Methylcholanthrene-induced sarcomas in nude mice have short induction times and relatively low levels of surface MHC class I expression

In order to study the role of the T-cell-mediated immune defense in tumor development, a total of 93 sarcomas were induced using different doses (8 micrograms (0.1%), 40 micrograms (0.5%) and 400 micrograms (5%)) of 3-methylcholanthrene in athymic nude Balb/c mice and phenotypically normal immunocompetent Balb/c mice. A shorter tumor induction time and a higher tumor incidence after treatment with low doses of methylcholanthrene were seen in nude mice than in immunocompetent mice, indicating that they have a lower resistance to the carcinogen. Contrary to expectations we found that the MHC class I expression of tumors from nude mice was lower than that of tumors from normal mice. Higher surface expression of MHC class I was demonstrated on high dose tumors from normal mice than on low dose tumors from normal mice. The cellular composition of the individual tumors raised in nude mice was more heterogeneous with respect to MHC class I expression. Since the mice differ genetically only with respect to the nu gene, these results indicate that a lack of T-cell-mediated defense mechanisms may confer upon the bearer a lower resistance to 3-methylcholanthrene and a different MHC profile of the ensuing tumor.     

Passivation Properties and Formation Mechanism of Amorphous Halide Perovskite Thin Films

Lead halide perovskites are among the most exciting classes of optoelectronic materials due to their unique ability to form high-quality crystals with tunable bandgaps in the visible and near-infrared using simple solution precipitation reactions. This facile crystallization is driven by their ionic nature; just as with other salts, it is challenging to form amorphous halide perovskites, particularly in thin-film form where they can most easily be studied. Here, rapid desolvation promoted by the addition of acetate precursors is shown as a general method for making amorphous lead halide perovskite films with a wide variety of compositions, including those using common organic cations (methylammonium and formamidinium) and anions (bromide and iodide). By controlling the amount of acetate, it is possible to tune from fully crystalline to fully amorphous films, with an interesting intermediate state consisting of crystalline islands embedded in an amorphous matrix. The amorphous lead halide perovskite has a large and tunable optical bandgap. It improves the photoluminescence quantum yield and lifetime of incorporated crystalline perovskite, opening up the intriguing possibility of using amorphous perovskite as a passivating contact, as is currently done in record efficiency silicon solar cells.     

Study of the temperature and organic bindings effects in the dielectric and structural properties of the lithium ferrite ceramic matrix (LiFe5O8)

In this study, the effects of the calcination temperature and of the organic bindings in the structural and dielectric properties of lithium ferrite (LiFe₅O₈) were investigated. The organic bindings used were glycerol, PVA (polyvinyl alcohol) and Galactomannan (Adenanthera pavonina). The investigated calcination temperature range was from 773 K to 1073 K. The structural properties were analyzed using differential scanning calorimetry, thermogravimetry, X-ray diffraction and infra-red spectroscopy. The electrical and magnetical properties were investigated using impedance dielectric spectroscopy and Mössbauer spectroscopy. The study of the structural and electrical properties of the lithium ferrites is an important issue in view to their attractive technological properties and low cost of fabrication. This work shows that the binding type, affects significantly the dielectric constant and loss of the LiFe₅O₈ ceramics.     

Real-time studies during coating and post-deposition annealing in organic semiconductors

In this contribution we explore the use of real time spectroscopic probes to gain useful insights into the kinetics of semiconductor polymer chains during thin film formation and upon post-deposition annealing treatments. In-situ ellipsometry is employed to monitor the deposition of thin films of the workhorse material system for organic photovoltaics (soluble derivative fullerene blended with poly(3-hexylthiophene)), when processed from solution using an analogous dip coating deposition method. This allows for detailed time investigation of the dynamics of film formation. Moreover, we applied spectroscopic photometry to study the in-situ crystallization and diffusion of polymer chains during post-deposition solvent annealing.     

Auger-decay dynamics of germanium nano-islands in silicon

The decay dynamics of self-assembled germanium islands is studied by time-resolved fluorescence spectroscopy. The scaling behavior of the decay rate with the number of excitons in the islands is shown to agree with expectations for an Auger-recombination-dominated process in the asymptotic limit of high exciton numbers. The multi-excitonic decay time and spectral behavior are compared to theoretical estimates.     

Microwave assisted synthesis of ruthenium electrocatalysts for oxygen reduction reaction in the presence and absence of aqueous methanol

In this work we present the synthesis of ruthenium based electrocatalysts for oxygen reduction reaction in 0.5 mol L⁻¹ H₂SO₄, using microwave irradiation at different power, time and temperature conditions. Ru₃(CO)₁₂ and 1,2-dichlorobenzene were used as precursor and solvent respectively. The materials obtained were structurally characterized by FT-IR spectroscopy and X-ray diffraction; their chemical composition was determined by energy-dispersive spectroscopy analysis. The rotating disk electrode technique was used for the electrochemical characterization of the catalysts; the oxygen reduction reaction was performed in the presence and absence of aqueous methanol solutions. The electrocatalytic activity towards the oxygen reduction reaction is similar to that of ruthenium catalysts synthesized using a conventional process reported in the literature.     

Primary thrombosis of pulmonary artery in a child with tetralogy of Fallot

A 34-month-old child with tetralogy of Fallot developed an acute, primary thrombosis of the pulmonary trunk. A greatly increased haematocrit was most probably a predisposing factor. An unusual postmortem finding was the large number of extremely dilated myocardial capillaries. In a review of a series of 394 consecutive necropsy cases with many kinds of cardiac anomalies, there was only one case (a 28-year-old man) with occluding thrombus formation in the pulmonary artery. This case also belonged to the Fallot group but a subacute glomerulonephritis seemed to be the major cause of death.     

Valency configuration of transition metal impurities in ZnO

We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn_1−xTM_xO, the localized TM²⁺ configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy ε_F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with ε_F close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.