Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 20
Filtrar
1.
Indian J Nucl Med ; 39(3): 216-219, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39291064

RESUMO

Extracranial metastasis from high-grade glial tumors is an extremely rare condition with its reported incidence being <1%. The most common sites reported in the literature are leptomeninges and spinal cord, followed by the liver, lung, and skeletal system. Its low incidence is thought to be related to the intrinsic aggressive biology of the tumor, thus reducing median overall survival in patients. As there is lack of knowledge about the mechanism of extracranial spread of glioma cells, its diagnosis and management remain a major challenge. We report two cases of extracranial metastases from glial tumors to cervical nodes and postoperative site involving preauricular region detected on F18 Fluoro ethyl tyrosine (FET) positron emission tomography-computed tomography and later on confirmed with histopathology Fluoro ethyl tyrosine.

2.
Chem Commun (Camb) ; 60(76): 10492-10495, 2024 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-39177224

RESUMO

A strategically designed redox-active ligand ensures proper electronic balance in an Mn(I)-carbonyl template to induce photostability and water solubility. This newly designed Mn-carbonyl complex showcased rapid CO2 reduction with preferential production of CO (faradaic efficiency ∼88%) as the only C1 product in pure water, even from a flue gas resource.

3.
Indian J Nucl Med ; 39(2): 71-76, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38989301

RESUMO

Purpose: We proposed to administer Lu-177-DOTATATE in intra-arterial (IA) mode for higher first-pass localization to somatostatin receptors, higher residence time in liver metastases, and more radiation to tumor. This study aimed at assessing early hematological, renal and hepatotoxicity; and objective response to IA peptide receptor radionuclide therapy (PRRT). Materials and Methods: Fourteen patients (4 females and 10 males) were prospectively assessed. 5/14 patients underwent 2 cycles, whereas 3/14 underwent 3 cycles, and 6/14 received 1 cycle of IA PRRT. 200 mCi of Lu-177-DOTATATE was administered in 15-20 min by IA route under angiographic guidance. Patients were asked to follow-up at 4 and 8 weeks with hematological, liver, and renal functional parameters, and Ga-68 DOTATATE positron emission tomography/computed tomography (PET/CT) after 8 weeks. Response was assessed using RECIST 1.1 and EORTC PET criteria. Results: Safety: 2/14 patients had high total and direct bilirubin, which reverted to normal after IA PRRT. Three patients had low albumin, which improved after 1 cycle. Nine patients showed no worsening of liver function. Two patients showed Grade 1 hematotoxicity which reverted to normal. Five patients showed high creatinine, but preserved glomerular filtration rate and EC clearance. On follow-up at 8 weeks, serum creatinine reverted to normal. Efficacy: In five patients who underwent 2 cycles of IA PRRT, 3 showed partial response (PR) on RECIST 1.1 and partial metabolic response (PMR) on EORTC criteria, whereas 2 showed stable disease (SD). In patients who underwent 3 cycles, 1 showed SD, whereas other patient showed PMR on DOTANOC PET/CT, with PR in size. Among the remaining seven patients, 5 showed PMR, whereas the other 2 showed SD. Thus 9/14 patients showed PR, whereas 5 showed SD on metabolic and size criteria. Conclusions: IA PRRT is a safe and efficacious approach for the treatment of liver dominant metastatic neuroendocrine tumors.

4.
Indian J Nucl Med ; 39(2): 129-134, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38989300

RESUMO

Prostate-specific membrane antigen (PSMA) is a widely accepted and used tracer in staging and biochemical recurrences of prostate cancer. PSMA is extensively expressed in normal prostatic epithelial cells and prostate cancer cells, with some amount of expression also in nonprostatic cells. False-positive PSMA uptake in nonmalignant lesions creates ambiguity in disease detection. In such cases, histopathological correlation and radiological follow-up assist in clinical decision-making. In this case series, we illustrate a few cases where PSMA uptake was incidentally found in some of the commonly occurring benign conditions.

5.
Artigo em Inglês | MEDLINE | ID: mdl-38949504

RESUMO

Hemibiotrophic fungi in the genus Colletotrichum employ a biotrophic phase invading host epidermal cells followed by a necrotrophic phase spreading through neighboring mesophyll and epidermal cells. We used serial block face scanning electron microscopy (SBF-SEM) to compare subcellular changes that occur in Medicago sativa (alfalfa) cotyledons during infection by Colletotrichum destructivum (compatible on M. sativa) and C. higginsianum (incompatible on M. sativa). Three-dimensional reconstruction of serial images revealed that alfalfa epidermal cells infected with C. destructivum undergo massive cytological changes during the first 60 hours following inoculation to accommodate extensive intracellular hyphal growth. Conversely, inoculation with the incompatible species C. higginsianum resulted in no successful penetration events and frequent formation of papilla-like structures and cytoplasmic aggregates beneath attempted fungal penetration sites. Further analysis of the incompatible interaction using focused ion beam-scanning electron microcopy (FIB-SEM) revealed formation of large multivesicular body-like structures that appeared spherical and were not visible in compatible interactions. These structures often fused with the host plasma membrane, giving rise to paramural bodies that appeared to be releasing extracellular vesicles (EVs). Isolation of EVs from the apoplastic space of alfalfa leaves at 60h post inoculation showed significantly more vesicles secreted from alfalfa infected with incompatible fungus compared to compatible fungus, which in turn was more than produced by non-infected plants. Thus, the increased frequency of paramural bodies during incompatible interactions correlated with an increase in EV quantity in apoplastic wash fluids. Together, these results suggest that EVs and paramural bodies contribute to immunity during pathogen attack in alfalfa.

6.
Neurol India ; 72(2): 278-284, 2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38691470

RESUMO

PURPOSE: Refractory and/or recurrent meningiomas have poor outcomes, and the treatment options are limited. Peptide receptor radionuclide therapy (PRRT) has been used in this setting with promising results. We have documented our experience of using intravenous (IV) and intra-arterial (IA) approaches of Lu-177 DOTATATE PRRT. METHODS: Eight patients with relapsed/refractory high-grade meningioma received PRRT with Lu-177 DOTATATE by IV and an IA route. At least 2 cycles were administered. Time to progression was calculated from the first PRRT session to progression. The response was assessed on MRI using RANO criteria, and visual analysis of uptake was done on Ga-68 DOTANOC PET/CT. Post-therapy dosimetry calculations for estimating the absorbed dose were performed. RESULTS: Median time to progression was 8.9 months. One patient showed disease progression, whereas seven patients showed stable disease at 4 weeks following 2 cycles of PRRT. Dosimetric analysis showed higher dose and retention time by IA approach. No significant peri-procedural or PRRT associated toxicity was seen. CONCLUSION: PRRT is a safe and effective therapeutic option for relapsed/refractory meningioma. The IA approach yields better dose delivery and should be routinely practised.


Assuntos
Neoplasias Meníngeas , Meningioma , Octreotida , Octreotida/análogos & derivados , Humanos , Meningioma/radioterapia , Meningioma/diagnóstico por imagem , Neoplasias Meníngeas/radioterapia , Neoplasias Meníngeas/diagnóstico por imagem , Feminino , Masculino , Octreotida/uso terapêutico , Octreotida/administração & dosagem , Pessoa de Meia-Idade , Adulto , Compostos Organometálicos/uso terapêutico , Idoso , Resultado do Tratamento , Compostos Radiofarmacêuticos/uso terapêutico , Receptores de Peptídeos , Centros de Atenção Terciária , Progressão da Doença
7.
Indian J Cancer ; 61(Suppl 1): S1-S28, 2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38424680

RESUMO

ABSTRACT: PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.


Assuntos
Neoplasias , Medicina Nuclear , Humanos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos/uso terapêutico , Radioisótopos , Fluordesoxiglucose F18
8.
Mol Plant Microbe Interact ; 37(4): 396-406, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38148303

RESUMO

We used serial block-face scanning electron microscopy (SBF-SEM) to study the host-pathogen interface between Arabidopsis cotyledons and the hemibiotrophic fungus Colletotrichum higginsianum. By combining high-pressure freezing and freeze-substitution with SBF-SEM, followed by segmentation and reconstruction of the imaging volume using the freely accessible software IMOD, we created 3D models of the series of cytological events that occur during the Colletotrichum-Arabidopsis susceptible interaction. We found that the host cell membranes underwent massive expansion to accommodate the rapidly growing intracellular hypha. As the fungal infection proceeded from the biotrophic to the necrotrophic stage, the host cell membranes went through increasing levels of disintegration culminating in host cell death. Intriguingly, we documented autophagosomes in proximity to biotrophic hyphae using transmission electron microscopy (TEM) and a concurrent increase in autophagic flux between early to mid/late biotrophic phase of the infection process. Occasionally, we observed osmiophilic bodies in the vicinity of biotrophic hyphae using TEM only and near necrotrophic hyphae under both TEM and SBF-SEM. Overall, we established a method for obtaining serial SBF-SEM images, each with a lateral (x-y) pixel resolution of 10 nm and an axial (z) resolution of 40 nm, that can be reconstructed into interactive 3D models using the IMOD. Application of this method to the Colletotrichum-Arabidopsis pathosystem allowed us to more fully understand the spatial arrangement and morphological architecture of the fungal hyphae after they penetrate epidermal cells of Arabidopsis cotyledons and the cytological changes the host cell undergoes as the infection progresses toward necrotrophy. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.


Assuntos
Arabidopsis , Colletotrichum , Cotilédone , Microscopia Eletrônica de Varredura , Doenças das Plantas , Colletotrichum/fisiologia , Colletotrichum/ultraestrutura , Colletotrichum/patogenicidade , Arabidopsis/microbiologia , Arabidopsis/ultraestrutura , Cotilédone/microbiologia , Cotilédone/ultraestrutura , Doenças das Plantas/microbiologia , Interações Hospedeiro-Patógeno , Hifas/ultraestrutura , Imageamento Tridimensional , Microscopia Eletrônica de Transmissão
9.
Nucl Med Commun ; 44(12): 1156-1162, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37706256

RESUMO

OBJECTIVE: Assessment of diagnostic accuracy of FDG-PET/CT in the detection of viable disease in post-chemotherapy seminomatous residual masses using visual interpretation, SUVmax, and T/L ratio. METHODS: This is a retrospective study assessing the post-chemotherapy seminomatous residual masses of size >3 cm. The PET/CT scan findings were interpreted visually for presence of residual disease which were validated from histopathology reports or imaging follow-up for a maximum of 3 years. SUVmax and T/L ratios were also determined for all the residual lesions. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value NPV were calculated and compared for all three parameters along with ROC analysis to obtain an optimal cutoff value for SUVmax and T/L ratio, respectively. RESULTS: Sample size was 49. Out of these 49 patients, 8 had validation of PET results with histopathology. Rest was validated with imaging follow-up. FDG-PET was positive in 30 patients and negative in 19 patients by visual interpretation. The sensitivity, specificity, PPV, and NPV by this method were 100%, 62.5%, 73%, and 100%, respectively. The SUVmax and T/L ratios were also calculated for these lesions. The cutoff for these two variables was 4.56 and 1.21, respectively. The sensitivity, specificity, PPV, and NPV at these cutoffs were 76%, 87.5%, 86%, 77.7%, and 92%, 87.5%, 88%, 91%, respectively. CONCLUSION: FDG-PET has a favorable diagnostic value in predicting viable disease in post-chemotherapy seminomatous residual masses and using T/L ratio cutoff of 1.21 will increase the specificity of the test.


Assuntos
Fluordesoxiglucose F18 , Neoplasias , Humanos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Compostos Radiofarmacêuticos , Estudos Retrospectivos , Fígado , Sensibilidade e Especificidade
10.
Chem Asian J ; 18(20): e202300706, 2023 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-37655885

RESUMO

Fragile hemiaminal ether linkages present in the backbone of koneramines (LR OR'), tridentate ligands, bound to copper(II) in stereoselectively self-assembled syn-[Cu(LR OR')X2 ] complexes were transformed into sturdy methylene linkages to make corresponding rac-[Cu(LR H)Cl2 ] complexes by late-stage ligand modification after coordination with the retention of coordination sphere. The generality of stereoselective self-assembly of koneramine complexes is shown by utilising a number of metal ions, anions, amines, alcohols and thiols with complete characterisations.

11.
Dalton Trans ; 51(41): 15659-15668, 2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36222417

RESUMO

The photophysical properties of the anthracene appended koneramines (LAn) were analyzed and utilized as a chemosensor for the selective detection of Cd2+ and Zn2+. The complexation-induced inhibition of PET (photo-induced electron transfer) from the chelating nitrogen atoms to the excited state of the anthracene moiety resulted in a fluorescence "turn-on" signal upon binding with Cd2+ and Zn2+. The confocal microscopic imaging studies performed on the MCF-7 cells validated that the compound is potentially useful for detecting Cd2+ and Zn2+ inside the cells. The cadmium complex exhibited unique bactericidal activity against clinically relevant human pathogens. The excellent activity against multidrug-resistant S. aureus makes the complex useful as a new, easily synthesizable antibiotic. The cadmium complex LAnCdCl2 was not cytotoxic against vero cells with a selectivity index of 40, exhibited concentration dependent bactericidal killing, was non-interactive with several other clinically approved standard drugs, exhibited prolonged post-antibiotic effect (PAE) against S. aureus ATCC 29213 and possesses antibiofilm activity.


Assuntos
Cádmio , Staphylococcus aureus Resistente à Meticilina , Chlorocebus aethiops , Animais , Humanos , Cádmio/química , Staphylococcus aureus , Zinco/química , Células Vero , Antibacterianos/farmacologia , Antibacterianos/química , Antracenos , Nitrogênio
12.
Clin Nucl Med ; 47(12): e765-e766, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-35867990

RESUMO

ABSTRACT: The incidence of congenital melanocytic nevi (CMNs) is 1% to 6% for small- to intermediate-size nevi to 1 in 500,000 for giant size nevi. Large and satellite CMNs are known to be associated with neurocutaneous melanosis and central nervous system malformations such as Dandy-Walker malformation, defects of the vertebra-skull, and intraspinal lipomas. We hereby present a case of CMN syndrome in an 18-year-old girl with leptomeningeal melanoma, evaluated with MRI, adequately staged, and screened with FDG PET.


Assuntos
Melanoma , Melanose , Neoplasias Meníngeas , Síndromes Neurocutâneas , Nevo Pigmentado , Neoplasias Cutâneas , Feminino , Humanos , Adolescente , Nevo Pigmentado/complicações , Nevo Pigmentado/diagnóstico por imagem , Nevo Pigmentado/congênito , Síndromes Neurocutâneas/complicações , Síndromes Neurocutâneas/diagnóstico por imagem , Melanose/complicações , Melanoma/complicações , Melanoma/diagnóstico por imagem , Neoplasias Cutâneas/complicações , Neoplasias Cutâneas/diagnóstico por imagem , Neoplasias Meníngeas/complicações , Neoplasias Meníngeas/diagnóstico por imagem
13.
Plant Sci ; 269: 85-93, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29606220

RESUMO

In due course of evolution many pathogens alter their effector molecules to modulate the host plants' metabolism and immune responses triggered upon proper recognition by the intracellular nucleotide-binding oligomerization domain containing leucine-rich repeat (NLR) proteins. Likewise, host plants have also evolved with diversified NLR proteins as a survival strategy to win the battle against pathogen invasion. NLR protein indeed detects pathogen derived effector proteins leading to the activation of defense responses associated with programmed cell death (PCD). In this interactive process, genome structure and plasticity play pivotal role in the development of innate immunity. Despite being quite conserved with similar biological functions in all eukaryotes, the intracellular NLR immune receptor proteins happen to be structurally distinct. Recent studies have made progress in identifying transcriptional regulatory complexes activated by NLR proteins. In this review, we attempt to decipher the intracellular NLR proteins mediated surveillance across the evolutionarily diverse taxa, highlighting some of the recent updates on NLR protein compartmentalization, molecular interactions before and after activation along with insights into the finer role of these receptor proteins to combat invading pathogens upon their recognition. Latest information on NLR sensors, helpers and NLR proteins with integrated domains in the context of plant pathogen interactions are also discussed.


Assuntos
Interações Hospedeiro-Patógeno/genética , Proteínas NLR/imunologia , Imunidade Vegetal , Plantas/imunologia , Interações Hospedeiro-Patógeno/imunologia , Proteínas NLR/genética , Plantas/genética
14.
BMC Microbiol ; 17(1): 87, 2017 04 04.
Artigo em Inglês | MEDLINE | ID: mdl-28376715

RESUMO

BACKGROUND: The nitrogen (N) cycle consists of complex microbe-mediated transformations driven by a variety of factors, including diversity and concentrations of N compounds. In this study, we examined taxonomic diversity and N substrate utilization by heterotrophic bacteria isolated from streams under complex and simple N-enrichment conditions. RESULTS: Diversity estimates differed among isolates from the enrichments, but no significant composition were detected. Substrate utilization and substrate range of bacterial assemblages differed within and among enrichments types, and not simply between simple and complex N-enrichments. CONCLUSIONS: N substrate use patterns differed between isolates from some complex and simple N-enrichments while others were unexpectedly similar. Taxonomic composition of isolates did not differ among enrichments and was unrelated to N use suggesting strong functional redundancy. Ultimately, our results imply that the available N pool influences physiology and selects for bacteria with various abilities that are unrelated to their taxonomic affiliation.


Assuntos
Bactérias/isolamento & purificação , Bactérias/metabolismo , Processos Heterotróficos/fisiologia , Nitrogênio/metabolismo , Bactérias/classificação , Bactérias/genética , Biodiversidade , DNA Bacteriano , Sedimentos Geológicos/microbiologia , Nitrogênio/química , Ciclo do Nitrogênio , RNA Ribossômico 16S/genética , Rios/microbiologia , Análise de Sequência
15.
J Clin Diagn Res ; 8(9): AC04-6, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25386413

RESUMO

OBJECTIVE: Styloid process of temporal bone is clinically important, because variations in length, as well as the angulations of styloid process are associated with the symptoms of stylalgia (Eagle's syndrome) and the surgical excision of the process could alleviate neck and cervicofacial pain in patients. This study was aimed to evaluate the length, angulation and distance between bases and tips of the styloid process. MATERIALS AND METHODS: We studied 114 dry skull bones with intact styloid processes. The length of styloid process and distance between bases and tips of the styloid process were measured with the help of vernier calipers. The angulation (anterior and medial angles) of the styloid process was measured directly from the digital images by the image analysis using Adobe Photoshop 7.0 and Image Tool 3.0 Program. A styloid process longer than 3 cm was identified as an elongated styloid process. RESULTS: The means of length of styloid process, distance between bases and tips of styloid process were 2.58 cm, 6.80 cm and 4.65 cm respectively, while means of anterior and medial angles were 62.45(o) and 74.15(o), respectively. Significant statistical difference was seen in anterior angles between groups with normal and elongated styloid processes (p>0.001). CONCLUSION: Anterior angulation and distance between bases and tips decreased in elongated styloid processes while medial angulation showed no significant change. Our findings highlight the importance of the examination of styloid process in patients with symptoms of stylalgia.

16.
J Clin Diagn Res ; 8(8): AC01-3, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25302179

RESUMO

INTRODUCTION: Knowledge of structural variations around patellofemoral joint has helped to understand postural behavior patterns of various population groups. The biomechanical impact of postures may lead to certain skeletal modifications which may contribute to knee pathologies like patellofemoral arthritis, patellar subluxation and trochlear dysplasia. This study was conducted to report the incidence of skeletal non-metric markers on femur in Indian population and to understand their correlation with some pathologies of patellofemoral joint. The traits studied were Martin's facet, Peritrochlear groove and Supratrochlear facet. MATERIALS AND METHODS: The study material was a collection of 152 adult femora from osteology museum in Department of Anatomy, Maulana Azad Medical College, New Delhi, India, with equal percentage of bones from each side and gender. All bones were evaluated for the above mentioned traits and results were obtained as percentage of incidence and Chi-Square test using SPSS version 17. RESULTS: The data showed that Martin's facet and Peritrochlear groove showed a higher occurrence in male femora. However, Supratrochlear facet was more commonly found in female bones. Martin's facet had an equal incidence on femora of each side while peritrochlear groove and supratrochlear facet had higher percentage of occurrence on right side. Supratrochlear facet revealed significant side variation. CONCLUSION: These data suggest that casual or occupational postures may impose structural adaptations around patell- ofemoral joint. The stress of these postures may have causal,consequential or co-incidental relationship with joint pathologies. The gender, special occupations like sports and genetic predisposition may possibly have a role to play.

17.
Appl Environ Microbiol ; 79(23): 7130-41, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24038688

RESUMO

In aquatic ecosystems, carbon (C) availability strongly influences nitrogen (N) dynamics. One manifestation of this linkage is the importance in the dissolved organic matter (DOM) pool of dissolved organic nitrogen (DON), which can serve as both a C and an N source, yet our knowledge of how specific properties of DOM influence N dynamics are limited. To empirically examine the impact of labile DOM on the responses of bacteria to DON and dissolved inorganic nitrogen (DIN), bacterial abundance and community composition were examined in controlled laboratory microcosms subjected to various combinations of dissolved organic carbon (DOC), DON, and DIN treatments. Bacterial communities that had colonized glass beads incubated in a stream were treated with various glucose concentrations and combinations of inorganic and organic N (derived from algal exudate, bacterial protein, and humic matter). The results revealed a strong influence of C availability on bacterial utilization of DON and DIN, with preferential uptake of DON under low C concentrations. Bacterial DON uptake was affected by the concentration and by its chemical nature (labile versus recalcitrant). Labile organic N sources (algal exudate and bacterial protein) were utilized equally well as DIN as an N source, but this was not the case for the recalcitrant humic matter DON treatment. Clear differences in bacterial community composition among treatments were observed based on terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes. C, DIN, and DON treatments likely drove changes in bacterial community composition that in turn affected the rates of DON and DIN utilization under various C concentrations.


Assuntos
Bactérias/metabolismo , Fenômenos Fisiológicos Bacterianos , Biofilmes , Carbono/metabolismo , Nitrogênio/metabolismo , Rios/microbiologia , Bactérias/classificação , Bactérias/isolamento & purificação , Biota , Compostos Inorgânicos/metabolismo , Compostos Orgânicos/metabolismo
18.
Can J Microbiol ; 58(11): 1316-26, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23145829

RESUMO

Acid mine drainage (AMD) represents a global threat to water resources, and as such, remediation of AMD-impacted streams is a common practice. During this study, we examined bacterial community structure and environmental conditions in a low-order AMD-impacted stream before, during, and after remediation. Bacterial community structure was examined via polymerase chain reaction amplification of 16S rRNA genes followed by denaturing gradient gel electrophoresis. Also, bacterial abundance and physicochemical data (including metal concentrations) were collected and relationships to bacterial community structure were determined using BIO-ENV analysis. Remediation of the study stream altered environmental conditions, including pH and concentrations of some metals, and consequently, the bacterial community changed. However, remediation did not necessarily restore the stream to conditions found in the unimpacted reference stream; for example, bacterial abundances and concentrations of some elements, such as sulfur, magnesium, and manganese, were different in the remediated stream than in the reference stream. BIO-ENV analysis revealed that changes in pH and iron concentration, associated with remediation, primarily explained temporal alterations in bacterial community structure. Although the sites sampled in the remediated stream were in relatively close proximity to each other, spatial variation in community composition suggests that differences in local environmental conditions may have large impacts on the microbial assemblage.


Assuntos
Bactérias/genética , Biodiversidade , Recuperação e Remediação Ambiental , Mineração , Rios/microbiologia , Microbiologia da Água , Ácidos/análise , Bactérias/classificação , Bactérias/efeitos dos fármacos , Carga Bacteriana , Concentração de Íons de Hidrogênio , Metais/análise , Filogenia , RNA Ribossômico 16S/genética , Rios/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/farmacologia
19.
Nat Mater ; 9(7): 555-8, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20453845

RESUMO

Graphene, in addition to its unique electronic and optical properties, reveals unusually high thermal conductivity. The fact that the thermal conductivity of large enough graphene sheets should be higher than that of basal planes of bulk graphite was predicted theoretically by Klemens. However, the exact mechanisms behind the drastic alteration of a material's intrinsic ability to conduct heat as its dimensionality changes from two to three dimensions remain elusive. The recent availability of high-quality few-layer graphene (FLG) materials allowed us to study dimensional crossover experimentally. Here we show that the room-temperature thermal conductivity changes from approximately 2,800 to approximately 1,300 W m(-1) K(-1) as the number of atomic planes in FLG increases from 2 to 4. We explained the observed evolution from two dimensions to bulk by the cross-plane coupling of the low-energy phonons and changes in the phonon Umklapp scattering. The obtained results shed light on heat conduction in low-dimensional materials and may open up FLG applications in thermal management of nanoelectronics.

20.
Nano Lett ; 8(3): 902-7, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18284217

RESUMO

We report the measurement of the thermal conductivity of a suspended single-layer graphene. The room temperature values of the thermal conductivity in the range approximately (4.84+/-0.44)x10(3) to (5.30+/-0.48)x10(3) W/mK were extracted for a single-layer graphene from the dependence of the Raman G peak frequency on the excitation laser power and independently measured G peak temperature coefficient. The extremely high value of the thermal conductivity suggests that graphene can outperform carbon nanotubes in heat conduction. The superb thermal conduction property of graphene is beneficial for the proposed electronic applications and establishes graphene as an excellent material for thermal management.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA