976 resultados para widely tunable


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Spectrin is an important structural component of the plasma membrane skeleton. Heretofore-unidentified isoforms of spectrin also associate with Golgi and other organelles. We have discovered another member of the β-spectrin gene family by homology searches of the GenBank databases and by 5′ rapid amplification of cDNA ends of human brain cDNAs. Collectively, 7,938 nucleotides of contiguous clones are predicted to encode a 271,294-Da protein, called βIII spectrin, with conserved actin-, protein 4.1-, and ankyrin-binding domains, membrane association domains 1 and 2, a spectrin dimer self-association site, and a pleckstrin-homology domain. βIII spectrin transcripts are concentrated in the brain and present in the kidneys, liver, and testes and the prostate, pituitary, adrenal, and salivary glands. All of the tested tissues contain major 9.0-kb and minor 11.3-kb transcripts. The human βIII spectrin gene (SPTBN2) maps to chromosome 11q13 and the mouse gene (Spnb3) maps to a syntenic region close to the centromere on chromosome 19. Indirect immunofluorescence studies of cultured cells using antisera specific to human βIII spectrin reveal a Golgi-associated and punctate cytoplasmic vesicle-like distribution, suggesting that βIII spectrin associates with intracellular organelles. This distribution overlaps that of several Golgi and vesicle markers, including mannosidase II, p58, trans-Golgi network (TGN)38, and β-COP and is distinct from the endoplasmic reticulum markers calnexin and Bip. Liver Golgi membranes and other vesicular compartment markers cosediment in vitro with βIII spectrin. βIII spectrin thus constitutes a major component of the Golgi and vesicular membrane skeletons.

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The synthesis of novel fluorogenic retro-aldol substrates for aldolase antibody 38C2 is described. These substrates are efficiently and specifically processed by antibody aldolases but not by natural cellular enzymes. Together, the fluorogenic substrates and antibody aldolases provide reporter gene systems that are compatible with living cells. The broad scope of the antibody aldolase allows for the processing of a range of substrates that can be designed to allow fluorescence monitoring at a variety of wavelengths. We also have developed the following concept in fluorescent protein tags. β-Diketones bearing a fluorescent tag are bound covalently by the aldolase antibody and not other proteins. We anticipate that proteins fused with the antibody can be tagged specifically and covalently within living cells with fluorophores of virtually any color, thereby providing an alternative to green fluorescent protein fusions.

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Objective: To compare the implications of four widely used cholesterol screening and treatment guidelines by applying them to a population in the United Kingdom.

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Glycoproteins expressing the Lutheran blood group antigens were isolated from human erythrocyte membranes and from human fetal liver. Amino acid sequence analyses allowed the design of redundant oligonucleotides that were used to generate a 459-bp, sequence-specific probe by PCR. A cDNA clone of 2400 bp was isolated from a human placental lambda gt 11 library and sequenced, and the deduced amino acid sequence was studied. The predicted mature protein is a type I membrane protein of 597 amino acids with five potential N-glycosylation sites. There are five disulfide-bonded, extracellular, immunoglobulin superfamily domains (two variable-region set and three constant-region set), a single hydrophobic, membrane-spanning domain, and a cytoplasmic domain of 59 residues. The overall structure is similar to that of the human tumor marker MUC 18 and the chicken neural adhesion molecule SC1. The extracellular domains and cytoplasmic domain contain consensus motifs for the binding of integrin and Src homology 3 domains, respectively, suggesting possible receptor and signal-transduction function. Immunostaining of human tissues demonstrated a wide distribution and provided evidence that the glycoprotein is under developmental control in liver and may also be regulated during differentiation in other tissues.

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Acknowledgements This work was supported by NSF DMR-1410378 and DMR-1121288. We thank V. Borshch for helping with preparation of illustrations, to Y. K. Kim for the help in experiments, V. A. Belyakov and S. V. Shiyanovskii for useful discussions.

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The obtention of spontaneous Raman photons is analyzed in singly charged p-doped quantum dots in the absence of an external magnetic field. The use of a far detuned single driving laser allows to obtain a Raman photon line which exhibits subnatural linewidth, and whose center can be tuned by changing the detuning and/or the Rabi frequency of the driving field. The Raman photons are produced along the undriven transition and they arise from the weak interaction of the trion states with the nuclear spins. The operating point for the gate voltage of the heterostructure can also be used to modify the linewidth and the peak value of the fluorescent signal.

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We study a single-electron transistor (SET) based upon a II–VI semiconductor quantum dot doped with a single-Mn ion. We present evidence that this system behaves like a quantum nanomagnet whose total spin and magnetic anisotropy depend dramatically both on the number of carriers and their orbital nature. Thereby, the magnetic properties of the nanomagnet can be controlled electrically. Conversely, the electrical properties of this SET depend on the quantum state of the Mn spin, giving rise to spin-dependent charging energies and hysteresis in the Coulomb blockade oscillations of the linear conductance.

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A high percentage of hydrocarbon (HC) emissions from gasoline vehicles occur during the cold-start period. Among the alternatives proposed to reduce these HC emissions, the use of zeolites before the three-way catalyst (TWC) is thought to be very effective. Zeolites are the preferred adsorbents for this application; however, to avoid high pressure drops, supported zeolites are needed. In this work, two coating methods (dip-coating and in situ crystallization) are optimized to prepare BETA zeolite thin films supported on honeycomb monoliths with tunable properties. The important effect of the density of the thin film in the final performance as a HC trap is demonstrated. A highly effective HC trap is prepared showing 100 % toluene retention, accomplishing the desired performance as a HC trap, desorbing propene at temperatures close to 300 °C, and remaining stable after cycling. The use of this material before the TWC is very promising, and works towards achieving the sustainability and environmental protection goals.

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This study describes a novel spectral LED-based tunable light source used for customized lighting solutions, especially for the reconstruction of CIE (Commission Internationale de l’Éclairage) standard illuminants. The light source comprises 31 spectral bands ranging from 400 to 700 nm, an integrating cube and a control board with a 16-bit resolution. A minimization algorithm to calculate the weighting values for each channel was applied to reproduce illuminants with precision. The differences in spectral fitting and colorimetric parameters showed that the reconstructed spectra were comparable to the standard, especially for the D65, D50, A and E illuminants. Accurate results were also obtained for illuminants with narrow peaks such as fluorescents (F2 and F11) and a high-pressure sodium lamp (HP1). In conclusion, the developed spectral LED-based light source and the minimization algorithm are able to reproduce any CIE standard illuminants with a high spectral and colorimetric accuracy able to advance available custom lighting systems useful in the industry and other fields such as museum lighting.

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A mixed set; imprint varies: v. 1, 2, and 7 as above; v. 3 and 6: sold by John White, Luke Hansard, printer, 1801; v. 4: Printed by H.L. Galabin and sold by R. Faulder, 1800; v. 5: Printed by C. and W. Galabin and sold by W. Richardson, 1801.

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The 23S rRNA-targeted probes GAM42a and BET42a provided equivocal results with the uncultured gammaproteobacterium 'Candidatus Competibacter phosphatis' where some cells bound GAM42a and other cells bound BET42a in fluorescence in situ hybridization (FISH) experiments. Probes GAM42a and BET42a span positions 1027-1043 in the 23S rRNAand differ from each other by one nucleotide at position 1033. Clone libraries were prepared from PCR products spanning the 16S rRNA genes, intergenic spacer region and 23S rRNA genes from two mixed cultures enriched in 'Candidatus C. phosphatis'. With individual clone inserts, the 16S rDNA portion was used to confirm the source organism as 'Candidatus C. phosphatis' and the 23S rDNA portion was used to determine the sequence of the GAM42a/BET42a probe target region. Of the 19 clones sequenced, 8 had the GAM42a probe target (T at position 1033) and 11 had G at position 1033, the only mismatch with GAM42a. However, none of the clones had the BET42a probe target (A at 1033). Non-canonical base-pairing between the 23S rRNA of 'Candidatus C. phosphatis' with G at position 1033 and GAM42a (G-A) or BET42a (G-T) is likely to explain the probing anomalies. A probe (GAM42_C1033) was optimized for use in FISH, targeting cells with G at position 1033, and was found to highlight not only some 'Candidatus C. phosphatis' cells, but also other bacteria. This demonstrates that there are bacteria in addition to 'Candidatus C. phosphatis' with the GAM42_C1033 probe target and not the BET42a or GAM42a probe target.

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We investigate resonant tunnelling through molecular states of an Aharonov-Bohm (AB) interferometer composed of two coupled quantum dots. The conductance of the system shows two resonances associated with the bonding and the antibonding quantum states. We predict that the two resonances are composed of a Breit-Wigner resonance and a Fano resonance, of which the widths and Fano factor depend on the AB phase very sensitively. Further, we point out that the bonding properties, such as the covalent and ionic bonding, can be identified by the AB oscillations.

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We demonstrate a compact tunable filter based on a novel microfluidic single beam Mach-Zehnder interferometer. The optical path difference occurs during propagation across a fluid-air interface ( meniscus), the inherent mobility of which provides tunability. Optical losses are minimized by optimizing the meniscus shape through surface treatment. Optical spectra are compared to a 3D beam propagation method simulations and good agreement is found. Tunability, low insertion loss and strength of the resonance are well reproduced. The device performance displays a resonance depth of - 28 dB and insertion loss maintained at - 4 dB. (C) 2004 Optical Society of America.

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Data provided by 7380 middle managers from 60 nations are used to determine whether demographic variables are correlated with managers’ reliance on vertical sources of guidance in different nations and whether these correlations differ depending on national culture characteristics. Significant effects of Hofstede’s national culture scores, age, gender, organization ownership and department function are found. After these main effects have been discounted, significant although weak interactions are found, indicating that demographic effects are stronger in individualist, low power distance nations than elsewhere. Significant non-predicted interaction effects of uncertainty avoidance and masculinity-femininity are also obtained. The implications for theory and practice of the use of demographic attributes in understanding effective management procedures in various parts of the world are discussed.