Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 39
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Assoc Physicians India ; 72(6): 20-22, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38881129

RESUMO

INTRODUCTION: Metabolic syndrome (MetS) is one of the most important emerging pandemics of the 21st century and is associated with renal dysfunction in a significant number of subjects, the association of which is shown to be of greater significance in the South Asian population. AIMS AND OBJECTIVES: The prevalence of renal dysfunction in patients with MetS is the primary outcome. The secondary outcome is to assess the strength and significance of the association between the individual components of MetS and the presence of renal dysfunction. MATERIALS AND METHODS: This is a hospital-based cross-sectional observational study conducted for 2 years in a tertiary care hospital in India. A total of 100 diagnosed subjects of MetS were taken as cases and underwent relevant blood tests. Data were collected and analyzed in a Statistical Package for the Social Sciences (SPSS) v29 sheet. RESULTS: Over a period of 18 months, 100 subjects with MetS were documented, among which 66% had albuminuria, with microalbuminuria being 24% and the rest being macroalbuminuria. Among the same subjects, 30% had an estimated glomerular filtration rate (eGFR) <60 mL/minute/1.73m2. Waist circumference (WC) [measured by the National Institutes of Health (NIH) protocol] had the strongest association with increased albuminuria (r = 0.540; p-value < 0.001) as well as reduced eGFR (r = 0.460; p-value < 0.001). CONCLUSION: All the components of MetS, for example, increased WC, hypertension, increased fasting glucose, raised triglyceride (TG), and low high-density lipoprotein (HDL), have statistically significant correlations with increased urine albumin-to-creatinine ratio (ACR) and decreased eGFR, signifying glomerular injury and renal dysfunction, respectively.


Assuntos
Taxa de Filtração Glomerular , Síndrome Metabólica , Humanos , Síndrome Metabólica/epidemiologia , Síndrome Metabólica/fisiopatologia , Síndrome Metabólica/diagnóstico , Estudos Transversais , Feminino , Prevalência , Masculino , Pessoa de Meia-Idade , Índia/epidemiologia , Adulto , Albuminúria/epidemiologia , Circunferência da Cintura
2.
Mar Environ Res ; 196: 106420, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38430642

RESUMO

Sedimentary processes are expected to play a crucial role in macronutrient cycling of the shallow Arabian Gulf. To investigate this aspect, sediment cores were collected from the shallow intertidal and subtidal expanses of the first Marine Protected Area (MPA) of Kuwait in the Northwestern Arabian Gulf (NAG). Porewater nutrient profiling and whole core incubation experiments were conducted to measure the nutrient fluxes, both with and without the addition of the nitrification inhibitor allylthiourea (ATU). The porewater data confirmed the potential of sediments to host multiple aerobic and anaerobic pathways of nutrient regeneration. The average (±SD) of net nutrient fluxes from several incubation experiments indicated that ammonium (NH4+) predominantly fluxed out of the sediment (3.81 ± 2.53 mmol m-2 d-1), followed by SiO44- (3.07 ± 1.21 mmol m-2 d-1). In contrast, the average PO43- flux was minimal, at only 0.06 ± 0.05 mmol m-2 d-1. Fluxes of NO3- (ranged from 0.07 ± 0.005 to 1.16 ± 0.35 mmol m-2 d-1) and NO2- (0.03 ± 0.003 to 0.71 ± 0.21 mmol m-2 d-1) were moderate, which either reduced or reversed in the presence of ATU (-0.001 ± 0.0001 to 0.01 ± 0.0001 mmol m-2 d-1 and -0.001 ± 0.0003 to 0.006 ± 0.001 mmol m-2 d-1 for NO3- and NO2- respectively). Thus, this study provides preliminary experimental evidence that nitrification can act as a source of NO3- and NO2- as well as contribute towards the relatively high concentrations of NO2- (>1 in the gulf waters.


Assuntos
Poluentes Químicos da Água , Água , Sedimentos Geológicos , Dióxido de Nitrogênio , Poluentes Químicos da Água/análise , Nutrientes , Nitrogênio/análise
3.
J Surg Case Rep ; 2024(3): rjae132, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38463733

RESUMO

Intestinal malrotation and duplication of the inferior vena cava are rarely diagnosed in adult patients; however, incidence is likely underestimated as they are usually asymptomatic. These congenital malformations have been previously reported in the same patient twice but never with colonic obstruction or ischaemia. A 25-year-old female presented with nausea, vomiting, obstipation, and abdominal pain, and on computed tomography of the abdomen and pelvis was diagnosed with a caecal volvulus and pneumatosis coli associated with intestinal malrotation requiring emergency right hemicolectomy. Incidentally, the patient was noted to have duplication of the inferior vena cava, azygos continuation of the inferior vena cava, and splenic fragmentation. This constellation of symptoms has not been reported in the literature previously. The pattern of malformations follows that of polysplenia syndrome. Although rare, awareness of these malformations can be useful to clinicians.

5.
Sci Total Environ ; 911: 168583, 2024 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-37981157

RESUMO

Aeolian dust is an essential source of growth-limiting nutrients for marine phytoplankton. Despite being at the core of the Global Dust Belt, the response of the Arabian Gulf ecosystem to such atmospheric forcing is rarely documented. Here, the hydro-biological effect of mineral dust was studied in the northern Arabian Gulf (NAG) off Kuwait through monthly water sampling (December 2020 to December 2021), dust-storm follow-up sampling, and mineral dust and nutrient addition in-situ experiments. The multivariate analysis of oceanographic data revealed pronounced hydro-biological seasonality. The mineral dust deposition during two severe dust storm events in March and June 2021 showed a spatially varying effect of dust on coastal waters. The dust storms elevated the surface dissolved iron levels by several magnitudes, increased the dissolved inorganic nitrogen and phosphorous levels, changed their stoichiometry, and offset the hydrobiological seasonality. In the microcosms, dust input temporarily reduced phytoplankton phosphorous limitation in a dose-dependent manner when mesozooplankton (copepods) grazing was minimal. The microphytoplankton response to mineral dust inputs was comparable to that with nitrogen and phosphorous treatment. While Both treatments increased diatom size structure and biomass, the abundance of single-celled diatoms was comparatively higher in dust treatment. Multivariate analysis indicated that dust deposition alters the hydrographical properties of the surface ocean during dust storm events. The effects, though transient, were traceable for 3-16 days post-storm in coastal waters. The response of the summer phytoplankton to these changes, if delayed or muted, should be interpreted with caution given the summer water column stratification, the high nitrogen: phosphorous ratio and the low phosphorous solubility of aerosol dust, and the complex pelagic microbial food web interactions in the NAG. This study thus underlines the importance of a multivariate approach in documenting the ecological implications of Aeolian dust storms on marine environments closer to the dust source regions.


Assuntos
Diatomáceas , Fitoplâncton , Fitoplâncton/fisiologia , Ecossistema , Poeira/análise , Diatomáceas/fisiologia , Fósforo , Água , Minerais , Nitrogênio/análise , Água do Mar/química
6.
Biomacromolecules ; 24(3): 1111-1120, 2023 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-36787188

RESUMO

Biopolymers are an attractive environmentally friendly alternative to common synthetic polymers, whereas primarily proteins and polysaccharides are the biomacromolecules that are used for making the biopolymer. Due to the breadth of side chains of such biomacromolecules capable of participating in hydrogen bonding, proteins and polysaccharide biopolymers were also used for the making of proton-conductive biopolymers. Here, we introduce a new platform for combining the merits of both proteins and polysaccharides while using a glycosylated protein for making the biopolymer. We use mucin as our starting point, whereas being a waste of the food industry, it is a highly available and low-cost glycoprotein. We show how we can use different chemical strategies to target either the glycan part or specific amino acids for both crosslinking between the different glycoproteins, thus making a free-standing biopolymer, as well as for introducing superior proton conductivity properties to the formed biopolymer. The resultant proton-conductive soft biopolymer is an appealing candidate for any soft bioelectronic application.


Assuntos
Polissacarídeos , Prótons , Biopolímeros/química , Polissacarídeos/química , Polímeros , Proteínas , Mucinas
7.
Mar Pollut Bull ; 175: 113394, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-35123275

RESUMO

A series of flash floods that swamped urban drainage systems in Kuwait in November-December 2018 drastically altered coastal hydrography. The phytoplankton responded quickly to the nutrient supply from land and reduced salinity despite elevated turbidity, as evident from rapid increases in chlorophyll a and net community production. Microphytoplankton was dominated by diatoms and the photosynthetic ciliate Myrionecta rubra. Both field observations and microcosm experiments suggested that although increased nutrient availability stimulates diatom growth, microzooplankton grazing controls their outbursts. This study revealed that in a hypersaline system similar to the northern Arabian Gulf, extreme events like flash floods have immediate but short-lived corollaries on coastal phytoplankton due to synergistic effects of bottom-up and top-down factors. The patterns are comparable to those reported from other tropical and sub-tropical systems.


Assuntos
Diatomáceas , Água do Mar , Clorofila A , Monitoramento Ambiental , Inundações , Fitoplâncton , Estações do Ano
8.
Environ Sci Technol ; 55(15): 10491-10501, 2021 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-34291927

RESUMO

Microplastic (MP) pollution-an emerging environmental challenge of the 21st century-refers to accumulation of environmentally weathered polymer-based particles with potential environmental and health risks. Because of technical and practical challenges when using environmental MPs for risk assessment, most available data are generated using plastic models of limited environmental relevancy (i.e., with physicochemical characteristics inherently different from those of environmental MPs). In this study, we assess the effect of dominant weathering conditions-including thermal, photo-, and mechanical degradation-on surface and bulk characteristics of polystyrene (PS)-based single-use products. Further, we augment the environmental relevance of model-enabled risk assessment through the design of engineered MPs. A set of optimized laboratory-based weathering conditions demonstrated a synergetic effect on the PS-based plastic, which was fragmented into millions of 1-3 µm MP particles in under 16 h. The physicochemical properties of these engineered MPs were compared to those of their environmental counterpart and PS microbeads often used as MP models. The engineered MPs exhibit high environmental relevance with rough and oxidized surfaces and a heterogeneous fragmented morphology. Our results suggest that this top-down synthesis protocol combining major weathering mechanisms can fabricate improved, realistic, and reproducible PS-based plastic models with high levels of control over the particles' properties. Through increased environmental relevancy, our plastic model bolsters the field of risk assessment, enabling more reliable estimations of risk associated with an emerging pollutant of global concern.


Assuntos
Microplásticos , Poluentes Químicos da Água , Monitoramento Ambiental , Poluição Ambiental , Plásticos , Poliestirenos , Poluentes Químicos da Água/análise
9.
Sci Total Environ ; 788: 147670, 2021 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-34029818

RESUMO

The rise of microplastic (MP) pollution in the environment has been bolstering concerns regarding MPs' unknown environmental fate, transport, and potential toxicity toward living forms. However, the use of real environmental plastics for risk assessment is often hindered due to technical and practical challenges such as plastics' heterogeneity and their wide size distribution in the environment. To overcome this issue, most available data in the field is generated using plastic models as surrogates for environmental samples. In this critical review, we describe the gaps in risk assessments drawn from these plastic models. Specifically, we compare physicochemical properties of real environmental plastic particles to synthesized polymeric micro-beads, one of the most commonly used plastic models in current literature. Several surface and bulk characteristics including size, surface chemistry, polymer type, and morphology are shown to not only be inherently different between environmental MP's and synthesized micro-beads, but also drive behavior in fate, transport, and toxicity assays. We highlight the importance of expressing real-world physicochemical characteristics in representative MP models and outline how current state-of-the-art models are limited in this regard. To address this issue, we suggest future areas of research such as combinations of mechanical, photochemical, and thermal degradation processes to simulate real-world weathering, all in an effort to increase realism of plastic modeling and allow more robust and reliable environmental MP risk assessment in the future.

10.
J Family Med Prim Care ; 10(2): 1057-1060, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34041124

RESUMO

Albeit, all forms of tuberculosis (TB) are endemic in India, spinal intramedullary TB and tubercular longitudinally extensive transverse myelitis (LETM) is deemed extremely rare. With recent advances in the field of neurology, autoimmune astrocytopathy (neuromyelitis optica spectrum disorders, NMOSD), myelin-oligodendrocyte glycoprotein associated encephalomyelitis (MOG-EM), metabolic myelopathy, connective tissue diseases and viral infections have gained considerable focus in the list of differentials of LETM whereas tubercular association is often forgotten. This report presents a rare case of acute transverse myelopathy which unveiled previously undiagnosed pulmonary tuberculosis in an adult rural Indian male. The patient responded well to anti-tubercular therapy and corticosteroids. Exact pathogenesis of LETM in TB remains elusive. Association of TB with MOG-EM has been one of the recent hot-cakes. However, an ill-defined immune-inflammatory response to the infectious agent is the likely cause of tubercular LETM. Hence, the primary care physicians who are the first medical contacts of acute LETM cases and in most cases due to diagnostic dilemma there is an unavoidable delay in accurate diagnosis and initiation of therapy. Primary care doctors should nurture a high index of suspicion to diagnose this potentially lifetime-debilitating yet absolutely treatable clinical condition i.e. tubercular LETM.

11.
Eur J Surg Oncol ; 47(6): 1406-1410, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33279358

RESUMO

BACKGROUND: Higher Peritoneal Cancer Index (PCI) requires more extensive surgery and maybe associated with more limited outcomes. The aim of this study in a high-volume centre in Australia was to analyse the outcomes in PCI 39 patients regarding short and long term outcomes in appendiceal tumours. METHODS: A retrospective analysis of prospectively maintained database of patients that underwent primary cytoreductive surgery (CRS) + hyperthermic intraperitoneal chemotherapy (HIPEC) with PCI 39 at St George Hospital, Sydney from 1996 to 2018. Patients with appendiceal tumours (inclusive of high and low grade) were analysed. Factors contributing to high grade (III/IV Clavien-Dindo) morbidity and mortality were assessed. RESULTS: Of the 1201 patients in the database, 58 patients had a PCI 39 from appendix tumours at their first operation. The overall survival rate at 1, 3 and 5 year was 91.2%, 79.5% and 62.9% respectively. The median survival was 87.2 months (96% CI 51.8-NR). The rate of major morbidity was 71%. The postoperative mortality incidence was 1.7%. The median hospital length of stay was 34 days (IQR:27-54 days). CONCLUSIONS: In an experienced centre CRS + HIPEC is safe in selected patients with PCI 39. Despite the high morbidity, the overall survival for appendiceal tumours appear considerably better than debulking surgery.


Assuntos
Neoplasias do Apêndice/patologia , Procedimentos Cirúrgicos de Citorredução , Quimioterapia Intraperitoneal Hipertérmica , Neoplasias Peritoneais/patologia , Neoplasias Peritoneais/terapia , Idoso , Neoplasias do Apêndice/cirurgia , Procedimentos Cirúrgicos de Citorredução/efeitos adversos , Feminino , Humanos , Estimativa de Kaplan-Meier , Tempo de Internação , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Neoplasia Residual , Neoplasias Peritoneais/secundário , Complicações Pós-Operatórias/etiologia , Estudos Retrospectivos , Índice de Gravidade de Doença , Taxa de Sobrevida , Carga Tumoral
13.
Waste Manag ; 113: 225-235, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32535374

RESUMO

In this study, banana peel (BP) and its derivatives after sequential extraction of biochemical components were evaluated for selective recovery of gold. In-depth instrumental characterizations including XPS, FTIR, XRD and HR-TEM were performed to understand the adsorption mechanisms. The biomass after lipid extraction, BP-L, demonstrated very good affinity and selectivity towards gold. In multi-metal systems containing 100 mg/L of Pt(IV), Au(III), Pd(II), Zn(II), Co(II), Ni(II) and Li(I), the selectivity coefficient increased from 978.45 in BP to 2034.70 in BP-L. Moreover, the equilibrium gold uptake was improved and reached 475.48 ± 3.08 mg/g owing to reduction-coupled adsorption mechanisms. The BP-L also showed improved gold nanoparticle formation properties that were pH-dependent. In a strategic adsorption-combined incineration process, metallic gold reaching 99.96% in purity was obtained. The BP and its derivative, BP-L have thus shown potentials for multiple applications in the areas of precious metal recovery and nanoscience.


Assuntos
Nanopartículas Metálicas , Musa , Adsorção , Ouro , Incineração
14.
Environ Sci Pollut Res Int ; 27(20): 24760-24771, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31925694

RESUMO

This study aimed to select a high-performance cation-exchange resin (CER) and estimate its uptake of positively ionized tricyclic antidepressants (TCAs), i.e., amitriptyline (AMI), imipramine (IMI), clomipramine (CLO), and desipramine (DES), which are frequently used, and detected in wastewater treatment systems. For the selection of the resin, the one-point check test of AMI in distilled water was examined using several CERs. As a result, the strong-acid polystyrene CER, Dowex 50WX4-200, was selected on the basis of its outstanding uptake of AMI. The maximum adsorption capacities of Dowex 50WX4-200 for removal of the TCAs ranged from 2.53 ± 0.20 mmol/g to 3.76 ± 0.12 mmol/g, which are significantly higher when compared with those of previously reported adsorbents. This is likely because the combination of electrostatic and π-π interactions between the TCAs and Dowex 50WX4-200 may lead to high uptakes of the TCAs. Additionally, the removal efficiency of DES as a representative of the TCAs was tested in actual wastewater system containing activated sludge and miscellaneous cations. Consequently, the removal efficiencies of the DES in distilled water, aerobic wastewater, and filtered wastewater were 95.68%, 77.99%, and 56.66%, respectively. It is interesting to note that the activated sludge could also contribute to adsorption of the DES, leading to increased removability, while the cations present in the wastewater acted as competing ions, decreasing the removal efficiency.


Assuntos
Amitriptilina , Antidepressivos Tricíclicos , Adsorção , Cátions , Imipramina
15.
Environ Sci Pollut Res Int ; 27(1): 1053-1068, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31814075

RESUMO

Dyes are colored compounds which are visible even at trace concentrations. Due to their recalcitrance and esthetic persistence, certain methods are unable to effectively eliminate them. So far, adsorptive treatment using activated carbons (ACs) is one of the most successful methods. In this study, we have employed orange peel (OP) as a cost-effective alternative to the expensive coal- and coir-based precursors to synthesize ACs for cationic methylene blue (MB) and anionic methyl orange (MO) dye adsorption. The pre-carbonized OP was activated via H2SO4, NaOH, KOH, ZnCl2, and H3PO4 to study the effects of activation reagents on dye removal efficiencies and mechanisms. Among several isotherm models employed to fit the adsorption data, the Langmuir and Sips models sufficiently estimated the maximum equilibrium uptakes close to the experimental values of 1012.10 ± 29.13, 339.82 ± 6.98, and 382.15 ± 8.62 mg/g, for ZnCl2-AC (MO), ZnCl2-AC (MB), and KOH-AC (MB), respectively. The adsorption mechanisms were suggested to involve electrostatic binding, pi-pi interactions, hydrogen bonding, and electron donor-acceptor reactions. Consequently, more than 99% removal efficiency was achieved from a laboratory organic wastewater sample bearing ~ 35 mg/L of MB. The results thus suggest that the synthesized ACs from agricultural waste have the tendencies to be applied to real dye wastewater treatment.


Assuntos
Carvão Vegetal/química , Corantes/química , Azul de Metileno/química , Adsorção , Agricultura , Compostos Azo , Citrus sinensis , Cinética , Águas Residuárias , Poluentes Químicos da Água/química
16.
Arch Microbiol ; 202(3): 623-635, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31773197

RESUMO

Pseudomonas aeruginosa is a potent biofilm forming organism causing several diseases on host involving biofilm. Several natural and synthetic molecules have been explored towards inhibiting the biofilm formation of Pseudomonas aeruginosa. In the current report, the role of a natural molecule namely caffeine was examined against the biofilm forming ability of P. aeruginosa. We have observed that caffeine shows substantial antimicrobial activity against P. aeruginosa wherein the minimum inhibitory concentration (MIC) of caffeine was found to be 200 µg/mL. The antibiofilm activity of caffeine was determined by performing a series of experiments using its sub-MIC concentrations (40 and 80 µg/mL). The results revealed that caffeine can significantly inhibit the biofilm development of P. aeruginosa. Caffeine has been found to interfere with the quorum sensing of P. aeruginosa by targeting the swarming motility. Molecular docking analysis further indicated that caffeine can interact with the quorum sensing proteins namely LasR and LasI. Thus, the result indicated that caffeine could inhibit the formation of biofilm by interfering with the quorum sensing of the organism. Apart from biofilm inhibition, caffeine has also been found to reduce the secretion of virulence factors from Pseudomonas aeruginosa. Taken together, the results revealed that in addition to biofilm inhibition, caffeine can also decrease the spreading of virulence factors from Pseudomonas aeruginosa.


Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Cafeína/farmacologia , Pseudomonas aeruginosa/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biofilmes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/genética , Percepção de Quorum/efeitos dos fármacos , Fatores de Virulência/genética , Fatores de Virulência/metabolismo
17.
Sci Data ; 6(1): 286, 2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31772255

RESUMO

The marine iodine cycle has significant impacts on air quality and atmospheric chemistry. Specifically, the reaction of iodide with ozone in the top few micrometres of the surface ocean is an important sink for tropospheric ozone (a pollutant gas) and the dominant source of reactive iodine to the atmosphere. Sea surface iodide parameterisations are now being implemented in air quality models, but these are currently a major source of uncertainty. Relatively little observational data is available to estimate the global surface iodide concentrations, and this data has not hitherto been openly available in a collated, digital form. Here we present all available sea surface (<20 m depth) iodide observations. The dataset includes values digitised from published manuscripts, published and unpublished data supplied directly by the originators, and data obtained from repositories. It contains 1342 data points, and spans latitudes from 70°S to 68°N, representing all major basins. The data may be used to model sea surface iodide concentrations or as a reference for future observations.

18.
Waste Manag ; 89: 141-153, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-31079727

RESUMO

After consumption of the inner fleshy fruit, the banana peel like many other fruit peels is usually disposed of unprocessed. For sustainable development, agro-wastes including banana peels need to be converted into valuable products that will be beneficial to human and the environment. In this study, biochemical components including lipids, proteins and structural polysaccharides were sequentially extracted from banana peel, and the residuals were characterized by FE-SEM/EDX, FTIR, XRD, TGA/DSC, XPS and elemental analysis. Owing to rapid industrialization, toxic species such as metals and dyes are consistently released into the aquatic environments. Therefore, the residual biomass samples were evaluated for environmental remediation application. The adsorption performances were outstanding, with uptakes reaching 1034, 279 and 152 mg/g, for methylene blue, lead and platinum, respectively. This study thus suggests that sequential extraction and detailed characterization are useful for identification of key contributing components for development of high-performance agro-waste-based adsorbents for water treatment.


Assuntos
Recuperação e Remediação Ambiental , Musa , Purificação da Água , Adsorção , Biomassa
19.
Materials (Basel) ; 12(3)2019 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-30736386

RESUMO

The aim of this investigation was to assess the corrosion behavior of gray cast iron (GCI) alloyed with copper. Alloyed GCI specimens were austempered isothermally at varying temperatures. After austenitizing at 927 °C, the samples were austempered at different temperatures ranging from 260 to 385 °C with an interval of 25 °C for 60 minutes. As a result, these samples developed an ausferrite matrix with different percentages of austenite. The resulting microstructures were evaluated and characterized by optical microscope (OM), scanning electron microscope (SEM), and X-ray diffraction (XRD). The corrosion characteristics were determined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) of these samples. These tests were carried out in a medium of 0.5 M H2SO4 and 3.5% NaCl solution. It was observed from the potentiodynamic polarization results that with increasing austempering temperature, the corrosion rate decreased. All results of the EIS were in accordance with a constant phase element (CPE) model. It was found that with an increase in austempering temperature, the polarization resistance (Rp) increased. The austenite content was also found to influence the corrosion behavior of the austempered gray cast iron (AGCI).

20.
J Basic Microbiol ; 59(4): 412-424, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30672596

RESUMO

Iron is an important element for growth and metabolism of all marine organisms, including bacteria. Most (99.9%) of iron in oceans are bound to organic ligands like siderophores and siderophore-like compounds. Distribution of bioavailable iron mainly depends on pH and temperature of the ocean. Due to global warming and ocean acidification, bioavailability of iron may alter and in turn effect the response of marine bacteria. In this study, we investigated the effect of growth conditions like pH, temperature, and iron (III) concentrations on growth and siderophore production in selected heterotrophic bacteria isolated from waters around Kerguelen Islands (KW) and Prydz Bay (PB). Microcosm experiments were carried out on two KW-isolates (Enterococcus casseliflavus and Psychrobacter piscatorii) and five PB-isolates (Pseudoalteromonas tetraodonis, Bacillus cereus, Psychrobacter pocilloporae, Micrococcus aloeverae, and Pseudomonas weihenstephanensis) which produced either hydroxamate-type or catecholate-type siderophores. Increasing iron concentrations (10 nM to 50 µM) increased the growth rate of all isolates while siderophore production (% siderophore) generally reduced at higher iron concentration. Siderophore production peaked at early log phase, probably in response to higher iron-demand. Temperature and pH experiments showed that most isolates produced more siderophore at 15 and 25 °C temperature and pH 8.5. These results reveal that in future ocean conditions (warmer and acidified waters), bacterial growth and siderophore production may get affected and thereby influencing iron uptake and associated biogeochemical processes.


Assuntos
Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Água do Mar/química , Água do Mar/microbiologia , Sideróforos/biossíntese , Microbiologia da Água , Bactérias/classificação , Disponibilidade Biológica , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Oceano Índico , Ferro/química , Ferro/metabolismo , Filogenia , RNA Ribossômico 16S/genética , Sideróforos/química , Temperatura
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...