Determining Curie temperature of (Ga,Mn)As samples based on electrical transport measurements: low Curie temperature case

In this paper we show that the widely accepted method of the determination of Curie temperature (TC) in (Ga,Mn)As samples, based on the position of the peak in the temperature derivative of the resistivity,completely fails in the case of non-metallic and low-TC unannealed samples. In this case we propose an alternative method, also based on electric transport measurements, which exploits temperature dependence of the second derivative of the resistivity upon magnetic field.Comment: 5 pages, 3 figure

Treatment of multiple myeloma patients with autologous stem cell transplantation — a fresh analysis

Patients with multiple myeloma (MM) treated with conventional chemotherapy have an average survival of approximately three years. High dose chemotherapy followed by autologous stem cell transplantation (ASCT), first introduced in the mid-1980s, is now considered the standard therapy for almost all patients with multiple myeloma, because it prolongs overall survival and disease free survival. Between November 1997 and October 2006, 122 patients with MM (58 females, 64 males, median age 51.0 years [± 7.98] range: 30–66 years) were transplanted in the Department of Hematooncology and Bone Marrow Transplantation at the Medical University of Lublin: 47 patients were in complete remission or in unconfirmed complete remission, 66 patients were in partial remission, and nine had stable disease. Of these, there were 95 patients with IgG myeloma, 16 with IgA myeloma, one with IgG/IgA, one with IgM myeloma, five with non secretory type, two with solitary tumor and two with LCD myeloma. According to Durie-Salmon, 62 patients had stage III of the disease, 46 had stage II and four had stage I. Most patients (69/122) were transplanted after two or more cycles of chemotherapy, 48 patients were transplanted after one cycle of chemotherapy, one patient after surgery and rtg- -therapy and four patients had not been treated. In mobilisation procedure, the patients received a single infusion of cyclophosphamide (4–6 g/m2) or etoposide 1.6 g/m2 followed by daily administration of G-CSF until the peripheral stem cells harvest. The number of median harvest sessions was 2.0 (± 0.89) (range: 1–5). An average of 7.09 (± 33.28) × 106 CD34+ cells/kg were collected from each patient (range: 1.8–111.0 × 106/kg). Conditioning regimen consisted of high dose melphalan 60–210 mg/m2 without TBI. An average of 3.04 (± 11.59) × 106 CD34+ cells/kg were transplanted to each patient. Fatal complications occured in four patients (treatment- -related mortality = 3.2%). In all patients there was regeneration of hematopoiesis. The median number of days for recovery to ANC > 0.5 × 109/l was 13 (± 4.69) (range: 10–38) and platelets recovery to > 50 × 109/l was 25 days (± 11.65) (range: 12–45). Median time of hospitalization was 22 days (± 7.14) (range: 14–50). Patients were evaluated on day 100 after transplantation: 74.9% achieved CR and nCR, 14.3% were in PR, 5.4% had SD and 5.4% had progressed. Median of OS was 45 months (± 30.67). OS at 3-years was 84% and at 7-years 59%. Median PFS was 25 months (± 26.13). PFS at 3-years was 68%, and at 7-years was 43%. At present (November 2009) 52 patients (42%) are still alive. High-dose chemotherapy followed by autologous stem cell transplantation is a valuable, well tolerated method of treatment for patients with MM that allows the achievement of long- -lasting survival. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 2, pp. 248–254

Nowe media w bibliotece : materiały z polsko-niemieckiej konferencji bibliotekarzy, Zielona Góra 14-16 kwietnia 2004 = Neue Medien in der Bibliothek : Materialien aus der deutsch-polnischen Konferenz der Bibliothekaren und Bibliothekarinnen, Zielona Góra den 14-16. April 2004

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Study of influence of domain structure on observed magnetoresistance anomalies in GaMnAs

Magneto-transport properties of a Ga0.93Mn0.07As ferromagnetic semiconductor film with strong epitaxial strain (Ga0.7In0.3As buffer) have been studied. The observed magnetoresistance showed peculiar peaks at the magnetic fields corresponding to magnetization switching probed by Hall voltage. Computer simulations showed that these anomalies could originate from the formation of complex, island-like magnetic domains, and their propagation in the sample

Optimizing the Energy Consumed by the Extremities of a Walking Robot

[EN] It presents a method of multi-objective optimization, applied to energy consumption of open kinematic chains, analyzing the case of the movement of an extremity of a walking electro- hydraulic robot. To demonstrate the effectiveness of the proposed method, it is applied in two cases of displacement. The first case shows the movement of the extremity without obstacles in its workspace and the second includes the evasion of an obstacle. The minimization of angular displacement of the links with higher energy consumption and the minimization of the maximum absolute value of the angular acceleration of the links are used as optimization criteria. In both cases a trajectory that reduces energy consumption by more than 25% over the other methods proposed in the literature, at the same time the dynamic behavior of the system by avoiding variations in the speed and the acceleration is improved during the phase of transference, besides increasing the precision and accuracy of the foot position.[ES] Se presenta un método de optimización multi-objetivo, aplicado al funcionamiento de las cadenas cinemáticas abiertas, analizando el caso del movimiento de una extremidad de un robot caminante electro-hidráulico. Para demostrar la efectividad del método propuesto, se aplica en dos casos de estudio. El primer caso muestra el movimiento de la extremidad sin obstáculos en su espacio de trabajo, y en el segundo se incluye la evasión de un obstáculo. Se usan como criterios de optimización, la minimización del desplazamiento angular de los eslabones con mayor consumo de energía y la minimización del valor absoluto máximo de la aceleración angular de los eslabones. En ambos casos se determinó una trayectoria que disminuye el consumo de energía en más de un 25% respecto de otros métodos planteados en la literatura, a la vez que se mejora el comportamiento dinámico del sistema evitando variaciones en la velocidad y la aceleración durante la fase de trasferencia, además de aumentar la precisión y exactitud de la posición del pie.Agradezco por su ayuda económica al Concejo Nacional de Ciencia y Tecnología (CONACYT), así como al personal del Centro Nacional de Investigación y Desarrollo Tecnológico (CENIDET) por el apoyo brindado para la realización de este trabajo.Calderón López, HE.; Bedolla Hernández, J.; Szwedowicz Wasik, D. (2015). Optimización de la Energía Consumida por las Extremidades de un Robot Caminante. Revista Iberoamericana de Automática e Informática industrial. 12(3):338-349. https://doi.org/10.1016/j.riai.2015.02.008OJS338349123Ayten, K., Sahinkaya, M., Iravani, P., 2011, Optimum Trajectory Planning for Redundant and Hyper Redundant Manipulators Through Inverse Dynamics, International Desing Engineering Technical Conferences & Computers and Information in Engineering Conference.Calderón, H., 2008, Diseño de un Robot Caminante Electro-hidráulico, Tesis de Maestría, Universidad Michoacana de San Nicolás de Hidalgo, Michoacán, México.Calderón, H., Szwedowicz, D., Bedolla, J., 2012, Principales Variables del Comportamiento Dinámico en Cadenas Cinemáticas Abiertas, XVIII Congreso Internacional Anual de la SOMIM, pp. 409-417.García, M. Gorrostieta, E., Vargas, J., Ramos, J., Sotomayor, A., Moya, J., 2012, Kinematic Analysis for Trajectory Generation in One Leg of a Hexapod Robot, The 2012 Iberoamerican Conference on Electronics Engineering and Computer Science, pp. 342-350.Gew, K., Hyeon, J., 2009, Trajectory Optimization with GA and Control for Quadruped Robots, Journal of Mechanical Science and Technology, Vol. 23, pp. 114-123.Gonzalez de Santos, P., García, E., Ponticelli, R., Armada, M., 2009, Minimizing Energy Consumption in Hexapod Robots, Advanced Robotics, Vol. 23, pp. 681-704.Gorrostieta, E., Vargas, J., 2004, Free Locomotion for Six Legged Robot, WSEAS Transactions on Computers, Vol. 3, No. 4, pp. 795-800.Gorrostieta, E., Vargas, J., 2008, Algoritmo Difuso de Locomoción Libre para un Robot Caminante de Seis Patas, Computación y Sistemas, Vol. 11, No. 3, pp. 260-287.Gregory, J., Olivares, A., Staffetti, E., 2012, Energy-optimal Trajectory Planning for Robot Manipulators with Holonomic Constraints, Elsevier Systems & Control Letter, pp. 279-291.Melanie, M., 1996, An Introduction to Genetic Algorithms, MIT Press.Pérez, W., Barrera, E., Juárez, I., Ramos, A., 2010, Mechanical Energy Optimization in Trajectory Planning for Six DOF Robot Manipulators Base don Eigth-Degree Polynomial Functions and a Genetic Algorithm, 7th International Conference on Electrical Engineering, Computing Science and Automatic Control, pp. 446-451.Rodrigues, R., Steffen, V., Pereira, S., 2010, Optimal Task Placement of a Serial Robot Manipulator for Manipulability and Mechanical Power Optimization, Intelligent Information Management, Vol. 2, pp. 512-525.Saravanan, R., Ramabalan, S., Balamurugan, C., Subash, A., 2010, Evolutionary Trajectory Planning for an Industrial Robot, International Journal of Automation and Computing, Vol. 7, No. 2, pp. 190-198.Sengupta, A., Chakraborti, T., Konar, A., Nagar, A., 2011, Energy Efficient Trajectory Planning by a Robot Arm Usisng Invasive Weed Optimization.Technique, Third World Congress on Nature and Biologically Inspired Computing, pp. 311-316.Shankar, G., Kaur, A., 2011, Optimization of Energy in Robotic Arm Using Genetic Algorithm, International Journal of Computer Science and Technology, pp. 315-317.Silva, M., Machado, J.A., 2011, A literature review on the optimization of legged robots, Journal of Vibration and Control.Solteiro, E., Tenreiro, J., Moura, P., 2007, Manipulator Trajectory Planning Using a MOEA, Applied Soft Computing, Vol. 7, pp. 659-667.Tian, L., Collins, C., 2004, An effective Robot Trajectory Planning Method Using a Genetic Algorithm, Elsevier Mechatronics, Vol. 14, pp. 455-470. Vargas, J.,;1; 1999, Free Locomotion Gaits for a Four Legged Machine, International Congress on Industrial Automation and Material Science Mexico-Hungary, Querétaro, México.Zapata, F., 2013, Análisis del Funcionamiento de las Extremidades en un Robot Hexapodo, Tesis de Licenciatura, Universidad de San Buenaventura, Colombia

Failure by deformation in the lateral contact between sinusoidal asperities

This article presents a study about the lateral force which produces the failure by deformation between asperities with the sine profile. This study begins with obtaining this force with experimental tests and numerical simulations by the finite element method, which shows good correspondence. The formulation of an analytical procedure to calculate the lateral force is also presented. This formulation is based on the theory of Hertz, which considers lateral contact between asperities, which causes deformation and eventually the failure. The results obtained by this method are compared to the results from tests and simulations using materials with different values of elasto-plasticity. The analysis of results shows the differences between analytical formulation and experimental data, according to which an empirical equation is formulated, whose results improve the approximation to the experimental data. The simplicity of the empirical equation formulated and adequate representation by the results of this, in tests and simulations, make it a numerical model useful for studies of surface wear

Structural and magnetic properties of MnAs/GaAs ferromagnetic semiconductor nanocomposite material

Self-organized (Ga,Mn)As nanoclusters, embedded in GaAs and formed during thermal annealing of Ga1-xMnxAs layer at 500 degrees C or 600 degrees C, were studied using Transmission Electron Microscopy (TEM) and Magnetic Force Microscopy (MFM). We found that 10-20 nm large NiAs-type hexagonal MnAs nanocrystals gave magnetic contrast in MFM images, whereas smaller zinc-blende nanoinclusions were not visible by means of this technique. Theoretical simulations showed that MFM contrasts reflect interaction between magnetic tip and many randomly distributed MnAs nanocrystals

Galvanomagnetic methods of Curie temperature determination in (Ga,Mn)As

We critically discuss various experimental methods to determine Curie temperature TC of (Ga,Mn)As thin layers or other conducting magnetic materials by means of electric charge transport measurements. They all base on the influence of sample magnetization on the magnetoresistivity tensor ρ̂ and are an alternative to the method based upon an analysis of the temperature derivative of the sample resistance (Novák et al., 2008). These methods can be applied even when standard SQUID magnetometers are difficult or impossible to use – for example for extremely small samples or in the case of experiments performed at very specific physical conditions, e.g. at high hydrostatic pressure inside the clamp cell. We show that the use of the so called Arrott plot prepared with the use of high magnetic field isotherms ρxx(H0),ρxy(H0) (H0 – external magnetic field) may lead to substantial (of the order of 10 K) divergence of the obtained TC values depending on the assumptions which are necessary to make in this case and depending on the direction of a magnetic anisotropy easy axis. We also propose a number of ways how to obtain, basing on low magnetic field isotherms ρxx(H0),ρxy(H0), clear and characteristic features which are closely related to the ferromagnetic–paramagnetic phase transition

The influence of thermal annealing on structure and oxidation of iron nanowires

Raman spectroscopy as well as Mössbauer spectroscopy were applied in order to study the phase composition of iron nanowires and its changes, caused by annealing in a neutral atmosphere at several temperatures ranging from 200°C to 800°C. As-prepared nanowires were manufactured via a simple chemical reduction in an external magnetic field. Both experimental techniques proved formation of the surface layer covered by crystalline iron oxides, with phase composition dependent on the annealing temperature (Ta). At higher Ta, hematite was the dominant phase in the nanowires