Tribology of hemiarthroplasty

Hip hemiarthroplasty (HA) is a conservative treatment for hip diseases (e.g. osteoporosis, femoral head necrosis) and injuries (e.g. femoral neck fractures) compared to total hip replacement (THR). HA is commonly used in elder patients who have low activity requirements and can be delivered with reduced blood loss, shorter operation time, and hospital stay. HA has been developed to unipolar and bipolar prostheses, and the range of motion has been improved with new designs of the bipolar prostheses. However, satisfaction of HA is not always positive due to the erosion, degradation of the acetabular cartilage, and the dislocation of femoral head which have reported in clinical studies. Hence, the mechanical factors which affect the tribological properties of articular cartilage in HA have been investigated experimentally in an in- vitro simulation of HA. In a simple geometry HA model, the articular cartilage coefficient of friction, deformation, and wear have been examined in a cartilage pin on metal plate model. The loading time, contact stress levels, contact areas, stroke lengths and sliding velocities were set as the input variables, and it was found that: 1) coefficient of friction was time- and load- dependent in short-term (1 hour) testing; 2) wear was load-dependent in long-term (24 hours) testing; 3) contact area only affected the coefficient of friction when both fluid and solid phase of cartilage supported the load due to the different aspect ratio; 4) the stroke length and sliding velocity affected the coefficient of friction only under low level of contact stress (≤2 MPa), but affected the cartilage wear under all levels of contact stresses. In an entire simulation of HA, the acetabular cartilage coefficient of friction, surface roughness, wear, and deformation have been studied with metal or ceramic heads articulating against acetabular cartilage in a pendulum friction simulator. The clearance between the head and acetabulum, loading types, and prosthesis design were set as the input variables, and it was demonstrated that: 1) a trend of decrease of the coefficient of friction was shown with increasing clearances under both constant and dynamic loading; 2) severe cartilage severe damage was observed when radial clearance was >1.8 mm under constant loading; 3) ceramic heads decreased the cartilage wear, and change of surface roughness compared to metal heads; 4) a novel bipolar design with a thin metal cup and metal head failed to reduce the coefficient of friction due to the cup locking in the acetabulum. The methodologies and findings in this research can currently adopted for related future studies, additionally the anatomic pendulum friction natural joint simulation can be used for the pre-clinical studies in less invasive procedures in the future

Essays On Corporate Political Strategies And Firm-Stakeholder Relationships

This dissertation examines the nonmarket strategies that firms use to respond to and to create change in the social and political environment. In the first chapter, I document the extent of corporate political connections across Europe and analyze the institutional contingencies of their impact. I find that a political connection increases the annual value of public procurement contracts awarded to firms, but that this positive impact is moderated by accountability institutions that enable different bodies of government to check one another’s power. When accountability institutions are weaker, firms become more likely to hold political connections, and the competition between rival firms to form political connections intensifies, suggesting that nonmarket competition in the political arena becomes increasingly consequential as the constraints of political patronage are weakened. In the second chapter, I analyze the grantmaking behavior of private foundations in the United States and find evidence consistent with philanthropy being used as a tax-advantaged method to influence politics through grantmaking to politically active nonprofits. In the third chapter, co-authored with Brian Ganson and Witold J. Henisz, we develop theories to explain how a firm’s relational strategies might impact the structure of relationships, and hence conflict risk, between groups in conflict-affected areas. Firms can affect broader societal outcomes when their actions, such as the unequal distribution of benefits to majority groups over minority groups, change the tenor of conflict and cooperation between identity groups delineated by ethnic, class, geographic, cultural, or other divides. As such, firms become implicated in shaping how they and their stakeholders reach mutually acceptable settlements in response to collective challenges. In the fourth chapter, co-authored with Anne S. Jamison, we propose a set of a methods to map the structure of relationships between firms and stakeholders in conflict-affected areas. We utilize geo- and time-tagged data from media reports and apply natural language processing techniques to construct a network of relationships between political figures, civil society actors, and firms in Rwanda

Comparison of the efficacy of lamivudine and telbivudine in the treatment of chronic hepatitis B: a systematic review

<p>Abstract</p> <p>Background</p> <p>Chronic viral hepatitis B remains a global public health concern. Currently, several drugs, such as lamivudine and telbivudine, are recommended for treatment of patients with chronic hepatitis B. However, there are no conclusive results on the comparison of the efficacy of lamivudine (LAM) and telbivudine (LdT) in the treatment of chronic hepatitis B.</p> <p>Results</p> <p>To evaluate the comparison of the efficacy of LAM and LdT in the treatment of chronic hepatitis B by a systematic review and meta-analysis of clinical trials, we searched PUBMED (from 1990 to April 2010), Web of Science (from 1990 to April 2010), EMBASE (from 1990 to April 2010), CNKI (National Knowledge Infrastructure) (from 1990 to April 2010), VIP database (from 1990 to April 2010), WANFANG database (from 1990 to April 2010), the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Review. At the end of one-year treatment, LdT was better than LAM at the biochemical response, virological response, HBeAg loss, therapeutic response, while less than at the viral breakthrough and viral resistance, but there was no significant difference in the HBeAg seroconversion and HBsAg response. LdT was better than LAM at the HBeAg seroconversion with prolonged treatment to two years.</p> <p>Conclusions</p> <p>In summary, LdT was superior in inhibiting HBV replication and preventing drug resistance as compared to LAM for CHB patients. But LdT may cause more nonspecific adverse events and can lead to more CK elevation than LAM. It is thus recommended that the LdT could be used as an option for patients but adverse events, for example CK elevation, must be monitored.</p

Proteomic analysis of differentially expressed proteins in hepatitis B virus-related hepatocellular carcinoma tissues

<p>Abstract</p> <p>Background</p> <p>Hepatocellular carcinoma (HCC), a major cause of cancer death in China, is preceded by chronic hepatitis and liver cirrhosis (LC). Although hepatitis B virus (HBV) has been regarded as a clear etiology of human hepatocarcinogenesis, the mechanism is still needs to be further clarified. In this study, we used a proteomic approach to identify the differential expression protein profiles between HCC and the adjacent non-tumorous liver tissues.</p> <p>Methods</p> <p>Eighteen cases of HBV-related HCC including 12 cases of LC-developed HCC and 6 cases of chronic hepatitis B (CHB)-developed HCC were analyzed by two-dimensional electrophoresis (2-DE) combined with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), and the results were compared to those of paired adjacent non-tumorous liver tissues.</p> <p>Results</p> <p>A total of 17 differentially expressed proteins with diverse biological functions were identified. Among these, 10 proteins were up-regulated, whereas the other 7 proteins were down-regulated in cancerous tissues. Two proteins, c-Jun N-terminal kinase 2 and ADP/ATP carrier protein were found to be up-regulated only in CHB-developed HCC tissues. Insulin-like growth factor binding protein 2 and Rho-GTPase-activating protein 4 were down-regulated in LC-developed and CHB-developed HCC tissues, respectively. Although 11 out of these 17 proteins have been already described by previous studies, or are already known to be involved in hepatocarcinogenesis, this study revealed 6 new proteins differentially expressed in HBV-related HCC.</p> <p>Conclusion</p> <p>These findings elucidate that there are common features between CHB-developed HCC and LC-developed HCC. The identified proteins are valuable for studying the hepatocarcinogenesis, and may be potential diagnostic markers or therapeutic targets for HBV-related HCC.</p

Detection of hepatitis B surface antigen, hepatitis B core antigen, and hepatitis B virus DNA in parotid tissues

SummaryObjectiveTo examine the presence of hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg), and hepatitis B virus (HBV) DNA in parotid tissues from patients with positive serum HBV markers.MethodsHBsAg and HBcAg were examined in parotid biopsy tissues from patients with suspected parotid tumor and positive serum HBV markers by immunocytochemistry, and HBV DNA was detected in parotid tissues by PCR.ResultsAmong the 22 patients with a parotid tumor, only one was pathologically confirmed as a neoplasm; all others were benign. HBsAg and HBcAg were present in parotid cells with positive rates of 45.5% (10/22) and 40.9% (9/22), respectively, with an overall positive rate of 54.5% (12/22). Of the 22 cases with serum markers of HBV infection, seven (31.8%) had both HBsAg and HBcAg in the parotid cells. HBV DNA was present in seven of the 12 samples in which hepatitis B antigen was detected (58.3%).ConclusionsHBV in saliva might originate from the infected salivary glands and the infectious saliva could transmit HBV