2,904 research outputs found
Formation of defects in multirow Wigner crystals
We study the structural properties of a quasi-one-dimensional classical
Wigner crystal, confined in the transverse direction by a parabolic potential.
With increasing density, the one-dimensional crystal first splits into a zigzag
crystal before progressively more rows appear. While up to four rows the ground
state possesses a regular structure, five-row crystals exhibit defects in a
certain density regime. We identify two phases with different types of defects.
Furthermore, using a simplified model, we show that beyond nine rows no stable
regular structures exist.Comment: 11 pages, 8 figure
Oscillatory pairing of fermions in spin-split traps
As a means of realizing oscillatory pairing between fermions, we study
superfluid pairing between two fermion "spin" species that are confined to
adjustable spin-dependent trapping potentials. Focusing on the one-dimensional
limit, we find that with increasing separation between the spin-dependent traps
the fermions exhibit distinct phases, including a fully paired phase, a
spin-imbalanced phase with oscillatory pairing, and an unpaired fully
spin-polarized phase. We obtain the phase diagram of fermions in such a
spin-split trap and discuss signatures of these phases in cold-atom
experiments.Comment: 5 pages, 5 figures, RevTe
Transition from a one-dimensional to a quasi-one-dimensional state in interacting quantum wires
Upon increasing the electron density in a quantum wire, the one-dimensional
electron system undergoes a transition to a quasi-one-dimensional state. In the
absence of interactions between electrons, this corresponds to filling up the
second subband of transverse quantization, and there are two gapless excitation
modes above the transition. On the other hand, strongly interacting
one-dimensional electrons form a Wigner crystal, and the transition corresponds
to it splitting into two chains (zigzag crystal). The two chains are locked, so
their relative motion is gapped, and only one gapless mode remains. We study
the evolution of the system as the interaction strength changes, and show that
only one gapless mode exists near the transition at any interaction strength.Comment: 4 pages, 2 figure
Quantum phase transition in quantum wires controlled by an external gate
We consider electrons in a quantum wire interacting via a long-range Coulomb
potential screened by a nearby gate. We focus on the quantum phase transition
from a strictly one-dimensional to a quasi-one-dimensional electron liquid,
that is controlled by the dimensionless parameter , where is the
electron density and is the characteristic length of the transverse
confining potential. If this transition occurs in the low-density limit, it can
be understood as the deformation of the one-dimensional Wigner crystal to a
zigzag arrangement of the electrons described by an Ising order parameter. The
critical properties are governed by the charge degrees of freedom and the spin
sector remains essentially decoupled. At large densities, on the other hand,
the transition is triggered by the filling of a second one-dimensional subband
of transverse quantization. Electrons at the bottom of the second subband
interact strongly due to the diverging density of states and become
impenetrable. We argue that this stabilizes the electron liquid as it
suppresses pair-tunneling processes between the subbands that would otherwise
lead to an instability. However, the impenetrable electrons in the second band
are screened by the excitations of the first subband, so that the transition is
identified as a Lifshitz transition of impenetrable polarons. We discuss the
resulting phase diagram as a function of .Comment: 18 pages, 8 figures, minor changes, published versio
Cooperative Effect of miR-141-3p and miR-145-5p in the Regulation of Targets in Clear Cell Renal Cell Carcinoma
Background Due to the poor prognosis for advanced renal cell carcinoma (RCC),
there is an urgent need for new therapeutic targets and for prognostic markers
to identify high risk tumors. MicroRNAs (miRNAs) are frequently dysregulated
in tumors, play a crucial role during carcinogenesis and therefore might be
promising new biomarkers. In previous studies, we identified miR-141-3p and
miR-145-5p to be downregulated in clear cell RCC (ccRCC). Our objective was to
investigate the functional association of these miRNAs, focusing on the
cooperative regulation of new specific targets and their role in ccRCC
progression. Methods The effect of miR-141-3p and miR-145-5p on cell migration
was examined by overexpression in 786-O cells. New targets of both miRNAs were
identified by miRWalk, validated in 786-O and ACHN cells and additionally
characterized in ccRCC tissue on mRNA and protein level. Results In functional
analysis, a tumor suppressive effect of miR-141-3p and miR-145-5p by
decreasing migration and invasion of RCC cells could be shown. Furthermore,
co-overexpression of the miRNAs seemed to result in an increased inhibition of
cell migration. Both miRNAs were recognized as post-transcriptional regulators
of the targets EAPP, HS6ST2, LOX, TGFB2 and VRK2. Additionally, they showed a
cooperative effect again as demonstrated by a significantly increased
inhibition of HS6ST2 and LOX expression after simultaneous overexpression of
both miRNAs. In ccRCC tissue, LOX mRNA expression was strongly increased
compared to normal tissue, allowing also to distinguish between non-metastatic
and already metastasized primary tumors. Finally, in subsequent tissue
microarray analysis LOX protein expression showed a prognostic relevance for
the overall survival of ccRCC patients. Conclusion These results illustrate a
jointly strengthening effect of the dysregulated miR-141-3p and miR-145-5p in
various tumor associated processes. Focusing on the cooperative effect of
miRNAs provides new opportunities for the development of therapeutic
strategies and offers novel prognostic and diagnostic capabilities
Distinct redox regulation in sub-cellular compartments in response to various stress conditions in Saccharomyces cerevisiae
Responses to many growth and stress conditions are assumed to act via changes to the cellular redox status. However, direct measurement of pH-adjusted redox state during growth and stress has never been carried out. Organellar redox state (EGSH) was measured using the fluorescent probes roGFP2 and pHluorin in Saccharomyces cerevisiae. In particular, we investigated changes in organellar redox state in response to various growth and stress conditions to better understand the relationship between redox-, oxidative- and environmental stress response systems. EGSH values of the cytosol, mitochondrial matrix and peroxisome were determined in exponential and stationary phase in various media. These values (-340 to -350 mV) were more reducing than previously reported. Interestingly, sub-cellular redox state remained unchanged when cells were challenged with stresses previously reported to affect redox homeostasis. Only hydrogen peroxide and heat stress significantly altered organellar redox state. Hydrogen peroxide stress altered the redox state of the glutathione disulfide/glutathione couple (GSSG, 2H+/2GSH) and pH. Recovery from moderate hydrogen peroxide stress was most rapid in the cytosol, followed by the mitochondrial matrix, with the peroxisome the least able to recover. Conversely, the bulk of the redox shift observed during heat stress resulted from alterations in pH and not the GSSG, 2H+/2GSH couple. This study presents the first direct measurement of pH-adjusted redox state in sub-cellular compartments during growth and stress conditions. Redox state is distinctly regulated in organelles and data presented challenge the notion that perturbation of redox state is central in the response to many stress conditions
Magnetotunneling spectroscopy of mesoscopic correlations in two-dimensional electron systems
An approach to experimentally exploring electronic correlation functions in
mesoscopic regimes is proposed. The idea is to monitor the mesoscopic
fluctuations of a tunneling current flowing between the two layers of a
semiconductor double-quantum-well structure. From the dependence of these
fluctuations on external parameters, such as in-plane or perpendicular magnetic
fields, external bias voltages, etc., the temporal and spatial dependence of
various prominent correlation functions of mesoscopic physics can be
determined. Due to the absence of spatially localized external probes, the
method provides a way to explore the interplay of interaction and localization
effects in two-dimensional systems within a relatively unperturbed environment.
We describe the theoretical background of the approach and quantitatively
discuss the behavior of the current fluctuations in diffusive and ergodic
regimes. The influence of both various interaction mechanisms and localization
effects on the current is discussed. Finally a proposal is made on how, at
least in principle, the method may be used to experimentally determine the
relevant critical exponents of localization-delocalization transitions.Comment: 15 pages, 3 figures include
Biocompatibility of the vital dye Acid Violet-17 on retinal pigment epithelial cells
Purpose: To examine the viability and differentiation of retinal pigment epithelial (RPE) cells after exposure to the vital dye Acid Violet-17 (AV-17). Methods: Bovine RPE cells were incubated with AV-17 (0.0625-0.5 mg/mL) for 30 seconds or 5 minutes. Viability was determined by live/dead staining, cleaved CASP3 immunostainings, and MTT test. Actin cytoskeleton was visualized by Alexa 488-phalloidin. Immunocytochemistry was performed to determine the levels of ZO-1, CTNNB1, and KRT19. Results: Exposure to AV-17 at the concentrations of 0.25-0.5 mg/mL resulted in a dose-dependent decrease in viability, the loss of ZO-1 from tight junctions, translocation of CTNNB1 into the cytoplasm and nucleus, disarrangement of the actin cytoskeleton, and a slight increase in KRT19. Conclusion: AV-17 at a concentration. 0.125 mg/mL is likely to be well tolerated by the RPE cells, whereas the concentrations from 0.25 mg/mL onward can reduce viability and induce dedifferentiation particularly after long-term exposure
- …