Immobilization of silver nanoparticles on silica microspheres

The silver nanoparticles (Ag NPs) have been immobilized onto silica microspheres through the adsorption and subsequent reduction of Ag⁺ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared through sol–gel processing; their surfaces were then functionalized using 3-mercaptopropyltrimethoxysilane (MPTMS). The major aims of this study were to immobilize differently sized Ag particles onto the silica microspheres and to understand the mechanism of formation of the Ag nano-coatings through the self-assembly/adsorption behavior of Ag NPs/Ag⁺ ions on the silica spheres. The obtained Ag NP/silica microsphere conglomerates were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). Their electromagnetic wave shielding effectiveness were also tested and studied. The average particle size of the obtained Ag NPs on the silica microsphere was found that could be controllable (from 2.9 to 51.5 nm) by adjusting the ratio of MPTMS/TEOS and the amount of AgNO₃.     

Tens of GHz Tantalum pentoxide‐based micro‐ring all‐optical modulator for Si photonics

A tantalum pentoxide‐based (Ta₂O₅‐based) micro‐ring all‐optical modulator was fabricated. The refractive index inside the micro‐ring cavity was modified using the Kerr effect by injecting a pumped pulse. The transmittance of the ring resonator was controlled to achieve all‐optical modulation at the wavelength of the injected probe. When 12 GHz pulses with a peak power of 1.2 W were coupled in the ring cavity, the transmission spectrum of the Ta₂O₅ resonator was red‐shifted by 0.04 nm because of the Kerr effect. The relationship between the modulation depth and gap of the Ta₂O₅ directional coupler is discussed. An optimized gap of 1100 nm was obtained, and a maximum buildup factor of 11.7 with 84% modulation depth was achieved. The nonlinear refractive index of Ta₂O₅ at 1.55 μm was estimated as 3.4 × 10^?14 cm²/W based on the Kerr effect, which is almost an order of magnitude higher than that of Si₃N₄. All results indicate that Ta₂O₅ has potential for use in nonlinear waveguide applications with modulation speeds as high as tens of GHz.

     

Characterization of long-term dose stability of N-isopropylacrylamide polymer gel dosimetry

In this study, the detailed characteristics, including spatial uniformity, dose distributions, inter-batch variability, reproducibility, and long-term temporal stability, of N-isopropylacrylamide (NIPAM) polymer gel dosimeter were investigated. A commercial 10x fast optical computed tomography scanner (OCTOPUS^TM-10×, MGS Research, Inc., Madison, CT, USA) was used to measure NIPAM polymer gel dosimeter. A cylindrical NIPAM gel phantom that measured 10 cm × 10 cm was irradiated via a single-field treatment plan with a field size of 4 cm × 4 cm. The maximum standard deviation of spatial uniformity for NIPAM gel was less than 0.29 %. The average standard deviation among the three batches of gel dosimeters was less than 1 %. The gamma pass rate could reach as high as 96.76 % when a 3 % dose difference and a 3 mm dose-to-agreement criteria were used. The long-term measurement of irradiated NIPAM gel dosimeter indicated that the dose maps attained a gradually stable value 15 h post-irradiation and remained stable until 72 h post-irradiation. The gamma pass rate could achieve a maximum value between 24 and 72 h post-irradiation. The edge enhancement effect that occurred around the irradiated region was observed 72 h post-irradiation. Thus, the results from this study suggest that NIPAM gel dosimeter should be measured approximately 24 h post-irradiation to reduce the occurrence of the edge enhancement effect.     

Families of intersecting finite vector spaces

The following theorem is proved. It is a generalization of the problem for finite vector spaces analogous to a theorem of Kleitman for finite sets.Let V be an n-dimensional vector space over a finite field F of q elements. Suppose we have two collections, one consisting of k- and the other of m-dimensional subspaces of V with the property that the intersection of each member of one with each member of the other has dimension no less than r.Then if n ? k + m + 2 or n ? k + m + 1 and q ? 3, there are either no more than $\text{[}\text{n?r}\text{k?r}\text{]}{}_{\mathrm{q}}$ members in the first family or fewer than $\text{[}\text{n?r}\text{m?r}\text{]}{}_{\mathrm{q}}$ members in the second.The method used leads to a similar result for sets, provided that n ? r + (r + 1)(k ? r)(m ? r + 1) with k ? m.     

On multidimensional discrete-time Beverton–Holt competition models

Following Ackleh et al. (2005), we study the multidimensional discrete-time competitive Beverton–Holt equations with equal interspecific competition coefficients. It is shown that competitive exclusion occurs if only one species has the largest carrying capacity. Otherwise, all the species with the largest carrying capacity coexist. In the former case, the system is globally asymptotically stable. In the latter case, the system has a linear stable manifold.     

Development and Optimization of Djulis Sourdough Bread Fermented by Lactic Acid Bacteria for Antioxidant Capacity

This study developed a nutritionally valuable product with bioactive activity that improves the quality of bread. Djulis (Chenopodium formosanum), a native plant of Taiwan, was fermented using 23 different lactic acid bacteria strains. Lactobacillus casei BCRC10697 was identified as the ideal strain for fermentation, as it lowered the pH value of samples to 4.6 and demonstrated proteolysis ability 1.88 times higher than controls after 24 h of fermentation. Response surface methodology was adopted to optimize the djulis fermentation conditions for trolox equivalent antioxidant capacity (TEAC). The optimal conditions were a temperature of 33.5 °C, fructose content of 7.7%, and dough yield of 332.8, which yielded a TEAC at 6.82 mmol/kg. A 63% increase in TEAC and 20% increase in DPPH were observed when compared with unfermented djulis. Subsequently, the fermented djulis was used in different proportions as a substitute for wheat flour to make bread. The total phenolic and flavonoid compounds were 4.23 mg GAE/g and 3.46 mg QE/g, marking respective increases of 18% and 40% when the djulis was added. Texture analysis revealed that adding djulis increased the hardness and chewiness of sourdough breads. It also extended their shelf life by approximately 2 days. Thus, adding djulis to sourdough can enhance the functionality of breads and may provide a potential basis for developing djulis-based functional food.     

New benzoyl glucosides and cytotoxic pterosin sesquiterpenes from Pteris ensiformis Burm

Three new compounds: 2R,3R-pterosin L 3-O-beta-D-glucopyranoside (1), beta-D-xylopyranosyl(1-->2)-7-O-benzoyl-beta-D-glucopyranoside (2) and 4-O-benzoyl-beta-D-xylo-pyranosyl(1-->2)-7-O-benzoyl-beta-D-glucopyranoside (3), together with nine known compounds, were isolated from the ethyl acetate extract of Pteris ensiformis. 5-[2-Hydroxyethylidene]-2(5H)-furanone (4), which had been synthesized, was isolated from natural sources for the first time. The structures of all isolated compounds were determined on the basis of mass and spectroscopic evidence. Compound 1 and pterosin B (5) show cytotoxicity against HL 60 cells (human leukemia) with the IC(50) values of 3.7 and 8.7 microg/mL, respectively.     

Sample stacking for the analysis of penicillins by microemulsion electrokinetic chromatography

In this study, on-line sample concentration methods, which coupled field-amplified sample injection and sweeping technology with MEEKC, were used to detect and analyze eight common penicillin antibiotics (nafcillin, dicloxacillin, ampicillin, oxacillin, penicillin V, cloxacillin, penicillin G, and amoxicillin). During the optimization of field-amplified sample injection-sweeping MEEKC, the composition of sample matrix and the length of acidic plug were found to be the predominant influences for penicillin stacking. Both zwitterionic ampicillin and amoxicillin could only be stacked through cation-selective-exhaustive-injection sweeping, whereas the other six penicillin compounds were found to be concentrated by anion-selective-exhaustive-injection sweeping. Hence, in order to simultaneously concentrate the eight penicillins in a single-run sweeping step, a combination of successive anion- and cation-selective injections was used. When compared with previous CE-UV methods, the proposed on-line concentration MEEKC method provided better detection sensitivity and faster separation for these penicillins either in single ion-selective injection or in successive anion-/cation-selective injection where the LODs were in the range of 0.2-2.8 microg/L and 0.5-5.8 microg/L, respectively.     

Thermal analysis on phase behavior of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) interacting with aliphatic polyesters

Abstract  

Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LM_w-PLLA) or high-molecular-weight PLLA (HM_w-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH₂/CO) ratio in main chains. The blends of LM_w-PLLA/PEA and LM_w-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LM_w-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LM_w-PLLA/PTA and LM_w-PLLA/PEA blends, HM_w-PLLA with polyesters are mostly immiscible; and HM_w-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LM_w-PLLA/PEA and LM_w-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LM_w-PLLA and PTA or PEA.     

A photoactive isoprenoid diphosphate analogue containing a stable phosphonate linkage: synthesis and biochemical studies with prenyltransferases

A number of biochemical processes rely on isoprenoids, including the post-translational modification of signaling proteins and the biosynthesis of a wide array of compounds. Photoactivatable analogues have been developed to study isoprenoid utilizing enzymes such as the isoprenoid synthases and prenyltransferases. While these initial analogues proved to be excellent structural analogues with good cross-linking capability, they lack the stability needed when the goals include isolation of cross-linked species, tryptic digestion, and subsequent peptide sequencing. Here, the synthesis of a benzophenone-based farnesyl diphosphate analogue containing a stable phosphonophosphate group is described. Inhibition kinetics, photolabeling experiments, as well as X-ray crystallographic analysis with a protein prenyltransferase are described, verifying this compound as a good isoprenoid mimetic. In addition, the utility of this new analogue was explored by using it to photoaffinity label crude protein extracts obtained from Hevea brasiliensis latex. Those experiments suggest that a small protein, rubber elongation factor, interacts directly with farnesyl diphosphate during rubber biosynthesis. These results indicate that this benzophenone-based isoprenoid analogue will be useful for identifying enzymes that utilize farnesyl diphosphate as a substrate.