https://www.uni-lj.si/mma/biomedicina%20Macek%20Influenza%20virus%20budding/2013090613550890/

Influenza virus assembly and budding.

Influenza Virus M2 Protein Mediates ESCRT-Independent Membrane Scission

The Interferon-Inducible Protein Viperin Inhibits Influenza Virus Release by Perturbing Lipid Rafts

https://escholarship.org/content/qt7548q7cp/qt7548q7cp.pdf?t=qaem19

Assembly and budding of influenza virus.

We derive a stochastic nonlinear continuum theory to describe the morphological evolution of amorphous surfaces eroded by ion bombardment. Starting from Sigmund's theory of sputter erosion, we calculate the coefficients appearing in the continuum equation in terms of the physical parameters characterizing the sputtering process. We analyze the morphological features predicted by the continuum theory, comparing them with the experimentally reported morphologies. We show that for short time scales, where the effect of nonlinear terms is negligible, the continuum theory predicts ripple formation. We demonstrate that in addition to relaxation by thermal surface diffusion, the sputtering process can also contribute to the smoothing mechanisms shaping the surface morphology. We explicitly calculate an effective surface diffusion constant characterizing this smoothing effect, and show that it is responsible for the low temperature ripple formation observed in various experiments. At long time scales the nonlinear terms dominate the evolution of the surface morphology. The nonlinear terms lead to the stabilization of the ripple wavelength and we show that, depending on the experimental parameters such as angle of incidence and ion energy, different morphologies can be observed: asymptotically, sputter eroded surfaces could undergo kinetic roughening, or can display novel ordered structures with rotated ripples. Finally, we discuss in detail the existing experimental support for the proposed theory, and uncover novel features of the surface morphology and evolution, that could be directly tested experimentally.

Morphology of Ion-Sputtered Surfaces

Doppler broadening of the electron positron annihilation γ-radiation spectra of single crystalline Bi2Sr2CaCu2O8+δ high Tc superconducting sample along the two different crystallographic orientations (c-axis and a–b-plane) have been analyzed by constructing ratio-curves with the reference spectra of defect free 99.9999% pure Al and Cu, respectively. The results indicate that the momentum component (pL) of the 2p electrons of oxygen ions and the 3d electrons of the Cu ions is relatively more towards the c-axis than the a–b-plane.

Doppler broadening measurements of positron annihilation in single crystalline Bi2Sr2CaCu2O8+δ high Tc superconductor along two different crystallographic directions

We report here the development of collinear laser spectroscopy (CLS) system at VECC for the study of hyperfine spectrum and isotopic shift of stable and unstable isotopes. The facility is first of its kind in the country allowing measurement of hyperfine splitting of atomic levels using atomic beams. The CLS system is installed downstream of the focal plane of the existing isotope separator online (ISOL) facility at VECC and is recently commissioned by successfully resolving the fluorescence spectrum of the hyperfine levels in $$^{85,87}$$
 Rb. The atomic beams of Rb were produced by charge exchange of 8 keV Rb ion beam which were produced, extracted and transported to the charge exchange cell using the ion sources, extractor and the beam-line magnets of the ISOL facility. The laser propagating opposite to the ion / atom beam direction was allowed to interact with the atom beam and fluorescence spectrum was recorded. The experimental set-up and the experiment conducted are reported in detail. The measures needed to be carried out for improving the sensitivity to a level necessary for studying short-lived exotic nuclei have also been discussed.

Development of a collinear laser spectrometer facility at VECC: First test result

Erratum: Comparison of yields of neutron-rich nuclei in proton- and photon-induced 238 U fission [Phys. Rev. C 94, 054605 (2016)]

Triangular and Sawtooth wave generation at RF frequency is one of the important tasks for the design of buncher circuit in particle accelerators to increase the bunching efficiency. On the basis of Fourier series method different non-sinusoidal signals like triangular, sawtooth etc. are generated with combination of harmonics of sinusoidal signal with different amplitude and phase. These multi harmonic non-sinusoidal waves can be generated using passive RF components like phase-shifter, hybrid-coupler, power combiner/divider etc. This paper deals with lumped element approach for design and implementation of line phase shifters, 3-dB hybrid coupler and power divider/combiner, which have been used for the generation of triangular and saw tooth wave forms at 25 MHz. The ABCD (transfer) matrix formulation is used for the analytical prediction of the performance of these components. Experiments have been carried out to validate the analytical results.

Design and implementation of multi-hormonics RF wave generator using lumped-element components

It is shown, using density matrix calculation, that high precision two-dimensional (2D) atom localization in V-type system can be achieved by applying an additional microwave coupling field between the excited states. In the present scheme, two lasers, probe and pump, form a V-type system by coupling the ground state to the excited states while an additional 2D standing microwave field is used to couple the excited states. The solutions of the density matrix equations reveal that the off-diagonal density matrix element $\rho_{31}$, which signify the coherence between the states connected by the probe laser, is position dependent. As the imaginary part of $\rho_{31}$ is proportional to the imaginary part of the susceptibility, the probe absorption also becomes position dependent and in this situation one can readily obtain information about the atom position from the probe absorption spectra. Perfect 2D atom localization can be achieved by carefully selecting different system parameters such as detuning, relative phase, dephasing and field strength. It is found that the atom localization is highly dependent on the probe and coupling field detuning values. In view of this, a systematic study is performed on the system parameters and different zones have been identified which give rise to different absorption shapes, e.g. "dip", "wall", "peak" as well as negative absorption or amplification. Probe absorption spectrum is also found to be dependent on relative phase between the applied fields. The dependence of the dephasing parameter on the probe absorption is investigated and found to be detrimental to atom localization. The effect of the microwave coupling strength on "wall" type absorption shape is also studied and the results are discussed. Finally, a possible practical realization of the present scheme is discussed in Conclusion section.

Alok Chakrabarti

Papers

Doppler broadening measurements of positron annihilation in single crystalline Bi2Sr2CaCu2O8+δ high Tc superconductor along two different crystallographic directions

Development of a collinear laser spectrometer facility at VECC: First test result

Erratum: Comparison of yields of neutron-rich nuclei in proton- and photon-induced 238 U fission [Phys. Rev. C 94, 054605 (2016)]

Design and implementation of multi-hormonics RF wave generator using lumped-element components

2D sub-half-wavelength atom localization in a three-level V-type atomic system