Silicon-chip-based ultrafast optical oscilloscope

With the realization of faster telecommunication data rates and an expanding interest in ultrafast chemical and physical phenomena, it has become important to develop techniques that enable simple measurements of optical waveforms with subpicosecond resolution. State-of-the-art oscilloscopes with high-speed photodetectors provide single-shot waveform measurement with 30-ps resolution. Although multiple-shot sampling techniques can achieve few-picosecond resolution, single-shot measurements are necessary to analyse events that are rapidly varying in time, asynchronous, or may occur only once. Further improvements in single-shot resolution are challenging, owing to microelectronic bandwidth limitations. To overcome these limitations, researchers have looked towards all-optical techniques because of the large processing bandwidths that photonics allow. This has generated an explosion of interest in the integration of photonics on standard electronics platforms, which has spawned the field of silicon photonics and promises to enable the next generation of computer processing units and advances in high-bandwidth communications. For the success of silicon photonics in these areas, on-chip optical signal-processing for optical performance monitoring will prove critical. Beyond next-generation communications, silicon-compatible ultrafast metrology would be of great utility to many fundamental research fields, as evident from the scientific impact that ultrafast measurement techniques continue to make. Here, using time-to-frequency conversion via the nonlinear process of four-wave mixing on a silicon chip, we demonstrate a waveform measurement technology within a silicon-photonic platform. We measure optical waveforms with 220-fs resolution over lengths greater than 100 ps, which represent the largest record-length-to-resolution ratio (>450) of any single-shot-capable picosecond waveform measurement technique. Our implementation allows for single-shot measurements and uses only highly developed electronic and optical materials of complementary metal-oxide-semiconductor (CMOS)-compatible silicon-on-insulator technology and single-mode optical fibre. The mature silicon-on-insulator platform and the ability to integrate electronics with these CMOS-compatible photonics offer great promise to extend this technology into commonplace bench-top and chip-scale instruments.     

Effects of intermediate Ni layer on mechanical properties of Al–Cu layered composites fabricated through cold roll bonding

Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature (either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.     

Influence of growth conditions on the electrochemical synthesis of SnS thin films and their optical properties

Tin sulfide (SnS) thin films were prepared by electrodeposition onto fluorine-doped tin oxide (FTO) glass substrates using an aqueous solution containing SnCl₂ and Na₂S₂O₃ at various deposition potentials (E) and bath concentrations. The pH value and temperature of the solution were kept constant. The deposited films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), photoluminescence (PL), and ultraviolet–visible (UV–Vis) spectroscopy. The FESEM images demonstrated that changes in the deposition potential (E) and solution concentration led to marked changes in the morphology of the deposited SnS films. Energy-dispersive X-ray analysis (EDXA) results showed that the Sn/S atomic ratio strongly depended on both the solution concentration and the deposition potential. To obtain an Sn/S atomic ratio approximately equal to 1, the optimal Sn2+/S₂O₃2- molar ratio and E parameter were 1/8 and -1.0 V, respectively. The XRD patterns showed that the synthesized SnS was obviously polycrystalline, with an orthorhombic structure. The effects of the variations of bath concentration and deposition potential on the band-gap energy (E_g) were studied using PL and UV–Vis experiments. The PL spectra of all the SnS films contained two peaks in the visible region and one peak in the infrared (IR) region. The UV–Vis spectra showed that the optical band-gap energy varies from 1.21 to 1.44 eV.     

PLGA/硬石复合涂层镁基纳米复合材料在植入应用时的体外生物活性和腐蚀行为

A type of polymer/ceramic coating was introduced on a magnesium-based nanocomposite, and the nanocomposite was evaluated for implant applications. The microstructure, corrosion, and bioactivity of the coated and uncoated samples were assessed. Mechanical alloying followed by sintering was applied to fabricate the Mg–3Zn–0.5Ag–15NiTi nanocomposite substrate. Moreover, different contents of poly(lactic-co-glycolic acid) (PLGA) coatings were studied, and 10wt% of PLGA content was selected. The scanning electron microscopy (SEM) images of the bulk nanocomposite showed an acceptable homogenous dispersion of the NiTi nanoparticles (NPs) in the Mg-based matrix. In the in vitro bioactivity evaluation, following the immersion of the uncoated and coated samples in a simulated body fluid (SBF) solution, the Ca/P atomic ratio demonstrated that the apatite formation amount on the coated sample was greater than that on the uncoated nanocomposite. Furthermore, assessing the corrosion resistance indicated that the coatings on the Mg-based substrate led to a corrosion current density (i_corr) that was considerably lower than that of the substrate. Such a condition revealed that the coating would provide an obstacle for the corrosion. Based on this study, the PLGA/hardystonite (HT) composite-coated Mg–3Zn–0.5Ag–15NiTi nanocomposite may be suitably applied as an orthopedic implant biomaterial.     

An in vitro evaluation of novel NHA/zircon plasma coating on 316L stainless steel dental implant

The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon(NHA/zircon) nanobiocomposite coating on 316L stainless steel(SS) dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0(control),5, 10, and 15 wt% of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method.Scanning electron microscopy(SEM) was used to evaluate surface morphology, and X-ray diffraction(XRD) was used to analyze phase composition and crystallinity(Xc). Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30–40 nm in diameter and a bone-like composition,which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity(Xc=41.1%) and maximum bioactivity occurred in the sample containing 10 wt% of zircon because of minimum Xcand maximum biodegradation of the coating sample.     

Facile cathodic electrosynthesis and characterization of iron oxide nano-particles

Fe2O3 nano-particles have been synthesized by simple cathodic electrodeposition from the low-temperature nitrate bath.The morphology and crystal structure of the obtained oxide powder were analyzed by means of scanning and transmission microscopy(SEM and TEM),X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.Thermal behavior and phase transformation during the heat treatment of as-deposited sample were investigated by differential scanning calorimetry(DSC) and thermogramimetric analysis(TGA).The results showed that the deposited Fe2O3 was composed of the nanoparticles with grain size of approximately 10-60 nm.A serious problem during cathodic electrodeposition of iron oxide was splashing of deposit into electrolyte due to its low adhesion.This problem was tackled by reducing the bath temperature and dielectric constant of solvent.     

Design and Manufacture of a Wax Injection Tool for Investment Casting Using Rapid Tooling

A rapid wax injection tool of a gearbox shift fork was designed, simulated, and manufactured using rapid prototyping and rapid tooling technology to save time and cost of producing wax models used for the investment casting process. CAE simulation softwares, in particular, MoldFlow, are used to get wax injection moulding parameters such as filling parameters, temperature profiles, freeze time, speed, and pressure. The results of this research were compared with conventional wax model production methods. The criteria of such comparison were based upon parameters such as time, cost, and other related characteristics, which resulted in saving of 50% in time and 60% in cost. In this research, design, assembly, and wax injection operation of the wax tool took 10 days. Considering the fact that wax melting temperature is as low as 70℃ and injection pressure of 0.5 MPa, the tool suffers no damage due to the thermal and pressure stresses, leading to the mass production of wax models.     

A heteromeric Texas coral snake toxin targets acid-sensing ion channels to produce pain

Natural products that elicit discomfort or pain represent invaluable tools for probing molecular mechanisms underlying pain sensation. Plant-derived irritants have predominated in this regard, but animal venoms have also evolved to avert predators by targeting neurons and receptors whose activation produces noxious sensations. As such, venoms provide a rich and varied source of small molecule and protein pharmacophores that can be exploited to characterize and manipulate key components of the pain-signalling pathway. With this in mind, here we perform an unbiased in vitro screen to identify snake venoms capable of activating somatosensory neurons. Venom from the Texas coral snake (Micrurus tener tener), whose bite produces intense and unremitting pain, excites a large cohort of sensory neurons. The purified active species (MitTx) consists of a heteromeric complex between Kunitz- and phospholipase-A2-like proteins that together function as a potent, persistent and selective agonist for acid-sensing ion channels (ASICs), showing equal or greater efficacy compared with acidic pH. MitTx is highly selective for the ASIC1 subtype at neutral pH; under more acidic conditions (pH < 6.5), MitTx massively potentiates (>100-fold) proton-evoked activation of ASIC2a channels. These observations raise the possibility that ASIC channels function as coincidence detectors for extracellular protons and other, as yet unidentified, endogenous factors. Purified MitTx elicits robust pain-related behaviour in mice by activation of ASIC1 channels on capsaicin-sensitive nerve fibres. These findings reveal a mechanism whereby snake venoms produce pain, and highlight an unexpected contribution of ASIC1 channels to nociception.     

Theory of Knowledge in System Dynamics Models

Having entered into the problem structuring methods, system dynamics (SD) is an approach, among systems’ methodologies, which claims to recognize the main structures of socio-economic behaviors. However, the concern for building or discovering strong philosophical underpinnings of SD, undoubtedly playing an important role in the modeling process, is a long-standing issue, in a way that there is a considerable debate about the assumptions or the philosophical foundations of it. In this paper, with a new perspective, we have explored theory of knowledge in SD models and found strange similarities between classic epistemological concepts such as justification and truth, and the mechanism of obtaining knowledge in SD models. In this regard, we have discussed related theories of epistemology and based on this analysis, have suggested some implications for moderating common problems in the modeling process of SD. Furthermore, this research could be considered a reword of system dynamics modeling principles in terms of theory of knowledge.     

Preparation,characterization, and antibacterial activity of γ-irradiated silver nanoparticles in aqueous gelatin

Colloidal silver nanoparticles (Ag-NPs) were obtained through γ-irradiation of aqueous solutions containing AgNO₃ and gelatin as a silver source and stabilizer, respectively. The absorbed dose of γ-irradiation influences the particle diameter of the Ag-NPs, as evidenced from surface plasmon resonance (SPR) and transmission electron microscopy (TEM) images. When the γ-irradiation dose was increased (from 2 to 50 kGy), the mean particle size was decreased continuously as a result of γ-induced Ag-NPs fragmentation. The antibacterial properties of the Ag-NPs were tested against Methicillinresistant Staphylococcus aureus (MRSA) (Gram-positive) and Pseudomonas aeruginosa (P.a) (Gram-negative) bacteria. This approach reveals that the γ-irradiation-mediated method is a promising simple route for synthesizing highly stable Ag-NPs in aqueous solutions with good antibacterial properties for different applications.