138 research outputs found
Color Gauge Invariance in Hard Processes
Within the theoretical framework we apply, a suggested origin for single spin
asymmetries is the presence of gauge links in transverse momentum dependent
distribution functions. Recently we found new gauge link structures in a number
of hard processes. These structures need to be considered in the evolution of
parton distribution functions and for establishing factorization.Comment: One reference corrected, 4 pages and 2 figures. Presented at
Light-Cone 200
Universality of Single Spin Asymmetries in Hard Processes
We discuss the use of time reversal symmetry in the classification of parton
correlators. Specifically, we consider the role of (small) intrinsic transverse
momenta in these correlators and the determination of the proper color gauge
link. The transverse momentum weighted correlators in hard processes can be
expressed as a product of universal gluonic pole matrix elements and gluonic
pole cross sections.Comment: Contributed paper at DIS2006, 4 page
Relativistic bound-state calculations in Light Front Dynamics
We calculated bound states in the quantum field theoretical approach. Using
the Wick-Cutkosky model and an extended version of this model (in which a
particle with finite mass is exchanged) we have calculated the bound states in
the scalar case.Comment: 3 pages, proceedings of the Light Cone Meeting Trento 2001, to be
published in Nucl. Phys. B - Proceedings Supplement
Gauge Link Structure in Quark-Quark Correlators in hard processes
Distribution functions in hard processes can be described by quark-quark
correlators, nonlocal matrix elements of quark fields. Color gauge invariance
requires inclusion of appropriate gauge links in these correlators. For
transverse momentum dependent distribution functions, in particular important
for describing T-odd effects in hard processes, we find that new link
structures containing loops can appear in abelian and non-abelian theories. In
transverse moments, e.g. measured in azimuthal asymmetries, these loops may
enhance the contribution of gluonic poles. Some explicit results for the link
structure are given in high-energy leptoproduction and hadron-hadron
scattering.Comment: 9 pages, 9 figure
Oxytocin as an indicator of psychological and social well-being in domesticated animals: a critical review
Mini reviewOxytocin is often portrayed as a hormone specific to social behavior, reflective of positive welfare states, and linked to mental states. Research on oxytocin in domesticated animal species has been few to date but is rapidly increasing (in dog, pig, cattle, sheep), with direct implications for animal welfare. This review evaluates the evidence for the specificity of oxytocin as an indicator of: 1. Social, 2. Positive, and 3. Psychological well-being. Oxytocin has most often been studied in socially relevant paradigms, with a lack of non-social control paradigms. Oxytocin research appears biased toward investigating positive valence, with a lack of control in valence or arousal. Oxytocin actions are modulated by the environmental and social contexts, which are important factors to consider. Limited evidence supports that oxytocin's actions are linked to psychological states; nevertheless whether this is a direct effect of oxytocin per se remains to be demonstrated. Overall, it is premature to judge oxytocin's potential as an animal welfare indicator given the few and discrepant findings and a lack of standardization in methodology. We cover potential causes for discrepancies and suggest solutions through appropriate methodological design, oxytocin sampling or delivery, analysis and reporting. Of particular interest, the oxytocinergic system as a whole remains poorly understood. Appreciation for the differences that social contact and group living pose in domesticated species and the way they interact with humans should be key considerations in using oxytocin as a psychosocial indicator of well-being.Jean-Loup Rault, Marleen van den Munkhof and Femke T. A. Buisman-Pijlma
Universality of T-odd effects in single spin and azimuthal asymmetries
We analyze the transverse momentum dependent distribution and fragmentation
functions in space-like and time-like hard processes involving at least two
hadrons, in particular 1-particle inclusive leptoproduction, the Drell-Yan
process and two-particle inclusive hadron production in electron-positron
annihilation. As is well-known, transverse momentum dependence allows for the
appearance of unsuppressed single spin azimuthal asymmetries, such as Sivers
and Collins asymmetries. Recently, Belitsky, Ji and Yuan obtained fully color
gauge invariant expressions for the relevant matrix elements appearing in these
asymmetries at leading order in an expansion in the inverse hard scale. We
rederive these results and extend them to observables at the next order in this
expansion. We observe that at leading order one retains a probability
interpretation, contrary to a claim in the literature and show the direct
relation between the Sivers effect in single spin asymmetries and the
Qiu-Sterman mechanism. We also study fragmentation functions, where the process
dependent gauge link structure of the correlators is not the only source of
T-odd observables and discuss the implications for universality.Comment: 29 pages, Revtex, 26 Postscript figures; abstract, introduction and
section VIIC significantly modified and appendix B replace
Implementation of laparoscopic hysterectomy for endometrial cancer over the past decade
Background: Laparoscopic hysterectomy (LH) for the treatment of early-stage endometrial carcinoma/cancer (EC) has demonstrated to be safe in several randomized controlled trials. Yet, data on implementation of LH in clinical practice are limited. In the present study, implementation of LH for EC was evaluated in a large oncology network in the Netherlands. Results: Retrospectively, a total of 556 EC patients with FIGO stage I-II were registered in the selected years. The proportion of LH gradually increased from 11% in 2006 to 85% in 2015. LH was more often performed in patients with low-grade EC and was not related to the studied patient characteristics. The introduction of TLH was frequently preceded by LAVH. Patients treated in teaching hospitals were more likely to undergo a LH compared to patients in non-teaching hospitals. The conversion rate was 7.7%, and the overall complication rates between LH and AH were comparable, but less postoperative complications in LH. Conclusions: Implementation of laparoscopic hysterectomy for early-stage EC increased from 11 to 85% in 10Â years. Implementation of TLH was often preceded by LAVH and was faster in teaching hospitals
Substance-Related Health Problems during Rave Parties in the Netherlands (1997–2008)
The objective of this study was to describe a 12-year (1997–2008) observation of substance-related incidents occurring at rave parties in the Netherlands, including length of visits to first-aid stations, substances used, and severity of the incidents. During rave parties, specifically trained medical and paramedical personnel staffed first aid stations. Visitors were diagnosed and treated, and their data were recorded using standardized methods. During the 12-year period with 249 rave parties involving about 3,800,000 visitors, 27,897 people visited a first aid station, of whom 10,100 reported having a substance-related problem. The mean age of these people was 22.3+/−5.4 years; 52.4% of them were male. Most (66.7%) substance-related problems were associated with ecstasy or alcohol use or both. Among 10,100 substance-related cases, 515 required professional medical care, and 16 of these cases were life threatening. People with a substance-related problem stayed 20 min at the first aid station, which was significantly longer than the 5 min that those without a substance-related health problem stayed. These unique data from the Netherlands identify a variety of acute health problems related to the use of alcohol, amphetamines, cannabis, cocaine, ecstasy, and GHB. Although most problems were minor, people using GHB more often required professional medical care those using the other substances. We recommended adherence to harm and risk reduction policy, and the use of first aid stations with specially trained staff for both minor and serious incidents
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