5,860 research outputs found
Analysis of leaf surfaces using scanning ion conductance microscopy
Leaf surfaces are highly complex functional systems with well defined chemistry and structure dictating the barrier and transport properties of the leaf cuticle. It is a significant imaging challenge to analyse the very thin and often complex wax-like leaf cuticle morphology in their natural state. Scanning electron microscopy (SEM) and to a lesser extent Atomic force microscopy are techniques that have been used to study the leaf surface but their remains information that is difficult to obtain via these approaches. SEM is able to produce highly detailed and high-resolution images needed to study leaf structures at the submicron level. It typically operates in a vacuum or low pressure environment and as a consequence is generally unable to deal with the in situ analysis of dynamic surface events at submicron scales. Atomic force microscopy also possess the high-resolution imaging required and can follow dynamic events in ambient and liquid environments, but can over exaggerate small features and cannot image most leaf surfaces due to their inherent roughness at the micron scale. Scanning ion conductance microscopy (SICM), which operates in a liquid environment, provides a potential complementary analytical approach able to address these issues and which is yet to be explored for studying leaf surfaces. Here we illustrate the potential of SICM on various leaf surfaces and compare the data to SEM and atomic force microscopy images on the same samples. In achieving successful imaging we also show that SICM can be used to study the wetting of hydrophobic surfaces in situ. This has potentially wider implications than the study of leaves alone as surface wetting phenomena are important in a range of fundamental and applied studies
Star-Forming or Starbursting? The Ultraviolet Conundrum
Compared to starburst galaxies, normal star forming galaxies have been shown
to display a much larger dispersion of the dust attenuation at fixed reddening
through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV
color "beta"). To investigate the causes of this larger dispersion and attempt
to isolate second parameters, we have used GALEX UV, ground-based optical, and
Spitzer infrared imaging of 8 nearby galaxies, and examined the properties of
individual UV and 24 micron selected star forming regions. We concentrated on
star-forming regions, in order to isolate simpler star formation histories than
those that characterize whole galaxies. We find that 1) the dispersion is not
correlated with the mean age of the stellar populations, 2) a range of dust
geometries and dust extinction curves are the most likely causes for the
observed dispersion in the IRX-beta diagram 3) together with some potential
dilution of the most recent star-forming population by older unrelated bursts,
at least in the case of star-forming regions within galaxies, 4) we also
recover some general characteristics of the regions, including a tight positive
correlation between the amount of dust attenuation and the metal content.
Although generalizing our results to whole galaxies may not be immediate, the
possibility of a range of dust extinction laws and geometries should be
accounted for in the latter systems as well.Comment: 18 pages, 17 figures, accepted for publication in Ap
Experimental demonstration of coupled optical springs
Optical rigidity will play an important role in improving the sensitivity of future generations of gravitational wave (GW) interferometers, which employ high laser power in order to reach and exceed the standard quantum limit. Several experiments have demonstrated the combined effect of two optical springs on a single system for very low-weight mirror masses or membranes. In this paper we investigate the complex interactions between multiple optical springs and the surrounding apparatus in a system of comparable dynamics to a large-scale GW detector. Using three 100 g mirrors to form a coupled cavity system capable of sustaining two or more optical springs, we demonstrate a number of different regimes of opto-mechanical rigidity and measurement techniques. Our measurements reveal couplings between each optical spring and the control loops that can affect both the achievable increase in sensitivity and the stability of the system. Hence this work establishes a better understanding of the realisation of these techniques and paves the way to their application in future GW observatories, such as upgrades to Advanced LIGO
Determining the motion of the solar system relative to the cosmic microwave background using type Ia supernovae
We estimate the solar system motion relative to the cosmic microwave
background using type Ia supernovae (SNe) measurements. We take into account
the correlations in the error bars of the SNe measurements arising from
correlated peculiar velocities. Without accounting for correlations in the
peculiar velocities, the SNe data we use appear to detect the peculiar velocity
of the solar system at about the 3.5 sigma level. However, when the
correlations are correctly accounted for, the SNe data only detects the solar
system peculiar velocity at about the 2.5 sigma level. We forecast that the
solar system peculiar velocity will be detected at the 9 sigma level by GAIA
and the 11 sigma level by the LSST. For these surveys we find the correlations
are much less important as most of the signal comes from higher redshifts where
the number density of SNe is insufficient for the correlations to be important.Comment: 6 pages, 6 figures; fixed a typo; matches version to appear in MNRA
Whey Protein Isolate Supplementation While Endurance Training Does Not Alter Cycling Performance or Immune Responses at Rest or After Exercise
This study examined whey protein isolate supplementation combined with endurance training on cycling performance, aerobic fitness and immune cell responses. Eighteen male cyclists were randomly assigned to either placebo (PLA) or whey protein supplementation (WS; 1.0 g·kg body mass−1·d−1 in addition to their dietary intake). Both groups completed the identical endurance training program, 4 days per week for 6 weeks. Blood samples were obtained at rest and after 5 and 60 min of recovery from a simulated 40 km cycling time trial (TT) and were repeated after training. Baseline dietary intake of protein prior to supplementation was 1.52 ± 0.45 and 1.46 ± 0.44 g·kg body mass−1·d−1 for the WS and PLA groups, respectively. There were similar improvements in TT performance (WS: 71.47 ± 12.17 to 64.38 ± 8.09 min; PLA: 72.33 ± 12.79 to 61.13 ± 8.97 min), and peak oxygen uptake (WS: 52.3 ± 6.1 to 56.1 ± 5.4 mL·kg−1·min−1; PLA: 50.0 ± 7.1 to 54.9 ± 5.1 mL·kg−1·min−1) after training in both groups. White blood cells (WBC) and neutrophil counts were elevated 5 min after the TT and further increased after 60 min (P < 0.05). The exercise-induced increase in WBC and neutrophil counts at 5 and 60 min after the TT were attenuated after training compared to before training (P < 0.05). Lymphocytes increased 5 min after the TT and decreased below rest after 60 min of recovery (P < 0.05). Following training lymphocytes were lower after 60 min of recovery compared to before training. There was no change in natural killer cell activity with exercise, training or between groups. It was concluded that whey protein isolate supplementation while endurance training did not differentially change cycling performance or the immune response at rest or after exercise. However, endurance training did alter performance, aerobic fitness and some post exercise immune cell counts
The Spitzer Local Volume Legacy: Survey Description and Infrared Photometry
The survey description and the near-, mid-, and far-infrared flux properties
are presented for the 258 galaxies in the Local Volume Legacy (LVL). LVL is a
Spitzer Space Telescope legacy program that surveys the local universe out to
11 Mpc, built upon a foundation of ultraviolet, H-alpha, and HST imaging from
11HUGS (11 Mpc H-alpha and Ultraviolet Galaxy Survey) and ANGST (ACS Nearby
Galaxy Survey Treasury). LVL covers an unbiased, representative, and
statistically robust sample of nearby star-forming galaxies, exploiting the
highest extragalactic spatial resolution achievable with Spitzer. As a result
of its approximately volume-limited nature, LVL augments previous Spitzer
observations of present-day galaxies with improved sampling of the
low-luminosity galaxy population. The collection of LVL galaxies shows a large
spread in mid-infrared colors, likely due to the conspicuous deficiency of 8um
PAH emission from low-metallicity, low-luminosity galaxies. Conversely, the
far-infrared emission tightly tracks the total infrared emission, with a
dispersion in their flux ratio of only 0.1 dex. In terms of the relation
between infrared-to-ultraviolet ratio and ultraviolet spectral slope, the LVL
sample shows redder colors and/or lower infrared-to-ultraviolet ratios than
starburst galaxies, suggesting that reprocessing by dust is less important in
the lower mass systems that dominate the LVL sample. Comparisons with
theoretical models suggest that the amplitude of deviations from the relation
found for starburst galaxies correlates with the age of the stellar populations
that dominate the ultraviolet/optical luminosities.Comment: Accepted for publication in ApJ; Figures 1,8,9 provided as jpeg
Polyunsaturated fatty acid metabolism in Atlantic salmon (Salmo salar) undergoing parr-smolt transformation and the effects of dietary linseed and rapeseed oils
Duplicate groups of Atlantic salmon parr were fed diets containing either fish oil (FO), rapeseed oil (RO), linseed oil (LO) or linseed oil supplemented with arachidonic acid (20:4n-6; AA) (LOA) from October (week 0) to seawater transfer in March (week 19). From March to July (weeks 20-34) all fish were fed a fish oil-containing diet. Fatty acyl desaturation and elongation activity in isolated hepatocytes incubated with [1-14C]18:3n-3 increased in all dietary groups, peaking in early March about one month prior to seawater transfer. Desaturation activities at their peak were significantly greater in fish fed the vegetable oils, particularly RO, compared to fish fed FO. Docosahexaenoic acid (22:6n-3:DHA) and AA in liver and gill polar lipids (PL) increased in all dietary groups during the freshwater phase whereas eicosapentaenoic acid (20:5n-3;EPA) increased greatly in all groups after seawater transfer. The AA/EPA ratio in tissue PL increased up to seawater transfer and then decreased after transfer. AA levels and the AA/EPA ratio in gill PL were generally higher in the LOA group. The levels of 18:3n-3 in muscle total lipid were increased significantly in the LO, LOA and, to a lesser extent, RO groups prior to transfer but were reduced to initial levels by the termination of the experiment (week 34). In contrast, 18:2n-6 in muscle total lipid was significantly increased after 18 weeks in fish fed the diets supplemented with RO and LO, and was significantly greater in the FO and RO groups at the termination of the experiment. Gill PGF production showed a large peak about two months after transfer to seawater. The production of total PGF post-transfer was significantly lower in fish previously fed the LOA diet. However, plasma chloride concentrations in fish subjected to a seawater challenge at 18 weeks were all lower in fish fed the diets with vegetable oils. This effect was significant in the case of fish receiving the diet with LOA, compared to those fed the diet containing FO. The present study showed that during parr-smolt transformation in Atlantic salmon there is a pre-adaptive increase in hepatocyte fatty acyl desaturation/elongation activities that is controlled primarily by environmental factors such as photoperiod and temperature but that can also be significantly modulated by diet. Feeding salmon parr diets supplemented with rapeseed or linseed oils prevented inhibition of the desaturase activities that is induced by feeding parr diets with fish oils and thus influenced the smoltification process by altering tissue PL fatty acid compositions and eicosanoid production. These effect, in turn, had a beneficial effect on the ability of the fish to osmoregulate and thus adapt to salinity changes
Dust heating sources in galaxies: the case of M33 (HERM33ES)
Dust emission is one of the main windows to the physics of galaxies and to
star formation as the radiation from young, hot stars is absorbed by the dust
and reemitted at longer wavelengths. The recently launched Herschel satellite
now provides a view of dust emission in the far-infrared at an unequaled
resolution and quality up to 500 \mu m. In the context of the Herschel HERM33ES
open time key project, we are studying the moderately inclined Scd local group
galaxy M33 which is located only 840 kpc away. In this article, using Spitzer
and Herschel data ranging from 3.6 \mu m to 500 \mu m, along with HI, H\alpha\
maps, and GALEX ultraviolet data we have studied the emission of the dust at
the high spatial resolution of 150 pc. Combining Spitzer and Herschel bands, we
have provided new, inclination corrected, resolved estimators of the total
infrared brightness and of the star formation rate from any combination of
these bands. The study of the colors of the warm and cold dust populations
shows that the temperature of the former is, at high brightness, dictated by
young massive stars but, at lower brightness, heating is taken over by the
evolved populations. Conversely, the temperature of the cold dust is tightly
driven by the evolved stellar populations.Comment: 29 pages, 12 figures, accepted for publication in A
Spitzer Observations of Cold Dust Galaxies
We combine new Spitzer Space Telescope observations in the mid- and
far-infrared with SCUBA 850 micron observations to improve the measurement of
dust temperatures, masses and luminosities for 11 galaxies of the SCUBA Local
Universe Galaxy Survey (SLUGS). By fitting dust models we measure typical dust
masses of 10E7.9 M_sol and dust luminosities of ~ 10E10 L_sol, for galaxies
with modest star formation rates. The data presented in this paper combined
with previous observations show that cold dust is present in all types of
spiral galaxies and is a major contributor to their total luminosity. Because
of the lower dust temperature of the SCUBA sources measured in this paper, they
have flatter Far-IR nu F_nu(160um)/nu F_nu(850um) slopes than the larger
Spitzer Nearby Galaxies Survey (SINGS), the sample that provides the best
measurements of the dust properties of galaxies in the nearby universe. The new
data presented here added to SINGS extend the parameter space that is well
covered by local galaxies, providing a comprehensive set of templates that can
be used to interpret the observations of nearby and distant galaxies.Comment: Accepted by A.J. 16 pages, 10 figures, 7 tables. High resolution
version at http://mips.as.arizona.edu/~cnaw/slugs_hires.pd
The Mid-IR Contribution Of Dust Enshrouded Stars In Six Nearby Galaxies
We measure the integrated contributions of dusty AGB stars and other luminous
red mid-IR sources to the mid-IR luminosities of 6 galaxies (M81, NGC 2403, NGC
300, M33 and the Magellanic Clouds). We find the dusty AGB stars whose mid-IR
fluxes are dominated by dust rather than photospheric emission contribute from
0.6% (M81) to 5.6% (SMC) of the 3.6 micron flux and 1.0% (M81) to 10.1% (SMC)
of the 4.5 micron flux. We find a trend of decreasing AGB contribution with
increasing galaxy metallicity, luminosity and mass and decreasing SSFR.
However, these galaxy properties are strongly correlated in our sample and the
simplest explanation of the trend is galaxy metallicity. Bright, red sources
other than dusty AGB stars represent a smaller fraction of the luminosity,
~1.2% at 3.6 microns, however their dust is likely cooler and their
contributions are likely larger at longer wavelengths. Excluding the SMC, the
contribution from these red sources correlates with the specific star formation
rate as we would expect for massive stars. In total, after correcting for dust
emission at other wavelengths, the dust around AGB stars radiates 0.1-0.8% of
the bolometric luminosities of the galaxies. Thus, hot dust emission from AGB
and other luminous dusty stars represent a small fraction of the total
luminosities of the galaxies but a significant fraction of their mid-IR
emissions.Comment: 9 pages, 6 figures, published in ApJ. For a brief video explaining
the key results of this paper, see http://www.youtube.com/user/OSUAstronom
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