Red clover (Trifolium pratense L.) isoflavones: determination of concentrations by plant stage,flower colour,plant part and cultivar

BACKGROUND: Red clover (Trifolium pratense L.), a widely used fodder, has recently received considerable interest as a valuable source of isoflavones for many health‐related applications. The aim of this study was to analyse the concentrations of four isoflavones, daidzein, genistein, formononetin and biochanin A, in extracts of leaves, stems, roots and different coloured flowers from red clover by high‐performance liquid chromatography and to determine the antifungal activities of the extracts. RESULTS: Among greenhouse‐grown samples the highest amounts of daidzein and genistein were found in petioles (0.11–0.28 and 0.30–0.54 mg g^?1 respectively), while leaves were rich in formononetin and biochanin A (5.57–9.05 and 10.94–14.59 mg g^?1 respectively). High formononetin concentrations were found in roots, but very little biochanin A. Among field‐grown samples the highest concentrations of daidzein and genistein were detected in stems collected in August (0.24 and 0.55 mg g^?1 respectively), while the highest amounts of formononetin and biochanin A were found in young leaves collected in June (7.47 and 9.69 mg g^?1 respectively). Most of the extracts inhibited the growth of Drechslera teres, while the root extract showed the strongest effect against Microdochium nivale. CONCLUSION: High levels of bioactive compounds found not only in inflorescences but also in roots, leaves and stems suggest that red clover may be an inexpensive and valuable resource for many applications. Copyright © 2007 Society of Chemical Industry     

Keeping secure to the end: a long-term perspective to understand employees’ consequence-delayed information security violation

Employees’ violation of information security policies is a major threat to an organisation. Some violations such as using an easy-to-guess password or storing confidential data on personal unencrypted flash drives usually do not cause immediate harm; instead, these actions create security flaws that can be attacked in the future and cause delayed consequences. We call such behaviour consequence-delayed information security violation (CDISV). The ignorance or denial of the possible delayed consequences is the main reason employees engage in such insecure behaviour. Due to the delay between the action and the consequence, a long-term mindset could play an important role in employees’ current decision-making. Specifically, in this study, we propose that long-term orientation is an influential factor in decreasing CDISV. The long-term orientation includes three dimensions: continuity, futurity, and perseverance. In addition, based on the stewardship theory and the needs theory, we further propose that value identification and the fulfilment of higher-order needs (trusted relationship and growth) are important drivers for employees to have a long-term orientation. We collected survey data using the 170 responses we received from a global company’s employees. The empirical results support our arguments. Our findings provide implications to organisations to encourage employees’ information security behaviours.     

Inkjet Printed Large‐Area Flexible Few‐Layer Graphene Thermoelectrics

Graphene‐based organic nanocomposites have ascended as promising candidates for thermoelectric energy conversion. In order to adopt existing scalable printing methods for developing thermostable graphene‐based thermoelectric devices, optimization of both the material ink and the thermoelectric properties of the resulting films are required. Here, inkjet‐printed large‐area flexible graphene thin films with outstanding thermoelectric properties are reported. The thermal and electronic transport properties of the films reveal the so‐called phonon‐glass electron‐crystal character (i.e., electrical transport behavior akin to that of few‐layer graphene flakes with quenched thermal transport arising from the disordered nanoporous structure). As a result, the all‐graphene films show a room‐temperature thermoelectric power factor of 18.7 µW m^?1 K^?2, representing over a threefold improvement to previous solution‐processed all‐graphene structures. The demonstration of inkjet‐printed thermoelectric devices underscores the potential for future flexible, scalable, and low‐cost thermoelectric applications, such as harvesting energy from body heat in wearable applications.     

A 700 MHz laser radar receiver realized in 0.18 μm HV-CMOS

This study presents a CMOS receiver chip realized in 0.18 µm High-Voltage CMOS (HV-CMOS) technology and intended for high precision pulsed time-of-flight laser range finding utilizing high-energy sub-ns laser pulses. The IC chip includes a trans-impedance preamplifier, a post-amplifier and a timing comparator. Timing discrimination is based on leading edge detection and the trailing edge is also discriminated for measuring the width of the pulse. The transimpedance of the channel is 25 kΩ, the uncompensated walk error is 470 ps in the dynamic range of 1:21,000 and the input referred equivalent noise current 450 nA (rms).     

The stiffness of laser stake welded T-joints in web-core sandwich structures

The purpose of this paper is to describe experiments carried out on laser stake welded T-joints of web-core steel sandwich structures. A special test setup was developed to measure the shear-induced rotation at the T-joint. The ratio of the shear force to rotation angle gave the joint stiffness. This stiffness was measured for specimens with two different face-plate thicknesses. The influence of weld thickness, root gap and occurrence of contact were further investigated with finite element simulations. Finally, the shear stiffness of the sandwich structure transverse to the web plate direction was determined using the experimentally obtained average joint stiffness value. The validation of the shear stiffness was carried out by considering a beam in four-point bending. The agreement between calculated deflection and stress and experimental results was found to be good.     

Multi-channel energy detection under phase noise: analysis and mitigation

For the development of highly integrated, flexible and low-cost cognitive radio (CR) devices, simple transceiver architectures, like direct-conversion receiver, are expected to be deployed and provide viable radio frequency (RF) spectrum sensing solutions for practical implementation. Yet, this can be very challenging task especially if spectrum sensing and down-conversion are conducted over multiple RF channels simultaneously for improved efficiency in channel scans. Then, the so-called dirty RF problem that degrades link performance of traditional transmission systems starts to be influential from spectrum sensing perspective as well. The unavoidable RF impairments, e.g., oscillator phase noise in direct-conversion receiver, could generate crosstalk between multiple channels that are down-converted simultaneously, and thus considerably limit the spectrum sensing capabilities. Most of the existing spectrum sensing studies in literature assume an ideal RF receiver and have not considered such practical RF hardware problem. In this article, we study the impact of oscillator phase noise on energy detection (ED) based spectrum sensing in multi-channel direct-conversion receiver scenario. With complex Gaussian primary user (PU) signal models, we first derive the detection and false alarm probabilities in closed-form expression. The analytical results, verified through extensive simulations, show that the wideband multi-channel sensing receiver is very sensitive to the neighboring channel crosstalk induced by oscillator phase noise. More specifically, it is shown that the false alarm probability of multi-channel energy detection increases significantly, compared to the ideal RF receiver case. The exact performance degradation depends on the power of neighboring channels as well as statistical characteristics of the phase noise in the deployed receiver. In order to prevent such performance degradation in spectrum identification, an enhanced energy detection technique is proposed. The proposed technique calculates the leakage power from neighboring channels for each channel and improves the sample energy statistics by subtracting this leakage power from the raw values. An analytical expression is derived for the leakage power which is shown to be a function of power spectral levels of neighboring channels and 3-dB bandwidth of phase noise process. Practical schemes for estimating these two quantities are discussed. Extensive computer simulations show that the proposed enhanced detection yields false alarm rates that are very close to those of an ideal RF receiver and hence clearly outperforms classical energy detection.     

200～1 100 nm光响应测试系统的研制

设计并制作了２００～１１００ｎｍ的光响应测试系统,该系统工作稳定可靠,并可消除光源拌动和突发性光源对测试的影响。