Statističko optimiranje proizvodnje α-galaktozidaze submerznim uzgojem aktinomicete Streptomyces griseoloalbus primjenom metodologije odzivnih površina

α-Galactosidase production by a novel actinomycete strain Streptomyces griseoloalbus in shake flask culture was optimized using response surface methodology. Screening of variables to find their relative effect on α-galactosidase production was done using Plackett-Burman design. Out of the eleven factors screened, salinity, magnesium sulphate and temperature were found to influence the enzyme production significantly. The optimal levels of these variables and the effect of their mutual interactions on enzyme production were determined using Box-Behnken design. The interaction between salinity and magnesium sulphate concentration was found to enhance α-galactosidase production, whereas temperature exhibited an influence independent of the other two factors. Using this statistical optimization method, the α-galactosidase production was increased from 17 to 50 U/mL.Primjenom metodologije odzivnih površina optimirana je proizvodnja α-galaktozidaze s pomoću novog soja aktinomiceta Streptomyces griseoloalbus u pokusima na tresilici. Primjenom Plackett-Burmanova statističkog plana ispitan je utjecaj varijabli na proizvodnju α-galaktozidaze. Od jedanaest ispitanih faktora, na proizvodnju enzima bitno su utjecali salinitet, koncentracija magnezijeva sulfata i temperatura. Optimalne vrijednosti tih varijabli i njihovo uzajamno djelovanje na proizvodnju enzima određeno je primjenom Box-Behnken statističkog plana. Međusobnim utjecajem saliniteta i koncentracije magnezijeva sulfata poboljšana je proizvodnja α-galaktozidaze, za razliku od temperature čiji utjecaj nije ovisio o ta dva faktora. Primjenom takva postupka proizvodnja α-galaktozidaze povećana je sa 17 na 50 U/mL

Impact of Rapid Urbanization on the Rates of Infection by Vibrio cholerae O1 and Enterotoxigenic Escherichia coli in Dhaka, Bangladesh

Bangladesh is a country where acute dehydrating diarrhea or cholera is common and is seen at least two times every year and additionally in natural disasters. In addition cholera cases have increased in the country, especially in urban settings such as in the capital city, Dhaka, where the number of hospitalized patients with more severe disease has tremendously increased. In the present observation, we have concentrated on determining the occurrence of diarrhoea caused by the two most common bacterial agents V. cholerae O1 and enterotoxigenic Escherichia coli (ETEC) in a densely populated, disease prone area Mirpur in Dhaka for two years from March 2008 to February 2010. Stool or rectal specimens from diarrheal patients coming to the ICDDR,B hospital from Mirpur were tested for the two bacterial pathogens. We found that V. cholerae O1 was the major bacterial pathogen and a cause of severe cholera disease in 23% of patients (2,647 of a total of 11,395 patients) from Mirpur. We surmise that cholera vaccines, as well as other public health tools that can target such high risk groups in the country, will be able to reduce the disease morbidity and the transmission of pathogens to improve the quality of life in urban settings

Statistical Optimization of α-Galactosidase Production in Submerged Fermentation by Streptomyces griseoloalbus Using Response Surface Methodology

α-Galactosidase production by a novel actinomycete strain Streptomyces griseoloalbus in shake flask culture was optimized using response surface methodology. Screening of variables to find their relative effect on α-galactosidase production was done using Plackett-Burman design. Out of the eleven factors screened, salinity, magnesium sulphate and temperature were found to influence the enzyme production significantly. The optimal levels of these variables and the effect of their mutual interactions on enzyme production were determined using Box-Behnken design. The interaction between salinity and magnesium sulphate concentration was found to enhance α-galactosidase production, whereas temperature exhibited an influence independent of the other two factors. Using this statistical optimization method, the α-galactosidase production was increased from 17 to 50 U/mL

Excellent EMI shielding performance and thermal insulating properties in lightweight, multifunctional carbon-cenosphere composite foams

Lightweight carbon foam has been considered as one of the most promising candidates for providing excellent EMI shielding performance in the fields of aerospace and portable electronics. Here, multifunctional lightweight carbon composite foams were developed by the impregnation of phenolic resin and cenospheres (0-40 wt.%) into polyurethane (PU) foam substrate. Subsequenty, impregnated foams were converted into carbon-cenosphere composite foams via heat treatment at 1000 degrees C. The influence of cenosphere particles on the morphological, physical, mechanical electrical and thermal properties of carbon-cenosphere composite foams was studied in details. EMI shielding of carbon-cenosphere composite foam was measured in X-band frequency region (8.2-12.4 GHz) using waveguide method. The total shielding effectiveness (SE) of carbon foam was increased from - 25.2 to - 48.6 dB by the loading of 30 wt.% cenosphere. The thermal conductivity achieves as low as 0.02 W/(m.K), which is similar to aerogel

Multi-component framework derived SiC composite paper to support efficient thermal transport and high EMI shielding performance

Carbon-based electromagnetic interference (EMI) shielding materials have witnessed a fast evolution in recent years. But challenges of lightweight, flexibility, and good heat dissipation properties required to explore new EMI shielding materials. Herein, a unique SiC-based hybrid composite paper was prepared, as an advanced thermally stable and conductive material for boosting the EMI performance. In this study, a lightweight and flexible network structure of mesocarbon microbeads (MCMB) and multiwall carbon nanotubes (MWCNTs) with polyacrylonitrile (PAN) was developed and SiC was incorporated during the fabrication process or synthesized directly within the matrix structure. EMI shielding effectiveness (SE) of the hybrid composite papers was studied in the X-band frequency region and a maximum EMI SE value of -67 dB was achieved at a frequency of 10.3 GHz. In addition to EMI shielding properties, the hybrid composite paper shows high thermal stability and good thermal conductivity required for proper heat dissipation from the system accompanied by robust mechanical properties. These outcomes make SiC-composite paper attractive material for applications in the lightweight and flexible modern electronic devices with good heat dissipation characteristics

Engineering novel synthetic strategy to develop mesocarbon microbeads for multi-functional applications

To assess the challenge of affordable technology, present synthetic strategies can be extended to new low-cost synthesis and processing methods that have potential to tailor the properties of the materials. Here we report, a novel method for the synthesis of mesocarbon microbeads (MCMB) through a preprocessing involved pyrolysis technique. The resulting MCMB is compressed into a product and effects of heat treatment temperature on different properties of MCMB is studied. The use of MCMB for the electromagnetic interference (EMI) shielding is new and hence, the effect of heat treatment temperature on EMI shielding effectiveness is studied in X-band. It is observed that EMI shielding effectiveness increases to -39.6 dB on increasing the heat treatment temperature. The high conductivity of MCMB plate heat treated up to 2500 degrees C contributes to highly conducting networks. Additionally, to investigate the electrochemical performance of MCMB as an anode material for lithium ion batteries, 2500 degrees C heat treated MCMB powder is used to fabricate the electrode. The MCMB electrode exhibits high discharge capacity of 345 mAh g(-1) with a stable capacity for over 50 cycles and good rate capability. Thus, MCMB synthesized by this novel approach can be used for the development of high performance anode materials for Li-ion batteries

Integration of MCMBs/MWCNTs with Fe3O4 in a flexible and light weight composite paper for promising EMI shielding applications

Insights into advances in portable and flexible electronic devices can be gained from the integration of magnetic nanoparticles with light weight and flexible conductive supports, especially in cases where the thickness of the material is challenging for future electromagnetic interference shielding applications. Here we report the fabrication of flexible shielding materials made up of Fe3O4 nanoparticles incorporated mesocarbon microbeads and multiwalled carbon nanotubes (MCMBs/MWCNTs) composite paper for efficient electromagnetic interference (EMI) shielding in the X-band frequency region (8.2-12.4 GHz). The incorporation of Fe3O4 nanoparticles in the MCMBs/MWCNTs composite paper significantly increases its interfacial polarization and anisotropy energy, which leads to an excellent absorption dominated EMI shielding effectiveness (SE) of -80 dB at 0.5 mm thickness. The composite paper also exhibits improved magnetic properties coupled with enhanced dielectric properties that increase with increasing concentration of Fe3O4 nanoparticles. Our measurements have provided a regime for designing conductive networks with advantages of light weight and flexibility, with promising EMI shielding applications

The Resistance Patterns in <i>E. coli</i> Isolates among Apparently Healthy Adults and Local Drivers of Antimicrobial Resistance: A Mixed-Methods Study in a Suburban Area of Nepal

Evidence-based decision-making to combat antimicrobial resistance (AMR) mandates a well-built community-based surveillance system for assessing resistance patterns among commensals and pathogenic organisms. As there is no such surveillance system in Nepal, we attempted to describe the antimicrobial resistance pattern in E. coli isolated from the fecal samples of apparently healthy individuals in Dhulikhel municipality and also explored the local drivers of AMR. We used a mixed-method design with a cross-sectional quantitative component and a descriptive qualitative component, with focus group discussion and key informant interviews as the data collection method. Fecal samples were collected from 424 individuals randomly selected for the study. E. coli was isolated from 85.9% of human fecal samples, of which 14% were resistant to ≥3 class of antimicrobials (multidrug resistant). Of the 368 isolates, resistance to ampicillin (40.0%), tetracycline (20.7%) and cefotaxime (15.5%) were most prevalent. The major drivers of AMR were: lack of awareness of AMR, weak regulations on sales of antimicrobials, poor adherence to prescribed medications, and incomplete dosage due to financial constraints. These findings indicate the need for strict implementation of a national drug act to limit the over-the-counter sales of antimicrobials. Additionally, awareness campaigns with a multimedia mix are essential for educating people on AMR

Antimicrobial Resistance in E. coli Isolated from Chicken Cecum Samples and Factors Contributing to Antimicrobial Resistance in Nepal

Microorganisms with antimicrobial resistance (AMR) are prevalent among humans and animals, and also found in the environment. Though organisms with AMR can spread to humans via food from animal sources, the burden of AMR in food-producing animals remains largely unknown. Thus, we assessed the resistance pattern among Escherichia coli isolated from chicken cecum samples and explored issues contributing to AMR in animals in the Dhulikhel Municipality of Nepal. We conducted a mixed-methods study, comprising a cross-sectional quantitative component, with collection of chicken cecal samples from slaughter houses/shops. In addition, a descriptive qualitative component was undertaken, with a focus group discussion and key informant interviews among stakeholders involved in animal husbandry. Of the 190 chicken cecum samples collected, 170 (89%) were subjected to culture and drug sensitivity testing, of which E. coli was isolated from 159 (94%) samples. Of the 159 isolates, 113 (71%) had resistance to &ge;3 antimicrobial class. Resistance to tetracycline (86%) and ciprofloxacin (66%) were most prevalent. Overuse of antimicrobials, easy availability of antimicrobials, and lack of awareness among farmers about AMR were major issues contributing to AMR. The high prevalence of resistance among E. coli in chicken cecal samples calls for rational use of antimicrobials, educating farmers, and multi-sectoral coordination