Magnetorotational Instability in Core-Collapse Supernovae

We discuss the relevance of the magnetorotational instability (MRI) in core-collapse supernovae (CCSNe). Our recent numerical studies show that in CCSNe, the MRI is terminated by parasitic instabilities of the Kelvin-Helmholtz type. To determine whether the MRI can amplify initially weak magnetic fields to dynamically relevant strengths in CCSNe, we performed three-dimensional simulations of a region close to the surface of a differentially rotating proto-neutron star in non-ideal magnetohydrodynamics with two different numerical codes. We find that under the conditions prevailing in proto-neutron stars, the MRI can amplify the magnetic field by (only) one order of magnitude. This severely limits the role of MRI channel modes as an agent amplifying the magnetic field in proto-neutron stars starting from small seed fields.Comment: Proceedings in Acta Physica Polonica B, Proceedings Supplement, Vol. 10, No. 2, p.361, 4 pages, 1 figur

Comparison of the results of laparoscopic appendectomies with application of different techniques for closure of the appendicular stump

BACKGROUND: Nowadays laparoscopy is used frequently not only in elective surgery but also in abdominal emergencies, including acute appendicitis. There are several techniques used to close the appendicular stump during laparoscopic appendectomy. The aim of the study was to present and compare the results of minimally invasive appendectomies performed with the use of endoscopic staplers (group A), titanium endoclips (group B) and invaginating sutures (group C). METHODS: Three hundred seven patients (mean age = 35.6; SD = 15.9; 178 males,129 females) operated on laparoscopically for acute appendicitis from January 2010 to December 2014 at our department were included in the study. We reviewed retrospectively patients’ data including: age, sex, duration of the surgical procedure and hospital stay, mortality, intraoperative and postoperative complication rates in all analyzed groups. RESULTS: There were 102 patients in group A (mean age = 35.8;SD = 15.4; 57 males, 45 females). The average hospital stay in this group was 4.3 days (SD = 1.7), average operation time was 62.0 min (SD = 15), postoperative complication rate was 5.9 %. There were 160 patients in group B (mean age = 35.0; SD = 16.3; 96 males, 64 females). The average hospital stay in this group was 3.6 days (SD = 1.4), average operation time was 62.9 min (SD = 13.5), postoperative complication rate was 5.6 %. There were 45 patients in group C (mean age =37.3; SD = 15.8; 25 males, 20 females). The average hospital stay in this group was 4.6 days (SD = 2.0), average operation time was 73.9 min (SD = 20.8), postoperative complication rate was 6.7 %. There were no intraoperative complications and no mortality in all compared groups of patients operated on laparoscopically for acute appendicitis. CONCLUSIONS: Laparoscopic appendectomies with application of different techniques for closure of the appendicular stump are useful and safe. In our study the shortest hospital stay and lowest complication rate were observed in patients operated with the use of titanium endoclips. The longest hospital stay and operation time and the highest complication rate was associated with the use of invaginating sutures

Employee shirking and overworking:modelling the unintended consequences of work organisation

Underworking (i.e. shirking) and overworking of employees can have detrimental effects for the individual and the organisation. We develop a computational model to investigate how work structure, specifically the way in which managers distribute work tasks amongst employees, impacts work intensity and working time. The model draws on theories from economics, psychology and management, and on empirical observations. The simulations show that when managers correctly estimate task difficulty, but undervalue the employee’s competence, opportunities for shirking are provided due to longer deadlines. Similarly, if managers overvalue the employee’s competence, they set tighter deadlines leading to overwork. If task difficulty is misjudged, initially only influence on employee working time is observed. However, it gradually generates competence misjudgements, indirectly impacting the employee’s effort level. An interaction between competence misjudgement and task uncertainty slows the manager’s ability to correctly estimate employee competence and prolongs initial competence misjudgements. The study highlights the importance of applying dynamic modelling methods, which allows for testing theory assumptions in silico, generating new hypotheses and offers a foundation for future research. Practitioner summary: A computational model was developed to investigate how the structure of work allocation influences opportunities for shirking and overworking by employees. The paper demonstrates how dynamic modelling can be used to explain workplace phenomena and develop new hypotheses for further research. Abbreviations: KSA: knowledge, skills, attitudes; MIT: motivation intensity theory

General Relativistic versus Newtonian: a universality in radiation hydrodynamics

We compare Newtonian and general relativistic descriptions of the stationary accretion of self-gravitating fluids onto compact bodies. Spherical symmetry and thin gas approximation are assumed. Luminosity depends, amongst other factors, on the temperature and the contribution of gas to the total mass, in both -- general relativistic ($L_{GR}$) and Newtonian ($L_N$) -- models. We discover a remarkable universal behaviour for transonic flows: the ratio of respective luminosities $L_{GR}/L_N$ is independent of the fractional mass of the gas and depends on asymptotic temperature. It is close to 1 in the regime of low asymptotic temperatures and can grow by one order of magnitude for high temperatures. These conclusions are valid for a wide range of polytropic equations of state.Comment: 8 pages, 4 figure

How to improve the adenoma detection rate in colorectal cancer screening? Clinical factors and technological advancements

Introduction: Colonoscopy has been widely regarded as the gold standard in colorectal cancer (CRC) screening. Within recent years different endoscopic imaging techniques have been introduced to improve the quality of colonoscopy. The adenoma detection rate (ADR) is the single most important quality indicator for colonoscopy. The aim of this study was to evaluate the quality of CRC screening expressed by ADR in two different eras of endoscopic technology advancement. Material and methods: We conducted a dual-center study that enrolled 24 055 patients, who underwent colonoscopy as part of a national screening program. Patients were sorted into two groups according to the advancement of endoscopic equipment used for colonoscopic examination: group I - 10 405 patients examined between 2004 and 2008 (standard electronic endoscopes); group II - 13 650 patients examined between 2009 and 2014 (modern endoscopes). The ADR in two different eras and the impact of endoscopic novelties were determined. Results: The ADR in group I was 29.14%, in group II 31.73% (p < 0.001). The overall ADR was 30.88% - 38.80% and 25.95% (p < 0.001) for the male and female patients, respectively. The mean adenoma number per colonoscopy was 0.366 (95% CI: 0.357-0.375; p < 0.001), 0.337 (0.321-0.352) and 0.380 (0.369-0.392) for patients in group I and group II, respectively. Conclusions: Our study shows that technological innovation, novel endoscopy devices and diagnostic techniques improve the quality in CRC screening by increasing the ADR. However, we need to determine which of the technologies are supreme to achieve excellence in colorectal cancer screening

Creativity and the entrepreneur's potential : a case study based on the opinion of students

PURPOSE: The article attempts to analyze and describe the relationship between the notions of creativity, creativity, innovation and relate them to the term entrepreneurship. Questions to be answered: Is creativity related to entrepreneurship understood as a founding initiative? Does the creative mindset allow you to find yourself in risky conditions more easily? Regardless of whether the reference point is entrepreneurship (as a founding activity) or intrapreneurship of employees - appropriate use of creativity resources lead to economic growth, which is the justification for the research.DESIGN/METHODOLOGY/APPROACH: Empirical research was conducted in the first quarter of 2021 among students of a private university with an economic profile (Poznań, Poland).FINDINGS: In the surveyed group, as many as 48.8% of respondents planned to start their own enterprise. The results of the research carried out show, unfortunately, that creativity is not a competence appreciated in the studied group of students at the economic university in Poznań. Even among people declaring the intention to start their own enterprise, the usefulness of a creative attitude in their professional work is not noticed.PRACTICAL IMPLICATIONS: The presented research results did not confirm a significant relationship between a creative attitude and the ease of coping with the risk of running a business.ORIGINALITY/VALUE: It is therefore worth introducing changes to the educational policy in the field of entrepreneurship aimed at enhancing creativity. This may significantly contribute to the development of innovative enterprises in the SME sector.peer-reviewe