Effect of Porosity and Heat Treatment on Mechanical Properties of Additive Manufactured CoCrMo Alloys.

To minimize the stress shielding effect of metallic biomaterials in mimicking bone, the body-centered cubic (bcc) unit cell-based porous CoCrMo alloys with different, designed volume porosities of 20, 40, 60, and 80% were produced via a selective laser melting (SLM) process. A heat treatment process consisting of solution annealing and aging was applied to increase the volume fraction of an ε-hexagonal close-packed (hcp) structure for better mechanical response and stability. In the present study, we investigated the impact of different, designed volume porosities on the compressive mechanical properties in as-built and heat-treated CoCrMo alloys. The elastic modulus and yield strength in both conditions were dramatically decreased with increasing designed volume porosity. The elastic modulus and yield strength of the CoCrMo alloys with a designed volume porosity of 80% exhibited the closest match to those of bone tissue. Different strengthening mechanisms were quantified to determine their contributing roles to the measured yield strength in both conditions. The experimental results of the relative elastic modulus and yield strength were compared to the analytical and simulation modeling analyses. The Gibson-Ashby theoretical model was established to predict the deformation behaviors of the lattice CoCrMo structures.

The role of pgaC in Klebsiella pneumoniae virulence and biofilm formation.

BACKGROUND: Klebsiella pneumoniae has emerged as one of the major pathogens for community-acquired and nosocomial infections. A four-gene locus that had a high degree similarity with Escherichia coli pgaABCD and Yersinia pestis hmsHFRS was identified in K. pneumoniae genomes. The pgaABCD in E. coli encodes the envelope-spanning Pga machinery for the synthesis and secretion of poly-ß-linked N-acetylglucosamine (PNAG). In a limited number of phylogenetically diverse bacteria, PNAG was demonstrated to mediate biofilm formation and had a role in the host-bacteria interactions. The presence of conserved pgaABCD locus among various K. pneumoniae strains suggested a putative requirement of PNAG for this bacterium. RESULTS: In this study, an in-frame deletion of pgaC was generated in K. pneumoniae CG43 and named ΔpgaC. The loss of pgaC affected the production of PNAG and attenuated the enhancement of in vitro biofilm formation upon the addition of bile salts mixture. In mouse models, ΔpgaC exhibited a weakened ability to colonize the intestine, to disseminate extraintestinally, and to induce a systemic infection when compared to K. pneumoniae CG43. CONCLUSIONS: Our study demonstrated that pgaC participated in the bile salts induced biofilm formation and was required for K. pneumoniae virulence in vivo.

Clinical manifestations of Japanese encephalitis in southern Taiwan.

BACKGROUND AND PURPOSE: Japanese encephalitis virus infection is a sporadic infectious disease in Taiwan. Despite progress in laboratory examinations and imaging studies, diagnosis of Japanese encephalitis remains underestimated. This study was conducted to identify clinical symptoms and laboratory findings that may assist in early identification of this disease. METHODS: This retrospective study included all patients diagnosed with Japanese encephalitis at Kaohsiung Veterans General Hospital from January 2000 through December 2007. Epidemiologic data, predisposing factors, neurological and non-neurological signs and symptoms, laboratory data, and treatment were analyzed. Outcomes and neurological complications were evaluated. RESULTS: Eleven patients had Japanese encephalitis, and 10 had sufficient information for enrolment into the study. Nine patients presented with non-significant constitutional symptoms of fever, nausea, or headache. Other signs and symptoms included rhinorrhea, sore throat, abdominal pain, cough, myalgia, or arthralgia. Eight patients had lymphocytic pleocytosis with elevated protein and borderline low glucose levels in the cerebrospinal fluid. Leptomeningeal enhancement and low density lesions were the most common computed tomography findings. T2 hyperintensity lesions and leptomeningeal enhancement were seen in 5 patients. Two patients presenting with acute flaccid paralysis had high intensity lesions on the thalamus and basal ganglion. There were no correlations between clinical, laboratory, and imaging findings. None of the patients had neurological sequelae. CONCLUSIONS: Presentations, laboratory examination, and clinical signs are not specific for Japanese encephalitis. Sporadic cases are usually seen from May to August, which are associated with monsoon rains. Hence increased awareness of this disease is recommended during these periods.