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Mei, Ming, Minju Kim, Minwoo Kim, Inhong Kim, Hong Seok Lee, Robert A. Taylor i Kwangseuk Kyhm. "Optical Gain of Vertically Coupled Cd0.6Zn0.4Te/ZnTe Quantum Dots". Nanomaterials 13, nr 4 (13.02.2023): 716. http://dx.doi.org/10.3390/nano13040716.
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The optical modal gain of Cd0.6Zn0.4Te/ZnTe double quantum dots was measured using a variable stripe length method, where large and small quantum dots are separated with a ZnTe layer. With a large (~18 nm) separation layer thickness of ZnTe, two gain spectra were observed, which correspond to the confined exciton levels of the large and small quantum dots, respectively. With a small (~6 nm) separation layer thickness of ZnTe, a merged single gain spectrum was observed. This can be attributed to a coupled state between large and small quantum dots. Because the density of large quantum dots (4 × 1010 cm−2) is twice the density of small quantum dots (2 × 1010 cm−2), the density of the coupled quantum dots is determined by that of small quantum dots. As a result, we found that the peak gain (123.9 ± 9.2 cm−1) with the 6 nm separation layer is comparable to that (125.2 ± 29.2 cm−1) of the small quantum dots with the 18 nm separation layer.
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Wang, Feng, Niladri S. Karan, Hue Minh Nguyen, Benjamin D. Mangum, Yagnaseni Ghosh, Chris J. Sheehan, Jennifer A. Hollingsworth i Han Htoon. "Quantum Dots: Quantum Optical Signature of Plasmonically Coupled Nanocrystal Quantum Dots (Small 38/2015)". Small 11, nr 38 (październik 2015): 5176. http://dx.doi.org/10.1002/smll.201570238.
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Shang, Xiangjun, Hanqing Liu, Xiangbin Su, Shulun Li, Huiming Hao, Deyan Dai, Zesheng Chen, Haiqiao Ni i Zhichuan Niu. "Light Hole Excitons in Strain-Coupled Bilayer Quantum Dots with Small Fine-Structure Splitting". Crystals 12, nr 8 (10.08.2022): 1116. http://dx.doi.org/10.3390/cryst12081116.
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In this work, we measure polarization-resolved photoluminescence spectra from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) at the telecom O-band with strain-coupled bilayer structure. QDs often show fine-structure splitting (FSS) ~100 μeV in uniform anisotropy and valence-band mixing of heavy holes (HH) and light holes (LH); the biaxial strain also induces LH excitons with small FSS (especially XX, <5 μeV, 70% of QDs); delocalized LH reduces the Coulomb interaction between holes Vhh and enhances population on LH excitons XX, XX11, X11+ and XX21+.
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Najdi, M. A., J. M. AL-Mukh i H. A. Jassem. "Theoretical Investigation in Coherent Manipulation throughout the Calculation of the Local Density of States in FM-DQD-FM Device". Materials Science Forum 1039 (20.07.2021): 451–69. http://dx.doi.org/10.4028/www.scientific.net/msf.1039.451.
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In this work, theoretical investigation in coherent manipulation throughout local density of states calculation for serially coupled double quantum dots embedded between ferromagnetic leads (FM-QD1-QD2-FM) by using the non-equilibrium Green's function approach. Since the local density of states are formulated incorporating the spin polarization and the type of spin configuration on the leads. Our model incorporates the inter-dot hopping, the intra-dot Coulomb correlation, the spin exchange energy and the coupling interactions between the quantum dots and leads. The results concerned to the parallel configuration at strong inter-dot coupling regime shows that the spin down electrons in the quantum dots may be more coupled coherently if the regime is tuned. The local density of states of the two dots for spin up electrons shows a broad hump with small splitting i.e. the case is decoherent for spin up electrons. In the case of weak interdot coupling it is obvious that the spin dependent density of states on the quantum dots show that the resonances are not well splitted. For the antiparallel configuration in the strong coupling regime, the spin dependent density of states of the double quantum dots show four peaks but with broaden and overlapping. In the case of weak coupling regime, the total spin dependent density of states, which have two peaks with certain board, one can conclude that the states are not coupled coherently. The case of the antiferromagnetic nature of the spin exchange interaction, our calculations for the parallel and antiparallel configurations (in strong and weak regimes) show a decoherence state.
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FORTUNA, LUIGI, i DOMENICO PORTO. "QUANTUM-CNN TO GENERATE NANOSCALE CHAOTIC OSCILLATORS". International Journal of Bifurcation and Chaos 14, nr 03 (marzec 2004): 1085–89. http://dx.doi.org/10.1142/s0218127404009624.
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In this letter we consider coupled quantum-dot cells, which are usually used for Quantum-dots Cellular Automata (QCA), to build Cellular Nonlinear Networks. In particular, it is shown how simple connection of few quantum-dot cells (even two of them) can cause the onset of chaotic oscillation only with small differences of polarizations and template between cells. An example of polarizations evolution in two adjacent cells is reported where hyperchaotic behavior has been observed. The richness of dynamics of Quantum CNN with only few dots is also emphasized.
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Shang, Xiangjun, Shulun Li, Hanqing Liu, Xiangbin Su, Huiming Hao, Deyan Dai, Xiaoming Li i in. "Single- and Twin-Photons Emitted from Fiber-Coupled Quantum Dots in a Distributed Bragg Reflector Cavity". Nanomaterials 12, nr 7 (5.04.2022): 1219. http://dx.doi.org/10.3390/nano12071219.
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In this work, we develop single-mode fiber devices of an InAs/GaAs quantum dot (QD) by bonding a fiber array with large smooth facet, small core, and small numerical aperture to QDs in a distributed Bragg reflector planar cavity with vertical light extraction that prove mode overlap and efficient output for plug-and-play stable use and extensive study. Modulated Si doping as electron reservoir builds electric field and level tunnel coupling to reduce fine-structure splitting (FSS) and populate dominant XX and higher excitons XX+ and XXX. Epoxy package thermal stress induces light hole (lh) with various behaviors related to the donor field: lh h1 confined with more anisotropy shows an additional XZ line (its space to the traditional X lines reflects the field intensity) and larger FSS; lh h2 delocalized to wetting layer shows a fast h2–h1 decay; lh h2 confined shows D3h symmetric higher excitons with slow h2–h1 decay and more confined h1 to raise h1–h1 Coulomb interaction.
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Zhang, Ming-Zhen, Yong Yu, Rong-Na Yu, Min Wan, Rong-Ying Zhang i Yuan-Di Zhao. "Quantum Dots: Tracking the Down-Regulation of Folate Receptor-α in Cancer Cells through Target Specific Delivery of Quantum Dots Coupled with Antisense Oligonucleotide and Targeted Peptide (Small 24/2013)". Small 9, nr 24 (12.12.2013): 4182. http://dx.doi.org/10.1002/smll.201370155.
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Song, Er-Qun, Zhi-Ling Zhang, Qing-Ying Luo, Wen Lu, Yun-Bo Shi i Dai-Wen Pang. "Tumor Cell Targeting Using Folate-Conjugated Fluorescent Quantum Dots and Receptor-Mediated Endocytosis". Clinical Chemistry 55, nr 5 (1.05.2009): 955–63. http://dx.doi.org/10.1373/clinchem.2008.113423.
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Abstract Background: Luminescent nanobioprobes with cell-targeting specificity are likely to find important applications in bioanalysis, biomedicine, and clinical diagnosis. Quantum dots (QDs) are unique and promising materials for such a purpose because of their fluorescence and large surface area for attaching cell-targeting molecules. Methods: We produced water-dispersible QDs by coating hydrophobic QDs with small amphiphilic polyethylene glycol (PEG) molecules via hydrophobic interactions. We covalently coupled folate (FA) onto the water-dispersible PEG-coated QDs (PEG-QDs) to produce FA-coupled PEG-QDs (FA-PEG-QDs). Results: These FA-PEG-QD nanoparticles functioned as fluorescent nanobioprobes that specifically recognized folate receptors (FRs) overexpressed in human nasopharyngeal cells (KB cells) but not in an FR-deficient lung carcinoma cell line (A549 cells). Using confocal fluorescence microscopy, we demonstrated uptake of FA-PEG-QDs by KB cells but no uptake of folate-free PEG-QDs. The specificity of this receptor-mediated internalization was confirmed by comparing the uptake by KB vs A549 cells. Conclusions: Our results suggest that such cell-targeting fluorescent nanobioprobes are potentially very powerful tools for recognizing target cells and delivering and tracking drugs and other therapeutic materials.
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Najdi, M. A. "The Charge and Spin Thermoelectric Properties across Double Quantum Dots Serially Coupled to Ferromagnetic Leads: The Case of Parallel Magnetic Configuration". BASRA JOURNAL OF SCIENCE 40, nr 1 (3.06.2022): 107–27. http://dx.doi.org/10.29072/basjs.20220106.
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In this article, the charge and spin thermoelectric properties of double quantum dots system connected to ferromagnetic leads with collinear magnetic configurations will be studied in the linear response regime. Our results are calculated in a strong interdot coupling regime by taking into consideration all parameters affecting the system such as interaction between dots and their coupling to the leads, intradot Coulomb correlation energy and spin-polarization on the leads. It is found that in the parallel magnetic configuration, the thermoelectric efficiency can reach a large value around the spin-down resonance levels when the tunneling coupling between the quantum dots and the leads for the spin-down electrons are small, which leads to the pure spin Seebeck contribution. As a result, this system can generate a spin-polarized current. The value of the spin figure of merit is enhanced by increasing the spin-polarization and decreasing the correlation energy.
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Gaumet, Jean-Jacques, Gabriel Gaiffe, Clément Dezanet, Stéphane Dalmasso, Pierre Magri, Lavinia Balan i Raphaël Schneider. "Monitoring the size and the stability of zinc oxide quantum dots in biological media: a soft ionization mass spectrometry technique (MALDI-TOF-MS)". MRS Proceedings 1793 (2015): 7–12. http://dx.doi.org/10.1557/opl.2015.620.
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ABSTRACTWe present herein a joint physical/physico-chemical study and, more specifically, the first application of Matrix Assisted Laser Desorption Ionization coupled with Time of Flight Mass Spectrometry (MALDI-TOF-MS) to analyze small-sized ZnO quantum dots (QDs) (2.8-3.1 nm diameter range) synthesized by sol-gel chemistry and stabilized through an aminosilane coating. A careful investigation of the stability of ZnO QDs was initiated once these dots were dispersed in different media (water, biological buffer) for a period up to 3 weeks. Positive ion mode mass spectra MALDI-TOF-MS combined with optical spectrometry was used to monitor the stability of ZnO QDs when aging. Such a unique combination of MALDI-TOF-MS and physico-chemical techniques is likely to bring new insights into the structure analysis, the stability and consequently the potential toxicity of QDs.
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KRÁL, KAREL, i CHUNG-YI LIN. "PHONON EXCESS HEATING IN ELECTRONIC RELAXATION THEORY IN QUANTUM DOTS". International Journal of Modern Physics B 22, nr 20 (10.08.2008): 3439–60. http://dx.doi.org/10.1142/s0217979208048577.
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When the usual operator of the Fröhlich's coupling between electrons and longitudinal optical phonons of semiconductor single quantum dot is used to calculate electronic energy relaxation, a permanent phonon generation in quantum dot is obtained, leading to an artificial effect of permanent heating up of the lattice. The mechanism of the phonon heating is identified here with the influence of the transverse part of the interaction operator. This part is responsible first of all for a tendency to build the polaronic well of an electron in a quantum dot. The effect of overheating is shown to be possibly eliminated to a considerable extent upon removing the transverse part of the interaction with the help of the Lang–Firsov canonical transformation and upon modifying accordingly the longitudinal part of the coupling. The resulting electronic relaxation and optical phonon generation is demonstrated numerically in a relatively simple approximation to electron and phonon self-energy, in which the model of quantum dot is reduced to an electron coupled to a single-LO-phonon mode. It is interesting to see that the removal of the phonon overheating based on the application of the Lang–Firsov canonical transformation has a rather small influence on electronic characteristics calculated with electronic transport equations. In this sense, the long-time limit properties of the electronic subsystem, like the electronic up-conversion and incomplete depopulation effect, calculated earlier, remain nearly untouched.
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Guslienko, K. Yu. "Magnetic Vortex State Stability, Reversal and Dynamics in Restricted Geometries". Journal of Nanoscience and Nanotechnology 8, nr 6 (1.06.2008): 2745–60. http://dx.doi.org/10.1166/jnn.2008.18305.
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Magnetic vortices are typically the ground states in geometrically confined ferromagnets with small magnetocrystalline anisotropy. In this article I review static and dynamic properties of the magnetic vortex state in small particles with nanoscale thickness and sub-micron and micron lateral sizes (magnetic dots). Magnetic dots made of soft magnetic material shaped as flat circular and elliptic cylinders are considered. Such mesoscopic dots undergo magnetization reversal through successive nucleation, displacement and annihilation of magnetic vortices. The reversal process depends on the stability of different possible zero-field magnetization configurations with respect to the dot geometrical parameters and application of an external magnetic field. The interdot magnetostatic interaction plays an important role in magnetization reversal for dot arrays with a small dot-to-dot distance, leading to decreases in the vortex nucleation and annihilation fields. Magnetic vortices reveal rich, non-trivial dynamical properties due to existance of the vortex core bearing topological charges. The vortex ground state magnetization distribution leads to a considerable modification of the nature of spin excitations in comparison to those in the uniformly magnetized state. A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized lateral dimensions possesses a characteristic dynamic excitation known as a translational mode that corresponds to spiral-like precession of the vortex core around its equilibrium position. The translation motions of coupled vortices are considered. There are, above the vortex translation mode eigenfrequencies, several dynamic magnetization eigenmodes localized outside the vortex core whose frequencies are determined principally by dynamic demagnetizing fields appearing due to restricted dot geometry. The vortex excitation modes are classified as translation modes and radially or azimuthally symmetric spin waves over the vortex ground state. Studying the spin eigenmodes in such systems provides valuable information to relate the particle dynamical response to geometrical parameters. Unresolved problems are identified to attract attention of researchers working in the area of nanomagnetism.
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Yakimov, Andrew I., Victor V. Kirienko, Dmitrii E. Utkin i Anatoly V. Dvurechenskii. "Light-Trapping-Enhanced Photodetection in Ge/Si Quantum Dot Photodiodes Containing Microhole Arrays with Different Hole Depths". Nanomaterials 12, nr 17 (30.08.2022): 2993. http://dx.doi.org/10.3390/nano12172993.
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Photodetection based on assemblies of quantum dots (QDs) is able to tie the advantages of both the conventional photodetector and unique electronic properties of zero-dimensional structures in an unprecedented way. However, the biggest drawback of QDs is the small absorbance of infrared radiation due to the low density of the states coupled to the dots. In this paper, we report on the Ge/Si QD pin photodiodes integrated with photon-trapping hole array structures of various thicknesses. The aim of this study was to search for the hole array thickness that provided the maximum optical response of the light-trapping Ge/Si QD detectors. With this purpose, the embedded hole arrays were etched to different depths ranging from 100 to 550 nm. By micropatterning Ge/Si QD photodiodes, we were able to redirect normal incident light laterally along the plane of the dots, therefore facilitating the optical conversion of the near-infrared photodetectors due to elongation of the effective absorption length. Compared with the conventional flat photodetector, the responsivity of all microstructured devices had a polarization-independent improvement in the 1.0–1.8-μm wavelength range. The maximum photocurrent enhancement factor (≈50× at 1.7 μm) was achieved when the thickness of the photon-trapping structure reached the depth of the buried QD layers.
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Liu, Qing, Yuan Pu, Zhijian Zhao, Jiexin Wang i Dan Wang. "Synthesis of Silver Sulfide Quantum Dots Via the Liquid–Liquid Interface Reaction in a Rotating Packed Bed Reactor". Transactions of Tianjin University 26, nr 4 (27.12.2019): 273–82. http://dx.doi.org/10.1007/s12209-019-00228-5.
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AbstractWe developed the high-gravity coupled liquid–liquid interface reaction technique on the basis of the rotating packed bed (RPB) reactor for the continuous and ultrafast synthesis of silver sulfide (Ag2S) quantum dots (QDs) with near-infrared (NIR) luminescence. The formation of Ag2S QDs occurs at the interface of microdroplets, and the average size of Ag2S QDs was 4.5 nm with a narrow size distribution. Ag2S QDs can disperse well in various organic solvents and exhibit NIR luminescence with a peak wavelength at 1270 nm under 980-nm laser excitation. The mechanism of the process intensification was revealed by both the computational fluid dynamics simulation and fluorescence imaging, and the mechanism is attributed to the small and uniform droplet formation in the RPB reactor. This study provides a novel approach for the continuous and ultrafast synthesis of NIR Ag2S QDs for potential scale-up.
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Feng, Wei, Lupei Qin i Xin-Qi Li. "Cross correlation mediated by Majorana island with finite charging energy". New Journal of Physics 23, nr 12 (1.12.2021): 123032. http://dx.doi.org/10.1088/1367-2630/ac3efc.
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Abstract Based on the many-particle-number-state treatment for transport through a pair of Majorana zero modes (MZMs) which are coupled to the leads via two quantum dots, we identify that the reason for zero cross correlation of currents at uncoupling limit between the MZMs is from a degeneracy of the teleportation and the Andreev process channels. We then propose a scheme to eliminate the degeneracy by introducing finite charging energy on the Majorana island which allows for coexistence of the two channels. We find nonzero cross correlation established even in the Majorana uncoupling limit (and also in the small charging energy limit), which demonstrates well the teleportation or nonlocal nature of the MZMs. More specifically, the characteristic structure of coherent peaks in the power spectrum of the cross correlation is analyzed to identify the nonlocal and coherent coupling mechanism between the MZMs and the quantum dots. We also display the behaviors of peak shift with variation of the Majorana coupling energy, which can be realized by modulating parameters such as the magnetic field.
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BHATTACHARYA, PALLAB. "QUANTUM DOT SEMICONDUCTOR LASERS". International Journal of High Speed Electronics and Systems 09, nr 04 (grudzień 1998): 1081–107. http://dx.doi.org/10.1142/s0129156498000427.
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The formation of coherently strained islands during the growth of strained heterostructures has been exploited to form an array of quantum dots. The shape and size of the islands vary with growth parameters, but exhibit the electronic properties of zero-dimensional systems. One or multiple, vertically coupled, layers of such quantum dots can form the gain region of a separately confined heterostructure (SCH) laser. The properties of such InGaAs/GaAs self-organized quantum dot lasers are described here. The lasers exhibit temperature independent operation up to 100 K and beyond. Typical threshold currents of 200 μm long room temperature lasers vary from 6 to 20 mA. The small-signal modulation bandwidths of ridge waveguide lasers are 5–7.5 GHz at 300 K and increased to >20 GHz at 80 K. We believe that electron-hole scattering intrinsically limits the high-speed performance of these devices, in spite of differential gains as high as ~ 7× 10-14 cm2 at room temperature. Wavelength switching is demonstrated in these devices and preliminary results on long-wavelengths intersubband quantum dot light emitters are also presented.
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Guskov, Vladislav, Fabian Langkabel, Matthias Berg i Annika Bande. "An Impurity Effect for the Rates of the Interparticle Coulombic Decay". Quarks: Brazilian Electronic Journal of Physics, Chemistry and Materials Science 3, nr 1 (28.11.2020): 17–30. http://dx.doi.org/10.34019/2674-9688.2020.v3.31928.
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The interparticle Coulombic decay is a synchronized decay and ionization phenomenon occurring on two separated and only Coulomb interaction coupled electron binding sites. This publication explores how drastically small environmental changes in between the two sites, basically impurities, can alter the ionization properties and process rate, although the involved electronic transitions remain unaltered. A comparison among the present electron dynamics calculations for the example of different types of quantum dots, accommodating a one- or a two-dimensional continuum for the outgoing electron, and the well-investigated atomic and molecular cases with three-dimensional continuum, reveals that the impurity effect is most pronounced the stronger that electron is confined. This necessarily leads to challenges and opportunities in a quantum dot experiment to prove the interparticle Coulombic decay.
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Zhai, Tianrui, Xiaojie Ma, Liang Han, Shuai Zhang, Kun Ge, Yanan Xu, Zhiyang Xu i Libin Cui. "Self-Aligned Emission of Distributed Feedback Lasers on Optical Fiber Sidewall". Nanomaterials 11, nr 9 (13.09.2021): 2381. http://dx.doi.org/10.3390/nano11092381.
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This article assembles a distributed feedback (DFB) cavity on the sidewalls of the optical fiber by using very simple fabrication techniques including two-beam interference lithography and dip-coating. The DFB laser structure comprises graduated gratings on the optical fiber sidewalls which are covered with a layer of colloidal quantum dots. Directional DFB lasing is observed from the fiber facet due to the coupling effect between the grating and the optical fiber. The directional lasing from the optical fiber facet exhibits a small solid divergence angle as compared to the conventional laser. It can be attributed to the two-dimensional light confinement in the fiber waveguide. An analytical approach based on the Bragg condition and the coupled-wave theory was developed to explain the characteristics of the laser device. The intensity of the output coupled laser is tuned by the coupling coefficient, which is determined by the angle between the grating vector and the fiber axis. These results afford opportunities to integrate different DFB lasers on the same optical fiber sidewall, achieving multi-wavelength self-aligned DFB lasers for a directional emission. The proposed technique may provide an alternative to integrating DFB lasers for applications in networking, optical sensing, and power delivery.
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HO, Y. L. D., T. CAO, P. S. IVANOV, M. J. CRYAN, I. J. CRADDOCK, C. J. RAILTON i J. G. RARITY. "OPTIMAL DESIGN OF SINGLE-PHOTON SOURCE EMISSION FROM A QUANTUM-DOT IN MICRO-PILLAR MICROCAVITY". International Journal of Quantum Information 03, supp01 (listopad 2005): 229–38. http://dx.doi.org/10.1142/s0219749905001419.
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We have modelled wavelength scale micro-pillar microcavities of group III-V semiconductor materials using the 3-D finite difference time domain (FDTD) method. A broad band dipole source within the microcavity probes the microcavity mode structure and spectrum. We then investigated the modifications to spontaneous emission of photons form narrowband emitters (e.g. quantum dots) at the centre of the resonance. We find strongly enhanced emission due to small modal volumes and high quality factor (Q-factor). A large fraction of the quantum-dot spontaneous emission is coupled into the fundamental cavity mode. Increasing the number of mirror pairs in the bottom distributed Bragg reflector (DBR) obviously reduces the bottom light leakage, leading to light collection efficiency up to 90%. Moreover, we are now looking at more sophisticated structures with both lateral and perpendicular confinements based on annular and photonic crystal defect cavities in order to suppress the remaining sidewall scattering.
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Cunha, Elisabete M., Maria João R. Oliveira, Paula G. Ferreira i Artur P. Águas. "Mercury intake by inflammatory phagocytes: in vivo cytology of mouse macrophages and neutrophils by X-ray elemental microanalysis coupled with scanning electron microscopy". Human & Experimental Toxicology 23, nr 9 (wrzesień 2004): 447–53. http://dx.doi.org/10.1191/0960327104ht472oa.
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Phagocytes remove and store mercury (Hg) that enters the body. Macrophages and granulocytes respond in opposite ways to Hg: macrophages loose cell viability, and neutrophils become protected from apoptosis. We have investigated the cytology of early intake of Hg by macrophages and neutrophils after a short period (2-4 min) of in vivo exposure to HgCl2. The two types of phagocytes were attracted either to a subcutaneous air pouch or to the peritoneal cavity of BALB/c mice by in situ BSA injection. BSA caused, 72 hours later, inflammatory exudates where neutrophils (air-pouch cavity) or macrophages (peritoneal cavity) were the predominant cell type. A lethal dose of HgCl2 (25 mg) was then injected in the two inflammatory cavities. The mice died 2-4 min later and the cell exudates were harvested and studied by scanning electron microscopy coupled with X-ray elemental microanalysis (SEM-XRM). More than half of the phagocytes showed ingested Hg; a higher percentage of macrophages (around 70%) than neutrophils (around 50%) were positive for the metal. Intracellular particles of Hg were spheroid and presented a small diameter (less than 20 nm). They could be seen in large numbers inside phagocytes (up to 20-30 Hg dots per cell); they were scattered throughout the cytoplasm of the cells. The ability of phagocytes to ingest Hg increased as the BSA-induced inflammation progressed. We conclude that (i) Hg is quickly ingested as small particles by phagocytes; (ii) endocytosis of Hg increases with the degree of activation of phagocytes; and (iii) phagocytes internalize Hg by pinocytosis.
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Peckys, Diana B., Dalia Alansary, Barbara A. Niemeyer i Niels de Jonge. "Visualizing Quantum Dot Labeled ORAI1 Proteins in Intact Cells Via Correlative Light and Electron Microscopy". Microscopy and Microanalysis 22, nr 4 (sierpień 2016): 902–12. http://dx.doi.org/10.1017/s1431927616011491.
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AbstractORAI1 proteins are ion channel subunits and the essential pore-forming units of the calcium release-activated calcium channel complex essential for T-cell activation and many other cellular processes. In this study, we used environmental scanning electron microscopy (ESEM) with scanning transmission electron microscopy (STEM) detection to image plasma membrane expressed ORAI1 proteins in whole Jurkat T cells in the liquid state. Utilizing a stably transfected Jurkat T cell clone expressing human ORAI1 with an extracellular human influenza hemagglutinin (HA) tag we investigated if liquid-phase STEM can be applied to detect recombinant surface expressed protein. Streptavidin coated quantum dots were coupled in a one-to-one stoichiometry to ORAI1 proteins detected by biotinylated anti-HA fragmented antibody fragments. High-resolution electron microscopic images revealed the individual label locations from which protein pair distances were determined. These data were analyzed using the pair correlation function and, in addition, an analysis of cluster size and frequency was performed. ORAI1 was found to be present in hexamers in a small fraction only, and ORAI1 resided mostly in monomers and dimers.
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Wang, Feng, Niladri S. Karan, Hue Minh Nguyen, Benjamin D. Mangum, Yagnaseni Ghosh, Chris J. Sheehan, Jennifer A. Hollingsworth i Han Htoon. "Quantum Optical Signature of Plasmonically Coupled Nanocrystal Quantum Dots". Small 11, nr 38 (3.07.2015): 5028–34. http://dx.doi.org/10.1002/smll.201500823.
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Sciortino, Alice, Andrea Cannizzo i Fabrizio Messina. "Carbon Nanodots: A Review—From the Current Understanding of the Fundamental Photophysics to the Full Control of the Optical Response". C 4, nr 4 (13.12.2018): 67. http://dx.doi.org/10.3390/c4040067.
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Carbon dots (CDs) are an emerging family of nanosystems displaying a range of fascinating properties. Broadly speaking, they can be described as small, surface-functionalized carbonaceous nanoparticles characterized by an intense and tunable fluorescence, a marked sensitivity to the environment and a range of interesting photochemical properties. CDs are currently the subject of very intense research, motivated by their possible applications in many fields, including bioimaging, solar energy harvesting, nanosensing, light-emitting devices and photocatalyis. This review covers the latest advancements in the field of CDs, with a focus on the fundamental understanding of their key photophysical behaviour, which is still very debated. The photoluminescence mechanism, the origin of their peculiar fluorescence tunability, and their photo-chemical interactions with coupled systems are discussed in light of the latest developments in the field, such as the most recent results obtained by femtosecond time-resolved experiments, which have led to important steps forward in the fundamental understanding of CDs. The optical response of CDs appears to stem from a very complex interplay between the electronic states related to the core structure and those introduced by surface functionalization. In addition, the structure of CD energy levels and the electronic dynamics triggered by photo-excitation finely depend on the microscopic structure of any specific sub-type of CD. On the other hand, this remarkable variability makes CDs extremely versatile, a key benefit in view of their very wide range of applications.
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Barba-Vicente, Víctor, María Jesús Almendral Parra, Juan Francisco Boyero-Benito, Carlota Auría-Soro, Pablo Juanes-Velasco, Alicia Landeira-Viñuela, Álvaro Furones-Cuadrado, Ángela-Patricia Hernández, Raúl Manzano-Román i Manuel Fuentes. "Detection of Human p53 In-Vitro Expressed in a Transcription-Translation Cell-Free System by a Novel Conjugate Based on Cadmium Sulphide Nanoparticles". Nanomaterials 10, nr 5 (21.05.2020): 984. http://dx.doi.org/10.3390/nano10050984.
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Here, cadmium sulphide quantum dots (CdS QDs) have been synthetized and functionalized with Bovine Serum Albumin (BSA) in a colloidal aqueous solution with a stability of over 3 months. Specific synthesis conditions, in homogeneous phase and at low temperature, have allowed limitation of S2− concentration, hence, as a consequence, there is restricted growth of the nanoparticles (NPs). This fact allows binding with BSA in the most favorable manner for the biomolecule. The presence of Cd2+ ions on the surface of the CdS nanoparticle is counteracted by the negatively charged domains of the BSA, resulting in the formation of small NPs, with little tendency for aggregation. Temperature and pH have great influence on the fluorescence characteristics of the synthetized nanoparticles. Working at low temperatures (4 °C) and pH 10–11 have proven the best result as shown by hydrolysis kinetic control of the thioacetamide precursor of S2− ion. Biological activity of the coupled BSA is maintained allowing subsequent bioconjugation with other biomolecules such as antibodies. The chemical conjugation with anti-Glutathione S-transferase (α-GST) antibody, a common tag employed in human recombinant fusion proteins, produces a strong quenching of fluorescence that proves the possibilities of its use in biological labelling. Finally, p53, onco-human recombinant protein (GST tagged in COOH terminus), has been in situ IVTT (in vitro transcription-translation) expressed and efficiently captured by the α-GST-CdS QD conjugate as a proof of the biocompatibility on IVTT systems and the functionality of conjugated antibody.
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Hasegawa, Hideki, Hajime Fujikura i Hiroshi Okada. "Molecular-Beam Epitaxy and Device Applications of III-V Semiconductor Nanowires". MRS Bulletin 24, nr 8 (sierpień 1999): 25–30. http://dx.doi.org/10.1557/s0883769400052866.
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A scaling-down of feature sizes into the nanometer range is a common trend in silicon and compound semiconductor advanced devices. That this trend will continue is clearly evidenced by the fact that the “roadmap” for the Si ultralarge-scale-integration circuit (USLI) industry targets production-level realization of a 70-nm minimum feature size for the year 2010. GaAs- and InP-based heterostructure devices such as high-electron-mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) have made remarkable progress by miniaturization, realizing ultrahigh speeds approaching the THz range with ultralow power consumption. Due to progress in nanofabrication technology, feature sizes of scaled-down transistors are rapidly approaching the Fermi wavelength of electrons in semiconductors, even at the production level. This fact may raise some concerns about the operation of present-day devices based on semiclassical principles.However, the progress of nanofabrication technology has opened up the exciting possibility of constructing novel quantum devices, based directly on quantum mechanics, by utilizing artificial structures such as quantum wells, wires, and dots. In these structures, new physical effects appear, such as the formation of new quantum states in single and coupled quantum structures, artificial miniband formation in superlattices, tunneling and resonant tunneling in single and multiple barriers, propagation of phase-coherent guided electron waves in quantum wires, conductance oscillations in small tunnel junctions due to single-electron tunneling, and so on. We expect that these effects will offer rich functionality in next-generation semiconductor quantum ULSIs based on artificial quantum structures, with feature sizes in the range of one to a few tens of nanometers. Beyond this, molecular-level ULSIs using exotic materials and various chemical and electrochemical processes other than the standard semiconductor ones may appear, butat present, they still seem to be too far in the future for realistic consideration for industrial applications.
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Peer, Akshit, Zhongjian Hu, Ajay Singh, Jennifer A. Hollingsworth, Rana Biswas i Han Htoon. "Photoluminescence Enhancement of CuInS2 Quantum Dots in Solution Coupled to Plasmonic Gold Nanocup Array". Small 13, nr 33 (5.07.2017): 1700660. http://dx.doi.org/10.1002/smll.201700660.
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Zhang, Cheng, Li Liu, Guangwen Yang, Ruizhe Li i Bin Wang. "A new adaptive data transfer library for model coupling". Geoscientific Model Development 9, nr 6 (9.06.2016): 2099–113. http://dx.doi.org/10.5194/gmd-9-2099-2016.
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Abstract. Data transfer means transferring data fields from a sender to a receiver. It is a fundamental and frequently used operation of a coupler. Most versions of state-of-the-art couplers currently use an implementation based on the point-to-point (P2P) communication of the message passing interface (MPI) (referred to as “P2P implementation” hereafter). In this paper, we reveal the drawbacks of the P2P implementation when the parallel decompositions of the sender and the receiver are different, including low communication bandwidth due to small message size, variable and high number of MPI messages, as well as network contention. To overcome these drawbacks, we propose a butterfly implementation for data transfer. Although the butterfly implementation outperforms the P2P implementation in many cases, it degrades the performance when the sender and the receiver have similar parallel decompositions or when the number of processes used for running models is small. To ensure data transfer with optimal performance, we design and implement an adaptive data transfer library that combines the advantages of both butterfly implementation and P2P implementation. As the adaptive data transfer library automatically uses the best implementation for data transfer, it outperforms the P2P implementation in many cases while it does not decrease the performance in any cases. Now, the adaptive data transfer library is open to the public and has been imported into the C-Coupler1 coupler for performance improvement of data transfer. We believe that other couplers can also benefit from this.
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Gao, Huihui, Hongcen Yang, Jinzhang Xu, Shouwei Zhang i Jiaxing Li. "Strongly Coupled g-C3 N4 Nanosheets-Co3 O4 Quantum Dots as 2D/0D Heterostructure Composite for Peroxymonosulfate Activation". Small 14, nr 31 (3.07.2018): 1801353. http://dx.doi.org/10.1002/smll.201801353.
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van Leeuwen, F. N., B. N. G. Giepmans, L. A. van Meeteren i W. H. Moolenaar. "Lysophosphatidic acid: mitogen and motility factor". Biochemical Society Transactions 31, nr 6 (1.12.2003): 1209–12. http://dx.doi.org/10.1042/bst0311209.
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LPA (lysophosphatidic acid), the simplest of al glycerophospholipids, is a potent inducer of cell proliferation, migration and survival. It does so by activating its cognate G-protein-coupled receptors, four of which have been identified. LPA receptors couple to at least three distinct G-proteins and thereby activate multiple signal transduction pathways, particularly those initiated by the small GTPases Ras, Rho and Rac. Our recent work has shown that LPA signals Rac activation via the Tiam1 GDP/GTP exchange factor and thereby stimulates cell migration. Here we discuss recent progress in our understanding of LPA action.
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Riano, Yvonne, Katharina Limacher, André Aschwanden, Sophie Hirsig i Doris Wastl-Walter. "Shaping gender inequalities: critical moments and critical places". Equality, Diversity and Inclusion: An International Journal 34, nr 2 (9.03.2015): 155–67. http://dx.doi.org/10.1108/edi-12-2013-0112.
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Purpose – There is much scientific interest in the connection between the emergence of gender-based inequalities and key biographical transition points of couples in long-term relationships. Little empirical research is available comparing the evolution of a couple’s respective professional careers over space and time. The purpose of this paper is to contribute to filling this gap by addressing the following questions: what are the critical biographical moments when gender (in)equalities within a relationship begin to arise and consolidate? Which biographical decisions precede and follow such critical moments? How does decision making at critical moments impact the opportunities of both relationship partners in gaining equal access to paid employment? Design/methodology/approach – These questions are addressed from the perspectives of intersectionality and economic citizenship. Biographical interviewing is used to collect the personal and professional narratives of Swiss-, bi-national and migrant couples. The case study of a Swiss-Norwegian couple illustrates typical processes by which many skilled migrant women end up absently or precariously employed. Findings – Analysis reveals that the Scandinavian woman’s migration to Switzerland is a primary and critical moment for emerging inequality, which is then reinforced by relocation (to a small town characterized by conservative gender values) and the subsequent births of their children. It is concluded that factors of traditional gender roles, ethnicity and age intersect to create a hierarchical situation which affords the male Swiss partner more weight in terms of decision making and career advancement. Practical implications – The paper’s findings are highly relevant to the formulation of policies regarding gender inequalities and the implementation of preventive programmes within this context. Originality/value – Little empirical research is available comparing the evolution of a couple’s respective professional careers over space and time. The originality of this paper is to fill this research gap; to include migration as a critical moment for gender inequalities; to use an intersectional and geographical perspective that have been given scant attention in the literature; to use the original concept of economic citizenship; and to examine the case of a bi-national couple, which has so far not been examined by the literature on couple relationships.
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An, Rui, Vera Gluscevic, Erminia Calabrese i J. Colin Hill. "What does cosmology tell us about the mass of thermal-relic dark matter?" Journal of Cosmology and Astroparticle Physics 2022, nr 07 (1.07.2022): 002. http://dx.doi.org/10.1088/1475-7516/2022/07/002.
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Abstract The presence of light thermally coupled dark matter affects early expansion history and production of light elements during the Big Bang Nucleosynthesis. Specifically, dark matter that annihilates into Standard Model particles can modify the effective number of light species in the universe N eff, as well as the abundance of light elements created buring BBN. These quantities in turn affect the cosmic microwave background (CMB) anisotropy. We present the first joint analysis of small-scale temperature and polarization CMB anisotropy from Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT), together with Planck data and the recent primordial abundance measurements of helium and deuterium to place comprehensive bounds on the mass of light thermal-relic dark matter. We consider a range of models, including dark matter that couples to photons and Standard-Model neutrinos. We discuss the sensitivity of the inferred mass bounds on measurements of N eff, primordial element abundances and the baryon density, and quantify the sensitivity of our results to a possible existence of additional relativistic species. We find that the combination of ACT, SPT, and Planck generally leads to the most stringent mass constraint for dark matter that couples to neutrinos, improving the lower limit by 40%–80%, with respect to previous Planck analyses. On the other hand, the addition of ACT and SPT leads to a slightly weaker bound on electromagnetically coupled particles, due to a shift in the preferred values of Y p and N eff driven by the ground based experiments. In most scenarios, the combination of CMB data has a higher constraining power than the primordial abundance measurements alone, with the best results achieved when all data are combined. Combining all CMB measurements with primordial abundance measurements, we rule out masses below ∼4 MeV at 95% confidence, for all models. We show that allowing for new relativistic species can weaken the mass bounds for dark matter that couples to photons by up to an order of magnitude or more. Finally, we discuss the reach of the next generation of the CMB experiments in terms of probing the mass of the thermal relic dark matter.
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Zajic, Lara B., Andrea K. Herndon, Liberty G. Sieberg, Amber L. Caress, Paula K. Morgan, Ryan J. Hansen, Luke A. Wittenburg, Daniel L. Gustafson i Jessica M. Quimby. "Assessment of absorption of transdermal ondansetron in normal research cats". Journal of Feline Medicine and Surgery 19, nr 12 (23.01.2017): 1245–48. http://dx.doi.org/10.1177/1098612x16688807.
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Objectives The objective of this study was to assess the absorption of transdermal ondansetron in healthy cats. Methods Five research cats with unremarkable complete blood count, biochemistry and urinalysis were used for both single- and multiple-dose application studies. For single-dose application, 4 mg ondansetron in 0.1 ml Lipoderm gel was applied once to the internal ear pinna. Blood samples were collected via jugular catheter over a 48 h period following administration (0, 15 mins, 30 mins, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h and 48 h). For multiple-dose application, 4 mg ondansetron in 0.1 ml Lipoderm gel was applied for five consecutive days before blood samples were obtained in the same manner. Serum was separated and frozen prior to analysis. Ondansetron was measured via liquid chromatography coupled to tandem mass spectrometry. Results Analysis revealed no clinically relevant drug levels in serum after either single- or multiple-dose administration of 4 mg transdermal ondansetron. Conclusions and relevance Transdermal application of 4 mg ondansetron does not result in clinically relevant serum concentrations of drug. Despite characteristics of the drug that imply suitability for transdermal application, this does not appear to be an acceptable method of drug delivery for this medication at this dose. This study highlights the importance of assessing the suitability of each medication for transdermal administration.
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Zhang, Ming-Zhen, Yong Yu, Rong-Na Yu, Min Wan, Rong-Ying Zhang i Yuan-Di Zhao. "Tracking the Down-Regulation of Folate Receptor-α in Cancer Cells through Target Specific Delivery of Quantum Dots Coupled with Antisense Oligonucleotide and Targeted Peptide". Small 9, nr 24 (5.07.2013): 4183–93. http://dx.doi.org/10.1002/smll.201300994.
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Williams, C. L., V. Y. Hayes, A. M. Hummel, J. E. Tarara i T. J. Halsey. "Regulation of E-cadherin-mediated adhesion by muscarinic acetylcholine receptors in small cell lung carcinoma." Journal of Cell Biology 121, nr 3 (1.05.1993): 643–54. http://dx.doi.org/10.1083/jcb.121.3.643.
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We present the first evidence that adhesion mediated by a member of the cadherin gene family can be regulated by a G protein-coupled receptor. We show that activating the M3 muscarinic acetylcholine receptor (mAChR) rapidly induces E-cadherin-mediated adhesion in a small cell lung carcinoma (SCLC) cell line. This response is inhibited by E-cadherin antibodies, and does not occur in another SCLC cell line which expresses functional mAChR but reduced levels of E-cadherin. Protein kinase C may be involved, since phorbol 12-myristate 13-acetate also induces E-cadherin-mediated aggregation. Immunofluorescence analyses indicate that mAChR activation does not grossly alter E-cadherin surface expression or localization at areas of cell-cell contact, suggesting mAChR activation may increase E-cadherin binding activity. Our findings suggest that G protein-coupled receptors may regulate processes involving cadherin-mediated adhesion, such as embryonic development, neurogenesis, and cancer metastasis.
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LIU, YUN, XIA-MENG SI i YAN-CHAO ZHANG. "COMPARING EFFECTS OF CLUSTER-COUPLED PATTERNS ON OPINION DYNAMICS". International Journal of Modern Physics C 23, nr 07 (lipiec 2012): 1250050. http://dx.doi.org/10.1142/s0129183112500507.
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Community structure is another important feature besides small-world and scale-free property of complex networks. Communities can be coupled through specific fixed links between nodes, or occasional encounter behavior. We introduce a model for opinion evolution with multiple cluster-coupled patterns, in which the interconnectivity denotes the coupled degree of communities by fixed links, and encounter frequency controls the coupled degree of communities by encounter behaviors. Considering the complicated cognitive system of people, the CODA (continuous opinions and discrete actions) update rules are used to mimic how people update their decisions after interacting with someone. It is shown that, large interconnectivity and encounter frequency both can promote consensus, reduce competition between communities and propagate some opinion successfully across the whole population. Encounter frequency is better than interconnectivity at facilitating the consensus of decisions. When the degree of social cohesion is same, small interconnectivity has better effects on lessening the competence between communities than small encounter frequency does, while large encounter frequency can make the greater degree of agreement across the whole populations than large interconnectivity can.
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Allegretto, W., i H. Xie. "Solutions for the microsensor thermistor equations in the small bias case". Proceedings of the Royal Society of Edinburgh: Section A Mathematics 123, nr 6 (1993): 987–99. http://dx.doi.org/10.1017/s0308210500029668.
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SynopsisThe behaviour of a microsensor thermistor is described by a system of nonlinear coupled elliptic equations subject to mixed Dirichlet-Neumann boundary conditions, to be solved on different domains. We employ the Implicit Function Theorem in Banach space to show that the system has a solution for small applied bias. It does not appear that earlier approaches for similar thermistor problems can be employed in this physically important situation. The fact that the problem is cast in a subset of R3 is significant in our presentation.
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Reif, U., F. M. Martini i G. Cosenza. "Tibial plateau levelling osteotomy in 69 small breed dogs using conically coupled 1.9/2.5 mm locking plates". Veterinary and Comparative Orthopaedics and Traumatology 28, nr 05 (2015): 347–54. http://dx.doi.org/10.3415/vcot-14-09-0135.
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SummaryObjective: To report clinical experiences with the tibial plateau levelling osteotomy (TPLO) procedure in small breed dogs with cranial cruciate ligament (CCL) disease using specific, conically coupled, 1.9/2.5 mm locking plates and evaluating short-term complications and outcome.Methods: Medical records of small breed dogs (<15 kg) that underwent TPLO using 1.9/2.5 mm locking plates were reviewed retrospectively. The preoperative, postoperative and six to eight weeks postoperative tibial plateau angle (TPA) measurements were determined from the radiographic images. Lameness evaluation was assessed subjectively preoperatively and six to eight weeks postoperatively.Results: Sixty-nine small breed dogs (n = 79 stifles) were included in the study. Mean (± SD) preoperative TPA was 29.0 ± 3.4°, postoperative TPA was 5.8 ± 2.5°, and six to eight weeks postoperative TPA was 7.3 ± 4.1°. Sixteen complications occurred in 12 out of 79 TPLO procedures: three were intra-operative (intra-articular screw placement) and 13 were postoperative complications, of which nine were identified as minor complications not requiring surgical reintervention, and four as major complications requiring additional surgical intervention, including tibial tuberosity fracture (n = 1), osteomyelitis (n = 1), screw failure (n = 1), and plate breakage (n = 1). Lameness scores by clinical assessment reduced from a median value of 3/4 preoperatively to 1/4 at six to eight weeks postoperatively.Clinical significance: 1.9/2.5 mm locking plates appear to be a valid choice of implant for the stabilization of unilateral TPLO in small breed dogs.
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Minati, Ludovico. "Experimental Implementation of Networked Chaotic Oscillators Based on Cross-Coupled Inverter Rings in a CMOS Integrated Circuit". Journal of Circuits, Systems and Computers 24, nr 09 (27.08.2015): 1550144. http://dx.doi.org/10.1142/s0218126615501443.
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A novel chaotic oscillator based on "cross-coupled" inverter rings is presented. The oscillator consists of a 3-ring to which higher odd n-rings are progressively coupled via diodes and pass gates; it does not contain reactive or resistive elements, and is thus suitable for area-efficient implementation on a CMOS integrated circuit. Numerical simulation based on piece-wise linear approximation predicted the generation of positive spikes having approximately constant periodicity but highly variable cycle amplitude. Simulation Program with Integrated Circuit Emphasis (SPICE) simulations and experimental data from a prototype realized on 0.7 μm technology confirmed this finding, and demonstrated increasing correlation dimension (D2) as 5-, 7- and 9-rings were progressively coupled to the 3-ring. Experimental data from a ring of 24 such oscillator cells showed phase synchronization and partial amplitude synchronization (formation of small clusters), emerging depending on DC gate voltage applied at NMOS transistors implementing diffusive coupling between neighboring cells. Thanks to its small area, simple synchronizability and digital controllability, the proposed circuit enables experimental investigation of dynamical complexity in large networks of coupled chaotic oscillators, and may additionally be suitable for applications such as broadband signal and random number generation.
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Chan, Ka Man Carmen, Ashley L. Arthur, Johannes Morstein, Meiyan Jin, Abrar Bhat, Dörte Schlesinger, Sungmin Son, Donté A. Stevens, David G. Drubin i Daniel A. Fletcher. "Evolutionarily related small viral fusogens hijack distinct but modular actin nucleation pathways to drive cell-cell fusion". Proceedings of the National Academy of Sciences 118, nr 1 (21.12.2020): e2007526118. http://dx.doi.org/10.1073/pnas.2007526118.
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Fusion-associated small transmembrane (FAST) proteins are a diverse family of nonstructural viral proteins. Once expressed on the plasma membrane of infected cells, they drive fusion with neighboring cells, increasing viral spread and pathogenicity. Unlike viral fusogens with tall ectodomains that pull two membranes together through conformational changes, FAST proteins have short fusogenic ectodomains that cannot bridge the intermembrane gap between neighboring cells. One orthoreovirus FAST protein, p14, has been shown to hijack the actin cytoskeleton to drive cell-cell fusion, but the actin adaptor-binding motif identified in p14 is not found in any other FAST protein. Here, we report that an evolutionarily divergent FAST protein, p22 from aquareovirus, also hijacks the actin cytoskeleton but does so through different adaptor proteins, Intersectin-1 and Cdc42, that trigger N-WASP–mediated branched actin assembly. We show that despite using different pathways, the cytoplasmic tail of p22 can replace that of p14 to create a potent chimeric fusogen, suggesting they are modular and play similar functional roles. When we directly couple p22 with the parallel filament nucleator formin instead of the branched actin nucleation promoting factor N-WASP, its ability to drive fusion is maintained, suggesting that localized mechanical pressure on the plasma membrane coupled to a membrane-disruptive ectodomain is sufficient to drive cell-cell fusion. This work points to a common biophysical strategy used by FAST proteins to push rather than pull membranes together to drive fusion, one that may be harnessed by other short fusogens responsible for physiological cell-cell fusion.
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MONTGOMERY-SMITH, STEPHEN. "Perturbations of the coupled Jeffery–Stokes equations". Journal of Fluid Mechanics 681 (29.06.2011): 622–38. http://dx.doi.org/10.1017/jfm.2011.237.
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This paper seeks to provide clues as to why experimental evidence for the alignment of slender fibres in semi-dilute suspensions under shear flows does not match theoretical predictions. This paper posits that the hydrodynamic interactions between the different fibres that might be responsible for the deviation from theory, can at least partially be modelled by the coupling between Jeffery's equation and Stokes' equation. It is proposed that if the initial data are slightly non-uniform, in that the probability distribution of the orientation has small spatial variations, then there is feedback via Stokes' equation that causes these non-uniformities to grow significantly in short amounts of time, so that the standard uncoupled Jeffery's equation becomes a poor predictor when the volume ratio of fibres to fluid is not extremely low. This paper provides numerical evidence, involving spectral analysis of the linearization of the perturbation equation, to support this theory.
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Mancuso, Lauren E., Irena P. Ilieva, Roy H. Hamilton i Martha J. Farah. "Does Transcranial Direct Current Stimulation Improve Healthy Working Memory?: A Meta-analytic Review". Journal of Cognitive Neuroscience 28, nr 8 (sierpień 2016): 1063–89. http://dx.doi.org/10.1162/jocn_a_00956.
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Transcranial direct current stimulation (tDCS) has been reported to improve working memory (WM) performance in healthy individuals, suggesting its value as a means of cognitive enhancement. However, recent meta-analyses concluded that tDCS has little or no effect on WM in healthy participants. In this article, we review reasons why these meta-analyses may have underestimated the effect of tDCS on WM and report a more comprehensive and arguably more sensitive meta-analysis. Consistent with our interest in enhancement, we focused on anodal stimulation. Thirty-one articles matched inclusion criteria and were included in four primary meta-analyses assessing the WM effects of anodal stimulation over the left and right dorsolateral pFC (DLPFC) and right parietal lobe as well as left DLPFC stimulation coupled with WM training. These analyses revealed a small but significant effect of left DLPFC stimulation coupled with WM training. Left DLPFC stimulation alone also enhanced WM performance, but the effect was reduced to nonsignificance after correction for publication bias. No other effects were significant, including a variety of tested moderators. Additional meta-analyses were undertaken with study selection criteria based on previous meta-analyses, to reassess the findings from these studies using the analytic methods of this study. These analyses revealed a mix of significant and nonsignificant small effects. We conclude that the primary WM enhancement potential of tDCS probably lies in its use during training.
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Zhang, C., L. Liu, G. Yang, R. Li i B. Wang. "Improving data transfer for model coupling". Geoscientific Model Development Discussions 8, nr 10 (20.10.2015): 8981–9020. http://dx.doi.org/10.5194/gmdd-8-8981-2015.
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Abstract. Data transfer, which means transferring data fields between two component models or rearranging data fields among processes of the same component model, is a fundamental operation of a coupler. Most of state-of-the-art coupler versions currently use an implementation based on the point-to-point (P2P) communication of the Message Passing Interface (MPI) (call such an implementation "P2P implementation" for short). In this paper, we reveal the drawbacks of the P2P implementation, including low communication bandwidth due to small message size, variable and big number of MPI messages, and jams during communication. To overcome these drawbacks, we propose a butterfly implementation for data transfer. Although the butterfly implementation can outperform the P2P implementation in many cases, it degrades the performance in some cases because the total message size transferred by the butterfly implementation is larger than that by the P2P implementation. To make the data transfer completely improved, we design and implement an adaptive data transfer library that combines the advantages of both butterfly implementation and P2P implementation. Performance evaluation shows that the adaptive data transfer library significantly improves the performance of data transfer in most cases and does not decrease the performance in any cases. Now the adaptive data transfer library is open to the public and has been imported into a coupler version C-Coupler1 for performance improvement of data transfer. We believe that it can also improve other coupler versions.
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Singh, Shakti, Nourhan El Sayed, Hazem Elgabra, Tamador ElBoshra, Maisam Wahbah i Mariam Al Zaabi. "Modeling of High Performance 4H-SiC Emitter Coupled Logic Circuits". Materials Science Forum 778-780 (luty 2014): 1009–12. http://dx.doi.org/10.4028/www.scientific.net/msf.778-780.1009.
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SiC, a wide band gap semiconductor, is capable of robust operation at temperatures well above 600°C. SiC bipolar transistors are well suited for applications at high temperatures as, unlike MOSFET, it does not have a critical gate oxide, and hence oxide reliability at high temperatures is not an issue. In this paper, the design of optimized emitter coupled logic technology circuits using 4H-SiC bipolar transistors is presented. The circuits work over a wide range of temperatures and power supply voltages at high speeds, demonstrating the potential of robust high speed ECL integrated circuits in SiC for small-scale logic applications.
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Garcia, M., K. Portney i S. Islam. "A question driven socio-hydrological modeling process". Hydrology and Earth System Sciences Discussions 12, nr 8 (24.08.2015): 8289–335. http://dx.doi.org/10.5194/hessd-12-8289-2015.
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Abstract. Human and hydrological systems are coupled: human activity impacts the hydrological cycle and hydrological conditions can, but do not always, trigger changes in human systems. Traditional modeling approaches with no feedback between hydrological and human systems typically cannot offer insight into how different patterns of natural variability or human induced changes may propagate through this coupled system. Modeling of coupled human and hydrological systems, also called socio-hydrological systems, recognizes the potential for humans to transform hydrological systems and for hydrological conditions to influence human behavior. However, this coupling introduces new challenges and existing literature does not offer clear guidance regarding the choice of modeling structure, scope, and detail. A shared understanding of important processes within the field is often used to develop hydrological models, but there is no such consensus on the relevant processes in socio-hydrological systems. Here we present a question driven process to address these challenges. Such an approach allows modeling structure, scope, and detail to remain contingent and adaptive to the question context. We demonstrate its utility by exploring a question: what is the impact of reservoir operation policy on the reliability of water supply for a growing city? Our example model couples hydrological and human systems by linking the rate of demand decreases to the past reliability to compare standard operating policy (SOP) with hedging policy (HP). The model shows that reservoir storage acts both as a buffer for variability and as a delay triggering oscillations around a sustainable level of demand. HP reduces the threshold for action thereby decreasing the delay and the oscillation effect. As a result per capita demand decreases during periods of water stress are more frequent but less drastic and the additive effect of small adjustments decreases the tendency of the system to overshoot available supplies. This distinction between the two policies was not apparent using a traditional non-coupled model.
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Song, Ruiheng, Thomas M. Henderson i Gustavo E. Scuseria. "A power series approximation in symmetry projected coupled cluster theory". Journal of Chemical Physics 156, nr 10 (14.03.2022): 104105. http://dx.doi.org/10.1063/5.0080165.
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Projected Hartree–Fock theory provides an accurate description of many kinds of strong correlations but does not properly describe weakly correlated systems. On the other hand, single-reference methods, such as configuration interaction or coupled cluster theory, can handle weakly correlated problems but cannot properly account for strong correlations. Ideally, we would like to combine these techniques in a symmetry-projected coupled cluster approach, but this is far from straightforward. In this work, we provide an alternative formulation to identify the so-called disentangled cluster operators, which arise when we combine these two methodological strands. Our formulation shows promising results for model systems and small molecules.
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Vernhet, Hélène, Roland Demaria, Jean-Marie Juan, Marie-Claire Oliva-Lauraire, Jean-Paul Senac i Michel Dauzat. "Arterial Stenting and Overdilation: Does it Change Wall Mechanics in Small-Caliber Arteries?" Journal of Endovascular Therapy 9, nr 6 (grudzień 2002): 855–62. http://dx.doi.org/10.1177/152660280200900620.
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Purpose: To evaluate changes in arterial wall mechanics induced by stent overdilation in the rabbit aorta. Methods: Twenty New Zealand white rabbits had initial stent deployment (3-mm × 8-mm Multilink) at 10% overdilation. Group A (n=11) had no subsequent balloon expansion of the stent and Group B (n=9) had 30% overdilation of the stent. A noninvasive B-mode ultrasound examination coupled with image processing allowed the measurement of systolic and diastolic diameter and the calculation of diameter compliance (Cd) and distensibility coefficient (DC) as indexes of arterial wall biomechanics. Measurements were performed before stenting in the infrarenal aorta, after initial stenting, and after stent overdilation at 3 locations: upstream, at the stent level, and downstream from the stent. Results: Cd was significantly lower in the stented aorta after initial stenting (p<0.0001) and after stent overdilation (p<0.0001) than before stenting. At the stent level, Cd and DC were significantly lower than downstream (p<0.0001) or upstream (p<0.0001) from the stent after initial stenting, as well as after stent overdilation. Downstream from the stent, Cd and DC were significantly lower after stent overdilation than before stenting (p<0.05). Conclusions: Endovascular stenting of the rabbit aorta produces a significant decrease in arterial wall compliance and distensibility. Stent overdilation is responsible for a slight additional decrease of compliance downstream from the stent.
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Xu, Lizhong, Yulei Liu i Xiaorui Fu. "Effects of the van der Waals Force on the Dynamics Performance for a Micro Resonant Pressure Sensor". Shock and Vibration 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/3426196.
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The micro resonant pressure sensor outputs the frequency signals where the distortion does not take place in a long distance transmission. As the dimensions of the sensor decrease, the effects of the van der Waals forces should be considered. Here, a coupled dynamic model of the micro resonant pressure sensor is proposed and its coupled dynamic equation is given in which the van der Waals force is considered. By the equation, the effects of the van der Waals force on the natural frequencies and vibration amplitudes of the micro resonant pressure sensor are investigated. Results show that the natural frequency and the vibrating amplitudes of the micro resonant pressure sensor are affected significantly by van der Waals force for a small clearance between the film and the base plate, a small initial tension stress of the film, and some other conditions.
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JELLAL, AHMED, MICHAEL SCHREIBER i EL HASSAN EL KINANI. "TWO COUPLED HARMONIC OSCILLATORS ON NONCOMMUTATIVE PLANE". International Journal of Modern Physics A 20, nr 07 (20.03.2005): 1515–29. http://dx.doi.org/10.1142/s0217751x05020835.
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We investigate a system of two coupled harmonic oscillators on the noncommutative plane [Formula: see text] by requiring that the spatial coordinates do not commute. We show that the system can be diagonalized by a suitable transformation, i.e. a rotation with a mixing angle α. The obtained eigenstates as well as the eigenvalues depend on the noncommutativity parameter θ. Focusing on the ground state wave function before the transformation, we calculate the density matrix ρ0(θ) and find that its traces Tr (ρ0(θ)) and [Formula: see text] are not affected by the noncommutativity. Evaluating the Wigner function on [Formula: see text] confirms this. The uncertainty relation is explicitly determined and found to depend on θ. For small values of θ, the relation is shifted by a θ2 term, which can be interpreted as a noncommutativity correction. The calculated entropy does not change with respect to the normal case. We consider the limits α = 0 and α = π/2. In the first case, by identifying θ to the squared magnetic length, one can recover basic features of the Hall system.
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Zou, Wei, Yuxuan Chen, D. V. Senthilkumar i Jürgen Kurths. "Oscillation quenching in diffusively coupled dynamical networks with inertial effects". Chaos: An Interdisciplinary Journal of Nonlinear Science 32, nr 4 (kwiecień 2022): 041102. http://dx.doi.org/10.1063/5.0087839.
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Self-sustained oscillations are ubiquitous and of fundamental importance for a variety of physical and biological systems including neural networks, cardiac dynamics, and circadian rhythms. In this work, oscillation quenching in diffusively coupled dynamical networks including “inertial” effects is analyzed. By adding inertia to diffusively coupled first-order oscillatory systems, we uncover that even small inertia is capable of eradicating the onset of oscillation quenching. We consolidate the generality of inertia in eradicating oscillation quenching by extensively examining diverse quenching scenarios, where macroscopic oscillations are extremely deteriorated and even completely lost in the corresponding models without inertia. The presence of inertia serves as an additional scheme to eradicate the onset of oscillation quenching, which does not need to tailor the coupling functions. Our findings imply that inertia of a system is an enabler against oscillation quenching in coupled dynamical networks, which, in turn, is helpful for understanding the emergence of rhythmic behaviors in complex coupled systems with amplitude degree of freedom.
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Rollinson, Njal, i Jeffrey A. Hutchings. "Why does egg size of salmonids increase with the mean size of population spawning gravels?" Canadian Journal of Fisheries and Aquatic Sciences 68, nr 8 (sierpień 2011): 1307–15. http://dx.doi.org/10.1139/f2011-069.
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Population mean egg size of salmonids increases with the mean size of gravels in which a population spawns. A long-standing hypothesis is that large larvae cannot navigate small-gravel interstices, so mothers must decrease per-offspring investment when spawning gravels are small. We manipulated the size of incubation gravels and egg size of Atlantic salmon (Salmo salar) to test whether size-related entombment of larvae occurs. We find little evidence of size-related entombment, but we find evidence that gravel size does not affect all larval sizes equally. Larger larvae emerge from small gravels before development is complete and with a visible yolk sac, possibly due to oxygen limitation in small gravels. Smaller larvae always complete development in the gravel and emerge without a yolk sac. Although growth and survival may increase with juvenile size following yolk-sac absorption, juveniles with yolk sacs may fare worse when depredation rates are high. The egg size – gravel size correlation may therefore reflect increased postemergence mortality among larger offspring in small-gravel environments. Alternatively, compaction stress in fine gravels coupled with size asymmetries in larval strength may have caused the patterns that we observed, in which case our data may not help explain the egg size – gravel size correlation.