Slave-boson Keldysh field theory for the Kondo effect in quantum dots

We present a {\it nonequilibrium nonperturbative} field theory for the Kondo effect in strongly interacting quantum dots at finite temperatures. Unifying the slave-boson representation with the Keldysh field integral an effective Keldysh action is derived and explored in the vicinity of the zero slave-bosonic field configuration. The theory properly reflects the essential features of the Kondo physics and at the same time significantly simplifies a field-theoretic treatment of the phenomenon, avoiding complicated saddle point analysis or 1/N expansions, used so far. Importantly, our theory admits a {\it closed analytical} solution which explains the mechanism of the Kondo effect in terms of an interplay between the real and imaginary parts of the slave-bosonic self-energy. It thus provides a convenient nonperturbative building block, playing the role of a "free propagator", for more advanced theories. We finally demonstrate that already this simplest possible field theory is able to correctly reproduce experimental data on the Kondo peak observed in the differential conductance, correctly predicts the Kondo temperature and, within its applicability range, has the same universal temperature dependence of the conductance as the one obtained in numerical renormalization group calculations.Comment: published versio

Non-collinear single-electron spin-valve transistors

We study interaction effects on transport through a small metallic cluster connected to two ferromagnetic leads (a single-electron spin-valve transistor) in the "orthodox model" for the Coulomb blockade. The non-local exchange between the spin accumulation on the island and the ferromagnetic leads is shown to affect the transport properties such as the electric current and spin-transfer torque as a function of the magnetic configuration, gate voltage, and applied magnetic field.Comment: 4 pages, 3 figure

The Tendency of Development and Application of Service Robots for Defense, Rescue and Security

The development of sensor, information and communication technology, or new technology, has contributed to the development of robot technology. A new generation of service robots has been developed, and the highest number of their practical applications is for defense and security. Progress and development of information technology, sensor technology and servo-drive is responsible for the development of over 600 different types or prototype service robots. Service robots are designed for professional jobs and service jobs that are used in everyday life. The rapid development of computer management enabled the rapid development of various service robots that can move independently, autonomously exchange information with their surroundings and act completely autonomously (UV Unmanned Vehicles - vehicles that operate autonomously without human management). They can be used in all operating conditions on land, air and water, which is most important for the development of service robots for defense and security. Different applications of service robots for defense and security have been developed, and some are described in the paper, as well as the tendency of their application in the recent years. A large number of service robots for defense and security were developed, which are used for obtaining information about the vulnerability of human populations during earthquakes, fires or military activities. After obtaining information, we can make proper decisions that will serve the purpose of rescue and assistance to the ones in danger. The tendency of application of service robots for security and defense is constantly rising in the past few years. It is estimated that the development of sophisticated service robots for defense, rescue and security will continue in the future, and the number of applications will increase

Transport properties of double-walled carbon nanotube quantum dots

The transport properties of quantum dot (QD) systems based on double-walled carbon nanotube (DWCNT) are investigated. The interplay between microscopic structure and strong Coulomb interaction is treated within a bosonization framework. The linear and nonlinear G-V-V_g characteristics of the QD system is calculated by starting from the Liouville equation for the reduced density matrix. Depending on the intershell couplings, an 8-electron periodicity of the Coulomb blockade peak spacing in the case of commensurate DWCNT QDs and a 4-electron periodicity in the incommensurate case are predicted. The contribution of excited states of DWCNTs to the nonlinear transport is investigated as well.Comment: 18 pages, 7 figure

Therapeutic alternatives with CPAP in obstructive sleep apnea

Obstructive Sleep Apnea (OSA), characterized by airflow cessation (apnea) or reduction (hypopnea) due to repeated pharyngeal obstructions during sleep, causes frequent disruption of sleep and hypoxic events. The condition is linked to many adverse health related consequences, such as neurocognitive and cardiovascular disorders, and metabolic syndrome. OSA is a chronic condition requiring long-term treatment, so treatment using continuous positive airway pressure (CPAP) has become the gold standard in cases of moderate or severe OSA. However, its effectiveness is influenced by patients’ adherence. Surgery for OSA or treatment with oral appliances can be successful in selected patients, but for the majority, lifestyle changes such as exercise and dietary control may prove useful. However, exercise training remains under-utilized by many clinicians as an alternative treatment for OSA. Other interventions such as oral appliance (OA), upper way stimulation, and oropharyngeal exercises are used in OSA. Because the benefit of all these techniques is heterogeneous, the major challenge is to associate specific OSA therapies with the maximum efficacy and the best patient compliance

Incorporating development of a patient-reported outcome instrument in a clinical drug development program: examples from a heart failure program.

BackgroundPatient-reported outcome (PRO) measures can be used to support label claims if they adhere to US Food & Drug Administration guidance. The process of developing a new PRO measure is expensive and time-consuming. We report the results of qualitative studies to develop new PRO measures for use in clinical trials of omecamtiv mecarbil (a selective, small molecule activator of cardiac myosin) for patients with heart failure (HF), as well as the lessons learned from the development process.MethodsConcept elicitation focus groups and individual interviews were conducted with patients with HF to identify concepts for the instrument. Cognitive interviews with HF patients were used to confirm that no essential concepts were missing and to assess patient comprehension of the instrument and items.ResultsDuring concept elicitation, the most frequently reported HF symptoms were shortness of breath, tiredness, fluid retention, fatigue, dizziness/light-headedness, swelling, weight fluctuation, and trouble sleeping. Two measures were developed based on the concepts: the Heart Failure Symptom Diary (HF-SD) and the Heart Failure Impact Scale (HFIS). Findings from cognitive interviews suggested that the items in the HF-SD and HFIS were relevant and well understood by patients. Multiple iterations of concept elicitation and cognitive interviews were needed based on FDA request for a broader patient population in the qualitative study. Lessons learned from the omecamtiv mecarbil PRO/clinical development program are discussed, including challenges of qualitative studies, patient recruitment, expected and actual timelines, cost, and engagement with various stakeholders.ConclusionDevelopment of a new PRO measure to support a label claim requires significant investment and early planning, as demonstrated by the omecamtiv mecarbil program

Seismic behavior of posttensioned self-centering precast concrete dual-shell steel columns

This paper describes an innovative bridge column technology for application in seismic regions. The proposed technology combines a precast posttensioned composite steel-concrete hollow-core column, with supplemental energy dissipation, in a way to minimize postearthquake residual lateral displacements. The column consists of two steel cylindrical shells, with high-performance concrete cast in between. Both shells act as permanent formwork; the outer shell substitutes for the longitudinal and transverse reinforcement, because it works in composite action with the concrete, whereas the inner shell removes unnecessary concrete volume from the column, prevents concrete implosion, and prevents buckling of energy dissipating dowels when embedded in the concrete. Large inelastic rotations can be accommodated at the end joints with minimal structural damage, since gaps are allowed to open at these locations and to close upon load reversal. Longitudinal posttensioned high-strength steel threaded bars, designed to respond elastically, in combination with gravity forces ensure self-centering behavior. Internal or external steel devices provide energy dissipation by axial yielding. This paper describes the main requirements for the design of these columns and also discusses the experimental findings from two quasi-static tests

Functional fine-tuning of metabolic pathways by the endocannabinoid system implications for health and disease

Although the biological components of the endocannabinoid system (ECS) are well known and have been explored in detail over many decades, its significance seems to enlarge with every new experimental study. The ECS employs a huge network of molecules (receptors, ligands, and enzymatic machinery molecules) whose interactions with other cellular networks have still not been fully elucidated. It has become evident that its historical role in pain alleviation is just the tip of an enormous iceberg of translationally significant information that can be derived from the so-called endocannabinoidome. The ECS is involved in the modulation of a large amount of cognitive and physiological processes involved in the homeostatic regulation of the body. The role and mechanism by which the ECS is involved in the regulation of metabolism is not fully known, but its action is in large part through cyclic AMP/receptor activation-related pathways activated by cannabinoid ligands [1,2]. Endogenous cannabinoids are molecules with the primary function of control of multiple metabolic pathways. They are pre-synthesized and stored in cellular vesicles and released upon endogenous and exogenous stimuli to regulate internal homeostasis. Their targets include classical cannabinoid receptors that belong to the G-protein coupled receptor (GPCR) family as well as their various heteromers (see below), contributing to the complexity of the ECS [3]. Cannabinoid ligands also act through various non-canonical pathways [4], employing secondary messenger systems (changes in intracellular Ca2+ levels, activation of protein kinases) thus preferentially triggering alternative outcomes depending on the initial stimuli. This work aims to contribute to the growing burden of evidence that the ECS might be significantly more used as a pharmacological target for various metabolic disorders, despite carrying a historical label of being legally and ethically compromised