Self-excited vibrations in turning: cutting moment analysis

This work aims at analysing the moment effects at the tool tip point and at the central axis, in the framework of a turning process. A testing device in turning, including a six-component dynamometer, is used to measure the complete torsor of the cutting actions in the case of self-excited vibrations. Many results are obtained regarding the mechanical actions torsor. A confrontation of the moment components at the tool tip and at the central axis is carried out. It clearly appears that analysing moments at the central axis avoids the disturbances induced by the transport of the moment of the mechanical actions resultant at the tool tip point. For instance, the order relation between the components of the forces is single. Furthermore, the order relation between the moments components expressed at the tool tip point is also single and the same one. But at the central axis, two different order relations regarding moments are conceivable. A modification in the rolling moment localization in the (y, z) tool plan is associated to these two order relations. Thus, the moments components at the central axis are particularly sensitive at the disturbances of machining, here the self-excited vibrations.Comment: 8 page

New method to characterize a machining system: application in turning

Many studies simulates the machining process by using a single degree of freedom spring-mass sytem to model the tool stiffness, or the workpiece stiffness, or the unit tool-workpiece stiffness in modelings 2D. Others impose the tool action, or use more or less complex modelings of the efforts applied by the tool taking account the tool geometry. Thus, all these models remain two-dimensional or sometimes partially three-dimensional. This paper aims at developing an experimental method allowing to determine accurately the real three-dimensional behaviour of a machining system (machine tool, cutting tool, tool-holder and associated system of force metrology six-component dynamometer). In the work-space model of machining, a new experimental procedure is implemented to determine the machining system elastic behaviour. An experimental study of machining system is presented. We propose a machining system static characterization. A decomposition in two distinct blocks of the system "Workpiece-Tool-Machine" is realized. The block Tool and the block Workpiece are studied and characterized separately by matrix stiffness and displacement (three translations and three rotations). The Castigliano's theory allows us to calculate the total stiffness matrix and the total displacement matrix. A stiffness center point and a plan of tool tip static displacement are presented in agreement with the turning machining dynamic model and especially during the self induced vibration. These results are necessary to have a good three-dimensional machining system dynamic characterization

Outcomes and Risk Score for Distal Pancreatectomy with Celiac Axis Resection (DP-CAR): An International Multicenter Analysis

Background: Distal pancreatectomy with celiac axis resection (DP-CAR) is a treatment option for selected patients with pancreatic cancer involving the celiac axis. A recent multicenter European study reported a 90-day mortality rate of 16%, highlighting the importance of patient selection. The authors constructed a risk score to predict 90-day mortality and assessed oncologic outcomes. Methods: This multicenter retrospective cohort study investigated patients undergoing DP-CAR at 20 European centers from 12 countries (model design 2000–2016) and three very-high-volume international centers in the United States and Japan (model validation 2004–2017). The area under receiver operator curve (AUC) and calibration plots were used for validation of the 90-day mortality risk model. Secondary outcomes included resection margin status, adjuvant therapy, and survival. Results: For 191 DP-CAR patients, the 90-day mortality rate was 5.5% (95 confidence interval [CI], 2.2–11%) at 5 high-volume (≥ 1 DP-CAR/year) and 18% (95 CI, 9–30%) at 18 low-volume DP-CAR centers (P = 0.015). A risk score with age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, multivisceral resection, open versus minimally invasive surgery, and low- versus high-volume center performed well in both the design and validation cohorts (AUC, 0.79 vs 0.74; P = 0.642). For 174 patients with pancreatic ductal adenocarcinoma, the R0 resection rate was 60%, neoadjuvant and adjuvant therapies were applied for respectively 69% and 67% of the patients, and the median overall survival period was 19 months (95 CI, 15–25 months). Conclusions: When performed for selected patients at high-volume centers, DP-CAR is associated with acceptable 90-day mortality and overall survival. The authors propose a 90-day mortality risk score to improve patient selection and outcomes, with DP-CAR volume as the dominant predictor

Antiulcer potential of Sapium indium aqueous extract: Towards the development of halal pharmaceutical ingredient with gastroprotective property

With the growing number of population suffering of gastro-related diseases such as ulcer and gastritis, the need to find novel halal pharmaceutical ingredients with gastroprotective activity is also increasing significantly, especially among the Muslim population. The conventional antiulcer drugs are over shaded with unwanted side effects. Plant kingdom is regarded as one of the valuable source to fulfill such need. One of the plants that currently caught our attention is Sapium indicum. Therefore, based on the traditional use of S. indicum to relieve pain and to heal wound, as well as the scientifically reported antimicrobial, antinociceptive and antioxidant properties, this study was intended to evaluate the antiulcer potential of S.indcium aqueous extract (SIAE) using established ethanol and indomethacine-induced models, followed by pylorus ligation model for antiulcer mechanisms. The SIAE was prepared at doses of 25, 125 and 250 mg/kg, together with distilled water (negative control) and ranitidine 100 mg/kg (positive control). In ethanol-and indomethacine-induced ulcer models, all doses of SIAE showed reduction in ulcer area formation with 250mg/kg exhibited the best activity with approximately 85.8% and 82% protection respectively when compared to the control group. This is supported by histological findings which showed reduction in epithelial and glandular disruption, congestion, oedema and hemorrhage score with the absence of necrosis and erosion when compared to negative control. The pylorus ligation study also confirmed that SIAE ability to retard ulcer formation by reducing the free and total acidity of gastric secretion in the rats, and enhancement of the gastric mucosal defence action by increased mucus secretion amount. In conclusion, the study suggested that SIAE illustrated good gastroprotective property, which will become s strong basis to develop Halal S.indicum-based pharmaceutical ingredients with gastroprotective property

Antiulcer potential of Sapium indicum aqueous extract: towards the development of halal pharmaceutical ingredient with gastroprotective property

With the growing number of population suffering of gastro-related diseases such as ulcer and gastritis, the need to find novel Halal pharmaceutical ingredients with gastroprotective activity is also increasing significantly, especially among the Muslim population. The conventional antiulcer drugs are overshadowed with unwanted side effects. Plant kingdom is regarded as one of the valuable source to fulfil such need. One of the plants that currently caught our attention is Sapium indicum. Therefore, based on the traditional use of S. indicum to relieve pain and to heal wound, as well as the scientifically reported antimicrobial, antinociceptive and antioxidant properties, this study was intended to evaluate the antiulcer potential of S. indicum aqueous extract (SIAE) using established ethanol- and indomethacin-induced ulcer models, followed by pylorus ligation model for antiulcer mechanisms. The SIAE was prepared at doses of 25, 125 and 250 mg/kg, together with distilled water (negative control) and ranitidine 100 mg/kg (positive control). In ethanol- and indomethacine-induced ulcer models, all doses of SIAE showed reduction in ulcer area formation with 250 mg/kg exhibited the best activity with approximately 85.8% and 82% protection respectively when compared to the control group. This is supported by histological findings which showed reduction in epithelial and glandular disruption, congestion, oedema and haemorrhage score with the absence of necrosis and erosion when compared to negative control. The pylorus ligation study also confirmed the SIAE ability to retard ulcer formation by reducing the free and total acidity of gastric secretion in the rats, and enhancement of the gastric mucosal defence action by increased mucus secretion amount. In conclusion, the study suggested that SIAE illustrated good gastroprotective property, which will become a strong basis to develop Halal S. indicum-based pharmaceutical ingredients with gastroprotective property