Effects of deformability, uneven surface charge distributions, and multipole moments on biocolloid electrophoretic migration

Liposomes have been widely used as cellular and bioparticle mimics due to their lipid bilayer structure and relative ease of production and manipulation. Such biocolloids are frequently characterized by capillary electrophoresis (CE), which promises a wealth of information about such properties as surface charge, composition, and rigidity. The applicability of this information is somewhat limited, however, since it is interpreted with colloidal theories that do not account for the unique properties of biocolloids. In this work, the effects of deformability, mobile surface charges, intrinsic polarizability, and uneven surface charge distributions are incorporated into colloidal theories in order to better model the electrophoretic behaviors of liposomes.     

Atomic origin of hysteresis during cyclic loading of Si due to bond rearrangements at the crack surfaces

The atomistic origin of fatigue failure in micron-sized silicon devices is not fully understood. Two series of density-functional theory calculations on cubic diamond Si explore the effect of surface bond formation on crack healing in systems which exhibit strong surface reconstruction. Both series introduce a separation between Si(100) layers (i.e., the crack) and allow the ions to relax to their minimum-energy configuration. The initial surface ionic positions are either bulk terminated or 2 x 1 reconstructed. A plot of the energy versus the introduced separation reveals that once the surfaces reconstruct, the crack is no longer able to return to the equilibrium configuration. Rather, the healed crack interface contains defects which places the flawed energy minimum at a finite strain of 3% and an increased energy of 1.13 Jm2 relative to the equilibrium configuration. The irreversible plastic deformation supports the mechanism proposed by Kahn et al. [Science 298 1215 (2002)] that invokes mechanically induced subcritical cracking to explain the delayed onset of failure.     

Kinetics of octadecyltrimethylammonium bromide self-assembled monolayer growth at mica from an aqueous solution

We have studied the growth kinetics of self-assembled monolayers (SAMs) ofoctadecyltrimethylammonium bromide (C18TAB) on mica below the critical micelle concentration at 22, 30, 40, and 50 degrees C. A combination of atomic force microscopy, contact angle goniometry, and transmission infrared spectroscopy was used to follow the growth processes to determine the rates involved in the growth of a C18TAB SAM on mica. The growth of a SAM consisted of four distinct processes: deposition of adsorbate molecules, growth of a disordered 2D liquid phase, nucleation of islands of an ordered 2D solid phase, and subsequent growth of the solid phase. The rates of these various processes are determined, and the activation energies for several processes were calculated including those for the adsorption onto a bare substrate (20 kJ/mol), adsorption into the saturated liquid phase (100 kJ/mol), and nucleation of islands (0.3 kJ/mol). Despite the small activation barrier to island nucleation, the nucleation rate is qualitatively slow, suggesting that entropic effects dominate the nucleation rate.     

Studies in qualitative inorganic analysis. V

Summary The interference of borate ion in the group separation of inorganic cations has been examined. Contrary to statements often made in text books, alkaline earth borates do not precipitate in Group III because they are soluble in the ammonium chloride present; Group IV metals [Zn, Co], which form more insoluble borates co-precipitate extensively in Group III when borate is present. It is essential, therefore, to remove most of the borate before precipitating Group III metals. A convenient-method for this removal is described.

---

Zusammenfassung Die störende Wirkung von Boration bei der Gruppentrennung anorganischer Kationen wurde untersucht. Im Gegensatz zu Feststellungen vieler Lehrbücher fallen Erdalkaliborate nicht in der 3. Gruppe aus, da sie in Ammoniumchlorid löslich sind. Metalle der 4. Gruppe (Zn, Co), die schwerer lösliche Borate bilden, fallen bei Gegenwart von Borat weitgehend in der 3. Gruppe aus. Es ist daher wichtig, Borat vor der Fällung der 3. Gruppe größtenteils zu entfernen. Eine dazu geeignete Methode wird beschrieben.

---

Résumé L'effet perturbateur de l'ion borate dans la séparation par groupes des cations minéraux a été étudié. Contrairement à ce qu'on peut lire souvent dans les livres d'analyse les borates alcalino-terreux ne précipitent pas dans le groupe III car ils sont solubles dans le chlorure d'ammonium qui est présent; les métaux du groupe IV (Zn, Co), qui donnent lieu à formation de borates plus insolubles, coprécipitent abondamment avec le groupe III en présence de borate. En conséquence, il est nécessaire d'éliminer la plus grande partie du borate avant de précipiter les métaux du groupe III. Les auteurs décrivent une méthode commode permettant de procéder à cette élimination.

---

---

Part IV: Mikrochim. Acta [Wien] 1957, 137.     

Aerial robotic data acquisition system

A small, unmanned aerial vehicle (UAV) equipped with sensors for physical and chemical measurements of remote environments, is described. A miniature helicopter airframe is used as a platform for sensor testing and development. The sensor output is integrated with the flight control system for real-time, interactive, data acquisition and analysis. Pre-programmed flight missions will be flown with several sensors to demonstrate the cost-effective surveillance capabilities of this new technology.     

The development of a sampler-sensor using a vanadium-oxinate-polymer film for the selective and direct determination of atmospheric ethanol

The development of a sensor for the direct and selective determination of atmospheric ethanol is in the initial stages. The sensor takes advantage of the selective chemical reaction between ethanol and vanadium oxinate. This reaction occurs in an organic medium where a red colored complex is the product. This reaction is determined spectrophotometrically where the absorbance maxima is 475 nm. The focus of this paper is to discuss the parameters necessary to develop a solid sorbent sampling-sensor which can be used to determine atmospheric ethanol.     

A convenient method for 3-pyrroline synthesis

[reaction: see text]. The synthesis of a range of 3-pyrrolines has been achieved from primary amine starting materials using a two-step alkylation/alkylidene carbene CH-insertion reaction sequence. We have shown that insertion into a range of CH-bond types is possible, and the formation of nitrogen-bearing quaternary stereocenters is a relatively facile process. The insertion reaction occurs with >95% retention of stereochemistry, but the presence of protecting groups on nitrogen is generally deleterious to the cyclization process.