bWe performed a meta-analysis to evaluate use of PCR assays for diagnosis of prosthetic joint infection (PJI). The pooled sensitivity and specificity were 0.86 (95% confidence interval [CI], 0.77 to 0.92) and 0.91 (CI, 0.81 to 0.96), respectively. Subgroup analyses showed that use of tissue samples may improve sensitivity, and quantitative PCR and sonication of prostheses fluid may improve specificity. The results showed that PCR is reliable and accurate for detection of PJI.P rosthetic joint infection (PJI) is one of the most common complications of total joint arthroplasty, with an incidence of 1 to 12%, and it always has catastrophic consequences (1, 2). The distinction between PJI and other causes of joint failure, such as aseptic loosening, is frequently difficult and still challenging. Several studies have assessed the diagnostic value of PCR techniques for diagnosing PJI. However, the true diagnostic capabilities of PCR assays remain controversial. Therefore, the aim of our study was to perform a meta-analysis to evaluate the detection validity of PCR in the diagnosis of PJI.We searched MEDLINE, EMBASE, and OVID for articles that were published between January 1990 and February 2013, using the following medical subject headings (MeSH) or free text words: (i) joint prosthesis, prosthesis infection, septic loosening, aseptic loosening, replacement, or arthroplasty and (ii) PCR. We also manually searched the reference lists of eligible studies and review articles. Our reviewers independently evaluated the selected studies using the following inclusion criteria: (i) the study reported the accuracy of PCR for the diagnosis of joint infection in comparison with visible purulence of joint aspirate or surgical site, presence of a sinus tract (fistula) communicating with the prosthesis, acute inflammation in histopathology sections of periprosthetic tissue, or simultaneously obtained microbiologic cultures from at least two periprosthetic tissue samples (the reference standard); (ii) sufficient data were reported to allow us to calculate the truepositive (TP), false-negative (FN), false-positive (FP), and truenegative (TN) values; (iii) the study reported evaluations of at least 10 patients, from which data could be extracted using our standardized data collection form (X. Qu and Z. Zhai). Discrepancies were resolved by discussion with other investigators and by consulting the original articles (Huiwu Li and K. Dai). We estimated the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the curve (AUC) of summary receiver operating characteristic (ROC) curves to evaluate the capability of PCR assays for diagnosing PJI. We performed meta-regression and subgroup analyses to assess potential heterogeneity, and we constructed Deeks' funnel plot asymmetry test to evaluate potential publication bias. All of the statistical analyses were undertaken using STATA version 11 (StataCorp, College Station, TX).Our research yielded 2,024 primary st...

In order to quantitatively predict Peierls stress, a semi-discrete variational Peierls-Nabarro model is improved by incorporating an additional gradient energy term into the energy functional. This gradient energy term is designed to effectively represent the influence of both the discreteness of atoms and the quick variations of the displacement profile in the dislocation core. Using face-centered-cubic metals as a model system for validation, we obtain a more accurate prediction of the displacement profile across the slip plane, and consequent precise Peierls stress, within few times the prediction from molecular dynamics calculations.

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