Design,Synthesis, and Self-Assembly Studies of a Suite of Monodisperse,Facially Amphiphilic,Protein–Dendron Conjugates

The custom design of protein–dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein–dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1–G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein–dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein–dendron bioconjugates.     

利用精密仪表放大器实现负压电流检测

监测正电源的电流时，通常使用高边检流放大器。然而，对于ISDN、电信电源，通常需要一个工作在负电源的检流放大器。本文介绍了一种采用MAX4460单电源仪表放大器设计负压检流放大器的方法。     

A novel microfluidic switch for pH control using Chitosan based hydrogels

We report a novel pH-sensitive hydrogel based micro-valve for metered flow that has applications in a laboratory made “Intelligent valving system”. The hydrogel solution was prepared through Chitosan and poly vinyl alcohol in acetic acid and crystallized using gluteraldehyde as the crosslinking agent in the form of thin wafers and it was found to be very sensitive to pH changes. The pore structure of hydrogel was investigated through Field Emission Scanning Electron Microscopy and thin wafers of the gel were physically placed inside PDMS microchannels. Flow metering in these channels was observed by controlled expansion of the hydrogel plug till complete valving was realized. This valving device was further precisely characterized with micro Particle Image Velocimetry using a solution containing fluorescent polymeric micro beads. The principle advantage of this hydrogel device is the smaller range of pH (varying between pH 3 and 7) over which the valving response is observed.     

Targeting and design of energy allocation networks with carbon capture and storage

The mathematical formulation for targeting during energy allocation with carbon capture and storage (CCS) is formally developed. For operating-cost optimization with zero excess, it is shown that CCS sources may be regarded as resources with their cost taken as the increment over the non-CCS option. CCS sources along with clean-carbon resources may then be targeted by profile matching with the limiting composite to establish optimal primary cases. The limiting composite curve is itself sacrosanct and obtained by a single computation of the composite table algorithm (CTA) including only non-CCS sources. Carbon emission networks (CENs) are designed by the nearest neighbors algorithm (NNA). A cost criterion is established to determine cost-factor ranges for optimality of the primary cases, and results validated by solving linear programming (LP) and mixed integer linear programming (MILP) formulations. The methodology essentially comprises four distinct stages – targeting, network design, cost analysis, and optimization – with the first two stages not requiring any cost data.     

Direct optical-structure correlation in atomically thin dichalcogenides and heterostructures

Atomically thin transition metal dichalcogenides (TMDs) have distinct opto-electronic properties including enhanced luminescence and high on-off current ratios, which can be further modulated by making more complex TMD heterostructures. However, resolution limits of conventional optical methods do not allow for direct nanoscale optical-structural correlation measurements in these materials, particularly of buried interfaces in TMD heterostructures. Here we use, for the first time, electron beam induced cathodoluminescence in a scanning transmission electron microscope (CL-STEM) to measure optical properties of monolayer TMDs (WS₂, MoS₂ and WSSe alloy) encapsulated between layers of hBN. We observe dark areas resulting from localized (~ 100 nm) imperfect interfaces and monolayer folding, which shows that the intimate contact between layers in this application-relevant heterostructure is required for proper inter layer coupling. We also realize a suitable imaging method that minimizes electron-beam induced changes and provides measurement of intrinsic properties. To overcome the limitation of small electron interaction volume in TMD monolayer (and hence low photon yield), we find that encapsulation of TMD monolayers with hBN and subsequent annealing is important. CL-STEM offers to be a powerful method to directly measure structure-optical correspondence in lateral or vertical heterostructures and alloys.

     

An investigation of sound absorption coefficient on sisal fiber poly lactic acid bio‐composites

In this research, the mechanical, acoustical, thermal, morphological, and infrared spectral properties of untreated, heat and alkaline‐treated sisal fiber‐reinforced poly‐lactic‐acid bio‐composites were analyzed. The bio‐composite samples were fabricated using a hot press molding machine. The properties mentioned above were evaluated and compared with heat‐treated and alkaline‐treated sisal fibers. Composites with heat‐treated sisal fibers were found to exhibit the best mechanical properties. Thermo‐gravimetric analysis (TGA) was conducted to study the thermal degradation of the bio‐composite samples. It was discovered that the PLA‐sisal composites with optimal heat‐treated at 160°C and alkaline‐treated fibers possess good thermal stability as compared with untreated fiber. The results indicated that the composites prepared with 30wt % of sisal had the highest sound absorption as compared with other composites. Evidence of the successful reaction of sodium hydroxide and heat treatment of the sisal fibers was provided by the infrared spectrum and implied by decreased bands at certain wavenumbers. Observations based on scanning electron microscopy of the fracture surface of the composites showed the effect of alkaline and heat treatment on the fiber surface and improved fiber‐matrix adhesion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42470.     

Investigation on electrostatic assist and gravure process parameters on solid mottle reduction for shrink films

Gravure is a high throughput printing process, normally associated with speed, quality, and long print runs. It is widely used for printing on shrink films and other substrates. The shrink films, in particular, polyvinyl chloride (PVC) and glycol-modified polyethylene terephthalate (PET-G), are two dominant substrates widely consumed and printed by gravure process. The PVC and PET-G offer different properties which greatly influence the printability. The surface energy of the substrate determines the adhesion and wettability of ink, while electrical properties such as surface and volume resistivity impact electrostatic assist (ESA) performance. The introduction of ESA in gravure further improved the print quality by eliminating dot skips with reduced impression pressure. However, print defects such as print mottle is inevitable. Print mottle occurs due to a discrepancy between substrate, ink, and process parameters which degrade the print quality. These complexities need to be addressed to deliver higher productivity with less print waste. Therefore, the study investigates the effect of process parameters, i.e., substrate type, line screen, air gap (distance between charge bar and impression roller), viscosity, voltage, and speed, and aims to quantify their effect numerically on defect minimization. The Design of Experiments (DOE) was generated for the above-mentioned parameters and analyzed to extract the best combination of process parameters. The optimized setting showed a reduction in solid mottle by 54% and 57% for PET-G and PVC, respectively.     

Experimental investigation on effects of dielectric mediums in near-dry electric discharge machining

Journal of Mechanical Science and Technology - A dielectric fluid plays a significant role on the machining efficiency of Electric discharge machining (EDM). Two phase (liquid-air) dielectric...     

Solar/visible light photocatalytic dye degradation using BaTi1−xFexO3 ceramics

BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were prepared via a solid-state reaction route. The presence of iron (Fe) in barium titanate (BaTiO₃) eventually decreased the energy bandgap; thus, its utilization for water cleaning application through photocatalysis process was explored (using methylene blue [MB] dye as an indicative pollutant in water). Characterization of the synthesized powder was performed through scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The bandgap of the synthesized powder was calculated as 3.2, 2.12, and 1.67 eV for BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), respectively. BaTi_0.8Fe_0.2O₃ powder showed excellent results, and ∼71% of the MB dye (∼5 mg/L concentrated) was degraded using the photocatalysis process under visible light. To check the potentiality of BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), the photocatalysis process was carried out by changing the concentration of MB dye (2.5–10 mg/L with a step of 2.5 mg/L) and the amount of BaTi_0.8Fe_0.2O₃ powder (0.05–0.2 g with a step of 0.05 g) for ∼5-mg/L concentrated MB dye. The treated water was further used as a growth parameter and phytotoxicity analysis through germination index on the wheat seeds. Lastly, the BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were explored for water cleaning applications under real-time solar irradiation.