1,168 research outputs found
Room temperature self-assembly of mixed nanoparticles into complex material systems and devices
The ability to manufacture nanomaterials with complex and structured
composition using otherwise incompatible materials increasingly underpins the
next generation of technologies. This is translating into growing efforts
integrating a wider range of materials onto key technology platforms1 - in
photonics, one such platform is silica, a passive, low loss and robust medium
crucial for efficient optical transport2. Active functionalisation, either
through added gain or nonlinearity, is mostly possible through the integration
of active materials3, 4. The high temperatures used in manufacturing of silica
waveguides, unfortunately, make it impossible to presently integrate many
organic and inorganic species critical to achieving this extended
functionality. Here, we demonstrate the fabrication of novel waveguides and
devices made up of complex silica based materials using the self-assembly of
nanoparticles. In particular, the room temperature fabrication of silica
microwires integrated with organic dyes (Rhodamine B) and single photon
emitting nanodiamonds is presented.Comment: Key words: nanotechnology, nanoparticles, self-assembly, quantum
science, singel photon emitters, telecommunications, sensing, new materials,
integration of incompatible materials, silica, glass, breakthrough scienc
Compact birefringent waveplates photo-induced in silica by femtosecond laser
© 2014 by the authors; licensee MDPI, Basel, Switzerland. Recently, we showed that femtosecond laser induced "nanogratings" consist of thin regions with a low refractive index (Δn = -0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide range of laser parameters to achieve very high retardance within a single layer; as much as 350 nm at λ = 546 nm but also to minimize the competing losses. We show that the total retardance depends on the number of layers present and can be accumulated in the direction of laser propagation to values higher than 1600 nm. This opens the door to using these nanostructures as refined building blocks for novel optical elements based on strong retardance
Time-resolved plasma measurements in Ge-doped silica exposed to infrared femtosecond laser
Using a time-resolved interferometric technique, we study the laser-induced carrier-trapping dynamics in SiO 2 and Ge-doped SiO 2. The fast trapping of electrons in the band gap is associated with the formation of self-trapped excitons (STE). The STE trapping is doping dependent in SiO 2. The mean trapping time of electrons excited in the conduction band was found to be significantly lower in Ge-doped silica (75 ± 5 fs) when compared to pure silica (155 ± 5 fs). At our concentration level, this indicates that the plasma properties are determined by the presence of easily ionizable states such as the presence of Ge atoms in the glass network. Therefore, we suggest that in Ge-doped silica there exist an additional trapping pathway that leads to a significantly faster excitons trapping and a higher plasma density when compared to undoped silica. © 2011 American Physical Society
Probing the extreme realm of AGN feedback in the massive galaxy cluster, RX J1532.9+3021
We present a detailed Chandra, XMM-Newton, VLA and HST analysis of one of the
strongest cool core clusters known, RX J1532.9+3021 (z=0.3613). Using new, deep
90 ks Chandra observations, we confirm the presence of a western X-ray cavity
or bubble, and report on a newly discovered eastern X-ray cavity. The total
mechanical power associated with these AGN-driven outflows is (22+/-9)*10^44
erg/s, and is sufficient to offset the cooling, indicating that AGN feedback
still provides a viable solution to the cooling flow problem even in the
strongest cool core clusters. Based on the distribution of the optical
filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map,
we suggest that the cluster harbours older outflows along the north to south
direction. The jet of the central AGN is therefore either precessing or
sloshing-induced motions have caused the outflows to change directions. There
are also hints of an X-ray depression to the north aligned with the 325 MHz
jet-like structure, which might represent the highest redshift ghost cavity
discovered to date. We further find evidence of a cold front (r=65kpc) that
coincides with the outermost edge of the western X-ray cavity and the edge of
the radio mini-halo. The common location of the cold front with the edge of the
radio mini-halo supports the idea that the latter originates from electrons
being reaccelerated due to sloshing induced turbulence. Alternatively, its
coexistence with the edge of the X-ray cavity may be due to cool gas being
dragged out by the outburst. We confirm that the central AGN is highly
sub-Eddington and conclude that a >10^10M_Sun or a rapidly spinning black hole
is favoured to explain both the radiative-inefficiency of the AGN and the
powerful X-ray cavities.Comment: Accepted for publication to ApJ (minor corrections), 16 pages, 16
figures, 5 tables. Full resolution at http://www.stanford.edu/~juliehl/M1532
The effects of ozone on immune function.
A review of the literature reveals that ozone (O3) exposure can either suppress or enhance immune responsiveness. These disparate effects elicited by O3 exposure depend, in large part, on the experimental design used, the immune parameters examined as well as the animal species studied. Despite the apparent contradictions, a general pattern of response to O3 exposure can be recognized. Most studies indicate that continuous O3 exposure leads to an early (days 0-3) impairment of immune responsiveness followed, with continued exposures, by a form of adaptation to O3 that results in a re-establishment of the immune response. The effects of O3 exposure on the response to antigenic stimulation also depend on the time at which O3 exposure occurred. Whereas O3 exposure prior to immunization is without effect on the response to antigen, O3 exposure subsequent to immunization suppresses the response to antigen. Although most studies have focused on immune responses in the lung, numerous investigators have provided functional and anatomical evidence to support the hypothesis that O3 exposure can have profound effects on systemic immunity
Sensitivity enhancement of fiber Bragg gratings to transverse stress by using microstructural fibers
We present simulation and experimental results of fiber Bragg grating responses to transverse stress in microstructure fibers. The grating wavelength shifts and peak splits are studied as a function of external load and fiber orientation. Both simulation and measurement results indicate that the sensitivity of grating sensors to the transverse stress can be enhanced by a factor of eight in a two-hole fiber over that in a standard fiber. © 2006 Optical Society of America
Cooling in the X-ray halo of the rotating, massive early-type galaxy NGC 7049
The relative importance of the physical processes shaping the thermodynamics
of the hot gas permeating rotating, massive early-type galaxies is expected to
be different from that in non-rotating systems. Here, we report the results of
the analysis of XMM-Newton data for the massive, lenticular galaxy NGC 7049.
The galaxy harbours a dusty disc of cool gas and is surrounded by an extended
hot X-ray emitting gaseous atmosphere with unusually high central entropy. The
hot gas in the plane of rotation of the cool dusty disc has a multi-temperature
structure, consistent with ongoing cooling. We conclude that the rotational
support of the hot gas is likely capable of altering the multiphase
condensation regardless of the ratio, which is here
relatively high, . However, the measured ratio of cooling time and
eddy turnover time around unity (-ratio ) implies significant
condensation, and at the same time, the constrained ratio of rotational
velocity and the velocity dispersion (turbulent Taylor number)
indicates that the condensing gas should follow non-radial orbits forming a
disc instead of filaments. This is in agreement with hydrodynamical simulations
of massive rotating galaxies predicting a similarly extended multiphase disc.Comment: 11 pages, 12 figures, accepted for publication in MNRA
Polarization mode coupling and related effects in fiber Bragg grating inscribed in polarization maintaining fiber
©2016 Optical Society of America. Polarization mode coupling (PMC) and related effects from writing fiber Bragg gratings in polarization maintaining fiber (FBGs-in- PMF) are observed experimentally for the first time by optical fiber coherence domain polarimetry (OCDP) using a broadband light source. PMC is another useful aspect of FBG-in-PMF besides Bragg wavelength and its possible potential is evaluated and discussed. A localized and long range temperature measurement based on the PMC and Bragg wavelength is given as an example
Thermally regenerated fiber Bragg-grating in twin-air-hole microstructure fiber for high temperature pressure sensing
We present thermally regnenerated fiber Bragg grating in air-hole microstructured fibers for high temperature hydrostatic pressure sensing application. Saturated type I gratings were inscribed in hydrogen-loaded two-hole optical fibers using 248-nm KrF laser, and regenerated during annealing at 800°C. The fiber Bragg grating resonance wavelength shift and peak splits were studied as a function of external hydrostatic pressure from 15 psi to 2400 psi. The grating pressure sensor shows stable and reproducible operation up to 800°C. This paper demonstrates a multiplexible pressure sensor network technology for high temperature harsh environment using a single fiber feedthrough. © 2011 SPIE
Selective expression of a sodium pump isozyme by cough receptors and evidence for its essential role in regulating cough
We have identified a distinct subtype of airway vagal afferent nerve that plays an essential role in regulating the cough reflex. These afferents are exquisitely sensitive to punctate mechanical stimuli, acid, and decreases in extracellular chloride concentrations, but are insensitive to capsaicin, bradykinin, histamine, adenosine, serotonin, or changes in airway intraluminal pressures. In this study we used intravital imaging, retrograde neuronal tracing, and electrophysiological analyses to characterize the structural basis for their peculiar mechanical sensitivity and to further characterize the regulation of their excitability. In completing these experiments, we uncovered evidence for an essential role of an isozyme of Na(+)-K(+) ATPase in regulating cough. These vagal sensory neurons arise bilaterally from the nodose ganglia and are selectively and brilliantly stained intravitally with the styryl dye FM2-10. Cough receptor terminations are confined and adherent to the extracellular matrix separating the airway epithelium and smooth muscle layers, a site of extensive remodeling in asthma and chronic obstructive pulmonary disease. The cough receptor terminals uniquely express the alpha(3) subunit of Na(+)-K(+) ATPase. Intravital staining of cough receptors by FM2-10, cough receptor excitability in vitro, and coughing in vivo are potently and selectively inhibited by the sodium pump inhibitor ouabain. These data provide the first detailed morphological description of the peripheral terminals of the sensory nerves regulating cough and identify a selective molecular target for their modulation
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