, 3 and 4） transition of Eu3＋ ions in the present glasses.The decay profiles were found to be non exponential for all the concentrations and the measured lifetimes（τmeas） were obtained from the decay profiles.The higher values of A, σE p, βR and quantum efficiency（η） for 5D0→7F2 emission transition at 617 nm confirmed the present glass was as active medium for red laser emission applications.

Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis

To classify different walnut varieties based on water and oil content of walnut,and determine their storage conditions,the low-field nuclear magnetic resonance(LFNMR)technology was used to obtain the NMR transverse relaxation time(T 2)of the samples based on the physical and chemical indicators of the walnut quality.The relationship between the relaxation time and phase state of the internal material of the sample was investigated,and the characteristic parameters of the NMR spectrum signals were statistically analyzed using cluster analysis to determine the different walnut varieties,and three different components,as well as their contents,were detected by a LFNMR spectrometer:firmly bound water,weakly bound water,and weakly bound oil.Test results indicated that the oil peak was dominant in the overall signal intensity compared to the water peaks,in which the firmly bound water phase contributed more to the overall water signal between the water peaks.Using the analytic hierarchy process of cluster analysis,21 walnut samples were classified into three different classes,based on the characteristic parameters of the water-content and oil-content spectrum signals.The first class contains four walnut varieties characterized by least water and highest oil contents;the third class contains two walnut varieties,with the highest water content and least oil content;whereas,the second class contains 15 walnut varieties,with both water and oil contents at medium levels.The results showed that LFNMR led to a rapid detection of moisture and oil contents in walnuts,while cluster analysis classified different walnuts varieties based on these parameters.This study also provided the basis for optimizing the storage methods and storage conditions of walnuts.

TIME-RESOLVED FLUORESCENCE SPECTROSCOPY OF HEMATOPORPHYRIN DERIVATIVE LASER No. 3

Ⅰ. INTRODUCTIONPhotodynamic therapy (PDT) which utilizes hematoporphyrin derivative (HpD) as a photosensitizing drug has increasingly being used for the local treatment of malignant tumors. The success of this method is attributed to the ability of HpD to accumulate to

Lifetime measurement for the 2^+1 state in^106Cd

The lifetime of the 2^+1 state in ^106Cd populated via the ^94Zr(^16O,4n)^106Cd reaction has been measured with the Recoil Distance Doppler Shift technique in combination with the Differential Decay Curve Method.By subtracting the contamination in the data,the mean lifetime of the I^π=2^+1633 keV state was determined as 9.9(12)ps.The B(E2)value calculated in this study is in good agreement with the experimental systematics and was compared to the shell model calculations.