Increasing productivity in heavy machining using a simulation based optimization method for porcupine milling cutters with a modified geometry

Porcupine milling cutters offer a high potential for increasing the metal removal rate in heavy machining of steel and titanium. Here, the available machine power and the maximum radial force represent important process limits. According to the current state of the art, mainly rectangular indexable inserts are used. Investigations show that the use of round inserts can significantly reduce the resulting radial force and cutting torque similar to serrated endmills. However, the design of such tools is a major challenge due to the complicated shape of cross-section of the undeformed chip. Therefore, this paper presents a new method for optimizing the position of individual indexable inserts by means of geometric material removal simulations. With the new method, the radial force can be reduced by 14%

Optimization of complex cutting tools using a multi-dexel based material removal simulation

Multi-dexel based material removal simulations provide a fast and flexible way to compute process forces and tool deflections for milling and turning operations. This allows an advanced process planning including detection of collisions for complex toolpaths. However, using dexel simulations for designing cutting tools has rarely been investigated. Especially the position of individual cutting edges is not considered, because current approaches only subtract the sweep volume of the tool envelop instead of the rake face. This paper presents a new method to design cutting tools using material removal simulations and a detailed tool geometry representation. The discretization of the tool allows an efficient calculation of the engagement conditions of individual cutting edges. The method is used to optimize novel porcupine milling cutters with round indexeble inserts, which produces a geometry analogous to serrated end mills. Based on the calculated forces, the positions of individual indexable inserts are adjusted to minimize the maximum radial force. An optimum has been found that reduces radial force by 12% compared to conventional porcupine milling cutters with squared inserts. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of The 17th CIRP Conference on Modelling of Machining Operation

Advanced process design for re-contouring using a time-domain dynamic material removal simulation

The repair of components often requires the removal of excess weld material. This removal is considered as re-contouring. Re-contouring processes have to be designed individually for each case of damage to fulfil the high quality requirements. Therefore, a prognosis of the machined surface topography is crucial. The material removal simulation introduced in this paper allows the prediction of process stability and surface topography for 5-axis ball end milling including dynamic effects. Different process strategies for re-contouring of Ti-6Al-4V welds are examined. It is shown, that selecting suitable process parameters can lead to high surface quality while maintaining productivity. © 2019 The Author(s)

Neuromuscular Blockade with Rocuronium Bromide Increases the Tolerance of Acute Normovolemic Anemia in Anesthetized Pigs

Background: The patient's individual anemia tolerance is pivotal when blood transfusions become necessary, but are not feasible for some reason. To date, the effects of neuromuscular blockade (NMB) on anemia tolerance have not been investigated. Methods: 14 anesthetized and mechanically ventilated pigs were randomly assigned to the Roc group (3.78 mg/kg rocuronium bromide followed by continuous infusion of 1 mg/kg/min, n = 7) or to the Sal group (administration of the corresponding volume of normal saline, n = 7). Subsequently, acute normovolemic anemia was induced by simultaneous exchange of whole blood for a 6% hydroxyethyl starch solution (130/0.4) until a sudden decrease of total body O-2 consumption (VO2) indicated a critical limitation of O-2 transport capacity. The Hb concentration quantified at this time point (Hb(crit)) was the primary end-point of the protocol. Secondary endpoints were parameters of hemodynamics, O-2 transport and tissue oxygenation. Results: Hb(crit) was significantly lower in the Roc group (2.4 +/- 0.5 vs. 3.2 +/- 0.7 g/dl) reflecting increased anemia tolerance. NMB with rocuronium bromide reduced skeletal muscular VO2 and total body O-2 extraction rate. As the cardiac index increased simultaneously, total body VO2 only decreased marginally in the Roc group (change of VO2 relative to baseline -1.7 +/- 0.8 vs. 3.2 +/- 1.9% in the Sal group, p < 0.05). Conclusion: Deep NMB with rocuronium bromide increases the tolerance of acute normovolemic anemia. The underlying mechanism most likely involves a reduction of skeletal muscular VO2. During acellular treatment of an acute blood loss, NMB might play an adjuvant role in situations where profound stages of normovolemic anemia have to be tolerated (e.g. bridging an unexpected blood loss until blood products become available for transfusion). Copyright (C) 2011 S. Karger AG, Base

Rural, urban and migrant differences in noncommunicable disease risk-factors in middle income countries: a cross-sectional study of WHO-SAGE Data

Understanding how urbanisation and rural-urban migration influence risk-factors for non-communicable disease (NCD) is crucial for developing effective preventative strategies globally. This study compares NCD risk-factor prevalence in urban, rural and migrant populations in China, Ghana, India, Mexico, Russia and South Africa.Study participants were 39,436 adults within the WHO Study on global AGEing and adult health (SAGE), surveyed 2007-2010. Risk ratios (RR) for each risk-factor were calculated using logistic regression in country-specific and all country pooled analyses, adjusted for age, sex and survey design. Fully adjusted models included income quintile, marital status and education.Regular alcohol consumption was lower in migrant and urban groups than in rural groups (pooled RR and 95%CI: 0.47 (0.31-0.68); 0.58, (0.46-0.72), respectively). Occupational physical activity was lower (0.86 (0.72-0.98); 0.76 (0.65-0.85)) while active travel and recreational physical activity were higher (pooled RRs for urban groups; 1.05 (1.00-1.09), 2.36 (1.95-2.83), respectively; for migrant groups: 1.07 (1.0 -1.12), 1.71 (1.11-2.53), respectively). Overweight, raised waist circumference and diagnosed diabetes were higher in urban groups (1.19 (1.04-1.35), 1.24 (1.07-1.42), 1.69 (1.15-2.47), respectively). Exceptions to these trends exist: obesity indicators were higher in rural Russia; active travel was lower in urban groups in Ghana and India; and in South Africa, urban groups had the highest alcohol consumption.Migrants and urban dwellers had similar NCD risk-factor profiles. These were not consistently worse than those seen in rural dwellers. The variable impact of urbanisation on NCD risk must be considered in the design and evaluation of strategies to reduce the growing burden of NCDs globally

Process design for 5-axis ball end milling using a real-time capable dynamic material removal simulation

For repairing turbine blades or die and mold forms, additive manufacturing processes are commonly used to build-up new material to damaged sections. Afterwards, a subsequent re-contouring process such as 5-axis ball end milling is required to remove the excess material restoring the often complex original geometries. The process design of the re-contouring operation has to be done virtually, because the individuality of the repair cases prevents actual running-in processes. Hard-to-cut materials e.g. titanium or nickel alloys, parts prone to vibration and long tool holders complicate the repair even further. Thus, a fast and flexible material removal simulation is needed. The simulation has to predict suitable processes focusing shape deviations under consideration of process stability for arbitrary complex engagement conditions. In this paper, a dynamic multi-dexel based material removal simulation is presented, which is able to predict high-resolution surface topography and stable parameters for arbitrary processes such as 5-axis ball end milling. In contrast to other works, the simulation is able to simulate an unstable process using discrete cutting edges in real-time. © 2020, The Author(s)

Fouryear review of admissions to a South African regional hospital general surgery department

Background. There are limited published data describing surgical admissions at a regional hospital level in the South African (SA) context.Objectives. To retrospectively review data from an electronic discharge summary  database at a regional SA hospital from 2012 to 2016 to describe the burden of surgical disease by analysing characteristics of the patients admitted.Methods. All discharge summary records for the 4-year period were reviewed after extraction from a database created for the surgery department. Admissions were classified into 5 types: (i) elective surgery or investigations (ESI); (ii) trauma; (iii) burns; (iv) non-traumatic surgical emergencies (NTSE); and (v) unplanned readmission within 30 days. Other variables reviewed were demographic data, the International Statistical Classification of Diseases and Related Health Problems – Version 10 (ICD-10) diagnosis; area of origin; and outcome (death, tertiary referral, discharge). Data were subgrouped into 12-month periods to facilitate trend analysis.Results. Discharge summaries (N=9 805) over the 4-year study period were assessed and 9 799 were included in the analysis. All data were entered by the attending medical personnel. A total of 5 647 male patients (57.6%) and 4 152 female patients (42.4%) were admitted, with a mean age of 43.3 years (95% confidence interval (CI) 43.0 - 43.8) and a mean length of stay of 4.9 days (95% CI 4.7 - 5.1). Male patients comprised a larger proportion of trauma (83.7%) and burn (63.9%) admissions. The mean length of stay ranged from 3.5 days for elective patients to 9.1 days for burn patients. The most common diagnoses for emergency admissions were appendicitis, peripheral vascular disease and peptic ulcer disease. Common diagnoses for elective admissions were gallstone disease, inguinal hernia, anal fistulas/fissures, and ventral and incisional hernia. The most common cancer diagnoses were of the colorectum, oesophagus, breast and stomach. The overall mortality rate was 2.2%, and highest by subtype was burn patients (6.3%). Trend analysis showed a statistically significant increase in admission for NTSE (p=0.019), trauma (p&lt;0.001) and 30-day readmission rates (p&lt;0.001), with a decrease in admissions for ESI (p=0.001) over the 4 years.Conclusions. A precise understanding of the burden of disease profile is essential for national, provincial and district budgeting and resource allocation. Ongoing surveillance such as that performed in the study provides this critical information

Flow-dependent regulation of endothelial Tie2 by GATA3 in vivo

BACKGROUND Reduced endothelial Tie2 expression occurs in diverse experimental models of critical illness, and experimental Tie2 suppression is sufficient to increase spontaneous vascular permeability. Looking for a common denominator among different critical illnesses that could drive the same Tie2 suppressive (thereby leak inducing) phenotype, we identified "circulatory shock" as a shared feature and postulated a flow-dependency of Tie2 gene expression in a GATA3 dependent manner. Here, we analyzed if this mechanism of flow-regulation of gene expression exists in vivo in the absence of inflammation. RESULTS To experimentally mimic a shock-like situation, we developed a murine model of clonidine-induced hypotension by targeting a reduced mean arterial pressure (MAP) of approximately 50% over 4 h. We found that hypotension-induced reduction of flow in the absence of confounding disease factors (i.e., inflammation, injury, among others) is sufficient to suppress GATA3 and Tie2 transcription. Conditional endothelial-specific GATA3 knockdown (B6-Gata3$^{tm1-Jfz}$ VE-Cadherin(PAC)-cerERT2) led to baseline Tie2 suppression inducing spontaneous vascular leak. On the contrary, the transient overexpression of GATA3 in the pulmonary endothelium (jet-PEI plasmid delivery platform) was sufficient to increase Tie2 at baseline and completely block its hypotension-induced acute drop. On the functional level, the Tie2 protection by GATA3 overexpression abrogated the development of pulmonary capillary leakage. CONCLUSIONS The data suggest that the GATA3-Tie2 signaling pathway might play a pivotal role in controlling vascular barrier function and that it is affected in diverse critical illnesses with shock as a consequence of a flow-regulated gene response. Targeting this novel mechanism might offer therapeutic opportunities to treat vascular leakage of diverse etiologies

Incidence of Fat Embolism Syndrome in Femur Fractures and Its Associated Risk Factors over Time—A Systematic Review

Background: Fat embolism (FE) continues to be mentioned as a substantial complication following acute femur fractures. The aim of this systematic review was to test the hypotheses that the incidence of fat embolism syndrome (FES) has decreased since its description and that specific injury patterns predispose to its development. Materials and Methods: Data Sources: MEDLINE, Embase, PubMed, and Cochrane Central Register of Controlled Trials databases were searched for articles from 1 January 1960 to 31 December 2019. Study Selection: Original articles that provide information on the rate of FES, associated femoral injury patterns, and therapeutic and diagnostic recommendations were included. Data Extraction: Two authors independently extracted data using a predesigned form. Statistics: Three different periods were separated based on the diagnostic and treatment changes: Group 1: 1 January 1960–12 December 1979, Group 2: 1 January 1980–1 December 1999, and Group 3: 1 January 2000–31 December 2019, chi-square test, χ2 test for group comparisons of categorical variables, p-value < 0.05. Results: Fifteen articles were included (n = 3095 patients). The incidence of FES decreased over time (Group 1: 7.9%, Group 2: 4.8%, and Group 3: 1.7% (p < 0.001)). FES rate according to injury pattern: unilateral high-energy fractures (2.9%) had a significantly lower FES rate than pathological fractures (3.3%) and bilateral high-energy fractures (4.6%) (p < 0.001). Conclusions: There has been a significant decrease in the incidence of FES over time. The injury pattern impacts the frequency of FES. The diagnostic and therapeutic approach to FES remains highly heterogenic to this day