Polyhedral and Macropolyhedral Metal-Rich Cobaltaboranes: A 25-Vertex Hourglass-Shaped Cluster.

In an effort to break the single-cage 16-vertex supraicosahedral barrier, we have explored the reaction of [Cp*CoCl2], 1 with [LiBH4·THF], followed by thermolysis with [BH3·SMe2] [Cp* = η5-C5Me5]. Although our objective to synthesize a high-nuclearity single-cage cluster was not achieved, we have isolated a 25-vertex macropolyhedral cluster [(Cp*Co)5Co2B18H17(CH3)S] (2). Cluster 2 is an exceptional fused hourglass-shaped macropolyhedral cluster composing two icosahedral cores ([Co3B9] and [Co4B8]) and three tetrahedral cores [Co2B2]. Although the fusion in cluster 2 is very complex, it follows Mingos fusion formalism, leading to an attractive hourglass-shaped cluster. Through subtle changes in reaction conditions, two new cobaltaborane clusters, nido-4,5,7-[(Cp*Co)3B7H11] (3) and nido-2,9-[(Cp*Co)2B8H12] (4), have been isolated. The observed core geometries of clusters 3 and 4 are similar to the parent deltahedra [B10H14] with (n + 2) SEP (SEP = skeletal electron pair, n = no. of vertices). All the synthesized cobaltaboranes have been characterized in solution by ESI-mass, nuclear magnetic resonance spectroscopy, infrared spectroscopy and structurally solved by single-crystal X-ray diffraction analysis.

Cobaltaelectro-Catalyzed C-H Activation for Central and Axial Double Enantio-Induction.

In recent years, enantioselective electrocatalysis has surfaced as an increasingly-effective platform for sustainable molecular synthesis. Despite indisputable progress, strategies that allow the control of two distinct stereogenic elements with high selectivity remain elusive. In contrast, we, herein, describe electrochemical cobalt-catalyzed C-H activations that enable the installation of chiral stereogenic centers along with a chiral axis with high levels of enantio- and diastereoselectivities. The developed electrocatalysis strategy allowed for C-H/N-H activations/annulations with cyclic and non-cyclic alkenes providing expedient access to various central as well as atropo-chiral dihydroisoquinolinones paired to the valuable hydrogen evolution reaction. Studies on the atropo-stability of the obtained compounds demonstrated that the exceedingly mild conditions ensured by the electrocatalytic process were key for the achieved high stereoselectivities.

Graphene-Coated Ni-Cu Alloys for Durable Degradation Resistance of Bi-Polar Plates for Proton Exchange Membrane Fuel Cells: Remarkable Role of Alloy Composition.

Bipolar plates, a critical component of proton exchange membrane fuel cell (PEMFC), are constructed out of alloys of Ti, Pt, Cr, or graphitic materials that have limitations. Electrical conductivity, cost, and corrosion resistance are among the critical considerations for bi-polar plate material. Graphene, which possesses impressive conductivity and toughness, is an attractive option as coating on metallic substrates of PEMFC bipolar plates. This study investigates corrosion resistance and its durability due to graphene developed by chemical vapor deposition on a pure Ni-Cu alloy and a commercial Ni-Cu alloy in 0.5 m H2 SO4 environment, with a view to exploring use of graphene coated Ni-Cu alloys for the construction of PEMFC bipolar plates. The graphene coating on the pure alloy shows remarkably superior corrosion resistance than the commercial alloy that is attributed to the former's ability to develop considerably defect-free graphene.

Remarkably Corrosion Resistant Graphene Coating on Steel Enabled Through Metallurgical Tailoring.

Graphene coatings developed by chemical vapor deposition (CVD) that possess extraordinary/unique characteristics as barrier against aggressive environment can improve the corrosion resistance of Ni and Cu by up to two orders of magnitude. However, because of some compelling technical reasons, it has thus far been a nontrivial challenge to develop graphene coatings on the most commonly used engineering alloy, mild steel (MS). To circumvent the challenge simply by first electroplating MS with a Ni layer is attempted, and then developing CVD graphene over the Ni layer. However, this approach proved too simplistic and does not work. This necessitated an innovative surface modification of MS (based on basic metallurgical principles) that enabled successful CVD of graphene coating on MS. The graphene coating thus developed is demonstrated to improve the corrosion resistance of mild steel by two orders of magnitude in an aggressive chloride solution, through electrochemical testing. This improvement was not only sustained for the entire test duration of >1000 h; but there is a clear trend for the resistance to be possibly everlasting. The optimized surface modification that enabled development of CVD graphene coating on mild steel is generic in nature, and it should enable graphene coating on other alloy systems, which would otherwise not be possible.

Chemistry of CS2 and CS3 Bridged Decaborane Analogues: Regular Coordination Versus Cluster Expansion.

In an effort to synthesize metallaheteroborane clusters of higher nuclearity, the reactivity of metallaheteroboranes, nido-[(Cp*M)2B6S2H4(CS3)] (Cp* = C5Me5) (1: M = Co; 2: M = Rh) with various metal carbonyls have been investigated. Photolysis of nido-1 and nido-2 with group 6 metal carbonyls, M'(CO)5.THF (M' = Mo or W) were performed that led to the formation of a series of adducts [(Cp*M)2B6S2H4(CS3){M'(CO)5}] (3: M = Co, M' = Mo; 4: M = Co, M' = W; 5: M = Rh, M' = Mo; 6: M = Rh, M' = W) instead of cluster expansion reactions. In these adducts, the S atom of C=S group of di(thioboralane)thione {B2CS3} moiety is coordinated to M'(CO)5 (M = Mo or W) in η1-fashion. On the other hand, thermolysis of nido-1 with Ru3(CO)12 yielded one fused metallaheteroborane cluster [{Ru(CO)3}3S{Ru(CO)}{Ru(CO)2}Co2B6SH4(CH2S2){Ru(CO)3}2S], 7. This 20-vertex-fused cluster is composed of two tetrahedral {Ru3S} and {Ru2B2}, a flat butterfly {Ru3S} and one octadecahedron {Co2RuB7S} core with one missing vertex, coordinated to {Ru2SCH2S2} through two boron and one ruthenium atom. On the other hand, the room temperature reaction of nido-2 with Co2(CO)8 produced one 19-vertex fused metallaheteroborane cluster [(Cp*Rh)2B6H4S4{Co(CO)}2{Co(CO)2}2(µ-CO)S{Co(CO)3}2], 8. Cluster 8 contains one nido-decaborane {Rh2B6S2}, one butterfly {Co2S2} and one bicapped square pyramidal {Co6S} unit that exhibits an intercluster fusion with two sulfur atoms in common. Clusters 3-6 have been characterized by multinuclear NMR and IR spectroscopy, mass spectrometry and structurally determined by XRD analyses. Furthermore, the DFT calculations have been carried out to gain insight into electronic, structural and bonding patterns of the synthesized clusters.

Is polypropylene mesh reconstruction functionally superior to non reconstructive group following total scapular resection? A retrospective analysis of 16 patients and a systematic review of the literature.

Background: Various reconstruction methods have been described in medical literature on scapular tumor resection depending on the type of resection and other factors. However the ideal method of reconstructions has been still debatable. The purpose of the current study was to assess whether polypropylene mesh reconstruction is superior as compared to non reconstructive group following total scapular resection.We also evaluated how our method of reconstruction fare as compared to reported reconstruction methods in the published literature. Methods: During 2014 to 2019; Total scapulectomy (Type III scapular resection) was performed in 16 patients for malignant tumor involving scapula bone. Reconstruction with polyprolene mesh(Group I) was performed in 56 % patient and non reconstruction technique (Group II) was observed in 44 % patient. The mean follow-up duration of current study was 28.3 months (range 13-67 months). The search method of PubMed and Cochrane databases provided 121 articles; of which 5 studies having 144 cases were utilised for final analysis. The reconstruction method used were dynamic humeral suspension (39.5%), non reconstruction method (35 %), scapular prosthesis (18 %) and static humeral suspension (5.5%). Results: The mean Musculoskeletal tumor society score (MSTS) of the study cohort was 19.8(0-23); and that in polyprolene mesh or static suspension method (Group I) and non reconstructive technique (Group II) was 67 % and 61% respectively. The emotional acceptance score in group I was 4.5 and that in group II was 4.2 points. There was no difference in the shoulder movements in both the groups. The mean surgical durations in group I and group II was was 186 min and 140 min respectively. The systematic review showed the mean Musculoskeletal tumor society score (MSTS) of dynamic suspension and non reconstruction method were 63 % and 63.5% respectively. The mean Musculoskeletal tumor society score (MSTS) of scapula prosthesis tended to be higher than those with dynamic suspension (77 % vs 65 %). Conclusions: The reconstruction with polypropylene mesh had better functional outcome and emotional acceptance as compared to non-reconstructive group in patients with total scapular resection surgery. The findings of systematic review suggest that; patients treated by reconstruction with polypropylene mesh and non-reconstructive group as compared to scapular prosthesis had limited shoulder movements with no difference in hand position, manual dexterity and lifting ability.

Connective tissue growth factor regulates retinal neovascularization through p53 protein-dependent transactivation of the matrix metalloproteinase (MMP)-2 gene.

BACKGROUND: The role of connective tissue growth factor (CTGF/CCN2) in pathological angiogenesis in the retina is unknown. RESULTS: CTGF/CCN2 stimulates retinal neovascularization through transactivation of p53 target genes such as matrix metalloproteinase (MMP)-2. CONCLUSION: CTGF/CCN2 effects on abnormal vessel formation in the retina are mediated by p53 and MMP-2. SIGNIFICANCE: CTGF/CCN2 and its downstream effectors are potential targets in the development of new antiangiogenic treatments. Pathological angiogenesis in the retina is driven by dysregulation of hypoxia-driven stimuli that coordinate physiological vessel growth. How the various components of the neovascularization signaling network are integrated to yield pathological changes has not been defined. Connective tissue growth factor (CTGF/CCN2) is an inducible matricellular protein that plays a major role in fibroproliferative disorders. Here, we show that CTGF/CCN2 was dynamically expressed in the developing murine retinal vasculature and was abnormally increased and localized within neovascular tufts in the mouse eye with oxygen-induced retinopathy. Consistent with its propitious vascular localization, ectopic expression of the CTGF/CCN2 gene further accelerated neovascularization, whereas lentivirus-mediated loss-of-function or -expression of CTGF/CCN2 harnessed ischemia-induced neovessel outgrowth in oxygen-induced retinopathy mice. The neovascular effects of CTGF/CCN2 were mediated, at least in part, through increased expression and activity of matrix metalloproteinase (MMP)-2, which drives vascular remodeling through degradation of matrix and non matrix proteins, migration and invasion of endothelial cells, and formation of new vascular patterns. In cultured cells, CTGF/CCN2 activated the MMP-2 promoter through increased expression and tethering of the p53 transcription factor to a highly conserved p53-binding sequence within the MMP-2 promoter. Concordantly, the neovascular effects of CTGF/CCN2 were suppressed by p53 inhibition that culminated in reduced enrichment of the MMP-2 promoter with p53 and decreased MMP-2 gene expression. Our data identified new gene targets and downstream effectors of CTGF/CCN2 and provided the rational basis for targeting the p53 pathway to curtail the effects of CTGF/CCN2 on neovessel formation associated with ischemic retinopathy.

Giant Cell Tumour of the Small Bones of Hand and Foot.

Introduction Giant cell tumor (GCT) or bony tumor mainly involving long bones of arms and legs is very rarely associated with the small bones of hands and feet. Due to its nonspecific signs and symptoms, it is not easy to diagnose based on clinical findings; therefore, histopathological evidence is required to confirm it. Method A total of 16 patients with positive histopathological bone lesions enriched with giant cells were included in our study. After a complete evaluation of their case records, the required radiological assessment was carried out. Campanacci's method of staging was used to evaluate the advancement of lesions. The Musculoskeletal Tumour Society (MSTS) score was recorded postoperatively. All the patients were followed up for a mean duration of 2.8 years until they were lost to follow-up. Result The result of the current study shows that 62.5% of our patients presented in their twenties and 81.25% of patients came at a reasonably advanced stage. Hand and foot were involved in 1:1 cases. Patients were treated by one of the following options: extended curettage with bone graft or cement, wide excision, or en bloc resection. Phenol, a neoadjuvant, was used in all patients. Two of our patients (6.25%) who underwent curettage with bone graft showed up with recurrence during follow-up - one was then treated with wide excision and the other with amputation. Conclusion Giant cell tumors should undoubtedly be aggressively approached with the goal of preserving limb function while reducing recurrence risk to as minimal as possible. GCT of hand is more aggressive comparatively and should be treated accordingly.

Effect of Carbon Nanotubes on the Na+ Intercalation Capacity of Binder Free Mn2V2O7-CNTs Electrode: A Structural Investigation.

Improvements in sodium intercalation in sodium cathodes have been debated in recent years. In the present work, we delineate the significant effect of the carbon nanotubes (CNTs) and their weight percent in the intercalation capacity of the binder-free manganese vanadium oxide (MVO)-CNTs composite electrodes. The performance modification of the electrode is discussed taking into account the cathode electrolyte interphase (CEI) layer under optimal performance. We observe an intermittent distribution of the chemical phases on the CEI, formed on these electrodes after several cycles. The bulk and superficial structure of pristine and Na+ cycled electrodes were identified via micro-Raman scattering and Scanning X-ray Photoelectron Microscopy. We show that the inhomogeneous CEI layer distribution strongly depends on the CNTs weight percentage ratio in an electrode nano-composite. The capacity fading of MVO-CNTs appears to be associated with the dissolution of the Mn2O3 phase, leading to electrode deterioration. This effect is particularly observed in electrodes with low weight percentage of the CNTs in which the tubular topology of the CNTs are distorted due to the MVO decoration. These results can deepen the understanding of the CNTs role on the intercalation mechanism and capacity of the electrode, where there are variations in the mass ratio of CNTs and the active material.

Imaging Interface and Particle Size Effects by In Situ Correlative Microscopy of a Catalytic Reaction.

The catalytic behavior of Rh particles supported by three different materials (Rh, Au, and ZrO2) in H2 oxidation has been studied in situ by correlative photoemission electron microscopy (PEEM) and scanning photoemission electron microscopy (SPEM). Kinetic transitions between the inactive and active steady states were monitored, and self-sustaining oscillations on supported Rh particles were observed. Catalytic performance differed depending on the support and Rh particle size. Oscillations varied from particle size-independent (Rh/Rh) via size-dependent (Rh/ZrO2) to fully inhibited (Rh/Au). For Rh/Au, the formation of a surface alloy induced such effects, whereas for Rh/ZrO2, the formation of substoichiometric Zr oxides on the Rh surface, enhanced oxygen bonding, Rh-oxidation, and hydrogen spillover onto the ZrO2 support were held responsible. The experimental observations were complemented by micro-kinetic simulations, based on variations of hydrogen adsorption and oxygen binding. The results demonstrate how correlative in situ surface microscopy enables linking of the local structure, composition, and catalytic performance.

Oxide Coating Role on the Bulk Structural Stability of Active LiMn2O4 Cathodes.

The protective coating of the electrode materials is a known source of improvement of the cycling performances in battery devices. In the case of the LiMn2O4 cathodes, the coating with a thin alumina layer has been proven to show performance efficiency. However, the precise mechanism of its effect on the performance improvement of the electrodes is still not clear. In this work we investigate alumina-coating-induced effects on the structural dynamics of the active materials in correlation to the modified solid electrolyte interface dynamics. The local structures of coated and uncoated samples at different galvanostatic points are studied by both soft X-ray absorption measurements at the Mn L-edges and O K-edge (in total electron yield mode) and hard X-ray absorption at the Mn K-edge (in transmission mode). The different probing depths of the employed techniques allowed us to study the structural dynamics both at the surface and within the bulk of the active material. We demonstrate that the coating successfully hinders the Mn3+ disproportionation and, hence, the degradation of the active material. Side products (layered Li2MnO3 and MnO) and changes in the local crystal symmetry with formation of Li2Mn2O4 are observed in uncoated electrodes. The role of alumina coating on the stability of the passivation layer and its consequent effect on the structural stability of the bulk active materials is discussed.

Highly Responsive Near-Infrared Si/Sb2Se3 Photodetector via Surface Engineering of Silicon.

The development of imaging technology and optical communication demands a photodetector with high responsiveness. As demonstrated by microfabrication and nanofabrication technology advancements, recent progress in plasmonic sensor technologies can address this need. However, these photodetectors have low optical absorption and ineffective charge carrier transport efficiency. Sb2Se3 is light-sensitive material with a high absorption coefficient, making it suitable for photodetector applications. We developed an efficient, scalable, low-cost near-infrared (NIR) photodetector based on a nanostructured Sb2Se3 film deposited on p-type micropyramidal Si (made via the wet chemical etching process), working on photoconductive phenomena. Our results proved that, at the optimized thickness of the Sb2Se3 layer, the proposed Si micropyramidal substrate enhanced the responsivity nearly two times, compared with that of the Sb2Se3 deposited on a flat Si reference sample and a glass/Sb2Se3 sample at 1064 nm (power density = 15 mW/cm2). More interestingly, the micropyramidal silicon-based device worked at 0 V bias, paving a path for self-bias devices. The highest specific detectivity of 2.25 × 1015 Jones was achieved at 15 mW/cm2 power density at a bias voltage of 0.5 V. It is demonstrated that the enhanced responsivity was closely linked with field enhancement due to the Kretschmann configuration of Si pyramids, which acts as hot spots for Si/Sb2Se3 junction. A high responsivity of 47.8 A W-1 proved it suitable for scalable and cost-effective plasmonic-based NIR photodetectors.

Na ion batteries: An India centric review.

Developing low-cost and safe energy storage devices is the primary goal of every country to make a carbon-neutral atmosphere by ∼2050. Batteries and supercapacitors are the backbones of future sustainable energy sources for electrical vehicles (EVs), smart electronic devices, electricity supply to off-grid regions, etc. Hence, these battery-dependent devices are substantially gaining the market. Although lithium-ion batteries account for powering most of these devices, lithium availability and price pose a severe problem since lithium resources are not abundant in nature. Thus, alternative research on sodium-ion or other multi-charged cations (Al3+/Mg2+/Ca2+/K+) based energy storage devices is needed to substitute lithium-ion batteries. India and many other countries have sodium in abundance. Sodium also has potential in designing and developing efficient charge storage devices. This review article discusses the status of sodium-ion battery research activities, cost, market analysis, and future strategies of the Indian government or private bodies, industries, and research institutes of India.

How the Environment Encourages the Natural Formation of Hydrated V2O5.

Herein, we report the microscopic and spectroscopic signatures of the hydrated V2O5 phase, prepared from the α-V2O5 powder, which was kept in deionized water inside an airtight glass container for approximately 2.5 years. The experimental results show an evolution of the V4+ component in V 2p3/2 core energy level spectra, and a peak corresponding to σ-OH- bond appeared in the valence band spectra in the hydrated V2O5 powder sample due to the water intercalation. Vanadium metal oxide particles were found to be self-nucleated into micro/nanorods after a long period of exposure to an extremely humid environment. The distinct features in the spectra obtained with high-resolution transmission electron microscopy, micro-Raman scattering, and X-ray photoelectron spectroscopy confirmed the presence of structural water molecules for the first time in the long-aged naturally hydrated V2O5 phase.

Temperature-Dependent n-p-n Switching and Highly Selective Room-Temperature n-SnSe2/p-SnO/n-SnSe Heterojunction-Based NO2 Gas Sensor.

Many toxic gases are mixed into the atmosphere because of increased air pollution. An efficient gas sensor is required to detect these poisonous gases with its ultrasensitive ability. We employed the thermal evaporation method to deposit an n-SnSe2/p-SnO/n-SnSe heterojunction and observed a temperature-dependent n-p-n switching NO2 gas sensor with high selectivity working at room temperature (RT). The structural and morphological properties of the material were studied using the characterization techniques such as XRD, SEM, Raman spectroscopy, XPS, and HRTEM, respectively. At RT, the device response was 256% for 5 ppm NO2. The response/recovery times were 34 s/272 s, respectively. The calculated limit of detection (LOD) was ∼115 ppb with a 38% response. The device response was better with NO2 gas than with SO2, NO, H2S, CO, H2, and NH3. The mechanism of temperature-dependent n-p-n switching, fast response, recovery, and selective detection of NO2 at RT has been discussed on the basis of physisorption and charge transfer. Thus, this work will add a new dimension to 2D materials as selective gas detectors at room temperature.

Cd-Free Zn(O,S) as Alternative Buffer Layer for Chalcogenide and Kesterite Based Thin Films Solar Cells: A Review.

Cd is categorized as a toxic material with restricted use in electronics as there are inherent problems of treating waste and convincing consumers that it is properly sealed inside without any threat of precarious leaks. Apart from toxicity, band-gap of CdS is about 2.40-2.50 eV, which results significant photon loss in short-wavelength range which restricts the overall performance of solar cells. Thin film of Zn(O,S) is a favorable contender to substitute CdS thin film as buffer layer for CuInGaSe2 (CIGS), CuInGa(S,Se)2 (CIGSSe), Cu2ZnSn(S,Se)4 (CZTSSe) Cu2ZnSnSe4 (CZTSe), Cu2ZnSnS4 (CZTS) thin film absorber material based photovoltaic due to it made from earth abundant, low cost, non-toxic materials and its ability to improve the efficiency of chalcogenide and kesterite based photovoltaic due to wider band-gap which results in reduction of absorption loss compared to CdS. In this review, apart from mentioning various deposition technique for Zn(O,S) thin films, changes in various properties i.e., optical, morphological, and opto-electrical properties of Zn(O,S) thin film deposited using various methods utilized for fabricating solar cell based on CIGS, CIGSSe, CZTS, CZTSe and CZTSSe thin films, the material has been evaluated for all the properties of buffer layer (high transparency for incident light, good conduction band lineup with absorber material, low interface recombination, high resistivity and good device stability).

Reconstruction with biological methods following intercalary excision of femoral diaphyseal tumors.

AIM: The aim of this study was to assess outcomes of biological (nonvascularized fibula grafts and extracorporeal irradiated autologous bone grafts) methods used for reconstruction of intercalary defects after resection of femoral diaphyseal tumors. MATERIALS AND METHODS: This study included 28 patients who had undergone intercalary resection in femoral diaphyseal tumors between 2011 and 2016. The mean follow-up period was 24 months (range 12-57 months). RESULTS: The mean union time for diaphyseo-diaphyseal union was 10.5 and 11 months in nonvascularized fibula group and extracorporeal radiotherapy (ECRT) group, respectively. The mean union time for metaphyseo-diaphyseal union was 6.5 months in both nonvascularized fibula and ECRT groups. Six patients had distant metastasis, and one patient had local recurrence. The mean Musculoskeletal Tumor Society score was 28 at the last follow-up. Two patients had surgical site infection in the nonvascularized fibula group. Implant failure was found in one patient of the ECRT group requiring revision surgery. Three patients had nonunion (two from the nonvascularized fibula group and one from the ECRT group). CONCLUSION: The present study indicates that the biological reconstruction modalities provide good functional outcomes in diaphyseal tumors of femur. Nonvasularized fibula and ECRT-treated autografts reconstruction provides good results, and union timing is comparable. The outcomes of the current study are promising as compared to the results in the reviewed literature. The reconstruction method depends on the resources available at the oncological center and the conversance with the method of the treating surgeon.