3,737 research outputs found
Hybrid exciton-polaritons in a bad microcavity containing the organic and inorganic quantum wells
We study the hybrid exciton-polaritons in a bad microcavity containing the
organic and inorganic quantum wells. The corresponding polariton states are
given. The analytical solution and the numerical result of the stationary
spectrum for the cavity field are finishedComment: 3 pages, 1 figure. appear in Communications in Theoretical Physic
Optical tuning of the diamond Fermi level measured by correlated scanning probe microscopy and quantum defect spectroscopy
Quantum technologies based on quantum point defects in crystals require
control over the defect charge state. Here we tune the charge state of shallow
nitrogen-vacancy and silicon-vacancy centers by locally oxidizing a
hydrogenated surface with moderate optical excitation and simultaneous spectral
monitoring. The loss of conductivity and change in work function due to
oxidation are measured in atmosphere using conductive atomic force microscopy
(C-AFM) and Kelvin probe force microscopy (KPFM). We correlate these scanning
probe measurements with optical spectroscopy of the nitrogen-vacancy and
silicon-vacancy centers created via implantation and annealing 15-25 nm beneath
the diamond surface. The observed charge state of the defects as a function of
optical exposure demonstrates that laser oxidation provides a way to precisely
tune the Fermi level over a range of at least 2.00 eV. We also observe a
significantly larger oxidation rate for implanted surfaces compared to
unimplanted surfaces under ambient conditions. Combined with knowledge of the
electron affinity of a surface, these results suggest KPFM is a powerful,
high-spatial resolution technique to advance surface Fermi level engineering
for charge stabilization of quantum defects
Inhibition of neddylation represses lipopolysaccharide-induced proinflammatory cytokine production in macrophage cells
Background: Lipopolysaccharides (LPSs) up-regulate proinflammatory cytokines in macrophages, partly through a NF-κB-dependent process.
Results: Blocking neddylation, which helps regulate NF-κB, represses LPS-induced up-regulation of proinflammatory cytokines.
Conclusion: Neddylation plays a role in the up-regulation of NF-κB-regulated proinflammatory cytokines produced by macrophages in response to LPS.
Significance: Inhibition of neddylation represents a novel and effective method for the prevention of LPS-induced proinflammatory cytokines
Bi-Large Neutrino Mixing See-Saw Mass Matrix with Texture Zeros and Leptogenesis
We study constraints on neutrino properties from texture zeros in bi-large
mixing See-Saw mass matrix and also from leptogenesis. Texture zeros may occur
in the light (class a)) or in the heavy (class b)) neutrino mass matrices. Each
of these two classes has 5 different forms which can produce non-trivial three
generation mixing with at least one texture zero. We find that two types of
texture zero mass matrices in both class a) and class b) can be consistent with
present data on neutrino masses, mixing and produce the observed baryon
asymmetry of the universe. None of the neutrinos can have zero masses with the
lightest of the light neutrinos having a mass larger than about 0.039 eV for
class a) and 0.002 eV for class b). In these models although CKM CP violating
phase vanishes, non-zero Majorana phases, however, can exist and play an
important role in producing the observed baryon asymmetry in our universe
through leptogenesis mechanism. The requirement of producing the observed
baryon asymmetry can further distinguish different models and also restrict the
See-Saw scale to be in the range GeV.Comment: 21 pages, 7 figures revised version, some references added, to be
submitted to PR
Active control of magnetoresistance of organic spin valves using ferroelectricity
Organic spintronic devices have been appealing because of the long spin life
time of the charge carriers in the organic materials and their low cost,
flexibility and chemical diversity. In previous studies, the control of
resistance of organic spin valves is generally achieved by the alignment of the
magnetization directions of the two ferromagnetic electrodes, generating
magnetoresistance.1 Here we employ a new knob to tune the resistance of organic
spin valves by adding a thin ferroelectric interfacial layer between the
ferromagnetic electrode and the organic spacer. We show that the resistance can
be controlled by not only the spin alignment of the two ferromagnetic
electrodes, but also by the electric polarization of the interfacial
ferroelectric layer: the MR of the spin valve depends strongly on the history
of the bias voltage which is correlated with the polarization of the
ferroelectric layer; the MR even changes sign when the electric polarization of
the ferroelectric layer is reversed. This new tunability can be understood in
terms of the change of relative energy level alignment between ferromagnetic
electrode and the organic spacer caused by the electric dipole moment of the
ferroelectric layer. These findings enable active control of resistance using
both electric and magnetic fields, opening up possibility for multi-state
organic spin valves and shed light on the mechanism of the spin transport in
organic spin valves
Microbial fuel cells: a green and alternative source for bioenergy production
Microbial fuel cell (MFC) represents one of the green technologies for the production of bioenergy. MFCs using microalgae produce bioenergy by converting solar energy into electrical energy as a function of metabolic and anabolic pathways of the cells. In the MFCs with bacteria, bioenergy is generated as a result of the organic substrate oxidation. MFCs have received high attention from researchers in the last years due to the simplicity of the process, the absence in toxic by-products, and low requirements for the algae growth. Many studies have been conducted on MFC and investigated the factors affecting the MFC performance. In the current chapter, the performance of MFC in producing bioenergy as well as the factors which influence the efficacy of MFCs is discussed. It appears that the main factors affecting MFC’s performance include bacterial and algae species, pH, temperature, salinity, substrate, mechanism of electron transfer in an anodic chamber, electrodes materials, surface area, and electron acceptor in a cathodic chamber. These factors are becoming more influential and might lead to overproduction of bioenergy when they are optimized using response surface methodology (RSM)
Intervention effects of Ganoderma lucidum spores on epileptiform discharge hippocampal neurons and expression of Neurotrophin-4 and N-Cadherin
Epilepsy can cause cerebral transient dysfunctions. Ganoderma lucidum spores (GLS), a traditional Chinese medicinal herb, has shown some antiepileptic effects in our previous studies. This was the first study of the effects of GLS on cultured primary hippocampal neurons, treated with Mg2+ free medium. This in vitro model of epileptiform discharge hippocampal neurons allowed us to investigate the anti-epileptic effects and mechanism of GLS activity. Primary hippocampal neurons from <1 day old rats were cultured and their morphologies observed under fluorescence microscope. Neurons were confirmed by immunofluorescent staining of neuron specific enolase (NSE). Sterile method for GLS generation was investigated and serial dilutions of GLS were used to test the maximum non-toxic concentration of GLS on hippocampal neurons. The optimized concentration of GLS of 0.122 mg/ml was identified and used for subsequent analysis. Using the in vitro model, hippocampal neurons were divided into 4 groups for subsequent treatment i) control, ii) model (incubated with Mg2+ free medium for 3 hours), iii) GLS group I (incubated with Mg2+ free medium containing GLS for 3 hours and replaced with normal medium and incubated for 6 hours) and iv) GLS group II (neurons incubated with Mg2+ free medium for 3 hours then replaced with a normal medium containing GLS for 6 hours). Neurotrophin-4 and N-Cadherin protein expression were detected using Western blot. The results showed that the number of normal hippocampal neurons increased and the morphologies of hippocampal neurons were well preserved after GLS treatment. Furthermore, the expression of neurotrophin-4 was significantly increased while the expression of N-Cadherin was decreased in the GLS treated group compared with the model group. This data indicates that GLS may protect hippocampal neurons by promoting neurotrophin-4 expression and inhibiting N-Cadherin expression
The Reproducibility of Lists of Differentially Expressed Genes in Microarray Studies
Reproducibility is a fundamental requirement in scientific experiments and clinical contexts. Recent publications raise concerns about the reliability of microarray technology because of the apparent lack of agreement between lists of differentially expressed genes (DEGs). In this study we demonstrate that (1) such discordance may stem from ranking and selecting DEGs solely by statistical significance (P) derived from widely used simple t-tests; (2) when fold change (FC) is used as the ranking criterion, the lists become much more reproducible, especially when fewer genes are selected; and (3) the instability of short DEG lists based on P cutoffs is an expected mathematical consequence of the high variability of the t-values. We recommend the use of FC ranking plus a non-stringent P cutoff as a baseline practice in order to generate more reproducible DEG lists. The FC criterion enhances reproducibility while the P criterion balances sensitivity and specificity
Recurrent corneal melting in the paraneoplastic pemphigus associated with Castleman’s disease
A Fluorescence-Based High-Throughput Assay for the Discovery of Exchange Protein Directly Activated by Cyclic AMP (EPAC) Antagonists
Background: The discovery, more than ten years ago, of exchange proteins directly activated by cAMP (EPAC) as a new family of intracellular cAMP receptors revolutionized the cAMP signaling research field. Extensive studies have revealed that the cAMP signaling network is much more complex and dynamic as many cAMP-related cellular processes, previously thought to be controlled by protein kinase A, are found to be also mediated by EPAC proteins. Although there have been many important discoveries in the roles of EPACs greater understanding of their physiological function in cAMP-mediated signaling is impeded by the absence of EPAC-specific antagonist. Methodology/Principal Findings: To overcome this deficit, we have developed a fluorescence-based high throughput assay for screening EPAC specific antagonists. Our assay is highly reproducible and simple to perform using the ‘‘mix and measure’ ’ format. A pilot screening using the NCI-DTP diversity set library led to the identification of small chemical compounds capable of specifically inhibiting cAMP-induced EPAC activation while not affecting PKA activity. Conclusions/Significance: Our study establishes a robust high throughput screening assay that can be effectively applied for the discovery of EPAC-specific antagonists, which may provide valuable pharmacological tools for elucidating th
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