5,273 research outputs found
Approaching the adiabatic timescale with machine-learning
The control and manipulation of quantum systems without excitation is
challenging, due to the complexities in fully modeling such systems accurately
and the difficulties in controlling these inherently fragile systems
experimentally. For example, while protocols to decompress Bose-Einstein
condensates (BEC) faster than the adiabatic timescale (without excitation or
loss) have been well developed theoretically, experimental implementations of
these protocols have yet to reach speeds faster than the adiabatic timescale.
In this work, we experimentally demonstrate an alternative approach based on a
machine learning algorithm which makes progress towards this goal. The
algorithm is given control of the coupled decompression and transport of a
metastable helium condensate, with its performance determined after each
experimental iteration by measuring the excitations of the resultant BEC. After
each iteration the algorithm adjusts its internal model of the system to create
an improved control output for the next iteration. Given sufficient control
over the decompression, the algorithm converges to a novel solution that sets
the current speed record in relation to the adiabatic timescale, beating out
other experimental realizations based on theoretical approaches. This method
presents a feasible approach for implementing fast state preparations or
transformations in other quantum systems, without requiring a solution to a
theoretical model of the system. Implications for fundamental physics and
cooling are discussed.Comment: 7 pages main text, 2 pages supporting informatio
Downregulation of E-Cadherin enhances proliferation of head and neck cancer through transcriptional regulation of EGFR
<p>Abstract</p> <p>Background</p> <p>Epidermal growth factor receptor (EGFR) has been reported to downregulate E-cadherin (E-cad); however, whether the downregulation of E-cad has any effect on EGFR expression has not been elucidated. Our previous studies have found an inverse correlation between EGFR and E-cad expression in tissue specimens of squamous cell carcinoma of the head and neck (SCCHN). To understand the biological mechanisms underlying this clinical observation, we knocked down E-cad expression utilizing E-cad siRNA in four SCCHN cell lines.</p> <p>Results</p> <p>It was observed that downregulation of E-cad upregulated EGFR expression compared with control siRNA-transfected cells after 72 hours. Cellular membrane localization of EGFR was also increased. Consequently, downstream signaling molecules of the EGFR signaling pathway, p-AKT, and p-ERK, were increased at 72 hours after the transfection with E-cad siRNA. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed EGFR mRNA was upregulated by E-cad siRNA as early as 24 hours. In addition, RT-PCR revealed this upregulation was due to the increase of EGFR mRNA stability, but not protein stability. Sulforhodamine B (SRB) assay indicated growth of E-cad knocked down cells was enhanced up to 2-fold more than that of control siRNA-transfected cells at 72-hours post-transfection. The effect of E-cad reduction on cell proliferation was blocked by treating the E-cad siRNA-transfected cells with 1 μM of the EGFR-specific tyrosine kinase inhibitor erlotinib.</p> <p>Conclusion</p> <p>Our results suggest for the first time that reduction of E-cad results in upregulation of EGFR transcriptionally. It also suggests that loss of E-cad may induce proliferation of SCCHN by activating EGFR and its downstream signaling pathways.</p
On the question of universality in \RPn and \On Lattice Sigma Models
We argue that there is no essential violation of universality in the
continuum limit of mixed \RPn and \On lattice sigma models in 2 dimensions,
contrary to opposite claims in the literature.Comment: 16 pages (latex) + 3 figures (Postscript), uuencode
A Study of a Wireless Smart Sensor Platform for Practical Training
[[abstract]]In order to overcome the obstacles in traditional experimenting and practical training courses, as well as in enhancing the functions of the present e-learning system, the study took sensor network technology as the foundation in developing a web services system. The system will be able to make presentations of the students ‘operations and results on an immediate basis, allowing the students to be guided adequately as they face problems during experiment and practical training.[[booktype]]紙
Homer 2 tunes G protein–coupled receptors stimulus intensity by regulating RGS proteins and PLCβ GAP activities
Homers are scaffolding proteins that bind G protein–coupled receptors (GPCRs), inositol 1,4,5-triphosphate (IP3) receptors (IP3Rs), ryanodine receptors, and TRP channels. However, their role in Ca2+ signaling in vivo is not known. Characterization of Ca2+ signaling in pancreatic acinar cells from Homer2−/− and Homer3−/− mice showed that Homer 3 has no discernible role in Ca2+ signaling in these cells. In contrast, we found that Homer 2 tunes intensity of Ca2+ signaling by GPCRs to regulate the frequency of [Ca2+]i oscillations. Thus, deletion of Homer 2 increased stimulus intensity by increasing the potency for agonists acting on various GPCRs to activate PLCβ and evoke Ca2+ release and oscillations. This was not due to aberrant localization of IP3Rs in cellular microdomains or IP3R channel activity. Rather, deletion of Homer 2 reduced the effectiveness of exogenous regulators of G proteins signaling proteins (RGS) to inhibit Ca2+ signaling in vivo. Moreover, Homer 2 preferentially bound to PLCβ in pancreatic acini and brain extracts and stimulated GAP activity of RGS4 and of PLCβ in an in vitro reconstitution system, with minimal effect on PLCβ-mediated PIP2 hydrolysis. These findings describe a novel, unexpected function of Homer proteins, demonstrate that RGS proteins and PLCβ GAP activities are regulated functions, and provide a molecular mechanism for tuning signal intensity generated by GPCRs and, thus, the characteristics of [Ca2+]i oscillations
High-Performance Screen-Printed Thermoelectric Films on Fabrics.
Printing techniques could offer a scalable approach to fabricate thermoelectric (TE) devices on flexible substrates for power generation used in wearable devices and personalized thermo-regulation. However, typical printing processes need a large concentration of binder additives, which often render a detrimental effect on electrical transport of the printed TE layers. Here, we report scalable screen-printing of TE layers on flexible fiber glass fabrics, by rationally optimizing the printing inks consisting of TE particles (p-type Bi0.5Sb1.5Te3 or n-type Bi2Te2.7Se0.3), binders, and organic solvents. We identified a suitable binder additive, methyl cellulose, which offers suitable viscosity for printability at a very small concentration (0.45-0.60 wt.%), thus minimizing its negative impact on electrical transport. Following printing, the binders were subsequently burnt off via sintering and hot pressing. We found that the nanoscale defects left behind after the binder burnt off became effective phonon scattering centers, leading to low lattice thermal conductivity in the printed n-type material. With the high electrical conductivity and low thermal conductivity, the screen-printed TE layers showed high room-temperature ZT values of 0.65 and 0.81 for p-type and n-type, respectively
Dissolution of Spinel Oxides and Capacity Losses in 4 V Li/LixMn2O4 Cells
Dissolution of spinel manganese oxides and the concomitant cathodic capacity losses were examined in 4 V Li/PC +
DME + LiClO4/LiMn2O4 cells where PC is propylene carbonate and DME is dimethoxyethane. Dissolved Mn2 contents
in the electrolytes were analyzed as a function of cathode potential and carbon contents in the composite cathodes.
Characteristically, manganese dissolution was notably high at the charged state (at >4.1 V vs. Li/Lit), in which potential
range an electrochemical oxidation of the solvent molecules was also prominent. From this and another observation
whereby the Mn dissolution increased with increasing carbon content in the composite cathodes, it was proposed that, at
the charged state of the cathode the solvent molecules are electrochemically oxidized on carbon surfaces and an as-generated
species promotes the manganese dissolution. Results of an ac impedance study revealed that Mn dissolution brings
about an increase in contact resistances at the Mn-depleted spinel/carbon interface, and also in the electrode reaction
resistances for Li intercalation/deintercalation. Thus, the Mn dissolution causes capacity losses in two different pathways;
material loss of the loaded spinel and polarization loss due to a cell resistance increment. The former prevailed
when cathodes contained excess amounts of carbon, while the latter became more of a problem as the carbon contents
decreased
Exponential Type Complex and non-Hermitian Potentials in PT-Symmetric Quantum Mechanics
Using the NU method [A.F.Nikiforov, V.B.Uvarov, Special Functions of
Mathematical Physics, Birkhauser,Basel,1988], we investigated the real
eigenvalues of the complex and/or - symmetric, non-Hermitian and the
exponential type systems, such as Poschl-Teller and Morse potentials.Comment: 14 pages, Late
Highly Oriented Liquid Crystal Semiconductor for Organic Field-Effect Transistors
We report a mesogenic compound which introduces nematic liquid crystal (LC) ordering into the benzothienobenzothiophene (BTBT) family of LCs, creating a new class of LC semiconducting materials which respond in a facile way to anisotropic surfaces, and can, thereby, be effectively processed into highly oriented monodomains. Measurement on these domains of the electrical conductivity, with in situ monitoring of domain quality and orientation using LC birefringence textures in electroded cells, brings a new era of precision and reliability to the determination of anisotropic carrier mobility in LC semiconductors
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