Multiple Trapping Research Articles

Non-Trapping, Non-Invasive, Rapid Surveillance Sampling Using Tracking Tunnels, Trail Cameras, and eDNA to Determine Presence of Pest Predator Species

A common challenge for land managers is knowing which vertebrate pest species are present in areas they manage, especially if such areas are remote like isolated habitats, rugged terrain, or infrequently traveled islands. Most invasive predator species, such as feral dogs, cats, mongoose, and commensal rodents pose great threat to human health and key resources such as native species. Animal trapping to determine the presence of a pest species can be expensive and dangerous, requiring permits, experienced personnel, multiple days, and multiple trapping methods. Furthermore, many invasive pest species may go unnoticed because they are nocturnal, secretive, or leave little evidence of their presence. Tracking tunnels, trail cameras, and environmental DNA (eDNA) are non-trapping methods that can be used to rapidly assess if vertebrate pest species are present in a given habitat or ecosystem, including before, during, and after pest suppression techniques are implemented. We share tracking tunnel dimensions and specifications so readers can make their own tracking tunnels for rodent and other small mammal sampling, and we provide some common distributers where tracking tunnels can be purchased. A brief overview of trail camera technology and eDNA forensic uses are described, as well as their applications for vertebrate pest identification, surveillance, and damage management. To demonstrate these methods, we share example case studies from the Caribbean, including first time records of house mouse presence at Sandy Point National Wildlife Refuge in St. Croix (US Virgin Islands) and along a rainforest elevation gradient in the Luquillo National Forest, Puerto Rico. Additionally, we describe case studies of trail camera use on Desecheo Island (Puerto Rico) to determine brodifacoum bait consumption, and eDNA use in Wyoming to determine native bird depredation events. Tracking tunnels and trail cameras are recommended as quick and inexpensive ways to reveal the vertebrate pest species that are present at a site or habitat. These non-trapping, non-invasive techniques can provide quick and efficient methods of surveillance, detection, and monitoring of vertebrate pests, and otherwise may be used as effective tools to aid in wildlife damage management.

Probing Charge Carrier Dynamics to Unveil the Role of Surface Ligands in HgTe Narrow Band Gap Nanocrystals

Colloidal nanocrystals are an interesting platform for the design of low cost optoelectronic devices especially in the infrared range of wavelengths. Mercury chalcogenides have reached high maturity to address wavelengths above the telecom range (1.5 μm). However, no screening of the surface chemistry influence has been conducted yet. In this paper, we systematically probe the influence of a series of ligands, Cl–, SCN–, 1,2-ethanedithiol, 1,4-benzenedithiol, 1-octanethiol, 1-butanethiol, As2S3, and S2–, on the photoconductive properties of HgTe nanocrystal thin films. A high bandwidth, large dynamic transient photocurrent setup is used to determine the photocarrier dynamics. Two regimes are clearly identified. At the early stage (few nanoseconds) a fast decay of the photocurrent is resulting from recombination and trapping. Then transport enters in a multiple trapping regime where carriers present a continuously decreasing effective value of their mobility. The power law dependence of the conductance can...

Generation of ultra-long pure magnetization needle and multiple spots by phase modulated doughnut Gaussian beam

Based on vector diffraction theory and inverse Faraday effect (IFE), the light induced magnetization distribution of a tightly focused azimuthally polarized doughnut Gaussian beam superimposed with a helical phase and modulated by an optimized multi belt complex phase filter (MBCPF) is analysed numerically. It is noted that by adjusting the radii of different rings of the complex phase filter, one can achieve many novel magnetization focal distribution such as sub wavelength scale (0.29λ) and super long (52.2λ) longitudinal magnetic probe suitable for all optical magnetic recording and the formation of multiple magnetization chain with four, six and eight sub-wavelength spherical magnetization spots suitable for multiple trapping of magnetic particles are achieved.

Delayed Exciton Formation Involving Energetically Shallow Trap States in Colloidal CsPbBr3 Quantum Dots

We report the occurrence of delayed exciton formation in highly emissive CsPbBr3 quantum dots, which results in anomalously slow buildup kinetics that are readily observed in a time-resolved photoluminescence trace. It is inferred from the dependence of the buildup kinetics on nanoparticle size, temperature, and excitation fluence that the delayed exciton formation originates from multiple carrier trapping and detrapping events between the band edge state and energetically shallow structural disorder states. A kinetic model that incorporates these carrier pathways produces fits that are in excellent agreement with the time-resolved data. Importantly, the kinetic model allows for the determination of photoluminescence quantum yield values that closely match those obtained from integrating sphere measurements, whereas merely accounting for the pathways associated with the decay kinetics produces large discrepancies. This work highlights the crucial role played by delayed exciton formation in the photolumine...

A drain current model for amorphous InGaZnO thin film transistors considering temperature effects

Temperature dependent electrical characteristics of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) are investigated considering the percolation and multiple trapping and release (MTR) conduction mechanisms. Carrier-density and temperature dependent carrier mobility in a-IGZO is derived with the Boltzmann transport equation, which is affected by potential barriers above the conduction band edge with Gaussian-like distributions. The free and trapped charge densities in the channel are calculated with Fermi-Dirac statistics, and the field effective mobility of a-IGZO TFTs is then deduced based on the MTR theory. Temperature dependent drain current model for a-IGZO TFTs is finally derived with the obtained low field mobility and free charge density, which is applicable to both non-degenerate and degenerate conductions. This physical-based model is verified by available experiment results at various temperatures.

REVIEW OF DOSE-RATE EFFECTS IN THE THERMOLUMINESCENCE OF Lif:mg,ti (HARSHAW).

The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) is reviewed. The total lack of glow curve analysis, coupled with inclusion of all or part of the high temperature TL and absence of parallel measurements of possible dose-rate effects in the irradiation stage severely limit the scientific and technical level of the experiments. In addition, the experimental procedures are far from sufficient to warrant any conclusion concerning the presence or absence of dose-rate effects in the TL of LiF:Mg,Ti. This decision is contrary to the widely held belief that there are no dose-rate effects in the TL of LiF:Mg,Ti. In addition, the literature on dose-rate effects in the optical absorption (irradiation stage) of LiF is reviewed and is found contradictory. No dose-rate studies have been carried out on optical absorption in LiF:Mg,Ti. Kinetic simulations demonstrating the possibility, even likelihood, of dose-rate effects are also reviewed. Dose-rate effects are shown to be likely due to competition between excitation and recombination in the irradiation stage. Some other possible mechanisms involving multiple charge carrier trapping are suggested. Further definitive experiments are sorely needed, but the interested researcher should beware, it is not an easy task.

Modeling and characterization of the low frequency noise behavior for amorphous InGaZnO thin film transistors in the subthreshold region

An analytical model of the low-frequency noise (LFN) for amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) in the subthreshold region is developed. For a-IGZO TFTs, relations between the device noise and the subgap defects are characterized based on the dominant multiple trapping and release (MTR) mechanism. The LFN is considered to be contributed from trapping/detrapping of carriers both into the border traps and the subgap density of states (DOS). It is revealed that the LFN behavior of a-IGZO TFTs in the subthreshold region is significantly influenced by the distribution of tail states, where MTR process prevails. The 1/f α (with α < 1) spectrum of the drain current noise is also related to the characteristic temperature of the tail states. The new method is introduced to calculate the LFN of devices by extracting the LFN-related DOS parameters from the current-voltage characteristics.

Direct and inverse problems in dispersive time-of-flight photocurrent revisited

Using the fact that the continuous time random walk (CTRW) scheme is a random process subordinated to a simple random walk under the operational time given by the number of steps taken by the walker up to a given time, we revisit the problem of strongly dispersive transport in disordered media, which first lead Scher and Montroll to introducing the power law waiting time distributions. Using a subordination approach permits to disentangle the complexity of the problem, separating the solution of the boundary value problem (which is solved on the level of normal diffusive transport) from the influence of the waiting times, which allows for the solution of the direct problem in the whole time domain (including short times, out of reach of the initial approach), and simplifying strongly the analysis of the inverse problem. This analysis shows that the current traces do not contain information sufficient for unique restoration of the waiting time probability densities, but define a single-parametric family of functions that can be restored, all leading to the same photocurrent forms. The members of the family have the power-law tails which differ only by a prefactor, but may look astonishingly different at their body. The same applies to the multiple trapping model, mathematically equivalent to a special limiting case of CTRW.

DFT study of anisotropy effects on the electronic properties of diamond nanowires with nitrogen-vacancy center.

In the development of quantum computing and communications, improvements in materials capable of single photon emission are of great importance. Advances in single photon emission have been achieved experimentally by introducing nitrogen-vacancy (N-V) centers on diamond nanostructures. However, theoretical modeling of the anisotropic effects on the electronic properties of these materials is almost nonexistent. In this study, the electronic band structure and density of states of diamond nanowires with N-V defects were analyzed through first principles approach using the density functional theory and the supercell scheme. The nanowires were modeled on two growth directions [001] and [111]. All surface dangling bonds were passivated with hydrogen (H) atoms. The results show that the N-V introduces multiple trap states within the energy band gap of the diamond nanowire. The energy difference between these states is influenced by the growth direction of the nanowires, which could contribute to the emission of photons with different wavelengths. The presence of these trap states could reduce the recombination rate between the conduction and the valence band, thus favoring the single photon emission. Graphical abstract Diamond nanowires with nitrogen-vacancy centerᅟ.

Trapping of Micro Particles in Nanoplasmonic Optical Lattice.

The plasmonic optical tweezer has been developed to overcome the diffraction limits of the conventional far field optical tweezer. Plasmonic optical lattice consists of an array of nanostructures, which exhibit a variety of trapping and transport behaviors. We report the experimental procedures to trap micro-particles in a simple square nanoplasmonic optical lattice. We also describe the optical setup and the nanofabrication of a nanoplasmonic array. The optical potential is created by illuminating an array of gold nanodiscs with a Gaussian beam of 980 nm wavelength, and exciting plasmon resonance. The motion of particles is monitored by fluorescence imaging. A scheme to suppress photothermal convection is also described to increase usable optical power for optimal trapping. Suppression of convection is achieved by cooling the sample to a low temperature, and utilizing the near-zero thermal expansion coefficient of a water medium. Both single particle transport and multiple particle trapping are reported here.

Trapping of Micro Particles in Nanoplasmonic Optical Lattice

The plasmonic optical tweezer has been developed to overcome the diffraction limits of the conventional far field optical tweezer. Plasmonic optical lattice consists of an array of nanostructures, which exhibit a variety of trapping and transport behaviors. We report the experimental procedures to trap micro-particles in a simple square nanoplasmonic optical lattice. We also describe the optical setup and the nanofabrication of a nanoplasmonic array. The optical potential is created by illuminating an array of gold nanodiscs with a Gaussian beam of 980 nm wavelength, and exciting plasmon resonance. The motion of particles is monitored by fluorescence imaging. A scheme to suppress photothermal convection is also described to increase usable optical power for optimal trapping. Suppression of convection is achieved by cooling the sample to a low temperature, and utilizing the near-zero thermal expansion coefficient of a water medium. Both single particle transport and multiple particle trapping are reported here.

Fractional Derivative Phenomenology of Percolative Phonon-Assisted Hopping in Two-Dimensional Disordered Systems

Anomalous advection-diffusion in two-dimensional semiconductor systems with coexisting energetic and structural disorder is described in the framework of a generalized model of multiple trapping on a comb-like structure. The basic equations of the model contain fractional-order derivatives. To validate the model, we compare analytical solutions with results of a Monte Carlo simulation of phonon-assisted tunneling in two-dimensional patterns of a porous nanoparticle agglomerate and a phase-separated bulk heterojunction. To elucidate the role of directed percolation, we calculate transient current curves of the time-of-flight experiment and the evolution of the mean squared displacement averaged over medium realizations. The variations of the anomalous advection-diffusion parameters as functions of electric field intensity, levels of energetic, and structural disorder are presented.

A new approach to the analysis of thermoluminescence glow-curve of TLD-600 dosimeters following Am-241 alpha particles irradiation.

A new approach to the analysis of thermoluminescence (TL) glow-curves of LiF:Mg, Ti (TLD-600) following alpha particles irradiation has been presented using general expressions derived from the one-trap-one recombination (OTOR)-level model. It has been found that the results of the deconvolution in the case of using these expressions are different from the case of using the other TL expressions, especially for the high-temperature region. The advantage of using the OTOR expressions is that, unlike the usual analysis, a good fit and reasonable kinetic parameter values could be obtained with a lower number of deconvoluted peaks. The kinetic parameters and the dosimetric properties of each peak have been investigated over different absorbed doses and new findings have been found. Improvement of the accuracy and the precision of the dose measurements at low-dose levels has been achieved using the glow-curve deconvolution algorithm. In addition, theoretical interpretations of some observed behaviors have been presented using the interactive multiple trap system model.

Charge carrier relaxation in InGaAs-GaAs quantum wire modulation-doped heterostructures

The time dependencies of the carrier relaxation in modulation-doped InGaAs-GaAs low-dimensional structures with quantum wires have been studied as functions of temperature and light excitation levels. The photoconductivity (PC) relaxation follows a stretched exponent with decay constant, which depends on the morphology of InGaAs epitaxial layers, presence of deep traps, and energy disorder due to inhomogeneous distribution of size and composition. A hopping model, where electron tunnels between bands of localized states, gives appropriate interpretation for temperature-independent PC decay across the temperature range 150–290 K. At low temperatures (T < 150 K), multiple trapping–retrapping via 1D states of InGaAs quantum wires (QWRs), sub-bands of two-dimensional electron gas of modulation-doped n-GaAs spacers, as well as defect states in the GaAs environment are the dominant relaxation mechanism. The PC and photoluminescence transients for samples with different morphologies of the InGaAs nanostructures are compared. The relaxation rates are found to be largely dependent on energy disorder due to inhomogeneous distribution of strain, nanostructure size and composition, and piezoelectric fields in and around nanostructures, which have a strong impact on efficiency of carrier exchange between bands of the InGaAs QWRs, GaAs spacers, or wetting layers; presence of local electric fields; and deep traps.

Optoelectronic Properties of Semiconductor Quantum Dot Solids for Photovoltaic Applications

Quantum dot (QD) solids represent a new type of condensed matter drawing high fundamental and applied interest. Quantum confinement in individual QDs, combined with macroscopic scale whole materials, leads to novel exciton and charge transfer features that are particularly relevant to optoelectronic applications. This Perspective discusses the structure of semiconductor QD solids, optical and spectral properties, charge carrier transport, and photovoltaic applications. The distance between adjacent nanoparticles and surface ligands influences greatly electrostatic interactions between QDs and, hence, charge and energy transfer. It is almost inevitable that QD solids exhibit energetic disorder that bears many similarities to disordered organic semiconductors, with charge and exciton transport described by the multiple trapping model. QD solids are synthesized at low cost from colloidal solutions by casting, spraying, and printing. A judicious selection of a layer sequence involving QDs with different size, composition, and ligands can be used to harvest sunlight over a wide spectral range, leading to inexpensive and efficient photovoltaic devices.

Hole- and electron-only transport in ratio-controlled organic co-deposited films observed by impedance spectroscopy

Abstract The dependences of the mobility, the lifetime of deep traps and the range for hole- and electron-only devices on the ratio of metal-free phthalocyanine and fullerene in co-deposited films were measured by impedance spectroscopy. The ranges of the carriers were shown to be independent of the ratio of the co-deposited molecules. A multiple trapping model in which the disorder of the co-deposited molecules gives rise to shallow traps that dominate the mobility is proposed. Very long hole and electron ranges of 0.34 and 9.4 μm, which are long enough to extract carriers from co-deposited films in organic photovoltaic cells, were observed.

Analysis of Carrier Transport Mechanism for p-Type SnO Thin-Film Transistor

Temperature effect on the I-V characteristics of tin monoxide thin film transistors (SnO TFTs) has been analyzed. The result shows that the drain current of the SnO TFT obeys the Meyer-Neldel rule under low temperature, where current conduction is a thermally activated process. The carrier transport would be dominated by multiple trapping conduction, while, percolation conduction mechanism holds as the temperature increase.

Temperature Dependence of Magnetophotoconductance in One-Dimensional Molecular Assembly of Hexabenzocoronene.

Temperature dependencies of transient photocharge and magnetophotoconductance effect of columnar self-assemblies of the hexabenzocoronene derivative (HBC-C14), which is a prospective one-dimensional photoconductor, presented different thermal activation processes for carrier generation and transportation, respectively. Thermal equilibrium between the low-lying short distance and high-lying long-distance geminate electron–hole (e–h) pairs is the origin for activation in carrier generation. The energy difference between these e–h pairs is estimated to be 7 meV, which was mainly due to the Coulomb interaction. On the other hand, the carrier transport with thermal activation was understood by the multiple trapping model. Carrier detrapping from localized states located in the band gap causes the thermal activation in the carrier transport. The shallow energy depth at the density peak of the localized state from the mobility edge (10 ± 3 meV) is a unique nature of HBC-C14 self-assemblies. A very narrow Gaussian distribution for density of the localized states was also clarified.

Abstract 4688: AVID200: a novel computationally-designed TGF beta trap promoting anti-tumor T cell activity

Abstract AVID200 is a computationally-designed, avidity-enhanced, receptor ectodomain-based trap that binds and neutralizes TGF-beta 1 and 3 with low pM potency. Of the three TGF-beta isoforms, blockade of TGF-beta 2 has been shown to promote cancer metastasis. Therefore, AVID200 is designed to inhibit TGF-beta 1 and 3 only. TGF-beta is a strongly immunosuppressive molecule that, when expressed by cancers, mediates escape from immune surveillance. Increased TGF-beta ligand promotes cancer progression by suppressing anti-tumor immunity, predominantly by suppressing recruitment and activation of anti-tumor T cells. Consequently, TGF-beta is an important therapeutic target in cancer.AVID200 immunotherapy blocks the capacity of TGF-beta 1 and 3 ligands to interact with their receptors. That blockage induces T cell infiltration into tumors, thereby promoting a "T cell-inflamed" tumor state. Multiple trap formats with differing in vitro blocking potency, biophysical traits, and circulating half-lives in rodents have been designed, synthesized, and tested. On the basis of favorable characteristics, the AVID200 molecule was selected for in vivo assessment of efficacy in inhibiting growth of syngeneic 4T1 triple negative breast cancer (TNBC) homografts in immunocompetent host mice. In addition, CD4+ and CD8+ T cells isolated from draining lymph nodes of 4T1 tumor-bearing mice, treated and untreated with AVID200 and other candidate TGF-beta traps, were assessed for activities important in anti-tumor immune activity. We report that AVID200 immunotherapy decreased T-cell apoptosis, stimulated T-cell proliferation in response to tumor cell lysate-loaded dendritic cells, and enhanced the capacity of T-cells to specifically recognize and kill 4T1 tumor cells in ex vivo 2D cultures. The effect of combining AVID200 with immune checkpoint inhibitors in the treatment of syngeneic homografts in immune-competent mice is being assessed. AVID200 is a promising new immunotherapy to selectively inhibit the TGF-beta 1 and 3 isoforms, thereby enhancing desirable anti-tumor immunity while avoiding the tumor-promoting effects resulting from TGF-beta 2 neutralization. Citation Format: Maureen D. O'Connor-McCourt, Anne E. Lenferink, John Zwaagstra, Traian Sulea, Catherine Collins, Renu Singh, Yves Durocher, Christiane Cantin, James Koropatnick. AVID200: a novel computationally-designed TGF beta trap promoting anti-tumor T cell activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4688. doi:10.1158/1538-7445.AM2017-4688

Assessing global patterns in mammalian carnivore occupancy and richness by integrating local camera trap surveys

AbstractAimBiodiversity loss is a major driver of ecosystem change, yet the ecological data required to detect and mitigate losses are often lacking. Recently, camera trap surveys have been suggested as a method for sampling local wildlife communities, because these observations can be collated into a global monitoring network. To demonstrate the potential of camera traps for global monitoring, we assembled data from multiple local camera trap surveys to evaluate the interchange between fine‐ and broad‐scale processes impacting mammalian carnivore communities.LocationArgentina, Belize, Botswana, Canada, Indonesia, Iran, Madagascar, Nepal, Norway, Senegal, South Africa, and the U.S.A.MethodsWe gathered camera trap data, totalling &gt; 100,000 trap nights, from across five continents. To analyse local and species‐specific responses to anthropogenic and environmental variables, we fitted multispecies occurrence models to each study area. To analyse global‐level responses, we then fitted a multispecies, multi‐area occurrence model.ResultsWe recorded 4,805 detections of 96 mammalian carnivore species photographed across 1,714 camera stations located in 12 countries. At the global level, our models revealed that carnivore richness and occupancy within study areas was positively associated with prey availability. Occupancy within study areas also tended to increase with greater protection and greater distances to roads. The strength of these relationships, however, differed among countries.Main conclusionsWe developed a research framework for leveraging global camera trap data to evaluate patterns of mammalian carnivore occurrence and richness across multiple spatial scales. Our research highlights the importance of intact prey populations and protected areas in conserving carnivore communities. Our research also highlights the potential of camera traps for monitoring wildlife communities and provides a case study for how this can be achieved on a global scale. We encourage greater integration and standardization among camera trap studies worldwide, which would help inform effective conservation planning for wildlife populations both locally and globally.