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2021 ◽  
pp. 118239
Author(s):  
M.Y. Espinosa-Cerón ◽  
A.N. Meza-Rocha ◽  
S. Carmona-Téllez ◽  
Cecilia Chacón ◽  
O. Soriano-Romero ◽  
...  

2021 ◽  
Author(s):  
Saif Al-Alul

A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.


2021 ◽  
Author(s):  
Saif Al-Alul

A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea Ferrario ◽  
James Rankin

AbstractIn the auditory streaming paradigm, alternating sequences of pure tones can be perceived as a single galloping rhythm (integration) or as two sequences with separated low and high tones (segregation). Although studied for decades, the neural mechanisms underlining this perceptual grouping of sound remains a mystery. With the aim of identifying a plausible minimal neural circuit that captures this phenomenon, we propose a firing rate model with two periodically forced neural populations coupled by fast direct excitation and slow delayed inhibition. By analyzing the model in a non-smooth, slow-fast regime we analytically prove the existence of a rich repertoire of dynamical states and of their parameter dependent transitions. We impose plausible parameter restrictions and link all states with perceptual interpretations. Regions of stimulus parameters occupied by states linked with each percept match those found in behavioural experiments. Our model suggests that slow inhibition masks the perception of subsequent tones during segregation (forward masking), whereas fast excitation enables integration for large pitch differences between the two tones.


2021 ◽  
pp. 118198
Author(s):  
N.C. Gatsi ◽  
A. Shnier ◽  
M. Mujaji ◽  
D. Wamwangi

2021 ◽  
Author(s):  
Corwin R. Butler ◽  
Gary L. Westbrook ◽  
Eric Schnell

SummaryHilar mossy cells control network function in the hippocampus through both direct excitation and di-synaptic inhibition of dentate granule cells (DGCs). Substantial mossy cell loss occurs after epileptic seizures; however the contribution of surviving mossy cells to network activity in the reorganized dentate gyrus is unknown. To examine functional circuit changes after pilocarpine-induced status epilepticus, we optogenetically stimulated mossy cells in acute hippocampal slices. In control mice, activation of mossy cells produced monosynaptic excitatory and di-synaptic GABAergic currents in DGCs. In pilocarpine-treated mice, mossy cell density and excitation of DGCs were reduced in parallel, with only a minimal reduction in feedforward inhibition, enhancing the inhibition:excitation ratio. Surprisingly, mossy cell-driven excitation of parvalbumin-positive basket cells, the primary mediators of feed-forward inhibition, was maintained, indicating increased connectivity between surviving mossy cells and these targets. Our results suggest that mossy cell outputs reorganize following seizures, increasing their net inhibitory effect in the hippocampus.


Photochem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 38-52
Author(s):  
Min Hee Joo ◽  
So Jeong Park ◽  
Hye Ji Jang ◽  
Sung-Min Hong ◽  
Choong Kyun Rhee ◽  
...  

The trivalent Eu(III) ion exhibits unique red luminescence and plays an significant role in the display industry. Herein, the amperometry electrodeposition method was employed to electrodeposit Eu(III) materials on porous Si and terpyridine-functionalized Si surfaces. The electrodeposited materials were fully characterized by scanning electron microscopy, X-ray diffraction crystallography, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Photoluminescence (PL) spectroscopy revealed that PL signals were substantially increased upon deposition on porous Si surfaces. PL signals were mainly due to direct excitation and charge-transfer-indirect excitations before and after thermal annealing, respectively. The as-electrodeposited materials were of a Eu(III) complex consisting of OH, H2O, NO3−, and CO32− groups. The complex was transformed to Eu2O3 upon thermal annealing at 700 °C. The electrodeposition on porous surfaces provide invaluable information on the fabrication of thin films for displays, as well as photoelectrodes for catalyst applications.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiaofei Qi ◽  
Kexin Lyu ◽  
Long Meng ◽  
Cuixian Li ◽  
Hongzheng Zhang ◽  
...  

Cochlear implantation is the first-line treatment for severe and profound hearing loss in children and adults. However, deaf patients with cochlear malformations or with cochlear nerve deficiencies are ineligible for cochlear implants. Meanwhile, the limited spatial selectivity and high risk of invasive craniotomy restrict the wide application of auditory brainstem implants. A noninvasive alternative strategy for safe and effective neuronal stimulation is urgently needed to address this issue. Because of its advantage in neural modulation over electrical stimulation, low-intensity ultrasound (US) is considered a safe modality for eliciting neural activity in the central auditory system. Although the neural modulation ability of low-intensity US has been demonstrated in the human primary somatosensory cortex and primary visual cortex, whether low-intensity US can directly activate auditory cortical neurons is still a topic of debate. To clarify the direct effects on auditory neurons, in the present study, we employed low-intensity US to stimulate auditory cortical neurons in vitro. Our data show that both low-frequency (0.8 MHz) and high-frequency (>27 MHz) US stimulation can elicit the inward current and action potentials in cultured neurons. c-Fos staining results indicate that low-intensity US is efficient for stimulating most neurons. Our study suggests that low-intensity US can excite auditory cortical neurons directly, implying that US-induced neural modulation can be a potential approach for activating the auditory cortex of deaf patients.


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