Shallow levels in the band gap of CdTe films deposited on metallic substrates

CdTe thin films were developed on flexible metallic substrates using close spaced sublimation and electrodeposition techniques. The films were nearly stiochiometric, highly uniform and exhibit good crystallinity. The films were characterized using XRD, SEM and AUGER. The shallow levels in the band gap of CdTe were determined using photoluminescence and photoinduced current transient spectroscopy. The photoluminescence studies revealed a defect dominated CdTe surface. The two lines detected at 1.587 and 1.589 eV at 15 K are assigned to the donor levels associated with Cl at the Te sites. The additional features observed in the photoluminescence spectra of the CdCl₂ treated films revealed that the CdCl₂ treatment improves the quality of the films and the close space sublimated films are better than the electrodeposited films. The photoinduced current transient spectroscopic technique was effectively used to identify the electron and hole traps. Two shallow levels with activation energy 0.056 and 0.13 eV were detected and assigned to electron and hole traps, respectively.     

A geometric model for an effective rescheduling after reducing service in public transportation systems

Railway systems in metropolitan areas carry a high density of traffic daily, heterogeneously distributed, and exposed to the negative consequences derived from service disruptions. An interesting topic in the literature is to obtain performance protocols in the presence of contingencies which can affect the system operation, avoiding the propagation of perturbation and minimizing its consequences. The objective of this paper is to assess the decision of rescheduling the train service, reducing the current supply along one transportation line in order to reinforce the service of another line, exploited by the same public operator, which has suffered an incidence or emergency. A methodology, based on a geometric representation of solutions which allows the use of discrete optimization techniques, is developed in order to attend to the underlying demand with efficiency criteria in this context of unexpected incidents.     

A new approach to evaluate bending forces for deep-drawing operations of a TRIP700 +EBT steel sheet

In this work, a new approach was developed to determine the bending, unbending and friction forces involved in deep-drawing processes of metallic sheets based on a sheet drawing-bending test. The procedure used both the experimental and deduced behavior of sheets in bending and unbending processes under tension. To obtain experimental data, a new apparatus was built to measure the reactions forces in the bending tool. These tests were applied to a TRIP700 +EBT steel sheet in diverse pure shear deformation states, with two different lubricants. The effect of the back tension and the state of the material were also studied by bending and unbending processes using tensile tests under diverse pure-shear conditions. Deduced forces, like bending and unbending forces, were determined by introducing these experimental data into an expressly created numerical method. The obtained results allowed us to state that the TRIP700 +EBT steels sheet displayed evolutional mechanical behavior since the induced martensite phase transformation effect depended on the deformation mode and intensity, had good formability and a low friction coefficient with steel tools, which was almost constant and independent of the pressure in the bending tool.     

Biohybrid Microtube Swimmers Driven by Single Captured Bacteria

Bacteria biohybrids employ the motility and power of swimming bacteria to carry and maneuver microscale particles. They have the potential to perform microdrug and cargo delivery in vivo, but have been limited by poor design, reduced swimming capabilities, and impeded functionality. To address these challenge, motile Escherichia coli are captured inside electropolymerized microtubes, exhibiting the first report of a bacteria microswimmer that does not utilize a spherical particle chassis. Single bacterium becomes partially trapped within the tube and becomes a bioengine to push the microtube though biological media. Microtubes are modified with “smart” material properties for motion control, including a bacteria‐attractant polydopamine inner layer, addition of magnetic components for external guidance, and a biochemical kill trigger to cease bacterium swimming on demand. Swimming dynamics of the bacteria biohybrid are quantified by comparing “length of protrusion” of bacteria from the microtubes with respect to changes in angular autocorrelation and swimmer mean squared displacement. The multifunctional microtubular swimmers present a new generation of biocompatible micromotors toward future microbiorobots and minimally invasive medical applications.     

The Photophysics of Polythiophene Nanoparticles for Biological Applications

In this work the photophysics of poly(3-hexylthiophene) nanoparticles (NPs) is investigated in the context of their biological applications. The NPs, made as colloidal suspensions in aqueous buffers, present a distinct absorption band in the low-energy region. On the basis of systematic analysis of absorption and transient absorption (TA) spectra taken under different pH conditions, this band is associated with charge-transfer states generated by the polarization of loosely bound polymer chains and originating from complexes formed with electron-withdrawing species. Importantly, the ground-state depletion of these states upon photoexcitation is active even on microsecond timescales, thus suggesting that they act as precursor states for long-living polarons; this could be beneficial for cellular stimulation. Preliminary transient absorption microscopy results for NPs internalized within the cells reveal the presence of long-living species, further substantiating their relevance in biointerfaces.     

Data-Based Models for the Prediction of Dam Behaviour: A Review and Some Methodological Considerations

Predictive models are an important element in dam safety analysis. They provide an estimate of the dam response faced with a given load combination, which can be compared with the actual measurements to draw conclusions about dam safety. In addition to numerical finite element models, statistical models based on monitoring data have been used for decades for this purpose. In particular, the hydrostatic-season-time method is fully implemented in engineering practice, although some limitations have been pointed out. In other fields of science, powerful tools such as neural networks and support vector machines have been developed, which make use of observed data for interpreting complex systems. This paper contains a review of statistical and machine-learning data-based predictive models, which have been applied to dam safety analysis. Some aspects to take into account when developing analysis of this kind, such as the selection of the input variables, its division into training and validation sets, and the error analysis, are discussed. Most of the papers reviewed deal with one specific output variable of a given dam typology and the majority also lack enough validation data. As a consequence, although results are promising, there is a need for further validation and assessment of generalisation capability. Future research should also focus on the development of criteria for data pre-processing and model application.     

Microbial Inactivation and Quality of Guava and Passion Fruit Nectars Treated by UV-C Light

Freshness attributes in food products continue to be a trend of relevance to consumers. UV-C light treatment of fluid foods is a non-thermal process potentially suitable to obtain high-quality fruit nectars. This study pursued to test the effect of UV-C light treatment on indigenous microorganisms and sensory quality of two tropical fruit nectars. Guava and passion fruit nectars were treated with light at λ = 253.7 nm up to 24 and 11 J/ml, respectively, in an annular reactor. The effects of this process on microbial inactivation were assessed by aerobic mesophilic count (AMC), yeast and mould count (YMC) and by triangle tests regarding sensory quality. Microbial inactivation increased with fluence. The highest fluence decreased AMC of guava and passion fruit nectars by 0.51 and 1.36 log colony-forming units (CFU) per millilitre, respectively, and YMC of guava by 0.53 log CFU/ml. However, the sensory panel detected differences due to treatments even at the lowest fluences (15 and 6 J/ml for guava and passion fruit, respectively). This work confirms the capability of UV light to inactivate microorganisms in fluid foods, but in sensitive products such as tropical fruit nectars, sensory changes may be a drawback for practical application of the technology for producing fresh-like stable products.