Alpha decay half-lives of heavy nuclei within a generalized liquid drop model

Theoretical alpha-decay half-lives of the heaviest nuclei are calculated using the experimental Q value. The barriers in the quasi-molecular shape path is determined within a Generalized Liquid Drop Model (GLDM) and the WKB approximation is used. The results are compared with calculations using the Density-Dependent, M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulae. The calculations provide consistent estimates for the half-lives of the a decay chains of these superheavy elements. The experimental data stand between the GLDM calculations and VSS ones in the most time.

Properties of alpha-decay to ground and excited states of heavy nuclei

Branching ratios and half-lives of alpha-decay to the ground-state rotational bands as well as the high-lying excited states of even-even nuclei have been calculated in the framework of the generalized liquid drop model (GLDM) and Royer's formula that we improved very recently. The calculation covers the isotopic chains from Ra to No in the mass regions 222 <= A <= 252 and 88 <= Z <= 102. The agreement between the calculated results and the experimental data indicates the reliability of investigating the properties of the unfavored alpha-decay with our method, especially the improved Royer's formula, which is very valuable for the analysis of experimental data. In addition, the dependence of half-lives on excitation energies of daughter nuclei has been investigated. It is shown that the influence on half-lives becomes stronger and stronger with the increase of the excitation energies.

alpha-decay half-lives and Q(alpha) values of superheavy nuclei

The alpha-decay half-lives of recently synthesized superheavy nuclei (SHN) are investigated by employing a unified fission model (UFM) where a new method to calculate the assault frequency of alpha emission is used. The excellent agreement with the experimental data indicates the UFM is a useful tool to investigate these alpha decays. It is found that the alpha-decay half-lives become more and more insensitive to the Q(alpha) values as the atomic number increases on the whole, which is favorable for us to predict the half-lives of SHN. In addition, a formula is proposed to compute the Q(alpha) values for the nuclei with Z >= 92 and N >= 140 with a good accuracy, according to which the long-lived SHN should be neutron rich. Several weeks ago, two isotopes of a new element with atomic number Z = 117 were synthesized and their alpha-decay chains have been observed. The Q(alpha) formula is found to work well for these nuclei, confirming its predictive power. The experimental half-lives are well reproduced by employing the UFM with the experimental Q(alpha) values. This fact that the experimental half-lives are compatible with experimental Q(alpha) values supports the synthesis of a new element 117 and the experimental measurements to a certain extent.

Synthesis and characterization of polyethylene chains grafted onto the sidewalls of single-walled carbon nanotubes via copolymerization

Polyethylene (PE) chains grafted onto the sidewalls of SWCNTs (SWCNT-g-PE) were successfully synthesized via ethylene copolymerization with functionalized single-walled carbon nanotubes (f-SWCNTs) catalyzed by rac-(en)(THInd)(2)ZrCl2/ MAO. Here f-SWCNTs, in which alpha-alkene groups were chemically linked on the sidewalls of SWCNTs, were synthesized by Prato reaction. The composition and microstructure of SWCNT-g-PE were characterized by means of H-1 NMR, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA), field-emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Nanosized cable-like structure was formed in the SWCNT-g-PE, in which the PE formed a tubular shell and several SWCNTs bundles existed as core. The formation of the above morphology in the SWCNT-g-PE resulted from successfully grafting of PE chains onto the surface of SWCNTs via copolymerization. The grown PE chains grafted onto the sidewall of the f-SWCNTs promoted the exfoliation of the mass nanotubes. Comparing with pure PE, the physical mixture of PE/f-SWCNTs and in situ PE/SWCNTs mixture, thermal stability, and mechanical properties of SWCNT-g-PE were higher because of the chemical bonding between the f-SWCNTs and PE chains.

Study of beta-alpha recrystallization of the polypropylene

The crystalline modifications alpha and beta of polypropylene (PP) were studied by using polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Typically beta crystals surrounded by alpha spherulites were observed at low temperature. With increasing temperature the beta crystals melted and a new crystal appeared. More interestingly, the melting temperature of the new crystal was about 5degrees higher than that of alpha spherulites originally present in the sample formed isothermally. It was assumed that this new crystal was the recrystalline alpha crystal. This assumption was supported by the DSC results. Furthermore, the crystallization kinetics of the PP used was studied on the basis of the traditional Avrami analysis. As a result, the Avrami exponents of crystallization temperature from 120 to 130degreesC ranged between 4.21 and 3.60, indicating that the crystallization mechanism of PP order melt was spherulitic growth and random nucleation.

Novel hydrogen-bonded three-dimensional networks encapsulating one-dimensional covalent chains: [M(4,4 '-bipy)(H2O)4](4-abs)2 center dot nH(2)O (4,4 '-bipy=4,4 '-Bipyridine; 4-abs=4-aminobenzenesulfonate) (M=Co, n=1; M=Mn, n=2)

Two novel compounds, [Co(4,4'-bipy)(H2O)(4)](4-abS)(2).H2O (1) and [Mn(4,4'-bipy)(H2O)(4)](4-abs)(2).2H(2)O (2) (4,4'-bipy = 4,4'-bipyridine; 4-abs = 4-aminobenzenesulfonate), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses, UV-vis and IR spectra, and TG analysis. X-ray structural analysis revealed that 1 and 2 both possess unusual hydrogen-bonded three-dimensional (3-D) networks encapsulating one-dimensional (1-D) covalently bonded infinite [M(4,4'-bipy)(H2O)(4)](2+) (M = Co, Mn) chains. The 4-abs anions in 1 form 1-D zigzag chains through hydrogen bonds. These chains are further extended through crystallization water molecules into 3-D hydrogen-bonded networks with 1-D channels, in which the [Co(4,4'-bipy)(H2O)(4)](2+) linear covalently bonded chains are located. Crystal data for 1: C22H30CoN4O11S2, monoclinic P2(1), a = 11.380(2) Angstrom, b = 8.0274(16) Angstrom, c = 15.670(3) Angstrom, alpha = gamma = 90degrees, beta = 92.82(3)degrees, Z = 2. Compound 2 contains interesting two-dimensional (2-D) honeycomb-like networks formed by 4-abs anions and lattice water molecules via hydrogen bonding, which are extended through other crystallization water molecules into three dimensions with 1-D hexagonal channels. The [Mn(4,4'-bipy)(H2O)(4)](2+) linear covalent chains exist in these channels. Crystal data for 2: C22H32WN4O12S2, monoclinic P2(1)/c, a = 15.0833(14) Angstrom, b = 8.2887(4) Angstrom, c = 23.2228(15) Angstrom, alpha = gamma = 90degrees, beta = 95.186(3)degrees, Z = 4.

Studies on enzymological properties of antibody elicited by meso-tetra(alpha, alpha, alpha, alpha-O-phenylacetyl benzene)porphyrin

meso-Tetra (alpha, alpha, alpha, alpha-O-phenylacetyl benzene) porphyrin was used as a complete antigen to elicit monoclonal antibody 1F2 through the immunization and cell fusion techniques. McAb 1F2 obtained was demonstrated very pure by HPLC and MALDI/TOFMS. The retention time of McAb 1F2 was 2. 63 min. The subtype of McAb 1F2 was IgG2a. The relative molecular weight was 156 678. 8. When the McAb 1F2-porphyrin was formed, the maximal absorption of the porphyrin soret region had a redshift from 408 to 416 nm and hyperchromical effect, showing that the antigen-antibody combination was rigid and intense, and the abzyme constancy was high. But compared with HRP, the activity of the abzyme was only 4. 687 5 U/mg and 1. 899 % of that of HRP. Its K-m was 20. 29 mmol/L, k(cat) 396. 82 min(-1), k(cat)/K-m. 1. 955 7 X 10(4) L . mol(-1) . min(-1).

A novel epitaxy of isotactic polypropylene (alpha phase) on PTFE and organic substrates

Isotactic polypropylene in its a modification (alpha iPP) crystallises epitaxially on polytetrafluoroethylene (PTFE) and several hemiacids or salts of substituted benzoic acids via a novel contact plane, namely (110): so far, the only known contact plane involved in alpha iPP homo- and hetero-epitaxies was (010). In spite of its complicated architecture (alternation of antichiral helices with different azimuthal settings), the (110)(alpha iPP) contact plane displays well defined, if not prominent, rows of methyl side chains parallel to the crystallographic (112) direction (at 57 degrees to the c-axis) and approximate to 5.5 Angstrom apart. The matching contact planes of the substrates display linear gratings made of rows of e.g. chlorine atoms or PTFE chains with similar approximate to 5.5 Angstrom inter-row or interchain distances. Various morphologies are observed in iPP thin films crystallised at different cooling rates in the presence of PTFE; they can be analysed in terms of a succession and interplay of successive epitaxies: initial alpha iPP/PTFE heteroepitaxy, followed by alpha iPP/alpha iPP and gamma iPP/alpha iPP homoepitaxies. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

SYNTHESIS AND CHARACTERIZATION OF ALPHA,BETA-TRIINDIUM SUBSTITUTED HETEROPOLYTUNGSTATES

The complexes of alpha,beta-K(a)H(b)XW(9)O(37)(InH2O)(3) . xH(2)O (X = Si, Ge; a+b = 7) were synthesized from their lacunary precursors alpha,beta-XW(9)O(34)(10-) (X = Si, Ge) and characterized by elemental analysis, W-183 NMR, IR and UV spectroscopy and polarography. W-183 NMR spectra of the title complexes consist of two lines with intensity ratio 2:1, as expected for the C-3 nu structure of trisubstituted A alpha- and A beta-Keggin anions.

Thermodynamics of the displacive mechanism of alpha(1) transformation in a beta

Thermodynamics of the displacive mechanism of plate-shaped phase alpha(1) was analyzed in beta'Cu-Zn alloys. It was proposed that the displacive transformation of the alpha(1) plate took place in the solute-depleted region formed in the parent phase during the incubation period. The thermodynamic analysis indicated that the driving force of alpha(1) transformation, Delta G, increased with the reduction of x(d), the solute concentration of the depleted region. And, Delta G could overcome-the transformation barrier with solute depletion to a certain degree. In addition, x(d) was higher than the equilibrium concentration in the phase diagram. Therefore, the shear formation of alpha(1) plate in the solute-depleted region was thermodynamically supported.

Pressure and thermal effects on elastic properties of single crystal alpha-Al2O3 from Monte-Carlo simulation

A rectangular structural unit cell of a-Al2O3 is generated from its hexagonal one. For the rectangular structural crystal with a simple interatomic potential [Matsui, Mineral Mag. 58A, 571 (1994)], the relations of lattice constants to homogeneous pressure and temperature are calculated by using Monte-Carlo method at temperature 298K and 0 GPa, respectively. Both numerical results agree with experimental ones fairly well. By comparing pair distribution function, the crystal structure of a-Al2O3 has no phase transition in the range of systematic parameters. Based on the potential model, pressure dependence of isothermal bulk moduli is predicted. Under variation of general strains, which include of external and internal strains, elastic constants of a-Al2O3 in the different homogeneous load are determined. Along with increase of pressure, axial elastic constants increase appreciably, but nonaxial elastic constants are slowly changed.

Molecular dynamics studies on dislocations in crystallites of nanocrystalline alpha-iron

Molecular dynamics simulations have been carried our to study the atomic structure of the crystalline component of nanocrystalline alpha-iron. A two-dimensional computational block is used to simulate the consolidation process. It is found that dislocations are generated in the crystallites during consolidation when the grain size is large enough. The critical value of the grain size for dislocation generation appears to be about 9 nm. This result agrees with experiment qualitatively. AN dislocations that are preset in the original grains glide out during consolidation. It shows that dislocations in the crystallites we generated in consolidation process, but not in the original grains. Higher consolidation pressure results in more dislocations. Furthermore, new interfaces are found within crystallites. These interfaces might result from the special environment of nanomaterial. (C) 1998 Acta Metallurgica Inc.

Dislocations in the crystallites of nanocrystalline alpha-Fe - A molecular dynamics study

Molecular dynamics simulations are carried out in order to study the atomic structure of crystalline component, of nanocrystalline alpha-Fe when it is consolidated from small grains. A two-dimensional computational block is used to simulate the consolidation process. All the preset dislocations in the original grains glide out of them in the consolidation process, but new dislocations can generate when the grain size is large enough. It shows that dislocations exist in the consolidated material rather than in the original grains. Whether dislocations exist in the crystalline component of the resultant model nana-material depends upon grain size. The critical value of grain size for dislocation generation appears to be about 9 nm. This result agrees with experiments qualitatively.

A study on stratification of concentration in crystal-growth of alpha-liio3 by holographic-interferometry

A new thermoplastic-photoconductor laser holographic recording system has been used for real-time and in situ observation of alpha-LiIO3 crystal growth. The influence of crystallization-driven convection on the concentration stratification in solution has been studied under gravity field. It is found that the stratification is closely related to the seed orientation of alpha-LiIO3 crystal. When the optical axis of crystal seed C is parallel to the gravity vector g, the velocity of the concentration stratification is two times larger than that in the case of C perpendicular-to g. It needs 40 h for the crystalline system of alpha-LiIO3 to reach stable concentration distribution (expressed as tau) at 47.6-degrees-C. The time tau is not sensitive to the seed orientation. Our results provide valuable data for designing the crystal growth experiments ia space.