Spatial Variation of Surface Residual Stress in Metallic Materials

Shot peening is commonly used to reduce fatigue failures in industrial parts by introducing compressive residual stress into the surface of a material. However, it is challenging to assess the performance of the parts without destroying them. Solving this problem requires a combined model that predicts both recrystallization and residual stress using experimental measurements and predictive computational modelling. Experiments were performed to prove that the surface properties of materials after thermal treatments can be accessed, and the spatial variation of residual stress in metallic materials, including the relationship between surface and subsurface behavior can be evaluated. This process involves investigating the surface residual stress profile using a spatially sensitive X-ray diffraction technique, followed by other procedures such as cutting and investigation of microstructure and subsurface residual stress. With a model like this, the performance of industrial parts can be assessed in a non-destructive way. It is crucial that the parts can still serve the original purpose after being tested

How big should your nanoindentation be? The implications of indentation size in assessing the properties of complex structure

Drivers for testing small volumes of materials for assessing the mechanical properties are either (1) the sample you want to test is very small in the first place, such as measuring the hardness of a wear resistant coating which is in thin film form or (2) you can well-characterize a small volume or the small volume has some spatially distinct feature, such as probing properties near a grain boundary, or in two phase systems. Small scale mechanical testing using instrumented indentation generally requires minimal sample preparation and has high spatial fidelity, but creates complex loading states as opposed to uniaxial or biaxial applied stress methods. However, the ease of use and wide range of samples which are amenable for indentation testing has made this a common tool both for experimental assessment studies and for experimental validation of providing comparisons to simulations and predictions of mechanical properties. Please click Additional Files below to see the full abstract

Purification and characterization of nitric oxide inhibitory peptides from Actinopyga lecanora through enzymatic hydrolysis

Actinopyga lecanora, commonly known as sea cucumber, is a rich protein source. This marine protein source was hydrolyzed using six proteases to generate anti-inflammatory hydrolysates and bioactive peptides. Bromelain hydrolysates after 1 h hydrolysis exhibited the highest nitric oxide (NO) inhibitory activity reflecting anti-inflammatory activity. A sequence of two fractionation methods was employed to fractionate the peptides based on their hydrophobicity using a semi-preparative RP-HPLC and isoelectric points using isoelectric focusing technique. Based on these fractionation methods, basic peptides with relatively higher hydrophobicity provided higher NO-inhibitory activity than did acidic peptides. Furthermore, using Q-TOF mass spectrometry; 12 peptide sequences were successfully identified. The inhibitory effect of the purified peptides from A. lecanora on NO production by lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was investigated. The three identified bioactive peptides, namely LREMLSTMCTARGA, AVGPAGPRG and VAPAWGPWPKG, exhibited the highest NO-inhibitory activity with values of 76.3, 66.6 and 69.9%, respectively. These results revealed that A. lecanora could be used as an economical protein source for the production of high-value bioactive peptides with potent anti-inflammatory activity using RAW 264.7 cell lines as model. These peptides may be useful ingredients in food and pharmaceutical applications

Enzymatic production of multifunctional bioactive peptides from sea cucumber (Actinopyga lecanora Jaeger)

Food protein-generated bioactive peptides are natural products that have nutraceutical and pharmaceutical properties. They have been reported to have antioxidative, anti-bacterial, anti-hypertensive and anti-inflammatory properties. Due to their potential, there is an increasing interest in the use of these peptides for general health maintenance and well-being. Sea cucumbers have been utilized as a folk remedy to cure some diseases in some Asian countries for decades. Among the species, Actinopyga lecanora, commonly known as stone fish was chosen due to its relatively high protein content (58.30%). Moreover, it is considered as a by-catch of the Malaysiaʼs fishing industry. This study was targeted to generate multifunctional bioactive peptides against cardiovascular diseases and its risk factors (hypertension and oxidative stress), inflammation and microbial infections, from an edible species of sea cucumber through enzymatic proteolysis. Thus, the protein was proteolysed using six proteases namely alkalase, papain, bromelain, flavourzyme, pepsin, and trypsin under their optimum conditions for 24 h. The degree of proteolysis and peptide content were evaluated using O-phthaldialdehyde based on a spectroscopic method. The amino acid compositions of A. lecanora and its generated proteolysates were evaluated. The multifunctional activities of the A. lecanora generated proteolysates including anti-hypertensive, anti-oxidative, anti-bacterial and inhibition of nitric oxide (NO) activities were determined. The anti-oxidative activity was measured using DPPH• radical scavenging and ferrous-ion chelating activities. The anti-bacterial activity was measured as growth inhibition (%) against Pseudomonas aeruginosa, Pseudomonas sp., Escherichia coli and Busilus subtilis and Staphylococcus aureus. The inhibition of NO-production was evaluated using Griess assay in RAW 264.7 cells. The bromelain-generated proteolysate showed the highest multifunctional activities after 1 h of proteolysis. The abilities of proteolysate to inhibit ACE, scavenge DPPH free radicals and chelate iron (Fe2+) were 48.80%, 40.00% and 30.24%, respectively. The potency of proteolysate to inhibit NOproduction in RAW 264.7 cell was 60.02%. Subsequently, this proteolysate showed the highest anti-bacterial activities against Pseudomonas sp., P. aeruginosa, E. coli and S. aureus of 51.85, 30.07, 30.00 and 24.30%, respectively. The proteolysate was further profiled by fractionation methods based on hydrophobicity using RP-HPLC and isoelectric properties using isoelectric focusing technique. The best fraction in terms of multifunctional properties was selected for peptide identification and sequencing using an UPLC-QTOF-MS system, where a total of 12 peptides were identified. The multifunctional activities of the identified peptides were studied. Based on the results obtained 3 peptides namely LREMLSTMCTARGA, VAPAWGPWPKG and ATSFREALRCGAE showed the strongest ACE inhibitory activities of 98.10, 95.23 and 59.95%, radical scavenging activity of 93.30, 70.44 and 78.20% and ferrous ion chelating activity of 57.00, 43.50 and 54.00%, respectively. NO-production was inhibited by these peptides with values of 76.30, 69.90 and 30.00% and their NO scavenging activities were 51.14, 50.32 and 34.85%, respectively. These peptides exhibited growth inhibition against P. aeruginosa, Pseudomonas sp., E. coli and S. aureus with values ranging from 50.00 to 75.30%. The effect of the proteolysate and its derived peptides on the viability of RAW 264.7 cells were evaluated using MTT assay. Results showed that these samples had no cytotoxic effect and the cell viability was higher than 90%. Kinetic studies of ACE inhibition of multifunctional peptides demonstrated un-competitive and mixed-mode patterns. Results showed that A. lecanora could be used as an economical protein source to generate invaluable multifunctional proteolysate and bioactive peptides which could be exploited in the formulation of various functional foods or used as a source of nutraceuticals

Angiotensin-I Converting Enzyme (ACE) Inhibitory and Anti-Oxidant Activities of Sea Cucumber (Actinopyga lecanora) Hydrolysates

In recent years, food protein-derived hydrolysates have received considerable attention because of their numerous health benefits. Amongst the hydrolysates, those with anti-hypertensive and anti-oxidative activities are receiving special attention as both activities can play significant roles in preventing cardiovascular diseases. The present study investigated the angiotensin-I converting enzyme (ACE) inhibitory and anti-oxidative activities of Actinopyga lecanora (A. lecanora) hydrolysates, which had been prepared by alcalase, papain, bromelain, flavourzyme, pepsin, and trypsin under their optimum conditions. The alcalase hydrolysate showed the highest ACE inhibitory activity (69.8%) after 8 h of hydrolysis while the highest anti-oxidative activities measured by 2,2-diphenyl 1-1-picrylhydrazyl radical scavenging (DPPH) (56.00%) and ferrous ion-chelating (FIC) (59.00%) methods were exhibited after 24 h and 8 h of hydrolysis, respectively. The ACE-inhibitory and anti-oxidative activities displayed dose-dependent trends, and increased with increasing protein hydrolysate concentrations. Moreover, strong positive correlations between angiotensin-I converting enzyme (ACE) inhibitory and anti-oxidative activities were also observed. This study indicates that A. lecanora hydrolysate can be exploited as a source of functional food owing to its anti-oxidant as well as anti-hypertension functions

Actinopyga lecanora Hydrolysates as Natural Antibacterial Agents

Actinopyga lecanora, a type of sea cucumber commonly known as stone fish with relatively high protein content, was explored as raw material for bioactive peptides production. Six proteolytic enzymes, namely alcalase, papain, pepsin, trypsin, bromelain and flavourzyme were used to hydrolyze A. lecanora at different times and their respective degrees of hydrolysis (DH) were calculated. Subsequently, antibacterial activity of the A. lecanora hydrolysates, against some common pathogenic Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas sp.) were evaluated. Papain hydrolysis showed the highest DH value (89.44%), followed by alcalase hydrolysis (83.35%). Bromelain hydrolysate after one and seven hours of hydrolysis exhibited the highest antibacterial activities against Pseudomonas sp., P. aeruginosa and E. coli at 51.85%, 30.07% and 30.45%, respectively compared to the other hydrolysates. Protein hydrolysate generated by papain after 8 h hydrolysis showed maximum antibacterial activity against S. aureus at 20.19%. The potent hydrolysates were further fractionated using RP-HPLC and antibacterial activity of the collected fractions from each hydrolysate were evaluated, wherein among them only three fractions from the bromelain hydrolysates exhibited inhibitory activities against Pseudomonas sp., P. aeruginosa and E. coli at 24%, 25.5% and 27.1%, respectively and one fraction of papain hydrolysate showed antibacterial activity of 33.1% against S. aureus. The evaluation of the relationship between DH and antibacterial activities of papain and bromelain hydrolysates revealed a meaningful correlation of four and six order functions

Inhibition kinetics, molecular docking, and stability studies of the effect of papain-generated peptides from palm kernel cake proteins on angiotensin-converting enzyme (ACE)

Three novel peptide sequences YGIKVGYAIP, GGIF, and GIFE from papain-generated protein hydrolysate of palm kernel cake proteins were used for stability study against ACE, ACE-inhibition kinetics, and molecular docking studies. Results showed that peptide YGIKVGYAIP was degraded, and its ACE-inhibitory activity decreased after 3 h pre-incubation with ACE, while peptides GGIF and GIFE were resistant. However, although the ACE-inhibitory activity of GIFE increased during this time, the ACE inhibitory activity of GGIF decreased after pre-incubation with ACE, indicating that peptide. YGIKVGYAIP and GGIF are substrate-type, whereas GIFE is a true-inhibitor type. Peptide YGIKVGYAIP showed the lowest Ki (0.054 mM) in the inhibition kinetics study compared to GGIF and GIFE, with Ki of 1.27 m M and 18 mM, respectively. In addition, YGIKVGYAIP revealed the lowest Km and Vmax and higher CE in different peptide concentrations, implying that the enzyme catalysis decreased, and peptides had some binding affinity to the enzyme in lower concentrations, which led to reduced catalytic ability. Furthermore, YGIKVGYAIP showed the lowest docking score of −14.733 and 21 interactions with tACE, while GGIF revealed the higher docking score of −8.006 with 15 interactions with tACE

Did Segregation Reduce Lethal Violence Against Southern Blacks? : A Generalized Difference-in-Differences Approach to Understand Lynchings and Executions in the US South

Up until the mid 1860s, an overwhelming majority of blacks in the US South were held in chattel slavery, from which they were freed after a Civil War (1861-1865). A recurring argument in institutional economics is that the institution of slavery did not disappear, but took other forms, e.g. segregation and violence. This is explored here, looking at the unsettling level of lethal violence against the black population 1875-1930. Literature empirically testing the legacy of slavery is hitherto scarce. I use a generalized difference-in-differences model to look at the effect of separate coach laws and disenfranchisement laws on lynchings and executions, respectively. All estimations are separated between blacks and non-blacks. I find precise and negative effects of disenfranchisement on executions of blacks and precise and positive effects of separate coach laws on executions of blacks. The same pattern holds true for lynchings of blacks, but only the estimate for separate coach laws is precise. No estimates are precise for lethal violence against non-blacks. This study lends support to the idea that lethal violence was used as an instrument to control the African American population

Angiotensin-I Converting Enzyme (ACE) Inhibitory and Anti-Oxidant Activities of Sea Cucumber (Actinopyga lecanora) Hydrolysates

In recent years, food protein-derived hydrolysates have received considerable attention because of their numerous health benefits. Amongst the hydrolysates, those with anti-hypertensive and anti-oxidative activities are receiving special attention as both activities can play significant roles in preventing cardiovascular diseases. The present study investigated the angiotensin-I converting enzyme (ACE) inhibitory and anti-oxidative activities of Actinopyga lecanora (A. lecanora) hydrolysates, which had been prepared by alcalase, papain, bromelain, flavourzyme, pepsin, and trypsin under their optimum conditions. The alcalase hydrolysate showed the highest ACE inhibitory activity (69.8%) after 8 h of hydrolysis while the highest anti-oxidative activities measured by 2,2-diphenyl 1-1-picrylhydrazyl radical scavenging (DPPH) (56.00%) and ferrous ion-chelating (FIC) (59.00%) methods were exhibited after 24 h and 8 h of hydrolysis, respectively. The ACE-inhibitory and anti-oxidative activities displayed dose-dependent trends, and increased with increasing protein hydrolysate concentrations. Moreover, strong positive correlations between angiotensin-I converting enzyme (ACE) inhibitory and anti-oxidative activities were also observed. This study indicates that A. lecanora hydrolysate can be exploited as a source of functional food owing to its anti-oxidant as well as anti-hypertension functions