Electrostatic control of dewetting dynamics

The stability of liquid films on surfaces are critically important in microscale patterning and the semiconductor industry. If the film is sufficiently thin it may spontaneously dewet from the surface. The timescale and rate of dewetting depend on the film repellency of the surface and the properties of the liquid. Therefore, control over the repellency requires modifying surface chemistry and liquid properties to obtain the desired rate of film retraction. Here, we report how the dynamics of a receding thin liquid stripe to a spherical cap droplet can be controlled by programming surface repellency through a non-contact electrostatic method. We observe excellent agreement between the expected scaling of the dynamics for a wide range of voltage-selected final contact angles. Our results provide a method of controlling the dynamics of dewetting with high precision and locality relevant to printing and directed templating

A viscous switch for liquid-liquid dewetting

The spontaneous dewetting of a liquid film from a solid surface occurs in many important processes, such as printing and microscale patterning. Experience suggests that dewetting occurs faster on surfaces of higher film repellency. Here, we show how, unexpectedly, a surrounding viscous phase can switch the overall dewetting speed so that films retract slower with increasing surface repellency. We present experiments and a hydrodynamic theory covering five decades of the viscosity ratio between the film and the surrounding phase. The timescale of dewetting is controlled by the geometry of the liquid-liquid interface close to the contact line and the viscosity ratio. At small viscosity ratio, dewetting is slower on low film-repellency surfaces due to a high dissipation at the edge of the receding film. This situation is reversed at high viscosity ratios, leading to a slower dewetting on high film-repellency surfaces due to the increased dissipation of the advancing surrounding phase

Bubble control, levitation and manipulation using dielectrophoresis

Bubbles attached to surfaces are ubiquitous in nature and in industry. However, bubbles are problematic in important technologies, including causing damage to the operation of microfluidic devices and being parasitic during heat transfer processes, so considerable efforts have been made to develop mechanical and electrical methods to remove bubbles from surfaces. In this work liquid dielectrophoresis is used to force a captive air bubble to detach away from an inverted solid surface and, crucially, the detached bubble is then held stationary in place below the surface at a distance controlled by the voltage. In this “levitated” state the bubble is separated from the surface by liquid layer with a voltage-selected thickness at which the dielectrophoresis force exactly counterbalances the gravitational buoyancy force. The techniques described here provide exceptional command over repeatable cycles of bubble detachment, levitation, and re-attachment. A theoretical analysis is presented that explains the observed detachment-reattachment hysteresis in which bubble levitation is maintained with voltages an order of magnitude lower than those used to create detachment. Our precision surface bubble removal and control concepts are relevant to situations such as nucleate boiling and micro-gravity environments, and offer an approach towards "wall-less" bubble microfluidic devices

Primer registro de la especie japonesa Grateloupia turuturu (Halymeniaceae, Rhodophyta) en la costa del Pacífico mexicano

Floristic surveys were conducted in November 2008, in which we collected specimens of Grateloupia turuturu, growing attached to different substrata in Ensenada Port, Baja California, Mexico. From this finding, monthly observations were performed until July 2010 to find a possible displacement. Populations with specimens average length of 40 cm were commonly found in the harbor. On the basis of morphological and molecular analyses of plastid rbcL gene sequences, we confirmed the taxonomic identity of G. turuturu. We present the first record of G. turuturu as introduced species in the Mexican Pacific coast. Considering this new finding in Mexico, we conclude that the colonization by this species in the Pacific coast has started, and hence its geographical range of distribution is increasing. Likewise, we found Grateloupia californica, and it is discuss its presences on Baja California coast.Se realizaron muestreos florísticos en noviembre de 2008, en los que se recolectaron ejemplares de Grateloupia turuturu creciendo adheridos a diferentes substratos en el puerto de Ensenada, Baja California, México. A partir de este hallazgo, se realizaron observaciones mensuales hasta julio de 2010 para conocer su posible desplazamiento. Poblaciones con especímenes de longitud promedio de 40 cm se encontraron con alta frecuencia en el puerto. Los análisis morfológicos y moleculares de las secuencias del gen rbcL de plastidios confirman la identidad taxonómica de G. turuturu. Se presenta el primer registro de G. turuturu como especie introducida en la costa del Pacífico mexicano. Considerando este nuevo hallazgo, concluimos que la colonización por esta especie en la costa del Pacífico mexicano ha iniciado y con ello se amplía su rango de distribución geográfica. Así mismo, durante los muestreos se encontró a Grateloupia californica de la cual se discute su presencia en las costas de Baja California

Top pair Asymmetries at Hadron colliders with general Z′Z' couplings

Recently it has been shown that measurement of charge asymmetry of top pair production at LHC excludes any flavor violating $Z'$ vector gauge boson that could explain Tevatron forward-backward asymmetry (FBA). We consider the general form of a $Z'$ gauge boson including left-handed, right-handed vector and tensor couplings to examine FBA and charge asymmetry. To evaluate top pair asymmetries at Tevatron and LHC, we consider $B^0_q$ mixing constraints on flavor changing $Z'$ couplings and show that this model still explain forward-backward asymmetry at Tevatron and charge asymmetry can not exclude it in part of parameters space.Comment: 18 pages, 7 figure

Chiral U(1) flavor models and flavored Higgs doublets: the top FB asymmetry and the Wjj

We present U(1) flavor models for leptophobic Z' with flavor dependent couplings to the right-handed up-type quarks in the Standard Model, which can accommodate the recent data on the top forward-backward (FB) asymmetry and the dijet resonance associated with a W boson reported by CDF Collaboration. Such flavor-dependent leptophobic charge assignments generally require extra chiral fermions for anomaly cancellation. Also the chiral nature of U(1)' flavor symmetry calls for new U(1)'-charged Higgs doublets in order for the SM fermions to have realistic renormalizable Yukawa couplings. The stringent constraints from the top FB asymmetry at the Tevatron and the same sign top pair production at the LHC can be evaded due to contributions of the extra Higgs doublets. We also show that the extension could realize cold dark matter candidates.Comment: 40 pages, 10 figures, added 1 figure and extended discussion, accepted for publication in JHE

Scalar-mediated ttˉt\bar t forward-backward asymmetry

A large forward-backward asymmetry in $t\bar t$ production, for large invariant mass of the $t\bar t$ system, has been recently observed by the CDF collaboration. Among the scalar mediated mechanisms that can explain such a large asymmetry, only the t-channel exchange of a color-singlet weak-doublet scalar is consistent with both differential and integrated $t\bar t$ cross section measurements. Constraints from flavor changing processes dictate a very specific structure for the Yukawa couplings of such a new scalar. No sizable deviation in the differential or integrated $t\bar t$ production cross section is expected at the LHC.Comment: 22 pages, 1 figure and 2 tables. v2: Corrected Eqs.(50,51,74), adapted Fig.1, Tab.1 and relevant discussions. Extended discussion of top decay and single to

Top quark forward-backward asymmetry in R-parity violating supersymmetry

The interaction of bottom squark-mediated top quark pair production, occurring in the R-parity violating minimal supersymmetric standard model (MSSM), is proposed as an explanation of the anomalously large $t\bar{t}$ forward-backward asymmetry (FBA) observed at the Tevatron. We find that this model can give a good fit to top quark data, both the inclusive and invariant mass-dependent asymmetries, while remaining consistent (at the 2-$\sigma$ level) with the total and differential production cross-sections. The scenario is challenged by strong constraints from atomic parity violation (APV), but we point out an extra diagram for the effective down quark-Z vertex, involving the same coupling constant as required for the FBA, which tends to weaken the APV constraint, and which can nullify it for reasonable values of the top squark masses and mixing angle. Large contributions to flavor-changing neutral currents can be avoided if only the third generation of sparticles is light.Comment: 24 pages, 7 figures. v3: included LHC top production cross section data; model still consistent at 2 sigma leve

Design of the Firstâ inâ Class, Highly Potent Irreversible Inhibitor Targeting the Meninâ MLL Proteinâ Protein Interaction

The structureâ based design of Mâ 525 as the firstâ inâ class, highly potent, irreversible smallâ molecule inhibitor of the meninâ MLL interaction is presented. Mâ 525 targets cellular menin protein at subâ nanomolar concentrations and achieves low nanomolar potencies in cell growth inhibition and in the suppression of MLLâ regulated gene expression in MLL leukemia cells. Mâ 525 demonstrates high cellular specificity over nonâ MLL leukemia cells and is more than 30 times more potent than its corresponding reversible inhibitors. Mass spectrometric analysis and coâ crystal structure of Mâ 525 in complex with menin firmly establish its mode of action. A single administration of Mâ 525 effectively suppresses MLLâ regulated gene expression in tumor tissue. An efficient procedure was developed to synthesize Mâ 525. This study demonstrates that irreversible inhibition of menin may be a promising therapeutic strategy for MLL leukemia.Irreversible inhibitor Mâ 525 targets the meninâ MLL interaction. It is demonstrated that irreversible inhibition of menin is a promising therapeutic strategy for the treatment of MLL leukemia and may have advantages over reversible inhibitors.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141532/1/anie201711828.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141532/2/anie201711828-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141532/3/anie201711828_am.pd

Design of the Firstâ inâ Class, Highly Potent Irreversible Inhibitor Targeting the Meninâ MLL Proteinâ Protein Interaction

The structureâ based design of Mâ 525 as the firstâ inâ class, highly potent, irreversible smallâ molecule inhibitor of the meninâ MLL interaction is presented. Mâ 525 targets cellular menin protein at subâ nanomolar concentrations and achieves low nanomolar potencies in cell growth inhibition and in the suppression of MLLâ regulated gene expression in MLL leukemia cells. Mâ 525 demonstrates high cellular specificity over nonâ MLL leukemia cells and is more than 30 times more potent than its corresponding reversible inhibitors. Mass spectrometric analysis and coâ crystal structure of Mâ 525 in complex with menin firmly establish its mode of action. A single administration of Mâ 525 effectively suppresses MLLâ regulated gene expression in tumor tissue. An efficient procedure was developed to synthesize Mâ 525. This study demonstrates that irreversible inhibition of menin may be a promising therapeutic strategy for MLL leukemia.Der irreversible Inhibitor Mâ 525 greift an der Meninâ MLLâ Wechselwirkung an. Die irreversible Inhibition von Menin erweist sich als vielversprechende Strategie für die Behandlung von MLLâ Leukämie, mit möglichen Vorteilen gegenüber dem Einsatz reversibler Inhibitoren.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141701/1/ange201711828_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141701/2/ange201711828.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141701/3/ange201711828-sup-0001-misc_information.pd