Resonance Oscillation Of Radiative Shock Waves In Accretion Disks Around Compact Objects

We extend our previous numerical simulation of accretion disks with shock waves when cooling effects are also included. We consider bremsstrahlung and other power law processes: $\Lambda \propto T^{\alpha} \rho^2$ to mimic cooling in our simulation. We employ {\it Smoothed Particle Hydrodynamics} technique as in the past. We observe that for a given angular momentum of the flow, the shock wave undergoes a steady, radial oscillation with the period is roughly equal to the cooling time. Oscillations seem to take place when the disk and cooling parameters (i.e., accretion rate, cooling process) are such that the infall time from shock is of the same order as the post-shock cooling time. The amplitude of oscillation could be up to ten percent of the distance of the shock wave from the black hole when the black hole is accreting. When the accretion is impossible due to the centrifugal barrier, the amplitude variation could be much larger. Due to the oscillation, the energy output from the disk is also seen to vary quasi-periodically. We believe that these oscillations might be responsible for the quasi periodic oscillation (QPO) behaviors seen in several black hole candidates, in neutron star systems as well as dwarf novae outbursts such as SS Cygni and VW Hyi.Comment: 24 pages of text plus 6 figures (in tar-compressed form); Astrophysical journal (in press

Zero-energy rotating accretion flows near a black hole

We characterize the nature of thin, axisymmetric, inviscid accretion flows of cold adiabatic gas with zero specific energy in the vicinity of a black hold by the specific angular momentum. Using two-dimensional hydrodynamic simulations in cylindrical geometry, we present various regimes in which the accretion flows behave distinctly differently. When the flow has a small angular momentum (lambda less than or similar to lambda(b)), most of the material is accreted into the black hold, forming a quasi-spherical flow or a simple disklike structure around it. When the flow has a large angular momentum (typically, larger than the marginally bound, value, lambda greater than or similar to(mb)), almost no accretion into the black hole occurs. Instead, the flow produces a stable shock with one or more vortices behind it and is deflected away at the shock as a conical, outgoing wind of higher entropy. If the flow has an angular momentum somewhat smaller than lambda(mb) (lambda less than or similar to lambda less than or similar to lambda(mb)), a fraction (typically 5%-10%) of the incoming material is accreted into the black hole, but the flow structure formed is similar to that for lambda greater than or similar to lambda(mb). Some of the deflected material is accreted back into the black hole while the rest is blown away as an outgoing wind. These two cases with lambda greater than or similar to lambda(u) correspond those studied in the previous works by Molteni, Lanzafame, & Chakrabarti, and Ryu et al. However, the flow with angular momentum close to the marginally stable value (lambda(ms)) is found to be unstable. More specifically, if lambda(b) less than or similar to lambda similar to lambda(ms) less than or similar to lambda(u), the flow displays a distinct periodicity in the sense that the inner part of the disk is built and destroyed regularly. The period is roughly equal to (4-6) x 10(3) R(g)/c, depending on the angular momentum of the flow. In this case, the internal energy of the flow around the black hold becomes maximum when the structure with the accretion shock and vortices is fully developed. But the mass accretion rate into the black hole reaches a maximum value when the structure collapses. Averaged over periods, more than half the incoming material is accreted into the black hole. We suggest the physical origin of these separate regimes from a global perspective. Then we discuss the possible relevance of the instability work to quasi-periodic oscillationsopen716

Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy

IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced colorectal cancers at diagnosis. OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced oncologic stage and change in clinical presentation for patients with colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all 17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December 31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period), in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was 30 days from surgery. EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery, palliative procedures, and atypical or segmental resections. MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding, lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery, and palliative surgery. The independent association between the pandemic period and the outcomes was assessed using multivariate random-effects logistic regression, with hospital as the cluster variable. RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years) underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142 (56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR], 1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03). CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for these patients

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Analysis of the presence of human papillomavirus in healthy skin exposed to sunlight in three seasons: longitudinal study in the city of Rosario in immunocompetent individuals

Los papilomavirus humanos (HPV) están presentes en la piel como flora normal. La evidencia científica sugiere un posible rol de ciertos tipos de los géneros β-PV y γ-PV en el desarrollo de cáncer de piel no melanoma (CPNM) actuando como cofactores sinergísticamente con la radiación ultravioleta (UV). Argentina, por su posición geográfica es una zona de alta exposición a UV por el paso del agujero de ozono en primavera.Objetivo: Determinar las características de la infección por HPV en piel sana expuesta a la luz solar en 3 estaciones climáticas en un grupo de individuos inmunocompetentes.Metodología: Estudio de tipo descriptivo realizado en 78 individuos sanos (edad media: 39 años; rango etario: 23-63 años; 55 mujeres y 23 hombres). Por voluntario se tomaron 3 muestras de piel sana expuesta a la luz solar (frente) con hisopo (Total: 234 muestras) en primavera, verano e invierno. El estado de infección y tipo de HPV se determinó mediante 2 sistemas de cebadores diferentes: FAP y CUT. Resultados: El 79.5% (62/78) de las personas resultó positiva para HPV en al menos una de las estaciones, mientras que el 20.5% (16/78) fue HPV-negativo en las 3 estaciones analizadas. La mayor prevalencia de infección se observó en primavera (54%; 42/78) respecto al verano (45%; 35/78) e invierno (47%; 37/78) (p = 0.43). Los individuos infectados tenían mayor edad y pasaban más horas al sol que los individuos HPV-negativos. Conclusiones: Se observó una mayor frecuencia de infección en primavera, coincidiendo con el paso del agujero de ozono. Dado que la infección con tipos del género β-PV es considerada un factor de riesgo para el desarrollo de CPNM en individuos sanos, estos resultados indican la necesidad de implementar campañas de educación para minimizar los daños acumulativos por exposición UV en una región de alto riesgo como es ArgentinaIntroduction: Human papillomaviruses (HPV) are detectable in healthy skin. The scientific evidence suggests a possible role of certain types of genres PV-β and γ-PV in the development of nonmelanoma skin cancers (NMSC), acting as cofactors synergistically with ultraviolet radiation (UV). Argentina, for its geographical position, is an area of high UV exposure due to the passage of the ozone hole in spring. Objective: To determine the characteristics of the HPV infection in healthy skin exposed to sunlight in three seasons in a group of immunocompetent individuals. Material and methods: Longitudinal study on 78 healthy people (mean age: 39 years; age range: 23-63 years; 55 women and 23 men). In each individual, three samples of healthy skin exposed to sunlight (forehead) were taken with cotton swabs (total: 234 samples) in spring, summer and winter. The state of infection and HPV type were determined by two sets of different primers: FAP and CUT. Results: 79.5% (62/78) of the people tested were positive for HPV in at least one of the seasons, while 20.5% (16/78) were HPV-negative in the three seasons analyzed. The highest prevalence of infection was observed in spring (54%, 42/78), compared to summer (45%; 35/78) and winter (47%; 37/78) (p = 0.43). Infected individuals were older and had more hours of sun exposure than HPV-negative persons. Conclusions: A higher frequency of infection was observed in spring, coinciding with the passage of the ozone hole. Since infection with types of the β-PV genre is considered a risk factor for the development of NMSC in healthy individuals, these results indicate the need to implement education campaigns to minimize cumulative damage from UV exposure in a high-risk region as is Argentina.Fil: Fernandez Bussy, H. R.. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Escuela de Ciencias Médicas; ArgentinaFil: Bolatti, Elisa Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Calegaris, M.. Universidad Nacional de Rosario; ArgentinaFil: Celotti, M.. Universidad Nacional de Rosario; ArgentinaFil: Sánchez, A.. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Escuela de Ciencias Médicas; ArgentinaFil: Chouhy, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Casal, Pablo. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; ArgentinaFil: Giri, Adriana Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Molteni, A.. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Escuela de Ciencias Médicas; ArgentinaFil: Fernandez Bussy, B. R. A.. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Escuela de Ciencias Médicas; Argentin