Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients.

The interstellar medium of the Milky Way is multiphase, magnetized and turbulent. Turbulence in the interstellar medium produces a global cascade of random gas motions, spanning scales ranging from 100 parsecs to 1,000 kilometres (ref. 4). Fundamental parameters of interstellar turbulence such as the sonic Mach number (the speed of sound) have been difficult to determine, because observations have lacked the sensitivity and resolution to image the small-scale structure associated with turbulent motion. Observations of linear polarization and Faraday rotation in radio emission from the Milky Way have identified unusual polarized structures that often have no counterparts in the total radiation intensity or at other wavelengths, and whose physical significance has been unclear. Here we report that the gradient of the Stokes vector (Q, U), where Q and U are parameters describing the polarization state of radiation, provides an image of magnetized turbulence in diffuse, ionized gas, manifested as a complex filamentary web of discontinuities in gas density and magnetic field. Through comparison with simulations, we demonstrate that turbulence in the warm, ionized medium has a relatively low sonic Mach number, M(s) ≲ 2. The development of statistical tools for the analysis of polarization gradients will allow accurate determinations of the Mach number, Reynolds number and magnetic field strength in interstellar turbulence over a wide range of conditions.

Transmission of acceleration from a synchronous vibration exercise platform to the head.

Exercise vibration platforms are becoming commonplace in homes and fitness centers. However, excessive mechanical energy transferred to the head and eye can cause injury. The purpose of this study was to evaluate how changes in platform frequency and knee flexion angle affect acceleration transmission to the head. Participants (N=12) stood on a whole-body vibration platform with knee flexion angles of 0°, 20°, and 40° to evaluate how changes in knee flexion affected head acceleration. 7 specific platform frequencies were tested between 20-50 Hz at 2 peak-to-peak displacement settings (1 and 2 mm nominal). Accelerations were measured with triaxial accelerometers at the platform and head to generate transmissibility ratios. Platform-to-head transmissibility was not significantly different between the 2 platform peak-to-peak amplitudes (P>0.05). Transmissibility measures varied depending on platform frequency and knee angle (P < 0.05). Flexing the knees resulted in reduced head transmissibility at all frequencies (P<0.05). Platform-to-head transmissibility values exceeded 1.0 at both 20 and 25 Hz platform vibration frequencies with the knees in full extension. To reduce the risk of injury to structures of the head during vibration exercise, using platforms frequencies below 30 Hz with small knee flexion angles (< 40°) should be avoided.

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations.

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631-1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s(2) and 0.14 rad/s(2). The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631-1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable. STATEMENT OF RELEVANCE: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.

Earth's Variable Rotation.

Recent improvements in geodetic data and practical meteorology have advanced research on fluctuations in the Earth's rotation. The interpretation of these fluctuations is inextricably linked with studies of the dynamics of the Earth-moon system and dynamical processes in the liquid metallic core of the Earth (where the geomagnetic field originates), other parts of the Earth's interior, and the hydrosphere and atmosphere. Fluctuations in the length of the day occurring on decadal time scales have implications for the topography of the core-mantle boundary and the electrical, magnetic, and other properties of the core and lower mantle. Investigations of more rapid fluctuations bear on meteorological studies of interannual, seasonal, and intraseasonal variations in the general circulation of the atmosphere and the response of the oceans to such variations.

The Earth's Angular Momentum Budget on Subseasonal Time Scales.

Irregular length of day (LOD) fluctuations on time scales of less than a few years are largely produced by atmospheric torques on the underlying planet. Significant coherence is found between the respective time series of LOD and atmospheric angular momentum (AAM) determinations at periods down to 8 days, with lack of coherence at shorter periods caused by the declining signal-to-measurement noise ratios of both data types. Refinements to the currently accepted model of tidal Earth rotation variations are required, incorporating in particular the nonequilibrium effect of the oceans. The remaining discrepancies between LOD and AAM in the 100- to 10-day period range may be due to either a common error in the AAM data sets from different meteorological centers, or another component of the angular momentum budget.

Lunar anorthosites.

Sixty-one of 1676 lunar rock fragments examined were found to be anorthosites, markedly different in composition, color, and specific gravity from mare basalts and soil breccias. Compositional similiarity to Tycho ejecta analyzed by Surveyor 7 suggests that the anorthosites are samples of highlands material, thrown to Tranquillity Base by cratering events. A lunar structural model is proposed in which a 25-kilometer anorthosite crust, produced by magmatic fractionation, floats on denser gabbro. Where early major impacts punched through the crust, basaltic lava welled up to equilibrium surface levels and solidified (maria). Mascons are discussed in this context.

An el nino signal in atmospheric angular momentum and Earth rotation.

Anomalously high values of atmospheric angular momentum and length of day were observed in late January 1983. This signal in the time series of these two coupled quantities appears to have been a consequence of the equatorial Pacific Ocean warming event of 1982-1983.

Lunar laser ranging: a continuing legacy of the apollo program.

On 21 July 1969, during the first manned lunar mission, Apollo 11, the first retroreflector array was placed on the moon, enabling highly accurate measurements of the Earthmoon separation by means of laser ranging. Lunar laser ranging (LLR) turns the Earthmoon system into a laboratory for a broad range of investigations, including astronomy, lunar science, gravitational physics, geodesy, and geodynamics. Contributions from LLR include the three-orders-of-magnitude improvement in accuracy in the lunar ephemeris, a several-orders-of-magnitude improvement in the measurement of the variations in the moon's rotation, and the verification of the principle of equivalence for massive bodies with unprecedented accuracy. Lunar laser ranging analysis has provided measurements of the Earth's precession, the moon's tidal acceleration, and lunar rotational dissipation. These scientific results, current technological developments, and prospects for the future are discussed here.

Contact mechanics of the ovine stifle during simulated early stance in gait. An in vitro study using robotics.

Ovine stifle joint contact pressures and contact areas were measured in vitro using a six degree-of-freedom (DOF) robotic system. The robot generated static joint loads of 1.875 times body weight (BW) compression, 0.15 BW medial shear and 0.625 BW cranial shear at 6.5 degrees of flexion for four specimens, simulating the early stance phase of gait (walking). This condition represents a period of intense loading and was implemented as a worst-case loading scenario for the joint at this gait. We determined that the medial and lateral compartments bore 5.5 +/- 0.9 MPa and 4.4 +/- 1.1 MPa of mean pressure, respectively, on 107.7 +/- 28.7 mm(2) and 60.8 +/- 56.3 mm(2) of area, respectively. The unique contribution of this study is that stifle contact pressures and areas were determined during loading which simulated physiological levels (early stance phase of gait). This information is important to our understanding of the stresses that must be borne by repair tissues/constructs that are implanted into human and animal tibio-femoral joints.

Mapping of donor and recipient site properties for osteochondral graft reconstruction of subchondral cystic lesions in the equine stifle joint.

REASONS FOR PERFORMING STUDY: To improve osteochondral graft reconstruction of subchondral cystic lesions in the medial and lateral femoral condyles by matching the material properties of donor and recipient sites. OBJECTIVES: To measure biomechanical and biochemical parameters that influence the function and healing of osteochondral grafts used to reconstruct subchondral cystic lesions. HYPOTHESIS: Suitable donor sites are available within the stifle joint for reconstructing the femoral condyles, despite considerable regional property variation. METHODS: Fifty-six osteochondral cores were harvested from 6 distal femurs for initial studies that determined subchondral bone modulus of elasticity and ultimate stress. In a second study, 28 osteochondral cores were harvested from 6 distal femurs to measure cartilage aggregate modulus, thickness and sulphated glycosaminoglycan (sGAG) content. Using micro-CT imaging, subchondral bone mineral density and bone volume fraction were also measured. In both studies 2-dimensional contour plots using a bicubic interpolation method and normalised data were generated to allow visual comparison of joint surface characteristics. Statistical comparisons between donor and recipient site raw data were made using an ANOVA for repeated measures with a post hoc Tukey test. RESULTS: Material properties of cartilage and bone vary considerably over the surface of the stifle joint but the central region of the medial condyle, where subchondral cystic lesions freqdently occur, typically demonstrated bone strength and modulus values of the highest observed. Cartilage thickness and aggregate modulus were highest in the medial femoral condyle and axial aspect of the lateral condyle. CONCLUSIONS: Material properties of the grafts from the trochlear groove and axial aspect of the lateral trochlear ridge were the closest match for those found in the medial condyle, whereas properties of the lateral condyle were most similar to those found in the trochlear groove and axial aspect of the medial trochlear ridge.

Salmon serum 22 kDa insulin-like growth factor-binding protein (IGFBP) is IGFBP-1.

Western ligand blotting of salmon serum typically reveals three insulin-like growth factor (IGF) binding proteins (IGFBPs) at 22, 28 and 41 kDa. Physiologic regulation of the 22 kDa IGFBP is similar to that of mammalian IGFBP-1; it is increased in catabolic states such as fasting and stress. On the other hand, its molecular mass on Western ligand blotting is closest to mammalian IGFBP-4. The conflict between physiology and molecular mass makes it difficult to determine the identity of the 22 kDa IGFBP. This study therefore aimed to identify the 22 kDa IGFBP from protein and cDNA sequences. The 22 kDa IGFBP was purified from chinook salmon serum by a combination of IGF-affinity chromatography and reverse-phase chromatography. The N-terminal aminoacid sequence of the purified protein was used to design degenerate primers. Degenerate PCR with liver template amplified a partial IGFBP cDNA, and full-length cDNA was obtained by 5'- and 3'-rapid amplification of cDNA ends (RACE). The 1915-bp cDNA clone encodes a 23.8 kDa IGFBP, and its N-terminal amino-acid sequence matched that of purified 22 kDa IGFBP. Sequence comparison with six human IGFBPs revealed that it is most similar to IGFBP-1 (40% identity and 55% similarity). These findings indicate that salmon 22 kDa IGFBP is IGFBP-1. Salmon IGFBP-1 mRNA is predominantly expressed in the liver, and its expression levels appear to reflect circulating levels. The 3'-untranslated region of salmon IGFBP-1 mRNA contains four repeats of the nucleotide sequence ATTTA, which is involved in selective mRNA degradation. In contrast, amino-acid sequence analysis revealed that salmon IGFBP-1 does not have an Arg-Gly-Asp (RGD) integrin recognition sequence nor a Pro, Glu, Ser and Thr (PEST)-rich domain (a segment involved in rapid turnover of protein), both of which are characteristic of mammalian IGFBP-1. These findings suggest that association with the cell surface and turnover rate may differ between salmon and mammalian IGFBP-1.

Effects of sex steroids on gonadotropin (FSH and LH) regulation in coho salmon (Oncorhynchus kisutch).

The effect of steroid hormone treatment on coho salmon (Oncorhynchus kisutch) was examined. The cDNAs for coho salmon FSH beta and LH beta subunits were cloned and sequenced using reverse transcriptase PCR. Northern blot analysis revealed that a single transcript of 1 kb for each of these subunits was present in the pituitaries of vitellogenic and spermiating coho salmon. RNase protection assays (RPAs) were developed to quantify FSH beta and LH beta subunit transcript levels. For the RPAs, antisense RNA probes and sense RNA standards were prepared from a region of the cDNAs which spanned the signal peptide and a portion of the mature protein. These RPAs were used to examine the effects of exogenous steroids including testosterone, estradiol-17beta (E2) and 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-P) in vivo, in coho salmon at three time points during the spring period of gonadal growth when plasma levels of FSH are increasing. Both testosterone and E2 increased steady state mRNA levels of LH beta, whereas E2 decreased steady state mRNA levels of FSH beta in one experiment. Thus, the RPAs were able to detect changes in steady state mRNA levels in response to exogenous steroid treatment. Plasma and pituitary levels of FSH and LH were also measured using RIA. Throughout the experimental series, FSH plasma levels decreased in response to exogenous testosterone and E2 administration, while 17alpha,20beta-P had no effect on FSH plasma levels. Plasma LH levels were not detected throughout the course of the experiment. Pituitary LH increased in response to testosterone and E2, while pituitary FSH levels did not change. 17alpha,20beta-P had no effect on pituitary FSH or LH content during the experiment. Thus, regulation of the gonadotropins in coho salmon occurs at both the transcriptional as well as the translational level. Testosterone and E2 appear to have negative feedback effects on FSH, but positive feedback on LH.

Discovery and structure-activity relationships of sulfonamide ETA-selective antagonists.

Random screening of compounds in an ETA receptor binding assay led to the discovery of a class of benzenesulfonamide ligands. Optimization led to the development of 5-amino-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamides which were functional antagonists. Structural features which were important to activity included a 1,5-substitution pattern on the naphthalene ring; a sulfonamide NH with a pK value < 7; an amine, preferably with alkyl substituents, at the 5-position; and methyl groups on both the 3- and 4-positions of the isoxazole.

Density dependence of expiratory flow and bronchodilator response in asthma.

Change in the magnitude of density dependence of the maximal expiratory flow (D/MEF) following inhalation of isoproterenol was used as a test for predicting the long term response to isoproterenol vs atropine in 24 adult patients with longstanding asthma. Eleven subjects showed a decrease in D/MEF manifested by increase in volume of isoflow (VisoV) and/or decrease in Vmax50 Helox/air following isoproterenol inhalation (group 1). Thirteen subjects manifested an opposite response (group 2). Atropine sulphate (0.08 mg/kg) and isoproterenol hydrochloride (2.5 mg) were then administered by inhalation, each four times a day for seven days in a randomized double-blind cross over fashion to all subjects. One of group 1 but ten of group 2 subjects had a greater subjective and objective improvement with atropine than with isoproterenol (P less than .005). An increase in D/MEF following isoproterenol can be used as a test to predict a better response to atropine than to isoproterenol over a one week period. Such a response occurs in almost half of the adult chronic asthmatic patients. The results are consistent with a preferential dilatation of the large airways by atropine.

Endogenous Candida endophthalmitis after intravenous anesthesia with propofol.

Propofol is an intravenous anesthetic agent that was approved by the US Food and Drug Administration in October 1989. It has gained rapid acceptance and is in widespread use. In June 1990, the Centers for Disease Control reported four clusters of postsurgical infections associated with the use of propofol. We describe one of those clusters, consisting of four cases of endogenous Candida albicans endophthalmitis. These infections occurred in nonimmunocompromised patients after they had undergone nonophthalmologic surgery in which propofol had been used as anesthesia. An investigation by the Centers for Disease Control concluded that the infections in these patients were due to extrinsic contamination of propofol during preparation for use at the hospital. Ophthalmologists should be aware of this new potential source of endogenous endophthalmitis.

Transient posterior subcapsular lens opacities in diabetes mellitus.

In three patients with transient cataracts the lenticular opacities were feathery in nature, and posterior subcapsular in location. They appeared to emanate from a dense central posterior subcapsular plaque. These opacities were examined with the slit lamp and documented photographically. The onset of cataract was abrupt in all three patients, and resolved over a three- to 36-day period. Two patients had bilateral reversible cataracts, and in one of these patients the lenticular opacities were recurrent. Two of the patients had been taking oral corticosteroids. Temporary cataracts have been previously reported in patients with poor diabetic control. Diabetes mellitus had been diagnosed in only one of our patients. Three-hour glucose tolerance testing of the other two patients disclosed mildly increased one-hour blood glucose levels. We believe that reversible lens opacities may occur in subclinical diabetes mellitus with normal or only mildly increased blood glucose levels.

Anterior chamber aspirate cultures after uncomplicated cataract surgery.

We cultured anterior chamber aspirates of 30 patients who had uncomplicated extracapsular cataract extraction or phacoemulsification. The aspirate was obtained at the time of wound closure. Of 30 patients, 13 (43%) had culture-positive anterior chamber aspirates. The total number of organisms recovered was 18, with three patients having multiple organisms identified. The most commonly isolated organisms were coagulase-negative Staphylococcus sp., occurring in eight of 18 isolates (44%). No eyes in our study developed endophthalmitis, even though almost one half had viable organisms growing from the anterior chamber aspirates. Inoculum sizes were extremely small (10 to 20 colony-forming units/ml). This study suggests that in humans, the anterior chamber is capable of clearing a low inoculum of bacteria after cataract surgery without the development of endophthalmitis.

Intraocular gentamicin sulfate and postcataract anterior chamber aspirate cultures.

We cultured anterior chamber aspirates of 28 patients who had uncomplicated cataract surgery. Fourteen patients had received 80 micrograms/ml of gentamicin in balanced salt solution through irrigation of the anterior chamber throughout cataract extraction, and 14 patients had received 8 micrograms/ml of gentamicin. Cultures of anterior chamber fluid obtained at the end of surgery from all 28 patients had no growth on two nonselective media. There was no clinical evidence of ocular toxicity. This study demonstrates that antibiotic in the intraocular irrigation fluid can reduce or eliminate the expected intraocular bacterial load after cataract surgery.

A continuous pure moment loading apparatus for biomechanical testing of multi-segment spine specimens.

An apparatus is described that enables the application of continuous pure moment loads to multi-segment spine specimens. This loading apparatus allows continuous cycling of the spine between specified flexion and extension (or right and left lateral bending) maximum load endpoints. Using a six-degree-of-freedom load cell and three-dimensional optoelectronic stereophotogrammetry, characteristic displacement versus load hysteresis curves can be generated and analyzed for different spinal constructs of interest. Unlike quasi-static loading, the use of continuous loading permits the analysis of the spine's behaviour within the neutral zone. This information is of particular clinical significance given that the instability of a spinal segment is related to its flexibility within the neutral zone. Representative curves for the porcine lumbar spine in flexion-extension and lateral bending are presented to illustrate the capabilities of this system.