Investigation of boron carbide and iridium thin films, an enabling technology for future x-ray telescopes.

We present an experimental examination of iridium and boron carbide thin-film coatings for the purpose of fabricating x-ray optics. We use a combination of x-ray reflectometry and x-ray photoelectron spectroscopy to model the structure, composition, density, thickness, and micro-roughness of the thin films. We demonstrate in our analyses how the two characterization techniques are complementary, and from this we derive that an overlayer originating from atmospheric contamination with a thickness between 1.0-1.6 nm is present on the surface. The magnetron sputtered iridium films are measured to have a density of 22.4g/cm3. The boron carbide film exhibits a change in chemical composition in the top ∼2nm of the film surface when exposed to the ambient atmosphere. The chemical reaction occurring on the surface is due to an incorporation of oxygen and hydrogen present in the ambient atmosphere. Lastly, we present a correlation between the absorption edges and the emission lines exhibited by the thin films in an energy range from 50-800 eV and the impact on the reflectivity performance due to contamination in thin films.

Supernovae. 44Ti gamma-ray emission lines from SN1987A reveal an asymmetric explosion.

In core-collapse supernovae, titanium-44 ((44)Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32-kilo-electron volt emission lines from decay of (44)Ti produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion.

Galaxy evolution. Black hole feedback in the luminous quasar PDS 456.

The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.

An ultraluminous X-ray source powered by an accreting neutron star.

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5-10 kiloelectronvolt energy band range from 10(39) to 10(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 10(40) ergs per second), which require black hole masses of 50-100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3-30 kiloelectronvolt range of 4.9 × 10(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3-10 kiloelectronvolt range of 1.8 × 10(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A.

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive (44)Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium, directly probes the explosion asymmetries. Cassiopeia A is a young, nearby, core-collapse remnant from which (44)Ti emission has previously been detected but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed (44)Ti emission to estimated (56)Ni emission, from optical light echoes, and from jet-like features seen in the X-ray and optical ejecta. Here we report spatial maps and spectral properties of the (44)Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the (44)Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae.

A rapidly spinning supermassive black hole at the centre of NGC 1365.

Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2 × 10(6) solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.

Video based analysis of dynamic midfoot function and its relationship with Foot Posture Index scores.

INTRODUCTION: Various studies have demonstrated significant as well as non-significant relationships between static evaluation of foot posture and injury likelihood. Therefore, the relationship of static and dynamic measures needs to be established as in clinical settings time consuming dynamic methods are often not feasible. PURPOSE: Assess reliability of a new method to quantify midfoot movement and validate the use of Foot Posture Index (FPI) classification as predictor of dynamic foot function during walking. METHOD: Foot type was classified using FPI in 280 randomly selected adult participants (mean age 43.4 years). A Video Sequence Analysis (VSA) system was used to quantify midfoot kinematics during walking. Navicula drop (DeltaNH) and minimal navicula height (NHL) were compared with FPI. RESULTS: The Intraclass Correlation Coefficients (ICC) for DeltaNH and NHL ranged from 0.65 to 0.95 with a coefficient of repeatability of 1.4 mm for DeltaNH and 4.5 mm for NHL. System precision was estimated at 0.99 mm for DeltaNH and 3.18 mm for NHL. DeltaNH was significantly positively correlated with FPI scores while NHL decreased with increasing FPI. However, the FPI model predicted only 13.2% of the variation in DeltaNH and 45% of the variation in NHL during walking (p<0.001). CONCLUSION: The VSA was proven as a reliable and precise method to quantify midfoot kinematics. FPI scores and individual components of the FPI show strong statistical relationships to dynamic measures but individual predictions remain questionable. Dynamic midfoot measures are recommended for clinical foot assessments.

Elevated pressure selectively blunts flow-evoked vasodilatation in rat mesenteric small arteries.

BACKGROUND AND PURPOSE: The present study investigated mechanisms underlying impaired endothelium-dependent vasodilatation elicited by elevating the intraluminal pressure in rat mesenteric small arteries. EXPERIMENTAL APPROACH: Arterial segments (internal diameter 316+/-2 microm, n=86) were mounted in a pressure myograph. The effect of elevating pressure from 50 to 120 mmHg for 1 h before resetting it to 50 mmHg was studied on endothelium-dependent vasodilatation. KEY RESULTS: In arteries constricted with U46619 in the presence of indomethacin, shear stress generated by flow, evoked vasodilatation that was abolished by an inhibitor of nitric oxide (NO) synthase, asymmetric dimethylarginine (1 mM), whereas acetylcholine-induced vasodilatation was unchanged. After elevation of intraluminal pressure for 1 h and then resetting it to 50 mmHg, vasodilatation induced by shear stress and the NO donor, S-nitrosopenicillamine was inhibited, while vasodilatation induced by a guanylyl cyclase activator, BAY 412272, and acetylcholine was unaltered. Superoxide levels sensitive to polyethylene glycol superoxide dismutase were increased in segments exposed to elevated pressure. A superoxide scavenger, tempol (300 microM), a general endothelin receptor antagonist, SB 217242 and the selective ET(A) receptor antagonist, BQ 123 preserved shear stress-evoked vasodilatation. CONCLUSIONS AND IMPLICATIONS: The present study shows that transient exposure to an elevated intraluminal pressure selectively inhibits flow-evoked NO-mediated vasodilatation, probably through activation of endothelin receptors and increased formation of superoxide. In contrast, elevation of pressure did not affect the acetylcholine-evoked endothelium-derived hyperpolarizing factor type vasodilatation in mesenteric small arteries.

Stabilisation surgery for chronic low back pain: indications, surgical procedures, and outcome.

Spinal fusion was introduced as a treatment option for chronic low back pain >70 years ago. However, few areas of spinal surgery have caused as much controversy. The debate about whether to use an anterior-, posterior- or anterior + posterior approach has persisted since the 1930s. Within the last 10 years, the effects of different spinal fusion procedures have been tested in 10 randomized controlled trails (RCT). A highly significant improvement over preoperative status was found in all 10 studies. Two recent RCTs have dealt with the question of conservative versus operative treatment of patients with low back pain, and both studies have shown a significant better functional outcome for spinal fusion in situ, compared with a more or less organized exercise programme at 2-year follow-up. The choice of postoperative rehabilitation strategy has also been shown to be of importance for overall functional outcome. One study has demonstrated the importance of the inclusion of coping schemes, and questioned the role of intensive exercises in a rehabilitation programme for spinal fusion patients.

Cross-over trial comparing maternal acceptance of two fetal movement charts.

OBJECTIVE: To compare two daily fetal movement charting techniques to determine which chart was preferred by patients and which promoted more patient adherence. METHODS: This randomized trial included patients with singleton gestations between 28 and 34 weeks' gestation, with intact membranes and not in labor. Consenting women were given a Hollister chart and a 'count to 10' chart in a cross-over manner over two consecutive 1-week periods. Each patient answered a questionnaire establishing which chart was preferred. All returned charts were evaluated for patient adherence. Data were analyzed using either the Yates-corrected chi2 test or Fisher's exact test when appropriate. RESULTS: Forty patients agreed to participate, and 31 completed and returned both charts. The 'count to 10' chart was clearly preferred over the Hollister chart (29 vs. 2; p = 0.002) because of the shorter recording period (median 23 min vs. 1 h; p < 0.01). The proportion of patients who fully completed the 'count to 10' chart during the week was significantly higher than the proportion completing the Hollister chart (68% vs. 26%; p < 0.001). CONCLUSION: The 'count to 10' fetal movement chart was clearly preferred and promoted a higher level of adherence.

Smoking as a predictor of negative outcome in lumbar spinal fusion.

STUDY DESIGN: A review of the smoking habits in 426 patients who had been followed prospectively for 2 years after a lumbar spinal fusion procedure was conducted. OBJECTIVE: To analyze the effect of pre- and postoperative smoking on clinical and functional outcome after lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: Several animal models have shown a negative effect of nicotine on spinal fusion. At this writing, the clinical effect of nicotine on spinal fusion has not been fully clarified. METHODS: The study comprised 426 patients who underwent lumbar spinal fusion between 1993 and 1997. These patients received a mailed questionnaire regarding their tobacco consumption before and after their surgery. All other data, including preoperative clinical and functional status, were collected prospectively during a 2-year follow-up period. To assess functional outcome, the Dallas Pain Questionnaire was used. RESULTS: The questionnaire was answered by 396 patients (93%). Of these patients, 54.5% (20% more than the background population) were smokers before the operation. Smoking of more than 10 cigarettes daily before the operation and attempted fusion at two or more levels increased the risk of nonunion: odds ratio, 2.01 (P < 0.016) and odds ratio, 3.03 (P < 0.001), respectively. Smoking cessation increased fusion rates to near those of nonsmokers. Smoking had no influence on functional outcome, as assessed by the Dallas Pain Questionnaire, but preoperative smoking predicted a negative answer to the question "Would you undergo the same treatment again, now that you know the result?" (odds ratio, 1.65; P < 0.054). CONCLUSIONS: Smoking was shown to have a negative effect on fusion and overall patient satisfaction, but no measurable influence on the functional outcome as assessed by the Dallas Pain Questionnaire.

Posterolateral spinal fusion at unintended levels due to bone-graft migration: no effect on clinical outcome in 19/130 patients.

In a prospective randomized study, we evaluated the risk of lumbar posterolateral spinal fusion at an unintended level due to bone graft migration. 130 patients underwent fusion supplemented by pedicle screw fixation (Cotrell-Dubousset, 64 patients) or uninstrumented fusion (66 patients). This was assessed by two independent observers on antero-posterior, and lateral radiographs taken 1 year after surgery. All patients had ben operated on at the preoperatively planned levels. Both observers agreed that fusion had taken place at an unintended level in 19 cases (14%). We found a tendency towards a higher risk of this "complication" when using supplementary pedicle screw fixation. The functional outcome, assessed by the Dallas Pain Questionnaire and the Low Back Pain Rating scale, was similar in patients having fusion at an unintended level and in patients fused only at the intended levels. There was no difference between the two groups concerning reoperation rates, postoperative smoking or social status. We conclude that unintended fusion occurs and tends to be commoner with the use of pedicle screw instrumentation. However, this complication seems not to affect the functional outcome if fusion has taken place at the intended level.

Postmodernism in marriage and family therapy training: doctoral students' understanding and experiences.

The purpose of this study is to advance our understanding of how doctoral students perceive postmodernism's influence in the field of Marriage and Family Therapy (MFT). According to the literature, postmodernism has had a profound impact on many fields, including MFT. However, tracking of how postmodernism is actually being rendered in theory, research, practice, and training warrants investigation. This study utilized focus group interviews to investigate the perceptions of MFT doctoral students. Findings suggest that while participants are attracted to postmodern tenets, they also report feeling a mixture of liberation and excitement with confusion and fear regarding how postmodernism is influencing MFT models of therapy.

Mandated preterm delivery: its prevalence and impact at a tertiary referral center.

OBJECTIVE: To determine the prevalence and impact of mandated preterm deliveries at a tertiary referral center. METHODS: A chart review was conducted at our institution on all livebirths from 24 weeks to completion of 37 weeks' gestation between 1 January 1998 and 31 December 1999. Mandated delivery was defined as intentional intervention because of a deteriorating maternal or fetal condition. Reasons for intervention and intrapartum courses were compared with two other preterm groups (premature ruptured membranes, spontaneous labor) delivering during the same period. Statistical analyses included the Student t test, univariate ANOVA, X2 test and Mann-Whitney test. RESULTS: A total of 894 pregnancies delivered preterm, with 132 (14.8%) being mandated. Primary reasons for mandated delivery included severe pre-eclampsia (69.0%), vaginal bleeding (11.4%), deteriorating maternal illness (10.6%), worsening fetal growth restriction (6.1%) or major fetal malformation (3.0%). Delivery at less than 34 weeks was more common in the mandated group (68.9%) than in the ruptured membranes group (41.2%, p < 0.005) or in the spontaneous labor group (46.5%; p < 0.01). Cesarean section rates were higher in the mandated group (69.7%) than in the ruptured membranes group (18.3%; p <0.001) or in the spontaneous labor group (21.5%; p < 0.001). The presence of an unfavorable cervix, unsuccessful trial of labor, non-cephalic fetal presentation, or fetal intolerance of labor explained the high rate of surgery. CONCLUSIONS: Conditions mandating delivery accounted for 14.8% of all preterm births. Mandated delivery is associated with a greater need for delivery before 34 weeks, often by Cesarean section.

Interobserver and intraobserver agreement of radiograph interpretation with and without pedicle screw implants: the need for a detailed classification system in posterolateral spinal fusion.

STUDY DESIGN: A prospective randomized clinical study in which four observers evaluated radiographs of posterolateral fusion masses. OBJECTIVES: To evaluate the accuracy of radiograph interpretation of the posterolateral spinal fusion mass when using a detailed classification system and to analyze the influence of metallic internal fixation devices on radiologic inaccuracy. SUMMARY OF BACKGROUND DATA: In general, the literature describing the classification criteria used for radiograph interpretation of spinal posterolateral fusion has serious deficiencies. There is a need for a detailed classification system. METHODS: Seventy patients were randomly allocated to receive no instrumentation (n = 36) or Cotrel-Dubousset instrumentation (n = 34) in posterolateral lumbar fusion. All four observers participated in a prestudy discussion and evaluated the radiographs (anteroposterior, lateral) taken at the 1-year follow-up evaluation. The observers scored the radiographs twice (30 days apart). Each level on each side was judged separately. A continuous intertransverse bony bridge involving at minimum one of the two sides indicated a fusion at that level. "Fusion" indicated this quality of fusion at all intended levels. If the fusion was doubtful on both sides of the interspace, the individual case could not be classified as "fused." RESULTS: The mean interobserver agreement was 86% (Kappa 0.53), and the mean intraobserver agreement was 93% (Kappa 0.78). No difference in interobserver and intraobserver agreement was found between patients with and without supplementary pedicle screw fixation. All mean Kappa values were classified as fair or good. The four observers identified a mean fusion rate of 81%. CONCLUSION: It is extremely difficult to interpret radiographic lumbar posterolateral fusion success. Such an assessment needs to be performed by use of a detailed radiographic classification system. The classification system presented here revealed good interobserver and intraobserver agreement, both with and without instrumentation. The classification showed acceptable reliability and may be one way to improve interstudy and intrastudy correlation of radiologic outcomes after posterolateral spinal fusion. Instrumentation did not influence reproducibility but may result in slightly underestimated fusion rates.

Titanium-alloy enhances bone-pedicle screw fixation: mechanical and histomorphometrical results of titanium-alloy versus stainless steel.

Several types of pedicle screw systems have been utilized to augment lumbar spine fusion. The majority of these systems are made of stainless steel (Ss), but titanium-alloy (Ti-alloy) devices have recently been available on the market. Ti-alloy implants have several potential advantages over Ss ones. High bioactivity and more flexibility may improve bone ingrowth and mechanical fixation, and the material also offers superior magnetic resonance imaging (MRI) and computed tomography (CT) resolution and significantly less signal interference. However, no data are available from loaded spinal constructs regarding bony ingrowth and mechanical fixation. The aim of this study was to analyse the effect of Ti-alloy versus Ss pedicle screws on mechanical fixation and bone ingrowth in a loaded mini-pig model. Eighteen adult mini-pigs underwent total laminectomy and posterolateral spinal fusion at L3-L4, and were randomly selected to receive either Ss (n = 9) or Ti (n = 9) pedicle screw devices. In both groups, the device used was compact Cotrel-Dubousset instrumentation (Sofamore Danek) of an identical size and shape. The postoperative observation time was 3 months. Screws from L3 were used for histomorphometric studies. Mechanical testing (torsional tests and pull-out tests) was performed on the screws from L4. The Ti screws had a higher maximum torque (P < 0.05) and angular stiffness (P < 0.07), measured by torsional testing. In the pull-out tests, no differences were found between the two groups with respect to the maximum load, stiffness and energy to failure. No correlation between removal torque and the pull-out strength was found (r = 0.1). Bone ongrowth on Ti was increased by 33% compared with Ss (P < 0.04), whereas no differences in bone volume around the screws were shown. Mechanical binding at the bone-screw interface was significantly greater for Ti pedicle screws than for Ss, which was explained by the fact that Ti screws had a superior bone ongrowth. There was no correlation between the screw removal torque and the pull-out strength, which indicates that the peripheral bone structure around the screw was unaffected by the choice of metal.

Dissolution of hydrocortisone in human and simulated intestinal fluids.

PURPOSE: To compare solubility and dissolution rate of hydrocortisone in aspirated human intestinal fluids (HIFs) with simulated intestinal fluids (SIFs) and buffer. METHODS: Solubility and flux from a rotating disk of hydrocortisone were measured. The bile salt content, pH and osmotic pressure were determined in HIFs. RESULTS: In fasted state the solubility of hydrocortisone was higher in HIFs than in the buffer and SIFs. The flux of hydrocortisone in HIFs was similar to the flux in the buffer but lower than the flux in SIFs at fasted state. Addition of intestinal surfactants in SIFs increased solubility and flux at both fasted and fed state. The increase in solubility was caused by micelle formation in SIFs. The increase in flux may partly be explained by increased solubility. The bile salt content of the HIFs did not correlate with the solubility or the flux but pH in the HIFs seems to have some effect on the components of the HIFs resulting in increased solubility. CONCLUSIONS: It is possible to perform comparable dissolution tests in HIFs and SIFs. The lack of correlation between the results in HIFs and the bile salt content may be explained by the relatively low lipophilicity of the model drug.

Prevention of group B streptococcus early-onset neonatal sepsis: comparison of the Center for Disease Control and prevention screening-based protocol to a risk-based protocol in infants at greater than 37 weeks' gestation.

OBJECTIVE: To compare the Center for Disease Control consensus guidelines' screening-based strategy to a risk-based strategy as regards the incidence of early-onset group B streptococcus (GBS) infection among term infants. STUDY DESIGN: A cohort of university hospital prenatal clinic mother-infant pairs who were screened for GBS at 35 to 37 weeks' gestation were compared to a matched control group of unscreened mother-infant pairs from the outreach satellite prenatal clinics who delivered at the same institution during the same time period. GBS screening was carried out with rectovaginal cultures plated on selective media. GBS-positive women received antimicrobial prophylaxis in labor whereas women of unknown GBS status were only treated intrapartum if they had a risk factor for GBS infection. Principal outcome variables included incidence of cases of neonatal early-onset GBS sepsis (blood, urine, or cerebrospinal fluid positive for GBS), incidence of cases of strongly suspected GBS sepsis (culture negative), and incidence of neonatal sepsis with non-GBS organisms. RESULTS: There were 3164 screened mother-infant pairs who were compared to 2684 unscreened pairs. The incidence of GBS carriage was 13.3%. A random sample of 420 screened women were compared to a matched sample of 407 women of unknown GBS carrier status for characterization of demographics and risk factors. No cases of documented GBS sepsis occurred in the infants of the screened women, but four cases occurred among the infants of the women who did not undergo screening (incidence 1.5/1000) (p = 0.04), only one of whom had a risk factor for GBS infection. Cases of suspected but culture negative sepsis were not more common in the screened population when compared to the unscreened. There was one case of Escherichia coli sepsis in an infant of a mother in the unscreened group. CONCLUSIONS: GBS screening at 35 to 37 weeks, with intrapartum antimicrobial prophylaxis of carriers, decreased the incidence of neonatal early-onset GBS sepsis and appears to have advantages over treatment based on risk factors alone in term infants.