The movement of a water droplet on a gradient surface prepared by photodegradation

A hydrophobic to hydrophilic gradient surface was prepared using the tuned photodegradation of an alkylsilane self-assembled monolayer (SAM) using irradiation of vacuum ultraviolet light (wavelength=172 nm). The water contact angle on the photodegraded SAM surface was adjusted using the intensity and time photoirradiation parameters. The formation of a gradient was confirmed by fluorescent labeling. The water drop moved from the hydrophobic to hydrophilic surface with a velocity that depended on the gradient. The higher the gradient, the faster the water moved. For the first time, we have prepared a gradient surface using photodegradation where the movement of a water drop was regulated by the degree of gradation. Considering that the photodegradation technique can be applied to various surfaces and to lithography, this technique will be useful for various material surfaces.     

Two-dimensional hopping motion of encapsulated La atoms in silylated La(2)@C(80)

The (139)La NMR study of the exohedrally functionalized derivatives of La(2)@C(80) metallofullerene, La(2)@C(80)(Ar(2)Si)(2)CH(2) (: Ar = Mes, Mes = mesityl, : Ar = Dep, Dep = 2,6-diethylphenyl), reveal that the two La atoms hop between two sites along the equator of the C(80) cage.     

Two‐Step Synthesis of 1,3‐Disubstituted 3,4‐Dihydro‐4‐thioxoquinazolin‐2(1H)‐ones from 1‐Bromo‐2‐fluorobenzenes

An efficient synthesis of 3‐alkyl‐3,4‐dihydro‐4‐thioxobenzoquinazolin‐2(1H)‐ones 3 has been accomplished in two steps and in satisfactory yields from 1‐bromo‐2‐fluorobenzenes 1 . Thus, the reaction of 1‐fluoro‐2‐lithiobenzenes, generated by the Br/Li exchange between 1 and BuLi, with alkyl isothiocyanates, gives N‐alkyl‐2‐fluorobenzothioamides 2 , which, in turn, react with a series of isocyanates in the presence of NaH to give the desired products 3 .     

Inhibition of bubble coalescence: effects of salt concentration and speed of approach

Bubble coalescence experiments have been performed using a sliding bubble apparatus, in which mm-sized bubbles in an aqueous electrolyte solution without added surfactant rose toward an air meniscus at different speeds obtained by varying the inclination of a closed glass cylinder containing the liquid. The coalescence times of single bubbles contacting the meniscus were monitored using a high speed camera. Results clearly show that stability against coalescence of colliding air bubbles is influenced by both the salt concentration and the approach speed of the bubbles. Contrary to the widespread belief that bubbles in pure water are unstable, we demonstrate that bubbles formed in highly purified water and colliding with the meniscus at very slow approach speeds can survive for minutes or even hours. At higher speeds, bubbles in water only survive for a few seconds, and at still higher speeds they coalesce instantly. Addition of a simple electrolyte (KCl) removes the low-speed stability and shifts the transition between transient stability and instant coalescence to higher approach speeds. At high electrolyte concentration no bubbles were observed to coalesce instantly. These observations are consistent with recent results of Yaminsky et al. (Langmuir 26 (2010) 8061) and the transitions between different regions of behavior are in semi-quantitative agreement with Yaminsky's model.     

Synthesis of (-)-homogalanthamine from naltrexone

Acetylcholinesterase inhibitor (-)-homogalanthamine 3 was synthesized from μ opioid antagonist naltrexone (2) in 16% total yield. The synthesis features Grob fragmentation as a key reaction, which was especially accelerated in the presence of 15-crown-5.     

Induction of thermotropic bicontinuous cubic phases in liquid-crystalline ammonium and phosphonium salts

Two series of wedge-shaped onium salts, one ammonium and the other phosphonium, having 3,4,5-tris(alkyloxy)benzyl moieties, exhibit thermotropic bicontinuous "gyroid" cubic (Cub(bi)) and hexagonal columnar liquid-crystalline (LC) phases by nanosegregation between ionophilic and ionophobic parts. The alkyl chain lengths on the cationic moieties, anion species, and alkyl chain lengths on the benzyl moieties have crucial effects on their thermotropic phase behavior. For example, triethyl-[3,4,5-tris(dodecyloxy)benzyl]ammonium hexafluorophosphate forms the thermotropic Ia3d Cub(bi) LC phase, whereas an analogous compound with trifluoromethanesulfonate anion shows no LC properties. Synchrotron small-angle diffraction intensities from the Ia3d Cub(bi) LC materials provide electron density maps in the bulk state. The resulting maps show convincingly that the Ia3d Cub(bi) structure is composed of three-dimensionally interconnected ion nanochannel networks surrounded by aliphatic domains. A novel differential mapping technique has been applied successfully. The map of triethyl-[3,4,5-tris(decyloxy)benzyl]ammonium tetrafluoroborate has been subtracted from that of the analogous ammonium salt with hexafluorophosphate anion in the Ia3d Cub(bi) phases. The differential map shows that the counteranions are located in the core of the three-dimensionally interconnected nanochannel networks. Changing from trimethyl- via triethyl- to tripropylammonium cation changes the phase from columnar to Cub(bi) to no mesophase, respectively. This sensitivity to the widened shape for the narrow end of the molecule is explained successfully by the previously proposed semiquantitative geometric model based on the radial distribution of volume in wedge-shaped molecules. The LC onium salts dissolve lithium tetrafluoroborate without losing the Ia3d Cub(bi) LC phase. The Cub(bi) LC materials exhibit efficient ion-transporting behavior as a result of their 3D interconnected ion nanochannel networks. The Ia3d Cub(bi) LC material formed by triethyl-[3,4,5-tris(decyloxy)benzyl]phosphonium tetrafluoroborate shows ionic conductivities higher than the analogous Ia3d Cub(bi) material based on ammonium salts. The present study indicates great potential of Cub(bi) LC nanostructures consisting of ionic molecules for development of transportation nanochannel materials.     

Relaxation of the topological T1 process in a two-dimensional foam

The so-called topological T1 process, during which bubbles within a foam exchange neighbours is studied. The Durand and Stone model (Phys. Rev. Lett., 97, 226101 (2006)) describes the growth of a film that is newly created during the T1 process, and also the evolution of surfactant concentration on this newly created film. Here some characteristic features of the Durand and Stone model (not previously described by Durand and Stone) are elucidated. In particular it is shown that the surfactant concentration on the newly created film is predicted to undergo an extremely rapid initial evolution, which occurs long before the film itself approaches anywhere near its final equilibrium length. Associated with this, the predicted length of the newly created film tends to exhibit an extremely rapid acceleration early on in its growth. An intermediate asymptotic analysis is developed to explain the above model predictions, by focussing on the regime when the film is several times larger than its initial length, but still several times smaller than its final length. A physical explanation is offered for these predictions in terms of slippage between material points instantaneously at the end of the newly created film, and the evolving location of the film endpoint itself: this slippage implies surfactant being transferred onto the newly created film from neighbouring films, overwhelming the amount of surfactant initially present. The implications of these predictions for the likely observations in an experimental study of the T1 process are discussed.     

Tetraaryl‐Substituted Benzo[1,2‐b:4,5‐b′]dipyrroles: Synthesis,Properties, and Applications to Hole‐Injection Materials in OLED Devices

Yes, HIMs can! A series of 2,3,6,7‐tetraarylbenzo[1,2‐b:4,5‐b′]dipyrroles (BDPs) were synthesized using zinc‐mediated double cyclization. Organic light‐emitting diodes consisting of BDP:PPB as a hole‐injection layer could be driven at a lower voltage than a PEDOT:PSS‐based device. Correlation of the IP values with the driving voltage shed some light on the mechanism of hole‐injection processes.

     

Ultralow-jitter passive timing stabilization of a mode-locked Er-doped fiber laser by injection of an optical pulse train

The pulse timing of a mode-locked Er-doped fiber laser was stabilized to a reference pulse train from a Cr:forsterite mode-locked laser by all-optical passive synchronization scheme. The reference pulses were injected into a ring cavity of the fiber laser by using a 1.3-1.5 mum wavelength-division multiplexer. The spectral shift induced by cross-phase modulation between copropagating two-color pulses realizes self-synchronization due to intracavity group-delay dispersion. The rms integration of timing jitter between the fiber laser pulse and the reference pulse was 3.7 fs in a Fourier frequency range from 1 Hz to 100 kHz.     

Improvement of estimation parameters in bio-speckle blood flow imaging

Two novel estimation parameters are proposed for bio-speckle blood flow imaging in skin tissue with reducing effects of a speckle contrast and random noises. Estimation parameters are introduced to reduce the effect of the speckle contrast on the sensitivity of the blood flow sensing and to eliminate an offset component due to random noises superimposed on the speckle images. Experiments were conducted for a sample model using ground-glass plates, human vein and finger to confirm the feasibility of the proposed parameters.