Combined DFT, SCAPS-1D, and wxAMPS frameworks for design optimization of efficient Cs2BiAgI6-based perovskite solar cells with different charge transport layers

In this study, combined DFT, SCAPS-1D, and wxAMPS frameworks are used to investigate the optimized designs of Cs2BiAgI6 double perovskite-based solar cells. First-principles calculations are employed to investigate the structural stability, optical responses, and electronic contribution of the constituent elements in Cs2BiAgI6 absorber material, where SCAPS-1D and wxAMPS simulators are used to scrutinize different configurations of Cs2BiAgI6 solar cells. Here, PCBM, ZnO, TiO2, C60, IGZO, SnO2, WS2, and CeO2 are used as ETL, and Cu2O, CuSCN, CuSbS2, NiO, P3HT, PEDOT:PSS, spiro-MeOTAD, CuI, CuO, V2O5, CBTS, CFTS are used as HTL, and Au is used as a back contact. About ninety-six combinations of Cs2BiAgI6-based solar cell structures are investigated, in which eight sets of solar cell structures are identified as the most efficient structures. Besides, holistic investigation on the effect of different factors such as the thickness of different layers, series and shunt resistances, temperature, capacitance, Mott-Schottky and generation-recombination rates, and J-V (current-voltage density) and QE (quantum efficiency) characteristics is performed. The results show CBTS as the best HTL for Cs2BiAgI6 with all eight ETLs used in this work, resulting in a power conversion efficiency (PCE) of 19.99%, 21.55%, 21.59%, 17.47%, 20.42%, 21.52%, 14.44%, 21.43% with PCBM, TiO2, ZnO, C60, IGZO, SnO2, CeO2, WS2, respectively. The proposed strategy may pave the way for further design optimization of lead-free double perovskite solar cells.

Recent Progress in Nanostructured Smart Drug Delivery Systems for Cancer Therapy: A Review

Traditional treatment approaches for cancer involve intravenous chemotherapy or other forms of drug delivery. These therapeutic measures suffer from several limitations such as nonspecific targeting, poor biodistribution, and buildup of drug resistances. However, significant technological advancements have been made in terms of superior modes of drug delivery over the last few decades. Technical capability in analyzing the molecular mechanisms of tumor biology, nanotechnology─particularly the development of biocompatible nanoparticles, surface modification techniques, microelectronics, and material sciences─has increased. As a result, a significant number of nanostructured carriers that can deliver drugs to specific cancerous sites with high efficiency have been developed. This particular maneuver that enables the introduction of a therapeutic nanostructured substance in the body by controlling the rate, time, and place is defined as the nanostructured drug delivery system (NDDS). Because of their versatility and ability to incorporate features such as specific targeting, water solubility, stability, biocompatibility, degradability, and ability to reverse drug resistance, they have attracted the interest of the scientific community, in general, and nanotechnologists as well as biomedical scientists. To keep pace with the rapid advancement of nanotechnology, specific technical aspects of the recent NDDSs and their prospects need to be reported coherently. To address these ongoing issues, this review article provides an overview of different NDDSs such as lipids, polymers, and inorganic nanoparticles. In addition, this review also reports the challenges of current NDDSs and points out the prospective research directions of these nanocarriers. From our focused review, we conclude that still now the most advanced and potent field of application for NDDSs is lipid-based, while other significantly potential fields include polymer-based and inorganic NDDSs. However, despite the promises, challenges remain in practical implementations of such NDDSs in terms of dosage and stability, and caution should be exercised regarding biocompatibility of materials. Considering these aspects objectively, this review on NDDSs will be particularly of interest for small-to-large scale industrial researchers and academicians with expertise in drug delivery, cancer research, and nanotechnology.

Insights into the physical properties and anisotropic nature of ErPdBi with an appearance of low minimum thermal conductivity

We theoretically study the structural, elastic and optical properties of ErPdBi together with its anisotropic behaviors using density functional theory. It is observed that ErPdBi satisfies the Born stability criteria nicely and possesses high quality of machinability. The anisotropic behavior of ErPdBi is reported with the help of theoretical anisotropy indices incorporating 3D graphical presentation, which suggests that ErPdBi is highly anisotropic in nature. It is noticed that the minimum thermal conductivity is very low for ErPdBi compared to the several species. This low value of minimum thermal conductivity introduces the potentiality of ErPdBi in high-temperature applications such as thermal barrier coatings. In addition, deep optical insights of ErPdBi reveal that our material can be used in different optoelectronic and electronic device applications ranging from organic light-emitting diodes, solar panel efficiency, waveguides etc. to integration of integrated circuits. Therefore, we believe that our results will provide a new insight into high-temperature applications and will benefit for the development of promising optoelectric devices as well.

Effects of nitrogen and potassium on growth and yield of gladiolus corms

A study was conducted at the Floriculture Research Field of Horticulture Research Centre of Bangladesh Agricultural Research Institute (BARI) during the period from November 2006 to May 2008 to determine the optimum rate of N and K for better growth and yield of corm and cormel of gladiolus. The treatment combination N150 K200 kg/ha produced the longest plant (42.1 cm), the broadest leaf (1.93 cm), the maximum percentage of spikes (88.1%), and corm (97.6%), the heaviest and the largest corm (19.5 g and 4.11 cm, respectively), cent percent flowering sized corm, and the highest corm number and cormel yield (1,20,000 and 1.66 t/ha, respectively). The corm produced from this treatment combination also showed better performances in the next year in respect of plant emergence (100%), florets/spike (13.1), spike and rachis length (82.2 cm and 45.4 cm, respectively), flower stick weight (57.1 g) and percentage of flower sticks (113%). DOI: http://dx.doi.org/10.3329/bjar.v37i4.14385 Bangladesh J. Agril. Res. 37(4): 607-616, December 2012

Evaluation of a non-radioactive chemiluminescent method for using oligonucleotide and polynucleotide probes to identify enterotoxigenic Escherichia coli

We compared the applicability of an enhanced chemiluminescent (ECL) method for using gene probes with that of radioactive probes to identify enterotoxigenic Escherichia coli (ETEC) in stools of Bangladeshi children with diarrhoea. Colony blots of E. coli isolates were hybridized using both [alpha-32P]-dCTP labelled and fluorescein-11-dUTP labelled polynucleotide and oligonucleotide gene probes for heat-labile enterotoxin (LT), and heat-stable enterotoxin (ST). Analysis of 1,620 isolates obtained from 540 patients gave similar results by both radioactive and chemiluminescent probes. The ECL method was faster than the radioactive method. Both polynucleotide and oligonucleotide probes could be used by the ECL method. Hybridization and detection by the ECL method appeared to be a convenient alternative to radioactive probes for screening E. coli isolates for ETEC.

Evaluation of a DNA probe to identify enteroaggregative Escherichia coli from children with diarrhoea in Bangladesh

Six hundred and seventy-five Escherichia coli isolates obtained from 225 diarrhoeal children less than five years of age were tested for adherence to HeLa cells and for hybridisation with DNA probes for genes conferring aggregative adherence (AggA), localised adherence (LA) and diffuse adherence (DA) to assess the usefulness of a recently developed DNA probe for AggA of enteroaggregative E. coli (EAggEC). The strains were further analysed with the DNA probes for heat--labile enterotoxin (LT), heat--stable enterotoxin (ST), Shiga--like toxins (SLT I and SLT II) and for enteroinvasiveness and adherent strains were all negative for these properties. The HeLa cell assay and DNA probe assays showed excellent agreement in identifying LA and DA positive isolates. However, significant disparities occurred in the case of AggA positive isolates, and the DNA probe failed to identify 31.9% (15 of 47) of the EAggEC identified by the HeLa cell adherence assay. The failure of the DNA probe to identify all the EAggEC indicated that there may be a high degree of genetic heterogeneity for the expression of AggA, and development of more DNA probes is necessary to detect all the possible genetic variants of EAggEC.

Surveillance of shigellosis in rural Bangladesh: a 10 years review

Over a period of 10 years 35,620 patients, admitted from a defined surveillance area, had a rectal swab culture done at a rural diarrhoea treatment centre in Bangladesh. Shigella spp. were isolated from 3,440 (9.7%) cases. Marked year to year variations were observed in isolation rates of Shigella spp. ranging from 5.7% to 16.7%. Sh. flexneri was the predominant isolate between 1978 to 1982 (56%-67%), Sh. dysenteriae type 1 predominated from 1983 to 1985 (45%-50%), and again Sh. flexneri became predominant in 1986 (55%) and 1987 (61%). Shigella were most commonly isolated from children aged 1-4 years followed by children 5-9 years and elderly people aged 45+ years. Sh. flexneri was isolated most frequently during August - January and Sh.dysenteriae type 1 during June to July. The overall case fatality rate in patients with shigellosis was 0.96%. It was 1.10% in children under 5 years of age. Prevalence of multiple antibiotic resistant strains increased over the years and at present most strains are resistant to commonly used antibiotics such as ampicillin and cotrimoxazole. Nalidixic acid is currently the drug of choice for Shigella infection in this area.

Surveillance of patients attending a rural diarrhoea treatment centre in Bangladesh

In May 1983, a surveillance system was set up at a rural diarrhoea treatment centre of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) to study a 20% systematic sample of all admissions. Between May 1983 and April 1984, 2,635 patients were studied. A recognized enteric pathogen was detected in 69% of the patients screened, 15% of whom had a mixed infection. Vibrio cholerae 0: 1 was the most common enteropathogen detected (39%), followed by enterotoxigenic Escherichia coli (ETEC) (14%), Shigella spp. (11%), and Campylobacter jejuni (11%). Detection of C. jejuni was highest in infants, Shigella spp. in children between 1-4 years and V. cholerae 0:1 in children between 3-9 years of age. 75% of patients presented with watery diarrhoea, a presentation that was significantly more common in patients infected with V. cholerae 0:1 (94%) and ETEC (88%). Bloody diarrhoea was the presenting complaint in 18% of all patients, but in 65% of patients in whom Shigella spp. was isolated. Although 91% of patients reported that they had prior experience of use of oral rehydration therapy (ORT), 54% of the patients came to the treatment centre with no or mild dehydration and more than half of them did not use ORT before coming to the treatment centre. Most of these patients could have been safely treated at home if ORT could be made available and acceptable.

A randomized, controlled trial of the toxin-blocking effects of B subunit in family members of patients with cholera

A randomized, controlled field trial was performed to test the ability of B subunit, the nontoxic, binding portion of cholera toxin, to block the toxin receptors (GM1 ganglioside) in the small intestine and thereby prevent diarrhea in individuals infected with Vibrio cholerae O1. Of 1,922 family contacts of 370 index patients selected randomly to receive orally on two successive days either B subunit (low dose, 1.0 mg; high dose, 5.0 mg) or placebo, 190 were asymptomatically infected on day 1 or day 2 of the study and within 24 hr of receiving B subunit. During the first 24-hr period of follow-up, the relative risk of disease among contacts receiving B subunit versus placebo was 0.18 for the low dose (P = .08) and 0.50 for the high dose (P = .22). Subsequently the relative risk increased toward 1.0 and was at no single point significantly reduced, although in five of the six follow-up periods the risk of disease was less in the B subunit group.

Phage types of Vibrio cholerae O1 biotype El Tor isolated from patients and family contacts in Bangladesh: epidemiologic implications

The epidemiology of Vibrio cholerae O1 El Tor in rural Bangladesh was examined with a new phage-typing system for characterization of individual strains. During a two-year period, 537 strains were typed with a set of standard and experimental phages. Four major and many minor patterns were identified, some associated with discrete outbreaks of disease and others persisting for the entire period. One outbreak-related phage type was associated with a C plasmid bearing multiple drug resistance. The yearly cholera seasons began with the emergence of strains of many different phage types in many different locations; this pattern is consistent with an environmental reservoir for V cholerae. Each patient with cholera excreted only one phage type over time, whereas some family members were infected with strains of different phage types. Phage typing can be a useful marker with which the spread of cholera strains can be traced in endemic settings.

Protection against cholera in breast-fed children by antibodies in breast milk

We performed a prospective study to examine whether the IgA antibodies against cholera that are present in breast milk protect breast-fed infants and children against colonization with Vibrio cholerae 01 and disease. Among families of patients with cholera, we collected breast milk from mothers who had not had diarrhea in the previous week and monitored them and their breast-fed children for cholera colonization and diarrhea for 10 days. Breast milk was assayed for IgA antibodies to cholera toxin and lipopolysaccharide. Ninety-three mother--child pairs were studied; 30 infants became colonized with V. cholerae 01 and disease developed in 19. There were no differences between the antibody levels in milk fed to children who became colonized and in milk fed to children who did not. However, among the children who became colonized, those who had diarrhea drank breast milk containing significantly lower levels of both kinds of cholera antibodies than were present in the milk consumed by children who had no symptoms. We conclude that breast-milk antibodies against cholera do not appear to protect children from colonization with V. cholerae 01 but do protect against disease in those who are colonized.

Lead, cadmium and nickel contents of vegetables grown in industrially polluted and non-polluted areas of Bangladesh

The levels of lead (Pb), cadmium (Cd), and nickel (Ni) in spinach (Spinacia oleracea), tomato (Lycopersicon esculentum) and cauliflower (Brassica oleracea) and in the rizosphere soils of the industrially polluted (Konabari, Gazipur; Keranigonj, Dhaka), and non-polluted (Bangladesh Agricultural Research Institute-BARI, Gazipur) areas were studied. Four samples from each area were collected during February 2008. Their concentrations varied with the metals and locations, showing the trend: Ni>Pb>Cd and directly polluted> indirectly polluted>non-polluted soils. The order of the elements in spinach, tomato, and cauliflower and their concentration ranges in μg/g of dry weight were Ni (1.265-5.369), (2.031-4.957), (1.698-4.447); Pd (0.767-1.440), (1.027-1.968), (0.486-1.119); and Cd (0.559-1.40), (0.630-1.303), (0.506-0.782), respectively. Similarly, the order of the elements in rizosphere soils of spinach, tomato, and cauliflower and their concentration ranges in μg/g of dry weight were Ni (12.29-31.52), (13.67-31.98), (14.20-34.34); Pd (3.560-7.980), (3.900-8.447), (3.718-7.337); and Cd (1.473-3.760), (1.553-3.833), (1.640-3.670), respectively. Lead concentration was higher in tomato, followed by spinach and the least in cauliflower irrespective of the location. Cadmium and Ni concentration were found in the order of spinach>tomato>cauliflower, especially in the industrially polluted areas. Concentrations of metals in vegetable samples were related to their concentration in the corresponding soils. Lead, Cd, and Ni concentrations in the studied vegetables were higher than those found in vegetables from other countries, but they were lower than the maximum level allowed in India. Metal transfer factors from soil to vegetables are found to be significant for Cd, Pb and Ni. Key Words: Cadmium; lead; nickel; polluted soils; vegetables. DOI: 10.3329/bjar.v34i4.5831Bangladesh J. Agril. Res. 34(4) : 545-554, December 2009