Effects Of Line Inclination On The Hydrodynamics Of Riser Transport In The Non-slugging Dense Phase Flow Regime

The present work was undertaken to evaluate the effects of slight line inclinations ({dollar}\theta\ \le\ 18\sp\circ{dollar} from the vertical) on the hydrodynamics of non-slugging dense phase upwards cocurrent gas-solids flows. Previous research and operating experience has focused on the dilute phase flow regime where ({dollar}\rm\partial(\partial P/\partial z)\rbrack/\partial U\sb{lcub}g{rcub}\ \u3e\ 0{dollar}. This thesis is restricted to the regime where ({dollar}\partial(\partial P/\partial z)\rbrack/\partial U\sb{lcub}g{rcub}\ \u3c\ 0{dollar} and for which refluxing of particles, without slug flow, dominates in the flow patterns.;Experiments were conducted with 197 {dollar}\mu{dollar}m sand particles and 441 {dollar}\mu{dollar}m glass beads in a 3.2 cm diameter Plexiglas tube. Use of the two particle sizes (Geldart Group B powders) enabled the characterization of different systems: the first with sand, showed a slow transition from the non-slugging dense (reflux flows) to the dense slugging regime; the other using glass beads, collapsed abruptly into a slugging flow with a slight decrease of gas velocity near the choking point.;The pressure gradient and solids holdup ({dollar}\alpha{dollar}) in the fully developed riser test section increased linearly with both the solids flux (50-300 kg/m{dollar}\sp2{dollar}s) and solids mass loading ratio (5-40), but decreased with the gas velocity for both sand (4.5-12 m/s) and glass beads (6-16 m/s). The solids-wall frictional pressure gradient contributed between {dollar}-{dollar}25% and 25% of the total gradient, and was negative whenever there was solids refluxing at the wall. A 2-parameter semi-empirical model was developed which was successfully employed for the correlation of negative solids-wall friction factors.;A lifting efficiency of 2-phase transport in oblique risers ({dollar}\eta{dollar}) was defined, which decreased with {dollar}\theta{dollar}, from 75% (of the theoretical single particle lifting efficiency in dilute phase transport), to 35-45% for {dollar}\theta\ \ge\ 11\sp\circ{dollar}. The decrease of {dollar}\eta{dollar} was attributed to extensive refluxing near choking. A previous study has shown that {dollar}\eta \u3c 10\%{dollar} for dilute phase transport.;The dominant frequency from the power spectrum of the pressure gradient time series was 5 Hz for sand and 3 Hz for glass beads. The pressure gradient time series could be stochastically modelled with a linear stationary ARIMA model of the form AR(2) or AR(3)

An unedited 1.1 kb mitochondrial orfB gene transcript in the Wild Abortive Cytoplasmic Male Sterility (WA-CMS) system of Oryza sativa L. subsp. indica

<p>Abstract</p> <p>Background</p> <p>The application of hybrid rice technology has significantly increased global rice production during the last three decades. Approximately 90% of the commercially cultivated rice hybrids have been derived through three-line breeding involving the use of WA-CMS lines. It is believed that during the 21^stcentury, hybrid rice technology will make significant contributions to ensure global food security. This study examined the poorly understood molecular basis of the WA-CMS system in rice.</p> <p>Results</p> <p>RFLPs were detected for <it>atp6 </it>and <it>orfB </it>genes in sterile and fertile rice lines, with one copy of each in the mt-genome. The RNA profile was identical in both lines for <it>atp6</it>, but an additional longer <it>orfB </it>transcript was identified in sterile lines. 5' RACE analysis of the long <it>orfB </it>transcript revealed it was 370 bp longer than the normal transcript, with no indication it was chimeric when compared to the genomic DNA sequence. cDNA clones of the longer <it>orfB </it>transcript in sterile lines were sequenced and the transcript was determined unedited. Sterile lines were crossed with the restorer and maintainer lines, and fertile and sterile F₁hybrids were respectively generated. Both hybrids contained two types of <it>orfB </it>transcripts. However, the long transcript underwent editing in the fertile F₁hybrids and remained unedited in the sterile lines. Additionally, the editing of the 1.1 kb <it>orfB </it>transcript co-segregated with fertility restoring alleles in a segregating population of F₂progeny; and the presence of unedited long <it>orfB </it>transcripts was detected in the sterile plants from the F₂segregating population.</p> <p>Conclusion</p> <p>This study helped to assign plausible operative factors responsible for male-sterility in the WA cytoplasm of rice. A new point of departure to dissect the mechanisms governing the CMS-WA system in rice has been identified, which can be applied to further harness the opportunities afforded by hybrid vigor in rice.</p

Dualities in Five Dimensions and Charged String Solutions

We consider an eleven dimensional supergravity compactified on $K3\times T^2$ and show that the resulting five dimensional theory has identical massless states as that of heterotic string compactified on a specific five torus $T^5$. The strong-weak coupling duality of the five dimensional theory is argued to represent a ten dimensional Type $IIA$ string compactified on $K3 \times S^1$, supporting the conjecture of string-string duality in six dimensions. In this perspective, we present magnetically charged solution of the low energy heterotic string effective action in five dimensions with a charge defined on a three sphere $S^3$ due to the two form potential. We use the Poincare duality to replace the antisymmetric two form with a gauge field in the effective action and obtain a string solution with charge on a two sphere $S^2$ instead of that on a three sphere $S^3$ in the five dimensional spacetime. We note that the string-particle duality is accompanied by a change of topology from $S^3$ to $S^2$ and viceversa.Comment: 22 pages, revtex (no figures

A retrospective analysis of COVID-19 infection among healthcare workers of south east Assam, India

Background: Health care workers (HCWs) are the frontline warriors, more prone to contracting coronavirus disease 2019 (COVID-19). They also have tremendous possibility of serving as transmission vectors to others. In India there is paucity of data on COVID-19 infection among HCWs. Therefore, it is important to evaluate the infection risk, clinical features, and source of infection, transmission and outcome in HCWs to safeguard them and to check further community spread.Methods: The aim of the study was to investigate the presence of COVID-19 infection among HCWs and to understand the risk factors for infection. Demographic and clinical data of HCWs declared SARS-COV-2 real time RT-PCR positive by VRDL, SMCH, Silchar during June 2020 to July 2021 was obtained from ICMR portal.Results: On data analysis it was found that during the study period a rate of 3.95% (316 out of 7997 cases) infection was among HCWs. Their mean age was 36 years. With maximum cases among male staffs (57.9%), and most common age group was young generation of 17-29 years. The peak acquisition of infection was in July 2020 during ATSP surveillance with 45.5% of infected HCWs. Of the infected HCWs majority were asymptomatic (74%) Although hospitalization rate was high i.e. 82.9% but severity was low with no mortality. Co-morbidity among infected cases was low 23.4%, usually in the aged group of ≥45 years. Doctors/PGTs and Nurses were the highly affected group.Conclusions: Safeguarding the HCWs from infection is the critical need for empowering the healthcare system and overcoming any pandemic in future as well. 

S-Duality and Cosmological Constant in String Theory

The S-duality invariance of the equations of motion of four dimensional string effective action with cosmological constant, $\Lambda$, is studied. It is demonstrated that the S-duality symmetry of the field equations are broken for nonzero $\Lambda$. The ``naturalness'' hypothesis is invoked to argue that $\Lambda$ should remain small since exact S-duality symmetry will force the cosmological constant to vanish in the string effective action.Comment: 13 pages, RevTex , slightly extended version with more discussions added ( To appear in Phys. Lett. B

D-Branes and Twelve Dimensions

We study the D-brane solutions to type IIB superstring in ten dimensions and find interpretation in terms of compactification of a twelve dimensional three-brane of (a specific) F-theory on a torus $T^2$. In this frame-work, there also exist a two-brane which may be argued to be equivalent to the three-brane by utilizing the electric-magnetic duality in eleven dimensions. In this context, we propose for the existence of an isometry in one of the transverse directions to the three-brane in F-theory. As a consequence the two-brane may be identified with the three-brane in twelve dimensions itself. The twelve dimensional picture of D-branes in type IIB theory suggests for the reformulation of type IIB superstring in terms of three-brane of F-theory.Comment: 20 pages, LaTex, references added, version to appear in Nucl.Phys.

Exact Type IIB Superstring Backgrounds

We obtain a family of type IIB superstring backgrounds involving Ramond-Ramond fields in ten dimensions starting from a heterotic string background with vanishing gauge fields. To this end the global $SL(2,R)$ symmetry of the type IIB equations of motion is implemented as a solution generating transformation. Using a geometrical analysis we show that the type IIB backgrounds obtained are solutions to all orders in $\alpha^{\prime}$.Comment: 14 pages, minor changes in some expressions, few remarks adde

Path-Integral Formulation of Dirichlet String in General Backgrounds

We investigate the dynamics of an arbitrary Dirichlet (D-) string in presence of general curved backgrounds following a path-integral formalism. In particular, we consider the interaction of D-string with the massless excitations of closed string in open bosonic string theory. The background fields induce invariant curvatures on the D-string manifold and the extrinsic curvature can be seen to contain a divergence at the disk boundary. The re-normalization of D-string coordinates, next to the leading order in its derivative expansion, is performed to handle the divergence. Then we obtain the generalized Dirac-Born-Infeld action representing the effective dynamics of D-string in presence of the non-trivial backgrounds. On the other hand, D-string acts as a source for the Ramond-Ramond two-form which induces an additional (lower) form due to its coupling to the U(1) gauge invariant fields on the D-string. These forms are reviewed in this formalism for an arbitrary D-string and is encoded in the Wess-Zumino action. Quantization of the D-string collective coordinates, in the U(1) gauge sector, is performed by taking into account the coupling to the lower form and the relevant features of D-string are analyzed in presence of the background fields.Comment: 23 pages, LaTex, corrected typos, added reference, version to appear in Nuclear Physics

hnRNP A1 and hnRNP F Modulate the Alternative Splicing of Exon 11 of the Insulin Receptor Gene

Exon 11 of the insulin receptor gene (INSR) is alternatively spliced in a developmentally and tissue-specific manner. Linker scanning mutations in a 5′ GA-rich enhancer in intron 10 identified AGGGA sequences that are important for enhancer function. Using RNA-affinity purification and mass spectrometry, we identified hnRNP F and hnRNP A1 binding to these AGGGA sites and also to similar motifs at the 3′ end of the intron. The hnRNPs have opposite functional effects with hnRNP F promoting and hnRNP A1 inhibiting exon 11 inclusion, and deletion of the GA-rich elements eliminates both effects. We also observed specific binding of hnRNP A1 to the 5′ splice site of intron 11. The SR protein SRSF1 (SF2/ASF) co-purified on the GA-rich enhancer and, interestingly, also competes with hnRNP A1 for binding to the splice site. A point mutation -3U→C decreases hnRNP A1 binding, increases SRSF1 binding and renders the exon constitutive. Lastly, our data point to a functional interaction between hnRNP F and SRSF1 as a mutant that eliminates SRSF1 binding to exon 11, or a SRSF1 knockdown, which prevents the stimulatory effect of hnRNP F over expression