Upper limit for thermal direct photon production in heavy-ion collisions at 60 and 200A·GeV

The production of direct photons has been investigated in reactions ofp and¹⁶O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and ⁰ spectra have been measured in the pseudorapidity range 1.52.1 for the transverse momentum region 0.4 GeV/cp _T 2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of ⁰ and mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed.     

N,N′‐Di­thio­bisphthal­imide–nitro­benzene (2/1): a Pn solvate with localized solvent mol­ecules ordered head‐to‐tail in channels

N,N′‐Di­thio­bisphthal­imide crystallizes from nitro­benzene solution as a solvate, 2C₁₆H₈N₂O₄S₂·C₆H₅NO₂, having space group Pn. The bisphthal­imide mol­ecules are linked by C—H?O hydrogen bonds and by aromatic π–π‐stacking interactions, forming a framework enclosing continuous channels running along the [100] direction and accounting for ca 20% of the unit‐cell volume. The nitro­benzene mol­ecules lie in these channels, ordered in a head‐to‐tail fashion and linked to the bis­phthal­imide framework by C—H?O and C—H?π(arene) hydrogen bonds.     

The origins of the colours of yellow,green and blue sapphires

The absorption spectra of natural yellow sapphires are shown to be due to single Fe³⁺ and Fe³⁺  O²⁻  Fe³⁺ pairs, with the latter dominant. Blue and green sapphires have spectra dominated by Fe³⁺  O²⁻  Ti⁴⁺ and Fe²⁺  O²⁻  Fe³⁺ pairs.     

Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): monomeric and polymeric adducts with 1,2‐bis(4‐pyridyl)­ethene and 1,6‐di­amino­hexane

In the adduct ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–1,2‐bis(4‐pyridyl)­ethene (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₂H₁₀N₂, there is an intramolecular O—H?O hydrogen bond in the ferro­cene­diol component and a single O—H?N hydrogen bond linking the diol to the di­amine, which is disordered over two sets of sites, so forming a finite monomeric adduct. In the adduct ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–1,6‐di­amino­hexane (2/1), 2[Fe(C₁₈H₁₅O)₂]·C₆H₁₆N₂, the amine lies across a centre of inversion in space group P. There is an intramolecular O—H?O hydrogen bond in the ferrocenediol, and the molecular components are linked by O—H?N and N—H?O hydrogen bonds, one of each type, into a C(13)[R(12)] chain of rings.     

Synthesis of S(+) and R(-)-3-(2-aminopropyl)indole from ethyl-D- and L-tryptophanate

A stereospecific requirement for hallucinogenesis applies to certain molecules containing an asymmetric center. Thus, only the R-isomers of substituted phenylisopropylamines and lysergic acid diethylamide are psychotomimetic. The enantiomers of a minor hallucinogen, S(+)- and R(-)-3-(2-aminopropyl)indole (α-methyltryptamine) ( 6a and 6b ) were synthesized via a 5-step manipulation from D - and L -tryptophan ethyl ester hydrochloride, respectively. Optical purity of these two isomers was determined by pmr spectroscopy of their complexes with a europium chiral shift reagent using the indole C₂ H signal.     

A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometry

Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected background electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings.     

Adducts of 1,1,1‐tris(4‐hydroxyphenyl)ethane with diamines: three‐dimensional hydrogen‐bonded frameworks formed with 1,6‐diaminohexane and 2,2′‐bipyridyl

The adduct 1,6‐di­amino­hexane–1,1,1‐tris(4‐hydroxy­phenyl)­ethane (1/2) is a salt {hexane‐1,6‐diyldiammonium–4‐[1,1‐bis(4‐hydroxyphenyl)ethyl]phenolate (1/2)}, C₆H₁₈N₂²⁺·2C₂₀H₁₇O₃^?, in which the cation lies across a centre of inversion in space group P. The anions are linked by two short O—H?O hydrogen bonds [H?O 1.74 and 1.76 Å, O?O 2.5702 (12) and 2.5855 (12) Å, and O—H?O 168 and 169°] into a chain containing two types of R(24) ring. Each cation is linked to four different anion chains by three N—H?O hydrogen bonds [H?O 1.76–2.06 Å, N?O 2.6749 (14)–2.9159 (14) Å and N—H?O 156–172°]. In the adduct 2,2′‐bipyridyl–1,1,1‐tris(4‐hydroxy­phenyl)­ethane (1/2), C₁₀H₈N₂·2C₂₀H₁₈O₃, the neutral di­amine lies across a centre of inversion in space group P2₁/n. The tris­(phenol) mol­ecules are linked by two O—H?O hydrogen bonds [H?O both 1.90 Å, O?O 2.7303 (14) and 2.7415 (15) Å, and O—H?O 173 and 176°] into sheets built from R(38) rings. Pairs of tris­(phenol) sheets are linked via the di­amine by means of a single O—H?N hydrogen bond [H?N 1.97 Å, O?N 2.7833 (16) Å and O—H?N 163°].     

The Application of High-Modulus Fibers to Ballistic Protection

A new family of experimental organic fibers (X-500) produced by the Monsanto Research Corporation has been evaluated ballistically. The development of this family of fibers made available for the first time a series of organic fibers with moduli and heac resistance more nearly comparable to inorganic fibers such as glass. Tensile analysis of three material types tested in yarn form at conventional loading rates showed physical properties ranging from typically brittle (10.1 g, den tenacity, 2.4% extension, and 550 g, den modulus) to moderately ductile (5.4 g, den tenacity, 15.4% extension, and 135 g/den modulus).

The three samples were evaluated ballistically in fabric, felt, and laminate form. The most ductile sample (Type III) showed considerable promise with a ballistic resistance significantly greater than normal for a material of such modest tensile strength. Tensile recovery tests on this Type-III material showed a large amount of permanent set compared to most commercially available yarns. It appears that this capacity for plastic flow, combined with the inherent high modulus, act in combination to provide good energy absorption.

Scanning electron micrographs of ballistic missile impact areas showed for the more brittle yarns, longitudinal splitting with little evidence of plastic deformation, or fusion of fibers around the hole produced by the missile. The more ductile yarns exhibited a combination of some longitudinal splitting with plastic deformation and fusion around the hole. This latter combination of energy absorbing mechanisms proved to more effective.     

Affinity Chromatography of Mushroom Tyrosinase

Abstract

The purification by column chromatography of a phenol-oxidizing enzyme, mushroom tyrosinase, was investigated using solid phase adsorbents designed to have specific affinity for the enzyme. Sepharose 4B, aminophenyl-bearing porous glass, and p-aminobenzylcellulose were chemically modified to introduce phenolic, catecholic, or benzoic groups on the polymer surface. The resulting preparations were tested for their effectiveness in separating tyrosinase from an impure protein mixture. The phenolic and benzoic polymers displayed no specific affinity for tyrosinase. Aminophenyl glass, with or without an attached phenolic group, adsorbed appreciable quantities of protein nonspecif-ically, thus complicating studies of its tyrosinase affinity properties. Dopamine, a dihydroxyphenyl derivative, was bound to Sepharose and was found to be effective in retaining tyrosinase at pH 5.5; elution of the enzyme by washing at pH 8.8 resulted in its purification by a factor of 10 to 14. Enzymatic oxidation of the adsorbent limited the number of purification cycles which could be carried out on a single column.     

Predicting the Outcome of Photocyclisation Reactions: A Joint Experimental and Computational Investigation

Photochemical oxidative cyclodehydrogenation reactions are a versatile class of aromatic ring‐forming reactions. They are tolerant to functional group substitution and heteroatom inclusion, so can be used to form a diverse range of extended polyaromatic systems by fusing existing ring substituents. However, despite their undoubted synthetic utility, there are no existing models—computational or heuristic—that predict the outcome of photocyclisation reactions across all possible classes of reactants. This can be traced back to the fact that “negative” results are rarely published in the synthetic literature and the lack of a general conceptual framework for understanding how photoexcitation affects reactivity. In this work, we address both of these issues. We present experimental data for a series of aromatically substituted pyrroles and indoles, and show that quantifying induced atomic forces upon photoexcitation provides a powerful predictive model for determining whether a given reactant will photoplanarise and hence proceed to photocyclised product under appropriate reaction conditions. The propensity of a molecule to photoplanarise is related to localised changes in charge distribution around the putative forming ring upon photoexcitation. This is promoted by asymmetry in molecular structures and/or charge distributions, inclusion of heteroatoms and ethylene bridging and well‐separated or isolated photocyclisation sites.