Multi Trap Research Articles

Trap crop selection and economic threshold based ecological management of Spilosoma obliqua Walker (Lepidoptera, Arctiidae) for sesame

The stage-specific life table and nutritional ecology of a Spilarctia obliqua (Walker) along with respective economic thresholds (ETs) on four different crops such as sesame (Sesamum indicum), castor (Ricinus communis), jute (Corchorus capsularis) and sunflower (Helianthus annuus) were studied during 2020-2022. The feeding and population dynamics of S. obliqua were significantly affected by the hosts in terms of host suitability or susceptibility (sunflower>jute>castor>sesame). The ET of S. obliqua on sesame (40.59±2.12 pests m-2 area) was significantly (F3,8=4.72, P=0.031) higher than the other crops (sunflower<jute<castor). Subsequently, the three most suitable hosts (sunflower> jute>castor) were tested in a multi trap cropping system for sesame as main crop in a specific pattern depending on respective susceptibility. Data from the model trap cropping (without pesticide) supported minimum infestation of S. obliqua and other pests along with more predators on sesame with higher benefit cost ratio (BCR) and more (11.82%) carbon sequestration (CS) in same area relative to monoculture (with pesticide) of sesame. It supports pesticide free high production and better CS than sole culture of sesame for climate smart agriculture.

Thermoluminescence glow curve analysis using temperature dependent frequency factor in OTOR model

The frequency factor in a thermoluminescent material depends on temperature which can be expressed as s(T)=s0Ta (−2≤a≤2). In practice, analysis of thermoluminescence (TL) glow curves are performed assuming the frequency factor to be temperature independent due to the difficulties involved in estimating a. Such assumption may introduce some limitations in estimating TL parameters of a material and hence, a thorough investigation on the effect of temperature dependent frequency factor (TDFF) on TL analysis has its own importance. In this communication, a comprehensive study using ‘One Trap One Recombination centre’ (OTOR) model considering TDFF is reported. The prerequisite for such a study is to reproduce the same curve for different values of ‘a’ as it is not possible to have a priori knowledge of ‘a’ in experimental scenario. This issue is addressed in this work and we have described a methodology for such peak simulation. The OTOR equations are solved and pioneering calculations to derive the peak maxima condition is developed using Lambert-W function considering TDFF. An analytical approach to evaluate the extended temperature integral of the form ∫TiTfTae−EkTdT is also presented. We have extracted the activation energy for different values of ‘a’ from a particular TL peak using peakshape method and estimated the subsequent error that may incur out of the assumption of temperature independent frequency factor. The present study has been extended to analyse experimental TL peak reported in literature. TL Peak simulation with TDFF based on Interactive Multi Trap System (IMTS) model has also been explored for a sample case.

Optical tunnels: long-range optical trapping and manipulation in aqueous media

In this study, we demonstrate an asymmetric counter-propagating beam system with engineered optical forces allowing for long-range particle trapping and manipulation. We achieved this by breaking the symmetry of the well-known counter-propagating optical trapping beams. By doing so, we extend the range of optical forces for particle confinement and transportation to significantly larger foci separations, creating an optical tunnel. These tunnels are capable of moving matter forward and back with controllable speeds for more than a millimeter length with the ability to bring them to a full stop at any point, creating a stable 3D trap. Our trap stiffness measurements for the asymmetric trapping system demonstrate at least one order of magnitude larger values with respect to the symmetric counter-propagating beams so far reported. Our system is quite versatile as it allows for single or multi trapping with flexible positioning of any size particle ranging from tens of nanometers to tens of microns with powers as low as a few milliwatts.

Study of hydrogen isotopes behavior in tungsten by a multi trapping macroscopic rate equation model

Density functional theory (DFT) studies show that in tungsten a mono vacancy can contain up to six hydrogen isotopes (HIs) at 300 K with detrapping energies varying with the number of HIs in the vacancy. Using these predictions, a multi trapping rate equation model has been built and used to model thermal desorption spectrometry (TDS) experiments performed on single crystal tungsten after deuterium ions implantation. Detrapping energies obtained from the model to adjust temperature of TDS spectrum observed experimentally are in good agreement with DFT values within a deviation below 10%. The desorption spectrum as well as the diffusion of deuterium in the bulk are rationalized in light of the model results.

Redox sensitivity of iron in phosphorus binding does not impede lake restoration

Iron salts have been regarded as unsuitable precipitants for sustainable sedimentary P retention, because Fe-bound P is released at low redox potential. The longevity of an Fe3+ application (500 g m−2) in 1992 was studied in a dimictic lake. Release of Fe and P as well as their co-precipitation were observed dependent on artificial aeration in 2010 and only natural oxygenation in 2011. Sediment core stratigraphy by μX-ray fluorescence analysis revealed that Fe is relocating towards the surface, representing a dynamic P trap with a molar Fe:P ratio of 7. Even at this favourable ratio, P release cannot be suppressed. Settling fluxes of Fe, Mn and P, determined by a multi trap at two day resolution, during aeration and oxygenation, showed that released P can be efficiently precipitated independent of the nature of the oxygen supply. Thus, P release is not relevant for the P supply to the epilimnion, since at overturn most P is co-precipitated by the concurrently hypolimnetically accumulated Fe. To increase the availability of reactive (dithionite extractable) Fe for P binding, our Fe dosage calculation considers Fe in surplus. Beside external and internal P sources to be precipitated in a stoichiometric Fe:P ratio of 5, additional Fe equivalents of 25% for sedimentary organic carbon and to bind soluble sulfides are required. A long-term effect can be achieved only if the external P loading is sufficiently reduced, and Fe is added to ≥200 g m−2.

Modelling thermally-stimulated currents in disordered semiconductors

We report a computer modelling study of thermally stimulated currents in thin film semiconductors. In a multi trapping context, we examine this method as a ‘spectroscopy’ of the energy distribution of localised states. We consider so-called ‘weak’ and ‘strong’ re-trapping conditions, the use of non-physical ‘effective’ attempt-to-escape frequencies and the effect of lifetime variation as distributions relax. We show that for strong re-trapping in distributed states, the energy scale can be better approximated by the quasi-Fermi level position and propose that the density of states may alternatively be computed using the easily determined derivative of the quasi-Fermi energy with respect to temperature.

Wave front engineering for microscopy of living cells

A new method to perform simultaneously three dimensional optical sectioning and optical manipulation is presented. The system combines a multi trap optical tweezers with a video microscope to enable axial scanning of living cells while maintaining the trapping configuration at a fixed position. This is achieved compensating the axial movement of the objective by shaping the wave front of the trapping beam with properly diffractive optical elements displayed on a computer controlled spatial light modulator. Our method has been validated in three different experimental configurations. In the first, we decouple the position of a trapping plane from the axial movements of the objective and perform optical sectioning of a circle of beads kept on a fixed plane. In a second experiment, we extend the method to living cell microscopy by showing that mechanical constraints can be applied on the dorsal surface of a cell whilst performing its fluorescence optical sectioning. In the third experiment, we trapped beads in a three dimensional geometry and perform, always through the same objective, an axial scan of the volume delimited by the beads.

Multi force optical tweezers to generate gradients of forces

We present a multi trap optical tweezes system that enables to generate two-dimensional dynamical configurations of focal spot where the trapping force of each element of the pattern can be individually changed. Force gradients in the pN range can be generated on a micrometer scale.

Monte-Carlo Simulation of Generation- Recombination Noise in Amorphous Semiconductors

AbstractWe compare the predictions of several analytical models for conductivity fluctuations in a homogeneous semiconductor containing discrete and distributed traps, using a Monte-Carlo simulation of the relevant multi – trapping (MT) transitions. The simulation directly embodies the statistical features associated with such processes, in a simple ‘model - independent’ approach, free of approximations and assumptions. We compare the results with those of several analytical approaches. In one, the noise spectrum is assumed to reflect separately, the characteristic individual release time constants of the various trapping centers in the material. In another, the trapping time into the ensemble of electron traps is taken to be the dominant time constant, and hence, in a material such as a-Si:H, where the trapping time into tail sates is of order 1ps, this is taken to imply that this component of the conductivity noise spectrum is unobservable in practice. Our own analytical approach, incorporates coupling (albeit weak) between traps, which necessarily communicate via the extended states. Preliminary results of the simulation support our thesis, and verify that the same information is contained in the real part of the modulated photoconductivity (MPC) spectrum. A ‘full Monte’ – Carlo simulation incorporating all gap states and spatial inhomogeneities is now a priority.