Multilayer mirror fluorescence detection system for photon‐in photon‐out in‐situ carbon k‐edge NEXAFS

The Second International Workshop on Imaging Techniques with Synchrotron Radiation (ITSR) was held November 6–10, 2009, at the beautiful beach resort city of Sanya on the tropical island of Hainan province in the south of China, and followed on from a similar successful meeting in Hefei in December 2008. The meeting was supported by the National Natural Science Foundation of China, National Synchrotron Radiation Laboratory (NSRL) in Hefei, Institute of High Energy Physics (IHEP) in Beijing, INFN, Xradia Inc., and the Italian Ministry of Foreign Affairs based on an agreement for bilateral collaboration. This enthusiasm for collaboration is a reflection of the increasing interest in synchrotron-based research, particularly in the area of imaging and microscopy, which has been stimulated by the successful commissioning of various projects in China, such as the new Shanghai synchrotron light source and the upgrade of the Hefei synchrotron sources. Some further new projects are proposed that will focus even more on advancing the imaging capability in China and its application in different domains of science and technology. The Sanya meeting was therefore held at an important time and designed to bring world experts together to help build the user community, foster new scientific applications, and nurture young scientists. It is encouraging to witness that more than 10 students participated in the meeting, which included 25 oral presentations contributed by 40 delegates from 8 countries including China, Australia, the U.S., France, Germany, Italy, Japan, and the Netherlands.     

Vacuum‐UV‐Radiation‐Induced Structural‐Functional Changes in Serum Albumin Molecules

Using the methods of spectrophotometry, luminescent analysis, and fluorescent probes, we have investigated the structural changes in bull serum albumin (BSA) molecules induced by the action of vacuum UV (VUV) radiation ( = 131161 nm, dose — 6300 kJ/m²). It has been found that the change in the spectralfluorescent properties of BSA molecules after irradiation under the conditions of different microsurroundings is caused by the unrolling of the protein globule due to the weakening and rupture of weak intramolecular bonds as well as by the photomodification of the aromatic amino acid residues in the composition of the protein macromolecule. A scheme of the phototransformation processes in the BSA molecules under the action of vacuum ultraviolet has been drawn. In accordance with this scheme the VUV light in the region of absorption of peptide bonds of protein molecules induces a disturbance in their thirdorder structure, which leads to a modification of the state of aromatic amino acid residues and a change in the functional properties of protein macromolecules.     

Intramolecular Hydrogen Bond in Steroid 5‐Hydroxy‐6‐Ketones and 5‐Hydroxy‐6‐Ketoximes of the Stigmastane Series

The intramolecular hydrogen bond in steroid 5hydroxy6ketones and 5hydroxy6ketoximes of the stigmastane series has been investigated by the method of IR spectroscopy. It is shown that 5hydroxy groups in cisA/Bsteroids are linked by the intramolecular hydrogen bond with polar substituents at C₃ and C₆. These hydrogen bonds are lacking in corresponding transA/Bsteroids. According to the IR spectra, intramolecular associates of polymer type are formed in 5hydroxy6hydroxyminosteroids.     

Spectral‐Luminescent Properties of 1,1‐Dioctadecyl‐3,3,3'3'‐Tetramethylindodicarbocyanineperchlorate in Binary Solutions

On the basis of investigation of the absorption and luminescence spectra of 1,1dioctadecyl3,3,3'3'tetramethylindodicarbocyanineperchlorate (D307) molecules and their nonamphiphilic analog in binary solutions of dimethylformamide and water of different composition, a mechanism underlying the quenching luminescence of the D307 molecules has been established which is related to the formation of nonluminescent associates. It is shown that the formation of the micelles of sodium dodecylsulfate (SDS) in a binary solution with 99% content of water destroys the associates, the D307 molecules are captured by the micelles, and their mobility in the micelles is limited.     

Crystallization Behavior of PEO in Nano‐Structured PEO‐b‐PS/PPO Blends

Blends of poly (ethylene oxide)‐b‐polystyrene (PEO‐b‐PS) diblock copolymer and poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) homopolymer were obtained by solution blending, and the morphologies of PEO dispersed nanoparticles in PPO/PS matrix were observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The isothermal crystallization kinetics was studied using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Nonisothermal crystallization kinetics was studied using DSC. The results showed that PEO segments were easier to crystallize in the blend than in the copolymer probably due to the interfaces of PPO acting as nucleation sites to promote the crystallization of PEO. The crystallization of PEO blocks destroyed the pre‐existing microdomain structure even though the glass transition temperature of the matrix was much higher than the crystallization temperature.     

8‐GeV SR facility project in Japan: SPring‐8

More than 1200 crystallographers from more than 50 nations gathered in Darmstadt (Germany) in August 2010 on the occasion of the 26th edition of the European Crystallographic Meeting (ECM 26) and the European Powder Diffraction Conference (EPDIC 12). It was the first time that both events were taking place at the same venue, with an overlap of one and a half days. The venue was the new Congress Center of the City and the University of Darmstadt, called Darmstadtium. This is the name of element 110 and reminds people that Darmstadt is the “City of Science” hosting the world famous GSI Helmholtzzentrum f?r Schwerionenforschung where about ten new elements were discovered. Furthermore, the European Space Agency (ESA) is located in Darmstadt as well as the Technical University.     

GIAO Calculations of Chemical Shifts in Ethene‐1,1,2,2‐tetrayltetramethylene tetrathiocyanate

Geometric optimization and gauge including atomic orbital (GIAO). ¹H and ¹³C NMR chemical shift calculations with Hartree–Fock (HF) method and density functional method (B3LYP), using the 6‐31G(d) and 6‐31+G(d) basis sets, are proposed as a tool to be applied in the structural characterization of ethene‐1,1,2,2‐tetrayltetramethylene tetrathiocyanate, thus providing useful support in the interpretation of experimental NMR data. Parameters related to linear correlation plot of computed versus experimental ¹³C NMR chemical shifts in DMSO‐d₆ are provided.     

Random‐field experiments in dilute antiferromagnets

Experiments in d = 2 and d = 3 random-field Ising systems are reviewed. Random fields destroy the phase transition for the d = 2 system Rb₂Co _x Mg_1-xF₄. The d = 3 Fe _x Zn_1-xF₄ system shows a new phase transition with unusual dynamics. Extreme critical slowing down plays an essential role in the d = 3 measurements. Experiments on the related d = 3 systems Mn _x Zn_1-xF₂ and Fe _x Mg_1-xC1₂ are also discussed.     

Kinetics of Photogel Formation in Anthracene‐Containing Copolymers in the Presence of Singlet‐Excitation Energy Acceptors

We suggest a technique to control the rate of photocrosslinking fluorescent polymers by introducing a consumable acceptor of the energy of singlet excitation. We have constructed a model of the processes occurring in a layer of a photocrosslinking anthracenecontaining copolymer with the addition of the acceptor which is spent in the reaction of photooxidation by oxygen of the air and the algorithm for calculating the curves of gel formation in the presence of the acceptor. Comparison of the experimental kinetics of the depletion of the acceptor and accumulation of a gel in a layer with the data of model calculations has proved their good agreement. The possibility of increasing the contrast coefficient of the characteristic curve of negative photoresists on the basis of fluorescent photocrosslinked polymers with the aid of singlet excitation energy acceptors is demonstrated.     

Characterization of Crystalline Phase‐Transformations in Theophylline by Time‐Domain Terahertz Spectroscopy

Time‐domain terahertz (THz) spectroscopy has been used to characterize polymorphic transformations in polycrystalline theophylline, a widely used pharmaceutical compound. On transformation, different intermolecular bonding arrangements arise owing to changes in the lattice structure of the molecular crystal, leading to distinct THz spectral signatures. Temperature‐dependent THz absorption measurements in anhydrous theophylline confirm that the observed vibrational modes originate from phonons within the crystal structure.     

Phase transitions in h-thiourea under electric‐field

Abstract

Dielectric constant, spontaneous polarization and pyroelectric response measurements were performed on thin samples (e < 100 μm) of H-thiourea as a function of temperature and applied electric field. Along with previous data obtained by optical birefringence, X-ray and neutron diffraction techniques, the results put in evidence three features in the modulated region between the ferroelectric state and the paraelectric one. The tricritical point is determined for E_tr ? 2075 V/mm and T_tr ? 192 K.     

Quantum‐Chemical Investigation of Hydrogen Bonds in Porphin

Using the DFT Becke–Lee–Yang–Parr exchangecorrelation threeparametric functional (B3LYP), we have calculated the geometry, the electron density distribution, and the vibration frequencies for pyrrole, porphin, and their 13 analogs with a regularly varying structure. It is shown that the determining role in the change in the frequencies of stretching and outofplane deformation vibrations of porphin compared to pyrrole is played by intramolecular hydrogen bonds at the porphyrin macroring center. We have separately considered and compared with the data for porphin complexes of pyrrole with different intermolecular hydrogen bonds: with an aromatic ring (NH··· cluster formed by the pyrrole selfaggregation in the liquid state) and an unshared electron pair (NH···OH₂ and NH···NC₄H₄ clusters). The degree of participation of the NH group in the hydrogen bonds increases in the series NH··· cluster, porphin, NH···OH₂ and NH···NC₄H₄ clusters.     

Azetidin‐2‐one Versus Chroman‐2‐one: Application of 1H‐13C COSY NMR and Mass Spectroscopy in Structure Elucidation–Class of Compounds

Azetidin‐2‐ones, commonly known as β‐lactams, constitute a biologically important class of compound. Treatment of azetidin‐2‐ones with alkali is known to form diverse types of compounds depending on the stability of the ring. In many cases, the ring is retained in the product at the cost of transformation of substituents. Spectroscopy is the most important tool to characterize the organic compounds. However, in some cases the structures of the products are so closely related that simple IR, ¹H NMR, and ¹³C NMR spectra do not lead to unambiguous structure elucidation. This article reports a novel application of ¹H‐¹³C COSY NMR and mass spectroscopy in determining unequivocally an azetidin‐2‐one ring structure instead of a chroman‐2‐one ring structure for the product obtained by treatment of 1‐benzhydryl‐3,3‐bis(4‐methylphenyl)‐4‐[2‐(o‐dip‐tolylacyl)hydroxyphenyl]‐2‐azetidinone with ethanolic sodium hydroxide at room temperature.     

Electroluminescence and Spectral Properties of N9‐Isobutyl‐2‐Oxo‐3‐Phenyl‐3N‐Benzo[F]Chromene‐9‐Sulfonamide

Experimental data on the synthesis and spectral properties (UV, IRFourier, xray photoelectronic, and luminescence spectra) of the sulfonamide derivative of benzocoumarin in an isopropanol solution and in a film applied by thermal vacuum deposition (TVD film) are reported. The use of TVD films of the investigated substance as electroluminophors is shown to be promising.     

Reaction‐Induced Phase‐Separation in Polyoxyethylene/Polystyrene Blends. II. Structure Development

Abstract

The morphology development in model polymer blends was investigated in relation to the processing pathway. Reaction‐induced phase separation was used to make polyoxyethylene (POE) and polystyrene (PS) blends from a solution of POE/styrene. As the styrene underwent polymerization by photo‐initiation with ultraviolet light, phase separation, and phase inversion were induced, whereby the POE became the matrix phase. Optical microscopy showed that liquid–liquid (L–L) phase separation occurred soon after the styrene polymerization was initiated. Nucleation and growth was identified as the mechanism of L–L phase separation. Polystyrene/styrene‐rich domains formed in a POE/styrene‐rich matrix. The domain size developed until arrested by the POE liquid–solid phase separating and crystallizing, since the experiments were conducted below the melt temperature of POE. The POE crystal growth process also followed a nucleation and growth mechanism. The time to the onset of crystallization was observed to decrease as the POE content increased, until the POE formed a saturated solution in styrene. As the crystallization onset time decreased, the PS‐rich domain size also decreased. The phase diagram previously established can now be used to describe (and predict) the number density and size of the PS‐rich domains in the POE matrix of the blends.     

Workshop on in‐situ studies of materials processing

More than eighty scientists from over ten different countries in Europe and America descended on Diamond Light Source in Oxfordshire to participate in the International Workshop on X-ray Spectroscopy of Magnetic Solids on June 10–21, 2010. The XRMS meetings have demonstrated to be a fruitful forum for informal discussion of recent results and future projects of synchrotron-radiation-based research on magnetism and also serve for the formation of new collaborations. The meetings are organized in sessions dedicated to specific scientific topics and experimental techniques. The absence of parallel sessions allows all the participants to take part in the discussion and to have a comprehensive view of the latest achievements and of the envisioned developments in the field. The previous meeting in the series was held last year at the synchrotron Soleil in St Aubin near Paris. The emerging new opportunities for magnetic spectroscopy, such as offered by the beamline for advanced dichroism experiments (BLADE), with its three intertwined assets of polarization, coherence, and time resolution, made it timely for the international community to convene at Diamond.     

Conformational and Structural Analysis of 6‐(4‐Methoxy‐phenyl)‐1,5,7a‐triphenyl‐tetrahydro‐imidazo[1,5‐b][1,2,4]oxadiazol‐2‐one

Abstract

The cis stereochemistry of 6‐(4‐methoxy‐phenyl)‐1,5,7a‐triphenyl‐tetrahydro‐imidazo[1,5‐b][1,2,4]oxadiazol‐2‐one was studied by use of a PM3 semi‐empirical quantum mechanical model, and x‐ray crystallographic analysis. It crystallizes in the monoclinic space group P2 ₁ /n with a = 10.812(1) Å, b = 16.464(2) Å, c = 13.379(1) Å, α = 90.00°, β = 98.39(1)°, γ = 90.00°, V = 2356.07(4) Å³, Z = 4, D _calc = 1.3067 g cm^?3, F(0 0 0) = 976.41, and μ = 0.086 mm^?1. The structure was solved by direct methods and refined to R = 0.066 for 1257 independent reflections [I > 4σ (I)]. The results from x‐ray diffraction were seen to be generally consistent with the results from previously reported spectroscopic investigations, beside theoretical calculations, except for conformations of five‐membered fused heterocycles. Two inter‐ and intramolecular weak interactions in addition to carbon atoms (C1 and C3) with different chiralities were found in the structure. The conformational study was performed by randomly scanning the potential energy surface belonging to the title compound with respect to selected torsion angles.     

Manifestation of Extracoordination in the Resonance Raman Spectra of Water‐Soluble Cation Co‐Porphyrins

Resonance Raman spectra (RRS) of Co(II) and Co(III)5,10,15,20tetrakis(4Nmethylpyridinium)porphyrin ((Co^II(TmpyP4), and Co^III(TMPyP4)) in aqueous solutions at different pH as well as in organic solvents (methanol, ethanol, DMSO, DMF) are obtained. The increased sensitivity of the oscillation frequencies ₂, ₄, ₈, and ₆ — the markers of the oxidation state of a metal — to the nature of an axial ligand has been revealed. For Co^III(TmpyP4), the shifts of the indicated frequencies in extracoordination have turned out to be twofold larger than those for Co^II(TmpyP4). The spectral effects observed are related to different electron influence of the extraligands on the system of the porphyrin ring. In the case of Co(III)porphyrin, interaction of the d orbitals of the metal and the e _g ^*orbitals of the macrocycle is more efficient since its ionic radius is smaller than for the Co(II)complex. For Co^III(TmpyP4), a linear correlation between the oscillation frequencies ₂, ₄, ₈, and ₆ and the experimental Gutmann parameters characterizing the electronacceptor properties of solvents is found.     

Crystal Structures of Tetrakis‐(4‐chlorophenylthio)‐butatriene and Tetrakis‐(tert‐butylthio)‐butatriene

Tetrakis‐(4‐chlorophenylthio)‐butatriene (3a) and tetrakis‐(tert‐butylthio)‐butatriene (3b) were synthesized, and their crystal structures were determined. The compound 3a is monoclinic, space group P2₁/c, a=6.9785(8), b=8.6803(9), c=22.884(2) Å, β=93.887(6)^o, V=1383.0(3) ų, Z=2. The compound 3b is monoclinic, space group P2₁/n, a=11.0615(6), b=10.8507(4), c=11.2717(6) Å, β =116.427(2)^o, V=1211.5(1) ų, Z=4. The title compounds 3a and 3b reside on an inversion center so that only half of the molecule is crystallographically unique. Both compounds are not planar. The crystal structures of 3a and 3b have cumulated double bonds. The C7–C8–C8ⁱ and C5–C6–C6ⁱ angles that show the linearity in both structures, respectively, are 176.4(3)° in 3a and 175.6(2)° in 3b.     

Spectrophotometric Determination of Ammonia in Estuarine Waters by Hybrid Reagent‐Injection Gas‐Diffusion Flow Analysis

Abstract

A flow‐injection gas‐diffusion technique is described for the online determination of ammonia in estuarine waters covering a salinity range of S=0 to 36. The flow analysis system, which is a hybrid of reagent injection and conventional sample‐injection flow systems, avoids the need for a rotary injection valve. Whereas gas‐diffusion techniques have been widely applied in conventional sample‐injection flow analysis, reagent‐injection flow analysis involving gas diffusion has been little used because it is susceptible to interference from dissolved gaseous species such as carbon dioxide coexisting with ammonia in the sample. This source of interference has been overcome by online adjustment of sample to pH 8.4 prior to the injection of the base that initiates gas diffusion of ammonia. The pore sizes of hydrophobic membranes used in gas diffusion were characterized by a bubble‐point test prior to use in the flow analysis system. These showed wide variation in pore size, and grading and careful selection was necessary in order to obtain reliable gas diffusion measurements of ammonia. The proposed flow‐injection system can be operated in a continuous flow mode, at a sample throughput of 135 measurements hr^?1 with a typical limit of detection (LOD) of 9 µg N L^?1, or in stopped‐flow mode at 60 measurements hr^?1 with a LOD of 3 µg N L^?1. The technique was validated using water samples containing a wide range of dissolved carbon dioxide concentrations, salinity, and pH. Excellent agreement (r=0.999) was observed between results obtained using the reagent‐injection system and an approved reference method.