Slow Passage through a Saddle-Node Bifurcation in Discrete Dynamical Systems

We study a discrete non-autonomous system whose autonomous counterpart (with the frozen bifurcation parameter) admits a saddle-node bifurcation, and in which the bifurcation parameter slowly changes in time and is characterized by a sweep rate constant $\epsilon$. The discrete system is more appropriate for modeling realistic systems since only time series data is available. We show that in contrast to its autonomous counterpart, when the time mesh size $\Delta t$ is less than the order $O(\epsilon)$, there is a bifurcation delay as the bifurcation time-varying parameter is varied through the bifurcation point, and the delay is proportional to the two-thirds power of the sweep rate constant $\epsilon$. This bifurcation delay is significant in various realistic systems since it allows one to take necessary action promptly before a sudden collapse or shift to different states. On the other hand, when the time mesh size $\Delta t$ is larger than the order $o(\epsilon)$, the dynamical behavior of the solution is dramatically changed before the bifurcation point. This behavior is not observed in the autonomous counterpart. Therefore, the dynamical behavior of the system strongly depends on the time mesh size. Finally. due to the very discrete feature of the system, there are no efficient tools for the analytical study of the system. Our approach is elementary and analytical

The Effects of Game Players’ Social Intelligence on Social Support and Psychosocial Problem Factors in a 2-Wave Longitudinal Study

Although digital gaming may be considered a social medium, no prior study has investigated how young players’ social intelligence affects their psychosocial problems (aggression, depression, loneliness, and stress) and social functioning (relationships with parents and peers). The primary aim of this study was to investigate the relations between social intelligence and psychosocial outcomes. Using data from 1364 online game players in Korea, we conducted a 2-wave longitudinal study at 6-month intervals for tracking the same person. The findings indicated that level of social intelligence was negatively related with all measures of adverse emotions and positively related with relationships with parents and peers over time. The findings and implications are discussed

Why should we switch chest compression providers every 2 minutes during cardiopulmonary resuscitation?

Objective. Tis study was conducted to determine whether trained male rescuers could maintain adequate chest compression depth (CCD) for longer than the current recommended guidelines of 2 minutes. Methods. Forty male medical doctors administered a 5-minute single rescuer cardiopulmonary resuscitation (CPR) to a manikin on the foor with conventional CPR or randomly administered continuous chest compressions (CCC). Te ratio of compression to ventilation was set to 30:2 with mouth-to-mouth technique during conventional CPR. Chest compression data were recorded with an accelerometer device and divided into 1-minute segments for analysis. Results. Although average CCD maintained the recommended depths throughout 5 minutes in conventional CPR, it decreased signifcantly with CCC (1 minute: 55.4 ± 4.5 mm; 2 minutes: 54.2 ± 5.4 mm; 3 minutes: 52.6 ± 5.6 mm; 4 minutes: 51.6 ± 5.5 mm; 5 minutes: 49.9 ± 5.8 mm, p < 0.001). Te average chest compression numbers (ACCN) per minute were maintained over 80/min and have not been changed signifcantly within 5 minutes in the CCC. However, it didn’t reach to the 80/min and decreased signifcantly afer 3minutes compared to the baseline ACCN during frst 1-minute segment in the conventional CPR. Conclusions. Despite the chest compression providers being limited to trained male medical doctors, the average CCD decreased signifcantly within 5minutes with CCC. Although maintaining adequate CCD, ACCN in each minute decreased signifcantly afer 3minutes in the conventional CPR. Terefore, we should rotate chest compression providers every 2minutes regardless of the rescuer’s qualifcations and CPR methods

Mobile resistome of human gut and pathogen drives anthropogenic bloom of antibiotic resistance

BACKGROUND:The impact of human activities on the environmental resistome has been documented in many studies, but there remains the controversial question of whether the increased antibiotic resistance observed in anthropogenically impacted environments is just a result of contamination by resistant fecal microbes or is mediated by indigenous environmental organisms. Here, to determine exactly how anthropogenic influences shape the environmental resistome, we resolved the microbiome, resistome, and mobilome of the planktonic microbial communities along a single river, the Han, which spans a gradient of human activities. RESULTS:The bloom of antibiotic resistance genes (ARGs) was evident in the downstream regions and distinct successional dynamics of the river resistome occurred across the spatial continuum. We identified a number of widespread ARG sequences shared between the river, human gut, and pathogenic bacteria. These human-related ARGs were largely associated with mobile genetic elements rather than particular gut taxa and mainly responsible for anthropogenically driven bloom of the downstream river resistome. Furthermore, both sequence- and phenotype-based analyses revealed environmental relatives of clinically important proteobacteria as major carriers of these ARGs. CONCLUSIONS:Our results demonstrate a more nuanced view of the impact of anthropogenic activities on the river resistome: fecal contamination is present and allows the transmission of ARGs to the environmental resistome, but these mobile genes rather than resistant fecal bacteria proliferate in environmental relatives of their original hosts. Video abstract

An Innovative Geocentric Decision Support Solution to Comprehensive Planning, Design, Operation, and Management of Urban Drainage Systems

Geographic Information System (GIS) is quickly becoming a critical component to develop and sustain asset management for today’s wastewater utilities as most of their data is geographically referenced. This technology offers sophisticated data management and spatial analysis capabilities that can greatly improve and facilitate urban drainage infrastructure modeling and analysis applications. This paper presents a comprehensive GIS-based decision support system that integrates several technologies for use in the effective management of urban stormwater collection systems. It explicitly integrates ESRI ArcGIS geospatial model with advanced hydrologic, hydraulic, and water quality simulation algorithms, nature-based global optimization techniques including genetic algorithms for design and calibration of stormwater management models, automated dry weather flow generation and allocation, and automated subcatchment delineation and parameter extraction tools to address every facet of urban drainage infrastructure management. The geocentric interface allows seamless communication among the various modules. The resulting decision support system effortlessly reads GIS datasets, extracts necessary modeling information, and automatically constructs, loads, designs, calibrates, analyzes and optimizes a representative urban drainage model considering hydrologic and hydraulic performance requirements. It also makes it easy to run, simulate and compare various modeling scenarios, identify system deficiencies, and determine cost-effective physical and operational improvements to achieve optimum performance and regulatory compliance. These combined capabilities provide favorable geospatial environment to assist wastewater utilities in planning, designing, and operating reliable systems and in optimizing their capital improvement programs

Effect of N-substitution in naphthalenediimides on the electrochemical performance of organic rechargeable batteries

We have demonstrated that even small structural variations on the imide nitrogens of naphthalenediimides bearing identical Li-ion binding sites can cause dramatic effects in the performance of organic rechargeable batteries. In particular, naphthalenedimide dilithium salt showed excellent cycling with a capacity of 130 mA h g(-1) at potentials as high as 2.5 V vs. Li/Li+.

The role of Cra in regulating acetate excretion and osmotic tolerance in E. coli K-12 and E. coli B at high density growth

<p>Abstract</p> <p>Background</p> <p><it>E. coli </it>B (BL21), unlike <it>E.coli </it>K-12 (JM109) is insensitive to glucose concentration and, therefore, grows faster and produces less acetate than <it>E. coli </it>K-12, especially when growing to high cell densities at high glucose concentration. By performing genomic analysis, it was demonstrated that the cause of this difference in sensitivity to the glucose concentration is the result of the differences in the central carbon metabolism activity. We hypothesized that the global transcription regulator Cra (FruR) is constitutively expressed in <it>E. coli </it>B and may be responsible for the different behaviour of the two strains. To investigate this possibility and better understand the function of Cra in the two strains, <it>cra </it>- negative <it>E. coli </it>B (BL21) and <it>E. coli </it>K-12 (JM109) were prepared and their growth behaviour and gene expression at high glucose were evaluated using microarray and real-time PCR.</p> <p>Results</p> <p>The deletion of the <it>cra </it>gene in <it>E. coli </it>B (BL21) minimally affected the growth and maximal acetate accumulation, while the deletion of the same gene in <it>E.coli </it>K-12 (JM109) caused the cells to stop growing as soon as acetate concentration reached 6.6 g/L and the media conductivity reached 21 mS/cm. <it>ppsA </it>(gluconeogenesis gene), <it>aceBA </it>(the glyoxylate shunt genes) and <it>poxB </it>(the acetate producing gene) were down-regulated in both strains, while <it>acs </it>(acetate uptake gene) was down-regulated only in <it>E.coli </it>B (BL21). These transcriptional differences had little effect on acetate and pyruvate production. Additionally, it was found that the lower growth of <it>E. coli </it>K-12 (JM109) strain was the result of transcription inhibition of the osmoprotectant producing <it>bet </it>operon (<it>betABT</it>).</p> <p>Conclusions</p> <p>The transcriptional changes caused by the deletion of <it>cra </it>gene did not affect the activity of the central carbon metabolism, suggesting that Cra does not act alone; rather it interacts with other pleiotropic regulators to create a network of metabolic effects. An unexpected outcome of this work is the finding that <it>cra </it>deletion caused transcription inhibition of the <it>bet </it>operon in <it>E. coli </it>K-12 (JM109) but did not affect this operon transcription in <it>E. coli </it>B (BL21). This property, together with the insensitivity to high glucose concentrations, makes this the <it>E. coli </it>B (BL21) strain more resistant to environmental changes.</p

Variations in chest compression time, ventilation time and rescuers’ heart rate during conventional cardiopulmonary resuscitation in trained male rescuers

Objective This study was conducted to determine why rescuers could maintain adequate chest compression depth for longer periods during conventional cardiopulmonary resuscitation (CPR). Methods Various CPR parameters, including average compression depth (ACD), average compression rate, average ventilation time (AVT), and rescuers’ heart rates were recorded in real-time when 20 health care providers performed 10 minutes of conventional CPR during a simulation experiment. Results The ACD was maintained above 50 mm and was not significantly different during 19 consecutive CPR cycles. The average compression rate increased from 114.9±10.0/min (2nd cycle) to 120.1±13.8/min (18th cycle) (P=0.007), and the AVT increased from 8.7±1.5 seconds (3rd cycle) to 10.1±2.6 seconds (18th cycle) (P=0.002). The rescuers’ heart rates also increased gradually for 10 min; however, they increased rapidly and were highest during the ventilation phase. Their heart rates then decreased and were lowest during the early chest compression phases of each CPR cycle. Decreases in heart rates were significant in all CPR cycles (average decrease: 14.5±4.5 beats/min, P<0.001). Conclusion The ACD was maintained adequately during 10 minutes of conventional CPR. However, the AVT increased significantly during the 10-minute period. The rescuers’ heart rates increased and decreased throughout all CPR cycles. These results showed that the ventilation phase might play a role as a resting period and be a reason for the maintenance of adequate chest compression depth for prolonged periods during conventional CPR

Acinetobacter baumannii invades epithelial cells and outer membrane protein A mediates interactions with epithelial cells

<p>Abstract</p> <p>Background</p> <p><it>Acinetobacter baumannii </it>is a nosocomial pathogen of increasing importance, but the pathogenic mechanism of this microorganism has not been fully explored. This study investigated the potential of <it>A. baumannii </it>to invade epithelial cells and determined the role of <it>A. baumannii </it>outer membrane protein A (AbOmpA) in interactions with epithelial cells.</p> <p>Results</p> <p><it>A. baumannii </it>invaded epithelial cells by a zipper-like mechanism, which is associated with microfilament- and microtubule-dependent uptake mechanisms. Internalized bacteria were located in the membrane-bound vacuoles. Pretreatment of recombinant AbOmpA significantly inhibited the adherence to and invasion of <it>A. baumannii </it>in epithelial cells. Cell invasion of isogenic AbOmpA^-mutant significantly decreased as compared with wild-type bacteria. In a murine pneumonia model, wild-type bacteria exhibited a severe lung pathology and induced a high bacterial burden in blood, whereas AbOmpA^-mutant was rarely detected in blood.</p> <p>Conclusion</p> <p><it>A. baumannii </it>adheres to and invades epithelial cells. AbOmpA plays a major role in the interactions with epithelial cells. These findings contribute to the understanding of <it>A. baumannii </it>pathogenesis in the early stage of bacterial infection.</p