Measurement of forces between and within bilayers of neutral phospholipids

Phospholipids in water form lamellar phases made up of alternating layers of water and bimolecular lipid leaflets. Three complementary methods, osmotic, mechanical, and vapour pressures, were used to measure the work of removing water from lamellar phases composed of frozen dipalmitoylphosphatidylcholine ( DPPC ), melted DPPC, egg phosphatidylethanolamine or equimolar mixtures of DPPC and cholesterol ( DPPC/CHOL ), Concurrently the structural changes that resulted from this water removal were measured using X-ray diffraction. The work was divided into that which forces the bilayers together ( F ) and that which compresses the molecules together within the bilayers ( F )# A large repulsive force exists between bilayers composed of each of the lipids studied and this force increases exponentially as bilayer separation is decreased. F is affected by the nature of the head groups, conformation of the acyl chains and heterogeneity of these chains. In general all of the melted phosphatidylcholines ( melted DPPC, egg lecithin and DPPC/CHOL ) have large equilibrium separations in excess water resulting from large repulsive hydration forces between these bilayers. By comparison, egg PE has an increased attractive force, and frozen DPPC has a decreased hydration force; each results in smaller separations in water for these two lipids. The chemical potentials of the water between the bilayers for all these lipids lie on a continuum, indicating that interbilayer water cannot be characterized by two discrete states, usually referred to as "bound" or "non**bound". For all lipids studied a maximum of 25 % of the total work done on the system goes into deforming the bilayers. The method used here viii to separate repulsion from deformation, developed for us by v. A. Parsegian, provides a unique method for the measurement of lateral pressure of a bilayer and its modulus of deformability ( Y ). Lateral pressure is affected by the nature of the head group, conformation and heterogeneity of the acyl chains. For small changes in molecular surface area ( A ) near equilibrium, both melted and frozen DPPC have similar values for the deformability modulus. Thus in this regime it requires about the same force to change the angle of tilt of frozen chains as it does to compress the fluid bilayer. The introduction of cholesterol into bilayers of DPPC reduces dramatically the lateral pressure of the bilayers over a large range of molecular surface areas ( A ). The variation in the magnitude of bilayer repulsion with different phospholipids provides a basis for the mechanism of lipid segregation in mixed lipid systems and suggests that interacting heterogeneous membranes may influence or modulate the composition of the opposing membrane. The measurements of deformabilities of bilayers provides a direct comparison of them with the properties of monolayers.

Measurement of repulsive forces between charged phospholipid bilayers

Electrostatic forces between membranes containing charged lipids were assumed to play an important role in influencing interactions between membranes long before quantitative measurements of such forces were available. ~ur measurements were designed to measure electrostatic forces between layers of lecithin charged with lipi~s carrying ionizable head groups. These experiments have shown that the interactions between charged lipid bila.yere are dominated by electrostatic forces only at separations greater than 30 A. At smaller separations the repulsion between charged bilayers is dominated by strong hydration forces. The net repulsive force between egg lecithin bilayers containing various amounts of cherged lipids (phosphatidylglycerol (PG) 5,10 ano 50 mole%, phosphatidyli. nosi tol (PI) 10 mole% and sodium oleate (Na-Ol) 3,5 and 10 mole%, where mole% gives the ratio of the number of moles' of .charged lipid to the total number of moles of all lipids present in the sample) was stuoied with the help ('If the osmotic streas technique described by LeNeveu et aI, (1977). Also, the forces between pure PG were j_nvestigated in the same manner. The results have been plotted showing variation of force as a function of bilay- _ er separation dw• All curVes 90 obtained called force curves, were found to be similar in sha.pe, showing two distinct regions, one when dw<.30 A is a region cf very rapid iiivariation of force with separation ( it is the region dominated by hydre,tion force) and second when dw> 40 A is a region of very slow variation of force with separB.tion ( it is the region dominated by the electrostatic force). Between these two regions there exists a transition area in which, in most systems studied, a phase separation of lipids into fractions containing different amounts of charged groups, was observed. A qualitative analysis showed that our results were v/ell described by the simple electrostatic double -le.yer theory. For quantitative agreement between measured and calculated force curves however, the charge density for the calculations had to be taken as half of that given by the number density of charged lipids present in the lecithin bilayers. It is not clear at the moment what causes such low apparent degree of ionization among the charged head groups, and further study is needed in this area.

Report of the Committee appointed to inquire into the Present condition and distribution of the flags, standards and colors, which have been taken by the forces of the United States from their enemies, and whether it would be expedient to make any provision in relation to them.--

Adam Seybet, Chairman.

The Flags, Standards and Colors Taken by the Forces of the United States

Full Title: Report of the Committee appointed to inquire into the Present condition and distribution of the flags, standards and colors, which have been taken by the forces of the United States from their enemies, and whether it would be expedient to make any provision in relation to them Adam Seybet, Chairman. Exhibit folded at end of text. February 4, 1814. Read, and committed to a committee of the whole House on Monday next. Printed by A and G Way

Interrogation of Prisoner - Heaquarters 1st Division, American Expeditionary Forces, 27 May 1918

A prisoner interrogation report dated 27 May 1918. The report reads: "I. PRISONER X. 1st. Battalion, 272 Res. Rogt., 82d Res. 1. CIRCUMSTANCES OF CAPTURE; Captured, while attempting to raid our trenches, at point 1719 at about 7A.M. 2. INFORMATION OBTAINED FROM PRISONER (a) Between point 1814 and point 175242 the German trenches appear to be held by three companies, each numbering 3 platoons, each platoon numbering about 40 men. Each company has 4 light machine guns in the first lines, these machine guns distributed along the first trench (one of them in particular is located at bond in hostile trench at point 17215 and another at about 17245. Each company, furthermore, has one platoon (weak in numbers) in support in the ravine north of Cantigny. These platoons are in dugouts dug into the side of the hill approximately between points 28215 and 2223. Each of these support platoons has two light machine guns at its disposal. Company commanders dugout is at some point along the line of dugouts occupied by the support platoons. Another company commander's dugout (Co.3) is at point 1815 about 15 meters behind the German trench which runs along the edge of the town of Cantigny. There is a communication trench between the cemetery at 2018 and the front line at 18179. It is believed that there is a machine gun at point 17245 kept in a dugout dug under the road. The reserve battalion is believed to be at a fairly great distance from the front (near Bouillancourt). The prisoner, on the other hand, states that it may have been moved up."

Canadian Military Institute: Officers of the British Forces in Canada during the War of 1812-1815

There is a note in the front cover written to Mary from B. Johnston on April 22, 1942. He refers to page 73 of the book in which William Woodruff is listed as a Lieutenant and Richard Woodruff is listed as an Ensign in the Niagara District. A full text version is available at the following link: http://www.archive.org/details/officersbritish00instgoog

La face et la figuration: une analyse interactionnelle tirée de l’instruction de base des Forces canadiennes

Le sujet de ce mémoire émane d’une volonté d’intégrer la recherche à ma réalité organisationnelle, celle des Forces canadiennes (FC). De cette aspiration est née l’idée d’étudier comment se dévoilent la face et la figuration lors de l’instruction de base. Partant d’une approche interactionniste, l’attention a été portée sur la face et la figuration d’un stagiaire au cours de trois interactions avec ses supérieurs. C’est plus précisément, la filature et l’analyse de conversation qui ont été mobilisées pour examiner cette problématique. La pertinence de la démarche est qu'elle met de l'avant une perspective de recherche peu présente dans la littérature, mais surtout, qu’elle s’insère dans un contexte organisationnel méconnu. L'entreprise vise d’une part, à nourrir la théorie en raffinant des concepts existants : la face et la figuration. D’autre part, elle cherche à éclairer la pratique en mettant en évidence des actes communicationnels difficilement observables dans le cadre habituel des activités militaires.

Impacts des migrations forcées sur les pays hôtes

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Encodage des forces tactiles dans le cortex somatosensoriel primaire

Les deux fonctions principales de la main sont la manipulation d’objet et l’exploration tactile. La détection du glissement, rapportée par les mécanorécepteurs de la peau glabre, est essentielle pour l’exécution de ces deux fonctions. Durant la manipulation d’objet, la détection rapide du micro-glissement (incipient slip) amène la main à augmenter la force de pince pour éviter que l’objet ne tombe. À l’opposé, le glissement est un aspect essentiel à l’exploration tactile puisqu’il favorise une plus grande acuité tactile. Pour ces deux actions, les forces normale et tangentielle exercées sur la peau permettent de décrire le glissement mais également ce qui arrive juste avant qu’il y ait glissement. Toutefois, on ignore comment ces forces contrôlées par le sujet pourraient être encodées au niveau cortical. C’est pourquoi nous avons enregistré l’activité unitaire des neurones du cortex somatosensoriel primaire (S1) durant l’exécution de deux tâches haptiques chez les primates. Dans la première tâche, deux singes devaient saisir une pastille de métal fixe et y exercer des forces de cisaillement sans glissement dans une de quatre directions orthogonales. Des 144 neurones enregistrés, 111 (77%) étaient modulés à la direction de la force de cisaillement. L’ensemble de ces vecteurs préférés s’étendait dans toutes les directions avec un arc variant de 50° à 170°. Plus de 21 de ces neurones (19%) étaient également modulés à l’intensité de la force de cisaillement. Bien que 66 neurones (59%) montraient clairement une réponse à adaptation lente et 45 autres (41%) une réponse à adaptation rapide, cette classification ne semblait pas expliquer la modulation à l’intensité et à la direction de la force de cisaillement. Ces résultats montrent que les neurones de S1 encodent simultanément la direction et l’intensité des forces même en l’absence de glissement. Dans la seconde tâche, deux singes ont parcouru différentes surfaces avec le bout des doigts à la recherche d’une cible tactile, sans feedback visuel. Durant l’exploration, les singes, comme les humains, contrôlaient les forces et la vitesse de leurs doigts dans une plage de valeurs réduite. Les surfaces à haut coefficient de friction offraient une plus grande résistance tangentielle à la peau et amenaient les singes à alléger la force de contact, normale à la peau. Par conséquent, la somme scalaire des composantes normale et tangentielle demeurait constante entre les surfaces. Ces observations démontrent que les singes contrôlent les forces normale et tangentielle qu’ils appliquent durant l’exploration tactile. Celles-ci sont également ajustées selon les propriétés de surfaces telles que la texture et la friction. Des 230 neurones enregistrés durant la tâche d’exploration tactile, 96 (42%) ont montré une fréquence de décharge instantanée reliée aux forces exercées par les doigts sur la surface. De ces neurones, 52 (54%) étaient modulés avec la force normale ou la force tangentielle bien que l’autre composante orthogonale avait peu ou pas d’influence sur la fréquence de décharge. Une autre sous-population de 44 (46%) neurones répondait au ratio entre la force normale et la force tangentielle indépendamment de l’intensité. Plus précisément, 29 (30%) neurones augmentaient et 15 (16%) autres diminuaient leur fréquence de décharge en relation avec ce ratio. Par ailleurs, environ la moitié de tous les neurones (112) étaient significativement modulés à la direction de la force tangentielle. De ces neurones, 59 (53%) répondaient à la fois à la direction et à l’intensité des forces. L’exploration de trois ou quatre différentes surfaces a permis d’évaluer l’impact du coefficient de friction sur la modulation de 102 neurones de S1. En fait, 17 (17%) neurones ont montré une augmentation de leur fréquence de décharge avec l’augmentation du coefficient de friction alors que 8 (8%) autres ont montré le comportement inverse. Par contre, 37 (36%) neurones présentaient une décharge maximale sur une surface en particulier, sans relation linéaire avec le coefficient de friction des surfaces. La classification d’adaptation rapide ou lente des neurones de S1 n’a pu être mise en relation avec la modulation aux forces et à la friction. Ces résultats montrent que la fréquence de décharge des neurones de S1 encode l’intensité des forces normale et tangentielle, le ratio entre les deux composantes et la direction du mouvement. Ces résultats montrent que le comportement d’une importante sous-population des neurones de S1 est déterminé par les forces normale et tangentielle sur la peau. La modulation aux forces présentée ici fait le pont entre les travaux évaluant les propriétés de surfaces telles que la rugosité et les études touchant à la manipulation d’objets. Ce système de référence s’applique en présence ou en absence de glissement entre la peau et la surface. Nos résultats quant à la modulation des neurones à adaptation rapide ou lente nous amènent à suggérer que cette classification découle de la manière que la peau est stimulée. Nous discuterons aussi de la possibilité que l’activité des neurones de S1 puisse inclure une composante motrice durant ces tâches sensorimotrices. Finalement, un nouveau cadre de référence tridimensionnel sera proposé pour décrire et rassembler, dans un même continuum, les différentes modulations aux forces normale et tangentielle observées dans S1 durant l’exploration tactile.

‘Driving Forces of Investment Decisions in Mutual Funds’

Unfortunately, in India it is a fact that most of the investors are not interested in mutual funds. Those who are investing, they are investing only very small amounts. But what is important to be noted here is that when compared to other financial instruments, investments in mutual funds are safer and also yields more returns on the investment portfolio. Moreover as an investment avenue mutual fund is available for those investors who are not willing to take any exposure directly in the security market. It also helps such investors to build their wealth over a period of time. At the retail level, investors are unique and are highly heterogeneous, and the mutual fund schemes' selection will also differ depends on their expectations. Hence, investors’ expectation is a very important factor in this regard that needs to be analysed by all the investment houses. Hence, the factors that drive the investment decisions of individual investors to meet their expectations by investing money in mutual funds need an in-depth analysis. These driving forces include the preference of investors on mutual fund compared to various available avenues of financial investments, risk attitude of investors, influence of characteristics of instruments of mutual funds on investors, the investment specific attitudes of investors, and influence of qualities of fund management on investors. The success of any mutual fund, a popular means of investment, depends on how effectively an Asset Management Company has been able to understand the level of influence of these factors on the decision of investors to invest in mutual funds. For a substantial growth in the mutual fund market, there must be a high level precision in the design and marketing of the products of mutual funds taking into account these driving forces by the Asset Management Companies. Therefore, there is a need to conduct a detailed study on investments in mutual funds in this direction. A review of available literature also revealed that no detailed study on mutual funds has so far been attempted in this direction; hence the present study on Driving Forces of Investment Decisions in Mutual Funds is undertaken.

Amenaza Interdependiente en la Región de los Grandes Lagos

El objetivo de esta monografía es analizar los alcances de la presencia de grupos armados ilegales como elementos determinantes en el origen de un subcomplejo de seguridad regional entre la República Democrática del Congo, Ruanda y Burundi. Se busca explicar cómo un conflicto étnico se traduce en la presencia de grupos insurgentes, y a su vez, establece una amenaza interdependiente entre los líderes políticos de dichos países, que permite hablar del subcomplejo de seguridad. Para lograr lo anterior, son pertinentes los postulados teóricos de los Complejos de Seguridad Regional de Barry Buzan, ya que identifican la manera como se estructuran, localizan, y evolucionan estas unidades de análisis. Finalmente, este análisis se complementa con el método de estudio propuesto por Jeremy M. Weinstein para comprender por qué y para qué se crean grupos insurgentes.