Preparation and characterization of a reduced chromium complex via vinyl oxidative coupling: formation of a self-activating catalyst for selective ethylene trimerization

Reaction of the divalent [(t-Bu)NP(Ph)(2)N(t-Bu)]CrCl(2)Li(THF)(2) (1) with 1 equiv of vinyl Grignard (CH(2)=CH)MgCl reproducibly afforded the triangulo {π-[(t-Bu)N-P(Ph)(2)-N(t-Bu)]Cr}(2)(μ,μ',η(4),η(4)'-C(4)H(4)){σ-[(t-Bu)N-P(Ph)(2)-N(t-Bu)]Cr} (2) containing a σ-/π-bonded butadiene-diyl unit. The diene-diyl moiety was generated by an oxidative coupling and deprotonation of two vinyl anions. The crystal structure revealed that of the three chromium atoms, each bearing one NPN ligand, two are perpendicularly bonded to the two sides of the π-system of the butadiene-diyl residue in a sort of inverted sandwich type of structure. The third is instead coplanar with the doubly deprotonated C(4) unit and σ-bonded to the two terminal carbon atoms. Despite the appearance as a Cr(II)/Cr(I) mixed valence species, DFT calculations have revealed that the structure of 2 consists of three divalent chromium atoms, while the additional electron resides on the π-system of the bridging organic residue. Complex 2 behaves as a single component selective catalyst for ethylene trimerization.     

Technology behind commercial devices for blood glucose monitoring in diabetes management: a review

The blood glucose monitoring devices (BGMDs) are an integral part of diabetes management now-a-days. They have evolved tremendously within the last four decades in terms of miniaturization, rapid response, greater specificity, simplicity, minute sample requirement, painless sample uptake, sophisticated software and data management. This article aims to review the developments in the technologies behind commercial BGMD, especially those in the areas of chemistries, mediators and other components. The technology concerns, on-going developments and future trends in blood glucose monitoring (BGM) are also discussed.     

Photochemically-Induced Fluorescence Dosage of Non-Fluorescent Pyrethroid (Etofenprox) in Natural Water Using a Cationic Micellar Medium

An analytical method based on the use of UV-irradiation to produce fluorescent derivatives from Etofenprox a non-fluorescent pyrethroid insecticide is described. The impact of cetyltrimethylammonium chloride (CTAC) micellar medium on the Etofenprox photochemically-induced fluorescence (PIF) is reported. Parameters influencing the sensitivity and repeatability of the PIF method have been optimized. The alkaline medium (NaOH 6 × 10⁻² M) + CTAC surfactant molecules (3.84 mg/ml) in acetonitrile is found to be very suitable for this pyrethroid insecticide analysis in environment matrices. Linear dynamic range is established over more than two orders of magnitude. The limit of detection is lower than 5 ng/ml. The method seems to be suitable for environmental matrices quality control. Application to the analysis of spiked natural waters gave recoveries rate ranged from 94 to 104% and 107 to 115% respectively for river and pound water.     

An investigation of the relationship between BOLD and perfusion signal changes during epileptic generalised spike wave activity

In pathological conditions interpretation of functional magnetic resonance imaging (fMRI) results can be difficult. This is due to a reliance on the assumed coupling between neuronal activity and changes in cerebral blood flow (CBF) and oxygenation. We wanted to investigate the coupling between blood oxygen level dependant contrast (BOLD) and CBF time courses in epilepsy patients with generalised spike wave activity (GSW) to better understand the underlying mechanisms behind the EEG-fMRI signal changes observed, especially in regions of negative BOLD response (NBR). Four patients with frequent GSW were scanned with simultaneous electroencephalographic (EEG)-fMRI with BOLD and arterial spin labeling (ASL) sequences. We examined the relationship between simultaneous CBF and BOLD measurements by looking at the correlation of the two signals in terms of percentage signal change on a voxel-by-voxel basis. This method is not reliant on coincident activation. BOLD and CBF were positively correlated in patients with epilepsy during background EEG activity and GSW. The subject average value of the Delta CBF/Delta BOLD slope lay between +19 and +36 and also showed spatial variation which could indicate areas with altered vascular response. There was not a significant difference between Delta CBF/Delta BOLD during GSW, suggesting that neurovascular coupling to BOLD signal is generally maintained between states and, in particular, within areas of NBR.     

Glassy phase and thermodynamics for random field Ising model on spherical lattice in magnetic field

Phase diagram and thermodynamic parameters of the random field Ising model (RFIM) on spherical lattice are studied by using mean field theory. This lattice is placed in an external magnetic field (B). The random field (hi) is assumed to be Gaussian distributed with zero mean and a variance     

Biaryl scaffold-focused virtual screening for anti-aggregatory and neuroprotective effects in Alzheimer’s disease

Background

Alzheimer’s disease (AD) is a primary cause of dementia in ageing population affecting more than 35 million people around the globe. It is a chronic neurodegenerative disease caused by defected folding and aggregation of amyloid beta (Aβ) protein. Aβ is formed by the cleavage of membrane embedded amyloid precursor protein (APP) by using enzyme ‘transmembrane aspartyl protease, β-secretase’. Inhibition of β-secretase is a viable strategy to prevent neurotoxicity in AD. Another strategy in the treatment of AD is inhibition of acetylcholinesterase. This inhibition reduces the degradation of acetylcholine and temporarily restores the cholinergic function of neurons and improves cognitive function. Monoamine oxidase and higher glutamate levels are also found to be linked with Aβ peptide related oxidative stress. Oxidative stress leads to reduced activity of glutamate synthase resulting in significantly higher level of glutamate in brain. The aim of this study is to perform in silico screening of a virtual library of biaryl scaffold containing compounds potentially used for the treatment of AD. Screening was done against the primary targets of AD therapeutics, acetylcholinesterase, β-secretase (BACE1), Monoamine oxidases (MAO) and N-Methyl-D-aspartate (NMDA) receptor. Compounds were screened for their inhibitory potential by employing molecular docking approach using AutoDock vina. Binding energy scores were embodied in the heatmap to display varies strengths of interactions of the ligands targeting AD.

Results

Several ligands showed notable interaction with at least two targets, but the strong interaction with all the targets is shown by very few ligands. The pharmacokinetics of the interacting ligands was also predicted. The interacting ligands have good drug-likeness and brain availability essential for drugs with intracranial targets.

Conclusion

These results suggest that biaryl scaffold may be pliable to drug development for neuroprotection in AD and that the synthesis of further analogues to optimize these properties should be considered.

     

Atomic structure and chemical order in binary Ge–Te and As–Te glasses: A Te K-edge X-ray absorption fine structure spectroscopic study

The nearest-neighbor coordination environments of Te atoms in Ge_xTe_100?x glasses with x = 15 and 20 and in As_xTe_100?x glasses with 40 ? x ? 65 have been studied with Te K-edge EXAFS spectroscopy. The average coordination number of Te atoms in all glasses is found to be ～2.0 and no violation of the 8-N rule is observed. The compositional makeup of the first coordination shell of Te atoms indicates that chemical order is largely preserved in both glass-forming binary systems. Sudden changes in the Te coordination environment and violation of chemical order are observed at the stoichiometric As₄₀Te₆₀ glass implying formation of a constrained network. The compositional dependence of the physical properties in both systems can be correlated to short-range chemical order.     

Sensitive and Selective Detection of Antibiotic D-Penicillamine Based on a Dual-Mode Probe of Fluorescent Carbon Dots and Gold Nanoparticles

This paper reported a dual-mode probe for D-penicillamine on the basis of pH-mediated gold nanoparticles aggregation and fluorescence resonance energy transfer (FRET) from carbon dots. D-penicillamine is a zwitterionic compound and has different forms depending on specific pH ranges. The thiol group of D-penicillamine has high affinity towards the surface of gold nanoparticles and can replace other surface ligands. When pH values were close to its isoelectrical point (pH(I)), the D-penicillamine capped gold nanoparticles aggregated through hydrogen bonding or electrostatic interactions, resulting in the releasing of carbon dots from gold nanoparticles. The dual-mode probe consisted of fluorescent carbon dots and gold nanoparticles, and the fluorescence of carbon dots was quenched by the attached gold nanoparticles due to the FRET. Then, the fluorescence can be recovered in presence of D-penicillamine due to the gold nanoparticles aggregation in specific pH range. Under the optimum conditions, the probe has linear response for D-penicillamine in the 0.25–1.5 μM concentration range with a detection limit of 0.085 μM. This method provides a potential application in sensitive detection of D-penicillamine.     

Magnetic and microstructural properties of M-type strontium hexaferrites with Pr–ZnAl substitution

We have investigated the influence of Pr–ZnAl substitution on the magnetic and microstructural properties of M-type strontium hexaferrites Sr_1.0-xPr_xFe_12.0-x(Zn_0.5Al_0.5)_xO₁₉ (0.0 ≤ x ≤ 0.5) synthesized by the standard ceramic method. X-ray diffraction (XRD) was carried out to determine the crystal structure and the phase identification of the hexaferrites showed that a single magnetoplumbite phase was exhibited in the hexaferrites with Pr–ZnAl content (x) from 0.0 to 0.4 and impurity phase α-Fe₂O₃ was observed in the structure when Pr–ZnAl content (x)?=?0.5. The morphology of the hexaferrites was analyzed by a field emission scanning electron microscopy (FE-SEM). The representative FE-SEM micrographs showed that the particles were regular hexagonal platelets and the average grain size basically kept unchanged with increasing Pr–ZnAl content (x). A magnetic property measurement system was used to measure the magnetic properties of the hexaferrites. The remanence (B_r), maximum energy product [(BH)_max] and H_k/H_cj ratio decreased with increasing Pr–ZnAl content (x) from 0.0 to 0.5. The intrinsic coercivity (H_cj) and magnetic induction coercivity (H_cb) first increased with increasing Pr–ZnAl content (x) from 0.0 to 0.1, and decreased with increasing Pr–ZnAl content (x) from 0.1 to 0.2, and then increased when Pr–ZnAl content (x) ≥ 0.2.     

Microstructural and magnetic properties of Pr–BiCo co-substituted M-type Sr–Ca hexaferrites

We have synthesized the Pr–BiCo substituted hexaferrites with compositions of Sr_0.8-xCa_0.2Pr_xFe_12.0-x(Bi_0.5Co_0.5)_xO₁₉ (0.0?≤?x?≤?0.5) by the standard ceramic method. Results of X-ray diffraction analysis exhibits that the synthesized hexaferrites with x from 0.0 to 0.3 are in single magetoplumbite structure, and impurity phases are observed when x?≥?0.4. The surface morphology of magnets shows that hexaferrite grains have a hexagonal platelet shape with clear grain boundaries. The remanence first increases with x from 0.0 to 0.1, and then decreases when x?≥?0.1. The intrinsic coercivity decreases with x from 0.0 to 0.1, and then increases when x?≥?0.1. With x from 0.0 to 0.4, the changing trend of magnetic induction coercivity is in agreement with that of H_cj, while at x?≥?0.4, H_cb decreases. The maximum energy product initially increases with x from 0.0 to 0.2, and then decreases when x?≥?0.2.