Biodegradable Polylactic Acid (PLA) Microstructures for Scaffold Applications

In this research, we present a simple and cost effective soft lithographic process to fabricate PLA scaffolds for tissue engineering. In which, the negative photoresist JSR THB-120N was spun on a glass subtract followed by conventional UV lithographic processes to fabricate the master to cast the PDMS elastomeric mold. A thin poly(vinyl alcohol) (PVA) layer was used as a mode release such that the PLA scaffold can be easily peeled off. The PLA precursor solution was then cast onto the PDMS mold to form the PLA microstructures. After evaporating the solvent, the PLA microstructures can be easily peeled off from the PDMS mold. Experimental results show that the desired microvessels scaffold can be successfully transferred to the biodegradable polymer PLA.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Iron Emission in the z=6.4 Quasar SDSS J114816.64+525150.3

We present near-infrared J and K-band spectra of the z = 6.4 quasar SDSS J114816.64+525150.3 obtained with the NIRSPEC spectrograph at the Keck-II telescope, covering the rest-frame spectral regions surrounding the C IV 1549 and Mg II 2800 emission lines. The iron emission blend at rest wavelength 2900-3000 A is clearly detected and its strength appears nearly indistinguishable from that of typical quasars at lower redshifts. The Fe II / Mg II ratio is also similar to values found for lower-redshift quasars, demonstrating that there is no strong evolution in Fe/alpha broad-line emission ratios even out to z=6.4. In the context of current models for iron enrichment from Type Ia supernovae, this implies that the SN Ia progenitor stars formed at z > 10. We apply the scaling relations of Vestergaard and of McLure & Jarvis to estimate the black hole mass from the widths of the C IV and Mg II emission lines and the ultraviolet continuum luminosity. The derived mass is in the range (2-6)x10^9 solar masses, with an additional uncertainty of a factor of 3 due to the intrinsic scatter in the scaling relations. This result is in agreement with the previous mass estimate of 3x10^9 solar masses by Willott, McLure, & Jarvis, and supports their conclusion that the quasar is radiating close to its Eddington luminosity.Comment: To appear in ApJ Letter

Flexible parylene actuator for micro adaptive flow control

This paper describes the first flexible parylene electrostatic actuator valves intended for micro adaptive flow control for the future use on the wings of micro-air-vehicle (MAV). The actuator diaphragm is made of two layers of parylene membranes with offset vent holes. Without electrostatic actuation, air can move freely from one side of the skin to the other side through the vent holes. With actuation, these vent holes are sealed and the airflow is controlled. The membrane behaves as a complete diaphragm. We have successfully demonstrated this function using a 2-mm x 2-mm parylene diaphragm electrostatic actuator valves. This work also includes the novel anti-stiction technology that is crucial to make such large-area parylene actuator diaphragm with the combined use of anti-stiction posts, self-assembled monolayers (SAM), surface roughening, and bromine trifluoride (BrFe) dry etching. With the help of SAM treatment, the operating voltage is lowered from 30 volts to 13 volts. The load deflection method is then used to measure the effective thickness of the composite diaphragm. The flexible parylene diaphragm can be deflected up to 100 μm when 150 Torr of pressure is applied. The result is fitted into a theoretical model and yields an effective thickness of 5.9 μm, which is agreeable with the actual thickness of 5.6 μm, thus proves the functionality of the device

The vertical metal insulator semiconductor tunnel transistor: A proposed Fowler-Nordheim tunneling device

We propose a new field-effect transistor, the vertical metal insulator semiconductor tunnel transistor (VMISTT) which operates using gate modulation of the Fowler-Nordheim tunneling current through a metal insulator semiconductor (M-I-S) diode. The VMISTT has significant advantages over the metal-oxide-semiconductor field-effect transistor in device scaling. In order to allow room-temperature operation of the VMISTT, the tunnel oxide has to be optimized for the metal-to-insulator barrier height and the current-voltage characteristics. We have grown TiO2 layers as the tunnel insulator by oxidizing 7 and 10 nm thick Ti metal films vacuum-evaporated on silicon substrates, and characterized the films by current-voltage and capacitance-voltage techniques. The quality of the oxide films showed variations, depending on the oxidation temperatures in the range of 450-550 degrees C. Fowler-Nordheim tunneling was observed at low temperatures at bias voltage of 2 V and above and a barrier height of approximately 0.4 eV was calculated. Leakage currents present were due Schottky-barrier emission at room-temperature, and hopping at liquid nitrogen temperature

Evaluation of MHOST analysis capabilities for a plate element

Results of the evaluation of the static, buckling, and free vibration analyses capabilities of MHOST for the plate elements are presented. Two large scale, general purpose finite element codes (MARC and MSC/NASTRAN) are used to validate MHOST. Comparisons of MHOST results with those from MARC and MSC/NASTRAN show good agreement and indicate that MHOST can be used with confidence to perform the aforementioned analyses using the plate element

Off-diagonal hyperfine interaction between the 6p1/2 and 6p3/2 levels in 133Cs

The off-diagonal hyperfine interaction between the 6p1/2 and 6p3/2 states in 133Cs is evaluated in third-order MBPT giving 37.3 Hz and 48.3 Hz, respectively, for second-order energies of the 6p3/2 F=3 and F=4 levels. This result is a factor of 10 smaller than one obtained from an uncorrelated first-order Dirac-Hartree-Fock calculation and used in the analysis of a recent high-precision (< 2 kHz) measurement of the 6p3/2 hyperfine structure [Gerginov et al. Phys. Rev. Lett. 91, 72301 (2003)]. The factor of 10 difference has negligible effect on the conclusions of the recent experiment but will become important for experiments carried out at a precision of better than 1 kHz

Anomalous Magnetic and Thermal Behavior in Some RMn2O5 Oxides

The RMn2O5 (R=Pr, Nd, Sm, and Eu) oxides showing magnetoelectric (ME) behavior have been prepared in polycrystalline form by a standard citrate route. The lattice parameters, obtained from the powder XRD analysis, follow the rare-earth contraction indicating the trivalent character of the R ions. Cusp-like anomalies in the magnetic susceptibility curve and sharp peaks in the specific heat were reported at the corresponding temperatures in RMn2O5 (R=Pr, Nd, Sm, and Eu) indicating the magnetic or electric ordering transitions.Comment: 2 pages, 1 table, 3 figures, will be published in the Proceedings of the 24th International Conference on Low Temperature Physic