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  • Author: M. Asai x
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Abstract

We propose a fractionally integrated matrix-exponential dynamic conditional correlation (FIEDCC) model to capture the asymmetric effects and long- and short-range dependence of a correlation process. We also propose employing an inverse Wishart distribution for the disturbance of a covariance structure, which gives an alternative interpretation for a multivariate t conditional distribution. Using the inverse Wishart distribution, we present a three-step procedure to obtain initial values for estimating a high-dimensional conditional covariance model with a multivariate t distribution. We investigated the finite-sample properties of the ML estimator. Empirical results for nine assets from chemical firms, banks, and oil and gas producers in the US indicate that the new FIEDCC model outperforms the other dynamic correlation models for the AIC and BIC and for forecasting value-at-risk thresholds. Furthermore, the new FIEDCC model captures the stronger connection among the nine assets for the period right after the global financial crisis.

Abstract

Production cross sections of fission product 99Mo produced in the reaction of 19F + 209Bi have been measured at the incident energies 135–83 MeV near and below the fusion barrier by radiochemical methods. The excitation function for the fusion-fission cross sections in this reaction were deduced down to 80 μb from the measured production cross sections. A systematic analysis of the fusion-fission excitation function shows that sub-barrier fusion hindrance in the heavy mass system 19F + 209Bi is different from that in the medium-heavy mass systems but similar to that in the medium-light mass system and in the heavy mass system. This work is the first radiochemical study of sub-barrier fusion hindrance in heavy mass systems.

Summary

Diabetes mellitus is one of the most common endocrine disorders and its continuous global increase is due to factors as population growth, urbanization, aging, and increasing prevalence of obesity and physical inactivity. The effect of pinworm infection on the development of hyperglycemia was examined in WBN/K-Lepf (fa/fa) rats, a new model of the obese type 2 diabetes mellitus (T2DM) with pancreatitis. The rats were orally administered Syphacia muris eggs (infected group) and distilled water (control group). Hyperglycemia onset in the infected group was significantly delayed compared to the control group. Neither body weight nor intake of food and water were affected by S. muris infection. This study demonstrated that S. muris infection delayed the onset of T2DM in fa/fa rats and suggested that elucidation of the underlying mechanism and relevant pathways in the helminth-mediated protection may lead to the development of a new strategy to prevent diabetes mellitus.

Summary

Syphacia muris is a ubiquitous nematode parasite and common contaminant of laboratory rats. A lthough S. muris infection is considered symptomless, it has some effects on the host’s immunity and therefore can interfere with experimental settings and interrupt final results. However, the molecular mechanisms involved in the alteration within the host’s immunity remain unclear because of the absence of information about mRNA expressed in this parasite. In this study we performed the transcriptome profiling of S. muris by next-generation sequencing. After de novo assembly and annotation, 14,821 contigs were found to have a sequence homology with any nematode sequence. Gene ontology analysis showed that the majority of the expressed genes are involved in cellular process, binding, and catalytic activity. Although the rate of expressed genes involved in the immune system was low, we found candidate genes that might be involved in the alteration within the host’s immunity by regulating the host’s innate immune response.

Abstract

Recent developments in econometric methods enable estimation and testing of general long memory processes, which include the general Gegenbauer process. This paper considers the error correction model for a vector general long memory process, which encompasses the vector autoregressive fractionally integrated moving average and general Gegenbauer processes. We modify the tests for unit roots and cointegration, based on the concept of heterogeneous autoregression. The Monte Carlo simulations show that the finite sample properties of the modified tests for unit roots are satisfactory, while the conventional tests suffer from size distortion. The experiments also indicate that the modified tests for cointegration improve the problem of finding too many cointegration relationships which arises for fractionally integrated series. Empirical results for interest rates series for the USA and Australia indicate that: (1) the modified unit root test detected unit roots for all series; (2) after differencing, all series favour the general Gegenbauer (GG) process; (3) the modified test for cointegration found only two cointegrating vectors; and (4) the zero interest rate policy in the USA had no effect on the cointegrating vectors for the two countries.

11-Deoxytetrodotoxin and 8,11-dideoxytetrodotoxin were synthesized from the same intermediate in the enantiomerically pure form.

The transactinide nuclides 261Rf and 262Db have been successfully produced in the 248Cm(18O,5n) reaction at 99 MeV and in the 248Cm(19F,5n) reaction at 100, 103, and 106 MeV, respectively, at the JAERI tandem accelerator. The on-line ion exchange experiments with an automated fast and repetitive liquid chromatography separation system were performed in the HNO3/HF system using Rf homologues 89mZr and 167,165Hf produced in the 89Y(p,n) and 152Gd(18O,xn) reactions, respectively. The radiotracers 88Zr, 175Hf, and 234Th were also prepared and the distribution coefficients on ion exchange resins were measured systematically in 1-11 M HCl and 1-14 M HNO3 with the batch method. It was found that anion exchange experiments of Rf in 8 M HNO3 and 9 M HCl provided information useful to extract the ionic radius of Rf and to verify the influence of relativistic effects.

Characteristics of nuclear deformation properties at scission of two fission modes, symmetric and asymmetric, are reviewed. Existence of two kinds of scission configurations associated with the symmetric and asymmetric fission modes is pointed out: elongated and compact configurations. Each symmetric and asymmetric scission property is discussed in terms of shape elongation evaluated from fragment total kinetic energy (TKE). Fragment deformation at scission is also discussed based on neutron multiplicity data. From the systematic study of the scission properties in a wide range of actinide fission, the bimodal fission observed in spontaneous fission (SF) of the heavy actinides is interpreted as the result of the presence of the two fission paths of the ordinary asymmetric mode and a strongly shell-influenced symmetric one. The correlation between the fragment shell structures and the asymmetric mass-yield curves is described.

Summary

Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 261Rf has been produced in the reaction 248Cm(18O, 5n) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO3 solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

Abstract

The cation-exchange behavior of 261Rf (T 1/2= 78 s) produced in the 248Cm(18O, 5n) reaction was studied on a “one-atom-at-a-time” scale in 0.15–0.69 M H2SO4/HNO3 mixed solutions ([H+]=1.0 M) using an automated ion-exchange separation apparatus coupled with the detection system for alpha-spectroscopy (AIDA). It was found that adsorption probabilities ( decrease with an increase of [HSO4 ], showing a successive formation of Rf sulfate complexes. Rf exhibits a weaker complex formation tendency compared to the lighter homologues Zr and Hf. This is in good agreement with theoretical predictions including relativistic effects.