Friction and wear behaviour of 18 polymers in contact with steel in environments of air and water

18 polymers were characterized with respect to their friction and wear behaviour in contact with steel in environments of air and water. These were six unfilled materials, i.e. polyamide 66 (PA 66), polyoxymethylene (POM), polyethyleneterephthalate (PETP), polyetheretherketone (PEEK), polyphenylenesulphide (PPS) and polyetherimide; also, the same base materials filled with polytetrafluoroethylene (PTFE) or PTFE plus glass fibre were used.\ud \ud Two types of experiments were performed, i.e. measurement of the coefficient of friction f as a function of the contact temperature Tc (¿f;¿Tc diagrams¿), and measurements of friction and wear in 20 h tests. The f¿Tc diagrams were obtained in air; the 20 h tests were performed in air and in water at a temperature of 20 °C. In air the polymers ran against rings of ball-bearing steel (AISI 52100); in water the rings were made of stainless steel (AISI 316).\ud \ud It turned out that in air addition of PTFE was generally beneficial; PA 66, POM, PETP and PEEK, all filled with PTFE, performed exceptionally well (specific wear rates k appreciably lower than 1×10¿15 m3 N¿1 m¿1). In water, however, PTFE did not function at all. Now PA (with or without PTFE), unfilled POM and PETP filled with PTFE and glass fibre met the k<1× 10¿15 m3 N¿1 m¿1 criterion. With a few exceptions, addition of glass fibre produced unfavourable effects, in air as well as in water.\ud \ud The observed phenomena are explained tentatively in terms of polymer structures and transfer and wear mechanisms, whereby special attention is paid to the ratio of friction over strength

Validation of fully automated VMAT plan generation for library-based plan-of-the-day cervical cancer radiotherapy

Purpose: To develop and validate fully automated generation of VMAT plan-libraries for plan-of-the-day adaptive radiotherapy in locally-advanced cervical cancer. Material and Methods: Our framework for fully automated treatment plan generation (Erasmus-iCycle) was adapted to create dual-arc VMAT treatment plan libraries for cervical cancer patients. For each of 34 patients, automatically generated VMAT plans (autoVMAT) were compared to manually generated, clinically delivered 9-beam IMRT plans (CLINICAL), and to dual-arc VMAT plans generated manually by an expert planner (manVMAT). Furthermore, all plans were benchmarked against 20-beam equi-angular IMRT plans (autoIMRT). For all plans, a PTV coverage of 99.5% by at least 95% of the prescribed dose (46 Gy) had the highest planning priority, followed by minimization of V45Gy for small bowel (SB). Other OARs considered were bladder, rectum, and sigmoid. Results: All plans had a highly similar PTV coverage, within the clinical constraints (above). After plan normalizations for exactly equal median PTV doses in corresponding plans, all evaluated OAR parameters in autoVMAT plans were on average lower than in the CLINICAL plans with an average reduction in SB V45Gy of 34.6% (p<0.001). For 41/44 autoVMAT plans, SB V45Gy was lower than for manVMAT (p<0.001, average reduction 30.3%), while SB V15Gy increased by 2.3% (p = 0.011). AutoIMRT reduced SB V45Gy by another 2.7% compared to autoVMAT, while also resulting in a 9.0% reduction in SB V15Gy (p<0.001), but with a prolonged delivery time. Differences between manVMAT and autoVMAT in bladder, rectal and sigmoid doses were ≤ 1%. Improvements in SB dose delivery with autoVMAT instead of manVMAT were higher for empty bladder PTVs compared to full bladder PTVs, due to differences in concavity of the PTVs. sponsored the appointment of STH for this project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Conclusions: Quality of automatically generated VMAT plans was superior to manually generated plans. Automatic VMAT plan generation for cervical cancer has been implemented in our clinical routine. Due to the achieved workload reduction, extension of plan libraries has become feasible

A sexual rehabilitation intervention for women with gynaecological cancer receiving radiotherapy (SPARC study): design of a multicentre randomized controlled trial

Background: Sexual problems are frequently reported after treatment with radiotherapy (RT) for gynaecological cancer (GC), in particular after combined external beam radiotherapy and brachytherapy (EBRT+BT). Studies demonstrate that psychosexual support should include cognitive behavioural interventions and involvement of the patient's partner, if available. Therefore, we developed a nurse-led sexual rehabilitation intervention, including these key components. The intervention was previously pilot-tested and results demonstrated that this intervention improves women's sexual functioning and increases dilator compliance. The objective of the current study is to investigate the (cost-)effectiveness of the intervention compared to optimal care as usual (CAU). We expect that women who receive the intervention will report a statistically significant greater improvement in sexual functioning and - for women who receive EBRT+BT - higher compliance with dilator use, from baseline to 12 months post-RT than women who receive optimal care as usual (CAU).Methods/design: The intervention is evaluated in the SPARC (Sexual rehabilitation Programme After Radiotherapy for gynaecological Cancer) study, a multicentre, randomized controlled trial (RCT). The primary endpoint is sexual functioning. Secondary outcomes include body image, fear of sexual activity, sexual-, treatment-related- and psychological distress, health-related quality of life and relationship satisfaction. A cost-effectiveness analysis (CEA) will be conducted in which the costs of the intervention will be related to shifts in other health care costs and the impact on patient outcome. The study sample will consist of 220 women with GC treated with RT in specialized GC treatment centres (N = 10). Participants are randomized to either the intervention- or CAU control group (1:1), and within each centre stratified by type of radiotherapy (EBRT+BT vs. EBRT only) and having a partner (yes/no). All women complete questionnaires at baseline (T1) and at 1, 3, 6, and 12 months post-RT (T2, T3, T4 and T5, respectively).Discussion: There is a need to improve sexual functioning after RT for GC. This RCT will provide evidence about the (cost-)effectiveness of a nurse-led sexual rehabilitation intervention. If proven effective, the intervention will be a much needed addition to care offered to GC survivors and will result in improved quality of life.Cervix cance

A nurse-led sexual rehabilitation intervention after radiotherapy for gynecological cancer

Purpose: Although vaginal dilator use after combined pelvic radiation therapy and brachytherapy (RT/BT) is recommended to prevent vaginal shortening and stenosis, women fail to use them and experience sexual problems. A nurse-led sexual rehabilitation intervention targeting sexual recovery and vaginal dilatation was developed. Its feasibility was investigated during a prospective, longitudinal, observational pilot study. Methods: Four oncology nurses were specifically trained to conduct the intervention. Gynecologic cancer patients treated with RT/BT were assessed using (i) questionnaires on frequency of dilator use (monthly), sexual functioning, and sexual distress (at baseline and 1, 6, and 12 months) and psychological and relational distress (at 1, 6, and 12 months); (ii) semi-structured interviews (between 6 and 12 months); and (iii) consultation recordings (a random selection of 21 % of all consults). Results: Twenty participants were 26–71 years old (mean = 40). Eight participants discontinued participation after 3 to 9 months. At 6 months after RT, 14 out of 16 (88 %), and at 12 months 9 out of 12 (75 %), participants dilated regularly, either by having sexual intercourse or by using dilators. Sexual functioning improved between 1 and 6 months after RT, with further improvement at 12 months. Most participants reported that the intervention was helpful and the nurses reported having sufficient expertise and counseling skills. Conclusions: According to the pilot results, the intervention was feasible and promising for sexual rehabilitation and regular dilator use after RT. Its (cost-)effectiveness will be investigated in a randomized controlled trial

PROTECT: prospective phase-II-trial evaluating adaptive proton therapy for cervical cancer to reduce the impact on morbidity and the immune system

Biological, physical and clinical aspects of cancer treatment with ionising radiatio

The effect of glassfibre, graphite and MoS2 on the tribological performance of a liquid crystalline polymer

A thermotropic liquid crystalline polymer (LCP) with a high melting point of approximately 400 °C, unfilled and filled with glassfibre, MoS2 or graphitic carbon was tested in dry sliding contact with steel. Three different test methods were applied, i.e. measurement of coefficient of friction and specific wear rate vs. contact temperature; determination of load-carrying capacities at three different values of sliding speed, and friction and wear behaviour in 20 h tests under relatively severe conditions of load and sliding speed.\ud \ud It turned out that only glassfibre-containing materials perform adequately as dry-running bearing materials, provided that the contact temperature quickly rises above a critical value of the order of 125¿140 °C. In load-carrying capacity tests and in 20 h tests under severe conditions, adding graphitic carbon to glassfibre-containing LCP is particularly beneficial, as this substantially increases the thermal diffusivity of the material. Thus it is concluded that glassfibre- and graphitic-carbon-containing LCP is perfectly suitable for use as a dry-running bearing material at elevated temperatures