A dispersive Raman spectrometer was used with three different excitation sources (Argon-ion, He-Ne, and Diode lasers operating at 514.5 nm, 633 nm, and 782 nm, resp.). The system was employed to a variety of Raman active compounds. Many of the compounds exhibit very strong fluorescence while being excited with a laser emitting at UV-VIS region, hereby imposing severe limitation to the detection efficiency of the particular Raman system. The Raman system with variable excitation laser sources provided us with a desired flexibility toward the suppression of unwanted fluorescence signal. With this Raman system, we could detect and specify the different vibrational modes of various hazardous organic compounds and some typical dyes (both fluorescent and nonfluorescent). We then compared those results with the ones reported in literature and found the deviation within the range of ±2 cm−1, which indicates reasonable accuracy and usability of the Raman system. Then, the surface enhancement technique of Raman spectrum was employed to the present system. To this end, we used chemically prepared colloidal suspension of silver nanoparticles as substrate and Rhodamine 6G as probe. We could observe significant enhancement of Raman signal from Rhodamine 6G using the colloidal solution of silver nanoparticles the average magnitude of which is estimated to be 103.

Abstract:Transition from latency to active tuberculosis requires Mycobacterium tuberculosis (Mtb) to penetrate the phagosomal membrane and translocate to the cytosol of the host macrophage. Quantitative twophoton fluorescence resonance energy transfer (FRET) microscopy is developed to measure cytosolic translocation using Mycobacterium marinum (Mm) as a model organism for Mtb. Macrophages were infected with Mm or non-pathogenic Mycobacterium smegmatis (Ms) as a control, then loaded with a FRET substrate. Once translocation occurs, mycobacterium-bearing β-lactamase cleaves the substrate, resulting in decrease of FRET signal. Quantification of this FRET signal change revealed that Mm, but not Ms, is capable of translocating to the cytosol.

Heavy-metal pollution of surface water, sediment and fish have been seen as a major global problem, with a significant proportion of developing countries like Bangladesh. This study assessed the intensity of alarming six toxic substances (Cr, Zn, Fe, Cu, Pb and Ni) throughout the River water, sediments as well as soft tissues of three widely consumed fishes (Heteropneustes fossilis, Channa punctatus and Channa striata) obtained from two urban streams of the Buriganga and Turag in the Dhaka metropolitan. For evaluating the comparative seasonal variation of heavy-metal concentration, water and sediment samples were collected from five selected sites for two different seasons (viz. 10 from winter seasons and 10 from summer seasons). Finally, a total of 20 water samples, 20 sediment and 12 fish samples were investigated by flame atomic absorption spectroscopy (FAAS) and graphite furnace atomic absorption spectrometer (GFAAS) corrected with the Zeeman effect background correction system. The hierarchy of mean concentration of selected heavy metals in Buriganga water is found to be Fe > Cr > Ni > Zn > Cu > Pb in the winter season whereas during the summer season the order is Fe > Cr > Zn > Ni > Cu > Pb. For the River Turag, the order is Fe > Zn > Cu > Ni > Cr > Pb and Fe > Zn > Ni > Cu > Cr > Pb during winter and summer season, respectively. The level of metals studied surpassed the acceptable level of drinkable water, implying the ineptitude of drinking and cooking water from these Rivers. However, this hierarchy of heavy metals for sediments of Buriganga River changed to Fe > Cr > Ni > Zn > Cu > Pb for the winter season and Fe > Cr > Ni > Cu > Zn > Pb for the summer season. Whereas, for the Turag River, the decreasing trend of metal concentration found in sediment was Fe > Zn > Cr > Ni > Cu > Pb for both seasons. For probable human health hazard implications, contamination factor (CF) and pollution load index (PLI) were studied. The CF values revealed the low-to-moderate pollution of sediment. The PLI value above one shows the degradation of the consistency of the sediments. Fe, Ni, Pb, Cr, Zn and Cu concentrations in fish species were found to be 19.66–45.1, 0.07–12.18, 1.2–10.18, 20.18–187.07, 11.08–68.25, 2.07–10.4 mg/kg, respectively. The metals studied differed considerably among organisms and seasons. Bioconcentration factor (BCF), the daily average consumption of metal (EDI), as well as target threat quotients (THQs) for specific metal indicated that Cr and Pb are harmful in fish muscles and possible risks remain for fish consumers. The obtained concentrations of some metals are higher than the WHO/FAO’s permissible limit, suggesting that the water and fish found in these Rivers are like to be harmful to the human being. This study shows that attention should be given to the risk assessment for heavy metals in these Rivers.

This research was conducted to bring out the appropriate level of heavy metal contamination in soil at the site of Buriganga river bank near the Hazaribagh tannery area and the normal agricultural area to evaluate heavy metal contamination in soil due to untreated tannery effluents. AAS flame method was used to determine the concentration of Chromium (Cr), lead (Pb), Cadmium (Cd), Zinc (Zn) in several depths of the soil. Results showed that, the heavy metal concentration in soil at the site of Buriganga river bank in the tannery vicinity and normal agricultural area significantly varies, such as Cr varies (561.71 -31.23) mg/kg, Zn varies (158.23 -73.5), Pb varies (70.58 -24) and Cd varies (2.25 -0.71) mg/kg in the river bank as well as in the normal agricultural area Cr varies ) and Cd varies (1.30 -0.64) mg/kg. The study indicated that heavy metals concentration was found to be significantly higher in river bank soils than in the normal agricultural area. This metal concentration in soil is responsible for the promotion of toxicity in agricultural products. Therefore, the human health and environment are affected by these areas.

Background The COVID-19 outbreak spillovers mental health burden where suicide is a common psychological public health issue that affects people all over the world. This study aimed to explore the factors associated with suicidal behavior among university students in Bangladesh after one year of the COVID-19 outbreak. Methods An online cross-sectional survey was conducted among 2100 Bangladeshi university students aged ≥ 18 years from April 29 to May 15, 2021. The survey questionnaire contained socio-demographic information, COVID-19 related physical and psychosocial factors (CRPPF), preventive response to psychological stress, and the Suicidal Behaviors Questionnaire-Revised (SBQ-R) scale. Descriptive statistics along with logistic regression were performed for statistical analysis. Results About 47.90% of the students were at risk of suicidal behavior, and female students were very likely to be at risk of suicidal behavior than their male counterparts (AOR= 2.28; 95% CI: 1.86 to 2.81). Keeping distance from friends or family (AOR= 1.66; 95% CI: 1.34 to 2.04), having relationship problems (AOR= 2.20; 95% CI: 1.79 to 2.70), feeling own selves as burden to families (AOR= 2.50; 95% CI: 2.02 to 3.11), and being stressed of lockdown (AOR= 1.56; 95% CI: 1.19 to 2.03) were highlighted as some of the significant factors associated with increased risk of suicidal behavior. Conclusion University students were exposed to several factors that impose the risk of developing suicidal behavior. Concerned authorities should design & implement appropriate strategies for ensuring suicidal prevention besides their mental well-being.