Solid state NMR study of segmented polymer networks: fine-tuning of phase morphology via their molecular design

Segmented polymer networks (SPNs) based on thermo-sensitive poly(N-isopropyl acryl amide) (PNIPAA) and poly(tetrahydrofuran) (PTHF) have been synthesized by free radical copolymerization of PTHF bis-macromonomers with N-isopropyl acrylamide. The nature of the polymerizable end group on the bis-macromonomer has been varied, respectively from acrylate to acrylamide end groups. The multiphase behaviour of the corresponding SPNs has been examined as a function of the nature of the end group by making use of solid-state ¹³C CP/MAS NMR relaxometry, ¹H wideline NMR relaxometry and dynamic mechanical analysis (DMA). When PTHF with acrylate end groups was used during the SPN formation, analysis of proton spin-lattice relaxation times (T_1H) and proton spin-lattice relaxation times in the rotating frame (T_1ρH) revealed phase separation with domain sizes larger than 5 nm when the PTHF fraction exceeds 10 wt%. Only for lower PTHF-amounts, the SPNs were homogeneous on the nanometer scale. On the other hand, when PTHF with acrylamide end groups was used as macromolecular cross-linker, the NMR results showed the absence of any domain formation for SPNs with PTHF fractions up to 50 wt%. The major impact of the molecular design on the ultimate phase morphology of bicomponent polymer networks has been confirmed in all cases by DMA-analysis.     

Comparative analysis and performance of two predictive fadedetection schemes for Ka-band fade countermeasures

The design of Ka-band satellite fade countermeasure (FCM) systems is conditioned by the detection/prediction algorithm to be included within practical DSP-based FCM controllers. It depends upon the ability of systems to efficiently integrate the dynamic and stochastic nature of the Ka-band fading process which is dominated by rain attenuation and amplitude scintillation. The paper analyzes the modeling and statistical performance of two predictive fade detection algorithms. Prediction is introduced as a way to minimize the impact of the finite response time on the BER/throughput of practical FCM systems. Both fixed (FDM) and variable (VDM) detection margin strategies are introduced and compared in terms of their margin requirements, FCM utilization factor, and channel capacity utilization. The VDM is shown to be more efficient than its fixed counterpart. The long-term BER availability and average user data throughput of a VDM/fixed-FEC/adaptive transmission rate FCM are then evaluated for a typical low-power low-rate Ka-band in-bound VSAT link     

Efficient allocation of elastic interfederation encrypted streaming sessions

Audio and video (A/V) collaboration platforms often use Internet cloud technologies to ensure elasticity. They generally operate on a best‐effort basis, without quality or delivery guarantees. However, such guarantees are a premise of business‐focused platforms, which often rely on static/dedicated infrastructure and hardware‐based components. This article presents results obtained in the final stage of the Elastic Media Distribution (EMD) project, which targets the migration of a business‐focused hardware‐based A/V collaboration tool towards a more elastic, reliable, and secure cloud‐based model. The use case under investigation is an educational scenario: teachers and students located at distributed sites collaborate under different data encryption policies. An existing model of collaboration streaming is extended to accommodate encryption‐enabled streaming components, and new resource allocation heuristics are proposed to deploy these components under stringent service level agreement (SLA) constraints. An extended version of our evaluation framework, based on the CloudSim simulator, manages encryption‐enabled components. A resource usage dataset was obtained by prototyping selected streaming components and evaluating their performance on the Virtual Wall large‐scale test bed. This dataset is fed into the extended simulation framework. Simulation results show longer than expected delays when loading streaming components, an issue that jeopardises the user experience that can be alleviated by the algorithms proposed in this article. Results show that the proposed algorithms enable policy‐based secured communications under bandwidth and virtual machine (VM) cost increases of 48% and 23%, respectively, if compared with a nonencrypted previous solution, and with set‐up times remaining under the required 2‐second deadline.     

Revised Estimates of Dimension and Exercise Variance Components in Assessment Center Postexercise Dimension Ratings.

The authors reanalyzed assessment center (AC) multitrait-multimethod (MTMM) matrices containing correlations among postexercise dimension ratings (PEDRs) reported by F. Lievens and J. M. Conway (2001). Unlike F. Lievens and J. M. Conway, who used a correlated dimension-correlated uniqueness model, we used a different set of confirmatory-factor-analysis-based models (1-dimension-correlated Exercise and 1-dimension-correlated uniqueness models) to estimate dimension and exercise variance components in AC PEDRs. Results of reanalyses suggest that, consistent with previous narrative reviews, exercise variance components dominate over dimension variance components after all. Implications for AC construct validity and possible redirections of research on the validity of ACs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multilevel optimization algorithms in computer aided production control in process industry

The use of optimization techniques in production control is discussed. Two optimization problems in relation to typical process industry complexes are formulated. A modified version of Tamura's algorithm is reviewed. The promising performance of the computerised algorithms is illustrated by numerical results. DISPATCHER, a practical operative decision support system, is described.     

Probing enzyme promiscuity of SGNH hydrolases

Several hydrolases of the SGNH superfamily, including the lipase SrLip from Streptomyces rimosus (Q93MW7), the acyl-CoA thioesterase I TesA from Pseudomonas aeruginosa (Q9HZY8) and the two lipolytic enzymes EstA (from P. aeruginosa, O33407) and EstP (from Pseudomonas putida, Q88QS0), were examined for promiscuity. These enzymes were tested against four chemically different classes of a total of 34 substrates known to be hydrolysed by esterases, thioesterases, lipases, phospholipases, Tweenases and proteases. Furthermore, they were also analysed with respect to their amino acid sequences and structural homology, and their phylogenetic relationship was determined. The Pseudomonas esterases EstA and EstP each have an N-terminal domain with catalytic activity together with a C-terminal autotransporter domain, and so the hybrid enzymes EstA(N)-EstP(C) and EstP(N)-EstA(C) were constructed by swapping the corresponding N- and C-terminal domains, and their hydrolytic activities were compared. Interestingly, substrate specificity and kinetic measurements indicated a significant influence of the autotransporter domains on the catalytic activities of these enzymes in solution. TesA, EstA and EstP were shown to function as esterases with different affinities and catalytic efficacies towards p-nitrophenyl butyrate. Of all the enzymes tested, only SrLip revealed lipase, phospholipase, esterase, thioesterase and Tweenase activities.     

Cadmium and zinc uptake by volunteer willow species and elder rooting in polluted dredged sediment disposal sites

Salix species and Sambucus nigra L. (elder) naturally invade dredged sediment landfills and are commonly encountered on substrates contaminated with heavy metals. Foliar concentrations of Cd and Zn in four Salix species and elder were explored in the field. Metal contents in dredged sediment derived soils were elevated compared to baseline concentration levels reported for Flanders. To evaluate foliar concentrations, reference data were compiled from observations in nurseries, young plantations and unpolluted sites with volunteer willow vegetation. Willows grown on polluted dredged sediment landfills showed elevated foliar Cd and Zn concentrations (>6.6 mg Cd/kg DW and >700 mg Zn/kg DW). This was not the case for elder. For willow, a significant relation was found between soil total Zn or Cd and foliar Zn or Cd, regardless of age, species, or clone. Willows proved to be useful bioindicators. Results indicated a possible threat in long-term habitat development of willow brushwood from transfer of Cd and Zn to the food web.     

The correlation between 1H MRS choline concentrations and MR diffusion trace values in human brain tumors

Objective  The aim of this study was to develop a method for evaluating the spatial distribution of human brain gliomas in individual subjects by evaluating the correlation between the Choline (Cho) signal intensity and the diffusion trace (Tr_ADC) values. Materials and methods  Eleven patients with different histopathologic diagnoses and five healthy subjects were examined with diffusion-weighted EPI-trace sequence and ¹H MR spectroscopic imaging. The calculation of the correlation between choline and Tr_ADC values on a pixel-by-pixel basis and simulations estimating the influence of partial volume effects on the result were performed. Results  Statistical evaluation of the data in the patients with a glioblastoma showed that pixels corresponding to different tissue states are situated in different areas in the Cho–Tr_ADC correlation graph. Namely, points forming an inverse linear dependence interpreted as an area of an active tumor were observed. Different types of correlations were found in grade II and III gliomas. No statistically significant correlation was found in healthy subjects. Simulations proved that the observed linear dependence cannot be attributed solely to partial volume effects. Conclusion  The analysis of the correlation between Cho concentrations and Tr_ADC values on a pixel-by-pixel basis should help the regional identification of the pathological state of a tissue in patients with a glioblastoma.     

Bewertung und Optimierung von dynamischen Dämmsystemen unter Berücksichtigung des Wiener Klimas

In den letzten Jahren fanden immer wieder Anstrengungen statt um den CO₂‐Haushalt der Erdatmosphäre zu senken. Begriffe wie “sparsamer”, “effizienter” oder “effektiver” werden häufig in diesem Zusammenhang verwendet. Auch das Fachgebiet Bauphysik kann einen wesentlichen Beitrag zur Energieeffizienz leisten. Das ist eine berechtigte Forderung, da Gebäudeheizung und Gebäudekühlung einen bedeutenden Anteil am Ausstoß schädlicher Treibhausgase besitzen. Grenzwerte für die U‐Werte werden immer niedriger angesetzt, was dickere und teurere Dämmsysteme zur Folge hat. Neben diesen trivialen Lösungen werden auch komplexere Systeme entwickelt und erprobt. In dieser Untersuchung werden zwei davon genauer betrachtet und bezugnehmend auf den Heiz wärmebedarf sowie den Kühlbedarf gegenüberstellt. Dabei handelt es sich um sogenannte schaltbare Dämmungen, und um ein neues System mit der Bezeichnung “Thermocollect”. Ein Vergleich beider Systeme ist mit Software‐Standardlösungen nicht möglich, da diese mit nichtvariablen Wärmeleitwerten arbeiten, weshalb ein eigenes Simulationsmodell entwickelt werden musste. Zunächst werden im Rahmen einer Einführung beide Systeme vorgestellt. Ein Abschnitt beinhaltet eine Ausführung zum Simulationsmodell und Erläuterungen zu seinen Eigenheiten. Abschließend folgen Ergebnisse von Parameterstudien, eine Interpretation der Ergebnisse sowie Schlussfolgerungen und die Optimierung der neuartigen Dämmsysteme. Evaluation and optimization of switchable insulation using the climatic conditions of Vienna. There have been numerous efforts to reduce CO₂ emissions in recent years. Terms such as ”more economical”, ”more efficient”, and ”more effective” are often used in discussion of this theme. The field of building physics can make a significant contribution to energy efficiency since building heating and cooling produces a significant portion of overall hazardous greenhouse gases. In response, heat transfer coefficient limits are being set lower and lower resulting in thicker and more expensive insulation systems. Very creative systems are being developed and tested parallel to conventional solutions. This study examines and contrasts two of the systems focusing upon the heating and cooling requirements: the so called ”switchable insulation” and a new system called ”Thermocollect”. The systems cannot be compared using standard software programs as the calculations are based on steady‐state thermal conductivities. Therefore, an in‐house simulation model was developed. Both systems are described in the introduction. A presentation of the basic thermodynamic concepts applied in the simulation fol lows. One section contains an explanation of the simulation model and its distinctive properties. The study is concluded by the results of the parametric studies, an interpretation of the results and implications, and engineering optimizations for the new insulation systems.