SURFACE RANDOM PARAMETERS FOR ENDOPROSTHESIS LUBRICATION

Tribologia ◽  
2016 ◽  
Vol 265 (1) ◽  
pp. 117-127
Author(s):  
Krzysztof WIERZCHOLSKI
Keyword(s):  
Bone Fractures ◽  
Humanoid Robots ◽  
Superficial Layer ◽  
Knee Joints ◽  
The European Union ◽  
Friction Forces ◽  
Non Invasive ◽  
Cartilage Cells ◽  
Gap Height ◽  
One Year

Within the last ten years in the European Union the number of bone fractures caused by the osteoarthritis increased twofold. More than 100000 hip or knee joints in total have been implanted in Germany during one year. Within ten years, 5% of them have failed by aseptic loosening. The non-invasive determination of friction forces and the control of their values during lubrication of cartilage cells on the superficial layer of human joint surfaces before implantation have a significant but not sufficient influence on the observation of the early abrasive wear of cartilage joint and the development of osteoporosis. From this fact was drawn the inspiration for the performed investigations referring the endoprosthesis surface parameters, because knowledge of the roughness of prosthesis surfaces and friction forces and their control methods makes it possible to provide the necessary random standard deviation of gap height and finally information about implantation possibility. This paper has been prepared based on the objective knowledge gained from the author’s experimental and theoretical experiences to represent the methodology and goal of the idea described in the study and to make possible a wider discussion on this subject for further developments during the realization of various bioengineering projects in the field of hydrodynamic artificial human and humanoid robots joints.

Geometrical Structure for Endoprosthesis Surface Lubrication and Wear Prognosis

2016 ◽  
Vol 251 ◽  
pp. 206-211 ◽  
Author(s):  
Krzysztof Wierzcholski
Keyword(s):  
Bone Fractures ◽  
Superficial Layer ◽  
Knee Joints ◽  
The European Union ◽  
Friction Forces ◽  
Non Invasive ◽  
Cartilage Cells ◽  
Gap Height ◽  
One Year ◽  
And Control

It can be stated that over the last ten years in the European Union, the number of bone fractures caused by osteoarthritis has increased twofold. More than 100,000 hip or knee joints in total were implanted in Germany during one year. Within ten years, 5% of them have failed by aseptic loosening.The non-invasive determination of friction forces and control of their values during lubrication of cartilage cells on the superficial layer of human joint surfaces before implantation has a significant but not sufficient impact on the observation of the early abrasive wear of the cartilage joint and development of osteoporosis. From this fact was drawn the inspiration for the performed investigations related to the endoprosthesis surface parameters because knowledge of the roughness of prosthesis surfaces and friction forces and their control methods permits provision of a necessary standard deviation of the gap height and finally information about the implantation possibility. This paper has been prepared based on the objective of European Project UE Grant IRSES,612593, 2013-2016 to represent the methodology and goal of the idea described in and make a wider discussion possible on this subject for further developments during the realization.

scholarly journals A New Progress in Random Hydrodynamic Lubrication for Movable Non-Rotational Curvilinear Biosurfaces with Phospholipid Bilayers

2020 ◽  
Vol 03 (02) ◽  
pp. 1-1
Author(s):  
Krzysztof Wierzcholski ◽  
Keyword(s):  
Dynamic Viscosity ◽  
Hydrodynamic Lubrication ◽  
Wrist Joint ◽  
Biological Fluid ◽  
Hydrodynamic Pressure ◽  
Superficial Layer ◽  
Estimation Methods ◽  
Friction Forces ◽  
Biological Surfaces ◽  
Gap Height

This paper aims to highlight the result of a new progression of mathematical estimation methods of stochastic bio-hydrodynamic lubrication parameters for arbitrary, curvilinear, non-rotational, co-operating, living biological surfaces coated with phospholipid bi-layers. Movable, non-rotational, co-operating surfaces occur in various biological friction nods like the collar bone, the blade bone, the jump joint, and the wrist joint. Specifically, the author presents a synthetic and comprehensive estimation of stochastic bio-hydrodynamic lubrication parameters for co-operating, rotational cartilage bio-surfaces with phospholipid bi-layers occurring in human spherical hip joints and cylindrical elbow joints. The method of research discussed in this paper focuses on a review of stochastic analytical considerations performed by the author. This research is based on the measurements of the gap height between two movable, non-rotational bio-surfaces. The gap is restricted between two co-operating biological surfaces. After several experiments, it could be inferred that there are symmetric as well as asymmetric random increments and decrements in the gap height. Such changes are applicable to the hydrodynamic pressure, load-carrying capacity, friction forces, and wear of the co-operating biological surfaces in human friction nods and contacts. The prime purpose of this paper is to demonstrate the influence of variations in the expected values and standard deviation of the gap height on the hydrodynamic lubrication parameters that occur during the friction process. It can thus be concluded that the apparent dynamic viscosity of biological lubricant varies in the ultra-thin gap height direction, depending on the susceptibility of the superficial layer of the lubricated bio-surface. The results presented in this paper are obtained considering the 3D variations in the dynamic viscosity of the biological fluid, particularly the random variations crosswise the film thickness in non-Newtonian biological fluid properties.

scholarly journals Estimation of Random Friction Forces on the Microbearing Cooperating Surfaces

2019 ◽  
Vol 26 (2) ◽  
pp. 167-174
Author(s):  
Krzysztof Wierzcholski ◽  
Andrzej Miszczak
Keyword(s):  
Dynamic Viscosity ◽  
Apparent Viscosity ◽  
Hydrodynamic Lubrication ◽  
Stochastic Theory ◽  
Superficial Layer ◽  
Mathematical Form ◽  
Friction Forces ◽  
Random Roughness ◽  
Load Carrying ◽  
Gap Height

Abstract Presented paper concerns a new mathematical form of stochastic theory of hydrodynamic friction forces occurring on the real cooperating surfaces in computer micro bearing fan and computer microbearing in hard disc driver HDD. This paper presents particularly a new-review of stochastic analytical considerations realized by the authors for friction forces estimation during hydrodynamic lubrication performed on the ground of the measurements of the gap height between two roughness surfaces. After numerous experimental measurements directly follows that the random unsymmetrical increments and decrements of the gap height of computer microbearings have important influence on the load carrying capacities and finally on the friction forces and wear of cooperating surfaces. The main topic demonstrates the influence of the variations of expectancy values and standard deviation of the computer microbearing gap height on the friction forces occurring in the HDD and microbearing fan. Moreover, it is observed the evident connection between the apparent dynamic viscosity and the features of the microbearing superficial surface. Hence after abovementioned remarks follows the corollary that the influence of the microbearing gap height stochastic variations connected with the surface roughness tend moreover indirect from the apparent viscosity into the friction forces variations. The synthetic, complex elaboration of obtained results indicates finally the influence of the random roughness in micro and nano level of microbearing surfaces on the friction forces distribution. A new results contained in this paper are obtained taking into account 3D variations of dynamic viscosity of the non-Newtonian lubricant, particularly variations crosswise the film thickness and influences of surface superficial layer features on the lubricant apparent viscosity.

The Union of Laughter and Forgetting? The European Union and the Construction of its own History

2006 ◽  
Author(s):  
Hernan Tesler-Mabe
Keyword(s):  
European Union ◽  
Great Part ◽  
The European Union ◽  
European Constitution ◽  
Close Study ◽  
Dramatic Shift ◽  
One Year ◽  
The Many ◽  
Teleological Interpretation ◽  
Compare And Contrast

As recently as one year ago, the European Union was seemingly on a direct path toward its avowed goal of "ever closer union." In numerous publications, EU authorities asserted that they had the confidence of European peoples desirous only of further integration. In the wake of the failed referenda for a European Constitution, however, enthusiasts of European Union can no longer be certain that their enterprise will succeed. The European Union, once strong and united, seems now an entity teetering on the edge of collapse. The reasons for such a dramatic shift are, of course, wide-ranging. Yet I would suggest that a great part of the general European disillusionment with European Union has come about as a result of the actions of the Europeanists themselves. Over the last decades, European officials have exhibited a frightfully high incidence of revisionism in their literature. This practice, I argue, has caused many Europeans to question the integrity of the project of European Union. For my presentation, I intend to undertake a close study of a selection of documents published by the European Communities. In this endeavour, I will compare and contrast the messages imparted in different editions of these works and consider the semiotic significance of the textual and non-textual language appearing therein. In this manner, I hope to achieve two aims. First, I mean to add a corrective element to a literature that, guided by a teleological interpretation of integration, endows integration with”logic" to be found only in hindsight. Second, I intend to examine the many meanings that the EU has had over its history and assess how closely policy has adhered to the ideological goals of prominent Europeanists. In sum, I hope to shed light on the fundamental disconnect between advocates of Europe and the "man on the street" and help establish a dialogue which may contribute to resolving the current impasse within the European Union. Full text available: https://doi.org/10.22215/rera.v2i4.178

DIFFERENCES IN GENOTYPE OF E. FAECALIS AND E. FAECIUM CLINICAL ISOLATES REGARDING CYTOLYSIN AND GELATINASE PRODUCTION IN BULGARIAN PATIENTS

2020 ◽  
Vol 18 (Suppl.1) ◽  
pp. 130-137
Author(s):  
R. Yordanova ◽  
S. Stanilova
Keyword(s):  
Virulence Genes ◽  
Clinical Isolates ◽  
University Hospitals ◽  
Gelatinase Activity ◽  
Non Invasive ◽  
Genotypic Analysis ◽  
Enterococcus Spp ◽  
Virulent Gene ◽  
One Year ◽  
Genotype Correlation

Purpose - compare the phenotype and genotype correlation of cytolysin and gelatinase production in clinical isolates Enterococcus spp. Materials and methods - 100 Enterococcus strains collected over a period of one year from inpatients of two Bulgarian university hospitals, were tested for phenotype production of cytolysin and gelatinase. Multiplex PCR was performed to screen the presence of gelE and cylA virulence genes. Results – 17% of the enterococcal isolates demonstrated only cytolysin production phenotypically. Gelatinase activity was found in 21% of the isolates. Only E. faecalis showed combined phenotypic production of cytolysin plus gelatinase (21%). Forty-five percent of the tested enterococci were identified negative for both hemolysin and gelatinase activity. GelE was the most prevalent virulent gene (48% of the isolates). CylA gene was present alone only in four non-invasive E. faecalis isolates. Twenty-six percent of the isolates possessed both cylA and gelE genes and 21% did not harbor any of the virulence factors genotypically. Conclusion - our results prove that it is appropriate to perform both phenotypic and genotypic analysis of the enterococci virulence profile in parallel in order to better characterize the strains, which in turn may serve to develop more effective methods to limit the spread of infections caused by these microorganisms.

Abstract 1787: Vertebral Artery Stent Placement for Symptomatic Patients: One-Year Follow-up

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Samir N Patel ◽  
J. Stephen Jenkins ◽  
Christopher J White ◽  
Paul McMullan ◽  
J.P. Reilly ◽  
...  
Keyword(s):  
Vertebral Artery ◽  
Stent Placement ◽  
Clinical Success ◽  
High Morbidity ◽  
Symptom Resolution ◽  
Non Invasive ◽  
Procedural Success ◽  
Repeat Angiography ◽  
One Year

Background : Symptomatic vertebral artery stenosis (VAS) has a five-year stroke risk of 30%–35%. Mortality associated with posterior circulation (PC) strokes is high, ranging from 20%–30%. Surgical revascularization is rarely performed due to high morbidity and mortality. Endovascular revascularization with stents offers a potential treatment option for these patients. Methods : One hundred nine patients (116 arteries, 70% male) underwent stent placement for extracranial (91%) and intracranial (9%) VAS from 1995–2006. Symptoms included vertigo (63%), visual changes (31%), syncope (11%), ataxia (7%), and drop attack (5%). Four patients had asymptomatic critical stenosis. Sixty-one patients (56%) had bilateral VAS, 74 patients (69%) had concomitant carotid disease, and 43 patients (39%) had a prior stroke. Procedural success was defined as residual stenosis of ≤ 20% without peri-procedural stroke or death. Clinical success was defined as procedural success with symptom resolution. Restenosis was defined as angiographic narrowing within the stent of ≥ 70% or > 50% with recurrent symptoms, or evidence of severe stenosis on non-invasive imaging (ultrasound, CT, or MR). Results : Procedural and clinical success was achieved in 108 (99.1%) and 95 (94.3%) patients, respectively. At one year, follow-up was obtained in 91 patients (83.5%), 6 patients (5.5%) had died, 5 patients (5.3%) experienced a PC stroke, and 47 patients (43.1%) underwent repeat angiography and/or non-invasive imaging. Eighty-seven of the 91 patients were initially symptomatic, 69 (79.3%) of which were symptom-free at one year. Three of those that had recurrent symptoms never achieved clinical success, 9 had developed restenosis, and 7 underwent successful re-intervention. At median follow-up of 31 months (lower and upper quartiles of 13.0 and 51.8 months), 72.5% were alive and 71.6% remained symptom-free. Conclusion : Our data demonstrates that stenting for VAS can be successfully performed in 99% of patients without peri-procedural stroke or death and is associated with durable symptom resolution in approximately 80% of patients at one year. In these high-risk patients, endovascular therapy for symptomatic VAS appears to be safe and effective at relieving symptoms.

MO794EVALUATION OF THE BONE ELASTIC STRUCTURE IN PERSONS WITH AND WITHOUT CHRONIC KIDNEY DISEASE ON DIALYSIS

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Pietro Manuel Ferraro ◽  
Alessandra Nicolosi ◽  
Alessandro Naticchia ◽  
Nicola Panocchia ◽  
Giuseppe Grandaliano ◽  
...  
Keyword(s):  
Chronic Kidney Disease ◽  
Kidney Disease ◽  
Linear Regression ◽  
Bone Structure ◽  
Bone Fractures ◽  
Elastic Structure ◽  
Absolute Difference ◽  
P Value ◽  
Non Invasive ◽  
Age And Sex

Abstract Background and Aims Chronic kidney disease is a frequent condition, characterized, especially in its more advanced stages, by an array of derangements in bone structure and density, resulting in a higher rate of bone fractures. Current strategies to monitor the bone status and assess the risk of bone fractures in CKD patients are limited. The Bone Elastic Structure (BES) test is a recently-developed non-invasive tool that measures the elastic characteristics of the trabecular bone by simulating the application of loads on a virtual biopsy obtained from radiographic images of the proximal epiphyses in the patient’s hand fingers. The simulation results are combined to obtain a parameter defined Bone Structure Index (BSI). The aim of our study is to explore whether the BES test could be a useful monitoring tool of bone status in patients with CKD on dialysis by exploring whether such patients have different BSI values compared with persons without CKD. Method The BES test was performed on a sample of 41 patients undergoing chronic hemodialysis (HD) and the BSI compared with a group of 374 persons with normal renal function who had undergone the BES test in previous studies. Differences in BSI and 95% confidence intervals (CIs) between the two groups were obtained and tested for statistical significance with a linear regression model including BSI as the dependent variable and kidney status (HD vs no HD) as the independent variable, adjusted for age and sex. Subgroup effects were explored by including interaction terms (age x kidney status, age x sex, kidney status x sex) in the model. Finally, to further remove the potential confounding by age and sex, each HD patient was individually matched with up to 4 non-HD participants based on sex and age (with a 5-year caliper) and a matched analysis was conducted on BSI values. Results Average (SD) age was 64 (17) years in the HD group and 60 (12) years in the non-HD group, with a prevalence of males of 49% and 16%, respectively. The individual values of BSI divided by kidney status and sex in Figure. The multivariate linear regression model showed that, after adjustment for age and sex, the BSI in the HD group was significantly lower compared with the non-HD group (HD 145, 95% CI 140, 154; non-HD 179, 95% CI 177, 181; absolute difference −32, 95% CI −40, −25; p-value < 0.001). There was no significant interaction between age, sex and kidney status on BSI values (all p-values > 0.05). Individual matching was successful for 36 out of 41 HD patients, who were matched to 127 non-HD participants; matched analysis confirmed the results (absolute difference −31, 95% CI −40, −23; p-value < 0.001). Conclusion The output of a non-invasive tool to determine the bone elastic structure appeared to be strongly associated with kidney function after control for differences in age and sex. Further studies are needed to determine the potential application of the BES test in patients with CKD.

Evaluation of Transient Elastography in Prediction Of De novo Recurrence of Hepatocellular Carcinoma after Radiofrequency Ablation

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Nadia abdelaty Abdelkader ◽  
Moustafa Hamed Abdelaleem ◽  
Mohammed El-Gharib Abo El- maaty ◽  
Heba Ismail Aly ◽  
Sayed Ahmed Sayed
Keyword(s):  
Hepatocellular Carcinoma ◽  
Radiofrequency Ablation ◽  
Transient Elastography ◽  
P Value ◽  
Hepatic Decompensation ◽  
Non Invasive ◽  
Prediction Of Mortality ◽  
The Mean ◽  
One Year

Abstract Background Hepatocellular carcinoma (HCC) is the sixth most common malignancy worldwide and it is also a common cause of death in patients with chronic liver disease. The curative treatment options for HCC that are currently available are surgical resection, liver transplantation and radiofrequency ablation .Despite progressive improvements in the efficacy of RFA, the survival of patients with HCC who undergo RFA remains disappointing, mainly due to frequent intrahepatic recurrence of HCC after RFA. Aim of the work To evaluate the role of transient elastography (as an indirect indicator to degree of liver fibrosis) in prediction of denovo recurrence of hepatocellular carcinoma after radiofrequency ablation in hepatitis C related hepatocellular carcinoma .And to compare between transient elastography and other non invasive fibrosis indices in prediction of denovo recurrence of hepatocellular carcinoma after radiofrequency ablation hepatitis C related hepatocellular carcinoma Patients and methods This prospective cohrt study was conducted on hepatocellular carcinoma patient, who underwent radiofrequency ablation in Tropical Medicine Department in Eldemerdash and Ain Shams Specialized Hospital, HCC clinic Ain Shams University Hospitals, Cairo, Egypt between march, 2017 and May, 2019. Data of the patient, who underwent radiofrequency ablation during the study period, were reviewed and the patients who fulfilled the inclusion criteria were enrolled into this study. The patients who fulfilled the inclusion criteria and underwent radiofrequency ablation were followed up for 12 months. Results TE revealed 28 patients with F4 and only 2 patients with F3, the mean measurement of liver stiffness was (22.45 ± 10.36) KPa. There was a significant negative correlation between LS and denovo recurrence of HCC (mean of LS in patients with complete response was 17.19 ± 3.32 and the mean of LS in patient with denovo recurrence was 36,94 ± 5.93,with the The best cut off value ≥24.65 (p value < 0.001)). There was no significant correlation between CDC, FIB4, API scores and denovo recurrence of HCC. Also it was found that the LS was significantly associated with prediction of manifestation of hepatic decompensation after RFA (means of LS in patient without manifestation decompensation after RFA (p value <0.001) .Regarding prediction of mortality, LS at cut off value > 42 .75 (p value = 0,031) was significantly associated with prediction of mortality after one year of RFA. As regard serum non invasive fibrosis indices our results showed correlation between FIB4 score and hepatic decompensation after one year of intervention (the mean of FIB4 score in patients ascites and jaundice was 6.05 ± 4.71 (p value = 0.05) ).Therewas no statistically significant correlation between CDS and API with hepatic decompensation after RFA .As regard role of serum non invasive fibrosis indices in prediction of mortality after RFA, FIB4 score, CDS and API were statistically non significant. Conclusion Our data suggest that LS measurement is a useful predictor of HCC de novorecurrence overall survival and possibility of hepatic decompensation after RFA

The impact of direct-acting antivirals on liver fibrosis in Egyptian hepatitis C virus patients: a single center experience

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Nadia Abdelaaty Abdelkader ◽  
Amira Mahmoud AlBalakosy ◽  
Ahmed Fouad Helmy Sherief ◽  
Mohamed Soliman Gado
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Liver Fibrosis ◽  
Transient Elastography ◽  
Liver Stiffness ◽  
Treatment Unit ◽  
Non Invasive ◽  
One Year ◽  
The Impact

Abstract Background Hepatitis C virus (HCV) infection affects approximately 170 million people worldwide, causing liver cirrhosis and hepatocellular carcinoma (HCC) and leading to liver transplantation and ultimately death. Accurate evaluation of liver fibrosis in patients with chronic liver diseases is crucial, as liver fibrosis is important in order to make therapeutic decisions, determine prognosis of liver disease and to follow-up disease progression. Multiple non-invasive methods have been used successfully in the prediction of fibrosis; however, early changes in noninvasive biomarkers of hepatic fibrosis under effective antiviral therapy are widely unknown. The aim of this study is to evaluate changes of transient elastography values as well as FIB-4 and AST to platelet ratio index (APRI) in patients treated with DAAs. Objectives The aim beyond this study is to evaluate the changes in liver stiffness in hepatitis C Egyptian patients before and at least one year after treatment with DAAs using transient elastography and non-invasive liver fibrosis indices as FIB-4 and APRI scores. Patients and methods The present study was conducted on 100 patients with chronic hepatitis C patients attended to Ain Shams University Hospitals, Viral hepatitis treatment unit between October 2017 and December 2018, who were followed-up during treatment and after treatment for at least one year (retrospective and prospective study). Total number of cases during the study period was 117 patients. 17 patients were excluded from the study due to missed follow-up. Eventually, 100 patients were enrolled in the study fulfilling the inclusion criteria. Results The mean age of our patients is 47.9 years with Male predominance (52 males and 48 females). There was a significant improvement of, platelets counts, ALT and AST levels, which in turn cause significant improvement in FIB-4 and APRI scores. There was a significant improvement of liver stiffness after end of treatment, regardless of the DAA regimen used, as evidenced by Fibroscan. Conclusion Fibrosis regression –assessed by non-invasive markers of fibrosis is achievable upon removal of the causative agent.

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