Deformation of a flexible fiber in a viscous flow past an obstacle

We study the deformation and transport of elastic fibers in a viscous Hele-Shaw flow with curved streamlines. The variations of the global velocity and orientation of the fiber follow closely those of the local flow velocity. The ratios of the curvatures of the fibers by the corresponding curvatures of the streamlines reflect a balance between elastic and viscous forces: this ratio is shown experimentally to be determined by a dimensionless {\it Sperm number} $Sp$ combining the characteristic parameters of the flow (transverse velocity gradient, viscosity, fiber diameter/cell gap ratio) and those of the fiber (diameter, effective length, Young's modulus). For short fibers, the effective length is that of the fiber; for long ones, it is equal to the transverse characteristic length of the flow. For $S\_p \lesssim 250$, the ratio of the curvatures increases linearly with $Sp$; For $S\_p \gtrsim 250$, the fiber reaches the same curvature as the streamlines

H3++H_3^{++} molecular ions can exist in strong magnetic fields

Using the variational method it is shown that for magnetic fields $B\geq 10^{11}$ G there can exist a molecular ion $H_3^{++}$.Comment: LaTeX, 7 pp, 1 table, 4 figures. Title modified. Consideration of the longitudinal size of the system was adde

Human papillomavirus E2 regulates SRSF3 (SRp20) to promote capsid protein expression in infected differentiated keratinocytes

The human papillomavirus (HPV) life cycle is tightly linked to differentiation of the infected epithelial cell suggesting a sophisticated interplay between host cell metabolism and virus replication. Previously we demonstrated in differentiated keratinocytes in vitro and in vivo that HPV16 infection caused increased levels of the cellular SR splicing factors (SRSFs) SRSF1 (ASF/SF2), SRSF2 (SC35) and SRSF3 (SRp20). Moreover, the viral E2 transcription and replication factor that is expressed at high levels in differentiating keratinocytes could bind and control activity of the SRSF1 gene promoter. Here we reveal that E2 proteins of HPV16 and HPV31 control expression of SRSFs 1, 2 and 3 in a differentiation-dependent manner. E2 has the greatest trans-activation effect on expression of SRSF3. siRNA depletion experiments in two different models of the HPV16 life cycle (W12E and NIKS16) and one model of the HPV31 life cycle (CIN612-9E) revealed that only SRSF3 contributed significantly to regulation of late events in the virus life cycle. Increased levels of SRSF3 are required for L1 mRNA and capsid protein expression. Capsid protein expression was regulated specifically by SRSF3 and appeared independent of other SRSFs. Taken together these data suggest a significant role of the HPV E2 protein in regulating late events in the HPV life cycle through transcriptional regulation of SRSF3 expression. IMPORTANCE Human papillomavirus replication is accomplished in concert with differentiation of the infected epithelium. Virus capsid protein expression is confined to the upper epithelial layers so as to avoid immune detection. In this study we demonstrate that the viral E2 transcription factor activates the promoter of the cellular SRSF3 RNA processing factor. SRSF3 is required for expression of the E4̂L1 mRNA and so controls expression of the HPV L1 capsid protein. Thus we reveal a new dimension of virus-host interaction crucial for production of infectious virus. SRSF proteins are known drug targets. Therefore, this study provides an excellent basis for developing strategies to regulate capsid protein production in the infected epithelium and production of new virions

Self-energy correction to the hyperfine structure splitting of the 1s and 2s states in hydrogenlike ions

The one-loop self-energy correction to the hyperfine structure splitting of the 1s and 2s states of hydrogenlike ions is calculated both for the point and finite nucleus. The results of the calculation are combined with other corrections to find the ground state hyperfine splitting in lithiumlike ^{209}Bi^{80+} and ^{165}Ho^{64+}.Comment: The table 2 is changed. 6 pages, 1 figure, Late

Cosmic ray energy changes at the termination shock and in the heliosheath

Voyager 1 crossed the termination shock of the solar wind in December 2004 at 94 AU and currently measures the cosmic ray intensity in the heliosheath. To better understand this modulation region beyond the shock, where adiabatic energy changes should be small, we review the net effect of energy changes during the modulation process, including adiabatic deceleration in the solar wind, acceleration at the termination shock, and the possibility that stochastic acceleration in the heliosheath may also make a contribution

A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere

We report on spectropolarimetric observations of a near-IR line of Mn I located at 15262.702 A whose intensity and polarization profiles are very sensitive to the presence of hyperfine structure. A theoretical investigation of the magnetic sensitivity of this line to the magnetic field uncovers several interesting properties. The most important one is that the presence of strong Paschen-Back perturbations due to the hyperfine structure produces an intensity line profile whose shape changes according to the absolute value of the magnetic field strength. A line ratio technique is developed from the intrinsic variations of the line profile. This line ratio technique is applied to spectropolarimetric observations of the quiet solar photosphere in order to explore the probability distribution function of the magnetic field strength. Particular attention is given to the quietest area of the observed field of view, which was encircled by an enhanced network region. A detailed theoretical investigation shows that the inferred distribution yields information on the average magnetic field strength and the spatial scale at which the magnetic field is organized. A first estimation gives ~250 G for the mean field strength and a tentative value of ~0.45" for the spatial scale at which the observed magnetic field is horizontally organized.Comment: 42 pages, 17 figures, accepted for publication in the Astrophysical Journal. Figures 1 and 9 are in JPG forma

Precision Electroweak Tests of the Minimal and Flipped SU(5) Supergravity Models

We explore the one-loop electroweak radiative corrections in the minimal $SU(5)$ and the no-scale flipped $SU(5)$ supergravity models via explicit calculation of vacuum polarization contributions to the $\epsilon_{1,2,3}$ parameters. Experimentally, $\epsilon_{1,2,3}$ are obtained from a global fit to the LEP observables, and $M_W/M_Z$ measurements. We include $q^2$-dependent effects which have been neglected in most previous ``model-independent" analyses of this type. These effects induce a large systematic negative shift on $\epsilon_{1,2,3}$ for light chargino masses (m_{\chi^\pm_1}\lsim70\GeV). In agreement with previous general arguments, we find that for increasingly large sparticle masses, the heavy sector of both models rapidly decouples, \ie, the values for $\epsilon_{1,2,3}$ quickly asymptote to the Standard Model values with a {\it light} Higgs (m_{H_{SM}}\sim100\GeV). Specifically, at present the $90\%$ CL upper limit on the top-quark mass is m_t\lsim175\GeV in the no-scale flipped $SU(5)$ supergravity model. These bounds can be strengthened for increasing chargino masses in the 50-100\GeV interval. In particular, for m_t\gsim160\GeV, the Tevatron may be able to probe through gluino($\tilde g$) and squark($\tilde q$) production up to m_{\tilde g}\approx m_{\tilde q}\approx250\GeV, exploring at least half of the parameter space in this model.Comment: 15 pages,(6 ps figures available upon request), TeX(harvmac), CTP-TAMU-19/93, ACT-07/9

SUSY signals at HERA in the no-scale flipped SU(5) supergravity model

Sparticle production and detection at HERA are studied within the recently proposed no-scale flipped $SU(5)$ supergravity model. Among the various reaction channels that could lead to sparticle production at HERA, only the following are within its limit of sensitivity in this model: $e^-p\to \tilde e^-_{L,R}\chi^0_i+X, \tilde \nu_e\chi^-_1+X$, where $\chi^0_i(i=1,2)$ are the two lightest neutralinos and $\chi^-_1$ is the lightest chargino. We study the elastic and deep-inelastic contributions to the cross sections using the Weizs\"acker-Williams approximation. We find that the most promising supersymmetric production channel is right-handed selectron ($\tilde e_{R}$) plus first neutralino ($\chi^0_1$), with one hard electron and missing energy signature. The $\tilde\nu_e\chi^-_1$ channel leads to comparable rates but also allows jet final states. A right-handedly polarized electron beam at HERA would shut off the latter channel and allow preferentially the former one. With an integrated luminosity of {\cal L}=100\ipb, HERA can extend the present LEPI lower bounds on $m_{\tilde e_R}, m_{\tilde\nu_e},m_{\chi^0_1}$ by \approx25\GeV, while {\cal L}=1000\ipb will make HERA competitive with LEPII. We also show that the Leading Proton Spectrometer (LPS) at HERA is an excellent supersymmetry detector which can provide indirect information about the sparticle masses by measuring the leading proton longitudinal momentum distribution.Comment: 11 pages, 8 figures (available upon request as uuencoded file or separate ps files), tex (harvmac) CTP-TAMU-15/93, CERN/LAA/93-1

Anomaly-Free Gauged R-Symmetry

We review the gauging of an R-symmetry in local and global susy. We then construct the first anomaly-free models. We break the R-symmetry and susy at the Planck scale and discuss the low-energy effects. We include a solution to the mu-problem, and the prediction of observable effects at HERA. The models also nicely allow for GUT-scale baryogenesis and R-parity violation without the sphaleron interactions erasing the baryon-asymmetry.Comment: 6 pages, latex, no figures. Talk presented at SUSY-95. Work done in collaboration with A. Chamseddin