Synthetic approaches to biologically active sulfonates and sulfonamides

This research describes the scope of 1,3-dipolar cycloaddition between selected 1,3-dipoles (nitrile oxide/nitrone) and dipolarophiles (PFP ethenesulfonate/PFP-1-bromoethenesulfonate). Nitrile oxide cycloaddition with PFP-1-bromoethenesulfonate furnished 3,5-isoxazoles in a regiospecific fashion; where solvent polarity, reaction temperature and the amount of base are the determining factors for efficient cycloaddition. Subsequent aminolysis with various amines were also carried out. Aminolysis with secondary and aromatic amines produced low yields, nevertheless a wide range of the corresponding sulfonamides were synthesized. A collection of the isoxazolidinyl PFP sulfonate esters, and the corresponding sulfonamides, were found to exhibit anti HIV-1 activity in micromolar scale. Synthesis of the isoxazolidinyl sulfonamides was also diversified in order to investigate the structure-activity relationships. Furthermore, synthesis of the candidate for immobilized medium for affinity chromatography was established, via a multi-step reaction sequence. Biological testing of the synthesized isoxazolidinyl PFP sulfonate esters, and sulfonamides show that the candidate molecules act on the host factors required for viral infection, rather than the virus itself. Furthermore, they show specific activity toward viral targets and do not exhibit toxicity toward live cells

Pseudo-Hall effect and anisotropic magnetoresistance in a micronscale Ni80Fe20 device

The pseudo-Hall effect (PHE) and anisotropic magnetoresistance (AMR) in a micronscale Ni80Fe20, six-terminal device, fabricated by optical lithography and wet chemical etching from a high quality UHV grown 30 Angstrom Au/300 Angstrom Ni80Fe20 film, have been studied. The magnetisation reversal in different parts of the device has been measured using magneto-optical Kerr effect (MOKE), The device gives a 50% change in PHE voltage with an ultrahigh sensitivity of 7.3%Oe(-1) at room temperature. The correlation between the magnetisation, magneto-transport properties, lateral shape of the device and directions of the external applied field is discussed based on extensive MOKE, AMR and PHE results

Enhancing Organizational Performance: An Investigation of the Impact of Employees’ Commitment

The purpose of this study is to investigate the impact of employee commitment on organizational performance in a paper manufacturing industry in Melaka, Malaysia.  Three components of employee commitments (Affective Commitment, Normative Commitment and Continuance Commitment) were identified as the independent variables and organizational performance as the dependent variables.  The data was collected using a survey from 150 employees of the paper manufacturing company.  Statistical Package for Social Science (SPSS) was used to analyze the data collected from the respondents.  Correlation and regression analysis were performed to determine the association between the dependent and independent variables.  The research findings revealed that affective and continuance commitments have effects on organizational performance while normative commitment has no significant effect on organizational performance.  These results are significant in guiding top management in deciding the actions that they can take which could have a great impact on the organization performance.  Therefore, top management could focus more on building affective commitment and continuance commitment within the organization to enhance organizational performance

Influence of lateral geometry on magnetoresistance and magnetisation reversal in Ni80Fe20 wires

The magnetisation reversal processes and magnetoresistance behaviour in micron-sized Ni80Fe20 wires with triangular and rectangular modulated width have been studied. The wires were fabricated by electron beam lithography and a lift-off process. A combination of magnetic force microscopy (MFM), magneto-optical Kerr effect (MOKE) and magnetoresistance (MR) measurements shows that the lateral geometry of the wires greatly influences the magnetic and transport properties. The width modulations modify not only the shape-dependent demagnetising fields, but also the current density. The correlation between the lateral geometry, the magnetic and the transport properties is discussed based on MFM, MOKE and MR results

Magnetic domain evolution in permalloy mesoscopic dots

Permalloy (Ni80Fe20) squares (30 nm thick and w mu m wide; 1 less than or equal to w less than or equal to 200 mu m) and circular disks (30 nm thick and r mu m diameter; 1 less than or equal to r less than or equal to 200 mu m) prepared on a GaAs (100) substrate were observed in both their demagnetized and remanent states by magnetic force microscopy (MFM) associated with non-contact atomic force microscopy (NC-AFM). The squares (2 less than or equal to w mu m) exhibited conventional closure domains and the corner plays a very important role in creating new walls. The circular disks, on the other hand, formed either vortex domain (5 less than or equal to r less than or equal to 20 mu m) or multi-domain (50 less than or equal to r mu m) states, The magnetization rotation is observed by MFM to change according to the size and shape of the elements, The MFM observations are supported by micromagnetic calculations which confirm the effect of the corner on the domain wall formation

Magnetization reversal in mesoscopic Ni80Fe20 wires: A magnetic domain launching device

The magnetization reversal process in mesoscopic permalloy (Ni80Fe20) wire structures has been investigated using scanning Kerr microscopy, magnetic force microscopy (MFM) and micromagnetic calculations. We find that the junction offers a site for reversed domain wall nucleation in the narrow part of the wires. As a consequence, the switching field is dominated by the domain nucleation field and the junction region initiates reversal by the wall motion following the nucleation of domains. Our results suggest the possibility of designing structures that can be used to “launch” reverse domains in narrow wires within a controlled field rang

Separation of Cholesterol from other Steroids Using Molecularly Imprinted Polymer Prepared by Seeded Suspension Polymerization

Micron-sized particles of cholesterol-imprinted polymers were synthesized by seeded suspension polymerization in a mixture of 2-propanol and water using polystyrene microbeads as the seeds. Methacrylic acid was employed as the functional monomer to form complexes with template (cholesterol), along with ethylene glycol dimethacrylate as the crosslinker. After removal of template molecules, the columns ( H=15 cm, Di= 0.46 cm ) packed with cholesterol-imprinted polymers were effective for the chromatographic separation of cholesterol from other steroids. When the sample of steroids was eluted isocratically at a flow-rate of Q = 0.5 mL min-1, using a mixture of acetonitrile and water (Ψ= 95:5) as the mobile phase, the retention times for estrone, -estradiol and cholesterol were respectively τ = 5.3, 12.3 and 17.2 min. The average retention times were = 5.3, 10.9 and 16.7 min respectively for estrone, progesterone and cholesterol in samples. The separation was based on the specific binding of cholesterol to recognition sites formed on the imprinted polymers. A separation factor of 1.6 for cholesterol and -estradiol was obtained. The chromatographic efficiency was dependent on the mobile phase composition. Reducing the water content in the non-polar mobile phase to zero could significantly enhance the separation. Compared with particles from bulk polymerization, the column packed with cholesterol-imprinted particles from seeded suspension polymerization had a higher chromatographic efficiency and the advantage of microanalysi

Magnetization reversal and magnetic anisotropy in Co network nanostructures

The magnetization reversal and magnetic anisotropy in Co network structures have been studied using magneto-optic Kerr effect (MOKE). An enhancement of the coercivity is observed in the network structures and is attributed to the pinning of domain walls by the hole edges in the vicinity of which the demagnetizing field spatially varies. We find that the magnetization reversal process is dominated by the intrinsic unaxial anisotropy (2K(u)/M(s)approximate to 200 Oe) in spite of the shape anisotropy induced by the hole edges. The influence of the cross-junction on the competition between the intrinsic uniaxial anisotropy and the induced shape anisotropy is discussed using micromagnetic simulations

Renormalization Effects in a Dilute Bose Gas

The low-density expansion for a homogeneous interacting Bose gas at zero temperature can be formulated as an expansion in powers of $\sqrt{\rho a^3}$, where $\rho$ is the number density and $a$ is the S-wave scattering length. Logarithms of $\rho a^3$ appear in the coefficients of the expansion. We show that these logarithms are determined by the renormalization properties of the effective field theory that describes the scattering of atoms at zero density. The leading logarithm is determined by the renormalization of the pointlike $3 \to 3$ scattering amplitude.Comment: 10 pages, 1 postscript figure, LaTe

Energy and Structure of Hard-Sphere Bose Gases in three and two dimensions

The energy and structure of dilute gases of hard spheres in three dimensions is discussed, together with some aspects of the corresponding 2D systems. A variational approach in the framework of the Hypernetted Chain Equations (HNC) is used starting from a Jastrow wavefunction that is optimized to produce the best two--body correlation factor with the appropriate long range. Relevant quantities describing static properties of the system are studied as a function of the gas parameter $x=\rho a^d$ where $\rho$, $a$ and $d$ are the density, $s$--wave scattering length of the potential and dimensionality of the space, respectively. The occurrence of a maximum in the radial distribution function and in the momentum distribution is a natural effect of the correlations when $x$ increases. Some aspects of the asymptotic behavior of the functions characterizing the structure of the systems are also investigated.Comment: Proceedings of the QFS2004 conference in Trento. To appear in JLT