First Molecular Detection of Aichivirus in Pediatric Patients with Acute Gastroenteritis in Iran

Background: Aichivirus as a new member of Picornaviridae family was detected and isolated in Japan. Aichivirus species, which belongs to genus Kobuvirus, include of three genotypes A, B and C. Based on previous reports to detect aichiviruses in stool samples as well as environmental samples such as river waters and sewage waters, it has been demonstrated that Aichivirus infect humans by fecal-oral routs. In order to establish an examination for the prevalence of Aichivirus among pediatric patients involved to acute gastroenteritis, we conducted a RT-qPCR assay for detection and quantification of Aichivirus in collected stool samples.Materials and Methods: In this study, a total of 160 stool samples from September 2018 to May 2019 were collected from presenting pediatric patients with acute gastroenteritis in Karaj hospital, Iran. After viral RNA extraction, the RT-PCR was performed to amplify the 3CD junction region of Aichivirus.Results: Out of the 160 samples tested, the Aichivirus genomic RNA was detected in 13/160 (8.1%) of stool samples. The maximum viral prevalence rate was related to December (30.7%). The co-infection of Aichivirus with Salivirus and Saffold virus also assessed, among which high double or triple mixed-infections were determined.Conclusion: This is the first documentation of Aichivirus detection in stool samples that demonstrates Aichivirus has been circulating among Iranian pediatric patients. Our results indicate that Aichivirus in association with Salivirus and Saffold virus may be considered as a causative agent of acute gastroenteritis.

Optical Synthesis of Transient Chirality in Achiral Plasmonic Metasurfaces

As much as chiral metasurfaces are significant in stereochemistry and polarization control, tunable chiroptical response is important for their dynamic counterparts. A single metasurface device with invertible chiral states can selectively harness or manipulate both handedness of circularly polarized light upon demand, where in fact chiral inversion in molecules is an active research field. Tactics for chirality switching can be classified into geometry modification and refractive index tuning. However, these generally confront slow modulation speed or restrained refractive index tuning effects in the visible regime with forbidden 'true' inversion. Here, we reconfigure the 'optical' geometry through inhomogeneous spatiotemporal distribution of hot carriers as a breakthrough, transforming a plasmonic achiral metasurface into an ultrafast transient chiral medium with near-perfectly-invertible handedness in the visible. The photoinduced chirality relaxes through the fast spatial diffusion process of electron temperature compared to electron-phonon relaxation, empowering hot-carrier-based devices to be particularly suitable for ultrafast chiroptics

Active and nonlinear nanophotonics facilitated by hot-carrier dynamics

The ever-increasing demand for bandwidth scalability and high-speed operation is the driving force for the discovery of ultrafast switches. As electronics approaches its intrinsic limitations, pursuing new computational paradigms for data processing is inevitable. In recent years, optical computing –replacing electrons with photons– has been introduced as a powerful alternative to boost computational capacities beyond that of solid-state electronics. Up to date, however, the primary role of optical technologies in data processors has been limited to the realization of communication links between electronic blocks, often through the incorporation of optical fibers and, more recently, photonic waveguides. Although “speed” is the biggest promise of optics, relying on electronic components to control light sources at input/output (I/O) end-facets is the major setback towards unlocking ultimate potentials of optical data processors. To extend the role of optics beyond ultrafast data transmission links, it is essential to implement optical switches within CMOS-integrable platforms. This goal is achievable through nonlinear optical effects. Indeed, by enabling active modulation of light waves and on-demand generation of new spectral components, nonlinear optics potentially has the capability to deliver advanced optical I/O segments with operation speeds well beyond the capabilities of electronic devices. This PhD thesis is focused on the exploration of new techniques for the implementation of ultrafast all-optical switches. During my PhD program at Georgia Tech, I did my best to pursue this goal at two equally important levels: (i) material-design level; and (ii) device-design level. It comes without saying that understanding the properties of active optical materials is a prerequisite of the device-level design too, as the intrinsic material properties obviously impact both linear and nonlinear responses of any photonic structure. In addition, empowered by the Maxwell’s description of light-matter interactions, predicting the performance of a nanophotonic platform at a device level is theoretically manageable, and most often very close to our in-lab observations. In sharp contrast, predicting properties of materials, especially in their out-of-equilibrium states, is numerically a very challenging task. Therefore, my research primarily aimed at “experimental” study of material properties to gain deep insights on the transient behavior of charge carriers in optical media. I believe that such knowledge provides numerically out-of-reach information regarding the capabilities of optical materials, required for the design of all-optical switches. I have provided some critical discussion regarding the design of prototypical nanophotonic structures as well, to guide the readers of this document towards necessary steps that should be taken for the successful design of optical switches from a device-level perspective. In the first half of this thesis, I propose and experimentally demonstrate that the semi-instantaneous transport of plasmonic hot electrons in hybrid metal/dielectric systems enables coherent control over the third-order nonlinear properties of noble metals. By relying on the ultrafast dynamic of hot-electron transport, we design prototypical plasmonic structures that can benefit from the inherently fast nature of the electron transport and therefore, facilitate the sub-picosecond all-optical switching of intensity, phase, and polarization of light. In the second half, we further expand the contribution of plasmonic hot carriers in the field of active and nonlinear nanophotonics and propose a fundamentally new paradigm for inducing optical nonlinearities of second-order type in centrosymmetric materials upon the transport of hot electrons. Our proposed method, allows for optically breaking the inversion symmetry in a wide range of optical materials, expanding the portfolio of second-order nonlinear media that could be adopted for the realization of functional nanophotonic devices. I believe our demonstrations and experimental observations reveal significant potentials of plasmonic hot carriers in the field of nonlinear nanophotonics and at the same time introduces a new problem set for physicists at the crossroads of nonlinear optics, hot-carrier physics, and nanophotonics.Ph.D

Evaluating the welfare aspects of the simple monetary ruls for Iran

This paper following a monetary growth rate rule aims to compare the properties of different monetary policy rules in Iran. In that regards, the paper draws on the New Keynesian Dynamic Stochastic General Equilibrium (DSGE) models. Within this framework, we rank the different policy rules based on the Impulse response Functions, the volatility of key macroeconomic variables and the welfare loss function. The paper concludes that the effects of alternative monetary rules depend on what shocks affect the economy, the exchange rate regime, and the choice of inflation index. When the economy experiences productivity shocks, domestic iflation targeting is welfare-superior to other monetary rules. However, in the case of other shocks except productivity shock a managed exchange rate is the best policy rule. Finally, the results of welfare loss of alternative monetary policy rules allowed noticing the nature of the shocks affecting the economy dictate the implication and choice of the best monetary policy rule

High-efficiency photoelectrochemical cathodic protection performance of the iron-nitrogen-sulfur-doped TiO(2)nanotube as new efficient photoanodes

Novel iron-nitrogen-sulfur-tridoped titanium dioxide nanotubes (Fe-N-S-TiO2NTs) have been synthesized via single step anodization of titanium using potassium ferricyanide, as a suitable additive, in dimethyl sulfoxide (DMSO) electrolyte and applied as photoanodes in the photocathodic protection of stainless steel 403 (SS403). Photocurrent density, open circuit potential and Tafel polarization curves have been used to study the photocathodic protection effect of the samples prepared. Upon the addition of potassium ferricyanide to the anodizing electrolyte and titanium dioxide nanotube doping, the light absorption of the Fe-N-S-TiO2NTs were increased to the visible region, comparable with pure TiO2NTs, according to the results obtained. Enhanced photoelectro-response activity and photocathodic protection performance for 403 stainless steel are exhibited by Fe-N-S-TiO2NTs under light illumination. In addition, the optimal sample electrode (FT4) potentials shifted negatively to -683 mV under illumination

Cell-imprinted substrates act as an artificial niche for skin regeneration

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed (involucrin, collagen type I, and keratin 10) together with protein expression data showed that human adipose-derived stem cells (ADSCs) seeded on these cell-imprinted substrates were driven to adopt the specific shape and characteristics of keratinocytes. The observed morphology of the ADSCs grown on the keratinocyte casts was noticeably different from that of stem cells cultivated on the stem-cell-imprinted substrates. Since the shape and geometry of the nucleus could potentially alter the gene expression, we used molecular dynamics to probe the effect of the confining geometry on the chain arrangement of simulated chromatin fibers in the nuclei. The results obtained suggested that induction of mature cell shapes onto stem cells can influence nucleus deformation of the stem cells followed by regulation of target genes. This might pave the way for a reliable, efficient, and cheap approach of controlling stem cell differentiation toward skin cells for wound healing applications

Influence of water saturation and water memory on CO2 hydrate formation/dissociation in porous media under flowing condition

Injection of high-pressure CO2 into depleted gas reservoirs can lead to low temperatures promoting formation of hydrate in the near wellbore area resulting in reduced injection rates. The design of effective mitigation methods requires an understanding of the impact of crucial parameters on the formation and dissociation of CO2 hydrate within the porous medium under flowing conditions. This study investigates the influence of water saturation (ranging from 20 % to 40 %) on the saturation and kinetics of CO2 hydrate during continuous CO2 injection. The experiments were conducted under a medical X-ray computed tomography (CT) to monitor the dynamics of hydrate growth inside the core and to calculate the hydrate saturation profile. The experimental data reveal increase in CO2 hydrate saturation with increasing water saturation levels. The extent of permeability reduction is strongly dependent on the initial water saturation: beyond a certain water saturation the core is fully blocked. For water saturations representative of the depleted gas fields, although the amount of generated hydrate is not sufficient to fully block the CO2 flow path, a significant reduction in permeability (approximately 80 %) is measured. It is also observed that the volume of water + hydrate phases increases during hydrate formation, indicating a lower-than-water density for CO2 hydrate. Having a history of hydrate at the same water saturation leads to an increase in CO2 consumption compared to the primary formation of hydrate, confirming the existence of the water memory effect in porous media.Reservoir Engineerin