Grain oriented NiMnSn and NiMnIn Heusler alloys ribbons produced by melt spinning: Martensitic transformation and magnetic properties

We outline the microstructural, martensitic transformation and magnetic properties of Heusler alloys with starting compositions Ni₅₀Mn₃₇Sn₁₃, Ni₅₀Mn₃₆In₁₄, and Mn₅₀Ni₄₀In₁₀, produced by melt spinning. The ribbons were obtained in argon environment at a high wheel linear speed of 48 m s⁻¹ (typical dimensions: 1.2-2.0 mm in width, 4-12 mm in length, and 7-12 μm in thickness). EDS microanalysis showed that the resulting average elemental chemical composition is slightly shifted with respect to the starting one. Ribbons are fully crystalline and tend to show a highly ordered columnar-like microstructure with grains running through the entire ribbon thickness; the larger dimension of the grains is perpendicular to the ribbon plane. As-spun alloys were single-phase with ferromagnetic bcc L2₁ austenite as high-temperature parent phase. At low temperatures austenite transforms into a structurally modulated martensite with a lattice symmetry that depends on the system (7 M orthorhombic for Ni₅₀Mn₃₇Sn₁₃, 10 M monoclinic for Ni₅₀Mn₃₆In₁₄, and 14 M monoclinic for Mn₅₀Ni₄₀In₁₀). Magnetization isotherms measured in the temperature interval where martensite thermally transforms into austenite confirmed the occurrence of field-induced reverse martensitic transition in the alloys studied.     

Generalized gain-spread expressions for the free electron laser

Starting from a many electron hamiltonian model we derive general expressions for the unsaturated gain and spread of a free electron laser that are valid for arbitrary magnetic field configurations. The general validity of a well known gain-spread relation is demonstrated.     

Instabilities and quantum initiation in the free-electron laser

We describe the quantum initiation of the free-electron laser, starting from the N-electron position and momentum quantum fluctuations, both in the small-gain and in the high-gain regime. The Glauber distribution P(α) for the field is derived, obtaining the displaced gaussian which represents the superposition of a coherent field (stimulated emission) and an incoherent one (spontaneous emission). In the experimental gain regime the build-up time of radiation is estimated, showing its proportionality to ln √N.     

Citrate-reduced silver hydrosol modified with omega-mercaptoalkanoic acids self-assembled monolayers as a substrate for surface-enhanced resonance Raman scattering. A study with cytochrome c

A new citrate-reduced silver hydrosol coated with omega-mercaptoalkanoic acids (mercaptopropionic and mercaptoundecanoic acids) self-assembled monolayers was prepared and characterized with surface-enhanced Raman spectroscopy. The structure and the quality of the coating monolayers are discussed and compared to similar coated and uncoated silver hydrosols previously developed. As an application, the new hydrosol was used as a biocompatible and efficient metal substrate for a surface-enhanced resonance Raman scattering (SERRS) study of cytochrome c. The high-quality SERRS spectra reported of cytochrome c (obtained using only 1 microL of a micromolar cytochrome solution) are discussed and compared with data available from literature studies.     

Isotonic boosting classification rules

Advances in Data Analysis and Classification - In many real classification problems a monotone relation between some predictors and the classes may be assumed when higher (or lower) values of those...     

A Far Infrared Super Radiant FEL

The basic physics, results of 3–D simulations, and relevant parameters for the design of a far infrared FEL, which operates in the SASE superradiant short bunch regime, are presented. It is shown that a quite interesting device can be easily developed, with rather new features, producing coherent laser pulses with ∼10 psec duration and around 7 MW peak power.     

pH-Induced changes in adsorbed cytochrome c. voltammetric and surface-enhanced resonance Raman characterization performed simultaneously at chemically modified silver electrodes

The influence of pH on the redox properties of cytochrome c (cyt c) adsorbed on roughened silver electrodes chemically modified with a self-assembled monolayer (SAM) of 11-mercapto-1-undecanoic acid (MUA) was studied with voltammetric techniques in combination with surface-enhanced resonance Raman scattering (SERRS). The experiments were performed simultaneously on the same electrode sample in a homemade spectroelectrochemical cell suitable for such applications. At pH 7.0 cyt c was found in its native state; at higher pH values (ranging from 8.0 to 9.0) the redox properties of the adsorbed protein varied considerably, featuring a redox behavior which does not resemble the one reported for the alkaline transition. Our results instead indicate the presence of an electrochemically inactive 6cLS species immobilized on MUA at pH 9.0. The pH-induced conformational changes observed for cyt c immobilized on the SAM of MUA were found to be repeatable and chemically reversible, meaning that the recovery of the electrochemical signal due to the native protein occurred instantaneously (on the second time scale) when the electrode was switched back to pH 7.0. The pH-induced changes observed were attributed to a conformational change involving a heme reorientation with respect to the electrode surface.     

Spatial distribution of heme species in erythrocytes infected with Plasmodium falciparum by use of resonance Raman imaging and multivariate analysis

The multivariate algorithm hierarchical cluster analysis is applied to sets of resonance Raman spectra collected from human erythrocytes infected with the malaria parasite Plasmodium falciparum. The images obtained yield information about the distribution of hemoglobin and hemozoin (or malaria pigment) within the parasitized cells and about their molecular structure. This method has the advantage of conveying more information than other imaging approaches based on resonance Raman spectroscopy, and it is a promising tool to study the hemozoin formation process and its interaction with antimalarial drugs within unstained, well-preserved parasites.