Order-disorder phase transition and molecular dynamics in the hybrid perovskite [(CH3)3NH][Mn(N3)3].

We present a temperature-dependent Raman scattering study of a [(CH3)3NH][Mn(N3)3] hybrid organic-inorganic azide-perovskite, in which we have analysed in detail the wavenumber and full width at half-maximum (FWHM) of lattice modes and internal modes of the NC3 skeleton, N3- and CH3 molecular groups. In general, the modes exhibited unusual behaviour during the phase transitions, including discontinuity in the phonon wavenumber, bandwidth, and unconventional shifts upon temperature variation. Spectral features on heating reveal the absence of significant distortions in the NC3 skeleton and a relatively restricted order-disorder process of the TrMA+ cations. On the other hand, linewidth anomalies of the δNC3 and νasNC3 modes have been attributed to the molecular dynamics of encapsulated cations. The unconventional blue shift of the symmetric stretching modes of azide ligands indicates the weakening of the intermolecular interactions between the TrMA+ cations and azido-bridges, and the strengthening of the intramolecular bonds. Additionally, we have used differential scanning calorimetry to confirm the subtle monoclinic to monoclinic (P21/c â†’ C2/c) phase transition at around 330 K; and the phase transition to trigonal structure (R3¯m) above 359 K, whose associated entropy variation turns to be |ΔS| ∼ 22.3 J·kg-1 K-1 and displays a barocaloric (BC) tunability |δTt/δP| ∼ 3.17 K kbar-1, according to our estimations using the Clausius-Clapeyron method. Although the obtained values of entropy change and BC tunability are very close to those reported on formate-perovskites and other important caloric materials, those parameters are much lower than the giant entropy change of ∼80 Jkg-1 K-1 and large BC tunability ∼12 K kbar-1 observed for the analogue azide-perovskite [(CH3)4N][Mn(N3)]3 (TMAMnN3). Very interestingly, our combined study shed light to understand such different behaviour, as they reveal that the hydrogen bonds created between the TrMA+ cations and the framework prevent an extensive order-disorder process that is needed to obtain large entropy changes and large BC coefficients as it occurs in the case of related azide-perovskites with no H-bonds between the A cations (for example TMA) and the framework.

Use of Comprehensive Geriatric Assessment and Geriatric Screening for Older Adults in the Radiation Oncology Setting: A Systematic Review.

AIMS: Comprehensive geriatric assessment (CGA) is a multidisciplinary diagnostic process that evaluates medical, psychological, social and functional capacity. No systematic review of the use of CGA in radiation oncology has been conducted. This paper reviews the use of CGA in radiation oncology, examines whether such assessments are feasible and evaluates the effectiveness of these assessments in predicting and modifying outcomes. MATERIALS AND METHODS: We searched Medline, EMBASE, PsycINFO, CINAHL and the Cochrane Library for articles published between 1 January 1996 and 24 January 2017. RESULTS: Twelve non-randomised studies were identified; four studies used a geriatric screening tool only and the eight other studies combined a screening tool with a CGA. Most studies had small samples (mean 63 participants). Two studies identified a significant (95% confidence interval 1.5-4.8 and 1.5-6.9) association between an abnormal screening and increased risk of mortality. One study showed an ability of the CGA to influence treatment decision making, whereas six papers suggested a non-significant association between the screening tool/CGA and treatment tolerance. CONCLUSION: The studies suggest the feasibility of using a screening tool to select patients for CGA. 'Vulnerability' showed a non-statistically significant association with treatment tolerance, but a significant association with mortality.

A combined experimental (IR, Raman and UV-Vis) and quantum chemical study of canadine.

Plant based natural products cover a major sector of the medicinal field, as such focus on plant research has been increased all over the world. As an attempt to aid that research, we have performed structural and spectroscopic analysis of a natural product, an alkaloid: canadine. Both ab initio Hartree-Fock (HF) and density functional theory (DFT) employing B3LYP using 6-311++G(d,p) basis set were used for the calculations. The calculated vibrational frequencies were scaled and compared with the experimental infrared and Raman spectra. The complete vibrational assignments were made using potential energy distribution. The structure-activity relation has also been interpreted by mapping electrostatic potential surface and evaluating the reactivity descriptors, which are valuable information for quality control of medicines and drug-receptor interactions. Natural bond orbital analysis has also been performed to understand the stability and hyperconjugative interactions of the molecule. Furthermore, UV-Vis spectra have been recorded in an ethanol solvent (EtOH) and the electronic property has been analyzed employing TD-DFT for both gaseous and solvent phase. The HOMO and LUMO calculation with their energy gap show that charge transfer occurs within the molecule. Additionally, the nonlinear optical properties of the title compound have been interpreted that predicts it's the best candidate for the NLO materials.

Spectroscopic (far or terahertz, mid-infrared and Raman) investigation, thermal analysis and biological activity of piplartine.

Research in the field of medicinal plants including Piper species like long pepper (Piper longum L.- Piperaceae) is increasing all over the world due to its use in traditional and Ayurvedic medicine. Piplartine (piperlongumine, 5,6-dihydro-1-[(2E)-1-oxo-3-(3,4,5-trimethoxyphenyl)-2-propenyl]-2(1H)-pyridinone), a biologically active alkaloid/amide was isolated from the phytochemical investigations of Piper species, as long pepper. This alkaloid has cytotoxic, anti-fungal, anti-diabetic, anti-platelet aggregation, anti-tumoral, anxiolytic, anti-depressant, anti-leishmanial, and genotoxic activities, but, its anticancer property is the most promising and has been widely explored. The main purpose of the work is to present a solid state characterization of PPTN using thermal analysis and vibrational spectroscopy. Quantum mechanical calculations based on the density functional theory was also applied to investigate the molecular conformation and vibrational spectrum, which was compared with experimental results obtained by Raman scattering, far (terahertz) and mid-infrared adsorption spectroscopy. NBO analysis has been performed which predict that most intensive interactions in PPTN are the hyperconjugative interactions between n(1) N6 and π*(O1C7) having delocalization energy of 50.53kcal/mol, Topological parameters have been analyzed using 'AIM' analysis which governs the three bond critical points (BCPs), one di-hydrogen, and four ring critical points (RCPs). MEP surface has been plotted which forecast that the most negative region is associated with the electronegative oxygen atoms (sites for nucleophilic activity). Theoretically, to confirm that the title compound has anti-cancer, anti-diabetic and anti-platelet aggregation activities, it was analyzed by molecular docking interactions with the corresponding target receptors. The obtained values of H-bonding parameters and binding affinity prove that its anti-cancer activity is the more prominent than the other properties.

Study of Cr→SmA phase transition and hydrogen bonding in four-ring bent-core liquid crystal.

A newly designed asymmetrical four-ring bent-core compound (4'-n-decyloxyphenylazo)-phenyl-4-yl-3-[N-(4'-n-octadecyloxy-2-hydroxybenzylidene) amino]-2-methyl benzoate exhibiting liquid crystalline behavior was synthesized and characterized. The thermal and textural morphology were studied using differential scanning calorimetry and polarizing optical microscopy, respectively. The study of hydrogen bonding and dynamics of the phase transition has been performed at the molecular level using temperature dependent Fourier transform infrared (FTIR) spectroscopy. The spectral analysis of OH, CH2/CH3, CO, and CN stretching vibrational bands revealed clear signatures of Cr→SmA phase transition at 125°C. Density functional theory has been adopted for the geometry optimization and conformational study of the monomer using the B3LYP/6-31G(d) method. The conformational analysis has been performed to predict the most stable conformer along with the possible conformers using one-dimensional potential energy scan employing the same level of theory. The combination of experimental findings and theoretical analysis helped to understand the mechanism of phase transitions at the molecular level.

Magnetoelectric effects in the spiral magnets CuCl2 and CuBr2.

The nature and symmetry of transition mechanisms in the spin-spiral copper halides CuCl2 and CuBr2 are analyzed theoretically. The magnetoelectric effects observed in the two multiferroic compounds are described and their phase diagram at zero and applied magnetic fields are worked out. The emergence of the electric polarization at zero field below the paramagnetic phase is shown to result from the coupling of two distinct spin-density waves and to be only partly related to the Dzialoshinskii-Moriya interactions. Applying a magnetic field along the two-fold monoclinic axis of CuCl2 yields a decoupling of the spin-density waves modifying the symmetry of the phase and the spin-spiral orientation. The remarkable periodic dependences of the magnetic susceptibility and polarization, on rotating the field in the monoclinic plane, are described theoretically.

The effectiveness of evidence summaries on health policymakers and health system managers use of evidence from systematic reviews: a systematic review

Systematic reviews are important for decision makers. They offer many potential benefits but are often written in technical language, are too long, and do not contain contextual details which make them hard to use for decision-making. There are many organizations that develop and disseminate derivative products, such as evidence summaries, from systematic reviews for different populations or subsets of decision makers. This systematic review aimed to (1) assess the effectiveness of evidence summaries on policymakers' use of the evidence and (2) identify the most effective summary components for increasing policymakers' use of the evidence. We present an overview of the available evidence on systematic review derivative products.

The temperature-dependent single-crystal Raman spectroscopy of a model dipeptide: L-Alanyl-L-alanine.

A single-crystal of peptide L-alanyl-L-alanine (C6H12N2O3) was studied by Raman spectroscopy at low-temperature, and a tentative assignment of the normal modes was given. Evidence of a second order structural phase transition was found through Raman spectroscopy between the temperatures of 80K and 60K. Group theory considerations suggest that the transition leads the sample from the tetragonal to a monoclinic structure. Additionally, our study suggests that the mechanism for the structural phase transition is governed by the occupation of non-equivalent C1 local symmetry sites by the CH3 molecular groups. Analysis based on group theory suggests L-alanyl-L-alanine presents C2 symmetry at low temperatures.

Study of polymorphism in imatinib mesylate: a quantum chemical approach using electronic and vibrational spectra.

Imatinib mesylate, 4-(4-methyl-piperazin-1-ylmethyl)-N-u[4-methyl-3-(4-pyridin-3-yl)pyrimidine-2-ylamino)phenyl]benzamide methanesulfonate is a therapeutic drug that is approved for the treatment of chronic myelogeneous leukemia (CML) and gastrointestinal stromal tumors (GIST). It is known that imatinib mesylate exists in two polymorphic forms α and ß. However, ß-form is more stable than the α-form. In this work, we present a detailed vibrational spectroscopic investigation of ß-form by using FT-IR and FT-Raman spectra. These data are supported by quantum mechanical calculations using DFT employing 6-311G(d,p) basis set, which allow us to characterize completely the vibrational spectra of this compound. The FT-IR spectrum of α-form has also been discussed. The importance of hydrogen-bond formation in the molecular packing arrangements of both forms has been examined with the vibrational shifts observed due to polymorphic changes. The red shift of the NH stretching bands in the infrared spectrum from the computed wavenumber indicates the weakening of the NH bond. The UV-vis spectroscopic studies along with the HOMO-LUMO analysis of both polymorphs (α and ß) were performed and their chemical activity has been discussed. The TD-DFT method was used to calculate the electronic absorption spectra in the gas phase as well as in the solvent environment using IEF-PCM model and 6-31G basis set. Finally, the results obtained complements to the experimental findings.

Study on the structure and vibrational spectra of efavirenz conformers using DFT: comparison to experimental data.

Efavirenz, (S)-6-chloro-4-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one, is an anti HIV agent belonging to the class of the non-nucleoside inhibitors of the HIV-1 virus reverse transcriptase. A systematic quantum chemical study of the possible conformations, their relative stabilities and vibrational spectra of efavirenz has been reported. Structural and spectral characteristics of efavirenz have been studied by vibrational spectroscopy and quantum chemical methods. Density functional theory (DFT) calculations for potential energy curve, optimized geometries and vibrational spectra have been carried out using 6-311++G(d,p) basis sets and B3LYP functionals. Based on these results, we have discussed the correlation between the vibrational modes and the crystalline structure of the most stable form of efavirenz. A complete analysis of the experimental infrared and Raman spectra has been reported on the basis of wavenumber of the vibrational bands and potential energy distribution. The infrared and the Raman spectra of the molecule based on DFT calculations show reasonable agreement with the experimental results. The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule.

Using phonon resonances as a route to all-angle negative refraction in the far-infrared region: the case of crystal quartz.

We consider how all-angle negative refraction may be induced in anisotropic crystals by making use of the phonon response. We investigate the example of crystal quartz at far-infrared wavelengths. Reflection and transmission measurements confirm the expected behavior, and show relatively high transmission efficiency at frequencies at which negative refraction occurs.

Molecular structure and vibrational spectroscopic investigation of secnidazole using density functional theory.

Secnidazole (alpha,2-dimethyl-5-nitro-1H-imidazole-1-ethanol) is an antimicrobical drug, and it is particularly effective in the treatment of amebiasis, giardiasis, trichomoniasis, and bacterial vaginosis. Secnidazole crystallizes as a hemihydrate, which belongs to a monoclinic system having space group P2(1)/c, with a = 12.424 A, b = 12.187 A, c = 6.662 A, and beta = 100.9 degrees. The optimized geometries and total energies of different conformers of the secnidazole molecule have been determined by the method of density functional theory (DFT). For both geometry and total energy, it has been combined with B3LYP functionals having extended basis sets 4-31G, 6-31G, and 6-311++G(d,p) for each of the three stable conformers of secnidazole. Using this optimized structure, we have calculated the infrared and Raman wavenumbers and compared them with the experimental data. The calculated wavenumbers are in an excellent agreement with the experimental values. Based on these results, we have discussed the correlation between the vibrational modes and the crystalline structure of the most stable conformer of secnidazole. A complete assignment is provided for the observed Raman and IR spectra.

Synthesis and characterization of a new mebendazole salt: mebendazole hydrochloride.

Mebendazole hydrochloride [(5-benzoyl-1H-benzimidazole-2-yl)-carbamic acid methyl ester hydrochloride, MBZ.HCl], a new stable salt of mebendazole (MBZ), has been synthesized and characterized. It can easily be obtained from recrystallization of forms A, B, or C of MBZ in diverse solvents with the addition of hydrochloric acid solution. Crystallographic data reveals that the particular conformation adopted by the carbamic group contributes to the stability of the network. The crystal packing is stabilized by the presence of three N-H...Cl intermolecular interactions that form chains along the b axis. The XRD analyses of the three crystalline habits found in the crystallization process (square-based pyramids, pseudohexagonal plates, and prismatic) show equivalent diffraction patterns. The vibrational behavior is consistent with crystal structure. The most important functional groups show shifts to lower or higher frequencies in relation to the MBZ polymorphs. The thermal study on MBZ.HCl indicates that the compound is stable up to 160 degrees C approximately. Decomposition occurs in four steps. In the first step the HCl group is eliminated, and after that the remaining MBZ polymorph A decomposes in three steps, as happens with polymorphs B and C. (

Low-temperature study of a new nevirapine pseudopolymorph.

THE TITLE COMPOUND (SYSTEMATIC NAME: 11-cyclo-propyl-4-methyl-5,11-dihydro-6H-dipyrido[3,2-b:2',3'-e][1,4]diazepin-6-one butanol 0.3-solvate), C(15)H(14)N(4)O·0.3C(4)H(9)OH, was crystallized in a new triclinic pseudopolymorphic form, a butanol solvate, and the crystal structure determined at 150 K. The mol-ecular conformation of this new form differs from that reported previously, although the main inter-molecular hydrogen-bond pattern remains the same. N-H⋯O hydrogen bonds [N⋯O = 2.957 (3) Å] form centrosymmetric dimers and the crystal packing of this new pseudopolymorph generates infinite channels along the b axis.

Solid state characterization of olanzapine polymorphs using vibrational spectroscopy.

FT-Raman, infrared and near infrared investigations of two polymorphs of olanzapine are presented, establishing the main features that allow the discrimination of these crystalline forms using vibrational spectroscopic methods. Ab initio calculations on the basis of the density functional theory were used to determine the stable conformations. The calculated vibrational spectra were compared to the experimental ones in order to identify the conformers corresponding to each polymorph and to assign the vibrational bands to the internal vibrations of the olanzapine molecule. Our results support the hydrogen bonding pattern proposed by the reported crystalline structure and provide valuable information on the structural and thermodynamical relationship between the investigated polymorphs.