Radiative transmission of lepton flavor hierarchies

We discuss a one loop model for neutrino masses which leads to a seesaw-like formula with the difference that the charged lepton masses replace the unknown Dirac mass matrix present in the usual seesaw case. This is a considerable reduction of parameters in the neutrino sector and predicts a strong hierarchical pattern in the right handed neutrino mass matrix that is easily derived from a U(1)_H family symmetry. The model is based on the left–right gauge group with an additional Z₄ discrete symmetry which gives vanishing neutrino Dirac masses and finite Majorana masses arising at the one loop level. Furthermore, it is one of the few models that naturally allow for large (but not necessarily maximal) mixing angles in the lepton sector. A generalization of the model to the quark sector requires three iso-spin singlet vector-like down type quarks, as in E₆. The model predicts an inert doublet type scalar dark matter.     

Fabrication of microelectrodes using flow layer-by-layer self assembly of gold nanoparticles

Microelectrodes to be used in microfluidic devices were prepared from the layer-by-layer flow deposition of gold nanoparticles. Pre-designed microfluidic channels were used as templates for the flow driven deposition of the nanoparticles in sequence with poly (diallyldimethyl amonium chloride) (PDADMAC). The electrical resistivity of the gold nanoparticle assembly was found to be strongly dependant on the concentration of sodium citrate used in the gold nanoparticle synthesis. As the electrical properties of the film changed from insulating to conducting when decreasing the citrate concentration, a 4 point probe setup was used to measure the resistivity of the film. Near bulk conductivity (5.42 × 10⁻⁶ Ω cm) was achieved with only 10 layers of film. The thickness and morphology of the flow-printed multilayer microelectrode was characterized using atomic force microscopy (AFM) and a field emission scanning electron microscope (FE-SEM). To demonstrate its usefulness, the microelectrode assembly was then tested toward the detection of KCl in solution, having a concentration ranging from 1 to 20 mM using AC current detection in a simple setup. Good linearity and stability of the electrode confirmed that this method could be very convenient for the fabrication of microelectrodes for lab-on-chip applications.     

DNA-binding properties of ruthenium(II) complexes with the bidentate ligand 5-chloro-2-(phenylazo)pyridine

A bidentate ligand, 5-chloro-2-(phenylazo)pyridine (Clazpy), and its two polypyridyl ruthenium(II) complexes, [Ru(Clazpy)₂bpy]Cl₂·7H₂O (1) and [Ru(Clazpy)₂phen]Cl₂·8H₂O (2), were synthesized and characterized. The DNA-binding properties of these complexes with DNA, the breast cancer susceptibility gene 1 (BRCA1), and the pBIND plasmid DNA were probed by photocleavage, electronic absorption titration, ethidium bromide quenching, and thermal denaturation. Both complexes were found to bind to the BRCA1 fragment through the intercalative mode into the base pairs of DNA, and the DNA-binding constants (K_b) for 1 and 2 were 7.0 × 10⁴ M⁻¹ and 5.1 × 10⁵ M⁻¹, respectively. In addition, both complexes enhanced the single-stranded cleavage of the plasmid DNA. Under comparable experimental conditions, 2 cleaved DNA more effectively than 1, in a dose–response manner. The data indicated that the binding affinity of these two complexes to DNA was dependent on the aromatic planarity and hydrophobicity of the intercalative polypyridyl ligand.     

Acid-Containing Tyrosine-Derived Polycarbonates: Wettability and Surface Reactivity

Tyrosine-derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4-6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (-COOH) to carboxylate ion (-COO⁻). The surface compositions of imidazole-labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N-hydroxysuccinimide.     

Electrochemical detection on electrowetting-on-dielectric digital microfluidic chip

In this work, the use of three-electrode electrochemical sensing system with an electrowetting-on-dielectric (EWOD) digital microfluidic device is reported for quantitative analysis of iodide. T-junction EWOD mixer device was designed using arrays of 50-μm spaced square electrodes for mixing buffer reagent and analyte droplets. For fabrication of EWOD chips, 5-μm thick silver EWOD electrodes were formed on a glass substrate by means of sputtering and lift-off process. PDMS and Teflon thin films were then coated on the electrodes by spin coating to yield hydrophobic surface. An external three-electrode system consisting of Au working, Ag reference and Pt auxiliary wires were installed over EWOD electrodes at the end of T-junction mixer. In experiment, a few-microliter droplets of Tris buffer and iodide solutions were moved toward the mixing junction and transported toward electrochemical electrodes by EWOD process. A short processing time within seconds was achieved at EWOD applied voltage of 300 V. The analyte droplets mixed with different concentrations were successfully analyzed by cyclic voltametry. Therefore, the combination of EWOD digital microfluidic and electrochemical sensing system has successfully been demonstrated for rapid chemical analysis with minimal reagent consumption.     

AAO-CNTs electrode on microfluidic flow injection system for rapid iodide sensing

In this work, carbon nanotubes (CNTs) nanoarrays in anodized aluminum oxide (AAO-CNTs) nanopore is integrated on a microfluidic flow injection system for in-channel electrochemical detection of iodide. The device was fabricated from PDMS (polydimethylsiloxane) microchannel bonded on glass substrates that contains three-electrode electrochemical system, including AAO-CNTs as a working electrode, silver as a reference electrode and platinum as an auxiliary electrode. Aluminum, stainless steel catalyst, silver and platinum layers were sputtered on the glass substrate through shadow masks. Aluminum layer was then anodized by two-step anodization process to form nanopore template. CNTs were then grown in AAO template by thermal chemical vapor deposition. The amperometric detection of iodide was performed in 500-μm-wide and 100-μm-deep microchannels on the microfluidic chip. The influences of flow rate, injection volume and detection potential on the current response were optimized. From experimental results, AAO-CNTs electrode on chip offers higher sensitivity and wider dynamic range than CNTs electrode with no AAO template.     

Enhancement of DNA hybridization under acoustic streaming with three-piezoelectric-transducer system

Recently, we have demonstrated that DNA hybridization using acoustic streaming induced by two piezoelectric transducers provides higher DNA hybridization efficiency than the conventional method. In this work, we refine acoustic streaming system for DNA hybridization by inserting an additional piezoelectric transducer and redesigning the locations of the transducers. The Comsol? Multiphysics was used to design and simulate the velocity field generated by the piezoelectric agitation. The simulated velocity vector followed a spiral vortex flow field with an average direction outward from the center of the transducers. These vortices caused the lower signal intensity in the middle of the microarray for the two-piezoelectric disk design. On the contrary, the problem almost disappeared in the three-piezoelectric-disk system. The optimum condition for controlling the piezoelectric was obtained from the dye experiments with different activation settings for the transducers. The best setting was to activate the side disks and middle disk alternatively with 1 second activating time and 3 second non-activating time for both sets of transducers. DNA hybridization using microarrays for the malaria parasite Plasmodium falciparum from the optimized process yielded a three-fold enhancement of the signal compared to the conventional method. Moreover, a greater number of spots passed quality control in the optimized device, which could greatly improve biological interpretation of DNA hybridization data.     

A review of monolithic multichannel quartz crystal microbalance: a review

Monolithic multichannel quartz crystal microbalance (MQCM) is an emerging technology for advanced sensing and measurement applications. In this report, a comprehensive review of MQCM technology is presented. Firstly, basic MQCM's design, simulation and characterization with emphasis on acoustic interference are described. Next, various MQCM schemes to minimize interference and enhance sensitivity of conventional MQCM devices based on modification of quartz substrate structure are digested. These include mesa, convex and x-axis inversion structures. Three important MQCM sensing platforms and their application areas are then discussed. These comprise MQCM as a static multichannel detector, series MQCM as a multichannel detector for the flow injection analysis and multi-frequency QCM for multi-sensitivity/multi-dynamic range detection. Finally, potential MQCM applications including electronic noses, bio-sensor arrays, and photocatatalytic measurement are illustrated and prospective MQCM applications including electronic tongues and electrochemical measurement are suggested.     

A screen-printed carbon electrode modified with gold nanoparticles,poly(3,4-ethylenedioxythiophene), poly(styrene sulfonate) and a molecular imprint for voltammetric determination of nitrofurantoin

A molecularly imprinted polymer (MIP) and a nanocomposite prepared from gold nanoparticles (AuNP) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) were deposited on a screen-printed carbon electrode (SPCE). The nanocomposite was prepared by one-pot simultaneous in-situ formation of AuNPs and PEDOT:PSS and was then inkjet-coated onto the SPCE. The MIP film was subsequently placed on the modified SPCE by co-electrodeposition of o-phenylenediamine and resorcinol in the presence of the antibiotic nitrofurantoin (NFT). Using differential pulse voltammetry (DPV), response at the potential of ~ 0.1 V (vs. Ag/AgCl) is linear in 1 nM to 1000 nM NFT concentration range, with a remarkably low detection limit (at S/N?=?3) of 0.1 nM. This is two orders of magnitude lower than that of the control MIP sensor without the nanocomposite interlayer, thus showing the beneficial effect of AuNP-PEDOT:PSS. The electrode is highly reproducible (relative standard deviation 3.1% for n?=?6) and selective over structurally related molecules. It can be re-used for at least ten times and was found to be stable for at least 45 days. It was successfully applied to the determination of NFT in (spiked) feed matrices and gave good recoveries.

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Graphical abstract Schematic representation of a voltammetric sensor for the determination of nitrofurantoin. The sensor is based on a screen-printed carbon electrode (SPCE) modified with an inkjet-printed gold nanoparticles-poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) nanocomposite and a molecularly imprinted polymer.

     

DNA hybridization enhancement using piezoelectric microagitation through a liquid coupling medium

In conventional DNA microarray hybridization, delivery of target cDNAs to surface-bounded probes depends solely on diffusion, which is notoriously slow, and thus typically requires 6-20 h to complete. In this study, piezoelectric microagitation through a liquid coupling medium is employed to enhance DNA hybridization efficiency and the results are compared with the standard static hybridization method. DNA hybridization was performed in a sealed aluminium chamber containing DNA microarray glass chip, coupling medium and piezoelectric transducers. 3×SSC (Saline Sodium Citrate) was used as a coupling medium to prevent overheating of the piezoelectric transducers and to effectively transmit ultrasonic wave to the glass chip. Flow visualization using fluidic dye and velocimetry (PTV) technique was applied to observe fluid transport in the hybridization chamber. It was revealed that the dye solution was homogeneously distributed within 10 min under dynamic agitation while it took over 1 h to reach the same level of homogeneity in static condition. Plasmodium falciparum DNA microarrays and total RNA extracted from parasite cells were used as a model for DNA microarray experiments. It was found that the required hybridization time may be substantially reduced from 16 h to 4 h by the use of dynamic hybridization scheme. With the same hybridization time of 16 h, dynamic hybridization resulted in higher fluorescent signals of ～33% and ～24% compared to static hybridization in Cy3 and Cy5 channels, respectively. Additionally, good/effective spots, some of which were not formed by static method, were enhanced and distributed more uniformly over the microarray. Therefore, the developed dynamic hybridization with integrated piezoelectric microagitation platform is highly promising for DNA analysis in molecular biology and medical applications.