pi N to Multi-pi N Scattering in the 1/N_c Expansion

We extend the 1/N_c meson-baryon scattering formalism to pi N to multi-pi N case. We first show that the leading-order large N_c processes proceed through resonant intermediate states (e.g., rho N or pi Delta). We find that the pole structure of baryon resonances can be uniquely identified by their (non)appearance in eta N or mixed partial-wave pi Delta final states.Comment: Invited talk at Exclusive Reactions at High Momentum Transfer workshop, JLAB, Newport News, VA, May 21-24, 2007, 4 pages, 3 figure

Integral comparison of static and dynamic ovarian reserve tests; a prospective study and a systematic review

Summary Summary In the introduction (chapter 1) of this thesis static and dynamic ovarian function tests are reviewed, which supposedly can predict ovarian reserve leading to a prognosis of the reproductive potential of a woman. Ovarian reserve is currently defined as the number and quality of the follicles left at any moment in the ovary. The aim of the studies described in this thesis was to find an answer to the following questions: a. Which ovarian reserve test or a certain combination can predict the cohort size of small antral follicles in the early follicular phase. b. Which ovarian reserve test or combination of ovarian reserve tests gives the best prognostic information on the probability of poor and hyper ovarian response in an IVF population. c. Which ovarian reserve test or combination of ovarian reserve tests gives the best prognostic information on the probability of pregnancy in an IVF population. We approached this questions in two ways. 1. A prospective study was conducted that compared in an integral way all currently available static ovarian reserve tests: early follicular phase blood values of follicle stimulating hormone (FSH), oestradiol (E2), inhibin B and anti-mullerian hormone (AMH), the dynamic ovarian reserve tests: the exogenous FSH ovarian reserve test (EFORT), the Clomiphene Citrate Challenge Test (CCCT), the ultrasound tests: antral follicle count (AFC), basal ovarian volume (BOV) and the intercycle variability of test results with regard to the prediction of the ovarian response after ovarian hyperstimulation in an IVF treatment. The results of this study are reported in chapters 2, 3, 4, 5 and 6. 2. A systematic review of the literature was provided including an a priori protocolised information retrieval on all currently available and applied tests, namely early follicular phase blood values of follicle stimulating hormone (FSH), oestradiol, inhibin B and anti-mullerian hormone (AMH), the antral follicle count (AFC), the ovarian volume and the ovarian blood flow and furthermore the clomiphene citrate challenge test (CCCT), the exogenous FSH ovarian reserve test (EFORT) and the gonadotropin releasing hormone agonist stimulation test (GAST) as measures to determine ovarian reserve and their capability to predict ovarian response and chance of pregnancy. This systematic review is reported in chapter 7. Chapter 2 presents the comparison between the endocrine tests, Clomiphene citrate Challenge Test (CCCT), Exogenous FSH Ovarian Reserve Test (EFORT) and basal FSH, basal E2, basal Inhibin B as an integral part of all CCCT’s and EFORT’s, with respect to their ability to estimate the stimulable cohort of follicles in the ovaries (ovarian reserve) and analysis which test or combination of tests would give the best prediction of ovarian reserve. One hundred and ten regularly menstruating patients, aged 18-39 years, participated in this prospective study, randomized, by a computer designed 4-blocks system study into two groups. Fifty six patients underwent a CCCT, and 54 patients underwent an EFORT. In all patients, the test was followed by an IVF treatment. The result of ovarian hyperstimulation during IVF treatment, expressed by the total number of follicles, was used as gold standard. We showed that the best prediction of ovarian reserve was seen, when E2-increment and Inhibin B-increment were used simultaneously in a stepforward multiple regression prediction model. The CCCT could not be used in a prediction model.This findings indicates that the EFORT is the endocrine test which gives the best prediction of ovarian reserve in a linear way. Chapter 3 reports the results of a comparison between the Clomiphene Citrate Challenge Test (CCCT) versus the Exogenous Follicle stimulation hormone Ovarian Reserve Test (EFORT) as single test for identification of poor and hyper responders to in vitro fertilization (IVF). We defined a ‘poor’ ovarian response as less than 6 oocytes after ovarian hyperstimulation in an IVF treatment and a ‘hyper’ response as more than 20 oocytes after such an IVF treatment. We showed that the best predictor for poor response is the CCCT.Homburg, R. [Promotor]Lambalk, C.B. [Copromotor

Positive Parity Pentaquarks Pragmatically Predicted

We consider the possibility that the lightest pentaquark is a parity even state, with one unit of orbital angular momentum. Working within the framework of a constituent quark model, we show that dominant spin-flavor interactions render certain parity-even states lighter than any pentaquark with all quarks in the spatial ground state. For such states, we focus on predicting the mass and decays of other members of the same SU(3) flavor multiplet. Specifically, we consider the strangeness -2 cascade pentaquarks, which are relatively immune to mixing. We take into account flavor SU(3) breaking effects originating from the strange quark mass as well as from the structure of the spin-flavor exchange interactions themselves. We predict the lightest cascade pentaquarks at approximately 1906 MeV, with a full width about 3 times larger than that of the Theta^+.Comment: 13 pages, 1 figure, 4 tables, Revtex

Pulmonary embolism in patients with COVID-19 and value of D-dimer assessment:a meta-analysis

Purpose To investigate, in a meta-analysis, the frequency of pulmonary embolism (PE) in patients with COVID-19 and whether D-dimer assessment may be useful to select patients for computed tomography pulmonary angiography (CTPA). Methods A systematic literature search was performed for original studies which reported the frequency of PE on CTPA in patients with COVID-19. The frequency of PE, the location of PE, and the standardized mean difference (SMD) of D-dimer levels between patients with and without PE were pooled by random effects models. Results Seventy-one studies were included. Pooled frequencies of PE in patients with COVID-19 at the emergency department (ED), general wards, and intensive care unit (ICU) were 17.9% (95% CI: 12.0-23.8%), 23.9% (95% CI: 15.2-32.7%), and 48.6% (95% CI: 41.0-56.1%), respectively. PE was more commonly located in peripheral than in main pulmonary arteries (pooled frequency of 65.3% [95% CI: 60.0-70.1%] vs. 32.9% [95% CI: 26.7-39.0%]; OR = 3.540 [95% CI: 2.308-5.431%]). Patients with PE had significantly higher D-dimer levels (pooled SMD of 1.096 [95% CI, 0.844-1.349]). D-dimer cutoff levels which have been used to identify patients with PE varied between 1000 and 4800 mu g/L. Conclusion The frequency of PE in patients with COVID-19 is highest in the ICU, followed by general wards and the ED. PE in COVID-19 is more commonly located in peripheral than in central pulmonary arteries, which suggests local thrombosis to play a major role. D-dimer assessment may help to select patients with COVID-19 for CTPA, using D-dimer cutoff levels of at least 1000 mu g/L

Peer review practices by medical imaging journals

ObjectiveTo investigate peer review practices by medical imaging journals.MethodsJournals in the category "radiology, nuclear medicine and medical imaging" of the 2018 Journal Citation Reports were included.ResultsOf 119 included journals, 62 (52.1%) used single-blinded peer review, 49 (41.2%) used double-blinded peer review, two (1.7%) used open peer review and one (0.8%) used both single-blinded and double-blinded peer reviews, while the peer review model of five journals (4.2%) remained unclear. The use of single-blinded peer review was significantly associated with a journal's impact factor (correlation coefficient of 0.218, P=0.022). On subgroup analysis, only subspecialty medical imaging journals had a significant association between the use of single-blinded peer review and a journal's impact factor (correlation coefficient of 0.354, P=0.025). Forty-eight journals (40.3%) had a reviewer preference option, 48 journals (40.3%) did not have a reviewer recommendation option, and 23 journals (19.3%) obliged authors to indicate reviewers on their manuscript submission systems. Sixty-four journals (53.8%) did not provide an explicit option on their manuscript submission Web site to indicate nonpreferred reviewers, whereas 55 (46.2%) did. There were no significant associations between the option or obligation to indicate preferred or nonpreferred reviewers and a journal's impact factor.ConclusionSingle-blinded peer review and the option or obligation to indicate preferred or nonpreferred reviewers are frequently employed by medical imaging journals. Single-blinded review is (weakly) associated with a higher impact factor, also for subspecialty journals. The option or obligation to indicate preferred or nonpreferred reviewers is evenly distributed among journals, regardless of impact factor

Unusual High-Energy Phenomenology of Lorentz-Invariant Noncommutative Field Theories

It has been suggested that one may construct a Lorentz-invariant noncommutative field theory by extending the coordinate algebra to additional, fictitious coordinates that transform nontrivially under the Lorentz group. Integration over these coordinates in the action produces a four-dimensional effective theory with Lorentz invariance intact. Previous applications of this approach, in particular to a specific construction of noncommutative QED, have been studied only in a low-momentum approximation. Here we discuss Lorentz-invariant field theories in which the relevant physics can be studied without requiring an expansion in the inverse scale of noncommutativity. Qualitatively, we find that tree-level scattering cross sections are dramatically suppressed as the center-of-mass energy exceeds the scale of noncommutativity, that cross sections that are isotropic in the commutative limit can develop a pronounced angular dependence, and that nonrelativistic potentials (for example, the Coloumb potential) become nonsingular at the origin. We consider a number of processes in noncommutative QED that may be studied at a future linear collider. We also give an example of scattering via a four-fermion operator in which the noncommutative modifications of the interaction can unitarize the tree-level amplitude, without requiring any other new physics in the ultraviolet.Comment: 24 pages LaTeX, 4 eps figures (v2: reference added, v3: minor clarifications