Fast convergence of path integrals for many-body systems

We generalize a recently developed method for accelerated Monte Carlo calculation of path integrals to the physically relevant case of generic many-body systems. This is done by developing an analytic procedure for constructing a hierarchy of effective actions leading to improvements in convergence of N-fold discretized many-body path integral expressions from 1/N to 1/Np for generic p. In this Letter we present explicit solutions within this hierarchy up to level p=5. Using this we calculate the low lying energy levels of a two particle model with quartic interactions for several values of coupling and demonstrate agreement with analytical results governing the increase in efficiency of the new method. The applicability of the developed scheme is further extended to the calculation of energy expectation values through the construction of associated energy estimators exhibiting the same speedup in convergence.     

A rapid and sensitive bioanalytical LC–MS/MS method for the quantitation of a novel CDK5 inhibitor 20–223 (CP668863) in plasma: Application to in vitro metabolism and plasma protein-binding studies

A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (MS/MS) method was developed and validated for the quantitation of the novel CDK5 inhibitor ‘20–223' in mouse plasma. Separation of analytes was achieved by a reverse-phase ACE Excel C₁₈ column (1.7 μm, 100 × 2.1 mm) with gradient elution using 0.1% formic acid (FA) in methanol and 0.1% FA as the mobile phase. Analytes were monitored by MS/MS with an electrospray ionization source in the positive multiple reaction monitoring mode. The MS/MS response was linear over the concentration range 0.2–500 ng/mL for 20–223. The within- and between-batch precision were within the acceptable limits as per Food and Drug Administration guidelines. The validated method was successfully applied to plasma protein binding and in vitro metabolism studies. Compound 20–223 was highly bound to mouse plasma proteins (>98% bound). Utilizing mouse S9 fractions, in vitro intrinsic clearance (CL_int) was 24.68 ± 0.99 μL/min/mg protein. A total of 12 phase I and II metabolites were identified with hydroxylation found to be the major metabolic pathway. The validate method required a low sample volume, was linear from 0.2 to 500 ng/mL, and had acceptable accuracy and precision.     

Vertical distribution and radiological risk assessment of natural radionuclides in the alluvial soil profile of south-west Punjab,India

Journal of Radioanalytical and Nuclear Chemistry - Natural radionuclide levels are studied in alluvial sediments upto the depth of 900 cm. Eighteen profiles are selected from agricultural...     

Deciphering Internal and External π-Conjugation in C3-Symmetric Multiple Azobenzene Connected Systems in Self-Assembly

Two tripodal C₃-symmetric photoswitchable molecular systems T1 and T2 are reported that have extended conjugation at external and internal positions using an acryl group. The influence of the extended π-bonds in their absorption properties, thermal relaxation of the photoisomers and their propensities in forming supramolecular self-assemblies have been explored through spectroscopy, and microscopic studies. In particular, the investigations on the self-assembly have been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), polarized optical microscopy (POM), X-ray diffraction studies (XRD) and atomic force microscopy (AFM). Remarkably, the position of the acryl group influences the behaviour of the two target molecules in supramolecular assembly, and also in the formation of photoresponsive organic hydrogels or microcrystals.     

Greener route for microwave enhanced syntheses of bioactive 1,5-benzodiazepines using heterogeneous calcium ferrite/graphene oxide nanocomposite as a novel and sustainable catalyst

In the present paper, a novel and benign protocol for microwave enhanced one pot syntheses of 2,3-dihydro-1,5 benzodiazepine derivatives from substituted acetophenones, aryl-aldehydes and o-phenylene diamine using heterogeneous calcium ferrite/graphene oxide (CF/GO) nanocomposite has been reported. The catalyst was prepared by ultrasonication method and characterized by spectral and analytical techniques. The CF/GO nanocomposite was employed for environmentally benign synthesis of 2,3-dihydro-1,5 benzodiazepines. The synthesized benzodiazepine derivatives were screened for their antimicrobial activities against various bacteria and fungi. The present synthetic strategy offered several advantages such as excellent yields in short span of time, simple modus operandi, ease of isolation and purification of products, simple recovery and reusability of the catalyst. A tentative mechanism for synthesis of 2,3-dihydro-1,5 benzodiazepine using CF/GO nanocatalyst has also been proposed.     

Synthesis,spectroscopic and X-ray structural study of [<Emphasis Type="Italic">trans</Emphasis>-di(4-aminobenzoato)bis(ethylenediamine) cobalt(III)] 4-aminobenzoate tetrahydrate

The title compound was synthesized by mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride and sodium 4-aminobenzoate in aqueous medium in 1:3 molar ratio and recrystallizing the product obtained, from hot water. Elemental analyses and spectroscopic techniques (IR, UV/visible, ¹H and ¹³C NMR) were used for characterizing the complex salt. X-ray structure determination revealed an ionic structure consisting of [Co(en)₂(C₇H₆NO₂)₂]⁺ cation, (C₇H₆NO₂)⁻ anion and four lattice water molecules. The complex salt crystallizes in the triclinic space group P with cell dimensions a = 9.985(1) Å, b = 11.522(1) Å, c = 14.233(1) Å, α = 80.20(1)^∘, β = 72.80(1)^∘, γ = 86.43(1)^∘, Z = 2, V = 1541.3(2) ų, R₁ = 0.0291, and wR₂ = 0.0751.     

Rapid identification of common hexapyranose monosaccharide units by a simple TOCSY matching approach

Solution NMR spectroscopy is a well established technique for non-destructive characterization of the structures and conformations of complex oligo- and polysaccharides. One of the key experiments involves the use of 2D TOCSY to collect the 1H spins into groups that can be associated with the individual saccharide units that are present in the molecule under study. It is well known that the magnetization transfer rate through the 1H spin system during the TOCSY spin lock period is sensitive to the intervening 3J(H,H) scalar couplings, and therefore also to the saccharide stereochemistry. Here, we have investigated the potential to extract information on the stereochemistry of hexapyranose monosaccharide units directly from TOCSY spectra. Through a systematic experimental investigation of the magnetization transfer initiated from the anomeric 1H resonance in D-glucose, D-galactose and D-mannose it is shown that a 100 ms spin lock time provides optimal spectroscopic discrimination between these three commonly occurring building blocks. A simple matching scheme is proposed as a new tool for rapid attribution of the TOCSY traces originating from the anomeric 1H resonances towards the underlying monosaccharide type. The scheme appears robust with regard to structural variations and fairly tolerant to incidental overlap. Its application provides useful guidance during the subsequent NMR assignment process, as demonstrated with the PS7F polysaccharide from Streptococcus pneumonia. In addition, we show that our scheme affords a clear-cut distinction between the alpha- and beta-epimers of D-mannose-type units, which can be difficult to discriminate by NMR analysis. Application to the N-glycan 100.2 demonstrates the potential and wide applicability of this new discrimination approach.     

Rod–disc oligomeric liquid crystal based on 4-cyanobiphenyl and truxene core

A facile synthesis of a novel covalently linked disc–rod mesogen is reported consisting of a truxene-based core attached to which are six 4-cyanobiphenyl units via flexible alkyl spacers. The compound formed a stable Langmuir monolayer at the air–water interface. The atomic force microscope study on the Langmuir–Blodgett film of the molecule reveals a tilted orientation at air–solid interfaces.     

One-pot synthetic approach to isolate a single isomer of bis(diethylenetriamine)cobalt(III) cation in bulk using benzoates and the isomeric effects of the cation on ion association with anions

Using a one-pot synthetic approach, a single isomer of bis(diethylenetriamine)cobalt(III) cation, [Co(dien)₂]³⁺ is obtained in bulk from the isomeric mixture (s-fac : u-fac : mer is 7 : 28 : 65) using sodium salts of benzoates (BBz-bromobenzoate, DNBz-dinitrobenzoate, MBz-methylbenzoate) in aqueous medium. Herein, we report the syntheses and characterization of three complexes of composition mer-[Co(dien)₂]Cl(p-BBz)₂·H₂O (1), s-fac-[Co(dien)₂](o,p-DNBz)₃·H₂O (2) and mer-[Co(dien)₂]Cl(p-MBz)₂·4H₂O (3) in the continuation of our earlier work, where benzoate (Bz), p-chlorobenzoate (CBz), p-nitrobenzoate (NBz) and p-aminobenzoate (ABz) were used. The isomeric identification of complex cation was initially made on the basis of spectroscopic characterization (UV–visible, IR and NMR). The binding properties of [Co(dien)₂]³⁺ with benzoates (p-BBz, o,p-DNBz, p-MBz, Bz, CBz, NBz or ABz) have been studied using standard UV–visible spectroscopic titrations in aqueous medium and comparison indicate ion association constants of s-fac > mer. The single-crystal X-ray diffraction structure analysis of 3 reveals the presence of discrete ions ([Co(dien)₂]³⁺, chloride, p-MBz) along with four lattice water molecules. The structure of 3, with formula [Co(dien)₂](p-MBz)₂Cl·4H₂O, consists of alternating layers made of benzoate ions and layers made of [Co(dien)₂]³⁺, chloride and water molecules. These layers result in the formation of their respective columns and intermolecular cohesion of p-MBz within the columns of [Co(dien)₂]³⁺ is achieved via electrostatic and H-bonding interactions.