Nove interdisciplinarne raziskave neolitskih in eneolitskih najdišč na območju Spodnje Volge

The Neolithic and Eneolithic sites in the Low Volga River region have been poorly investigated in comparison with other territories due to a small number of excavated sites. On the Algay site and the Oroshaemoe I settlement there is evidence of the earliest appearance of Neolithic pottery and the first sign of domestication in the Eneolithic period within the Volgo-Ural territory. Archaeological, lithological, grain-size analyses, mineralogical-geochemical methods and radiocarbon dating of cultural deposits have been applied to reconstruct the palaeoenvironment in the Holocene in this area. The results show that the landscape-climatic conditions in the steppe area of the Lower Volga basin strongly affected the development and adaptation of ancient societies.Neolitska in eneolitska najdišča na območju Spodnje Volge so bila v preteklosti zaradi maloštevilnih izkopavanj slabše raziskana v primerjavi z drugimi regijami. Na najdiščih Algay in Oroshaemoe I smo odkrili najstarejši pojav neolitske lončenine in prve znake domestikacije v obdobju eneolitika na območju Volge in Urala. Za rekonstruiranje holocenskega paleookolja na tem območju smo uporabili arheološke, litološke metode, analize velikosti zrn, mineraloško-geokemične metode in radiokarbonsko datiranje kulturnih ostalin. Rezultati kažejo, da so okoljski in klimatski pogoji na območju stepe ob Spodnji Volgi močno vplivali na razvoj in prilagoditve preteklih družb

Effects of DC-Field Excitation on the Incremental Inductance of a Variable Flux Reluctance Machine

This paper presents a method for the computation of the incremental inductances in a 12/10 variable flux reluctance machine using the hybrid analytical modeling coupled with a fixed-point nonlinear solver. The variation of incremental and apparent inductance with respect to the dc-field excitation is investigated for both zero and non-zero ac-field excitations. The results show that the difference between both inductance values is not negligible after 25 A/mm2 dc-current density for the investigated benchmark without the ac field. Moreover, when a non-zero ac field is introduced in addition to the dc-field, the apparent inductance becomes misleading not only under magnetic saturation but also under low excitation in the linear region of the saturation curve. The results obtained with the proposed nonlinear hybrid model are compared with the finite element method in terms of magnetic flux density distribution and incremental inductance value. The root-mean-square discrepancy of magnetic flux density distribution is found to be 37.6 mT. Furthermore, the discrepancy between incremental inductance results of the proposed method and the finite element model is calculated as 1.43%, while the proposed approach requires less post-processing and necessitates ten times less number of degrees-of-freedom

Convergence analysis of the fixed-point method with the hybrid analytical modeling for 2-D nonlinear magnetostatic problems

This paper presents the convergence analysis of the fixed-point method (FPM) to model the nonlinear magnetic characteristics of a 2-D magnetostatic problem. In this study, FPM is used as the iterative nonlinear solver of the hybrid analytical modeling (HAM) technique for the accurate computation of the magnetic field distribution. The benchmark consists of a stator with excitation windings, an airgap, and a slotless mover. The relative errors between two successive iterations are calculated using different error estimators: the attraction force on the mover, the Fourier coefficients defined in the airgap, the magnetic flux density, and the magnetic scalar potential distributions. The effect of the number of mesh elements and harmonics on the accuracy and computational cost of the model is investigated for different levels of magnetic saturation. It is observed that the maximum rate of change in the relative difference of attraction force during the iterations is found to be 0.52 under the magnetic saturation. In addition, the absolute error of the attraction force between the developed hybrid model with FPM and the finite element method (FEM) is achieved to be 0.18%, while HAM has approximately three times less number of degrees-of-freedom compared to FEM

A task and performance analysis of endoscopic submucosal dissection (ESD) surgery

BACKGROUND: ESD is an endoscopic technique for en bloc resection of gastrointestinal lesions. ESD is a widely-used in Japan and throughout Asia, but not as prevalent in Europe or the US. The procedure is technically challenging and has higher adverse events (bleeding, perforation) compared to endoscopic mucosal resection. Inadequate training platforms and lack of established training curricula have restricted its wide acceptance in the US. Thus, we aim to develop a Virtual Endoluminal Surgery Simulator (VESS) for objective ESD training and assessment. In this work, we performed task and performance analysis of ESD surgeries. METHODS: We performed a detailed colorectal ESD task analysis and identified the critical ESD steps for lesion identification, marking, injection, circumferential cutting, dissection, intraprocedural complication management, and post-procedure examination. We constructed a hierarchical task tree that elaborates the order of tasks in these steps. Furthermore, we developed quantitative ESD performance metrics. We measured task times and scores of 16 ESD surgeries performed by four different endoscopic surgeons. RESULTS: The average time of the marking, injection, and circumferential cutting phases are 203.4 (σ: 205.46), 83.5 (σ: 49.92), 908.4 s. (σ: 584.53), respectively. Cutting the submucosal layer takes most of the time of overall ESD procedure time with an average of 1394.7 s (σ: 908.43). We also performed correlation analysis (Pearson's test) among the performance scores of the tasks. There is a moderate positive correlation (R = 0.528, p = 0.0355) between marking scores and total scores, a strong positive correlation (R = 0.7879, p = 0.0003) between circumferential cutting and submucosal dissection and total scores. Similarly, we noted a strong positive correlation (R = 0.7095, p = 0.0021) between circumferential cutting and submucosal dissection and marking scores. CONCLUSIONS: We elaborated ESD tasks and developed quantitative performance metrics used in analysis of actual surgery performance. These ESD metrics will be used in future validation studies of our VESS simulator

Influence of vitreoretinal traction localization on horseshoe tear configuration and risk of rhegmatogenous retinal detachment

Purpose. To evaluate the relationship between the shape of horseshoe tear and the localization of vitreoretinal tractions (VRT) using methods of the peripheral vitreoretinal interface visualization and classify horseshoe tears by shape for sur gical planning.Material and methods. We studied horseshoe tears parameters of 52 patients (52 eyes). The localization of VRT was determined by widefield OCT, the horseshoe tear shape was determined as the ratio of length to width of the tear (l/b) by multispectral laser scanning. The ratio of the obtained data was evaluated by the Spearman correlation analysis. We used Ward’s method of hierarchical clustering to classify the horseshoe tears by shape. The obtained data were used to perform YAG-laser excision of the vitreoretinal adhesion zone in patients with rhegmatogenous retinal detachment as part of the combined microinvasive laser-surgical technology.Results. The l/b ratio ranged from 1/4 to 3/1. A strong negative correlation has been revealed between the horseshoe tear shape and the fixation of vitreoretinal tractions (rs -0.95; p <0.05). Horseshoe tears were identified in 4 groups using Ward’s method of clustering. Each group corresponded to a specific localization of VRT. The extension of VRT beyond the tear was associated with a high risk of rhegmatogenous retinal detachment.Conclusion. A significant correlation has been found between the studied factors confirm the possibility of using data on the horseshoe tear shape for an approximate evaluation of vitreoretinal adhesion localization. The obtained data allows to determine the exact VRT excision zone when performing combined laser-surgical technology without the need for preoperative wide-field OCT

High prevalence of radiological vertebral fractures in adult patients with Ehlers-Danlos syndrome

Previous studies have reported an increased prevalence of osteoporosis in Ehlers–Danlos syndrome (EDS), but these were limited by a small number of patients and lack of information on fragility fractures. In this cross-sectional study, we evaluated the prevalence of radiological vertebral fractures (by quantitative morphometry) and bone mineral density (BMD, at lumbar spine, total hip and femoral neck by dual-energy X-ray absorptiometry) in 52 consecutive patients with EDS (10 males, 42 females; median age 41 years, range: 21–71; 12 with EDS classic type, 37 with EDS hypermobility type, 1 with classic vascular-like EDS, and 2 without specific classification) and 197 control subjects (163 females and 34 males; median age 49 years, range: 26–83) attending an outpatient bone clinic. EDS patients were also evaluated for back pain by numeric pain rating scale (NRS-11).Vertebral fractures were significantly more prevalent in EDS as compared to the control subjects (38.5% vs. 5.1%; p < 0.001) without significant differences in BMD at either skeletal sites. In EDS patients, the prevalence of vertebral fractures was not significantly (p = 0.72) different between classic and hypermobility types. BMD was not significantly different between fractured and non-fractured EDS patients either at lumbar spine (p = 0.14), total hip (p = 0.08), or femoral neck (p = 0.21). Severe back pain (≥ 7 NRS) was more frequent in EDS patients with vertebral fractures as compared to those without fractures (60% vs. 28%; p = 0.04). In conclusion, this is the first study showing high prevalence of vertebral fractures in a relatively large population of EDS patients. Vertebral fractures were associated with more severe back pain suggesting a potential involvement of skeletal fragility in determining poor quality of life. The lack of correlation between vertebral fractures and BMD is consistent with the hypothesis that bone quality may be impaired in EDS