Effect of Adding Al on the Phase Structure and Gettering Performance of TiZrV Non-Evaporable Getter Materials

Titanium zirconium vanadium (TiZrV) is a widely used non-evaporable getter (NEG) material with the characteristics of a low activation temperature and a large gas absorption capacity. At present, the research on TiZrV getters mainly focuses on the thin-film state, with little research on the bulk state. In this paper, a TiZrV getter was optimized by adding Al, and the phase structure, activation properties, and gettering performance were studied. With the addition of Al, the α-Zr phase and Ti2Zr phase changed into the Ti-Zr phase and Al-Zr, Al-Ti phase. The newly generated phase promoted the diffusion of hydrogen and oxygen atoms. The activation temperature decreased significantly, as shown in the in situ XPS results. The H2 and CO gettering performance of TiZrVAl samples was promoted to 2073 cm3·s-1 and 1912.8 cm3·s-1, increased by 40.7% and 40.3%. This paper provides valuable ideas for optimizing the properties of bulk TiZrV getters.

Assessment of gene set analysis methods based on microarray data

Gene set analysis (GSA) incorporates biological information into statistical knowledge to identify gene sets differently expressed between two or more phenotypes. It allows us to gain an insight into the functional working mechanism of cells beyond the detection of differently expressed gene sets. In order to evaluate the competence of GSA approaches, three self-contained GSA approaches with different statistical methods were chosen; Category, Globaltest and Hotelling's T(2) together with their assayed power to identify the differences expressed via simulation and real microarray data. The Category does not take care of the correlation structure, while the other two deal with correlations. In order to perform these methods, R and Bioconductor were used. Furthermore, venous thromboembolism and acute lymphoblastic leukemia microarray data were applied. The results of three GSAs showed that the competence of these methods depends on the distribution of gene expression in a dataset. It is very important to assay the distribution of gene expression data before choosing the GSA method to identify gene sets differently expressed between phenotypes. On the other hand, assessment of common genes among significant gene sets indicated that there was a significant agreement between the result of GSA and the findings of biologists.

Comparative evaluation of the Bio-Rad Geenius HIV-1/2 Confirmatory Assay and the Bio-Rad Multispot HIV-1/2 Rapid Test as an alternative differentiation assay for CLSI M53 algorithm-I

INTRODUCTION

The CLSI-M53-A, Criteria for Laboratory Testing and Diagnosis of Human Immunodeficiency Virus (HIV) Infection; Approved Guideline includes an algorithm in which samples that are reactive on a 4th generation EIA screen proceed to a supplemental assay that is able to confirm and differentiate between antibodies to HIV-1 and HIV-2. The recently CE-marked Bio-Rad Geenius HIV-1/2 Confirmatory Assay was evaluated as an alternative to the FDA-approved Bio-Rad Multispot HIV-1/HIV-2 Rapid Test which has been previously validated for use in this new algorithm.

METHODS

This study used reference samples submitted to the Canadian - NLHRS and samples from commercial sources. Data was tabulated in 2×2 tables for statistical analysis; sensitivity, specificity, predictive values, kappa and likelihood ratios.

RESULTS

The overall performance of the Geenius and Multispot was very high; sensitivity (100%, 100%), specificity (96.3%, 99.1%), positive (45.3, 181) and negative (0, 0) likelihood ratios respectively, high kappa (0.96) and low bias index (0.0068). The ability to differentiate HIV-1 (99.2%, 100%) and HIV-2 (98.1%, 98.1%) Ab was also very high.

CONCLUSION

The Bio-Rad Geenius HIV-1/2 Confirmatory Assay is a suitable alternative to the validated Multispot for use in the second stage of CLSI M53 algorithm-I. The Geenius has additional features including traceability and sample and cassette barcoding that improve the quality management/assurance of HIV testing. It is anticipated that the CLSI M53 guideline and assays such as the Geenius will reduce the number of indeterminate test results previously associated with the HIV-1 WB and improve the ability to differentiate HIV-2 infections.