Masses of constituent quarks confined in open bottom hadrons

We apply color-spin and flavor-spin quark-quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this paper was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi-Breit (FB) and flavor-spin Glozman-Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially $b$ quark mass). Another aim was to discern between the FB and GR HFI because our previous findings had indicated that both interactions were satisfactory. Our improved fitting procedure of constituent quark masses showed that on average color-spin (Fermi-Breit) hyperfine interaction yields better fits. The method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.Comment: 15 pages, 6 tables, 1 figure. Accepted for publication in Mod. Phys. Lett.

The First Spectroscopically Resolved Sub-parsec Orbit of a Supermassive Binary Black Hole

One of the most intriguing scenarios proposed to explain how active galactic nuclei are triggered involves the existence of a supermassive binary black hole system in their cores. Here we present an observational evidence for the first spectroscopically resolved sub-parsec orbit of a such system in the core of Seyfert galaxy NGC 4151. Using a method similar to those typically applied for spectroscopic binary stars we obtained radial velocity curves of the supermassive binary system, from which we calculated orbital elements and made estimates about the masses of components. Our analysis shows that periodic variations in the light and radial velocity curves can be accounted for an eccentric, sub-parsec Keplerian orbit of a 15.9-year period. The flux maximum in the lightcurve correspond to the approaching phase of a secondary component towards the observer. According to the obtained results we speculate that the periodic variations in the observed H{\alpha} line shape and flux are due to shock waves generated by the supersonic motion of the components through the surrounding medium. Given the large observational effort needed to reveal this spectroscopically resolved binary orbital motion we suggest that many such systems may exist in similar objects even if they are hard to find. Detecting more of them will provide us with insight into black hole mass growth process.Comment: 29 pages, 10 figures, published in ApJ, 759, 11

The influence of professional stress in permanent working capability of workers with arterial hypertension and its complications

Arterial hypertension is widespread in the population of workers. Stress at work has a significant impact on the emergence of many psychosomatic diseases including arterial hypertension. The aim of this research is to show the influence of professional stress on the occurrence of arterial hypertension, its complications and the permanent working ability of exposed workers in construction. The survey covered 1900 construction workers. The standardized questionnaire has assessed the level of stress and professional stressors in their workplaces. The survey group consisted of 1350 workers whose level of total professional stress index (OSI) was over 60, and a control group of 550 workers with an OSI level below 60. The prevalence of arterial hypertension and its complications is statistically significantly more frequent in the examined than in the control group. In the investigated group, a statistically significant number of workers were registered, who, due to their complete loss of working ability, were sent to the disability commission. With an increase in OSI values above 71, the number of workers with complete loss of working capacity is significantly increased in relation to the number of workers who are capable of working. Professional stress is a significant factor that affects the occurrence of arterial hypertension, its complications on vital organs, which lead to a complete permanent loss of working ability of exposed workers in construction

Work stress related lipid disorders and arterial hypertension in professional drivers: A cross-sectional study

Background/Aim. Occupational stress is a term used to define ongoing stress that is related to the workplace. The study was conducted to determine association of occupational stress index (OSI) and its aspects with arterial hypertension and lipid disorders using data from a cross-sectional survey of male professional drivers. Methods. The cross-sectional study was performed in 439 professional drivers divided into groups (city- and intercity bus drivers, truck and taxi drivers). The OSI and OSI aspects (high demands, strictness, underload, extrinsic time pressure, noxious exposure, avoidance and conflict) were calculated using the standardized questionnaire. Determination of serum lipids, blood pressure (BP) and cardiovascular risk factors were done. Results. A significant difference in prevalence of diagnosed hypertension and dyslipidemia was found along with a difference in total OSI and OSI aspects among examined subgroups of drivers. A total OSI was highest in city, high in intercity bus drivers, and the lowest one in truck and taxi drivers (82.79 ± 3.5, 81.28 ± 3.7, 73.75 ± 3.5, 71.61 ± 4.4, respectively; p < 0.01). Similar pattern showed triglycerides (TG), total cholesterol (TC) and LDL cholesterol and BP, while HDL-cholesterol showed reverse order (p < 0.01). Logistic regression analyses with multiple OSI aspects adjusted for age and years of exposure showed associations of total OSI with arterial hypertension [OR 5.5; 95% CI (2.24-7.95)] and dyslipidemia [OR 1.43 95% CI (1.09-2.80)]. Underload was the most important OSI aspect associated with the arterial hypertension [OR 1.18; 95% CI (1.04-2.58)] and elevated LDL cholesterol [1.26; 95 CI (1.19-2.1)]. A total OSI had a significant association with elevated LDL cholesterol [2.64; 95% CI (1.19- 7.7)], triglycerides [OR 3.27; 95% CI (1.20-5.1)] and low HDL cholesterol [OR 3.29; 95% CI (1.8-5.8)] (p < 0.01). Conclusion. The study provides the evidence for the significant association of total OSI and underload with lipid disorders and elevated blood pressure in professional drivers, which could be a possible link between job stress and coronary heart disease. Regular periodical examinations and workplace interventions aimed to decrease total OSI and underload are important aspects in primary prevention and additional reduction of cardiovascular risk. [Projekat Ministarstva nauke Republike Srbije, br. 43012 i br. 41018

Uticaj opterećenja različitim nivoima profesionalnog stresa na koncentraciju serumskih lipida službenika obezbeđenja

The aim of this work is to analyze the relationship between the level of professional stress and the concentration of total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides in the serum of security employees. . The study included 415 security officers (exposed group) divided into four sub-groups and 150 administrative workers (control group). By applying a standardized questionnaire, the level of professional stress in their workplaces was calculated. To determine the serum lipid concentration in the all subjects, venous blood samples were taken in the morning after a twelve-hour food abstinence Security officers are exposed to a high level of professional stress, where the level of stress index depends on the type of the job they are engaged in. The highest values of the total index of professional stress, total cholesterol, LDL cholesterol and triglycerides were registered with the employees who transport money and those carrying firearms. The lowest total index of professional stress, total cholesterol, LDL cholesterol and triglycerides were registered with property security officers and persons who do not carry firearms. The correlation between the level of stress index at work, an increase in total cholesterol, LDL cholesterol, triglycerides and HDL cholesterol levels is statistically significant. We believe that there is a significant correlation between the level of the overall stress index at work and the risk of atherosclerosis in security officers.Cilj rada je analiza povezanosti nivoa profesionalnog stresa i koncentracija ukupnog holesterola, HDL holesterola, LDL holesterola i triglicerida u serumu službenika angažovanih na različitim vrstama obezbeđenja. Ispitivanjem je obuhvaćeno 415 službenika obezbeđenja (ispitivana grupa) podeljenih u četiri podgrupe i 150 administrativnih radnika (kontrolna grupa). Primenom standardizovanog upitnika, je izračunavan nivo profesionalnog stresa na njihovim radnim mestima. Radi određivanja koncentracije lipida u serumu od svih ispitanika je uziman uzorak venske krvi ujutru posle dvanaestočasovne apstinencije od hrane. Službenici obezbeđenja su izloženi visokom nivou profesionalnog stresa, pri čemu nivo indeksa stresa zavisi od vrste poslova na kojima su angažovani. Najviše vrednosti ukupnog indeksa profesionalnog stresa, ukupnog holesterola, LDL holesterola i triglicerida su registrovane kod službenika na obezbedjenju transporta novca sa nošenjem vatrenog oružja. Najniže vrednosti ukupnog indeksa profesionalnog stresa, ukupnog holesterola, LDL holesterola i triglicerida su registrovane kod službenika na obezbedjenju imovine i lica bez nošenja vatrenog oružja. Utvrđena je statistički značajna korelacija između nivoa indeksa stresa na poslu, povećanja vrednosti ukupnog holesterola, LDL holesterola, triglicerida i smanjenja nivoa HDL holesterola. Smatramo da postoji značajna povezanost između nivoa ukupnog indeksa stresa na poslu i rizika od ateroskleroze kod službenika obezbeđenja

A Streamwise Constant Model of Turbulence in Plane Couette Flow

Streamwise and quasi-streamwise elongated structures have been shown to play a significant role in turbulent shear flows. We model the mean behavior of fully turbulent plane Couette flow using a streamwise constant projection of the Navier Stokes equations. This results in a two-dimensional, three velocity component ($2D/3C$) model. We first use a steady state version of the model to demonstrate that its nonlinear coupling provides the mathematical mechanism that shapes the turbulent velocity profile. Simulations of the $2D/3C$ model under small amplitude Gaussian forcing of the cross-stream components are compared to DNS data. The results indicate that a streamwise constant projection of the Navier Stokes equations captures salient features of fully turbulent plane Couette flow at low Reynolds numbers. A system theoretic approach is used to demonstrate the presence of large input-output amplification through the forced $2D/3C$ model. It is this amplification coupled with the appropriate nonlinearity that enables the $2D/3C$ model to generate turbulent behaviour under the small amplitude forcing employed in this study.Comment: Journal of Fluid Mechanics 2010, in pres

Adaptation “in the Wild”: Ontology-Based Personalization of Open-Corpus Learning Material

Abstract. Teacher and students can use WWW as a limitless source of learning material for nearly any subject. Yet, such abundance of content comes with the problem of finding the right piece at the right time. Conventional adaptive educational systems cannot support personalized access to open-corpus learning material as they rely on manually constructed content models. This paper presents an approach to this problem that does not require intervention from a human expert. The approach has been implemented in an adaptive system that recommends students supplementary reading material and adaptively annotates it. The results of the evaluation experiment have demonstrated several significant effects of using the system on students ’ learning

Adaptation “in the Wild”: Ontology-Based Personalization of Open-Corpus Learning Material

Teacher and students can use WWW as a limitless source of learning material for nearly any subject. Yet, such abundance of content comes with the problem of finding the right piece at the right time. Conventional adaptive educational systems cannot support personalized access to open-corpus learning material as they rely on manually constructed content models. This paper presents an approach to this problem that does not require intervention from a human expert. The approach has been implemented in an adaptive system that recommends students supplementary reading material and adaptively annotates it. The results of the evaluation experiment have demonstrated several significant effects of using the system on students’ learning.\u