Multi-Objective Optimization in Single-Shot Drilling of CFRP/Al Stacks Using Customized Twist Drill

In recent years, the use of CFRP with titanium and/or aluminum to form materials for stacking has gained popularity for aircraft construction. In practice, single-shot drilling is used to create perfectly aligned holes for the composite-metal stack. Usually, standard twist drills, which are commonly available from tool suppliers, are used for practical reasons. However, existing twist drill bits exhibit rapid wear upon the drilling of composite-metal stack layers in single shot, due to the widely contrasting properties of the composite-metal stack, which causes poor surface quality. The stringent quality requirements for aircraft component manufacturing demands frequent drill bit replacement and thus incurs additional costs, a concern still unresolved for aircraft component manufacturers. Owing to highly contrasting properties of a composite-metal stack, it is obvious that standard twist drill cannot fulfil the rigorous drilling requirements, as it is pushed to the limit for the fabrication of high-quality, defect-free holes. In this work, customised twist drills of a tungsten carbide (WC) material with different geometric features were specially fabricated and tested. Twenty drill bits with customised geometries of varying chisel edge angle (30–45°), primary clearance angle (6–8°), and point angle (130–140°) were fabricated. The stacked-up materials used in this study was CFRP and aluminum alloy 7075-T6 (Al7075-T6) with a total thickness of 3.587 mm. This study aims to investigate the effect of twist drill geometry on hole quality using drilling thrust force signature as indicator. All drilling experiments were performed at spindle speed of 2600 rev/min and feed rate of 0.05 mm/rev. Design of experiments utilising response surface methodology (RSM) method was used to construct the experimental array. Analysis of variance (ANOVA) was used to study the effect of parameters and their significance to the thrust force and thus the hole quality. The study shows that the most significant parameter affecting the drilling thrust force and hole surface roughness is primary clearance angle, followed by chisel edge angle. Correlation models of CFRP thrust force (Y₁), Al7075-T6 thrust force (Y₂), CFRP hole surface roughness (Y₃), Al7075-T6 hole surface roughness (Y₄) as a function of the tool geometry were established. The results indicated that the proposed correlation models could be used to predict the performance indicators within the limit of factors investigated. The optimum twist drill geometry was established at 45° of chisel edge angle, 7° of primary clearance angle, and 130° of point angle for the drilling of CFRP/Al7075-T6 stack material in a single-shot process. The error between the predicted and actual experiment values was between 6.64% and 8.17% for the optimum drill geometry. The results from this work contribute new knowledge to drilling thrust force signature and hole quality in the single-shot drilling of composite-metal stacks and, specifically, could be used as a practical guideline for the single-shot drilling of CFRP/Al7075-T6 stack for aircraft manufacturing.     

Influence of two-electrode montages on the level-specific (LS) CE-Chirp auditory brainstem response (ABR) at multiple intensity levels

Objective: To investigate the influence of two different electrode montages (ipsilateral: reference to mastoid and vertical: reference to nape of neck) to the ABR results recorded using a level-specific (LS)-CE-Chirp® in normally hearing subjects at multiple intensities levels. Design: Quasi-experimental and repeated measure study designs were applied in this study. Two different stopping criteria were used, (1) a fixed-signal averaging 4000 sweeps and, (2) a minimum quality indicator of Fmp?=?3.1 with a minimum of 800 sweeps. Study sample: Twenty-nine normally hearing adults (18 females, 11 male) participated. Results: Wave V amplitudes were significantly larger in the LS CE-Chirp® recorded from the vertical montage than the ipsilateral montage. Waves I and III amplitudes were significantly larger from the ipsilateral LS CE-Chirp® than from the other montages and stimulus combinations. The differences in the quality of the ABR recording between the vertical and ipsilateral montages were marginal. Conclusions: Overall, the result suggested that the vertical LS CE-Chirp® ABR had a high potential for a threshold-seeking application, because it produced a higher wave V amplitude. The Ipsilateral LS CE-Chirp® ABR, on the other hand, might also have a high potential for the site of lesion application, because it produced larger waves I and III amplitudes.     

Impact of seasonality on the prevalence and risk factors of Giardia lamblia infections among the aborigines

Objective: To determine the prevalence and risk factors of Giardia(G.) lamblia infections among the aboriginal community during the wet and dry seasons. Methods: A total of 473 stool samples from the aborigines in Temerloh, Pahang, Malaysia were collected during wet(n=256) and dry seasons(n=217). Smear of all the PVA-preserved stool samples were subjected to Trichrome staining and microscopic examination under 1 000 伊magnification(Nikon eclipse E100) for the detection of G. lamblia. Positivity was recorded based on the presence of G. lamblia in trophozoite and/or cyst forms. Results: The prevalence of giardiasis was 12.10% and 8.29% during the wet and dry season, respectively. Age of less or equal to 15 years old and presence of other family members with G. lamblia infection were found to be the significant risk factors to acquire G. lamblia infections during both seasons. Untreated water supply was the significant risk factor of giardiasis during the dry season. This study highlighted the possibility of anthroponotic transmission of G. lamblia during both seasons and waterborne transmission during the dry season in the aboriginal community. Conclusions: This study suggests that seasonal variation plays an important role in the prevalence and risk factor of G. lamblia infection in the aboriginal community. Therefore, close contact with Giardia-infected family members and water-related activities or usage of untreated water must be avoided to reduce the burden of G. lamblia infection in this community.     

Selenium: more than just a micronutrient mineral

Selenium is a micronutrient mineral found mainly in soils. Studies on selenium have increased rapidly worldwide especially after it has been shown to reduce the risk of certain types of cancer in humans and animals. The exact mechanism of action on how selenium inhibits diseases, in particular cancer, is still unknown. To date, the use of selenium in preventing or treating diseases is limited. However, many aspects about the biochemistry of selenium have been identified. This article reviews a number of key clinical, experimental and epidemiological studies on selenium as an anti-carcinogenic agent for some types of cancers. Some nutritional information on selenium and its recommended intake are also included. More clinical and experimental studies are needed to confirm previous findings on the role of selenium as an anticarcinogenic agent.     

Requirement of extracellular calcium in fish pituitary gonadotropin release by gonadotropin hormone-releasing hormone

Influence of extracellular calcium on gonadotropin hormone-releasing hormone (GnRH)-stimulated gonadotropin hormone (GtH) release from a teleostean fish (Channa punctatus) pituitary was examined in vitro by preparing enzymatically dispersed pituitary cell incubation. Effect of Ca2+ on GnRH-augmented GtH release was evaluated with partially purified C. punctatus GnRH (cGnRH) and synthetic mammalian GnRH (mGnRH). Cells were dispersed by 0.3% collagenase plus 0.05% trypsin in culture medium and a high yield of viable cells were obtained. Addition of cGnRH (10 micrograms/ml) to pituitary cells in Ca2+-free medium resulted in a significant increase in GtH release, but the addition of Ca2+ (2 mM) enhanced it to about four- and threefold over cGnRH and mGnRH, respectively. Increasing concentrations of Ca2+ (0.1-2.0 mM/well) with fixed concentrations of GnRH (10 micrograms/ml) or increasing doses of GnRH (2.5 to 20 micrograms/ml) with fixed amount of Ca2+ (2 mM/well) resulted in a dose dependent increase in GtH release. EDTA or EGTA (2 mM/well) completely suppressed the Ca2+-augmenting effect of GnRH-stimulated GtH release. Addition of lanthanum (La3+, 4 mM/well), a competitive inhibitor of Ca2+, reduced 60% of the Ca2+ (2 mM/well) stimulation. Verapamil, a specific Ca2+ channel blocker, when added in increasing concentrations (1-100 microM/well) to pituitary cell incubations containing GnRH-stimulated GtH release in Ca2+-free medium could be waived by EGTA (2 mM/well), indicating availability of extracellular calcium from tissue sources. The uptake of radioactive Ca2+ by pituitary cells was greatly enhanced by GnRH while the addition of verapamil (10 microM/well) not only inhibited the GnRH-stimulated uptake, but also reduced it below the control level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation, density purification, and in vitro culture maintenance of functional caprine islets of Langerhans as an alternative islet source for diabetes study

Hani H, TengkuAzmi TI, Abas MO, Mohd‐Azmi ML, Zeenathul NA. Isolation, density purification, and in vitro culture maintenance of functional caprine islets of Langerhans as an alternative islet source for diabetes study. Xenotransplantation 2010; 17: 469–480. © 2010 John Wiley & Sons A/S. Abstract: Background: Insufficient availability of human donors makes the search for alternative source of islet cells mandatory for future developments in pancreatic transplantation. The present study investigates the potential of caprine as an alternative source of pancreatic islets. The objectives of the study were to optimize techniques for caprine islet isolation and purification for culture establishment, and to subsequently assess their viable and functional potential. Methods: Caprine pancreatic tissues were collected from a local slaughterhouse and prior transported to the laboratory by maintaining the cold chain. Islets were obtained by a collagenase‐based digestion and optimized isolation technique. Islet cell purity and viability were determined by dithizone and trypan blue staining, respectively. Islet clusters of different sizes were positively identified by staining methods and demonstrated 90% viability in the culture system. Following static incubation, an in vitro insulin secretion assay was carried out and analyzed by ELISA. Results: The islets remained satisfactorily viable for 5 days in the culture system following regular media changes. The current study has successfully optimized the isolation, purification and culture maintenance of caprine islets. Conclusion: The successful yield, viability and functionality of islets isolated from the optimized protocol provide promising potential as an alternative source of islets for diabetes and transplantation researches.     

Nephron-sparing surgery and percutaneous biopsies in renal-cell carcinoma: a global impression among endourologists

BACKGROUND AND PURPOSE: On the one hand, nephron-sparing surgery (NSS) in small renal tumors is a safe and effective alternative to radical nephrectomy. On the other hand, the role of preoperative percutaneous needle biopsies (PNB) remains controversial. The purpose of this study was to evaluate the global current use of NSS in the treatment of renal-cell carcinoma (RCC) and the use of PNB among endourologists. MATERIALS AND METHODS: One thousand questionnaires were distributed during the 23rd World Congress of Endourology and SWL. Six questions regarding NSS and two questions regarding PNB were presented. Two hundred twenty-two questionnaires were returned. RESULTS: Of the respondents, 86.6% perform NSS for small renal tumors, whereas 13.4% perform only radical nephrectomies; 7.5% will consider NSS only in patients with a solitary kidney, and 0.5% will never consider NSS. The techniques for NSS, in descending order of preference, are partial nephrectomy, enucleation, cryoablation, radiofrequency ablation, and high-intensity focused ultrasound. The mean and maximum diameter of the tumor in patients with a normal contralateral kidney for which the urologists perform NSS is 4.0 cm. For a centrally located tumor, NSS is an option for 27.2% of the respondents. Regarding PNB in patients with suspicion of RCC, 55.9% of respondents never obtain renal biopsies in the preoperative assessment and 41.8% obtain them only in rare cases. The majority (90%) prefer histologic over cytologic biopsies. CONCLUSIONS: Nephron-sparing surgery is evolving to a global worldwide standard treatment for small renal tumors. Percutaneous needle biopsy remains a highly debated procedure.     

Body mass index and factors related to overweight among women workers in electronic factories in Peninsular Malaysia

Factors related to overweight were examined in a cross-sectional survey that included 1612 women workers from 10 large electronics assembly factories in Peninsular Malaysia. Respondents were Malaysian citizens, direct production workers below the supervisory level, and had worked at least a year in the factory where they were presently employed. Heights and weights were taken to calculate the body mass index (BMI). Weights and BMI increased with increasing age. After adjusting for age, odds ratios for overweight were significantly raised for married women in relation to not married women (OR 1.5, 95% CI=1.15-2.02), lower secondary education in relation to higher than upper secondary education (OR 1.8, 95% CI=1.06-3.14), monthly income RM800-999 (OR 1.7, 95% CI=1.21-2.45) and >/=RM1,000 (OR 1.8, 95% CI=1.23-2.72) in relation to 相似文献   

Methanolic extract of Pereskia bleo (Kunth) DC. (Cactaceae) induces apoptosis in breast carcinoma, T47-D cell line

Currently, breast cancer is the leading cause of cancer-related death in women. Therefore, there is an urgent need to develop alternative therapeutic measures against this deadly disease. Here, we report the cytotoxicity activity and the mechanism of cell death exhibited by the methanol extract prepared from Pereskia bleo (Kunth) DC. (Cactaceae) plant against human breast carcinoma cell line, T-47D. In vitro cytotoxicity screening of methanol extract of Pereskia bleo plant indicated the presence of cytotoxicity activity of the extract against T-47D cells with EC50 of 2.0 microg/ml. T-47D cell death elicited by the extract was found to be apoptotic in nature based a clear indication of DNA fragmentation which is a hallmark of apoptosis. In addition, ultrastructural analysis also revealed apoptotic characteristics (the presence of chromatin margination and apoptotic bodies) in the extract-treated cells. RT-PCR analysis showed the mRNA expression levels of c-myc, and caspase 3 were markedly increased in the cells treated with the plant extract. However, p53 expression was only slightly increased as compared to caspase 3 and c-myc. Thus, the results from this study strongly suggest that the methanol extract of Pereskia bleo may contain bioactive compound(s) that caused breast carcinoma, T-47D cell death by apoptosis mechanism via the activation of caspase-3 and c-myc pathways.