Colorimetric detection of Escherichia coli using engineered bacteriophage and an affinity reporter system

Analytical and Bioanalytical Chemistry - Reporter phage systems have emerged as a promising technology for the detection of bacteria in foods and water. However, the sensitivity of these assays is...     

44-Methylgambierone,a new gambierone analogue isolated from Gambierdiscus australes

A new analogue of gambierone, 44-methylgambierone, was isolated from the benthic dinoflagellate Gambierdiscus australes collected from Raoul Island (Rangitahua/Kermadec Islands). This molecule has been previously reported as maitotoxin-3. The structure of 44-methylgambierone was elucidated using 1D- and 2D-nuclear magnetic resonance spectroscopy and mass spectrometry techniques. The nine-ring polyether backbone (A–I) and functional groups (carbonyl, terminal diol, 1,3-diene and monosulphate) are the same for both compounds with the addition of an olefinic methyl group being the only modification in 44-methylgambierone.     

Discovery of a Potent GLUT Inhibitor from a Library of Rapafucins by Using 3D Microarrays

Glucose transporters play an essential role in cancer cell proliferation and survival and have been pursued as promising cancer drug targets. Using microarrays of a library of new macrocycles known as rapafucins, which were inspired by the natural product rapamycin, we screened for new inhibitors of GLUT1. We identified multiple hits from the rapafucin 3D microarray and confirmed one hit as a bona fide GLUT1 ligand, which we named rapaglutin A (RgA). We demonstrate that RgA is a potent inhibitor of GLUT1 as well as GLUT3 and GLUT4, with an IC₅₀ value of low nanomolar for GLUT1. RgA was found to inhibit glucose uptake, leading to a decrease in cellular ATP synthesis, activation of AMP‐dependent kinase, inhibition of mTOR signaling, and induction of cell‐cycle arrest and apoptosis in cancer cells. Moreover, RgA was capable of inhibiting tumor xenografts in vivo without obvious side effects. RgA could thus be a new chemical tool to study GLUT function and a promising lead for developing anticancer drugs.     

Dots,QWISPs, and BIRDs

We report work on several quantum structure based infrared detectors. We describe the concept of the submonolayer quantum dot based infrared photodetectors, report device results, and present imaging results from a megapixel focal plane array. We describe the concept and experimental progress of the quantum well intra-subband photodetector (QWISP), which is closely related to the quantum well infrared photodetector (QWIP), but uses the dopant-assisted intra-subband absorption mechanism in quantum wells for normal-incidence far infrared/terahertz radiation detection. We discuss aspects of superlattice heterostructure based barrier infrared detectors (BIRDs).     

The migration of alkali metal (Na+, Li+, and K+) ions in single crystalline vanadate nanowires: Rasch-Hinrichsen resistivity

We report the synthesis of single crystalline alkali metal vanadate nanowires, Li-vanadate (Li₄V₁₀O₂₇), Na-vanadate (NaV₆O₁₅), and K-vanadate (KV₄O₁₀) and their electrical properties in a single nanowire configuration. Alkali metal vanadate nanowires were obtained by a simple thermal annealing process with vanadium hydroxides(V(OH)₃) nanoparticles containing Li⁺, Na⁺, and K⁺ ions and further the analysis of the migration of charged particles (Li⁺, Na⁺, and K⁺) in vanadate by measuring the conductivity of them. We found that their ionic conductivities can be empirically explained by the Rasch-Hinrichsen resistivity and interpreted on the basis of transition state theory. Our results thus indicate that the Li ion shows the lowest potential barrier of ionic conduction due to its small ionic size. Additionally, Na-vanadate has the lowest ion number per unit V₂O₅, resulting in increased distance to move without collision, and ultimately in low resistivity at room temperature.     

Loop statistics in complex networks

We study a scaling property of the number M_h(N) of loops of size h in complex networks with respect to a network size N. For networks with a bounded second moment of degree, we find two distinct scaling behaviors: M_h(N) ~ (constant) and M_h(N) ~ lnN as N increases. Uncorrelated random networks specified only with a degree distribution and Markovian networks specified only with a nearest neighbor degree-degree correlation display the former scaling behavior, while growing network models display the latter. The difference is attributed to structural correlation that cannot be captured by a short-range degree-degree correlation.     

Single-body lensed photonic crystal fibers as side-viewing probes for optical imaging systems

We report the fabrication and performance of a lensed photonic crystal fiber (PCF) designed as a compact but effective side-viewing optical imaging probe. The lensed-PCF probe was implemented in a single body without using any other fibers or additional optics. The beam expansion region and a focusing ball lens, necessary for a focuser, were simultaneously formed along a small piece of PCF by applying arc discharges. The side-viewing ability was provided by polishing the ball lens with a femtosecond laser to form a total internal reflection surface. The working distance and the transverse resolution of the fabricated single-body lensed-PCF were experimentally measured to be 570 and 6.8 microm, respectively. With the proposed lensed-PCF probe, optical coherence tomography images of an in vitro biological sample were successfully obtained.     

Femtosecond laser ablation of polypropylene for breathable film

A polypropylene (PP) film was ablated using a femtosecond laser with a center wavelength of 785 nm, a pulse width of 184 fs and a repetition rate of 1 kHz. Increments of both the pulse energy and the shot number of pulses lead to co-occurrence of photochemical and thermal effect, demonstrated by the spatial expansion of rim on the surface of PP. The shapes of the laser-ablated PP films were imaged by a scanning electron microscope (SEM) and measured by a 3D optical measurement system (NanoFocus). And, the gas and water vapor transmission rate, mechanical properties of PP film micropatterned by fs laser pulses was characterized. Our results demonstrate that a femtosecond pulsed laser is an efficient tool for breathable packaging films in modifying the flow of air and gas, where the micropatterns are specifically tailored in size, location and number of which is easily controlled by laser processing conditions.     

A nonlinear finite-element model of the newborn middle ear

A three-dimensional static nonlinear finite-element model of a 22-day-old newborn middle ear is presented. The model includes the tympanic membrane (TM), malleus, incus, and two ligaments. The effects of the middle-ear cavity are taken into account indirectly. The geometry is based on a computed-tomography scan and on the published literature, supplemented by histology. A nonlinear hyperelastic constitutive law is applied to model large deformations. The middle-ear cavity and the Young's modulus of the TM have significant effects on TM volume displacements. The TM volume displacement and its nonlinearity and asymmetry increase as the middle-ear cavity volume increases. The effects of the Young's moduli of the ligaments and ossicles are found to be small. The simulated TM volume changes do not reach a plateau when the pressure is varied to either -3 kPa or +3 kPa, which is consistent with the nonflat tails often found in tympanograms in newborns. The simulated TM volume displacements, by themselves and also together with previous ear-canal model results, are compared with equivalent-volume differences derived from tympanometric measurements in newborns. The results suggest that the canal-wall volume displacement makes a major contribution to the total canal volume change, and may be larger than the TM volume displacement.