Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R² = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R² = 0.95), rather than the strongly attached biofilm (R² = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry     

Locally clocked pipelines and dynamic logic

Micropipelines and most of its variants use a delay-insensitive controller to moderate a pipeline. In search of improved performance, we depart from the delay-insensitive model in favor of a bounded-delay model for the controller. In particular, we demonstrate how a general delay-insensitive controller for level-sensitive pipelines can be improved by assuming a bounded-delay model and taking advantage of delay information to make the controller faster and more efficient. The new control scheme is referred to as locally clocked (LC) control. A highly pipelined logic technique called LC dynamic logic is presented that combines the bounded-delay controller for their comments and suggestions. with a latching dynamic logic gate design. Simulations comparing LC control with its delay-insensitive counterpart are presented. Also, an 8 × 8 bit multiplier with a maximum frequency of 715 MHz for a 1 μm CMOS process that uses LC dynamic logic is presented     

Maternal High‐Fat‐Diet Programs Rat Offspring Liver Fatty Acid Metabolism

In offspring exposed in utero to a maternal diet high in fat (HF), we have previously demonstrated that despite similar birth weights, HF adult offspring at 6 months of age had significantly higher body weights, greater adiposity, and increased triacylglycerol (TAG) levels as compared to controls. We hypothesized that a maternal HF diet predisposes to offspring adiposity via a programmed increase in the synthesis of monounsaturated fatty acids in the liver and hence increased substrate availability for liver TAG synthesis. We further hypothesized that programmed changes in offspring liver fatty acid metabolism are associated with increased liver expression of the lipogenic enzyme stearoyl‐CoA desaturase‐1 (SCD‐1). Female rats were maintained on a HF diet rich in monounsaturated fatty acids (MUFA) prior to and throughout pregnancy and lactation. After birth, newborns were nursed by the same dam, and all offspring were weaned to control diet. Plasma and liver fatty acid compositions were determined using gas chromatography/mass spectrometry. Fatty acid C16 desaturation indices of palmitoleic/palmitic and (vaccenic + palmitoleic)/palmitic and the C18 desaturation index of oleic/stearic were calculated. Liver protein abundance of SCD‐1 was analyzed in newborns and adult offspring. Plasma and liver C16 desaturation indices were decreased in HF newborns, but increased in the adult offspring. Liver SCD‐1 expression was increased in the HF adult offspring. These data show that the maternal HF diet during pregnancy and lactation increases offspring liver SCD‐1 protein abundance and alters the liver C16 desaturase pathway.     

Sinterability of Forsterite Prepared via Solid‐State Reaction

In this work, the sinterability of forsterite powder synthesized via solid‐state reaction was investigated. X‐ray diffraction (XRD) analyses indicate that the synthesized powder possessed peaks that correspond to stoichiometric forsterite. Scanning electron micrographs revealed that the powders were formed agglomerates, which were made up of loosely packed fine particles. Subsequently, the forsterite powders were cold isostatically pressed into a disk shape under 200 MPa and sintered in air at temperature ranging from 1200°C to 1500°C (interval of 50°C) with ramp rate of 10°C/min and dwelling time of 2 h. The sinterability of each sintered samples was examined in terms of phase stability, relative density, Vickers hardness, fracture toughness, and microstructural examination. XRD examination on all the sintered samples exhibited pure forsterite, in which the generated peaks were found to be in a good agreement with JCPDS card no. 34‐0189. The densification of forsterite progressed to reach a maximum relative density of ~91% at 1500°C. This study also revealed that high‐strength forsterite ceramic can be synthesized via solid‐state reaction as forsterite attained favorable mechanical properties, having fracture toughness of 4.88 MPam^1/2 and hardness of 7.11 GPa at 1400°C.     

Distance-Enhancing Constrained Codes with Parity-Check Constraints for Data Storage Channels

This paper proposes efficient distance-enhancing constrained codes with parity-check (PC) constraints for data storage channels. We first propose simple and efficient finitestate encoding methods to design various distance-enhancing constrained codes, including a repeated minimum transition runlength (RMTR) code for optical recording channels, as well as a maximum transition run (MTR) code for magnetic recording channels. We further propose a general and systematic code design methodology, which can efficiently combine constrained codes with PC codes. The constrained codes can be any distanceenhancing constrained codes. The PC codes can be any linear binary PC codes. The rates of the designed codes are only a few tenths of a percent below the theoretical maximum. The proposed method enables soft information to be available to the PC decoder and soft decoding of PC codes. Examples of several newly designed distance-enhancing constrained PC codes are illustrated. Simulation results with blu-ray disc (BD) systems show that the proposed new RMTR code and RMTR constrained 4-bit PC code perform 0.2 dB and 0.85 dB better than the standard 17PP code, respectively, at error correction code (ECC) failure rate (EFR) of 10^-12 and high recording density.     

Determination Of The Phase Current Waveform For A Disc‐Type Axial‐Flux Wheel Motor

An optimal design of the driving current pattern for a disc‐type axial‐flux brushless DC wheel motor of an electric vehicle is proposed in this paper. The electro‐magnetic dynamic model of the motor is established with magnetic circuits, describing the relationship between the output torque and excitation current. The optimal current pattern, in terms of magnitude and phase angle, is then obtained by maximizing the output torque with respect to the rotor shift. Compared with the traditional three‐phase‐on current pattern of fixed 120–degree phase shift, both the average torque and efficiency with the driving current of an optimal advanced switching angle are seen to be improved under various loading conditions. The motor performance with the optimal driving waveform is simulated and verified by experiments.     

The adsorption of chlordane by wheat flour from chlordane-treated shelf paper

Packaged wheat flour stored in direct contact with chlordane-treated shelf paper adsorbed with time appreciable amounts of the pesticide from the paper. Direct contact of the package with the paper was more conducive to flour contamination than it was from exposure of the flour to the vaporized pesticide components from the paper. Sorption effects of the pesticide with flour varied with the mode of exposure and the type of bag used, i.e. when the bags were in direct contact with the shelf paper, the flour packaged in polyethylene bags contained the largest amount of chlordane residue (29 ppm), which decreased about 10 per cent when packaged in single-thickness kraft paper bags and about 35 per cent in double-thickness kraft paper bags. When the bags were separated from direct contact with the shelf paper by means of open glass containers, contamination of the flour was tangibly decreased, whereby the amounts of residue found in the kraft single- and double-thickness paper bags were 0·4 and 0·3 ppm, respectively, compared to only 0·06 ppm in the polyethylene bags.