Measurement of the Earth tides with a MEMS gravimeter.

The ability to measure tiny variations in the local gravitational acceleration allows, besides other applications, the detection of hidden hydrocarbon reserves, magma build-up before volcanic eruptions, and subterranean tunnels. Several technologies are available that achieve the sensitivities required for such applications (tens of microgal per hertz(1/2)): free-fall gravimeters, spring-based gravimeters, superconducting gravimeters, and atom interferometers. All of these devices can observe the Earth tides: the elastic deformation of the Earth's crust as a result of tidal forces. This is a universally predictable gravitational signal that requires both high sensitivity and high stability over timescales of several days to measure. All present gravimeters, however, have limitations of high cost (more than 100,000 US dollars) and high mass (more than 8 kilograms). Here we present a microelectromechanical system (MEMS) device with a sensitivity of 40 microgal per hertz(1/2) only a few cubic centimetres in size. We use it to measure the Earth tides, revealing the long-term stability of our instrument compared to any other MEMS device. MEMS accelerometers--found in most smart phones--can be mass-produced remarkably cheaply, but none are stable enough to be called a gravimeter. Our device has thus made the transition from accelerometer to gravimeter. The small size and low cost of this MEMS gravimeter suggests many applications in gravity mapping. For example, it could be mounted on a drone instead of low-flying aircraft for distributed land surveying and exploration, deployed to monitor volcanoes, or built into multi-pixel density-contrast imaging arrays.

Silicate bonding of sapphire to SESAMs: adjustable thermal lensing for high-power lasers.

Silicate bonding is a flexible bonding method that enables room-temperature bonding of many types of materials with only moderate flatness constraints. It is a promising approach for bonding components in high power laser systems, since it results in a thin and low-absorption interface layer between the bonded materials. Here we demonstrate for the first time silicate bonding of a sapphire window to a SEmiconductor Saturable Absorber Mirror (SESAM) and use the composite structure to mode-lock a high-power thin-disk laser. We characterize the fabricated devices both theoretically and experimentally and show how the thermally induced lens of the composite structure can be tuned both in magnitude and sign via the thickness of the sapphire window. We demonstrate mode-locking of a high-power thin-disk laser oscillator with these devices. The altered thermal lens allows us to increase the output power to 233 W, a 70-W-improvement compared to the results achieved with a state-of-the-art SESAM in the same cavity.

High Precision Detection of Change in Intermediate Range Order of Amorphous Zirconia-Doped Tantala Thin Films Due to Annealing.

Understanding the local atomic order in amorphous thin film coatings and how it relates to macroscopic performance factors, such as mechanical loss, provides an important path towards enabling the accelerated discovery and development of improved coatings. High precision x-ray scattering measurements of thin films of amorphous zirconia-doped tantala (ZrO_{2}-Ta_{2}O_{5}) show systematic changes in intermediate range order (IRO) as a function of postdeposition heat treatment (annealing). Atomic modeling captures and explains these changes, and shows that the material has building blocks of metal-centered polyhedra and the effect of annealing is to alter the connections between the polyhedra. The observed changes in IRO are associated with a shift in the ratio of corner-sharing to edge-sharing polyhedra. These changes correlate with changes in mechanical loss upon annealing, and suggest that the mechanical loss can be reduced by developing a material with a designed ratio of corner-sharing to edge-sharing polyhedra.

Silicon-Based Optical Mirror Coatings for Ultrahigh Precision Metrology and Sensing.

Thermal noise of highly reflective mirror coatings is a major limit to the sensitivity of many precision laser experiments with strict requirements such as low optical absorption. Here, we investigate amorphous silicon and silicon nitride as an alternative to the currently used combination of coating materials, silica, and tantala. We demonstrate an improvement by a factor of ≈55 with respect to the lowest so far reported optical absorption of amorphous silicon at near-infrared wavelengths. This reduction was achieved via a combination of heat treatment, final operation at low temperature, and a wavelength of 2 µm instead of the more commonly used 1550 nm. Our silicon-based coating offers a factor of 12 thermal noise reduction compared to the performance possible with silica and tantala at 20 K. In gravitational-wave detectors, a noise reduction by a factor of 12 corresponds to an increase in the average detection rate by three orders of magnitude (≈12^{3}).

Amorphous Silicon with Extremely Low Absorption: Beating Thermal Noise in Gravitational Astronomy.

Amorphous silicon has ideal properties for many applications in fundamental research and industry. However, the optical absorption is often unacceptably high, particularly for gravitational-wave detection. We report a novel ion-beam deposition method for fabricating amorphous silicon with unprecedentedly low unpaired electron-spin density and optical absorption, the spin limit on absorption being surpassed for the first time. At low unpaired electron density, the absorption is no longer correlated with electron spins, but with the electronic mobility gap. Compared to standard ion-beam deposition, the absorption at 1550 nm is lower by a factor of ≈100. This breakthrough shows that amorphous silicon could be exploited as an extreme performance optical coating in near-infrared applications, and it represents an important proof of concept for future gravitational-wave detectors.

Determination of the refractive index and thickness of a hydroxide-catalysis bond between fused silica from reflectivity measurements.

Hydroxide-catalysis bonding is a high precision jointing technique producing strong, transparent and thin bonds, the use of which in the delicate fused silica mirror suspensions of aLIGO have been instrumental in the first detections of gravitational radiation. More sensitive future gravitational wave detectors will require more accurate (ideally in situ) measurements of properties such as bond thickness. Here a non-destructive technique is presented in which the thickness and refractive index of a bond are determined from measurements of optical reflectivity. The reflectivity of a bond made between two fused silica discs using sodium silicate solution is less than 1⋅10-3 after 3 months. The thickness decreases to a constant value of around 140 nm at its minimum and the refractive index increases from 1.36 to 1.45. This proves that as well as determination of bond thickness in situ this bonding technique is highly interesting for optical applications.

The rotating wind of the quasar PG 1700+518.

It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the disk to shed angular momentum that would otherwise inhibit accretion. Such winds are capable of depositing large amounts of mechanical energy in the host galaxy and its environs, profoundly affecting its formation and evolution, and perhaps regulating the formation of large-scale cosmological structures in the early Universe. Although there are good theoretical grounds for believing that outflows from active galactic nuclei originate as disk winds, observational verification has proven elusive. Here we show that structures observed in polarized light across the broad Halpha emission line in the quasar PG 1700+518 originate close to the accretion disk in an electron scattering wind. The wind has large rotational motions (approximately 4,000 km s(-1)), providing direct observational evidence that outflows from active galactic nuclei are launched from the disks. Moreover, the wind rises nearly vertically from the disk, favouring launch mechanisms that impart an initial acceleration perpendicular to the disk plane.

Circular polarization in star-formation regions: implications for biomolecular homochirality.

Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules.

A plant-based cholera toxin B subunit-insulin fusion protein protects against the development of autoimmune diabetes.

Oral administration of disease-specific autoantigens can prevent or delay the onset of autoimmune disease symptoms. We have generated transgenic potato plants that synthesize human insulin, a major insulin-dependent diabetes mellitus autoantigen, at levels up to 0.05% of total soluble protein. To direct delivery of plant-synthesized insulin to the gut-associated lymphoid tissues, insulin was linked to the C-terminus of the cholera toxin B subunit (CTB). Transgenic potato tubers produced 0.1% of total soluble protein as the pentameric CTB-insulin fusion, which retained GM1-ganglioside binding affinity and native antigenicity of both CTB and insulin. Nonobese diabetic mice fed transformed potato tuber tissues containing microgram amounts of the CTB-insulin fusion protein showed a substantial reduction in pancreatic islet inflammation (insulitis), and a delay in the progression of clinical diabetes. Feeding transgenic potato tissues producing insulin or CTB protein alone did not provide a significant reduction in insulitis or diabetic symptoms. The experimental results indicate that food plants are feasible production and delivery systems for immunotolerization against this T cell-mediated autoimmune disease.

Revision tympanoplasty including anterior perforations and lateralization of grafts.

Not long ago, the restoration of a perforated tympanic membrane by grafting over an air-containing tympanic cavity seemed impossible. Fortunately, successful results are so consistent and universal today that restoration of the tympanic membrane is expected, and a failure calls for careful evaluation as to "why". If known principles are observed, few complications need occur. Usually, complications are the result of either the choice and placement of the graft used in the repair, or the presence of unresolved upper respiratory pathology. When revision tympanoplasty is necessary, use of the underplay fascial graft technique, properly applied, usually can solve any difficult problems.

Comparison of various methods for in vitro cholesteryl ester labeling of lipoproteins from hypercholesterolemic rabbits.

Little or no information is available on biologically valid labeling of hypercholesterolemic plasma lipoproteins with cholesteryl ester. The esterification of labeled unesterified cholesterol in hypercholesterolemic rabbit plasma by the lecithin: cholesterol acyltransferase reaction is inefficient. The use of the d greater than 1.063 plasma fraction for this reaction greatly improves the efficiency, but some labeled unesterified cholesterol remains in the end products. The latter disadvantage can be avoided by the addition to whole plasma of labeled cholesteryl ester dissolved in DMSO or acetone. However, in hypercholesterolemic rabbit plasma only a small fraction of the added cholesteryl ester was associated with lipoproteins. When phosphatidylcholine/cholesteryl ester liposomes were incubated with hypercholesterolemic rabbit plasma for 18-24 h at 37 degrees C the labeled cholesteryl ester was quantitatively incorporated into lipoproteins. Chylomicron-like, cholesteryl ester-rich particles were removed by centrifugation (10(6) g X min) and the subsequently isolated d less than 1.019 and d = 1.019-1.063 (LDL) fractions were injected intravenously into normal and hypercholesterolemic rabbits. The disappearance of d less than 1.019 and LDL cholesteryl ester and the appearance of cholesteryl ester in other lipoprotein fractions was indistinguishable from that of in vivo-labeled lipoproteins. In vivo and in vitro cholesteryl ester-labeled lipoproteins were also compared by measuring the exchangeability of their cholesteryl ester with HDL cholesteryl ester in vitro. Equal exchangeability of the two labels was observed in the d less than 1.019 fraction from which the chylomicron-like particles had been removed. These findings demonstrate that when cholesteryl ester is incorporated by the liposome procedure, the distribution of labeled cholesteryl ester within the lipoprotein complex corresponds closely to that of the in vivo-incorporated labeled cholesteryl ester.

A review of current murine models of multiple myeloma used to assess the efficacy of therapeutic agents on tumour growth and bone disease.

Pre-clinical in vivo models of multiple myeloma are essential tools for investigating the pathophysiology of multiple myeloma and for testing new therapeutic agents and strategies prior to their potential use in clinical trials. Over the last five decades, several different types of murine models of multiple myeloma have been developed ranging from immunocompetent syngeneic models, e.g. the 5 T series of myeloma cells, to immunocompromised models including the SCID xenograft models, which use human myeloma cell lines or patient-derived cells. Other models include hybrid models featuring the implantation of SCID mice with bone chips (SCID-hu or SCID-rab) or 3-D bone scaffolds (SCID-synth-hu), and mice that have been genetically engineered to develop myeloma. Bearing in mind the differences in these models, it is not surprising that they reflect to varying degrees different aspects of myeloma. Here we review the past and present murine models of myeloma, with particular emphasis on their advantages and limitations, characteristics, and their use in testing therapeutic agents to treat myeloma tumour burden and bone disease.

Consideration of radiation quality in treatment planning with p(66)/Be(40) neutrons.

A thorough microdosimetric investigation of a p(66)/Be(40) neutron therapy beam has been performed employing a commercial tissue equivalent proportional counter. Using y* as a monoparameter of radiation quality, variations in the potency of the beam have been discerned with spatial position and for different field sizes in a water phantom. The identified variations with depth are attributed solely to changes in the character of the neutron component of the beam. When increasing the field size, neutron effects are tempered by an increasing photon component. To accommodate these quality changes in the prescription of absorbed dose, the concept of effective dose is invoked and elementary expressions are proposed to assess this quantity. A simple four-field treatment plan is calculated to show that if unaccounted for, the quality changes with depth alone would result in a 4% discrepancy between the prescribed and effective dose delivered to the tumor volume. The implications for optimum dose delivery in clinical practice are discussed in terms of these findings.

A d(16) + Be fast neutron beam for therapy.

A fast neutron therapy facility has been established utilizing the classical solid-pole cyclotron of the National Accelerator Centre (CSIR) in Pretoria. The neutron field is generated from the 9Be(d,n)10B reaction using 16 MeV deuterons on a thick target, yielding 0.51 cGy.min-1.microA-1 at an SSD of 135 cm. Essentially the beam characteristics concur with those measured at other centres with comparable energies.

Effect of vitamin A on longevity.

Increasing the dietary content of Vitamin A from inadequate to adequate during the developmental stages of Drosophila increased the median life span by as much as 17.5%. The optimum dietary range of concentrations of Vitamin A for increasing the life span of Drosophila was found to be between 4 and 8 IU/g food. The maximum life span was reduced as dietary concentrations of Vitamin A exceeded this value. Vitamin A palmitate and retinal inhibited the peroxidation of linolenic acid induced by the generation of superoxide radicals from acetaldehyde. Other forms of Vitamin A, such as retinol and retinoic acid, moderately inhibited lipid peroxidation at low concentrations but stimulated peroxidation considerably when present at high concentrations. Based upon the ability of these retinoids to inhibit the reduction of cytochrome c by superoxide radicals, we propose that retinoids can inhibit and stimulate lipid peroxidation depending upon their concentration by reacting with superoxide radicals. We suggest that this reaction is the basis for the apparent ability of Vitamin A to prolong and shorten life span depending upon the dietary intake.

Very high Q measurements on a fused silica monolithic pendulum for use in enhanced gravity wave detectors

We present for the first time the results of very high Q factor measurements for a 2.8 kg fused silica mass suspended by two fused quartz fibers attached by a novel technique for joining fused silica or quartz. The Q for the pendulum mode at 0.93 Hz was (2.3+/-0. 2)x10(7), the highest value demonstrated to date for a mass of this size. By employing such a new suspension system the sensitivity of the gravitational wave detectors currently under construction can be increased up to 1 order of magnitude.

Air in the aorta: treatment by reversed perfusion.

A ventricular septal defect was repaired in a 3 1/2-year-old child on cardiopulmonary bypass. Because of excessive pulmonary venous return, a period of circulatory arrest under deep hypothermia was used. A large volume of air was found in the arterial line and the ascending aorta before perfusion was reinstituted. The air probably entered the arterial system through a large aortopulmonary collateral artery during circulatory arrest. This artery was not visualized on angiocardiography and could have caused excessive pulmonary venous return during perfusion. Air was successfully expelled by reversed perfusion. There were no neurological sequelae.

Suppression of sexual behavior and localization of [3H] puromycin after intracranial injection in the rat.

Bilateral intracranial injections of puromycin (10 micrograms/0.5 microliter vehicle) into the preoptic area (POA) of steroid-primed ovariectomized rats resulted in a significant decrease in the lordosis response when compared to saline treated controls. To determine the extent of puromycin diffusion after intracranial injection, [3H] puromycin was injected into the right POA of ovariectomized rats. Neural regions anterior, posterior and superior to the POA, and the right and left POA were assessed for tritium activity 0.5, 6 and 24 hours after stereotaxic surgery. The activity was primarily located at the injection site or in the injection tract. The highest amount of activity external to the injection site or injection tract was found in the right ventromedial hypothalamus.

A modified lead attenuation method to determine the fast neutron sensitivity kU of a photon dosemeter.

Various lead attenuation techniques to determine the fast neutron sensitivity kU of a photon dosemeter are reviewed and a modified method is proposed to determine the kU value of a commercially available Geiger--Müller detector. The dependence on the 'effective' photon energy of the gamma-component of the mixed n--gamma field is illustrated and the most probable photon energy is deduced from measurements outside the radiation field. Using the relevant photon mass attenuation coefficient, measurements carried out with a well-collimated neutron beam at the MRC Cyclotron, Hammersmith Hospital, London, show that the Dg component contributes 2.41 +/- 0.13% to the total radiation field. Using a detector with a PTFE sleeve in the place of a Perspex sleeve, highly consistent results are obtained and the enhancement of the kU value by the Perspex is demonstrated. The neutron sensitivities of two MX 163 GM detectors with Perspex and PTFE sleeves were respectively determined as 0.73 +/- 0.07% and 0.98 +/- 0.14%.

The evaluation of nylon and polyethylene as build-up material in a neutron therapy beam.

In high-energy neutron beams a substantial amount of build-up material is required to irradiate biological samples under conditions of charged particle equilibrium. Ideally A-150 tissue-equivalent plastic is used for this purpose. This material is however not always readily available and hence the need for a substitute compound. The selected hydrocarbon should satisfy two requirements: the quality of the radiation on the distal side needs to be the same as that measured for A-150 plastic and the absorbed dose should remain consistent. A tissue-equivalent proportional counter operating at reduced pressure not only measures the absorbed dose accurately but provides a means for assessing the nature of a radiation field in terms of a secondary charged particle spectrum. Using build-up caps manufactured from nylon (type 6) and polyethylene, it is shown that the former is an acceptable substitute for A-150 plastic. The data further demonstrate that both the absorbed dose and the spectral character of the measured single-event distribution are altered when polyethylene is used and that these discrepancies are attributable to the higher hydrogen content of polyethylene.