Analysis of a Preloaded Bolted Joint in a Ceramic Composite Combustor

NASA Technical Reports Server (NTRS)

Hissam, D. Andy; Bower, Mark V.

2003-01-01

This paper presents the detailed analysis of a preloaded bolted joint incorporating ceramic materials. The objective of this analysis is to determine the suitability of a joint design for a ceramic combustor. The analysis addresses critical factors in bolted joint design including preload, preload uncertainty, and load factor. The relationship between key joint variables is also investigated. The analysis is based on four key design criteria, each addressing an anticipated failure mode. The criteria are defined in terms of margin of safety, which must be greater than zero for the design criteria to be satisfied. Since the proposed joint has positive margins of safety, the design criteria are satisfied. Therefore, the joint design is acceptable.

Effect of a protein preload on food intake and satiety feelings in response to duodenal fat perfusions in healthy male subjects.

PubMed

Oesch, Sibylle; Degen, Lukas; Beglinger, Christoph

2005-10-01

The control of food intake and satiety requires a coordinated interplay. Oral protein and duodenal fat inhibit food intake and induce satiety, but their interactive potential is unclear. Our aim was therefore to investigate the interactions between an oral protein preload and intraduodenal (ID) fat on food intake and satiety feelings. Twenty healthy male volunteers were studied in a randomized, double-blind, four-period crossover design. On each study day, subjects underwent one of the following treatments: 1) water preload plus ID saline perfusion, 2) water preload plus ID fat perfusion, 3) protein preload plus ID saline perfusion, or 4) protein preload plus ID fat perfusion. Subjects were free to eat and drink as much as they wished. An oral protein preload significantly reduced caloric intake (19%, P < 0.01). Simultaneous administration of an oral protein preload and ID fat did not result in a positive synergistic effect with respect to caloric consumption, rejecting the initial hypothesis that the two nutrients exert a positive synergistic effect on food intake. An oral protein preload but not ID fat altered the feelings of hunger and fullness. These data indicate that the satiety effect of an oral protein preload is not amplified by ID fat; indeed, the effect of a protein preload does not seem to be mediated by cholecystokinin, glucagon-like peptide-1, or peptide YY. Much more information is necessary to understand the basic physiological mechanisms that control food intake and satiety.

Adjustable bias column end joint assembly

NASA Technical Reports Server (NTRS)

Wallsom, Richard E. (Inventor); Bush, Harold G. (Inventor)

1994-01-01

An adjustable mechanical end joint system for connecting structural column elements and eliminating the possibility of free movement between joint halves during loading or vibration has a node joint body having a cylindrical engaging end and a column end body having a cylindrical engaging end. The column end joint body has a compressible preload mechanism and plunger means housed therein. The compressible preload mechanism may be adjusted from the exterior of the column end joint body through a port.

Effects of High-Intensity Intermittent Exercise Training on Appetite Regulation.

PubMed

Sim, Aaron Y; Wallman, Karen E; Fairchild, Timothy J; Guelfi, Kym J

2015-11-01

An acute bout of high-intensity intermittent exercise suppresses ad libitum energy intake at the postexercise meal. The present study examined the effects of 12 wk of high-intensity intermittent exercise training (HIIT) compared with moderate-intensity continuous exercise training (MICT) on appetite regulation. Thirty overweight inactive men (body mass index, 27.2 ± 1.3 kg·m(-2); V˙O2peak, 35.3 ± 5.3 mL·kg(-1)·min(-1) were randomized to either HIIT or MICT (involving 12 wk of training, three sessions per week) or a control group (CON) (n = 10 per group). Ad libitum energy intake from a laboratory test meal was assessed after both a low-energy (847 kJ) and a high-energy preload (2438 kJ) before and after the intervention. Perceived appetite and appetite-related blood variables were also measured. There was no significant effect of the intervention period on energy intake at the test meal after the two different preloads (P ≥ 0.05). However, the 95% confidence interval indicated a clinically meaningful decrease in energy intake after the high-energy preload compared with the low-energy preload in response to HIIT (516 ± 395 kJ decrease), but not for MICT or CON, suggesting improved appetite regulation. This was not associated with alterations in the perception of appetite or the circulating concentration of a number of appetite-related peptides or metabolites, although insulin sensitivity was enhanced with HIIT only (P = 0.003). HIIT seems to benefit appetite regulation in overweight men. The mechanisms for this remain to be elucidated.

Fatigue response of a PZT multilayer actuator under high-field electric cycling with mechanical preload

NASA Astrophysics Data System (ADS)

Wang, Hong; Wereszczak, Andrew A.; Lin, Hua-Tay

2009-01-01

An electric fatigue test system was developed for evaluating the reliability of piezoelectric actuators with a mechanical loading capability. Fatigue responses of a lead zirconate titanate (PZT) multilayer actuator with a platethrough electrode configuration were studied under an electric field (1.7 times that of the coercive field of PZT material) and a concurrent mechanical preload (30.0 MPa). A total of 109 cycles was carried out. Variations in charge density and mechanical strain under the high electric field and constant mechanical loads were observed during the fatigue test. The dc and the first harmonic (at 10 Hz) dielectric and piezoelectric coefficients were subsequently characterized using fast Fourier transformation. Both the dielectric and the piezoelectric coefficients exhibited a monotonic decrease prior to 2.86×108 cycles under certain preloading conditions, and then fluctuated. Both the dielectric loss tangent and the piezoelectric loss tangent also fluctuated after a decrease. The results are interpreted and discussed with respect to domain wall activities, microdefects, and other anomalies.

Hyperphagia induced by sucrose: relation to circulating and CSF glucose and corticosterone and orexigenic peptides in the arcuate nucleus.

PubMed

Gaysinskaya, V A; Karatayev, O; Shuluk, J; Leibowitz, S F

2011-01-01

Sucrose-rich diets compared to starch-rich diets are known to stimulate overeating under chronic conditions. The present study in normal-weight rats established an acute "preload-to-test meal" paradigm for demonstrating sucrose-induced hyperphagia and investigating possible mechanisms that mediate this behavioral phenomenon. In this acute paradigm, the rats were first given a small (15 kcal) sucrose preload (30% sucrose) for 30 min compared to an equicaloric, starch preload (25% starch with 5% sucrose) and then allowed to freely consume a subsequent test meal of lab chow. The sucrose preload, when compared to a starch preload equal in energy density and palatability, consistently increased food intake in the subsequent test meal occurring between 60 and 120 min after the end of the preload. Measurements of hormones, metabolites and hypothalamic peptides immediately preceding this hyperphagia revealed marked differences between the sucrose vs starch groups that could contribute to the increase in food intake. Whereas the sucrose group compared to the starch group immediately after the preload (at 10 min) had elevated levels of glucose in serum and cerebrospinal fluid (CSF) along with reduced expressions of neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus (ARC), the subsequent effects (at 30-60 min) just preceding the test meal hyperphagia were the reverse. Along with lower levels of glucose, they included markedly elevated serum and CSF levels of corticosterone and mRNA levels of NPY and AgRP in the ARC. In addition to establishing an animal model for sucrose-induced hyperphagia, these results demonstrate peripheral and central mechanisms that may mediate this behavioral phenomenon. Copyright © 2010 Elsevier Inc. All rights reserved.

HYPERPHAGIA INDUCED BY SUCROSE: RELATION TO CIRCULATING AND CSF GLUCOSE AND CORTICOSTERONE AND OREXIGENIC PEPTIDES IN THE ARCUATE NUCLEUS

PubMed Central

Gaysinskaya, V. A.; Karatayev, O.; Shuluk, J.; Leibowitz, S. F.

2010-01-01

Sucrose-rich diets compared to starch-rich diets are known to stimulate overeating under chronic conditions. The present study in normal-weight rats established an acute “preload-to-test meal” paradigm for demonstrating sucrose-induced hyperphagia and investigating possible mechanisms that mediate this behavioral phenomenon. In this acute paradigm, the rats were first given a small (15 kcals) sucrose preload (30% sucrose) for 30 min compared to an equicaloric, starch preload (25% starch with 5% sucrose) and then allowed to freely consume a subsequent test meal of lab chow. The sucrose preload, when compared to a starch preload equal in energy density and palatability, consistently increased food intake in the subsequent test meal occurring between 60–120 min after the end of the preload. Measurements of hormones, metabolites and hypothalamic peptides immediately preceding this hyperphagia revealed marked differences between the sucrose vs starch groups that could contribute to the increase in food intake. Whereas the sucrose group compared to starch group immediately after the preload (at 10 min) had elevated levels of glucose in serum and cerebrospinal fluid (CSF) along with reduced expression of neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus (ARC), the subsequent effects (at 30–60 min) just preceding the test meal hyperphagia were the reverse. Along with lower levels of glucose, they included markedly elevated serum and CSF levels of corticosterone and mRNA levels of NPY and AgRP in the ARC. In addition to establishing an animal model for sucrose-induced hyperphagia, these results demonstrate peripheral and central mechanisms that may mediate this behavioral phenomenon. PMID:21036188

Ratios of soluble and insoluble dietary fibers on satiety and energy intake in overweight pre- and postmenopausal women1

PubMed Central

Burton-Freeman, Britt; Liyanage, Dhanesh; Rahman, Sajida; Edirisinghe, Indika

2017-01-01

BACKGROUND: Fibers’ properties impact different mechanisms involved in satiety and energy intake regulation and metabolic outcomes. OBJECTIVE: Evaluate the effect of fiber types and menopausal status on satiety and metabolic responses in overweight women. METHODS: In a randomized within-subjects design, 19 overweight/obese women [9 premenopausal and 10 postmenopausal] consumed 3 preloads that varied by fiber content and source: 1) 3:1 ratio of soluble:insoluble fiber (SF), 2) 1:3 ratio of soluble:insoluble fiber (IF), 3) no fiber control (NFC). Subjective satiety, cholecystokinin (CCK), glucose, insulin, and triglyceride (TG) were measured for 3 h post-preload followed by in-lab ad libitum test meal and 32 hour food intake monitoring. RESULTS: Significant preload, time and preload by menopausal status interaction was apparent for hunger and fullness (p < 0.05 for both) with SF preload predominantly more satiating in postmenopausal women. CCK and insulin were significantly lower after SF preload (p < 0.0001 for both). Post-preload glucose responses differed by menopausal status: postmenopausal women distinguished between fiber types unlike premenopausal women (p = 0.02). TG was significantly elevated after the IF preload compared to NFC and SF (p = 0.007 and p = 0.008, respectively). CONCLUSIONS: Customized/personalized dietary recommendations for women during their premenopausal and postmenopausal years can help maximize metabolic and appetite control. PMID:28447070

Preloaded joint analysis methodology for space flight systems

NASA Technical Reports Server (NTRS)

Chambers, Jeffrey A.

1995-01-01

This report contains a compilation of some of the most basic equations governing simple preloaded joint systems and discusses the more common modes of failure associated with such hardware. It is intended to provide the mechanical designer with the tools necessary for designing a basic bolted joint. Although the information presented is intended to aid in the engineering of space flight structures, the fundamentals are equally applicable to other forms of mechanical design.

Examination of Disk-Type Multidegree-of-Freedom Ultrasonic Motor

NASA Astrophysics Data System (ADS)

Aoyagi, Manabu; Nakajima, Toshinori; Tomikawa, Yoshiro; Takano, Takehiro

2004-05-01

A multidegree-of-freedom (MDOF) ultrasonic motor using the multimode of a disk vibrator is realized. A spherical rotor can rotate around arbitrary axes. However, at the beginning of research on the MDOF ultrasonic motor, the MDOF ultrasonic motor did not have any mechanisms for supporting a spherical rotor. Since the preload was given by only the rotor’s own weight, the friction between the rotor and the stator vibrator was very small, but the torque characteristics of the MDOF motor were insufficient for practical use. The purpose of this study is to improve the motor performance further. In this paper, some support and preload mechanisms using a support plate were examined for the improvement of the motor performance. In addition to these methods, a sandwich structure in which two stator vibrators hold a spherical rotor is proposed. This structure has both a rotor support mechanism and a preload mechanism, and high torque by the torque composition of two stator vibrators can be obtained.

An Indirect Method to Measure Abutment Screw Preload: A Pilot Study Based on Micro-CT Scanning.

PubMed

Rezende, Carlos Eduardo E; Griggs, Jason Alan; Duan, Yuanyuan; Mushashe, Amanda M; Nolasco, Gisele Maria Correr; Borges, Ana Flávia Sanches; Rubo, José Henrique

2015-01-01

This study aimed to measure the preload in different implant platform geometries based on micro-CT images. External hexagon (EH) implants and Morse Tapered (MT) implants (n=5) were used for the preload measurement. The abutment screws were scanned in micro-CT to obtain their virtual models, which were used to record their initial length. The abutments were screwed on the implant with a 20 Ncm torque and the set composed by implant, abutment screw and abutment were taken to the micro-CT scanner to obtain virtual slices of the specimens. These slices allowed the measurement of screw lengths after torque application and based on the screw elongation. Preload values were calculated using the Hooke's Law. The preloads of both groups were compared by independent t-test. Removal torque of each specimen was recorded. To evaluate the accuracy of the micro-CT technique, three rods with known lengths were scanned and the length of their virtual model was measured and compared with the original length. One rod was scanned four times to evaluate the measuring method variation. There was no difference between groups for preload (EH = 461.6 N and MT = 477.4 N), but the EH group showed higher removal torque values (13.8 ± 4.7 against 8.2 ± 3.6 N cm for MT group). The micro-CT technique showed a variability of 0.053% and repeatability showed an error of 0.23 to 0.28%. Within the limitations of this study, there was no difference between external hexagon and Morse taper for preload. The method using micro-CT may be considered for preload calculation.

Influence of design and clinical factors on the removal force ratio in tapered implant-abutment interfaces.

PubMed

Aguirrebeitia, Josu; Abasolo, Mikel; Müftü, Sinan; Vallejo, Javier

2017-04-01

A previous study investigated the effects of the preload and taper-angle mismatch in tapered implant systems on the removal force characteristics of the self-locking mechanism. The present study builds upon the previous one and introduces the effects of the time elapsed between insertion and removal and the presence of saliva in the implant-abutment interface as 2 new additional parameters. The purpose of this in vitro study was to elucidate the influences of design and clinical parameters on the removal force for implant systems that use tapered interference fit (TIF) type connections by measuring the force needed to remove an abutment from an implant. Ninety-six implants with tapered abutment-implant interfaces specifically built for an unreplicated factorial design were tested on a custom-built workbench for removal force. Four levels were chosen for the preload, F P , and the taper mismatch Δθ; 3 levels for the wait time t; and 2 levels for the saliva presence s at the interface. A regression model was used based on physical reasoning and a theoretical understanding of the interface. A 4-way ANOVA was used to evaluate the influence of the main effects and interactions (α=.05). The experiments strongly indicated that preload, taper mismatch, and saliva presence are relevant variables in removal force. The wait time becomes important when its effect is evaluated along with the preload. The results of this study can be used for decision making in the design and use of TIF type systems. The study supports the use of artificial saliva in any implant design experiment because of its significance in the removal force of the abutment. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Automatic control of the preload in adaptive friction drives of chemical production machines

NASA Astrophysics Data System (ADS)

Balakin, P. D.

2017-08-01

Being based on the principle of providing the systems with adaptation property to the real parameters and operational condition, the energy effective mechanical system constructed on the base of friction gear with automated preload is offered and this allows keeping mechanical efficiency value adequate transforming drive path to in the terms of multimode operation. This is achieved by integrated control loop, operating on the basis of the laws of motion with the energy of the main power flow by changing automatically the kinematic dimension of the section and, hence, the value of preload in the friction contact. The given ratios of forces and deformations in the control loop are required at the stage of conceptual design to determine design dimensions of power transmission elements with new properties.

Efficient preloading of the ventricles by a properly timed atrial contraction underlies stroke work improvement in the acute response to cardiac resynchronization therapy

PubMed Central

Hu, Yuxuan; Gurev, Viatcheslav; Constantino, Jason; Trayanova, Natalia

2013-01-01

Background The acute response to cardiac resynchronization therapy (CRT) has been shown to be due to three mechanisms: resynchronization of ventricular contraction, efficient preloading of the ventricles by a properly timed atrial contraction, and mitral regurgitation reduction. However, the contribution of each of the three mechanisms to the acute response of CRT, specifically stroke work improvement, has not been quantified. Objective The goal of this study was to use an MRI-based anatomically accurate 3D model of failing canine ventricular electromechanics to quantify the contribution of each of the three mechanisms to stroke work improvement and identify the predominant mechanisms. Methods An MRI-based electromechanical model of the failing canine ventricles assembled previously by our group was further developed and modified. Three different protocols were used to dissect the contribution of each of the three mechanisms to stroke work improvement. Results Resynchronization of ventricular contraction did not lead to significant stroke work improvement. Efficient preloading of the ventricles by a properly timed atrial contraction was the predominant mechanism underlying stroke work improvement. Stroke work improvement peaked at an intermediate AV delay, as it allowed ventricular filling by atrial contraction to occur at a low diastolic LV pressure but also provided adequate time for ventricular filling before ventricular contraction. Diminution of mitral regurgitation by CRT led to stroke work worsening instead of improvement. Conclusion Efficient preloading of the ventricles by a properly timed atrial contraction is responsible for significant stroke work improvement in the acute CRT response. PMID:23928177

Mechanisms of decreased left ventricular preload during continuous positive pressure ventilation in ARDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhainaut, J.F.; Devaux, J.Y.; Monsallier, J.F.

1986-07-01

Continuous positive pressure ventilation is associated with a reduction in left ventricular preload and cardiac output, but the mechanisms responsible are controversial. The decrease in left ventricular preload may result exclusively from a decreased systemic venous return due to increased pleural pressure, or from an additional effect such as decreased left ventricular compliance. To determine the mechanisms responsible, we studied the changes in cardiac output induced by continuous positive pressure ventilation in eight patients with the adult respiratory distress syndrome. We measured cardiac output by thermodilution, and biventricular ejection fraction by equilibrium gated blood pool scintigraphy. Biventricular end-diastolic volumes weremore » then calculated by dividing stroke volume by ejection fraction. As positive end-expiratory pressure increased from 0 to 20 cm H/sub 2/O, stroke volume and biventricular end-diastolic volumes fell about 25 percent, and biventricular ejection fraction remained unchanged. At 20 cm H/sub 2/O positive end-expiratory pressure, volume expansion for normalizing cardiac output restored biventricular end-diastolic volumes without markedly changing biventricular end-diastolic transmural pressures. The primary cause of the reduction in left ventricular preload with continuous positive pressure ventilation appears to be a fall in venous return and hence in right ventricular stroke volume, without evidence of change in left ventricular diastolic compliance.« less

Miniature piezo electric vacuum inlet valve

DOEpatents

Keville, Robert F.; Dietrich, Daniel D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability. The low power (<1.6 watts), high pulse rate (<2 milliseconds), variable flow inlet valve is utilized for mass spectroscopic applications or other applications where pulsed or continuous flow conditions are needed. The inlet valve also has a very minimal dead volume of less than 0.01 std/cc. The valve can utilize, for example, a 12 Vdc input/750 Vdc, 3 mA output power supply compared to conventional piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three.

Fatigue responses of lead zirconate titanate stacks under semibipolar electric cycling with mechanical preload

NASA Astrophysics Data System (ADS)

Wang, Hong; Cooper, Thomas A.; Lin, Hua-Tay; Wereszczak, Andrew A.

2010-10-01

Lead zirconate titanate (PZT) stacks that had an interdigital internal electrode configuration were tested to more than 108 cycles. A 100 Hz semibipolar sine wave with a field range of +4.5/-0.9 kV/mm was used in cycling with a concurrently-applied 20 MPa preload. Significant reductions in piezoelectric and dielectric responses were observed during the cycling depending on the measuring condition. Extensive partial discharges were also observed. These surface events resulted in the erosion of external electrode and the exposure of internal electrodes. Sections prepared by sequential polishing technique revealed a variety of damage mechanisms including delaminations, pores, and etch grooves. The scale of damage was correlated with the degree of fatigue-induced reduction in piezoelectric and dielectric responses. The results from this study demonstrate the feasibility of using a semibipolar mode to drive a PZT stack under a mechanical preload and illustrate the potential fatigue and damages of the stack in service.

Mechanical behavior and failure analysis of prosthetic retaining screws after long-term use in vivo. Part 3: Preload and tensile fracture load testing.

PubMed

Al Jabbari, Youssef S; Fournelle, Raymond; Ziebert, Gerald; Toth, Jeffrey; Iacopino, Anthony M

2008-04-01

The aim of this study was to determine the preload and tensile fracture load values of prosthetic retaining screws after long-term use in vivo compared to unused screws (controls). Additionally, the investigation addressed whether the preload and fracture load values of prosthetic retaining screws reported by the manufacturer become altered after long-term use in vivo. For preload testing, 10 new screws (controls) from Nobel Biocare (NB) and 73 used retaining screws [58 from NB and 15 from Sterngold (SG)] were subjected to preload testing. For tensile testing, eight controls from NB and 58 used retaining screws (46 from NB and 12 from SG) were subjected to tensile testing. Used screws for both tests were in service for 18-120 months. A custom load frame, load cell, and torque wrench setup were used for preload testing. All 83 prosthetic screws were torqued once to 10 Ncm, and the produced preload value was recorded (N) using an X-Y plotter. Tensile testing was performed on a universal testing machine and the resulting tensile fracture load value was recorded (N). Preload and tensile fracture load values were analyzed with 2-way ANOVA and Tukey post-hoc tests. There was a significant difference between preload values for screws from NB and screws from SG (p < 0.001). The preload values for gold alloy screws from NB decreased as the number of years in service increased. There was a significant difference between tensile fracture values for the three groups (gold alloy screws from NB and SG and palladium alloy screws from NB) at p < 0.001. The tensile fracture values for gold alloy screws from NB and SG decreased as the number of years in service increased. In fixed detachable hybrid prostheses, perhaps as a result of galling, the intended preload values of prosthetic retaining screws may decrease with increased in-service time. The reduction of the fracture load value may be related to the increase of in-service time; however, the actual determination of this relationship is not possible from this study alone.

Method and apparatus for preloading a joint by remotely operable means

NASA Technical Reports Server (NTRS)

Kahn, Jon B. (Inventor)

1993-01-01

The invention is a method and apparatus for joining structures, an active structure and a passive structure, and imposing a tensile pre-load on the joint by a remotely operable mechanism comprising a heat contractible joining element. The method and apparatus include mounting on the structure, a probe shaft of material which is transformable from an expanded length to a contracted length when heated to a specific temperature range. The shaft is provided with a probe head which is receivable in a receptacle opening formed in the passive structure, when the active structure is moved into engagement therewith by an appropriate manipulator mechanism. A latching system mounted on the structure adjacent to the receptacle opening captures the probe head, when the probe head is inserted a predetermined amount. A heating coil on the shaft is energizable by remote control for heating the shaft to a temperature range which transforms the shaft to its contracted length, whereby a latching shoulder thereof engages latching elements of the latching system and imposes a tensile preload on the structural joint. Provision is also made for manually adjusting the probe head on the shaft to allow for manual detachment of the structures or manual preloading of the structural joint.

Method and apparatus for preloading a joint by remotely operable means

NASA Technical Reports Server (NTRS)

Shelton, Robert O. (Inventor)

1992-01-01

The invention is a method and apparatus for joining structures, an active structure and a passive structure, and imposing a tensile pre-load on the joint by a remotely operable mechanism comprising a heat contractible joining element. The method and apparatus include mounting on the structure, a probe shaft of material which is transformable from an expanded length to a contracted length when heated to a specific temperature range. The shaft is provided with a probe head which is receivable in a receptacle opening formed in the passive structure, when the active structure is moved into engagement therewith by an appropriate manipulator mechanism. A latching system mounted on the structure adjacent to the receptacle opening captures the probe head, when the probe head is inserted a predetermined amount. A heating coil on the shaft is energizable by remote control for heating the shaft to a temperature range which transforms the shaft to its contracted length, whereby a latching shoulder thereof engages latching elements of the latching system and imposes a tensile preload on the structural joint. Provision is also made for manually adjusting the probe head on the shaft to allow for manual detachment of the structures or manual preloading of the structural joint.

Preload-Based Starling-Like Control for Rotary Blood Pumps: Numerical Comparison with Pulsatility Control and Constant Speed Operation

PubMed Central

Mansouri, Mahdi; Salamonsen, Robert F.; Lim, Einly; Akmeliawati, Rini; Lovell, Nigel H.

2015-01-01

In this study, we evaluate a preload-based Starling-like controller for implantable rotary blood pumps (IRBPs) using left ventricular end-diastolic pressure (PLVED) as the feedback variable. Simulations are conducted using a validated mathematical model. The controller emulates the response of the natural left ventricle (LV) to changes in PLVED. We report the performance of the preload-based Starling-like controller in comparison with our recently designed pulsatility controller and constant speed operation. In handling the transition from a baseline state to test states, which include vigorous exercise, blood loss and a major reduction in the LV contractility (LVC), the preload controller outperformed pulsatility control and constant speed operation in all three test scenarios. In exercise, preload-control achieved an increase of 54% in mean pump flow (QP-) with minimum loading on the LV, while pulsatility control achieved only a 5% increase in flow and a decrease in mean pump speed. In a hemorrhage scenario, the preload control maintained the greatest safety margin against LV suction. PLVED for the preload controller was 4.9 mmHg, compared with 0.4 mmHg for the pulsatility controller and 0.2 mmHg for the constant speed mode. This was associated with an adequate mean arterial pressure (MAP) of 84 mmHg. In transition to low LVC, QP- for preload control remained constant at 5.22 L/min with a PLVED of 8.0 mmHg. With regards to pulsatility control, QP- fell to the nonviable level of 2.4 L/min with an associated PLVED of 16 mmHg and a MAP of 55 mmHg. Consequently, pulsatility control was deemed inferior to constant speed mode with a PLVED of 11 mmHg and a QP- of 5.13 L/min in low LVC scenario. We conclude that pulsatility control imposes a danger to the patient in the severely reduced LVC scenario, which can be overcome by using a preload-based Starling-like control approach. PMID:25849979

The mechanism of bolt loading

NASA Technical Reports Server (NTRS)

Lee, H. M.

1992-01-01

It is shown that the mechanism of bolt loading for preloaded fasteners can be effectively portrayed through simple spring models and some algebraic manipulations. Understanding schematically what is involved in such joints provides insight into the distribution of loads. The developed equations confirm that for both symmetric and nonsymmetric joints the loading plane factor and the stiffness factor directly affect the load seen in preloaded fasteners. The manner in which an external loading is transferred through the joint can be explained as energy dissipated in the various springs of both the abutment and the bolt itself.

Miniature piezo electric vacuum inlet valve

DOEpatents

Keville, R.F.; Dietrich, D.D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability is disclosed. The low power (<1.6 watts), high pulse rate (<2 milliseconds), variable flow inlet valve is utilized for mass spectroscopic applications or other applications where pulsed or continuous flow conditions are needed. The inlet valve also has a very minimal dead volume of less than 0.01 std/cc. The valve can utilize, for example, a 12 Vdc input/750 Vdc, 3 mA output power supply compared to conventional piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three. 6 figs.

PRELOAD AND TORQUE REMOVAL EVALUATION OF THREE DIFFERENT ABUTMENT SCREWS FOR SINGLE STANDING IMPLANT RESTORATIONS

PubMed Central

Stüker, Rafael Augusto; Teixeira, Eduardo Rolim; Beck, João Carlos Pinheiro; da Costa, Nilza Pereira

2008-01-01

Several authors still consider the mechanical problems of fracture and component loosening as the main causes of failure of implant-supported restorations. The purpose of this in vitro study was to compare the preload of three types of screw for transmucosal abutment attachment used in single implant-supported prosthesis through strain gauge and removal torque measurements. Three external hex fixtures were used, and each received a transmucosal abutment (Cera One®), which was fixed to the implant with its respective screw: Group A- gold screw, Group B- titanium screw and Group C- surface-treated titanium screw (Ti-Tite®). Ten screws of each type were attached applying a 30.07±0.28 Ncm torque force and maintained in position for 5 minutes. After this, the preload values were measured using strain gauges and a measurement cell. Gold screws presented higher preload values (131.72±8.98 N), followed by surface-treated titanium screws (97.78±4.68 N) and titanium screws (37.03±5.69 N). ANOVA (p<0.05) and Tukey's test (p<0.05) were applied. Statistically significant differences were found among the groups for both preload and removal torque values. In conclusion, gold screws may be indicated to achieve superior longevity of the abutment-implant connection and, consequently, prosthetic restoration due to greater preload values yielded. PMID:19089290

The impact of liquid preloads varying in macronutrient content on postprandial kinetics of amino acids relative to appetite in healthy adults.

PubMed

Korompokis, Konstantinos; Östman, Elin; Dougkas, Anestis

2016-12-01

The underlying mechanisms for the effect of proteins on appetite regulation, especially in presence of variable macronutrient composition, are not fully elucidated. The present study investigated the absorption kinetics of proteins after co-ingestion with the other macronutrients and examined the impact of circulating amino acids on appetite and satiety-related gut hormones. A randomized, within-subjects, 2-level full factorial design was implemented, where thirty six healthy subjects consumed seven preloads with similar energy density (3.1 kJ/g) and volume (670 mL) but with varying macronutrient content. The energy from protein (%) and the CHO:fat ratio were the two factors combined in three levels of 9, 24, 40 and 0.4, 2, 3.6 respectively. Blood and appetite parameters were evaluated until the serving of the ad libitum lunch after 210 min and the amino acid concentrations were measured in a subgroup of seven male subjects. The amino acid concentrations peaked at 90 min after all preloads and returned to the baseline values until 210 min. Protein intake affected amino acid profiles (P < 0.05), while no differences (P > 0.05) were detected between the two high protein preloads despite the different CHO:fat ratio (40%/0.4 CHO:fat and 40%/3.6 CHO:fat), indicating that neither carbohydrate nor fat influenced the profiles. Most of the amino acids were not related to appetite sensations or gut hormones (P > 0.05), while glutamate was positively associated with prospective consumption and inversely related to ghrelin (P < 0.05). Valine, leucine, isoleucine, lysine and α-aminobutyric acid were inversely associated with energy intake (P < 0.05). Overall, postprandial amino acid profiles were solely affected by protein content and were not consistently related to appetite regulation. Further investigation of glutamate's effect on appetite is needed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mechanical performance evaluation of the CFETR central solenoid model coil design

NASA Astrophysics Data System (ADS)

Liu, Xiaogang; Wang, Zhaoliang; Ren, Yong; Li, Junjun; Yin, Dapeng; Li, Lei; Gao, Xiang; Wu, Yu

2018-01-01

The Chinese Fusion Engineering Test Reactor (CFETR) Central Solenoid Model Coil is being fabricated by the Institute of Plasma Physics Chinese Academy of Sciences. The Model Coil is comprised of Nb3Sn and NbTi modules held together by a preload structure. It will operate at 4.5 K to produce a peak field of 12 T at 48 kA. In order to investigate the feasibility and integrity of the Model Coil design before its manufacturing, the mechanical performance has been evaluated for the room temperature preload, 4.5 K stand-by and 48 kA operating conditions. A 1/15 3D detailed model that consists of jackets, insulations, bladders, buffers and preload structure, is constructed and simulated using the coupled structural-thermal-electromagnetic solver of ANSYS. In contrary to a smeared winding pack model, our analysis with the detailed model can directly and precisely simulate the differential thermal contraction effect of the preload structure, jacket and insulations, as well as the electromagnetic load acting on the jacket. The detailed deformation and stress behaviors of the Model Coil are illustrated and discussed. The results indicate that the final design of the CFETR Central Solenoid Model Coil is reasonably conservative and satisfy the design criteria.

Identification of Nonlinear Micron-Level Mechanics for a Precision Deployable Joint

NASA Technical Reports Server (NTRS)

Bullock, S. J.; Peterson, L. D.

1994-01-01

The experimental identification of micron-level nonlinear joint mechanics and dynamics for a pin-clevis joint used in a precision, adaptive, deployable space structure are investigated. The force-state mapping method is used to identify the behavior of the joint under a preload. The results of applying a single tension-compression cycle to the joint under a tensile preload are presented. The observed micron-level behavior is highly nonlinear and involves all six rigid body motion degrees-of-freedom of the joint. it is also suggests that at micron levels of motion modelling of the joint mechanics and dynamics must include the interactions between all internal components, such as the pin, bushings, and the joint node.

Enhanced model of gear transmission dynamics for condition monitoring applications: Effects of torque, friction and bearing clearance

NASA Astrophysics Data System (ADS)

Fernandez-del-Rincon, A.; Garcia, P.; Diez-Ibarbia, A.; de-Juan, A.; Iglesias, M.; Viadero, F.

2017-02-01

Gear transmissions remain as one of the most complex mechanical systems from the point of view of noise and vibration behavior. Research on gear modeling leading to the obtaining of models capable of accurately reproduce the dynamic behavior of real gear transmissions has spread out the last decades. Most of these models, although useful for design stages, often include simplifications that impede their application for condition monitoring purposes. Trying to filling this gap, the model presented in this paper allows us to simulate gear transmission dynamics including most of these features usually neglected by the state of the art models. This work presents a model capable of considering simultaneously the internal excitations due to the variable meshing stiffness (including the coupling among successive tooth pairs in contact, the non-linearity linked with the contacts between surfaces and the dissipative effects), and those excitations consequence of the bearing variable compliance (including clearances or pre-loads). The model can also simulate gear dynamics in a realistic torque dependent scenario. The proposed model combines a hybrid formulation for calculation of meshing forces with a non-linear variable compliance approach for bearings. Meshing forces are obtained by means of a double approach which combines numerical and analytical aspects. The methodology used provides a detailed description of the meshing forces, allowing their calculation even when gear center distance is modified due to shaft and bearing flexibilities, which are unavoidable in real transmissions. On the other hand, forces at bearing level were obtained considering a variable number of supporting rolling elements, depending on the applied load and clearances. Both formulations have been developed and applied to the simulation of the vibration of a sample transmission, focusing the attention on the transmitted load, friction meshing forces and bearing preloads.

Whey protein preloads are more beneficial than soy protein preloads in regulating appetite, calorie intake, anthropometry, and body composition of overweight and obese men.

PubMed

Tahavorgar, Atefeh; Vafa, Mohammadreza; Shidfar, Farzad; Gohari, Mahmoodreza; Heydari, Iraj

2014-10-01

High-protein diets exert beneficial effects on appetite, anthropometry, and body composition; however, the effects of protein preloads depend on the amount, type, and time of consumption. Therefore, we hypothesized that long-term supplemental preloads of whey protein concentrate (WPC) and soy protein isolate (SPI) consumed 30 minutes before the largest meal would decrease appetite, calorie intake (CI), and anthropometry and improve body composition in overweight and obese men in free-living conditions. The subjects included 45 men with a body mass index between 25 and 40 kg/m(2) and who were randomly allocated to either the WPC (n = 26) or SPI (n = 19) groups. For 12 weeks, the subjects consumed 65 g WPC or 60 g SPI that was dissolved in 500 mL water 30 minutes before their ad libitum lunch. Appetite, CI, anthropometry, and body composition were assessed before and after the study and biweekly throughout. After 12 weeks, mean changes between the groups were significant for appetite (P = .032), CI (P = .045), anthropometry (body weight [P = .008], body mass index [P = .006], and waist circumference), and body composition (body fat mass and lean muscle [P < .001]). Relative to baseline, within-group mean changes from WPC were significant for appetite, CI, anthropometry, and body composition (P < .001). In the SPI group, mean changes were significant, relative to baseline, for all variables except lean muscle (P = .37). According to this 12-week study, WPC preloads conducted 30 minutes prior to the ad libitum main meal exerted stronger beneficial effects than did SPI preloads on appetite, CI, anthropometry, and body composition of free-living overweight and obese men. Copyright © 2014 Elsevier Inc. All rights reserved.

A model to simulate the haemodynamic effects of right heart pulsatile flow after modified Fontan procedure.

PubMed

Tamaki, S; Kawazoe, K; Yagihara, T; Abe, T

1992-02-01

The effect of pulsatile pulmonary flow after the modified Fontan procedure was examined in a model that simulated the right heart. An inlet overflow tank (preload), axial pulsatile pump, Wind-Kessel model (afterload), and an outlet overflow tank were connected in series. The standard conditions were flow 2.00 l/min with 12 mm Hg preload pressure, 3.0 Wood units resistance, and an outlet overflow tank pressure at 6 mm Hg. The pump rate was set at 80 beats/min. The simulated pulmonary arterial pressure and pulmonary flow waves produced by this model closely resembled those obtained from patients who had undergone the modified Fontan procedure. All variables except the preload were fixed and changes in pulmonary flow were examined at preload pressures of 8, 12, 15, and 17 mm Hg. As the peak pulmonary arterial pressure increased so did pulmonary flow, until it was greater than during the non-pulsatile state. Because the afterload of this model was fixed, this result suggests that there was a concomitant decrease in resistance. This model indicates that pulsatile pulmonary blood flow is likely to have a beneficial effect on the pulmonary circulation after the modified Fontan procedure.

Mechanical qualification of the support structure for MQXF, the Nb 3Sn low-β quadrupole for the high luminosity LHC

DOE PAGES

Juchno, M.; Ambrosio, G.; Anerella, M.; ...

2016-01-26

Within the scope of the High Luminosity LHC project, the collaboration between CERN and U.S. LARP is developing new low-β quadrupoles using the Nb 3Sn superconducting technology for the upgrade of the LHC interaction regions. The magnet support structure of the first short model was designed and two units were fabricated and tested at CERN and at LBNL. The structure provides the preload to the collars-coils subassembly by an arrangement of outer aluminum shells pre-tensioned with water-pressurized bladders. For the mechanical qualification of the structure and the assembly procedure, superconducting coils were replaced with solid aluminum “dummy coils”, the structuremore » was preloaded at room temperature, and then cooled-down to 77 K. Mechanical behavior of the magnet structure was monitored with the use of strain gauges installed on the aluminum shells, the dummy coils and the axial preload system. As a result, this paper reports on the outcome of the assembly and the cool-down tests with dummy coils, which were performed at CERN and at LBNL, and presents the strain gauge measurements compared to the 3D finite element model predictions.« less

Comparison of Separation Shock for Explosive and Nonexplosive Release Actuators on a Small Spacecraft Panel

NASA Technical Reports Server (NTRS)

Lucy, M. H.; Buehrle, R. D.; Woolley, J. P.

1996-01-01

Functional shock, safety, overall system costs, and emergence of new technologies, have raised concerns regarding continued use of pyrotechnics on spacecraft. NASA Headquarters-Office of Chief Engineer requested Langley Research Center (LaRC) study pyrotechnic alternatives using non-explosive actuators (NEA's), and LARC participated with Lockheed Martin Missile and Space Co. (LMMSC)-Sunnyvale, CA in objectively evaluating applicability of some NEA mechanisms to reduce small spacecraft and booster separation event shock. Comparative tests were conducted on a structural simulator using five different separation nut mechanisms, consisting of three pyrotechnics from OEA-Aerospace and Hi-Shear Technology and two NEA's from G&H Technology and Lockheed Martin Astronautics (LMA)-Denver, CO. Multiple actuations were performed with preloads up to 7000 pounds, 7000 being the comparison standard. All devices except LMA's NEA rotary flywheel-nut concept were available units with no added provisions to attenuate shock. Accelerometer measurements were recorded, reviewed, processed into Shock Response Spectra (SRS), and comparisons performed. For the standard preload, pyrotechnics produced the most severe and the G&H NEA the least severe functional shock levels. Comparing all results, the LMA concept produced the lowest levels, with preload limited to approximately 4200 pounds. Testing this concept over a range of 3000 to 4200 pounds indicated no effect of preload on shock response levels. This report presents data from these tests and the comparative results.

Decreased lung compliance increases preload dynamic tests in a pediatric acute lung injury model.

PubMed

Erranz, Benjamín; Díaz, Franco; Donoso, Alejandro; Salomón, Tatiana; Carvajal, Cristóbal; Torres, María Fernanda; Cruces, Pablo

2015-01-01

Preload dynamic tests, pulse pressure variation (PPV) and stroke volume variation (SVV) have emerged as powerful tools to predict response to fluid administration. The influence of factors other than preload in dynamic preload test is currently poorly understood in pediatrics. The aim of our study was to assess the effect of tidal volume (VT) on PPV and SVV in the context of normal and reduced lung compliance in a piglet model. Twenty large-white piglets (5.2±0.4kg) were anesthetized, paralyzed and monitored with pulse contour analysis. PPV and SVV were recorded during mechanical ventilation with a VT of 6 and 12mL/kg (low and high VT, respectively), both before and after tracheal instillation of polysorbate 20. Before acute lung injury (ALI) induction, modifications of VT did not significantly change PPV and SVV readings. After ALI, PPV and SVV were significantly greater during ventilation with a high VT compared to a low VT (PPV increased from 8.9±1.2 to 12.4±1.1%, and SVV from 8.5±1.0 to 12.7±1.2%, both P<0.01). This study found that a high VT and reduced lung compliance due to ALI increase preload dynamic tests, with a greater influence of the latter. In subjects with ALI, lung compliance should be considered when interpreting the preload dynamic tests. Copyright © 2015 Sociedad Chilena de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.

Reduced left ventricular filling following blood volume extraction does not result in compensatory augmentation of cardiac mechanics.

PubMed

Lord, Rachel; MacLeod, David; George, Keith; Oxborough, David; Shave, Rob; Stembridge, Mike

2018-04-01

What is the central question of this study? A reduction in left ventricular (LV) filling, and concomitant increase in heart rate, augments LV mechanics to maintain stroke volume (SV); however, the impact of reduced LV filling in isolation on SV and LV mechanics is currently unknown. What is the main finding and its importance? An isolated decrease in LV filling did not provoke a compensatory increase in mechanics to maintain SV; in contrast, LV mechanics and SV were reduced. These data indicate that when LV filling is reduced without changes in heart rate, LV mechanics do not compensate to maintain SV. An acute non-invasive reduction in preload has been shown to augment cardiac mechanics to maintain stroke volume and cardiac output. Such interventions induce concomitant changes in heart rate, whereas blood volume extraction reduces preload without changes in heart rate. Therefore, the purpose of this study was to determine whether a preload reduction in isolation resulted in augmented stroke volume achieved via enhanced cardiac mechanics. Nine healthy volunteers (four female, age 29 ± 11 years) underwent echocardiography for the assessment of left ventricular (LV) volumes and mechanics in a supine position at baseline and end extraction after the controlled removal of 25% of total blood volume (1062 ± 342 ml). Arterial blood pressure was monitored continuously by a pressure transducer attached to an indwelling radial artery catheter. Heart rate and total peripheral resistance were unchanged from baseline to end extraction, but systolic blood pressure was reduced (from 148 to 127 mmHg). From baseline to end extraction there were significant reductions in left ventricular end-diastolic volume (from 89 to 71 ml) and stroke volume (from 56 to 37 ml); however, there was no change in LV twist, basal or apical rotation. In contrast, LV longitudinal strain (from -20 to -17%) and basal circumferential strain (from -22 to -19%) were significantly reduced from baseline to end extraction. In conclusion, a reduction in preload during blood volume extraction does not result in compensatory changes in stroke volume or cardiac mechanics. Our data suggest that LV strain is dependent on LV filling and consequent geometry, whereas LV twist could be mediated by heart rate. © 2018 The Authors. Experimental Physiology © 2018 The Physiological Society.

Mechanical coupling for a rotor shaft assembly of dissimilar materials

DOEpatents

Shi, Jun [Glastonbury, CT; Bombara, David [New Hartford, CT; Green, Kevin E [Broad Brook, CT; Bird, Connic [Rocky Hill, CT; Holowczak, John [South Windsor, CT

2009-05-05

A mechanical coupling for coupling a ceramic disc member to a metallic shaft includes a first wedge clamp and a second wedge clamp. A fastener engages a threaded end of a tie-bolt to sandwich the ceramic disc between the wedge clamps. An axial spring is positioned between the fastener and the second wedge clamp to apply an axial preload along the longitudinal axis. Another coupling utilizes a rotor shaft end of a metallic rotor shaft as one wedge clamp. Still another coupling includes a solid ceramic rotor disc with a multiple of tie-bolts radially displaced from the longitudinal axis to exert the preload on the solid ceramic rotor disc.

[The anesthesiological procedure for correcting preloading in the surgery of acquired mitral valve defects].

PubMed

Kiselev, V O; Shipulin, V M; Evtushenko, A V; Podoksenov, Iu K; Shishneva, E V

2000-01-01

Intraoperative correction of preload in patients with acquired valvular disease (AVD) complicated by right-ventricular failure and severe pulmonary hypertension necessitates search for pathogenetically based algorithms of anesthesiological strategy. The objective of this study was to develop a strategy of assessing and treating the preload at the stage of induction anesthesia in patients with right-ventricular failure. During surgery central hemodynamic parameters and their response to a short head-down-tilt (15-20 degrees) were evaluated in patients (n = 42) with cardiac index (CI) less than 2 l/min/m2 after induction anesthesia. The patients were divided into 2 groups with different severity of preoperative status. Group 1 (main) included 24 patients with stages II-III cardiac failure (according to N. Strazhesko and B. Vasilenko) and group 2 (control) consisted of 18 patients with stage IIA cardiac failure. Progressing preoperative cardiac failure resulted in decrease of cardiac index and failure of compensatory hemodynamic mechanisms in AVD patients. The level of right-ventricular preload, pulmonary resistance, and stroke index were lower in group 1 than in the controls; however, 8% of group 1 patients responded positively to increased preload. In the control group 50% responded favorably to head-down-tilt. Hence, comprehensive assessment of cardiac index, central hemodynamic parameters and their response to head-down tilt help individually choose the anesthesiological strategy.

Thermal Preload Relaxation of Bolted CFRP Structures for Flexible Life Time Design Methodology

NASA Astrophysics Data System (ADS)

Hubbertz, Hendrik; Friedrich, Christoph

2014-06-01

Taking into account the assembly, maintenance and repair of component systems, it becomes clear that mechanical fastening is necessary also for CFRP structures besides adhesive bonding. Threaded fasteners usually prestress CFRP materials perpendicular to the fibres. In this direction the high strength-increase by the carbon fibres is subordinated and the material properties are dominated by the relatively low strength plastic matrix. The following chapters explain the basics of preload loss at threaded fasteners and show the results of experiments with different influences on preload relaxation with CFRP materials. As the presented studies were carried out under the influence of temperature, thermal load plastification will be regarded as priority. The structural changes in the material are also documented with microscope images as well as an outlook for further research is given.

Mechanical stimulation in the engineering of heart muscle.

PubMed

Liaw, Norman Yu; Zimmermann, Wolfram-Hubertus

2016-01-15

Recreating the beating heart in the laboratory continues to be a formidable bioengineering challenge. The fundamental feature of the heart is its pumping action, requiring considerable mechanical forces to compress a blood filled chamber with a defined in- and outlet. Ventricular output crucially depends on venous loading of the ventricles (preload) and on the force generated by the preloaded ventricles to overcome arterial blood pressure (afterload). The rate of contraction is controlled by the spontaneously active sinus node and transmission of its electrical impulses into the ventricles. The underlying principles for these physiological processes are described by the Frank-Starling mechanism and Bowditch phenomenon. It is essential to consider these principles in the design and evaluation of tissue engineered myocardium. This review focuses on current strategies to evoke mechanical loading in hydrogel-based heart muscle engineering. Copyright © 2015. Published by Elsevier B.V.

Cardiovascular response to acute normovolemic hemodilution in patients with coronary artery diseases: Assessment with transesophageal echocardiography.

PubMed

Licker, Marc; Ellenberger, Christoph; Sierra, Jorge; Christenson, Jan; Diaper, John; Morel, Denis

2005-03-01

Preoperative acute normovolemic hemodilution induces an increase in circulatory output that is thought to be limited in patients with cardiac diseases. Using multiple-plane transesophageal echocardiography, we investigated the mechanisms of cardiovascular adaptation during acute normovolemic hemodilution in patients with severe coronary artery disease. Prospective case-control study. Operating theater in a university hospital. Consecutive patients treated with beta-blockers, scheduled to undergo coronary artery bypass (n = 50). After anesthesia induction, blood withdrawal and isovolemic exchange with iso-oncotic starch (1:1.15 ratio) to achieve a hematocrit value of 28%. In addition to heart rate and intravascular pressures, echocardiographic recordings were obtained before and after acute normovolemic hemodilution to assess cardiac preload, afterload, and contractility. In a control group, not subjected to acute normovolemic hemodilution, hemodynamic variables remained stable during a 20-min anesthesia period. Following acute normovolemic hemodilution, increases in cardiac stroke volume (+28 +/- 4%; mean +/- sd) were correlated with increases in central venous pressure (+2.0 +/- 1.3 mm Hg; R = .56) and in left ventricular end-diastolic area (+18 +/- 5%, R = .39). The unchanged left ventricular end-systolic wall stress and preload-adjusted maximal power indicated that neither left ventricular afterload nor contractility was affected by acute normovolemic hemodilution. Diastolic left ventricular filling abnormalities (15 of 22 cases) improved in 11 patients and were stable in the remaining four patients. Despite reduction in systemic oxygen delivery (-20.5 +/- 7%, p < .05), there was no evidence for myocardial ischemia (electrocardiogram, left ventricular wall motion abnormalities). In anesthetized patients with coronary artery disease, moderate acute normovolemic hemodilution did not compromise left ventricular systolic and diastolic function. Lowering blood viscosity resulted in increased stroke volume that was mainly related to increased venous return and higher cardiac preload.

Associations among left ventricular systolic function, tachycardia, and cardiac preload in septic patients.

PubMed

Lanspa, Michael J; Shahul, Sajid; Hersh, Andrew; Wilson, Emily L; Olsen, Troy D; Hirshberg, Eliotte L; Grissom, Colin K; Brown, Samuel M

2017-12-01

In sepsis, tachycardia may indicate low preload, adrenergic stimulation, or both. Adrenergic overstimulation is associated with septic cardiomyopathy. We sought to determine whether tachycardia was associated with left ventricular longitudinal strain, a measure of cardiac dysfunction. We hypothesized an association would primarily exist in patients with high preload. We prospectively observed septic patients admitted to three study ICUs, who underwent early transthoracic echocardiography. We measured longitudinal strain using speckle tracking echocardiography and estimated preload status with an echocardiographic surrogate (E/e'). We assessed correlation between strain and heart rate in patients with low preload (E/e' < 8), intermediate preload (E/e' 8-14), and high preload (E/e' > 14), adjusting for disease severity and vasopressor dependence. We studied 452 patients, of whom 298 had both measurable strain and preload. Abnormal strain (defined as >-17%) was present in 54%. Patients with abnormal strain had higher heart rates (100 vs. 93 beat/min, p = 0.001). After adjusting for vasopressor dependence, disease severity, and cardiac preload, we observed an association between heart rate and longitudinal strain (β = 0.05, p = 0.003). This association persisted among patients with high preload (β = 0.07, p = 0.016) and in patients with shock (β = 0.07, p = 0.01), but was absent in patients with low or intermediate preload and those not in shock. Tachycardia is associated with abnormal left ventricular strain in septic patients with high preload. This association was not apparent in patients with low or intermediate preload.

Design, Development and Test Challenges: Separation Mechanisms for the Orion Pad Abort-1 Flight Test

NASA Technical Reports Server (NTRS)

Dinsel, Alison; Morrey, Jeremy M.; OMalley, Patrick; Park, Samuel

2011-01-01

On May 6, 2010, NASA launched the first successful integrated flight test, Pad Abort-1, of the Orion Project from the White Sands Missile Range in Las Cruces, New Mexico. This test demonstrated the ability to perform an emergency pad abort of a full-scale 4.8 m diameter, 8200 kg crew capsule. During development of the critical separation mechanisms for this flight test, various challenges were overcome related to environments definition, installation complications, separation joint retraction speed, thruster ordnance development issues, load path validation and significant design loads increases. The Launch Abort System retention and release (LAS R&R) mechanism consisted of 6 discrete structural connections between the LAS and the crew module (CM) simulator, each of which had a preloaded tension tie, Superbolt torque-nut and frangible nut. During the flight test, the frangible nuts were pyrotechnically split, permitting the CM to separate from the LAS. The LAS separation event was the driving case in the shock environment for many co-located hardware items. During development testing, it was necessary to measure the source shock during the separation event so the predicted shock environment could be validated and used for certification testing of multiple hardware items. The Lockheed Martin test team measured the source separation shock due to the LAS R&R function, which dramatically decreased the predicted environment by 90% at 100 Hz. During development testing a hydraulic tensioner was used to preload the joint; however, the joint relaxation with the tensioner proved unsatisfactory so the design was modified to include a Superbolt torque-nut. The observed preload creep during lab testing was 4% after 30 days, with 2.5% occurring in the first 24 hours. The conversion of strain energy (preload) to kinetic energy (retraction) was measured to be 50-75%. Design features and careful monitoring of multiple strain gauges on each tension tie allowed a pure tensile load to be applied after stacking at the launch pad. Following installation, preload in each joint was monitored for 24 hours. Due to unforeseen complications and the influence of temperature on the portable data acquisition system, the team encountered difficulty in tracking the joint relaxation. In some cases, bond-line failure of the strain gauges occurred.

Additional mechanism for left ventricular dysfunction: chronic pulmonary regurgitation decreases left ventricular preload in patients with tetralogy of Fallot.

PubMed

Ylitalo, Pekka; Jokinen, Eero; Lauerma, Kirsi; Holmström, Miia; Pitkänen-Argillander, Olli M

2018-02-01

Right ventricular dysfunction in patients with tetralogy of Fallot and significant pulmonary regurgitation may lead to systolic dysfunction of the left ventricle due to altered ventricular interaction. We were interested in determining whether chronic pulmonary regurgitation affects the preload of the left ventricle. In addition, we wanted to study whether severe chronic pulmonary regurgitation would alter the preload of the left ventricle when compared with patients having preserved pulmonary valve annulus. The study group comprised 38 patients with tetralogy of Fallot who underwent surgical repair between 1990 and 2003. Transannular patching was required in 21 patients to reconstruct the right ventricular outflow tract. Altogether, 48 age- and gender-matched healthy volunteers were recruited. Cardiac MRI was performed on all study patients to assess the atrial and ventricular volumes and function. Severe pulmonary regurgitation (>30 ml/m2) was present in 13 patients, of whom 11 had a transannular patch, but only two had a preserved pulmonary valve annulus. The ventricular preload volumes from both atria were significantly reduced in patients with severe pulmonary regurgitation, and left ventricular stroke volumes (44.1±4.7 versus 58.9±10.7 ml/m2; p<0.0001) were smaller compared with that in patients with pulmonary regurgitation <30 ml/m2 or in controls. In patients with tetralogy of Fallot, severe pulmonary regurgitation has a significant effect on volume flow through the left atrium. Reduction in left ventricular preload volume may be an additional factor contributing to left ventricular dysfunction.

Influence of natural organic matter on equilibrium adsorption of neutral and charged pharmaceuticals onto activated carbon.

PubMed

de Ridder, D J; Verliefde, A R D; Heijman, S G J; Verberk, J Q J C; Rietveld, L C; van der Aa, L T J; Amy, G L; van Dijk, J C

2011-01-01

Natural organic matter (NOM) can influence pharmaceutical adsorption onto granular activated carbon (GAC) by direct adsorption competition and pore blocking. However, in the literature there is limited information on which of these mechanisms is more important and how this is related to NOM and pharmaceutical properties. Adsorption batch experiments were carried out in ultrapure, waste- and surface water and fresh and NOM preloaded GAC was used. Twenty-one pharmaceuticals were selected with varying hydrophobicity and with neutral, negative or positive charge. The influence of NOM competition and pore blocking could not be separated. However, while reduction in surface area was similar for both preloaded GACs, up to 50% lower pharmaceutical removal was observed on wastewater preloaded GAC. This was attributed to higher hydrophobicity of wastewater NOM, indicating that NOM competition may influence pharmaceutical removal more than pore blocking. Preloaded GAC was negatively charged, which influenced removal of charged pharmaceuticals significantly. At a GAC dose of 6.7 mg/L, negatively charged pharmaceuticals were removed for 0-58%, while removal of positively charged pharmaceuticals was between 32-98%. Charge effects were more pronounced in ultrapure water, as it contained no ions to shield the surface charge. Solutes with higher log D could compete better with NOM, resulting in higher removal.

Effect of mechanical pre-loadings on corrosion resistance of chromium-electroplated steel rods in marine environment

NASA Astrophysics Data System (ADS)

Shubina Helbert, Varvara; Dhondt, Matthieu; Homette, Remi; Arbab Chirani, Shabnam; Calloch, Sylvain

2018-03-01

Providing high hardness, low friction coefficient, as well as, relatively good corrosion resistance, chromium-plated coatings (∼20 μm) are widely used for steel cylinder rods in marine environment. However, the standardized corrosion test method (ISO 9227, NSS) used to evaluate efficiency of this type of coatings does not take into account in-service mechanical loadings on cylinder rods. Nevertheless, the uniform initial network of microcracks in chromium coating is changing under mechanical loadings. Propagation of these microcracks explains premature corrosion of the steel substrate. The aim of the study was to evaluate relationship between mechanical loadings, propagation of microcracks network and corrosion resistance of chromium coatings. After monotonic pre-loading tests, it was demonstrated by microscopic observations that the microcracks propagation started at stress levels higher than the substrate yield stress (520 MPa). The microcracks become effective, i.e. they have instantly undergone through the whole coating thickness to reach the steel substrate. The density of effective microcracks increases with the total macroscopic level, i.e. the intercrack distance goes from 60 ± 5 μm at 1% of total strain to approximately 27 ± 2 μm at 10%. Electrochemical measurements have shown that the higher the plastic strain level applied during mechanical loading, the more the corrosion potential of the sample decreased until reaching the steel substrate value of approximately ‑0.65 V/SCE after 2 h of immersion. The polarization curves have also highligthed an increase in the corrosion current density with the strain level. Therefore, electrochemical measurements could be used to realize quick and comprehensive assesment of the effect of monotonic pre-loadings on corrosion properties of the chromium coating.

3-D Analysis of Flanged Joints Through Various Preload Methods Using ANSYS

NASA Astrophysics Data System (ADS)

Murugan, Jeyaraj Paul; Kurian, Thomas; Jayaprakash, Janardhan; Sreedharapanickar, Somanath

2015-10-01

Flanged joints are being employed in aerospace solid rocket motor hardware for the integration of various systems or subsystems. Hence, the design of flanged joints is very important in ensuring the integrity of motor while functioning. As these joints are subjected to higher loads due to internal pressure acting inside the motor chamber, an appropriate preload is required to be applied in this joint before subjecting it to the external load. Preload, also known as clamp load, is applied on the fastener and helps to hold the mating flanges together. Generally preload is simulated as a thermal load and the exact preload is obtained through number of iterations. Infact, more iterations are required when considering the material nonlinearity of the bolt. This way of simulation will take more computational time for generating the required preload. Now a days most commercial software packages use pretension elements for simulating the preload. This element does not require iterations for inducing the preload and it can be solved with single iteration. This approach takes less computational time and thus one can study the characteristics of the joint easily by varying the preload. When the structure contains more number of joints with different sizes of fasteners, pretension elements can be used compared to thermal load approach for simulating each size of fastener. This paper covers the details of analyses carried out simulating the preload through various options viz., preload through thermal, initial state command and pretension element etc. using ANSYS finite element package.

Inertial piezoelectric linear motor driven by a single-phase harmonic wave with automatic clamping mechanism

NASA Astrophysics Data System (ADS)

He, Liangguo; Chu, Yuheng; Hao, Sai; Zhao, Xiaoyong; Dong, Yuge; Wang, Yong

2018-05-01

A novel, single-phase, harmonic-driven, inertial piezoelectric linear motor using an automatic clamping mechanism was designed, fabricated, and tested to reduce the sliding friction and simplify the drive mechanism and power supply control of the inertial motor. A piezoelectric bimorph and a flexible hinge were connected in series to form the automatic clamping mechanism. The automatic clamping mechanism was used as the driving and clamping elements. A dynamic simulation by Simulink was performed to prove the feasibility of the motor. The finite element method software COMSOL was used to design the structure of the motor. An experimental setup was built to validate the working principle and evaluate the performance of the motor. The prototype motor outputted a no-load velocity of 3.178 mm/s at a voltage of 220 Vp-p and a maximum traction force of 4.25 N under a preload force of 8 N. The minimum resolution of 1.14 μm was achieved at a driving frequency of 74 Hz, a driving voltage of 50 Vp-p, and a preload force of 0 N.

48-hours administration of fenoterol in spontaneous preterm labor - does it affect fetal preload?

PubMed

Grzesiak, Mariusz; Forys, Sebastian; Sobczak, Malgorzata; Ahmed, Rehana B; Wilczynski, Jan

2013-01-01

to investigate whether any changes in the preload index (PLI) occur within the first 48 hours of fenoterol intravenous tocolysis. Doppler evaluation of placental and fetal circulation was performed in 36 pregnant women prior to fenoterol administration and after 24/48 hours. Measurements were obtained from a longitudinal section of the inferior vena cava (IVC) and preload index was calculated. To determine changes over time, an all study variable analysis of variance (ANOVA) for repeated measurements, followed by Tukey-Kramer's multiple comparison test was used. The effects of additional clinical covariates were checked. The maternal heart rate values were significantly increased after 24 hours and 48 hours in comparison to pre-treatment values. No significant changes in fetal heart rate were observed during treatment. The fetal IVC PLI values were significantly reduced after 24 hours and 48 hours of treatment. The increase in PLI values when comparing 24 and 48 hours results were not statistically significant. These observations were consistent with ANOVA post-hoc analysis. 48 hours intravenous administration of fenoterol appears not to alter inferior vena cava blood flow by itself. The reduction in PLI values may reflect lower fetal preload conditions during the course of successful tocolytic treatment. Therefore, Doppler IVC PLI measurement should be considered as a possible additional assessment method of effectiveness of treatment. However, other Doppler venous blood flow parameters should be assessed to confirm the results and clarify whether maternal corticosteroids administration may be interfering with the results.

An investigation of the self-heating phenomenon in viscoelastic materials subjected to cyclic loadings accounting for prestress

NASA Astrophysics Data System (ADS)

de Lima, A. M. G.; Rade, D. A.; Lacerda, H. B.; Araújo, C. A.

2015-06-01

It has been demonstrated by many authors that the internal damping mechanism of the viscoelastic materials offers many possibilities for practical engineering applications. However, in traditional procedures of analysis and design of viscoelastic dampers subjected to cyclic loadings, uniform, constant temperature is generally assumed and do not take into account the self-heating phenomenon. Moreover, for viscoelastic materials subjected to dynamic loadings superimposed on static preloads, such as engine mounts, these procedures can lead to poor designs or even severe failures since the energy dissipated within the volume of the material leads to temperature rises. In this paper, a hybrid numerical-experimental investigation of effects of the static preloads on the self-heating phenomenon in viscoelastic dampers subjected to harmonic loadings is reported. After presenting the theoretical foundations, the numerical and experimental results obtained in terms of the temperature evolutions at different points within the volume of the viscoelastic material for various static preloads are compared, and the main features of the methodology are discussed.

Effect of humic acid preloading on phosphate adsorption onto zirconium-modified zeolite.

PubMed

Lin, Jianwei; Zhang, Zhe; Zhan, Yanhui

2017-05-01

A zirconium-modified zeolite (ZrMZ) was prepared, and then, humic acid (HA) was immobilized on the ZrMZ surface to prepare HA-loaded ZrMZ (HA-ZrMZ). The obtained ZrMZ and HA-ZrMZ were characterized by energy dispersive X-ray spectroscopy, elemental analyzer, N 2 adsorption/desorption isotherms, pH at the point of zero charge, and X-ray photoelectron spectroscopy. The adsorption characteristics of phosphate on ZrMZ and HA-ZrMZ were comparatively investigated in batch mode. The adsorption mechanism of phosphate on ZrMZ and HA-ZrMZ was investigated by ionic strength effect and 31 P nuclear magnetic resonance. The mechanism for phosphate adsorption onto ZrMZ was the formation of inner-sphere phosphate complexes at the solid/solution interface. The preloading of HA on ZrMZ reduced the phosphate adsorption capacity, and the more the HA loading amount, the lower the phosphate adsorption capacity. However, the preloading of HA on ZrMZ did not change the phosphate adsorption mechanism; i.e., the formation of inner-sphere phosphate surface complexes was still responsible for the adsorption of phosphate on HA-ZrMZ. The decreased phosphate adsorption capacity for ZrMZ after HA coating could be attributed to the fact that the coating of HA on ZrMZ reduced the amount of binding active sites available for phosphate adsorption, changed the adsorbent surface charges, and reduced the specific surface areas and pore volumes of ZrMZ.

Competitive effects of humic acid and wastewater on adsorption of Methylene Blue dye by activated carbon and non-imprinted polymers.

PubMed

Murray, Audrey; Örmeci, Banu

2018-04-01

Natural organic matter (NOM), present in natural waters and wastewater, decreases adsorption of micropollutants, increasing treatment costs. This research investigated mechanisms of competition for non-imprinted polymers (NIPs) and activated carbon with humic acid and wastewater. Three different types of activated carbons (Norit PAC 200, Darco KB-M, and Darco S-51) were used for comparison with the NIP. The lower surface area and micropore to mesopore ratio of the NIP led to decreased adsorption capacity in comparison to the activated carbons. In addition, experiments were conducted for single-solute adsorption of Methylene Blue (MB) dye, simultaneous adsorption with humic acid and wastewater, and pre-loading with humic acid and wastewater followed by adsorption of MB dye using NIP and Norit PAC 200. Both the NIP and PAC 200 showed significant decreases of 27% for NIP (p=0.087) and 29% for PAC 200 (p=0.096) during simultaneous exposure to humic acid and MB dye. There was no corresponding decrease for NIP or PAC 200 pre-loaded with humic acid and then exposed to MB. In fact, for PAC 200, the adsorption capacity of the activated carbon increased when it was pre-loaded with humic acid by 39% (p=0.0005). For wastewater, the NIP showed no significant increase or decrease in adsorption capacity during either simultaneous exposure or pre-loading. The adsorption capacity of PAC 200 increased by 40% (p=0.001) for simultaneous exposure to wastewater and MB. Pre-loading with wastewater had no effect on MB adsorption by PAC 200. Copyright © 2017. Published by Elsevier B.V.

Self-Aligning Mechanical And Electrical Coupling

NASA Technical Reports Server (NTRS)

Vranish, John M.

1993-01-01

Two mating assemblies of mechanical and electrical coupling designed to align itself and so easy to use that robot can operate it. Rollers and v-grooves enforce required alignment when upper and lower assemblies brought into firm contact. Mechanism inside lower assembly provides spring preload between two assemblies plus mating of electrical connectors, all actuated by rotation of driver engaged with bolt via splines.

Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

NASA Astrophysics Data System (ADS)

Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun

2016-10-01

A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.

Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels

PubMed Central

Anton, Stephen D.; Martin, Corby K.; Han, Hongmei; Coulon, Sandra; Cefalu, William T.; Geiselman, Paula; Williamson, Donald A.

2010-01-01

Consumption of sugar-sweetened beverages may be one of the dietary causes of metabolic disorders, such as obesity. Therefore, substituting sugar with low-calorie sweeteners may be an efficacious weight management strategy. We tested the effect of preloads containing stevia, aspartame, or sucrose on food intake, satiety, and postprandial glucose and insulin levels. Design: 19 healthy lean (BMI = 20.0 – 24.9) and 12 obese (BMI = 30.0 – 39.9) individuals 18 to 50 years old completed three separate food test days during which they received preloads containing stevia (290 kcal), aspartame (290 kcal), or sucrose (493 kcal) before the lunch and dinner meal. The preload order was balanced, and food intake (kcal) was directly calculated. Hunger and satiety levels were reported before and after meals, and every hour throughout the afternoon. Participants provided blood samples immediately before and 20 minutes after the lunch preload. Despite the caloric difference in preloads (290 vs. 493 kcals), participants did not compensate by eating more at their lunch and dinner meals when they consumed stevia and aspartame versus sucrose in preloads (mean differences in food intake over entire day between sucrose and stevia = 301 kcal, p < .01; aspartame = 330 kcal, p < .01). Self-reported hunger and satiety levels did not differ by condition. Stevia preloads significantly lowered postprandial glucose levels compared to sucrose preloads (p < .01), and postprandial insulin levels compared to both aspartame and sucrose preloads (p < .05). When consuming stevia and aspartame preloads, participants did not compensate by eating more at either their lunch or dinner meal and reported similar levels of satiety compared to when they consumed the higher calorie sucrose preload. PMID:20303371

Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels.

PubMed

Anton, Stephen D; Martin, Corby K; Han, Hongmei; Coulon, Sandra; Cefalu, William T; Geiselman, Paula; Williamson, Donald A

2010-08-01

Consumption of sugar-sweetened beverages may be one of the dietary causes of metabolic disorders, such as obesity. Therefore, substituting sugar with low calorie sweeteners may be an efficacious weight management strategy. We tested the effect of preloads containing stevia, aspartame, or sucrose on food intake, satiety, and postprandial glucose and insulin levels. 19 healthy lean (BMI=20.0-24.9) and 12 obese (BMI=30.0-39.9) individuals 18-50 years old completed three separate food test days during which they received preloads containing stevia (290kcal), aspartame (290kcal), or sucrose (493kcal) before the lunch and dinner meal. The preload order was balanced, and food intake (kcal) was directly calculated. Hunger and satiety levels were reported before and after meals, and every hour throughout the afternoon. Participants provided blood samples immediately before and 20min after the lunch preload. Despite the caloric difference in preloads (290kcal vs. 493kcal), participants did not compensate by eating more at their lunch and dinner meals when they consumed stevia and aspartame versus sucrose in preloads (mean differences in food intake over entire day between sucrose and stevia=301kcal, p<.01; aspartame=330kcal, p<.01). Self-reported hunger and satiety levels did not differ by condition. Stevia preloads significantly reduced postprandial glucose levels compared to sucrose preloads (p<.01), and postprandial insulin levels compared to both aspartame and sucrose preloads (p<.05). When consuming stevia and aspartame preloads, participants did not compensate by eating more at either their lunch or dinner meal and reported similar levels of satiety compared to when they consumed the higher calorie sucrose preload. Published by Elsevier Ltd.

Torquing preload in a lubricated bolt

NASA Technical Reports Server (NTRS)

Seegmiller, H. L.

1978-01-01

The tension preload obtained by torquing a 7/8 in. diam UNC high strength bolt was determined for lubricated and dry conditions. Consistent preload with a variation of + or - 3% was obtained when the bolt head area was lubricated prior to each torque application. Preload tensions nearly 70% greater than the value predicted with the commonly used formula occurred with the lubricated bolt. A reduction to 39% of the initial preload was observed during 50 torque applications without relubrication. Little evidence of wear was noted after 203 cycles of tightening.

Using the Theory of Planned Behavior to predict implementation of harm reduction strategies among MDMA/ecstasy users.

PubMed

Davis, Alan K; Rosenberg, Harold

2016-06-01

This prospective study was designed to test whether the variables proposed by the Theory of Planned Behavior (TPB) were associated with baseline intention to implement and subsequent use of 2 MDMA/ecstasy-specific harm reduction interventions: preloading/postloading and pill testing/pill checking. Using targeted Facebook advertisements, an international sample of 391 recreational ecstasy users were recruited to complete questionnaires assessing their ecstasy consumption history, and their attitudes, subjective norms, perceived behavioral control, habit strength (past strategy use), and intention to use these two strategies. Attitudes, subjective norms, and perceived behavioral control were significantly associated with baseline intention to preload/postload and pill test/pill check. Out of the 391 baseline participants, 100 completed the two-month follow-up assessment. Baseline habit strength and frequency of ecstasy consumption during the three months prior to baseline were the only significant predictors of how often participants used the preloading/postloading strategy during the follow-up. Baseline intention to pill test/pill check was the only significant predictor of how often participants used this strategy during the follow-up. These findings provide partial support for TPB variables as both correlates of baseline intention to implement and predictors of subsequent use of these two strategies. Future investigations could assess whether factors related to ecstasy consumption (e.g., subjective level of intoxication, craving, negative consequences following consumption), and environmental factors (e.g., accessibility and availability of harm reduction resources) improve the prediction of how often ecstasy users employ these and other harm reduction strategies. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Supplemental nicotine preloading for smoking cessation in posttraumatic stress disorder: Results from a randomized controlled trial.

PubMed

Dennis, Paul A; Kimbrel, Nathan A; Dedert, Eric A; Beckham, Jean C; Dennis, Michelle F; Calhoun, Patrick S

2016-08-01

Individuals with posttraumatic stress disorder (PTSD) are more likely to smoke and more likely to relapse following a quit attempt than individuals without PTSD. Thus, there is a significant need to study promising interventions that might improve quit rates for smokers with PTSD. One such intervention, supplemental nicotine patch-preloading, entails the use of nicotine replacement therapy prior to quitting. Objective The objective of this study was to conduct a randomized controlled trial of the efficacy of supplemental nicotine patch-preloading among smokers with PTSD. We hypothesized that, relative to participants in the placebo condition, participants in the nicotine patch-preloading condition would: (1) smoke less and experience reduced craving for cigarettes during the nicotine patch-preloading phase; (2) experience less smoking-associated relief from PTSD symptoms and negative affect during the preloading phase; and (3) exhibit greater latency to lapse, and higher short- and long-term abstinence rates. Sixty-three smokers with PTSD were randomized to either nicotine or placebo patch for three weeks prior to their quit date. Ecological momentary assessment was used to assess craving, smoking, PTSD symptoms, and negative affect during the preloading period. Nicotine patch-preloading failed to reduce smoking or craving during the preloading phase, nor was it associated with less smoking-associated relief from PTSD symptoms and negative affect. Moreover, no differences were observed between the treatment conditions for time to lapse, 6-week abstinence, or 6-month abstinence. The findings from the present research suggest that supplemental nicotine patch-preloading is unlikely to substantially enhance quit rates among smokers with PTSD. Published by Elsevier Ltd.

Understanding inhibitory mechanisms of lumbar spinal manipulation using H-reflex and F-wave responses: a methodological approach.

PubMed

Dishman, J Donald; Weber, Kenneth A; Corbin, Roger L; Burke, Jeanmarie R

2012-09-30

The purpose of this research was to characterize unique neurophysiologic events following a high velocity, low amplitude (HVLA) spinal manipulation (SM) procedure. Descriptive time series analysis techniques of time plots, outlier detection and autocorrelation functions were applied to time series of tibial nerve H-reflexes that were evoked at 10-s intervals from 100 s before the event until 100 s after three distinct events L5-S1 HVLA SM, or a L5-S1 joint pre-loading procedure, or the control condition. Sixty-six subjects were randomly assigned to three procedures, i.e., 22 time series per group. If the detection of outliers and correlograms revealed a pattern of non-randomness that was only time-locked to a single, specific event in the normalized time series, then an experimental effect would be inferred beyond the inherent variability of H-reflex responses. Tibial nerve F-wave responses were included to determine if any new information about central nervous function following a HVLA SM procedure could be ascertained. Time series analyses of H(max)/M(max) ratios, pre-post L5-S1 HVLA SM, substantiated the hypothesis that the specific aspects of the manipulative thrust lead to a greater attenuation of the H(max)/M(max) ratio as compared to the non-specific aspects related to the postural perturbation and joint pre-loading. The attenuation of the H(max)/M(max) ratio following the HVLA SM procedure was reliable and may hold promise as a translational tool to measure the consistency and accuracy of protocol implementation involving SM in clinical trials research. F-wave responses were not sensitive to mechanical perturbations of the lumbar spine. Copyright © 2012 Elsevier B.V. All rights reserved.

Functional requirements of a mathematical model of the heart.

PubMed

Palladino, Joseph L; Noordergraaf, Abraham

2009-01-01

Functional descriptions of the heart, especially the left ventricle, are often based on the measured variables pressure and ventricular outflow, embodied as a time-varying elastance. The fundamental difficulty of describing the mechanical properties of the heart with a time-varying elastance function that is set a priori is described. As an alternative, a new functional model of the heart is presented, which characterizes the ventricle's contractile state with parameters, rather than variables. Each chamber is treated as a pressure generator that is time and volume dependent. The heart's complex dynamics develop from a single equation based on the formation and relaxation of crossbridge bonds. This equation permits the calculation of ventricular elastance via E(v) = partial differentialp(v)/ partial differentialV(v). This heart model is defined independently from load properties, and ventricular elastance is dynamic and reflects changing numbers of crossbridge bonds. In this paper, the functionality of this new heart model is presented via computed work loops that demonstrate the Frank-Starling mechanism and the effects of preload, the effects of afterload, inotropic changes, and varied heart rate, as well as the interdependence of these effects. Results suggest the origin of the equivalent of Hill's force-velocity relation in the ventricle.

Study on parameters affecting the mechanical properties of dry fiber bundles during continuous composite manufacturing processes

NASA Astrophysics Data System (ADS)

Maier, A.; Schledjewski, R.

2016-07-01

For continuous manufacturing processes mechanical preloading of the fibers occurs during the delivery of the fibers from the spool creel to the actual manufacturing process step. Moreover preloading of the dry roving bundles might be mandatory, e.g. during winding, to be able to produce high quality components. On the one hand too high tensile loads within dry roving bundles might result in a catastrophic failure and on the other hand the part produced under too low pre-tension might have low quality and mechanical properties. In this work, load conditions influencing mechanical properties of dry glass fiber bundles during continuous composite manufacturing processes were analyzed. Load conditions, i.e. fiber delivery speed, necessary pre-tension and other effects of the delivery system during continuous fiber winding, were chosen in process typical ranges. First, the strain rate dependency under static tensile load conditions was investigated. Furthermore different free gauge lengths up to 1.2 m, interactions between fiber points of contact regarding influence of sizing as well as impregnation were tested and the effect of twisting on the mechanical behavior of dry glass fiber bundles during the fiber delivery was studied.

Reducing Bolt Preload Variation with Angle-of-Twist Bolt Loading

NASA Technical Reports Server (NTRS)

Thompson, Bryce; Nayate, Pramod; Smith, Doug; McCool, Alex (Technical Monitor)

2001-01-01

Critical high-pressure sealing joints on the Space Shuttle reusable solid rocket motor require precise control of bolt preload to ensure proper joint function. As the reusable solid rocket motor experiences rapid internal pressurization, correct bolt preloads maintain the sealing capability and structural integrity of the hardware. The angle-of-twist process provides the right combination of preload accuracy, reliability, process control, and assembly-friendly design. It improves significantly over previous methods. The sophisticated angle-of-twist process controls have yielded answers to all discrepancies encountered while the simplicity of the root process has assured joint preload reliability.

Effects of abutment screw coating on implant preload.

PubMed

Park, Jae-Kyoung; Choi, Jin-Uk; Jeon, Young-Chan; Choi, Kyung-Soo; Jeong, Chang-Mo

2010-08-01

The aim of the present study was to investigate the effects of tungsten carbide carbon (WC/CTa) screw surface coating on abutment screw preload in three implant connection systems in comparison to noncoated titanium alloy (Ta) screws. Preload of WC/CTa abutment screws was compared to noncoated Ta screws in three implant connection systems. The differences in preloads were measured in tightening rotational angle, compression force, initial screw removal torque, and postload screw removal torque after 1 million cyclic loads. Preload loss percent was calculated to determine the efficacy of maintaining the preload of two abutment screw types in relation to implant connection systems. WC/CTa screws provided 10 degrees higher tightening rotational angle than Ta screws in all three connection systems. This difference was statistically significant (p < 0.05). External-hex butt joint implant connections had a higher compression force than the two internal conical implant connections. WC/CTa screws provided a statistically significantly higher compression force than Ta screws in all three implant connections (p < 0.05). Ta screws required statistically higher removal torque than WC/CTa screws in all three implant connections (p < 0.05); however, Ta screws needed statistically lower postload removal torque than WC/CTa screws in all three implant connections (p < 0.05). Ta screws had a statistically higher preload loss percent than WC/CTa screws in all three implant connections (p < 0.05), indicating that WC/CTa screws were superior in maintaining the preload than Ta screws. Within the limits of present study, the following conclusions were made: (1) WC/CTa screws provided higher preload than noncoated Ta screws in all three implant connection systems. (2) The initial removal torque for Ta screws required higher force than WC/CTa screws, whereas postload removal torque for Ta screws was lower than WC/CTa screws. Calculated Ta screw preload loss percent was higher than for WC/CTa screws, suggesting that WC/CTa screws were more effective in maintaining the preload than Ta screws. (3) Internal conical connections were more effective in maintaining the screw preload in cyclic loads than external-hex butt joint connections.

No difference in compensation for sugar in a drink versus sugar in semi-solid and solid foods.

PubMed

Gadah, Nouf S; Kyle, Lesley A; Smith, Jessica E; Brunstrom, Jeffrey M; Rogers, Peter J

2016-03-15

It is claimed that sugar consumed in a drink is poorly compensated for by a reduction in subsequent energy intake, however very little research has tested directly the effect on appetite of adding sugar to a drink versus food. In this between subjects study, 144 participants (72 men) consumed preloads sweetened with either sucrose or the low-energy sweetener, sucralose (preload energy difference 162kcal) in the form of a blackcurrant drink, jelly or candy. The different preload viscosities were achieved by varying the amount of thickener (carrageenan) and water in the recipes. Participants completed hunger ratings before and 5, 10 and 20min after consuming their preload. After the 20-minute rating they were served a test-meal comprising an excess of bite-sized sandwiches and a sweet dessert. Energy intake measured for the same meal consumed the previous day (baseline day, no preload consumed) was used in the data analyses to control for individual differences in energy intake. Overall, there was 36% compensation for the energy difference in the preloads, but this did not vary with preload viscosity - if anything compensation was greater for the drink preload, and greater in men. The drink preload also showed an effect of sucrose versus sucralose for hunger. The lack of the predicted effect of viscosity on compensation could not be explained by differences in blood-glucose concentration 20min after the preload (measured in a separate study) or by differences in preload sweetness, flavour intensity, liking or familiarity. Comparison of baseline and test-meal food intakes indicated that, irrespective of energy content, the sweet drinks reduced the relative intake of sweet food. In conclusion, short-term energy compensation did not differ across a set of realistic drink and food stimuli. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments.

PubMed

Pedullà, E; Lo Savio, F; Boninelli, S; Plotino, G; Grande, N M; Rapisarda, E; La Rosa, G

2015-11-01

To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel-titanium (NiTi), M-Wire or CM-Wire. Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two-way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two-way analyses of variance. Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M-wire and CM-wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Supplemental nicotine preloading for smoking cessation in posttraumatic stress disorder: Results from a randomized controlled trial

PubMed Central

Dennis, Paul A.; Kimbrel, Nathan A.; Dedert, Eric A.; Beckham, Jean C.; Dennis, Michelle F.; Calhoun, Patrick S.

2016-01-01

Background Individuals with posttraumatic stress disorder (PTSD) are more likely to smoke and more likely to relapse following a quit attempt than individuals without PTSD. Thus, there is a significant need to study promising interventions that might improve quit rates for smokers with PTSD. One such intervention, supplemental nicotine patch-preloading, entails the use of nicotine replacement therapy prior to quitting. Objective The objective of this study was to conduct a randomized controlled trial of the efficacy of supplemental nicotine patch-preloading among smokers with PTSD. We hypothesized that, relative to participants in the placebo condition, participants in the nicotine patch-preloading condition would: (1) smoke less and experience reduced craving for cigarettes during the nicotine patch-preloading phase; (2) experience less smoking-associated relief from PTSD symptoms and negative affect during the preloading phase; and (3) exhibit greater latency to lapse, and higher short- and long-term abstinence rates. Methods Sixty-three smokers with PTSD were randomized to either nicotine or placebo patch for three weeks prior to their quit date. Ecological momentary assessment was used to assess craving, smoking, PTSD symptoms, and negative affect during the preloading period. Results Nicotine patch-preloading failed to reduce smoking or craving during the preloading phase, nor was it associated with less smoking-associated relief from PTSD symptoms and negative affect. Moreover, no differences were observed between the treatment conditions for time to lapse, 6-week abstinence, or 6-month abstinence. Conclusions The findings from the present research suggest that supplemental nicotine patch-preloading is unlikely to substantially enhance quit rates among smokers with PTSD. PMID:27046670

A comparison of preload values in gold and titanium dental implant retaining screws.

PubMed

Doolabh, R; Dullabh, H D; Sykes, L M

2014-08-01

This in vitro investigation compared the effect of using either gold or titanium retaining screws on preload in the dental implant- abutment complex. Inadequate preload can result in screw loosening, whilst fracture may occur if preload is excessive. These are the most commonly reported complications in implant-retained prostheses, and result in unscheduled, costly and time-consuming visits for the patient and the clinician. This study investigated changes in preload generation after repeated torque applications to gold and titanium screws. The test set-up consisted of an implant body, a cylindrical transmucosa abutment, and the test samples of gold and of titanium retaining screws. The implant bodies were anchored using a load cell, and the transmucosal abutments were attached using either gold or titanium retaining screws. A torque gauge was used to apply torque of 20Ncm, 32Ncm, and 40Ncm to the retaining screws. The preloads generated in each screw type were compared at each torque setting, and after repeated tightening episodes. In addition, the effect of applying torque beyond the manufacturers' recommendations was also examined. Gold retaining screws were found to achieve consistently higher preload values than titanium retaining screws. Preload values were not significantly different from the first to the tenth torque cycle. Titanium screws showed more consistent preload values, albeit lower than those of the gold screws. However due to possible galling of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on the findings of this study, gold retaining screws generate better preload than titanium. Torque beyond the manufacturers' recommendations resulted in a more stable implant complex. However, further investigations, with torque applications repeated until screw breakage, are needed to advise on ideal maintenance protocols.

Methodology for Determining Limit Torques for Threaded Fasteners

NASA Technical Reports Server (NTRS)

Hissam, Andy

2011-01-01

In aerospace design, where minimizing weight is always a priority, achieving the full capacity from fasteners is essential. To do so, the initial bolt preload must be maximized. The benefits of high preload are well documented and include improved fatigue resistance, a stiffer joint, and resistance to loosening. But many factors like elastic interactions and embedment tend to lower the initial preload placed on the bolt. These factors provide additional motivation to maximize the initial preload. But, to maximize bolt preload, you must determine what torque to apply. Determining this torque is greatly complicated by the large preload scatter generally seen with torque control. This paper presents a detailed methodology for generating limit torques for threaded fasteners. This methodology accounts for the large scatter in preload found with torque control, and therefore, addresses the statistical nature of the problem. It also addresses prevailing torque, a feature common in aerospace fasteners. Although prevailing torque provides a desired locking feature, it can also increase preload scatter. In addition, it can limit the amount of preload that can be generated due to the torsion it creates in the bolt. This paper discusses the complications of prevailing torque and how best to handle it. A wide range of torque-tension bolt testing was conducted in support of this research. The results from this research will benefit the design engineer as well as analyst involved in the design of bolted joints, leading to better, more optimized structural designs.

Supplementing chicken broth with monosodium glutamate reduces energy intake from high fat and sweet snacks in middle-aged healthy women.

PubMed

Imada, Toshifumi; Hao, Susan Shuzhen; Torii, Kunio; Kimura, Eiichiro

2014-08-01

Monosodium L-glutamate (MSG) and inosine monophosphate-5 (IMP) are flavor enhancers for umami taste. However, their effects on appetite and food intake are not well-researched. The objective of the current study was to test their additions in a broth preload on subsequent appetite ratings, energy intake and food choice. Eighty-six healthy middle-aged women with normal body weight received three preload conditions on 3 test days 1 week apart - a low-energy chicken flavor broth (200 ml) as the control preload, and broths with added MSG alone (0.5 g/100 ml, MSG broth) or in combination with IMP (0.05 g/100 ml) (MSG+ broth) served as the experimental conditions. Fifteen minutes after preload administration subjects were provided an ad libitum testing meal which consisted of 16 snacks varying in taste and fat content. MSG and MSG+ enhanced savory taste and broth properties of liking and pleasantness. In comparison with control, the MSG preload resulted in less consumption of total energy, as well as energy from sweet and high-fat snacks. Furthermore, MSG broth preload reduced added sugar intake. These findings were not observed after MSG+ preload. Appetite ratings were not different across the three preloads. Results suggest a potential role of MSG addition to a low-energy broth preload in subsequent energy intake and food choice. This trial was registered at clinicaltrials.gov as NCT01761045. Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect of 3 torque delivery systems on gold screw preload at the gold cylinder-abutment screw joint.

PubMed

Tan, Keson B; Nicholls, Jack I

2002-01-01

This study measured the gold screw preload at the gold cylinder-abutment screw joint interface obtained by 3 torque delivery systems. Using a precalibrated, strain-gauged standard abutment as the load cell, 3 torque delivery systems tested were shown to have significant differences in gold screw preload when a gold cylinder was attached. Mean preloads measured were 291.2 N for hand torque drivers set at 10 Ncm, 340.3 N for electronic torque controllers at low setting/10 Ncm, 384.4 N for electronic torque controllers at high setting/10 Ncm; and 140.8 N for hand-tightening with a prosthetic slot screwdriver. Significant differences in screw preload were also found between operators using a hand torque driver. Hand-tightening delivered insufficient preload and cannot be recommended for final gold screw tightening. Different electronic torque controller units set at 10 Ncm induced mean gold screw preloads that ranged from 264.1 N to as high as 501.2 N. Electronic torque controllers should be regularly recalibrated to ensure optimal output.

Adsorption of selected pharmaceuticals and an endocrine disrupting compound by granular activated carbon. 1. Adsorption capacity and kinetics.

PubMed

Yu, Zirui; Peldszus, Sigrid; Huck, Peter M

2009-03-01

The adsorption of two representative PhACs (naproxen and carbamazepine) and one EDC (nonylphenol) were evaluated on two granular activated carbons (GAC). The primary objective was to investigate preloading effects by natural organic matter (NOM) on adsorption capacity and kinetics under conditions and concentrations (i.e., ng/L) relevantfor drinking water treatment Isotherms demonstrated that all compounds were significantly negatively impacted by NOM fouling. Adsorption capacity reduction was most severe for the acidic naproxen, followed by the neutral carbamazepine and then the more hydrophobic nonylphenol. The GAC with the wider pore size distribution had considerably greater NOM loading, resulting in lower adsorption capacity. Different patterns forthe change in Freundlich K(F) and 1/n with time revealed different competitive mechanisms for the different compounds. Mass transport coefficients determined by short fixed-bed (SFB) tests with virgin and preloaded GAC demonstrated thatfilm diffusion primarily controls mass transfer on virgin and preloaded carbon. Naproxen suffered the greatest deteriorative effect on kinetic parameters due to preloading, followed by carbamazepine, and then nonylphenol. A type of surface NOM/biofilm, which appeared to add an additional masstransfer resistance layer and thus reduce film diffusion, was observed. In addition, electrostatic interactions between NOM/biofilm and the investigated compounds are proposed to contribute to the reduction of film diffusion. A companion paper building on this work describes treatability studies in pilot-scale GAC adsorbers and the effectiveness of a selected fixed-bed model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Z.; Peldszus, S.; Huck, P.M.

The adsorption of two representative PhACs (naproxen and carbamazepine) and one EDC (nonylphenol) were evaluated on two granular activated carbons (GAC) namely coal-based Calgon Filtrasorb 400 and coconut shell-based PICA CTIF TE. The primary objective was to investigate preloading effects by natural organic matter (NOM) on adsorption capacity and kinetics under conditions and concentrations (i.e., ng/L) relevant for drinking water treatment. Isotherms demonstrated that all compounds were significantly negatively impacted by NOM fouling. Adsorption capacity reduction was most severe for the acidic naproxen, followed by the neutral carbamazepine and then the more hydrophobic nonylphenol. The GAC with the wider poremore » size distribution had considerably greater NOM loading, resulting in lower adsorption capacity. Different patterns for the change in Freundlich KF and 1/n with time revealed different competitive mechanisms for the different compounds. Mass transport coefficients determined by short fixed-bed (SFB) tests with virgin and preloaded GAC demonstrated that film diffusion primarily controls mass transfer on virgin and preloaded carbon. Naproxen suffered the greatest deteriorative effect on kinetic parameters due to preloading, followed by carbamazepine, and then nonylphenol. A type of surface NOM/biofilm, which appeared to add an additional mass transfer resistance layer and thus reduce film diffusion, was observed. In addition, electrostatic interactions between NOM/biofilm and the investigated compounds are proposed to contribute to the reduction of film diffusion. A companion paper building on this work describes treatability studies in pilot-scale GAC adsorbers and the effectiveness of a selected fixed-bed model. 32 refs., 3 figs., 2 tabs.« less

Apparatus for accurately preloading auger attachment means for frangible protective material

NASA Technical Reports Server (NTRS)

Wood, K. E.

1983-01-01

Apparatus for preloading a spring loaded threaded member is described. The apparatus is formed of three telescoping tubes. The innermost tube has means to prevent rotation of the threaded member. The middle tube is threadedly engaged with the threaded member and by axial movement applies a preload thereto. The outer tube engages a nut which may be rotated to retain the threaded member in axial position to maintain the preload.

Monitoring of Pre-Load on Rock Bolt Using Piezoceramic-Transducer Enabled Time Reversal Method.

PubMed

Huo, Linsheng; Wang, Bo; Chen, Dongdong; Song, Gangbing

2017-10-27

Rock bolts ensure structural stability for tunnels and many other underground structures. The pre-load on a rock bolt plays an important role in the structural reinforcement and it is vital to monitor the pre-load status of rock bolts. In this paper, a rock bolt pre-load monitoring method based on the piezoceramic enabled time reversal method is proposed. A lead zirconate titanate (PZT) patch transducer, which works as an actuator to generate stress waves, is bonded onto the anchor plate of the rock bolt. A smart washer, which is fabricated by sandwiching a PZT patch between two metal rings, is installed between the hex nut and the anchor plate along the rock bolt. The smart washer functions as a sensor to detect the stress wave. With the increase of the pre-load values on the rock bolt, the effective contact surface area between the smart washer and the anchor plate, benefiting the stress wave propagation crossing the contact surface. With the help of time reversal technique, experimental results reveal that the magnitude of focused signal clearly increases with the increase of the pre-load on a rock bolt before the saturation which happens beyond a relatively high value of the pre-load. The proposed method provides an innovative and real time means to monitor the pre-load level of a rock bolt. By employing this method, the pre-load degradation process on a rock bolt can be clearly monitored. Please note that, currently, the proposed method applies to only new rock bolts, on which it is possible to install the PZT smart washer.

The impact of a preloaded intraocular lens delivery system on operating room efficiency in routine cataract surgery.

PubMed

Jones, Jason J; Chu, Jeffrey; Graham, Jacob; Zaluski, Serge; Rocha, Guillermo

2016-01-01

The aim of this study was to evaluate the operational impact of using preloaded intraocular lens (IOL) delivery systems compared with manually loaded IOL delivery processes during routine cataract surgeries. Time and motion data, staff and surgery schedules, and cost accounting reports were collected across three sites located in the US, France, and Canada. Time and motion data were collected for manually loaded IOL processes and preloaded IOL delivery systems over four surgery days. Staff and surgery schedules and cost accounting reports were collected during the 2 months prior and after introduction of the preloaded IOL delivery system. The study included a total of 154 routine cataract surgeries across all three sites. Of these, 77 surgeries were performed using a preloaded IOL delivery system, and the remaining 77 surgeries were performed using a manual IOL delivery process. Across all three sites, use of the preloaded IOL delivery system significantly decreased mean total case time by 6.2%-12.0% (P<0.001 for data from Canada and the US and P<0.05 for data from France). Use of the preloaded delivery system also decreased surgeon lens time, surgeon delays, and eliminated lens touches during IOL preparation. Compared to a manual IOL delivery process, use of a preloaded IOL delivery system for cataract surgery reduced total case time, total surgeon lens time, surgeon delays, and eliminated IOL touches. The time savings provided by the preloaded IOL delivery system provide an opportunity for sites to improve routine cataract surgery throughput without impacting surgeon or staff capacity.

A pilot investigation to optimise methods for a future satiety preload study.

PubMed

Hobden, Mark R; Guérin-Deremaux, Laetitia; Commane, Daniel M; Rowland, Ian; Gibson, Glenn R; Kennedy, Orla B

2017-01-01

Preload studies are used to investigate the satiating effects of foods and food ingredients. However, the design of preload studies is complex, with many methodological considerations influencing appetite responses. The aim of this pilot investigation was to determine acceptability, and optimise methods, for a future satiety preload study. Specifically, we investigated the effects of altering (i) energy intake at a standardised breakfast (gender-specific or non-gender specific), and (ii) the duration between mid-morning preload and ad libitum lunch meal, on morning appetite scores and energy intake at lunch. Participants attended a single study visit. Female participants consumed a 214-kcal breakfast ( n  = 10) or 266-kcal breakfast ( n  = 10), equivalent to 10% of recommended daily energy intakes for females and males, respectively. Male participants ( n  = 20) consumed a 266-kcal breakfast. All participants received a 250-ml orange juice preload 2 h after breakfast. The impact of different study timings was evaluated in male participants, with 10 males following one protocol (protocol 1) and 10 males following another (protocol 2). The duration between preload and ad libitum lunch meal was 2 h (protocol 1) or 2.5 h (protocol 2), with the ad libitum lunch meal provided at 12.00 or 13.00, respectively. All female participants followed protocol 2. Visual analogue scale (VAS) questionnaires were used to assess appetite responses and food/drink palatability. Correlation between male and female appetite scores was higher with the provision of a gender-specific breakfast, compared to non-gender-specific breakfast (Pearson correlation of 0.747 and 0.479, respectively). No differences in subjective appetite or ad libitum energy intake were found between protocols 1 and 2. VAS mean ratings of liking, enjoyment, and palatability were all > 66 out of 100 mm for breakfast, preload, and lunch meals. The findings of this pilot study confirm the acceptability of this methodology for future satiety preload studies. Appetite scores increased from preload to ad libitum lunch meal; however, no specific differences were found between protocols. The results highlight the importance of considering energy intake prior to preload provision, with a gender-specific breakfast improving the correlation between male and female appetite score responses to a morning preload.

The effects of compressive preloads on the compression-after-impact strength of carbon/epoxy

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Lance, D. G.

1992-01-01

A preloading device was used to examine the effects of compressive prestress on the compression-after-impact (CAI) strength of 16-ply, quasi-isotropic carbon epoxy test coupons. T300/934 material was evaluated at preloads from 200 to 4000 lb at impact energies from 1 to 9 joules. IM7/8551-7 material was evaluated at preloads from 4000 to 10,000 lb at impact energies from 4 to 16 joules. Advanced design of experiments methodology was used to design and evaluate the test matrices. The results showed that no statistically significant change in CAI strength could be contributed to the amount of compressive preload applied to the specimen.

Analysis of influence of different pressure and different depth of pvd on soft foundation treatment

NASA Astrophysics Data System (ADS)

Li, Bin; Wang, XueKui

2018-02-01

According to the depth of plastic vertical drainage (pvd), the arrangement mode and the loading mode to analyze the influence of Vacuum preloading near the existing road. An arrangement mode of vacuum preloading to reduce the impact was put forward. The combination of different depth of pvd and loading modes are used to analyze the effect of vacuum preloading treatment and its influence range. The calculations show that the deformation and the influence distance are smaller by using the 40kPa vacuum loading and 41kPa surcharge load preloading. Reducing the depth of the pvd and vacuum combined surcharge preloading can weaken the influence to the existing highway.

A new method for measuring the rotational accuracy of rolling element bearings

NASA Astrophysics Data System (ADS)

Chen, Ye; Zhao, Xiangsong; Gao, Weiguo; Hu, Gaofeng; Zhang, Shizhen; Zhang, Dawei

2016-12-01

The rotational accuracy of a machine tool spindle has critical influence upon the geometric shape and surface roughness of finished workpiece. The rotational performance of the rolling element bearings is a main factor which affects the spindle accuracy, especially in the ultra-precision machining. In this paper, a new method is developed to measure the rotational accuracy of rolling element bearings of machine tool spindles. Variable and measurable axial preload is applied to seat the rolling elements in the bearing races, which is used to simulate the operating conditions. A high-precision (radial error is less than 300 nm) and high-stiffness (radial stiffness is 600 N/μm) hydrostatic reference spindle is adopted to rotate the inner race of the test bearing. To prevent the outer race from rotating, a 2-degrees of freedom flexure hinge mechanism (2-DOF FHM) is designed. Correction factors by using stiffness analysis are adopted to eliminate the influences of 2-DOF FHM in the radial direction. Two capacitive displacement sensors with nano-resolution (the highest resolution is 9 nm) are used to measure the radial error motion of the rolling element bearing, without separating the profile error as the traditional rotational accuracy metrology of the spindle. Finally, experimental measurements are performed at different spindle speeds (100-4000 rpm) and axial preloads (75-780 N). Synchronous and asynchronous error motion values are evaluated to demonstrate the feasibility and repeatability of the developed method and instrument.

Lipopolysaccharide-induced endotoxemia in corn oil-preloaded mice causes an extended course of lung injury and repair and pulmonary fibrosis: A translational mouse model of acute respiratory distress syndrome.

PubMed

Wu, Chaomin; Evans, Colin E; Dai, Zhiyu; Huang, Xiaojia; Zhang, Xianming; Jin, Hua; Hu, Guochang; Song, Yuanlin; Zhao, You-Yang

2017-01-01

Acute respiratory distress syndrome (ARDS) is characterized by acute hypoxemia respiratory failure, bilateral pulmonary infiltrates, and pulmonary edema of non-cardiac origin. Effective treatments for ARDS patients may arise from experimental studies with translational mouse models of this disease that aim to delineate the mechanisms underlying the disease pathogenesis. Mouse models of ARDS, however, can be limited by their rapid progression from injured to recovery state, which is in contrast to the course of ARDS in humans. Furthermore, current mouse models of ARDS do not recapitulate certain prominent aspects of the pathogenesis of ARDS in humans. In this study, we developed an improved endotoxemic mouse model of ARDS resembling many features of clinical ARDS including extended courses of injury and recovery as well as development of fibrosis following i.p. injection of lipopolysaccharide (LPS) to corn oil-preloaded mice. Compared with mice receiving LPS alone, those receiving corn oil and LPS exhibited extended course of lung injury and repair that occurred over a period of >2 weeks instead of 3-5days. Importantly, LPS challenge of corn oil-preloaded mice resulted in pulmonary fibrosis during the repair phase as often seen in ARDS patients. In summary, this simple novel mouse model of ARDS could represent a valuable experimental tool to elucidate mechanisms that regulate lung injury and repair in ARDS patients.

Effect of preload reduction by hemodialysis on left atrial volume and echocardiographic Doppler parameters in patients with end-stage renal disease.

PubMed

Barberato, Silvio H; Mantilla, Diego E V; Misocami, M Arcio; Gonçalves, Simone M; Bignelli, Alexandre T; Riella, Miguel C; Pecoits-Filho, Roberto

2004-11-01

Left atrial (LA) volume has been proposed as a less preload-dependent parameter of diastolic function than Doppler mitral inflow. We hypothesize that in the absence of mitral regurgitation and atrial fibrilation, LA enlargement could be a more practical (and relatively preload-independent) method for the evaluation of left ventricular diastolic function. The aim of the present study was to determine the effects of preload reduction by hemodialysis on LA volume.

Preloading To Accelerate Slow-Crack-Growth Testing

NASA Technical Reports Server (NTRS)

Gyekenyesi, John P.; Choi, Sung R.; Pawlik, Ralph J.

2004-01-01

An accelerated-testing methodology has been developed for measuring the slow-crack-growth (SCG) behavior of brittle materials. Like the prior methodology, the accelerated-testing methodology involves dynamic fatigue ( constant stress-rate) testing, in which a load or a displacement is applied to a specimen at a constant rate. SCG parameters or life prediction parameters needed for designing components made of the same material as that of the specimen are calculated from the relationship between (1) the strength of the material as measured in the test and (2) the applied stress rate used in the test. Despite its simplicity and convenience, dynamic fatigue testing as practiced heretofore has one major drawback: it is extremely time-consuming, especially at low stress rates. The present accelerated methodology reduces the time needed to test a specimen at a given rate of applied load, stress, or displacement. Instead of starting the test from zero applied load or displacement as in the prior methodology, one preloads the specimen and increases the applied load at the specified rate (see Figure 1). One might expect the preload to alter the results of the test and indeed it does, but fortunately, it is possible to account for the effect of the preload in interpreting the results. The accounting is done by calculating the normalized strength (defined as the strength in the presence of preload the strength in the absence of preload) as a function of (1) the preloading factor (defined as the preload stress the strength in the absence of preload) and (2) a SCG parameter, denoted n, that is used in a power-law crack-speed formulation. Figure 2 presents numerical results from this theoretical calculation.

Immediate pre-meal water ingestion decreases voluntary food intake in lean young males.

PubMed

Corney, Robert A; Sunderland, Caroline; James, Lewis J

2016-03-01

Consuming 375-500 ml of water 30 min before a meal has been shown to reduce energy intake in older, but not younger adults. This study investigated the effects of ingesting a water preload immediately pre-meal (<1 min before eating) on within-meal ad libitum energy intake in non-obese young males. Fourteen healthy males [mean (SD) age 27 (3) years, height 1.83 (0.05) m, body weight 80.47 (9.89) kg, body fat 17.5 (4.0) %, body mass index 24.0 (2.5) kg/m(2)] completed a familiarisation trial and two experimental trials in randomised counterbalanced order. Subjects arrived at the laboratory overnight fasted and consumed an ad libitum porridge breakfast. Immediately prior to the meal, subjects consumed either a 568 ml (1 pint) water preload (preload trial) or no preload (control trial). Visual analogue scale questionnaires to assess hunger, fullness and satisfaction were completed before and after the meal in both trials, as well as after the water preload. Ad libitum energy intake was greater (P < 0.001) during control [2551 (562) kJ] than preload [1967 (454) kJ]. Ad libitum water intake was also greater (P < 0.001) during control [318 (226-975) ml] than preload [116 (0-581) ml]. The water preload increased fullness and satisfaction and decreased hunger compared to pre-trial (P < 0.001) and the control trial (P < 0.001). This study demonstrates that consumption of a 568 ml water preload immediately before a meal reduces energy intake in non-obese young males. This might therefore be an effective strategy to suppress energy intake in this population and possibly assist with weight management.

The effects of tensile preloads on the impact response of carbon/epoxy laminates

NASA Technical Reports Server (NTRS)

Nettles, Alan; Daniel, Vince; Branscomb, Caleb

1995-01-01

The effects of tensile preloads on the tension-after-impact (TAI) strength of composite laminates of IM7/8551-7 were examined. A failure threshold curve was first determined so the most informative values for preload/impact energy combinations could be determined. The impact tests were instrumented so maximum load of impact, as well as several other parameters could be measured. The elastic response data indicate that as the tensile preload is increased, the maximum load of impact also increases. The damage data show that at low impact energies, the damage/failure is an 'all-or-nothing' event but at higher impact energies, a region of preload values exists where the coupons could sustain damage, yet not fail catastrophically.

A novel phenomenological multi-physics model of Li-ion battery cells

NASA Astrophysics Data System (ADS)

Oh, Ki-Yong; Samad, Nassim A.; Kim, Youngki; Siegel, Jason B.; Stefanopoulou, Anna G.; Epureanu, Bogdan I.

2016-09-01

A novel phenomenological multi-physics model of Lithium-ion battery cells is developed for control and state estimation purposes. The model can capture electrical, thermal, and mechanical behaviors of battery cells under constrained conditions, e.g., battery pack conditions. Specifically, the proposed model predicts the core and surface temperatures and reaction force induced from the volume change of battery cells because of electrochemically- and thermally-induced swelling. Moreover, the model incorporates the influences of changes in preload and ambient temperature on the force considering severe environmental conditions electrified vehicles face. Intensive experimental validation demonstrates that the proposed multi-physics model accurately predicts the surface temperature and reaction force for a wide operational range of preload and ambient temperature. This high fidelity model can be useful for more accurate and robust state of charge estimation considering the complex dynamic behaviors of the battery cell. Furthermore, the inherent simplicity of the mechanical measurements offers distinct advantages to improve the existing power and thermal management strategies for battery management.

Development of hypersonic engine seals: Flow effects of preload and engine pressures

NASA Technical Reports Server (NTRS)

Cai, Zhong; Mutharasan, Rajakkannu; Ko, Frank K.; Steinetz, Bruce M.

1993-01-01

A new type of engine seal is being developed to meet the needs of advanced hypersonic engines. A seal braided of emerging high temperature ceramic fibers comprised of a sheath-core construction was selected for study based on its low leakage rates. Flexible, low-leakage, high temperature seals are required to seal the movable engine panels of advanced ramjet-scramjet engines either preventing potentially dangerous leakage into backside engine cavities or limiting the purge coolant flow rates through the seals. To predict the leakage through these flexible, porous seal structures as a function of preload and engine pressures, new analytical flow models are required. An empirical leakage resistance/preload model is proposed to characterize the observed decrease in leakage with increasing preload. Empirically determined compression modulus and preload factor are used to correlate experimental leakage data for a wide range of seal architectures. Good agreement between measured and predicted values are observed over a range of engine pressures and seal preloads.

Nondestructive ultrasonic measurement of bolt preload using the pulsed-phase locked-loop interferometer

NASA Technical Reports Server (NTRS)

Allison, S. G.; Heyman, J. S.

1985-01-01

Achieving accurate preload in threaded fasteners is an important and often critical problem which is encountered in nearly all sectors of government and industry. Conventional tensioning methods which rely on torque carry with them the disadvantage of requiring constant friction in the fastener in order to accurately correlate torque to preload. Since most of the applied torque typically overcomes friction rather than tensioning the fastener, small variations in friction can cause large variations in preload. An instrument called a pulsed phase locked loop interferometer, which was recently developed at NASA Langley, has found widespread use for measurement of stress as well as material properties. When used to measure bolt preload, this system detects changes in the fastener length and sound velocity which are independent of friction. The system is therefore capable of accurately establishing the correct change in bolt tension. This high resolution instrument has been used for precision measurement of preload in critical fasteners for numerous applications such as the space shuttle landing gear and helicopter main rotors.

A general model for preload calculation and stiffness analysis for combined angular contact ball bearings

NASA Astrophysics Data System (ADS)

Zhang, Jinhua; Fang, Bin; Hong, Jun; Wan, Shaoke; Zhu, Yongsheng

2017-12-01

The combined angular contact ball bearings are widely used in automatic, aerospace and machine tools, but few researches on the combined angular contact ball bearings have been reported. It is shown that the preload and stiffness of combined bearings are mutual influenced rather than simply the superposition of multiple single bearing, therefore the characteristic calculation of combined bearings achieved by coupling the load and deformation analysis of a single bearing. In this paper, based on the Jones quasi-static model and stiffness analytical model, a new iterative algorithm and model are proposed for the calculation of combined bearings preload and stiffness, and the dynamic effects include centrifugal force and gyroscopic moment have to be considered. It is demonstrated that the new method has general applicability, the preload factors of combined bearings are calculated according to the different design preloads, and the static and dynamic stiffness for various arrangements of combined bearings are comparatively studied and analyzed, and the influences of the design preload magnitude, axial load and rotating speed are discussed in detail. Besides, the change rule of dynamic contact angles of combined bearings with respect to the rotating speed is also discussed. The results show that bearing arrangement modes, rotating speed and design preload magnitude have a significant influence on the preload and stiffness of combined bearings. The proposed formulation provides a useful tool in dynamic analysis of the complex bearing-rotor system.

Is Doppler tissue velocity during early left ventricular filling preload independent?

NASA Technical Reports Server (NTRS)

Yalcin, F.; Kaftan, A.; Muderrisoglu, H.; Korkmaz, M. E.; Flachskampf, F.; Garcia, M.; Thomas, J. D.

2002-01-01

BACKGROUND: Transmitral Doppler flow indices are used to evaluate diastolic function. Recently, velocities measured by Doppler tissue imaging have been used as an index of left ventricular relaxation. OBJECTIVE: To determine whether Doppler tissue velocities are influenced by alterations in preload. METHODS: Left ventricular preload was altered in 17 patients (all men, mean (SD) age, 49 (8) years) during echocardiographic measurements of left ventricular end diastolic volume, maximum left atrial area, peak early Doppler filling velocity, and left ventricular myocardial velocities during early filling. Preload altering manoeuvres included Trendelenberg (stage 1), reverse Trendelenberg (stage 2), and amyl nitrate (stage 3). Systolic blood pressure was measured at each stage. RESULTS: In comparison with baseline, left ventricular end diastolic volume (p = 0.001), left atrial area (p = 0.003), peak early mitral Doppler filling velocity (p = 0.01), and systolic blood pressures (p = 0.001) were all changed by preload altering manoeuvres. Only left ventricular myocardial velocity during early filling remained unchanged by these manoeuvres. CONCLUSIONS: In contrast to standard transmitral Doppler filling indices, Doppler tissue early diastolic velocities are not significantly affected by physiological manoeuvres that alter preload. Thus Doppler tissue velocities during early left ventricular diastole may provide a better index of diastolic function in cardiac patients by providing a preload independent assessment of left ventricular filling.

Effects of consuming mycoprotein, tofu or chicken upon subsequent eating behaviour, hunger and safety.

PubMed

Williamson, Donald A; Geiselman, Paula J; Lovejoy, Jennifer; Greenway, Frank; Volaufova, Julia; Martin, Corby K; Arnett, Cheryl; Ortego, Lauren

2006-01-01

This study tested if: (1) a preload of mycoprotein and tofu consumed before a lunch meal have a greater effect on satiety when compared to a chicken preload, (2) the mycoprotein and tofu preloads, compared to chicken, are not associated with compensation or eating more food at a subsequent dinner meal. These hypotheses were tested in a controlled laboratory study using universal eating monitors to measure food intake and visual analogue scales to monitor hunger and satiety. Forty-two overweight adult females consumed three meals in the laboratory on 3 test days. At lunch, isocaloric pasta preloads, containing mycoprotein, tofu, or chicken, varied across the days in a balanced order. The findings of the study supported the two hypotheses. Mycoprotein and tofu preloads, in comparison to the chicken preload, were associated with lower food intake shortly after consuming the preload at lunch. Food intake following consumption of mycoprotein and tofu did not differ, and participants did not compensate for lower food intake at lunch by consuming more food at dinner. The findings suggest that mycoprotein and tofu have satiating properties that persist for several hours after a meal. These findings have significant implications for the development of foods that are low in kilojoules, but are also filling.

Altered Left Ventricular Geometry and Torsional Mechanics in High Altitude-Induced Pulmonary Hypertension: A Three-Dimensional Echocardiographic Study.

PubMed

De Boeck, Bart W; Toma, Aurel; Kiencke, Stephanie; Dehnert, Christoph; Zügel, Stefanie; Siebenmann, Christoph; Auinger, Katja; Buser, Peter T; Maggiorini, Marco; Kaufmann, Beat A

2018-03-01

Changes in left ventricular (LV) torsion have been related to LV geometry in patients with concomitant long-standing myocardial disease or pulmonary hypertension (PH). We evaluated the effect of acute high altitude-induced isolated PH on LV geometry, volumes, systolic function, and torsional mechanics. Twenty-three volunteers were prospectively studied at low altitude and after the second (D3) and third night (D4) at high altitude (4,559 m). LV ejection fraction, multidirectional strains and torsion, LV volumes, sphericity, and eccentricity were derived by speckle-tracking on three-dimensional echocardiographic data sets. Pulmonary pressure was estimated from the transtricuspid pressure gradient (TRPG), LV preload from end-diastolic LV volume, and transmitral over mitral annular E velocity (E/e'). At high altitude, oxygen saturation decreased by 15%-20%, heart rate and cardiac index increased by 15%-20%, and TRPG increased from 21 ± 2 to 37 ± 9 mm Hg (P < .01). LV volumes, preload, ejection fraction, multidirectional strains, and sphericity remained unaffected, but diastolic (1.04 ± 0.07 to 1.09 ± 0.09 on D3/D4, P < .05) and systolic (1.00 ± 0.06 to 1.08 ± 0.1 [D3] and 1.06 ± 0.07 [D4], P < .05) eccentricity slightly increased, indicating mild septal flattening. LV torsion decreased from 2.14 ± 0.85 to 1.34 ± 0.68 (P < .05) and 1.65 ± 0.54 (P = .08) degrees/cm on D3/D4, respectively. Changes in torsion showed a weak inverse relationship to changes in systolic (r = -0.369, P = .013) and diastolic (r = -0.329, P = .032) eccentricity but not to changes in TRPG, heart rate or preload. High-altitude exposure was associated with mild septal flattening of the LV and reduced ventricular torsion at unchanged global LV function and preload, suggesting a relation between LV geometry and torsional mechanics. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Preloads generated with repeated tightening in three types of screws used in dental implant assemblies.

PubMed

Byrne, Declan; Jacobs, Stuart; O'Connell, Brian; Houston, Frank; Claffey, Noel

2006-01-01

Abutment screw loosening, especially in the case of cemented single tooth restorations, is a cause of implant restoration failure. This study compared three screws (titanium alloy, gold alloy, and gold-coated) with similar geometry by recording the preload induced when torques of 10, 20, and 35 Ncm were used for fixation. Two abutment types were used-prefabricated preparable abutments and cast-on abutments. A custom-designed rig was used to measure preload in the abutment-screw-implant assembly with a strain gauge. Ten screws of each type were sequentially tightened to 10, 20, and 35 Ncm on ten of the two abutment types. The same screws were then loosened and re-tightened. This procedure was repeated. Thus, each screw was tightened on three occasions to the three insertion torques. A linear regression model was used to analyze the effects on preload values of screw type and abutment type for each of the three insertion torques. The results indicated that the gold-coated screw generated the highest preloads for all insertion torques and for each tightening episode. Further analysis focused on the effects of screw type and abutment type for each episode of tightening and for each fixation torque. The gold-coated screw, fixed to the prefabricated abutment, displayed higher preloads for the first tightening at 10, 20, and 35 Ncm. Conversely, the same screw fixed to the cast-on abutment showed higher values for the second and third tightening for all fixation torques. All screws showed decay in preload with the number of times tightened. Given the higher preloads generated using the gold-coated screw with both abutment types, it is more likely that this type of screw will maintain a secure joint when tightened for the second and third time. All screw types displayed some decay in preload with repeated tightening, irrespective of abutment type and insertion torque. The gold-coated screw showed markedly higher preloads for all insertion torques and for all instances of tightening when compared with the uncoated screws.

Modeling and Evaluation of Canted Coil Springs as High Temperature Seal Preloading Devices

NASA Technical Reports Server (NTRS)

Oswald, Jay J.; Mullen, Robert L.; Dunlap, Patrick H., Jr.; Steinetz, Bruce M.

2004-01-01

Future reusable launch vehicles will require advanced structural seals. This includes propulsion seals along edges and hinge lines in hypersonic engines, and control surface seals for movable flaps and elevons on proposed reentry vehicles. Seals must remain in sealing engagement with opposing surfaces, for multiple missions, even though the seal gap may be opening and closing due to thermal and structural loads. To meet this requirement either the seals themselves must be resilient or there must be a resilient structural element behind the seals. Case Western Reserve University is working with NASA s Glenn Research Center to develop more resilient high temperature seal components and preloading devices. Results are presented for a finite element analysis of a canted coil spring that is being considered as a high temperature seal preloading device. This type of spring is a leading candidate due to its ability to provide nearly constant force over a large deflection. The finite element analyses were verified by comparing them to experimental results of canted coil springs of three different stiffnesses, measured at Glenn Research Center. Once validated the parameterized model was combined with a scripting algorithm to assess the effects of key spring design variables (wire diameter, coils per inch, cant amplitude, eccentricity, and spring width) on spring stiffness and maximum Von Mises stress to aid in subsequent design.

Preload Torque Limiting Shaft Coupling

NASA Technical Reports Server (NTRS)

Harmening, W. A. (Inventor)

1975-01-01

A torque limiting spring for a rotating shaft system which acts bidirectionally and is preloaded is examined. The spring is a split circular ring compressed into cavities on facing surfaces of matching shafts. The spring is preloaded by varying the width of a tang in the shaft cavity relative to the split in the spring.

The influence of tightening sequence and method on screw preload in implant superstructures.

PubMed

Al-Sahan, Maha M; Al Maflehi, Nassr S; Akeel, Riyadh F

2014-01-01

This study evaluated the effect of six screw-tightening sequences and two tightening methods on the screw preload in implant-supported superstructures. The preload was measured using strain gauges following the screw tightening of a metal framework connected to four implants. The experiment included six sequences ([1] 1-2-3-4, [2] 4-2-3-1, [3] 4-3-1-2, [4] 1-4-2-3, [5] 2-3-4-1, and [6] 3-2-4-1), two methods (onestep, three-step), and five replications. Significant differences were found between tightening sequences and methods. In the three-step method, a higher total preload was found in sequences 2 (312 ± 85 N), 3 (246 ± 54 N), and 4 (310 ± 96 N). In the one-step method, a higher total preload was found in sequences 1 (286 ± 94 N), 5 (764 ± 142 N), and 6 (350 ± 69 N). It is concluded that the highest total screw preload was achieved when anterior implants of the superstructure were first tightened in one step, followed by posterior implants.

ICESat-2 ATLAS Beam Steering Mechanism (BSM)

NASA Technical Reports Server (NTRS)

Hinkle, Matthew

2015-01-01

This work covers the design and test of a beam steering mechanism (BSM) used to accurately guide a laser on the Advanced Topographic Laser Altimeter System (ATLAS) down to Earth in order to measure elevation. It describes the main components in the BSM that allows it to perform and meet stringent requirements. Requirements of the BSM include two-axis steering of the transmitted laser beam, +-5000 uRad mechanical motion in each axis, and 1.5 uRad RMS pointing stability among many other requirements. The BSM uses four voice coil actuators in order to locate the mirror at the angle we need. There are four Differential Position Sensors that determine the position and angle of the mirror at all times. These sensors were verified through optical testing in both ambient and thermal conditions. Testing and extensive analyses were performed on the two-axis flexure throughout the program to check flexure thickness, positive margins, and infinite life. The mirror mount design has been modified to eliminate radial preload, while incorporating a titanium wave spring to provide an axial preload of 10.8N. The BSM underwent multiple tests in order to verify all components work as required under various conditions.

Experimental investigations on thermo mechanical behaviour of aluminium alloys subjected to tensile loading and laser irradiation

NASA Astrophysics Data System (ADS)

Jelani, Mohsan; Li, Zewen; Shen, Zhonghua; Sardar, Maryam; Tabassum, Aasma

2017-05-01

The present work reports the investigation of the thermal and mechanical behaviour of aluminium alloys under the combined action of tensile loading and laser irradiations. The two types of aluminium alloys (Al-1060 and Al-6061) are used for the experiments. The continuous wave Ytterbium fibre laser (wavelength 1080 nm) was employed as irradiation source, while tensile loading was provided by tensile testing machine. The effects of various pre-loading and laser power densities on the failure time, temperature distribution and on deformation behaviour of aluminium alloys are analysed. The experimental results represents the significant reduction in failure time and temperature for higher laser powers and for high load values, which implies that preloading may contribute a significant role in the failure of the material at elevated temperature. The reason and characterization of material failure by tensile and laser loading are explored in detail. A comparative behaviour of under tested materials is also investigated. This work suggests that, studies considering only combined loading are not enough to fully understand the mechanical behaviour of under tested materials. For complete characterization, one must consider the effect of heating as well as loading rate.

The Molecular Basis of Cardiac Mechanics: Regulation of Motor Unit Recruitment

DTIC Science & Technology

2001-10-25

sensitivity, Cooperativity. I. INTRODUCTION The biological linear motor, that produces cardiac and skeletal muscle contraction , is by far smaller than...who have described the role of the mechanical initial loading condition (Preload) on muscle contraction and by Fenn (1923) who has showed that the...2437, 1982. [4] E. Eisenberg, and T. L. Hill. Muscle contraction and energy transduction in biological system. Science 227: 999-1006, 1985. [5

A Comparison of the Satiety Effects of a Fruit Smoothie, Its Fresh Fruit Equivalent and Other Drinks

PubMed Central

Rogers, Peter J.; Shahrokni, Roya

2018-01-01

Energy-containing liquids are claimed to have relatively low satiating power, although energy in liquids is not without effect on appetite. Using the preload test-meal method, effects on fullness and energy intake compensation were compared across four drinks (water, blackcurrant squash, milk and fruit smoothie) and the fresh fruit equivalent of the smoothie. Preload volumes were similar, and the energy value of each preload was 569 kJ, except for water (0 kJ). Healthy, adult participants rated the preloads for liking, enjoyment, satisfaction, familiarity and how ‘food-like’ they seemed. The preload to test-meal interval was 2 min (n = 23) or 2 h (n = 24). The effects of the preloads on fullness varied with food-likeness and the rate at which they were consumed. In contrast, energy intake compensation versus water did not differ between the energy-containing preloads, although it decreased over time (from 82% at 2 min to 12% at 2 h). In conclusion, although fullness increased with food-likeness, subsequent energy intake compensation did not differ for energy/nutrients consumed in drinks compared with a food. The results also support the proposal that food intake is influenced predominantly by the immediate, but rapidly waning, post-ingestive effects of the previous ‘meal’ (rather than by changes in energy balance). PMID:29601488

Slimming starters. Intake of a diet-congruent food reduces meal intake in active dieters.

PubMed

Buckland, Nicola J; Finlayson, Graham; Hetherington, Marion M

2013-12-01

Dietary restraint is known to break down in the face of tempting foods. Previous research suggests exposure to cues associated with slimming such as images or odours act as prompts to restrict intake of a tempting snack in dieters. The effects of consuming diet-congruent foods on subsequent intake of a meal have not yet been investigated. Thus, using a repeated measures design 26 female participants (dieters or non-dieters) consumed a diet-congruent (100 kcal salad), hedonic (100 kcal garlic bread) or neutral (0 kcal water) preload. A lexical decision task measured the salience of diet and hedonic thoughts and participants were then offered pizza as a main meal. Appetite sensations were measured throughout the study. Compared to the hedonic and neutral preload, a diet-congruent preload reduced dieters' entire meal intake by 21%. In contrast, non-dieters consumed 9% more in the hedonic preload condition compared to the neutral preload, yet showed no differences between the diet-congruent and other conditions. Salad lowered participants desire to eat and increased fullness compared to garlic bread and water preloads. Dieters were also less hungry after the salad compared to the garlic bread and water preloads. Consuming a diet-congruent first course may prompt lower intake at a meal, in part due to facilitating resolve to refrain from overeating a tempting second course. Copyright © 2013. Published by Elsevier Ltd.

Dissociation of the effects of preload volume and energy content on subjective appetite and food intake.

PubMed

Gray, Richard; French, Stephen; Robinson, Tristan; Yeomans, Martin

2002-05-01

Previous research suggests that enhancing the volume of a food preload without altering energy content can result in reduced appetite, although the limited evidence means that the conditions under which this effect will occur are not yet clear. In the present study, we used a Universal Eating Monitor (UEM) to record test meal intake constantly, in parallel with appetite ratings, following soup-based preloads that varied both in volume (150 vs. 450 ml) and energy density (1.4 vs. 4.2 kJ/ml). Healthy young men (n=20) received four different preload conditions (repeated measures) followed by unlimited hot pasta test meals (interval 30 min). They completed appetite ratings during and after each laboratory session, and food diaries for the afternoon and evening following each session. Subjective appetite after the preloads was reduced by the high-volume preloads relative to low-volume preloads, with no difference between the two at each volume level. This indicates an effect of volume, but no effect of energy. Test meal intake in the high-volume, high-energy-density condition was reduced relative to the other conditions, which did not differ from one another. This indicates an effect of total energy, but no effect of volume. The dissociation between these different measures of appetite might be explained in terms of largely cognitive influences on subjective appetite between preload and test meal, contrasted with stronger physiological influences on actual intake during the test meal. With regard to previous studies, it is argued that food volume is more influential under circumstances where gastric volume is closer to its normal limits.

Effect of alloy type on the life-time of torsion-preloaded nickel-titanium endodontic instruments.

PubMed

Ha, Jung-Hong; Kim, Sung Kyo; Cheung, Gary Shun-Pan; Jeong, Seong Hwa; Bae, Yong Chul; Kim, Hyeon-Cheol

2015-01-01

This study was aimed to evaluate the effect of torsional preloads on the cyclic fatigue life of nickel-titanium (NiTi) instruments with different history of heat treatments by manufacturers. WaveOne (Primary) made of M-wire, K3XF (#30/0.06) of R-phase, and ProTaper (F2) of conventional NiTi alloy was used. Each file was preloaded at four conditions (nil, 25, 50, and 75% of their mean ultimate torsional strength) before fatigue testing. The torsional preloads 10-, 30-, or 50-times were applied by securing 5 mm of the file tip, rotating it until the preset torque was attained before returning to the origin. Then, the number of cycles to failure (NCF) was evaluated by rotational bending in a simulated canal. Data were analyzed using multiple linear regression analysis and two-way ANOVA. Fractured instruments were examined under scanning electron microscope (SEM). SEM showed that most WaveOne after 75% preloading, regardless of repetitions, showed some longitudinal cracks parallel to the long axis of the file, which were rare for K3XF. Regression analysis revealed that the brand of instrument was the most critical factor. At up to 75% preloading, ProTaper and K3XF did not show any significant decline in NCF. For 30-repetition groups of WaveOne, the 50 and 25% torsion preloaded groups showed a significantly higher NCF than the 0 and 75% groups. Within the limitations of this study, the alloy type of NiTi instrument have a significant effect on the phenomenon that a certain amount of torsional preload may improve the cyclic fatigue resistance of NiTi rotary instruments. © Wiley Periodicals, Inc.

Experimental Investigation of a Preloaded Spring-tab Flutter Model

NASA Technical Reports Server (NTRS)

Smith, N H; Clevenson, S A; Barmby, J G

1947-01-01

An experimental investigation was made of a preloaded spring-tab flutter model to determine the effects on flutter speed of aspect ratio, tab frequency, and preloaded spring constant. The rudder was mass-balanced, and the flutter mode studied was essentially one of three degrees of freedom (fin bending coupled with rudder and tab oscillations). Inasmuch as the spring was preloaded, the tab-spring system was a nonlinear one. Frequency of the tab was the most significant parameter in this study, and an increase in flutter speed with increasing frequency is indicated. At a given frequency, the tab of high aspect ratio is shown to have a slightly lower flutter speed than the one of low aspect ratio. Because the frequency of the preloaded spring tab was found to vary radically with amplitude, the flutter speed decreased with increase in initial displacement of the tab.

L-DOPA Preloading Increases the Uptake of Borophenylalanine in C6 Glioma Rat Model: A New Strategy to Improve BNCT Efficacy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capuani, Silvia; Enrico Fermi Center, Rome; Gili, Tommaso

Purpose: Boron neutron capture therapy (BNCT) is a radiotherapeutic modality based on {sup 10}B(n,{alpha}){sup 7}Li reaction, for the treatment of malignant gliomas. One of the main limitations for BNCT effectiveness is the insufficient intake of {sup 10}B nuclei in the tumor cells. This work was aimed at investigating the use of L-DOPA as a putative enhancer for {sup 10}B-drug 4-dihydroxy-borylphenylalanine (BPA) uptake in the C6-glioma model. The investigation was first performed in vitro and then extended to the animal model. Methods and Materials: BPA accumulation in C6-glioma cells was assessed using radiowave dielectric spectroscopy, with and without L-DOPA preloading. Twomore » L-DOPA incubation times (2 and 4 hours) were investigated, and the corresponding effects on BPA accumulation were quantified. C6-glioma cells were also implanted in the brain of 32 rats, and tumor growth was monitored by magnetic resonance imaging. Rats were assigned to two experimental branches: (1) BPA administration; (2) BPA administration after pretreatment with L-DOPA. All animals were sacrificed, and assessments of BPA concentrations in tumor tissue, normal brain, and blood samples were performed using high-performance liquid chromatography. Results: L-DOPA preloading induced a massive increase of BPA concentration in C6-glioma cells only after a 4-hour incubation. In the animal model, L-DOPA pretreatment produced a significantly higher accumulation of BPA in tumor tissue but not in normal brain and blood samples. Conclusions: This study suggests the potential use of L-DOPA as enhancer for BPA accumulation in malignant gliomas eligible for BNCT. L-DOPA preloading effect is discussed in terms of membrane transport mechanisms.« less

SPAR reference manual update SPAR level 15

NASA Technical Reports Server (NTRS)

Whetstone, W. D.

1980-01-01

Command runstream elements are presented for analyzing structural systems that are composed of a number of cyclically symmetrical sectors. Provisions are included for systems in which each cyclically symmetrical sector also possesses a plane of reflective symmetry. The following types of analysis may be performed: static analysis with and without preload, vibrational analysis with and without preload, and buckling analysis with and without preload.

Experimental and numerical investigation on laser-assisted bending of pre-loaded metal plate

NASA Astrophysics Data System (ADS)

Nowak, Zdzisław; Nowak, Marcin; Widłaszewski, Jacek; Kurp, Piotr

2018-01-01

The laser forming technique has an important disadvantage, which is the limitation of plastic deformation generated by a single laser beam pass. To increase the plastic deformation it is possible to apply external forces in the laser forming process. In this paper, we investigate the influence of external pre-loads on the laser bending of steel plate. The pre-loads investigated generate bending towards the laser beam. The thermal, elastic-plastic analysis is performed using the commercial nonlinear finite element analysis package ABAQUS. The focus of the paper is to identify how this pattern of the pre-load influence the final bend angle of the plate.

Preload, Coefficient of Friction, and Thread Friction in an Implant-Abutment-Screw Complex.

PubMed

Wentaschek, Stefan; Tomalla, Sven; Schmidtmann, Irene; Lehmann, Karl Martin

To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex. In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm. Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component. These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload.

Research on construction settlement of different soft foundation under vacuum preloading condition

NASA Astrophysics Data System (ADS)

Bin, LI; Changquan, YIN

2017-11-01

Vacuum preloading, rigid foundation, raft foundation and piled raft foundation are more commonly used in soft foundation treatment. PLAXIS is large finite element software of rock and soil, which can simulate the influence of different foundation forms. After the vacuum preloading treatment, the foundation settlement is reduced by 80%, the raft foundation settlement is reduced by 60%, the pile raft foundation settlement is reduced by 40%. It is suggested that the vacuum preloading is used to deal with the foundation of the building. If the time limit, the pile raft foundation is used as the foundation form of the foundation is better than others.

Evaluation of satiety sensations and food intake after different preloads.

PubMed

Porrini, M; Crovetti, R; Testolin, G; Silva, S

1995-08-01

The reproducibility of three questions, related to fullness, satiety and desire to eat, rated on an unmarked triangle was verified. In four sessions 12 volunteers ate pasta with tomato sauce (520 kcal) and were asked to rate the sensations felt. There was no difference in rating scores of the replications so the proposed questionnaire provides a stable measure of sensations related to satiety. Subsequently three satiety conditions were studied. Two foods, one rich in carbohydrate, pasta (baked macaroni) and the other in protein, polpette (meatballs), were used as loads at two calorie levels and as preload before an "ad libitum" meal. All the three questions proved useful in discriminating between the different satiety conditions. The food intake underlines the specificity of satiety: subjects, after eating a preload which previously had satiated them, ate other foods in different amounts depending on the kind of preload eaten. Food intake was significantly higher after the pasta preload, furthermore "fullness" and "satiety" ratings were significantly highest after the meatball preload, suggesting that in our experimental conditions, meatballs were more satiating than pasta. In conclusion, this study highlights the validity of using several quite different questions to study hunger and satiety, together with the actual food intake.

Soup preloads in a variety of forms reduce meal energy intake.

PubMed

Flood, Julie E; Rolls, Barbara J

2007-11-01

Consuming soup can enhance satiety and reduce energy intake. Little is known about the influence on energy intake and satiety of varying the form of soup by altering the blending of ingredients. We tested the effects on meal intake of consuming different forms of soup as a preload: broth and vegetables served separately, chunky vegetable soup, chunky-pureed vegetable soup, or pureed vegetable soup. Normal-weight men and women (n = 60) came to the laboratory for lunch once a week for 5 weeks. Each week, one of four compulsory preloads, or no preload, was consumed prior to lunch. A test meal was consumed ad libitum 15 min after the soup was served. Results showed that consuming soup significantly reduced test meal intake and total meal energy intake (preload + test meal) compared to having no soup. When soup was consumed, subjects reduced meal energy intake by 20% (134+/-25 kcal; 561+/-105 kJ). The type of soup had no significant effect on test meal intake or total meal energy intake. Consuming a preload of low-energy-dense soup, in a variety of forms, is one strategy for moderating energy intake in adults.

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening.

PubMed

Dincer Kose, Onur; Karataslı, Burcin; Demircan, Sabit; Kose, Taha Emre; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload.

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening

PubMed Central

Demircan, Sabit; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload. PMID:28473988

Effects of Fat and Protein Preloads on Pouch Emptying, Intestinal Transit, Glycaemia, Gut Hormones, Glucose Absorption, Blood Pressure and Gastrointestinal Symptoms After Roux-en-Y Gastric Bypass.

PubMed

Nguyen, Nam Q; Debreceni, Tamara L; Burgstad, Carly M; Neo, Melissa; Bellon, Max; Wishart, Judith M; Standfield, Scott; Bartholomeusz, Dylan; Rayner, Chris K; Wittert, Gary; Horowitz, Michael

2016-01-01

The aim was to determine the effects of fat and protein preloads on pouch emptying (PE), caecal arrival time (CAT), glucose absorption, blood glucose (BSL), gut hormones, haemodynamics and gastrointestinal (GI) symptoms in subjects who had undergone Roux-en-Y gastric bypass (RYGB) >12 months previously. Ten RYGB subjects were studied on three occasions, in randomised order, receiving 200-ml preloads of either water, fat (30 ml olive oil) or whey protein (55 g), 30 min before a mixed meal. PE, CAT, BSL, plasma 3-O-methyl-D-glucopyranose (3-OMG), insulin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1) and glucagon, blood pressure (BP), heart rate (HR) and GI symptoms were assessed over 270 min. Although fat and protein preloads did not alter PE of either solids or liquids, the CAT of solids, but not liquids, was longer than that after the water preload (fat 68 ± 5 min and protein 71 ± 6 min vs. water 46 ± 5 min; P = 0.02). BSL elevated promptly after the meal on all days (P < 0.001), but after protein, the magnitude and integrated increases in the first 75 min were less than fat and water preloads (area under the curve (AUC(0-75 min)), 18.7 ± 18.2 vs. 107.2 ± 30.4 and 76.1 ± 19.3 mmol/L/min; P < 0.05). Compared to water preload, the protein and fat preloads were associated with greater increases in plasma insulin, GLP-1 and glucagon concentrations, a reduction in BP, and greater increases in HR, fullness, bloating and nausea. Plasma 3-OMG levels were lower after the protein than after the water and fat preloads (P < 0.001). Given its effects to attenuate post-prandial glycaemia, reduce intestinal glucose absorption and potentiate the "incretin response", without inducing more adverse post-prandial GI symptom, protein preload may prove clinically useful in RYGB patients and warrant further evaluation, particularly in those with type 2 diabetes (T2DM) and/or dumping syndrome.

Traction Drives for Zero Stick-Slip Robots, and Reaction Free, Momentum Balanced Systems

NASA Technical Reports Server (NTRS)

Anderson, William J.; Shipitalo, William; Newman, Wyatt

1995-01-01

Two differential (dual input, single output) drives (a roller-gear and a pure roller), and a momentum balanced (single input, dual output) drive (pure roller ) were designed, fabricated, and tested. The differential drives are each rated at 295 rad/sec (2800 rpm) input speed, 450 N-m (4,000 in-lbf) output torque. The momentum balanced drive is rated at 302 rad/sec (2880 rpm) input speed, and dual output torques of 434N-m (3840 in-lbf). The Dual Input Differential Roller-Gear Drive (DC-700) has a planetary roller-gear system with a reduction ratio (one input driving the output with the second input fixed) of 29.23: 1. The Dual Input Differential Roller Drive (DC-500) has a planetary roller system with a reduction ratio of approximately 24:1. Each of the differential drives features dual roller-gear or roller arrangements consisting of a sun, four first row planets, four second row planets, and a ring. The Momentum Balanced (Grounded Ring) Drive (DC-400) has a planetary roller system with a reduction ratio of 24:1 with both outputs counterrotating at equal speed. Its single roller cluster consists of a sun, five first and five second row planets, a roller cage or spider and a ring. Outputs are taken from both the roller cage and the ring which counterrotate. Test results reported for all three drives include angular and torque ripple (linearity and cogging), viscous and Coulomb friction, and forward and reverse power efficiency. Of the two differential drives, the Differential Roller Drive had better linearity and less cogging than did the Differential Roller-Gear Drive, but it had higher friction and lower efficiency (particularly at low power throughput levels). Use of full preloading rather than a variable preload system in the Differential Roller Drive assessed a heavy penalty in part load efficiency. Maximum measured efficiency (ratio of power out to power in) was 95% for the Differential Roller-Gear Drive and 86% for the Differential Roller Drive. The Momentum Balanced (Grounded Ring) Drive performed as expected kinematically. Reduction r-atios to the two counterrotating outputs (design nominal=24:1) were measured to be 23.98:1 and 24.12:1 at zero load.. At 25ONm (2200 in-lbf) output torque the ratio changed 2% due to roller creep. This drive was the smoothest of all three as determined from linearity and cogging tests, and maximum measured efficiency (ratio of power out to power in) was 95%. The disadvantages of full preloading as comvared to variable preload were apparent in this drive as in the Differential Roller Drive. Efficiencies at part load were low, but improved dramatically with increases in torque. These were consistent with friction measurements which indicated losses primarily from Coulomb friction. The initial preload level setting was low so roller slip was encountered at higher torques during testing.

High-temperature, flexible, thermal barrier seal

NASA Technical Reports Server (NTRS)

Sirocky, Paul J. (Inventor); Steinetz, Bruce M. (Inventor)

1991-01-01

This device seals the sliding interfaces between structural panels that are roughly perpendicular to each other or whose edges are butted against one another. The nonuniformity of the gap between the panels requires significant flexibility along the seal length. The seal is mounted in a rectangular groove in a movable structural panel. A plurality of particles or balls is densely packed in an outer sheathing. The balls are laterally preloaded to maintain sealing contact with the adjacent wall using a pressurized linear bellows. Distortions in the adjacent panel are accommodated by rearrangement of the particles within the outer sheathing. Leakage through the seal is minimized by densely compacting the internal particles and by maintaining positive preload along the back side of the seal. The braid architecture of the outer sheathing is selected to minimize leakage through the seal and to resist mechanical abrasion.

REACT: Resettable Hold Down and Release Actuator for Space Applications

NASA Astrophysics Data System (ADS)

Nava, Nestor; Collado, Marcelo; Cabás, Ramiro

2014-07-01

A new HDRA based on SMA technology, called REACT, has been designed for development of loads and appendixes in space applications. This design involves a rod supported by spheres that block its axial movement during a preload application. The rod shape allows misalignment and blocks the rotation around axial axis for a proper installation of the device. Because of the high preload requirements for this type of actuators, finite element analysis (FEA) has been developed in order to check the structure resistance. The results of the FEA have constrained the REACT design, in terms of dimensions, materials, and shape of the mechanical parts. A complete test campaign for qualification of REACT is proposed. Several qualification models are intended to be built for testing in parallel. Therefore, it is a way to demonstrate margins which allows getting some statistics.

Determinants of diastolic myocardial tissue Doppler velocities: influences of relaxation and preload.

PubMed

Firstenberg, M S; Greenberg, N L; Main, M L; Drinko, J K; Odabashian, J A; Thomas, J D; Garcia, M J

2001-01-01

Myocardial tissue Doppler echocardiography (TDE) has been proposed as a tool for the assessment of diastolic function. Controversy exists regarding whether TDE measurements are influenced by preload. In this study, left ventricular volume and high-fidelity pressures were obtained in eight closed-chest dogs during intermittent caval occlusion. The time constant of isovolumic ventricular relaxation (tau) was altered with varying doses of dobutamine and esmolol. Peak early diastolic myocardial (E(m)) and transmitral (E) velocities were measured before and after preload reduction. The relative effects of changes in preload and relaxation were determined for E(m) and compared with their effects on E. The following results were observed: caval occlusion significantly decreased E (DeltaE = 16.4 +/- 3.3 cm/s, 36.6 +/- 13.7%, P < 0.01) and E(m) (DeltaE(m) = 1. 3 +/- 0.4 cm/s, 32.5 +/- 26.1%, P < 0.01) under baseline conditions. However, preload reduction was similar for E under all lusitropic conditions (P = not significant), but these effects on E(m) decreased with worsening relaxation. At tau < 50 ms, changes in E(m) with preload reduction were significantly greater (DeltaE(m) = 2.8 +/- 0.6 cm/s) than at tau = 50-65 ms (DeltaE(m) = 1.2 +/- 0.2 cm/s) and at tau >65 ms (DeltaE(m) = 0.5 +/- 0.1 cm/s, P < 0.05). We concluded that TDE E(m) is preload dependent. However, this effect decreases with worsening relaxation.

Accelerated Testing Methodology for the Determination of Slow Crack Growth of Advanced Ceramics

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Salem, Jonathan A.; Gyekenyesi, John P.

1997-01-01

Constant stress-rate (dynamic fatigue) testing has been used for several decades to characterize slow crack growth behavior of glass and ceramics at both ambient and elevated temperatures. The advantage of constant stress-rate testing over other methods lies in its simplicity: Strengths are measured in a routine manner at four or more stress rates by applying a constant crosshead speed or constant loading rate. The slow crack growth parameters (n and A) required for design can be estimated from a relationship between strength and stress rate. With the proper use of preloading in constant stress-rate testing, an appreciable saving of test time can be achieved. If a preload corresponding to 50 % of the strength is applied to the specimen prior to testing, 50 % of the test time can be saved as long as the strength remains unchanged regardless of the applied preload. In fact, it has been a common, empirical practice in strength testing of ceramics or optical fibers to apply some preloading (less then 40%). The purpose of this work is to study the effect of preloading on the strength to lay a theoretical foundation on such an empirical practice. For this purpose, analytical and numerical solutions of strength as a function of preloading were developed. To verify the solution, constant stress-rate testing using glass and alumina at room temperature and alumina silicon nitride, and silicon carbide at elevated temperatures was conducted in a range of preloadings from O to 90 %.

Increasing preload volume with water reduces rated appetite but not food intake in healthy men even with minimum delay between preload and test meal.

PubMed

Gray, Richard W; French, Stephen J; Robinson, Tristan M; Yeomans, Martin R

2003-02-01

The role of gastric volume in the short-term control of eating in humans remains unclear, with some studies reporting that food volume alone can reduce appetite but others finding no such effect. A recent study in our laboratory, found effects of preload volume on subjective appetite (hunger, fullness) but not intake, and found effects of preload energy on intake but not appetite. That study used an interval of 30 min between serving preloads and the test meal, and the present study attempted to maximise the effects of the volume manipulation by removing the delay between the preload and test meal. We administered four soup-based preloads varying in volume (150 and 450 ml) using water, and energy density (1.4 and 4.2 kJ/ml) using maltodextrin, producing three energy levels (209, 629, 629 and 1886 kJ; repeated measures). These were followed immediately by an unlimited hot pasta lunch, during which food weight was monitored continuously by computer. Increasing soup volume at constant energy (629 kJ) reduced appetite ratings, but not intake. In contrast, increasing soup energy at constant volume (450 ml) reduced intake, without affecting appetite. The discrepancies between our results and other reported studies suggest that volume is more influential when intakes are large, or that there may be a threshold concentration for nutrients in the GI tract before volume alone is tangibly expressed in subsequent eating.

Effects of Screw Configuration on the Preload Force of Implant-Abutment Screws.

PubMed

Zipprich, Holger; Rathe, Florian; Pinz, Sören; Schlotmann, Luca; Lauer, Hans-Christoph; Ratka, Christoph

The aim of this study was to investigate the effects of tightening torque, screw head angle, and thread number on the preload force of abutment screws. The test specimens consisted of three self-manufactured components (ie, a thread sleeve serving as an implant analog, an abutment analog, and an abutment screw). The abutment screws were fabricated with metric M1.6 external threads. The thread number varied between one and seven threads. The screw head angles were produced in eight varying angles (30 to 180 degrees). A sensor unit simultaneously measured the preload force of the screw and the torsion moment inside the screw shank. The tightening of the screw with the torque wrench was performed in five steps (15 to 35 Ncm). The torque wrench was calibrated before each step. Only the tightening torque and screw head angle affected the resulting preload force of the implant-abutment connection. The thread number had no effect. There was an approximately linear correlation between tightening torque and preload force. The tightening torque and screw head angle were the only study parameters that affected the resulting preload force of the abutment screw. The results obtained from this experiment are valid only for a single torque condition. Further investigations are needed that analyze other parameters that affect preload force. Once these parameters are known, it will add value for a strong, but detachable connection between the implant and abutment. Short implants and flat-to-flat connections especially will benefit significantly from this knowledge.

Viscosity of fiber preloads affects food intake in adolescents.

PubMed

Vuksan, V; Panahi, S; Lyon, M; Rogovik, A L; Jenkins, A L; Leiter, L A

2009-09-01

Dietary fiber that develops viscosity in the gastrointestinal tract is capable of addressing various aspects of food intake control. The aim of this study was to assess subsequent food intake and appetite in relation to the level of viscosity following three liquid preloads each containing 5 g of either a high (novel viscous polysaccharide; NVP), medium (glucomannan; GLM), or low (cellulose; CE) viscosity fiber. In this double-blind, randomized, controlled and crossover trial, 31 healthy weight adolescents (25 F:6 M; age 16.1+/-0.6 years; BMI 22.2+/-3.7 kg/m(2)) consumed one of the three preloads 90 min prior to an ad libitum pizza meal. Preloads were identical in taste, appearance, nutrient content and quantity of fiber, but different in their viscosities (10, 410, and 700 poise for CE, GLM, and NVP, respectively). Pizza intake was significantly lower (p=0.008) after consumption of the high-viscosity NVP (278+/-111 g) compared to the medium-viscosity GLM (313+/-123 g) and low-viscosity CE (316+/-138 g) preloads, with no difference between the GLM and CE preloads. Appetite scores, physical symptoms and 24-h intake did not differ among treatment groups. A highly viscous NVP preload leads to reduced subsequent food intake, in terms of both gram weight and calories, in healthy weight adolescents. This study provides preliminary evidence of an independent contribution of viscosity on food intake and may form a basis for further studies on factors influencing food intake in adolescents.

Cable-driven elastic parallel humanoid head with face tracking for Autism Spectrum Disorder interventions.

PubMed

Su, Hao; Dickstein-Fischer, Laurie; Harrington, Kevin; Fu, Qiushi; Lu, Weina; Huang, Haibo; Cole, Gregory; Fischer, Gregory S

2010-01-01

This paper presents the development of new prismatic actuation approach and its application in human-safe humanoid head design. To reduce actuator output impedance and mitigate unexpected external shock, the prismatic actuation method uses cables to drive a piston with preloaded spring. By leveraging the advantages of parallel manipulator and cable-driven mechanism, the developed neck has a parallel manipulator embodiment with two cable-driven limbs embedded with preloaded springs and one passive limb. The eye mechanism is adapted for low-cost webcam with succinct "ball-in-socket" structure. Based on human head anatomy and biomimetics, the neck has 3 degree of freedom (DOF) motion: pan, tilt and one decoupled roll while each eye has independent pan and synchronous tilt motion (3 DOF eyes). A Kalman filter based face tracking algorithm is implemented to interact with the human. This neck and eye structure is translatable to other human-safe humanoid robots. The robot's appearance reflects a non-threatening image of a penguin, which can be translated into a possible therapeutic intervention for children with Autism Spectrum Disorders.

Mechanical end joint system for connecting structural column elements

NASA Technical Reports Server (NTRS)

Bush, Harold G. (Inventor); Mikulas, Martin M., Jr. (Inventor); Wallsom, Richard E. (Inventor)

1990-01-01

A mechanical end joint system is presented that eliminates the possibility of free movements between the joint halves during loading or vibration. Both node joint body (NJB) and column end joint body (CEJB) have cylindrical engaging ends. Each of these ends has an integral semicircular tongue and groove. The two joint halves are engaged transversely - the tongue of the NJB mating with the groove of the CEJB and vice versa. The joint system employs a spring loaded internal latch mechanism housed in the CEJB. During mating, this mechanism is pushed away from the NJB and enters the NJB when mating is completed. In order to lock the joint and add a preload across the tongue and groove faces, an operating ring collar is rotated through 45 deg causing an internal mechanism to compress a Belleville washer preload mechanism. This causes an equal and opposite force to be exerted on the latch bolt and the latch plunger. This force presses the two joint halves tightly together. In order to prevent inadvertent disassembly, a secondary lock is also engaged when the joint is closed. Plungers are carried in the operating ring collar. When the joint is closed, the plungers fall into tracks on the CEJB, which allows the joint to be opened only when the operating ring collar and plungers are pushed directly away from the joining end. One application of this invention is the rapid assembly and disassembly of diverse skeletal framework structures which is extremely important in many projects involving the exploration of space.

Cardiovascular studies using the chimpanzee (Pan troglodytes)

NASA Technical Reports Server (NTRS)

Hinds, J. E.; Cothran, L. N.; Hawthorne, E. W.

1977-01-01

Despite the phylogenetic similarities between chimpanzees and man, there exists a paucity of reliable data on normal cardiovascular function and the physiological responses of the system to standard interventions. Totally implanted biotelemetry systems or hardwire analog techniques were used to examine the maximum number of cardiovascular variables which could be simultaneously monitored without significantly altering the system's performance. This was performed in order to acquire base-line data not previously obtained in this species, to determine cardiovascular response to specific forcing functions such as ventricular pacing, drug infusions, and lower body negative pressure. A cardiovascular function profile protocol was developed in order to adjust independently the three major factors which modify ventricular performance, namely, left ventricular performance, left ventricular preload, afterload, and contractility. Cardiac pacing at three levels above the ambient rate was used to adjust end diastolic volume (preload). Three concentrations of angiotensin were infused continuously to evaluate afterload in a stepwide fashion. A continuous infusion of dobutamine was administered to raise the manifest contractile state of the heart.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Yi; Keller, Jonathan; Zhang, Zhiwei

The planetary load sharing characteristics of wind turbine gearboxes supported by cylindrical roller bearings (CRBs) and preloaded tapered roller bearings (TRBs) when subjected to rotor moments are compared in this work. Planetary bearing loads were measured in field-representative dynamometer tests and compared to loads predicted by finite-element models. Load sharing was significantly improved with preloaded TRBs. In pure torque conditions, the upwind planet bearing loads in the gearbox with preloaded TRBs were a maximum of 1.14 compared to 1.47 in the gearbox with CRBs. Consequently, the predicted fatigue life of the complete set of planetary bearings for the gearbox withmore » preloaded TRBs is 3.5 times greater than that of the gearbox with CRBs.« less

The impact of caloric preloading on attempts at food and eating-related thought suppression in restrained and unrestrained eaters.

PubMed

O'Connell, Cara; Larkin, Kevin; Mizes, J Scott; Fremouw, William

2005-07-01

The current study examined the impact of dietary restraint and caloric preload on thought suppression in a sample of 64 college females classified as either restrained or unrestrained eaters. Participants engaged in a 60-min laboratory session. One half of the participants were preloaded with a high-calorie milkshake and all participants were randomly assigned to a food and eating-related thought suppression condition or a no suppression control condition. Food-related thoughts were assessed with a digital counter and verbal references to food were tracked with an audio recorder. Restrained participants instructed to suppress food-related thoughts demonstrated significantly more food and eating-related thoughts than unrestrained participants. Preloading was associated with an increase in the frequency of indirect mentions to food and eating. Although the hypothesized "rebound" effect did not occur for any study groups, these findings indicate that both restraint status and preloading impact food and eating-related thoughts. Copyright 2005 by Wiley Periodicals, Inc

Impaired Left Ventricular Filling in COPD and Emphysema: Is It the Heart or the Lungs?

PubMed Central

Smith, Benjamin M.; Prince, Martin R.; Hoffman, Eric A.; Bluemke, David A.; Liu, Chia-Ying; Rabinowitz, Dan; Hueper, Katja; Parikh, Megha A.; Gomes, Antoinette S.; Michos, Erin D.; Lima, João A. C.; Barr, R. Graham

2013-01-01

Background: COPD and heart failure with preserved ejection fraction overlap clinically, and impaired left ventricular (LV) filling is commonly reported in COPD. The mechanism underlying these observations is uncertain, but may include upstream pulmonary dysfunction causing low LV preload or intrinsic LV dysfunction causing high LV preload. The objective of this study is to determine if COPD and emphysema are associated with reduced pulmonary vein dimensions suggestive of low LV preload. Methods: The population-based Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited smokers aged 50 to 79 years who were free of clinical cardiovascular disease. COPD was defined by spirometry. Percent emphysema was defined as regions < −910 Hounsfield units on full-lung CT scan. Ostial pulmonary vein cross-sectional area was measured by contrast-enhanced cardiac magnetic resonance and expressed as the sum of all pulmonary vein areas. Linear regression was used to adjust for age, sex, race/ethnicity, body size, and smoking. Results: Among 165 participants, the mean (± SD) total pulmonary vein area was 558 ± 159 mm2 in patients with COPD and 623 ± 145 mm2 in control subjects. Total pulmonary vein area was smaller in patients with COPD (−57 mm2; 95% CI, −106 to −7 mm2; P = .03) and inversely associated with percent emphysema (P < .001) in fully adjusted models. Significant decrements in total pulmonary vein area were observed among participants with COPD alone, COPD with emphysema on CT scan, and emphysema without spirometrically defined COPD. Conclusions: Pulmonary vein dimensions were reduced in COPD and emphysema. These findings support a mechanism of upstream pulmonary causes of underfilling of the LV in COPD and in patients with emphysema on CT scan. PMID:23764937

Influence of abutment type and esthetic veneering on preload maintenance of abutment screw of implant-supported crowns.

PubMed

Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

2014-02-01

The effect of veneering materials on screw joint stability remains inconclusive. Thus, this study evaluated the preload maintenance of abutment screws of single crowns fabricated with different abutments and veneering materials. Sixty crowns were divided into five groups (n = 12): UCLA abutment in gold alloy with ceramic (group GC) and resin (group GR) veneering, UCLA abutment in titanium with ceramic (group TiC) and resin (group TiR) veneering, and zirconia abutment with ceramic veneering (group ZiC). Abutment screws made of gold were used with a 35 Ncm insertion torque. Detorque measurements were obtained initially and after mechanical cycling. Data were analyzed by ANOVA and Fisher's exact test at a significance level of 5%. For the initial detorque means (in Ncm), group TiC (21.4 ± 1.78) exhibited statistically lower torque maintenance than groups GC (23.9 ± 0.91), GR (24.1 ± 1.34), and TiR (23.2 ± 1.33) (p < 0.05, Fisher's exact test). Group ZiC (21.9 ± 2.68) exhibited significantly lower torque maintenance than groups GC, GR, and TiR (p < 0.05, Fisher's exact test). After mechanical cycling, there was a statistically significant difference between groups TiC (22.1 ± 1.86) and GR (23.8 ± 1.56); between groups ZiC (21.7 ± 2.02) and GR; and also between groups ZiC and TiR (23.6 ± 1.30) (p < 0.05, Fisher's exact test). Detorque reduction occurred regardless of abutment type and veneering material. More irregular surfaces in the hexagon area of the castable abutments were observed. The superiority of any veneering material concerning preload maintenance was not established. © 2013 by the American College of Prosthodontists.

The effect of fruit in different forms on energy intake and satiety at a meal.

PubMed

Flood-Obbagy, Julie E; Rolls, Barbara J

2009-04-01

Consuming whole fruit reduces ratings of satiety more than fruit juice, but little is known about the effects of different forms of fruit on subsequent energy intake. This study tested how consuming preloads of apples in different forms prior to a meal (apple, applesauce, and apple juice with and without added fiber) influences satiety and energy intake at meal. Preloads were matched for weight, energy content, energy density, and ingestion rate. Once a week for 5 weeks, 58 adults consumed one of four preloads (266 g; 125 kcal [523 kJ]), or no preload (control), followed by a test meal consumed ad libitum 15 min later. Results showed that eating apple reduced lunch energy intake (preload+test meal) by 15% (187+/-36 kcal [782+/-151 kJ]) compared to control (p<0.0001) and decreased energy intake compared to applesauce and both juices. Fullness ratings differed significantly after preload consumption (apple>applesauce>both juices>control). Overall, whole apple increased satiety more than applesauce or apple juice. Adding naturally occurring levels of fiber to juice did not enhance satiety. These results suggest that solid fruit affects satiety more than pureed fruit or juice, and that eating fruit at the start of a meal can reduce energy intake.

The effect of fruit in different forms on energy intake and satiety at a meal

PubMed Central

Flood-Obbagy, Julie E.; Rolls, Barbara J.

2009-01-01

Consuming whole fruit reduces ratings of satiety more than fruit juice, but little is known about the effects of different forms of fruit on subsequent energy intake. This study tested how consuming preloads of apples in different forms prior to a meal (apple, applesauce, and apple juice with and without added fiber) influences satiety and energy intake at meal. Preloads were matched for weight, energy content, energy density, and ingestion rate. Once a week for 5 weeks, 58 adults consumed one of four preloads (266 g; 125 kcal [523 kJ]), or no preload (control), followed by a test meal consumed ad libitum 15 min later. Results showed that eating apple reduced lunch energy intake (preload + test meal) by 15% (187 ± 36 kcal [782 ± 151 kJ]) compared to control (p < 0.0001) and decreased energy intake compared to applesauce and both juices. Fullness ratings differed significantly after preload consumption (apple > applesauce > both juices > control). Overall, whole apple increased satiety more than applesauce or apple juice. Adding naturally occurring levels of fiber to juice did not enhance satiety. These results suggest that solid fruit affects satiety more than pureed fruit or juice, and that eating fruit at the start of a meal can reduce energy intake. PMID:19110020

Influence of activated carbon preloading by EfOM fractions from treated wastewater on adsorption of pharmaceutically active compounds.

PubMed

Hu, Jingyi; Shang, Ran; Heijman, Bas; Rietveld, Luuk

2016-05-01

In this study, the preloading effects of different fractions of wastewater effluent organic matter (EfOM) on the adsorption of trace-level pharmaceutically active compounds (PhACs) onto granular activated carbon (GAC) were investigated. A nanofiltration (NF) membrane was employed to separate the EfOM by size, and two GACs with distinct pore structures were chosen for comparison. The results showed that preloading with EfOM substantially decreased PhAC uptake of the GACs; however, comparable PhAC adsorption capacities were achieved on GACs preloaded by feed EfOM and the NF-permeating EfOM. This indicates that: (1) the NF-rejected, larger EfOM molecules with an expectation to block the PhAC adsorption pores exerted little impact on the adsorbability of PhACs; (2) the smaller EfOM molecules present in the NF permeate contributed mainly to the decrease in PhAC uptake, mostly due to site competition. Of the two examined GACs, the wide pore-size-distributed GAC was found to be more susceptible to EfOM preloading than the microporous GAC. Furthermore, among the fourteen investigated PhACs, the negatively charged hydrophilic PhACs were generally subjected to a greater EfOM preloading impact. Copyright © 2016 Elsevier Ltd. All rights reserved.

Standardized static and dynamic evaluation of myocardial tissue properties.

PubMed

Ramadan, Sherif; Paul, Narinder; Naguib, Hani E

2017-03-20

Quantifying the mechanical behaviors of soft biological tissues is of considerable research interest. However, validity and reproducibility between different researchers and apparatus is questionable. This study aims to quantify the mechanical properties of myocardium while investigating methodologies that can standardize biological tissue testing. Tensile testing was performed to obtain Young's modulus and a dynamic mechanical analysis (DMA) determined the viscoelastic properties. A frequency range of 0.5 Hz (30bpm) to 3.5 Hz (210bpm) was analyzed. For tensile testing three different preconditioning settings were tested: no load, 0.05 N preload, and a cyclic preload at 2.5% strain and 10 cycles. Samples were placed in saline and tested at 37 °C. Five ovine and five porcine hearts were tested. Cyclic loading results in the most consistent moduli values. The modulus of ovine/porcine tissue was mean = 0.05/.06 MPa, SD = 0.02/0.03 MPa. The storage/loss modulus varied from = 0.02/0.003 MPa at 0.5 Hz to 0.04/0.008 MPa at 3.5 Hz; Stiffness increases linearly from 400 to 800 N m -1 with a tan delta around 0.175. Static analysis of the mechanical properties of myocardial tissue confirms that; preconditioning is necessary for reproducibility, and DMA provides a platform for reproducible testing of soft biological tissues.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

PubMed

Bezci, Semih E; Eleswarapu, Ananth; Klineberg, Eric O; O'Connell, Grace D

2018-02-12

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Analog-Computer Investigation of Effects of Friction and Preload on the Dynamic Longitudinal Characteristics of a Pilot-Airplane Combination

NASA Technical Reports Server (NTRS)

Crane, Harold L.

1961-01-01

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of these four friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the air-plane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 deg. out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

Analog-computer investigation of effects of friction and preload on the dynamic longitudinal characteristics of a pilot-airplane combination

NASA Technical Reports Server (NTRS)

Crane, Harold L

1957-01-01

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of thesefour friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the airplane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 degrees out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

The Effects of Torsional Preloading on the Torsional Resistance of Nickel-titanium Instruments.

PubMed

Oh, Seung-Hei; Ha, Jung-Hong; Kwak, Sang Won; Ahn, Shin Wook; Lee, WooCheol; Kim, Hyeon-Cheol

2017-01-01

This study evaluated the effect of torsional preloading on the torsional resistance of nickel-titanium (NiTi) endodontic instruments. WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper Universal F2 (Dentsply Maillefer) files were used. The ultimate torsional strength until fracture was determined for each instrument. In the phase 1 experiment, the ProTaper and WaveOne files were loaded to have a maximum load from 2.0 up to 2.7 or 2.8 Ncm, respectively. In the phase 2 experiment, the number of repetitions of preloading for each file was increased from 50 to 200, whereas the preloading torque was fixed at 2.4 Ncm. Using torsionally preloaded specimens from phase 1 and 2, the torsional resistances were calculated to determine the ultimate strength, distortion angle, and toughness. The results were analyzed using 1-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of 5 specimens per group were examined under a scanning electron microscope. All preloaded groups showed significantly higher ultimate strength than the unpreloaded groups (P < .05). There was no significant difference among all groups for distortion angle and toughness. Although WaveOne had no significant difference between the repetition groups for ultimate strength, fracture angle, and toughness, ProTaper had a higher distortion angle and toughness in the 50-repetition group compared with the other repetition groups (P < .05). Scanning electron microscopic examinations of the fractured surface showed typical features of torsional fracture. Torsional preloading within the ultimate values could enhance the torsional strength of NiTi instruments. The total energy until fracture was maintained constantly, regardless of the alloy type. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Loss of preload in screwed implant joints as a function of time and tightening/untightening sequences.

PubMed

Bernardes, Sérgio Rocha; da Gloria Chiarello de Mattos, Maria; Hobkirk, John; Ribeiro, Ricardo Faria

2014-01-01

The purpose of this study was to determine whether abutment screw tightening and untightening influenced loss of preload in three different implant/abutment interfaces, or on the implant body. Five custom-fabricated machined titanium implants were used, each with its respective abutment, with different connection types, retention screws, and torque values (external hexagon with titanium screw/32 Ncm, external hexagon with coated screw/32 Ncm, internal hexagon/20 Ncm and internal conical/20 and 32 Ncm). Each implant tested had two strain gauges attached and was submitted to five tightening/untightening sequences. External hexagons resulted in the lowest preload values generated in the implant cervical third (mean of 27.75 N), while the internal hexagon had the highest values (mean of 219.61 N). There was no immediate significant loss of preload after screw tightening. Tightening/untightening sequences, regardless of the implant/abutment interface design or type of screw used in the study, did not result in any significant loss of initial preload. Conical implant connections demonstrated greater structural reinforcement within the internal connections.

The vibration behavior of railway track at high frequencies under multiple preloads and wheel interactions

PubMed

Wu; Thompson

2000-09-01

The track foundation is preloaded by multiple wheel loads due to the train weight and, as the pad and ballast are nonlinear, their stiffness depends upon the preload in them. Due to the influence of these resilient components of the track, the track vibration is affected by the wheel loads. It is also affected by the wheel/rail interactions. In this article the preloads in the pad and ballast are calculated by considering the nonlinear properties of the track foundation, and thus the preloaded pad and ballast stiffnesses are determined. The vibration properties are explored for the track under multiple wheel loads and multiple wheel/rail interactions by comparing the results from different track models with and without these effects. It is found that the point receptance of the track is reduced and the vibration decay rate is enhanced at low frequencies due to the wheel loads. The effects of the wheel/rail interactions are most significant for frequencies 400-2000 Hz. Because of the wheel/rail interactions, the point receptance fluctuates and the vibration decay is enhanced in the regions around the wheels.

Incorporating general race and housing flexibility and deadband in rolling element bearing analysis

NASA Technical Reports Server (NTRS)

Davis, R. R.; Vallance, C. S.

1989-01-01

Methods for including the effects of general race and housing compliance and outer race-to-housing deadband (clearance) in rolling element bearing mechanics analysis is presented. It is shown that these effects can cause significant changes in bearing stiffness characteristics, which are of major importance in rotordynamic response of turbomachinery and other rotating systems. Preloading analysis is demonstrated with the finite element/contact mechanics hybrid method applied to a 45 mm angular contact ball bearing.

Simplified Design Method for Tension Fasteners

NASA Astrophysics Data System (ADS)

Olmstead, Jim; Barker, Paul; Vandersluis, Jonathan

2012-07-01

Tension fastened joints design has traditionally been an iterative tradeoff between separation and strength requirements. This paper presents equations for the maximum external load that a fastened joint can support and the optimal preload to achieve this load. The equations, based on linear joint theory, account for separation and strength safety factors and variations in joint geometry, materials, preload, load-plane factor and thermal loading. The strength-normalized versions of the equations are applicable to any fastener and can be plotted to create a "Fastener Design Space", FDS. Any combination of preload and tension that falls within the FDS represents a safe joint design. The equation for the FDS apex represents the optimal preload and load capacity of a set of joints. The method can be used for preliminary design or to evaluate multiple pre-existing joints.

Stud hardware with self-contained stud anti-rotation feature and method of installing studs

DOEpatents

Kartik, John S.; Richardson, William M.

1986-03-04

Disclosed herein is a method and apparatus for preventing the rotation of a stud member during preloading. The apparatus comprises a stud member having a shaft portion extending into the member to be clamped and a hex or double hex portion carrying a locking nut. Extending outward from the hex or double hex portion of the stud there is a threaded portion carrying a nut which is torqued to preload the stud. Between the locking nut and the member to be clamped is a locking ring which engages the locking nut to prevent the stud from rotating during preloading. Also disclosed is a method of preloading a stud without the use of an external restraint to prevent the stud from rotating when a torque is applied.

Ultrasonic extensometer measures bolt preload

NASA Technical Reports Server (NTRS)

Daniels, C. M., Jr.

1978-01-01

Extensometer using ultrasonic pulse reflections to measure elongations in tightened belts and studs is much more accurate than conventional torque wrenches in application of specified preload to bolts and other threaded fasteners.

Tool Preloads Screw and Applies Locknut

NASA Technical Reports Server (NTRS)

Wood, K. E.

1982-01-01

Special tool reaches through structural members inside Space Shuttle fasten nut on preloaded screw that holds thermal protection tile against outside skin of vehicle. Tool attaches tiles with accuratelycontrolled tensile loading.

External Catalyst Breakup Phenomena

DTIC Science & Technology

1976-06-01

catalyst particle can cause high internal pressures which result in particle destruction. Analytical results suggest rhat erosion effects from solid...mechanisms. * Pressure Forces. High G loadings and bed pressure drops should be avoided. Bed pre-loads should be kept at a minimum value. Thruster...5.2.7.1 Failure Theories ............................ 243 5.2.7.2 Maximum Tension Stress Criterion ............ 244 5.2.7.3 Distortion Energy Approach

Caloric compensation in preschool children: Relationships with body mass and differences by food category.

PubMed

Carnell, S; Benson, L; Gibson, E L; Mais, L A; Warkentin, S

2017-09-01

Maintaining a healthy weight may involve compensating for previously consumed calories at subsequent meals. To test whether heavier children demonstrated poorer caloric compensation across a range of conditions, and to explore whether compensation failure was the result of inadequate adjustment of overall intake or specific over-consumption of highly palatable, high energy-density 'junk' foods, we administered two compensation tests to a sample of 4-5 y olds. For Test A, preloads varied only in carbohydrate content and were organoleptically indistinguishable (200 ml orange-flavored beverage [0 kcal vs. 200 kcal]). For Test B, the preloads varied substantially in both macronutrient composition and learned gustatory cues to caloric content (200 ml water [0 kcal] vs. 200 ml strawberry milkshake [200 kcal]). Each preload was followed 30 min later by a multi-item ad-libitum meal containing junk foods (chocolate cookies, cheese-flavored crackers) and core foods (fruits and vegetables, bread rolls, protein foods). Testing took place at the children's own school under normal lunch-time conditions. Children were weighed and measured. Caloric compensation occurred in both tests, in terms of total, junk and core food intake (RMANOVA, all p < 0.01). Higher BMI z scores were associated with greater average caloric compensation (r = -0.26; p < 0.05), such that overweight/obese children showed least compensation (41%), children over the 50 th centile the next least (59%), and children under the 50 th centile (80%) the most. For Test A only, obese/overweight children compensated less well than normal-weight children in terms of junk food intake (RMANOVA preload-by-weight group interaction p < 0.05), with no significant effect for core foods. Our results suggest that caloric compensation is consistently poorer in heavier children, and that overweight/obese children's preferences for junk foods may overwhelm intake regulation mechanisms within meals containing those foods. Copyright © 2017 Elsevier Ltd. All rights reserved.

Noninvasive Assessment of Preload Reserve Enhances Risk Stratification of Patients With Heart Failure With Reduced Ejection Fraction.

PubMed

Matsumoto, Kensuke; Onishi, Akira; Yamada, Hirotsugu; Kusunose, Kenya; Suto, Makiko; Hatani, Yutaka; Matsuzoe, Hiroki; Tatsumi, Kazuhiro; Tanaka, Hidekazu; Hirata, Ken-Ichi

2018-05-01

The leg-positive pressure maneuver can safely and noninvasively apply preload stress without increase in total body fluid volume. The purpose of this study was to determine whether preload stress could be useful for risk stratification of patients with heart failure with reduced ejection fraction. For this study, 120 consecutive patients with heart failure with reduced ejection fraction were prospectively recruited. The stroke work index was estimated as product of stroke volume index and mean blood pressure, and the E/e' ratio was calculated to estimate ventricular filling pressure. The echocardiographic parameters were obtained both at rest and during leg-positive pressure stress. During the median follow-up period of 20 months, 30 patients developed adverse cardiovascular events. During preload stress, stroke work index increased significantly (from 3280±1371 to 3857±1581 mm Hg·mL/m 2 ; P <0.001) along with minimal changes in ventricular filling pressure (E/e', from 16±10 to 17±9; P <0.05) in patients without cardiovascular events. However, patients with cardiovascular events showed impairment of Frank-Starling mechanism (stroke work index, from 2863±969 to 2903±1084 mm Hg·mL/m 2 ; P =0.70) and a serious increase in E/e' ratio (from 19±11 to 25±14; P <0.001). Both the patients without contractile reserve and those without diastolic reserve exhibited worse event-free survival than the others ( P <0.001). In a Cox proportional-hazards analysis, the changes in stroke work index (hazard ratio: 0.44 per 500 mm Hg·mL/m 2 increase; P =0.001) and in E/e' (hazard ratio: 2.58 per 5-U increase; P <0.001) were predictors of cardiovascular events. Contractile reserve and diastolic reserve during leg-positive pressure stress are important determinants of cardiovascular outcomes for patients with heart failure with reduced ejection fraction. © 2018 American Heart Association, Inc.

Implications of the center of rotation concept for the reconstruction of anterior column lordosis and axial preloads in spinal deformity surgery.

PubMed

Koller, Heiko; Mayer, Michael; Zenner, Juliane; Resch, Herbert; Niederberger, Alfred; Fierlbeck, Johann; Hitzl, Wolfgang; Acosta, Frank L

2012-07-01

In thoracolumbar deformity surgery, anterior-only approaches are used for reconstruction of anterior column failures. It is generally advised that vertebral body replacements (VBRs) should be preloaded by compression. However, little is known regarding the impact of different techniques for generation of preloads and which surgical principle is best for restoration of lordosis. Therefore, the authors analyzed the effect of different surgical techniques to restore spinal alignment and lordosis as well as the ability to generate axial preloads on VBRs in anterior column reconstructions. The authors performed a laboratory study using 7 fresh-frozen specimens (from T-3 to S-1) to assess the ability for lordosis reconstruction of 5 techniques and their potential for increasing preloads on a modified distractable VBR in a 1-level thoracolumbar corpectomy. The testing protocol was as follows: 1) Radiographs of specimens were obtained. 2) A 1-level corpectomy was performed. 3) In alternating order, lordosis was applied using 1 of the 5 techniques. Then, preloads during insertion and after relaxation using the modified distractable VBR were assessed using a miniature load-cell incorporated in the modified distractable VBR. The modified distractable VBR was inserted into the corpectomy defect after lordosis was applied using 1) a lamina spreader; 2) the modified distractable VBR only; 3) the ArcoFix System (an angular stable plate system enabling in situ reduction); 4) a lordosizer (a customized instrument enabling reduction while replicating the intervertebral center of rotation [COR] according to the COR method); and 5) a lordosizer and top-loading screws ([LZ+TLS], distraction with the lordosizer applied on a 5.5-mm rod linked to 2 top-loading pedicle screws inserted laterally into the vertebra). Changes in the regional kyphosis angle were assessed radiographically using the Cobb method. The bone mineral density of specimens was 0.72 ± 22.6 g/cm(2). The maximum regional kyphosis angle reconstructed among the 5 techniques averaged 9.7°-16.1°, and maximum axial preloads averaged 123.7-179.7 N. Concerning correction, in decreasing order the LZ+TLS, lordosizer, and ArcoFix System outperformed the lamina spreader and modified distractable VBR. The order of median values for insertion peak load, from highest to lowest, were lordosizer, LZ+TLS, and ArcoFix, which outperformed the lamina spreader and modified distractable VBR. In decreasing order, the axial preload was highest with the lordosizer and LZ+TLS, which both outperformed the lamina spreader and the modified distractable VBR. The technique enabling the greatest lordosis achieved the highest preloads. With the ArcoFix System and LZ+TLS, compression loads could be applied and were 247.8 and 190.6 N, respectively, which is significantly higher than the insertion peak load and axial preload (p < 0.05). Including the ability for replication of the COR in instruments designed for anterior column reconstructions, the ability for lordosis restoration of the anterior column and axial preloads can increase, which in turn might foster fusion.

Testing of the new tuner design for the CEBAF 12 GeV upgrade SRF cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edward Daly; G. Davis; William Hicks

2005-05-01

The new tuner design for the 12 GeV Upgrade SRF cavities consists of a coarse mechanical tuner and a fine piezoelectric tuner. The mechanism provides a 30:1 mechanical advantage, is pre-loaded at room temperature and tunes the cavities in tension only. All of the components are located in the insulating vacuum space and attached to the helium vessel, including the motor, harmonic drive and piezoelectric actuators. The requirements and detailed design are presented. Measurements of range and resolution of the coarse tuner are presented and discussed.

Accelerated Testing Methodology Developed for Determining the Slow Crack Growth of Advanced Ceramics

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

1998-01-01

Constant stress-rate ("dynamic fatigue") testing has been used for several decades to characterize the slow crack growth behavior of glass and structural ceramics at both ambient and elevated temperatures. The advantage of such testing over other methods lies in its simplicity: strengths are measured in a routine manner at four or more stress rates by applying a constant displacement or loading rate. The slow crack growth parameters required for component design can be estimated from a relationship between strength and stress rate. With the proper use of preloading in constant stress-rate testing, test time can be reduced appreciably. If a preload corresponding to 50 percent of the strength is applied to the specimen prior to testing, 50 percent of the test time can be saved as long as the applied preload does not change the strength. In fact, it has been a common, empirical practice in the strength testing of ceramics or optical fibers to apply some preloading (<40 percent). The purpose of this work at the NASA Lewis Research Center is to study the effect of preloading on measured strength in order to add a theoretical foundation to the empirical practice.

Comparison of tricuspid inflow and superior vena caval Doppler velocities in acute simulated hypovolemia: new non-invasive indices for evaluating right ventricular preload.

PubMed

Liu, Jie; Cao, Tie-Sheng; Yuan, Li-Jun; Duan, Yun-You; Yang, Yi-Lin

2006-05-16

Assessment of cardiac preload is important for clinical management of some emergencies related to hypovolemia. Effects of acute simulated hypovolemia on Doppler blood flow velocity indices of tricuspid valve (TV) and superior vena cava (SVC) were investigated in order to find sensitive Doppler indices for predicting right ventricular preload. Doppler flow patterns of SVC and TV in 12 healthy young men were examined by transthoracic echocardiography (TTE) during graded lower body negative pressure (LBNP) of up to -60 mm Hg which simulated acute hypovolemia. Peak velocities of all waves and their related ratios (SVC S/D and tricuspid E/A) were measured, calculated and statistically analyzed. Except for the velocity of tricuspid A wave, velocities of all waves and their related ratios declined during volume decentralization. Of all indices measured, the peak velocities of S wave and AR wave in SVC correlated most strongly with levels of LBNP (r = -0.744 and -0.771, p < 0.001). The S and AR velocities are of good values in assessing right ventricular preload. Monitoring SVC flow may provide a relatively noninvasive means to assess direct changes in right ventricular preload.

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

Mechanical modeling and characterization of meniscus tissue using flat punch indentation and inverse finite element method.

PubMed

Seyfi, Behzad; Fatouraee, Nasser; Imeni, Milad

2018-01-01

In this paper, to characterize the mechanical properties of meniscus by considering its local microstructure, a novel nonlinear poroviscoelastic Finite Element (FE) model has been developed. To obtain the mechanical response of meniscus, indentation experiments were performed on bovine meniscus samples. The ramp-relaxation test scenario with different depths and preloads was designed to capture the mechanical characteristics of the tissue in different regions of the medial and lateral menisci. Thereafter, a FE simulation was performed considering experimental conditions. Constitutive parameters were optimized by solving a FE-based inverse problem using the heuristic Simulated Annealing (SA) optimization algorithm. These parameters were ranged according to previously reported data to improve the optimization procedure. Based on the results, the mechanical properties of meniscus were highly influenced by both superficial and main layers. At low indentation depths, a high percentage relaxation (p < 0.01) with a high relaxation rate (p < 0.05) was obtained, due to the poroelastic and viscoelastic nature of the superficial layer. Increasing both penetration depth and preload level involved the main layer response and caused alterations in hyperelastic and viscoelastic parameters of the tissue, such that for both layers, the shear modulus was increased (p < 0.01) while the rate and percentage of relaxation were decreased (p < 0.01). Results reflect that, shear modulus of the main layer in anterior region is higher than central and posterior sites in medial meniscus. In contrast, in lateral meniscus, posterior side is stiffer than central and anterior sides. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Gas-Spring-Loaded X-Y-Z Stage System for X-ray Microdiffraction Sample Manipulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu Deming; Cai Zhonghou; Lai, Barry

2007-01-19

We have designed and constructed a gas-spring-loaded x-y-z stage system for x-ray microdiffraction sample manipulation at the Advanced Photon Source XOR 2-ID-D station. The stage system includes three DC-motor-driven linear stages and a gas-spring-based heavy preloading structure, which provides antigravity forces to ensure that the stage system keeps high-positioning performance under variable goniometer orientation. Microdiffraction experiments with this new stage system showed significant sample manipulation performance improvement.

A Gas-Spring-Loaded X-Y-Z Stage System for X-ray Microdiffraction Sample Manipulation

NASA Astrophysics Data System (ADS)

Shu, Deming; Cai, Zhonghou; Lai, Barry

2007-01-01

We have designed and constructed a gas-spring-loaded x-y-z stage system for x-ray microdiffraction sample manipulation at the Advanced Photon Source XOR 2-ID-D station. The stage system includes three DC-motor-driven linear stages and a gas-spring-based heavy preloading structure, which provides antigravity forces to ensure that the stage system keeps high-positioning performance under variable goniometer orientation. Microdiffraction experiments with this new stage system showed significant sample manipulation performance improvement.

WaterWorld, a spatial hydrological model applied at scales from local to global: key challenges to local application

NASA Astrophysics Data System (ADS)

Burke, Sophia; Mulligan, Mark

2017-04-01

WaterWorld is a widely used spatial hydrological policy support system. The last user census indicates regular use by 1029 institutions across 141 countries. A key feature of WaterWorld since 2001 is that it comes pre-loaded with all of the required data for simulation anywhere in the world at a 1km or 1 ha resolution. This means that it can be easily used, without specialist technical ability, to examine baseline hydrology and the impacts of scenarios for change or management interventions to support policy formulation, hence its labelling as a policy support system. WaterWorld is parameterised by an extensive global gridded database of more than 600 variables, developed from many sources, since 1998, the so-called simTerra database. All of these data are available globally at 1km resolution and some variables (terrain, land cover, urban areas, water bodies) are available globally at 1ha resolution. If users have access to better data than is pre-loaded, they can upload their own data. WaterWorld is generally applied at the national or basin scale at 1km resolution, or locally (for areas of <10,000km2) at 1ha resolution, though continental (1km resolution) and global (10km resolution) applications are possible so it is a model with local to global applications. WaterWorld requires some 140 maps to run including monthly climate data, land cover and use, terrain, population, water bodies and more. Whilst publically-available terrain and land cover data are now well developed for local scale application, climate and land use data remain a challenge, with most global products being available at 1km or 10km resolution or worse, which is rather coarse for local application. As part of the EartH2Observe project we have used WFDEI (WATCH Forcing Data methodology applied to ERA-Interim data) at 1km resolution to provide an alternative input to WaterWorld's preloaded climate data. Here we examine the impacts of that on key hydrological outputs: water balance, water quality and outline the remaining challenges of using datasets like these for local scale application.

Effects of different sweet preloads on incretin hormone secretion, gastric emptying, and postprandial glycemia in healthy humans.

PubMed

Wu, Tongzhi; Zhao, Beiyi R; Bound, Michelle J; Checklin, Helen L; Bellon, Max; Little, Tanya J; Young, Richard L; Jones, Karen L; Horowitz, Michael; Rayner, Christopher K

2012-01-01

Macronutrient "preloads" can stimulate glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), slow gastric emptying, and reduce postprandial glycemic excursions. After sweet preloads, these effects may be signaled by sodium-glucose cotransporter-1 (SGLT1), sweet taste receptors, or both. We determined the effects of 4 sweet preloads on GIP and GLP-1 release, gastric emptying, and postprandial glycemia. Ten healthy subjects were studied on 4 separate occasions each. A preload drink containing 40 g glucose, 40 g tagatose/isomalt mixture (TIM), 40 g 3-O-methylglucose (3OMG; a nonmetabolized substrate of SGLT1), or 60 mg sucralose was consumed 15 min before a (13)C-octanoic acid-labeled mashed potato meal. Blood glucose, plasma total GLP-1 and GIP, serum insulin, and gastric emptying were determined. Both glucose and 3OMG stimulated GLP-1 and GIP release in advance of the meal (each P < 0.05), whereas TIM and sucralose did not. The overall postprandial GLP-1 response was greater after glucose, 3OMG, and TIM than after sucralose (P < 0.05), albeit later after TIM than the other preloads. The blood glucose and insulin responses in the first 30 min after the meal were greatest after glucose (each P < 0.05). Gastric emptying was slower after both 3OMG and TIM than after sucralose (each P < 0.05). In healthy humans, SGLT1 substrates stimulate GLP-1 and GIP and slow gastric emptying, regardless of whether they are metabolized, whereas the artificial sweetener sucralose does not. Poorly absorbed sweet tastants (TIM), which probably expose a greater length of gut to nutrients, result in delayed GLP-1 secretion but not in delayed GIP release. These observations have the potential to optimize the use of preloads for glycemic control. This trial was registered at www.actr.org.au as ACTRN12611000775910.

Knee joint passive stiffness and moment in sagittal and frontal planes markedly increase with compression.

PubMed

Marouane, H; Shirazi-Adl, A; Adouni, M

2015-01-01

Knee joints are subject to large compression forces in daily activities. Due to artefact moments and instability under large compression loads, biomechanical studies impose additional constraints to circumvent the compression position-dependency in response. To quantify the effect of compression on passive knee moment resistance and stiffness, two validated finite element models of the tibiofemoral (TF) joint, one refined with depth-dependent fibril-reinforced cartilage and the other less refined with homogeneous isotropic cartilage, are used. The unconstrained TF joint response in sagittal and frontal planes is investigated at different flexion angles (0°, 15°, 30° and 45°) up to 1800 N compression preloads. The compression is applied at a novel joint mechanical balance point (MBP) identified as a point at which the compression does not cause any coupled rotations in sagittal and frontal planes. The MBP of the unconstrained joint is located at the lateral plateau in small compressions and shifts medially towards the inter-compartmental area at larger compression forces. The compression force substantially increases the joint moment-bearing capacities and instantaneous angular rigidities in both frontal and sagittal planes. The varus-valgus laxities diminish with compression preloads despite concomitant substantial reductions in collateral ligament forces. While the angular rigidity would enhance the joint stability, the augmented passive moment resistance under compression preloads plays a role in supporting external moments and should as such be considered in the knee joint musculoskeletal models.

Passive control of a biventricular assist device with compliant inflow cannulae.

PubMed

Gregory, Shaun David; Pearcy, Mark John; Timms, Daniel

2012-08-01

Rotary ventricular assist device (VAD) support of the cardiovascular system is susceptible to suction events due to the limited preload sensitivity of these devices. This may be of particular concern with rotary biventricular support (BiVAD) where the native, flow balancing Starling response is diminished in both ventricles. The reliability of sensor and sensorless-based control systems which aim to control VAD flow based on preload has limitations, and, thus, an alternative solution is desired. This study introduces a compliant inflow cannula (CIC) which could improve the preload sensitivity of a rotary VAD by passively altering VAD flow depending on preload. To evaluate the design, both the CIC and a standard rigid inflow cannula were inserted into a mock circulation loop to enable biventricular heart failure support using configurations of atrial and ventricular inflow, and arterial outflow cannulation. A range of left (LVAD) and right VAD (RVAD) rotational speeds were tested as well as step changes in systemic/pulmonary vascular resistance to alter relative preloads, with resulting flow rates recorded. Simulated suction events were observed, particularly at higher VAD speeds, during support with the rigid inflow cannula, while the CIC prevented suction events under all circumstances. The compliant section passively restricted its internal diameter as preload was reduced, which increased the VAD circuit resistance and thus reduced VAD flow. Therefore, a CIC could potentially be used as a passive control system to prevent suction events in rotary left, right, and biventricular support. © 2012, Copyright the Authors. Artificial Organs © 2012, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Assessing the impact of preload on pyrite-rich sediment and groundwater quality.

PubMed

Karikari-Yeboah, Ohene; Addai-Mensah, Jonas

2017-02-01

Pyrite-rich sediments would, invariably, undergo redox reactions which would lead to acidic aqueous environment containing solubilized toxic metal species. When such sediments are subjected to preload, a technique employed by geotechnical engineers to improve the load-bearing capacity of highly compressible formation, transient flow of pore water, accompanied by acidity transfer, would occur as a response. Despite the concomitant environmental and socio-economic significance, to date, there has been limited interdisciplinary research on the underpinning geotechnical engineering and geo-environmental science issues for pyrite-rich sediments under preload. In this study, we investigate the effect of pyrite-rich sediment pore water transfer under preload surcharge on the receiving environment and the impact on the groundwater speciation and quality. Sediment samples were obtained at close depth intervals from boreholes established within pristine areas and those subjected to the preload application. Soil and pore water samples were subjected to solid/solution speciation, moisture contents, soil pH and the Atterberg Limits' analyses using standard analytical techniques and methods. Standpipes were also installed in the boreholes for groundwater sampling and in situ monitoring of water quality parameters. It is shown that the imposition of preload surcharge over pyritic sediment created a reducing environment rich in SO 4 2- , iron oxide minerals and organic matter. This reducing environment fostered organic carbon catabolism to generate excess pyrite and bicarbonate alkalinity, which would invariably impact adversely on soil quality and plant growth. These were accompanied by increase in pH, dissolved Al, Ca, Mg and K species beneath the surcharge.

Protein-Enriched Liquid Preloads Varying in Macronutrient Content Modulate Appetite and Appetite-Regulating Hormones in Healthy Adults.

PubMed

Dougkas, Anestis; Östman, Elin

2016-03-01

Dietary protein is considered the most satiating macronutrient, yet there is little evidence on whether the effects observed are attributable to the protein or to the concomitant manipulation of carbohydrates and fat. The aim was to examine the effect of consumption of preloads varying in macronutrient content on appetite, energy intake, and biomarkers of satiety. Using a randomized, within-subjects, 2-level factorial design, 36 adults [mean ± SD age: 27 ± 5 y; body mass index (in kg/m(2)): 24.3 ± 1.6) received a breakfast consisting of 1 of 7 isovolumetric (670 mL) and isoenergetic (2100 kJ) liquid preloads matched for energy density and sensory properties but with different macronutrient composition (levels: 9%, 24%, or 40% of energy from protein combined with a carbohydrate-to-fat ratio of 0.4, 2, or 3.6, respectively). Appetite ratings and blood samples were collected and assessed at baseline and every 30 and 60 min, respectively, until a lunch test meal, which participants consumed ad libitum, was served 3.5 h after breakfast. Prospective consumption was 12% lower after intake of the high-protein (40%)/3.6 carbohydrate:fat preload than after intake of the low-protein (9%)/0.4 carbohydrate:fat preload (P = 0.02) solely because of the increased protein, irrespective of the manipulation of the other macronutrients. Most appetite ratings tended to be suppressed (13%) with increasing protein content of the preloads (P < 0.06). Carbohydrate elicited greater increases in fullness and postprandial responses of glucose and insulin than did protein and fat. The glucose concentration was suppressed and glucagon-like peptide 1 increased more after intake of the high-protein (40%)/0.4 carbohydrate:fat preload than after the other preloads (P < 0.001). No statistically significant differences in postprandial ghrelin release or ad libitum energy intake at lunch were found. By varying all 3 macronutrients simultaneously and in a systematically balanced manner, we found that protein had a more pronounced effect on suppressing appetite than did carbohydrates and fat. Modulating the nutritional profile of a meal by replacing fat with protein can influence appetite in healthy adults. This trial was registered at www.clinicaltrials.gov as NCT01849302. © 2016 American Society for Nutrition.

Solid Rocket Booster Hydraulic Pump Port Cap Joint Load Testing

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; Murphy, N. C.

2004-01-01

The solid rocket booster uses hydraulic pumps fabricated from cast C355 aluminum alloy, with 17-4 PH stainless steel pump port caps. Corrosion-resistant steel, MS51830 CA204L self-locking screw thread inserts are installed into C355 pump housings, with A286 stainless steel fasteners installed into the insert to secure the pump port cap to the housing. In the past, pump port cap fasteners were installed to a torque of 33 Nm (300 in-lb). However, the structural analyses used a significantly higher nut factor than indicated during tests conducted by Boeing Space Systems. When the torque values were reassessed using Boeing's nut factor, the fastener preload had a factor of safety of less than 1, with potential for overloading the joint. This paper describes how behavior was determined for a preloaded joint with a steel bolt threaded into steel inserts in aluminum parts. Finite element models were compared with test results. For all initial bolt preloads, bolt loads increased as external applied loads increased. For higher initial bolt preloads, less load was transferred into the bolt, due to external applied loading. Lower torque limits were established for pump port cap fasteners and additional limits were placed on insert axial deformation under operating conditions after seating the insert with an initial preload.

Effects on abstinence of nicotine patch treatment before quitting smoking: parallel, two arm, pragmatic randomised trial.

PubMed

2018-06-13

To examine the effectiveness of a nicotine patch worn for four weeks before a quit attempt. Randomised controlled open label trial. Primary care and smoking cessation clinics in England, 2012-15. 1792 adults who were daily smokers with tobacco dependence. 899 were allocated to the preloading arm and 893 to the control arm. Participants were randomised 1:1, using concealed randomly permuted blocks stratified by centre, to either standard smoking cessation pharmacotherapy and behavioural support or the same treatment supplemented by four weeks of 21 mg nicotine patch use before quitting: "preloading." The primary outcome was biochemically confirmed prolonged abstinence at six months. Secondary outcomes were prolonged abstinence at four weeks and 12 months. Biochemically validated abstinence at six months was achieved by 157/899 (17.5%) participants in the preloading arm and 129/893 (14.4%) in the control arm: difference 3.0% (95% confidence interval -0.4% to 6.4%), odds ratio 1.25 (95% confidence interval 0.97 to 1.62), P=0.08 in the primary analysis. There was an imbalance between arms in the frequency of varenicline use as post-cessation treatment, and planned adjustment for this gave an odds ratio for the effect of preloading of 1.34 (95% confidence interval 1.03 to 1.73), P=0.03: difference 3.8% (0.4% to 7.2%). At four weeks, the difference in prolonged abstinence unadjusted for varenicline use was odds ratio 1.21 (1.00 to 1.48), difference 4.3% (0.0% to 8.7%), P=0.05, and adjusted for varenicline use was 1.32 (1.08 to 1.62) P=0.007. At 12 months the odds ratio was 1.28 (0.97 to 1.69), difference 2.7% (-0.4% to 5.8%), P=0.09 unadjusted for varenicline use and after adjustment was 1.36 (1.02 to 1.80) P=0.04. 5.9% of participants discontinued preloading owing to intolerance. Gastrointestinal symptoms-chiefly nausea-occurred in 4.0% (2.2% to 5.9%) more people in the preloading arm than control arm. Eight serious adverse events occurred in the preloading arm and eight in the control arm (odds ratio 0.99, 0.36 to 2.75). Evidence was insufficient to confidently show that nicotine preloading increases subsequent smoking abstinence. The beneficial effect seems to have been masked by a concurrent reduction in the use of varenicline in people using nicotine preloading, and future studies should explore ways to mitigate this unintended effect. Current Controlled Trials ISRCTN33031001. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

No differences in satiety or energy intake after high-fructose corn syrup, sucrose, or milk preloads.

PubMed

Soenen, Stijn; Westerterp-Plantenga, Margriet S

2007-12-01

It is unclear whether energy-containing drinks, especially those sweetened with high-fructose corn syrup (HFCS), promote positive energy balance and thereby play a role in the development of obesity. The objective was to examine the satiating effects of HFCS and sucrose in comparison with milk and a diet drink. The effects of four 800-mL drinks [corrected] containing no energy or 1.5 MJ from sucrose, HFCS, or milk on satiety were assessed, first in 15 men and 15 women with a mean (+/-SD) body mass index (BMI; in kg/m(2)) of 22.1 +/- 1.9 according to visual analogue scales (VAS) and blood variables and second in 20 men and 20 women (BMI: 22.4 +/- 2.1) according to ingestion of a standardized ad libitum meal (granola cereal + yogurt, 10.1 kJ/g). Fifty minutes after consumption of the 1.5-MJ preload drinks containing sucrose, HFCS, or milk, 170%-mm VAS changes in satiety were observed. Glucagon-like peptide 1 (GLP-1) (P < 0.001) and ghrelin (P < 0.05) concentrations changed accordingly. Compensatory energy intake did not differ significantly between the 3 preloads and ranged from 30% to 45%. Energy intake compensations were related to satiety (r = 0.35, P < 0.05). No differences were observed between the effects of the sucrose- and HFCS-containing drinks on changes in VAS and on insulin, glucose, GLP-1, and ghrelin concentrations. Changes in appetite VAS ratings were a function of changes in GLP-1, ghrelin, insulin, and glucose concentrations. Energy balance consequences of HFCS-sweetened soft drinks are not different from those of other isoenergetic drinks, eg, a sucrose-drink or milk.

Development of a non-explosive release actuator using shape memory alloy wire.

PubMed

Yoo, Young Ik; Jeong, Ju Won; Lim, Jae Hyuk; Kim, Kyung-Won; Hwang, Do-Soon; Lee, Jung Ju

2013-01-01

We have developed a newly designed non-explosive release actuator that can replace currently used release devices. The release mechanism is based on a separation mechanism, which relies on segmented nuts and a shape memory alloy (SMA) wire trigger. A quite fast and simple trigger operation is made possible through the use of SMA wire. This actuator is designed to allow a high preload with low levels of shock for the solar arrays of medium-size satellites. After actuation, the proposed device can be easily and instantly reset. Neither replacement, nor refurbishment of any components is necessary. According to the results of a performance test, the release time, preload capacity, and maximum shock level are 50 ms, 15 kN, and 350 G, respectively. In order to increase the reliability of the actuator, more than ten sets of performance tests are conducted. In addition, the proposed release actuator is tested under thermal vacuum and extreme vibration environments. No degradation or damage was observed during the two environment tests, and the release actuator was able to operate successfully. Considering the test results as a whole, we conclude that the proposed non-explosive release actuator can be applied reliably to intermediate-size satellites to replace existing release systems.

EVALUATING CAPACITIES OF GAC PRELOADED WITH NATURAL WATER

EPA Science Inventory

Adsorption studies are conducted to determine how preloading a natural groundwater onto GAC affects the adsorption of cis-1,2-dichloroexthene in small-scale and pilot-scale columns. Capacities are determined from batch-isotherm tests, microcolumns, and pilot columns, which are p...

Effects of Consuming Preloads with Different Energy Density and Taste Quality on Energy Intake and Postprandial Blood Glucose

PubMed Central

Tey, Siew Ling; Salleh, Nurhazwani; Forde, Ciaran G.

2018-01-01

Consumption of reduced energy dense foods and drink has the potential to reduce energy intake and postprandial blood glucose concentrations. In addition, the taste quality of a meal (e.g., sweet or savoury) may play a role in satiation and food intake. The objective of this randomised crossover study was to examine whether energy density and taste quality has an impact on energy intake and postprandial blood glucose response. Using a preload design, participants were asked to consume a sweet (“Cheng Teng”) or a savoury (broth) preload soup in high energy density (HED; around 0.50 kcal/g; 250 kcal) or low energy density (LED; around 0.12 kcal/g; 50 kcal) in mid-morning and an ad libitum lunch was provided an hour after the preload. Participants recorded their food intake for the rest of the day after they left the study site. Energy compensation and postprandial blood glucose response were measured in 32 healthy lean males (mean age = 28.9 years, mean BMI = 22.1 kg/m2). There was a significant difference in ad libitum lunch intake between treatments (p = 0.012), with higher intake in sweet LED and savoury LED compared to sweet HED and savoury HED. Energy intake at subsequent meals and total daily energy intake did not differ between the four treatments (both p ≥ 0.214). Consumption of HED preloads resulted in a larger spike in postprandial blood glucose response compared with LED preloads, irrespective of taste quality (p < 0.001). Energy density rather than taste quality plays an important role in energy compensation and postprandial blood glucose response. This suggests that regular consumption of low energy-dense foods has the potential to reduce overall energy intake and to improve glycemic control. PMID:29385055

A twin study of differences in the response of plasma ghrelin to a milkshake preload in restrained eaters

PubMed Central

Myhre, Rachel; Kratz, Mario; Goldberg, Jack; Polivy, Janet; Melhorn, Susan; Buchwald, Dedra; Cummings, David E.; Schur, Ellen A.

2014-01-01

Background Genetic, physiological, and psychological factors can affect food intake, but twin studies can distinguish inherited from environmental contributors. We examined the influence of attempted cognitive control of eating (“restrained eating”) on levels of appetite-regulating hormones. Methods Sixteen female, monozygotic twin pairs, discordant for Restraint Scale score (i.e., one twin a restrained eater with score > 15 whereas the co-twin was unrestrained), were selected from the University of Washington Twin Registry. Serial plasma ghrelin concentrations were monitored during meals and a preload study paradigm involving intake of a milkshake followed by an ad libitum ice cream “taste test.” Results Body weight, body mass index, resting energy expenditure, and fasting leptin levels were very similar between restrained and unrestrained twins. In a preload study, twins ate similar amounts of ice cream shortly after drinking identical milkshakes (mean ±SD; restrained 239 ±158 vs. unrestrained 228 ±132 kilocalories; P = 0.83). However, ghrelin concentrations during the preload study were significantly higher (P = 0.03) in restrained twins than in their unrestrained co-twins. Regardless of restraint status, ghrelin levels prior to the preload study were prospectively and positively associated with ice cream intake (P = 0.001). Conclusions Compared to their unrestrained co-twins, restrained twins had higher endogenous ghrelin levels during a preload study, but ate similar amounts. This finding is consistent with exertion of cognitive control relative to the state of physiologic appetite stimulation. Moreover, these findings in twins suggest that higher ghrelin levels result from restrained eating behavior and not from genetic predisposition. PMID:24534168

Effects of fruit and vegetable, consumed in solid vs. beverage forms on acute and chronic appetitive responses in lean and obese adults

PubMed Central

Houchins, Jenny A.; Tan, Sze-Yen; Campbell, Wayne W.; Mattes, Richard D.

2012-01-01

Background The effects of fruits and vegetables in solid vs. beverage forms on human appetite and food intake acutely and over eight weeks, are unclear. Methods This 21-week, randomised, crossover study assessed appetitive ratings following the inclusion of fruits and vegetables, in solid and beverage form, into the habitual diet of healthy lean (n=15) and overweight/obese (n=19) adults with low customary consumption. The primary acute outcomes were satiation (amount of challenge meal consumed), satiety (latency of subsequent eating event), and dietary compensation after a 400 kcal fruit preload. Ratings of appetite were also obtained before and after 8 weeks of required increased fruit and vegetable consumption (20% estimated energy requirement). Results Acutely, overweight/obese participants reported smaller reductions of hunger after consuming the fruit preload in beverage compared to solid form (preload × form × BMI effects, P=0.030). Participants also consumed significantly less of a challenge meal (in both gram and energy) after the ingestion of the solid fruit preload (P<0.005). However, the subsequent meal latency was not significantly different between the solid and the beverage fruit preloads. Total daily energy intake was significantly higher when the obese participants consumed the beverage fruit preload compared to the solid (P<0.001). Daily energy intake was markedly, but not significantly, higher among the lean with the beverage versus solid food-form. Hunger and fullness ratings remained stable when participants consumed fruits and vegetables in solid or beverage form for eight weeks each. Conclusion Acute post-ingestive appetitive responses were weaker following consumption of fruits in beverage versus solid food-forms. Consumption of beverage or solid fruit and vegetable food loads for 8 weeks did not chronically alter appetitive responses. PMID:23164702

Effects of Consuming Preloads with Different Energy Density and Taste Quality on Energy Intake and Postprandial Blood Glucose.

PubMed

Tey, Siew Ling; Salleh, Nurhazwani; Henry, Christiani Jeyakumar; Forde, Ciaran G

2018-01-31

Consumption of reduced energy dense foods and drink has the potential to reduce energy intake and postprandial blood glucose concentrations. In addition, the taste quality of a meal (e.g., sweet or savoury) may play a role in satiation and food intake. The objective of this randomised crossover study was to examine whether energy density and taste quality has an impact on energy intake and postprandial blood glucose response. Using a preload design, participants were asked to consume a sweet ("Cheng Teng") or a savoury (broth) preload soup in high energy density (HED; around 0.50 kcal/g; 250 kcal) or low energy density (LED; around 0.12 kcal/g; 50 kcal) in mid-morning and an ad libitum lunch was provided an hour after the preload. Participants recorded their food intake for the rest of the day after they left the study site. Energy compensation and postprandial blood glucose response were measured in 32 healthy lean males (mean age = 28.9 years, mean BMI = 22.1 kg/m²). There was a significant difference in ad libitum lunch intake between treatments ( p = 0.012), with higher intake in sweet LED and savoury LED compared to sweet HED and savoury HED. Energy intake at subsequent meals and total daily energy intake did not differ between the four treatments (both p ≥ 0.214). Consumption of HED preloads resulted in a larger spike in postprandial blood glucose response compared with LED preloads, irrespective of taste quality ( p < 0.001). Energy density rather than taste quality plays an important role in energy compensation and postprandial blood glucose response. This suggests that regular consumption of low energy-dense foods has the potential to reduce overall energy intake and to improve glycemic control.

The effect of sensory-nutrient congruency on food intake after repeated exposure: do texture and/or energy density matter?

PubMed

Hogenkamp, P S

2014-09-01

Sensory properties guide the amount that people eat. In particular, food texture plays an important role in a food's 'expected satiation', which in turn affects the food-related decision making process. One hypothesis is that incongruent pairing of a textural cue with a post-ingestive outcome compromises this process, leading to poor energy compensation. Several studies examined the effect of both energy density and sensory characteristics (i.e. increased creaminess and thickness) on expectations, subjective appetite and food intake. To add to this literature, a re-analysis of data assessed whether the effect of sensory-nutrient pairings on energy intake compensation persisted after repeated exposure to a food. In this cross-over design, 27 participants consumed two preloads with 'congruent' (low-energy/liquid; high-energy/semi-solid) and two preloads with 'incongruent' (low-energy/semi-solid; high-energy/liquid) texture-nutrient combinations for nine subsequent meals, during which ad libitum intake was measured. Intake at first exposure did not differ between the low-energy (280±150kcal) and high-energy preloads (292±183kcal) in the incongruent conditions. By contrast, it was greater after the low-energy (332±203kcal) than after the high-energy (236±132kcal) preload in the congruent conditions (energy∗incongruent/congruent, p=0.04). Post-exposure, this pattern changed: intake depended on the energy density of the preloads in all conditions, and was greater after low-energy preloads (day∗energy∗incongruent/congruent-interaction for breakfast: p=0.02). Thus, manipulating the sensory properties of a food influenced energy compensation and meal size, but only at initial exposure. Repeated exposure 'corrected' the initial lack of compensation observed in conditions with incongruent sensory-nutrient pairings. Copyright © 2014 Elsevier Inc. All rights reserved.

'Snack' versus 'meal': The impact of label and place on food intake.

PubMed

Ogden, Jane; Wood, Chloe; Payne, Elise; Fouracre, Hollie; Lammyman, Frances

2018-01-01

Eating behaviour is influenced by both cognitions and triggers in the environment. The potential difference between a 'snack' and a 'meal' illustrates these factors and the way in which they interact, particularly in terms of the label used to describe food and the way it is presented. To date no research has specifically explored the independent and combined impact of label and presentation on eating behaviour. Using a preload/taste test design this experimental study evaluated the impact of label ('snack' vs. 'meal') and place ('snack' vs. 'meal') of a preload on changes in desire to eat and subsequent food intake. Eighty female participants consumed a pasta preload which labelled as either a 'snack' or a 'meal' and presented as either a 'snack' (standing and eating from a container) or a 'meal' (eating at a table from a plate), generating four conditions. The results showed main effects of label and place with participants consuming significantly more sweet mass (specifically chocolate) at the taste test when the preload had been labelled a 'snack' and more total mass and calories when the preload had been presented as a 'snack'. No label by place interactions were found. The results also showed a combined effect of both label and place with those who had eaten the preload both labelled and presented as a 'snack' consuming significantly more in terms of nearly all measures of food intake than those in the other conditions. To conclude, label and presentation influence subsequent food intake both independently and combined which is pertinent given the increase in 'snacking' in contemporary culture. Copyright © 2017 Elsevier Ltd. All rights reserved.

Doing the counter-regulation shuffle: The importance of flexibility and hunger for predicting food consumption following a preload.

PubMed

Broadbent, Jaclyn; Fuller-Tyszkiewicz, Matthew; Dennerstein, Michelle; Greenwood, Jesse; Hancock, Naomi; Thavapalan, Nithyyaa; White, Melissa

This study utilised the preload paradigm to evaluate whether trait-like dieting attitudes and behaviours (dietary restraint and flexibility in dieting rules) and context-specific factors (negative mood and hunger) predict food consumption among male and female participants. Following a high calorie preload, 79 participants aged 18-40 completed a deceptive taste test in which they were encouraged to eat as much of the taste test foods as desired, and this ad libitum intake was measured. Although each predictor (except negative mood) predicted consumption when tested individually, regression analyses revealed that dieting flexibility and current hunger were the strongest unique predictors of intake. Mood failed to directly predict food consumption, nor did it moderate the relationship between restraint and food intake. Collectively, findings suggest that emphasis on dietary restraint in preload studies may be misplaced, as other proximal and stable factors may better predict food consumption. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

TRICHLOROETHYLENE ADSORPTION BY ACTIVATED CARBON PRELOADED WITH HUMIC SUBSTANCES: EFFECTS OF SOLUTION CHEMISTRY. (R828157)

EPA Science Inventory

Abstract

Trichloroethylene (TCE) adsorption by activated carbon previously loaded ("preloaded") with humic substances was found to decrease with increasing concentrations of monovalent ions (NaCl), calcium (until solubility was exceeded), or dissolved oxygen in...

Adsorption of organic contaminants by graphene nanosheets, carbon nanotubes and granular activated carbons under natural organic matter preloading conditions.

PubMed

Ersan, Gamze; Kaya, Yasemin; Apul, Onur G; Karanfil, Tanju

2016-09-15

The effect of NOM preloading on the adsorption of phenanthrene (PNT) and trichloroethylene (TCE) by pristine graphene nanosheets (GNS) and graphene oxide nanosheet (GO) was investigated and compared with those of a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), and two coal based granular activated carbons (GACs). PNT uptake was higher than TCE by all adsorbents on both mass and surface area bases. This was attributed to the hydrophobicity of PNT. The adsorption capacities of PNT and TCE depend on the accessibility of the organic molecules to the inner regions of the adsorbent which was influenced from the molecular size of OCs. The adsorption capacities of all adsorbents decreased as a result of NOM preloading due to site competition and/or pore/interstice blockage. However, among all adsorbents, GO was generally effected least from the NOM preloading for PNT, whereas there was not observed any trend of NOM competition with a specific adsorbent for TCE. In addition, SWCNT was generally affected most from the NOM preloading for TCE and there was not any trend for PNT. The overall results indicated that the fate and transport of organic contaminants by GNSs and CNTs type of nanoadsorbents and GACs in different natural systems will be affected by water quality parameters, characteristics of adsorbent, and properties of adsorbate. Copyright © 2016 Elsevier B.V. All rights reserved.

The effects of two torque values on the screw preload of implant-supported prostheses with passive fit or misfit.

PubMed

Al-Otaibi, Hanan Nejer; Akeel, Riyadh Fadul

2014-01-01

To determine the effect of increased torque of the abutment screw and retorquing after 10 minutes on implant-supported fixed prostheses. Two strain gauges (SGs) were attached to four implants stabilized on an acrylic resin mandible. Four implant-supported frameworks were constructed to represent passive fit (PF) and different amounts of misfit (MF1, MF2, and MF3). Vertical misfit was measured using a traveling microscope. Each framework was torqued to 35 Ncm (the manufacturer's recommendation) and 40 Ncm, and the preload was recorded immediately and again after retorquing 10 minutes later (torque stage). The smallest gap was observed under the PF framework. Three-way analysis of variance revealed significant effects of the framework, torque value, and torque stage on preload. The PF showed the highest mean preload under both torque values. An independent-sample t test between the torque values revealed a statistically significant difference only for MF1 and MF2. A dependent-sample t test of the torque stage revealed a statistically significant difference at a torque value of 35 Ncm under the PF and MF3 frameworks. Increasing the torque value beyond the manufacturer's recommended amount and retorquing of the screws at 10 minutes after the initial torque did not necessarily lead to a significant increase in preload in full-arch implant-supported fixed prostheses, particularly under non-passively fitting frameworks.

Strain energy release rate as a function of temperature and preloading history utilizing the edge delamination fatique test method

NASA Technical Reports Server (NTRS)

Zimmerman, Richard S.; Adams, Donald F.

1989-01-01

Static laminate and tension-tension fatigue tests of IM7/8551-7 composite materials was performed. The Edge Delamination Test (EDT) was utilized to evaluate the temperature and preloading history effect on the critical strain energy release rate. Static and fatigue testing was performed at room temperature and 180 F (82 C). Three preloading schemes were used to precondition fatigue test specimens prior to performing the normal tension-tension fatigue EDT testing. Computer software was written to perform all fatigue testing while monitoring the dynamic modulus to detect the onset of delamination and record the test information for later retrieval and reduction.

Tube support grid and spacer therefor

DOEpatents

Ringsmuth, Richard J.; Kaufman, Jay S.

1986-01-01

A tube support grid and spacers therefor provide radially inward preloading of heat exchange tubes to minimize stress upon base welds due to differential thermal expansion. The grid comprises a concentric series of rings and spacers with opposing concave sides for conforming to the tubes and V-shaped ends to provide resilient flexibility. The flexibility aids in assembly and in transmitting seismic vibrations from the tubes to a shroud. The tube support grid may be assembled in place to achieve the desired inwardly radial preloading of the heat exchange tubes. Tab and slot assembly further minimizes stresses in the system. The radii of the grid rings may be preselected to effect the desired radially inward preloading.

Axisymmetric deformations and stresses of unsymmetrically laminated composite cylinders in axial compression with thermally-induced preloading effects

NASA Technical Reports Server (NTRS)

Paraska, Peter J.

1993-01-01

This report documents an analytical study of the response of unsymmetrically laminated cylinders subjected to thermally-induced preloading effects and compressive axial load. Closed-form solutions are obtained for the displacements and intralaminar stresses and recursive relations for the interlaminar shear stress were obtained using the closed-form intralaminar stress solutions. For the cylinder geometries and stacking sequence examples analyzed, several important and as yet undocumented effects of including thermally-induced preloading in the analysis are observed. It should be noted that this work is easily extended to include uniform internal and/or external pressure loadings and the application of strain and stress failure theories.

Mechanically metastable structures generated by single pulse laser-induced periodic surface structures (LIPSS) in the photoresist SU8.

PubMed

Reinhardt, Hendrik; Peschke, Patrick; Riedel, René; Hampp, Norbert

2018-07-27

Laser-induced periodic surface structures (LIPSS) with a periodicity of 351 nm are generated in the negative photoresist SU8 by single nanosecond laser pulse impact. Friction scans indicate the periodic pattern to comprise alternating regions of crosslinked and non-crosslinked SU8. Intriguingly, even minor mechanical stimuli in the order of nanonewtons cause the unfolding or rather the deletion of the characteristic periodic pattern similarly to the release of a pre-loaded spring. This feature combined with high resilience to heat and photon irradiation makes SU8-LIPSS attractive for applications such as mechanical stress monitors, self-destructing memory and passive micro actuators.

Mechanically metastable structures generated by single pulse laser-induced periodic surface structures (LIPSS) in the photoresist SU8

NASA Astrophysics Data System (ADS)

Reinhardt, Hendrik; Peschke, Patrick; Riedel, René; Hampp, Norbert

2018-07-01

Laser-induced periodic surface structures (LIPSS) with a periodicity of 351 nm are generated in the negative photoresist SU8 by single nanosecond laser pulse impact. Friction scans indicate the periodic pattern to comprise alternating regions of crosslinked and non-crosslinked SU8. Intriguingly, even minor mechanical stimuli in the order of nanonewtons cause the unfolding or rather the deletion of the characteristic periodic pattern similarly to the release of a pre-loaded spring. This feature combined with high resilience to heat and photon irradiation makes SU8-LIPSS attractive for applications such as mechanical stress monitors, self-destructing memory and passive micro actuators.

Teach Graphic Design Basics with PowerPoint

ERIC Educational Resources Information Center

Lazaros, Edward J.; Spotts, Thomas H.

2007-01-01

While PowerPoint is generally regarded as simply software for creating slide presentations, it includes often overlooked--but powerful--drawing tools. Because it is part of the Microsoft Office package, PowerPoint comes preloaded on many computers and thus is already available in many classrooms. Since most computers are not preloaded with good…

Simulation of Degraded Properties of 2D plain Woven C/SiC Composites under Preloading Oxidation Atmosphere

NASA Astrophysics Data System (ADS)

Chen, Xihui; Sun, Zhigang; Sun, Jianfen; Song, Yingdong

2017-12-01

In this paper, a numerical model which incorporates the oxidation damage model and the finite element model of 2D plain woven composites is presented for simulation of the oxidation behaviors of 2D plain woven C/SiC composite under preloading oxidation atmosphere. The equal proportional reduction method is firstly proposed to calculate the residual moduli and strength of unidirectional C/SiC composite. The multi-scale method is developed to simulate the residual elastic moduli and strength of 2D plain woven C/SiC composite. The multi-scale method is able to accurately predict the residual elastic modulus and strength of the composite. Besides, the simulated residual elastic moduli and strength of 2D plain woven C/SiC composites under preloading oxidation atmosphere show good agreements with experimental results. Furthermore, the preload, oxidation time, temperature and fiber volume fractions of the composite are investigated to show their influences upon the residual elastic modulus and strength of 2D plain woven C/SiC composites.

Monosodium glutamate delivered in a protein-rich soup improves subsequent energy compensation.

PubMed

Masic, Una; Yeomans, Martin R

2014-01-01

Previous research suggests that monosodium glutamate (MSG) may have a biphasic effect on appetite, increasing appetite within a meal with its flavour-enhancing effect, but enhancing subsequent satiety due to its proposed role as a predictor of protein content. The present study explored this by assessing the impact of a 450 g soup preload differing in MSG concentration (1 % MSG added (MSG+) or no MSG (MSG-)) and nutrient content (low-energy control or high-energy carbohydrate or high-energy protein) on rated appetite and ad libitum intake of a test meal in thirty-five low-restraint male volunteers using a within-participant design. Protein-rich preloads significantly reduced intake at the test meal and resulted in more accurate energy compensation than did carbohydrate-rich preloads. This energy compensation was stronger in the MSG+ protein conditions when compared with MSG+ carbohydrate conditions. No clear differences in rated appetite were seen in MSG or the macronutrient conditions alone during preload ingestion or 45 min after intake. Overall, these findings indicate that MSG may act to further improve energy compensation when provided in a protein-rich context.

Failure analysis of blots for diesel engine intercooler

NASA Astrophysics Data System (ADS)

Ren, Ping; Li, Zongquan; Wu, Jiangfei; Guo, Yibin; Li, Wanyou

2017-05-01

In diesel generating sets, it will lead to the abominable working condition if the fault couldn’t be recovered when the bolt of intercooler cracks. This paper aims at the fault of the blots of diesel generator intercooler and completes the analysis of the static strength and fatigue strength. Static intensity is checked considering blot preload and thermal stress. In order to obtain the thermal stress of the blot, thermodynamic of intercooler is calculated according to the measured temperature. Based on the measured vibration response and the finite element model, using dynamic load identification technique, equivalent excitation force of unit was solved. In order to obtain the force of bolt, the excitation force is loaded into the finite element model. By considering the thermal stress and preload as the average stress while the mechanical stress as the wave stress, fatigue strength analysis has been accomplished. Procedure of diagnosis is proposed in this paper. Finally, according to the result of intensity verification the fatigue failure is validation. Thereby, further studies are necessary to verification the result of the intensity analysis and put forward some improvement suggestion.

Braided reinforced composite rods for the internal reinforcement of concrete

NASA Astrophysics Data System (ADS)

Gonilho Pereira, C.; Fangueiro, R.; Jalali, S.; Araujo, M.; Marques, P.

2008-05-01

This paper reports on the development of braided reinforced composite rods as a substitute for the steel reinforcement in concrete. The research work aims at understanding the mechanical behaviour of core-reinforced braided fabrics and braided reinforced composite rods, namely concerning the influence of the braiding angle, the type of core reinforcement fibre, and preloading and postloading conditions. The core-reinforced braided fabrics were made from polyester fibres for producing braided structures, and E-glass, carbon, HT polyethylene, and sisal fibres were used for the core reinforcement. The braided reinforced composite rods were obtained by impregnating the core-reinforced braided fabric with a vinyl ester resin. The preloading of the core-reinforced braided fabrics and the postloading of the braided reinforced composite rods were performed in three and two stages, respectively. The results of tensile tests carried out on different samples of core-reinforced braided fabrics are presented and discussed. The tensile and bending properties of the braided reinforced composite rods have been evaluated, and the results obtained are presented, discussed, and compared with those of conventional materials, such as steel.

A traveling wave ultrasonic motor with a metal/polymer-matrix material compound stator

NASA Astrophysics Data System (ADS)

Li, Jinbang; Liu, Shuo; Zhou, Ningning; Yu, Aibing; Cui, Yuguo; Chen, Pengfei

2018-01-01

This study proposes a traveling wave ultrasonic motor with a metal/polymer-matrix material compound stator. The stator is composed of a metal ring and polymer-matrix teeth. The resonance frequency of the stator with different structural dimensions was analyzed by the finite element method. From the results, the structure parameters of the metal ring were obtained. The effects of the density and elastic modulus of the tooth material on the resonance frequency were also investigated. A viscoelastic contact model was built to explore the contact state between the compound stator and rotor. Considering the density, elastic modulus and tribological properties, the tooth material was prepared by a molding process. The load-torque and efficiency-torque characteristics of the motor with different tooth thicknesses were measured under different preloads using a preload controlled ultrasonic motor test device. The maximum no-load speed of the motor was about 85 r min-1 with a tooth thickness of 3 mm and a preload of 100 N, the maximum stall torque of the motor was about 0.5 N · m with a tooth thickness of 4 mm and a preload of 125 N, and a maximum efficiency of about 5.5% occurred with a tooth thickness of 4 mm, a preload of 100 N and a torque of 0.3 N · m. The main merits of the proposed ultrasonic motor are low cost, light weight, high processing efficiency and long life.

Effect of the coefficient of friction and tightening speed on the preload induced at the dental implant complex with the finite element method.

PubMed

Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Geramipanah, Farideh; Safari, Hamed; Paknejad, Mojgan

2015-05-01

To prevent screw loosening, a clear understanding of the factors influencing secure preload is necessary. The purpose of this study was to investigate the effect of coefficient of friction and tightening speed on screw tightening based on energy distribution method with exact geometric modeling and finite element analysis. To simulate the proper boundary conditions of the screw tightening process, the supporting bone of an implant was considered. The exact geometry of the implant complex, including the Straumann dental implant, direct crown attachment, and abutment screw were modeled with Solidworks software. Abutment screw/implant and implant/bone interfaces were designed as spiral thread helixes. The screw-tightening process was simulated with Abaqus software, and to achieve the target torque, an angular displacement was applied to the abutment screw head at different coefficients of friction and tightening speeds. The values of torque, preload, energy distribution, elastic energy, and efficiency were obtained at the target torque of 35 Ncm. Additionally, the torque distribution ratio and preload simulated values were compared to theoretically predicted values. Upon reducing the coefficient of friction and enhancing the tightening speed, the angle of turn increased at the target torque. As the angle of turn increased, the elastic energy and preload also increased. Additionally, by increasing the coefficient of friction, the frictional dissipation energy increased but the efficiency decreased, whereas the increase in tightening speed insignificantly affected efficiency. The results of this study indicate that the coefficient of friction is the most influential factor on efficiency. Increasing the tightening speed lowered the response rate to the frictional resistance, thus diminishing the coefficient of friction and slightly increasing the preload. Increasing the tightening speed has the same result as reducing the coefficient of friction. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Effect of a low dose whey/guar preload on glycemic control in people with type 2 diabetes--a randomised controlled trial.

PubMed

Clifton, Peter M; Galbraith, Claire; Coles, Leah

2014-10-25

Large preloads of protein and fat have been shown to lower glucose after a carbohydrate-rich meal in people with type 2 diabetes but add a considerable energy burden. Low calorie preloads [<5% of daily energy intake] have been tested in this study in people with prediabetes and with type 2 diabetes. This was an unblinded randomised crossover study with two placebo days and two active treatment days. Glucose was measured for 3 hours with fingerprick samples as well as continuous glucose monitoring [CGMS]. Twenty-four subjects with pre-diabetes or moderately controlled type 2 diabetes [fasting glucose < 10 and HbA1c < 8.5%] were recruited. The preload contained 17 g whey protein plus 3 g lactose and 5 g guar, and 1 g flavour material [including sucralose] dissolved in 150 ml cold water or 150 ml cold water with no additives. The breakfast test meal consisted of 2 slices of bread, margarine and jam [3 slices for men] with the test drink 15 minutes beforehand. Peak fingerprick glucose was reduced by 2.1 mmol/L at 45 min [p < 0.0001]. Average fingerprick glucose over 3 hours was reduced by 0.8 mmol/L [p = 0.0003]. There was no difference between those with diabetes or prediabetes or those on medication or not on medication. An 80 kcal whey protein/fibre preload can lower average glucose over 3 hours by 0.8 mmol/L. If used long term before at least two carbohydrate-rich meals/day this preload could lower HbA1c by up to 1%. The trial was registered with the Australian New Zealand Clinical Trials Registry number ACTRN12612001251819.

Short-term effects of a low glycemic index carob-containing snack on energy intake, satiety, and glycemic response in normal-weight, healthy adults: Results from two randomized trials.

PubMed

Papakonstantinou, Emilia; Orfanakos, Nickolaos; Farajian, Paul; Kapetanakou, Anastasia E; Makariti, Ifigenia P; Grivokostopoulos, Nikolaos; Ha, Marie-Ann; Skandamis, Panagiotis N

2017-10-01

The potential positive health effects of carob-containing snacks are largely unknown. Therefore, the aims of these studies were to determine the glycemic index (GI) of a carob snack compared with chocolate cookie containing equal amounts of available carbohydrates and to compare the effects of a carob versus chocolate cookie preload consumed as snack before a meal on (a) short-term satiety response measured by subsequent ad libitum meal intake, (b) subjective satiety as assessed by visual analog scales and (c) postprandial glycemic response. Ten healthy, normal-weight volunteers participated in GI investigation. Then, 50 healthy, normal-weight individuals consumed, crossover, in random order, the preloads as snack, with 1-wk washout period. Ad libitum meal (lunch and dessert) was offered. Capillary blood glucose samples were collected at baseline, 2 h after breakfast, just before preload consumption, 2 h after preload, 3 h after preload, just before meal (lunch and dessert), 1 h after meal, and 2 h after meal consumption. The carob snack was a low GI food, whereas the chocolate cookie was a high GI food (40 versus 78, respectively, on glucose scale). Consumption of the carob preload decreased the glycemic response to a following meal and to the individual's feelings of hunger, desire to eat, preoccupation with food, and thirst between snack and meal, as assessed with the use of visual analog scales. Subsequently, participants consumed less amounts of food (g) and had lower total energy intake at mealtimes. The carob snack led to increased satiety, lower energy intake at meal, and decreased postmeal glycemic response possibly due to its low GI value. Identifying foods that promote satiety and decrease glycemic response without increasing the overall energy intake may offer advantages to body weight and glycemic control. Copyright © 2017 Elsevier Inc. All rights reserved.

Metallic Seal Development for Advanced Docking/Berthing System

NASA Technical Reports Server (NTRS)

Oswald, Jay; Daniels, Christopher; Dunlap, Patrick, Jr.; Steinetz, Bruce

2006-01-01

Feasibility of metal-to-metal androgenous seals has been demonstrated. Techniques to minimize surface irregularities must be examined. Two concepts investigated: 1) Flexible metal interface with elastomeric preloader; 2) Flexibility will accommodate any surface irregularities from the mating surface. Rigid metal interface with elastomeric preloader. Rigidity of the metal surface will prevent irregularities (waves) from occurring.

Emulsion oil droplet size significantly affects satiety: A pre-ingestive approach.

PubMed

Lett, Aaron M; Norton, Jennifer E; Yeomans, Martin R

2016-01-01

Previous research has demonstrated that the manipulation of oil droplet size within oil-in-water emulsions significantly affects sensory characteristics, hedonics and expectations of food intake, independently of energy content. Smaller oil droplets enhanced perceived creaminess, increased Liking and generated greater expectations of satiation and satiety, indicating that creaminess is a satiety-relevant sensory cue within these systems. This paper extends these findings by investigating the effect of oil droplet size (d4,3: 2 and 50 μm) on food intake and appetite. Male participants (n = 34 aged 18-37; BMI of 22.7 ± 1.6 kg/m(2); DEBQ restricted eating score of 1.8 ± 0.1.) completed two test days, where they visited the laboratory to consume a fixed-portion breakfast, returning 3 h later for a "drink", which was the emulsion preload containing either 2 or 50 μm oil droplets. This was followed 20 min later with an ad libitum pasta lunch. Participants consumed significantly less at the ad libitum lunch after the preload containing 2 μm oil droplets than after the 50 μm preload, with an average reduction of 12% (62.4 kcal). Despite the significant differences in intake, no significant differences in sensory characteristics were noted. The findings show that the impact that an emulsion has on satiety can be enhanced without producing significantly perceivable differences in sensory properties. Therefore, by introducing a processing step which results in a smaller droplets, emulsion based liquid food products can be produced that enhance satiety, allowing covert functional redesign. Future work should consider the mechanism responsible for this effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dynamic nature of abutment screw retightening: finite element study of the effect of retightening on the settling effect.

PubMed

Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Safari, Hamed; Samandari, Mohammad Mahdi; Geramipanah, Farideh

2015-05-01

A fundamental problem in fully understanding the dynamic nature of screw loosening is lack of recognition of the entire process of screw tightening and retightening. The purpose of this study was to explain the dynamic nature of abutment screw retightening by using finite element methods to investigate the effect of the coefficient of friction and retightening on the settling effect. Precise computer models were designed of a Straumann dental implant, a directly attached crown, an abutment screw, and the bone surrounding the implant. All threaded interfaces were designed with a spiral thread helix with a specific coefficient of static and kinetic friction, and the surfaces were characterized as fine, regular, and rough. Abaqus software was used for dynamic simulation, which involved applying rotational displacement to the abutment screw and torque controlling during the steps of tightening, relaxation, retightening, and second relaxation and at different coefficients of friction. The obtained torque and preload values were compared to the predicted values. When surfaces changed from fine to rough, the remaining torque and preload decreased, and the settling effect increased. Upon retightening, the remaining torque and preload increased, and the settling effect also decreased. The reduction of the coefficient of friction contributes to increases in the preload and decreases in the settling effect. Retightening reduced the settling effect and had an insignificant effect on the preload. At high coefficients of friction, the retightening effect was intensified. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Deconstructing alcohol use on a night out in England: promotions, preloading and consumption.

PubMed

McClatchley, Kirstie; Shorter, Gillian W; Chalmers, Jenny

2014-07-01

To examine alcohol consumed during a drinking event (a single drinking occasion) by those attending public house/on-trade establishments on nights with standard pricing and nights with promotional prices. Data (n = 425) were collected in an ecological momentary assessment over eight nights in two locations (Midlands and London) on both promotional and standard (Saturday) nights. Multiple regression was used to predict event alcohol consumption by sex, age, type of night, alcohol preloading behaviour, marital and employment status, education, Alcohol Use Disorders Identification Test alcohol consumption questions separately or total AUDIT-C and social group size. Mean (UK) units consumed were 11.8 (London) and 14.4 (Midlands). In London, consumption was similar on promotional and standard nights, but in the Midlands, standard night consumption was three units higher. Preloading was reported by 30%; more common on standard nights. Regression analyses revealed being male, preloading and past-year total AUDIT-C were associated with higher event consumption. However, when AUDIT-C questions were added separately, being a standard night was associated with increased event consumption and different AUDIT-C questions were significantly associated with event consumption in each location. Event consumption reflected heavy episodic drinking and was influenced by price. Promotional night consumption either matched standard Saturday night consumption or was slightly lower. In London, there was a significant preference for drinking at least one promotional beverage on promotional nights. On standard nights, consumption was over a wider range of venues, and preloading with off-trade alcohol was more likely. © 2014 Australasian Professional Society on Alcohol and other Drugs.

Evaluation of a six-DOF electrodynamic shaker system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregory, Danny Lynn; Smallwood, David Ora

2009-03-01

The paper describes the preliminary evaluation of a 6 degree of freedom electrodynamic shaker system. The 8 by 8 inch (20.3 cm) table is driven by 12 electrodynamic shakers producing motion in all 6 rigid body modes. A small electrodynamic shaker system suitable for small component testing is described. The principal purpose of the system is to demonstrate the technology. The shaker is driven by 12 electrodynamic shakers each with a force capability of about 50 lbs (220 N). The system was developed through an informal cooperative agreement between Sandia National Laboratories, Team Corp. and Spectral Dynamics Corporation. Sandia providedmore » the laboratory space and some development funds. Team provided the mechanical system, and Spectral Dynamics provided the control system. Spectral Dynamics was chosen to provide the control system partly because of their experience in MIMO control and partly because Sandia already had part of the system in house. The shaker system was conceived and manufactured by TEAM Corp. Figure 1 shows the overall system. The vibration table, electrodynamic shakers, hydraulic pumps, and amplifiers are all housed in a single cabinet. Figure 2 is a drawing showing how the electrodynamic shakers are coupled to the table. The shakers are coupled to the table through a hydraulic spherical pad bearing providing 5 degrees of freedom and one stiff degree of freedom. The pad bearing must be preloaded with a static force as they are unable to provide any tension forces. The horizontal bearings are preloaded with steel springs. The drawing shows a spring providing the vertical preload. This was changed in the final design. The vertical preload is provided by multiple strands of an O-ring material as shown in Figure 4. Four shakers provide excitation in each of the three orthogonal axes. The specifications of the shaker are outlined in Table 1. Four shakers provide inputs in each of the three orthogonal directions. By choosing the phase relationships between the shakers all six rigid body modes (three translation, and three rotations) can be excited. The system is over determined. There are more shakers than degrees of freedom. This provided an interesting control problem. The problem was approached using the input-output transformation matrices provided in the Spectral control system. Twelve accelerometers were selected for the control accelerometers (a tri-axial accelerometer at each corner of the table (see Figure 5). Figure 6 shows the nomenclature used to identify the shakers and control accelerometers. A fifth tri-axial accelerometer was placed at the center of the table, but it was not used for control. Thus we had 12 control accelerometers and 12 shakers to control a 6-dof shaker. The 12 control channels were reduced to a 6-dof control using a simple input transformation matrix. The control was defined by a 6x6 spectral density matrix. The six outputs in the control variable coordinates were transformed to twelve physical drive signals using another simple output transformation matrix. It was assumed that the accelerometers and shakers were well matched such that the transformation matrices were independent of frequency and could be deduced from rigid body considerations. The input/output transformations are shown in Equations 1 and 2.« less

Impulsive movements lead to high hops on sand

NASA Astrophysics Data System (ADS)

Aguilar, Jeffrey; Goldman, Daniel I.

2014-03-01

Various animals exhibit locomotive behaviors (like sprinting and hopping) involving transient bursts of actuation coupled to the ground through internal elastic elements. The performance of such maneuvers is subject to reaction forces on the feet from the environment. On substrates like dry granular media, the laws that govern these forces are not fully understood, and can vary with foot size and shape, material compaction (measured by the volume fraction ϕ) and intrusion kinematics. To gain insight into how such interactions affect jumps on granular media, we study the performance of an actuated spring mass robot. We compare performance between two jump strategies: a single-cycle sine-wave actuation (a ``single jump'') and this actuation preceded by an impulsive preload (a ``preload jump''). We vary ϕ for both strategies, and find that ϕ significantly affects performance: we observe a 200% increase in the single jump height with only a 5% increase in volume fraction using a 7.62 cm diameter flat foot. The preload jump outperforms the single jump height by 150% for all ϕ. We hypothesize that this increase in performance results from higher intrusion velocities and accelerations associated with the preload. NSF POLS CAREER, Burroughs Wellcome Fund, and ARO.

Release of ( sup 14 C)5-hydroxytryptamine from human platelets by red wine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarman, J.; Glover, V.; Sandler, M.

1991-01-01

Red wine, at a final dilution of 1/50, caused released of ({sup 14}C)5-hydroxytryptamine (5-HT) from preloaded platelets, an effect which was not observed with any white wines or beers tested. Since 5-HT, is probably released from body stores during migraine attacks and red wine is known to provoke migraine episodes in susceptible individuals, release of 5-HT, possibly from central stores, could represent a plausible mechanism for its mode of action.

Estimation of bearing contact angle in-situ by X-ray kinematography

NASA Technical Reports Server (NTRS)

Fowler, P. H.; Manders, F.

1982-01-01

The mounted, preloaded contact angle of the structural bearings in the assembled design mechanical assembly was measured. A modification of the Turns method is presented, based upon the clarity and definition of moving parts achieved with X-ray technique and cinematic display. Contact angle is estimated by counting the number of bearings passing a given point as a function of number of turns of the shaft. Ball and pitch diameter variations are discussed. Ball train and shaft angle uncertainties are also discussed.

Comparison of Preloaded Bougie versus Standard Bougie Technique for Endotracheal Intubation in a Cadaveric Model.

PubMed

Baker, Jay B; Maskell, Kevin F; Matlock, Aaron G; Walsh, Ryan M; Skinner, Carl G

2015-07-01

We compared intubating with a preloaded bougie (PB) against standard bougie technique in terms of success rates, time to successful intubation and provider preference on a cadaveric airway model. In this prospective, crossover study, healthcare providers intubated a cadaver using the PB technique and the standard bougie technique. Participants were randomly assigned to start with either technique. Following standardized training and practice, procedural success and time for each technique was recorded for each participant. Subsequently, participants were asked to rate their perceived ease of intubation on a visual analogue scale of 1 to 10 (1=difficult and 10=easy) and to select which technique they preferred. 47 participants with variable experience intubating were enrolled at an emergency medicine intern airway course. The success rate of all groups for both techniques was equal (95.7%). The range of times to completion for the standard bougie technique was 16.0-70.2 seconds, with a mean time of 29.7 seconds. The range of times to completion for the PB technique was 15.7-110.9 seconds, with a mean time of 29.4 seconds. There was a non-significant difference of 0.3 seconds (95% confidence interval -2.8 to 3.4 seconds) between the two techniques. Participants rated the relative ease of intubation as 7.3/10 for the standard technique and 7.6/10 for the preloaded technique (p=0.53, 95% confidence interval of the difference -0.97 to 0.50). Thirty of 47 participants subjectively preferred the PB technique (p=0.039). There was no significant difference in success or time to intubation between standard bougie and PB techniques. The majority of participants in this study preferred the PB technique. Until a clear and clinically significant difference is found between these techniques, emergency airway operators should feel confident in using the technique with which they are most comfortable.

Development of Cryogenic Filter Wheels for the HERSCHEL Photodetector Array Camera & Spectrometer (PACS)

NASA Technical Reports Server (NTRS)

Koerner, Christian; Kampf, Dirk; Poglitsch, Albrecht; Schubert, Josef; Ruppert, U.; Schoele, M.

2014-01-01

This paper describes the two PACS Filter Wheels that are direct-drive rotational mechanisms operated at a temperature below 5K inside the PACS focal plane unit of the Herschel Satellite. The purpose of the mechanisms is to switch between filters. The rotation axis is pivoted to the support structure via a slightly preloaded pair of ball bearings and driven by a Cryotorquer. Position sensing is realized by a pair of Hall effect sensors. Powerless positioning at the filter positions is achieved by a magnetic ratchet system. The key technologies are the Cryotorquer design and the magnetic ratchet design in the low temperature range. Furthermore, we will report on lessons learned during the development and qualification of the mechanism and the paint.

Planetary Load Sharing in Three-Point Mounted Wind Turbine Gearboxes: A Design and Test Comparison

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, Jonathan; Guo, Yi; Zhang, Zhiwei

This work compares the planetary load-sharing characteristics of wind turbine gearboxes supported by cylindrical roller bearings (CRBs) and preloaded tapered roller bearings (TRBs) when subjected to rotor moments. Planetary bearing loads were measured in field-representative dynamometer tests and compared to loads predicted by finite-element models. Preloaded TRBs significantly improved load sharing. In pure torque conditions, the upwind planet bearing load in the gearbox with preloaded TRBs was only 14% more than the assumed load compared to 47% more for the gearbox with CRBs. Consequently, the predicted fatigue life of the complete set of planetary bearings for the gearbox with preloadedmore » TRBs is 3.5 times greater than that of the gearbox with CRBs.« less

Analytical solution for vacuum preloading considering the nonlinear distribution of horizontal permeability within the smear zone.

PubMed

Peng, Jie; He, Xiang; Ye, Hanming

2015-01-01

The vacuum preloading is an effective method which is widely used in ground treatment. In consolidation analysis, the soil around prefabricated vertical drain (PVD) is traditionally divided into smear zone and undisturbed zone, both with constant permeability. In reality, the permeability of soil changes continuously within the smear zone. In this study, the horizontal permeability coefficient of soil within the smear zone is described by an exponential function of radial distance. A solution for vacuum preloading consolidation considers the nonlinear distribution of horizontal permeability within the smear zone is presented and compared with previous analytical results as well as a numerical solution, the results show that the presented solution correlates well with the numerical solution, and is more precise than previous analytical solution.

Simulating the Structural Response of a Preloaded Bolted Joint

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Phillips, Dawn R.; Raju, Ivatury S.

2008-01-01

The present paper describes the structural analyses performed on a preloaded bolted-joint configuration. The joint modeled was comprised of two L-shaped structures connected together using a single bolt. Each L-shaped structure involved a vertical flat segment (or shell wall) welded to a horizontal segment (or flange). Parametric studies were performed using elasto-plastic, large-deformation nonlinear finite element analyses to determine the influence of several factors on the bolted-joint response. The factors considered included bolt preload, washer-surface-bearing size, edge boundary conditions, joint segment length, and loading history. Joint response is reported in terms of displacements, gap opening, and surface strains. Most of the factors studied were determined to have minimal effect on the bolted-joint response; however, the washer-bearing-surface size affected the response significantly.

Analytical solution for vacuum preloading considering the nonlinear distribution of horizontal permeability within the smear zone

PubMed Central

Peng, Jie; He, Xiang; Ye, Hanming

2015-01-01

The vacuum preloading is an effective method which is widely used in ground treatment. In consolidation analysis, the soil around prefabricated vertical drain (PVD) is traditionally divided into smear zone and undisturbed zone, both with constant permeability. In reality, the permeability of soil changes continuously within the smear zone. In this study, the horizontal permeability coefficient of soil within the smear zone is described by an exponential function of radial distance. A solution for vacuum preloading consolidation considers the nonlinear distribution of horizontal permeability within the smear zone is presented and compared with previous analytical results as well as a numerical solution, the results show that the presented solution correlates well with the numerical solution, and is more precise than previous analytical solution. PMID:26447973

Knee joint kinematics after dynamic intraligamentary stabilization: cadaveric study on a novel anterior cruciate ligament repair technique.

PubMed

Schliemann, Benedikt; Lenschow, Simon; Domnick, Christoph; Herbort, Mirco; Häberli, Janosch; Schulze, Martin; Wähnert, Dirk; Raschke, Michael J; Kösters, Clemens

2017-04-01

Dynamic intraligamentary stabilization (DIS) has been introduced for the repair of acute anterior cruciate ligament (ACL) tears as an alternative to delayed reconstruction. The aim of the present study was to compare knee joint kinematics after DIS to those of the ACL-intact and ACL-deficient knee under simulated Lachman/KT-1000 and pivot-shift tests. We hypothesized that DIS provides knee joint kinematics equivalent to an intact ACL. With the use of a robotic knee simulator, knee kinematics were determined in simulated Lachman/KT-1000 and pivot-shift tests at 0°, 15°, 30°, 60°, and 90° of flexion in eight cadaveric knees under the following conditions: (1) intact ACL, (2) ACL deficiency, (3) DIS with a preload of 60 N, and (4) DIS with a preload of 80 N. Statistical analyses were performed using two-factor repeated-measures analysis of variance. The significance level was set at a p value of <0.05. After DIS with a preload of either 60 N or 80 N, the anterior translation was significantly reduced in the simulated Lachman/KT-1000 and pivot-shift tests when compared to the ACL-deficient knee (p < 0.05). No significant differences were observed between the DIS reconstruction with a preload of 80 N and the intact ACL with regard to anterior laxity in either test. However, DIS with a preload of only 60 N was not able to restore knee joint kinematics to that of an intact knee in all degrees of flexion. DIS with a preload of 80 N restores knee joint kinematics comparable to that of an ACL-intact knee and is therefore capable of providing knee joint stability during ACL healing. DIS therefore provides a new technique for primary ACL repair with superior biomechanical properties in comparison with other techniques that have been described previously, although further clinical studies are required to determine its usefulness in clinical settings.

Sucrose preload reduces snacking after mild mental stress in healthy participants as a function of 5-hydroxytryptamine transporter gene promoter polymorphism.

PubMed

Markus, C Rob; Jonkman, Lisa M; Capello, Aimee; Leinders, Sacha; Hüsch, Fabian

2015-01-01

Brain serotonin (5-hydroxytryptamine, 5-HT) dysfunction is considered to promote food intake and eating-related disturbances, especially under stress or negative mood. Vulnerability for 5-HT disturbances is considered to be genetically determined, including a short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) that is associated with lower serotonin function. Since 5-HT function may be slightly increased by carbohydrate consumption, S-allele 5-HTTLPR carriers in particular may benefit from a sugar-preload due to their enhanced 5-HT vulnerability. The aim of the current study was to investigate whether a sugar-containing preload may reduce appetite and energy intake after exposure to stress to induce negative mood, depending on genetic 5-HT vulnerability. From a population of 771 healthy young male and female genotyped college students 31 S/S carriers (8 males, 23 females) and 26 long allele (L/L) carriers (9 males, 17 females) (mean ± S.D. 22 ± 1.6 years; body mass index, BMI, 18-33 kg/m(2)) were monitored for changes in appetite and snacking behavior after stress exposure. Results revealed an increased energy intake after mild mental stress (negative mood) mainly for high-fat sweet foods, which was significantly greater in S/S carriers, and only in these genotypes this intake was significantly reduced by a sucrose-containing preload. Although alternative explanations are possible, it is suggested that S/S participants may have enhanced brain (hypothalamic) 5-HT responsiveness to food that makes them more susceptible to the beneficial satiation effects of a sucrose-preload as well as to the negative effects of mild mental stress on weight gain.

Appetite influences the responses to meal ingestion.

PubMed

Pribic, T; Nieto, A; Hernandez, L; Malagelada, C; Accarino, A; Azpiroz, F

2017-08-01

We have previously shown that the postprandial experience includes cognitive sensations, such as satiety and fullness, with a hedonic dimension involving digestive well-being and mood. Preload conditioning has been shown to modulate appetite and food consumption under certain conditions, but its effects on the responses to meal ingestion are not clear. We hypothesized that appetite modulation by preload conditioning has differential effects on the cognitive and the emotive responses to meal ingestion. The effects of preload conditioning (ingestion of a low- vs a high-calorie breakfast) on appetite and on the cognitive and emotive responses to a comfort probe meal ingested 2 hours later (ham and cheese sandwich with orange juice; 300 mL, 425 Kcal) was tested in healthy subjects (n=12) in a cross-over design. Sensations were measured at regular intervals 15 minutes before and 60 minutes after the probe meal. As compared to the low-calorie breakfast, the high-calorie breakfast reduced basal hunger sensation and influenced the responses to the subsequent probe meal: it increased satiety (4.3±0.2 score vs 2.7±0.2 score; P<.001) and fullness (5.4±0.5 score vs 3.1±0.5; P<.001), but reduced the expected postprandial experience of digestive well-being after a palatable meal (1.3±0.7 score vs 3.0±0.3; P=.045). Appetite modulation by preload conditioning has differential effects on the cognitive and emotive responses to a meal. Preload conditioning of the postprandial experience may be applicable to dietary planning and prevention of postprandial symptoms. © 2017 John Wiley & Sons Ltd.

Influence of ballistic bench press on upper body power output in professional rugby players.

PubMed

West, Daniel J; Cunningham, Daniel J; Crewther, Blair T; Cook, Christian J; Kilduff, Liam P

2013-08-01

The use of heavy resistance exercise provides an effective preload stimulus for inducing postactivation potentiation (PAP) and increasing peak power output (PPO). However, this approach has limited application in many sporting situations (e.g., incorporation in a precompetition warm-up); and therefore, more practical strategies for inducing PAP need to be investigated. The aim of the present study was to compare the PPO changes after performing a preload stimulus of either a ballistic exercise or a traditional heavy resistance exercise. Twenty professional rugby union players completed 3 testing sessions, each separated by 48 hours. On the first occasion, subjects underwent a 3 repetition maximum (3RM)-bench press testing session. On the next 2 occasions, subjects performed a ballistic bench throw at baseline (30% of 1RM), followed by a preload stimulus of either heavy resistance training (HRT) (heavy bench press: 3 sets of 3 repetitions at 87% 1RM) or BBP (3 sets of 3 repetitions at 30% on 1RM) followed by ballistic bench throw after 8 minutes recovery. The trials were randomized and counterbalanced. Both preload stimuli protocols increased PPO compared with baseline (BBP baseline 892 ± 108 vs. 8 minutes 924 ± 119 W, p < 0.001; HRT baseline 893 ± 104 vs. 8 minutes 931 ± 116 W; p < 0.001). There were no conditional differences between PPO at 8 minutes (p = 0.141); moreover, the change in PPO from baseline was also similar between conditions (BBP Δ + 33 ± 18; HRT Δ + 38 ± 21 W; p = 0.112). In conclusion, a ballistic exercise provided an effective method of inducing PAP and increasing upper-body PPO; moreover, this elicited similar increases in PPO as a traditional heavy resistance exercise preloading stimulus.

The Acute Effect of Upper-Body Complex Training on Power Output of Martial Art Athletes as Measured by the Bench Press Throw Exercise

PubMed Central

Liossis, Loudovikos Dimitrios; Forsyth, Jacky; Liossis, Ceorge; Tsolakis, Charilaos

2013-01-01

The purpose of this study was to examine the acute effect of upper body complex training on power output, as well as to determine the requisite preload intensity and intra-complex recovery interval needed to induce power output increases. Nine amateur-level combat/martial art athletes completed four distinct experimental protocols, which consisted of 5 bench press repetitions at either: 65% of one-repetition maximum (1RM) with a 4 min rest interval; 65% of 1RM with an 8 min rest; 85% of 1RM with a 4 min rest; or 85% of 1RM with an 8 min rest interval, performed on different days. Before (pre-conditioning) and after (post-conditioning) each experimental protocol, three bench press throws at 30% of 1RM were performed. Significant differences in power output pre-post conditioning were observed across all experimental protocols (F=26.489, partial eta2=0.768, p=0.001). Mean power output significantly increased when the preload stimulus of 65% 1RM was matched with 4 min of rest (p=0.001), and when the 85% 1RM preload stimulus was matched with 8 min of rest (p=0.001). Moreover, a statistically significant difference in power output was observed between the four conditioning protocols (F= 21.101, partial eta2=0.913, p=0.001). It was concluded that, in complex training, matching a heavy preload stimulus with a longer rest interval, and a lighter preload stimulus with a shorter rest interval is important for athletes wishing to increase their power production before training or competition. PMID:24511352

Biomechanical Changes in Disc Pressure and Facet Strain after Lumbar Spinal Arthroplasty with CharitéTM in the Human Cadaveric Spine under Physiologic Compressive Follower Preload.

PubMed

Choi, Jong-Il; Kim, Se-Hoon; Lim, Dong-Jun; Ha, Sung-Kon; Kim, Sang-Dae

2017-01-01

Arthroplasty maintains the biomechanical features of a healthy disc, decreases the adjacent segment disease rate, and decreases the accelerated degeneration rate of the neighboring discs in traditional fusion procedures. However, there are only a few reports on adjacent disc pressure (DP) and facet strain (FS) after lumbar arthroplasty under a physiologic compressive preload. Baseline DP and FS measurements were obtained from five intact cadaveric human lumbosacral spines for different modes of motion. DP was measured by inserting pressure transducer needle tips into the L3-L4 and L5-S1 discs. FS gauges were fixed on both sides of the laminae near the L3-L4, L4-L5, and L5-S1 facet joints. After SB Charité < sup > TM < /sup > III implantation at the L4-L5 level, the measurements were repeated at preload and compared with those of the intact spine. Under the preload condition, the central DP of the upper disc was decreased during extension and bending, and it significantly increased during rotation (p < 0.05). In the lower disc, the central DP insignificantly decreased during bending and increased during extension and flexion. A statistically significant increase in FS was observed during rotation at the operative facet (p < 0.05). Compared to the intact spine, all FS values were insignificantly decreased during lateral bending but increased during axial rotation. In an ex-vivo physiologic preload setting, the SB Charité < sup > TM < /sup > III provided relatively inconsistent and sometimes increased DP or FS at the operative and adjacent levels after arthroplasty.

Dynamic characterization of human breast cancer cells using a piezoresistive microcantilever.

PubMed

Shim, Sangjo; Kim, Man Geun; Jo, Kyoungwoo; Kang, Yong Seok; Lee, Boreum; Yang, Sung; Shin, Sang-Mo; Lee, Jong-Hyun

2010-10-01

In this paper, frequency response (dynamic compression and recovery) is suggested as a new physical marker to differentiate between breast cancer cells (MCF7) and normal cells (MCF10A). A single cell is placed on the laminated piezoelectric actuator and a piezoresistive microcantilever is placed on the upper surface of the cell at a specified preload displacement (or an equivalent force). The piezoelectric actuator excites the single cell in a sinusoidal fashion and its dynamic deformation is then evaluated from the displacement converted by measuring the voltage output through a piezoresistor in the microcantilever. The microcantilever has a flat contact surface with no sharp tip, making it possible to measure the overall properties of the cell rather than the local properties. These results indicate that the MCF7 cells are more deformable in quasi-static conditions compared with MCF10A cells, consistent with known characteristics. Under conditions of high frequency of over 50 Hz at a 1 μm preload displacement, 1 Hz at a 2 μm preload displacement, and all frequency ranges tested at a 3 μm preload displacement, MCF7 cells showed smaller deformation than MCF10A cells. MCF7 cells have higher absorption than MCF10A cells such that MCF7 cells appear to have higher deformability according to increasing frequency. Moreover, larger preload and higher frequencies are shown to enhance the differences in cell deformability between the MCF7 cells and MCF10A cells, which can be used as a physical marker for differentiating between MCF10A cells and MCF7 cells, even for high-speed screening devices.

Prevention of altered hemodynamics after spinal anesthesia: A comparison of volume preloading with tetrastarch, succinylated gelatin and ringer lactate solution for the patients undergoing lower segment caesarean section

PubMed Central

Mitra, Tapobrata; Das, Anjan; Majumdar, Saikat; Bhattacharyya, Tapas; Mandal, Rahul Deb; Hajra, Bimal Kumar

2014-01-01

Background: Spinal anesthesia has replaced general anesthesia in obstetric practice. Hemodynamic instability is a common, but preventable complication of spinal anesthesia. Preloading the circulation with intravenous fluids is considered a safe and effective method of preventing hypotension following spinal anesthesia. We had conducted a study to compare the hemodynamic stability after volume preloading with either Ringer's lactate (RL) or tetrastarch hydroxyethyl starch (HES) or succinylated gelatin (SG) in the patients undergoing cesarean section under spinal anesthesia. Materials and Methods: It was a prospective, double-blinded and randomized controlled study. Ninety six ASA-I healthy, nonlaboring parturients were randomly divided in 3 groups HES, SG, RL (n = 32 each) and received 10 ml/kg HES 130/0.4; 10 ml/kg SG (4% modified fluid gelatin) and 20 ml/kg RL respectively prior to SA scheduled for cesarean section. Heart rate, blood pressure (BP), oxygen saturation was measured. Results: The fall in systolic blood pressure (SBP) (<100 mm Hg) noted among 5 (15.63%), 12 (37.5%) and 14 (43.75%) parturients in groups HES, SG, RL respectively. Vasopressor (phenylephrine) was used to treat hypotension when SBP <90 mm Hg. Both the results and APGAR scores were comparable in all the groups. Lower preloading volume and less intra-operative vasopressor requirement was noted in HES group for maintaining BP though it has no clinical significance. Conclusion: RL which is cheap, physiological and widely available crystalloid can preload effectively and maintain hemodynamic stability well in cesarean section and any remnant hypotension can easily be manageable with vasopressor. PMID:25422601

Detecting Protein-Glycolipid Interactions Using CaR-ESI-MS and Model Membranes: Comparison of Pre-loaded and Passively Loaded Picodiscs.

PubMed

Li, Jun; Han, Ling; Li, Jianing; Kitova, Elena N; Xiong, Zi Jian; Privé, Gilbert G; Klassen, John S

2018-04-13

Catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS), implemented using model membranes (MMs), is a promising approach for the discovery of glycolipid ligands of glycan-binding proteins (GBPs). Picodiscs (PDs), which are lipid-transporting complexes composed of the human sphingolipid activator protein saposin A and phospholipids, have proven to be useful MMs for such studies. The present work compares the use of conventional (pre-loaded) PDs with passively loaded PDs ( PL PDs) for CaR-ESI-MS screening of glycolipids against cholera toxin B subunit homopentamer (CTB 5 ). The pre-loaded PDs were prepared from a mixture of purified glycolipid and phospholipid or a mixture of lipids extracted from tissue, while the PL PDs were prepared by incubating PDs containing only phospholipid with glycolipid-containing lipid mixtures in aqueous solution. Time-dependent changes in the composition of the PL PDs produced by incubation with glycomicelles of the ganglioside GM1 were monitored using collision-induced dissociation of the gaseous PD ions and from the extent of ganglioside binding to CTB 5 measured by ESI-MS. GM1 incorporation into PDs was evident within a few hours of incubation. At incubation times ≥ 10 days, GM1 binding to CTB 5 was indistinguishable from that observed with pre-loaded PDs produced directly from GM1 at the same concentration. Comparison of ganglioside binding to CTB 5 measured for pre-loaded PDs and PL PDs prepared from glycolipids extracted from pig and mouse brain revealed that the PL PDs allow for the detection of a greater number of ganglioside ligands. Together, the results of this study suggest PL PDs may have advantages over conventionally prepared PDs for screening glycolipids against GBPs using CaR-ESI-MS. Graphical Abstract ᅟ.

Detecting Protein-Glycolipid Interactions Using CaR-ESI-MS and Model Membranes: Comparison of Pre-loaded and Passively Loaded Picodiscs

NASA Astrophysics Data System (ADS)

Li, Jun; Han, Ling; Li, Jianing; Kitova, Elena N.; Xiong, Zi Jian; Privé, Gilbert G.; Klassen, John S.

2018-04-01

Catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS), implemented using model membranes (MMs), is a promising approach for the discovery of glycolipid ligands of glycan-binding proteins (GBPs). Picodiscs (PDs), which are lipid-transporting complexes composed of the human sphingolipid activator protein saposin A and phospholipids, have proven to be useful MMs for such studies. The present work compares the use of conventional (pre-loaded) PDs with passively loaded PDs (PLPDs) for CaR-ESI-MS screening of glycolipids against cholera toxin B subunit homopentamer (CTB5). The pre-loaded PDs were prepared from a mixture of purified glycolipid and phospholipid or a mixture of lipids extracted from tissue, while the PLPDs were prepared by incubating PDs containing only phospholipid with glycolipid-containing lipid mixtures in aqueous solution. Time-dependent changes in the composition of the PLPDs produced by incubation with glycomicelles of the ganglioside GM1 were monitored using collision-induced dissociation of the gaseous PD ions and from the extent of ganglioside binding to CTB5 measured by ESI-MS. GM1 incorporation into PDs was evident within a few hours of incubation. At incubation times ≥ 10 days, GM1 binding to CTB5 was indistinguishable from that observed with pre-loaded PDs produced directly from GM1 at the same concentration. Comparison of ganglioside binding to CTB5 measured for pre-loaded PDs and PLPDs prepared from glycolipids extracted from pig and mouse brain revealed that the PLPDs allow for the detection of a greater number of ganglioside ligands. Together, the results of this study suggest PLPDs may have advantages over conventionally prepared PDs for screening glycolipids against GBPs using CaR-ESI-MS. [Figure not available: see fulltext.

Preload of slowly digestible carbohydrate microspheres decreases gastric emptying rate of subsequent meal in humans.

PubMed

Cisse, Fatimata; Pletsch, Elizabeth A; Erickson, Daniel P; Chegeni, Mohammad; Hayes, Anna M R; Hamaker, Bruce R

2017-09-01

Gastric emptying rate influences how fast the nutrients of a meal are delivered to the body, and when slow, it moderates glycemic response and may impact satiety. Carbohydrates are one of the macronutrients that trigger the ileal brake, and we hypothesized that slowly digestible carbohydrate (SDC) administered in a premeal load would delay gastric emptying. A crossover design study was conducted with 10 healthy adults using fabricated SDC-microspheres (cooked) that were given 20 minutes before a non-nutritive viscous paste meal. There were 4 treatment arms, each separated by a 1-week washout period, consisting of (1) the paste alone, (2) a rapidly digesting maltodextrin (Polycose) preload followed by the paste 20 minutes later, (3) an SDC-microsphere preload followed by the paste, and (4) a comparably slower SDC-microsphere preload followed by the paste. A 13 C-labeled octanoic acid breath test method was used to measure gastric emptying, with the label incorporated into the non-nutritive paste. The microspheres were less than 1 mm in diameter (a size that does not require breakdown in the stomach before emptying) and, after cooking, were of the same density value. Compared with the paste alone, both of the SDC-microsphere preloads (slow and comparably slower digesting) decreased gastric emptying rate of the paste, with the latter having the most effect (half-emptying times of 1.7, 2.3, and 2.8 hours, respectively [each different at P<.05]). In conclusion, SDCs decreased gastric emptying rate, and this was suggested to be due to a triggering of the ileal brake. Copyright © 2017 Elsevier Inc. All rights reserved.

Improvement on the auxiliary total artificial heart (ATAH) left chamber design.

PubMed

Andrade, Aron; Fonseca, Jeison; Legendre, Daniel; Nicolosi, Denys; Biscegli, Jose; Pinotti, Marcos; Ohashi, Yukio; Nosé, Yukihiko

2003-05-01

The auxiliary total artificial heart (ATAH) is an electromechanically driven artificial heart with reduced dimensions, which is able to be implanted in the right thoracic or abdominal cavities of an average human patient without removing the natural heart or the heart neurohumoral inherent control mechanism for the arterial pressure. This device uses a brushless direct current motor and a mechanical actuator (roller screw) to move two diaphragms. The ATAH's beating frequency is regulated through the change of the left preload, based on Frank-Starling's law, assisting the native heart in obtaining adequate blood flow. The ATAH left and right stroke volumes are 38 ml and 34 ml, respectively, giving approximately 5 L/min of cardiac output at 160 bpm. Flow visualization studies were performed in critical areas on the ATAH left chamber. A closed circuit loop was used with water and glycerin (37%) at 25 degrees C. Amberlite particles (80 mesh) were illuminated by a 1 mm planar helium-neon laser light. With left mean preload fixed at 10 mm Hg and the afterload at 100 mm Hg, the heart rate varied from 60 to 200 bpm. Two porcine valves were used on the inlet and outlet ports. The flow pattern images were obtained using a color micro-camera and a video recorder. Subsequently, these images were digitized using a PC computer. A persistent stagnant flow was detected in the left chamber inlet port. After improvement on the left chamber design, this stagnant flow disappeared.

Parallel kinematic mechanisms for distributed actuation of future structures

NASA Astrophysics Data System (ADS)

Lai, G.; Plummer, A. R.; Cleaver, D. J.; Zhou, H.

2016-09-01

Future machines will require distributed actuation integrated with load-bearing structures, so that they are lighter, move faster, use less energy, and are more adaptable. Good examples are shape-changing aircraft wings which can adapt precisely to the ideal aerodynamic form for current flying conditions, and light but powerful robotic manipulators which can interact safely with human co-workers. A 'tensegrity structure' is a good candidate for this application due to its potentially excellent stiffness and strength-to-weight ratio and a multi-element structure into which actuators could be embedded. This paper presents results of an analysis of an example practical actuated tensegrity structure consisting of 3 ‘unit cells’. A numerical method is used to determine the stability of the structure with varying actuator length, showing how four actuators can be used to control movement in three degrees of freedom as well as simultaneously maintaining the structural pre-load. An experimental prototype has been built, in which 4 pneumatic artificial muscles (PAMs) are embedded in one unit cell. The PAMs are controlled antagonistically, by high speed switching of on-off valves, to achieve control of position and structure pre-load. Experimental and simulation results are presented, and future prospects for the approach are discussed.

[The Contribution of Vascular Capacity and Blood Volume to Maintain Stable Blood Circulation during General Anesthesia].

PubMed

Shigemi, Kenji

2016-05-01

To maintain proper cardiac preload is one of the most effective procedures for the systemic circulation remaining stable. In particular, the balance between vascular capacity and total blood volume must be maintained within appropriate range by the administration of fluids, blood and/or vasoactive drugs with mean circulatory filling pressure (Pmcf), central venous pressure (CVP) or stroke volume variation (SVV). End-diastolic left ventricular volume (Ved) is theoretically the best index of cardiac preload; however, without transesophageal echocardbalanceiogram we cannot directly monitor Ved during anesthesia. The infused fluid volume remaining in intravascular space, the vascular capacity controlled by autonomic nervous system and/or vasoactive agents, and the unstressed blood volume properly mobilized to excess blood volume are the crucial factors to maintain cardiac output The knowledge of vascular physiology contribute the decision making to manipulate such factors to control blood circulation during general anesthesia. For example, CVP is usually maintained in the narrow range and seems to be stable; however, it must be changed just after the circulatory disturbances, such as acute bleeding, blood transfusion, and fluid infusion, and followed by gradual returning to initial value, because of the solid mechanism to preserve cardiac output

Modelling and testing of a piezoelectric ultrasonic micro-motor suitable for in vivo micro-robotic applications

NASA Astrophysics Data System (ADS)

Watson, B.; Friend, J.; Yeo, L.

2010-11-01

A piezoelectric ultrasonic resonant micro-motor is developed with a stator diameter of 241 μm and an overall diameter of 400 μm. The motor is shown to produce a start-up torque of 1.2 nN m and a peak output power of 0.25 μW as designed, with a preload of 46.6 μN. An increase in preload to 2264 μN improved the performance to a start-up torque of 29 nN m and a peak output power of 9.1 μW. The motor is five times smaller than the current smallest piezoelectric ultrasonic resonant motor produced by Kanda et al. The motor is designed to operate at approximately 771 kHz, matching the fundamental axial, second harmonic torsional and electro-mechanical resonant frequencies. This is achieved through the use of a novel design process that uses scaling theories to greatly reduce the computational time to design the device. The resultant size and performance of the motor make it the first motor design capable of meeting the requirements of a drive system in a tetherless swimming in vivo micro-robot.

A one-stage, high-load capacity separation actuator using anti-friction rollers and redundant shape memory alloy wires.

PubMed

Xiaojun, Yan; Dawei, Huang; Xiaoyong, Zhang; Ying, Liu; Qiaolong, Yang

2015-12-01

This paper proposes a SMA (shape memory alloy) wire-based separation actuator with high-load capacity and simple structure. The novel actuator is based on a one-stage locking mechanism, which means that the separation is directly driven by the SMA wire. To release a large preload, a group of anti-friction rollers are adopted to reduce the force for triggering. In addition, two SMA wires are used redundantly to ensure a high reliability. After separation, the actuator can be reset automatically without any auxiliary tool or manual operation. Three prototypes of the separation actuator are fabricated and tested. According to the performance test results, the actuator can release a maximum preload of 40 kN. The separation time tends to decrease as the operation current increases and it can be as short as 0.5 s under a 7.5 A (the voltage is 5.8 V) current. Lifetime test indicates that the actuator has a lifetime of more than 50 cycles. The environmental tests demonstrate that the actuator can endure the typical thermal and vibration environment tests without unexpected separation or structure damage, and separate normally after these environment tests.

Effect of simulated sampling disturbance on creep behaviour of rock salt

NASA Astrophysics Data System (ADS)

Guessous, Z.; Gill, D. E.; Ladanyi, B.

1987-10-01

This article presents the results of an experimental study of creep behaviour of a rock salt under uniaxial compression as a function of prestrain, simulating sampling disturbance. The prestrain was produced by radial compressive loading of the specimens prior to creep testing. The tests were conducted on an artifical salt to avoid excessive scattering of the results. The results obtained from several series of single-stage creep tests show that, at short-term, the creep response of salt is strongly affected by the preloading history of samples. The nature of this effect depends upon the intensity of radial compressive preloading, and its magnitude is a function of the creep stress level. The effect, however, decreases with increasing plastic deformation, indicating that large creep strains may eventually lead to a complete loss of preloading memory.

Protein-Containing Multilayer Capsules by Templating on Mesoporous CaCO3 Particles: POST- and PRE-Loading Approaches.

PubMed

Balabushevich, Nadezhda G; Lopez de Guerenu, Anna V; Feoktistova, Natalia A; Skirtach, Andre G; Volodkin, Dmitry

2016-01-01

Encapsulation of model proteins (catalase, insulin, aprotinin) into multilayer dextran sulphate/protamin capsules by templating on CaCO3 microparticles is investigated employing: (i) PRE-loading into CaCO3 particles by adsorption or co-synthesis and (ii) POST-loading into performed capsules. Protein encapsulation is governed by both its size and electrostatic interactions with the carbonate microparticles and multilayer shell. PRE-loading enables improved encapsulation compared to POST-loading (catalase content in capsules 630 and 70 mg · g(-1)). Bioactivity of encapsulated protein is not affected by interaction with multilayers but may be reduced at slightly alkaline pH due to CaCO3 hydrolysis. This study might help to successfully encapsulate fragile bio-macromolecules into multilayer capsules. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dietary fibers reduce food intake by satiation without conditioned taste aversion in mice.

PubMed

Rasoamanana, Rojo; Even, Patrick C; Darcel, Nicolas; Tomé, Daniel; Fromentin, Gilles

2013-02-17

It is well known that intake of dietary fiber (DF) potently decreases food intake and feelings of hunger and/or promotes satiety ratings. However, the mechanisms explaining these effects are not well characterized. This work was performed to determine which of satiation and/or satiety mechanisms provoke the decrease of food intake induced by DF in mice. We tested in an intra-group protocol a low-viscosity (LV, fructo-oligosaccharide), a viscous (VP, guar gum) and a high-viscosity (HV, mixture of guar gum and fructo-oligosaccharide) preload. These were given to mice by intra-gastric gavage. It appeared that viscous preloads such as VP and HV reduced the daily energy intake by 14% and 21% respectively. The strong effect of HV was mainly due to a large decrease of meal size (by 57%) and meal duration (by 65%) with no effect on ingestion rate during the first 30 min after administration. Therefore, the DF-induced decrease of energy intake was due to a satiation mechanism. This is further supported by a 3-fold increased sensitization of neurons in the nucleus of the solitary tract as observed by c-Fos protein immunolabelling. No compensation of food intake was observed during the rest of the day, a phenomenon that may be explained by the fact that metabolic rate remained high despite the lower food intake. We have also shown that the DF-induced inhibition of food intake was not paired with a conditioned taste aversion. To conclude, this work demonstrates that DF inhibits food intake by increasing satiation during ~1h after administration. Copyright © 2012 Elsevier Inc. All rights reserved.

Pneumatic preloaded scanning science launch latch system

NASA Technical Reports Server (NTRS)

Kievit, J. C.

1979-01-01

A relatively simple system using a preloaded pneumatic piston latch with a pyrotechnic valve release was developed. The system was the only candidate that met all the imposed requirements utilizing reliable state-of-art components. The development of the latch system from its first use on Mariner '69 Mars Flyby Spacecraft through its most recent use on the Voyager Spacecraft that will fly to Jupiter and Saturn is reviewed.

Cardiorespiratory interactions and blood flow generation during cardiac arrest and other states of low blood flow.

PubMed

Sigurdsson, Gardar; Yannopoulos, Demetris; McKnite, Scott H; Lurie, Keith G

2003-06-01

Recent advances in cardiopulmonary resuscitation have shed light on the importance of cardiorespiratory interactions during shock and cardiac arrest. This review focuses on recently published studies that evaluate factors that determine preload during chest compression, methods that can augment preload, and the detrimental effects of hyperventilation and interrupting chest compressions. Refilling of the ventricles, so-called ventricular preload, is diminished during cardiovascular collapse and resuscitation from cardiac arrest. In light of the potential detrimental effects and challenges of large-volume fluid resuscitations, other methods have increasing importance. During cardiac arrest, active decompression of the chest and impedance of inspiratory airflow during the recoil of the chest work by increasing negative intrathoracic pressure and, hence, increase refilling of the ventricles and increase cardiac preload, with improvement in survival. Conversely, increased frequency of ventilation has detrimental effects on coronary perfusion pressure and survival rates in cardiac arrest and severe shock. Prolonged interruption of chest compressions for delivering single-rescuer ventilation or analyzing rhythm before shock delivery is associated with decreased survival rate. Cardiorespiratory interactions are of profound importance in states of cardiovascular collapse in which increased negative intrathoracic pressure during decompression of the chest has a favorable effect and increased intrathoracic pressure with ventilation has a detrimental effect on survival rate.

Preload Monitoring of Bolted L-Shaped Lap Joints Using Virtual Time Reversal Method.

PubMed

Du, Fei; Xu, Chao; Wu, Guannan; Zhang, Jie

2018-06-13

L-shaped bolt lap joints are commonly used in aerospace and civil structures. However, bolt joints are frequently subjected to loosening, and this has a significant effect on the safety and reliability of these structures. Therefore, bolt preload monitoring is very important, especially at the early stage of loosening. In this paper, a virtual time reversal guided wave method is presented to monitor preload of bolted L-shaped lap joints accurately and simply. In this method, a referenced reemitting signal (RRS) is extracted from the bolted structure in fully tightened condition. Then the RRS is utilized as the excitation signal for the bolted structure in loosening states, and the normalized peak amplitude of refocused wave packet is used as the tightness index (TI A ). The proposed method is experimentally validated by L-shaped bolt joints with single and multiple bolts. Moreover, the selections of guided wave frequency and tightness index are also discussed. The results demonstrate that the relationship between TI A and bolt preload is linear. The detection sensitivity is improved significantly compared with time reversal (TR) method, particularly when bolt loosening is at its embryo stage. The results also show that TR method is an effective method for detection of the number of loosening bolts.

Effect of sucrose and safflower oil preloads on short term appetite and food intake of young men.

PubMed

Woodend, D M; Anderson, G H

2001-12-01

The effects of carbohydrate and fat on satiety have been examined primarily through meal composition studies. The purpose of this study was to compare the effects of pure sucrose and safflower oil, isovolumetric beverage preloads, on appetite (measured every 15 minutes by visual analogue scales) and food intake 60 minutes later. Young men consumed 0, 418, 836 and 1254 kJ of sucrose in the first two experiments and these same doses of safflower oil in the third. Finally, the largest doses of sucrose and safflower oil were compared. Sucrose, but not safflower oil, suppressed average appetite compared with control. In experiment 2, food intake was reduced (p<0.05) by 518 kJ after the 418 and 836 kJ preloads and by 1129 kJ after the 1254 kJ sucrose preload. Only the 1254 kJ dose of safflower oil significantly suppressed food intake by 480 kJ in the third experiment. When the 1254 kJ doses were compared directly, sucrose suppressed food intake by 653 kJ compared with control where as safflower oil did not. It is concluded that, in the short-term, sucrose produces a dose dependent reduction in appetite and food intake that is greater than that produced by safflower oil.

Quantifying the variability in stiffness and damping of an automotive vehicle's trim-structure mounts

NASA Astrophysics Data System (ADS)

Abolfathi, Ali; O'Boy, Dan J.; Walsh, Stephen J.; Dowsett, Amy; Fisher, Stephen A.

2016-09-01

Small plastic clips are used in large numbers in automotive vehicles to connect interior trims to vehicle structures. The variability in their properties can contribute to the overall variability in noise and vibration response of the vehicle. The variability arises due to their material and manufacturing tolerances and more importantly due to the boundary condition. To measure their stiffness and damping, a simple experimental rig is used where a mass is supported by the clip which is modelled as a single degree of freedom system. The rig is designed in a way that it simulates the boundary condition as those of the real vehicle. The variability in clip and also due to the boundary condition at the structure side is first examined which is 7% for stiffness and 8% for damping. To simulate the connection of the trim side, a mount is built using a 3D printer. Rattling occurs in the response of the clips with loose connections, however by preloading the mount the effective stiffness increases and the rattling is eliminated. The variability due to the boundary condition at the trim side was as large as 40% for stiffness and 52% for damping.

Preloadable vector sensitive latch

NASA Technical Reports Server (NTRS)

Acres, William R. (Inventor)

1987-01-01

A preloadable vector-sensitive latch which automatically releases when the force vector from a latch memebr reaches a specified release angle is presented. In addition, it contains means to remove clearance between the latched members and to preload the latch to prevent separation at angles less than the specified release angle. The latch comprises a triangular main link, a free link connected between a first corner of the main link and a yoke member, a housing, and an actuator connected between the yoke member and the housing. A return spring bias means connects the main link to a portion of the housing. A second corner of the main link is slidably and pivotally connected to the housing via a slot in a web portion of the housing. The latch housing has a rigid docking ring alignable with a mating locking ring which is engageable by a locking roller journalled on the third corner of the triangular main link.

Can alginate-based preloads increase weight loss beyond calorie restriction? A pilot study in obese individuals.

PubMed

Georg Jensen, M; Kristensen, M; Astrup, A

2011-12-01

This randomized, controlled, 2-week intervention study in 24 obese subjects tested the effect on body weight loss and gastrointestinal tolerance of consuming low viscous alginate fibre-based preloads of 3% concentration (500 ml volume) three times a day as an adjuvant to a calorie-restricted diet. The pilot study showed that intake of the alginate preloads was moderately acceptable to the majority of subjects but did not produce additional body weight loss beyond calorie restriction (-1.42 ± 0.38 kg) (n=12) compared to control group (-1.56 ± 0.21 kg) (n=8). These results do not support that alginate supplementation enhance the weight loss effects of a hypo-caloric diet, but a sufficiently powered long-term study is needed to explore whether alginate could be an aid for improving weight loss during caloric-restriction. Copyright © 2011 Elsevier Ltd. All rights reserved.

Q-switched oscillation in thulium-doped fiber lasers using preloaded dynamic microbending technique

NASA Astrophysics Data System (ADS)

Sakata, H.; Takahashi, N.; Ushiro, Y.

2018-01-01

We demonstrate Q-switched pulse generation in thulium-doped fiber lasers by introducing piezoelectric-driven microbend with preloaded stress. We employed a pair of corrugated chips each attached on piezoelectric actuators (PAs) to clamp the fiber in a ring laser resonator. The thulium-doped fiber is pumped by a laser diode emitting at 1.63 μm and generates the Q-switched laser pulses at around 1.9 μm by switching off the PAs. The laser pulse performance is improved by optimizing the preload and switch-off period for the PAs. The Q-switched pulses with a peak power of 2.8 W and a pulsewidth of 900 ns are observed for a launched pump power of 161 mW. We expect that the in-fiber Q-switching technique will provide efficient laser systems for environmental sensing and medical applications.

Pre-load on oral implants after screw tightening fixed full prostheses: an in vivo study.

PubMed

Duyck, J; Van Oosterwyck, H; Vander Sloten, J; De Cooman, M; Puers, R; Naert, I

2001-03-01

The fit of implant supported fixed prostheses is said to be of clinical concern because of the rigid fixation of an oral implant in its surrounding bone. The influence of the torque sequence of the set screws during fixation of implant supported fixed full prostheses on the final pre-load was investigated in vitro. No significant effect of the torque sequence of the set screws on the final pre-load was observed. The main objective of this study was to quantify and qualify the pre-load in vivo on implants supporting a fixed full prosthesis. This was performed when the prostheses were supported by all five or six implants and was repeated when the prostheses were supported by only four and three implants. A total of 13 patients with a fixed full implant supported prosthesis were selected. The existing abutments were changed for strain gauged abutments. After tightening the set screws with a torque of 10 N cm, the pre-load conditions were registered. The average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 323 N (43 N), 346 N (59 N), 307 N (60 N) 21 N cm (3 N cm) and 21 N cm (2 N cm), 23 N cm (5 N cm), respectively. In addition, the pre-load was registered after fixation of a machined gold cylinder, as delivered by the manufacturer, on each of the supporting implants, representing the 'optimal fit' situation. The corresponding average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 426 N (36 N), 405 N (40 N), 413 N (46 N) and 8 N cm (1 N cm), 8 N cm (1 N cm), 8 N cm (1 N cm), respectively. The induced axial forces after tightening the prostheses were significantly lower then after tightening the gold cylinder in case of five or six supporting implants (P < 0.02). The induced bending moments after tightening the prostheses were statistically significantly higher (P < 0.0001) then after tightening the gold cylinder in all test conditions (five or six, four or three supporting implants). This study underlines the static load present after screw tightening implant supported fixed full prostheses.

A space release/deployment system actuated by shape memory wires

NASA Astrophysics Data System (ADS)

Fragnito, Marino; Vetrella and, Sergio

2002-11-01

In this paper, the design of an innovative hold down/release and deployment device actuated by shape memory wires, to be used for the first time for the S MA RT microsatellite solar wings is shown. The release and deployment mechanisms are actuated by a Shape Memory wire (Nitinol), which allows a complete symmetrical and synchronous release, in a very short time, of the four wings in pairs. The hold down kinematic mechanism is preloaded to avoid vibration nonlinearities and unwanted deployment at launch. The deployment mechanism is a simple pulley system. The stiffness of the deployed panel-hinge system needs to be dimensioned in order to meet the on-orbit requirement for attitude control. One-way roller clutches are used to keep the panel at the desired angle during the mission. An ad hoc software has been developed to simulate both the release and deployment operations, coupling the SMA wire behavior with the system mechanics.

Development of the Aquarius Antenna Deployment Mechanisms and Spring/Damper Actuator

NASA Technical Reports Server (NTRS)

Johnson, Joel A.

2008-01-01

The Aquarius Instrument s large radar reflector dish needed to be stowed for launch, and then deployed on-orbit. The Deployment Subsystem consisted of a cantilevered boom structure and two single-axis hinge mechanisms to accurately deploy and position the reflector dish relative to the radar feed horns. The cantilevered design demanded high stiffness and accuracy from the deployment mechanism at the root of the boom. A preload-generating end-of-travel latch was also required. To largely eliminate the need for control systems, each deployment mechanism was actuated by a passive spring motor with viscous-fluid damping. Tough requirements and adaptation of a heritage actuator to the new application resulted in numerous challenges. Fabrication, assembly, and testing encountered additional problems, though ultimately the system was demonstrated very successfully. This paper revisits the development to highlight which design concepts worked and the many important lessons learned.

Design of a Combined Ballistic Simulator and Primer Force Experimental Fixture

DTIC Science & Technology

2015-08-01

preload bolt and breech, and between the breech and chamber, were found to be too loose. When heavy grease or Teflon tape was used to tighten the...increase the difficulty of removing and tightening the breech. The preload bolt does not have to be removed between firing and in future designs could use... tightened it could loosen the primer plate, so left-handed threads were machined on the primer plate. The ballistic simulator fixture was occasionally

Efficacy of water preloading before main meals as a strategy for weight loss in primary care patients with obesity: RCT.

PubMed

Parretti, Helen M; Aveyard, Paul; Blannin, Andrew; Clifford, Susan J; Coleman, Sarah J; Roalfe, Andrea; Daley, Amanda J

2015-09-01

To investigate the efficacy of water preloading before meals as a weight loss strategy for adults with obesity. A two-group randomized controlled trial was conducted in Birmingham, England. Eighty-four adults with obesity were recruited from general practices. All participants were given a face-to-face weight management consultation at baseline (30 min) and a follow-up telephone consultation at 2 weeks (10 min). At baseline, participants were randomized to either drinking 500 ml of water 30 min before their main meals or an attention control group where participants were asked to imagine their stomach was full before meals. The primary outcome was weight change at 12-week follow-up. Several measures of adherence were also used, including 24 h total urine collections. 41 participants were randomized to the intervention group and 43 to the comparator group. The water preloading group lost -1.3 kg (95% CI -2.4 to -0.1, P = 0.028) more than comparators at follow up. Adjusting for ethnicity, deprivation, age, and gender resulted in the intervention group losing -1.2 kg (95% CI -2.4 to 0.07, P = 0.063) more than the comparator. There is preliminary evidence that water preloading before main meals leads to a moderate weight loss at follow up. ISRCTN33238158. © 2015 The Obesity Society.

Movement of unlined landfill under preloading surcharge.

PubMed

Al-Yaqout, Anwar F; Hamoda, Mohamed F

2007-01-01

As organic solid waste is decomposed in a landfill and mass is lost due to gas and leachate formation, the landfill settles. Settlement of a landfill interferes with the rehabilitation and subsequent use of the landfill site after closure. This study examined the soil/solid waste movement at the Al-Qurain landfill in Kuwait after 15 years of closure as plans are underway for redevelopment of the landfill site that occupies about a km(2) with an average depth of 8-15m. Field experiments were conducted for 6 mo to measure soil/solid waste movement and water behavior within the landfill using two settlement plates with a level survey access, Casagrande-type piezometers, pneumatic piezometers, and magnetic probe extensometers. Previous results obtained indicated that biological decomposition of refuse continued after closure of the landfill site. The subsurface water rise enhanced the biological activities, which resulted in the production of increasing quantities of landfill gas. The refuse fill materials recorded a high movement rate under the imposed preloading as a result of an increase in the stress state. Up to 55% of the total movement was observed during the first 2 weeks of fill placement and increased to 80% within the first month of the 6-mo preloading test. Pneumatic piezometers showed an increase in water head, which is attributed to the developed pressure of gases escaping during the preloading period.

Corneal incision architecture after IOL implantation with three different injectors: an environmental scanning electron microscopy study.

PubMed

Mencucci, Rita; Favuzza, Eleonora; Salvatici, Maria Cristina; Spadea, Leopoldo; Allen, David

2018-02-01

To evaluate by Environmental Scanning Electron Microscopy (ESEM) the corneal incision architecture after intraocular lens (IOL) implantation in pig eyes, using manual, automated injectors or preloaded delivery systems. Twenty-four pig eyes underwent IOL implantation in the anterior chamber using three different injectors: manual (Monarch III) (n = 8), automated (AutoSert) (n = 8), or a preloaded system (UltraSert) (n = 8). Acrysof IQ IOLs, 21 Dioptres (D) (n = 12) and 27D (n = 12), were implanted through 2.2 mm clear corneal incisions. Incision width was measured using corneal calipers. The endothelial side of the incision was analyzed with ESEM. In each group, the final size of the corneal wound after IOL implantation, measured by calipers, was 2.3-2.4 mm. The incision architecture resulted more irregular in the Monarch group compared with the other injectors. In every group the 27D IOL-implanted specimens showed more alterations than in 21D IOL-implanted samples, and this was less evident in the UltraSert group. The Descemet tear length was higher in the Monarch group than AutoSert and UltraSert group. The automated and preloaded delivery systems provided a good corneal incision architecture; after high-power IOL implantation the incisions were more regular and less damaged with the preloaded system than with the other devices.

Monitoring of intrathoracic volemia and cardiac output in critically ill children.

PubMed

Cecchetti, C; Stoppa, F; Vanacore, N; Barbieri, M A; Raucci, U; Pasotti, E; Tomasello, C; Marano, M; Pirozzi, N

2003-12-01

Hemodynamic monitoring is an important step in the management of critically ill children despite the difficulty in measuring preload indices continuously. The aim of the study was to analyze cardiac output parameters and preload indices after acute changes in mean airway pressure and volemia. Twenty-three children treated at our unit were enrolled in a prospective non randomized cohort study. Respiration was supported by controlled mechanical ventilation with positive expiratory-end pressure (PEEP), peak inspiratory pressure <20 cm H(2)O and mean airway pressure <10 cm H(2)O, and hemodynamic monitoring using the PiCCO system. Hemodynamic parameters were measured at T0 (base line), T(1) (after an increase in PEEP of 5 cm H(2)O for 10 min), and T(2) (after fluid challenge). The statistical analysis (BMPD New System software package) comprised comparison of changes at T(0) vs T(1), T(1) vs T(2) and T(0) vs T(2), construction of 3 correlation matrices and multiple linear regression analysis. Sixty-nine hemodynamic parameters were measured in the 23 patients. A comparison between T(0) and T(1) showed no significant changes; differences between T(0) and T(2) were found for cardiac index (CI), (p=0.003); between T(0) and T(2) significant differences were found for CI (p=0.0015), intrathoracic blood volume index (ITBVI) (p=0.04) and stroke volume index (SVI) (p=0.06). The analysis of the correlation matrices yielded ITBVI with CI (p=0.0006), ITBVI with SVI (p=1 x 10(-5)), CI with SVI (p=0.002); a significant correlation between CI and extravascular lung water index (EVLWI) was found only at T(1). Multiple linear regression analysis showed that ITBVI and SVI were predictive for variance of CI at each time point. ITBVI measured by a volumetric monitoring system such as the PiCCO may be considered a sensitive preload indicator also in critically ill children.

Pleural effusion decreases left ventricular pre-load and causes haemodynamic compromise: an experimental porcine study.

PubMed

Wemmelund, K B; Lie, R H; Juhl-Olsen, P; Frederiksen, C A; Hermansen, J F; Sloth, E

2012-08-01

Although pleural effusion is a common complication in critically ill patients, detailed knowledge is missing about the haemodynamic impact and the underlining mechanisms. The aim of this study was to evaluate the haemodynamic effect of incremental pleural effusion by means of invasive haemodynamic parameters and transthoracic echocardiography. This experimental interventional study was conducted using 22 female piglets (17.5-21.5 kg) randomized for right-side (n = 9) and left-side (n = 9) pleural effusion, or sham operation (n = 4). Pleural effusion was induced by infusing incremental volumes of saline into the pleural cavity. Invasive haemodynamic measurements and echocardiographical images were obtained at baseline, a volume of 45 ml/kg, a volume of 75 ml/kg and 45 min after drainage. No difference (all P > 0.147) was found between right- and left-side pleural effusion, and the groups were thus pooled. At 45 ml/kg cardiac output, mean arterial pressure, stroke volume and mixed venous saturation decreased (all P < 0.003); central venous pressure and pulmonary arterial pressure increased (both P > 0.003) at this point. The changes accelerated at 75 ml/kg. At 45 ml/kg left ventricular pre-load in terms of end-diastolic area decreased significantly (P < 0.001). The effect on haemodynamics and cardiac dimensions changed dramatically at 75 ml/kg. Cardiac output, mean arterial pressure, central venous pressure and left ventricular end-diastolic area returned to normal during a recovery period of 45 min (all P > 0.061). Incremental volumes of unilateral pleural effusion induced a significant haemodynamic impact fully reversible after drainage. Pleural effusion causes a significant decrease of left ventricular pre-load in a diverse picture of haemodynamic compromise. © 2012 The Authors. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation.

A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

NASA Astrophysics Data System (ADS)

Paleu, V.; Gurău, G.; Comăneci, R. I.; Sampath, V.; Gurău, C.; Bujoreanu, L. G.

2018-07-01

A new application of Fe-Mn-Si based shape memory alloys (SMAs) was developed under the form of truncated cone-shaped module, for self-adaptive axial preload control in angular contact bearings. The modules were processed by high-speed high-pressure torsion (HS-HPT), from circular crowns cut from axially drilled ingots of Fe-28Mn-6Si-9Cr (mass%) SMA. The specimens were mechanically tested in the hot rolled state, prior to HS-HPT processing, demonstrating free-recovery shape memory effect (SME) and high values for ultimate tensile stress and strain as well as low cycle fatigue life. The HS-HPT modules were subjected to static loading–unloading compression, without/with lubrication at specimen-tool interface, both individually and in different coupling modes. Dry compression cycles revealed reproducible stress plateaus both during loading and unloading stages, being associated with hardness gradient, along cone generator, caused by HS-HPT processing. Constrained recovery tests, performed using compressed modules, emphasized the continuous generation of stress during heating, by one way SME, at a rate of ∼9.3 kPa/%. Dynamic compression tests demonstrated the capability of modules to develop closed stress–strain loops after 50 000 cycles, without visible signs of fatigue. HS-HPT caused the fragmentation of crystalline grains, while compression cycles enabled the formation of ε hexagonal close-packed stress-induced martensite (ε), which is characterized by a high density of stacking faults. Using an experimental setup, specifically designed and manufactured for this purpose, both feasibility and functionality tests were performed using HS-HPT modules. The feasibility tests proved the existence of a general tendency of both axial force and friction torque to increase in time, favoured by the increase of initial preloading force and the augmentation of rotation speed. Functionality tests, performed on two pairs of HS-HPT modules fastened in base-to-base coupling mode, demonstrated the capacity of modules to accommodate high preloads while maintaining both axial force and friction torque at constant values in time. These preliminary results suggest that, for the time being, the modules can operate only as single use applications, more effective during the running-in period. This bevahior recommends HS-HPT modules as a new application of Fe-Mn-Si SMAs, with the potential to be used for the development of new temperature-responsive compression displacement systems.

A Protein Preload Enhances the Glucose-Lowering Efficacy of Vildagliptin in Type 2 Diabetes.

PubMed

Wu, Tongzhi; Little, Tanya J; Bound, Michelle J; Borg, Malcolm; Zhang, Xiang; Deacon, Carolyn F; Horowitz, Michael; Jones, Karen L; Rayner, Christopher K

2016-04-01

Nutrient "preloads" given before meals can attenuate postprandial glycemic excursions, at least partly by slowing gastric emptying and stimulating secretion of the incretins (i.e., glucagon-like peptide-1 [GLP-1] and glucose-dependent insulinotropic polypeptide [GIP]). This study was designed to evaluate whether a protein preload could improve the efficacy of the dipeptidyl peptidase-4 (DPP-4) inhibitor vildagliptin to increase incretin concentrations, slow gastric emptying, and lower postprandial glycemia in type 2 diabetes. Twenty-two patients with type 2 diabetes treated with metformin were studied on four occasions, receiving either 50 mg vildagliptin (VILD) or placebo (PLBO) on both the evening before and the morning of each study day. The latter dose was followed after 60 min by a preload drink containing either 25 g whey protein (WHEY) or control flavoring (CTRL), and after another 30 min by a (13)C-octanoate-labeled mashed potato meal. Plasma glucose and hormones, and gastric emptying, were evaluated. Compared with PLBO/CTRL, PLBO/WHEY reduced postprandial peak glycemia, increased plasma insulin, glucagon, and incretin hormones (total and intact), and slowed gastric emptying, whereas VILD/CTRL reduced both the peak and area under the curve for glucose, increased plasma intact incretins, and slowed gastric emptying but suppressed plasma glucagon and total incretins (P < 0.05 each). Compared with both PLBO/WHEY and VILD/CTRL, VILD/WHEY was associated with higher plasma intact GLP-1 and GIP, slower gastric emptying, and lower postprandial glycemia (P < 0.05 each). In metformin-treated type 2 diabetes, a protein preload has the capacity to enhance the efficacy of vildagliptin to slow gastric emptying, increase plasma intact incretins, and reduce postprandial glycemia. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Real time bolt preload monitoring using piezoceramic transducers and time reversal technique—a numerical study with experimental verification

NASA Astrophysics Data System (ADS)

Parvasi, Seyed Mohammad; Ho, Siu Chun Michael; Kong, Qingzhao; Mousavi, Reza; Song, Gangbing

2016-08-01

Bolted joints are ubiquitous structural elements, and form critical connections in mechanical and civil structures. As such, loosened bolted joints may lead to catastrophic failures of these structures, thus inspiring a growing interest in monitoring of bolted joints. A novel energy based wave method is proposed in this study to monitor the axial load of bolted joint connections. In this method, the time reversal technique was used to focus the energy of a piezoelectric (PZT)-generated ultrasound wave from one side of the interface to be measured as a signal peak by another PZT transducer on the other side of the interface. A tightness index (TI) was defined and used to correlate the peak amplitude to the bolt axial load. The TI bypasses the need for more complex signal processing required in other energy-based methods. A coupled, electro-mechanical analysis with elasto-plastic finite element method was used to simulate and analyze the PZT based ultrasonic wave propagation through the interface of two steel plates connected by a single nut and bolt connection. Numerical results, backed by experimental results from testing on a bolted connection between two steel plates, revealed that the peak amplitude of the focused signal increases as the bolt preload (torque level) increases due to the enlarging true contact area of the steel plates. The amplitude of the focused peak saturates and the TI reaches unity as the bolt axial load reaches a threshold value. These conditions are associated with the maximum possible true contact area between the surfaces of the bolted connection.

Ground-based testing of the dynamics of flexible space structures using band mechanisms

NASA Technical Reports Server (NTRS)

Yang, L. F.; Chew, Meng-Sang

1991-01-01

A suspension system based on a band mechanism is studied to provide the free-free conditions for ground based validation testing of flexible space structures. The band mechanism consists of a noncircular disk with a convex profile, preloaded by torsional springs at its center of rotation so that static equilibrium of the test structure is maintained at any vertical location; the gravitational force will be directly counteracted during dynamic testing of the space structure. This noncircular disk within the suspension system can be configured to remain unchanged for test articles with the different weights as long as the torsional spring is replaced to maintain the originally designed frequency ratio of W/k sub s. Simulations of test articles which are modeled as lumped parameter as well as continuous parameter systems, are also presented.

What is the normal haemodynamic response to passive leg raise? A study of healthy volunteers.

PubMed

Elwan, Mohammed H; Roshdy, Ashraf; Reynolds, Joseph A; Elsharkawy, Eman M; Eltahan, Salah M; Coats, Timothy J

2018-05-04

Passive leg raise (PLR) is used as self-fluid challenge to optimise fluid therapy by predicting preload responsiveness. However, there remains uncertainty around the normal haemodynamic response to PLR with resulting difficulties in application and interpretation in emergency care. We aim to define the haemodynamic responses to PLR in spontaneously breathing volunteers using a non-invasive cardiac output monitor, thoracic electrical bioimpedance, TEB (PLR-TEB). We recruited healthy volunteers aged 18 or above. Subjects were monitored using TEB in a semirecumbent position, followed by PLR for 3 min. The procedure was repeated after 6 min at the starting position. Correlation between the two PLRs was assessed using Spearman's r (r s ). Agreement between the two PLRs was evaluated using Cohen Kappa with responsiveness defined as ≥10% increase in stroke volume. Parametric and non-parametric tests were used as appropriate to evaluate statistical significance of baseline variables between responders and non-responders. We enrolled 50 volunteers, all haemodynamically stable at baseline, of whom 49 completed the study procedure. About half of our subjects were preload responsive. The ∆SV in the two PLRs was correlated (r s =0.68, 95% CI 0.49 to 0.8) with 85% positive concordance. Good agreement was observed with Cohen Kappa of 0.67 (95% CI 0.45 to 0.88). Responders were older and had significantly lower baseline stroke volume and cardiac output. Our results suggest that the PLR-TEB is a feasible method in spontaneously breathing volunteers with reasonable reproducibility. The age and baseline stroke volume effect suggests a more complex underlying physiology than commonly appreciated. The fact that half of the volunteers had a positive preload response, against the 10% threshold, leads to questions about how this measurement should be used in emergency care and will help shape future patient studies. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Scaling trace organic contaminant adsorption capacity by granular activated carbon.

PubMed

Corwin, Christopher J; Summers, R Scott

2010-07-15

The role of particle size on the reduction of granular activated carbon (GAC) adsorption capacity for trace organic contaminants by dissolved organic matter (DOM) is examined and applied to performance scale-up. The adsorption capacity reduction, termed fouling, must be scalable in order to use bench scale tests, such as the rapid small-scale column test (RSSCT) to predict full-scale breakthrough. Equilibrium adsorption capacity tests with GAC preloaded with DOM and RSSCT breakthrough curves at three different GAC particle sizes indicate that GAC adsorption capacity is dependent on GAC particle size when DOM is present. Thus, the RSSCT cannot be expected to match full-scale results regardless of which RSSCT design approach is used (constant or proportional diffusivity), unless a scaling factor is applied to the results. Proportional diffusivity RSSCT breakthrough curves demonstrate that surface concentration of DOM is not a good measure of fouling. It is hypothesized that pore blockage is the mechanism responsible for the dependence on particle size. As GAC particle size increases, the microporous surface area behind a constricted pore also increases. The result is lower adsorption capacity per mass of adsorbent in the larger GAC particles. A scaling methodology for equilibrium and breakthrough data is presented that accounts for the dependence of NOM preloading effects on GAC particle diameter.

Physiological Characterization of the SynCardia Total Artificial Heart in a Mock Circulation System

PubMed Central

Crosby, Jessica R.; DeCook, Katrina J.; Tran, Phat L.; Smith, Richard G.; Larson, Douglas F.; Khalpey, Zain I.; Burkhoff, Daniel; Slepian, Marvin J.

2014-01-01

The SynCardia total artificial heart (TAH) has emerged as an effective, life-saving bi-ventricular replacement system for a wide variety of patients with end-stage heart failure. While the clinical performance of the TAH is established, modern physiologic characterization, in terms of elastance behavior and pressure-volume characterization has not been defined. Herein we examine the TAH in terms of elastance using a non-ejecting left-ventricle, and then characterize the pressure-volume relationship of the TAH by varying preload and afterload parameters using a Donovan Mock Circulatory System. We demonstrate that the TAH does not operate with time-varying elastance, differing from the human heart. Further, we show that the TAH has a pressure-volume relationship behavior that also differs from that of the human heart. The TAH does exhibit Starling-like behavior, with output increasing via preload dependent mechanisms, without reliance on an alteration of inotropic state within the operating window of the TAH. Within our testing range, the TAH is insensitive to variations in afterload, however this insensitivity has a limit, the limit being the maximum driving pressure of the pneumatic driver. Understanding the physiology of the TAH affords insight into the functional parameters that govern artificial heart behavior providing perspective on differences compared to the human heart. PMID:25551416

Physiological characterization of the SynCardia total artificial heart in a mock circulation system.

PubMed

Crosby, Jessica R; DeCook, Katrina J; Tran, Phat L; Smith, Richard G; Larson, Douglas F; Khalpey, Zain I; Burkhoff, Daniel; Slepian, Marvin J

2015-01-01

The SynCardia total artificial heart (TAH) has emerged as an effective, life-saving biventricular replacement system for a wide variety of patients with end-stage heart failure. Although the clinical performance of the TAH is established, modern physiological characterization, in terms of elastance behavior and pressure-volume (PV) characterization has not been defined. Herein, we examine the TAH in terms of elastance using a nonejecting left ventricle, and then characterize the PV relation of the TAH by varying preload and afterload parameters using a Donovan Mock Circulatory System. We demonstrate that the TAH does not operate with time-varying elastance, differing from the human heart. Furthermore, we show that the TAH has a PV relation behavior that also differs from that of the human heart. The TAH does exhibit Starling-like behavior, with output increasing via preload-dependent mechanisms, without reliance on an alteration of inotropic state within the operating window of the TAH. Within our testing range, the TAH is insensitive to variations in afterload; however, this insensitivity has a limit, the limit being the maximum driving pressure of the pneumatic driver. Understanding the physiology of the TAH affords insight into the functional parameters that govern artificial heart behavior providing perspective on differences compared with the human heart.

The dynamic natures of implant loading.

PubMed

Wang, Rui-Feng; Kang, Byungsik; Lang, Lisa A; Razzoog, Michael E

2009-06-01

A fundamental problem in fully understanding the dynamic nature of implant loading is the confusion that exists regarding the torque load delivered to the implant complex, the initial force transformation/stress/strain developed within the system during the implant complex assembly, and how the clamping forces at the interfaces and the preload stress impact the implant prior to any external loading. The purpose of this study was to create an accurately dimensioned finite element model with spiral threads and threaded bores included in the implant complex, positioned in a bone model, and to determine the magnitude and distribution of the force transformation/stress/strain patterns developed in the modeled implant system and bone and, thus, provide the foundational data for the study of the dynamic loading of dental implants prior to any external loading. An implant (Brånemark Mark III), abutment (CeraOne), abutment screw (Unigrip), and the bone surrounding the implant were modeled using HyperMesh software. The threaded interfaces between screw/implant and implant/bone were designed as a spiral thread helix assigned with specific coefficient of friction values. Assembly simulation using ABAQUS and LS-DYNA was accomplished by applying a 32-Ncm horizontal torque load on the abutment screw (Step 1), then decreasing the torque load to 0 Ncm to simulate the wrench removal (Step 2). The postscript data were collected and reviewed by HyperMesh. A regression analysis was used to depict the relationships between the torque load and the mechanical parameters. During the 32-Ncm tightening sequence, the abutment screw elongated 13.3 mum. The tightening torque generated a 554-N clamping force at the abutment/implant interface and a 522-N preload. The von Mises stress values were 248 MPa in the abutment at the abutment-implant interface, 765 MPa at the top of the screw shaft, 694 MPa at the bottom of the screw shaft, 1365 MPa in the top screw thread, and 21 MPa in the bone at the top of the implant-bone interface. This study also identified various characteristic isosurface stress patterns. The maximum stress magnitude to complete the von Mises stress joint pattern in the present model was 107 MPa during screw tightening, and was reduced to 104 MPa with removal of the wrench. Various specific stress patterns were identified within all elements of the implant complex during the assembly simulation. During the torque moment application, the abutment screw was elongated, and every 1.0-mum elongation of the screw was equivalent to a 47.9-N increase of the preload in the implant complex. The ideal index to determine the preload amount was the contact force at the interface between the screw threads and the threaded screw bore. The isosurface mode identified various characteristic stress patterns developed within the implant complex at the various interfaces during the assembly simulation. These patterns are the (1) spiral and ying-yang pattern of the XY stress, (2) spring, cap, clamping, and preload pattern of the ZZ stress, and (3) bone holding and joint pattern of the von Mises stress.

Noninvasive continuous cardiac output by the Nexfin before and after preload-modifying maneuvers: a comparison with intermittent thermodilution cardiac output.

PubMed

Bubenek-Turconi, Serban Ion; Craciun, Mihaela; Miclea, Ion; Perel, Azriel

2013-08-01

The Nexfin uses an uncalibrated pulse contour method for the continuous measurement of cardiac output (CO) in a totally noninvasive manner. Since the accuracy of pulse contour methods and their ability to track changes in CO have been repeatedly questioned, we have compared the CO measured by the Nexfin (NAPCO) with the CO measured by the pulmonary artery catheter (PACCO) in cardiosurgical patients before and after preload-modifying maneuvers. Twenty-eight patients who underwent on-pump cardiac surgery, of whom 18 were receiving vasopressor and/or inotropic therapy, were studied during the first postoperative hours. Preload modification, in the form of either a fluid challenge or a passive leg raising maneuver, was done whenever clinically indicated, with PACCO and NAPCO being simultaneously measured before and after each intervention. A fluid challenge was administered to 22 patients, and the passive leg raising maneuver was performed in 6 patients. These interventions were repeated in 19 patients producing a total of 47 pairs of measurements. At baseline, mean (±SD) CO was 4.9 ± 1.1 and 5.0 ± 1.4 L·min(-1), for the PACCO and NAPCO, respectively, bias 0.1 ± 1.0, 95% prediction interval -2.5 to 2.4 L·min(-1), and 39% of error. After preload modification, the mean CO was 5.6 ± 1.3 and 5.6± 1.5 L·min(-1) for the PACCO and NAPCO, respectively, bias -0.0 ± 1.1, 95% prediction interval -2.6 to 2.7 L·min(-1), and 38% of error. The correlation coefficients (r) between the PACCO and NAPCO before and after preload modification were 0.71 (95% confidence interval [95% CI], 0.53-0.82) and 0.70 (95% CI, 0.52-0.82), respectively. Preload modification induced similar absolute changes in PACCO and NAPCO (r = 0.9, P < 0.0001). A 4-quadrant scatter plot showed a concordance rate of 100% (95% CI, 80.5%-100%) between the changes in NAPCO and PACCO. Polar plot analysis demonstrated a small polar angle and radial limits of agreement well below the 30° benchmark. The area under a receiver operating characteristic curve, testing the ability of Nexfin to detect an increase of ≥15% in PACCO, was 0.974 (95% CI, 0.93-0.99). Although the Nexfin has limited accuracy when compared with the pulmonary artery catheter, it can reliably track preload-induced changes in CO in stable patients after cardiac surgery in the presence of moderate vasopressor and inotropic therapy. This ability, combined with its total noninvasiveness, fast installation, and ease of use, make the Nexfin a suitable monitor for the perioperative continuous measurement of CO. The reliability of this monitor in tracking the CO when significant changes in peripheral resistance take place still needs to be established.

High speed cylindrical roller bearing analysis, SKF computer program CYBEAN. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Kleckner, R. J.; Pirvics, J.

1978-01-01

The CYBEAN (Cylindrical Bearing Analysis) was created to detail radially loaded, aligned and misaligned cylindrical roller bearing performance under a variety of operating conditions. Emphasis was placed on detailing the effects of high speed, preload and system thermal coupling. Roller tilt, skew, radial, circumferential and axial displacement as well as flange contact were considered. Variable housing and flexible out-of-round outer ring geometries, and both steady state and time transient temperature calculations were enabled. The complete range of elastohydrodynamic contact considerations, employing full and partial film conditions were treated in the computation of raceway and flange contacts. Input and output architectures containing guidelines for use and a sample execution are detailed.

Distributed friction damping of travelling wave vibration in rods.

PubMed

Tangpong, Xiangqing W; Wickert, Jonathan A; Akay, Adnan

2008-03-13

A ring damper can be affixed to a rotating base structure such as a gear, an automotive brake rotor or a gas turbine's labyrinth air seal. Depending on the frequency range, wavenumber and level of preload, vibration of the base structure can be effectively and passively attenuated by friction that develops along the interface between it and the damper. The assembly is modelled as two rods that couple in longitudinal vibration through spatially distributed hysteretic friction, with each rod having periodic boundary conditions in a manner analogous to an unwrapped ring and disc. As is representative of rotating machinery applications, the system is driven by a travelling wave disturbance, and for that form of excitation, the base structure's and the damper's responses are determined without the need for computationally intensive simulation. The damper's performance can be optimized with respect to normal preload, and its effectiveness is insensitive to variations in preload or the excitation's magnitude when its natural frequency is substantially lower than the base structure's in the absence of contact.

Evaluation of bearing mounting design and excessive wear phenomena

NASA Technical Reports Server (NTRS)

Kannel, J. W.

1982-01-01

The effect of bearing thermal growth on the effectiveness of the bearing preload springs on the space shuttle main engine high pressure oxygen turbopump (SSME HPTOP) were examined. The SSME HPTOP turbine end bearings, preload spring, and bearing mounting design were evaluated relative to spalling, excessive ball wear, possible thermal problems, and cage delamination. The magnitude of the thermal stresses required to cause high levels of ball wear were calculated. Plots of maximum sheer stress and maximum reversing shear versus the axial load for the 57 mm SSME HPTOP bearing were created. A plot of the bearing thermal growth versus preload spring deflection was generated. It was determined that metallic wear, rather than thermal growth, caused enlargement of the contact zone between ball and races, that high fatigue-inducing shear stresses are generated under increased loads, and that at temperatures between 100 and 150 deg C, the springs bottom out and very high loads are developed in the bearing. Allowance for adequate spring movement after assembly is recommended.

Impact of Nonlinearity of The Contact Layer Between Elements Joined in a Multi-Bolted System on Its Preload

NASA Astrophysics Data System (ADS)

Grzejda, R.

2017-12-01

The paper deals with modelling and calculations of asymmetrical multi-bolted joints at the assembly stage. The physical model of the joint is based on a system composed of four subsystems, which are: a couple of joined elements, a contact layer between the elements, and a set of bolts. The contact layer is assumed as the Winkler model, which can be treated as a nonlinear or linear model. In contrast, the set of bolts are modelled using simplified beam models, known as spider bolt models. The theorem according to which nonlinearity of the contact layer has a negligible impact on the final preload of the joint in the case of its sequential tightening has been verified. Results of sample calculations for the selected multi-bolted system, in the form of diagrams of preloads in the bolts as well as normal contact pressure between the joined elements during the assembly process and at its end, are presented.

Experimental and numerical analysis of clamped joints in front motorbike suspensions

NASA Astrophysics Data System (ADS)

Croccolo, D.; de Agostinis, M.; Vincenzi, N.

2010-06-01

Clamped joints are shaft-hub connections used, as an instance, in front motorbike suspensions to lock the steering plates with the legs and the legs with the wheel pin, by means of one or two bolts. The preloading force, produced during the tightening process, should be evaluated accurately, since it must lock safely the shaft, without overcoming the yielding point of the hub. Firstly, friction coefficients have been evaluated on “ad-hoc designed” specimens, by applying the Design of Experiment approach: the applied tightening torque has been precisely related to the imposed preloading force. Then, the tensile state of clamps have been evaluated both via FEM and by leveraging some design formulae proposed by the Authors as function of the preloading force and of the clamp geometry. Finally, the results have been compared to those given by some strain gauges applied on the tested clamps: the discrepancies between numerical analyses, the design formulae and the experimental results remains under a threshold of 10%.

No appetite efficacy of a commercial structured lipid emulsion in minimally processed drinks.

PubMed

Smit, H J; Keenan, E; Kovacs, E M R; Wiseman, S A; Mela, D J; Rogers, P J

2012-09-01

Fabuless (Olibra) is a commercially structured lipid emulsion, claimed to be a food ingredient that is effective for food intake and appetite reduction. The present study assessed its efficacy in a yoghurt-based mini-drink undergoing low or minimal food manufacturing (thermal and shear) processes. Study 1: Twenty-four healthy volunteers (16 female, 8 male; age: 18-47 years; body mass index (BMI): 17-28 kg m(-2)) took part in a randomised, placebo-controlled, double-blind parallel crossover trial. Consumption of a minimally processed 'preload' mini-drink (containing two different doses of Fabuless or a control fat) at 2 h after breakfast was followed by appetite and mood ratings, and food intake measured in ad libitum meals at 3 and 7 h post consumption of the preload. Study 2: As Study 1 (16 female, 8 male; age: 20-54 years; BMI: 21-30 kg m(-2)). A chilled, virtually unprocessed, preload breakfast mini-drink (containing minimally processed Fabuless or a control fat) was provided 5 min after a standardised breakfast, followed by appetite and mood ratings, and food intake measured in ad libitum meals at 4 and 8 h post consumption of the preload. The structured lipid emulsion tested had no significant effect on the primary measures of food intake or appetite. Even when exposed to minimal food-manufacturing conditions, Fabuless showed no efficacy on measures of appetite and food intake.

An analytical solution for two-dimensional vacuum preloading combined with electro-osmosis consolidation using EKG electrodes

PubMed Central

Qiu, Chenchen; Li, Yande

2017-01-01

China is a country with vast territory, but economic development and population growth have reduced the usable land resources in recent years. Therefore, reclamation by pumping and filling is carried out in eastern coastal regions of China in order to meet the needs of urbanization. However, large areas of reclaimed land need rapid drainage consolidation treatment. Based on past researches on how to improve the treatment efficiency of soft clay using vacuum preloading combined with electro-osmosis, a two-dimensional drainage plane model was proposed according to the Terzaghi and Esrig consolidation theory. However, the analytical solution using two-dimensional plane model was never involved. Current analytical solutions can’t have a thorough theoretical analysis of practical engineering and give relevant guidance. Considering the smearing effect and the rectangle arrangement pattern, an analytical solution is derived to describe the behavior of pore-water and the consolidation process by using EKG (electro-kinetic geo synthetics) materials. The functions of EKG materials include drainage, electric conduction and corrosion resistance. Comparison with test results is carried out to verify the analytical solution. It is found that the measured value is larger than the applied vacuum degree because of the stacking effect of the vacuum preloading and electro-osmosis. The trends of the mean measured value and the mean analytical value processes are comparable. Therefore, the consolidation model can accurately assess the change in pore-water pressure and the consolidation process during vacuum preloading combined with electro-osmosis. PMID:28771496

New Doppler echocardiographic applications for the study of diastolic function

NASA Technical Reports Server (NTRS)

Garcia, M. J.; Thomas, J. D.; Klein, A. L.

1998-01-01

Doppler echocardiography is one of the most useful clinical tools for the assessment of left ventricular (LV) diastolic function. Doppler indices of LV filling and pulmonary venous (PV) flow are used not only for diagnostic purposes but also for establishing prognosis and evaluating the effect of therapeutic interventions. The utility of these indices is limited, however, by the confounding effects of different physiologic variables such as LV relaxation, compliance and filling pressure. Since alterations in these variables result in changes in Doppler indices of opposite direction, it is often difficult to determine the status of a given variable when a specific Doppler filling pattern is observed. Recently, color M-mode and tissue Doppler have provided useful insights in the study of diastolic function. These new Doppler applications have been shown to provide an accurate estimate of LV relaxation and appear to be relatively insensitive to the effects of preload compensation. This review will focus on the complementary role of color M-mode and tissue Doppler echocardiography and traditional Doppler indices of LV filling and PV flow in the assessment of diastolic function.

Use of an iPad App to simulate pressure-volume loops and cardiovascular physiology.

PubMed

Leisman, Staci; Burkhoff, Daniel

2017-09-01

The purpose of this laboratory exercise is to model the changes in preload, afterload, and contractility on a simulated pressure-volume loop and to correlate those findings with common measurements of clinical cardiovascular physiology. Once students have modeled these changes on a healthy heart, the students are asked to look at a simulated case of cardiogenic shock. Effects on preload, contractility, and afterload are explored, as well as the hemodynamic effects of a number of student-suggested treatment strategies. Copyright © 2017 the American Physiological Society.

Support arrangement for core modules of nuclear reactors

DOEpatents

Bollinger, Lawrence R.

1987-01-01

A support arrangement is provided for the core modules of a nuclear reactor which provides support access through the control drive mechanisms of the reactor. This arrangement provides axial support of individual reactor core modules from the pressure vessel head in a manner which permits attachment and detachment of the modules from the head to be accomplished through the control drive mechanisms after their leadscrews have been removed. The arrangement includes a module support nut which is suspended from the pressure vessel head and screw threaded to the shroud housing for the module. A spline lock prevents loosening of the screw connection. An installation tool assembly, including a cell lifting and preloading tool and a torquing tool, fits through the control drive mechanism and provides lifting of the shroud housing while disconnecting the spline lock, as well as application of torque to the module support nut.

Support arrangements for core modules of nuclear reactors. [PWR

DOEpatents

Bollinger, L.R.

1983-11-03

A support arrangement is provided for the core modules of a nuclear reactor which provides support access through the control drive mechanisms of the reactor. This arrangement provides axial support of individual reactor core modules from the pressure vessel head in a manner which permits attachment and detachment of the modules from the head to be accomplished through the control drive mechanisms after their leadscrews have been removed. The arrangement includes a module support nut which is suspended from the pressure vessel head and screw threaded to the shroud housing for the module. A spline lock prevents loosening of the screw connection. An installation tool assembly, including a cell lifting and preloading tool and a torquing tool, fits through the control drive mechanism and provides lifting of the shroud housing while disconnecting the spline lock, as well as application of torque to the module support nut.

Temperature-Controlled Clamping and Releasing Mechanism

NASA Technical Reports Server (NTRS)

Rosing, David; Ford, Virginia

2005-01-01

A report describes the development of a mechanism that automatically clamps upon warming and releases upon cooling between temperature limits of approx. =180 K and approx. =293 K. The mechanism satisfied a need specific to a program that involved repeated excursions of a spectrometer between a room-temperature atmospheric environment and a cryogenic vacuum testing environment. The mechanism was also to be utilized in the intended application of the spectrometer, in which the spectrometer would be clamped for protection during launch of a spacecraft and released in the cold of outer space to allow it to assume its nominal configuration for scientific observations. The mechanism is passive in the sense that its operation does not depend on a control system and does not require any power other than that incidental to heating and cooling. The clamping and releasing action is effected by bolt-preloaded stacks of shape-memory-alloy (SMA) cylinders. In designing this mechanism, as in designing other, similar SMA mechanisms, it was necessary to account for the complex interplay among thermal expansion, elastic and inelastic deformation under load, and SMA thermomechanical properties.

Pulse oximeter as a sensor of fluid responsiveness: do we have our finger on the best solution?

PubMed Central

Monnet, Xavier; Lamia, Bouchra; Teboul, Jean-Louis

2005-01-01

The pulse oximetry plethysmographic signal resembles the peripheral arterial pressure waveform, and the degree of respiratory variation in the pulse oximetry wave is close to the degree of respiratory arterial pulse pressure variation. Thus, it is tempting to speculate that pulse oximetry can be used to assess preload responsiveness in mechanically ventilated patients. In this commentary we briefly review the complex meaning of the pulse oximetry plethysmographic signal and highlight the advantages, limitations and pitfalls of the pulse oximetry method. Future studies including volume challenge must be performed to test whether the pulse oximetry waveform can really serve as a nonivasive tool for the guidance of fluid therapy in patients receiving mechanical ventilation in intensive care units and in operating rooms. PMID:16277729

Intragastric preloads of l-tryptophan reduce ingestive behavior via oxytocinergic neural mechanisms in male mice.

PubMed

Gartner, Sarah N; Aidney, Fraser; Klockars, Anica; Prosser, Colin; Carpenter, Elizabeth A; Isgrove, Kiriana; Levine, Allen S; Olszewski, Pawel K

2018-06-01

Human and laboratory animal studies suggest that dietary supplementation of a free essential amino acid, l-tryptophan (TRP), reduces food intake. It is unclear whether an acute gastric preload of TRP decreases consumption and whether central mechanisms underlie TRP-driven hypophagia. We examined the effect of TRP administered via intragastric gavage on energy- and palatability-induced feeding in mice. We sought to identify central mechanisms through which TRP suppresses appetite. Effects of TRP on consumption of energy-dense and energy-dilute tastants were established in mice stimulated to eat by energy deprivation or palatability. A conditioned taste aversion (CTA) paradigm was used to assess whether hypophagia is unrelated to sickness. c-Fos immunohistochemistry was employed to detect TRP-induced activation of feeding-related brain sites and of oxytocin (OT) neurons, a crucial component of satiety circuits. Also, expression of OT mRNA was assessed with real-time PCR. The functional importance of OT in mediating TRP-driven hypophagia was substantiated by showing the ability of OT receptor blockade to abolish TRP-induced decrease in feeding. TRP reduced intake of energy-dense standard chow in deprived animals and energy-dense palatable chow in sated mice. Anorexigenic doses of TRP did not cause a CTA. TRP failed to affect intake of palatable yet calorie-dilute or noncaloric solutions (10% sucrose, 4.1% Intralipid or 0.1% saccharin) even for TRP doses that decreased water intake in thirsty mice. Fos analysis revealed that TRP increases activation of several key feeding-related brain areas, especially in the brain stem and hypothalamus. TRP activated hypothalamic OT neurons and increased OT mRNA levels, whereas pretreatment with an OT antagonist abolished TRP-driven hypophagia. We conclude that intragastric TRP decreases food and water intake, and TRP-induced hypophagia is partially mediated via central circuits that encompass OT. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dampers for Stationary Labyrinth Seals

NASA Technical Reports Server (NTRS)

El-Aini, Yehia; Mitchell, William; Roberts, Lawrence; Montgomery, Stuart; Davis, Gary

2011-01-01

Vibration dampers have been invented that are incorporated as components within the stationary labyrinth seal assembly. These dampers are intended to supplement other vibration-suppressing features of labyrinth seals in order to reduce the incidence of high-cycle-fatigue failures, which have been known to occur in the severe vibratory environments of jet engines and turbopumps in which labyrinth seals are typically used. A vibration damper of this type includes several leaf springs and/or a number of metallic particles (shot) all held in an annular seal cavity by a retaining ring. The leaf springs are made of a spring steel alloy chosen, in conjunction with design parameters, to maintain sufficient preload to ensure effectiveness of damping at desired operating temperatures. The cavity is vented via a small radial gap between the retaining ring and seal housing. The damping mechanism is complex. In the case of leaf springs, the mechanism is mainly friction in the slippage between the seal housing and individual dampers. In the case of a damper that contains shot, the damping mechanism includes contributions from friction between individual particles, friction between particles and cavity walls, and dissipation of kinetic energy of impact. The basic concept of particle/shot vibration dampers has been published previously; what is new here is the use of such dampers to suppress traveling-wave vibrations in labyrinth seals. Damping effectiveness depends on many parameters, including, but not limited to, coefficient of friction, mode shape, and frequency and amplitude of vibrational modes. In tests, preloads of the order of 6 to 15 lb (2.72 to 6.8 kilograms) per spring damper were demonstrated to provide adequate damping levels. Effectiveness of shot damping of vibrations having amplitudes from 20 to 200 times normal terrestrial gravitational acceleration (196 to 1,960 meters per square second) and frequencies up to 12 kHz was demonstrated for shot sizes from 0.032 to 0.062 in. (0.8 to 1.6 millimeters) at fill levels of from 70 to 95 percent.

The forces applied by female and male chiropractors during thoracic spinal manipulation.

PubMed

Forand, D; Drover, J; Suleman, Z; Symons, B; Herzog, Walter

2004-01-01

On average, women weigh less, have a smaller frame, and are less muscular than men. Since the peak thrust force applied during spinal manipulative treatments can be quite high and must be reached in a very short period of time, one might question the physical ability of women to generate such high forces. To study the forces generated by male and female chiropractors as they deliver spinal manipulation to the thoracic spine. Fourteen male and 14 female experience-matched chiropractors participated in this study. They each manipulated 1 of 9 asymptomatic male adult subjects of similar height and weight. The clinicians were asked to manipulate a transverse process in the vicinity of T4 and T9. Any technique could be used as long as the treatment thrust was in a posterior to anterior direction and the hand contact fit onto the sensor pad (area = 100 cm2). There were no significant differences (P<.05) between male and female chiropractors for any measurements in the upper thoracic area. For the lower thoracic manipulations, the preload forces for the male chiropractors were significantly greater (P<.05) than those for the female chiropractors. The remaining variables were the same between the 2 groups. Female chiropractors produce, from a mechanical point of view, similar manual treatments as their male colleagues.

Frequency spectrum analysis of finger photoplethysmographic waveform variability during haemodialysis.

PubMed

Javed, Faizan; Middleton, Paul M; Malouf, Philip; Chan, Gregory S H; Savkin, Andrey V; Lovell, Nigel H; Steel, Elizabeth; Mackie, James

2010-09-01

This study investigates the peripheral circulatory and autonomic response to volume withdrawal in haemodialysis based on spectral analysis of photoplethysmographic waveform variability (PPGV). Frequency spectrum analysis was performed on the baseline and pulse amplitude variabilities of the finger infrared photoplethysmographic (PPG) waveform and on heart rate variability extracted from the ECG signal collected from 18 kidney failure patients undergoing haemodialysis. Spectral powers were calculated from the low frequency (LF, 0.04-0.145 Hz) and high frequency (HF, 0.145-0.45 Hz) bands. In eight stable fluid overloaded patients (fluid removal of >2 L) not on alpha blockers, progressive reduction in relative blood volume during haemodialysis resulted in significant increase in LF and HF powers of PPG baseline and amplitude variability (P < 0.01), when expressed in mean-scaled units. The augmentation of LF powers in PPGV during haemodialysis may indicate the recovery and possibly further enhancement of peripheral sympathetic vascular modulation subsequent to volume unloading, whilst the increase in respiratory HF power in PPGV is most likely a sign of preload reduction. Spectral analysis of finger PPGV may provide valuable information on the autonomic vascular response to blood volume reduction in haemodialysis, and can be potentially utilized as a non-invasive tool for assessing peripheral circulatory control during routine dialysis procedure.

Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading.

PubMed

Paepoemsin, T; Reichart, P A; Chaijareenont, P; Strietzel, F P; Khongkhunthian, P

2016-01-01

The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer's recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, P<.05). After cyclic loading, removal torque in all groups decreased significantly (P<.05). Group C revealed significantly less removal torque than groups A and B (P<.005). Tensile force in all groups significantly increased after cyclic loading (P<.05), group A had significantly less tensile force than groups B and C (P<.005). Removal torque reduced significantly after cyclic loading. Before cyclic loading, tapered screws maintained more preload than did flat head screws. After cyclic loading, tapered and flat head screws maintained even amounts of preload. The tensile force that dislodged abutment from implant fixture increased immensely after cyclic loading.

Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading

PubMed Central

PAEPOEMSIN, T.; REICHART, P. A.; CHAIJAREENONT, P.; STRIETZEL, F. P.; KHONGKHUNTHIAN, P.

2016-01-01

SUMMARY Purpose The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. Methods The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer’s recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. Results Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, P<.05). After cyclic loading, removal torque in all groups decreased significantly (P<.05). Group C revealed significantly less removal torque than groups A and B (P<.005). Tensile force in all groups significantly increased after cyclic loading (P<.05), group A had significantly less tensile force than groups B and C (P<.005). Conclusions Removal torque reduced significantly after cyclic loading. Before cyclic loading, tapered screws maintained more preload than did flat head screws. After cyclic loading, tapered and flat head screws maintained even amounts of preload. The tensile force that dislodged abutment from implant fixture increased immensely after cyclic loading. PMID:28042450

Heavy metal removal mechanisms of sorptive filter materials for road runoff treatment and remobilization under de-icing salt applications.

PubMed

Huber, Maximilian; Hilbig, Harald; Badenberg, Sophia C; Fassnacht, Julius; Drewes, Jörg E; Helmreich, Brigitte

2016-10-01

The objective of this research study was to elucidate the removal and remobilization behaviors of five heavy metals (i.e., Cd, Cu, Ni, Pb, and Zn) that had been fixed onto sorptive filter materials used in decentralized stormwater treatment systems receiving traffic area runoff. Six filter materials (i.e., granular activated carbon, a mixture of granular activated alumina and porous concrete, granular activated lignite, half-burnt dolomite, and two granular ferric hydroxides) were evaluated in column experiments. First, a simultaneous preloading with the heavy metals was performed for each filter material. Subsequently, the remobilization effect was tested by three de-icing salt experiments in duplicate using pure NaCl, a mixture of NaCl and CaCl2, and a mixture of NaCl and MgCl2. Three layers of each column were separated to specify the attenuation of heavy metals as a function of depth. Cu and Pb were retained best by most of the selected filter materials, and Cu was often released the least of all metals by the three de-icing salts. The mixture of NaCl and CaCl2 resulted in a stronger effect upon remobilization than the other two de-icing salts. For the material with the highest retention, the effect of the preloading level upon remobilization was measured. The removal mechanisms of all filter materials were determined by advanced laboratory methods. For example, the different intrusions of heavy metals into the particles were determined. Findings of this study can result in improved filter materials used in decentralized stormwater treatment systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of central set on anticipatory and triggered grip-force adjustments

NASA Technical Reports Server (NTRS)

Winstein, C. J.; Horak, F. B.; Fisher, B. E.; Peterson, B. W. (Principal Investigator)

2000-01-01

The effects of predictability of load magnitude on anticipatory and triggered grip-force adjustments were studied as nine normal subjects used a precision grip to lift, hold, and replace an instrumented test object. Experience with a predictable stimulus has been shown to enhance magnitude scaling of triggered postural responses to different amplitudes of perturbations. However, this phenomenon, known as a central-set effect, has not been tested systematically for grip-force responses in the hand. In our study, predictability was manipulated by applying load perturbations of different magnitudes to the test object under conditions in which the upcoming load magnitude was presented repeatedly or under conditions in which the load magnitudes were presented randomly, each with two different pre-load grip conditions (unconstrained and constrained). In constrained conditions, initial grip forces were maintained near the minimum level necessary to prevent pre-loaded object slippage, while in unconstrained conditions, no initial grip force restrictions were imposed. The effect of predictable (blocked) and unpredictable (random) load presentations on scaling of anticipatory and triggered grip responses was tested by comparing the slopes of linear regressions between the imposed load and grip response magnitude. Anticipatory and triggered grip force responses were scaled to load magnitude in all conditions. However, regardless of pre-load grip force constraint, the gains (slopes) of grip responses relative to load magnitudes were greater when the magnitude of the upcoming load was predictable than when the load increase was unpredictable. In addition, a central-set effect was evidenced by the fewer number of drop trials in the predictable relative to unpredictable load conditions. Pre-load grip forces showed the greatest set effects. However, grip responses showed larger set effects, based on prediction, when pre-load grip force was constrained to lower levels. These results suggest that anticipatory processes pertaining to load magnitude permit the response gain of both voluntary and triggered rapid grip force adjustments to be set, at least partially, prior to perturbation onset. Comparison of anticipatory set effects for reactive torque and lower extremity EMG postural responses triggered by surface translation perturbations suggests a more general rule governing anticipatory processes.

Ultrasonic measurement and monitoring of loads in bolts used in structural joints

NASA Astrophysics Data System (ADS)

Koshti, Ajay M.

2015-04-01

The paper is an overview of work by the author in measuring and monitoring loads in bolts using an ultrasonic extensometer. A number of cases of bolted joints are covered. These include, a clamped joint with clearance fit between the bolt and hole, a clamped joint with bolt in an interference fit with the hole, a flanged joint which allows the flange and bolt to bend; and a shear joint in a clevis and tang configuration. These applications were initially developed for measuring and monitoring preload in National Aeronautics and Space Administration (NASA) Space Shuttle Orbiter critical joints but are also applicable for monitoring loads in other critical bolted joints of structures such as transportation bridges and other aerospace structures. The papers cited here explain how to set-up a model to estimate the ultrasonic load factor and accuracy for the ultrasonic preload application in a clamped joint with clearance fit. The ultrasonic preload application for clamped joint with bolt in an interference fit can also be used to measure diametrical interference between the bolt shank and hole, as well as interference pressure on the bolt shank. Results of simulation and experimental data are given to demonstrate use of ultrasonic measurements in a shear joint. A bolt in a flanged joint experiences both tensile and bending loads. This application involves measurement of bending and tensile preload in a bolt. The ultrasonic beam bends due to bending load on the bolt. Results of a numerical technique to compute the trace of ultrasonic ray are presented.

Water incorporated into a food but not served with a food decreases energy intake in lean women.

PubMed

Rolls, B J; Bell, E A; Thorwart, M L

1999-10-01

Previous research showed that decreasing the energy density (kJ/g) of foods by adding water to them can lead to reductions in energy intake. Few studies have examined how water consumed as a beverage affects food intake. This study examined the effects of water, both served with a food and incorporated into a food, on satiety. In a within-subjects design, 24 lean women consumed breakfast, lunch, and dinner in our laboratory 1 d/wk for 4 wk. Subjects received 1 of 3 isoenergetic (1128 kJ) preloads 17 min before lunch on 3 d and no preload on 1 d. The preloads consisted of 1) chicken rice casserole, 2) chicken rice casserole served with a glass of water (356 g), and 3) chicken rice soup. The soup contained the same ingredients (type and amount) as the casserole that was served with water. Decreasing the energy density of and increasing the volume of the preload by adding water to it significantly increased fullness and reduced hunger and subsequent energy intake at lunch. The equivalent amount of water served as a beverage with a food did not affect satiety. Energy intake at lunch was 1209 +/- 125 kJ after the soup compared with 1657 +/- 148 and 1639 +/- 148 kJ after the casserole with and without water, respectively. Subjects did not compensate at dinner for this reduction in lunch intake. Consuming foods with a high water content more effectively reduced subsequent energy intake than did drinking water with food.

Quantitative Analysis of Endothelial Cell Loss in Preloaded Descemet Membrane Endothelial Keratoplasty Grafts.

PubMed

Wolle, Meraf A; DeMill, David L; Johnson, Lauren; Lentz, Stephen I; Woodward, Maria A; Mian, Shahzad I

2017-11-01

Availability of preloaded Descemet membrane endothelial keratoplasty (pDMEK) tissue may increase acceptance of DMEK in surgical management of endothelial disease. The goal of this study was to determine the safety of pDMEK grafts for 24 hours before surgery by analyzing endothelial cell loss (ECL) using 2 image analysis software programs. A total of 18 cadaveric corneas were prepared for DMEK using a standardized technique and loaded in a modified Jones tube injector. Nine of the corneas were injected into Calcein AM vital dye after 1 minute (controls), and the remaining 9 corneas were left preloaded for 24 hours before injection into vital dye for staining. The stained corneas were imaged using an inverted confocal microscope. ECL was then analyzed and quantified by 2 different graders using 2 image analysis software programs. The control DMEK tissue resulted in 22.0% ± 4.0% ECL compared with pDMEK tissue, which resulted in 19.2% ± 7.2% ECL (P = 0.31). Interobserver agreement was 0.93 for MetaMorph and 0.92 for Fiji. The average time required to process images with MetaMorph was 2 ± 1 minutes and with Fiji was 20 ± 10 minutes. Intraobserver agreement was 0.97 for MetaMorph and 0.93 for Fiji. Preloading DMEK tissue is safe and may provide an alternative technique for tissue distribution and surgery for DMEK. The use of MetaMorph software for quantifying ECL is a novel and accurate imaging method with increased efficiency and reproducibility compared with the previously validated Fiji.

Individually timing high-protein preloads has no effect on daily energy intake, peptide YY and glucagon-like peptide-1.

PubMed

Willbond, S M; Doucet, É

2011-01-01

Gut hormones have been shown to influence energy intake (EI). To our knowledge, no study has investigated the effects of dietary patterns aimed at optimizing fullness on EI, appetite and gut hormones. To determine whether individually timing high-protein preloads would impact EI, appetite, and peptide YY and glucagon-like peptide-1 (GLP-1) levels. Ten men (body mass index = 25.5 ± 2.6 kg/m(2)) participated in a randomized crossover trial. The three conditions consisted of the self-selection of snacks (condition 1), or the consumption of a preload (300 kcal: 40% protein, 40% carbohydrates and 20% fat) at either 15 min (condition 2) or ∼ 50 min (individually set) (condition 3) before lunch and dinner. During each condition, a standardized breakfast was served, whereas lunch and dinner were self-selected from a five-item menu, and eaten ad libitum. Mealtime and daily EI were measured. Appetite, peptide YY and GLP-1 were sampled over 9 h. No differences in daily EI were noted across conditions (1 = 3078 ± 720 kcal; 2 = 2929 ± 264 kcal; 3 = 2998 ± 437 kcal; not significant). For the most part, daily profiles as well as premeal levels of peptide YY and GLP-1 were not different between conditions. Desire to eat, hunger and prospective food consumption were found to be lowest during condition 1 (P < 0.05). According to these results, it would seem that individually timing high-protein preloads does not reduce daily EI in healthy human subjects.

The effect of covert changes in energy density of preloads on subsequent ad libitum energy intake in lean and obese human subjects.

PubMed

Durrant, M L; Royston, J P; Wloch, R T; Garrow, J S

1982-01-01

1. Covert changes in energy intake were made by giving preloads of disguised energy density three times daily to 14 obese and 6 lean subjects. 2. The preloads contained 2.51 MJ (600 kcal)/d on days 2 and 3 and either 3.77 MJ (900 kcal)/d or 1.26 MJ (300 kcal/d) on days 4 and 5 and 1.26 MJ (300 kcal)/d or 3.77 MJ (900 kcal)/d on days 6 and 7. The order of testing was alternated for each subject. 3. Subsequent energy intake at each meal (lunch, dinner and breakfast) was measured with an automated food-dispensing machine. 4. Overall the obese subjects ate significantly less from the machine, 3.28 +/- 1.89 MJ (785 +/- 452 kcal)/d, than the lean subjects, 6.03 +/- 1.26 MJ (1442 +/- 300 kcal)/d. 5. Both groups of subjects adjusted their energy intake in the right direction to counterbalance the effect of the preloads but the lean subjects changed their intake by an average of 0.74 MJ (176 kcal)/d compared with the obese subjects who changed their intake by an average of 0.29 MJ (70 kcal)/d. 6. Although the lean subjects were better at adjusting their energy intake than the obese subjects, regulation was still imprecise relative to the 2.51 MJ (600 kcal)/d difference in energy intake that was imposed. 7. There were no significant differences in hunger or appetite between subjects or test situations.

Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems.

PubMed

Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung; Jeong, Chang-Mo

2014-12-01

This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

An investigation of preload relaxation behaviour of three zinc- aluminum alloys

NASA Astrophysics Data System (ADS)

Mir, A. A.

2016-08-01

Zinc alloy castings are usually assembled together or mounted by screwed steel fasteners, and are tightened to a predetermined torque to develop the required tensile preload in the fastener. Due to relaxation processes in the castings, creep may cause a partial preload loss at an elevated temperature. The equipment used for load relaxation tests consists of a loadmonitoring device, an oil bath, and a data-acquisition system. A load cell monitoring device is used to monitor the load loss in an ISO-metric M6*1 steel screw set into sand castings made from alloys No. 3, No. 5 and No. 2 and tightened to produce an initial preload of 6 kN. The castings were held at constant temperature in the range 80 - 120°C in an oil bath. The oil bath maintains the desired test temperature throughout the experiment. All tests were conducted for periods of up to 160 h. For all alloys, the initial load loss was high, decreasing gradually with time, but not ceasing. The load loss increased rapidly with test temperature, and almost all of the relaxation curves approximated to a logarithmic decay of load with time. Alloy No. 2 had the best resistance to load loss, with No. 5 next and No. 3 worst at all temperatures. The lower resistance to relaxation of alloy No. 3 was mainly due to the lower relaxation strength of copper-free primary dendrites, whereas in alloys No. 5 and No. 2, the higher copper contents contribute greatly to their relaxation strength in the form of second-phase particles.

Persistence of long term isokinetic strength deficits in subjects with lateral ankle sprain as measured with a protocol including maximal preloading.

PubMed

Perron, Marc; Moffet, Hélène; Nadeau, Sylvie; Hébert, Luc J; Belzile, Sylvain

2014-12-01

The assessment of muscle function is a cornerstone in the management of subjects who have sustained a lateral ankle sprain. The ankle range of motion being relatively small, the use of preloading allows to measure maximal strength throughout the whole amplitude and therefore to better characterize ankle muscles weaknesses. This study aimed to assess muscle strength of the injured and uninjured ankles in subjects with a lateral ankle sprain, to document the timeline of strength recovery, and to determine the influence of sprain grade on strength loss. Maximal torque of the periarticular muscles of the ankle in a concentric mode using a protocol with maximal preloading was tested in 32 male soldiers at 8 weeks and 6 months post-injury. The evertor muscles of the injured ankles were weaker than the uninjured ones at 8 weeks and 6 months post-injury (P<0.0001, effect size=0.31-0.42). Muscle weaknesses also persisted in the plantarflexors of the injured ankles at 8 weeks (P=0.0014, effect size=0.52-0.58) while at 6 months, only the subjects with a grade II sprain displayed such weaknesses (P<0.0001, effect size 0.27-0.31). The strength of the invertor and dorsiflexor muscles did not differ between sides. The use of an isokinetic protocol with preloading demonstrates significant but small strength deficits in the evertor and plantarflexor muscles. These impairments may contribute to the high incidence of recurrence of lateral ankle sprain in very active individuals. Copyright © 2014 Elsevier Ltd. All rights reserved.

Permanent magnets as biasing mechanism for improving the performance of circular dielectric elastomer out-of-plane actuators

NASA Astrophysics Data System (ADS)

Loew, P.; Rizzello, G.; Seelecke, S.

2017-04-01

Dielectric Elastomers (DE) represent an attractive technology for the realization of mechatronic actuators, due to their lightweight, high energy density, high energy efficiency, scalability, and low noise features. In order to produce a stroke, a DE membrane needs to be pre-loaded with a mechanical biasing mechanism. In our previous works, we compared the stroke achieved with different biasing mechanisms for a circular out-of-plane DE Actuator (DEA), i.e., hanging masses, linear and bi-stable springs. The novel contribution of this paper is the investigation of a biasing design approach based on permanent magnets. The resulting magnet-based actuators are usually more compact than the spring-based ones, allowing to obtain more compact systems. Two design solutions are proposed and compared, namely a first one characterized by a stable actuation, and a second one which permits to achieve a higher stroke, but it is intrinsically unstable. The effectiveness of the novel design solution is assessed by means of several experiments.

Interim Report on Fatigue Characteristics of a Typical Metal Wing

NASA Technical Reports Server (NTRS)

Kepert, J L; Payne, A O

1956-01-01

Constant amplitude fatigue tests of seventy-two P-51D "Mustang" wings are reported. The tests were performed by a vibrational loading system and by an hydraulic loading device for conditions with and without varying amounts of pre-load. The results indicate that: (a) the frequency of occurrence of fatigue at any one location is related to the range of the loads applied, (b) the rate of propagation of visible cracks is more or less constant for a large portion of the life of the specimen, (c) the fatigue strength of the structure is similar to that of notched material having a theoretical stress concentration factor of more than 3.0, (d) the frequency distribution of fatigue life is approximately logarithmic normal, (e) the relative increase in fatigue life for a given pre-load depends on the maximum load of the loading cycle only, while the optimum pre-load value is approximately 85 percent of the ultimate failing load, and (f) that normal design procedure will not permit the determination of local stress levels with sufficient accuracy to determine the fatigue strength of an element of a redundant structure.

Development of braided rope engine seals

NASA Technical Reports Server (NTRS)

Ko, Frank K.; Cai, Zhong; Mutharasan, Rajakkannu; Steinetz, Bruce M.

1994-01-01

In this study, after reviewing current seal design concepts, the potential of textile structures for seal design is examined from the material, structural, and fabrication points of view. Braided structures are identified as potential candidates for hypersonic seal structures because of their conformability and design flexibility. A large family of braided structures using 2-D and 3-D architecture can be designed using well established methods to produce a wide range of braiding yarn orientation for wear resistance as well as seal porosity control. As a first demonstration of the approach, 2-D braided fiberglass seals were fabricated according to a factorial design experiment by varying braiding angles, fractional longitudinal fibers, and preload pressure levels. Factorial diagrams and response surfaces were constructed to elucidate the inter-relationship of the braiding parameters as well as the effect of preload pressures on leakage resistance of the seal. It was found that seal resistance is a strong function of fractional longitudinal fiber content. As braiding angle increases, seal leakage resistance increases, especially at high preload pressures and in seals having high proportion of longitudinal fibers.

Study on Single-yarn Pullout Test of Ballistic Resistant Fabric under Different Preloads

NASA Astrophysics Data System (ADS)

Fang, Q. C.; Lei, Z. K.; Y Qin, F.; Li, W. K.; Bai, R. X.

2017-12-01

During bullet penetrating fabric, the pull-out force of yarn in fabric is related to the impact resistance of fabric when the yarn is pulled out from the fabric. The complex uncrimping and friction slip behavior occur during the yarn pullout process, which is critical to learn the impact resistance of fabric. Based on digital image correlation technique, the deformation behavior of Kevlar 49 fabric subjected to preload during the single-yarn pullout process was studied in this paper. The pullout force and displacement curve shows a straight rise and an oscillated decrease. In the linear rise stage, the yarn uncrimping causes a static friction effect. The maximum of the pullout force is not linearly increased with the preload. In the oscillating descending stage, the local descent of the pullout force indicates that the yarn end is gradually withdrawn from the fabric, and the local rise indicates that the yarn end moves to the next weft/warp interaction until the yarn is completely pulled out. The shear deformation of fabric corresponds to the single-yarn pullout process.

Complete Decomposition of Li 2 CO 3 in Li–O 2 Batteries Using Ir/B 4 C as Noncarbon-Based Oxygen Electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Shidong; Xu, Wu; Zheng, Jianming

Incomplete decomposition of Li2CO3 during charge process is a critical barrier for rechargeable Li-O2 batteries. Here we report complete decomposition of Li2CO3 in Li-O2 batteries using ultrafine iridium-decorated boron carbide (Ir/B4C) nanocomposite as oxygen electrode. The systematic investigation on charging the Li2CO3 preloaded Ir/B4C electrode in an ether-based electrolyte demonstrates that Ir/B4C electrode can decompose Li2CO3 with an efficiency close to 100% at below 4.37 V. In contrast, the bare B4C without Ir electrocatalyst can only decompose 4.7% of preloaded Li2CO3. The reaction mechanism of Li2CO3 decomposition in the presence of Ir/B4C electrocatalyst has been further investigated. A Li-O2 batterymore » using Ir/B4C as oxygen electrode material shows highly enhanced cycling stability than that using bare B4C oxygen electrode. These results clearly demonstrate that Ir/B4C is an effecitive oxygen electrode amterial to completely decompose Li2CO3 at relatively low charge voltages and is of significant importance in improving the cycle performanc of aprotic Li-O2 batteries.« less

Behavior of Three Metallic Alloys Under Combined Axial-Shear Stress at 650 C

NASA Technical Reports Server (NTRS)

Colaiuta, Jason F.; Lerch, Bradley (Technical Monitor)

2001-01-01

Three materials, Inconel 718, Haynes 188, and 316 stainless steel, were tested under an axial-torsional stress state at 650 C. The objective of this study was to quantify the evolution of the material while in the viscoplastic domain. Initial and subsequent yield surfaces were experimentally determined to quantify hardening. Subsequent yield surfaces (yield surfaces taken after a preload) had a well-defined front side, in the prestrain direction, but a poorly defined back side, opposite the prestrain direction. Subsequent yield surfaces exhibited isotropic hardening by expansion of the yield surface, kinematic hardening by translation of the yield surface, and distortional hardening by flattening of the yield surface in the direction opposite to the last prestrain. An existing yield function capable of representing isotropic, kinematic, and distortional hardening was used to fit each yield surface. Four variables are used to describe each surface. These variables evolve as the material state changes and have been regressed to the yield surface data.

Surface acoustic wave solid-state rotational micromotor

NASA Astrophysics Data System (ADS)

Shilton, Richie J.; Langelier, Sean M.; Friend, James R.; Yeo, Leslie Y.

2012-01-01

Surface acoustic waves (SAWs) are used to drive a 1 mm diameter rotor at speeds exceeding 9000 rpm and torque of nearly 5 nNm. Unlike recent high-speed SAW rotary motors, however, the present design does not require a fluid coupling layer but interestingly exploits adhesive stiction as an internal preload, a force usually undesirable at these scales; with additional preloads, smaller rotors can be propelled to 15 000 rpm. This solid-state motor has no moving parts except for the rotor and is sufficiently simple to allow integration into miniaturized drive systems for potential use in microfluidic diagnostics, optical switching and microrobotics.

Massive haemothorax after pulmonary endostapling preloaded with bioabsorbable tissue reinforcement material

PubMed Central

Kanai, Yoshihiko; Endo, Shunsuke; Tetsuka, Kenji; Yamamoto, Shinichi

2012-01-01

Reinforced endostapling can prevent postoperative air leakage from surgical stumps. We herein present a 58-year old woman with idiopathic interstitial pneumonia who developed lethal haemothorax after a thoracoscopic lung biopsy with the use of an endostapler preloaded with bioabsorbable tissue reinforcement material. This lethal haemothorax, which occurred on the day after the lung biopsy, required an emergency operation. The bleeding point was an intercostal artery of the inferior chest wall adjacent to the surgical stump. The operative findings suggested that the reinforced material on the surgical stump scratched the chest wall through respiratory movement. PMID:22184467

Massive haemothorax after pulmonary endostapling preloaded with bioabsorbable tissue reinforcement material.

PubMed

Kanai, Yoshihiko; Endo, Shunsuke; Tetsuka, Kenji; Yamamoto, Shinichi

2012-03-01

Reinforced endostapling can prevent postoperative air leakage from surgical stumps. We herein present a 58-year old woman with idiopathic interstitial pneumonia who developed lethal haemothorax after a thoracoscopic lung biopsy with the use of an endostapler preloaded with bioabsorbable tissue reinforcement material. This lethal haemothorax, which occurred on the day after the lung biopsy, required an emergency operation. The bleeding point was an intercostal artery of the inferior chest wall adjacent to the surgical stump. The operative findings suggested that the reinforced material on the surgical stump scratched the chest wall through respiratory movement.

Acute right ventricular dysfunction: real-time management with echocardiography.

PubMed

Krishnan, Sundar; Schmidt, Gregory A

2015-03-01

In critically ill patients, the right ventricle is susceptible to dysfunction due to increased afterload, decreased contractility, or alterations in preload. With the increased use of point-of-care ultrasonography and a decline in the use of pulmonary artery catheters, echocardiography can be the ideal tool for evaluation and to guide hemodynamic and respiratory therapy. We review the epidemiology of right ventricular failure in critically ill patients; echocardiographic parameters for evaluating the right ventricle; and the impact of mechanical ventilation, fluid therapy, and vasoactive infusions on the right ventricle. Finally, we summarize the principles of management in the context of right ventricular dysfunction and provide recommendations for echocardiography-guided management.

A Coarse Pointing Assembly for Optical Communication

NASA Technical Reports Server (NTRS)

Szekely, G.; Blum, D.; Humphries, M.; Koller, A.; Mussett, D.; Schuler, S.; Vogt, P.

2010-01-01

In the framework of a contract with the European Space Agency, RUAG Space are developing a Coarse Pointing Assembly for an Optical Communication Terminal with the goal to enable high-bandwidth data exchange between GEO and/or LEO satellites as well as to earth-bound ground stations. This paper describes some development and testing aspects of such a high precision opto-mechanical device, with emphasis on the influence of requirements on the final design, the usage of a Bearing Active Preload System, some of the lessons learned on the BAPS implementation, the selection of a flex print design as rotary harness and some aspects of functional and environmental testing.

A versatile system for biological and soil chemical tests on a planetary landing craft. II - Hardware development

NASA Technical Reports Server (NTRS)

Martin, J. P.; Kok, B.; Radmer, R.

1976-01-01

A system has been under development which is designed to seek remotely for clues to life in planetary soil samples. The basic approach is a set of experiments, all having a common sensor, a gas analysis mass spectrometer which monitors gas composition in the head spaces above sealed, temperature controlled soil samples. Versatility is obtained with up to three preloaded, sealed fluid injector capsules for each of eleven soil test cells. Tests results with an engineering model has demonstrated performance capability of subsystem components such as soil distribution, gas sampling valves, injector mechanisms, temperature control, and test cell seal.

A BAPTA employing rotary transformers, stepper motors and ceramic ball bearings

NASA Technical Reports Server (NTRS)

Auer, W.

1981-01-01

The utilization of rotary transformers as an alternative to slip rings for the power transfer from solar panels to a satellite's main body could be advantageous, especially if an ac bus system is taken into consideration. Different approaches with main emphasis on the electromagnetic design were investigated and showed efficiencies of up to 99% with a 3 kW power capability. A solidly preloaded pair of ball bearings with ceramic balls assures proper transformer air gaps and acceptable torque changes over temperature and temperature gradients. The bearing and power transfer assembly is driven by a direct drive stepper motor with inherent redundancy properties and needs no caging mechanism.

Simulated Space Environment Effects on the Blocking Force of Silicone Adhesive

NASA Technical Reports Server (NTRS)

Boeder, Paul; Mikatarian, Ron; Koontz, Steve; Albyn, Keith; Finckenor, Miria

2005-01-01

The International Space Station (ISS) solar arrays utilize MD-944 diode tape to protect the underlying diodes in the solar array panel circuit and also provide thermal conditioning and mechanical support. The diode tape consists of silicone pressure sensitive adhesive (Dow Coming QC-7725) with a protective Kapton over-layer. On-orbit, the Kapton over-layer will erode under exposure to atomic oxygen (AO) and the underlying exposed silicone adhesive will ultimately convert, under additional AO exposure, to a glass like silicate. The current operational plan is to retract ISS solar array P6 and leave it stored under load for a long duration (6 months or more) during ISS assembly. With the Kapton over-layer eroded away, the exposed silicone adhesive must not cause the solar array to stick to itself or cause the solar array to fail during redeployment. Previous testing by Lockheed-Martin Space Systems (LMSS) characterized silicone blocking following exposure to low energy atomic oxygen (AO) in an asher facility, but this is believed to be conservative. An additional series of tests was performed by the Environmental Effects Group at MSFC under direction from the ISS Program Office Environments Team. This test series included high energy AO (5 eV), near ultraviolet (NUV) radiation and ionizing radiation, singly and in combination. Additional samples were exposed to thermal energy AO (<0.1 ev) for comparison to the LMSS tests. Diode tape samples were exposed to each environment constituent individually, put under preload for seven days and then the resulting blocking force was measured using a tensile machine. Additional samples were exposed to AO, NUV and electrons in series and then put under long term (three to ten months) preload to determine the effect of preload duration on the resulting blocking force of the silicone-to-silicone bond. Test results indicate that high energy AO, ultraviolet radiation and electron ionizing radiation exposure all reduce the blocking force for a silicone-to-silicone bond. AO exposure produces the most significant reduction in blocking force.

Centrifugally decoupling touchdown bearings

DOEpatents

Post, Richard F

2014-06-24

Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.

Caloric compensation and eating in the absence of hunger in 5- to 12-y-old weight-discordant siblings.

PubMed

Kral, Tanja V E; Allison, David B; Birch, Leann L; Stallings, Virginia A; Moore, Reneé H; Faith, Myles S

2012-09-01

An impaired ability to compensate for calories and increased eating in the absence of hunger (EAH) has been associated with increased energy intake and weight gain in unrelated children. The aims of this study were to compare caloric compensation [the percentage compensation index (%COMPX)] and EAH in weight-discordant siblings aged 5-12 y. In a crossover, behavioral genetics design, 47 same-sex sibling pairs (53% female, 55% full siblings) were served dinner once a week for 3 wk. Across conditions, siblings were served the same dinner, but 25 min before dinner, they either consumed in full or did not consume 1 of 2 preloads that varied in energy density (ED; 0.57 or 0.97 kcal/g). On the day when no preload was consumed, EAH was assessed after dinner and defined as the number of calories consumed from snacks. Overweight/obese siblings undercompensated [%COMPX: -48.8 ± 56.3 (mean ± SEM)] and therefore overate after the high-ED preload, whereas normal-weight siblings showed accurate compensation (%COMPX: 101.3 ± 51.9; P = 0.03). Furthermore, overweight/obese siblings consumed 34% more calories (93 kcal) in the absence of hunger than did normal-weight siblings (P = 0.01). Within-pair resemblances for %COMPX and EAH were stronger for full siblings (P < 0.049) than for half siblings (P > 0.23). An impaired ability to regulate short-term energy intake, which includes incomplete adjustment for calorie differences in a preload and eating when satiated, may represent a behavioral phenotype for obesity in children. Future studies should test whether teaching children to focus on internal satiety cues may prevent at-risk children from overeating.

Color M-mode Doppler flow propagation velocity is a preload insensitive index of left ventricular relaxation: animal and human validation.

PubMed

Garcia, M J; Smedira, N G; Greenberg, N L; Main, M; Firstenberg, M S; Odabashian, J; Thomas, J D

2000-01-01

To determine the effect of preload in color M-mode Doppler flow propagation velocity (v(p)). The interpretation of Doppler filling patterns is limited by confounding effects of left ventricular (LV) relaxation and preload. Color M-mode v(p) has been proposed as a new index of LV relaxation. We studied four dogs before and during inferior caval (IVC) occlusion at five different inotropic stages and 14 patients before and during partial cardiopulmonary bypass. Left ventricular (LV) end-diastolic volumes (LV-EDV), the time constant of isovolumic relaxation (tau), left atrial (LA) pre-A and LV end-diastolic pressures (LV-EDP) were measured. Peak velocity during early filling (E) and v(p) were extracted by digital analysis of color M-mode Doppler images. In both animals and humans, LV-EDV and LV-EDP decreased significantly from baseline to IVC occlusion (both p < 0.001). Peak early filling (E) velocity decreased in animals from 56 +/- 21 to 42 +/- 17 cm/s (p < 0.001) without change in v(p) (from 35 +/- 15 to 35 +/- 16, p = 0.99). Results were similar in humans (from 69 +/- 15 to 53 +/- 22 cm/s, p < 0.001, and 37 +/- 12 to 34 +/- 16, p = 0.30). In both species, there was a strong correlation between LV relaxation (tau) and v(p) (r = 0.78, p < 0.001, r = 0.86, p < 0.001). Our results indicate that color M-mode Doppler v(p) is not affected by preload alterations and confirms that LV relaxation is its main physiologic determinant in both animals during varying lusitropic conditions and in humans with heart disease.

Exploring molecular sieve capabilities of activated carbon fibers to reduce the impact of NOM preloading on trichloroethylene adsorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanju Karanfil; Seyed A. Dastgheib; Dina Mauldin

2006-02-15

Adsorption of trichloroethylene (TCE) by two activated carbon fibers ACF10 and ACF20H and two granular activated carbons, coal-based F400 and Macro preloaded with hydrophobic and transphilic fractions of natural organic matter (NOM) was examined. ACF10, the most microporous activated carbon used in this study, had over 90% of its pore volume in pores smaller than 10 {angstrom}. It also had the highest volume in pores 5-8 {angstrom}, which is the optimum pore size region for TCE adsorption, among the four activated carbons. Adsorption of NOM fractions by ACF10 was, in general, negligible. Therefore, ACF10, functioning as a molecular sieve duringmore » preloading, exhibited the least NOM uptake for each fraction, and subsequently the highest TCE adsorption. The other three sorbents had wider pore size distributions, including high volumes in pores larger than 10 {angstrom}, where NOM molecules can adsorb. As a result, they showed a higher degree of uptake for all NOM fractions, and subsequently lower adsorption capacities for TCE, as compared to ACF10. The results obtained in this study showed that understanding the interplay between the optimum pore size region for the adsorption of target synthetic organic contaminant (SOC) and the pore size region for the adsorption of NOM molecules is important for controlling NOM-SOC competitions. Experiments with different NOM fractions indicated that the degree of NOM loading is important in terms of preloading effects; however the way that the carbon pores are filled and loaded by different NOM fractions can be different and may create an additional negative impact on TCE adsorption. 40 refs., 3 figs., 2 tabs.« less

Outcomes of Descemet Stripping Endothelial Keratoplasty Using Eye Bank-Prepared Preloaded Grafts.

PubMed

Palioura, Sotiria; Colby, Kathryn

2017-01-01

To evaluate the feasibility of Descemet stripping endothelial keratoplasty using grafts preloaded by an eye bank in a commercially available insertion device. In this retrospective case series, a series of 35 eyes in 34 consecutive patients who underwent Descemet stripping endothelial keratoplasty for Fuchs endothelial dystrophy or previously failed full-thickness grafts at a single tertiary care center from March 2013 to March 2014 was included. The donor tissue had undergone pre-lamellar dissection, trephination, and loading into EndoGlide Ultrathin inserters at the Lions Eye Institute for Transplant and Research (Tampa, FL) and was shipped overnight in Optisol GS to the surgeon (K.C.). Surgery was performed within 24 hours from tissue preparation and loading by the eye bank. Donor and recipient characteristics, endothelial cell density (ECD), best-corrected visual acuity, and central corneal thickness were recorded. The main outcome measures were intraoperative and postoperative complications and ECD loss at 3, 6, and 12 months. One primary graft failure (2.8%), 2 rebubblings (5.7%), and 1 graft rejection (2.8%) occurred. Mean preoperative donor ECD was 2821 ± 199 cells/mm. Six months postoperatively, the mean endothelial cell loss was 25.3% ± 17.2% (n = 32), which remained stable at 1 year (31.5% ± 17.9%, n = 32). Mean best-corrected visual acuity improved from 20/100 preoperatively to 20/25 at a mean follow-up of 1 year (n = 32). Mean central corneal thickness was reduced from 711 ± 110 μm to 638 ± 66 μm at the last follow-up visit. Donor graft tissue preloaded by an eye bank can be used successfully for endothelial keratoplasty. Preloading reduces intraoperative tissue manipulation.

Color M-mode Doppler flow propagation velocity is a preload insensitive index of left ventricular relaxation: animal and human validation

NASA Technical Reports Server (NTRS)

Garcia, M. J.; Smedira, N. G.; Greenberg, N. L.; Main, M.; Firstenberg, M. S.; Odabashian, J.; Thomas, J. D.

2000-01-01

OBJECTIVES: To determine the effect of preload in color M-mode Doppler flow propagation velocity (v(p)). BACKGROUND: The interpretation of Doppler filling patterns is limited by confounding effects of left ventricular (LV) relaxation and preload. Color M-mode v(p) has been proposed as a new index of LV relaxation. METHODS: We studied four dogs before and during inferior caval (IVC) occlusion at five different inotropic stages and 14 patients before and during partial cardiopulmonary bypass. Left ventricular (LV) end-diastolic volumes (LV-EDV), the time constant of isovolumic relaxation (tau), left atrial (LA) pre-A and LV end-diastolic pressures (LV-EDP) were measured. Peak velocity during early filling (E) and v(p) were extracted by digital analysis of color M-mode Doppler images. RESULTS: In both animals and humans, LV-EDV and LV-EDP decreased significantly from baseline to IVC occlusion (both p < 0.001). Peak early filling (E) velocity decreased in animals from 56 +/- 21 to 42 +/- 17 cm/s (p < 0.001) without change in v(p) (from 35 +/- 15 to 35 +/- 16, p = 0.99). Results were similar in humans (from 69 +/- 15 to 53 +/- 22 cm/s, p < 0.001, and 37 +/- 12 to 34 +/- 16, p = 0.30). In both species, there was a strong correlation between LV relaxation (tau) and v(p) (r = 0.78, p < 0.001, r = 0.86, p < 0.001). CONCLUSIONS: Our results indicate that color M-mode Doppler v(p) is not affected by preload alterations and confirms that LV relaxation is its main physiologic determinant in both animals during varying lusitropic conditions and in humans with heart disease.

Effect of Preload Alterations on Left Ventricular Systolic Parameters Including Speckle-Tracking Echocardiography Radial Strain During General Anesthesia.

PubMed

Weber, Ulrike; Base, Eva; Ristl, Robin; Mora, Bruno

2015-08-01

Frequently used parameters for evaluation of left ventricular systolic function are load-sensitive. However, the impact of preload alterations on speckle-tracking echocardiographic parameters during anesthesia has not been validated. Therefore, two-dimensional (2D) speckle-tracking echocardiography radial strain (RS) was assessed during general anesthesia, simulating 3 different preload conditions. Single-center prospective observational study. University hospital. Thirty-three patients with normal left ventricular systolic function undergoing major surgery. Transgastric views of the midpapillary level of the left ventricle were acquired at 3 different positions. Fractional shortening (FS), fractional area change (FAC), and 2D speckle-tracking echocardiography RS were analyzed in the transgastric midpapillary view. Considerable correlation above 0.5 was found for FAC and FS in the zero and Trendelenburg positions (r = 0.629, r = 0.587), and for RS and FAC in the anti-Trendelenburg position (r = 0.518). In the repeated-measures analysis, significant differences among the values measured at the 3 positions were found for FAC and FS. For FAC, there were differences up to 2.8 percentage points between the anti-Trendelenburg position and the other 2 positions. For FS, only the difference between position zero and anti-Trendelenburg was significant, with an observed change of 1.66. Two-dimensional RS was not significantly different at all positions, with observed changes below 1 percentage point. Alterations in preload did not result in clinically relevant changes of RS, FS, or FAC. Observed changes for RS were smallest; however, the variation of RS was larger than that of FS or FAC. Copyright © 2015 Elsevier Inc. All rights reserved.

Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems

PubMed Central

Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung

2014-01-01

PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material. PMID:25551010

Pre-meal video game playing and a glucose preload suppress food intake in normal weight boys.

PubMed

Branton, Alyson; Akhavan, Tina; Gladanac, Branka; Pollard, Damion; Welch, Jo; Rossiter, Melissa; Bellissimo, Nick

2014-12-01

Increased food intake (FI) during television viewing has been reported in children, but it is unknown if this occurs following pre-meal video game playing (VGP). The objective was to determine the effect of pre-meal VGP for 30 min on subjective appetite and emotions, and FI in normal weight (NW) boys after a glucose or control preload. On four test mornings, NW boys (n = 19) received equally sweetened preloads of a non-caloric sucralose control or 50 g glucose in 250 mL of water, with or without VGP for 30 min. Food intake from an ad libitum pizza meal was measured immediately after. Subjective appetite was measured at 0, 15, 30, and 60 min. Subjective emotions were determined by visual analog scale at baseline and immediately before lunch. Both VGP (p = 0.023) and glucose (p <0.001) suppressed FI. Pre-meal VGP compared with no-VGP, and glucose compared with the non-caloric control, decreased FI by 59 and 170 kcal, respectively. Subjective average appetite increased to 30 min (p = 0.003), but was lower after glucose (p = 0.01) in both the VGP and no-VGP conditions compared with the control. Frustration and aggression scores increased after VGP (p <0.05), but did not correlate with FI. However, baseline and pre-meal happiness and excitement scores were inversely associated with FI. In conclusion, both pre-meal VGP and the glucose preload suppressed FI, supporting the roles of both physiologic and environmental factors in the regulation of short-term FI in 9- to 14-year-old NW boys. Copyright © 2014 Elsevier Ltd. All rights reserved.

Maternal and anaesthesia-related risk factors and incidence of spinal anaesthesia-induced hypotension in elective caesarean section: A multinomial logistic regression.

PubMed

Fakherpour, Atousa; Ghaem, Haleh; Fattahi, Zeinabsadat; Zaree, Samaneh

2018-01-01

Although spinal anaesthesia (SA) is nowadays the preferred anaesthesia technique for caesarean section (CS), it is associated with considerable haemodynamic effects, such as maternal hypotension. This study aimed to evaluate a wide range of variables (related to parturient and anaesthesia techniques) associated with the incidence of different degrees of SA-induced hypotension during elective CS. This prospective study was conducted on 511 mother-infant pairs, in which the mother underwent elective CS under SA. The data were collected through preset proforma containing three parts related to the parturient, anaesthetic techniques and a table for recording maternal blood pressure. It was hypothesized that some maternal (such as age) and anaesthesia-related risk factors (such as block height) were associated with occurance of SA-induced hypotension during elective CS. The incidence of mild, moderate and severe hypotension was 20%, 35% and 40%, respectively. Eventually, ten risk factors were found to be associated with hypotension, including age >35 years, body mass index ≥25 kg/m 2 , 11-20 kg weight gain, gravidity ≥4, history of hypotension, baseline systolic blood pressure (SBP) <120 mmHg and baseline heart rate >100 beats/min in maternal modelling, fluid preloading ≥1000 ml, adding sufentanil to bupivacaine and sensory block height >T 4 in anaesthesia-related modelling ( P < 0.05). Age, body mass index, weight gain, gravidity, history of hypotension, baseline SBP and heart rate, fluid preloading, adding sufentanil to bupivacaine and sensory block hieght were the main risk factors identified in the study for SA-induced hypotension during CS.

Email notification combined with off site signing substantially reduces resident approval to faculty verification time.

PubMed

Deitte, Lori A; Moser, Patricia P; Geller, Brian S; Sistrom, Chris L

2011-06-01

Attending radiologist signature time (AST) is a variable and modifiable component of overall report turnaround time. Delays in finalized reports have potential to undermine radiologists' value as consultants and adversely affect patient care. This study was performed to evaluate the impact of notebook computer distribution and daily automated e-mail notification on reducing AST. Two simultaneous interventions were initiated in the authors' radiology department in February 2010. These included the distribution of a notebook computer with preloaded software for each attending radiologist to sign radiology reports and daily automated e-mail notifications for unsigned reports. The digital dictation system archive and the radiology information system were queried for all radiology reports produced from January 2009 through August 2010. The time between resident approval and attending radiologist signature before and after the intervention was analyzed. Potential unintended "side effects" of the intervention were also studied. Resident-authored reports were signed, on average, 2.53 hours sooner after the intervention. This represented a highly significant (P = .003) decrease in AST with all else held equal. Postintervention reports were authored by residents at the same rate (about 70%). An unintended "side effect" was that attending radiologists were less likely to make changes to resident-authored reports after the intervention. E-mail notification combined with offsite signing can reduce AST substantially. Notebook computers with preloaded software streamline the process of accessing, editing, and signing reports. The observed decrease in AST reflects a positive change in the timeliness of report signature. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

Influence of abutment screw preload on stress distribution in marginal bone.

PubMed

Khraisat, Ameen

2012-01-01

Changes in an implant assembly after abutment connection might possibly cause deformation in the implant/abutment joint and even in the marginal bone. The aim of this study was to evaluate the influence of abutment screw preload through the implant collar on marginal bone stress without external load application. Models of three implant parts made of titanium (implant, abutment, and abutment screw) and cortical bone were built and positioned with computer-aided design software. Meshing and generation of boundary conditions, loads, and interactions were performed. Each part was meshed independently. The sole load applied to the model was a torque of 32 Ncm on the abutment screw about its axis of rotation. The implant collar was deformed axially after the screw was tightened (3 μm). This deformation resulted in 60 MPa of stress in the marginal bone. Moreover, pressure on the marginal bone in a radial direction was observed. It can be concluded that, without any external load application, abutment screw preload exerts stresses on the implant collar and the marginal bone. These findings should help guide the development of new implant/abutment joint designs that exert less stress on the marginal bone.

The head module of Mediator directs activation of preloaded RNAPII in vivo.

PubMed

Lee, Sarah K; Chen, Xu; Huang, Liangqun; Stargell, Laurie A

2013-12-01

The successful synthesis of a transcript by RNA polymerase II (RNAPII) is a multistage process with distinct rate-limiting steps that can vary depending on the particular gene. A growing number of genes in a variety of organisms are regulated at steps after the recruitment of RNAPII. The best-characterized Saccharomyces cerevisiae gene regulated in this manner is CYC1. This gene has high occupancy of RNAPII under non-inducing conditions, defining it as a poised gene. Here, we find that subunits of the head module of Mediator, Med18 and Med20, and Med19 are required for activation of transcription at the CYC1 promoter in response to environmental cues. These subunits of Mediator are required at the preloaded promoter for normal levels of recruitment and activity of the general transcription factor TFIIH. Strikingly, these Mediator components are dispensable for activation by the same activator at a different gene, which lacks a preloaded polymerase in the promoter region. Based on these results and other studies, we speculate that Mediator plays an essential role in triggering an inactive polymerase at CYC1 into a productively elongating form.

High Temperature Propulsion System Structural Seals for Future Space Launch Vehicles

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; DeMange, Jeffrey J.

2004-01-01

Durable, flexible sliding seals are required in advanced hypersonic engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures of 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA s Glenn Research Center is developing advanced seals and preloading devices to overcome these shortfalls. An advanced ceramic wafer seal design and two types of seal preloading devices were evaluated in a series of compression, scrub, and flow tests. Silicon nitride wafer seals survived 2000 in. 1000 cycles) of scrubbing at 1600 F against an Inconel 625 rub surface with no chips or signs of damage. Flow rates measured for the wafers before and after scrubbing were almost identical and were up to 32 times lower than those recorded for the best braided rope seal flow blockers. Canted coil springs and silicon nitride compression springs showed promise conceptually as potential seal preloading devices to help maintain seal resiliency. A finite element model of the canted coil spring revealed that it should be possible to produce a spring out of high temperature materials for applications at 2000+ F.

The effect of the use of a counter-torque device on the abutment-implant complex.

PubMed

Lang, L A; May, K B; Wang, R F

1999-04-01

Little is known about the condition of the abutment-screw joint before loading, after the development of the preload. This study examined the tightening force transmitted to the implant with and without the use of a counter-torque device during the tightening of the abutment screw. Forty Brânemark implants and 10 CeraOne, Estheticone, Procera, and AurAdapt abutments formed the experimental populations. Samples in each group were further divided into 2 groups, 1 group was tightened with a torque controller without the use of a counter-torque device, whereas the other used the counter-torque device. Samples were positioned in a special holder within the grips of a Tohnichi BTG-6 torque gauge for measuring transmitted forces. There were significant differences (P =. 0001) in the tightening forces transmitted to the implant with and without the use of a counter-torque device when tightening the abutment screws. An average of 91% of the recommended preload tightening torque was transmitted to the implant-bone interface in the absence of a counter-torque device. In all abutment systems, less than 10% of the recommended preload tightening torque was transmitted to the implant when the counter-torque device was used.

High Temperature Propulsion System Structural Seals for Future Space Launch Vehicles

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; DeMange, Jeffrey J.

2003-01-01

Durable, flexible sliding seals are required in advanced hypersonic engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures of 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA's Glenn Research Center is developing advanced seals and preloading devices to overcome these shortfalls. An advanced ceramic wafer seal design and two types of seal preloading devices were evaluated in a series of compression, scrub, and flow tests. Silicon nitride wafer seals survived 2000 in. (1000 cycles) of scrubbing at room temperature against an Inconel 625 rub surface with no chips or signs of damage. Flow rates measured for the wafers before and after scrubbing were almost identical and were much lower than those recorded for the best braided rope seal flow blockers. Canted coil springs and silicon nitride compression springs showed promise conceptually as potential seal preloading devices to help maintain seal resiliency. A finite element model of the canted coil spring revealed that it should be possible to produce a spring out of high temperature materials for applications at 2000+ F.

On the applicability of [18F]FBPA to predict L-BPA concentration after amino acid preloading in HuH-7 liver tumor model and the implication for liver boron neutron capture therapy.

PubMed

Grunewald, Catrin; Sauberer, Michael; Filip, Thomas; Wanek, Thomas; Stanek, Johann; Mairinger, Severin; Rollet, Sofia; Kudejova, Petra; Langer, Oliver; Schütz, Christian; Blaickner, Matthias; Kuntner, Claudia

2017-01-01

In recent years extra-corporal application of boron neutron capture therapy (BNCT) was evaluated for liver primary tumors or liver metastases. A prerequisite for such a high-risk procedure is proof of preferential delivery and high uptake of a 10 B-pharmaceutical in liver malignancies. In this work we evaluated in a preclinical tumor model if [ 18 F]FBPA tissue distribution measured with PET is able to predict the tissue distribution of [ 10 B]L-BPA. Tumor bearing mice (hepatocellular carcinoma cell line, HuH-7) were either subject of a [ 18 F]FBPA-PET scan with subsequent measurement of radioactivity content in extracted organs using a gamma counter or injected with [ 10 B]L-BPA with tissue samples analyzed by prompt gamma activation analysis (PGAA) or quantitative neutron capture radiography (QNCR). The impact of L-tyrosine, L-DOPA and L-BPA preloading on the tissue distribution of [ 18 F]FBPA and [ 10 B]L-BPA was evaluated and the pharmacokinetics of [ 18 F]FBPA investigated by compartment modeling. We found a significant correlation between [ 18 F]FBPA and [ 10 B]L-BPA uptake in tumors and various organs as well as high accumulation levels in pancreas and kidneys as reported in previous studies. Tumor-to-liver ratios of [ 18 F]FBPA ranged from 1.2 to 1.5. Preloading did not increase the uptake of [ 18 F]FBPA or [ 10 B]L-BPA in any organ and compartment modeling showed no statistically significant differences in [ 18 F]FBPA tumor kinetics. [ 18 F]FBPA-PET predicts [ 10 B]L-BPA concentration after amino acid preloading in HuH-7 hepatocellular carcinoma models. Preloading had no effect on tumor uptake of [ 18 F]FBPA. Despite differences in chemical structure and administered dose [ 18 F]FBPA and [ 10 B]L-BPA demonstrate an equivalent biodistribution in a preclinical tumor model. IMPLICATIONS FOR PATIENT CARE: [ 18 F]FBPA-PET is suitable for treatment planning and dose calculations in BNCT applications for liver malignancies. However, alternative tracers with more favorable tumor-to-liver ratios should be investigated. Copyright © 2016 Elsevier Inc. All rights reserved.

Control of large thermal distortions in a cryogenic wind tunnel

NASA Technical Reports Server (NTRS)

Gustafson, J. C.

1983-01-01

The National Transonic Facility (NTF) is a research wind tunnel capable of operation at temperatures down to 89K (160 R) and pressures up to 900,000 Pa (9 atmospheres) to achieve Reynolds numbers approaching 120,000,000. Wide temperature excursions combined with the precise alignment requirements of the tunnel aerodynamic surfaces imposed constraints on the mechanisms supporting the internal structures of the tunnel. The material selections suitable for this application were also limited. A general design philosophy of utilizing a single fixed point for each linear degree of freedom and guiding the expansion as required was adopted. These support systems allow thermal expansion to take place in a manner that minimizes the development of thermally induced stresses while maintaining structural alignment and resisting high aerodynamic loads. Typical of the support mechanisms are the preload brackets used in the fan shroud system and the Watts linkage used to support the upstream nacelle. The design of these mechanisms along with the basic design requirements and the constraints imposed by the tunnel system are discussed.

Sonodynamic therapy--a review of the synergistic effects of drugs and ultrasound.

PubMed

Rosenthal, Ionel; Sostaric, Joe Z; Riesz, Peter

2004-09-01

Sonodynamic therapy, the ultrasound dependent enhancement of cytotoxic activities of certain compounds (sonosensitizers) in studies with cells in vitro and in tumor bearing animals, is reviewed. The attractive features of this modality for cancer treatment emerges from the ability to focus the ultrasound energy on malignancy sites buried deep in tissues and to locally activate a preloaded sonosensitizer. Possible mechanisms of sonodynamic therapy include generation of sonosensitizer derived radicals which initiate chain peroxidation of membrane lipids via peroxyl and/or alkoxyl radicals, the physical destabilization of the cell membrane by the sonosensitizer thereby rendering the cell more susceptible to shear forces or ultrasound enhanced drug transport across the cell membrane (sonoporation). Evidence against the role of singlet oxygen in sonodynamic therapy is discussed. The mechanism of sonodynamic therapy is probably not governed by a universal mechanism, but may be influenced by multiple factors including the nature of the biological model, the sonosensitizer and the ultrasound parameters. The current review emphasizes the effect of ultrasound induced free radicals in sonodynamic therapy.

Finite Element Analysis of New Crankshaft Automatic Adjustment Mechanism of Pumping Unit

NASA Astrophysics Data System (ADS)

Wu, Jufei; Wang, Qian

2017-12-01

In this paper, the crankshaft automatic adjustment mechanism designed on CYJY10-4.2-53HF pumping unit is used as the research object. The simulation of the friction and bending moment of the crank is carried out by ANSYS Workbench, and the finite element simulation results are compared with the theoretical calculation results to verify the theoretical calculation. The final result is that the finite element analysis of the friction of the crank is basically consistent with the theoretical calculation; The analysis and calculation of the stress and deformation about the two kinds of ultimate conditions of the guide platform are carried out too; The dynamic state analysis of the mechanism is carried out to obtain the vibration modes and natural frequencies of the vibration of the different parts of the counterweight under the condition of no preload force so that the frequency of the array can avoid the natural frequency, and can effectively avoid the resonance phenomenon, and for different modes we can improve the stiffness of the structure.

Perfusion index and plethysmographic variability index in patients with interscalene nerve catheters.

PubMed

Sebastiani, Anne; Philippi, Larissa; Boehme, Stefan; Closhen, Dorothea; Schmidtmann, Irene; Scherhag, Anton; Markstaller, Klaus; Engelhard, Kristin; Pestel, Gunther

2012-12-01

Interscalene nerve blocks provide adequate analgesia, but there are no objective criteria for early assessment of correct catheter placement. In the present study, pulse oximetry technology was used to evaluate changes in the perfusion index (PI) in both blocked and unblocked arms, and changes in the plethysmographic variability index (PVI) were evaluated once mechanical ventilation was instituted. The PI and PVI values were assessed using a Radical-7™ finger pulse oximetry device (Masimo Corp., Irvine, CA, USA) in both arms of 30 orthopedic patients who received an interscalene catheter at least 25 min before induction of general anesthesia. Data were evaluated at baseline, on application of local anesthetics; five, ten, and 15 min after onset of interscalene nerve blocks; after induction of general anesthesia; before and after a 500 mL colloid fluid challenge; and five minutes thereafter. In the 25 patients with successful blocks, the difference between the PI values in the blocked arm and the PI values in the contralateral arm increased within five minutes of the application of the local anesthetics (P < 0.05) and increased progressively until 15 min. After induction of general anesthesia, the PI increased in the unblocked arm while it remained relatively constant in the blocked arm, thus reducing the difference in the PI. A fluid challenge resulted in a decrease in PVI values in both arms. The perfusion index increases after successful interscalene nerve blockade and may be used as an indicator for successful block placement in awake patients. The PVI values before and after a fluid challenge can be useful to detect changes in preload, and this can be performed in both blocked and unblocked arms.

Increased temperature, not cardiac load, activates heat shock transcription factor 1 and heat shock protein 72 expression in the heart.

PubMed

Staib, Jessica L; Quindry, John C; French, Joel P; Criswell, David S; Powers, Scott K

2007-01-01

The expression of myocardial heat shock protein 72 (HSP72) postexercise is initiated by the activation of heat shock transcription factor 1 (HSF1). However, it remains unknown which physiological stimuli govern myocardial HSF1 activation during exercise. These experiments tested the hypothesis that thermal stress and mechanical load, concomitant with simulated exercise, provide independent stimuli for HSF1 activation and ensuing cardiac HSP72 gene expression. To elucidate the independent roles of increased temperature and cardiac workload in the exercise-mediated upregulation of left-ventricular HSP72, hearts from adult male Sprague-Dawley rats were randomly assigned to one of five simulated exercise conditions. Upon reaching a surgical plane of anesthesia, each experimental heart was isolated and perfused using an in vitro working heart model, while independently varying temperatures (i.e., 37 degrees C vs. 40 degrees C) and cardiac workloads (i.e., low preload and afterload vs. high preload and afterload) to mimic exercise responses. Results indicate that hyperthermia, independent of cardiac workload, promoted an increase in nuclear translocation and phosphorylation of HSF1 compared with normothermic left ventricles. Similarly, hyperthermia, independent of workload, resulted in significant increases in cardiac levels of HSP72 mRNA. Collectively, these data suggest that HSF1 activation and HSP72 gene transcriptional competence during simulated exercise are linked to elevated heart temperature and are not a direct function of increased cardiac workload.

Effect of Consuming Oat Bran Mixed in Water before a Meal on Glycemic Responses in Healthy Humans-A Pilot Study.

PubMed

Steinert, Robert E; Raederstorff, Daniel; Wolever, Thomas M S

2016-08-26

Viscous dietary fibers including oat β-glucan are one of the most effective classes of functional food ingredients for reducing postprandial blood glucose. The mechanism of action is thought to be via an increase in viscosity of the stomach contents that delays gastric emptying and reduces mixing of food with digestive enzymes, which, in turn, retards glucose absorption. Previous studies suggest that taking viscous fibers separate from a meal may not be effective in reducing postprandial glycemia. We aimed to re-assess the effect of consuming a preload of a commercially available oat-bran (4.5, 13.6 or 27.3 g) containing 22% of high molecular weight oat β-glucan (O22 (OatWell(®)22)) mixed in water before a test-meal of white bread on glycemic responses in 10 healthy humans. We found a significant effect of dose on blood glucose area under the curve (AUC) (p = 0.006) with AUC after 27.3 g of O22 being significantly lower than white bread only. Linear regression analysis showed that each gram of oat β-glucan reduced glucose AUC by 4.35% ± 1.20% (r = 0.507, p = 0.0008, n = 40) and peak rise by 6.57% ± 1.49% (r = 0.582, p < 0.0001). These data suggest the use of oat bran as nutritional preload strategy in the management of postprandial glycemia.

Space Shuttle Main Engine (SSME) LOX turbopump pump-end bearing analysis

NASA Technical Reports Server (NTRS)

1986-01-01

A simulation of the shaft/bearing system of the Space Shuttle Main Engine Liquid Oxygen turbopump was developed. The simulation model allows the thermal and mechanical characteristics to interact as a realistic simulation of the bearing operating characteristics. The model accounts for single and two phase coolant conditions, and includes the heat generation from bearing friction and fluid stirring. Using the simulation model, parametric analyses were performed on the 45 mm pump-end bearings to investigate the sensitivity of bearing characteristics to contact friction, axial preload, coolant flow rate, coolant inlet temperature and quality, heat transfer coefficients, outer race clearance and misalignment, and the effects of thermally isolating the outer race from the isolator.

The properties of thin-section, four-point-contact ball bearings in space

NASA Technical Reports Server (NTRS)

Rowntree, R. A.

1985-01-01

Thin section, four-point-contact ball bearings are increasinly employed in spacecraft mechanisms because of the potential advantages they offer. However, litte was previously known of their torque, thermal conductance and stiffness properties at conditions anticipated for their use in space. An investigation of these properties are described. It was found that frictional (Coulomb) torque, thermal conductance and stiffness all show marked dependence on the bearing preload, the housing design, the bearing external fit (i.e., free fit or interference) and on the thermal gradient across the races. Optimum bearing performance is achieved only if these properties are well understood. The necessary data to understand these properties are provided.

Characterization of the bending stiffness of large space structure joints

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey

1989-01-01

A technique for estimating the bending stiffness of large space structure joints is developed and demonstrated for an erectable joint concept. Experimental load-deflection data from a three-point bending test was used as input to solve a closed-form expression for the joint bending stiffness which was derived from linear beam theory. Potential error sources in both the experimental and analytical procedures are identified and discussed. The bending stiffness of a mechanically preloaded erectable joint is studied at three applied moments and seven joint orientations. Using this technique, the joint bending stiffness was bounded between 6 and 17 percent of the bending stiffness of the graphite/epoxy strut member.

Examination of Sandwich-Type Multidegree-of-Freedom Spherical Ultrasonic Motor

NASA Astrophysics Data System (ADS)

Lu, Bo; Aoyagi, Manabu; Takano, Takehiro; Tamura, Hideki

2010-07-01

A sandwich-type multidegree-of-freedom (MDOF) spherical ultrasonic motor (SUSM) is newly proposed. The motor consists of a spherical rotor and two stator vibrators holding the rotor. This structure has both a rotor support and a preload mechanism. The stator excites five vibration modes, and the rotor can rotate on three axes. An experiment of a torque composition of two stators was carried out. The contact surface between the rotor and the stators forms a spherical surface. Moreover, a displacement magnification mechanism, which was used in the former model to rotate on the Z-axis, is no longer necessary. Hence the stator is simpler in construction than the former model. In this paper, we describe the construction and the operating principle of the MDOF ultrasonic motor, modal analysis results for the stator, and some measurement results from trial manufacturing. The miniaturization of the motor and increase in torque were successfully realized.

An info-gap application to robust design of a prestressed space structure under epistemic uncertainties

NASA Astrophysics Data System (ADS)

Hot, Aurélien; Weisser, Thomas; Cogan, Scott

2017-07-01

Uncertainty quantification is an integral part of the model validation process and is important to take into account during the design of mechanical systems. Sources of uncertainty are diverse but generally fall into two categories: aleatory due to random process and epistemic resulting from a lack of knowledge. This work focuses on the behavior of solar arrays in their stowed configuration. To avoid impacts during launch, snubbers are used to prestress the panels. Since the mechanical properties of the snubbers and the associated preload configurations are difficult to characterize precisely, an info-gap approach is proposed to investigate the influence of such uncertainties on design configurations obtained for different values of safety factors. This eventually allows to revise the typical values of these factors and to reevaluate them with respect to a targeted robustness level. The proposed methodology is illustrated using a simplified finite element model of a solar array.

New Terfenol-D actuator design with applications to multiple DOF active vibration control

NASA Astrophysics Data System (ADS)

Haynes, Leonard S.; Geng, Zheng J.; Teter, Joseph P.

1993-09-01

A linear actuator system for multi-dimensional structure control using the magnetostrictive material Terfenol-D has been designed, built, and tested by the Intelligent Automation, Inc. The actuator assembly incorporates an instrumented Terfenol-D rod, an excitation coil to provide the magnetic field, a permanent magnet assembly to provide a magnetic bias field, and a mechanical preload mechanism. The prototype of the actuator is 2.0 inches in diameter and 8 inches long, and provides a peak-to-peak stroke of 0.01 inches. A linear model was also established to characterize the behavior of the actuator for small motion. Based on the prototype of the actuator, we have performed a study of a six degree-of-freedom active vibration isolation system using a Stewart Platform in a new configuration. IAI's final system is intended for precision control of a wide range of space-based structures as well as earth- base systems.

Microstructural and Mechanical Aspects of Reinforcement Welds for Lightweight Components Produced by Friction Hydro Pillar Processing

NASA Astrophysics Data System (ADS)

Pinheiro, Gustavo; dos Santos, Jorge; Hort, Norbert; Kainer, Karl Ulrich

The development of new creep resistant and cost effective die casting magnesium alloys such as AE, MRI, MEZ, ACM, AXJ, AJ, WE have emerged as an alternative to fulfil the actual demands in structural relevant applications as engines blocks, gear and converter boxes. However, magnesium components are in most of the cases screwed with aluminium and steel bolts, which lead the screwed joint to lose the preload force due to relaxation. This barrier limits thus the broad use of magnesium within this segment and should somehow find an adequate solution to be implemented and to help overcoming this limitation. In this context Friction Welding (FW) and particularly Friction Hydro Pillar Processing (FHPP), which can be described as a drill and fill process, appears as an alternative to widespread the use of magnesium. In this context, FHPP is intended to be used to locally reinforce mechanical fastened magnesium components.

Transfer having a coupling coefficient higher than its active material

NASA Technical Reports Server (NTRS)

Lesieutre, George A. (Inventor); Davis, Christopher L. (Inventor)

2001-01-01

A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices.

Hyperthyroidism and cardiovascular complications: a narrative review on the basis of pathophysiology

PubMed Central

Cicero, Arrigo F.

2013-01-01

Cardiovascular complications are important in hyperthyroidism because of their high frequency in clinical presentation and increased mortality and morbidity risk. The cause of hyperthyroidism, factors related to the patient, and the genetic basis for complications are associated with risk and the basic underlying mechanisms are important for treatment and management of the disease. Besides cellular effects, hyperthyroidism also causes hemodynamic changes, such as increased preload and contractility and decreased systemic vascular resistance causes increased cardiac output. Besides tachyarrythmias, impaired systolic ventricular dysfunction and diastolic dysfunction may cause thyrotoxic cardiomyopathy in a small percentage of the patients, as another high mortality complication. Although the medical literature has some conflicting data about benefits of treatment of subclinical hyperthyroidism, even high-normal thyroid function may cause cardiovascular problems and it should be treated. This review summarizes the cardiovascular consequences of hyperthyroidism with underlying mechanisms. PMID:24273583

Multistable wireless micro-actuator based on antagonistic pre-shaped double beams

NASA Astrophysics Data System (ADS)

Liu, X.; Lamarque, F.; Doré, E.; Pouille, P.

2015-07-01

This paper presents a monolithic multistable micro-actuator based on antagonistic pre-shaped double beams. The designed micro-actuator is formed by two rows of bistable micro-actuators providing four stable positions. The bistable mechanism for each row is a pair of antagonistic pre-shaped beams. This bistable mechanism has an easier pre-load operation compared to the pre-compressed bistable beams method. Furthermore, it solves the asymmetrical force output problem of parallel pre-shaped bistable double beams. At the same time, the geometrical limit is lower than parallel pre-shaped bistable double beams, which ensures a smaller stroke of the micro-actuator with the same dimensions. The designed micro-actuator is fabricated using laser cutting machine on medium density fiberboard (MDF). The bistability and merits of antagonistic pre-shaped double beams are experimentally validated. Finally, a contactless actuation test is performed using 660 nm wavelength laser heating shape memory alloy (SMA) active elements.

Launch Lock Assemblies with Reduced Preload and Spacecraft Isolation Systems Including the Same

NASA Technical Reports Server (NTRS)

Barber, Tim Daniel (Inventor); Young, Ken (Inventor); Hindle, Timothy (Inventor)

2016-01-01

Launch lock assemblies with reduced preload are provided. The launch lock assembly comprises first and second mount pieces, a releasable clamp device, and a pair of retracting assemblies. Each retracting assembly comprises a pair of toothed members having interacting toothed surfaces. The releasable clamp device normally maintains the first and second mount pieces in clamped engagement. When the releasable clamp device is actuated, the first and second mount pieces are released from clamped engagement and one toothed member of each retracting assembly moves in an opposite direction relative to the other one toothed member of the other retracting assembly to define an axial gap on each side of the first mount piece.

Muscle contributions to elbow joint rotational stiffness in preparation for sudden external arm perturbations.

PubMed

Holmes, Michael W R; Keir, Peter J

2014-04-01

Understanding joint stiffness and stability is beneficial for assessing injury risk. The purpose of this study was to examine joint rotational stiffness for individual muscles contributing to elbow joint stability. Fifteen male participants maintained combinations of three body orientations (standing, supine, sitting) and three hand preloads (no load, solid tube, fluid filled tube) while a device imposed a sudden elbow extension. Elbow angle and activity from nine muscles were inputs to a biomechanical model to determine relative contributions to elbow joint rotational stiffness, reported as percent of total stiffness. A body orientation by preload interaction was evident for most muscles (P<.001). Brachioradialis had the largest change in contribution while standing (no load, 18.5%; solid, 23.8%; fluid, 26.3%). Across trials, the greatest contributions were brachialis (30.4±1.9%) and brachioradialis (21.7±2.2%). Contributions from the forearm muscles and triceps were 5.5±0.6% and 9.2±1.9%, respectively. Contributions increased at time points closer to the perturbation (baseline to anticipatory), indicating increased neuromuscular response to resist rotation. This study quantified muscle contributions that resist elbow perturbations, found that forearm muscles contribute marginally and showed that orientation and preload should be considered when evaluating elbow joint stiffness and safety.

Stress analysis of bolted joints under centrifugal force

NASA Astrophysics Data System (ADS)

Imura, Makoto; Iizuka, Motonobu; Nakae, Shigeki; Mori, Takeshi; Koyama, Takayuki

2014-06-01

Our objective is to develop a long-life rotary machine for synchronous generators and motors. To do this, it is necessary to design a high-strength bolted joint, which is responsible for fixing a salient pole on a rotor shaft. While the rotary machine is in operation, not only centrifugal force but also moment are loaded on a bolted joint, because a point of load is eccentric to a centre of a bolt. We tried to apply the theory proposed in VDI2230-Blatt1 to evaluate the bolted joint under eccentric force, estimate limited centrifugal force, which is the cause of partial separation between the pole and the rotor shaft, and then evaluate additional tension of a bolt after the partial separation has occurred. We analyzed the bolted joint by FEM, and defined load introduction factor in that case. Additionally, we investigated the effect of the variation of bolt preload on the partial separation. We did a full scale experiment with a prototype rotor to reveal the variation of bolt preload against tightening torque. After that, we verified limited centrifugal force and the strength of the bolted joint by the VDI2230-Blatt1 theory and FEM considering the variation of bolt preload. Finally, we could design a high-strength bolted joint verified by the theoretical study and FEM analysis.

Experimental validation of more realistic computer models for stent-graft repair of abdominal aortic aneurysms, including pre-load assessment.

PubMed

Roy, David; Lerouge, Sophie; Inaekyan, Karina; Kauffmann, Claude; Mongrain, Rosaire; Soulez, Gilles

2016-12-01

Although the endovascular repair of abdominal aortic aneurysms is a less invasive alternative than classic open surgery, complications such as endoleak and kinking still need to be addressed. Numerical simulation of endovascular repair is becoming a valuable tool in stent-graft (SG) optimization, patient selection and surgical planning. The experimental and numerical forces required to produce SG deformations were compared in a range of in vivo conditions in the present study. The deformation modes investigated were: bending as well as axial, transversal and radial compressions. In particular, an original method was developed to efficiently account for radial pre-load because of the pre-compression of stents to match the graft dimensions during manufacturing. This is important in order to compute the radial force exerted on the vessel after deployment more accurately. Variations of displacement between the experimental and numerical results ranged from 1.39% for simple leg bending to 5.93% for three-point body bending. Finally, radial pre-load was modeled by increasing Young's modulus of each stent. On average, it was found that Young's modulus had to be augmented by a factor of 2. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Maternal and anaesthesia-related risk factors and incidence of spinal anaesthesia-induced hypotension in elective caesarean section: A multinomial logistic regression

PubMed Central

Fakherpour, Atousa; Ghaem, Haleh; Fattahi, Zeinabsadat; Zaree, Samaneh

2018-01-01

Background and Aims: Although spinal anaesthesia (SA) is nowadays the preferred anaesthesia technique for caesarean section (CS), it is associated with considerable haemodynamic effects, such as maternal hypotension. This study aimed to evaluate a wide range of variables (related to parturient and anaesthesia techniques) associated with the incidence of different degrees of SA-induced hypotension during elective CS. Methods: This prospective study was conducted on 511 mother–infant pairs, in which the mother underwent elective CS under SA. The data were collected through preset proforma containing three parts related to the parturient, anaesthetic techniques and a table for recording maternal blood pressure. It was hypothesized that some maternal (such as age) and anaesthesia-related risk factors (such as block height) were associated with occurance of SA-induced hypotension during elective CS. Results: The incidence of mild, moderate and severe hypotension was 20%, 35% and 40%, respectively. Eventually, ten risk factors were found to be associated with hypotension, including age >35 years, body mass index ≥25 kg/m2, 11–20 kg weight gain, gravidity ≥4, history of hypotension, baseline systolic blood pressure (SBP) <120 mmHg and baseline heart rate >100 beats/min in maternal modelling, fluid preloading ≥1000 ml, adding sufentanil to bupivacaine and sensory block height >T4in anaesthesia-related modelling (P < 0.05). Conclusion: Age, body mass index, weight gain, gravidity, history of hypotension, baseline SBP and heart rate, fluid preloading, adding sufentanil to bupivacaine and sensory block hieght were the main risk factors identified in the study for SA-induced hypotension during CS. PMID:29416149

Caloric compensation and eating in the absence of hunger in 5- to 12-y-old weight-discordant siblings123

PubMed Central

Kral, Tanja VE; Allison, David B; Birch, Leann L; Stallings, Virginia A; Moore, Reneé H; Faith, Myles S

2012-01-01

Background: An impaired ability to compensate for calories and increased eating in the absence of hunger (EAH) has been associated with increased energy intake and weight gain in unrelated children. Objective: The aims of this study were to compare caloric compensation [the percentage compensation index (%COMPX)] and EAH in weight-discordant siblings aged 5–12 y. Design: In a crossover, behavioral genetics design, 47 same-sex sibling pairs (53% female, 55% full siblings) were served dinner once a week for 3 wk. Across conditions, siblings were served the same dinner, but 25 min before dinner, they either consumed in full or did not consume 1 of 2 preloads that varied in energy density (ED; 0.57 or 0.97 kcal/g). On the day when no preload was consumed, EAH was assessed after dinner and defined as the number of calories consumed from snacks. Results: Overweight/obese siblings undercompensated [%COMPX: −48.8 ± 56.3 (mean ± SEM)] and therefore overate after the high-ED preload, whereas normal-weight siblings showed accurate compensation (%COMPX: 101.3 ± 51.9; P = 0.03). Furthermore, overweight/obese siblings consumed 34% more calories (93 kcal) in the absence of hunger than did normal-weight siblings (P = 0.01). Within-pair resemblances for %COMPX and EAH were stronger for full siblings (P < 0.049) than for half siblings (P > 0.23). Conclusions: An impaired ability to regulate short-term energy intake, which includes incomplete adjustment for calorie differences in a preload and eating when satiated, may represent a behavioral phenotype for obesity in children. Future studies should test whether teaching children to focus on internal satiety cues may prevent at-risk children from overeating. This trial was registered at clinicaltrials.gov as NCT01598389. PMID:22854400

Idiopathic recurrent calcium urolithiasis (IRCU): an acid meal challenge uncovers inappropriate pH of postprandial, fasting and daily urine: a cross-sectional study of male patients providing insight into post- and pre-load urinary stone substances, crystallization risk, presence of stones, renal transport and systemic metabolic factors.

PubMed

Schwille, Paul O; Wipplinger, J

2008-07-28

In IRCU the possible role of urinary pH (U-pH) as risk factor of calcium (Ca) stones is poorly understood. To evaluate in IRCU the response to an oral acid load, focussing on post- and pre-load U-pH, other urinary, renal and extra-renal factors, and linkage with Ca stones. - 237 male patients, either Ca stone-free (SF) or -bearing (SB), but without overt signs of systemic metabolic acidosis underwent a standardized laboratory programme that included, besides collection of urine and blood, the intake of an oxalate-free acid test meal (proton content 120 mM). Established analytical methods were used. In 79 patients the post-meal load U-pH was < or = 5.30 (in healthy individuals accepted as the upper limit after the same proton load), but >5.30 in 158; in these two subsets the mean fasting pre-load U-pH was 5.84 and 6.37 (p <0.001), the mean U-pH in 24 h urine 5.70 and 6.03 (p <0.001), the mean score of stone formation activity 32 and 42 (p = 0.12), the SF/SB ratio 35/44 and 76/82 (not significant). However, when in pre-load urine undissociated uric acid concentration was low due to the high pH, the SF/SB ratio was 53/66 (p = 0.038), whereas isolated increase of U-pH with SF/SB ratio 54/65 (p = 0.059), urinary supersaturation with Ca phosphate (hydroxyapatite), Ca oxalate, uric acid, and isolated decrease of concentration of total protein, total uric acid and the crystallization inhibitors magnesium and citrate failed to affect significantly the frequency distribution of SF and SB patients. Pre-load U-pH was positively associated with urinary ratio sodium/proton excretion, renal reclaim of sodium and protein, negatively associated with body mass index, fasting insulinemia and uricemia, urinary protein concentration, renal reclaim of phosphate. In IRCU 1) inappropriately high U-pH combined with increase of proteinuria and alteration of renal-tubular transport are frequent; 2) disturbed interactions of renal proton generation with sodium handling, urinary physico-chemical and systemic metabolic factors may initiate the development of Ca-containing concretions, presumably Ca phosphate, at some yet unknown renal anatomic site.

Comparative analysis of international standards for the fatigue testing of posterior spinal fixation systems: the importance of preload in ISO 12189.

PubMed

La Barbera, Luigi; Ottardi, Claudia; Villa, Tomaso

2015-10-01

Preclinical evaluation of the mechanical reliability of fixation devices is a mandatory activity before their introduction into market. There are two standardized protocols for preclinical testing of spinal implants. The American Society for Testing Materials (ASTM) recommends the F1717 standard, which describes a vertebrectomy condition that is relatively simple to implement, whereas the International Organization for Standardization (ISO) suggests the 12189 standard, which describes a more complex physiological anterior support-based setup. Moreover, ASTM F1717 is nowadays well established, whereas ISO 12189 has received little attention: A few studies tried to accurately describe the ISO experimental procedure through numeric models, but these studies totally neglect the recommended precompression step. This study aimed to build up a reliable, validated numeric model capable of describing the stress on the rods of a spinal fixator assembled according to ISO 12189 standard procedure. Such a model would more adequately represent the in vitro testing condition. This study used finite element (FE) simulations and experimental validation testing. An FE model of the ISO setup was built to calculate the stress on the rods. Simulation was validated by comparison with experimental strain gauges measurements. The same fixator has been previously virtually mounted in an L2-L4 FE model of the lumbar spine, and stresses in the rods were calculated when the spine was subjected to physiological forces and moments. The comparison between the FE predictions and experimental measurements is in good agreement, thus confirming the suitability of the FE method to evaluate the stresses in the device. The initial precompression induces a significant extension of the assembled construct. As the applied load increases, the initial extension is gradually compensated, so that at peak load the rods are bent in flexion: The final stress value predicted is thus reduced to about 50%, if compared with the previous model where the precompression was not considered. Neglecting the initial preload due to the assembly of the overall construct according to ISO 12189 standard could lead to an overestimation of the stress on the rods up to 50%. To correctly describe the state of stress on the posterior spinal fixator, tested according to the ISO procedure, it is important to take into account the initial preload due to the assembly of the overall construct. Copyright © 2015 Elsevier Inc. All rights reserved.

Left ventricular rotation and right-left ventricular interaction in congenital heart disease: the acute effects of interventional closure of patent arterial ducts and atrial septal defects.

PubMed

Laser, Kai T; Haas, Nikolaus A; Fischer, Markus; Habash, Sheeraz; Degener, Franziska; Prinz, Christian; Körperich, Hermann; Sandica, Eugen; Kececioglu, Deniz

2014-08-01

Left ventricular rotation is physiologically affected by acute changes in preload. We investigated the acute effect of preload changes in chronically underloaded and overloaded left ventricles in children with shunt lesions. A total of 15 patients with atrial septal defects (Group A: 7.4 ± 4.7 years, 11 females) and 14 patients with patent arterial ducts (Group B: 2.7 ± 3.1 years, 10 females) were investigated using 2D speckle-tracking echocardiography before and after interventional catheterisation. The rotational parameters of the patient group were compared with those of 29 matched healthy children (Group C). Maximal torsion (A: 2.45 ± 0.9°/cm versus C: 1.8 ± 0.8°/cm, p < 0.05), apical peak systolic rotation (A: 12.6 ± 5.7° versus C: 8.7 ± 3.5°, p < 0.05), and the peak diastolic torsion rate (A: -147 ± 48°/second versus C: -110 ± 31°/second, p < 0.05) were elevated in Group A and dropped immediately to normal values after intervention (maximal torsion 1.5 ± 1.1°/cm, p < 0.05, apical peak systolic rotation 7.2 ± 4.1°, p < 0.05, and peak diastolic torsion rate -106 ± 35°/second, p < 0.05). Patients in Group B had decreased maximal torsion (B: 1.8 ± 1.1°/cm versus C: 3.8 ± 1.4°/cm, p < 0.05) and apical peak systolic rotation (B: 8.3 ± 6.1° versus C: 13.9 ± 4.3°, p < 0.05). Defect closure was followed by an increase in maximal torsion (B: 2.7 ± 1.4°/cm, p < 0.05) and the peak diastolic torsion rate (B: -133 ± 66°/second versus -176 ± 84°/second, p < 0.05). Patients with chronically underloaded left ventricles compensate with an enhanced apical peak systolic rotation, maximal torsion, and quicker diastolic untwisting to facilitate diastolic filling. In patients with left ventricular dilatation by volume overload, the peak systolic apical rotation and the maximal torsion are decreased. After normalisation of the preload, they immediately return to normal and diastolic untwisting rebounds. These mechanisms are important for understanding the remodelling processes.

Deformation mechanisms in negative Poisson's ratio materials - Structural aspects

NASA Technical Reports Server (NTRS)

Lakes, R.

1991-01-01

Poisson's ratio in materials is governed by the following aspects of the microstructure: the presence of rotational degrees of freedom, non-affine deformation kinematics, or anisotropic structure. Several structural models are examined. The non-affine kinematics are seen to be essential for the production of negative Poisson's ratios for isotropic materials containing central force linkages of positive stiffness. Non-central forces combined with pre-load can also give rise to a negative Poisson's ratio in isotropic materials. A chiral microstructure with non-central force interaction or non-affine deformation can also exhibit a negative Poisson's ratio. Toughness and damage resistance in these materials may be affected by the Poisson's ratio itself, as well as by generalized continuum aspects associated with the microstructure.

Ultrasonic rotary-hammer drill

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph (Inventor); Badescu, Mircea (Inventor); Sherrit, Stewart (Inventor); Kassab, Steve (Inventor); Bao, Xiaoqi (Inventor)

2010-01-01

A mechanism for drilling or coring by a combination of sonic hammering and rotation. The drill includes a hammering section with a set of preload weights mounted atop a hammering actuator and an axial passage through the hammering section. In addition, a rotary section includes a motor coupled to a drive shaft that traverses the axial passage through the hammering section. A drill bit is coupled to the drive shaft for drilling by a combination of sonic hammering and rotation. The drill bit includes a fluted shaft leading to a distal crown cutter with teeth. The bit penetrates sampled media by repeated hammering action. In addition, the bit is rotated. As it rotates the fluted bit carries powdered cuttings helically upward along the side of the bit to the surface.

Strontium, barium, and manganese metabolism in isolated presynaptic nerve terminals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasgado-Flores, H.; Sanchez-Armass, S.; Blaustein, M.P.

1987-06-01

To gain insight into the mechanisms by which the divalent cations Sr, Ba, and Mn affect neurotransmitter release from presynaptic nerve terminals, the authors examined the sequestration of these cations, ion comparison to Ca, by mitochondrial and nonmitochondrial organelles and the extrusion of these cations from isolated nerve terminals. Sequestration was studied in synaptosomes made leaky to small ions by treatment with saponin; efflux was examined in intact synaptosomes that were preloaded with the divalent cations by incubation in depolarizing (K rich) media. The selectivity sequence for ATP-dependent mitochondrial uptake that they observed was Mn>>Ca>Sr>>Ba, whereas that for the SERmore » was Ca greater than or equal to Mn>Sr>>Ba. When synaptosomes that were preloaded with divalent cations were incubated in Na- and Ca-free media, there was little efflux of /sup 45/Ca, /sup 133/Ba, /sup 85/Sr, or /sup 54/Mn. When the incubation was carried out in media containing Na without Ca, there was substantial stimulation of Ca and Sr efflux, but only slight stimulation of Ba or Mn efflux. In Na-free media, the addition of 1 mM Ca promoted the efflux of all four divalent cations, probably via Ca-divalent cation exchange. In summary, the sequestration and extrusion data suggest that, with equal loads, Mn will be buffered to the greatest extent, whereas Ba will be least well buffered. These results may help to explain why Mn has a very long-lasting effect on transmitter release, while the effect of Sr is much briefer.« less

Myocardial mechanics, energetics, and hemodynamics during intraaortic balloon and transvalvular axial flow hemopump support with a bovine model of ischemic cardiac dysfunction.

PubMed

Marks, J D; Pantalos, G M; Long, J W; Kinoshita, M; Everett, S D; Olsen, D B

1999-01-01

Unlike the mechanisms of intraaortic balloon pump (IABP) support, the mechanisms by which transvalvular axial flow Hemopump (HP) support benefit dysfunctional myocardium are less clearly understood. To help elucidate these mechanisms, hemodynamic, metabolic, and mechanical indexes of left ventricular function were measured during conditions of control, ischemic dysfunction, IABP support, and HP support. A large animal (calf) model of left ventricular dysfunction was created with multiple coronary ligations. Peak intraventricular pressure increased with HP support and decreased with IABP support. Intramyocardial pressure (an indicator of intramyocardial stress), time rate of pressure change (an indicator of contractility), and left ventricular myocardial oxygen consumption decreased with IABP and HP support. Left ventricular work decreased with HP support and increased with IABP support. During HP support, indexes of wall stress, work, and contractility, all primary determinants of oxygen consumption, were reduced. During IABP support, indexes of wall stress and contractility were reduced and external work increased. These changes were attributed primarily to changes in ventricular preload, and geometry for HP support, and to a reduction in afterload for IABP support. These findings support the hypothesis that both HP and IABP support reduce intramyocardial stress development and the corresponding oxygen consumption, although via different mechanisms.

Biaxial analysis of synthetic scaffolds for hernia repair demonstrates variability in mechanical anisotropy, non-linearity and hysteresis.

PubMed

Deeken, Corey R; Thompson, Dominic M; Castile, Ryan M; Lake, Spencer P

2014-10-01

Over the past 60 years, the soft tissue repair market has grown to include over 50 types of hernia repair materials. Surgeons typically implant these materials in the orientation that provides maximum overlap of the mesh over the defect, with little regard for mechanical properties of the mesh material. If the characteristics of the meshes were better understood, an appropriate material could be identified for each patient, and meshes could be placed to optimize integration with neighboring tissue and avoid the mechanical mis-match that can lead to impaired graft fixation. The purpose of this study was to fully characterize and compare the mechanical properties of thirteen types of hernia repair materials via planar biaxial tensile testing. Equibiaxial (i.e., equal simultaneous loading in both directions) and strip biaxial (i.e., loading in one direction with the other direction held fixed) tests were utilized as physiologically relevant loading regimes. After applying a 0.1N pre-load on each arm, samples were subjected to equibiaxial cyclic loading using a triangular waveform to 2.5mm displacement on each arm at 0.1Hz for 10 cycles. Samples were then subjected to two strip biaxial tests (using the same cyclic loading protocol), where extension was applied along a single axis with the other axis held fixed. The thirteen evaluated mesh types exhibited a wide range of mechanical properties. Some were nearly isotropic (C-QUR™, DUALMESH(®), PHYSIOMESH™, and PROCEED(®)), while others were highly anisotropic (Ventralight™ ST, Bard™ Mesh, and Bard™ Soft Mesh). Some displayed nearly linear behavior (Bard™ Mesh), while others were non-linear with a long toe region followed by a sharp rise in tension (INFINIT(®)). These materials are currently utilized in clinical settings as if they are uniform and interchangeable, and clearly this is not the case. The mechanical properties most advantageous for successful hernia repairs are currently only vaguely described in the clinical literature. The characteristics of the human abdominal wall must be extensively characterized to provide a thorough understanding of the tissue being reinforced/replaced by these meshes. A better understanding of these mechanical differences would enable matching of patient characteristics to a specific mesh with the properties best suited to that particular repair. Copyright © 2014 Elsevier Ltd. All rights reserved.

Clinical review: Positive end-expiratory pressure and cardiac output

PubMed Central

Luecke, Thomas; Pelosi, Paolo

2005-01-01

In patients with acute lung injury, high levels of positive end-expiratory pressure (PEEP) may be necessary to maintain or restore oxygenation, despite the fact that 'aggressive' mechanical ventilation can markedly affect cardiac function in a complex and often unpredictable fashion. As heart rate usually does not change with PEEP, the entire fall in cardiac output is a consequence of a reduction in left ventricular stroke volume (SV). PEEP-induced changes in cardiac output are analyzed, therefore, in terms of changes in SV and its determinants (preload, afterload, contractility and ventricular compliance). Mechanical ventilation with PEEP, like any other active or passive ventilatory maneuver, primarily affects cardiac function by changing lung volume and intrathoracic pressure. In order to describe the direct cardiocirculatory consequences of respiratory failure necessitating mechanical ventilation and PEEP, this review will focus on the effects of changes in lung volume, factors controlling venous return, the diastolic interactions between the ventricles and the effects of intrathoracic pressure on cardiac function, specifically left ventricular function. Finally, the hemodynamic consequences of PEEP in patients with heart failure, chronic obstructive pulmonary disease and acute respiratory distress syndrome are discussed. PMID:16356246

Electromagnetic brake/clutch device

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1994-01-01

An electromagnetic brake/clutch device includes a drive shaft supported by at least one bearing for transmitting torque, a housing, affixed to prevent its rotation, surrounding the drive shaft, and an electromagnetically activated device within the housing to selectively prevent and allow rotation of the drive shaft. The electromagnetically activated device includes a plurality of cammed rollers to prevent counter-clockwise rotation of the drive shaft. The drive shaft includes a circumferential disk and the housing includes a reaction ring for engagement with the plurality of cammed rollers. The plurality of cammed rollers are released from engagement with the circumferential disk and the reaction ring by a plurality of tripping mechanisms within the housing. The tripping action uses the locking force to act as a release force merely by changing the boundary conditions of the roller interface angles. The tripping mechanisms include trippers for disengaging the plurality of cammed rollers and an anvil shaped portion for providing lateral movement of the trippers. The plurality of cammed rollers is preloaded to engagement with the circumferential disk and reaction ring by a spring, and is located with respect to an adjacent tripping mechanism with another spring.

Quantification of the fungal fraction released from various preloaded fibrous filters during a simulated ventilation restart.

PubMed

Morisseau, K; Joubert, A; Le Coq, L; Andres, Y

2017-05-01

This study aimed to demonstrate that particles, especially those associated with fungi, could be released from fibrous filters used in the air-handling unit (AHU) of heating, ventilation and air-conditioning (HVAC) systems during ventilation restarts. Quantification of the water retention capacity and SEM pictures of the filters was used to show the potential for fungal proliferation in unused or preloaded filters. Five fibrous filters with various particle collection efficiencies were studied: classes G4, M5, M6, F7, and combined F7 according to European standard EN779:2012. Filters were clogged with micronized rice particles containing the fungus Penicillium chrysogenum and then incubated for three weeks at 25°C and 90% relative humidity. The results indicated that the five clogged tested filters had various fungal growth capacities depending on their water retention capacity. Preloaded filters were subjected to a simulated ventilation restart in a controlled filtration device to quantify that the fraction of particles released was around 1% for the G4, 0.1% for the M5 and the M6, and 0.001% for the F7 and the combined F7 filter. The results indicate that the likelihood of fungal particle release by low efficiency filters is significantly higher than by high efficiency filters. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Incubation of sucrose craving: effects of reduced training and sucrose pre-loading

PubMed Central

Grimm, Jeffrey W.; Fyall, Amber M.; Osincup, Dan P.

2010-01-01

Time-dependent increases in cue-induced reward seeking after forced abstinence were described in rats with a history of cocaine or sucrose self-administration, suggesting reward craving incubates over time. In the present study, we examined the effects of reduced training experience, or sucrose pre-loading just prior to testing, on the incubation of sucrose craving. Sucrose seeking (responding in extinction and then for a sucrose-paired cue) increased over time in groups of rats that self-administered sucrose 6 h/day for 10 days and were tested at 1, 7, or 30 days of forced abstinence. We found that groups of rats that had self-administered 2 instead of 6 h/day showed a similar profile of responding. Incubation of sucrose craving was attenuated by free access to sucrose in home cages for 17 h immediately prior to testing assessed as extinction responding on days 1 and 30. However, this sucrose pre-loading had no effect on the time-dependent increase in responding for the sucrose-paired cue. In summary, reducing the training experience had no effect on the incubation of sucrose craving and free access to sucrose had only a limited effect–attenuating extinction responding. These results illustrate the strength of the incubation of craving and further suggest long-term changes in brain motivational circuitry following sucrose self-administration. PMID:15642609

Long term ingestion of a preload containing fructo-oligosaccharide or guar gum decreases fat mass but not food intake in mice.

PubMed

Hadri, Zouheyr; Chaumontet, Catherine; Fromentin, Gilles; Even, Patrick C; Darcel, Nicolas; Bouras, Abdelkader Dilmi; Tomé, Daniel; Rasoamanana, Rojo

2015-08-01

Fermentable dietary fibre such as fructo-oligosaccharide and viscous dietary fibers such as guar gum and alginate affect energy homeostasis. The goal of this study was to compare the impact of long term intake of these three dietary fibers on food intake, meal pattern, body weight and fat accumulation in mice. Over a period of 3weeks, the mice were fed daily with a preload containing 32mg of fructo-oligosaccharide or alginate or 13mg of guar gum. Food intake and body weight were monitored weekly, while meal patterns, adiposity and the expression of hypothalamic neuropeptide genes were evaluated at the end of the study period. The 3 dietary fibers produced a similar decrease in total daily food intake (14 to 22%) at the end of the first week, and this effect disappeared over time. The 3 dietary fibers induced a slight variation in satiation parameters. Body weight and expression of hypothalamic neuropeptide genes were not affected by any of the treatment. Preload of fructo-oligosaccharide and guar gum induced a similar and substantial decrease in the development of adiposity (17% and 14%, respectively), while alginate had no effect. Our results demonstrate mainly that the inhibitory effect of dietary fiber on food intake is lost over time, and that guar gum limits fat storage. Copyright © 2015. Published by Elsevier Inc.

Infrared Risley beam pointer

NASA Astrophysics Data System (ADS)

Harford, Steven T.; Gutierrez, Homero; Newman, Michael; Pierce, Robert; Quakenbush, Tim; Wallace, John; Bornstein, Michael

2014-03-01

Ball Aerospace & Technologies Corp. (BATC) has developed a Risley Beam Pointer (RBP) mechanism capable of agile slewing, accurate pointing and high bandwidth. The RBP is comprised of two wedged prisms that offer a wide Field of Regard (FOR) and may be manufactured and operated with diffraction limited optical quality. The tightly packaged mechanism is capable of steering a 4 inch beam over a 60° half angle cone with better than 60 μrad precision. Absolute accuracy of the beam steering is better than 1 mrad. The conformal nature of the RBP makes it an ideal mechanism for use on low altitude aircraft and unmanned aerial vehicles. Unique aspects of the opto-mechanical design include i) thermal compliance to maintain bearing preload and optical figure over a wide temperature range; and ii) packaging of a remote infrared sensor that periodically reports the temperature of both prisms for accurate determination of the index of refraction. The pointing control system operates each prism independently and employs an inner rate loop nested within an outer position loop. Mathematics for the transformation between line-of-sight coordinates and prism rotation are hosted on a 200 MHz microcontroller with just 516 KB of RAM.

A Paper-Based Electrochromic Array for Visualized Electrochemical Sensing.

PubMed

Zhang, Fengling; Cai, Tianyi; Ma, Liang; Zhan, Liyuan; Liu, Hong

2017-01-31

We report a battery-powered, paper-based electrochromic array for visualized electrochemical sensing. The paper-based sensing system consists of six parallel electrochemical cells, which are powered by an aluminum-air battery. Each single electrochemical cell uses a Prussian Blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. Each electrochemical cell is preloaded with increasing amounts of analyte. The sample activates the battery for the sensing. Both the preloaded analyte and the analyte in the sample initiate the color change of Prussian Blue to Prussian White. With a reaction time of 60 s, the number of electrochemical cells with complete color changes is correlated to the concentration of analyte in the sample. As a proof-of-concept analyte, lactic acid was detected semi-quantitatively using the naked eye.

Power Law Versus Exponential Form of Slow Crack Growth of Advanced Structural Ceramics: Dynamic Fatigue

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

2002-01-01

The life prediction analysis based on an exponential crack velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ("dynamic fatigue") and preload testing at ambient and elevated temperatures. The data fit to the strength versus In (stress rate) relation was found to be very reasonable for most of the materials. It was also found that preloading technique was equally applicable for the case of slow crack growth (SCG) parameter n > 30. The major limitation in the exponential crack velocity formulation, however, was that an inert strength of a material must be known priori to evaluate the important SCG parameter n, a significant drawback as compared to the conventional power-law crack velocity formulation.

The Biomechanics of the Modern Golf Swing: Implications for Lower Back Injuries.

PubMed

Cole, Michael H; Grimshaw, Paul N

2016-03-01

The modern golf swing is a complex and asymmetrical movement that places an emphasis on restricting pelvic turn while increasing thorax rotation during the backswing to generate higher clubhead speeds at impact. Increasing thorax rotation relative to pelvic rotation preloads the trunk muscles by accentuating their length and allowing them to use the energy stored in their elastic elements to produce more power. As the thorax and pelvis turn back towards the ball during the downswing, more skilled golfers are known to laterally slide their pelvis toward the target, which further contributes to final clubhead speed. However, despite the apparent performance benefits associated with these sequences, it has been argued that the lumbar spine is incapable of safely accommodating the forces they produce. This notion supports a link between the repeated performance of the golf swing and the development of golf-related low back injuries. Of the complaints reported by golfers, low back injuries continue to be the most prevalent, but the mechanism of these injuries is still poorly understood. This review highlights that there is a paucity of research directly evaluating the apparent link between the modern golf swing and golf-related low back pain. Furthermore, there has been a general lack of consensus within the literature with respect to the methods used to objectively assess the golf swing and the methods used to derived common outcome measures. Future research would benefit from a clear set of guidelines to help reduce the variability between studies.

Universal null DTE (data terminal equipment)

DOEpatents

George, M.; Pierson, L.G.; Wilkins, M.E.

1987-11-09

A communication device in the form of data terminal equipment permits two data communication equipments, each having its own master clock and operating at substantially the same nominal clock rate, to communicate with each other in a multi-segment circuit configuration of a general communication network even when phase or frequency errors exist between the two clocks. Data transmitted between communication equipments of two segments of the communication network is buffered. A variable buffer fill circuit is provided to fill the buffer to a selectable extent prior to initiation of data output clocking. Selection switches are provided to select the degree of buffer preload. A dynamic buffer fill circuit may be incorporated for automatically selecting the buffer fill level as a function of the difference in clock frequencies of the two equipments. Controllable alarm circuitry is provided for selectively generating an underflow or an overflow alarm to one or both of the communicating equipments. 5 figs.

Structural design of an in-line bolted joint for the space shuttle solid rocket motor case segments

NASA Technical Reports Server (NTRS)

Dorsey, John T.; Stein, Peter A.; Bush, Harold G.

1987-01-01

Results of a structural design study of an in-line bolted joint concept which can be used to assemble Space Shuttle Solid Rocket Motor (SRM) case segments are presented. Numerous parametric studies are performed to characterize the in-line bolted joint behavior as major design variables are altered, with the primary objective always being to keep the inside of the joint (where the O-rings are located) closed during the SRM firing. The resulting design has 180 1-inch studs, an eccentricity of -0.5 inch, a flange thickness of 3/4 inch, a bearing plate thickness of 1/4 inch, and the studs are subjected to a preload which is 70% of ultimate. The mass penalty per case segment joint for the in-line design is 346 lbm more than the weight penalty for the proposed capture tang fix.

SCBUCKLE user's manual: Buckling analysis program for simple supported and clamped panels

NASA Technical Reports Server (NTRS)

Cruz, Juan R.

1993-01-01

The program SCBUCKLE calculates the buckling loads and mode shapes of cylindrically curved, rectangular panels. The panel is assumed to have no imperfections. SCBUCKLE is capable of analyzing specially orthotropic symmetric panels (i.e., A(sub 16) = A(sub 26) = 0.0, D(sub 16) = D(sub 26) = 0.0, B(sub ij) = 0.0). The analysis includes first-order transverse shear theory and is capable of modeling sandwich panels. The analysis supports two types of boundary conditions: either simply supported or clamped on all four edges. The panel can be subjected to linearly varying normal loads N(sub x) and N(sub y) in addition to a constant shear load N(sub xy). The applied loads can be divided into two parts: a preload component; and a variable (eigenvalue-dependent) component. The analysis is based on the modified Donnell's equations for shallow shells. The governing equations are solved by Galerkin's method.

Universal null DTE

DOEpatents

George, Michael; Pierson, Lyndon G.; Wilkins, Mark E.

1989-01-01

A communication device in the form of data terminal equipment permits two data communication equipments, each having its own master clock and operating at substantially the same nominal clock rate, to communicate with each other in a multi-segment circuit configuration of a general communication network even when phase or frequency errors exist between the two clocks. Data transmitted between communication equipments of two segments of the communication network is buffered. A variable buffer fill circuit is provided to fill the buffer to a selectable extent prior to initiation of data output clocking. Selection switches are provided to select the degree of buffer preload. A dynamic buffer fill circuit may be incorporated for automatically selecting the buffer fill level as a function of the difference in clock frequencies of the two equipments. Controllable alarm circuitry is provided for selectively generating an underflow or an overflow alarm to one or both of the communicating equipments.

Biomechanical studies of spinal manipulative therapy

PubMed Central

Herzog, Walter

1991-01-01

The purpose of this article is to present a review of our research related to spinal manipulative therapy (SMT). The first part of this review will concentrate on studies that were aimed at quantifying possible changes in the mechanics of locomotion associated with SMT. The second part will focus on studies that were aimed at measuring the forces exerted by chiropractors on patients during SMT. In the locomotion studies, we found that SMT was associated with changes in the mechanics of walking. In particular, sacroiliac joint patients were found to become more symmetrical in their ground reaction force patterns with increasing exposure to SMT. In the force studies we found that the force-time histories of SMT on the sacroiliac joint and thoracic spine were similar, however, the mean peak and preload forces recorded for SMT on the thoracic spine were about 60 N larger than those recorded on the sacroiliac joint. Treatments on the cervical spine were executed faster and with less force than treatments on the sacroiliac joint or the thoracic spine.

Resonant-Type Smooth Impact Drive Mechanism Actuator Operating at Lower Input Voltages

NASA Astrophysics Data System (ADS)

Morita, Takeshi; Nishimura, Takuma; Yoshida, Ryuichi; Hosaka, Hiroshi

2013-07-01

We report on the design and fabrication of a resonant-type smooth impact drive mechanism (SIDM) actuator based on a multilayered piezoelectric ceramic transducer. Conventional SIDMs use off-resonant sawtooth-shaped displacement in developing stick-slip motion of a slider, but require large input voltages for high-speed operation. In contrast, in resonant-type SIDMs, a quasi-sawtooth-shaped displacement is obtained by combining two resonant vibrational modes. This driving principle enables low input voltage operations. In combining the modes, their frequency ratio must be 1:2. To design and optimize the stator transducer to generate sawtooth-shaped displacements, a transfer matrix method was adopted. With a preload of 270 mN, the no-load speed was 40 mm/s under a driving voltage of 1.6 V (peak to peak). This input voltage was one-sixth that of previous SIDMs for the same performance. Concurrently, heat generation was significantly reduced because dielectric losses were suppressed under the lower input voltage operation.

Resonant-type Smooth Impact Drive Mechanism (SIDM) actuator using a bolt-clamped Langevin transducer.

PubMed

Nishimura, Takuma; Hosaka, Hiroshi; Morita, Takeshi

2012-01-01

The Smooth Impact Drive Mechanism (SIDM) is a linear piezoelectric actuator that has seen practically applied to camera lens modules. Although previous SIDM actuators are easily miniaturized and enable accurate positioning, these actuators cannot actuate at high speed and cannot provide powerful driving because they are driven at an off-resonant frequency using a soft-type PZT. In the present study, we propose a resonant-type SIDM using a bolt-clamped Langevin transducer (BLT) with a hard-type PZT. The resonant-type SIDM overcomes the above-mentioned problems and high-power operation becomes possible with a very simple structure. As a result, we confirmed the operation of resonant-type SIDM by designing a bolt-clamped Langevin transducer. The properties of no-load maximum speed was 0.28m/s at driving voltages of 80V(p-p) for 44.9kHz and 48V(p-p) for 22.45kHz with a pre-load of 3.1N. Copyright © 2011 Elsevier B.V. All rights reserved.

Bio-inspired piezoelectric linear motor driven by a single-phase harmonic wave with an asymmetric stator.

PubMed

Pan, Qiaosheng; Miao, Enming; Wu, Bingxuan; Chen, Weikang; Lei, Xiujun; He, Liangguo

2017-07-01

A novel, bio-inspired, single-phase driven piezoelectric linear motor (PLM) using an asymmetric stator was designed, fabricated, and tested to avoid mode degeneracy and to simplify the drive mechanism of a piezoelectric motor. A piezoelectric transducer composed of two piezoelectric stacks and a displacement amplifier was used as the driving element of the PLM. Two simple and specially designed claws performed elliptical motion. A numerical simulation was performed to design the stator and determine the feasibility of the design mechanism of the PLM. Moreover, an experimental setup was built to validate the working principles, as well as to evaluate the performance, of the PLM. The prototype motor outputs a no-load speed of 233.7 mm/s at a voltage of 180 V p-p and a maximum thrust force of 2.3 N under a preload of 10 N. This study verified the feasibility of the proposed design and provided a method to simplify the driving harmonic signal and structure of PLMs.

Effect of a High-Protein, High-Fiber Beverage Preload on Subjective Appetite Ratings and Subsequent Ad Libitum Energy Intake in Overweight Men and Women: A Randomized, Double-Blind Placebo-Controlled, Crossover Study.

PubMed

Sharafi, Mastaneh; Alamdari, Nima; Wilson, Michael; Leidy, Heather J; Glynn, Erin L

2018-06-01

Dietary protein and fiber have been shown to independently improve subjective measures of appetite control. The aim of this study was to determine the acute effects of a high-protein, high-fiber (HP/HFb) beverage taken as a preload compared with an isocaloric lower-protein, lower-fiber (LP/LFb) placebo beverage on subjective appetite ratings and subsequent energy intake at an ad libitum meal in healthy adults. A total of 50 overweight/obese men and women [ n  = 25 men, 25 women; age 30 ± 2 y; body mass index (BMI) 29.6 ± 0.3 kg/m 2 ] received a 160 kcal HP/HFb beverage containing 17 g protein and 6 g fiber on one occasion and an isocaloric LP/LFb placebo beverage containing 1 g protein and 3 g fiber on another occasion in a randomized, double-blind, crossover design. Thirty min after consumption of the beverage preload, an ad libitum pizza meal was provided to be consumed over a 30-min period. Visual analog scales (VAS) were used to assess subjective appetite ratings throughout the testing period. The Revised Restraint Scale (RRS) was used to classify participants as restrained or unrestrained eaters. HP/HFb led to greater reductions in postprandial desire to eat and hunger compared with LP/LFb (both, P  < 0.05) but did not significantly affect postprandial fullness or prospective food consumption. Subsequent meal energy intake tended to be lower after HP/HFb compared with LP/LFb ( P  = 0.09). A subanalysis showed lower energy intake after HP/HFb in older participants (≥25 y) compared with LP/LFb, which was not observed in the younger participants (<25 y). Compared with LP/LFb, a HP/HFb beverage preload reduced hunger, desire to eat, and tended to reduce subsequent food intake. Dietary restraint and age appear to influence subsequent energy intake and should be taken into account when designing nutrition interventions for weight reduction and/or maintenance. This trial was registered at clinicaltrials.gov as NCT02979717.

Biomechanical Characteristics of an Integrated Lumbar Interbody Fusion Device

PubMed Central

Voronov, Leonard I.; Vastardis, Georgios; Zelenakova, Julia; Carandang, Gerard; Havey, Robert M.; Waldorff, Erik I.; Zindrick, Michael R.

2014-01-01

Introduction We hypothesized that an Integrated Lumbar Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) plus posterior instrumentation (FIREBIRD, Orthofix, Lewisville, TX). Purpose of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA) can stabilize single motion segments as well as an anterior interbody spacer (PILLAR AL) + pedicle screw construct (FIREBIRD). Methods Eight cadaveric lumbar spines (age: 43.9±4.3 years) were used. Each specimen's range of motion was tested in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) under intact condition, after L4-L5 PILLAR SA with intervertebral screws and after L4-L5 360° fusion (PILLAR AL + Pedicle Screws and rods (FIREBIRD). Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload. Results Integrated fusion using the PILLAR SA device demonstrated statistically significant reductions in range of motion of the L4-L5 motion segment as compared to the intact condition for each test direction. PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR. A comparison between the PILLAR SA integrated fusion device versus 360° fusion construct with spacer and bilateral pedicle screws was statistically significant in FE and LB. The 360° fusion yielded motion of 1.0±0.5° in FE, 1.0±0.8° in LB (p0.05). Conclusions The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws. The residual segmental motions compare very favorably with published biomechanical studies of other interbody integrated fusion devices. PMID:25694931

Consumption of a high-fat soup preload leads to differences in short-term energy and fat intake between PROP non-taster and super-taster women.

PubMed

Shafaie, Yasmine; Hoffman, Daniel J; Tepper, Beverly J

2015-06-01

Taste blindness to the bitterness of PROP (6-n-propylthiouracil) has been used as a genetic marker for food selection and adiposity. We have shown that PROP non-taster (NT) women have higher BMIs and habitually consume more fat and energy than either medium-taster (MT) or super-taster (ST) women. These data imply that differences in dietary selection underlie the body weight differences among PROP taster groups. However, no studies investigated energy compensation in women classified by PROP status. We investigated if NTs would compensate less accurately for the calories and fat in a high-fat soup preload in a subsequent test meal compared to MTs and STs. Energy intake from a buffet meal was measured in 75 healthy non-diet-restrained, lean women 30 min after the ingestion of a high-fat soup preload (0.8 kcal/g; 55% calories from fat), calculated to represent 10% of resting energy expenditure for each subject, or the same volume of water. Subjects (n = 20-28/taster group) ate a standard breakfast followed 3 hr later by an ad-libitum buffet lunch, on two occasions. There were no differences in energy intake or macronutrient selection across taster groups after water. After soup, NTs consumed more energy than STs. Fat intake (as %-energy) was higher in NTs (46.4% ± 2.4) compared to either MTs (36.1 ± 1.9%) or STs (38.1% ± 2.3; p < 0.05). NTs overate by 11% ± 5 after the soup compared to MTs and STs who underrate by 16% ± 6 and 26% ± 10, respectively (p < 0.01). These data suggest that small discrepancies in short-term energy compensation and selection of fat after a mixed-nutrient, high-fat preload may play a role in positive energy balance and increased adiposity in women with the PROP non-taster phenotype. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Understanding heart failure].

PubMed

Boo, José Fernando Guadalajara

2006-01-01

Heart failure is a disease with several definitions. The term "heart failure" is used by has brougth about confusion in the terminology. For this reason, the value of the ejection fraction (< 0.40 or < 0.35) is used in most meganalyses on the treatment of heart failure, avoiding the term "heart failure" that is a confounding concept. In this paper we carefully analyze the meaning of contractility, ventricular function or performance, preload, afterload, heart failure, compensation mechanisms in heart failure, myocardial oxygen consumption, inadequate, adequate and inappropriate hypertrophy, systole, diastole, compliance, problems of relaxation, and diastolic dysfunction. Their definitions are supported by the original scientific descriptions in an attempt to clarify the concepts about ventricular function and heart failure and, in this way, use the same scientific language about the meaning of ventricular function, heart failure, and diastolic dysfunction.

Investigation into discretization methods of the six-parameter Iwan model

NASA Astrophysics Data System (ADS)

Li, Yikun; Hao, Zhiming; Feng, Jiaquan; Zhang, Dingguo

2017-02-01

Iwan model is widely applied for the purpose of describing nonlinear mechanisms of jointed structures. In this paper, parameter identification procedures of the six-parameter Iwan model based on joint experiments with different preload techniques are performed. Four kinds of discretization methods deduced from stiffness equation of the six-parameter Iwan model are provided, which can be used to discretize the integral-form Iwan model into a sum of finite Jenkins elements. In finite element simulation, the influences of discretization methods and numbers of Jenkins elements on computing accuracy are discussed. Simulation results indicate that a higher accuracy can be obtained with larger numbers of Jenkins elements. It is also shown that compared with other three kinds of discretization methods, the geometric series discretization based on stiffness provides the highest computing accuracy.

Effects of non-nutritive (artificial vs natural) sweeteners on 24-h glucose profiles.

PubMed

Tey, S L; Salleh, N B; Henry, C J; Forde, C G

2017-09-01

Replacing nutritive sweetener with non-nutritive sweeteners (NNS) has the potential to improve glycaemic control. The objective of this study was to investigate the effects of consuming artificial NNS (that is, aspartame), natural NNS (that is, monk fruit and stevia), and sucrose-sweetened beverages on 24-h glucose profiles. Ten healthy males took part in this randomised, crossover study with the following four treatments: aspartame-, monk fruit-, stevia-, and sucrose- (65 g) sweetened beverages. Participants were asked to consume the test beverage as a preload mid-morning. Medtronic iPro2 continuous glucose monitoring system was used to measure mean 24-h glucose, incremental area under the curve (iAUC) and total area under the curve (AUC) for glucose, and 24-h glycaemic variability. Overall no significant differences were found in mean 24-h glucose, iAUC and total AUC for glucose, and 24-h glycaemic variability between the four test beverages. Twenty-four-hour glucose profiles did not differ between beverages sweetened with non-nutritive (artificial vs natural) and nutritive sweeteners. The simple exchange of a single serving of sucrose-sweetened beverage with NNS over a day appears to have minimal effect on 24-h glucose profiles in healthy males.

Performance of active vibration control technology: the ACTEX flight experiments

NASA Astrophysics Data System (ADS)

Nye, T. W.; Manning, R. A.; Qassim, K.

1999-12-01

This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I (ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 °C to 129 °C. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed spacecraft bus smart structures by developing over 20 new technologies. As pathfinders, experience was gained in the implications of space system analyses, verification tests, and for ways to leverage this technology to meet new satellite performance requirements.

Apparatus and method of preloading vibration-damping bellows

DOEpatents

Cutburth, Ronald W.

1988-01-01

An improved vibration damping bellows mount or interconnection is disclosed. In one aspect, the bellows is compressively prestressed along its length to offset vacuum-generated tensile loads and thereby improve vibration damping characteristics.

Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 2; Constant Stress Rate Experiments

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

2002-01-01

The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress rate and preload testing at ambient and elevated temperatures. The data fit to the relation of strength versus the log of the stress rate was very reasonable for most of the materials. Also, the preloading technique was determined equally applicable to the case of slow-crack-growth (SCG) parameter n greater than 30 for both the power-law and exponential formulations. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important SCG parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

Development of procedures for calculating stiffness and damping properties of elastomers in engineering applications. Part 2: Elastomer characteristics at constant temperature

NASA Technical Reports Server (NTRS)

Gupta, P. K.; Tessarzik, J. M.; Cziglenyi, L.

1974-01-01

Dynamic properties of a commerical polybutadiene compound were determined at a constant temperature of 32 C by a forced-vibration resonant mass type of apparatus. The constant thermal state of the elastomer was ensured by keeping the ambient temperature constant and by limiting the power dissipation in the specimen. Experiments were performed with both compression and shear specimens at several preloads (nominal strain varying from 0 to 5 percent), and the results are reported in terms of a complex stiffness as a function of frequency. Very weak frequency dependence is observed and a simple power law type of correlation is shown to represent the data well. Variations in the complex stiffness as a function of preload are also found to be small for both compression and shear specimens.

Thermal buckling behavior of defective CNTs under pre-load: A molecular dynamics study.

PubMed

Mehralian, Fahimeh; Tadi Beni, Yaghoub; Kiani, Yaser

2017-05-01

Current study is concentrated on the extraordinary properties of defective carbon nanotubes (CNTs). The role of vacancy defects in thermal buckling response of precompressed CNTs is explored via molecular dynamics (MD) simulations. Defective CNTs are initially compressed at a certain ratio of their critical buckling strain and then undergo a uniform temperature rise. Comprehensive study is implemented on both armchair and zigzag CNTs with different vacancy defects including monovacancy, symmetric bivacancy and asymmetric bivacancy. The results reveal that defects have a pronounced impact on the buckling behavior of CNTs; interestingly, defective CNTs under compressive pre-load show higher resistance to thermal buckling than pristine ones. In the following, the buckling response of defective CNTs is shown to be dependent on the vacancy defects, location of defects and chirality. Copyright © 2017 Elsevier Inc. All rights reserved.

Transport of Nitric Oxide by Perfluorocarbon Emulsion

PubMed Central

Ortiz, Daniel; Briceño, Juan C.; Cabrales, Pedro

2014-01-01

Perfluorocarbon (PFC) emulsions can transport and release various gases based on concentration gradients. The objective of this study was to determine the possibility of carrying and delivering exogenous nitric oxide (NO) into the circulation by simply loading PFC emulsion with NO prior infusion. PFC was equilibrated with room air (PFC) or 300 ppm NO (PFC-NO) at atmospheric pressure. Isotonic saline solution was used as a volume control (Saline). PFC and PFC-NO were infused at a dose of 3.5 mL/kg in the hamster window chamber model. Blood chemistry, and systemic and microvascular hemodynamic response were measured. Infusion of PFC preloaded with NO reduced blood pressure, induced microvascular vasodilation and increased capillary perfusion; although these changes lasted less than 30 min post infusion. On the other hand, infusion of PFC (without NO) produced vasoconstriction; however, the vasoconstriction was followed by vasodilatation at 30 min post infusion. Plasma nitrite and nitrate increased 15 min after infusion of NO preloaded PFC compared to PFC, 60 min after infusion nitrite and nitrate were not different, and 90 min after infusion plasma S-nitrosothiols increased in both groups. Infusion of NO preloaded PFC resulted in acute vascular relaxation, where as infusion of PFC (without NO) produced vasoconstriction, potentially due to NO sequestration by the PFC micelles. The late effects of PFC infusion are due to NO redistribution and plasma S-nitrosothiols. Gas solubility in PFC can provide a tool to modulate plasma vasoactive NO forms availability and improve microcirculatory function and promote increased blood flow. PMID:23966236

Comparative effect of implant-abutment connections, abutment angulations, and screw lengths on preloaded abutment screw using three-dimensional finite element analysis: An in vitro study.

PubMed

Kanneganti, Krishna Chaitanya; Vinnakota, Dileep Nag; Pottem, Srinivas Rao; Pulagam, Mahesh

2018-01-01

The purpose of this study is to compare the effect of implant-abutment connections, abutment angulations, and screw lengths on screw loosening (SL) of preloaded abutment using three dimensional (3D) finite element analysis. 3D models of implants (conical connection with hex/trilobed connections), abutments (straight/angulated), abutment screws (short/long), and crown and bone were designed using software Parametric Technology Corporation Creo and assembled to form 8 simulations. After discretization, the contact stresses developed for 150 N vertical and 100 N oblique load applications were analyzed, using ABAQUS. By assessing damage initiation and shortest fatigue load on screw threads, the SL for 2.5, 5, and 10 lakh cyclic loads were estimated, using fe-safe program. The obtained values were compared for influence of connection design, abutment angulation, and screw length. In straight abutment models, conical connection showed more damage (14.3%-72.3%) when compared to trilobe (10.1%-65.73%) at 2.5, 5, and 10 lakh cycles for both vertical and oblique loads, whereas in angulated abutments, trilobe (16.1%-76.9%) demonstrated more damage compared to conical (13.5%-70%). Irrespective of the connection type and abutment angulation, short screws showed more percentage of damage compared to long screws. The present study suggests selecting appropriate implant-abutment connection based on the abutment angulation, as well as preferring long screws with more number of threads for effective preload retention by the screws.

In vitro effect of chlorhexidine gel on torque and detorque values of implant abutment screw.

PubMed

Asli, Hamid Neshandar; Saberi, Bardia Vadiati; Fatemi, Arezoo Sadat

2017-01-01

Use of chlorhexidine (CHX) gel to eliminate the malodor of implant cavity may decrease the friction coefficient and effective preload and result in abutment screw loosening. This study aimed to assess the effect of CHX gel on the preload, torque, and detorque values. This in vitro experimental study was conducted on three groups of five implants. Group A (G1) was the control group and no material was applied to the implant cavity. In Group B (G2), implant cavity was filled with saliva before abutment screw tightening. In Group C (G3), implant cavity was first filled with saliva and then with CHX gel. The abutments were torqued to 24 N/cm2 according to the manufacturer's instructions and were then loosened. These processes were repeated five times. The ratio of the mean percentage of detorque to torque values was measured in all groups. The collected data were analyzed using ANOVA and post hoc Tukey's test. No significant difference was noted between G1 and G2. Group G2 had significantly higher detorque value (p < 0.05). ANOVA detected a significant difference in the mean torque (p < 0.05) and detorque (p < 0.001) values among the three groups. G3 showed maximum difference between torque and detorque values; the minimum difference was noted in G2. Application of CHX gel (to decrease the malodor of the implant cavity) decreases the detorque and preload values and increases the risk of screw loosening.

Efficacy of Sealing Agents on Preload Maintenance of Screw-Retained Implant-Supported Prostheses.

PubMed

Seloto, Camila Berbel; Strazzi Sahyon, Henrico Badaoui; Dos Santos, Paulo Henrique; Delben, Juliana Aparecida; Assunção, Wirley Gonçalves

The aim of this study was to evaluate the effect of sealing agents on preload maintenance of screw joints. A total of four groups (n = 10 in each group) of abutment/implant systems, including external hexagon implants and antirotational UCLA abutments with a metallic collar in cobalt-chromium alloy, were assessed. In the control group (CG), no sealing agent was used at the abutment screw/implant interface. In the other groups, three different sealing agents were used at the abutment screw/implant interface: anaerobic sealing agent for medium torque (ASMT), anaerobic sealing agent for high torque (ASHT), and cyanoacrylate-based bonding agent (CYAB). All abutments were attached to the implants at 32 ± 1 N.cm. After 48 ± 2 hours of initial tightening, loosing torque (detorque) was measured using a digital torque wrench. Data were analyzed using Shapiro-Wilk, Wilcoxon, and Kruskal-Wallis tests, at 5% level of significance. In the CG and ASMT groups, detorque was lower than the insertion torque (24.6 ± 1.5 N.cm and 24.3 ± 1.1 N.cm, respectively). In the ASHT and CYAB groups, mean detorque increased in comparison to the insertion torque (51.0 ± 7.4 N.cm and 47.7 ± 15.1 N.cm, respectively). The ASHT was more efficient than the other sealing agents, increasing the remaining preload (detorque value) 58.88%. Although the cyanoacrylate-based bonding agent also generated high detorque values, the high standard deviation suggested its lower reliability.

Mechanical characteristics of distension-evoked peristaltic contractions in the esophagus of systemic sclerosis patients.

PubMed

Gregersen, Hans; Villadsen, Gerda E; Liao, Donghua

2011-12-01

Systemic sclerosis (SS) patients with severe esophageal affection have impaired peristalsis. However, motor function evaluated in vivo by manometry and fluoroscopy does not provide detailed information about the individual contraction cycles. To apply, for the first time in gastrointestinal (GI) patients, a method and principles modified from cardiac research to study esophageal muscle behavior in SS patients. Muscle contraction cycles were analyzed using pressure-cross-sectional area (P-CSA) loops during distension pressure up to 5 kPa. The probe with bag and electrodes for CSA measurements was positioned 7 and 15 cm above the lower esophageal sphincter (LES) in eleven healthy volunteers and eleven SS patients. The P-CSA, the wall tension, Δtension (afterload tension - preload tension), contraction velocity, work output (area of the tension-CSA loops), and power output (preload tension × CSA rate) were analyzed. The P-CSA loops consisted of phases with relaxation and contraction behavior. The tension-stretch ratio loops in patients were shifted to the left at both distension sites, indicative of a stiffer wall in patients. Lower contraction amplitudes and smaller P-CSA loops were observed for the SS patients. The work output, power output, Δtension, and contraction velocity were lower in patients (P < 0.001). Association was found between disease duration and the work output, Δtension, and velocity at pressure steps higher than 3 kPa (P < 0.05). Distension-evoked esophageal contraction can be studied in vivo and analyzed with advanced methods. Increased esophageal stiffness and impaired muscle function that depended on disease duration were observed for SS patients. The analysis may be useful for characterization of other diseases affecting GI function.

Effects of intra-aortic balloon pump versus centrifugal pump on myocardial energetics and systemic circulation in a porcine model of rapidly worsening acute heart failure.

PubMed

Ntalianis, Argyrios S; Drakos, Stavros G; Charitos, Christos; Dolou, Paraskevi; Pierrakos, Charalampos N; Terrovitis, John V; Papaioannou, Theodoros; Charitos, Efstratios; Nanas, John N

2008-01-01

The present experimental study compared the effectiveness of counterpulsation provided by the intra-aortic balloon pump (IABP) versus that of a nonpulsatile, radial-flow centrifugal pump (CFP) in rapidly worsening acute heart failure (HF). Eighteen pigs were included in the study. After the induction of acute moderate HF, circulatory support was randomly provided with either the IABP or CFP. No significant change in cardiac output (CO) and mean aortic pressure (MAP) was observed with either pump. The IABP caused a significantly greater decrease than the CFP in 1) double product (13.138 +/- 2.476 mm Hg/min vs. 14.217 +/- 2.673 mm Hg/min, p = 0.023), 2) left ventricular systolic pressure (LVSP, 100 +/- 8 mm Hg vs. 106 +/- 10 mm Hg, p = 0.046), and 3) end-diastolic aortic pressure (EDAP, 70 +/- 6 mm Hg vs. 86 +/- 6 mm Hg, p = 0.000). The effects of both pumps on total tension time index and LAD flow were similar. After the induction of severe HF, the IABP had its main effects on afterload and decreased LVSP from 88 +/- 6 mm Hg to 78 +/- 9 mm Hg, (p = 0.008), and EDAP from 57 +/- 9 mm Hg to 49 +/- 14 mm Hg, (p = 0.044), whereas the CFP exerted its effects mainly on preload, lowering LV end-diastolic pressure from 19 +/- 5 mm Hg to 11 +/- 4 mm Hg, (p = 0.002). CO and MAP were similarly increased by both assist systems. The IABP (by lowering afterload) and CFP (by lowering preload) both offered significant mechanical support in acute HF. However, afterload reduction offered principally by the IABP seems preferable for the recovery of the acutely failing heart.

Multiseed liposomal drug delivery system using micelle gradient as driving force to improve amphiphilic drug retention and its anti-tumor efficacy.

PubMed

Zhang, Wenli; Li, Caibin; Jin, Ya; Liu, Xinyue; Wang, Zhiyu; Shaw, John P; Baguley, Bruce C; Wu, Zimei; Liu, Jianping

2018-11-01

To improve drug retention in carriers for amphiphilic asulacrine (ASL), a novel active loading method using micelle gradient was developed to fabricate the ASL-loaded multiseed liposomes (ASL-ML). The empty ML were prepared by hydrating a thin film with empty micelles. Then the micelles in liposomal compartment acting as 'micelle pool' drove the drug to be loaded after the outer micelles were removed. Some reasoning studies including critical micelle concentration (CMC) determination, influencing factors tests on entrapment efficiency (EE), structure visualization, and drug release were carried out to explore the mechanism of active loading, ASL location, and the structure of ASL-ML. Comparisons were made between pre-loading and active loading method. Finally, the extended drug retention capacity of ML was evaluated through pharmacokinetic, drug tissue irritancy, and in vivo anti-tumor activity studies. Comprehensive results from fluorescent and transmission electron microscope (TEM) observation, encapsulation efficiency (EE) comparison, and release studies demonstrated the formation of ML-shell structure for ASL-ML without inter-carrier fusion. The location of drug mainly in inner micelles as well as the superiority of post-loading to the pre-loading method , in which drug in micelles shifted onto the bilayer membrane was an additional positive of this delivery system. It was observed that the drug amphiphilicity and interaction of micelles with drug were the two prerequisites for this active loading method. The extended retention capacity of ML has been verified through the prolonged half-life, reduced paw-lick responses in rats, and enhanced tumor inhibition in model mice. In conclusion, ASL-ML prepared by active loading method can effectively load drug into micelles with expected structure and improve drug retention.

Characterization of a small Terfenol-D transducer in mechanically blocked configuration

NASA Astrophysics Data System (ADS)

Faidley, LeAnn E.; Dapino, Marcelo J.; Flatau, Alison B.

2001-08-01

In numerous applications, smart material transducers are employed to actuate upon virtually immovable structures, that is, structures whose stiffness approaches infinity in comparison with that of the transducer itself. Such mechanically blocked transducer configurations can be found in applications ranging from seismic testing and isolation of civil structures, to clamping mechanisms in linear or rotational inchworm motors. In addition to providing high blocking forces, smart materials for this type of applications must often be small in size and lightweight in order for design constraints to be met. This paper provides a characterization of the force produced by a 0.9 cm (0.35 in) diameter, 2.0 cm (0.79i in) long Terfenol-D operated under mechanically blocked conditions. Experimental results are shown for several mechanical preloads as well as various magnetic field intensities, waveforms, and frequencies. Optimal levels are deduced and discussed and the results are compared to published data for a PZT transducer of similar size operated in mechanically blocked configuration. The comparison reveals that the Terfenol-D rod provides higher blocking forces than its PZT counterpart. It is thus feasible to employ small magnetostrictive drivers in applications involving zero or near-zero displacement, particularly those based on hybrid magnetostrictive/piezoelectric designs in which high efficiencies are achieved by driving the two electrically complementary transducer materials at electrical resonance.

Knotless anchors with sutures external to the anchor body may be at risk for suture cutting through osteopenic bone

PubMed Central

Ono, Y.; Woodmass, J. M.; Nelson, A. A.; Boorman, R. S.; Thornton, G. M.

2016-01-01

Objectives This study evaluated the mechanical performance, under low-load cyclic loading, of two different knotless suture anchor designs: sutures completely internal to the anchor body (SpeedScrew) and sutures external to the anchor body and adjacent to bone (MultiFIX P). Methods Using standard suture loops pulled in-line with the rotator cuff (approximately 60°), anchors were tested in cadaveric bone and foam blocks representing normal to osteopenic bone. Mechanical testing included preloading to 10 N and cyclic loading for 500 cycles from 10 N to 60 N at 60 mm/min. The parameters evaluated were initial displacement, cyclic displacement and number of cycles and load at 3 mm displacement relative to preload. Video recording throughout testing documented the predominant source of suture displacement and the distance of ‘suture cutting through bone’. Results In cadaveric bone and foam blocks, MultiFIX P anchors had significantly greater initial displacement, and lower number of cycles and lower load at 3 mm displacement than SpeedScrew anchors. Video analysis revealed ‘suture cutting through bone’ as the predominant source of suture displacement in cadaveric bone (qualitative) and greater ‘suture cutting through bone’ comparing MultiFIX P with SpeedScrew anchors in foam blocks (quantitative). The greater suture displacement in MultiFIX P anchors was predominantly from suture cutting through bone, which was enhanced in an osteopenic bone model. Conclusions Anchors with sutures external to the anchor body are at risk for suture cutting through bone since the suture eyelet is at the distal tip of the implant and the suture directly abrades against the bone edge during cyclic loading. Suture cutting through bone may be a significant source of fixation failure, particularly in osteopenic bone. Cite this article: Y. Ono, J. M. Woodmass, A. A. Nelson, R. S. Boorman, G. M. Thornton, I. K. Y. Lo. Knotless anchors with sutures external to the anchor body may be at risk for suture cutting through osteopenic bone. Bone Joint Res 2016;5:269–275. DOI: 10.1302/2046-3758.56.2000535. PMID:27357383

Functional adaptation to mechanical loading in both cortical and cancellous bone is controlled locally and is confined to the loaded bones.

PubMed

Sugiyama, Toshihiro; Price, Joanna S; Lanyon, Lance E

2010-02-01

In order to validate whether bones' functional adaptation to mechanical loading is a local phenomenon, we randomly assigned 21 female C57BL/6 mice at 19 weeks of age to one of three equal numbered groups. All groups were treated with isoflurane anesthesia three times a week for 2 weeks (approximately 7 min/day). During each anaesthetic period, the right tibiae/fibulae in the DYNAMIC+STATIC group were subjected to a peak dynamic load of 11.5 N (40 cycles with 10-s intervals between cycles) superimposed upon a static "pre-load" of 2.0 N. This total load of 13.5 N engendered peak longitudinal strains of approximately 1400 microstrain on the medial surface of the tibia at a middle/proximal site. The right tibiae/fibulae in the STATIC group received the static "pre-load" alone while the NOLOAD group received no artificial loading. After 2 weeks, the animals were sacrificed and both tibiae, fibulae, femora, ulnae and radii analyzed by three-dimensional high-resolution (5 mum) micro-computed tomography (microCT). In the DYNAMIC+STATIC group, the proximal trabecular percent bone volume and cortical bone volume at the proximal and middle levels of the right tibiae as well as the cortical bone volume at the middle level of the right fibulae were markedly greater than the left. In contrast, the left bones in the DYNAMIC+STATIC group showed no differences compared to the left or right bones in the NOLOAD or STATIC group. These microCT data were confirmed by two-dimensional examination of fluorochrome labels in bone sections which showed the predominantly woven nature of the new bone formed in the loaded bones. We conclude that the adaptive response in both cortical and trabecular regions of bones subjected to short periods of dynamic loading, even when this response is sufficiently vigorous to stimulate woven bone formation, is confined to the loaded bones and does not involve changes in other bones that are adjacent, contra-lateral or remote to them. (c) 2009 Elsevier Inc. All rights reserved.

Knotless anchors with sutures external to the anchor body may be at risk for suture cutting through osteopenic bone.

PubMed

Ono, Y; Woodmass, J M; Nelson, A A; Boorman, R S; Thornton, G M; Lo, I K Y

2016-06-01

This study evaluated the mechanical performance, under low-load cyclic loading, of two different knotless suture anchor designs: sutures completely internal to the anchor body (SpeedScrew) and sutures external to the anchor body and adjacent to bone (MultiFIX P). Using standard suture loops pulled in-line with the rotator cuff (approximately 60°), anchors were tested in cadaveric bone and foam blocks representing normal to osteopenic bone. Mechanical testing included preloading to 10 N and cyclic loading for 500 cycles from 10 N to 60 N at 60 mm/min. The parameters evaluated were initial displacement, cyclic displacement and number of cycles and load at 3 mm displacement relative to preload. Video recording throughout testing documented the predominant source of suture displacement and the distance of 'suture cutting through bone'. In cadaveric bone and foam blocks, MultiFIX P anchors had significantly greater initial displacement, and lower number of cycles and lower load at 3 mm displacement than SpeedScrew anchors. Video analysis revealed 'suture cutting through bone' as the predominant source of suture displacement in cadaveric bone (qualitative) and greater 'suture cutting through bone' comparing MultiFIX P with SpeedScrew anchors in foam blocks (quantitative). The greater suture displacement in MultiFIX P anchors was predominantly from suture cutting through bone, which was enhanced in an osteopenic bone model. Anchors with sutures external to the anchor body are at risk for suture cutting through bone since the suture eyelet is at the distal tip of the implant and the suture directly abrades against the bone edge during cyclic loading. Suture cutting through bone may be a significant source of fixation failure, particularly in osteopenic bone.Cite this article: Y. Ono, J. M. Woodmass, A. A. Nelson, R. S. Boorman, G. M. Thornton, I. K. Y. Lo. Knotless anchors with sutures external to the anchor body may be at risk for suture cutting through osteopenic bone. Bone Joint Res 2016;5:269-275. DOI: 10.1302/2046-3758.56.2000535. © 2016 Lo et al.

HAWQS Beta Flyer

EPA Pesticide Factsheets

HAWQS is a web-based interactive water quantity and quality modeling system that provides users with interactive web interfaces and maps; pre-loaded input data; outputs that include tables, charts, graphs and raw output data; and a user guide.

HAWQS beta flyer

EPA Pesticide Factsheets

HAWQS is a web-based interactive water quantity and quality modeling system that provides users with interactive web interfaces and maps; pre-loaded input data; outputs that include tables, charts, graphs and raw output data; and a user guide.

Inhibition of sweet chemosensory receptors alters insulin responses during glucose ingestion in healthy adults: a randomized crossover interventional study.

PubMed

Karimian Azari, Elnaz; Smith, Kathleen R; Yi, Fanchao; Osborne, Timothy F; Bizzotto, Roberto; Mari, Andrea; Pratley, Richard E; Kyriazis, George A

2017-04-01

Background: Glucose is a natural ligand for sweet taste receptors (STRs) that are expressed on the tongue and in the gastrointestinal tract. Whether STRs directly contribute to the regulation of glucose homeostasis in response to glucose ingestion is unclear. Objective: We sought to determine the metabolic effects of the pharmacologic inhibition of STRs in response to an oral glucose load in healthy lean participants. Design: Ten healthy lean participants with a body mass index (in kg/m 2 ) of 22.4 ± 0.8 were subjected to an oral-glucose-tolerance test (OGTT) on 4 separate days with the use of a randomized crossover design. Ten minutes before the 75-g OGTT, participants consumed a preload solution of either 300 parts per million (ppm) saccharin or water with or without the addition of 500 ppm lactisole, a human-specific inhibitor of STRs. When present, lactisole was included in both the preload and OGTT solutions. We assessed plasma responses of glucose, insulin, C-peptide, glucagon, glucagon-like peptides 1 and 2, gastric inhibitory peptide, acetaminophen, and 3- O -methylglucose. With the use of mathematical modeling, we estimated gastric emptying, glucose absorption, β-cell function, insulin sensitivity and clearance, and the portal insulin:glucagon ratio. Results: The addition of lactisole to the OGTT caused increases in the plasma responses of insulin ( P = 0.012), C-peptide ( P = 0.004), and the insulin secretory rate ( P = 0.020) compared with the control OGTT. The addition of lactisole also caused a slight reduction in the insulin sensitivity index independent of prior saccharin consumption ( P < 0.025). The ingestion of saccharin before the OGTT did not alter any of the measured variables but eliminated the effects of lactisole on the OGTT. Conclusion: The pharmacologic inhibition of STRs in the gastrointestinal tract alters insulin responses during an oral glucose challenge in lean healthy participants. This trial was registered at clinicaltrials.gov as NCT02835859. © 2017 American Society for Nutrition.

Comparative biomechanical investigation of a modular dynamic lumbar stabilization system and the Dynesys system

PubMed Central

Gédet, Philippe; Haschtmann, Daniel; Thistlethwaite, Paul A.

2009-01-01

The goal of non-fusion stabilization is to reduce the mobility of the spine segment to less than that of the intact spine specimen, while retaining some residual motion. Several in vitro studies have been conducted on a dynamic system currently available for clinical use (Dynesys®). Under pure moment loading, a dependency of the biomechanical performance on spacer length has been demonstrated; this variability in implant properties is removed with a modular concept incorporating a discrete flexible element. An in vitro study was performed to compare the kinematic and stabilizing properties of a modular dynamic lumbar stabilization system with those of Dynesys, under the influence of an axial preload. Six human cadaver spine specimens (L1–S1) were tested in a spine loading apparatus. Flexibility measurements were performed by applying pure bending moments of 8 Nm, about each of the three principal anatomical axes, with a simultaneously applied axial preload of 400 N. Specimens were tested intact, and following creation of a defect at L3–L4, with the Dynesys implant, with the modular implant and, after removal of the hardware, the injury state. Segmental range of motion (ROM) was reduced for flexion–extension and lateral bending with both implants. Motion in flexion was reduced to less than 20% of the intact level, in extension to approximately 40% and in lateral bending a motion reduction to less than 40% was measured. In torsion, the total ROM was not significantly different from that of the intact level. The expectations for a flexible posterior stabilizing implant are not fulfilled. The assumption that a device which is particularly compliant in bending allows substantial intersegmental motion cannot be fully supported when one considers that such devices are placed at a location far removed from the natural rotation center of the intervertebral joint. PMID:19565278

Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold.

PubMed

Lin, Hsin-Yi; Chen, Hsin-Hung; Chang, Shih-Hsin; Ni, Tsung-Sheng

2013-01-01

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young's modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds' swelling ratios decreased by 55% after 60 min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.

Reusable Solid Rocket Motor Nozzle Joint 5 Redesign

NASA Technical Reports Server (NTRS)

Lui, R. C.; Stratton, T. C.; LaMont, D. T.

2003-01-01

Torque tension testing of a newly designed Reusable Solid Rocket Motor nozzle bolted assembly was successfully completed. Test results showed that the 3-sigma preload variation was as expected at the required input torque level and the preload relaxation were within the engineering limits. A shim installation technique was demonstrated as a simple process to fill a shear lip gap between nozzle housings in the joint region. A new automated torque system was successfully demonstrated in this test. This torque control tool was found to be very precise and accurate. The bolted assembly performance was further evaluated using the Nozzle Structural Test Bed. Both current socket head cap screw and proposed multiphase alloy bolt configurations were tested. Results indicated that joint skip and bolt bending were significantly reduced with the new multiphase alloy bolt design. This paper summarizes all the test results completed to date.

Modal parameters of space structures in 1 G and 0 G

NASA Technical Reports Server (NTRS)

Bicos, Andrew S.; Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Masters, Brett

1993-01-01

Analytic and experimental results are presented from a study of the changes in the modal parameters of space structural test articles from one- to zero-gravity. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, which were made on a spring-wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, reassembly, shipset, suspension, and ambient gravity level.

Performance Characterization of Loctite (Registered Trademark) 242 and 271 Liquid Locking Compounds (LLCs) as a Secondary Locking Feature for International Space Station (ISS) Fasteners

NASA Technical Reports Server (NTRS)

Dube, Michael J.; Gamwell, Wayne R.

2011-01-01

Several International Space Station (ISS) hardware components use Loctite (and other polymer based liquid locking compounds (LLCs)) as a means of meeting the secondary (redundant) locking feature requirement for fasteners. The primary locking method is the fastener preload, with the application of the Loctite compound which when cured is intended to resist preload reduction. The reliability of these compounds has been questioned due to a number of failures during ground testing. The ISS Program Manager requested the NASA Engineering and Safety Center (NESC) to characterize and quantify sensitivities of Loctite being used as a secondary locking feature. The findings and recommendations provided in this investigation apply to the anaerobic LLCs Loctite 242 and 271. No other anaerobic LLCs were evaluated for this investigation. This document contains the findings and recommendations of the NESC investigation

Middeck zero-gravity dynamics experiment - Comparison of ground and flight test data

NASA Technical Reports Server (NTRS)

Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Masters, Brett; Bicos, Andrew S.

1992-01-01

An analytic and experimental study of the changes in the modal parameters of space structural test articles from one- to zero-gravity is presented. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, made on a spring/wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, and ambient gravity level.

Effects of partial interlaminar bonding on impact resistance and loaded-hole behavior of graphite/epoxy quasi-isotropic laminates

NASA Technical Reports Server (NTRS)

Illg, W.

1986-01-01

A partial-bonding interlaminar toughening concept was evaluated for resistance to impact and for behavior of a loaded hole. Perforated Mylar sheets were interleaved between all 24 plies of a graphite/epoxy quasi-isotropic lay-up. Specimens were impacted by aluminum spheres while under tensile or compressive loads. Impact-failure thresholds and residual strengths were obtained. Loaded-hole specimens were tested in three configurations that were critical in bearing, shear, or tension. Partial bonding reduced the tensile and compressive strengths of undamaged specimens by about one-third. For impact, partial bonding did not change the threshold for impact failure under tensile preload. However, under compressive preload, partial bonding caused serious degradation of impact resistance. Partial bonding reduced the maximum load-carrying capacity of all three types of loaded-hole specimens. Overall, partial bonding degraded both impact resistance and bearing strength of holes.

Nonlinear analysis of a rotor-bearing system using describing functions

NASA Astrophysics Data System (ADS)

Maraini, Daniel; Nataraj, C.

2018-04-01

This paper presents a technique for modelling the nonlinear behavior of a rotor-bearing system with Hertzian contact, clearance, and rotating unbalance. The rotor-bearing system is separated into linear and nonlinear components, and the nonlinear bearing force is replaced with an equivalent describing function gain. The describing function captures the relationship between the amplitude of the fundamental input to the nonlinearity and the fundamental output. The frequency response is constructed for various values of the clearance parameter, and the results show the presence of a jump resonance in bearings with both clearance and preload. Nonlinear hardening type behavior is observed in the case with clearance and softening behavior is observed for the case with preload. Numerical integration is also carried out on the nonlinear equations of motion showing strong agreement with the approximate solution. This work could easily be extended to include additional nonlinearities that arise from defects, providing a powerful diagnostic tool.

Silicon force sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galambos, Paul C.; Crenshaw, Thomas B.; Nishida, Erik E.

The various technologies presented herein relate to a sensor for measurement of high forces and/or high load shock rate(s), whereby the sensor utilizes silicon as the sensing element. A plate of Si can have a thinned region formed therein on which can be formed a number of traces operating as a Wheatstone bridge. The brittle Si can be incorporated into a layered structure comprising ductile and/or compliant materials. The sensor can have a washer-like configuration which can be incorporated into a nut and bolt configuration, whereby tightening of the nut and bolt can facilitate application of a compressive preload uponmore » the sensor. Upon application of an impact load on the bolt, the compressive load on the sensor can be reduced (e.g., moves towards zero-load), however the magnitude of the preload can be such that the load on the sensor does not translate to tensile stress being applied to the sensor.« less

A magnetostrictive composite-fiber Bragg Grating sensor.

PubMed

Quintero, Sully M M; Braga, Arthur M B; Weber, Hans I; Bruno, Antonio C; Araújo, Jefferson F D F

2010-01-01

This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor.

A Magnetostrictive Composite-Fiber Bragg Grating Sensor

PubMed Central

Quintero, Sully M. M.; Braga, Arthur M. B.; Weber, Hans I.; Bruno, Antonio C.; Araújo, Jefferson F. D. F.

2010-01-01

This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor. PMID:22163644

Examining longitudinal train dynamics in ore car tipplers

NASA Astrophysics Data System (ADS)

Cole, Colin; Spiryagin, Maksym; Bosomworth, Chris

2017-04-01

Train simulation has been adapted in this paper to model the behaviour of indexing operations in ore car tippler operations. An important consideration in simulations at these low speeds (less than 4 km/h) is the increased rolling resistance transitioning from stationary conditions to motion. Most formulations of rolling resistance equations do not include this range although there are empirical values in some railway standards. The indexer control utilised here has a target trapezoidal velocity profile. The indexer to train connection was modelled as a stiff linear spring, a damper and a gap element. A sensitivity analysis was completed considering variations in wagon connections including wedge static friction, preload, coupling slack and tippler slack. Track topography including downhill grades of 0.1% and 0.2% and a valley profile were also investigated. Results showed high sensitivity to draft gear parameters of static friction and preload, but minimal benefit from downhill grades and changes in coupling slack.

Influence of mass moment of inertia on normal modes of preloaded solar array mast

NASA Technical Reports Server (NTRS)

Armand, Sasan C.; Lin, Paul

1992-01-01

Earth-orbiting spacecraft often contain solar arrays or antennas supported by a preloaded mast. Because of weight and cost considerations, the structures supporting the spacecraft appendages are extremely light and flexible; therefore, it is vital to investigate the influence of all physical and structural parameters that may influence the dynamic behavior of the overall structure. The study primarily focuses on the mast for the space station solar arrays, but the formulations and the techniques developed in this study apply to any large and flexible mast in zero gravity. Furthermore, to determine the influence on the circular frequencies, the mass moment of inertia of the mast was incorporated into the governing equation of motion for bending. A finite element technique (MSC/NASTRAN) was used to verify the formulation. Results indicate that when the mast is relatively flexible and long, the mass moment inertia influences the circular frequencies.

Modeling of rolling element bearing mechanics. Theoretical manual

NASA Technical Reports Server (NTRS)

Merchant, David H.; Greenhill, Lyn M.

1994-01-01

This report documents the theoretical basis for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings; duplex angular contact ball bearings; and cylindrical roller bearings. The model includes the effects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program; and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. A companion report addresses the input instructions for and features of the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knight, Marlene E.; Sanborn, Brett; Song, Bo

Elastomeric materials are used as shock isolation materials in a variety of environments to dampen vibrations and/or absorb energy from external impact to minimize energy transfer between two objects or bodies. Some applications require the shock isolation materials to behave as a low-pass mechanical filter to mitigate the shock/impact at high frequencies but transmit the energy at low frequencies with minimal attenuation. To fulfill this requirement, a shock isolation material needs to be carefully evaluated and selected with proper experimental design, procedures, and analyses. In this study, a Kolsky bar was modified with precompression (up to 15.5 kN) and confinementmore » capabilities to evaluate low-pass shock isolation performance in terms of acceleration attenuation through a variety of elastomers. Also investigated were the effects of preload and specimen geometry on the low-pass shock isolation response.« less

Calcium ions and osteoclastogenesis initiate the induction of bone formation by coral-derived macroporous constructs

PubMed Central

Klar, Roland M; Duarte, Raquel; Dix-Peek, Therese; Dickens, Caroline; Ferretti, Carlo; Ripamonti, Ugo

2013-01-01

Coral-derived calcium carbonate/hydroxyapatite macroporous constructs of the genus Goniopora with limited hydrothermal conversion to hydroxyapatite (7% HA/CC) initiate the induction of bone formation. Which are the molecular signals that initiate pattern formation and the induction of bone formation? To evaluate the role of released calcium ions and osteoclastogenesis, 7% HA/CC was pre-loaded with either 500 μg of the calcium channel blocker, verapamil hydrochloride, or 240 μg of the osteoclast inhibitor, biphosphonate zoledronate, and implanted in the rectus abdominis muscle of six adult Chacma baboons Papio ursinus. Generated tissues on days 15, 60 and 90 were analysed by histomorphometry and qRT-PCR. On day 15, up-regulation of type IV collagen characterized all the implanted constructs correlating with vascular invasion. Zoledronate-treated specimens showed an important delay in tissue patterning and morphogenesis with limited bone formation. Osteoclastic inhibition yielded minimal, if any, bone formation by induction. 7% HA/CC pre-loaded with the Ca++ channel blocker verapamil hydrochloride strongly inhibited the induction of bone formation. Down-regulation of bone morphogenetic protein-2 (BMP-2) together with up-regulation of Noggin genes correlated with limited bone formation in 7% HA/CC pre-loaded with either verapamil or zoledronate, indicating that the induction of bone formation by coral-derived macroporous constructs is via the BMPs pathway. The spontaneous induction of bone formation is initiated by a local peak of Ca++ activating stem cell differentiation and the induction of bone formation. PMID:24106923

Importance of the mitral apparatus for left ventricular function: an experimental approach.

PubMed

Gams, E; Hagl, S; Schad, H; Heimisch, W; Mendler, N; Sebening, F

1992-01-01

In an experimental study of 31 anesthetized dogs the importance of the mitral apparatus for the left ventricular function was investigated. During extracorporeal circulation bileaflet mitral valve prostheses were implanted preserving the mitral subvalvular apparatus. Flexible wires were slung around the chordae tendineae and exteriorized through the left ventricular wall to cut the chordae by electrocautery from the outside when the heart was beating again. External and internal left ventricular dimensions were measured by sonomicrometry, left ventricular stroke volume by electromagnetic flowmeters around the ascending aorta, left ventricular end-diastolic volume by dye dilution technique, and left ventricular pressure by catheter tip manometers. Different preload levels were achieved by volume loading with blood transfusion before and after cutting the chordae tendineae. When the chordae had been divided peak systolic left ventricular pressure did not change. Heart rate only increased at the lowest left ventricular end-diastolic pressures of 3-4 mmHg, but remained unchanged at higher preload levels. Cardiac output decreased significantly up to -9% at left ventricular end-diastolic pressures of 5-10 mmHg, while left ventricular dp/dtmax showed a consistent reduction of up to -15% at any preload level. Significant reductions were also seen in systolic shortening in the left ventricular major axis (by external measurements -27%, by internal recording -43%). Left ventricular end-diastolic dimensions increased in the major axis by +2% when recorded externally, by +10% when measured internally. Systolic and diastolic changes in the minor axis were not consistent and different in the external and internal recordings.(ABSTRACT TRUNCATED AT 250 WORDS)

Conflicting internal and external eating cues: Impact on food intake and attributions.

PubMed

Vartanian, Lenny R; Spanos, Samantha; Herman, C Peter; Polivy, Janet

2017-04-01

Social factors have a powerful influence on people's food intake but people typically fail to acknowledge the influence of such external cues, instead explaining their food intake in terms of factors such as how hungry they are. We examined whether the tendency to explain one's food intake in terms of internal cues (i.e., hunger) rather than external cues (i.e., other people's behavior) would be apparent when those cues are in conflict with one another. Female participants (n = 104) took part in a pizza taste test after having been food deprived for 18-hr or after consuming a meal-replacement preload. Half of the participants were also exposed to a social norm that conflicted with their deprivation condition: deprived participants were exposed to a low-intake norm, whereas preloaded participants were exposed to a high-intake norm. After completing the taste test, participants indicated the extent to which their food intake was influence by how hungry they were and how much other people ate. Deprived participants ate less when exposed to a low-intake norm than when no norm was present, but reported that the behaviors of others had no impact on their food intake. In contrast, preloaded participants did not eat significantly more when exposed to a high-intake norm, but reported that the behavior of others made them eat more. Participants are generally inaccurate in the attributions they make for their food intake, and we suggest that these inaccuracies may be because of motivated misreporting. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Personalized Digital Interventions Showed no Impact on Risky Drinking in Young Adults: A Pilot Randomized Controlled Trial.

PubMed

Davies, Emma L; Lonsdale, Adam J; Hennelly, Sarah E; Winstock, Adam R; Foxcroft, David R

2017-11-01

To assess the effectiveness of two personalized digital interventions (OneTooMany and Drinks Meter) compared to controls. Randomized controlled trial (AEARCTR-0,001,082). Volunteers for the study, aged 18-30, were randomly allocated to one of two interventions or one of two control groups and were followed up 4 weeks later. Primary outcomes were AUDIT-C, drinking harms and pre-loading. Drinks Meter provided participants with brief screening and advice for alcohol in addition to normative feedback, information on calories consumed and money spent. OneTooMany presented a series of socially embarrassing scenarios that may occur when drinking, and participants were scored according to if/how recently they had been experienced. The study failed to recruit and obtain sufficient follow-up data to reach a prior estimated power for detecting a difference between groups and there was no indication in the analysable sample of 402 subjects of a difference on the primary outcome measures (Drinks Meter; AUDIT-C IRR = 0.98 (0.89-1.09); Pre-loading IRR = 1.01 (0.95-1.07); Harms IRR = 0.97 (0.79-1.20); OneTooMany; AUDIT-C IRR = 0.96 (0.86-1.07); Pre-loading IRR = 0.99 (0.93-1.06); Harms IRR = 1.16 (0.94-1.43). Further research is needed on the efficacy of such instruments and their ingredients. However, recruitment and follow-up are a challenge. © The Author 2017. Medical Council on Alcohol and Oxford University Press. All rights reserved.

International Space Station Powered Bolt Nut Anomaly and Failure Analysis Summary

NASA Technical Reports Server (NTRS)

Sievers, Daniel E.; Warden, Harry K.

2010-01-01

A key mechanism used in the on-orbit assembly of the International Space Station (ISS) pressurized elements is the Common Berthing Mechanism. The mechanism that effects the structural connection of the Common Berthing Mechanism halves is the Powered Bolt Assembly. There are sixteen Powered Bolt Assemblies per Common Berthing Mechanism. The Common Berthing Mechanism has a bolt which engages a self aligning Powered Bolt Nut (PBN) on the mating interface (Figure 1). The Powered Bolt Assemblies are preloaded to approximately 84.5 kN (19000 lb) prior to pressurization of the CBM. The PBNs mentioned below, manufactured in 2009, will be used on ISS future missions. An on orbit functional failure of this hardware would be unacceptable and in some instances catastrophic due to the failure of modules to mate and seal the atmosphere, risking loss of crew and ISS functions. The manufacturing processes that create the PBNs need to be strictly controlled. Functional (torque vs. tension) acceptance test failures will be the result of processes not being strictly followed. Without the proper knowledge of thread tolerances, fabrication techniques, and dry film lubricant application processes, PBNs will be, and have been manufactured improperly. The knowledge gained from acceptance test failures and the resolution of those failures, thread fabrication techniques and thread dry film lubrication processes can be applied to many aerospace mechanisms to enhance their performance. Test data and manufactured PBN thread geometry will be discussed for both failed and successfully accepted PBNs.

Auto-Gopher: A Wireline Deep Sampler Driven by Piezoelectric Percussive Actuator and EM Rotary Motor

NASA Technical Reports Server (NTRS)

Badescu, Mircea; Ressa, Aaron; Jae Lee, Hyeong; Bar-Cohen, Yoseph; Sherrit, Stewart; Zacny, Kris; Paulsen, Gale L.; Beegle, Luther; Bao, Xiaoqi

2013-01-01

The ability to penetrate subsurfaces and perform sample acquisition at depth of meters may be critical for future NASA in-situ exploration missions to bodies in the solar system, including Mars and Europa. A corer/sampler was developed with the goal of enabling acquisition of samples from depths of several meters where if used on Mars would be beyond the oxidized and sterilized zone. For this purpose, we developed a rotary-hammering coring drill, called Auto-Gopher, which employs a piezoelectric actuated percussive mechanism for breaking formations and an electric motor that rotates the bit to remove the powdered cuttings. This sampler is a wireline mechanism that can be fed into and retrieved from the drilled hole using a winch and a cable. It includes an inchworm anchoring mechanism allowing the drill advancement and weight on bit control without twisting the reeling and power cables. The penetration rate is being optimized by simultaneously activating the percussive and rotary motions of the Auto-Gopher. The percussive mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) mechanism that is driven by piezoelectric stack and that was demonstrated to require low axial preload. The design and fabrication of this device were presented in previous publications. This paper presents the results of laboratory and field tests and lessons learned from this development.

Mechanisms of microgravity induced orthostatic intolerance: implications for effective countermeasures

NASA Technical Reports Server (NTRS)

Convertino, Victor A.

2002-01-01

The development of orthostatic hypotension and instability immediately after return from spaceflight has been a significant operational problem to astronauts for more than four decades. Significant reductions in stroke volume and peripheral vascular resistance contribute to ineffective maintenance of systemic arterial blood pressure during standing after spaceflight despite compensatory elevations in heart rate. The primary mechanism underlying reduced stroke volume appears to be a reduction in preload associated with reduced circulating blood volume, although cardiac atrophy might also contribute. Space flight and ground based experiments have demonstrated that an inability to provide adequate peripheral vasoconstriction in astronauts that become presyncopal may be associated with several mechanisms including reduced sympathetic nerve activity, arterial smooth muscle atrophy and/or hyporeactivity, hypersensitivity of beta-adrenergic receptors, etc. In addition, an inability to provide adequate tachycardia in presyncopal subjects may be associated with reduced carotid-cardiac baroreflex sensitivity. Based on the current knowledge and understanding of cardiovascular mechanisms that are altered during exposure to microgravity, a major focus of future research should be directed to the systematic evaluation of potential countermeasures that specifically target and restore the function of these mechanisms. Based on a preliminary systematic evaluation presented in this review, acute physical exercise designed to elicit maximal effort, G-suit inflation, artificial gravity, and specific pharmacological interventions, alone or in combination, have shown promise as successful countermeasures that provide protection against post-flight orthostatic intolerance.

Mechanisms of microgravity induced orthostatic intolerance: implications for effective countermeasures.

PubMed

Convertino, Victor A

2002-12-01

The development of orthostatic hypotension and instability immediately after return from spaceflight has been a significant operational problem to astronauts for more than four decades. Significant reductions in stroke volume and peripheral vascular resistance contribute to ineffective maintenance of systemic arterial blood pressure during standing after spaceflight despite compensatory elevations in heart rate. The primary mechanism underlying reduced stroke volume appears to be a reduction in preload associated with reduced circulating blood volume, although cardiac atrophy might also contribute. Space flight and ground based experiments have demonstrated that an inability to provide adequate peripheral vasoconstriction in astronauts that become presyncopal may be associated with several mechanisms including reduced sympathetic nerve activity, arterial smooth muscle atrophy and/or hyporeactivity, hypersensitivity of beta-adrenergic receptors, etc. In addition, an inability to provide adequate tachycardia in presyncopal subjects may be associated with reduced carotid-cardiac baroreflex sensitivity. Based on the current knowledge and understanding of cardiovascular mechanisms that are altered during exposure to microgravity, a major focus of future research should be directed to the systematic evaluation of potential countermeasures that specifically target and restore the function of these mechanisms. Based on a preliminary systematic evaluation presented in this review, acute physical exercise designed to elicit maximal effort, G-suit inflation, artificial gravity, and specific pharmacological interventions, alone or in combination, have shown promise as successful countermeasures that provide protection against post-flight orthostatic intolerance.

Deep Drilling and Sampling via the Wireline Auto-Gopher Driven by Piezoelectric Percussive Actuator and EM Rotary Motor

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Badescu, Mircea; Sherrit, Stewart; Zacny, Kris; Paulsen, Gale L; Beegle, Luther; Bao, Xiaoqi

2012-01-01

The ability to penetrate subsurfaces and perform sample acquisition at depths of meters is critical for future NASA in-situ exploration missions to bodies in the solar system, including Mars and Europa. A corer/sampler was developed with the goal of acquiring pristine samples by reaching depths on Mars beyond the oxidized and sterilized zone. To developed rotary-hammering coring drill, called Auto-Gopher, employs a piezoelectric actuated percussive mechanism for breaking formations and an electric motor rotates the bit to remove the powdered cuttings. This sampler is a wireline mechanism that is incorporated with an inchworm mechanism allowing thru cyclic coring and core removal to reach great depths. The penetration rate is being optimized by simultaneously activating the percussive and rotary motions of the Auto-Gopher. The percussive mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) mechanism that is driven by piezoelectric stack and that was demonstrated to require low axial preload. The Auto-Gopher has been produced taking into account the a lessons learned from the development of the Ultrasonic/Sonic Gopher that was designed as a percussive ice drill and was demonstrated in Antarctica in 2005 to reach about 2 meters deep. A field demonstration of the Auto-Gopher is currently being planned with objective of reaching as deep as 3 to 5 meters in tufa subsurface.

Combination Space Station Handrail Clamp and Pointing Device

NASA Technical Reports Server (NTRS)

Hughes, Stephen J. (Inventor)

1999-01-01

A device for attaching an experiment carrier to a space station handrail is provided. The device has two major components, a clamping mechanism for attachment to a space station handrail, and a pointing carrier on which an experiment package can be mounted and oriented. The handrail clamp uses an overcenter mechanism and the carrier mechanism uses an adjustable preload ball and socket for carrier positioning. The handrail clamp uses a stack of disk springs to provide a spring loaded button. This configuration provides consistent clamping force over a range of possible handrail thicknesses. Three load points are incorporated in the clamping mechanism thereby spreading the clamping load onto three separate points on the handrail. A four bar linkage is used to provide for a single actuation lever for all three load points. For additional safety, a secondary lock consisting of a capture plate and push lock keeps the clamp attached to the handrail in the event of main clamp failure. For the carrier positioning mechanism, a ball in a spring loaded socket uses friction to provide locking torque; however. the ball and socket are torque limited so that the ball ran slip under kick loads (125 pounds or greater). A lead screw attached to disk spring stacks is used to provide an adjustable spring force on the socket. A locking knob is attached to the lead screw to allow for hand manipulation of the lead screw.

Source strength verification and quality assurance of preloaded brachytherapy needles using a CMOS flat panel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golshan, Maryam, E-mail: maryam.golshan@bccancer.bc.ca; Spadinger, Ingrid; Chng, Nick

2016-06-15

Purpose: Current methods of low dose rate brachytherapy source strength verification for sources preloaded into needles consist of either assaying a small number of seeds from a separate sample belonging to the same lot used to load the needles or performing batch assays of a subset of the preloaded seed trains. Both of these methods are cumbersome and have the limitations inherent to sampling. The purpose of this work was to investigate an alternative approach that uses an image-based, autoradiographic system capable of the rapid and complete assay of all sources without compromising sterility. Methods: The system consists of amore » flat panel image detector, an autoclavable needle holder, and software to analyze the detected signals. The needle holder was designed to maintain a fixed vertical spacing between the needles and the image detector, and to collimate the emissions from each seed. It also provides a sterile barrier between the needles and the imager. The image detector has a sufficiently large image capture area to allow several needles to be analyzed simultaneously.Several tests were performed to assess the accuracy and reproducibility of source strengths obtained using this system. Three different seed models (Oncura 6711 and 9011 {sup 125}I seeds, and IsoAid Advantage {sup 103}Pd seeds) were used in the evaluations. Seeds were loaded into trains with at least 1 cm spacing. Results: Using our system, it was possible to obtain linear calibration curves with coverage factor k = 1 prediction intervals of less than ±2% near the centre of their range for the three source models. The uncertainty budget calculated from a combination of type A and type B estimates of potential sources of error was somewhat larger, yielding (k = 1) combined uncertainties for individual seed readings of 6.2% for {sup 125}I 6711 seeds, 4.7% for {sup 125}I 9011 seeds, and 11.0% for Advantage {sup 103}Pd seeds. Conclusions: This study showed that a flat panel detector dosimetry system is a viable option for source strength verification in preloaded needles, as it is capable of measuring all of the sources intended for implantation. Such a system has the potential to directly and efficiently estimate individual source strengths, the overall mean source strength, and the positions within the seed-spacer train.« less

Effect of a High-Protein, High-Fiber Beverage Preload on Subjective Appetite Ratings and Subsequent Ad Libitum Energy Intake in Overweight Men and Women: A Randomized, Double-Blind Placebo-Controlled, Crossover Study

PubMed Central

Sharafi, Mastaneh; Alamdari, Nima; Wilson, Michael; Leidy, Heather J; Glynn, Erin L

2018-01-01

Abstract Background Dietary protein and fiber have been shown to independently improve subjective measures of appetite control. Objective The aim of this study was to determine the acute effects of a high-protein, high-fiber (HP/HFb) beverage taken as a preload compared with an isocaloric lower-protein, lower-fiber (LP/LFb) placebo beverage on subjective appetite ratings and subsequent energy intake at an ad libitum meal in healthy adults. Methods A total of 50 overweight/obese men and women [n = 25 men, 25 women; age 30 ± 2 y; body mass index (BMI) 29.6 ± 0.3 kg/m2] received a 160 kcal HP/HFb beverage containing 17 g protein and 6 g fiber on one occasion and an isocaloric LP/LFb placebo beverage containing 1 g protein and 3 g fiber on another occasion in a randomized, double-blind, crossover design. Thirty min after consumption of the beverage preload, an ad libitum pizza meal was provided to be consumed over a 30-min period. Visual analog scales (VAS) were used to assess subjective appetite ratings throughout the testing period. The Revised Restraint Scale (RRS) was used to classify participants as restrained or unrestrained eaters. Results HP/HFb led to greater reductions in postprandial desire to eat and hunger compared with LP/LFb (both, P < 0.05) but did not significantly affect postprandial fullness or prospective food consumption. Subsequent meal energy intake tended to be lower after HP/HFb compared with LP/LFb (P = 0.09). A subanalysis showed lower energy intake after HP/HFb in older participants (≥25 y) compared with LP/LFb, which was not observed in the younger participants (<25 y). Conclusions Compared with LP/LFb, a HP/HFb beverage preload reduced hunger, desire to eat, and tended to reduce subsequent food intake. Dietary restraint and age appear to influence subsequent energy intake and should be taken into account when designing nutrition interventions for weight reduction and/or maintenance. This trial was registered at clinicaltrials.gov as NCT02979717.

Candida albicans Biofilms Do Not Trigger Reactive Oxygen Species and Evade Neutrophil Killing

PubMed Central

Xie, Zhihong; Thompson, Angela; Sobue, Takanori; Kashleva, Helena; Xu, Hongbin; Vasilakos, John; Dongari-Bagtzoglou, Anna

2012-01-01

Neutrophils are found within Candida albicans biofilms in vivo and could play a crucial role in clearing the pathogen from biofilms forming on catheters and mucosal surfaces. Our goal was to compare the antimicrobial activity of neutrophils against developing and mature C. albicans biofilms and identify biofilm-specific properties mediating resistance to immune cells. Antibiofilm activity was measured with the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)2H-tetrazolium-5-carboxanilide assay and a molecular Candida viability assay. Reactive oxygen species generation was assessed by measuring fluorescence of 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate, acetyl ester in preloaded neutrophils. We found that mature biofilms were resistant to leukocytic killing and did not trigger reactive oxygen species, even though neutrophils retained their viability and functional activation potential. Beta-glucans found in the extracellular matrix negatively affected antibiofilm activities. We conclude that these polymers act as a decoy mechanism to prevent neutrophil activation and that this represents an important innate immune evasion mechanism of C. albicans biofilms. PMID:23033146

Positron cooling of antiprotons: precursor of recombination

NASA Astrophysics Data System (ADS)

Tan, J. N.; Estrada, J.; Yesley, P.; Bowden, N.; Oxley, P.; Storry, C.; Wessels, M.; Tan, J.; Gabrielse, G.; Oelert, W.; Scheppers, G.; Gronzonka, D.; Sefsick, T.; Fermann, H.; Zmeskal, H.; Breunlich, W.; Kalinowsky, H.; Wesdorp, C.

2001-05-01

The quest for cold antihydrogen, interrupted with the shut-down of LEAR, resumed with the operation of the newest antiproton decelerator (AD) at CERN.[See G.Gabrielse,Adv. in AMO Physics,vol.45,pp.1-38(2001).] Antiprotons injected into the AD with 2.75 GeV of kinetic energy slow to 5.31 MeV before extraction into the ATRAP apparatus, built for antihydrogen recombination experiments. Antiprotons extracted from the AD and positrons emitted from a 112 mCi ^22Na source are simultaneously accumulated in the ultra-high vacuum and 6 T field of a prototype Penning trap incorporating a miniature rotatable electrode. Preloaded electrons are used to thermalize ~ 10^5 antiprotons with the LHe-cooled trap (4.2K). Over 10^6 positrons/hr can be loaded with a new mechanism involving Rydberg positronium. After accumulation, the positrons are moved through the rotatable electrode into close proximity with the antiprotons to study their interactions. We report the first observation of positron cooling of antiprotons in a nested trap configuration suited for three-body recombination and other mechanisms.

Linear ultrasonic motor for absolute gravimeter.

PubMed

Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

2017-05-01

Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters. Copyright © 2017 Elsevier B.V. All rights reserved.

Low-Thermal-Resistance Baseplate Mounting

NASA Technical Reports Server (NTRS)

Perreault, W. T.

1984-01-01

Low-thermal-resistance mounting achieved by preloading baseplate to slight convexity with screws threaded through beam. As mounting bolts around edge of base-place tightened, baseplate and cold plate contact first in center, with region of intimate contact spreading outward as bolts tightened.

Gauge Measures Thicknesses Of Blankets

NASA Technical Reports Server (NTRS)

Hagen, George R.; Yoshino, Stanley Y.

1991-01-01

Tool makes highly repeatable measurements of thickness of penetrable blanket insulation. Includes commercial holder for replaceable knife blades, which holds needle instead of knife. Needle penetrates blanket to establish reference plane. Ballasted slider applies fixed preload to blanket. Technician reads thickness value on scale.

High speed cylindrical roller bearing analysis. SKF computer program CYBEAN. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Dyba, G. J.; Kleckner, R. J.

1981-01-01

CYBEAN (CYlindrical BEaring ANalysis) was created to detail radially loaded, aligned and misaligned cylindrical roller bearing performance under a variety of operating conditions. Emphasis was placed on detailing the effects of high speed, preload and system thermal coupling. Roller tilt, skew, radial, circumferential and axial displacement as well as flange contact were considered. Variable housing and flexible out-of-round outer ring geometries, and both steady state and time transient temperature calculations were enabled. The complete range of elastohydrodynamic contact considerations, employing full and partial film conditions were treated in the computation of raceway and flange contacts. The practical and correct implementation of CYBEAN is discussed. The capability to execute the program at four different levels of complexity was included. In addition, the program was updated to properly direct roller-to-raceway contact load vectors automatically in those cases where roller or ring profiles have small radii of curvature. Input and output architectures containing guidelines for use and two sample executions are detailed.

Radial Clearance Found To Play a Key Role in the Performance of Compliant Foil Air Bearings

NASA Technical Reports Server (NTRS)

Radil, Kevin C.

2003-01-01

Compliant foil air bearings are at the forefront of the Oil-Free turbomachinery revolution, which supports gas turbine engines with hydrodynamic bearings that use air instead of oil as the working fluid. These types of bearings have been around for almost 50 years and have found a home in several commercial applications, such as in air cycle machines, turbocompressors, and microturbines, but are now being aggressively pursued for use in small and midrange aircraft gas turbine engines. Benefits include higher operating speeds and temperatures, lower maintenance costs, and greater reliability. The Oil-Free Turbomachinery team at the NASA Glenn Research Center is working to foster the transition of Oil-Free technology into gas turbine engines by performing in-house experiments on foil air bearings in order to gain a greater insight into their complex operating principles. A research program recently undertaken at Glenn focused on the concept of radial clearance and its influence on bearing performance. The tests were conducted on foil bearings with different radial clearances. As defined for a foil bearing, radial clearance is a measure of the small amount of shaft radial motion that is present from play that exists in the elastic support structure, such as between the top and bump foils and the bump foils and bearing shell (see the drawing). With an insufficient amount of radial clearance, the bearing imparts a high preload on the shaft, which when excessive, can reduce the loadcarrying capability of the bearing. On the other hand, systems using foil bearings with excessive radial clearance may experience rotordynamic instabilities because of low bearing preload. Therefore, without a more thorough understanding of radial clearance, it is difficult to accurately predict the performance of a given bearing design. The test program demonstrated that there is a direct correlation between radial clearance and the performance of foil air bearings. As shown in the graph, an optimum radial clearance exists that will maximize the amount of load that the bearing is capable of supporting. With respect to this optimum, two different performance regimes were observed that are a function of the amount of radial clearance. Tests showed that bearings with radial clearances below the optimum in regime I were susceptible to sudden seizure, a failure mode indicative of thermal runaway caused by high preload. The high preload is in response to an insufficient amount of radial clearance available to accommodate the thermal growth of the bearing and shaft. However, radial clearances greater than the optimum in regime II resulted in low bearing preloads that did not cause any heat-related problems, and the failure mode was due to fluid-film breakdown. In fact, bearings operating with radial clearances twice as much as the optimum suffered a decrease in the maximum load capacity of only about 20 percent. Therefore, special attention has to be given to the range of operating conditions expected in the bearing/shaft system since changes in temperature, centrifugal, and hydrodynamic effects can all affect radial clearance. This enhanced understanding of foil air bearing behavior will greatly aid our efforts to transition Oil-Free technology to future aircraft engines.

Replacement of fluid-filter elements without interruption of flow

NASA Technical Reports Server (NTRS)

Kotler, R. A.; Ward, J. B.

1969-01-01

Gatling-type filter assembly, preloaded with several filter elements enables filter replacement without breaking into the operative fluid system. When the filter element becomes contaminated, a unit inner subassembly is rotated 60 degrees to position a clean filter in the line.

The influence of superior labrum anterior to posterior (SLAP) repair on restoring baseline glenohumeral translation and increased biceps loading after simulated SLAP tear and the effectiveness of SLAP repair after long head of biceps tenotomy.

PubMed

Patzer, Thilo; Habermeyer, Peter; Hurschler, Christof; Bobrowitsch, Evgenij; Wellmann, Mathias; Kircher, Joern; Schofer, Markus D

2012-11-01

Biomechanical studies have shown increased glenohumeral translation and loading of the long head biceps (LHB) tendon after superior labrum anterior to posterior (SLAP) tears. This may explain some of the typical clinical findings, including the prevalence of humeral chondral lesions, after SLAP lesions. The first hypothesis was that SLAP repair could restore the original glenohumeral translation and reduce the increased LHB load after SLAP lesions. The second hypothesis was that SLAP repair after LHB tenotomy could significantly reduce the increased glenohumeral translation. Biomechanical testing was performed on 21 fresh frozen human cadaveric shoulders with an intact shoulder girdle using a sensor-guided industrial robot to apply 20 N of compression in the joint and 50 N translational force at 0°, 30°, and 60° of abduction. LHB loading was measured by a load-cell with 5 N and 25 N preload. Type IIC SLAP lesions were created arthroscopically, and a standardized SLAP repair was done combined with or without LHB tenotomy. No significant difference of glenohumeral translation and increased LHB load in SLAP repair compared with the intact shoulder was observed under 5 N and 25 LHB preload, except for anterior translation under 25 N LHB preload. After LHB tenotomy after SLAP lesions, no significant difference of translation was observed with or without SLAP repair. SLAP repair without associated LHB tenotomy helps normalize glenohumeral translation and LHB loading. The stabilizing effect of the SLAP complex is dependent on the LHB. After biceps tenotomy, SLAP repair does not affect glenohumeral translation. Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

Reconfiguring the violent encounter? Preloading, security staff and breathalyser use in the night-time economy.

PubMed

Farrimond, Hannah; Boyd, Katharine; Fleischer, Dreolin

2018-06-01

In a culture of preloading and late-night licenses, alcohol-related violence remains a persistent problem for police and public health. Understood as a ritualized 'micro-social' interaction (Collins 2009a, 2009b), entry into bars and clubs is a particular flashpoint for violence between bouncers/door staff and customers. A police-led initiative to deter excessive drunkenness and preloading using hand-held breathalysers (the #RU2Drunk scheme) was investigated from the perspective of security and bar staff using the devices. Interviews (n = 18 + 12), a focus group with security staff (n = 22) and a focus group with a security company (n = 3) were conducted in two seaside towns in the South-West of England, UK. A qualitative thematic analysis was conducted. Door staff emphasised the normality of 'determined drunkenness' and associated violence in their working lives. Breathalyser use appeared to disrupt the 'ritual' of the violent encounter by reconfiguring it into an interaction between customer and technology. This depersonalized the judgement about who was 'too drunk' to enter the venue, with the more discretionary nature of who to breathalyse hidden from customers. Other door staff found it less useful and saw it as a challenge to their authority and expertise. At a managerial level there was concern about the transfer of responsibility for policing the night time economy (NTE). There is potential to reconfigure the violent encounter for door staff using breathalyser devices. However, this is more likely to succeed where other structural limits (e.g. restrictions on late licenses) are in place, and as part of wider policy initiatives to reconfigure the alcohol-saturated NTE leisure scene. Copyright © 2018 Elsevier B.V. All rights reserved.

No evidence of enhanced satiety following whey protein- or sucrose-enriched water beverages: a dose response trial in overweight women.

PubMed

Wiessing, K R; Xin, L; Budgett, S C; Poppitt, S D

2015-11-01

To compare the effect of low-dose whey protein-enriched and sucrose-enriched water beverages on postprandial satiety and energy intake. Sixty overweight and obese women were given water-based protein and carbohydrate (CHO) beverages or placebo on six different occasions in a double-blind, randomised cross-over study. The beverages were 2 (178 kJ) and 4% (348 kJ) protein-enriched water (Clear Protein8855), 2 (157 kJ), 4 (314 kJ) and 10% (785 kJ) sucrose-enriched water, and a sweetened water control. Beverages were matched for volume, colour, flavour and sweetness. A standardised evening meal was provided before each study day and a standardised breakfast upon arrival at the clinic at 0900 hours. The beverage preload was given midmorning at 1100 hours, and an ad libitum outcome lunch meal at 1300 hours. Subjective appetitive responses were recorded through the day until 1500 hours using visual analogue scales. Fifty-five participants completed all six beverage conditions. Neither protein nor sucrose preloads decreased any of hunger, fullness, thoughts of food or satisfaction when compared with the sweetened water control beverage (all, P>0.05). There was also no significant effect on ad libitum energy or macronutrient intake at the outcome meal (P>0.05), with no compensation for the energy consumed within the preload beverages. There was no evidence of increased postprandial satiety or compensation for energy content at an outcome lunch meal when a water beverage was supplemented with up to 4% (w/w) whey protein or 10% (w/w) sucrose, in a group of overweight but unrestrained young and middle-aged women.

The influence of isometric preload on power expressed during bench press in strength-trained men.

PubMed

Bartolomei, Sandro; Fukuda, David H; Hoffman, Jay R; Stout, Jeffrey R; Merni, Franco

2017-03-01

The purpose of this study was to compare the power expressed during the bench press exercise in resistance-trained men following different pre-activation conditions. Twenty-two trained men (age 24.1 ± 1.7 years, height 178.6 ± 6.1 cm, body mass 81.1 ± 10.6 kg) completed a maximal effort bench press (1-RM) test (100.0 kg ± 8.1 kg). In a subsequent assessment, each participant performed concentric bench press movements with loads of 20%, 30%, 40% and 50% of their 1-RM preceded by either a concentric contraction (CC), a low isometric preload (LIP; 70% 1-RM) or a high isometric preload (HIP; 100% 1-RM) conditions. All movements were performed in a Smith machine with a settable quick-release device. Participants performed all three conditions in randomized fashion. Results indicated that power outputs during the bench press exercise following HIP were significantly (p < 0.05) greater than CC at 20% 1-RM (+9%), 30% 1-RM (+16%) and 40% 1-RM (+14%), and LIP at 20% 1-RM (+4%), 30% 1-RM (+20%) and 40% 1-RM (+15%). No differences were found between conditions at 50% 1-RM. Area under the force-power curve with HIP was greater (p < 0.05) than with CC and LIP. In conclusion, results of this study indicate that the use of a HIP (100% 1-RM) in trained participants results in significantly greater power output during the concentric phase of a multi-joint exercise when compared to standard concentric movement.

The effects of loading on the preload and dimensions of the abutment screw for a 3-unit cantilever-fixed prosthesis design.

PubMed

Setia, Gaurav; Yousef, Hoda; Ehrenberg, David; Luke, Allyn; Weiner, Saul

2013-08-01

The purpose of this study was to use an in vitro model system to compare the effects on the screw torque and screw dimensions within 2 commercially available implant systems from occlusal loading on a cantilevered-fixed partial denture. Cantilevered implant-supported 3-unit prostheses with 2 premolar abutments and 1 premolar pontic (7.3 mm in length) were made on resin casts containing 2 implant analogs for 2 implant systems: BioLok Silhouette Tapered Implant System (Birmingham, AL) and Zimmer Tapered Screw-Vent Implant System (Carlsbad, CA) with 10 samples in each group. Each sample was loaded with either of 2 protocols: (1) a load of 50 N on the cantilevered pontic unit and (2) a loading of 150 N on all 3 units. The outcome measures were (1) changes in residual torque of the abutment screws and (2) changes in screw dimension. The BioLok Silhouette Tapered Implant group demonstrated slight but statistically significant torque loss 18.8% to 28.5% in both abutment screws for both protocols, P ≤ 0.05, without any changes in screw dimension. In the Zimmer Tapered Screw-Vent Implant group, there was a significant elongation of the abutment screws and a markedly significant 44.4%, (P ≤ 0.01) loss in torque in the mesial screw and a 28.5%, (P ≤ 0.05) loss in torque in the distal screw when the cantilever alone was loaded. Differences in screw design influence the maintenance of preload and distortion of the shank. The influence of the interface design, namely an internal hex of 1 mm versus an external hex did not influence the preload. Cantilevered prostheses can cause loss of torque and dimensional changes in abutment screws.

A Comparison of Mixed-Method Cooling Interventions on Preloaded Running Performance in the Heat.

PubMed

Stevens, Christopher J; Bennett, Kyle J M; Sculley, Dean V; Callister, Robin; Taylor, Lee; Dascombe, Ben J

2017-03-01

Stevens, CJ, Bennett, KJM, Sculley, DV, Callister, R, Taylor, L, and Dascombe, BJ. A comparison of mixed-method cooling interventions on preloaded running performance in the heat. J Strength Cond Res 31(3): 620-629, 2017-The purpose of this investigation was to assess the effect of combining practical methods to cool the body on endurance running performance and physiology in the heat. Eleven trained male runners completed 4 randomized, preloaded running time trials (20 minutes at 70% V[Combining Dot Above]O2max and a 3 km time trial) on a nonmotorized treadmill in the heat (33° C). Trials consisted of precooling by combined cold-water immersion and ice slurry ingestion (PRE), midcooling by combined facial water spray and menthol mouth rinse (MID), a combination of all methods (ALL), and control (CON). Performance time was significantly faster in MID (13.7 ± 1.2 minutes; p < 0.01) and ALL (13.7 ± 1.4 minutes; p = 0.04) but not PRE (13.9 ± 1.4 minutes; p = 0.24) when compared with CON (14.2 ± 1.2 minutes). Precooling significantly reduced rectal temperature (initially by 0.5 ± 0.2° C), mean skin temperature, heart rate and sweat rate, and increased iEMG activity, whereas midcooling significantly increased expired air volume and respiratory exchange ratio compared with control. Significant decreases in forehead temperature, thermal sensation, and postexercise blood prolactin concentration were observed in all conditions compared with control. Performance was improved with midcooling, whereas precooling had little or no influence. Midcooling may have improved performance through an attenuated inhibitory psychophysiological and endocrine response to the heat.

Planetary Load Sharing in Three-Point- Mounted Wind Turbine Gearboxes: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Yi; Keller, Jonathan A

Wind turbine gearboxes do not achieve their expected design life. The cost of gearbox replacements and rebuilds and the downtime associated with these failures increase the cost of wind energy. In 2007, the U.S. Department of Energy established the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC). Its goals are to understand the root causes of premature gearbox failures and improve their reliability. To date, the GRC has focused on a 750-kW drivetrain with a three-stage, three-point-mounted gearbox. A nonproprietary version of the gearbox containing CRBs with C3 clearances in the planetary stage was customized. Two of these gearboxes,more » GB1 and GB2, were manufactured and then tested in the National Wind Technology Center's 2.5-MW dynamometer and in the field. Major GRC findings include the detrimental effect of rotor moments on planetary load sharing and predicted fatigue, and the risk of bearing sliding in low-torque conditions for three-point configuration drivetrains. Based on the knowledge gained from testing and analysis of the original design, the GRC gearbox was redesigned to improve its load-sharing characteristics and predicted fatigue. This new gearbox is named GB3. As shown in Figure 1, its key improvement is the incorporation of preloaded TRBs that support the planet carrier and planets. Roller loads can be optimized and bearing life maximized with a small preload [4]. These preloaded bearings, along with interference-fitted planet pins, improve alignments and load-sharing characteristics. A semi-integrated planet bearing design also increases capacity and eliminates outer race fretting. Romax Technology, with Powertrain Engineers and the Timken Company (Timken), completed the redesign. Timken manufactured and instrumented the planet gears and bearings. Brad Foote Gearing manufactured the other gearing and assembled the gearbox.« less

Advanced Control Surface Seal Development for Future Space Vehicles

NASA Technical Reports Server (NTRS)

DeMange, J. J.; Dunlap, P. H., Jr.; Steinetz, B. M.

2004-01-01

NASA s Glenn Research Center (GRC) has been developing advanced high temperature structural seals since the late 1980's and is currently developing seals for future space vehicles as part of the Next Generation Launch Technology (NGLT) program. This includes control surface seals that seal the edges and hinge lines of movable flaps and elevons on future reentry vehicles. In these applications, the seals must operate at temperatures above 2000 F in an oxidizing environment, limit hot gas leakage to protect underlying structures, endure high temperature scrubbing against rough surfaces, and remain flexible and resilient enough to stay in contact with sealing surfaces for multiple heating and loading cycles. For this study, three seal designs were compared against the baseline spring tube seal through a series of compression tests at room temperature and 2000 F and flow tests at room temperature. In addition, canted coil springs were tested as preloaders behind the seals at room temperature to assess their potential for improving resiliency. Addition of these preloader elements resulted in significant increases in resiliency compared to the seals by themselves and surpassed the performance of the baseline seal at room temperature. Flow tests demonstrated that the seal candidates with engineered cores had lower leakage rates than the baseline spring tube design. However, when the seals were placed on the preloader elements, the flow rates were higher as the seals were not compressed as much and therefore were not able to fill the groove as well. High temperature tests were also conducted to asses the compatibility of seal fabrics against ceramic matrix composite (CMC) panels anticipated for use in next generation launch vehicles. These evaluations demonstrated potential bonding issues between the Nextel fabrics and CMC candidates.

Innovative design of composite structures: Axisymmetric deformations of unsymmetrically laminated cylinders loaded in axial compression

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Paraska, P. J.

1990-01-01

The study focuses on the axisymmetric deformation response of unsymmetrically laminate cylinders loaded in axial compression by known loads. A geometrically nonlinear analysis is used. Though buckling is not studied, the deformations can be considered to be the prebuckling response. Attention is directed at three 16 layer laminates: a (90 sub 8/0 sub 8) sub T; a (0 sub 8/90 sub 8) sub T and a (0/90) sub 4s. The symmetric laminate is used as a basis for comparison, while the two unsymmetric laminates were chosen because they have equal but opposite bending-stretching effects. Particular attention is given to the influence of the thermally-induced preloading deformations that accompany the cool-down of any unsymmetric laminate from the consolidation temperature. Simple support and clamped boundary conditions are considered. It is concluded that: (1) The radial deformations of an unsymmetric laminate are significantly larger than the radial deformations of a symmetric laminate, although for both symmetric and unsymmetric laminates the large deformations are confined to a boundary layer near the ends of the cylinder; (2) For this nonlinear problem the length of the boundary layer is a function of the applied load; (3) The sign of the radial deformations near the supported end of the cylinder depends strongly on the sense (sign) of the laminate asymmetry; (4) For unsymmetric laminates, ignoring the thermally-induced preloading deformations that accompany cool-down results in load-induced deformations that are under predicted; and (5) The support conditions strongly influence the response but the influence of the sense of asymmetry and the influence of the thermally-induced preloading deformations are independent of the support conditions.

Temperature dependent mechanical property of PZT film: an investigation by nanoindentation.

PubMed

Li, Yingwei; Feng, Shangming; Wu, Wenping; Li, Faxin

2015-01-01

Load-depth curves of an unpoled Lead Zirconate Titanate (PZT) film composite as a function of temperature were measured by nanoindentation technique. Its reduce modulus and hardness were calculated by the typical Oliver-Pharr method. Then the true modulus and hardness of the PZT film were assessed by decoupling the influence of substrate using methods proposed by Zhou et al. and Korsunsky et al., respectively. Results show that the indentation depth and modulus increase, but the hardness decreases at elevated temperature. The increasing of indentation depth and the decreasing of hardness are thought to be caused by the decreasing of the critical stress needed to excite dislocation initiation at high temperature. The increasing of true modulus is attributed to the reducing of recoverable indentation depth induced by back-switched domains. The influence of residual stress on the indentation behavior of PZT film composite was also investigated by measuring its load-depth curves with pre-load strains.

Modeling of rolling element bearing mechanics. Computer program user's manual

NASA Technical Reports Server (NTRS)

Greenhill, Lyn M.; Merchant, David H.

1994-01-01

This report provides the user's manual for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings, duplex angular contact ball bearings, and cylindrical roller bearings. The model includes the defects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program, and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. This report addresses input instructions for and features of the computer codes. A companion report addresses the theoretical basis for the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

Mechanics of Re-Torquing in Bolted Flange Connections

NASA Technical Reports Server (NTRS)

Gordon, Ali P.; Drilling Brian; Weichman, Kyle; Kammerer, Catherine; Baldwin, Frank

2010-01-01

It has been widely accepted that the phenomenon of time-dependent loosening of flange connections is a strong consequence of the viscous nature of the compression seal material. Characterizing the coupled interaction between gasket creep and elastic bolt stiffness has been useful in predicting conditions that facilitate leakage. Prior advances on this sub-class of bolted joints has lead to the development of (1) constitutive models for elastomerics, (2) initial tightening strategies, (3) etc. The effect of re-torque, which is a major consideration for typical bolted flange seals used on the Space Shuttle fleet, has not been fully characterized, however. The current study presents a systematic approach to characterizing bolted joint behavior as the consequence of sequentially applied torques. Based on exprimenta1 and numerical results, the optimal re-torquing parameters have been identified that allow for the negligible load loss after pre-load application

High field gradient targeting of magnetic nanoparticle-loaded endothelial cells to the surfaces of steel stents

PubMed Central

Polyak, Boris; Fishbein, Ilia; Chorny, Michael; Alferiev, Ivan; Williams, Darryl; Yellen, Ben; Friedman, Gary; Levy, Robert J.

2008-01-01

A cell delivery strategy was investigated that was hypothesized to enable magnetic targeting of endothelial cells to the steel surfaces of intraarterial stents because of the following mechanisms: (i) preloading cells with biodegradable polymeric superparamagnetic nanoparticles (MNPs), thereby rendering the cells magnetically responsive; and (ii) the induction of both magnetic field gradients around the wires of a steel stent and magnetic moments within MNPs because of a uniform external magnetic field, thereby targeting MNP-laden cells to the stent wires. In vitro studies demonstrated that MNP-loaded bovine aortic endothelial cells (BAECs) could be magnetically targeted to steel stent wires. In vivo MNP-loaded BAECs transduced with adenoviruses expressing luciferase (Luc) were targeted to stents deployed in rat carotid arteries in the presence of a uniform magnetic field with significantly greater Luc expression, detected by in vivo optical imaging, than nonmagnetic controls. PMID:18182491

Physiological pump loading of isolated cardiac muscle.

PubMed

Paulus, W J; Claes, V A; Brutsaert, D L

1976-05-01

Cat papillary muscles were subjected to a continuously changing load, resulting from an analysis of the left ventricle as a muscle pump system. The papillary muscle was assumed to be part of a circumferential bundle of muscle fibers of a simplified ejecting ventricle. The load included the pressure--stress relationship of this ventricle and the peripheral vascular load with its inertial, resistive and capacitive components. When this loading function was imposed on a shortening muscle through an electronic feedback circuit, the time course of force development and the velocity versus force plots closely resembled data obtained in the intact heart. Analysis of mechanical work (delta 1 X f) and power (V X f) and their respective time course permitted distinction between changes of contractile performance due to (1) positive or negative inotropic interventions, (2) altered hypothetical ventricular dimensions and changed preload, and (3) the long-term load-dependent memory of cardiac muscle.

Experimental evaluation of low-pass shock isolation performance of elastomers using frequency-based Kolsky bar analyses

DOE PAGES

Knight, Marlene E.; Sanborn, Brett; Song, Bo; ...

2017-01-26

Elastomeric materials are used as shock isolation materials in a variety of environments to dampen vibrations and/or absorb energy from external impact to minimize energy transfer between two objects or bodies. Some applications require the shock isolation materials to behave as a low-pass mechanical filter to mitigate the shock/impact at high frequencies but transmit the energy at low frequencies with minimal attenuation. To fulfill this requirement, a shock isolation material needs to be carefully evaluated and selected with proper experimental design, procedures, and analyses. In this study, a Kolsky bar was modified with precompression (up to 15.5 kN) and confinementmore » capabilities to evaluate low-pass shock isolation performance in terms of acceleration attenuation through a variety of elastomers. Also investigated were the effects of preload and specimen geometry on the low-pass shock isolation response.« less

Contact analysis and experimental investigation of a linear ultrasonic motor.

PubMed

Lv, Qibao; Yao, Zhiyuan; Li, Xiang

2017-11-01

The effects of surface roughness are not considered in the traditional motor model which fails to reflect the actual contact mechanism between the stator and slider. An analytical model for calculating the tangential force of linear ultrasonic motor is proposed in this article. The presented model differs from the previous spring contact model, the asperities in contact between stator and slider are considered. The influences of preload and exciting voltage on tangential force in moving direction are analyzed. An experiment is performed to verify the feasibility of this proposed model by comparing the simulation results with the measured data. Moreover, the proposed model and spring model are compared. The results reveal that the proposed model is more accurate than spring model. The discussion is helpful for designing and modeling of linear ultrasonic motors. Copyright © 2017 Elsevier B.V. All rights reserved.

Fast valve based on double-layer eddy-current repulsion for disruption mitigation in Experimental Advanced Superconducting Tokamak.

PubMed

Zhuang, H D; Zhang, X D

2015-05-01

A fast valve based on the double-layer eddy-current repulsion mechanism has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to a double-layer eddy-current coil, a preload system was added to improve the security of the valve, whereby the valve opens more quickly and the open-valve time becomes shorter, making it much safer than before. In this contribution, testing platforms, open-valve characteristics, and throughput of the fast valve are discussed. Tests revealed that by choosing appropriate parameters the valve opened within 0.15 ms, and open-valve times were no longer than 2 ms. By adjusting working parameter values, the maximum number of particles injected during this open-valve time was estimated at 7 × 10(22). The fast valve will become a useful tool to further explore disruption mitigation experiments on EAST in 2015.

Extrinsic Cognitive Load Impairs Spoken Word Recognition in High- and Low-Predictability Sentences.

PubMed

Hunter, Cynthia R; Pisoni, David B

Listening effort (LE) induced by speech degradation reduces performance on concurrent cognitive tasks. However, a converse effect of extrinsic cognitive load on recognition of spoken words in sentences has not been shown. The aims of the present study were to (a) examine the impact of extrinsic cognitive load on spoken word recognition in a sentence recognition task and (b) determine whether cognitive load and/or LE needed to understand spectrally degraded speech would differentially affect word recognition in high- and low-predictability sentences. Downstream effects of speech degradation and sentence predictability on the cognitive load task were also examined. One hundred twenty young adults identified sentence-final spoken words in high- and low-predictability Speech Perception in Noise sentences. Cognitive load consisted of a preload of short (low-load) or long (high-load) sequences of digits, presented visually before each spoken sentence and reported either before or after identification of the sentence-final word. LE was varied by spectrally degrading sentences with four-, six-, or eight-channel noise vocoding. Level of spectral degradation and order of report (digits first or words first) were between-participants variables. Effects of cognitive load, sentence predictability, and speech degradation on accuracy of sentence-final word identification as well as recall of preload digit sequences were examined. In addition to anticipated main effects of sentence predictability and spectral degradation on word recognition, we found an effect of cognitive load, such that words were identified more accurately under low load than high load. However, load differentially affected word identification in high- and low-predictability sentences depending on the level of sentence degradation. Under severe spectral degradation (four-channel vocoding), the effect of cognitive load on word identification was present for high-predictability sentences but not for low-predictability sentences. Under mild spectral degradation (eight-channel vocoding), the effect of load was present for low-predictability sentences but not for high-predictability sentences. There were also reliable downstream effects of speech degradation and sentence predictability on recall of the preload digit sequences. Long digit sequences were more easily recalled following spoken sentences that were less spectrally degraded. When digits were reported after identification of sentence-final words, short digit sequences were recalled more accurately when the spoken sentences were predictable. Extrinsic cognitive load can impair recognition of spectrally degraded spoken words in a sentence recognition task. Cognitive load affected word identification in both high- and low-predictability sentences, suggesting that load may impact both context use and lower-level perceptual processes. Consistent with prior work, LE also had downstream effects on memory for visual digit sequences. Results support the proposal that extrinsic cognitive load and LE induced by signal degradation both draw on a central, limited pool of cognitive resources that is used to recognize spoken words in sentences under adverse listening conditions.

Adsorption of Estrogen Contaminants by Graphene Nanomaterials under Natural Organic Matter Preloading: Comparison to Carbon Nanotube, Biochar, and Activated Carbon.

PubMed

Jiang, Luhua; Liu, Yunguo; Liu, Shaobo; Zeng, Guangming; Hu, Xinjiang; Hu, Xi; Guo, Zhi; Tan, Xiaofei; Wang, Lele; Wu, Zhibin

2017-06-06

Adsorption of two estrogen contaminants (17β-estradiol and 17α-ethynyl estradiol) by graphene nanomaterials was investigated and compared to those of a multi-walled carbon nanotube (MWCNT), a single-walled carbon nanotube (SWCNT), two biochars, a powdered activated carbon (PAC), and a granular activate carbon (GAC) in ultrapure water and in the competition of natural organic matter (NOM). Graphene nanomaterials showed comparable or better adsorption ability than carbon nanotubes (CNTs), biochars (BCs), and activated carbon (ACs) under NOM preloading. The competition of NOM decreased the estrogen adsorption by all adsorbents. However, the impact of NOM on the estrogen adsorption was smaller on graphenes than CNTs, BCs, and ACs. Moreover, the hydrophobicity of estrogens also affected the uptake of estrogens. These results suggested that graphene nanomaterials could be used to removal estrogen contaminants from water as an alternative adsorbent. Nevertheless, if transferred to the environment, they would also adsorb estrogen contaminants, leading to great environmental hazards.

Performances estimation of a rotary traveling wave ultrasonic motor based on two-dimension analytical model.

PubMed

Ming, Y; Peiwen, Q

2001-03-01

The understanding of ultrasonic motor performances as a function of input parameters, such as the voltage amplitude, driving frequency, the preload on the rotor, is a key to many applications and control of ultrasonic motor. This paper presents performances estimation of the piezoelectric rotary traveling wave ultrasonic motor as a function of input voltage amplitude and driving frequency and preload. The Love equation is used to derive the traveling wave amplitude on the stator surface. With the contact model of the distributed spring-rigid body between the stator and rotor, a two-dimension analytical model of the rotary traveling wave ultrasonic motor is constructed. Then the performances of stead rotation speed and stall torque are deduced. With MATLAB computational language and iteration algorithm, we estimate the performances of rotation speed and stall torque versus input parameters respectively. The same experiments are completed with the optoelectronic tachometer and stand weight. Both estimation and experiment results reveal the pattern of performance variation as a function of its input parameters.

Toward an Improved Hypersonic Engine Seal

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; DeMange,Jeffrey J.; Taylor, Shawn C.

2003-01-01

High temperature, dynamic seals are required in advanced engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures from 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA s Glenn Research Center (GRC) is developing advanced seals to overcome these shortfalls. Two seal designs and two types of seal preloading devices were evaluated in a series of compression tests at room temperature and 2000 F and flow tests at room temperature. Both seals lost resiliency with repeated load cycling at room temperature and 2000 F, but seals with braided cores were significantly more flexible than those with cores composed of uniaxial ceramic fibers. Flow rates for the seals with cores of uniaxial fibers were lower than those for the seals with braided cores. Canted coil springs and silicon nitride compression springs showed promise conceptually as potential seal preloading devices to help maintain seal resiliency.

A Study of Time-dependent and Anisotropic Effects on the Deformation Response of Two Flywheel Designs

NASA Technical Reports Server (NTRS)

Saleeb, Atef F.; Arnold, Steven M.; Al-Zoubi, Nasser R.

2003-01-01

The influence of material time dependency and anisotropy in the context of two specific flywheel designs-preload and multi-directional composite (MDC)--is investigated. In particular, we focus on the following aspects: 1) geometric constraints, 2) material constraints, 3) loading type, and 4) the fundamental character of the time-dependent response, i.e., reversible or irreversible. The bulk of the results presented were obtained using a composite (PMC IM7/8552 at 135 C) material system. The material was characterized using a general multimechanism hereditary (viscoelastoplastic) model. As a general conclusion, the results have clearly shown that both the preload and the MDC rotor designs are significantly affected by time-dependent material behavior, which may impact the state of rotor balance and potentially reduce its operating life. In view of the results of the parametric studies and predictions made in the present study, the need for actual experimentation focusing on the time-dependent behavior of full-scale flywheel rotors is self-evident.

A sample preparation method for recovering suppressed analyte ions in MALDI TOF MS.

PubMed

Lou, Xianwen; de Waal, Bas F M; Milroy, Lech-Gustav; van Dongen, Joost L J

2015-05-01

In matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS), analyte signals can be substantially suppressed by other compounds in the sample. In this technical note, we describe a modified thin-layer sample preparation method that significantly reduces the analyte suppression effect (ASE). In our method, analytes are deposited on top of the surface of matrix preloaded on the MALDI plate. To prevent embedding of analyte into the matrix crystals, the sample solution were prepared without matrix and efforts were taken not to re-dissolve the preloaded matrix. The results with model mixtures of peptides, synthetic polymers and lipids show that detection of analyte ions, which were completely suppressed using the conventional dried-droplet method, could be effectively recovered by using our method. Our findings suggest that the incorporation of analytes in the matrix crystals has an important contributory effect on ASE. By reducing ASE, our method should be useful for the direct MALDI MS analysis of multicomponent mixtures. Copyright © 2015 John Wiley & Sons, Ltd.

Variation in the modal parameters of space structures

NASA Technical Reports Server (NTRS)

Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Bicos, Andrew S.

1992-01-01

An analytic and experimental study of gravity and suspension influences on space structural test articles is presented. A modular test article including deployable, erectable, and rotary modules was assembled in three one- and two-dimensional structures. The two deployable modules utilized cable diagonal bracing rather than rigid cross members; within a bay of one of the deployable modules, the cable preload was adjustable. A friction lock was used on the alpha joint to either allow or prohibit rotary motion. Suspension systems with plunge fundamentals of 1, 2, and 5 Hz were used for ground testing to evaluate the influences of suspension stiffness. Assembly and reassembly testing was performed, as was testing on two separate shipsets at two test sites. Trends and statistical variances in modal parameters are presented as a function of force amplitude, joint preload, reassembly, shipset and suspension. Linear finite element modeling of each structure provided analytical results for 0-g unsuspended and 1-g suspended models, which are correlated with the analytical model.

New valve and bonding designs for microfluidic biochips containing proteins.

PubMed

Lu, Chunmeng; Xie, Yubing; Yang, Yong; Cheng, Mark M-C; Koh, Chee-Guan; Bai, Yunling; Lee, L James; Juang, Yi-Je

2007-02-01

Two major concerns in the design and fabrication of microfluidic biochips are protein binding on the channel surface and protein denaturing during device assembly. In this paper, we describe new methods to solve these problems. A "fishbone" microvalve design based on the concept of superhydrophobicity was developed to replace the capillary valve in applications where the chip surface requires protein blocking to prevent nonspecific binding. Our experimental results show that the valve functions well in a CD-like ELISA device. The packaging of biochips containing pre-loaded proteins is also a challenging task since conventional sealing methods often require the use of high temperatures, electric voltages, or organic solvents that are detrimental to the protein activity. Using CO2 gas to enhance the diffusion of polymer molecules near the device surface can result in good bonding at low temperatures and low pressure. This bonding method has little influence on the activity of the pre-loaded proteins after bonding.

Silicon force sensor and method of using the same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galambos, Paul C.; Crenshaw, Thomas B.; Nishida, Erik E.

The various technologies presented herein relate to a sensor for measurement of high forces and/or high load shock rate(s), whereby the sensor utilizes silicon as the sensing element. A plate of Si can have a thinned region formed therein on which can be formed a number of traces operating as a Wheatstone bridge. The brittle Si can be incorporated into a layered structure comprising ductile and/or compliant materials. The sensor can have a washer-like configuration which can be incorporated into a nut and bolt configuration, whereby tightening of the nut and bolt can facilitate application of a compressive preload uponmore » the sensor. Upon application of an impact load on the bolt, the compressive load on the sensor can be reduced (e.g., moves towards zero-load), however the magnitude of the preload can be such that the load on the sensor does not translate to tensile stress being applied to the sensor.« less

Further Investigations of Hypersonic Engine Seals

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; DeMange, Jeffrey J.

2004-01-01

Durable, flexible sliding seals are required in advanced hypersonic engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures of 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA's Glenn Research Center is developing advanced seals and preloading devices to overcome these shortfalls. An advanced ceramic wafer seal design and two silicon nitride compression spring designs were evaluated in a series of compression, scrub, and flow tests. Silicon nitride wafer seals survived 2000 in. (50.8 m) of scrubbing at 2000 F against a silicon carbide rub surface with no chips or signs of damage. Flow rates measured for the wafers before and after scrubbing were almost identical and were up to 32 times lower than those recorded for the best braided rope seal flow blockers. Silicon nitride compression springs showed promise conceptually as potential seal preload devices to help maintain seal resiliency.

Quick actuating closure

NASA Technical Reports Server (NTRS)

White, III, Dorsey E. (Inventor); Updike, deceased, Benjamin T. (Inventor); Allred, Johnny W. (Inventor)

1989-01-01

A quick actuating closure for a pressure vessel 80 in which a wedge ring 30 with a conical outer surface 31 is moved forward to force shear blocks 40, with conical inner surfaces 41, radially outward to lock an end closure plug 70 within an opening 81 in the pressure vessel 80. A seal ring 60 and a preload ramp 50 sit between the shear blocks 40 and the end closure plug 70 to provide a backup sealing capability. Conical surfaces 44 and 55 of the preload ramp 50 and the shear blocks 40 interact to force the seal ring 60 into shoulders 73 and 85 in the end closure plug 70 and opening 81 to form a tight seal. The end closure plug 70 is unlocked by moving the wedge ring 30 rearward, which causes T-bars 32 of the wedge ring 30 riding within T -slots 42 of the shear blocks 40 to force them radially inward. The end closure plug 70 is then removed, allowing access to the interior of the pressure vessel 80.

Design and performance testing of an ultrasonic linear motor with dual piezoelectric actuators.

PubMed

Smithmaitrie, Pruittikorn; Suybangdum, Panumas; Laoratanakul, Pitak; Muensit, Nantakan

2012-05-01

In this work, design and performance testing of an ultrasonic linear motor with dual piezoelectric actuator patches are studied. The motor system consists of a linear stator, a pre-load weight, and two piezoelectric actuator patches. The piezoelectric actuators are bonded with the linear elastic stator at specific locations. The stator generates propagating waves when the piezoelectric actuators are subjected to harmonic excitations. Vibration characteristics of the linear stator are analyzed and compared with finite element and experimental results. The analytical, finite element, and experimental results show agreement. In the experiments, performance of the ultrasonic linear motor is tested. Relationships between velocity and pre-load weight, velocity and applied voltage, driving force and applied voltage, and velocity and driving force are reported. The design of the dual piezoelectric actuators yields a simpler structure with a smaller number of actuators and lower stator stiffness compared with a conventional design of an ultrasonic linear motor with fully laminated piezoelectric actuators.

Twist planet drive

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1996-01-01

A planetary gear system includes a sun gear coupled to an annular ring gear through a plurality of twist-planet gears, a speeder gear, and a ground structure having an internal ring gear. Each planet gear includes a solid gear having a first half portion in the form of a spur gear which includes vertical gear teeth and a second half portion in the form of a spur gear which includes helical gear teeth that are offset from the vertical gear teeth and which contact helical gear teeth on the speeder gear and helical gear teeth on the outer ring gear. One half of the twist planet gears are preloaded downward, while the other half are preloaded upwards, each one alternating with the other so that each one twists in a motion opposite to its neighbor when rotated until each planet gear seats against the sun gear, the outer ring gear, the speeder gear, and the inner ring gear. The resulting configuration is an improved stiff anti-backlash gear system.

Electromagnetic attachment mechanism

NASA Technical Reports Server (NTRS)

Monford, Leo G., Jr. (Inventor)

1992-01-01

An electromagnetic attachment mechanism is disclosed for use as an end effector of a remote manipulator system. A pair of electromagnets, each with a U-shaped magnetic core with a pull-in coil and two holding coils, are mounted by a spring suspension system on a base plate of the mechanism housing with end pole pieces adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate of a grapple fixture affixed to a target object. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery backup is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary source. A centerline mounted camera and video monitor are used in cooperation with a target pattern on the reflective surface of the strike plate to effect targeting and alignment.

Analysis of the attenuation of railway squeal noise by preloaded rings inserted in wheels.

PubMed

Brunel, J F; Dufrénoy, P; Charley, J; Demilly, F

2010-03-01

Squeal from railway wheels occurring in short radius curves produces a very intense and highly annoying noise in the range 400-8000 Hz. When the excitation, due to lateral forces acting on the wheel, cannot be avoided, additional systems can be added on the wheel to limit acoustic emission. A very economical approach is the use of metal rings inserted into grooves machined in the wheels. Unfortunately the effectiveness of these so called damping rings varies from one wheel to another and for different rings. Because the mechanisms of attenuation are not well understood, these variations have not to date been explained. The aim of this paper is to clarify the attenuation mechanisms for damping rings especially for the first three axial wheel modes, which are the predominant sound radiated ones in curve passage and for which the effectiveness of the treatment is lower. It has been generally assumed that friction between the ring and the groove has been the mechanism for squeal noise attenuation. Here it is shown that the vibration attenuation is due to modal coupling between the wheel and the ring. The validity of this proposed mechanism is investigated using experimental measurements and theoretical and numerical models. The results presented here will provide an avenue for optimization of the damping ring noise control treatment to obtain significant levels of squeal noise attenuation notably for the first three axial modes.

Performance of PZT8 Versus PZT4 Piezoceramic Materials in Ultrasonic Transducers

NASA Astrophysics Data System (ADS)

DeAngelis, Dominick A.; Schulze, Gary W.

PZT8 and PZT4 are the common "hard" piezoceramic materials used in power ultrasonic transducers (e.g., welding, cutting, sonar, etc.). PZT8 is perceived as the better choice for resonant devices, primarily due to its higher mechanical quality factor Qm. PZT8 is also considered a "harder" material compared to PZT4, since it has better stability at higher preloads and drive levels. Many transducer designers never consider PZT4 for their applications, even though it has clear advantages such as higher output (i.e., higher d33). Even the perceived advantage of PZT8 regarding Qm may not be significant for most Langevin, bolted stack type transducers if the mechanical joint losses dominate. This research is a case study on the performance of identical ultrasonic transducers used for semiconductor wire bonding, assembled with either PZT8 or PZT4 materials. The main purpose of the study is to establish rule-of-thumb transducer design guidelines for the selection of PZT8 versus PZT4 materials. Several metrics are investigated such as impedance, frequency, capacitance, dielectric loss, Qm, heating, displacement gain, and electro-mechanical coupling factor. The experimental and theoretical research methods include Bode plots, thermal IR camera imaging, scanning laser vibrometry and coupled-field finite element analysis.

The effect of donor treatment with hydrogen on lung allograft function in rats.

PubMed

Kawamura, Tomohiro; Huang, Chien-Sheng; Peng, Ximei; Masutani, Kosuke; Shigemura, Norihisa; Billiar, Timothy R; Okumura, Meinoshin; Toyoda, Yoshiya; Nakao, Atsunori

2011-08-01

Because inhaled hydrogen provides potent anti-inflammatory and antiapoptotic effects against acute lung injury, we hypothesized that treatment of organ donors with inhaled hydrogen during mechanical ventilation would decrease graft injury after lung transplantation. Orthotopic left lung transplants were performed using a fully allogeneic Lewis to Brown Norway rat model. The donors were exposed to mechanical ventilation with 98% oxygen plus 2% nitrogen or 2% hydrogen for 3 h prior to harvest, and the lung grafts underwent 4 h of cold storage in Perfadex (Vitrolife, Göteborg, Sweden). The graft function, histomorphologic changes, and inflammatory reactions were assessed. The combination of mechanical ventilation and prolonged cold ischemia resulted in marked deterioration of gas exchange when the donors were ventilated with 2% nitrogen/98% oxygen, which was accompanied by upregulation of proinflammatory cytokines and proapoptotic molecules. These lung injuries were attenuated significantly by ventilation with 2% hydrogen. Inhaled hydrogen induced heme oxygenase-1, an antioxidant enzyme, in the lung grafts prior to implantation, which might contribute to protective effects afforded by hydrogen. Preloaded hydrogen gas during ventilation prior to organ procurement protected lung grafts effectively from ischemia/reperfusion-induced injury in a rat lung transplantation model. Copyright © 2011 Mosby, Inc. All rights reserved.

Unpacking Assumptions in Research Synthesis: A Critical Construct Synthesis Approach

ERIC Educational Resources Information Center

Wolgemuth, Jennifer R.; Hicks, Tyler; Agosto, Vonzell

2017-01-01

Research syntheses in education, particularly meta-analyses and best-evidence syntheses, identify evidence-based practices by combining findings across studies whose constructs are similar enough to warrant comparison. Yet constructs come preloaded with social, historical, political, and cultural assumptions that anticipate how research problems…

A comparison of the fracture resistance of three machinable ceramics after thermal and mechanical fatigue.

PubMed

Yang, Rui; Arola, Dwayne; Han, Zhihui; Zhang, Xiuyin

2014-10-01

Mechanical and thermal fatigue may affect ceramic restorations in the oral environment. The purpose of this study was to determine the influence of thermal and mechanical cycling on the fracture load and fracture patterns of 3 machinable ceramics. Seventy-two human third molar teeth were prepared for bonding ceramic specimens of Sirona CEREC Blocs, IPS e.maxCAD, or inCoris ZI meso blocks. The 24 specimens of each ceramic were divided into 4 groups (n=6), which underwent no preloading (control), thermocycling (5°C-55°C, 2000 cycles), mechanical cycling (10(5) cycles, 100 N), and thermocycling (5°C-55°C, 2000 cycles) plus mechanical cycling (10(5) cycles, 100 N). The specimens were subsequently loaded to failure, and both stereomicroscopy and scanning electron microscopy were used to investigate the fracture patterns. The data were analyzed with 2-way ANOVA and the Fisher exact probability test (α=.05). Mechanical and thermal cycling had a significant influence on the critical load to failure of the 3 ceramics. No significant difference was found between mechanical cycling for 10(5) times and thermocycling for 2000 times within the same ceramic. The specimens of inCoris ZI experienced significantly higher fracture loads for all the groups. The fracture patterns of the 3 machinable ceramics showed that failure mainly occurred at the cement-dentin interface. The effects of combined thermal and mechanical cycling on the fracture load of ceramics were more significant than any individual mode of cyclic fatigue. Overall, the inCoris ZI resisted thermal and mechanical fatigue better than the Sirona CEREC and IPS e.maxCAD. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Biomechanics of an Expandable Lumbar Interbody Fusion Cage Deployed Through Transforaminal Approach

PubMed Central

Mica, Michael Conti; Voronov, Leonard I.; Carandang, Gerard; Havey, Robert M.; Wojewnik, Bartosz

2017-01-01

Introduction A novel expandable lumbar interbody fusion cage has been developed which allows for a broad endplate footprint similar to an anterior lumbar interbody fusion (ALIF); however, it is deployed from a minimally invasive transforaminal unilateral approach. The perceived benefit is a stable circumferential fusion from a single approach that maintains the anterior tension band of the anterior longitudinal ligament. The purpose of this biomechanics laboratory study was to evaluate the biomechanical stability of an expandable lumbar interbody cage inserted using a transforaminal approach and deployed in situ compared to a traditional lumbar interbody cage inserted using an anterior approach (control device). Methods Twelve cadaveric spine specimens (L1-L5) were tested intact and after implantation of both the control and experimental devices in two (L2-L3 and L3-L4) segments of each specimen; the assignments of the control and experimental devices to these segments were alternated. Effect of supplemental pedicle screw-rod stabilization was also assessed. Moments were applied to the specimens in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). The effect of physiologic preload on construct stability was evaluated in FE. Segmental motions were measured using an optoelectronic motion measurement system. Results The deployable expendable TLIF cage and control devices significantly reduced FE motion with and without compressive preload when compared to the intact condition (p<0.05). Segmental motions in LB and AR were also significantly reduced with both devices (p<0.05). Under no preload, the deployable expendable TLIF cage construct resulted in significantly smaller FE motion compared to the control cage construct (p<0.01). Under all other testing modes (FE under 400N preload, LB, and AR) the postoperative motions of the two constructs did not differ statistically (p>0.05). Adding bilateral pedicle screws resulted in further reduction of ROM for all loading modes compared to intact condition, with no statistical difference between the two constructs (p>0.05). Conclusions The ability of the deployable expendable interbody cage in reducing segmental motions was equivalent to the control cage when used as a stand-alone construct and also when supplemented with bilateral pedicle screw-rod instrumentation. The larger footprint of the fully deployed TLIF cage combined with preservation of the anterior soft-tissue tension band may provide a better biomechanical fusion environment by combining the advantages of the traditional ALIF and TLIF approaches. PMID:29372129

Experimental Investigation of the Influence of Confining Stress on Hard Rock Fragmentation Using a Conical Pick

NASA Astrophysics Data System (ADS)

Li, Xibing; Wang, Shaofeng; Wang, Shanyong

2018-01-01

High geostress is a prominent condition in deep excavations and affects the cuttability of deep hard rock. This study aims to determine the influence of confining stress on hard rock fragmentation as applied by a conical pick. Using a true triaxial test apparatus, static and coupled static and dynamic loadings from pick forces were applied to end faces of cubic rock specimens to break them under biaxial, uniaxial and stress-free confining stress conditions. The cuttability indices (peak pick force, insertion depth and disturbance duration), failure patterns and fragment sizes were measured and compared to estimate the effects of confining stress. The results show that the rock cuttabilities decreased in order from rock breakages under stress-free conditions to uniaxial confining stress and then to biaxial confining stress. Under biaxial confining stress, only flake-shaped fragments were stripped from the rock surfaces under the requirements of large pick forces or disturbance durations. As the level of uniaxial confining stress increased, the peak pick force and the insertion depth initially increased and then decreased, and the failure patterns varied from splitting to partial splitting and then to rock bursts with decreasing average fragment sizes. Rock bursts will occur under elastic compression via ultra-high uniaxial confining stresses. There are two critical uniaxial confining stress levels, namely stress values at which peak pick forces begin to decrease and improve rock cuttability, and those at which rock bursts initially occur and cutting safety decreases. In particular, hard rock is easiest to split safely and efficiently under stress-free conditions. Moreover, coupled static preloading and dynamic disturbance can increase the efficiency of rock fragmentation with increasing preloading levels and disturbance amplitudes. The concluding remarks confirm hard rock cuttability using conical pick, which can improve the applicability of mechanical excavation in deep hard rock masses.

Assessment of pulmonary arterial compliance evaluated using harmonic oscillator kinematics

PubMed Central

Hayabuchi, Yasunobu; Ono, Akemi; Homma, Yukako; Kagami, Shoji

2017-01-01

We hypothesized that KPA, a harmonic oscillator kinematics-derived spring constant parameter of the pulmonary artery pressure (PAP) profile, reflects PA compliance in pediatric patients. In this prospective study of 33 children (age range = 0.5–20 years) with various cardiac diseases, we assessed the novel parameter designated as KPA calculated using the pressure phase plane and the equation KPA = (dP/dt_max)2/([Pmax – Pmin])/2)2, where dP/dt_max is the peak derivative of PAP, and Pmax – Pmin is the difference between the minimum and maximum PAP. PA compliance was also calculated using two conventional methods: systolic PA compliance (sPAC) was expressed as the stroke volume/Pmax – Pmin; and diastolic PA compliance (dPAC) was determined according to a two-element Windkessel model of PA diastolic pressure decay. In addition, data were recorded during abdominal compression to determine the influence of preload on KPA. A significant correlation was observed between KPA and sPAC (r = 0.52, P = 0.0018), but not dPAC. Significant correlations were also seen with the time constant (τ) of diastolic PAP (r = −0.51, P = 0.0026) and the pulmonary vascular resistance index (r = −0.39, P = 0.0242). No significant difference in KPA was seen between before and after abdominal compression. KPA had a higher intraclass correlation coefficient than other compliance and resistance parameters for both intra-observer and inter-observer variability (0.998 and 0.997, respectively). These results suggest that KPA can provide insight into the underlying mechanisms and facilitate the quantification of PA compliance. PMID:28621582

Assessment of pulmonary arterial compliance evaluated using harmonic oscillator kinematics.

PubMed

Hayabuchi, Yasunobu; Ono, Akemi; Homma, Yukako; Kagami, Shoji

2017-01-01

We hypothesized that K PA , a harmonic oscillator kinematics-derived spring constant parameter of the pulmonary artery pressure (PAP) profile, reflects PA compliance in pediatric patients. In this prospective study of 33 children (age range = 0.5-20 years) with various cardiac diseases, we assessed the novel parameter designated as K PA calculated using the pressure phase plane and the equation K PA  = (dP/dt_max) 2 /([Pmax - Pmin])/2) 2 , where dP/dt_max is the peak derivative of PAP, and Pmax - Pmin is the difference between the minimum and maximum PAP. PA compliance was also calculated using two conventional methods: systolic PA compliance (sPAC) was expressed as the stroke volume/Pmax - Pmin; and diastolic PA compliance (dPAC) was determined according to a two-element Windkessel model of PA diastolic pressure decay. In addition, data were recorded during abdominal compression to determine the influence of preload on K PA . A significant correlation was observed between K PA and sPAC (r = 0.52, P = 0.0018), but not dPAC. Significant correlations were also seen with the time constant (τ) of diastolic PAP (r = -0.51, P = 0.0026) and the pulmonary vascular resistance index (r = -0.39, P = 0.0242). No significant difference in K PA was seen between before and after abdominal compression. K PA had a higher intraclass correlation coefficient than other compliance and resistance parameters for both intra-observer and inter-observer variability (0.998 and 0.997, respectively). These results suggest that K PA can provide insight into the underlying mechanisms and facilitate the quantification of PA compliance.

What's New with MS Office Suites

ERIC Educational Resources Information Center

Goldsborough, Reid

2012-01-01

If one buys a new PC, laptop, or netbook computer today, it probably comes preloaded with Microsoft Office 2010 Starter Edition. This is a significantly limited, advertising-laden version of Microsoft's suite of productivity programs, Microsoft Office. This continues the trend of PC makers providing ever more crippled versions of Microsoft's…

Evaluating removal of microcystin-LR from drinking water using Granular Activated Carbon with various amounts of NOM Preloading

EPA Science Inventory

Increases in cyanotoxin containing harmful algal blooms in recent years has raised the level of concern within the water treatment industry to remove these dangerous bacteria and chemicals. Typical methods used to treat intracellular and extracellular cyanotoxins include pretreat...

Construction of a Lower Body Negative Pressure Chamber

ERIC Educational Resources Information Center

Esch, Ben T. A; Scott, Jessica M.; Warburton, Darren E. R.

2007-01-01

Lower body negative pressure (LBNP) is an established and important technique used to physiologically stress the human body, particularly the cardiovascular system. LBNP is most often used to simulate gravitational stress, but it has also been used to simulate hemorrhage, alter preload, and manipulate baroreceptors. During experimentation, the…

VERY LOW FREQUENCY 16 HZ AMPLITUDE MODULATED ELECTROMAGNETIC RADIATION INCREASES CALCIUM EFFLUX FROM THE FROG HEART

EPA Science Inventory

The effects of continuous and amplitude-modulated radiofrequency electromagnetic waves on calcium efflux from 45Ca preloaded frog hearts were examined. rog hearts, electrically stimulated at their natural beating frequency, were exposed for 30 min to 240 MHz radiowaves in a Crawf...

Exploring the Contribution of a Content-Infused Interactive Whiteboard for School Readiness

ERIC Educational Resources Information Center

McManis, Lilla D.; Gunnewig, Susan B.; McManis, Mark H.

2010-01-01

This exploratory study examined the relationship between use of an interactive (touchscreen) whiteboard and development of school readiness skills. Over one school year, public school regular education prekindergarten classrooms used an interactive whiteboard with preloaded literacy and math activities. The children were low-income and English…

Development and Flight Test of an Active Flutter Suppression System for the F-4F with Stores. Part I. Design of the Active Flutter Suppression System.

DTIC Science & Technology

1982-09-01

of the wing-pylon-store changed considerably with excitation amplitude due to free play and preload. The active flutter suppression system worked well and provided an increase in flutter speed. (Author)

Evaluating the precision of passive sampling methods using PRCs in the water column.

EPA Science Inventory

To assess these models, four different thicknesses of low-density polyethylene (LDPE) passive samplers were co-deployed for 28 days in the water column at three sites in New Bedford Harbor, MA, USA. Each sampler was pre-loaded with six PCB performance reference compounds (PRCs) t...

Validation of the force and frequency characteristics of the activator adjusting instrument: effectiveness as a mechanical impedance measurement tool.

PubMed

Keller, T S; Colloca, C J; Fuhr, A W

1999-02-01

To determine the dynamic force-time and force-frequency characteristics of the Activator Adjusting Instrument and to validate its effectiveness as a mechanical impedance measurement device; in addition, to refine or optimize the force-frequency characteristics of the Activator Adjusting Instrument to provide enhanced dynamic structural measurement reliability and accuracy. An idealized test structure consisting of a rectangular steel beam with a static stiffness similar to that of the human thoracolumbar spine was used for validation of a method to determine the dynamic mechanical response of the spine. The Activator Adjusting Instrument equipped with a load cell and accelerometer was used to measure forces and accelerations during mechanical excitation of the steel beam. Driving point and transfer mechanical impedance and resonant frequency of the beam were determined by use of a frequency spectrum analysis for different force settings, stylus masses, and stylus tips. Results were compared with beam theory and transfer impedance measurements obtained by use of a commercial electronic PCB impact hammer. The Activator Adjusting Instrument imparted a very complex dynamic impact comprising an initial high force (116 to 140 N), short duration pulse (<0.1 ms) followed by several lower force (30 to 100 N), longer duration impulses (1 to 5 ms). The force profile was highly reproducible in terms of the peak impulse forces delivered to the beam structure (<8% variance). Spectrum analysis of the Activator Adjusting Instrument impulse indicated that the Activator Adjusting Instrument has a variable force spectrum and delivers its peak energy at a frequency of 20 Hz. Added masses and different durometer stylus tips had very little influence on the Activator Adjusting Instrument force spectrum. The resonant frequency of the beam was accurately predicted by both the Activator Adjusting Instrument and electronic PCB impact hammer, but variations in the magnitude of the driving point impedance at the resonant frequency were high (67%) compared with the transfer impedance measurements obtained with the electronic PCB impact hammer, which had a more uniform force spectrum and was more repeatable (<10% variation). The addition of a preload-control frame to the Activator Adjusting Instrument improved the characteristics of the force frequency spectrum and repeatability of the driving point impedance measurements. These findings indicate that the Activator Adjusting Instrument combined with an integral load cell and accelerometer was able to obtain an accurate description of a steel beam with readily identifiable geometric and dynamic mechanical properties. These findings support the rationale for using the device to assess the dynamic mechanical behavior of the vertebral column. Such information would be useful for SMT and may ultimately be used to evaluate the [corrected] biomechanical effectiveness of various manipulative, surgical, and rehabilitative spinal procedures.

Mechanical performance of short models for MQXF, the Nb3Sn low-β quadrupole for the Hi-Lumi LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vallone, Giorgio; Ambrosio, Giorgio; Anderssen, Eric

In the framework of the Hi-Lumi LHC Project, CERN and U.S. LARP are jointly developing MQXF, a 150-mm aperture high-field Nb3Sn quadrupole for the upgrade of the inner triplet of the low-beta interaction regions. The magnet is supported by a shell-based structure, providing the preload by means of bladder-key technology and differential thermal contraction of the various components. Two short models have been produced using the same cross section currently considered for the final magnet. The structures were preliminarily tested replacing the superconducting coils with blocks of aluminum. This procedure allows for model validation and calibration, and also to setmore » performance goals for the real magnet. Strain gauges were used to monitor the behavior of the structure during assembly, cool down and also excitation in the case of the magnets. The various structures differ for the shell partitioning strategies adopted and for the presence of thick or thin laminations. This study presents the results obtained and discusses the mechanical performance of all the short models produced up to now.« less

An innovative alt-alt telescope for small observatories and amateur astronomers

NASA Astrophysics Data System (ADS)

Riva, M.; Basso, S.; Canestrari, R.; Conconi, P.; Fugazza, D.; Ghigo, M.; Landoni, M.; Pareschi, G.; Spanó, P.; Tomelleri, R.; Zerbi, F. M.

2012-09-01

This paper want to show an innovative amateur oriented telescope with an unconventional alt-alt conguration. The goal is to make a telescope with good optical quality reducing production costs by adopting a gimbal based mounting to develop an alt-alt conguration suitable for a telescope. Reduce costs while preserving the optical quality is a necessary condition to allow small groups of amateur astronomers, schools and cultural clubs, with reduced economic resources, to acquire an astronomical instrument that encourages learning and advancing astrophysical knowledge. This unconventional mechanism for the realization of a telescope alt-alt provides signicant advantages. The traditional rotary motors coupled with expensive precision bearings are replaced with two simple linear actuators coupled to a properly preloaded gimbal joint and the cell becomes the primary structure of the telescope. A second advantage would be secured by mechanical simplicity evident in the easy portability of the instrument. The frame alt-alt has some limitations on the horizon pointing but does not show the zenith blind spot of the alt-az mount. A dedicated alt-alt pointing and tracking model is under development to be compatible with commercial telescope softwares and with the proposed new mounting.

Probabilistic Analysis of Space Shuttle Body Flap Actuator Ball Bearings

NASA Technical Reports Server (NTRS)

Oswald, Fred B.; Jett, Timothy R.; Predmore, Roamer E.; Zaretsky, Erin V.

2007-01-01

A probabilistic analysis, using the 2-parameter Weibull-Johnson method, was performed on experimental life test data from space shuttle actuator bearings. Experiments were performed on a test rig under simulated conditions to determine the life and failure mechanism of the grease lubricated bearings that support the input shaft of the space shuttle body flap actuators. The failure mechanism was wear that can cause loss of bearing preload. These tests established life and reliability data for both shuttle flight and ground operation. Test data were used to estimate the failure rate and reliability as a function of the number of shuttle missions flown. The Weibull analysis of the test data for a 2-bearing shaft assembly in each body flap actuator established a reliability level of 99.6 percent for a life of 12 missions. A probabilistic system analysis for four shuttles, each of which has four actuators, predicts a single bearing failure in one actuator of one shuttle after 22 missions (a total of 88 missions for a 4-shuttle fleet). This prediction is comparable with actual shuttle flight history in which a single actuator bearing was found to have failed by wear at 20 missions.

Mechanical Design of HD2, a 15 T Nb3Sn Dipole Magnet with a 35 mm Bore

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferracin, P.; Bartlett, S.E.; Caspi, S.

2006-06-01

After the fabrication and test of HD1, a 16 T Nb{sub 3}Sn dipole magnet based on flat racetrack coil configuration, the Superconducting Magnet Program at Lawrence Berkeley National Laboratory (LBNL) is developing the Nb{sub 3}Sn dipole HD2. With a dipole field above 15 T, a 35 mm clear bore, and nominal field harmonics within a fraction of one unit, HD2 represents a further step towards the application of block-type coils to high-field accelerator magnets. The design features tilted racetrack-type ends, to avoid obstructing the beam path, and a 4 mm thick stainless steel tube, to support the coil during themore » preloading operation. The mechanical structure, similar to the one used for HD1, is based on an external aluminum shell pretensioned with pressurized bladders. Axial rods and stainless steel plates provide longitudinal support to the coil ends during magnet excitation. A 3D finite element analysis has been performed to evaluate stresses and deformations from assembly to excitation, with particular emphasis on conductor displacements due to Lorentz forces. Numerical results are presented and discussed.« less

Central venous pulse pressure analysis using an R-synchronized pressure measurement system.

PubMed

Fujita, Yoshihisa; Hayashi, Daisuke; Wada, Shinya; Yoshioka, Naoki; Yasukawa, Takeshi; Pestel, Gunther

2006-12-01

The information derived from central venous catheters is underused. We developed an EKG-R synchronization and averaging system to obtained distinct CVP waveforms and analyzed components of these. Twenty-five paralyzed surgical patients undergoing CVP monitoring under mechanical ventilation were studied. CVP and EKG signals were analyzed employing our system, the mean CVP and CVP at end-diastole during expiration were compared, and CVP waveform components were measured using this system. CVP waveforms were clearly visualized in all patients. They showed the a peak to be 1.8+/- 0.7 mmHg, which was the highest of three peaks, and the x trough to be lower than the y trough (-1.6+/- 0.7 mmHg and -0.9+/- 0.5 mmHg, respectively), with a mean pulse pressure of 3.4 mmHg. The difference between the mean CVP and CVP at end-diastole during expiration was 0.58+/- 0.81 mmHg. The mean CVP can be used as an index of right ventricular preload in patients under mechanical ventilation with regular sinus rhythm. Our newly developed system is useful for clinical monitoring and for education in circulatory physiology.

Cardiopulmonary physiology: why the heart and lungs are inextricably linked.

PubMed

Verhoeff, Kevin; Mitchell, Jamie R

2017-09-01

Because the heart and lungs are confined within the thoracic cavity, understanding their interactions is integral for studying each system. Such interactions include changes in external constraint to the heart, blood volume redistribution (venous return), direct ventricular interaction (DVI), and left ventricular (LV) afterload. During mechanical ventilation, these interactions can be amplified and result in reduced cardiac output. For example, increased intrathoracic pressure associated with mechanical ventilation can increase external constraint and limit ventricular diastolic filling and, therefore, output. Similarly, high intrathoracic pressures can alter blood volume distribution and limit diastolic filling of both ventricles while concomitantly increasing pulmonary vascular resistance, leading to increased DVI, which may further limit LV filling. While LV afterload is generally considered to decrease with increased intrathoracic pressure, the question arises if the reduced LV afterload is primarily a consequence of a reduced LV preload. A thorough understanding of the interaction between the heart and lungs can be complicated but is essential for clinicians and health science students alike. In this teaching review, we have attempted to highlight the present understanding of certain salient aspects of cardiopulmonary physiology and pathophysiology, as well as provide a resource for multidisciplined health science educators and students. Copyright © 2017 the American Physiological Society.

Mechanical performance of short models for MQXF, the Nb3Sn low-β quadrupole for the Hi-Lumi LHC

DOE PAGES

Vallone, Giorgio; Ambrosio, Giorgio; Anderssen, Eric; ...

2016-12-23

In the framework of the Hi-Lumi LHC Project, CERN and U.S. LARP are jointly developing MQXF, a 150-mm aperture high-field Nb3Sn quadrupole for the upgrade of the inner triplet of the low-beta interaction regions. The magnet is supported by a shell-based structure, providing the preload by means of bladder-key technology and differential thermal contraction of the various components. Two short models have been produced using the same cross section currently considered for the final magnet. The structures were preliminarily tested replacing the superconducting coils with blocks of aluminum. This procedure allows for model validation and calibration, and also to setmore » performance goals for the real magnet. Strain gauges were used to monitor the behavior of the structure during assembly, cool down and also excitation in the case of the magnets. The various structures differ for the shell partitioning strategies adopted and for the presence of thick or thin laminations. This study presents the results obtained and discusses the mechanical performance of all the short models produced up to now.« less

Intestinal absorption of the acetamiprid neonicotinoid by Caco-2 cells: transepithelial transport, cellular uptake and efflux.

PubMed

Brunet, Jean-Luc; Maresca, Marc; Fantini, Jacques; Belzunces, Luc P

2008-01-01

The human intestinal absorption of acetamiprid (AAP) using the Caco-2 cell line reveals that AAP flux was active in a bidirectional mode with an apparent permeability coefficient of 26 x 10(-6) cm x s(-1) at 37 degrees C. Apical uptake was concentration-dependent and unsaturated for AAP concentrations up to 200 micro M. AAP cell preloading demonstrated the involvement of active transport mechanisms. Arrhenius plot analysis revealed an unusual profile with two apparent activation energies suggesting two transport processes. Uptake Vi studies indicated the involvement of a sodium-dependent transporter, the presence of a common transporter of AAP and nicotine and the involvement of Ti-sensitive ATP-dependent efflux transporters. Apical efflux investigations showed the involvement of inward active transporter(s). Whereas vincristine had no effect on intracellular accumulation, taxol and daunorubicin treatments unexpectedly led to 10% and 23% reductions respectively, suggesting that the latter shared a common inward transporter with AAP. All these results suggest full and express AAP absorption in vivo with transport involving both inward and outward, passive and active mechanisms. Thus, AAP or its metabolites could be representative of a risk for human health after its ingestion in food.

Probabilistic Analysis of Space Shuttle Body Flap Actuator Ball Bearings

NASA Technical Reports Server (NTRS)

Oswald, Fred B.; Jett, Timothy R.; Predmore, Roamer E.; Zaretsky, Erwin V.

2008-01-01

A probabilistic analysis, using the 2-parameter Weibull-Johnson method, was performed on experimental life test data from space shuttle actuator bearings. Experiments were performed on a test rig under simulated conditions to determine the life and failure mechanism of the grease lubricated bearings that support the input shaft of the space shuttle body flap actuators. The failure mechanism was wear that can cause loss of bearing preload. These tests established life and reliability data for both shuttle flight and ground operation. Test data were used to estimate the failure rate and reliability as a function of the number of shuttle missions flown. The Weibull analysis of the test data for the four actuators on one shuttle, each with a 2-bearing shaft assembly, established a reliability level of 96.9 percent for a life of 12 missions. A probabilistic system analysis for four shuttles, each of which has four actuators, predicts a single bearing failure in one actuator of one shuttle after 22 missions (a total of 88 missions for a 4-shuttle fleet). This prediction is comparable with actual shuttle flight history in which a single actuator bearing was found to have failed by wear at 20 missions.

Study on a new self-sensing magnetorheological elastomer bearing

NASA Astrophysics Data System (ADS)

Li, Rui; Zhou, Mengjiao; Wang, Minglian; Yang, Ping-an

2018-06-01

The complexity of a semi-active vibration isolation system results in the difficulty of realizing its role on impact load effectively. Thus, a new self-sensing bearing based on modified anisotropic magnetorheological elastomer (MRE) is proposed in this study. This self-sensing bearing was fabricated by dispersed multi-walled carbon nanotubes and carbonyl iron particles into polydimethylsiloxane matrix under a magnetic field. The working conditions of the bearing were analyzed and decoupled. An optimal structure size of the bearing was selected and used for setting up the experiment test system. The self-sensing characteristic of the MRE bearing under the multi-field coupling of load and magnetic fields was then investigated by this test system. Results showed that the resistance of the modified MRE, in which a preload was applied by the bearing, could change approximately 28%-56% under extrusion force, mechanical force, and external magnetic field. The vibration isolation performance was tested based on the self-sensing characteristic. The bearing had excellent mechanical properties, which could reduce at least 30% of vibration. Thus, the modified MRE of the magnetorheological elastomer bearing could be simultaneously used as an actuator and a sensor.

49 CFR 571.225 - Standard No. 225; Child restraint anchorage systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... N of preload prior to the test. The strap is fitted at one end with a high strength steel tether... systems to ensure their proper location and strength for the effective securing of child restraints, to... manufactured on or after September 1, 1999, shall comply with the configuration, location, marking and strength...

Pregaming: A High-Risk Behavior. Prevention Update

ERIC Educational Resources Information Center

Higher Education Center for Alcohol, Drug Abuse, and Violence Prevention, 2010

2010-01-01

"Pregaming" or "pre-loading" is what college students call the practice of drinking alcohol in a private setting prior to attending an organized event or social activity where alcohol might or might not be served. According to one student, "Pregames are usually a fun part of the night because you're just with a few close…

Development and Flight Test of an Active Flutter Suppression System for the F-4F with Stores. Part 3. Flight Demonstration of the Active Flutter Suppression System.

DTIC Science & Technology

1983-06-01

that the dynamic behavior of the wing-pylon-store changed considerably with excitation amplitude due to free play and preload. The active flutter suppression system worked well and provided an increase in flutter speed.

16 CFR 1203.11 - Marking the impact test line.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Section 1203.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION CONSUMER PRODUCT SAFETY ACT... (HPI), with the brow parallel to the basic plane. Place a 5-kg (11-lb) preload ballast on top of the... helmet coinciding with the intersection of the surface of the helmet with the impact line planes defined...

Stirling engine piston ring

DOEpatents

Howarth, Roy B.

1983-01-01

A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

16 CFR 1203.4 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... would be purchased for other than their stated use. However, a multi-purpose helmet—one marketed or... § 1203.17(b)(1). (i) Preload ballast is a “bean bag” filled with lead shot that is placed on the helmet...) Reference headform is a headform used as a measuring device and contoured in the same configuration as one...

16 CFR 1203.4 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... would be purchased for other than their stated use. However, a multi-purpose helmet—one marketed or... § 1203.17(b)(1). (i) Preload ballast is a “bean bag” filled with lead shot that is placed on the helmet...) Reference headform is a headform used as a measuring device and contoured in the same configuration as one...