Point Absorber Limits to Future Gravitational-Wave Detectors.

High-quality optical resonant cavities require low optical loss, typically on the scale of parts per million. However, unintended micron-scale contaminants on the resonator mirrors that absorb the light circulating in the cavity can deform the surface thermoelastically and thus increase losses by scattering light out of the resonant mode. The point absorber effect is a limiting factor in some high-power cavity experiments, for example, the Advanced LIGO gravitational-wave detector. In this Letter, we present a general approach to the point absorber effect from first principles and simulate its contribution to the increased scattering. The achievable circulating power in current and future gravitational-wave detectors is calculated statistically given different point absorber configurations. Our formulation is further confirmed experimentally in comparison with the scattered power in the arm cavity of Advanced LIGO measured by in situ photodiodes. The understanding presented here provides an important tool in the global effort to design future gravitational-wave detectors that support high optical power and thus reduce quantum noise.

An Introduction to Network Psychometrics: Relating Ising Network Models to Item Response Theory Models.

In recent years, network models have been proposed as an alternative representation of psychometric constructs such as depression. In such models, the covariance between observables (e.g., symptoms like depressed mood, feelings of worthlessness, and guilt) is explained in terms of a pattern of causal interactions between these observables, which contrasts with classical interpretations in which the observables are conceptualized as the effects of a reflective latent variable. However, few investigations have been directed at the question how these different models relate to each other. To shed light on this issue, the current paper explores the relation between one of the most important network models-the Ising model from physics-and one of the most important latent variable models-the Item Response Theory (IRT) model from psychometrics. The Ising model describes the interaction between states of particles that are connected in a network, whereas the IRT model describes the probability distribution associated with item responses in a psychometric test as a function of a latent variable. Despite the divergent backgrounds of the models, we show a broad equivalence between them and also illustrate several opportunities that arise from this connection.

First Demonstration of Electrostatic Damping of Parametric Instability at Advanced LIGO.

Interferometric gravitational wave detectors operate with high optical power in their arms in order to achieve high shot-noise limited strain sensitivity. A significant limitation to increasing the optical power is the phenomenon of three-mode parametric instabilities, in which the laser field in the arm cavities is scattered into higher-order optical modes by acoustic modes of the cavity mirrors. The optical modes can further drive the acoustic modes via radiation pressure, potentially producing an exponential buildup. One proposed technique to stabilize parametric instability is active damping of acoustic modes. We report here the first demonstration of damping a parametrically unstable mode using active feedback forces on the cavity mirror. A 15 538 Hz mode that grew exponentially with a time constant of 182 sec was damped using electrostatic actuation, with a resulting decay time constant of 23 sec. An average control force of 0.03 nN was required to maintain the acoustic mode at its minimum amplitude.

Effects of transients in LIGO suspensions on searches for gravitational waves.

This paper presents an analysis of the transient behavior of the Advanced LIGO (Laser Interferometer Gravitational-wave Observatory) suspensions used to seismically isolate the optics. We have characterized the transients in the longitudinal motion of the quadruple suspensions during Advanced LIGO's first observing run. Propagation of transients between stages is consistent with modeled transfer functions, such that transient motion originating at the top of the suspension chain is significantly reduced in amplitude at the test mass. We find that there are transients seen by the longitudinal motion monitors of quadruple suspensions, but they are not significantly correlated with transient motion above the noise floor in the gravitational wave strain data, and therefore do not present a dominant source of background noise in the searches for transient gravitational wave signals. Using the suspension transfer functions, we compared the transients in a week of gravitational wave strain data with transients from a quadruple suspension. Of the strain transients between 10 and 60 Hz, 84% are loud enough that they would have appeared above the sensor noise in the top stage quadruple suspension monitors if they had originated at that stage at the same frequencies. We find no significant temporal correlation with the suspension transients in that stage, so we can rule out suspension motion originating at the top stage as the cause of those transients. However, only 3.2% of the gravitational wave strain transients are loud enough that they would have been seen by the second stage suspension sensors, and none of them are above the sensor noise levels of the penultimate stage. Therefore, we cannot eliminate the possibility of transient noise in the detectors originating in the intermediate stages of the suspension below the sensing noise.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data.

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

Search for gravitational-wave bursts from soft gamma repeaters.

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190 lesser events from SGR 1806-20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the model-dependent isotropic GW emission energies (at a nominal distance of 10 kpc) between 3x10;{45} and 9x10;{52} erg depending on waveform type, detector antenna factors and noise characteristics at the time of the burst. These upper limits are within the theoretically predicted range of some SGR models.

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.

Lock acquisition of a gravitational-wave interferometer.

Interferometric gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) detectors currently under construction, are based on kilometer-scale Michelson interferometers, with sensitivity that is enhanced by addition of multiple coupled optical resonators. Reducing the relative optic motions to bring the system to the resonant operating point is a significant challenge. We present a new approach to lock acquisition, used to lock a LIGO interferometer, whereby the sensor transformation matrix is dynamically calculated to sequentially bring the cavities into resonance.

Readout and control of a power-recycled interferometric gravitational-wave antenna.

Interferometric gravitational-wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by the addition of multiple coupled optical resonators. The use of optical cavities is essential for reaching the required sensitivity but sets challenges for the control system, which must maintain the cavities near resonance. The goal for the strain sensitivity of the Laser Interferometer Gravitational-Wave Observatory (LIGO) is 10(-21) rms, integrated over a 100-Hz bandwidth centered at 150 Hz. We present the major design features of the LIGO length and frequency sensing and control system, which will hold the differential length to within 5 x 10(-14) m of the operating point. We also highlight the restrictions imposed by couplings of noise into the gravitational-wave readout signal and the required immunity against them.

Mechanisms controlling competence gene expression in murine fibroblasts stimulated with minimally modified LDL.

Mildly oxidized low density lipoprotein (minimally modified low density lipoprotein [MM-LDL] is capable of inducing gene expression in cells of the artery wall. In this study, we investigated the mechanisms that control the mRNA expression of JE, KC, c-myc, and c-fos in quiescent mouse L-cell fibroblasts stimulated with MM-LDL. The data demonstrate that MM-LDL induces increases greater than or equal to 20-fold in the levels of transcripts of these genes within 15-60 minutes. Of the four genes examined, JE and KC mRNA showed the greatest response to MM-LDL. The pattern of induction by MM-LDL is distinct from that observed in fibroblasts stimulated with serum, a known inducer of these genes. Treatment with cycloheximide (10 micrograms/ml) did not block the MM-LDL-induced increase in the mRNA levels of these genes. The increase of JE and KC mRNA levels in response to MM-LDL could be blocked by treatment with actinomycin D (5 micrograms/ml). In nuclear runoff studies, MM-LDL increased the transcription rate of JE and KC at 4 hours by 13-fold and fivefold, respectively. Small but reproducible stimulations of c-fos and c-myc transcription by MM-LDL were also observed. In addition, the half-life of JE mRNA was increased after addition of MM-LDL to fibroblasts, suggesting that the MM-LDL-induced accumulation of these mRNAs might be accomplished by both transcriptional and posttranscriptional mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.

Incubation of cocultures of human aortic endothelial (HAEC) and smooth muscle cells (HASMC) with LDL in the presence of 5-10% human serum resulted in a 7.2-fold induction of mRNA for monocyte chemotactic protein 1 (MCP-1), a 2.5-fold increase in the levels of MCP-1 protein in the coculture supernatants, and a 7.1-fold increase in the transmigration of monocytes into the subendothelial space of the cocultures. Monocyte migration was inhibited by 91% by antibody to MCP-1. Media collected from the cocultures that had been incubated with LDL induced target endothelial cells (EC) to bind monocyte but not neutrophil-like cells. Media collected from cocultures that had been incubated with LDL-induced monocyte migration into the subendothelial space of other cocultures that had not been exposed to LDL. In contrast, media from separate cultures of EC or smooth muscle cells (SMC) containing equal number of EC or SMC compared to coculture and incubated with the same LDL did not induce monocyte migration when incubated with the target cocultures. High density lipoprotein HDL, when presented to cocultures together with LDL, reduced the increased monocyte transmigration by 91%. Virtually all of the HDL-mediated inhibition was accounted for by the HDL2 subfraction. HDL3 was essentially without effect. Apolipoprotein AI was also ineffective in preventing monocyte transmigration while phosphatidylcholine liposomes were as effective as HDL2 suggesting that lipid components of HDL2 may have been responsible for its action. Preincubating LDL with beta-carotene or with alpha-tocopherol did not reduce monocyte migration. However, pretreatment of LDL with probucol or pretreatment of the cocultures with probucol, beta-carotene, or alpha-tocopherol before the addition of LDL prevented the LDL-induced monocyte transmigration. Addition of HDL or probucol to LDL after the exposure to cocultures did not prevent the modified LDL from inducing monocyte transmigration in fresh cocultures. We conclude that cocultures of human aortic cells can modify LDL even in the presence of serum, resulting in the induction of MCP-1, and that HDL and antioxidants prevent the LDL induced monocyte transmigration.

Characterization of mRNA species related to human liver cytochrome P-450 nifedipine oxidase and the regulation of catalytic activity.

P-450NF is the major enzyme in human liver involved in the metabolism of the calcium-channel blocker nifedipine. By screening a bacteriophage lambda gt11 expression library, a cDNA clone designated NF 10 with an insert length of 2.8 kilobases (kb) was isolated. This clone was sequenced and found to be highly similar in its overlapping section with sequences of two other cDNA clones previously isolated from the same expression library, NF 25 (Beaune, P. H., Umbenhauer, D. R., Bork, R. W., Lloyd, R. S., and Guengerich, F. P. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 8064-8068) and HLp (Molowa, D. T., Schuetz, E. G., Wrighton, S. A., Watkins, P. B., Kremers, P., Mendez-Picon, G., Parker, G. A., and Guzelian, P. S. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 5311-5315). However, clone NF 10 had an extra 814 or 813 bases of 3'-noncoding sequence relative to NF 25 or HLp, respectively, and this additional sequence contained a second consensus polyadenylation signal. Specific oligonucleotides were synthesized to differentiate between these three clones at the mRNA level. Oligonucleotides specific to the protein coding region of each clone were found to hybridize to mRNAs of 2.2 and 3.0 kb in size at a ratio of approximately 10:1. The major species of hybridizable mRNA was specific to clone NF 25, and levels of this mRNA could be correlated with levels of immunochemically detectable P-450NF and nifedipine oxidase activity in individual human liver samples. In addition, an oligonucleotide specific to the 3'-noncoding region of clone NF 10 hybridized only with the 3.0-kb mRNA. We conclude that alternative use of the second polyadenylation signal present in clone NF 10 results in production of the 3.0-kb mRNA species and that a pretranslational control mechanism is primarily involved in the regulation of nifedipine oxidase activity.

Characterization of cDNAs, mRNAs, and proteins related to human liver microsomal cytochrome P-450 (S)-mephenytoin 4'-hydroxylase.

A cytochrome P-450 (P-450) multigene family codes for several related human liver enzymes, including the P-450 responsible for (S)-mephenytoin 4'-hydroxylation. This enzyme activity has previously been shown to be associated with a genetic polymorphism. Genomic (Southern) blot analysis using non-overlapping 5' and 3' portions of a cDNA clone suggests that approximately seven related sequences are present in this gene family. In this study four cDNA clones, all nearly full-length, were isolated from a bacteriophage lambda gt11 library prepared from a single human liver. These clones can be grouped into two categories that are approximately 85% identical at the level of DNA sequence. The cDNA clones in one category (MP-4, MP-8) both match the N-terminal sequences of the P-450MP-1 and P-450MP-2 proteins, which had previously been shown to be catalytically active in (S)-mephenytoin 4'-hydroxylation. These two cDNAs, MP-4 and MP-8, differ in only two bases in the coding region but are quite distinct in their 3' noncoding regions. Another protein (P-450MP-3) was isolated on the basis of its immunochemical similarity to P-450MP-1 but was found to be catalytically inactive; amino acid sequencing of tryptic peptides of P-450MP-3 showed a correspondence to the second category of cDNA clones (MP-12, MP-20), which differ from each other in only four (nonsilent) base changes. Oligonucleotides specific for the two groups of cDNA clones were used as probes of human liver mRNAs--individual liver samples examined expressed both types of mRNAs but no correlation was observed between the abundance levels of any mRNA and catalytic activity. Further, oligonucleotide probes indicated that mRNAs corresponding to both the MP-4 and MP-8 clones were apparently present in individual liver samples. A monoclonal antibody was isolated that recognized P-450MP-1 but not P-450MP-2 or P-450MP-3; the amount of protein detected by the antibody in different liver samples was not correlated with the mephenytoin 4'-hydroxylase activity. These results indicate that several closely related P-450 genes are all expressed in individual human livers. The MP-4/MP-8 gene products are proposed to be the ones most likely involved in mephenytoin 4'-hydroxylation, and much of the variation in catalytic activity among individuals is not a result of differences in levels of P-450MP-1 or mRNA but may be due to base differences in the structural gene(s).

[Roentgenologic documentation of findings in coloscopy]. / Röntgenologische Befunddokumentation bei der Coloskopie.

This contribution covers the X-ray documentation of primary coloscopy findings in 29 patients. High coloscopy as a primary method of diagnosis used to have the disadvantage that when dealing with a circumscribed lesion requiring surgery, a barium enema had to be administered on order to localize it and determine its extent. The endoscopic-radiological coloscopy method described here combines primary coloscopy with a spatial visualization of the colon on an X-ray picture. It should bei applied wherever coloscopy is used as the primary method of examining the colon.

Isolation and sequence determination of a cDNA clone related to human cytochrome P-450 nifedipine oxidase.

Human liver cytochrome P-450NF is the form of cytochrome P-450 responsible for the oxidation of the calcium-channel blocker nifedipine, which has been reported to show polymorphism in clinical studies. By screening a bacteriophage lambda gt11 expression cDNA library, we isolated two clones: NF95 with an insert length of 0.8 kilobases which gave a stable fusion protein and NF25 with an insert length of 2.2 kilobases. The two clones were both sequenced and shown to be identical in their overlapping section. The sequence of NF25 is 77% similar to that reported for a rat cytochrome "P-450PCN" cDNA (PCN = pregnenolone-16 alpha-carbonitrile). The similarity decreases to 45-53% when the sequence is compared to human cytochromes P-450 belonging to other families [i.e., "pH P-450(1)," "P1-450," "P3-450," and "P-450MP." The deduced amino acid sequence is 73% similar to that of rat cytochrome P-450PCN, and the first 21 amino acids are identical to those reported for human liver cytochrome "P-450p." Sections of these clones were nick-translated and used as probes for analyses of human mRNA and genomic DNA. The number and size of bands indicate that P-450NF belongs to a multigene family, the so-called pregnenolone-16 alpha-carbonitrile-inducible family.