Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 30
Filtrar
1.
Rev Sci Instrum ; 95(5)2024 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-38814363

RESUMEN

Scanning Thermal Microscopy (SThM) has become an important measurement technique for characterizing the thermal properties of materials at the nanometer scale. This technique requires a SThM probe that combines an Atomic Force Microscopy (AFM) probe and a very sensitive resistive thermometer; the thermometer being located at the apex of the probe tip allows for the mapping of temperature or thermal properties of nanostructured materials with very high spatial resolution. The high interest of the SThM technique in the field of thermal nanoscience currently suffers from a low temperature sensitivity despite its high spatial resolution. To address this challenge, we developed a high vacuum-based AFM system hosting a highly sensitive niobium nitride (NbN) SThM probe to demonstrate its unique performance. As a proof of concept, we utilized this custom-built system to carry out thermal measurements using the 3ω method. By measuring the V3ω voltage on the NbN resistive thermometer under vacuum conditions, we were able to determine the SThM probe's thermal conductance and thermal time constant. The performance of the probe is demonstrated by performing thermal measurements in-contact with a sapphire sample.

2.
Eur J Paediatr Dent ; 24(1): 15-19, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36853219

RESUMEN

AIM: The aim of the study is to investigate the association between social capital and dental caries among 3-5-year-old preschool children in a rural region of southern India. METHODS: A cross-sectional study was conducted among 260 children ranging from 3 to 5 years-old and their parents from 13 preschools of the Udupi region of south India between December 2018, and February 2019. A 16-item Social Capital Scale (SCS) was used to collect data from the children's parents regarding their social capital. The diet history was collected from the parents and the children were examined for dental caries using the dmft index in their schools. CONCLUSION: Dental caries among preschool children had a negative association with parental social capital, and significantly contributed to variances in dental caries along with socioeconomic and dietary factors.


Asunto(s)
Caries Dental , Capital Social , Preescolar , Humanos , Estudios Transversales , Caries Dental/epidemiología , Escolaridad , Padres
3.
Lymphology ; 56(2): 41-60, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38621383

RESUMEN

The generalizability of findings from Clinical Trials (CTs) investigating lymphedema treatment modalities requires an accurate representation of the target population. This study aims to evaluate racial and ethnic reporting and representation in lymphedema CTs. A comprehensive systematic literature search was conducted during May 2023 using multiple databases, following the PRISMA guidelines. All CTs published from 2018 to 2023 were included. A total of 84 articles were included in this review, from which 6,546 participants were included in the analysis. Seventy-four (88.1%) articles addressed secondary lymphedema, of which 60 (81.1%) were related to breast cancer. Only 12 (13%) of CTs reported at some extend race or ethnicity. Of these, five (41.6%) reported race and two (16.6%) reported ethnicity according to FDA guidelines. White race had the highest pooled prevalence (80%; 95% CI 72-86%; I2=90%), followed by Black (7%; 95% CI 2- 15%; I2= 94.3%) and Asian (4%; 95% CI 1-8%; I2= 89.9%). In studies reporting ethnicity, participants were predominantly non-Hispanic (92.1%; 95% CI 90 - 94%). There is an underreporting and underrepresentation of racial and ethnic minorities among lymphedema CTs, limiting their generalizability. It is imperative to future development of strategies to enhance diversity in the study sample.


Asunto(s)
Ensayos Clínicos como Asunto , Minorías Étnicas y Raciales , Linfedema , Humanos , Linfedema/terapia , Linfedema/etnología , Linfedema/epidemiología , Minorías Étnicas y Raciales/estadística & datos numéricos , Etnicidad/estadística & datos numéricos , Femenino
4.
Lymphology ; 56(4): 160-167, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-39207408

RESUMEN

There are very limited studies on the relationship of inguinal lymph node number and volume correlated with lower extremity lymphedema severity. In this IRB-approved retrospective study, patients who obtained an MRI for lower extremity lymphedema and who did not have lymph node resection or biopsy were identified. The MRI images were used to determine the number and volume of inguinal lymph nodes for each limb in addition to fat and fluid-based scoring using a validated grading system. Wilcoxon signed-rank tests were used to compare the greater-affected limbs with the lesser-affected limbs. The spear-man-rank correlation was performed on a 'per limb' basis for MRI-based scoring and clinical parameters with ipsilateral lymph node number and volume and for differences between the limbs. A total of 32 patients were included. The greater-affected limb had higher MRI fluid scores (median (interquartile range) = 3 (3 - 3) vs. 0 (0 - 1), (p < 0.01) relative to the contra-lateral limb and had a median fat asymmetry score of 2 (1 - 3). On the per-limb analysis, lymph node number and volume inversely correlated with total MRI scores (ρ = -0.47, p < 0.01 for node number and volume). The difference of lymph node number and volume correlated with MRI score difference (node number: ρ = -0.66, p < 0.01; node volume: ρ = -0.64, p < 0.01) and perometer difference (node number: ρ = -0.58, p < 0.01; node volume: ρ = -0.59, p < 0.01). Inguinal lymph node number and volume inversely correlate with lower extremity edema presence and severity.

6.
Malays Orthop J ; 15(3): 71-77, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34966498

RESUMEN

INTRODUCTION: Pre-operative identification of patients with inadequate hamstring graft for anterior cruciate ligament reconstruction is still a subject of interest. The purpose of this study is to correlate dimension of a harvested dimensions graft with patient physical anthropometric variables. MATERIALS AND METHODS: This cohort study included 280 patients (male = 226, female = 54) scheduled for primary anterior cruciate ligament (ACL) reconstruction. Interrelationships between quadruple semitendinosus (ST) graft and anthropometric parameters (age, sex, height, weight, and BMI) were assessed using Pearson Correlation test and regression analysis. Difference among gender was analysed using Mann Whitney and t test. The observed graft diameter was also compared with the literature using Bland - Altman plot. RESULTS: Mean age of cohort was 29 years (range, 17-50 years), mean height was 1.69m (range, 1.6-1.9m), mean weight was 75 kg (range, 50-116kg) and mean BMI was 26kg/m2 (range 16.65-40.40kg/m2). Mean quadruple length of harvested ST graft was 7cm (7.1±0.6 cm, range, 5.6-8.8cm) and mean diameter was 8mm (8.2±0.8mm, range, 6.5-10mm). Only height and weight were significantly correlated with graft length and diameter in both sex (p value <0.05). Female, compared to male, had significantly smaller (p<0.0001) and thinner graft (p<0.0001). There was a strong agreement between the literature and our observed graft diameter, but with an overestimated graft diameter in 18.5% of the cases. CONCLUSION: Among anthropometric parameter, only height and weight had moderate positive correlation with graft diameter. Males had longer and wider ST graft in contrast to age-matched female group.

7.
J Postgrad Med ; 67(4): 228-231, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34845891

RESUMEN

Meningoencephaloceles (MECs) occur due to herniation of brain tissue through a bony defect in the skull base. They can be spontaneous or acquired. These are secondary to trauma, infection or neoplasia. Adult-onset spontaneous or idiopathic MECs are rare. Temporal bone MECs can present with watery discharge from the ear, conductive hearing loss or symptoms of meningitis like headache, fever, vomiting or seizures. These symptoms mimic chronic suppurative or serous otitis media. Computed tomography scan and magnetic resonance imaging differentiate between them. Awareness of this disease entity is necessary for early detection to avoid complications. We report a case of bilateral idiopathic temporal bone MECs with a rare presentation of autophony as the chief complaint. The differentiating features on computed tomography scan and magnetic resonance imaging and the surgical management are discussed.


Asunto(s)
Meningocele , Adulto , Encefalocele/diagnóstico por imagen , Encefalocele/cirugía , Humanos , Imagen por Resonancia Magnética , Meningocele/diagnóstico por imagen , Meningocele/cirugía , Hueso Temporal/diagnóstico por imagen , Hueso Temporal/cirugía , Tomografía Computarizada por Rayos X
8.
Artículo en Inglés | WPRIM (Pacífico Occidental) | ID: wpr-923061

RESUMEN

@#Introduction: Pre-operative identification of patients with inadequate hamstring graft for anterior cruciate ligament reconstruction is still a subject of interest. The purpose of this study is to correlate dimension of a harvested dimensions graft with patient physical anthropometric variables. Materials and methods: This cohort study included 280 patients (male = 226, female = 54) scheduled for primary anterior cruciate ligament (ACL) reconstruction. Interrelationships between quadruple semitendinosus (ST) graft and anthropometric parameters (age, sex, height, weight, and BMI) were assessed using Pearson Correlation test and regression analysis. Difference among gender was analysed using Mann Whitney and t test. The observed graft diameter was also compared with the literature using Bland – Altman plot. Results: Mean age of cohort was 29 years (range, 17-50 years), mean height was 1.69m (range, 1.6-1.9m), mean weight was 75 kg (range, 50-116kg) and mean BMI was 26kg/m2 (range 16.65-40.40kg/m2). Mean quadruple length of harvested ST graft was 7cm (7.1±0.6 cm, range, 5.6- 8.8cm) and mean diameter was 8mm (8.2±0.8mm, range, 6.5-10mm). Only height and weight were significantly correlated with graft length and diameter in both sex (p value <0.05). Female, compared to male, had significantly smaller (p<0.0001) and thinner graft (p<0.0001). There was a strong agreement between the literature and our observed graft diameter, but with an overestimated graft diameter in 18.5% of the cases. Conclusion: Among anthropometric parameter, only height and weight had moderate positive correlation with graft diameter. Males had longer and wider ST graft in contrast to age-matched female group.

9.
Int J Oral Maxillofac Surg ; 44(4): 424-6, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25533901

RESUMEN

For total rhinectomy defects, the decision to proceed with a prosthetic versus surgical reconstruction is multifactorial, taking into account patient risk factors, availability of donor tissues, the need for tumor surveillance, and personal preferences. When a prosthetic approach is chosen, the reconstructive surgeon is tasked with preparing the defect to maximize prosthetic retention and prevent ulcerations. Stable bone coverage is critical to achieve this aim. Although skin grafting has been described previously for bone coverage, the periosteum is often stripped. We present a novel use of the inferior turbinate flap for preparation of rhinectomy defects that can be utilized regardless of the presence or absence of the periosteum and provides a more durable coverage than skin grafts.


Asunto(s)
Carcinoma de Células Escamosas/cirugía , Neoplasias Nasales/cirugía , Rinoplastia/métodos , Colgajos Quirúrgicos , Cornetes Nasales/cirugía , Anciano , Humanos , Masculino , Prótesis e Implantes
10.
Eur Arch Paediatr Dent ; 16(2): 191-7, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25367819

RESUMEN

AIM: To develop a socio-dental impact locus of control scale (SILOC) and to study its relationship with oral health status as well as dental attendance. STUDY DESIGN: Observational cross-sectional study design. METHOD: A seven-item SILOC scale based on locus of control and the WHO international classification of diseases' criteria for "Disability" in relation to oral health was developed. In the pilot study, 100 adolescent school children returned completed forms containing the multidimensional health locus of control (MHLC) and the (SILOC) scale. After confirmation of reliability and validity, 509 adolescent school children returned completed SILOC questionnaires and were examined for caries, plaque and gingivitis. A history of postponement of needed dental treatment was also elicited. RESULTS: The SILOC scores were highly correlated with the MHLC scores. Factor analysis revealed a two-factor solution accounting for 59 % of the variance. A Cronbach's alpha of 0.75 showed its internal consistency. Those with higher SILOC scores had greater levels of caries, plaque, gingivitis, and a history of postponing needed dental visits. Multiple logistic regression analysis after adjusting for potential confounders showed that those with high SILOC scores were more likely to have caries (OR = 3.32, p < 0.001), plaque (OR = 1.83, p = 0.026), gingivitis (OR = 1.80, p = 0.012) and a history of 'Postponement of needed dental treatment' (OR = 4.5, p < 0.001) as compared with the others. CONCLUSIONS: The SILOC scale showed satisfactory reliability and validity in measuring locus of control orientation in an Indian adolescent population.


Asunto(s)
Actitud Frente a la Salud , Control Interno-Externo , Salud Bucal , Adolescente , Estudios Transversales , Atención Odontológica/psicología , Caries Dental/clasificación , Caries Dental/psicología , Placa Dental/clasificación , Placa Dental/psicología , Escolaridad , Femenino , Gingivitis/clasificación , Gingivitis/psicología , Humanos , Renta , India , Masculino , Ocupaciones , Proyectos Piloto , Análisis de Componente Principal , Reproducibilidad de los Resultados , Clase Social
11.
J Laryngol Otol ; 127 Suppl 2: S24-8, 2013 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-23544818

RESUMEN

AIM: This study aimed to validate the use of the Adelaide Disease Severity Score for the assessment of chronic rhinosinusitis. STUDY DESIGN: A prospective cohort study supplying level 2b evidence. METHODS: Forty-eight patients, scheduled for endoscopic sinus surgery for failed management of chronic rhinosinusitis, completed the Sino-Nasal Outcome Test 22 and the Adelaide Disease Severity Score tool (the latter assessing symptoms (i.e. nasal obstruction, rhinorrhoea, post-nasal drip, headache or facial pain, and olfaction) and quality of life). Lund-Mackay computed tomography scores and Lund-Kennedy endoscopic scores were also recorded. The Adelaide Disease Severity Score results were then compared with those of the other three tools to assess correlation. RESULTS: Mean scores (95 per cent confidence intervals) were 22.31 (21.47-24.15) for the Adelaide Disease Severity Score and 30.6 (27.15-34.05) for the Sino-Nasal Outcome Test 22; there was a statistically significant correlation (Spearman coefficient = 0.45; p = 0.0015). A statistically significant correlation was also noted with the Lund-Mackay score (p = 0.04) and with the Lund-Kennedy score (p = 0.03). CONCLUSION: The Adelaide Disease Severity Score is a simple, valid tool for clinical assessment of chronic rhinosinusitis, which correlates well with the Sino-Nasal Outcome Test 22, Lund-Mackay and Lund-Kennedy tools.


Asunto(s)
Rinitis/diagnóstico , Índice de Severidad de la Enfermedad , Sinusitis/diagnóstico , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad Crónica , Estudios de Cohortes , Endoscopía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Senos Paranasales , Estudios Prospectivos , Calidad de Vida , Rinitis/cirugía , Autoinforme , Sinusitis/cirugía , Adulto Joven
12.
Environ Monit Assess ; 157(1-4): 11-21, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18791802

RESUMEN

A number of low cost waste sorbent have been used for removal of heavy metals, however, few studies have been carried out on the sorption process on riverbed sediments in their natural state of occurrence. Stream sediments adsorb certain solutes from streams, thereby significantly changing the solute composition, but little is known about quantitatively describing sorption phenomena and rates of these processes. In the present investigation, sorption of lead ions on river bed sediments of river Hindon, a tributary of river Yamuna, India has been studied to demonstrate the role of bed sediments in controlling metal pollution. The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time and particle size has been studied. The sorption of lead ions increased with respect to pH and sorbent dose and decreased with sorbent particle size. Two important geochemical phases, iron and manganese oxide, also play important role in the sorption process. The sorption data were analysed using Langmuir and Freundlich isotherm models to determine the mechanistic parameters related to the sorption process. Further, although lead ions have more affinity for the fine fraction of the sediment, but the overall contribution of coarser fraction to sorption is more as compared to clay and silt fraction. The kinetic data suggest that the sorption of lead on bed sediments is an endothermic process, which is spontaneous at low temperature. The uptake of lead is controlled by both bulk and intraparticle diffusion mechanism.


Asunto(s)
Sedimentos Geológicos/química , Plomo/análisis , Ríos/química , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , Concentración de Iones de Hidrógeno , India , Cinética , Modelos Químicos , Tamaño de la Partícula
14.
Environ Monit Assess ; 134(1-3): 385-96, 2007 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17616829

RESUMEN

The river Hindon is one of the important tributaries of river Yamuna in western Uttar Pradesh (India) and carries pollution loads from various municipal and industrial units and surrounding agricultural areas. The main sources of pollution in the river include municipal wastes from Saharanpur, Muzaffarnagar and Ghaziabad urban areas and industrial effluents of sugar, pulp and paper, distilleries and other miscellaneous industries through tributaries as well as direct inputs. In this paper, chemical mass balance approach has been used to assess the contribution from non-point sources of pollution to the river. The river system has been divided into three stretches depending on the land use pattern. The contribution of point sources in the upper and lower stretches are 95 and 81% respectively of the total flow of the river while there is no point source input in the middle stretch. Mass balance calculations indicate that contribution of nitrate and phosphate from non-point sources amounts to 15.5 and 6.9% in the upper stretch and 13.1 and 16.6% in the lower stretch respectively. Observed differences in the load along the river may be attributed to uncharacterized sources of pollution due to agricultural activities, remobilization from or entrainment of contaminated bottom sediments, ground water contribution or a combination of these sources.


Asunto(s)
Nitratos/análisis , Fosfatos/análisis , Ríos/química , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , Concentración de Iones de Hidrógeno , India , Residuos Industriales , Oxígeno/análisis , Aguas del Alcantarillado , Movimientos del Agua
15.
Cochrane Database Syst Rev ; (3): CD005202, 2007 Jul 18.
Artículo en Inglés | MEDLINE | ID: mdl-17636789

RESUMEN

BACKGROUND: Although the small intestine represents 75% of the length and over 90% of the mucosal surface of the alimentary tract, it is the site of only about 2% of malignant gastrointestinal tumours. Adenocarcinoma is the most common histological subtype, accounting for about 40% of all malignant small intestinal tumours. The infrequent occurrence when compared with malignancies of the stomach and colon is accompanied by non-specific clinical symptoms. The consequences are a significant delay in diagnosis and the finding of advanced, incurable disease at operation. Wide surgical resection of early lesions is the only potentially curative treatment, but it is possible only in a minority of patients. The rare nature of adenocarcinomas of the small intestine has led to a paucity of information about the benefits of adjuvant chemotherapy but there are reports of overall better survival for those patients that receive combination treatment. Most chemotherapy regimens consist of 5-fluorouracil (5-FU), alone or in combination with a variety of other agents like doxorubicin, cisplatin, mitomycin C, cyclophosphamide and oxaliplatin. OBJECTIVES: To determine the role of adjuvant chemotherapy in the management of adenocarcinoma of the small intestine compared to another adjuvant treatment, a placebo or no other adjuvant treatment. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to 2006), EMBASE (1974 to 2006), PubMed and CINHAL using the Cochrane highly sensitive search strategy for randomised controlled trials. SELECTION CRITERIA: Phase III randomised controlled trials comparing post-operative adjuvant chemotherapy for adenocarcinoma of the small intestine with other adjuvant therapies, placebo or no adjuvant treatment. DATA COLLECTION AND ANALYSIS: No suitable trials were identified. MAIN RESULTS: No studies fulfilled the inclusion criteria. AUTHORS' CONCLUSIONS: There is a need for high quality randomised controlled trials to evaluate the effectiveness of adjuvant chemotherapy in the management of adenocarcinoma of the small intestine.


Asunto(s)
Adenocarcinoma/tratamiento farmacológico , Neoplasias Intestinales/tratamiento farmacológico , Intestino Delgado , Quimioterapia Adyuvante , Humanos
17.
World J Surg ; 31(5): 1130-5, 2007 May.
Artículo en Inglés | MEDLINE | ID: mdl-17429567

RESUMEN

BACKGROUND: Solid-pseudopapillary neoplasms (SPNs) of the pancreas are increasingly diagnosed, but the exact surgical management in terms of extent of the resection is not well defined. MATERIALS AND METHODS: Patients operated on in our hospital between January 1993 and March 2005 formed the study groups. RESULTS: From 659 consecutive resections for pancreatic neoplasms, 12 female patients (1.8%) with a median age of 21 years who underwent resection for (SPN) are compared with the remaining 647 pancreatic resection patients. Jaundice (SPN 0 versus PR 73%, p < 0.001) and weight loss (SPN 0 versus PR 49%, p = 0.001) occurred significantly less often. Neoplasms were distributed equally among the pancreatic head (SPN 5 out of 12 patients versus PR 88%, p < 0.001) and corpus/tail (SPN 6 out of 12 patients versus PR 8%, p < 0.001). The operative time was significantly shorter (SPN 233 min versus PR 280 min, p = 0.012), and there were significantly fewer complications (SPN 1 of 12 patients versus PR 48%, p = 0.007). The mortality was not different (SPN 0 versus PR 1.6%, p = 1.000), and the hospital stay was significantly shorter (SPN 9 days versus PR 15 days, p = 0.012). The median size of the neoplasms was significantly larger (SPN 6.9 cm versus PR 2.5 cm). The median number of lymph nodes harvested was significantly fewer (SPN 1 versus PR 6, p = 0.001), and lymph node metastases occurred significantly less often (SPN 0 versus PR 64%, p < 0.001). The 5-year survival of SPN patients was 100% and is significantly better compared with survival of patients with pancreatic adenocarcinoma (12%, p < 0.001) and ampulla of Vater adenocarcinoma (22%, p = 0.005). CONCLUSIONS: Patients with solid-pseudopapillary neoplasms of the pancreas present differently and the course of the disease is more benign. These patients can be adequately managed by pylorus-preserving pancreatoduodenectomy or spleen-preserving distal pancreatectomy with excellent early and long-term results.


Asunto(s)
Adenocarcinoma/patología , Adenocarcinoma/cirugía , Pancreatectomía/métodos , Neoplasias Pancreáticas/patología , Neoplasias Pancreáticas/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Distribución de Chi-Cuadrado , Femenino , Humanos , Tiempo de Internación/estadística & datos numéricos , Persona de Mediana Edad , Complicaciones Posoperatorias , Estudios Prospectivos , Tasa de Supervivencia , Resultado del Tratamiento
18.
Surg Oncol ; 14(2): 59-74, 2005 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-16019208

RESUMEN

Around 80% of the patients with hilar cholangiocarcinoma are candidates for palliative management due to extensive co-morbidity for major surgery, metastases or advanced loco-regional disease. The primary aim of treatment is to provide biliary drainage with long-term relief from pruritus, cholangitis, pain and jaundice. Endoscopically placed self-expanding metallic biliary stent has low procedure-related complications and is probably the modality of choice for patients with unresectable tumour on preoperative assessment. Percutaneous biliary drainage has comparable results and is an alternative when endoscopic expertise is not available or has failed or there are multiple isolated segments with cholangitis. Surgical cholangiojejunostomy provides lasting biliary drainage but has limitations of associated morbidity and mortality. In the absence of high-quality studies, comparing these modalities the choice of biliary drainage procedure should be guided by the available local expertise. Other modalities of treatment like radiotherapy, chemotherapy and photodynamic therapy currently remain investigational.


Asunto(s)
Neoplasias de los Conductos Biliares/cirugía , Conductos Biliares Intrahepáticos , Colangiocarcinoma/cirugía , Drenaje/métodos , Cuidados Paliativos , Bilis , Neoplasias de los Conductos Biliares/clasificación , Neoplasias de los Conductos Biliares/diagnóstico , Colangiocarcinoma/clasificación , Colangiocarcinoma/diagnóstico , Procedimientos Quirúrgicos del Sistema Digestivo , Endoscopía , Humanos , Implantación de Prótesis , Stents
19.
Environ Monit Assess ; 105(1-3): 193-207, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15952520

RESUMEN

The metal pollution in water and sediment of the River Hindon in western Uttar Pradesh (India) was assessed for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The metal concentrations in water showed wide temporal variation compared with bed sediment because of variability in water discharge and variations in suspended solid loadings. Metal concentrations in bed sediments provided a better evaluation of the degree and the extent of contamination in the aquatic environment, Santagarh and Atali being the most polluted sites of the river. The ratio of heavy metals to conservative elements (Fe, Al, etc.) may reveal the geochemical imbalances due to the elevated metal concentrations normally attributed to anthropogenic sources. Metal/A1 ratios for the bed sediments of the river Hindon were used to determine the relative mobility and general trend of relative mobility occurred Fe > Mn > Zn > Cr > Ni > Pb > Cu > Cd.


Asunto(s)
Sedimentos Geológicos/química , Metales Pesados/análisis , Ríos/química , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , India , Residuos Industriales , Aguas del Alcantarillado , Espectrofotometría Atómica
20.
J Hazard Mater ; 114(1-3): 231-9, 2004 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-15511595

RESUMEN

The paper presents a study of zinc adsorption using the experimental data on bed sediments of River Hindon in western Uttar Pradesh (India). The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time, and particle size, have been studied. The optimum contact time needed to reach equilibrium was of the order of 60 min and was independent of initial concentration of zinc ions. The extent of adsorption increased with an increase of pH. Furthermore the adsorption of zinc increases with increasing adsorbent doses and decreases with the adsorbent particle size. The content of iron, manganese and organic matter in various fraction of sediment decreases with increasing particle size indicating the possibility of the two geochemical phases to act as the active support material for the adsorption of zinc ions. The adsorption data follows both Langmuir and Freundlich adsorption models. Isotherms were used to determine thermodynamic parameters, viz., free energy change, enthalpy change and entropy change. The negative values of free energy change indicate spontaneous nature of the adsorption while positive values of enthalpy change suggest the endothermic nature of the adsorption of zinc on bed sediment of the River Hindon. The positive values of entropy change indicate randomness at the solid/solution interface.


Asunto(s)
Sedimentos Geológicos/química , Zinc/química , Adsorción , Difusión , Concentración de Iones de Hidrógeno , India , Cinética , Modelos Químicos , Termodinámica
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA