Transitional cluster dynamics in a model for delay-coupled chemical oscillators

Cluster synchronization is a fundamental phenomenon in systems of coupled oscillators. Here, we investigate clustering patterns that emerge in a unidirectional ring of four delay-coupled electrochemical oscillators. A voltage parameter in the experimental set-up controls the onset of oscillations via a Hopf bifurcation. For a smaller voltage, the oscillators exhibit simple, so-called primary, clustering patterns, where all phase differences between each set of coupled oscillators are identical. However, upon increasing the voltage, additional secondary states, where phase differences differ, are detected. Previous work on this system saw the development of a mathematical model that explains how the existence, stability, and common frequency of the experimentally observed cluster states can be accurately controlled by the delay time of the coupling. In this study, we revisit the mathematical model of the electrochemical oscillators to address open questions by means of bifurcation analysis. Our analysis reveals how the stable cluster states, corresponding to experimental observations, lose their stability via an assortment of bifurcation types. The analysis further reveals a complex interconnectedness between branches of different cluster types; in particular, we find that each secondary state provides a continuous transition between certain primary states. These connections are explained by studying the phase space and parameter symmetries of the respective states. Furthermore, we show that it is only for a larger value of the voltage parameter that the branches of secondary states develop intervals of stability. Otherwise, for a smaller voltage, all the branches of secondary states are completely unstable and therefore hidden to experimentalists.Comment: 13 pages, 14 figure

Benefit of second-line therapy for advanced esophageal squamous cell carcinoma: a tri-center propensity score analysis

BACKGROUND: The level of evidence for palliative second-line therapy in advanced esophageal squamous cell carcinoma (aESCC) is limited. This is the first study that reports efficacy data comparing second-line therapy + active symptom control (ASC) versus ASC alone in aESCC. METHODS: We conducted a tri-center retrospective cohort study (n = 166) including patients with aESCC who had experienced disease progression on palliative first-line therapy. A propensity score model using inverse probability of treatment weighting (IPTW) was implemented for comparative efficacy analysis of overall survival (OS) in patients with second-line + ASC (n = 92, 55%) versus ASC alone (n = 74, 45%). RESULTS: The most frequent second-line regimens used were docetaxel (36%) and paclitaxel (18%). In unadjusted primary endpoint analysis, second-line + ASC was associated with significantly longer OS compared with ASC alone [hazard ratio (HR) = 0.49, 95% confidence interval (CI): 0.35–0.69, p < 0.0001]. However, patients in the second-line + ASC group were characterized by more favorable baseline features including a better Eastern Cooperative Oncology Group (ECOG) performance status, a longer first-line treatment duration and lower C-reactive protein levels. After rigorous adjusting for baseline confounders by re-weighting the data with the IPTW the favorable association between second-line and longer OS weakened but prevailed. The median OS was 6.1 months in the second-line + ASC group and 3.2 months in the ASC group, respectively (IPTW-adjusted HR = 0.40, 95% CI: 0.24–0.69, p = 0.001). Importantly, the benefit of second-line was consistent across several clinical subgroups, including patients with ECOG performance status ⩾1 and age ⩾65 years. The most common grade 3 or 4 adverse events associated with palliative second-line therapy were hematological toxicities. CONCLUSION: This real-world study supports the concept that systemic second-line therapy prolongs survival in patients with aESCC

PCF-Based Cavity Enhanced Spectroscopic Sensors for Simultaneous Multicomponent Trace Gas Analysis

A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + δ) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a “quasi continuum” mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given

The Gozi group: a criminal firm in cyberspace?

The relative glut of data on cybercriminal forums has led to a growing understanding of the functioning of these virtual marketplaces. But with a focus on illicit online trading, less attention has been paid to the structures of groups that carry out cybercrimes in an operational sense. In economic parlance, some such groups may be known as “firms”. This concept has been a significant part of the literature on more traditional forms of organised crime, but is not widely discussed in the cybercrime discourse. The focus of this article is, by way of a case study of the Gozi malware group, to explore the applicability of the concept of firms to the novel environment of cybercrime