A genetical and biochemical investigation of the uptake of DNA by mammalian cells in culture

The published evidence relating to the uptake and genetic effects of purified DNA is reviewed, and the nature of polyoma pseudovirions is discussed. The characteristics of the biochemically-marked cell lines used in this work are described, and conditions for the labelling of DNA with bromodeoxyuridine and tritium are investigated. Experiments on the uptake of isolated DNA indicate that up to 5% of the DNA complement of the recipient cell is absorbed from the medium. There is a lag of 2-3 hours after addition of DNA to the medium before uptake becomes detectable, after which time uptake is much more rapid. Even at the earliest time at which donor DNA is detectable in recipient cells by autoradiography, all of it is found in the nuclei, unless DEAE-dextran is present in the medium, in which case the donor label appears in clumps in the cytoplasm. Density-labelling experiments are consistent with this, for in the presence of DEAE-dextran the donor DNA does not become associated with the density band characteristic of the recipient material. DEAE-dextran also prevents the association of donor DNA with high molecular-weight DNA in sucrose gradients, and renders the majority of DNA uptake insensitive to arabinosylcytosine. In addition to this, DNA absorbed in the presence of DEAE-dextran is lost from the cell over a period of about 48 hours after its removal from the medium. There is evidence that, even in the absence of DEAE-dextran, there is a fraction of the donor DNA which survives intact, although they are associated with' the recipient density band. Experiments are described which did not detect genetic changes in cells treated with polyoma pseudovirions or with pure DNA under a variety of conditions

Microfabrication of Optically Flat Silicon Micro-Mirrors for Fully Programmable Micro-Diffraction Gratings

AbstractWe have fabricated and characterized a Fully Programmable Micro-Diffraction Grating (FPMDG) with 64 silicon micro-mirrors for spectral shaping in the visible and near-infrared wavelength range. The FPMDG arrays of 50μm and 80μm wide and 700μm long silicon micro-mirrors have been fabricated in a process based on anodic bonding of an 8μm-SOI wafer and a borosilicate glass wafer. The detrimental bending of the micro-mirrors during electrostatic actuation has been minimized through separation of the mechanical and optical sections of the device. Flexures incorporating serpentine structures have been used to reduce the actuation dependence on length and thickness. Independent addressing of the micro-mirrors with negligible cross-talk and with bending of the micro-mirrors smaller than 0.14μm over 700μm have been demonstrated

Targeting a critical step in fungal hexosamine biosynthesis

Acknowledgements We wish to thank the Dundee Drug Discovery Unit for access to the Fragment library and the European Synchrotron Radiation Facility, Grenoble and Diamond Light Source, Oxford for time at the beamline. The assistance from Mr Martin Kierans, School of Life Sciences, University of Dundee with the Electron Microscopy is gratefully acknowledged. Funding and additional information This work was supported by a Wellcome Trust Postdoctoral Research Training Fellowship for Clinicians (WT105772/A/14/Z) to DL and an MRC Programme Grant (MR/M004139/1) to DMFvA. DB was funded by a University of Aberdeen Summer Research Scholarship.Peer reviewedPostprintPublisher PD

1980: Abilene Christian College Bible Lectures - Full Text

UNTIL HE COMES Being the Abilene Christian University Annual Bible Lectures 1980 Published by Abilene Christian University Book Store ACU Station Abilene, Texas 7969

ESD testing and combdrive snap-in in a MEMS tunable grating under shock and vibration

This work describes a method for tracking the dynamics of electrostatic discharge (ESD) sensitive MEMS structures during ESD events, as well as a model for determining the reduced combdrive snap-in voltage under vibration and shock. We describe our ESD test setup, based on the human body model, and optimized for high impedance devices. A brief description of the MEMS tunable grating, the test structure used here, and its operation is followed by results of the measured complex device dynamics during ESD events. The device fails at a voltage up to four times higher than that required to bring the parts into contact. We then present a model for the snap-in of combfingers under shock and vibration. We combine the results of the analytical model for combdrive snap-in developed here with a shock response model to compute the critical shock acceleration conditions that can result in combdrive snap-in as a function of the operating voltage. We discuss the validity regimes for the combdrive snap-in model and show how restricting the operation voltage below the snap-in voltage is not a sufficient criterion to ensure reliable operation especially in environments with large disturbances

Vibration and shock reliability of MEMS: modeling and experimental validation

A methodology to predict shock and vibration levels that could lead to the failure of MEMS devices is reported as a function of vibration frequency and shock pulse duration. A combined experimental–analytical approach is developed, maintaining the simplicity and insightfulness of analytical methods without compromising on the accuracy characteristic of experimental methods. The minimum frequency-dependent acceleration that will lead to surfaces coming into contact, for vibration or shock inputs, is determined based on measured mode shapes, damping, resonant frequencies, and an analysis of failure modes, thus defining a safe operating region, without requiring shock or vibration testing. This critical acceleration for failure is a strong function of drive voltage, and the safe operating region is predicted for transport (unbiased) and operation (biased condition). The model was experimentally validated for overdamped and underdamped modes of a comb-drive driven SOI-based tunable grating. In-plane and outofplane vibration (up to 65 g) and shock (up to 6000 g) tests were performed for biased and unbiased conditions, and very good agreement was found between predicted and observed critical accelerations

Atmospheric Pressure Deposition of Fluorinedoped SnO2 Thin Films from Organotin Fluorocarboxylate Precursors.

Nine organotin fluorocarboxylates RnSnO2CRf (n = 3, R = Bu, Rf = CF3, C2F5, C3F7, C7F15; R = Et, Rf = CF3, C2F5; R = Me, Rf = C2F5; n = 2, R =Me, Rf = CF3) have been synthesised; key examples have been used to deposit F-doped SnO2 thin films by atmospheric pressure CVD. Et3SnO2CC2F5, in particular, gives high quality films with fast deposition rates despite adopting a polymeric, carboxylate-bridged structure in the solid state, as determined by x-ray crystallography. Gas phase electron diffraction on the model compound Me3SnO2CC2F5 shows that accessible conformations do not allow contact between tin and fluorine, and that direct transfer is therefore unlikely to be part of the mechanism for fluorine incorporation in SnO2 films. The structure of Me2Sn(O2CCF3)2(H2O) has also been determined and adopts a trans- Me2SnO3 coordination sphere about tin in which each carboxylate group is monodentat

1968: Abilene Christian College Bible Lectures - Full Text

CROWNING FIFTY YEARS” Being the Fiftieth Annual ABILENE CHRISTIAN COLLEGE BIBLE LECTURES - 1968 J. D. THOMAS, LECTURESHIP DIRECTOR, EDITOR Published by ABILENE CHRISTIAN COLLEGE ACC Station, Abilene, Texas 7960