On phase-locking of oscillators with delay coupling

We consider two oscillators with delayed direct and velocity coupling. The oscillators have frequencies close or equal to 1:1 resonance. Due to the coupling the oscillations of the subsystems are in or out of phase. For these synchronized and anti-phase solutions, we use averaging for analytical stability results for small parameters. We also determine bifurcation curves of the delay system numerically. We identify regions in the parameter space (two coupling constants and the delay) where both solutions are stable or only one. For small parameters the averaging and numerical results are in good agreement. For larger values of the delay, we find multiple synchronized and anti-phase solutions. For small detuning we show that a minimal coupling value is needed to have almost synchronous or anti-phase behaviour

The organization of transactions research with the Trust and Tracing Game

This paper presents empirical results of research on the influence of social aspects on the organization of transactions in the domain of chains and networks. The research method used was a gaming simulation called the Trust and Tracing game in which participants trade commodity goods with a hidden quality attribute. Previous sessions of this gaming simulation identified a list of variables for further investigation (Meijer et al., 2006). The use of gaming simulation as data gathering tool for quantitative research in supply chains and networks is a proof-of-principle. This paper shows results from 27 newly conducted sessions and previously unused data from 3 older sessions. Tests confirmed the use of network and market modes of organization. Pre-existing social relations influenced the course of the action in the sessions. Being socially embedded was not beneficial for the score on the performance indicators money and points. The hypothesized reduction in measurable transaction costs when there was high trust between the participants could not be found. Further analysis revealed that participants are able to suspect cheats in a session based on other factors than tracing. Testing hypotheses with data gathered in a gaming simulation proved feasible. Experiences with the methodology used are discusse

Gap junctions as modulators of synchrony in Parkinson's disease

Parkinson's disease (PD) patients show abnormal levels of synchrony and low-frequency oscillations in the basal ganglia and the motor cortex. This altered neural activity is often associated with the motor symptoms of PD, but the mechanisms for the emergence of synchrony and oscillations remain debated. We suggest that neural gap junctions in cortex and basal ganglia contribute to this transition in activity. While gap junctions between interneurons of cortex and striatum are well described, we do not know whether they appear in GPe and internal globus pallidus (GPi). Using confocal microscopy, we were able to detect the gap junction protein Cx36 in the human GPe and GPi, which was up-regulated in PD patients. Also the corresponding rat tissue showed Cx36 expression. Dopamine has already been described to modulate the conductance of gap junctions [1], especially also in the rat striatum, where dye coupling was increased after dopamine depleting 6-OHDA lesions [2]. In a conductance-based network model of the basal ganglia, we investigate the effect of gap junctional coupling in GPe and GPi on synchrony. While chemical synapses normally desynchronize the network, gap junctional coupling of sufficient strength is able to synchronize the whole basal ganglia. Also synchronized input from cortex to subthalamic nucleus has impact on synchronization, in particular in the case of numerous gap junctions in GPe. To describe the effect of gap junctional coupling between cortical interneurons on synchronized oscillations in the cortex, we introduce a diffusion term in a mean-field model. For high gap junctional coupling, large-amplitude oscillations of low frequency occur which are absent for low gap junctional coupling. Via the hyperdirect pathway, these oscillations could further synchronize the basal ganglia. We conclude that gap junctions can be a powerful trigger of synchrony in the basal ganglia. Their dependence on dopamine could explain the shifts of synchrony in PD. References 1. Li, H, Zhang, Z, Blackburn, MR, Wang, SW, Ribelayga, CP and O'Brien, J Adenosine and dopamine receptors coregulate photoreceptor coupling via gap junction phosphorylation in mouse retina. (2013) The Journal of Neuroscience, 33(7), 3135-3150. 2. Onn, SP and Grace, AA: Alterations in electrophysiological activity and dye coupling of striatal spiny and aspiny neurons in dopamine-denervated rat striatum recorded in vivo. (1999) Synapse, 33(1):1- 15

Computational modeling of Adelta-fiber-mediated nociceptive detection of electrocutaneous stimulation

Sensitization is an example of malfunctioning of the nociceptive pathway in either the peripheral or central nervous system. Using quantitative sensory testing, one can only infer sensitization, but not determine the defective subsystem. The states of the subsystems may be characterized using computational modeling together with experimental data. Here, we develop a neurophysiologically plausible model replicating experimental observations from a psychophysical human subject study. We study the effects of single temporal stimulus parameters on detection thresholds corresponding to a 0.5 detection probability. To model peripheral activation and central processing, we adapt a stochastic drift-diffusion model and a probabilistic hazard model to our experimental setting without reaction times. We retain six lumped parameters in both models characterizing peripheral and central mechanisms. Both models have similar psychophysical functions, but the hazard model is computationally more efficient. The model-based effects of temporal stimulus parameters on detection thresholds are consistent with those from human subject data

Combination of PCR targeting the VD2 of omp1 and reverse line blot analysis for typing of urogenital Chlamydia trachomatis serovars in cervical scrape specimens.

50% contained both serovars D and E. The nested VD2 PCR-RLB developed is a simple, fast, and specific method for the identification of individual urogenital C. trachomatis serovars previously detected by using plasmid PCR. Moreover, it is an appropriate method for studying multiple C. trachomatis infections and for use in large epidemiological studies

The autophagic response to Staphylococcus aureus provides an intracellular niche in neutrophils

Staphylococcus aureus is a major human pathogen causing multiple pathologies, from cutaneous lesions to life-threatening sepsis. Although neutrophils contribute to immunity against S. aureus, multiple lines of evidence suggest that these phagocytes can provide an intracellular niche for staphylococcal dissemination. However, the mechanism of neutrophil subversion by intracellular S. aureus remains unknown. Targeting of intracellular pathogens by macroautophagy/autophagy is recognized as an important component of host innate immunity, but whether autophagy is beneficial or detrimental to S. aureus-infected hosts remains controversial. Here, using larval zebrafish, we showed that the autophagy marker Lc3 rapidly decorates S. aureus following engulfment by macrophages and neutrophils. Upon phagocytosis by neutrophils, Lc3-positive, non-acidified spacious phagosomes are formed. This response is dependent on phagocyte NADPH oxidase as both cyba/p22phox knockdown and diphenyleneiodonium (DPI) treatment inhibited Lc3 decoration of phagosomes. Importantly, NADPH oxidase inhibition diverted neutrophil S. aureus processing into tight acidified vesicles, which resulted in increased host resistance to the infection. Some intracellular bacteria within neutrophils were also tagged by Sqstm1/p62-GFP fusion protein and loss of Sqstm1 impaired host defense. Together, we have shown that intracellular handling of S. aureus by neutrophils is best explained by Lc3-associated phagocytosis (LAP), which appears to provide an intracellular niche for bacterial pathogenesis, while the selective autophagy receptor Sqstm1 is host-protective. The antagonistic roles of LAP and Sqstm1-mediated pathways in S. aureus-infected neutrophils may explain the conflicting reports relating to anti-staphylococcal autophagy and provide new insights for therapeutic strategies against antimicrobial-resistant Staphylococci

Ultrafast photoinduced charge transport in Pt(II) donor-acceptor assembly bearing naphthalimide electron acceptor and phenothiazine electron donor

Visible light-induced charge transfer dynamics were investigated in a novel transition metal triad acceptor–chromophore–donor, (NDI–phen)Pt(II)(–C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (1), designed for photoinduced charge separation using a combination of time-resolved infrared (TRIR) and femtosecond electronic transient absorption (TA) spectroscopy. In 1, the electron acceptor is 1,4,5,8-naphthalene diimide (NDI), and the electron donor is phenothiazine (PTZ), and [(phen)Pt(–C[triple bond, length as m-dash]C–Ph–)], where phen is 1,10-phenanthroline, represents the chromophoric core. The first excited state observed in 1 is a 3MLCT/LL′CT, with {Pt(II)–acetylide}-to-phen character. Following that, charge transfer from the phen-anion onto the NDI subunit to form NDI−–phen–[Pt–(C[triple bond, length as m-dash]C)2]+–PTZ2 occurs with a time constant of 2.3 ps. This transition is characterised by appearance of the prominent NDI-anion features in both TRIR and TA spectra. The final step of the charge separation in 1 proceeds with a time constant of [similar]15 ps during which the hole migrates from the [Pt–(C[triple bond, length as m-dash]C)2] subunit to one of the PTZ groups. Charge recombination in 1 then occurs with two distinct time constants of 36 ns and 107 ns, corresponding to the back electron transfer to each of the two donor groups; a rather rare occurrence which manifests that the hole in the final charge-separated state is localised on one of the two donor PTZ groups. The assignment of the nature of the excited states and dynamics in 1 was assisted by TRIR investigations of the analogous previously reported ((COOEt)2bpy)Pt(C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (2), (J. E. McGarrah and R. Eisenberg, Inorg. Chem., 2003, 42, 4355; J. E. McGarrah, J. T. Hupp and S. N. Smirnov, J. Phys. Chem. A, 2009, 113, 6430) as well as (bpy)Pt(C[triple bond, length as m-dash]C–Ph–C7H15)2, which represent the acceptor-free dyad, and the chromophoric core, respectively. Thus, the step-wise formation of the full charge-separated state on the picosecond time scale and charge recombination via tunnelling have been established; and the presence of two distinct charge recombination pathways has been observed