ALBERT

Description: SUMMARYGenetically modified (GM) plants expressing Bt toxin provide protection against lepidopteran pests. The only GM crop in Pakistan is Bt cotton, which was illegally imported and adopted rapidly by cotton producers. Farmers gained access to the seed of many unapproved Bt genotypes before the matter was picked up and formal approval granted by the relevant governmental agencies. The present study was conducted to evaluate the samples of Bt cotton, collected from farmers and seed dealer, for transgene integration and expression. Seeds of 52 cotton genotypes, labelled as Bt, were collected from various farmers and seed dealers. An immunoblot strip test was carried out, which showed that only 0·86 of the samples collected were synthesizing Cry1Ac toxin. According to multiplexed polymerase chain reaction (PCR) results, 0·86 of the genotypes tested were positive for the Mon531 event (an ‘event’ is a specific genetic modification in a specific species) and 0·14 were negative for any transgene. Transcript analysis of transgenes in positive genotypes by real-time Rt-PCR confirmed the synthesis of mRNA in all genotypes but with significant variation. The concentration of Bt toxin revealed by enzyme linked immunosorbent assay (ELISA) showed that only 0·02 genotypes had the reported optimum level. The real-time PCR and ELISA results further confirmed the attenuation of transgene expression at transcriptional and translational level by various internal and external factors. The same type of event was found in all genotypes, with significant variation in toxin level, revealing the impact of genetic background on transgene expression. The findings support the recommendation to improve the existing quality criteria for transgenic cotton variety approval and certification in Pakistan, with the inclusion of toxin concentration in the list of parameters to be considered.

Description: 〈div data-abstract-type="normal"〉〈p〉This work combines very detailed measurements from terrestrial laser scanner (TLS), ground-based interferometry radar (GB-SAR) and ground-penetrating radar (GPR) to diagnose current conditions and to analyse the recent evolution of the Monte Perdido Glacier in the Spanish Pyrenees from 2011 to 2017. Thus, this is currently one of the best monitored small glacier (2) worldwide. The evolution of the glacier surface was surveyed with a TLS evidencing an important decline of 6.1 ± 0.3 m on average, with ice losses mainly concentrated over 3 years (2012, 2015 and 2017). Ice loss is unevenly distributed throughout the study period, with 10–15 m thinning in some areas while unchanged areas in others. GB-SAR revealed that areas with higher ice losses are those that are currently with no or very low ice motion. In contrast, sectors located beneath the areas with less ice loss are those that still exhibit noticeable ice movement (average 2–4.5 cm d〈span〉─1〈/span〉 in summer, and annual movement of 9.98 ma〈span〉─1〈/span〉 from ablation stakes data). GPR informed that ice thickness was generally 〈/p〉〈/div〉

Description: 〈div data-abstract-type="normal"〉〈p〉We present the first general theory of glacier surging that includes both temperate and polythermal glacier surges, based on coupled mass and enthalpy budgets. Enthalpy (in the form of thermal energy and water) is gained at the glacier bed from geothermal heating plus frictional heating (expenditure of potential energy) as a consequence of ice flow. Enthalpy losses occur by conduction and loss of meltwater from the system. Because enthalpy directly impacts flow speeds, mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow. If not, glaciers undergo out-of-phase mass and enthalpy cycles, manifest as quiescent and surge phases. We illustrate the theory using a lumped element model, which parameterizes key thermodynamic and hydrological processes, including surface-to-bed drainage and distributed and channelized drainage systems. Model output exhibits many of the observed characteristics of polythermal and temperate glacier surges, including the association of surging behaviour with particular combinations of climate (precipitation, temperature), geometry (length, slope) and bed properties (hydraulic conductivity). Enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework, and offers an answer to the wider question of why the majority of glaciers do not surge.〈/p〉〈/div〉

Description: 〈div data-abstract-type="normal"〉〈p〉A feeding trial involving growing piglets was undertaken to establish whether feed supplemented with whey protein concentrate (WPC), exhibiting antioxidant properties, had any effects on welfare and meat quality. For that purpose, 48 weaned piglets (20-days-old) were assigned to two experimental groups receiving standard or experimental diet for 30 days. Blood and tissue collection were performed at various time-points. The following oxidative stress markers were assessed: reduced glutathione (GSH), catalase activity, total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS), protein carbonyls (CARB) and hydrogen peroxide (H〈span〉2〈/span〉O〈span〉2〈/span〉) decomposition activity. The effects on bacterial growth and the fatty acid profile of meat were also assessed. Results showed that piglets fed with the WPC-supplemented diet had significantly increased antioxidant mechanisms in almost all tissues tested, as indicated by increases in GSH, H〈span〉2〈/span〉O〈span〉2〈/span〉 decomposition activity and TAC compared with the control group. Piglets fed with the experimental diet exhibited decreased oxidative stress-induced damage to lipids and proteins, as shown by decreases in TBARS and CARB in the WPC group compared with the control group. In addition, the experimental diet enhanced growth of facultative probiotic bacteria and lactic acid bacteria and inhibited growth of pathogen populations. In addition, WPC inclusion in piglets' diet increased 〈span〉n〈/span〉-3 fatty acids significantly and decreased 〈span〉n〈/span〉-6/〈span〉n〈/span〉-3 ratio significantly compared with the control group. The current study showed that WPC inclusion in the diet had a significant effect on welfare and meat quality of growing piglets.〈/p〉〈/div〉

Description: Compound-specific radiocarbon analysis (CSRA) of benzene polycarboxylic acids (BPCAs) yields molecular-level, source-specific information necessary to constrain isotopic signatures of pyrogenic carbon. However, the purification of individual BPCAs requires a multistep procedure that typically results in only microgram quantities of the target analyte(s). Such small samples are highly susceptible to contamination by extraneous carbon, which needs to be minimized and carefully accounted for in order to yield accurate results. Here, we undertook comprehensive characterization and quantification of contamination associated with molecular radiocarbon (14C) BPCA analyses through systematic processing of multiple authentic standards with both fossil and modern 14C signatures at various concentrations. Using this approach, we precisely apportion the contribution of extraneous carbon with respect to the four implemented subprocedures. Assuming a constant source and quantity of extraneous carbon we correct and statistically evaluate uncertainties in resulting 14C data. Subsequently, we examine the results of triplicate analyses of reference materials representing four different environmental matrices (sediment, soil, aerosol, riverine natural organic matter) and apportion their BPCA sources in terms of carbon residues derived from biomass or fossil fuel combustion. This comprehensive approach to CSRA facilitates retrieval of robust 14C data, with application in environmental studies of the continuum of pyrogenic carbon.

Description: We explore the feasibility of a novel method for the regulation of heat transfer across a cavity, by using a controllable yield stress in order to suppress the convective heat transfer. Practically, this type of control can be actuated with electro-rheological or magneto-rheological fluids. We demonstrate that above a given critical yield stress value only static steady regimes are possible, i.e. a purely conductive unyielded fluid fills the cavity. We show that this limit is governed by a balance of yield stress and buoyancy stresses, here described by . With proper formulation the critical state can be described as a function of the domain geometry, and is independent of other dimensionless flow parameters (Rayleigh number, , and Prandtl number, ). On the theoretical side, we examine the conditional stability of the static regime. We derive conservative conditions on disturbance energy to ensure that perturbations from a static regime decay to zero. Assuming stability, we show that the kinetic energy of the perturbed field decays to zero in a finite time, and give estimates for the stopping time, . This allows us to predict the response of the system in suppressing advective heat transfer. The unconditional stability is also considered for the first time, illustrating the role of yield stress. We focus on the hydrodynamic characteristics of Bingham fluids in transition between conductive and convective limits. We use computational simulations to resolve the Navier-Stokes and energy equations for different yield stresses, and for different imposed controls. We show that depending on the initial conditions, a yield stress less than the critical value can result in temporary arrest of the flow. The temperature then develops conductively until the fluid yields and the flow restarts. We provide estimates of the hydrodynamic timescales of the problem and examples of flow transitions. In total, the theoretical and computational results establish that this methodology is feasible as a control, at least from a hydrodynamic perspective. © 2015 Cambridge University Press.

Description: Mathematicians and physicists have long been interested in the subject of water waves. The problems formulated in this subject can be considered fundamental, but many questions remain unanswered. For instance, a satisfactory analytic theory of such a common and important phenomenon as wave breaking has yet to be developed. Our knowledge of the formation of rogue waves is also fairly poor despite the many efforts devoted to this subject. One of the most important tasks of the theory of water waves is the construction of simplified mathematical models that are applicable to the description of these complex events under the assumption of weak nonlinearity. The Zakharov equation, as well as the nonlinear Schrödinger equation (NLSE) and the Dysthe equation (which are actually its simplifications), are among them. In this article, we derive a new modification of the Zakharov equation based on the assumption of unidirectionality (the assumption that all waves propagate in the same direction). To derive the new equation, we use the Hamiltonian form of the Euler equation for an ideal fluid and perform a very specific canonical transformation. This transformation is possible due to the 'miraculous' cancellation of the non-trivial four-wave resonant interaction in the one-dimensional wave field. The obtained equation is remarkably simple. We call the equation the 'super compact water wave equation'. This equation includes a nonlinear wave term (à la NLSE) together with an advection term that can describe the initial stage of wave breaking. The NLSE and the Dysthe equations (Dysthe Proc. R. Soc. Lond. A, vol. 369, 1979, pp. 105-114) can be easily derived from the super compact equation. This equation is also suitable for analytical studies as well as for numerical simulation. Moreover, this equation also allows one to derive a spatial version of the water wave equation that describes experiments in flumes and canals. © 2017 Cambridge University Press.

Description: The fluctuating drag forces acting on spherical roughness elements comprising the bed of an open-channel flow have been recorded along with synchronous measurements of the surrounding velocity field using stereoscopic particle image velocimetry. The protrusion of the target particle, equipped with a force sensor, was systematically varied between zero and one-half diameter relative to the hexagonally packed adjacent spheres. Premultiplied spectra of drag force fluctuations were found to have bimodal shapes with a low-frequency peak corresponding to the presence of very-large-scale motions (VLSMs) in the turbulent flow. The high-frequency region of the drag force spectra cannot be explained by velocity time series extracted from points around the particle, but instead appears to be dominated by the action of pressure gradients in the overlying flow field. For small particle protrusions, this high-frequency region contributes a majority of the drag force variance, while the relative importance of the low-frequency drag force fluctuations increases with increasing protrusion. The amplitude of high-frequency drag force fluctuations is modulated by the VLSMs irrespective of particle protrusion. These results provide some insight into the mechanics of bed particle stability and indicate that the optimum conditions for particle entrainment may occur when a low-pressure region embedded in the high-velocity portion of a VLSM overlays a particle. © 2019 Cambridge University Press.

Description: High resolution large eddy simulations (LES) are performed to study the interaction of a stationary shock with fully developed turbulent flow. Turbulent statistics downstream of the interaction are provided for a range of weakly compressible upstream turbulent Mach numbers, shock Mach numbers and Taylor-based Reynolds numbers. The LES displays minimal Reynolds number effects once an inertial range has developed for 100$]]〉. The inertial range scales of the turbulence are shown to quickly return to isotropy, and downstream of sufficiently strong shocks this process generates a net transfer of energy from transverse into streamwise velocity fluctuations. The streamwise shock displacements are shown to approximately follow a decay with wavenumber as predicted by linear analysis. In conjunction with other statistics this suggests that the instantaneous interaction of the shock with the upstream turbulence proceeds in an approximately linear manner, but nonlinear effects immediately downstream of the shock significantly modify the flow even at the lowest considered turbulent Mach numbers. © 2018 Cambridge University Press.