Fluorescent Liquid Tetrazines

Tetrazines with branched alkoxy substituents are liquids at ambient temperature that despite the high chromophore density retain the bright orange fluorescence that is characteristic of this exceptional fluorophore. Here, we study the photophysical properties of a series of alkoxy-tetrazines in solution and as neat liquids. We also correlate the size of the alkoxy substituents with the viscosity of the liquids. We show using time-resolved spectroscopy that intersystem crossing is an important decay pathway competing with fluorescence, and that its rate is higher for 3,6-dialkoxy derivatives than for 3-chloro-6-alkoxytetrazines, explaining the higher fluorescence quantum yields for the latter. Quantum chemical calculations suggest that the difference in rate is due to the activation energy required to distort the tetrazine core such that the [Formula: see text] [Formula: see text] and the higher-lying [Formula: see text] [Formula: see text] states cross, at which point the spin-orbit coupling exceeding 10 cm [Formula: see text] allows for efficient intersystem crossing to occur. Femtosecond time-resolved anisotropy studies in solution allow us to measure a positive relationship between the alkoxy chain lengths and their rotational correlation times, and studies in the neat liquids show a fast decay of the anisotropy consistent with fast exciton migration in the neat liquid films

Molecular rotors to probe the local viscosity of a polymer glass

We investigate the local viscosity of a polymer glass around its glass transition temperature using environment-sensitive fluorescent molecular rotors embedded in the polymer matrix. The rotors' fluorescence depends on the local viscosity, and measuring the fluorescence intensity and lifetime of the probe therefore allows to measure the local free volume in the polymer glass when going through the glass transition. This also allows us to study the local viscosity and free volume when the polymer film is put under an external stress. We find that the film does not flow homogeneously, but undergoes shear banding that is visible as a spatially varying free volume and viscosity.Comment: 8 pages, 7 figure

The scope of application of incremental rapid prototyping methods in foundry engineering

Abstract The article presents the scope of application of selected incremental Rapid Prototyping methods in the process of manufacturing casting models, casting moulds and casts. The Rapid Prototyping methods (SL, SLA, FDM, 3DP, JS) are predominantly used for the production of models and model sets for casting moulds. The Rapid Tooling methods, such as: ZCast-3DP, ProMetalRCT and VoxelJet, enable the fabrication of casting moulds in the incremental process. The application of the RP methods in cast production makes it possible to speed up the prototype preparation process. This is particularly vital to elements of complex shapes. The time required for the manufacture of the model, the mould and the cast proper may vary from a few to several dozen hours

The Accuracy of the Gear`s Measurement with the Co-ordinate Measuring Machine

Niektórzy producenci współrzędnościowych maszyn pomiarowych (WMP) oferują dodatkowe specjalizowane programy pomiarowe jak na przykład programy do pomiaru kół zębatych. Bardzo istotną sprawą jest dokładna metrologiczna analiza procesu i dokładności pomiaru koła zębatego z wykorzystaniem WMP. Z powodu braku analiz metrologicznych istniejących programów i braku możliwości dotarcia do poszczególnych algorytmów pomiarowych autor stworzył własne algorytmy i przeprowadził dokładną metrologiczną analizę błędów pomiaru elementarnych odchyłek wykonawczych kół zębatych. Powstałe alagorytmy, program i analiza metrologiczna dokładności pomiaru kół zebatych z wykorzystaniem współrzędnościowej techniki pomiarowej (WTP) są podstawą do zrealizowania kompleksowych pomiarów kół zębatych. Metoda pomiarów kompleksowych kół zębatych wiąże ze sobą nowoczesną technikę pomiarową oraz symulację współpracy jednostronnej kół zębatych, dając w efekcie końcowym odchyłki: kinematyczną i dynamiczną, jako całościowe parametry dokładności opisujące badane koła zębate.Some of the producers of the co-ordinate measuring machines (CMM) deliver many additional measuring programs for the measurement of the gears. It is of great importance to carry out the accurate metrological analysis of the measuring process and the final error of the gears` measurement with the CMM. Because it appeared impossible to analyze existing algorithms, the author created his own version and carried out the precise metrological analysis of the accuracy of basic gears` deviations measurement. The worked out algorithms, software and metrological analysis of the CMM`s gears measurement accuracy is a basis for the complex measurement of the gears. The complex measuring method includes modern measuring devices and single flank measurement simulation. The final results are cinematic and dynamic deviations of the gear, the complex parameters describing the whole gear

To Use Coordinate Measuring technology and 3D CAD Systems in Reverse Engineering

W artykule zaprezentowano koncepcję systemu inżynierii odwrotnej wykorzystującego współrzędnościową technikę pomiarową oraz komputerowe techniki CAx wspomagające pracę inżyniera. Na przykład przedstawiono sposób odtwarzania elementów i ocenę dokładności ich zamodelowania w systemie CAD. Do digitalizacji przekrojów i powierzchni swobodnych została wykorzystana współrzędnościowa maszyna pomiarowa sterowana CNC, wyposażona w oprogramowanie metrologiczne.The paper conception the reserve engineering system using coordinate measuring technology as well as computer techniques CAx to aid work of engineer was presented. Where presented basing on examples a way of reproduction of elements and evaluation of modeling accuracy theirs insystem CAD. Coordinate measure machine controlled CNC, equipped into metrology software has been used for the digitalization of the sections and free surfaces