Hydrothermal–galvanic couple synthesis of directionally oriented BaTiO3 thin films on TiN-coated substrates

AbstractBaTiO3 films were synthesized on TiN-coated Si substrate below 100°C by a hydrothermal–galvanic couple technique in barium contained alkaline solutions. X-ray diffraction and electron backscatter diffraction results show that the BaTiO3 thin films were directionally oriented grown on the TiN/Si substrates, i.e., (111) BaTiO3 over (111) TiN. The surface morphologies revealed that BaTiO3 nucleated and grew over the TiN surface with a single layer. From kinetic analyses, the growth rates of BaTiO3 films prepared by the hydrothermal–galvanic couple technique were faster than a hydrothermal method. The galvanic effects were confirmed by investigating the induced currents and energies. The galvanic currents were generated and controlled by both the dissolution of TiN and the formation of BaTiO3. The output electric energies increased rapidly with the reaction time and leveled off at the full coverage of BaTiO3

Liquid-Crystal-Based Phase Gratings and Beam Steerers for Terahertz Waves

We review our theoretical and experimental studies on a class of liquid crystal (LC) photonic devices, i.e., terahertz (THz) phase gratings and beam steerers by using LCs. Such gratings can function as a THz polarizer and tunable THz beam splitters. The beam splitting ratio of the zeroth-order diffraction to the first-order diffraction by the grating can be tuned from 10:1 to 3:5. Gratings with two different base dimensions were prepared. The insertion loss is lower by approximately 2.5 dB for the one with the smaller base. The response times of the gratings were also studied and were long (tens of seconds) as expected because of the thick LC layer used. Accordingly, the devices are not suitable for applications that require fast modulation. However, they are suitable for instrumentation or apparatuses that require precise control, e.g., an apparatus requiring a fixed beam splitting ratio with occasional fine tuning. Schemes for speeding up the device responses were proposed. Based on the grating structure, we also achieved an electrically tunable THz beam steerer. Broadband THz radiation can be steered by 8.5° with respect to the incident beam by varying the driving voltages to yield the designed phase gradient

Cortical and Subcortical Neural Correlates for Respiratory Sensation in Response to Transient Inspiratory Occlusions in Humans

Cortical and subcortical mechanosensation of breathing can be measured by short respiratory occlusions. However, the corresponding neural substrates involved in the respiratory sensation elicited by a respiratory mechanical stimulus remained unclear. Therefore, we applied the functional magnetic resonance imaging (fMRI) technique to study cortical activations of respiratory mechanosensation. We hypothesized that thalamus, frontal cortex, somatosensory cortex, and inferior parietal cortex would be significantly activated in response to respiratory mechanical stimuli. We recruited 23 healthy adults to participate in our event-designed fMRI experiment. During the 12-min scan, participants breathed with a specialized face-mask. Single respiratory occlusions of 150 ms were delivered every 2–4 breaths. At least 32 successful occlusions were collected for data analysis. The results showed significant neural activations in the thalamus, supramarginal gyrus, middle frontal gyrus, inferior frontal triangularis, and caudate (AlphaSim corrected p < 0.05). In addition, subjective ratings of breathlessness were significantly correlated with the levels of neural activations in bilateral thalamus, right caudate, right supramarginal gyrus, left middle frontal gyrus, left inferior triangularis. Our results demonstrated cortical sources of respiratory sensations elicited by the inspiratory occlusion paradigm in healthy adults were located in the thalamus, supramarginal gyrus, and the middle frontal cortex, inferior frontal triangularis, suggesting subcortical, and cortical neural sources of the respiratory mechanosensation are thalamo-cortical based, especially the connections to the premotor area, middle and ventro-lateral prefrontal cortex, as well as the somatosensory association cortex. Finally, level of neural activation in thalamus is associated with the subjective rating of breathlessness, suggesting respiratory sensory information is gated at the thalamic level

Carbon Dioxide Angiography in Lower Limbs: A Prospective Comparative Study With Selective Iodinated Contrast Angiography

This was a prospective comparison of the accuracy and image quality of carbon dioxide digital subtraction angiography (CO2 DSA) and iodinated contrast digital subtraction angiography (ICDSA) in evaluating lower extremity arteries and patient tolerance of the procedures. Selective DSA was performed in 14 Taiwanese patients who were diagnosed with peripheral artery occlusive disease (PAOD). Both contrast materials were administered through mechanical injectors. Post-processing of the image used pixel shifting. Images of vessels were divided into 22 anatomic segments and evaluated by two experienced radiologists. A four-point scale was used to classify diseased vessels. Two interpreters rated the CO2 DSA image against the ICDSA image on a three-point scale. Patient tolerance was assessed from verbal descriptions. Cohen's kappa was used to determine interobserver agreement and descriptive statistics were used to summarize patient experience. Interobserver agreement ranged from fair to excellent, with most being good or excellent. Three patients (21.4%) could not tolerate the whole procedure and nine patients (64.3%) reported discomfort during the CO2 DSA procedure. CO2 DSA image quality was better for the thigh than the distal runoff and pelvic regions. Our results showed that selective CO2 DSA cannot replace ICDSA as a routine diagnostic tool for PAOD because it does not give images of comparative quality

Growth mechanism and magnon excitation in NiO nanowalls

The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature

Exploring the Mechanism Responsible for Cellulase Thermostability by Structure-Guided Recombination

Cellulases from Bacillus and Geobacillus bacteria are potentially useful in the biofuel and animal feed industries. One of the unique characteristics of these enzymes is that they are usually quite thermostable. We previously identified a cellulase, GsCelA, from thermophilic Geobacillus sp. 70PC53, which is much more thermostable than its Bacillus homolog, BsCel5A. Thus, these two cellulases provide a pair of structures ideal for investigating the mechanism regarding how these cellulases can retain activity at high temperature. In the present study, we applied the SCHEMA non-contiguous recombination algorithm as a novel tool, which assigns protein sequences into blocks for domain swapping in a way that lessens structural disruption, to generate a set of chimeric proteins derived from the recombination of GsCelA and BsCel5A. Analyzing the activity and thermostability of this designed library set, which requires only a limited number of chimeras by SCHEMA calculations, revealed that one of the blocks may contribute to the higher thermostability of GsCelA. When tested against swollen Avicel, the highly thermostable chimeric cellulase C10 containing this block showed significantly higher activity (22%-43%) and higher thermostability compared to the parental enzymes. With further structural determinations and mutagenesis analyses, a 3_(10) helix was identified as being responsible for the improved thermostability of this block. Furthermore, in the presence of ionic calcium and crown ether (CR), the chimeric C10 was found to retain 40% residual activity even after heat treatment at 90°C. Combining crystal structure determinations and structure-guided SCHEMA recombination, we have determined the mechanism responsible for the high thermostability of GsCelA, and generated a novel recombinant enzyme with significantly higher activity