Chemistry of 2-(phenylazo)pyridine complexes of osmium: synthesis, characterization and reactivities

Reaction of 2-(phenylazo)pyridine (pap) with [Os(PPh3)3Br2] afforded a mixed ligand complex of the type [Os(PPh3)2(pap)Br2]. The structure of this complex was determined by X-ray crystallography. The PPh3 ligands are trans and the bromides are in cis positions. The pap ligand is coordinated to osmium as a bidentate N,N-donor forming a five-membered chelate ring. The complex is diamagnetic (low-spin d6, S=0) and in dichloromethane solution shows intense MLCT transitions in the visible region. The two bromides were replaced from the coordination sphere of [Os(PPh3)2(pap)Br2] under mild conditions by a series of anionic ligands L (where L=quinolin-8-olate (q), picolinate (pic), oxalate (Hox), 1-nitroso-2-naphtholate (nn) and acetyl acetonate (acac)) to afford complexes of the type [Os(PPh3)2(pap)(L)]+, which were isolated and characterized as the perchlorate salt. The structure of the [Os(PPh3)2(pap)(acac)]ClO4 complex was determined by X-ray crystallography. The PPh3 ligands occupy trans positions and the acetylacetonate anion is coordinated to osmium as a bidentate O,O-donor forming a six-membered chelate ring. The [Os(PPh3)2(pap)(L)]+ complexes are diamagnetic and show multiple MLCT transitions in the visible region. [Os(PPh3)2(pap)Br2] shows an osmium(II)-osmium(III) oxidation at 0.49 V versus SCE. The same oxidation is displayed by the [Os(PPh3)2(pap)(L)]+ complexes within 0.69 to 0.96 V versus SCE. Two successive one-electron reductions of the coordinated pap ligand are also observed in all the complexes below -0.90 V versus SCE

Chemistry of ruthenium with some dioxime ligands. Syntheses, structures and reactivities

Reaction of two dioxime ligands, viz. dimethylglyoxime (H2dmg) and diphenylglyoxime (H2dpg), (abbreviated in general as H2L, where H stands for the oxime protons) with [Ru(PPh3)3Cl2] in 1¦1 mole ratio affords complexes of type [Ru(PPh3)2(H2L)Cl2]. Structure of the [Ru(PPh3)2(H2dpg)Cl2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium is N2P2Cl2 with the two PPh3 ligands in trans and the two chlorides in cis positions. Reaction of the dioxime ligands with [Ru(PPh3)3Cl2] in 2¦1 mole ratio in the presence of a base affords complexes of type [Ru(PPh3)2(HL)2]. Structure of the [Ru(PPh3)2(Hdmg)2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium is N4P2 with the two PPh3 ligands in trans positions. Reaction of the [Ru(PPh3)2(H2dpg)Cl2] complex with a group of bidentate acidic ligands, viz. picolinic acid (Hpic), quinolin-8-ol (Hq) and 1-nitroso-2-naphthol (Hnn), (abbreviated in general as HL′, where H stands for the acidic proton) in the presence of a base affords complexes of type [Ru(PPh3)2(H2dpg)(L′)]+ isolated as perchlorate salts. All the complexes are diamagnetic (low-spin d6, S=0) and in dichloromethane solution show several intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a reversible ruthenium(II)-ruthenium(III) oxidation within 0.36-0.98 V versus SCE followed by a quasi-reversible ruthenium(III)-ruthenium(IV) oxidation within 0.94-1.60 V versus SCE

Role of liquid-based cytology and cell block study of pleural fluid in the evaluation of cases of malignant Pleural effusion with special reference to immunohistochemistry

Introduction- Lung cancer is the most common primary tumor associated with malignant pleural effusion (MPE). In this study, we aim to use cell remnants for cell block preparation after performing liquid-based cytology (LBC) of effusion fluid. Immunohistochemistry was helpful to evaluate those cases having diagnostic dilemmas in LBC and cell block. Method: It was a cross-sectional, prospective, single institution-based study, conducted in the department of Pathology in collaboration with the Department of Respiratory Medicine IPGMER & SSKM Hospital, from January 2018 to June 2019 in the institution. Result: Most of the study population were in between the age group of 51 to 60 years with male predominance and with fever and cough being the predominant symptoms. Liquid-based cytology was positive for malignancy in 58% of cases and suspicious of malignancy in 22% of cases of malignant pleural effusion and it had 95.35% sensitivity, 58.82% specificity in diagnosing malignant pleural effusion.LBC was done followed by cell block preparations are studied further by Immunohistochemistry. Discussion: Morphological features were better identified by the cell block method when compared to LBC. Multiple sections can be obtained for special stain or IHC study which bridges the gap between cytology and histology

Combination of Continuous Dexmedetomidine Infusion with Titrated Ultra-Low-Dose Propofol-Fentanyl for an Awake Craniotomy : Case report

An awake craniotomy is a continuously evolving technique used for the resection of brain tumours from the eloquent cortex. We report a 29-year-old male patient who presented to the Khoula Hospital, Muscat, Oman, in 2016 with a two month history of headaches and convulsions due to a space-occupying brain lesion in close proximity with the left motor cortex. An awake craniotomy was conducted using a scalp block, continuous dexmedetomidine infusion and a titrated ultra-low-dose of propofol-fentanyl. The patient remained comfortable throughout the procedure and the intraoperative neuropsychological tests, brain mapping and tumour resection were successful. This case report suggests that dexmedetomidine in combination with titrated ultra-low-dose propofolfentanyl are effective options during an awake craniotomy, ensuring optimum sedation, minimal disinhibition and a rapid recovery. To the best of the authors’ knowledge, this is the first awake craniotomy conducted successfully in Oman

Chemistry of ruthenium with some phenolic ligands: synthesis, structure and redox properties

Reaction of three phenolate ligands, viz. salicylaldehyde (HL1), 2-hydroxyacetophenone (HL2) and 2-hydroxynaphthylaldehyde (HL3), (abbreviated in general as HL, where H stands for the phenolic proton) with [Ru(PPh3)3Cl2] in 1¦1 mole ratio gives complexes of the type[Ru(PPh3)2(L)Cl2]. The structure of the [Ru(PPh3)2(L2)Cl2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium isO2P2Cl2 with a cis-trans-cis geometry, respectively. The [Ru(PPh3)2(L)Cl2] complexes are one-electron paramagnetic (low-spin d5, S=½) and show rhombic ESR spectra in 1¦1 dichloromethane-toluene solution at 77 K. In dichloromethane solution the [Ru(PPh3)2(L)Cl2] complexes show several intense LMCT transitions in the visible region. Reaction between the phenolic ligands and [Ru(PPh3)3Cl2] in 2¦1 mole ratio in the presence of a base affords the [Ru(PPh3)2(L)2] complexes in two isomeric forms. 1H NMR spectra of one isomer shows that it does not have any C2 symmetry and has the cis-cis-cis disposition of the three sets of donor atoms. 1H NMR spectra of the other isomer shows that it has C2 symmetry. The structure of the isomer of the [Ru(PPh3)2(L1)2] complex has been solved by X-ray crystallography. The coordination sphere around ruthenium is O4P2 with a cis-trans-cis disposition of the carbonylic oxygens, phenolate oxygens and phosphorus atoms, respectively. The [Ru(PPh3)2(L)2] complexes are diamagnetic (low-spin d6, S=O) and show intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru(PPh3)2(L)Cl2] complexes shows a ruthenium(III)---ruthenium(II) reduction near -0.3 V versus SCE and a ruthenium(III)---ruthenium(IV) oxidation in the range 1.08-1.24 V versus SCE. Cyclic voltammetry on both isomers of the [Ru(PPh3)2(L)2] complexes shows a ruthenium(II)---ruthenium(III) oxidation within 0.09-0.41 V versus SCE, followed by a ruthenium(III)-ruthenium(IV) oxidation within 1.31-1.52 V versus SCE

Improved infrared photoluminescence characteristics from circularly ordered self-assembled Ge islands

The formation of circularly ordered Ge-islands on Si(001) has been achieved because of nonuniform strain field around the periphery of the holes patterned by focused ion beam in combination with a self-assembled growth using molecular beam epitaxy. The photoluminescence (PL) spectra obtained from patterned areas (i.e., ordered islands) show a significant signal enhancement, which sustained till 200 K, without any vertical stacking of islands. The origin of two activation energies in temperature-dependent PL spectra of the ordered islands has been explained in detail

Observation of room temperature gate tunable quantum confinement effect in photodoped junctionless MOSFET

In the pursuit of room temperature quantum hardware, our study introduces a gate voltage tunable quantum wire within a tri-gated n-type junctionless MOSFET. The application of gate voltage alters the parabolic potential well of the tri-gated junctionless MOSFET, enabling modification of the nanowire's potential well profile. In the presence of light, photogenerated electrons accumulate at the center of the junctionless nanowire, aligning with the modified potential well profile influenced by gate bias. These carriers at the center are far from interfaces and experience less interfacial noise. Therefore, such clean photo-doping shows clear, repeatable peaks in current for specific gate biases compared to the dark condition, considering different operating drain-to-source voltages at room temperature. We propose that photodoping-induced subband occupation of gate tunable potential well of the nanowire is the underlying phenomenon responsible for this kind of observation. This study reveals experimental findings demonstrating gate-induced switching from semi-classical to the quantum domain, followed by the optical occupancy of electronic sub-bands at room temperature. We developed a compact model based on the Nonequilibrium Green's function formalism to understand this phenomenon in our illuminated device better. This work reveals the survival of the quantum confinement effect at room temperature in such semi-classical transport.Comment: 12 pages, 6 figure

Primitive Sca-1 Positive Bone Marrow HSC in Mouse Model of Aplastic Anemia: A Comparative Study through Flowcytometric Analysis and Scanning Electron Microscopy

Self-renewing Hematopoietic Stem Cells (HSCs) are responsible for reconstitution of all blood cell lineages. Sca-1 is the “stem cell antigen” marker used to identify the primitive murine HSC population, the expression of which decreases upon differentiation to other mature cell types. Sca-1+ HSCs maintain the bone marrow stem cell pool throughout the life. Aplastic anemia is a disease considered to involve primary stem cell deficiency and is characterized by severe pancytopenia and a decline in healthy blood cell generation system. Studies conducted in our laboratory revealed that the primitive Sca-1+ BM-HSCs (bone marrow hematopoietic stem cell) are significantly affected in experimental Aplastic animals pretreated with chemotherapeutic drugs (Busulfan and Cyclophosphamide) and there is increased Caspase-3 activity with consecutive high Annexin-V positivity leading to premature apoptosis in the bone marrow hematopoietic stem cell population in Aplastic condition. The Sca-1bright, that is, “more primitive” BM-HSC population was more affected than the “less primitive” BM-HSC Sca-1dim  population. The decreased cell population and the receptor expression were directly associated with an empty and deranged marrow microenvironment, which is evident from scanning electron microscopy (SEM). The above experimental evidences hint toward the manipulation of receptor expression for the benefit of cytotherapy by primitive stem cell population in Aplastic anemia cases

Alteration in Marrow Stromal Microenvironment and Apoptosis Mechanisms Involved in Aplastic Anemia: An Animal Model to Study the Possible Disease Pathology

Aplastic anemia (AA) is a heterogeneous disorder of bone marrow failure syndrome. Suggested mechanisms include a primary stem cell deficiency or defect, a secondary stem cell defect due to abnormal regulation between cell death and differentiation, or a deficient microenvironment. In this study, we have tried to investigate the alterations in hematopoietic microenvironment and underlying mechanisms involved in such alterations in an animal model of drug induced AA. We presented the results of studying long term marrow culture, marrow ultra-structure, marrow adherent and hematopoietic progenitor cell colony formation, flowcytometric analysis of marrow stem and stromal progenitor populations and apoptosis mechanism involved in aplastic anemia. The AA marrow showed impairment in cellular proliferation and maturation and failed to generate a functional stromal microenvironment even after 19 days of culture. Ultra-structural analysis showed a degenerated and deformed marrow cellular association in AA. Colony forming units (CFUs) were also severely reduced in AA. Significantly decreased marrow stem and stromal progenitor population with subsequently increased expression levels of both the extracellular and intracellular apoptosis inducer markers in the AA marrow cells essentially pointed towards the defective hematopoiesis; moreover, a deficient and apoptotic microenvironment and the microenvironmental components might have played the important role in the possible pathogenesis of AA

Optical and electrical properties of undoped and doped Ge nanocrystals

Size-dependent photoluminescence characteristics from Ge nanocrystals embedded in different oxide matrices have been studied to demonstrate the light emission in the visible wavelength from quantum-confined charge carriers. On the other hand, the energy transfer mechanism between Er ions and Ge nanocrystals has been exploited to exhibit the emission in the optical fiber communication wavelength range. A broad visible electroluminescence, attributed to electron hole recombination of injected carriers in Ge nanocrystals, has been achieved. Nonvolatile flash-memory devices using Ge nanocrystal floating gates with different tunneling oxides including SiO2, Al2O3, HfO2, and variable oxide thickness [VARIOT] tunnel barrier have been fabricated. An improved charge storage characteristic with enhanced retention time has been achieved for the devices using VARIOT oxide floating gate