Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2−x Ce x Cu3O10+δ system

We have investigated the superconducting properties of the Bi_1.7 Pb_0.3Sr₂Ca_2−xCe _x Cu₃O_10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T _c (2 : 2 : 2 : 3) phase decreases and low T _c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca²⁺ → Ce⁴⁺ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T _c of the system.     

Encapsulation dehydration colligative cryoprotective strategies and amplified fragment length polymorphism markers to verify the identity and genetic stability of euglenoids following cryopreservation

An encapsulation/dehydration procedure was developed for Euglena gracilis Klebs as a 'model alga' to examine various cryoprotective regimes combined with controlled rate cooling to cryopreserve other Euglenoid taxa. Cryoprotective variables were optimised to enable reproducible growth following a combination of alginate encapsulation, sucrose osmotic dehydration, air desiccation, methanol treatment, cooling to -40 degrees C and plunging into liquid nitrogen (LN). Amplified Fragment Length Polymorphism (AFLP) analysis was adapted to: (i) verify algal identity by discriminating between different Euglenoids and (ii) examine the genetic stability of algal cultures prior to various stages of cryoprotective treatments and following exposure to LN. AFLPs were highly reproducible (> 99%) as reliable diagnostic markers, where a single DNA fragment change accounted for -0.4% of the detectable variation in an AFLP pattern. AFLP changes were detected in cryoprotective treatments following LN exposure. Successive stages of the dehydration and desiccation treatments did not accumulate AFLP changes indicating these are random events.     

Charged-particle multiplicity near midrapidity in central Au+Au collisions at sqrt[SNN]=56 and 130 GeV

We present the first measurement of pseudorapidity densities of primary charged particles near midrapidity in Au+Au collisions at sqrt[s(NN)] = 56 and 130 GeV. For the most central collisions, we find the charged-particle pseudorapidity density to be dN/deta|(|eta|<1) = 408+/-12(stat)+/-30(syst) at 56 GeV and 555+/-12(stat)+/-35(syst) at 130 GeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.     

Chromosomal localization of the HYP2-gene in Saccharomyces cerevisiae and use of pulsed-field gel electrophoresis for detection of irregular recombination events in gene disruption experiments.

In the hypusine-containing protein (HP), a specific lysine residue is modified by spermidine to form the unusual amino acid hypusine (4-amino-2-hydroxybutyllysine). The HP has been designated as an eucaryotic translation initiation factor--eIF-5A--because of its stimulating effect in the methionyl-puromycin in vitro assay. Nevertheless, the precise function of this protein remains to be elucidated. In the yeast Saccharomyces cerevisiae two genes, HYP1 and HYP2, coding for two different forms of the HP, are present. The HYP1-gene is identical to the ANB1-gene and has already been localized on chromosome X. However, the chromosomal localization of the HYP2-gene has not been elucidated. By using pulsed-field gel electrophoresis (PFGE) and subsequent Southern blotting, we determined the localization of the HYP2-gene to chromosome V. Furthermore, PFGE was used for the detection of irregular recombination events, such as misintegration or integration into a duplicated gene, and in gene disruption experiments using haploid and diploid yeast cells. The obtained data support the critical role of the HP for cell viability.     

Control of column influence on the wide range pH gradient in ion-exchange chromatography

Summary A method for optimization of the mobile phase composition in ion exchange chromatography with a wide range external pH gradient (approx. over 5 pH units) has been formulated. It is shown that programming of various wide range pH profiles which are not impaired by buffer interactions of the mobile phase with sorbent is possible. Utilization of the wide range external pH gradient in cation-exchange chromatography of bovine haemoglobin is also demonstrated.     

Über die Temperatur-und Konzentrationsabhängigkeit der Bildung und Struktur von Molekülschichten der Arachinund der Stearinsäure

Zusammenfassung An der Phasengrenze Dekalin/Phosphatpufferlösung kommt es bei Verwendung von Archin- oder Stearinsäure als grenzflächenaktive Substanzen nur dann zu einer sofortigen Einstellung der Gleichgewichtswerte der Grenzflächenspannung, wenn kondensierte Molekülschichten gebildet werden. Die für die Bildung expandierter Schichten erforderliche Zeit von mehreren Stunden ergibt sich als Folge der nur sehr langsamen Einstellung des Gleichgewichtes zwischen den Assoziaten in der Lösung und den Einzelmolekülen in der Grenzschicht. Auch das Schmelzen kondensierter Schichten ist im Gegensatz zur Kondensation ein langsam verlaufender Vorgang; letztere ist mit einer Abnahme des Spreitungsdruckes, bzw. mit einer Zunahme der Grenzflächenspannung verbunden, aus der sich die Kohäsion der Moleküle im zweidimensionalen Kristallgitter ermitteln läßt. Die Lage des Schmelzpunktes der Molekülschicht ist vom SpreitungsdruckP _S () abhängig. Die experimentell ermittelte Konzentrationsabhängigkeit der Grenzflächenspannung entspricht nicht der GleichungSzyszkowskis, da die Assoziation der Fettsäuren in Dekalin konzentrationsabhängig ist und die Assoziate weniger grenzflächenaktiv sind als die Einzelmoleküle.Unter bestimmten Bedingungen kann eine Erhöhung der Temperatur eine beträchtliche Erhöhung der Grenzflächenspannung zur Folge haben; dieser Effekt ist reversibel und beruht auf der Erhöhung der Löslichkeit der Fettsäure in Dekalin bei Temperaturzunahme. Aus dem Verlauf der Grenzflächenspannung/Temperaturkurve läßt sich die Lage des Schmelzpunktes kondensierter Molekülschichten entnehmen und auf diesem Wege mit einer Fehlerbreite von zirka 1°C bestimmen.Es wird auf die Bedeutung der beschriebenen Reaktionsmöglichkeiten mehrphasiger Systeme für das Verständnis biologischer Reaktionen hingewiesen.Mit 11 Abbildungen.     

Fluorescein-based pI markers for capillary isoelectric focusing with laser-induced fluorescence detection

We prepared a series of low-molecular-mass fluorescent ampholytes with narrow pI range. These fluorescein-based ampholytes are detection compatible with argon laser-induced fluorescence (LIF) detection. The selected properties, important for their routine use as fluorescent pI markers, were examined. The pI values of new fluorescein-based pI markers were determined by capillary isoelectric focusing (CIEF) using currently available low-molecular-mass pI markers for CIEF with photometric detection. The examples of CIEF with fluorometric detection of new compounds together with fluorescein isothiocyanate (FITC) derivatized proteins are presented.