Optical studies on ZnO films prepared by sol‐gel method

A standard sol‐gel method was used to deposit ZnO thin films of suitable thickness on glass substrate.The optical characteristics of the visible to infrared range on thermal stress were critically observed. Morphological signature of the films was detected by X‐ray diffraction (XRD) and the crystallite size determined by Scherrer method from XRD data were consistent with grain size estimated from spectroscopic data through Meulenkamp equation. The optical band gap value from the transmission spectrum was found to corroborate with the existing works. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Angular momentum transfer in incomplete fusion

Isomeric cross-section ratios of evaporation residues formed in¹²C+⁹³Nb and¹⁶O+⁸⁹Y reactions were measured by recoil catcher technique followed by off-line γ-ray spectrometry in the beam energy range of 55.7–77.5 MeV for¹²C and 68–81 MeV for¹⁶O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical deexcitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.     

Minimal textures in seesaw mass matrices and their low and high energy phenomenology

In an attempt to find minimal scenarios we study the implications of Dirac and Majorana mass matrices with texture zeros within the type I seesaw mechanism. For the Dirac mass matrices we consider 5 zero textures which we show to be the most minimal form that can successfully account for low energy phenomenology if the Majorana mass matrices are chosen minimal as well. For those, we consider both diagonal and even more minimal non-diagonal forms. The latter can be motivated e.g. by simple U(1)$U(1)$ flavour symmetries and have two degenerate eigenvalues. We classify the allowed textures and discuss the ramifications for leptogenesis and lepton flavour violation.     

Turnover rates in microorganisms by laser ablation electrospray ionization mass spectrometry and pulse-chase analysis

Biochemical processes rely on elaborate networks containing thousands of compounds participating in thousands of reaction. Rapid turnover of diverse metabolites and lipids in an organism is an essential part of homeostasis. It affects energy production and storage, two important processes utilized in bioengineering. Conventional approaches to simultaneously quantify a large number of turnover rates in biological systems are currently not feasible. Here we show that pulse-chase analysis followed by laser ablation electrospray ionization mass spectrometry (LAESI-MS) enable the simultaneous and rapid determination of metabolic turnover rates. The incorporation of ion mobility separation (IMS) allowed an additional dimension of analysis, i.e., the detection and identification of isotopologs based on their collision cross sections. We demonstrated these capabilities by determining metabolite, lipid, and peptide turnover in the photosynthetic green algae, Chlamydomonas reinhardtii, in the presence of ¹⁵N-labeled ammonium chloride as the main nitrogen source. Following the reversal of isotope patterns in the chase phase by LAESI-IMS-MS revealed the turnover rates and half-lives for biochemical species with a wide range of natural concentrations, e.g., chlorophyll metabolites, lipids, and peptides. For example, the half-lives of lyso-DGTS(16:0) and DGTS(18:3/16:0), t_1/2 = 43.6 ± 4.5 h and 47.6 ± 2.2 h, respectively, provided insight into lipid synthesis and degradation in this organism. Within the same experiment, half-lives for chlorophyll a, t_1/2 = 24.1 ± 2.2 h, and a 2.8 kDa peptide, t_1/2 = 10.4 ± 3.6 h, were also determined.     

A Trimodal Closomer Drug‐Delivery System Tailored with Tracing and Targeting Capabilities

The construction and application of a unique monodisperse closomer drug‐delivery system (CDDS) integrating three different functionalities onto an icosahedral closo‐dodecaborane [B₁₂]^2? scaffold is described. Eleven B‐OH vertices of [closo‐B₁₂(OH)₁₂]^2? were used to attach eleven copies of the anticancer drug chlorambucil and the targeting vector glucosamine through a bifurcating lysine linker. The remaining twelfth vertex was used to attach a fluorescent imaging probe. The presence of multiple glucosamine units offered a monodisperse and highly water‐soluble CDDS with a high payload of therapeutic cargo. This array enhanced the penetration of the drug into cancer cells by exploiting the overexpression of GLUT‐1 receptors present on cancer cells. About 15‐fold enhancement in cytotoxicity was observed for CDDS‐1 against Jurkat cells, compared to CDDS‐2, which lacks the GLUT‐1 targeting glucosamine. A cytotoxicity comparison of CDDS‐1 against colorectal RKO cells and its GLUT‐1 knock‐out version confirmed that GLUT‐1 mediates endocytosis. Using fluorescent markers both CDDS‐1 and ‐2 were traced to the mitochondria, a novel target for alkylating agents.     

Impact of Zn-doping on the composition,stability, luminescence properties of silica coated all-inorganic cesium lead bromide nanocrystals and their biocompatibility

Cesium lead halide (CsPbX₃: X = I, Br, Cl) nanocrystals (NCs) are believed to be potential candidates for bioimaging applications. However, their low structural stability against polar solvents remains as a major limitation. To improve the NCs stability and maintain high emission intensity, we synthesized silica coated Zn-doped core@shell perovskite NCs via modified ligand assisted reprecipitation (LARP) synthetic method under relatively high humid condition. We systemically varied the composition inside the perovskite structure and then studied their photophysical properties and stability. Interestingly, the Zn-doping amount controls the ratio of CsPbBr₃ to Cs₄PbBr₆ perovskites inside the core and also facilitates the growth of (OA)₂PbBr₄ shell, enables overall increase in NCs emission intensity and stability. We observed green color emission from these NCs in the spectral range of 494-506 nm with a maximum photoluminescence quantum yield (PLQY) up to 88%. The optimized Zn-doped NCs exhibited nearly four times better water stability compared to the bare NCs and retain emission properties for several months even in highly polar solvents. Finally, we performed biocompatibility test of the NCs generated on biological samples and hydroponics test in a gardenia leaf for their potential bioimaging applications.     

Some remarks on a model for internal structure of black holes

Some clarifications about a model for the internal structure of black holes developed in an earlier paper are presented to remove confusion in the interpretation of certain results.     

Molecular reorientation in polypropylene

The molecular reorientation occurring within deformation bands in one-way drawn polypropylene films has been studied by optical microscopy. The deformation bands formed at the yield stress in tension tests on specimens cut at various angles to the initial drawing direction. It is shown that the principal axes of the refractive index ellipsoid in the deformation band coincide with the principal axes of the plastic strain ellipsoid, provided that the strains are referred to the initial isotropic state, i.e., prior to the initial drawing process. This result is similar to the results obtained previously for poly(ethylene terephthalate), but differes somewhat from the results obtained by other workers for poly(vinyl chloride). A possible reason for these differences is discussed.