Characterization of morphology controlled polyethersulfone hollow fiber membranes by the addition of polyethylene glycol to the dope and bore liquid solution

The preparation of polyethersulfone (PES) hollow fiber membranes has been studied using N-methylpyrrolidone (NMP) as solvent, polyethylene glycol 400 (PEG 400) as weak nonsolvent and water as strong nonsolvent. When PEG 400 is used as polymeric additive to the spinning dope the viscosity of the PES solution is strongly enhanced. Furthermore, it was observed that PEG 400 could be added to the solution in large amounts without causing phase separation (NMP/PEG ratio 1:9, PES concentration approximately 11 wt.%). Membranes prepared from a solution containing a NMP/PEG ratio of 1:1 results in higher fluxes than when a ratio of 1:4 is used. Similar fluxes were obtained for PES concentrations of 16 and 20 wt.%. Looking at the fiber cross-section it became clear that macrovoid formation could not be suppressed by the addition of PEG 400 alone, not even at concentrations as high as 38 wt.%. Only when relatively large amounts of water were added to the dope solution macrovoids disappeared and nice spongy structures were obtained. Variation of the bore liquid composition using the components NMP, PEG 400 and water showed to be a powerful method to control the pore size of the bore surface. Pores of 5–28 nm were obtained in combination with high pure water fluxes; e.g. a membrane with pores of 7 nm had a pure water flux of 940 l/(m2 h bar) and showed 100% BSA retention. When an air gap larger than 10 mm was applied the shell surface contained relatively large pores. Spinning directly in water (airgap=0) resulted in shell side pores of 8–10 nm, while an air gap of 10 mm resulted in pore sizes of 40–54 nm

Public sector reforms, privatisation and regimes of control in a Chinese enterprise

The Chinese economic reform has recently become a major focus of attention around the world. The underlying rationale for the Chinese government's privatisation and public sector reforms is the view that reformed state enterprises and privately managed firms will demonstrate superior management control and better performance, and hence encourage economic growth and employment. There are very few intensive case studies published in English journals studying whether firms privatised in China have reversed previous losses and introduced better management controls, leading to increased investment, productivity, and overall organizational effectiveness and efficiency. The researchers do not seek to deny the control problems of Chinese SOEs, but question the consequences of the new controls installed during the post-privatisation period. The paper also reveals a declining tendency in employment; altered distributions of wealth ? especially to the state ? and labour, and a lack of improvements in the accountability of privatised companies. Overall, the paper argues, the aims of reform policies in China, including better control, increased profitability and an improved working life for Chinese people, have not materialized. The paper calls for more research on the above issues in the Chinese context

Quantum phase transition of condensed bosons in optical lattices

In this paper we study the superfluid-Mott-insulator phase transition of ultracold dilute gas of bosonic atoms in an optical lattice by means of Green function method and Bogliubov transformation as well. The superfluid- Mott-insulator phase transition condition is determined by the energy-band structure with an obvious interpretation of the transition mechanism. Moreover the superfluid phase is explained explicitly from the energy spectrum derived in terms of Bogliubov approach.Comment: 13 pages, 1 figure

Added Alkane Allows Thermal Thinning of Supramolecular Columns by Forming Superlattice-An X-ray and Neutron Study.

We report a columnar superlattice formed by blends of dendron-like Li 3,4,5-tris(n-alkoxy)benzoates with n-alkanes. Without the alkane, the wedge-shaped molecules form liquid crystal columns with 3 dendrons in a supramolecular disk. The same structure exists in the blend, but on heating one dendron is expelled from the disks in every third column and is replaced by the alkane. This superlattice of unequal columns is confirmed by complementary X-ray and neutron diffraction studies. Lateral thermal expansion of dendrons normally leads to the expulsion of excess molecules from the column, reducing the column diameter. However, in the already narrow columns of pure Li salt, expulsion of one of only three dendrons in a disk is not viable. The added alkane facilitates the expulsion, as it replaces the missing dendron. Replacing the alkane with a functional compound can potentially lead to active nanoarrays with relatively large periodicity by using only small molecules

Complex-valued Burgers and KdV-Burgers equations

Spatially periodic complex-valued solutions of the Burgers and KdV-Burgers equations are studied in this paper. It is shown that for any sufficiently large time T, there exists an explicit initial data such that its corresponding solution of the Burgers equation blows up at T. In addition, the global convergence and regularity of series solutions is established for initial data satisfying mild conditions

Nucleon-nucleon momentum correlation function for light nuclei

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.Comment: Talk given at the 18th International IUPAP Conference on Few-Body Problems in Physics (FB18), Santos, Brasil, August 21-26, 2006. To appear in Nucl. Phys.

Search for Fragmented M1 Strength in 48-Ca

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Detection of quasi-periodic micro-structure in three millisecond pulsars with the Large European Array for Pulsars

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