Transverse Spin in QCD. I. Canonical Structure

In this work we initiate a systematic investigation of the spin of a composite system in an arbitrary reference frame in QCD. After a brief review of the difficulties one encounters in equal-time quantization, we turn to light-front quantization. We show that, in spite of the complexities, light-front field theory offers a unique opportunity to address the issue of relativistic spin operators in an arbitrary reference frame since boost is kinematical in this formulation. Utilizing this symmetry, we show how to introduce transverse spin operators for massless particles in an arbitrary reference frame in analogy with those for massive particles. Starting from the manifestly gauge invariant, symmetric energy momentum tensor in QCD, we derive expressions for the interaction dependent transverse spin operators ${\cal J}^i$ ($i=1,2$) which are responsible for the helicity flip of the nucleon in light-front quantization. In order to construct ${\cal J}^i$, first we derive expressions for the transverse rotation operators $F^i$. In the gauge $A^+=0$, we eliminate the constrained variables. In the completely gauge fixed sector, in terms of the dynamical variables, we show that one can decompose ${\cal J}^i= {\cal J}^i_I + {\cal J}^i_{II} + {\cal J}^i_{III}$ where only ${\cal J}^i_{I}$ has explicit coordinate ($x^-, x^i$) dependence in its integrand. The operators ${\cal J}^i_{II}$ and ${\cal J}^i_{III}$ arise from the fermionic and bosonic parts respectively of the gauge invariant energy momentum tensor. We discuss the implications of our results.Comment: 22 pages, revte

Prevalence of Helicobacter pylori in patients with gastro-oesophageal reflux disease : systematic review.

Objectives: To ascertain the prevalence of Helicobacter pylori in patients with gastro-oesophageal reflux disease and its association with the disease. Design: Systematic review of studies reporting the prevalence of H pylori in patients with and without gastro-oesophageal reflux disease. Data sources: Four electronic databases, searched to November 2001, experts, pharmaceutical companies, and journals. Main outcome measure: Odds ratio for prevalence of H pylori in patients with gastro-oesophageal reflux disease. Results: 20 studies were included. The pooled estimate of the odds ratio for prevalence of H pylori was 0.60 (95% confidence interval 0.47 to 0.78), indicating a lower prevalence in patients with gastro-oesophageal reflux disease. Substantial heterogeneity was observed between studies. Location seemed to be an important factor, with a much lower prevalence of H pylori in patients with gastro-oesophageal reflux disease in studies from the Far East, despite a higher overall prevalence of infection than western Europe and North America. Year of study was not a source of heterogeneity. Conclusion: The prevalence of H pylori infection was significantly lower in patients with than without gastro-oesophageal reflux, with geographical location being a strong contributor to the heterogeneity between studies. Patients from the Far East with reflux disease had a lower prevalence of H pylori infection than patients from western Europe and North America, despite a higher prevalence in the general population

Visualization Of Supersonic Flows In Shock Tunnels, Using The Background Oriented Schlieren Technique

Visualisation of supersonic compressible flows using the Background Oriented Schlieren (BOS) technique is presented. Results from experiments carried out in a reflected shock tunnel with models of a 20-degree semi-vertex angle circular cone and a re-entry body in the test section are presented. This technique uses a simple optical set-up consisting of a structured background pattern, an electronic camera with a high shutter speed and a high intensity light source. Tests were conducted with a Mach 4 conical nozzle, with nozzle supply pressure of 2 MPa and nozzle supply temperature of 2000 K respectively. The images captured during the test were compared using PIV style image processing code. The intensity of light at each point in the processed image was proportional to the density at that point. Qualitative visualization of shock shapes, with images clearly indicating regions of subsonic and supersonic flows was achieved. For the cone, the shock angle measured from the BOS image agreed with theoretical calculations to within 0.5 degrees. Shock standoff distances could be measured from the BOS image for the re-entry body

Frozen storage studies of composite fish mince drom dhooma (Sciaenid sp.) and lactarius (Lactarius lactarius)

Fish minces from dhoma and lactarius were mixed in the ratio of 40:60 respectively, and quick frozen along with individual minces at -40°C and stored at -20°C. Shelf life was evaluated by following biochemical, physical and organoleptic changes occurred during storage up to 44 weeks. Rapid decreases were noted in water soluble nitrogen and salt soluble nitrogen fractions during the initial period of 16 weeks. A good correlation was observed between changes in salt-soluble nitrogen and organoleptic evaluation. The minces were in good and acceptable condition up to 32 weeks of storage

Transverse Spin in QCD and Transverse Polarized Deep Inelastic Scattering

We address the long standing problem of the construction of relativistic spin operators for a composite system in QCD. Exploiting the kinematical boost symmetry in light front theory, we show that transverse spin operators for massless particles can be introduced in an arbitrary reference frame, in analogy with those for massive particles. In light front QCD, the complete set of transverse spin operators are identified for the first time, which are responsible for the helicity flip of the nucleon. We establish the direct connection between transverse spin in light front QCD and transverse polarized deep inelastic scattering. We discuss the theoretical and phenomenological implications of our results.Comment: Title and presentation slightly changed, results unchanged, accepted for publication in Phys. Lett.

New Time-Space Upperbounds for Directed Reachability in High-genus and H-minor-free Graphs

We obtain the following new simultaneous time-space upper bounds for the directed reachability problem. (1) A polynomial-time, O(n^{2/3} * g^{1/3})-space algorithm for directed graphs embedded on orientable surfaces of genus g. (2) A polynomial-time, O(n^{2/3})-space algorithm for all H-minor-free graphs given the tree decomposition, and (3) for K_{3,3}-free and K_5-free graphs, a polynomial-time, O(n^{1/2 + epsilon})-space algorithm, for every epsilon > 0. For the general directed reachability problem, the best known simultaneous time-space upper bound is the BBRS bound, due to Barnes, Buss, Ruzzo, and Schieber, which achieves a space bound of O(n/2^{k * sqrt(log(n))}) with polynomial running time, for any constant k. It is a significant open question to improve this bound for reachability over general directed graphs. Our algorithms beat the BBRS bound for graphs embedded on surfaces of genus n/2^{omega(sqrt(log(n))}, and for all H-minor-free graphs. This significantly broadens the class of directed graphs for which the BBRS bound can be improved

The tight skin mouse: demonstration of mutant fibrillin-1 production and assembly into abnormal microfibrils

Mice carrying the Tight skin (Tsk) mutation harbor a genomic duplication within the fibrillin-1 (Fbn 1) gene that results in a larger than normal in-frame Fbn 1 transcript. In this study, the consequences of the Tsk mutation for fibrillin-containing microfibrils have been examined. Dermal fibroblasts from Tsk/+ mice synthesized and secreted both normal fibrillin (approximately 330 kD) and the mutant oversized Tsk fibrillin-1 (approximately 450 kD) in comparable amounts, and Tsk fibrillin-1 was stably incorporated into cell layers. Immunohistochemical and ultrastructural analyses of normal and Tsk/+ mouse skin highlighted differences in the gross organization and distribution of microfibrillar arrays. Rotary shadowing of high Mr preparations from Tsk/+ skin demonstrated the presence of abundant beaded microfibrils. Some of these had normal morphology and periodicity, but others were distinguished by diffuse interbeads, longer periodicity, and tendency to aggregate. The presence of a structurally abnormal population of microfibrils in Tsk/+ skin was unequivocally demonstrated after calcium chelation and in denaturating conditions. Scanning transmission electron microscopy highlighted the presence of more mass in Tsk/+ skin microfibrils than in normal mice skin microfibrils. These data indicate that Tsk fibrillin-1 polymerizes and becomes incorporated into a discrete population of beaded microfibrils with altered molecular organization

Semiflexible polymer conformation, distribution and migration in microcapillary flows

The flow behavior of a semiflexible polymer in microchannels is studied using Multiparticle Collision Dynamics (MPC), a particle-based hydrodynamic simulation technique. Conformations, distributions, and radial cross-streamline migration are investigated for various bending rigidities, with persistence lengths Lp in the range 0.5 < Lp/Lr < 30. The flow behavior is governed by the competition between a hydrodynamic lift force and steric wall-repulsion, which lead to migration away from the wall, and a locally varying flow-induced orientation, which drives polymer away from the channel center and towards the wall. The different dependencies of these effects on the polymer bending rigidity and the flow velocity results in a complex dynamical behavior. However, a generic effect is the appearance of a maximum in the monomer and the center-of-mass distributions, which occurs in the channel center for small flow velocities, but moves off-center at higher velocities.Comment: in press at J. Phys. Condens. Matte