White-light fluorescent nanoparticles from self-assembly of rhodamine B-anchored amphiphilic poly(poly(ethylene glycol)methacrylate)-b-poly(glycidyl methacrylate) block copolymer

Rhodamine B (RhB)-anchored amphiphilic poly(poly(ethylene glycol)methacrylate)-b-poly(glycidyl methacrylate) block copolymer (PPEGMA-b-PGMA/RhB) has been prepared by a sequential atom transfer radical polymerization and post-functionalization of RhB. The chemical structure of PPEGMA-b-PGMA/RhB is characterized with gel-permeation chromatography, Fourier-transform infrared spectroscopy, and ¹H nuclear magnetic resonance spectroscopy. PPEGMA-b-PGMA/RhB has shown self-assembly behaviors in tetrahydrofuran and aqueous solutions. The RhB aggregation induced with the inter-molecular interaction of RhB results in the various core–shell structures of the assembled nanoparticles. The photoluminescent properties of the PPEGMA-b-PGMA/RhB nanoparticles are structure-dependent and exhibit yellow-light, blue-light, and white-light emissions. The fluorescent organic nanoparticles of PPEGMA-b-PGMA/RhB in aqueous solution show low cytotoxicity and have been used as a bio-dye for cell labelling. Internalization of PPEGMA-b-PGMA/RhB nanoparticles into HELA cells to exhibit fluorescent images has been demonstrated.     

Simultaneous purification and site-specific modification of pyrroline-carboxy-lysine proteins

Sticky residue: Pyrroline-carboxy-lysine (Pcl) can be readily incorporated into proteins expressed in E. coli and mammalian cells by using the pyrrolysyl tRNA/tRNA synthetase pair. Pcl can be used as a single amino acid purification tag and can be site-specifically modified with functional probes during the elution process.     

The Analysis of Photocuring Behavior of Polyester Acrylate by Means of Differential Photo Calorimeter (DPC) and Rigid-Body Pendulum Rheometer (RPT)

This study aims to understand the different photocuring behaviors of acrylated polyester by adding different photoinitiators and monomers. Differential photo calorimeter (DPC) is used to understand the exothermal effects during photocuring. The self-catalyst model of dynamic analysis software was then used to obtain the relationships between reaction speed, reaction extent, and rate of reaction. In addition, this study also tried to understand the formation of photocuring resin from the rigid-body pendulum rheometer (RPT) experiment. The results showed that the extent of reaction, conversion rate and speed varies directly with the concentration of the photoinitiator and monomer. The reaction level of propoxylated pentaerithritol triacrylate was higher than propoxylated neopentyl-glycol diacrylate. Moreover, the method using RPT shows better view of the molecule reaction status inside the photopolymer.     

Supercritical carbon dioxide extraction of triglycerides from Jatropha curcas L. seeds

This study examines the effects of pressure, temperature and solvent to solid ratio (SSR) on extraction efficiency of triglycerides from powdered Jatropha seeds by using supercritical carbon dioxide extraction. Supercritical extractions were designed for pressures ranging from 250 to 350 bar, temperatures ranging from 313 to 333 K and SSR values ranging from 65:1 to 125:1. All values were selected using response surface methodology in order to determine their effects on the concentration of triglycerides from the extracted oil. Using 3750 g of carbon dioxide over 5 h, a supercritical carbon dioxide extraction (at 350 bar, 333 K and an SSR value of 125:1) yielded 43.51% oil. The concentration and extraction efficiency (i.e. recovery) of triglycerides in the extract reached 657.1 mg/g and 97.62%, respectively. Changes in pressure presented more effective in increasing the recovery of triglycerides, but both temperature and the SSR value are important in obtaining high concentration of triglycerides from the Jatropha seeds that are useful for biodiesel materials.     

Filling mechanism in microvia metallization by copper electroplating

This work explores the mechanism of microvia filling by copper electroplating using a printed circuit board (PCB) with a specific pattern design. The microvias employed in this work had no sidewall copper layer. The outer and inner copper layers of these microvias that had no sidewall copper layer were together connected to the cathode during electroplating in order to clarify the mechanism of bottom-up filling. A plating formula that was composed of CuSO₄, H₂SO₄, polyethylene glycol (PEG), bis(3-sulfopropyl) disulfide (SPS), Cl⁻ and Janus Green B (JGB) was employed as a model formula for studying the filling mechanism. The results showed that bottom-up filling stemmed from two crucial factors. One was the sidewall growth of the microvia, increasing the surface coverage of an accelerator; the other was the convection-dependent adsorption (CDA) of additives, leading to different copper deposition rates on the outer and inner copper layers. When a leveler was present in the plating solution, CDA behavior dominated the filling mechanism, regardless of whether a sidewall copper layer was present. On the other hand, the mechanism of coverage accumulation of the accelerator was dominant only when the microvia possessed a sidewall copper layer and no leveler was present in the plating solution.     

Melting temperature depression for low ether content polyether-polyester block copolymers with amide linkages

Melting behavior of a series of polyether-polyester block copolymers with low ether contents was studied. Significant melting-reorganization-remelting was suggested by means of differential scanning calorimetry. The equilibrium melting temperature of the copolymers was obtained by using the Hoffman-Weeks extrapolation. It has been found that the use of the on-set melting temperature for the Hoffman-Weeks plots is less reliable than the use of the corrected peak melting temperature. Copolymerization of polyetheramides with polyesters leads to a significant melting temperature suppression for the polyester crystal. We hypothesize that the locations of the junction points between blocks can be treated as chain ends for the crystallizable polyester blocks: the polyether-polyesters grow to form extended chain-like crystals with lamellar thickness limited by the polyester block length. For comparison, the nonlinear Hoffman-Weeks treatment, recently proposed by Marand, has also been applied to examine the behavior of melting temperature depression. Although the T _m ^o obtained from nonlinear extrapolation is much higher than the T _m ^o obtained from the Hoffman-Weeks extrapolation, similar trend regarding the composition dependence of T _m ^o have been found.     

Experimental investigations on liquid flow and heat transfer in rectangular microchannel with longitudinal vortex generators

The behaviors of improved Heat transfer and the associated higher pressure drop for liquid flow in rectangular micochannels with longitudinal vortex generators (LVGs) were determined experimentally for the Reynolds numbers of 170–1200 with hydraulic diameter of 187.5 μm and aspect ratio of 0.067 for LVGs with different number of pairs and angles of attack. It was found that the range of critical Reynolds numbers (600–730) were at a much smaller value by adding LVGs than the one without (Re ～ 2300); heat transfer performance was improved (9–21% higher for those with laminar flow and 39–90% for those with turbulent flow), while encountering larger pressure drop (34–83% for laminar flow and 61–169% for turbulent flow). Empirical correlations for these two parameters were then obtained by curve-fittings for a variety of rectangular microchannels under study.     

Experimental investigation of heat-transfer characteristics of aluminum-foam heat sinks

The demand of high speed and miniaturization of electronic components results in increased power dissipation requirement for thermal management. In this work, the effects of porosity (ε), pore density (PPI) and air velocity on the heat-transfer characteristics of aluminum-foam heat sinks are investigated experimentally. The phenomenon of non-local thermal equilibrium (NLTE) is also observed and reported. Results show that the Nu increases as the pore density increases, due to the fact that aluminum foam with a larger pore density has a larger heat-transfer area. The Nusselt number also increases with the increase of porosity due to the same reason. It is noted that temperatures of the solid and gas phases of the aluminum foam decrease as Reynolds number increases, caused by the increased convective heat-transfer rate at higher Reynolds number. The deduced temperature difference between the solid and gas phases clearly indicates the existence of non-local thermal equilibrium condition within the aluminum-foam heat sink. The increase of the porosity and the pore density enhances the phenomenon of non-local thermal equilibrium. The temperature difference increases with the decrease of Reynolds number and the distance away from the heat source.     

TEMPERATURE DISTRIBUTION OF AN OPTICAL FIBER TRAVERSING THROUGH A CHEMICAL VAPOR DEPOSITION REACTOR

A fundamental understanding of how reactor parameters influence the fiber surface temperature is essential to manufacturing high-quality optical fiber coatings by chemical vapor deposition (CVD). In an attempt to understand this process better, a finite-volume model has been developed to study the gas flow and heat transfer of an optical fiber as it travels through a CVD reactor. This study showed that draw speed significantly affects fiber temperature inside the reactor, with temperature changes over 50% observed under the conditions studied. Other parameters affecting fiber temperature include fiber radius, fiber coating emissivity, and gas flow velocity at inlet. Multiple heat transfer modes contribute to these phenomena, with convection and radiation heat transfer dominating the process. The numerical model is validated against analytical cases.