138 research outputs found
Zeptonewton force sensing with nanospheres in an optical lattice
Optically trapped nanospheres in high-vaccum experience little friction and
hence are promising for ultra-sensitive force detection. Here we demonstrate
measurement times exceeding seconds and zeptonewton force sensitivity
with laser-cooled silica nanospheres trapped in an optical lattice. The
sensitivity achieved exceeds that of conventional room-temperature solid-state
force sensors, and enables a variety of applications including electric field
sensing, inertial sensing, and gravimetry. The optical potential allows the
particle to be confined in a number of possible trapping sites, with precise
localization at the anti-nodes of the optical standing wave. By studying the
motion of a particle which has been moved to an adjacent trapping site, the
known spacing of the lattice anti-nodes can be used to calibrate the
displacement spectrum of the particle. Finally, we study the dependence of the
trap stability and lifetime on the laser intensity and gas pressure, and
examine the heating rate of the particle in high vacuum in the absence of
optical feedback cooling.Comment: 5 pages, 4 figures, minor changes, typos corrected, references adde
U.S. Construction Management Students\u27 Comfort Level with and Knowledge of Mobile Technologies
Mobile technologies are becoming increasingly common on U.S. construction sites as companies become aware of how they can simplify and automate the capturing of information in the field, and communicate that information back to company management systems. Field personnel are now being equipped with smart phones or tablets to check email, look at blueprints, take progress photos, or create punchlists, all with one device. These technologies are being used to make work efforts more efficient, raise productivity, reduce costs, and positively impact project profitability.
As the U.S. construction industry moves to these mobile technologies, so too should university construction management programs move to mobile education and learning applications to ensure that students are prepared for a mobile construction industry. This study uses university provided iPads in construction management classes to expose students to mobile technologies before they enter the workforce. Pre- and post-test surveys collected data about first-year and upper-level construction management students comfort with mobile technologies, their knowledge about mobile technologies in construction, and their views on whether they think they will use mobile technologies in the workplace and for what tasks.
While some students entered with a very low comfort level with mobile devices, there were gains in comfort level by nearly all students. Most, even first-year students, were able to envision how a mobile device could be used within the construction industry to perform various tasks, and their visions increased from the beginning of the semester to the end, even though no formal instruction was done in this area. The gains were primarily due to exposure to the device and general usage. By gaining a greater understanding of student comfort with and knowledge of emerging technologies, more effective educational and training methodologies can be developed to facilitate instruction and improve the effectiveness of students upon graduation
Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z
The classification of galaxy mergers and isolated disks is key for
understanding the relative importance of galaxy interactions and secular
evolution during the assembly of galaxies. The kinematic properties of galaxies
as traced by emission lines have been used to suggest the existence of a
significant population of high-z star-forming galaxies consistent with isolated
rotating disks. However, recent studies have cautioned that post-coalescence
mergers may also display disk-like kinematics. To further investigate the
robustness of merger/disk classifications based on kinematic properties, we
carry out a systematic classification of 24 local (U)LIRGs spanning a range of
galaxy morphologies: from isolated spiral galaxies, ongoing interacting
systems, to fully merged remnants. We artificially redshift the WiFeS
observations of these local (U)LIRGs to z=1.5 to make a realistic comparison
with observations at high-z, and also to ensure that all galaxies have the same
spatial sampling of ~900 pc. Using both kinemetry-based and visual
classifications, we find that the reliability of kinematic classification shows
a strong trend with the interaction stage of galaxies. Mergers with two nuclei
and tidal tails have the most distinct kinematic properties compared to
isolated disks, whereas a significant population of the interacting disks and
merger remnants are indistinguishable from isolated disks. The high fraction of
late-stage mergers showing disk-like kinematics reflects the complexity of the
dynamics during galaxy interactions. However, the exact fractions of
misidentified disks and mergers depend on the definition of kinematic
asymmetries and the classification threshold when using kinemetry-based
classifications. Our results suggest that additional indicators such as
morphologies traced by stars or molecular gas are required to further constrain
the merger/disk classifications at high-z.Comment: 16 pages, 5 figures, ApJ accepte
Discovery of a red backsplash galaxy candidate near M81
Understanding quenching mechanisms in low-mass galaxies is essential for
understanding galaxy evolution overall. In particular, isolated galaxies are
important tools to help disentangle the complex internal and external processes
that impact star formation. Comparisons between quenched field and satellite
galaxies in the low mass regime offer a substantial opportunity for discovery,
although very few quenched galaxies with masses below are known outside the virial radius, , of any host halo.
Importantly, simulations and observations suggest that an in-between population
of backsplash galaxies also exists that may complement interpretations of
environmental quenching. Backsplash galaxies -- like field galaxies -- reside
outside the virial radius of a host halo, but their star formation can be
deeply impacted by previous interactions with more massive systems. In this
paper, we report the discovery of a low-mass () quenched galaxy approximately in projection from the
M81 group. We use surface brightness fluctuations (SBF) to investigate the
possibility that the new galaxy, dubbed dw0910p7326 (nicknamed Blobby), is a
backsplash galaxy or a more distant field galaxy. The measured SBF distance of
Mpc indicates that Blobby likely
lies between outside the combined M81--M82 system.
Given its distance and quiescence, Blobby is a good candidate for a backsplash
galaxy and could provide hints about the formation and evolution of these
interesting objects.Comment: 15 pages, 8 figures, to be submitted to MNRAS, comments welcome
Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women
Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justastoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO)
Spectral Energy Distributions of Local Luminous And Ultraluminous Infrared Galaxies
Luminous and ultraluminous infrared galaxies ((U)LIRGs) are the most extreme
star forming galaxies in the universe. The local (U)LIRGs provide a unique
opportunity to study their multi-wavelength properties in detail for comparison
to their more numerous counterparts at high redshifts. We present common large
aperture photometry at radio through X-ray wavelengths, and spectral energy
distributions (SEDs) for a sample of 53 nearby LIRGs and 11 ULIRGs spanning log
(LIR/Lsun) = 11.14-12.57 from the flux-limited Great Observatories All-sky LIRG
Survey (GOALS). The SEDs for all objects are similar in that they show a broad,
thermal stellar peak and a dominant FIR thermal dust peak, where nuLnu(60um) /
nuLnu(V) increases from ~2-30 with increasing LIR. When normalized at
IRAS-60um, the largest range in the luminosity ratio,
R(lambda)=log[nuLnu(lambda)/nuLnu(60um)] observed over the full sample is seen
in the Hard X-rays (HX=2-10 keV). A small range is found in the Radio (1.4GHz),
where the mean ratio is largest. Total infrared luminosities, LIR(8-1000um),
dust temperatures, and dust masses were computed from fitting thermal dust
emission modified blackbodies to the mid-infrared (MIR) through submillimeter
SEDs. The new results reflect an overall ~0.02 dex lower luminosity than the
original IRAS values. Total stellar masses were computed by fitting stellar
population synthesis models to the observed near-infrared (NIR) through
ultraviolet (UV) SEDs. Mean stellar masses are found to be log(M/Msun) =
10.79+/-0.40. Star formation rates have been determined from the infrared
(SFR_IR~45Msun/yr) and from the monochromatic UV luminosities
(SFR_UV~1.3Msun/yr), respectively. Multiwavelength AGN indicators have be used
to select putative AGN: about 60% of the ULIRGs would have been classified as
an AGN by at least one of the selection criteria.Comment: 39 pages, including 12 figures and 11 tables; accepted for
publication in ApJ
Beyond Ultra-Diffuse Galaxies I: Mass-Size Outliers Among the Satellites of Milky Way Analogs
Large diffuse galaxies are hard to find, but understanding the environments
where they live, their numbers, and ultimately their origins, is of intense
interest and importance for galaxy formation and evolution. Using Subaru's
Hyper Suprime-Cam Strategic Survey Program, we perform a systematic search for
low surface brightness galaxies and present novel and effective methods for
detecting and modeling them. As a case study, we surveyed 922 Milky Way analogs
in the nearby Universe () and build a large sample of
satellite galaxies that are outliers in the mass-size relation. These
``ultra-puffy'' galaxies (UPGs), defined to be above the average
mass-size relation, represent the tail of the satellite size distribution. We
find that each MW analog hosts ultra-puffy
galaxies on average, which is consistent with but slightly lower than the
observed abundance at this halo mass in the Local Volume. We also construct a
sample of ultra-diffuse galaxies (UDGs) in MW analogs and find an abundance of
per host. With literature results, we confirm that
the UDG abundance scales with the host halo mass following a sublinear power
law. We argue that our definition for ultra-puffy galaxies, which is based on
the mass-size relation, is more physically-motivated than the common definition
of ultra-diffuse galaxies, which depends on surface brightness and size cuts
and thus yields different surface mass density cuts for quenched and
star-forming galaxies.Comment: 19 pages, 7 figures, submitted to Ap
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