3,139 research outputs found
Anatomy of Cirrus Clouds: Results from the Emerald Airborne Campaigns
2000 FLORIDA AVE NW, WASHINGTON, USA, DC,
2000
Precision Pastoralism‐Advanced Systems for Management and Integration of Livestock and Forage Resources in the Semi‐Arid Rangelands in South Eastern Australia
Single-level degenerative cervical disc disease and driving disability: Results from a prospective, randomized trial
Study Design Post hoc analysis of prospective, randomized trial. Objective To investigate the disability associated with driving and single-level degenerative, cervical disc disease and to investigate the effect of surgery on driving disability. Methods Post hoc analysis of data obtained from three sites participating in a multicenter, randomized, controlled trial comparing cervical disc arthroplasty (TDA) with anterior cervical discectomy and fusion (ACDF). The driving subscale of the Neck Disability Index (NDI) was analyzed for all patients. A dichotomous severity score was created from the NDI. Statistical comparisons were made within and between groups. Results Two-year follow-up was available for 118/135 (87%) patients. One half of the study population (49.6%) reported moderate or severe preoperative driving difficulty. This disability associated with driving was similar among the two groups (ACDF: 2.5 ± 1.1, TDA: 2.6 ± 1.0, p = 0.646). The majority of patients showed improvement, with no or little driving disability, at the sixth postoperative week (ACDF: 75%, TDA: 90%, p = 0.073). At no follow-up point did a difference exist between groups according to the severity index. Conclusions Many patients suffering from radiculopathy or myelopathy from cervical disc disease are limited in their ability to operate an automobile. Following anterior cervical spine surgery, most patients are able to return to comfortable driving at 6 weeks
Calnexin, calreticulin and cytoskeleton-associated proteins modulate uptake and growth of Legionella pneumophila in Dictyostelium discoideum.
UV/Ozone treatment to reduce metal-graphene contact resistance
We report reduced contact resistance of single-layer graphene devices by
using ultraviolet ozone (UVO) treatment to modify the metal/graphene contact
interface. The devices were fabricated from mechanically transferred, chemical
vapor deposition (CVD) grown, single layer graphene. UVO treatment of graphene
in the contact regions as defined by photolithography and prior to metal
deposition was found to reduce interface contamination originating from
incomplete removal of poly(methyl methacrylate) (PMMA) and photoresist. Our
control experiment shows that exposure times up to 10 minutes did not introduce
significant disorder in the graphene as characterized by Raman spectroscopy. By
using the described approach, contact resistance of less than 200 {\Omega}
{\mu}m was achieved, while not significantly altering the electrical properties
of the graphene channel region of devices.Comment: 17 pages, 5 figure
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Including a non-holonomic constraint in the FSP (full space parameterization) method for mobile manipulators` motion planning
The efficient utilization of the motion capabilities of mobile manipulators, i.e.. manipulators mounted on mobile platforms, requires the resolution of the kinematically redundant system formed by the addition of the degrees of freedom (d.o.f.) of the platform to those of the manipulator. At the velocity level, the linearized Jacobian equation for such a redundant system represents an underspecified system of algebraic equations, which can be subject to a set of constraints such as obstacles in the workspace and various limits on the joint motions. A method, which we named the FSP (Full Space Parameterization), has recently been developed to resolve such underspecified systems with constraints that may vary in time and in number during a single trajectory. The application of the method to motion planning problems with obstacle and joint limit avoidance was discussed in some of our previous work. In this paper, we present the treatment in the FSP of a non-holonomic constraint on the platform motion, and give corresponding analytical solutions for resolving the redundancy with a general optimization criterion. Comparative trajectories involving a 10 d.o.f. mobile manipulator testbed moving with and without a non-holonomic constraint for the platform motion, are presented to illustrate the use and efficiency of the FSP approach in motion planning problems for highly kinematically redundant and constrained systems
Observations and modelling of microphysical variability, aggregation and sedimentation in tropical anvil cirrus outflow regions
Aircraft measurements of the microphysics of a tropical convective anvil (at
temperatures ~−60 °C) forming above the Hector storm, over the
Tiwi Islands, Northern Australia, have been conducted with a view to
determining ice crystal aggregation efficiencies from in situ measurements.
The observed microphysics have been compared to an explicit bin-microphysical
model of the anvil region, which includes crystal growth by vapour diffusion
and aggregation and the process of differential sedimentation.
It has been found in flights made using straight and level runs perpendicular
to the storm that the number of ice crystals initially decreased with
distance from the storm as aggregation took place resulting in larger
crystals, followed by their loss from the cloud layer due to sedimentation.
The net result was that the mass (i.e. Ice Water Content) in the anvil
Ci cloud decreased, but also that the average particle size (weighted by
number) remained relatively constant along the length of the anvil outflow.
Comparisons with the explicit microphysics model showed that the changes in
the shapes of the ice crystal spectra as a function of distance from the
storm could be explained by the model if the aggregation efficiency was set
to values of Eagg~0.5 and higher. This result is supported by
recent literature on aggregation efficiencies for complex ice particles and
suggests that either the mechanism of particle interlocking is important to
the aggregation process, or that other effects are occuring, such as
enhancement of ice-aggregation by high electric fields that arise as a
consequence of charge separation within the storm.
It is noteworthy that this value of the ice crystal aggregation efficiency is
much larger than values used in cloud resolving models at these temperatures,
which typically use E~0.0016. These results are important to
understanding how cold clouds evolve in time and for the treatment of the
evolution of tropical Ci in numerical models
Dynamics of DNA replication loops reveal temporal control of lagging-strand synthesis
In all organisms, the protein machinery responsible for the replication of DNA, the replisome, is faced with a directionality problem. The antiparallel nature of duplex DNA permits the leading-strand polymerase to advance in a continuous fashion, but forces the lagging-strand polymerase to synthesize in the opposite direction. By extending RNA primers, the lagging-strand polymerase restarts at short intervals and produces Okazaki fragments. At least in prokaryotic systems, this directionality problem is solved by the formation of a loop in the lagging strand of the replication fork to reorient the lagging-strand DNA polymerase so that it advances in parallel with the leading-strand polymerase. The replication loop grows and shrinks during each cycle of Okazaki fragment synthesis. Here we use single-molecule techniques to visualize, in real time, the formation and release of replication loops by individual replisomes of bacteriophage T7 supporting coordinated DNA replication. Analysis of the distributions of loop sizes and lag times between loops reveals that initiation of primer synthesis and the completion of an Okazaki fragment each serve as a trigger for loop release. The presence of two triggers may represent a fail-safe mechanism ensuring the timely reset of the replisome after the synthesis of every Okazaki fragment.
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