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Observation Time (observation + time)
Selected AbstractsJoint Modeling and Analysis of Longitudinal Data with Informative Observation TimesBIOMETRICS, Issue 2 2009Yu Liang Summary In analysis of longitudinal data, it is often assumed that observation times are predetermined and are the same across study subjects. Such an assumption, however, is often violated in practice. As a result, the observation times may be highly irregular. It is well known that if the sampling scheme is correlated with the outcome values, the usual statistical analysis may yield bias. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times via latent variables. A two-step estimation procedure is developed for parameter estimation. We show that the resulting estimators are consistent and asymptotically normal, and that the asymptotic variance can be consistently estimated using the bootstrap method. Simulation studies and a real data analysis demonstrate that our method performs well with realistic sample sizes and is appropriate for practical use. [source] Design and Analysis of Arm-in-Cage Experiments: Inference for Three-State Progressive Disease Models with Common Periodic Observation TimesBIOMETRICS, Issue 2 2008B. A. Griffin Summary We develop statistical methods for designing and analyzing arm-in-cage experiments used to test the efficacy of insect repellents and other topical treatments. In these experiments, a controlled amount of the treatment is applied to a volunteer's forearm, which then is exposed to the insects by being placed into a special cage. Arms are not kept in the cages continuously, but rather placed there periodically for a brief period of time, during which it is noted whether an insect lands (but does not bite) or (lands and) bites. Efficacy of a repellent can be described using a progressive three-state model in which the first two states represent varying degrees of protection (no landing and landing without biting) and the third state occurs once protection is completely lost (biting). Because subjects within a treatment group follow the same cage visit schedule, transition times between states are interval censored into one of several fixed intervals. We develop an approach that uses a mixture of nonparametric and parametric techniques for estimating the parameters of interest when sojourn times are dependent. Design considerations for arm-in-cage experiments are addressed and the proposed methods are illustrated on data from a recent arm-in-cage experiment as well as simulated data. [source] Clinical and histological alterations in the surrounding periodontium of dog's teeth submitted for an intrusive luxationDENTAL TRAUMATOLOGY, Issue 3 2008Janaína Cristina Gomes An impact device was used on 12 teeth of six adult dogs with the purpose of making a dislocation on the long axis of these teeth. Of the teeth that suffer intrusion luxation, two did not receive treatment and ten were replaced by orthodontic extrusion with activated springs of 100 gf. The traction was initiated either immediately after the trauma or 7 days later. Observation time was 40 days. Endodontic therapy with calcium hydroxide was performed on the fourteenth day after the intrusive luxation. The intruded teeth that did not receive appropriate treatment had signs of extensive and progressive inflammatory resorption. The teeth that were moved immediately after the trauma had lesser degree of replacement resorption compared with those that were extruded 7 days after the trauma. [source] Complement analysis in children with idiopathic membranoproliferative glomerulonephritis: A long-term follow-upPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 3 2001Rainer Schwertz Fifty children with idiopathic membranoproliferative glomerulonephritis (MPGN), aged 2,14 years at apparent onset, were monitored for the presence of C3 nephritic factor (C3 NeF) and signs of complement activation in serum. In addition, C3 allotyping was performed in 32 patients. Observation time ranged from 2 to 20 (median 11) years. C3 NeF activity was detected at least once in 60% of the patients (in 11 of 26 with type I, in 15 of 17 with type II, and in four of seven with type III). C3 NeF-positive patients had significantly reduced levels of CH50 and C3 and elevated levels of C3dg/C3d. During follow-up, C3 levels were persistently normal in 62% of the patients with MPGN type I and in 43% with type III but in only 18% with type II. C3 allotype frequencies differed from those found in healthy controls with a significant shift to the C3F/C3FS variants in C3 NeF-positive patients. C3b(Bb)P as a marker for alternative pathway activation was not increased in C3 NeF-positive patients. Despite the presence of C3 NeF activity, C3 levels remained normal in six patients throughout the observation period. C3 NeF became undetectable in six patients, whereas seven developed C3 NeF activity during follow-up. There was no significant difference in renal survival probability in patients with or without C3 NeF activity. Neither C3 variants nor continous low C3 or low CH50 levels had any prognostic value for the clinical outcome. No factor H deficiency was detected. [source] Healing and prognosis of teeth with intra-alveolar fractures involving the cervical part of the rootDENTAL TRAUMATOLOGY, Issue 2 2002Miomir Cvek Abstract Healing and long-term prognosis of 94 cervical root fractures were evaluated. The teeth were divided into two groups according to type of fracture: transverse fractures limited to the cervical third of the root (51 incisors) and oblique fractures involving both the cervical and middle parts of the root (43 incisors). Neither the frequency nor the type of fracture healing differed significantly between the two groups. In the material as a whole, healing of the fracture with hard tissue formation was observed in 17 teeth (18%), and healing with interposition of periodontal ligament (PDL) and, in some cases, hard tissue between the fragments in 62 teeth (66%). Fifteen teeth (16%) showed no healing and a radiolucency adjacent to the fracture. Statistical analyses revealed that incomplete root formation and a positive sensibility test at the time of injury were significantly related to both healing and hard tissue repair. The same applied to concussion or subluxation compared with dislocation of coronal fragment, as well as optimal compared with suboptimal reposition of displaced coronal fragments. The type and duration of splinting (or no splinting) appeared to be of no significance for frequency or type of healing of cervical root fractures. During the observation time (mean = 75 months), 19 (44%) of the teeth with transverse fractures and 3 (8%) of those with oblique fractures were lost after healing. In conclusion, fractures in the cervical part of the root had a healing potential and the predictive parameters identified for fractures in other parts of the root seemed to be valid for the healing of cervical root fractures. Transverse fractures appeared to have a significantly poorer long-term prognosis compared to oblique fractures, apparently due to a marked post-treatment mobility, which often led to new luxation caused by even minor impacts. [source] Relationship between GABAergic interneurons migration and early neocortical network activityDEVELOPMENTAL NEUROBIOLOGY, Issue 2-3 2009Ana D. de Lima Abstract Available evidence converges to suggest that during the early development of the cerebral cortex, the emergence of the spontaneous network activity chronologically overlap with the end of the cell migration period in the developing cortex. We approached the functional regulation of neuronal migration in a culture model of neocortical networks, using time lapses to detect migratory movements, calcium-imaging to assess the activity of migratory neurons, and immunocytochemical methods to identify the migratory cells retrospectively. In cell cultures, early physiological development and cell migration are reproduced at a local network level, thus allowing the study of the interrelationships between cell migration and network development independent of the topographical complexity. Neurons migrate at least until 12 days in vitro and GABAergic neurons migrate faster compared with non-GABAergic neurons. A decline of migratory activity was coincident with the development of spontaneous synchronous network activity. Migrating interneurons did not participate in synchronous network activity, but interneurons that ended cell migration during observation time frequently engaged in synchronous activity within less than an hour. Application of GABAA and ionotropic glutamate receptor antagonists significantly increased the number of migrating GABAergic neurons without changing the dynamics of the migratory movements. Thus, neurotransmitters released by early network activity might favor the termination of neuronal migration. These results reinforce the idea that network activity plays an important role in the development of late-born GABAergic cells. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Successful angiographic embolization of recurrent elbow and knee joint bleeds in seven patients with severe haemophiliaHAEMOPHILIA, Issue 1 2009R. KLAMROTH Summary., In haemophilic joints with high-grade arthropathy, bleeds occur that do not respond to replacement therapy of the deficient coagulation factor. The reason may be pathologically reactive angiogenesis in chronic synovitis. Seven patients with severe haemophilia A or haemophilia B experienced recurrent massive bleeds of one elbow joint or knee joint in the absence of trauma. After initial application of factor VIII or IX (fVIII/fIX; 50 IU kg,1 bodyweight), there was only slow and never complete relief of symptoms. Despite intensive secondary prophylaxis maintaining the plasma level of factor concentrate at minimum 50%, new massive bleeds at the same location occurred. Vascular bleeding was suspected. Angiography of the arteries was performed via the femoral artery. Vessels identified as potential bleeding sources were embolized with embolization fluid (ONYX) in eight joints (six elbow and two knee joints). Under low-dose prophylactic treatment (15 IU fVIII or fIX per kg bodyweight for three times per week), no recurrent severe bleed unresponsive to coagulation factor replacement occurred after a mean observation time of 16 months after embolization. The consumption of factor concentrate decreased to one-third of the amount consumed before embolization. In conclusion, angiographic embolization with a non-adhesive liquid embolic agent might be considered as a promising therapeutic and coagulation factor saving option in joint bleeds not responding to replacement of coagulation factor to normal levels. [source] A Comparison of CV-Catheters (CV) Grafts (GR) and Fistulae (FI) in Quotidian HemodialysisHEMODIALYSIS INTERNATIONAL, Issue 1 2003C Kjellstrand We studied longevity and complications from CV, GR, and FI in 23 patients on quotidian hemodialysis. There were a total of 409 patient months, mean 18,10 months observation and a total of 9209 dialyses. There were 14 FI, 5 GR and 4 CV. 1, 1 and 2 replacements were necessary during a total observation time of 254, 105 and 50 patient months, respectively. For fistulae there were 0.02 replacements/year vs. 0.30 for GR and 0.41 for CV. P = 0.042 FI vs. other. The cumulative survival at 15 months was 100% for FI, 80% for GR and 20% for CV. P = 0.041. The cumulative survival at 3 years were 80% for fistulae and grafts, no CV lasted beyond 15 months. P = 0.013. There were 27 events requiring hospitalization or outpatient intervention. FI: 0.42/patient year, GR 1.22/patient year and CV 1.36/patient year. P = 0.080, FI vs. Other. Patients reported more problems between dialysis for FI, 3.2% of the days and least on GR (0.2%), CV (0.4%). P < 0.0001. Of the problems 85% were pain and redness. To the contrary there were more problems during dialysis with CV, 9.1% vs. FI 2.7%, and GR 0.9%. P < 0.0001. The complications and survival data are similar to those reported by others for quotidian hemodialysis and no different from reports on conventional 3 times per week dialyses. Conclusion: Daily hemodialysis does not adversely affect the different types of blood access. The survival and intervention need of accesses is best for fistulae, worst for CV, but GR, when functioning, have fewer problems between and during dialyses. [source] Emotional availability: Differential predictions to infant attachment and kindergarten adjustment based on observation time and contextINFANT MENTAL HEALTH JOURNAL, Issue 4 2005Zeynep Biringen Two studies are used to illustrate the importance of context and length of time in the use of the Emotional Availability Scales (EAS) to predict aspects of child development. The purpose of the first study was to examine whether prediction of attachment by the EAS is better with increasing amounts of time. We scored emotional availability (EA) every 15 min for a total of 2 hr, with correlations showing an increasingly stronger relation with attachment with increasing time. In addition, difference scores were calculated between the first and the last 15 min for each EAS dimension. The difference score was significantly higher for the insecure group, suggesting that we need more observation time for the prediction of insecure attachments than is the case for the prediction of secure attachments. The second study investigated whether EA is differentially predictive based on context. We explored play contexts versus reunion contexts. We also explored the relations with other indices of child development. Results revealed that some dimensions of EA (e.g., maternal nonhostility) are difficult to detect outside of a stress context. Maternal nonhostility during the reunion (but not the play situation) was correlated with child aggression in the kindergarten classroom. In addition, most dimensions of EA assessed in the reunion context were better predictors of teacher reports of kindergarten adjustment than was EA assessed in the play situation. [source] Larger tidal volume increases sevoflurane uptake in blood: a randomized clinical studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010B. ENEKVIST Background: The rate of uptake of volatile anesthetics is dependent on alveolar concentration and ventilation, blood solubility and cardiac output. We wanted to determine whether increased tidal volume (VT), with unchanged end-tidal carbon dioxide partial pressure (PETCO2), could affect the arterial concentration of sevoflurane. Methods: Prospective, randomized, clinical study. ASA physical status 2 and II patients scheduled for elective surgery of the lower abdomen were randomly assigned to one of the two groups with 10 patients in each: one group with normal VT (NVT) and one group with increased VT (IVT) achieved by increasing the inspired plateau pressure 0.04 cmH2O/kg above the initial plateau pressure. A corrugated tube added extra apparatus dead space to maintain PETCO2 at 4.5 kPa. The respiratory rate was set at 15 min,1, and sevoflurane was delivered to the fresh gas by a vaporizer set at 3%. Arterial sevoflurane tensions (Pasevo), Fisevo, PETsevo, PETCO2, PaCO2, VT and airway pressure were measured. Results: The two groups of patients were similar with regard to gender, age, weight, height and body mass index. The mean PETsevo did not differ between the groups. Throughout the observation time, arterial sevoflurane tension (mean±SE) was significantly higher in the IVT group compared with the NVT group, e.g. 1.9±0.23 vs. 1.6±0.25 kPa after 60 min of anesthesia (P<0.05). Conclusion: Ventilation with larger tidal volumes with isocapnia maintained with added dead-space volume increases the tension of sevoflurane in arterial blood. [source] Gentamicin used as an adjunct to GTRJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 5 2003An experimental study in rats Abstract Objectives: To evaluate in a discriminating "capsule" model whether local application of gentamicin may have an added effect on bone formation produced by Bio-Oss® and guide tissue regeneration (GTR). Material and Methods: Thirty male 3-month-old Wistar rats were used. After elevation of muscle-periosteal flaps, a rigid hemispherical Teflon capsule, loosely packed with 0.025 g of Bio-Oss® impregnated with 2 mg/ml gentamicin sulfate (Garamycin®), was placed with its open part facing the lateral bone surface of the mandibular ramus (test) in one side of the jaw. A capsule filled only with Bio-Oss® (control) was placed on the contralateral side of the jaw. After healing periods of 1, 2 and 4 months, groups of 10 animals were sacrificed and the specimens were processed for histological examination. The volumes of (1) the space created by the capsule, (2) newly formed bone, (3) Bio-Oss® particles, (4) loose connective tissue, and (5) acellular space in the capsule were estimated by a point-counting technique in three to four histological sections of each specimen, taken by uniformly random sampling. Results: The histological evaluation showed limited but increasing bone fill in the capsules from 1 to 4 months in both the test and control sides. After 4 months, the newly formed bone occupied 11.9% (CV: 0.39) of the space created by the capsules at the test sides versus 13.2% (CV: 0.41) at the control sides. There was no statistical significant difference between test and control specimens at any observation time (p>0.05). Conclusion: It is concluded that local application of gentamicin has no added effect on bone formation when combined with Bio-Oss® and GTR. Zussamenfassung Gentamycin als Adjunktiv zur GTR genutzt. Eine experimentelle Studie bei Ratten Ziele:Überprüfung in einem "unterscheidenden" Kapselmodell, ob die lokale Applikation von Gentamycin einen zusätzlichen Effekt bei der Knochenbildung, die durch Bio-Oss® bei der GTR hervorgerufen wurde, hat. Material und Methoden: 30 männliche 3monatige Wistar-Ratten wurden genutzt. Nach der Elevation von Muskel-Periost-Lappen wurde eine rigide halbsphärische Teflonkapsel, die locker mit 0,025 g von Bio-Oss®, was mit Gentamycinsulfat 2mg/ml (Garamycin®) imprägniert war, auf einer Seite des Unterkieferramus (Test) so platziert, dass der offene Teil zur lateralen Knochenoberfläche gerichtet war. Eine Kapsel, die nur mit Bio-Oss gefüllt war (Kontrolle), wurde auf der kontralateralen Seite des Kiefers platziert. Nach der Heilungsperiode von 1, 2 und 4 Monaten wurden Gruppen von 10 Tieren getötet und die Proben für die histologische Überprüfung aufbereitet. Das Volumen von 1) dem Spalt, der durch die Kapsel geschaffen wurde, 2) dem neu gebildeten Knochen, 3) den Bio-Oss Partikeln, 4) dem lockeren Bindegewebe und 5) dem azellulären Spalt in der Kapsel wurden mit einer Punktzähltechnik in 3 bis 4 histologischen Schnitten von jeder Probe unter Nutzung einer allgemeinen Zufallsauswahl bestimmt. Ergebnisse: Die histologische Überprüfung zeigte eine limitierte aber zunehmende Knochenfüllung in der Kapsel vom 1. zum 4. Monat sowohl in der Test- als auch der Kontrollseite. Nach 4 Monaten besetzte der neu gebildete Knochen 11,9% (cv: 0,39) des von der Kapsel geschaffenen Spaltes bei den Testseiten verglichen mit 13,2% (cv: 0,41) bei den Kontrollseiten. Es gab keine statistisch signifikante Differenz zwischen Test- und Kontrollproben zu irgendeiner Beobachtungszeit (p>0,05). Schlussfolgerung: Es wird geschlossen, dass die lokale Applikation von Gentamycin keinen zusätzlichen Effekt auf die Knochenbildung hat, wenn eine Kombination mit Bio-Oss und der GTR erfolgt. Résumé La gentamycine utilisée en association à la GTR. Une étude expérimentale chez le rat Le but de cette étude a été d'évaluer si l'application locale de gentamycine dans un modèle de capsule discriminatoire pouvait avoir un effet additionnel bénéfique sur la formation osseuse produite par le Bio-Oss® et la GTR. Cette étude a eu recours à trente rats Wistar mâles de trois mois. Après l'élévation de lambeaux muscle-périoste, une capsule en téflon hémisphérique rigide, remplie de manière lâche avec 0,025 g de Bio-Oss® imprégnée avec 2mg/ml de sulfate de gentamycine (Garamycin®) a été placée avec sa face ouverte en regard de la surface osseuse latérale de la branche mandibulaire (test) d'un côté de la mâchoire. Une capsule remplie uniquement de Bio-Oss® (contrôle) a été placée dans le site contralatéral. Après des périodes de guérison de un, deux et quatre mois, des groupes de dix animaux ont été tués et les spécimens analysés histologiquement. Les volumes de 1) l'espace créé par la capsule, 2) l'os néoformé, 3) les particules de Bio-Oss®, 4) le tissu conjonctif lâche et 5) l'espace acellulaire dans la capsule ont été estimés par la technique de comptage par points dans trois à quatre coupes histologiques de chaque échantillon, pris de manière uniformément et randomisée. L'évaluation histologique a montré une augmentation limitée d'os dans les caspsules de un à quatre mois tant dans les sites tests que contrôles. Après quatre mois l'os néoformé occupait 11,9% (cv : 0,39) de l'espace créé par les capsules au niveau des sites tests vs 13,2% (cv : 0,41) au niveau des contrôles. Il n'y avait aucune différence statistique entre les échantillons tests et contrôles à aucun des temps d'observation (p>0,05). L'application locale de gentamycine n'aurait donc aucun effet sur la formation osseuse lorsqu'elle est placée avec le Bio-Oss® en association avec la GTR. [source] Determinants of Serum Creatinine Trajectory in Acute Contrast NephropathyJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 5 2002NOEL V. GUTTTEREZ M.D. The aim of this study was to describe the trajectory of creatinine (Cr) rise and its determinants after exposure to radiocontrast media. Included were 98 subjects who underwent cardiac catheterization and were randomized to forced diuresis with IV crystalloid, furosemide, mannitol (if pulmonary capillary wedge pressure was<20 mmHg), and low dose dopamine versus intravenous crystalloid and matching placebos. Baseline and postcatheterization serum Cr levels were analyzed in a longitudinal fashion, allowing for differences in the time between blood draws, to determine the different critical trajectories of serum Cr. The mean age, baseline serum Cr, and Cr clearance (CrCl) were 69.3 ± 10.8 years, 2.5 ± 0.9 mg/dL, and 31.4 ± 12.1 mL/min, respectively. The clinically driven postprocedural observation time was 5.5 ± 5.1 days (range 19 hours and one Cr value to 25.7 days and 18 values). The mean maximum Cr was 3.3 ± 1.4, range 1.7,8.7 mg/dL). Longitudinal models support baseline Cr clearance predictions for the change in Cr at 24 hours, time as the determinant of Cr trajectory, and requisite monitoring. For any given individual, a rise in Cr of , 0.5 mg/dL in the first 24 hours after contrast exposure predicted a favorable outcome. Baseline renal function is the major determinant of the rate of rise, height, and duration of Cr trajectory after contrast exposure. Length of observation and frequency of laboratory measures can be anticipated from these models. [source] Rehabilitation by means of osseointegrated implants in oral cancer patients with about four to six years follow-upJOURNAL OF ORAL REHABILITATION, Issue 3 2006J. SEKINE summary, This paper describes the reconstruction of mandibular defects in four oral cancer patients using iliac crest bone grafts and osseointegrated implants. In three patients, reconstructive surgery using a reconstruction plate and free forearm skin flap was performed following tumour and segmental mandibular resection. After 7,9 months, mandibular reconstruction with a free iliac bone graft was carried out. In one patient, reconstructive surgery was performed with vascularized iliac bone grafting with an anterolateral thigh flap at the same time as the tumour resection. Fixtures were placed in the transplanted bone, and abutments were connected 6,9 months later together with vestibuloplasty. Gingival grafts were used to replace the skin flap around abutments. All implants survived throughout the approximately 4,6 years observation time. Marginal bone loss of the graft was originally several millimetres but less than 1·5 mm. Bone loss as well as management of peri-implant soft tissue was also discussed. [source] Activation of large lons in FT-ICR mass spectrometryMASS SPECTROMETRY REVIEWS, Issue 2 2005Julia Laskin Abstract The advent of soft ionization techniques, notably electrospray and laser desorption ionization methods, has enabled the extension of mass spectrometric methods to large molecules and molecular complexes. This both greatly extends the applications of mass spectrometry and makes the activation and dissociation of complex ions an integral part of these applications. This review emphasizes the most promising methods for activation and dissociation of complex ions and presents this discussion in the context of general knowledge of reaction kinetics and dynamics largely established for small ions. We then introduce the characteristic differences associated with the higher number of internal degrees of freedom and high density of states associated with molecular complexity. This is reflected primarily in the kinetics of unimolecular dissociation of complex ions, particularly their slow decay and the higher energy content required to induce decomposition,the kinetic shift (KS). The longer trapping time of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) significantly reduces the KS, which presents several advantages over other methods for the investigation of dissociation of complex molecules. After discussing general principles of reaction dynamics related to collisional activation of ions, we describe conventional ways to achieve single- and multiple-collision activation in FT-ICR MS. Sustained off-resonance irradiation (SORI),the simplest and most robust means of introducing the multiple collision activation process,is discussed in greatest detail. Details of implementation of this technique, required control of experimental parameters, limitations, and examples of very successful application of SORI-CID are described. The advantages of high mass resolving power and the ability to carry out several stages of mass selection and activation intrinsic to FT-ICR MS are demonstrated in several examples. Photodissociation of ions from small molecules can be effected using IR or UV/vis lasers and generally requires tuning lasers to specific wavelengths and/or utilizing high flux, multiphoton excitation to match energy levels in the ion. Photodissociation of complex ions is much easier to accomplish from the basic physics perspective. The quasi-continuum of vibrational states at room temperature makes it very easy to pump relatively large amounts of energy into complex ions and infrared multiphoton dissociation (IRMPD) is a powerful technique for characterizing large ions, particularly biologically relevant molecules. Since both SORI-CID and IRMPD are slow activation methods they have many common characteristics. They are also distinctly different because SORI-CID is intrinsically selective (only ions that have a cyclotron frequency close to the frequency of the excitation field are excited), whereas IRMPD is not (all ions that reside on the optical path of the laser are excited). There are advantages and disadvantages to each technique and in many applications they complement each other. In contrast with these slow activation methods, the less widely appreciated activation method of surface induced dissociation (SID) appears to offer unique advantages because excitation in SID occurs on a sub-picosecond time scale, instantaneously relative to the observation time of any mass spectrometer. Internal energy deposition is quite efficient and readily adjusted by altering the kinetic energy of the impacting ion. The shattering transition,instantaneous decomposition of the ion on the surface,observed at high collision energies enables access to dissociation channels that are not accessible using SORI-CID or IRMPD. Finally, we discuss some approaches for tailoring the surface to achieve particular aims in SID. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:135,167, 2005 [source] Proportional Intensity Models Robustness with Overhaul IntervalsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 3 2006Shwu-Tzy Jiang Abstract The class of semi-parametric proportional intensity (PI) models applies to recurrent failure event modeling for a repairable system with explanatory variables (covariates). Certain repairable systems (e.g. aircraft and electrical power generating plants) experience a substantial period of downtime due to performing maintenance (i.e. major overhaul) at scheduled intervals or following a major failure. Other systems (e.g. emergency power units) experience extended periods of non-operating dormancy. These discontinuities in observation time have potential effects on the accuracy of estimation for covariate effects, particularly where calendar time is the life metric. This paper examines the robustness of two PI methods (Prentice,Williams,Peterson gap time (PWP-GT) and Andersen,Gill (AG)) as a function of the overhaul or dormancy duration. The PWP-GT model proves to perform well for sample size of 60 (30 per level of a class covariate), constant or moderately decreasing/increasing rate of occurrence of failures, and relative overhaul (dormancy) durations less than half of the immediately preceding interval between failures. The AG model performs consistently well for a small sample size of 20 (10 per level of a class covariate) for homogeneous Poisson processes, regardless of the relative overhaul (dormancy) duration. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of data selection and error specification on the assimilation of AIRS data,THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 622 2007J. Joiner Abstract The Atmospheric InfraRed Sounder (AIRS), flying aboard NASA's Aqua satellite with the Advanced Microwave Sounding Unit-A (AMSU-A) and four other instruments, has been providing data for use in numerical weather prediction and data assimilation systems for over three years. The full AIRS data set is currently not transmitted in near-real-time to the prediction/assimilation centres. Instead, data sets with reduced spatial and spectral information are produced and made available within three hours of the observation time. In this paper, we evaluate the use of different channel selections and error specifications. We achieve significant positive impact from the Aqua AIRS/AMSU-A combination during our experimental time period of January 2003. The best results are obtained using a set of 156 channels that do not include any in the H2O band between 1080 and 2100 cm,1. The H2O band channels have a large influence on both temperature and humidity analyses. If observation and background errors are not properly specified, the partitioning of temperature and humidity information from these channels will not be correct, and this can lead to a degradation in forecast skill. Therefore, we suggest that it is important to focus on background error specification in order to maximize the impact from AIRS and similar instruments. In addition, we find that changing the specified channel errors has a significant effect on the amount of data that enters the analysis as a result of quality control thresholds that are related to the errors. However, moderate changes to the channel errors do not significantly impact forecast skill with the 156 channel set. We also examine the effects of different types of spatial data reduction on assimilated data sets and NWP forecast skill. Whether we pick the centre or the warmest AIRS pixel in a 3 × 3 array affects the amount of data ingested by the analysis but does not have a statistically significant impact on the forecast skill. Copyright © Published in 2007 by John Wiley & Sons, Ltd. [source] Serum concentration of baseline mast cell tryptase: evidence for a decline during long-term immunotherapy for Hymenoptera venom allergyCLINICAL & EXPERIMENTAL ALLERGY, Issue 4 2010S. Dugas-Breit Summary Background Baseline serum mast cell tryptase concentration (BTC) is thought to reflect the constitutive mast cell load or activity of an individual patient. Little is known about the individual stability of BTC during long-term venom immunotherapy (VIT). Objective To investigate the intra-individual stability of BTC over time in patients with Hymenoptera venom allergy. Methods Three hundred and two patients were studied. BTC was measured before and at least twice during VIT. At least 4 weeks lay between BTC measurements and the most recent field sting, in-hospital sting, or preceding venom injection. Multifactorial mixed linear models were used to analyse BTC changes over time. Results Median observation time was 4.2 years (range 2,12 years). Before VIT, the median BTC was 6.8 ,g/L (range 1.14,177 ,g/L). The median coefficient of variation (CV) over time was 15.3% (range 1.9,63.8%). The median CV was significantly smaller in patients presenting with an elevated BTC (>11.4 ,g/L) than in patients with a normal BTC (11.4%, range 2.6,39.5%; vs. 17.6%, range 1.9, 63.8%; P<0.001). During VIT and after adjusting for age and gender, we found a slight but significant decrease of BTC over time (2.5% per year, 95% confidence interval 2.0,3.0%, P<0.001). Conclusion Individual variation of BTC during VIT does not rise when BTC is increased before therapy. VIT is associated with a small, but continuous decrease of BTC over time possibly indicating a dampened mast cell function or a decline in mast cell burden. Cite this as: S. Dugas-Breit, B. Przybilla, M. Dugas, A. Arnold, G. Pfundstein, H. Küchenhoff and F. Ruëff, Clinical & Experimental Allergy, 2010 (40) 643,649. [source] Syncrystallization: A Technique for Temporization of Immediately Loaded Implants with Metal-Reinforced Acrylic Resin RestorationsCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 3 2006Marco Degidi MD ABSTRACT Background, Rigid temporization has been recognized to have a significant impact on the peri-implant tissue response in immediate implant loading since it reduces the mechanical stress exerted on each implant. Purpose, A successful protocol for immediate loading of multiple implants depends on an adequate fixation and immobility of the implants to prevent the risk of micromovements in relation to the surrounding bone. The objective of this article was to evaluate a prosthetic concept for an accelerated rigid splinting of multiple implants for same-day immediate loading with metal-reinforced provisional restorations using a technique of welding temporary implant abutments with a prefabricated titanium bar directly in the oral cavity (syncrystallization). Materials and Methods, Between June 2004 and January 2005, immediate loading of threaded implants with a metal- reinforced acrylic resin provisional restoration at stage 1 surgery was evaluated in 40 consecutive patients. A total of 192 implants were placed in selected edentulous or partially edentulous patients using the syncrystallization technique. Once the titanium bar was welded intraorally to the abutments, opaque was applied and the provisional restoration was relined and screw-retained the same day. In addition, a comparison of deformations and stress distributions in implant-supported, metal-reinforced and nonmetal-reinforced resin provisional restorations was analyzed in the edentulous mandible by a three-dimensional finite element model (FEM). Results, All of the 192 rigidly temporized immediately loaded implants osseointegrated. An implant success rate of 100% was achieved over a period of 6 months postplacement. No fracture or luting cement failure of the provisional restoration occurred during the observation time. Compared to mere acrylic superstructures, a significant reduction of deformation and strain within metal-reinforced provisional restorations was detected by FEM analysis. Conclusion, The results of this study indicate that the syncrystallization technique allows an expedite and adequate rigid splinting of multiple immediately loaded implants. The advantages of the technique are: (1) reduction of treatment time for immediate temporization at stage 1 surgery; (2) predictable fixation and immobility of implants in the early stages of bone healing; and (3) less time for repairing provisional restorations as a result of no or rare fracture. [source] Significance of primary stability for osseointegration of dental implantsCLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2006Natalia Lioubavina-Hack Abstract Aim: To investigate the significance of the initial stability of dental implants for the establishment of osseointegration in an experimental capsule model for bone augmentation. Material and methods: Sixteen male rats were used in the study. In each rat, muscle-periosteal flaps were elevated on the lateral aspect of the mandibular ramus on both sides, resulting in exposure of the bone surface. Small perforations were then produced in the ramus. A rigid, hemispherical Teflon® capsule with a diameter of 6 mm and a height of 4 mm and with a hole in its middle portion, prepared to fit the circumference of an ITI® HC titanium implant of 2.8 mm in diameter, was fixed to the ramus using 4 mini-screws. On one side of the jaw, the implant was placed through the hole in such a way that its apex did not make contact with the mandibular ramus (test). This placement of the implant did not ensure primary stability. On the other side of the jaw, a similar implant was placed through the hole of the capsule in such a way that contact was made between the implant and the surface of the ramus (control). This provided primary stability of the implant. After placement of the implants, the soft tissues were repositioned over the capsules and sutured. After 1, 3, 6 and 9 months, four animals were sacrificed and subjected to histometric analysis. Results: The mean height of direct bone-to-implant contact of implants with primary stability was 38.8%, 52.9%, 64.6% and 81.3% of the implant length at 1, 3, 6 and 9 months, respectively. Of the bone adjacent to the implant surface, 28.1%, 28.9%, 52.6% and 69.6%, respectively, consisted of mineralized bone. At the test implants, no bone-to-implant contact was observed at any observation time or in any of these non-stabilized specimens. Conclusion: The findings of the present study indicate that primary implant stability is a prerequisite for successful osseointegration, and that implant instability results in fibrous encapsulation, thus confirming previously made clinical observations. [source] Reconstruction of maxillary and mandibular defects using prefabricated microvascular fibular grafts and osseointegrated dental implants , a prospective studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2004Claude Jaquiéry Abstract: The fibular flap can be used for a variety of indications. Recently, the treatment of four patients with severely atrophied upper jaws using a method to prefabricate the vascularized fibular graft has been published. This technique consists of a two-stage operation procedure that allows simultaneous prosthodontic rehabilitation and immediate placement of dental implants. In this paper eight patients with 29 ITI implants (Straumann AG, Waldenburg, Switzerland) who had reconstruction of either the upper or lower jaw are presented. The aim of the study was (i) to evaluate the behavior of the newly formed soft tissue around implants inserted in the fibula by applying periodontal parameters, (ii) to monitor prospectively the integration of the implants in the fibular graft, and (iii) to assess the osseous integration of the fibular graft used for reconstruction of the upper or lower jaw. Two implants failed during the observation time because of avascular bone at the distal end of the fibular graft. Stabilization of the graft, however, was never compromised. Due to the prefabrication firmly attached gingiva-like soft tissue could be provided preventing periimplant soft tissue inflammation and facilitating oral hygiene. After 1 year of observation the mean attachment level was similar to implants placed in original bone whereas vertical bone loss measured radiographically was lower in the present study. This may indicate that the remodeling of a bicortical bone requires a longer period of time compared with the bone of the alveolar crest. The prospective 1-year results are promising but long-term evaluation of periodontal and radiological parameters are required. Résumé Le lambeau péroné peut être utilisé pour une variété d'indications. Récemment le traitement de quatre patients avec une atrophie sévère des mâchoires supérieures et utilisant une méthode pour préfabriquer un greffon péroné vascularisé a été publié. Cette technique consiste en une opération en deux étapes qui permet la réhabilitation prothétique simultanée et le placement immédiat des implants dentaires. Dans ce rapport huit patients avec 29 implants ITI (Straumann AG, Waldenburg, Switzerland) ont eu une reconstruction de la mâchoire supérieure ou inférieure. Le but de cette étude a été 1) d'évaluer le comportement des tissus mous nouvellement formés autour des implants insérés dans le péroné en appliquant les paramètres parodontaux, 2) de suivre d'une manière prospective l'intégration des implants dans le greffon péroné et 3) d'examiner l'intégration osseuse de l'implant péroné utilisé pour la reconstruction de ces mâchoires. Deux implants ont échoué durant la période d'observation parce que l'os alvéolaire n'était pas vasculariséà la partie distale du greffon. La stabilisation du greffon n'a cependant jamais été compromise. La préfabrication d'un tissu ressemblant à de la gencive préfabriquée a permit d'éviter l'inflammation gingivale et de faciliter l'hygiène buccale. Après une année d'observation le niveau d'attache moyen était semblable au niveau des implants placés dans l'os original tandis que la perte osseuse verticale mesurée radiographiquement était inférieure dans l'étude présente. Ceci peut indiquer que le remodelage de l'os bicortical requiert une période plus importante comparée à l'os du rebord alvéolaire. Ces résultats prospectifs à une année sont encourageants mais l'évaluation à long terme des paramètres parodontaux et radiologiques reste encore nécessaire. Zusammenfassung Der Fibula-Lappen kann bei einer Vielzahl von Indikationen angewendet werden. Kürzlich wurde eine Publikation über die Behandlung von vier Patienten mit stark atrophierten Oberkiefern mittels vorfabrizierten vaskularisierten Fibula transplantaten veröffentlicht. Diese Technik besteht aus einer Operation in zwei Phasen, welche die Sofortimplantation von dentalen Implantaten und gleichzeitige prothetische Rekonstruction erlaubt. In diesem Artikel werden acht Patienten mit 29 Implantaten (Straumann AG, Waldenburg, Switzerland), bei welchen entweder eine OK- oder UK-Rekonstruktion durchgeführt wurde, präsentiert. Das Ziel der Studie war (i) das Verhalten des neu gebildeten Gewebes um die Implantate, welche in die Fibula eingesetzt worden waren mittels parodontalen Parametern zu untersuchen, (ii) die Integration der Implantate in das Fibula-Transplantat prospektiv aufzuzeichnen und (iii) die ossäre Integration des für die Rekonstruktion des OK oder UK verwendeten Fibula-Transplantats zu ermitteln. Zwei Implantate zeigten während der Beobachtungsperiode Misserfolge wegen avaskulärem Knochen an den distalen Enden des Fibula-Transplantats. Die Stabilisierung des Transplantats war jedoch niemals beeinträchtigt. Durch die Vorfabrizierung konnten gut angewachsene gingiva-ähnliche Weichgewebe geschaffen werden, welche eine periimplantäre Entzündung der Weichgewebe verhinderten und die Mundhygiene erleichterten. Nach einer Beobachtungszeit von einem Jahr war das mittlere Attachmentniveau ähnlich dem von Implantaten, welche in alveolären Knochen inseriert worden waren, während der radiologisch gemessene Knochenverlust in der vorliegenden Studie geringer war. Dies könnte ein Indiz dafür sein, dass die Remodellierung eines bikortikalen Knochens im Vergleich zum Alveolarknochen längere Zeit benötigt. Die prospektiven Resultate nach einem Jahr sehen vielversprechend aus, aber es muss eine Auswertung der parodontalen und radiologischen Parameter über einen längeren Zeitraum durchgeführt werden. Resumen El colgajo peroneal puede ser usado para una variedad de indicaciones. Recientemente se ha publicado el tratamiento de cuatro pacientes con maxilares superiores severamente atróficos usando un método para prefabricar el injerto peroneal vascularizado. Esta técnica consiste en un procedimiento de operación de dos fases que permite la rehabilitación prostodóntica y la colocación inmediata de implantes dentales simultáneamente. En este artículo se presentan ocho pacientes con 29 implantes ITI (Strauman AG, Waldenburg) teniendo una reconstrucción de tanto el maxilar superior como del inferior. La intención del presente estudio fue (i) evaluar el comportamiento de del tejido blando neoformado alrededor de los implantes insertados en la tibia aplicando parámetros periodontales, (ii) monitorizar prospectivamente la integración de los implantes en el injerto perineal y (iii) valorar la integración ósea del injerto perineal usado para la reconstrucción del maxilar superior o inferior. Dos implantes fracasaron durante el periodo de observación debido a hueso sin vascularización en el final distal del injerto perineal. De todos modos, la estabilización del injerto no se vio nunca comprometida. Debido a la prefabricación se pudo suministrar un tejido blando tipo encía adherida previniendo inflamación del tejido blando periimplantario y facilitando la higiene oral. Tras un año de observación el nivel de inserción medio fue similar a los implantes insertados en las áreas de hueso original mientras que la pérdida de hueso vertical medida radiograficamente fue menor en el presente estudio. Esto puede indicar que el remodelado de un hueso bicortical requiere un periodo mas largo de tiempo comparado con el hueso de la cresta alveolar. Los resultados prospectivos de un año son prometedores pero se requieren evaluaciones de los parámetros periodontales y radiológicos a largo plazo. [source] Nanometre localization of single ReAsH moleculesJOURNAL OF MICROSCOPY, Issue 3 2004H. PARK Summary ReAsH is a red-emitting dye that binds to the unique sequence Cys-Cys-Xaa-Xaa-Cys-Cys (where Xaa is a noncysteine amino acid) in the protein. We attached a single ReAsH to a calmodulin with an inserted tetracysteine motif and immobilized individual calmodulins to a glass surface at low density. Total internal reflection fluorescence microscopy was used to image individual ReAsH molecules. We determined the centre of the distribution of photons in the image of a single molecule in order to determine the position of the dye within 5 nm precision and with an image integration time of 0.5 s. The photostability of ReAsH was also characterized and observation times ranging from several seconds to over a minute were observed. We found that 2-mercaptoethanesulphonic acid increased the number of collected photons from ReAsH molecules by a factor of two. Individual ReAsH molecules were then moved via a nanometric stage in 25 or 40 nm steps, either at a constant rate or at a Poisson-distributed rate. Individual steps were clearly seen, indicating that the observation of translational motion on this scale, which is relevant for many biomolecular motors, is possible with ReAsH. [source] The impact of stellar oscillations on doppler velocity planet searchesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008S. J. O'Toole ABSTRACT We present a quantitative investigation of the effect of stellar oscillations on Doppler velocity planet searches. Using data from four asteroseismological observation campaigns, we find a power-law relationship between the noise impact of these oscillations on Doppler velocities and both the luminosity-to-mass of the target stars, and observed integration times. Including the impact of oscillation, jitter should improve the quality of Keplerian fits to Doppler velocity data. The scale of the effect these oscillations have on Doppler velocity measurements is smaller than that produced by stellar activity, but is most significant for giant and subgiant stars, and at short integration times (i.e. less than a few minutes). Such short observation times tend to be used only for very bright stars. However, since it is these very same stars that tend to be targeted for the highest precision observations, as planet searches probe to lower and lower planet masses, oscillation noise for these stars can be significant and needs to be accounted for in observing strategies. [source] Long-term glomerular filtration rate following pediatric liver transplantionPEDIATRIC TRANSPLANTATION, Issue 5 2005Silke Wiesmayr Abstract:, In adult patients a significant proportion of chronic renal failure after liver transplantation (LTX) has been described. This was attributed mainly to nephrotoxicity caused by Calcineurin inhibitors (CNI). If these results are transferable to pediatric patients was the aim of this study. Forty-five pediatric patients with a LTX performed between 1988 and 2003 were evaluated. Glomerular filtration rate was calculated using the Schwartz formula (calculated GFR (cGFR) (mL/min/1.73 m2) = k× height (cm)/serum creatinine (mg/dL)). Median age at LTX was 4 yr (range 0.3,18.1). Pretransplant median cGFR was significantly elevated with 157.5 mL/min/1.73 m2. Within the first 3 months after LTX median cGFR normalized to a median value of 102.7 (p < 0.05 vs. pretransplant cGFR). During long-term follow-up median cGFR remained stable with calculated values of 108.0 two years and 112.6 five years after transplantation. Using a linear and an exponential one compartment mathematical modeling of renal function the calculated GFR was stable even for very long observation times (n > 10 yr). Liver insufficiency prior to transplantation was associated with glomerular hyperfiltration. After successful liver transplantation cGFR normalized within the first 3 month and, in contrast to the reported GFR impairment in adult liver transplant recipients, remained stable, even in long-term follow-up. [source] Joint Modeling and Analysis of Longitudinal Data with Informative Observation TimesBIOMETRICS, Issue 2 2009Yu Liang Summary In analysis of longitudinal data, it is often assumed that observation times are predetermined and are the same across study subjects. Such an assumption, however, is often violated in practice. As a result, the observation times may be highly irregular. It is well known that if the sampling scheme is correlated with the outcome values, the usual statistical analysis may yield bias. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times via latent variables. A two-step estimation procedure is developed for parameter estimation. We show that the resulting estimators are consistent and asymptotically normal, and that the asymptotic variance can be consistently estimated using the bootstrap method. Simulation studies and a real data analysis demonstrate that our method performs well with realistic sample sizes and is appropriate for practical use. [source] Nucleosome Immobilization Strategies for Single-Pair FRET Microscopy,CHEMPHYSCHEM, Issue 14 2008Wiepke J. A. Koopmans Abstract All genomic transactions in eukaryotes take place in the context of the nucleosome, the basic unit of chromatin, which is responsible for DNA compaction. Overcoming the steric hindrance that nucleosomes present for DNA-processing enzymes requires significant conformational changes. The dynamics of these have been hard to resolve. Single-pair Fluorescence Resonance Energy Transfer (spFRET) microscopy is a powerful technique for observing conformational dynamics of the nucleosome. Nucleosome immobilization allows the extension of observation times to a limit set only by photobleaching, and thus opens the possibility of studying processes occurring on timescales ranging from milliseconds to minutes. It is crucial however, that immobilization itself does not introduce artifacts in the dynamics. Here we report on various nucleosome immobilization strategies, such as single-point attachment to polyethylene glycol (PEG) or surfaces coated with bovine serum albumin (BSA), and confinement in porous agarose or polyacrylamide gels. We compare the immobilization specificity and structural integrity of immobilized nucleosomes. A crosslinked star polyethylene glycol coating performs best with respect to tethering specificity and nucleosome integrity, and enables us to reproduce for the first time bulk nucleosome unwrapping kinetics in single nucleosomes without immobilization artifacts. [source] The bone,metal interface of defect and press-fit ingrowth of microwave plasma-chemical vapor deposition implants in the rabbit modelCLINICAL ORAL IMPLANTS RESEARCH, Issue 1 2005Stephan Rupprecht Abstract Purpose: The histological differences between the defect and contact areas of the implant surface to bone were tested in 35 New Zealand White rabbits in a standardized model. Microwave plasma chemical vapor-coated implant probes were tested in control and uncoated materials. Material and methods:, In each femur of 35 rabbits, cylindrical implant rods with a planed side were inserted. Three groups, divided in coated and uncoated material at half, were observed 42, 84 and 168 days. The probes were examined histologically for bone,implant contact in the curved and plane (defect area) sides. Results: Generally the bone,implant contact seems to be nearly constant in time in the curved area of coated and uncoated probes. Here the implant was inserted in the press-fit mode. Diamond-coated probes showed similar bone,implant contact (51.9% (42 days), 62.5% (84 days), 56.1% (168 days)) compared to uncoated material (56.2%, 65.4%, 62.9%). The defect area (plane side) had no bone,implant contact at the time of insertion and showed increasing values on longer observation times with only significant differences in the 42-day group between coated (17.85%, 35.2%, 47.7%) and uncoated materials (35.5%, 40.55%, 51.81%). Conclusion: The evaluation of the curved side of the implant probe showed no great variation of bone,implant contact within the described observation times. This model simulates the usual implant insertion situation. The diamond-coated material becomes osseointegrated at a later time point. The bone,implant contact was only statistically relevant in one group in comparison to uncoated material. Résumé Les différences histologiques entre la lésion et les aires de contact de la surface implantaire à l'os ont été testées chez 35 lapins blancs de Nouvelle-Zélande dans un modèle standardisé. Des sondes implantaires recouvertes d'une vapeur chimique de plasma par micro-ondes ont été testées par rapport à du matériel non-recouvert. Dans chaque fémur des 35 lapins, des baguettes implantaires cylindriques avec un côté plat ont été insérées. Trois groupes, divisés en matériel couvert et non-couvert à moitié ont été observés après 42, 84 et 168 jours. Les sondes ont été examinées histologiquement pour le contact os-implant dans les sites courbe et plat (aire de la lésion). Généralement le contact os-implant semblait constant dans la durée dans la zone courbe des sondes couvertes et non-couvertes. Ici l'implant a été inséré par la méthode de pressé-fixé (=fit après insertion). Les sondes recouvertes de diamant montraient un contact os-implant semblable (52%à 42 J, 63%à 84 J et 56%à 168 J) comparées au matériel non-recouvert (56%, 65%, 63%). L'aire de la lésion (partie plate) n'avait pas de contact os-implant au moment de l'insertion et montrait des valeurs grandissantes avec le temps avec seulement des différences significatives dans les groupes à 42 jours entre le matériel recouvert (18%, 35% et 48%) et le non-recouvert (36%, 41% et 52%). L'évaluation du côté arrondi de la sonde implantaire ne montrait pas de grande variation dans le contact os-implant dans les temps d'observation décrits. Ce modèle simule la situation d'insertion implantaire usuelle. Le matériel recouvert de diamant devient ostéoïntégré plus tardivement. Le contact os-implant n'était statistiquement valable que dans un groupe en comparaison avec le matériel non-recouvert. Zusammenfassung Ziel: Mit einem standartisierten Modell untersuchte man an 35 weissen New Zealand Kaninchen die histologischen Unterschiede zwischen in direktem Kontakt mit dem Implantat stehendem Knochen und Defektstellen. Testimplantate, die mit Diamant beschichtet worden sind, verglich man mit unbeschichtetem Material als Kontrolle. Material und Methode: In jeden Femur der 35 Kaninchen inserierte man zylindrische Implantate, die auf einer Seite abgeplattet waren. Man beobachtete drei Gruppen, je hälftig unterteilt in beschichtete und unbeschichtete Implantate, während 42, 84 und 168 Tagen. Die Blockbiopsien wurden in der runden und abgeflachten (Defektzone) Region histologisch auf ihren Implantat-Knochen-Kontakt hin untersucht. Resultate: Allgemein stellte man fest, dass der Knochen-Implantat-Kontakt während der ganzen Beobachtungszeit in der runden Region der beschichteten und unbeschichteten Implantate ziemlich konstant zu bleiben scheint. Die Implantate sind eingeklopft worden. Die diamantbeschichteten Prüfkörper zeigten einen ähnlichen Knochen-Implantat-Kontakt (51.9% (42d), 62.5% (84d), 56.1% (168d)) wie die unbeschichteten Prüfkörper (56.2%, 65.4%, 62.9%). Die Defektzonen (abgeflechte Stellen) hatten zum Zeitpunkt der Implantation natürlich keinen Kontakt zum Knochen, zeigten aber während der Beobachtungszeit zunehmend Kontakt. Einzig nach 42 Tagen zeigten sich zwischen den beschichteten (17.85%, 35.2%, 47.7%) und den unbeschichteten Implantaten (35.5%, 40.55%, 51.81%) signifikante Unterschiede. Zusammenfassung: Innerhalb der umschriebenen Beobachtungszeit zeigte die Untersuchung der runden Seite der Implantate keine grossen Unterschiede bei der Ausdehnung der Kontaktflächen zum Knochen. Dieses Modell empfindet die übliche Implantationssituation nach. Das mit Diamant beschichtete Material wird zu einem etwas späteren Zeitpunkt osseointegriert. Die Unterschiede im Knochen-Implantat-Kontakt waren im Vergleich mit dem unbeschichteten Material nur in einer Gruppe statistisch gesehen von Bedeutung. Resumen Propósito: Se probaron las diferencias histológicas entre los defectos y las áreas de contacto de la superficie del implante al hueso en 35 conejos blancos de Nueva Zelanda en un modelo estandarizado. Se investigaron implantes de prueba cubiertos de plasma de vapor químico de microonda frente a material sin cubierta como control. Material y Métodos: Se insertaron en cada fémur de 35 conejos barras cilíndricas de implantes con un lado plano. Se observaron tres grupos divididos en material cubierto y no cubierto a la mitad durante 42, 84 y 168 días. Las pruebas se examinaron histológicamente para contacto hueso-implante en los lados curvado y plano (área de defecto). Resultados: Generalmente el contacto hueso implante suele ser constante en el tiempo en el área curvada de las pruebas cubiertas y no cubiertas. Aquí el implante se insertó en el modo press-fit. Las pruebas cubiertas de diamantes mostraron un contacto hueso implante similar (51.9% (42d), 62.5% (84d), 56.1% (168)) comparados con el material no cubierto (56.2%, 65.4%, 62.9%). El área de defecto (lado plano) no tuvo contacto hueso implante en el momento de la inserción y mostró valores crecientes en periodos mas largos de observación con solo diferencias significativas en el grupo del día 42 entre materiales cubiertos (17.85, 32.2%, 47%) y no cubiertos (35.5%, 40.55%, 51.81%). Conclusión: La evaluación del lado curvado del implante de prueba no mostró una gran variación del contacto hueso implante dentro de los tiempos de observación descritos. Este modelo simula la situación usual de inserción del implante. El material cubierto de diamante se osteointegra en un momento posterior. El contacto hueso implante fue solo estadísticamente relevante en un grupo en comparación con el material no cubierto. 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