The non-linear dynamics of a rigid rotor levitated by active magnetic bearings is investigated. The vibrations in the horizontal and vertical directions are analyzed on the center manifold near the ...double-zero degenerate point by using normal-form method. The resulting normal forms in the horizontal and vertical directions are different due to the effect of rotor weight. It is shown that the vibratory behavior in the vertical direction can be reduced on the center manifold to the Bogdanov–Takens form. For the autonomous case, there exist saddle-node bifurcation and Hopf bifurcation for local analysis, and a saddle-connection bifurcation for global analysis. For non-autonomous case, the Melnikov technique is used to determine the critical parameter at which the homoclinic orbits intersect transversally. For the vibrations in the horizontal direction, the essential non-linear terms of the truncated normal form are third order. The behaviors of zero solutions are given. Finally, numerical simulations are performed to verify the analytical predictions.
To test the hypothesis that prognostication of treatment outcome is feasible by biomarker response at midcourse of chemoradiotherapy (CRT)/radiotherapy (RT), with respect to the plasma load of ...Epstein–Barr viral (EBV) DNA in nasopharyngeal carcinoma (NPC).
One hundred seven patients with stage IIB–IV NPC were prospectively studied. Plasma EBV DNA load was measured by quantitative PCR before therapy (pre-DNA), at completion of 4 weeks of CRT/RT (mid-DNA), and within 3 months of completion of therapy (post-DNA). The end points are post-DNA load, a recognized surrogate of survival, and clinical outcome.
Ninety-three percent of patients had detectable EBV DNA before therapy (median load = 972 copies/ml). EBV DNA became undetectable in 55 (51%) patients at the end of week 4 of therapy. Detectable mid-DNA was associated with worse clinical outcome (median follow-up time, 6.2 years), for distant failure hazard ratio (HR) 12.02, 95% confidence interval (CI) 2.78–51.93; P < 0.0001, progression-free survival (PFS; HR 4.05, 95% CI 1.89–8.67, P < 0.0001), and overall survival (OS; HR 3.29, 95% CI 1.37–7.90, P = 0.0077). Seventy-four percent of all failures were associated with detectable mid-DNA, whereas 34% of all failures were associated with detectable post-DNA. Stratification by tumor stage (IIB, III, IV) has no significant prognostic effect.
Unfavorable EBV DNA response at midcourse of RT/CRT is an adverse prognosticator for treatment outcome, is linked to majority of all failures, and discriminates outcome better than tumor stage. The data could provide a basis for trial design that addresses alteration of therapy intensity during the latter phase of CRT, and adjuvant therapy. Validation studies are awaited.
Nasopharyngeal carcinoma (NPC) is highly sensitive to both radiotherapy (RT) and chemotherapy. This randomized phase III trial compared concurrent cisplatin-RT (CRT) with RT alone in patients with ...locoregionally advanced NPC.
Patients with Ho's N2 or N3 stage or N1 stage with nodal size > or = 4 cm were randomized to receive cisplatin 40 mg/m(2) weekly up to 8 weeks concurrently with radical RT (CRT) or RT alone. The primary end point was progression-free survival (PFS).
Three hundred fifty eligible patients were randomized. Baseline patient characteristics were comparable in both arms. There were significantly more toxicities, including mucositis, myelosuppression, and weight loss in the CRT arm. There were no treatment-related deaths in the CRT arm, and one patient died during treatment in the RT-alone arm. At a median follow-up of 2.71 years, the 2-year PFS was 76% in the CRT arm and 69% in the RT-alone arm (P =.10) with a hazards ratio of 1.367 (95% confidence interval CI, 0.93 to 2.00). The treatment effect had a significant covariate interaction with tumor stage, and a subgroup analysis demonstrated a highly significant difference in favor of the CRT arm in Ho's stage T3 (P =.0075) with a hazards ratio of 2.328 (95% CI, 1.26 to 4.28). For T3 stage, the time to first distant failure was statistically significantly different in favor of the CRT arm (P =.016).
Concurrent CRT is well tolerated in patients with advanced NPC in endemic areas. Although PFS was not significantly different between the concurrent CRT arm and the RT-alone arm in the overall comparison, PFS was significantly prolonged in patients with advanced tumor and node stages.
Tuned mass dampers (TMD) have been widely used to attenuate undesirable vibrations in engineering. Most optimization problems of TMD are solved by either numerical iteration technique or conventional ...mathematical methods that require substantial gradient information. The selection of the starting values is very important to ensure convergence. In this paper, we use a novel evolutionary algorithm of particle swarm optimization (PSO) for optimization of the required parameters of a TMD. Optimum parameters of the TMD system attached to a viscously damped single degree-of-freedom main system are obtained by minimizing some response quantities, for examples, the mean square displacement responses and displacement amplitude of the main system under various combinations of different kinds of excitations. The excitations considered include external force and base acceleration modeled as Gaussian white-noise random processes. Harmonic base acceleration with frequency invariant amplitude is also considered. The PSO can be used to find the optimum mass ratio, damper damping and tuning frequency of the TMD system and can be easily programmed for practical engineering applications. Explicit expressions of the optimum TMD parameters are given for engineering designers.
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•Experiments were done on cyclone separators with/without bottom down-comer tubes.•Cyclone performance parameters were evaluated for different solid loading rates.•Discussed ...improvements of fine particle collection (PM 2.5) with down-comer tubes.•Results were compared with established theories.
Enhancement of fine particle (PM2.5) separation is important for cyclone separators to reduce any extra purification process required at the outlet. Therefore, the present experimental research was performed to explore the performance of cyclone separators modified with down-comer tubes at solid loading rates from 0 to 8.0g/m3 with a 10m/s inlet velocity. The study proved the effectiveness of down-comer tubes in reducing the particle re-entrainment and increasing the finer separation with acceptable pressure drops, which was pronounced at low solid loading conditions. The experimental results were compared with theories of Smolik and Muschelknautz. Theories were acceptable for certain ranges, and theory breakdown was mainly due to the neglect of particle agglomeration, re-entrainment and the reduction of swirling energy, as well as the increase of wall friction due to presence of particles.
We investigated antibacterial activity of ZnO nanorods prepared by a hydrothermal method against a gram-negative bacterium
Escherichia coli and a gram-positive bacterium
Bacillus atrophaeus. ...Antibacterial activity of ZnO nanorod coatings was studied on solid substrates covered with nutrient agar, as well as in liquid nutrient broth for different concentrations of ZnO nanorods, nanoparticles, and powder. ZnO exhibited antibacterial activity against both
E. coli and
B. atrophaeus, but it was considerably more effective in the latter case (at 15 mM vs. 5 mM concentration, respectively, showing zero viable cell count). For both organisms, damage of the cell membranes was found, and the effect was more pronounced for
B. atrophaeus. Chemiluminescence analysis has been used to detect the release of hydrogen peroxide from ZnO structures, and the effect of H
2O
2 on the
E. coli and
B. atrophaeus was studied. Since significant differences were observed in the effect of ZnO nanostructures and H
2O
2 on
B. atrophaeus, it can be concluded that there are other mechanisms contributing to the antibacterial activity of ZnO nanostructures.
This study aimed to conduct a systematic review to sum up evidence of the associations between different aspects of night shift work and female breast cancer using a dose–response meta-analysis ...approach.
We systematicly searched all cohort and case–control studies published in English on MEDLINE, Embase, PSYCInfo, APC Journal Club and Global Health, from January 1971 to May 2013. We extracted effect measures (relative risk, RR; odd ratio, OR; or hazard ratio, HR) from individual studies to generate pooled results using meta-analysis approaches. A log-linear dose–response regression model was used to evaluate the relationship between various indicators of exposure to night shift work and breast cancer risk. Downs and Black scale was applied to assess the methodological quality of included studies.
Ten studies were included in the meta-analysis. A pooled adjusted relative risk for the association between ‘ever exposed to night shift work’ and breast cancer was 1.19 95% confidence interval (CI) 1.05–1.35. Further meta-analyses on dose–response relationship showed that every 5-year increase of exposure to night shift work would correspondingly enhance the risk of breast cancer of the female by 3% (pooled RR = 1.03, 95% CI 1.01–1.05; Pheterogeneity < 0.001). Our meta-analysis also suggested that an increase in 500-night shifts would result in a 13% (RR = 1.13, 95% CI 1.07–1.21; Pheterogeneity = 0.06) increase in breast cancer risk.
This systematic review updated the evidence that a positive dose–response relationship is likely to present for breast cancer with increasing years of employment and cumulative shifts involved in the work.
Summary The study cohort comprised 196 females and 163 males. Lumbar spine bone mineral density (BMD) and magnetic resonance imaging (MRI) were acquired. Females had more severe disc degeneration ...than males. Lumbar spine lower BMD was associated with less severe disc degeneration. Lumbar disc spaces were more likely to be narrower when vertebral BMD was higher. Introduction The purpose of this paper is to study the relationship between gender, BMD, and disc degeneration in the lumbar spine. Methods The study cohort comprised 196 females and 163 males (age range 67-89 years) with no age difference between the two groups. Lumbar spine BMD was measured with dual X-ray densitometry, and MRI was acquired at 1.5 T. A subgroup of 48 males had additional lumbar vertebral quantitative computerized tomography densitometry. Lumbar disc degeneration was assessed using a MRI-based eight-level grading system. Results Female subjects had more severe disc degeneration than male subjects. After removing age effect, a positive trend was observed between T-score and severity of lumbar disc degeneration. This was significant in female subjects while not significant in male subjects. Lumbar disc spaces were more likely to be narrowed when vertebral BMD was higher. These observations were more significant in the midlumbar region (L3/4 and L4/5) and less so at the thoracolumbar junction. Conclusion Female subjects tended to have slightly more severe lumbar disc degeneration than male subjects. Lower lumbar spine BMD was associated with less severe disc degeneration.
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