Signie Cant Research Articles

Adhesive-based selection by a tentacle-feeding polychaete for particle size, shape and bacterial coating in silt and sand

We tested particle selection by a surface deposit-feeding, tentaculate spionid polychaete, Pseudopolydora kempi japonica Imajima and Hartman. In experiments with peroxide-cleaned, sizegraded but otherwise natural silts and sands, individual worms showed peak preference for particles 80‐99 mm in diameter, compared with previous (Self and Jumars, 1988) documentation of peak preference for particles of 7 mm in experiments conducted with plastic and glass beads. These results imply that microtektites will not in general be good tracers of mixing of mineral grains of comparable size. Animals exhibited statistically signie cant but not marked differences in size selectivity for subrounded versus subangular grain shapes; the size preference peak was broader in subangular grains, for which orientation of the grain can alter probabilities of both contact and retention. When one size class of grains was coated with the bacterium Halomonas halodurans (ATCC 29686), animals in general showed enhanced selection (relative to controls with no food value on any size class) of that size and smaller grains, even though these smaller grains lacked food value. Greatest selection, however, generally occurred for the coated size class. Results frominclusion of glass beads in some of the experiments and from separate experiments with tentacle analogs imply that this selective capability may be largely passive and mechanical. Natural grains, due to surface texture, have more surface area for adhesive contact than do smooth glass beads so that larger grains than beads are retained. Bacteria-coated grains, in turn, appear to be picked up preferentially due to adhesion with the bacterial coating; petroleum jelly-coated microscope slides also succeed in selective retention of the size class that is bacterially coated. Substantial selection by adhesiveutilizing deposit feeders apparently can be achieved without investment in complex, time- and energy-consuming sensory systems and behaviors. Experiments with natural grains showed notably more scatter than prior experiments with glass beads, but this difference is consistent with the mechanism. For nonspherical particles, both contact and retention depend on orientation as well as size.

Dispersal, home range establishment, survival, and reproduction of translocated eastern box turtles, Terrapene c. carolina

The feasibility of translocation to establish a population of the eastern box turtle ( Terrapene c.carolina) was studied at Floyd Bennett Field, Brooklyn, NewYork, USA. The 579 ha site,originally salt marsh, was e lled during the 1920' s to construct a now-abandoned airport. It consists primarily of grasslands, native shrub thickets and woodlands, and mixed stands dominated by giant reed (Phragmites australis ). These human-created uplands are managed by the U.S. National Park Service for recreation and ecological restoration. Prior to this work, the site did not support a population of this species, but it is historically native to adjacent uplands. T. c. carolina were collected from sites on Long Island, New York, that were undergoing development, and released after data on size, mass, age, and sex were recorded. From 1987 through 1990, 335 individuals were released into developing woodlands. To provide data on dispersal, home range establishment, and initial survival, e fty-three of these were radio-tracked for up to seven years. Though individually variable, the T. carolina dispersed homeward. Of the 53 radio-tagged individuals, 13 (24.6%) left the site, 25 (47.2%) established home ranges, and 15 (28.3%) died before determination of home range establishment could be made. Most individuals established home ranges within a kilometer of the release point. However, some dispersed greater distances. Of the 25 individuals that established home ranges, 17 (68%) did so in the release year, two (8%) in outyear 1, three (12%) in outyear 2, and three (12%) in outyear 3. Annual known survival over e ve years post-release was 71%. Though not statistically signie cant, annual survival was 64% over the e rst two years and 84% over the e nal three. Principal causes of mortality were dispersal from the site and pneumonia, both of which were greatest initially, plus winter kill, a random event. Patterns of growth, home range size, activity season, habitat use, annual reproductive output, and production of young were generally comparable to natural populations of T. carolina. These results suggest that translocation may have potential for establishing new populations of T. carolina, though long term viability is still uncertain. However, any contemplated translocation would need to address the initially high loss to dispersal and disease. Moreover, since there are few sites of adequate size and quality, at least 500 ha of predominantly woody habitat, lacking populations of this species, its appropriateness is very limited.

Sensitivity of raindrop formation in ascending cloud parcels to cloud condensation nuclei and thermodynamic conditions

AbstractThis paper uses a 2000‐bin spectral microphysics cloud parcel model to investigate the effects of aerosol particles on droplet spectrum evolution and warm rain formation in ascending cloud parcels under maritime, intermediate, and continental unstable thermodynamic conditions. Cloud parcels of different cloud depth are simulated for each thermodynamic condition. Concentration and size distribution of cloud condensation nuclei (CCN) were varied within a wide range for each cloud depth.Cloud parcels were divided into three groups with respect to the relationship between cloud depth Hc and the distance of the collision triggering level Hcol above cloud base. The sensitivity of precipitation to CCN variations is quite different for the different groups. Parcels of the first group (Hc < Hcol) do not precipitate. Precipitation from cloud parcels belonging to the second group, in which collisions start at a small distance below the maximum cloud‐top height (Hc ≃ Hcol), turns out to be highly sensitive to the variation of CCN concentration and size distribution. For these parcels an increase in the concentration of large CCN can result in an increase in precipitation amount by several factors. Many cloud parcels arising under continental and intermediate conditions, as well as not very deep maritime clouds, can be assigned to this group. The precipitation amount from cloud parcels belonging to the third group (Hc ≫ Hcol), represented by deep tropical clouds, turns out to be insensitive to CCN distribution and droplet concentration within a wide range of their variations. Comparable effects of small and large CCN on precipitation formation are analysed for each group of cloud parcels.These results are closely related to the problem of rain enhancement via hygroscopic seeding. It is shown that there is a certain range of cloud depths within which cloud seeding can potentially lead to a significant (several times) increase in rain within ascending parcels. Rain formed in cloud parcels with depths beyond this range is only slightly sensitive to the CCN concentration. Copyright © 2004 Royal Meteorological Society

Relationships between underwater vocalizations and mating systems in phocid seals

In this paper, we considered the number and diversity of underwater vocalizations given by aquaticbreeding phocids, and two species that copulate both in the water and on ice, in relation to what is known or hypothesized about their mating systems. Underwater recordings made throughout the year by both bearded ( Erignathus barbatus ) and Weddell (Leptonychotes weddellii ) seals indicated that most of the vocalizations could be attributed to males and were given almost exclusively during the breeding season. Less extensive studies of other species indicated the same pattern. Thus, for this study, we considered only underwater vocalizations known, or suspected, to be given by adult males during intra-specie c agonistic behaviour, defence of territories or access to females, or attraction of females. A one-way ANOVA and linear regression indicated a signie cant relationship between the numbers of underwater vocalizations given by individual species and their mating systems. A Pearson’ s correlation analysis discerned the following: the mating system and the number of vocalizations were positively correlated; female gregariousness was positively correlated with the number of underwater vocalizations and geographic variation in vocalizations, but there was no correlation with the duration of lactation. The degree of predation was negatively correlated with the number of vocalizations, geographic variation in vocalizations, and the number of days of lactation. A principal component analysis showed that 66.1% of the variation in this data set was explained by Factor 1, a suite of variables that included mating system, number of underwater vocalizations, intensity of predation, female gregariousness, and geographic variation in vocalizations. The number of days of lactation explained an additional 19.5% of the variability. These results suggest that additional selection pressures, more specie c to the ecological circumstances of individual species, also ine uence the size of the underwater repertoire. The development of a diverse underwater repertoire with geographic variations was consistently associated with the development of population genetic structure and geographic e delity. Within each category of social system, the species with the greatest number of underwater vocalizations consistently occurred at higher densities during the breeding season than did the species with the lowest vocal diversity. The role of predators on the evolution of social systems is not well known, but could be signie cant for some species. Characteristics of the underwater vocalizations of walruses during the breeding season were found to share similar characteristics to phocids occurring at similar densities in similar habitats, suggesting that the most important selection factors ine uenced both phocids and odobenids similarly. On the basis of the available information from better-studied species, some testable hypotheses are proposed for further investigations of spotted ( Phoca largha ), Ross (Ommatophoca rossii ), Hawaiian monk (Monachus schauinslandi), and ribbon ( Phoca fasciata) seals.

Interactive effects of the ACE DD polymorphism with the NOS III homozygous G849T (Glu298-Asp) variant in determining endothelial function in coronary artery disease

a Abstract: The products of nitric oxide synthase (NOS) and angiotensin-converting enzyme (ACE) play a critical role in determining vessel wall structure and function. Polymorphisms in both genes have been independently demonstrated to ine uence propensity to cardiovascular events. The purpose of this study was to determine the ine uence of the homozygous G849T(Glu298 ! Asp) polymorphism in NOS III on peripheral conduit artery endothelial function and to elucidate the modie er role, if any, of a common ACE polymorphism. Three hundred and ninety-seven consecutive subjects presenting to the cardiac catheteriz- ation laboratory of the University of Michigan over a period of 18 months were recruited. DNA was extracted and polymerase chain reaction (PCR) analysis for ACE and NOS polymorphisms performed. Patients with homozygosity for G849T at both loci (TT) who belong to DD and II ACE genotype (groups 1 and 2) and those who are negative for this polymorphism (GG) and belong to either DD or II genotype (groups 3 and 4) were identie ed. The four groups then underwent determination of conduit endothelial function. Heterozygosity of Glu298-Asp or the ID variant of the ACE were not studied. Median FMD value in the TT-DD group was 0.20 ( -3.17, 2.01) compared with 2.23% ( -0.29, 4.17) in the GG-II group. Median values in the TT-II and the GG-DD groups were 3.04 ( -1.16, 6.61) and 2.46% ( -1.83, 6.52) respectively. These values were not statistically signie cant ( p > 0.05 by one-way ANOVA). Median nitroglycerin-mediated dilation in the four groups did not differ between the four groups ( p = NS by ANOVA). Atherosclerosis burdens as assessed by angiography were not different across the groups. In conclusion, the homozygous NOS III variant (GG) status does not seem to interact addi- tively with the ACE homozygous DD genotype in determining e ow-mediated vasodilation in individuals with established atherosclerosis and pre-existent endothelial dysfunction.

Prediction of Rod-Airfoil Interaction Noise Using the Ffowcs-Williams-Hawkings Analogy

SoundgeneratedatlowMachnumberbyanairfoilin thewakeofarodisinvestigatednumerically.TheGaussian spanwise loss of coherence of the vortex shedding is shown to have a signie cant ine uence on the broadband noise. Spanwise effects are successfully introduced into a time-domain formulation of the Ffowcs-Williams ‐Hawkings analogy, which is applied to aerodynamicdata computed on various contoursaround the sourceregion. Itisshown that a careful choice of these contours is required. The e owe eld is obtained from a two-dimensional Reynolds averaged Navier ‐Stokes calculation. Computed far-e eld spectra compare very well to measurements obtained in an accompanying experiment. Nomenclature Cp = pressure coefe cient c = airfoil chord d = rod diameter f = frequency g = integration surface, 0 k = turbulent kinetic energy Lg = Gaussian correlation length l = span length Mi = Mach number of g D0 Moi = observer Mach number vector Mref = reference Mach number M1 = ine ow Mach number

Heat Transfer Behavior of Gaseous Mixtures Containing Helium and Argon or Nitrogen

The relative heat transfer behavior of pure helium, argon, and nitrogen, as well as selected binary gaseous mixturescontainingheliumandeitherargonornitrogen,wasstudiedexperimentallybymeasuringthetemperature increase that each of these gases, or gas mixtures, experienced as they were forced to e ow through the bore side of a steam-heated copper “ tube” at progressively increasing gas e ow rates. The experimental results demonstrated that certain gaseous mixtures, and even some pure gases, under well-dee ned and specie c operating conditions, are moreefe cient in selected heattransferapplicationsthan purehelium alone. The costsavingsthat may bea result of diluting helium with another less expensive gas, and using that mixture in place of pure helium in certain gaseous heat exchange applications, can be signie cant. In addition, the use of more efe cient gas mixtures in selected heat transfer applications can also result in more compact, and less costly, heat exchanger hardware.

Microphysical modes of precipitation growth determined by S‐band vertically pointing radar in orographic precipitation during MAP

AbstractHigh‐resolution vertically pointing S‐band Doppler radar data obtained within orographic rain by the University of Washington Orographic Precipitation Radar (OPRA) at Locarno‐Monti, Switzerland during the Mesoscale Alpine Programme (MAP) Intensive Observing Periods (IOPs) 2b and 8 are examined to characterize the fine‐scale precipitation structure. The relative roles of collection of cloud water by raindrops versus collection of cloud water by ice particles (riming) in the same column are assessed with a one‐dimensional (1D) Kessler water‐continuity model using the observed data characteristics as input.The OPRA data reveal nearly ubiquitous small‐scale fallstreaks each <5 minutes in duration occurring within a wide range of precipitation intensities. Periods of higher rain rates >10 minutes in duration associated with convective cells evident in coarser‐resolution data manifested as increased frequency and intensity of fallstreaks in the OPRA data. A subset of fallstreaks had sufficient magnitude in reflectivity to indicate a clear connection from the snow region, across the melting layer and into the rain region. The small‐scale inhomogeneities in microphysical structure associated with fallstreaks are likely to be associated with convective overturning in the unstable IOP 2b case. In the more stable IOP 8 case, shear‐driven turbulence near the melting layer, evident in truck‐borne and airborne X‐band Doppler‐radar data shown in companion studies, is a likely contributor to fallstreak formation.The vertical profile of vertical air velocity (w) is critical to understanding the relationship between collection and riming, and their contributions to precipitation efficiency. Characteristics of the w profile within precipitating cloud were estimated in both rain and snow using observed radar parameters from the OPRA data. In rain, reflectivity‐weighted fall speed was derived from observed reflectivity and assumptions about the raindrop size distribution. The derived fall velocity was subtracted from the observed Doppler radial velocity to estimate w in rain regions to within ∼1.5 m s−1. In snow regions, a lower bound on peak updraught velocity was estimated from the observed maximum Doppler velocity. For the data examined from MAP IOP 2b, typical peak updraught velocities at Locarno‐Monti were between 2 and 5 m s−1.These estimated peak updraught velocities were used to construct plausible parabolic profiles of w that were in turn used as input to a 1D Kessler water‐continuity model. Model output shows local maxima in the riming rate and mixing ratio of ice within 2 km of the freezing level, indicating a favourable environment for graupel formation. The location of this layer in the model is consistent with the observed occurrence of graupel in National Center for Atmospheric Research S‐Pol radar data in the IOP 2b storm in a companion study. The modelled rates of collection and riming are comparable, and both make significant contributions to the growth by accretion of precipitation within the storm updraughts. Within the rain layer, liquid‐water coalescence (autoconversion and collection) in updraughts with peak velocities of 5 m s−1 can account for up to ∼40% of column‐integrated cloud water.Our analysis of the observational data and the 1D model results confirms and extends previous work indicating that a combination of liquid‐water coalescence and ice‐phase processes is needed to obtain high precipitation efficiencies >40% in orographic precipitation. Copyright © 2003 Royal Meteorological Society.

Assessment of Rotor Blade Angle of Attack from Experimental Inflow Data

A series of experiments was conducted by NASA Langley Research Center and the U.S. Army, over a 10-year period beginning in the mid-1980s, to provide some insight into the nature of helicopter rotor-system-induced velocity and to provide calibration data for many promising computational methods. Rotor-induced velocities were measured above the rotor system for several forward e ight-test conditions in the NASA Langley Research Center 14 by 22 Foot Subsonic Tunnel using a 15%-scale, fully articulated, stiff-in-torsion rotor and in a joint government/industry partnershipwith Bell HelicopterTextron,Inc.,foralarger,aeroelastically scaled, bearingless rotor. Atwo-componentlaservelocimeterwasused to makethesemeasurements in thefacility.Thedata fromthese tests have been published previously as NASA quick release reports and conference papers, and they are available electronically. Further analyses of the data to assess the local angle of attack of the rotor blades as a function of azimuth, span, and test condition aredocumented. The results indicatethat assessing ine owusing thetime average ofa rotorrevolutiondoesnotalwayscaptureadequately thelocaleffectsofbladepassageontheine owdistribution. The ine ow distribution should be assessed using the average of the blade azimuth-dependent ine ow. At advance ratioslessthan0.30, theeffectsof theindividual trailing vorticeswereevidentintheine owmeasurements, andthey have a signie cant impact on the local blade e ow angle. For higher advance ratios, the blade azimuth-dependent ine ow velocities differed very little from the time-averaged ine ow characteristics. The analyses demonstrated that dynamic twist is signie cant for aeroelastically scaled rotors and must be measured or modeled to assess the rotor performance accurately.

Monitoring of Geostationary Earth Orbit Satellites in Russian Space Surveillance Center

Cataloging of geostationary-Earth-orbit (GEO)satellites commenced in the Russian Space Surveillance Center (SSC) in the 1980s. Enhancement of the software tools for catalog maintenance has continued since that time. The current status of this software complex is described. The characteristics of the sensors and the observed satellites that determine the structure of the catalog maintenance algorithms are discussed. There are certain essential limitations of the range of the observed longitudes of GEO satellites, the frequency of the observations, and their accuracy. Under these conditions, the loss of measurement data is unacceptable; the algorithms must use any observational data for catalog maintenance. The correlation of measurements with the cataloged orbits and subsequent orbit updating must be possible for the very wide range of the accuracy of the measurements. A fast and accurate prediction algorithm was developed to solve this task successfully. Thus, it became possible to develop and implement in the SSC an efe cient complex of software tools for catalog maintenance. The general scheme is described of this complex and of its most signie cant components: primary determination of orbits, correlation of the observations with the cataloged satellites, updating of orbits using the measurements, planning of the observations and targeting of the sensors, and preliminary tracking of new satellites. Some results of the testing, based on real data, are presented.

Efficient Multiple Model Adaptive Estimation in Ballistic Missile Interception Scenarios

A novel efe cient algorithm, featuring a highly reduced computational load, is presented for multiple model adaptive estimation in a future real-life ballistic missile defense scenario, where the blind incoming target (having no information on the interceptor’ s state ) performs a bang ‐bang evasive maneuver characterized by a random switching time. The efe ciency of the algorithm derives mainly from its exploitation of the special structure of the hypothesis space in this problem to drastically reduce the number of concurrently active e lters in the bank without incurring any signie cant performance degradation. The proposed algorithm’ s efe ciency allows a substantial increase in the resolution of the discretized hypothesis space, thus enhancing considerably the attainable estimation performance. The effect of the new estimator’ s performance on guidance accuracy is examined. The homing performance of various perfect information guidance laws using this efe cient estimation method is compared, via Monte Carlo simulations, to the use of a Kalman e lter incorporating a shaping e lter representing the random target maneuver. The results demonstrate the superiority and viability of the proposed method.

Solid-Fuel Regression Rate Behavior of Vortex Hybrid Rocket Engines

Aseriesofstaticenginee ringswereconductedtoinvestigatethesolid-fuelregressionratebehaviorandoperating characteristicsofvortexhybridrocketengines.Thevortexhybridenginecone gurationischaracterizedbyacoaxial, coswirling, countere owing vortex combustion e eld in a cylindrical fuel port. To generate this e owe eld, oxidizer is injected through a swirl injector located between the aft end of the fuel grain and the inlet to the converging portion of the exit nozzle. Test e rings with thrusts up to 960 N were conducted with gaseous oxygen and hydroxylterminated polybutadiene solid fuel. Average fuel regression rates up to seven times larger than those in similar classical hybrids were measured. Empirical correlations were developed to describe accurately the experimental regression rates over more than an order of magnitude variation in mass e ux. In addition to local mass e ux and oxygeninjectionvelocity,geometricenginevariables,suchasenginecontractionratioand length-to-diameterratio, had a signie cant ine uence on the measured regression rates. Nondimensional regression rate and heat transfer correlations were also developed. Throttling and restart capability were demonstrated. Nomenclature A = cross-sectional area, cm 2 B = blowing parameter cp = isobaric specie c heat, J/kg ¢K D = port diameter, cm Ea = activation energy, kcal/mole G = local mass e ux, kg/m 2 ¢s Ginj = injection mass velocity, kg/m 2 ¢s GO = gaseous oxygen mass e ux, kg/m 2 ¢s

Ammonite and inoceramid radiations after the Santonian‐Campanian bioevent in Sakhalin, Far East Russia

Study of several marine Santonian‐Campanian successions from Sakhalin Island, Far East Russia, has revealed that evolution of the ammonites and inoceramid bivalves proceeded at different rates after the major faunal turnover at the (locally dee ned) Santonian‐Campanian boundary. Sometimes changes in the inoceramid assemblages were more frequent and rapid than changes in the ammonite assemblages, and sometimes vice versa. Signie cant levels of inoceramid turnover and radiation events have been identie ed at the (locally dee ned) Santonian‐Campanian and lower-upper Campanian boundaries. Changes in ammonite and inoceramid diversity, and in the proportions of endemic and cosmopolitan species, were investigated in the context of the local relative sea-level curve and inferred environmental changes. In Far East Russia, the main ammonite and inoceramid radiation after the local Santonian‐Campanian faunal turnover occurred in the early Late Campanian Pachydiscus (P.) aff. egertoni ammonite Zone and the coeval Schmidticeramus schmidti inoceramid Zone. This condensed interval of ammonite and inoceramid maximum diversity provides a perfect stratigraphic marker that is recognizable in Sakhalin, North-East Russia and Japan. The succession of Santonian‐Campanian assemblages identie ed in Sakhalin enabled the establishment of seven ammonite and six inoceramid zones, which correlate relatively well with those of North-East Russia and Japan. The problems of placing the Santonian‐Campanian boundary in Sakhalin and in the adjacent Japanese island of Hokkaido are reviewed. & Ammonites, Campanian, diversity, endemism, inoceramids, radiation, Sakhalin, Santo

Mean Flow Features Around the Inline Wheels of Four-Wheel Landing Gear

Landing gear are noted to be a signie cant, sometimes dominant, airframe noise source for commercial aircraft. Aerodynamicnoiseis a directresultofthee uctuating e owand its interaction with surfacecomponents. Knowledge of the mean e ow, however, can be used to aid in the determination of noise sources. The complex geometry of multiple-wheel-set landing gear has thus far precluded even this basic information. In this study the mean e owe eld is determined in a streamwise plane surrounding the inline wheels of a generic four-wheel landing-gear cone guration using digital particle image velocimetry. The velocity and vorticity e elds highlight a vortex that persists between the wheels on the ground side of the axle midplane. The formation of this vortex is believed to resultfrom thegeometricasymmetry caused by the presenceofthecentersupportstrut.Evidenceis also presented that shows the vortex does not remain stationary, but oscillates between the fore and aft wheels. Its position is hypothesized to dependon thestateofan unstablevorticity layerthatdevelopson theground sideoftheforewheel.

Design Optimization of Springback in a Deepdrawing Process

The design optimization of springback in a deepdrawing process is proposed to control the e nal shape of the workpiece. The manufacturing process design problem is formulated to minimize the difference between the shape of the desired workpiece geometry and the e nal analysis result after elastic springback. The rigid die shape and the workpiece thickness are treated as design variables. A nonlinear structural problem that includes e nitedeformation elastoplasticity withfrictional contactissolved usinga mesh-freemethod in which thestructural domain is discretized by a set of particles. Continuum-based design sensitivity analysis is carried out to obtain gradient information for the optimization efe ciently. The accuracy of the sensitivity result is compared with the e nite difference result with excellent agreement. The optimum deepdrawing process signie cantly improves the quality of the e nal product. ESPITE signie cant simulation and design capability developments in modern technology, gaps still remain between the simulation-based design and the manufacturing process itself. One major reason for these gaps is the lack of efe cient and accurate numerical methods in the design process. First, accurate numerical methods have to be used to simulate manufacturing processes, and these methods must take into account large deformations, complicated constitutive relations, and a sliding contact between workpiece and die. Second, efe cient numerical methods have to be used to make the deepdrawing optimization process practical. It is the purpose of this paper to demonstrate that these two obstacles can be resolved by using accurate numerical methods and an efe cient design sensitivity analysis (DSA). The deepdrawingprocessinvolvesa large degree ofplastic deformation and rigid-body rotations, as well as a complicated contact between workpiece and die. Many simplie ed approaches have been proposedinsimulationanddesignofthemetalformingprocess.One

Liver Fibrosis: What's the Beginning of Autonomic Deficit?

Histologic diagnoses were made using standard criteria and two independent observers scored all samples using the Scheuer staging system (3). We distinguished between patients affected by moderate e brosis (scores 2 and 3) and those affected by severe e brosis, corresponding to cirrhosis (score 4). Cardiac index was determined using pulsed-wave Doppler echocardiography (Hewlett-Packard Sonos 2000, Andover, Mass., USA). Peripheral vascular resistance (PVR) was calculated as the mean arterialpressure/cardiacoutput £80.Heartratevariabilitywas evaluated in the frequency domain using appropriate software (Rozinn Electronics H4W 3.6F, Glendale, N.Y., USA). A series of consecutive 5-min intervals was calculated from the Holter ECG as a function of beat numbers. Power spectral analysis of the intervals between adjacent R waves of the electrocardiogram (RR) was performed using the fast Fourier transform mathematical function (5). Low frequency (LF; 0.04‐0.15 Hz) and high frequency (HF; 0.15‐0.40 Hz) spectral powers and the ratio of LF to HF (LF/HF) were calculated and expressed in normalized units (nU). The recordings were obtained with 5 min in the supine position and 5 min in passive head-up tilt (70°). Statistical analysis was performed using an appropriate t test. P values lower than 0.05 were regarded as statistically signie cant. None of the patients included in this study, with either chronic viral hepatitis or with cirrhosis, showed evidence of hyperdynamic circulation. Cardiac index and peripheral vascular resistances were not signie cantly different from those of healthy subjects. Moreover, our results showed no differences between patients and controls in mean systolic and diastolic arterial pressures, either in the supine or in the tilt position. The power spectral analysis showed the occurrence of a

Single-Point and Multipoint Aerodynamic Shape Optimization of High-Speed Civil Transport

Single-point and multipoint aerodynamicshapeoptimization methods weredeveloped and demonstrated forthe designofanadvancedsupersonictransportsubjecttomanygeometricconstraints.Thestartingpointcone guration baseline was developed in support of the NASA High-Speed Research program using linear-theory-based methods and multidisciplinary system analyses. The single-point design method simulated the presence of nacelles and diverters at supersonic cruise by superimposing nacelles-on/nacelles-off pressure differences, from complete cone gurationanalyses,ontosingle-block-gridwing/bodycalculations.Themultipointdesignmethodusedamultiblock gridto treatthecompletecone guration,including nacelles/diverters, canard,empennage,and wing e aps/slats.Two forms of multipoint optimization were performed at Mach 2.4, 1.1, and 0.9: sequential (design at cruise followed by e ap and canard/tail incidence angle optimization at the two transonic conditions ) and multipoint (simultaneous design at the three e ight conditions via a composite objective function ). Euler-based optimization using a combination of the two methods achieved signie cant performance gains derived from the nonlinear effects. The single-point approach produced much of the improvement, lowering the appropriately weighted thrust coefe cient by 4.28 counts after trimming the full cone guration at the three design points. (A seven count drag reduction was achieved at cruise for the untrimmed vehicle. ) The sequential and multipoint methods achieved 6.03 and 7.55 counts of composite thrust reduction, respectively.

Analysis of a Boeing 747 Aircraft Fuel Tank Vent System

This monograph presents an analysis of a 747 aircraft fuel vent system. The system is comprised of several fuel tanks feeding into a single vent tube. The analysis consisted of formulating equations that govern the venting and heating of the center tank. Flow losses along each section of the vent system were applied to correct the ideal e ow from the center fuel tank. These equations were programmed for solution on a digital computer. Results were computed for a e ight from Athens, Greece, to New York with a 5-hour delay on the ground before taking off again from New York. The heating caused by air conditioning and bleed air from the engines on the ground during the long delay caused vaporization of fuel and increased the density of the air-fuel vapor. The result was very sluggish venting and “ choked” e ow producing a signie cant overpressure, at 13,000 ft altitude, sufe cient to fail some component of the center tank. This was a precursor event leading to serious consequences. The analysis supports a hypothesis of overpressure as the cause of the Trans World Airlines Flight 800 accident and shows that heating caused by air conditioning contributed to the sequence of events.

Numerical Simulation of Three-Dimensional Augmented Burnett Equations for Hypersonic Flow

For computation of hypersonic e owe elds about space vehicles in low Earth orbits, where the local Knudsen numbers Kn lie in the continuum-transition regime, a set of extended three-dimensional hydrodynamic equations is required that is more accurate than the Navier ‐Stokes equations and computationally more efe cient than the direct simulation Monte Carlo (DSMC) computations. The three-dimensional augmented Burnett equations are derived from the Chapman ‐Enskog expansion of the Boltzmann equation to O(Kn 2) and adding the augmented terms (linear third-order super Burnett terms with coefe cients determined from linearized stability analysis to ensure stability of the augmented Burnett equations to small wavelength disturbances ). The three-dimensional augmentedBurnettequationsareappliedtocomputethehypersonicblunt-bodye owsforvariousrangeofKnudsen numbers (0:0884 < ‐ Kn < ‐ 0:227) and Mach numbers (10 < ‐ M < ‐ 25:3). The computational results are compared with the Navier ‐Stokes solutions, the existing augmented Burnett solutions, and the available DSMC results. The comparisons show that the difference between the Navier ‐Stokes and the augmented Burnett solutions is very small (less than 3% for the shock layer thickness ) at Knudsen numbers less than 0.01; the difference becomes signie cant as the Knudsen number increases. The comparisons also show that the augmented Burnett solutions are signie cantly closer to the DSMC results for the temperature distributions in the continuum-transition regime than the Navier ‐Stokes calculations.

Evolution of Debris Clouds to Microscopically Chaotic Motion

An evaluation is presented of the effects of orbital perturbations that arise in the early phase of debris cloud evolution. This assessment enables the dee nition of various characteristic timescales associated with the cloud evolution to a mature debris population, characterized by a “ chaotic” distribution, required for the statistical description of debris as provided by the direct simulation Monte Carlo method (DSMC). The ine uences of gravitational harmonic terms J2, J3, and J4 together with that for solar radiation pressure upon both the precession of the argument of perifocus (resulting in the familiar torus ) and regression of the line of nodes (resulting in a band structure) are presented. Dimensionless characteristic timescales indicating the rate at which the evolution in the orbital parameters, subject to each of theperturbations relativeto the orbital lifetime, are dee ned. From this modeling approach to debris studies, it is noted that the dimensionless ratio f perturbation evolutionary timescale g to f orbital lifetime g must be greater than unity. A general conclusion is that it is found that for objects of centimetric size above an altitude of approximately 350 km the DSMC methodology is appropriate. The presented analytic approach highlights the signie cant ine uence during the early phase of J3. The methodology is applied to several scenarios for the fragmentation caused by collisions and explosions. The results show clearly how the evolution to a fully chaotic debris distribution is mass specie c and scenario dependent. Debris particles ejected with forward component velocity vectorsresult with a mass spectrum, which differsfrom thoseejected with rearward velocities. Assumptions of isotropic fragmentation must therefore only be considered as approximations.