Hypothermic Oxygenated Machine Perfusion of the Human Donor Pancreas.

Background: Transplantation of beta cells by pancreas or islet transplantation is the treatment of choice for a selected group of patients suffering from type 1 diabetes mellitus. Pancreata are frequently not accepted for transplantation, because of the relatively high vulnerability of these organs to ischemic injury. In this study, we evaluated the effects of hypothermic machine perfusion (HMP) on the quality of human pancreas grafts.

Effect of the fluorination technique on the surface-fluorination patterning of double-walled carbon nanotubes.

Double-walled carbon nanotubes (DWCNTs) are fluorinated using (1) fluorine F at 200 °C, (2) gaseous BrF at room temperature, and (3) CF radio-frequency plasma functionalization. These have been comparatively studied using transmission electron microscopy and infrared, Raman, X-ray photoelectron, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A formation of covalent C-F bonds and a considerable reduction in the intensity of radial breathing modes from the outer shells of DWCNTs are observed for all samples.

A computational study on the role of noncovalent interactions in the stability of polymer/graphene nanocomposites.

Understanding the interaction between graphene and polymers is of essential interest when designing novel nanocomposites with reinforced mechanical and electrical properties. In this computational study, the interaction of pristine graphene (PG) and graphene oxide (GO) with a series of functional groups, representative of the functionalised buildings blocks occurring in different polymers, and attached to aliphatic and aromatic chains, is analyzed using dispersion-corrected semi-empirical methods (PM6-D3H4X) and density functional theory calculations with empirical dispersion corrections. Functional groups include alkyl, hydroxyl, aldehyde, carboxyl, amino and nitro groups, and the binding energies of these groups with graphene derivatives (PG and GO) are determined.

Tuning aromaticity patterns and electronic properties of armchair graphene nanoribbons with chemical edge functionalisation.

Tuning the band gap of graphene nanoribbons by chemical edge functionalisation is a promising approach towards future electronic devices based on graphene. The band gap is closely related to the aromaticity distribution and therefore tailoring the aromaticity patterns is a rational way for controlling the band gap. In the present work, it is shown how the three distinct classes of aromaticity patterns already found for armchair graphene nanoribbons can be rationally tuned by chemical edge functionalisation to modify their electronic arrangement and band gap.

Effect of structural defects and chemical functionalisation on the intrinsic mechanical properties of graphene.

Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposites. We analyse the Young's modulus of graphene at the semi-empirical PM6 level of theory. The internal forces are calculated and the Young's modulus is predicted for a finite graphene sheet when external strain is applied on the system.

Electronic structure and aromaticity of graphene nanoribbons.

We analyse the electronic structure and aromaticity of graphene nanoribbons and carbon nanotubes through a series of delocalisation and geometry analysis methods. In particular, the six-centre index (SCI) is found to be in good agreement with the mean bond length (MBL) and ring bond dispersion (RBD) geometry descriptors. Based on DFT periodic calculations, three distinct classes of aromaticity patterns have been found for armchair graphene nanoribbons, appearing periodically as the width of the ribbon is increased.

Controlling fullerene addition sequences, regioselectivity and magic numbers via metal encapsulation.

A systematic density functional study of chlorine addition to C(70) up to C(70)Cl(12) confirms experimental observations of regioselectivity and stability of C(70)Cl(10). We show that K@C(70) follows an alternative addition sequence with different isomers and magic numbers to C(70) such as KC(70)Cl(3). This prediction is important for controlling functionalisation behaviour via encapsulation and endofullerene purification.

Theoretical analysis of carbon nanotube wetting in polystyrene nanocomposites.

Besides chemical functionalisation, the use of surfactants can be applied to debundle and disperse carbon nanotubes before further application in polymer nanocomposites. In this work we present a theoretical analysis of the interaction between single-walled carbon nanotubes and sodium dodecyl sulfate as surfactant and/or polystyrene as polymer matrix using semi-empirical AM1 calculations. Results indicate that the use of short potassium sulfate-terminated polystyrene chains as an extra component can help to remove the surfactant from the nanotube surface within the matrix, resulting in improved electronic properties of the nanocomposite.

Comparison between early stage oxygenation behavior of fullerenes and carbon nanotubes.

We explore early stage oxygen addition to C60 buckminsterfullerene, and compare its oxygenation behavior to that of both pristine and defective metallic carbon nanotubes, using ab initio theoretical modeling. For fullerene oxygen addition up to C60O4, in general oxygenation preferentially occurs at the pentagon-hexagon bonds ([5,6] type addition), leading to open annulene structures, as opposed to the closed [6, 6] epoxide isomers. For carbon nanotubes the preference for annulene structures is significantly more pronounced as all epoxide addition is endothermic.

Local aromaticity of pristine and fluorinated carbon nanotubes.

We examine the use of nucleus independent chemical shifts (NICS) as a tool for analysis of pristine and fluorinated finite-length carbon nanotubes. The introduction of both variable molecule length and different nanotube curvatures introduces additional subtleties to NICS analysis not present in analysis of more conventional 2D molecules. Notably the precise length of tube segment considered can strongly influence calculated NICS values.

Theoretical prediction of the solubility of fluorinated C(60).

Although extensive theoretical and experimental research has been conducted on fluorinated fullerenes, little detailed information exists on their solubility in different solvents. However, this solubility is crucial for their processability and possible application. In this work, we predict the solubility of fluorinated C(60) in various polar and non-polar solvents, based on a correlation between experimentally measured solubilities for C(60) from the literature and theoretically predicted solubilisation energies.

Spectroscopy and defect identification for fluorinated carbon nanotubes.

Finely tuned: Carbon nanotubes are exposed to a CF(4) radio-frequency plasma (see picture). High-resolution photoelectron spectroscopy shows that the treatment effectively grafts fluorine atoms onto the MWCNTs, altering the valence electronic states. Fluorine surface concentration can be tuned by varying the exposure time.

Super-robust, lightweight, conducting carbon nanotube blocks cross-linked by de-fluorination.

We produced large binder-free multi-walled carbon nanotube (MWNT) blocks from fluorinated MWNTs using thermal heating and a compressing method in vacuo. This technique resulted in the formation of covalent MWNT networks generated by the introduction of sp(3)-hybridized carbon atoms that cross-link between nanotubes upon de-fluorination. The resulting carbon nanotube blocks are lighter than graphite, can be machined and polished, and possess average bending strengths of 102.

Psoriasis of the tongue.

Introduction: Psoriasis is a common, chronic dermatologic disease. Cases affecting the oral mucous membranes are rarely reported in the international literature, in particular tongue lesions are hardly ever documented.

Material And Methods: This article presents a 61 year old patient with persistent whitish lesion on his tongue.

Oxidation and reactivity of nitrogen- and phosphorus-doped heterofullerenes.

Density functional theory (DFT) calculations suggest significantly different oxidation behaviour for phosphorus-doped heterofullerenes compared to their pure and nitrogen-doped counterparts, due to formation of a phosphene oxide. This oxide is not thermally labile, suggesting stable phosphofullerenes are likely to be C(59)POH and (C(59)PO)(2). In contrast, azafullerenes form stable epoxides when oxidised.

Meta-code for systematic analysis of chemical addition (SACHA): application to fluorination of C70 and carbon nanostructure growth.

We present a new computer program able to systematically study chemical addition to and growth or evolution of carbon nanostructures. SACHA is a meta-code able to exploit a wide variety of pre-existing molecular structure codes, automating the otherwise onerous task of constructing, running, and analyzing the large number of input files that are required when exploring structural isomers and addition paths. By way of examples we consider fluorination of the fullerene cage C70 and carbon nanostructure growth through C2 addition.

A new method of monitoring osteomyelitis.

Chronic infections of bone such as osteomyelitis are frequent events, especially in immunocompromised or diabetic patients, and costly on a national level. Incorrect treatment or delayed diagnosis may lead to loss of the affected extremity or mandible. The aim of this study was to assess the possible value of urinary lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) concentrations in the monitoring of mandibular osteomyelitis.

Theoretical analysis of fluorine addition to single-walled carbon nanotubes: functionalization routes and addition patterns.

We present a theoretical investigation on the chemical addition patterns governing the fluorination of single wall carbon nanotubes. Monte Carlo calculations based on a Hückel model suggest that fluorination is stabilized in a bandlike pattern due to electronic confinement effects on the tube bond network topology. Ab initio analysis of the fluorination of small nanotubes show that fluorine addition along the nanotube axis direction is favored by a mechanism of carbon framework distortion.

Pattern formation on carbon nanotube surfaces.

Calculations of fluorine binding and migration on carbon nanotube surfaces show that fluorine forms varying surface superlattices at increasing temperatures. The ordering transition is controlled by the surface migration barrier for fluorine atoms to pass through next neighbor sites on the nanotube, explaining the transition from semi-ionic low coverage to covalent high coverage fluorination observed experimentally for gas phase fluorination between 200 and 250 degrees C. The effect of solvents on fluorine binding and surface diffusion is explored.

Atomic nanotube welders: boron interstitials triggering connections in double-walled carbon nanotubes.

Here we demonstrate that the incorporation of boron (B) atoms between double-walled carbon nanotubes (DWNTs) during thermal annealing (1400-1600 degrees C) results in covalent nanotube "Y" junctions, DWNT coalescence, and the formation of flattened multiwalled carbon nanotubes (MWNTs). These processes occur via the merging of adjacent tubes, which is triggered by B interstitial atoms. We observe that B atom interstitials between DWNTs are responsible for the rapid establishment of covalent connections between neighboring tubes (polymerization), thereby resulting in the fast annealing of the carbon cylinders with B atoms embedded in the newly created carbon nanotube network.

Theoretical study of the addition patterns of C60 fluorination: C60Fn (n = 1-60).

A systematic study is presented of addition patterns occurring upon fluorination of C60. We use the program SACHA, which increments the number of fluorine addends, tests all available addition sites within a given cutoff radius, and selects the most energetically stable structure for further addition on the basis of full AM1 optimizations for every isomer. The lowest energy structures are optimized at HF/3-21G level of theory.

Quantum chemical study of the reactivity of C60HR and C60(CHR) derivatives.

In the present work a quantum chemical study of a series of substituted hydrofullerenes, C(60)HR, and a series of methanofullerenes, C(60)(CHR), is presented. Their reactivity and geometrical, energetic, electronic, and magnetic properties, as well as the influence of the substituent, are discussed. As a probe of the reactivity, the acidic properties of these fullerene derivatives were predicted, based on the calculated deprotonation energies, with a previously set up scheme.

Ring currents as probes of the aromaticity of inorganic monocycles : P5-, As5-, S2N2, S3N3-, S4N3+, S4N42+, S5N5+, S42+ and Se42+.

Current-density maps were calculated by the ipsocentric CTOCD-DZ/6-311G** (CTOCD-DZ=continuous transformation of origin of current density-diamagnetic zero) approach for three sets of inorganic monocycles: S(4) (2+), Se(4) (2+), S(2)N(2), P(5) (-) and As(5) (-) with 6 pi electrons; S(3)N(3) (-), S(4)N(3) (+) and S(4)N(4) (2+) with 10 pi electrons; and S(5)N(5) (+) with 14 pi electrons. Ipsocentric orbital analysis was used to partition the currents into contributions from small groups of active electrons and to interpret the contributions in terms of symmetry- and energy-based selection rules. All nine systems were found to support diatropic pi currents, reinforced by sigma circulations in P(5) (-), As(5) (-), S(3)N(3) (-), S(4)N(3) (+), S(4)N(4) (2+) and S(5)N(5) (+), but opposed by them in S(4) (2+), Se(4) (2+) and S(2)N(2).