[en] The effectiveness of piezoelectric photothermal spectroscopy (PPTS) to investigate surface states and bulk properties of single crystal silicon was demonstrated. PPTS measurements were conducted on p- and n-type, single crystal silicon. A broad peaked signal around 1.18±0.01 eV at room temperature showed the characteristics of slow states present on silicon surface. Another signal bearing a peak around 1.07±0.005 eV at room temperature was due to bulk effect. In the indirect band gap of silicon, the excitation of electrons from valence band to conduction band (so called band-to-band excitation) is not possible without phonon assistance. The PPTS measurements conducted at various temperatures revealed band-to-band and valence band-to-excitons states transition with phonon assistance. The measurements at 4.2 and 110 K resolved four types of phonon participation. A good agreement between theoretical expressions and experimental data substantiated the phonon participation in band-to-band and valence band-to-excitons states transitions

[en] Conservation laws for partially conservative variable mass dynamical systems under symmetric infinitesimal transformations are determined. A generalization of Lagrange-d'Alembert's principle for a variable mass system in terms of asynchronous virtual variation is presented. The generalized Killing equations are obtained such that their solution yields the transformations and the associated conservation laws. An example illustrative of the theory is furnished at the end as well. (authors)

[en] Pakistan like other countries is also faced with energy crisis, for which there is a need to identify indigenous technologies along with renewable energy sources to satisfy the energy footprint of the country. Use of MFC (Microbial Fuel Cell) technique is currently a step towards this direction that can play an effective role in solving the dual problems of environmental pollution and energy shortage. In this study, sewage sludge from a wastewater treatment plant was collected and used as a substrate for electricity generation in association with other biomass sources. Effect of relevant parameters such as oxygen flow rate, pH and concentration on voltage generation was also analyzed. The experimental results yielded in voltage generation of 2500 mv/l for sewage sludge in comparison to that obtained using carbon manure (270 mv/l), wastewater (229 mv/l) and cow manure (330 mv/l) suggesting towards the potential of sewage sludge for power generation. (author)

[en] Pakistan is a gas rich but power poor country. It consumes approximately 1, 559 Billion cubic feet of natural gas annually. Gas is transported around the country in a system of pressurized transmission pipelines under a pressure-range of 600-1 000 psig exclusively operated by two state owned companies i.e. SNGPL (Sui Northern Gas Pipelines Limited) and SSGCL (Sui Southern Gas Company Limited). The gas is distributed by reducing from the transmission pressure into distribution pressure up to maximum level of 150 psig at the city gate stations normally called SMS (Sales Metering Station). As a normal practice gas pressure reduction at those SMSs is accomplished in pressure regulators (PCVs or in of natural gas is an untapped energy resource which is currently wasted by its throttling. This pressure reduction at SMS (pressure drop through SMS) may also be achieved by expansion of natural gas in TE, which converts its pressure into the mechanical energy, which can be transmitted any loading device for example electric generator. The aim of present paper is to explore the expected power production potential of various Sales Metering Stations of SSGCL company in Pakistan. The model of sales metering station was developed in a standard flow sheeting software Aspen HYSYS at the rate 7.1 to calculate power and study other parameters when an expansion turbine is used instead of throttling valves. It was observed from the simulation results that a significant power (more than 140 KW) can be produced at pressure reducing stations of SSGC network with gas flows more than 2.2 MMSCFD and pressure ration more than 1.3. (author)

[en] Bioremediation of aliphatic HC (Hydrocarbons) in the oily sludge of Kunnar oil and gas field, Pakistan was attempted by means of previously isolated and developed Bacillus sp. Both autoclaved and non-autoclaved sludge samples were analyzed for a reaction time of 30 days with pH 7 and temperature of 380C in 50 ml MSM growth media for the sludge concentration of 5, 10 and 50% with 2, 4 and 6ml of Bacillus sp. relatively, in air atmosphere. Stabilization of the samples by microbial activity resulted in the decrease in TPH (Total Petroleum Hydrocarbon) concentration by 60, 69 and 87% in autoclaved samples in contrast to the decrease of 70, 84 and 94% observed in non-autoclaved samples, relatively. Hydrocarbon degradation in oily sludge was investigated via GC which transpired that 97 and 99% concentration of aliphatic hydrocarbons in autoclaved and non-autoclaved samples was removed at 5% of TPH concentration, relatively. However, with 10% TPH concentration aliphatic hydrocarbons reduction was 68% in autoclaved samples to that of 87% in non-autoclaved samples. Further increase in the hydrocarbons concentration by 50% yielded in the removal of aliphatic hydrocarbons by 65% in autoclaved samples as compared to 98% decrease in non-autoclaved samples. (author)

[en] This paper outlines the static and fatigue behavior of two different cast-in-place second generation steel-free bridge decks, which are: hybrid carbon fiber reinforced polymer (CFRP); and glass fiber reinforced polymer (GFRP) and steel strap design. Although cast monolithically, the first deck slab was divided into three segments with different reinforcement configurations. All three segments were tested under a 222kN cyclic loading to investigate fatigue behavior. The second bridge deck comprised an internal panel and two cantilevers and was equipped with a civionics system. The internal panel static test that this paper deals with is useful in the development of fatigue theory derived from fatigue testing of the first bridge deck. Test results form the cyclic loading of the first bridge deck indicated that the cross-sectional area of the reinforcement used in the test bridge deck can be reduced by 40% based on the reinforcement provided in the deck under service loads. The hybrid system also reduced the development of longitudinal crack widths to approximately 0.4 mm under service conditions, compared to the cracks that occurred approximately halfway between adjacent bridge girders that were determined to be roughly 1 mm in several first generation steel-free bridge decks constructed in Canada. Civionics, also discussed in the paper, is a new term coined from Civil-Electronics, which is the application of electronics to civil structures. The Civionics Specifications (2004) developed by ISIS Canada researchers are a helpful design tool for engineers and contractors to develop civionics and structural health monitoring systems for civil infrastructure that will last the lifetime of a structure. The use of civionics for the second test bridge deck ensured the survival of 100% of the 63 internal sensors throughout the rigors of the construction and casting of the deck. (author)

[en] Objective: To determine the effect of Dexamethasone on post-operative delirium in adults following general anaesthesia among patients operated at Pakistan Navy Hospital Shifa. Study Design: Prospective comparative study. Place and Duration of Study: Anaesthesia and Pain Medicine Departments, Pakistan Navy Hospital Shifa, Karachi Pakistan, from Oct 2019 to Jan 2021. Methodology: Patients operated in the main operation theatre of our hospital during the study period without any complication fulfilling the exclusion/inclusion criteria, were included in the study. They were randomly divided into two groups, with Group-A receiving 4mg Dexamethasone and other routine pre-anaesthetic medications. In contrast, Group-B just received the routine pre-anaesthetic medications but no Dexamethasone. An independent assessor assessed post-operative delirium using the Confusion assessment method (CAM). Results: A total of 250 patients were included in the study, which met the inclusion criteria. The mean age of the study participants was 34.419±4.329 years. 27(10.8%) patients showed post-operative delirium, while 223(89.2%) did not show postoperative delirium on the Confusion assessment method. The chi-square test revealed that none of the factors studied, including the administration of pre-operative Dexamethasone, had any statistically significant relationship with the presence or absence of delirium among the target population (p-value >0.05). Conclusion: Delirium was a fairly common finding in adult patients 24 hours after routine surgical procedures. None of the factors studied, including Dexamethasone, was related to the presence or absence of delirium in our study. (author)

[en] Objective: To determine the combined effects of continuous positive airway pressure (C-PAP) and physical exercise rehabilitation on a cycle ergometer on postcoronary artery bypass surgery patients. Study Design: Randomised controlled trial. Place and Duration of the Study: Rawalpindi Institute of Cardiology, from December 2020 to May 2021. Methodology: Patients, who underwent coronary artery bypass graft surgery, were divided into two equal groups of each 51. The control group received standard physiotherapy from the 1st postoperative day which included breathing exercises, passive mobilisation in the sitting position, and ambulation. The interventional group also had standard physiotherapy from 1st postoperative day; but also the 2nd to 4th postoperative day had additional dynamic exercises on cycle ergometry in combination with CPAP (continuous positive airway pressure). Results: There was a significant improvement in functional capacity measured by 6-minute walk test in the interventional group (p<0.001). Length of hospital and ICU stay mean rank (68.88 and 58) were also significantly decreased in the interventional group (p<0.001). There was no improvement in maximum inspiratory pressure and maximum expiratory pressure. One-minute sit-to-stand test was increased on 4th postoperative day in the interventional group. There was no significant difference observed in arterial blood gases between these two groups. Conclusion: Cycle ergometry combined with continuous positive airway pressure (C-PAP) applied earlier on patients undergoing coronary artery bypass grafting improves the functional capacity, decreases the ICU and hospital length of stay and also improves lower limb muscle strength. But no difference in respiratory muscle strength and arterial blood gases was observed between the control and interventional groups. (author)

[en] Objective: To compare the efficacy of subtenon with peribulbar local anesthesia without hyaluronidase in patients undergoing cataract surgery. Study Design: A randomized controlled trial. Place and Duration of Study: Eye B Unit, Khyber Teaching Hospital, Peshawar, from October 2009 to October 2010. Methodology: Patients undergoing cataract surgery were divided into two groups. Group A received subtenon anesthesia and group B received peribulbar anesthesia. Pain score, akinesia and intraocular pressure were compared in the two groups. Statistical Package for Social Sciences-14.0 was used for data analysis. Results: There were 304 patients, 152 patients in each group. At the time of injection, there was less pain in group A as compared to group B (p < 0.001). At the time of surgery and till 90 minutes after administration of anesthesia, there was no significant difference in pain between the 2 groups (p = 0.999 and 0.59 respectively). Group A had better akinesia as compared to group B (p = 0.04). There was a greater rise in mean intraocular pressure just after injection in group B as compared to group A (p < 0.001); in both groups, the intraocular pressure declined to its base level 10 minutes after the injection (p = 0.52). Conclusion: Subtenon anesthesia is less painful at the time of its administration, provides better akinesia and leads to smaller rise in intraocular pressure just after the injection than peribulbar anesthesia. (author)

[en] The highly porous power plant waste ashes have been utilized to treat toxic effluent of a dyes manufacturing plant. An attempt has been made for the first time in Pakistan, to generate an effective and economically sound treatment facility for the toxic effluent of a dyes manufacturing plant. This is an indigenous bed which could replace expensive treatment facilities, such as reverse osmosis (RO), granulated activated carbon (GAC) bed, etc. The treatment efficiency was improved by coupling coagulants with fly ash adsorbent bed. The ash was collected from coal fired boilers of power plant at Lakhra Power Generation Company, Jamshoro, Pakistan. The use of this ash resolved the disposal and environmental issues by treating wastewater of chemical, dyes and pigment industry. The treatment bed comprised of briquettes of coal fly ash coupled with commercial coagulant ferrous sulfate-lime reduced COD, color, turbidity and TSS of effluent remarkably. An adsorption capacity and chemical behavior of fly ash bed was also studied. In coagulation treatment, coagulant FeSO/sun 4/-lime influenced reduction of COD, color, turbidity and TSS by 32 percentage, 48 percentage, 50 percentage and 51 percentage, respectively. The CFAB coupled with coagulant, resulted an excessive removal of color, TSS, COD, and turbidity by 88 percentage, 92 percentage, 67 percentage and 89 percentage, respectively. (author)