3,076 research outputs found
The Casimir force on a surface with shallow nanoscale corrugations: Geometry and finite conductivity effects
We measure the Casimir force between a gold sphere and a silicon plate with
nanoscale, rectangular corrugations with depth comparable to the separation
between the surfaces. In the proximity force approximation (PFA), both the top
and bottom surfaces of the corrugations contribute to the force, leading to a
distance dependence that is distinct from a flat surface. The measured Casimir
force is found to deviate from the PFA by up to 15%, in good agreement with
calculations based on scattering theory that includes both geometry effects and
the optical properties of the material
A simplicial gauge theory
We provide an action for gauge theories discretized on simplicial meshes,
inspired by finite element methods. The action is discretely gauge invariant
and we give a proof of consistency. A discrete Noether's theorem that can be
applied to our setting, is also proved.Comment: 24 pages. v2: New version includes a longer introduction and a
discrete Noether's theorem. v3: Section 4 on Noether's theorem has been
expanded with Proposition 8, section 2 has been expanded with a paragraph on
standard LGT. v4: Thorough revision with new introduction and more background
materia
Variation in the Response of Three Different Pinus Radiata Kraft Pulps to Xylanase Treatments
Two xylanase preparations (Pulpzyme HC and Xylanasc E) were assessed for their ability to enhance the refining properties of three different Pinus radiata kraft pulps. Both preparations selectively solubilized a significant proportion of the available xylan; however, xylanase E proved to be more aggressive, regardless of the pulp type. The selective removal of pulp xylan improved pulp beatability by increasing the apparent densities of the resultant handsheets over their corresponding controls. There were, however, variations in the response of the different pulp types, with an unbleached kappa 70 pulp showing the greatest improvement in sheet densification, as compared to an isothermal-cooked (kappa 33) and a fully bleached pulp. In general, xylanase treatments improved tear strength at a given density without significant loss in tensile strength and intrinsic fiber strength. These results suggest that xylanase treatments may be a means of enhancing the collapsibility/flexibility of certain kraft fibers while maintaining intrinsic strength
A TaqMan qPCR method for detecting kdr resistance in Aphis gossypii demonstrates improved sensitivity compared to conventional PCR–RFLP
© 2015, Springer-Verlag Berlin Heidelberg. Cotton aphid, Aphis gossypii Glover, has emerged as a prominent pest in Australian cotton production, and monitoring pesticide resistance including pyrethroids in field populations is crucial for its sustainable management. We examined the distribution of kdr resistance in 35 field-collected A. gossypii populations and used TaqMan qPCR assays with pooled samples. The study demonstrated proof of concept that pooled insect qPCR methodology provided effective detection with better sensitivity than individual PCR–RFLP genotyping techniques for the kdr resistance allele. The practical outcome is that routine resistance monitoring can examine more sites while increasing the likelihood of detecting incipient resistance at those sites. More importantly, the method is adaptable to any genetically caused resistance and so not limited to A. gossypii or even insect control. It cannot be overstressed that the ability to detected resistance at very low frequencies is critical to all sustainable resistance management. Early detection of resistance provides critical time for the modification of chemical use prior to potential insecticide control failure
Neutron, electron and X-ray scattering investigation of Cr1-xVx near Quantum Criticality
The weakness of electron-electron correlations in the itinerant
antiferromagnet Cr doped with V has long been considered the reason that
neither new collective electronic states or even non Fermi liquid behaviour are
observed when antiferromagnetism in CrV is suppressed to zero
temperature. We present the results of neutron and electron diffraction
measurements of several lightly doped single crystals of CrV in
which the archtypal spin density wave instability is progressively suppressed
as the V content increases, freeing the nesting-prone Fermi surface for a new
striped charge instability that occurs at x=0.037. This novel nesting
driven instability relieves the entropy accumulation associated with the
suppression of the spin density wave and avoids the formation of a quantum
critical point by stabilising a new type of charge order at temperatures in
excess of 400 K. Restructuring of the Fermi surface near quantum critical
points is a feature found in materials as diverse as heavy fermions, high
temperature copper oxide superconductors and now even elemental metals such as
Cr.Comment: 6 pages, 6 figures. Accepted to Physical Review
On the enhancement of nuclear reaction rates in high-temperature plasma
We argue that the Maxwellian approximation can essentially underestimate the
rates of some nuclear reactions in hot plasma under conditions very close to
thermal equilibrium. This phenomenon is demonstrated explicitly on the example
of reactions in self-sustained DT fusion plasma with admixture of light
elements X = Li, Be, C. A kinetic analysis shows that the reactivity
enhancement results from non-Maxwellian knock-on perturbations of ion
distributions caused by close collisions with energetic fusion products. It is
found that although the fraction of the knock-on ions is small, these particles
appreciably affect the D+X and T+X reaction rates. The phenomenon discussed is
likely to have general nature and can play role in other laboratory and
probably astrophysical plasma processes.Comment: 12 pages, 4 figures, to be published in Phys. Lett.
11-Year Experience with Anatomical and Extra-anatomical Repair of Mycotic Aortic Aneurysms
AbstractBackground. We have reviewed our management, of both ruptured and non-ruptured, abdominal and thoraco-abdominal mycotic aneurysms in order to determine the safety and efficacy of in situ and extra-anatomical prosthetic repairs.Methods. Data regarding presenting symptoms, investigations, operative techniques and outcome, were collected on patients treated at a singe centre over 11 years.Results. There were 11 men and four women, with a median age of 70 years (range, 24–79). All but one patient were symptomatic and six had a contained leak on admission. In six patients no organisms were identified in either blood or tissue cultures. Pre-operative CT identified; four infra-renal, four juxta-renal, three (Crawford thoraco-abdominal) type IV, three type III and one type II, aortic aneurysms. Thirteen were repaired with in situ prostheses and two required axillo-femoral prosthetic grafts. There were four early deaths. All surviving patients have been followed-up for a median duration of 38 months (range 1/2–112 months). There were two late deaths at 3 months (juxta-renal) and at 2 years (type III), the latter relating to graft infection.Conclusions. In the absence of uncontrolled sepsis, repair of mycotic aortic aneurysms using prosthetic grafts can achieve durable results
Sensitivity of cold acclimation to elevated autumn temperature in field-grown Pinus strobus seedlings
Climate change will increase autumn air temperature, while photoperiod decrease will remain unaffected. We assessed the effect of increased autumn air temperature on timing and development of cold acclimation and freezing resistance in Eastern white pine (EWP, Pinus strobus) under field conditions. For this purpose we simulated projected warmer temperatures for southern Ontario in a Temperature Free-Air-Controlled Enhancement (T-FACE) experiment and exposed EWP seedlings to ambient (Control) or elevated temperature (ET, +1.5°C/+3°C during day/night). Photosynthetic gas exchange, chlorophyll fluorescence, photoprotective pigments, leaf non-structural carbohydrates (NSC), and cold hardiness were assessed over two consecutive autumns. Nighttime temperature below 10°C and photoperiod below 12 h initiated downregulation of assimilation in both treatments. When temperature further decreased to 0°C and photoperiod became shorter than 10 h, downregulation of the light reactions and upregulation of photoprotective mechanisms occurred in both treatments. While ET seedlings did not delay the timing of the downregulation of assimilation, stomatal conductance in ET seedlings was decreased by 20–30% between August and early October. In both treatments leaf NSC composition changed considerably during autumn but differences between Control and ET seedlings were not significant. Similarly, development of freezing resistance was induced by exposure to low temperature during autumn, but the timing was not delayed in ET seedlings compared to Control seedlings. Our results indicate that EWP is most sensitive to temperature changes during October and November when downregulation of photosynthesis, enhancement of photoprotection, synthesis of cold-associated NSCs and development of freezing resistance occur. However, we also conclude that the timing of the development of freezing resistance in EWP seedlings is not affected by moderate temperature increases used in our field experiments
Confidential Boosting with Random Linear Classifiers for Outsourced User-generated Data
User-generated data is crucial to predictive modeling in many applications.
With a web/mobile/wearable interface, a data owner can continuously record data
generated by distributed users and build various predictive models from the
data to improve their operations, services, and revenue. Due to the large size
and evolving nature of users data, data owners may rely on public cloud service
providers (Cloud) for storage and computation scalability. Exposing sensitive
user-generated data and advanced analytic models to Cloud raises privacy
concerns. We present a confidential learning framework, SecureBoost, for data
owners that want to learn predictive models from aggregated user-generated data
but offload the storage and computational burden to Cloud without having to
worry about protecting the sensitive data. SecureBoost allows users to submit
encrypted or randomly masked data to designated Cloud directly. Our framework
utilizes random linear classifiers (RLCs) as the base classifiers in the
boosting framework to dramatically simplify the design of the proposed
confidential boosting protocols, yet still preserve the model quality. A
Cryptographic Service Provider (CSP) is used to assist the Cloud's processing,
reducing the complexity of the protocol constructions. We present two
constructions of SecureBoost: HE+GC and SecSh+GC, using combinations of
homomorphic encryption, garbled circuits, and random masking to achieve both
security and efficiency. For a boosted model, Cloud learns only the RLCs and
the CSP learns only the weights of the RLCs. Finally, the data owner collects
the two parts to get the complete model. We conduct extensive experiments to
understand the quality of the RLC-based boosting and the cost distribution of
the constructions. Our results show that SecureBoost can efficiently learn
high-quality boosting models from protected user-generated data
Short-term angiotensin II treatment regulates cardiac nanomechanics via microtubule modifications.
Mechanical properties of single myocytes contribute to the whole heart performance, but the measurement of mechanics in living cells at high resolution with minimal force interaction remains challenging. Angiotensin II (AngII) is a peptide hormone that regulates a number of physiological functions, including heart performance. It has also been shown to contribute to cell mechanics by inducing cell stiffening. Using non-contact high-resolution Scanning Ion Conductance Microscopy (SICM), we determine simultaneously cell topography and membrane transverse Young's modulus (YM) by a constant pressure application through a nanopipette. While applying pressure, the vertical position is recorded and a deformation map is generated from which YM can be calculated and corrected for the uneven geometry. High resolution of this method also allows studying specific membrane subdomains, such as Z-grooves and crests. We found that short-term AngII treatment reduces the transversal YM in isolated adult rat cardiomyocytes acting via an AT1 receptor. Blocking either a TGF-β1 receptor or Rho kinase abolishes this effect. Analysis of the cytoskeleton showed that AngII depletes microtubules by decreasing long-lived detyrosinated and acetylated microtubule populations. Interestingly, in the failing cardiomyocytes, which are stiffer than controls, the short-term AngII treatment also reduces the YM, thus normalizing the mechanical state of cells. This suggests that the short-term softening effect of AngII on cardiac cells is opposite to the well-characterized long-term hypertrophic effect. In conclusion, we generate a precise nanoscale indication map of location-specific transverse cortical YM within the cell and this can substantially advance our understanding of cellular mechanics in a physiological environment, for example in isolated cardiac myocytes
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