Hard sphere behaviour of arborescent polystyrenes: viscosity and differential scanning calorimetry studies

Two series of arborescent polystyrenes were prepared by successive cycles of functionalization and anionic grafting reactions. A target branching functionality of around 15 side chains per backbone chain and a constant branch molecular weight of either 5000 g mol⁻¹ (S05 series) or 30 000 g mol⁻¹ (S30 series) were used for each generation. The intrinsic viscosity of each polymer series was relatively insensitive to molecular weight, a behaviour typical of hard spheres. The S30 polymers expanded considerably in toluene relative to cyclohexane, but the S05 polymers were unaffected by change in solvent quality. Analysis by d.s.c. showed that limiting T_g values are reached in the upper generations of each polymer series, similarly to polymer networks prepared from primary chains with a low molecular weight. A lower ΔC_p and a broader transition range observed for the upper generation S05 polymers may be related to a decrease in chain mobility inside the molecules. No similar effects were observed in the S30 polymers. © 1997 Elsevier Science Ltd.     

Discrete plane segmentation and estimation from a point cloud using local geometric patterns

This paper presents a method for segmenting a 3D point cloud into planar surfaces using recently obtained discretegeometry results. In discrete geometry, a discrete plane is defined as a set of grid points lying between two parallel planes with a small distance, called thickness. In contrast to the continuous case, there exist a finite number of local geometric patterns （LGPs） appearing on discrete planes. Moreover, such an LGP does not possess the unique normal vector but a set of normal vectors. By using those LGP properties, we first reject non-linear points from a point cloud, and then classify non-rejected points whose LGPs have common normal vectors into a planar-surface-point set. From each segmented point set, we also estimate the values of parameters of a discrete plane by minimizing its thickness.     

Codiagnosability of networked discrete event systems subject to communication delays and intermittent loss of observation

Failure diagnosis is a crucial task in modern industrial systems, and several works in the literature address this problem by modeling the system as a Discrete-Event System (DES). Most of them assume perfect communication between sensors and diagnosers, i.e., no loss of observation of events, or event communication delays between the measurement sites and the diagnosers. However, industrial systems can be large and physically distributed, in which cases, communication networks are used to provide an efficient way to establish communication between devices. In diagnosis systems, the use of networks can introduce delays in the communication of event occurrences from measurement sites to the local diagnosers, leading to an incorrect observation of the order of occurrence of events generated by the system and, as a consequence, to an incorrect diagnosis decision by the local diagnoser. In this paper, we address the problem of decentralized diagnosis of networked Discrete-Event Systems subject to event communication delays, and we introduce the definition of network codiagnosability of the language generated by a DES subject to both event communication delays and intermittent loss of observation, and present necessary and sufficient conditions for a language to be network codiagnosable, for short. We also propose an algorithm to verify this property.     

Structural features of the polysaccharide gum from Acacia glomerosa

Acacia glomerosa, Benth. (Vulgares Series) exudates a clear gum which produces gels easily. The physico-chemical data and sugar composition are very close to gum arabic from Acacia senegal, except that A. glomerosa gum contains a high nitrogen content. A series of degraded products was prepared by acid hydrolysis and Smith-degradation. The characterization of the degraded products by partial hydrolysis, sugar composition and by the application of uni- and bidimensional spectroscopy led to know interesting structural features of the polysaccharide isolated from A. glomerosa gum. This polysaccharide, as that from A. senegal gum, consists of 1,3-β- -galactopyranosyl backbone. There are side-chains of 1,3-β- -galactopyranosyl oligosaccharides attached to position six of the galactan main chain. Arabinose (furanosyl and pyranosyl) residues may be up to four units long because it was necessary to prepare four polysaccharides to remove them from the gum structure. Uronic acid residues were difficult to remove as has been observed in other Acacia gums.     

Telerehabilitation using a virtual environment improves upper extremity function in patients with stroke.

In this paper, we describe our experience in designing a virtual environment-based (VE) telerehabilitation system, and the results of a clinical study of the first 11 subjects with stroke to use the system. Our telerehabilitation system allows a therapist to conduct interactive VE treatment sessions remotely with a patient who is located at home. The system, software architecture, and development experience are described. Results of the clinical study on subjects with stroke showed significant improvements in upper extremity function following 30 1-h VE treatment sessions as measured by three standard clinical tests: Fugl-Meyer test of motor recovery (FM) (p < 0.0001), Wolf motor test (WMT) (p = 0.0097, and shoulder strength (ShS) (p = 0.0027). Grip strength (GS) showed a trend toward improvement (p = 0.025). These changes were maintained, for the most part, at four-months follow-up (FM +7.6, WMT -18.4 s, ShS, +169%, GS, +53%).     

Reverse osmosis technology for water treatment: State of the art review

This paper presents a review of recent advances in reverse osmosis technology as related to the major issues of concern in this rapidly growing desalination method. These issues include membrane fouling studies and control techniques, membrane characterization methods as well as applications to different water types and constituents present in the feed water. A summary of the major advances in RO performance and mechanism modeling is also presented and available transport models are introduced. Moreover, the two important issues of RO brine discharge and energy costs and recovery methods are discussed. Finally, future research trends and needs relevant to RO are highlighted.     

Simulating the effect of aerobic biodegradation on soil vapor intrusion into buildings: influence of degradation rate, source concentration, and depth

Steady-state vapor intrusion scenarios involving aerobically biodegradable chemicals are studied using a three-dimensional multicomponent numerical model. In these scenarios, sources of aerobically biodegradable chemical vapors are placed at depths of 1-14 m beneath a 10 m x 10 m basement or slab-on-grade construction building, and the simultaneous transport and reaction of hydrocarbon and oxygen vapors are simulated. The results are presented as Johnson and Ettinger attenuation factors alpha (predicted indoor air hydrocarbon concentration/source vapor concentration), and normalized contour plots of hydrocarbon and oxygen concentrations. In addition to varying the vapor source depth, the effects of source concentration (2-200 mg chemical/L vapor) and oxygen-limited first-order reaction rates (0.018-1.8 h(-1)) are studied. Hydrocarbon inputs were specific to benzene, although the relevant properties are similar to those for a range of hydrocarbons of interest. Overall, the results suggest that aerobic biodegradation could play a significant role in reducing vapor intrusion into buildings (decreased alpha-values) relative to the no-biodegradation case, with the significance of aerobic biodegradation increasing with increasing vapor source depth, decreasing vapor source concentration, and increasing first-order biodegradation rate. In contrast to the no-biodegradation case, differences in foundation construction can be significant in some settings. The significance of aerobic biodegradation is directly related to the extent to which oxygen is capable of migrating beneath the foundation. For example, in the case of a basement scenario with a 200 mg/L vapor source located at 3 m bgs, oxygen is consumed before it can migrate beneath the foundation, so the attenuation factors for simulations with and without aerobic biodegradation are similar for all first-order rates studied. For the case of a 2 mg/L vapor source located at 8 m bgs, the oxygen is widely distributed beneath the foundation, and the attenuation factor for the biodegradation case ranges from about 3 to 18 orders-of-magnitude less than that for the no-biodegradation case.     

Dynamic Reaction Cell-ICP-MS as a Powerful Tool for Quality Control of a Se-Enriched Dietary Supplement

The aim of this work was to evaluate different approaches employing a reaction cell to circumvent spectral interferences over ⁸⁰Se⁺ to increase the sensitivity in the determination of Se by inductively coupled plasma mass spectrometry (ICP-MS). Different gases (NH₃, CH₄, and O₂) were employed, and the operating conditions were optimized by a central composite design, evaluating the effect of the reaction gas flow rate and the rejection parameter q (Rpq) on the limit of detection (LOD) of the method. All reaction gases studied reduced the interference by ⁴⁰Ar₂ ⁺ over ⁸⁰Se⁺, reducing the LOD when compared to the LOD obtained with ICP-MS operating in the standard mode (LOD = 0.2 μg kg^?1). A better LOD (0.01 μg kg^?1) was obtained with CH₄, while 0.1 μg kg^?1 was the LOD with NH₃. The use of O₂ as a reaction gas enabled the determination of Se at m/z 96 (⁸⁰Se¹⁶O⁺) with adequate analytical performance (LOD = 0.03 μg kg^?1). The accuracy of the method was evaluated by analyzing the certified reference material (CRM) Selm-1, and the results obtained ranged from 99 to 104% of the certified value. In addition, Se dietary supplements of four different brands and commercial yeast were analyzed, and the major sources of uncertainty were studied. The dietary supplements followed the criteria adopted by Brazilian legislation, although the uncertainty study highlighted the great variation in the Se content of each brand. Clearly, the manufacturing process of dietary supplements needs more rigorous quality control, considering that this product can affect the health of consumers.     

Effects of Antimicrobial Edible Coating of Thymol Nanoemulsion/Quinoa Protein/Chitosan on the Safety,Sensorial Properties,and Quality of Refrigerated Strawberries (<Emphasis Type="Italic">Fragaria × ananassa</Emphasis>) Under Commercial Storage Environment

The effectiveness of the edible coating with thymol nanoemulsion on the safety, sensorial properties, and quality of refrigerated strawberries was investigated under commercial storage conditions. Spontaneous emulsification was used to obtain the thymol nanoemulsion that was included on quinoa protein/chitosan coatings. During the entire storage time, strawberries coated with thymol-antimicrobial packaging had a lower fungal and yeast load compared with the controls (uncoated and coated with quinoa protein/chitosan). The flavour and aroma of the coated strawberries was initially affected, although this sensory appreciation was improved from the fifth day of storage and showed similar scores than the controls, and presenting better aroma score at day 12 of storage. Furthermore, the shelf life of the thymol nanoemulsion-coated strawberries increased in 4 days, unlike that in the both controls. Further, the application of these biocoatings on strawberries significantly decreased the weight loss relative to that in the control, during 16 days of storage at 5 °C and 90% relative humidity, and did not alter the quality parameters (pH, titrable acidity, and percentage of soluble solids). These results suggest that the application of thymol/nanomulsion-loaded edible films is an effective strategy to increase the shelf life of highly perishable products such as strawberries.     

响应面试验优化莲蓬壳总黄酮超声提取条件及其抗氧化活性

对莲蓬壳总黄酮的超声提取工艺和抗氧化活性进行研究。在单因素试验基础上,采用响应面分析法对超声辅助提取的工艺参数进行优化,得到最优工艺条件为液料比40∶1（mL/g）、乙醇体积分数48%、提取温度60 ℃、提取时间10 min。在此条件下测得莲蓬壳总黄酮提取率为8.32%。抗氧化实验结果表明：莲蓬壳总黄酮具有较强清除1,1-二苯基-2-三硝基苯肼自由基能力和还原力,同时可显著性抑制H2O2诱导的人皮肤纤维细胞氧化应激损伤,是一种极具开发潜力的天然抗氧化剂。