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1.
Environ Pollut ; 341: 122975, 2024 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-37992951

RESUMO

The Himalayan region is adversely affected by the increasing anthropogenic emissions from the adjacent Indo-Gangetic plain. However, source apportionment studies for the Himalayan region that are crucial for estimating CO concentration, are grossly insufficient, to say the least. It is in this context that our study reported here assumes significance. This study utilizes five years (2014-2018) of ground-based observations of eBC and multiple linear regression framework (MLR) to estimate CO and segregate its fossil fuel and biomass emission fractions at a high-altitude (1958 m) site in the Central Himalayas. The results show that MERRA2 always underestimates the observed CO; MOPITT has a high monthly difference ranging from -32% to +57% while WRF-Chem simulations underestimate CO from February to June and overestimate in other months. In contrast, CO estimated from MLR replicates diurnal and monthly variations and estimates CO with an r2 > 0.8 for 2014-2017. The CO predicted during 2018 closely follows the observed variations, and its mixing ratios lie within ±17% of the observed CO. The results reveal a unimodal diurnal variation of CO, COff (ff: fossil fuel) and CObb (bb: biomass burning) governed by the boundary layer evolution and upslope winds. COff has a higher diurnal amplitude (39.1-67.8 ppb) than CObb (5.7-33.5 ppb). Overall, COff is the major contributor (27%) in CO after its background fraction (58%). CObb fraction reaches a maximum (28%) during spring, a period of increased agricultural and forest fires in Northern India. In comparison, WRF-Chem tracer runs underestimate CObb (-38% to -98%) while they overestimate the anthropogenic CO during monsoon. This study thus attempts to address the lack of continuous CO monitoring and the need to segregate its fossil fuel and biomass sources, specifically over the Central Himalayas, by employing a methodology that utilizes the existing network of eBC observations.


Assuntos
Poluentes Atmosféricos , Incêndios Florestais , Poluentes Atmosféricos/análise , Biomassa , Combustíveis Fósseis/análise , Monitoramento Ambiental/métodos , Estações do Ano , Aerossóis/análise , Carbono/análise
2.
QJM ; 116(1): 47-56, 2023 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-36053197

RESUMO

OBJECTIVES: This study aims to describe the demographic and clinical profile and ascertain the determinants of outcome among hospitalized coronavirus disease 2019 (COVID-19) adult patients enrolled in the National Clinical Registry for COVID-19 (NCRC). METHODS: NCRC is an on-going data collection platform operational in 42 hospitals across India. Data of hospitalized COVID-19 patients enrolled in NCRC between 1st September 2020 to 26th October 2021 were examined. RESULTS: Analysis of 29 509 hospitalized, adult COVID-19 patients [mean (SD) age: 51.1 (16.2) year; male: 18 752 (63.6%)] showed that 15 678 (53.1%) had at least one comorbidity. Among 25 715 (87.1%) symptomatic patients, fever was the commonest symptom (72.3%) followed by shortness of breath (48.9%) and dry cough (45.5%). In-hospital mortality was 14.5% (n = 3957). Adjusted odds of dying were significantly higher in age group ≥60 years, males, with diabetes, chronic kidney diseases, chronic liver disease, malignancy and tuberculosis, presenting with dyspnoea and neurological symptoms. WHO ordinal scale 4 or above at admission carried the highest odds of dying [5.6 (95% CI: 4.6-7.0)]. Patients receiving one [OR: 0.5 (95% CI: 0.4-0.7)] or two doses of anti-SARS CoV-2 vaccine [OR: 0.4 (95% CI: 0.3-0.7)] were protected from in-hospital mortality. CONCLUSIONS: WHO ordinal scale at admission is the most important independent predictor for in-hospital death in COVID-19 patients. Anti-SARS-CoV2 vaccination provides significant protection against mortality.


Assuntos
COVID-19 , Adulto , Humanos , Masculino , Pessoa de Meia-Idade , COVID-19/prevenção & controle , SARS-CoV-2 , Mortalidade Hospitalar , Estudos de Tempo e Movimento , Vacinação , Doença Crônica
3.
J Neonatal Perinatal Med ; 15(3): 667-669, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35694937

RESUMO

Melena is reported in 1 of 350 to 400 new-borns. Significant upper gastrointestinal bleeding in a neonate with an antenatally diagnosed abdominal mass has not been reported before. This case highlights an unusual presentation of a gastric teratoma and proposes a probable embryological explanation for the site of occurrence.


Assuntos
Melena , Teratoma , Hemorragia Gastrointestinal , Humanos , Recém-Nascido
5.
J Family Med Prim Care ; 10(5): 1818-1822, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34195109

RESUMO

The COVID-19 pandemic gave an opportunity to adopt many appropriate changes in the behavior of the people in India. The major gears of those behavior changes were the enforcement by the government, fear, motivation (self and induced), and self-experiences or realizations with time. If those changes are fitted in the Trans-Theoretical Model, Indian people have passed through the "Pre-Contemplation" to "Action" stage of behavior changes during different phases of this pandemic. Frequent hand hygiene, maintaining physical distancing, use of face mask, cough etiquettes, avoid greetings through physical contacts, fear in spitting and urination at public places, refrain from gatherings and avoiding outside food are some of the examples of those appropriate behaviors which were enforced or learnt during the COVID pandemic. The continuous lockdown made people understand the difference between "want" and "need," the importance of local production, and the significance of social media and technology in routine life. The work-from-home strategy gave a chance to appreciate the work--life balance in a more applied way. The first-ever lifetime experience of unbelievable rejuvenating nature because of lack of human play taught people to appreciate nature. Although the current focus is on responding to the pandemic and on coping with its immediate effects, yet this is the time when there is an urgent need to create an enabling environment to support and sustain these COVID-19 appropriate behaviors (maintenance stage) to reap the maximum benefits out of them. Sustaining these appropriate behaviors is also important considering the bimodal distribution of the COVID-19 and possibility of advent of the second wave of COVID-19 in near future.

7.
QJM ; 113(8): 556-560, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32609360

RESUMO

BACKGROUND: Duration of persistence of SARS-CoV-2 in the upper respiratory tract of infected individuals has important clinical and epidemiological implications. AIM: We aimed to establish the duration and risk factors for persistence of SARS-CoV-2 in the upper respiratory tract of asymptomatic infected individuals. METHODS: Data of repeat rRT-PCR (real-time reverse transcription-polymerase chain reaction) test done for SARS-CoV-2 infected individuals at our institute at Jodhpur, India were analysed from 19 March to 21 May 2020. Duration of virus persistence was estimated with parametric regression models based on weibull, log-normal, log-logistic, gamma and generalized gamma distributions. Factors associated with prolonged viral persistence were analysed with the best-fitting model. RESULTS: Fifty-one SARS-CoV-2 infected individuals with repeat rRT-PCR test were identified with 44 asymptomatics. The asymptomatic individuals had median virus persistence duration of 8.87 days (95% CI: 7.65-10.27) and 95 percentile duration of 20.70 days (95% CI: 16.08-28.20). The overall median virus persistence including both symptomatic and asymptomatic individuals was found to be 9.18 days (95% CI: 8.04-10.48). Around one-fourth asymptomatics (10/44) demonstrated SARS-CoV-2 persistence beyond 2 weeks. Age <60 years and local transmission were found to be significantly associated with longer virus persistence among asymptomatic individuals on univariate regression but not in multivariate analysis. CONCLUSION: Recommended home isolation duration for SARS-CoV-2 infected individuals in India should be extended from 17 days to at least 3 weeks. Prolonged persistence of SARS-CoV-2 in a considerable proportion of asymptomatic individuals merits attention with regard to ensuring universal infection prevention precautions irrespective of symptomatic status.


Assuntos
Infecções Assintomáticas , Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/virologia , Nasofaringe/virologia , Orofaringe/virologia , Pneumonia Viral/virologia , Adolescente , Adulto , Fatores Etários , Idoso , COVID-19 , Teste para COVID-19 , Técnicas de Laboratório Clínico/métodos , Infecções por Coronavirus/diagnóstico , Infecções por Coronavirus/transmissão , Feminino , Humanos , Índia , Masculino , Pessoa de Meia-Idade , Pandemias , Pneumonia Viral/diagnóstico , Pneumonia Viral/transmissão , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Fatores de Risco , SARS-CoV-2 , Fatores de Tempo , Eliminação de Partículas Virais , Adulto Jovem
8.
Malays Orthop J ; 13(1): 20-24, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31001379

RESUMO

Introduction: Carpal collapse of wrist occurs in disorders like rheumatoid arthritis and Kienbock's disease. Three techniques have been described to measure carpal collapse. First, the carpal height ratio (CHR), measured by dividing carpal height by 3rd metacarpal length. Second, the revised carpal height ratio (RCH ratio), measured by dividing carpal height by length of capitate. Third, capitate radius distance (CR index), measured by shortest distance between distal edge of radius and the proximal edge of capitate. The index publications describe good reliability of all these but which method out of the three is best in terms of intra- and inter-observer variability is not known. The purpose of this study was to find out which method had the least inter- and intra-observer variability for determining carpal collapse. Materials and Methods: Fifty normal wrist postero-anterior radiographs were studied by three assessors who measured CHR, RCH ratio and CR index separately. The measurements were repeated after one month by all the three observers. The results were then statistically analysed. Results: The p-value was <0.001 in all the three assessors in CR index meaning that the intra-observer variability was least in CR index. For the inter-observer variability intra class coefficient of 0.9 indicated that the CR index has the least variability. Conclusion: CR index is the most reproducible method to measure carpal collapse. The method which provides accurate measurement of carpal collapse will allow better staging of carpal disorders.

9.
Artigo em Inglês | WPRIM (Pacífico Ocidental) | ID: wpr-771096

RESUMO

@#Introduction:Carpal collapse of wrist occurs in disorders like rheumatoid arthritis and Kienbock's disease. Three techniques have been described to measure carpal collapse. First, the carpal height ratio (CHR), measured by dividing carpal height by 3rd metacarpal length. Second, the revised carpal height ratio (RCH ratio), measured by dividing carpal height by length of capitate. Third, capitate radius distance (CR index), measured by shortest distance between distal edge of radius and the proximal edge of capitate. The index publications describe good reliability of all these but which method out of the three is best in terms of intra- and inter-observer variability is not known. The purpose of this study was to find out which method had the least inter- and intra-observer variability for determining carpal collapse. Materials and Methods: Fifty normal wrist postero-anterior radiographs were studied by three assessors who measured CHR, RCH ratio and CR index separately. The measurements were repeated after one month by all the three observers. The results were then statistically analysed. Results: The p-value was <0.001 in all the three assessors in CR index meaning that the intra-observer variability was least in CR index. For the inter-observer variability intra class coefficient of 0.9 indicated that the CR index has the least variability. Conclusion: CR index is the most reproducible method to measure carpal collapse. The method which provides accurate measurement of carpal collapse will allow better staging of carpal disorders.

10.
Int J Obes (Lond) ; 42(4): 711-720, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29104286

RESUMO

BACKGROUND/OBJECTIVES: Obesity (body mass index (BMI)⩾30 kg m-2) is associated with an increased risk of estrogen-dependent breast cancer after menopause. Levels of aromatase, the rate-limiting enzyme in estrogen biosynthesis, are elevated in breast tissue of obese women. Recently, the regulation of aromatase by the p53-hypoxia-inducible factor-1α (HIF1α)/pyruvate kinase M2 (PKM2) axis was characterized in adipose stromal cells (ASCs) of women with Li-Fraumeni Syndrome, a hereditary cancer syndrome that predisposes to estrogen-dependent breast cancer. The current study aimed to determine whether stimulation of aromatase by obesity-associated adipokine leptin involves the regulation of the p53-HIF1α/PKM2 axis. SUBJECTS/METHODS: Human breast ASCs were used to characterize the p53-HIF1α/PKM2-aromatase axis in response to leptin. The effect of pharmacological or genetic modulation of protein kinase C (PKC), mitogen-activated protein kinase (MAPK), p53, Aha1, Hsp90, HIF1α and PKM2 on aromatase promoter activity, expression and enzyme activity was examined. Semiquantitative immunofluorescence and confocal imaging were used to assess ASC-specific protein expression in formalin-fixed paraffin-embedded tissue sections of breast of women and mammary tissue of mice following a low-fat (LF) or high-fat (HF) diet for 17 weeks. RESULTS: Leptin-mediated induction of aromatase was dependent on PKC/MAPK signaling and the suppression of p53. This, in turn, was associated with an increase in Aha1 protein expression, activation of Hsp90 and the stabilization of HIF1α and PKM2, known stimulators of aromatase expression. Consistent with these findings, ASC-specific immunoreactivity for p53 was inversely associated with BMI in breast tissue, while HIF1α, PKM2 and aromatase were positively correlated with BMI. In mice, HF feeding was associated with significantly lower p53 ASC-specific immunoreactivity compared with LF feeding, while immunoreactivity for HIF1α, PKM2 and aromatase were significantly higher. CONCLUSIONS: Overall, findings demonstrate a novel mechanism for the obesity-associated increase in aromatase in ASCs of the breast and support the study of lifestyle interventions, including weight management, which may reduce breast cancer risk via effects on this pathway.


Assuntos
Aromatase/metabolismo , Neoplasias da Mama/metabolismo , Leptina/metabolismo , Obesidade/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Adipócitos/metabolismo , Animais , Aromatase/genética , Índice de Massa Corporal , Mama/citologia , Mama/metabolismo , Proteínas de Transporte/metabolismo , Células Cultivadas , Feminino , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Glândulas Mamárias Animais/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Transdução de Sinais , Hormônios Tireóideos/metabolismo , Proteínas de Ligação a Hormônio da Tireoide
11.
J Hand Surg Eur Vol ; 42(2): 170-175, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27289052

RESUMO

This study reports an objective assessment of postoperative function of 11 triple transfers for high radial palsies, using pronator teres for wrist extension, flexor carpi ulnaris for finger extension and palmaris longus for thumb extension. The mean follow-up was 3.3 years. Assessment was done by recording the active ranges of wrist motion, grip strength, wrist and finger strength and work simulation. The mean strength and range of wrist extension were 42% and 86%, respectively, of the contralateral wrist. Other measured movements were within the functional range and work simulation confirmed good restoration of function. The mean DASH score was 3.45, with no patient reporting any specific functional complaints. This study shows that even though the range of wrist motion and the strength of the wrist and fingers are less than normal, hand function remains good. We conclude that the flexor carpi ulnaris set of tendon transfer works well. LEVEL OF EVIDENCE: 3.


Assuntos
Neuropatia Radial/fisiopatologia , Neuropatia Radial/cirurgia , Recuperação de Função Fisiológica/fisiologia , Transferência Tendinosa , Adolescente , Adulto , Feminino , Seguimentos , Força da Mão/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Amplitude de Movimento Articular/fisiologia , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
12.
Environ Sci Pollut Res Int ; 23(5): 4397-410, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26503008

RESUMO

The seasonal, interannual, and long-term variations in biomass burning activity and related emissions are not well studied over South Asia. In this regard, active fire location retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), the retrievals of aerosol optical depth (AOD) from MODIS Terra, and tropospheric column NO2 from Ozone Monitoring Instrument (OMI) are used to understand the effects of biomass burning on the tropospheric pollution loadings over South Asia during 2003-2013. Biomass burning emission estimates from Global Fire Emission Database (GFED) and Global Fire Assimilation System (GFAS) are also used to quantify uncertainties and regional discrepancies in the emissions of carbon monoxide (CO), nitrogen oxide (NOx), and black carbon (BC) due to biomass burning in South Asia. In the Asian continent, the frequency of fire activity is highest over Southeast Asia, followed by South Asia and East Asia. The biomass burning activity in South Asia shows a distinct seasonal cycle that peaks during February-May with some differences among four (north, central, northeast, and south) regions in India. The annual biomass burning activity in north, central, and south regions shows an increasing tendency, particularly after 2008, while a decrease is seen in northeast region during 2003-2013. The increase in fire counts over the north and central regions contributes 24 % of the net enhancement in fire counts over South Asia. MODIS AOD and OMI tropospheric column NO2 retrievals are classified into high and low fire activity periods and show that biomass burning leads to significant enhancement in tropospheric pollution loading over both the cropland and forest regions. The enhancement is much higher (110-176 %) over the forest region compared to the cropland (34-62 %) region. Further efforts are required to understand the implications of biomass burning on the regional air quality and climate of South Asia.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Incêndios , Plantas , Estações do Ano , Aerossóis , Ásia , Biomassa , Clima , Monitoramento Ambiental/instrumentação , Índia , Óxidos de Nitrogênio/análise , Ozônio/análise , Imagens de Satélites
13.
Med J Armed Forces India ; 71(4): 324-9, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26663958

RESUMO

BACKGROUND: Competitive sports training causes structural and conductive system changes manifesting by various electrocardiographic alterations. We undertook this study to assess the prevalence of abnormal ECG in trained Indian athletes and correlate it with the nature of sports training, that is endurance or strength training. METHODS: We evaluated a standard resting, lying 12 lead Electrocardiogram (ECG) in 66 actively training Indian athletes. Standard diagnostic criteria were used to define various morphological ECG abnormalities. RESULTS: 33/66 (50%) of the athletes were undertaking endurance training while the other 33 (50%) were involved in a strength-training regimen. Overall 54/66 (81%) sportsmen had significant ECG changes. 68% of these changes were considered as normal training related features, while the remaining 32% were considered abnormal. There were seven common training related ECG changes-Sinus Bradycardia (21%), Sinus Arrhythmia (16%), 1st degree Atrioventricular Heart Block (6%), Type 1 2nd-degree Atrioventicular Heart Block (3%), Incomplete Right bundle branch block (RBBB) (24%), Early Repolarization (42%), Left Ventricular Hypertrophy (LVH) (14%); while three abnormal ECG changes--T-wave inversion (13%), RBBB(4%), Right ventricular hypertrophy (RVH) with strain (29%) were noted. Early repolarization (commonest change), sinus bradycardia, and incomplete RBBB were the commoner features noticed, with a significantly higher presence in the endurance trained athletes. CONCLUSION: A high proportion of athletes undergoing competitive level sports training are likely to have abnormal ECG recordings. Majority of these are benign, and related to the physiological adaptation to the extreme levels of exertion. These changes are commoner during endurance training (running) than strength training (weightlifting).

14.
J Minim Invasive Gynecol ; 22(6S): S123, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-27678657
16.
Vet Microbiol ; 174(1-2): 239-46, 2014 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-25301283

RESUMO

HoBi-like pestiviruses have been sporadically reported from naturally infected cattle in South America, Asia and Europe. While the closely related bovine viral diarrhoea virus 1 (BVDV-1) and BVDV-2 have been reported from cattle in India, the prevalence and diversity of HoBi-like viruses have not yet been studied. Here we report the genetic diversity and molecular characteristics of HoBi-like viruses, through systematic surveillance in cattle (n=1049) from 21 dairy farms across India during 2012-2013. On the basis of real-time RT-PCR, virus isolation and nucleotide sequencing results, of the 20 pestivirus positive cattle, HoBi-like viruses were identified in 19 cattle from four farms in three states and BVDV-1b in one cattle. Phylogenetic analysis of 5'-UTR and N(pro) region identified the circulation of two lineages of HoBi-like viruses in India, that were distinct to those circulating globally, highlighting the independent evolution of at least three lineages of HoBi-like viruses globally. Antigenic differences were also evident between the two Indian lineages. In addition to revealing that HoBi-like virus may be more widespread in Indian cattle than previously reported, this study shows greater genetic divergence of HoBi-like viruses indicating a need for continued pestivirus surveillance in cattle.


Assuntos
Doença das Mucosas por Vírus da Diarreia Viral Bovina/epidemiologia , Vírus da Diarreia Viral Bovina/isolamento & purificação , Variação Genética , Regiões 5' não Traduzidas/genética , Animais , Sequência de Bases , Bovinos , Indústria de Laticínios , Vírus da Diarreia Viral Bovina/classificação , Vírus da Diarreia Viral Bovina/genética , Índia/epidemiologia , Funções Verossimilhança , Modelos Genéticos , Dados de Sequência Molecular , Testes de Neutralização/veterinária , Filogenia , Prevalência , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Reação em Cadeia da Polimerase Via Transcriptase Reversa/veterinária , Análise de Sequência de DNA/veterinária
17.
Free Radic Res ; 47(11): 941-9, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23668832

RESUMO

Chronic pancreatitis (CP) is characterized by pain, and exocrine and endocrine insufficiency of pancreas. Several hypotheses have been put forward to explain the hitherto partially understood pathophysiology of CP. In the past decade, animal and clinical studies have suggested that an increased chronic oxidative stress (OS) plays a key role in pathophysiology of CP and perpetuates its clinical and histological symptoms (pain and fibrosis-necrosis, respectively). Mounting OS in pancreatic acinar cells is a result of overproduction of free radicals (FR) during xenobiotic metabolism. It has been shown that Phase I cytochrome P450 enzymes of xenobiotic pathway are induced when exposed to a xenobiotic overload including alcohol, tobacco, smoke and other dietary toxins, which exceeds the capacity of Phase II conjugation due to limited glutathione availability. Consequently, there is an overload of toxic metabolites as well as FR. Additionally, bioactivation of subsequently entering compounds may occur increasing their toxicity. Such an imbalance overwhelms the antioxidant capacity of the body resulting in undefended chronic OS that derails the normal physiology of pancreatic acinar cells since FR act as second messengers controlling the cellular signaling. OS hypothesis is further supported by the studies that demonstrated that antioxidant supplementation ameliorated pain. Moreover, animal studies have demonstrated a cessation of fibrotic cascade with antioxidant supplementation. In a recent large randomized controlled trial, it was demonstrated that antioxidant supplementation led to a significant reduction in pain, and also lowered the OS in patients with alcoholic or idiopathic CP.


Assuntos
Antioxidantes/metabolismo , Radicais Livres/metabolismo , Pancreatite Crônica/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Animais , Humanos , Estresse Oxidativo/fisiologia
18.
Lung India ; 29(1): 11-4, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22345907

RESUMO

CONTEXT: Bronchopleural fistula (BPF) is a communication between the pleural space and bronchial tree. MATERIALS AND METHODS: A series of 9 cases are reported where BPF was identified and managed with intrabronchial instillation of glue (N-butyl-cyanoacrylate) through a video bronchoscope. RESULTS: Out of 9 patients the BPF was successfully sealed in 8 cases (88.88%). In 1 patient of postpneumonectomy, the fistula was big, that is >8 mm who had a recurrence after the procedure. In one case of pyopneumothorax the leak reduced slowly and it took us 14 days to remove the intercostal drainage tube. Rest of the patients had a favorable outcome. No complications were observed in a follow-up of 6 months. CONCLUSIONS: In our opinion, it is a cost-effective, viable, and safe alternative compared with costly, time-consuming, and high-risk surgical procedures.

19.
Lab Chip ; 11(23): 4012-21, 2011 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-22028066

RESUMO

This paper presents theoretical analysis, design, simulation, fabrication and test of a microfluidic device ('Micro-hydrocyclone') for separation of micron and submicron size solid particles from liquid in a particle liquid mixture. A theoretical analysis of the micro-hydrocyclone is performed to understand the physics and develop suitable design models. The structure of the proposed device is designed based on the Bradley model, as it offers lower cut-size thus making it suitable for microfluidics applications. The operational parameters are derived from the dimensional group model. The particle separation process inside the micro-hydrocyclone is simulated by solving fluid flows using Navier-Stokes equations and particle dynamics using a Lagrangian approach in a Eulerian fluid. The influence of inlet velocity and density on separation efficiency is investigated. The device is fabricated with SU-8 photoresist on a PMMA substrate using a combination of photolithography and micro-milling. Experiments are performed to demonstrate particle-liquid separation using polystyrene microbeads suspended in PBS as the feed sample. The influence of inlet velocity and particle size on particle separation efficiency is measured and compared with that obtained from simulations and a good match was found. The proposed device can be easily integrated with micro-environments thus it is suitable for lab-on-chip and microsystems development. The device may have applications in chemical analysis, materials research, point-of-care, blood sample preparation and other biomedical applications.


Assuntos
Técnicas Analíticas Microfluídicas/métodos , Desenho de Equipamento , Técnicas Analíticas Microfluídicas/instrumentação , Modelos Teóricos , Tamanho da Partícula , Polimetil Metacrilato/química
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