711 research outputs found

    A Kinetic Approach to Soil Phosphorus Mobilisation By Inoculant Biofertiliser

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    The research reported in this thesis examines on the feasibility of selecting soil bacteria able to convert insoluble forms of soil phosphorus (P) to mobile forms more available for plant growth. A kinetic approach was used in which rates of P-mobilisation were measured. Bacteria were isolated from soils sampled from three locations, 1) a neutral to alkaline vertisol soil cultivated with cotton and wheat (Narrabri, NSW), 2), a neutral grassland rhizosphere soil (Wee Waa, NSW), and 3) an acid red soil cultivated with wheat (Wagga Wagga, NSW). Seven bacterial strains were successfully isolated using minimal medium containing Ca3(PO4)2 as the sole source of P. The isolates were characterised using selective media and identified using 16S rDNA sequence analysis. The P-mobilising bacteria were identified by the clear ‘halo’ zones surrounding their colonies on agar containing insoluble P. The most effective P-mobilising bacterial isolates were obtained from the grassland and acid wheat soils and identified as Pantoea ananatis (FA001) and Pantoea agglomerans (FA010), respectively, belonging to the Enterobacteriaceae family. The other strains isolated were classified as Enterobacter cloacae, also belonging to the Enterobacteriaceae family, and several Burkholderia sp.; these were found to be less effective in P-mobilisation, indicated by smaller halos surrounding their colonies and solubilisation in liquid culture. Several tests were conducted to validate the P-mobilising ability of these bacteria. In liquid minimal media containing 500 mg L-1 of different types of insoluble P, the strain (FA001) identified as Pantoea ananatis mobilised the highest P from Ca3(PO4)2 at the highest kinetic rate (50.32 mg L-1 day-1) followed by the strain FA010 identified as Pantoea agglomerans (45.77 mg L-1 day-1), using (NH4)2SO4 as source of N. With NH4NO3 as source of N, P. ananatis (FA001) also mobilised the highest amount of P (35.31 mg L-1 day-1) from Ca3(PO4)2 followed by P. agglomerans (FA010) (18.68 mg L-1 day-1). But this was reversed when rock phosphate was the source of P. P. agglomerans (FA010) mobilised the highest P (27.27 mg L-1 day-1), followed by P. ananatis (FA001) (24.53 mg L-1 day-1) from rock phosphate-containing medium. Of these isolated strains, P. ananatis (FA001) mobilised small amounts of P from AlPO4 and FePO4. P. agglomerans (FA010) also mobilised small amounts of P from AlPO4, but not from FePO4. There was very good correlation between acid production and P mobilisation, suggesting acid production as a major mechanism used for mobilising P by these isolated strains. There was some indication that chelation may also play a role, since both P. ananatis (FA001) and P. agglomerans (FA010) produced citric acid (2.55 mg L-1 day-1 and 2.89 g L-1 day-1, respectively). The strong organic anion, citrate, can potentially chelate cations such as Ca2+ and Al3+, reducing their chance of immobilising P. To confirm that the results of these in vitro experiments were relevant for plant growth, glasshouse experiments were conducted in a P-depleted soil to examine the effect of the P mobilising bacteria on the grain yield of wheat. Two yield experiments were conducted, using Ca3(PO4)2, CaHPO4.2H2O and rock phosphate as sources of P. Consistent with the in vitro data results, for all the sources of P, P. ananatis (FA001) and P. agglomerans (FA010) resulted in significantly higher grain and straw yields in trials conducted in 2003 (Experiment 1) and in 2004 (Experiment 2). In Experiment 2 the percentage P content of the grain and straw was the same in treatments with bacteria and the controls. Another glasshouse experiment (Experiment 3) was conducted to evaluate the plant growth-promoting (PGPR) effects of these bacteria, using soluble phosphorus with Hoagland solution. In this experiment, P. ananatis (FA001) and P. agglomerans (FA010) were compared with some other recognised PGPR strains. The results suggest that both of these bacteria can increase grain yield of wheat by about 10 per cent compared to uninoculated controls, independently of the P-mobilising effects. Since understanding the role of bacteria in P-mobilisation in relation to the chemical behaviour of P in soil was a principal objective of this thesis, P. ananatis (FA001) and P. agglomerans (FA010) were also used in an experiment to examine P adsorption to and desorption from soil. Two soils i) a brown sandy clay loam of pH 4.07 from Griffith, and ii) a heavy clay vertisol of pH 7.42 (Narrabri soil), were used for the desorption experiment. It was revealed that both these bacteria (P. ananatis (FA001) and P. agglomerans (FA010)) could significantly mobilise P from the vertisol with neutral pH, but not from the sandy clay soil with low pH. From Langmuir and Temkin adsorption isotherms which are indicative of P adsorption behaviour of these soils, it was concluded that for soils having high P-buffering capacity and high maximum P adsorption capacity these bacteria could not significantly mobilise phosphorus. Therefore it can be concluded that before applying P mobilising biofertiliser, maximum adsorption capacity and retention behaviour of soil should be estimated, so that the feasibility of effectively applying a particular biofertiliser can be predicted. From the set of P-mobilising biofertiliser strains studied in this thesis, P. ananatis (FA001) was indicated as the best strain, meeting the criteria for mobilisation in the different tests. It is, therefore recommended for further testing as a biofertiliser strain in different soil types. However, whether this strain will be effective under field conditions remains to be tested

    Disease problems in shrimp sector in Khulna district of Bangladesh: a question of sustainability

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    Disease is the main restraining factor for the development of shrimp sector in Bangladesh. Both brackish water shrimp bagda (Penaeus monodon) and freshwater prawn golda, (Macrobrachium rosenbergii) farming in Bangladesh have been facing disease problem. A study on disease outbreak in both brackish water and freshwater small-scale shrimp farms (gher) in Khulna district was carried out through interviewing randomly selected 3-5% of shrimp farmers with a structured questionnaire during March to December, 2002. The study showed that 97% bagda farming ghers and 80% golda farming ghers were affected by disease. White spot disease was the severe disease for bagda, whereas, antenna rot was the main disease for freshwater prawn. Change of water and liming were carried out as control measures of disease for bagda shrimp farming, while it was only liming for golda farming. A small number of shrimp farmers (15%) used chemicals for treatment of shrimp diseases. Development of suitable farming technology to prevent disease contamination and innovation of proper treatments for diseases are required to overcome the disease problems for sustainable shrimp farming in Bangladesh

    Biological features of Chanda nama (Ambassidae) in the Old Brahmaputra River, Bangladesh

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    Biological features including sex ratio, length-frequency distributions (LFDs), size at sexual maturity, spawning season, length-weight relationships (LWRs) and condition factor of Chanda nama were studied in the Old Brahmaputra River, Bangladesh. There was no significant difference in sex ratio. LFDs indicated no significant differences in size between the sexes. Size at sexual maturity was estimated at ~3.0 cm standard length. Monthly variations in gonadosomatic index indicate that the main spawning season is from July to August. The LWRs showed isometric growth in males and positive allometric growth in females. Fulton’s condition factor varied in both sexes and was attributed to variations in GSI with maturity. The findings of this study will be helpful to formulate conservation and management strategies of C. nama population in the Old Brahmaputra River and surrounding ecosystems

    The Double Edged Blade of Consumerism & the Impossible Trinity – Bangladesh

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    This paper demonstrates how a change in monetary policy by lowering the interest rates can lead to a decline in savings in the short run. Almost perfect correlation coefficient exists between declined marginal savings and increased household desire to either invest or spend; hoarding proves to be minimal but there are limits to household investments. Corporate investment is also possibly affected by the new policy as consumerism and lower cost of capital encourages the firms to invest. Consumption also leads to indebtedness. However, the consumption patterns, capital flight and borrowing motives proves to be of alarming significance to the policy makers. In the long-run, monetary expansionary policy is forecasted to be ineffective. Keywords: Monetary policy, interest rate, Saving-Consumption-Investment Imbalance, Product Influx, Impossible Trinity, Consumption Pattern, Debt Motivations, Capital Fligh

    Population Biology of the Indian River Shad, Gudusia chapra (Clupeidae) in the Old Brahmaputra River, North-Eastern Bangladesh

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    Population biology including population structure, reproduction, length-weight relationship and condition factor of a commercially important clupeid freshwater fish, Gudusia chapra was studied in the Old Brahmaputra River, Bangladesh during January-December 2009. In the present study, a total of 2032 specimens (1091 male; 941 female) were collected. The overall sex ratio showed significant difference from the expected value 1:1 (male: female = 1:0.86, χ2 = 11.07, p<0.001). Length-frequency distribution showed a size predominance of females over males, where mean female size consistently exceeded that of males throughout the year. Female size at first sexual maturity was estimated as 8.3 cm in standard length (SL). Monthly gonadosomatic index (GSI) was higher during March-September with a peak in April, indicating this was the main spawning season. The allometric coefficient b of the length-weight relationship (LWR) indicated negative allometric growth in males and females, but the analysis of covariance (ANCOVA) showed significant differences in slope and intercept between the sexes (p<0.001). Fulton’s condition factor by months and SLs varied in both sexes and was attributed to variations in GSI with maturity

    Numerical Analysis of a Highly Sensitive SOI MRR Refractive Index Sensor with Performance Enhancement using Graphene and Gold

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    This study proposes a simulation-based design for a Silicon-On-Insulator (SOI) ring resonator with a Figure of Merit (FOM) of 56.15 and a high sensitivity of up to 730 nm/RIU. The Finite-Difference Time-Domain (FDTD) technique was used to assess and evaluate the design quantitatively. Our design demonstrates higher sensitivity compared to many recent studies conducted on SOI-based sensors. The device structure follows a conventional ring resonator arrangement with a single waveguide, incorporating a 2D graphene layer on top of the SiO2 wafer and a gold nano-disc positioned at the center of the ring. Our findings highlight the device's susceptibility to refractive index variations, making it a desirable choice for various sensing applications. We have investigated the sensor's capabilities for sensing different concentrations of milkmilk. Graphene and gold materials enhance the device's response to light and provide comparatively higher sensitivity. The suggested design can serve as a blueprint for device fabrication, considering the practicality of implementing an SOI-based device using standard techniques for silicon processing.Comment: 23 pages, 29 figures, Journal: Heliyon by Cell Press (Accepted

    Investigations of 2-Thiazoline-2-thiol as a Ligand: Synthesis and X-ray Structures of [Mn\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e7\u3c/sub\u3e(\u3cem\u3eμ\u3c/em\u3e-NS\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e3\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e] and [Mn(CO)\u3csub\u3e3\u3c/sub\u3e(PPh\u3csub\u3e3\u3c/sub\u3e)(\u3cem\u3eκ\u3c/em\u3e\u3csup\u3e2\u3c/sup\u3e-NS\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e3\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)]

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    Treatment of Mn2(CO)10 with 2-thiazoline-2-thiol in the presence of Me3NO at room temperature afforded the dimanganese complexes [Mn2(CO)7(μ-NS2C3H4)2] (1) and [Mn2(CO)6(μ-NS2C3H4)2] (2) in 51 and 34% yields, respectively. Compound 1 was quantitatively converted into 2 when reacted with one equiv of Me3NO. Reaction of 1 with triphenylphosphine at room temperature furnished the mononuclear complex [Mn(CO)3(PPh3)(κ 2-NS2C3H4)] (3) in 66% yield. All three new complexes have been characterized by elemental analyzes and spectroscopic data together with single crystal X-ray diffraction studies for 1 and 3. Compound 1 crystallizes in the orthorhombic space group Pbca with a = 12.4147(2), b = 16.2416(3), c = 19.0841(4) Å, β = 90°, Z = 8 and V = 3848.01(12) Å3 and 3 crystallizes in the monoclinic space group P 21/n with a = 10.41730(10), b = 14.7710(2), c = 14.9209(2) Å, β = 91.1760(10)°, Z = 4 and V = 2295.45(5) Å3

    Dirhenium Carbonyl Complexes Bearing 2-Vinylpyridine, Morpholine and 1-Methylimidazole Ligands

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    Treatment of the labile compound [Re2(CO)8(MeCN)2] with 2-vinylpyridine in refluxing benzene affords exclusively the new compound [Re2(CO)8(μ-η1:η2-NC5H4CHCH2)] (1) in 39% yield in which the μ-η1:η2-vinylpyridine ligand is coordinated to one Re atom through the nitrogen and to the other Re atom via the olefinic double bond. Reaction of [Re2(CO)8(MeCN)2] with morpholine in refluxing benzene furnishes two compounds, [Re2(CO)9(η1-NC4H9O)] (2) and [Re2(CO)8(η1-NC4H9O)2] (3) in 5% and 29% yields, respectively. Reaction of [Re2(CO)8(MeCN)2] with 1-methylimidazole gives [Re2(CO)8{η1-NC3H3N(CH3)}2] (4) and the mononuclear compound fac-[ReCl(CO)3{η1-NC3H3N(CH3)}2] (5) in 18% and 26% yields, respectively. In the disubstituted compounds 2 and 4, the heterocyclic ligands occupy equatorial coordination sites. The mononuclear compound 5 consists of three CO groups, two N coordinated η1-1-methylimidazole ligands and a terminal Cl ligand. The XRD structures of complexes 1, 3 and 5 are reported

    Prevalence of exclusive breastfeeding and associated factors among mothers in rural Bangladesh: a cross-sectional study

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    This article was published in International Breastfeeding Journal [© 2014 BioMed Central Ltd.] and the definite version is available at: https://internationalbreastfeedingjournal.biomedcentral.com/articles/10.1186/1746-4358-9-7Background: Exclusive breastfeeding (EBF) means that the infant receives only breast milk for the first six months of life after birth. In Bangladesh, the prevalence of EBF remained largely unchanged for nearly two decades and was 43% in 2007. However, in 2011, a prevalence of 64% was reported, an increase by 21 percentage points. The reasons for this large change remain speculative at this point. Thus to investigate the issue further, this study was conducted. The objective was to assess the prevalence of EBF and associated factors among mothers having children aged 0-6 months in rural Bangladesh. Methods: A cross-sectional study was conducted in Mirzapur Upazilla (sub district) among 121 mothers of infants aged 0-6 months. Eligible mothers were identified and randomly selected using the demographic surveillance system's computerized database that is updated weekly. A semi-structured questionnaire was used for interviews that inquired information on socio-demographic characteristics, obstetric, health service, breastfeeding related factors (initiation of breastfeeding, prelacteal feeding and colostrum feeding) and economic factors. EBF prevalence was calculated using 24 hour recall method. In multivariate analysis, a logistic regression model was developed using stepwise modeling to analyze the factors associated with EBF. Results: The prevalence of EBF in the last 24 hours preceding the survey was 36%. Bivariate and multivariate analysis revealed no significant association between EBF and its possible predictors at 0.05 level of alpha. However, there was some evidence of an association between EBF and having a caesarean delivery (OR = 0.47, 95% CI: 0.21, 1.06). In multivariate analysis, type of delivery: caesarean (AOR = 0.45, 95% CI: 0.19, 1.03) and wealth quintile: richer (AOR = 2.40, 95% CI: 0.94, 6.16) also showed some evidence of an association with EBF. Conclusion: The prevalence of EBF in Mirzapur (36%) is lower than the national figure (64%). Prelacteal feeding was not uncommon. These findings suggest that there is a need for breastfeeding support provided by health services. Hence, promotion of EBF during the first six months of life needs to be addressed and future breastfeeding promotion programmes should give special attention to those women who are not practicing EBF.Publishe

    Reactivity of [Re\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e8\u3c/sub\u3e(MeCN)\u3csub\u3e2\u3c/sub\u3e] with Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles in Different Coordination Modes

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    Reactions of the labile compound [Re2(CO)8(MeCN)2] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re2(CO)7{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}(μ-H)] (1, R = H; 2, R = CH3), [Re2(CO)6{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}2(μ-H)] (3, R = H; 4, R = CH3) and fac-[Re(CO)3(Cl){η1-NC3H2(4-R)S}2] (5, R = H; 6, R = CH3). Compounds 1 and 2 contain two rhenium atoms, one bridging thiazolide ligand, coordinated through the C(2) and N atoms and a η1-thiazole ligand coordinated through the nitrogen atom to the same Re as the thiazolide nitrogen. Compounds 3 and 4 contain a Re2(CO)6 group with one bridging thiazolide ligand coordinated through the C(2) and N atoms and two N-coordinated η1-thiazole ligands, each coordinated to one Re atom. A hydride ligand, formed by oxidative-addition of C(2)–H bond of the ligand, bridges Re–Re bond opposite the thiazolide ligand in compounds 1–4. Compound 5 contains a single rhenium atom with three carbonyl ligands, two N-coordinated η1-thiazole ligands and a terminal Cl ligand. Treatment of both 1 and 2 with 5 equiv. of thiazole and 4-methylthiazole in the presence of Me3NO in refluxing benzene afforded 3 and 4, respectively. Further activation of the coordinated η1-thiazole ligands in 1–4 is, however, unsuccessful and results only nonspecific decomposition. The single-crystal XRD structures of 1–5 are reported
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