The strength of plants Shah, Darshil U.; Reynolds, Thomas P.S.; Ramage, Michael H.
Journal of experimental botany,
07/2017, Letnik:
68, Številka:
16
Journal Article
Recenzirano
Odprti dostop
From the stems of agricultural crops to the structural trunks of trees, studying the mechanical behaviour of plant stems is critical for both commerce and science. Plant scientists are also ...increasingly relying on mechanical test data for plant phenotyping. Yet there are neither standardized methods nor systematic reviews of current methods for the testing of herbaceous stems. We discuss the architecture of plant stems and highlight important micro- and macrostructural parameters that need to be controlled and accounted for when designing test methodologies, or that need to be understood in order to explain observed mechanical behaviour. Then, we critically evaluate various methods to test structural properties of stems, including flexural bending (two-, three-, and four-point bending) and axial loading (tensile, compressive, and buckling) tests. Recommendations are made on best practices. This review is relevant to fundamental studies exploring plant biomechanics, mechanical phenotyping of plants, and the determinants of mechanical properties in cell walls, as well as to application-focused studies, such as in agro-breeding and forest management projects, aiming to understand deformation processes of stem structures. The methods explored here can also be extended to other elongated, rod-shaped organs (e.g. petioles, midribs, and even roots).
‘Perytons’ are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion of an astrophysical pulse that has propagated through tenuous cold plasma. ...In fact, their similarity to FRB 010724 had previously cast a shadow over the interpretation of ‘fast radio bursts’ (FRBs), which otherwise appear to be of extragalactic origin. Until now, the physical origin of the dispersion-mimicking perytons had remained a mystery. We have identified strong out-of-band emission at 2.3–2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explains all of the observed properties of the peryton signals. Now that the peryton source has been identified, we furthermore demonstrate that the microwave ovens on site could not have caused FRB 010724. This and other distinct observational differences show that FRBs are excellent candidates for genuine extragalactic transients.
The static loading is one of the key unknowns in the structural design process. While weigh in-motion stations and load cells allow load to be measured over small areas or small structures, they are ...not viable for more complex structures such as long-span bridges or larger buildings, and can be prohibitively expensive. Operational modal analysis can reveal changes in the dynamic behaviour of civil structures measured with accelerometers, potentially offering a low-cost, durable technique for estimating changes of mass in-service. In order to do this, the dynamic parameters of the structure must be estimated with sufficient accuracy, and then processed using a mass change estimation method robust enough to accommodate noise and measurement error. In this paper a new technique for estimating changes in mass, random sampling mass estimation (RSME), is introduced and applied to experimental data for a laboratory-scale beam structure. RSME incorporates the uncertainty in the estimates of the dynamic parameters and allows least-squares estimation of the total change in mass applied to a structure if the locations of the changes in mass are known, or prediction of both the magnitude and location of a single concentrated change in mass through a novel graphical implementation. For individual masses added to the beam, 92.0% of mass location predictions have errors smaller than 2% of the length of the span and 69.4% of added mass magnitude predictions are within ±10 g, approximately 0.05% of the mass of the beam. For concurrent added mass locations, the mean error of the estimates for the total change in mass where 2 or more added masses are present on the beam is -2 g, approximately 0.011% of the mass of the beam.
•Changes in dynamic structural behaviour tracked using ambient vibrations.•A novel method incorporates uncertainty in the modal parameters.•Mass and location estimated using changes in multiple modes of vibration.•Changes in stiffness could also be estimated this way.•Methods demonstrated using laboratory tests on a steel beam.
Chronic periodontitis (CP) is a common oral disease that confers substantial systemic inflammatory and microbial burden and is a major cause of tooth loss. Here, we present the results of a ...genome-wide association study of CP that was carried out in a cohort of 4504 European Americans (EA) participating in the Atherosclerosis Risk in Communities (ARIC) Study (mean age-62 years, moderate CP-43% and severe CP-17%). We detected no genome-wide significant association signals for CP; however, we found suggestive evidence of association (P < 5 × 10(-6)) for six loci, including NIN, NPY, WNT5A for severe CP and NCR2, EMR1, 10p15 for moderate CP. Three of these loci had concordant effect size and direction in an independent sample of 656 adult EA participants of the Health, Aging, and Body Composition (Health ABC) Study. Meta-analysis pooled estimates were severe CP (n = 958 versus health: n = 1909)-NPY, rs2521634 G: odds ratio OR = 1.49 (95% confidence interval (CI = 1.28-1.73, P = 3.5 × 10(-7))); moderate CP (n = 2293)-NCR2, rs7762544 G: OR = 1.40 (95% CI = 1.24-1.59, P = 7.5 × 10(-8)), EMR1, rs3826782 A: OR = 2.01 (95% CI = 1.52-2.65, P = 8.2 × 10(-7)). Canonical pathway analysis indicated significant enrichment of nervous system signaling, cellular immune response and cytokine signaling pathways. A significant interaction of NUAK1 (rs11112872, interaction P = 2.9 × 10(-9)) with smoking in ARIC was not replicated in Health ABC, although estimates of heritable variance in severe CP explained by all single nucleotide polymorphisms increased from 18 to 52% with the inclusion of a genome-wide interaction term with smoking. These genome-wide association results provide information on multiple candidate regions and pathways for interrogation in future genetic studies of CP.
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the ...western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 10
erg at infrared and radio wavelengths but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.
•Experimental investigation on cold-formed steel and timber board composite panel was performed.•Mechanical properties, connector behaviour and flexural strength of the composite panel were ...obtained.•Structural benefits due to the composite action between the two materials were quantified.•Existing design rules to predict moment capacity and flexural stiffness were assessed.
Timber panels and cold-formed steel sheeting are widely used in the construction industry, especially in prefabricated structures, temporary housing and informal settlements. This is because these materials are widely available, can be cut and fixed with hand tools, and their lightweight makes them easy to transport and build with. When used together, there is a potential for composite action developing between the timber panels and the underlying steel sheeting, which is currently ignored in design. A composite panel of oriented strand boards and cold-formed steel sheeting is proposed herein and its overall structural behaviour is experimentally investigated. Based on results obtained from material, push-out and flexural tests, its mechanical properties are determined and the predominant failure modes are highlighted. The feasibility of mobilising composite action between the components of the proposed system is proven and the derived benefits, both in terms of load carrying capacity and stiffness, are quantified. It is demonstrated that harnessing the beneficial influence of composite action can lead to substantial improvements of the overall structural performance of the proposed composite panel, offering the potential to improve significantly the quality of housing in informal developments and rapidly urbanising areas.
The identification and recovery of suspected human biofluid evidence can present a bottleneck in the crime scene investigation workflow. Crime Scene Investigators typically deploy one of a number of ...presumptive enhancement reagents, depending on what they perceive an analyte to be; the selection of this reagent is largely based on the context of suspected evidence and their professional experience. Positively identified samples are then recovered to a forensic laboratory where confirmatory testing is carried out by large lab-based instruments, such as through mass-spectrometry-based techniques. This work proposes a proof-of-concept study into the use of a small, robust and portable ion mobility spectrometry device that can analyse samples in situ, detecting, identifying and discriminating commonly encountered body fluids from interferences. This analysis exploits the detection and identification of characteristic volatile organic compounds generated by gentle heating, at ambient temperature and pressure, and categorises samples using machine learning, providing investigators with instant identification. The device is shown to be capable of producing characteristic mobility spectra using a dual micro disc pump configuration which separates blood and urine from three visually similar interferences using an unsupervised PCA model with no misclassified samples. The device has the potential to reduce the need for potentially contaminating and destructive presumptive tests, and address the bottleneck created by the time-consuming and laborious detection, recovery and analysis workflow currently employed.
Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation and inverse-Compton scattering ...processes while propagating within the Galaxy, and these losses limit their propagation distance. For electrons with TeV energies, the limit is on the order of a kiloparsec. Within that distance, there are only a few known astrophysical objects capable of accelerating electrons to such high energies. It is also possible that the CREs are the products of the annihilation or decay of heavy dark matter (DM) particles. VERITAS, an array of imaging air Cherenkov telescopes in southern Arizona, is primarily utilized for gamma-ray astronomy but also simultaneously collects CREs during all observations. We describe our methods of identifying CREs in VERITAS data and present an energy spectrum, extending from 300 GeV to 5 TeV, obtained from approximately 300 hours of observations. A single power-law fit is ruled out in VERITAS data. We find that the spectrum of CREs is consistent with a broken power law, with a break energy at 710±40stat±140syst GeV.
ABSTRACT In a search with the Parkes radio telescope of 56 unidentified Fermi-Large Area Telescope (LAT) gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 of them discoveries, of ...which five were reported by Kerr et al. We did not detect radio pulsations from six other pulsars now known in these sources. We describe the completed survey, which included multiple observations of many targets conducted to minimize the impact of interstellar scintillation, acceleration effects in binary systems, and eclipses. We consider that 23 of the 39 remaining sources may still be viable pulsar candidates. We present timing solutions and polarimetry for five of the MSPs and gamma-ray pulsations for PSR J1903-7051 (pulsations for five others were reported in the second Fermi-LAT catalog of gamma-ray pulsars). Two of the new MSPs are isolated and five are in day circular orbits with 0.2-0.3 presumed white dwarf companions. PSR J0955-6150, in a 24 day orbit with a companion but eccentricity of 0.11, belongs to a recently identified class of eccentric MSPs. PSR J1036-8317 is in an 8 hr binary with a companion that is probably a white dwarf. PSR J1946-5403 is in a 3 hr orbit with a companion with no evidence of radio eclipses.
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