Temperature-dependent Raman investigation of rolled up InGaAs/GaAs microtubes

Large arrays of multifunctional rolled-up semiconductors can be mass-produced with precisely controlled size and composition, making them of great technological interest for micro- and nano-scale device fabrication. The microtube behavior at different temperatures is a key factor towards further engineering their functionality, as well as for characterizing strain, defects, and temperature-dependent properties of the structures. For this purpose, we probe optical phonons of GaAs/InGaAs rolled-up microtubes using Raman spectroscopy on defect-rich (faulty) and defect-free microtubes. The microtubes are fabricated by selectively etching an AlAs sacrificial layer in order to release the strained InGaAs/GaAs bilayer, all grown by molecular beam epitaxy. Pristine microtubes show homogeneity of the GaAs and InGaAs peak positions and intensities along the tube, which indicates a defect-free rolling up process, while for a cone-like microtube, a downward shift of the GaAs LO phonon peak along the cone is observed. Formation of other type of defects, including partially unfolded microtubes, can also be related to a high Raman intensity of the TO phonon in GaAs. We argue that the appearance of the TO phonon mode is a consequence of further relaxation of the selection rules due to the defects on the tubes, which makes this phonon useful for failure detection/prediction in such rolled up systems. In order to systematically characterize the temperature stability of the rolled up microtubes, Raman spectra were acquired as a function of sample temperature up to 300°C. The reversibility of the changes in the Raman spectra of the tubes within this temperature range is demonstrated.     

Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing

Auristatins are a class of ultrapotent microtubule inhibitors, whose growing clinical popularity in oncology is based upon their use as payloads in antibody-drug conjugates (ADCs). The most widely utilized auristatin, MMAE, has however been shown to cause apoptosis in non-pathological cells proximal to the tumour (“bystander killing”). Herein, we introduce azastatins, a new class of auristatin derivatives encompassing a side chain amine for antibody conjugation. The synthesis of Cbz-azastatin methyl ester, which included the C2-elongation and diastereoselective reduction of two proteinogenic amino acids as key transformations, was accomplished in 22 steps and 0.76 % overall yield. While Cbz-protected azastatin methyl ester (0.13–3.0 nM) inhibited proliferation more potently than MMAE (0.47–6.5 nM), removal of the Cbz-group yielded dramatically increased IC₅₀-values (9.8–170 nM). We attribute the reduced apparent cytotoxicity of the deprotected azastatin methyl esters to a lack of membrane permeability. These results clearly establish the azastatins as a novel class of cytotoxic payloads ideally suited for use in next-generation ADC development.     

cis-9,trans-11 and trans-10,cis-12 CLA affect lipid metabolism differently in primary white and brown adipocytes of Djungarian hamsters

We explored whether CLA isomers and other C₁₈ FA affect (i) lipid content and FA concentrations in total adipocyte lipids, (ii) FA synthesis from glucose in TAG and phospholipids of primary brown (BAT) and white adipocytes (WAT), and (iii) mRNA expression of uncoupling protein 1 (UCP1) in primary brown adipocytes of Djungarian hamsters (Phodopus sungorus). c9,t11-CLA, oleic, linoleic, and α-linolenic acid increased whereas t10,c12-CLA decreased lipid accumulation in both adipocyte types. t10,c12-CLA treatment affected FA composition mainly in BAT cells. CLA incorporation into lipids, in particular c9,t11-CLA, was higher in BAT. In both cell types, t10,c12-CLA treatment reduced the incorporation of glucose ¹³C carbon into FA of TAG and phospholipids, whereas c9,t11-CLA, linoleic, and α-linolenic acid either did not influence or dose-dependently increased glucose carbon incorporation into FA. UCP1 mRNA expression was inhibited by t10,c12-CLA but increased by c9,t11-CLA, linoleic, and α-linolenic acid. It is concluded that c9,t11-CLA and t10,c12-CLA have distinctly different effects on lipid metabolism in primary adipocytes. The effects of c9,t11-CLA are similar to those of other unsaturated C₁₈ FA. The opposite effects of c9,t11-CLA and t10,c12-CLA are evident in both WAT and BAT cultures; however, brown adipocytes seem to be more susceptible to CLA treatment.     

The Interaction between microRNAs and the Wnt/β-Catenin Signaling Pathway in Osteoarthritis

Osteoarthritis (OA) is a chronic disease affecting the whole joint, which still lacks a disease-modifying treatment. This suggests an incomplete understanding of underlying molecular mechanisms. The Wnt/β-catenin pathway is involved in different pathophysiological processes of OA. Interestingly, both excessive stimulation and suppression of this pathway can contribute to the pathogenesis of OA. microRNAs have been shown to regulate different cellular processes in different diseases, including the metabolic activity of chondrocytes and osteocytes. To bridge these findings, here we attempt to give a conclusive overview of microRNA regulation of the Wnt/β-catenin pathway in bone and cartilage, which may provide insights to advance the development of miRNA-based therapeutics for OA treatment.     

Electrochemical investigations on the corrosion behaviour of galvanized reinforcing steels in concrete with chromate‐reduced cements

The reduction of the chromate contents in cements affects the electrochemical reactions of galvanized reinforcing steels in fresh concrete. By means of electrochemical measurements and bar pull‐out tests the effect of chromates on the formation of protective coatings at the zinc and the bond behaviour have been investigated using chromate‐containing and chromate‐reduced cements. The results have shown that the bond zone was affected as a result of chromate reduction for cement types CEM I and CEM II. The disturbance to the bond zone should be considered as long‐term in relation to the pore structure which is formed. The effects on the bond are largely compensated for as the concrete ages. The results of the related bond strength with displacement paths of 0.1 and 0.5 mm, respectively, are still within the range of expected figures for non‐galvanized reinforcing steel despite the structural disturbance. Under practical aspects it is not necessary that the existing structural disturbance with respect to bond strength is taken into consideration.     

Exciplexes of zinc meso-tetraphenylporphyrin with arenediazonium salts,oxygen and p-benzoquinone

Zinc meso-tetraphenylporphyrin (ZnTPP) forms triplet exciplexes with different arenediazonium salts (p-Et₂N, p-MeO, p-Me, p-t-Bu, p-H, p-Cl, p-Br) and p-benzoquinone, and a singlet exciplex with oxygen (probably formed after energy transfer from excited ZnTPP to ³O₂ to yield ¹O₂). The absorption spectra of these exciplexes are nearly identical and – except of pronounced fine structures – similar to the spectrum of ³(ZnTPP)*. By means of WARE treatment of flash-photolytically determined rate constants or of quantum yields equilibrium constants, lifetimes and further data of diazonium salt exciplexes are determined. The equilibrium constants and lifetimes are very similar and amount to about 10⁴ M⁻¹ and 20 μs, respectively. The equilibrium constants of the oxygen and p-benzoquinone exciplexes are determined by competition experiments; they amount also to about 10⁴ M⁻¹. The diazonium salt exciplexes belong to the charge-shift type. Their equilibrium constants are, therefore, independent of the solvent polarity, as is interestingly also observed for the oxygen exciplex which formally belongs to the charge-separation type. The p-benzoquinone exciplex dissociates in acetonitrile as has been found also by other authors.     

Oxidative Kupplung CH-acider Verbindungen mit p-Phenylendiaminen. VIII [1]. Synthese von 5H-Benzo[a]phenothiazin-5-onen aus Naphth[2,1-d]1,3-oxathiol-2-onen

Oxidative Coupling of CH-acid Compounds with p-Phenylenediamines. VIII. Synthesis of 5H-Benzo[a]phenothiazin-5-ones from Naphth[2,1-d]1,3-oxathiol-2-ones Reaction of 5-hydroxynaphth[2,1-d]1,3-oxathiol-2-ones with N,N-diethyl-quinone-1,4-diimine leads to 5H-benzo[a]phenothiazin-5-ones 1 – 21 . The same dyes are available by use of p-substituted nitrosobenzenes in acetic acid, or in methanol in the presence of oxygen acceptors. The mechanisms of dye formation are discussed.