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588 results on '"Dabrowski, Roman"'

35. Enhanced stability of the nematic phase of 4-pentyl-4ʹ-cyanobiphenyl due to the dispersion of copper nanoparticles.

Author

Srivastava, Geetanjali, Jaiswal, Mayank, Singh, Praveen Kumar, Iqbal, Amir, Dabrowski, Roman, and Dhar, Ravindra

Subjects
COPPER, TRANSITION temperature, NANOPARTICLES, NANOPARTICLE size, MOLECULAR rotation, LYOTROPIC liquid crystals
Abstract

Embedding of nanoparticles in nematic liquid crystalline materials has received huge attention in recent years. In most of the work, nanoparticles decrease nematic-isotropic transition temperature along with an undesired increase in conductivity. Interestingly, there are few reports where nematic-isotropic transition temperature has increased along with improvement in other relevant properties due to presence of ferroelectric and/or functionalised nanoparticles of small size. Here, we are reporting enhanced nematic-isotropic transition temperature of 4-pentyl-4′-cyanobiphenyl (5CB) due to dispersion of metallic copper nanoparticles (CuNPs). Low concentrations (0.2 and 0.5 weight%) of CuNPs have been dispersed in 5CB to prepare nanocomposites. Thermodynamic results on unaligned samples and dielectric results on planar and homeotropic aligned samples show enhancement of isotropic to nematic transition temperature of 5CB in the presence of CuNPs without any substantial change of conductivity. Optical studies show a marginal decrease in the band gap of the dispersed samples as compared to those of the pure 5CB which validates conductivity results. The relaxation frequency corresponding to the rotation of molecules about their short axes has increased due to the presence of CuNPs in the nematic matrix of 5CB. These observed results are useful for the electro-optical applications as well as for fundamental aspects. [ABSTRACT FROM AUTHOR]

Published
2023
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44. Improvement in the electro-optical and electronic properties of the reduced graphene oxide dispersed in a liquid crystalline material 4'-octyl-4-cyano-biphenyl.

Author

Singh, Praveen Kumar, Dubey, Prashant, Dhar, Ravindra, and Dabrowski, Roman

Subjects
DIELECTRIC measurements, ELASTIC constants, THRESHOLD voltage, TRANSITION temperature, ACTIVATION energy
Abstract

Herein, a small concentration (0.05 wt %) of reduced graphene oxide is dispersed in the liquid crystalline media. Thermodynamic study shows the reduction of the transition temperature, enthalpy and entropy of the reduced graphene oxide dispersed nanocomposite. Optical study suggests the decrease of the optical bandgap of the dispersed nanocomposite as compared to that of the pure sample. Dielectric spectroscopic measurement is done for measuring the permittivity and conductivity of the pure and the dispersed samples. The value of dielectric anisotropy has decreased for the dispersed nanocomposite whereas the value of ionic (DC) conductivity of the dispersed nanocomposite has increased by 3 orders of the magnitude as compared to that of the pristine sample. The activation energy for DC conductivity has reduced in the dispersed nanocomposite which is responsible for the increment in DC conductivity of the system. The cut-off region of DC conductivity has increased in the dispersed nanocomposite. Electro-optical studies suggest the reduction of the threshold voltage for the Freedericksz transition, splay elastic constant and rotational viscosity for the dispersed nanocomposite. [ABSTRACT FROM AUTHOR]

Published
2023
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45. Enhancement of the physical parameters due to the dispersion of functionalised gold nanoparticles in a room temperature nematic liquid crystal.

Author

Tripathi, Pratibha, Uttam, Rahul, Kumar, Sandeep, Dabrowski, Roman, and Dhar, Ravindra

Subjects
GOLD nanoparticles, NEMATIC liquid crystals, ELASTIC constants, TRANSITION temperature, THRESHOLD voltage
Abstract

A room temperature nematic liquid crystal (N-3017) mixed with surface-stabilised gold nanoparticles was examined for its thermodynamic, dielectric, and electro-optical properties. The isotropic to nematic transition temperature decreases in both the nanocomposites as compared to that of the pure nematic material, according to thermodynamic findings. In the frequency range of 1 Hz to 40 MHz, dielectric data of both the dispersed nanocomposites in homeotropic and planar aligned samples are collected. The dispersion of capped GNPs enhanced the dielectric anisotropy of the dispersed nanocomposites, according to the dielectric results. As the quantity of capped GNPs in the host matrix increases, the threshold voltage for LC reorientation decreases due to the decreased elastic constant and increased dielectric anisotropy. The dielectric study also signifies a prominent relaxation mode due to the flip-flop motion of the nematic molecules about their short axes. To analyse this mode, experimental data have been fitted with the modified Cole–Cole equation. This removes the parasitic effects in the low- and high-frequency domains. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Changes in serum proteome in canine pyometra

Author

Franco Martínez, Lorena, Horvatić, Anita, Gelemanović, Andrea, Samardžija, Marko, Mrljak, Vladimir, Contreras Aguilar, Maria Dolores, Martínez-Subiela, Silvia, Dabrowski, Roman, and Tvarijonaviciute, Asta

Subjects
endocrine system, tandem mass tag, proteomics, serum, canine pyometra
Abstract

Introduction: Pyometra is the most common disease of the uterus in intact adult bitches after non- pregnant oestrous cycles. This disease can develop a wide range of clinical signs from subclinical to a fatal illness, which could make the early diagnostic of pyometra challenging, especially when there is no vaginal discharge. Objectives: To compare the serum proteome in healthy bitches and bitches with pyometra through a highthroughput quantitative proteomic analysis. The differentially expressed proteins could reflect the physiopathological changes occurring in canine pyometra and may be considered as potential biomarkers of the disease. Methods: Serum sample surplus left after routine serum analysis was used. In any case, additional sample was extracted from dogs for this study. Serum samples from six healthy (H) and six client-owned bitches with pyometra (P) were analysed by Tandem Mass Tags (TMT) analysis. Results: Proteomic analysis quantified 389 proteins in serum. When the two groups were compared, three unique proteins were modulated: keratin type I were down-regulated ; while serotransferrin and immunoglobin A were up- regulated in canine pyometra. Conclusions: There are changes in serum proteome in bitches with pyometra in comparison to healthy ones. Keratin type I, serotransferrin, and immunoglobulin A have potential as biomarkers of diagnosis in this disease.

Published
2021

49. The salivary proteome in canine pyometra

Author

Franco Martínez, Lorena, Horvatić, Anita, Gelemanović, Andrea, Samardžija, Marko, Mrljak, Vladimir, Contreras Aguilar, Maria Dolores, Martínez-Subiela, Silvia, Dabrowski, Roman, and Tvarijonaviciute, Asta

Subjects
Canine pyometra, TMT-based proteomics, Saliva
Abstract

Introduction: Pyometra is the most common disease of the uterus in intact adult bitches. It consists of a suppurative bacterial infection of the uterus which may cause accumulation of inflammatory exudate and produces a variety of clinical manifestations. Objectives: To evaluate the changes in the salivary proteome in bitches with pyometra through a highthroughput quantitative proteomic analysis with the aims to explore whether saliva composition could reflect the physiopathological changes occurring in canine pyometra. Methods: Saliva samples from client-owned dogs were collected for diagnostic purposes, divided into two groups: healthy (H, n=6) and bitches with pyometra (P, n=6), and analysed using Tandem Mass Tags (TMT) - based approach. Results: Proteomic analysis quantified 707 proteins in saliva. Comparison of two groups revealed 16 unique proteins significantly modulated in saliva. According to Protein Analysis Through Evolutionary Relationships (PANTHER) classification tool, these proteins belong to two molecular functions: catalytic activity (80%) and binding (20%). Six different biological processes were involved, being metabolic and cellular process the majoritarian with 39.9 and 33.3% of proteins, respectively. Six biological pathways were involved, being blood coagulation, integrin signalling pathway, and plasminogen activating cascade the most represented with 22.2% of proteins each. Finally, in relation with protein class, 41% were hydrolases, followed by oxidoreductases (25%). Conclusions: There are changes in various proteins in saliva in canine pyometra reflecting different physiopathological changes occurring in this disease. These proteins could be a source of potential non-invasive biomarkers for this disease that should be confirmed in future studies.

Published
2021

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