Research Institute Orion

STUDY DESIGN: A prospective clinical study of thoracic pedicle screws monitored with triggered electromyographic testing. OBJECTIVE: To evaluate the sensitivity of recording rectus abdominis triggered electromyographs to assess thoracic screw placement. SUMMARY OF BACKGROUND DATA: Triggered electromyographic testing from lower extremity myotomes has identified medially placed lumbar pedicle screws. Higher thresholds indicate intraosseous placement because of increased resistance to current flow. Lower thresholds correspond to compromised pedicles with potential for nerve impingement. No clinical study has correlated an identical technique with rectus muscle recordings, which are innervated from T6 to T12. METHODS: A total of 677 thoracic screws were placed in 92 consecutive patients. Screws placed from T6 and T12 were evaluated using an ascending method of stimulation until a compound muscle action potential was obtained from the rectus abdominis. Threshold values were compared both in absolute terms and also in relation to other intrapatient values. RESULTS: Screws were separated into three groups: Group A (n = 650 screws) had thresholds >6.0 mA and intraosseus placement. Group B (n = 21) had thresholds <6.0 mA but an intact medial pedicle border on reexamination and radiographic confirmation. Group C (n = 6) had thresholds <6.0 mA and medial wall perforations confirmed by tactile and/or visual inspection. Thus, 3.9% (27 of 677) of all screws had thresholds <6.0 mA. Only 22% (6 of 27) had medial perforation. Group B screws averaged a 54% decrease from the mean as compared with a 69% decrease for Group C screws (P = 0.0160). There were no postoperative neurologic deficits or radicular chest wall complaints. CONCLUSION: To assess thoracic pedicle screw placement, triggered electromyographic thresholds <6.0 mA, coupled with values 60-65% decreased from the mean of all other thresholds in a given patient, should alert the surgeon to suspect a medial pedicle wall breach.

The performance of total joint arthroplasty (TJA) depends on the size/shape, material, and amounts of implant debris. Much remains unknown in terms of which types of debris are most reactive. We compared the responses of human periimplant cells, osteoblasts, fibroblasts, and macrophages, exposed to particles of different metal-based particles (i.e., cobalt-chromium-molybdenum (CoCrMo) alloy, titanium (Ti) alloy, zirconium (Zr) oxide, and Zr alloy. CoCrMo-alloy particles were by far the most toxic (p < 0.05) and decreased viability and proliferation of human osteoblasts, fibroblasts, and macrophages by >50% at a dose of only 50 particles per cell. All particle types induced the production of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-8 by osteoblasts, fibroblasts, and monocytes/macrophages. However, the greatest cytokine responses of macrophages were to CoCrMo alloy (TNF-α and IL-8) and Ti alloy (IL-1β). Likewise, the greatest responses of fibroblasts and osteoblasts were to CoCrMo alloy (IL-6 and TNF-α) (i.e., IL-6 300 pg/mL; 30-fold max, TNF-α 150 pg/mL; 15-fold max) versus controls. For macrophages, CoCrMo particles induced IL-8 (> 2000 pg/mL; approx 100-fold max) above controls and were also significantly elevated above levels produced by Zr-based particles. Submicron sized (0.2-0.9 μm) Zr-based particles (originally presumed to be more reactive) induced less toxicity and inflammatory responses when compared with larger (approx 1 μm) CoCrMo-alloy and Ti-alloy particles.

An historical review of the development of shielding techniques for indirectly ionizing radiation is presented, along with a summary of techniques at various levels of sophistication for shielding design and analysis.

STUDY DESIGN: This in vitro human cadaveric study tested the loss of thoracic motion segment flexion stiffness after sequential posterior upper instrumented vertebra anchor placement techniques and posterior column destabilization. OBJECTIVE: This study was designed to determine the possible destabilizing effects of upper thoracic instrumentation anchor site preparation. SUMMARY OF BACKGROUND DATA: Proximal junctional kyphosis after instrumentation and arthrodesis for scoliosis and related spine deformities has recently been reported to range from 10% to 46%. The effect of posterior skeletal dissection associated with upper instrumented vertebra anchor placement on adjacent motion segment flexion stiffness has not been previously studied. METHODS.: Twenty-three intact thoracic motion segments were obtained from 6 human cadavers. Biomechanical testing was performed with each motion segment flexed to approximately 3.2 degrees at a rate of 0.1 Hz, with corresponding torques recorded. Data were collected after a series of 6 posterior procedures. Differences with P value <0.01 were considered significant and those with P value <0.05 marginally significant. RESULTS: Supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal done, bilaterally, produced similar, small (range, 2.09%-6.03%), nonsignificant reductions in motion segment flexion stiffness. But when totaled, these 4 procedures resulted in a significant 16.31% loss of flexion stiffness. The fifth procedure of supraspinous and interspinous process ligament transection added a marginally significant 6.59% incremental loss of flexion stiffness. Supralaminar hook site preparation combined with supraspinous and interspinous process ligament transection resulted in a marginally significant 12.62% incremental loss of flexion stiffness. Transection of the remaining posterior structures (facet joints and all other posterior soft tissue structures) produced a significant additional flexion stiffness loss of 44.72%. The anterior column alone provided only 32.39% of the total motion segment flexion stiffness. Transection of all posterior stabilizing structures, similar to a Smith-Peterson/chevron/Ponte resection, decreased motion segment flexion stiffness significantly, 67.61%. CONCLUSION: Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Summary Nine 115- to 180-kg, hay-adapted, Holstein steers were fed an experimental diet with added sodium sulfate that induces polioencephalomalacia ( pem ). Five calves developed the disease. Thiamine concentrations in blood, csf , brain, and liver were not indicative of thiamine deficiency. The odor of hydrogen sulfide in eructated rumen gas was associated with the onset of pem . Sulfide concentrations in rumen fluid were measured 1 or 2 times a week by 2 techniques. Sulfide concentrations progressively increased in all 9 calves after the feeding of the pem -inducing diet commenced. The highest concentrations coincided with the onset of clinical signs of pem and were significantly higher in the calves that developed pem than in those that did not. This suggests that pem can result from sulfide toxicosis following excess production of sulfide in the rumen.

Study Design. A study was conducted to investigate the biomechanical, histochemical, and biologic ingrowth characteristics of the most widely used total disc prosthesis, the hydroxyapatite-coated SB Charité prosthesis. Objective. To compare the porous ingrowth, linear apposition, or bony ingrowth in total disc replacement with published reports of porous ingrowth prostheses in the appendicular skeleton. Methods. Seven mature baboons (Papio cynocephalus) underwent L5–L6 total disc replacement through an anterior transperitoneal approach. The SB Charité prosthetic vertebral endplates (n = 14) were cobalt-chrome covered by two layers of thin titanium with a hydroxyapatite coating, which was electrochemically bonded to the implant surface. Results. At 6 months after surgery, the range of motion exhibited by the SB Charité and the nonoperative control subjects under axial compression, flexion–extension, and lateral bending showed no statistical difference (P > 0.05). Plain film radiographic analysis showed no lucencies or loosening of any prosthetic vertebral endplate. Gross histopathologic analysis of the hydroxyapatite-coated SB Charité prosthesis demonstrated excellent ingrowth at the level of the implant–bone interface, without evidence of fibrous tissue or synovium. Histochemical assays showed no accumulation of particulate wear debris (no titanium, ultrahigh molecular weight polyethylene, or cobalt-chrome) nor cytokines (tumor necrosis factor-α, prostaglandin E2, interleukin-1, -2, or -6). Total endplate area showed a mean ingrowth (volume fraction) of 47.9% ± 9.12% and a total ingrowth range of 35.5% to 58.8%. Conclusions. The porous ingrowth (percentage of pore ingrowth coverage at the bone–metal interface) was more favorable for total disc replacement than for cementless total joint components in the appendicular skeleton (range, 10–30%). The reason for the improved degree of porous ingrowth in total disc replacement prostheses probably is that ligamentotaxis causes sustained compression across the metal–bone interface.

We present Spitzer IRS spectra (R ~600, 10 - 38 micron) of 38 positions in the Galactic Center (GC), all at the same Galactic longitude and spanning plus/minus 0.3 degrees in latitude. Our positions include the Arches Cluster, the Arched Filaments, regions near the Quintuplet Cluster, the ``Bubble'' lying along the same line-of-sight as the molecular cloud G0.11-0.11, and the diffuse interstellar gas along the line-of-sight at higher Galactic latitudes. From measurements of the [O IV], [Ne II], [Ne III], [Si II], [S III], [S IV], [Fe II], [Fe III], and H_2 S(0), S(1), and S(2) lines we determine the gas excitation and ionic abundance ratios. The Ne/H and S/H abundance ratios are ~ 1.6 times that of the Orion Nebula. The main source of excitation is photoionization, with the Arches Cluster ionizing the Arched Filaments and the Quintuplet Cluster ionizing the gas nearby and at lower Galactic latitudes including the far side of the Bubble. In addition, strong shocks ionize gas to O^{+3} and destroy dust grains, releasing iron into the gas phase (Fe/H ~ 1.3 times 10^{-6} in the Arched Filaments and Fe/H ~ 8.8 times 10^{-6} in the Bubble). The shock effects are particularly noticeable in the center of the Bubble, but O$^{+3}$ is present in all positions. We suggest that the shocks are due to the winds from the Quintuplet Cluster Wolf-Rayet stars. On the other hand, the H_2 line ratios can be explained with multi-component models of warm molecular gas in photodissociation regions without the need for H_2 production in shocks.

The Scythian Platform (ScP) with a heterogeneous basement of Baikalian-Variscan-Cimmerian age is located between the East European Craton (EEC) on the north and the Crimean-Caucasus orogenic belt and the Black Sea (BS) Basin on the south. In order to get new constrains on the basin architecture and crustal structure of the ScP and a better understanding of the tectonic processes and evolution of the southern margin of the EEC during Mesozoic and Cenozoic time, a 630-km-long seismic wide-angle refraction and reflection (WARR) profile DOBRE-5 was acquired in 2011 October. It crosses in a W-E direction the Fore-Dobrudja Trough, the Odessa Shelf of the BS and the Crimean Plain. The field acquisition included eight chemical shot points located every 50 km and recorded by 215 stations placed every 2.0 km on the land. In addition, the offshore data from existing profile 26, placed in the Odessa Shelf, were used. The obtained seismic model shows clear lateral segmentation of the crust within the study region on four domains: the Fore-Dobrudja Domain (km 20-160), an offshore domain of the Karkinit Trough at the Odessa Shelf of the BS (km 160-360), an onshore domain of the Central Crimean Uplift (Crimean Plain, km 360-520) and the Indolo-Kuban Trough at the Kerch Peninsula (km 520-620) that is the easternmost part of the Crimea. Two contrasting domains of the ScP within the central part of the DOBRE-5 profile, the Karkinit Trough and the Central Crimean Uplift, may represent different stages of the ScP formation. A deep Karkinit Trough with an underlying high-velocity (>7.16 km s -1 ) lower crust body suggests its rifting-related origin during Early Cretaceous time. The Central Crimean Uplift represents a thick (up to 47 km) crustal domain consisting of three layers with velocities 5.8-6.4, 6.5-6.6 and 6.7-7.0 km s -1 , which could be evidence of this part of the ScP originating on the crust of Precambrian craton (EEC). The thick heterogeneous basement of the Central Crimean Uplift shows inclusions of granitic bodies associated with magmatic activity related with Variscan orogeny within the ScP. General bending and crustal scale buckling of the Central Crimean Uplift with a wavelength of 230 km could be an effect of the Alpine compressional tectonics in the adjacent Crimean Mountains. The extended/rifted continental margin of the ScP (EEC) at the Odessa Shelf and buckling/uplifted domain of the

We reexamine the spectroscopic underpinnings of recent suggestions that [O I] and [Fe II] lines from the Orion H II region are produced in gas where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new observations show that previous detections of [O I] 5577 were dominated by telluric emission. Our limits are consistent with a moderate density (10^4 cm^{-3}) photoionized gas. We show that a previously proposed model of the Orion H II region reproduces the observed [O I] and [Fe II] spectrum. These lines are fully consistent with formation in a dusty region of moderate density.

We are engaged in a comprehensive program to find reliable elemental abundances in and to probe the physical structure of the Orion Nebula, the brightest and best-resolved H II region. In the course of developing a robust extinction correction covering our optical and ultraviolet FOS and STIS observations, we examined the decrement within various series of He I lines. The decrements of the 2^3S-n^3P, 2^3P-n^3S and 3^3S-n^3P series are not in accord with caseB recombination theory. None of these anomalous He I decrements can be explained by extinction, indicating the presence of additional radiative transfer effects in He I lines ranging from the near-IR to the near-UV. CLOUDY photoionization equilibrium models including radiative transfer are developed to predict the observed He I decrements and the quantitative agreement is quite remarkable. Following from these results, select He I lines are combined with H I and [O II] lines and stellar extinction data to validate a new normalizable analytic expression for the wavelength dependence of the extinction. In so doing, the He+/H+ abundance is also derived.

4H-SiC p/sup +/-n-n/sup +/ diodes of low series resistivity (<1/spl times/10/sup -4/ /spl Omega//spl middot/cm/sup 2/) were fabricated and packaged. The diodes exhibited homogeneous avalanche breakdown at voltages U/sub b/=250-270 V according to the doping level of the n layer. The temperature coefficient of the breakdown voltage was measured to be 2.6/spl times/10/sup -4/ k/sup -1/ in the temperature range 300 to 573 K. These diodes were capable of dissipating a pulsed power density of 3.7 MW/cm/sup 2/ under avalanche current conditions. The transient thermal resistance of the diode was measured to be 0.6 K/W for a 100-ns pulse width, An experimental determination of the electron saturated drift velocity along the c-axis in 4H-SIC was performed for the first time, It was estimated to be 0.8/spl times/10/sup 7/ cm/s at room temperature and 0.75/spl times/10/sup 7/ cm/s at approximately 360 K.

Nuclear weapons testing was conducted in the atmosphere at numerous sites worldwide between 1946 and 1980, which resulted in exposures to local populations as a consequence of fallout of radioactive debris. The nuclear tests were conducted by five nations (United States, Soviet Union, United Kingdom, France, and China) primarily at 16 sites. The 16 testing sites, located in nine different countries on five continents (plus Oceania) contributed nearly all of the radioactive materials released to the environment by atmospheric testing; only small amounts were released at a fewother minor testing sites. The 16 sites discussed here are Nevada Test Site, USA (North American continent), Bikini and Enewetak, Marshall Islands (Oceania); Johnston Island, USA (Oceania), Christmas and Malden Island, Kiribati (Oceania); Emu Field, Maralinga, and Monte Bello Islands, Australia (Australian continent); Mururoa and Fangataufa, French Polynesia (Oceania), Reggane, Algeria (Africa), Novaya Zemlya and Kapustin Yar, Russia (Europe), Semipalatinsk, Kazakhstan (Asia), and Lop Nor, China (Asia). There were large differences in the numbers of tests conducted at each location and in the total explosive yields. Those factors, as well as differences in population density, lifestyle, environment, and climate at each site, led to large differences in the doses received by local populations. In general, the tests conducted earliest led to the highest individual and population exposures, although the amount of information available for a few of these sites is insufficient to provide any detailed evaluation of radiation exposures. The most comprehensive information for any site is for the Nevada Test Site. The disparities in available information add difficulty to determining the radiation exposures of local populations at each site. It is the goal of this paper to summarize the available information on external and internal doses received by the public living in the regions near each of the mentioned nuclear test sites as a consequence of local fallout deposition.

Although variations in elemental abundance ratios in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in G333.6-0.2 with the Kuiper Airborne Observatory and reobserved the central position with the Infrared Space Observatory's Long Wavelength Spectrometer in far-infrared lines of S++, N++, N+, and O++. We also added the N+ lines at 122 and 205 micron to the suite of lines measured in W43 by Simpson et al. (1995). The measured electron densities range from ~40 to over 4000 cm-3 in a single H II region, indicating that abundance analyses must consider density variations, since the critical densities of the observed lines range from 40 to 9000 cm-3. We propose a method to handle density variations and make new estimates of the S/H and N/H abundance ratios. We find that our sulfur abundance estimates for G333.6-0.2 and W43 agree with the S/H abundance ratios expected for the S/H abundance gradient previously reported by Simpson et al. The estimated N/H, S/H, and N/S ratios are the most reliable because of their small corrections for unseen ionization states (< 10%). We compute models of the two H II regions to estimate corrections for the other unseen ionization states. We discuss these predictions and conclude that only a few of the latest models adequately reproduce H II region observations, including the well-known, relatively-large observed Ne++/O++ ratios in low- and moderate-excitation H II regions.

Mechanism of charge transport in a diode of a silicon carbide’s Schottky barrier formed by a quasi-amorphous interstitial phase TiB x on the surface of n-6H-SiC (0001) single crystals with an uncompensated donor (nitrogen) concentration of ∼1018 cm−3 and dislocation density of ∼(106–108) cm−2 has been studied. It is demonstrated that, at temperatures T ≲ 400 K, the charge transport is governed by the tunneling current along dislocations intersecting the space charge region. At T > 400 K, the mechanism of charge transport changes to a thermionic mechanism with a barrier height of ∼0.64 eV and ideality factor close to 1.3.

dry) and diverse filler characteristics modulate fragment release and polymer matrix degradation. In doing so, it expanded the established NanoRelease protocol, previously used for analyzing fragment emission, by evaluating two significant additions: (1) simulated weathering with rain events and (2) fractionation of sample leachate prior to analysis. Comparing different composite materials and protocols demonstrated that the polymer matrix is the most significant factor in NEP aging. Wet weathering is more realistic than dry weathering, but dry weathering seems to provide a more controlled release of material over wet. Wet weathering studies could be complicated by leaching, and the addition of a fractionation step can improve the quality of UV-vis measurements.

The Galactic center H II region, G0.18[0.04, also known as the "" Sickle, is located where the nonthermal "" Arc crosses the Galactic plane. The Sickle appears to be the ionized edge of a dense molecular cloud. The source of ionization has been ascribed to both the interaction of the cloud with the magnetic eld of the Arc and to the hot stars in the adjacent cluster, AFGL 2004, also known as the "" Quintuplet Cluster. This paper addresses the relative locations of the stars, the ionized and molecular gas, and the sources of gas excitation and dust heating. The far-infrared forbidden lines of [S III] 18.7 and 33.5 km, [Si II] 34.8 km, [Ne III] 36.0 km, [O III] 51.8 and 88.4 km, [N III] 57.3 km, [O I] 63.2 and 146 km, [C II] 158 km, and [N II] 205 km and the adjacent continua were observed with NASAs Kuiper Airborne Observatory at 11 positions around G0.18[0.04, including G0.15[0.05, also known as the "" Pistol. The beam size was 40A60A. The electron density, the ionic abundances, and the ionization structure of the H II region were estimated from the doubly ionized line uxes. The density and radiation eld found in the photodissociation region (PDR) between the H II region and the molecular cloud were estimated from the [C II] and [O I] line

Using the Goddard High-Resolution Spectrograph on the Hubble Space Telescope, we measured the flux of [Fe IV] (3d5 4P5/2 --> 3d5 6S5/2) λvac = 2836.56 Å in the Orion Nebula, the first detection of an [Fe IV] line in an H II region. A useful upper limit is set on the sum of fluxes of [Fe IV] (3d5 4D5/2, 3/2 --> 3d5 6S5/2) λvac = 2568.4, 2568.2 Å. By comparing these observations with predicted fluxes from simply ``retrofitting'' our two previous photoionization models, we are able to derive (or set an upper limit on) the Fe/H abundance ratio: 70, 200 times lower than solar from the 2837 Å line, and ≥38, ≥120 times lower than solar from the 2568 Å line limit. If collisional excitation from the ground state were indeed the dominant mechanism for populating the respective upper levels of these lines, then the inferred Fe/H from the 2837 Å line and limit from the 2568 Å line would be ~3.0 and ~3.4 times larger than above. All these ratios are much lower than several recent determinations of gas-phase Fe/H ~ 3 × 10-6 in Orion, which themselves are a factor ~10 depleted relative to solar. Because the inferred Fe/H should be at least as high in the Fe+3 zone as in the Fe+ and Fe+2 zones, a reexamination of the Fe+3 atomic data and improved modeling would be valuable. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at STScI, which is operated by AURA, Inc., under NASA contract NAS5-26555.

The results of studies on the strength at bending and volumetric electrical resistance of composite materials based on AlN–SiC with additions from 2 to 6 wt % Y2O3. It is shown that at increasing the content of Y2O3 in the mixture from 2 to 6 wt % the compaction of the composites intensifies their electrical resistance from (1.4–5.4) × 106 to (1.8–5.94) × 107 Ohm·cm (at 20°C), which at the increasing temperature decreases exponentially and at 800°C for all composites is (5–6) × 104 Ohm·cm. It was determined that materials with the smaller content of Y2O3 have somewhat higher value of the ultimate strength during bending, namely, 110 MPa.

STUDY DESIGN: Experimental and analytical study of transverse plane pelvic rotation. OBJECTIVES: To determine how pelvic rotation projected onto the transverse plane relates to coronal plane anatomic landmark location. SUMMARY OF BACKGROUND DATA: Current spine deformity instrumentation may be used to apply transverse plane loads to the spine that may be transmitted to regions not included in the instrumentation, including the pelvis. METHODS: An anatomically correct, sawbones model of an adult female pelvis was marked with lead shot at prominent radiographic landmarks, rotated at different angles in the sagittal, transverse, and coronal planes, and left/right (L/R) ratios of the medial-lateral distances between similar landmarks determined. An analytical equation was also derived to determine the degree of rotation in the transverse plane, using medial-lateral and anterior-posterior distances between same landmarks. RESULTS: The L/R ratio for the coronal plane distance between the inferior ilium at the sacro iliac joint (SI) and anterior superior iliac spine (ASIS), the SI-ASIS measurement, proved the most reliable of the four ratios studied to determine the extent of pelvic rotation in the transverse plane. Assuming the pelvis is symmetric, the most important factor is location of the compared landmarks. A long distance between the landmarks in both the coronal and transverse plane and a large angle between the line joining the two landmarks and the coronal plane of the pelvis, as viewed in the transverse plane, are best. Transverse plane pelvic rotation up to 20 degrees is accurately reflected nearly linearly by L/R SI-ASIS ratios. CONCLUSIONS: Bony pelvis landmarks visible on coronal plane radiographs can be used to estimate transverse plane pelvic rotation, but precise conversion to degrees rotation requires additional information on specific patient pelvic morphology.

A mechanism of charge transport in Au-TiB x -n-GaN Schottky diodes with a space charge region considerably exceeding the de Broglie wavelength in GaN is studied. Analysis of temperature dependences of current-voltage (I–V) characteristics of forward-biased Schottky barriers showed that, in the temperature range 80–380 K, the charge transport is performed by tunneling along dislocations intersecting the space charge region. Estimation of dislocation density ρ by the I–V characteristics, in accordance with a model of tunneling along the dislocation line, gives the value ρ ≈ 1.7 × 107 cm−2, which is close in magnitude to the dislocation density measured by X-ray diffractometry.