Asymmetric-cut variable-incident-angle monochromator

A novel asymmetric-cut variable-incident-angle monochromator was constructed and tested in 1997 at the Advanced Photon Source of Argonne National Laboratory. The monochromator was originally designed as a high heat load monochromator capable of handling 5-10 kW beams from a wiggler source. This was accomplished by spreading the x-ray beam out on the surface an asymmetric-cut crystal and by using liquid metal cooling of the first crystal. The monochromator turned out to be a highly versatile monochromator that could perform many different types of experiments. The monochromator consisted of two 18° asymmetrically cut Si crystals that could be rotated about 3 independent axes. The first stage (Φ) rotates the crystal around an axis perpendicular to the diffraction plane. This rotation changes the angle of the incident beam with the surface of the crystal without changing the Bragg angle. The second rotation (Ψ) is perpendicular to the first and is used to control the shape of the beam footprint on the crystal. The third rotation (Θ) controls the Bragg angle. Besides the high heat load application, the use of asymmetrically cut crystals allows one to increase or decrease the acceptance angle for crystal diffraction of a monochromatic x-ray beam and allows one to increase or decrease the wavelength bandwidth of the diffraction of a continuum source like a bending-magnet beam or a normal x-ray-tube source. When the monochromator is used in the doubly expanding mode, it is possible to expand the vertical size of the double-diffracted beam by a factor of 10-15. When this was combined with a bending magnet source, it was possible to generate an 8 keV area beam, 16 mm wide by 26 mm high with a uniform intensity and parallel to 1.2 arc sec that could be applied in imaging experiments.

Interface Temperatures and Temperature Gradients in Silicon During Pulsed Laser Irradiation

Nanosecond-resolution x-ray diffraction has been used to measure the interface and lattice temperatures of silicon during rapid, pulsed-laser induced melting and regrowth in silicon. Measurements have been carried out on <100> and <111> oriented silicon using the (100) and (111) reflections to measure the thermal strain during 30 ns, 1.1 J/cm2 KrF laser pulses. The results indicate overheating to be low (< 2 K/m/s) for both orientations with undercooling rates of 5.6 K/m/s and 11.4 K/m/s for the <100> and <111> orientations, respectively. Observations of higher than expected temperature gradients below the liquidsolid interface have been discussed in terms of restricted heat flow under high gradients.

Overheating In Silicon During Pulsed-Laser Irradiation?

Nanosecond resolution time-resolved x-ray diffraction measurements of thermal strain have been used to measure the interface temperatures in silicon during pulsed-laser irradiation. The pulsed-time-structure of the Cornell High Energy Synchrotron Source (CHESS) was used to measure the temperature of the liquid-solid interface of <111> silicon during melting with an interface velocity of 11 m/s, at a time of near zero velocity, and at a regrowth velocity of 6 m/s. The results of these measurements indicate 110 K difference between the temperature of the interface during melting and regrowth, and the measurement at zero velocity shows that most of the difference is associated with undercooling during the regrowth phase.

Time-Resolved Study of Silicon During Pulsed-Laser Annealing

Near surface temperatures and temperature gradients have been studied in silicon during pulsed laser annealing. The investigation was carried out using nanosecond resolution x-ray diffraction measurements made at the Cornell High Energy Synchrotron Source. Thermal-induced-strain analyses of these real-time, extended Bragg scattering measurements have shown that the lattice temperature reached the melting point during 15 ns, 1.1–1.5 J/cm2 ruby laser pulses and that the temperature of the liquid-solid interface remained at that temperature throughout the high reflectivity phase, after which time the surface temperature subsided rapidly. The temperature gradients below the liquid-solid interface were found to be in the range of 107°C/cm.

Time-Resolved X-ray Absorption Spectroscopy of Carbon Monoxide-Myoglobin Recombination After Laser Photolysis

Results are presented for the first time-resolved x-ray absorption measurements with a time resolution of 300 microseconds on a dynamically evolving chemical system. By synchronizing a neodymium: yttrium-aluminum-garnet pulsed laser with the bursts of x-rays emitted from the Cornell High Energy Synchrotron Source, it was possible to monitor at room temperature the recombination of carbon monoxide with myoglobin after laser photolysis. Changes in the pre-edge structure and in the position of the iron edge of this protein were detected as a function of time.

Clocking femtosecond X rays

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Two functional O-polysaccharide polymerase wzy (rfc) genes are present in the rfb gene cluster of Group E1 Salmonella enterica serovar Anatum

Defined regions of the rfb gene cluster of Group E1 Salmonella enterica serovar Anatum were introduced into a mutated derivative of this strain that lacks O-polysaccharide polymerase activity. Three different kinds of assays performed on the various transformants all indicate that two functional wzy (rfc) genes reside within the Group E1 Salmonella rfb gene cluster. The product of ORF9.6, positioned near the center of the rfb gene cluster, joins O-polysaccharide repeat units together by alpha-glycosidic linkages to produce antigen O10, the major serological determinant of Group E1 S. enterica. The product of ORF17.4, positioned at the downstream end of the rfb gene cluster, can join repeat units together by beta-glycosidic linkages to produce antigen O15, the major serological determinant of Group E2 S. enterica.

Air pollution and respiratory symptoms: results from three panel studies in Bangkok, Thailand

Several studies in North American cities have reported associations between air pollution and respiratory symptoms. Replicating these studies in cities with very different population and weather characteristics is a useful way of addressing uncertainties and strengthening inferences of causality. To this end we examined the responses of three different panels to particulate matter (PM) air pollution in Bangkok, Thailand, a tropical city characterized by a very warm and humid climate. Panels of schoolchildren, nurses, and adults were asked to report daily upper and lower respiratory symptoms for 3 months. Concentrations of daily PM(10) (PM with a mass median aerodynamic diameter less than 10 microm) and PM(2.5) (airborne particles with aerodynamic diameters less than 2.5 microm) were collected at two sites. Generally, associations were found between these pollution metrics and the daily occurrence of both upper and lower respiratory symptoms in each of the panels. For example, an interquartile increase of 45 microg/m(3) in PM(10) was associated with about a 50% increase in lower respiratory symptoms in the panel of highly exposed adults, about 30% in the children, and about 15% in the nurses. These estimates were not appreciably altered by changes in the specification of weather variables, stratification by temperature, or inclusion of individual characteristics in the models; however, time trends in the data cause some uncertainty about the magnitude of the effect of PM on respiratory symptoms. These pollutants were also associated with the first day of a symptom episode in both adult panels but not in children. The estimated odds ratios are generally consistent with and slightly higher than the findings of previous studies conducted in the United States.

Distortion product otoacoustic emission and auditory brainstem responses in the echidna (Tachyglossus aculeatus)

The auditory function of four wild-caught echidnas was measured using distortion product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). Emission audiograms were constructed by finding the stimulus levels required to produce a criterion emission amplitude at a given stimulus frequency. For an emission amplitude of -10 dB SPL, the median "best threshold" was 28 dB SPL, and this minimum threshold occurred between 4 and 8 kHz for all animals. The relative effective range of auditory function was defined by the frequencies at which the audiogram was 30 dB above its best threshold. For the emission audiograms, the median lower-frequency limit was 2.3 kHz, the upper limit was 18.4 kHz, and the effective range was 2.7 octaves. The audiogram as measured by ABR was also found to be strongly "U" shaped with similar low- and high-frequency limits, i.e., from 1.6 to 13.9 kHz, with an effective range of 3.1 octaves. These results suggest that the echidna has a behavioral hearing sensitivity comparable to that of typical therian mammals (e.g., rabbits and gerbils) but with a significantly narrower frequency range. DPOAE responses were also measured in selected animals as a function of the variation of all four stimulus parameters (frequencies and intensities of both stimulus tones). Overall, the measured emission responses establish that the echidna does have a cochlear amplifier, and that it could be the same type as in therian mammals. The amplification mechanism in the echidna, currently unidentified, clearly operates to frequencies above 20 kHz, higher than the hearing function observed in any birds or reptiles but lower than for typical therian mammals. This raises the possibility that at least some aspects of the mammalian cochlear amplifier developed early in evolution, before the divergence of the monotremes (echidna and platypus) from the mainstream therian mammals (marsupials and placentals). In this respect, the presence or absence of outer hair cell electromotility in monotremes would have important consequences for understanding the function and evolution of the vertebrate inner ear.

The effects of critical incident stress debriefing (CISD) on emergency medical services personnel following the Los Angeles Civil Disturbance

This study examined the effects of Critical Incident Stress Debriefing (CISD) upon technicians who provided emergency medical services in South Central Los Angeles during the 1992 Los Angeles Civil Disturbance. The relationships between exposure, debriefing and symptoms of stress were identified and examined. The Frederick Reaction Index-Adult (FRI-A) was used to measure the presence of symptoms characteristic of posttraumatic stress disorder. EMTs who had the opportunity to participate in Critical Incident Stress Debriefings (n = 42) following the incident reported fewer symptoms and scored significantly lower on the FRI-A than those not participating in Critical Incident Stress Debriefing (n = 23).

Frequency responses of two- and three-tone distortion product otoacoustic emissions in Mongolian gerbils

The frequency responses of distortion product otoacoustic emission (DPOAEs) were investigated in adult Mongolian gerbils. The main goal was to investigate in this species the extent to which DPOAE measurements might be useful in estimating cochlear frequency-tuning characteristics. Specifically, this study investigated the parameter space for generation of DPOAEs to determine those regions, if any, where the emission responses gave "simple" frequency responses, i.e., responses similar in form to typical neural responses. At the same time, it was desired to determine in this species the existence, extent, and nature of the more complex three-tone emission frequency responses as observed in some other species [e.g., Martin et al., Hearing Res. 136, 105-123 (1999)]. In the present work, two-tone frequency response curves (f2/f1 ratio functions) were obtained by varying the lower frequency, f1, while holding the f2 frequency and both amplitudes (L1, L2) constant. Only for frequencies, f2, near 8 kHz did the response at the emission frequency, 2 f1-f2, form a simple, relatively broad peak. At all lower frequencies, the two-tone frequency response curve was typically complex and composed of multiple peaks. In comparison, three-tone frequency responses were constructed by fixing the primary stimulus pair (f1, f2) and varying a third tone widely in frequency (f3) and intensity (L3). Points in f3 and L3 which caused a criterion reduction in primary emission amplitude (at 2 f1-f2) were used to construct emission suppression tuning curves (STCs). Only for primary frequencies, f2, at 8 kHz and above were the emission STCs found to be simple, with shapes similar to neural frequency-tuning curves. At lower primary frequencies, particularly for relatively low primary frequency ratios (low f2/f1), three-tone responses were very complex. This complex response usually included a region of anomalous suppression in which very low suppression levels (L3) could result in significant decreases in the primary emission amplitude, often exceeding 12 dB. Regions of such anomalous suppression were typically observed under the following conditions: (1) for all f2 frequencies from 0.5 to 4 kHz; (2) for f3 frequencies between 1.4 and 8 kHz; (3) i.e., for f3 frequencies 1-3 octaves above the primary frequency, f2; (4) at L3 levels often 10 dB lower or more than the usual "best frequency" threshold, i.e., even lower than the relative minimum threshold found near the primary stimulus frequencies; (5) exhibiting sharp amplitude decreases often accompanied by emission phase shifts of about 180 deg; (6) present in both cubic emissions (2 f1-f2 and 2 f2-f1); (7) to be less extreme at larger primary stimulus frequency ratios (larger f2/f1); and (8) less extreme at larger intensity ratios (larger L1/L2). Because of the anomalous behavior at f2 frequencies below 8 kHz, "simple" emission STCs were typically only obtainable, if at all, near the extreme boundaries of the parameter space giving measurable emission amplitudes.

The historical development of cryogenically cooled monochromators for third-generation synchrotron radiation sources

In the period of the late-1980s, before the construction of multi-GeV third-generation storage rings with their intense insertion-device sources, the perceived number one problem for X-ray instrumentation was proper cooling of the first optical element in the beamline. This article, first given as an acceptance speech for the Compton Award ceremony at the Advanced Photon Source, presents a somewhat historical and anecdotal overview of how cryogenically cooled monochromator optics have been developed to provide a monochromator cooling solution adequate for today's power levels. A series of workshops and international collaborations were the key components for the progress and final success of this development.

Parametric down conversion of X-ray photons

Parametric down conversion of X-ray photons in diamond crystals was detected in two experiments, both using the phase-matching scheme first employed in the X-ray regime by Eisenberger & McCall [Phys. Rev. Lett. (1971), 26, 684-688]. The conversion events were detected by a combination of time-correlation spectroscopy and energy discrimination, using Si drift-chamber detectors. The time-correlation spectra give a direct comparison of the conversion rate over the accidental coincidence rate. Mechanisms for possible detection of false events and ways to cross check against them are discussed in detail.

Performance limits of direct cryogenically cooled silicon monochromators - experimental results at the APS

The successful use of cryogenically cooled silicon monochromators at third-generation synchrotron facilities is well documented. At the Advanced Photon Source (APS) it has been shown that, at 100 mA operation with the standard APS undulator A, the cryogenically cooled silicon monochromator performs very well with minimal (<2 arcsec) or no observable thermal distortions. However, to date there has not been any systematic experimental study on the performance limits of this approach. This paper presents experimental results on the performance limits of these directly cooled crystals. The results show that if the beam is limited to the size of the radiation central cone then, at the APS, the crystal will still perform well at twice the present 100 mA single 2.4 m-long 3.3 cm-period undulator heat load. However, the performance would degrade rapidly if a much larger incident white-beam size is utilized.

A new high-speed beam chopper for time-resolved X-ray studies

A new high-speed X-ray beam chopper, which can be phase locked to the temporal structure of the Advanced Photon Source (APS) storage ring, has been developed and tested. The open window time of the chopper is 2450 ns, which corresponds to approximately 67% of the revolution time of the APS storage ring. By phase locking the rotation of the beam chopper to the storage-ring orbital frequency, any portion of the storage-ring fill pattern can be positioned within the beam-chopper transmission-time window.

Total condylar knee arthroplasty. 16- to 21-year results

This study presents long term results of arthroplasty with posterior cruciate retention using the Total Condylar Knee implant. From 1976 to 1982, 139 patients had 159 knee arthroplasties using Total Condylar Knee prostheses. Sixty-three patients (72 knees) were available for followup at a minimum of 16 years (range, 16-21 years). The average age of the patients at the time of surgery was 61 years. There were 21 men and 42 women. Patients with 68 knees had osteoarthrosis, three had rheumatoid arthritis and one had posttraumatic arthritis. There were five delayed complications. One patient (one knee) underwent revision surgery and two patients (two knees) declined revision surgery because they were considered to be high surgical risks, as determined by their internists. The average preoperative score was 40.3 points and improved to 88.4 points at followup. Eighty-seven percent of the patients had a score equal to or more than 85 points at last evaluation. Prosthesis survivorship at 20 years was 98.6% for patients who had revision surgery. No femoral components were revised for aseptic loosening. Retention of the posterior cruciate in Total Condylar Knee prosthesis produces results comparable with the results of the original Total Condylar Knee prosthesis with cruciate sacrifice.

Genomic-sequence comparison of two unrelated isolates of the human gastric pathogen Helicobacter pylori

Helicobacter pylori, one of the most common bacterial pathogens of humans, colonizes the gastric mucosa, where it appears to persist throughout the host's life unless the patient is treated. Colonization induces chronic gastric inflammation which can progress to a variety of diseases, ranging in severity from superficial gastritis and peptic ulcer to gastric cancer and mucosal-associated lymphoma. Strain-specific genetic diversity has been proposed to be involved in the organism's ability to cause different diseases or even be beneficial to the infected host and to participate in the lifelong chronicity of infection. Here we compare the complete genomic sequences of two unrelated H. pylori isolates. This is, to our knowledge, the first such genomic comparison. H. pylori was believed to exhibit a large degree of genomic and allelic diversity, but we find that the overall genomic organization, gene order and predicted proteomes (sets of proteins encoded by the genomes) of the two strains are quite similar. Between 6 to 7% of the genes are specific to each strain, with almost half of these genes being clustered in a single hypervariable region.

Cochlear implant performance after reimplantation: a multicenter study

OBJECTIVE

This study compares auditory performance between original and replacement cochlear implants.

STUDY DESIGN AND SETTING

Data from 18 U.S. cochlear implant programs were obtained by retrospective chart review. Patients received and returned subjective questionnaires.

PATIENTS

Twenty-eight adults with once-functioning Nucleus 22 cochlear implants that failed received replacement Nucleus 22 cochlear implants in the same ears.

MAIN OUTCOME MEASURES

Objective measures included sentence (CID Everyday Sentences or Iowa Sentences) and monosyllabic word (NU-6 Words or CNC Words) speech discrimination scores. Patients also rated and compared performance using subjective scales.

RESULTS

Thirty-seven percent of patients had significantly higher sentence or word scores with their replacement cochlear implants than with their original implants, 26% had no significant change, and 37% had significantly poorer scores. Subjectively, 57% of patients reported that the performance of their replacement device was better or the same and 43% reported that it was poorer. There was no correlation between performance with the replacement cochlear implant and cause of the original device failure, duration of original device use before failure, surgical complications with either implantation, changes in electrode insertion depths, or preoperative variables, such as age, etiology, or duration of deafness.

CONCLUSIONS

Speech recognition ability with a replacement cochlear implant may significantly increase or decrease from that with the original implant. Experienced cochlear implant patients facing reimplantation must be counseled regarding the possibility of differences in sound quality and speech recognition performance with their replacement device.

Multi-layered PZT/polymer composites to increase signal-to-noise ratio and resolution for medical ultrasound transducers

Increasing transducer bandwidth and signal-to-noise ratio (SNR) is fundamental to improving the quality of medical ultrasound images. In previous work, the authors have proposed the use of multi-layer 1-3 PZT/epoxy composites to increase both but have encountered significant fabrication challenges. These difficulties include making the bond thickness between the layers extremely small relative to the ultrasound wavelength and aligning the posts of the composite to increase the coupling coefficient. The authors have routinely achieved a bond thickness of less than 5 mum but aligning the posts is more complicated. Finite element (PZFlex; Weidlinger, Assoc., New York, NY and Los Altos, CA) simulations show that the pulse-echo SNR and bandwidth degrade significantly with misalignment of the posts. Alignment of greater than 90% of the post pitch (i.e., tolerance of 10 to 20 mum) is required to obtain significant increases in SNR and bandwidth relative to conventional transducer arrays. This will be a difficult tolerance for large-scale production. Thus, the authors have developed a multi-layer composite hybrid array that will not require post alignment. This structure consists of a layer of 5 MHz 1-3 composite material on top of conventional 5 MHz PZT, which will provide greater SNR relative to conventional composites and increased bandwidth over multi-layer PZT. PZFlex simulations show that for a 2 MHz linear array element, the 2 layer hybrid structure increases the pulse-echo SNR by 7.5 dB over that from a single layer PZT element. Even without a matching layer, an increase in the -6 dB pulse-echo fractional bandwidth from 22% for the PZT element to 35% for the hybrid element was also predicted. Experimentally, in a 32 element array, the authors achieved an increase of 5.2 dB in SNR and an increased -6 dB bandwidth from 23 to 30%. In vitro and in vivo images showed corresponding improvements.

Development of the base of the cochlea: place code shift in the gerbil

Distortion product otoacoustic emission measurements were made at 1/12 octave intervals before and after the injection of furosemide in gerbils aged 15 days after birth to adult, in order to obtain estimates of cochlear amplifier gain as a function of stimulus frequency. The frequency at which the gains went sharply to zero, defined as the 'base cutoff frequency', increased from about 20 kHz to over 50 kHz during development. This increase provides further confirmation of the hypothesis that the place code changes during development in the basal part of the cochlea. If the measured base cutoff frequency is identified with the characteristic frequency at the basal end of the cochlea, as defined by electrophysiological measures, then these emission data can be used to generate a frequency-place map as a function of age. The derived place code shift is consistent with published electrophysiological measures, and can be used to extend these measures. Near the base cutoff frequency, the observed cochlear amplifier gain typically dropped sharply from a relative maximum to zero, over a distance of about a half octave. Specifically, this distance appeared to exhibit a curvilinear variation with age, reaching a maximum of 3/4 of an octave at 19-21 days. After transforming from frequency to place using the map derived from emissions, however, the distance between the extreme base and the place associated with the peak gain decreased monotonically from about 1.2 mm at age 15-19 days to 0.6 mm at maturity. This distance is assumed to be characteristic of the length of the active amplification zone for the cochlear amplifier in the base region. Over the same time period, there was approximately a doubling of the rate of amplification with distance from the base, so that the cochlear amplifier gain at the peak actually changed very little from 15 days to adult.

Interpretation of distortion product otoacoustic emission measurements. II. Estimating tuning characteristics using three stimulus tones

The simple model introduced in Part I [J. Acoust. Soc. Am. 102, 413-429 (1997)] is used to simulate the response of the cochlea to three stimulus tones. The focus is on "emission suppression tuning curves" constructed using a third tone to suppress the cubic distortion tone emission (CDT, 2f1-f2) generated by two primary tones at frequencies f1 and f2 (intensities L1 and L2). A criterion decrease (here, 5 dB) of the CDT emission amplitude defines the 2f1-f2 emission suppression tuning curve. Applying traditional tuning curve measures to emission suppression tuning curves appears ineffective in determining the underlying cochlear amplifier characteristics. However, it is shown that there are three characteristics of emission suppression tuning curves which are particularly useful: (1) the "f2 threshold" which is the level of the third tone, L3, required for the criterion CDT amplitude decrease, under the condition that the third tone frequency, f3, is approximately equal to f2; (2) the "shoulder threshold" similarly defined for f3 << f2; and (3) the "tuning width," w40. The tuning width is defined to be the distance (in octaves) from the frequency f2 to the upper f3 frequency for which there is a criterion CDT decrease, in this case using the L3 level which is 40 dB above the f2 threshold. Model calculations appropriate to gerbils show that these measures are most accurately related to the underlying cochlear amplifier characteristics for parameters where the primary stimulus amplitudes satisfy L1/L2 > 20 dB and for which L1 is 25 dB or more below the sharp "notch" seen in the two tone input-output function. In this parameter region, the cochlear amplifier characteristics are related to measured quantities by the relationships wr approximately equal to w40 and Ga approximately equal to TE + w40gp. Here, Ga is the gain (dB) of the cochlear amplifier, defined as the total increase in cochlear response over the passive response, wr is the distance (octaves) over which the active cochlear response rises to a maximum, and gp is the passive increase (dB/octave) of the traveling wave along the basilar membrane. The measured quantities are TE, the difference (dB) between the shoulder threshold and the f2 threshold, and the tuning width, w40 (octaves), defined above. Model predictions are confirmed by measurements in adult gerbils.

In situ surface monitoring system for synchrotron mirrors under high heat load

A portable electro-optical system capable of real-time measurements of surface slope distortions down to 0.5 murad is described; the system is limited primarily by its short-term stability. The system employs an angle measurement technique that, in combination with the least-squares signal extraction method, reduces system fluctuations. In addition, a multireflection technique is used to enhance the detectable resolution. Although designed for use with mirrors for synchrotron radiation sources, this system has the flexibility to be applied to other optical components. The prototype system has been tested on a sample mirror piece, and preliminary results are presented. A brief discussion about the extension of this metrology unit to adaptive optics is also given.

Interpretation of distortion product otoacoustic emission measurements. I. Two stimulus tones

The interpretation of common but poorly understood observed characteristics of distortion product emissions is assisted by the development of a simple model. This model essentially includes only saturation of the cochlear amplifier, with emissions arising naturally from the same nonlinear processes which cause the saturation. The model provides useful physical explanations of emission behaviour, particularly considered as a function of the stimulus intensities of the two primaries, i.e., behavior with fixed stimulus frequencies. It is assumed that emission generation consists of two main components which are always present in the total emission, but which most often have approximately opposite, i.e., canceling, phases. One component arises in a small region centered about the peak of the emission generation function, while the other arises from the region basal to this peak. At low stimulus levels with normal cochlear amplifier operation, the peak of the emission generation function is sharp, so the emission from the peak region dominates the total emission. This "peak" emission has typically been characterized as the "active" emission. At high stimulus levels where saturation is important, or at all levels when the gain of the cochlear amplifier is reduced, the summed "basal" component dominates the total emission. The characteristics of this basal emission are similar to, and continuous with, the characteristics of the truly "passive" emission, i.e., the emission observed when the cochlear amplifier gain is identically zero. Under circumstances when the emissions from the peak and basal components are approximately equal, there is seen a sharp "notch" characteristic of phase cancellation. The simple model produces emission distributions as a function of independent variation of the two stimulus amplitudes which are in good agreement with observation. It is shown that the furosemide assay provides a good estimate of cochlear amplifier gain when a correction factor of about 10 dB is added. However, when using two stimulus tones, neither absolute emission amplitudes, or emission input-output functions, or the furosemide assay can adequately distinguish between cases of moderate versus poor cochlear amplifier dysfunction when the cochlear amplifier gains are in the range from about half normal to zero.

X-ray optics developments at the APS for the third generation of high-energy synchrotron radiation sources

Third-generation hard-X-ray synchrotron radiation sources simultaneously provide both a need and an opportunity for the development of new short-wavelength optical components. The high power and power densities of the insertion-device-produced X-ray beams have forced researchers to consider what may seem like exotic approaches, such as cryogenically cooled silicon and highly perfect diamond crystals, to mitigate thermal distortions in the first optical components. Once the power has been successfully filtered while maintaining the high beam brilliance, additional specialized optical components can be inserted into the monochromatic beam that take advantage of that brilliance. This paper reviews the performance of such optical components that have been designed, fabricated and tested at the Advanced Photon Source, starting with high-heat-load components and followed by examples of several specialized devices, such as an meV resolution (in-line) monochromator, a high-energy X-ray phase retarder and a phase-zone plate with submicrometer focusing capability.

Development of distortion product emissions in the gerbil: "filter" response and signal delay

Amplitude and phase responses of distortion product otoacoustic emissions as a function of stimulus frequency ratio were measured for frequencies between 2 and 48 kHz, in Mongolian gerbils (Meriones unguiculates) aged 15 to 30 days after birth. After baseline measurements, furosemide was administered to distinguish active from passive emissions. At all ages, structure in the form of multiple peaks was observed in the amplitude responses of specific odd-order emissions. This structure depended on the emission frequency, not the stimulus frequency ratio, and did not generally depend on the stimulus amplitude. Nor was it dependent on the functioning of the cochlear amplifier: At moderate stimulus levels, the observed emission distribution simply shifted to lower amplitudes when the cochlear amplifier was made temporarily dysfunctional by furosemide injection. The center frequencies and widths of the peaks in the amplitude response did not generally change with age, except that the relative amplitudes of the higher-frequency peaks were increased in younger animals. At 2 kHz, however, the distribution showed other evidence of maturation, with the frequency of maximum emission moving downward with age. The phase responses yielded estimates of the round trip signal (group or traveling wave) delay. At a given frequency, the active signal delay typically decreased substantially with increasing stimulus level. However, there was a rapid variation in delay as the stimulus level passed the normal active-passive crossover level. At stimulus levels measured relative to the active-passive crossover level, i.e., either 20 or 30 dB lower, the active signal delay decreased only slightly with age. Overall, both filter response and signal delay characteristics were found to be essentially mature near the onset of hearing.

5- to 18-year follow-up study of cemented total knee arthroplasty for patients 55 years old or younger

Seventy-two cemented total knee arthroplasties were performed on 52 patients who were 55 years old or younger. Results on 68 knees in 50 patients with an average follow-up period of 9.92 years are reported. The average age of the patients was 50.7 years (range, 30-55) at the time of surgery. The diagnosis was osteoarthritis in 37 knees, rheumatoid arthritis in 29 knees, and ankylosing spondylitis in 2 knees. The average preoperative Knee Society knee score was 23 and the average follow-up knee score was 97. All knees were rated as good or excellent for knee score. The average latest function score was 75 (preoperative, 36). Both knees in one patient required revision for loose components. This review demonstrates that cemented total knee arthroplasty in younger patients with osteoarthritis and rheumatoid arthritis can attain results comparable to the excellent results obtained in the older age groups.

Development of the cochlear amplifier

The development of the cochlear amplifier was examined in gerbils aged 14 days after birth (dab) to adult, for stimulus frequencies from 1 to 48 kHz. Distortion product otoacoustic emissions (DPOAEs) were employed to determine the characteristics of active emissions associated with cochlear amplifier operation. DPOAEs were also used to determine the characteristics of "passive" emissions remaining when the cochlear amplifier operation was interrupted by acute furosmide intoxication. The input-output functions of the passive emissions, and of the active emissions at low stimulus levels, could be approximated by parallel straight lines. The horizontal distance between these parallel lines, i.e., the increase in stimulus level required to obtain a passive emission amplitude equal to the active emission, is an estimate of the gain of the cochlear amplifier. Further, the lowest stimulus level at which active and passive emissions become approximately equal defines a passive threshold level. At 14 dab, the cochlear amplifier gain was already at adult levels for the midfrequencies (4-8 kHz), but no emissions were detected at the extremes (at 1 kHz, and 24 kHz and above). During the period over which the endocochlear potential (EP) is known to increase most sharply (14 to 18 dab), the gain at all frequencies increased. At low frequencies there was little or no gain in the youngest age group, but matured by 23 dab. The gain at the middle frequencies subsequently decreased, resulting by 30 dab in a gain that was remarkably flat across frequency from 1 to 32 kHz. The passive thresholds generally improved with age at all frequencies, but most dramatically at the high frequencies. Results are consistent with the view that the elements of the cochlear amplifier are functional in the base of the cochlea at all ages, but that auditory function is primarily limited by the lower passive base cutoff frequency at younger ages. The proposed increase in passive base cutoff frequency with age accounts for the known place code shift.

Effects of furosemide on distortion product otoacoustic emissions and on neuronal responses in the anteroventral cochlear nucleus

1. The objective of this study was to precisely evaluate the relationship between the threshold of neurons in the anteroventral cochlear nucleus (AVCN) and the properties of distortion product otoacoustic emissions (DPOAEs). Response areas of multiunit clusters in the AVCN and DPOAEs in the ear canal were measured alternately in the adult gerbil during furosemide-induced changes of the endocochlear potential. Stimulus frequencies of the probe tones for DPOAE measurement were in the range of f1 = 1.7-7.6 kHz and f2 = 2.0-9.0 kHz; the ratio f2:f1 was always 1.18. Stimulus amplitudes were varied in 5-dB steps from 30 to 80 dB SPL, with either equal amplitudes (L1 = L2) or unequal, with L1 set 10 dB above L2. Multiunit response areas were determined from cluster responses to a series of 100-ms tone bursts presented with a pseudo-random sequence in frequency and intensity. 2. Changes in the multiunit discharge properties after 50-75 mg/kg furosemide injection were as follows: the best frequency (BF) threshold increased from initial values in the range of 20-30 dB SPL to 50-80 dB SPL at 10-20 min postinjection and then recovered fully by 60-90 min. The spontaneous discharge activity decreased to zero before any changes in the frequency threshold curve were observed and did not return to initial values for several hours. Likewise, total discharge rates of stimulus elicited responses were reduced and tended to stay reduced even after BF threshold had fully recovered. 3. From the DPOAE measurements, the changes observed in the cubic distortion tone (CDT, 2f1-f2) emission after furosemide injection were as follows: at high levels of the probe tones, changes in the emission intensities generally stayed within a 10-dB range. The CDT amplitudes for low stimulus levels, however, were typically reduced by up to 40 dB, but recovered (depending on the furosemide dosage) by approximately 60-90 min. 4. At low to moderate stimulus levels of 40-60 dB SPL, there was a near perfect, minute-by-minute covariation of the ear canal CDT amplitude and the BF threshold measured in the AVCN. A 10-dB increase in threshold was associated with a 5- to 7-dB decrease in the CDT emission. 5. The optimum stimulus parameter set for the noninvasive estimation of cochlear performance from the CDT response was for stimulus amplitudes L1 = 50, L2 = 40 dB SPL. 6. This experiment demonstrates that CDT emissions at low stimulus levels are very good predictors of the thresholds of cochlear afferents, but this validity is lost for BF thresholds greater than approximately 60-70 dB SPL. 7. The ear canal CDT amplitude is better correlated with the BF threshold sensitivity of neuronal response areas in the AVCN than with the spontaneous discharge rate or absolute above-threshold discharge rates.

A 40 kb chromosomal fragment encoding Salmonella typhimurium invasion genes is absent from the corresponding region of the Escherichia coli K-12 chromosome

Many Salmonella typhimurium genes are required for bacterial entry into host cells. P22 transduction analysis has localized several invasion loci near minute 59 on the S. typhimurium chromosome. To further characterize the 59-60 min chromosomal region, we determined the physical and genetic map of 85 kb of S. typhimurium DNA between srl and cysC. It was previously shown that some of the invasion genes from this region are not present in Escherichia coli K-12. We examined whether other S. typhimurium genes on the 85 kb of DNA were similarly absent from E. coli. We found that a contiguous 40 kb fragment of the S. typhimurium chromosome which encodes invasion genes is absent from the corresponding region of the E. coli K-12 chromosome and may represent a 'pathogenicity island'. We speculate that acquisition of the 40 kb region must have significantly advanced the evolution of Salmonella as a pathogen.

Variation of distortion product otoacoustic emissions with furosemide injection

Cochlear function was monitored in adult gerbils using distortion product otoacoustic emissions (DPOAE) during intraperitoneal injection of furosemide. All stimulus parameters were varied independently over a wide range, the stimulus frequencies f1 and f2 from 1 to 16 kHz, and the stimulus levels L1 and L2 from 20 to 80 dB SPL. The observed emissions at 2f1-f2 and 3f1-2f2 could be considered to be made up of two distinct components: (1) an 'active' source which depended in a complex way on the stimulus frequencies and levels, which was dominant at low and moderate stimulus levels, and which, by definition, was eliminated by sufficient furosemide intoxication; and (2) a 'passive' source which was essentially the same at all frequencies, with a level dependence given approximately by a simple power law distribution. The change from the active to the passive source was usually accompanied by an abrupt shift in emission phase angle. A simple summation model was shown to account for the observed form of this transition. The amount of the decrease in 2f1-f2 emission amplitude after furosemide injection was approximately independent of frequency and consistent for the middle frequency ratios and intensity levels (f2/f1 approximately equal to 1.3, L1 x L2 approximately equal to 55 x 50 dB SPL). It was concluded that the combination of DPOAE with furosemide injection can usefully be employed as a probe of active cochlear mechanics.

Vulnerability and adaptation of distortion product otoacoustic emissions to endocochlear potential variation

The endocochlear potential (EP) was reversibly decreased in adult gerbils by the intraperitoneal injection of furosemide, while cochlear functioning was monitored by measurement of distortion production otoacoustic emissions (DPE) at a range of stimulus intensities. Stimulus frequencies for DPEs were f1 = 6.8 and f2 = 8 kHz (f2/f1 = 1.18). Emissions monitored in the ear canal and scala media were 2f1-f2, 3f1-2f2, 2f2-f1, and f2-f1. Typically, the EP decreased smoothly, reached a minimum one-half hour after injection, then recovered slowly over several hours. Emissions at 2f1-f2 and 3f1-2f2 at low stimulus levels were particularly vulnerable to the change in EP. These vulnerable emissions showed characteristic trajectories in which the amplitudes changed little with the initial EP decrease, then dropped sharply as the EP continued to decrease. However, the amplitudes then began to recover even before the EP reached minimum, and recovered completely while the EP remained subnormal. The trajectories of the other odd order emissions were similar, but lacked the abrupt decrease. The variation of the even order (f2-f1) component was completely different, but appeared related to the odd order trajectories in a complex fashion. During the initial decrease for the vulnerable components, the decrease in emission amplitude (in dB) was found to be proportional to the square of the change in EP (in mV). The recovery with a subnormal EP was interpreted as an adaptive effect with a time constant of about 15 min.

Binaural cochlear implants

With the success of monaural cochlear implantation, patients frequently ask about having a second implant. We have performed binaural cochlear implants in 12 adult patients. Desire not to disrupt a functioning implant was the primary consideration in implanting the contralateral ear. Seven patients received a second 3M/House single-channel implant to upgrade to a magnetic external receiver. Four patients with a 3M/House device in one ear elected to place a Nucleus multichannel implant in the opposite ear. One patient with a poorly functioning Nucleus device elected to have a second Nucleus device. Four patients with a Nucleus and a 3M/House implant, one with binaural 3M/House implants, and one with binaural Nucleus implants were tested for auditory discrimination in order to quantify monaural versus binaural differences. The functional benefit of the second implant was mixed, but all patients showed some degree of objective improvement on one or more tests. Five of the six are regular users of both devices; the patient with binaural Nucleus implants wears only one. Despite the differing processing schemes, patients with a Nucleus device in one ear and a 3M/House device in the other ear are able to combine the two signals to advantage. We feel that cochlear implantation in the contralateral ear is an acceptable option in selected patients desiring an upgraded implant without placing a functioning implant at risk.

Long-term follow-up evaluation of 1000 consecutive cemented total knee arthroplasties

This is a report of a retrospective study of 1000 consecutive, cemented total knee arthroplasties performed by one surgeon from January 1976 to August 1989. Eighty-five percent of the patients were available after a mean of 51 months. Using The Knee Society Clinical Rating System, a good to excellent result was found in 95% of the knees; function was good to excellent in 54% of the knees. By using an actuarial method, 94% of the knees can be expected to survive 13 years. A deep venous thrombosis or pulmonary embolus was found in 1.7% and was no less common in the 25% of the patients who received pharmacologic anticoagulation. The mortality rate was 0.4%. The infection rate was 0.7% and did not correlate with intraoperative cultures. There were 14 failures for a variety of reasons, and six unsuccessful knees were revised. Preoperative medical problems did not generally predict the postoperative complications. The average duration of hospitalization during the last five years of the study was 9.7 days. Careful and consistent preoperative, intraoperative, and postoperative care is responsible for the low complication rate. The cemented knee arthroplasty consistently continues to yield good results.

Proteinaceous lymphadenopathy due to monoclonal nonamyloid immunoglobulin deposit disease

We report two cases of lymph node enlargement due to massive extracellular nonamyloid immunoglobulin deposits that obscured the underlying cellular pathologic condition. In both cases, the deposits were demonstrated to be restricted to a single heavy and light chain, consistent with a monoclonal paraprotein, and cytoplasmic staining in the lymphocytes or plasma cells was identical to that of the paraprotein. The use of the protein A-gold technique was instrumental in revealing a monoclonal pattern in one case in which light microscopic immunohistochemistry did not reveal a clear-cut monoclonal pattern in the extracellular deposits. This case was subsequently shown to have multiple myeloma, while the second case has had an unusual history of hypocomplementemic vasculitis and normal bone marrow. Neither case had evidence of significant renal disease.

Extended X-ray absorption fine structure of Mn2+ and Mn2+ X ATP complex bound to coupling factor 1 of the H+-ATPase from chloroplasts

The spinach chloroplast ATPase, coupling factor 1, contains three tight Mn2+-binding sites which interact cooperatively. The bound manganese coordinations were studied by x-ray absorption fine structure analysis. Mn2+ was found to be bound to the enzyme with an average Mn-O bond length of 2.15 +/- 0.15 A, significantly shorter than the 2.15 +/- 0.15 A of the Mn-O bond of the average first hydration shell for Mn2+ in aqueous solution. On adding ATP to the manganese-enzyme mixture, a tertiary complex of Mn2+ X ATP X enzyme was formed as indicated by the appearance of a second shell. Mn-P bond distances were estimated at 4.95 +/- 0.15 A in the tertiary Mn2+ X ATP X enzyme complex, which was considerably longer than the Mn-P bond distance of 3.36 +/- 0.15 A for the Mn2+ X ATP complex in aqueous solution. The Mn-P bond distance in the tertiary Mn2+ X ATP X enzyme complex decreased to 4.32 +/- 0.15 A when selenite, a potent effector of ATPase activity, was added. Based on these results, it is suggested that the tertiary complex is required for catalysis. The stimulation of ATP hydrolysis by anions such as selenite may be the result of shortening the distance between Mn2+ and the ATP phosphates in the enzyme active site.

Oncocytoma of the lacrimal caruncle

Two cases of oncocytoma of the lacrimal caruncle are presented. This benign tumour is characterized by a uniform population of epithelial cells with abundant, finely granular, eosinophilic cytoplasm. The granules stain blue with Mallorys phosphotungstic acid hematoxylin and can be identified as mitochondria by electron microscopy. An additional 35 cases from the literature are reviewed. The tumour usually occurs in people over the age of 60 years and is more common in women (male:female ratio of 1:5).

Chronic ileal obstruction in adults due to peri-ileal vitelline vascular remnants

Two young adults had distal ileal obstruction at sites where a fold of mesentery extended from its posterior leaf to the antimesenteric border of the bowel. No Meckel's diverticulum or mesoumbilical band was present in either case. Clinical, gross and microscopic findings suggested that the mesenteric fold represented a remnant of vitelline vessel that persisted in the peri-ileal portion of its course. Chronic ileal obstruction was apparently due to disordered peristalsis caused by the fold tethering the adjoining posterior bowel wall. In one patient, a chronic ulcer at the site of obstruction was interpreted as being an additional complication of the congenital lesion.

Latency and amplitude effects of electrode placement on the early auditory evoked response

This study examined the effects of electrode placement on the early auditory evoked response in normally hearing subjects. The electrodes are termed noninverting, inverting, and common. Ten commonly used electrode combinations were evaluated. Both amplitudes and latencies of Waves I, III, and V were measured for each electrode combination. No mean differences in latencies were observed for Waves I, III, or V with any of the 10 electrode combinations. Similarly, no statistically significant Wave I or Wave III amplitude differences were found among the 10 electrode montages. However, larger Wave V amplitudes were found with placement of the noninverting electrode at the vertex (0.53 mu v) as compared to the upper forehead (0.39 mu v). Moreover, Wave V amplitudes were larger for inverting/common electrode placements at the seventh cervical vertebra/forehead, neck/forehead, and neck/neck (approximately 0.50 mu v) than for mastoid/mastoid and mastoid/forehead placements (approximately 0.40 mu v). Thus, three combinations of electrodes gave the largest Wave V amplitudes. These placements for the noninverting, inverting, and common electrodes, respectively, were (a) vertex-seventh-forehead, (b) vertex-neck-forehead, and (c) vertex-neck-neck.