HS-SPME coupled to GC/MS for quality control of Juniperus communis L. berries used for gin aromatization

HS-SPME coupled to GC/MS was applied to the analysis of the volatile fraction of Juniperus communis L. berries, which are the principal ingredient used for gin aromatization. Seventy seven compounds were identified by comparison with reference compounds or tentatively identified by comparing their mass spectra and retention index with those reported in mass spectra libraries and literature, respectively. Seventy four were detected by SPME and sixty eight were detected by solvent distillation extraction (SDE). These were mainly mono- and sesquiterpenic compounds that represented more than the 80% of the gin’s volatile composition. A high percent content was due to monoterpenoids, whose analysis could be important for the assessment of sensory quality control of juniper due to their impact on gin aroma. The main monoterpenoids detected in the headspace of the juniper berries from two periods of collection were terpinen-4-ol, p-cymene, β-myrcene, γ-terpinene, α-pinene and limonene. These represented more than the 70% of the sample’s volatile fraction. The proposed SPME method required short times and the low cost of analysis and enabled to detect a number of compounds comparable with SDE or much higher than the number of compounds reported by other extraction techniques. The results suggested the suitability of this technique for the assessment of the volatile composition of juniper berries intended for gin flavouring.     

Infrared Faraday rotation on thin film In2O3+SnO2 semiconductors

Two sets of thin film sputtered In₂O₃+SnO₂ samples, one prepared in argon atmosphere with oxigen, and the other without, at various temperatures between 100°C and 250°C, have been studied by measuring their Farday rotation from optical to infrared frequencies, as well as their optical transmission spectra. The effect of the different treatments on the carrier densities and mobilities, show values that grow with deposition temperature. This can be attributed to an increase in the number of oxygen vacancies. On the other hand, the presence of O₂ in the atmosphere during deposition, leads to smaller values at the same temperatures, compared to those obtained in samples prepared in atmosphere without oxygen, seemingly as a result of the filling of the vacancies.     

New thermosets obtained by copolymerization of DGEBA with 1,5,7,11-tetraoxaspiro[5,5]undecane catalyzed by lanthanide triflates

DGEBA epoxy resin was cured with different proportions of 1,5,7,11-tetraoxaspiro[5,5]undecane (TOSU) with ytterbium and lanthanum triflates as catalysts. The curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated-total-reflexion mode (FTIR/ATR).FITR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the epoxide, orthocarbonate, linear carbonate and other groups formed in the curing process. The T_g of the cured materials decreased when the proportion of TOSU increased. The kinetics were studied by DSC experiments and analyzed with iso-conversional procedures. The systems catalyzed by ytterbium triflate had a higher curing rate and reached a higher degree of cross-linking. The addition of TOSU reduced the degree of overall shrinkage and even led to one material expanding. The flexibility and the degradability of these materials were improved by introducing higher proportions of TOSU.     

Back-end manager: an interface between a knowledge-based front end and its application subsystems

Front Ends for Open and Closed User Systems (FOCUS) is an ESPRIT/2 (no. 2620) project aimed at designing tools and techniques for the construction of knowledge-based front ends (KBFEs) for open-user systems (reusable software components, libraries, etc) and closed-user systems (free-standing software, packages, etc). An important part of the project involves the establishment of an architecture for KBFEs and the specification of the KBFE/back-end interface. This paper describes the properties and related issues of such an interface, known as the back-end manager (BEM), and its relationship to the proposed KBFE architecture.     

冷喷涂单颗粒铜在铝基体上的显微结构研究

采用冷喷涂法在铝(Al)基体上沉积单颗粒铜(Cu),利用聚焦离子束/电子束(FIB/SEM)系统精确定位并原位制备了完整单个颗粒Cu沉积在Al基体上的透射样品,分析其显微结构及形成原因。实验结果表明,撞击过程中温度与应力分布不均匀,导致沉积Cu颗粒不均匀形变。Cu/Al界面受影响较大:颗粒动能转化为形变能和热能,打破了界面处氧化膜,使界面附近温度迅速升高,发生动态再结晶,生成金属间化合物Cu_9Al_4;Cu颗粒内距界面越远的区域,受温度和应力的影响越小,其变形主要是通过晶体内位错增殖和移动;沉积颗粒顶部,远离Cu/Al界面,几乎不受应力和温度影响,保持原始显微结构。     

Propagation delay influence in IEEE 802.11 outdoor networks

Originally, Wireless Local Area Networks served only small indoor areas. Nevertheless, the idea of employing IEEE 802.11 networks in large outdoor environments is a very attractive possibility. IEEE 802.11 technology offers several advantages: the low cost of equipment, its operation in the unlicensed spectrum and its higher data rates. Since the advent of the first IEEE 802.11 standard, a great deal of research has been carried out. So-called Wifi-based Long Distance networks are currently being deployed. In this paper, we study the suitability of employing IEEE 802.11 networks in large outdoor environments without modifying the standard working procedure. In such scenarios, IEEE 802.11 networks should offer coverage ranges of several kilometer, which leads to high propagation delay values. Thus, we analyze the influence of increasing propagation delay in the IEEE 802.11 MAC protocol. To carry out our analysis we present a mathematical model and simulation results. We provide an operating range in which IEEE 802.11 performance is feasible and establish a throughput threshold according to the propagation delay.     

Experimental evaluation of slack management in real-time control systems: Coordinated vs. self-triggered approach

Effective slack management, i.e., management of unused computing resources, for real-time control tasks mandates to redistribute the available resources between controllers as a function of the state of the controlled plants. Slack can be allocated to control tasks to alter their rate of progress via e.g., the controllers’ period, in order to adapt their behavior to changes in the computing platform and in the environment. This paper presents an experimental evaluation of two representative slack redistribution policies for multitasking real-time control systems: “coordinated” vs. “self-triggered”. In the coordinated policy a resource manager is responsible for modifying each control task progress. Alternatively, in the self-triggered policy, each control task decides its progress. The demands that each policy poses to the computing platform are analyzed and different operating system architectures providing flexibility and adaptivity are discussed. A proof-of-concept implementation including the real-time control of three double integrator plants in the form of electronic circuits is presented, and a complete performance analysis is reported.     

The Need for Fast Communication in Hardware-Based Speculative Chip Multiprocessors

Chip-multiprocessor (CMP) architectures are a promising design alternative to exploit the ever-increasing number of transistors that can be put on a die. To deliver high performance on applications that cannot be easily parallelized, CMPs can use additional support for speculatively executing the possibly data-dependent threads of an application. For cross-thread dependences that must be handled dynamically, the threads can be made to synchronize and communicate either at the register level or at the memory level. In the past, it has been unclear whether the higher hardware cost of register-level communication is cost-effective. In this paper, we show that the wide-issue dynamic processors that will soon populate CMPs, make fast communication a requirement for high performance. Consequently, we propose an effective hardware mechanism to support communication and synchronization of registers between on-chip processors. Our scheme adds enough support to enable register-level communication without specializing the architecture toward speculation much. Finally, our scheme allows the system to achieve near ideal performance.