Investigation of hybrid ultrasonic machining process of Nomex honeycomb composite using a toothed disc cutter.

Nomex honeycomb composite (NHC) has been increasingly used in the automotive, aerospace and defence applications due to its excellent thermal and mechanical properties. Its complex cellular hexagonal thin-walled configuration along with heterogeneous, soft and brittle nature pose substantial processing defects such as burr formation, tearing of walls, surface roughness, dimensional inaccuracy and low machining quality during conventional machining (CM). These surface defects have a substantial influence on the operating life and functional performance of its sandwiched structural members. Hybrid ultrasonic vibration assisted machining (HUSVAM) technology has been introduced to overcome such limitations. For an in depth research on HUSVAM of NHC using ultrasonic toothed disc cutter (UTDC), three dimensional finite element model was developed and experimental validation was carried out. The numerical simulation and experimental results were found to be in good agreement with one another. The influence of various machining parameters including the ultrasonic tool vibration amplitude (UTVA), feed rate (FR), depth of cut (DoC) and spindle angular speed (SAS) on NHC cutting forces, chip formation and surface quality was investigated using both HUSVAM and CM techniques. Furthermore, stresses, deformation and forces near tool-workpiece interaction along with the surface topography and morphologies were also analysed and compared for various operating conditions. A reduction in the cutting forces was found with the increase of SAS and UTVA (up to 65.47 % and 65.74 %, respectively). Although, the cutting forces were observed to increase by increasing the DoC and FR (up to 159.45 % and 126.33 %, respectively). DoC has a greater impact on the cutting forces among all machining parameters according to 4 levels, 4 factors (L16) orthogonal experiments based on Taguchi method. The results show that the chip formation and machining quality of NHC core can be improved with HUSVAM technique using UTDC. HUSVAM also reduced the cutting forces (up to 73 %) compared to CM. The ultrasonic toothed disc cutter generated large number of burr with very short length, no tearing defects and no uncut fibers as observed from scanning electron microscopy of NHC hexagonal cell structure, walls and triple points. A burr formation of less than 10 % was realized during HUSVAM of NHC cores for Fx≤3N, while it was found up to 20 % if Fx>3N, compared to at least 40 % during CM. The finite element model developed can be used to investigate the influence of HUSVAM on modern difficult to machine materials for enhanced surface quality.

Selenide-chitosan as High-performance Nanophotocatalyst for Accelerated Degradation of Pollutants.

Water pollution is one of the major global challenges today. Water bodies are contaminated by the heavy release of waste effluents of textile industries, which includes intensively colored dye pollutants. Herein, a ternary nanocomposite of bismuth copper selenide with small particle size and ternary metal selenide (TMS)-chitosan microspheres (TMS-CM) of the spherical porous surface were successfully synthesized. SEM, XRD, EDX, FTIR, and UV/Vis spectrophotometry analysis revealed the structural and morphological characteristics of the newly synthesized nanocomposites. SEM imaging showed the average diameter of TMS nanoparticle to be 33 nm. The crystal size was calculated as 6.33 nm and crystalline structure as orthorhombic using XRD findings. EDX confirmed the presence of Bi, Cu, and Se in the ternary nanocomposite. The bandgap of 1.8 eV was calculated from Tauc's plot for the TMS nanocomposite. SEM confirmed the successful synthesis of spherical TMS-CM microspheres of porous surface morphology with an average size of 885.6 µm. The presence of chitosan microspheres in the synthesis of TMS nanocomposite was identified by FTIR spectral analysis. Furthermore, highly efficient photocatalytic degradation (up to 95.4%) of ARS was achieved within 180 min at pH 4.0 using 0.5 g of TMS-CM in sunlight. The first-order kinetic model fitted well to the photocatalytic decontamination of ARS using TMS-CM with a rate constant of 6.1x10-2  min-1 . The TMS-CM gave attractive results and high efficiency in photocatalytic degradation of ARS dye after reusing and regeneration of up to seven successive cycles. The newly synthesized nanophotocatalyst could be efficiently used for the decontamination of dye polluted water from textile industries.

Distribution of Toxoplasma gondii IgM and IgG antibody seropositivity among age groups and gestational periods in pregnant women.

Background: Toxoplasmosis is a globally distributed parasitic disease. The present study aimed to estimate the prevalence and geographic distribution of toxoplasmosis, as well assess the risk of animal contact in disease development and determine the percentage of toxoplasmois-associated IgM and IgG seropositivity among different age groups. In addition, it aimed to estimate the proportion of toxoplasma IgM seropositivity among pregnancy trimesters. Methods: A total of 500 pregnant women were included in this study. From each participant, a 5-ml venous blood sample was collected and centrifuged to obtain serum that was tested for Toxoplasma gondii IgM and IgG antibodies using immunochromatographic testing and ELISA. Results: The overall seroprevalence of toxoplasmosis was 24.8%, with rates of acute infection of 8%. Among positive cases in every trimester, 54.34% of first trimester positive cases had a serologic marker of acute toxoplasmosis. Out of the 40 pregnant women with previous history of cow/buffalo contact and toxoplasmosis, 40% were seropositive for toxoplasma IgM; and out of 30 women with prior history of dog contact, 16.66% had serological marker of acute toxoplasmosis. Conclusions: In this study, there is a high prevalence of toxoplasmosis and contact with domestic animals is a risk factor for this illness. Therefore, it is necessary to test every pregnant women for toxoplasmosis and distinguish the type of infection, as well as the conduction of public health education programs to generate the awareness.

Burn wound infections and antibiotic susceptibility patterns at pakistan institute of medical sciences, islamabad, pakistan.

BACKGROND: Burn wound infections carry considerable mortality and morbidity amongst burn injury victims who have been successfully rescued through the initial resuscitation. This study assessed the prevalent microrganisms causing burn wound infections among hospitalized patients; their susceptibility pattern to commonly used antibiotics; and the frequency of infections with respect to the duration of the burn wounds. METHODS: This study was carried out at Burn Care Centre, Pakistan Institute of Medical Sciences (PIMS), Islamabad, Pakistan over a period of two years (i.e. from June 2010 to May 2012). The study included all wound-culture-positive patients of either gender and all ages, who had sustained deep burns and underwent definitive management with wound excisions and skin auto-grafting. Patients with negative cultures of the wounds were excluded. Tissue specimens for culture and sensitivity were collected from burn wounds using standard collection techniques and analyzed at microbiological laboratory. RESULTS: Out of a total of 95 positive microbial growths, 36 were Pseudomonas aeruginosa (35.29%) as the most frequent isolate found, followed by 21 Klebsiella pneumoniae (20.58%), 19 Staphylococcus aureaus (18.62%), 10 Proteus (9.80%), 7 E. coli (6.86%), 7 Acinetobacter (6.86%), and 4 Candida (3.92%). A variable antibiotic susceptibility pattern was observed among the grown microbes. Positive cultures were significantly more frequent among patients with over two weeks duration of burn wounds. CONCLUSION: P. aeruginosa, K. pneumoniae and S. aureus constituted the most common bacterial microbes of burn wounds in our in-patients cases. Positive cultures were more frequent among patients with over two weeks duration of burn wounds. Early excision and skin grafting of deep burns and adherence to infection control measures can help to effectively reduce the burden of these infections.

Successful propranolol treatment of a large size infantile hemangioma of the face causing recurrent bleeding and visual field disruption.

A 29 days old Pakistani female infant was presented to our outpatient department with two weeks history of a rapidly progressing large size facial hemangioma involving most of the right cheek and right eyelids. The infant was unable to open the right eye. There was also a small hemangioma on the right second toe. Additionally, three similar lesions were found on the right side of the palate and adjoining buccogingival surfaces. The parents were particularly concerned about the explosive progression of the lesions, recurrent bleeding episodes from ulcerated areas of the cheek lesion and complete occlusion of the right eye. Following four weeks therapy with propranolol in a dose of 2 mg/kg/day, the hemangiomas rapidly regressed, the bleeding episodes ceased and the infant started opening the eye.