Magnetocaloric effect of monovalent K doped manganites Pr0.6Sr0.4−xKxMnO3 (x=0 to 0.2)

peer reviewedMagnetic and magnetocaloric properties are reported for polycrystalline monovalent potassium doped manganites Pr0.6Sr0.4−xKxMnO3 (x=0, 0.05, 0.1, 0.15 and 0.2) crystallized in orthorhombic structure with Pnma space group. The increasing K content shifts the paramagnetic to ferromagnetic transition temperature from 310 K for x=0 to 269 K for x=0.2. The magnetic entropy change under magnetic field variation of 2 T is found to be 1.95, 3.09, 2.89, 3.05 and 3.2 J/kgK for x varying from 0 to 0.2, respectively. The highest relative cooling power of 102 J/kg is observed for the undoped sample. The sensitivity of magnetic entropy change to magnetic field is estimated by a local N(T) exponent exhibiting the characteristic temperature variation. Phenomenological universal curves of entropy change and Arrott plots confirm the second order phase transition

Isotropic magnetization response of electrodeposited nanocrystalline Ni–W alloy nanowire arrays

Isotropic magnetization response was demonstrated in electrodeposited nanocrystalline Ni–15 % W alloy nanowire arrays, which can be applied to nanoscale magnetic field sensors. The Ni–W alloy nanowire arrays were electrochemically synthesized on a nanochannel template electrode from an aqueous electrolytic solution. X-ray and electron diffraction patterns revealed that Ni–15 % W alloy deposits were composed of ultrafine crystal grains with a supersaturated solid solution phase. The magnetization of the Ni–15 % W alloy thin films reached saturation at around 2.5 kOe in a perpendicular direction to the film plane, whereas the pure Ni thin films hardly magnetized in the perpendicular direction. On the contrary, Ni–15 % W alloy nanowire arrays were easily magnetized, and reach saturation at around 1.0 kOe, even in a perpendicular direction to the array film plane that corresponds to the long-axis direction of the alloy nanowires

Tannic Acid Modified Silver Nanoparticles Show Antiviral Activity in Herpes Simplex Virus Type 2 Infection

The interaction between silver nanoparticles and herpesviruses is attracting great interest due to their antiviral activity and possibility to use as microbicides for oral and anogenital herpes. In this work, we demonstrate that tannic acid modified silver nanoparticles sized 13 nm, 33 nm and 46 nm are capable of reducing HSV-2 infectivity both in vitro and in vivo. The antiviral activity of tannic acid modified silver nanoparticles was size-related, required direct interaction and blocked virus attachment, penetration and further spread. All tested tannic acid modified silver nanoparticles reduced both infection and inflammatory reaction in the mouse model of HSV-2 infection when used at infection or for a post-infection treatment. Smaller-sized nanoparticles induced production of cytokines and chemokines important for anti-viral response. The corresponding control buffers with tannic acid showed inferior antiviral effects in vitro and were ineffective in blocking in vivo infection. Our results show that tannic acid modified silver nanoparticles are good candidates for microbicides used in treatment of herpesvirus infections.This work was supported by the Polish National Science Centre grant No. 2011/03/B/NZ6/04878 (for MK) and Centre for Preclinical Research and Technology (CePT) Project No. POIG.02.02.00-14-024/08-0 (for MG and MD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

A consistent picture of the proton release mechanism of oNBA in water by ultrafast spectroscopy and ab initio molecular dynamics

With a combination of transient pump-probe IR spectroscopy and ab initio molecular dynamics, the controversial pico- and nanosecond steps of the o-nitrobenzaldehyde (oNBA) photoreaction have been investigated in aqueous solution. In this way, the measured reaction kinetics have been complemented with an atomistic picture of the reactive events as obtained with unbiased simulations in explicit solvent. Our results allow for a detailed description of the oNBA proton photorelease, a process of fundamental importance and relevant to the use of oNBA as a proton cage in many experiments. In a first step, a stable ketene intermediate is formed on a subpicosecond time scale. This intermediate reacts in a solvent assisted way with an OH transfer to produce nitrosobenzoic acid with a characteristic time of 7 ps. Finally, in permitting pH conditions, this product molecule dissociates a carboxyl proton with a 21 ns time constant. The particular combination of theory and experiment employed in this work appears to be sufficiently general and powerful to find widespread application in the study of ultrafast reactive systems

pH jump induced α-helix folding.

pH can be used to impact the folding equilibrium of peptides and proteins. This fact is utilized, similarly to temperature jumps, in pH jump experiments employing laser time-resolved spectroscopy to study the function and structural dynamics of these molecules. Here the application of pH jumps in folding experiments was investigated. Experiments with poly-L-glutamic acid alpha-helix formation shown the critical aspects of pH jump experiments and yielded direct information about the folding kinetics monitored with the amide I IR band