Electrochemical detection of ascorbic acid (vitamin C) using a glassy carbon electrode

A method for the detection of ascorbic acid (AA) was developed using square wave anodic stripping voltammetric (SWASV) analysis with a glassy carbon electrode (GCE). The results indicated a sensitive oxidation peak current of AA on the GCE. A linear curve was obtained within a concentration range of 1-130.0 microg/L with a preconcentration time of 270 s. The relative standard deviation of 30.0 microg/L observed was 0.1016% (n = 12) under optimum conditions. The low detection limit (S/N) was pegged at 0.30 microg/L. Results showed that the method developed can be used to assay biological and pharmaceutical samples, and food samples, as well as other materials requiring AA analyses.     

On-Line Construction of Two-Dimensional Suffix Trees in O(n<Superscript>2</Superscript> log n) Time

The two-dimensional suffix tree of an n × n square matrix A is a compacted trie that represents all square submatrices of A[11]. For the off-line case, i.e., A is given in advance to the algorithm, it is known how to build it in optimal time, for any type of alphabet size [11],[18]. Motivated by applications in Image Compression[22[, Giancarlo and Guaiana [14] considered the on-line version of the two-dimensional suffix tree and presented an O(n² log² n)-time algorithm, which we refer to as GG. That algorithm is a nontrivial generalization of Ukkonen's on-line algorithm for standard suffix trees [23]. The main contribution in this paper is an O(log n) factor improvement in the time complexity of the GG algorithm, making it optimal for unbounded alphabets [9]. Moreover, the ideas presented here also lead to a major simplification of the GG algorithm. Technically, we are able to preserve most of the structure of the original GG algorithm, by reducing a computational bottleneck to a primitive operation, i.e., comparison of Lcharacters, which is here implemented in constant time rather than O(log n) time as in GG. However, preserving that structure comes at a price. Indeed, in order to make everything work, we need a careful reorganization of another fundamental algorithm: Weiner's algorithm for the construction of standard suffix trees [24]. Specifically, here we provide a version of that algorithm which takes linear time and works on-line and concurrently over a set of strings.     

Electroactive Shape Memory Effect of Polyurethane Composites Filled with Carbon Nanotubes and Conducting Polymer

We report the electroactive shape memory composites obtained by shape memory polyurethane block copolymer (PU) and multi-walled carbon nanotubes (MWNTs), and polypyrrole (PPy). An addition of combined MWNTs and PPy contributed to an enhancement in conductivity of PU-MWNTs composites. PU containing 2.5% MWNTs showed better mechanical and thermal properties than other composites, but conductivity was not sufficient for showing the shape memory effect by applying electrical voltages. However, when the composite was lightly coated by PPy (2.5%), its conductivity was the highest than other composites. Such the conductivity of this composite was enough to show electroactive shape recovery by heating above transition temperature of 40-48°C due to melting of polycaprolactone soft segment domain. The good shape recovery of 90-96% could be obtained in the shape recovery test when an electric field of 25 V was applied.     

Shifting the MIMO Paradigm

Multi-user MIMO (MU-MIMO) networks reveal the unique opportunities arising from a joint optimization of antenna combining techniques with resource allocation protocols. Furthermore, it brings robustness with respect to multipath richness, allowing for compact antenna spacing at the BS and, crucially, yielding the diversity and multiplexing gains without the need for multiple antenna user terminals. To realize these gains, however, the BS should be informed with the user's channel coefficients, which may limit practical application to TDD or low-mobility settings. To circumvent this problem and reduce feedback load, combining MU-MIMO with opportunistic scheduling seems a promising direction. The success for this type of scheduler is strongly traffic and QoS-dependent, however.     

Video Service Delivery Over a Repeater-Based Optical Access Network

A low-cost and bandwidth-efficient scheme for delivering video services to customers over a long reach, large split repeater-based optical access network is proposed and experimentally demonstrated. Video channels that are on radio-frequency subcarriers are electrically combined with regenerated downstream data at the repeater and delivered to the customers on a single wavelength channel. Experimental results show that error-free transmission can be obtained for all channels with adequate power budget to support a split ratio more than 64.     

Effects of introducing silica particles on the rheological properties and crystallization behavior of poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET)/silica composites were prepared by melt compounding, and their rheological properties and isothermal crystallization were discussed. Introduction of silica particles (0.5–2 wt.%) increased the storage modulus (G′) and decreased loss tangent (tanδ). However, the effect of the particles on rheological properties became negligible at a high frequency more than ca. 70 rad/s. In the Cole–Cole plot, the PET/silica composites showed little deviation from the master curve regardless of the presence of silica particles. The particles increased the relaxation time of PET at particularly low frequency. The isothermal crystallization kinetics of PET/silica was examined using a differential scanning calorimeter (DSC). The half-time of crystallization was decreased with increasing the silica content. The incorporation of silica particles decreased the equilibrium melting temperature by ca. 5.5 °C. In addition, the composites exhibited higher average value of Avrami exponent (2.7–2.9) in comparison with that of pure PET (2.2).     

Solid-state spun fibers and yarns from 1-mm long carbon nanotube forests synthesized by water-assisted chemical vapor deposition

We report continuous carbon nanotube (CNT) fibers and yarns dry-drawn directly from water-assisted chemical vapor deposition (CVD) grown forests with about 1-mm height. As-drawn CNT fibers exist as aerogel and can be transformed into more compact fibers through twisting or densification with a volatile organic liquid. CNT fibers are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman microscopy, and wide-angle X-ray diffraction. Mechanical properties and electrical conductivity of the post-treated CNT fibers are investigated. The resulting fibers show the work of rupture of 30 J/g and DC electrical conductivity of 5.0 × 10⁴ S/m.     

Deoxycholate‐Based Glycosides (DCGs) for Membrane Protein Stabilisation

Detergents are an absolute requirement for studying the structure of membrane proteins. However, many conventional detergents fail to stabilise denaturation‐sensitive membrane proteins, such as eukaryotic proteins and membrane protein complexes. New amphipathic agents with enhanced efficacy in stabilising membrane proteins will be helpful in overcoming the barriers to studying membrane protein structures. We have prepared a number of deoxycholate‐based amphiphiles with carbohydrate head groups, designated deoxycholate‐based glycosides (DCGs). These DCGs are the hydrophilic variants of previously reported deoxycholate‐based N‐oxides (DCAOs). Membrane proteins in these agents, particularly the branched diglucoside‐bearing amphiphiles DCG‐1 and DCG‐2, displayed favourable behaviour compared to previously reported parent compounds (DCAOs) and conventional detergents (LDAO and DDM). Given their excellent properties, these agents should have significant potential for membrane protein studies.     

Enhanced efficiency of white polymer light-emitting diodes with inorganic nanodots

Enhanced efficiency of white polymer light-emitting diodes (PLEDs) was observed by incorporating polysilicic acid (PSA) nanodots into the hole-injection layer (HIL). The PLEDs employed three different phosphorescent dyes in a single emissive layer with a host polymer of poly(vinylcarbazole) (PVK). The optimal composition of the phosphorescent dyes has been found to accomplish the white emission. By incorporating 1.5 wt% of PSA nanodots into the HIL, the maximum efficiency has been found to increase about 65%, from 13.7 cd/A to 22.9 cd/A. This remarkable improvement in efficiency may be attributed to the introduction of the PSA nanodots, which leads to the better carrier balance in the PLEDs.