Interface driven magnetoelectric effects in granular CrO2

Antiferromagnetic and magnetoelectric Cr2O3-surfaces strongly affect the electronic properties in half metallic CrO2. We show the presence of a Cr2O3 surface layer on CrO3 grains by high-resolution transmission electron microscopy. The effect of these surface layers is demonstrated by measurements of the temperature variation of the magnetoelectric susceptibility. A major observation is a sign change at about 100 K followed by a monotonic rise as a function of temperature. These electric field induced moments in CrO3 are correlated with the magnetoelectric susceptibility of pure Cr2O3. This study indicates that it is important to take into account the magnetoelectric character of thin surface layers of Cr2O3 in granular CrO2 for better understanding the transport mechanism in this system. The observation of a finite magnetoelectric susceptibility near room temperature may find utility in device applications.Comment: Figure 1 with strongly reduced resolutio

Development of a heating reactor for a continuous flow-through application in urea measurement

In most biochemical analyses, a flow-through heating arrangement is needed to reduce the reaction time or maintain a constant temperature. A rectangular reactor is described that is constructed of aluminium, is hollow inside and is filled with silicone oil. The glass coil through which the solution flows is immersed in the silicone oil. The heater, a Peltier-effect heat pump, on one side and the temperature sensor on the other side of the reactor body are embedded for heating and temperature control. The brief performance evaluation of the reactor is discussed by measuring the absorbance of urea concentration at different temperatures

Selective substitution in orbital domains of a low doped manganite : an investigation from Griffiths phenomenon and modification of glassy features

An effort is made to study the contrast in magnetic behavior resulting from minimal disorder introduced by substitution of 2.5% Ga or Al in Mn-site of La${_{0.9}}$Sr$_{0.1}$MnO${_3}$. It is considered that Ga or Al selectively creates disorder within the orbital domains or on its walls, causing enhancement of Griffiths phase (GP) singularity for the former and disappearance of it in the later case. It is shown that Ga replaces Mn$^{3+}$ which is considered to be concentrated within the domains, whereas Al replaces Mn$^{4+}$ which is segregated on the hole-rich walls, without causing any significant effect on structure or ferromagnetic transition temperatures. Thus, it is presumed that the effect of disorder created by Ga extend across the bulk of the domain having correlation over similar length-scale resulting in enhancement of GP phenomenon. On the contrary, effect of disorder created by Al remains restricted to the walls resulting in the modification of the dynamics arising from the domain walls and suppresses the GP. Moreover contrasting features are observed in the low temperature region of the compounds; a re-entrant spin glass like behavior is observed in the Ga doped sample, while the observed characteristics for the Al doped sample is ascribed only to modified domain wall dynamics with the absence of any glassy phase. Distinctive features in third order susceptibility measurements reveals that the magnetic ground state of the entire series comprises of orbital domain states. These observations bring out the role of the nature of disorder on GP phenomenon and also reconfirms the character of self-organization in low-doped manganites

Mathematical model for predicting solidification and cooling of steel inside mould and in air

A two-dimensional mathematical model has been developed to describe the solidification and cooling of steel inside the mould after teeming and in the air after stripping. Partial differential equations describing the processes have been discretized using control volume approach. The discretization equations obtained are of Tri-diagonal matrix form, which have been solved using well known Tri-diagonal matrix algorithm (TDMA) and Alternate direction implicit (ADI) solver. The model has been validated by measuring surface temperatures of mould and ingot using Infrared thermo-vision scanner. This is then used to compute charging temperature and solidification status of ingot as function of track time and type of ingot

Evidence for the possible involvement of the superoxide radicals in the photodegradation of bilirubin

The photodecomposition of bilirubin follows first order kinetics with ak B value of 12.5 × 10-3 min-1. In the presence of a model system generating superoxide anions, such as xanthine-xanthine oxidase, the k B value was 103 × 10-3 min-1 This ten-fold enhancement ofk B value by xanthine-xanthine oxidase was abolished when the reaction mixture was supplemented with a superoxide ion scavenger- superoxide dismustase. Further, known singlet oxygen quenchers like β -carotene and bistidine did not prevent the enhancement of bilirubin oxidation by xanthine-xanthine oxidase, thereby ruling out the obligatory conversion of Superoxide anion to singlet oxygen. It is concluded that radical oxygen mediated bilirubin degradation might be a natural catabolic route for the bile pigment degradation during oxygen stress

alpha-Amylase Production in Fed BatchCultivation of Bacillus caldolyticus: An Interpretation of FermentationCourseUsing 2-D Gel Electrophoresis

The conditions for increased production of thermostable a-amylase from Bacillus caldolyticus DSM 405 were investigated. Preliminary experiments in batch shake flasks led to an optimized initial cultivation medium. Shake flask experiments in extended-batch and in fed-batch mode of operation indicated that the a-amylase production was enhanced by continuous feeding of starch. The activity of the a-amylase with optimized initial medium in batch-operated shake flasks was 5.7 U mL–1 compared to 15.4U mL–1 in the extended-batch culture and 21 U mL–1 in fed-batch culture. The improvements were achieved by avoiding any excess of starch in medium that led to accumulation of glucose followed by acetate formation. Adding casitone as the second component of the feeding solution in an aerated and agitated fed-batch bioreactor (3-liter working volume) led to an increased -amylase activity of up to 163.7 U mL.–1 All phases of cultivation were analyzed using 2D-gel electrophoresis in combination with nano LC-ESI-MS/MS for identification of altered proteins. Pyruvate kinase, 6-phosphofructokinase, GltC, anti-sigma F factor, glycogen synthase and several important variable proteins were detected. With help of these results, potential improvements of a two-component feeding strategy are discussed

Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superparamagnetic behaviour of the single domain magnetic clusters inside the nonmagnetic host, their blocking by the anisotropy barriers and thermal fluctuation over the barriers accompanied by relaxation of magnetization. From magnetic viscosity analysis based on thermal relaxation over the anisotropy barriers it is found out that magnetic clusters occupy the characteristic volume from 25 up to 200 nm3 . The validity of the superparamagnetic model of Hf_{57}Fe_{43} is based on the concentration of iron in the Hf_{100-x}Fe_{43} system that is just below the threshold for the long range magnetic ordering. This work throws more light on magnetic behaviour of other amorphous alloys, too