Polycrystalline Ni nanotubes under compression: a molecular dynamics study.

Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures. Since grain boundary structures and surface modifications can be used as a route to modify nanostructured materials, it is of interest to understand how they affect material strength and plasticity. We report large-scale atomistic simulations to determine the mechanical response of nickel nanowires and nanotubes subject to uniaxial compression. Our results suggest that the incorporation of nanocrystalline structure allows completely flexible deformation, in sharp contrast with single crystals. While crystalline structures at high compression are dominated by dislocation pinning and the multiplication of highly localized shear regions, in nanocrystalline systems the dislocation distribution is significantly more homogeneous. Therefore, for large compressions (large strains) coiling instead of bulging is the dominant deformation mode. Additionally, it is observed that nanotubes with only 70% of the nanowire mass but of the same diameter, exhibit similar mechanical behavior up to 0.3 strain. Our results are useful for the design of new flexible and light-weight metamaterials, when highly deformable struts are required.

Health-related quality of life in chronic liver disease: the impact of type and severity of disease.

OBJECTIVE: The type and severity of chronic liver disease may have different effects on health-related quality of life (HRQL). The aim of our study was to determine whether HRQL in patients with chronic liver disease differs by type and severity of disease and to identify which clinical and physiological factors affect this impairment. METHODS: In this study, HRQL was measured with a generic (Short Form 36) and a liver disease-specific (Chronic Liver Disease Questionnaire) questionnaire. Clinical, demographic, and laboratory data were collected at office visits. Patient's HRQL scores were compared with the published norms and to the chronically ill populations. A total of 353 patients (mean age 50 yr, 51% men) with chronic liver disease, either viral disease (hepatitis B and C), cholestatic disease (primary biliary cirrhosis or primary sclerosing cholangitis), or hepatocellular disease were enrolled in the study. RESULTS: In general, HRQL in patients with chronic liver disease was lower than the normal population and was similar to that of patients with chronic obstructive pulmonary disease or congestive heart failure. In cirrhotic patients, some dimensions of HRQL were less impaired in patients with cholestatic disease than in those with hepatocellular diseases. More severe disease (higher Child's class) was associated with a lower Chronic Liver Disease Questionnaire score and the Short Form 36's physical component summary scores. Older age had a weak negative association with the physical aspects of HRQL. CONCLUSIONS: We conclude that chronic liver disease substantially reduces HRQL, and this impact does not differ markedly by type of disease. Older age and measures of disease severity were associated with poorer HRQL.

Hepatitis C virus RNA assays: a comparison of SuperQuant and Monitor.

Hepatitis C RNA testing has been used extensively to assess the efficacy of antiviral therapy and has increasingly become an integral part of clinical management of patients with chronic hepatitis C. A variety of commercially available hepatitis C virus (HCV) RNA tests are used to detect HCV RNA qualitatively or quantitatively. These commercial tests have fundamental differences that are reflected on the values they generate. We compared two widely used assays, HCV SuperQuant (SQ) and Amplicor HCV Monitor (M1 and M2), in sera of patients with chronic hepatitis C. A total of 506 sera from 79 patients were tested with both assays. The data were logarithmically transformed and analyzed by linear regression and measurement of agreement. Two hundred thirty-eight sera had HCV RNA values within the dynamic range of both assays. The correlation between the assays was fair, with a correlation coefficient (r) of 0.699. Overall, SQ generated higher values than M1 with a mean difference of 0.558 log (SD = 0.624). One hundred ninety-four (38%) and 121 (24%) of the sera were below the dynamic range of M1 and SQ, respectively. Seventy-three sera, undetectable by M1, were positive by SQ. The Amplicor HCV Monitor 2.0 (M2) was performed in 66 sera. All were positive by SQ and M2, but only 38 were within the dynamic range of M1. The correlations between these tests were good (r = 0.68-0.78), but the agreement was rather poor. In conclusion, this study confirms that both SQ and M2 are more sensitive than M1. Additionally, our results show rather poor agreements between these assays. The recent attempts in standardizing the reporting of these assays should make their results more easily interchangeable.

Cholestatic liver diseases and health-related quality of life.

OBJECTIVE: Symptoms associated with primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) negatively affect health-related quality of life (HRQL). The aim of this study was to measure HRQL in patients with chronic cholestatic liver diseases and to determine factors associated with more severe impairment. METHODS: We conducted a cross-sectional study in which we documented patients' demographic and clinical characteristics, and measured their HRQL using the Short Form-36 and Chronic Liver Disease Questionnaire. We assessed the association of HRQL impairment with disease severity (Child's-Pugh class and Mayo PBC Risk Score) and compared patients' HRQL with those of a healthy population, and patients with congestive heart failure, chronic obstructive pulmonary disease, and diabetes. RESULTS: One hundred and four patients with PBC and PSC participated, of whom 73% were women, with an average age of 55+/-12 yr. Of these patients, 61% had cirrhosis (37% Child's A, 23% Child's B, and 2% Child's C). Patients with cholestatic liver disease showed more HRQL impairment than the healthy population and were similar to patients with other chronic conditions. Additionally, patients who experienced severe itching showed profound HRQL impairment. In patients with PBC, Physical Component Summary (PCS) scores of the SF-36 and Chronic Liver Disease Questionnaire (CLDQ) scores fell from noncirrhotic to Child's A to Child's B/C and with worsening Mayo PBC Risk Scores. No other clinicodemographic data were associated with patients' well-being. CONCLUSIONS: Patients with cholestatic liver disease (PBC and PSC) showed substantial impairment of HRQL, which is further affected by worsening disease severity. Disease-specific measures were better able to discriminate patients with varying severities.

Development of a disease specific questionnaire to measure health related quality of life in patients with chronic liver disease.

BACKGROUND AND AIMS: To develop and assess a disease specific instrument for measuring health related quality of life (HRQL) in patients with chronic liver disease (CLD). METHODS: Based on responses from 60 patients with chronic liver disease, from 20 liver experts, and from a Medline search of the literature, items potentially affecting the HRQL of these patients were identified. A separate sample of 75 patients identified which items they found problematic and rated their importance. Results were explored using factor analysis; domains were chosen and items placed within domains. Redundant questions were eliminated and the final questionnaire was pretested in 10 patients. Using this instrument, HRQL was assessed in a further 133 patients with various types and stages of liver disease. RESULTS: Patients, experts, and the literature search identified 156 items of potential importance. Of these, 35 proved important to over 50% of 75 respondents in the item reduction sample. The factor analysis suggested six domains. After eliminating redundancies, the Chronic Liver Disease Questionnaire (CLDQ) included 29 items in the following domains: fatigue, activity, emotional function, abdominal symptoms, systemic symptoms, and worry. In pretesting, patients found the CLDQ clear and easy to complete in 10 minutes. In another 133 patients, the CLDQ showed a gradient between patients without cirrhosis, Child's A cirrhosis, and those with Child's B or C cirrhosis. CLDQ has evidence for moderate reliability at six months and seems to be responsive. CONCLUSION: The CLDQ is short, easy to administer, produces both a summary score and domain scores, and correlates with the severity of liver disease.