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1.
Cornea ; 2024 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-38478754

RESUMO

PURPOSE: This study describes the technique of simple limbal epithelial transplantation (SLET) without amniotic membrane grafting (AMG) in limbal stem cell deficiency (LSCD). METHODS: Retrospective, interventional case series of 6 patients who underwent SLET without AMG were included. The procedure followed the standard technique, involving limbal biopsy from the healthy eye, resection of symblephera, and pannus dissection in the affected eye. Following host bed preparation, limbal explants were placed on the bare cornea and secured with fibrin glue. A large-diameter bandage contact lens was applied post surgery. No amniotic membrane was used. Preoperative data, including age, gender, cause of LSCD, best-corrected visual acuity, and previous ocular surgeries, were recorded. Postoperative clinical information, such as the duration of follow-up and recurrence of LSCD, best-corrected visual acuity, and other ocular examination findings, was recorded in an excel sheet. RESULTS: Preoperatively, 2 patients had total LSCD (secondary to a firecracker injury and excision biopsy for ocular surface squamous neoplasia). 4 patients had partial LSCD (3 chemical injuries, 1 firecracker injury). The mean age of participants was 30.67 ± 15.91 years, with a mean follow-up duration of 9.33 ± 8.04 months. Intraoperatively, all patients exhibited a smooth corneal surface after pannus removal. Postoperatively, all limbal explants remained securely attached, with complete corneal epithelialization achieved within 2 to 3 weeks. The ocular surface remained stable throughout, and no recurrence of LSCD was observed in any patient. No loss of explants was seen. CONCLUSIONS: The present series suggests that AMG may not be a necessary step for performing SLET.

2.
Heliyon ; 10(5): e27509, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38468955

RESUMO

Several deep-learning assisted disease assessment schemes (DAS) have been proposed to enhance accurate detection of COVID-19, a critical medical emergency, through the analysis of clinical data. Lung imaging, particularly from CT scans, plays a pivotal role in identifying and assessing the severity of COVID-19 infections. Existing automated methods leveraging deep learning contribute significantly to reducing the diagnostic burden associated with this process. This research aims in developing a simple DAS for COVID-19 detection using the pre-trained lightweight deep learning methods (LDMs) applied to lung CT slices. The use of LDMs contributes to a less complex yet highly accurate detection system. The key stages of the developed DAS include image collection and initial processing using Shannon's thresholding, deep-feature mining supported by LDMs, feature optimization utilizing the Brownian Butterfly Algorithm (BBA), and binary classification through three-fold cross-validation. The performance evaluation of the proposed scheme involves assessing individual, fused, and ensemble features. The investigation reveals that the developed DAS achieves a detection accuracy of 93.80% with individual features, 96% accuracy with fused features, and an impressive 99.10% accuracy with ensemble features. These outcomes affirm the effectiveness of the proposed scheme in significantly enhancing COVID-19 detection accuracy in the chosen lung CT database.

3.
Sci Rep ; 14(1): 7336, 2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38538667

RESUMO

Electric vehicles (EVs) have become an attractive alternative to IC engine cars due to the increased interest in lowering the consumption of fossil fuels and pollution. This paper presents the design and simulation of a 4 kW solar power-based hybrid EV charging station. With the increasing demand for electric vehicles and the strain they pose on the electrical grid, particularly at fast and superfast charging stations, the development of sustainable and efficient charging infrastructure is crucial. The proposed hybrid charging station integrates solar power and battery energy storage to provide uninterrupted power for EVs, reducing reliance on fossil fuels and minimizing grid overload. The system operates using a three-stage charging strategy, with the PV array, battery bank, and grid electricity ensuring continuous power supply for EVs. Additionally, the system can export surplus solar energy to the grid, reducing the load demand. The paper also discusses the use of MPPT techniques, PV cell modeling, and charge controller algorithms to optimize the performance of the hybrid charging station.

4.
Indian J Ophthalmol ; 71(9): 3203-3209, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37602609

RESUMO

Purpose: Outcome of topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software-"Bharat Protocol." Methods: Retrospective case record review of 30 eyes of 17 patients of stage 1-3 keratoconus who underwent the procedure was performed. Data collected were for visual acuity, distortion-induced eye pain, and keratometry. Pachymetry, lower order and higher order aberrations, spherical aberrations, and topographic cylinder were documented from by Scheimpflug imaging (Pentacam 70700: Oculus, Wetzlar, Germany). Results: At a minimum follow-up of 6 months (range 6.2-13 months), there was significant improvement in UCVA (P < 0.00001), BCVA (P = 0.0061), decrease in Kmax (P = 0.0349), Ksteep (P < 0.0411), Kflat (P = 0.0099), and pachymetry (P = 0.0001). Significant improvement was also seen in distortion-induced eye pain (27/30 to 2/30; P < 0.00001). A more than two-line improvement in UCVA and BCVA was seen in 23/30 and 17/30 cases, respectively. Ectasia was stabilized in all cases at the last follow-up, and no complications were seen. Conclusions: The "Bharat" Protocol to arrest keratectasia progression and improve corneal regularity is a safe and efficacious alternative as a keratoconus management option. This is the first such study on Nidek Platform for the same.


Assuntos
Ceratocone , Humanos , Ceratocone/diagnóstico , Ceratocone/tratamento farmacológico , Ceratocone/cirurgia , Projetos Piloto , Dor Ocular , Estudos Retrospectivos , Córnea/cirurgia
5.
Indian J Ophthalmol ; 71(7): 2885-2888, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37417139

RESUMO

This article describes 1-year outcomes of a new intra-ocular implant, "Glauco-Claw," in refractory chronic angle-closure glaucoma (ACG). Glauco-Claw is a novice polymethylmethacrylate implant with a central ring and five claws placed circumferentially. It was placed in the anterior chamber and the peripheral iris was tucked into the claws, thus causing goniosynechialysis and preventing the reformation of goniosynechiae. It was implanted in five eyes of five patients, and they were followed up for 1 year. Target intra-ocular pressure was achieved and maintained in all the patients till the last follow-up. Two patients did not require any anti-glaucoma medication. No significant complications were observed in any patient. Glauco-Claw could be another armamentarium in the management of refractory chronic ACG.


Assuntos
Glaucoma de Ângulo Fechado , Glaucoma , Doenças da Íris , Humanos , Glaucoma de Ângulo Fechado/diagnóstico , Glaucoma de Ângulo Fechado/cirurgia , Glaucoma de Ângulo Fechado/complicações , Iris/cirurgia , Glaucoma/complicações , Pressão Intraocular , Doenças da Íris/complicações
6.
Indian J Ophthalmol ; 71(5): 2247-2250, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-37202961

RESUMO

We report the outcomes of a custom-designed toric piggyback intraocular lens in a patient with high postoperative residual astigmatism. A 60-year-old male patient underwent customized toric piggyback IOL for postoperative residual astigmatism of 13 D, with follow-up examinations for IOL stability and refractive outcomes. The refractive error stabilized at two months and remained stable at one year, with a correction of nearly 9 D of astigmatism. The IOP remained within normal limits, and there were no postoperative complications. The IOL remained stable in the horizontal position. To our knowledge, this is the first case report of correction of unusually high astigmatism by a novel smart toric design of piggyback IOL.


Assuntos
Astigmatismo , Implante de Lente Intraocular , Lentes Intraoculares , Humanos , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias , Astigmatismo/etiologia , Astigmatismo/cirurgia , Erros de Refração , Implante de Lente Intraocular/efeitos adversos , Lentes Intraoculares/efeitos adversos , Facoemulsificação/métodos , Acuidade Visual , Refração Ocular
7.
Sci Rep ; 13(1): 7051, 2023 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-37120640

RESUMO

Malignant cancer angiogenesis has historically attracted enormous scientific attention. Although angiogenesis is requisite for a child's development and conducive to tissue homeostasis, it is deleterious when cancer lurks. Today, anti-angiogenic biomolecular receptor tyrosine kinase inhibitors (RTKIs) to target angiogenesis have been prolific in treating various carcinomas. Angiogenesis is a pivotal component in malignant transformation, oncogenesis, and metastasis that can be activated by a multiplicity of factors (e.g., VEGF (Vascular endothelial growth factor), (FGF) Fibroblast growth factor, (PDGF) Platelet-derived growth factor and others). The advent of RTKIs, which primarily target members of the VEGFR (VEGF Receptor) family of angiogenic receptors has greatly ameliorated the outlook for some cancer forms, including hepatocellular carcinoma, malignant tumors, and gastrointestinal carcinoma. Cancer therapeutics have evolved steadily with active metabolites and strong multi-targeted RTK inhibitors such as E7080, CHIR-258, SU 5402, etc. This research intends to determine the efficacious anti-angiogenesis inhibitors and rank them by using the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE- II) decision-making algorithm. The PROMETHEE-II approach assesses the influence of growth factors (GFs) in relation to the anti-angiogenesis inhibitors. Due to their capacity to cope with the frequently present vagueness while ranking alternatives, fuzzy models constitute the most suitable tools for producing results for analyzing qualitative information. This research's quantitative methodology focuses on ranking the inhibitors according to their significance concerning criteria. The evaluation findings indicate the most efficacious and idle alternative for inhibiting angiogenesis in cancer.


Assuntos
Inibidores da Angiogênese , Neoplasias Gastrointestinais , Criança , Humanos , Inibidores da Angiogênese/farmacologia , Inibidores da Angiogênese/uso terapêutico , Fator A de Crescimento do Endotélio Vascular/metabolismo , Fatores de Crescimento do Endotélio Vascular , Receptores de Fatores de Crescimento do Endotélio Vascular/uso terapêutico , Fator de Crescimento Derivado de Plaquetas/metabolismo , Fatores de Crescimento de Fibroblastos/uso terapêutico , Neovascularização Patológica/metabolismo
8.
Indian J Ophthalmol ; 71(3): 994-995, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36872724

RESUMO

Ong speculum is used in glaucoma surgeries such as trabeculectomy to expose the superior part of the globe. The large inferior blade pushes the inferior conjunctival fornix, due to which the eyeball rotates downwards. It has not been used in other anterior segment surgeries before. We used this speculum in simple limbal epithelial transplantation (SLET) and pterygium surgery to expose superior bulbar conjunctiva for harvesting limbal and conjunctival grafts, respectively. As the superior conjunctiva and sclera become exposed, it facilitates the steps of harvesting limbal biopsy and conjunctival graft in SLET and pterygium surgery. This eliminated the need for a superior rectus suture or an assistant who would keep the globe rotated downwards. Its position could also be maneuvered to adjust the site of exposure when dissecting the area of pannus in SLET. Thus, it makes the superior conjunctiva more accessible.


Assuntos
Pterígio , Humanos , Túnica Conjuntiva , Biópsia , Procedimentos Neurocirúrgicos , Instrumentos Cirúrgicos
9.
Indian J Ophthalmol ; 71(3): 996-998, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36872725

RESUMO

A novel simulation model (without using human corneas) has been described for understanding the surgical concepts and developing tactile reflexes of Descemet membrane (DM) endothelium scroll manipulation and orientation in the anterior chamber, which are necessary for performing Descemet membrane endothelial keratoplasty (DMEK). Termed the "DMEK aquarium," this model helps facilitate the understanding of different maneuvers of the DM graft needed inside the fluid-filled anterior chamber, like unrolling or unfolding, flipping or inversion, and checking orientation and centration in the host cornea. A stepwise plan for surgeons starting to learn DMEK utilizing various available resources is also suggested.


Assuntos
Transplante de Córnea , Mergulho , Humanos , Lâmina Limitante Posterior , Córnea , Aprendizagem
10.
Cornea ; 42(6): 739-743, 2023 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-36977127

RESUMO

PURPOSE: The objective of this report is to describe a modification of a previously reported technique with an aim of improving the corneal topography and visual outcomes in progressive keratoconus along with stabilization of ectasia. METHOD: In a 26-year-old man with progressive keratoconus, corneal collagen cross-linking was performed in one eye. The other eye had a keratometry of 69.6 D and thinnest pachymetry of 397 µm for which a customized Bowman-stromal inlay surgery was performed. The technique involved the harvesting of Bowman-stromal inlay (anterior 180-µm human donor cornea having the Bowman's layer and anterior stroma) using the femtosecond laser and central ablation of this inlay was done on the stromal side using an excimer laser. This customized inlay was placed in the anterior stromal pocket of the patient's cornea using a regular intraocular lens injector. RESULTS: Stabilization of keratoconus could be achieved in the present case along with improvement in the corrected distance visual acuity and pachymetry. Maximum keratometry decreased from 69.6 D to 57.3 D. CONCLUSIONS: Customized Bowman-stromal inlay technique appears to be a step towards creating an ideal inlay for the keratoconus cornea.


Assuntos
Ceratocone , Masculino , Humanos , Adulto , Ceratocone/cirurgia , Substância Própria/cirurgia , Córnea/cirurgia , Acuidade Visual , Topografia da Córnea , Reagentes de Ligações Cruzadas , Fármacos Fotossensibilizantes , Riboflavina
11.
Mycoses ; 66(6): 515-526, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36790120

RESUMO

BACKGROUND: The aetiology of the major outbreak of COVID-19-associated mucormycosis (CAM) in India in spring 2021 remains incompletely understood. Herein, we provide a multifaceted and multi-institutional analysis of clinical, pathogen-related, environmental and healthcare-related factors during CAM outbreak in the metropolitan New Delhi area. METHODS: We reviewed medical records of all patients diagnosed with biopsy-proven CAM (n = 50) at 7 hospitals in the New Delhi, and NCR area in April-June 2021. Two multivariate logistic regression models were used to compare clinical characteristics of CAM cases with COVID-19-hospitalised contemporary patients as controls (n = 69). Additionally, meteorological parameters and mould spore concentrations in outdoor air were analysed. Selected hospital fomites were cultured. Mucorales isolates from CAM patients were analysed by ITS sequencing and whole-genome sequencing (WGS). RESULTS: Independent risk factors for CAM identified by multivariate analysis were previously or newly diagnosed diabetes mellitus, active cancer and severe COVID-19 infection. Supplemental oxygen, remdesivir therapy and ICU admission for COVID-19 were associated with reduced CAM risk. The CAM incidence peak was preceded by an uptick in environmental spore concentrations in the preceding 3-4 weeks that correlated with increasing temperature, high evaporation and decreasing relative humidity. Rhizopus was the most common genus isolated, but we also identified two cases of the uncommon Mucorales, Lichtheimia ornata. WGS found no clonal population of patient isolates. No Mucorales were cultured from hospital fomites. CONCLUSIONS: An intersection of host and environmental factors contributed to the emergence of CAM. Surrogates of access to advanced COVID-19 treatment were associated with lower CAM risk.


Assuntos
COVID-19 , Mucormicose , Humanos , Mucormicose/tratamento farmacológico , Tratamento Farmacológico da COVID-19 , COVID-19/epidemiologia , COVID-19/complicações , Fatores de Risco , Surtos de Doenças , Índia/epidemiologia
12.
Indian J Ophthalmol ; 71(1): 281-286, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36588252

RESUMO

This article reports a novel surgical technique of partial-thickness compression sutures without descemetopexy with air or gas for the management of acute hydrops in keratoconus. Two patients presented with localized corneal edema with a Descemet membrane (DM) tear in the left eye. Tomography of the right eye revealed localized steepening with increased maximum keratometry and decreased central pachymetry. They were diagnosed with keratoconus in the right eye and acute corneal hydrops (ACH) in the left eye. Compression sutures were passed through the stroma without touching the DM. The anterior chamber was not entered at all at any point during the surgery. Resolution of edema was noted intraoperatively itself. Further resolution of edema was noted from the first postoperative day which markedly reduced within the first week. A corneal scar with no edema was seen at six weeks. In both the patients, vision at presentation was counting fingers close to face which improved to 20/60 and 20/50, respectively, at the last visit.


Assuntos
Edema da Córnea , Ceratocone , Humanos , Ceratocone/complicações , Ceratocone/diagnóstico , Ceratocone/cirurgia , Lâmina Limitante Posterior/cirurgia , Doença Aguda , Edema , Edema da Córnea/diagnóstico , Edema da Córnea/etiologia , Edema da Córnea/cirurgia , Suturas
13.
IJID Reg ; 3: 44-53, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35720143

RESUMO

Objective: To gain better insight into the extent of secondary bacterial and fungal infections in hospitalized patients in India, and to assess how these alter the course of coronavirus disease 2019 (COVID-19) so that control measures can be suggested. Methods: In this retrospective, multicentre study, the data of all patients who tested positive for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) on reverse transcriptase polymerase chain reaction (RT-PCR), admitted to hospital between March 2020 and July 2021, were accessed from the electronic health records of a network of 10 hospitals across five states in North India. Results: Of 19,852 patients testing positive for SARS-CoV-2 on RT-PCR and admitted to the study hospitals during the study period, 1940 (9.8%) patients developed secondary infections (SIs). Patients with SIs were, on average, 8 years older than patients without SIs (median age 62.6 vs 54.3 years; P<0.001). The risk of SIs was significantly (P<0.001) associated with age, severity of disease at admission, diabetes, admission to the intensive care unit (ICU), and ventilator use. The most common site of infection was urine (41.7%), followed by blood (30.8%) and sputum/bronchoalveolar lavage/endotracheal fluid (24.8%); the least common was pus/wound discharge (2.6%). Gram-negative bacilli (GNB) were the most common organisms (63.2%), followed by Gram-positive cocci (GPC) (19.6%) and fungi (17.3%). Most patients with SIs were on multiple antimicrobials. The most commonly used antibiotics against GNB were beta-lactam/beta-lactamase inhibitors (76.9%), carbapenems (57.7%), cephalosporins (53.9%), and antibiotics against carbapenem-resistant Enterobacteriaceae (47.1%). Empirical use of antibiotics against GPC was seen in 58.9% of patients with SIs, and empirical use of antifungals was observed in 56.9% of patients with SIs. The average length of hospital stay for patients with SIs was almost twice as long as that of patients without SIs (median 13 vs 7 days). Overall mortality among patients with SIs (40.3%) was more than eight times higher than that among patients without SIs (4.6%). Only 1.2% of patients with SIs with mild COVID-19 at admission died, compared with 17.5% of those with moderate COVID-19 at admission and 58.5% of those with severe COVID-19 at admission (P<0.001). The mortality rate was highest in patients with bloodstream infections (49.8%), followed by those with hospital-acquired pneumonia (47.9%), urinary tract infections (29.4%), and skin and soft tissue infections (29.4%). The mortality rate in patients with diabetes with SIs was 45.2%, compared with 34.3% in those without diabetes (P<0.001). Conclusions: SIs complicate the course of patients hospitalized with COVID-19. These patients tend to have a much longer hospital stay, a higher requirement for oxygen and ICU care, and a significantly higher mortality rate compared with those without SIs. The groups most vulnerable to SIs are patients with more severe COVID-19, elderly patients and patients with diabetes. Judicious empirical use of combination antimicrobials in these groups of vulnerable patients can save lives. It is desirable to have region- or country-specific guidelines for appropriate use of antibiotics and antifungals to prevent their overuse.

14.
Clin Gastroenterol Hepatol ; 20(8): 1795-1802.e2, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-33662594

RESUMO

OBJECTIVE: There has been increased interest in interventions to promote hepatocellular carcinoma (HCC) surveillance given low utilization and high proportions of late stage detection. Accurate prediction of patients likely versus unlikely to respond to interventions could allow a cost-effective approach to outreach and facilitate targeting more intensive interventions to likely non-responders. DESIGN: We conducted a secondary analysis of a randomized clinical trial evaluating a mailed outreach strategy to promote HCC surveillance among 1200 cirrhosis patients at a safety-net health system between December 2014 and March 2017. We developed regularized logistic regression (RLR) and gradient boosting machine (GBM) algorithm models to predict surveillance completion during each of the 3 screening rounds in a training set (n = 960). Model performance was assessed using multiple performance metrics in an independent test set (n = 240). RESULTS: Among 1200 patients, surveillance was completed in 41-47% of patients over the three rounds. The RLR and GBM models demonstrated good discriminatory accuracy, with area under receiver operating characteristic (AUROC) curves of 0.67 and 0.66 respectively in the first surveillance round and improved to 0.77 by the third surveillance round after incorporating prior screening behavior as a feature. Additional performance characteristics including the Brier score, Hosmer-Lemeshow test and reliability diagrams were also evaluated. The most important variables for the predictive model were prior screening completion status and past primary care contact. CONCLUSIONS: Predictive models can help stratify patients' likelihood to respond to surveillance outreach invitations, facilitating tailored strategies to maximize effectiveness and cost-effectiveness of HCC surveillance population health programs.


Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Carcinoma Hepatocelular/complicações , Carcinoma Hepatocelular/diagnóstico , Carcinoma Hepatocelular/epidemiologia , Humanos , Cirrose Hepática/complicações , Cirrose Hepática/diagnóstico , Neoplasias Hepáticas/complicações , Neoplasias Hepáticas/diagnóstico , Neoplasias Hepáticas/epidemiologia , Programas de Rastreamento , Reprodutibilidade dos Testes
17.
Food Chem ; 369: 130983, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34500208

RESUMO

In this study, date syrup waste extract (DSWE) (15 wt%) and different content of silver doped sepiolite hybrid (Ag-Sep, 0.25-3 wt%) were incorporated into gelatin matrix to develop a series of active composite packaging films. Incorporating 2 wt% of Ag-Sep increased the modulus of blend film by 98% compared to unmodified gelatin/DSWE blend film. The active gelatin composite film exhibited superior active compounds migration to aqueous food simulants. Besides, Ag-Sep provided a tortuous pathway to the composite film, resulting in high 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition efficiency (91%) and slow-release kinetics of active compounds to the food simulant. The Ag-Sep hybrid was improved the antimicrobial property of the gelatin/DSWE blend film against both gram-negative and gram-positive microbes. Thus, this study demonstrated that the Ag-Sep hybrid exhibits significant properties in the active gelatin composite films, implying that this hybrid could be an effective additive for various active packaging films.


Assuntos
Embalagem de Alimentos , Gelatina , Silicatos de Magnésio , Extratos Vegetais , Prata
18.
J Cataract Refract Surg ; 47(12): e49-e55, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34846349

RESUMO

A simple approach for transplanting Bowman layer and anterior stroma Bowman-stromal inlay (BSI) in keratoconic patients as an intervention to cease progression of ectasia and increase the overall thickness is described. A femtosecond laser was used to create BSI from human eye bank donor corneas and form an intrastromal pocket in the host cornea. The inlay was placed in the intrastromal space using an intraocular lens injector. This technique was performed successfully in 10 eyes of patients with progressive corneal ectasia. Postoperatively, the increased host pachymetry was as per BSI thickness. The tomography parameters remained stable, suggesting stabilization of keratoconus over a mean 15.9 months of follow-up. The BSI may offer a technically easy and safe technique of stromal augmentation to arrest keratoconus progression. It also opens up the possibility of surface ablation in the future for visual rehabilitation.


Assuntos
Transplante de Córnea , Ceratocone , Lentes Intraoculares , Substância Própria/cirurgia , Topografia da Córnea , Humanos , Ceratocone/cirurgia , Refração Ocular
20.
J Nanosci Nanotechnol ; 21(11): 5569-5582, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-33980366

RESUMO

The presence of microcapacitors near percolatrion threshold determines dielectric permittivity of a material. Motivated by this concept, we focused our work by preferentially allocating functionalized reduced graphene oxide (FRGO) in hard segment (disperse phase) of Thermoplastic polyurethane (TPU) by solution blending method and characterized. Morphological studies of TPU/FRGO nanocomposites established homogeneous dispersion of FRGO throughout the TPU matrix. It is noted that TPU/FRGO (1 phr) nanocomposites exhibit maximum increase in tensile strength (33%) and elongation at break (10%). Thermogravimetric analysis (TGA) showed maximum enhancement in onset of decomposition temperature (~6 °C) in 2 phr FRGO loaded TPU. Differential scanning calorimetry (DSC) analysis showed maximum reduction (~2 °C) in glass transition temperature (Tg) of soft segment of TPU followed by maximum improvements in melting temperature (~4 °C) as well as crystallization temperature (~22 °C) of hard segment compared to neat TPU. Further, a significantly high value of dielectric permittivity (401) is achieved in 1.5 phr loaded FRGO at 100 Hz due to the formation of significantly higher number of microcapacitors near the percolation threshold. It is anticipated that such thermally stable and mechanically strong high dielectric TPU/FRGO nanocomposites can find applications in the field of electronic devices.

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