Spin Hall and longitudinal conductivity of a conserved spin current in two dimensional heavy-hole gases

The spin Hall and longitudinal conductivity of a 2D heavy-hole gas with {\it k}-cubic Rashba and Dresselhaus spin-orbit interaction is studied in the ac frequency domain. Using Kubo linear-response theory and a recently proposed definition for the (conserved) spin current operator suitable for spin-3/2 holes, it is shown that the spin conductivity tensor exhibit very distinguishable features from those obtained with the standard definition of the spin current. This is due to a significant contribution of the spin-torque term arisen from the alternative definition of spin current which strongly affects the magnitude and the sign of the dynamic spin current. In the dc (free of disorder) limit, the spin Hall conductivity for only (or dominant) {\it k}-cubic Rashba coupling is $\sigma^{s,z}_{xy}(0)=-9e/8\pi$, whereas $\sigma^{s,z}_{xy}(0)=-3e/8\pi$ for only (or dominant) {\it k}-cubic Dresselhaus coupling. Such anisotropic response is understood in terms of the absence of mapping the {\it k}-cubic Rashba $\leftrightarrow$ Dresselhaus Hamiltonians. This asymmetry is also responsible for the non-vanishing dc spin Hall conductivity ($\sigma^{s,z}_{xy}(0)=-6e/8\pi$) when the Rashba and Dresselhaus parameters have the same strength, in contrast with its corresponding case for electrons. These results are of relevance to validate the alternative definition of spin-current through measurements in the frequency domain of the spin accumulation and/or spin currents in 2D hole gases.Comment: 12 pages, 6 figures; typos added; Recommendations from referees added. Title change

Kondo effect in graphene with Rashba spin-orbit coupling

We study the Kondo screening of a magnetic impurity adsorbed in graphene in the presence of Rashba spin-orbit interaction. The system is described by an effective single-channel Anderson impurity model, which we analyze using the numerical renormalization group. The nontrivial energy dependence of the host density of states gives rise to interesting behaviors under variation of the chemical potential or the spin-orbit coupling. Varying the Rashba coupling produces strong changes in the Kondo temperature characterizing the many-body screening of the impurity spin, and at half filling allows approach to a quantum phase transition separating the strong-coupling Kondo phase from a free-moment phase. Tuning the chemical potential close to sharp features of the hybridization function results in striking features in the temperature dependences of thermodynamic quantities and in the frequency dependence of the impurity spectral function.Comment: 11 pages, 9 figures. Minor changes. Accepted in PR

Measuring the level of lean readiness of the Hong Kong's manufacturing industry

Increasingly competitive business environments have forced manufacturing organisations to continuously seek improvements in their production processes as an alternative to achieve operational excellence. Lean manufacturing principles and techniques based on the elimination waste have been widely used by manufacturing organisations around the world to drive such improvements. The purpose of this paper is to present an empirical study that evaluates the readiness level of the Hong Kong’s manufacturing industry to provide a foundation for the successful implementation and/or sustainment of lean practices. To conduct this study, the paper adapts an assessment framework developed by Al-Najem et al. [16]. Thus, the lean readiness assessment is based on six quality practices (i.e. planning & control; processes; human resources; customer relations; supplier relations; and top management & leadership) related to lean manufacturing. One research question and three hypotheses were formulated and tested using a combination of inferential statics (i.e. Levene’s test and t-test) and descriptive statistics. Data were collected through a survey questionnaire responded by 9 manufacturing organisations with operations in Hong Kong. The findings suggest that the Hong Kong’s manufacturing organisations surveyed do not currently have a well-developed foundation to implement or sustain lean manufacturing. In particular, these organisations present important opportunities to further develop some quality practices such as processes, planning & control, customer relations, supplier relations, human resources, and top management & leadership. The improvement of these quality practices will ensure, according to Al-Najem et al.’s [16] framework, a more effective implementation and sustainment of lean manufacturing in their operations

Spin torque contribution to the a.c. spin Hall conductivity

Using the recently proposed definition of a conserved spin-current operator [J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency dependent spin Hall conductivity for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interaction in response to an oscillating electric field. We show that the optical spectrum of the spin Hall conductivity exhibit remarkable changes when the new definition of spin current is applied. Such behavior is mainly due to a significant contribution of the spin torque term which is absent in the conventional form of the spin current. In addition, it is observed that the magnitude and direction of the dynamic spin Hall current strongly depends on the electric field frequency as with the interplay of the spin-orbit coupling strengths.Comment: 8 pages, 4 figures, pape

Machine Learning System for the Effective Diagnosis and Survival Prediction of Breast Cancer Patients

Breast cancer is one of the most significant global health challenges. Effective diagnosis and prognosis prediction are crucial for improving patient outcomes in the case of this disease. As machine learning (ML) has significantly improved prediction models in many disciplines, the goal of this study is to develop a ML system for medical specialists that can accurately predict tumor diagnosis and patient survival for breast cancer patients. For the training of diagnosis and survival prediction, five algorithmic models—decision tree (DT), random forest (RF), naive bayes (NB), support vector machines (SVMs), and gradient boosting—were trained with 569 records from the Breast Cancer Wisconsin dataset and 1,980 records from the Breast Cancer Gene Expression Profiles dataset. The results showed that the NB model exhibited better performance for tumor diagnosis, achieving an accuracy of 95.0%, while RF presented the best results for patient survival, with an accuracy of 76.0%. A survey of medical experts’ experience with the resulting system showed high scores in reliability, performance, satisfaction, usability, and efficiency, confirming that ML systems have the potential to improve breast cancer patient outcomes

Signatures of quantum phase transitions in parallel quantum dots: Crossover from local-moment to underscreened spin-1 Kondo physics

We study a strongly interacting "quantum dot 1" and a weakly interacting "dot 2" connected in parallel to metallic leads. Gate voltages can drive the system between Kondo-quenched and non-Kondo free-moment phases separated by Kosterlitz-Thouless quantum phase transitions. Away from the immediate vicinity of the quantum phase transitions, the physical properties retain signatures of first-order transitions found previously to arise when dot 2 is strictly noninteracting. As interactions in dot 2 become stronger relative to the dot-lead coupling, the free moment in the non-Kondo phase evolves smoothly from an isolated spin-one-half in dot 1 to a many-body doublet arising from the incomplete Kondo compensation by the leads of a combined dot spin-one. These limits, which feature very different spin correlations between dot and lead electrons, can be distinguished by weak-bias conductance measurements performed at finite temperatures.Comment: 7 pages, 7 figures. Accepted for publication in Phys. Rev.

Evaluación del efecto condroprotetor del tratamiento con plasma rico en plaquetas y reína en condrocitos humanos

La osteoartrosis (OA) es una enfermedad crónico-degenerativa de origen multifactorial prevalente en el mundo que causa dolor, rigidez y limitación del movimiento, por lo cual se han propuesto diversos tratamientos alternativos Objetivo. Investigar y comparar el efecto antiinflamatorio de la terapia combinada de plasma rico en plaquetas y reina para el tratamiento de la OA de rodilla en un modelo in vitro. Material y Métodos. Se recuperó el tejido articular proveniente de los cóndilos femorales y cápsula sinovial de 20 pacientes de donde se obtuvieron condrocitos y posteriormente se generaron 5 grupos experimentales: control (medio basal), IL-1β (medio basal + IL-1β), PRP (+ IL-1β), Reina (+ IL-1β) y Reina + PRP (IL-1β). De cada grupo se obtuvieron muestras a las 0, 24 y 48 horas y se midió la producción de Óxido nítrico, Factor de necrosis tumoral y ensayos de migración y expresión génica. Resultados. Se determinó la solubilidad de la reina en 1.8mg/mL, el número de células en 50,000 condrocitos y una concentración de reina de 50 mg/L, la producción de óxido nítrico y factor de necrosis tumoral alfa no tuvieron una reducción significativa con respecto al resto de los tratamientos (p<0.05) la producción génica mantuvo el mismo patrón en los resultados con una respuesta parcial en la terapia combinada y en los ensayos de migración (p<0.05). Conclusiones. El tratamiento de la osteoartrosis con la terapia combinada Plasma Rico en Plaquetas y reina puede ser una opción terapéutica que puede ayudar para contrarrestar el catabolismo producido por el estado inflamatorio en la OA de rodilla de una forma parcial