We analyze spin-dependent transport through spin valves composed of an interacting quantum dot coupled to two ferromagnetic leads. The spin on the quantum dot and the linear conductance as a function ...of the relative angle theta of the leads' magnetization directions is derived to lowest order in the dot-lead coupling strength. Because of the applied bias voltage spin accumulates on the quantum dot, which for finite charging energy experiences a torque, resulting in spin precession. The latter leads to a nontrivial, interaction-dependent, theta dependence of the conductance. In particular, we find that the spin-valve effect is reduced for all theta not equal pi.
The break-junction technique is widely used to measure electronic properties of nanoscale junctions including metal point-contacts and single-molecule junctions. In these measurements, conductance is ...measured as a function of electrode displacement yielding data that is analyzed by constructing conductance histograms to determine the most frequently observed conductance values in the nanoscale junctions. However much of the rich physics in these measurements is lost in this simple analysis technique. Conductance histograms cannot be used to study the statistical relation of distinct junction configurations, to distinguish structurally different configurations that have similar conductance values, or to obtain information on the relation between conductance and junction elongation. Here, we give a detailed introduction to a novel statistical analysis method based on the two-dimensional cross-correlation histogram (2DCH) analysis of conductance traces and show that this method provides new information about the relation of different junction configurations that occur during the formation and evolution of metal and single-molecule junctions. We first illustrate the different types of correlation effects by using simulated conductance traces. We then apply this analysis method to several different experimental examples. We show from break-junction measurements of different metal point-contacts that in aluminum, the first conductance histogram peak corresponds to two different junction structures. In tantalum, we identify the frequent absence of adhesive instability. We show that conductance plateaus shift in a correlated manner in iron and vanadium junctions. Finally, we highlight the applicability of the correlation analysis to single-molecule platinum–CO–platinum and gold–4,4′-bipyridine–gold junctions.
The Kondo Effect in the Presence of Ferromagnetism Pasupathy, Abhay N.; Bialczak, Radoslaw C.; Martinek, Jan ...
Science (American Association for the Advancement of Science),
10/2004, Letnik:
306, Številka:
5693
Journal Article
Recenzirano
We measured Kondo-assisted tunneling via C60molecules in contact with ferromagnetic nickel electrodes. Kondo correlations persisted despite the presence of ferromagnetism, but the Kondo peak in the ...differential conductance was split by an amount that decreased (even to zero) as the moments in the two electrodes were turned from parallel to antiparallel alignment. The splitting is too large to be explained by a local magnetic field. However, the voltage, temperature, and magnetic field dependence of the signals agree with predictions for an exchange splitting of the Kondo resonance. The Kondo effect leads to negative values of magnetoresistance, with magnitudes much larger than the Julliere estimate.
Several studies have reported partial recovery of peristalsis in patients with achalasia after myotomy. The aim of our study is to analyze esophageal motility patterns after peroral endoscopic ...myotomy (POEM) and to assess the potential predictors and clinical impact of peristaltic recovery.
We performed a retrospective analysis of prospectively collected data of consecutive patients with achalasia undergoing POEM at a tertiary center. High-resolution manometry (HRM) studies prior to and after POEM were reviewed and the Chicago classification was applied.
A total of 237 patients were analyzed. The initial HRM diagnoses were achalasia type I, 42 (17.7%); type II, 173 (73.0%); and type III, 22 (9.3%). Before POEM, peristaltic fragments were present in 23 (9.7%) patients. After POEM the Chicago classification diagnoses were: 112 absent contractility, 42 type I achalasia, 15 type II, 11 type III, 26 ineffective esophageal motility, 18 esophagogastric junction outflow obstruction, 10 fragmented peristalsis, and 3 distal esophageal spasm. Altogether 68 patients (28.7%) had signs of contractile activity, but the contractions newly appeared in 47 patients (47/214, 22.0%). Type II achalasia showed a trend for appearance of contractions (
= 0.097). Logistic regression analysis did not identify any predictors of peristaltic recovery. The post-POEM Eckardt score did not differ between patients with and without contractions nor did the parameters of timed barium esophagogram.
More than 20% of achalasia patients have signs of partial recovery of esophageal peristalsis after POEM. It occurs predominantly in type II achalasia but the clinical relevance seems to be negligible.
SU(3) Kondo effect in spinless triple quantum dots López, Rosa; Rejec, Tomaž; Martinek, Jan ...
Physical review. B, Condensed matter and materials physics,
01/2013, Letnik:
87, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We discuss a device-a purely capacitively coupled interacting triple quantum dot system in an external magnetic field-for the observation of the SU(3) Kondo effect, identified by the conductance ...being pinned to a characteristic value of 3/4 of the unitary limit. The Kondo effect occurs in two plateaus where the dot occupancy is pinned to an integer value, either 1 or 2. We discuss the thermodynamic and spectral properties of the corresponding triple-impurity model and establish how the presence of SU(3) Kondo screening can be identified in the temperature dependence of the conductance through one of the dots. We report results about the robustness of the SU(3) Kondo effect against various perturbations present in real experimental setups, namely unequal reservoir-dot tunneling couplings, gating effects, and nonvanishing interdot tunneling rates. Finally, we describe possible mechanisms to restore the SU(3) Kondo physics by properly tuning the on-site dot potentials. We briefly comment on the spinful case (i.e., the same system in the absence of the magnetic field), which has very different behavior and shows Kondo plateaus in conductance for all integer values of the occupancy, including at the particle-hole symmetric point.
Abstract
Introduction
Esophageal achalasia is a primary motility disorder. Although the exact pathogenesis is unknown, autoimmune, and neurodegenerative processes seem to be involved similarly to ...neurodegenerative and/or demyelinating disorders (NDDs). We hypothesized that the prevalence of NDD may be higher among patients with achalasia and vice versa as the background pathogenetic mechanisms are similar.
Methods
This was a prospective, comparative questionnaire-based study. Patients with achalasia and patients with NDD were enrolled. Selected patients with achalasia were thoroughly examined by a neurologist and selected patients with NDD were examined by a gastroenterologist to confirm or rule out NDD or achalasia. We assessed the prevalence of both achalasia and NDD and compared them with their prevalence in general population.
Results
A total of 150 patients with achalasia and 112 patients with NDD were enrolled. We observed an increased prevalence of NDD among patients with achalasia (6.0% (9/150); 95% CI (confidence interval): 3.1–11.2%) as compared to the estimated 2.0% prevalence in general population (
p
= 0.003). Although 32 out of 112 patients (28.6%) with NDD reported dysphagia, we did not observe significantly increased prevalence of achalasia in these patients (1.8% (2/112) vs 0.8% in general population,
p
= 0.226).
Conclusion
The prevalence of NDD was significantly higher among patients with achalasia (6.0%) compared to general population (2.0%), suggesting an association of these disorders. Large-volume studies are necessary to confirm this finding.
The ARP2/3 complex and formins are the only known plant actin nucleators. Besides their actin-related functions, both systems also modulate microtubule organization and dynamics. Loss of the main ...housekeeping
Class I membrane-targeted formin FH1 (At3g25500) is known to increase cotyledon pavement cell lobing, while mutations affecting ARP2/3 subunits exhibit an opposite effect. Here we examine the role of FH1 and the ARP2/3 complex subunit ARPC5 (At4g01710) in epidermal cell morphogenesis with focus on pavement cells and trichomes using a model system of single
and
, as well as double
mutants. While cotyledon pavement cell shape in double mutants mostly resembled single
mutants, analysis of true leaf epidermal morphology, as well as actin and microtubule organization and dynamics, revealed a more complex relationship between the two systems and similar, rather than antagonistic, effects on some parameters. Both
and
mutations increased actin network density and increased cell shape complexity in pavement cells and trichomes of first true leaves, in contrast to cotyledons. Thus, while the two actin nucleation systems have complementary roles in some aspects of cell morphogenesis in cotyledon pavement cells, they may act in parallel in other cell types and developmental stages.
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