Fracture modes and acoustic emission characteristics of hydrogen-assisted cracking in high-strength low-alloy steel weldment

The aim of the present paper is to study the relationship between the fracture modes in hydrogen-assisted cracking (HAC) in microalloied steel and the emission of acoustic signals during the fracturing process. For this reason, a flux-cored arc weld (FCAW) was used in a high-strength low-alloy steel. The consumable used were the commercially available AWS E120T5-K4 and had a diameter of 1.6 mm. Two different shielding gases were used (CO2 and CO2+5% H2) to obtain complete phenomenon characterization. The implant test was applied with three levels of restriction stresses. An acoustic emission measurement system (AEMS) was coupled to the implant test apparatus. The output signal from the acoustic emission sensor was passed through an electronic amplifier and processed by a root mean square (RMS) voltage converter. Fracture surfaces were examined by scanning electron microscopy (SEM) and image analysis. Fracture modes were related with the intensity, the energy and the number of the peaks of the acoustic emission signal. The shielding gas CO2+5% H2 proved to be very useful in the experiments. Basically, three different fracture modes were identified in terms of fracture appearance: microvoid coalescence (MVC), intergranular (IG) and quasi-cleavage (QC). The results show that each mode of fracture presents a characteristic acoustic signal.

Cell migration in the postnatal subventricular zone

New neurons are constantly added to the olfactory bulb of rodents from birth to adulthood. This accretion is not only dependent on sustained neurogenesis, but also on the migration of neuroblasts and immature neurons from the cortical and striatal subventricular zone (SVZ) to the olfactory bulb. Migration along this long tangential pathway, known as the rostral migratory stream (RMS), is in many ways opposite to the classical radial migration of immature neurons: it is faster, spans a longer distance, does not require radial glial guidance, and is not limited to postmitotic neurons. In recent years many molecules have been found to be expressed specifically in this pathway and to directly affect this migration. Soluble factors with inhibitory, attractive and inductive roles in migration have been described, as well as molecules mediating cell-to-cell and cell-substrate interactions. However, it is still unclear how the various molecules and cells interact to account for the special migratory behavior in the RMS. Here we will propose some candidate mechanisms for roles in initiating and stopping SVZ/RMS migration.

Functional changes of human quadriceps muscle injured by eccentric exercise

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion). The isometric torque of the quadriceps (knee at 90º flexion) decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63%) and VMO (66%) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.

A spectral analysis of the myoelectric activity of the left colon in patients with schistosomiasis mansoni

The objective of the present study was to perform a spectral analysis of the electrical activity of the left colon of patients with hepatosplenic schistosomiasis. Thirty patients were studied, divided into 2 groups: group A was composed of 14 patients (9 males and 5 females) with hepatosplenic schistosomiasis and group B was composed of 16 female patients without schistosomiasis mansoni. Three pairs of electrodes were implanted in the left colon at the moment of the surgical treatment. The signals of the electric activity of the colon were captured after postoperative recovery from the ileus and fed into a computer by means of a DATAQ data collection system which identified and captured frequencies between 0.02 and 10 Hz. Data were recorded, stored and analyzed using the WINDAQ 200 software. For electrical analysis, the average voltage of the electrical wave in the three electrodes of all patients, expressed as millivolts (mV), was considered, together with the maximum and minimum values, the root mean square (RMS), the skewness, and the results of the fast Fourier transforms. The average RMS of the schistosomiasis mansoni patients was 284.007 mV. During a long period of contraction, the RMS increased in a statistically significant manner from 127.455 mV during a resting period to 748.959 mV in patients with schistosomiasis mansoni. We conclude that there were no statistically significant differences in RMS values between patients with schistosomiasis mansoni and patients without the disease during the rest period or during a long period of contraction.

The effect of an aerobic training program on the electrical remodeling of the heart: high-frequency components of the signal-averaged electrocardiogram are predictors of the maximal aerobic power

Increased heart rate variability (HRV) and high-frequency content of the terminal region of the ventricular activation of signal-averaged ECG (SAECG) have been reported in athletes. The present study investigates HRV and SAECG parameters as predictors of maximal aerobic power (VO2max) in athletes. HRV, SAECG and VO2max were determined in 18 high-performance long-distance (25 ± 6 years; 17 males) runners 24 h after a training session. Clinical visits, ECG and VO2max determination were scheduled for all athletes during thew training period. A group of 18 untrained healthy volunteers matched for age, gender, and body surface area was included as controls. SAECG was acquired in the resting supine position for 15 min and processed to extract average RR interval (Mean-RR) and root mean squared standard deviation (RMSSD) of the difference of two consecutive normal RR intervals. SAECG variables analyzed in the vector magnitude with 40-250 Hz band-pass bi-directional filtering were: total and 40-µV terminal (LAS40) duration of ventricular activation, RMS voltage of total (RMST) and of the 40-ms terminal region of ventricular activation. Linear and multivariate stepwise logistic regressions oriented by inter-group comparisons were adjusted in significant variables in order to predict VO2max, with a P < 0.05 considered to be significant. VO2max correlated significantly (P < 0.05) with RMST (r = 0.77), Mean-RR (r = 0.62), RMSSD (r = 0.47), and LAS40 (r = -0.39). RMST was the independent predictor of VO2max. In athletes, HRV and high-frequency components of the SAECG correlate with VO2max and the high-frequency content of SAECG is an independent predictor of VO2max.

Moisture adsorption characteristics of ginger slices

The moisture adsorption characteristics of dried ginger slices was studied to determine the effect of storage conditions on moisture adsorption for the purpose of shelf life prediction, selection of appropriate packaging materials, evaluate the goodness-of-fit of sorption models, and determine the thermodynamics of moisture adsorption for application in drying. There was a highly significant effect (p < 0.05) of water activity (a w), temperature, and pre-treatment on the equilibrium moisture content (EMC) of the dried ginger slices. At constant a w, the EMC decreased as temperature increased. The EMC of all samples increased as the a w increased at constant temperature. The sorbed moisture of the unpeeled ginger slices was higher than the peeled while those of unblanched samples were higher than the blanched. Henderson equation allows more accurate predictions about the isotherms with the lowest %RMS, and therefore, it describes best the adsorption data followed by GAB, Oswin, and Halsey models in that order. The monolayer moisture generally decreased with temperature for all samples. The isosteric heat decreased with moisture content approaching the asymptotic value or the latent heat of vaporization of pure water (∆Hst = 0) while the entropy of sorption was observed to increase with moisture content.