Characterization of the anticipated synchronization regime in the coupled FitzHugh--Nagumo model for neurons

We characterize numerically the regime of anticipated synchronization in the coupled FitzHugh-Nagumo model for neurons. We consider two neurons, coupled unidirectionally (in a master-slave configuration), subject to the same random external forcing and with a recurrent inhibitory delayed connection in the slave neuron. We show that the scheme leads to anticipated synchronization, a regime in which the slave neuron fires the same train of pulses as the master neuron, but earlier in time. We characterize the synchronization in the parameter space (coupling strength, anticipation time) and introduce several quantities to measure the degree of synchronization.Comment: 8 pages. Proceedings of the conference on "Stochastic Systems: From Randomness to"Complexit

The secondary structure of apolipoprotein A-I on 9.6-nm reconstituted high-density lipoprotein determined by EPR spectroscopy.

Apolipoprotein A-I (ApoA-I) is the major protein component of high-density lipoprotein (HDL), and is critical for maintenance of cholesterol homeostasis. During reverse cholesterol transport, HDL transitions between an array of subclasses, differing in size and composition. This process requires ApoA-I to adapt to changes in the shape of the HDL particle, transiting from an apolipoprotein to a myriad of HDL subclass-specific conformations. Changes in ApoA-I structure cause alterations in HDL-specific enzyme and receptor-binding properties, and thereby direct the HDL particle through the reverse cholesterol transport pathway. In this study, we used site-directed spin label spectroscopy to examine the conformational details of the ApoA-I central domain on HDL. The motional dynamics and accessibility to hydrophobic/hydrophilic relaxation agents of ApoA-I residues 99-163 on 9.6-nm reconstituted HDL was analyzed by EPR. In previous analyses, we examined residues 6-98 and 164-238 (of ApoA-I's 243 residues), and combining these findings with the current results, we have generated a full-length map of the backbone structure of reconstituted HDL-associated ApoA-I. Remarkably, given that the majority of ApoA-I's length is composed of amphipathic helices, we have identified nonhelical residues, specifically the presence of a β-strand (residues 149-157). The significance of these nonhelical residues is discussed, along with the other features, in the context of ApoA-I function in contrast to recent models derived by other methods

The role of treatment delays in surgical site infection after appendicectomy in a South African rural regional hospital

Background. Delays to surgery for acute appendicitis in low- and middle-income countries lead to significant morbidity.Objectives. To investigate the role of time to surgery in the development of complicated appendicitis and surgical site infection (SSI) in a rural referral hospital in South Africa (SA).Methods. A prospective cohort study was conducted of all patients presenting to a regional hospital in SA with acute appendicitis during 2017. Inpatient interview and data collection were followed by 30-day post-surgical follow-up to assess time periods to surgery and operative outcomes.Results. A total of 188 patients underwent surgery for acute appendicitis. The median (interquartile range (IQR)) age was 19 (3 - 73) years, and 62% were male. The median (IQR) time from symptoms to surgery was 60 (42 - 86) hours and from hospital admission to surgery 8 (4 - 16) hours. Forty-one percent were managed laparoscopically, 62% had complicated appendicitis, and 25% developed SSI. Time from symptoms to surgery >72 hours was associated with an increased risk of complicated appendicitis (odds ratio (OR) 4.32; 95% confidence interval (CI) 1.36 - 13.75; p=0.013). Patients with SSI had an increased median delay of 15 hours (p=0.05) compared with those without SSI. Multivariable analysis showed that the risk of SSI increased with complicated appendicitis (OR 8.96; 95% CI 2.73 - 29.41; p<0,001) and decreased with laparoscopic surgery (OR 0.21; 95% CI 0.07 - 0.59; p=0.003). Time to surgery had no effect on the risk of SSI in adjusted analyses.Conclusions. Delays to surgery beyond 72 hours significantly increased complicated appendicitis, an important risk factor for SSI. Access to facilities with surgical capability and the use of laparoscopic surgery are modifiable risk factors for SSI

Competition between Two Kinds of Correlations in Literary Texts

A theory of additive Markov chains with long-range memory is used for description of correlation properties of coarse-grained literary texts. The complex structure of the correlations in texts is revealed. Antipersistent correlations at small distances, L 300 define this nontrivial structure. For some concrete examples of literary texts, the memory functions are obtained and their power-law behavior at long distances is disclosed. This property is shown to be a cause of self-similarity of texts with respect to the decimation procedure.Comment: 7 pages, 7 figures, Submitted to Physica

Statistical comparison of clouds and star clusters

The extent to which the projected distribution of stars in a cluster is due to a large-scale radial gradient, and the extent to which it is due to fractal sub-structure, can be quantified -- statistically -- using the measure ${\cal Q} = \bar{m}/\bar{s}$. Here $\bar{m}$ is the normalized mean edge length of its minimum spanning tree (i.e. the shortest network of edges connecting all stars in the cluster) and $\bar{s}$ is the correlation length (i.e. the normalized mean separation between all pairs of stars). We show how ${\cal Q}$ can be indirectly applied to grey-scale images by decomposing the image into a distribution of points from which $\bar{m}$ and $\bar{s}$ can be calculated. This provides a powerful technique for comparing the distribution of dense gas in a molecular cloud with the distribution of the stars that condense out of it. We illustrate the application of this technique by comparing ${\cal Q}$ values from simulated clouds and star clusters.Comment: Accepted 2010 October 27. Received 2010 October 25; in original form 2010 September 13 The paper contains 7 figures and 2 table

Effects of External Ankle Support on Dynamic Movements: A Randomized Controlled Trial

Ankle sprains, are one of the most common injuries among athletes and individuals that perform dynamic activities on a daily basis. A common treatment or prevention for ankle sprain is the use of external ankle support in the form of braces or tape. This study\u27s purpose was to determine whether external ankle support influenced dynamic performance measures. The study consisted of 15 males and 15 females totaling thirty participants with a mean age of24.67 years old. Subjects were included if they were healthy and had no previous ankle injuries. Using the NeuroCom Balance Master 8.2, each subject performed two dynamic tests consisting of the Step Up and Over (SUO) and the Forward Lunge (FL) test. Each test was performed with the subject wearing ankle tape, an ankle brace, and no external support in addition to an athletic shoe on the right lower extremity. Forward lunge results revealed that lunge distances were highest with ankle tape but significant differences were seen only between the taping group and the bracing group. Movement time in the SUO test was shortest in the control group with significance achieved between the control group and the taping group. A significant difference was also demonstrated in this maneuver in impact index. No other significant differences were found between groups. In conclusion, these results indicate that the use of external ankle support for protection influences dynamic performance activities, some negatively, others positively, and extension may ultimately have an effect on more intense activities, such as cutting, jumping, changing direction, and other dynamic functional movements. In addition, the use of external support may also subject the ankle, knee, or hip to abnormal forms of stress when impacting the surface during these activities, which in turn may predispose these joints to injury or other problems