640 research outputs found
Single Hadronic-Spin Asymmetries in Weak Interaction Processes
We show that measurements of single-spin asymmetries (SSAs) in charged
current weak interaction processes such as deep inelastic neutrino scattering
on a polarized target and inclusive production in polarized hadron-hadron
collisions discriminate between the two fundamental QCD mechanisms (the Sivers
and Collins effects) which have been proposed to explain such time-reversal-odd
asymmetries. It has recently been shown that QCD final-state interactions due
to gluon exchange between the struck quark and the proton spectators in
semi-inclusive deep inelastic lepton scattering will produce non-zero
Sivers-type single-spin asymmetries which survive in the Bjorken limit. We show
that this QCD final-state interaction produces identical SSAs in charged and
neutral current reactions. Furthermore, the contribution of each quark to the
SSA from this mechanism is proportional to the contribution of that quark to
the polarized baryon's anomalous magnetic moment. In contrast, the Collins
effect contribution to SSAs depends on the transversity distribution of quarks
in the polarized target. Since the charged current only couples to quarks of
one chirality, it cannot sense the transversity distribution of the target, and
thus it gives no Collins-type contribution to single-spin correlations.Comment: 12 pages, 1 figur
Light-Cone Representation of the Spin and Orbital Angular Momentum of Relativistic Composite Systems
The matrix elements of local operators such as the electromagnetic current,
the energy momentum tensor, angular momentum, and the moments of structure
functions have exact representations in terms of light-cone Fock state
wavefunctions of bound states such as hadrons. We illustrate all of these
properties by giving explicit light-cone wavefunctions for the two-particle
Fock state of the electron in QED, thus connecting the Schwinger anomalous
magnetic moment to the spin and orbital momentum carried by its Fock state
constituents. We also compute the QED one-loop radiative corrections for the
form factors for the graviton coupling to the electron and photon. Although the
underlying model is derived from elementary QED perturbative couplings, it in
fact can be used to simulate much more general bound state systems by applying
spectral integration over the constituent masses while preserving all of the
Lorentz properties, giving explicit realization of the spin sum rules and other
local matrix elements. The role of orbital angular momentum in understanding
the "spin crisis" problem for relativistic systems is clarified. We also prove
that the anomalous gravitomagnetic moment B(0) vanishes for any composite
system. This property is shown to follow directly from the Lorentz boost
properties of the light-cone Fock representation and holds separately for each
Fock state component. We show how the QED perturbative structure can be used to
model bound state systems while preserving all Lorentz properties. We thus
obtain a theoretical laboratory to test the consistency of formulae which have
been proposed to probe the spin structure of hadrons.Comment: Version to be published in Nuclear Physics B. Includes illustrations
of graviton-lepton form factors at one loop in QE
Endoscopic Submucosal Dissection versus Surgery for Undifferentiated-Type Early Gastric Cancer: A Systematic Review and Meta-Analysis
Background/Aims The use of endoscopic submucosal dissection (ESD) for treating undifferentiated-type early gastric cancer is controversial. The objective of this study was to perform a meta-analysis to compare the long-term outcomes of ESD and surgery for undifferentiated-type early gastric cancer. Methods The PubMed, Cochrane Library, and EMBASE databases were used to search for relevant studies comparing ESD and surgery for undifferentiated-type early gastric cancer. The methodological quality of the included publications was evaluated using the Risk of Bias Assessment tool for Nonrandomized Studies. The rates of overall survival, recurrence, adverse event, and complete resection were determined. Odds ratios (ORs) and 95% confidence intervals (CIs) were also evaluated. Results This meta-analysis enrolled five studies with 429 and 1,236 participants undergoing ESD and surgery, respectively. No significant difference was found in the overall survival rate between the ESD and surgery groups (OR, 2.29; 95% CI, 0.98–5.36; p=0.06). However, ESD was associated with a higher recurrence rate and a lower complete resection rate. The adverse event rate was similar between the two groups. Conclusions ESD with meticulous surveillance esophagogastroduodenoscopy may be as effective and safe as surgery in patients with undifferentiated-type early gastric cancer. Further large-scale, randomized, controlled studies from additional regions are required to confirm these findings
MR Imaging of Central Diabetes Insipidus: A Pictorial Essay
Central diabetes insipidus (DI) can be the outcome of a number of diseases that affect the hypothalamic-neurohypophyseal axis. The causes of the condition can be classified as traumatic, inflammatory, or neoplastic. Traumatic causes include postoperative sella or transection of the pituitary stalk, while infectious or inflammatory causes include meningitis, lymphocytic hypophysitis, and granulomatous inflammations such as sarcoidosis and Wegener's granulomatosis. Various neoplastic conditions such as germinoma, Langerhans cell histiocytosis, metastasis, leukemic infiltration, lymphoma, teratoma, pituitary adenoma, craniopharyngioma, Rathke cleft cyst, hypothalamic glioma, and meningioma are also causes of central DI. In affected patients, careful analysis of these MR imaging features and correlation with the clinical manifestations can allow a more specific diagnosis, which is essential for treatment
Anti-Inflammatory Potential of Carpomitra costata
Marine algae have valuable health and dietary benefits. The present study aimed to investigate whether an ethanol extract of Carpomitra costata (CCE) could inhibit the inflammatory response to LPS. CCE attenuated the production of proinflammatory mediators, such as prostaglandin E2 (PGE2) and nitric oxide (NO), by inhibiting inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-induced RAW264.7 macrophages. CCE also inhibited the expression of proinflammatory cytokines such as IL-1β, TNF-α, and IL-6. CCE suppressed the LPS-induced DNA-binding activity of (NF-κB) and activator protein-1 (AP-1). In addition, CCE attenuated the LPS-stimulated phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK) and phosphatidylinositol 3′-kinase/Akt (PI3K/Akt). Functional aspects of the JNK and Akt signaling pathways were analyzed using specific inhibitors, which attenuated the LPS-induced production of proinflammatory cytokines, and NO and PGE2 expression by suppressing AP-1 and NF-κB activity. In particular, the AP-1 signaling pathway is not involved in the production of inflammatory cytokines, such as IL-6, TNF-α, and IL-1β. These results suggested that CCE might exert its anti-inflammatory action by downregulating transcriptional factors (NF-κB and AP-1) through JNK and Akt signaling pathways. The current study suggested that CCE might be a valuable candidate for the treatment of inflammatory disorders
Effects of Air Pollutants on Childhood Asthma
Epidemiologic studies have suggested the association between environmental exposure to volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) and the increased risk of incurring asthma. Yet there is little data regarding the relationship between personal exposure to air pollution and the incidence of asthma in children. This study was designed to evaluate the effect of exposure to air pollution on children with asthma by using exposure biomarkers. We assessed the exposure level to VOCs by measuring urinary concentrations of hippuric acid and muconic acid, and PAHs by 1-OH pyrene and 2-naphthol in 30 children with asthma and 30 children without asthma (control). The mean level of hippuric acid was 0.158 ± 0.169 µmol/mol creatinine in the asthma group and 0.148 ± 0.249 µmol/mol creatinine in the control group, with no statistical significance noted (p=0.30). The mean concentration of muconic acid was higher in the asthma group than in the control group (7.630 ± 8.915 µmol/mol creatinine vs. 3.390 ± 4.526 µmol/mol creatinine p=0.01). The mean level of urinary 1-OHP was higher in the asthma group (0.430 ± 0.343 µmol/mol creatinine) than the control group (0.239 ± 0.175 µmol/mol creatinine), which was statistically significant (p=0.03). There was no difference in the mean concentration of 2-NAP between the two groups (9.864 ± 10.037 µmol/mol in the asthma group vs. 9.157 ± 9.640 µmol/mol in the control group, p=0.96). In conclusion, this study suggests that VOCs and PAHs have some role in asthma
- …