Golden Crystals Research Articles

Detection and Crystal Structure of Hydrogenated Bipentacene as an Intermediate in Thermally Induced Pentacene Oligomerization.

6,6′,13,13′-Tetrahydro-6,6′-bipentacene (HBP), the intermediate molecule connecting pentacene to previously observed peripentacene and extended pentacene oligomers through the formation of a carbon–carbon bond, is synthesized and crystallographically characterized. Heating pentacene to 300 °C under vacuum for 200 h results in pale golden crystals of HBP and amorphous material containing pentacene oligomers, offering experimental evidence that pentacene preferentially dimerizes at the 6,6′-position. Continued heating of HBP results in co-crystals of 6,13-dihydrogenated pentacene and pentacene and further amorphous pentacene oligomers. The amorphous material consists of layered carbonaceous species with a graphenic nature, as determined by Raman spectroscopy and electron microscopy, and suggests HBP as an intermediate to hydrogenated pentacene species and pentacene oligomers, such as peripentacene, of interest in organic electronics.

Multi‐scale modeling of plastic deformations in nano‐scale materials; Transition to plastic limit

SummaryA large amount of research in computational mechanics has biased toward atomistic simulations. This trend, on one hand, is due to the increased demand to perform computations in nanoscale and, on the other hand, is due to the rather simple applications of pairwise potentials in modeling the interactions between atoms of a given crystal. The Cauchy–Born (CB) hypothesis has been used effectively to model the behavior of crystals under different loading conditions, in which the comparison with molecular dynamics simulations presents desirable coincidence between the results. A number of research works have been devoted to the validity of CB hypothesis and its application in post‐elastic limit. However, the range of application of CB hypothesis is limited, and it remains questionable whether it is still applicable beyond the validity limit. In this paper, a multi‐scale technique is developed for modeling of plastic deformations in nanoscale materials. The deformation gradient is decomposed into the plastic and elastic parts, i.e., F = FpFe. This decomposition is in contrast to the conventional decomposition, F = FeFp, generally encountered in continuum and crystal plasticity. It is shown that the former decomposition is more appropriate for the problem dealt within this work. Inspired by crystal plasticity, the plastic part is determined from the slip on potential slip systems. Based on the assumption that the CB hypothesis remains valid in the homogeneous deformation, the elastic deformation gradient resulting from the aforementioned decomposition is employed in conjunction with the CB hypothesis to update the state variables for face‐centered cubic crystals. The assumption of homogeneity of elastic deformation gradient is justified by the fact that elastic deformations are considerably smaller than the plastic deformations. The computational algorithms are derived in details, and numerical simulations are presented through several examples to demonstrate the capability of the proposed computational algorithm in the modeling of golden crystals under different loading conditions. Copyright © 2016 John Wiley & Sons, Ltd.

New species ofArthonialesfrom NE Brazil

AbstractThe new speciesConiarthonia aurataE. L. Lima, M. Cáceres & Aptroot,Cresponea endosulphureaA. A. Menezes, M. Cáceres & Aptroot,Cryptothecia macrocephalaE. L. Lima, M. Cáceres & Aptroot, andSynarthonia sarcographoidesAptroot, A. A. Menezes, E. L. Lima & M. Cáceres are described from Caatinga vegetation in NE Brazil. They were found in the Chapada do Araripe in the state of Ceará and/or the Vale do Catimbau National Park in Pernambuco.Coniarthonia auratahas weakly organized, semiglobose apothecia with golden crystals, and on first impression looks like the anamorph of aTylophoron.Cresponea endosulphureahas a pigment of the group of xantholepinones in the thallus. It is the first time that a substance from this group is reported from theArthoniales.Cryptothecia macrocephalahas strongly macrocephalic ascospores and contains psoromic acid in the thallus.Synarthonia sarcographoidesis only the third species in this rarely found genus. It is characterized within the genus by muriform, brown ascospores, but it is assigned with hesitation to the genus. It is locally quite common.

Sedimentological and geochemical evidence to elucidate an evaporitic–carbonate paleoenvironment, Middle Miocene Red Sea coast, Egypt

Lithologic succession, microscopic examination as well as X-ray diffraction and chemical data revealed that the surface Middle Miocene evaporites of Wadi Quei are composed of anhydrite beds intercalated with carbonate and green shale, whilst the subsurface evaporites of Gemsa locality are composed of gypsum, anhydrite, carbonates and celestite with a rare amount of halite. The anhydrite is found to be formed diagenetically after gypsum. The carbonate is interpreted as having been of biogenic origin. The strong smell of H2S and golden crystals of pyrite at Wadi Quei beds are indications of the biogenic action of sulphate-reducing bacteria in the presence of organic matter. It is suggested that the evaporite sequence which was deposited in a supratidal sabkha environment is characterized by alkaline-reducing conditions. The presence of nodular gypsum at Gemsa locality is probably deposited in a supratidal environment with oscillation of sea level.

Ln13Br18B3 (Ln: Gd, Tb) — A Compound Containing a Combination of Discrete and Condensed Clusters.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Anion-controlled electrocrystallization of perylene cation radical salts

Formation of perylene cation radical salts initiated by the electrochemical oxidation was observed directly on a Pt electrode surface using a microscopic CCD detection system. Depending on the sort of the coexisting anions (X −) as supporting electrolytes, considerable changes were observed in the deposition processes in acetonitrile. That is, while no deposition was observed with PF 6 −, the formation of bold needle-like black crystals were observed to grow sparsely on the electrode surface in the case with BF 4 −. In the latter, the following reduction and re-oxidation experiments revealed that golden crystals were formed in diverse shapes as a result of the redox reactions. On the other hand, in the oxidation of perylene with ClO 4 −, very thin golden whisker crystals were found to grow proportionally on the whole electrode surface, and then they became dense in course of time. However, after 1 min, black thin needle-like crystals were initiated to form over the golden micro whisker crystals that grew densely on the electrode. The difference in color is expected to be in relation to the redox states of perylene cation radical salts.

Munchausen syndrome presenting as pulmonary talcosis.

We describe a patient with self-induced inhalational pulmonary talcosis originally diagnosed as asthma. A 35-year-old female respiratory technologist developed severe asthma that was refractory to steroids and methotrexate. An open lung biopsy specimen showed scattered aggregates of refractile golden crystals within membranous and respiratory bronchioles. The particles ranged in size from 30 to 100 microm and were birefringent when viewed with polarized light. Following review of the lung biopsy specimen, the patient admitted to regularly inhaling large amounts of hospital baby powder. Analysis of the lung biopsy specimen and a sample of the hospital baby powder by x-ray energy dispersion showed identical spectroscopic peaks, including elemental peaks for magnesium silicate. Many patients with self-induced illness lack the picturesque symptomatology classically attributed to Munchausen syndrome. Awareness of these more subtle and varied patterns of presentation may aid in earlier recognition.

Canthaxanthin Deposition in the Retina: A Biostatistical Evaluation of 411 Patients

AbstractCanthaxanthin (4,4′-diketo-β-carotene) is a naturally occurring carotenoid that has been used in both medical applications and for cosmetic skin coloration. In some individuals who have histories of long-term, high-dosage canthaxanthin intake, there has been reported an associated asymptomatic appearance of reversible golden crystals in the retina. Because of the potential for continued medical use of this agent, it is important to ascertain whether a dose-response relationship can be described for canthaxanthin-related crystal formation. In addition, the delineation of a dose-response relationship is important in assessing the safety of the much lower dose food coloring applications of canthaxanthin, and would provide a statistical basis for the establishment of a “no-effect level.”The possibility of a dose-response relationship between crystal formation in the retina and high-dosage canthaxanthin use was investigated biostatistically by analyzing the dosage information from 691 cases, as describ...

Oxoniobates with 13 and 15 electrons in [Nb6O12] clusters: the structures of KNb8O14and LaNb8O14

Black powders and golden plate-like crystals of KNb8O14 have been prepared by heating a pellet of KF, NbO2 and NbO (1:5:3) at 750 °C for 5 d in a gold ampoule. Crystals from such a batch were always twinned. Untwinned crystals were obtained from KNbO3, NbO2 NbO (4:5:7) with B2O3(as mineralizer) at 1050 °C (7 d). Black powders and golden crystals of LaNb8O142 result from La2O3, NbO2 and NbO (1:9:7) with NaF or Na2B4O7 at 1000 °C (3 d). Crystals of 2 were always twinned. Cluster 1 is isotypic to SrNb8O14 and crystallizes in space group Pbam with a= 935.2(2), b= 1026.8(2) and c= 592.9(1) pm. The structure was refined using single-crystal data (four-circle CAD4 diffractometer, 553 Icompfn(hkl), Mo-Kα, R′= 0.0629). Compound 2 is also isotypic to SrNb8O14 and the Guinier pattern could be indexed with a= 919.4(2), b= 1033.7(8) and c= 596.2(5) pm in space group Pbam. Weak superstructure reflections on precession photographs of a crystal of 2 show that b′= 2b and c′= 6c and indicate that the true structure is more complicated. Characteristic building units in 1 and 2 are NbO6 octahedra (Nb5+), MO12 cuboctahedra and [Nb6O12] clusters: 1 is the first compound which contains 13 electrons in metal–metal bonding states of an empty [M6X12] cluster, whereas the number of 15 in 2 has been found in several other reduced oxoniobates. Both compounds are semiconductors with ρ≈ 100 and ≈ 3000 Ω cm at 293 K for 1 and 2 respectively. Measurements of the magnetic susceptibility show that they have a weak temperature-independent paramagnetism. The Madelung part of the lattice energy has been calculated and discussed.

Cholesterolosis of the Anterior Chamber

To the Editor. —The letter by Drs Hemady and Foster 1 brought back some fond memories. In 1973, as a first-year resident in the Massachusetts Eye and Ear Infirmary General Eye Clinic, Boston, I saw an eye with beautiful golden crystals shimmering and floating in the anterior chamber, exactly as depicted in a picture sent by Drs Hemady and Foster. All the residents and attending surgeons gathered to examine this patient. This ocular finding was deemed to be of sufficient interest and rarity to warrant reporting, which was duly done. 2 However, continued curiosity with this case led me to further research. We reviewed almost 11000 records (1964 to 1974) from the Ocular Pathology Laboratory at the Massachusetts Eye and Ear Infirmary. Cholesterol crystals were noted in only 12 eyes. All 12 eyes had no useful vision, all had previous ocular injury, and all had a retinal detachment. Three eyes

Absence of Retinal Crystals in High-Dosage Beta-Carotene Administration

AbstractPatients with erythropoietic protoporphyria (EPP) are photosensitive to short-wavelength solar exposure due to the endogenous presence of pro-toporphyrin in their tissues. Treatment has involved administration of high dosages of carotenoids, which are considered to protect the patient by quenching singlet oxygen and scavenging photically generated free radical species within the skin. β-Carotene and canthaxanthin have been used in Europe as a mixture in the treatment of EPP and have been associated with the presence of golden crystals in the retinae of some patients. However, the production of crystals has been attributed only to canthaxanthin.In this study, 13 patients with EPP, treated in the United States only with β-carotene, were examined for the presence of crystals. None were found, even though several patients had taken large lifetime doses of up to 821.52 g for periods of up to 19 years. This report presents the β-carotene dosage, blood levels, and retinal findings from these patients.

Effect of Delocalization of d-Electrons on the Optical Reflectivity Spectra of CuGa1-xFexS2 and CuAl1-xFexS2 Systems

Single crystals of CuGa1-xFexS2 and CuAl1-xFexS2 have been grown by the chemical transport reaction. Crystals with x<xc were black while those with x≥xc were golden-colored, where xc=0.14 for CuGa1-xFexS2 and xc=0.12 for CuAl1-xFexS2 Optical reflectivity spectra of these crystals have been measured using a microcomputer-controlled reflectance spectrometer. The difference between black and golden crystals is quantitatively characterized; reflectivity at 1.5–3 eV region of the golden crystals is much higher than the black crystals. Absorption spectra obtained by the Kramers-Kronig analysis reveal that this reflectivity enhancement is associated with the broadening of d-orbital energies due to delocalization.

Successive Stages of a Graphite–Potassium Compound and its Thermal Expansion

GRAPHITE and potassium amalgamate easily, resulting in golden crystals, and the colour changes to brown, then to dark blue as the potassium is driven off by heating. Schleede and Wellmann1 analysed two stable forms of the lamellar compounds with intercalated potassium atoms in one and two graphite layers respectively. Later, higher stages up to five were analysed2 with the less controllable compounds of graphite–sulphuric acid. Quite recently, Hooley3 proposed a sealed-edge theory to account for the stepwise formation of the compounds concerned. I have also been interested in this point and have performed some experiments which will be described here.