85 research outputs found
Investigation of electroless nickel undercoat for duplex nickel chromium electrodeposition onto aluminium and its alloys
No full textA thesis submitted in partial fulfillment of the requirement of the University of Wolverhampton for the
Degree of Master of Philosophy.The study investigates the deposition of a multilayer coating onto two aluminium alloys: Al 1050 and Al 6061. Of particular interest has been the treatment of the surface of both these samples for deposition of metallic coatings through a zincate based immersion process. The zinc immersion layer chemically displaces the oxide film on Al 1050 and Al 6061 and then zinc is deposited followed by nickel and chromium electrodeposition. Superior adhesion was associated with uniform, thin and fine grained deposits from Bondal solution which exhibited rapid and complete coverage of both aluminium samples. The metallurgical characteristics of the aluminium alloys and the processing sequence developed had a significant influence on the growth and morphology of the deposits from the Bondal solution and affected subsequent adhesion of electroplated nickel and chromium. This engendered the treated surface with sufficient catalytic nature to be able to receive a subsequent electroless nickel layer together with finishing layers of electrolytic nickel and chromium respectively. Due to the favourable physical properties of aluminium and its alloys (density, strength to weight ratio), there is a growing demand for nickel/chromium coated aluminium components for automotive and other applications. The most common method currently is to directly electroplate nickel onto the aluminium substrate. However, this can lead to problems with components having complex geometry in that chemical attack on the pretreated aluminium can occur in low current density areas before the substrate can be completely covered with nickel due to the acidic nature and high temperature of the nickel electroplating process. One way of preventing this current density related problem is to use an electroless nickel undercoat before the nickel/chromium deposit is applied. The mechanism by which this occurs is not fully understood and it is an objective of the current research to investigate the mechanism of nucleation of the electroless nickel layer on zincated aluminium. Results of X-ray photoelectron spectroscopy showed that the zincated layer was dissolved in the electroless nickel bath but zinc was detected below 10 nm from the top surface of the homogenous nickel phosphorus film, while aluminium and alloying elements from both alloys have diffused into the film. Hexavalent chromium electroplating from chromic acid is under pressure due to its health hazard and environmental problems and is subjected to increasingly stringent control and legislation. Health and safety considerations have prompted the electroplating industry to consider alternatives to coating processes that involve hexavalent chromium. It is a further objective of the research to compare the properties of nickel/chromium coated aluminium with top coats of chromium deposited from hexavalent and trivalent (chloride based) electrolytes. Duplex nickel and chromium electrodeposition were modified with an electroless nickel undercoat, thus four coatings were studied for the aluminium samples. Results obtained from the hardness measurements of Al 1050 and Al 6061 were compared for four coatings. Hardness tests profiles obtained for Al 1050 and Al 6061 show that deposits from trivalent chromium electrolytes were not as hard as hexavalent chromium deposits. However, the hardness of duplex nickel/chromium coatings was improved by use of an electroless nickel undercoat. Scratch adhesion tests were focused on the failure mode of coatings evaluated on the basis of scratch channels, frictional force and acoustic emission signals. The adhesion test showed buckling and chipping of the coatings with no sign of spallation or delamination. Four coatings exhibited a higher critical load for both aluminium alloy samples. This confirmed that failure occurred within the coatings, rather than adhesive failure at the coating/substrate interface. Results obtained from copper acetic acid salt spray and electrochemical corrosion tests for Al 1050 and Al 6061 exhibited excellent corrosion resistance. Scanning electron microscope images showed initiation and propagation of small pits which did not coalesce to form large and deep craters that could result in the eventual failure of the coatings. Micro discontinuous chromium deposits spread the corrosion current, thus improving corrosion performance. Icorr values obtained from linear polarization corrosion tests show higher values for duplex nickel/chromium coatings on Al 1050 than Al 6061. Icorr values show similar trends for duplex nickel/chromium coating on Al 1050 and Al 6061 modified with an electroless nickel undercoat. In conclusion results showed a significant improvement in the chromium electroplating characteristics of Al 1050 and Al 6061 with an electroless nickel undercoat
Pre-operative voriconazole in patients undergoing surgery for central nervous system fungal infections: Special report
No full textFungal infections of the central nervous system (CNS) are uncommon. Despite several advancements in diagnosis and treatment of these infections, the mortality rates remain high. The current retrospective study was planned to define the demographic and clinical features of patients with CNS fungal infections. Conducted at Aga Khan University Hospital, Karachi, and comprising CNS fungal infections operated between January 2000 and December 2015. The study analysed whether a short course of pre-operative anti-fungal therapy may improve outcomes in these patients. There were 47 cases confirmed on histopathology and/or microbiology. Outcome measures used were Glasgow coma score (GCS), Glasgow outcome score (GOS) and Karnofsky performance score (KPS). The overall 30-day mortality was 20(42.5%). Fungal infections of the CNS can occur in both immune-compromised and immune-competent patients. Early diagnosis, radical surgery, pre-operative anti-fungal therapy for at least 2 weeks, pre- and postoperative Voriconazole therapy results in more favourable outcomes
Endoscopic third ventriculostomy for obstructive hydrocephalus: Outcome analysis of 120 consecutively treated patients from a developing country
No full textObjectives: Endoscopic third ventriculostomy (ETV) for the treatment of obstructive hydrocephalus is a relatively new concept amongst neurosurgeons of the developing world. Therefore, this study was conducted to report our experience, patient selection, success rates and complications of ETV and compare our results with the literature from the developed countries.Methods: We performed ETV on 120 patients at our centre and prospectively collected their clinical data on pre designed questionnaires. Success was defined as clinical improvement on 3rd month post operative clinic visit. The data was analyzed using SPSS version 20.Results: There were 79 male and 41 female patients. The mean age was 36.1 ± 14.3 years. Overall, ETV was successful in 107 (89.2%) of patients. 4 patients had intra operative bleeding, 4 patients developed CSF leaks while 1 patient had a transient gaze palsy. There was no mortality.Conclusion: ETV is a very effective treatment modality for treating obstructive hydrocephalus in well selected patients and can be successfully practiced by neurosurgeons in the developing countries
Enduring improvement in Oswestry Disability Index outcomes following lumbar microscopic interlaminar decompression: An appraisal of prospectively collected patient outcomes
No full textObjectives: Our present study aims to assess the short and long-term postoperative outcome of microscopic interlaminar decompression from a neurosurgical center in a developing country and also aims to further determine any predictors of functional outcome. Materials and Methods: All patients with moderate to severe symptomatic stenosis undergoing elective posterior lumbar spinal decompression were prospectively enrolled in a database. Preoperative, 2 weeks and 2 years postoperative Oswestry Disability Index (ODI) scores were determined for all patients. These scores were retrospectively compared using repeated measures analysis of variance. Further, linear regression modelling was applied to determine the effect of preoperative ODI, body mass index, age, prior physiotherapy, duration of symptoms, and single or multiple level decompression on the change in ODI at 2 weeks and 2 years follow-up respectively. Results: A total of 60 consecutive patients (40 males, 20 females) were included for statistical analysis. The percentage of patients with a minimum clinically important difference (MCID), using an ODI threshold value of 10, was 86.7% (n = 52) at the 2 weeks postoperative follow-up. At the 2 years follow-up assessment, 3.3% (n = 2) patients who had earlier not achieved MCID did so, 78.3% (n = 47) of patients were found to have a change in ODI score of <10 or no change, while 18.3% (n = 11) reported a deterioration in their ODI scores. The preoperative ODI score was an independent predictor of change in ODI score at 2 weeks and 2 years respectively (P < 0.0005). The duration of symptoms prior to surgery was found to predict the change in ODI at 2 years follow-up (P = 0.04). Conclusion: The evidence regarding the long-term and short-term efficacy of microscopic interlaminar decompression in symptomatic lumbar stenosis is overwhelming. Preoperative ODI scores and duration of symptoms prior to surgery can predict postoperative outcomes
Enduring improvement in oswestry disability index outcomes following lumbar microscopic interlaminar decompression: An appraisal of prospectively collected patient outcomes
No full textObjectives: Our present study aims to assess the short and long-term postoperative outcome of microscopic interlaminar decompression from a neurosurgical center in a developing country and also aims to further determine any predictors of functional outcome.Materials and methods: All patients with moderate to severe symptomatic stenosis undergoing elective posterior lumbar spinal decompression were prospectively enrolled in a database. Preoperative, 2 weeks and 2 years postoperative Oswestry Disability Index (ODI) scores were determined for all patients. These scores were retrospectively compared using repeated measures analysis of variance. Further, linear regression modelling was applied to determine the effect of preoperative ODI, body mass index, age, prior physiotherapy, duration of symptoms, and single or multiple level decompression on the change in ODI at 2 weeks and 2 years follow-up respectively.Results: A total of 60 consecutive patients (40 males, 20 females) were included for statistical analysis. The percentage of patients with a minimum clinically important difference (MCID), using an ODI threshold value of 10, was 86.7% (n = 52) at the 2 weeks postoperative follow-up. At the 2 years follow-up assessment, 3.3% (n = 2) patients who had earlier not achieved MCID did so, 78.3% (n = 47) of patients were found to have a change in ODI score of \u3c10 or no change, while 18.3% (n = 11) reported a deterioration in their ODI scores. The preoperative ODI score was an independent predictor of change in ODI score at 2 weeks and 2 years respectively (P \u3c 0.0005). The duration of symptoms prior to surgery was found to predict the change in ODI at 2 years follow-up (P = 0.04).Conclusion: The evidence regarding the long-term and short-term efficacy of microscopic interlaminar decompression in symptomatic lumbar stenosis is overwhelming. Preoperative ODI scores and duration of symptoms prior to surgery can predict postoperative outcomes
Pengembangan Teori Pendidikan Islam Perspektif Muhammad Jawwad Ridla (Religius Konservatif, Religius Rasional, Pragmatis Instrumental)
No full textAbstract: Development of Islamic Education Theory Perspective of Muhammad Jawwad Ridla (Conservative Religious, Rational Religious, Pragmatic Instrumental) This article discusses the study of the theory of Islamic education in the perspective of Muhammad Jawwad Ridla with six theories of Islamic Education built by Jawwad Ridla and Analysis of Jawwad Ridla concerning the three schools of Islamic education philosophy with the main characters who tend to these schools. The method of writing scientific papers uses library research. Namely, the author looks for data sources by prioritizing concepts and theories that refer to writing literature related to the specific research theme. The approach to writing scientific papers uses a philosophical approach. The results of this study are 1) The theory of Islamic education built by Muhammad Jawwad Ridla has several aspects, among them are the Concept of Teaching / Learning, Psychological Basics of the learning process, Understanding of student subjects, teaching methods, Teaching (teachers) and preparing individuals to participate active in the economic life of the community. 2) Muhammad Jawwad Ridla classifies the three main schools of Islamic education philosophy: 1) Conservative Religious Flow which is only covered by religious teachings. The main figures in this school are al-Ghazali, 2) Religious-rational, Ikhwan al-Shafa considers all disciplines as important with the flow they adhere to, 3) Pragmatic instrumentalism, adherents of this sect, Ibn Khaldun. He revealed that education is to gain worldly expertise and ukhrowi, both of which must provide benefits.Abstrak: Pengembangan Teori Pendidikan Islam Perspektif Muhammad Jawwad Ridla (Religius Konservatif, Religius Rasional, Pragmatis Instrumental). Artikel ini membahas tentang kajian teori pendidikan Islam dalam perspektif Muhammad Jawwad Ridla dengan enam teori Pendidikan Islam yang dibangun oleh Jawwad Ridla dan Analisis Jawwad Ridla mengenai tiga aliran filsafat pendidikan Islam dengan tokoh utama yang berkecenderungan ke aliran-aliran tersebut. Metode penelitian karya ilmiah ini menggunakan kajian pustaka (library research). Yaitu penulis mencari sumber data dengan mengedepankan konsep dan teori yang mengacu pada literatur-literatur kepenulisan terkait dengan tema penelitian secara spesifik. Adapun pendekatan penulisan karya ilmiah ini menggunakan pendekatan filosofis. Hasil penelitian ini yaitu 1) Teori pendidikan Islam yang dibangun oleh Muhammad Jawwad Ridla terdapat beberapa aspek yaitu diantaranya adalah Konsep Pengajaran/Pembelajaran, Dasar-dasar psikologis proses pembelajaran, Pemahaman tentang subjek didik, metode pengajaran, Ppengajaran (guru) dan penyiapan individu untuk berpartisipasi aktif dalam kehidupan ekonomi masyarakat. 2) Muhammad Jawwad Ridla mengklasifikasikan tiga aliran utama filsafat pendidikan Islam : 1) Aliran Religius Konservatif yang hanya dilingkupkan pada ajaran keagamaan saja. Tokoh utama pada aliran ini yakni al-Ghazali, 2) Religius-rasional, Ikhwan al-Shafa menganggap semua disiplin ilmu adalah penting dengan aliran yang dianutnya, 3) Aliran pragmatis instrumental, penganut aliran ini yakni Ibnu Khaldun. Beliau mengungkapkan pendidikan adalah untuk mendapatkan keahlian duniawi dan ukhrowi, keduanya harus memberikan keuntungan.
Prospective case control evaluation of epidural midazolam for improving pain and ambulation after microdiscectomy
No full textObjective: To evaluate midazolam as an epidural analgesic in patients undergoing single-level microdiscectomy.Methods: This prospective case control study was carried out at the Aga Khan University Hospital, Karachi, from January 20 to September 20, 2007, on patients undergoing microdiscectomy. Cases (group A) received midazolam with saline, while controls (group B) received saline only, placed intra-operatively over involved nerve root. Post-operatively, patients were monitored for various variables. Data was analysed using SPSS 13.0 and groups were compared using student\u27s t-test for continuous variables and chi square for categorical variables. P-value \u3c0.05 was considered significant.Results: Patients in group A ambulated earlier (p = 0.005) and although they did not show significantly better post-operative pain control, but post-operative nausea and vomiting (PONV) score was better at six hours (p = 0.020). There was no difference in other variables such as requirement of analgesics, anti-emetics, hospital stay and complications.Conclusion: Midazolam may improve post-operative nausea and vomiting score, and may lead to earlier ambulation, without affecting patient\u27s vitals, consciousness, lower extremity power or sensations, and is not associated with adverse effects
Peer-led surgery education: A model for a surgery interest group
No full textWe present a systematic, sustainable, student-led model for a Surgery Interest Group in a low and middle-income country setting to encourage other medical students to establish similar groups in their institutions. Our model was developed at the Aga Khan University Medical College, Karachi, and is comprised of medical students, teaching associates, residents, faculty and alumni. The group focuses on connecting medical students with an interest in surgery with opportunities to help them match in surgery training programs. The opportunities include, but are not limited to, skill development, personal development, mentorship and research. Our model has shown growth and expansion over the last four years, and can be successfully replicated in medical colleges across similar settings
Thoracic and lumbar spinal surgery under local anesthesia for patients with multiple comorbidities: A consecutive case series
No full textBackground: Although some patients with symptomatic spinal disease may benefit greatly from surgery, their multiple attendant comorbidities may make general anesthesia risky or contraindicated. However, there is scarce literature describing the efficacy and safety of local anesthesia to perform these operations. Here we report seven patients who successfully underwent spinal surgery utilizing local anesthesia to limit the risks and complications of general anesthesia.Methods: Seven patients for whom general anesthesia was contraindicated were prospectively followed for a minimum of 3 months following spinal surgery performed under local anesthesia. Pain and functional improvement were assessed utilizing the Visual Analog Scores (VAS) and Oswestry Disability Index (ODI) scores.Results: Five patients had interlaminar decompressions for stenosis alone, while two patients had laminectomies for debulking of tumors. The mean duration of surgery was 79.8 ± 16.6 min, the mean estimated blood loss was 157.1 ± 53.4 ml, the mean dose of local anesthetic was 1.9 ± 0.7 mg/kg, and the mean length of hospital stay after surgery was 3.2 ± 1.2 days. There were no intraoperative complications. The surgery resulted in improved VAS and ODI scores consistent with significant improvement in pain (P = 0.017) and functionality (P = 0.011).Conclusions: Performing spinal surgery under local anesthesia is a safe and effective alternative when patient\u27s major comorbidities preclude a general anesthetic. For all the seven patients studied, spinal surgery, performed under a local anesthetic, resulted in a statistically significant reduction in pain and improvement in function
Awake craniotomy for brain tumours in Pakistan: An initial case series from a developing country
No full textAwake craniotomy offers safe resection of brain tumours in eloquent area. Aga Khan University Hospital, Karachi, recently started the programme in Pakistan, and the current study was planned to assess our experience of the first 16 procedures. The retrospective study comprised all such procedures done from November 2015 to May 2016. Pre-operative and post-operative variables were analysed. Of the 16 patients, 11(68.75%) were males and 5(31.25%) were females. The overall median age was 37 years (interquartile range[IQR]: 23-62 years). The most common presenting complaint was seizures 8(50%), followed by headache6(38%). The common pathologies operated include oligodendroglioma and glioblastoma. Pre-operative mean Karnofsky Performance Status score was 76±10, which increased to 96±7 post-operatively at discharge. Besides, 2(12.5%) intra-operative complications were observed, i.e. seizure and brain oedema, in the series. The study had median operative time of 176 minutes (IQR: 115-352) and median length of stay of 4 days (IQR: 3-7).Awake craniotomy was highly effective in maintaining post-operative functionality of the patient following glioma resection. It was also associated with shorter hospital course and so lower cost of management
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