bluuebunny/crossref_metadata_2025 huggingface dataset:
Orientation and Related Buoyancy Effects in Low‐velocity Flow Boiling
Authors: Merte, Jr. Herman , Schultz William W. , Liu Quanyi , Keller Robert B.
Published: April 2009

This work is an extension of experimental results reported previously, which might provide design guidance for approximating certain aspects of the flow boiling process in microgravity but taking place in Earth gravity. In that research the buoyancy effects on the bubble dynamics were minimized by the imposition of a liquid velocity parallel to a flat heater surface in the inverted horizontal position, or nearly horizontal (within ±5°), thus holding the heated liquid and vapor formed close to the heater surface. For the fluid used, liquid velocities in the range U= 5–10 cm/s were judged to be critical for changes in the behavior of the flow boiling process. Using the hydraulic diameter of the rectangular duct used, with the heater surface embedded in one side, this velocity range gives rise to flow Reynolds numbers on the order of 4400–8800. It was subsequently judged to be of interest to extend the range of orientation of the flat heater surface relative to gravity to the full circular range of 0–360°, in increments of 45°, and the results of this work are presented here. A solid massive copper heater with a gold‐plated boiling heat transfer surface 19 × 38 mm in size, previously used for critical heat flux measurements with boiling, provided a near‐uniform surface temperature. Only steady measurements of heat flux and surface temperature were possible with the copper heater. R‐113 was the fluid used; the velocity was varied over the interval of 4–28 cm/s; bulk liquid subcooling was varied over 5–11°C; and heat flux varied over 0–10 w/cm2.
Conjugate Problems of Transport Phenomena under Quasi‐steady Microaccelerations in Realistic Spaceflight
Authors: Polezhaev V. I. , Nikitin S. A.
Published: April 2009

A new model for spatial convective transport processes conjugated with the measured or calculated realistic quasi‐steady microaccelerations is presented. Rotation around the mass center, including accelerated rotation, gravity gradient, and aerodynamical drag are taken into account. New results of the effect on mixing and concentration inhomogeneities of the elementary convective processes are presented. The mixing problem in spacecraft enclosures, concentration inhomogeneities due to convection induced by body forces in realistic spaceflight, and the coupling of this kind of convection with thermocapillary convection on the basis of this model are discussed.
Heating and Sterilization Technology for Long‐duration Space Missions
Authors: Sastry Sudhir K. , Jun Soojin , Somavat Romel , Samaranayake Chaminda , Yousef Ahmed , Pandit Ram B.
Published: April 2009

Long‐duration space missions require a high‐quality, shelf‐stable food supply but must also contend with packaging waste after use. We have developed a package, adapted from a military pouch, that enables heating of foods to serving temperature. After the food is consumed, the package may be reused for containment and sterilization of waste, and, potentially, for packaging and sterilizing foods grown on a Mars base. Packages are equipped with electrodes to permit ohmic heating of internal constituents. Heat transfer within the package was modeled using the energy transport equation, coupled with the Laplace equation for electric field strength distribution. The model was verified by temperature measurements during a sample experimental run, and it was used to optimize the package design. Waste sterilization within the package was also studied and confirmed. Mass transfer (electrode component migration) was studied by inductively coupled plasma mass spectrometry; the findings have shown concentrations within products to be well below current daily dietary exposure levels. Microbiological studies for sterilization indicated the need for package redesign to ensure parallel electrode configuration, as well as the use of supplemental external heaters along the nonelectrode walls of the package. Temperature profiles during heating of these packages have been determined.
Coalescence of Drops and Bubbles Rising through a Non‐Newtonian Fluid in a Tube
Authors: Al‐Matroushi Eisa , Borhan Ali
Published: April 2009

We conducted an experimental study of the interaction and coalescence of two drops (of the same fluid) or bubbles translating under the action of buoyancy in a cylindrical tube. The close approach of two Newtonian fluid particles of different size in a non‐Newtonian continuous phase was examined using image analysis, and measurements of the coalescence time are reported for various particle size ratios, Bond numbers, and particle‐to‐suspending‐fluid viscosity ratios. The flow disturbance behind the leading bubble and the viscoelastic nature of the continuous phase seemed to retard bubble coalescence. The time scale for coalescence of liquid drops in highly elastic continuous phase was influenced by the relative motion of the drops and their coalescence behavior.
Effects of Gravity on Transpiration of Plant Leaves
Authors: Hirai Hiroaki , Kitaya Yoshiaki
Published: April 2009

To clarify effects of gravity on the water vapor exchange between plants and the ambient air, we evaluated the transpiration rate of plant leaves at 0.01, 1.0, and 2.0 g for 20 s each during parabolic airplane flights. The transpiration rates of a strawberry leaf and a replica leaf made of wet cloth were determined using a chamber method with humidity sensors. Absolute humidity at 3 and 8 mm below the lower surface of leaves was measured to evaluate the effect of gravity on humidity near leaves and estimate their transpiration rate. The transpiration rate of the replica leaf decreased by 42% with decreasing gravity levels from 1.0 to 0.01 g and increased by 31% with increasing gravity levels from 1.0 to 2.0 g. Absolute humidity near the intact strawberry leaf was 5 g m−3 at ambient absolute humidity of 2.3 g m−3 and gravity of 1.0 g. The absolute humidity increased by 2.5 g m−3 with decreasing gravity levels from 1.0 to 0.01 g. The transpiration rate of the intact leaf decreased by 46% with decreasing gravity levels from 1.0 to 0.01 g and increased by 32% with increasing gravity levels from 1.0 to 2.0 g. We confirmed that the transpiration rate of leaves was suppressed by retarding the water vapor transfer due to restricted free air convection under microgravity conditions.
Molecular Dynamics of Ions in Two Forms of an Electroactive Polymer
Authors: Morton‐Blake D. A. , Leith Darren
Published: April 2009

Molecular dynamics (MD) are performed in all‐atom simulations of two polymer species based on polythiophene. In one case the amphiphilic polymer forms a monolayer interface between a vacuum and an aqueous layer containing ions. The electroactive nature of the polymer is invoked by conferring a negative charge on it to compensate for charge imbalance in the Na+ and Cl− concentrations of the aqueous layer. The effects of hydrostatic pressure and charge imbalance on the stability of the monolayer are investigated. In another simulation a polythiophene oligomer is wound into a helix where it serves as an ion channel between two aqueous regions on both sides of a phospholipid bilayer membrane.
Nitrilase enzymes and their role in plant–microbe interactions
Authors: Howden Andrew J. M. , Preston Gail M.
Published: April 2009

Nitrilase enzymes (nitrilases) catalyse the hydrolysis of nitrile compounds to the corresponding carboxylic acid and ammonia, and have a wide range of industrial and biotechnological applications, including the synthesis of industrially important carboxylic acids and bioremediation of cyanide and toxic nitriles. Nitrilases are produced by a wide range of organisms, including plants, bacteria and fungi, but despite their biotechnological importance, the role of these enzymes in living organisms is relatively underexplored. Current research suggests that nitrilases play important roles in a range of biological processes. In the context of plant–microbe interactions they may have roles in hormone synthesis, nutrient assimilation and detoxification of exogenous and endogenous nitriles. Nitrilases are produced by both plant pathogenic and plant growth‐promoting microorganisms, and their activities may have a significant impact on the outcome of plant–microbe interactions. In this paper we review current knowledge of the role of nitriles and nitrilases in plants and plant‐associated microorganisms, and discuss how greater understanding of the natural functions of nitrilases could be applied to benefit both industry and agriculture.
Translocation and insecticidal activity of Bacillus thuringiensis living inside of plants
Authors: Monnerat Rose Gomes , Soares Carlos Marcelo , Capdeville Guy , Jones Gareth , Martins Érica Soares , Praça Lilian , Cordeiro Bruno Arrivabene , Braz Shélida Vasconcelos , Dos Santos Roseane Cavalcante , Berry Colin
Published: April 2009

The major biological pesticide for the control of insect infestations of crops, Bacillus thuringiensis was found to be present naturally within cotton plants from fields that had never been treated with commercial formulations of this bacterium. The ability of B. thuringiensis to colonize plants as an endophyte was further established by the introduction of a strain marked by production of green fluorescent protein (GFP). After inoculation of this preparation close to the roots of cotton and cabbage seedlings, GFP‐marked bacteria could be re‐isolated from all parts of the plant, having entered the roots and migrated through the xylem. Leaves taken from the treated plants were able to cause toxicity when fed to the Lepidoptera Spodoptera frugiperda (cotton) and Plutella xylostella (cabbage). These results open up new horizons for understanding the natural ecology and evolution of B. thuringiensis and use of B. thuringiensis in insect control.
Contribution of In‐Channel Processes to Sediment Yield of an Urbanizing Watershed1
Authors: Fraley Lisa M. , Miller Andrew J. , Welty Claire
Published: April 2009

Abstract:  A study was conducted between September 2003 and September 2006 to obtain baseline sediment inventories and monitor sediment transport and storage along a 3.7 km length of the channel of Valley Creek within Valley Forge National Historical Park, Pennsylvania. Valley Creek is a tributary of the Schuylkill River and drains an urbanizing 60.6 km2 watershed that currently has 18% impervious land cover. Numerous field methods were employed to measure the suspended sediment yield, longitudinal profile, cross‐sections, banklines, and particle size distribution of the streambed. Suspended sediment yield for the watershed was measured at a USGS gage located just upstream of the park boundary between July 2004 and July 2005, the period corresponding to field surveys of bank erosion and channel change. The estimated suspended sediment yield of 95.7 t/km2/year is representative of a year with unusually high discharge, including a storm event that produced a peak of 78 m3/s, the second highest discharge on record for the USGS gage. Based on the median annual streamflow for the 24 years of record at the USGS gage from 1983 to 2006, the median annual sediment yield is estimated to be closer to 34 t/km2/year, considerably lower than median and mean values for other sites within the region. The mass of silt, clay, and fine sand derived from bank erosion along the 3.7 km study reach during the field survey period accounts for an estimated 2,340 t, equivalent to about 43% of the suspended sediment load. The mass of fine sediment stored in the bed along the study reach was estimated at 1,500 t, with about 330 t of net erosion during the study period. Although bank erosion appears to be a potentially dominant source of sediment by comparison with annual suspended sediment load, bed sediment storage and potential for remobilization is of the same order of magnitude as the mass of sediment derived from bank erosion.
Daily Updating of Operational Statistical Seasonal Water Supply Forecasts for the western U.S.1
Authors: Pagano Thomas C , Garen David C , Perkins Tom R , Pasteris Phillip A
Published: April 2009

Abstract:  Official seasonal water supply outlooks for the western United States are typically produced once per month from January through June. The Natural Resources Conservation Service has developed a new outlook product that allows the automated production and delivery of this type of forecast year‐round and with a daily update frequency. Daily snow water equivalent and water year‐to‐date precipitation data from multiple SNOTEL stations are combined using a statistical forecasting technique (“Z‐Score Regression”) to predict seasonal streamflow volume. The skill of these forecasts vs. lead‐time is comparable to the official published outlooks. The new product matches the intra‐monthly trends in the official forecasts until the target period is partly in the past, when the official forecasts begin to use information about observed streamflows to date. Geographically, the patterns of skill also match the official outlooks, with highest skill in Idaho and southern Colorado and lowest skill in the Colorado Front Range, eastern New Mexico, and eastern Montana. The direct and frequent delivery of objective guidance to users is a significant new development in the operational hydrologic seasonal forecasting community.
Twenty‐two polymorphic microsatellite loci aimed at detecting illegal trade in the Cape parrot,Poicephalus robustus(Psittacidae, AVES)
Authors: PILLAY KERUSHA , DAWSON DEBORAH A. , HORSBURGH GAVIN J. , PERRIN MIKE R. , BURKE TERRY , TAYLOR TIAWANNA D.
Published: April 2009

Twenty‐two polymorphic microsatellite loci were characterized in the Cape parrot,Poicephalus robustus. Nineteen loci were newly isolated from two Cape parrot genomic libraries, and three loci isolated from other parrot species. Loci were characterized in 40 unrelated captive Cape parrots held by aviculturalists. The loci displayed between two and 24 alleles, with the observed heterozygosities ranging between 0.10 and 0.94. This locus set is suitable for identifying clarifying parentage (parentage exclusion probabilities ofPE1 = 0.0004 andPE2 = 0.000001). Candidate parents for any Cape parrot individual can now be genotyped to distinguish between individuals, which are truly captive bred and those suspected of being wild‐caught birds. Cross‐species analysis found up to 31 loci to be polymorphic across 24 additional parrot species tested.
Amygdalus kurdistanica and A. orazii spp. nov. (Rosaceae) from Iran
Authors: Attar Farideh , Maroofi Hossein , Vafadar Mahnaz
Published: April 2009

Amygdalus kurdistanica Attar, Maroofi & Vafadar and A. orazii Maroofi, Attar & Vafadar, two new species of the genus Amygdalus L. from western Iran are described and illustrated. Amygdalus kurdistanica is closely related to A. haussknechtii (C. K. Schneider) Bornm. var. pubescens but differs by leaf and petiole size, drupe shape, pedicel indumentum and style length. Amygdalus orazii is closely related to A. communis L. but can be distinguished from A. communis by the following characters: leaf and petiole size, drupe size, pedicel length and sepal length.
Liparis angustioblonga sp. nov. (Malaxideae: Orchidaceae) from Shaanxi, China
Authors: Yang Pinghou , Jin Xiaohua , Wu Zhenhai
Published: April 2009

Liparis angustioblonga P. H. Yang & X. H. Jin sp. nov. from Shaanxi, China, is described and illustrated. It is restricted to the Qinling Mountains at an elevation of 1060 m where it grows in deciduous broadleaf forest. Liparis angustioblonga is similar to L. pauliana but differs from it by having lateral sepals connate at base, lip rectangular–oblong, 14–15 mm long, 5–6 mm wide, with two lamellae forked divergent towards the margin.
Laparoscopic sentinel node navigation surgery for early gastric cancer
Authors: Takeuchi H , Saikawa Y , Kitagawa Y
Published: April 2009

The sentinel node (SN) concept has revolutionized how the surgical staging of both melanoma and breast cancer are approached. Applying this concept can yield benefits for the patient by avoiding various complications relating to unnecessary prophylactic regional lymph node dissection in cases with negative SN for cancer metastasis. Clinical application of SN mapping for early gastric cancer had been controversial for years. However, single institutional results of laparoscopic SN mapping for early gastric cancer are considered acceptable in terms of detection rate and accuracy in determining lymph node status. For early stage gastric cancer such as cT1N0M0 – in which a better prognosis was generally achieved through conventional surgical approaches – an individualized, minimally invasive surgery that might retain the patient's quality of life should be established as the next surgical challenge. Although there are many issues still to resolve, laparoscopic minimized gastrectomy with SN navigation surgery or combined endoscopic mucosal resection and endoscopic submucosal dissection has the potential to achieve this goal.
Recent interpretations of Denonvilliers' fascia and the lateral ligament of the rectum
Authors: Sakai Y , Nomura A , Masumori K , Kawamura J , Nagayama S
Published: April 2009

The terms “Denonvilliers' fascia” and “lateral ligament of the rectum” will be very familiar to colorectal surgeons. However, how these structures are conceptualized remains controversial. Here, we review past and recent interpretations of these two terms. Denonvilliers' fascia is likely derived from the fusion of the two walls of an embryonic cul‐de‐sac to form a clear boundary between the neurovascular bundle and the mesorectum. When performing anterior dissection for mobilization of the rectum, it remains unclear whether the optimal dissection plane is in front of or behind Denonvilliers' fascia. Anatomical studies have shown that the lateral ligament may not be a clearly definable structure and that the middle rectal artery is not clinically significant. In the future, careful laparoscopic observations will give us a better understanding of these currently controversial anatomical features.
Efficacy of preoperative gonadotropin‐releasing hormone agonist therapy for laparoscopic myomectomy
Authors: Kotani Y , Shiota M , Umemoto M , Tobiume T , Shimaoka M , Hoshiai H
Published: April 2009

Objective: In this article, we evaluate efficacy of preoperative gonadotropin‐releasing hormone agonist (GnRHa) therapy prior to laparoscopic myomectomy (LM).

Materials and Methods: There were 161 subjects who underwent LM between 1995 and 2007. They were divided into two groups: group A (58 cases), who underwent four to six cycles of preoperative GnRHa therapy, and group B (103 cases), the untreated group. To determine the efficacy of preoperative GnRHa therapy, the recurrence rate after LM was evaluated by comparing the number of myoma confirmed on the preoperative MRI and the number actually enucleated. For this purpose, the cases were divided into the matched group (group I) and the discrepancy group (group II) whose enucleated number was smaller than the estimated number.

Results: No statistically significant difference was observed between groups A and B in the surgical performance. The 4 year cumulative recurrence rate was estimated to be 27.3% for group A and 25.8% for group B without any significant difference. In group A, the postoperative recurrence rate was statistically significantly higher in group II (44.4%) than in group I (12.1%). While in group I, it was 12.1% in group A and 14.3% in group B without a statistically significant difference.

Discussion: Preoperative GnRHa therapy did not compromise surgical outcome or recurrence rate, rather it acted as an effective pretreatment for LM in terms of expanding its indications. Also, completing surgery by enucleating all the myomas without any left in situ, as confirmed by the precise preoperative myoma status on the MRI, contributes to a reduction in the postoperative recurrence rate.
Unusual “erythroid loops” in canine blood smears after viper‐bite envenomation
Authors: Masserdotti Carlo
Published: April 2009

Abstract: Northern Italy is a habitat for many species of viper; Vipera aspis is responsible for most reported bites of humans and animals. Five dogs of different breeds and ages were presented by their owners to a veterinary clinic in northern Italy between September 2004 and August 2007 with a history of being bitten by a viper within the past 2 hours. On physical examination, all of the dogs were depressed, had pale mucous membranes, and had a painful area consistent with a recent viper bite wound on the nose (2), distal front leg (2), or lip (1). Hemoglobinemia and hemoglobinuria were observed in plasma and urine from all dogs. CBCs were done at the time of presentation, daily for 4 days, and 10 days after presentation in all dogs with the exception of one dog that died after 2 days. All dogs had an acute decrease in HCT within 24 hours of presentation; all dogs had neutrophilia, 3/5 had a mildly toxic left shift, and 4/5 had thrombocytopenia. On Diff‐Quik‐stained blood smears, moderate numbers of echinocytes, spherocytes, and erythrocyte ghosts were observed. In addition, moderate numbers of unusual erythrocyte membrane‐like structures (“erythroid loops”) were observed. The loops were annular in shape and sometimes disrupted, appearing as thin pale blue bands. Erythrocyte morphologic abnormalities decreased by day 3 and were no longer observed on day 10. The unique appearance of the erythroid loops together with evidence for intravascular hemolysis and other erythrocyte morphologic changes suggest they may be a consequence of erythrocyte lysis. Echinocytes, spherocytes, and erythrocyte ghosts are known to result from the action of phospholipase in viper venom; however, erythroid loops have not been reported previously and their exact mechanism of formation is unknown.
The Effects of Changing Fuels on Hot Gas Path Conditions in Syngas Turbines
Authors: Sabau Adrian S. , Wright Ian G.
Published: April 2009

Gas turbines in integrated gasification combined cycle power plants burn a fuel gas (syngas (SG)) in which the proportions of hydrocarbons, H2, CO, water vapor, and minor impurity levels may differ significantly from those in natural gas (NG). Such differences can yield changes in the temperature, pressure, and corrosive species that are experienced by critical components in the hot gas path, with important implications for the design, operation, and reliability of the turbine. A new data structure and computational methodology is presented for the numerical simulation of a turbine thermodynamic cycle, with emphasis on the hot gas path components. The approach used allows efficient handling of turbine components and variable constraints due to fuel changes. Examples are presented for a turbine with four stages, in which the vanes and blades are cooled in an open circuit using air from the appropriate compressor stages. For an imposed maximum metal temperature, values were calculated for the fuel, air, and coolant flow rates and through-wall temperature gradients for cases where the turbine was fired with NG or SG. A NG case conducted to assess the effect of coolant pressure matching between the compressor extraction points and corresponding turbine injection points indicated that this is a feature that must be considered for high combustion temperatures. The first series of SG simulations was conducted using the same inlet mass flow and pressure ratios as those for the NG case. The results showed that higher coolant flow rates and a larger number of cooled turbine rows were needed for the SG case to comply with the imposed temperature constraints. Thus, for that case, the turbine size would be different for SG than for NG. A second series of simulations examined scenarios for maintaining the original turbine configuration (i.e., geometry, diameters, blade heights, angles, and cooling circuit characteristics) used for the SG simulations. In these, the inlet mass flow was varied while keeping constant the pressure ratios and the amount of hot gas passing the first vane of the turbine. The effects of turbine matching between the NG and SG cases were increases—for the SG case of approximately 7% and 13% for total cooling flows and cooling flows for the first-stage vane, respectively. In particular, for the SG case, the vanes in the last stage of the turbine experienced inner wall temperatures that approached the maximum allowable limit.
Supplementary Backward Equations v(p,T) for the Critical and Supercritical Regions (Region 3) of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
Authors: Kretzschmar H.-J. , Harvey A. H. , Knobloch K. , Mareš R. , Miyagawa K. , Okita N. , Span R. , Stöcker I. , Wagner W. , Weber I.
Published: April 2009

When steam power cycles are modeled, thermodynamic properties as functions of pressure and temperature are required in the critical and supercritical regions (region 3 of IAPWS-IF97). With IAPWS-IF97, such calculations require cumbersome iterative calculations, because temperature and volume are the independent variables in the formulation for this region. In order to reduce the computing time, the International Association for the Properties of Water and Steam (IAPWS) adopted a set of backward equations for volume as a function of pressure and temperature in region 3. The necessary numerical consistency is achieved by dividing the region into 20 subregions, plus auxiliary subregions near the critical point in which the consistency requirements are relaxed due to the singular behavior at the critical point. In this work, we provide complete documentation of these equations, along with a discussion of their numerical consistency and the savings in computer time. The numerical consistency of these equations should be sufficient for most applications in heat-cycle, boiler, and steam-turbine calculations; if even higher consistency is required, the equations may be used to generate guesses for iterative procedures.
Experimental Study of Oxygen-Enriched Diesel Combustion Using Simulated Exhaust Gas Recirculation
Authors: Perez Peter L. , Boehman Andre L.
Published: April 2009

The techniques of design of experiments were applied to study the best operational conditions for oxygen-enriched combustion in a single-cylinder direct-injection diesel engine in order to reduce particulate matter (PM) emissions, with minimal deterioration in nitrogen oxide (NOx) emissions, by controlling fuel injection timing, carbon dioxide (CO2) and O2 volume fractions in intake air. The results showed that CO2 addition reduced average combustion temperatures and minimized the rate of increase in NOx emissions observed during oxygen-enriched conditions. It was also observed that oxygen enrichment minimized the deterioration in brake-specific fuel consumption and hydrocarbon and PM emissions that occurred at the highest level of CO2 addition.
Cylinder-to-Cylinder Variations in a V6 Gasoline Direct Injection HCCI Engine
Authors: Misztal Jacek , Xu Hongming , Wyszynski Miroslaw L. , Tsolakis Athanasios , Qiao Jun
Published: April 2009

Despite the fact that homogeneous charge compression ignition (HCCI) has been demonstrated as a combustion technology feasible for implementation with different fuels in various types of engines, cylinder-to-cylinder variations (CTCVs) in multicylinder HCCI engines remain one of the technical obstacles to overcome. A reduction in CTCV requires further developments in control technology. This study has been carried out with regard to the overall engine parameters, involving geometric differences between individual cylinders, coolant paths through the engine, combustion chamber deposits, and also the differences in the inlet temperature distributions between the cylinders. Experimental investigations on the Jaguar V6 HCCI research engine with negative valve overlapping and cam profile switching show that the differences in the rate of pressure rise between the cylinders can be larger than 1 bar/CA deg and that the load differences can be as high as 5–10%. It has been found that some individual cylinders will approach the misfiring limit far earlier than the others. The complex interaction between a number of parameters makes the control of the multicylinder engine a serious challenge. In order to avoid these differences, an active cylinder balancing strategy will be required. It has been observed that spark assistance and split injection strategy deliver the best control for the cylinder balance. However, spark assistance is restricted to low loads and low engine speeds, while split injection requires a considerable effort to optimize its possible settings. This paper defines the most important parameters influencing cylinder-to-cylinder variations in the HCCI engine and aims to put forward suggestions that can help to minimize the effect of cylinder-to-cylinder variations on the overall engine performance.
Dynamic Tensile Failure Mechanics of the Musculoskeletal Neck Using a Cadaver Model
Authors: Yliniemi Eno M. , Pellettiere Joseph A. , Doczy Erica J. , Nuckley David J. , Perry Chris E. , Ching Randal P.
Published: April 2009

Although the catapult phase of pilot ejections has been well characterized in terms of human response to compressive forces, the effect of the forces on the human body during the ensuing ejection phases (including windblast and parachute opening shock) has not been thoroughly investigated. Both windblast and parachute opening shock have been shown to induce dynamic tensile forces in the human cervical spine. However, the human tolerance to such loading is not well known. Therefore, the main objective of this research project was to measure human tensile neck failure mechanics to provide data for computational modeling, anthropometric test device development, and improved tensile injury criteria. Twelve human cadaver specimens, including four females and eight males with a mean age of 50.1±9 years, were subjected to dynamic tensile loading through the musculoskeletal neck until failure occurred. Failure load, failure strain, and tensile stiffness were measured and correlated with injury type and location. The mean failure load for the 12 specimens was 3100±645 N, mean failure strain was 16.7±5.4%, and mean tensile stiffness was 172±54.5 N/mm. The majority of injuries (8) occurred in the upper cervical spine (Oc-C3), and none took place in the midcervical region (C3–C5). The results of this study assist in filling the existing void in dynamic tensile injury data and will aid in developing improved neck injury prevention strategies.
Determination of Low-Pass Filter Cutoff Frequencies for High-Rate Biomechanical Signals Obtained Using Videographic Analysis
Authors: Fijalkowski Ronald J. , Ropella Kristina M. , Stemper Brian D.
Published: April 2009

Diffuse brain injury (DBI) commonly results from blunt impact followed by sudden head rotation, wherein severity is a function of rotational kinematics. A noninvasive in vivo rat model was designed to further investigate this relationship. Due to brain mass differences between rats and humans, rotational acceleration magnitude indicative of rat DBI (≈350 krad/s2) has been estimated as approximately 60 times greater than that of human DBI (≈6 krad/s2). Prior experimental testing attempted to use standard transducers such as linear accelerometers to measure loading kinematics. However, such measurement techniques were intrusive to experimental model operation. Therefore, initial studies using this experimental model obtained rotational displacement data from videographic images and implemented a finite difference differentiation (FDD) method to obtain rotational velocity and acceleration. Unfortunately, this method amplified high-frequency, low-amplitude noise, which interfered with signal magnitude representation. Therefore, a coherent average technique was implemented to improve the measurement of rotational kinematics from videographic images, and its results were compared with those of the previous FDD method. Results demonstrated that the coherent method accurately determined a low-pass filter cutoff frequency specific to pulse characteristics. Furthermore, noise interference and signal attenuation were minimized compared with the FDD technique.
System Analysis of Nuclear-Assisted Syngas Production From Coal
Authors: Harvego E. A. , McKellar M. G. , O’Brien J. E.
Published: April 2009

A system analysis has been performed to assess the efficiency and carbon utilization of a nuclear-assisted coal gasification process. The nuclear reactor is a high-temperature helium-cooled reactor that is used primarily to provide power for hydrogen production via high-temperature electrolysis. The supplemental hydrogen is mixed with the outlet stream from an oxygen-blown coal gasifier to produce a hydrogen-rich gas mixture, allowing most of the carbon dioxide to be converted into carbon monoxide, with enough excess hydrogen to produce a syngas product stream with a hydrogen/carbon monoxide molar ratio of about 2:1. Oxygen for the gasifier is also provided by the high-temperature electrolysis process. The results of the analysis predict 90.5% carbon utilization with a syngas production efficiency (defined as the ratio of the heating value of the produced syngas to the sum of the heating value of the coal plus the high-temperature reactor heat input) of 64.4% at a gasifier temperature of 1866 K for the high-moisture-content lignite coal considered. Usage of lower moisture coals such as bituminous can yield carbon utilization approaching 100% and 70% syngas production efficiency.
Effect of Mechanical Loading on Electrical Conductivity in Human Intervertebral Disk
Authors: Jackson Alicia R. , Travascio Francesco , Gu Wei Yong
Published: April 2009

The intervertebral disk (IVD), characterized as a charged, hydrated soft tissue, is the largest avascular structure in the body. Mechanical loading to the disk results in electromechanical transduction phenomenon as well as altered transport properties. Electrical conductivity is a material property of tissue depending on ion concentrations and diffusivities, which are in turn functions of tissue composition and structure. The aim of this study was to investigate the effect of mechanical loading on electrical behavior in human IVD tissues. We hypothesized that electrical conductivity in human IVD is strain-dependent, due to change in tissue composition caused by compression, and inhomogeneous, due to tissue structure and composition. We also hypothesized that conductivity in human annulus fibrosus (AF) is anisotropic, due to the layered structure of the tissue. Three lumbar IVDs were harvested from three human spines. From each disk, four AF specimens were prepared in each of the three principal directions (axial, circumferential, and radial), and four axial nucleus pulposus (NP) specimens were prepared. Conductivity was determined using a four-wire sense-current method and a custom-designed apparatus by measuring the resistance across the sample. Resistance measurements were taken at three levels of compression (0%, 10%, and 20%). Scanning electron microscopy (SEM) images of the human AF tissue were obtained in order to correlate tissue structure with conductivity results. Increasing compressive strain significantly decreased conductivity for all groups (p<0.05, analysis of variance (ANOVA)). Additionally, specimen orientation significantly affected electrical conductivity in the AF tissue, with conductivity in the radial direction being significantly lower than that in the axial or circumferential directions at all levels of compressive strain (p<0.05, ANOVA). Finally, conductivity in the NP tissue was significantly higher than that in the AF tissue (p<0.05, ANOVA). SEM images of the AF tissues showed evidence of microtubes orientated in the axial and circumferential directions, but not in the radial direction. This may suggest a relationship between tissue morphology and the anisotropic behavior of conductivity in the AF. The results of this investigation demonstrate that electrical conductivity in human IVD is strain-dependent and inhomogeneous, and that conductivity in the human AF tissue is anisotropic (i.e., direction-dependent). This anisotropic behavior is correlated with tissue structure shown in SEM images. This study provides important information regarding the effects of mechanical loading on solute transport and electrical behavior in IVD tissues.
Motion Estimation Using Point Cluster Method and Kalman Filter
Authors: Senesh M. , Wolf A.
Published: April 2009

The most frequently used method in a three dimensional human gait analysis involves placing markers on the skin of the analyzed segment. This introduces a significant artifact, which strongly influences the bone position and orientation and joint kinematic estimates. In this study, we tested and evaluated the effect of adding a Kalman filter procedure to the previously reported point cluster technique (PCT) in the estimation of a rigid body motion. We demonstrated the procedures by motion analysis of a compound planar pendulum from indirect opto-electronic measurements of markers attached to an elastic appendage that is restrained to slide along the rigid body long axis. The elastic frequency is close to the pendulum frequency, as in the biomechanical problem, where the soft tissue frequency content is similar to the actual movement of the bones. Comparison of the real pendulum angle to that obtained by several estimation procedures—PCT, Kalman filter followed by PCT, and low pass filter followed by PCT—enables evaluation of the accuracy of the procedures. When comparing the maximal amplitude, no effect was noted by adding the Kalman filter; however, a closer look at the signal revealed that the estimated angle based only on the PCT method was very noisy with fluctuation, while the estimated angle based on the Kalman filter followed by the PCT was a smooth signal. It was also noted that the instantaneous frequencies obtained from the estimated angle based on the PCT method is more dispersed than those obtained from the estimated angle based on Kalman filter followed by the PCT method. Addition of a Kalman filter to the PCT method in the estimation procedure of rigid body motion results in a smoother signal that better represents the real motion, with less signal distortion than when using a digital low pass filter. Furthermore, it can be concluded that adding a Kalman filter to the PCT procedure substantially reduces the dispersion of the maximal and minimal instantaneous frequencies.
The Nuclear DNA Base 5-Hydroxymethylcytosine Is Present in Purkinje Neurons and the Brain
Authors: Kriaucionis Skirmantas , Heintz Nathaniel
Published: April 2009

Methylation Mediation

Methylation of cytosine bases, 5-methylcytosine (5mC), in DNA plays an important regulatory role in mammalian genomes. Methylation patterns are often inherited across generations, but they can also be dynamic, suggesting that active DNA demethylation pathways exist. One such pathway, best characterized in plants, involves the removal of the 5mC base, and its replacement by C, via a DNA repair mechanism.
Kriaucionis and Heintz
(p.
929
, published online 16 April) now show that, as well as 5mC in mammalian genomes, there are also significant amounts of 5-hydroxymethylcytosine (5hmC) in DNA of Purkinje neurons, which have large nuclei with apparently very little heterochromatin.

Tahiliani
et al.

(p. 930, published online 16 April) find that the protein TET1 is capable of converting 5mC into 5hmC both in vitro and in vivo. 5-Hydroxymethylcytosine is also present in embryonic stem cells, and levels of 5hmC and TET1 show correlated variation during cell differentiation.
Different Fecal Microbiotas and Volatile Organic Compounds in Treated and Untreated Children with Celiac Disease
Authors: Di Cagno Raffaella , Rizzello Carlo G. , Gagliardi Francesca , Ricciuti Patrizia , Ndagijimana Maurice , Francavilla Ruggiero , Guerzoni M. Elisabetta , Crecchio Carmine , Gobbetti Marco , De Angelis Maria
Published: April 2009

This study aimed at investigating the fecal microbiotas of children with celiac disease (CD) before (U-CD) and after (T-CD) they were fed a gluten-free diet and of healthy children (HC). Brothers or sisters of T-CD were enrolled as HC. Each group consisted of seven children. PCR-denaturing gradient gel electrophoresis (DGGE) analysis with V3 universal primers revealed a unique profile for each fecal sample. PCR-DGGE analysis with group- or genus-specific 16S rRNA gene primers showed that the
Lactobacillus
community of U-CD changed significantly, while the diversity of the
Lactobacillus
community of T-CD was quite comparable to that of HC. Compared to HC, the ratio of cultivable lactic acid bacteria and
Bifidobacterium
to
Bacteroides
and enterobacteria was lower in T-CD and even lower in U-CD. The percentages of strains identified as lactobacilli differed as follows: HC (ca. 38%) > T-CD (ca. 17%) > U-CD (ca. 10%).
Lactobacillus brevis
,
Lactobacillus rossiae
, and
Lactobacillus pentosus
were identified only in fecal samples from T-CD and HC.
Lactobacillus fermentum
,
Lactobacillus delbrueckii
subsp.
bulgaricus
, and
Lactobacillus gasseri
were identified only in several fecal samples from HC. Compared to HC, the composition of
Bifidobacterium
species of T-CD varied, and it varied even more for U-CD. Forty-seven volatile organic compounds (VOCs) belonging to different chemical classes were identified using gas-chromatography mass spectrometry-solid-phase microextraction analysis. The median concentrations varied markedly for HC, T-CD, and U-CD. Overall, the
r
2
values for VOC data for brothers and sisters were equal to or lower than those for unrelated HC and T-CD. This study shows the effect of CD pathology on the fecal microbiotas of children.
The anterior cruciate ligament injury controversy: is “valgus collapse” a sex-specific mechanism?
Authors: Quatman C E , Hewett T E
Published: April 2009

Background:

Anterior cruciate ligament (ACL) injury is a devastating injury that puts an athlete at high risk of future osteoarthritis. Identification of risk factors and development of ACL prevention programmes likely decrease injury risk. Although studies indicate that sagittal plane biomechanical factors contribute to ACL loading mechanisms, it is unlikely that non-contact ACL injuries occur solely in a sagittal plane. Some authors attempt to ascribe the solely sagittal plane injury mechanism to both female and male ACL injuries and rebuff the concept that knee “valgus” is associated with isolated ACL injury. Prospective studies that utilise coupled biomechanical and epidemiological approaches demonstrated that frontal knee motions and torques are strong predictors of future non-contact ACL injury risk in female athletes. Video analysis studies also indicate a frontal plane “valgus collapse” mechanism of injury in women. As load sharing between knee ligaments is complex, frontal as well as sagittal and transverse plane loading mechanisms likely contribute to non-contact ACL injury. The purpose of this review is to summarise existing evidence regarding ACL injury mechanisms and to propose that sex-specific mechanisms of ACL injury may occur, with women sustaining injuries by a predominantly “valgus collapse” mechanism.

Conclusion:

Prevention programmes and interventions that only target high-risk sagittal plane landing mechanics, especially in the female athlete, are likely to be less effective in ameliorating important frontal and transverse plane contributions to ACL injury mechanisms and could seriously hamper ACL injury prevention efforts. Programmes that target the reduction of high-risk valgus and sagittal plane movements will probably prove to be superior for ACL injury prevention.
Compensatory mechanisms for reproductive costs in the dioecious tree Salix integra
Authors: Tozawa Munetaka , Ueno Naoto , Seiwa Kenji
Published: April 2009

In dioecious plants, females often incur greater reproductive costs than males, owing to the production of seed. This has led to evolution of cost-compensatory mechanisms in females. In trees, however, reproductive cost and compensatory mechanisms are not always detectable, probably because costs and compensation traits change with time, plant size, and modular level (i.e., individual shoots and whole plants). Herein we investigated sex-specific reproductive allocation, growth, and carbon acquisition mechanisms at different hierarchical levels in a dioecious tree, Salix integra Thunb. At both shoot and whole-plant levels, females invested more resources into reproduction than males, but without an associated reduction in vegetative growth, suggesting compensatory mechanisms in females. Females had greater biomass allocation to photosynthetic organs and higher photosynthetic rates than males. Although photosynthetic rates decreased with age, higher shoot turnover in females maintained higher productivity by consistently locating new leaves in favourable light. Females had larger areas of leafy bracts beneath peduncles, suggesting a reduction in the translocation distance of the assimilation to mature seeds. Females meet greater reproductive costs not by reducing growth, but by increasing the carbon uptake ability of different modular units in well-illuminated microenvironments.
Flowering period, thermogenesis, and pattern of visiting insects in Arisaema triphyllum (Araceae) in Quebec
Authors: Barriault Isabelle , Gibernau Marc , Barabé Denis
Published: April 2009

Jack-in-the-Pulpit ( Arisaema triphyllum (L.) Torr.) is a perennial forest herb of southern Canada and the eastern United States. The flowering periods of male and female inflorescences in relation to the temperature of the inflorescence and the activity pattern of visiting insects were studied in one population in western Montreal Island (Quebec, Canada). The flowering period of A. triphyllum was long (20 d in male and female plants), which is unusual in temperate Aroideae. This floral trait could have evolved secondarily as an adaptation to increase pollination efficiency under highly variable weather conditions at high latitude. In male and female plants, no significant temperature increase of the appendix was recorded. The warming effect of sunlight during the day could be sufficient for the emission of the attractive odour. Two Dipteran families, the Mycetophilidae and the Cecidomyiidae, were the most frequent insect visitors of A. triphyllum. Our observations showed that odour production is linked with the pollination activity beginning with insect visits.
Hybrid intermediacy between pollination syndromes inPenstemon, and the role of nectar in affecting hummingbird visitation
Authors: Wilson Paul , Jordan Elizabeth Anne
Published: April 2009

Flower size dimensions, colour, and nectar quantities potentially account for differences in pollinator species between Penstemon centranthifolius (Benth.) Benth. (tubular, red, nectar-rich, hummingbird pollinated) and Penstemon spectabilis Thurber (wide, purple, nectar-poor, hymenopteran pollinated). For this study, floral characters and pollinator attraction were measured for the two species, F1hybrids, and backcrosses. Floral dimensions, nectar characters, and color spectra combined in the hybrids in a largely linear fashion, consistent with an interpretation of net additive gene expression. In other words, the changes from one pollination syndrome to another appeared to be quantitative. There were some deviations from linearity, but not so much as to obscure the linear effect. Generally, backcrosses were not more variable than F1hybrids or pure parents. Hummingbirds preferred P. centranthifolius over P. spectabilis. The strength of this preference varied by year, and the birds did not respond to hybrids in a strictly linear fashion. When there was a preference, adding nectar hourly to under-visited plants quickly changed the foraging of hummingbirds. Bees in the genus Ceratina preferred the bee-pollination syndrome of P. spectabilis.