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Time resolved spectroscopy provides unique insight into the structure and function of cobalamins. In these experiments, the cobalamin is initially excited by a short "pump" pulse in the UV-visible region and then characterized at some later time using a short "probe" pulse. The emphasis in this chapter is on both UV-visible and X-ray probe pulses, with a particular focus on the unique information provided by the latter. The principles of time-resolved spectroscopy are reviewed, with an emphasis on ultrafast measurements (time scales less than ~10ps) to characterize short-lived cobalamin excited states. Several practical considerations are discussed, with a focus on the technical details that are necessary to obtain high quality, interpretable data. These include sample delivery, polarization, and excitation power. Some of the theoretical approaches to interpreting data are discussed.

Femtosecond X-ray spectroscopy is used to characterize the internal conversion and coherent excited state evolution of typical cobalamins. Cobalt Kα and Kβ emission probes electronic dynamics while Cobalt K-edge XANES probes structural evolution.

We investigated strontium oxide (SrO) as an interlayer material to enhance the UV stability of a CH3NH3PbI3 perovskite solar cell. Moisture and over 400 nm wavelength of light were excluded to investigate the effect of UV light only. Two different interlayer fabrication processes were examined to optimize the performance of this solar cell. Devices fabricated by dipping for 30 min in SrO solution exhibited photoconversion efficiencies of 15.5%, whereas those fabricated with 60-min dipping showed photoconversion efficiencies of 15% and exhibited local Sr agglomeration. Devices with SrO displayed lower initial efficiencies than those without any SrO layer (17.6%), However, a device without SrO retained only 34.4% of its initial efficiency after 100 h of UV exposure. In contrast, SrO-incorporated devices retained almost 60.0% of their initial efficiency. Severe μ-PL mapping intensity degradation was observed in devices that did not include the interlayer, but no degradation was observed in those with the SrO interlayer. This can be attributed to the passivation of the degradation sites by SrO.

Organic–inorganic halide Perovskite solar cells have extremely high power conversion efficiencies of 22.1%, as officially recognized by the US National Renewable Energy Laboratory (NREL). These solar cells are therefore attractive candidates for use in next generation photovoltaic applications. Perovskite materials for incorporation into solar cells are prepared by a two-step solution fabrication process to generate polycrystalline structures with diverse grain sizes. PbI2 is the main material used in the synthesis of organic–inorganic hybrid perovskite, particularly when the sequential deposition method is employed, as it facilitates the formation of a well-organized perovskite layer. To improve the performance of these devices, the properties of PbI2 properties need to be investigated. We therefore examined the effects of PbI2 concentration in mesoporous perovskite solar cells prepared using a two-step solution deposition method. Samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis spectrometry, and atomic force microscopy (AFM). The results of this work confirm the importance of the PbI2 layer in high efficiency perovskite solar cells.

In conventional sequential deposition, PbI 2 -free CH 3 NH 3 PbI 3 perovskite films can be achieved when the PbI 2 substrate reacts with a relatively low-concentration CH 3 NH 3 I solution ( 3 NH 3 I per 1 mL of IPA) but the film that is formed has only sparse and uneven coverage. On the other hand, a dense CH 3 NH 3 PbI 3 perovskite film can be formed on a mesoporous TiO 2 substrate when the PbI 2 substrate reacts with a relatively high-concentration MAI solution (>8 mg of CH 3 NH 3 I per 1 mL of IPA), but unreacted PbI 2 is still present in CH 3 NH 3 PbI 3 layer in such cases. Here, we developed organic-inorganic perovskite solar cells with high efficiency by preparing dense and PbI 2 -free films using a modified sequential deposition process. By utilizing the reaction behavior between PbI 2 and MAI, solar cells with an average power-conversion efficiency of 15.1% and high reproducibility and stability were achieved.

The stabilization characteristics of premixed flames in an axisymmetric curved-wall jet burner have been experimentally investigated. This burner utilized the Coanda effect on top of a burner tip. The initially spherical burner tip was modified to a flat tip and a concave tip in order to improve flame stabilization by providing enough space for flow recirculation above the burner tip region. The flow characteristics have been visualized using a schlieren technique. Small-scale turbulence structure has been observed mainly in the interaction jet region (located downstream of the recirculation region) for large jet velocity (Reynolds number > 11,500). An appreciable amount of air entrainment was exhibited from the half-angle of the jet spread, approximately 20°. The averaged planar laser-induced fluorescence images of the flames for this large velocity demonstrated that the strong signal of OH radicals, representing reaction zones, existed in the recirculation zone, while it was weak in the interaction jet ...

One stress-inducing task and two cognitive tasks were used to investigate how these tasks influence one’s cognitive capability. First, the participants performed stress-inducing tasks for 5 minutes. They were then divided into two separate groups, and were given two kinds of cognitive load tasks which differed in difficulty levels. Finally, a cognitive task for evaluating cognitive capabilities of the two groups was conducted. This procedure was repeated 4 times, 2 minutes for each task, which showed that there was a tendency of improved performance over time. We found no reaction time and performance rate changes with respect to processing difficulty. However, the interaction between difficulty and repetition was significant, which meant participants who were assigned to easier tasks showed unstable performance compared to those who were assigned to high-difficulty tasks. These results suggest that imposing a proper amount of stress and cognitive load could promote cognitive performance in general.

This study examined the effect of word recall among Korean native students learning English vocabulary as their second language. The aim was to determine if there would be an effect of word recall on English vocabulary learning after the participants had studied 160 English-Korean word pairs using the computer. Participants were assigned to three different learning conditions (Control, Recall, Encode) and they learned lists of word pairs across multiple study trials and were given an immediate recall test. A final delayed recall test was also given 1 week after learning. The results from the delayed recall test indicated that the learning conditions (Control, Recall) which required the participants to actively recall the words resulted in a better recall of words 1 week after the initial learning period. In addition, the results from the survey which investigated the participants’ preferred strategy when studying, demonstrated that 63.5% of the participants preferred to engage in self-testing or retrieval practice while studying. However, participants did not regard retrieval practice via self-testing alone as an effective learning strategy for studying.