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Cohesive band structure of carbon nanotubes for applications in quantum transport

Arora VK, Bhattacharyya A

Nanoscale, 2013 Nov 21;5(22):10927-35.
PMID: 24061093 DOI: 10.1039/c3nr03814a

An integrated cohesive band structure of carbon nanotubes (CNTs) applicable to all chirality directions (n, m), starting from the Dirac cone of a graphene nanolayer in k-space, is demarcated, in direct contrast to dissimilar chiral and achiral versions in the published literature. The electron wave state of a CNT is quantized into one-dimensional (1-D) nanostructure with a wrapping mode, satisfying the boundary conditions from one Dirac K-point to an equivalent neighboring one with an identical phase and returning to the same K point. The repetitive rotation for an identical configuration with added band index (n-m)mod3, yields one metallic (M) with zero bandgap corresponding to (n-m)mod3 = 0, semiconducting state SC1 with (n-m)mod3 = 1 and SC2 with (n-m)mod3 = 2. The band gap and effective mass of SC2 state are twice as large as those of SC1 state. A broad-spectrum expression signifying the linear dependence of the effective mass on the bandgap is obtained. Both the Fermi energy and the intrinsic velocity limiting the current to the saturation level is calculated as a function of the carrier concentration. Limitations of the parabolic approximation are pointed out. Several new features of the band structure are acquired in a seamlessly unified mode for all CNTs, making it suitable for all-encompassing applications. Applications of the theory to high-field transport are advocated with an example of a metallic CNT, in agreement with experimental observations. The mechanism behind the breakdown of the linear current-voltage relation of Ohm's law and the associated surge in resistance are explained on the basis of the nonequilibrium Arora's distribution function (NEADF). These results are important for the performance evaluation and characterization of a variety of applications on CNT in modern nanoscale circuits and devices.
Fulltext Contralateral pleural effusion during chemotherapy for tuberculous pleural effusion

Puri MM, Arora VK

Med J Malaysia, 2000 Sep;55(3):382-4.
PMID: 11200723

A 25 year old woman developed a right pleural effusion 6 weeks after commencement of short course chemotherapy for left sided tuberculous pleural effusion. Since the patient improved following continuation of the same treatment, it is presumed to be a case of paradoxical response to anti-tuberculosis treatment.
Fulltext A case of tuberculosis of the thyroid gland

Puri MM, Dougall P, Arora VK

Med J Malaysia, 2002 Jun;57(2):237-9.
PMID: 24326661

We report a case of tuberculosis of the thyroid gland associated with mediastinal lymphadenitis in a 30 years-old male, who presented with dysphagia and a mid line anterior neck swelling. Fine needle aspiration was positive for acid fast bacilli. He made an uneventful recovery with antituberculous drugs. Although seldom observed, tuberculosis should be kept in mind in te differential diagnisis of nodular lesions of the thyroid.
Acinic cell carcinoma of the parotid gland: A diagnostic dilemma on cytology

Sharma A, Ahuja S, Diwaker P, Wadhwa N, Arora VK

Malays J Pathol, 2019 Aug;41(2):191-194.
PMID: 31427555

INTRODUCTION: Acinic cell carcinoma (ACC) represents 1-6% of parotid gland neoplasms.
CASE REPORT: We report cytomorphological features of two uncommon variants of acinic cell carcinoma. The first case was an eleven-year-old female with a nodular mass in parotid and the FNA smears demonstrated a lymphoepithelial lesion composed of epithelial tumour cells with features of acinar cells in a lymphoid background. The second case was a 62-year-old male with a large parotid mass. The FNA smears revealed presence of extracellular, acellular amyloid-like material with tumour cells arranged in follicles.
DISCUSSION: Awareness of cytomorphological features of these unusual variants of acinic cell carcinoma may help to avoid diagnostic pitfall.
Fulltext An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications

Akbari E, Arora VK, Enzevaee A, Ahmadi MT, Saeidmanesh M, Khaledian M, et al.

Beilstein J Nanotechnol, 2014;5:726-34.
PMID: 24991510 DOI: 10.3762/bjnano.5.85

Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs), holds great potential for applications in variety of sensors because of dangling π-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs) and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET) based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding current-voltage (I-V) characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions.