8,335 research outputs found
AgRISTARS: Supporting research. Spring small grains planting date distribution model
A model was developed using 996 planting dates at 51 LANDSAT segments for spring wheat and spring barley in Minnesota, Montana, North Dakota, and South Dakota in 1979. Daily maximum and minimum temperatures and precipitation were obtained from the cooperative weather stations nearest to each segment. The model uses a growing degree day summation modified for daily temperature range to estimate the beginning of planting and uses a soil surface wetness variable to estimate how a fixed number of planting days are distributed after planting begins. For 1979, the model predicts first, median, and last planting dates with root mean square errors of 7.91, 6.61, and 7.09 days, respectively. The model also provides three or four dates to represent periods of planting activity within the planting season. Although the full model was not tested on an independent data set, it may be suitable in areas other than the U.S. Great Plains where spring small grains are planted as soon as soil and air temperatures become warm enough in the spring for plant growth
Extending Quantum Coherence in Diamond
We experimentally demonstrate over two orders of magnitude increase in the
coherence time of nitrogen vacancy centres in diamond by implementing
decoupling techniques. We show that equal pulse spacing decoupling performs
just as well as non-periodic Uhrig decoupling and has the additional benefit
that it allows us to take advantage of "revivals" in the echo (due to the
coherent nature of the bath) to explore the longest coherence times. At short
times, we can extend the coherence of particular quantum states out from
T_2*=2.7 us out to an effective T_2 > 340 us. For preserving arbitrary states
we show the experimental importance of using pulse sequences, that through
judicious choice of the phase of the pulses, compensate the imperfections of
individual pulses for all input states. At longer times we use these
compensated sequences to enhance the echo revivals and show a coherence time of
over 1.6 ms in ultra-pure natural abundance 13C diamond.Comment: 7 pages, 7 figures; minor syntax/typo. changes and updated reference
Variability of crop calendar stage dates
There are no author-identified significant results in this report
Universal Control of Nuclear Spins Via Anisotropic Hyperfine Interactions
We show that nuclear spin subsystems can be completely controlled via
microwave irradiation of resolved anisotropic hyperfine interactions with a
nearby electron spin. Such indirect addressing of the nuclear spins via
coupling to an electron allows us to create nuclear spin gates whose
operational time is significantly faster than conventional direct addressing
methods. We experimentally demonstrate the feasibility of this method on a
solid-state ensemble system consisting of one electron and one nuclear spin.Comment: RevTeX4, 8 pages, 8 figure
Comparison of laser speckle contrast imaging with laser Doppler for assessing microvascular function
Objective: To compare the inter-day reproducibility of post-occlusive reactive hyperaemia (PORH) and sympathetic vasomotor reflexes assessed by single-point laser Doppler flowmetry (SP-LDF), integrating-probe LDF (IP-LDF) and laser speckle contrast imaging (LSCI), and the spatial variability of PORH assessed by IP-LDF and LSCI. We also evaluated the relationship between IP-LDF and LSCI perfusion values across a broad range of skin blood flows.
Methods: Eighteen healthy adults (50% male, age 27 ± 4 years) participated in this study. Using SP-LDF, IP-LDF and LSCI, an index of skin blood flow was measured on the forearm during PORH (1-, 5- and 10-min occlusions) and on the finger pad during inspiratory gasp and cold pressor tests. These tests were repeated 3-7 days later. Data were converted to cutaneous vascular conductance (CVC; laser Doppler flow/mean arterial pressure) and expressed as absolute and relative changes from pre-stimulus CVC (ÎCVCABS and ÎCVCREL, respectively), as well as normalised to peak CVC for the PORH tests. Reproducibility was expressed as within-subjects coefficients of variation (CV, in %) and intraclass correlation coefficients.
Results: The reproducibility of PORH on the forearm was poorer when assessed with SP-LDF and IP-LDF compared to LSCI (e.g., CV for 5-min PORH ÎCVCABS = 35, 27 and 19%, respectively), with no superior method of data expression. In contrast, the reproducibility of the inspiratory gasp and cold pressor test responses on the finger pad were better with SP-LDF and IP-LDF compared to LSCI (e.g., CV for inspiratory gasp ÎCVCREL = 13, 7 and 19%, respectively). The spatial variability of PORH responses was poorer with IP-LDF compared to LSCI (e.g., CV ranging 11-35% versus 3-16%, respectively). The association between simultaneous LSCI and IP-LDF perfusion values was non-linear.
Conclusion: The reproducibility of cutaneous PORH was better when assessed with LSCI compared to SP-LDF and IP-LDF; probably due to measuring larger skin areas (lower inter-site variability). However, when measuring sympathetic vasomotor reflexes on the finger pad, reproducibility was better with SP-LDF and IP-LDF, perhaps due to the high sensitivity of LSCI to changes in skin blood flow at low levels
Vitamin K catabolite inhibition of ovariectomy-induced bone loss: Structureâactivity relationship considerations
The potential benefit of vitamin K as a therapeutic in osteoporosis is controversial and the vitamin K regimen being used clinically (45 mg/day) employs doses that are many times higher than required to ensure maximal gammaâcarboxylation of the vitamin Kâdependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5âcarbon (CAN5C) and 7âcarbon carboxylic acid (CAN7C) aliphatic sideâchain derivatives of the naphthoquinone moiety exert an osteotrophic role consistent with the treatment of osteoporosis
Magnetic properties of Yb2Mo2O7 and Gd2Mo2O7 from rare earth Mossbauer measurements
Using 170-Yb and 155-Gd Mossbauer measurements down to 0.03K, we have
examined the semiconducting pyrochlore Yb2Mo2O7 where the Mo intra-sublattice
interaction is anti-ferromagnetic and the metallic pyrochlore Gd2Mo2O7 where
this interaction is ferromagnetic. Additional information was obtained from
susceptibility, magnetisation and 172-Yb perturbed angular correlation
measurements. The microscopic measurements evidence lattice disorder which is
important in Yb2Mo2O7 and modest in Gd2Mo2O7. Magnetic irreversibilities occur
at 17K in Yb2Mo2O7 and at 75K in Gd2Mo2O7 and below these temperatures the rare
earths carry magnetic moments which are induced through couplings with the Mo
sublattice. In Gd2Mo2O7, we observe the steady state Gd hyperfine populations
at 0.027K are out of thermal equilibrium, indicating that Gd and Mo spin
fluctuations persist at very low temperatures. Frustration is thus operative in
this essentially isotropic pyrochlore where the dominant Mo intra-sublattice
interaction is ferromagnetic.Comment: 9 pages, 9 figure
Generalized Effective Reducibility
We introduce two notions of effective reducibility for set-theoretical
statements, based on computability with Ordinal Turing Machines (OTMs), one of
which resembles Turing reducibility while the other is modelled after Weihrauch
reducibility. We give sample applications by showing that certain (algebraic)
constructions are not effective in the OTM-sense and considerung the effective
equivalence of various versions of the axiom of choice
A Chandra X-ray detection of the L dwarf binary Kelu-1: Simultaneous Chandra and Very Large Array observations
Magnetic activity in ultracool dwarfs, as measured in X-rays and H,
shows a steep decline after spectral type M7-M8. So far, no L dwarf has been
detected in X-rays. In contrast, L dwarfs may have higher radio activity than M
dwarfs. We observe L and T dwarfs simultaneously in X-rays and radio to
determine their level of magnetic activity in the context of the general
decline of magnetic activity with cooler effective temperatures. The field L
dwarf binary Kelu-1 was observed simultaneously with Chandra and the Very Large
Array. Kelu-1AB was detected in X-rays with erg/s, while it remained undetected in the radio down to a limit of erg/s/Hz. We argue that,
whereas the X-ray and H emissions decline in ultracool dwarfs with
decreasing effective temperature, the radio luminosity stays (more or less)
constant across M and early-L dwarfs. The radio surface flux or the luminosity
may better trace magnetic activity in ultracool dwarfs than the ratio of the
luminosity to the bolometric luminosity. Deeper radio observations (and at
short frequencies) are required to determine if and when the cut-off in radio
activity occurs in L and T dwarfs, and what kind of emission mechanism takes
place in ultracool dwarfs.Comment: Accepted for publication as a Letter in Astronomy & Astrophysic
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