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  • Author: Zoran Radojičić x
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Shedding Light on the Doing Business Index: a Machine Learning Approach

Abstract

Background: The World Bank (WB) acknowledged the importance of business regulatory environment and therefore created a metric which ranks 190 countries based on their level of business regulation for domestic firms measured by the Doing Business Index (DBI).

Objectives: The question which attracted our attention is whether all the observed entities should be given the same weighting scheme.

Methods/Approach: The approach we propose as an answer is two-fold. First, we cluster the countries covered by the DBI. In the next step, we apply the statistical multivariate Composite I-distance Indicator (CIDI) methodology to determine new, data-driven weights for each of the retained clusters.

Results: The obtained results show that there is a difference between the weighting schemes proposed by the CIDI methodology.

Conclusions: One can argue that one weighting scheme does not fit all the observed countries, meaning that additional analyses on the DBI are suggested to explore its stability and its weighting scheme.

Open access
Multivariate approach to imposing additional constraints on the Benefit-of-the-Doubt model: The case of QS World University Rankings by Subject

Abstract

Composite indexes have become a valuable asset for stakeholders as they provide ranks of entities and information upon which decisions are made. However, certain questions about their development procedure have been raised recently, especially regarding the weighting process. To tackle the observed issue, in this paper we propose a new multivariate approach for defining weights. Namely, the model based on the Data Envelopment Analysis (DEA), the Benefit-of-the-Doubt (BoD) model, has been used with significant success in the process of composite index development. On the other hand, the Composite I-distance Indicator (CIDI) methodology stands out as an impartial method for assigning weights to indicators. By combining these two approaches, some of the limitations of the original BoD model could be overcome. As a result, new entity-specific weights which maximize the value of the composite index can be proposed. As a case study, we analysed the Quacquarelli Symonds (QS) World University Rankings by Subject in the field of statistics and operational research. The obtained results, which are based on the data-driven weights, can provide new insights into the nature of the observed ranking. The approach presented here might provoke further research on the topic of composite index weights and on the university rankings by subject.

Open access
Relationship of High Circulating Cystatin C to Biochemical Markers of Bone Turnover and Bone Mineral Density in Elderly Males with a Chronic Heart Failure

Summary

Background: The aim of the study was to investigate the association of Cystatin C (CysC) to biochemical markers of bone turnover and bone mass, and to evaluate its prognostic significance in elderly males with chronic heart failure (CHF).

Methods: A prospective cohort study was executed on sixtyeight males (mean age 68±7 years) with mild to moderate CHF, together with 19 of corresponding age- and body mass index-matched healthy individuals who underwent cardio vascular, bone mineral density (BMD), and body com position assessment. Biochemical assessment of all subjects included NT-pro-BNP, parathyroid hormone (PTH), 25-hydroxy vitamin D (25(OH)D), CysC, and biochemical markers of bone turnover including osteocalcin (OC), alkaline phosphatase (ALP), β-CrossLaps (β-CTx), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (RANKL).

Results: Serum CysC was significantly increased in males with CHF in comparison to healthy control ones. A significant positive association was found between CysC levels and OC in males with CHF, while OC and β-CTx increased in increasing CysC tertiles. In multivariate regression analysis, OC and smoking were a significant determinant of CysC in males with CHF. Level of CysC was found to be positively associated with an increased fatal risk in males with CHF.

Conclusions: Serum osteocalcin is an independent predictor of CysC level in elderly males with CHF. Higher CysC level showed a negative relation to survival and bone loss in males with CHF. Further research is needed to confirm the potential role of CysC in the crosstalk between heart, kidney, bone, and energy metabolism in CHF.

Open access
Relationship of High Circulating Cystatin C to Biochemical Markers of Bone Turnover and Bone Mineral Density in Elderly Males with a Chronic Heart Failure

Summary

Background: The aim of the study was to investigate the association of Cystatin C (CysC) to biochemical markers of bone turnover and bone mass, and to evaluate its prognostic significance in elderly males with chronic heart failure (CHF).

Methods: A prospective cohort study was executed on sixtyeight males (mean age 68±7 years) with mild to moderate CHF, together with 19 of corresponding age- and body mass index-matched healthy individuals who underwent cardio vascular, bone mineral density (BMD), and body com position assessment. Biochemical assessment of all subjects included NT-pro-BNP, parathyroid hormone (PTH), 25-hydroxy vitamin D (25(OH)D), CysC, and biochemical markers of bone turnover including osteocalcin (OC), alkaline phosphatase (ALP), β-CrossLaps (β-CTx), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (RANKL).

Results: Serum CysC was significantly increased in males with CHF in comparison to healthy control ones. A significant positive association was found between CysC levels and OC in males with CHF, while OC and β-CTx increased in increasing CysC tertiles. In multivariate regression analysis, OC and smoking were a significant determinant of CysC in males with CHF. Level of CysC was found to be positively associated with an increased fatal risk in males with CHF.

Conclusions: Serum osteocalcin is an independent predictor of CysC level in elderly males with CHF. Higher CysC level showed a negative relation to survival and bone loss in males with CHF. Further research is needed to confirm the potential role of CysC in the crosstalk between heart, kidney, bone, and energy metabolism in CHF.

Open access
Effects of Chronic Psychosocial Stress on Reduction of Basal Glucocorticoid Levels and Suppression of Glucocorticoid Levels Following Dexamethasone Administration in Animal Model of PTSD

Abstract

Aim: To further examine the neurobiological mechanisms and their outcomes responsible for the PTSD sequelae induced by laboratory animal model and to explore the effects of chronic psychosocial paradigm. We tested the hypothesis that our animal model of PTSD would display abnormalities in glucocorticoid levels that are manifest in people with PTSD and that psychosocially stressed rats exhibit a significantly greater suppression of corticosterone levels than control rats following the administration of dexamethasone.

Methods: Animals were divided into two groups. The experimental group was scheduled to exposure to two types of stressors: double exposure to acute immobilization stress, and combined predator-threat stress and daily social stress. There was also administration of dexamethasone in combination with stress exposure.

Results: There was a statistical difference between masses of thymus in the stress group and stress group with dexamethasone appliance (p=0.024). We found statistical significance between baseline cortisol and stress induced levels of cortisol and between stress induced group and return to baseline group.

Conclusion: Significant changes in HPA activity, reductions in basal glucocorticoid levels and enhanced dexamethasone induced inhibition of glucocorticoid levels have been manifested. All of this is manifested in PTSD patients also as many other stress induces changes.

Open access
Molecular Evidence of Q Fever Agent Coxiella Burnetii in Ixodid Ticks Collected from Stray Dogs in Belgrade (Serbia)

Abstract

Q fever is a zoonotic disease caused by Coxiella burnetii, a gram-negative coccobacillus, which has been detected in a wide range of animal species, mostly domestic ruminants, but also in wild mammals, pets, birds, reptiles, arthropods (especially ticks), as well as in humans. Although the exposure to domestic animals in rural areas is regarded as the most common cause of the disease in humans, recent studies have shown that the role of pets in the epidemiology of Q fever has been increasingly growing. Although the primary route of infection is inhalation, it is presumed that among animals the infection circulates through ticks and that they are responsible for heterospecifi c transmission, as well as spatial dispersion among vertebrates. The aim of this study was to determine the presence and prevalence of C. burnetii in ticks removed from stray dogs, as well as to examine the distribution of tick species parasitizing dogs on the territory of Belgrade city. A PCR protocol targeting IS1111 repetitive transposon-like region of C. burnetii was used for the detection of C. burnetii DNA in ticks and the results were confi rmed by sequence analysis. In total, 316 ticks were collected from 51 stray dogs - 40 females (78.43%) and 11 males (21.57%). Three species of ticks were identifi ed: Rhipicephalus s anguineus (72.15%), Ixodes ricinus (27.53%) and Dermacentor reticulatus (0.32%). Out of 316 examined ticks, C. burnetii DNA was detected only in the brown dog tick R. sanguineus, with a total prevalence of 10.53% (24/228) . The high prevalence of C. burnetii in R. sanguineus, which is primarily a dog tick, indicates the importance of dogs in the epidemiology of Q fever in the territory of Belgrade.

Open access