243 research outputs found
Relationship between bone tissue strain and lattice strain of HAp crystals in bovine cortical bone under tensile loading.
No full textCortical bone is a composite material composed of hydroxyapatite (HAp) and collagen. As HAp is a crystalline structure, an X-ray diffraction method is available to measure the strain of HAp crystals. However, HAp crystals in bone tissue have been known to have the low degree of crystallization. Authors have proposed an X-ray diffraction method to measure the lattice strain of HAp crystals from the diffusive intensity profile due to low crystallinity. The precision of strain measurement was greatly improved by this method. In order to confirm the possibility of estimating the bone tissue strain with measurements of the strain of HAp crystals, this work investigates the relationship between bone tissue strain on a macroscopic scale and the lattice strain of HAp crystals on a microscopic scale. The X-ray diffraction experiments were performed under tensile loading. Strip bone specimens of 40×6×0.8 mm in size were cut from the cortical region of a shaft of bovine femur. A stepwise tensile load was applied in the longitudinal direction of the specimen. By detecting the diffracted X-ray beam transmitted through the specimen, the lattice strain was directly measured in the loading direction. As a result, the lattice strain of HAp crystals showed lower value than the bone tissue strain measured by a strain gage. The bone tissue strain was described with the mean lattice strain of the HAp crystals and the elastic modulus
Influence of osteon area fraction and degree of orientation of HAp crystals on mechanical properties in bovine femur
No full textCortical bone has a hierarchical structure, spanning from the macrostructure at several millimeters or whole bone level, the microstructure at several hundred micrometers level, to the nanostructure at hydroxyapatite (HAp) crystals and collagen fibrils levels. The aim of the study is to understand the relationship between the HAp crystal orientation and the elastic modulus and the relationship between the osteon area fraction and the deformation behavior of HAp crystals in cortical bone. In the experiments, five strip specimens (40×2×1 mm3) aligned with the bone axis were taken from the cortical bone of a bovine femur. The degree of c-axis orientation of HAp crystals in the specimens was measured with the X-ray diffraction technique with the imaging plate. To measure the deformation behavior of HAp crystals in the specimens, tensile tests under X-ray irradiation were conducted. The specimens were cut at the X-ray measurement positions and osteon area fraction and porosity at the transverse cross-sections were observed. Further, the volume fraction of HAp of the specimens was measured. Results showed the degree of c-axis orientation of HAp crystals was positively correlated with the elastic modulus of the specimens (r=0.94). The volume fraction of HAp and the porosity showed no statistical correlation with the elastic modulus and the tensile strength. The HAp crystal strain εH increased linearly with the bone tissue strain ε. The average value of εH/ε was 0.69±0.13 and there was no correlation between the osteon area fraction and εH/ε (r=−0.27, p=0.33). The results suggest that the degree of c-axis orientation of HAp crystals affects the elastic modulus and the magnitude of HAp crystal strain does not depend on the osteon area fraction
A method on strain measurement of HAP in cortical bone from diffusive profile of X-ray diffraction
No full textBone tissue is a composite material composed of hydroxyapatite (HAp) and collagen matrix. As HAp is a crystalline structure, an X-ray diffraction method is available to measure the lattice strain of HAp crystals. However, mineral particles of HAp in bone have much lower crystallinity than usual crystalline materials, which show a diffusive intensity profile of X-ray diffraction. It is not easy to determine quantitatively an infinitesimal strain of HAp from the peak position of diffusive profile. In order to improve the accuracy of strain measurement of HAp in bone tissue and to obtain reproducible results, this paper proposes an X-ray diffraction method applied to a diffusive profile for low crystallinity. This method is to estimate the lattice strain of HAp using not a peak position but a whole diffraction profile. In this experiment, a strip specimen of 28×8×2 mm was made from bone axial, outside circumferential and cross sectional circumferential region in the cortical bone of bovine femur. The X-ray diffraction measurements were carried out before and after applying an external load. As a result, the precision of strain measurement was much improved by this method. Although a constant value of macroscopic strain was applied in the specimen, the lattice strain had a lower value than the macroscopic strain and had a different value in each specimen
Hap -- A Reactive, Adaptive Architecture for Agents
No full textThe Hap reactive agent architecture provides many of the same mechanisms to authors as other goal-directed reactive architectures: arbitrary demons, multiple active goals and situated, runtime interpretation of plans. It also provides three unique features: convenient mechanisms for taking advantage of opportunities as they arise and for changing the agent's course of action when unfortunate events dictate; explicit mechanisms for allowing easy extension of the plan library; and flexible mechanisms for determining the success of goals without necessarily requiring the author to explicitly characterize the criteria for success. Hap was designed as part of the Oz project which is concerned with developing a rich framework for both interactive fiction and virtual realities. Oz is intended to provide a human user with the experience of living in a dramatically interesting simulated world which includes simulated intelligent and emotional agents
Reducing inpatient hospital acquired pneumonia (HAP) using a structured oral care program
No full textThesis (M.A.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at [email protected]. Thank you.Hospital acquired pneumonia (HAP) causes significant mortality and morbidity and is now no longer reimbursed by Centers for Medicare and Medicaid (CMS). For all of these reasons, hospitals want to minimize their HAP rates. Aggressive oral care (tooth brushing 3 times a day) has been shown to reduce the incidence of HAP in the intensive care unit setting, but this has not been tested in the acute care setting, in which patients are more stable, less sick, and more ambulatory.
In an attempt to address HAP rates in acute care settings, this clinical trial entailed providing all patients in four wards with a 3 times per day tooth-brushing oral care protocol, which was implemented or supervised by the nurses on each ward. Six matched wards on a separate campus that received normal standard of care served as controls. The goal of this clinical trial was to cut the pneumonia rate in half, from 2% to 1%.
This clinical trial was conducted to determine whether an oral care regimen would reduce the incidence of aspiration pneumonia over the three months of intervention in the experimental group (HAC) versus the control group (ENC) from Nov 5, 2012 to Feb 15, 2013.2031-01-0
Authorship in a multicenter clinical trial: The Heart Failure-A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) Authorship and Publication (HAP) scoring system results
No full textBACKGROUND: Few guidelines exist regarding authorship on manuscripts resulting from large multicenter trials. The HF-ACTION investigators devised a system to address assignment of authorship on trial publications and tested the outcomes in the course of conducting the large, multicenter, National Heart, Lung, and Blood Institute-funded trial (n = 2,331; 82 clinical sites; 3 countries). The HF-ACTION Authorship and Publication (HAP) scoring system was designed to enhance rate of dissemination, recognize investigator contributions to the successful conduct of the trial, and harness individual expertise in manuscript generation.
METHODS: The HAP score was generated by assigning points based on investigators\u27 participation in trial enrollment, follow-up, and adherence, as well as participation in committees and other trial activity. Overall publication rates, publication rates by author, publication rates by site, and correlation between site publication and HAP score using a Poisson regression model were examined.
RESULTS: Fifty peer-reviewed, original manuscripts were published within 6.5 years after conclusion of study enrollment. In total, 137 different authors were named in at least 1 publication. Forty-five (55%) of the 82 sites had an author named to at least 1 article. A Poisson regression model examining incident rate ratios revealed that a higher HAP score resulted in a higher incidence of a manuscript, with a 100-point increase in site score corresponding to an approximately 32% increase in the incidence of a published article.
CONCLUSIONS: Given the success in publishing a large number of manuscripts and widely distributing authorship, regular use of a transparent, objective authorship assignment system for publishing results from multicenter trials may be recommended to optimize fairness and dissemination of trial results
Hydrogels toughened by biominerals providing energy-dissipative sacrificial bonds
No full textInspired by bone tissues, we mineralized low crystalline hydroxyapatite (HAp) particles in double network (DN) hydrogels, and we observed that the HAp minerals toughen the gels. The contribution of dissipated energy from HAp minerals was over 500% higher than that from the polymer during tensile deformation. We elucidated that the amorphous parts in the HAp minerals break at deformation, acting as energy-dissipative sacrificial bonds. This result implies that not only brittle polymer networks but also minerals can provide sacrificial bonds to toughen soft materials
Beta-tricalcium phosphate shows superior absorption rate and osteoconductivity compared to hydroxyapatite in open-wedge high tibial osteotomy
No full textThe purpose of this study was to clinically and radiologically compare the utility, osteoconductivity, and absorbability of hydroxyapatite (HAp) and beta-tricalcium phosphate (TCP) spacers in medial open-wedge high tibial osteotomy (HTO). Thirty-eight patients underwent medial open-wedge HTO with a locking plate. In the first 19 knees, a HAp spacer was implanted in the opening space (HAp group). In the remaining 19 knees, a TCP spacer was implanted in the same manner (TCP group). All patients underwent clinical and radiological examinations before surgery and at 18 months after surgery. Concerning the background factors, there were no statistical differences between the two groups. Post-operatively, the knee score significantly improved in each group. Concerning the post-operative knee alignment and clinical outcome, there was no statistical difference in each parameter between the two groups. Regarding the osteoconductivity, the modified van Hemert's score of the TCP group was significantly higher (p = 0.0009) than that of the HAp group in the most medial osteotomy zone. The absorption rate was significantly greater in the TCP group than in the HAp group (p = 0.00039). The present study demonstrated that a TCP spacer was significantly superior to a HAp spacer concerning osteoconductivity and absorbability at 18 months after medial open-wedge HTO. Retrospective comparative study, Level III
Orientation and deformation of mineral crystals in tooth surfaces
No full textTooth enamel is the hardest material in the human body, and it is mainly composed of hydroxyapatite (HAp)-like mineral particles. As HAp has a hexagonal crystal structure, X-ray diffraction methods can be used to analyze the crystal structure of HAp in teeth. Here, the X-ray diffraction method was applied to the surface of tooth enamel to measure the orientation and strain of the HAp crystals. The c-axis of the hexagonal crystal structure of HAp was oriented to the surface perpendicular to the tooth enamel covering the tooth surface. Thus, the strain of HAp at the surface of teeth was measured by X-ray diffraction from the (004) lattice planes aligned along the c-axis. The X-ray strain measurements were conducted on tooth specimens with intact surfaces under loading. Highly accurate strain measurements of the surface of tooth specimens were performed by precise positioning of the X-ray irradiation area during loading. The strains of the (004) lattice plane were measured at several positions on the surface of the specimens under compression along the tooth axis. The strains were obtained as tensile strains at the labial side of incisor tooth specimens. In posterior teeth, the strains were different at different measurement positions, varying from tensile to compressive types
HAAGERUP APPROXIMATION PROPERTY VIA BIMODULES
No full textThe Haagerup approximation property (HAP) is defined for finite von Neumann algebras in such a way that the group von Neumann algebra of a discrete group has the HAP if and only if the group itself has the Haagerup property. The HAP has been studied extensively for finite von Neumann algebras and it was recently generalized to arbitrary von Neumann algebras by Caspers-Skalski and Okayasu-Tomatsu. One of the motivations behind the generalization is the fact that quantum group von Neumann algebras are often infinite even though the Haagerup property has been defined successfully for locally compact quantum groups by Daws-Fima-Skalski-White. In this paper, we fill this gap by proving that the von Neumann algebra of a locally compact quantum group with the Haagerup property has the HAP. This is new even for genuine locally compact groups
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