Theoretical study on spherical proton emission

The proton radioactivity half-lives of spherical proton emitters are investigated within a generalized liquid drop model (GLDM), including the proximity effects between nuclei in a neck and the mass and charge asymmetry. The penetrability is calculated in the WKB approximation and the assault frequency is estimated by the quantum mechanism method considering the structure of the parent nucleus. The spectroscopic factor is taken into account in half-life calculation, which is obtained by employing the relativistic mean field (RMF) theory. The half-lives within the GLDM are compared with the experimental data and other theoretical values. The results show that the GLDM works quite well for spherical proton emitters when the assault frequency is estimated by the quantum mechanical method and the spectroscopic factor is considered.

The beta decay of N-21

The beta-delayed neutron and gamma energy spectra taken from the decay of neutron-rich nucleus N-21 were measured by using the beta - gamma and beta - n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98 MeV and with a total branching ratio of 88.7 +/- 4.2% were observed and presented. One gamma transition with an energy of 1222 keV emitted from the excited state of O-21, and four gamma transitions with energies of 1674, 2397, 2780, and 3175 keV emitted from the excited states of O-20 were identified in the 3 decay chain of N-21. The beta decay half-life for N-21 is determined to be 82.9 +/- 1.9 ms. The uncertainty of half-life is much smaller than the previous result.

beta-delayed neutron decay of N-21

The beta-delayed neutron and gamma spectra of neutron-rich nucleus N-21 using beta-gamma and beta-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7 +/- 4.2% were observed. One gamma transition among the excited states of O-21 and foury transitions among the excited states of O-20 were identified in the beta decay chain of N-21. The ungated half-life of 83.8 +/- 2.1 ms was also determined for N-21.

beta(+)/EC decay and systematic analysis of Ir-176,Ir-178

The gamma rays following the beta(+)/EC decay of Ir-176,Ir-178 nuclei have been investigated using in-beam gamma-ray experiment. In addition, with the aid of a helium-jet recoil fast tape transport system, the beta(+)/EC decay of Ir-176 was further studied, the new gamma rays were proved and a low-spin isomer was proposed in Ir-176. The isomeric state was analysized according to the systematics in neighboring nuclei.

Pa-239 may influence astrophysics study

The estimation method of the universe age using the nuclear cosmochronology by the heavy chronometers is essentialized. The influence of the novel long half-life of Pa-239 on the universe age estimation is simply mentioned.

Alpha-decay for heavy nuclei in the ground and isomeric states

The alpha-decay half-lives of nuclei in the ground states and Isomeric states have been calculated within the WKB approximation and Royer's formulas. The barrier in the quasimolecular shape path is determined within a generalized liquid drop model (GLDM). in which the centrifugal potential energy has been introduced to study the unfavored a-decay The agreement between the calculated results and experimental data indicates the reliability of studying alpha-decay of isomeric states with the generalized liquid drop model We find that their is no significant difference of preformation probability between Isomeric states and the corresponding ground states generally in favored alpha-decay Additionally. we extended Royer's formulas by taking account of the role of centrifugal harrier to study the unfavored alpha-decay, and some predicts oil the a decay half-lives of Isomers are made Finally. the effects of angular momontum transfer and Q(alpha) on alpha-decay half-life have been discussed Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved

Unified fission model for proton emission

The unified fission model (UFM) combining with the phenomenological assault frequency has been carried out to investigate the proton-radioactivity half-lives of spherical proton emitters. The results are in good agreement with the experimental data and other theoretical values, and newly observed spherical proton emitters have been analyzed. Finally, the effect of angular momentum transfer on half-life of proton emission has been discussed in detail and a formula can be used to describe this relationship.

Insulin-like growth factor-binding protein-3 plays an important role in regulating pharyngeal skeleton and inner ear formation and differentiation

Insulin-like growth factor-binding protein (IGFBP)-3 is the major insulin-like growth factor (IGF) carrier protein in the bloodstream. IGFBP-3 prolongs the half-life of circulating IGFs and prevents their potential hypo-glycemic effect. IGFBP-3 is also expressed in many peripheral tissues in fetal and adult stages. In vitro, IGFBP-3 can inhibit or potentiate IGF actions and even possesses IGF-independent activities, suggesting that local IGFBP-3 may also have paracrine/autocrine function(s). The in vivo function of IGFBP-3, however, is unclear. In this study, we elucidate the developmental role of IGFBP-3 using the zebrafish model. IGFBP-3 mRNA expression is first detected in the migrating cranial neural crest cells and subsequently in pharyngeal arches in zebrafish embryos. IGFBP-3 mRNA is also persistently expressed in the developing inner ears. To determine the role of IGFBP-3 in these tissues, we ablated the IGFBP-3 gene product using morpholino-modified antisense oligonucleotides (MOs). The IGFBP-3 knocked down embryos had delayed pharyngeal skeleton morphogenesis and greatly reduced pharyngeal cartilage differentiation. Knockdown of IGFBP-3 also significantly decreased inner ear size and disrupted hair cell differentiation and semicircular canal formation. Furthermore, reintroduction of a MO-resistant form of IGFBP-3 "rescued" the MO-induced defects. These findings suggest that IGFBP-3 plays an important role in regulating pharyngeal cartilage and inner car development and growth in zebrafish.

Isolation, characterization and electron microscopic single particle analysis of the NADH : ubiquinone oxidoreductase (complex I) from the hyperthermophilic eubacterium Aquifex aeolicus

The proton-translocating NADH:ubiquinone oxidoreductase (complex I) has been purified from Aquifex aeolicus, a hyperthermophilic eubacterium of known genome sequence. The purified detergent solubilized enzyme is highly active above 50 degreesC. The specific activity for electron transfer from NADH to decylubiquinone is 29 U/mg at 80 degreesC. The A. aeolicus complex I is completely sensitive to rotenone and 2-n-decyl-quinazoline-4-yl-amine. SDS polyacrylamide gel electrophoresis shows that it may contain up to 14 subunits. N-terminal amino acid sequencing of the bands indicates the presence of a stable subcomplex, which is composed of subunits E, F, and G. The isolated complex is highly stable and active in a temperature range from 50 to 90 degreesC, with a half-life of about 10 h at 80 degreesC. The activity shows a linear Arrhenius plot at 50-85 degreesC with an activation energy at 31.92 J/mol K. Single particle electron microscopy shows that the A. aeolicus complex I has the typical L-shape. However, visual inspection of averaged images reveals many more details in the external arm of the complex than has been observed for complex I from other sources. In addition, the angle (90degrees) between the cytoplasmic peripheral arm and the membrane intrinsic arm of the complex appears to be invariant.

Interaction between Thymidylate Synthase and Its Cognate mRNA in Zebrafish Embryos

Thymidylate synthase (TS), which catalyzes the de novo synthesis of dUMP, is an important target for cancer therapy. In this report, the effects of 5-fluorouracil (5-FU) and ZD1694 on the regulation of TS gene expression were evaluated in zebrafish embryos. Our results revealed that the expression of TS was increased by about six-fold when embryos were treated with 1.0 mu M 5-FU and there was a greater than 10-fold increase in the TS protein level after treatment with 0.4 mu M ZD1694. Northern blot analysis confirmed that expression of TS mRNA was identical in treated or untreated embryos. Gel shift and immunoprecipitation assays revealed that zebrafish TS was specifically bound with its cognate mRNA in vitro and in vivo. We identified a 20 nt RNA sequence, TS:N20, localized to the 5'-UTR of TS mRNA, which corresponded to nt 13-32; TS:N20 bound to the TS protein with an affinity similar to that of the full-length TS mRNA. The MFold program predicted that TS:N20 formed a stable stem-loop structure similar to that of the cis-acting element found in human TS mRNA. Variant RNAs with either a deletion or mutation in the core motif of TS:N20 were unable to bind to the TS protein. In vitro translation experiments, using the rabbit lysate system, confirmed that zebrafish TS mRNA translation was significantly repressed when an excess amount of TS protein was included in the system. Additionally, a TS stability experiment confirmed that treatment of zebrafish embryos with 5-FU could increase the TS stability significantly, and the half life of TS protein was about 2.7 times longer than in untreated embryos. Our study revealed a structural requirement for the interaction of TS RNA with TS protein. These findings also demonstrated that the increase in TS protein induced by 5-FU occurs at the post-transcriptional level and that increased stability and translation efficiency both contributed to the increase in TS protein levels induced by TS inhibitors.

Interaction between Thymidylate Synthase and Its Cognate mRNA in Zebrafish Embryos

Thymidylate synthase (TS), which catalyzes the de novo synthesis of dUMP, is an important target for cancer therapy. In this report, the effects of 5-fluorouracil (5-FU) and ZD1694 on the regulation of TS gene expression were evaluated in zebrafish embryos. Our results revealed that the expression of TS was increased by about six-fold when embryos were treated with 1.0 mu M 5-FU and there was a greater than 10-fold increase in the TS protein level after treatment with 0.4 mu M ZD1694. Northern blot analysis confirmed that expression of TS mRNA was identical in treated or untreated embryos. Gel shift and immunoprecipitation assays revealed that zebrafish TS was specifically bound with its cognate mRNA in vitro and in vivo. We identified a 20 nt RNA sequence, TS:N20, localized to the 5'-UTR of TS mRNA, which corresponded to nt 13-32; TS:N20 bound to the TS protein with an affinity similar to that of the full-length TS mRNA. The MFold program predicted that TS:N20 formed a stable stem-loop structure similar to that of the cis-acting element found in human TS mRNA. Variant RNAs with either a deletion or mutation in the core motif of TS:N20 were unable to bind to the TS protein. In vitro translation experiments, using the rabbit lysate system, confirmed that zebrafish TS mRNA translation was significantly repressed when an excess amount of TS protein was included in the system. Additionally, a TS stability experiment confirmed that treatment of zebrafish embryos with 5-FU could increase the TS stability significantly, and the half life of TS protein was about 2.7 times longer than in untreated embryos. Our study revealed a structural requirement for the interaction of TS RNA with TS protein. These findings also demonstrated that the increase in TS protein induced by 5-FU occurs at the post-transcriptional level and that increased stability and translation efficiency both contributed to the increase in TS protein levels induced by TS inhibitors.

Identification of archaeon-producing hyperthermophilic alpha-amylase and characterization of the alpha-amylase

The extremely thermophilic anaerobic archaeon strain, HJ21, was isolated from a deep-sea hydrothermal vent, could produce hyperthermophilic alpha-amylase, and later was identified as Thermococcus from morphological, biochemical, and physiological characteristics and the 16S ribosomal RNA gene sequence. The extracellular thermostable alpha-amylase produced by strain HJ21 exhibited maximal activity at pH 5.0. The enzyme was stable in a broad pH range from pH 5.0 to 9.0. The optimal temperature of alpha-amylase was observed at 95 degrees C. The half-life of the enzyme was 5 h at 90 degrees C. Over 40% and 30% of the enzyme activity remained after incubation at 100 degrees C for 2 and 3 h, respectively. The enzyme did not require Ca2+ for thermostability. This alpha-amylase gene was cloned, and its nucleotide sequence displayed an open reading frame of 1,374 bp, which encodes a protein of 457 amino acids. Analysis of the deduced amino acid sequence revealed that four homologous regions common in amylases were conserved in the HJ21 alpha-amylase. The molecular weight of the mature enzyme was calculated to be 51.4 kDa, which correlated well with the size of the purified enzyme as shown by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Screening of surfactants for harmful algal blooms mitigation

Screening experiments were conducted in order to find promising synthetic surfactants for harmful algal blooms (HABs) mitigation. The chemically synthesized surfactant cocamidopropyl betaine (CAPB) showed characteristics of relatively high inhibition efficiency, high biodegradability and low cost. The motility inhibition ratios of 10 mg/L CAPB on Cochlodinium polykrikoides and Alexandrium tamarense were about 60% after 5 min. The biodegradation test indicated that the half-life of CAPB in seawater was shorter than one day and 90% was biodegraded after five days under the initial concentration of 100 mg/L at 25degreesC. Further cell lysis experiments revealed the selective lysis effect of CAPB on different HAB organisms. More than 90% of C. polykrikoides lysed at the concentration of 10 mg/L CAPB after 24 h and at 15 mg/L CAPB after 4 h, whereas the lysis effect of CAPB on A. tamarense was slight, no more than 10% after 2 h interaction with 50 mg/L CAPB. This research provided preliminary data for CAPB as a candidate in harmful algal blooms mitigation and pointed out unresolved problems for its practical application in the meantime. (C) 2003 Elsevier Ltd. All rights reserved.

Seasonal variations in growth and clearance rate of the Zhikong scallop Chlamys farreri suspended in the deep water of Haizhou Bay, China

The growth and survival of the Zhikong scallop Chlamys farreri suspended in deep water of Haizhou Bay were studied from July 2007 to June 2008, and the biodeposition method was used to estimate the clearance rate of C. farreri under field conditions. Results showed that the scallop grew fast during all the culture time, with the exception of summer. The condition index of the scallop increased with time and reached the highest value in spring of the second year. The survival of scallops was 60.8 +/- A 3.9% at the end of this study, mortality occurring mainly during the summer and autumn of the first year. The clearance rate fluctuated obviously with season,with the highest value in September 2007, and the lowest value in March 2008. Factors accounting for variations in growth and clearance rate of scallops are also discussed.