Measurement methods of Gas-Solid Interactions

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Reproducibility of the Quantification of Reversible Wall Interactions in VOC Sampling Lines

Volatile Organic Compounds (VOCs) are widely measured at ppb and ppt level in many contexts, from therapeutic drug control in respiratory diseases to monitoring of climate change and indoor air quality. The need for accuracy is a common denominator in all these fields. The interactions between gas mixtures and solid surfaces in sampling lines and instruments play an important role in calculating the total uncertainty of the amount of VOC. The amount of substances in the gas mixture is affected by its reversible and irreversible interactions with the sampling line. The main aim of this paper is to propose and discuss a method to quantify the amount of substance segregated by reversible interactions on sampling lines. To validate the proposed method, the areic amount of a VOC (Acetone) is measured for a commercial test pipe (Sulfinert®) as the amount of substance per unit area of the internal surface of the test pipe segregated from the flowing gas mixture. Stainless steel coated by Sulfinert® was chosen as a test material because of its wide use and its limited irreversible and permeation effects. A certified gas mixture of Acetone in air with a nominal mole fraction of 10 µmol mol−1 was used for validation. Broad temperature control was used and the sensibility of the method to the temperature and the pressure has been evaluated to correct the bias due to physical condition. The sensitivity to the residence time and the Reynolds number of the gas flow has been evaluated to verify the reaching of equilibrium and the limits of the applicability of the method. The areic amount of Acetone at equilibrium on Sulfinert® coated pipe was measured as 40 nmol m−2, and an equilibrium constant value of around 0.2 m was calculated as the ratio between the superficial amount segregated on the wall and the amount concentration of Acetone in the mixture, both at the equilibrium. The observed reproducibility was better than 2.5%. This method is aimed to investigate VOC losses due to interactions for many VOC/material systems at a lower amount of substance levels

Outcome of Surgically Managed Depress Skull Fracture in a Tertiary Care Hospital

Objective: To know about the outcome of depress skull fracture (DSF) in a tertiary care hospital.Material and Methods: This study was conducted at the department of neurosurgery PGMI/LRH from 20th December 2012 to 19th June, 2013. A total of 83 patients operated during this time were reviewed and the data including age, sex, location of fracture, timings of surgery, post operative status of the patient, presence or absence of any neurological deficit as well as post operative complications was enlarged.Results: In this study there were 64 males and 19 females with a male to female ratio of 4: 1. Age range was 1 to 58 years commonest decades were 5 – 10 years 36.10% (group 2) and 10 – 20 (16.9%) and 20 – 30 (15.7%) years (group 3 and 4) comprising respectively. The most common region was the parietal 30 (36.1%) followed by frontal 26 (31.3%). The right side was more affected than the left side (60.2% vs. 39.8%). The time of surgery was mostly in the interval between 9pm to 6am. More than 90% has good outcome with minimal neurologic deficit, while three patients expired who initially had a very low GCS score. One patient has dysphasia post operatively and 2 had weakness of the upper limbs who were operated for the frontoparietal fracture.Conclusion: DSF is a common emergency encountered in a neurosurgical unit and the timely management of these patients is crucial to avoid any complication. If managed timely they have very gratifying results

Diagnostic yield of transthoracic echocardiography for stroke patients in a developing country

OBJECTIVE: To assess the utility and cost effectiveness of transthoracic echocardiography (TTE) as part of stroke workup in a developing country. METHODS: All patients over the age of 14 years with acute stroke were prospectively enrolled in Aga Khan University stroke databank from August 1999 to May 2001 (22 month period). All patients were evaluated by a consultant neurologist and underwent standard stroke work up such as neuroimaging, TTE, carotid doppler sonography and blood tests e.g. serum glucose, lipid profile, blood urea nitrogen and serum creatinine. For the purpose of this study, patients with ischemic stroke were identified and their echocardiographic data was retrieved and analyzed. TOAST criteria was used to identify findings indicating cardioembolic stroke. RESULTS: Ischaemic stroke was identified in 393 (76%) patients. Of these 278 (71%) patients underwent transthoracic echocardiography as part of stroke workup. Although 199 (73%) patients had abnormal echocardiogram; only 43 (15.5%) had findings suggestive of possible cardioembolism as defined by the TOAST criteria. CONCLUSION: Tranthoracic echocardiography is a valid diagnostic modality for stroke workup. However there is a need to further investigate the specific indications which can be used to prioritize patients for undergoing echocardiography to minimize cost

Incidental Durotomy in Lumbar Microdiskectomy; Incidence, Management and Early Sequelae

Objective: To know about the incidence, management and early sequelae of incidental durotomy during lumbar microdiskectomy.Materials and Methods: This was a retrospective study. The duration of the study was six months from January 24th to 20th July 2013. The charts and records of the patient from the operation notes were reviewed and the parameters like the age, sex, side and location of the disc, mean hospital stay and any documented leak or neural deficit were recorded on a designed proforma. All patients undergoing lumbar microdiskectomy for the first time were included in the study and the patients having a repeated surgery as well as other indications (stenosis, tumor, trauma) excluded from the study.Results: A total of 147 patients were included in the study including 87 males and 60 females with a male to female ratio of 1.5 to 1. The age range was 18 – 63 years with a mean age of 34 ± 6 years. The most common level was L4 – L5. Right side was more common than the left side and the four patients (2.7%) had an incidental durotomy which was repaired intra-operatively. The patient with an incidental have any focal deficit apart from the prolongation of the hospital stay.Conclusion: Incidental durotomy is an infrequent complication of lumbar microdiskectomy and there is little early clinical sequelae apart from prolongation of hospital stay

Clinical profile and outcome of infective endocarditis at the Aga Khan University Hospital

Background: The spectrum of infective endocarditis (IE) is significantly different in developed and developing countries. The present study was conducted to study the clinical profile and outcome of infective endocarditis in Pakistan.Methods: A descriptive cross-sectional study with review of medical records for 188 patients admitted to our teaching hospital with a diagnosis of IE from January 1988 to December 2001. One hundred fifty-nine subjects fulfilled the modified Duke diagnostic criteria.Results: Definite IE was found in 59.7% (95/159) patients, while the rest had possible IE. One-third of subjects had acute IE 55/159 (34.5%). Subacute IE was found in 62% (99/159) and Nosocomial IE in 3% of the cases. Eighty six (54%) were classified as having culturenegative endocarditis and 73 (46%) as culture positive. Ninty four patients (59%) had an underlying predisposing factor including congenital heart disease (31%) and rheumatic heart disease (21%). The most frequently isolated organisms were streptococci (52%) and followed by staphylococci (29%). Fourteen (8.1%) patients had right-sided cardiac involvement. Using univariate analysis, patients with heart failure, neurologic or renal complications, septicemia, nosocomial endocarditis, and prosthetic valve endocarditis were at increased risk of death (p ≤ 0.05), however no individual microorganism, or specific site, size, or morphology of vegetation seen on echocardiogram were significantly associated with death. Thirty-seven (23%) patients died of endocarditis or its complications.Conclusion: Endocarditis continues to be an important contributor to morbidity and mortality in Pakistan, especially in young adults. Our patients differ from the west in terms of epidemiology, predisposing factors, microbiology, complications, and outcom

Evaluation of Gas Potential in Early Cretaceous Shale Lower Indus Basin, Pakistan

The shale gas potential of the early Cretaceous Talhar shale member of the lower Goru Formation in lower Indus basin of Sanghar district, Sindh province, has been evaluated using 2D seismic and well logs data. Graphical and empirical techniques were applied to calculate various geochemical parameters for the evaluation of shale plays. Total Organic Carbon (TOC) is calculated by Passey's (∆LogR) Overlay technique and its values are about 2.44 wt.%. Vitrinite Reflectance (Ro) is estimated by graphical and empirical relation and the value lies between 0.95-1.0 which implies that the Talhar shale member is in peak oil and initial gas generation phase. Log-derived Maturity Index (LMI) is calculated by NPHI, RHOB or density log and uranium logs. The average value is about 0.55 which reflects that the formation is probably in the initial maturation phase. Kerogen Volume (Vk) is estimated by empirical relation using RHOB log as input and it is about 13 wt. % which reflects that the formation has enough potential of oil/gas expulsion. The results are compared and validated with a study of the adjacent field of the same basin. This study reveals that Talhar member of lower Goru Formation could be the future probable potential unconventional reservoir for exploration in lower Indus basin of Pakistan

Causes of Carpal Tunnel syndrome (CTS)

Objective: To know about the pathological causes of carpal tunnel syndrome.Materials and Methods: This is retrospective cross sectional study on the patients operated by the senior author at his private clinic between January 2008 and March 2014. All the patients operated for carpal tunnel syndrome during the study period were included while those managed conservatively were excluded from the study. Pre-operatively all patients had undergone Nerve conduction studies and the procedure was performed under local anaesthesia. The pathology responsible for causing CTS was noted.Results: A total of 73 patients were operated for CTS during the study period by the senior author. There were 18 males and 55 females with a male to female ratio approaching 3.0:1. The age range was from 24 – 58 years with a mean age of 43.6 ± 4 years. The pathology was hypertrophied transverse carpal ligament in 66 (90%) cases, abnormal vessels in 1 (1%), neuroma in 1 (1%), fracture distal end of the radius in 2 (5%), ganglion com-pressing the nerve in 1 (1%), post cellulitis in 1 (1%) and direct trauma to the nerve in 1 (1%).Conclusion: Thickened ligamentum flavum is the most common cause of carpal tunnel syndrome and space occupying lesion constitute a considerable percent of pathology