Microfluidic Mixing: A Review

The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Broadly speaking, microfluidic mixing schemes can be categorized as either “active”, where an external energy force is applied to perturb the sample species, or “passive”, where the contact area and contact time of the species samples are increased through specially-designed microchannel configurations. Many mixers have been proposed to facilitate this task over the past 10 years. Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers

A meson-exchange piN model up to energies sqrt(s) < 2.0 GeV

A meson-exchange piN model, previously constructed using three-dimensional reduction scheme of the Bethe-Salpeter equation for a model Lagrangian involving \pi, \eta, N, \Delta, rho, and \sigma fields, is extended to energies up to 2 GeV by including the \eta N channel and all the four stars \pi N resonances up to the F-waves. The effects of other 2 pion channels are taken into account phenomenologically. The extended model gives an excellent fit to both piN phase shifts and inelasticity parameters in all channels up to the F-waves. However, a few of the extracted resonance parameters differ considerably from the PDG values.Comment: 5 pages, 1 figire, 1 table. Talk presented at the 18th International Conference on "Few-Body Problems in Physics", Aug. 21-26, 2006, Santos, Brazi

Community-onset bacteremia in kidney transplant recipients: The recipients fare well in terms of mortality and kidney injury

BackgroundBloodstream infection is not uncommon in kidney transplant recipients (KTRs) and is associated with mortality, graft loss, and increased medical expenses. Whether these septic patients are more vulnerable to serious complications, resistant strains, or worse clinical outcomes than other patient groups in the community-onset settings remains undetermined.MethodsA retrospective study was conducted at a medical center in southern Taiwan. Community-onset bacteremia in the KTRs and a control population at the emergency department were identified. Demographic data, clinical characteristics, bacteremic pathogens, antimicrobial resistance, and clinical outcomes were recorded.ResultsForty-one bacteremic episodes in the KTRs and 82 episodes in control patients were studied. The KTR group had younger age, fewer malignancies, more urosepsis (61% vs. 22%, p = 0.004), and fewer biliary tract infections (0% vs. 13.4%, p = 0.018). Escherichia coli was the most commonly isolated pathogen in both the groups (51.2% and 41.5%, respectively). No Klebsiella pneumoniae bacteremia was noted in the KTRs, compared with 14 (17.1%) episodes in the control group (p = 0.010). Antimicrobial resistance profiles of bacteremic pathogens were similar (all p > 0.6). The KTRs with community-onset bacteremia did not have a worse outcome (in-hospital mortality rate: 2.4% vs. 10%, p = 0.172) nor more incomplete resolution of kidney injury after acute kidney injury events (21.1% vs. 25%, p > 0.99) than the control group.ConclusionKTRs with community-onset bacteremia did not fare worse in terms of clinical outcome and kidney injury

Fluoroquinolone therapy for bloodstream infections caused by extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae

AbstractBackground/PurposeFor extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae infections, carbapenems are recommended as first line therapy, and clinical data on the therapeutic efficacy of fluoroquinolones (FQs) is limited. This study compares the efficacy of FQs and carbapenems for bloodstream infections caused by ESBL-producing Escherichia coli or Klebsiella pneumoniae.MethodsBetween 2008 and 2010, adults with ESBL-producing E. coli or K. pneumoniae bacteremia at two medical centers were reviewed. Adults receiving definitive FQ or carbapenem therapy were compared in a propensity score-matched analysis, and 30-day mortality was the primary endpoint.ResultsA total of 299 patients were eligible. Patients receiving a FQ (n = 24), either ciprofloxacin or levofloxacin, had a lower 30-day mortality rate than those with carbapenem therapy (8.3%, 2/24 vs. 23.3%, 64/275; p = 0.12). Multivariate regression analysis revealed that a critical illness [Pitt bacteremia score ≥ 4 points; odds ratio (OR), 7.09; p < 0.001], rapidly fatal underlying disease (OR, 5.73; p < 0.001), and hospital-associated infection (OR, 2.57; p = 0.01) were independently associated with 30-day mortality. By contrast, FQ definitive therapy was a protective factor compared with carbapenems (OR, 0.18; p = 0.04). There were 72 matched cases with carbapenem therapy in a propensity score-matched analysis, and a difference in the 30-day mortality rate of two groups was noted (8.3% vs. 29.2%; p = 0.05).ConslusionFor ESBL-producing E. coli or K. pneumoniae bacteremia, ciprofloxacin or levofloxacin, if active in vitro, can be considered as a carbapenem-sparing alternative

Bacteremic pneumonia caused by extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: Appropriateness of empirical treatment matters

BackgroundClinical information about bacteremic pneumonia caused by extended-spectrum beta-lactamase (ESBL)-producing organism is limited.MethodsA retrospective study was conducted at two medical centers in Taiwan. From May 2002 to August 2010, clinical information and outcome of adults with bacteremic pneumonia caused by ESBL-producing Escherichia coli and Klebsiella pneumoniae were analyzed. The primary outcome is the 30-day mortality.ResultsA total of 111 patients with bacteremic pneumonia caused by E. coli (37 patients, 33.3%) and K. pneumoniae (74, 66.7%) were identified. Their mean age was 69.2 years and 51.4% were male patients. Fifty-seven (51.3%) episodes were classified as hospital-acquired infections, 19 (17.1%) as health-care-associated infections, and four (3.6%) as community-acquired infections. Fifty-one (45.9%) patients received appropriate empiric antimicrobial therapy. The 30-day mortality rate was 40.5% (45 patients). In the multivariate analysis, several independent risk factors, including rapidly fatal underlying disease [odds ratio (OR), 5.75; 95% confidence interval (CI), 1.54–21.48; p = 0.009], severe sepsis (OR, 4.84; 95% CI, 1.55–15.14; p = 0.007), critical illness (OR, 4.28; 95% CI, 1.35–13.57; p = 0.013), and receipt of appropriate empirical therapy (OR, 0.19; 95% CI, 0.07–0.55; p = 0.002), were associated with 30-day mortality. The survival analysis consistently found that individuals with appropriate empiric therapy had a higher survival rate (log-rank test, p < 0.001).ConclusionESBL-producing bacteremic pneumonia, especially health-care-associated infections, often occurred in adults with comorbidities. Appropriate empirical therapy was associated with a favorable outcome

Age-based spatial distribution of workers is resilient to worker loss in a subterranean termite

Elaborate task allocation is key to the ecological success of eusocial insects. Termite colonies are known for exhibiting age polyethism, with older instars more likely to depart the reproductive center to access food. However, it remains unknown how termites retain this spatial structure against external disturbances. Here we show that a subterranean termite Coptotermes formosanus Shiraki combines age polyethism and behavioral flexibility to maintain a constant worker proportion at the food area. Since this termite inhabits multiple wood pieces by connecting them through underground tunnels, disastrous colony splitting events can result in the loss of colony members. We simulated this via weekly removal of all individuals at the food area. Our results showed that termites maintained a worker proportion of ~ 20% at the food area regardless of changes in total colony size and demographic composition, where younger workers replaced food acquisition functions to maintain a constant worker proportion at the food area. Food consumption analysis revealed that the per-capita food consumption rate decreased with younger workers, but the colony did not compensate for the deficiency by increasing the proportion of workers at the feeding site. These results suggest that termite colonies prioritize risk management of colony fragmentation while maintaining suitable food acquisition efficiency with the next available workers in the colony, highlighting the importance of task allocation for colony resiliency under fluctuating environments

High Prevalence of Mutations in Quinolone-resistance-determining Regions and mtrR Loci in Polyclonal Neisseria gonorrhoeae Isolates at a Tertiary Hospital in Southern Taiwan

Background/PurposeThe emergence of multidrug-resistant Neisseria gonorrhoeae is a great challenge in controlling gonorrhea. This study was conducted to survey the prevalence of molecular mechanisms of antimicrobial resistance among 45 clinical isolates of N. gonorrhoeae collected at a university hospital in Southern Taiwan during 1999-2004.MethodsMutations in mtrR loci and quinolone-resistance-determining regions (QRDRs) were examined by gene sequencing. Polymerase chain reactions with specific primers were performed to detect ermA, ermB, ermC, and ermF. Serogroups and serovars were determined by commercial kits.ResultsThe percentage of multidrug resistance, that is, resistance to penicillin, tetracycline, erythromycin, and ciprofloxacin, among the 45 isolates was 40%. Ceftriaxone and spectinomycin were active against all isolates in vitro. The frequency of mutations in the QRDR and mtrR promoter was 82.2% and 93.3%, respectively. Eighty-two percent of the isolates carried mutations both in the QRDR and mtrR loci. Of nine mutation profiles with QRDR mutations (n =37), gyrA-Ser91Phe/gyrA-Asp95Gly/parC-Ser87Arg was the most common type (56.8%). Acquired genes for rRNA methylase were detected in 11 isolates (10 ermB and 1 ermA). Twenty-seven serovars were identified and all belonged to serogroup B, which suggested that multiple clones of N. gonorrhoeae were circulating in the community in the Tainan area.ConclusionThe high prevalence of multidrug resistance caused by varied resistance mechanisms in N. gonorrhoeae limits the drug choice. Ongoing surveillance of antimicrobial resistance and discovery of new effective antibiotic therapy are warranted in endemic areas