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41.
Zusammenfassung Es wird beschrieben, wie man unter Verwendung einer Zerstäuber-Brenner-Kombination und eines Lichtstrahloscillographen die benötigte Probenmenge für flammenphotometrische Emissions-oder Absorptions-analysen drastisch senken kann, um eine vorherige Anreicherung des Analysengutes bei kleinen Probenmengen zu ermöglichen. Dazu werden im einzelnen die Meßergebnisse mitgeteilt bezüglich der relativen Schwan-kung des Photostromes, der Einstellzeit der quasistationären Atom-konzentration in der Flamme, der benötigten Probenmenge pro Analyse und die erreichten relativen und absoluten unteren Nachweisgrenzen.
Unterstützt mit Mitteln der Deutschen Forschungsgemeinschaft. 相似文献
Summary A method is given by which a preliminary enrichment of the analytically essential material is accomplished so that the amount of sample needed for a flame-photometric determination may be drastically reduced. This is accomplished by using an atomizer-burner combination and a light ray oscillograph. The data regarding the relative fluctuation of the photoflame, the weight of the sample required per analysis and the relative and absolute lower detection limits reached are given in detail.
Résumé On décrit l'emploi d'un système pulvériseur-brûleur et d'un oscillographe permettant de diminuer considérablement la quantité de prise d'essai nécessaire pour les analyses par photométrie de flamme en émission ou en absorption, ce qui rend possible l'enrichissement préable du produit à analyser dans le cas de petites prises d'essai. On communique en détail les résultats d'analyse concernant la variation relative du courant photoélectrique, la durée d'établissement de la concentration atomique quasi-stationnaire dans la flamme, la prise d'essai nécessaire par analyse et les limites de dilution inférieures atteintes en valeur absolue et en valeur relative.
Unterstützt mit Mitteln der Deutschen Forschungsgemeinschaft. 相似文献
42.
E. Herrmann 《Fresenius' Journal of Analytical Chemistry》1939,118(7-8):303-304
Ohne Zusammenfassung 相似文献
43.
E. Herrmann Nguyen Thi Thu Chau O. Navratil G. Ohms L. Beyer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The new 1,1-disubstituted 3-diphenoxy(thio)phosphoryl-(thio)ureas, R1R2NC(X)NHP(0Ph)2, HA, with X,Y = O,S, were synthesized by addition of secondary mines to the corresponding P-iso(thio)cyanates. This reaction is reversible if X,Y = S. (PhO)2P(Y)Cl reacts with H2NC(X)NR2 in the presence of an HCl acceptor only if X,Y a 0. Side reactions are observed. Phosphorylated derivatives of biuret were isolated from such a reaction mixture. 相似文献
44.
Ring closure of 1,2-bis(1-pyrrolylmethyl)benzene in the acid-catalysed condensation with acetone yields the 1,5-diazacyclononatriene [ O -C6H4(CH2NC4H3-2)2C(CH3)2] as the sole identifiable product. The twisted or saddle conformation of the 1,5-diazacyclononatriene, which was confirmed by X-ray crystal structure determination, is conformationally rigid in solution. The conformation of the 1,5-diazacyclononatriene prevents the formation of the target N,N′-bridged calix[4]pyrrole by further acid-catalysed condensation with acetone, the reaction affording unidentified oligomers/polymers instead. The acid-catalysed condensation of 1,3- and 1,4-bis(1-pyrrolylmethyl)benzene with acetone also yields unidentified oligomers/polymers. 相似文献
45.
Miancheng Zou Pengkun Zhao Jilin Fan Robert Göstl Andreas Herrmann 《Journal of polymer science. Part A, Polymer chemistry》2022,60(12):1864-1870
The ultrasound-induced cleavage of covalent and non-covalent bonds to activate drugs (sonopharmacology) is a promising concept to gain control over the action of active pharmaceutical ingredients by an external trigger. Previously, linear polymer architectures bearing drug payloads were exploited for drug release by using the principles of polymer mechanochemistry. In this work, the carrier design is altered by the polymer topology to improve the ultrasound-triggered release of covalently anchored drugs from polymer scaffolds. We use microgels crosslinked by mechanoresponsive disulfides and copolymerized with Diels-Alder adducts of furylated payload molecules and acetylenedicarboxylate. Force-induced thiol formation induces a Michael-type addition liberating the payload from the microgels. The use of microgels significantly reduces sonication times compared to linear polymer chains and shields the cargo efficiently from non-triggered activation using ultrasound that produces inertial cavitation at a frequency of 20 kHz as model condition. 相似文献
46.
Dr. Andreas A. Bastian Dr. Maria Bastian Dr. Manuel Jäger Mark Loznik Dr. Eliza M. Warszawik Xintong Yang Dr. Nabil Tahiri Dr. Peter Fodran Prof. Dr. Martin D. Witte Anne Thoma Dr. Jens Köhler Prof. Dr. Adriaan J. Minnaard Prof. Dr. Andreas Herrmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(36):e202200883
The continuous emergence of antimicrobial resistance is causing a threat to patients infected by multidrug-resistant pathogens. In particular, the clinical use of aminoglycoside antibiotics, broad-spectrum antibacterials of last resort, is limited due to rising bacterial resistance. One of the major resistance mechanisms in Gram-positive and Gram-negative bacteria is phosphorylation of these amino sugars at the 3’-position by O-phosphotransferases [APH(3’)s]. Structural alteration of these antibiotics at the 3’-position would be an obvious strategy to tackle this resistance mechanism. However, the access to such derivatives requires cumbersome multi-step synthesis, which is not appealing for pharma industry in this low-return-on-investment market. To overcome this obstacle and combat bacterial resistance mediated by APH(3’)s, we introduce a novel regioselective modification of aminoglycosides in the 3’-position via palladium-catalyzed oxidation. To underline the effectiveness of our method for structural modification of aminoglycosides, we have developed two novel antibiotic candidates overcoming APH(3’)s-mediated resistance employing only four synthetic steps. 相似文献
47.
Friedrich-Rust M Romenski O Meyer G Dauth N Holzer K Grünwald F Kriener S Herrmann E Zeuzem S Bojunga J 《Ultrasonics》2012,52(1):69-74
Purpose
Real-time tissue elastography, a qualitative elastography method, has shown promising results in the diagnostic work up of thyroid nodules. However, to our knowledge no study has evaluated a quantitative elastography method in the thyroid gland. The present study is a feasibility study evaluating Acoustic Radiation Force Impulse-Imaging, a novel quantitative elastography method in the thyroid gland.Methods
ARFI-imaging involves the mechanical excitation of tissue using short-duration acoustic pulses to generate localized displacements in tissue. The displacements induce a lateral shear-wave propagation which is tracked using multiple laterally positioned ultrasound “tracking“ beams. Inclusion criteria were: thyroid nodules ?1 cm, non-functioning or hypo-functioning on radionuclide scanning, and cytological/histological assessment of thyroid nodule as reference method. All patients received conventional ultrasound, and examination of the thyroid gland including Power Doppler Ultrasound using a 9 MHz linear transducer, in addition real-time elastography (RTE) was performed at 9 MHz frequency and ARFI-imaging was performed at 4 MHz using Siemens (ACUSON S2000) B-mode-ARFI combination transducer.Results
Sixty nodules in 55 patients were analyzed. Three nodules were papillary carcinoma. The stiffer the tissue the faster the shear wave propagates. The results obtained indicated that the shear wave velocity in thyroid lobes ranged between 0.5 and 4.9 m/s. The median velocity of ARFI-imaging in the healthy nodule-free thyroid gland, as well as in benign and malignant thyroid nodules was 1.98 m/s (range: 1.20-3.63 m/s), 2.02 m/s (range: 0.92-3.97 m/s), and 4.30 m/s (range: 2.40-4.50 m/s), respectively. While no significant difference in median velocity was found between healthy thyroid tissue and benign thyroid nodules, a significant difference was found between malignant thyroid nodules on the one hand and healthy thyroid tissue (p = 0.018) or benign thyroid nodules (p = 0.014) on the other hand. Specificity of ARFI-imaging for the differentiation of benign and malignant thyroid nodules was comparable with RTE (91-95%).Conclusions
ARFI can be performed in the thyroid tissue with reliable results. 相似文献48.
Aluminium oxides doped with 1% 57Fe were prepared by sol-gel method, and annealed for 3 hours at various temperatures between 550°C and 1100°C. Amorphous phases were obtained below 1000°C, and crystalline α–Al2O3 was formed at 1100°C. Although Al2O3 itself shows diamagnetism, the light doping of Fe ions into aluminium oxide induced a very weak ferromagnetism, but the ferromagnetism disappeared by longer annealing. M?ssbauer spectra were composed of paramagnetic Fe2?+? and Fe3?+? species for samples heated below 750°C, and of paramagnetic Fe3?+? above 850°C, in addition to a magnetic sextet and relaxation peaks of Fe3?+?. The magnetic and quadrupole interactions of the sextet and the relaxation peaks and the density functional calculations suggest that the lightly doped Fe3?+? ions are substituted at Al sites in the Al2O3 lattice. 相似文献
49.
Christian Herrmann 《Algebra Universalis》2010,63(1):45-64
Extending work of von Neumann, Jónsson has shown that each complemented modular lattice, L admitting a large partial n-frame with n ≥ 4, or with n ≥ 3 and L Arguesian, can be coordinatized as the lattice of all principal right ideals of some regular ring. His proof built on the
embedding of L into the subgroup lattice of an abelian group which follows from Frink’s embedding of L into to a direct product of subspace lattices of irreducible projective spaces and coordinatization of the latter. We offer
a proof which, in addition to these results, employs only some elementary linear algebra. Luca Giudici’s thesis [6] is an
important source for this approach. 相似文献
50.
A split of a polytope is a (necessarily regular) subdivision with exactly two maximal cells. A polytope is totally splittable if each triangulation (without additional vertices) is a common refinement of splits. This paper establishes a complete classification
of the totally splittable polytopes. 相似文献