Effect of successive recycling and reuse of acid liquor for the synthesis of graphene oxides with higher oxygen-to-carbon ratios

Graphene has recently drawn exponential attention due to its surprising physicochemical properties and diversified field of applications. Although graphene oxides (GOs), itself is an exclusive material, it is also an intermediate product for the production of reduced graphene oxides (rGOs), graphene and their derivatives, which are other more superficial materials. In this study, GOs with higher oxygen to carbon ratios were synthesized following the Tour method, where the excess feed acid liquor (FAL) of mixed concentrated sulfuric and orthophosphoric acids at a ratio of 90:10 was recovered from the reaction slurries by applying the centrifugation technique. About 80-90 % of the FAL was recycled and reused as feed for the subsequent batches. The changes in the properties of FAL for the five consecutive recycling and reuse were studied. The properties of recycled FALs were investigated by measuring density, moisture content, pH, and ion concentration. The consecutive recycling of FALs tends to increase the moisture content about 0.5% in each recycles. Ion-chromatography (IC) was used to measure the variation in SO42- and PO43- ions in the FALs. The H2SO4 reacts with KMnO4 and crystalized out from the recovered FAL faster than the phosphoric acid. So, sulfuric acid content in the makeover FALs must be greater than primary FAL. The product GOs were characterized using FT-IR, FT-Raman, UVVis, STA, SEM, XPS, Zeta-potential, and particle size analyzers. The variation of the properties of GOs with the changes in the reaction parameters such as temperature and time were investigated and correlated with the product yield. It was observed that the effect of temperature on the reaction rate was found to be negatively and positive with the reaction time. The oxygen-to-carbon atomic ratio from XPS analysis was found 66.7%, which supported the increase in product yields 66.9% in the experimental results. The effect of acid concentration, reaction temperature, and time on the GOs properties were satisfactory, correlated, and easily controllable with the reaction conditions. A higher extent of oxidation and enhanced product yields 65-70% were observed at 60-70 °C and 14-18 h. A mixture of nano- and macro-molecular GOs was obtained, and their compositions were easily controllable and separable by controlling the reaction conditions. A correlation was made among the properties of synthesized GOs, FAL, and recycled FAL and reaction conditions.

Exploring the biomedical competency of gamma-radiation aided hydroxyapatite and its composite fabricated with nano-cellulose and chitosan

The well-known biomaterial Ca-hydroxyapatite (Hap) in its pristine form holds the top ranking position in the field of biomedical research and extensive investigation is continuing across the globe to enhance its competency. Hence, having the intention to introduce superior physiognomies (e.g. cytotoxicity, haemocompatibility, and bioactivity coupled with antimicrobial and antioxidant activity) in Hap, in this research work, we exposed Hap to 200 kGy γ-radiation. As a result, γ-radiated Hap exhibited extreme antimicrobial (more than 98%) and moderate (∼34%) antioxidant properties. On the other hand, cytotoxicity and haemocompatibility of γ-radiated Hap were in good agreement with the ISO 10993-5 and ISO 10993-4 standards respectively. Since, bone and joint infections as well as degenerative disorders e.g. osteoarthritis, osteomyelitis, bone injury, and spinal problems have emerged as serious issues and urge a remedial way out, application of γ-radiated Hap could be a promising solution in this regard.

Synthesis and characterization of nano crystallite plaster of Paris prepared from waste eggshells and exploration of cytotoxicity, hemolysis and antimicrobial properties

Plaster of Paris, a well-known biomaterial, was synthesized from waste eggshells, which were chosen as an available bio-source of calcium. The produced plaster of Paris was characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman spectroscopy, UV-Vis spectroscopy, and SEM images along with a few crystallographic parameters such as crystallite size (Scherrer equation and different model equations), lattice parameters, crystallinity index, the volume of the unit cell, microstrain, dislocation density, growth preference, and residual stress from the XRD-sin² Ψ technique. The biomedical competency of the prepared plaster of Paris was evaluated utilizing the cytotoxicity, hemolysis, and antimicrobial activity of E. coli and S. aureus. The cytotoxicity assessment has revealed that the percentages of viable cells were 93-98% and a highly hemocompatible nature (<5%) was exerted by the sample. The plaster of Paris only revealed antimicrobial properties against Gram-positive bacteria (S. aureus), and no effect was noticed for Gram-negative bacteria (E. coli).

Development of ceramic grade red iron oxide pigment from waste iron source

Ceramic grade red iron oxide (α-Fe₂O₃) nanoparticles pigments have been synthesized from waste condensed milk containers which contain a prominent amount of iron (93.2%). The synthesis method comprised of two steps: in the first step ferrous sulfate was prepared following an acid leaching method; while the second step was oxidation and calcination of ferrous sulfate to produce desired α-Fe₂O₃ in nano form. The structure, functional groups, chemical state, morphology, particle size, surface area, elemental, thermal analysis and magnetic properties of the samples were investigated using XRD, FTIR, XPS, SEM, BET, EDS, TG-DT and VSM respectively. Pure hematite (α-Fe₂O₃) phase was confirmed by XRD and the average crystal sizes were in the range 34-126 nm have been performed by Debye-Scherer's formula, which are consistent with the results as achieved from SEM images. Agglomerated irregular spherical nanoparticles (45-149 nm) were found in SEM image. The surface chemistry and the chemical state (Fe³⁺) of the hematite nanoparticles was also confirmed by XPS. The mesoporous nature of the nanoparticles with high surface area were measured by BET and it has been revealed that the BET specific surface area (33.55 m²/g) was marginally higher than the commercial one. The magnetic nature of the nanoparticles was portrayed by VSM and the nanoparticles showed the ferromagnetic behavior. Moreover, particle size distributions and zeta potential values have been also measured by DLS.

Day-care management of severe and very severe pneumonia, without associated co-morbidities such as severe malnutrition, in an urban health clinic in Dhaka, Bangladesh

BACKGROUND

Management of severe and very severe pneumonia in children relies on hospital-based treatment, but practical barriers often prevent children in areas with the highest rates from receiving hospital care.

OBJECTIVE

To develop and prospectively evaluate a day-care clinic approach, which provided antibiotics, feeding and supportive care during the day with continued care provided by parents at home, as an effective alternative to hospitalisation.

METHODS

Children aged 2-59 months with severe or very severe pneumonia without associated co-morbidities, denied admission to hospital because of lack of beds, were enrolled at Radda Clinic, Dhaka and received antibiotics, feeding and supportive care from 08:00 to 17:00 every day, while mothers were educated on continuation of care at home during the night.

RESULTS

From June 2003 to May 2005, 251 children were enrolled. Severe and very severe pneumonia was present in 189 (75%) and 62 (25%) children, respectively, and 143 (57%) were hypoxaemic with a mean (SD) oxygen saturation of 93 (4)%, which increased to 98 (3)% on oxygen therapy. The mean (SD) day-care period was 7 (2) days. Successful management was possible in 234 children (93% (95% CI 89% to 96%)), but 11 (4.4% (95% CI 2.5% to 7.7%)) had to be referred to hospital, and six (2.4% (95% CI 1.1% to 5.1%)) discontinued treatment. There were no deaths during the day-care study period; however, four children (1.6% (95% CI 0.6% to 4.0%)) died during the 3-month follow-up period, and 11 (4.4% (95% CI 2.5% to 7.7%)) required hospital admission.

CONCLUSION

Severe and very severe pneumonia in children without associated co-morbidities such as severe malnutrition can be successfully managed at day-care clinics.

Coping with changing conditions: alternative strategies for the delivery of maternal and child health and family planning services in Dhaka, Bangladesh

The door-to-door distribution of contraceptives and information on maternal and child health and family planning (MCH-FP) services, through bimonthly visits to eligible couples by trained fieldworkers, has been instrumental in increasing the contraceptive prevalence rate and immunization coverage in Bangladesh. The doorstep delivery strategy, however, is labour-intensive and costly. More cost-effective service delivery strategies are needed, not only for family planning services but also for a broader package of reproductive and other essential health services. Against this backdrop, operations research was conducted by the Centre for Health and Population Research at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) from January 1996 to May 1997, in collaboration with government agencies and a leading national nongovernmental organization, with a view to developing and field-testing alternative approaches to the delivery of MCH-FP services in urban areas. Two alternative strategies featuring the withdrawal of home-based distribution and the delivery of basic health care from fixed-site facilities were tested in two areas of Dhaka. The clinic-based service delivery strategy was found to be a feasible alternative to the resource-intensive doorstep system in urban Dhaka. It did not adversely affect programme performance and it allowed the needs of clients to be addressed holistically through a package of essential health and family planning services.

A review of the literature for whole-body FDG PET in the management of patients with melanoma

BACKGROUND

A review and meta-analysis of the literature on the use of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in the detection of recurrent melanoma was conducted. The goals were to evaluate the quality of data reporting and to determine the overall values for the sensitivity and specificity of whole body FDG PET and management changes.

METHODS

Guidelines to evaluate reporting within articles were formulated based on the United States medical payer source criteria for assessing studies reporting information on the utilization of new medical technology. A meta-analysis was conducted using methodology described in the peer reviewed literature.

RESULTS

Our MEDLINE PLUS search resulted in a universe of 89 total articles. Within these 89, 19 were categorized in our targeted content area of which 13 were selected for analysis in our targeted subset, with the remaining 70 covering 24 different related content areas. Five of 13 (38%) articles in the target subset reported data which was adequate for incorporation into modeling objectives based on PET sensitivity and specificity values, with 1 of 13 (8%) in the same target subset reporting data adequate for modeling based on change-in-management data. Through a meta-analysis of the 13 target articles we determined, within a 95% confidence level, an overall sensitivity of 92% (95% confidence level 88.41%-95.82%) and an overall specificity of 90% (95% confidence level 83.26%-96.05%) as calculated by number of lesions, for FDG PET detecting recurrent melanoma throughout the whole body. Furthermore, limited data available for change-in-management suggests an overall FDG PET directed change-in-management value of 22%.

CONCLUSIONS

Our review suggests that improvements can be made to more effectively report the results of these FDG PET studies. The overall values determined through the meta-analysis indicate the potential benefits of using FDG PET as a diagnostic/management tool. Furthermore, these values should prove useful to assessing the cost effectiveness of utilizing FDG PET in the management of recurrent melanoma.