3D track reconstruction capability of a silicon hybrid active pixel detector

Timepix3 detectors are the latest generation of hybrid active pixel detectors of the Medipix/Timepix family. Such detectors consist of an active sensor layer which is connected to the readout ASIC (application specific integrated circuit), segmenting the detector into a square matrix of 256 \(\times \) 256 pixels (pixel pitch 55 \(\upmu \)m). Particles interacting in the active sensor material create charge carriers, which drift towards the pixelated electrode, where they are collected. In each pixel, the time of the interaction (time resolution 1.56 ns) and the amount of created charge carriers are measured. Such a device was employed in an experiment in a 120 GeV/c pion beam. It is demonstrated, how the drift time information can be used for “4D” particle tracking, with the three spatial dimensions and the energy losses along the particle trajectory (dE/dx). Since the coordinates in the detector plane are given by the pixelation (x,y), the x- and y-resolution is determined by the pixel pitch (55 \(\upmu \)m). A z-resolution of 50.4 \(\upmu \)m could be achieved (for a 500 \(\upmu \)m thick silicon sensor at 130 V bias), whereby the drift time model independent z-resolution was found to be 28.5 \(\upmu \)m.     

Nickel-induced magnetic behaviour of nano-structured α-Fe2O3, synthesised by facile wet chemical route

We report the synthesis of pristine and nickel containing iron oxide (α-Fe₂O₃) nanocrystallites by facile environmentally benign wet chemical process. The magnetic behaviour of the samples has been found to change progressively with nickel content. The Mössbauer spectra revealed the precipitation of secondary phase of nickel ferrite (NiFe₂O₄) at ～2?wt% nickel contents. The transmission electron micrographs together with asymmetric magnetic hysteresis loop have confirmed the formation of core–shell structure. The Morin temperature of nanostructured α-Fe₂O₃ as estimated by superconducting quantum interference device has been found to be 257, 245, 247 and 242?K at nickel content of 0, 1, 2 and 4?wt%, respectively. The similar trends of increase/decrease in Morin temperature have been noticed by Mössbauer analysis. Furthermore, below Morin temperature, the temperature range of coexisted antiferromagnetic and ferromagnetic states has been found to increase with increase in nickel content.     

Multiaxial ratcheting with advanced kinematic and directional distortional hardening rules

Ratcheting is defined as the accumulation of plastic strains during cyclic plastic loading. Modeling this behavior is extremely difficult because any small error in plastic strain during a single cycle will add to become a large error after many cycles. As is typical with metals, most constitutive models use the associative flow rule which states that the plastic strain increment is in the direction normal to the yield surface. When the associative flow rule is used, it is important to have the shape of the yield surface modeled accurately because small deviations in shape may result in large deviations in the normal to the yield surface and thus the plastic strain increment in multi-axial loading. During cyclic plastic loading these deviations will accumulate and may result in large errors to predicted strains.This paper compares the bi-axial ratcheting simulations of two classes of plasticity models. The first class of models consists of the classical von Mises model with various kinematic hardening (KH) rules. The second class of models introduce directional distortional hardening (DDH) in addition to these various kinematic hardening rules. Directional distortion describes the formation of a region of high curvature on the yield surface approximately in the direction of loading and a region of flattened curvature approximately in the opposite direction. Results indicate that the addition of directional distortional hardening improves ratcheting predictions, particularly under biaxial stress controlled loading, over kinematic hardening alone.     

Preliminary pharmaceutico-analytical evaluation of transkarbam 12 using liquid chromatography

This paper deals with the search for optimal conditions for the identification of Transkarbam 12 (T 12) as a substance used for acceleration of transdermal penetration. Such substances are used in cases when drugs do not pass through the skin barrier under normal conditions. Other advantages are that they do not irritate the digestive system, provide continuous administration to an organism, and reduce fluctuations of drug concentration in blood. TLC and HPLC were used for identification. In the case of TLC, Silufol UV254 was used as stationary phase and the mobile phase consisted of chloroform, ethanol, and acetic acid. Detection was performed with iodine vapour. In the case of HPLC, the following three chromatographic columns were tested for the analysis of T 12: Silasorb SPH C 18, Silasorb SPH nitrile, and LiChrosorb Si-60. Because of the absence of any chromophore in the structure of T 12, work was performed on the derivatized compound. Detection was carried out at 230 nm. Quantification was studied on LiChrosorb Si-60 and the linearity, precision, and accuracy were evaluated.     

Highly Hydrogenated Graphene through Microwave Exfoliation of Graphite Oxide in Hydrogen Plasma: Towards Electrochemical Applications

Hydrogenated graphenes exhibit a variety of properties with potential applications in devices, ranging from a tunable band gap to fluorescence, ferromagnetism, and the storage of hydrogen. We utilize a one‐step microwave‐irradiation process in hydrogen plasma to create highly hydrogenated graphene from graphite oxides. The procedure serves the dual purposes of deoxygenation and concurrent hydrogenation of the carbon backbone. The effectiveness of the hydrogenation process is investigated on three different graphite oxides (GOs), which are synthesized by using the Staudenmaier, Hofmann, and Hummers methods. A systematic characterization of our hydrogenated graphenes is performed using UV/Vis spectroscopy, SEM, AFM, Raman spectroscopy, FTIR spectroscopy, X‐ray photoelectron spectroscopy (XPS), combustible elemental analysis, and electrical conductivity measurements. The highest hydrogenation extent is observed in hydrogenated graphene produced from the Hummers‐method GO, with a hydrogen content of 19 atomic % in the final product. In terms of the removal of oxygen groups, microwave exfoliation yields graphenes with very similar oxygen contents despite differences in their parent GOs. In addition, we examine the prospective application of hydrogenated graphenes as electrochemical transducers through a cyclic voltammetry (CV) study. The highly hydrogenated graphenes exhibit fast heterogeneous electron‐transfer rates, suggestive of their suitability for electrochemical applications in electrodes, supercapacitors, batteries, and sensors.     

The Deoxygenation and Isomerization of Artemisinin and Artemether and Their Relevance to Antimalarial Action

The treatment of artemisinin ( 1 ) and β-artemether ( 6 ) with Zn dissolving in AcOH for a few hours results in mono-deoxygenation giving deoxyartemisinin ( 5 ) and deoxy-β-artemether ( 7 ), respectively, as the sole product. In contrast, submission of 1 to FeCl₂ · 4 H₂O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)-octahydro-4,7-dimethyl-8-oxo-2H-10H-furo[3,2-i] benzopyran-10-yl acetate ( 8 ) and (3R)-3-hydroxydeoxyartemisinin ( 9 ) being produced in 78 and 17% yield, respectively. The action of FeCl₂ · 4 H₂O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2-[4-methyl-2-oxo-3-(3-oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe²⁺ is attributed to the redox properties of the Fe²⁺/Fe³⁺ system.     

Dynamic capillary diffusion system for monoterpene and sesquiterpene calibration: quantitative measurement and determination of physical properties

This article describes a method for preparation of low concentration gas standard mixtures of biogenic volatile organic compounds (BVOCs) emitted primarily by plants. A set of 10 plant volatiles including α-pinene, β-pinene, 3-carene, linalool, methyl salicylate, α-cedrene, β-caryophyllene, β-farnesene, aromadendrene and α-humulene was used in the study. Gas standard mixture of these compounds was generated using a capillary diffusion system (CDS). Diffusion coefficient (D) and saturation vapour pressure (p _s) data of these compounds were calculated from experimentally determined gas chromatographic retention indices (RI) and empirical relationships between D and p _s versus RI. A comparison of the calculated and measured concentrations of investigated compounds has proved that designed CDS can be successfully used for the proper quantification of BVOCs.