Publications by authors named "Somnath Ghosh"

54 Publications

Nitric oxide monooxygenation (NOM) reaction of cobalt-nitrosyl {Co(NO)} to Co-nitrito {Co(NO)}: base induced hydrogen gas (H) evolution.

Chem Sci 2020 Apr 24;11(19):5037-5042. Epub 2020 Apr 24.

Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati 517507 India

Here, we report the nitric oxide monooxygenation (NOM) reactions of a Co-nitrosyl complex (, {Co-NO}) in the presence of mono-oxygen reactive species, , a base (OH, tetrabutylammonium hydroxide (TBAOH) or NaOH/15-crown-5), an oxide (O or NaO/15-crown-5) and water (HO). The reaction of with OH produces a Co-nitrito complex {, (Co-NO)} and hydrogen gas (H), the formation of a putative N-bound Co-nitrous acid intermediate (, {Co-NOOH}). The homolytic cleavage of the O-H bond of proposed [Co-NOOH] releases H a presumed Co-H intermediate. In another reaction, generates Co-NO when reacted with O an expected Co-nitro () intermediate. However, complex is found to be unreactive towards HO. Mechanistic investigations using N-labeled-NO and H-labeled-NaOH (NaOD) evidently revealed that the N-atom in Co-NO and the H-atom in H gas are derived from the nitrosyl ligand and OH moiety, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0sc01572eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159239PMC
April 2020

Baseline Optical Coherence Tomography Parameters That May Influence 6 Months Treatment Outcome of Polypoidal Choroidal Vasculopathy Eyes with Combination Therapy: A Short-Term Pilot Study.

Int J Environ Res Public Health 2021 05 18;18(10). Epub 2021 May 18.

Department of Ophthalmology, Hospital Shah Alam, Persiaran Kayangan, Seksyen 7, Shah Alam 40000, Malaysia.

Although optical coherence tomography (OCT) parameters have assisted in the diagnosis of polypoidal choroidal vasculopathy (PCV), its potential to evaluate treatment outcomes has not been established. The purpose of this pilot study was to evaluate baseline OCT parameters that may influence treatment outcome in PCV eyes with combination therapy. In this single-centered, prospective study, patients were recruited with at least one treatment-naïve PCV eye and treated with combination therapy of intravitreal anti-vascular endothelial growth factor and photodynamic therapy. Best-corrected distance and near visual acuity (DVA and NVA), and contrast sensitivity (CS) were recorded at baseline and six months after treatment. OCT parameters were determined. Twenty-six eyes of 26 patients aged between 51 to 83 years were evaluated. In eyes that had disrupted external limiting membrane (ELM), photoreceptors inner and outer segment (IS-OS) junction at 1000 micron of fovea at baseline showed low mean visual functions after 6 months of treatment. Eyes with foveal sub-retinal fluid (SRF) and polyp at central 1000 micron of fovea at baseline showed significantly worse DVA and CS after six months. Thus, the presence of foveal SRF, foveal polyp, disrupted ELM, and IS-OS junction at baseline significantly influenced the six months' visual outcome in PCV eyes treated with combination therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijerph18105378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8158141PMC
May 2021

On-Board Ship Detection for Medium Resolution Optical Sensors.

Sensors (Basel) 2021 Apr 28;21(9). Epub 2021 Apr 28.

U.R. Rao Satellite Centre, Bengaluru 560017, India.

In recent years there has been an increased interest in ocean surveillance. The activity includes control and monitoring of illegal fisheries, manmade ocean pollution and illegal sea traffic surveillance, etc. The key problem is how to identify ships and ship-like objects accurately and in a timely manner. In this context, currently, many solutions have been proposed based on high resolution optical and radar remote sensing systems. Most often, these systems suffer from two major limitations viz., limited swath, thereby requiring multiple satellites to cover the region of interest and huge volumes of data being transmitted to ground, even though effective per-pixel information content is minimal. Another limitation is that the existing systems are either simulated on ground or built using the non-space qualified/Commercial Of-The-Shelf (COTS) components. This paper proposes an efficient on-board ship detection system/package connected with medium resolution wide swath optical camera. The methodology adopted has three major components, viz., onboard data processing for improving the radiometric fidelity, followed by a ship detection using modified Constant False Alarm Rate algorithm (CFAR) and a false alarm suppression module to mask false identifications. Finally, the package outputs only the locations of the ships, which is transmitted to the ground. The proposed system reduces the effective volume of data to be transmitted and processed on ground and also significantly cuts down the turnaround time for achieving the end objective. The system is built on radiation hardened Field Programmable Gate Array (FPGA) devices to meet the various engineering constraints such as real-time performance, limited onboard power, radiation hardness, handling of multiple custom interfaces etc. The system is tested with one of the medium resolution Multispectral Visual and Near Infra-Red (MX-VNIR) sensor having a spatial resolution of around 50 m and swath of around 500 Kms, which would be flown with one of the upcoming satellites. The systems performance is also verified on ground with Indian Remote Sensing (IRS) Satellite's Resourcesat's Advanced Wide Field Sensor (AWiFS) data and the results are found to be quite encouraging as well as meeting the mission objectives.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/s21093062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8125028PMC
April 2021

Visual Parameters and Retinal Morphology for Polypoidal Choroidal Vasculopathy Pre- and Post-Intravitreal Ranibizumab with or without Photodynamic Therapy: A Short-Term Prospective Study.

Int J Environ Res Public Health 2021 03 4;18(5). Epub 2021 Mar 4.

Department of Ophthalmology, Hospital Shah Alam, Persiaran Kayangan, Seksyen 7, Shah Alam 40000, Malaysia.

The objective of this study was to compare visual parameters and retinal layers' morphology pre-treatment (baseline) and 6 months post-treatment in polypoidal choroidal vasculopathy (PCV) eyes. A single centre, longitudinal, prospective study was conducted at a public tertiary hospital of Malaysia. Visual parameters including distance and near visual acuity (DVA and NVA), contrast sensitivity (CS), reading speed (RS), and different qualitative and quantitative optical coherence tomography (OCT) parameters were evaluated pre- and 6 months post-treatment. Thirty-three naïve PCV eyes of 32 patients (mean age of 67.62 years) were evaluated pre- and post-treatment of intravitreal ranibizumab with and without photodynamic therapy. After treatment, sub retinal fluid decreased from 27 eyes (84.35%) at baseline to 7 eyes (21.88%) at 6 months while pigment epithelium detachment decreased from 32 eyes (100%) at base line to 15 eyes (46.87%) at 6 months. Mean pre-treatment quantitative morphological OCT retinal parameters including thickness and volume of central sub field, center thickness, center minimum, and maximum thickness reduced significantly. Similarly, all visual parameters including DVA, NVA, CS, and RS showed statistically significant improvement. While 89% of the eyes showed improvement in CS, 78%, 71%, and 65% of the eyes showed improvement in NVA, RS, and DVA, respectively. Thus, CS was the most treatment responsive visual parameter.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijerph18052581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7967335PMC
March 2021

Activation of DNA damage response signaling in mammalian cells by ionizing radiation.

Free Radic Res 2021 Jan 27:1-14. Epub 2021 Jan 27.

Radiation Signaling Group, Radiation Biology and Health Science Division, Bhabha Atomic Research Centre, Mumbai, India.

Cellular responses to DNA damage are fundamental to preserve genomic integrity during various endogenous and exogenous stresses. Following radiation therapy and chemotherapy, this DNA damage response (DDR) also determines development of carcinogenesis and therapeutic outcome. In humans, DNA damage activates a robust network of signal transduction cascades, driven primarily through phosphorylation events. These responses primarily involve two key non-redundant signal transducing proteins of phosphatidylinositol 3-kinase-like (PIKK) family - ATR and ATM, and their downstream kinases (hChk1 and hChk2). They further phosphorylate effectors proteins such as p53, Cdc25A and Cdc25C which function either to activate the DNA damage checkpoints and cell death mechanisms, or DNA repair pathways. Identification of molecular pathways that determine signaling after DNA damage and trigger DNA repair in response to differing types of DNA lesions allows for a far better understanding of the consequences of radiation and chemotherapy on normal and tumor cells. Here we highlight the network of DNA damage response pathways that are activated after treatment with different types of radiation. Further, we discuss regulation of cell cycle checkpoint and DNA repair processes in the context of DDR in response to radiation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/10715762.2021.1876853DOI Listing
January 2021

Correlation between Visual Functions and Retinal Morphology in Eyes with Early and Intermediate Age-Related Macular Degeneration.

Int J Environ Res Public Health 2020 09 2;17(17). Epub 2020 Sep 2.

Department of Ophthalmology, Hospital Shah Alam, Persiaran Kayangan, Seksyen 7, Shah Alam 40000, Selangor, Malaysia.

In early and intermediate age related macular degeneration (ARMD), visual acuity alone has failed to explain the complete variation of vision. The aim of the present study was to determine correlation between different visual functions and retinal morphology in eyes with early and intermediate ARMD. In this single center cross sectional study, patients diagnosed as early or intermediate ARMD in at least one eye were recruited. Visual functions measured were best- corrected distance visual acuity (DVA), near vision acuity (NVA), reading speed (RS), and contrast sensitivity (CS). Parameters such as thickness (RT) and volume (RV) of the retina, outer retinal layer thickness (ORLT) and volume (ORLV), outer nuclear layer thickness (ONLT) and volume (ONLV), retinal pigment epithelium layer-Bruch's membrane complex thickness (RPET) and volume (RPEV) were assessed employing semi-auto segmentation method of Spectralis optical coherence tomography (OCT). Twenty-six eyes were evaluated. DVA, CS, and RS showed significantly good correlation with RPET, ONLT, and ONLV, whereas NVA showed good correlation with ONLV and RPET. The present study concluded that RS, CS, NVA, and DVA represent the morphological alteration in early stages and should be tested in clinical settings. ONLT, ONLV, and RPET morphological parameters can be employed as important biomarkers in diagnosis of early to intermediate ARMD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijerph17176379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7503555PMC
September 2020

Patient-Perceived Benefit of Treatment in Polypoidal Choroidal Vasculopathy: A Pilot Study.

Int J Environ Res Public Health 2020 09 2;17(17). Epub 2020 Sep 2.

Department of Ophthalmology, Hospital Shah Alam, Persiaran Kayangan, Seksyen 7, Shah Alam 40000, Selangor, Malaysia.

Polypoidal choroidal vasculopathy (PCV), a subtype of neovascular age-related macular degeneration, requires repeated treatment. The objective of this pilot study was to evaluate and compare vision-targeted quality of life (QOL) at baseline and after 6 months of treatment in patients with PCV. Naive PCV patients were recruited. Visual functions assessed were distance visual acuity (DVA), near visual acuity (NVA), contrast sensitivity (CS), reading speed (RS), and QOL at baseline and after 6 months of treatment. Thirty patients (average age of 67.62 ± 8.05 years) revealed mean DVA and NVA improvements of 0.24 logMAR and 0.30 logMAR, respectively. Mean CS and RS improved by 0.39 log contrast and 25.58 words per minute, respectively. The National Eye Institute Visual Function Questionnaire 25 (NEI-VFQ-25) composite score significantly increased from a baseline of 66.73 ± 13.74 to 73.54 ± 14.26. Twenty-eight of the patients showed overall improvement in QOL score by 5 units or more or remained stable. Subscales of NEI-VFQ-25 significantly improved, with general vision, mental health, and role difficulties improving by 10 or more units. The present pilot study reports a significant improvement of QOL in PCV patients after 6 months of treatment, with mental health, role difficulties, social functioning, and distance vision activities being the most improved subscales.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijerph17176378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7504237PMC
September 2020

Fumaric acid incorporated Ag/agar-agar hybrid hydrogel: A multifunctional avenue to tackle wound healing.

Mater Sci Eng C Mater Biol Appl 2020 Jun 13;111:110743. Epub 2020 Feb 13.

Department of Research and Development, Saveetha Institute of Medical and Technical Sciences (Deemed University), Thandalam, Chennai, Tamilnadu 602105, India. Electronic address:

Wound and its treatment is one of the major health concerns throughout the globe. Various extrinsic and intrinsic factors can influence the dynamics of healing mechanism. One such extrinsic factor is moist environment in wound healing. The advantages of optimum hydration in wound healing are enhanced autolytic debridement, angiogenesis and accelerated cell proliferation and collagen formation. But hydrated wounds often end up with patient's uncomfortability, associated infection, and tissue lipid peroxidation. Healing process prefers antimicrobial, anti-inflammatory and optimum moist microenvironment. Here, we have synthesized fumaric acid incorporated agar-silver hydrogel (AA-Ag-FA); characterized by UV-Visible spectroscopy, FTIR spectroscopy and TEM. The surface morphology is evaluated through SEM. The size of the silver nanoparticles (Ag NPs) was found to be 10-15 nm. The hydrogel shows potential antibacterial effect against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa which are predominantly responsible for wound infection. The gel shows reasonable antioxidant property evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Topical application of the gel on the wound site heals the wound at much faster rate even compared to standard (Mega heal, Composition: Colloidal silver 32 ppm hydrogel) gel. Histological analysis reveals better tissue proliferation (i.e. epithelialization), more granulation tissue formation, neovascularisation, fibroblast and mature collagen bundles. The lipid peroxidation of wound tissue estimated through malondialdehyde (MDA) assay was found to be reasonably less when treated with AA-Ag-FA hydrogel compared to standard (Mega heal). Cytotoxicity of the samples tested through MTT assay and live-dead cell staining shows its nontoxic biocompatibility nature. In our hydrogel scaffold, the bio-degradable agar-agar provides the moist environment; the Ag NPs inside the gel acts as bactericidal agent and fumaric acid facilities the antioxidant and angiogenesis path implicitly.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.msec.2020.110743DOI Listing
June 2020

Chirality breakdown in the presence of multiple exceptional points and specific mode excitation.

Opt Lett 2020 Mar;45(6):1439-1442

The dynamical parametric encirclement around a second-order exceptional point (EP) enables the time-asymmetric nonadiabatic evolution of light, which follows the chirality of the underlying system. Such light dynamics in the presence of multiple EPs and the corresponding chiral aspect is yet to be explored. In this Letter, we report a gain-loss assisted four-mode-supported optical waveguide that hosts a parameter space to dynamically encircle multiple EPs. In the presence of multiple EPs, we establish a unique nonadiabatic behavior of light, where beyond the chiral aspect of the system, light is switched to a particular mode, irrespective of the choice of the input mode. Proposed scheme certainly opens a step-forward approach in light manipulation to facilitate next-generation integrated photonic systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.383749DOI Listing
March 2020

Comparative Evaluation of Efficacy of Platelet-Rich Fibrin and Hank's Balanced Salt Solution as a Storage Medium for Avulsed Teeth: An Study.

Eur Endod J 2019 21;4(3):118-121. Epub 2019 Oct 21.

Department of Conservative Dentistry and Endodontics (S.G. C.C., S.Adiga), Bommanhalli, India.

Objective: To compare the efficacy of platelet-rich fibrin (PRF) and Hank's balanced salt solution (HBSS) in the preservation of the periodontal ligament (PDL) cells viability of avulsed teeth.

Methods: A total of 30 non-carious third molars with healthy periodontium, indicated for extraction for orthodontic reasons or chronic pericoronitis, were selected for the study. Samples were divided into four groups: one standard group and one experimental group in addition to two control groups (positive and negative). The positive and negative control group corresponded to immediate and 2-hour dry time respectively. The experimental teeth were bench dried for 40 minutes and then immersed in one of the two storage media: HBSS (standard storage media) and PRF (experimental storage media) for 45 minutes. The teeth in each group were treated with dispase II and collagenase for 30 minutes and later centrifuged for 4 minutes at 1000 rpm. The supernatant was removed with sterile micropipette, the cells were labeled with 0.4% trypan blue, and the number of viable PDL cells was counted with a hemocytometer under a light microscope. One-way Kruskal-Wallis test and Mann-Whitney U test with Boneferroni correction were used for statistical analysis.

Results: Results did not demonstrate any statistically significant differences in the viability of PDL cells between the groups with standard and experimental storage media. Group 1 showed a statistically significant difference of mean compared to Groups 2, 3 and 4. When Group 2 was compared with Groups 3 and 4, a P-value>0.05 suggested no statistical significance.

Conclusion: Within the parameters of this study, HBSS and PRF demonstrated a similar number of viable PDL cells. Hence, PRF could be a used as a good substitute of HBSS as a storage media for avulsed teeth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.14744/eej.2019.24633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7006589PMC
October 2019

A Droplet-Based Microfluidics Route to Temperature-Responsive Colloidal Molecules.

J Phys Chem B 2019 10 17;123(43):9260-9271. Epub 2019 Oct 17.

NanoLund , SE-22100 Lund , Sweden.

Small clusters of spherical colloids that mimic real molecules, so-called colloidal molecules, hold great promise as building blocks in bottom-up routes to new materials. However, their typical hard sphere nature has hampered their assembly into ordered structures, largely due to a lack of control in the interparticle interactions. To provide easy external control of the interactions, the present work focuses on the preparation of colloidal molecules from temperature-responsive microgel particles that undergo a transition from a soft repulsive to a short-range attractive state as their characteristic volume phase transition temperature (VPTT) is crossed. Preparation of the colloidal molecules starts with the use of a droplet-based microfluidics device to form highly uniform water-in-oil (W/O) emulsion droplets containing, on average and with a narrow distribution, four microgels per droplet. Evaporation of the water then leads to the formation of colloidal molecule-like clusters, which can be harvested following cross-linking and phase transfer. We use a mixture of two types of microgels, one based on poly(-isopropylacrylamide) (PNIPAM) and the other on poly(-isopropylmethacrylamide) (PNIPMAM), to prepare bicomponent colloidal molecules, and show that the difference in VPTT between the two allows for induction of attractive interparticle interactions between the PNIPAM interaction sites at temperatures in between the two VPTTs, analogous to the interactions among patchy biomacromolecules such as many proteins.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpcb.9b07754DOI Listing
October 2019

Finding a new pathway for acid-induced nitrite reduction reaction: formation of nitric oxide with hydrogen peroxide.

Dalton Trans 2019 Oct 9;48(37):13916-13920. Epub 2019 Sep 9.

Department of Chemistry, Indian Institute of Science Education and Research (IISER), Tirupati 517507, India.

Here, we report a new pathway for nitrite reduction chemistry, formation of cobalt-nitrosyl ({Co-NO}) with HO in the reaction of a Co-nitrito complex with a one-fold acid (H) via the formation of a Co-nitrous acid intermediate ({Co-ONOH}). Mechanistic investigations using N-labeled-NO revealed that the N-atom in the {Co-NO} complex is derived from the nitrito ligand, and HO came from the homolysis of the ON-OH moiety. Spectral evidence supporting the formation of the Co-ONOH intermediate and the generation of HO is also presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9dt02834jDOI Listing
October 2019

Asymmetric propagation and limited wavelength translation of optical pulses through a linear dispersive time-dynamic system.

Opt Lett 2019 Jun;44(12):3022-3025

We study optical pulse propagation through a linear, dispersive, gain-loss-assisted bulk medium whose refractive index is time-varying. To analyze the dynamics, we have used a novel technique of time transformation that provides universal formulas of pulse propagation. Our analytical and numerical investigations reveal that optical pulses show asymmetric behavior while propagating in opposite direction through such a medium, in both the temporal and spectral domains. Moreover, the wavelength shift during this process is the most interesting outcome which is limited in range, but could be tuned by varying the refractive index with time. Phenomena that are observed in this Letter are novel and realizable in practical devices such as coupled waveguides where the refractive index is a function of time.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.44.003022DOI Listing
June 2019

Novel 1,4-dihydropyridine induces apoptosis in human cancer cells through overexpression of Sirtuin1.

Apoptosis 2018 10;23(9-10):532-553

Department of Biochemistry and Biophysics, University of Kalyani, Nadia, Kalyani, West Bengal, 741235, India.

1,4-Dihydropyridines (1,4-DHPs) are important as a class of heterocyclic compounds that exhibit wide range of biological actions. Many of its derivatives are already characterized as medicinally important drugs and used worldwide. In this study, we have screened some novel Hantzsch 1,4-DHP compounds using both in silico (QSAR and Pharmacophore) and in vitro (cytotoxic screening). 1,4-DHP showed selective cytotoxicity against five human cancerous cell lines; A375, A549, HeLa, HepG2 and SH-SY5Y but limited effect towards normal skin keratinocyte (HaCaT), lung fibroblast (WL-38) and healthy peripheral blood mononuclear cells. In A375 and HepG2 cells, one of the 1,4-DHP derivative (DHP-8) was found to inhibit cell proliferation, and simultaneously increased the apoptotic population as well as mitochondrial membrane depolarization. Furthermore, the mitochondrial signal was triggered with the activation of cleaved Caspase9, Caspase3 and PARP. The treatment with DHP-8 also increased the expression level of SIRT1, subsequently decreasing the level of pAKT and survivin. Reduced pAKT expression led to decrease the phosphorylated inactive form of GSK3β and as a result, proteasomal degradation of Mcl-1 occurred in both the cell lines. Here, we suggest that the apoptotic effect of DHP-8 in A375 and HepG2 cells was mediated by AKT and survivin pathways through SIRT1 activation. The involvement of DHP-8 in SIRT1 activation was further verified by co-treatment of nicotinamide with DHP-8 in both A375 and HepG2 cells. Overall, this study emphasizes the possible potential and therapeutic role of DHP-8 in skin and liver cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10495-018-1483-6DOI Listing
October 2018

Propagation and asymmetric behavior of optical pulses through time-dynamic loss-gain-assisted media.

Appl Opt 2018 Sep;57(25):7167-7171

We report an asymmetric behavior of optical pulses during their propagation through a time-varying linear optical medium. The refractive index of the medium is considered to be varying with time and complex, such that a sufficient amount of gain and loss is present to realize their effect on pulse propagation. We have exploited the universal formula for optical fields in time-varying media. Numerically simulated results reveal that pulses undergo opposite temporal shifts around their initial center position during their bi-directional propagation through the medium along with corresponding spectral shifts. Moreover, the peak power and accumulated chirp (time derivative of accumulated phase) of the output pulse in both propagation directions are also opposite in nature, irrespective of their initial state. Numerically simulated behavior of the pulses agrees well with the analytical solutions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/AO.57.007167DOI Listing
September 2018

Signature of phase singularities in diffusive regimes in disordered waveguide lattices: interplay and qualitative analysis.

Authors:
Somnath Ghosh

Appl Opt 2018 May;57(14):3669-3673

Coexistence and interplay between mesoscopic light dynamics with singular optics in spatially disordered waveguide lattices are reported. Two CW light beams of a 1.55 μm operating wavelength are launched as inputs to 1D waveguide lattices with controllable weak disorder in a complex refractive index profile. Direct observation of phase singularities in the speckle pattern along the length is numerically demonstrated. Quantitative analysis of the onset of such singular behavior and diffusive wave propagation is analyzed for the first time, to the best of our knowledge.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/AO.57.003669DOI Listing
May 2018

Dioxygenation Reaction of a Cobalt-Nitrosyl: Putative Formation of a Cobalt-Peroxynitrite via a {Co(NO)(O)} Intermediate.

Inorg Chem 2017 Dec 13;56(23):14438-14445. Epub 2017 Nov 13.

Department of Chemistry, Indian Institute of Technology Guwahati , North Guwahati, Assam 781039, India.

A cobalt-nitrosyl complex, [(BPI)Co(NO)(OAc)], 1 {BPI = 1,3-bis(2'-pyridylimino)isoindol} was prepared and characterized. Structural characterization revealed that the cobalt center has a distorted square pyramidal geometry with the NO group coordinated from the apical position in a bent fashion. The addition of dioxygen (O) to the dichloromethane solution of complex 1 resulted in the formation of nitro complex, [(BPI)Co(NO)(OAc)], 2. It was characterized structurally. Kinetic studies suggested the involvement of an associative mechanism. FT-IR spectroscopic studies suggested the formation of the intermediate 1a [(BPI)Co(NO)(O)(OAc)] in the reaction. The intermediate 1a decomposed to complex 2 via a presumed peroxynitrite intermediate which was implicated by its characteristic phenol ring nitration reaction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.7b01673DOI Listing
December 2017

Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites.

Nanoscale 2017 Sep;9(37):14215-14228

Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.

Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d) of the specimen with the lowest Young's modulus (∼0.45 MPa at 5% strain) were ∼120 pC N, while the one with the highest Young's modulus (∼1.3 MPa at 5% strain) were ∼62 pC N. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were ∼0.625 MPa and ∼0.485 MPa, while the loss moduli were ∼0.108 MPa and ∼0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d') measured at 40 Hz (∼53 pC N) was larger than that at 50 Hz (∼47 pC N) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7nr05163hDOI Listing
September 2017

Corneal Cell Morphology in Keratoconus: A Confocal Microscopic Observation.

Malays J Med Sci 2017 Mar 14;24(2):44-54. Epub 2017 Apr 14.

Department of Ophthalmology, Hospital Sungai Buloh, Jalan Hospital, 47000 Sungai Buloh, Selangor, Malaysia.

Purpose: To evaluate corneal cell morphology in patients with keratoconus using an in vivo slit scanning confocal microscope.

Methods: A cross-sectional study was conducted to evaluate the corneal cell morphology of 47 keratoconus patients and 32 healthy eyes without any ocular disease. New keratoconus patients with different disease severities and without any other ocular co-morbidity were recruited from the ophthalmology department of a public hospital in Malaysia from June 2013 to May 2014. Corneal cell morphology was evaluated using an in vivo slit-scanning confocal microscope. Qualitative and quantitative data were analysed using a grading scale and the Nidek Advanced Visual Information System software, respectively.

Results: The corneal cell morphology of patients with keratoconus was significantly different from that of healthy eyes except in endothelial cell density ( = 0.072). In the keratoconus group, increased level of stromal haze, alterations such as the elongation of keratocyte nuclei and clustering of cells at the anterior stroma, and dark bands in the posterior stroma were observed with increased severity of the disease. The mean anterior and posterior stromal keratocyte densities and cell areas among the different stages of keratoconus were significantly different ( < 0.001 and = 0.044, respectively). However, the changes observed in the endothelium were not significantly different ( > 0.05) among the three stages of keratoconus.

Conclusion: Confocal microscopy observation showed significant changes in corneal cell morphology in keratoconic cornea from normal healthy cornea. Analysis also showed significant changes in different severities of keratoconus. Understanding the corneal cell morphology changes in keratoconus may help in the long-term monitoring and management of keratoconus.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.21315/mjms2017.24.2.6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5566061PMC
March 2017

Reaction of a Co(III)-Peroxo Complex and NO: Formation of a Putative Peroxynitrite Intermediate.

Inorg Chem 2017 Sep 29;56(18):10932-10938. Epub 2017 Aug 29.

Department of Chemistry, Indian Institute of Technology Guwahati , North Guwahati, Assam 781039, India.

A Co(II) complex, [Co(L)]Cl, 1 of the ligand L (L = bis(2-ethyl-4-methylimidazol-5-yl)methane) upon reaction with HO in methanol solution at -40 °C resulted in the formation of the corresponding Co(III)-peroxo complex [Co(L)(O)] (2). The addition of NO gas to the freshly generated solution of the complex 2 led to the formation of the Co(II)-nitrato complex 3 through the putative formation of a Co(II)-peroxynitrite intermediate, 2a. The intermediate 2a was found to mediate the nitration of the externally added phenol resembling the nitration of tyrosine in biological systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.7b01110DOI Listing
September 2017

Reaction of a Nitrosyl Complex of Cobalt Porphyrin with Hydrogen Peroxide: Putative Formation of Peroxynitrite Intermediate.

Inorg Chem 2017 Jul 26;56(14):7781-7787. Epub 2017 Jun 26.

Department of Chemistry, Indian Institute of Technology Guwahati , North Guwahati, Assam 781039, India.

The cobalt porphyrin complex [(ClTPP)Co], 1, {ClTPP = 5,10,15,20-tetrakis(4'-chlorophenyl)porphyrinate dianion} in dichloromethane solution was subjected to react with nitric oxide (NO) gas and resulted in the formation of the corresponding nitrosyl complex [(ClTPP)Co(NO)], 2, having {CoNO} description. It was characterized by spectroscopic studies and single-crystal X-ray structure determination. It did not react with dioxygen. However, in CHCl/CHCN solution, it reacted with HO to result in the Co-nitrito complex [(ClTPP)Co(NO)], 3, with the simultaneous release of O. It induced ring nitration to the added phenol in an appreciable yield. The reaction presumably proceeds through the formation of corresponding Co-peroxynitrite intermediate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.7b00491DOI Listing
July 2017

Nitric Oxide Reactivity of a Cu(II) Complex of an Imidazole-Based Ligand: Aromatic C-Nitrosation Followed by the Formation of N-Nitrosohydroxylaminato Complex.

Inorg Chem 2017 May 7;56(9):5034-5040. Epub 2017 Apr 7.

Department of Chemistry, Indian Institute of Technology Guwahati , North Guwahati, Assam 781039, India.

A binuclear Cu(II) complex, 1, [Cu(L)(OAc)](OAc) of imidazole-based ligand LH {LH = 2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)phenol} was synthesized and characterized spectroscopically and structurally. Addition of an equivalent amount of nitric oxide (NO) by a gastight syringe to the acetonitrile:methanol (5:1, v/v) solution of complex 1 at room temperature resulted in the reduction of Cu(II) center to Cu(I) with concomitant C-nitrosation of the ligand. Spectroscopic characterization of the resulting Cu(I) complex (1a) of the C-nitrosylated ligand, L' {L' = 2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)-4-nitroso-phenol} has been done. The Cu(I) complex, 1a, further reacted with NO to result in the corresponding N-nitrosohydroxylaminato complex, 2, [Cu(L-ONNO)](OAc) through the formation of a Cu(I)-nitrosyl intermediate. A small fraction of the nitrosyl intermediate decomposed to the corresponding Cu(II) complex 3, [Cu(L')], and NO in a parallel reaction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.7b00069DOI Listing
May 2017

Effects of contact lens wearing on keratoconus: a confocal microscopy observation.

Int J Ophthalmol 2017 18;10(2):228-234. Epub 2017 Feb 18.

Department of Ophthalmology, Hospital Sungai Buloh, Jalan Hospital, Sungai Buloh 47000, Malaysia.

Aim: To evaluate the corneal cell morphology of new keratoconus patients wearing two different types of rigid gas-permeable (RGP) contact lenses for 1y.

Methods: Thirty nine eyes of 39 new keratoconus patients were selected and randomly fitted with two types of RGP contact lenses. Group 1 had 21 eyes with regular rigid gas-permeable (RRGP) contact lens and rest 18 eyes were in group 2 with specially designed rigid gas-permeable (SRGP) contact lens. Corneal cell morphology was evaluated using a slit scanning confocal microscope at no-lens wear and after 1y of contact lens wearing.

Results: After 1y of contact lens wearing in group 1, the mean anterior and posterior stromal keratocyte density were significantly less (=0.006 and =0.001, respectively) compared to no-lens wear. The mean cell area of anterior and posterior stromal keratocyte were also significantly different (=0.005 and =0.001) from no-lens wear. The anterior and posterior stromal haze increased by 18.74% and 23.81%, respectively after 1y of contact lens wearing. Whereas in group 2, statistically significant changes were observed only in cell density & area of anterior stroma (=0.001 and =0.001, respectively) after 1y. While, level of anterior and posterior stromal haze increased by 16.67% and 11.11% after 1y of contact lens wearing. Polymegathism and pleomorphism also increased after 1y of contact lens wearing in both the contact lens groups.

Conclusion: Confocal microscopy observation shows the significant alterations in corneal cell morphology of keratoconic corneas wearing contact lenses especially in group 1. The type of contact lens must be carefully selected to minimize changes in corneal cell morphology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.18240/ijo.2017.02.08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5313545PMC
February 2017

In vivo slit scanning confocal microscopic observation in a patient with moderate and severe keratoconus: a case report.

Clin Optom (Auckl) 2016 26;8:79-83. Epub 2016 Aug 26.

Optometry and Vision Sciences Programme, Faculty of Health Sciences, University Kebangsaan Malaysia, Kuala Lumpur, Malaysia,

A 22-year-old Indian female was referred to Sg Buloh hospital with the diagnosis of bilateral keratoconus. On examination, slit lamp biomicroscopy and corneal topography revealed stage 3 keratoconus in the right eye and stage 2 keratoconus in the left eye. Corneal cell morphology in both eyes was evaluated using confocal microscope. In qualitative observation, almost all corneal layers in right eye except endothelium were partially or completely obscured by haze. Additionally, morphological alterations, such as elongation of keratocyte nuclei and cluster of cells, and dark bands in the anterior stroma were observed in right eye. In the left eye, the amount of haze was less, allowing better visibility of the corneal layers compared with the right eye. The dark bands were evident in the posterior stroma. Quantitative analysis showed that anterior and posterior stromal keratocyte density and endothelium cell density were relatively low in the right eye (834.0, 700.5, and 2,133 cells/mm, respectively) compared with the left eye (934.1, 750.6, and 2,361 cells/mm, respectively). In this case, the right eye, exhibiting stage 3 keratoconus, showed more morphological alteration, particularly in the anterior stroma compared with the left eye with stage 2 keratoconus. Increased severity of the disease can explain these differences in corneal cell morphology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2147/OPTO.S106421DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095362PMC
August 2016

Effect of ligand denticity on the nitric oxide reactivity of cobalt(ii) complexes.

Dalton Trans 2016 Jul;45(27):10979-88

Department of Chemistry, Indian Institute of Technology Guwahati, Assam-781039, India.

The activation of nitric oxide (NO) by transition metal complexes has attracted a wide range of research activity. To study the role of ligand denticity on the NO reactivity of Co(ii) complexes, three complexes (, and ) were prepared with ligands , and [ = N(1),N(2)-bis(2,4,6-trimethylbenzyl)ethane-1,2-diamine; = N(1)-(2,4,6-trimethylbenzyl)-N(2)-(2-((2,4,6-trimethylbenzyl)amino)ethyl)ethane-1,2-diamine] and = N(1)-(2,4,6-trimethylbenzyl)-N(2),N(2)-bis(2-((2,4,6-trimethylbenzyl)amino)ethyl)ethane-1,2-diamine], respectively. The complexes differ from each other in terms of denticity and flexibility of the ligand frameworks. In degassed methanol solution, they were exposed to NO gas and their reactivity was studied using various spectroscopic techniques. In the case of complex with a bidentate ligand, reductive nitrosylation of the metal ion with concomitant dinitrosation of the ligand framework was observed. Complex with a tridentate ligand did not undergo reductive nitrosylation; rather, the formation of [Co(III)(NO(-))] was observed. The nitrosyl complexes were isolated and structurally characterized. On the other hand, complex with a tetradentate tripodal ligand did not react with NO. This can be attributed to the geometry of the complex as well as due to the accessibility of the corresponding redox potential.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6dt01169aDOI Listing
July 2016

Reductive nitrosylation of nickel(ii) complex by nitric oxide followed by nitrous oxide release.

Dalton Trans 2016 Jun;45(25):10200-8

Department of Chemsitry, Indian Institute of Technology Guwahati, Assam 781039, India.

Ni(ii) complex of ligand ( = bis(2-ethyl-4-methylimidazol-5-yl)methane) in methanol solution reacts with an equivalent amount of NO resulting in a corresponding Ni(i) complex. Adding further NO equivalent affords a Ni(i)-nitrosyl intermediate with the {NiNO}(10) configuration. This nitrosyl intermediate upon subsequent reaction with additional NO results in the release of N2O and formation of a Ni(ii)-nitrito complex. Crystallographic characterization of the nitrito complex revealed a symmetric η(2)-O,O-nitrito bonding to the metal ion. This study demonstrates the reductive nitrosylation of a Ni(ii) center followed by N2O release in the presence of excess NO.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6dt00826gDOI Listing
June 2016

Suppression of excess noise of longer-lived high-quality states in nonuniformly pumped optical microcavities.

Opt Lett 2016 Mar;41(5):942-5

We study the formation of longer-lived states via internal coupling near a special avoided resonance crossing between the interacting states in an open optical system. Away from the parity-time symmetry limit, we discuss unconventional cavity resonance states created by a spatially varying gain/loss profile. Now, via S-matrix formalism, we have numerically demonstrated that with suitably chosen system openness and coupling strengths, the excess noise generation among the interacting nonorthogonal states (calculated as Petermann factor K) can be suppressed close to the ideal value of one with a simultaneous order of magnitude enhancement in the quality-factor of the longer-lived state.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.41.000942DOI Listing
March 2016

Role of ATM in bystander signaling between human monocytes and lung adenocarcinoma cells.

Mutat Res Genet Toxicol Environ Mutagen 2015 Dec 23;794:39-45. Epub 2015 Oct 23.

Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.

The response of a cell or tissue to ionizing radiation is mediated by direct damage to cellular components and indirect damage mediated by radiolysis of water. Radiation affects both irradiated cells and the surrounding cells and tissues. The radiation-induced bystander effect is defined by the presence of biological effects in cells that were not themselves in the field of irradiation. To establish the contribution of the bystander effect in the survival of the neighboring cells, lung carcinoma A549 cells were exposed to gamma-irradiation, 2Gy. The medium from the irradiated cells was transferred to non-irradiated A549 cells. Irradiated A549 cells as well as non-irradiated A549 cells cultured in the presence of medium from irradiated cells showed decrease in survival and increase in γ-H2AX and p-ATM foci, indicating a bystander effect. Bystander signaling was also observed between different cell types. Phorbol-12-myristate-13-acetate (PMA)-stimulated and gamma-irradiated U937 (human monocyte) cells induced a bystander response in non-irradiated A549 (lung carcinoma) cells as shown by decreased survival and increased γ-H2AX and p-ATM foci. Non-stimulated and/or irradiated U937 cells did not induce such effects in non-irradiated A549 cells. Since ATM protein was activated in irradiated cells as well as bystander cells, it was of interest to understand its role in bystander effect. Suppression of ATM with siRNA in A549 cells completely inhibited bystander effect in bystander A549 cells. On the other hand suppression of ATM with siRNA in PMA stimulated U937 cells caused only a partial inhibition of bystander effect in bystander A549 cells. These results indicate that apart from ATM, some additional factor may be involved in bystander effect between different cell types.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mrgentox.2015.10.003DOI Listing
December 2015

Copper(II) mediated phenol ring nitration by nitrogen dioxide.

Dalton Trans 2015 Dec;44(46):19909-17

Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India.

Cu(II) complexes of N2O2 type ligands, L(1)H2 and L(2)H2 [L(1)H2 = 6,6'-(((pyridin-2-ylmethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol); L(2)H2 = 2,4-di-tert-butyl-6-(((3-(tert-butyl)-2-hydroxy-5-methylbenzyl)(pyridin-2-yl-methyl)amino)methyl)phenol], have been synthesized. Addition of nitrogen dioxide (NO2) in THF solutions of the complexes resulted in the nitration at the 4-position of a coordinated equatorial phenolate ring of the ligand frameworks. This nitration did not occur at the phenol ring which is axially coordinated to the metal center. Spectroscopic evidence suggests that the reaction proceeds through a phenoxyl radical complex formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c5dt02318aDOI Listing
December 2015

Osteomeatal Complex: A Study of Its Anatomical Variation Among Patients Attending North Bengal Medical College and Hospital.

Indian J Otolaryngol Head Neck Surg 2015 Sep 30;67(3):281-6. Epub 2015 Jun 30.

Department of Oto Rhino Laryngology and Head Neck Surgery, North Bengal Medical College and Hospital, Siliguri, 734012 West Bengal India.

Lateral nasal wall of each nasal cavity provides the final common pathway of drainage of the mucociliary clearance of frontal, maxillary and anterior ethmoidal air cells. Anatomical variants like concha bullosa, Haller cells, agger nasi cells, enlarged bulla ethmoidalis may obstruct the mucociliary clearance through osteomeatal complex and cause rhino sinusitis. The objectives were to find out the anatomical variation of osteomeatal complex and its dimensions when present. The present study was a descriptive, hospital based cross sectional study carried out in the outpatient departments of North Bengal Medical College and Hospital, West Bengal, India, among patients aged 15 years and above. Coronal CT scan of paranasal sinus and orbit region was done. Data was collected with the help of semi structured predesigned and pretested questionnaire. Of the 44 study patients, 15.9 % had concha bullosa, 11.36 % had paradoxical middle concha, 27.3 % had Haller cell, 18.2 % had agger nasi cell. Lateral attachment and medial free margin of uncinate process were also measured in respect to medial body line. 77.3, 59.1 and 47.7 % had sneezing, rhinorrhoea and headache respectively. The harmony of mucociliary clearance and obstruction free osteomeatal complex is the key factor for ventilation and drainage of maxillary, frontal and anterior ethmoidal air cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12070-015-0874-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4575670PMC
September 2015