Simple Patterning of Cells on a Biocompatible Nonchemically Amplified Resist

Summary: A simple lithographic process in conjunction with a novel biocompatible nonchemically amplified photoresist material was successfully used for cell patterning. UV light irradiation on selected regions of the nonchemically amplified resist film renders the exposed regions hydrophilic by the formation of carboxylic groups. Mouse fibroblast cells were found to be preferentially aligned and proliferated on the UV light exposed regions of the nonchemically amplified resist film where carboxylic groups were present.

Schematic representation of the simplified lithographic process used for cell patterning.     

Gating the mechanistic pathway to the elusive 4-membered ring azeteoporphyrin

Photolysis of metalated (Cu and Ni) and free base 2-diazo-3-oxochlorins within a frozen matrix (λ = 457.9 nm, toluene, 80 K) generates a single photointermediate with a hypsochromically shifted electronic absorption spectrum relative to the starting diazochlorins. The appearance of ketene (~2131 cm(-1)) and azete (~1670 cm(-1)) vibrations in infrared absorption and Raman spectra, respectively, identifies this intermediate as resulting from the Wolff rearrangement of the diazochlorins upon N(2) loss. Computational modeling of the vibrational spectra and TDDFT simulation of the electronic transitions of potential photointermediates corroborate this assignment. Isolation and analysis of photoproducts of these diazochlorins formed within n-butanol-doped frozen toluene matrices indicate near exclusive formation of azeteoporphyrins. In sharp contrast, room temperature laser photolysis of these materials yields a mixture of photoproducts deriving from the presence of both carbene and ketene intermediates. Computational modeling of the intramolecular reactivity of the proposed sp(2) carbene intermediate shows exclusive bond insertion to the adjacent phenyl group, and no evidence of Wolff rearrangement. Computational reaction profile analyses reveal that the barrierless Wolff rearrangement proceeds via an out-of-plane carbene electronic configuration that is generated directly during the loss of N(2). The formation of out-of-plane carbene, resulting in the exclusive formation of the observed ketene photointermediate at low temperatures, is consistent with orbital symmetry considerations and by the geometric constraints imposed by the frozen matrix. Combined, this leads to a model showing that azeteoporphyrin formation via the Wolff rearrangement is dependent upon the structural disposition of the adjacent framework, and the specific reaction intermediate formed is very sensitive to this feature.     

Bimetallic Co–Ni/TiO<Subscript>2</Subscript> catalysts for selective hydrogenation of cinnamaldehyde

Bimetallic Co–Ni catalysts in the composition range Co_(1?x)Ni_x with x?=?0.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0, with total metal loading of 15% w/w and supported on TiO₂-P25, have been prepared by chemical reduction of the metal acetates by glucose in aqueous alkaline medium and characterized by XRD, TEM, TPR, XPS and H₂-TPD techniques. Selective hydrogenation of cinnamaldhyde (CAL) to hydrocinnamaldehyde (HCAL), cinnamyl alcohol (COL) and hydrocinnamyl alcohol (HCOL) has been investigated at 20 bar pressure, in the temperature range 120–140 °C. Co/Ni crystallite sizes in the range 6.0?±?1 nm are observed by TEM. TPR and XPS results indicate the formation of nanoscale Co–Ni alloys, which tend to weaken M–H bond strength, as revealed by H₂-TPD measurements. Ni/TiO₂ displays very high conversion of CAL (86.9%) with high selectivity (78.7%) towards HCAL formation at 140 °C. Co/TiO₂, on the other hand, exhibits relatively lower CAL conversion (55%) and higher selectivity (61.3%) for COL formation at the same temperature. However, bi-metallic Co–Ni catalysts in the composition range x?=?0.3–0.6 display very high conversion (>?98%) due to alloy formation and weakening of M–H bonds. Bimetallic Co_0.7Ni_0.3 catalyst displays high conversion of CAL (98.1%) and high selectivity (82.9%) towards HCOL. Overall CAL hydrogenation activity at 140 °C, when expressed as TOF, displays a maximum value at the composition Co_0.5Ni_0.5. Activity and selectivity patterns have been rationalized based on the reaction pathways observed on the catalysts and the influence of Co–Ni alloy formation and M–H bond strength. Thus, a synergetic effect, originating from an appropriate composition of base metal catalysts and reaction conditions, could result in hydrogenation activity comparable with noble metal based catalysts.     

Turbulent flow inside the cylinder of a Diesel engine — an experimental investigation using hot wire anemometer

This paper describes the measurement of mean velocity and turbulence intensity using hot-wire anemometry inside the cylinder of a Diesel engine under motoring (non-firing) conditions. The effects of engine speed and compression ratio on mean velocity and turbulence intensity have been studied. In addition, turbulence scales have also been evaluated using auto-correlation function and power spectrum which are obtained from fluctuating velocity. The measurements were carried out at 4 different locations inside the piston cavity. Mean velocity and turbulence intensity are found to increase with speed. Increase in compression ratio has significantly increased the mean velocity at all crank angles. The main feature of this investigation is that the experiments have been conducted at higher compression ratios and a relatively high speed using a single high temperature straight wire probe.List of symbols A constant - B constant - D hot-wire diameter - F(f) normalized one-dimensional energy spectral density function - f frequency - i current through the hot-wire - k thermal conductivity of air at any temperature - k ₀ thermal conductivity of air at reference temperature - L hot-wire length - L _t macro or integral time scale of turbulence - L _x macro or integral length scale of turbulence - N number of cycles - Nu Nusselt number - n constant - R hot-wire resistance - Re Reynolds number - R () auto-correlation coefficient - T period of measurement and temperature - T ₀ reference temperature - T _g cylinder gas temperature - T _w hot-wire temperature - U instantaneous velocity - U mean velocity - u _I fluctuating velocity - u turbulence intensity - _t absolute viscosity of air at any temperature - ₀ absolute viscosity of air at reference temperature - engine crank angle - correlation time - _t micro-time scale of turbulence - _x micro-length scale of turbulence     

An accurate finite element scheme with moving meshes for computing 3D‐axisymmetric interface flows

An accurate finite element scheme for computing 3D‐axisymmetric incompressible free surface and interface flows is proposed. It is based on the arbitrary Lagrangian Eulerian (ALE) approach using free surface/interface‐resolved moving meshes. Key features like the surface force, consisting of surface tension and the local curvature, and jumps in the density and viscosity over different fluid phases are precisely incorporated in the finite element formulation. The local curvature is approximated by using the Laplace–Beltrami operator technique combined with a boundary approximation by isoparametric finite elements. A new approach is used to derive the 3D‐axisymmetric form from the variational form in 3D‐Cartesian coordinates. Several test examples show the high accuracy and the robustness of the proposed scheme. Copyright © 2007 John Wiley & Sons, Ltd.     

Nonlinear optical characteristics of self-assembled films of ZnO

In the present work, we have investigated the nonlinear optical properties of self-assembled films formed from ZnO colloidal spheres by z-scan technique. The sign of the nonlinear component of refractive index of the material remains the same; however, a switching from reverse saturable absorption to saturable absorption has been observed as the material changes from colloid to self-assembled film. These different nonlinear characteristics can be mainly attributed to ZnO defect states and electronic effects when the colloidal solution is transformed into self-assembled monolayers. We investigated the intensity, wavelength and size dependence of saturable and reverse saturable absorption of ZnO self-assembled films and colloids. Values of the imaginary part of third-order susceptibility are calculated for particles of size in the range 20–300 nm at different intensity levels ranging from 40 to 325 MW/cm² within the wavelength range of 450–650 nm. PACS 81.16.Dn; 42.65.-k; 42.65.An; 42.70.-a; 42.70.Nq; 78.20.Ci     

Multi-channel gain and noise figure evaluation of Raman/EDFA hybrid amplifiers

We present detailed multi-channel experimental characterization of different configurations of single pump hybrid Raman-erbium doped fiber (EDF) amplifiers. The incorporation of an EDF section in a dispersion compensating Raman amplifier is demonstrated to provide superior performance than Raman only system. It is shown that the multi-channel gain spectrum is quite different form the single-channel case. We have also measured the polarization dependent gain (PDG) of the hybrid amplifier configurations and results show that different configurations of hybrid amplifiers have different PDG effects on long-haul optically amplified link.     

An Epidemic Model with a Time Delay in Transmission

We study a mathematical model which was originally suggested by Greenhalgh and Das and takes into account the delay in the recruitment of infected persons. The stability of the equilibria are also discussed. In addition, we show that the introduction of a time delay in the transmission term can destabilize the system and periodic solutions can arise by Hopf bifurcation.