Exactly separable version of the Bohr Hamiltonian with the Davidson potential

An exactly separable version of the Bohr Hamiltonian is developed using a potential of the form u(beta)+u(gamma)/beta^2, with the Davidson potential u(beta)= beta^2 + beta_0^4/beta^2 (where beta_0 is the position of the minimum) and a stiff harmonic oscillator for u(gamma) centered at gamma=0. In the resulting solution, called exactly separable Davidson (ES-D), the ground state band, gamma band and 0_2^+ band are all treated on an equal footing. The bandheads, energy spacings within bands, and a number of interband and intraband B(E2) transition rates are well reproduced for almost all well-deformed rare earth and actinide nuclei using two parameters (beta_0, gamma stiffness). Insights regarding the recently found correlation between gamma stiffness and the gamma-bandhead energy, as well as the long standing problem of producing a level scheme with Interacting Boson Approximation SU(3) degeneracies from the Bohr Hamiltonian, are also obtained.Comment: 35 pages, 11 postscript figures, LaTe

High-spin States in \u3csup\u3e191, 193\u3c/sup\u3eAu and \u3csup\u3e192\u3c/sup\u3ePt: Evidence for Oblate Deformation and Triaxial Shapes

High-spin states of 191, 193Au and 192Pt have been populated in the 186W(11B, xn) and 186W(11B, p4n) reactions, respectively, at a beam energy of 68 MeV and their γ decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory at Yale University. The level scheme of 193Au has been extended up to Iπ = 55/2+. New transitions were observed also in 191Au and 192Pt. Particle-plus-Triaxial-Rotor (PTR) and Total Routhian Surface (TRS) calculations were performed to determine the equilibrium deformations of the Au isotopes. The predictions for oblate deformations in these nuclei are in agreement with the experimental data. Development of nonaxial shapes is discussed within the framework of the PTR model

Triaxial Deformation and Nuclear Shape Transition in \u3csup\u3e192\u3c/sup\u3eAu

Background: Nuclei in the A≈190 mass region show gradual shape changes from prolate through nonaxial deformed shapes and ultimately towards spherical shapes as the Pb region is approached. Exploring how this shape evolution occurs will help us understand the evolution of collectivity in this region. Purpose: The level scheme of the 192Au nucleus in A ≈ 190 region was studied in order to deduce its deformations. Methods: High-spin states of 192Au have been populated in the 186W(11B, 5n) reaction at a beam energy of 68 MeV and their γ decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory (WNSL), Yale University. Results: Based on double and triple γ-ray coincidence data the level scheme of 192Au has been extended up to Iπ = 32+ at an excitation energy of ∼6 MeV. Conclusion: The results are discussed in the framework of pairing and deformation self-consistent total Routhian surface (TRS) and cranked shell model (CSM) calculations. The comparison of the experimental observations with the calculations indicates that this nucleus takes a nonaxial shape similar to other Au nuclei in this region

ADAMTS4 and ADAMTS5 Knockout Mice Are Protected from Versican but Not Aggrecan or Brevican Proteolysis during Spinal Cord Injury

The chondroitin sulfate proteoglycans (CSPGs) aggrecan, versican, and brevican are large aggregating extracellular matrix molecules that inhibit axonal growth of the mature central nervous system (CNS). ADAMTS proteoglycanases, including ADAMTS4 and ADAMTS5, degrade CSPGs, representing potential targets for ameliorating axonal growth-inhibition by CSPG accumulation after CNS injury. We investigated the proteolysis of CSPGs in mice homozygous for Adamts4 or Adamts5 null alleles after spinal cord injury (SCI). ADAMTS-derived 50-60 kDa aggrecan and 50 kDa brevican fragments were observed in Adamts4−/−, Adamts5−/−, and wt mice but not in the sham-operated group. By contrast Adamts4−/− and Adamts5−/− mice were both protected from versican proteolysis with an ADAMTS-generated 70 kDa versican fragment predominately observed in WT mice. ADAMTS1, ADAMTS9, and ADAMTS15 were detected by Western blot in Adamts4−/− mice' spinal cords after SCI. Immunohistochemistry showed astrocyte accumulation at the injury site. These data indicate that aggrecan and brevican proteolysis is compensated in Adamts4−/− or Adamts5−/− mice by ADAMTS proteoglycanase family members but a threshold of versican proteolysis is sensitive to the loss of a single ADAMTS proteoglycanase during SCI. We show robust ADAMTS activity after SCI and exemplify the requirement for collective proteolysis for effective CSPG clearance during SCI

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions

In this comprehensive review, we report on the preparation of graft-copolymers of cellulose and cellulose derivatives using atom transfer radical polymerization (ATRP) under homogeneous conditions. The review is divided into four sections according to the cellulosic material that is graft-copolymerised; (i) cellulose, (ii) ethyl cellulose, (iii) hydroxypropyl cellulose and (iv) other cellulose derivatives. In each section, the grafted synthetic polymers are described as well as the methods used for ATRP macro-initiator formation and graft-copolymerisation. The physical properties of the graft-copolymers including their self-assembly in solution into nanostructures and their stimuli responsive behaviour are described. Potential applications of the self-assembled graft copolymers in areas such as nanocontainers for drug delivery are outline

Adsorption of hexavalent chromium from aqueous solutions using 4-vinyl pyridine grafted poly(ethylene terephthalate) fibers

Arslan, Metin/0000-0001-9432-6877WOS: 000232030400005Sorption of hexavalent chromium ions from aqueous solution by 4- vinyl pyridine (4-VP) grafted poly(ethylene terephthalate) (PET) fibers was studied. The Influences of adsorption time, pH of solution and Cr(VI) concentration on the adsorbed amount were investigated. 30 minutes of treatment time was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value in the process. The maximum adsorption capacity of the material (k(s)) was found to be 263.16 mg g(-1). It was found that the reactive fibers are stable and regenerable by acid or base without losing their activity

The study of kinetic models for ligand exchange of anions as ligands using ligand-exchange resin

Ersoz, Mustafa/0000-0002-9409-9157WOS: A1997WU50400024A comparative study of kinetic models for ligand exchange of I- --> Cl- and Br- --> Cl- as ligands as a function of pH and concentration using diaminoethyl-sporopollenin (DAE-sporopollenin) resin were investigated during the ligand-exchange reaction of the liquid phase. A batch technique was employed for the study of the kinetics of I and Br/Cl exchange as ligands. Five kinetic models were applied to the experimental data. The rate of ligand exchange was increased with decreasing of the hydrated ionic radius and pH. The curve fitting of the mathematical models and the behavior of the kinetic curves are discussed for direct ligand exchange under the conditions employed. (C) 1997 John Wiley & Sons, Inc