Quasi Periodic Oscillations (QPOs) and frequencies in an accretion disk and comparison with the numerical results from non-rotating black hole computed by the GRH code

The shocked wave created on the accretion disk after different physical phenomena (accretion flows with pressure gradients, star-disk interaction etc.) may be responsible observed Quasi Periodic Oscillations (QPOs) in $X-$ray binaries. We present the set of characteristics frequencies associated with accretion disk around the rotating and non-rotating black holes for one particle case. These persistent frequencies are results of the rotating pattern in an accretion disk. We compare the frequency's from two different numerical results for fluid flow around the non-rotating black hole with one particle case. The numerical results are taken from our papers Refs.\refcite{Donmez2} and \refcite{Donmez3} using fully general relativistic hydrodynamical code with non-selfgravitating disk. While the first numerical result has a relativistic tori around the black hole, the second one includes one-armed spiral shock wave produced from star-disk interaction. Some physical modes presented in the QPOs can be excited in numerical simulation of relativistic tori and spiral waves on the accretion disk. The results of these different dynamical structures on the accretion disk responsible for QPOs are discussed in detail.Comment: 13 figures, added reference, accepted for publication in Modern Physics Letters

Comparison of the maternal and neonatal effects of bupivacaine plus fentanyl and ropivacaine plus fentanyl during cesarean delivery

Purpose: The aim of the present study was to compare the anesthetic efficacy, and fetal and maternal effects of 7.5 mg (1 ml) intrathecal 0.75% hyperbaric ropivacaine + 25 ìg (0.5 ml) fentanyl versus 5 mg (l ml) intrathecal 0.5% hyperbaric bupivacaine + 25 ìg (0.5 ml) fentanyl in elective cesarean delivery.Materials and Methods: The study included 40 ASA I–II cases scheduled for cesarean delivery that were randomized into two groups of 20 cases each. Cases in the RF group were administered 0.75% hyperbaric ropivacaine + 25 ìg (0.5 ml) fentanyl and those in the BF group were administered 5 mg (l ml) hyperbaric bupivacaine + 25 ìg (0.5 ml)fentanyl into the spinal space. The time until spinal anesthesia in the T4 dermatome, overall duration of analgesia, hemodynamic parameters, Apgar score of newborns at 1–5 min, fetal blood gas values (pH, PO2, PCO2, HCO3., and BE), maternal side effects, the degree of motor block, maternal need for ephedrine, objective pain scale score, and patient satisfaction were recorded in each group.Results: There were no significant differences between the groups in terms of the parameters evaluated (P > 0.05).Conclusion: In elective cesarean delivery, the combinations of bupivacaine + fentanyl or ropivacaine + fentanyl exhibited similar anesthetic efficacy, and fetal and maternal effects.Key words: Bupivacaine, cesarean, opioid, ropivacain

On the development of QPOs in Bondi-Hoyle accretion flows

The numerical investigation of Bondi-Hoyle accretion onto a moving black hole has a long history, both in Newtonian and in general-relativistic physics. By performing new two-dimensional and general-relativistic simulations onto a rotating black hole, we point out a novel feature, namely, that quasi-periodic oscillations (QPOs) are naturally produced in the shock cone that develops in the downstream part of the flow. Because the shock cone in the downstream part of the flow acts as a cavity trapping pressure perturbations, modes with frequencies in the integer ratios 2:1 and 3:1 are easily produced. The frequencies of these modes depend on the black-hole spin and on the properties of the flow, and scale linearly with the inverse of the black-hole mass. Our results may be relevant for explaining the detection of QPOs in Sagittarius A*, once such detection is confirmed by further observations. Finally, we report on the development of the flip-flop instability, which can affect the shock cone under suitable conditions; such an instability has been discussed before in Newtonian simulations but was never found in a relativistic regime.Comment: 11 pages, 7 figure

Numerical simulation of small perturbation on an accretion disk due to the collision of a star with the disk near the black hole

In this paper, perturbations of an accretion disk by a star orbiting around a black hole are studied. We report on a numerical experiment, which has been carried out by using a parallel-machine code originally developed by D\"{o}nmez (2004). An initially steady state accretion disk near a non-rotating (Schwarzschild) black hole interacts with a "star", modeled as an initially circular region of increased density. Part of the disk is affected by the interaction. In some cases, a gap develops and shock wave propagates through the disk. We follow the evolution for order of one dynamical period and we show how the non-axisymetric density perturbation further evolves and moves downwards where the material of the disk and the star become eventually accreted onto the central body. When the star perturbs the steady state accretion disk, the disk around the black hole is destroyed by the effect of perturbation. The perturbed accretion disk creates a shock wave during the evolution and it loses angular momentum when the gas hits on the shock waves. Colliding gas with the shock wave is the one of the basic mechanism of emitting the $X-$rays in the accretion disk. The series of supernovae occurring in the inner disk could entirely destroy the disk in that region which leaves a more massive black hole behind, at the center of galaxies.Comment: 20pages, 8 figures, accepted for publication in Astrophysics and Space Scienc

Validity and Reliability of the Instruments to Measure Colorectal Cancer Screening Benefits and Barriers—Turkish Version

Background Perceptions of benefits and barriers are important determinants in understanding colorectal cancer screening (CRCS) behaviors. There is a need for standardized Turkish tools that measure the benefits and barriers of fecal occult blood test (FOBT) and colonoscopy (COL). Objective The aim of this study was to assess the validity and reliability of the Turkish version of the “Instruments to Measure CRCS Benefits and Barriers.” Methods This methodological study was carried out in 2 stages in primary care and in 394 adults between the ages of 50 and 70 years. In the first stage, some items of the scales demonstrated low/unacceptable corrected item-total and factor loadings, and in the second stage, it was decided to add emoji-based facial scales, which include emoji expressions. Results Results with the emoji-based facial scales included internal consistency coefficients of 0.85 for FOBT benefits, 0.79 for FOBT barriers, 0.84 for COL benefits, and 0.86 for COL barriers; the item-total correlations of FOBT varied between 0.39 and 0.73, whereas those of COL varied between 0.38 and 0.76. The factor loadings of all items were higher than 0.40. Conclusions The emoji-based facial scale for CRC Screening Benefits and Barriers is a valid and reliable tool for measuring the benefits and barriers perceptions of 50- to 70-year-old Turkish adults. Implications for Practice The Instruments to Measure CRCS Benefits and Barriers–Turkish version can provide insights for nurses and healthcare professionals to understand individuals’ perceived FOBT and COL benefits and barriers and to develop effective interventions to increase CRCS rates

General relativistic radiation hydrodynamics of accretion flows. I: Bondi-Hoyle accretion

We present a new code for performing general-relativistic radiation-hydrodynamics simulations of accretion flows onto black holes. The radiation field is treated in the optically-thick approximation, with the opacity contributed by Thomson scattering and thermal bremsstrahlung. Our analysis is concentrated on a detailed numerical investigation of hot two-dimensional, Bondi-Hoyle accretion flows with various Mach numbers. We find significant differences with respect to purely hydrodynamical evolutions. In particular, once the system relaxes to a radiation-pressure dominated regime, the accretion rates become about two orders of magnitude smaller than in the purely hydrodynamical case, remaining however super-Eddington as are the luminosities. Furthermore, when increasing the Mach number of the inflowing gas, the accretion rates become smaller because of the smaller cross section of the black hole, but the luminosities increase as a result a stronger emission in the shocked regions. Overall, our approach provides the first self-consistent calculation of the Bondi-Hoyle luminosity, most of which is emitted within r~100 M from the black hole, with typical values L/L_Edd ~ 1-7, and corresponding energy efficiencies eta_BH ~ 0.09-0.5. The possibility of computing luminosities self-consistently has also allowed us to compare with the bremsstrahlung luminosity often used in modelling the electromagnetic counterparts to supermassive black-hole binaries, to find that in the optically-thick regime these more crude estimates are about 20 times larger than our radiation-hydrodynamics results.Comment: With updated bibliographyc informatio

Characterisation and microleakage of a new hydrophilic fissure sealant – UltraSeal XT® hydro™

Objectives: The new hydrophilic fissure sealant, UltraSeal XT® hydro™ (Ultradent Products, USA), was characterised and its in vitro resistance to microleakage after placement on conventionally acid etched and sequentially lased and acid etched molars was investigated. Materials and Methods: The sealant was characterised by Fourier transform infra-red spectroscopy, (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Vickers indentation test. Occlusal surfaces of extracted human molars were either conventionally acid etched (n = 10), or sequentially acid etched and laser irradiated (n = 10). UltraSeal XT® hydro™ was applied to both groups of teeth which were then subjected to 2500 thermocycles between 5 and 55 °C prior to microleakage assessment by fuchsin dye penetration. Results: UltraSeal XT® hydro™ is an acrylate-based sealant which achieved a degree of conversion of 50.6 ± 2.2% and a Vickers microhardness of 24.2 ± 1.5 under standard light curing (1000 mWcm-2 for 20 s). Fluoride ion release was negligible within a 14-day period. SEM and EDX analyses indicated that the sealant comprises irregular sub-micron and nano-sized silicon-, barium- and aluminium-bearing filler phases embedded within a ductile matrix. Laser preconditioning was found to significantly reduce microleakage (Mann-Whitney U test, p < 0.001). The lased teeth presented enhanced surface roughness on a 50 to 100 μm scale which caused the segregation and concentration of the filler particles at the enamel-sealant interface. Conclusion: Laser preconditioning significantly decreased microleakage and increased enamel surface roughness which caused zoning of the filler particles at the enamel-sealant interface

Collaboration scripts - a conceptual analysis

This article presents a conceptual analysis of collaboration scripts used in face-to-face and computer-mediated collaborative learning. Collaboration scripts are scaffolds that aim to improve collaboration through structuring the interactive processes between two or more learning partners. Collaboration scripts consist of at least five components: (a) learning objectives, (b) type of activities, (c) sequencing, (d) role distribution, and (e) type of representation. These components serve as a basis for comparing prototypical collaboration script approaches for face-to-face vs. computer-mediated learning. As our analysis reveals, collaboration scripts for face-to-face learning often focus on supporting collaborators in engaging in activities that are specifically related to individual knowledge acquisition. Scripts for computer-mediated collaboration are typically concerned with facilitating communicative-coordinative processes that occur among group members. The two lines of research can be consolidated to facilitate the design of collaboration scripts, which both support participation and coordination, as well as induce learning activities closely related to individual knowledge acquisition and metacognition. In addition, research on collaboration scripts needs to consider the learners’ internal collaboration scripts as a further determinant of collaboration behavior. The article closes with the presentation of a conceptual framework incorporating both external and internal collaboration scripts

Report of the Special-purpose Committee on Virtual Participation in the Nomenclature Section

The Special-purpose Committee on Virtual Participation in the Nomenclature Section was established by the XIX International Botanical Congress (IBC) in Shenzhen, China in 2017, with the mandate “to investigate the possibility of and mechanisms for virtual participation and voting in the Nomenclature Section of an International Botanical Congress via the internet” and to report to the XX IBC. The wide access to the World Wide Web and availability of software for virtual meetings makes the possibility for virtual (online) attendance and voting at a Nomenclature Section seem attainable and advisable. In order to make informed recommendations, we discussed various aspects of online attendance and voting, such as: who should be able to observe?; what would qualify a person to cast institutional votes and personal votes?; if the accumulation of institutional votes should be allowed by an online voter; registration of online voters; how costs would be covered; and recommendations for online attendees. This report provides a synthesis of our discussions and is necessary for interpreting the proposals of this Special-purpose Committee to change aspects of Div. III (Provisions for governance) of the Code (Landrum & al. in Taxon 70: 1397–1398. 2021). This report and those proposals should be consulted together.Fil: Landrum, Leslie R.. Arizona State University; Estados UnidosFil: Fortunato, Renee Hersilia. Universidad de Morón. Facultad de Agronomía y Ciencias Agroalimentarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Barkworth, Mary. State University of Utah; Estados UnidosFil: Breitwieser, Ilse. Manaaki Whenua – Landcare Research; Nueva ZelandaFil: Demissew, Sebsebe. Addis Ababa University; EtiopíaFil: Dönmez, Ali A.. Hacettepe University; TurquíaFil: Dutta, Suchandra. Rishi Dayaram And Seth Hassaram National College And Seth Wassiamull Assomull Science College; IndiaFil: Freire Fierro, Alina. Universidad Regional Amazónica Ikiam; EcuadorFil: Kim, Young Dong. Hallym University; Corea del SurFil: León, Blanca. Universidad Nacional Mayor de San Marcos; PerúFil: Moore, Gerry. United States Department of Agriculture; Estados UnidosFil: Mosyakin, Sergei L.. Academy of Sciences of Ukraine; UcraniaFil: Oh, Sang Hun. Daejeon University; Corea del SurFil: Parra-O, Carlos. Universidad Nacional de Colombia; ColombiaFil: Prado, Jefferson. Instituto de Botânica de Sao Paulo; BrasilFil: Rico Arce, Lourdes. Comisión Nacional para el Conocimiento y Uso de la Biodiversidad; México. Royal Botanic Gardens; Reino UnidoFil: Sennikov, Alexander N.. Russian Academy of Sciences; Rusia. University of Helsinki; FinlandiaFil: Smith, Gideon F.. Nelson Mandela University; Sudáfric

The impact of Er:YAG laser enamel conditioning on the microleakage of a new hydrophilic sealant — UltraSeal XT® hydro™

UltraSeal XT® hydro™ is a new hydrophilic, light-cured, methacrylate-based pit and fissure sealant which has been developed by Ultradent Products, USA. The sealant is highly filled with a 53 wt.% mixture of inorganic particles which confer both thixotropy and radiopacity. The principal purpose of this study was to investigate the microleakage of UltraSeal XT® hydro™ as a function of different enamel etching techniques. The occlusal surfaces of sound, extracted human molars were either acid etched, Er:YAG laser irradiated or successively laser irradiated and acid etched. UltraSeal XT® hydro™ was applied to each group of teeth (n=10) which were subjected to a thermocycling process consisting of 2500 cycles between 5 and 50°C with a dwell time of 30s. Microleakage assessments were then carried out using 0.5 % fuchsin dye and optical microscopy. The microleakage score data were analysed using the Kruskal-Wallis, Mann–Whitney U test with Bonferroni adjustment. No significant differences in microleakage were noted between the individually acid etched and laser-irradiated groups (p>0.05); however, teeth treated with a combination of laser irradiation and acid etching demonstrated significantly lower microleakage scores (p<0.001). Electron microscopy with energy-dispersive X-ray analysis revealed that the mineral filler component of UltraSeal XT® hydro™ essentially comprises micrometre-sized particles of inorganic silicon-, aluminium- and barium-bearing phases. Laser etching increases the roughness of the enamel surface which causes a concentrated zoning of the filler particles at the enamel-sealant interface