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PubMed1990

Cup containment and orientation in cemented total hip arthroplasties.

We reviewed the radiographs of 864 Charnley and STH (Zimmer) cemented total hip arthroplasties with a mean follow-up of seven years (maximum 16 years). Survivorship analysis was used to assess the correlation between radiographic performance and the bony containment or the coronal orientation of the acetabular cup. The cup orientation and containment were interrelated; all vertically oriented cups were completely contained, whereas 25% of more horizontal cups were only partially contained. Completely contained cups had significantly lower incidences of complete cement-bone radiolucency (p = 0.02) and of wear (p = 0.09). Vertically oriented cups had a lower incidence of continuous radiolucency than neutrally oriented cups, but this was not statistically significant (p = 0.25). Our results confirm the importance of complete bony containment, and also indicate that it is better to accept vertical orientation and obtain full bony coverage than to have a more horizontal orientation with partial containment.

Alloys↗
PubMed2002

Goal orientation, perceived task outcome and task demands in mathematics tasks: effects on students' attitude in actual task settings.

BACKGROUND: In earlier studies, it has been found that students' domain-specific cognitions and personal learning goals (goal orientation) influence task-specific appraisals of actual learning tasks. The relations between domain-specific and task-specific variables have been specified in the model of adaptive learning. In this study, additional influences, i.e., perceived task outcome on a former occasion and variations in task demands, were investigated. AIM: The purpose of this study was to identify personality and situational variables that mediate students' attitude when confronted with a mathematics task. Students worked on a mathematics task in two subsequent sessions. Effects of perceived task outcome at the first session on students' attitude at the second session were investigated. In addition, we investigated how differences in task demands influenced students' attitude. Variations in task demands were provoked by different conditions in task-instruction. In one condition, students were told that the result on the test would add to their mark on mathematics. This outcome orienting condition was contrasted with a task-orienting condition where students were told that the results on the test would not be used to give individual grades. SAMPLE: Participants were sixth grade students (N = 345; aged 11-12 years) from 14 primary schools. METHOD: Multivariate and univariate analyses of (co)variance were applied to the data. Independent variables were goal orientation, task demands, and perceived task outcome, with task-specific variables (estimated competence for the task, task attraction, task relevance, and willingness to invest effort) as the dependent variables. RESULTS: The results showed that previous perceived task outcome had a substantial impact on students' attitude. Additional but smaller effects were found for variation in task demands. Furthermore, effects of previous perceived task outcome and task demands were related to goal orientation. CONCLUSION: The resulting pattern confirmed that, in general, performance-oriented learning goals emphasised the negative impact of failure experiences, whereas task-oriented learning goals had a strengthening effect on how success experiences influenced students' attitude.

Attitude↗
PubMed2001

A note about preferred orientations at the first and second stages of complex (second-order) texture channels.

Complex (second-order) channels have been useful in explaining many of the phenomena of perceived texture segregation. These channels contain two stages of linear filtering with an intermediate pointwise nonlinearity. One unanswered question about these hypothetical channels is that of the relationship between the preferred orientations of the two stages of filtering. Is a particular orientation at the second stage equally likely to occur with all orientations at the first stage, or is there a bias in the "mapping" between the two stages' preferred orientations? In this study we consider two possible mappings: that where the orientations at the two stages are identical (called "consistent" here) and that where the orientations at the two stages are perpendicular ("inconsistent"). We explore these mappings using a texture-segregation task with textures composed of arrangements of grating-patch elements. The results imply that, to explain perceived texture segregation, complex channels with a consistent orientation mapping must be either somewhat more prevalent or more effective than those with an inconsistent mapping.

Contrast Sensitivity↗
PubMed2003

Molecular composition and orientation of interstitial versus surface silicon oxides for Si(111)/SiO2 and Si(100)/SiO2 interfaces using FT-IR and X-ray photoelectron spectroscopies.

This work represents a characterization study of silicon oxide on Si(111) and Si(100) surfaces intended for use as substrates in organic light-emitting diodes (OLEDs) on chip devices. Samples have been prepared using either native oxide formation or thermal oxidation, and they have also been treated for activation of hydroxyl groups on their surface. Both Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used in order to understand the molecular orientation as well as the chemical composition of the various oxide types formed during these different oxidation processes. These spectroscopic studies reveal the formation of two different types of oxides on these substrates. The first type is a thin oxide layer on the surface, whereas the second type, called interstitial, is found deeper in the substrate. Specifically, it was found that the Si(100) substrate forms a randomly oriented interstitial oxide, whereas the presence of a lower quantity but more oriented interstitial oxide was found for the Si(111) substrate. In addition, we report for the first time the position of the impurity oxygen for Si(111) substrates at 1122 cm(-1). Finally, in both Si(100) and Si(111) substrates, the thin (<15 A) silicon oxide layers are oriented and appear to contain silicon atoms of similar oxidation states. In contrast, both the thicker surface film (100 A) as well as the interstitial oxide produced by the thermal oxidation procedure show random orientation and relative uniformity. Overall these orientation studies clearly show that the formation process of surface oxides in different substrates clearly creates species that are oriented differently with respect to the surface.

Anisotropy↗
PubMed2001

Cursor orientation and computer screen positioning movements.

Implicit directional cues in arrowhead cursors could influence positioning of a cursor on the screen of the computer. Performance during cursor placement may benefit from compatibilities between cursor orientation and direction of movement. Arrowheads could also elicit illusory processes that may affect judgments of (a) the distances on the screen or (b) the location of the point of the arrowhead. To address the impact of the cursor's orientation on its positioning, we had 12 participants move cursors (crosshairs, leftward, or rightward arrow) leftward or rightward to targets (near, far) on a computer screen. Movement amplitude was more important than cursor orientation for initiation of rightward movements, whereas cursor orientation affected the duration of leftward movements and movements to farther targets. Arrowhead orientation contributed to the greater overshooting of far targets. There was little evidence that compatibility of orientation and direction of movement assisted response initiation or execution, and there was little indication that arrowhead cursors led to illusory effects that influenced cursor placement. Arrowhead cursors can provide irrelevant stimulus dimensions that distract users. This work can be applied to the design of cursors in graphical user interfaces. The use of orientation-neutral cursors or cursors whose stimulus dimensions are more relevant is recommended.

Adult↗
PubMed2006

Lack of patchy horizontal connectivity in primary visual cortex of a mammal without orientation maps.

In the cerebral cortex of mammals, horizontal connections link cells up to several millimeters apart. In primary visual cortex (V1) of mammals with orientation maps, horizontal connections ramify in periodic patches across the cortical surface, connecting cells with similar orientation preferences. Rodents have orientation-selective cells but lack orientation maps, raising questions about relationships of horizontal connections to functional maps and receptive field properties. To address these questions, we studied anatomy of horizontal connections and characterized horizontal functional interactions in V1 of the gray squirrel, a highly visual rodent. Long-range intrinsic connections in squirrel V1 extended 1-2 mm but were not patchy or periodic. This result suggests that periodic and patchy connectivity is not a universal organizing principle of cortex, and the existence of patchy and periodic connectivity and functional maps may be linked. In multielectrode and intracellular recordings, we found evidence of unselective local interactions among cells, similar to pinwheel centers of carnivores. These data suggest that, in mammals with and without orientation maps, local connections link near neighbors without regard to orientation selectivity. In single-unit recordings, we found length-summing and end-stopped cells that were similar to those in other mammals. Length-summing cell surrounds were orientation selective, whereas surrounds of end-stopped cells were not. Receptive field response classes are quite similar across mammals, and therefore patchy and columnar connectivity may not be essential for these properties.

Animals↗
PubMed2004

Molecular dynamics simulation of transmembrane polypeptide orientational fluctuations.

The orientation and motion of a model lysine-terminated transmembrane polypeptide were investigated by molecular dynamics simulation. Recent 2H NMR studies of synthetic polypeptides with deuterated alanine side chains suggest that such transmembrane polypeptides undergo fast, axially symmetric reorientation about the bilayer normal but have a preferred average azimuthal orientation about the helix axis. In this work, interactions that might contribute to this behavior were investigated in a simulated system consisting of 64 molecules of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and one alpha-helical polypeptide with the sequence acetyl-KK-(LA)11-KK-amide. In one simulation, initiated with the peptide oriented along the bilayer normal, the system was allowed to evolve for 8.5 ns at 1 atm of pressure and a temperature of 55 degrees C. A second simulation was initiated with the peptide orientation chosen to match a set of experimentally observed alanine methyl deuteron quadrupole splittings and allowed to proceed for 10 ns. Simulated alanine methyl group orientations were found to be inequivalent, a result that is consistent with 2H NMR observations of specifically labeled polypeptides in POPC bilayers. Helix tilt varied substantially over the durations of both simulations. In the first simulation, the peptide tended toward an orientation about the helix axis similar to that suggested by experiment. In the second simulation, orientation about the helix axis tended to return to this value after an excursion. These results provide some insight into how interactions at the bilayer surface can constrain reorientation about the helix axis while accommodating large changes in helix tilt.

Alanine↗
PubMed2006

Orientation of a beta-hairpin antimicrobial peptide in lipid bilayers from two-dimensional dipolar chemical-shift correlation NMR.

The orientation of a beta-sheet membrane peptide in lipid bilayers is determined, for the first time, using two-dimensional (2D) (15)N solid-state NMR. Retrocyclin-2 is a disulfide-stabilized cyclic beta-hairpin peptide with antibacterial and antiviral activities. We used 2D separated local field spectroscopy correlating (15)N-(1)H dipolar coupling with (15)N chemical shift to determine the orientation of multiply (15)N-labeled retrocyclin-2 in uniaxially aligned phosphocholine bilayers. Calculated 2D spectra exhibit characteristic resonance patterns that are sensitive to both the tilt of the beta-strand axis and the rotation of the beta-sheet plane from the bilayer normal and that yield resonance assignment without the need for singly labeled samples. Retrocyclin-2 adopts a transmembrane orientation in dilauroylphosphatidylcholine bilayers, with the strand axis tilted at 20 degrees +/- 10 degrees from the bilayer normal, but changes to a more in-plane orientation in thicker 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC) bilayers with a tilt angle of 65 degrees +/- 15 degrees . These indicate that hydrophobic mismatch regulates the peptide orientation. The 2D spectra are sensitive not only to the peptide orientation but also to its backbone (phi, psi) angles. Neither a bent hairpin conformation, which is populated in solution, nor an ideal beta-hairpin with uniform (phi, psi) angles and coplanar strands, agrees with the experimental spectrum. Thus, membrane binding orders the retrocyclin conformation by reducing the beta-sheet curvature but does not make it ideal. (31)P NMR spectra of lipid bilayers with different compositions indicate that retrocyclin-2 selectively disrupts the orientational order of anionic membranes while leaving zwitteronic membranes intact. These structural results provide insights into the mechanism of action of this beta-hairpin antimicrobial peptide.

Antimicrobial Cationic Peptides↗
PubMed1998

The association between health risk behaviors and sexual orientation among a school-based sample of adolescents.

OBJECTIVE: This study is one of the first to examine the association between sexual orientation and health risk behaviors among a representative, school-based sample of adolescents. DESIGN: This study was conducted on an anonymous, representative sample of 4159 9th- to 12th-grade students in public high schools from Massachusetts' expanded Centers for Disease Control and Prevention 1995 Youth Risk Behavior Survey. Sexual orientation was determined by the following question: "Which of the following best describes you?" A total of 104 students self-identified as gay, lesbian, or bisexual (GLB), representing 2.5% of the overall population. Of GLB youth, 66.7% were male and 70% were white (not Hispanic). Health risk and problem behaviors were analyzed comparing GLB youth and their peers. Those variables found to be significantly associated with GLB youth were then analyzed by multiple logistic regression models. RESULTS: GLB youth were more likely than their peers to have been victimized and threatened and to have been engaged in a variety of risk behaviors including suicidal ideation and attempts, multiple substance use, and sexual risk behaviors. Four separate logistic regression models were constructed. Model I, Onset of Behaviors Before Age 13, showed use of cocaine before age 13 years as strongly associated with GLB orientation (odds ratio [OR]: 6.10; 95% confidence interval [CI] = 2.45-15.20). Early initiation of sexual intercourse (2.15; 10.6-4.38), marijuana use (1.98; 1.04-4.09), and alcohol use (1.82; 1.03-3.23) also was associated with GLB orientation. Model II, Lifetime Frequencies of Behaviors, showed that frequency of crack cocaine use (1.38; 1.06-1.79), inhalant use (1.30; 1.05-1.61), and number of sexual partners (1.27; 1.06-1.43) was associated with GLB orientation. Model III, Frequency of Recent Behaviors, showed smokeless tobacco use in the past 30 days (1.38; 1. 20-1.59) and number of sexual partners in the previous 3 months (1. 47; 1.31-1.65) were associated with GLB orientation. Model IV, Frequency of Behaviors at School, showed having one's property stolen or deliberately damaged (1.23; 1.08-1.40) and using marijuana (1.29; 1.05-1.59) and smokeless tobacco (1.53; 1.30-1.81) were associated with GLB orientation. Overall, GLB respondents engaged disproportionately in multiple risk behaviors, reporting an increased mean number of risk behaviors (mean = 6.81 +/- 4.49) compared with the overall student population (mean = 3.45 +/- 3.15). CONCLUSION: GLB youth who self-identify during high school report disproportionate risk for a variety of health risk and problem behaviors, including suicide, victimization, sexual risk behaviors, and multiple substance use. In addition, these youth are more likely to report engaging in multiple risk behaviors and initiating risk behaviors at an earlier age than are their peers. These findings suggest that educational efforts, prevention programs, and health services must be designed to address the unique needs of GLB youth.

Adolescent↗
PubMed2003

Trusted online sources of health information: differences in demographics, health beliefs, and health-information orientation.

BACKGROUND: The recent surge in online health information and consumer use of such information has led to expert speculations and prescriptions about the credibility of health information on the World Wide Web. In spite of the growing concern over online health information sources, existing research reveals a lacuna in the realm of consumer evaluations of trustworthiness of different health information sources on the Internet. OBJECTIVE: This study examines consumer evaluation of sources of health information on the World Wide Web, comparing the demographic, attitudinal, and cognitive differences between individuals that most trust a particular source of information and individuals that do not trust the specific source of health information. Comparisons are made across a variety of sources. METHODS: The Porter Novelli HealthStyles database, collected annually since 1995, is based on the results of nationally-representative postal-mail surveys. In 1999, 2636 respondents provided usable data for the HealthStyles database. Independent sample t tests were conducted to compare the respondents in the realm of demographic, attitudinal, and cognitive variables. RESULTS: The most trusted sources of online health information included the personal doctor, medical university, and federal government. The results demonstrated significant differences in demographic and health-oriented variables when respondents who trusted a particular online source were compared with respondents that did not trust the source, suggesting the need for a segmented approach to research and application. Individuals trusting the local doctor were younger (t2634 = 4.02, P <.001) and held stronger health beliefs (F1 = 5.65, P =.018); individuals trusting the local hospital were less educated (t2634 = 3.83, P <.001), low health information oriented (F1 = 6.41, P =.011), and held weaker health beliefs (F1 = 5.56, P =.018). Respondents with greater trust in health insurance companies as online health information sources were less educated (t2634 = 1.90, P =.05) and less health information oriented (F1 = 4.30, P =.04). Trust in medical universities was positively associated with education (t2634 = 11.83, P <.001), income (t2634 = 10.19, P <.001), and health information orientation (F1 = 10.32, P <.001). Similar results were observed in the realm of federal information credibility, with individuals with greater trust in federal sources being more educated (t2634 = 7.45, P <.001) and health information oriented (F1 = 4.45, P =.04) than their counterparts. CONCLUSIONS: The results suggest systematic differences in the consumer segment based on the different sources of health information trusted by the consumer. While certain sources such as the local hospital and the health insurance company might serve as credible sources of health information for the lower socioeconomic and less health-oriented consumer segment, sources such as medical universities and federal Web sites might serve as trustworthy sources for the higher socioeconomic and more health-oriented groups.

Academic Medical Centers↗
PubMed2003

Pilot study comparing market orientation culture of businesses and schools of business.

A market orientation culture has been described as one that blends an organization's commitment to customer value with a process of continuously creating superior value for customers. Developing such a culture is further described as (1) obtaining information about customers, competitors, and markets, (2) examining the gathered information from a total organizational perspective, (3) deciding how to deliver superior customer value, and (4) implementing actions to provide value to customers. A market orientation culture focuses on the customer, identifies issues in the competitive environment, and coordinates all functional areas to achieve organizational objectives. Research has found businesses with higher market orientation are more successful in achieving organizational objectives. The measurement of market orientation within businesses has been empirically tested and validated. However, empirical research on market orientation in nonprofit organizations such as universities has not been examined. This study investigated market orientation within the university setting, specifically Schools of Business Administration, and compared these data with previously published data within the business sector. Data for comparative purposes were collected via a national survey. Hypothesis testing was conducted. Results indicated significantly lower market orientation culture within the schools of business as reported by AACSB Business School Deans vis-à-vis managers of business enterprises.

Commerce↗
PubMedDate not supplied

Locus of control and depression as a function of sex role orientation in two age groups of mental health nurses.

The purpose of the study reported in this article was to examine the relationships between locus of control and level of depression in younger adult and midlife registered mental health nurses (MHNs) in relation to each other and as a function of sex role orientation. On the basis of C. G. Jung's (1954) theory of individuation, the following hypotheses were derived: (a) MHNs with an androgynous sex role orientation will have a higher internal locus of control than MHNs with a nonandrogynous sex role orientation; (b) MHNs with an androgynous sex role orientation will be less depressed than nonandrogynous sex role-oriented MHNs, and (c) midlife MHNs will be more androgynous in sex role orientation than younger MHNs. Thirty-six participants, all working female registered mental health nurses between the ages of 30 and 59, were placed in the midlife group (age 41-59) or the young adult group (age 31-40) on the basis of self-indicated age. Two groups of female MHNs (younger adult and midlife women) were compared with each other by means of the Personal Attributes Questionnaire (Spence, Helmreich, & Stapp, 1975), used to assess sex role orientation (androgynous or nonandrogynous: cross-typed, sex-typed, or undifferentiated); Rotter's (1966) Locus of Control Scale, used to assess internal or external (I-E) locus of control; and the Beck Depression Inventory (Beck, Ward, Mendelson, Mock, & Erbaugh, 1961), used to assess level of depression. In regards to all three hypotheses, no statistically significant associations were found among the study variables. The strengths and weakness of the present study were reviewed. The theoretical and practical implications of the results were discussed, and directions for future research were considered.

Adult↗
PubMed2004

The contribution of symmetry and motion to the recognition of faces at novel orientations.

In three experiments, we examined the recognition of faces at novel orientations. Although performance tended to decay as difference between the study and the test angles increased, an orientation that was symmetric with respect to the study orientation showed strong performance--in many cases, better than the frontal view. We investigated the properties of this particular facility in perception and memory tasks. Symmetrized faces showed surprisingly different patterns of behavior than did unsymmetrized faces, despite the fact that many faces were already fairly symmetric. In memory experiments, the subjects showed robust symmetric orientation effects and could differentiate between the original study views and the symmetric orientation. In a third experiment, we demonstrated that smooth motion improved performance at the symmetric orientation, whereas two control motions did not. Together, the three experiments support the view that multiple representations are at work during the recognition of faces at the symmetric orientation and that, during memory tasks, subjects tend to rely on representations that are more robust against texture asymmetries and that may include limited depth information.

Face↗
PubMed1999

Orientation-specific effects in picture matching and naming.

In two experiments, subjects made timed decisions about the second of two sequentially presented rotated drawings of objects. When the two objects were physically identical, response times to decide whether the two drawings depicted the same object varied as a function of the shortest distance between the orientation of the second drawing and either the orientation of the previous drawing or the upright. This was found for both short (250-msec) and long (2-sec) interstimulus-intervals. The result was also obtained when subjects named the second drawing after deciding whether the first drawing faced left or right. Following repeated experience with the drawings in the left/right task over four blocks of trials, time to name the second drawing in the same-object sequences was independent of orientation. These results suggest that, initially, object- and orientation-specific representations can be formed following a single presentation of a rotated object and subsequently used to identify drawings of the same object at either the same or different orientations. Alignment of the second drawing with either the canonical representation or the new representation at the previous orientation is achieved by normalization through the shortest path. Following experience with the objects, orientation-invariant representations are formed.

Adult↗
PubMedDate not supplied

Developing an orientation program.

When the local area experienced tremendous growth and change, the radiology department at Maury Hospital in Columbia, Tennessee looked seriously at its orientation process in preparation for hiring additional personnel. It was an appropriate time for the department to review its orientation process and to develop a manual to serve as both a tool for supervisors and an ongoing reference for new employees. To gather information for the manual, supervisors were asked to identify information they considered vital for new employees to know concerning the daily operations of the department, its policies and procedures, the organizational structure of the hospital, and hospital and departmental computer systems. That information became the basis of the orientation manual, and provided an introduction to the hospital and radiology department; the structure of the organization; an overview of the radiology department; personnel information; operating procedures and computer systems; and various policies and procedures. With the manual complete, the radiology department concentrated on an orientation process that would meet the needs of supervisors who said they had trouble remembering the many details necessary to teach new employees. A pre-orientation checklist was developed, which contained the many details supervisors must handle between the time an employee is hired and arrives for work. The next step was the creation of a checklist for use by the supervisor during a new employee's first week on the job. A final step in the hospital's orientation program is to have each new employee evaluate the entire orientation process. That information is then used to update and revise the manual.

Hospitals, Community↗
PubMed1978

Cell wall biogenesis in Oocystis: experimental alteration of microfibril assembly and orientation.

Cell wall biogenesis in the unicellular green alga Oocystis apiculata has been studied. Under normal growth conditions, a cell wall with ordered microfibrils is synthesized. In each layer there are rows of parallel microfibrils. Layers are nearly perpendicular to each other. Terminal linear synthesizing complexes are located in the plasma membrane, and they are capable of bidirectional synthesis of cellulose microfibrils. Granule bands associated with the inner leaflet of the plasma membrane appear to control the orientation of newly synthesized microfibrils. Subcortical microtubules also are present during wall synthesis. Patterns of cell wall synthesis were studied after treatment with EDTA and EGTA as well as divalent cations (MgSO4, CaSO4, Cacl2). 0.1 M EDTA treatment for 15 min results in the disassociation of the terminal complexes from the ends of microfibrils. EDTA-treated cells followed by 15 min treatment with MgSO4 results in reaggregation of the linear complexes into a paired state, remote from the original ends to which they were associated. After 90 min treatment with MgSO4, normal synthesis resumes. EGTA and calcium salts do not affect the linear complexes or microfibril orientation. Treatments with colchicine and vinblastine sulphate do not depolymerize the microtubles, but the wall microfibril orientation is altered. With colchicine or vinblastine, the change in orientation from layer to layer is inhibited. The process is reversible upon removal of the drugs. Lumicolchicine has no effect upon microfibril orientation, but granule bands are disorganized. Treatment with coumarin, a known inhibitor of cellulose synthesis, causes the loss of visualization of subunits of the terminal complexes. The possibility of the existence of a membrane-associated colchicine-sensitive orientation protein for cellulose microfibrils is discussed. Transmembrane modulation of microfibril synthesis and orientation is presented.

Calcium↗
PubMed2001

The wear of oriented UHMWPE under isotropically rough and scratched counterface test conditions.

Unidirectional wear tests of UHMWPE against smooth counterfaces show that molecular chains at the surface of virgin material become oriented parallel to the sliding direction giving low wear rate. It is postulated that under more abrasive conditions and predominantly unidirectional motion as in knee prostheses, it may proof beneficial to provide molecular orientation of the bulk material. Therefore strips of UHMWPE were oriented by die drawing at elevated temperature and the resulting anisotropic material subjected to tensile tests, small punch tests and also unidirectional wear tests both parallel and perpendicular to the draw direction. The tensile tests showed that, in the parallel direction, the oriented UHMWPE became stiffer and less ductile compared to the virgin UHMWPE. In the perpendicular direction, there were reductions in yield stress, 5% proof stress and energy to failure compared to the virgin material. The small punch test showed that the oriented UHMWPE exhibited apparent hardening when tested in both parallel and perpendicular directions but the mechanical behaviour in the perpendicular direction was comparable to the virgin UHMWPE. The wear tests demonstrated that the oriented UHMWPE did not show any significant improvement of wear resistance for sliding against either isotropically rough or scratched counterfaces. There was no clear dependency between the mechanical properties and wear factors of the oriented UHMWPE.

Biocompatible Materials↗
PubMed2001

[Turbulence and high intensity transient signals (HITS) as a parameter for optimum orientation of mechanical heart valves].

BACKGROUND: In previous studies, the impact of valve orientation on the hemodynamic performance of mechanical aortic valves has been demonstrated. This study investigates Turbulence (RNS values) and High Intensity Transient Signals (HITS) as a new and objective parameter for hemodynamics in various orientations of Medtronic Hall (MH) and St. Jude Medical (SJM) aortic valves. METHODS: Rotation devices carrying a MH or SJM valve were implanted into four pigs. The device allowed valve rotation without reopening the aorta. In various orientations, turbulent shear stresses (RNS values) and HITS were measured. RESULTS: RNS and HITS changed for both valve designs in the different orientations, with superior results for the MH in the hemodynamically best orientation. Downstream turbulence (RNS) and HITS varied in the same direction, but a one to one correlation was not observed. CONCLUSIONS: RNS and HITS vary with respect to valve orientation and design with superior results for the tilting disc valve. Both MH and SJM valves showed lower turbulence and HITS counts in their hemodynamically best orientations. HITS were related to downstream turbulence and the hemodynamic performance of the mechanical aortic valves.

Animals↗