bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Repaired Slope Using a GEONET or GEOPIPE Drain to Lower Ground-Water Table
Authors: Tan S-A , Chew S-H , Karunaratne G-P , Wong S-F
Published: April 2008

A 70 m long by 5 m high slope with gradient of 1(V):2(H) was cut into a medium-stiff residual soil of undrained shear strength better than 60 kPa, with drained strength parameters of about c' = 10 kPa, and ϕ' = 22°, to form the bank for an effluent pond used for irrigation of a racetrack turfing. Both drained and undrained slope stability analysis indicates stable slopes under reasonable ground-water (GW) levels expected in the cut slope. However, after a period of intense rainfall during construction, the slope suffered a shallow slip of about 1 m to 1.5 m depth over a 30m stretch of the slope length with a vertical scarp near the top of the cut slope. This paper examines the causes of slope failure, and the strategy adopted for a permanent repair of the slope by providing internal geosynthetic drains beneath the re-compacted slope, using either a GEONET or closely spaced geo-pipe inclusions in the slope. For design, the GEONET or geo-pipe drains used must have adequate factored transmissivity to conduct expected heavy rainfall infiltration water safely out of the slope mass. Under a steady-state very heavy rainfall condition of 150 mm/h on the racetrack, it is demonstrated by the Finite Element Method (FEM) analysis, that GEONET must be provided to at least as far back as the mid-depth of the slope (about 4 m depth) to produce sufficient GW lowering to give stable slopes. The construction method of the slope repair to avoid further failure is described briefly, and the performance of the sub-soil drains in enhancing slope stability is demonstrated in the field project.
Key Installation Issues Impacting the Performance of Geocomposite Pavement Edgedrain Systems
Authors: Elfino MK , Riley DG , Baas TR
Published: April 2008

This paper addresses the key installation issues impacting the performance of geocomposite pavement edgedrain systems. This includes maintaining the verticality of the drain panel in the trench, proper positioning of the drain panel within the trench, backfilling with open-graded coarse aggregate, timely installation of outlet fittings and pipe, and the use of outlet pipes with adequate pipe stiffness. Three highway rehabilitation projects involving the installation of approximately 120 km (400,000 L.F.) of geocomposite edgedrains in Virginia and Ohio are investigated, and lessons learned documented in this paper. Actual cost savings, Up to 50%, were realized due to the use of geocomposite edgedrain compared to conventional edgedrains. Conclusions and recommendations are presented in support of successful installations, and lasting performance to meet pavement design life requirements.
Review Clogging Behavior by the Modified Gradient Ratio Test Device with Implanted Piezometers
Authors: Chang DT-T , Hsieh C , Chen S-Y , Chen Y-Q
Published: April 2008

A modified implanted Gradient Ratio (GR) test system was proposed in the study. In comparison with the conventional GR test device, all the piezometers are implanted into the soil specimen, and an additional piezometer is installed at soilgeotextile interface, in order to precisely measure the pore pressure variation of the soil-geotextile system. By using the modified GR test apparatus, 120 tests were conducted to study the clogging behavior of soil-geotextile system. Four types of needle-punched nonwoven geotextiles and five gap-graded soil mixtures were used in the program. These soils are the mixture of the Ottawa sand and various percentages of weathered mudstone. Three hydraulic gradients were used in the GR tests. The results of the study indicated that the modified implanted GR test system is able to provide pore pressure head measurement within the test specimen. In general, GR values obtained from the implanted GR test system are greater than those obtained from the conventional GR tests.
Characteristics of Beryllium Oxide and Beryllium Metal Powders for Use as Reference Materials
Authors: Stefaniak AB , Hoover MD , Day GA , Ekechukwu AA , Whitney GE , Brink CA , Scripsick RC
Published: April 2008

Laboratory evaluations of commercially available powders of beryllium oxide (BeO) and beryllium metal, with special emphasis on type UOX-125 BeO and type I-400 beryllium metal, are ongoing to develop reference materials for evaluating analytical chemistry digestion methods and facilitating occupational health studies. Measured properties of the powders include morphology, size, density, specific surface area (SSA); crystalline and elemental composition; surface chemistry, and in vitro dissolution in hydrochloric acid (HCl) (pH 1), phagolysosomal simulant fluid (PSF) (pH 4.5), and serum ultrafiltrate (pH 7.3). The powders were also used to evaluate the digestion and recovery efficiencies for commonly used U.S. Environmental Protection Agency (EPA), National Institute for Occupational Safety and Health (NIOSH), and Occupational Safety and Health Administration (OSHA) standard analytical methods. UOX-125 BeO powder has high-purity and aggregate cluster morphology with SSA independent of aerodynamic particle cluster size, which results in dissolution kinetics that are independent of cluster size. I-400 beryllium metal powder has high-purity and compact particle morphology with SSA that increases as particle size decreases, which causes size-dependent dissolution kinetics (i.e., smaller particles dissolve more quickly than larger particles). The PSF and HCl chemical dissolution rate constants (g·cm−2day−1) for the BeO powder were a factor of 10 lower than for the metal powder. Concomitantly, the EPA and NIOSH analytical methods, which used aggressive digestion procedures (e.g., microwave-assisted sample digestion or perchloric acid), gave more complete recovery of beryllium from BeO compared to the OSHA analytical method. Our characterization data suggest that these BeO and metal powders hold promise for use as analytical reference materials. We recommend continued laboratory collaborations to evaluate and apply these BeO and beryllium metal powders as analytical reference materials.
Determination of Beryllium Compounds by NIOSH 7303
Authors: Amer S , Smieja D , Loughrin J , Reichmann L
Published: April 2008

The fourth edition of the National Institute for Occupational Safety and Health (NIOSH) Manual of Analytical Methods contains a new, simplified procedure for elemental analysis in workplace atmospheres by Inductively Coupled Argon Plasma Atomic Emission Spectroscopy (ICP-AES) titled NIOSH 7303. This method uses hot block digestion with hydrochloric acid (HCl) and nitric acid (HNO3). The method was presented as fully valid for elemental beryllium. It was further investigated and also found to be valid for beryllium sulfate tetrahydrate and has a recovery efficiency of about 80 % for beryllium oxide. Additionally, no matrix effect on beryllium analysis is apparent by NIOSH 7303 for five common sampling media: polyvinylchloride filters, mixed cellulose ester filters, Whatman® 42 filters, Ghost™ wipes, and Palintest® wipes. Finally, the method has been reevaluated and found to produce a beryllium detection level of 0.0002 μg/mL (0.005 μg/sample for air samples) and a quantifiable level of 0.0005 (0.0125 μg/sample). At this detection limit, the Occupational Safety and Health Administration Permissible Exposure Limit (PEL) of 0.002 mg/m3 can be achieved at the method's detection level with an air sample of 2.5 L or one tenth of the PEL with a sample of 25 L under the prescribed preparation and analytical conditions.
Development of a New Fluorescence Method for the Detection of Beryllium on Surfaces
Authors: Minogue EM , Ehler DS , Burrell AK , McCleskey TM , Taylor TP
Published: April 2008

A rapid, quantitative, sensitive test for the detection of beryllium on surfaces has been developed. The method is based on the fluorescence of beryllium bound to sulfonated hydroxybenzoquinoline at pH 12.8, which emits at 475 nm when excited at 380 nm and includes a novel dissolution technique. The intensity of fluorescence is linear with respect to beryllium concentration. A detection limit of 0.02 μg Be/100 cm2 has been achieved, which is ten times lower than the DOE recommended working limit for non-beryllium work areas [1]. Interference studies have been carried out with a variety of metals including Al, Fe, Pb, U, Cd, Cr, Hg, Ca, W, Ni, Co, and Cu with minimal or no interferences found for detection of Be at 100 nM in the presence 0.4 mM of the other metal. The method has proven successful under various operating conditions, including the detection of beryllium on a variety of surfaces both in laboratory settings and in field trials. It fulfills the requirements for a fast, inexpensive, field deployable method of detection of beryllium on surfaces.
Interlaboratory Evaluation of a Portable Fluorescence Method for the Measurement of Trace Beryllium in the Workplace
Authors: Ashley K , McCleskey TM , Brisson MJ , Goodyear G , Cronin J , Agrawal A
Published: April 2008

Researchers at Los Alamos National Laboratory (LANL) developed a field-portable fluorescence method for the measurement of trace beryllium in workplace samples such as surface dust and air filters. The technology has been privately licensed and is commercially available. In cooperation with the Analytical Subcommittee of the Beryllium Health and Safety Committee, we have carried out a collaborative interlaboratory evaluation of the LANL field-portable fluorescence method. The interlaboratory study was conducted for the purpose of providing performance data that can be used to support standard methods. Mixed cellulose ester (MCE) membrane filters and Whatman 541 filters were spiked with beryllium standard solutions so that the filters spanned the range ≈0.05 – ≈0.5 μg Be per sample. Sets of these filters were then coded (to ensure blind analysis) and sent to participating laboratories, where they were analyzed. Analysis consisted of the following steps: 1. Removal of the filters from transport cassettes and placement of them into 15-mL centrifuge tubes; 2. mechanically-assisted extraction of the filters in 5 mL of 1 % ammonium bifluoride solution (aqueous) for 30 min; 3.–4. filtration and transfer of sample extract aliquots (100 μL) into fluorescence cuvettes; 5. introduction of 1.9 mL of detection solution (to effect reaction of the fluorescence reagent with beryllium in the extracted sample); and 6. measurement of fluorescence at ≈75 nm using a portable fluorometer. This work presents performance data in support of a procedure that is targeted for publication as a National Institute for Occupational Safety and Health (NIOSH) method and as an ASTM International standard.
Predicting Oxidation and Deuterium Ingress for Zr-2.5Nb CANDU Pressure Tubes
Authors: Bahurmuz AA , Muir IJ , Urbanic VF
Published: April 2008

The pressure boundary of a CANDU® fuel channel is composed of a cold-worked Zr-2.5Nb pressure tube, which has each end rolled into a stainless-steel end fitting. Heavy-water (D2O) coolant (250–310°C) flows over and through twelve or thirteen fuel bundles contained in each pressure tube. During operation, some deuterium generated by aqueous corrosion of the tube surface enters the metal. Additional deuterium also enters through the rolled joint between the tube and the end fitting.

Predictive models for deuterium ingress are required for fitness-for-service assessments for operating pressure tubes and for the development of new reactor designs. A predictive model for assessing the long-term oxidation of, and deuterium ingress into, the body of the pressure tubes has been developed from in-reactor tests of samples which had been pre-oxidized to obtain oxide thickness values representative of long-term behavior. Deuterium ingress is modeled based on a fraction (2–10 %) of the corrosion-freed deuterium entering the metal. The current version of the model contains relationships describing the oxidation rate as a function of oxide thickness, temperature, concentration of dissolved oxygen in the water, and fast neutron flux and fluence. It can successfully predict the observed deuterium-uptake history of pressure tubes in existing CANDU reactors. The model projects a slight increase in the rate of oxidation and deuterium ingress over time. This increase is much less than for Zircaloy-2, a material used in early CANDU units.

In parallel with model development, there are experimental programs involving detailed surface analysis of removed pressure tubes and irradiation tests focused on elucidating the mechanisms of oxidation and deuterium ingress. As the results of these programs become available, they will be incorporated into the predictive model. This presentation will focus on the model and recent results from the supporting experimental programs.
Influence of Structure—Phase State of Nb Containing Zr Alloys on Irradiation-Induced Growth
Authors: Shishov VN , Peregud MM , Nikulina AV , Pimenov YV , Kobylyansky GP , Novoselov AE , Ostrovsky ZE , Obukhov AV
Published: April 2008

On account of the search for the optimal composition and structure-phase state of Zr alloys much attention is paid to upgrade the E110 (Zr-1 %Nb) and E635 (Zr-1 %Nb-0.35 %Fe-1.2 %Sn) alloys that have proved well in terms of irradiation-induced creep and growth, high strength characteristics, and corrosion. The difference between the alloy properties is determined by their states related to their compositions. The structure-phase state of the Zr-Nb and Zr-Nb-Fe-Sn systems has been studied after heat treatment in the α-- and β + β- regions and its influence on the irradiation-induced growth (IIG) during BOR-60 irradiation at T =315–350 %C was investigated. A substantial difference has been shown in the deformation effected by IIG of those alloys; it is less for Zr-Nb-Fe-Sn alloys in dissimilar structure-phase states. The incubation period of the accelerated growth stage is determined by the α-matrix composition, the phase state and the initial dislocation structure. Neutron irradiation leads to a redistribution of alloying elements between the matrix and the precipitates, and to changes in the α-solid solution composition. These changes affect accumulation and mobility of irradiation defects, anisotropy and formation of vacancy c-component dislocation loops. The appearance of c-loops usually correlates with an axial direction acceleration of the IIG of tubes conforming to their texture. The basic regularities of the phase transformation have been established: a) β-Nb precipitates in Zr-Nb alloys are altered in composition to reduce the Nb content from 85–90 % to ∼ 50 %, fine precipitates likely enriched in Nb are formed; b) β-Zr precipitates are subject to irradiation-stimulated decomposition; c) Laves phase precipitates change composition (the content of Fe decreases) and crystal structure, HCP to BCC (α-Nb); d) (Zr,Nb)2Fe precipitates having the FCC lattice retain their composition and crystal structure; e) no amorphization of any secondary phase precipitates is observable under the given conditions of irradiation (T = 315–350 °C). Based on the dpa, the results were compared pertaining to Zr-alloy IIG deformation vs. fluence in various reactors at different energies of fast neutrons. The presented graphs enable comparison between the results of numerous experiments and enable predictions of Zr-material behavior in long-term operation and at high burn-up in commercial reactors.
Damage Dependence of Irradiation Deformation of Zr-2.5Nb Pressure Tubes
Authors: Griffiths M , Christodoulou N , Donohue SA
Published: April 2008

The diametral expansion and elongation rates of Zr-2.5Nb pressure tubes in CANDU™ (CANada Deuterium Uranium) nuclear reactors are important properties that limit their useful life and the maximum power level for reactor operation.

For a given set of operating conditions there is considerable variability in the deformation rates because of the variations in as-fabricated microstructure and chemistry from tube-to-tube — specifically grain size, crystallographic texture, and oxygen content. The as-fabricated microstructure also varies within a given tube, the largest variation occurring along the length, and this is a result of cooling of the tube during the extrusion process. During service in a nuclear reactor, the microstructure evolves further, and this additional change in microstructure is primarily dependent on the rate of radiation damage (determined by the fast neutron flux), the temperature, and the time. Both the fast neutron flux and temperature vary at all points within the pressure tube.

For a given material microstructure, the deformation is a function of the operating conditions: coolant pressure (stress), temperature, and neutron flux. In principle, the deformation rate is a linear function of fast neutron flux, and this is mostly true for fast neutron fluxes of the order of 1017 n.m-2.s-1. Recent analyses of data from pressure tubes measured over long periods of operation in reactor have shown that the steady-state diametral creep rates are not linear with fast neutron flux for fluxes up to about 0.5 × 1017 n.m-2.s-1. A qualitative model has been developed to account for the observed behavior based on the modifying effects of neutron flux and temperature on the microstructure. The model describes the suppression of thermal creep and the transition from thermal to irradiation creep with increasing neutron flux.
Creation of Oxidized Zirconium Ortliopaedic Implants
Authors: Hunter G , Dickinson J , Herb B , Graham R
Published: April 2008

More demanding performance expectations for total joint arthroplasty are driving the development of alternative bearing materials. Oxidized zirconium was developed as an alternative to cobalt-chromium alloy for knee and hip femoral components in order to reduce wear of the polyethylene counterface and to address the needs of metal-sensitive patients. Oxidation in high temperature air transforms the metallic Zr-2.5Nb alloy surface into a stable, durable, low-friction oxide ceramic without creating the risk for brittle fracture associated with monolithic ceramic components. This presentation reviews aspects of this technology with a historical perspective, including standards for the zirconium alloy, non-medical applications for oxidized zirconium, and previous orthopaedic applications for zirconium. Manufacturing processes for oxidized zirconium components are described, beginning with refining of the zirconium from beach sand, to producing the alloy ingot and bar, to fabricating the component shape, and finally to oxidizing the surface and burnishing it to a smooth finish. Conditions are described for producing the oxide with excellent integrity, which is nominally 5 μm thick and predominantly monoclinic phase. The metal and oxide microstructures are characterized and related to the mechanical properties of the components and durability of the oxide. Laboratory hip and knee simulator tests are reviewed, which indicate that oxidized zirconium components reduce wear of the polyethylene counterface by 40–90 % depending on test conditions. As evidenced by promising early clinical experience, oxidized zirconium components have characteristics that provide an alternative to conventional cobalt-chromium components with an interchangeable surgical technique, while providing the potential for superior performance.
Comparison of Stress Corrosion Cracking and Corrosion Fatigue (Anodized and Non-Anodized Grade 4 CP Ti)
Authors: Zardiackas LD , Roach MD , Williamson RS
Published: April 2008

In light of the possible effects of anodization on stress corrosion cracking (SCC) and corrosion fatigue (CF) of CP titanium, a research project has been completed recently in our laboratories to evaluate and compare SCC and CF of anodized versus non-anodized samples from a single lot of Grade 4 CPTi. Initial evaluation of alloy composition, microstructure, Vickers microhardness, and mechanical properties including the tensile and yield strength, % elongation and reduction of area was performed. After these tests ensured the material met the standards of ASTM Standard Specification for Unalloyed Titanium for Surgical Implant Applications (F 67), samples were prepared using low stress grinding techniques. Samples were divided into two groups, and the non-anodized SCC and CF testing was initiated. The surface of the second group of samples was anodized by Synthes to provide a green̸gold surface consistent with standard production processing and then tested using the identical methodology as used for the non-anodized samples.

Results of the slow strain rate SCC testing on both smooth and notched anodized and non-anodized samples in both distilled de-ionized water and Ringers solution at 37°C showed no effect of anodization. Results of corrosion fatigue testing indicated that, while there was no effect of anodization on corrosion fatigue, there was a significant effect of the notch on the fatigue characteristics regardless of the two different surface conditions.
Comparison of the Corrosion Fatigue Characteristics of CP Ti-Grade 4, Ti-6AI-4V ELI, Ti-6AI-7Nb, and Ti-15Mo
Authors: Roach MD , Williamson RS , Zardiackas LD
Published: April 2008

The purpose of this study was to evaluate and compare the corrosion fatigue (CF) characteristics of a series of titanium alloys including Grade 4 CP Ti (ASTM F 67), Ti-6A1-4V (ASTM F 136), Ti-6Al-7Nb (ASTM F 1295), and Ti-15 Mo (ASTM F 2066). Evaluation of alloy composition, microstructure, and Vicker's microhardness was performed to ensure that each material met the required specification. Smooth and notched CF tensile samples of each alloy were machined using low stress grind techniques and tested at 1Hz according to ASTM F 1801 in both Ringer's solution and distilled̸de-ionized water at 37°C. Smooth CF samples had a 10 mm gauge length and a 2.5 mm gauge diameter, and notched CF samples had a 2.5 mm notch root diameter (K,=3.2). A minimum of three samples was tested at five tension-tension sinusoidal load levels including a run-out level at 106 cycles. SEM analysis was performed on the fractured surfaces of representative samples of each alloy to characterize and compare the failure mechanisms.

Fatigue results revealed no differences between the smooth and notched samples of each alloy run in distilled water and those run in Ringer's solution. Results indicated corrosion fatigue mechanisms were not contributing to the fractures under these conditions. However, a significant reduction of fatigue strength was observed for the notched samples of each alloy compared to the smooth samples in identical solutions. These results suggest that even though there is no notch sensitivity in these alloys under static conditions, a notch under dynamic fatigue mechanisms may cause a substantial reduction in cycles to implant fracture. SEM analysis showed typical fatigue fracture morphologies on both the smooth and notched samples. Notch samples, however, did show more defined fluting in terracing due to the higher tri-axial stress state at the root of the notch. In conclusion, corrosion fatigue mechanisms were not contributing to the fracture of these alloys under the given conditions, but the presence of a notch significantly reduced the fatigue strength of all alloys tested.
Comparison of Stress Corrosion Cracking Characteristics of CP Ti, Ti-6AI-7Nb, Ti-6AI-4V, and Ti-15IVIo
Authors: Williamson RS , Roach MD , Zardiackas LD
Published: April 2008

The purpose of this research was to evaluate and compare the stress corrosion cracking (SCC) of Ti-15 Mo (ASTM F2066), Ti-6Al-7Nb (ASTM1295), Ti-6A1-4V ELI (ASTM F136), and Grade 4 CPTi (ASTM F67). Evaluation of alloy composition, microstructure, Vickers microhardness, and tensile properties was performed to determine compliance with the appropriate ASTM specification. For SCC testing, smooth tensile samples with a gauge length of 10 mm and a gauge diameter of 4 mm and notched samples with a notch root diameter of 4 mm (Kt=3.2) were prepared using low stress grinding procedures. Three smooth and three notched samples were tested in distilled HiO and Ringer's solution at 37°C. Testing was performed using the slow extension rate method at a stroke rate of 10-5 mm/s according to the guidelines established in ASTM G129. The ratio of the percent elongation (PER) and reduction of area (ROAR) of smooth and notched samples tested in Ringer's solution and distilled water were evaluated. The fracture surfaces of representative samples were also examined for fracture mode identification using SEM.

Results showed that all alloys complied with the appropriate ASTM specification. SCC may be considered to occur in a material if the ductile properties in an aggressive media are inferior to the ductile properties in a non-aggressive media. Evaluations of the PER and ROAR ratios in smooth and notched samples for each alloy in Ringer's and distilled water showed no indication of SCC failure mechanisms. SEM examination of the fracture surfaces showed no differences in the fracture morphology regardless of the testing solution. These results were consistent with the mechanical testing data. It is therefore concluded that SCC mechanisms were not operating or contributing to the fracture of these alloys under the conditions evaluated.
Zirconium and Niobium Affect Human Osteoblasts, Fibroblasts, and Lymphocytes in a Similar Manner to More Traditional Implant Alloy Metals
Authors: Hallab NJ , Anderson S , Caicedo M , Jacobs JJ
Published: April 2008

Implant debris remains the major factor limiting the longevity of total joint replacements. Whether soluble implant debris of Zr and Nb containing implant alloys constitute a greater risk than other implant metals remains unknown. We evaluated the relative effects of soluble forms of Zr+4 and Nb+5 (0.001–10.0 mM) relative to Cr+3, Mo+5, Al+3, Co+2, Ni+2 , Fe+3, Cu+2, Mn+2, Mg+2, Na+2, and V+3 chloride solutions on human peri-implant cells (i.e., osteoblast-like MG-63 cells, fibroblasts, and lymphocytes). Metals were ranked using a 50 % decrease in proliferation and viability to determine toxic concentrations. Lymphocytes, fibroblasts, and osteoblasts were, generally, similarly affected by metals where the most toxic metals, Co, Ni, Nb, and V required <1.0 mM to induce toxicity. Less toxic metals Al, Cr, Fe, Mo, and Zr generally required >1.0 mM challenge to produce toxicity. Overall, Co and V were the most toxic metals tested, thus Zr and Nb containing implant alloys would not likely be more toxic than traditional implant alloys. Below concentrations of 0.1 mM, neither Zr nor Nb reduced osteoblast, lymphocyte, or fibroblast proliferation. Zr was generally an order of magnitude less toxic than Nb to lymphocytes, fibroblasts, and osteoblasts. Our results indicated that soluble Zr and Nb resulting from implant degradation likely act in a metal- and concentration-specific manner capable of producing adverse local and remote tissue responses to the same degree as metals from traditional implant alloys, e.g., Ti-6AI-4V (ASTM F 138) and Co-Cr-Mo alloys (ASTM F 75).
Comparison of Delamination Characterization for IM7/8552 Composite Woven and Tape Laminates
Authors: Paris I , Minguet PJ , O'Brier TK
Published: April 2008

The interlaminar fracture toughness of a plain-weave carbon-epoxy composite was studied under Mode I, Mode II and Mixed-Mode I and II loading. The objective was to compare results for a composite material with two different fiber forms: unidirectional tape and plain-weave fabric (PW). Tests were performed using the double-cantilever beam (DCB), four-point end-notch flexure (4ENF) and mixed-mode bending (MMB) configurations. Delamination initiation values were obtained as well as propagation values. The specimens were made of 24 layers of IM7/8552 plain-weave fabric. The results were compared with tests performed by Hansen and Martin [1] on IM7/8552 unidirectional tape. For all Mode I, Mode II and Mixed-Mode tests, the woven initiation Gc are quite similar to the corresponding initiation values for the tape material. The woven Gc propagation values, however, are much higher (2.6 times in Mode I and 3.1 times in Mode II) than the corresponding propagation values for the tape material. Furthermore, these propagation values may have more significance to structural components than propagation values for tape laminates.
Head Injury in Snowboarding: Evaluating the Protective Role of Helmets
Authors: Scher I , Richards D , Carhart M
Published: April 2008

According to a 1999 report by the U.S. Consumer Product Safety Commission, head injuries represent approximately 14 % of all skiing and snowboarding injuries. In a recent retrospective study of patients treated for snowboarding-related head injuries, Nakaguchi and Tsutsumi (2002) found that major head injuries were most often associated with backward falls (68 %) resulting in occipital impacts (66 % of falls) occurring on a gentle or moderate slope. They concluded that the majority of severe snowboarding head injuries were caused by the “opposite-edge phenomenon” where the snowboarder falls backward and contacts the occiput. In order to determine if the use of skiing helmets would reduce the likelihood of head injury associated with catching an edge snowboarding, we conducted a two-part study. In the first part, we measured the speeds of over 180 snowboarders on beginner and intermediate slopes at Mammoth, CA. Across all locations at the resort, the average speeds of beginner and intermediate snowboarders were 17.7 kph (11.0 mph) and 31.9 kph (19.8 mph), respectively. In the second part of the study, we used an instrumented 50th percentile male Hybrid III anthropomorphic test device (ATD) to determine the head accelerations and neck loads associated with a backward fall onto the occiput, both with and without wearing a helmet. For these tests, the ATD was fitted with snowboarding equipment and accelerated to the speeds associated with an intermediate snowboarder (as measured in the first part of the study). Once the ATD was at speed, the snowboard was snubbed on the back edge, simulating the “opposite-edge phenomena” and the posterior aspect of the ATD head was propelled toward the snow surface or a simulated tree. Film analysis of the ATD fall kinematics demonstrated a rapid transition to whole-body angular motion at opposite edge catch. The use of a helmet reduced substantially the linear accelerations and head injury criterion associated with head-to-ground contact on hard, icy snow and during the simulated tree contact. Also, the neck loads were reduced modestly with helmet use. These findings indicate that helmets can mitigate head-to-ground contact severity associated with a common snowboarding fall scenario, the “opposite-edge-phenomenon.”
Functional and Release Characteristics of Alpine Ski Equipment
Authors: Ettlinger CF , Johnson RJ , Shealy J
Published: April 2008

Releasable bindings were developed to reduce the risk of lower leg injuries. However, the relationship between the incidence of specific alpine injury groups and the function and calibration of the release system has not been well understood. Over the 32 years between December 1972 and April 2004, the authors conducted a case control study at a northern Vermont ski area involving 17 967 injuries and 3617 uninjured controls. During that time, approximately 6.4 million skier visits were recorded at the area. Injured skiers were treated at clinic in the base lodge and their injuries diagnosed by the clinic staff. Data relating to the accident, the injury, and the equipment used were recorded. The release moments of equipment associated with lower extremity injuries and uninjured controls were measured using a commercially available test device. Case studies of 43 anterior cruciate ligament (ACL) sprains, 79 lower leg injuries, and 99 uninjured controls were conducted using data collected over seven years between December 1997 and April 2004. In terms of quantitative critical defects, 17 % of the control group, 14 % of the ACL group, and 39 % of the lower leg group exhibited release levels more than 30 % above recommended. When qualitative critical defects were considered, 27 % of the control group, 25 % of the ACL group, and 54 % of the lower leg group were found to exhibit one or more defects capable of having a significant effect on equipment function. The authors concluded that sprains, fractures, strains, and contusions of the lower leg among alpine skiers were associated with measurable or observable qualities of the release system. Serious sprains of the knee were not. A substantial reduction of injuries below the knee can be expected if potentially defective equipment can be identified and repaired, or replaced.
Bone Marrow-Derived Mesenchymal Stem Cells Ameliorate Autoimmune Enteropathy Independently of Regulatory T Cells
Authors: Parekkadan Biju , Tilles Arno W. , Yarmush Martin L.
Published: April 2008

Cell-based tolerogenic therapy is a relatively new approach for the treatment of autoimmune diseases. Mesenchymal stem cells (MSCs) have been shown to be potent immunomodulatory agents in a number of experimental and clinical scenarios; however, their use in various autoimmune diseases is undefined. Herein, we report the efficacy of MSC transplantation in a multiorgan autoimmunity model. Mice with defective peripheral tolerance caused by a deficiency in regulatory T cells were used as a testbed for therapy. After screening multiple target tissues of autoimmune attack, we observed an MSC-specific improvement in the histopathology of the distal ileum of treated mice. We then showed that MSCs can reduce mesenteric lymph node (MLN) cellularity in autoimmune mice during active disease and decrease activated T-cell populations in the MLN. Trafficking studies using enhanced green fluorescent protein (eGFP)-reporter MSCs revealed no appreciable engraftment in the intestine, but it did reveal the presence of eGFP+ cells organized in clusters within the MLN, as well as ancillary nodes. Semiquantitative analysis showed no difference in the number of clusters; however, eGFP+ cells in MLNs compared with ancillary nodes had distinct fibroblastoid morphology and formed a network with neighboring eGFP+ cells. Finally, we show evidence that transplantation of MSCs caused global immunosuppression, as measured by increased CD4+ CD8+ thymocyte production and serum interleukin-10 and decreased serum interferon-γ. These data implicate the intestine as a new site of MSC tolerance induction and should motivate additional studies evaluating the use of MSCs as a treatment for autoimmune enteropathies.

Disclosure of potential conflicts of interest is found at the end of this article.
Developmental changes in the human GH receptor and its signal transduction pathways
Authors: Kenth Gurvinder , Mergelas Jennifer A Manalo , Goodyer Cynthia Gates
Published: April 2008

We previously reported the presence of functional human GH receptors (hGHRs) in the human fetal hepatocyte (FH) as early as the first trimester. Interestingly, fetal serum levels of hGH are in the acromegalic range, yet certain hGH-dependent factors are expressed at very low levels (IGF-I, IGF-binding protein-3), suggesting that fetal liver has limited responsiveness to hGH. To determine whether this is due to the fetal tissue levels of hGHR or factors in the hGH/hGHR axis that might influence hGHR function, we compared hGHR isoforms and downstream signaling proteins in FH versus human adult liver (HAL). Immunoprecipitation/immunoblotting (IB) analyses found similar precursor and mature hGHR forms while RT-PCR assays of truncated (T) hGHR1–279, dominant negative for the full-length (FL) receptor, showed similar T/FL mRNA ratios in FH and HAL. IB demonstrated that Janus kinase (JAK) 2, signal transducers and activators of transcription (STAT(1, 3, 5A/B)), and suppressors of cytokine signaling (SOCS(1, 2, 3, cytokine-inducible SH2-containing protein (CIS))) proteins were detectable in all FH and HAL tested (12 weeks of fetal age to 60 years); the levels were similar (STAT5B) or lower (JAK2/STAT1/STAT3/STAT5A: 38–53%, SOCS/CIS: 58–76%) in FH compared with HAL. Our studies to date demonstrate that, during hepatocyte development, hGHR levels are lower in the fetal cells but the hGHR isoforms, including the relative amount of truncated versus FL, remain unchanged. The JAK2/STAT/SOCS signaling molecules are present in the FH as early as the first trimester. However, they are generally at <50% level in postnatal liver. These data suggest that low expression of both hGHR and major hGHR signaling components may explain the limited responsiveness of the fetal cells to the high circulating levels of hGH.
Acute toxicity of thioarsenates to Vibrio fischeri
Authors: Planer-Friedrich Britta , Franke Doreen , Merkel Broder , Wallschläger Dirk
Published: April 2008

Thioarsenic species often are the predominant arsenic species in sulfidic environments, yet little is known about their toxicity. We report to our knowledge the first determination of acute toxicity of mono-, di-, and trithioarsenate to the bioluminescent bacterium Vibrio fischeri, which increases with an increasing number of thio(SH)-groups. Whereas mono- and dithioarsenate are much less toxic (effective analyte concentration causing a 50% decrease in luminescence [EC50], 676 and 158 mg/L, respectively), the toxicity of trithioarsenate (EC50, 14.4 mg/L) is comparable to the toxicities of arsenate and arsenite (EC50, 9.1 and 26.1 mg/L, respectively). The low toxicity of monothioarsenate is remarkable, because it has chemical properties very similar to those of arsenate. In contrast to the toxicities of arsenite and arsenate, the toxicity of thioarsenates increases with exposure time, suggesting a lack of detoxification mechanisms or a conversion of thioarsenic species into arsenic oxyanions after uptake. We determined the acute toxicity of synthetic arsenite solutions with varying sulfide concentration to V. fischeri. Arsenic speciation in these solutions was measured by ion chromatography–inductively coupled plasma–mass spectrometry, and the observed toxicity was related to the different arsenic species present. High inhibition of luminescence was observed at low and high ratios of sulfur to arsenic, in which arsenite or a mixture of di-, tri-, and tetrathioarsenate dominated arsenic speciation. Acute toxicity decreased at sulfur to arsenic ratios of from 1 to 10, with a minimum luminescence inhibition of 30% at a ratio of 3.5, at which concentrations of 55 mg/L of arsenite and 30 mg/L of trithioarsenate were determined. The toxicity observed under these conditions is much lower than that anticipated from the individual dose–response curves that predict each species alone already should cause 70 to 80% inhibition. The low toxicity suggests an antagonistic toxicological interaction between arsenite and trithioarsenate.
Coculture of Spermatogonia With Somatic Cells in a Novel Three‐Dimensional Soft‐Agar‐Culture‐System
Authors: Stukenborg Jan‐Bernd , Wistuba Joachim , Luetjens C. Marc , Elhija Mahmoud Abu , Huleihel Mahmoud , Lunenfeld Eitan , Gromoll Jörg , Nieschlag Eberhard , Schlatt Stefan
Published: April 2008

ABSTRACT: Isolation and culture of spermatogonial stem cells (SSCs) has become an approach to study the milieu and the factors controlling their expansion and differentiation. Traditional conventional cell culture does not mimic the complex situation in the seminiferous epithelium providing a basal, intraepithelial, and adluminal compartment to the developing male germ cells. SSCs are located in specific stem cell niches whose features and functional parameters are thus far poorly understood. It was the aim of this study to isolate SSCs and to explore their expansion and differentiation potential in a novel three‐dimensional Soft‐Agar‐Culture‐System (SACS). This system provides three‐dimensional structural support and multiple options for manipulations through the addition of factors, cells, or other changes. The system has revolutionized research on blood stem cells by providing a tool for clonal analysis of expanding and differentiating blood cell lineages. In our studies, SSCs are enriched using Gfrα‐1 as a specific surface marker and magnetic‐activated cell sorting as a separation approach. At termination of the culture, we determined the type and number of germ cells obtained after the first 24 hours of culture. We also determined cell types and numbers in expanding cell clones of differentiating germ cells during the subsequent 15 days of culture. We analyzed a supportive effect of somatic cell lineages added to the solid part of the culture system. We conclude that our enrichment and culture approach is highly useful for exploration of SSC expansion and have found indications that the system supports differentiation up to the level of postmeiotic germ cells.
Gestational Exposure to Atrazine: Effects on the Postnatal Development of Male Offspring
Authors: Rosenberg Brian G. , Chen Haolin , Folmer Janet , Liu June , Papadopoulos Vassilios , Zirkin Barry R.
Published: April 2008

ABSTRACT: Atrazine is an herbicide used worldwide to control grasses and weeds. Previous studies have shown that, depending on atrazine's administered dose, exposure of male rats during the early postnatal or peripubertal periods can result in alterations in endocrine function. The gestational period is particularly vulnerable to environmental agents; however, the possible effects of atrazine exposure during this period have received only limited attention. Herein we examine the dose effects of atrazine exposure during Sprague‐Dawley rat gestation on the postnatal development of male offspring. Pregnant dams were treated by oral gavage with atrazine at 0 to 100 mg/kg/d from gestational day 14 to parturition. Thereafter, neither the pups nor the dams received atrazine. Atrazine had no effect on the number of live births per dam. Neonatal pup survival was affected, however, with increased pup death seen at doses of 10 mg/kg/d and higher. There was no effect of atrazine on the testosterone concentration within the testes of newborn pups. Anogenital distance, an androgen‐dependent process, decreased from the control level at the 75 and 100 mg/kg/d doses, with the decrease reaching significance at 100 mg/kg/d. Preputial separation, also an androgen‐dependent process, was delayed significantly compared with that in controls in response to the 50 and 100 mg/kg/d doses. At postnatal day 60, serum testosterone concentrations were reduced significantly from controls in the 50 to 100 mg/kg/d groups. However, these decreases had little effect on seminal vesicle or ventral prostate weights. These results, taken together, are suggestive of antiandrogenic effects of gestational atrazine exposure on male offspring, although for most parameters, the doses used in this study are unlikely to be experienced under any but experimental conditions.
Altered Expression of Muscle‐ and Cytoskeleton‐Related Genes in a Rat Strain With Inherited Cryptorchidism
Authors: Barthold Julia S. , McCahan Suzanne M. , Singh Amar V. , Knudsen Thomas B. , Si Xiaoli , Campion Liam , Akins Robert E.
Published: April 2008

ABSTRACT: Development of the fetal gubernaculum is a prerequisite for testicular descent and dependent on insulin‐like 3 and androgen, but knowledge of downstream effectors is limited. We analyzed transcript profiles in gubernaculum and testis to address changes occurring during normal and abnormal testicular descent in Long Evans wild‐type (wt) and cryptorchid (orl) fetuses. Total RNA from male wt and orl gubernacula (gestational days [GD]18–20), wt female gubernacula (GD18), and testis (GD17 and 19) was hybridized to Affymetrix GeneChips. Statistical analysis of temporal, gender, and strain‐specific differences in gene expression was performed with the use of linear models analysis with empirical Bayes statistics and analysis of variance (gubernaculum) and linear analysis (testis). Overrepresented common gene ontology functional categories and pathways were identified in groups of differentially expressed genes with the Database for Annotation, Visualization, and Integrated Discovery. Transcript profiles were dynamic in wt males between GD18–19 and GD20, comparatively static in orl GD18–20 gubernaculum, and similar in wt and orl testis. Functional analysis of differentially expressed genes in wt and orl gubernaculum identified categories related to metabolism, cellular biogenesis, small GTPase‐mediated signal transduction, cytoskeleton, muscle development, and insulin signaling. Genes involved in androgen receptor signaling, regulated by androgens, or both were overrepresented in differentially expressed gubernaculum and testis gene groups. Quantitative reverse transcription polymerase chain reaction (RT‐PCR) confirmed differential expression of genes related to muscle development, including Myog, Tnnt2, Fst, Igf1, Igfbp5, Id2, and Msx1. These data suggest that the orl mutation results in a primary gubernacular defect that affects muscle development and cytoskeletal function and might alter androgen‐regulated pathways.
Pharmacokinetics and Pharmacodynamics of Oral Testosterone Enanthate Plus Dutasteride for 4 Weeks in Normal Men: Implications for Male Hormonal Contraception
Authors: Amory John K. , Kalhorn Thomas F. , Page Stephanie T.
Published: April 2008

ABSTRACT: Oral administration of testosterone enanthate (TE) and dutasteride increases serum testosterone and might be useful for male hormonal contraception. To ascertain the contraceptive potential of oral TE and dutasteride by determining the degree of gonadotropin suppression mediated by 4 weeks of oral TE plus dutasteride, 20 healthy young men were randomly assigned to 4 weeks of either 400 mg oral TE twice daily or 800 mg oral TE once daily in a double‐blinded, controlled fashion at a single site. All men received 0.5 mg dutasteride daily. Blood for measurement of serum luteinizing hormone (LH), follicle‐stimulating hormone (FSH), testosterone, dihydrotesterone (DHT), and estradiol was obtained prior to treatment, weekly during treatment, and 1, 2, 4, 8, 12, 13, 14, 16, 20, and 24 hours after the morning dose on the last day of treatment. FSH was significantly suppressed throughout treatment with 800 mg TE once daily and after 4 weeks of treatment with 400 mg TE twice daily. LH was significantly suppressed after 2 weeks of treatment with 800 mg TE, but not with 400 mg TE. Serum DHT was suppressed and serum estradiol increased during treatment in both groups. High‐density lipoprotein cholesterol was suppresed during treatment, but liver function tests, hematocrit, creatinine, mood, and sexual function were unaffected. The administration of 800 mg oral TE daily combined with dutasteride for 28 days significantly suppresses gonadotropins without untoward side effects and might have utility as part of a male hormonal contraceptive regimen.