Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Upper limits on a stochastic background of gravitational waves

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.

Limits on gravitational-wave emission from selected pulsars using LIGO data

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

Molecular patterning on carbon based surfaces through photobiotin activation

We have demonstrated the site-specific adhesion of photobiotin as a method of producing protein micropatterns. These patterns were created by the selective UV irradiation of a thin film of deposited photobiotin. The UV activated areas of photobiotin were then developed using fluorescently labelled avidin. The size of pattern produced is an order of magnitude smaller than those previously reported by this method. The patterns were characterised, using atomic force microscopy (AFM) to determine their microstructure. It was found that the AFM could discriminate between the areas of protein immobilised to the surface through the activated photobiotin, and the bare substrate surface where the inactivated photobiotin had been removed during the washing process. The potential of these patterns as sensing surfaces is demonstrated through the creation of a spatially patterned immunosensing surface. In this case, a biotinylated antibody was bound to the surface and the pattern developed using a second antibody specific to the immobilised biotinylated antibody. This technique could thus provide a simple and efficient method of producing high density immunoassay systems.

In-situ atomic force microscopy study of beta-amyloid fibrillization

We report the use of atomic force microscopy to observe the initial stages of beta-amyloid fibrillization in situ. The growth of individual beta-amyloid protofibrils on a mica substrate was followed over several hours. The first in situ visualization of protofibril formation from single aggregate units of beta-amyloid is reported. The growth of these protofibrils through the subsequent addition of these aggregate units is also observed. Growth of the protofibrils is bi-directional and the outgrowth of protofibrils from a common amyloid/heterogeneous core is also observed. Elongation also occurred by the addition of protofibrils from solution. This data provides an exciting insight into the early stages of beta-amyloid fibrillization and can be used to enhance the understanding of the mechanism(s) by which beta-amyloid fibrillizes and may consequently enable inhibition of one or more stages of fibrillization as a potential therapeutic strategy.

Discrimination of polymorphic forms of a drug product by localized thermal analysis

In chemical processing, it is important to distinguish between and identify polymorphic forms. We demonstrate the novel use of scanning thermal microscopy (SThM) and localized thermal analysis to distinguish and identify polymorphic forms of the drug cimetidine. These forms cannot be resolved by classical bulk thermal analysis. SThM reveals a sample consisting of a 50 : 50 mixture of the polymorphs contains regions of different thermal conductivity, corresponding to the different polymorphs. Localized thermal analysis of small volumes of pure polymorphic samples (approximately 50 microm3) shows that the origin of the thermal conductivity contrast lies, at least in part, with the presence of a surface water layer on the more hydrophilic polymorph.

Spatially controlled cell engineering on biodegradable polymer surfaces

Controlling receptor-mediated interactions between cells and template surfaces is a central principle in many tissue engineering procedures (1-3). Biomaterial surfaces engineered to present cell adhesion ligands undergo integrin-mediated molecular interactions with cells (1, 4, 5), stimulating cell spreading, and differentiation (6-8). This provides a mechanism for mimicking natural cell-to-matrix interactions. Further sophistication in the control of cell interactions can be achieved by fabricating surfaces on which the spatial distribution of ligands is restricted to micron-scale pattern features (9-14). Patterning technology promises to facilitate spatially controlled tissue engineering with applications in the regeneration of highly organized tissues. These new applications require the formation of ligand patterns on biocompatible and biodegradable templates, which control tissue regeneration processes, before removal by metabolism. We have developed a method of generating micron-scale patterns of any biotinylated ligand on the surface of a biodegradable block copolymer, polylactide-poly(ethylene glycol). The technique achieves control of biomolecule deposition with nanometer precision. Spatial control over cell development has been observed when using these templates to culture bovine aortic endothelial cells and PC12 nerve cells. Furthermore, neurite extension on the biodegradable polymer surface is directed by pattern features composed of peptides containing the IKVAV sequence (15, 16), suggesting that directional control over nerve regeneration on biodegradable biomaterials can be achieved.

Regulation of growth of cultured hepatic epithelial cells by transferrin

Late-passage cells of a nontumorigenic and anchorage-dependent hepatic epithelial line (WB-F344), which produce insulinlike growth factor II and transforming growth factor beta constitutively, grow in serum-free medium supplemented only with transferrin. In the presence of transferrin, epidermal growth factor further augments population growth, although epidermal growth factor alone is without effect. Insulin, platelet-derived growth factor, and several inorganic iron salts are also ineffective in supporting cell growth in the absence of transferrin; furthermore, these factors do not augment the action of transferrin. The population growth-promoting effect of transferrin occurs at concentrations of 0.5 nM or greater and the maximal effect is reached with a concentration of approximately 6 nM. A lipophilic iron chelator, ferric pyridoxal isonicotinoyl hydrazone (FePIH), can fully mimic the effect of transferrin on the proliferation of WB-F344 cells, but the molar concentration of transferrin. These results suggest that the critical function of transferrin in the proliferation of WB-F344 cells may be in the delivery of iron to the cells. In the absence of transferrin the proliferation of WB-F344 cells is arrested in serum-free medium in the G0/G1 phase, and a period of protein synthesis after the addition of transferrin is necessary before the cells can proceed to S phase and initiate DNA synthesis. Replacement of transferrin causes quiescent WB-F344 cells to cycle parasynchronously. Epidermal growth factor does not alter the length of the latency period prior to S phase but appears to stimulate the uptake of [3H]thymidine subsequently. Transferrin may act as a "competence" and/or "progression" factor, allowing the replication of these epithelial cell in vitro.

Are keratoacanthomas really squamous cell carcinomas?

Controversy continues to exist as to whether or not a keratoacanthoma is a benign lesion and can be accurately differentiated from a squamous cell carcinoma. From a review of the available evidence and clinical experience, we believe an attempt to make this distinction is unwise. It is dangerous to assume these lesions are benign. Many lesions diagnosed as keratoacanthomas have gone on to behave very aggressively and even to metastasize. We believe all lesions suspected of being keratoacanthomas should be managed by surgical excision and not observed in the hope that spontaneous involution will occur.