527 research outputs found
Is ESN releasing fast enough to supply winter wheat nitrogen demand?
Non-Peer ReviewedThe purpose of this study is to investigate nitrogen release from various split rate applications of seed-placed environmentally smart nitrogen (ESN) and spring-applied dribble banded Agrotain-UAN (urea and ammonium nitrate solution) and broadcast Agrotain-urea in winter wheat. Cool spring soil conditions have the potential to limit nitrogen (N) release from ESN potentially limiting grain yield potential. Plant root simulator (PRSâ˘) probes were used to monitor N soil supply. It was discovered that N supply did not vary significantly between the split-rate treatments. There were also no significant differences between grain yield and protein content. These results suggest that N release from ESN was not limited by cool spring temperatures and allowed plant vigour similar to traditional spring-applied methods
Evaluation of two lyophilized molecular assays to rapidly detect foot-and-mouth disease virus directly from clinical samples in field settings
Accurate, timely diagnosis is essential for the control, monitoring and eradication of footâandâmouth disease (FMD). Clinical samples from suspect cases are normally tested at reference laboratories. However, transport of samples to these centralized facilities can be a lengthy process that can impose delays on critical decision making. These concerns have motivated work to evaluate simpleâtoâuse technologies, including molecularâbased diagnostic platforms, that can be deployed closer to suspect cases of FMD. In this context, FMD virus (FMDV)âspecific reverse transcription loopâmediated isothermal amplification (RTâLAMP) and realâtime RTâPCR (rRTâPCR) assays, compatible with simple sample preparation methods and in situ visualization, have been developed which share equivalent analytical sensitivity with laboratoryâbased rRTâPCR. However, the lack of robust âreadyâtoâuse kitsâ that utilize stabilized reagents limits the deployment of these tests into field settings. To address this gap, this study describes the performance of lyophilized rRTâPCR and RTâLAMP assays to detect FMDV. Both of these assays are compatible with the use of fluorescence to monitor amplification in realâtime, and for the RTâLAMP assays end point detection could also be achieved using molecular lateral flow devices. Lyophilization of reagents did not adversely affect the performance of the assays. Importantly, when these assays were deployed into challenging laboratory and field settings within East Africa they proved to be reliable in their ability to detect FMDV in a range of clinical samples from acutely infected as well as convalescent cattle. These data support the use of highly sensitive molecular assays into field settings for simple and rapid detection of FMDV
Bespoke Diblock Copolymer Nanoparticles Enable Production of Relatively Stable Oil-in-Water Pickering Nanoemulsions
Sterically-stabilized diblock copolymer nanoparticles with an intensity-average diameter of 25 nm are prepared in the form of a concentrated aqueous dispersion using polymerization-induced self-assembly (PISA). Addition of n-dodecane followed by high-shear homogenization produces n-dodecane-in-water Pickering macroemulsions of 22-46 ¾m diameter. If the nanoparticles are present in sufficient excess, subsequent processing using a high-pressure microfluidizer leads to formation of Pickering nanoemulsions with a mean droplet diameter below 200 nm. The size of these Pickering nanoemulsions can be tuned by systematically varying the nanoparticle concentration, applied pressure, the number of passes and the oil volume fraction. High internal phase emulsions can also be achieved by increasing the n-dodecane volume fraction up to 0.80. TEM studies of (dried) n-dodecane droplets confirm the presence of intact nanoparticles and suggest a relatively high surface coverage, which is consistent with model packing calculations based on radius ratios. Such Pickering nanoemulsions proved to be remarkably stable with respect to Ostwald ripening, with no significant change in the mean DLS droplet diameter after storage for approximately four months at 20 °C
Core Alzheimerâs disease cerebrospinal fluid biomarker assays are not affected by aspiration or gravity drip extraction methods
Background
CSF biomarkers are well-established for routine clinical use, yet a paucity of comparative assessment exists regarding CSF extraction methods during lumbar puncture. Here, we compare in detail biomarker profiles in CSF extracted using either gravity drip or aspiration.
Methods
Biomarkers for β-amyloidopathy (Aβ1â42, Aβ1â40), tauopathy (total tau), or synapse pathology (BACE1, Neurogranin Trunc-p75, Îą-synuclein) were assessed between gravity or aspiration extraction methods in a sub-population of the Australian Imaging, Biomarkers and Lifestyle (AIBL) study (cognitively normal, N =â36; mild cognitive impairment, N =â8; Alzheimerâs disease, N =â6).
Results
High biomarker concordance between extraction methods was seen (concordance correlation >â0.85). Passing Bablock regression defined low beta coefficients indicating high scalability.
Conclusions
Levels of these commonly assessed CSF biomarkers are not influenced by extraction method. Results of this study should be incorporated into new consensus guidelines for CSF collection, storage, and analysis of biomarkers
Fast Non-Adiabatic Two Qubit Gates for the Kane Quantum Computer
In this paper we apply the canonical decomposition of two qubit unitaries to
find pulse schemes to control the proposed Kane quantum computer. We explicitly
find pulse sequences for the CNOT, swap, square root of swap and controlled Z
rotations. We analyze the speed and fidelity of these gates, both of which
compare favorably to existing schemes. The pulse sequences presented in this
paper are theoretically faster, higher fidelity, and simpler than existing
schemes. Any two qubit gate may be easily found and implemented using similar
pulse sequences. Numerical simulation is used to verify the accuracy of each
pulse scheme
Electron Exchange Coupling for Single Donor Solid-State Qubits
Inter-valley interference between degenerate conduction band minima has been
shown to lead to oscillations in the exchange energy between neighbouring
phosphorus donor electron states in silicon \cite{Koiller02,Koiller02A}. These
same effects lead to an extreme sensitivity of the exchange energy on the
relative orientation of the donor atoms, an issue of crucial importance in the
construction silicon-based spin quantum computers. In this article we calculate
the donor electron exchange coupling as a function of donor position
incorporating the full Bloch structure of the Kohn-Luttinger electron
wavefunctions. It is found that due to the rapidly oscillating nature of the
terms they produce, the periodic part of the Bloch functions can be safely
ignored in the Heitler-London integrals as was done by Koiller et. al. [Phys.
Rev. Lett. 88,027903(2002),Phys. Rev. B. 66,115201(2002)], significantly
reducing the complexity of calculations.
We address issues of fabrication and calculate the expected exchange coupling
between neighbouring donors that have been implanted into the silicon substrate
using an 15keV ion beam in the so-called 'top down' fabrication scheme for a
Kane solid-state quantum computer. In addition we calculate the exchange
coupling as a function of the voltage bias on control gates used to manipulate
the electron wavefunctions and implement quantum logic operations in the Kane
proposal, and find that these gate biases can be used to both increase and
decrease the magnitude of the exchange coupling between neighbouring donor
electrons. The zero-bias results reconfirm those previously obtained by
Koiller.Comment: 10 Pages, 8 Figures. To appear in Physical Review
Carbon clusters near the crossover to fullerene stability
The thermodynamic stability of structural isomers of ,
, and , including
fullerenes, is studied using density functional and quantum Monte Carlo
methods. The energetic ordering of the different isomers depends sensitively on
the treatment of electron correlation. Fixed-node diffusion quantum Monte Carlo
calculations predict that a isomer is the smallest stable
graphitic fragment and that the smallest stable fullerenes are the
and clusters with and
symmetry, respectively. These results support proposals that a
solid could be synthesized by cluster deposition.Comment: 4 pages, includes 4 figures. For additional graphics, online paper
and related information see http://www.tcm.phy.cam.ac.uk/~prck
Systemic perturbations of the kynurenine pathway precede progression to dementia independently of amyloid-β
Increasing evidence suggests that kynurenine pathway (KP) dyshomeostasis may promote disease progression in dementia. Studies in Alzheimer's disease (AD) patients confirm KP dyshomeostasis in plasma and cerebrospinal fluid (CSF) which correlates with amyloid-β and tau pathology. Herein, we performed the first comprehensive study assessing baseline levels of KP metabolites in participants enrolling in the Australian Imaging Biomarkers Flagship Study of Aging. Our purpose was to test the hypothesis that changes in KP metabolites may be biomarkers of dementia processes that are largely silent. We used a cross-sectional analytical approach to assess non-progressors (N = 73); cognitively normal (CN) or mild cognitive impairment (MCI) participants at baseline and throughout the study, and progressors (N = 166); CN or MCI at baseline but progressing to either MCI or AD during the study. Significant KP changes in progressors included increased 3-hydroxyanthranilic acid (3-HAA) and 3-hydroxyanthranilic acid/anthranilic acid (3-HAA/AA) ratio, the latter having the largest effect on the odds of an individual being a progressor (OR 35.3; 95% CI between 14 and 104). 3-HAA levels were hence surprisingly bi-phasic, high in progressors but low in non-progressors or participants who had already transitioned to MCI or dementia. This is a new, unexpected and interesting result, as most studies of the KP in neurodegenerative disease show reduced 3-HAA/AA ratio after diagnosis. The neuroprotective metabolite picolinic acid was also significantly decreased while the neurotoxic metabolite 3-hydroxykynurenine increased in progressors. These results were significant even after adjustment for confounders. Considering the magnitude of the OR to predict change in cognition, it is important that these findings are replicated in other populations. Independent validation of our findings may confirm the utility of 3-HAA/AA ratio to predict change in cognition leading to dementia in clinical settings
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