Ejection Forces and Friction Coefficients from Injection Molding Experiments Using Rapid Tooling Inserts

Experiments have been performed with injection mold inserts made using solid freeform fabrication processes in an effort to further study such applications for economic production of small quantities of parts. Static friction coefficients were determined for HDPE and HIPS against P-20 steel, sintered LaserForm ST-100, and stereolithography SL 5170 using the ASTM D 1894 standard. Injection mold inserts were constructed of the same three materials and were used to inject cylindrical parts using HDPE and HIPS. Ejection forces were measured, and a model was used to calculate ejection forces and apparent coefficients of static friction. Statistical analyses were used to determine the effects of packing time, cooling time and packing pressure on ejection force for the three insert types. This paper compares experimental and calculated ejection forces, compares standard friction test results to calculated apparent coefficients of friction, summarizes the statistical results, and comments on the feasibility of using rapid tooled inserts for injection molding.Mechanical Engineerin

Gauge-invariant observables, gravitational dressings, and holography in AdS

This paper explores construction of gauge (diffeomorphism)-invariant observables in anti de Sitter (AdS) space and the related question of how to find a "holographic map" providing a quantum equivalence to a boundary theory. Observables are constructed perturbatively to leading order in the gravitational coupling by gravitationally dressing local field theory operators in order to solve the gravitational constraints. Many such dressings are allowed and two are explicitly examined, corresponding to a gravitational line and to a Coulomb field; these also reveal an apparent role for more general boundary conditions than considered previously. The observables obey a nonlocal algebra, and we derive explicit expressions for the boundary generators of the SO(D-1,2) AdS isometries that act on them. We examine arguments that gravity {\it explains} holography through the role of such a boundary Hamiltonian. Our leading-order gravitational construction reveals some questions regarding how these arguments work, and indeed construction of such a holographic map appears to require solution of the non-perturbative generalization of the bulk constraint equations.Comment: 29 pages. v2: minor corrections; refs adde

Critical care provision after colorectal cancer surgery

Background: Colorectal cancer (CRC) is the 2nd largest cause of cancer related mortality in the UK with 40 000 new patients being diagnosed each year. Complications of CRC surgery can occur in the perioperative period that leads to the requirement of organ support. The aim of this study was to identify pre-operative risk factors that increased the likelihood of this occurring. Methods: This is a retrospective observational study of all 6441 patients who underwent colorectal cancer surgery within the West of Scotland Region between 2005 and 2011. Logistic regression was employed to determine factors associated with receiving postoperative organ support. Results: A total of 610 (9 %) patients received organ support. Multivariate analysis identified age ≥65, male gender, emergency surgery, social deprivation, heart failure and type II diabetes as being independently associated with organ support postoperatively. After adjusting for demographic and clinical factors, patients with metastatic disease appeared less likely to receive organ support (p = 0.012). Conclusions: Nearly one in ten patients undergoing CRC surgery receive organ support in the post operative period. We identified several risk factors which increase the likelihood of receiving organ support post operatively. This is relevant when consenting patients about the risks of CRC surgery

Persistent pain after caesarean section and its association with maternal anxiety and socioeconomic background

Background: Pain, both from the surgical site, and from other sources such as musculoskeletal backache, can persist after caesarean section. In this study of a predominantly socially deprived population we have sought to prospectively examine the association between antenatal maternal anxiety and socioeconomic background and the development of persistent pain of all sources after caesarean section. Methods: Demographic details and an anxiety questionnaire were completed by 205 women before elective caesarean section. On the first postoperative day, pain scores were recorded, and at four months patients were asked to complete a Brief Pain Inventory and an Edinburgh Postnatal Depression Score. Results: Of 205 parturients recruited, 186 records were complete at the hospital admission phase and 98 (52.7%) were complete at the four-month follow-up phase. At recruitment, 15.1% reported pain. At four months 41.8% (95% CI 32.1 to 51.6%) reported pain, of whom pain was a new finding in 35.7% (95% CI 26.2 to 45.2%). Antenatal anxiety was not a significant predictor of severity of new pain at four months (P=0.43 for state anxiety, P=0.52 for trait anxiety). However, four-month pain severity did correlate with social deprivation (P=0.011), postnatal depression (P<0.001) and pain at 24 h (P=0.018). Conclusion: Persistent pain from a variety of sources after caesarean section is common. Our findings do not support the use of antenatal anxiety scoring to predict persistent pain in this setting, but suggest that persistent pain is influenced by acute pain, postnatal depression and socioeconomic deprivation

Monitoring of carbon steel corrosion by use of electrochemical noise and recurrence quantification analysis

The corrosion of carbon steel in aqueous media resulting in uniform corrosion, pitting corrosion and passivation was investigated on a laboratory scale. Recurrence quantification analysis was applied to short segments of electrochemical current noise measurements. These segments were converted to recurrence variables, which could be used as reliable predictors in a multilayer perceptron neural network model to identify the type of corrosion. In addition, an automated corrosion monitoring scheme is proposed, based on the principal component scores of the recurrence variables. This approach used the uniform corrosion measurements as reference data and could differentiate between uniform and non-uniform corrosion

Regulating the effects of GPR21, a novel target for type 2 diabetes

Type 2 diabetes is a chronic metabolic disorder primarily caused by insulin resistance to which obesity is a major contributor. Expression levels of an orphan G protein-coupled receptor (GPCR), GPR21, demonstrated a trend towards a significant increase in the epididymal fat pads of wild type high fat high sugar (HFHS)-fed mice. To gain further insight into the potential role this novel target may play in the development of obesity-associated type 2 diabetes, the signalling capabilities of the receptor were investigated. Overexpression studies in HEK293T cells revealed GPR21 to be a constitutively active receptor, which couples to Gα(q) type G proteins leading to the activation of mitogen activated protein kinases (MAPKs). Overexpression of GPR21 in vitro also markedly attenuated insulin signalling. Interestingly, the effect of GPR21 on the MAPKs and insulin signalling was reduced in the presence of serum, inferring the possibility of a native inhibitory ligand. Homology modelling and ligand docking studies led to the identification of a novel compound that inhibited GPR21 activity. Its effects offer potential as an anti-diabetic pharmacological strategy as it was found to counteract the influence of GPR21 on the insulin signalling pathway