Catanionic surfactants in polar cohesive solvents. Impact of solvent physical parameters on their aggregation behavior

On trouve peu d'études, dans la littérature, sur les tensioactifs (TA) catanioniques - formés d'une paire d'ions entre un TA anionique et un TA cationique - en milieu nonaqueux. Nous avons voulu rationaliser, dans ce travail, le comportement d'agr´egation de ce type de tensioactifs en les étudiant comparativement dans l'eau, dans le formamide, dans le glycérol et dans des mélanges de ces solvants polaires et cohésifs. Nous avons pour ce faire synthétis´e trois différents types de TA catanioniques (alcanoate d'alkylammonium, tétradécanoate de norbornène méthylène ammonium, alcanoate de N-alkylammonium-1-d´eoxy-D-glucitol). Les TA catanioniques ont la propriété de s'agréger en vésicules dans l'eau. Dans le cas des autres solvants ou mélanges des solvants, nous avons constat que le type d'agrégat que forment les TA catanioniques dépend de deux principaux facteurs : la constante diélectrique du solvant et le degré d'interaction entre les deux TA. En effet, le formamide ayant une constante diélectrique plus élevée que l'eau, il exerce une force dissociative sur la paire d'ions qui peut ainsi être séparée pour conduire `a un mélange de TA ioniques monocaténaires formant alors des micelles. D'autre part, une augmentation de l'effet hydrophobe, obtenu en utilisant des chaînes hydrophobes plus longues, renforce la paire d'ions et conduit `a la formation de vésicules dans le formamide pur. Par ailleurs, l'étude du système tétradécanoate de norbornène méthylène ammonium a également montré l'importance des interactions hydrophobes entre les têtes polaires, un autre facteur pouvant favoriser la formation de vésicules dans le formamide pur.In the literature, little work has been done on catanionic surfactants in non-aqueous solution. Catanionic surfactants are ion pairs composed of an anionic and a cationic surfactant. In the frame of this work, we wanted to rationalize the aggregation behavior of this surfactant type by studying them in water, in formamide, in glycerol and in some mixtures of these polar and cohesive solvents. For this issue, we synthesized three different types of catanionic surfactants (alkylammonium alkanoate, norbornene methyleneammonium tetradecanoate, N-alkylammonium-1-deoxy-D-glucitol alkanoate). Catanionic surfactants usually form vesicles in water. In the case of non-aqueous solvents and mixtures of solvents, we could observe that the type of aggregates formed with catanionic surfactants depends on two major factors: the dielectric constant of the solvent and the degree of interaction between the two surfactants. Effectively, formamide having a higher dielectric constant than water exerts a dissociative force on the ion pair. The ion pair can be separated leading to a mixture of monocatenar ionic surfactants, which then forms micelles. On the other hand, hydrophobic effects can be increased using longer hydrophobic chains, which reinforce the ion pair and lead to the formation of vesicles in pure formamide. Moreover, the study on the norbornene methyleneammonium tetradecanoate showed the importance of hydrophobic headgroup-headgroup interactions, an additional parameter which can favor vesicle formation in pure formamide

Implementation des ATKIS in GIS mit relationaler Attributverwaltung unter dem Aspekt der Fortführung

Das Amtliche Topographisch-Kartographische Informationssystem (ATKIS) ist ein Vorhaben der Landesvermessungsverwaltungen der Bundesrepublik Deutschland zum Aufbau digitaler Landschaftmodelle (DLM) und digitaler Kartenmodelle (DKM). In der Arbeit werden zunächst die Grundideen von ATKIS und von temporalen Datenmodellen dargestellt. Auf Grund einer Analyse des ATKIS-Objektartenkatalogs wurde ein Metainformationssystem DST entwickelt und mit Unterstützung des Instituts für Angewandte Geodäsie / Außenstelle Leipzig (IfAG) praktisch eingeführt. Weiterhin wurden Vorschläge für temporale Erweiterungen des DLM unterbreitet, die insbesondere die Gewinnung inkrementeller Fortführungsinformationen unterstützen

Passive microrheology as a useful tool for milk gel analyses

Passive microrheology based on Diffusing Wave Spectroscopy (DWS) [1,2] is presented as a straightforward tool for the analysis of milk gel preparation. Diffusing Wave Spectroscopy consists of analysing the interferential images of light, which is backscattered by the sample. This so called speckles images, which are detected by a CCD camera, change in time due to the Brownian motion of the particles that scatter the light. The variation of the images as a function of time can be directly correlated to the viscoelastic properties of the sample. As it is an optical method, it is perfectly adapted to study the weak gels of milk products. Nowadays, milk gels such as yogurts or chees have attracted lots of interest due to its growing market. The milk properties, such as pH, calcium content and protein content are very important and change significantly the cheese properties. This work shows how passive microrheology can be used to follow up the milk gel formation with exact gel time determination. Gel time was determined by a new rescaling method, namely Time-Cure Superposition (TCS) [3,4]. This data processing determines the gel point according to the Winter-Chambon criterion [5]. Moreover, the viscoelastic properties of the preparation can be compared according to parameters, such as the protein enrichment, calcium ion addition or others. Results were compared to other instruments (texturometers, rheometer, Optigraph®, etc.). References: [1] D. A. Weitz et al., in Dynamic Light Scattering, W. Brown (Ed.) (Oxford Univ. Press, New York (1993), Chap. 16. [2] D. J. Pine et al., Phys. Rev. Lett. 1988, 60, 1434. [3] T. H. Larsen, E. M. Furst, Phys. Rev. Letters, 2008, 100, 14600 [4] K. M. Schultz, E. M. Furst, Soft Matter, 2012, 8, 6198 [5] H. H. Winter, F. Chambon, J. Rheology 1986, 30, 364-38

Adaptive Guideline-based Treatment Workflows with AdaptFlow

One goal in modern medicine is to increase the treatment quality. A major step towards this aim is to support the execution of standardized, guideline-based clinical protocols, which are used in many medical domains, e.g., for oncological chemotherapies. Standardized chemotherapy protocols contain detailed and structured therapy plans describing the single therapy steps (e.g., examinations or drug applications). Therefore, workflow management systems offer good support for these processes. However, the treatment of a particular patient often requires modifications due to unexpected infections, toxicities, or social factors. The modifications are described in the treatment protocol but not as part of the standard process. To be able to further execute the therapy workflows in case of exceptions running workflows have to be adapted dynamically. Furthermore, the physician should be supported by automated exception detection and decision support for derivation of necessary modifications. The AdaptFlow prototype offers the required support for the field of oncological chemotherapies by enhancing a workflow system with dynamic workflow adaptation and rule based decision support for exception detection and handling

Metabolism of the dihydropyridine calcium channel blockers mebudipine and dibudipine by isolated rat hepatocytes

The prototype 1,4-dihydropyridine (1,4-DHP) nifedipine, indicated for the management of hypertension and angina pectoris, has drawbacks of rapid onset of vasodilating action and a short half-life. Several newer analogues have been designed to offset these problems and these include mebudipine and dibudipine. These analogues contain t-butyl substituents that have been selected to alter the fast metabolism without altering pharmacological activity. In this study, the metabolism of mebudipine and dibudipine by isolated rat hepatocytes has been investigated. These compounds were extensively metabolized in 2 h by oxidative pathways, analogous to those known for nifedipine, and by O-glucuronidation after hydroxylation of the t-butyl substituents. The in-vitro half-lives of mebudipine (22 ± 7.1 min) and dibudipine (40 ± 9.8 min) were significantly longer than that of nifedipine (5.5 ± 1.1 min), which was investigated in parallel in this study. These newer 1,4-DHPs address the problem of the short half-life of nifedipine and have potential for further development in view of their comparable potency to nifedipine

Prediction of collapse time of polymer stabilized O/W emulsions

Polymers are widely used in the industry as an ingredient to increase the stability of formulations. Depending on their concentration, they can act as depletion agents or gel agent. The stability of these systems is driven by the polymers and the structure of the network of droplets and can lead to collapse of the emulsions. In this work, Multiple Light Scattering device is used to monitor the behaviour of w/o emulsions stabilized with polymers. The heart of the optical scanning analyser is a detection head, which moves up and down along a flat-bottomed cylindrical glass cell (see figure). The detection head is composed of a pulsed near infrared light source (wavelength = 880 nm) and two synchronous detectors. The transmission detector (at 180°) receives the light, which goes through the sample, while the backscattering detector (at 45°) receives the light scattered backward by the sample. The detection head scans the entire height of the sample, acquiring transmission and backscattering data every 40 µm. Please click Additional Files below to see the full abstract

Improved combined working organ for excavation of root crops

У статті наведено загальний аналіз конструктивно-компонувальних схем викопуючих робочих органів, які призначені для викопування коренеплодів, і основні положення функціонування технологічних процесів копачів, які найбільш широко застосовуються в сучасних коренезбиральних машинах. Вказано основні недоліки процесу викопування та наведено тенденції покращення і підвищення експлуатаційно-технологічних показників роботи коренезбиральних машин шляхом удосконалення та застосування адаптивного робочого органу комбінованого типу.The global analysis of design-layout charts of digging up workers of organs, which are intended for excavation of root crops substantive provisions of functioning of technological processes of to dig which are most widely used in modern root crop machines, is resulted in the article. The basic lacks of process of excavation are indicated and resulted the tendencies of improvement and increase of operating-technological indexes of work of root crop machines by the improvement and application of adaptive worker of organ of the combined type

Flexible, protokollbasierte Therapie auf Basis adaptiver Workflows

Viele medizinische Therapien basieren auf standardisierten Protokollen, z.B. Chemotherapien in der Onkologie. Die darin festgelegten Behandlungsprozesse sind stark strukturiert und sehr detailliert formuliert. So werden in typischen Chemotherapieprotokollen die Therapieschritte bis hin zu einzelnen Medikamentengaben spezifiziert. Workflow-Management-Systeme (WfMS) sind deshalb ein geeignetes Werkzeug, um die Durchführung solcher Protokolle zu unterstützen. In früheren Untersuchungen(3) wurde deutlich, dass die Therapien trotz der genauen Vorgaben einen gewissen Grad an Flexibilität besitzen. Bei einer signifikanten Anzahl von Fällen treten Ausnahmen auf, bei denen in vorgeschriebener, aber nicht im Workflow modellierter Weise vom geplanten Behandlungsverlauf abgewichen werden muss. Um Workflow-Systeme dennoch einsetzen zu können, ist es notwendig die laufenden Workflows zu adaptieren (d.h. zu verändern), um sie an die neue Therapiesituation anzupassen. Aufgrund der hohen Komplexität der Therapieprotokolle und der großen Datenmenge (10-30 Befunde pro Patient und Tag bei unterschiedlichen Protokollen) ist es außerdem notwendig, den behandelnden Arzt bei der Erkennung der Ausnahmen und der Auswahl der passenden Adaption zu unterstützen. Um das medizinische Personal von der manuellen Ausnahmebehandlung zu entlasten, ist ein System erforderlich, das Ausnahmen erkennt und durch automatische Adaptionen sicherstellt, dass laufende Therapien trotz Ausnahmen weiter durchgeführt werden können. Ein solches System ist insbesondere für den Einsatz in klinischen Studien geeignet, da dort die Protokoll-Konformität der Behandlung besonders wichtig ist. Infolge der Verbesserung der Protokoll-Konformität ist dann auch eine Erhöhung der Behandlungsqualität zu erwarten

Self-synchronized duty-cycling for mobile sensor networks with energy harvesting capabilities: A swarm intelligence study

When asked if ants rest or if they work untiringly all day long, most people would probably respond that they had no idea. In fact, when watching the bustling life of an ant hill it is hard to imagine that ants take a rest from now and then. However, biologists discovered that ants rest quite a large fraction of their time. Surprisingly, not only single ants show alternate phases of resting and being active, but whole ant colonies exhibit synchronized activity phases that result from self-organization. Inspired by this self-synchronization behaviour of ant colonies, we develop a mechanism for self-synchronized duty-cycling in mobile sensor networks. In addition, we equip sensor nodes with energy harvesting capabilities such as, for example, solar cells. We show that the self-synchronization mechanism can be made adaptive depending on the available energy.Postprint (published version