Effect of WEDM Process Parameters on Surface Morphology of Nitinol Shape Memory Alloy.

Nickel-titanium shape memory alloys (SMAs) have started becoming popular owing to their unique ability to memorize or regain their original shape from the plastically deformed condition by means of heating or magnetic or mechanical loading. Nickel-titanium alloys, commonly known as nitinol, have been widely used in actuators, microelectromechanical system (MEMS) devices, and many other applications, including in the biomedical, aerospace, and automotive fields. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. There are several challenges faced when machining nitinol SMA with conventional machining techniques. Noncontact operation of the wire electrical discharge machining (WEDM) process between the tool (wire) and workpiece significantly eliminates the problems of conventional machining processes. The WEDM process consists of multiple input parameters that should be controlled to obtain great surface quality. In this study, the effect of WEDM process parameters on the surface morphology of nitinol SMA was studied using 3D surface analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. 3D surface analysis results indicated a higher value of surface roughness (SR) on the top of the work surface and a lower SR on the bottom portion of the work surface. The surface morphology of the machined sample obtained at optimized parameters showed a reduction in microcracks, micropores, and globules in comparison with the machined surface obtained at a high discharge energy level. EDX analysis indicated a machined surface free of molybdenum (tool electrode).

Surface Analysis of Wire-Electrical-Discharge-Machining-Processed Shape-Memory Alloys.

Shape-memory alloys such as nitinol are gaining popularity as advanced materials in the aerospace, medical, and automobile sectors. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape-memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. Anunconventional machining process like wire-electrical-discharge-machining (WEDM) can be effectively and efficiently used for the machining of such alloys,although the WEDM-induced surface integrity of nitinol hassignificant impact on material performance. Therefore, this work investigated the surface integrity of WEDM-processed nitinol samples using digital microscopy imaging, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. Three-dimensional analysis of the surfaces was carried out in two different patterns (along the periphery and the vertical plane of the machined surface) andrevealed that surface roughness was maximalat the point where the surface was largely exposed to the WEDM dielectric fluid. To attain the desired surface roughness, appropriate discharge energy is required that,in turn, requires the appropriate parameter settings of the WEDM process. Different SEM image analyses showed a reduction in microcracks and pores,and in globule-density size at optimized parameters. EDX analysis revealed the absence of wire material on the machined surface.

Multi-Response Optimization of WEDM Process Parameters for Machining of Superelastic Nitinol Shape-Memory Alloy Using a Heat-Transfer Search Algorithm.

Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to render the process viable for industry, a systematic approach comprising response surface methodology (RSM) and a heat-transfer search (HTS) algorithm has been strategized for optimization of process parameters. Pulse-on time, pulse-off time and current were considered as input process parameters, whereas material removal rate (MRR), surface roughness, and micro-hardness were considered as output responses. Residual plots were generated to check the robustness of analysis of variance (ANOVA) results and generated mathematical models. A multi-objective HTS algorithm was executed for generating 2-D and 3-D Pareto optimal points indicating the non-dominant feasible solutions. The proposed combined approach proved to be highly effective in predicting and optimizing the wire electrical discharge machining (WEDM) process parameters. Validation trials were carried out and the error between measured and predicted values was negligible. To ensure the existence of a shape-memory effect even after machining, a differential scanning calorimetry (DSC) test was carried out. The optimized parameters were found to machine the alloy appropriately with the intact shape memory effect.

Prohormone convertase 2 (PC2) null mice have increased mu opioid receptor levels accompanied by altered morphine-induced antinociception, tolerance and dependence.

Chronic morphine treatment increases the levels of prohormone convertase 2 (PC2) in brain regions involved in nociception, tolerance and dependence. Thus, we tested if PC2 null mice exhibit altered morphine-induced antinociception, tolerance and dependence. PC2 null mice and their wild-type controls were tested for baseline hot plate latency, injected with morphine (1.25-10mg/kg) and tested for antinociception 30min later. For tolerance studies, mice were tested in the hot plate test before and 30min following morphine (5mg/kg) on day 1. Mice then received an additional dose so that the final dose of morphine was 10mg/kg on this day. On days 2-4, mice received additional doses of morphine (20, 40 and 80mg/kg on days 1, 2, 3, and 4, respectively). On day 5, mice were tested in the hot plate test before and 30min following morphine (5mg/kg). For withdrawal studies, mice were treated with the escalating doses of morphine (10, 20, 40 and 80mg/kg) for 4days, implanted with a morphine pellet on day 5 and 3 days later injected with naloxone (1mg/kg) and signs of withdrawal were recorded. Morphine dose-dependently induced antinociception and the magnitude of this response was greater in PC2 null mice. Tolerance to morphine was observed in wild-type mice and this phenomenon was blunted in PC2 null mice. Withdrawal signs were also reduced in PC2 null mice. Immunohistochemical studies showed up-regulation of the mu opioid receptor (MOP) protein expression in the periaqueductal gray area, ventral tegmental area, lateral hypothalamus, medial hypothalamus, nucleus accumbens, and somatosensory cortex in PC2 null mice. Likewise, naloxone specific binding was increased in the brains of these mice compared to their wild-type controls. The results suggest that the PC2-derived peptides may play a functional role in morphine-induced antinociception, tolerance and dependence. Alternatively, lack of opioid peptides led to up-regulation of the MOP and altered morphine-induced antinociception, tolerance and dependence.

The effectiveness of a musical toothbrush for dental plaque removal: a comparative study.

BACKGROUND AND OBJECTIVES: the purpose of this study was to clinically evaluate and compare the efficacy of "Brush Buddies" musical tooth brush and Colgate Smile tooth brush in the reduction of established plaque and gingivitis. MATERIALS AND METHODS: for this study, 120 healthy kids (73 boys and 47 Girls) were selected. The subjects were randomly assigned into two groups by a second examiner; one group used Colgate Smile brush and the other group used "Brush Buddies" musical tooth brush. Plaque index (Quigley and Hein), Modified Gingival Index (Lobene and Associates) and Gingival Bleeding Index (Ainamo and Bay) were assessed at baseline, 30th day, 60th day, and 90th day. RESULTS: all the baseline indices appeared to be well balanced. At the end of the study, reduction in plaque index, modified gingival index and gingival bleeding index were statistically highly significant during each interval for both the toothbrushes. For "Brush Buddies" musical tooth brush, the reduction in all clinical parameters were statistically significant for 30 days and 60 days interval, while nonsignificant at 90 days interval. INTERPRETATION AND CONCLUSION: both the tooth brushes used in this study were clinically effective in removing plaque, improving gingival health. Musical tooth brush is more effective initially but as the time period increases both tooth brushes give almost similar results.

Prevalence and characteristics of Molar Incisor Hypomineralisation (MIH) in the child population residing in Gandhinagar, Gujarat, India.

UNLABELLED: Most prevalence studies on Molar Incisor Hypomineralisation (MIH) have been carried out in European countries and data from Asia especially south Asian populations are lacking. AIM: To investigate the prevalence and clinical characteristics of MIH in children residing in a western region of India. METHOD: A cross-sectional survey including 1,366 children from 5 age cohorts, 8-12 years, studying in primary schools or attending the University Department, was carried out in the area of Gandhinagar, Gujarat, India. The dental examination was performed by a single well-trained and calibrated examiner in day light conditions. Full mouth inspection of wet teeth was conducted using the EAPD 2003 criteria for diagnosis of MIH. Results were recorded and statistically analysed using Chi-square test, independent sample t-test and Pearson correlations. RESULTS: Prevalence of MIH was 9.2% in the examined population. Males and females were equally affected. Among 12 index teeth involved in the examination, the most commonly affected were in descending order 46, 36, 16, 11 [FDI] and the least 42, 32, and 22. 17.4% of the cases revealed only molars involved, the remaining 72.6% having both molars and incisors affected; all four first permanent molars showed in 23% of the cases while no cases of only affected incisors were found. Of the MIH teeth 77.3% revealed mild defects and 22.7% severe defects. All incisors were mildly affected, as compared with only 67.1% of the molars, the remaining 32.9% being severely affected. As age increased, a statistically significant larger total number and severity level of affected teeth were recorded. CONCLUSION: Prevalence of MIH using EAPD 2003 criteria was found to be similar to other studies evaluating children in different geographic locations such as Europe, South America etc. Using the EAPD standardised criteria, more studies should be conducted in other Indian regions, in order to further evaluate prevalence, characteristics and treatment needs for this clinically demanding condition.

Warfarin therapeutic monitoring: is 70% time in the therapeutic range the best we can do?

WHAT IS KNOWN AND OBJECTIVE: Warfarin, an oral anticoagulant, which has been in clinical use for over sixty years, remains a challenge for clinicians to utilize, given the multiplicity of items which can limit its efficacy. Our objective is to review the evidence and comment on whether INR control can be better than has been currently reported in various studies. COMMENT: The duration of time a patient's international normalized ratio (INR) is maintained within the therapeutic range (time in the therapeutic range, TTR) for his or her particular indication for the drug impacts the effectiveness and safety of warfarin therapy. Maintaining a therapeutic INR while on warfarin is difficult, and numerous studies employing various strategies confirm the challenge, but not the impossibility of achieving a TTR above 70%. WHAT IS NEW AND CONCLUSION: Maintaining a therapeutic INR requires a dedicated multi-faceted approach. With diligence, skill and various therapeutic strategies, a TTR >70% can be achieved.

Study of lead exposure to children residing near a lead-zinc mine.

This lead exposure study was conducted in a total of 452 school children in the age group of 9-14 years. Two hundred and ninety-eight exposed children came from the villages situated within a 2.5 km radius of the lead-zinc mine whereas the comparative group children were selected from the villages at least 10 km away from mine. Environmental monitoring study suggested that lead levels in air and water samples near the mining areas were within the Central Pollution Control Board prescribed standards. Lead levels in about 80% of the children were less than 10 µg/dl. Medical examination of all children did not show any signs related to lead toxicity but central nervous system-related symptoms, as reported by the subjects during medical examination, were found to be higher in the exposed group when compared with the comparative group. The values of physical growth parameters of the exposed group were comparable with that of the comparative group for both girls and boys. Hence, the physical growth of children was found to be unaffected by the observed level of lead exposure. To safeguard the health of the children residing near the mining area, various preventive and control measures were suggested.

Is the routine placement of a CSF reservoir following endoscopic third ventriculostomy justified?

Endoscopic third ventriculostomy (ETV) is a well established treatment for selected cases of obstructive hydrocephalus. However, it does carry a significant rate of failure, which can be abrupt and life threatening. The present study analyses the benefits versus the risks of routine CSF reservoir insertion during ETV. Clinical data obtained from the medical records of patients from a single neurosurgical centre who underwent ETV between August 2002 and February 2007 were analysed retrospectively. A total of 34 records were available with follow-up ranging from 3-56 months (Median 26 months) and with patient age range between 6 months - 75 yrs (median 19 years). During this period, one neurosurgeon routinely placed reservoirs in all patients undergoing ETV (n = 34). In all instances of reservoir insertion, Ommaya reservoirs were used. The number of patients in which the reservoir was tapped for diagnostic and/or therapeutic reasons was quantified, and all complications resulting from reservoir placement recorded. ETV success was defined by a lack of subsequent need for cerebrospinal fluid diversion. In total 13 of 34 (38%) reservoirs inserted were tapped at a later date and there were no complications associated with their insertion. Tapping of reservoirs helped determine which patients required subsequent ventriculoperitoneal (VP) shunting. In at least one case reservoir tapping was carried out as an emergency and was a crucial intermediate intervention prior to further surgery. The overall success rate of ETV was 65% (95% CI, 49-81%) with four complications associated with ETV: short-term memory loss, psychosis, and two cases of post-operative seizures. These complications were not attributed to CSF reservoir insertion but the ETV procedure itself. The routine placement of CSF reservoir following ETV thus seems justified with respect to the observed benefits and lack of complications associated with its placement.

Acoustical evaluation of carbonized and activated cotton nonwovens.

An activated carbon fiber nonwoven (ACF) was manufactured from a cotton nonwoven fabric. For the ACF acoustic application, a nonwoven composite of ACF with cotton nonwoven as a base layer was developed. Also produced were the composites of the cotton nonwoven base layer with a layer of glassfiber nonwoven, and the cotton nonwoven base layer with a layer of cotton fiber nonwoven. Their noise absorption coefficients and sound transmission loss were measured using the Brüel and Kjaer impedance tube instrument. Statistical significance of the differences between the composites was tested using the method of Duncan's grouping. The study concluded that the ACF composite exhibited a greater ability to absorb normal incidence sound waves than the composites with either glassfiber or cotton fiber. The analysis of sound transmission loss revealed that the three composites still obeyed the mass law of transmission loss. The composite with the surface layer of cotton fiber nonwoven possessed a higher fabric density and therefore showed a better sound insulation than the composites with glassfiber and ACF.

Endobronchial obstruction from an intubation stylet sheath.

Many clinicians intubate newborns using a stylet, but how many always check if the device is intact after use? We describe a case of endobronchial obstruction by a plastic sheath coating the metal stylet, and suggest ways to reduce the incidence of this serious iatrogenic complication.

Oesophageal replacement in children.

INTRODUCTION: The usual indications for oesophageal replacement in childhood are intractable corrosive strictures and long-gap oesophageal atresia. Generally, paediatric surgeons attempt to preserve the native oesophagus with repeat dilatations. However, when this is not successful, an appropriate conduit must be fashioned to replace the oesophagus. The neo-oesophagus should allow normal oral feeding, not have gastro-oesophageal reflux, and be able to function well for the life-time of the patient. PATIENTS AND METHODS: A Medline search for oesophageal replacement, oesophageal atresia, gastric transposition, colon transposition, gastric tube, caustic stricture was conducted. The commonest conduits including whole stomach, gastric tube, colon and jejunum are all discussed. RESULTS: No randomised controlled studies exist comparing the different types of conduits available for children. The techniques used tend to be based on personal preference and local experience rather than on any discernible objective data. The biggest series with long-term outcome are reported for gastric transposition and colon replacement. Comparison of a number of studies shows no significant difference in early or late complications. Early operative complications include graft necrosis, anastomotic leaks and sepsis. Late problems include strictures, poor feeding, gastro-oesophageal reflux, tortuosity of the graft and the development of Barrett's oesophagus. The biggest series, however, seem to have lower complications than small series probably reflecting the experience, built up over years, in their respective centres. CONCLUSIONS: Long-term follow-up is recommended because of the risks of late strictures, excessive tortuosity of the neo-oesophagus and the development of Barrett's oesophagus.

Poisoning of workers working in small lead-based units.

BACKGROUND: No data are available with the labor departments among the workers of small-scale lead-based units with regard to lead poisoning. One hundred and ninety-five workers were investigated for lead exposure and three were found exceeding the limit of 80 mg/dL, which required a treatment for lead poisoning. AIM: To assess the exposure and health risk in workers working in small lead-based units. SETTING AND DESIGN: Random sampling is selected from the cross-sectional medical study. METHODS AND MATERIALS: Medical examination cum biochemical/hematological investigations along with blood lead estimation were carried out in these workers. STATISTICAL ANALYSIS: Epi-Info and SPSS 16.0 were used for statistical analysis. RESULTS AND CONCLUSION: Workers' blood lead levels were brought down from 114.4, 110.0 and 120.6 mg/dL with treatment of D-penicillamine to 40 mg/dL. It may be concluded that lead poisoning is a preventable public health problem that particularly affects the industrial workers in small lead-based units.

Chromium exposure study in chemical based industry.

176 chromium-exposed and 30 control subjects were selected for this study. Blood samples (3 ml) were collected for the estimation of chromium. The data on chromium concentration indicated a significant higher level of chromium in the blood of the exposed workers as compared to the control. There was no significant correlation between the mean blood and environmental chromium level. This study suggests that exposure to chromium may have some effect on the health of workers, even though the dose response relationship could not be established between blood chromium and environmental chromium levels. This study suggests that exposure to chromium may have some effect on the health of workers, even though the dose response relationship could not be established between blood chromium and environmental chromium levels. Study also indicates that the environmental levels to Cr are well below the permissible levels at all the sites of the industry at the time of survey even though the blood Cr levels were observed high in 14.8% of workers and some of them were having Cr related morbidity. Therefore, preventive and engineering control measures are suggested to minimize the chromium exposure in the chromium based industry located in Gorwa industrial estate at Baroda, Gujarat. About three months period was taken to complete this study.

Oesophageal substitution with free and pedicled jejunum: short- and long-term outcomes.

In children, the indications for oesophageal substitution are principally, long gap oesophageal atresia (OA), severe anastomotic disruption following primary repair of OA and severe caustic or peptic strictures. We present an outcome review of eight cases who underwent oesophageal substitution with jejunum at our institution between 1986 and 2001. The purpose of this study was to evaluate our experience with free/pedicled jejunal grafts and its long-term outcome as an oesophageal substitute. Operative and postoperative outcome with free and pedicled jejunal grafts in four cases of pure OA, two cases of OA and distal tracheo-oesophageal fistula (TOF), one patient with a high retrolaryngeal oesophageal web and one case of severe caustic oesophageal stricture. Six patients had an oesophagostomy and a gastrostomy fashioned previously. Eleven free jejunal grafts were performed in six patients (three intraoperative redo interpositions for immediate graft loss, three separate grafts in one patient and two free grafts in two patients). One patient's pedicled jejunal graft proximally required microvascular anastomosis while the other had a pedicled graft without microvascular anastomosis. Early postoperative complications included four upper anastomotic leaks (three free grafts, one pedicled with microvascular support), pneumothorax requiring prolonged ventilation and Horner's syndrome. Recurrent laryngeal nerve injury occurred in the patient who had a high retrolaryngeal oesophageal web. During follow up (5-18 years) late complications of upper anastomotic stricture in four patients and graft redundancy with subsequent kinking of the lower anastomosis were observed in one patient. Three patients established a complete oral diet; a further three patients relied on supplemental gastrostomy feeds and one patient is entirely gastrostomy fed. There were two late deaths, one from aspiration and the other from a severe asthmatic attack (5 and 7 months postoperatively, respectively). Our results indicate that there are significant complications related to the use of free jejunal grafts. Early recognition and treatment are of paramount importance in the ultimate achievement of a successful technical outcome.

Emergency transjugular intrahepatic portosystemic shunt for uncontrolled variceal bleeding.

This study was designed to retrospectively evaluate transjugular intrahepatic portosystemic shunt (TIPS) performed on an emergency basis in patients with hemorrhagic shock from recurrent uncontrolled variceal bleeding. Over a 3.5-year period we reviewed the medical records as well as the imaging studies of 16 patients who had uncontrolled variceal bleeding and presented to our department for an emergent placement of TIPS. In our study the technical success was 88% (14/16 patients), the overall mortality was 36% (5/14 patients), and the shunt immediately reduced the portal venous pressure gradient by a mean of 64%. Given the poor outcome of other alternatives, aggressive treatment and placement of TIPS is justified regardless of the severity of the bleeding episode.

Gas chromatographic-mass spectroscopic determination of benzene in indoor air during the use of biomass fuels in cooking time.

A gas chromatography-mass spectroscopic method in electron ionization (EI) mode with MS/MS ion preparation using helium at flow rate 1 ml min(-1) as carrier gas on DB-5 capillary column (30 m x 0.25 mm i.d. film thickness 0.25 microm) has been developed for the determination of benzene in indoor air. The detection limit for benzene was 0.002 microg ml(-1) with S/N: 4 (S: 66, N: 14). The benzene concentration for cooks during cooking time in indoor kitchen using dung fuel was 114.1 microg m(-3) while it was 6.6 microg m(-3) for open type kitchen. The benzene concentration was significantly higher (p < 0.01) in indoor kitchen with respect to open type kitchen using dung fuels. The wood fuel produces 36.5 microg m(-3) of benzene in indoor kitchen. The concentration of benzene in indoor kitchen using wood fuel was significantly (p < 0.01) lower in comparison to dung fuel. This method may be helpful for environmental analytical chemist dealing with GC-MS in confirmation and quantification of benzene in environmental samples with health risk exposure assessment.