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- Chowdhary, Ramesh
(författare)
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On efficacy of implant thread design for bone stimulation
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction – The mechanism and efficiency of force transfer by dental implants to surrounding biologic tissues are important determinants in the development of the implant-to-bone/tissue interface and implant longevity. Threads are used to improve the initial stability by maximizing bone contact through an enlarged implant surface area and thereby favor distribution of interfacial stresses. However, knowledge about optimal thread design for an enhanced implant integration in bone tissue is still lacking. Aim – The aim of this thesis was to evaluate the efficacy of implant micro thread design when combined with macro threads, for bone stimulation. The hypothesis is that the short threads will contribute with compression forces that may stimulate bone healing, while the larger threads will provide with primary stability necessary during the healing process. A further aim was to use an FEA model to describe the optimal thread form for reduced stress concentration immediately after implant insertion as well as after completed bone healing. Materials and methods – In study 1, Two-dimensional finite element models were made from 8 different thread designs. The crest module and apex of the implants were removed from the implant models, in order to enhance the effect of the thread designs only. Thus, the suprastructures and microstructures of the implants were not considered. All the eight implant models were assumed to be embedded in cortical bone. In addition, a 3D model was used to evaluate stress in the bone generated by 6 different thread designed implants when the implant models included the entire implant. In the In vivo studies 2 and 3, experimental turned implants with a diameter of 4mm and 8mm in length were prepared with micro threads in between macro threads along the body of the implants. These were used as test implants. Implants without micro-threads were used as controls. In study 4, similar implants were made but with alteration in depth of the macro-thread to improve the possibility for bone stimulation by compression during healing. Insertion and removal torque analysis along with histomophometric analyses were done to evaluate the bone response. Results – In study 1, stresses were calculated using von Mises stress analysis. The stress levels in the bone were in the range of 5-13 MPa in osseointegrated model and 14-107 MPa in immediate 2D models. 3D Analysis results showed the von Mises stress in the range of 4.8-30.9 MPa, when a load of 100N was applied vertically. In Study 4 FEA demonstrated stress levels in the range of 0.28 MPa to 62MPa for the control implant model designs, whereas the test implant models displayed a range of 0.28 MPa to 31Mpa. In study 2, the mean values of the ITQ for the control and test groups in the tibia were 15 and 20 Ncm respectively, and in the femur, the values were 11 and 12 Ncm, respectively. In study 4, the ITQ values were 11Ncm and 14 Ncm respectively in the tibia, and in the femur 13 Ncm and 19 Ncm respectively. The RTQ values for the control and test groups in tibia was 11Ncm and 17Ncm, respectively and in the femur, 13Ncm and 23Ncm, respectively. The histomorphometric analysis of study 3, showed the mean total bone area, BA% (SD) to be higher in the test implants, when compared to the control implants in both the tibia 24 (4), and 21(4), the femoral bone 29 (5), and 25 (7), respectively with no statistical significance. In study 4, the total bone area BA% was higher for the test implants with a mean value of 72% compared to 48% for the control group in tibial bone. In femural bone, the bone area was 63% for the test and 38 % for the control group implants with p value of 0.10 for both tibia and femur. Bone to implant contact showed significantly higher value for the test implants in the femur, p= 0.04. Conclusion – The impact of different thread designs, with respect to the magnitude of the transferred stress peak in the bone, was higher for the immediately inserted implants than for the osseointegrated implant model. The stress distribution was more effective in experimental micro-thread implant models, when compared to the non-micro thread models. The addition of pitch shortened threads in the test implant, did significantly improve the primary and secondary stability of the test implants, when mechanically evaluated with ITQ and RTQ analysis in corticular or trabecular bone rabbit bone. Histomophometrical analysis showed that the addition of the pitch shortened threads in between the macro threads did have a bone stimulatory effect in the femur of the rabbits.
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- Goolaup, Sandhiya, 1985
(författare)
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A study on the nature of the food tourist’s experience: the tourist’s viewpoint
- 2014
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Ingår i: The 23 rd Nordic Symposium On Tourism And Hospitality Research, 2-4 October 2014,Copenhagen Denmark.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Food is increasingly being recognized as an integral part of the tourist experience and sometimes it is one of the key reasons for travelers to visit a particular destination. Even though, the importance of food in tourism experience has been widely acknowledged (e.g., Kim et al. 2009; Chang et al. 2011) research has yet to take a holistic approach to understand the nature of the food tourist experience. Several authors have looked upon factors influencing the experience of a meal in a restaurant or the nature of the wine tourist experience. For instance, in a study conducted by Charters (2006) it was found out that the wine tourists seek experience which comprised of an interaction between the natural setting, wine, food, cultural and historical inputs and the people who service them. However, it is not clear what makes up a food tourist experience. According to Hall and Mitchell (2001), the food tourists are primarily motivated by the desire to experience the produce of a specific region or a particular type of food. Hence, an important question remains; is food the main element in the food tourist experience or is it other factors? So far, this aspect of the study has not received significant attention. An understanding of this particular phenomenon is important as it provides an in-depth understanding of what the food tourists are looking for. It can also help destination marketers in the development and promotion of gastronomic experience. To obtain insight on the food tourist experience, the study relies on observations and in-depth interviews with 16 food tourists who visited an oyster bar situated on the West Coast of Sweden. The result suggests that the food tourists look not only for food but rather an amalgam of other components which contribute significantly in their food tourist experiences. Result from this study further indicates that the atmosphere, host, product, story and theme, learning/educational and social aspect all contribute equally in the food tourist experience.
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- Picca, Anna, et al.
(författare)
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Biomarkers shared by frailty and sarcopenia in older adults : A systematic review and meta-analysis
- 2022
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Ingår i: Ageing Research Reviews. - : Elsevier BV. - 1568-1637 .- 1872-9649. ; 73
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Forskningsöversikt (refereegranskat)abstract
- Background: Physical frailty and sarcopenia show extensive clinical similarities. Whether biomarkers exist that are shared by the two conditions is presently unclear.Methods: We conducted a systematic review and meta-analysis of cross-sectional and longitudinal studies that investigated the association of frailty and/or sarcopenia with biomarkers as a primary or secondary outcome in adults aged 60 years and older. Only studies published in English that defined frailty using a validated scale and/ or questionnaire and diagnosed sarcopenia according to the presence of muscle atrophy plus dynapenia or low physical function were included. Studies were identified from a systematic search of MEDLINE and SCOPUS databases from inception through August 2020. The quality of reporting of each study was assessed by using the Quality Assessment Tool for Observational Cohort, Cross-Sectional and Case-Control studies of the National Institute of Health. A meta-analysis was conducted when at least three studies investigated the same biomarker in both frailty and sarcopenia. Pooled effect size was calculated based on standard mean differences and randomeffect models. Sensitivity analysis was performed based on age and the setting where the study was conducted.Results: Eighty studies (58 on frailty and 22 on sarcopenia) met the inclusion criteria and were included in the qualitative analysis. Studies on frailty included 33,160 community-dwellers, hospitalized, or institutionalized older adults (60-88 years) from 21 countries. Studies on sarcopenia involved 4904 community-living and institutionalized older adults (68-87.6 years) from 9 countries. Several metabolic, inflammatory, and hematologic markers were found to be shared between the two conditions. Albumin and hemoglobin were negatively associated with both frailty and sarcopenia. Interleukin 6 was associated with frailty and sarcopenia only in people aged < 75. Community-dwelling older adults with frailty and sarcopenia had higher levels of tumor necrosis factor alpha compared with their robust and non-sarcopenic counterparts.Conclusions: A set of metabolic, hematologic, and inflammatory biomarkers was found to be shared by frailty and sarcopenia. These findings fill a knowledge gap in the quest of biomarkers for these conditions and provide a rationale for biomarker selection in studies on frailty and sarcopenia.
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- Risacher, Christophe, 1976, et al.
(författare)
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A 275-370 GHz SIS Mixer for the APEX Telescope
- 2004
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Ingår i: in “Proceedings of SPIE in Millimeter and Submillimeter Detectors for Astronomy II”, 23-25 June 2004, Glasgow, Scotland, United Kingdom, eds. J. Zmuidzinas, W. Holland, S. Withington, SPIE. ; 5498, s. 140-148
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Konferensbidrag (refereegranskat)
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| 10. |
- Suslov, Michail
(författare)
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K. P. Stepanov
- 2010
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Ingår i: Russkii konservatizm serediny XVIII – nachala XX veka: Entsiklopedia. - Moscow : ROSSPEN. ; , s. 487-489
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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