Broadband near-infrared luminescence properties of Sc2(MoO4)3:Cr3+ molybdates.

The structural and spectroscopic properties of Sc2(MoO4)3 molybdate containing various concentrations of Cr3+ ions were investigated in a temperature range of 80-300 K. The samples were prepared using hydrothermal as well as solid-state reaction methods. The influence of synthesis conditions and the molybdenum source on the structural properties was studied by X-ray diffraction (XRD), IR (infrared), and Raman methods. The optical properties of Sc2(MoO4)3 samples doped with 0.1, 0.5, 1.0, and 2.0 % of Cr3+ ions were investigated. The broadband near-infrared (NIR) luminescence spectra generated from the 4T2 and 2E levels of Cr3+ ions may be attractive for NIR light-emitting diode (LED) applications. Emission decay profiles and the crystal field parameters of Cr3+ ions are discussed. In particular, the mechanism of photoluminescence generation and the thermal quenching path are described in detail.

THz, Raman, IR and DFT studies of noncentrosymmetric metal dicyanamide frameworks comprising benzyltrimethylammonium cations.

We report density functional theory (DFT) studies of vibrational modes for benzyltrimethylammonium cations (BeTriMe+) as well as THz, IR and Raman studies of [BeTriMe][M(dca)3(H2O)] (dca = N(CN)2-, dicyanamide; M = Mn2+, Co2+, Ni2+) and their anhydrous analogues. These studies show that the anhydrous BeTriMeMn and BeTriMeNi have the same or very similar structures and loss of water molecules leads to significant changes in the metal-dicyanamide frameworks. In particular, the number of dca modes decreases, suggesting increase of crystal symmetry, probablly related with decrease in the number of non-equivalent dca bridges from two to one. Although it is possible that dehydration leads to a replacement of the coordinate Mn-O (Ni-O) bonds by Mn-N (Ni-N) bonds, wherein N atoms come from the C≡N groups of previously non-bridged dca units, reversibility of the dehydration process indicates that such new bonds are either not formed or are very weak. The anhydrous Mn and Ni compounds undergo similar reversible phase transitions to lower symmetry phases. The driving force for these transitions is most likely ordering of dca linkers but this process is accompanied by weak distortion of the metal-dicyanamide frameworks. In the case of BeTriMeCo, the loss of water molecules also leads to significant changes in the cobalt-dicyanamide framework. However, the structure of this analogue is different from the structures of the Mn and Ni counterparts, the number of unique dca linkers is preserved and the dehydration process is irreversible, suggesting more drastic rearrangement of the metal-dicynamide framework.

Magnetic excitation and readout of methyl group tunnel coherence.

Methyl groups are ubiquitous in synthetic materials and biomolecules. At sufficiently low temperature, they behave as quantum rotors and populate only the rotational ground state. In a symmetric potential, the three localized substates are degenerate and become mixed by the tunnel overlap to delocalized states separated by the tunnel splitting ν t . Although ν t can be inferred by several techniques, coherent superposition of the tunnel-split states and direct measurement of ν t have proven elusive. Here, we show that a nearby electron spin provides a handle on the tunnel transition, allowing for its excitation and readout. Unlike existing dynamical nuclear polarization techniques, our experiment transfers polarization from the electron spin to methyl proton spins with an efficiency that is independent of the magnetic field and does not rely on an unusually large tunnel splitting. Our results also demonstrate control of quantum states despite the lack of an associated transition dipole moment.

Phonon properties and mechanism of order-disorder phase transition in formamidinium manganese hypophosphite single crystal.

The detailed temperature-dependent IR and Raman spectra were used to study and understand the mechanism of structural phase transition occurring at 175 K in manganese hypophosphite templated with formamidinium (FA+) ions, [FA]Mn(H2POO)3, which adopts a perovskite-like architecture. The structural transformation between the C2/c and the P21/c monoclinic phases has a complicated nature and is mainly driven by re-orientational motions of the FA+ cations but it is also accompanied by a significant distortion of the MnO6 octahedral units as well as steric-forced changes of the PH2 groups determining the off-center shifts of FA+ cations in the cages. The re-orientational motions of formamidinium cations at 175 K are followed by slight changes of their geometry and re-arrangement of hydrogen bonds (HBs). The strong temperature-dependences of bands corresponding to vibrations involving hydrogen bonding reveal the highly-dynamic character of this phase transition and strong nature of created HBs. The most pronounced changes are observed for the modes corresponding to the formamidinium cation, proving that the phase transition has an order-disorder character.

Structural and optical characterization of RbLaP4O12:Ln3+ (Ln3+ = Ce3+, Nd3+, Tm3+, or Yb3+).

In this work, for the first time, detailed structural and optical characterization of RbLaP4O12 doped with different concentrations of Ce3+, Nd3+, Tm3+, or Yb3+ ions is reported. The samples were obtained via a precipitation technique. Their structural characterization was performed using X-ray diffraction (XRD), and infrared and Raman spectroscopies. Following XRD data, the unit cell parameters of host lattices were calculated using Rietveld refinement. It was found that an increase in the dopant content leads to a decrease in the unit cell volume. The optical characterization of RbLaP4O12:Ln3+ was carried out by collecting absorption and emission spectra, as well as luminescence decay profiles. Following absorption spectra, the energy band gap of the studied matrix was determined. It was found that the broad absorption band located in the ultra-violet range, in most cases ascribed to charge transfer or f-d transitions, is in fact related to the absorption of the host lattice. The analysis of luminescence properties allowed us to investigate possible ways of depopulation emission levels of impurities.

Detection of bridging veins rupture and subdural haematoma onset using a finite element head model.

BACKGROUND: One of the most severe traumatic brain injuries, the subdural haematoma, is related to damage and rupture of the bridging veins, generating an abnormal collection of blood between the dura mater and arachnoid mater. Current numerical models of these vessels rely on very simple geometries and material laws, limiting its accuracy and bio-fidelity. METHODS: In this work, departing from an existing human head numerical model, a realistic geometry for the bridging veins was developed, devoting special attention to the finite elements type employed. A novel and adequate constitutive model including damage behavior was also successfully implemented. FINDINGS: Results attest that vessel tearing onset was correctly captured, after comparison against experiments on cadavers. INTERPRETATION: Doing so, the model allow to precisely predict the individual influence of kinematic parameters such as the pulse duration, linear and rotational accelerations in promoting vessel tearing.

The mechanism of phase transitions in azide perovskites probed by vibrational spectroscopy.

The temperature-dependent IR and Raman spectroscopy has been used to study the phase transitions in manganese-azide frameworks with either dimethylammonium (DMA+) or tetramethylammonium (TMA+) cations which adopt a perovskite-like crystal structure. The phase transition in DMA-analogue seems to be associated with cooperative tilting of MnN6 octahedra and order-disorder of hydrogen bonds while in TMA-analogue it is more complex and composed of several processes, including the motions of both manganese-azide framework and tetramethylammonium cations and their possible coupling. Our results are in agreement with the data received from crystallographic and dielectric measurements in the case of TMA-analogue and we have demonstrated the importance of order-disorder of hydrogen bonds in the case of DMA-analogue which previously has not been taken into account.

Spectroscopic properties and molecular structure of copper phytate complexes: IR, Raman, UV-Vis, EPR studies and DFT calculations.

The copper phytate IP6Cu, IP6Cu2 and IP6Cu3 complexes were synthesized changing the phytate to metal mole ratio. The obtained products have been characterized by means of chemical and spectroscopic studies. Spectroscopic ATR/IR, FT-Raman, UV-Vis, EPR and magnetic measurements were carried out. The structures of these compounds have been proposed on the basis of the group theory and geometry optimization taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of the phosphate group and metal-oxygen polyhedron. The role of the inter- and intra-hydrogen bonds in stabilization of the structure has been discussed. EPR studies showed that a local rhombic symmetry of copper ions appears in the studied phytates. Dominant interactions show antiferromagnetic properties depending on the content of paramagnetic ions.

Spectroscopic investigation and DFT modelling studies of Eu3+ complex with 1-(2,6-dihydroxyphenyl)ethanone.

Eu3+ complex with 1-(2,6-dihydroxyphenyl)ethanone in the solid state has been synthesized and characterized by elemental analysis, UV-visible, FT-IR and FT-Raman spectroscopies, powder X-ray diffraction, electron emission under femtosecond laser excitation. The stoichiometry and the formula of the studied complex have been proposed. Its physicochemical properties have been analyzed in terms of the structure and DFT calculations performed for the ligand. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. Spectral and energetic transformation of femtosecond light impulses has been studied and possibility of the energy transfer between the ligand and the Eu3+ electron levels has been analyzed.

Structural, optical and phonon properties of formate-based MOF phosphors with ethylammonium cations.

We report the synthesis, crystal structure, IR, Raman and luminescence studies of four metal-organic frameworks of the following formulas: [CH3CH2NH3]Y1-x-yYbyErx(HCOO)4 (x = 1, y = 0; x = 0.2, y = 0.8; x = 0.02, y = 0.07) and [CH3CH2NH3]Y0.92Eu0.08(HCOO)4. All the compounds are isostructural and crystallize in a polar and non-centrosymmetric monoclinic system (P21 space group). They have been characterized by single crystal and powder X-ray diffraction methods as well as by vibrational spectroscopy (IR and Raman). The assignment of the external and internal modes has been discussed and presented. Furthermore, the optical properties of the Er3+ and Eu3+ ions have been assessed using diffuse absorption, excitation and emission spectra. The site symmetry of the Eu3+ ions has been analyzed using the emission spectrum and the luminescence decay of the red emission.

Dielectric relaxation and anhydrous proton conduction in [C2H5NH3][Na0.5Fe0.5(HCOO)3] metal-organic frameworks.

Metal-organic frameworks (MOFs), in which metal clusters are coupled by organic moieties, exhibit inherent porosity and crystallinity. Although these systems have been examined for vast potential applications, the elementary proton conduction in anhydrous MOFs still remains elusive. One of the approaches to deal with this problem is the utilization of protic organic molecules, to be accommodated in the porous framework. In this work we report the temperature-dependent crystal structure and proton conduction in [C2H5NH3][Na0.5Fe0.5(HCOO)3] metal-organic frameworks using X-ray diffraction and broadband dielectric spectroscopic techniques. The detailed analysis of the crystal structure reveals disorder of the terminal ethylene groups in the polar phase (space group Pn). The structural phase transition from Pn to P21/n at T ≈ 363 K involves the distortion of the metal formate framework and ordering of EtA+ cations due to the reduction of the cell volume. The dielectric data have been presented in the dynamic window of permittivity formalism to understand the ferroelectric phase transition. The relaxation times have been estimated from the Kramers-Kronig transformation of the dielectric permittivity. A Grotthuss type mechanism of the proton conduction is possible at low temperatures with the activation energy of 0.23 eV. This type of experimental observation is expected to provide new prospective on the fundamental aspect of elementary proton transfer in anhydrous MOFs.

A new approach in the synthesis of La(1-x)Gd(x)FeO3 perovskite nanoparticles--structural and magnetic characterization.

A series of highly crystalline orthoferrite nanoparticles (type La(1-x)Gd(x)FeO3, where x = 0 to 1) were prepared using the self-combustion method. Extensive studies including X-ray diffraction, Rietveld refinement and Fourier transform infrared spectroscopy as well as Raman spectroscopy confirmed the orthorhombic space group Pnma of the obtained materials. The calculated average grain size for powders is in the range of 30 to 80 nm. Magnetic characterization of the La(1-x)Gd(x)FeO3 series, performed at 1.72 K, indicated an antiferromagnetic state characterized by some canting of iron magnetic moments, in good agreement with the data reported for similar fine-particle systems.

Polarized Raman and IR spectra of oriented Cd(0.9577)Gd(0.0282)□(0.0141)MoO4 and Cd(0.9346)Dy(0.0436)□(0.0218)MoO4 single crystals where □ denotes the cationic vacancies.

Polarized Fourier Transform IR and Raman spectra of Cd0.9577Gd0.0282□0.0141MoO4 and Cd0.9346Dy0.0436□0.0218MoO4 oriented single crystals have been recorded and analyzed using the factor group approach (□ denotes the cationic vacancies). The tetragonal I41/a (C4h(6)) space group with Z=2 has been applied in the discussion. The influence of the structural changes induced by the defects in the CdMoO4 host lattice on the vibrational symmetry rules has been analyzed. The assignment of the observed bands to the internal and external modes has been proposed.

FT-Raman spectroscopic study of human skin subjected to uniaxial stress.

Fourier Transform Raman Spectroscopy was used to investigate the molecular changes of structural proteins in human skin subjected to strain. In the Raman spectrum of unstrained skin, bands assigned mainly to collagen and elastin were observed at 1658 cm(-1) (amide I), 1271 and 1255 cm(-1) (amide III), and 935 and 817 cm(-1) (C-C stretching modes of the protein backbone). Moreover, bands characteristic for amino acids were observed at 1336 cm(-1) (desmosine), 1004 cm(-1) (phenylalanine), 919 and 856 cm(-1) (proline), and 877 cm(-1) (hydroxyproline). Positions and intensities of the listed Raman bands were analysed as a function of applied strain. A clear correlation between Raman wavenumbers and the level of mechanical stress was established. Wavenumbers of the analysed bands changed gradually with increasing strain. Distinct responses, depending on the sample cutting direction, i.e. longitudinal or perpendicular to the Langer's lines, were noticed. It was concluded that elastin and non-helical domains of collagen are initially involved in the load transfer and triple helices of collagen are gradually joining this process. It was proved that Raman spectroscopy give insight into skin deformation micromechanics.

High-pressure Raman scattering and an anharmonicity study of multiferroic wolframite-type Mn0.97Fe0.03WO4.

A high-pressure Raman scattering study of wolframite-type Mn(0.97)Fe(0.03)WO(4) is presented up to 10.4 GPa. The phonon wavenumbers vary linearly with pressure. The mode Grüneisen parameters are larger for many bending and lattice modes when compared to the stretching modes due to the larger compressibility of Mn(Fe)O(6) octahedra when compared to WO(6) octahedra. Combining the pressure-dependent Raman data of this work with the temperature-dependent Raman data on this crystal previously reported by us has allowed estimation of the temperature-dependent pure lattice and intrinsic anharmonic contributions to the observed total Raman shifts as a function of temperature. It has been found that the observed unusual hardening of the 884, 698 and 674 cm(-1) stretching modes upon heating from 4 to about 150-200 K followed by the usual softening above 150-200 K is a result of a positive intrinsic anharmonic contribution and a negative pure lattice contribution; i.e., up to about 150-200 K the anharmonic contribution surpasses the lattice contribution and the total Raman shift is slightly positive whereas above 150-200 K the lattice contribution becomes dominant and the Raman bands exhibit the usual softening with increasing temperature.

Temperature-dependent Raman and IR studies of multiferroic MnWO4 doped with Ni2+ ions.

Temperature-dependent Raman and IR studies of MnWO(4) crystal doped with Ni(2+) ions were performed in the 4.2-300 K range. These studies were complemented by magnetization and specific heat measurements in the 2-100K range, which revealed that MnWO(4) crystal doped with Ni(2+) ions exhibits two phase transitions at 13.9 and 12.5K. Temperature evolution of Raman wavenumbers and linewidths revealed anomalous behaviour at low temperatures. These anomalies have been attributed to spin-phonon coupling, which appear due to onset of antiferromagnetic spin ordering. The observed anomalies extend above T(N)=13.9 K. This behaviour is consistent with the fact that MnWO(4) is a moderately magnetically frustrated material.

The influence of collagenase treatment on the production of TNF-alpha, IL-6 and IL-10 by testicular macrophages.

Testicular macrophages (TMf) are located in the interstitial tissue of the male gonad. Highly purified TMf populations can be prepared either by the mechanical shaking of dispersed testicular tissues or by enzymatic digestion with collagenase followed by cell adherence, rosetting and gradient centrifugation. TMf obtained by the enzymatic procedure produced significantly more cytokines (IL-6, IL-10 and TNF-alpha) than TMf isolated by the mechanical method and this effect is long-lasting. Our results indicate that isolation of tissue macrophages by enzymatic digestion may influence their functional activity, and suggest that critical evaluation of the method used to obtain these cells should be the regular practice.

Association between CYP2C9 slow metabolizer genotypes and severe hypoglycaemia on medication with sulphonylurea hypoglycaemic agents.

AIMS: The genetically polymorphic cytochrome P450 (CYP) enzyme CYP2C9 metabolizes most sulphonylurea oral hypoglycaemic agents. The aim of this study was to test the hypothesis that individuals with genotypes predicting low CYP2C9 activity may be at a higher risk of severe drug-associated hypoglycaemia. METHODS: In a case-control study, 20 diabetic patients admitted to the emergency department with severe hypoglycaemia during sulphonylurea drug treatment were compared with a control group of 337 patients with type 2 diabetes but without a history of severe hypoglycaemia. A large sample of 1988 healthy Caucasian subjects served as a second control group. RESULTS: The CYP2C9 genotypes *3/*3 and *2/*3 that are predictive of low enzyme activity were more common in the hypoglycaemic group than in the comparison groups (10%vs <2%, respectively: odds ratio 5.2; 95% confidence interval 1.01, 27). Furthermore, the diabetic patient group with severe hypoglycaemia exhibited lower body mass indexes, higher rates of renal failure, were older compared with the diabetic group without severe hypoglycaemia, and were being treated with higher doses of glibenclamide. CONCLUSIONS: These findings suggest that among other factors, individuals with genetically determined low CYP2C9 activity are at an increased risk of sulphonylurea-associated severe hypoglycaemia. Thus, genotyping might be a tool for the better prediction of adverse effects caused by oral hypoglycaemic agents.

Hormonal counterregulation during severe hypoglycaemia under everyday conditions in patients with type 1 and insulin-treated type 2 diabetes mellitus.

AIM: To determine the counterregulatory hormonal responses to severe hypoglycaemia (SH) in type 1 versus insulin-treated type 2 diabetic patients under everyday conditions. METHODS: Counterregulatory hormones were determined in 28 consecutive type 1 and thirteen insulin-treated type 2 diabetic patients (age 54 +/- 18 vs. 75 +/- 13 yrs; diabetes duration 27 +/- 16 vs. 21 +/- 6 yrs) with SH requiring emergency treatment. Blood samples were taken prior to and after effective treatment of SH. SH was defined as an event with neuroglycopenic presentation requiring external intervention by administration of intravenous glucose or oral carbohydrates. 68 % (19/28) of type 1 diabetic patients but none of those with type 2 diabetes had reduced awareness of hypoglycaemia. RESULTS: Plasma glucose levels were 30 +/- 14 prior to and 179 +/- 82 mg/dl after treatment of SH; the time between the two measurements was 54 +/- 26 minutes. With the exception of higher levels of human growth hormone in type 1 patients - which were attributed to younger age - the other counterregulatory responses to SH showed no significant differences in type 1 vs. type 2 diabetic patients. In both groups glucagon responses were virtually absent while moderate catecholamine responses could be demonstrated. Treatment with beta-blockers did not affect hormonal counterregulation in type 1 diabetic patients. CONCLUSIONS: In patients approaching the insulin-deficient end of the spectrum of type 2 diabetes the hormonal responses to SH are comparable to those in patients with longstanding type 1 diabetes. Thus, in advanced type 2 diabetes the risk of developing SH may be similar to that in individuals with type 1 diabetes.