967 research outputs found
Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions
Dealuminated zeolite HY was used to support Ir(CO)_2 complexes formed from Ir(CO)_2(C_5H_7O_2). Infrared and X-ray absorption spectra and atomic resolution electron microscopy images identify these complexes, and the images and ^(27)Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate the value of electron microscopy in characterizing the amorphous impurity regions of zeolites and a significant stability limitation of metals in these regions of zeolite catalyst supports
Emission Features and Source Counts of Galaxies in Mid-Infrared
In this work we incorporate the newest ISO results on the mid-infrared
spectral-energy-distributions (MIR SEDs) of galaxies into models for the number
counts and redshift distributions of MIR surveys. A three-component model, with
empirically determined MIR SED templates of (1) a cirrus/PDR component (2) a
starburst component and (3) an AGN component, is developed for infrared
(3--120\micron) SEDs of galaxies. The model includes a complete IRAS 25\micron
selected sample of 1406 local galaxies (; Shupe et al. 1998a).
Results based on these 1406 spectra show that the MIR emission features cause
significant effects on the redshift dependence of the K-corrections for fluxes
in the WIRE 25\micron band and ISOCAM 15\micron band. This in turn will affect
deep counts and redshift distributions in these two bands, as shown by the
predictions of two evolution models (a luminosity evolution model with
and a density evolution model with ).
The dips-and-bumps on curves of MIR number counts, caused by the emission
features, should be useful indicators of evolution mode. The strong emission
features at --8\micron will help the detections of relatively high
redshift () galaxies in MIR surveys. On the other hand, determinations
of the evolutionary rate based on the slope of source counts, and studies on
the large scale structures using the redshift distribution of MIR sources, will
have to treat the effects of the MIR emission features carefully. We have also
estimated a 15\micron local luminosity function from the predicted 15\micron
fluxes of the 1406 galaxies using the bivariate (15\micron vs. 25\micron
luminosities) method. This luminosity function will improve our understanding
of the ISOCAM 15\micron surveys.Comment: 24 pages, 14 EPS figures. Accepted by Ap
Tunable anisotropy in inverse opals and emerging optical properties
Using self-assembly, nanoscale materials can be fabricated from the bottom up. Opals and inverse opals are examples of self-assembled nanomaterials made from crystallizing colloidal particles. As self-assembly requires a high level of control, it is challenging to use building blocks with anisotropic geometry to form complex opals, which limits the realizable structures. Typically, spherical colloids are employed as building blocks, leading to symmetric, isotropic superstructures. However, a significantly richer palette of directionally dependent properties are expected if less symmetric, anisotropic structures can be created, especially originating from the assembly of regular, spherical particles. Here we show a simple method to introduce anisotropy into inverse opals by subjecting them to a post-assembly thermal treatment that results in directional shrinkage of the silica matrix caused by condensation of partially hydrated sol-gel silica structures. In this way, we can tailor the shape of the pores, and the anisotropy of the final inverse opal preserves the order and uniformity of the self-assembled structure, while completely avoiding the need to synthesize complex oval-shaped particles and crystallize them into such target geometries. Detailed X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies clearly identify increasing degrees of sol-gel condensation in confinement as a mechanism for the structure change. A computer simulation of structure changes resulting from the condensation-induced shrinkage further confirmed this mechanism. As an example of property changes induced by the introduction of anisotropy, we characterized the optical spectra of the anisotropic inverse opals and found that the optical properties can be controlled in a precise way using calcination temperature
Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs. I. ISO~CAM and ISO~SWS Observations
Mid-infrared (MIR) imaging and spectroscopic observations are presented for a
well defined sample of eight closely interacting (CLO) pairs of spiral galaxies
that have overlapping disks and show enhanced far-infrared (FIR) emission. The
goal is to study the star formation distribution in CLO pairs, with special
emphasis on the role of 'overlap starbursts'. Observations were made with the
Infrared Space Observatory (ISO) using the CAM and SWS instruments. The ISO~CAM
maps, tracing the MIR emission of warm dust heated by young massive stars, are
compared to new ground based H and R-band images. We identify three
possible subgroups in the sample, classified according to the star formation
morphology: (1) advanced mergers (Arp~157, Arp~244 and Arp~299), (2) severely
disturbed systems (Arp~81 and Arp~278), and (3) less disturbed systems
(Arp~276, KPG 347 and KPG 426). Localized starbursts are detected in the
overlap regions in all five pairs of subgroups (1) and (2), suggesting that
they are a common property in colliding systems. Except for Arp~244, the
'overlap starburst' is usually fainter than the major nuclear starburst in CLO
pairs. Star formation in 'less disturbed systems' is often distributed
throughout the disks of both galaxies with no 'overlap starburst' detected in
any of them. These systems also show less enhanced FIR emission, suggesting
that they are in an earlier interaction stage than pairs of the other two
subgroups where the direct disk collisions have probably not yet occurred.Comment: 27 pages text, 4 JPEG figures, 3 PS figures. To be accepted by ApJ.
High quality figures (included in a PS file of the paper) can be found in
http://spider.ipac.caltech.edu/staff/cxu/papers/ss_iso.ps.g
Modulating signaling networks by CRISPR/Cas9-mediated transposable element insertion
In a recent past, transposable elements (TEs) were referred to as selfish genetic components only capable of copying themselves with the aim of increasing the odds of being inherited. Nonetheless, TEs have been initially proposed as positive control elements acting in synergy with the host. Nowadays, it is well known that TE movement into host genome comprises an important evolutionary mechanism capable of increasing the adaptive fitness. As insights into TE functioning are increasing day to day, the manipulation of transposition has raised an interesting possibility of setting the host functions, although the lack of appropriate genome engineering tools has unpaved it. Fortunately, the emergence of genome editing technologies based on programmable nucleases, and especially the arrival of a multipurpose RNA-guided Cas9 endonuclease system, has made it possible to reconsider this challenge. For such purpose, a particular type of transposons referred to as miniature inverted-repeat transposable elements (MITEs) has shown a series of interesting characteristics for designing functional drivers. Here, recent insights into MITE elements and versatile RNA-guided CRISPR/Cas9 genome engineering system are given to understand how to deploy the potential of TEs for control of the host transcriptional activity.Fil: Vaschetto, Luis Maria Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; Argentin
Acquisition of pneumococci specific effector and regulatory Cd4+ T cells localising within human upper respiratory-tract mucosal lymphoid tissue
The upper respiratory tract mucosa is the location for commensal Streptococcus (S.) pneumoniae colonization and therefore represents a major site of contact between host and bacteria. The CD4(+) T cell response to pneumococcus is increasingly recognised as an important mediator of immunity that protects against invasive disease, with data suggesting a critical role for Th17 cells in mucosal clearance. By assessing CD4 T cell proliferative responses we demonstrate age-related sequestration of Th1 and Th17 CD4(+) T cells reactive to pneumococcal protein antigens within mucosal lymphoid tissue. CD25(hi) T cell depletion and utilisation of pneumococcal specific MHCII tetramers revealed the presence of antigen specific Tregs that utilised CTLA-4 and PDL-1 surface molecules to suppress these responses. The balance between mucosal effector and regulatory CD4(+) T cell immunity is likely to be critical to pneumococcal commensalism and the prevention of unwanted pathology associated with carriage. However, if dysregulated, such responses may render the host more susceptible to invasive pneumococcal infection and adversely affect the successful implementation of both polysaccharide-conjugate and novel protein-based pneumococcal vaccines
Plasmon-phonon coupling in large-area graphene dot and antidot arrays
Nanostructured graphene on SiO2 substrates pave the way for enhanced
light-matter interactions and explorations of strong plasmon-phonon
hybridization in the mid-infrared regime. Unprecedented large-area graphene
nanodot and antidot optical arrays are fabricated by nanosphere lithography,
with structural control down to the sub-100 nanometer regime. The interaction
between graphene plasmon modes and the substrate phonons is experimentally
demonstrated and structural control is used to map out the hybridization of
plasmons and phonons, showing coupling energies of the order 20 meV. Our
findings are further supported by theoretical calculations and numerical
simulations.Comment: 7 pages including 6 figures. Supporting information is available upon
request to author
ALMA [N \i\i ] 205 \mu m Imaging Spectroscopy of the Lensed Submillimeter galaxy ID 141 at redshift 4.24
We present the Atacama Large Millimeter/submillimeter Array (ALMA)
observation of the Sub-millimeter galaxy (SMG) ID 141 at z=4.24 in the [N II]
205 m line (hereafter [N II]) and the underlying continuum at (rest-frame)
197.6 m. Benefiting from lensing magnification by a galaxy pair at
z=0.595, ID 141 is one of the brightest z SMGs. At the angular resolutions
of to ( kpc), our observation clearly
separates, and moderately resolves the two lensed images in both continuum and
line emission at . Our continuum-based lensing model implies an
averaged amplification factor of and reveals that the de-lensed
continuum image has the S\'ersic index and the S\'ersic radius of
kpc). Furthermore, the reconstructed [N II] velocity
field in the source plane is dominated by a rotation component with a maximum
velocity of km/s at large radii, indicating a dark matter halo mass
of . This, together with the reconstructed velocity
dispersion field being smooth and modest in value ( km/s) over much of
the outer parts of the galaxy, favours the interpretation of ID 141 being a
disk galaxy dynamically supported by rotation. The observed [N II]/CO (7-6) and
[N II]/[C II] 158 m line luminosity ratios, which are consistent with the
corresponding line ratio vs. far-infrared color correlation from local luminous
infrared galaxies, imply a de-lensed star formation rate of (/yr and provide an independent estimate on the size of
the star-forming region kpc in radius.Comment: 13 pages, 6 figures, 2 tables, accepted by ApJ, lensing model code
can be found here https://gitlab.com/cxylzlx/tiny_len
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