A note on the reference configurations of a thermoelastic solid

Summary We show that in Continuum Thermodynamics if one natural reference configuration at uniform temperature exists, for which the solid is homogeneous and isotropic, there is an endless number of these configurations, temperatures of which vary in a given range.

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Sommario Si ammette comunemente che, comunque si scelga un valore della temperatura in un certo intervallo, esiste una configurazione di riferimento naturale e a temperatura uniforme, rispetto alla quale un solido termoelastico sia omogeneo ed isotropo. In questa nota si fa vedere che basta supporre che esiste una sola di tali configurazioni per potere affermare che, sotto ipotesi facilmente ammissibili, di tali configurazioni ne esistono infinite al variare della temperatura in un opportuno intorno.

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Work performed under the auspices of CNR and MPI.     

Combining single wall carbon nanotubes and photoactive polymers for photoconversion

A combination of van der Waals and electrostatic interactions was used to integrate SWNT and a suitably functionalized polythiophene into nanostructured ITO electrodes. In the resulting electron donor/acceptor nanocomposites, polythiophene represents the light-harvesting chromophore that readily donates an excited-state electron to the ground-state electron-accepting SWNT. Upon illumination, monochromatic incident photoconversion efficiencies between 1.2 and 9.3% were determined for single and eight-sandwiched layers, respectively.     

An Animal Model for Human Melanoma

Abstract— Experimental animal models that are directly relevant to human melanoma are lacking. We propose the Angora goat as a potentially useful field model with experimental potential and to this end have examined the prevalence and site distribution of all skin cancers in 28 Angora goat herds in Queensland, Australia. The prevalence of benign melanocytic lesions (lentigines) and their experimental induction by sunlight were also investigated. Among 1731 goats over 2 years of age, 139 malignant skin tumors were excised from 95 affected animals. The prevalence of squamous cell carcinoma (SCC) was 3.8% and of melanoma, 2.2%. Main site of occurrence of melanoma (83%) was the dorsal surface of the ear; in contrast SCC occurred mostly (84%) on the perineum. Lentigines were darker and more prevalent on the exposed compared with the unexposed surface of the ear in Angoras, analogous to the higher prevalence of nevi on the exposed compared with the less exposed inner surface of the arm in humans. Lentigines, which were also found on the perineum though lighter in color than on the dorsal ear, were absent in young animals under 3 months but were numerous in 1–3 year olds. Furthermore in an experimental substudy eight goats, having one flank repeatedly shorn and the contralateral flank left unshorn, revealed consistently more solar lentigines on the shorn flank ( P < 0.05) when both sides were examined after 9 months. Histopathological examination of paired skin biopsies from five of these goats also showed more abundant pigmentation in skin from the exposed, as compared with the unexposed flank. These findings indicate that sunlight induces tumors and lentigines in goats in a highly site-specific manner. The Angora goat model may suggest paradigms for explaining the site differences observed for human melanoma and may also be useful in the future clarification of molecular changes following carcinogenic levels of sun exposure.     

Seasonal Variation in Measured Solar Ultraviolet Radiation Exposure of Adults in Subtropical Australia

Generating accurate population-specific public health messages regarding sun protection requires knowledge about seasonal variation in sun exposure in different environments. To address this issue for a subtropical area of Australia, we used polysulphone badges to measure UVR for the township of Nambour (26° latitude) and personal UVR exposure among Nambour residents who were taking part in a skin cancer prevention trial. Badges were worn by participants for two winter and two summer days. The ambient UVR was approximately three times as high in summer as in winter. However, participants received more than twice the proportion of available UVR in winter as in summer (6.5%vs 2.7%, P < 0.05), resulting in an average ratio of summer to winter personal UVR exposure of 1.35. The average absolute difference in daily dose between summer and winter was only one-seventh of a minimal erythemal dose. Extrapolating from our data, we estimate that ca. 42% of the total exposure received in the 6 months of winter (June–August) and summer (December–February) is received during the three winter months. Our data show that in Queensland a substantial proportion of people’s annual UVR dose is obtained in winter, underscoring the need for dissemination of sun protection messages throughout the year in subtropical and tropical climates.     

Susceptibility to basal cell carcinoma is associated with high dermal mast cell prevalence in non-sun-exposed skin for an Australian populations

In a Danish population, basal cell carcinoma (BCC) patients have a higher dermal mast cell prevalence in buttock skin than controls. This finding was supported by a functional link in mice between histamine-staining dermal mast cells and the extent of susceptibility to UV-B-induced systemic immunomodulation. It was important to confirm that this association was maintained in an Australian population with very different ancestry and sun exposure patterns. Australian BCC patients (n = 26) had significantly higher densities of mast cells in the dermis of buttock skin than control subjects (n = 25) (P = 0.0003, Mann-Whitney U-test). However, this correlation was lost at the sun-exposed site of the hand (P = 0.547, Mann-Whitney U-test). To further evaluate whether a relationship exists between dermal mast cell prevalence in sun-exposed skin and incidence of BCC in a larger study, biopsies of dorsal hand skin were obtained from an age-stratified random sample of 166 Queensland subjects, together with the 51 South Australian subjects, and dermal mast cell prevalence was quantified. Older subjects (over the median age of 42 years) had a greater incidence of BCC development (P = 0.0001, chi-square test) and significantly higher mast cell densities in hand skin (P = 0.0001, chi-square test) than younger subjects. However, mast cell density in sun-exposed hand skin was not significantly associated with BCC incidence. Finally, cellular expression of c-kit correlated with mast cell prevalence in non-sun-exposed skin, thereby implicating the stem cell factor-c-kit axis in the intrinsic mechanisms that regulate prevalence. These results show that high prevalence of dermal mast cells in buttock skin but not hand is associated with BCC development in an Australian population.     

Reaction of o-aminophenol and p-benzoquinone in acetic acid

The reaction of o-aminophenol and p-benzoquinone in acetic acid yields phenoxazinones 1, 5 and 6 , phenoxazine 7 , triphenodioxazine 2 , ditriphenodioxazine 3 and the phenoxazinonyltriphenodioxazine 4 .     

Complexes of platinum(II) containing neutral and deprotonated 9-methyladenine. Synthesis, x-ray structures, and NMR studies on the cyclic trimer cis-[L2Pt[9-MeAd([bond]H)]]3(NO3)3 and the Dinuclear cis-[L2Pt(ONO2)[9-MeAd([bond]H)]PtL2](NO3)2 (L = PMePh2)

The dinuclear hydroxo complex cis-[L(2)Pt(mu-OH)](2)(NO(3))(2) (L = PMePh(2), 1), in CH(2)Cl(2), CH(3)CN, or DMF solution, deprotonates the NH(2) group of 9-methyladenine (9-MeAd) to give the complex cis-[L(2)Pt[9-MeAd(-H)]](3)(NO(3))(3), 2, which was isolated in good yield. The X-ray structure shows that the nucleobase binds symmetrically the metal centers through the N(1),N(6) atoms forming a cyclic trimer with Pt...Pt distances in the range 5.202(1)-5.382(1) A. Dissolution of 2 in DMSO or DMF determines the partial (or total) dissociation of the cyclic structure to form several fragments. A multinuclear NMR analysis of the resulting mixture supports the presence of the mononuclear species cis-[L(2)Pt[9-MeAd(-H)]](+), 3, in which the deprotonated nucleobase chelates the metal center with the N(6),N(7) atoms. Addition of a stoichiometric amount of the nitrato complex cis-[L(2)Pt(ONO(2))(2)] (L = PMePh(2), 4) to a DMSO or DMF solution of 2 affords quantitatively the diplatinated compound cis-[L(2)Pt(ONO(2))[9-MeAd(-H)]PtL(2)](NO(3))(2), 5. The single-crystal X-ray analysis shows that the adenine behaves as a tridentate ligand bridging two cis-L(2)Pt units at the N(1) and N(6),N(7) sites, respectively [Pt(1)-N(1) = 2.109(5) A, Pt(2)-N(6) = 2.095(7) A, Pt(2)-N(7) = 2.126(7) A]. The N(1)-bonded metal center completes the coordination sphere through an oxygen atom of a nitrate group, and its coordination plane is arranged orthogonally with respect the second one. The Pt-O distance [2.109(5) A] is similar to those found in the nitrato complex 4 [2.110 A, average]. The related complex cis-[[L(2)Pt(ONO(2))](2)(9-MeAd)](NO(3))(2), 6, containing the neutral adenine platinated at the N(1),N(7) atoms, was isolated and its stability in solution investigated by NMR spectroscopy. In DMSO, 6 undergoes decomposition forming a mixture of the species 4, 5, and the adenine mono- and bis-adducts cis-[L(2)Pt(9-MeAd)(DMSO)](2+), 7, and cis-[L(2)Pt(9-MeAd)(2)](2+), 8, respectively. This last complex, quantitatively formed upon addition of 9-MeAd (Pt/adenine = 1:2) to the mixture, was also isolated and characterized.     

Bonding energetics in HF and their relation to H2 and F2

The changes in total and kinetic energies of the HF molecule have been studied as a function of internuclear separation R. In addition the variation of the electron-electron potential energy with R has been displayed. The relation to energy changes in H₂ and F₂ is discussed.