BACKGROUND/PURPOSE: Prosthetic joint infection (PJI) has become an important issue in the management of patients who receive prostheses. We compared the clinical outcomes of PJIs caused by Gram-negative bacteria (GN PJIs) and Gram-positive bacteria (GP PJIs). METHODS: Patients with culture-proven PJIs admitted to China Medical University Hospital between March 2001 and March 2009 were included in this retrospective study. RESULTS: Fifty-nine patients were diagnosed with PJI during the study period. Nineteen patients had GN PJIs (mean age: 68 years) and 40 had GP PJIs (mean age: 61 years). The most common comorbid condition was diabetes mellitus (23.7%) and the most common presentation was joint pain (79.7%). Staphylococcus aureus was the most common pathogen, whereas Klebsiella pneumoniae was the most common Gram-negative pathogen. The GN PJI group included more cases of hematogenous infection (36.8% vs. 20%; p < 0.001), showed a shorter interval between onset of infection symptoms and surgical intervention (median: 8 days vs. 21 days; p = 0.04), and required longer medical treatment (median: 259 days vs. 161 days; p = 0.04). In comparison with patients whose prostheses were eventually removed, patients whose prostheses were not removed had a shorter interval between onset of infection symptoms and surgical intervention (median: 6 days vs. 90 days; p = 0.004 and median: 6 days vs. 44 days; p = 0.04) in the GP PJI and GN PJI groups, respectively. CONCLUSION: GN PJI was less common than GP PJI, but GN PJI was more complicated and required longer treatment. Prospective randomized clinical studies are needed to investigate whether prosthesis implantation should be reserved if the patient undergoes early surgical intervention for PJI.

Uncertainty in arterial input function (AIF) estimation is one of the major errors in the quantification of dynamic contrast-enhanced MRI. A blind source separation algorithm was proposed to determine the AIF by selecting the voxel time course with maximum purity, which represents a minimal contamination from partial volume effects. Simulations were performed to assess the partial volume effect on the purity of AIF, the estimation accuracy of the AIF, and the influence of purity on the derived kinetic parameters. In vivo data were acquired from six patients with hypopharyngeal cancer and eight rats with brain tumor. Results showed that in simulation the AIF with the highest purity is closest to the true AIF. In patients, the manually selection had reduced purity, which could lead to underestimations of K(trans) and V(e) and an overestimation of V(p) when compared with those obtained by the proposed blind source separation algorithm. The derived kinetic parameters in the tumor were more susceptible to the changes in purity when compared with those in the muscle. The animal experiment demonstrated good reproducibility in blind source separation-AIF derived parameters. In conclusion, the blind source separation method is feasible and reproducible to identify the voxel with the tracer concentration time course closest to the true AIF. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

The carbohydrate binding specificities are different among avian and human influenza A viruses and may affect the tissue tropism and transmission of these viruses. The glycan binding biology for influenza B, however, has not been systematically characterized. Glycan binding specificities of influenza B viral isolates were analyzed and correlated to hemagglutinin (HA) genotypes and clinical manifestations. A newly developed solution glycan array was applied to characterize the receptor binding specificities of influenza B virus clinical isolates from 2001 to 2007 in Taiwan. Thirty oligosaccharides which include α-2,3 and α-2,6 linkage glycans were subjected to analysis. The glycan binding patterns of 53 influenza B isolates could be categorized into three groups and were well correlated to their HA genotypes. The Yamagata-like strains predominantly bound to α-2,6-linkage glycan (24:29, 83%) while Victoria-like strains preferentially bound to both α-2,3- and α-2,6-linkage glycans (13:24, 54%). A third group of viruses bound to sulfated glycans and these all belonged to Victoria-like strains. Based on the HA sequences, Asn-163, Glu-198, Ala-202, and Lys-203 were conserved among Victoria-like strains which may influence their carbohydrate recognition. The viruses bound to dual type glycans were more likely to be associated with the development of bronchopneumonia and gastrointestinal illness than those bound only to α-2,6 sialyl glycans (P < 0.05). Glycan binding analyses provide additional information to monitor the antigenic shift, tissue tropism, and transmission capability of influenza B viruses, and will contribute to virus surveillance and vaccine strain selection. J. Med. Virol. 84:679-685, 2012. © 2011 Wiley Periodicals, Inc.

Flow coefficients v_{n} for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at sqrt[s_{NN}]=200  GeV, are measured relative to event planes Ψ_{n}, determined at large rapidity. We report v_{n} as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v_{n} are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.

Back-to-back hadron pair yields in d+Au and p+p collisions at sqrt[s_{NN}]=200  GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p_{T}, and η points to cold nuclear matter effects arising at high parton densities.

We present measurements of J/ψ yields in d+Au collisions at sqrt[s_{NN}]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

SUMMARY In vivo dynamic contrast-enhanced imaging tools provide non-invasive methods for analyzing various functional changes associated with disease initiation, progression and responses to therapy. The quantitative application of these tools has been hindered by its inability to accurately resolve and characterize targeted tissues due to spatially mixed tissue heterogeneity. Convex Analysis of Mixtures - Compartment Modeling (CAM-CM) signal deconvolution tool has been developed to automatically identify pure-volume pixels located at the corners of the clustered pixel time series scatter simplex and subsequently estimate tissue-specific pharmacokinetic parameters. CAM-CM can dissect complex tissues into regions with differential tracer kinetics at pixel-wise resolution and provide a systems biology tool for defining imaging signatures predictive of phenotypes. AVAILABILITY The MATLAB source code can be downloaded at the authors' website www.cbil.ece.vt.edu/software.htm CONTACT yuewang@vt.edu SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) provides a noninvasive method for evaluating tumor vasculature patterns based on contrast accumulation and washout. However, due to limited imaging resolution and tumor tissue heterogeneity, tracer concentrations at many pixels often represent a mixture of more than one distinct compartment. This pixel-wise partial volume effect (PVE) would have profound impact on the accuracy of pharmacokinetics studies using existing compartmental modeling (CM) methods. We, therefore, propose a convex analysis of mixtures (CAM) algorithm to explicitly mitigate PVE by expressing the kinetics in each pixel as a nonnegative combination of underlying compartments and subsequently identifying pure volume pixels at the corners of the clustered pixel time series scatter plot simplex. The algorithm is supported theoretically by a well-grounded mathematical framework and practically by plug-in noise filtering and normalization preprocessing. We demonstrate the principle and feasibility of the CAM-CM approach on realistic synthetic data involving two functional tissue compartments, and compare the accuracy of parameter estimates obtained with and without PVE elimination using CAM or other relevant techniques. Experimental results show that CAM-CM achieves a significant improvement in the accuracy of kinetic parameter estimation. We apply the algorithm to real DCE-MRI breast cancer data and observe improved pharmacokinetic parameter estimation, separating tumor tissue into regions with differential tracer kinetics on a pixel-by-pixel basis and revealing biologically plausible tumor tissue heterogeneity patterns. This method combines the advantages of multivariate clustering, convex geometry analysis, and compartmental modeling approaches. The open-source MATLAB software of CAM-CM is publicly available from the Web.

BACKGROUND In Taiwan, liver transplantation is a common treatment of end-stage liver diseases. Infection has a negative impact on the survival of these patients and their grafts. We evaluated the timing and frequency of infections, and the risk factors associated with infection and mortality in liver transplant recipients from Taiwan. METHODS This retrospective study enrolled all adult patients who underwent orthotopic liver transplantation from January 2004 to November 2008 at a tertiary hospital in Taiwan. RESULTS Sixty-eight patients were enrolled (male/female = 46/22) and average age was 51.3 years. Bacterial infection (26/68, 38.2%) was the most common infectious disease, with a rate of 0.3/1,000 person-days in the perioperative period, 0.27/1,000 person-days in the early operative period, and 0.38/1,000 person-days in the late-operative period. Operation-related complications increased the risk of bacterial infection. Biliary stricture was the most common operation-related complication, and this was associated with biliary tract infection (p < 0.001). The average time from first stent placement for biliary stricture by endoscopic retrograde cholangiography to biliary tract infection was 34.5 days. The overall mortality rate was 11.7%, and the mortality rate was 14% for patients with infections. CONCLUSIONS Bacterial infection was the most common type of infection in liver transplant recipients. Surgery-related complication, especially biliary tract stricture was risk factor for infection. We suggest that the current recommendations about the timing of endoscopic retrograde cholangiography intervention be reevaluated.

Large parity-violating longitudinal single-spin asymmetries A(L)(e+)=-0.86(-0.14)(+0.30) and A(L)(e-)= 0.88(-0.71)(+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s]= 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e))= 144.1 ± 21.2(stat)(-10.3)(+3.4)(syst) ± 21.6(norm)  pb, and σ(pp → W- X) × BR(W- → e- ν[over ¯](e))= 31.7 ± 12.1(stat)(-8.2)(+10.1)(syst) ± 4.8(norm)  pb.