These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Hydrostatic bearing support  

NASA Technical Reports Server (NTRS)

A hydrostatic bearing support system is provided which comprises a bearing housing having a polygonally configured outer surface which defines at least three symmetrically disposed working faces and a plurality of pressure plates, each of which is disposed relatively opposite a corresponding working face and spaced therefrom to define a gap therebetween. A hydrostatic support film is created in the gap for supporting the housing in spaced relationship to the pressure plates.

Cunningham, R. E. (inventor)

1977-01-01

2

Design of a low cost hydrostatic bearing  

E-print Network

This thesis presents the design and manufacturing method for a new surface self compensating hydrostatic bearing. A lumped resistance model was used to analyze the performance of the bearing and provide guidance on laying ...

Wong, Anthony Raymond

2012-01-01

3

Design, dynamic modeling, simulation and feedback control of hydrostatic bearing  

E-print Network

A hydrostatic bearing carriage (Hydrocline) that uses an open face linear motor to drive the carriage as well as to preload the hydrostatic bearings has been developed by Professor Alexander Slocum and Gerald Rothenhöfer ...

Rothenhöfer, Gerald S. (Gerald Sven)

2007-01-01

4

Hydrostatic shoe bearing system for the TIM  

NASA Astrophysics Data System (ADS)

We present an active, low cost hydrostatic shoe bearing system for the Mexican Infrared Telescope which solves the suspension and motion of a 100 ton, 7.8 m telescope. Different geometries are analyzed to optimize the shoe's pressure print. These designs offer a self-adjusting action between the shoe's sliding path and the girth track. Different parameters such as pressure, temperature and proximity are measured and implemented into a control system in order to stabilize the bearing from the fluid's thermal viscosity effects. A simple method for fluid injection is discussed.

Ruiz Schneider, Elfego; Sohn, Erika; Quiros-Pacheco, Fernando; Godoy, Javier; Farah Simon, Alejandro; Quintanilla, R.; Soto, P.; Salas, Luis; Cruz-Gonzales, Irene

2000-08-01

5

Hybrid hydrostatic/ball bearings in high-speed turbomachinery  

NASA Technical Reports Server (NTRS)

A high speed, high pressure liquid hydrogen turbopump was designed, fabricated, and tested under a previous contract. This design was then modified to incorporate hybrid hydrostatic/ball bearings on both the pump end and turbine end to replace the original conventional ball bearing packages. The design, analysis, turbopump modification, assembly, and testing of the turbopump with hybrid bearings is presented here. Initial design considerations and rotordynamic performance analysis was made to define expected turbopump operating characteristics and are reported. The results of testing the turbopump to speeds of 9215 rad/s (88,000 rpm) using a wide range of hydrostatic bearing supply pressures are presented. The hydrostatic bearing test data and the rotordynamic behavior of the turbopump was closely analyzed and are included in the report. The testing of hybrid hydrostatic/ball bearings on a turbopump to the high speed requirements has indicated the configuration concept is feasible. The program has presented a great deal of information on the technology requirements of integrating the hybrid bearing into high speed turbopump designs for improved bearing life.

Nielson, C. E.

1983-01-01

6

Error correction in hydrostatic spindles by optimal bearing tuning  

Microsoft Academic Search

In this paper a high precision grinding wheel is considered as a rigid rotor mounted on two hydrostatic bearings. The equations for small perturbations of the wheel on the bearings are derived in the form of a multi-input, multi-output transfer function matrix, enabling the frequency response function of the wheel to be determined. Thereafter an optimisation algorithm is proposed which

M. Aleyaasin; R. Whalley; M. Ebrahimi

2000-01-01

7

Static Characteristics of Conical Hydrostatic Journal Bearing Under Micropolar Lubrication  

NASA Astrophysics Data System (ADS)

A theoretical analysis for static characteristics of a conical hydrostatic journal bearing for a multirecess constant flow valve compensated under micropolar lubrication has been carried out in this work. The numerical solution of the modified Reynolds equation for the conical bearing has been done using Finite Element Method (FEM) using necessary boundary conditions. The various static characteristics have been presented to analyze the performance of bearing at zero speed.

Rana, N. K.; Gautam, S. S.; Verma, S.

2014-08-01

8

Dynamic analysis of liquid-lubricated hydrostatic journal bearings  

SciTech Connect

A hybrid bearing reduces the dependency of its behavior on the lubricant viscosity, bearing clearance, bearing surface area by combining the hydrostatic and hydrodynamic effects. The combination permits the hybrid bearing to be incorporated into rotor designs, where the working fluids of the rotor may be used in place of externally supplied lubricants. An effective and practical method to predict the static and dynamic behavior of hybrid bearings is developed. The model includes the three major fluid effects in the bearing; the orifice restriction, inertia losses at the pocket edges, and hydrodynamic effects on the bearing land regions. Lubrication is modeled and calculated using a finite element solution of Reynolds equation with turbulence corrections.

Kocur, J.A. Jr.

1990-01-01

9

Static properties of hydrostatic thrust gas bearings with curved surfaces.  

NASA Technical Reports Server (NTRS)

The classical treatment of circular, hydrostatic, orifice-regulated thrust gas bearings, in which perfectly plane bearing plates are assumed, is extended to include axisymmetric, but otherwise arbitrary, plate profiles. Plate curvature has a strong influence on bearing load capability, static stiffness, tilting stiffness, and side force per unit misalignment angle. By a suitable combination of gas inlet impedance and concave plate profile, the static stiffness can be made almost constant over a wide load range, and to remain positive at the closure load. Extensive measurements performed with convex and concave plates agree with theory to within the experimental error throughout and demonstrate the practical feasibility of using curved plates.

Rehsteiner, F. H.; Cannon, R. H., Jr.

1971-01-01

10

Notes 12. (a) Annular pressure (damper) seals, and (b) Hydrostatic journal bearings  

E-print Network

power cryogenic turbo-pumps (TP) are compact, operate at high speeds, and require of externally pressurized fluid film bearings to support radial and thrust loads. Hybrid thrust & radial bearings enable smaller and lighter turbopumps with no DN...-viscous fluids, including gases and cryogens. Table 1. Hydrostatic Bearings: Advantages and Disadvantages Advantages Disadvantages Support very large loads. The load support is a function of the pressure drop across the bearing and the area of fluid...

San Andres, Luis

2009-01-01

11

Clearance sensing hydrostatic bearing restrictor for the homopolar generator systems tester  

SciTech Connect

This work documents the development of an advanced hydrostatic bearing system for the subcritical operation of the Homopolar Generator Systems Tester. Since this Systems Tester is unique in that it was built with stationary shaft bearings, several new hydrostatic bearing ideas were developed. First, a new clearance sensing variable restrictor was developed to accommodate the almost five fold increase in radial bearing clearance intrinsic to the machine geometry encountered during each machine cycle. A new dynamic hydrostatic thrust-bearing model was developed that permits tilt about any axis perpendicular to the axis of rotation as well as axial motion. These bearings are well instrumented providing data to verify the models both at rest and during operation. In addition to the bearing advances, overall machine design decisions, as well as the factors which influenced them, are examined. Magnetic effects are discussed with respect to both rotor dynamic effects and thrust bearing loading. Bearing sump and sealing philosophies are also discussed. Decisions concerning rotor geometry are similarly reviewed. Finally, the results of the experiment are evaluated in terms of the future impact on not only homopolar generators, but on rotating machinery in general.

Vaughn, M.R.

1985-01-01

12

Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing  

NASA Astrophysics Data System (ADS)

The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the pressure energy. The sliding bearing is weighted down by axial force, which can be changed during the process. That's why in front of the particular oil grooves control components adjusting pressure and flow size are located. This paper deals with a project of a hydraulic circuit for regulation of fluid layer in the annular hydrostatic thrust bearing and the testing equipment for measuring its physical properties. It will include the issue of measuring loading capacity and height of the fluid layer in the annular hydrostatic thrust bearing.

Kozdera, Michal; Drábková, Sylva; Bojko, Marian

2014-03-01

13

Mixed Lubrication Simulation of Hydrostatic Spherical Bearings for Hydraulic Piston Pumps and Motors  

NASA Astrophysics Data System (ADS)

Mixed and fluid film lubrication characteristics of hydrostatic spherical bearings for swash-plate-type axial piston pumps and motors are studied theoretically under non-steady-state conditions. The basic equations incorporating interference and contact of surface roughness are derived fundamentally through combination of the GW and PC models. Furthermore, a programming code that is applicable to the caulked-socket-type and open-socket-type bearings is developed. Effects of caulking, operating conditions, and the bearing dimension on the motion of the sphere and tribological performance of the bearings are examined. Salient conclusions are the following: The sphere's eccentricity increases in the low supply pressure period. The time-lag of the load change engenders greater motion of the sphere. Caulking of the bearing socket suppresses the sphere's motion. The bearing stiffness increases and power loss decreases for smaller recess angles. Minimum power loss is given under the condition that the bearing socket radius nearly equals the equivalent load radius.

Kazama, Toshiharu

14

Effect of design parameter variations on hybrid (combination hydrostatic and hydrodynamic) bearings for use in high speed turbomachinery  

E-print Network

Hybrid (combination hydrostatic and hydrodynamic) bearings have been proposed for use as a support element in cryogenic high speed turbomachinery for primary and auxiliary space power applications because of their long lifetime, low friction...

Mosher, Phillip Andrew

2012-06-07

15

A test apparatus and facility to identify the rotordynamic coefficients of high-speed hydrostatic bearings  

NASA Technical Reports Server (NTRS)

A facility and apparatus are described which determine stiffness, damping, and added-mass rotordynamic coefficients plus steady-state operating characteristics of high speed hydrostatic journal bearings. The apparatus has a current top speed of 29,800 rpm with a bearing diameter of 7.62 cm (3 in.). Purified warm water, 55 C (130 F), is used as a test fluid to achieve elevated Reynolds numbers during operation. The test-fluid pump yields a bearing maximum inlet pressure of 6.9 Mpa (1000 psi). Static load on the bearing is independently controlled and measured. Orthogonally mounted external shakers are used to excite the test stator in the direction of, and perpendicular to, the static load. The apparatus can independently calculate all rotordynamic coefficients at a given operating condition.

Childs, Dara; Hale, Keith

1994-01-01

16

Oil pocket's bearing capacity analysis of liquid hydrostatic worktable in gantry moving milling center  

NASA Astrophysics Data System (ADS)

Durning the design process of hydrostatic rotary worktable, the processing and assembly tolerance, (the offset of worktable and the gap of the oil film's thickness) is ignored. But it will cause that the real bearing of oil pocket deviates from the initial design value, and then the performance of rotary worktable will be reduced significantly. Up to now, no effort is found toward the research of influence of the processing and assembly tolerance on the performance of the rotary worktable. So the hydrostatic oil film is assumed as the elastomer in this paper, and then the bearing capacity of the oil pocket is studied with and without the mass offset of the worktable by taking an expression between the bearing capacity and the oil film's thickness of the oil pocket as the deform compatibility equation. The influence of the processing tolerance of the oil sealing belt's gap on the bearing capacity of the oil pocket is analyzed. In the light of the liquid hydrostatic worktable of Gantry Moving Milling Center using on the scene, the oil pocket's pressure of the worktable is tested using Rotary Worktable Test System under the circumstance of the mass offset of the worktable and the gap tolerance of the oil sealing belt, and then the equivalent offset of worktable, the average pressure of the oil pocket and the actual thickness of the oil film are analyzed respectively. The test results show that the bearing capacity component of the oil pocket caused by G is consistent, and the component caused by M is relative to the position of the oil pocket. When the oil sealing belt's gap is larger than the theoretical value, the bearing capacity of the oil pocket is smaller than the others; whereas the bearing capacity of the oil pocket is larger than the others. The maximum and minimum equivalent offsets are 0.256 4 mm and 0.047 5 mm, respectively, and the average oil pocket pressure varies from 0.345 MPa to 0.460 MPa, the maximum and minimum value of the actual oil film thickness are 109.976 ?m (No. 7 oil pocket) and 93.467 ?m (No. 10 oil pocket), respectively. The research results can be used to detect the offset of the worktable and the actual thickness of the oil film under processing and assembly tolerance, and provides a basis way for detecting the processing and assembly tolerance of rotary worktable signing reasonably of Gantry Moving Milling Center.

Zhao, Jianhua; Liang, Yingna; Gao, Dianrong

2014-08-01

17

A new type of hydrostatic\\/hydrodynamic gas journal bearing and its optimization for maximum stability  

Microsoft Academic Search

The orifice annular and shallow pocket restricted hybrid has journal bearing is a new type of gas bearing which has good high-speed stability performance. In this paper, the stability of this bearing with three shallow pockets is studied theoretically, and the optimization for its maximum stability is carried out by use of the Complex Method. Some useful conclusions are obtained.

Rui-Qian Zhang; H. S. Chang

1995-01-01

18

A new type of hydrostatic/hydrodynamic gas journal bearing and its optimization for maximum stability  

SciTech Connect

The orifice annular and shallow pocket restricted hybrid has journal bearing is a new type of gas bearing which has good high-speed stability performance. In this paper, the stability of this bearing with three shallow pockets is studied theoretically, and the optimization for its maximum stability is carried out by use of the Complex Method. Some useful conclusions are obtained.

Zhang, R.; Chang, H.S. [Beijing Univ. of Aeronautics and Astronautics, Beijing (China)

1995-07-01

19

Non-Newtonian temperature and pressure effects of a lubricant slurry in a rotating hydrostatic step bearing  

SciTech Connect

The purpose of this research was to investigate the pressure and temperature effects of graphite powder lubricant when added to a Newtonian carrier fluid and applied in a rotating hydrostatic step bearing. Temperature and pressure profiles were determined both analytically and experimentally. The rheological behavior of the non-Newtonian lubricant was modeled using a power law model previously shown to approximate experimental data for this fluid. Ethylene glycol was used as the Newtonian lubricant, providing a check on the test apparatus and a base line for comparison with the non-Newtonian graphite slurry. Data revealed a temperature increase with bearing rotational speed for both fluids and compared favorably with the mathematical predictions. A significantly higher temperature rise was seen in the non- Newtonian lubricant due to the higher shear rates. The pressure profile was not directly dependent on bearing rotational speed in the mathematical model, but experimental data demonstrated a reduction in pressure at higher rotation speeds. This loss was greater for the non-Newtonian lubricant and attributed to temperature dependence of power law constants. It was concluded that the effects of operating speed and temperature on a non-Newtonian lubricant should be considered as well as their greater load-carrying capacity.

Peterson, J.; Finn, W.E.; Dareing, D.W. [Univ. of Florida, Gainsville, FL (United States)]|[Univ. of Southwestern Louisiana, Lafayette, LA (United States)

1994-10-01

20

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing  

NASA Technical Reports Server (NTRS)

A new fluid film bearing package has been tested in the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most importantly, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance during testing on the NASA Technology Test Bed (TTB) Engine located at MSFC. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at ten percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65% of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

1994-01-01

21

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing  

NASA Astrophysics Data System (ADS)

A new fluid film bearing package has been tested in the SSME High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most important, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at 10 percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65 percent of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

1993-06-01

22

Hydrostatic bearing arrangement for high stiffness support of the Large Synoptic Survey Telescope  

Microsoft Academic Search

Meeting the stringent slew and settling requirements of the Large Synoptic Survey Telescope (LSST) will require an exceptionally stiff mount. The unique three mirror design and large, 64 cm diameter, focal plane preclude the use of a fast steering mirror or active focal plane. Consequently, a smooth (low vibrations) drive and bearing system is also required. This combination of smooth

Douglas R. Neill; Victor L. Krabbendam; Mario Romero; Karl-Olof Olsson; Thomas G. Benigni

2008-01-01

23

Amplitude effects on the dynamic performance of a hydrostatic gas thrust bearing  

NASA Technical Reports Server (NTRS)

The Reynolds' equation is applied to a strip gas thrust bearing to analyze amplitude disturbance effects on its dynamic performance. The Reynolds' equation is numerically approximated using finite difference techniques. The time dependent load carrying capacity is represented by a Fourier series up to and including the third harmonics. Design curves for the load capacity and the linear stiffness and damping are presented as a function of inlet location, restrictor coefficient, supply pressure, amplitude of oscillation, and squeeze number. For the range of amplitudes investigated the dimensionless load capacity, stiffness and damping does not exhibit an appreciable change in magnitude; thus, only one design curve is needed to represent each relationship. A design methodology is presented.

Stiffler, A. K.; Tapia, R. R.

1975-01-01

24

Measurements versus Predictions for a Hybrid (Hydrostatic plus Hydrodynamic Thrust Bearing for a Range of Orifice Diameters  

E-print Network

A fixed geometry hybrid thrust bearing is investigated with three different supply orifice diameters. The test rig uses a face-to-face thrust bearing design, with the test bearing acting as the rotor loading mechanism. A hydraulic shaker applies...

Esser, Paul R.

2011-08-08

25

Damping Bearings In High-Speed Turbomachines  

NASA Technical Reports Server (NTRS)

Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).

Von Pragenau, George L.

1994-01-01

26

Hybrid air foil bearing with external pressurization  

E-print Network

loaded bearing under hydrostatic mode demonstrates the high potential of hybrid air foil bearings. The load capacity of the hybrid foil bearing was measured at 20,000 rpm, and compared with that of hydrodynamic foil bearing. The hybrid foil bearing has...

Park, Soongook

2009-05-15

27

The Hydrostatic Paradox.  

ERIC Educational Resources Information Center

Presents an example demonstrating the quantitative resolution of the hydrostatic paradox which is the realization that the force due to fluid pressure on the bottom of a vessel can be considerably greater or considerably less than the weight of the fluid in the vessel. (JRH)

Wilson, Alpha E.

1995-01-01

28

Rotordynamic evaluation of a tangential-injection hybrid bearing  

E-print Network

: : Issued also on microfiche from Lange Micrographics. For future high-speed cryogenic turbomachinery, ball bearings will be replaced by hybrid bearings that combine hydrostatic and hydrodynamic effects. Hybrid bearings develop cross...

Laurant, Franck Jean

2012-06-07

29

Rotordynamic evaluation of a roughened-land hybrid bearing  

E-print Network

Hybrid bearings (combinations of hydrostatic and hydrodynamic bearings) represent an attractive alternative to ball bearings for use in high-speed cryogenic turbopumps. However, the internally-developed cross-coupled forces can generate...

Fayolle, Patrice Gerard

2012-06-07

30

Rotordynamic evaluation of a roughened-land hybrid bearing.  

E-print Network

??Hybrid bearings (combinations of hydrostatic and hydrodynamic bearings) represent an attractive alternative to ball bearings for use in high-speed cryogenic turbopumps. However, the internally-developed cross-coupled… (more)

Fayolle, Patrice Gerard

2012-01-01

31

Performance of gas-lubricated nonconforming pivoted-pad journal bearings and a flexibly mounted spiral-groove thrust bearing  

NASA Technical Reports Server (NTRS)

A test program was conducted to determine the performance characteristics of gas-lubricated nonconforming pivoted-pad journal bearings and a spiral-groove thrust bearing designed for the Brayton cycle rotating unit (BRU). Hydrostatic, hybrid (simultaneously hydrostatic and hydrodynamic), and hydrodynamic tests were conducted in argon gas at ambient pressure and temperature ranges representative of hydrostatic operation up to the 10.5-kWe BRU power-generating level. Performance of the gas lubricated bearings is presented, including hydrostatic gas flow rates, bearing clearances, bearing temperatures, and transient performance.

Ream, L. W.

1973-01-01

32

A bulk-flow model of angled injection Lomakin bearings  

E-print Network

to dimensionless fields 1 1. INTRODUCTION Current trends in high-performance turbomachinery drive towards higher operational speeds and pressures to increase their power. In particular, in cryogenic turbopumps, hydrostatic annular seals along with hydrostatic... features; and thus, could be an effective alternative to hydrostatic journal bearings in cryogenic turbopumps for aero-space applications. Indeed, experimental measurements conducted on tangential-against-rotation injection Lomakin bearings demonstrate...

Soulas, Thomas Antoine Theo

2012-06-07

33

Notes 15. Gas Bearings for oil-free MTM  

E-print Network

speeds null Unknown hydrodynamic performance Vespel, Torlon, Peek Graphalloy Limits: PV 300,000 psi ft/min Low Temperature 14 Ceramic Rolling Element Bearings silicon nitride (Si 3 N 4 ) balls and hardened steel outer and inner raceways. Cage... Ceramic ? steel Contained lubricant $33.00 unit 1 2 C Rigid geometry gas bearings Hydrodynamic/ hydrostatic $2-$4 unit 2 3 D Tilting pad gas bearings Hydrodynamic/ hydrostatic $50 Hypad? 2 3 E Foil bearings Hydrodynamic $ 100 MITI 3 2...

San Andres, Luis

2010-01-01

34

Theory versus experimental results and comparisons for five orifice-compensated hybrid bearing configurations  

E-print Network

. Bearing Test Facility D. Experimental Analysis E. Background Hydrostatic Effects Hydrodynamic Effects Hybrid Bearings F. Hydrodynamic Stability Problem UL Literature Review H. Contributions II EXPERIMENTAL RESULTS A. Parameters of Interest B..., 1983) Pressure Generation in a Hydrodynamic Bearing (Vance, 1988), 27 Baseline Bearing Flowrate versus Eccentricity Ratio . . . . . 37 Baseline Bearing Flowrate versus Supply Pressure . . . . . . 38 Baseline Bearing Flowrate versus Running Speed...

Franchek, Nancy Marie

2012-06-07

35

Orbit transfer vehicle engine technology program. Task B-6 high speed turbopump bearings  

NASA Technical Reports Server (NTRS)

Bearing types were evaluated for use on the Orbit Transfer Vehicle (OTV) high pressure fuel pump. The high speed, high load, and long bearing life requirements dictated selection of hydrostatic bearings as the logical candidate for this engine. Design and fabrication of a bearing tester to evaluate these cryogenic hydrostatic bearings was then conducted. Detailed analysis, evaluation of bearing materials, and design of the hydrostatic bearings were completed resulting in fabrication of Carbon P5N and Kentanium hydrostatic bearings. Rotordynamic analyses determined the exact bearing geometry chosen. Instrumentation was evaluated and data acquisition methods were determined for monitoring shaft motion up to speeds in excess of 200,000 RPM in a cryogenic atmosphere. Fabrication of all hardware was completed, but assembly and testing was conducted outside of this contract.

1992-01-01

36

Performance of gas-lubricated cruciform-mounted tilting-pad journal bearings and a damped flexibly mounted spiral-groove thrust bearing  

NASA Technical Reports Server (NTRS)

A test program was conducted to determine the performance characteristics of gas-lubricated cruciform-mounted tilting-pad journal bearings and a damped spiral-groove thrust bearing designed for the Brayton cycle rotating unit (BRU). Hydrostatic, hybrid (simultaneously hydrostatic and hydrodynamic), and hydrodynamic tests were conducted in argon gas at ambient pressure and temperature ranges representative of operation to the 10.5 kWe BRU power-generating level. Performance of the gas lubricated bearings is presented including hydrostatic gas flow rates, bearing clearances, bearing temperatures, and transient performance.

Ream, L. W.

1974-01-01

37

Computing Flows In Turbine End Bearings  

NASA Technical Reports Server (NTRS)

Computer program implements mathematical model of flow through turbine and bearings of high-pressure-oxygen turbopump of Space Shuttle main engine. Intended to determine rate of flow and margin before vaporization in these bearings for various types of geometries. Effects of hydrostatic damper and/or back-pressure seal included. Modified for application to other turbomachines and fluids other than oxygen.

Smith, Tyn S.

1990-01-01

38

SSME Long-life Bearings  

NASA Technical Reports Server (NTRS)

Hybrid hydrostatic/ball bearings for LH2 and LO2 service in turbopumps were studied as a means of improving speed and life capabilities. Four hybrid bearing configurations were designed with emphasis on achieving maximum stiffness and damping. Parallel load bearings were tested at steady-state and transient conditions with LH2 (externally fed) and LN2 (internally fed). The hydrostatic elements were tested with Freon 113 for empirical determination of dynamic characteristics. Tests using an eccentric journal for loading showed the externally and internally fed hydrostatic bearings to have significant separated coefficients of direct stiffness and damping. For the internally fed bearing, the strongly speed-dependent cross-coupling stiffness arising from fluid swirl, along with significant cross-coupling damping, resulted in low net effective stiffness and damping. The test method used can produce separated coefficients with a sufficiently elliptic journal orbit; otherwise, only net effective coefficients combining direct and cross-coupling terms can be determined. Testing with nonsynchronous excitation is recommended to avoid this restriction. Investigation of hard materials, including ceramics, is recommended as a means of eliminating the need for the rolling bearing for startup and shutdown support. The testing was performed in 1984 (LH2), 1985 (LN2) and 1985-86 (Freon).

Butner, M. F.; Murphy, B. T.

1986-01-01

39

Hydrostatic Hyperbaric Chamber Ventilation System  

NASA Technical Reports Server (NTRS)

The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications, including the treatment of medical conditions. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy available in the developing world for the treatment of a variety of medical conditions. Specifically, hyperbaric oxygen therapy is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. Hyperbaric oxygen therapy is simply too expensive and too dangerous to implement in the developing world using standard equipment. The hydrostatic hyperbaric chamber technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system that will provide controlled pressurization of the system, and provide adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the patient and operating personnel, and physiological considerations. The simple schematic, comprised of easily acquired commercial hardware, supports sustainability.

Sargusingh, Miriam M.

2011-01-01

40

Hydrostatic compaction of Microtherm HT.  

SciTech Connect

Two samples of jacketed Microtherm{reg_sign}HT were hydrostatically pressurized to maximum pressures of 29,000 psi to evaluate both pressure-volume response and change in bulk modulus as a function of density. During testing, each of the two samples exhibited large irreversible compactive volumetric strains with only small increases in pressure; however at volumetric strains of approximately 50%, the Microtherm{reg_sign}HT stiffened noticeably at ever increasing rates. At the maximum pressure of 29,000 psi, the volumetric strains for both samples were approximately 70%. Bulk modulus, as determined from hydrostatic unload/reload loops, increased by more than two-orders of magnitude (from about 4500 psi to over 500,000 psi) from an initial material density of {approx}0.3 g/cc to a final density of {approx}1.1 g/cc. An empirical fit to the density vs. bulk modulus data is K = 492769{rho}{sup 4.6548}, where K is the bulk modulus in psi, and {rho} is the material density in g/cm{sup 3}. The porosity decreased from 88% to {approx}20% indicating that much higher pressures would be required to compact the material fully.

Broome, Scott Thomas; Bauer, Stephen J.

2010-09-01

41

46 CFR 64.83 - Hydrostatic test.  

Code of Federal Regulations, 2010 CFR

...tank with water and pressurizing to the test pressure indicated on the metal identification...heating coil passing a hydrostatic test at a pressure of 200 psig or more or 50 percent or more above the rated pressure of the coil, whichever is greater...If the tank passes the hydrostatic test required in paragraph (a) of...

2010-10-01

42

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2011-10-01

43

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2010-10-01

44

Hydrostatic Hyperbaric Chamber Ventilation System  

NASA Technical Reports Server (NTRS)

The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy (HBOT) available in the developing world for the treatment of a variety of medical conditions. Specifically, HBOT is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. HBOT is simply too expensive and too dangerous to implement in the developing world using standard equipment. The HHC technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system to provide controlled pressurization and adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the patient and operating personnel, and physiological considerations. The simple schematic, comprised of easily acquired commercial hardware, supports sustainability.

Sarguisingh, Miriam J.

2012-01-01

45

Dynamic Cores in Hydrostatic Disguise  

NASA Astrophysics Data System (ADS)

We discuss the column density profiles of ``cores'' in three-dimensional smoothed particle hydrodynamics (SPH) numerical simulations of turbulent molecular clouds. The SPH scheme allows us to perform a high spatial resolution analysis of the density maxima (cores) at scales between ~0.003 and 0.3 pc. We analyze simulations in three different physical conditions: large-scale driving (LSD), small-scale driving (SSD), and random Gaussian initial conditions without driving (GC), each one at two different time steps: just before self-gravity is turned on (t0) and when gravity has been operating such that 5% of the total mass in the box has been accreted into cores (t1). For this data set, we perform Bonnor-Ebert fits to the column density profiles of cores found by a clump-finding algorithm. We find that, for the particular fitting procedure we use, 65% of the cores can be matched to Bonnor-Ebert (BE) profiles, and of these, 47% correspond to stable equilibrium configurations with ?max<6.5, even though the cores analyzed in the simulations are not in equilibrium but instead are dynamically evolving. The temperatures obtained with the fitting procedure vary between 5 and 60 K (in spite of the simulations being isothermal, with T=11.3 K), with the peak of the distribution being at T=11 K and most clumps having fitted temperatures between 5 and 30 K. Central densities obtained with the BE fit tend to be smaller than the actual central densities of the cores. We also find that for the LSD and GC cases, there are more BE-like cores at t0 than at t1 with ?max<=20, while in the case of SSD, there are more such cores at t1 than at t0. We interpret this as a consequence of the stronger turbulence present in the cores of run SSD, which prevents good BE fits in the absence of gravity, and delays collapse in its presence. Finally, in some cases we find substantial superposition effects when we analyze the projection of the density structures, even though the scales over which we project are small (<~0.18 pc). As a consequence, different projections of the same core may give very different values of the BE fits. Finally, we briefly discuss recent results claiming that Bok globule B68 is in hydrostatic equilibrium, stressing that they imply that this core is unstable by a wide margin. We conclude that fitting BE profiles to observed cores is not an unambiguous test of hydrostatic equilibrium and that fit-estimated parameters such as mass, central density, density contrast, temperature, or radial profile of the BE sphere may differ significantly from the actual values in the cores.

Ballesteros-Paredes, Javier; Klessen, Ralf S.; Vázquez-Semadeni, Enrique

2003-07-01

46

Nonlinear Study of a Misaligned Hydrodynamic Journal Bearing  

Microsoft Academic Search

Hydrodynamic\\/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The main objective of this paper is to study the nonlinear effects in a hydrodynamic journal bearing with special attention to the effects of journal axial misalignment. The

F. K. Choy; M. J. Braun; Y. Hu

1993-01-01

47

Polar Bears  

NSDL National Science Digital Library

Use the following websites to answer questions about the rapid disappearance of polar bears in the Arctic region. Polar Bear picture Polar Bear Tracker 1: What region in the world has the fewest polar bears? 2: Using the internet as a resource, provide some reasons as to why this region is suffering from the most polar bear differences? Polar Bears Change Diet 1: Why are polar bears having to change their diets? 2: List some other factors (besides diet) in the ...

Thomas, Mr.

2010-09-27

48

Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings  

NASA Technical Reports Server (NTRS)

A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis.

Andres, Luis San

1993-01-01

49

ME 379M Lubrication, Wear, and Bearing Technology ABET EC2000 syllabus  

E-print Network

, Lubrication & Lubricants 5. Hydrodynamic Lubrication & Film Bearings 6. Boundary & Mixed Film Lubrication 7 & Design, Greases, 11. Elasto-Hydrodynamic Lubrication 12. Hydrostatic Lubrication & Pressurized BearingsME 379M � Lubrication, Wear, and Bearing Technology Page 1 ABET EC2000 syllabus ME 379M

Ben-Yakar, Adela

50

Fault Tolerant Magnetic Bearing Testing and Conical Magnetic Bearing Development for Extreme Temperature Environments  

NASA Technical Reports Server (NTRS)

During the six month tenure of the grant, activities included continued research of hydrostatic bearings as a viable backup-bearing solution for a magnetically levitated shaft system in extreme temperature environments (1000 F), developmental upgrades of the fault-tolerant magnetic bearing rig at the NASA Glenn Research Center, and assisting in the development of a conical magnetic bearing for extreme temperature environments, particularly turbomachinery. It leveraged work from the ongoing Smart Efficient Components (SEC) and the Turbine-Based Combined Cycle (TBCC) program at NASA Glenn Research Center. The effort was useful in providing technology for more efficient and powerful gas turbine engines.

Keith, Theo G., Jr.; Clark, Daniel

2004-01-01

51

Effect of recess pressure ratio on the characteristics of a hybrid bearing  

E-print Network

Hybrid (Combination Hydrostatic and Hydrodynamic) bearings have shown good properties in testing and in consideration for applications such as the Space Shuttle Main Engine High Pressure Oxygen Turbopump. However, properties have not been examined...

Ingram, Michael William

2012-06-07

52

Polar Bear Polar Bear  

NSDL National Science Digital Library

In this lesson, students will listen for key details in a nonfiction text about polar bears. They will work at completing a graphic organizer with the teacher to help organize their thinking and understanding of key details about a text. They will also complete an independent assignment where they will draw or write two things that they learned about the topic.

Burgess, Kelly

2012-09-11

53

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Hydrostatic testing of boilers. 230.36 Section 230.36 Transportation...LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Pressure Testing of Boilers § 230.36 Hydrostatic testing of...

2013-10-01

54

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Hydrostatic testing of boilers. 230.36 Section 230.36 Transportation...LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Pressure Testing of Boilers § 230.36 Hydrostatic testing of...

2012-10-01

55

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Hydrostatic testing of boilers. 230.36 Section 230.36 Transportation...LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Pressure Testing of Boilers § 230.36 Hydrostatic testing of...

2011-10-01

56

Polar Bear  

NSDL National Science Digital Library

This site from the World Wildlife Fund (WWF) International provides general information about polar bears as well as data on the movements of two radio-collared bears, along with the ice status, through a series of online maps.

2007-01-01

57

Scaling Symmetry and Integrable Spherical Hydrostatics  

E-print Network

Any symmetry reduces a second-order differential equation to a first integral: variational symmetries of the action (exemplified by central field dynamics) lead to conservation laws, but symmetries of only the equations of motion (exemplified by scale-invariant hydrostatics) yield first-order {\\em non-conservation laws} between invariants. We obtain these non-conservation laws by extending Noether's Theorem to non-variational symmetries and present an innovative variational formulation of spherical adiabatic hydrostatics. For the scale-invariant case, this novel synthesis of group theory, hydrostatics, and astrophysics allows us to recover all the known properties of polytropes and define a {\\em core radius}, inside which polytropes of index $n$ share a common core mass density structure, and outside of which their envelopes differ. The Emden solutions (regular solutions of the Lane-Emden equation) are obtained, along with useful approximations. An appendix discusses the $n=3$ polytrope in order to emphasize how the same mechanical structure allows different thermal structures in relativistic degenerate white dwarfs and zero age main sequence stars.

Sidney Bludman; Dallas C. Kennedy

2011-12-19

58

Fluid Film Bearing Code Development  

NASA Technical Reports Server (NTRS)

The next generation of rocket engine turbopumps is being developed by industry through Government-directed contracts. These turbopumps will use fluid film bearings because they eliminate the life and shaft-speed limitations of rolling-element bearings, increase turbopump design flexibility, and reduce the need for turbopump overhauls and maintenance. The design of the fluid film bearings for these turbopumps, however, requires sophisticated analysis tools to model the complex physical behavior characteristic of fluid film bearings operating at high speeds with low viscosity fluids. State-of-the-art analysis and design tools are being developed at the Texas A&M University under a grant guided by the NASA Lewis Research Center. The latest version of the code, HYDROFLEXT, is a thermohydrodynamic bulk flow analysis with fluid compressibility, full inertia, and fully developed turbulence models. It can predict the static and dynamic force response of rigid and flexible pad hydrodynamic bearings and of rigid and tilting pad hydrostatic bearings. The Texas A&M code is a comprehensive analysis tool, incorporating key fluid phenomenon pertinent to bearings that operate at high speeds with low-viscosity fluids typical of those used in rocket engine turbopumps. Specifically, the energy equation was implemented into the code to enable fluid properties to vary with temperature and pressure. This is particularly important for cryogenic fluids because their properties are sensitive to temperature as well as pressure. As shown in the figure, predicted bearing mass flow rates vary significantly depending on the fluid model used. Because cryogens are semicompressible fluids and the bearing dynamic characteristics are highly sensitive to fluid compressibility, fluid compressibility effects are also modeled. The code contains fluid properties for liquid hydrogen, liquid oxygen, and liquid nitrogen as well as for water and air. Other fluids can be handled by the code provided that the user inputs information that relates the fluid transport properties to the temperature.

1995-01-01

59

Engine bearings  

SciTech Connect

This patent describes a hydrodynamic journal bearing combination comprising: a rotary journal shaft having a circular cross section; a journal bearing surrounding the rotary journal shaft. The journal bearing has at least two symmetrical arcuate bearing surfaces, each arcuate surface having the same radius. The radius is slightly greater than that of the rotary journal shaft. Each arcuate bearing surface defines less than 180/sup 0/ and has a mid point intermediate it ends. The arcuate bearing surfaces are disposed with their mid points diametrically opposed. The journal shaft is positioned within the area covered by the two arcuate surfaces whereby a small clearance is maintained therebetween at all points under both load and no-load lubricant filling the aforesaid clearance between the journal shaft and the two arcuate surfaces.

Showalter, M.R.

1987-05-26

60

Acoustic cymbal performance under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Continual awareness about the need to develop light-weight, low-volume, broadband, underwater acoustic projector and receive arrays that perform consistently in diverse environments is evident in recent Navy acoustic system initiatives. Acoustic cymbals, so named for resemblance to the percussive musical instruments, are miniature flextensional transducers that may perhaps meet the performance criteria for consistent performance under hydrostatic pressure after modifications in the design. These acoustic cymbals consist of a piezoceramic disk (or ring) bonded to two opposing cymbal-shaped metal shells. Operating as mechanical transformers, the two metal shells convert the large generative force inherently within the disk's radial mode into increased volume displacement at the metal shell surface to obtain volume displacement that translates into usable source levels and/or sensitivities at sonar frequencies in a relatively broad band. The air-backed design for standard acoustic cymbal transducers presents a barrier to deepwater applications. A new acoustic cymbal design for high-pressure applications will be presented for the first time. This practical pressure compensation is designed to diminish the effects of hydrostatic pressure to maintain consistent acoustic cymbal performance. Transmit and receive performance data, determined at the Naval Undersea Warfare Center's (NUWC) Acoustic Pressure Tank Facility (APTF), is presented.

Jenne, Kirk E.; Huang, Dehua; Howarth, Thomas R.

2001-05-01

61

Polar Bear  

USGS Publications Warehouse

Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

Amstrup, S.D.

1988-01-01

62

Hydrostatic pressure plants for desalination via reverse osmosis  

Microsoft Academic Search

Renewable energies (solar and wind energies) associated to reverse osmosis (RO) are gaining renewed interest for brackish and seawater desalination. Another potential source of energy is the hydrostatic pressure at a sufficient operative depth or height to perform the RO process. This article provides a comparison of the energy requirement of various hydrostatic pressure-RO plants. For submarine and underground plants,

C. Charcosset; C. Falconet; M. Combe

2009-01-01

63

Interaction between hydrostatic pressure and temperature on bacteria  

Microsoft Academic Search

The effects of hydrostatic pressure and temperature on organisms in the biosphere are studied. It was found that the sensitivity of pressure-temperature treatment on bacteria varies widely. Because of this situation, each bacterial species in question should be investigated. In floodwater operations, it can be seen that the parameter of hydrostatic pressure can contribute to plugging by changing the cellular

Morita

1966-01-01

64

78 FR 70324 - Thy Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...  

Federal Register 2010, 2011, 2012, 2013

...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard for General Industry...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard are necessary...

2013-11-25

65

75 FR 48728 - The Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...  

Federal Register 2010, 2011, 2012, 2013

...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard for General Industry...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard are necessary...

2010-08-11

66

The performance and application of high speed long life LH2 hybrid bearings for reusable rocket engine turbomachinery  

NASA Technical Reports Server (NTRS)

Data are presented for two different experimental programs which were conducted to investigate the characteristics of a hybrid (hydrostatic/ball) bearing operating in liquid hydrogen. The same bearing design was used in both programs. Analytical predictions were made of the bearing characteristics and are compared with the experimental results when possible. The first program used a bearing tester to determine the steady state, transient, and cyclic life characteristics of the bearing over a wide range of operating conditions. The second program demonstrated the feasibility of applying hybrid bearings to an actual high speed turbopump by retrofitting and then testing an existing liquid hydrogen turbopump with the bearings.

Hannum, N. P.; Nielson, C. E.

1983-01-01

67

Magnetic Bearing  

NASA Technical Reports Server (NTRS)

AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

1996-01-01

68

Hydrostatic Stress Effect On the Yield Behavior of Inconel 100  

NASA Technical Reports Server (NTRS)

Classical metal plasticity theory assumes that hydrostatic stress has no effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of notched geometries. New experiments and nonlinear finite element analyses (FEA) of Inconel 100 (IN 100) equal-arm bend and double-edge notch tension (DENT) test specimens have revealed the effect of internal hydrostatic tensile stresses on yielding. Nonlinear FEA using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions was performed. In all test cases, the von Mises constitutive model, which is independent of hydrostatic pressure, overestimated the load for a given displacement or strain. Considering the failure displacements or strains, the Drucker-Prager FEMs predicted loads that were 3% to 5% lower than the von Mises values. For the failure loads, the Drucker Prager FEMs predicted strains that were 20% to 35% greater than the von Mises values. The Drucker-Prager yield function seems to more accurately predict the overall specimen response of geometries with significant internal hydrostatic stress influence.

Allen, Phillip A.; Wilson, Christopher D.

2002-01-01

69

Gravity, the hydrostatic indifference concept and the cardiovascular system  

Microsoft Academic Search

Gravity, like any acceleration, causes a hydrostatic pressure gradient in fluid-filled bodily compartments. At a force of\\u000a 1G, this pressure gradient amounts to 10 kPa\\/m. Postural changes alter the distribution of hydrostatic pressure patterns according\\u000a to the body’s alignment to the acceleration field. At a certain location—referred to as hydrostatically indifferent—within\\u000a any given fluid compartment, pressure remains constant during a given

Helmut Hinghofer-Szalkay

2011-01-01

70

Abscisic Acid increases terrestrial plant cell resistance to hydrostatic pressure.  

PubMed

Cells of the terrestrial plant species bromegrass (Bromus inermis L.) are not naturally adapted to withstand the hydrostatic pressures encountered in aquatic environments. However, after treatment with the natural plant growth hormone abscisic acid (75 micromolar), bromegrass cells survived a hydrostatic pressure of 101.3 megapascals, approximating the limits of ocean depth (10,860 m). The increased resistance to hydrostatic pressure from 1 to 7 days of abscisic acid treatment paralleled the induced elevation of cell tolerance to freezing stress. PMID:16668704

Tanino, K K; Chen, T H; Fuchigami, L H; Weiser, C J

1992-02-01

71

Cave Bear  

NSDL National Science Digital Library

Decoding an ancient cave bear. A two-ton, thirteen-foot cave bear, extinct for ten thousand years, has just experienced a rebirth of sorts. From a tooth and a bone, scientists have recovered its entire genetic code.Eddy Rubin, director of the Department of Energy's Joint Genome Institute, says finding genuine cave bear DNA was like looking for a needle in a haystack. The haystack were all the other organisms that were living in the bones and in the tooth of this ancient creature. And the needle was the little bit of the ancient creature's genome DNA, or genes.They used state-of-the-art computer technology to separate the bear genes from the clutter. Jurassic Park fans should note that they can't clone a new cave bear, nor can they recover DNA from creatures as old as the dinosaurs. But they do hope to reconstruct the genetic code of Neanderthals, our closest non-human relatives, to better understand how our own species evolved. This resource contains detailed text description of the research as well as likes for further inquiry.

American Association for the Advancement of Science (;)

2005-08-15

72

Thermopower of Cuprate Superconductors under Hydrostatic Pressure  

SciTech Connect

Measurements of thermopower versus temperature under hydrostatic pressure are reported for La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} having no charge reservoir and the underdoped YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, which we demonstrate to have a pressure-induced electron transfer from the CuO{sub 2} sheets to the Cu(1)O{sub 1{minus}{delta}} reservoir planes. The CuO{sub 2} sheets exhibit a thermopower {alpha}({ital T})={alpha}{sub 0}+{delta}{alpha}({ital T}) in which {alpha}{approx_equal}{alpha}{sub 0} at room temperature decreases with increasing hole concentration, and {delta}{alpha}({ital T}) is an enhancement having a maximum at {ital T}{sub max}=100{endash}140K. Correlation between {ital dT}{sub {ital c}}/{ital dP} and {ital d}({delta}{alpha})/{ital dP} are discussed. {copyright} {ital 1996 The American Physical Society.}

Zhou, J.; Goodenough, J.B. [Center for Materials Science and Engineering, ETC 9.102, University of Texas at Austin, Austin, Texas 78712-1063 (United States)] [Center for Materials Science and Engineering, ETC 9.102, University of Texas at Austin, Austin, Texas 78712-1063 (United States)

1996-07-01

73

Designing a high-efficiency hydrostatic bicycle transmission  

E-print Network

Hydrostatic bicycle drives use a working fluid instead of the common roller-chain to transmit power to the drive wheel. These transmissions are typically considered too inefficient for human power applications. An experiment ...

Socks, Matthew T. (Matthew Tristram)

2006-01-01

74

46 CFR 61.30-10 - Hydrostatic test.  

Code of Federal Regulations, 2012 CFR

...2 times the maximum allowable working pressure. The test must be conducted in the...inspection is made of all accessible parts under pressure. The thermal fluid may be used as the hydrostatic test...

2012-10-01

75

46 CFR 61.30-10 - Hydrostatic test.  

Code of Federal Regulations, 2013 CFR

...2 times the maximum allowable working pressure. The test must be conducted in the...inspection is made of all accessible parts under pressure. The thermal fluid may be used as the hydrostatic test...

2013-10-01

76

46 CFR 61.30-10 - Hydrostatic test.  

Code of Federal Regulations, 2011 CFR

...2 times the maximum allowable working pressure. The test must be conducted in the...inspection is made of all accessible parts under pressure. The thermal fluid may be used as the hydrostatic test...

2011-10-01

77

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2012 CFR

...preparation for the hydrostatic pressure test. For metal IBCs, the test must be carried out before the fitting of any thermal insulation equipment. For all IBCs, pressure relief devices and vented closures must be removed and their apertures...

2012-10-01

78

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2013 CFR

...preparation for the hydrostatic pressure test. For metal IBCs, the test must be carried out before the fitting of any thermal insulation equipment. For all IBCs, pressure relief devices and vented closures must be removed and their apertures...

2013-10-01

79

Hydrostatic pressure and aquatic plant growth: a laboratory study  

Microsoft Academic Search

A method was tested for growing aquatic vascular plants at elevated hydrostatic pressure so that the influence of other factors\\u000a will not mask the specific plant-pressure interaction.\\u000a \\u000a Eighteen species of submersed vascular plants, belonging to twelve families and several distinct growth forms, were subjected\\u000a to series of hydrostatic pressures including those well in excess of those encountered by the species

H. M. Dale

1984-01-01

80

Bear Bones  

NSDL National Science Digital Library

An estimated ten million Americans have osteoporosis, an age-related disease in which the bones gradually become brittle and weak. Now, scientists are looking to animals for clues on how to combat this condition. This resource describes the study of sustaining bone strength of hibernating bears.

Science Update;

2004-03-08

81

Hydrostatic pressure differentially regulates outer and inner annulus fibrosus cell matrix production in 3D scaffolds.  

PubMed

Mechanical stimulation may be used to enhance the development of engineered constructs for the replacement of load bearing tissues, such as the intervertebral disc. This study examined the effects of dynamic hydrostatic pressure (HP) on outer and inner annulus (OA, IA) fibrosus cells seeded on fibrous poly(glycolic acid)-poly(L-lactic acid) scaffolds. Constructs were pressurized (5 MPa, 0.5 Hz) for 4 h/day from day 3 to day 14 of culture and analyzed using ELISAs and immunohistochemistry (IHC) to assess extracellular matrix (ECM) production. Both cell types were viable, with OA cells exhibiting more infiltration into the scaffold, which was enhanced by HP. ELISA analyses revealed that HP had no effect on type I collagen production while a significant increase in type II collagen (COL II) was measured in pressurized OA constructs compared to day 14 unloaded controls. Both OA and IA dynamically loaded scaffolds exhibited more uniform COL II elaboration as shown by IHC analyses, which was most pronounced in OA-seeded scaffolds. Overall, HP resulted in enhanced ECM elaboration and organization by OA-seeded constructs, while IA-seeded scaffolds were less responsive. As such, hydrostatic pressurization may be beneficial in annulus fibrosus tissue engineering when applied in concert with an appropriate cell source and scaffold material. PMID:18026839

Reza, Anna T; Nicoll, Steven B

2008-02-01

82

Hydrostatic Microextrusion of Steel and Copper  

SciTech Connect

The paper presents an experimental investigation based on hydrostatic micro extrusion of billets in low carbon steel and commercially pure copper, and the relevant results. The starting billets have a diameter of 0.3 mm and are 5 mm long; a high pressure generator consisting of a manually operated piston screw pump is used to pressurize the fluid up to 4200 bar, the screw pump is connected through a 3-way distribution block to the extrusion die and to a strain gauge high pressure sensor. The sensor has a full scale of 5000 bar and the extrusion pressure is acquired at a sampling rate of 2 kHz by means of an acquisition program written in the LabVIEW environment. Tests have been conducted at room temperature and a lubricant for wire drawing (Chemetall Gardolube DO 338) acts both as the pressurizing fluid and lubricant too. In addition, billets were graphite coated. Different fluid pressures and process durations have been adopted, resulting in different extrusion lengths. The required extrusion pressure is much higher than in non-micro forming operations (this effect is more evident for steel). On the cross section of the extruded parts, hardness and grain size distribution have been measured, the former through Vickers micro hardness (10 g load) tests. In the case of the extrusion of copper, the material behaves as in microdrawing process. In the case of the extrusion of steel, the hardness increases from the core to the surface as in the drawing process, but with lower values. The analysis evidenced the presence of the external layer, but its thickness is about 1/3 of the external layer in the drawn wire and the grains appear smaller than in the layer of the drawn wire. The extruding force required along the extruding direction is higher (22-24 N) than the drawing force along the same direction (12 N): being the material, the reduction ratio, the die sliding length the same in both cases, the higher extrusion force should be caused by a higher tangential friction force and/or a higher redundant work of deformation and/or a different material behaviour. Which is the real mechanism is not clear at present, but surface layer grains in extrusion are more deformed than in wire drawing. For this reason the deformation inhomogeneity increases in extrusion and the material under the highly deformed surface layer should be subjected to lower strains, strain hardening and finally resulting in lower hardness.

Berti, Guido; Monti, Manuel [University of Padua, DTG, Stradella San Nicola 3, I-36100 Vicenza (Italy); D'Angelo, Luciano [University of Ferrara, Dept. of Engineering, via Saragat 3, 44100 Ferrara (Italy)

2011-05-04

83

Hydrostatic Microextrusion of Steel and Copper  

NASA Astrophysics Data System (ADS)

The paper presents an experimental investigation based on hydrostatic micro extrusion of billets in low carbon steel and commercially pure copper, and the relevant results. The starting billets have a diameter of 0.3 mm and are 5 mm long; a high pressure generator consisting of a manually operated piston screw pump is used to pressurize the fluid up to 4200 bar, the screw pump is connected through a 3-way distribution block to the extrusion die and to a strain gauge high pressure sensor. The sensor has a full scale of 5000 bar and the extrusion pressure is acquired at a sampling rate of 2 kHz by means of an acquisition program written in the LabVIEW environment. Tests have been conducted at room temperature and a lubricant for wire drawing (Chemetall Gardolube DO 338) acts both as the pressurizing fluid and lubricant too. In addition, billets were graphite coated. Different fluid pressures and process durations have been adopted, resulting in different extrusion lengths. The required extrusion pressure is much higher than in non-micro forming operations (this effect is more evident for steel). On the cross section of the extruded parts, hardness and grain size distribution have been measured, the former through Vickers micro hardness (10 g load) tests. In the case of the extrusion of copper, the material behaves as in microdrawing process. In the case of the extrusion of steel, the hardness increases from the core to the surface as in the drawing process, but with lower values. The analysis evidenced the presence of the external layer, but its thickness is about 1/3 of the external layer in the drawn wire and the grains appear smaller than in the layer of the drawn wire. The extruding force required along the extruding direction is higher (22-24 N) than the drawing force along the same direction (12 N): being the material, the reduction ratio, the die sliding length the same in both cases, the higher extrusion force should be caused by a higher tangential friction force and/or a higher redundant work of deformation and/or a different material behaviour. Which is the real mechanism is not clear at present, but surface layer grains in extrusion are more deformed than in wire drawing. For this reason the deformation inhomogeneity increases in extrusion and the material under the highly deformed surface layer should be subjected to lower strains, strain hardening and finally resulting in lower hardness.

Berti, Guido; Monti, Manuel; D'Angelo, Luciano

2011-05-01

84

Fabrication and characterization of a micro turbine\\/bearing rig  

Microsoft Academic Search

This paper reports on a process to build, package, and instrument a 5-level wafer-bonded micromachined turbine\\/bearing rig. The process flow involves the use of 5 wafers, 16 masks, and 9 deep silicon etching steps, as well as utilizing aligned wafer bonding, double-sided deep reactive ion etching and laser-assisted-etching. This paper also shows experimental results on flow characteristics of the hydrostatic

Chuang-Chia Lin; Reza Ghodssi; Arturo A. Ayon; Dye-Zone Chen; Stuart Jacobson; Kenneth Breuer; Alan H. Epstein; Martin A. Schmidt

1999-01-01

85

Hydrostatic Stress Effect on the Yield Behavior of Inconel 100  

NASA Technical Reports Server (NTRS)

Classical metal plasticity theory assumes that hydrostatic stress has negligible effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of various geometries. Fatigue tests and nonlinear finite element analyses (FEA) of Inconel 100 (IN100) equal-arm bend specimens and new monotonic tests and nonlinear finite element analyses of IN100 smooth tension, smooth compression, and double-edge notch tension (DENT) test specimens have revealed the effect of internal hydrostatic tensile stresses on yielding. Nonlinear FEA using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions were performed. A new FEA constitutive model was developed that incorporates a pressure-dependent yield function with combined multilinear kinematic and multilinear isotropic hardening using the ABAQUS user subroutine (UMAT) utility. In all monotonic tensile test cases, the von Mises constitutive model, overestimated the load for a given displacement or strain. Considering the failure displacements or strains for the DENT specimen, the Drucker-Prager FEM s predicted loads that were approximately 3% lower than the von Mises values. For the failure loads, the Drucker Prager FEM s predicted strains that were up to 35% greater than the von Mises values. Both the Drucker-Prager model and the von Mises model performed equally-well in simulating the equal-arm bend fatigue test.

Allen, Phillip A.; Wilson, Christopher D.

2003-01-01

86

Characterization and measurement of hybrid gas journal bearings  

NASA Astrophysics Data System (ADS)

This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to "basics" to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner's permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow "compensation" should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an "apples-to-apples" comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing's mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the "near surface effect" and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the "CFD microscope". This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the "cause" of the "near surface effect". A gedanken experiment is performed based on these results which indicates that a bearing with a "stronger aerostatic strength" component should be more stable than one with a low aerostatic strength component. Numerical instability "speed limits" are found that are also relate

Lawrence, Tom Marquis

87

Hydrostatic levelling systems: Measuring at the system limits  

NASA Astrophysics Data System (ADS)

Three hydrostatic displacement monitoring system applications in Switzerland are discussed; the first concerns experience gained monitoring the foundation of the Albigna dam, the second relating to the underground stability of the Swiss Light Source synchrotron and the third concerning the deformation of a bridge near the city of Lucerne. Two different principles were applied, the Hydrostatic Levelling System (HLS) using the “half-filled pipe principle” developed by the Paul Scherrer Institute and the Large Area Settlement System (LAS) using the “differential pressure principle”. With both systems ground deformations induced by tidal forces can be seen. However, high accuracy of single sensors is not sufficient. A well-designed configuration of the complete system is equally important. On the other hand there are also limits imposed by installation logistics and by the environmental conditions. An example is the bridge monitoring application, where the acceleration along the bridge due to the passage of heavy trucks limits the feasibility of using hydrostatic levelling measurements.

Meier, Edi; Geiger, Alain; Ingensand, Hilmar; Licht, Hans; Limpach, Philippe; Steiger, Andreas; Zwyssig, Roger

2010-09-01

88

Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing  

NASA Technical Reports Server (NTRS)

The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers.

Buckmann, P. S.; Hayden, W. R.; Lorenc, S. A.; Sabiers, R. L.; Shimp, N. R.

1990-01-01

89

Theory for hydrostatic gas journal bearings for micro-electro-mechanical systems  

E-print Network

The goal of the MIT micro-engine project is to develop high-speed rotating Power MEMS (Micro-Electro-Mechanical Systems) using computer chip fabrication technologies. To produce high power (10-50 W) in a small volume (less ...

Liu, Lixian, Ph. D. Massachusetts Institute of Technology

2005-01-01

90

Wheel drives for large telescopes: save the cost and keep the performance over hydrostatic bearings  

NASA Astrophysics Data System (ADS)

The use of steel wheels on steel tracks has been around since steel was invented, and before that it was iron wheels on iron tracks. Not to be made obsolete by the passage of time, this approach for moving large objects is still valid, even optimal, but the detailed techniques for achieving high performance and long life have been much improved. The use of wheel-and-track designs has been very popular in radio astronomy for the largest of the large radio telescopes (RT), including such notables as the 305m Arecibo RT, the 100m telescopes at Effelsberg, Germany (at 3600 tonnes) and the Robert C. Byrd, Greenbank Telescope (GBT, 7600 tonnes) at Greenbank, West Virginia. Of course, the 76m Lovell Telescope at Jodrell Bank is the grandfather of all large aperture radio telescopes that use wheel drives. Smaller sizes include NRAO's Very Long Baseline Array (VLBA) telescopes at 25m and others. Wheel drives have also been used on large radars of significance such as the 410 tonne Ground Based Radar-Prototype (GBR-P) and the 150 foot (45.7m) Altair Radar, and the 2130 tonne Sea Based X-Band Radar (SBX). There are also many examples of wheel driven communications antennas of 18 meters and larger. All of these instruments have one thing in common: they all use steel wheels that run in a circle on one or more flat, level, steel tracks. This paper covers issues related to designing for wheel driven systems. The intent is for managing motion to sub arc-second levels, and for this purpose it is primary for the designer to manage measurement and alignment errors, and to establish repeatability through dimensional control, structural and drive stiffness management, adjustability and error management. In a practical sense, there are very few, if any, fabricators that can machine structural and drive components to sufficiently small decimal places to matter. In fact, coming within 2-3 orders of magnitude of the precision needed is about the best that can be expected. Further, it is incumbent on the design team to develop the servo control system features, correction algorithms and structural features in concert with each other. Telescope designers are generally adept at many of these practices, so the scope of this paper is not that, but is limited to those items that pertain to a precision wheel driven system.

Campbell, Marvin F.

2014-07-01

91

SSME long-life bearings. Final Report, January 1982-July 1986  

SciTech Connect

Hybrid hydrostatic/ball bearings for LH2 and LO2 service in turbopumps were studied as a means of improving speed and life capabilities. Four hybrid bearing configurations were designed with emphasis on achieving maximum stiffness and damping. Parallel load bearings were tested at steady-state and transient conditions with LH2 (externally fed) and LN2 (internally fed). The hydrostatic elements were tested with Freon 113 for empirical determination of dynamic characteristics. Tests using an eccentric journal for loading showed the externally and internally fed hydrostatic bearings to have significant separated coefficients of direct stiffness and damping. For the internally fed bearing, the strongly speed-dependent cross-coupling stiffness arising from fluid swirl, along with significant cross-coupling damping, resulted in low net effective stiffness and damping. The test method used can produce separated coefficients with a sufficiently elliptic journal orbit; otherwise, only net effective coefficients combining direct and cross-coupling terms can be determined. Testing with nonsynchronous excitation is recommended to avoid this restriction. Investigation of hard materials, including ceramics, is recommended as a means of eliminating the need for the rolling bearing for startup and shutdown support. The testing was performed in 1984 (LH2), 1985 (LN2) and 1985-86 (Freon).

Butner, M.F.; Murphy, B.T.

1986-07-01

92

Cryogenic turbopump bearing materials  

NASA Technical Reports Server (NTRS)

Materials used for modern cryogenic turbopump bearings must withstand extreme conditions of loads and speeds under marginal lubrication. Naturally, these extreme conditions tend to limit the bearing life. It is possible to significantly improve the life of these bearings, however, by improving the fatigue and wear resistance of bearing alloys, and improving the strength, liquid oxygen compatibility and lubricating ability of the bearing cage materials. Improved cooling will also help to keep the bearing temperatures low and hence prolong the bearing life.

Bhat, Biliyar N.

1989-01-01

93

46 CFR 56.97-30 - Hydrostatic tests (modifies 137.4).  

Code of Federal Regulations, 2013 CFR

...during the hydrostatic test may any part of the piping system be subjected to a stress greater than 90 percent of its yield strength (0.2 percent offset) at test temperature. (g) Hydrostatic test pressure holding time. The...

2013-10-01

94

46 CFR 56.97-30 - Hydrostatic tests (modifies 137.4).  

Code of Federal Regulations, 2012 CFR

...during the hydrostatic test may any part of the piping system be subjected to a stress greater than 90 percent of its yield strength (0.2 percent offset) at test temperature. (g) Hydrostatic test pressure holding time. The...

2012-10-01

95

Non-hydrostatic general circulation model of the Venus atmosphere  

Microsoft Academic Search

We present the first non-hydrostatic global circulation model of the Venus atmosphere based on the complete set of gas dynamics equations. The model employs a spatially uniform triangular mesh that allows to avoid artificial damping of the dynamical processes in the polar regions, with altitude as a vertical coordinate. Energy conversion from the solar flux into atmospheric motion is described

Alexander V. Rodin; Igor Mingalev; Konstantin Orlov; Nikolay Ignatiev

2010-01-01

96

Punching Tests on Disks of Rock Under Hydrostatic Pressure  

Microsoft Academic Search

A simple apparatus for making punching tests on disks of rock subjected to an additional hydrostatic pressure is described. Experiments have been made on marble, slate, and sandstone. They give an approximate value for the variation of shear strength with con- fining pressure. For marble and slate, confining pressure has a considerable strengthening effect, but for sandstone this effect is

J. C. Jaeger

1962-01-01

97

Hydrostatic levels in precision geodesy and crustal deformation measurement  

Microsoft Academic Search

Previous attempts to apply the principles of hydrostatic leveling to precision geodesy have been limited by the uniformity of the fluid density attainable in field environments. This largely due to the effects of temperature variations in the fluid tube. We have overcome this difficulty by using water maintained near its maxium density at 3.98°C inside a counterflow heat exchanger to

Kenneth Hurst; Roger Bilham

1986-01-01

98

High Hydrostatic Pressure Processing of Fruit and Vegetable Products  

Microsoft Academic Search

High hydrostatic pressure (HHP) as a minimal thermal technology is a valuable tool for microbiologically safe and shelf-stable fruit and vegetable production. Microorganisms and deteriorative enzymes can be inhibited or inactivated depending on the amount of pressure and time applied to the product. The resistance of microorganisms and enzymes to pressure in fruit and vegetable products also is dependent on

José A. Guerrero-Beltrán; Gustavo V. Barbosa-Cánovas; Barry G. Swanson

2005-01-01

99

Numerical simulation of impact and liftoff events in the hydrostatic skeleton of the leech  

E-print Network

Numerical simulation of impact and lift­off events in the hydrostatic skeleton of the leech of the hydrostatic skeleton and simulate the collision with an obstacle. The model is based on the worm­like shape. 1 Introduction The constructional principle of the hydrostatic (or fluid) skeleton is found in many

Bielefeld, Universität

100

Optimal Synchronizability of Bearings  

E-print Network

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with ...

Seybold, Hansjorg

101

Bearing Remover And Presser  

NASA Technical Reports Server (NTRS)

Document describes simple bearing-servicing tool consisting of only three parts capable of removing and replacing rotary bearing within race. Threaded drive operates between guide and pressure plate for dislodging bearing from race.

Boyce, Rex A.

1995-01-01

102

Angled Injection: Turbulent Flow Hybrid Bearings Comparison to Test Results  

NASA Technical Reports Server (NTRS)

Hydrostatic/hydrodynamic (hybrid) journal bearings handling process liquids have limited dynamic stability characteristics and their application as support elements to high speed flexible rotating systems is severely restricted. Measurements on water hybrid bearings with angled orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and null or negative whirl frequency ratios. A bulk-flow model for prediction of the static performance and force coefficients of hybrid bearings with angled orifice injection is advanced. The analysis reveals that the fluid momentum exchange at the orifice discharge produces a pressure rise in the hydrostatic recess retards the shear flow induced by journal rotation, and thus, reduces cross-coupling forces. The predictions from the model are compared with experimental measurements for a 45 deg. angled orifice injection, 5 recess water hybrid bearing operating at 10.2, 17.4, and 24.6 krpm and with supply pressures of 4, 5.5, and 7 MPa. The correlations include recess pressures, flow rates, and rotordynamic force coefficients at the journal centered position.

SanAndres, Luis; Childs, Dara

1997-01-01

103

Hydrostatic compression of Fe(1-x)O wuestite  

NASA Technical Reports Server (NTRS)

Hydrostatic compression measurements on Fe(0.95)O wuestite up to 12 GPa yield a room temperature value for the isothermal bulk modulus of K(ot) = 157 (+ or - 10) GPa at zero pressure. This result is in accord with previous hydrostatic and nonhydrostatic measurements of K(ot) for wuestites of composition: 0.89 = Fe/O 0.95. Dynamic measurements of the bulk modulus by ultrasonic, shock-wave and neutron-scattering experiments tend to yield a larger value: K(ot) approximately 180 GPa. The discrepancy between static and dynamic values cannot be explained by the variation of K(ot) with composition, as has been proposed. This conclusion is based on high-precision compression data and on theoretical models of the effects of defects on elastic constants. Barring serious errors in the published measurements, the available data suggest that wuestite exhibits a volume relaxation under pressure.

Jeanloz, R.; Sato-Sorensen, Y.

1986-01-01

104

Hybrid photonic crystal fiber sensing of high hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The opto-mechanical response of Hybrid Photonic Crystal Fiber (HPCF) with Ge-doped inclusions is numerically modeled for high hydrostatic pressure sensing purpose. A typical photonic crystal fiber (PCF) consists of a silica solidcore and a cladding with a hexagonal lattice of air-holes. The HPCF is similar to the regular PCF, but a horizontal line of air-holes is substituted by solid high index rods of Ge-doped silica. The optical guidance in HPCFs is supported combining two physical effects: the modified total internal reflection and the photonic bandgap. In such fibers, the Gedoped inclusions induce residual birefringence. In our analysis, we evaluate the susceptibility of the phase modal birefringence and group birefringence to hydrostatic pressure. The analyses were performed at a photonic bandgap with central wavelength near to 1350 nm. The polarimetric pressure sensitivity is about 10 rad/MPa x m at ? = 1175 nm.

Franco, Marcos A. R.; Serrão, Valdir A.; Pitarello, Tânia R.; Cerqueira S., Arismar, Jr.

2011-05-01

105

Hybrid photonic crystal fiber sensing of high hydrostatic pressure  

Microsoft Academic Search

The opto-mechanical response of Hybrid Photonic Crystal Fiber (HPCF) with Ge-doped inclusions is numerically modeled for high hydrostatic pressure sensing purpose. A typical photonic crystal fiber (PCF) consists of a silica solidcore and a cladding with a hexagonal lattice of air-holes. The HPCF is similar to the regular PCF, but a horizontal line of air-holes is substituted by solid high

Marcos A. R. Franco; Valdir A. Serrão; Tânia R. Pitarello; Arismar Cerqueira S. Jr.

2011-01-01

106

Magnetotransport studies of FeSe under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The discoveries of iron-based superconductors with relatively high transition temperature are under intense experimental and theoretical investigation. Here we present magnetotransport measurements on FeSe superconductor under hydrostatic pressure. We show that in Fe-deficient tetragonal FeSe binary compound, the onset of superconducting transition is almost doubled under 1.98 GPa pressure and the estimated upper critical field of 26.7 Tesla is increased to 47.5 Tesla.

Tiwari, Brajesh; Jha, Rajveer; Awana, V. P. S.

2014-06-01

107

Getting Your Bearings  

NSDL National Science Digital Library

In this activity, learners explore the concept of friction and how ball bearings reduce friction. Learners investigate different uses for ball bearings, how the design has changed over time to incorporate roller bearings, test friction using marbles, and identify the use of ball bearings in everyday items.

Ieee

2013-08-30

108

Bearings for Your Whirligig  

NSDL National Science Digital Library

Experiment with friction and make bearings for a whirligig! This activity is a nice introduction to friction and bearings and demonstrates why bearings are useful for spinning. A related video show Vollis Simpson, an artist who creates kinetic sculptures and whirligigs, explain how he uses bearings in all of his spinning pieces so that they move smoothly.

Minnesota, Science M.

1995-01-01

109

Passive magnetic bearing configurations  

DOEpatents

A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

Post, Richard F. (Walnut Creek, CA)

2011-01-25

110

Introduction to ball bearings  

NASA Technical Reports Server (NTRS)

The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

Hamrock, B. J.; Dowson, D.

1981-01-01

111

High efficiency magnetic bearings  

NASA Technical Reports Server (NTRS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

1993-01-01

112

High efficiency magnetic bearings  

NASA Astrophysics Data System (ADS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

113

Potential Vorticity Conservation, Hydrostatic Adjustment, and the Anelastic Approximation.  

NASA Astrophysics Data System (ADS)

An examination of the anelastic equations of Lipps and Hemler shows that the approximation requires the temperature and potential temperature scale heights of the base state are large compared to the pressure and density scale heights. As a consequence the fractional changes of the temperature and potential temperature fields relative to their base state values are equivalent. Alternatively this equivalency requires that the ratio of the ideal gas constant to the specific heat capacity at constant pressure is small.The anelastic equations are examined for their ability to conserve potential vorticity (PV). The equations are shown to be `PV correct' in the sense that they conserve potential vorticity in a manner consistent with Ertel's theorem and with the assumptions of the anelastic approximation.The ability to conserve potential vorticity helps the anelastic system capture the integrated effect of the acoustic modes in Lamb's hydrostatic adjustment problem. This prototype problem considers the response of a stably stratified atmosphere to an instantaneous heating that is vertically confined but horizontally uniform. In the anelastic case, the state variables adjust instantaneously to be in hydrostatic balance with the potential temperature perturbation generated by the heating. The anelastic solutions for the pressure, density, and temperature fields are identical to those for the compressible case. In contrast there is a mutual adjustment of the pressure, density, and thermal fields in the compressible case, which is not instantaneous. The total energy in the final state for the two cases is the same.The other versions of the anelastic approximation are examined for their PV correctness and for their ability to parameterize Lamb's acoustic hydrostatic adjustment process.

Bannon, Peter R.

1995-06-01

114

Effect of hydrostatic pressure on the plasticity of copper  

NASA Astrophysics Data System (ADS)

A new technique is designed to plot stress-strain curves during torsion at hydrostatic pressure up to 250 MPa. It is used to study the effect of pressure on the torsional strain to failure of copper. The experimental results demonstrate that the plasticity of the material increases in the pressure range 0-150 MPa and remains constant in the range 150-250 MPa. This reaction of the material is likely to be related to the fact that pressure can increase the dislocation density required for plastic flow.

Egorov, S. A.

2013-11-01

115

Multicore MgB 2 wires made by hydrostatic extrusion  

NASA Astrophysics Data System (ADS)

Seven-filament MgB 2/Fe and MgB 2/Nb/Cu wires have been made by in situ process using hydrostatic extrusion, drawing and two-axial drawing deformation into the wire size of 1.1 × 1.1 mm 2. The conductors were sintered at 650 °C/0.5 h and studied in terms of field-dependent transport critical current density and thermal stability. XRD, SEM and EDX analysis were applied for structural characterization. Transport current property and compositional/structural differences are compared and discussed in connection to used powders and metallic materials.

Ková?, P.; Pachla, W.; Hušek, I.; Kulczyk, M.; Melišek, T.; Holúbek, T.; Diduszko, R.; Reissner, M.

2008-12-01

116

46 CFR 185.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2012 CFR

...DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 185.740 Periodic servicing of hydrostatic...

2012-10-01

117

46 CFR 185.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2013 CFR

...DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 185.740 Periodic servicing of hydrostatic...

2013-10-01

118

46 CFR 185.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2011 CFR

...DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 185.740 Periodic servicing of hydrostatic...

2011-10-01

119

Experiments with needle bearings  

NASA Technical Reports Server (NTRS)

Experiments and results are presented in testing needle bearings, especially in comparison with roller bearings. Reduction in coefficient of friction is discussed as well as experimental methods and recording devices.

Ferretti, Pericle

1933-01-01

120

Axial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

121

Polar Bears Change Diet  

NSDL National Science Digital Library

This radio broadcast from 2001 explains how polar bears have adjusted their diet due to the climate warming around Hudson Bay, Canada. The ringed seals that polar bears normally eat have been harder for polar bears to get to, due to disappearing ice. This has forced polar bears to begin eating harbor seals and bearded seals. The clip is 4 minutes and 15 seconds in length.

Schneider, Doug

2007-12-12

122

Grizzly bears and forestry  

Microsoft Academic Search

Today's growing demand for timber is increasing road development in once roadless forest ecosystems. Roads create both local changes in plant communities and landscape-level changes in forest connectivity. Roads also increase human access, which can be detrimental to species such as grizzly bears. Because most grizzly bear mortalities occur near roads, we examined grizzly bear attractants near roads, which could

C. L. Roever; M. S. Boyce; G. B. Stenhouse

2008-01-01

123

Donor states in GaAs under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Spectroscopic studies have been carried out for GaAs crystals under hydrostatic pressure, intended for the investigation of effective-mass donor levels associated with different conduction-band minima and the DX center. Our results reveal the existence of three donor states appearing in the band gap. These are labeled D?, D*, and DX. The donor state D?, normally observed at atmospheric pressure, successively crosses two other donor states (D* and DX) as the hydrostatic pressure exceeds 28 kbar. D*, in turn, crosses DX at pressures of about 44 kbar. From their corresponding donor-acceptor pair luminescence, we know that D? and DX have pressure dependences that track the ?- and X-band minimum, and are believed to be effective-mass donor states associated with the ?- and X-band edges, respectively. The third donor state D* has a pressure dependence that does not seem to agree with any known conduction-band minimum. However, it is in many respects similar to the DX center, although it has not, in studies of radiative emission, revealed evidence of a large lattice relaxation and photoquenching effects.

Liu, X.; Samuelson, L.; Pistol, M.-E.; Gerling, M.; Nilsson, S.

1990-12-01

124

Glycine Insertion Makes Yellow Fluorescent Protein Sensitive to Hydrostatic Pressure  

PubMed Central

Fluorescent protein-based indicators for intracellular environment conditions such as pH and ion concentrations are commonly used to study the status and dynamics of living cells. Despite being an important factor in many biological processes, the development of an indicator for the physicochemical state of water, such as pressure, viscosity and temperature, however, has been neglected. We here found a novel mutation that dramatically enhances the pressure dependency of the yellow fluorescent protein (YFP) by inserting several glycines into it. The crystal structure of the mutant showed that the tyrosine near the chromophore flipped toward the outside of the ?-can structure, resulting in the entry of a few water molecules near the chromophore. In response to changes in hydrostatic pressure, a spectrum shift and an intensity change of the fluorescence were observed. By measuring the fluorescence of the YFP mutant, we succeeded in measuring the intracellular pressure change in living cell. This study shows a new strategy of design to engineer fluorescent protein indicators to sense hydrostatic pressure. PMID:24014139

Watanabe, Tomonobu M.; Imada, Katsumi; Yoshizawa, Keiko; Nishiyama, Masayoshi; Kato, Chiaki; Abe, Fumiyoshi; Morikawa, Takamitsu J.; Kinoshita, Miki; Fujita, Hideaki; Yanagida, Toshio

2013-01-01

125

Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions  

NASA Astrophysics Data System (ADS)

Sandstones display non-linear and inelastic behaviour such as hysteresis when subjected to cyclic loading. We present three hydrostatic compaction experiments with multiple loading-unloading cycles on Berea and Darley Dale sandstones and explain their hysteretic behaviour using non-linear inelastic compaction and dilation. Each experiment included eight to nine loading-unloading cycles with increasing maximum pressure in each subsequent cycle. Different pressure-volumetric strain relations during loading and unloading were observed. During the first cycles, under relatively low pressures, not all of the volumetric strain is recovered at the end of each cycle whereas at the last cycles, under relatively high pressures, the strain is recovered and the pressure-volumetric strain hysteresis loops are closed. The observed pressure-volumetric strain relations are non-linear and the effective bulk modulus of the sandstones changes between cycles. Observations are modelled with two inelastic deformation processes: irreversible compaction caused by changes in grain packing and recoverable compaction associated with grain contact adhesion, frictional sliding on grains or frictional sliding on cracks. The irreversible compaction is suggested to reflect rearrangement of grains into a more compact mode as the maximum pressure increases. Our model describes the `inelastic compaction envelope' in which sandstone sample will follow during hydrostatic loading. Irreversible compaction occurs when pressure is greater than a threshold value defined by the `inelastic compaction envelope'.

Shalev, Eyal; Lyakhovsky, Vladimir; Ougier-Simonin, Audrey; Hamiel, Yariv; Zhu, Wenlu

2014-05-01

126

Photomultiplier tube failure under hydrostatic pressure in future neutrino detectors  

NASA Astrophysics Data System (ADS)

Failure of photomultiplier tubes (PMTs) under hydrostatic pressure is a concern in neutrino detection, specifically, in the proposed Long-Baseline Neutrino Experiment (LBNE) project. Controlled hydrostatic implosion tests were performed on prototypic PMT bulbs of 10-inch diameter and recorded using high-speed filming techniques to capture failures in detail. These high-speed videos were analyzed frame-by-frame in order to identify the origin of a crack, measure the progression of individual crack along the surface of the bulb as it propagates through the glass, and estimate crack velocity. Crack velocity was calculated for each individual crack and an average velocity was determined for all measurable cracks on each bulb. Overall, 32 cracks were measured in 9 different bulbs tested. Finite element modeling (FEM) of crack formation and growth in prototypic PMT shows stress concentration near the middle section of the PMT bulbs that correlates well with our crack velocity measurements in that section. The FEM model predicts a crack velocity value that is close to the terminal crack velocity reported. Our measurements also reveal significantly reduced crack velocities compared to terminal crack velocities measured in glasses using fracture mechanics testing and reported in literature.

Chambliss, K.; Sundaram, S. K.; Simos, N.; Diwan, M. V.

2014-10-01

127

Non-hydrostatic sound-proof equations of motion for gravity-dominated compressible flows  

NASA Astrophysics Data System (ADS)

Non-hydrostatic sound-proof equations of motion for gravity-dominated compressible flows Compressible non-hydrostatic equations of motion with density diagnosed from potential temperature through hydrostatic balance are derived from Hamilton's principle of least action. The corresponding local budgets of energy, potential vorticity and momentum are obtained. Slaving density to potential temperature suppresses the degrees of freedom supporting the propagation of acoustic waves and results in a sound-proof system. The linear normal modes and dispersion relationship for infinitesimal departures from an isothermal state of rest on f- and ?- planes are studied and found to be very accurate from hydrostatic to non-hydrostatic scales. Especially the Lamb wave and long Rossby waves are not distorted, unlike with anelastic or pseudo-incompressible systems. Compared to similar equations derived by Arakawa and Konor (2009), the unified system derived here possesses an additional term in the horizontal momentum budget. This apparent force is crucial for the derivation of a well-defined linear elliptic problem. Unlike with anelastic/pseudo-incompressible systems or the equations obtained by Arakawa and Konor (2009), the elliptic problem is vertically fourth-order, reflecting the fact that the hydrostatic constraint satisfied by density involves a vertical derivative. As with hydrostatic equations, vertical velocity is diagnosed through Richardson's equation. Our unified system has therefore precisely the same degrees of freedom as the hydrostatic primitive equations, while retaing accuracy from hydrostatic to non-hydrostatic scales. These equations may be useful as the basis of global non-hydrostatic numerical models. They also provide an accurate way to filter out the acoustic component from a given flow. Variational data assimilation systems may benefit from such a filter, restricting the optimization space to physically relevant motion. Similarly, filtering may be useful to prevent the transient emission of acoustic waves in a fully-compressible model at initialization or after physics parameterizations have acted.

Dubos, Thomas; Voitus, Fabrice

2014-05-01

128

Cryogenic Hybrid Magnetic Bearing  

NASA Technical Reports Server (NTRS)

Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.

Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.

1994-01-01

129

Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps  

NASA Technical Reports Server (NTRS)

A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs on a Windows 95/NT personal computer. The program, help files and examples are licensed by Texas A&M University Technology License Office. The study of the static and dynamic performance of two hydrostatic/hydrodynamic bearings demonstrates the importance of centrifugal and advection fluid inertia effects for operation at high rotational speeds. The first example considers a conceptual hydrostatic thrust bearing for an advanced liquid hydrogen turbopump operating at 170,000 rpm. The large axial stiffness and damping coefficients of the bearing should provide accurate control and axial positioning of the turbopump and also allow for unshrouded impellers, therefore increasing the overall pump efficiency. The second bearing uses a refrigerant R134a, and its application in oil-free air conditioning compressors is of great technological importance and commercial value. The computed predictions reveal that the LH2 bearing load capacity and flow rate increase with the recess pressure (i.e. increasing orifice diameters). The bearing axial stiffness has a maximum for a recess pressure rati of approx. 0.55. while the axial damping coefficient decreases as the recess pressure ratio increases. The computer results from three flow models are compared. These models are a) inertialess, b) fluid inertia at recess edges only, and c) full fluid inertia at both recess edges and film lands. The full inertia model shows the lowest flow rates, axial load capacity and stiffness coefficient but on the other hand renders the largest damping coefficients and inertia coefficients. The most important findings are related to the reduction of the outflow through the inner radius and the appearance of subambient pressures. The performance of the refrigerant hybrid thrust bearing is evaluated at two operating speeds and pressure drops. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The a

SanAndres, Luis

1998-01-01

130

The effect of high hydrostatic pressure on the anthocyanins of raspberry ( Rubus idaeus)  

Microsoft Academic Search

The colour stability of fruit puree made from raspberries (Rubus idaeus), which were subjected to high hydrostatic pressure, was studied by measuring the anthocyanin content. High hydrostatic pressure is an alternative method of food preservation to heat treatment. In this study, we assess the impact of high pressure on the colour molecules in raspberries. Fruit samples were pressured under 200,

Winai Suthanthangjai; Paul Kajda; Ioannis Zabetakis

2005-01-01

131

Birefringence and dispersion properties of elliptical hollow core optical fiber under hydrostatic pressure  

Microsoft Academic Search

Highly birefringent elliptical hollow core optical fiber under hydrostatic pressure is analyzed in this work using finite element method. The combined effects of thermal stress generated during fabrication and external applied stress have been considered. Birefringence increases while group velocity dispersion decreases when the fiber is under hydrostatic pressure. Higher birefringence, lower material dispersion and moderate effective area can make

Ahmad Zubair; Saima Afroz Siddiqui; M. Shah Alam

2009-01-01

132

Mechanoluminescence of ZnS:Mn phosphors excited by hydrostatic pressure steps and pressure pulses  

NASA Astrophysics Data System (ADS)

When a hydrostatic pressure step is applied rapidly on ZnS:Mn phosphor introduced into a pressure cell as oil suspension, initially the mechanoluminescence (ML) intensity increases linearly with time, attains a peak value for a particular time, and then it decreases with time (G. Alzetta, N. Minnaja, S. Santucci, Nuovo Cimento 23, 1962, 910). When a hydrostatic pressure pulse is applied onto ZnS:Mn phosphor, then two ML pulses of equal intensity are emitted; one during the application of pressure and the other during the release of pressure. In case of ZnS:Mn phosphor, at low hydrostatic pressure the energy produced during the electron-hole recombination excites the Mn2+ centres; however, at high hydrostatic pressure, the impact of accelerated electrons with the Mn2+ centres causes the light emission. Considering the piezoelectrically-induced detrapping model of ML at low pressure and the piezoelectrically-induced impact excitation model of ML at high pressure, expressions are derived for different characteristics of ML, in which a good agreement is found between the theoretical and experimental results. At low hydrostatic pressure in the range from 3 MPa to 40 MPa, piezoelectrically-induced detrapping model of ML becomes applicable in ZnS:Mn phosphors; while at high hydrostatic pressure beyond 40 MPa, the piezoelectrically-induced impact excitation model of ML becomes applicable. The ML induced by hydrostatic pressure can be used for sensing both the magnitude and rise time of applied hydrostatic pressure.

Chandra, V. K.; Chandra, B. P.; Jha, Piyush

2014-11-01

133

Nonlinear study of a misaligned hydrodynamic journal bearing  

SciTech Connect

Hydrodynamic/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The main objective of this paper is to study the nonlinear effects in a hydrodynamic journal bearing with special attention to the effects of journal axial misalignment. The numerical model that couples the Reynolds equation with the dynamics of the rotor is solved by means of a finite difference solution technique. Fluid film pressures that resulted from an iterative scheme are integrated to generate bearing supporting forces. A two-dimensional Newton-Raphson iteration method is used to locate the journal equilibrium position from which both linear and nonlinear bearing stiffness are evaluated by means of the small perturbation technique. The effects of axial misalignment on bearing equilibrium position, lubricant fluid film thickness, pressure distribution, and stiffness characteristics are examined. General conclusions are drawn from the parametric studies in load, speed, inlet temperature, and axial misalignment. 24 refs.

Choy, F.K.; Braun, M.J.; Hu, Y. (Akron Univ., OH (United States))

1993-07-01

134

Theoretical study of boron nitride modifications at hydrostatic pressures  

NASA Astrophysics Data System (ADS)

This paper presents a detailed study of boron nitride modifications at hydrostatic pressures. Cohesive properties of zinc blende (c-BN), wurtzite (w-BN), hexagonal (h-BN), rhombohedral (r-BN), and rocksalt structure are calculated by systematic optimization of unit cell parameters and atomic positions using total-energy density-functional methods. With focus on the very rarely discussed layered modifications the p-V equations of states are derived. It is confirmed that the isothermal bulk modulus of the sp2-bonded phases is more than 10 times smaller in comparison to the dense phases. Additionally, the equilibrium line of c-BN and h-BN in phase p-T diagram is calculated. According to recent experimental reports c-BN is predicted as a stable modification at standard conditions.

Albe, Karsten

1997-03-01

135

Porcine radial artery decellularization by high hydrostatic pressure.  

PubMed

Many types of decellularized tissues have been studied and some have been commercially used in clinics. In this study, small-diameter vascular grafts were made using HHP to decellularize porcine radial arteries. One decellularization method, high hydrostatic pressure (HHP), has been used to prepare the decellularized porcine tissues. Low-temperature treatment was effective in preserving collagen and collagen structures in decellularized porcine carotid arteries. The collagen and elastin structures and mechanical properties of HHP-decellularized radial arteries were similar to those of untreated radial arteries. Xenogeneic transplantation (into rats) was performed using HHP-decellularized radial arteries and an untreated porcine radial artery. Two weeks after transplantation into rat carotid arteries, the HHP-decellularized radial arteries were patent and without thrombosis. In addition, the luminal surface of each decellularized artery was covered by recipient endothelial cells and the arterial medium was fully infiltrated with recipient cells. Copyright © 2012 John Wiley & Sons, Ltd. PMID:23233238

Negishi, Jun; Funamoto, Seiichi; Kimura, Tsuyoshi; Nam, Kwangoo; Higami, Tetsuya; Kishida, Akio

2012-12-12

136

Hydrostatic factors affect the gravity responses of algae and roots  

NASA Technical Reports Server (NTRS)

The hypothesis of Wayne et al. (1990) that plant cells perceive gravity by sensing a pressure differential between the top and the bottom of the cell was tested by subjecting rice roots and cells of Caracean algae to external solutions of various densities. It was found that increasing the density of the external medium had a profound effect on the polar ratio (PR, the ratio between velocities of the downwardly and upwardly streaming cytoplasm) of the Caracean algae cells. When these cells were placed in solutions of denser compound, the PR decreased to less than 1, as the density of the external medium became higher than that of the cell; thus, the normal gravity-induced polarity was reversed, indicating that the osmotic pressure of the medium affects the cell's ability to respond to gravity. In rice roots, an increase of the density of the solution inhibited the rate of gravitropism. These results agree with predictions of a hydrostatic model for graviperception.

Staves, Mark P.; Wayne, Randy; Leopold, A. C.

1991-01-01

137

Melting of icosahedral nickel clusters under hydrostatic pressure.  

PubMed

The thermal stabilities and melting behavior of icosahedral nickel clusters under hydrostatic pressure have been studied by constant-pressure molecular dynamics simulation. The potential energy and Lindemann index are calculated. The overall melting temperature exhibits a strong dependence on pressure. The Lindemann index of solid structure before melting varies slowly and is almost independent of pressure. However, after the clusters melt completely, the Lindemann index at the overall melting point strongly depends on pressure. The overall melting temperature is found to be increasing nonlinearly with increasing pressure, while the volume change during melting decreases linearly with increasing pressure. Under a high pressure and temperature environment, similar angular distributions were found between liquid and solid structures, indicating the existence of a converging local structure. © 2014 Wiley Periodicals, Inc. PMID:25241855

Fu, Bing; Chen, Li; Wang, Feifei; Xie, Yiqun; Ye, Xiang

2014-12-01

138

Effect of hydrostatic pressure on ligand binding to hemoglobin.  

PubMed

Increase in hydrostatic pressure to 1000 atm increased the affinity of human and menhaden (Brevoortia tyrannus) hemoglobins for oxygen. With necessary assumptions about the form of the equilibrium curve, and after correction for changes in pH and volume due to pressure, the increase in affinity is about 2-fold for both hemoglobins. At pH 6.5, Hill's n for menhaden hemoglobin is near 1, and it is believed to remain in the T state, whereas human hemoglobin undergoes a T to R transition. This suggests that the R-T equilibrium is not disturbed by pressure. In direct experiments the binding of a fluorescent effector (8 hydroxy-1,3,6-pyrene (trisulfonic acid) to deoxyhemoglobin was not changed by pressure. The binding of n-butylisocyanide to hemoglobin and to myoglobin is also greater at high pressures, similarly suggesting that the R-T transition is not involved in the pressure effect. PMID:16924

Carey, F G; Knowles, F; Gibson, Q H

1977-06-25

139

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection  

NASA Astrophysics Data System (ADS)

A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly in vitro, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution or culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection in vivo; the mechanism is perfectly consistent with phage genome ejection in vitro.

Lemay, Serge G.; Panja, Debabrata; Molineux, Ian J.

2013-02-01

140

A feasibility assessment of magnetic bearings for free-piston Stirling space power converters  

NASA Technical Reports Server (NTRS)

This report describes a design and analysis study performed by Mechanical Technology Incorporated (MTI) under NASA Contract NAS3-26061. The objective of the study was to assess the feasibility and efficacy of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery of the type currently being evaluated for possible use in long-term space missions. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) system consisting of two 25-kWe free-piston Stirling engine modules. Two different versions of the RSSPC engine modules have been defined under NASA Contract NAS3-25463. These modules currently use hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Results of this study show that active magnetic bearings of the attractive electromagnetic type are technically feasible for RSSPC application provided that wire insulation with 60,000-hr life capability at 300 C can be developed for the bearing coils. From a design integration standpoint, both versions of the RSSPC were found to be conceptually amenable to magnetic support of the power piston assembly. However, only one version of the RSSPC was found to be amendable to magnetic support of the displacer assembly. Unacceptable changes to the basic engine design would be required to incorporate magnetic displacer bearings into the second version. Complete magnetic suspension of the RSSPC can potentially increase overall efficiency of the Stirling cycle power converter by 0.53 to 1.4 percent (0.15 to 0.4 efficiency points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. However, these advantages are accompanied by a 5 to 8 percent increase in specific mass of the RSSPC, depending on the RSSPC version employed. Additionally, magnetic bearings are much more complex, both mechanically and particularly electronically, than hydrostatic bearings. Accordingly, long-term stability and reliability represent areas of uncertainty for magnetic bearings. Considerable development effort will be required to establish the long-term suitability of these bearings for Stirling space power applications.

Curwen, Peter W.; Rao, Dantam K.; Wilson, Donald R.

1992-01-01

141

Bearings: Technology and needs  

NASA Technical Reports Server (NTRS)

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

Anderson, W. J.

1982-01-01

142

The Incredible Water Bear  

NSDL National Science Digital Library

This image-rich Micscape Magazine article explores how water bears can be found almost everywhere yet are still unknown to almost everybody, why there are relatively few light microscope photographs of water bears in the literature and on the Web, and how light microscopy can outperform scanning electron microscopy when viewing these animals. It includes a list of historical references, early sketches, and colorful images of water bears, also known as tardigrades.

Mach, Martin; Magazine, Micscape

143

Bear Spray Safety Program  

USGS Publications Warehouse

A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

Blome, C.D.; Kuzniar, R.L.

2009-01-01

144

Novel bidirectional air bearing  

NASA Astrophysics Data System (ADS)

Fluid lubricated bearings (ball or journal) exhibit problems of life and contamination in high speed polygonal scanners, particularly at speeds above 15,000 rpm. Grooved air bearings are limited to relatively high manufacturing cost, vertical only attitude, unidirectional rotation, and they tend to ingest debris. A plain journal air bearing is described which is bidirectional, any attitude operation, is free of whirl instability and has low manufacturing cost.

Sherman, Randy J.

1993-12-01

145

Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings, phase 2  

NASA Technical Reports Server (NTRS)

The Phase 2 (1994) Annual Progress Report presents two major report sections describing the thermal analysis of tilting- and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings. A literature review on the subject of two-phase flow in fluid film bearings and part of the proposed work for 1995 are also included. The programs delivered at the end of 1994 are named hydroflext and hydrotran. Both codes are fully compatible with the hydrosealt (1993) program. The new programs retain the same calculating options of hydrosealt plus the added bearing geometries, and unsteady flow and transient forced response. Refer to the hydroflext & hydrotran User's Manual and Tutorial for basic information on the analysis and instructions to run the programs. The Examples Handbook contains the test bearing cases along with comparisons with experimental data or published analytical values. The following major tasks were completed in 1994 (Phase 2): (1) extension of the thermohydrodynamic analysis and development of computer program hydroflext to model various bearing geometries, namely, tilting-pad hydrodynamic journal bearings, flexure-pad cylindrical bearings (hydrostatic and hydrodynamic), and cylindrical pad bearings with a simple elastic matrix (ideal foil bearings); (2) improved thermal model including radial heat transfer through the bearing stator; (3) calculation of the unsteady bulk-flow field in fluid film bearings and the transient response of a point mass rotor supported on bearings; and (4) a literature review on the subject of two-phase flows and homogeneous-mixture flows in thin-film geometries.

Sanandres, Luis

1994-01-01

146

Bearing fatigue investigation 3  

NASA Technical Reports Server (NTRS)

The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

1982-01-01

147

Bearing servicing tool  

NASA Technical Reports Server (NTRS)

A tool for removing and/or replacing bearings in situ is presented. The tool is comprised of a brace having a first end adapted to engage a first end of the bearing housing, and a second end adapted to engage a second end of the bearing housing. If the two ends of the bearing housing are different in configuration, then the respective ends of the brace are configured accordingly. An elongate guide member integral with the brace has two parts, each projecting endwise from a respective end of the brace. A removable pressure plate can be mounted on either part of the guide member for longitudinal movement therealong and has first and second ends of different configurations adapted to engage the first and second ends of the bearing. A threaded-type drive is cooperative between the guide and the pressure plate to move the pressure plate longitudinally along the guide and apply a force to the bearing, either to remove the bearing from its housing, or to emplace a new bearing in the housing.

Boyce, Rex A. (inventor)

1992-01-01

148

Bearing Thermal Performance Prediction  

NASA Technical Reports Server (NTRS)

Parameter called lubricant percent volume or cavity factor (XCAV) used primarily in calculation of ball or roller drag and, therefore, significantly affects calculated bearing-heat generation and temperature distribution. New equation accounts for sensitivity of XCAV to shaft speed, lubricant flow rate, and bearing size, and provides significant improvement over previous estimation methods.

Parker, R. J.

1986-01-01

149

Grizzly bears and forestry  

Microsoft Academic Search

We assessed the occurrence and fruit production of 13 grizzly bear foods in west-central Alberta, Canada, to better understand use of clearcuts by grizzly bears. Comparisons were made between clearcuts and upland forest stands, while specific models describing food or fruit occurrence within clearcuts were developed from canopy, clearcut age, scarification, and terrain-related variables using logistic regression. Ants, Equisetum spp.,

S. E. Nielsen; R. H. M. Munro; E. L. Bainbridge; G. B. Stenhouse; M. S. Boyce

2004-01-01

150

Linear kinematic air bearing  

NASA Technical Reports Server (NTRS)

Bearing provides continuous, smooth movement of the cat's-eye mirror, eliminating wear and deterioration of bearing surface and resulting oscillation effects in servo system. Design features self-aligning configuration; single-point, pivotal pad mounting, having air passage through it; and design of pads that allows for precise control of discharge path of air from pads.

Mayall, S. D.

1974-01-01

151

Hollow rolling element bearings  

NASA Technical Reports Server (NTRS)

A low mass rolling element with a lightweight core and hollow center was developed for use in bearings. The core is plated so as to provide a hard surface and increase the life and reliability of the high speed ball bearings.

Parker, R. J. (inventor)

1973-01-01

152

Antident Bearing-Ball Retainer  

NASA Technical Reports Server (NTRS)

Jig prevents indentation of bearing balls by hard contact with edges of inner bearing rings during assembly. Jig is retaining ring which includes fingers that separates balls and pushes them against outer bearing and out of contact with inner bearing rings. Eliminates need for ball-retaining tabs on bearing cage.

Thomas, Larry L., Jr.

1995-01-01

153

Arcturus and the Bears  

NASA Astrophysics Data System (ADS)

Arcturus is the brightest star in Bootes. The ancient Greek name Arktouros means Bear Guard. The star, however, is not close to Ursa Maior (Big She-Bear) and Ursa Minor (Little She-Bear), as the name would suggest. This curious discrepancy could be explained by the star proper motion, assuming the name Bear Guard is a remote cultural heritage. The proper motion analysis could allow us to get an insight also into an ancient myth regarding Ursa Maior. Though we cannot explain scientifically such a myth, some interesting suggestions can be obtained about its possible origin, in the context of the present knowledge of the importance of the cult of the bear both during the Palaeolithic times and for several primitive populations of modern times, as shown by the ethnological studies.

Antonello, E.

2009-08-01

154

The elastic stiffness constants and their hydrostatic pressure derivatives for TGS  

NASA Astrophysics Data System (ADS)

The thirteen adiabatic elastic stiffness moduli of triglycine sulphate (TGS) have been determined at room temperature from measurements of the ultrasound wave velocities. Results are used to describe the elastic behavior of TGS. Accidental pure mode directions have been found at 9.4 and 106.5 deg. A method has been developed for obtaining the hydrostatic pressure derivatives of the elastic constants of a monoclinic crystal from the hydrostatic pressure dependences of ultrasound wave velocities. This method has been applied to find the hydrostatic pressure derivatives of the elastic constants for TGS. There is no evidence for acoustic phonon mode softening under pressure.

Dunk, A.; Saunders, G. A.

1984-01-01

155

Study of Catcher Bearings for High Temperature Magnetic Bearing Application  

E-print Network

temperature permanent magnet based magnetic bearings. The magnetic bearings are made of high temperature resistant permanent magnets (up to 1000 degrees F). A test rig has been developed to test these magnetic bearings. The test rig mainly consists of two...

Narayanaswamy, Ashwanth

2011-08-08

156

Creep of wet gypsum aggregates under hydrostatic loading conditions  

NASA Astrophysics Data System (ADS)

Gypsum-dominated evaporite sequences are known to play an important role in controlling the mechanics of foreland thrust and nappe tectonics, as well as occasionally forming large-scale halokinetic structures associated with oil and gas accumulations. However, relatively little is known regarding the relevant deformation mechanisms and mechanical behaviour of gypsum. In this study, attention is focused on determining the compaction creep behaviour of wet granular gypsum aggregates with the aim of assessing the importance of pressure solution. Hydrostatic compaction experiments were performed at room temperature and applied effective pressures in the range 0.4-3.9 MPa, using grain sizes ranging from 15 to 125 ?m. The microstructure of the wet-tested samples showed that compaction occurred by a process of dissolution within grain contacts and precipitation on pore walls. In addition, for most of the range of conditions investigated, the mechanical data were found to be broadly consistent with models for interface-reaction-controlled grain boundary diffusional pressure solution. Combining the mechanical data with kinetic data taken from the crystal growth / dissolution literature it is suggested that for the bulk of conditions studied, creep of our wet granular gypsum aggregates was probably rate-limited by precipitation on the pore walls. This is in sharp contrast to the diffusion-controlled pressure solution creep behaviour recently reported for highly soluble salts, such as NaCl and NaNO 3, under similar conditions.

de Meer, Siese; Spiers, Christopher J.

1995-05-01

157

Scaling of the hydrostatic skeleton in the earthworm Lumbricus terrestris.  

PubMed

The structural and functional consequences of changes in size or scale have been well studied in animals with rigid skeletons, but relatively little is known about scale effects in animals with hydrostatic skeletons. We used glycol methacrylate histology and microscopy to examine the scaling of mechanically important morphological features of the earthworm Lumbricus terrestris over an ontogenetic size range from 0.03 to 12.89 g. We found that L. terrestris becomes disproportionately longer and thinner as it grows. This increase in the length to diameter ratio with size means that, when normalized for mass, adult worms gain ~117% mechanical advantage during radial expansion, compared with hatchling worms. We also found that the cross-sectional area of the longitudinal musculature scales as body mass to the ~0.6 power across segments, which is significantly lower than the 0.66 power predicted by isometry. The cross-sectional area of the circular musculature, however, scales as body mass to the ~0.8 power across segments, which is significantly higher than predicted by isometry. By modeling the interaction of muscle cross-sectional area and mechanical advantage, we calculate that the force output generated during both circular and longitudinal muscle contraction scales near isometry. We hypothesize that the allometric scaling of earthworms may reflect changes in soil properties and burrowing mechanics with size. PMID:24871920

Kurth, Jessica A; Kier, William M

2014-06-01

158

Hydrostatic pressure sensation in cells: integration into the tensegrity model.  

PubMed

Hydrostatic pressure (HP) is a mechanical stimulus that has received relatively little attention in the field of the cell biology of mechanotransduction. Generalized models, such as the tensegrity model, do not provide a detailed explanation of how HP might be detected. This is significant, because HP is an important mechanical stimulus, directing cell behaviour in a variety of tissues, including cartilage, bone, airways, and the vasculature. HP sensitivity may also be an important factor in certain clinical situations, as well as under unique environmental conditions such as microgravity. While downstream cellular effects have been well characterized, the initial HP sensation mechanism remains unclear. In vitro evidence shows that HP affects cytoskeletal polymerization, an effect that may be crucial in triggering the cellular response. The balance between free monomers and cytoskeletal polymers is shifted by alterations in HP, which could initiate a cellular response by releasing and (or) activating cytoskeleton-associated proteins. This new model fits well with the basic tenets of the existing tensegrity model, including mechanisms in which cellular HP sensitivity could be tuned to accommodate variable levels of stress. PMID:17901896

Myers, Kenneth A; Rattner, Jerome B; Shrive, Nigel G; Hart, David A

2007-10-01

159

High hydrostatic pressure treatment of porcine oocytes induces parthenogenetic activation.  

PubMed

An innovative technique called high hydrostatic pressure (HHP) treatment has recently been reported to improve the cryosurvival of gametes and embryos in certain mammalian species, including the mouse, pig, and cattle. In the present study the parthenogenetic activation (PA) of pig oocytes caused by HHP treatment was investigated in different holding media with or without Ca(2+). The efficiency of activation was tested at different pressure levels and media including T2 (HEPES-buffered TCM-199 containing 2% cattle serum), and mannitol-PVA fusion medium with (MPVA + Ca(2+)) or without Ca(2+) and Mg(2+)(MPVA). The results showed that HHP cannot induce PA in T2, but only in MPVA + Ca(2+) with low Ca(2+) concentration and MPVA without Ca(2+). The highest activation efficiency was achieved with 10 min HHP treatment using 100 or 200 bars for oocytes in MPVA + Ca(2+) or MPVA, respectively. In the light of these results, the possible source of Ca(2+) during activation was investigated. It was found that even after a total of 30-min wash with TL-HEPES-PVA buffer without Ca(2+) before HHP treatment in MPVA, the oocytes could still be activated, indicating the possibility of an intracellular Ca(2+) source caused cytoplasmic free Ca(2+) elevation. In conclusion, parthenogenetic activation could be induced by HHP in certain holding media with low or zero Ca(2+) content. Further experiments are needed to identify the exact mechanisms of activation. PMID:20698785

Lin, Lin; Pribenszky, Csaba; Molnár, Miklós; Kragh, Peter M; Du, Yutao; Zhang, Xiuqing; Yang, Huanming; Bolund, Lars; Callesen, Henrik; Macháty, Zoltán; Vajta, Gábor

2010-08-01

160

Hydrostatic gas distributions: global estimates of temperature and abundance  

E-print Network

Estimating the temperature and metal abundance of the intracluster and the intragroup media is crucial to determine their global metal content and to determine fundamental cosmological parameters. When a spatially resolved temperature or abundance profile cannot be recovered from observations (e.g., for distant objects), or deprojection is difficult (e.g., due to a significant non-spherical shape), only global average temperature and abundance are derived. After introducing a general technique to build hydrostatic gaseous distributions of prescribed density profile in potential wells of any shape, we compute the global mass weighted and emission weighted temperature and abundance for a large set of barotropic equilibria and an observationally motivated abundance gradient. We also compute the spectroscopic-like temperature that is recovered from a single temperature fit of observed spectra. The derived emission weighted abundance and temperatures are higher by 50% to 100% than the corresponding mass weighted quantities, with overestimates that increase with the gas mean temperature. Spectroscopic temperatures are intermediate between mass and luminosity weighted temperatures. Dark matter flattening does not lead to significant differences in the values of the average temperatures or abundances with respect to the corresponding spherical case (except for extreme cases).

L. Ciotti; S. Pellegrini

2008-04-10

161

Optimization of hydrostatic transmissions by means of virtual instrumentation technique  

NASA Astrophysics Data System (ADS)

Obtaining mathematical models, as close as possible to physical phenomena which are intended to be replicated or improved, help us in deciding how to optimize them. The introduction of computers in monitoring and controlling processes caused changes in technological systems. With support from the methods for identification of processes and from the power of numerical computing equipment, researchers and designers can shorten the period for development of applications in various fields by generating a solution as close as possible to reality, since the design stage [1]. The paper presents a hybrid solution of modeling / simulation of a hydrostatic transmission with mixed adjustment. For simulation and control of the examined process we have used two distinct environments, AMESim and LabVIEW. The proposed solution allows coupling of the system's model to the software control modules developed using virtual instrumentation. Simulation network of the analyzed system was "tuned" and validated by an actual model of the process. This paper highlights some aspects regarding energy and functional advantages of hydraulic transmissions based on adjustable volumetric machines existing in their primary and secondary sectors [2].

Ion Guta, Dragos Daniel; Popescu, Teodor Costinel; Dumitrescu, Catalin

2010-11-01

162

Raman study of radiation-damaged zircon under hydrostatic compression  

NASA Astrophysics Data System (ADS)

Pressure-induced changes of Raman band parameters of four natural, gem-quality zircon samples with different degrees of self-irradiation damage, and synthetic ZrSiO4 without radiation damage, have been studied under hydrostatic compression in a diamond anvil cell up to ~10 GPa. Radiation-damaged zircon shows similar up-shifts of internal SiO4 stretching modes at elevated pressures as non-damaged ZrSiO4. Only minor changes of band-widths were observed in all cases. This makes it possible to estimate the degree of radiation damage from the width of the ?3(SiO4) band of zircon inclusions in situ, almost independent from potential “fossilized pressures” or compressive strain acting on the inclusions. An application is the non-destructive analysis of gemstones such as corundum or spinel: broadened Raman bands are a reliable indicator of self-irradiation damage in zircon inclusions, whose presence allows one to exclude artificial color enhancement by high-temperature treatment of the specimen.

Nasdala, Lutz; Miletich, Ronald; Ruschel, Katja; Váczi, Tamás

2008-12-01

163

Sex Conversion Induced by Hydrostatic Pressure in the Marine Copepod Tigriopus californicus.  

PubMed

High hydrostatic pressure applied to the naupliar larval stages of the marine copepod Tigriopus californicus converts some individuals that would have become males into females. The copepodid stages are not sensitive to pressureinduced conversion. PMID:17743973

Vacquier, V D; Belser, W L

1965-12-17

164

Identifying and quantifying nonconservative energy production/destruction terms in hydrostatic Boussinesq primitive equation models  

E-print Network

Identifying and quantifying nonconservative energy production/destruction terms in hydrostatic that physical inconsistencies between thermodynamics and dynamics usually introduce nonconservative production/destruction terms in the local total energy balance equation in numerical ocean general circulation models (OGCMs

Tailleux, Remi

165

46 CFR 122.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2013 CFR

...VESSELS CARRYING MORE THAN 150 PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 122.740 Periodic servicing of hydrostatic...

2013-10-01

166

46 CFR 122.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2011 CFR

...VESSELS CARRYING MORE THAN 150 PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 122.740 Periodic servicing of hydrostatic...

2011-10-01

167

46 CFR 122.740 - Periodic servicing of hydrostatic release units.  

Code of Federal Regulations, 2012 CFR

...VESSELS CARRYING MORE THAN 150 PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS OPERATIONS Operational Readiness, Maintenance, and Inspection of Lifesaving Equipment § 122.740 Periodic servicing of hydrostatic...

2012-10-01

168

Ball Bearing Mechanics  

NASA Technical Reports Server (NTRS)

Load-deflection relationships for different types of elliptical contacts such as those found in a ball bearing are developed. Simplified expressions that allow quick calculations of deformation to be made simply from a knowledge of the applied load, the material properties, and the geometry of the contacting elements are presented. Ball bearings subjected to radial, thrust and combined ball loads are analyzed. A design criterion for fatigue life of ball bearings is developed. The section of a satisfactory lubricant, as well as describing systems that provide a constant flow of lubricant to the contact, is considered.

Hamrock, B. J.; Dowson, D.

1981-01-01

169

EVOLUTION OF THE MERGER-INDUCED HYDROSTATIC MASS BIAS IN GALAXY CLUSTERS  

SciTech Connect

In this work, we examine the effects of mergers on the hydrostatic mass estimate of galaxy clusters using high-resolution Eulerian cosmological simulations. We utilize merger trees to isolate the last merger for each cluster in our sample and follow the time evolution of the hydrostatic mass bias as the systems relax. We find that during a merger, a shock propagates outward from the parent cluster, resulting in an overestimate in the hydrostatic mass bias. After the merger, as a cluster relaxes, the bias in hydrostatic mass estimate decreases but remains at a level of -5%-10% with 15%-20% scatter within r{sub 500}. We also investigate the post-merger evolution of the pressure support from bulk motions, a dominant cause of this residual mass bias. At r{sub 500}, the contribution from random motions peaks at 30% of the total pressure during the merger and quickly decays to {approx}10%-15% as a cluster relaxes. Additionally, we use a measure of the random motion pressure to correct the hydrostatic mass estimate. We discover that 4 Gyr after mergers, the direct effects of the merger event on the hydrostatic mass bias have become negligible. Thereafter, the mass bias is primarily due to residual bulk motions in the gas which are not accounted for in the hydrostatic equilibrium equation. We present a hydrostatic mass bias correction method that can recover the unbiased cluster mass for relaxed clusters with 9% scatter at r{sub 500} and 11% scatter in the outskirts, within r{sub 200}.

Nelson, Kaylea; Nagai, Daisuke [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Rudd, Douglas H.; Shaw, Laurie, E-mail: kaylea.nelson@yale.edu [Department of Physics, Yale University, New Haven, CT 06520 (United States)

2012-06-01

170

High hydrostatic pressure processing on microstructure of probiotic low-fat yogurt  

Microsoft Academic Search

The effect of milk processing on the microstructure of probiotic low-fat yogurt was studied. Skim milk fortified with skim milk powder was subjected to three treatments prior to innoculation: thermal treatment at 85°C for 30min, high hydrostatic pressure at 676MPa for 5min, and combined treatments of high hydrostatic pressure (HHP) and heat. The processed milk was then fermented by using

A. L. B. Penna; G. V. Barbosa-Cánovas

2007-01-01

171

Development and trend of high-speed hydrodynamic and hydrostatic hybrid spindle unit  

Microsoft Academic Search

High-speed hydrodynamic and hydrostatic hybrid spindle unit is a new product of spindle in recent years, and it is the most promising high-speed spindle product to be developed with our own intellectual property and brand in the field of high- speed spindle in China. By researching in the current development in high-speed hydrodynamic and hydrostatic hybrid spindle unit and the

Fengkui Cui; Peng Liu

2011-01-01

172

Day-night variations in malate concentration, osmotic pressure, and hydrostatic pressure in Cereus validus  

SciTech Connect

Malate concentration and stem osmotic pressure concomitantly increase during nighttime CO/sub 2/ fixation and then decrease during the daytime in the obligate Crassulacean acid metabolism (CAM) plant, Cereus validus (Cactaceae). Changes in malate osmotic pressure calculated using the Van't Hoff relation match the changes in stem osmotic pressure, indicating that changes in malate level affected the water relations of the succulent stems. In contrast to stem osmotic pressure, stem water potential showed little day-night changes, suggesting that changes in cellular hydrostatic pressure occurred. This was corroborated by direct measurements of hydrostatic pressure using the Juelich pressure probe where a small oil-filled micropipette is inserted directly into chlorenchyma cells, which indicated a 4-fold increase in hydrostatic pressure from dusk to dawn. A transient increase of hydrostatic pressure at the beginning of the dark period was correlated with a short period of stomatal closing between afternoon and nighttime CO/sub 2/ fixation, suggesting that the rather complex hydrostatic pressure patterns could be explained by an interplay between the effects of transpiration and malate levels. A second CAM plant, Agave deserti, showed similar day-night changes in hydrostatic pressure in its succulent leaves. It is concluded that, in addition to the inverted stomatal rhythm, the oscillations of malate markedly affect osmotic pressures and hence water relations of CAM plants. 13 references, 4 figures.

Luettge, U.; Nobel, P.S.

1984-07-01

173

Nanoprecipitation in bearing steels  

Microsoft Academic Search

?-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C–1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to

A. T. W. Barrow; P. E. J. Rivera-Díaz-del-Castillo

2011-01-01

174

Load responsive hydrodynamic bearing  

DOEpatents

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)

2002-01-01

175

Hydrostatic strain enhancement in laterally confined SiGe nanostripes  

NASA Astrophysics Data System (ADS)

Strain engineering in SiGe nanostructures is fundamental for the design of optoelectronic devices at the nanoscale. Here we explore a new strategy, where SiGe structures are laterally confined by the Si substrate, to obtain high tensile strain yet avoid the use of external stressors, thus improving the scalability. Spectromicroscopy techniques, finite element method simulations, and ab initio calculations are used to investigate the strain state of laterally confined Ge-rich SiGe nanostripes. Strain information is obtained by tip-enhanced Raman spectroscopy with an unprecedented lateral resolution of ˜30 nm. The nanostripes exhibit a large tensile hydrostatic strain component, which is maximal at the center of the top free surface and becomes very small at the edges. The maximum lattice deformation is larger than the typical values of thermally relaxed Ge/Si(001) layers. This strain enhancement originates from a frustrated relaxation in the out-of-plane direction, resulting from the combination of the lateral confinement induced by the substrate side walls and the plastic relaxation of the misfit strain in the (001) plane at the SiGe/Si interface. The effect of this tensile lattice deformation at the stripe surface is probed by work function mapping, which is performed with a spatial resolution better than 100 nm using x-ray photoelectron emission microscopy. The nanostripes exhibit a positive work function shift with respect to a bulk SiGe alloy, quantitatively confirmed by electronic structure calculations of tensile-strained configurations. The present results have a potential impact on the design of optoelectronic devices at a nanometer-length scale.

Vanacore, G. M.; Chaigneau, M.; Barrett, N.; Bollani, M.; Boioli, F.; Salvalaglio, M.; Montalenti, F.; Manini, N.; Caramella, L.; Biagioni, P.; Chrastina, D.; Isella, G.; Renault, O.; Zani, M.; Sordan, R.; Onida, G.; Ossikovski, R.; Drouhin, H.-J.; Tagliaferri, A.

2013-09-01

176

Splined Ball-Bearing Carrier  

NASA Technical Reports Server (NTRS)

Ball-bearing carrier includes splined outer surface mating with slightly larger splined inner surface of housing and provides constant deadband, unaffected by movements of other components. Deadband needed to establish radial spring rate and provide for axial movement of bearing for thrust balance. Bearing carrier and bearing intended for use in high-pressure turbopump.

Moore, Jerry H.

1992-01-01

177

American Black Bear: Ursus americanus  

E-print Network

3/21/2011 1 USFWS American Black Bear: Ursus americanus www.bear.org LDWF Historic Distribution Bear: Ursus americanus Louisiana Florida Eastern Olympic New Mexico California Cinnamon Mexican: Ursus americanus luteolus American black bear Historically abundant in Louisiana, eastern Texas

Gray, Matthew

178

Fault tolerant magnetic bearings  

SciTech Connect

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.

Maslen, E.H.; Sortore, C.K.; Gillies, G.T.; Williams, R.D.; Fedigan, S.J. [Univ. of Virginia, Charlottesville, VA (United States); Aimone, R.J. [Mobile Technology Co., Paulsboro, NJ (United States)

1999-07-01

179

Solving bearing overheating problems  

SciTech Connect

Overheating is a major indicator, along with vibration and noise, of an underlying problem affecting a bearing or related components. Because normal operating temperatures vary widely from one application to another, no single temperature is a reliable sign of overheating in every situation. By observing an application when it is running smoothly, a technician can establish a benchmark temperature for a particular bearing arrangement. Wide deviations from this accepted norm generally indicate troublesome overheating. The list of possible causes of over-heating ranges from out-of-round housings and oversize shaft diameters to excessive lubrication and bearing preloading. These causes fall into two major categories: improper or faulty lubrication and mechanical problems, such as incorrect fits and tolerances. These are discussed along with solutions.

Jendzurski, T. [SKF Bearing Services, King of Prussia, PA (United States)

1995-05-08

180

Partial tooth gear bearings  

NASA Technical Reports Server (NTRS)

A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

Vranish, John M. (Inventor)

2010-01-01

181

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

2000-01-01

182

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

Methods and apparatus are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

1999-01-01

183

Lubricant effects on bearing life  

NASA Technical Reports Server (NTRS)

Lubricant considerations for rolling-element bearings have within the last two decades taken on added importance in the design and operation of mechanical systems. The phenomenon which limits the useful life of bearings is rolling-element or surface pitting fatigue. The elastohydrodynamic (EHD) film thickness which separates the ball or roller surface from those of the raceways of the bearing directly affects bearing life. Chemical additives added to the lubricant can also significantly affect bearings life and reliability. The interaction of these physical and chemical effects is important to the design engineer and user of these systems. Design methods and lubricant selection for rolling-element bearings are presented and discussed.

Zaretsky, Erwin V.

1986-01-01

184

Bearing-Cartridge Damping Seal  

NASA Technical Reports Server (NTRS)

In proposed design for improved ball-bearing cartridge, damping seal in form of thin-layer fluid journal bearing incorporated into cartridge. Damping seal acts as auxiliary bearing, relieving bearing balls of significant portions of both static and dynamic bearing loads. Damping from seal reduces dynamic loads even further by reducing amplitude of vibrations in second vibrational mode of rotor, which mode occurs when rotor turning at nearly full operating speed. Intended for use in high-pressure-oxygen turbopump of Space Shuttle main engine, also applicable to other turbomachinery bearings.

Goggins, David G.; Scharrer, Joseph K.; Chen, Wei C.

1991-01-01

185

Flexure Bearing Reduces Startup Friction  

NASA Technical Reports Server (NTRS)

Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.

Clingman, W. Dean

1991-01-01

186

Hybrid superconductor magnet bearings  

NASA Astrophysics Data System (ADS)

Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

Chu, Wei-Kan

1995-04-01

187

History of ball bearings  

NASA Technical Reports Server (NTRS)

The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.

Dowson, D.; Hamrock, B. J.

1981-01-01

188

The Teddy Bears' Disc.  

ERIC Educational Resources Information Center

Reports an evaluation of the Teddy Bear disc, an interactive videodisc developed at the Open University for a second-level course in metallurgy and materials technology. Findings from observation of students utilizing the videodisc are reviewed; successful design features and design problems are considered; and development costs are outlined. (MBR)

Laurillard, Diana

1985-01-01

189

Bear vs Bee  

NSDL National Science Digital Library

This interactive Java applet is a game that challenges a student to solve problems by using logic and rudimentary engineering skills. The goal in each case is to create a conveyance that gets the bear to the pot of honey, avoiding the bees. The game has 32 stages of increasing complexity.

2012-01-01

190

Magnetically leviated superconducting bearing  

DOEpatents

A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.

Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT)

1993-01-01

191

Titan's Hydrostatic Figure and a Possible Dynamic Tidal Variation  

NASA Astrophysics Data System (ADS)

An archive of radio Doppler data from the Cassini mission can be found in NASA's PDS Atmospheres Node as a series of binary files called Orbit Data Files (ODF). We have downloaded six ODFs from the Cassini mission for six Titan gravity passes T11 (27-Feb-2006), T22 (28-Dec-2006), T33 (29-Jun-2007), T45 (31-Jul-2008), T68 (20-May-2010) and T74 (18-Feb-2011). After converting to text files with JPL space-navigation software (ODDUMP), we convert the observed Doppler shift for the Cassini spacecraft to radial velocity along the line of sight (LOS) at one-second sample interval. These data can be fit by a numerical integration of the equations of motion for the craft with respect to Titan, and a subsequent projection of the velocity so obtained along the LOS. The orbital parameters are represented by six standard Kepler elements with the plane of sky as the fundamental reference system, the system used for spectroscopic binary stars. While the systemic velocity Vs is taken as a constant for binary stars, it is represented for spacecraft by six parameters in a function developed for the Doppler detection of gravitational waves. We adopt well-determined values for the GM of Titan and Saturn and add a 13th gravity parameter C22 for an ellipsoidal hydrostatic Titan distorted by the Saturn tide and synchronous rotation (J2 = (10/3) C22). Also, we adopt the IAU definition for the pole and prime meridian of Titan in the ICRF/J2000 reference system. The interval of observation for each flyby is held to two hours, centered as closely as possible on the time of closest approach to Titan. This interval is sufficiently long for purposes of including all the detectable signal from C22, but short enough that spacecraft-generated translational forces can be neglected. By iterating on a linear least-squares system, 13 converged parameters and associated covariance matrix are found by singular-value decomposition of the least-squares design matrix for each of the six flybys. With reasonably good starting conditions from JPL's Horizons web site, convergence is achieved in about 10 iterations. The weighted mean of the six independent values of C22 is (10.479 ± 0.074) × 10-6, in good agreement with published values by the Cassini Radio Science Team, especially SOL1a at (10.121 ± 0.029) × 10-6. However, our independent analysis of the data does not result in a significantly improved fit when a 14th parameter, the Love number k2, is added to the parameter list. It seems that a dynamic tidal variation is not required in order to fit the data, even though it might very well represent a more realistic fitting model.

Anderson, J. D.; Schubert, G.

2012-12-01

192

Numerical Simulation of Damage during Forging with Superimposed Hydrostatic Pressure by Active Media  

SciTech Connect

The effective reduction of energy consumption and a reasonable treatment of resources can be achieved by minimizing a component's weight using lightweight metals. In this context, aluminum alloys play a major role. Due to their material-sided restricted formability, the mentioned aluminum materials are difficult to form. The plasticity of a material is ascertained by its maximum forming limit. It is attained, when the deformation causes mechanical damage within the material. Damage of that sort is reached more rapidly, the greater the tensile strength rate in relation to total tension rate. A promising approach of handling these low ductile, high-strength aluminum alloys within a forming process, is forming with a synchronized superposition of comprehensive stress by active media such as by controlling oil pressure. The influence of superimposed hydrostatic pressure on the flow stress was analyzed as well as the formability for different procedures at different hydrostatic pressures and temperature levels. It was observed that flow stress is independent of superimposed hydrostatic pressure. Neither the superimposed pressure has an influence on the plastic deformation, nor does a pressure dependent material hardening due to increasing hydrostatic pressure take place. The formability increases with rising hydrostatic pressure. The relative gain at room temperature and increase of the superimposed pressure from 0 to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore in this paper, based on these experimental observations, it is the intended to develop a numerical simulation in order to predict ductile damage that occurs in the bulk forging process with superimposed hydrostatic pressure based Lemaitre's damage model.

Behrens, B.-A.; Hagen, T.; Roehr, S.; Sidhu, K. B. [Institute for Metal Forming and Metal-Forming Machines, Leibniz University of Hanover, An der Universitaet 2, 30823 Garbsen (Germany)

2007-05-17

193

Numerical Simulation of Damage during Forging with Superimposed Hydrostatic Pressure by Active Media  

NASA Astrophysics Data System (ADS)

The effective reduction of energy consumption and a reasonable treatment of resources can be achieved by minimizing a component's weight using lightweight metals. In this context, aluminum alloys play a major role. Due to their material-sided restricted formability, the mentioned aluminum materials are difficult to form. The plasticity of a material is ascertained by its maximum forming limit. It is attained, when the deformation causes mechanical damage within the material. Damage of that sort is reached more rapidly, the greater the tensile strength rate in relation to total tension rate. A promising approach of handling these low ductile, high-strength aluminum alloys within a forming process, is forming with a synchronized superposition of comprehensive stress by active media such as by controlling oil pressure. The influence of superimposed hydrostatic pressure on the flow stress was analyzed as well as the formability for different procedures at different hydrostatic pressures and temperature levels. It was observed that flow stress is independent of superimposed hydrostatic pressure. Neither the superimposed pressure has an influence on the plastic deformation, nor does a pressure dependent material hardening due to increasing hydrostatic pressure take place. The formability increases with rising hydrostatic pressure. The relative gain at room temperature and increase of the superimposed pressure from 0 to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore in this paper, based on these experimental observations, it is the intended to develop a numerical simulation in order to predict ductile damage that occurs in the bulk forging process with superimposed hydrostatic pressure based Lemaitre's damage model.

Behrens, B.-A.; Hagen, T.; Röhr, S.; Sidhu, K. B.

2007-05-01

194

Coexistence of Dirac and massive carriers in ?-(BEDT-TTF)2I3 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Transport measurements were performed on the organic layered compound ?-(BEDT-TTF)2I3 under hydrostatic pressure. The carrier types, densities, and mobilities are determined from the magnetoconductance of ?-(BEDT-TTF)2I3. While evidence of high-mobility massless Dirac carriers has already been given, we report here their coexistence with low-mobility massive holes. This coexistence seems robust as it has been found up to the highest studied pressure. Our results are in agreement with recent DFT calculations of the band structure of this system under hydrostatic pressure. A comparison with graphene Dirac carriers has also been done.

Monteverde, M.; Goerbig, M. O.; Auban-Senzier, P.; Navarin, F.; Henck, H.; Pasquier, C. R.; Mézière, C.; Batail, P.

2013-06-01

195

Particle migration through sealed bearings  

SciTech Connect

Tests were performed to determine the ability of various types of shielded bearings to isolate particulate from a clean environment in support of the Direct Optical Initiation (DOI) program. In the DOI firing system, a stronglink mechanism will share the same environment with a high-powered laser which needs uncontaminated optics to perform properly. Two commercially available shielded and sealed bearings were tested along with a sealed bearing designed at Allied Signal Inc., Kansas City Division (KCD). The KCD-designed bearing proved to be the best barrier, but the torque required to function the bearing was magnitudes above the commercial bearings. The commercial sealed bearing was an effective barrier, allowing a small fraction of particles to migrate through, and had a relatively low running torque. The shielded bearing was not acceptable as a particle barrier.

Sundvold, P.D.

1993-08-01

196

Magnetic bearings grow more attractive  

SciTech Connect

Advances in materials and electronics have enabled designers to devise simpler, smaller magnetic bearings. As a result, costs have dropped, widening the applications for these very-low-friction devices. Avcon (Advanced Controls Technology) has patented a permanent-magnet bias actively controlled bearing. Here high-energy rare earth permanent-magnet materials supply the basic bearing load levitation, while servo-driven electromagnets generate stabilization and centering forces for motion contol. Previous heavy-duty magnetic bearings used electromagnets entirely for suspension and control, which led to large bearings and control systems with higher power requirements. Avcon has developed several types of permanent-magnet bias bearings. The simplest is the radial repulsion bearing. Avcon's homopolar permanent-magnet bias active bearing is the most versatile of the company's designs.

Not Available

1993-10-01

197

Compliant hydrodynamic fluid journal bearing  

NASA Technical Reports Server (NTRS)

An air bearing structure is described that prevents destructive bending moments within the top foil. Welds are eliminated by mounting the top bearing foil in the bearing cartridge sleeve without using a space block. Tabs or pins at the end of the top bearing foil are restrained by slots or stops formed in the cartridge sleeve. These structural members are free to move in a direction normal to the shaft while being restrained from movement in the direction of shaft rotation.

Warren, E. L. (inventor)

1985-01-01

198

Research Trends on Magnetic Bearings  

Microsoft Academic Search

Use of magnetic bearings for high-speed rotor and application in clean environment or in special circumstance have been gradually increasing. This article overviews research trends and application presented before the Eighth International Symposium on Magnetic Bearings (ISMB-8). Interesting research topics are the combined realization of motor and magnetic bearing, low loss magnetic bearings and self-sensing techniques. New application fields include

Yohji Okada; Kenzo Nonami

2003-01-01

199

Effect of hydrostatic pressure on the crystal structure of sodium oxalate: X-ray diffraction study and ab initio simulations  

E-print Network

Effect of hydrostatic pressure on the crystal structure of sodium oxalate: X-ray diffraction study diffraction structure analysis / X-ray diffraction / Sodium oxalate Abstract. Effect of hydrostatic pressures isosymmetric first-order phase transition without hysteresis occurred. The orienta- tion of the oxalate anions

Oganov, Artem R.

200

First order ball bearing kinematics  

NASA Technical Reports Server (NTRS)

Two first order equations are given connecting geometry and internal motions in an angular contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.

Kingbury, E.

1984-01-01

201

Night of the Bear  

NSDL National Science Digital Library

The NOAA Ocean Exploration program strives to engage broad audiences to enhance America's environmental literacy through the excitement of ocean discovery. Increasing this literacy requires high-quality, effective collaborations between ocean explorers and America's teachers. NOAA is forming such collaborations to reach out in new ways to the public to improve the literacy of learners with respect to ocean issues. This site is a daily log of exploration in the Arctic and research on the Polar Bear.

Debenham, Casey; Timmermans, Mary-Louise

2002-08-25

202

Big Bear Solar Observatory  

NASA Astrophysics Data System (ADS)

Big Bear Solar Observatory (BBSO) is located at the end of a causeway in a mountain lake more than 2 km above sea level. The site has more than 300 sunny days a year and a natural inversion caused by the lake which makes for very clean images. BBSO is the only university observatory in the US making high-resolution observations of the Sun. Its daily images are posted at http://www.bbso.njit.e...

Murdin, P.

2000-11-01

203

Laser glazed bearings  

SciTech Connect

In the past decade high power, reliable, carbon dioxide lasers have become commercially available. Laser glazing is a process in which a focused laser beam is used to melt a very small portion of a component. As the beam moves away from the melted region, the underlying mass of the component causes the liquid pool to rapidly solidify. A major advantage of laser glazing is that the refined structure is only created in areas where high load carrying capacity is required. Initially rods manufactured from BG 42 and M 50 steels were laser glazed. Laser glazing transformed the normal, fine grain, martensitic steel matrix into a very fine dendritic microstructure. The carbides in the laser glazed material were greatly reduced in size due to very rapid solidification. Using a standard ball/rod rolling contact fatigue tester, enhanced rolling contact fatigue life was realized from the laser glazing process. LM 12749 tapered roller bearing cones were fabricated from M 50 high speed steel and laser glazed. At 200% catalog load, the L{sub 15.9%} life of the laser glazed M 50 bearings was 370% greater than the wrought cones. Similarly, when tested at 300% catalog load, the laser glazed bearings had L{sub 15.9%} life 580% greater than the wrought cones. Laser processing has been applied to 440 C stainless steel. In this alloy similar reduction in the size and distribution of large chromium carbides was achieved. The glazed 440 C was approximately 20 Knoop hardness points higher than the wrought alloy. Examples and properties of glazed microstructures in ball bearings and other alloy systems are discussed.

Hetzner, D.W. [Timken Co., Canton, OH (United States)

1998-12-31

204

Magnetic translator bearings  

NASA Technical Reports Server (NTRS)

A magnetic bearing system for enabling translational motion includes a carriage and a shaft for movably supporting the carriage; a first magnetic bearing fixed to one of the carriage and shaft and slidably received in a first channel of the other of the carriage and shaft. The first channel is generally U shaped with two side walls and a back wall. The magnetic bearing includes a pair of spaced magnetic pole pieces, each pole piece having a pair of electromagnetic coils mounted on poles on opposite ends of the pole piece proximate the side walls, and a third electromagnetic coil mounted on a pole of the pole piece proximate the backwall; a motion sensor for sensing translational motion along two axes and rotationally about three axes of the carriage and shaft relative to each other; and a correction circuit responsive to the sensor for generating a correction signal to drive the coils to compensate for any misalignment sensed between the carriage and the shaft.

Hockney, Richard L. (Inventor); Downer, James R. (Inventor); Eisenhaure, David B. (Inventor); Hawkey, Timothy J. (Inventor); Johnson, Bruce G. (Inventor)

1990-01-01

205

Anti-backlash gear bearings  

NASA Technical Reports Server (NTRS)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.

Vranish, John M. (Inventor)

2009-01-01

206

Hybrid Bearing Prognostic Test Rig  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center has developed a new Hybrid Bearing Prognostic Test Rig to evaluate the performance of sensors and algorithms in predicting failures of rolling element bearings for aeronautics and space applications. The failure progression of both conventional and hybrid (ceramic rolling elements, metal races) bearings can be tested from fault initiation to total failure. The effects of different lubricants on bearing life can also be evaluated. Test conditions monitored and recorded during the test include load, oil temperature, vibration, and oil debris. New diagnostic research instrumentation will also be evaluated for hybrid bearing damage detection. This paper summarizes the capabilities of this new test rig.

Dempsey, Paula J.; Certo, Joseph M.; Handschuh, Robert F.; Dimofte, Florin

2005-01-01

207

Simple Experimental Procedure under Quasi-Hydrostatic Pressure up to 15 GPa at Low Temperature  

Microsoft Academic Search

We have demonstrated the precise measurement of electrical resistance under high pressure at low temperature. By using Bridgman anvils made of tungsten carbide, quasi-hydrostatic pressure is generated up to ˜15 GPa in the working space, which is one order of magnitude larger than that of a typical diamond anvil cell. The application of this technique is demonstrated by the measurement

Masashi Ohashi; Gendo Oomi

2009-01-01

208

Hydrostatic pressure as the controlling factor in the depth distribution of Eurasian watermilfoil, Myriophyllum spicatum L  

Microsoft Academic Search

These experimental studies have shown that this plant will grow successfully at pressures encountered in water at depths as great as 17 m. When there were suitable levels of light, temperature, nutrients and aeration, the plants grown under constant hydrostatic pressure for three weeks showed variations in the measured amounts of new growth but no measure could be associated with

H. M. Dale

1981-01-01

209

Hydrostatic Pressure Affects In Vitro Maturation of Oocytes and Follicles and Increases Granulosa Cell Death  

PubMed Central

Objective: This study examines the effects of hydrostatic pressure on in vitro maturation (IVM) of oocytes derived from in vitro grown follicles. Materials and Methods: In this experimental study, preantral follicles were isolated from 12-day-old female NMRI mice. Each follicle was cultured individually in Alpha Minimal Essential Medium (?-MEM) under mineral oil for 12 days. Then, follicles were induced for IVM and divided into two groups, control and experiment. In the experiment group follicles were subjected to 20 mmHg pressure for 30 minutes and cultured for 24-48 hours. We assessed for viability and IVM of the oocytes. The percentage of apoptosis in cumulus cells was determined by the TUNEL assay. A comparison between groups was made using the student’s t test. Results: The percentage of metaphase II oocytes (MII) increased in hydrostatic pressuretreated follicles compared to controls (p<0.05). Cumulus cell viability reduced in hydrostatic pressure-treated follicles compared to controls (p<0.05). Exposure of follicles to pressure increased apoptosis in cumulus cells compared to controls (p<0.05). Conclusion: Hydrostatic pressure, by inducing apoptosis in cumulus cells, participates in the cumulus oocyte coupled relationship with oocyte maturation. PMID:24381852

Rashidi, Zahra; Azadbakht, Mehri; Amini, Ali; Karimi, Isac

2014-01-01

210

Regulation of Cell Cycle and Stress Responses to Hydrostatic Pressure in Fission Yeast  

PubMed Central

We have investigated the cellular responses to hydrostatic pressure by using the fission yeast Schizosaccharomyces pombe as a model system. Exposure to sublethal levels of hydrostatic pressure resulted in G2 cell cycle delay. This delay resulted from Cdc2 tyrosine-15 (Y-15) phosphorylation, and it was abrogated by simultaneous disruption of the Cdc2 kinase regulators Cdc25 and Wee1. However, cell cycle delay was independent of the DNA damage, cytokinesis, and cell size checkpoints, suggesting a novel mechanism of Cdc2-Y15 phosphorylation in response to hydrostatic pressure. Spc1/Sty1 mitogen-activated protein (MAP) kinase, a conserved member of the eukaryotic stress-activated p38, mitogen-activated protein (MAP) kinase family, was rapidly activated after pressure stress, and it was required for cell cycle recovery under these conditions, in part through promoting polo kinase (Plo1) phosphorylation on serine 402. Moreover, the Spc1 MAP kinase pathway played a key role in maintaining cell viability under hydrostatic pressure stress through the bZip transcription factor, Atf1. Further analysis revealed that prestressing cells with heat increased barotolerance, suggesting adaptational cross-talk between these stress responses. These findings provide new insight into eukaryotic homeostasis after exposure to pressure stress. PMID:17699598

George, Vinoj T.; Brooks, Gavin

2007-01-01

211

Germination and inactivation of Bacillus subtilis spores induced by moderate hydrostatic pressure  

E-print Network

1 Germination and inactivation of Bacillus subtilis spores induced by moderate hydrostatic pressure-pressure treatments. Bacillus subtilis spores were first subjected to different pressure treatments ranging from 90 with any holding time or pressure level. Keywords: bacterial spores; Bacillus subtilis; high pressure

Paris-Sud XI, Université de

212

Evaluation of high hydrostatic pressure effects on bovine red blood cells and platelets  

Microsoft Academic Search

The objective of this study was to investigate the effects of high hydrostatic pressure (HHP) on the stability of red blood cells (RBCs) and platelets. Bovine blood cells (n=5) were treated with the pressure of 55, 110, 154 and 220 MPa at 25 °C for 5 min. Light microscopy, atomic force microscopy and flow cytometry studies revealed that RBCs were morphologically stable up

Cagatay Ceylan; Mete Severcan; Faruk Bozoglu; Feride Severcan

2009-01-01

213

Hydrostatic pressures developed by osmotically swelling vesicles bound to planar membranes  

Microsoft Academic Search

When phospholipid vesicles bound to a planar membrane are osmoti- cally swollen, they develop a hydrostatic pressure (Ap) and fuse with the mem- brane. We have calculated the steady-state &P, from the equations of irreversible thermodynamics governing water and solute flows, for two general methods of osmotic swelling. In the first method, vesicles are swollen by adding a solute to

WALTER D. NILES; FREDRIC S. COHEN; ALAN FINKELSTEIN

1989-01-01

214

Vol 440|20 April 2006 A pneumo-hydrostatic skeleton in land crabs  

E-print Network

Vol 440|20 April 2006 1005 A pneumo-hydrostatic skeleton in land crabs A sophisticated dual support system enables a crab to stay mobile immediately after moulting. Liketheiraquaticcounterparts, terrestrialcrabsrepeatedlyshed their rigid exoskeleton during moulting. But in the case of land crabs, little water is avail

Kier, William M.

215

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2012 CFR

...pressure vessel, multiplied by the ratio of the stress value “S” at the test temperature to the stress value “S” at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2012-10-01

216

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2011 CFR

...pressure vessel, multiplied by the ratio of the stress value “S” at the test temperature to the stress value “S” at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2011-10-01

217

Transcriptomics Reveal Several Gene Expression Patterns in the Piezophile Desulfovibrio hydrothermalis in Response to Hydrostatic Pressure  

PubMed Central

RNA-seq was used to study the response of Desulfovibrio hydrothermalis, isolated from a deep-sea hydrothermal chimney on the East-Pacific Rise at a depth of 2,600 m, to various hydrostatic pressure growth conditions. The transcriptomic datasets obtained after growth at 26, 10 and 0.1 MPa identified only 65 differentially expressed genes that were distributed among four main categories: aromatic amino acid and glutamate metabolisms, energy metabolism, signal transduction, and unknown function. The gene expression patterns suggest that D. hydrothermalis uses at least three different adaptation mechanisms, according to a hydrostatic pressure threshold (HPt) that was estimated to be above 10 MPa. Both glutamate and energy metabolism were found to play crucial roles in these mechanisms. Quantitation of the glutamate levels in cells revealed its accumulation at high hydrostatic pressure, suggesting its role as a piezolyte. ATP measurements showed that the energy metabolism of this bacterium is optimized for deep-sea life conditions. This study provides new insights into the molecular mechanisms linked to hydrostatic pressure adaptation in sulfate-reducing bacteria. PMID:25215865

Amrani, Amira; Bergon, Aurelie; Holota, Helene; Tamburini, Christian; Garel, Marc; Ollivier, Bernard; Imbert, Jean; Dolla, Alain; Pradel, Nathalie

2014-01-01

218

Hamiltonian particle-mesh simulations for a non-hydrostatic vertical slice model  

E-print Network

particle based methods such as smoothed particle hydrodynamics (SPH) (Gingold & Monaghan 1977, Lucy 1977Hamiltonian particle-mesh simulations for a non-hydrostatic vertical slice model Seoleun Shin Sebastian Reich May 6, 2009 Abstract A Lagrangian particle method is developed for the simulation

Reich, Sebastian

219

A three-dimensional spectral element model for the solution of the hydrostatic primitive equations  

E-print Network

is an intercomparison of spectral element and finite-difference model solutions to the adjustment of a density front­p type finite element method that approximates the solution within each quadrilateral element with a highA three-dimensional spectral element model for the solution of the hydrostatic primitive equations

220

Elastic properties of carbon nanotubes under hydrostatic pressure S. Reich and C. Thomsen  

E-print Network

report an ab initio calculation of carbon nano- tube bundles under hydrostatic stress. The volume of the bulk and linear moduli of carbon nanotube bundles and individual tubes. The calculations were done and not capped. This is a good approximation to the real bundles in which the nano- tubes are of finite but very

Nabben, Reinhard

221

Effect of high hydrostatic pressure on the physiology of Manila mango.  

PubMed

Manila mangoes (Mangifera indica L.) have sensory characteristics that make them attractive for consumption as a fresh fruit. A large portion of the annual yield of this fruit is infested by the Mexican fruit fly (Anastrepha ludens), adversely impacting the quality of the crop. Hence, it is necessary to develop economically viable postharvest treatments to reduce the damage caused by this insect. Currently, high hydrostatic pressures are used to guarantee the safety of many processed foods. The objective of this work was to assess the effects of high hydrostatic pressure on mangoes at their physiological maturity. High hydrostatic pressures were applied to mangoes at three levels: 50, 100 and 200 megapascals applied for four different time periods (0, 5, 10 and 20 min). Physiologically mature mangoes were more resistant to changes in response to the pressure of 50 MPa. Reduction of physiological activity by application of high hydrostatic pressure opens a new avenue for the research on treatments intended to enhance preservation of whole fresh fruit. PMID:23504511

Vargas-Ortiz, M A; De la Cruz-Medina, J; de Los Monteros, J J Espinosa; Oliart-Ros, R M; Rebolledo-Martinez, A; Ramírez, J A; García, H S

2013-06-01

222

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body School of Engineering Science  

E-print Network

surface. Because no shear stress exists in a static fluid, all hydrostatic forces on any element-section. Hence, the force due to weight of the water always produces the same moment referred to the pinpoint how appended weight, , and its lever arm, , are related to resultant force and its lever arm: . . (13

Bahrami, Majid

223

Cyclic hydrostatic pressure and cotton particles stimulate synthesis by human lung macrophages of cytokines in vitro  

PubMed Central

Background Inhalation of particulates is a leading cause of the development of lung diseases and current understanding of the complex relationship between lung metabolism and airborne particulates is incomplete. It is well established that mechanical load is important in the development of the lung and in lung cell differentiation. The interaction between particle exposure and physical forces on alveolar macrophages is a physiologically relevant issue, but as yet understudied. This study examines the effect of cyclic hydrostatic pressure and cotton particles on synthesis of cytokines by human alveolar macrophages. Methods Alveolar macrophages were obtained from patients with lung disease, either from lavage samples or from lung tissue resection. The commonly used cell line THP-1 was included in the experiments. Cell cultures were exposed to cotton particles and/cyclic hydrostatic pressure (3 or 5 psi); control cultures were exposed to medium only. TNF?, IL-1? and IL-6 were assayed in the culture media using specific ELISAs. Cells were characterized using morphology and markers specific for macrophages (Jenner/Giemsa staining, CD14 and CD68). Results Exposure to cotton particles stimulated cytokine synthesis by macrophages from all three sources; exposure to cyclic hydrostatic pressure alone did not stimulate cytokine synthesis significantly. However, the combination of both particles and cyclic hydrostatic pressure increased the simulation of cytokine synthesis still further. Cell characterization demonstrated that the large majority of cells had a macrophage morphology and were positive for CD14 and CD68. Conclusion These data suggest an interaction between cyclic hydrostatic pressure and particulate exposure, which increases alveolar macrophage cytokine production. This interaction was only observed at the higher cyclic hydrostatic pressure. However, in patient samples, there was considerable variation in the amount by which secretion of an individual cytokine increased and there was also variation in the mechanosensitivity of cells from the three different sources. Cyclic hydrostatic pressure, therefore, may be an important modulator of the response of alveolar macrophages to cotton particles, but the source of the cells may be a confounding factor which demands further investigation. PMID:19490623

Lewis, Sarah; Singh, Dave; Evans, Carol E

2009-01-01

224

Bearing construction for refrigeration compresssor  

DOEpatents

A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.

Middleton, Marc G. (Wyoming, MI); Nelson, Richard T. (Worthington, OH)

1988-01-01

225

History of Space Shuttle Main Engine Turbopump Bearing Testing at the Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

The Space Shuttle is propelled into orbit by two solid rocket motors and three liquid fed main engines. After the solid motors fall away, the shuttle engines continue to run for a total time of 8 minutes. These engines are fed propellants by low and high pressure turbopumps. A critical part of the turbopump is the main shaft that supports the drive turbine and the pump inducer and impeller. Rolling element bearings hold the shaft in place during rotation. If the bearings were to fail, the shaft would move, allowing components to rub in a liquid oxygen or hydrogen environment, which could have catastrophic results. These bearings are required to spin at very high speeds, support radial and axial loads, and have high wear resistance without the benefit of a conventional means of lubrication. The Rocketdyne built Shuttle turbopumps demonstrated their capability to perform during launches; however, the seven hour life requirement was not being met. One of the limiting factors was the bearings. In the late 1970's, an engineering team was formed at the Marshall Space Flight Center (MSFC), to develop a test rig and plan for testing the Shuttle s main engine high pressure oxygen turbopump (HPOTP) bearings. The goals of the program were to better understand the operation of bearings in a cryogenic environment and to further develop and refine existing computer models used to predict the operational limits of these bearings. In 1982, testing began in a rig named the Bearing and Seal Material Tester or BSMT as it was commonly called. The first testing investigated the thermal margin and thermal runaway limits of the HPOTP bearings. The test rig was later used to explore potential bearing improvements in the area of increased race curvatures, new cage materials for better lubrication, new wear resistant rolling element materials, and other ideas to improve wear life. The most notable improvements during this tester s time was the incorporation of silicon nitride balls and bronze filled polytetrafluoroethylene (PTFE) cage inserts into the bearings and the anchoring of the SHABERTH bearing model and SINDA thermal computer model for cryogenic bearing analysis. In the mid 1990's, Pratt and Whitney (P&W) won the contract to deliver new high pressure turbopumps for the Shuttle s engines. P&W used two new bearing materials for the rings, Cronidur 30 and AISI 9310 steel and testing was needed on these new materials. A test rig had been designed and delivered to MSFC for testing hydrostatic bearings but with the need by Pratt to validate their bearings, the rig was reconfigured for testing of two ball bearings or a ball bearing and a roller bearing. The P&W bearings are larger than the Rocketdyne bearings and could not be installed in the BSMT. This new test rig was called the LH2 test rig and began operation in 1995. The LH2 test rig accumulated 75,000 seconds of run time in hydrogen. This test rig was valuable in two areas: validating the use of silicon nitride balls and rollers in Alternate Turbopump Development (ATD) bearings, which Pratt eventually used, and in proving the robustness of the balls and rollers after river marks appeared on the surface of the rolling elements. Individual test reports have been presented at conferences and symposiums throughout the years. This paper is a comprehensive report of all the bearing testing done at Marshall. It represents thousands of hours of dedication and labor in all engineering and technical fields that made this program a success.

Gibson, Howard; Thom, Robert; Moore, Chip; Haluck, Dave

2010-01-01

226

Description of a magnetic bearing test fixture  

NASA Technical Reports Server (NTRS)

A description of a microcomputer controlled magnetic bearing test fixture is presented. Parameters which are controlled are magnetic bearing current and gaps. Parameters which are measured are magnetic bearing gaps, magnetic flux in the bearing gaps, and bearing forces. The test fixture is configured for bearing elements similar to those used in a laboratory test model Annular Momentum Control Device (AMCD).

Groom, Nelson J.; Poole, William L.

1987-01-01

227

Gold-bearing skarns  

USGS Publications Warehouse

In recent years, a significant proportion of the mining industry's interest has been centered on discovery of gold deposits; this includes discovery of additional deposits where gold occurs in skarn, such as at Fortitude, Nevada, and at Red Dome, Australia. Under the classification of Au-bearing skarns, we have modeled these and similar gold-rich deposits that have a gold grade of at least 1 g/t and exhibit distinctive skarn mineralogy. Two subtypes, Au-skarns and byproduct Au-skarns, can be recognized on the basis of gold, silver, and base-metal grades, although many other geological factors apparently are still undistinguishable largely because of a lack of detailed studies of the Au-skarns. Median grades and tonnage for 40 Au-skarn deposits are 8.6 g/t Au, 5.0 g/t Ag, and 213,000 t. Median grades and tonnage for 50 byproduct and Au-skarn deposits are 3.7 g/t Au, 37 g/t Ag, and 330,000 t. Gold-bearing skarns are generally calcic exoskarns associated with intense retrograde hydrosilicate alteration. These skarns may contain economic amounts of numerous other commodities (Cu, Fe, Pb, Zn, As, Bi, W, Sb, Co, Cd, and S) as well as gold and silver. Most Au-bearing skarns are found in Paleozoic and Cenozoic orogenic-belt and island-arc settings and are associated with felsic to intermediate intrusive rocks of Paleozoic to Tertiary age. Native gold, electru, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, sphalerite, galena, bismuth minerals, and magnetite or hematite are the most common opaque minerals. Gangue minerals typically include garnet (andradite-grossular), pyroxene (diopside-hedenbergite), wollastonite, chlorite, epidote, quartz, actinolite-tremolite, and (or) calcite.

Theodore, Ted G.; Orris, Greta J.; Hammerstrom, Jane M.; Bliss, James D.

1991-01-01

228

Linear magnetic bearings  

NASA Technical Reports Server (NTRS)

A self regulating, nonfrictional, active magnetic bearing is disclosed which has an elongated cylindrical housing for containing a shaft type armature with quadrature positioned shaft position sensors and equidistantly positioned electromagnets located at one end of the housing. Each set of sensors is responsive to orthogonal displacement of the armature and is used to generate control signals to energize the electromagnets to center the armature. A bumper magnet assembly is located at one end of the housing for dampening any undesired axial movement of the armature or to axially move the armature either continuously or fixedly.

Goldowskiy, M. P.

1984-01-01

229

PNA bearing 5-azidomethyluracil  

PubMed Central

Fmoc- and Boc-protected modified monomers bearing 5-azidomethyluracil nucleobase were synthesized. Four different solid-phase synthetic strategies were tested in order to evaluate the application of this series of monomers for the solid-phase synthesis of modified PNA. The azide was used as masked amine for the introduction of amide-linked functional groups, allowing the production of a library of compounds starting from a single modified monomer. The azide function was also exploited as reactive group for the modification of PNA in solution via azide-alkyne click cycloaddition. PMID:22772040

Manicardi, Alex; Accetta, Alessandro; Tedeschi, Tullia; Sforza, Stefano; Marchelli, Rosangela; Corradini, Roberto

2012-01-01

230

HYDROSTATIC GAS CONSTRAINTS ON SUPERMASSIVE BLACK HOLE MASSES: IMPLICATIONS FOR HYDROSTATIC EQUILIBRIUM AND DYNAMICAL MODELING IN A SAMPLE OF EARLY-TYPE GALAXIES  

SciTech Connect

We present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M {sub BH}) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGC 4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with M {sub BH} measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than {approx}10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M-dot{sub bondi}), finding that the two galaxies with the highest M-dot{sub bondi} exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.

Humphrey, Philip J.; Buote, David A. [Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575 (United States); Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, Bologna 40127 (Italy); Gebhardt, Karl [Astronomy Department, University of Texas, Austin, TX 78712 (United States); Mathews, William G. [University of California Observatories, Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)

2009-10-01

231

An efficient semi-implicit method for three-dimensional non-hydrostatic flows in compliant arterial vessels.  

PubMed

Blood flow in arterial systems can be described by the three-dimensional Navier-Stokes equations within a time-dependent spatial domain that accounts for the elasticity of the arterial walls. In this article, blood is treated as an incompressible Newtonian fluid that flows through compliant vessels of general cross section. A three-dimensional semi-implicit finite difference and finite volume model is derived so that numerical stability is obtained at a low computational cost on a staggered grid. The key idea of the method consists in a splitting of the pressure into a hydrostatic and a non-hydrostatic part, where first a small quasi-one-dimensional nonlinear system is solved for the hydrostatic pressure and only in a second step the fully three-dimensional non-hydrostatic pressure is computed from a three-dimensional nonlinear system as a correction to the hydrostatic one. The resulting algorithm is robust, efficient, locally and globally mass conservative, and applies to hydrostatic and non-hydrostatic flows in one, two and three space dimensions. These features are illustrated on nontrivial test cases for flows in tubes with circular or elliptical cross section where the exact analytical solution is known. Test cases of steady and pulsatile flows in uniformly curved rigid and elastic tubes are presented. Wherever possible, axial velocity development and secondary flows are shown and compared with previously published results. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24842268

Fambri, Francesco; Dumbser, Michael; Casulli, Vincenzo

2014-11-01

232

Robust and intelligent bearing estimation  

DOEpatents

A method of bearing estimation comprising quadrature digital filtering of event observations, constructing a plurality of observation matrices each centered on a time-frequency interval, determining for each observation matrix a parameter such as degree of polarization, linearity of particle motion, degree of dyadicy, or signal-to-noise ratio, choosing observation matrices most likely to produce a set of best available bearing estimates, and estimating a bearing for each observation matrix of the chosen set.

Claassen, John P. (Albuquerque, NM)

2000-01-01

233

Prototype testing of magnetic bearings  

NASA Technical Reports Server (NTRS)

The testing and evaluation of the performance of a magnetic bearing assembly for flywheel energy storage applications are discussed. The experimental set up for determining the passive radial stiffness, active radial stiffness, and curent force sensitivity of the coils follows the method developed by Frommer (1986). Magnetic bearings design should preclude saturation and current limiting in the desired operating range, so that the system will be linear. A larger linear range will lead to a more stable magnetic bearing.

Plant, David P.; Jayaraman, Chaitanya P.; Frommer, David A.; Kirk, James A.; Anand, Davinder K.

1987-01-01

234

Primarily Pro-bear-bility  

NSDL National Science Digital Library

In this probability lesson plan students make predictions about the color of the bear they are likely to draw from a bag, and then draw and record the color of the bear they actually draw. Students complete this activity in cooperative learning groups and take turns removing a bear, without replacing it, and seeing if their predictions become more accurate. The lesson plan includes four student activity worksheets and extension questions and suggestions (PDF).

2006-01-01

235

Research Trends on Magnetic Bearings  

NASA Astrophysics Data System (ADS)

Use of magnetic bearings for high-speed rotor and application in clean environment or in special circumstance have been gradually increasing. This article overviews research trends and application presented before the Eighth International Symposium on Magnetic Bearings (ISMB-8). Interesting research topics are the combined realization of motor and magnetic bearing, low loss magnetic bearings and self-sensing techniques. New application fields include small spindles for data storage devices, energy storage flywheels, and artificial heart pumps. Various new technologies are reported related to these new application fields.

Okada, Yohji; Nonami, Kenzo

236

Evaluation of shuttle turbopump bearings  

NASA Technical Reports Server (NTRS)

Because the high pressure turbopumps used on the space shuttle main engine (SSME) are high speed machines and rotor dynamics analysis of these units is very complicated, it was considered necessary to verify calculated turbomachinery shaft bearing loads by analysis of ball bearing load tracks. This report presents the methods used and the results of load track analysis on one set of bearings removed from a high pressure liquid oxygen turbopump which had been subjected to SSME static firing tests. This type of analysis was found useful in determining bearing operating conditions and for verifying rotor dynamics computer models.

Dufrane, K. F.; Kannel, J. W.

1978-01-01

237

Hydrostatic pressure and magnetic field effects on donor states in pyramidal quantum dots  

NASA Astrophysics Data System (ADS)

The simultaneous effects of the hydrostatic pressure and magnetic field on the ground state of impurity confined by a GaAs pyramid-shaped QD are investigated within the effective mass approximation. By using a variational method, the binding energy and the extent of the electron wavefunction in the structure are examined for different dot sizes and impurity positions. The influence of above mentioned parameters on the diamagnetic shift of the impurity energy is also discussed. We found that the diamagnetic coefficient could be appreciably tuned by a proper tailoring of the heterostructure parameters (dot size, impurity position) as well as by changing the hydrostatic pressure and/or the magnetic field strength.

Tiriba, G. C.; Niculescu, E. C.; Burileanu, L. M.

2014-11-01

238

Controlled hydrostatic sinus elevation: a novel method of elevating the sinus membrane.  

PubMed

Maxillary sinus elevation surgery has been practiced successfully over the past several decades with good outcomes, but tears and perforations still occur in significant numbers. The presumed cause of these problems is the fact that all methods currently used place "point sources" of lifting pressure on the Schneiderian membrane. A new procedure, controlled hydrostatic sinus lift, is presented herein as a safer, more controlled "lifting pressure" which simultaneously places equal force per square millimeter of bone-membrane interface. Hydraulic pressure in a closed system places equal pressure on all surfaces within the system, thereby eliminating "point sources" of pressure and gently elevating the Schneiderian membrane equally at all points of attachment. This controlled hydrostatic sinus lift procedure is accomplished by using a calibrated, hand-controlled pump and in-line pressure sensor meter. PMID:22067599

Kao, Daniel W K; DeHaven, Harold A

2011-12-01

239

Zinc phosphate chain length study under high hydrostatic pressure by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The aim of this study is to combine a diamond anvil cell with in-situ Raman spectroscopy to simulate and analyze the effect of pure pressure on the length of phosphate chains in an antiwear film formed in a tribological contact. In-situ Raman spectra of Zn2P2O7 glass, ?-Zn3(PO4)2, and ?-Zn2P2O7 crystals submitted to high hydrostatic pressure up to 20 GPa were recorded. Evolution of Raman spectra as a function of pressure was studied in the characteristic high frequency range of PO4 tetrahedra molecular resonance (650-1300 cm-1). When exposed to high pressure, the structure of the sample becomes less ordered. Phase transitions in ?-Zn3(PO4)2 structure are observed during compression from ambient pressure to 3 GPa. The length of the phosphate chains is conserved up to 20 GPa when samples are subjected to hydrostatic pressure.

Gauvin, M.; Dassenoy, F.; Minfray, C.; Martin, J. M.; Montagnac, G.; Reynard, B.

2007-03-01

240

Filtration coefficient of the axon membrane as measured with hydrostatic and osmotic methods.  

PubMed

The hydraulic conductivity of the membranes surrounding the giant axon of the squid, Dosidicus gigas, was measured. In some axons the axoplasm was partially removed by suction. Perfusion was then established by insertion of a second pipette. In other axons the axoplasm was left intact and only one pipette was inserted. In both groups hydrostatic pressure was applied by means of a water column in a capillary manometer. Displacement of the meniscus in time gave the rate of fluid flowing across the axon sheath. In both groups osmotic differences across the membrane were established by the addition of a test molecule to the external medium which was seawater. The hydraulic conductivity determined by application of hydrostatic pressure was 10.6 +/- 0.8.10(-8) cm/sec cm H(2)O in perfused axons and 3.2 +/- 0.6.10(-8) cm/sec cm H(2)O in intact axons. When the driving force was an osmotic pressure gradient the conductivity was 4.5 +/- 0.6 x 10(-10) cm/sec cm H(2)O and 4.8 +/- 0.9 x 10(-10) cm/sec cm H(2)O in perfused and intact axons, respectively. A comparable result was found when the internal solution was made hyperosmotic. The fluid flow was a linear function of the hydrostatic pressure up to 70 cm of water. Glycerol outflux and membrane conductance were increased 1.6 and 1.1 times by the application of hydrostatic pressure. These increments do not give an explanation of the difference between the filtration coefficients. Other possible explanations are suggested and discussed. PMID:5642470

Vargas, F F

1968-01-01

241

M. Bahrami ENSC 283 Tutorial # 3 1 ENSC 283 Week # 4, Tutorial # 3 Hydrostatic Forces  

E-print Network

M. Bahrami ENSC 283 Tutorial # 3 1 ENSC 283 Week # 4, Tutorial # 3­ Hydrostatic Forces Problem 1: Prepare a data table Data Value Unit 4 2 Water 2 m O z x 4 m D B C A #12;M. Bahrami ENSC 283 Tutorial # 3. Bahrami ENSC 283 Tutorial # 3 3 , sin 1 12 1 2 sin 90° 5 2 0.0667 (Eq7) Note that , is calculated

Bahrami, Majid

242

Effect of High Hydrostatic Pressure on Physicochemical and Structural Properties of Rice Starch  

Microsoft Academic Search

Rice starch–water suspension (20%) were subjected to high hydrostatic pressure (HHP) treatment at 120, 240, 360, 480, and\\u000a 600 MPa for 30 min. Polarizing light microscope, scanning electron microscopy (SEM), rapid visco analyzer (RVA), differential\\u000a scanning calorimeter (DSC), and X-ray diffraction were used to investigate the physicochemical and structural changes of starch.\\u000a Microscopy studies showed that the treatment of starch with HHP

Wenhao Li; Yunfei Bai; Saleh A. S. Mousaa; Qing Zhang; Qun Shen

243

Method for correcting laboratory model deep-well disposal system data for hydrostatic pressure effects.  

PubMed

A pressure chamber for determining the effect of increased hydrostatic pressure on growth and metabolic activities of groundwater bacteria is described. The chamber was used to show that moderate increases in pressure (to about 100 atmospheres) result in increased growth of mixed cultures of industrial-injection-well bacteria and in the more complete degradation of formate and nitrate by these bacteria, as compared with identical cultures at atmospheric pressure. PMID:16345295

Horvath, E; Elkan, G H

1978-06-01

244

Isostructural phase transitions of tetragonal perovskite titanates under negative hydrostatic pressure  

Microsoft Academic Search

Phase transitions within the tetragonal space group P4mm associated with anomalous enhancement of tetragonality in PbTiO3 and BaTiO3 under negative hydrostatic pressure were theoretically predicted by Tinte et al (2003 Phys. Rev. B 68 144105). In the present study, with special interest in the origin of the phase transition, we made a series of analogous calculations for six perovskite titanates

Hiroki Moriwake; Yukinori Koyama; Katsuyuki Matsunaga; Tsukasa Hirayama; Isao Tanaka

2008-01-01

245

An Update on High Hydrostatic Pressure, from the Laboratory to Industrial Applications  

Microsoft Academic Search

High hydrostatic pressure has become an industrial reality, and although there are still many aspects under research, today\\u000a it is possible to buy high-pressurized products in many countries. Indeed, pasteurization of food products using elevated\\u000a pressure at room temperature has been accepted by regulatory agencies for commercial use. The quality displayed in such products\\u000a includes better nutritional retention, fresh-like flavor,

Daniela Bermúdez-Aguirre; Gustavo V. Barbosa-Cánovas

2011-01-01

246

Hemoglobin hydrolysates from porcine blood obtained through enzymatic hydrolysis assisted by high hydrostatic pressure processing  

Microsoft Academic Search

The purpose of this work was to obtain discoloured hemoglobin (Hb) hydrolysates from porcine red blood cells fraction by combining enzymatic hydrolysis and high hydrostatic pressure (HHP) treatments. Samples of Hb were submitted to treatments of enzymatic hydrolysis by trypsin (EC 3.4.21.4) or pepsin (EC 3.4.23.1), under controlled conditions of temperature and pH, for 2, 6 and 24h, and pressurization

M. Toldrà; D. Parés; E. Saguer; C. Carretero

2011-01-01

247

COORDINATION OF RESPIRATORY AND HYDROSTATIC FUNCTIONS OF THE SWIMBLADDER IN THE CENTRAL MUDMINNOW, UMBRA LIMI  

Microsoft Academic Search

SUMMARY 1. Observations of behaviour and changes in buoyancy of Umbra limi, a facultative air-breathing fish, were studied to understand coordination of respiratory and hydrostatic functions of the swimbladder. 2. Fish were exposed to either normoxic or hypoxic water in either undisturbed or disturbed (simulating predator presence) conditions. Declines in swimbladder volume occurred between air-breaths as O2 was removed. These

JOHN H. GEE

248

The effects of defects on copper melting under hydrostatic and shock loading  

SciTech Connect

With molecular dynamics (MD) simulations, we investigate the effects of defects on Cu melting under hydrostatic and shock wave loading. We explore preexistent defects including vacancies, stacking faults and grain boundaries, as well as shock-induced defects. Depending on defect characteristics (energy and concentration), defects may have negligible or considerable effects on melting at MD scales However, it is expected that defects have more pronounced effects at heating rates lower than the MD rates.

Luo, Shengnian [Los Alamos National Laboratory; An, Qi [Los Alamos National Laboratory; German, Timothy C [Los Alamos National Laboratory; Han, Li - Bo [USTC

2009-01-01

249

Proteolysis of type III collagen by collagenase and cathepsin B under high hydrostatic pressure  

Microsoft Academic Search

The effects of high hydrostatic pressures on the kinetics of hydrolysis of type III collagen from calf skin by collagenase and cathepsin B were studied. Collagen hydrolysates sampled at different time intervals (0–90 min) and at different pressures (0.1–300 MPa) were analysed by reverse-phase high pressure liquid chromatography. The rate of collagen hydrolysis decreased up to 300 MPa for both

Eric Dufour; Michèle Dalgalarrondo; Guy Hervé; René Goutefongea; Tomasz Haertlé

1996-01-01

250

Density Measurement of Tridecane by using Hydrostatic Weighing System at Density Laboratory, NML-SIRIM  

SciTech Connect

This paper presents the density measurement of tridecane by using hydrostatic weighing system, which is currently practised in Density Laboratory of National Metrology Laboratory (NML), SIRIM Berhad. This system weighed the crystal sphere while the crystal sphere was immersed in the tridecane. The volume and mass in air of the crystal sphere were calibrated at KRISS, Korea. The uncertainties of volume and mass in air of the crystal sphere were 4 ppm and 0.3 ppm respectively.

Nor, Mohd. Fazrul Hisyam Mohd.; Othman, Hafidzah; Abidin, Abd. Rashid Zainal [National Metrology Laboratory, SIRIM Berhad (Malaysia)

2009-07-07

251

WEIGHING GALAXY CLUSTERS WITH GAS. I. ON THE METHODS OF COMPUTING HYDROSTATIC MASS BIAS  

SciTech Connect

Mass estimates of galaxy clusters from X-ray and Sunyeav-Zel'dovich observations assume the intracluster gas is in hydrostatic equilibrium with their gravitational potential. However, since galaxy clusters are dynamically active objects whose dynamical states can deviate significantly from the equilibrium configuration, the departure from the hydrostatic equilibrium assumption is one of the largest sources of systematic uncertainties in cluster cosmology. In the literature there have been two methods for computing the hydrostatic mass bias based on the Euler and the modified Jeans equations, respectively, and there has been some confusion about the validity of these two methods. The word 'Jeans' was a misnomer, which incorrectly implies that the gas is collisionless. To avoid further confusion, we instead refer these methods as 'summation' and 'averaging' methods respectively. In this work, we show that these two methods for computing the hydrostatic mass bias are equivalent by demonstrating that the equation used in the second method can be derived from taking spatial averages of the Euler equation. Specifically, we identify the correspondences of individual terms in these two methods mathematically and show that these correspondences are valid to within a few percent level using hydrodynamical simulations of galaxy cluster formation. In addition, we compute the mass bias associated with the acceleration of gas and show that its contribution is small in the virialized regions in the interior of galaxy clusters, but becomes non-negligible in the outskirts of massive galaxy clusters. We discuss future prospects of understanding and characterizing biases in the mass estimate of galaxy clusters using both hydrodynamical simulations and observations and their implications for cluster cosmology.

Lau, Erwin T.; Nagai, Daisuke [Department of Physics, Yale University, New Haven, CT 06520 (United States); Nelson, Kaylea, E-mail: erwin.lau@yale.edu [Department of Astronomy, Yale University, New Haven, CT 06520 (United States)

2013-11-10

252

The Effect of Size and Species on Lens Intracellular Hydrostatic Pressure  

PubMed Central

Purpose. Previous experiments showed that mouse lenses have an intracellular hydrostatic pressure that varied from 335 mm Hg in central fibers to 0 mm Hg in surface cells. Model calculations predicted that in larger lenses, all else equal, pressure should increase as the lens radius squared. To test this prediction, lenses of different radii from different species were studied. Methods. All studies were done in intact lenses. Intracellular hydrostatic pressures were measured with a microelectrode-manometer–based system. Membrane conductances were measured by frequency domain impedance analysis. Intracellular Na+ concentrations were measured by injecting the Na+-sensitive dye sodium-binding benzofuran isophthalate. Results. Intracellular hydrostatic pressures were measured in lenses from mice, rats, rabbits, and dogs with radii (cm) 0.11, 0.22, 0.49, and 0.57, respectively. In each species, pressure varied from 335 ± 6 mm Hg in central fiber cells to 0 mm Hg in surface cells. Further characterization of transport in lenses from mice and rats showed that the density of fiber cell gap junction channels was approximately the same, intracellular Na+ concentrations varied from 17 mM in central fiber cells to 7 mM in surface cells, and intracellular voltages varied from ?45 mV in central fiber cells to ?60 mV in surface cells. Fiber cell membrane conductance was a factor of 2.7 times larger in mouse than in rat lenses. Conclusions. Intracellular hydrostatic pressure is an important physiological parameter that is regulated in lenses from these different species. The most likely mechanism of regulation is to reduce the density of open Na+-leak channels in fiber cells of larger lenses. PMID:23211824

Gao, Junyuan; Sun, Xiurong; Moore, Leon C.; Brink, Peter R.; White, Thomas W.; Mathias, Richard T.

2013-01-01

253

Effects of Hydrostatic Pressure on the Location of PRODAN in Lipid Bilayers: A FT-IR Study.  

National Technical Information Service (NTIS)

The effects of hydrostatic pressure on the location of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN), an environmentally sensitive fluorescent probe, in phosphatidylcholine lipid bilayers have been studied by Fourier-transform infrared spect (FT-IR) o...

P. Chong, S. Capes, P. T. Wong

1989-01-01

254

Resonant frequency analysis on an electrostatically actuated microplate under uniform hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The resonant frequency of a microplate is influenced by various physical parameters such as mass, surface stress, hydrostatic pressure and electrostatic force. In this paper, the effects of both electrostatic force and uniform hydrostatic pressure on the resonant frequency of a clamped circular microplate are investigated. An approximate solution is derived for the fundamental resonance frequency of the mciroplate under both types of loads using an energy equivalent method. It is found that both electrostatic force and uniform hydrostatic pressure decrease the resonant frequency of the microplate under small deflections. Additionally, the linearized expression of this solution shows that the resonant frequency varies linearly with pressure in the low and ultra-low range, and the corresponding pressure sensitivity depends on the voltage applied to the microplate. The analytical results are well validated by the finite element method. This study may be helpful for the design and optimization of electrostatically actuated resonance devices based on microplates, especially electrostatically actuated low- or ultra-low-pressure sensors.

Li, Zhikang; Zhao, Libo; Ye, Zhiying; Wang, Hongyan; Zhao, Yulong; Jiang, Zhuangde

2013-05-01

255

Effects of hydrostatic pressure on steelhead survival in air-supersaturated water  

SciTech Connect

Juvenile steelheads (Salmo gairdneri) were placed in cages and suspended at various depths in water supersaturated with air at levels from 120 to 140% of normal atmospheric gas pressure. Survival times of fish held at 10, 50, and 100 cm depth increased with increasing depth at a given level of supersaturation. When the hydrostatic pressure (7.4 mm Hg per 10 cm of water depth) was subtracted from the excess gas pressure (relative to surface barometric pressure) mortality curves (times to 50% mortality versus excess gas pressure) for fish at all three depths essentially coincided. The significant measure of supersaturation appears to be the pressure of dissolved gases in excess of the sum of barometric and hydrostatic pressures. Steelheads held near the surface in supersaturated water for a near-lethal period and then lowered to a depth providing total hydrostatic compensation appeared to recover completely in about 2 hours. The longer fish remained at depth, the longer their survival time when they subsequently were reexposed to surface conditions.

Knittel, M.D.; Chapman, G.A.; Garton, R.R.

1980-11-01

256

Non-hydrostatic effect on the thermospheric density and vertical wind: data-model comparisons  

NASA Astrophysics Data System (ADS)

The pressure gradient in the vertical direction is exactly balanced by the gravity force under hydrostatic equilibrium. The simulations from the non-hydrostatic Global Ionosphere Thermosphere Model (GITM) however show that for an idealized case with a sudden intense enhancement of high-latitude Joule heating, the vertical pressure gradient force can locally be 25% larger than the gravity force, resulting in a significant vertical wind (250 m/s) and large neutral density disturbance (100%) at 430 km altitude. Several real case studies have also been conducted to examine the density and wind disturbance related with non-hydrostatic processes. The comparison of Resolute Bay Fabry-Perot Interferometer (FPI) observations with both GITM and the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General-Circulation Model (NCAR-TIEGCM) simulations shows very good consistency of horizontal winds and temperature. On the other hand, GITM predicts strong, rapidly fluctuating vertical motions that the TIEGCM does not. Peak vertical velocities from GITM are of the same order as those from the FPI. The simulated density disturbance will also be compared with observations, such as measurements from CHAMP satellite.

Deng, Y.; Wu, Q.; Richmond, A. D.; Ridley, A.; Roble, R. G.

2008-05-01

257

Hydrostatic pressure effect on micro air bubbles deposited on surfaces with a retreating tip.  

PubMed

The effect of hydrostatic pressure on 6 ?L air bubbles formed on micropillar structured PDMS and silicone surfaces using a 2 mm diameter stainless steel tip retreated at 1 mm/s was investigated. Dimensional analysis of the tip retraction process showed the experiments to be conducted in the condition where fluid inertial forces are comparable in magnitude with surface tension forces, while viscous forces were lower. Larger bubbles could be left behind on the structured PDMS surface. For hydrostatic pressures in excess of 20 mm H2O (196 Pa), the volume of bubble deposited was found to decrease progressively with pressure increase. The differences in width of the deposited bubbles (in contact with the substrate) were significant at any particular pressure but marginal in height. The attainable height before rupture reduced with pressure increase, thereby accounting for the reducing dispensed volume characteristic. On structured PDMS, the gaseous bridge width (in contact with the substrate) was invariant with tip retraction, while on silicone it was initially reducing before becoming invariant in the lead up to rupture. With silicone, hence, reductions in the contact width and height were both responsible for reduced volumes with pressure increase. Increased hydrostatic pressure was also found to restrict the growth in contact width on silicone during the stage when air was injected in through the tip. The ability to effect bubble size in such a simple manner may already be harnessed in nature and suggests possibilities in technological applications. PMID:24810460

Huynh, So Hung; Wang, Jingming; Yu, Yang; Ng, Tuck Wah

2014-06-01

258

Hydrostatic and shear consolidation tests with permeability measurements on Waste Isolation Pilot Plant crushed salt  

SciTech Connect

Crushed natural rock salt is a primary candidate for use as backfill and barrier material at the Waste Isolation Pilot Plant (WIPP) and therefore Sandia National Laboratories (SNL) has been pursuing a laboratory program designed to quantify its consolidation properties and permeability. Variables that influence consolidation rate that have been examined include stress state and moisture content. The experimental results presented in this report complement existing studies and work in progress conducted by SNL. The experiments described in this report were designed to (1) measure permeabilities of consolidated specimens of crushed salt, (2) determine the influence of brine saturation on consolidation under hydrostatic loads, and 3) measure the effects of small applied shear stresses on consolidation properties. The laboratory effort consisted of 18 individual tests: three permeability tests conducted on specimens that had been consolidated at Sandia, six hydrostatic consolidation and permeability tests conducted on specimens of brine-saturated crushed WIPP salt, and nine shear consolidation and permeability tests performed on crushed WIPP salt specimens containing 3 percent brine by weight. For hydrostatic consolidation tests, pressures ranged from 1.72 MPa to 6.90 MPa. For the shear consolidation tests, confining pressures were between 3.45 MPa and 6.90 MPa and applied axial stress differences were between 0.69 and 4.14 MPa. All tests were run under drained conditions at 25{degrees}C.

Brodsky, N.S. [RE/SPEC, Inc., Rapid City, SD (United States)

1994-03-01

259

Polar Bears and Climate Change  

NSDL National Science Digital Library

The issue-focused, peer reviewed article discusses how a warming climate is altering sea ice conditions, which affects polar bears in many ways, including more difficulty in getting to and hunting prey, fewer den areas and lower cub survival, increased interactions between bears and humans, and lower survival rate of the species in general.

Andrew E. Derocher (University of Alberta, Canada;)

2008-05-01

260

Corrosion-Resistant Ball Bearings  

NASA Technical Reports Server (NTRS)

Self-lubricating bearing system withstands highly corrosive environment of wastewater-recycling unit. New bearings contain cobalt-based-alloy balls and races, graphite/polyimide polymer ball cages, and single integral polytetrafluoroethylene seals on wet sides. Materials and design prevent corrosion by acids and provide lubrication.

Zdankiewicz, E. M.; Linaburg, E. L.; Lytle, L. J.

1990-01-01

261

Zero-Deadband Ball Bearings  

NASA Technical Reports Server (NTRS)

Proposed supports for ball bearings press outer races against balls without radial clearance. Diaphragm-like axially flexible springs eliminate deadband and consequent nonlinear radial vibrational response of rotor. If shaft needs two bearings at each end, they are supported independently or connected in series by U-spring. Mechanical stops limit axial travel of shaft.

Hine, Michael J.

1988-01-01

262

Identifying Bearing Balls With Radioisotopes  

NASA Technical Reports Server (NTRS)

Proposed scheme for identification of members of manufactured lot of bearing balls based on detection of characteristic isotopes. All balls in lot irradiated to produce easily recognized radioactive isotopes in known concentrations and/or known ratios of concentrations and known rates of decay on their surfaces. Scheme conceived to track precise bearing balls through various stages of assembly, disassembly, and processing.

Butner, Myles F.; Collins, John J.

1990-01-01

263

Service Lives Of Restored Bearings  

NASA Technical Reports Server (NTRS)

Rebuilt units last almost as long as new ones. Report describes theoretical and experiemental studies of lifetimes of restored ball and cylindrical-roller bearings. Results of this and related studies have implications of economy and safety in modern high-speed machinery, especially in aircraft industry, where inspection and rejection or replacing of bearings are new standard practice.

Zaretsky, Erwin V.

1988-01-01

264

High-Performance Ball Bearing  

NASA Technical Reports Server (NTRS)

High-performance bearing features strong, lightweight, self-lubricating cage with self-lubricating liners in ball apertures. Designed to operate at high speed (tens of thousands of revolutions per minute) in cryogenic environment like liquid-oxygen or liquid-hydrogen turbopump. Includes inner race, outer race, and cage keeping bearing balls equally spaced.

Bursey, Roger W., Jr.; Haluck, David A.; Olinger, John B.; Owen, Samuel S.; Poole, William E.

1995-01-01

265

HUMAN IMPACTS ON BEAR HABITAT USE1  

Microsoft Academic Search

Human effects on bear habitat use are mediated through food biomass changes, bear tolerance of humans and their impacts, and human tolerance of bears. Large- scale changes in bear food biomass have been caused by conversion of wildlands and waterways to intensive human use, and by the introduction of exotic pathogens. Bears consume virtually all human foods that have been

DAVID J. MATTSON

266

Evaluation of Solid Lubricated Ball Bearing Performance  

Microsoft Academic Search

This paper describes an evaluation of solid lubricated ball bearings with both plain (ungrooved) and grooved inner race lands. The intent of the grooves was to pump ambient air into the bearing to lower the stabilized bearing operating temperature. Nineteen tests were run at various bearing loads and speeds. Bearing stabilization temperature and torque were monitored at each operating condition.

R. D. Dayton; M. A. Sheets; J. B. Schrand

1978-01-01

267

Geophagy by yellowstone grizzly bears  

USGS Publications Warehouse

We documented 12 sites in the Yellowstone ecosystem where grizzly bears (Ursus arctos horribilis) had purposefully consumed soil (an activity known as geophagy). We also documented soil in numerous grizzly bear feces. Geophagy primarily occurred at sites barren of vegetation where surficial geology had been modified by geothermal activity. There was no evidence of ungulate use at most sites. Purposeful consumption of soil by bears peaked first from March to May and again from August to October, synchronous with peaks in consumption of ungulate meat and mushrooms. Geophageous soils were distinguished from ungulate mineral licks and soils in general by exceptionally high concentrations of potassium (K) and high concentrations of magnesium (Mg) and sulphur (S). Our results do not support the hypotheses that bears were consuming soil to detoxify secondary compounds in grazed foliage, as postulated for primates, or to supplement dietary sodium, as known for ungulates. Our results suggest that grizzly bears could have been consuming soil as an anti-diarrheal.

Mattson, D.J.; Green, G.I.; Swalley, R.

1999-01-01

268

Space Station alpha joint bearing  

NASA Technical Reports Server (NTRS)

Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

1987-01-01

269

Nonlinear control of magnetic bearings  

NASA Technical Reports Server (NTRS)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular sliding mode controllers, time optimal controllers, winding algorithm based controllers, nested switching controllers, fractional controllers, and synchronous switching controllers for the magnetic bearing. We show existence of solutions to systems governed by discontinuous control laws, and prove stability and robustness of the chosen control laws in a rigorous setting. We design sliding mode observers for the magnetic bearing and prove the convergence of the state estimates to their true values. We present simulation results of the performance of the magnetic bearing subject to the aforementioned control laws, and conclude with comments on design.

Pradeep, A. K.; Gurumoorthy, R.

1994-01-01

270

Hydrostatic Pressure Independently Increases Elastin and Collagen Co-expression in Small-diameter Engineered Arterial Constructs  

PubMed Central

Prior studies have demonstrated that smooth muscle cell (SMC) proliferation, migration, and extracellular matrix production increase with hydrostatic pressure in vitro. We have engineered highly compliant small-diameter arterial constructs by culturing primary adult arterial SMCs under pulsatile perfusion on tubular, porous, elastomeric scaffolds composed of poly(glycerol sebacate) (PGS). This study investigates the effect of hydrostatic pressure on the biological and mechanical properties of PGS-based engineered arterial constructs. Pressure was raised using a downstream needle valve during perfusion while preserving flow rate and pulsatility, and constructs were evaluated by pressure-diameter testing and biochemical assays for collagen and elastin. Pressurized constructs contained half as much insoluble elastin as baboon common carotid arteries but were significantly less compliant, while constructs cultured at low hydrostatic pressure contained one third as much insoluble elastin as baboon carotids and were similar in compliance. Hydrostatic pressure significantly increased construct burst pressure, collagen and insoluble elastin content, and soluble elastin concentration in culture medium. All arteries and constructs exhibited elastic recovery during pressure cycling. Hydrostatic pressure did not appear to affect radial distribution of SMCs, collagens I and III, and elastin. These results provide insights into the control of engineered smooth muscle tissue properties using hydrostatic pressure. PMID:21268239

Crapo, Peter M.; Wang, Yadong

2011-01-01

271

Effects of bearing cleaning and lube environment on bearing performance  

NASA Astrophysics Data System (ADS)

Running torque data of SR6 ball bearings are presented for different temperatures and speeds. The data are discussed in contrast to generally used torque prediction models and point out the need to obtain empirical data in critical applications. Also, the effects of changing bearing washing techniques from old, universally used CFC-based systems to CFC-free aqueous/alkaline solutions are discussed. Data on wettability, torque and lubricant life using SR3 ball bearings are presented. In general, performance is improved using the new aqueous washing techniques.

Ward, Peter C.

1995-05-01

272

Bears, Big and Little. Young Discovery Library Series.  

ERIC Educational Resources Information Center

This book is written for children 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume describes: (1) the eight species of bears, including black bear, brown bear, grizzly bear, spectacled bear, sun bear, sloth bear, polar bear, and giant panda; (2) geographical habitats of bears; (3)…

Pfeffer, Pierre

273

Magnetic bearings at Draper Laboratory  

SciTech Connect

Magnetic bearings, unlike traditional mechanical bearings, consist of a series of components which when mated together form a stabilized system. The correct design of the actuator and sensor will provide a cost effective device with low power requirements. The proper choice of a control system utilizes the variables necessary to control the system in an efficient manner. The specific application will determine the optimum design of the magnetic bearing system including the touch down bearing. Draper for the past 30 years has been a leader in all these fields. This paper summaries the results carried out at Draper in the field of magnetic bearing development. A 3-D radial magnetic bearing is detailed in this paper. Data obtained from recently completed projects using this design are included. One project was a high radial load (1000 pound) application. The second was a high speed (35,000 RPM), low loss flywheel application. The development of a low loss axial magnetic bearing is also included in this paper.

Kondoleon, A.S.; Kelleher, W.P.; Possel, P.D. [C.S. Draper Lab., Cambridge, MA (United States)

1995-12-31

274

ATM CMG bearing failure analysis  

NASA Technical Reports Server (NTRS)

The cause or causes for the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2) were investigated. Skylab telemetry data were reviewed and presented in the form of parameter distributions. The theory that the problems were caused by marginal bearing lubrication was studied along with the effects of orbital conditions on lubricants. Bearing tests were performed to investigate the effect of lubricant or lack of lubricant in the ATM CMG bearings and the dispersion and migration of the lubricant. The vacuum and weightless conditions of space were simulated in the bearing tests. Analysis of the results of the tests conducted points to inadequate lubrication as the predominant factor causing the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2).

1975-01-01

275

A Passive Magnetic Bearing Flywheel  

NASA Technical Reports Server (NTRS)

A 100 percent passive magnetic bearing flywheel rig employing no active control components was designed, constructed, and tested. The suspension clothe rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which is 65 percent above the first critical speed of 3336 rpm. Operation was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment in case of failure. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Siebert, Mark; Ebihara, Ben; Jansen, Ralph; Fusaro, Robert L.; Morales, Wilfredo; Kascak, Albert; Kenny, Andrew

2002-01-01

276

Myrmecophagy by Yellowstone grizzly bears  

USGS Publications Warehouse

I used data collected during a study of radio-marked grizzly bears (Ursus arctos horribilis) in the Yellowstone region from 1977 to 1992 to investigate myrmecophagy by this population. Although generally not an important source of energy for the bears (averaging 8 mm long) nested in logs over small ants (6 mm long) nested under stones. Optimal conditions for consumption of ants occurred on the warmest sites with ample substrate suitable for ant nests. For ants in mounds, this occurred at low elevations at non-forested sites. For ants in logs, this occurred at low elevations or on southerly aspects where there was abundant, large-diameter, well-decomposed woody debris under an open forest canopy. Grizzly bears selected moderately decomposed logs 4a??5 dm in diameter at midpoint. Ants will likely become a more important food for Yellowstone's grizzly bears as currently important foods decline, owing to disease and warming of the regional climate.

Mattson, D.J.

2001-01-01

277

Complications of unilateral weight bearing.  

PubMed

The most common and significant complication of excessive unilateral weight bearing in adult horses is support limb laminitis. Young horses with unilateral lameness problems develop support limb laminitis infrequently compared with adult horses. PMID:19203705

Baxter, Gary M; Morrison, Scott

2008-12-01

278

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing is disclosed including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure. 9 figs.

Hull, J.R.; Mulcahy, T.M.

1998-03-03

279

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure.

Hull, John R. (Hinsdale, IL); Mulcahy, Thomas M. (Western Springs, IL)

1998-01-01

280

Predicting Temperatures In Ball Bearings  

NASA Technical Reports Server (NTRS)

Computer simulations speed design studies. Analyses performed in two or three dimensions. Sizes and shapes of components approximated by zones or nodes connected by gridlines. From geometric information about grids and boundary conditions, properties of bearing and lubricant materials, and information supplied by users, thermal-analysis programs generate mathematical models for thermal transport. Thermal analysis of high-speed rolling contact bearings matured so much that computerized numerical simulations replace expensive time consuming full scale experiments.

Wagner, William R.; Hemmings, Brad R.

1988-01-01

281

Lateral dampers for thrust bearings  

NASA Technical Reports Server (NTRS)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D. H.; Szafir, D. R.

1985-01-01

282

Therapeutic Vaccination against Adjuvant Arthritis Using Autoimmune T Cells Treated with Hydrostatic Pressure  

NASA Astrophysics Data System (ADS)

An ideal treatment for autoimmune diseases would be a nontoxic means of specifically neutralizing the autoreactive lymphocytes responsible for the disease. This goal has been realized in experimental autoimmunity models by immunizing rats or mice against their own autoimmune cells such that the animals generate an immune response specifically repressive to the disease-producing lymphocytes. This maneuver, termed lymphocyte vaccination, was demonstrated to be effective using some, but not all, autoimmune helper T-lymphocyte lines. We now report that T lymphocytes, otherwise incapable of triggering an immune response, can be transformed into effective immunogens by treating the cells in vitro with hydrostatic pressure. Clone A2b, as effector clone that recognized cartilage proteoglycan and caused adjuvant arthritis in Lewis rats, is such a cell. Untreated A2b could not trigger an immune response, but inoculating rats with pressure-treated A2b induced early remission of established adjuvant arthritis as well as resistance to subsequent disease. Specific resistance to arthritis was associated with anti-idiotypic T-cell reactivity to clone A2b and could be transferred from vaccinated rats to naive recipients using donor lymphoid cells. Aggregation of T-lymphocyte membrane components appeared to be important for an immune response because the effects of hydrostatic pressure could be reproduced by treatment of A2b with chemical cross-linkers or with agents disrupting the cytoskeleton. Populations of lymph node cells from antigen-primed rats, when treated with hydrostatic pressure, could also induce suppression of disease. Thus, effective vaccines can be developed without having to isolate the autoimmune T lymphocytes as lines or clones. These results demonstrate that effector T lymphocytes suitably treated may serve as agents for specifically controlling the immune system.

Lider, Ofer; Karin, Nathan; Shinitzky, Meir; Cohen, Irun R.

1987-07-01

283

A New Experimental System for the Extended Application of Cyclic Hydrostatic Pressure to Cell Culture  

PubMed Central

Mechanical forces have been shown to be important stimuli for the determination and maintenance of cellular phenotype and function. Many cells are constantly exposed in vivo to cyclic pressure, shear stress, and/or strain. Therefore, the ability to study the effects of these stimuli in vitro is important for understanding how they contribute to both normal and pathologic states. While there exist commercial as well as custom-built devices for the extended application of cyclic strain and shear stress, very few cyclic pressure systems have been reported to apply stimulation longer than 48 h. However, pertinent responses of cells to mechanical stimulation may occur later than this. To address this limitation, we have designed a new cyclic hydrostatic pressure system based upon the following design variables: minimal size, stability of pressure and humidity, maximal accessibility, and versatility. Computational fluid dynamics (CFD) was utilized to predict the pressure and potential shear stress within the chamber during the first half of a 1.0 Hz duty cycle. To biologically validate our system, we tested the response of bone marrow progenitor cells (BMPCs) from Sprague Dawley rats to a cyclic pressure stimulation of 120/80 mm Hg, 1.0 Hz for 7 days. Cellular morphology was measured using Scion Image, and cellular proliferation was measured by counting nuclei in ten fields of view. CFD results showed a constant pressure across the length of the chamber and no shear stress developed at the base of the chamber where the cells are cultured. BMPCs from Sprague Dawley rats demonstrated a significant change in morphology versus controls by reducing their size and adopting a more rounded morphology. Furthermore, these cells increased their proliferation under cyclic hydrostatic pressure. We have demonstrated that our system imparts a single mechanical stimulus of cyclic hydrostatic pressure and is capable of at least 7 days of continuous operation without affecting cellular viability. Furthermore, we have shown for the first time that BMPCs respond to cyclic hydrostatic pressure by alterations in morphology and increased proliferation. PMID:17227105

Maul, Timothy M.; Hamilton, Douglas W.; Nieponice, Alejandro; Soletti, Lorenzo

2007-01-01

284

A High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Applications  

SciTech Connect

Since 1998 several hydrostatic leveling systems (HLS) have been installed in different locations at Fermilab. This work was in collaboration with Budker Institute and SLAC. All systems were either half-filled pipe (HF) or full-filled pipe (FF). Issues assembling HLS are covered in this article. An improved and cost-effective water system with temperature stabilized of water media is presented. This proposal is a double-tube full-filled DT-FF system. Examples of hardware configurations are included for systems located at Fermilab.

Singatulin, Shavkat; Volk, J.; Shiltsev, V.; Chupyra, A.; Medvedko, A.; Kondaurov, M.

2006-09-01

285

Effect of Hydrostatic Pressure on Growth and Viability of Vibrio parahaemolyticus  

PubMed Central

Six strains of marine bacteria, including three strains of Vibrio parahaemolyticus, two Vibrio spp isolated from coastal regions, and the deep ocean isolate Pseudomonas bathycetes, were examined for ability to survive and grow at deep ocean hydrostatic pressures. V. parahaemolyticus and the coastal Vibrio spp. were unable to survive or grow at 200, 400, 600, 800, or 1,000 atm of pressure. In contrast, the deep ocean isolate P. bathycetes was capable of survival and growth at these pressures. The evidence strongly supports the neritic or estuarine origin and habitat for V. parahaemolyticus. PMID:4451378

Schwarz, J. R.; Colwell, R. R.

1974-01-01

286

Hydrostatic-pressure dependence of the photoconductivity of single-crystal pentacene and tetracene  

NASA Astrophysics Data System (ADS)

Pentacene and tetracene show readily observable photoconductivity when illuminated with light in the blue part of the visible spectrum. We measured the change of photoconductivity with hydrostatic pressure in single-crystal samples of both materials. Possible mechanisms for the observed increase in photoconductivity with pressure are discussed. We conclude that a carrier-mobility increase under pressure is most likely to cause the increase in photoconductivity in the case of pentacene. For tetracene, changes in the absorption spectrum in the range of the excitation wavelengths may also be significant. We also observe a phase transition near 0.3 GPa in tetracene, in agreement with previous results.

Rang, Zhenlin; Haraldsson, Anders; Kim, Dong M.; Ruden, P. Paul; Nathan, Marshall I.; Chesterfield, Reid J.; Frisbie, C. Daniel

2001-10-01

287

Enhancement of Jahn-Teller isomerism in Mn12Ac under high quasi-hydrostatic pressure  

Microsoft Academic Search

The behavior of Mn12O12(O2CCH3)16(H2O)4 (Mn12Ac) under high quasi-hydrostatic pressure at 2.0 K is examined using a miniature Be-Cu high-pressure cell and a superconducting quantum interference device magnetometer. Under these conditions, Mn12Ac behaves as a single molecule magnet, and, as the pressure is increased, the stepped magnetization curve undergoes a gradual shape change. The most characteristic of these changes is an

Yoshihito Suzuki; Keiji Takeda; Kunio Awaga

2003-01-01

288

X-ray and calorimetric detection of a hydrostatic pressure-induced AgI polytype  

NASA Astrophysics Data System (ADS)

Freshly prepared hexagonal polycrystalline AgI( a0, c0) subjected to hydrostatic pressures up to 12.75 MPa yield a major, metastable phase with a = a0, c ? ?2 c0. This phase which is stable upon release of pressure, is further characterised by an additional endotherm in DSC at 150.2°C, besides the minor endotherm at 148.6°C both characteristic of the transformation of AgI to the disordered b.c.c. structure. The metastable phase is, however, restored upon thermal cycling from high temperature. SEM of pressurised samples support these observations.

Radha Krishna Murphy, N.; Sunandana, C. S.

1992-07-01

289

Assessment of the non-hydrostatic effect on the upper atmosphere using a general circulation model (GCM)  

NASA Astrophysics Data System (ADS)

Under hydrostatic equilibrium, a typical assumption used in global thermosphere ionosphere models, the pressure gradient in the vertical direction is exactly balanced by the gravity force. Using the non-hydrostatic Global Ionosphere Thermosphere Model (GITM), which solves the complete vertical momentum equation, the primary characteristics of non-hydrostatic effects on the upper atmosphere are investigated. Our results show that after a sudden intense enhancement of high-latitude Joule heating, the vertical pressure gradient force can locally be 25% larger than the gravity force, resulting in a significant disturbance away from hydrostatic equilibrium. This disturbance is transported from the lower altitude source region to high altitudes through an acoustic wave, which has been simulated in a global circulation model for the first time. Due to the conservation of perturbation energy, the magnitude of the vertical wind perturbation increases with altitude and reaches 150 (250) m/s at 300 (430) km during the disturbance. The upward neutral wind lifts the atmosphere and raises the neutral density at high altitudes by more than 100%. These large vertical winds are not typically reproduced by hydrostatic models of the thermosphere and ionosphere. Our results give an explanation of the cause of such strong vertical winds reported in many observations.

Deng, Yue; Richmond, Arthur D.; Ridley, Aaron J.; Liu, Han-Li

2008-01-01

290

RESIDUAL GAS MOTIONS IN THE INTRACLUSTER MEDIUM AND BIAS IN HYDROSTATIC MEASUREMENTS OF MASS PROFILES OF CLUSTERS  

SciTech Connect

We present analysis of bulk and random gas motions in the intracluster medium using high-resolution Eulerian cosmological simulations of 16 simulated clusters, including both very relaxed and unrelaxed systems and spanning a virial mass range of 5 x 10{sup 13} - 2 x 10{sup 15} h{sup -1} M-odot. We investigate effects of the residual subsonic gas motions on the hydrostatic estimates of mass profiles and concentrations of galaxy clusters. In agreement with previous studies, we find that the gas motions contribute up to approx5%-15% of the total pressure support in relaxed clusters with contribution increasing with the cluster-centric radius. The fractional pressure support is higher in unrelaxed systems. This contribution would not be accounted for in hydrostatic estimates of the total mass profile and would lead to systematic underestimate of mass. We demonstrate that total mass can be recovered accurately if pressure due to gas motions measured in simulations is explicitly taken into account in the equation of hydrostatic equilibrium. Given that the underestimate of mass is increasing at larger radii, where gas is less relaxed and contribution of gas motions to pressure is larger, the total density profile derived from hydrostatic analysis is more concentrated than the true profile. This may at least partially explain some high values of concentrations of clusters estimated from hydrostatic analysis of X-ray data.

Lau, Erwin T.; Kravtsov, Andrey V. [Department of Astronomy and Astrophysics, 5640 South Ellis Ave., University of Chicago, Chicago, IL 60637 (United States); Nagai, Daisuke, E-mail: ethlau@oddjob.uchicago.ed [Department of Physics, Yale University, New Haven, CT 06520 (United States)

2009-11-10

291

Design Formulas for Permanent-Magnet Bearings  

Microsoft Academic Search

The development of high-energy product permanent magnet ~PM! materials has made PM magnetic bearings an attractive op- tion for applications ranging from turbo machinery to energy- storage flywheels. In small high-speed turbo compressors, bearing longevity is a problem that can be resolved with PM magnetic bearings. In space instrument applications, magnetic bearings eliminate the need for lubricants, which can contaminate

Brad Paden; Nelson Groom; James F. Antaki

2008-01-01

292

Journal gas bearing for curved surfaces  

NASA Technical Reports Server (NTRS)

Optimizing bearing length and permissible axis curvature alleviates distortion of film gap of gas lubricated journal bearing in deployment mechanisms. Required bearing length is divided into two shorter bearings interconnected by links which allow satisfactory conformity with the bent, load-carrying member.

Redmon, J. W.

1969-01-01

293

Application of foil bearings to helium turbocompressor  

SciTech Connect

Hydrodynamic gas-lubricated foil bearings are ideal for machinery that operates at high speed or in extreme-temperature environments. As motors and generators run at higher speeds with more torque capacity, the need for commonly available, robust, high-speed, low-loss foil bearings is clear. This paper presents an application example of the successful replacement of a tape-type bearing for a bump-type bearing in a helium turbocompressor. Both bearing types are described, as are the steps involved in design and fabrication of the bump bearing, and results of comparison tests between the original and replacement bearings. Methods to analyze bump-type foil bearings with commercially available software are reviewed to further emphasize the inherent simplicity of these bearings. By providing the engineering community with the understanding needed to successfully apply foil bearings, the authors hope that the benefits and true potential of this technology will finally be realized.

Chen, H.Ming; Howarth, R.; Bernard, Geren; Theilacker, Jay C.; Soyars, William M.; /Fermilab

2001-01-01

294

Development and evaluation of a hydrostatic dynamical core using the spectral element/discontinuous Galerkin methods  

NASA Astrophysics Data System (ADS)

In this paper, we present a dynamical core for the atmospheric primitive hydrostatic equations using a unified formulation of spectral element (SE) and discontinuous Galerkin (DG) methods in the horizontal direction with a finite difference (FD) method in the radial direction. The CG and DG horizontal discretization employs high-order nodal basis functions associated with Lagrange polynomials based on Gauss-Lobatto-Legendre (GLL) quadrature points, which define the common machinery. The atmospheric primitive hydrostatic equations are solved on the cubed-sphere grid using the flux form governing equations in a three-dimensional (3-D) Cartesian space. By using Cartesian space, we can avoid the pole singularity problem due to spherical coordinates and this also allows us to use any quadrilateral-based grid naturally. In order to consider an easy way for coupling the dynamics with existing physics packages, we use a FD in the radial direction. The models are verified by conducting conventional benchmark test cases: the Rossby-Haurwitz wavenumber 4, Jablonowski-Williamson tests for balanced initial state and baroclinic instability, and Held-Suarez tests. The results from those tests demonstrate that the present dynamical core can produce numerical solutions of good quality comparable to other models.

Choi, S.-J.; Giraldo, F. X.

2014-06-01

295

Hydrostatic equilibrium of insular, static, spherically symmetric, perfect fluid solutions in general relativity  

E-print Network

An analysis of insular solutions of Einstein's field equations for static, spherically symmetric, source mass, on the basis of exterior Schwarzschild solution is presented. Following the analysis, we demonstrate that the {\\em regular} solutions governed by a self-bound (that is, the surface density does not vanish together with pressure) equation of state (EOS) or density variation can not exist in the state of hydrostatic equilibrium, because the source mass which belongs to them, does not represent the `actual mass' appears in the exterior Schwarzschild solution. The only configuration which could exist in this regard is governed by the homogeneous density distribution (that is, the interior Schwarzschild solution). Other structures which naturally fulfill the requirement of the source mass, set up by exterior Schwarzschild solution (and, therefore, can exist in hydrostatic equilibrium) are either governed by gravitationally-bound regular solutions (that is, the surface density also vanishes together with pressure), or self-bound singular solutions (that is, the pressure and density both become infinity at the centre).

P. S. Negi

2002-10-01

296

TESTING MODELS FOR MOLECULAR GAS FORMATION IN GALAXIES: HYDROSTATIC PRESSURE OR GAS AND DUST SHIELDING?  

SciTech Connect

Stars in galaxies form in giant molecular clouds that coalesce when the atomic hydrogen is converted into molecules. There are currently two dominant models based on the property of the galactic disk that determines its molecular fraction: either hydrostatic pressure driven by the gravity of gas and stars, or a combination of gas column density and metallicity. To assess the validity of these models, we compare theoretical predictions to the observed atomic gas content of low-metallicity dwarf galaxies with high stellar densities. The extreme conditions found in these systems are optimal for distinguishing the two models, otherwise degenerate in nearby spirals. Locally, on scales <100 pc, we find that the state of the interstellar medium is mostly sensitive to the gas column density and metallicity rather than hydrostatic pressure. On larger scales where the average stellar density is considerably lower, both pressure and shielding models reproduce the observations, even at low metallicity. We conclude that models based on gas and dust shielding more closely describe the process of molecular formation, especially at the high resolution that can be achieved in modern galaxy simulations or with future radio/millimeter arrays.

Fumagalli, Michele; Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Hunt, Leslie K., E-mail: mfumagalli@ucolick.or [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze (Italy)

2010-10-10

297

Hydrostatically coupled dielectric elastomer actuators for tactile displays and cutaneous stimulators  

NASA Astrophysics Data System (ADS)

Hydrostatic coupling has been recently reported as a means to improve versatility and safety of dielectric elastomer (DE) actuators. Hydrostatically coupled DE actuators rely on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load. In this paper, we present ongoing development of bubble-like versions of such transducers, made of silicone and oil. In particular, the paper describes millimeter-scale actuators, currently being developed as soft, light, acoustically silent and cheap devices for two types of applications: tactile displays and cutaneous stimulators. In both cases, the most significant advantages of the proposed technology are represented by high versatility for design (due to the fluid based transmission mechanism), tailorable stiffness perceived by the user (obtained by adjusting the internal fluid pressure), and suitable electrical safety (enabled by both a passive interface with the user and the insulating internal fluid). Millimeter-scale prototypes showed a resonance frequency of about 250 Hz, which represents the value at which Pacinian cutaneous mechanoreceptors exhibit maximum sensitivity; this provides an optimum condition to eventually code tactile information dynamically, either in combination or as an alternative to static driving.

Carpi, Federico; Frediani, Gabriele; De Rossi, Danilo

2010-04-01

298

Hydrogenic impurity states in a parabolic quantum dot: Hydrostatic pressure and electric field effects  

NASA Astrophysics Data System (ADS)

The binding energy of hydrogenic impurity associated with the ground state and some low-lying states in a GaAs spherical parabolic quantum dot with taking into account hydrostatic pressure and electric field are theoretically studied by using the configuration-integration method. The binding energies of these low-lying states of the impurity depend sensitively on the hydrostatic pressure, electric field and the strength of the parabolic confinement. Based on the analysis of these impurity states, we propose a way for preparation of quantum bit (qubit) by using the strong quantum confinement to the impurity in the quantum dot. Also we calculate the wave functions of some low-lying states to discuss the oscillator strength which is related to the electronic dipole-allowed transitions from 0s state to 0p state. The results show that the electronic dipole-allowed transitions mostly happen between the 0s state and 0p state, especially for the quantum confinement large enough.

Yuan, Jian-Hui; Zhang, Yan; Li, Meng; Wu, Zhi-Hui; Mo, Hua

2014-10-01

299

Cryogenic strength and microstructure of a hydrostatically extruded austenitic steel 1.4429 (AISI 316LN)  

NASA Astrophysics Data System (ADS)

The as-received material with the average equivalent grain diameter of 45 ?m was subjected to a hydrostatic extrusion process to a total true strain of 0.25, 0.84 and 1.36. Static tensile tests of the extruded material, performed at the room temperature, in liquid nitrogen and liquid helium. The material extruded to the strain of 1.36 and tested in liquid helium revealed ultimate strength 2.6 GPa. The results obtained for strengthened material were compared with the properties of as-received state. The effect of extrusion on the structure of this material was examined by transmission and scanning electron microscopy. The presence of necking and the nature of fracture surfaces in the specimens subjected to tensile tests confirm ductile behaviour of the extruded material even at liquid helium temperature, despite limited ductility. The results show that the hydrostatically extruded austenitic stainless steel is a promising material for relatively small, heavy loaded components working at cryogenic conditions.

Czarkowski, P.; Krawczy?ska, A. T.; Brynk, T.; Nowacki, M.; Lewandowska, M.; Kurzyd?owski, K. J.

2014-11-01

300

Two-electrode voltage clamp of Xenopus oocytes under high hydrostatic pressure.  

PubMed

Functional assays of cloned ion channels and other transport systems under various hydrostatic pressures provide information on the apparent changes in protein volume occurring during conformational rearrangements. Thus, they are valuable tools in the detailed study of the molecular steps underlying the functioning of such proteins. Here we present details of a set-up which can be used for two-electrode voltage-clamp experiments on Xenopus oocytes, commonly used for heterologous protein expression, at hydrostatic (oil) pressures as high as 60 MPa (approximately 600 atm.). The advantages of this set-up over pneumatic systems include the minimization of compression/decompression-induced temperature changes, and an increased safety of handling due to the small volume (< 10 ml) of compression medium (oil) required. The performance of the system is illustrated using experimental data on the effects of high pressure on currents recorded from oocytes expressing a Shaker potassium channel mutant. This set-up is suitable for the investigation of all electrically measurable transport systems expressed in Xenopus oocytes. PMID:9696303

Schmalwasser, H; Neef, A; Elliott, A A; Heinemann, S H

1998-06-01

301

Validity conditions of the hydrostatic approach for self-gravitating systems: a microcanonical analysis  

NASA Astrophysics Data System (ADS)

We consider a system of hard spheres with gravitational interactions in a stationary state described in terms of the microcanonical ensemble. We introduce a set of similar auxiliary systems with increasing sizes and numbers of particles. The masses and radii of the hard spheres of the auxiliary systems are rescaled in such a way that the usual extensive properties are maintained despite the long-range nature of the gravitational interactions, while the mass density and packing fractions are kept fixed. We show, within that scaling limit, that a local thermalization spontaneously emerges as a consequence of both extensive properties and the relative smallness of the fluctuations. The resulting mass density profile for the infinite system can be determined within a hydrostatic approach, where the gradient of the local hard-sphere pressure is balanced by the average gravitational field. The derivation sheds light on the mechanisms which ensure that the local equilibrium in the infinite system is entirely controlled by hard-core interactions, while gravitational interactions can be treated at the mean-field level. This allows us to determine the conditions under which the hydrostatic approach is also valid for the actual finite system of interest. We provide simple tests of such conditions for a few astrophysical examples.

Champion, M.; Alastuey, A.; Dauxois, T.; Ruffo, S.

2014-06-01

302

Hg,Re-1223 system: Tc dependence on hydrostatic pressure and thermopower measurements  

NASA Astrophysics Data System (ADS)

Samples of Hg 1- xRe xBa 2Ca 2Cu 3O 8+ ? superconductor (Hg,Re-1223) were prepared with varying rhenium (Re) nominal content (0.15? x?0.20) in order to study the changes on the critical temperature under external hydrostatic pressure. At low pressures the ? Tc/? P depends strongly on the Re doping and the sample with x=0.18 shows the largest measured value. However, thermopower measurements reveal that there is no significant change in the numbers of carriers for the different Re content (0.15? x?0.20) meaning that ? Tc/? n is the same for all samples which, in principle, have an optimal oxygen content. Taking into account that d Tc/d P=? Tci/? P+[? Tc/? n][? n/? P] and ? Tc/? n does not depend on the Re content we can argue that the intrinsic term (? Tci/? P) determines the influence of external hydrostatic pressure on Tc.

Orlando, M. T. D.; de Mello, E. V. L.; Passos, C. A. C.; Caputo, M. R. C.; Martinez, L. G.; Zeini, B.; Yugue, E. S.; Vanoni, W.; Baggio-Saitovitch, E.

2001-11-01

303

Superconductor bearings, flywheels and transportation  

NASA Astrophysics Data System (ADS)

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

2012-01-01

304

Wave Journal Bearing. Part 1: Analysis  

NASA Technical Reports Server (NTRS)

A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

Dimofte, Florin

1995-01-01

305

Wave journal bearing. Part 1: Analysis  

SciTech Connect

A wave journal bearing concept features a waved inner ring diameter and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing`s design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of the applied load. Increasing the number of waves reduces the wave bearing`s sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

Dimofte, F. [Univ. of Toledo, Cleveland, OH (United States)

1995-12-31

306

Estimating Wear Of Installed Ball Bearings  

NASA Technical Reports Server (NTRS)

Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.

Keba, John E.; Mcvey, Scott E.

1993-01-01

307

Tardigrades: Bears of the Moss  

NSDL National Science Digital Library

This online PowerPoint presentation is dedicated to the phylum Tardigrada. It discusses distinguishing characteristics of Tardigrades (also known as water bears), their relationship to arthropods and nematodes, internal structures, life stages, cryptobiosis, research opportunities, classification, identification, habitat, distribution, ease of study in the lab, and more. Each slide contains illustrations and descriptions of the microscopic animal.

Miller, William; College, Southwestern

308

The correct "ball bearings" data.  

PubMed

The famous data on fatigue failure times of ball bearings have been quoted incorrectly from Lieblein and Zelen's original paper. The correct data include censored values, as well as non-fatigue failures that must be handled appropriately. They could be described by a mixture of Weibull distributions, corresponding to different modes of failure. PMID:12471947

Caroni, C

2002-12-01

309

Flywheel Challenge: HTS Magnetic Bearing  

Microsoft Academic Search

A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh\\/280 kW flywheel energy storage system (COM -

F N Werfel; U Floegel-Delor; T Riedel; R Rothfeld; D Wippich; B Goebel

2006-01-01

310

Superconductor bearings, flywheels and transportation  

Microsoft Academic Search

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared

F N Werfel; U Floegel-Delor; R Rothfeld; T Riedel; B Goebel; D Wippich; P Schirrmeister

2012-01-01

311

Losses of Superconductor Journal Bearing  

NASA Astrophysics Data System (ADS)

A high-temperature superconductor (HTS) journal bearing was studied for rotational loss. Two HTS bearings support the rotor at top and bottom. The rotor weight is 4 kg and the length is about 300 mm. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Each HTS journal bearing is composed of six pieces of superconductor blocks of size 35×25×10 mm. The HTS blocks are encased in a cryochamber through which liquid nitrogen flows. The inner spool of the cryochamber is made from G-10 to reduce eddy current loss, and the rest of the cryochamber is stainless steel. The magnetic field from the PM rings is < 10 mT on the stainless part. The rotational drag was measured over the same speed range at several chamber pressures. Results indicate that a chamber pressure of 0.4 mtorr is sufficiently low to minimize windage loss, and the 10 mT design criterion for the magnetic field on the stainless part of the cryochamber is too high.

Han, Y. H.; Hull, J. R.; Han, S. C.; Jeong, N. H.; Oh, J. M.; Sung, T. H.

2004-06-01

312

Generation of large volume hydrostatic pressure to 8 GPa for ultrasonic studies  

NASA Astrophysics Data System (ADS)

The design and performance of a liquid-solid hybrid cell to generate high hydrostatic pressures in a relatively large volume (for use in measurements of the pressure dependence of the physical properties of materials) are reported. A 4:1 methanol-ethanol mixture is employed in 12-mm-side and 20-mm-side versions of an eight-cubic-anvil apparatus driven by a 10-kt press. Pressures up to 8 GPa are obtained safely in a 16-cu cm volume by applying uniaxial force of 3 kt. The cell is used to obtain measurements of the velocity of ultrasonic waves in fused quartz: the experimental setup is described, and sample results are presented graphically.

Kozuki, Yasushi; Yoneda, Akira; Fujimura, Akio; Sawamoto, Hiroshi; Kumazawa, Mineo

1986-09-01

313

The effect of high hydrostatic pressure on black truffle (tuber melanosporum) flavour compounds  

NASA Astrophysics Data System (ADS)

The effects of high hydrostatic pressure (HHP), at 4°C or -18°C, on black truffle flavour compounds, alteration enzymes (lipoxigenase (LOX), peroxidase (POD) and polyphenoloxidase (PPO)) and microbiological qualities were evaluated. The choosen analytes for this study are six alcohols, three aldehydes, one ketone and on sulfur component. The highest flavour stability was observed when samples were pressurized at 300 MPa / 4°C / 10 min. All the treatments induced a drastic decrease of LOX activity and a slight decrease of POD activity. On the other hand, the PPO was not inactivated by pressurization at sub-zero (200 MPa / -18°C / 10 min) and was strongly increased after the 300 MPa / 4°C / 10 min treatment. Pressurization at 300 and 550 MPa lead to an almost complete Pseudomonas fluorescens reduction (6 and 6.5 log destruction, respectively) whereas pressurization at -18°C (200MPa) allowed to obtain only 3 log reduction.

Verret, C.; Ballestra, P.; Cruz, C.; Pardon, P.; Largeteau, A.; Moueffak, A. H. E.

2008-07-01

314

Vibrational, electronic and structural properties of wurtzite GaAs nanowires under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The structural, vibrational, and electronic properties of GaAs nanowires have been studied in the metastable wurtzite phase via Resonant Raman spectroscopy and synchrotron X-ray diffraction measurements in diamond anvil cells under hydrostatic conditions between 0 and 23 GPa. The direct band gap E0 and the crystal field split-off gap E0 + ? of wurtzite GaAs increase with pressure and their values become close to those of zinc-blende GaAs at 5 GPa, while being reported slightly larger at lower pressures. Above 21 GPa, a complete structural transition from the wurtzite to an orthorhombic phase is observed in both Raman and X-ray diffraction experiments.

Zhou, Wei; Chen, Xiao-Jia; Zhang, Jian-Bo; Li, Xin-Hua; Wang, Yu-Qi; Goncharov, Alexander F.

2014-09-01

315

A coupled analytical model for hydrostatic response of 1-3 piezocomposites.  

PubMed

This study presents a fully coupled analysis of a unit cell of a 1-3 piezocomposite under hydrostatic loading. The governing equations for coupled axisymmetric electroelastic field of a transversely isotropic piezoelectric medium and a transversely isotropic elastic medium are used. A reduced form of the analytical general solutions expressed in terms of series of modified Bessel functions of the first and second kind are used. The solution of the boundary-value problem corresponding to a unit cell is presented. The effective properties of a 1-3 piezocomposite are obtained for different fiber volume fractions, polymer and piezoceramic properties, and fiber aspect ratios. Comparisons with previously reported simplified and uncoupled models are made. PMID:18986927

Rajapakse, Nimal; Chen, Yue

2008-08-01

316

Vibrational, electronic and structural properties of wurtzite GaAs nanowires under hydrostatic pressure.  

PubMed

The structural, vibrational, and electronic properties of GaAs nanowires have been studied in the metastable wurtzite phase via Resonant Raman spectroscopy and synchrotron X-ray diffraction measurements in diamond anvil cells under hydrostatic conditions between 0 and 23?GPa. The direct band gap E0 and the crystal field split-off gap E0 + ? of wurtzite GaAs increase with pressure and their values become close to those of zinc-blende GaAs at 5?GPa, while being reported slightly larger at lower pressures. Above 21?GPa, a complete structural transition from the wurtzite to an orthorhombic phase is observed in both Raman and X-ray diffraction experiments. PMID:25253566

Zhou, Wei; Chen, Xiao-Jia; Zhang, Jian-Bo; Li, Xin-Hua; Wang, Yu-Qi; Goncharov, Alexander F

2014-01-01

317

Vibrational, electronic and structural properties of wurtzite GaAs nanowires under hydrostatic pressure  

PubMed Central

The structural, vibrational, and electronic properties of GaAs nanowires have been studied in the metastable wurtzite phase via Resonant Raman spectroscopy and synchrotron X-ray diffraction measurements in diamond anvil cells under hydrostatic conditions between 0 and 23?GPa. The direct band gap E0 and the crystal field split-off gap E0 + ? of wurtzite GaAs increase with pressure and their values become close to those of zinc-blende GaAs at 5?GPa, while being reported slightly larger at lower pressures. Above 21?GPa, a complete structural transition from the wurtzite to an orthorhombic phase is observed in both Raman and X-ray diffraction experiments. PMID:25253566

Zhou, Wei; Chen, Xiao-Jia; Zhang, Jian-Bo; Li, Xin-Hua; Wang, Yu-Qi; Goncharov, Alexander F.

2014-01-01

318

Islet amyloid polypeptide and high hydrostatic pressure: towards an understanding of the fibrillization process  

NASA Astrophysics Data System (ADS)

Type II Diabetes Mellitus is a disease which is characterized by peripheral insulin resistance coupled with a progressive loss of insulin secretion that is associated with a decrease in pancreatic islet ?-cell mass and the deposition of amyloid in the extracellular matrix of ?-cells, which lead to islet cell death. The principal component of the islet amyloid is a pancreatic hormone called islet amyloid polypeptide (IAPP). High-pressure coupled with FT-IR, CD, ThT fluorescence spectroscopic and AFM studies were carried out to reveal information on the aggregation pathway as well as the aggregate structure of IAPP. Our data indicate that IAPP pre-formed fibrils exhibit a strong polymorphism with heterogeneous structures very sensitive to high hydrostatic pressure, indicating a high percentage of ionic and hydrophobic interactions being responsible for the stability the IAPP fibrils.

Lopes, D. H. J.; Smirnovas, V.; Winter, R.

2008-07-01

319

The magnetic and magnetocaloric properties of Gd5Ge2Si2 compound under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The Gd5Ge2Si2 compound presents a giant magnetocaloric effect with transition temperature at around 276 K and is a very good candidate for application as an active regenerator material in room temperature magnetic refrigerators. Recently it has been shown that pressure induces a colossal magnetocaloric effect in MnAs, a material that presents a giant magnetocaloric effect and a strong magnetoelastic coupling, as also happens with the Gd5Ge2Si2 compound. This motivated a search of the colossal effect in the Gd5Ge2Si2 compound. This work reports our measurements on the magnetic properties and the magnetocaloric effect of Gd5Ge2Si2 under hydrostatic pressures up to 9.2 kbar and as a function of temperature. Contrary to what happens with MnAs, pressure increases the Curie temperature of the compound, does not affect the saturation magnetization and decreases markedly its magnetocaloric effect.

Carvalho, A. Magnus G.; Alves, Cleber S.; de Campos, Ariana; Coelho, Adelino A.; Gama, Sergio; Gandra, Flavio C. G.; von Ranke, Pedro J.; Oliveira, Nilson A.

2005-05-01

320

Superconductivity in the topological insulator Bi2Te3 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

We report the resistivity and ac susceptibility measurements of the topological insulator Bi2Te3 single crystals at pressures up to 11 GPa. Under highly hydrostatic pressure conditions generated in a multi-anvil high-pressure apparatus, a pressure-induced superconductivity only appears above a critical pressure PC˜7 GPa, coinciding with a structural transition from a rhombohedral to a monoclinic structure. The absence of superconductivity in the rhombohedral phase at pressures below PC, which is contrary to previous studies using the high-pressure apparatus with a solid pressure medium, suggests that the occurrence of superconductivity in the rhombohedral phase is sensitive to pressure conditions such as pressure inhomogeneity or uniaxial stress.

Matsubayashi, K.; Terai, T.; Zhou, J. S.; Uwatoko, Y.

2014-09-01

321

High structural stability of single wall carbon nanotube under quasi-hydrostatic high pressures  

SciTech Connect

In quasi-hydrostatic conditions, single wall carbon nanotubes (SWNTs) exhibit high structural stability to {approx}35 GPa, well beyond the stability of sp{sup 2} C{double_bond}C bonds in graphite, carbon fullerenes, benzene, and other hydrocarbons. The pressure-induced Raman changes of SWNT are completely reversible below 16 GPa, partially reversible between 16 and 35 GPa, and irreversible beyond 35 GPa where it turns into highly disordered graphite. We explain the high stability in terms of the pressure-induced structural modification to an interlinked configuration, which occurs reversibly under substantial sp{sup 3} hybridization ({approx}20%) and, thus, increases the stability of sp{sup 2} C{double_bond}C bonds in the SWNTs.

Chen, Jing-Yin; Kim, Minseob; Yoo, Choong-Shik; (WSU)

2009-11-23

322

Raman scattering in strained Si1-xGex layers under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The Si-Si Raman mode in Si1-xGex layers pseudomorphically strained to Si and in bulk Si1-xGex was investigated as a function of externally applied hydrostatic pressure. The experiments demonstrate that bulk elastic properties can be derived from the pressure-dependent Raman investigations of thin strained hetero-epitaxial layers. Our experimental results are favourably analysed using linear interpolation for the components of elastic stiffness tensor of the Si1-xGexcompounds. It was found that the pressure derivative of strained Si1-xGex increases with the Ge concentration. Our analysis suggests that the Grüneisen parameter for strained Si1-xGex is higher than expected from linear interpolation between the Si and the Ge values and that it has slight negative pressure dependence.

Gerling, Maria; Dietrich, Burkhart

2001-07-01

323

Presence of parimagnetism in HoCo2 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

This paper deals with a pressure evolution of newly observed phenomenon -parimagnetism in HoCo2. HoCo2 containing localized Ho magnetic moments and itinerant Co magnetic moments order ferrimagnetically below TC = 79.5 K at ambient pressure. The corresponding Ho and Co magnetic sublattices are ferromagnetic and coupled mutually antiparallel. In paramagnetic range, the Co moments form ferromagnetic clusters which hold short range antiparallel configuration with the nearest Ho moments at temperatures up to the flipping temperature Tf = 125 K. The decay of Co clusters was observed by muon spin relaxation spectroscopy (?SR) at T* ~ 170 K. Our results of AC-magnetic susceptibility and zero-field ?SR measurements of HoCo2 at ambient and hydrostatic pressures presented in this paper reveal strong pressure dependence of the characteristic temperatures which is closely related to the itinerant character of Co magnetism and variations of exchange interactions.

Valenta, J.; Prchal, J.; Khasanov, R.; Kratochvílová, M.; Míšek, M.; Vališka, M.; Sechovský, V.

2014-05-01

324

Suppression of first cleavage in the Mexican axolotl (Ambystoma mexicanum) by heat shock or hydrostatic pressure  

SciTech Connect

Androgenetic diploid axolotls were produced by ultraviolet inactivation of the egg pronucleus shortly after fertilization, followed by suppression of the first cleavage division by hydrostatic pressure or heat shock. After treatment at 14,000 psi for 8 minutes, diploidy was restored in 74% of the embryos, but only 0.8% survived to hatching. A 36-37 degrees C heat shock of 10-minutes duration, applied 5.5 hours after the eggs were collected, yielded a slightly lower percentage of diploids. However, the proportion surviving to hatching was significantly greater (up to 4.6%). A second generation of androgenetic diploids was produced from one of the oldest of the first generation males with a similar degree of success. The lack of significant improvement suggests that the low survival is due to the heat shock per se and not to the uncovering of recessive lethal genes carried by the parent.

Gillespie, L.L.; Armstrong, J.B.

1981-12-01

325

A system for acoustical and optical analysis of encapsulated microbubbles at ultrahigh hydrostatic pressures.  

PubMed

Acoustics are commonly used for borehole (i.e., oil well) imaging applications, under conditions where temperature and pressure reach extremes beyond that of conventional medical ultrasonics. Recently, there has been an interest in the application of encapsulated microbubbles as borehole contrast agents for acoustic assessment of fluid composition and flow. Although such microbubbles are widely studied under physiological conditions for medical imaging applications, to date there is a paucity of information on the behavior of encapsulated gas-filled microbubbles at high pressures. One major limitation is that there is a lack of experimental systems to assess both optical and acoustic data of micrometer-sized particles data at these extremes. In this paper, we present the design and application of a high-pressure cell designed for acoustical and optical studies of microbubbles at hydrostatic pressures up to 27.5 MPa (271 atm). PMID:23742587

Zhushma, Aleksandr; Lebedeva, Natalia; Sen, Pabitra; Rubinstein, Michael; Sheiko, Sergei S; Dayton, Paul A

2013-05-01

326

Optical properties of BP, BAs and BSb compounds under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

We present results of a study of the electronic and optical properties of zinc-blende BP, BAs and BSb compounds. The refractive index and its variation with hydrostatic pressure are well described. Accurate calculation of linear optical function (index of refraction and its pressure derivative, and both imaginary and real parts of dielectric function) are performed in photon energy range up to 30 eV. We have worked out calculations non-relativistic with the FP-LAPW method using the WIEN 97 code, these calculations are based on the density functional theory (DFT) with the local density approximation (LDA). We compared our results with those found by pseudopotential plane wave approach.

Zaoui, A.; Kacimi, S.; Yakoubi, A.; Abbar, B.; Bouhafs, B.

2005-10-01

327

Initiation of Germination and Inactivation of Bacillus pumilus Spores by Hydrostatic Pressure  

PubMed Central

The effect of hydrostatic pressures as high as 1,700 atm at 25 C on the heat and radiation resistance of Bacillus pumilus spores was studied. Phosphate-buffered spores were more sensitive to compression than spores suspended in distilled water. Measurements of the turbidity of suspensions, the viability, refractility, stainability, dry weight, and respiratory activity of spores, and calcium and dipicolinic acid release were made for different pressures and times. Initiation of germination occurred at pressures exceeding 500 atm and was the prerequisite for inactivation by compression. The rate of initiation increased with increasing pressure at constant temperature. This result is interpreted as a net decrease in the volume of the system during initiation as a result of increased solvation of the spore components. PMID:5773022

Clouston, J. G.; Wills, Pamela A.

1969-01-01

328

Wave Response during Hydrostatic and Geostrophic Adjustment. Part I: Transient Dynamics.  

NASA Astrophysics Data System (ADS)

The adjustment of a compressible, stably stratified atmosphere to sources of hydrostatic and geostrophic imbalance is investigated using a linear model. Imbalance is produced by prescribed, time-dependent injections of mass, heat, or momentum that model those processes considered “external” to the scales of motion on which the linearization and other model assumptions are justifiable. Solutions are demonstrated in response to a localized warming characteristic of small isolated clouds, larger thunderstorms, and convective systems.For a semi-infinite atmosphere, solutions consist of a set of vertical modes of continuously varying wavenumber, each of which contains time dependencies classified as steady, acoustic wave, and buoyancy wave contributions. Additionally, a rigid lower-boundary condition implies the existence of a discrete mode—the Lamb mode— containing only a steady and acoustic wave contribution. The forced solutions are generalized in terms of a temporal Green's function, which represents the response to an instantaneous injection.The response to an instantaneous warming with geometry representative of a small, isolated cloud takes place in two stages. Within the first few minutes, acoustic and Lamb waves accomplish an expansion of the heated region. Within the first quarter-hour, nonhydrostatic buoyancy waves accomplish an upward displacement inside of the heated region with inflow below, outflow above, and weak subsidence on the periphery—all mainly accomplished by the lowest vertical wavenumber modes, which have the largest horizontal group speed. More complicated transient patterns of inflow aloft and outflow along the lower boundary are accomplished by higher vertical wavenumber modes. Among these is an outwardly propagating rotor along the lower boundary that effectively displaces the low-level inflow upward and outward.A warming of 20 min duration with geometry representative of a large thunderstorm generates only a weak acoustic response in the horizontal by the Lamb waves. The amplitude of this signal increases during the onset of the heating and decreases as the heating is turned off. The lowest vertical wavenumber buoyancy waves still dominate the horizontal adjustment, and the horizontal scale of displacements is increased by an order of magnitude. Within a few hours the transient motions remove the perturbations and an approximately trivial balanced state is established.A warming of 2 h duration with geometry representative of a large convective system generates a weak but discernible Lamb wave signal. The response to the conglomerate system is mainly hydrostatic. After several hours, the only signal in the vicinity of the heated region is that of inertia-gravity waves oscillating about a nontrivial hydrostatic and geostrophic state.This paper is the first of two parts treating the transient dynamics of hydrostatic and geostrophic adjustment. Part II examines the potential vorticity conservation and the partitioning of total energy.

Chagnon, Jeffrey M.; Bannon, Peter R.

2005-05-01

329

SUZAKU OBSERVATIONS OF THE OUTSKIRTS OF A1835: DEVIATION FROM HYDROSTATIC EQUILIBRIUM  

SciTech Connect

We present results of four-pointing Suzaku X-ray observations (total {approx}200 ks) of the intracluster medium (ICM) in the A1835 galaxy cluster (kT {approx} 8 keV, z = 0.253) out to the virial radius (r{sub vir} {approx} 2.9 Mpc) and beyond. Faint X-ray emission from the ICM out to r{sub vir} is detected. The temperature gradually decreases with radius from {approx}8 keV in the inner region to {approx}2 keV at r{sub vir}. The entropy profile is shown to flatten beyond r{sub 500}, in disagreement with the r {sup 1.1} dependence predicted from the accretion shock heating model. The thermal pressure profile in the range 0.3r{sub 500} {approx}< r {approx}< r{sub vir} agrees well with that obtained from the stacked Sunyaev-Zel'dovich effect observations with the Planck satellite. The hydrostatic mass profile in the cluster outskirts (r{sub 500} {approx}< r {approx}< r{sub vir}) falls well short of the weak-lensing one derived from Subaru/Suprime-Cam observations, showing an unphysical decrease with radius. The gas mass fraction at r{sub vir} defined with the lensing total mass agrees with the cosmic baryon fraction from the Wilkinson Microwave Anisotropy Probe seven-year data. All these results indicate, rather than the gas-clumping effect, that the bulk of the ICM in the cluster outskirts is far from hydrostatic equilibrium and infalling matter retained some of its kinetic energy. Finally, combining with our recent Suzaku and lensing analysis of A1689, a cluster of similar mass, temperature, and redshift, we show that the cluster temperature distribution in the outskirts is significantly correlated with the galaxy density field in the surrounding large-scale environment at (1-2)r{sub vir}.

Ichikawa, Kazuya; Matsushita, Kyoko; Sato, Kosuke [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjyuku-ku, Tokyo 162-8601 (Japan)] [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjyuku-ku, Tokyo 162-8601 (Japan); Okabe, Nobuhiro; Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)] [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Zhang, Y.-Y. [Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)] [Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Haellstroemin katu 2a, FI-00014 Helsinki (Finland)] [Department of Physics, University of Helsinki, Gustaf Haellstroemin katu 2a, FI-00014 Helsinki (Finland); Fujita, Yutaka [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)] [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Fukazawa, Yasushi [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)] [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Kawaharada, Madoka; Tamura, Takayuki [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)] [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nakazawa, Kazuhiro [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)] [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ohashi, Takaya [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)] [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Ota, Naomi [Department of Physics, Nara Women's University, Kitauoyanishi-machi, Nara, Nara 630-8506 (Japan)] [Department of Physics, Nara Women's University, Kitauoyanishi-machi, Nara, Nara 630-8506 (Japan); Takizawa, Motokazu, E-mail: j1211602@ed.tus.ac.jp, E-mail: j1207016@gmail.com, E-mail: matusita@rs.kagu.tus.ac.jp [Department of Physics, Yamagata University, Yamagata, Yamagata 990-8560 (Japan)] [Department of Physics, Yamagata University, Yamagata, Yamagata 990-8560 (Japan)

2013-04-01

330

Effects of High Hydrostatic Pressure on Bacterial Growth on Human Ossicles Explanted from Cholesteatoma Patients  

PubMed Central

Background High hydrostatic pressure (HHP) treatment can eliminate cholesteatoma cells from explanted human ossicles prior to re-insertion. We analyzed the effects of HHP treatment on the microbial flora on ossicles and on the planktonic and biofilm states of selected isolates. Methodology Twenty-six ossicles were explanted from cholesteatoma patients. Five ossicles were directly analyzed for microbial growth without further treatment. Fifteen ossicles were cut into two pieces. One piece was exposed to HHP of 350 MPa for 10 minutes. Both the treated and untreated (control) pieces were then assessed semi-quantitatively. Three ossicles were cut into two pieces and exposed to identical pressure conditions with or without the addition of one of two different combinations of antibiotics to the medium. Differential effects of 10-minute in vitro exposure of planktonic and biofilm bacteria to pressures of 100 MPa, 250 MPa, 400 MPa and 540 MPa in isotonic and hypotonic media were analyzed using two patient isolates of Staphylococcus epidermidis and Neisseria subflava. Bacterial cell inactivation and biofilm destruction were assessed by colony counting and electron microscopy. Principal Findings A variety of microorganisms were isolated from the ossicles. Irrespective of the medium, HHP treatment at 350 MPa for 10 minutes led to satisfying but incomplete inactivation especially of Gram-negative bacteria. The addition of antibiotics increased the efficacy of elimination. A comparison of HHP treatment of planktonic and biofilm cells showed that the effects of HPP were reduced by about one decadic logarithmic unit when HPP was applied to biofilms. High hydrostatic pressure conditions that are suitable to inactivate cholesteatoma cells fail to completely sterilize ossicles even if antibiotics are added. As a result of the reduced microbial load and the viability loss of surviving bacteria, however, there is a lower risk of re-infection after re-insertion. PMID:22291908

Ostwald, Jurgen; Lindner, Tobias; Zautner, Andreas Erich; Arndt, Kathleen; Pau, Hans Wilhelm; Podbielski, Andreas

2012-01-01

331

The Astrophysical Journal Supplement Revised, 2002 Apr 29 Analytical Approximations to Hydrostatic Solutions and Scaling Laws of  

E-print Network

and stellar coronae can be simulated for a variety of heating functions. Subject headings: Sun: Corona tools to explore the physical processes of plasma heating and cooling in solar and stellar coronae to hydrostatic solutions of coronal loop atmospheres, applicable to uniform and non­uniform heating in a large

Schrijver, Karel

332

Flying-patch patch-clamp study of G22E-MscL mutant under high hydrostatic pressure.  

PubMed

High hydrostatic pressure (HHP) present in natural environments impacts on cell membrane biophysical properties and protein quaternary structure. We have investigated the effect of high hydrostatic pressure on G22E-MscL, a spontaneously opening mutant of Escherichia coli MscL, the bacterial mechanosensitive channel of large conductance. Patch-clamp technique combined with a flying-patch device and hydraulic setup allowed the study of the effects of HHP up to 90 MPa (as near the bottom of the Marianas Trench) on the MscL mutant channel reconstituted into liposome membranes, in addition to recording in situ from the mutant channels expressed in E. coli giant spheroplasts. In general, against thermodynamic predictions, hydrostatic pressure in the range of 0.1-90 MPa increased channel open probability by favoring the open state of the channel. Furthermore, hydrostatic pressure affected the channel kinetics, as manifested by the propensity of the channel to gate at subconducting levels with an increase in pressure. We propose that the presence of water molecules around the hydrophobic gate of the G22E MscL channel induce hydration of the hydrophobic lock under HHP causing frequent channel openings and preventing the channel closure in the absence of membrane tension. Furthermore, our study indicates that HHP can be used as a valuable experimental approach toward better understanding of the gating mechanism in complex channels such as MscL. PMID:21463576

Petrov, Evgeny; Rohde, Paul R; Martinac, Boris

2011-04-01

333

Flying-Patch Patch-Clamp Study of G22E-MscL Mutant under High Hydrostatic Pressure  

PubMed Central

High hydrostatic pressure (HHP) present in natural environments impacts on cell membrane biophysical properties and protein quaternary structure. We have investigated the effect of high hydrostatic pressure on G22E-MscL, a spontaneously opening mutant of Escherichia coli MscL, the bacterial mechanosensitive channel of large conductance. Patch-clamp technique combined with a flying-patch device and hydraulic setup allowed the study of the effects of HHP up to 90 MPa (as near the bottom of the Marianas Trench) on the MscL mutant channel reconstituted into liposome membranes, in addition to recording in situ from the mutant channels expressed in E. coli giant spheroplasts. In general, against thermodynamic predictions, hydrostatic pressure in the range of 0.1–90 MPa increased channel open probability by favoring the open state of the channel. Furthermore, hydrostatic pressure affected the channel kinetics, as manifested by the propensity of the channel to gate at subconducting levels with an increase in pressure. We propose that the presence of water molecules around the hydrophobic gate of the G22E MscL channel induce hydration of the hydrophobic lock under HHP causing frequent channel openings and preventing the channel closure in the absence of membrane tension. Furthermore, our study indicates that HHP can be used as a valuable experimental approach toward better understanding of the gating mechanism in complex channels such as MscL. PMID:21463576

Petrov, Evgeny; Rohde, Paul R.; Martinac, Boris

2011-01-01

334

SulA-independent filamentation of Escherichia coli during growth after release from high hydrostatic pressure treatment  

Microsoft Academic Search

To improve the efficiency of sterilization by high hydrostatic pressure treatment (HPT), it is desirable to know the biochemical process of bacteria most sensitive to the treatment. We investigated growth properties after release from HPT of exponentially growing Escherichia coli K-12 cells. We observed growth retardation after treatment (30 min at 37°C) above 75 MPa. Long filamentous cells of about eight times

T. Kawarai; M. Wachi; H. Ogino; S. Furukawa; K. Suzuki; H. Ogihara; M. Yamasaki

2004-01-01

335

Determination of Unit Cell Parameters of Molecular Organic Crystals Under Hydrostatic Compression at Pressures up to 5.0 GPa  

NASA Astrophysics Data System (ADS)

An accurate determination of the unit cell parameters of large organic molecules under hydrostatic compression at static high pressure is now possible at pressures up to 5.0 GPa. A new high pressure diamond anvil cell has been developed to enable the determination of accurate unit cell lattice parameters during hydrostatic compression at static high pressure on a Seimens Plattform Diffractometer using a CCD detector. The hydrostatic compression of hexanitrohexaazaisowurtzitane (HNIW) has been determined up to 2.0 GPa. A sample of ?-HNIW was statically compressed and a phase transition to the high pressure ?-HNIW phase was observed at 0.7 GPa. The compression of the unit cell parameters of ?-HNIW up to 0.7 GPa and the compression of the unit cell parameters of ?-HNIW from 0.7-2.0 GPa is presented. In addition, changes in molecular structure associated with hydrostatic compression and the molecular structure changes associated with this ?-? first order phase transition are under investigation.

Russell, T. P.; Hardie, Michaele J.; Kirschbaum, Kristin; Martin, Anthony; Pinkerton, A. Alan; Tanbug, Rasim; Piermarini, G. J.

1997-07-01

336

The effects of high hydrostatic pressure on ?-glucosidase, peroxidase and polyphenoloxidase in red raspberry ( Rubus idaeus) and strawberry ( Fragaria × ananassa)  

Microsoft Academic Search

The effects of high hydrostatic pressure on 3 important enzymes involved in flavour and colour bioformation, namely ?-glucosidase, peroxidase and polyphenoloxidase, in red raspberry (Rubus idaeus) and strawberry (Fragaria×ananassa) were studied. Fruit samples were pressurised under 400, 600 and 800 MPa for 5, 10 and 15 min at a temperature controlled between 18 and 22 °C. After application of pressure,

Alberto Garcia-Palazon; Winai Suthanthangjai; Paul Kajda; Ioannis Zabetakis

2004-01-01

337

Influence of hydrostatic compression on the sliding of a pair of edge dislocations in metals with a high impurity concentration  

NASA Astrophysics Data System (ADS)

The dynamic drag of dislocations by point defects in hydrostatically compressed metals is theoretically investigated. Account is taken of the influence of a high pressure on dislocation-dislocation and dislocation-point defect interactions. It is shown that the pressure dependence of the force causing dynamic drag of dislocations is determined by competition between these interactions.

Malashenko, V. V.; Belykh, N. V.

2013-12-01

338

Weighing Galaxy Clusters with Gas. II. On the Origin of Hydrostatic Mass Bias in ?CDM Galaxy Clusters  

NASA Astrophysics Data System (ADS)

The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (lsim 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

Nelson, Kaylea; Lau, Erwin T.; Nagai, Daisuke; Rudd, Douglas H.; Yu, Liang

2014-02-01

339

High dose vitamin C counteracts the negative interstitial fluid hydrostatic pressure and early edema generation in thermally injured rats  

Microsoft Academic Search

Background and objective: edema formation after thermal injury is rapid and fulminant within the first hour after injury and increased microvascular permeability has been claimed to be the main responsible mechanism. An acute decrease in interstitial fluid hydrostatic pressure (Pif) down to ?150 mm Hg has recently been reported in dermal burns. This strong negative tissue pressure creates a ‘suction’

Hideharu Tanaka; Tjostolv Lund; Helge Wiig; Rolf K Reed; Tetsuo Yukioka; Hiroharu Matsuda; Syuji Shimazaki

1999-01-01

340

High hydrostatic pressure effects on mold flora, citrinin mycotoxin, hydroxytyrosol, oleuropein phenolics and antioxidant activity of black table olives  

Microsoft Academic Search

High hydrostatic pressure (HHP) as a non-thermal technology is an effective tool for microbiologically safe and shelf-stable fruits. Mycotoxin citrinin (CIT) is a toxic secondary metabolite, especially produced from filamentous fungus Penicillium citrinum and is also produced by other species of Penicillium, Aspergillus, and Monascus that are able to develop on olive after harvest, during brine and storage of olives.

Özlem Toku?o?lu; Hami Alpas; Faruk Bozo?lu

2010-01-01

341

Short-bearing approximation for full journal bearings  

NASA Technical Reports Server (NTRS)

A short-bearing approximation of pressure distribution in the oil film is presented which is an extension of the pressure-distribution function of Michell and Cardullo and includes end-leakage effects. Equations giving applied load, attitude angle, location and magnitude of peak film pressure, friction, and required oil flow rate as functions of the eccentricity ratio are also given. The capacity number, a basic non dimensional quantity resulting from this analysis is the product of the Sommerfeld number and the square of the length-diameter ratio. Curves determined by this analysis are compared with previously published experimental data and theoretical curves of Sommerfeld and Cameron and Wood. Conclusions reached indicate that this approximation is of practical value for analysis of short bearings.

Ocvirk, F W

1952-01-01

342

High Temperature, Permanent Magnet Biased Magnetic Bearings  

E-print Network

The Electron Energy Corporation (EEC) along with the National Aeronautics and Space Administration (NASA) is researching magnetic bearings. The purpose of this research was to design and develop a high-temperature (1000?F) magnetic bearing system...

Gandhi, Varun R.

2010-07-14

343

Detecting Wear In Ball Bearings During Operation  

NASA Technical Reports Server (NTRS)

Strain-gauge signals at harmonics of ball-bearing-cage frequencies signify wear. Brief report describes experiments in continuing effort to interpret vibrations of machinery in terms of wear in ball bearing.

Hine, Michael J.

1988-01-01

344

Self-bearing motor design & control  

E-print Network

This thesis presents the design, implementation and control of a new class of self-bearing motors. The primary thesis contributions include the design and experimental demonstration of hysteresis self-bearing motors, novel ...

Imani Nejad, Mohammad

2013-01-01

345

Hunting for 'bears' in the backyard  

NSDL National Science Digital Library

This Micscape Magazine article offers practical hints about how to collect and study tardigrades, or water bears, from mosses in your backyard. It features a general introduction of water bears, a video, and a section of references for further reading.

Walker, Dave; Magazine, Micscape

346

Rubber bearings for precision positioning systems  

E-print Network

In this thesis we investigate the use of thin rubber sheets or laminates of metal and rubber sheets as bearings in precision positioning systems. Such bearings have the potential to replace more conventional flexures ...

Barton Martinelli, Augusto E

2005-01-01

347

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2010 CFR

... RAILROAD LOCOMOTIVE SAFETY STANDARDS Safety Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to the extent that it will leak...

2010-10-01

348

Happy Birthday Smokey Bear from Joe Acaba  

NASA Video Gallery

Expedition 32 Flight Engineer Joe Acaba wishes Smokey Bear a Happy Birthday. For 68 years Smokey Bear has been promoting fire safety and prevention through the message, â??Only You Can Prevent Wild...

349

Effects of bearing deadbands on bearing loads and rotor stability  

NASA Technical Reports Server (NTRS)

A generic model of a turbopump, simplified to bring out these effects is examined. This model demonstrates that bearing deadbands which are of the same order of magnitude or larger than the center-of-mass offset of a rotor due to mass imbalances cause significantly different dynamic behavior than would be expected of a linear, dynamical system. This fundamentally nonlinear behavior yields altered stability characteristics and altered bearing loading tendencies. It is shown that side forces can enhance system stability in the small, i.e., as long as the mass imbalance does not exceed some thresholds value or as long as no large, impulsive disturbances cause the motion to depart significantly from the region of stability. Limit cycles are investigated in this report and techniques for determining these limit cycles are developed. These limit cycles are the major source of bearing loading and appear in both synchronous and nonsynchronous forms. The synchronous limit cycles are driven by rotor imbalances. The nonsynchronous limit cycles (also called subsynchronous whirls) are self-excited and are the sources of instability.

1984-01-01

350

Bears and Pipeline Construction in Alaska  

Microsoft Academic Search

Serious problems were encountered with bears during construction of the 1274-km-long trans-Alaska oil pipelinebetween Prudhoe Bay and Valdez. This multi-billion-dollar project traversed both black bear (Ursus americanus Pallas) and grizzly bear (U. arctos L.) habitat throughout its entire length. Plans for dealing with anticipated problems with bears were often inadequate. Most (71 %) problems occurred north of the Yukon River

ERICH H. FOLLMANN; JOHN L. HECHTEL

351

Bearing fault diagnosis based on rough set  

Microsoft Academic Search

Bearing defects were categorized as localized and distributed. For on-line bearing fault diagnosis, in this paper, the time-domain kurtosis calculation and the frequency domain wavelet analysis were used to extract the transitory features of non-stationary vibration signal produced by the bearing distributed defects. To distributed defects, bearing fault diagnosis was built on the reducing decision based on rough set. According

Chen Xin; Yuhua Chen; Guofeng Wang; Hu Dong

2010-01-01

352

Cartridge Bearing System for Space Applications  

NASA Technical Reports Server (NTRS)

Conventional spin axis ball bearings have been unreliable in spacecraft, often failing by two heretofore uncontrolled processes: ball retainer instability and lubricant breakdown. The Space Cartridge Bearing System (SCBS) addresses each of these mechanisms directly, leading to a bearing system with absolute freedom from retainer instability and negligible lubricant degradation rate. The result is a reliable plug-in bearing cartridge with a definite design life.

Kingsbury, Edward P.; Hanson, Robert A.; Jones, William R.; Mohr, Terry W.

1999-01-01

353

Hydrology of the Bear Lake Basin, Utah  

Microsoft Academic Search

Bear Lake’s natural watershed is made up of relatively low mountains covered with sagebrush at lower elevations and southern exposures and fir-aspen forests at higher elevations and northern exposures. The basin is traversed by the Bear River that begins high in the Unita Mountains and flows through Utah, Idaho, and Wyoming before feeding the Great Salt Lake. The Bear River

Patsy Palacios; Chris Luecke; Justin Robinson

2007-01-01

354

Hydrodynamic squeeze-film bearings for gyroscopes  

NASA Technical Reports Server (NTRS)

Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action.

Chiang, T.; Smith, R. L.

1970-01-01

355

Optimum energy loss in electro magnetic bearing  

Microsoft Academic Search

This paper includes weight optimization method of rotor and analysis of total power loss in radial magnetic bearing consisting of four, eight and twelve poles. Weight optimization reduces copper loss in bearing since the electromagnetic force is reduced due to optimized rotor. Further numbers of poles in magnetic bearing are varied for same electromagnetic force 350 N and stator is

Santosh Shelke; R. V. Chalam

2011-01-01

356

49 CFR 229.69 - Side bearings.  

Code of Federal Regulations, 2010 CFR

... Suspension System § 229.69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not...than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in contact unless designed to...

2010-10-01

357

49 CFR 229.69 - Side bearings.  

Code of Federal Regulations, 2012 CFR

... Suspension System § 229.69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not...than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in contact unless designed to...

2012-10-01

358

FOSTERING BLACK BEAR CUBS IN THE WILD  

Microsoft Academic Search

Three black bear (Ursus americanus) cubs were abandoned, at approximately 2 weeks of age, on 4 February 1976, in New York State's Catskill region. The dens of 4 radio-telemetered adult female bears were located by the Department of Environmental Conservation during research on the black bear population in the Catskills. Two of the abandoned cubs were placed in the only

STEPHEN H. CLARKE; CHARLES HACKFORD

359

The Dynamic Behaviour of Ball Bearings  

Microsoft Academic Search

In cooperation with SKF, a research project was started on the dynamics of ball bearings. The research is motivated by the demand for silent bearings in noise sensitive applications, especially in the household appliance and automotive industry. The investigations should bring a clear understanding about the role of the bearing in the application with respect to the design, the quality

J. A. Wensing

1998-01-01

360

A Spherical Gas Bearing for Airborne Application  

Microsoft Academic Search

A spherical gas bearing is analyzed and tested for an airborne application. The externally pressurized bearing supports an inertially stabilized 36-in aperture, infrared telescope. The bearing provides the isolation of rotary motion from the aircraft and also serves as a seal between the aircraft cabin and cavity condition at 50, 000 ft altitude. The accompanying temperature gradient of 135 F

Anton Bouvier; John C. Schmertz

1975-01-01

361

Steels For Rolling-Element Bearings  

NASA Technical Reports Server (NTRS)

Bearing lives increased by attention to details of processing and applications. NASA technical memorandum discusses selection of steels for long-life rolling-element bearings. After brief review of advances in manufacturing, report discusses effect of cleanliness of bearing material on fatigue in rolling element. Also discusses fracture toughnesses of through-hardened and case-hardened materials.

Zaretsky, Erwin V.

1988-01-01

362

DAMAGE MECHANICS APPROACH FOR BEARING LIFETIME PROGNOSTICS  

Microsoft Academic Search

The ability to achieve accurate bearing prognostics is critical to the optimal maintenance of rotating machinery in the interest of cost and productivity. However, techniques to real time predict the lifetime of a bearing under practical operating conditions have not been well developed. In this paper, a stiffness-based prognostic model for bearing systems based on vibration response analysis and damage

Jing Qiu; Brij B. Seth; STEVEN Y. LIANG; Cheng Zhang

2002-01-01

363

Encapsulated HTS bearings: technical and cost considerations  

Microsoft Academic Search

Thermal encapsulation of HTS is one way to fabricate high-efficient HTS magnetic bearings for flywheels, motors and generators. We have been designed, manufactured and tested 200 mm axial and radial bearings for loads close to 300 kg. The maximum load to bearing weight is in the 10 to 1 ratio. At 77 K, a vacuum cryostat around the HTS reduces

F. N. Werfel; U. Floegel-Delor; T. Riedel; R. Rothfeld; D. Wippich; B. Goebel

2005-01-01

364

Bearing-Mounting Concept Accommodates Thermal Expansion  

NASA Technical Reports Server (NTRS)

Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.

Nespodzany, Robert; Davis, Toren S.

1995-01-01

365

Surface Roughness Evolution of Ball Bearing Components  

Microsoft Academic Search

An accurate knowledge of the expected life is essential to the proper selection of ball bearings. Bearings principally fail owing to fatigue if they are properly lubricated, mounted and sealed against the entrance of dirt. Fatigue life is strongly correlated to the surface roughness. Experiments were performed to evaluate the effects of different ball bearings materials on the surface roughness,

O. Goepfert; J. Ampuero; P. Pahud; H. J. Boving

2000-01-01

366

A Laser Surface Textured Parallel Thrust Bearing  

Microsoft Academic Search

The potential use of a new technology of laser surface texturing (LST) in parallel thrust bearings is theoretically investigated. The surface texture has the form of micro-dimples with pre-selected diameter, depth, and area density. It can be applied to only a portion of the bearing area (partial LST) or the full bearing area (full LST). Optimum parameters of the dimples,

V. Brizmer; Y. Kligerman; I. Etsion

2003-01-01

367

Lightweight, high speed bearing balls: A concept  

NASA Technical Reports Server (NTRS)

Low mass bearing balls with hardened iron-plated surfaces can eliminate problems of low fatigue strength and flexure fatigue, and lead to increased life and reliability of high speed ball bearings. Low mass balls exert lower centrifugal forces on outer race of bearing thus eliminating detrimental effect of high speed operation.

Parker, R. J.

1974-01-01

368

Thin film superconductor magnetic bearings  

DOEpatents

A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

Weinberger, Bernard R. (Avon, CT)

1995-12-26

369

PANEL 5: BEARS AND HUMAN BEINGS Bears and Man in Glacier National Park,  

E-print Network

is an increas- ingly valuable ecological resource that continues to be a stronghold of the grizzly bearPANEL 5: BEARS AND HUMAN BEINGS Bears and Man in Glacier National Park, British Columbia, 1880 can only be achieved if the bear/man relationship pertaining there is fully under- stood. Thirdly

Smith, Dan

370

Fault Tolerant Homopolar Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert

2003-01-01

371

Skeletal manifestations of bear scavenging.  

PubMed

In many partially or fully skeletonized forensic cases, postmortem animal damage is simply attributed to rodents or carnivores; little effort is made to determine the general size or assign a genus to the scavenger. As one of the largest wild carnivores to inhabit mountainous and forested areas throughout the continental United States, Alaska, and Canada, black bears (Ursus americanus) must be considered possible suspects when skeletonized remains are located showing marks of carnivore damage. Since 1995, three cases of known bear scavenging have been referred to the Maxwell Museum's Laboratory of Human Osteology by the New Mexico Office of the Medical Investigator for skeletal analysis. These cases comprise a total of seven individuals, and all of the remains were deposited in high altitude forests of New Mexico along the western border with Arizona with a minimum of 4 months exposure before recovery. When analyzed, all cases shared a similar pattern of element survivorship and damage. We suggest that bears can be distinguished from members of the canid family, the other common scavenger of human remains, based on the representation of skeletal elements at the scene. Rates and patterns of damage are not as accurate as element recovery in the discrimination of scavenger genus. Use of this information should allow forensic anthropologists to better understand the postmortem taphonomic processes that shaped the skeletal remains, and hopefully prevent misdiagnoses of perimortem trauma on elements not typically scavenged by canids. PMID:10855954

Carson, E A; Stefan, V H; Powell, J F

2000-05-01

372

Polar Bears International : Wrangel Island, Russia  

NSDL National Science Digital Library

This site describes the ongoing research of the polar bears in the Russian High Arctic. Wrangel Island with neighboring small island, Herald Island, are the key reproductive areas for the Chukchi-Alaskan polar bear population. Marine areas and Wrangel and Herald islands provide optimum foraging habitats for polar bears, and polar bear densities in these marine habitats are high all year round. Approximately 350-500 pregnant female polar bears construct their maternity dens on Wrangel and Herald islands every fall, emerging with their cubs in spring. The research is described in terms of goals and objectives, structure, methods, equipment, staff, and implementations.

2007-12-12

373

Polar Bears International: Wrangel Island, Russia  

NSDL National Science Digital Library

This site describes the ongoing research of the polar bears in the Russian High Arctic. Wrangel Island with neighboring small island, Herald Island, are the key reproductive areas for the Chukchi-Alaskan polar bear population. Marine areas and Wrangel and Herald islands provide optimum foraging habitats for polar bears, and polar bear densities in these marine habitats are high all year round. Approximately 350-500 pregnant female polar bears construct their maternity dens on Wrangel and Herald islands every fall, emerging with their cubs in spring. The research is described in terms of goals and objectives, structure, methods, equipment, staff, and implementations.

374

Computing Thermal Performances Of Shafts And Bearings  

NASA Technical Reports Server (NTRS)

SHABERTH computer program developed to predict steady-state and transient thermal performance of multi-bearing shaft system operating with either wet or dry friction. Calculates loads, torques, temperatures, and fatigue lives for ball and/or roller bearings on single shaft. Enables study of many causes of instabilities in bearings. Also provides for analysis of reaction of system to termination of supply of lubricant to bearings and other lubricated mechanical elements. Valuable software tool in design and analysis of shaft bearing systems. Written in FORTRAN IV.

Woods, Claudia M.

1992-01-01

375

Equations For Elastohydrodynamic Lubrication Of Bearings  

NASA Technical Reports Server (NTRS)

Equation for thickness of elastohydrodynamic (EHD) lubricant film in rolling-element bearing reduced to simplified form involving only inside and outside diameters of bearing, speed of rotation, parameter related to type of lubricant, and viscosity of lubricant at temperature of bearing. In addition, experimentally derived graph of EHD-film-thickness-reduction factor as function of contact-lubricant-flow number. Accounts for lubricant starvation within Hertzian contact. Graph relating ratio of minimum film thickness to composite roughness of bearing surfaces and to lubrication-life correction factor also provided. Life-correction factor used to determine resultant life of bearing.

Zaretsky, Erwin V.

1993-01-01

376

Bearing/Bypass Material-Testing System  

NASA Technical Reports Server (NTRS)

System developed to test specimens in compression as well as tension while maintaining constant bearing/bypass ration. Test specimen with centrally located hole is clamped between two bearing-guide plates using one bolt. Bearing-guide plates then secured to two bearing-load cells. Test specimen independently loaded at both ends, using two separate control systems identified as applied and bypass. If two end loads unequal, difference between them reacted as bolt-bearing load on specimen. Throughout test, two control systems synchronized by common input signal (increasing voltage). As result, loads remain proportional as they increase.

Crews, John H., Jr.

1988-01-01

377

Effect of Bearing Surroundings on the High-Speed Spindle-Bearing Compliance  

Microsoft Academic Search

This paper investigates the effect of bearing assembly tolerance on spindle-bearing compliance. In a high-speed spindle system,\\u000a the bearing characteristics are influenced significantly by the initial assembly tolerances and the thermal deformation of\\u000a the bearing surroundings. In the very early stage of spindle operation, spindle bearings could be under hazardous conditions\\u000a owing to the rapid change of the internal pressure

S.-M. Kim; S.-K. Lee; K.-J. Lee

2002-01-01

378

Analytical and experimental investigations of hybrid air foil bearings  

E-print Network

Air foil bearings offer several advantages over oil-lubricated bearings in high speed micro-turbomachinery. With no contact between the rotor and bearings, the air foil bearings have higher service life and consequently lesser standstills between...

Kumar, Manish

2009-05-15

379

Design review of fluid film bearing testers  

NASA Technical Reports Server (NTRS)

The designs of three existing testers (Hybrid Bearing Tester, OTV Bearing Tester, and Long Life Bearing Tester) owned by NASA were reviewed for their capability to serve as a multi-purpose cryogenic fluid film bearing tester. The primary tester function is the validation of analytical predictions for fluid film bearing steady state and dynamic performance. Evaluation criteria were established for test bearing configurations, test fluids, instrumentation, and test objectives. Each tester was evaluated with respect to these criteria. A determination was made of design improvements which would allow the testers to meet the stated criteria. The cost and time required to make the design changes were estimated. A recommendation based on the results of this study was made to proceed with the Hybrid Bearing Tester.

Scharrer, Joseph K.

1993-01-01

380

Wave Journal Bearings Under Dynamic Loads  

NASA Technical Reports Server (NTRS)

The dynamic behavior of the wave journal bearing was determined by running a three-wave bearing with an eccentrically mounted shaft. A transient analysis was developed and used to predict numerical data for the experimental cases. The three-wave journal bearing ran stably under dynamic loads with orbits well inside the bearing clearance. The orbits were almost circular and nearly free of the influence of, but dynamically dependent on, bearing wave shape. Experimental observations for both the absolute bearing-housing-center orbits and the relative bearing-housing-center-to-shaft-center orbits agreed well with the predictions. Moreover, the subsynchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds.

Hendricks, Robert C.; Dimofte, Florin

2002-01-01

381

Chromatographic (TLC) differentiation of grizzly bear and black bear scats  

USGS Publications Warehouse

While past work concluded that thin-layer chromatography (TLC) was inadequate for the separation of grizzly (Ursus arctos horribilis) and black bear (U. americanus) scats, our study found differences adequate for species separation. A key was constructed using 19 of 40 data points recorded on each(N)=356 profiles of 178) know-species scat. Accuracy was best for late summer scats (94%). Methods for specimen preparation, analysis, and reading the TLC profiles are discussed. Factors involved in scat variation were tested.

Picton, Harold D.; Kendall, Katherine C.

1994-01-01

382

Paraelectric Resonance of the Lithium Ion in Potassium Chloride Under Hydrostatic Pressure.  

NASA Astrophysics Data System (ADS)

Paraelectric resonance (PER) in KCl: Li ^{+} (for both the ^6 Li^{+} and ^7Li^{+} isotopes) has been investigated under hydrostatic pressure (1 bar-2200 bars) for a wide range of microwave frequency (43-300 GHz) and electric field (0-140 kV/cm). Data were collected at a number of temperatures, from 2.2 K to 8.0 K. The measurement is done by fixing the microwave frequency and sweeping the E field. We have measured zero field field splittings (ZFSs) of all the allowed transitions in the ground state multiplet, and proposed an empirical expression for the change of each ZFS with pressure for each Li^{+ } isotope. Three tunneling parameters for each isotope have been obtained. All the tunneling parameters increase quadratically with pressure. The electric dipole moment decreases linearly with hydrostatic pressure at pressures below 2.1 kbars. The dipole moment decreases 19% over the pressure range of 1 to 2100 bars as a result of a reduction in the separation between adjacent potential wells. No critical pressure for the off-center to on-center transition is observed. The extensive data collected are interpreted in terms of the standard < 111> tunneling model. We have calculated the energy levels and transition matrix elements from the model to compare with the experimental observations. The remarkable agreement indicates that the tunneling model provides an excellent description of an off-center defect, and supports using the KCl: Li^{+} as a model tunneling system. At high pressures new absorption lines are found in the KCl: Li^{+} samples. These new lines cannot be explained within the standard tunneling model. We have proposed that the physical origin of these new lines is the existence of several new tunneling clusters in the KCl: Li^{+} system. The exact configurations of these new clusters, however, are still unknown. The glitch problem in the X-ray Absorption Fine Structure (XAFS) spectrum has also been investigated. A simple glitch model has been developed based on the experimental observations. The model successfully predicts the formation of a glitch when a sample with a nonuniform thickness is used. Based on this model, some measures are outlined for minimizing the glitches in XAFS data.

Wang, Xun

383

Public attitudes towards brown bears ( Ursus arctos) in Slovenia  

Microsoft Academic Search

In northern Slovenia a radical change in brown bear (Ursus arctos) management – from a policy of bear suppression to a policy of bear protection – resulted in a sharp increase in sheep predation by bears. In the bear core area in southern Slovenia, on the other hand, bears have always been present, cause little damage and are an important

Petra Kaczensky; Mateja Blazic; Hartmut Gossow

2004-01-01

384

Investigation of the Initial State of the Moon-Forming Disk: Bridging SPH Simulations and Hydrostatic Models  

E-print Network

According to the standard giant impact hypothesis, the Moon formed from a partially vaporized disk generated by a collision between the proto Earth and a Mars sized impactor. The initial structure of the disk significantly affects the Moon forming process, including the Moons mass, its accretion time scale, and its isotopic similarity to Earth. The dynamics of the impact event determines the initial structure of a nearly hydrostatic Moon forming disk. However, the hydrostatic and hydrodynamic models have been studied separately and their connection has not previously been well quantified. Here, we show the extent to which the properties of the disk can be inferred from Smoothed Particle Hydrodynamic (SPH) simulations. By using entropy, angular momentum and mass distributions of the SPH outputs as approximately conserved quantities, we compute the two dimensional disk structure. We investigate four different models: (a) standard, the canonical giant impact model, (b) fast spinning Earth, a collision between a ...

Nakajima, Miki

2014-01-01

385

Hydrostatic equation of state and anisotropic Constitutive Relationships in 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)  

NASA Astrophysics Data System (ADS)

TATB is an energetic molecular crystal which exhibits remarkable insensitivity to shock, heating and electrical sparks. Despite its high stability and relative safety, TATB is a highly powerful explosive which makes it an interesting target for both theoretical and experimental studies. We performed first-principles van-der-Waals Density Functional Theory (vdW-DFT) studies of the equilibrium properties and hydrostatic equation of state (EOS) for TATB and compared with experiment. The vdW-DFT showed better agreement with the experimentally determined hydrostatic EOS and unit cell parameters compared standard DFT, which suffers from the lack of proper description of long-range dispersive interactions. The anisotropic EOS as a function of uniaxial compression in the 001, 010, 011 , 100 , 101 , 110, and 111 crystallographic directions was also studied. Calculated mechanical properties such as the principal and shear stresses, energy gap, and the energy per atom show a clear anisotropy in the TATB molecular crystal upon uniaxial compression.

Budzevich, Mikalai; Conroy, Michael; Landerville, Aaron; Lin, You; Oleynik, Ivan; White, Carter

2009-06-01

386

Room-temperature vibrational properties of multiferroic MnWO4 under quasi-hydrostatic compression up to 39 GPa  

NASA Astrophysics Data System (ADS)

The multiferroic manganese tungstate (MnWO4) has been studied by high-pressure Raman spectroscopy at room temperature under quasi-hydrostatic conditions up to 39.3 GPa. The low-pressure wolframite phase undergoes a phase transition at 25.7 GPa, a pressure around 8 GPa higher than that found in previous works, which used less hydrostatic pressure-transmitting media. The pressure dependence of the Raman active modes of both the low- and high-pressure phases is reported and discussed comparing with the results available in the literature for MnWO4 and related wolframites. A gradual pressure-induced phase transition from the low- to the high-pressure phase is suggested on the basis of the linear intensity decrease of the Raman mode with the lowest frequency up to the end of the phase transition.

Ruiz-Fuertes, J.; Errandonea, D.; Gomis, O.; Friedrich, A.; Manjón, F. J.

2014-01-01

387

Phylum: Tardigrada (water bears, tardigrades)  

NSDL National Science Digital Library

This web page describes water bears, minute animals that can remain dormant in a dry state for over 100 years. The page addresses what they are, where they are found, their general biology, cryptobiosis, their ability to resist environmental extremes, implications and further research regarding their cryptobiosis, where they fit in with other animals, and their existence in South Africa. It also describes how someone could collect and see them. The page is part of Biodiversity Explorer, a web site hosted by Iziko Museums of Cape Town that features the diversity of life in South Africa.

Middleton, Roger; Town, Iziko M.

388

Monitoring grizzly bear population trends  

USGS Publications Warehouse

A simple different equation model was developed to provide additional perspective on observed mortality and trend data on Yellowstone grizzly bears (Ursus arctos horribilis). Records of mortalities of adult females from 1959 to 1985 were utilized, in conjunction with data on females with cubs. The overall downward trend of observed numbers of females with cubs generally agrees with the model calculations but does not adequately reflect mortality from 1970 to 1974. The model may be useful in developing a composite index of population trend.

Eberhardt, L.L.; Knight, R.R.; Blanchard, B.M.

1986-01-01

389

Transfer Lubrication For Cryogenic Bearings  

NASA Technical Reports Server (NTRS)

Report presents evaluation of bronze-filled polytetrafluoroethylene (PTFE), known as Salox M, as cage material for ball bearings in high-pressure turbopumps for liquid oxygen. Material evaluated as potentially longer-lived replacement for glass-filled PTFE, known as Armalon. Cage transfers PTFE to balls to form solid lubricant film. However, glass fibers in glass-filled material tend to interfere with transfer. Two cage-design concepts developed; one involves metal-reinforced cage of bronze-filled PTFE; other calls for bronze-filled PTFE inserts in metal structure.

Barber, S. A.; Kannel, J. W.; Dufrane, K. F.

1988-01-01

390

Current leads and magnetic bearings  

SciTech Connect

Since the discovery of high-temperature superconductors (HTSs), Argonne National Laboratory (ANL) has been active in a broad spectrum of activities in developing these materials for applications. Work at every stage of development has involved industrial collaboration in order to accelerate commercialization. While most of the development work has been devoted to improving the properties of current-carrying wires, some effort has been devoted to applications that can utilize HTSs with properties available now or in the near future. In this paper, I discuss advances made at my laboratory in the area of current leads and magnetic bearings.

Hull, J.R.

1993-12-31

391

Hunting Bears with a Microscope  

NSDL National Science Digital Library

In this online activity, students use lichens and tardigrades (water bears) to investigate their use as bioindicators of key air pollutants. When lichens are exposed to some kinds of air pollutants, especially to sulfur dioxide, the lichens are injured and die. The lichen coverage in a specified area should be a good indicator of the level of air quality. The diversity of the tardigrade species on the lichens will be used to develop another level for bioindication of air quality. Sections of this activity include: introduction, sulfur dioxide and lichens, sampling procedure for lichen coverage, tardigrade sampling, sampling procedure for tardigrades, calculating diversity using the Simpson Diversity Index, interpretation of results, and references.

Case, Steve

2010-02-10

392

Hunting Bears with a Microscope  

NSDL National Science Digital Library

In this online activity, students use lichens and tardigrades (water bears) to investigate their use as bioindicators of key air pollutants. When lichens are exposed to some kinds of air pollutants, especially to sulfur dioxide, the lichens are injured and die. The lichen coverage in a specified area should be a good indicator of the level of air quality. The diversity of the tardigrade species on the lichens will be used to develop another level for bioindication of air quality. Sections of this activity include: introduction, sulfur dioxide and lichens, sampling procedure for lichen coverage, tardigrade sampling, sampling procedure for tardigrades, calculating diversity using the Simpson Diversity Index, interpretation of results, and references.

Case, Steve; Excellence, The N.

393

Effect of hydrostatic pressure on lysozyme and chymotrypsinogen detected by fluorescence polarization  

SciTech Connect

The effect of hydrostatic pressure upon solutions of chymotrypsinogen and lysozyme at room temperature has been followed by employing a new technique that permits the measurement of fluorescence polarization at pressures of up to 10 kbar. Lysozyme shows a stable, reversible 60% increase in apparent volume when the pressure is raised to 9 kbar. This can be given a simple interpretation in terms of solvent penetration of the structure at higher pressures. In contrast, the results with chymotrypsinogen are time dependent and only partially reversible on release of the pressure. They involve conversion (t/sub l///sub e/ = 5 min) to a form with a lower rotational rate at approximately 6 kbar and return to a fast-rotating form at higher pressure. This latter form persists on pressure release. The possibility of generating what are clearly metastable conformations, not only in chymotrypsinogen but also in flavodoxins indicates that there are unresolved questions about the relative stability of protein conformations which can be profitably investigated by high-pressure experiments.

Chryssomallis, G.S.; Torgerson, P.M.; Drickamer, H.G.; Weber, G.

1981-01-01

394

Effect of high hydrostatic pressure (HHP) on slowly digestible properties of rice starches.  

PubMed

The slowly digestible properties of high hydrostatic pressure (HHP)-gelatinized non-waxy and waxy rice starches during the retrogradation were evaluated in this study. The results show that slowly digestible starch (SDS) was observed at a higher percentage in HHP-gelatinized, non-waxy and waxy rice starches than in heat-gelatinized starches, after retrogradation for 7 days. The HHP treatment significantly reduced the enthalpy change of starch retrogradation and retarded the freezable water transformation into unfreezable water during retrogradation. This indicated that the SDS percentage was not positively correlated to the retrogradation degree of starch. Furthermore, X-ray diffraction (XRD) data revealed that the HHP treatment decreased the perfect crystallites of the 7 day-retrograded. Non-waxy and waxy starches from 19.5% to 12.1% and 15.7% to 11.4%, while increased imperfect crystallites from 26.4% to 30.7% and 28.6% to 31.3%, respectively. These findings suggest that the higher SDS percentage can be attributed to the formation of less perfect crystallites and more imperfect crystallites during the HHP and retrogradation treatments. PMID:24444930

Tian, Yaoqi; Li, Dandan; Zhao, Jianwei; Xu, Xueming; Jin, Zhengyu

2014-01-01

395

Acoustic Emission Monitoring of ASME Section III Hydrostatic Test: Watts Bar Unit 1 Nuclear Reactor  

SciTech Connect

Through the cooperation of the Tennessee Valley Authority, Pacific Northwest Laboratory has installed instrumentation on Watts Bar Nuclear Power Plant Unit 1 for the purpose of test and evaluation of acoustic emission (AE) monitoring of nuclear reactor pressure vessels and piping for flaw detection. This report describes the acoustic emission monitoring performed during the ASME Section III hydrostatic testing of Watts Bar Nuclear Power Plant Unit 1 and the results obtained. Highlights of the results are: • Spontaneous AE was detected from a nozzle area during final pressurization. • Evaluation of the apparent source of the spontaneous AE using an empirically derived AE/fracture mechanics relationship agreed within a factor of two with an evaluation by ASME Section XI Code procedures. • AE was detected from a fracture specimen which was pressure coupled to the 10-inch accumulator nozzle. This provided reassurance of adequate system sensitivity. • High background noise was observed when all four reactor coolant pumps were operating. Work is continuing at Watts Bar Unit 1 toward AE monitoring hot functional testing and subsequently monitoring during reactor operation.

Hutton,, P. H.; Taylor,, T. T.; Dawson,, J. F.; Pappas,, R. A.; Kurtz,, R. J.

1982-06-01

396

Ultra-Fine Grain Structures Of Model Al-Mg-Si Alloys Produced By Hydrostatic Extrusion  

SciTech Connect

Microstructure and mechanical properties were studied in model Al-Mg-Si alloys (Al-1 % Mg-0.8% Si and Al-0.5% Mg-0.3% Si-wt %) deformed by hydrostatic extrusion (HE) to strains of 1.4 and 3.8. In these alloys the different percentage of two hardening second-phase precipitates (Mg{sub 2}Si and Si) were observed. The microstructure was characterized by transmission electron microscopy and optical microscopy. The microstructure of the alloys in the initial state was built of coarse grains of an average diameter of {approx}30 rim. The refined microstructure was examined qualitatively and quantitatively using the stereological method and a computer image analysis. The deformation-processed structures evolved very rapidly, forming ultrafine grained (UFG) materials with grains of about 0.4 {mu}m. In addition, the grain refinement in the HE-treated materials has a substantial effect on their properties, such as the mechanical strength and micro-hardness which increase significantly. It has been found that, after {epsilon} = 3.8 in the Al-1% Mg-0.8% Si alloy, the micro-hardness increases approximately twofold. The yield stress is more than four times higher in the UFG alloys, in comparison to the initial state. Similar results were identified in the Al-0.5% Mg-0.3% Si. This is due to the very rapid refinement of the microstructure during the deformation and presence of second-phase particles.

Adamczyk-Cieslak, Boguslawa; Mizera, Jaroslaw [Warsaw University of Technology, Faculty of Materials Science and Engineering, Woloska 141, 02-507 Warsaw (Poland)

2011-01-17

397

Sustainable production of pectin from lime peel by high hydrostatic pressure treatment.  

PubMed

The application of high hydrostatic pressure technology for enzymatic extraction of pectin was evaluated. Cellulase and xylanase under five different combinations (cellulase/xylanase: 50/0, 50/25, 50/50, 25/50, and 0/50 U/g lime peel) at ambient pressure, 100 and 200 MPa were used to extract pectin from dried lime peel. Extraction yield, galacturonic acid (GalA) content, average molecular weight (M(w,ave)), intrinsic viscosity [?](w), and degree of esterification (DE) were compared to those parameters obtained for pectins extracted using acid and aqueous processes. Pressure level, type and concentration of enzyme significantly (p<0.05) influenced yield and DE of pectin. Enzyme and high pressure extraction resulted in yields which were significantly (p<0.05) higher than those using acid and aqueous extraction. Although pressure-induced enzymatic treatment improves pectin yield, it does not have any significant effect on M(w,ave) and [?](w) of pectin extracts indicating the potential of high pressure treatment for enzymatic pectin production as a novel and sustainable process. PMID:23122086

Naghshineh, Mahsa; Olsen, Karsten; Georgiou, Constantinos A

2013-01-15

398

The role of calcium signalling in the chondrogenic response of mesenchymal stem cells to hydrostatic pressure.  

PubMed

The object of this study was to elucidate the role of Ca++ signalling in the chondrogenic response of mesenchymal stem cells (MSCs) to hydrostatic pressure (HP). MSCs were seeded into agarose hydrogels, subjected to HP or kept in free swelling conditions, and were cultured either with or without pharmacological inhibitors of Ca++ mobility and downstream targets. Chelating free Ca++, inhibiting voltage-gated calcium channels, and depleting intracellular calcium storessuppressed the beneficial effect of HP on chondrogenesis, indicating that Ca++ mobility may play an important role in the mechanotransduction of HP. However, inhibition of stretch-activated calcium channels in the current experiment yielded similar results to the control group, suggesting that mechanotransduction of HP is distinct from loads that generate cell deformations. Inhibition of the downstream targets calmodulin, calmodulin kinase II, and calcineurin all knocked down the effect of HP on chondrogenesis, implicating these targets in MSCs response to HP. All of the pharmacological inhibitors that abolished the chondrogenic response to HP also maintained a punctate vimentin organisation in the presence of HP, as opposed to the mechanoresponsive groups where the vimentin structure became more diffuse. These results suggest that Ca++ signalling may transduce HP via vimentin adaptation to loading. PMID:25350251

Steward, A J; Kelly, D J; Wagner, D R

2014-01-01

399

Adaptive hydrostatic blood pressure calibration: development of a wearable, autonomous pulse wave velocity blood pressure monitor.  

PubMed

A technique for calibrating non-invasive peripheral arterial sensor signals to peripheral arterial blood pressure (BP) is proposed. The adaptive system identification method utilizes a measurable intra-arterial hydrostatic pressure change in the sensor outfitted appendage to identify the transduction dynamics relating the peripheral arterial blood pressure and the measured arterial sensor signal. The proposed algorithm allows identification of the calibration dynamics despite unknown physiologic fluctuations in arterial pressure during the calibration period under certain prescribed conditions. By employing unique wearable sensor architecture to estimate pulse wave velocity (PWV), this technique is used to calibrate peripheral pulse transit time measurements to arterial blood pressure. This sensor architecture is comprised of two inline photoplethysmograph sensors one in the form of a wristwatch measuring the pulse waveform in the ulnar artery and one in the form of a ring measuring the pulse waveform from the digital artery along the base of the little finger. Experimental results using the proposed algorithm to calibrate PTT to BP on human subjects will be presented. PMID:18001967

McCombie, Devin B; Shaltis, Phillip A; Reisner, Andrew T; Asada, H

2007-01-01

400

On the shape of a hydrostatic meniscus attached to a corrugated plate or wavy cylinder.  

PubMed

The shape of a hydrostatic meniscus attached at a fixed contact angle to a vertical plate or circular cylinder with periodic corrugations is studied by analytical and numerical methods, and the effect of wall irregularities on the shape of the contact line and vertical component of the capillary force is discussed. An asymptotic analysis for a plate with small-amplitude sinusoidal corrugations is carried out to first order with respect to the corrugation amplitude, and a boundary-value problem is formulated and solved by a shooting method to determine the meniscus shape and elevation of the contact line. The meniscus attached to a corrugated plate with rounded corners produced by a Schwarz-Christoffel mapping function for a triangular wave is considered by numerical methods. The Laplace-Young equation determining the meniscus shape is solved in orthogonal curvilinear coordinates generated by conformal mapping using a finite-difference method. The numerical results are successfully compared with the predictions of the perturbation expansion for small amplitudes and discussed with reference to the rise of a meniscus inside a dihedral angle for large amplitudes. A companion asymptotic analysis is presented for a meniscus outside a vertical circular cylinder with small-amplitude sinusoidal corrugations. The analytical predictions are successfully compared with numerical solutions of the Laplace-Young equation for a meniscus outside an elliptical cylinder with aspect ratio near unity, regarded as a deformed circle. PMID:21315363

Hill, A I; Pozrikidis, C

2011-04-15

401

Heat shock protein-mediated resistance to high hydrostatic pressure in Escherichia coli.  

PubMed

A random library of Escherichia coli MG1655 genomic fragments fused to a promoterless green fluorescent protein (GFP) gene was constructed and screened by differential fluorescence induction for promoters that are induced after exposure to a sublethal high hydrostatic pressure stress. This screening yielded three promoters of genes belonging to the heat shock regulon (dnaK, lon, clpPX), suggesting a role for heat shock proteins in protection against, and/or repair of, damage caused by high pressure. Several further observations provide additional support for this hypothesis: (i). the expression of rpoH, encoding the heat shock-specific sigma factor sigma(32), was also induced by high pressure; (ii). heat shock rendered E. coli significantly more resistant to subsequent high-pressure inactivation, and this heat shock-induced pressure resistance followed the same time course as the induction of heat shock genes; (iii). basal expression levels of GFP from heat shock promoters, and expression of several heat shock proteins as determined by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins extracted from pulse-labeled cells, was increased in three previously isolated pressure-resistant mutants of E. coli compared to wild-type levels. PMID:15128516

Aertsen, Abram; Vanoirbeek, Kristof; De Spiegeleer, Philipp; Sermon, Jan; Hauben, Kristel; Farewell, Anne; Nyström, Thomas; Michiels, Chris W

2004-05-01

402

Anomalous properties of antiferroelectric PbZrO3 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

First-principles calculations are performed to investigate several low-enthalpy phases of the prototype PbZrO3 antiferroelectric material under hydrostatic pressure. They are the orthorhombic Pbam and Pnma states, the monoclinic P21/c and rhombohedral R3c phases, and possess different ionic degrees of freedom (e.g., antipolar motions, oxygen octahedral tilting, and polarization). Several anomalous features are discovered, including a change in pressure behavior of the polarization in the R3c state, which renders such ferroelectric phase the ground state of PbZrO3 (PZO) (along with the nearly degenerate P21/c phase) for pressure ranging between ?30 and ?85 GPa. Another example is the strong first-order isostructural transition exhibited by Pbam at 70 GPa, which results in the reentrance of this phase as the ground state of PZO for pressure above 85 GPa. Another more continuouslike isostructural transition is also predicted for the Pnma phase at ?50 GPa. Experiments are conducted to confirm some of these predictions.

Prosandeev, S.; Xu, Changsong; Faye, R.; Duan, Wenhui; Liu, H.; Dkhil, B.; Janolin, P.-E.; Íñiguez, Jorge; Bellaiche, L.

2014-06-01

403

The role of sarcoplasmic protein in hydrostatic pressure-induced myofibrillar protein denaturation.  

PubMed

To observe the role of sarcoplasmic protein (SP) on myofibrillar protein (MP) denaturation under a hydrostatic pressure (HP), MP isolated from bovine muscle was treated with 300 MPa by increasing concentrations of SP (0, 0.8, 1.6, and 3.2 mg/ml) from bovine. SDS-PAGE patterns of soluble proteins in 0.1M NaCl (pH 7.4) indicated that a protein (about 100 kDa) from MP decreased with increasing concentrations of SP and that a 97 kDa protein from SP observed with 0.1 MPa was not observed with 300 MPa. SDS-PAGE patterns of soluble proteins in 0.6 M NaCl (pH 7.4) and Ca-ATPase activity showed that the denaturation of myosin heavy chain (MHC) was accelerated with increasing SP concentrations with the 300 MPa treatment. Thus, the addition of SP enhanced HP-induced denaturation of MHC and of a protein from MP of about 100 kDa. PMID:21074947

Lee, Eun-Jung; Kim, Young-Ho; Lee, Nam-Hyouck; Hong, Suk-In; Yamamoto, Katsuhiro; Kim, Yun-Ji

2011-03-01

404

Potential for high hydrostatic pressure processing to control quarantine insects in fruit.  

PubMed

Tests were conducted to determine the potential for high hydrostatic pressure (HPP) to control codling moth, Cydia pomonella (L.), and western cherry fruit fly, Rhagoletis indifferens Curran. Apples (Malus spp.) with codling moth larvae or eggs were treated at 24 and 72 h, respectively, after infestation at a series of pressures between 14,000 and 26,000 pounds per inch2 (psi). Survivorship was determined the next day for larvae and after 10 d for eggs. Codling moth eggs were more tolerant of HPP treatment than larvae. Mortality of larvae was 97% at 22,000 psi, whereas mortality of eggs at this dose was 29% and not significantly different from the untreated controls. In a second study, no codling moth eggs hatched at any high pressure treatment between 30,000 and 80,000 psi, indicating these pressures were lethal. Various stages of western cherry fruit fly were treated at pressures from 10,000 to 45,000 psi, and survivorship was determined after 24 h. Eggs and third instars were more tolerant of HPP than the first and second instars. Mortality was 100% in western cherry fruit fly eggs and larvae at pressures > or =25,000 psi. Apple and sweet cherry quality after high pressure treatment was poor, but high pressure may have applications to control quarantine pests in other fruits. PMID:17972625

Neven, Lisa; Follett, Peter A; Raghubeer, Errol

2007-10-01

405

Isostructural phase transitions of tetragonal perovskite titanates under negative hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Phase transitions within the tetragonal space group P4mm associated with anomalous enhancement of tetragonality in PbTiO3 and BaTiO3 under negative hydrostatic pressure were theoretically predicted by Tinte et al (2003 Phys. Rev. B 68 144105). In the present study, with special interest in the origin of the phase transition, we made a series of analogous calculations for six perovskite titanates (ATiO3, where A = Ca, Sr, Cd, Ba, Eu or Pb). All six compounds are found to undergo similar phase transitions. One of the Ti-O bonds is virtually broken at the transition. The transition pressures for CaTiO3, CdTiO3 and PbTiO3 are near -4 GPa, which is significantly different from the case for those of BaTiO3, EuTiO3 and SrTiO3: they are near -10 GPa. The transition pressure and volume change at the transition cannot be correlated with the A cation radius. Instead, they depend on the tetragonality of the original crystal, which is influenced by the relative stability of the cubic structures under zero pressure.

Moriwake, Hiroki; Koyama, Yukinori; Matsunaga, Katsuyuki; Hirayama, Tsukasa; Tanaka, Isao

2008-08-01

406

Structural rearrangement of ethanol-denatured soy proteins by high hydrostatic pressure treatment.  

PubMed

The effects of high hydrostatic pressure (HHP) treatment (100-500 MPa) on solubility and structural properties of ethanol (EtOH)-denatured soy ?-conglycinin and glycinin were investigated using differential scanning calorimetry, Fourier transform infrared and ultraviolet spectroscopy. HHP treatment above 200 MPa, especially at neutral and alkaline pH as well as low ionic strength, significantly improved the solubility of denatured soy proteins. Structural rearrangements of denatured ?-conglycinin subjected to high pressure were confirmed, as evidenced by the increase in enthalpy value (?H) and the formation of the ordered supramolecular structure with stronger intramolecular hydrogen bond. HHP treatment (200-400 MPa) caused an increase in surface hydrophobicity (F(max)) of ?-conglycinin, partially attributable to the exposure of the Tyr and Phe residues, whereas higher pressure (500 MPa) induced the decrease in F(max) due to hydrophobic rearrangements. The Trp residues in ?-conglycinin gradually transferred into a hydrophobic environment, which might further support the finding of structural rearrangements. In contrast, increasing pressure induced the progressive unfolding of denatured glycinin, accompanied by the movement of the Tyr and Phe residues to the molecular surface of protein. These results suggested that EtOH-denatured ?-conglycinin and glycinin were involved in different pathways of structural changes during HHP treatment. PMID:21609024

Wang, Jin-Mei; Yang, Xiao-Quan; Yin, Shou-Wei; Zhang, Ye; Tang, Chuan-He; Li, Bian-Sheng; Yuan, De-Bao; Guo, Jian

2011-07-13

407

Single-Molecule Analysis of the Rotation of F1-ATPase under High Hydrostatic Pressure  

PubMed Central

F1-ATPase is the water-soluble part of ATP synthase and is an ATP-driven rotary molecular motor that rotates the rotary shaft against the surrounding stator ring, hydrolyzing ATP. Although the mechanochemical coupling mechanism of F1-ATPase has been well studied, the molecular details of individual reaction steps remain unclear. In this study, we conducted a single-molecule rotation assay of F1 from thermophilic bacteria under various pressures from 0.1 to 140 MPa. Even at 140 MPa, F1 actively rotated with regular 120° steps in a counterclockwise direction, showing high conformational stability and retention of native properties. Rotational torque was also not affected. However, high hydrostatic pressure induced a distinct intervening pause at the ATP-binding angles during continuous rotation. The pause was observed under both ATP-limiting and ATP-saturating conditions, suggesting that F1 has two pressure-sensitive reactions, one of which is evidently ATP binding. The rotation assay using a mutant F1(?E190D) suggested that the other pressure-sensitive reaction occurs at the same angle at which ATP binding occurs. The activation volumes were determined from the pressure dependence of the rate constants to be +100 Å3 and +88 Å3 for ATP binding and the other pressure-sensitive reaction, respectively. These results are discussed in relation to recent single-molecule studies of F1 and pressure-induced protein unfolding. PMID:24094404

Okuno, Daichi; Nishiyama, Masayoshi; Noji, Hiroyuki

2013-01-01

408

Nonthermal pasteurization of fermented green table olives by means of high hydrostatic pressure processing.  

PubMed

Green fermented olives cv. Halkidiki were subjected to different treatments of high hydrostatic pressure (HHP) processing (400, 450, and 500?MPa for 15 or 30?min). Total viable counts, lactic acid bacteria and yeasts/moulds, and the physicochemical characteristics of the product (pH, colour, and firmness) were monitored right after the treatment and after 7 days of storage at 20(°)C to allow for recovery of injured cells. The treatments at 400?MPa for 15 and 30?min, 450?MPa for 15 and 30?min, and 500?MPa for 15?min were found insufficient as a recovery of the microbiota was observed. The treatment at 500?MPa for 30?min was effective in reducing the olive microbiota below the detection limit of the enumeration method after the treatment and after 1 week of storage and was chosen as being more appropriate for storing olives for an extended time period (5 months). After 5 months of storage at 20(°)C, no microbiota was detected in treated samples, while significant changes for both HHP treated and untreated olives were observed for colour parameters only (minor degradation). In conclusion, HHP treatment may introduce a reliable nonthermal pasteurization method to extend the microbiological shelf-life of fermented table olives. PMID:25243146

Argyri, Anthoula A; Panagou, Efstathios Z; Nychas, George-John E; Tassou, Chrysoula C

2014-01-01

409

Transmission with a first-stage hydrostatic mode and two hydromechanical stages  

DOEpatents

A power transmission having two planetary assemblies, each having at least one carrier with planet gears, at least one sun gear, and at least one ring gear. A speed-varying module is connected in driving relation to the input shaft and in driving relationship to the sun gear or gears of the first planetary assembly. The speed-varying means may comprise a pair of hydraulic units hydraulically interconnected so that one serves as a pump while the other serves as a motor and vice versa, one of the units having a variable stroke and being connected in driving relation to the input shaft, the other unit, which may have a fixed stroke, being connected in driving relation to the sun gear. The input shaft is also connected directly to a sun gear of the second planetary assembly and is further connectable by a clutch to a carrier of the first planetary assembly. Another clutch enables connecting the carrier of the first planetary assembly to a ring gear of the second planetary assembly. A brake grounds the first carrier in the first range and in reverse and causes drive to be delivered to the output through a ring gear of the first planetary assembly in a hydrostatic mode. The carrier of the second planetary assembly is connected in rigid driving relationship to that first ring gear, and in all ranges these two elements transmit the drive to the output shaft.

Orshansky, Jr., deceased, Elias (late of San Fransisco, CA); Weseloh, William E. (San Diego, CA)

1981-01-01

410

pH dependence of the dissociation of multimeric hemoglobin probed by high hydrostatic pressure.  

PubMed

We investigated the thermodynamic features of the classic alkaline dissociation of multimeric hemoglobin (3.1 MDa) from Glossoscolex paulistus (Annelidea) using high hydrostatic pressure. Light scattering measurements up to microscopic thermodynamic equilibrium indicated a high pH dependency of dissociation and association. Electron microscopy and gel filtration corroborated these findings. The volume change of dissociation decreased in absolute values from -48.0 mL/mol of subunit at pH 6.0 to -19.2 mL/mol at pH 9.0, suggesting a lack of protein interactions under alkaline conditions. Concomitantly, an increase in pH reduced the Gibbs free energy of dissociation from 37.7 to 27.5 kJ/mol of subunit. The stoichiometry of proton release calculated from the pressure-induced dissociation curves was +0.602 mol of H(+)/mol of subunit. These results provide a direct quantification of proton participation in stabilizing the aggregated state of the hemoglobin, and contribute to our understanding of protein-protein interactions and of the surrounding conditions that modulate the process of aggregation. PMID:17046147

Bispo, Jose A C; Santos, Jose L R; Landini, Gustavo F; Goncalves, Juliana M; Bonafe, Carlos F S

2007-02-01

411

Current Status of Hybrid Bearing Damage Detection  

NASA Technical Reports Server (NTRS)

Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high pressure oxidizer turbopump, on the space shuttle main engine, led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si3N4 balls. The aerospace industry is currently studying the use of hybrid bearings and naturally the failure modes of these bearings become an issue in light of the limited data available. In today s turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Since the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure. The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris, in oil, using a commercial particle counter.

Dempsey, Paula J.; Certo, Joseph M.; Morales, Wilfredo

2004-01-01

412

TRPV1: Contribution to Retinal Ganglion Cell Apoptosis and Increased Intracellular Ca2+ with Exposure to Hydrostatic Pressure  

PubMed Central

Purpose Elevated hydrostatic pressure induces retinal ganglion cell (RGC) apoptosis in culture. The authors investigated whether the transient receptor potential vanilloid 1 (TRPV1) channel, which contributes to pressure sensing and Ca2+-dependent cell death in other systems, also contributes to pressure-induced RGC death and whether this contribution involves Ca2+. Methods trpv1 mRNA expression in RGCs was probed with the use of PCR and TRPV1 protein localization through immunocytochemistry. Subunit-specific antagonism (iodo-resiniferatoxin) and agonism (capsaicin) were used to probe how TRPV1 activation affects the survival of isolated RGCs at ambient and elevated hydrostatic pressure (+70 mm Hg). Finally, for RGCs under pressure, the authors tested whether EGTA chelation of Ca2+ improves survival and whether, with the Ca2+ dye Fluo-4 AM, TRPV1 contributes to increased intracellular Ca2+. Results RGCs express trpv1 mRNA, with robust TRPV1 protein localization to the cell body and axon. For isolated RGCs under pressure, TRPV1 antagonism increased cell density and reduced apoptosis to ambient levels (P ? 0.05), whereas for RGCs at ambient pressure, TRPV1 agonism reduced density and increased apoptosis to levels for elevated pressure (P ? 0.01). Chelation of extracellular Ca2+ reduced RGC apoptosis at elevated pressure by nearly twofold (P ? 0.01). Exposure to elevated hydrostatic pressure induced a fourfold increase in RGC intracellular Ca2+ that was reduced by half with TRPV1 antagonism. Finally, in the DBA/2 mouse model of glaucoma, levels of TRPV1 in RGCs increased with elevated IOP. Conclusions RGC apoptosis induced by elevated hydrostatic pressure arises substantially through TRPV1, likely through the influx of extracellular Ca2+. PMID:18952924

Sappington, Rebecca M.; Sidorova, Tatiana; Long, Daniel J.; Calkins, David J.

2013-01-01

413

Influence of several environmental factors on the initiation of germination and inactivation of Bacillus cereus by high hydrostatic pressure  

Microsoft Academic Search

The influence of pH, aw, l-alanine, and fat concentration of milk on the initiation of germination and inactivation by high hydrostatic pressure (HHP) (250 mPa at 25°C for 15 min and 690 mPa at 40°C for 2 min) of Bacillus cereus sporulated at 20, 30 and 37°C was investigated. B. cereus sporulated at the lowest temperature was found to be

Javier Raso; M. Marcela Góngora-Nieto; Gustavo V. Barbosa-Cánovas; Barry G. Swanson

1998-01-01

414

Elastic Moduli of Germanium Versus Hydrostatic Pressure at 25.0°C and -195.8°C  

Microsoft Academic Search

Ultrasonic wave velocities and elastic moduli for high purity germanium have been measured as a function of hydrostatic pressure and temperature in the ranges 0 to 30 000 psi and ?195.8° to 25°C. The high degree of self-consistency of results provides a further check on the pulse superposition method used. [H. J. Mc-Skimin and P. Andreatch, J. Acoust. Soc. Am.

H. J. McSkimin; P. Andreatch Jr.

1963-01-01

415

Systematic analysis of HSP gene expression and effects on cell growth and survival at high hydrostatic pressure in Saccharomyces cerevisiae  

Microsoft Academic Search

We systematically investigated the role of HSP genes in the growth and survival of Saccharomyces\\u000a cerevisiae under high hydrostatic pressure together with analysis of pressure-regulated gene expression. Cells of strain BY4742 were capable of growth at moderate pressure of 25 MPa. When pressure of 25 MPa was applied to the cells, the expression of HSP78, HSP104, and HSP10 was upregulated by about

Takeshi Miura; Hiroaki Minegishi; Ron Usami; Fumiyoshi Abe

2006-01-01

416

Quadrupole coupling and crystal-field shielding in CaF2:Eu3+:O2- under hydrostatic pressure  

Microsoft Academic Search

The nuclear quadrupole interactions in the 7F0 ground electronic state and the 5D0 excited state of the 151Eu3+ and 153Eu3+ ions have been investigated by optical means. The optically detected nuclear quadrupole resonance, excitation, and luminescence of the Eu3+-O2- C3v symmetry center have been studied at 4.2 K in single crystals of CaF2:Eu:O under hydrostatic pressure up to 7.5 kbar.

Andrzej P. Radlinski; A. J. Silversmith

1986-01-01

417

Verification of a non-hydrostatic dynamical core using horizontally spectral element vertically finite difference method: 2-D aspects  

NASA Astrophysics Data System (ADS)

The non-hydrostatic (NH) compressible Euler equations of dry atmosphere are solved in a simplified two dimensional (2-D) slice framework employing a spectral element method (SEM) for the horizontal discretization and a finite difference method (FDM) for the vertical discretization. The SEM uses high-order nodal basis functions associated with Lagrange polynomials based on Gauss-Lobatto-Legendre (GLL) quadrature points. The FDM employs a third-order upwind biased scheme for the vertical flux terms and a centered finite difference scheme for the vertical derivative terms and quadrature. The Euler equations used here are in a flux form based on the hydrostatic pressure vertical coordinate, which are the same as those used in the Weather Research and Forecasting (WRF) model, but a hybrid sigma-pressure vertical coordinate is implemented in this model. We verified the model by conducting widely used standard benchmark tests: the inertia-gravity wave, rising thermal bubble, density current wave, and linear hydrostatic mountain wave. The results from those tests demonstrate that the horizontally spectral element vertically finite difference model is accurate and robust. By using the 2-D slice model, we effectively show that the combined spatial discretization method of the spectral element and finite difference method in the horizontal and vertical directions, respectively, offers a viable method for the development of a NH dynamical core.

Choi, S.-J.; Giraldo, F. X.; Kim, J.; Shin, S.

2014-06-01

418

The dual action gas thrust bearing - A new high load bearing concept  

NASA Technical Reports Server (NTRS)

The principle of utilizing hydrodynamic effects in diverging films for improving load capacity in gas thrust bearings is discussed. A new concept of dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and improve their efficiency.

Etsion, I.

1976-01-01

419

Prospects for Yellowstone grizzly bears  

USGS Publications Warehouse

Recent analyses of data on the grizzly bear (Ursus arctos horribilis) population of Yellowstone National Park and its environs suggest the likelihood of a continuing decline in numbers if losses of fully adult females are not reduced. The size of the population is not known, and a simple projection model has been used to identify some inconsistencies in the available index data. Population dynamics calculations, based on Lotka's equation or a stochastic model, indicate a continuing decrease in numbers, although continued observations through radio-telemetry are needed to verify these trends. The margin between stabilizing the population and a continued decrease appears to be roughly the loss of 2 fully adult female bears per year. At present, the risk of extirpation of this population over the next 30 years appears to be small. Continued monitoring of survivorship will be needed, particularly because "recovery" of the population may be mainly characterized by a shift in the pattern of mortality, from adults to subadults, and not necessarily a reduction in absolute number of losses.

Knight, R.R.; Eberhardt, L.L.

1987-01-01

420

Optical rectification coefficient of a two-dimensional parabolic quantum dot: Effects of hydrogenic impurity, external fields, hydrostatic pressure and temperature  

NASA Astrophysics Data System (ADS)

Simultaneous effects of hydrogenic impurity, hydrostatic pressure, temperature and external electric and magnetic fields on the intersubband optical rectification coefficient of a two-dimensional parabolic quantum dot are studied. Energy eigenvalues and eigenvectors are calculated using the direct matrix diagonalization method and optical rectification coefficient is obtained via the compact density matrix approach. The results indicate that the optical rectification coefficient is affected by the hydrogenic impurity, hydrostatic pressure, temperature and external fields.

Rezaei, G.; Kish, S. Shojaeian; Vaseghi, B.; Taghizadeh, S. F.

2014-10-01

421

A Comparison of Hydrostatic Weighing and the Tanita Body Fat Analyzer for Estimating Percent Body Fat in NCAA Division III Collegiate Wrestlers  

Microsoft Academic Search

Abstract. Bruflat L, Hetman S, Lozano J. A Comparison of Hydrostatic Weighing and the Tanita Body Fat Analyzer for Estimating Percent Body Fat in NCAA Division III Collegiate Wrestlers. J. Undergrad. Kin. Res. 2005:1(1):60-66. The purpose of this study was to compare percent body fat (%BF) estimated by leg-to-leg bioelectrical impedance analysis (LBIA) with hydrostatic weighing (HW) in a group

Lucas Bruflat; Sarah Hetman; Joe Lozano

422

Magnetic bearings - State of the art  

NASA Technical Reports Server (NTRS)

Magnetic bearings have existed for many years, at least in theory. Earnshaw's theorem, formulated in 1842, concerns stability of magnetic suspensions, and states that not all axes of a bearing can be stable without some means of active control. In Beam's widely referenced experiments, a tiny (1/64 in diameter) rotor was rotated to the astonishing speed of 800,000 rps while it was suspended in a magnetic field. Despite a long history, magnetic bearings have only begun to see practical application since about 1980. The development that finally made magnetic bearings practical was solid state electronics, enabling power supplies and controls to be reduced in size to where they are now comparable in volume to the bearings themselves. An attempt is made to document the current (1991) state of the art of magnetic bearings. The referenced papers are large drawn from two conferences publications published in 1988 and 1990 respectively.

Fleming, David P.

1993-01-01

423

Magnetic bearings for inertial energy storage  

SciTech Connect

The selection of a noncontacting bearing technique with no wear out phenomena and which is vacuum compatible which is the decisive factor in selecting magnetic bearings for kinetic energy storage was investigated. Unlimited cycle life without degradation is a primary goal. Storage efficiency is a key parameter which is defined as the ratio of the energy remaining to energy stored after a fixed time interval at no load conditions. Magnetic bearings, although noncontacting, are not perfectly frictionless in that magnetic losses due to eddy currents and hysteresis can occur. Practical magnetic bearings, however, deviate from perfect symmetry and have discontinuities and asymmetric flux paths either by design or when controlled in the presence of disturbances, which cause losses. These losses can be kept smaller in the bearings than in a high power motor/generator, however, are a significant factor in selecting the magnetic bearing type.

Studer, P.A.

1983-12-01

424

Magnetic bearings-state of the art  

NASA Technical Reports Server (NTRS)

Magnetic bearings have existed for many years, at least in theory. Earnshaw's theorem, formulated in 1842, concerns stability of magnetic suspensions, and states that not all axes of a bearing can be stable without some means of active control. In Beam's widely referenced experiments, a tiny (1/64 in diameter) rotor was rotated to the astonishing speed of 800,000 rps while it was suspended in a magnetic field. Despite a long history, magnetic bearings have only begun to see practical application since about 1980. The development that finally made magnetic bearings practical was solid state electronics, enabling power supplies and controls to be reduced in size to where they are now comparable in volume to the bearings themselves. An attempt is made to document the current (1991) state of the art of magnetic bearings. The referenced papers are large drawn from two conferences publications published in 1988 and 1990 respectively.

Fleming, David P.

1991-01-01

425

Effect of Rolling Bearing Refurbishment and Restoration on Bearing Life and Reliability  

NASA Technical Reports Server (NTRS)

For nearly four decades it has been a practice in commercial and military aircraft application that rolling-element bearings removed at maintenance or overhaul be reworked and returned to service. The work presented extends previously reported bearing life analysis to consider the depth (Z(45)) to maximum shear stress (45) on stressed volume removal and the effect of replacing the rolling elements with a new set. A simple algebraic relationship was established to determine the L(10) life of bearing races subject to bearing rework. Depending on the extent of rework and based upon theoretical analysis, representative life factors (LF) for bearings subject to rework ranged from 0.87 to 0.99 the lives of new bearings. Based on bearing endurance data, 92 percent of the bearing sets that would be subject to rework would result in L(10) lives equaling and/or exceeding that predicted for new bearings with the remaining 8 percent having the potential to achieve the analytically predicted life of new bearings when one of the rings is replaced at rework.. The potential savings from bearing rework varies from 53 to 82 percent that of new bearings depending on the cost, size and complexity of the bearing.

Zaretsky, Erwin V.; Branzai, Emanuel V.

2005-01-01

426

Cantilever mounted resilient pad gas bearing  

NASA Technical Reports Server (NTRS)

A gas-lubricated bearing is described, employing at least one pad mounted on a rectangular cantilever beam to produce a lubricating wedge between the face of the pad and a moving surface. The load-carrying and stiffness characteristics of the pad are related to the dimensions and modulus of elasticity of the beam. The bearing is applicable to a wide variety of types of hydrodynamic bearings.

Etsion, I. (inventor)

1978-01-01

427

Acoustical properties of hydrodynamic journal bearings  

Microsoft Academic Search

Results of theoretical investigations on acoustical properties of hydrodynamic journal bearings are presented. Nonlinear analysis including rotor imbalance is performed for a rotor-bearing system in order to obtain acoustical properties of the bearing. Furthermore, a cavitation algorithm, implementing the Jakobsson–Floberg–Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties are investigated through frequency analysis of

Byoung-Hoo Rho; Kyung-Woong Kim

2003-01-01

428

First-order ball-bearing kinematics  

NASA Technical Reports Server (NTRS)

Two first-order equations are given connecting geometry and internal motions in an angular-contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first-order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.

Kingsbury, E.

1985-01-01

429

Ceramic Materials in Hybrid Ball Bearings  

Microsoft Academic Search

A computational study was conducted to make comparisons regarding heat generation, frictional torque, and ball wear between conventional all steel bearings using M50 steel balls and hybrid bearings using silicon nitride (Si3N4) ceramic balls. Both were modeled using M50 steel races and the study was accomplished for radially loaded bearings only. Although most realistic applications also include axial loads on

Pete Cento; Don W. Dareing

1999-01-01

430

Static forces in a superconducting magnet bearing  

SciTech Connect

Static levitation forces and stiffnesses in a superconducting bearing consisting of concentric ring magnets and a superconducting YBaCuO ring are investigated. In the field-cooled mode a levitation force of 20 N has been achieved. The axial and radial stiffnesses have values of 15 N/mm and 10 N/mm, respectively. An arrangement with two bearings supporting a high speed shaft is now under development. A possible application of superconducting magnetic bearings is flywheels for energy storage.

Stoye, P.; Fuchs, G. [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany)] [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany); Gawalek, W.; Goernert, P. [Institut fuer Physikalische Hochtechnologie, Jena (Germany)] [Institut fuer Physikalische Hochtechnologie, Jena (Germany); Gladun, A. [Technische Univ., Dresden (Germany)] [Technische Univ., Dresden (Germany)

1995-11-01

431

Mechanical characteristics of a thrust magnetic bearing  

Microsoft Academic Search

Static and dynamic mechanical characteristics of a thrust magnetic bearing are studied owing to the inclination of the runner\\u000a disk. The application refers to a thrust magnetic bearing for a turbo-expander\\/compressor. The static tilt of the runner disk\\u000a has remarkable influence on the mechanical characteristics of thrust magnetic bearing, it can change the static load distribution\\u000a between two radial magnetic

Gang Zhang; Li-qun Chen; Lie Yu; You-bai Xie

2000-01-01

432

Notes 16. Analysis of tilting pad bearings  

E-print Network

Figure 1 shows a tilting pad journal bearing comprised of four pads. Each pad tilts about its pivot making a hydrodynamic film that generates a pressure reacting to the static load applied on the spinning journal. This type of bearing is typically... Figure 1 shows a tilting pad journal bearing comprised of four pads. Each pad tilts about its pivot making a hydrodynamic film that generates a pressure reacting to the static load applied on the spinning journal. This type of bearing is typically...

San Andres, Luis

2010-01-01

433

Oil film pressure in hydrodynamic journal bearings.  

E-print Network

??Hydrodynamic journal bearings are critical power transmission components that are carrying increasingly high loads because of the increasing power density in various machines. Therefore, knowing… (more)

Valkonen, Antti

2009-01-01

434

Permanent Magnetic Bearing for Spacecraft Applications  

NASA Technical Reports Server (NTRS)

A permanent, totally passive magnetic bearing rig was designed, constructed, and tested. The suspension of the rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm using an air impeller. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Morales, Winfredo; Fusaro, Robert; Kascak, Albert

2008-01-01

435

Fractional Whirl Motion in Wave Journal Bearings  

NASA Technical Reports Server (NTRS)

Unloaded gas, plain journal bearings experience sub-synchronous whirl motion due to fluid film instabilities and wall contact usually occurs immediately after the onset of the whirl motion. An alternative is the wave journal bearing which significantly improves bearing stability. The predicted threshold where the sub-synchronous whirl motion starts was well confirmed by the experimental observation. In addition, both a two-wave and a three-wave journal bearing can operate free of sub-synchronous whirl motion over a large range in speeds. When the sub-synchronous whirl motion occurs, both the two-wave and three-wave bearing can run in a whirl orbit well within the bearing clearance. At large clearances and wave amplitudes a two-wave bearing, unliKe other bearings, can exhibit a sub-synchronous whirl movement at both low and high speeds, but can run extremely stable and without whirl at intermediate speeds. Moreover, in these cases, the whirl frequencies are close to a quarter of the synchronous speed. The three-wave bearing can exhibit sub-synchronous whirl motion only after a specific threshold when the speed increases and the whirl frequencies are close to half of the synchronous speed.

Dimofte, Florin; Hendricks, Robert C.

1996-01-01

436

Polar Bears International: Vital Maternity Den Study  

NSDL National Science Digital Library

This report describes a journalist's participation in a study of polar bear denning sites in the Alaska National Wildlife Refuge (ANWR). It is thought that cubs born in those dens play an important role in maintaining the Beaufort Sea population of polar bears. Prior to the study, no complete map existed pinpointing the ANWR's denning areas. The study data will be available to manage human activities, thus protecting the sensitive areas in which a mother polar bear may den. The study will also provide baseline data to assess how climate change may alter the distribution of polar-bear denning habitat.

437

A spherical gas bearing for airborne application  

NASA Technical Reports Server (NTRS)

A spherical gas bearing is analyzed and tested for an airborne application. The externally pressurized bearing supports an inertially stabilized 36-in aperture, infrared telescope. The bearing provides the isolation of rotary motion from the aircraft and also serves as a seal between the aircraft cabin and cavity condition at 50,000 ft altitude. The accompanying temperature gradient of 135 F across the 16-in.-diam bearing created special design and manufacturing considerations. Test data on the static load under temperature and vacuum environment are presented in support of the analysis.

Bouvier, A.; Schmertz, J. C.

1974-01-01

438

Technical Development Path for Foil Gas Bearings  

NASA Technical Reports Server (NTRS)

Foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as turbochargers, auxiliary power units and propulsion gas turbines. Though not well known, foil bearing technology is well over fifty years old. Recent technological developments indicate that their full potential has yet to be realized. This paper investigates the key technological developments that have characterized foil bearing advances. It is expected that a better understanding of foil gas bearing development path will aid in future development and progress towards more advanced applications.

DellaCorte, Christopher

2008-01-01

439

The application of ICOM, a non-hydrostatic, fully unstructured mesh model in large scale ocean domains  

NASA Astrophysics Data System (ADS)

There are many apparent advantages of the application of unstructured meshes in ocean modelling: a much better representation of the coastal boundaries, the ability to focus resolution in areas of interest, or areas of intensified flow, such as boundary currents, etc. In particular with adaptive mesh technology, where the mesh is adapted during the simulation as the flow evolves, one is able to resolve much smaller features in the often turbulent ocean flow, than would be possible with fixed, structured mesh models. The Imperial College Ocean Model[1], is a non-hydrostatic ocean model that employs fully unstructured adaptive meshes, that allow focussing of resolution not only in the horizontal but also in the vertical. This enables the modelling of physical processes, such as open ocean deep convection, density driven flows on a steep bottom topography, etc. that are very important for the global ocean circulation. The Imperial College Ocean Model has been applied succesfully in the modelling of many of these processes. On the other hand hydrostatic, layered ocean models have a significant advantage in large areas of the oceans where the hydrostatic assumption is valid. The fact that with fully unstructured meshes it is no longer straightforward to separate horizontal, baroptropic modes and vertical, baroclinic dynamics, has consequences for both numerical accuracy and the efficiency of the linear solvers. It has therefore been a challenge for ICOM to remain competitive in these areas with layered mesh models. These problems have been overcome by, amongst others, the development of a new mesh adaptation technique that maintains a columnar structure of the mesh in such areas. The application of multigrid techniques has improved the effiency of the non-hydrostatic pressure solve[2] in such a way that convergence is now independent of aspect ratio, which makes the pressure solve competitive with that of a hydrostatic model. In this contribution an overview will be given of some of the difficulties that were encountered in the application of ICOM in large scale, high aspect ratio ocean domains and how they have been overcome. A large scale application in the form of a baroclinic, wind-driven double gyre will be presented and the results are compared to two other models, the MIT general circulation model (MITgcm, [3]) and NEMO (Nucleus for European Modelling of the Ocean, [4]). Also a comparison of the performance and parallel scaling of the models on a supercomputing platform will be made. References [1] M.D. Piggott, G.J. Gorman, C.C. Pain, P.A. Allison, A.S. Candy, B.T. Martin and W.R. Wells, "A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes", International Journal for Numerical Methods in Fluids 56, pp 1003 - 1015, 2008 [2] S.C. Kramer, C.J. Cotter and C.C. Pain, "Solving the Poisson equation on small aspect ratio domains using unstructured meshes", submitted to Ocean Modelling [3] J. Marshall, C. Hill, L. Perelman, and A. Adcroft, "Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling", J. Geophysical Res., 102(C3), pp 5733-5752, 1997 [4] G. Madec, "NEMO ocean engine", Note du Pole de modélisation, Institut Pierre-Simon Laplace (IPSL), France, No 27 ISSN No 1288-1619

Kramer, Stephan C.; Piggott, Matthew D.; Cotter, Colin J.; Pain, Chris C.; Nelson, Rhodri B.

2010-05-01

440

Dynamic modelling and response characteristics of a magnetic bearing rotor system including auxiliary bearings  

NASA Technical Reports Server (NTRS)

Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.

Free, April M.; Flowers, George T.; Trent, Victor S.

1993-01-01

441

Oil exchange between ball bearings and cotton-phenolic ball-bearing retainers  

NASA Astrophysics Data System (ADS)

Experiments have been performed that determine for the first time the transfer of oil between cotton-phenolic ball-bearing retainers and operating ball bearings. A full retainer exchanges oil with the metal parts of the bearing, probably by diffusional mixing. There is no net delivery of oil from the retainer to the metal parts of the bearing. A partially filled retainer (such as one that has been incompletely impregnated) absorbs oil from the bearing even during operation, thus drying the bearing. A fully-impregnated retainer does not deliver any significant amount of additional oil to the metal parts of a poorly lubricated bearing. The retainer will not prevent lubricant degradation and premature bearing failure under the conditions of these experiments.

Bertrand, P. A.; Carre, D. J.; Bauer, R.

1994-09-01

442

Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material  

NASA Technical Reports Server (NTRS)

It has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing.

Keith, Theo G., Jr.; Dimofte, Florin

2001-01-01

443

Dynamic modelling and response characteristics of a magnetic bearing rotor system with auxiliary bearings  

NASA Technical Reports Server (NTRS)

Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied.

Free, April M.; Flowers, George T.; Trent, Victor S.

1995-01-01

444

Donor spectroscopy at large hydrostatic pressures and transport studies in compound semiconductors  

SciTech Connect

In the first part of this work, the author describes studies of donors in AlSb and in GaAs at large hydrostatic pressures, two materials in which the conduction band minimum is not parabolic, but has a camel`s back shape. These donors were found to display only one or two absorption lines corresponding to ground to bound excited state transitions. It is shown that due to the non-parabolic dispersion, camel`s back donors may have as few as one bound excited state and that higher excited states are auto-ionized. Thus, it is possible that transitions to these other states may be lost in the continuum. In the second part, calculations of mobilities in GaN and other group III-Nitride based structures were performed. GaN is interesting in that the carriers in nominally undoped material are thought to originate from impurities which have an ionization energy level resonant with the conduction band, rather than located in the forbidden gap. These donors have a short range potential associated with them which can be effective in scattering electrons in certain situations. It was found that effects of these resonant donors can be seen only at high doping levels in III-Nitride materials and in Al{sub x}Ga{sub 1{minus}x}N alloys, where the defect level can be pushed into the forbidden gap. Calculations were also performed to find intrinsic mobility limits in Al{sub x}Ga{sub 1{minus}x}N/GaN modulation doped heterostructures. Theoretical predictions show that electron mobilities in these devices are capable of rivaling those found in the best Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures structures today. However, the currently available nitride heterostructures, while displaying mobilities superior to those in bulk material, have sheet carrier concentrations too large to display true two-dimensional electron gas behavior.

Hsu, L.

1997-06-01

445

Comprehensive study of hydrostatic pressure treated human umbilical cord blood cells via response surface method.  

PubMed

Amelioration of the survival parameters of cryopreserved samples after thawing has already been addressed through several techniques including vitrification to avoid the formation of ice cores. However, this approach cannot be followed in the case of samples with higher volumes. Hydrostatic pressure (HP) treatment has been proven to increase some qualifying parameters (e.g., motility, insemination efficiency) of certain biological samples. Accordingly, the preparation of umbilical cord blood (UCB) samples through an active (mechanical) pre-stressing process to increase the survival rate of cryopreserved samples can be regarded as a novel strategy that calls for basic experimental studies. The goal of our study was to assess the effects of HP treatment on the qualifying parameters (DNA fragmentation by agarose gel electrophoresis and capillary electrophoresis, Total Nucleotide Cell (TNC) count, CD34+/CD45+ count, and superoxide dismutase activity (SOD) of human umbilical cord blood (UCB) derived cells). The experimental arrangement was set to provide data for response-surface analysis to take into account the common effects of the individual variables of pressure and time exposure. 3D visualization of experimental data revealed that 50-min long HP treatment at 12.5MPa can significantly (?=0.05) enhance white blood cell (WBC) and CD34+/CD45+ cell counts. However no DNA fragmentation was observed even at higher pressures, SOD activity was triggered over 15.0MPa. As a conclusion, HP treatment may contribute to the optimal cryopreservation of UCB cells by significantly increasing WBC and CD34+/CD45+ cell counts without adverse effects neither on DNA stability nor on triggering SOD activity. PMID:25106745

Száraz, Leonóra; Szénási, Dóra; Oldak, Tomasz; Balogh, István

2014-10-01

446

Effect of high hydrostatic pressure on salmonella inoculated into creamy peanut butter with modified composition.  

PubMed

Peanut butter has been associated with several large foodborne salmonellosis outbreaks. This research investigates the potential of high hydrostatic pressure processing (HPP) for inactivation of Salmonella in peanut butter of modified composition, both by modifying its water activity as well by the addition of various amounts of nisin. A cocktail of six Salmonella strains associated with peanut butter and nut-related outbreaks was used for all experiments. Different volumes of sterile distilled water were added to peanut butter to increase water activity, and different volumes of peanut oil were added to decrease water activity. Inactivation in 12% fat, light roast, partially defatted peanut flour, and peanut oil was also quantified. Nisaplin was incorporated into peanut butter at four concentrations corresponding to 2.5, 5.0, 12.5, and 25.0 ppm of pure nisin. All samples were subjected to 600 MPa for 18 min. A steady and statistically significant increase in log reduction was seen as added moisture was increased from 50 to 90%. The color of all peanut butter samples containing added moisture contents darkened after high pressure processing. The addition of peanut oil to further lower the water activity of peanut butter further reduced the effectiveness of HPP. Just over a 1-log reduction was obtained in peanut flour, while inactivation to below detection limits (2 log CFU/g) was observed in peanut oil. Nisin alone without HPP had no effect. Recovery of Salmonella after a combined nisin and HPP treatment did show increased log reduction with longer storage times. The maximum log reduction of Salmonella achieved was 1.7 log CFU/g, which was comparable to that achieved by noncycling pressure treatment alone. High pressure processing alone or with other formulation modification, including added nisin, is not a suitable technology to manage the microbiological safety of Salmonella-contaminated peanut butter. PMID:25285482

D'Souza, Tanya; Karwe, Mukund; Schaffner, Donald W

2014-10-01

447

A 3-D Finite-Volume Non-hydrostatic Icosahedral Model (NIM)  

NASA Astrophysics Data System (ADS)

The Nonhydrostatic Icosahedral Model (NIM) formulates the latest numerical innovation of the three-dimensional finite-volume control volume on the quasi-uniform icosahedral grid suitable for ultra-high resolution simulations. NIM's modeling goal is to improve numerical accuracy for weather and climate simulations as well as to utilize the state-of-art computing architecture such as massive parallel CPUs and GPUs to deliver routine high-resolution forecasts in timely manner. NIM dynamic corel innovations include: * A local coordinate system remapped spherical surface to plane for numerical accuracy (Lee and MacDonald, 2009), * Grid points in a table-driven horizontal loop that allow any horizontal point sequence (A.E. MacDonald, et al., 2010), * Flux-Corrected Transport formulated on finite-volume operators to maintain conservative positive definite transport (J.-L, Lee, ET. Al., 2010), *Icosahedral grid optimization (Wang and Lee, 2011), * All differentials evaluated as three-dimensional finite-volume integrals around the control volume. The three-dimensional finite-volume solver in NIM is designed to improve pressure gradient calculation and orographic precipitation over complex terrain. NIM dynamical core has been successfully verified with various non-hydrostatic benchmark test cases such as internal gravity wave, and mountain waves in Dynamical Cores Model Inter-comparisons Projects (DCMIP). Physical parameterizations suitable for NWP are incorporated into NIM dynamical core and successfully tested with multimonth aqua-planet simulations. Recently, NIM has started real data simulations using GFS initial conditions. Results from the idealized tests as well as real-data simulations will be shown in the conference.

Lee, Jin

2014-05-01

448

Effect of high hydrostatic pressure on cashew apple (Anacardium occidentale L.) juice preservation.  

PubMed

High hydrostatic pressure is an alternative to thermal processing to inactivate spoilage and pathogenic microorganisms. Cashew apple juice has a pleasant flavor and is rich in vitamin C. Studies to determine the effect of high pressure on microorganisms in cashew apple juice are still lacking. In this study, the inactivation of natural micropopulation and inoculated Escherichia coli by high pressure was evaluated in fresh cashew apple juice. The microbiological stability of pressure-treated juice was also evaluated. The applied high pressure levels ranged from 250 to 400 MPa for periods of 3 to 7 min. Treatments with 350 MPa for 7 min and 400 MPa for either 3 or 7 min reduced the aerobic mesophilic bacteria count to a level below the detection limit. Pressure treatments were also efficient in inactivating yeast and filamentous fungi. The inoculated E. coli (10(6) CFU/mL) was reduced to below 10 CFU/mL after a pressure treatment of 400 MPa for 3 min. The inactivation of this microorganism followed a 1st-order reaction kinetics. The decimal reduction time (D-value) ranged from 1.21 to 16.43 min, while pressure resistance value (z-value) was 123.46 MPa. Neither natural micropopulation growth nor E. coli repair was observed in postprocessed (400 MPa for 3 min) cashew apple juice kept under refrigerated storage (at 4 degrees C) during 8 wk. The results of this study demonstrated the efficacy of high-pressure treatment for preserving cashew apple juice. PMID:19241557

Lavinas, F C; Miguel, M A L; Lopes, M L M; Valente Mesquita, V L

2008-08-01

449

Application of high hydrostatic pressure to eliminate Listeria monocytogenes from fresh pork sausage.  

PubMed

Ground pork patties were inoculated separately with 10(9) CFU/g each of three strains of Listeria monocytogenes obtained from the National Animal Disease Center (NADC). Inoculated patties were packaged under vacuum and treated at 414 megapascals (60,000 lb/in2) for up to 60 min by high hydrostatic pressure (HHP). Survivors were determined by surface plating onto modified Oxford agar and trypticase soy agar with yeast extract, as well as by the most probable number method using Listeria enrichment broth. Average D values ranged from 1.89 to 4.17 min, depending on the strain, with the most virulent strain (reported by the NADC) having the highest D value. We tested the usefulness of applying a mild heat treatment at 50 degrees C, simultaneously with HHP, to lower these values. Average D values ranged from 0.37 to 0.63 min, depending on the strain. Thus, a 10-log10 reduction could be achieved even in the most pressure-resistant strain of L. monocytogenes by a 6-min application of heat and HHP. Shelf life studies were also conducted, with spoilage levels reached after 5 days of storage at 4 degrees C for controls versus 28 days for treated samples. Sensory evaluation of uninoculated grilled patties showed that panelists could not distinguish between those treated by heat and HHP and untreated controls (P<0.05). Thus, treatment by HHP in combination with mild heating can be used successfully to produce safer, longer-lasting fresh pork without affecting quality. PMID:10340668

Murano, E A; Murano, P S; Brennan, R E; Shenoy, K; Moreira, R G

1999-05-01

450

Spoilage of blood sausages morcilla de Burgos treated with high hydrostatic pressure.  

PubMed

In this study, the microbial ecology of the blood sausage morcilla de Burgos, subjected to high hydrostatic pressure treatment (HPP), was studied by culture-dependent and -independent methods. Morcilla de Burgos is the most traditional and famous blood sausage in Spain. The producers are interested in extending its shelf-life in order to expand their market and to reduce losses attributed to spoilage. Sausage batter prior to stuffing and blood sausages HPP treated or not (control) were analyzed at 0, 9, 14, 21, 28 and 35 days of storage at 4 degrees C. Lactic acid bacteria, Pseudomonas spp. and aerobic mesophilic bacteria were investigated by traditional plating. PCR-denaturing gradient gel electrophoresis (DGGE) was used to analyze the DNA and the RNA extracted directly from the blood sausages, as well as bulk cells of LAB and Pseudomonas spp. The results showed that HPP improved the shelf life of morcilla de Burgos to 28 days in comparison with control samples. The populations responsible for spoilage, namely LAB, remained lower in HPP treated samples when compared with the control samples. Only at 35 days of storage they reached values of 10(8) cfu/g, leading to the spoilage of the product. Although, HPP affected the LAB population, they were able to recover the injury provoked by the treatment. Lastly, HPP seemed to affect differently LAB species detected. While Leuconostoc mesenteroides was completely inactivated by HPP, Weissella viridescens was able to recover and carry out the typical spoilage of the product. Pseudomonas spp. remained under detection level (<10(2) CFU/g) after the HPP treatment. PMID:18367280

Diez, Ana M; Urso, Rosalinda; Rantsiou, Kalliopi; Jaime, Isabel; Rovira, Jordi; Cocolin, Luca

2008-04-30

451

High Hydrostatic Pressure Induces Counterclockwise to Clockwise Reversals of the Escherichia coli Flagellar Motor  

PubMed Central

The bacterial flagellar motor is a reversible rotary machine that rotates a left-handed helical filament, allowing bacteria to swim toward a more favorable environment. The direction of rotation reverses from counterclockwise (CCW) to clockwise (CW), and vice versa, in response to input from the chemotaxis signaling circuit. CW rotation is normally caused by binding of the phosphorylated response regulator CheY (CheY-P), and strains lacking CheY are typically locked in CCW rotation. The detailed mechanism of switching remains unresolved because it is technically difficult to regulate the level of CheY-P within the concentration range that produces flagellar reversals. Here, we demonstrate that high hydrostatic pressure can induce CW rotation even in the absence of CheY-P. The rotation of single flagellar motors in Escherichia coli cells with the cheY gene deleted was monitored at various pressures and temperatures. Application of >120 MPa pressure induced a reversal from CCW to CW at 20°C, although at that temperature, no motor rotated CW at ambient pressure (0.1 MPa). At lower temperatures, pressure-induced changes in direction were observed at pressures of <120 MPa. CW rotation increased with pressure in a sigmoidal fashion, as it does in response to increasing concentrations of CheY-P. Application of pressure generally promotes the formation of clusters of ordered water molecules on the surfaces of proteins. It is possible that hydration of the switch complex at high pressure induces structural changes similar to those caused by the binding of CheY-P. PMID:23417485

Sowa, Yoshiyuki; Kimura, Yoshifumi; Homma, Michio; Ishijima, Akihiko; Terazima, Masahide

2013-01-01

452

Inactivation of Human Norovirus in Contaminated Oysters and Clams by High Hydrostatic Pressure  

PubMed Central

Human norovirus (NoV) is the most frequent causative agent of food-borne disease associated with shellfish consumption. In this study, the effect of high hydrostatic pressure (HHP) on inactivation of NoV was determined. Genogroup I.1 (GI.1) or genogroup II.4 (GII.4) NoV was inoculated into oyster homogenates and treated at 300 to 600 MPa at 25, 6, and 1°C for 5 min. After HHP, samples were treated with RNase and viral particles were extracted with porcine gastric mucin (PGM)-conjugated magnetic beads (PGM-MBs). Viral RNA was then quantified by real-time reverse transcription (RT)-PCR. Since PGM contains histo-blood group-like antigens, which can act as receptors for NoV, deficiency for binding to PGM is an indication of loss of infectivity of NoV. After binding to PGM-MBs, RT-PCR-detectable NoV RNA in oysters was reduced by 0.4 to >4 log10 by HHP at 300 to 600 MPa. The GI.1 NoV was more resistant to HHP than the GII.4 NoV (P < 0.05). HHP at lower temperatures significantly enhanced the inactivation of NoV in oysters (P < 0.05). Pressure treatment was also conducted for clam homogenates. Treatment at 450 MPa at 1°C achieved a >4 log10 reduction of GI.1 NoV in both oyster and clam homogenates. It is therefore concluded that HHP could be applied as a potential intervention for inactivating NoV in raw shellfish. The method of pretreatment of samples with RNase, extraction of viral particles using PGM-MB binding, and quantification of viral RNA using RT-PCR can be explored as a practical means of distinguishing between infectious and noninfectious NoV. PMID:24487534

Ye, Mu; Li, Xinhui; Kingsley, David H.; Jiang, Xi

2014-01-01

453

Hydrostatic Pressure and Temperature Effects on the Membranes of a Seasonally Migrating Marine Copepod  

PubMed Central

Marine planktonic copepods of the order Calanoida are central to the ecology and productivity of high latitude ecosystems, representing the interface between primary producers and fish. These animals typically undertake a seasonal vertical migration into the deep sea, where they remain dormant for periods of between three and nine months. Descending copepods are subject to low temperatures and increased hydrostatic pressures. Nothing is known about how these organisms adapt their membranes to these environmental stressors. We collected copepods (Calanoides acutus) from the Southern Ocean at depth horizons ranging from surface waters down to 1000 m. Temperature and/or pressure both had significant, additive effects on the overall composition of the membrane phospholipid fatty acids (PLFAs) in C. acutus. The most prominent constituent of the PLFAs, the polyunsaturated fatty acid docosahexanoic acid [DHA – 22:6(n-3)], was affected by a significant interaction between temperature and pressure. This moiety increased with pressure, with the rate of increase being greater at colder temperatures. We suggest that DHA is key to the physiological adaptations of vertically migrating zooplankton, most likely because the biophysical properties of this compound are suited to maintaining membrane order in the cold, high pressure conditions that persist in the deep sea. As copepods cannot synthesise DHA and do not feed during dormancy, sufficient DHA must be accumulated through ingestion before migration is initiated. Climate-driven changes in the timing and abundance of the flagellated microplankton that supply DHA to copepods have major implications for the capacity of these animals to undertake their seasonal life cycle successfully. PMID:25338196

Pond, David W.; Tarling, Geraint A.; Mayor, Daniel J.

2014-01-01

454

Effect of high hydrostatic pressure on mycelial development, spore viability and enzyme activity of Penicillium Roqueforti.  

PubMed

This study investigated the effect of high hydrostatic pressure treatments on mycelial development, spore viability, and total proteolytic and lipolytic activity of Penicillium roqueforti PV-LYO 10 D. Fungus growing in liquid medium was pressure-treated at 300, 400, and 500 MPa for 10 min at 20°C following seven days of incubation at 25°C and analyzed periodically up to day 9 after treatments to evaluate the effect on fungal growth. Mycelial mass of P. roqueforti was significantly affected at all pressure treatments evaluated, being 15.48%, 22.28%, 30.03%, and 12.53% lower than controls on day 1, 3, 6, and 9 after 300 MPa treatment, respectively. In a similar way, at 400 and 500 MPa, mycelial mass was 31.08% and 60.34% lower than controls one day after treatments and 49.74% and 80.85% lower on day 9, respectively. The viability of P. roqueforti spores decreased by 36.53% at 300 MPa, and complete inactivation took place at ?400 MPa from an initial count of 7 log cfu/mL. Total proteolytic activity was not significantly affected at 300 MPa but was reduced by 18.22% at 400 MPa and by 43.18% at 500 MPa. Total lipolytic activity also decreased as the intensity of the pressure treatments increased. 21.69%, 39.12%, and 56.26% activity reductions were observed when treatments of 300, 400 and 500 MPa were applied, respectively. The results from this study show that pressure treatments are able to control growth, inactivate spores, and alter enzyme activity of P. roqueforti, which could be of interest in extending the shelf-life of blue-veined cheeses and other food products. PMID:24239974

Martínez-Rodríguez, Yamile; Acosta-Muñiz, Carlos; Olivas, Guadalupe I; Guerrero-Beltrán, José; Rodrigo-Aliaga, Dolores; Mujica-Paz, Hugo; Welti-Chanes, Jorge; Sepulveda, David R

2014-01-01

455

Lift and drag in intruders moving through hydrostatic granular media at high speeds  

E-print Network

Recently, experiments showed that forces on intruders dragged horizontally through dense, hydrostatic granular packings mainly depend on the local surface orientation and can be seen as the sum of the forces exerted on small surface elements. In order to understand such forces more deeply, we perform 2D soft-sphere molecular dynamics simulation, on similar set up, of an intruder dragged through a 50-50 bi-disperse granular packing, with diameters 0.30 and 0.34 cm. We measure, for both circular and half-circle shapes, the forces parallel (drag) and perpendicular (lift) to the drag direction as functions of the drag speed, with V=10.3-309 cm/s, and intruder depths, with D=3.75-37.5 cm. The drag forces on an intruder monotonically increase with V and D, and are larger for the circle. However, the lift force does not depend monotonically on V and D, and this relationship is affected by the shape of the intruder. The vertical force was negative for the half-circle, but for a small range of V and D, we measure positive lift. We find no sign change for the lift on the circle, which is always positive. The explanation for the nonmonotonic dependence is related to the decrease in contacts on the intruder as V increases. This is qualitatively similar to supersonic flow detachment from an obstacle. The detachment picture is supported by simulation measurements of the velocity field around the intruder and force profiles measured on its surface.

Fabricio Q. Potiguar; Yang Ding

2013-06-25

456

Inactivation of human norovirus in contaminated oysters and clams by high hydrostatic pressure.  

PubMed

Human norovirus (NoV) is the most frequent causative agent of food-borne disease associated with shellfish consumption. In this study, the effect of high hydrostatic pressure (HHP) on inactivation of NoV was determined. Genogroup I.1 (GI.1) or genogroup II.4 (GII.4) NoV was inoculated into oyster homogenates and treated at 300 to 600 MPa at 25, 6, and 1°C for 5 min. After HHP, samples were treated with RNase and viral particles were extracted with porcine gastric mucin (PGM)-conjugated magnetic beads (PGM-MBs). Viral RNA was then quantified by real-time reverse transcription (RT)-PCR. Since PGM contains histo-blood group-like antigens, which can act as receptors for NoV, deficiency for binding to PGM is an indication of loss of infectivity of NoV. After binding to PGM-MBs, RT-PCR-detectable NoV RNA in oysters was reduced by 0.4 to >4 log10 by HHP at 300 to 600 MPa. The GI.1 NoV was more resistant to HHP than the GII.4 NoV (P < 0.05). HHP at lower temperatures significantly enhanced the inactivation of NoV in oysters (P < 0.05). Pressure treatment was also conducted for clam homogenates. Treatment at 450 MPa at 1°C achieved a >4 log10 reduction of GI.1 NoV in both oyster and clam homogenates. It is therefore concluded that HHP could be applied as a potential intervention for inactivating NoV in raw shellfish. The method of pretreatment of samples with RNase, extraction of viral particles using PGM-MB binding, and quantification of viral RNA using RT-PCR can be explored as a practical means of distinguishing between infectious and noninfectious NoV. PMID:24487534

Ye, Mu; Li, Xinhui; Kingsley, David H; Jiang, Xi; Chen, Haiqiang

2014-04-01

457

The NCEP Eulerian Non-hydrostatic Multi-scale Model (NMMB)  

NASA Astrophysics Data System (ADS)

The development of the unified Non-hydrostatic Multi-scale Model (NMMB) has continued at NCEP. The model dynamics preserve a number of important properties of differential operators and conserve a variety of first order and quadratic quantities. The nonlinear dynamics is controlled by conserving energy and enstrophy in case of non-divergent flow. Over-specification of vertical velocity is avoided. The physical package was developed from the WRF NMM's physics, but other physics options are also available. The regional version of the NMMB is run operationally as the main deterministic North American short-range forecasting model (NAM) and in a number of other applications. The global NMMB also has been run over the last few years experimentally in order to assess its capabilities and develop it further. In terms of large scale metrics, the performance of the global NMMB in medium range weather forecasting has been generally comparable to that of other major medium range forecasting systems. Its computational efficiency satisfies and exceeds the current and projected operational requirements. Recently, the transition has started of the operational hurricane forecasting system HWRF from the WRF NMM dynamics to those of the NMMB. This system involves the use of a hierarchy of