3,401 research outputs found
Thin film dielectric microstrip kinetic inductance detectors
Microwave Kinetic Inductance Detectors, or MKIDs, are a type of low
temperature detector that exhibit intrinsic frequency domain multiplexing at
microwave frequencies. We present the first theory and measurements on a MKID
based on a microstrip transmission line resonator. A complete characterization
of the dielectric loss and noise properties of these resonators is performed,
and agrees well with the derived theory. A competitive noise equivalent power
of 5 W Hz at 1 Hz has been demonstrated. The
resonators exhibit the highest quality factors known in a microstrip resonator
with a deposited thin film dielectric.Comment: 10 pages, 4 figures, APL accepte
Electric-field noise from carbon-adatom diffusion on a Au(110) surface: first-principles calculations and experiments
The decoherence of trapped-ion quantum gates due to heating of their motional
modes is a fundamental science and engineering problem. This heating is
attributed to electric-field noise arising from the trap-electrode surfaces. In
this work, we investigate the source of this noise by focusing on the diffusion
of carbon-containing adsorbates on the surface of Au(110). We show by density
functional theory, based on detailed scanning probe microscopy, how the carbon
adatom diffusion on the gold surface changes the energy landscape, and how the
adatom dipole moment varies with the diffusive motion. A simple model for the
diffusion noise, which varies quadratically with the variation of the dipole
moment, qualitatively reproduces the measured noise spectrum, and the estimate
of the noise spectral density is in accord with measured values.Comment: 8 pages, 6 figure
Thermally induced magnetic relaxation in square artificial spin ice
The properties of natural and artificial assemblies of interacting elements,
ranging from Quarks to Galaxies, are at the heart of Physics. The collective
response and dynamics of such assemblies are dictated by the intrinsic
dynamical properties of the building blocks, the nature of their interactions
and topological constraints. Here we report on the relaxation dynamics of the
magnetization of artificial assemblies of mesoscopic spins. In our model
nano-magnetic system - square artificial spin ice - we are able to control the
geometrical arrangement and interaction strength between the magnetically
interacting building blocks by means of nano-lithography. Using time resolved
magnetometry we show that the relaxation process can be described using the
Kohlrausch law and that the extracted temperature dependent relaxation times of
the assemblies follow the Vogel-Fulcher law. The results provide insight into
the relaxation dynamics of mesoscopic nano-magnetic model systems, with
adjustable energy and time scales, and demonstrates that these can serve as an
ideal playground for the studies of collective dynamics and relaxations.Comment: 15 pages, 5 figure
Covariation of vegetation and climate constrains present and future T/ET variability
The reliable partitioning of the terrestrial latent heat flux into evaporation (E) and transpiration (T) is important for linking carbon and water cycles and for better understanding ecosystem functioning at local, regional and global scales. Previous research revealed that the transpiration-to-evapotranspiration ratio (T/ET) is well constrained across ecosystems and is nearly independent of vegetation characteristics and climate. Here we investigated the reasons for such a global constancy in present-day T/ET by jointly analysing observations and process-based model simulations. Using this framework, we also quantified how the ratio T/ET could be influenced by changing climate. For present conditions, we found that the various components of land surface evaporation (bare soil evaporation, below canopy soil evaporation, evaporation from interception), and their respective ratios to plant transpiration, depend largely on local climate and equilibrium vegetation properties. The systematic covariation between local vegetation characteristics and climate, resulted in a globally constrained value of T/ET = ~70 ± 9% for undisturbed ecosystems, nearly independent of specific climate and vegetation attributes. Moreover, changes in precipitation amounts and patterns, increasing air temperatures, atmospheric CO2 concentration, and specific leaf area (the ratio of leaf area per leaf mass) was found to affect T/ET in various manners. However, even extreme changes in the aforementioned factors did not significantly modify T/ET
Endogenous retinoids in rat epididymal tissue and rat and human spermatozoa
Recent work has demonstrated high levels of retinoid binding proteins in rat epididymis, and a lumenal retinoic acid binding protein has been purified. These findings suggested that vitamin A may be involved in spermatozoal maturation in the epididymis. We further addressed this question by quantifying retinol, retinyl esters, and retinoic acid isomers from perfused epididymal tissue, from rat testicular and epididymal spermatozoa, and from human ejaculate sperm. HPLC showed vitamin A levels to be higher in caput than in corpus or cauda tissue. Retinoic acid and 9-cis-retinoic acid were found to be graded from lowest levels in caput to highest in cauda. Spermatozoa from caput epididymidis and enriched testicular spermatozoa were found to have higher levels of vitamin A than did spermatozoa from corpus or cauda epididymidis. Spermatozoal retinyl esters had acyl substituents similar to those seen in whole epididymis, and diminished in quantity in sperm from distal segments. Human ejaculate sperm were found to retain high levels of retinyl palmitate and stearate. Retinol and retinoic acid were only marginally detectable in human sperm. Retention of retinoids in mature spermatozoa suggests roles for vitamin A in spermatozoal reproductive physiology beyond the epididymal stage
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