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

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

Systematic Review and Meta-Analysis on the Value of Chest CT in the Diagnosis of Coronavirus Disease (COVID-19):Sol Scientiae, Illustra Nos

OBJECTIVE. The purpose of this article is to systematically review and meta-analyze the diagnostic accuracy of chest CT in detecting coronavirus disease (COVID-19). MATERIALS AND METHODS. MEDLINE was systematically searched for publications on the diagnostic performance of chest CT in detecting COVID-19. Methodologic quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Meta-analysis was performed using a bivariate random-effects model. RESULTS. Six studies were included, comprising 1431 patients. All six studies included patients at high risk of COVID-19, and five studies explicitly reported that they included only symptomatic patients. Mean prevalence of COVID-19 was 47.9% (range, 27.6–85.4%). High or potential risk of bias was present throughout all QUADAS-2 domains in all six studies. Sensitivity ranged from 92.9% to 97.0%, and specificity ranged from 25.0% to 71.9%, with pooled estimates of 94.6% (95% CI, 91.9–96.4%) and 46.0% (95% CI, 31.9–60.7%), respectively. The included studies were statistically homogeneous in their estimates of sensitivity (p = 0.578) and statistically heterogeneous in their estimates of specificity (p < 0.001). CONCLUSION. Diagnostic accuracy studies on chest CT in COVID-19 suffer from methodologic quality issues. Chest CT appears to have a relatively high sensitivity in symptomatic patients at high risk of COVID-19, but it cannot exclude COVID-19. Specificity is poor. These data, along with other local factors such as COVID-19 prevalence, available real-time reverse transcriptase–polymerase chain reaction tests, staff, hospital, and CT scanning capacity, can be useful to healthcare professionals and policy makers to decide on the utility of chest CT for COVID-19 detection in the hospital setting

Chest CT Imaging Signature of Coronavirus Disease 2019 Infection In Pursuit of the Scientific Evidence:in pursuit of the scientific evidence

BACKGROUND: Chest CT may be used for the diagnosis of coronavirus disease 2019 (COVID-19), but clear scientific evidence is lacking. Therefore, we systematically reviewed and meta-analyzed the chest CT imaging signature of COVID-19.RESEARCH QUESTION: What is the chest CT imaging signature of COVID-19 infection?STUDY DESIGN AND METHODS: A systematic literature search was performed for original studies on chest CT imaging findings in patients with COVID-19. Methodologic quality of studies was evaluated. Pooled prevalence of chest CT imaging findings were calculated with the use of a random effects model in case of between-study heterogeneity (predefined as I-2 =50); otherwise, a fixed effects model was used.RESULTS: Twenty-eight studies were included. The median number of patients with COVID-19 per study was 124 (range, 50-476), comprising a total of 3,466 patients. Median prevalence of symptomatic patients was 99% (range, &gt;76.3%-100%). Twenty-seven of the studies (96%) had a retrospective design. Methodologic quality concerns were present with either risk of or actual referral bias (13 studies), patient spectrum bias (eight studies), disease progression bias (26 studies), observer variability bias (27 studies), and test review bias (14 studies). Pooled prevalence was 10.6% for normal chest CT imaging findings. Pooled prevalences were 90.0% for posterior predilection, 81.0% for ground-glass opacity, 75.8% for bilateral abnormalities, 73.1% for left lower lobe involvement, 72.9% for vascular thickening, and 72.2% for right lower lobe involvement. Pooled prevalences were 5.2% for pleural effusion, 5.1% for lymphadenopathy, 4.1% for airway secretions/tree-in-bud sign, 3.6% for central lesion distribution, 2.7% for pericardial effusion, and 0.7% for cavitation/cystic changes. Pooled prevalences of other CT imaging findings ranged between 10.5% and 63.2%.INTERPRETATION: Studies on chest CT imaging findings in COVID-19 suffer from methodologic quality concerns. More high-quality research is necessary to establish diagnostic CT criteria for COVID-19. Based on the available evidence that requires cautious interpretation, several chest CT imaging findings appear to be suggestive of COVID-19, but normal chest CT imaging findings do not exclude COVID-19, not even in symptomatic patients.</p

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

We extend the 1/N_c expansion meson-baryon scattering formalism to cases in which the final state contains more than two particles. We first show that the leading-order large N_c processes proceed through resonant intermediate states (e.g., rho N or pi Delta). We then tabulate linear amplitude expressions for relevant processes and 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. We also show that quantitative predictions of pi N to pi Delta branching ratios predicted at leading order alone do not agree with measurements, but the inclusion of 1/N_c corrections is ample to explain the discrepancies.Comment: 23 pages, 3 eps figures, ReVTeX4, added reference and discussion, identical to PRD versio

Stabilized High Power Laser for Advanced Gravitational Wave Detectors

Second generation gravitational wave detectors require high power lasers with several 100W of output power and with very low temporal and spatial fluctuations. In this paper we discuss possible setups to achieve high laser power and describe a 200W prestabilized laser system (PSL). The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described. Special emphasis will be given to the most demanding power stabilization requiremets and new results (RIN ≤ 4×10-9/surdHz) will be presented

Single-frequency master-oscillator photonic crystal fiber amplifier with 148 W output power

We report on a high-power ytterbium doped photonic crystal fiber amplifier using a single-frequency Nd:YAG non-planar ring oscillator seed source. With a large-mode-area photonic crystal fiber, operation below the threshold of stimulated Brillouin scattering is demonstrated with up to 148 W of continuous-wave output power and a slope efficiency of 75%. At maximum output power the amplified spontaneous emission was suppressed by more than 40 dB and the polarization extinction ratio was better than 22 dB. In order to investigate the overlap of the photonic crystal fiber transverse-mode with a Gaussian fundamental mode, sensitive beam quality measurements with a Fabry-Perot ring-cavity are presented

Multimodal therapy in an inpatient setting

Inpatient Multimodal Therapy (imt) is a residential treatment program, lasting a maximum of 36 weeks, for patients with severe neurotic symptoms. A group of 44 chronic obsessive-compulsive patients and a group of 40 chronic phobic patients were treated in order to assess the outcome and the process of treatment and to identify prognostic factors associated with the effect. At follow-up-on average, eight months after discharge-it was found that 60% had improved, 32% had remained the same, and 8% had deteriorated, indicating that, in general, the treatment was beneficial. That these effects were long-lasting is supported by the fact that, at follow-up, 78% of all patients were no longer receiving treatment, 18% were receiving outpatient or day treatment, and 4% were receiving inpatient treatment. Phobic patients appear to have gained more from the multimodal approach than did obsessive-compulsive patients, as indicated by the fact that the severity of symptoms decreased as they improved in rational thinking, assertiveness, and arousal. By contrast, obsessive-compulsive patients relapsed more than phobic patients did. This was attributed to the fact that the former gained less from the rational-emotive training, denied problems with assertiveness, and did not practice the acquired relaxation skills. It further appeared that a favorable outcome could be induced in patients who (1) expressed relatively mild symptoms in this otherwise severe group, (2) reported relatively few additional complaints, (3) could clearly indicate interpersonal problems, and (4) did not use psychotropic drugs. These prognostic factors are so widespread that not much weight can be ascribed to them. Yet they are useful for indication of imt until better predictors are found

Stabilized lasers for advanced gravitational wave detectors

Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described