Growth Tests Research Articles

Detecção dos genes Fur, AmoA e pvcAB em Aeromonas hydrophila isoladas de organismos aquáticos e o impacto da presença desses genes sobre o crescimento bacteriano com diferentes concentrações de ferro

ABSTRACT Infection caused by Aeromonas brings great harm to fish farming. Among the factors associated with bacterial pathogenesis, iron uptake can contribute to the survival and virulence of bacteria within hosts. The aim of this study was to check the presence of genes related to iron uptake in Aeromonas hydrophila deriving from aquatic organisms in the São Francisco Valley and associate the presence of these genes with the ability to grow in media containing different concentrations of iron. The DNAs of 41 isolates were extracted and used in PCRs to verify the presence of the Fur, AmoA and pvcAB genes related to iron uptake. The growth of the isolates belonging to different genetic profiles was verified in culture media containing different iron concentrations. Two isolates were positive for the presence of the Fur gene, seven for the AmoA gene and two for the pvcAB gene. The growth test showed that the low availability of iron did not interfere in the growth of the isolates, nor in the isolate that did not contain any of the genes evaluated in this study, suggesting that the iron uptake’s mechanisms of the tested isolates may be related to other genes and proteins.

Revisiting stress-corrosion cracking and hydrogen embrittlement in 7xxx-Al alloys at the near-atomic-scale

The high-strength 7xxx series aluminium alloys can fulfil the need for light, high strength materials necessary to reduce carbon-emissions, and are extensively used in aerospace for weight reduction purposes. However, as all major high-strength materials, these alloys can be sensitive to stress-corrosion cracking (SCC) through anodic dissolution and hydrogen embrittlement (HE). Here, we study at the near-atomic-scale the intra- and inter-granular microstructure ahead and in the wake of a propagating SCC crack. Moving away from model alloys and non-industry standard tests, we perform a double cantilever beam (DCB) crack growth test on an engineering 7xxx Al-alloy. H is found segregated to planar arrays of dislocations and to grain boundaries that we can associate to the combined effects of hydrogen-enhanced localised plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanisms. We report on a Mg-rich amorphous hydroxide on the corroded crack surface and evidence of Mg-related diffusional processes leading to dissolution of the strengthening η-phase precipitates ahead of the crack.

Metallurgical, mechanical and corrosion characteristics of vibration assisted gas metal arc AA6061-T6 welded joints

Microstructure, mechanical properties and corrosion performance of gas metal arc AA6061-T6 aluminum alloy welded joints under the effect of mechanical vibration during welding have been investigated. The vibration frequencies, f used in this study were in the range of 0-500 Hz. Subsequently, several experiments were performed including microstructural observation, microhardness measurements, tensile tests, fatigue crack growth tests combined with fractography study and electrochemical polarization tests in 3.5% NaCl solution. Results indicated that the application of mechanical vibration increased tensile strength of the welded joints up to 83.3 % higher than the weld without vibration achieved at a frequency of 300 Hz. It was found that the strengthening mechanisms in the vibrated weld joints occurred mainly by the grain refinement of columnar dendritic and equiaxed dendritic microstructures in the weld metal region. Such microstructures could contribute to fatigue crack growth inhibition in the weld metal. Based on electrochemical corrosion tests, the vibration assisted weld joints were found to have better corrosion resistance than as-welded weld joint. The improved corrosion performance was likely attributable to suppression of intermetallic compound formation such as Mg2Si by mechanical vibration during weld solidification.

Effect of Zr content on the physicochemical, electrochemical, and biological properties of Ti80Nb20-based alloys

The β-Ti alloys have become very attractive in the area of biomedical materials due to their corrosion resistance, biocompatibility, and low elastic modulus as compared with other materials. In this context, the Ti-Nb-Zr ternary system has gained more interest because Zr acts as secondary β-Ti stabilizing element when it is added together with β-stabilizing element such as Nb or Mo. According to the d-electron theory, the higher the Zr content, the lower elastic modulus values are obtained, which would allow to produce alloys with low elastic modulus, corrosion resistance, and shape memory. However, determining the ideal amount of Zr in a Ti-Nb-Zr alloy is still a matter of investigation. In this work, alloys with a nominal chemical composition of Ti80−x-Nb20-Zrx (x = 5, 10, 20, 30, and 40 at%) were produced by electric arc casting. The results show that the addition of Zr causes a decrease in both the elastic modulus and the hardness of the molten alloys, reaching values of 50.5 GPa for a sample with 40 at% Zr. The increase in the Zr content caused a microstructural difference between the phases, and the α” phase was detected for the Ti80Nb20, Ti75Nb20Zr5, and Ti60Nb20Zr20 alloys. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the environment influences the Ti-Nb-Zr surfaces, showing the growth of oxide layers, mainly Ti, Zr and, to a lesser extent, Nb oxides. All alloys with different Zr amounts showed wide passivation regions and no sign of pitting in the potential range that is characteristic of the human body. The Ti-Nb-Zr alloys showed good compatibility in cell growth tests, with the best results for the 20 at% Zr alloy, and a decrease in biocompatibility for higher Zr amounts due to reactions of Zr4+ with body fluids.

Ranking Methodology for Evaluating Region-Wise COVID-19 Testing Performance in India.

For containment of COVID-19, most countries are following the isolate, test, treat and trace approach. Following the approach, India scaled up COVID-19 testing from about 5,000 tests per day at the end of March 2020 to more than 1 M tests per day in September 2020. Testing scale-up has seen a huge variation across states and union territories (UTs) with respect to growth rates, testing strategies, testing infrastructure, and deployment of various kit types (RT-PCR, Antigen, CBNAAT, etc). To understand the gaps in testing and prioritize appropriate interventions, it is important for national stakeholders to evaluate and rank states/UTs based on their testing performance. Indicators like total samples tested, total samples positive, tests per million, and positives per million are currently being used by epidemiologists and researchers for comparing the performance of various regions. This article proposes a robust ranking methodology to rank the states/UTs in India based on a comprehensive scoring developed by combining multiple variables for evaluating the testing performance of states/UTs. Since RT-PCR testing is considered the gold standard for COVID-19 testing, the composite score for testing performance in this article is defined by the ability of states/UTs to successfully deploy RT-PCR testing and reduce its positivity over time. Evaluating region-wise ranking can enable the identification of areas requiring immediate attention in poorly performing regions, thus channelizing efforts and resources in the right direction.

In Silico Conformation of the Drug Colchicine into Tubulin Models and Acute Phytotoxic Activity on Cucumis sativus Radicles.

Many tests are used to determine the toxic activity of miscellaneous substances, and those that are simple, fast, and inexpensive are useful for screening compounds with applications in different fields. The Cucumis sativus root growth inhibition test is an example of acute toxicity determinations. On the other hand, colchicine has been used as a herbicide to generate polyploids in plant species finally reaching the environment; for this reason, colchicine could become a point of attention in ecotoxicology. This work established that Cucumis sativus, at the colchicine binding site (CBS) in tubulin, shares 100% similarity with humans. Colchicine was docked on seven Cucumis sativus computational models of the αβ-tubulin heterodimer, allowing us to understand a possible conformation in tubulin to trigger its antimitotic effect. Furthermore, an in vitro phytotoxicity assay of colchicine-treated cucumber radicles indicated a hormetic-type concentration-dependent response with macroscopic changes in radicles and hypocotyl. These results support the highly preserved grade of tubulins in several species, and using microtubule inhibitors could require attention in ecotoxicological issues. The Cucumis sativus root growth test could help evaluate small molecules (colchicine analogs), chiefly by CBS interactions, a known druggable site, still a target in the search for antimitotic compounds.

Significance of Financial and Non-financial Incentives in Shaping Employee Motivation in Tea Industry: A Sri Lankan Case Study

Sri Lankan Tea sector is experiencing a considerable decline in the labor force, as many workers are moving away from the tea plantations. Incentives are one of the prime factors in reducing labor turnover. However, the role of incentives in employee motivation in the tea sector is questionable. Therefore, the main aim of this study was to identify the role of financial and non-financial incentives in motivating employees in the tea sector in Sri Lanka. Data were collected using pre-tested structured questionnaires from all 60 tea factory workers in Morapitiya Tea Factory, Sri Lanka. In the data analysis, Wilcoxon Sign Rank Test results revealed, bonuses (test value=7.285), over-time payments (test value=7.208), granting EPF/ETF (test value=6.822), job security (test value=7.039), recognition (test value=6.647), positive working environment (test value=6.659) and promotion and career growth (test value=6.548) proven to have a significant (

Fatigue crack growth determination under in-phase and out-of-phase mixed-mode loading conditions using an automated DIC evaluation tool

In this study Digital Image Correlation (DIC) is utilized for measuring complex fatigue crack paths under spatial mixed-mode loading conditions. Therefore, an existing automated script was extended by two criteria for measuring the crack length versus the number of load cycles. Experimental investigations were conducted under mode I conditions, to calibrate the new evaluation routine. Moreover, in-phase and out-of-phase mixed-mode experiments under superimposed tension-torsion loading were performed to validate the method. The results show that the newly presented procedure provides an accurate, automated evaluation tool for mixed-mode fatigue crack growth tests, independent of the crack orientation and possible branching.

Isolation, Identification, and Biochemical Characterization of Lactic Acid Bacteria from Okara

During the process of making soymilk, soybean pulp (okara) is produced as a solid waste product. However, this waste product is rich in nutrient contents such as essential fatty acids, proteins, carbohydrates, vitamins, and minerals. Hence okara is favorable for the growth of microorganisms such as lactic acid bacteria (LAB). The purpose of this study was to isolate, identify and characterize LAB from fermented okara. Isolation of LAB was carried out on MRS agar media supplemented with CaCO 3. LAB was selectively screened based on their morphological, biochemical, and physiological characterizations. A total of 133 different colonies were selected from fermented okara, of which 20 colonies were confirmed as LAB. The entire LAB isolates were catalase negative, indicating that all the identified isolates did not produce the enzyme catalase. Out of 20 LAB, 14 isolates were whitish and six isolates were found to be creamy in colony appearance. The entire LAB isolates were circular in colony shape and found to be rod in cell shape. Based on the cell shape of LAB; isolates were belongs to the genera Lactobacillus. Out of 20 isolates; SL-3, SL-7, SL-10, SL-14, and SL-19 were hetero-fermentative; and the remaining fifteen (15) isolates were found to be homo fermentative. Further studies on the properties of LAB isolate was conducted through a growth test at different temperature (15 0 C, 37 0 C, and 45 0 C) and in different NaCl concentrations. The result of the present study will contribute to the future applications and utilization of LAB as starter cultures for the production of soybean yoghurt and its use in food preservation. Keywords: Lactic acid bacteria, Soybean, Okara DOI: 10.7176/FSQM/117-03 Publication date: July 31 st 2022

EFFECT OF D-RIBOSE ON FUSOBACTERIUM NUCLEATUM PLANKTONIC PROLIFERATION AND BIOFILM MATURATION

Purpose: Periodontopathogenic biofilm structure is one of the most important factors in the etiology of inflammatory periodontal diseases. Quorum Sensing inhibitors (QSi) can inhibit biofilm development/maturation by inhibiting bacterial communication mechanism. In this study, we examined the effects of D-ribose (QSi) on the planktonic growth and bio.film formation characteristics of Fusobacterium nucleatum, an important periodontopathogenic species that has a binding function on early and late colonization types for the development of periodontopathogenic biofilm. 
 Methods: The strain of F. nucleatum (ATCC 25586) and two clinical isolated strains (AHN 9910 and AHN 9508) were used in all tests. Planktonic proliferation (measured as colony forming units) and established biofilm tests (measured as total biofilm mass) were performed in the presence of 50mM D-ribose.
 Results: In planktonic growth tests, statistically significant increase was observed for F. nucleatum ATCC 25586 and AHN 9508 strains (p

Factorial Analysis of Variance of the Inhibiting Effects of Iso-Alpha Acids, Alpha Acids, and Sulfur Dioxide on the Growth of Beer-Spoilage Bacteria in Beer

Growth tests in beers supplemented with specific chemical substances were conducted to investigate the growth control method of beer-spoilage bacteria. Lactobacillus brevis and Pectinatus frisingensis were inoculated into beers in which the pH was set and chemical substances had been added to form a matrix. Supplementation of the beer with hop bitter compounds (iso-α-acids, α-acids, or SO2), had an inhibitory effect on the growth of the tested strains in beer. Furthermore, the growth inhibiting compounds had a synergistic effect when used simultaneously. Two-way repeated measures analysis of variance showed that the interaction effects of combinations of iso-α-acids and α-acids in addition to α-acids and SO2 on the growth of L. brevis and P. frisingensis in beer were highly significant. To verify the contribution degree of pH, iso-α-acids, α-acids, and SO2 on the growth of L. brevis and P. frisingensis, growth test results using a combination of these factors set at different levels were subject to stepwise regression. The contributions of undissociated α-acids, undissociated SO2, and multiplications of undissociated α-acids and undissociated SO2 were especially high in the control of L. brevis growth. The contributions of pH, undissociated SO2, and multiplications of pH and undissociated iso-α-acids were especially high in the control of P. frisingensis growth. The difference in the contributions of antibacterial compounds between L. brevis and P. frisingensis may be due to the difference in the cell wall/membrane structure. Such factorial analysis may be useful for parameter setting in future product designs and process adjustments.

PENGARUH PROPORSI LIMBAH DAUN DAN JENIS MOL TERHADAP MUTU BOKASI

[EFFECT OF LEAF WASTE PROPORTION AND TYPES OF LOCAL MIKROORGANISM ON THE QUALITY OF BOKASHI]. The purpose of this study was to get a combination of the treatment of the leaf waste proportion and local microorganism (MOL) type to the quality of bokashi. The use of specific MOL as a bioactivator is expected to produce a good bokashi. The production of bokashi was conducted at the Garbage Collection Center of Syiah Kuala University, Banda Aceh, Indonesia. The experimental design was a completely randomized design (CRD) with 2 factors including the proportion of leaves (D) and the type of MOL (M). The first factor consisted of two levels (50% and 70% leaf) and the second factor consisted of 4 levels (rice MOL, soil MOL, bokashi MOL, and leaf waste MOL). The quality of bokashi was measured based on the total cell counts of microbes, pH, C/N ratio, descriptive test (texture, aroma, and colour), and plant growth tests on corn. The results showed that all bokashi have complied with SNI 19-7030- 2004. The best bokasi was obtained from the combination between 50% leaf waste proportion and MOL type of rice. This bokashi had a total microbes of 4.1 x 108 CFU/g, pH value of 7.4, C/N ratio of 10.2, with organoleptic characteristics of loose texture and slightly moisture, slightly soil-scented, blackish color and the hight of test plant of 61 cm. The main advantage of this bokashi compared to others was in the highest number of microbes total and the best texture.

Thermomechanical and isothermal fatigue crack propagation testing method for 316LN austenitic stainless steel

AbstractInvestigating fatigue crack growth behavior of materials is crucial to the life design and safety evaluation of engineering structures. During the practical service condition, the temperature keeps changing, which cannot be studied by the traditional fatigue crack growth test method at constant temperature. In this study, we focus on constructing a new thermomechanical fatigue (TMF) crack propagation testing method, developing a thermal deformation compensation method, and proposing an equivalent compliance method suitable for variable temperature conditions based on ASTM E647 standard to measure the crack length. Furthermore, the load‐ and strain‐controlled TMF tests under different phase angles are carried out to prove the validity of the new method.

Microstructure and mechanical properties of crack - free Ni - based GH3536 superalloy fabricated by laser solid forming

Laser solid forming (LSF) was used to fabricate dense and crack-free specimens from solution-strengthened nickel-based superalloy GH3536 in this study. Tensile, and fatigue crack growth (FCG) testing was carried out in both horizontal and vertical build orientations with the condition at 25 °C and 500 °C. Three regions can be detected in the specimen: the additive manufacturing zone (AM), the heat affected zone (HAZ) and the substrate. M23C6 and M6C carbides were found in the specimens, only a small amount of hole defects was observed in the samples, and no cracks were found. The tensile test results show that the specimens have obvious anisotropy, and the horizontal specimens displayed higher strength (up to 855.3 MPa ultimate tensile strength at 25 °C). It is worth noting that there is no obvious anisotropy in the FCG rates of the specimens in different directions, and only when the ΔK is about 45–60 MPa m1/2, the FCG rates of the vertical specimens are higher. The increase in temperature will significantly reduce the tensile performance and increase the FCG rate of the specimens.

A unified in-time correction-based testability growth model and its application on test planning

Test management is a critical problem for in-time correction-based testability growth test. For the existing testability growth model, they are either too complex to be implemented in practice, or do not have the ability to draw a smooth test planning/projecting curve. This paper proposes a unified model for in-time correction-based testability growth test and presents its application on the test planning. Firstly, a simple model with only three parameters is developed, and its compatibility with the original Markov model is proved. The revised model only has three parameters, which can reduce the complexity of parameters estimation and increase the certainty of the test planning. Secondly, the paper incorporates the simplified transition probability model with the test cost model and studies the optimal test planning method with the minimum test cost criterion. To illustrate the efficacy of the proposed model, an application of the model to an attitude control system of a helicopter available in the open literature is given. The simulation demonstrates that the model and the method proposed in this paper are reasonable, and they are useful for effectively managing the testability growth test planning problem during system maturation.

Couple effects of temperature and fatigue, creep-fatigue interaction and thermo-mechanical loading conditions on crack growth rate of nickel-based alloy

The ambient and high-temperature fatigue crack growth behaviors in C(T) and SENT specimens of Ni-based superalloy for turbine disk application were studied in a wide interval of temperatures 25–750°C using a combination a electro- and servohydraulic test systems and fractographic investigations. The fatigue, creep-fatigue interaction and thermo-mechanical in-phase fatigue (TMF IP) crack growth tests are performed under isothermal and dynamic waveforms loading conditions. The interpretation of the experimental results is given in terms of the traditional stress intensity factors and C-integral as well as new normalized cyclic fracture diagrams. It is found that there are definite temperature-sensitive regions separate for harmonic fatigue and creep-fatigue interaction loading conditions in which the crack growth rate of Ni-based alloy increases sharply. Scanning electron microscopy in longitudinal sections containing cracks revealed the mechanisms responsible for fatigue crack initiation and growth. The couple effect of temperature ranging and isothermal and dynamic waveforms loading conditions on fatigue life was discussed.

Effect of Levels of Nitrogen and Seed Rate on Growth and Yield of Wheat (Triticum aestivum L.)

The effect of nitrogen and seed rate on wheat trails like growth and yield was studied through an experiment conducted during Rabi 2021 at Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj (U.P). The soil of experimental plot was sandy loam in texture, nearly neutral in soil reaction (pH 7.1), low in organic carbon (0.36 %), available nitrogen (171.48 kg/ha), available phosphorous (15.2 kg/ha) and available pottasium (232.5 kg/ha). The experiment was laid out in Randomized Block Design with nine treatments each replicated thrice on the basis of one year experimentation. The treatments which are T1: nitrogen 80kg/ha + seed rate 75kg/ha, T2: nitrogen 100kg/ha + seed rate 75kg/ha, T3: nitrogen 120kg/ha + seed rate 75kg/ha, T4: nitrogen 80kg/ha + seed rate 100kg/ha, T5: nitrogen 100kg/ha + seed rate 100kg/ha, T6: nitrogen 120kg/ha + seed rate 100kg/ha, T7: nitrogen 80kg/ha + seed rate 125kg/ha, T8: nitrogen 100kg/ha + seed rate 125kg/ha, T9: nitrogen 120kg/ha + seed rate 125kg/ha are used. The results showed that among different seed rate and nitrogen, the treatment with nitrogen 120kg/ha and seed rate 75kg/ha produced significantly highest plant height (101.20 cm). The treatment combination with nitrogen 120kg/ha + seed rate 100kg/ha produced significantly higher No. of Tillers/plant (7.27), Plant dry weight (21.60 g/plant), Crop growth rate (0.48 g/m2/day), Relative Growth Rate (0.014g/g/day), spikelets/spike (20.07), Grains/spike (58.53), Test weight (46.23 g) and Grain yield (5.91 t/ha). However, the treatment with nitrogen 120kg/ha and seed rate 100kg/ha was found to be effective in highest gross returns (89060.00 INR/ha), net return (58360.03 INR/ha) and benefit/cost ratio (2.90) when compared to other treatments.

Antifungal Activity of Nanoemulsion of Iranian Tarragon (Artemisia dracunculus L.) Essential Oil

Background: Despite the considerable activity of herbal Essential Oils (EOs) as safe food preservatives, problems such as high volatility, low water solubility, and low stability in adverse environmental conditions restrict their use in food products. This work aimed to investigate in vitro antifungal activity of oil-in-water nanoemulsion of Iranian Artemisia dracunculus L. (tarragon) EO.
 Methods: Nanoemulsion of tarragon EO was formed by ultrasound method through blending 10 wt% of tarragon EO, 85 wt% water, and the mixture of 5 wt% surfactants (Tween® 80/Span® 80). The droplet size and zeta potential were measured. The antifungal activity was evaluated against four different fungi, Aspergillus niger, Penicillium spp., Fusarium spp., and Saccharomyces cerevisiae through determining Minimum Inhibitory Concentration (MIC), Minimum Fungicidal Concentration (MFC), and mycelial growth test. Data were statistically analyzed by the software of SPSS 22.0.
 Results: Main fragments of tarragon EO found to be beta-cis-ocimene, estragole, and beta-trans-ocimene. Nanodroplets had a zeta potential of -30 mV and an average diameter of 50 nm. For A. niger, Penicillium spp., Fusarium spp., and S. cerevisiae, the MIC and MFC values of nanoemulsion were identical and obtained at 1.50, 2.05, 1.61, and 1.14 µg/ml, respectively, while these values of free EO were higher and as follows: 2.81, 4.52, 3.75, and 2.40 µg/ml, respectively. Mycelial growth showed that encapsulated EO had the most fungitoxic potential against A. niger (inhibition 41%) and S. cerevisiae (inhibition 68%). Also, Penicillium spp. was the most resistant against both EO and nanoemulsion.
 Conclusion: The growth inhibitory activity of tarragon was significantly enhanced when encapsulated as nanoemulsion.

Creep, fatigue, and creep-fatigue crack growth behaviours of P92 steel at 600 °C

High-temperature components in power generation plant are exposed to creep, fatigue, and creep-fatigue environment during service. The components are usually under multiaxial state of stress condition. Understanding how the material behaves under these loading and environment is essential in order to sustain and keep the plant safe. The present paper aims to investigate the creep rupture and crack growth behaviours of P92 steel at 600 °C. For creep rupture test, notched bars with two different notch radii were prepared and tested under creep condition between 250 and 3500 hours at 600 °C, while the C-shaped specimen was prepared for fatigue and creep-fatigue crack growth tests. The material tested under creep condition showed notch strengthening effect where the life of notched bar specimen increased compared to smooth specimens when the net stress against creep time data was plotted. The effect was more significant as the notch radius decreased. It was also observed that the rupture life of all specimens was von-Mises stress controlled. Based on the fatigue test, it was found that the frequency in a range of 0.1 Hz–10 Hz was insignificantly affecting the crack growth rate. Under creep-fatigue, however, the material showed frequency-dependent behaviour. Observation on the fracture surface revealed that the ductile dimple associated with plasticity was dominant for all creep specimens. In addition, frequency independent specimen was associated with the transgranular fracture, thus flat appearance was evident, while fracture surface of frequency dependent specimen was roughly associated with intergranular fracture.

Modelling of the transition from mode I to crystallographic crack growth in a single crystal gas turbine blade alloy under service-like loading conditions

In fatigue life prediction of single crystal gas turbine blades, the risk of rapid crystallographic crack growth along the close-packed planes poses a large uncertainty. A criterion is proposed to predict the transition from mode I to crystallographic crack growth, which is necessary for reliable prediction of the number of cycles from crack initiation to the onset of crystallographic crack growth. The proposed criterion is calibrated against tests performed under a wide range of conditions representative for a gas turbine blade, including isothermal fatigue crack growth tests and thermomechanical fatigue crack growth tests, some including hold times and pre-test aging.