Extraction of kinetic freeze-out properties and effect of resonance decays

We present STAR results from identified particle spectra measured in $\sqrt {s_{NN} } = 62.4$ GEV Au-Au collisions. Particle production and system dynamics are compared to results at $\sqrt {s_{NN} } = 200$ GeV. We extract kinetic and chemical freeze-out parameters using blast wave model parametrization and statistical model. We discuss the effect of resonance decays on the extracted kinetic freeze-out parameters.     

Supercritical CO2 Extract from Microalga Tetradesmus obliquus: The Effect of High-Pressure Pre-Treatment

High-pressure pre-treatment followed by supercritical carbon dioxide (ScCO₂) extraction (300 bar, 40 °C) was applied for the attainment of the lipophilic fraction of microalga Tetradesmus obliquus. The chemical profile of supercritical extracts of T. obliquus was analyzed by ultra-high-performance liquid chromatography–high-resolution mass spectrometry with electrospray ionization (UHPLC-ESI-HRMS). Moreover, the impact of ScCO₂ on the microbiological and metal profile of the biomass was monitored. The application of the pre-treatment increased the extraction yield approximately three-fold compared to the control. In the obtained extracts (control and pre-treated extracts), the identified components belonged to triacylglyceroles, fatty acid derivatives, diacylglycerophosphocholines and diacylglycerophosphoserines, pigments, terpenes, and steroids. Triacylglycerols (65%) were the most dominant group of compounds in the control extract. The pre-treatment decreased the percentage of triacylglycerols to 2%, while the abundance of fatty acid derivatives was significantly increased (82%). In addition, the pre-treatment led to an increase in the percentages of carotenoids, terpenoids, and steroids. Furthermore, it was determined that ScCO₂ extraction reduced the number of microorganisms in the biomass. Considering its microbiological and metal profiles, the biomass after ScCO₂ can potentially be used as a safe and important source of organic compounds.     

Herstellung und Behandlung von HPLC-Säulen unter Routinebedingungen

Zusammenfassung In dieser Arbeit werden einige theoretische und zahlreiche praktische Aspekte der Herstellung und der Benutzung von HPLC-Säulen zusammengefaßt. Die Behandlung der Bandenverbreiterung von verschiedenen Autoren wird kurz erörtert. Der Aufbau von HPLC-Säulen mit besonderer Betonung auf Qualität der Leersäulen wird behandelt. Das Säulenfüllen nach verschiedenen Verfahren und die Reproduzierbarkeit des Füllens werden diskutiert. Es werden Güteparameter einer HPLC-Säule angegeben. Bei dem routinemäßigen Betrieb von HPLC-Säulen werden die häufigsten Gründe des Säulenversagens besprochen und Maßnahmen zur Verlängerung der Lebensdauer einer HPLC-Säule empfohlen.

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Manufacturing and treatment of HPLC-columns under routine conditions

Summary This paper deals with only a few theoretical and numerous practical aspects of the manufacturing and use of HPLC-Column. The treatment of band spreading of different authors is mentioned briefly. The construction of HPLC-Columns with emphasis on the quality of empty columns is treated. The packing of columns according to different procedures and the reproducibility of the packing are discussed. Quality parameters of a HPLC-Column are shown. The most common reasons for the failure of a column under routine conditions are discussed and recommendations of practices for the extension of column life-time are given.

     

Tautomerism of diazepines fused with pyrimidine rings

The tautomerism of 1,4‐diazepines fused with pyrimidine rings was studied by means of nmr spec‐troscopy, X‐ray analysis and quantum chemical calculations. It was found that in the case of 6,8‐diphenyl‐pyrimido[4,5‐b][1,4]diazepin‐4‐ols (7a ‐ e) the enamine form is more stable than the diimine form. This result is rationalized with the electron‐withdrawing effect of the 4‐hydroxypyrimidine ring and with the formation of intermolecular hydrogen bonds. In contrast to 7a ‐ e , the 6,8‐diaryl‐2,3,4,7‐tetrahydro‐1,3‐dimethyl‐1H‐pyrimido[4,5‐b][1,4]diazepine‐2,4‐diones (9a, c, f) exist in the diimine form.     

Accuracy bounds for the solution of the linear optimal filtering problem in the presence of colored noise in the observations

Translated from Vychislitel'nye Metody i Sistemy Obrabotki Dannykh na ÉVM, pp. 19–32.     

Crystal structure of 1,4,8,12-tetraazacyclopentadecane copper(II) tribromocuprate(I)

The title compound is a mixed valence compound obtained as one of the products of the reaction of Cu(15-ane N₄)Br₂ with CoBr₂·6H₂O in water/acetone solvent (15-ane N₄=1,4,8,12-tetraazacyclopentadecane). The compound is tetragonal, space group P4₂/mbc witha=16.675(2)Å,c=13.185(3)Å,V=3666(1)ų, withZ=8, for p_calc=2.106 g/cc. Refinement of 674 unique observed reflection yielded final values ofR=0.088 andR _w=0.083. The compound contains chains of alternating Cu(15-ane N₄)²⁺ cations and CuBr ₃ ^2– anions. The chains run perpendicular to thec axis, and are arranged in alternate layers running parallel toa andb. The chains lie athwart the mirror planes atz=0 andz=1/2, with disorder observed for both the (15-ane N₄) rings and the CuBr ₃ ^2– anions. The Cu(II) ion is coordinated by the tetradentate macrocycle to yield an approximate square planar coordination. The CuBr ₃ ^2– anions are nearly planar with Cu–Br(ave.)=2.37Å. Long semi-coordinate Cu(II)...Br bonds of 3.0Å link the cations and anions.     

Preconcentration of trace elements by aluminium hydroxide

Summary Coprecipitation of traces of cobalt, zinc, chromium, ruthenium and mercury with freshly precipitated aluminium hydroxide has been investigated by a radiotracer method. Investigations were performed over a wide range of pH. The results indicate that traces of cobalt, zinc and chromium could be almost completely coprecipitated between pH 6 and 10. On the other hand coprecipitation yield for ruthenium in this pH range do not exceed 95%, which is believed to be the consequence of the various physicochemical states of ruthenium. The coprecipitation yields for mercury are very low as a consequence of the presence of non-ionized HgCl₂.

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Zusammenfassung Die Mitfällung von Spuren Kobalt, Zink, Chrom, Ruthenium und Quecksilber mit frisch gefälltem Aluminiumhydroxid wurde radiochemisch untersucht. Die dazu nötigen Experimente erstreckten sich über ein weites pH-Gebiet. Die Ergebnisse zeigen, daß Spuren Kobalt, Zink und Chrom zwischen pH 6 und 10 fast vollständig mitgefällt werden konnten. Andrerseits sind die Mitfällungsausbeuten für Ruthenium in diesem pH-Gebiet nicht größer als 95%, was vermutlich die Folge der verschiedenen physikalischchemischen Zustände des Rutheniums ist. Die Mitfällungsausbeuten für Queckilber sind infolge der nur geringen Dissoziation des HgCl₂ sehr gering.