Bifurcations of families of 1D-tori in 4D symplectic maps

The regular structures of a generic 4D symplectic map with a mixed phase space are organized by one-parameter families of elliptic 1D-tori. Such families show prominent bends, gaps, and new branches. We explain these features in terms of bifurcations of the families when crossing a resonance. For these bifurcations no external parameter has to be varied. Instead, the longitudinal frequency, which varies along the family, plays the role of the bifurcation parameter. As an example we study two coupled standard maps by visualizing the elliptic and hyperbolic 1D-tori in a 3D phase-space slice, local 2D projections, and frequency space. The observed bifurcations are consistent with analytical predictions previously obtained for quasi-periodically forced oscillators. Moreover, the new families emerging from such a bifurcation form the skeleton of the corresponding resonance channel.Comment: 14 pages, 10 figures. For videos of 3D phase-space slices see http://www.comp-phys.tu-dresden.de/supp

Ready, set, crisis – transitioning to crisis mode in local public administration

Local public administrations are typically the first responders during disruptive crisis events. Building on literature on fast-response organizations, this study theorizes on their ability to transition effectively from routine bureaucracy to crisis mode. Empirically, we study early responses to COVID-19 in Germany with agency-level survey data. The findings suggest that an effective switch between practices cannot be explained by crisis severity alone. Instead, organizational, technical, and individual preparedness of local administrations matter. These results provide insights into the conditions that enable administrations to respond effectively to crisis events, offering a comprehensive understanding of crisis management capabilities at the local level

COMMUNICATION ANONYMIZERS: PERSONALITY, INTERNET PRIVACY LITERACY AND THEIR INFLUENCE ON TECHNOLOGY ACCEPTANCE

Despite the fact that many individuals are concerned about privacy issues on the Internet and know about the existence of communication anonymizers, very few individuals actually use them. This discrepancy can only partially be explained by evident factors such as a small degree of knowledge about Internet privacy issues, or the latency of the Internet connection caused by communication anonymizers. In this study, we determine factors that influence the acceptance of communication anonymizers: the role of personality traits of individuals, the actual knowledge about privacy issues on the Internet and how much individuals really know about them, as well as the time an individual is willing to wait when using a communication anonymizer. Our study shows that the personality traits ?Agreeableness,? ?Extroversion? and ?Conscientiousness? do not influence an individual?s acceptance of communication anonymizers. Further, we can show that individuals with a strong personality trait of neuroticism are more likely to have strong privacy concerns and that individuals that can be characterized as ?open? are more likely to use communication anonymizers. With regard to the knowledge about privacy issues on the Internet, we find that individuals generally possess a low knowledge. Surprisingly, we find a negative correlation between an individual?s ?stated? and his/her ?actual? knowledge of privacy issues. Last, we find that individuals are willing to wait slightly longer (3.5 seconds) when using communication anonymizers

ARE YOU WILLING TO WAIT LONGER FOR INTERNET PRIVACY?

It becomes increasingly common for governments, service providers and specialized data aggregators to systematically collect traces of personal communication on the Internet without the user’s knowledge or approval. An analysis of these personal traces by data mining algorithms can reveal sensitive personal information, such as location data, behavioral patterns, or personal profiles including preferences and dislikes. Recent studies show that this information can be used for various purposes, for example by insurance companies or banks to identify potentially risky customers, by governments to observe their citizens, and also by repressive regimes to monitor political opponents. Online anonymity software, such as Tor, can help users to protect their privacy, but often comes at the prize of low usability, e.g., by causing increased latency during surfing. In this exploratory study, we determine factors that influence the usage of Internet anonymity software. In particular, we show that Internet literacy, Internet privacy awareness and Internet privacy concerns are important antecedents for determining an Internet user’s intention to use anonymity software, and that Internet patience has a positive moderating effect on the intention to use anonymity software, as well as on its perceived usefulness

Forced dynamic dewetting of structured surfaces: Influence of surfactants

We analyse the dewetting of printing plates for gravure printing with well-defined gravure cells. The printing plates were mounted on a rotating horizontal cylinder that is half immersed in an aqueous solution of the anionic surfactant sodium 1-decanesulfonate. The gravure plates and the presence of surfactants serve as one example of a real-world dewetting situation. When rotating the cylinder, a liquid meniscus was partially drawn out of the liquid forming a dynamic contact angle at the contact line. The dynamic contact angle is decreased on a structured surface as compared to a smooth one. This is due to contact line pinning at the borders of the gravure cells. Additionally, surfactants tend to decrease the dynamic receding contact angle. We consider the interplay between these two effects. We compare the height differences of the meniscus on the structured and unstructured area as function of dewetting speeds. The height difference increases with increasing dewetting speed. With increasing size of the gravure cells this height difference and the induced changes in the dynamic contact angle increased. By adding surfactant, the height difference and the changes in the contact angle for the same surface decreased. We further note that although the liquid dewets the printing plates some liquid is always left in the gravure cell. At high enough surfactant concentrations or high enough dewetting speed, the dynamic contact angles in the structured surface approach those in flat surfaces. We conclude that surfactant reduces the influence of surface structure on dynamic dewetting

Distributed Performance Measurement and Usability Assessment of the Tor Anonymization Network

While the Internet increasingly permeates everyday life of individuals around the world, it becomes crucial to prevent unauthorized collection and abuse of personalized information. Internet anonymization software such as Tor is an important instrument to protect online privacy. However, due to the performance overhead caused by Tor, many Internet users refrain from using it. This causes a negative impact on the overall privacy provided by Tor, since it depends on the size of the user community and availability of shared resources. Detailed measurements about the performance of Tor are crucial for solving this issue. This paper presents comparative experiments on Tor latency and throughput for surfing to 500 popular websites from several locations around the world during the period of 28 days. Furthermore, we compare these measurements to critical latency thresholds gathered from web usability research, including our own user studies. Our results indicate that without massive future optimizations of Tor performance, it is unlikely that a larger part of Internet users would adopt it for everyday usage. This leads to fewer resources available to the Tor community than theoretically possible, and increases the exposure of privacy-concerned individuals. Furthermore, this could lead to an adoption barrier of similar privacy-enhancing technologies for a Future Internet. View Full-Tex

Structure and properties of fluorinated and non‐fluorinated Ba‐coordination polymers – the position of fluorine makes the difference

As the most electronegative element, fluorine has a strong influence on material properties such as absorption behaviour or chemical and thermal stability. Fluorine can be easily integrated into coordination polymers (CPs) via a fluorinated acetate, here trifluoroacetate in Ba(CF3COO)2, or directly via a metal fluorine bond (BaF(CH3COO)). In the present study both possibilities of fluorine integration were tested and their effect on structure and properties of barium coordination polymers was investigated in comparison with the non-fluorinated barium acetate (Ba(CH3COO)2). In addition to the study of their thermal behaviour and their decomposition temperature, the CPs structures were tested for their application as possible anode materials in lithium ion batteries and for their sorption of water and ammonia. The properties of the CPs can be traced back to the individual structural motifs and could thus trigger new design ideas for CPs in LIBs and/or catalysis.HU BerlinBAMPeer Reviewe

Predictors of trajectories of obsessive-compulsive symptoms during the COVID-19 pandemic in the general population in Germany

The COVID-19 pandemic has been associated with an increase in obsessive-compulsive disorder/symptoms (OCD/OCS). However, knowledge is limited regarding the trajectories of OCS during the pandemic, as well as their predictors and mechanisms (e.g., experiential avoidance, EA). The aim of this study was to describe the trajectories of OCS and the identification of associated factors. We assessed 1207 participants of the general population in March 2020 (t1) and June 2020 (t2). Pre-pandemic data was available from March 2014 for a subsample (n=519). To define trajectories, we determined OCS status (OCS+/-). We performed a hierarchical multinomial logistic regression to investigate predictors of trajectories. Between t1 and t2, 66% of participants had an asymptomatic trajectory (OCS-/OCS-); 18% had a continuously symptomatic trajectory (OCS+/OCS+). Ten percent had a delayed-onset trajectory (OCS-/OCS+), and the recovery trajectory group (OCS+/OCS-) was the smallest group (6%). Higher education reduced the odds of an OCS+/OCS- trajectory. OCS in 2014 was associated with increased odds of showing an OCS+/OCS+ or OCS-/OCS+ trajectory. When EA at t1 and change in EA from t1 to t2 were added to the model, higher EA at t1 was associated with increased odds of scoring above the cut score on one or more of the assessments. A higher decrease in EA from t1 to t2 reduced the probability of showing an OCS+/OCS+ and an OCS-/OCS+ trajectory. While the current data supports a slight increase in OCS during the pandemic, trajectories differed, and EA seems to represent an important predictor for an unfavorable development

Family predictors of physical activity change during the COVID-19 lockdown in preschool children in Germany

The COVID-19 pandemic is associated with crucial changes in children’s daily life including their physical activity (PA) and screen time (ST). Among preschool children, the family represents an important factor for sufficient PA levels by being the gatekeeper for PA. Thus, the aim of this study was to investigate the influence of the family environment, specifically SES, parental support, and having siblings on COVID-19-related changes of PA and ST behavior in 317 (170 boys, 147 girls) German preschool children using longitudinal data. Our results indicate a decline in total amount of sports-related PA, an increase in outdoor play, as well as an increase in leisure ST in preschool children. The changes in total amount of PA differed between children with different levels of parental support as well as in dependence on having siblings. Furthermore, levels of outdoor play and ST in preschool children were influenced by environmental factors like having access to their own garden. We conclude that the family environment (parental support as well as physical environment) is highly relevant for PA and ST levels in preschool children. To provide every child with PA opportunities during potential future lockdowns, restriction policies should be adapted and parents need sophisticated information about the importance of their support and thus the PA levels of their children

Diagnostic accuracy of C-reactive protein and white blood cell counts in the early detection of inflammatory complications after open resection of colorectal cancer: a retrospective study of 1,187 patients

Purpose: Although widely used, there is a lack of evidence concerning the diagnostic accuracy of C-reactive protein (CRP) and white blood cell counts (WBCs) in the postoperative period. The aim of this study was to evaluate the diagnostic accuracy of CRP and WBCs in predicting postoperative inflammatory complications after open resection of colorectal cancer. Methods: In this retrospective study, clinical data and the CRP and WBCs, routinely measured until postoperative day5 (POD 5), were available for 1,187 patients who underwent colorectal cancer surgery between 1997 and 2009. Using the receiver-operating characteristic (ROC) methodology, the diagnostic accuracy was evaluated according to the area under the curve (AUC). Results: Three hundred forty-seven patients (29.2%; 95% CI, 26.7-31.9%) developed various inflammatory complications. Anastomotic leakage occurred in 8.0% (95% CI, 6.1-9.1%) of patients. The CRP level on POD 4 (AUC 0.76; 95% CI, 0.71-0.81) had the highest diagnostic accuracy for the early detection of inflammatory complications. With a cutoff of 123mg/l, the sensitivity was 0.66 (95% CI, 0.56-0.74), and the specificity was 0.77 (95% CI, 0.71-0.82). The diagnostic accuracy of the WBC was significantly lower compared to CRP. Conclusion: Measurement of CRP on POD 4 is recommended to screen for inflammatory complications. CRP values above 123mg/l on POD 4 should raise suspicion of inflammatory complications, although the discriminatory performance was insufficient to provide a single threshold that could be used to correctly predict inflammatory complications in clinical practice. WBC measurement contributes little to the early detection of inflammatory complications. Registered at www.clinicaltrials.gov (NCT01221324