727 research outputs found

    Synthetic Applications of Oxidative Aromatic Coupling : From Biphenols to Nanographenes

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    Oxidative aromatic coupling occupies a fundamental place in the modern chemistry of aromatic compounds. It is a method of choice for the assembly of large and bewildering architectures. Considerable effort was also devoted to applications of the Scholl reaction for the synthesis of chiral biphenols and natural products. The ability to form biaryl linkages without any prefunctionalization provides an efficient pathway to many complex structures. Although the chemistry of this process is only now becoming fully understood, this reaction continues to both fascinate and challenge researchers. This is especially true for heterocoupling, that is, oxidative aromatic coupling with the chemoselective formation of a C−C bond between two different arenes. Analysis of the progress achieved in this field since 2013 reveals that many groups have contributed by pushing the boundary of structural possibilities, expanding into surface‐assisted (cyclo)dehydrogenation, and developing new reagents

    Matching CIE illuminants to measured spectral power distributions: A method to evaluate non-visual potential of daylight in two European cities

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    Abstract The evaluation of non-visual effects of light is a crucial topic in lighting design research and practice. Performing such analysis requires precise information about the spectral distribution of the tested light source. Assessing non-visual effects of daylight is complicated due to its spectral composition continuously changing, depending on many factors. Currently there are no available databases with spectral and spatial radiation patterns of the sky vault for locations spread all over the world, and an easy and common method to evaluate non-visual effects of daylight is lacking. The goal of the paper is to provide a simple method to evaluate the non-visual potential of daylight, accounting for its variability. In order to present it, spectral measurements were conducted in two European cities in spring and summer. Horizontal and vertical illuminance toward the four cardinal directions was measured. Daylight variability was analysed in terms of illuminance, Correlated Colour Temperature (CCT) and Melanopic to Photopic (M/P) ratio. A comparison between the measured spectra and the CIE standard illuminants was performed and it was found that the usefulness of this method to evaluate non-visual effects of light in terms of M/P is adequate and provides reliable results. Therefore, a simple method to estimate the non-visual potential of daylight based on the use of D series of illuminants was presented and validated by comparing the results with the measured data. Using this method to calculate M/P always achieves RMSPEs below 6%

    Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

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    Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be negative, indicating transmission via the hydrogen bond. In addition unusual long-range effects are seen. Structures, NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using DFT methods. Two-bond deuterium isotope effects on 13C chemical shifts are correlated with calculated OH stretching frequencies. Isotope effects on chemical shifts are calculated for systems with OH exchanged by OD. Hydrogen bond potentials are discussed. New and more soluble nitro derivatives are synthesized

    Matrix metalloproteinase 2 and tissue inhibitor of matrix metalloproteinases 2 in the diagnosis of colorectal adenoma and cancer patients.

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    The aim of the study was to assess the importance of the measurement of matrix metalloproteinase 2 (MMP-2) and tissue inhibitor of matrix metalloproteinases 2 (TIMP-2) in patients with colorectal cancer (CRC) in relation to clinicopathological features of tumor and patients' survival. Additionally, we determined serum MMP-2 and TIMP-2 in colorectal adenoma (CA) patients and healthy controls and compared them with tumor markers, CEA and CA 19-9. The serum levels of MMP-2 and TIMP-2 in 91 CRC patients, 28 CA subjects and 91 healthy controls were determined by ELISA method, but concentrations of CEA and CA 19-9 using MEIA method. Nonparametric statistical analyses were used. Serum levels of MMP-2 and TIMP-2 were significantly lower in CRC patients than in healthy subjects and decreased with tumor stage. Additionally, MMP-2 concentrations were significantly lower in patients with CRC than in CA group. Diagnostic sensitivity of TIMP-2 (59%) was the highest among biomarkers tested and increased in combined use with CEA (79%). Moreover, the area under ROC curve (AUC) of TIMP-2 was larger than AUC of MMP-2 in differentiation between CRC and healthy subjects, but lower than AUC of matrix metalloproteinase 2 in differentiation between colorectal cancer and adenoma. Our findings suggest clinical usefulness of TIMP-2 as a biomarker in the diagnosis of CRC, especially in combination with CEA. However, further investigation is necessary

    High-speed two-photon polymerization 3D printing with a microchip laser at its fundamental wavelength

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    High-resolution, high-speed 3D printing by two-photon polymerization (2PP) with a Nd:YVO4 Q-switched microchip laser at its fundamental wavelength of 1064 nm is demonstrated. Polymerization scan speeds of up to 20 mm/s and feature sizes of 250 nm are achieved using a high repetition rate Q-switched microchip laser with a semiconductor saturable absorber mirror (SESAM) and photoresist with a new photo-initiator bearing 6-dialkylaminobenzufuran as electron donor and indene-1,3-dione moiety as electron acceptor. The obtained results demonstrate the high potential of Q-switched microchip lasers for applications in 2PP 3D printing

    Effect of low level laser irradiation on VEGF gene expression in cultured endothelial cells

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    Background. Endothelial cells play a crucial role in the angiogenesis which is initiated by vascular endothelial growth factor (VEGF). Low level laser therapy (LLLT) stimulates repair processes which are based on the formation of new blood vessels.Aim. The aim of this study was to evaluate the impact of LLLT on VEGF gene expression in endothelial cells cultured in vitro.Material and methods. Freshly isolated endothelial cells from the human umbilical vein endothelial cells (HUVEC) line were used in the study. The cells were irradiated with a semiconductor laser emitting visiblelaser radiation at the wave length of 630 nm and the power of 30 mW, and radiation at the wavelength of 808 nm and the power of 60 mW in the infrared range. The study was performed with cell cultures subjected to four different procedures: I — control cells (not subjected to irradiation); II — cells subjected to an energy dose of 2 J/cm2; III — cells subjected to an energy dose of 4 J/cm2; and IV — cells subjected to an energy dose of 8 J/cm2. The cells were cultured for six days, and exposed to irradiation twice. The next step was to evaluate the VEGF gene expression by applying real-time PCR.Results. By using low power laser irradiation, we obtained a statistically significant increase in VEGF gene expression, particularly at doses of 2 and 8 J/cm2 in the wave length range of 630 nm. The wave length of 808 nm had a similar effect on increases in gene expression. However, the differences were statistically non-significant when compared to the control cells.Conclusions. This study has shown that low-power laser radiation in the visible light spectrum (630 nm) results in de novo formation of VEGF-A in the endothelial cells in culture
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