Publications by authors named "Apurba Kalita"

The electrocatalytic water oxidation activity of three copper(II) complexes [Cu(L1H)(L)](ClO) (1), [Cu(L2H)(L)(HO)](ClO) (2) and [Cu(L3H)(L)](ClO) (3) with aryl oxime ligands L1H, L2H and L3H [L1H = 1-(pyridin-2-yl)methanone oxime, L2H = 1-(pyridin-2-yl)ethanone oxime and L3H = 1-(pyridin-2-yl)propanone oxime] was investigated. All the three ligands have in common a pyridyl group attached to the carbon centre of the oxime moiety and differ in the second substituent attached to the carbon centre. Electrochemical investigation of the catalytic activity of complexes 1, 2 and 3 shows that the nature of the substituent attached to the carbon centre has an influence on the catalytic pathway and overall catalytic activity of these complexes.

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The article explores AI and ML's transformative potential in reshaping the radiation therapy landscape. The article navigates through the evolving field of radiation oncology, highlighting the constant influx of information facilitated by advanced imaging techniques. The technical scrutiny of AI's potential within radiation oncology is explored, contrasting definitions by Russell and Norvig with Goel's more insightful perspective.

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Purpose: The current study aims to compare the split x-jaw planning technique of volumetric modulated arc radiotherapy (VMAT) with the traditional open and limited jaw techniques of VAMT in nasopharyngeal carcinoma treatment. The multi-leaf collimators on the varian linear accelerator move on a carriage with a maximum leaf span of 15 cm. Therefore, treatment of larger planning target volumes, such as in nasopharyngeal cancer with traditional open and limited jaw technique, yields compromised dose distribution.

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Article Synopsis
  • The study aimed to evaluate treatment outcomes and patterns of failure in non-metastatic nasopharyngeal carcinoma (NPC) patients who received radiation therapy with or without chemotherapy at a cancer center in northeast India between February 2018 and February 2022.
  • Researchers analyzed the treatment results of 99 patients, focusing on survival rates and the influence of tumor and nodal volumes on prognosis, using statistical methods like the Cox proportional hazards model and ROC analysis.
  • Key findings revealed that 35.4% of patients experienced recurrence, with significant associations between tumor volume and survival outcomes; specifically, both primary tumor and nodal volumes were identified as important independent prognostic indicators for overall and progression-free survival.
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This review explores the difficulties encountered in the management of head and neck cancer (HNC), with special attention to the challenges presented by locoregional recurrences, which impact a substantial number of patients. While maximal surgical resection remains the gold standard for treatment, surgery is often not feasible due to various factors. In such cases, reirradiation has emerged as a potential strategy, albeit with a heightened risk of severe toxicity.

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Purpose This study compares the dosimetry and dose sparing of cardiac substructures in single isocenter and dual isocenter RapidArc™ (Varian Medical Systems, Palo Alto, California, United States) radiotherapy planning for synchronous bilateral breast cancer. Methodology Six synchronous bilateral breast cancer (SBBC) patients received adjuvant radiation with the prescribed dose of 40.05 Gy in 15 fractions to the planning target volume (PTV) without local lymph nodal regions.

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Purpose: The extranodal extension (ENE) in head and neck squamous cell carcinoma (HNSCC) is a potential poor prognostic factor. Clinical ENE (cENE) was incorporated in the HNSCC staging system in the 8th edition of AJCC. There is not much evidence to support the treatment of HNSCC with cN3b with radiotherapy in radical intent.

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Head and neck cancer incidence is relatively higher in north-eastern states than in other parts of India. Intensity-modulated radiotherapy (IMRT) was first introduced in our institute in 2012 to cater the entire north-east. This study attempts to assess the treatment outcomes and prognostic factors of head and neck cancer patients who had been treated with definitive radiotherapy in our institute from 2012 to 2016 using IMRT.

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Purpose: High-grade gliomas are highly fatal disease with poor prognosis despite multimodality management. Inflammatory biomarkers are widely used for prognostication in various solid malignancies to stratify high risk patients. The current research was conducted to investigate whether any change in neutrophil-lymphocyte ratio (NLR) during adjuvant chemoradiotherapy has any prognostic significance in high-grade glioma patients.

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Article Synopsis
  • High-grade gliomas (HGG) are aggressive brain tumors that lead to significant cognitive decline in patients receiving treatment despite advanced care methods.
  • A study involving 53 patients revealed that 56.6% experienced cognitive impairment following treatment, with specific tumor types and treatment factors correlated to this decline.
  • The findings suggest that neurocognitive decline in HGG is influenced by a combination of tumor characteristics, patient factors, and treatment effects, highlighting its multifactorial nature.
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The aim is to retrospectively evaluate the clinical outcomes and prognostic factors in patients of locally advanced nasopharyngeal cancer (NPC) treated with intensity-modulated radiotherapy (IMRT). The northeastern states report relatively more NPC cases in comparison to other states of India. This study is an attempt to assess the treatment outcomes and prognostic factors of locally advanced NPC who had been treated with definitive radiotherapy with or without chemotherapy in our institute from 2012 to 2016 using IMRT.

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Head and neck cancer (HNC) patients undergoing curative radiotherapy (RT) are at risk of malnutrition due to disease process as well as effects of therapy. Identifying the nutritional status of these patients at the earliest, helps to introduce adequate and timely interventions that can improve compliance and outcomes of treatment. Various tools for nutritional assessment in cancer patients have been proposed.

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Background: Almost all the patients receiving curative radiotherapy for head and neck cancer develop radiation dermatitis, which many a times leads to treatment interruption and reduce patient compliance. In this study, we evaluated the effect of potent topical steroid (Betamethasone Valerate 0.1%) cream on acute radiation dermatitis in head and neck cancer patients receiving curative radiotherapy.

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Aim: The aim is to retrospectively evaluate the clinical outcomes and treatment related toxicities in patients of synchronous esophageal and head & neck cancer when treated with definitive radiotherapy with or without concurrent chemotherapy.

Background: Patients of esophageal cancer with a synchronous second primary in head and neck region can be treated with definitive radiotherapy but the clinical outcome has been reported to be poor.

Method And Design: This is a single institutional retrospective study.

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The electrocatalytic water oxidation activity of a copper(ii) complex, 1, [Cu(L1H)(L1)(OH2)](ClO4), with a redox active aryl oxime ligand, L1H [L1H = 1-(pyridin-2-yl) ethanone oxime] has been investigated. Complex 1 shows a remarkably high turnover frequency of ∼100 s-1 in neutral phosphate buffer at about 675 mV overpotential with ∼94% faradaic efficiency. Electrochemical analysis suggests the involvement of a ligand moiety in a proton-coupled-electron-transfer (PCET) step during the catalytic cycle of complex 1, which in turn provides a route for accumulation of high oxidizing equivalents at the reaction center.

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Context: In advanced radiotherapy techniques such as three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT), geometrical uncertainties are very crucial as they may lead to under dosing of tumor and over dosing of the nearby critical structures and hence, it is important to determine planning target volume (PTV) margins which are specific for every center.

Aims: The aim of this study is to determine adequate clinical target volume (CTV) to PTV margins specific to our radiotherapy center.

Settings And Design: To calculate CTV to PTV margins for rectal cancer patients in prone position using kV cone beam CBCT data sets.

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Background: To evaluate the role of sonography (US) in assessing hypopharyngeal carcinoma when compared with CT.

Methods: A randomized prospective study was performed on 40 biopsy-proven cases of hypopharyngeal carcinoma.Contrast-enhanced CT of the neck was performed in all patients, followed by US.

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Copper(II) complex, 1, with the histidine-derived ligand L (L = methyl 2-(2-hydroxybenzylamino)-3-(1H-imidazol-5-yl)propanoate) has been synthesized and characterized. Single-crystal structure determination reveals a diphenolato-bridged dicopper(II) core in 1. Addition of (•)NO to an acetonitrile solution of 1 affords the corresponding mononuclear copper(II)-nitrosyl complex, 2.

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Background: Persistent infection of one or more of about 15 high-risk human papillomaviruses (HR-HPVs), most commonly HPV types 16/18, has a significant role in cervical cancer initiation and progression. There are limited data available from north-east India about HPV prevalence though this region has high incidence rates of cervical cancer. The aim of this study was to investigate the HPV genotypes prevalent in cervical cancer patients of north-east India.

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Four Cu(II) complexes, 1, 2, 3 and 4, are synthesized with ligands, L1, L2, L3 and L4 [L1 = N1,N2-bis((pyridin-2-yl)methyl)ethane-1,2-diamine; L2 = N1,N3-bis((pyridin-2-yl)methyl)propane-1,3-diamine; L3 = N1,N1,N2-tris((pyridin-2-yl)methyl)ethane-1,2-diamine; L4 = N1-((1-methyl-1H-imidazol-2-yl)methyl)-N1,N2-bis((pyridin-2-yl)methyl)ethane-1,2-diamine], respectively, as their perchlorate salts. The complexes were characterized by various spectroscopic techniques as well as single crystal X-ray structure determination. Nitric oxide reactivities of the complexes were studied in acetonitrile as well as methanol solvent.

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Two copper(II) complexes, 1 and 2, of two tridentate N-donor ligands, L(1) and L(2) [L(1) = dansyl derivative of bis-[3-(dimethylamino)-propyl]amine; L(2) = dansyl derivative of dipropylenetriamine] were synthesized and characterized. The quenched fluorescence intensity of complexes 1 and 2, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide.

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The reaction of a Cu(II)-nitrosyl complex (1) with hydrogen peroxide at -20 °C in acetonitrile results in the formation of the corresponding Cu(I)-peroxynitrite intermediate. The reduction of the Cu(II) center was monitored by UV-visible spectroscopic studies. Formation of the peroxynitrite intermediate has been confirmed by its characteristic phenol ring nitration reaction as well as isolation of corresponding Cu(I)-nitrate (2).

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Copper(II) complex, 1, of the bidentate ligand, L [L = bis(2-ethyl-4-methyl-imidazol-5yl)methane] has been synthesized and structurally characterized. Addition of nitric oxide gas to a degassed acetonitrile solution of 1 yielded the corresponding copper(ii)-nitrosyl complex, 2. In acetonitrile, complex 2 on reaction with water afforded the corresponding copper(I)-nitrite complex, 3.

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The nitric oxide reactivity of two copper(II) complexes, 1 and 2 with ligands L(1) and L(2), respectively, [L(1) = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, L(2) = 5,5,7-trimethyl-[1,4]-diazepane] have been studied. The copper(II) center in complex 1 was found to be unreactive toward nitric oxide in pure acetonitrile; however, it displayed reduction in methanol solvent in presence of base. The copper(II) center in 2, in acetonitrile solvent, on exposure to nitric oxide has been found to be reduced to copper(I).

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Two copper complexes, 1 and 2, with tridentate N-donor ligands, L(1) and L(2) [L(1)= (1-methyl-1H-imidazol-2-ylmethyl)-(2-pyridin-2-yl-ethyl)amine, L(2) = (2-pyridin-2-yl-ethyl)-pyridin-2 yl-methylamine] respectively, have been synthesized and characterized. On exposure to nitric oxide, the copper(II) centers in complexes 1 and 2 were found to undergo reduction in various solvents. In acetonitrile solvent the reduction was accompanied by a simultaneous N-nitrosation on the secondary amine center on the ligand frameworks.

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