Kondo effect in an integer-spin quantum dot

The Kondo effect is a key many-body phenomenon in condensed matter physics. It concerns the interaction between a localised spin and free electrons. Discovered in metals containing small amounts of magnetic impurities, it is now a fundamental mechanism in a wide class of correlated electron systems. Control over single, localised spins has become relevant also in fabricated structures due to the rapid developments in nano-electronics. Experiments have already demonstrated artificial realisations of isolated magnetic impurities at metallic surfaces, nanometer-scale magnets, controlled transitions between two-electron singlet and triplet states, and a tunable Kondo effect in semiconductor quantum dots. Here, we report an unexpected Kondo effect realised in a few-electron quantum dot containing singlet and triplet spin states whose energy difference can be tuned with a magnetic field. This effect occurs for an even number of electrons at the degeneracy between singlet and triplet states. The characteristic energy scale is found to be much larger than for the ordinary spin-1/2 case.Comment: 12 page

Electron Cotunneling in a Semiconductor Quantum Dot

We report transport measurements on a semiconductor quantum dot with a small number of confined electrons. In the Coulomb blockade regime, conduction is dominated by cotunneling processes. These can be either elastic or inelastic, depending on whether they leave the dot in its ground state or drive it into an excited state, respectively. We are able to discriminate between these two contributions and show that inelastic events can occur only if the applied bias exceeds the lowest excitation energy. Implications to energy-level spectroscopy are discussed.Comment: To be published in Phys. Rev. Let

A Reference Database of Standardised Continuous Lumbar Intervertebral Motion Analysis for Conducting Patient-Specific Comparisons

Lumbar instability has long been thought of as the failure of lumbar vertebrae to maintain their normal patterns of displacement. However, it is unknown what these patterns consist of. Research using quantitative fluoroscopy (QF) has shown that continuous lumbar intervertebral patterns of rotational displacement can be reliably measured during standing flexion and return motion using standardised protocols and can be used to assess patients with suspected lumbar spine motion disorders. However, normative values are needed to make individualised comparisons. One hundred and thirty-one healthy asymptomatic participants were recruited and performed guided flexion and return motion by following the rotating arm of an upright motion frame. Fluoroscopic image acquisition at 15fps was performed and individual intervertebral levels from L2-3 to L5-S1 were tracked and analysed during separate outward flexion and return phases. Results were presented as proportional intervertebral motion representing these phases using continuous means and 95%CIs, followed by verification of the differences between levels using Statistical Parametric Mapping (SPM). A secondary analysis of 8 control participants matched to 8 patients with chronic, non-specific low back pain (CNSLBP) was performed for comparison. One hundred and twenty-seven asymptomatic participants’ data were analysed. Their ages ranged from 18 to 70 years (mean 38.6) with mean body mass index 23.8 kg/m2 48.8% were female. Both the flexion and return phases for each level evidenced continuous change in mean proportional motion share, with narrow confidence intervals, highly significant differences and discrete motion paths between levels as confirmed by SPM. Patients in the secondary analysis evidenced significantly less L5-S1 motion than controls (p < 0.05). A reference database of spinal displacement patterns during lumbar (L2-S1) intersegmental flexion and return motion using a standardised motion protocol using fluoroscopy is presented. Spinal displacement patterns in asymptomatic individuals were found to be distinctive and consistent for Edited by: Babak Bazrgari, University of Kentucky, United States Reviewed by: Navid Arjmand, Sharif University of Technology, Iran Ameet Krishnan Aiyangar, Swiss Federal Laboratories for Materials Science and Technology, Switzerland *Correspondence: Alan Breen [email protected] Specialty section: This article was submitted to Biomechanics, a section of the journal Frontiers in Bioengineering and Biotechnology Received: 22 July 2021 Accepted: 08 September 2021 Published: 27 September 2021 Citation: Breen A, De Carvalho D, Funabashi M, Kawchuk G, Pagé I, Wong AYL and Breen A (2021) A Reference Database of Standardised Continuous Lumbar Intervertebral Motion Analysis for Conducting Patient- Specific Comparisons. Front. Bioeng. Biotechnol. 9:745837. doi: 10.3389/fbioe.2021.745837 Frontiers in Bioengineering and Biotechnology | www.frontiersin.org 1 September 2021 | Volume 9 | Article 745837 ORIGINAL RESEARCH published: 27 September 2021 doi: 10.3389/fbioe.2021.745837 each intervertebral level, and to continuously change during bending and return. This database may be used to allow continuous intervertebral kinematics to drive dynamic models of joint and muscular forces as well as reference values against which to make patient-specific comparisons in suspected cases of lumbar spine motion disorders

Reshaping Regional Institutions: APEC and the IMF in East Asia

One of the most striking aspects of attempts to manage the crisis in East Asia has been the very differing roles played by APEC and the IMF. Although both organisations have similar market-centred reform agendas, APEC has been conspicuous by its absence in the wake of the crisis. This paper considers the actions of both organisations, and their very dfferent approaches to institutional reform. It is suggested that the crisis in general and the actions of these two organisations in particular provides a timely opportunity to review the more influential varieties of institutional theory to see whether they provide either useful tools for understanding the roles and activities of APEC and the IMF, or plausible models of reform for policy makers