The effect of the external lateral electric field on the luminescence intensity of InAs/GaAs quantum dots

We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications. The text was submitted by the authors in English.     

Laser-induced ablation of polymers using a patterned dopant generated from a leuco-dye precursor via flood exposure: A “portable conformable mask” approach to laser ablation of PMMA at 351 nm

A two-stage laser ablation process is described, which initially generates a laser-light absorbing image from a conventional photolithographic mask via a UV-flood exposure step. For this purpose a colorless precursor of a dye, i.e., itsleuco form, is imbedded into the polymer to be ablated as a dopant. For poly(methyl methacrylate) as such a polymer, triphenylmethanol, the leuco precursor for the corresponding triphenylmethyl dye represents a good choice for ablation with excimer lasers operating at the wavelength 351 nm. In this fashion conventional masks and exposure tools of UV-photolithography may be used in combination with laser ablation. The resulting images are characterized by a good contrast and reasonably sharp contours. The photochemical mechanism and additional aspects of this two-step process, which resembles the portable conformal mask approach of photolithography, are outlined.     

Efficient and stereoselective synthesis of bicyclo[3.2.1]octan-8-ones: synthesis and palladium-catalyzed isomerization of functionalized 2-vinyl-2,3,3a,4,5,6-hexahydro-2,3-benzofurans

A new C,O-cyclodialkylation of dilithiated cyclic beta-keto esters and beta-keto sulfones with 1,4-dibromo-2-butene is reported which results in regio- and diastereoselective formation of 2-vinyl-2,3,3a,4,5,6-hexahydro-2,3-benzofurans. The products could be efficiently transformed into functionalized bicyclo[3.2.1]octan-8-ones by a palladium-catalyzed rearrangement reaction. In case of sulfone derivatives, this rearrangement proceeds with high stereospecifity to give exclusively the endo-configured diastereomers. The bicyclo[3.2.1]octane skeleton is present in a large number of pharmacologically important natural products.     

Modelling and design of a novel air-spring for a suspension seat

Air-springs used in conjunction with auxiliary volumes provide both spring stiffness and damping. The damping is introduced through the flow restriction connecting the two air volumes. This article presents a simplified model of an air-spring with an auxiliary volume derived from first principles for simulation and design of an air-spring coupled to an auxiliary volume for a suspension seat. Tests were performed on an experimental apparatus to validate the model. The simulation model of the air-spring and auxiliary volume followed the trend predicted by the literature but showed approximately 27% lower transmissibility amplitude and 21% lower system natural frequency than that obtained by tests when using large diameter flow restrictions. This inaccuracy is assumed to be introduced by the simplified mass transfer equations defining the flow restriction between air-spring and auxiliary volume. The model showed closer correlation to the experimental results when the auxiliary volume size was decreased by two-thirds of the volume actually used for the experiment. A procedure, using the developed simulation model, for the design of a prototype air-spring and auxiliary volume, is presented for application in a typical articulated or rigid frame dump truck. The goal of the study was to design a suspension seat for this application and to obtain a SEAT value below 1.1. The design was optimised by varying auxiliary volume size and flow restriction diameters for different loads. A SEAT value of less than 0.9 was achieved, clearly indicating the effectiveness of using an auxiliary volume with an air-spring as seat suspension.     

Design,Synthesis and Preclinical Assessment of 99mTc-iFAP for In Vivo Fibroblast Activation Protein (FAP) Imaging

Fibroblast activation protein (FAP) is expressed in the microenvironment of most human epithelial tumors. ⁶⁸Ga-labeled FAP inhibitors based on the cyanopyrrolidine structure (FAPI) are currently used for the detection of the tumor microenvironment by PET imaging. This research aimed to design, synthesize and preclinically evaluate a new FAP inhibitor radiopharmaceutical based on the ^99mTc-((R)-1-((6-hydrazinylnicotinoyl)-D-alanyl) pyrrolidin-2-yl) boronic acid (^99mTc-iFAP) structure for SPECT imaging. Molecular docking for affinity calculations was performed using the AutoDock software. The chemical synthesis was based on a series of coupling reactions of 6-hidrazinylnicotinic acid (HYNIC) and D-alanine to a boronic acid derivative. The iFAP was prepared as a lyophilized formulation based on EDDA/SnCl₂ for labeling with ^99mTc. The radiochemical purity (R.P.) was verified via ITLC-SG and reversed-phase radio-HPLC. The stability in human serum was evaluated by size-exclusion HPLC. In vitro cell uptake was assessed using N30 stromal endometrial cells (FAP positive) and human fibroblasts (FAP negative). Biodistribution and tumor uptake were determined in Hep-G2 tumor-bearing nude mice, from which images were acquired using a micro-SPECT/CT. The iFAP ligand (Ki = 0.536 nm, AutoDock affinity), characterized by UV-Vis, FT-IR, ¹H–NMR and UPLC-mass spectroscopies, was synthesized with a chemical purity of 92%. The ^99mTc-iFAP was obtained with a R.P. >98%. In vitro and in vivo studies indicated high radiotracer stability in human serum (>95% at 24 h), specific recognition for FAP, high tumor uptake (7.05 ± 1.13% ID/g at 30 min) and fast kidney elimination. The results found in this research justify additional dosimetric and clinical studies to establish the sensitivity and specificity of the ^99mTc-iFAP.