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Search Results: 1 - 10 of 672797 matches for " M. C. de Ruiter "
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The Inter- and Intraindividual Anatomical Relationship of the Femoral Anteversion and Distal Femoral Rotation. A Cadaveric Study on the Femoral Anteversion Angle, Posterior and Inferior Condylar Angle Using Computed Tomography  [PDF]
H. M. J. van der Linden-van der Zwaag, L. C. D. Konijn, T. J. van der Steenhoven, H. J. L. van der Heide, M. C. de Ruiter, R. G. H. H. Nelissen
Advances in Computed Tomography (ACT) , 2015, DOI: 10.4236/act.2015.41002
Malrotation following Total Knee Arthroplasty (TKA) is directly related to poor outcome. Knowledge of the rotational axes (torsion) and angles is therefore important. The aim of the study was to determine whether an association existed between the Femoral Anteversion Angle (FAA) Posterior Condylar Angle (PCA) and the Inferior Condylar Angle (ICA) in individuals. A CT scan of 50 (25 paired) cadaver femora was made. The FAA, PCA and ICA were measured. Statistical analysis of comparative relationships between these different angles was examined by calculating Pearson correlation coefficients and a paired t-test. The mean FAA, PCA and ICA for the whole group were respectively 11.7° (range 0 - 32, SD 8.2), 5.18° (range 0 - 12, SD 2.4) and 4.4° (range 0 - 10, SD 2.1). A correlation of 0.82 (p = 0.01) of the FAA was found between left versus right. For the overall group a correlation coefficient between the PCA of the left and right femur was r = 0.59, p = 0.01. The Pearson correlation between the FAA and PCA in the whole group was r = 0.27, p = 0.06. In females this was r = 0.54 (p = 0.03). Although the difference of the mean ICA and PCA was very small (0.7°), there was no correlation between these angles (r = 0.14, p = 0.23). In conclusion, one should be aware that, considering the weak correlation of the FAA and PCA, an individual rotational variation exists. Furthermore, no correlation was found between the PCA and ICA. Therefore, for now, this angle cannot be assumed to be helpful in TKA. A more individual approach in total knee arthroplasty seems essential for future TKA.
Diets of impala from Kruger National Park: evidence from stable carbon isotopes
M. Sponheimer,C.C. Grant,D.J. de Ruiter,J.A. Lee-Thorp
Koedoe : African Protected Area Conservation and Science , 2003, DOI: 10.4102/koedoe.v46i1.43
Abstract: Impala are known to exhibit dietary flexibility, relying primarily on browse in some areas and graze in others. In this study we use stable isotope analysis of faeces and hair to examine the diets of Impala in Kruger National Park. As expected, the data show that Impala are mixed-feeders and highly distinct from grazing buffalo and browsing kudu. Moreover, Impala, Buffalo, and Kudu faeces contain 2.1 %, 1.4 %, and 2.9 % nitrogen respectively, suggesting that Impala diets are of intermediate quality. There are also marked differences between Impala populations in the northern and southern regions of the park. The northern Impala graze less than their southern counterparts. This difference probably reflects decreased availability of herbaceous forage in the mopane-dominated north. Males and females also have different diets, with males grazing more than females.
Changes in Natural Foxp3+Treg but Not Mucosally-Imprinted CD62LnegCD38+Foxp3+Treg in the Circulation of Celiac Disease Patients
Marieke A. van Leeuwen, M. Fleur du Pré, Roy L. van Wanrooij, Lilian F. de Ruiter, H. (Rolien) C. Raatgeep, Dicky J. Lindenbergh-Kortleve, Chris J. Mulder, Lissy de Ridder, Johanna C. Escher, Janneke N. Samsom
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068432
Abstract: Background Celiac disease (CD) is an intestinal inflammation driven by gluten-reactive CD4+ T cells. Due to lack of selective markers it has not been determined whether defects in inducible regulatory T cell (Treg) differentiation are associated with CD. This is of importance as changes in numbers of induced Treg could be indicative of defects in mucosal tolerance development in CD. Recently, we have shown that, after encounter of retinoic acid during differentiation, circulating gut-imprinted T cells express CD62LnegCD38+. Using this new phenotype, we now determined whether alterations occur in the frequency of natural CD62L+Foxp3+ Treg or mucosally-imprinted CD62LnegCD38+Foxp3+ Treg in peripheral blood of CD patients. In particular, we compared pediatric CD, aiming to select for disease at onset, with adult CD. Methods Cell surface markers, intracellular Foxp3 and Helios were determined by flow cytometry. Foxp3 expression was also detected by immunohistochemistry in duodenal tissue of CD patients. Results In children, the percentages of peripheral blood CD4+Foxp3+ Treg were comparable between CD patients and healthy age-matched controls. Differentiation between natural and mucosally-imprinted Treg on the basis of CD62L and CD38 did not uncover differences in Foxp3. In adult patients on gluten-free diet and in refractory CD increased percentages of circulating natural CD62L+Foxp3+ Treg, but normal mucosally-imprinted CD62LnegCD38+Foxp3+ Treg frequencies were observed. Conclusions Our data exclude that significant numeric deficiency of mucosally-imprinted or natural Foxp3+ Treg explains exuberant effector responses in CD. Changes in natural Foxp3+ Treg occur in a subset of adult patients on a gluten-free diet and in refractory CD patients.
The lives of FR I radio galaxies
P. Parma,M. Murgia,H. R. de Ruiter,R. Fanti
Physics , 1999, DOI: 10.1016/S1387-6473(01)00201-9
Abstract: After a brief introduction to the morphological properties of FRI radio sources, we discuss the possibility that FRI jets are relativistic at their bases and decelerate quickly to non-relativistic velocities. From two-frequency data we determine spectral index distributions and consequently the ages of FRI sources. We show that in the large majority of cases synchrotron theory provides unambiguous and plausible answers; in a few objects re-acceleration of electrons may be needed. The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources. The linear sizes of FRI and FRII sources make it unlikely that many FRII's evolve into FRI's. A brief discussion is given of the possibility that radio sources go through different cycles of activity.
The VLA-VIRMOS Deep Field I. Radio observations probing the microJy source population
M. Bondi. P. Ciliegi,G. Zamorani,L. Gregorini,G. Vettolani,P. Parma,H. de Ruiter,O. Le Fevre,M. Arnaboldi,L. Guzzo,D. Maccagni,R. Scaramella,C. Adami,S. Bardelli,M. Bolzonella,D. Bottini,A. Cappi,S. Foucaud,P. Franzetti,B. Garilli,S. Gwyn O. Ilbert,A. Iovino,V. Le Brun,B. Marano,C. Marinoni,H. J. McCracken,B. Meneux,A. Pollo,L. Pozzetti,M. Radovich,V. Ripepi,D. Rizzo,M. Scodeggio,L. Tresse,A. Zanichelli,E. Zucca
Physics , 2003, DOI: 10.1051/0004-6361:20030382
Abstract: We have conducted a deep survey (r.m.s noise 17 microJy) with the Very Large Array (VLA) at 1.4 GHz, with a resolution of 6 arcsec, of a 1 square degree region included in the VIRMOS VLT Deep Survey. In the same field we already have multiband photometry down to I(AB)=25, and spectroscopic observations will be obtained during the VIRMOS VLT survey. The homogeneous sensitivity over the whole field has allowed to derive a complete sample of 1054 radio sources (5 sigma limit). We give a detailed description of the data reduction and of the analysis of the radio observations, with particular care to the effects of clean bias and bandwidth smearing, and of the methods used to obtain the catalogue of radio sources. To estimate the effect of the resolution bias on our observations we have modelled the effective angular-size distribution of the sources in our sample and we have used this distribution to simulate a sample of radio sources. Finally we present the radio count distribution down to 0.08 mJy derived from the catalogue. Our counts are in good agreement with the best fit derived from earlier surveys, and are about 50 % higher than the counts in the HDF. The radio count distribution clearly shows, with extremely good statistics, the change in the slope for the sub-mJy radio sources.
Social Presence and Use of Internet-Delivered Interventions: A Multi-Method Approach
Rik Crutzen, Dianne Cyr, Hector Larios, Robert A. C. Ruiter, Nanne K. de Vries
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0057067
Abstract: Objective Internet-delivered interventions can effectively change health risk behaviors and their determinants, but adherence to intervention websites once they are accessed is very low. This study tests whether and how social presence elements can increase website use. Methods A website about Hepatitis A, B, and C virus infections was used in a preparatory lab-based eye-tracking study assessing whether social presence elements attract participants' attention, because this is a prerequisite for affecting website use. In the following field study, 482 participants representative of the Dutch population were randomized to either a website with or a website without social presence elements. Participants completed a questionnaire of validated measures regarding user perceptions immediately after exposure to the website. Server registrations were used to assess website use. Results Participants in the experimental condition focused on the social presence elements, both in terms of frequency (F(1, 98) = 40.34, p<.001) and duration (F(1, 88) = 39.99, p<.001), but did not differ in website use in comparison with the control condition; neither in terms of the number of pages visited (t(456) = 1.44, p = .15), nor in terms of time on the website (t(456) = 0.01, p = .99). Conclusions Adding social presence elements did not affect actual use of an intervention website within a public health context. Possible reasons are limited attention for these elements in comparison with the main text and the utilitarian value of intervention websites.
Radiative ages in a representative sample of low luminosity radio galaxies
P. Parma,M. Murgia,R. Morganti,A. Capetti,H. R. de Ruiter,R. Fanti
Physics , 1998,
Abstract: Two frequency observations, mainly at 1.4 and 5 GHz from the VLA, have been used to study spectral variations along the lobes of some nearby low luminosity radio galaxies that constitute a representative sample selected from the B2 catalogue. The variations of the spectral index have been interpreted as being due to synchrotron and inverse Compton losses and characteristic spectral ages are deduced for the relativistic electrons. The radiative ages are in the range of several 10^7 years. These ages correlate well with the source sizes. They also appear to be consistent with dynamical ages determined from ram-pressure arguments, if we make reasonable assumptions about the ambient gas density and allow for very moderate deviations from the equipartition conditions. There appears to be a significant difference between the radiative ages of sources in our sample and those of more powerful 3CR radio sources. We briefly discuss the possibility of re-acceleration processes and indicate some objects where these may occur.
The HST survey of the B2 sample of radio-galaxies: optical nuclei and the FRI/BL Lac unified scheme
A. Capetti,A. Celotti,M. Chiaberge,H. R. de Ruiter,R. Fanti,R. Morganti,P. Parma
Physics , 2001, DOI: 10.1051/0004-6361:20011714
Abstract: We examine the optical properties of the nuclei of low luminosity radio-galaxies using snapshot HST images of the B2 sample. In agreement with the results obtained from the analysis of the brighter 3C/FRI sample, we find a correlation between fluxes (and luminosities) of the optical and radio cores. This provides further support for the interpretation that the optical nuclear emission in FRI is dominated by synchrotron emission and that accretion in these sources takes place in a low efficiency radiative regime. In the framework of the FRI/BL Lacs unified scheme, we find that the luminosity difference between FRI and BL Lac nuclei can be reproduced with a common beaming factor in both the radio and the optical band, independent of the extended radio luminosity, thus supporting such a scenario. The corresponding bulk Lorentz factor is significantly smaller than is expected from observational and theoretical considerations in BL Lacs: this can be interpreted as due to a velocity structure in the jet, with a fast spine surrounded by a slower layer.
The HST snapshot survey of the B2 sample of low luminosity radio-galaxies: a picture gallery
A. Capetti,H. R. de Ruiter,R. Fanti,R. Morganti,P. Parma,M. -H. Ulrich
Physics , 2000,
Abstract: A Hubble Space Telescope snapshot survey of the B2 sample of low luminosity radio galaxies has, at present, produced V and I images of 41 objects. Together with 16 images of B2 sources taken from the HST archive, there are now high resolution optical data for 57 % of the sample. All host galaxies are luminous ellipticals, except one which is a spiral galaxy, while another one turns out to be a misidentification. We present an album of the images of the B2 radio galaxies observed so far, and give a brief description of the optical morphology of the galaxies. Dust features (in the form of disks, lanes or irregular patches) are seen in most of the galaxies of the sample, 58 %. Compact optical cores are also very common (18/57). A preliminary analysis has revealed the presence of an optical jet in three objects, indicating they can be detected in a sizeable percentage in these low luminosity radio sources. Brightness profiles of dust-free galaxies are well represented by a Nuker law and all shows the existence of a resolved shallow cusp.
The Nature of the Faint Radio Population
I. Prandoni,L. Gregorini,P. Parma,H. R. de Ruiter,G. Vettolani,M. Wieringa,R. Ekers
Physics , 2001,
Abstract: We present the results obtained so far from the optical follow-up of the ATESP sub-mJy radio survey. The ATESP results are then compared with the ones obtained from other deep radio samples and we show how the existing discrepancies about the nature of the faint radio population can be explained in terms of selection effects.
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