591 research outputs found
Spin splitting of X-related donor impurity states in an AlAs barrier
We use magnetotunneling spectroscopy to observe the spin splitting of the
ground state of an X-valley-related Si-donor impurity in an AlAs barrier. We
determine the absolute magnitude of the effective Zeeman spin splitting factors
of the impurity ground state to be g= 2.2 0.1. We also investigate
the spatial form of the electron wave function of the donor ground state, which
is anisotropic in the growth plane
Magnetic-field-induced singularities in spin dependent tunneling through InAs quantum dots
Current steps attributed to resonant tunneling through individual InAs
quantum dots embedded in a GaAs-AlAs-GaAs tunneling device are investigated
experimentally in magnetic fields up to 28 T. The steps evolve into strongly
enhanced current peaks in high fields. This can be understood as a
field-induced Fermi-edge singularity due to the Coulomb interaction between the
tunneling electron on the quantum dot and the partly spin polarized Fermi sea
in the Landau quantized three-dimensional emitter.Comment: 5 pages, 4 figure
Strong quantum memory at resonant Fermi edges revealed by shot noise
Studies of non-equilibrium current fluctuations enable assessing correlations
involved in quantum transport through nanoscale conductors. They provide
additional information to the mean current on charge statistics and the
presence of coherence, dissipation, disorder, or entanglement. Shot noise,
being a temporal integral of the current autocorrelation function, reveals
dynamical information. In particular, it detects presence of non-Markovian
dynamics, i.e., memory, within open systems, which has been subject of many
current theoretical studies. We report on low-temperature shot noise
measurements of electronic transport through InAs quantum dots in the
Fermi-edge singularity regime and show that it exhibits strong memory effects
caused by quantum correlations between the dot and fermionic reservoirs. Our
work, apart from addressing noise in archetypical strongly correlated system of
prime interest, discloses generic quantum dynamical mechanism occurring at
interacting resonant Fermi edges.Comment: 6 pages, 3 figure
Shot noise of coupled semiconductor quantum dots
The low-frequency shot noise properties of two electrostatically coupled
semiconductor quantum dot states which are connected to emitter/collector
contacts are studied. A master equation approach is used to analyze the bias
voltage dependence of the Fano factor as a measure of temporal correlations in
tunneling current caused by Pauli's exclusion principle and the Coulomb
interaction. In particular, the influence of the Coulomb interaction on the
shot noise behavior is discussed in detail and predictions for future
experiments will be given. Furthermore, we propose a mechanism for negative
differential conductance and investigate the related super-Poissonian shot
noise.Comment: submitted to PR
Zebrafish reward mutants reveal novel transcripts mediating the behavioral effects of amphetamine
Transcriptome analysis of a zebrafish mutant that does not respond to amphetamine identifies a network of coordinated gene regulation that may underlie the susceptibility to addiction
Dll1 Haploinsufficiency in Adult Mice Leads to a Complex Phenotype Affecting Metabolic and Immunological Processes
BACKGROUND: The Notch signaling pathway is an evolutionary conserved signal transduction pathway involved in embryonic patterning and regulation of cell fates during development and self-renewal. Recent studies have demonstrated that this pathway is integral to a complex system of interactions, involving as well other signal transduction pathways, and implicated in distinct human diseases. Delta-like 1 (Dll1) is one of the known ligands of the Notch receptors. The role of the Notch ligands is less well understood. Loss-of-function of Dll1 leads to embryonic lethality, but reduction of Delta-like 1 protein levels has not been studied in adult stage. METHODOLOGY/PRINCIPAL FINDINGS: Here we present the haploinsufficient phenotype of Dll1 and a missense mutant Dll1 allele (Dll1(C413Y)). Haploinsufficiency leads to a complex phenotype with several biological processes altered. These alterations reveal the importance of Dll1 mainly in metabolism, energy balance and in immunology. The animals are smaller, lighter, with altered fat to lean ratio and have increased blood pressure and a slight bradycardia. The animals have reduced cholesterol and triglyceride levels in blood. At the immunological level a subtle phenotype is observed due to the effect and fine-tuning of the signaling network at the different levels of differentiation, proliferation and function of lymphocytes. Moreover, the importance of the proteolytic regulation of the Notch signaling network emphasized. CONCLUSIONS/SIGNIFICANCE: In conclusion, slight alterations in one player of Notch signaling alter the entire organism, emphasizing the fine-tuning character of this pathway in a high number of processes
Binding of Soluble Yeast β-Glucan to Human Neutrophils and Monocytes is Complement-Dependent
The immunomodulatory properties of yeast β-1,3/1,6 glucans are mediated through their ability to be recognized by human innate immune cells. While several studies have investigated binding of opsonized and unopsonized particulate β-glucans to human immune cells mainly via complement receptor 3 (CR3) or Dectin-1, few have focused on understanding the binding characteristics of soluble β-glucans. Using a well-characterized, pharmaceutical grade, soluble yeast β-glucan, this study evaluated and characterized the binding of soluble β-glucan to human neutrophils and monocytes. The results demonstrated that soluble β-glucan bound to both human neutrophils and monocytes in a concentration-dependent and receptor-specific manner. Antibodies blocking the CD11b and CD18 chains of CR3 significantly inhibited binding to both cell types, establishing CR3 as the key receptor recognizing the soluble β-glucan in these cells. Binding of soluble β-glucan to human neutrophils and monocytes required serum and was also dependent on incubation time and temperature, strongly suggesting that binding was complement-mediated. Indeed, binding was reduced in heat-inactivated serum, or in serum treated with methylamine or in serum reacted with the C3-specific inhibitor compstatin. Opsonization of soluble β-glucan was demonstrated by detection of iC3b, the complement opsonin on β-glucan-bound cells, as well as by the direct binding of iC3b to β-glucan in the absence of cells. Binding of β-glucan to cells was partially inhibited by blockade of the alternative pathway of complement, suggesting that the C3 activation amplification step mediated by this pathway also contributed to binding
Selenium Utilization by GPX4 Is Required to Prevent Hydroperoxide-Induced Ferroptosis
open24siSelenoproteins are rare proteins among all kingdoms of life containing the 21st amino acid, selenocysteine. Selenocysteine resembles cysteine, differing only by the substitution of selenium for sulfur. Yet the actual advantage of selenolate- versus thiolate-based catalysis has remained enigmatic, as most of the known selenoproteins also exist as cysteine-containing homologs. Here, we demonstrate that selenolate-based catalysis of the essential mammalian selenoprotein GPX4 is unexpectedly dispensable for normal embryogenesis. Yet the survival of a specific type of interneurons emerges to exclusively depend on selenocysteine-containing GPX4, thereby preventing fatal epileptic seizures. Mechanistically, selenocysteine utilization by GPX4 confers exquisite resistance to irreversible overoxidation as cells expressing a cysteine variant are highly sensitive toward peroxide-induced ferroptosis. Remarkably, concomitant deletion of all selenoproteins in Gpx4cys/cys cells revealed that selenoproteins are dispensable for cell viability provided partial GPX4 activity is retained. Conclusively, 200 years after its discovery, a specific and indispensable role for selenium is provided.openIngold, Irina; Berndt, Carsten; Schmitt, Sabine; Doll, Sebastian; Poschmann, Gereon; Buday, Katalin; Roveri, Antonella; Peng, Xiaoxiao; Porto Freitas, Florencio; Seibt, Tobias; Mehr, Lisa; Aichler, Michaela; Walch, Axel; Lamp, Daniel; Jastroch, Martin; Miyamoto, Sayuri; Wurst, Wolfgang; Ursini, Fulvio; Arnér, Elias S J; Fradejas-Villar, Noelia; Schweizer, Ulrich; Zischka, Hans; Friedmann Angeli, José Pedro; Conrad, MarcusIngold, Irina; Berndt, Carsten; Schmitt, Sabine; Doll, Sebastian; Poschmann, Gereon; Buday, Katalin; Roveri, Antonella; Peng, Xiaoxiao; Porto Freitas, Florencio; Seibt, Tobias; Mehr, Lisa; Aichler, Michaela; Walch, Axel; Lamp, Daniel; Jastroch, Martin; Miyamoto, Sayuri; Wurst, Wolfgang; Ursini, Fulvio; Arnér, Elias S J; Fradejas-Villar, Noelia; Schweizer, Ulrich; Zischka, Hans; Friedmann Angeli, José Pedro; Conrad, Marcu
Control of Grain-Boundary Pinning in Al 2 O 3 /ZrO 2 Composites with Ce 3+ /Ce 4+ Doping
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65897/1/j.1151-2916.1992.tb04147.x.pd
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