1,405 research outputs found
Electrically controlled topological micro cargo transportation
We demonstrate electrically controlled linear translation and precision positioning of a colloidal particle in a soft matter device. The basis of transportation is the time dependent electric field reconfiguration and manipulation of a topological line defect between two distinct hybrid aligned nematic liquid crystal domains having opposing tilt orientations. Deliberately tuning an applied voltage relative to a low threshold value (5.7 V at 1 kHz) permits defect trapping of the colloidal particle and allows subsequent control over the particleâs velocity and bidirectional linear movement over millimeter distances, without the need for externally imposed flow nor for lateral confining walls
Deformation of a nearly hemispherical conducting drop due to an electric field: theory and experiment
We consider, both theoretically and experimentally, the deformation due to an electric field of a pinned nearly-hemispherical static sessile drop of an ionic fluid with a high conductivity resting on the lower substrate of a parallel plate capacitor. Using both numerical and asymptotic approaches we find solutions to the coupled electrostatic and augmented YoungâLaplace equations which agree very well with the experimental results. Our asymptotic solution for the drop interface extends previous work in two ways, namely to drops that have zero-field contact angles that are not exactly Ï/2 and to higher order in the applied electric field, and provides useful predictive equations for the changes in the height, contact angle and pressure as functions of the zero-field contact angle, drop radius, surface tension and applied electric field. The asymptotic solution requires some numerical computations, and so a surprisingly accurate approximate analytical asymptotic solution is also obtained
Ion traps fabricated in a CMOS foundry
We demonstrate trapping in a surface-electrode ion trap fabricated in a 90-nm
CMOS (complementary metal-oxide-semiconductor) foundry process utilizing the
top metal layer of the process for the trap electrodes. The process includes
doped active regions and metal interconnect layers, allowing for co-fabrication
of standard CMOS circuitry as well as devices for optical control and
measurement. With one of the interconnect layers defining a ground plane
between the trap electrode layer and the p-type doped silicon substrate, ion
loading is robust and trapping is stable. We measure a motional heating rate
comparable to those seen in surface-electrode traps of similar size. This is
the first demonstration of scalable quantum computing hardware, in any
modality, utilizing a commercial CMOS process, and it opens the door to
integration and co-fabrication of electronics and photonics for large-scale
quantum processing in trapped-ion arrays.Comment: 4 pages, 3 figure
A Search for Molecular Gas in GHz Peaked Spectrum Radio Sources
We present searches for molecular gas (CO, OH, CS, and Ammonia) in six GHz
Peaked Spectrum (GPS) radio sources. We do not detect gas in any source and
place upper limits on the mass of molecular gas which are generally in the
range 1E9 to a few times 1E10 solar masses. These limits are consistent with
the following interpretations: (1) GPS sources do not require very dense gas in
their hosts, and (2) The GPS sources are unlikely to be confined by dense gas
and will evolve to become larger radio sources
Pulmonary hypertension and measurement of exercise capacity remotely: evaluation of the 1-min sit-to-stand test (PERSPIRE) â a cohort study
Background Multiparameter risk assessment is recommended to aid treatment decisions in patients with pulmonary arterial hypertension. The 1-min sit-to-stand test (1MSTS) has been validated for use in other respiratory illnesses. The aim of this study was to evaluate its safety in the hospital setting and potential utility in remote assessment in patients with pulmonary hypertension.
Methods In a prospective cohort study design patients performed the 1MSTS and incremental shuttle walk test (ISWT) on the same day. The primary aim of the study was to assess safety signals and correlations with other metrics used in risk assessment.
Results 60 patients with pulmonary arterial hypertension and 15 with chronic thromboembolic pulmonary hypertension were enrolled. No adverse events were recorded. Post-test change in physiological parameters was lower for the 1MSTS than for the ISWT in heart rate (mean±sd change +9.4±8.0 versus +38.3±25.9 beats per min, p<0.001), oxygen saturation (â3.8±4.0% versus â8.9±7.3%, p<0.01) and systolic blood pressure (+10.1±10.5 versus +17.7±19â
mmHg, p<0.001). There were significant correlations between the 1MSTS and ISWT (r=0.702, p<0.01), World Health Organization functional class (r=ââ0.449, p<0.01), emPHAsis-10 (â0.436, p<0.001) and N-terminal pro-b-type natriuretic peptide (r=ââ0.270, p=0.022). 97% of patients were willing to perform the test at home.
Conclusion This study has demonstrated the safety, sub-maximal characteristics of the 1MSTS in pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension in the hospital setting, its positive correlation with the ISWT and potential role in remote risk assessment. Further evaluation of this exercise test is now warranted
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Frequency-controlled dielectrophoresis-driven wetting of nematic liquid crystals
We show that surface-localized dielectrophoresis-driven wetting of anisotropic nematic liquid crystal sessile droplets obeys the same relationship, cosâĄ[Ξ(Vo)]=cosâĄ[Ξy]-ÎČ(Vo^2), which has previously been found for isotropic liquid droplets, even though the nematic liquid crystal phase possesses a uniaxial dielectric permittivity tensor. We also demonstrate that the dielectrowetting coefficient ÎČ, which determines the magnitude of the reduction in the contact angle, from Ξy to Ξ(Vo ), through the action of a potential difference Vo, can be controlled by the frequency of the applied voltage between interdigitated electrodes beneath a droplet of highly dispersive nematic liquid crystal. Our Q-tensor modelling of the electric field-induced 2-dimensional n-director distortions within a nematic droplet elucidates how this linear relationship holds for voltages when |Ξ(Vo )-Ξy| exceeds 3-4 degrees
The Extraordinary `Superthin' Spiral Galaxy UGC7321. I. Disk Color Gradients and Global Properties from Multiwavelength Observations
We present B- and R-band imaging and photometry, H-alpha narrow-band imaging,
NIR H-band imaging, and HI 21-cm spectroscopy of the nearby Sd spiral galaxy
UGC7321. UGC7321 exhibits a remarkably thin stellar disk with no bulge
component. The galaxy has a very diffuse, low surface brightness disk, which
appears to suffer little internal extinction in spite of its edge-on geometry.
The UGC7321 disk shows significant B-R color gradients in both the radial and
vertical directions. These color gradients cannot be explained solely by dust
and are indicative of changes in the mix of stellar ages and/or metallicity as
a function of both radius and height above the galaxy plane. The outer regions
of the UGC7321 disk are too blue to be explained by low metallicity alone
(B-R<0.6), and must be relatively young. However, the galaxy also contains
stellar populations with B-R>1.1, indicating it is not a young or
recently-formed galaxy. The disk of UGC7321 is not a simple exponential, but
exhibits a light excess at small radii, as well as distinct surface brightness
zones. Together the properties of UGC7321 imply that it is an under-evolved
galaxy in both a dynamical and in a star-formation sense. (Abridged)Comment: Accepted to the Astronomical Journal; 28 pages, 1 table and 21
figures (GIF and postscript
Search for Blue Compact Dwarf Galaxies During Quiescence
Blue Compact Dwarf (BCD) galaxies are metal poor systems going through a
major starburst that cannot last for long. We have identified galaxies which
may be BCDs during quiescence (QBCD), i.e., before the characteristic starburst
sets in or when it has faded away. These QBCD galaxies are assumed to be like
the BCD host galaxies. The SDSS/DR6 database provides ~21500 QBCD candidates.
We also select from SDSS/DR6 a complete sample of BCD galaxies to serve as
reference. The properties of these two galaxy sets have been computed and
compared. The QBCD candidates are thirty times more abundant than the BCDs,
with their luminosity functions being very similar except for the scaling
factor, and the expected luminosity dimming associated with the end of the
starburst. QBCDs are redder than BCDs, and they have larger HII region based
oxygen abundance. QBCDs also have lower surface brightness. The BCD candidates
turn out to be the QBCD candidates with the largest specific star formation
rate (actually, with the largest H_alpha equivalent width). One out of each
three dwarf galaxies in the local universe may be a QBCD. The properties of the
selected BCDs and QBCDs are consistent with a single sequence in galactic
evolution, with the quiescent phase lasting thirty times longer than the
starburst phase. The resulting time-averaged star formation rate is low enough
to allow this cadence of BCD -- QBCD phases during the Hubble time.Comment: Accepted for publication in ApJ. 17 pages. 13 Fig
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