Synthesis of graphene nanoribbons encapsulated in single-walled carbon nanotubes

A novel material, graphene nanoribbons encapsulated in single-walled carbon nanotubes (GNR@SWNT), was synthesized using confined polymerization and fusion of polycyclic aromatic hydrocarbon (PAH) molecules. Formation of the GNR is possible due to confinement effects provided by the one-dimensional space inside nanotubes, which helps to align coronene or perylene molecules edge to edge to achieve dimerization and oligomerization of the molecules into long nanoribbons. Almost 100% filling of SWNT with GNR is achieved while nanoribbon length is limited only by the length of the encapsulating nanotube. The PAH fusion reaction provides a very simple and easily scalable method to synthesize GNR@SWNT in macroscopic amounts. First-principle simulations indicate that encapsulation of the GNRs is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of the GNR@SWNT structures in photonics and nanoelectronics.     

Induction of apoptosis by organotin compounds in vitro: neuronal protection with antisense oligonucleotides directed against stannin

Immortalized cell lines and primary neuronal cultures were used to characterize the selective toxicity of trimethyltin (TMT),triethyltin (TET) and tributyltin (TBT). TBT and TET were cytotoxic at similar concentrations in the immortalized cell lines tested; the 50% toxic concentration (TC50) was 1 to 11 microM. In contrast, immortalized cell lines varied considerably in their sensitivity to TMT, with sensitive cell lines (neuroblastomas, T-, B-cell lines) showing TC50 values of 2 to 8 microM, whereas insensitive cells (NIH-3T3 fibroblast, HTB-14 glioma, TC-7 kidney cells) had TC 50 values > 100 microM. Primary neuronal cell cultures were very sensitive to organotins (TC50 values, 1-10nM), and showed patterns of selective toxicity with respect to neuronal and glial cells. Because organotin toxicity evolves over 24 to 48 hr. we determined whether these compounds induced apoptosis in primary cultures. TMT increased (P < .05) the fraction of apoptotic cells 6 and 12 hr after treatment with TMT at TC50 concentrations. Prior studies suggested that a protein, stannin, was localized in cells sensitive to organotins. Stannin was expressed in several TMT-sensitive cell lines (PC12, T, B cells) and in primary neurons in culture. Stannin was absent in the resistant HTB-14 glioma cell line. The role of stannin in mediating TMT toxicity in primary cultures was investigated by blocking stannin expression with specific antisense oligonucleotides. Treatment of primary cultures with antisense oligonucleotides for 48 hr before and during TMT treatment significantly protected neurons from the neurotoxic and apoptotic effects of TMT. This effect was not observed with scrambled oligonucleotide controls. Thus, TMT may induce apoptosis in sensitive cells, which is partly mediated by stannin. Based on the available data we conclude that stannin expression is necessary, but not sufficient for TMT toxicity.     

Novel indium(III) complexes with sterically hindered o-iminobenzoquinone

The first examples of indium(III) derivatives based on sterically hindered 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (imQ) were synthesized and characterized in details. The interaction of sodium o-iminobenzosemiquinolate with indium(III) iodide produces bis[4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinonato]-iodo-indium(III) (1). The same product 1 was obtained by the reactions of imQ with InI or imQ disodium derivative with indium(III) iodide. The interaction of imQ with InI₃ results in the formation of indium(III) compound (2) containing neutral form of o-iminobenzoquinone ligand. Structures of complexes 1 and 2 were determined by X-ray diffraction analysis.     

NMR Studies of Fluorine in Aluminosilicate–Lanthanum Fluoride Glasses and Glass-Ceramics

NMR determinations of fluorine environments in transparent oxyfluoride glass-ceramics were made to learn about the crystallization of LaF₃, as well as to ascertain the structural role of fluorine in the surrounding glassy matrix. The fraction of fluorine in LaF₃ was measured as a function of heat treatments, demonstrating significant differences between glasses modified with barium and those containing sodium. The results of these measurements showed that not all of the fluorine formed LaF₃ in these glass-ceramics, with resolution of additional fluoride sites at −135 and −185 ppm, due primarily to Si–F and Al–F bonding, respectively. Not only is the evidence of Si–F bonding unexpected, given the presence of aluminum, but the amount of Si–F bonding is sensitive to the type of modifier in the glass. Samples containing barium oxide as the modifier showed a higher fraction of Si–F bonding than those modified with sodium oxide.     

Creep of the eye sclera

 Irreversible stretching (creep) of the eye sclera, considered as a cause of the high myopia, has been studied experimentally. Both dramatic acceleration and significant deceleration of the sclera creep have been observed in the presence of some enzymes. Creep of various connective tissues caused by static and cyclic mechanical stresses (gravity, blood pressure, etc.) can manifest in many age and pathological changes in human body. Authors express the hope that investigations in this area and finding appropriate inhibitors may replace surgery (eye, cosmetic) by prophylactic therapy. Received: 21 July 1998 / Accepted: 28 August 1998     

Fluoride and calcium-phosphate coated sponges of the magnesium alloy AX30 as bone grafts: a comparative study in rabbits

Biocompatibility and degradation of magnesium sponges (alloy AX30) with a fluoride (MgF₂ sponge, n = 24, porosity 63 ± 6 %, pore size 394 ± 26 μm) and with a fluoride and additional calcium-phosphate coating (CaP sponge, n = 24, porosity 6 ± 4 %, pore size 109 ± 37 μm) were evaluated over 6, 12 and 24 weeks in rabbit femurs. Empty drill holes (n = 12) served as controls. Clinical and radiological examinations, in vivo and ex vivo μ-computed tomographies and histological examinations were performed. Clinically both sponge types were tolerated well. Radiographs and XtremeCT evaluations showed bone changes comparable to controls and mild gas formation. The μCT80 depicted a higher and more inhomogeneous degradation of the CaP sponges. Histomorphometrically, the MgF₂ sponges resulted in the highest bone and osteoid fractions and were integrated superiorly into the bone. Histologically, the CaP sponges showed more inflammation and lower vascularization. MgF₂ sponges turned out to be better biocompatible and promising, biodegradable bone replacements.     

Study of the formation processes of gold droplet arrays on Si substrates by high temperature anneals

In this study, the peculiarities of the transformations of gold films deposited on the Si wafer surfaces as a result of high temperature anneals are investigated experimentally depending on the conditions of wafer surface preparation and the annealing regimes. The morphology and the distribution functions of the crystallites of gold films as well as the gold droplets formed as a result of anneals are studied as functions of annealing temperature, type of annealing (rapid thermal or rapid furnace annealing), and the state of the surface of Si wafers. The results obtained can be used for the controlled preparation of the arrays of catalytic gold droplets for subsequent growth of Si wire-like crystals.     

Biodegradation of Single‐Walled Carbon Nanotubes by Eosinophil Peroxidase

Eosinophil peroxidase (EPO) is one of the major oxidant‐producing enzymes during inflammatory states in the human lung. The degradation of single‐walled carbon nanotubes (SWCNTs) upon incubation with human EPO and H₂O₂ is reported. Biodegradation of SWCNTs is higher in the presence of NaBr, but neither EPO alone nor H₂O₂ alone caused the degradation of nanotubes. Molecular modeling reveals two binding sites for SWCNTs on EPO, one located at the proximal side (same side as the catalytic site) and the other on the distal side of EPO. The oxidized groups on SWCNTs in both cases are stabilized by electrostatic interactions with positively charged residues. Biodegradation of SWCNTs can also be executed in an ex vivo culture system using primary murine eosinophils stimulated to undergo degranulation. Biodegradation is proven by a range of methods including transmission electron microscopy, UV‐visible‐NIR spectroscopy, Raman spectroscopy, and confocal Raman imaging. Thus, human EPO (in vitro) and ex vivo activated eosinophils mediate biodegradation of SWCNTs: an observation that is relevant to pulmonary responses to these materials.     

Li collection experiments on T-11M and T-10 in framework of Li closed loop concept

The concept of a steady state tokamak with plasma facing components (PFC) on the basis of liquid lithium circulation demands the decision of three tasks: lithium injection to the plasma, lithium ions collection before their deposition on the vacuum vessel and lithium returning to the injection zone. Main subject of paper is the investigations of Li collection by different types of limiters intersected the scrape-of-layer (SOL) in T-10 and T-11M tokamaks. For finding solution for this problem in T-11M and T-10, experiments have been applied with Li-, C-rail limiters and ring SS R-limiter-collector (T-11M). The efficiency of Li collection by limiters in T-11M and T-10 tokamaks was investigated by post mortem sample–witness analysis and (T-11M) by the use of the mobile graphite probe (limiter) as a recombination target in the stream of lithium ions. The characteristic depth of lithium penetration in the SOL area of T-11M is about 2 cm and 4 cm in SOL of T-10. The quantitative analysis of the sample–witnesses located on T-11M limiters showed that 60 ± 20% of the lithium injected during plasma operating of T-11M had been collected by limiters. It confirms an opportunity of the lithium ions collection by limiters in tokamak SOL.     

Determination of photophysical parameters of red fluorescent protein mRFP1 under ultraviolet excitation by methods of laser fluorimetry

We investigate photophysical processes that take place in macromolecules of a fluorescent protein mRFP1 under UV excitation [when the energy transfer in a localized donor-acceptor (LDA) pair, which is presented in the molecules of the protein, becomes apparent]. We used a special approach based on the fluorescence laser spectroscopy technique. The energy transfer rates in LDA pairs and photophysical parameters of fluorophores (chromophores) of three spectral forms, which coexist in the ensemble of the macromolecules of this protein, were determined under pulse UV laser excitation.