Effects of crystallinity and molecular weight on crack behavior in crystalline poly(L‐lactic acid)

The crack behavior and spherulitic morphology in melt‐crystallized poly(L ‐lactic acid) (PLLA) were found to be molecular weight (MW) and crystallinity dependent, along with other key factors. With increasing MW in PLLA, the size of spherulites, band spacing of ring‐banded spherulites, and degree of crystallinity decreased, whereas cracks were increasingly less likely to occur. Multiple types of cracks, that is, circumferential and/or radial cracks, were massively present in low‐MW PLLA (PLLA‐11k), which had a high crystallinity. Upon cooling, in PLLA‐11k at most crystallization temperatures (T_c's), cracks formed, and the crack patterns were dependent on the lamellar morphology within the spherulites. Hexagonal, rather than circular, cracks occurred spontaneously during the cooling process of PLLA of a medium‐MW grade (PLLA‐120k) in PLLA film samples crystallized only at high T_c (135–138°C) and cooled to ambient temperature. However, no cracks of any types at all were present in PLLA films of high enough MWs (PLLA‐152k and PLLA‐258k) upon either slow air cooling or quench cooling when the samples were dipped into liquid nitrogen. Apparently, cooling‐induced contraction differences in different directions were invalid or not sufficient to address the complex cracking behavior in PLLA. In addition, for PLLA‐11k with a substantially high crystallinity, cracks were so prone to occur that even cover constraint imposed another factor in determining the crack and ring‐band patterns. More plausible mechanisms and correlations between the cracks, MW, crystallinity, spherulite size, and spherulite lamellar patterns of PLLA were analyzed in detail and proposed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Distributed Resource Allocation for Femtocell Networks: Regret Learning with Proportional Self-belief

Femtocell networks promise improvement in network quality and performance for dense wireless networks, but will suffer from inter-cell interference if resource management is not properly employed. This paper presents distributed joint resource allocation (sub-channel and power) to address co- and cross-tier interference issues in two-tier heterogeneous femtocell networks. Due to uncoordinated nature of femtocell base stations (HeNB) deployment, the interactions among self-interested HeNBs are formulated using game-theoretical tools. Then, we designed individual utility function for every HeNB in order to enforce cooperative behaviour among HeNBs as well as to avoid cross-tier interference towards macrocell user equipments within HeNB coverage. Based on the designed utility function, we propose a fully distributed adaptive learning algorithm with a proportional self-belief concept that can lead to correlated equilibrium with fast and decisive convergence. Finally, performance analysis on the proposed algorithm done in simulated environment showed positive results indicating improvements in terms of co- and cross-tier interference mitigation as compared to generic regret-based learning scheme and utility functions.     

Scleral melting 16 years after pterygium excision with topical Mitomycin C adjuvant therapy.

PURPOSE: To report a case of scleral melting noted 16 years after pterygium excision with postoperative adjuvant topical Mitomycin C (MMC). METHOD: Case report. RESULTS: A 61-year-old Malay gentleman underwent right nasal pterygium excision using bare sclera technique followed by topical MMC 0.1% for a week, 16 years ago. He was noted to have a right nasal scleral thinning with calcified plaque and granuloma. He was successfully treated conservatively without further progression of the scleral melting. CONCLUSION: Long-term complication of pterygium excision with adjuvant topical Mitomycin C may occur. The case shows that early detection and recognition of the complication can be sight saving.     

Optimal Control of Active Power of Two Micro-grids Interconnected with Two AC Tie-Lines

Active power balance and frequency control are important tasks in the daily management of a power system. With the integration of several microgrids in the modern power system, the balancing of sources of energy has become a major concern for electrical power engineers and researchers worldwide. New power systems require more flexibility in optimization and control design to ensure their ability to maintain the balance between generation and load of the system. The present paper discusses an optimal control design for minimization of the power flow in tie-lines and frequency deviations in the microgrid, which will lead to power balance between the generation and load demand of the system. The system being studied consists of two microgrids, each made up of a wind farm, conventional power system (large hydro or thermal plant), photovoltaic system, battery energy storage system and the system load. Optimal control theory is applied to control the power flow between two microgrids. The Matlab environment is used for simulations.     

Design of Wideband Rectangular-Shaped Coupler with Virtual Short Stubs for Wireless Communication Applications

This article presents the design of the sectional rectangular-shaped directional couplers with tight coupling of 3-dB over frequency of 2–6 GHz. The designed coupler consists of two substrates and one common ground plane between the substrate layers. It also formed by two conducting strips with virtual short stubs are placed to the middle section at the top and bottom layer, which coupled through three-section rectangular slots at the ground plane. The effect of these additional stubs in the design is studied and observed. The design and analysis are performed with the use of full-wave electromagnetic simulation software package, CST Microwave Studio. This designed coupler has been fabricated and its wideband performance is verified.     

3,4-Dichlorophenoxyacetate interleaved into anionic clay for controlled release formulation of a new environmentally friendly agrochemical

A new layered organic–inorganic nanohybrid material, zinc-aluminum-3,4-dicholorophenoxyacetate (N3,4-D) in which an agrochemical, 3,4-dichlorophenoxyacetic acid (3,4-D), is intercalated into zinc-aluminum-layered double hydroxide (ZAL), was synthesized by coprecipitation method. A well-ordered nanomaterial was formed with a percentage loading of 53.5% (w/w). Due to the inclusion of 3,4-D, basal spacing expanded from 8.9 Å in ZAL to 18.7 Å in N3,4-D. The Fourier transform infrared study shows that the absorption bands of the resulting nanohybrid composed of both the 3,4-D and ZAL further confirmed the intercalation episode. Thermal analysis shows that ZAL host enhances the thermal stability of 3,4-D. Controlled-release experiment shows that the release of 3,4-D in the aqueous media is in the order of phosphate > carbonate > sulfate > chloride. These studies demonstrate the successful intercalation of the 3,4-D and its controlled release property in various aqueous media.     

Extraction of β–glucan by hydrothermal liquidization of barley grain in a semi-batch reactor

Subcritical water is a natural and green way for extraction of plant biomass components. Here, subcritical water was employed as a media to extract β–glucan from barley (Hordeum vulgare L.) at 130–170°C and 10 MPa. MALDI TOF–MS revealed that main massed peaks of water soluble products were distributed at 500-2900 m/z with a peak to peak mass difference of 162 m/z, consistent with the repeating unit of β–glucan. At 170°C, all amount of water soluble β–glucan has been extracted. Next, the liquid fraction products were atomized directly to produce microsphere particles.     

Herbicide-intercalated zinc layered hydroxide nanohybrid for a dual-guest controlled release formulation

Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously.     

Neuroprotective Effects of Germinated Brown Rice against Hydrogen Peroxide Induced Cell Death in Human SH-SY5Y Cells

The neuroprotective and antioxidative effects of germinated brown rice (GBR), brown rice (BR) and commercially available γ-aminobutyric acid (GABA) against cell death induced by hydrogen peroxide (H(2)O(2)) in human neuroblastoma SH-SY5Y cells have been investigated. Results show that GBR suppressed H(2)O(2)-mediated cytotoxicity and induced G0/G1 phase cell cycle arrest in SH-SY5Y cells. Moreover, GBR reduced mitochondrial membrane potential (MMP) and prevented phosphatidylserine (PS) translocation in SH-SY5Y cells, key features of apoptosis, and subsequent cell death. GBR exhibited better neuroprotective and antioxidative activities as compared to BR and GABA. These results indicate that GBR possesses high antioxidative activities and suppressed cell death in SH-SY5Y cells by blocking the cell cycle re-entry and apoptotic mechanisms. Therefore, GBR could be developed as a value added functional food to prevent neurodegenerative diseases caused by oxidative stress and apoptosis.