Muhammad Nasir Amin

Synthesis of ZnO nanostructures for low temperature CO and UV sensing.

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature using a vapor transport method. Needle-like ZnO nanobelts are unique as, according to our knowledge, there is no evidence of such morphology in previous literature. The structural, morphological and optical characterization was carried out using X-ray diffraction, scanning electron microscopy and diffused reflectance spectroscopy techniques. It was observed that the sensing response of comb-like structures for UV light was greater as compared to the other grown structures. Comb-like structure based gas sensors successfully detect CO at 75 °C while other structures did not show any response.

Airflow Dynamics of Coughing in Healthy Human Volunteers by Shadowgraph Imaging: An Aid to Aerosol Infection Control

Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.2±12.9 years; 10 men, mean age 25.3±2.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 1–10), their maximum detectable cough propagation distances ranged from 0.16–0.55 m, with maximum derived velocities of 2.2–5.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.010–0.11 m2, with maximum derived expansion rates of 0.15–0.55 m2/s. For the 10 males (cases 11–20), their maximum detectable cough propagation distances ranged from 0.31–0.64 m, with maximum derived velocities of 3.2–14 m/s, and their maximum detectable 2-D projected areas ranged from 0.04–0.14 m2, with maximum derived expansion rates of 0.25–1.4 m2/s. These peak velocities were measured when the visibility of the exhaled airflows was optimal and compare favorably with those reported previously using other methods, and may be seen as a validation of these previous approaches in a more natural setting. However, the propagation distances can only represent a lower limit due to the inability of the shadowgraph method to visualize these cough airflows once their temperature cools to that of the ambient air, which is an important limitation of this methodology. The qualitative high-speed video footage of these volunteers coughing into their sleeves demonstrates that although this method rarely completely blocks the cough airflow, it decelerates, splits and redirects the airflow, eventually reducing its propagation. The effectiveness of this intervention depends on optimum positioning of the arm over the nose and mouth during coughing, though unsightly stains on sleeves may make it unacceptable to some.

Solar Disinfection of Pseudomonas aeruginosa in Harvested Rainwater: A Step towards Potability of Rainwater

Efficiency of solar based disinfection of Pseudomonas aeruginosa (P. aeruginosa) in rooftop harvested rainwater was evaluated aiming the potability of rainwater. The rainwater samples were exposed to direct sunlight for about 8–9 hours and the effects of water temperature (°C), sunlight irradiance (W/m2), different rear surfaces of polyethylene terephthalate bottles, variable microbial concentrations, pH and turbidity were observed on P. aeruginosa inactivation at different weathers. In simple solar disinfection (SODIS), the complete inactivation of P. aeruginosa was obtained only under sunny weather conditions (>50°C and >700 W/m2) with absorptive rear surface. Solar collector disinfection (SOCODIS) system, used to improve the efficiency of simple SODIS under mild and weak weather, completely inactivated the P. aeruginosa by enhancing the disinfection efficiency of about 20% only at mild weather. Both SODIS and SOCODIS systems, however, were found inefficient at weak weather. Different initial concentrations of P. aeruginosa and/or Escherichia coli had little effects on the disinfection efficiency except for the SODIS with highest initial concentrations. The inactivation of P. aeruginosa increased by about 10–15% by lowering the initial pH values from 10 to 3. A high initial turbidity, adjusted by adding kaolin, adversely affected the efficiency of both systems and a decrease, about 15–25%; in inactivation of P. aeruginosa was observed. The kinetics of this study was investigated by Geeraerd Model for highlighting the best disinfection system based on reaction rate constant. The unique detailed investigation of P. aeruginosa disinfection with sunlight based disinfection systems under different weather conditions and variable parameters will help researchers to understand and further improve the newly invented SOCODIS system.

Improving test methods to measure early age autogenous shrinkage in concrete based on air cooling

In this study, we investigate and improve the testing methods for more accurate measurement of the early-age autogenous shrinkage (AS) in concrete. During the first 24 h after casting, the temperature of concrete rises due to hydration heat and causes the simultaneous development of thermal deformation (TD) and AS. Because there is no general agreement on evolution of coefficient of thermal expansion (CTE) in the literature, the most commonly adopted approach of subtracting the TD based on an assumed constant value of CTE results in incorrect values of early-age AS. To avoid such errors, we propose improvements in measuring rig and control of hydration-induced temperature, which serves as an aid in achieving isothermal conditions in concrete specimens right after casting. The validity of the proposed improvements is investigated by performing a series of tests under semi-adiabatic (including TD) and artificially controlled isothermal conditions (excluding TD). Results indicate that the AS calculated from semi-adiabatic tests is significantly underestimated at early ages, which is probably due to considering inaccurate values of CTE at early ages. Therefore, we recommend the incorporation of proposed improvements into existing test methods or that an appropriate method of determining the evolution of CTE be considered.

Shake Table Tests on FRP Retrofitted Masonry Building Models

AbstractThe current study is devised to evaluate the seismic performance of fiber-reinforced polymer (FRP) retrofitted buildings with openings at different FRP reinforcement levels. Required objectives are achieved by performing five shake table tests on 1/4-scale models of single-story boxlike masonry buildings. Out of five building models, one was an unreinforced masonry (URM) building model whereas the other four were retrofitted with different quantities and layouts of FRP reinforcement. FRP reinforcement is reduced by decreasing FRP strip widths and strip spacing and applying FRP strips on either the inside or outer faces of walls. Each building model was subjected to the same series of input ground motions with gradually increasing amplitudes. A series of diagonal compression tests was also conducted to decide the appropriate type of FRP and trial FRP reinforcement ratios for the masonry building models. Descriptions of the tested models are provided, including the structural response in terms of ba...

Aging and Curing Temperature Effects on Compressive Strength of Mortar Containing Lime Stone Quarry Dust and Industrial Granite Sludge

In this study, the researchers investigated the potential use of locally available waste materials from the lime stone quarry and the granite industry as a partial replacement of cement. Quarry sites and granite industry in the eastern province of Saudi Arabia produces tons of powder wastes in the form of quarry dust (QD) and granite sludge (GS), respectively, causing serious environmental problems along with frequent dust storms in the area. According to ASTM C109, identical 50-mm3 specimens were cast throughout this study to evaluate the compressive strength development of mortars (7, 28 and 91 days) containing these waste materials. Experimental variables included different percentage replacement of cement with waste materials (GS, QD), fineness of GS, various curing temperatures (20, 40 and 60 °C as local normal and hot environmental temperatures) and curing moisture (continuously moist and partially moist followed by air curing). Finally, the results of mortar containing waste materials were compared to corresponding results of control mortar (CM) and mortar containing fly ash (FA). The test results indicated that under normal curing (20 °C, moist cured), the compressive strength of mortar containing the different percentage of waste materials (QD, GS, FA and their combinations) remained lower than that of CM at all ages. However, the compressive strength of mortar containing waste materials slightly increased with increased fineness of GS and significantly increased under high curing temperatures. It was recommended that more fineness of GS be achieved to use its high percentage replacement with cement (30% or more) incorporating local environmental conditions.

Cost-effective and sustainable solutions to enhance the solar disinfection efficiency improving the microbiological quality of rooftop-harvested rainwater

AbstractThis paper investigates the efficiency of solar-based disinfection methods for improving the microbial quality of rooftop-harvested rainwater. Bacteriological water quality indicators including total and fecal coliforms, Escherichia coli, and Heterotrophic Plate Count were examined under different sunlight radiations. The efficiency of simple solar disinfection (SODIS) was enhanced at low pH values of the exposed rainwater. To enhance the concentrating effects of radiations, solar collector disinfection (SOCODIS) system was used. In addition, very simple and cost-effective techniques were employed to enhance the disinfection efficiency. This includes the wrapping of polyethylene terephthalate bottles with heat-resistant plastic bags to enhance the thermal/synergistic effects of radiations and the addition of natural acids (lemon/vinegar) for getting a low pH value of the rainwater in a natural way. Both simple SODIS and SOCODIS systems remained ineffective even under strong radiations and the best...

Optical and gas sensing properties of SnO2 nanowires grown by vapor–liquid–solid mechanism

SnO2 nanowires were synthesized via vapor transport method by modulating the thickness of the Gold (Au) catalyst. The effect of morphology and photoluminescence properties of nanowires on gas sensing was investigated. The structural and morphological studies reveal that the synthesized nanowires are crystalline in nature with high density. The nanowires were evenly spread on the surface of the substrate. These nanowires were tested for gas sensing properties based on change in resistance under exposure to air and gases (CO, CH4, Methanol). The results showed an improved response as compared to the previous studied. These sensors have potential applications in advanced sensing devices.

Assessment of cracking in concrete due to hydration heat and autogenous shrinkage

An experimental study was conducted to simulate the generation of thermal stresses due to hydration heat and restraint by using a thermal stress measuring device (TSD). The net effects of time-dependent properties of hardening concrete can be well incorporated in TSD due to simultaneous development of temperature and corresponding stress in restrained specimen. Moreover, experiments were conducted to measure a precise value of early-age autogenous shrinkage (AS) and to evaluate the basic creep model with respect to AS. In cracking risk analysis, precise value of early-age AS must accurately predict the time of shrinkage-induced cracking. A significant difference exists between apparent (including AS) and real basic creep (excluding AS) for low water-cement ratio concrete and early-age normal strength concrete. To improve the crack sensitivity analysis, it is recommended to precisely measure early-age AS and modify the basic creep model to prevent from possible errors and computational problems.

The efficacy of excision followed by intralesional 5-fluorouracil and triamcinolone acetonide versus excision followed by radiotherapy in the treatment of ear keloids: A randomized control trial

BACKGROUND The ear is the common site for keloid formation especially in women after ear piercing. Surgery is the main stay of treatment in these lesions but there are large numbers of treatment failures in surgery alone. OBJECTIVE The objective of this study was to compare the efficacy of post-excision intralesional 5-fluorouracil/triamcinolone acetonide (5-FU/TAC) and post-excision radiotherapy in the treatment of ear keloids. STUDY DESIGN A randomized controlled trial. SETTING The study was conducted from May 2014 to January 2015 at Jinnah Burn and Reconstructive Surgery Centre, Allama Iqbal Medical College, Lahore. SUBJECT & METHODOLOGY After approval from the hospital ethical committee, 60 patients presented in the outpatient department fulfilling the inclusion criteria were selected and randomly assigned in two groups with the help of the random number table. Patients in group A had excision followed by intralesional 5-FU/TAC injections while patients of group B had excision followed by radiotherapy. Patients were assessed at 6 months after completion of treatment for efficacy (no recurrence within 6 months of treatment). RESULTS In our study total of 60 patients completed the study, with 30 patients in each group. 7 patients (23.34%) in Group-A and 9 patients (30%) in Group-B were males while 23 patients (76.67%) in Group-A and 21 patients (70%) in Group-B were females i.e. male to female ratio is 1:2.75. Mean age was 31.8+6.48years. The comparison of frequency of efficacy in both groups showed that 73.33% (n=22) in Group-A and 43.33% (n=13) in Group-B had efficacy, p value was calculated as 0.01, showing a significant statistical difference. CONCLUSION Excision and intralesional 5-FU/TAC is an effective treatment for keloids on the ears.