Dissipation production in a closed two-level quantum system as a test of the irreversibility of the dynamics.

Irreversible behavior in open stochastic dynamical systems is quantified by stochastic entropy production, a property that measures the difference in likelihoods of forward and subsequent backward system evolution. But for a closed system, governed by deterministic dynamics, such an approach is not appropriate. Instead, we can consider the difference in likelihoods of forward and "obverse" behavior: the latter being a backward trajectory initiated at the same time as the forward trajectory. Such a comparison allows us to define "dissipation production," an analog of stochastic entropy production. It quantifies the breakage of a property of the evolution termed "obversibility" just as stochastic entropy production quantifies a breakage of reversibility. Both are manifestations of irreversibility. In this study we discuss dissipation production in a quantum system. We consider a simple, deterministic, two-level quantum system characterized by a statistical ensemble of state vectors, and we provide numerical results to illustrate the ideas. We consider cases that both do and do not satisfy an Evans-Searles Fluctuation Theorem for the dissipation production, and hence identify conditions under which the system displays time-asymmetric average behavior: an arrow of time.

Diagnostic value of symptoms for pediatric SARS-CoV-2 infection in a primary care setting.

PURPOSE: To evaluate the diagnostic value of symptoms used by daycares and schools to screen children and adolescents for SARS-CoV-2 infection, we analyzed data from a primary care setting. METHODS: This cohort study included all patients ≤17 years old who were evaluated at Providence Community Health Centers (PCHC; Providence, U.S.), for COVID-19 symptoms and/or exposure, and received SARS-CoV-2 polymerase chain reaction (PCR) testing between March-June 2020. Participants were identified from PCHC electronic medical records. For three age groups- 0-4, 5-11, and 12-17 years-we estimated the sensitivity, specificity, and area under the receiver operating curve (AUC) of individual symptoms and three symptom combinations: a case definition published by the Rhode Island Department of Health (RIDOH), and two novel combinations generated by different statistical approaches to maximize sensitivity, specificity, and AUC. We evaluated symptom combinations both with and without consideration of COVID-19 exposure. Myalgia, headache, sore throat, abdominal pain, nausea, anosmia, and ageusia were not assessed in 0-4 year-olds due to the lower reliability of these symptoms in this group. RESULTS: Of 555 participants, 217 (39.1%) were SARS-CoV-2-infected. Fever was more common among 0-4 years-olds (p = 0.002); older children more frequently reported fatigue (p = 0.02). In children ≥5 years old, anosmia or ageusia had 94-98% specificity. In all ages, exposure history most accurately predicted infection. With respect to individual symptoms, cough most accurately predicted infection in <5 year-olds (AUC 0.69) and 12-17 year-olds (AUC 0.62), while headache was most accurate in 5-11 year-olds (AUC 0.62). In combination with exposure history, the novel symptom combinations generated statistically to maximize test characteristics had sensitivity >95% but specificity <30%. No symptom or symptom combination had AUC ≥0.70. CONCLUSIONS: Anosmia or ageusia in children ≥5 years old should raise providers' index of suspicion for COVID-19. However, our overall findings underscore the limited diagnostic value of symptoms.

Urogenital symptoms after sexual abuse vs irritant contact in premenarchal girls.

OBJECTIVES: Sexually abused (SA) girls report urogenital symptoms temporally related to inappropriate genital contact. Since girls also experience symptoms following genital irritant exposure and mostly all girls are exposed to genital irritants, we describe overall symptoms reported by girls that disclosed SA compared to those that did not and we compare how girls describe symptoms following a specific episode of contact SA vs a genital irritant exposure. DESIGN: Cross-sectional study. Parents/girls interviewed; medical records reviewed. PARTICIPANTS: Five to 12-year-old premenarchal girls/parents. SETTING: An urban and a suburban pediatric practice; a regional treatment center for child abuse. OUTCOME MEASURES: Prevalence of histories of urogenital symptoms in SA girls compared to girls attending well-child exams (controls); girls' description of urogenital symptoms following specific episodes of contact SA compared to specific episodes of genital irritant exposure. RESULTS: More parents/girls in SA group reported prior urogenital symptoms. Most SA girls said past symptoms were caused by inappropriate genital touching; most control girls could not identify causes for prior symptoms. Girls' responses following specific irritant exposures: 76% SA vs 24% control girls used negative terms to describe how it felt, 69% SA vs 6% control girls said it bothered her body and her feelings, and 33% SA vs 12% control girls described experiencing dysuria afterwards (all ps < 0.05). CONCLUSIONS: Girls can relate urogenital symptoms to specific genital contacts; more SA girls reported unpleasant symptoms with an emotional component. A skilled medical history can help differentiate these conditions and diagnose sexual abuse with greater certainty.