Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber‐reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10–12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100–600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced post‐use shelf life as composites, with benefits while in use and at the same time post‐use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43290.     

Minimising total weighted earliness and tardiness penalties on identical parallel machines using a fast ruin-and-recreate algorithm

This paper studies the scheduling problem of minimising total weighted earliness and tardiness penalties on identical parallel machines against a restrictive common due date. This problem is NP-hard in the strong sense and arises in many just-in-time production environments. A fast ruin-and-recreate (FR&R) algorithm is proposed to obtain high-quality solutions to this complex problem. The proposed FR&R algorithm is tested on a well-known set of benchmark test problems that are taken from the literature. Computational results provide evidence of the efficiency of FR&R, which consistently outperform existing algorithms when applied to benchmark instances. This work provides a viable alternative approach for efficiently solving this practical but complex scheduling problem.     

The Performance of Small‐Pore Microporous Aluminophosphates in Low‐Temperature Solar Energy Storage: The Structure–Property Relationship

The utilization of the reversible chemical and physical sorption of water on solids provides a new thermal energy storage concept with a great potential for lossless long‐term storage. The performance of microporous aluminophosphates in heat storage applications is highlighted by a comparative thermogravimetric and calorimetric study of three known materials (SAPO‐34, AlPO₄‐18, APO‐Tric) and is correlated with their structural features. The maximum water sorption capacity is similar for all three samples and results in a stored energy density of 240 kWh m^?3 in the 40–140 °C range. The elemental composition influences the gradual (silicoaluminophosphate SAPO‐34) or sudden (aluminophosphates AlPO₄‐18, APO‐Tric) water uptake, with the latter being favourable in storage systems. The driving force for the determined sorption process is the formation of highly ordered water clusters in the pores, which is enabled by rapid and reversible changes in the Al coordination and optimal pore diameters. The ease with which changes in the Al coordination can occur in APO‐Tric is related to the use of the fluoride route in the synthesis. The understanding of these fundamental structure/sorption relationships forms an excellent basis for predicting the storage potential of numerous known or new microporous aluminophosphates and other porous materials from their crystal structures.     

Hydrogen-sensitive sensor with stabilized Pd-mixture forming sensing nanoparticles on an interlayer

Pd-based mixtures comprising silicon dioxide (SiO₂) were used as sensing materials in fabrication of GaN-based hydrogen sensors. The mixture as-deposited has a rough surface with many pores. After wet selectively etching to remove SiO₂, the mixture turns into Pd nanoparticles with a size of ∼ 30 nm on an interlayer with oxygen, as indicated by SEM, EDX, and SIMS methods. A careful study of the Pd-mixture on a metal-semiconductor-metal type of hydrogen sensor provides significant information on the roles of oxygen and the interlayer. Experimental results reveal that hydrogen atoms trapped inside the mixture as-deposited cannot contribute to changes in barrier height as an applied voltage is not large enough. Improved sensing properties such as hydrogen dissociation rate, diffusion rate, and storage capability were obtained when Pd nanoparticles were formed by selectively etching the mixture. The situation that hydrogen atoms were blocked and disturbed by oxygen will exist no more. Uniform sensing responses of higher than 10⁵ (defined as (J_H2-J_N2)/J_N2, J_H2 and J_N2 are current densities measured in H₂/N₂ and N₂ ambiences, respectively), voltage shifts of larger than 20 V were obtained at 2.13 ppm H₂/N₂. In addition, hydrogen transport through grain boundaries of Pd nanoparticles is much faster than diffusion through a Pd-mixture layer. A much shorter response time was obtained from the sensors with the Pd-mixture wet etched. Furthermore, stable and reliable sensing characteristics were also expected.     

A cross‐layer partner‐based fast handoff mechanism for IEEE 802.11 wireless networks

In wireless/mobile networks, users freely and frequently change their access points (APs) while they are communicating with other users. To support the mobility of mobile nodes (MNs), Mobile IPv6 (MIPv6) is used to inform the information of MN's home address and current care‐of‐address (CoA) to its home agent. MIPv6 suffers from a long delay latency and high packet losses (PLs) because MIPv6 does not support micromobility. A Hierarchical Mobile IPv6 (HMIPv6) is proposed which provides micromobility and macromobility to reduce handoff latency (HL) by employing a hierarchical network structure. In this paper, we propose a cross‐layer partner‐based fast handoff mechanism based on HMIPv6, called the PHMIPv6 protocol. Our PHMIPv6 protocol is a cross‐layer, layer‐2 + layer‐3, and cooperative approach. A cooperative node, called a partner node (PN), is adopted in the PHMIPv6 protocol. A new layer‐2 trigger scheme used in the PHMIPv6 protocol accurately predicts the next AP and then invites a cooperative PN in the area of the next AP. With the cooperation of the PN, the CoA can be pre‐acquired and duplicate address detection operation can be pre‐executed by the PN before the MN initializes the handoff request. The PHMIPv6 protocol significantly reduces the handoff delay time and PLs. In the mathematical analysis, we verified that our PHMIPv6 protocol offers a better HL than the MIPv6, HMIPv6, and SHMIPv6 protocols. Finally, the experimental results also illustrate that the PHMIPv6 protocol actually achieves performance improvements in the handoff delay time, PL rate, and handoff delay jitter. Copyright © 2009 John Wiley & Sons, Ltd.     

Low temperature Ni-nanocrystals-assisted hybrid polycrystalline silicon thin film transistor for non-volatile memory applications

The nickel-nanocrystals (Ni-NCs)-embedded silicon nitride acting as a trapping layer has been successfully demonstrated to manipulate the charging and discharging of electrons in a thin film transistor (TFT) for non-volatile memory (NVM) applications. Regarding device performance, with and without Ni-NCs in the stack and under a programming/erasing condition of +/−18 V for 1 s, a better threshold voltage shift of 3.2 V can be reached compared to a shift of 2.0 V for a stack without Ni-NCs. The shift is an index representing the value required to differentiate “0” or “1” states during operation. In this case, the diameter range and number density of Ni-NCs are 5-13 nm and 5.3 × 10¹¹ cm⁻², respectively.     

Pharmacological effects of propylthiouracil on corticosterone secretion in male rats

BACKGROUND: We investigated the direct effects of propylthiouracil (PTU) on corticosterone secretion both in vivo and in vitro. METHODS: Male rats were divided into 4 groups and then injected subcutaneously with saline, PTU, PTU plus thyroxine (T4), or T4 once daily for 2 weeks. After 2 weeks, rats were decapitated or received adrenocorticotropic hormone (ACTH), intravenously. Zona fasciculata-reticularis (ZFR) cells from normal, saline-, PTU-, PTU plus T4-, or T4-treated rats were incubated with ACTH, forskolin, 8-Br-cAMP, deoxycorticosterone (DOC) +/- PTU (1, 2, or 5 mg/mL) at 37 degrees C for 2 hours. Corticosterone concentrations in plasma and cell media, and 3':5'-cyclic adenosine monophosphate (cAMP) production in ZFR cells were determined by radioimmunoassay. The effects of PTU on the activities of steroidogenic enzymes in ZFR cells were measured by the amounts of intermediate steroidal products separated by thin-layer chromatography. RESULTS: The basal and ACTH-stimulated levels of plasma corticosterone in PTU-treated rats were lower as compared to saline-treated animals. Both basal and ACTH-stimulated corticosterone secretion were inhibited by PTU > 2 mg/mL in rat ZFR cells. The cAMP production induced by forskolin was lower in PTU, PTU plus T4, or T4-treated rats than in saline-treated animals. Chronic administration of PTU or PTU plus T4 inhibited the 3 beta-hydroxysteroid dehydrogenase, 21 beta-hydroxylase, and 11 beta-hydroxylase activities. Administration of PTU (1, 2, and 5 mg/mL) suppressed the basal, ACTH, 8-Br-cAMP, forskolin, and DOC-stimulated corticosterone secretion in rat ZFR cells. Likewise, PTU > 2 mg/mL inhibited the ACTH and 8-Br-cAMP-stimulated levels of intracellular cAMP in rat ZFR cells. CONCLUSIONS: These results suggest that PTU counteracts both basal and ACTH-induced adrenal steroidogenesis through their attenuation of the activity of 11 beta-hydroxylase and cAMP production in rat ZFR cells.     

Comparison of measured and self-reported anthropometric information among firefighters: implications and applications

This study evaluated the accuracy of self-reported body weight and height compared to measured values among firefighters and identified factors associated with reporting error. A total of 863 male and 88 female firefighters in four US regions participated in the study. The results showed that both men and women underestimated their body weight ( ? 0.4 ± 4.1, ? 1.1 ± 3.6 kg) and overestimated their height (29 ± 18 , 17 ± 16 mm). Women underestimated more than men on weight (p = 0.022) and men overestimated more than women on height (p < 0.001). Reporting errors on weight were increased with overweight status (p < 0.001) and were disproportionate among subgroups. About 27% men and 24% women had reporting errors on weight greater than ± 2.2 kg, and 59% men and 28% women had reporting errors on height greater than 25 mm.

Practitioner Summary: This study along with literature revealed that the self-reported approach is not a sustainable option for anthropometric surveys, even for gathering data from physically active professional groups, such as firefighters, who presumably are knowledgeable of their body dimensions. Self-reported anthropometric information is undependable in important population subgroups.     

Location determination of mobile devices for an indoor WLAN application using a neural network

Due to the popularity of location-based services, determining the location of a device at all times has become a subject of great interests. Although many GPS-based applications have been developed and successfully deployed in various fields, their applicabilities are hindered by the obstruction of the objects in the environment. Essentially, as satellite signals cannot penetrate the walls of buildings, the coverage of GPS systems is limited to outdoor environments. To fully exploit the benefit of location-based services, approaches that determine the location of a device in indoor environments need to be established. This study presents a novel location determination mechanism that uses an indoor WLAN and back-propagation neural network (BPN). A museum is taken as the context of the example indoor environment. Location determination is achieved using the combined strengths of 802.11b wireless access signals. With a significant number of access points (APs) installed in the museum, hand-held devices can sense the strengths of the signals from all APs to which the devices can connect. Using a back-propagation network, device locations can be estimated with sufficient accuracy. A novel adaptive algorithm is implemented for enhancing the accuracy of the estimation.

Human responses to augmented virtual scaffolding models

This study investigated the effect of adding real planks, in virtual scaffolding models of elevation, on human performance in a surround-screen virtual reality (SSVR) system. Twenty-four construction workers and 24 inexperienced controls performed walking tasks on real and virtual planks at three virtual heights (0, 6 m, 12 m) and two scaffolding-platform-width conditions (30, 60 cm). Gait patterns, walking instability measurements and cardiovascular reactivity were assessed. The results showed differences in human responses to real vs. virtual planks in walking patterns, instability score and heart-rate inter-beat intervals; it appeared that adding real planks in the SSVR virtual scaffolding model enhanced the quality of SSVR as a human - environment interface research tool. In addition, there were significant differences in performance between construction workers and the control group. The inexperienced participants were more unstable as compared to construction workers. Both groups increased their stride length with repetitions of the task, indicating a possibly confidence- or habit-related learning effect. The practical implications of this study are in the adoption of augmented virtual models of elevated construction environments for injury prevention research, and the development of programme for balance-control training to reduce the risk of falls at elevation before workers enter a construction job.