An elliptic problem with an indefinite nonlinearity and a parameter in the boundary condition

We establish the existence of solutions of nonlinear elliptic boundary value problems involving a positive parameter on the boundary. We also examine a profile of solutions of problem (1.2) when a parameter λ tends to 0.     

Characterisation of heavy oils using near-infrared spectroscopy: optimisation of pre-processing methods and variable selection

In this study, chemometric predictive models were developed from near infrared (NIR) spectra for the quantitative determination of saturates, aromatics, resins and asphaltens (SARA) in heavy petroleum products. Model optimisation was based on adequate pre-processing and/or variable selection. In addition to classical methods, the potential of a genetic algorithm (GA) optimisation, which allows the co-optimisation of pre-processing methods and variable selection, was evaluated. The prediction results obtained with the different models were compared and decision regarding their statistical significance was taken applying a randomization t-test. Finally, the results obtained for the root mean square errors of prediction (and the corresponding concentration range) expressed in %(w/w), are 1.51 (14.1-99.1) for saturates, 1.59 (0.7-61.1) for aromatics, 0.77 (0-34.5) for resins and 1.26 (0-14.7) for asphaltens. In addition, the usefulness of the proposed optimisation method for global interpretation is shown, in accordance with the known chemical composition of SARA fractions.     

Raman imaging of single living cells: probing effects of non-cytotoxic doses of an anti-cancer drug

Identifying cell response to a chemotherapy drug treatment, in particular at the single cell level, is an important issue in patient management. This study aims at evaluating the effect of gemcitabine on single living cells using micro-Raman imaging. We used as a model the non-small lung cancer cell line, Calu-1, exposed to cytostatic doses (1 nM to 1 μM for 24 h and 48 h) of gemcitabine, an antitumor drug currently used in the treatment of lung cancer. Following drug treatment as a function of doses and incubation times, the Raman maps of single living cells were acquired. Cell biomolecules (DNA, RNA, and proteins) were chemically extracted and their spectral signatures used to evaluate their respective distribution in the cellular spectral information of control and treated cells. The quantification of these distributions reveals a significant effect of 100 nM gemcitabine at 48 h incubation (concomitant decrease of nucleic acids and increase of proteins). PCA analyses performed both on nuclear and extracted biomolecules spectra show a time-dependent effect of the drug. These promising results reveal that effects of subtoxic doses can be monitored at the single cell level highlighting the importance of such studies for clinical applications.     

A THEORETICAL TREATMENT OF THE SULFUR-CONTAINING ANALOGS OF CYCLOBUTADIENE,CYCLOOCTATETRAENE, BUTALENE,AND OCTALENE

Abstract

Several coordination complexes of cyclobutadiene (I) have been prepared (e.g., cyclobutadiene iron tricarbonyl [1]) and cyclooctatetraene (II) is a well-known compound (for a potentially planar form of cyclooctatetraene, see [2]). Although butalene [3] (III) has not been synthesized so far, octalene (IV) has been obtained by Vogel and co-workers [4,5]. Recently we have carried out a theoretical study of the physical and chemical properties of butalene (III) and octalene (IV), and of the various annelated butalenes and octalenes [6,7] using the HMO and SCF-MO (PPP) quantum-chemical methods as well as the structure-resonance theory and graph theoretical methods. Numerous theoretical data are available in the literature on cyclobutadiene (I) and cyclooctatetraene (II).     

FTIR spectro-imaging of collagen scaffold formation during glioma tumor development

Evidence has recently emerged that solid and diffuse tumors produce a specific extracellular matrix (ECM) for division and diffusion, also developing a specific interface with microvasculature. This ECM is mainly composed of collagens and their scaffolding appears to drive tumor growth. Although collagens are not easily analyzable by UV-fluorescence means, FTIR imaging has appeared as a valuable tool to characterize collagen contents in tissues, specially the brain, where ECM is normally devoid of collagen proteins. Here, we used FTIR imaging to characterize collagen content changes in growing glioma tumors. We could determine that C6-derived solid tumors presented high content of triple helix after 8–11 days of growth (typical of collagen fibrils formation; 8/8 tumor samples; 91 % of total variance), and further turned to larger α-helix (days 12–15; 9/10 of tumors; 94 % of variance) and β-turns (day 18–21; 7/8 tumors; 97 % of variance) contents, which suggest the incorporation of non-fibrillar collagen types in ECM, a sign of more and more organized collagen scaffold along tumor progression. The growth of tumors was also associated to the level of collagen produced (P?<?0.05). This study thus confirms that collagen scaffolding is a major event accompanying the angiogenic shift and faster tumor growth in solid glioma phenotypes.     

The role of asbestos morphology on their cellular toxicity: an in vitro 3D Raman/Rayleigh imaging study

Amphiboles caused cohorts of deaths in exposed workers, leading to some of the largest class actions in the industry. Once inhaled, these inorganic fibers are thought to be both chemically and morphologically toxic, and their biopersistence in the lungs over decades lead to progressive pathologies, mesothelioma, and asbestosis. However, this exceptionally long chronicity for human pathologies suggests that chemical toxicity is certainly low, suggesting that morphological parameters could be more relevant in the pathology. Here, we developed a 3D Raman/optical imaging methodology in vitro to characterize both morphological and chemical parameters of cell/fiber interactions. We determined that lung cells could vesiculate amphiboles with length below 5 μm or could embed those not exceeding 15 μm in their fibrous extracellular matrix. Lung cells can thus develop defense strategies for handling the biopersistence of inorganic species, which may thus have major impact for biosafety issues related to nanomaterials.     

Low Bandgap Semiconducting Copolymer Nanoparticles by Suzuki Cross‐Coupling Polymerization in Alcoholic Dispersed Media

The synthesis and formulation of organic semiconductors for the emerging technology of organic electronics requires the use of preparative methods and solvents being environment friendly. Today most of the active layer materials for the organic photovoltaic devices and modules are using chlorinated solvents, which are toxic and hazardous. In this work, the synthesis of poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4,7‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole] (PCDTBT) in propan‐1‐ol is presented as the dispersant continuous phase in the presence of poly(vinylpyrrolidone) used as stabilizer. Suzuki–Miyaura polycondensation of 9‐(9‐heptadecanyl)‐9H‐carbazole‐2,7‐diboronic acid bis(pinacol) ester and 4,7‐bis(2‐bromo‐5‐thienyl)‐2,1,3‐benzothiadiazole in alcohol dispersion yields colloidally stable nanoparticles of PCDTBT with particles size of 330–1300 nm, depending on the stabilizer concentration. Other reaction parameters are also discussed such as the amount of base or Pd catalyst.

     

2-Substituted vs 4-substituted-9,9′-spirobifluorene host materials for green and blue phosphorescent OLEDs: a structure–property relationship study

We report a structure–property relationship study of four 9,9′-spirobifluorene (SBF) derivatives (4-5Pm-SBF, 2-5Pm-SBF, 4-Ph-SBF and 2-Ph-SBF), substituted with either phenyl or pyrimidine at the C2 or C4 position of the SBF core. Structural, thermal, electrochemical and photophysical properties have been examined and correlated to theoretical calculations in order to study the influence of the nature and the position of the substituent. The emission properties of 4- versus 2-substituted SBFs are noticeably different highlighting, in the excited state, the remarkable effect of substitution in ortho position of SBF. All compounds have been used as host material for green dopant in PhOLEDs with very high performances (2-5Pm-SBF: CE>58 cd/A, PE>35 lm/W, EQE>14%). More importantly, the two 4-substituted SBFs have been used as host materials in blue PhOLEDs, displaying high performance and a decrease of V_TH for 4-5Pm-SBF due to the incorporation of the electron-withdrawing pyrimidine.