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Engineering a serum-resistant and thermostable vesicular stomatitis virus G glycoprotein for pseudotyping retroviral and lentiviral vectors.
Vesicular stomatitis virus G glycoprotein (VSV-G) is the most widely used envelope protein for retroviral and lentiviral vector pseudotyping; however, serum inactivation of VSV-G pseudotyped vectors is a significant challenge for in vivo gene delivery. To address this problem, we conducted directed evolution of VSV-G to increase its resistance to human serum neutralization. After six selection cycles, numerous common mutations were present. On the basis of their location within VSV-G, we analyzed whether substitutions in several surface exposed residues could endow viral vectors with higher resistance to serum. S162T, T230N and T368A mutations enhanced serum resistance, and additionally K66T, T368A and E380K substitutions increased the thermostability of VSV-G pseudotyped retroviral vectors, an advantageous byproduct of the selection strategy. Analysis of a number of combined mutants revealed that VSV-G harboring T230N+T368A or K66T+S162T+T230N+T368A mutations exhibited both higher in vitro resistance to human serum and higher thermostability, as well as enhanced resistance to rabbit and mouse serum. Finally, lentiviral vectors pseudotyped with these variants were more resistant to human serum in a murine model. These serum-resistant and thermostable VSV-G variants may aid the application of retroviral and lentiviral vectors to gene therapy
Dominant mobility modulation by the electric field effect at the LaAlO_3 / SrTiO_3 interface
Caviglia et al. [Nature (London) 456, 624 (2008)] have found that the
superconducting LaAlO_3 / SrTiO_3 interface can be gate modulated. A central
issue is to determine the principal effect of the applied electric field. Using
magnetotransport studies of a gated structure, we find that the mobility
variation is almost five times as large as the sheet carrier density.
Furthermore, superconductivity can be suppressed at both positive and negative
gate bias. These results indicate that the relative disorder strength strongly
increases across the superconductor-insulator transition.Comment: 4 pages, 4 figure
Anisotropic strains and magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3}
Thin films of perovskite manganite La_{0.7}Ca_{0.3}MnO_{3} were grown
epitaxially on SrTiO_3(100), MgO(100) and LaAlO_3(100) substrates by the pulsed
laser deposition method. Microscopic structures of these thin film samples as
well as a bulk sample were fully determined by x-ray diffraction measurements.
The unit cells of the three films have different shapes, i.e., contracted
tetragonal, cubic, and elongated tetragonal for SrTiO_3, MgO, and LaAlO_3
cases, respectively, while the unit cell of the bulk is cubic. It is found that
the samples with cubic unit cell show smaller peak magnetoresistance than the
noncubic ones do. The present result demonstrates that the magnetoresistance of
La_{0.7}Ca_{0.3}MnO_{3} can be controlled by lattice distortion via externally
imposed strains.Comment: Revtex, 10 pages, 2 figure
Electron-boson spectral density of LiFeAs obtained from optical data
We analyze existing optical data in the superconducting state of LiFeAs at 4 K, to recover its electron-boson spectral density. A maximum entropy
technique is employed to extract the spectral density from
the optical scattering rate. Care is taken to properly account for elastic
impurity scattering which can importantly affect the optics in an -wave
superconductor, but does not eliminate the boson structure. We find a robust
peak in centered about 8.0 meV or 5.3 (with 17.6 K). Its position in energy agrees well with a similar
structure seen in scanning tunneling spectroscopy (STS). There is also a peak
in the inelastic neutron scattering (INS) data at this same energy. This peak
is found to persist in the normal state at 23 K. There is evidence that
the superconducting gap is anisotropic as was also found in low temperature
angular resolved photoemission (ARPES) data.Comment: 17 pages, 6 figure
Parity violation in deuteron photo-disintegration
We analyze the energy dependence for two types of parity-non-conserving
(PNC) asymmetries in the reaction in the near-threshold
region. The first one is the asymmetry in reaction with circularly polarized
photon beam and unpolarized deuteron target. The second one corresponds to
those with an unpolarized photon beam and polarized target. We find that the
two asymmetries have quite different energy dependence, and their shapes are
sensitive to the PNC-meson exchange coupling constants.
The predictions for the future possible experiments to provide definite
constraints for the PNC-coupling constants are discussed.Comment: 22 pages, 12 figures. Submitted to Phys.Rev.C 10Oct.0
A review of near-wall Reynolds-stress
The advances made in second-order near-wall turbulence closures are summarized. All closures examined are based on some form of high Reynolds number models for the Reynolds stress and the turbulent kinetic energy dissipation rate equations. Consequently, most near-wall closures proposed to data attempt to modify the high Reynolds number models for the dissipation rate equation so that the resultant models are applicable all the way to the wall. The near-wall closures are examined for their asymptotic behavior so that they can be compared with the proper near-wall behavior of the exact equations. A comparison of the closure's performance in the calculation of a low Reynolds number plane channel flow is carried out. In addition, the closures are evaluated for their ability to predict the turbulence statistics and the limiting behavior of the structure parameters compared to direct simulation data
Studies of new media radiation induced laser
Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed
Non-abelian dynamics in first-order cosmological phase transitions
Bubble collisions in cosmological phase transitions are explored, taking the
non-abelian character of the gauge fields into account. Both the QCD and
electroweak phase transitions are considered. Numerical solutions of the field
equations in several limits are presented.Comment: 8 pages, 2 figures. Contribution to the CosPA 2003 Cosmology and
Particle Astrophysics Symposium. Typos correcte
Unified Analysis of Cosmological Perturbations in Generalized Gravity
In a class of generalized Einstein's gravity theories we derive the equations
and general asymptotic solutions describing the evolution of the perturbed
universe in unified forms. Our gravity theory considers general couplings
between the scalar field and the scalar curvature in the Lagrangian, thus
includes broad classes of generalized gravity theories resulting from recent
attempts for the unification. We analyze both the scalar-type mode and the
gravitational wave in analogous ways. For both modes the large scale evolutions
are characterized by the same conserved quantities which are valid in the
Einstein's gravity. This unified and simple treatment is possible due to our
proper choice of the gauges, or equivalently gauge invariant combinations.Comment: 4 pages, revtex, no figure
Role of Charged Gauge Fields in Generating Magnetic Seed Fields in Bubble Collisions during the Cosmological Electroweak Phase Transition
We calculate the magnetic field generated during bubble collisions in a
first-order electroweak phase transition that may occur for some choices of
parameters in the minimal supersymmetric Standard Model. We show that for
sufficiently gentle collisions, where the Higgs field is relatively unperturbed
in the bubble overlap region, the equations of motion can be linearized so that
in the absence of fermions the charged W fields are the source of the
electromagnetic current for generating the seed fields. Solutions of the
equations of motion for the charged gauge fields and Maxwell's equations for
the magnetic field in O(1,2) space-time symmetry are expressed in closed form
by applying boundary conditions at the time of collision. Our results indicate
that the magnetic fields generated by charged fields in the collision
are comparable to those found in previous work. The magnetic fields so produced
could seed galactic and extra-galactic magnetic fields observed today.Comment: 15 Pages, 7 Figure
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