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A common problem in ecology is identifying the relationship between relief and site properties obtainable only by point measurements. The method of Multi-Scale Landscape Analysis (MSLA) identifies such correlations. MSLA combines frequency filtering of the digital elevation model (DEM) with an estimation of the optimum filter coefficients using an optimization procedure. Tested using point data of soil decarbonation from a German young moraine landscape, MSLA provided significant results. Implemented within open source software SAMT. MSLA is comfortable and flexible to use, offering applications for numerous other spatial analysis problems.
This study monitors regional changes in the crystallinity of carbonaceous matter (CM) by applying Micro-Raman spectroscopy to a total of 214 metasediment samples (largely so-called Bundnerschiefer) dominantly metamorphosed under blueschist- to amphibolite-facies conditions. They were collected within the northeastern margin of the Lepontine dome and easterly adjacent areas of the Swiss Central Alps. Three-dimensional mapping of isotemperature contours in map and profile views shows that the isotemperature contours associated with the Miocene Barrow-type Lepontine metamorphic event cut across refolded nappe contacts, both along and across strike within the northeastern margin of the Lepontine dome and adjacent areas. Further to the northeast, the isotemperature contours reflect temperatures reached during the Late Eocene subduction-related blueschist-facies event and/or during subsequent near-isothermal decompression; these contours appear folded by younger, large-scale post-nappe-stacking folds. A substantial jump in the recorded maximum temperatures across the tectonic contact between the frontal Adula nappe complex and surrounding metasediments indicates that this contact accommodated differential tectonic movement of the Adula nappe with respect to the enveloping Bundnerschiefer after maximum temperatures were reached within the northern Adula nappe, i.e. after Late Eocene time.
Vorwort
(2011)
Fraenkel, E., Der Doppelstaat, Recht und Justiz im Dritten Reich; Frankfurt am Main, Fischer, 1984
(2011)
Wiedergelesen
(2011)
Seit 2008 ergänzt die sowohl kleine als auch feine Rubrik "Wiedergelesen" die Ausgaben des außenpolitischen Fachjournals WeltTrends. Berühmte Bücher der Politologie und schätzenswerte Raritäten werden für die Füllung dieser Rubrik aus Bücherregalen herausgefischt, abgestaubt und in aktuellem Interesse gelesen - wieder gelesen. Stets ist es das Anliegen, die Schriften sowohl aus ihrer Zeit zu verstehen als auch für unsere Zeit nutzbar zu machen - z. B. Huntingtons The Clash of Civilizations, Lipsets Political Man, Paines Die Rechte des Menschen oder An Authoritarian Regime: The Case of Spain von Linz.
Behemoth und Doppelstaat
(2011)
Wer bildete das Herrschaftszentrum im Deutschland der Jahre 1933 bis 1945? Welche Gruppen stabilisierten das System bis zur Niederlage im Zweiten Weltkrieg? Ernst Fraenkels "Der Doppelstaat" und Franz Neumanns "Behemoth" gelten als wegweisende analytische Zugänge zum Verständnis der nationalsozialistischen Herrschaftspraxis. Beide Bücher sind bereits Anfang der 1940er Jahre erschienen. Es sind Klassiker: also Bücher, mit denen noch heute etwas anzufangen ist. Der kompakte Lehrtext ist insbesondere für den studentischen Haus- und Seminargebrauch verfasst worden. Er ist eine Handreichung für Einsteiger und Studierende aller Semester, die sich erstmals mit den schwierigen Texten beschäftigen
Kennen Sie Randegg?
(2011)
Seit seiner berühmt-berüchtigten Friedenspreisrede von 1998 nimmt die Anzahl der literaturwissenschaftlichen und -politischen Publikationen, die Martin Walsers Werk eine nationalistische und antisemitische Tendenz unterstellen, zu. Bisweilen wird behauptet, Walser suche über die Ausschließung des Jüdischen das Nationale zu stärken und postuliere die Unversöhnlichkeit von Tätergemeinschaft und Opfergemeinschaft nach 1945. Das bislang in der Forschung wenig beachtete Hörspiel „Das Gespenst von Gattnau“ lässt die Annahme einer anderen Tendenz zu: die Tendenz zur Versöhnung.
The East African Plateau provides a spectacular example of geodynamic plateau uplift, active continental rifting, and associated climatic forcing. It is an integral part of the East African Rift System and has an average elevation of approximately 1,000 m. Its location coincides with a negative Bouguer gravity anomaly with a semi-circular shape, closely related to a mantle plume, which influences the Cenozoic crustal development since its impingement in Eocene-Oligocene time. The uplift of the East African Plateau, preceding volcanism, and rifting formed an important orographic barrier and tectonically controlled environment, which is profoundly influenced by climate driven processes. Its location within the equatorial realm supports recently proposed hypotheses, that topographic changes in this region must be considered as the dominant forcing factor influencing atmospheric circulation patterns and rainfall distribution. The uplift of this region has therefore often been associated with fundamental climatic and environmental changes in East Africa and adjacent regions. While the far-reaching influence of the plateau uplift is widely accepted, the timing and the magnitude of the uplift are ambiguous and are still subject to ongoing discussion. This dilemma stems from the lack of datable, geomorphically meaningful reference horizons that could record surface uplift. In order to quantify the amount of plateau uplift and to find evidence for the existence of significant relief along the East African Plateau prior to rifting, I analyzed and modeled one of the longest terrestrial lava flows; the 300-km-long Yatta phonolite flow in Kenya. This lava flow is 13.5 Ma old and originated in the region that now corresponds to the eastern rift shoulders. The phonolitic flow utilized an old riverbed that once drained the eastern flank of the plateau. Due to differential erosion this lava flow now forms a positive relief above the parallel-flowing Athi River, which is mimicking the course of the paleo-river. My approach is a lava-flow modeling, based on an improved composition and temperature dependent method to parameterize the flow of an arbitrary lava in a rectangular-shaped channel. The essential growth pattern is described by a one-dimensional model, in which Newtonian rheological flow advance is governed by the development of viscosity and/or velocity in the internal parts of the lava-flow front. Comparing assessments of different magma compositions reveal that length-dominated, channelized lava flows are characterized by high effusion rates, rapid emplacement under approximately isothermal conditions, and laminar flow. By integrating the Yatta lava flow dimensions and the covered paleo-topography (slope angle) into the model, I was able to determine the pre-rift topography of the East African Plateau. The modeling results yield a pre-rift slope of at least 0.2°, suggesting that the lava flow must have originated at a minimum elevation of 1,400 m. Hence, high topography in the region of the present-day Kenya Rift must have existed by at least 13.5 Ma. This inferred mid-Miocene uplift coincides with the two-step expansion of grasslands, as well as important radiation and speciation events in tropical Africa. Accordingly, the combination of my results regarding the Yatta lava flow emplacement history, its location, and its morphologic character, validates it as a suitable “paleo-tiltmeter” and has thus to be considered as an important topographic and volcanic feature for the topographic evolution in East Africa.
A new class of fluorescent dyes based on 1,3-benzodioxole and [1,3]-dioxolo[4.5-f]benzodioxole
(2011)
We report on synthesis and photophysical properties of a new class of fluorescent dyes. They are characterized by large Stokes-shifts, long fluorescence lifetimes in organic solvents and a pronounced dependency of the fluorescence lifetime on the solvent polarity. Also worthy of note is the high bleaching stability. To provide access to biochemical and medical applications a series of derivatives were prepared, which exhibit specific reactivity towards different biologically relevant functional groups (carboxylic acids, amines, maleimides, N-hydroxysuccinimide esters). Furthermore, two alkynes were prepared, which could be used in 'Click' chemistry.
A new concept of a stereoselective synthesis of axially chiral biaryls, formed in the course of the dehydro-Diels-Alder (DDA) reaction, has been disclosed. It is based on asymmetric induction of the newly formed chirality axis by a chirality center, which is present in the two synthesized DDA reactants. Depending on the different length of the linkers joining the alkyne moieties the DDA reaction may be triggered photochemically or thermally, where only the thermal variant was stereoselective.
Five alkynyl pyridines were prepared and cyclized to naphthylpyridines as the main products in the course of a Photo-Dehydro-Diels-Alder reaction. Four of the final products are axially chiral and the determination of the rotational barrier by DFT calculations, dynamic NMR and H PLC experiments is demonstrated. (C) 2011 Elsevier B.V. All rights reserved.
The photo-dehydro-Diels-Alder (PDDA) reaction is a valuable extension of the classical Diels-Alder (DA) reaction. The PDDA reaction differs from the DA reaction by the replacement of one of the C-C-double bonds of the diene moiety by a C-C triple bond and by the photochemical triggering of the reaction. This entails that, in contrast to the DA reaction, the PDDA reaction proceeds according to a multistage mechanism with biradicals and cycloallenes as intermediates. The PDDA reaction provides access to a considerable variety of compound classes. For example, 1-phenylnaphthlenes, 1,1'-binaphthyls, N-heterocyclic biaryls, and naphthalenophanes could be obtained by this reaction.
Preparation of Strained Axially Chiral (1,5)Naphthalenophanes by Photo-dehydro-Diels-Alder Reaction
(2011)
The preparation of 10 (1,5)naphthalenophanes (10a-j) by photo-dehydro-Diels-Alder (PDDA) reaction is described. Owing to hindered rotation around the biaryl axis, compounds 10 are axially chiral and the separation of enantiomers by chiral HPLC was demonstrated in three cases (10a,b,e). The absolute configuration of the isolated enantiomers could be unambiguously determined by comparison of calculated and measured circular dichroism (CD) spectra. Furthermore, we analyzed ring strain phenomena of (1,5)naphthalenophanes 10. Depending on the length of the linker units, one can distinguish three classes of naphthalenophanes. Compounds 10a-c are highly strained (E-STR = 7-31 kcal/mol), and the strain is caused by small bond angles in the linker unit and deformation of the naphthalene moiety. Another type of strain is observed if the linker unit becomes relatively long (10g,h) originating from transannular interactions and is comparable with the well-known strain of medium sized rings. The naphthalenophanes 10d-f with a linker length of 10-14 atoms are only marginally strained. To clearly discriminate the different sources of strain, we defined two geometrical parameters (average central dihedral angle delta(C) and naphthalene thickness D-N) and demonstrated that they are well-suited to indicate naphthalene deformation of our naphthalenophanes 10 as well as of ten model naphthalenophanes (I-X) with different linker lengths and linking positions.
This article deals with the claim that the MAGNITUDE ESTIMATION (ME) method of gathering acceptability judgments produces data that are more informative for linguists than binary or n-point scale judgments. We performed three acceptability-rating experiments that directly compared ME data to binary and seven-point scale data. The results clearly falsify the hypothesis that data gathered by the ME method carry a larger amount of information about the acceptability of a given linguistic phenomenon. The three measures are largely equivalent with respect to informativity. Moreover, ME judgments are shown to be more liable to producing spurious variance under certain circumstances.*
In der vorliegenden Arbeit analysiert Yann Wernert die Rolle der Afrikanischen Union im Rahmen von Regionalkonflikten in Afrika. Dabei wird insbesondere Wert auf die konkrete Vorgehensweise der Afrikanischen Union in den jeweiligen Konflikten gelegt. Untersucht wird der Bürgerkrieg in Somalia sowie die Versuche seitens der internationalen Gemeinschaft, eine stabile politische Ordnung wieder aufzubauen. Ebenfalls analysiert wird der Darfur-Konflikt im Sudan und die Möglichkeiten, den regelmäßig stattfindenden Massakern Einhalt zu gebieten. Der Untersuchungszeitraum erstreckt sich von 2003 bis 2007.
Objectives: Stroke, frequently a consequence of hypertension, is one of the leading causes of death and neurological disabilities worldwide. In the ischemic brain, levels of endothelin-1, one of the most potent vasoconstrictors, are raised. Anti-inflammatory and neuroprotective effects of endothelin antagonists after stroke have been described in literature. Based on these findings, we investigated the protective effect of the endothelin converting enzyme/neutral endopeptidase blocker, SLV 338, in salt-loaded, stroke-prone, spontaneously hypertensive rats.
Methods: Male, 8-week-old spontaneously hypertensive stroke-prone rats were put on a high salt diet and treated with either 30 mg/kg or 100 mg/kg SLV 338 or vehicle for 27 weeks. Blood pressure, neurological outcome, body weight, and mortality were investigated throughout treatment. In weeks 1 and 9, animals were housed in metabolic cages for collection of urinary and blood samples and assessment of salt water and food intake. In weeks 22 and 27, additional blood samples were taken. At the end of the study, all brains were analyzed using magnetic resonance imaging.
Results: SLV 338 was well tolerated in all animals. Neurological outcome and infarct size were similar in all groups. Albuminuria was considerably delayed and the incidence of stroke significantly lowered in treated animals. In spontaneously hypertensive stroke-prone rats, treatment with SLV 338 significantly (P=0.01) improved survival in comparison to the vehicle treated group in a blood pressure-independent manner.
Discussion: Our data in spontaneously hypertensive stroke-prone rats demonstrate that combined endothelin converting enzyme/neutral endopeptidase inhibition could offer a new therapeutic approach for primary stroke prevention and improvement of mortality. The mechanism seems to be blood pressure-independent.
Die Arbeit beschreibt die humanistische Reform des 'Triviums', also der grammatischen, dialektischen (logisch-argumentativen) und rhetorischen Ausbildung, wie sie sich in dem Zeitraum von 1480 bis 1540 an Schulen und Universitäten durchsetzte. Die Arbeit ist dabei sowohl historisch wie systematisch angelegt, indem sie die Lehrinhalte der jeweiligen Kunst an ausgewählten Lehrbüchern darstellt, gleichzeitig aber unter ständigem Rückbezug auf die scholastisch-mittelalterliche Tradition die humanistischen Neuerungen davon abgrenzt. Im Zentrum stehen Werke von Lorenzo Valla, Rudolf Agricola, Erasmus, Juan Luis Vives und Philipp Melanchthon. Es stellt sich dabei heraus, daß die humanistischen Neuerungen in erster Linie die Praxisbezogenheit des Triviums betreffen, erst aus dieser ergeben sich dann die inhaltlichen Neuerungen. Unter Praxisbezogenheit ist dabei sowohl die Ableitung von Grammatik, Dialektik und Rhetorik aus der Beobachtung ihrer immer schon vorgängigen Anwendung zu verstehen, als auch ihre Anwendung zum Zweck der sprachlichen, argumentativ-logischen und rhetorischen Analyse. D.h. das grammatische, dialektische und rhetorische Regelwerk wird auf deskriptivem Wege gewonnen, um wiederum in der Analyse auf die Praxis zurückgewendet zu werden. Dieser Analyse werden dabei von alltäglichen Äußerungen, politischen, religiösen oder sonstigen sachlichen Texten bis hin zu literarischen Werken alles unterzogen. In einem letzten Teil stellt die Arbeit drei solcher Analysen vor und versucht sich schließlich selbst an einer dialektisch-rhetorischen Analyse dreier dramatischer Bearbeitungen der Parabel vom verlorenen Sohn.
Der Aufsatz zeigt, dass es sich bei der averroischen Bearbeitung der aristotelischen ‚Poetik‘ um eine in sich konsistente Theorie der Dichtung handelt, die allerdings mit der aristotelischen Konzeption der Dichtung nur wenig zu tun hat. Ausgehend von der Übersetzung von ‚Tragödie‘ und ‚Komödie‘ mit ‚Lob‘ und ‚Tadel‘ entwickelt Averroes einen Begriff von Dichtung als moralphilosophisches Argument zum Lob der Tugend und zum Tadel des Lasters. Im Mittelpunkt steht die Interpretation des aristotelischen Begriffs der mimesis als similitudo, das heißt als Gleichnis. Als gleichnishaftes Argument ist Dichtung nur graduell von anderen argumentativen Formen wie der demonstrativen Logik und der Rhetorik unterschieden.
Der Aufsatz umreißt die Wirkung von Averroes’ Bearbeitung der aristotelischen ‚Poetik‘ als argumentativer Disziplin. Beginnend mit Al-Farabi und Al-Gazali im zehnten Jahrhundert wird die ‚Poetik‘ den logischen Disziplinen des ‚Organon‘ zugerechnet. Während die Theorie eines ‚poetischen Syllogismus‘ nicht rezipiert worden ist, wurde der argumentative Status der Dichtung vom zwölften Jahrhundert an auch im lateinischen Westen bekannt. Mit unterschiedlichen Begründungen übernahmen Dominicus Gundissalinus, Vincenz von Beauvais, Albertus Magnus, Roger Bacon und Thomas von Aquin die Klassifizierung der Poetik als argumentative Disziplin. Am Ende des Aufsatzes steht ein Ausblick auf Coluccio Salutatis ‚De laboribus Herculis‘ und die humanistische Rezeption dieser Tradition.
Der Aufsatz zeigt, dass es sich bei der averroischen Bearbeitung der aristotelischen ‚Poetik‘ um eine in sich konsistente Theorie der Dichtung handelt, die allerdings mit der aristotelischen Konzeption der Dichtung nur wenig zu tun hat. Ausgehend von der Übersetzung von ‚Tragödie‘ und ‚Komödie‘ mit ‚Lob‘ und ‚Tadel‘ entwickelt Averroes einen Begriff von Dichtung als moralphilosophisches Argument zum Lob der Tugend und zum Tadel des Lasters. Im Mittelpunkt steht die Interpretation des aristotelischen Begriffs der mimesis als similitudo, das heißt als Gleichnis. Als gleichnishaftes Argument ist Dichtung nur graduell von anderen argumentativen Formen wie der demonstrativen Logik und der Rhetorik unterschieden.
Der Aufsatz umreißt die Wirkung von Averroes’ Bearbeitung der aristotelischen ‚Poetik‘ als argumentativer Disziplin. Beginnend mit Al-Farabi und Al-Gazali im zehnten Jahrhundert wird die ‚Poetik‘ den logischen Disziplinen des ‚Organon‘ zugerechnet. Während die Theorie eines ‚poetischen Syllogismus‘ nicht rezipiert worden ist, wurde der argumentative Status der Dichtung vom zwölften Jahrhundert an auch im lateinischen Westen bekannt. Mit unterschiedlichen Begründungen übernahmen Dominicus Gundissalinus, Vincenz von Beauvais, Albertus Magnus, Roger Bacon und Thomas von Aquin die Klassifizierung der Poetik als argumentative Disziplin. Am Ende des Aufsatzes steht ein Ausblick auf Coluccio Salutatis ‚De laboribus Herculis‘ und die humanistische Rezeption dieser Tradition.
The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris is of great interest because of its ability to catalyze the hydrolysis of highly toxic organophosphates. In this work, the enzyme structure in solution (native state) was studied by use of different scattering methods. The results are compared with those from hydrodynamic model calculations based on the DFPase crystal structure. Bicontinuous microemulsions made of sugar surfactants are discussed as host systems for the DFPase. The microemulsion remains stable in the presence of the enzyme, which is shown by means of scattering experiments. Moreover, activity assays reveal that the DFPase still has high activity in this complex reaction medium. To complement the scattering experiments cryo-SEM was also employed to study the microemulsion structure.
Der Band enthält die Vorträge einer Konferenz vom November 2009 in Potsdam. Die Texte untersuchen anhand ausgewählter Beispiele die Entwicklungen der zurückliegenden zwanzig Jahre im Zivilrecht, Strafrecht und öffentlichen Recht. Die Bundesrepublik Deutschland sieht sich seit der Wiedervereinigung und dem Ende des Kalten Krieges in einer ganz neuen Situation. Dies gilt für den völkerrechtlichen Rahmen ihrer Außenpolitik, für den Wettbewerb der Rechtsordnungen, für die mit erhöhter Dynamik fortschreitende europäische Einigung und ihre Konsequenzen. Die bei der Grundrechtsinterpretation im Mehrebenensystem auftauchenden Divergenzen und die Auswirkungen technischer Neuerungen auf das Sozialverhalten prägen Rechtswirklichkeit und Rechtsdogmatik.
In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.
Microviridins are unique protease inhibitors from bloom-forming cyanobacteria that have both ecological and pharmacological relevance. Their peptide backbones are produced ribosomally, and ATP grasp ligases introduce omega-ester and omega-amide bonds to yield rare cage-like structures. Bioinformatic analysis of the microviridin biosynthesis gene cluster suggests a novel type of processing machinery, which could rationalize the challenging in vivo/in vitro reconstitution of the pathway. In this work, we report the establishment of a minimal expression system for microviridins. Through bioinformatics and mutational analysis of the MdnA leader peptide we identified and characterized a strictly conserved binding motif that is specific for microviridin ligases. Furthermore, we showed that the ABC transporter MdnE is crucial for cyclization and processing of microviridins and demonstrated that MdnE is essential for stability of the microviridin biosynthesis complex.
It is currently controversially discussed if the same freshwater microorganisms occur worldwide wherever their required habitats are realized, i.e., without any adaptation to local conditions below the species level. We performed laboratory experiments with flagellates and ciliates from three acidic mining lakes (AML, pH similar to 2.7) to investigate if similar habitats may affect similar organisms differently. Such man-made lakes provide suitable ecosystem models to test for the significance of strong habitat selection. To this end, we analyzed the growth response of three protist taxa (three strains of the phytoflagellate Chlamydomonas acidophila, two isolates of the phytoflagellate Ochromonas and two species of the ciliate genus Oxytricha) by exposing them to lake water of their origin and from the two other AML in a cross-factorial design. Population growth rates were measured as a proxy for their fitness. Results revealed significant effects of strain, lake (= habitat), and strain X habitat interaction. In the environmentally most adverse AML, all three protist taxa were locally adapted. In conclusion, our study demonstrates that (1) the same habitat may affect strains of the same species differently and that (2) similar habitats may harbor ecophysiologically different strains or species. These results contradict the 'everything is everywhere' paradigm.
Temperature-induced self-assembly of triple-responsive triblock copolymers in aqueous solutions
(2011)
A series of triple-thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (PNPAM, A), poly(methoxydiethylene glycol acrylate) (PMDEGA, B), and poly(N-ethylacrylamide) (PNEAM, C) was synthesized by sequential reversible addition-fragmentation chain transfer polymerizations. Polymers of differing block sequences, ABC, BAC, and ACB, with increasing phase transition temperatures in the order A < B < C were prepared. Their aggregation behavior in dilute aqueous solution was investigated using dynamic light scattering, turbidimetry, and NMR spectroscopy. The self-organization of such polymers was found to dependent strongly on the block sequence. While polymers with a terminal low-LCST (lower critical solution temperature) block undergo aggregation above the first phase transition temperature at 20-25 degrees C, triblock copolymers with the low-LCST block in the middle show aggregation only above the second phase transition. The collapse of the middle block is not sufficient to induce aggregation but produces instead stable, unimolecular micelles with a collapsed middle block, as supported by NMR and fluorescence probe data. Continued heating of all copolymers led to two additional thermal transitions at 40-55 and 70-80 degrees C, which could be correlated to the phase transitions of the B and C blocks, respectively. All polymers show a high tendency for cluster formation, once aggregation is induced. The carrier abilities of the triple responsive triblock copolymers for hydrophobic agents were probed with the solvatochromic fluorescence dye Nile Red. With passing through the first thermal transition, the block copolymers are capable of solubilizing Nile Red. In the case of block copolymers with sequences ABC or ACB, which bear the low-LCST block at one terminus, notable amounts of dye are solubilized already at this stage. In contrast, the hydrophobic probe is much less efficiently incorporated by the BAC triblock copolymer, which forms unimolecular micelles. Only after the collapse of the B block, when reaching the second phase transition at about 45 degrees C, does aggregation occur and solubilization becomes efficient. In the case of ABC and ACB polymers, the hydrophobic probe seems to partition between the originally collapsed A chains and the additional hydrophobic chains formed after the collapse of the less hydrophobic B block.
A set of double thermoresponsive diblock copolymers poly(N-n-propylacrylamide)-block-poly(N-ethylacrylamide) (PNPAM-b-PNEAM) was synthesised by sequential reversible addition-fragmentation chain transfer (RAFT) polymerisations. Using a twofold trimethylsilyl (TMS)-labeled RAFT-agent, the relative size of the two blocks was varied. While soluble as unimers below 15 degrees C, all copolymers exhibited thermally induced two-step self-assembly in water, due to distinct lower critical solution temperature (LCST) phase transitions of PNPAM (around 20 degrees C) and PNEAM (around 70 degrees C). Their temperature-dependent self-organisation in dilute aqueous solution was studied by turbidimetry, dynamic light scattering, transmission electron microscopy, and (1)H NMR spectroscopy. The copolymers show distinct, two-step self-organisation behaviour with respect to transition temperatures, aggregate type and size, which can be correlated to the relative lengths of the low and high LCST blocks. For polymers having short blocks with low LCST, the first thermal transition induces the formation of individual micelles. Further heating above the second thermal transition results reversibly either in a shrink of the micelle size or in aggregation of the micelles, with hydrodynamic diameters below 250 nm. In contrast in the case of polymers having a long block with low LCST, the first thermal transition already leads to clusters of micelles, while the second thermal transition makes the clusters shrink. Noteworthy, the twofold TMS-labeled end groups report not only on the molar masses of the polymers, but can simultaneously serve as NMR-probes for the self-assembly process. The signal of the TMS-aryl end group displays a reversible temperature dependent, two-step splitting that is indicative of the self-organisation of the block copolymers.
We propose a novel strategy for global sensitivity analysis of ordinary differential equations. It is based on an error-controlled solution of the partial differential equation (PDE) that describes the evolution of the probability density function associated with the input uncertainty/variability. The density yields a more accurate estimate of the output uncertainty/variability, where not only some observables (such as mean and variance) but also structural properties (e.g., skewness, heavy tails, bi-modality) can be resolved up to a selected accuracy. For the adaptive solution of the PDE Cauchy problem we use the Rothe method with multiplicative error correction, which was originally developed for the solution of parabolic PDEs. We show that, unlike in parabolic problems, conservation properties necessitate a coupling of temporal and spatial accuracy to avoid accumulation of spatial approximation errors over time. We provide convergence conditions for the numerical scheme and suggest an implementation using approximate approximations for spatial discretization to efficiently resolve the coupling of temporal and spatial accuracy. The performance of the method is studied by means of low-dimensional case studies. The favorable properties of the spatial discretization technique suggest that this may be the starting point for an error-controlled sensitivity analysis in higher dimensions.
Die Konsequenzen des Grollens in der arabischen Welt seit Anfang 2011 werden sich möglicherweise als weniger hilfreich für die Lösung des Nahostkonflikts erweisen als erhofft. Zumindest auf kurze Sicht hat sich die Nachbarschaft Israels in einen noch unberechenbareren und instabileren Ort verwandelt. Israel würde die Entstehung guten und repräsentativen Regierens in der arabischen Welt willkommen heißen. Doch sind die weiteren Entwicklungen in der Region kaum abzuschätzen.