Possible charge ordering and anomalous transport in graphene/graphene quantum dot heterostructure.

Observations of superconductivity and charge density waves (CDW) in graphene have been elusive thus far due to weak electron-phonon coupling (EPC) interactions. Here, we report a unique observation of anomalous transport and multiple charge ordering phases at high temperatures (T1∼213K,T2∼325K) in a 0D-2D van der Waals (vdW) heterostructure comprising of single layer graphene (SLG) and functionalized (amine) graphene quantum dots (GQD). The presence of functionalized GQD contributed to charge transfer with shifting of the Dirac point ∼ 0.05 eV above the Fermi level (ab initio simulations) and carrier densityn∼-0.3×1012 cm-2confirming p-doping in SLG and two-fold increase in EPC interaction was achieved. Moreover, we elucidate the interplay between electron-electron and electron-phonon interactions to substantiate high temperature EPC driven charge ordering in the heterostructure through analyses of magnetotransport and weak anti-localization (WAL) framework. Our results provide impetus to investigate strongly correlated phenomena such as CDW and superconducting phase transitions in novel graphene based heterostructures.

Capturing functional relations in fluid-structure interaction via machine learning.

While fluid-structure interaction (FSI) problems are ubiquitous in various applications from cell biology to aerodynamics, they involve huge computational overhead. In this paper, we adopt a machine learning (ML)-based strategy to bypass the detailed FSI analysis that requires cumbersome simulations in solving the Navier-Stokes equations. To mimic the effect of fluid on an immersed beam, we have introduced dissipation into the beam model with time-varying forces acting on it. The forces in a discretized set-up have been decoupled via an appropriate linear algebraic operation, which generates the ground truth force/moment data for the ML analysis. The adopted ML technique, symbolic regression, generates computationally tractable functional forms to represent the force/moment with respect to space and time. These estimates are fed into the dissipative beam model to generate the immersed beam's deflections over time, which are in conformity with the detailed FSI solutions. Numerical results demonstrate that the ML-estimated continuous force and moment functions are able to accurately predict the beam deflections under different discretizations.

Lumbar spine instrumented fusion surgery under spinal anaesthesia versus general anaesthesia-A retrospective study of 239 cases.

OBJECTIVE: Conventionally spinal surgeries are done under general anaesthesia (GA). Plenty of literature is available on lumbar spine non-instrumented surgeries under spinal anaesthesia (SA) but handful of literature is there on lumbar spinal instrumented fusion surgeries under SA. We retrospectively analysed the data of 131 patients operated under SA and 108 patients under GA. Aim of the study was to evaluate the safety, advantages and disadvantages of doing lumbar spine instrumented fusion surgeries under SA.In time of COVID-19 pandemic, aerosol generating procedure like intubation, can be avoided if lumbar spine instrumented fusion surgeries are performed under SA. METHODS: 239 patients aged between 20 and 79 years operated from January 2014 to December 2019 were included in this study. Indications for surgery were lumbar canal stenosis, degenerative or lytic spondylolisthesis. They underwent L4-L5 or L5-S1 fusion surgeries either TLIF or pedicle screw fixation postero lateral fusion (PLF) and decompression. Out of 239 patients,131 were operated under SA and 108 patients under GA. Heart rate, mean arterial pressure (MAP), blood loss, operating room time, post-op pain relief and need of analgesics, cost of surgery and anaesthesia related complications were analysed. RESULTS: The study found significantly less blood loss (p<.05), less OR time, better post-op analgesia and lesser incidence of nausea and vomiting in SA (8.4%) than GA (29.6%). We observed average 10% cost reduction in SA. This study did not find any prone position related complication in regional anaesthesia but one transient brachial plexus palsy and one post-op shoulder pain in GA group. CONCLUSION: SA is a safe alternative to GA for lumbar spine instrumented fusion surgery with significant less blood loss, OR time, better post-op analgesia, average 10% overall cost reduction and no reported prone-position related complications.

Negative capacitance switching in size-modulated Fe3O4 nanoparticles with spontaneous non-stoichiometry: confronting its generalized origin in non-ferroelectric materials.

Persistent low-frequency negative capacitance (NC) dispersion has been detected in half-metallic polycrystalline magnetite (Fe3O4) nanoparticles with varying sizes from 13 to 236 nm under the application of moderate dc bias. Using the Havriliak-Negami model, 3D Cole-Cole plots were employed to recapitulate the relaxation times (τ) of the associated oscillating dipoles, related shape parameters (α, ß) and resistivity for the nanoparticles with different sizes. The universal Debye relaxation (UDR) theory requires a modification to address the shifted quasi-static NC-dispersion plane in materials showing both +ve and -ve capacitances about a transition/switching frequency (f0). A consistent blue-shift in 'f0' is observed with increasing external dc field and decreasing particle size. Based on this experimental data, a generalized dispersion scheme is proposed to fit the entire positive and negative capacitance regime, including the diverging transition point. In addition, a comprehensive model is discussed using phasor diagrams to differentiate the underlying mechanisms of the continuous transition from -ve to +ve capacitance involving localized charge recombination or time-dependent injection/displacement currents, which has been adequately explored in the scientific literature, and the newly proposed 'capacitive switching' phenomenon. An inherent non-stoichiometry due to iron vacancies [Fe3(1-δ)O4], duly validated from first principles calculations, builds up p-type nature, which consequently promotes more covalent and heavier dipoles and slows the dipolar relaxations; this is incommensurate with Maxwell-Wagner interfacial polarization (MWIP) dynamics. This combinatorial effect is likely responsible for the sluggish response of the associated dipoles and the stabilization of NC.

Size-modulation of functionalized Fe3O4: nanoscopic customization to devise resolute piezoelectric nanocomposites.

Magnetite (Fe3O4), a representative relaxor multiferroic material, possesses fundamentally appealing multifaceted size-dependent properties. Herein, to evaluate a prototype spinel transition metal oxide (STMO), monodispersed and highly water-dispersible spherical magnetite nanoparticles (MNPs) with an enormous size range (3.7-242.8 nm) were synthesized via a facile microwave-assisted and polyol-mediated solvothermal approach at a controlled temperature and pressure using unique crystallite growth inhibitors. The excellent long-term colloidal stability of the MNPs in a polar environment and increase in their zeta potential confirmed the coordinative effect of the carboxylate groups derived from the covalent surface functionalization, which was also validated by FTIR spectroscopy, TGA and XPS analysis. The optical bandgap (Eg) between the crystal field split-off bands, which was calculated using the absorption spectra, increased gradually with a decrease in size of the MNPs within a broad UV-Vis range (1.59-4.92 eV). The red-shifting of the asymmetric Raman peaks with a smaller size and short-range electron-phonon coupling could be explained by the modified phonon confinement model (MPCM), whereas ferrimagnetic nature rejigged by superparamagnetism was verified from Mössbauer analysis. These stoichiometric, non-toxic, polar and magnetic nanocrystals are not only ideal for biomedical applications, but also suitable as electroactive porous host networks. Finally, the size-modulated MNPs were incorporated in poly(vinylidene fluoride) [PVDF]-based polytype nanogenerators as an electret filler to demonstrate their piezoelectric performance (VOC∼115.95 V and ISC∼1.04 µA), exhibiting substantial electromagnetic interference shielding.

CsPbBrCl2/g-C3N4 type II heterojunction as efficient visible range photocatalyst.

Photocatalytic activity of low band gap semiconductor largely restrained by high recombination rate of photogenerated charge carriers. To enhance the catalytic performance numerous protocols were adopted amongst which designing of novel hybrid via coupling of semiconductors are very intriguing from modest application point of view. Here, we report facile realization of type II heterojunctions embracing polymeric graphitic carbon nitride (g-C3N4/GCN) and all-inorganic cesium lead halide perovskite (CsPbBrCl2) for degradation complex organic effluents under visible-light illumination. Synthesized hybrid presented much improved performance in toxic cationic and anionic dyes degradation as compared to individual building units. Signature of favorable staggered gap junction's formation at interface was confirmed via Mott-Schottky analysis. Such kind of junctions delay the recombination of photogenerated electron holes and facilitates active radical generation at catalyst surface thereby ensures improved photocatalytic performance. Charge transfer process in heterojunction further illustrated via Density functional theory (DFT) based calculations. Several scavenger tests have been performed to examine the impact of different active radicals in the photocatalysis which suggests manifold performance improvement in the presence of very small concentrations of EDTA. A plausible photocatalytic mechanism in accordance with the type II junction has been proposed.

Synthesis, spectroscopic characterization and magnetic properties of homo- and heterodinuclear complexes of transition and non-transition metal ions with a new Schiff base ligand.

Four homodinuclear complexes of Ni(II)-Ni(II), Cu(II)-Cu(II), Co(II)-Co(II) and Co(III)-Co(II) and five heterodinuclear complexes of Co(III)-Zn(II), Co(III)-Cu(II), Co(III)-Ni(II), Cu(II)-Zn(II) and Zn(II)-Cu(II) with the octadentate Schiff base compartmental ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H4fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV-vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes.

Spectroscopy, crystal structure, valance molecular orbital energy level diagram and DFT study of cis-[Cr(2,2'-bipy)2Cl2](Cl)0.38(PF6)0.62.

A new octahedral chromium(III) complex having 2,2'-bipyridine as ligand system was synthesized in methanol. Single crystal X-ray diffraction analysis shows that it possesses non-stoichiometry in its anionic primary covalency. It has also been studied by elemental analyses, optical spectroscopy (UV-vis, IR) and magnetic susceptibility data. DFT calculations (with B3LYP functional and double-xi quality LANLDZ(D95V) basis set) were carried out to interpret the electronic and infrared spectra of the complex. The DFT optimized geometric structure for the complex is compared with the X-ray crystallographic data; the theory-experiment agreement is satisfactory.

New route to the synthesis of bis[N-(2-aminoethyl) salicylaldiminato] chromium(III) chloride monohydrate Spectroscopic characterization, crystal structure and interaction with DNA.

The reaction of [Cr(urea)(6)]Cl(3).3H(2)O with H(2)salen (H(2)salen=N,N(')-ethylenebis(salicylaldimine) in water-methanol mixture (40:60v/v) under reflux yielded the complex bis[N-(2-aminoethyl)salicylaldiminato]chromium(III) chloride monohydrate, [Cr(aesaldmn)(2)]Cl.H(2)O. The complex was characterized by elemental analysis, molar conductance, magnetic susceptibility, spectroscopic (UV-vis and IR) data and X-ray diffraction studies. The new ligand, N-(2-aminoethyl)salicylaldimine, Haesaldmn, possibly resulted from the hydrolytic cleavage of one end of the H(2)salen ligand during reflux. Binding of this chromium(III) complex to CT DNA has been studied using UV-vis spectroscopy with an apparent binding constant of 2.68 x 10(3)M(-1). It shows that the binding mode is electrostatic while the emission of ethidium bromide to CT DNA in the absence and in the presence of the complex show that it binds DNA with partial intercalation.

Synthesis and spectroscopic characterization of some transition metal complexes of a new hexadentate N(2)S(2)O(2) Schiff base ligand.

A novel interesting hexadentate dibasic N(2)S(2)O(2) donor Schiff base ligand, H(4)dcsalpte, was synthesized by the condensation of 3-formylsalicylic acid and 1,2-di(o-aminophenylthio)ethane and characterized. The reactions of the ligand with different metal(II/III)salts under varied reaction conditions afforded a series of metal complexes. The ligand, H(4)dcsalpte, behaves either as a dibasic or neutral hexadentate one, depending on the reaction conditions. Structural investigations on the ligand and their complexes have been made based on elemental analyses, molar conductance values, magnetic moment values, cryomagnetic and spectral (UV-vis, IR, (1)H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe(III)(H(2)dcsalpte)]ClO(4) (8), isolated in the present investigation, it is inferred that the spin states 5/2 and 1/2 are in equilibrium. Similarly a tri-iron(III) complex [Fe(III)(3)(H(2)dcsalpte)(H(3)dcsalpte)Cl(3)]Cl(3) (7), isolated in this study, has been inferred to contain two iron(III) sites in tetrahedral environment and one in the octahedral environment. The aerial oxidation of an equimolar mixture of H(4)dcsalpte and Co(CH(3)COO)(2).4H(2)O in ethanol under reflux gave two products, [Co(H(2)dcsalpte)]CH(3)COO (10) and [(Hbtcsaldm)Co(Hbvcsaldm)] (11), a cobalt(III) complex bound to two dissimilar tridentate NSO donor ligands formed as a result of the oxidative cleavage of the CS bond. In the complex 11, Hbtcsaldm stands for the dianion of the tridentate Schiff base ligand N-(2'-benzenethiol)-3-carboxysalicylaldimine and Hbvcsaldm stands for the mono anion of the tridentate Schiff base ligand N-(benzene-2'-S-vinyl)-3-carboxysalicylaldimine, both being formed as a result of the oxidative cleavage of H(4)dcsalpte.

A global optimization paradigm based on change of measures.

A global optimization framework, COMBEO (Change Of Measure Based Evolutionary Optimization), is proposed. An important aspect in the development is a set of derivative-free additive directional terms, obtainable through a change of measures en route to the imposition of any stipulated conditions aimed at driving the realized design variables (particles) to the global optimum. The generalized setting offered by the new approach also enables several basic ideas, used with other global search methods such as the particle swarm or the differential evolution, to be rationally incorporated in the proposed set-up via a change of measures. The global search may be further aided by imparting to the directional update terms additional layers of random perturbations such as 'scrambling' and 'selection'. Depending on the precise choice of the optimality conditions and the extent of random perturbation, the search can be readily rendered either greedy or more exploratory. As numerically demonstrated, the new proposal appears to provide for a more rational, more accurate and, in some cases, a faster alternative to many available evolutionary optimization schemes.

Internal noise-driven generalized Langevin equation from a nonlocal continuum model.

Starting with a micropolar formulation, known to account for nonlocal microstructural effects at the continuum level, a generalized Langevin equation (GLE) for a particle, describing the predominant motion of a localized region through a single displacement degree of freedom, is derived. The GLE features a memory-dependent multiplicative or internal noise, which appears upon recognizing that the microrotation variables possess randomness owing to an uncertainty principle. Unlike its classical version, the present GLE qualitatively reproduces the experimentally measured fluctuations in the steady-state mean square displacement of scattering centers in a polyvinyl alcohol slab. The origin of the fluctuations is traced to nonlocal spatial interactions within the continuum, a phenomenon that is ubiquitous across a broad class of response regimes in solids and fluids. This renders the proposed GLE a potentially useful model in such cases.

Diffusing-wave spectroscopy in an inhomogeneous object: local viscoelastic spectra from ultrasound-assisted measurement of correlation decay arising from the ultrasound focal volume.

We demonstrate diffusing-wave spectroscopy (DWS) in a localized region of a viscoelastically inhomogeneous object by measurement of the intensity autocorrelation [g(2)(τ)] that captures only the decay introduced by the temperature-induced Brownian motion in the region. The region is roughly specified by the focal volume of an ultrasound transducer which introduces region specific mechanical vibration owing to insonification. Essential characteristics of the localized non-Markovian dynamics are contained in the decay of the modulation depth [M(τ)], introduced by the ultrasound forcing in the focal volume selected, on g(2)(τ). The modulation depth M(τ(i)) at any delay time τ(i) can be measured by short-time Fourier transform of g(2)(τ) and measurement of the magnitude of the spectrum at the ultrasound drive frequency. By following the established theoretical framework of DWS, we are able to connect the decay in M(τ) to the mean-squared displacement (MSD) of scattering centers and the MSD to G*(ω), the complex viscoelastic spectrum. A two-region composite polyvinyl alcohol phantom with different viscoelastic properties is selected for demonstrating local DWS-based recovery of G*(ω) corresponding to these regions from the measured region specific M(τ(i))vsτ(i). The ultrasound-assisted measurement of MSD is verified by simulating, using a generalized Langevin equation (GLE), the dynamics of the particles in the region selected as well as by the usual DWS experiment without the ultrasound. It is shown that whereas the MSD obtained by solving the GLE without the ultrasound forcing agreed with its experimental counterpart covering small and large values of τ, the match was good only in the initial transients in regard to experimental measurements with ultrasound.

Titanium elastic nail - Complications in the treatment of paediatric diaphyseal fracture of femur [corrected].

BACKGROUND: Femoral shaft fracture is the most common major paediatric orthopaedic. For generations traction and casting was the standard treatment for all femoral shaft fractures in children. Over the past two decades the advantages of fixation and rapid mobilisation have been increasingly recognised. METHODS: A prospective study was conducted in five private hospitals in the district of Bankura, West Bengal over a period of two years (April 2010 to March 2012) on 70 patients with closed shaft femur fractures between 6- 14 years age of either sex. The aim was to find out the short term complications of titanium elastic nailing in diaphyseal fracture of femur in children and compare the findings of this study with pre- existing studies in this field. RESULTS: In our study the most common complication was pain at nail entry site (60%). 5.71% had local inflammatory reaction due to nails. Superficial infection occurred in 2.85%. At the end of 1 year, 2.85% had limb length discripancies. Proximal migration occurred in 2.85%. 2.85% encountered acute reactive synovitis, 5.71% developed angulation of fracture site and 2.85% developed per operative breakage of nail. CONCLUSION: The treatment of paediatric shaft femur fracture has been drastically changed over the last two decades to internal fixation by elastically stable intra- medullary nail (ESIN). In our study, we encountered only a few complications most of them being minor. Most of the complications were surgical technique related and were seen at the initial phase of the learning curve.

A series of transition and non-transition metal complexes from a N4O2 hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities.

Some transition and non-transition metal complexes of the hexadentate N4O2 donor Schiff base ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H4fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H4fsatrien, is found to act as a dibasic hexadentate ligand using N2N2O2 donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO²(+) and UO2²(+). However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO2²(+) and VO²(+), respectively. In case of divalent metal complexes they have the general formula [M(H2fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H2fsatrien)]X·nH2O (where M stands for Cr, Mn, Fe, Co and X stands for CH3COO, Cl, NO3, ClO4) and for the complexes of VO²(+) and UO2²(+), [M(H4fsatrien)]Y (where M=VO and Y=SO4); M=UO2 and Y=2 NO3). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities.