A supramolecular polymer formed by N,N′,N″-tris(3,7-dimethyloctyl)benzene-1,3,5-tricarboxamide (DO3B) in n-decane (C10) possesses large macro-dipoles naturally generated by three-fold inter-molecular hydrogen bonding aligned along its helical columnar structure connected by defective portions, which are DO3B molecules containing failure in the hydrogen bond formation, in the order of head to tail arrangement without dipole inversion like type-A polymers. 相似文献
Following the success of the First Workshop on the Usage of NetFlow/IPFIX (Pras et al. in J Netw Syst Manag 17(4), 2009) in 2008, the European EMANICS Network of Excellence organized a second workshop
in October 2009, held at Jacobs University Bremen. This report summarizes the workshop and presents its main conclusions. 相似文献
Modern interaction techniques like non-intrusive gestures provide means for interacting with distant displays and smart objects without touching them. We were interested in the effects of feedback modality (auditory, haptic or visual) and its combined effect with input modality on user performance and experience in such interactions. Therefore, we conducted two exploratory experiments where numbers were entered, either by gaze or hand, using gestures composed of four stroke elements (up, down, left and right). In Experiment 1, a simple feedback was given on each stroke during the motor action of gesturing: an audible click, a haptic tap or a visual flash. In Experiment 2, a semantic feedback was given on the final gesture: the executed number was spoken, coded by haptic taps or shown as text. With simultaneous simple feedback in Experiment 1, performance with hand input was slower but more accurate than with gaze input. With semantic feedback in Experiment 2, however, hand input was only slower. Effects of feedback modality were of minor importance; nevertheless, semantic haptic feedback in Experiment 2 showed to be useless at least without extensive training. Error patterns differed between both input modes, but again not dependent on feedback modality. Taken together, the results show that in designing gestural systems, choosing a feedback modality can be given a low priority; it can be chosen according to the task, context and user preferences. 相似文献
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment. 相似文献
Gas-wall partitioning of organic compounds (OC) that included C8–C16n-alkanes and 1-alkenes and C8–C13 2-alcohols and 2-ketones was investigated in two Teflon FEP chambers whose walls were either untreated, oxidized in sunlight, or previously exposed to secondary organic aerosol (SOA). Partitioning was nearly independent of chamber treatment, reversible, and obeyed Henry's law. The fraction of an OC that partitioned to the walls at equilibrium ranged from 0 to ~65%. Values increased with increasing carbon number within an OC class and for OC with similar vapor pressures increased in the order n-alkanes <1-alkenes <2-alcohols <2-ketones. Estimated time constants for achieving partitioning equilibrium ranged from ~60 min for n-alkanes to ?8 min for 2-ketones. The observations are consistent with a sorption mechanism in which OC dissolve into the film but are restricted to the near-surface region by a sharp permeability gradient that develops in response to OC-induced stresses in polymer chains. When the results were analyzed using a model analogous to one commonly employed for gas-particle partitioning, it was estimated that the sorption properties of the chamber walls were equivalent to organic aerosol mass concentrations of 2, 4, 10, and 24 mg m–3 with respect to the partitioning of n-alkanes, 1-alkenes, 2-alcohols, and 2-ketones. These values are up to ~4 orders of magnitude larger than concentrations used in most laboratory studies of SOA, which are typically 1–103μg m–3, meaning that if full partitioning equilibrium is established in the chamber then semi-volatile OC will reside overwhelmingly in the chamber walls. Model simulations of gas-particle-wall partitioning were also carried out using the experimental data, and demonstrate quantitatively the large potential effects of Teflon walls on measured yields of gas-phase OC products and SOA. 相似文献
This study determined the proximate composition and fatty acid profile of the lipid fraction in muscle tissue (fillet) of
seven fish species from the Miranda River, Brazil. Total lipid content had the largest coefficient of variation among species
(73%), while protein content had the smallest (4.5%), allowing Pimelodus argenteus (mandi-prateado) to be categorized as lean fish; Pimelodus maculatus (mandi-amarelo), Hemisorubim platyrhynchos (jurupoca), and Pinirampus pirinampu (barbado) as species with medium fat content, and Paulicea luetkeni (jaú) and Surubim lima (jurupensém) as fatty fish. In all the species investigated, palmitic acid (23.76–25.99%) was the predominant saturated fatty
acid. Oleic acid (16.09–32.90%) was the most abundant monounsaturated fatty acid. Total omega-6 polyunsaturated fatty acids
(5.99–15.56%) were the predominant polyunsaturated fatty acids, except in Ageneiosus brevifilis (palmito), in which total omega-3 polyunsaturated fatty acids predominated (10.30%). All the species had favorable indices
of nutritional quality for total lipids, with respect to human consumption. 相似文献
Understanding the driving forces that generate emerging topics (ETs or Emerging Research Topics) will assist in the sound development of science and technologies. In the present study, we aim to clarify the researcher dynamics of generating and developing ETs in life sciences and medicine over the past half-century by analyzing the pre-, contemporary-, and post-participation of researchers publishing articles containing the emerging keywords that are elements of ETs. Our results suggest that, while manpower needs for publication have increased, less manpower is actually required to generate ETs these days and that pre-participation in certain research topics has become important to generate regular ETs but not Nobel Prize-class ones. Finally, we discovered that, in this post-genomic era, those researchers who generate ETs also continue to focus on those fields. These trends illustrate a mode shift in the scientific practice of researchers that have generated and developed ETs over the last 50 years as well as highlight the significance of funding projects with high probabilities of generating high-impact ETs.
Come together right now with L ‐DOPA : Chemical cross‐linking is widely used to study protein–protein interactions. However, many cross‐linking agents suffer from low reactivity or selectivity. An efficient and selective reaction of site‐specific protein cross‐linking was achieved using genetically incorporated 3,4‐dihydroxy‐L ‐phenylalanine.