Necessary Conditions for Reliable Propagation of Slowly Time-Varying Firing Rate.

Reliable propagation of slow-modulations of the firing rate across multiple layers of a feedforward network (FFN) has proven difficult to capture in spiking neural models. In this paper, we explore necessary conditions for reliable and stable propagation of time-varying asynchronous spikes whose instantaneous rate of changes-in fairly short time windows [20-100] msec-represents information of slow fluctuations of the stimulus. Specifically, we study the effect of network size, level of background synaptic noise, and the variability of synaptic delays in an FFN with all-to-all connectivity. We show that network size and the level of background synaptic noise, together with the strength of synapses, are substantial factors enabling the propagation of asynchronous spikes in deep layers of an FFN. In contrast, the variability of synaptic delays has a minor effect on signal propagation.

Finite Element Analysis of the Mechanism of Traumatic Aortic Rupture (TAR).

As many as 80% of patients with TAR die on the spot while out of those reaching a hospital, 30% would die within 24 hours. Thus, it is essential to better understand and prevent this injury. The exact mechanics of TAR are unknown. Although most researchers approve it as a common-sense deceleration injury, the exact detailed mechanism of TRA still remains unidentified. In this work, a deceleration mechanism of TAR was carried out using finite element analysis (FEA). The FE analysis aimed to predict internal kinematics of the aorta and assist to comprehend the mechanism of aorta injury. The model contains the heart, lungs, thoracic aorta vessel, and rib cage. High-resolution computerized tomography (HR CT scan) was used to provide pictures that were reconstructed by MIMICS software. ANSYS FE simulation was carried out to investigate the behavior of the aorta in the thoracic interior after deceleration occurred during a car crash. The finite element analysis indicated that maximum stress and strain applied to the aorta were from 5.4819e5 to 2.614e6 Pa and 0.21048 to 0.62676, respectively, in the Y-direction when the initial velocity increased from 10 to 25 m/s. Furthermore, in the X-direction when the velocity changed from 15 to 25 m/s, the stress and strain values increased from 5.17771e5 to 2.3128e6 and from 0.22445 to 0.618, respectively.

Doppler assessment of children with liver cirrhosis and portal hypertension in comparison with a healthy control group: An analytical cross-sectional study.

BACKGROUND: Doppler ultrasonography (Doppler US) plays an important role in evaluating patients with liver cirrhosis. This study aims to investigate the hemodynamic alterations of hepatic artery and portal vein among children with liver cirrhosis and portal hypertension (esophageal varices). MATERIALS AND METHODS: We conducted an analytical cross-sectional study in Imam Hossein Children's Hospital, Isfahan, Iran, in 2016. A number of 33 cirrhotic children with or without esophageal varices were selected through convenience sampling method to be compared with 19 healthy children as controls using color and spectral Doppler US. RESULTS: Portal vein mean velocities were 15.03 ± 7.3 cm/s in cirrhotics, 16.47 ± 6.4 cm/s in controls (P = 0.51), 11.6 ± 4.7 cm/s in patients with varices, and 17.9 ± 7.3 cm/s in patients without varices (P = 0.015). Mean diameters of caudate lobe, portal vein, and splenic vein, as well as the mean values of liver and spleen span, were significantly higher in cirrhotic children. The frequency of flow reversal (hepatofugal flow) was not detected significantly different in cirrhotics. Peak systolic velocity, end diastolic velocity, pulsatility index, and resistive index for hepatic artery as well as liver vascular index were not significantly different in cirrhotics in comparison with controls. CONCLUSION: Alterations in Doppler parameters of portal vein including diameter and velocity may be the helpful indicators of liver cirrhosis and esophageal varices in children, respectively. Parameters of hepatic artery may not differentiate children with liver cirrhosis.

Bioaccumulation and distribution of metals in sediments and Avicenna marina tissues in the Hara Biosphere Reserve, Iran.

The metal pollution in Sediments and Avicenna marina tissues in the Hara Biosphere Reserve was monitored for Lead (Pb), Cadmium (Cd), and Nickel (Ni) with atomic absorption spectrometer. The results showed that the mean concentration of Pb, Cd, and Ni in the water and sediments were much higher than the recommended threshold limits in the most stations, also the highest means of Pb, Cd, and Ni were observed in Avicenna roots and it were 25.26 ± 4.86, 2.17 ± 0.74, and 26.72 ± 6.17 (µg g(-1)) respectively. Calculating BCF (bioconcentration factor) index illustrates that A. marina accumulates Pb, Cd, and Ni 1.62, 1.52 and 0.73 times greater than sediment levels respectively, So it can show that A. marina may be employed as a biological indicator exposure of Cd, Pb, and Ni with temporal monitoring, also the factories were main sources of metals contamination in the Hara Biosphere Reserve.

Bioaccumulation of heavy metals in freshwater fish species, Anzali, Iran.

The main objectives of study were to monitor the metals concentrations, in freshwater fish species, Carassius gibelio and Esox lucius; and to identify any relationships between species and bioaccumulation of metals. The highest concentration of metals (cadmium, 1.96; copper, 24.2; zinc, 49.6; lead, 5.4; chromium, 4.4) between the fish species and tissues was in the liver of Esox lucius, while the lowest (cadmium,0.21; copper,7.2; zinc,19.4; lead,0.9; chromium,0.6 µg/g) found in the muscle of Carassius gibelio. Results showed that the metal concentrations were in fishes in descending order of zinc > copper > lead > chromium > cadmium, similarly in the tissue liver > kidney > gill ~ intestine > muscle.