Improved chitin production by pretreatment of shrimp shells

Pretreatment of shrimp shells was investigated in order to lower the costs and to improve the sustainability of chitin production. Physical pretreatment comprising drying, grinding and sieving is attractive for the recovery of 50% of shrimp protein as a dry powder. Pretreatment of shells by shearing in acidified water results in the removal of up to 60% of the protein and a reduction of their mineral content without a decrease in the chitin yield. Both pretreatment procedures will lead to cleaner technology for chitin production, to a considerably lower need for chemicals, to useful protein by‐products, and to less‐contaminated industrial effluent. Copyright © 2004 Society of Chemical Industry     

A simplified in vivo drug sensitivity test for malaria in the field

Using a derivative of the plasmid pBR322 we have tested the dimer catastrophe hypothesis of plasmid instability. Most of the theory was confirmed by our observations, but our data suggest that some of the quantitative aspects need modification. In a recF strain of Escherichia coli we estimated the difference in loss rate between the plasmid in the monomeric and the dimeric state to be a factor of 13-14 and the difference in the loss rate between the plasmid in the monomeric and the trimeric state to be a factor of 14-50. We were able to confirm that plasmid oligomers were heterogeneously distributed within a rec+ population, but we were unable to detect any pronounced difference in the level of growth inhibition exerted by the plasmid when in the monomeric, dimeric, or trimeric state. This leaves open the question as to whether runaway plasmid multimerization was prevented (i) by a small correlation between the inhibition of growth and the 'multimeric status' of the plasmid, (ii) by intramolecular homologous recombination, or (iii) whether the process of runaway multimerization is too slow to be recognized within the duration of the experiments, i.e. 200 generations of growth.     

适合于脆性材料受拉性能试验的试验机辅助吸能装置

为测定混凝土、石料等脆性材料的抗拉应力应变关系全过程曲线，作者在普通材料试验机上研制了一种采用薄壁金属套筒及球铰方式对中的受拉辅助吸能装置。通过对高强混凝土试件的实测表明，该装置能减少轴拉过程中偏心的影响，有效地吸收在试件破坏瞬间试验机所释放的弹性变形能，延缓试件的破坏过程，不失为一种解决问题的新途径。     

Dimensional aspects of aerosol deposition on cylinders with rebound

Net deposition efficiency of particles on infinite cylinders is shown to be a unique function of the Stokes number and a new dimensionless parameter, the Critical Stokes number. This number is formed with the use of the critical rebound speed. Dimensional analysis and numerical methods can be used to establish the relationship between the net deposition efficiency and the Stokes numbers, and some empirical evidence supports the relationship.     

An Efficient Triple-Tandem Polymer Solar Cell

We present an efficient triple-tandem polymer solar cell with identical poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6)C₆₁ (PCBM) bulk heterojunction as the active layers and highly transparent Al (1 nm)/ MoO₃ (15 nm) as the intermediate layer. This intermediate layer is structurally smooth as characterized by atomic force microscopy. Although identical organic active layers are used to construct such triple-tandem cell, a tripled open-circuit voltage of 1.73 V and power conversion efficiency of 2.03% are obtained under simulated solar irradiation of 100 mW/cm² (AM1.5), demonstrating a viable technique for fabricating triple-tandem polymer cell with the intermediate layer of Al/MoO₃.     

A direct digital frequency synthesizer with high-speed current-steering DAC

A high-speed SiGe BiCMOS direct digital frequency synthesizer (DDS) is presented. The design in tegrates a high-speed digital DDS core, a high-speed differential current-steering mode 10-bit D/A converter, a serial/parallel interface, and clock control logic. The DDS design is processed in 0.35 μm SiGe BiCMOS standard process technology and worked at 1 GHz system frequency. The measured results show that the DDS is capable of generating a frequency-agile analog output sine wave up to 400+ MHz.     

Feedforward Controller of Ill-Conditioned Hysteresis Using Singularity-Free Prandtl–Ishlinskii Model

Piezoelectric, magnetostrictive, and shape memory alloy actuators are gaining importance in high-frequency precision applications constrained by space. Their intrinsic hysteretic behavior makes control difficult. The Prandtl-Ishlinskii (PI) operator can model hysteresis well, albeit a major inadequacy: the inverse operator does not exist when the hysteretic curve gradient is not positive definite, i.e., ill condition occurs when slope is negative. An inevitable tradeoff between modeling accuracy and inversion stability exists. The hysteretic modeling improves with increasing number of play operators. But as the piecewise continuous interval of each operator reduces, the model tends to be ill-conditioned, especially at the turning points. Similar ill-conditioned situation arises when these actuators move heavy loads or operate at high frequency. This paper proposes an extended PI operator to map hysteresis to a domain where inversion is well behaved. The inverse weights are then evaluated to determine the inverse hysteresis model for the feedforward controller. For illustration purpose, a piezoelectric actuator is used.     

Phosphor-Free GaN-Based Transverse Junction White-Light Light-Emitting Diodes With Regrown n-Type Regions

In this study, we demonstrate a GaN-based phosphor-free white-light light-emitting diode (LED), which is composed of GaN-based dual-wavelength (blue and yellow-green) multiple-quantum-wells (MQWs) and a transverse p-n junction. The device was realized by the regrowth of n-type GaN layers on the sidewall of p-type GaN and undoped MQWs. The problems related to the bias-dependent shape of the electroluminescence spectra that occur in traditional phosphor-free white-light LEDs (with vertical p-n junctions) are greatly minimized. The current-voltage performance of our device is comparable to that of the commercially available phosphor white-light LEDs. In addition, the dynamic measurement results indicate that we can attain a much higher modulation bandwidth (22 versus 3 MHz) with this device than with the currently available commercial ones.     

Acrylamide Formation in Foods during Thermal Processing with a Focus on Frying

This paper summarizes the current state of knowledge on acrylamide formation in foods during thermal processing. The main pathway of acrylamide formation in foods is linked to the Maillard reaction, and in particular, the amino acid asparagine. Effects of several factors related to food composition and processing conditions on the formation levels of acrylamide, and also, other quality characteristics in thermally processed foods are discussed in detail. From a process control point of view, it is also addressed that there is a need to develop viable models for the estimation of acrylamide contents in heated foods during the stages of process design and optimization. Fried potato products, as one of the most encountered category of thermally processed foods, are specifically emphasized for acrylamide formation, potential ways of mitigation, and modeling its formation during frying.