Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914

On September 14, 2015, a gravitational wave signal from a coalescing black hole binary system was observed by the Advanced LIGO detectors. This paper describes the transient noise backgrounds used to determine the significance of the event (designated GW150914) and presents the results of investigations into potential correlated or uncorrelated sources of transient noise in the detectors around the time of the event. The detectors were operating nominally at the time of GW150914. We have ruled out environmental influences and non-Gaussian instrument noise at either LIGO detector as the cause of the observed gravitational wave signal.

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4_{-0.9}^{+0.7}×10^{-22}. The inferred source-frame initial black hole masses are 14.2_{-3.7}^{+8.3}M_{⊙} and 7.5_{-2.3}^{+2.3}M_{⊙}, and the final black hole mass is 20.8_{-1.7}^{+6.1}M_{⊙}. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440_{-190}^{+180}  Mpc corresponding to a redshift of 0.09_{-0.04}^{+0.03}. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

Properties of the Binary Black Hole Merger GW150914

On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a gravitational-wave transient (GW150914); we characterize the properties of the source and its parameters. The data around the time of the event were analyzed coherently across the LIGO network using a suite of accurate waveform models that describe gravitational waves from a compact binary system in general relativity. GW150914 was produced by a nearly equal mass binary black hole of masses 36_{-4}^{+5}M_{⊙} and 29_{-4}^{+4}M_{⊙}; for each parameter we report the median value and the range of the 90% credible interval. The dimensionless spin magnitude of the more massive black hole is bound to be <0.7 (at 90% probability). The luminosity distance to the source is 410_{-180}^{+160}  Mpc, corresponding to a redshift 0.09_{-0.04}^{+0.03} assuming standard cosmology. The source location is constrained to an annulus section of 610  deg^{2}, primarily in the southern hemisphere. The binary merges into a black hole of mass 62_{-4}^{+4}M_{⊙} and spin 0.67_{-0.07}^{+0.05}. This black hole is significantly more massive than any other inferred from electromagnetic observations in the stellar-mass regime.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 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 203000 years, equivalent to a significance greater than 5.1 σ.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 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 203000 years, equivalent to a significance greater than 5.1 σ.

Tests of General Relativity with GW150914

The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 10^{13}  km. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.

GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes

The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses ≳30M_{⊙}, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and Advanced Virgo band for stochastic backgrounds (near 25 Hz), we predict Ω_{GW}(f=25  Hz)=1.1_{-0.9}^{+2.7}×10^{-9} with 90% confidence. This prediction is robustly demonstrated for a variety of formation scenarios with different parameters. The differences between models are small compared to the statistical uncertainty arising from the currently poorly constrained local coalescence rate. We conclude that this background is potentially measurable by the Advanced LIGO and Advanced Virgo detectors operating at their projected final sensitivity.

GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of 10^{-23}/sqrt[Hz] at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14, 2015, the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [B. P. Abbott et al., Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. Here, we present the main features of the detectors that enabled this observation. At full sensitivity, the Advanced LIGO detectors are designed to deliver another factor of 3 improvement in the signal-to-noise ratio for binary black hole systems similar in mass to GW150914.

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.

Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo

We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg2 to 20 deg2 will require at least three detectors of sensitivity within a factor of ∼ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Improved upper limits on the stochastic gravitational-wave background from 2009-2010 LIGO and Virgo data

Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of Ω_{GW}(f)=Ω_{α}(f/f_{ref})^{α}, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5-1726 Hz. In the frequency band of 41.5-169.25 Hz for a spectral index of α=0, we constrain the energy density of the stochastic background to be Ω_{GW}(f)<5.6×10^{-6}. For the 600-1000 Hz band, Ω_{GW}(f)<0.14(f/900  Hz)^{3}, a factor of 2.5 lower than the best previously reported upper limits. We find Ω_{GW}(f)<1.8×10^{-4} using a spectral index of zero for 170-600 Hz and Ω_{GW}(f)<1.0(f/1300  Hz)^{3} for 1000-1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.

Directional limits on persistent gravitational waves using LIGO S5 science data

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10(-50)  strain(2) Hz(-1) and 5-35×10(-49)  strain(2) Hz(-1) sr(-1) for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10(-25) in the most sensitive frequency range near 160 Hz.

A single-band envelope cue as a supplement to speechreading of segmentals: a comparison of auditory versus tactual presentation

OBJECTIVE

The objective of this study was to compare the effects of a single-band envelope cue as a supplement to speechreading of segmentals and sentences when presented through either the auditory or tactual modality.

DESIGN

The supplementary signal, which consisted of a 200-Hz carrier amplitude-modulated by the envelope of an octave band of speech centered at 500 Hz, was presented through a high-performance single-channel vibrator for tactual stimulation or through headphones for auditory stimulation. Normal-hearing subjects were trained and tested on the identification of a set of 16 medial vowels in /b/-V-/d/ context and a set of 24 initial consonants in C-/a/-C context under five conditions: speechreading alone (S), auditory supplement alone (A), tactual supplement alone (T), speechreading combined with the auditory supplement (S+A), and speechreading combined with the tactual supplement (S+T). Performance on various speech features was examined to determine the contribution of different features toward improvements under the aided conditions for each modality. Performance on the combined conditions (S+A and S+T) was compared with predictions generated from a quantitative model of multi-modal performance. To explore the relationship between benefits for segmentals and for connected speech within the same subjects, sentence reception was also examined for the three conditions of S, S+A, and S+T.

RESULTS

For segmentals, performance generally followed the pattern of T < A < S < S+T < S+A. Significant improvements to speechreading were observed with both the tactual and auditory supplements for consonants (10 and 23 percentage-point improvements, respectively), but only with the auditory supplement for vowels (a 10 percentage-point improvement). The results of the feature analyses indicated that improvements to speechreading arose primarily from improved performance on the features low and tense for vowels and on the features voicing, nasality, and plosion for consonants. These improvements were greater for auditory relative to tactual presentation. When predicted percent-correct scores for the multi-modal conditions were compared with observed scores, the predicted values always exceeded observed values and the predictions were somewhat more accurate for the S+A than for the S+T conditions. For sentences, significant improvements to speechreading were observed with both the auditory and tactual supplements for high-context materials but again only with the auditory supplement for low-context materials. The tactual supplement provided a relative gain to speechreading of roughly 25% for all materials except low-context sentences (where gain was only 10%), whereas the auditory supplement provided relative gains of roughly 50% (for vowels, consonants, and low-context sentences) to 75% (for high-context sentences).

CONCLUSIONS

The envelope cue provides a significant benefit to the speechreading of consonant segments when presented through either the auditory or tactual modality and of vowel segments through audition only. These benefits were found to be related to the reception of the same types of features under both modalities (voicing, manner, and plosion for consonants and low and tense for vowels); however, benefits were larger for auditory compared with tactual presentation. The benefits observed for segmentals appear to carry over into benefits for sentence reception under both modalities.

Information transmission with a multifinger tactual display

In this work, the tactual information transmission capabilities of a tactual display designed to provide stimulation along a continuum from kinesthetic movements to cutaneous vibrations are assessed. The display is capable of delivering arbitrary waveforms to three digits (thumb, index, and middle finger) within an amplitude range from absolute detection threshold to about 50 dB sensation level and a frequency range from dc to above 300 Hz. Stimulus sets were designed at each of three signal durations (125, 250, and 500 msec) by combining salient attributes, such as frequency (further divided into low, middle, and high regions), amplitude, direction of motion, and finger location. Estimated static information transfer (IT) was 6.5 bits at 500 msec, 6.4 bits at 250 msec, and 5.6 bits at 125 msec. Estimates of IT rate were derived from identification experiments in which the subject's task was to identify the middle stimulus in a sequence of three stimuli randomly selected from a given stimulus set. On the basis of the extrapolations from these IT measurements to continuous streams, the IT rate was estimated to be about 12 bits/sec, which is roughly the same as that achieved by Tadoma users in tactual speech communication.

Effects of rate of presentation on the reception of American Sign Language

Previous research on the visual reception of fingerspelled English suggests that communication rates are limited primarily by constraints on production. Studies of artificially accelerated fingerspelling indicate that reception of fingerspelled sentences is highly accurate for rates up to 2 to 3 times those that can be produced naturally. The current paper reports on the results of a comparable study of the reception of American Sign Language (ASL). Fourteen native deaf ASL signers participated in an experiment in which videotaped productions of isolated ASL signs or ASL sentences were presented at normal playback speed and at speeds of 2, 3, 4, and 6 times normal speed. For isolated signs, identification scores decreased from 95% correct to 46% correct across the range of rates that were tested; for sentences, the ability to identify key signs decreased from 88% to 19% over the range of rates tested. The results indicate a breakdown in processing at around 2.5-3 times the normal rate as evidenced both by a substantial drop in intelligibility in this region and by a shift in error patterns away from semantic and toward formational. These results parallel those obtained in previous studies of the intelligibility of the auditory reception of time-compressed speech and the visual reception of accelerated fingerspelling. Taken together, these results suggest a modality-independent upper limit to language processing.

Information transmission with a multi-finger tactual display

Motivated by the highly successful Tadoma method of speech communication, a multi-finger positional display (the TACTUATOR) was developed to study perception via the kinesthetic and vibrotactile aspects of the tactual sensory system of the hand. The information transmission capabilities with the TACTUATOR were assessed through a series of absolute identification experiments. An information transfer (IT) of 5.6 to 6.5 bits for stimulus durations of 125 to 500 msec was obtained in absolute-identification experiments with sets of signals derived by varying frequency, amplitude, and site of stimulation of multicomponent waveforms. An estimated IT rate of 12 bits/sec was obtained by sequencing three random stimuli and (a) having the subject identify only the middle stimulus and (b) extrapolating this IT to that for continuous streams. This IT rate is roughly the same as that achieved by Tadoma users in tactual speech communication.

Reception of Morse code through motional, vibrotactile, and auditory stimulation

The potential for communication through the kinesthetic aspect of the tactual sense was examined in a series of experiments employing Morse code signals. Experienced and inexperienced Morse code operators were trained to identify Morse code signals that were delivered as sequences of motional stimulation through up-down displacements (roughly 10 mm) of the fingertip. Performance on this task was compared with that obtained for both vibrotactile and acoustic presentation of Morse code using a 200-Hz tone delivered either to the fingertip through a minishaker or diotically to the two ears under headphones. For all three modalities, the ability to receive Morse code was examined as a function of presentation rate for tasks including identification of single letters, random three-letter sequences, common words, and sentences. Equivalent word-rate measures (i.e., product of percent correct scores and stimulus presentation rate) were nearly twice as high for auditory presentation as for vibrotactile stimulation, which in turn was about 1.3 times that for motional stimulation. The experienced subjects outperformed the inexperienced subjects by amounts that increased with task complexity. For example, the former were able to receive sentences at 18 words/min with motional stimulation, whereas the latter, following 75 h of training, were unable to perform this task. The present results and those of other research with tactual communication systems are compared, particularly regarding estimates of information-transfer rates.

Controlling conditioning-related emesis in children undergoing bone marrow transplantation

PURPOSE/OBJECTIVES

To compare the efficacy of two antiemetic regimens, ondansetron alone versus perphenazine with diphenhydramine, on emesis control in children undergoing conditioning therapy for bone marrow transplantation (BMT).

DESIGN

Single-center, prospective, open, randomized, crossover study.

SETTING

Pediatric BMT unit in an urban area in the northeastern United States.

SAMPLE

28 children, ages 4-17, undergoing BMT for a variety of underlying diseases.

METHODS

After randomization to one of the two antiemetic regimens, emesis control was evaluated during conditioning therapy. If a participant experienced more than five episodes of emesis during any 12-hour period, he or she was crossed over to the other antiemetic regimen. If emesis control still was not achieved, the participant was removed from the study and other medications were administered to control vomiting.

MAIN RESEARCH VARIABLES

Number of emetic episodes and incidence of side effects.

FINDINGS

10 of 15 patients (67%) who received ondansetron experienced major emesis control (no more than two episodes) compared with 0 of 13 patients (0%) who received perphenazine with diphenhydramine (p = 0.044, Fisher exact test). Of those who crossed over to ondansetron after failure with perphenazine and diphenhydramine, 38% were able to achieve major emesis control.

CONCLUSIONS

Ondansetron offers superior antiemetic control over the combination of perphenazine and diphenhydramine for children undergoing high-dose chemotherapy with or without total body irradiation for BMT.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses must develop an understanding of the etiology of therapy-induced emesis and the mechanisms of action of the various classes of antiemetic agents designed to control it. Implementing documentation to describe events of emesis will help to tailor antiemetic therapy to a patient's specific situation. Further research is necessary to determine alternate strategies, including different combinations or sequences of antiemetics to provide optimum emetic control during acute and delayed phases of emesis. The higher cost of ondansetron therapy must be considered within the context of superior efficacy.

Speaking clearly for the hard of hearing IV: Further studies of the role of speaking rate

The contribution of reduced speaking rate to the intelligibility of "clear" speech (Picheny, Durlach, & Braida, 1985) was evaluated by adjusting the durations of speech segments (a) via nonuniform signal time-scaling, (b) by deleting and inserting pauses, and (c) by eliciting materials from a professional speaker at a wide range of speaking rates. Key words in clearly spoken nonsense sentences were substantially more intelligible than those spoken conversationally (15 points) when presented in quiet for listeners with sensorineural impairments and when presented in a noise background to listeners with normal hearing. Repeated presentation of conversational materials also improved scores (6 points). However, degradations introduced by segment-by-segment time-scaling rendered this time-scaling technique problematic as a means of converting speaking styles. Scores for key words excised from these materials and presented in isolation generally exhibited the same trends as in sentence contexts. Manipulation of pause structure reduced scores both when additional pauses were introduced into conversational sentences and when pauses were deleted from clear sentences. Key-word scores for materials produced by a professional talker were inversely correlated with speaking rate, but conversational rate scores did not approach those of clear speech for other talkers. In all experiments, listeners with normal hearing exposed to flat-spectrum background noise performed similarly to listeners with hearing loss.

Dye coupling in the muscles controlling squid chromatophore expansion

Dye coupling between the cone-shaped radial muscle fibres, which control the expansion and closing of a squid chromatophore organ, was investigated in the squid Loligo vulgaris. Particular attention was paid to the role of the myomuscular junctions located between the muscle fibres. Lucifer Yellow was injected ionophoretically into single muscle fibres under normal artificial sea water (ASW) and under various concentrations of calcium in ASW. Under ASW, 44% of muscle fibres examined were dye-coupled, 82% were coupled under calcium-free sea water and 67% were coupled under sea water containing high concentrations of calcium. Dye transfer was blocked by octanol. Muscle fibres were never seen to link adjacent chromatophore organs. Results are discussed in terms of the role of the myomuscular junctions in the regulation of chromatophore expansion in the living animal.

The ultrastructure and innervation of muscles controlling chromatophore expansion in the squid, Loligo vulgaris

Squid chromatophores are organs of colour change, consisting of a pigment sac opened by contraction of 10-24 radial muscle fibres. The ultrastructure and innervation of these muscle fibres were examined by electron microscopy and diagramatic reconstructions made on the basis of serial ultra-thin sections. At the proximal end of the fibre, nearest the pigment sac a cortical myofilament zone surrounds 2 cores containing mitochrondria; further along the fibre these merge to form one central core. The myofilament zone forms a groove containing a nerve bundle consisting of 2 to 4 axons per muscle fibre. The axons are surrounded by glial cell processes, and either originate from a neighbouring fibre, or join the fibre at some point along its length. Axons twist around each other, forming a series of synapses with the muscle fibre. As many as 6-37 synapses exist along the length of each muscle fibre; the mean synapse interval is 9.05 microm, but the largest may be 123 microm. At the distal end of the muscles, the nerve is located towards the middle of the fibre, which it penetrates as the muscle splits up. Electron-lucent vesicles are present in all synaptic regions, but electron-dense vesicles are only found towards the distal end of the fibre. There is thus a possibility that more than one neurotransmitter is present in the nerves innervating chromatophores. Electron-lucent and dense-cored vesicles are not colocalised.

A study of the tactual reception of sign language

One of the natural methods of tactual communication in common use among individuals who are both deaf and blind is the tactual reception of sign language. In this method, the receiver (who is deaf-blind) places a hand (or hands) on the dominant (or both) hand(s) of the signer in order to receive, through the tactual sense, the various formational properties associated with signs. In the study reported here, 10 experienced deaf-blind users of either American Sign Language (ASL) or Pidgin Sign English (PSE) participated in experiments to determine their ability to receive signed materials including isolated signs and sentences. A set of 122 isolated signs was received with an average accuracy of 87% correct. The most frequent type of error made in identifying isolated signs was related to misperception of individual phonological components of signs. For presentation of signed sentences (translations of the English CID sentences into ASL or PSE), the performance of individual subjects ranged from 60-85% correct reception of key signs. Performance on sentences was relatively independent of rate of presentation in signs/sec, which covered a range of roughly 1 to 3 signs/sec. Sentence errors were accounted for primarily by deletions and phonological and semantic/syntactic substitutions. Experimental results are discussed in terms of differences in performance for isolated signs and sentences, differences in error patterns for the ASL and PSE groups, and communication rates relative to visual reception of sign language and other natural methods of tactual communication.

Intensity perception. XIV. Intensity discrimination in listeners with sensorineural hearing loss

Intensity discrimination of pulsed tones (also called level discrimination) was measured as a function of level in 13 listeners with sensorineural hearing impairment of primarily cochlear origin, one listener with a vestibular schwannoma, and six listeners with normal hearing. Measurements were also made in normal ears presented with masking noise spectrally shaped to produce audiograms similar to those of the cochlearly impaired listeners. For unilateral impairments, tests were made at the same frequency in the normal and impaired ears. For bilateral-sloping impairments, tests were made at different frequencies in the same ear. The normal listeners showed results similar to other data in the literature. The listener with a vestibular schwannoma showed greatly reduced intensity resolution, except at a few levels. For listeners with recruiting sensorineural impairments, the results are discussed according to the configuration of the impairment and are compared across configurations at equal SPL, equal SL, and equal loudness level. Listeners with increasing hearing losses at frequencies above the test frequency generally showed impaired resolution, especially at high levels, and less deviation from Weber's law than normal listeners. Listeners with decreasing hearing loss at frequencies above the test frequency showed nearly normal intensity-resolution functions. Whereas these trends are generally present, there are also large differences among individuals. Results obtained from normal listeners who were tested in the presence of masking noise indicate that elevated thresholds and reduced dynamic range account for some, but not all, of the effects of recruiting sensorineural impairment on intensity resolution.

Spectrum of disease in persons with human immunodeficiency virus infection in the United States

OBJECTIVE

To describe the spectrum of disease in persons with human immunodeficiency virus (HIV) infection.

DESIGN

Retrospective survey of medical records.

SETTING

More than 50 clinics, hospitals, and private medical practices in nine US cities.

PATIENTS

A total of 626 women and 7008 men 13 years of age or older with HIV infection who received medical care from January 1990 through March 1991 were consecutively enrolled.

MAIN OUTCOME MEASURES

Any history of diseases in the 1987 case definition for the acquired immunodeficiency syndrome (AIDS), and during the 12-month period preceding enrollment (baseline period), the occurrence of other major diseases, hospitalizations, and results of CD4+ lymphocyte counts.

RESULTS

Thirty-two percent of persons met the 1987 case definition for AIDS. The occurrence of an AIDS-indicator disease during the baseline period ranged from 3% (33/1011) to 46% (1254/2748) among persons with CD4+ lymphocyte counts of 0.50 x 10(9)/L or greater and fewer than 0.20 x 10(9)/L (greater than or equal to 500 and less than 200 CD4+ lymphocytes per microliter), respectively, and, at comparable CD4+ lymphocyte levels, was similar among women compared with men, and among persons who reported intravenous drug use compared with men who reported male-to-male sex. The frequency of one or more other major infectious diseases (eg, other pneumonias, bacterial sepsis, pulmonary tuberculosis) ranged from 6% to 16% among persons with CD4+ lymphocyte counts of 0.50 x 10(9)/L or greater and fewer than 0.20 x 10(9)/L, respectively; these illnesses were also associated with a history of intravenous drug use. Among persons who did not meet the 1987 AIDS case definition, 30% of those with an available CD4+ lymphocyte count had fewer CD4+ cells than 0.20 x 10(9)/L, 8% had one or more major infectious diseases, and 14% had one or more hospital admissions.

CONCLUSIONS

For every person with AIDS at these sites, two additional persons with HIV infection were receiving medical care, many of whom had severe immunosuppression and a broad spectrum of serious HIV-related disease.

Development and testing of artificial low-frequency speech codes

In a new approach to the frequency-lowering of speech, artificial codes were developed for 24 consonants (C) and 15 vowels (V) for two values of lowpass cutoff frequency F (300 and 500 Hz). Each individual phoneme was coded by a unique, nonvarying acoustic signal confined to frequencies less than or equal to F. Stimuli were created through variations in spectral content, amplitude, and duration of tonal complexes or bandpass noise. For example, plosive and fricative sounds were constructed by specifying the duration and relative amplitude of bandpass noise with various center frequencies and bandwidths, while vowels were generated through variations in the spectral shape and duration of a ten-tone harmonic complex. The ability of normal-hearing listeners to identify coded Cs and Vs in fixed-context syllables was compared to their performance on single-token sets of natural speech utterances lowpass filtered to equivalent values of F. For a set of 24 consonants in C-/a/ context, asymptotic performance on coded sounds averaged 90 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 75 percent and 40 percent for lowpass filtered speech. For a set of 15 vowels in /b/-V-/t/ context, asymptotic performance on coded sounds averaged 85 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 85 percent and 50 percent for lowpass filtered speech. Identification of coded signals for F = 500 Hz was also examined in CV syllables where C was selected at random from the set of 24 Cs and V was selected at random from the set of 15 Vs. Asymptotic performance of roughly 67 percent correct and 71 percent correct was obtained for C and V identification, respectively. These scores are somewhat lower than those obtained in the fixed-context experiments. Finally, results were obtained concerning the effect of token variability on the identification of lowpass filtered speech. These results indicate a systematic decrease in percent-correct score as the number of tokens representing each phoneme in the identification tests increased from one to nine.

The benefit of cesarean section in acute myocardial infarction complicated by premature labor

A 42-year-old woman with no known risk factors had an acute myocardial infarction at 32 weeks' gestation and went into premature labor. She required invasive hemodynamic monitoring and inotropic support. Congestive heart failure improved dramatically after cesarean section. During the acute infarction, ventricular dysfunction was out of proportion to the ultimate ventricular damage. The concept of the stunned myocardium is used to explain this finding and to justify early cesarean section. Another complication of her infarction, left ventricular thrombosis, has not previously been described in pregnancy.

Epidemiological aspects of a St. Louis encephalitis outbreak in Harris County, Texas, 1986

An outbreak of St. Louis encephalitis (SLE) resulted in 28 cases of the disease in Harris County, Texas, in 1986. The cases occurred principally in Baytown, in eastern Harris County, but five cases were also recognized in Houston. The risk of illness increased sharply with age, and all five fatal cases were in persons greater than 55 y. Case-control methods were used for the first time to study factors associated with the risk of acquiring SLE. Risk was associated with residences poorly sealed against mosquitoes (non-air-conditioned residences and those with inadequate screens). The number of hours spent outdoors and in outdoor activities, except sitting immediately outside residences, were not associated with risk. Our observations suggest that exposure to vector mosquitoes may have occurred indoors. No host factors were significantly associated with risk of acquiring SLE, but more cases were cigarette smokers and had family histories of hypertension or cerebrovascular disease.

Human cutaneous leishmaniasis acquired in Texas

Four cases of autochthonous human cutaneous leishmaniasis have been identified in south-central Texas since 1980. The patients presented with chronic ulcerating papules on the face, earlobe, and lateral thigh. In two patients, the infections healed without treatment. In the other two patients, the lesions healed following treatment with intramuscular sodium stibogluconate or topical antimony potassium tartrate. Serologic testing of family members, using four different techniques, indicates that asymptomatic infections may occur. These are the first reported cases of cutaneous leishmaniasis acquired in Texas since 1974. Organisms isolated from patients in 1974 and 1980 belonged to the Leishmania mexicana complex when tested by the isoenzyme technique. Although no animal reservoir or insect vector has been identified, six species of sand flies belonging to the genus Lutzomyia do inhibit this part of Texas. Accumulated evidence strongly suggests that cutaneous leishmaniasis is endemic in south-central Texas.

Nosocomial transmission of hepatitis A from a hospital-acquired case

An outbreak of hepatitis A occurred in a pediatric hospital in Texas. The index case had been admitted during the incubation period for cardiac surgery and developed symptoms while hospitalized. A child in a nearby bed acquired hepatitis A, as did three staff members. The second child was still hospitalized when she developed symptoms and infected 12 nurses, 3 physicians, 2 medical students, 2 patients and 1 respiratory therapist. Children with diarrhea can effectively disseminate this virus even when normal hospital routines and rules of hygiene are observed.

Discrimination of speech processed by low-pass filtering and pitch-invariant frequency lowering

Consonant discriminability by normal-hearing listeners was studied for monosyllables processed using frequency lowering with either uniform (linear) or nonuniform (warped) compression of the frequency axis. The bandwidth of the compressed signal was either 2500 or 1250 Hz and five compression characteristics were studied, in addition to low-pass filtering, for each of the two bandwidths. Stimuli were 24 consonant-vowel syllables made up of 24 consonants and three vowels, recorded three times by each of two male and female speakers. A "roving-speaker, roving-vowel, roving-utterance," two-interval, forced-choiced procedure with feedback was employed. As expected, performance for the 2500-Hz bandwidth was superior to that for the 1250-Hz bandwidth. For each bandwidth, compression schemes which accomplished greater lowering of the high frequencies relative to the low frequencies resulted in the highest performance. Overall performance for the best frequency-lowering system studied, however, was roughly comparable to that obtained for low-pass filtering. Patterns of performance over articulatory features were different for frequency lowering and filtering. In general, lowering was superior to filtering for contrasts of fricative sounds but inferior for contrasts of nasals and semivowels.

The epidemiology of heat-related deaths, Texas--1950, 1970-79, and 1980

A study of the deaths during a 1980 heat wave in Texas revealed death rates that were highest in males, the elderly, Blacks and those engaged in heavy labor, the latter two factors perhaps reflecting socioeconomic status. The data suggest that persistent high temperatures were related to death to a greater degree than the temperature peaks reached. Higher heat death rates in earlier years are believed to be attributable to the limited availability of air conditioning in those years.

Analytic study of the Tadoma method: further experiments with inexperienced observers

Results are presented for two studies of speechreading through the Tadoma method using normal subjects with simulated deafness and blindness. In the first study, subjects received training on the identification of consonant and vowel stimuli through Tadoma. In posttraining tests, an average score of 73% was obtained on a set of 24 consonants presented in CV syllables, and an average score of 82% was obtained on a set of 15 vowels and diphthongs presented in /g/-V-/d/ syllables. An analysis of the confusion matrices derived from the identification tests in terms of of various articulatory/phonological features indicated that the features place, voicing, frication, and round were well-perceived for consonants and round, tense, vertical lip separation, and low, for vowels. In the second study, subjects received training through Tadoma on comprehension of sentences composed of words from a 43-item vocabulary. In tests for which sentence stimuli were repeated until a correct response was obtained, the subjects identified an average of 30% of the words correctly on the first presentation and required an average of roughly four presentations for complete identification of the stimulus.

Analytic study of the Tadoma method: identification of consonants and vowels by an experienced Tadoma user

Performance on identifying consonant and vowel stimuli through the Tadoma methods of speechreading was studied for a deaf-blind, experienced user of Tadoma. For a set of 24 consonants in CV syllables, performance averaged 55%. For a set of 15 vowels and diphthongs in CVC syllables, performance averaged 56%. Confusion matrices derived from the identification tests were analyzed for performance on a set of articulatory/phonological features, the results of the feature analysis for consonants indicated that the features voicing, lip rounding frication, and place were well-perceived; for vowels, and features lip rounding, tenseness, and vertical lip separation were well-perceived.

Analytic study of the Tadoma method: discrimination ability of untrained observers

This study reports the ability of two observers with normal-hearing and sight to discriminate pairs of speech elements through the Tadoma method of speechreading. The observers were blindfolded and exposed to masking noise to eliminate visual and auditory cues. They placed their right hand over the speaker's face and neck so that the thumb rested lightly on the lips and the fingers fanned out over the cheek and neck. The discrimination tests were conducted using an ABX procedure. Average discrimination scores for the five types of test materials used in the ABX tests were 87% on W-22 words, 83% on Modified Rhyme Test words, 70% on vowels, 77% on CV and VC nonsense syllables, and 71% on consonant clusters. In all of the ABX tests, the inexperienced observers performed at least as well as the experienced Tadoma user studied by Norton, et al (1977). This finding indicates that the basic tactile sensitivity of inexperienced observers is comparable to that of an experienced deaf-blind Tadoma user.

A comparison of the effects of filtering and sensorineural hearing loss on patients of consonant confusions

It has been found that listeners with sensorineural hearing loss who show similar patterns of consonant confusions also tend to have similar audiometric profiles. The present study determined whether normal listeners, presented with filtered speech, would produce consonant confusions similar to those previously reported for the hearing-impaired listener. Consonant confusion matrices were obtained from eight normal-hearing subjects for four sets of CV and VC nonsense syllables presented under six high-pass and six-low pass filtering conditions. Patterns of consonant confusion for each condition were described using phonological features in sequential information analysis. Severe low-pass filtering produced consonant confusions comparable to those of listeners with high-frequency hearing loss. Severe high-pass filtering gave a result comparable to that of patients with flat or rising audiograms. And, mild filtering resulted in confusion patterns comparable to those of listeners with essentially normal hearing. An explanation in terms of the spectrum, the level of speech, and the configuration of this individual listener's audiogram is given.