Proper Stress Research Articles

Hot stretch forming of titanium sheet by resistance heating

Titanium alloys are important aerospace materials due to excellent comprehensive performance, but it is difficult to form at room temperature. Electrically assisted hot stretch forming is used to form the titanium panels of aircraft. This paper studies the effect of temperature, strain, stress relaxation time and cooling rate on forming accuracy by stress relaxation test, tensile test and forming experiment. It is shown that for the influence of temperature on forming accuracy, there is no large difference among 773K, 873K, 973K. And with increase of strain, the forming accuracy becomes lower. For the influence of stress relaxation time, there is no large difference among 0min, 15mins, 30mins. And with decrease of cooling rate, the forming accuracy is improved significantly. It’s concluded that when the temperature reaches a high level, temperature and stress relaxation time have no great influence on forming accuracy. And the forming accuracy is mainly influenced by strain and cooling rate. Electrically assisted hot stretch forming is an effective method to form titanium alloy. And the part with high forming accuracy can be obtained by adopting high temperature, low strain, proper stress relaxation time and low cooling rate.

STUDYING THE EFFECT OF THE PRELOAD INDUCED BY SCREW TIGHTENING ON STRESS DISTRIBUTION OF A DENTAL IMPLANT

The success of implants is largely dependent on initial stability and long-term osseointegration due to optimal stress distribution around the bone and implant. The purpose of this study is the numerical analysis of stress distribution in jaw bone and implant using finite element analysis considering the static forces caused by screw tightening and masticatory preloads. These forces and design limitations have been applied in accordance with implant science in dentistry to provide a proper stress distribution. First, all the parts were modelled with Solidworks software and then transferred to Abaqus software for analysis and applying the forces. For a better and more exact stress distribution analysis in the bone and implant, this analysis was conducted by two steps, that after determining the properties of each part, boundary conditions, loading and finally meshing the complex using hexahedral meshes and Match mesh technique, the abutment was tightened inside the implant with different tightening torques through six tests to apply preload in first step which this force applying induced stress in jaw and implant. Then, the amount of jaw force was applied to the crown surface. The results showed that the preload is quite effective in bone and implant stress distribution. However, its value only affects the surface stresses of the implant and has little effect on the of jaw bone stress value. This study can be carried on to evaluate the implants life considering Preload.

TRMT1-Catalyzed tRNA Modifications Are Required for Redox Homeostasis To Ensure Proper Cellular Proliferation and Oxidative Stress Survival.

Mutations in the tRNA methyltransferase 1 (TRMT1) gene have been identified as the cause of certain forms of autosomal-recessive intellectual disability (ID). However, the molecular pathology underlying ID-associated TRMT1 mutations is unknown, since the biological role of the encoded TRMT1 protein remains to be determined. Here, we have elucidated the molecular targets and function of TRMT1 to uncover the cellular effects of ID-causing TRMT1 mutations. Using human cells that have been rendered deficient in TRMT1, we show that TRMT1 is responsible for catalyzing the dimethylguanosine (m2,2G) base modification in both nucleus- and mitochondrion-encoded tRNAs. TRMT1-deficient cells exhibit decreased proliferation rates, alterations in global protein synthesis, and perturbations in redox homeostasis, including increased endogenous ROS levels and hypersensitivity to oxidizing agents. Notably, ID-causing TRMT1 variants are unable to catalyze the formation of m2,2G due to defects in RNA binding and cannot rescue oxidative stress sensitivity. Our results uncover a biological role for TRMT1-catalyzed tRNA modification in redox metabolism and show that individuals with TRMT1-associated ID are likely to have major perturbations in cellular homeostasis due to the lack of m2,2G modifications.

Characteristics of a Regulator of G-Protein Signaling (RGS) rgsC in Aspergillus fumigatus.

The regulator of G-protein signaling (RGS) proteins have a conserved RGS domain that facilitates the intrinsic GTPase activity of an activated Gα subunit of heterotrimeric G protein, thereby attenuating signal transduction. Among six predicted RGS proteins in the opportunistic human pathogenic fungus Aspergillus fumigatus, only three (FlbA, GprK, and Rax1) have been studied. The unexplored RgsC composed of the Phox-associated (PXA), RGS, Phox homology (PX), and Nexin_C superfamily domains is highly conserved in many ascomycete fungi, suggesting a crucial role of RgsC in fungal biology. To address this, we have investigated functions of the rgsC gene. The deletion (Δ) of rgsC causes impaired vegetative growth and asexual development coupled with reduced expression of key developmental regulators. Moreover, ΔrgsC results in accelerated and elevated conidial germination regardless of the presence or absence of an external carbon source. Furthermore, ΔrgsC causes reduced conidial tolerance to oxidative stress. In addition, activities and expression of catalases and superoxide dismutases (SODs) are severely decreased in the ΔrgsC mutant. The deletion of rgsC results in a slight reduction in conidial tolerance to cell wall damaging agents, yet significantly lowered mRNA levels of cell wall integrity/biogenesis transcription factors, indicating that RgsC may function in proper activation of cell wall stress response. The ΔrgsC mutant exhibits defective gliotoxin (GT) production and decreased virulence in the wax moth larvae, Galleria mellonella. Transcriptomic studies reveal that a majority of transporters is down-regulated by ΔrgsC and growth of the ΔrgsC mutant is reduced on inorganic and simple nitrogen medium, suggesting that RgsC may function in external nitrogen source sensing and/or transport. In summary, RgsC is necessary for proper growth, development, stress response, GT production, and external nutrients sensing.

IMPLEMENTATION OF TURKISH TEXT-TO-SPEECH SYNTHESIS ON A VOICE SYNTHESIZER CARD WITH PROSODIC FEATURES

This study is on hardware implementation of the Turkish text-to-speech (TTS) synthesis with a voice synthesizer card. Here, a fully functional TTS system, capable of synthesizing every Turkish text, including abbreviations, numbers, etc. is designed and implemented. The system is additionally enriched by applying some prosodic attributes for more intelligible and natural speech production. A set of rules required for proper pronunciation and stress patterns are precisely defined in a lexicon utilized for synthesizing Turkish speech. Performance of the developed system is assessed by the Mean Opinion Score (MOS) test. An average score of 3.8 out of 5 is achieved. It indicates that the proposed synthesizer can be successfully integrated to many practical Turkish TTS applications.

Effects of different indentation methods on fatigue life extension of cracked specimens

AbstractIn this paper, 3 different indentation methods have been investigated for crack arresting and fatigue life enhancement of cracked components. The influence of residual stresses induced by indentation on fatigue crack growth (FCG) rate was explored by experiments and numerical simulations. Fatigue tests were conducted on a group of specimens which were indented on the crack tip by various indentation load magnitudes. For another group of specimens, the double indentation and triple indentation methods were applied on the cracked specimens with the aim of obtaining proper residual stress fields that contribute to higher crack growth retardations. Both the numerical and experimental results revealed that the higher indentation loads led to larger domain of compressive residual stress around the crack tip and consequently to higher fatigue life extension. In addition, the triple indentation method resulted in more FCG retardation compared with single and double indentation methods. Furthermore, for the specimens repaired by double and triple indentation methods, indenting ahead of the crack tip led to retardation in more crack growth compared with the other horizontal positions of indentation.

Strain-dependent internal parameters in hyperelastic biological materials

The behavior of hyperelastic energies depending on an internal parameter, which is a function of the deformation gradient, is discussed. As an example, the analysis of two models where the parameter describes the activation of a tetanized skeletal muscle tissue is presented. In those models, the activation parameter depends on the strain and it is shown the importance of considering the derivative of the parameter with respect to the strain in order to capture the proper stress–strain relations.

SETD4 Regulates Cell Quiescence and Catalyzes the Trimethylation of H4K20 during Diapause Formation in Artemia

As a prominent characteristic of cell life, the regulation of cell quiescence is important for proper development, regeneration, and stress resistance and may play a role in certain degenerative diseases. However, the mechanism underlying quiescence remains largely unknown. Encysted embryos of Artemia are useful for studying the regulation of this state because they remain quiescent for prolonged periods during diapause, a state of obligate dormancy. In the present study, SET domain-containing protein 4, a histone lysine methyltransferase from Artemia, was identified, characterized, and named Ar-SETD4. We found that Ar-SETD4 was expressed abundantly in Artemia diapause embryos, in which cells were in a quiescent state. Meanwhile, trimethylated histone H4K20 (H4K20me3) was enriched in diapause embryos. The knockdown of Ar-SETD4 reduced the level of H4K20me3 significantly and prevented the formation of diapause embryos in which neither the cell cycle nor embryogenesis ceased. The catalytic activity of Ar-SETD4 on H4K20me3 was confirmed by an in vitro histone methyltransferase (HMT) assay and overexpression in cell lines. This study provides insights into the function of SETD4 and the mechanism of cell quiescence regulation.

Rice calcium-dependent protein kinase OsCPK17 targets plasma membrane intrinsic protein and sucrose-phosphate synthase and is required for a proper cold stress response.

Calcium-dependent protein kinases (CDPKs) are involved in plant tolerance mechanisms to abiotic stresses. Although CDPKs are recognized as key messengers in signal transduction, the specific role of most members of this family remains unknown. Here, we test the hypothesis that OsCPK17 plays a role in rice cold stress response by analysing OsCPK17 knockout, silencing and overexpressing rice lines under low temperature. Altered OsCPK17 gene expression compromises cold tolerance performance, without affecting the expression of key cold stress-inducible genes. A comparative phosphoproteomic approach led to the identification of six potential in vivo OsCPK17 targets, which are associated with sugar and nitrogen metabolism, and with osmotic regulation. To test direct interaction, in vitro kinase assays were performed, showing that the sucrose-phosphate synthase OsSPS4 and the aquaporin OsPIP2;1/OsPIP2;6 are phosphorylated by OsCPK17 in a calcium-dependent manner. Altogether, our data indicates that OsCPK17 is required for a proper cold stress response in rice, likely affecting the activity of membrane channels and sugar metabolism.

Sputtering gas pressure and target power dependence on the microstructure and properties of DC-magnetron sputtered AlB2-type WB2 films

The study is mainly to optimize the process parameters (sputtering pressure and sputtering power) of the AlB2-type WB2 films deposited by DC magnetron sputtering by comparing their microstructure, elemental composition, and tribo-mechanical properties. As the argon pressure (PAr) increases (0.3–1.0 Pa), the particle density increases first and then decreases, with a corresponding decrease for particle energy. Under this condition, both the deposition rate and the B/W atomic ratio of the WB2 films increase first and then decrease under the competition effect between the sputtering and scattering process, the film orientation changes from (0 0 1) to (1 0 1), the microstructure changes from dense fine-fiber to porous column coupled with the stress evolution from compressive stress to increased tensile stress. Consequently, films deposited at PAr > 0.5 Pa have the poor hardness and wear-resistance. As the sputtering power increases (150–310 W), both the particle density and particle energy increase. Thus, the deposition rate increases greatly, the B/W atomic ratio declines slightly due to the resputtering process, the film structure becomes dense but rough by the particle bombardment causing the stress change from tensile stress to enhanced compressive stress, and the film orientation changes from the well-crystallized (0 0 1) to poor-crystallized (1 0 1). In conclusion, films with (0 0 1) orientation, high B/W atomic ratio, dense structure and proper compressive stress, which can be deposited at PAr = 0.5 Pa and sputtering current 0.5 A (corresponding to target power about 150 W), show the excellent tribo-mechanical properties with high hardness about 39.4 GPa and low wear rate of 2.2 × 10−7 mm3/mN.

Analysis of cortisol in hair samples as an indicator of stress in pigs

Abstract Detection of cortisol is one of the most widely used methods to assess stress in animals because it provides information about hypothalamic-pituitary-adrenal axis activity. The most common biological samples are plasma, saliva, urine, feces, milk, and hair. Hair cortisol analysis could be a good noninvasive procedure to detect chronic stress because cortisol is incorporated and stored inside growing hair. The aim of this study was to determine whether cortisol could be detected in pig hair and could serve as a proper chronic stress indicator. Hair samples from 2 regions (craniodorsal [D] and dorsolumbar [L]) of 20 crossbred entire male pigs were taken at 8 and 22 weeks of age. The pigs were subjected to a weekly remixing procedure. The mean cortisol level for the hair samples was 19.30 ± 0.63 pg/mg (range, 6.4-43.88). Hair for second sampled day had higher cortisol values ( P = 0.002) than hair from first sampled day. Furthermore, L region had higher values than D region at every age measurement ( P P = 0.019) and region L (r = 0.523; P P P

Proper Nominal Stress Distribution Subjected to Combination of Wedge-Splitting and Bended Geometry Tests

The paper focuses on the determination of proper value of the nominal stress distribution on the combination of wedge-splitting/bended test geometry during the loading through steel platens. Since past, the parameters like stress intensity factor (e.g.) have been obtained with stress value simplified into same formulation, which means that the stress distribution is uniform. But during the real testing the stress is definitely not uniform because the splitting forces produce bending of the test specimen. That is the main goal of this study.

Evaluation of psychological stress in orthodontic PG students in India

Introduction: Psychological stress is associated with many professions including dental surgery and is commonly encountered among BDS students, which later increases during post graduation (MDS). In this study we intended to identify the perceived sources and the extent of the psychological stress in the Orthodontic post-graduate students, and also evaluate the influence of different variables on overall stress and the effect of various stress relievers among the PG students. Material and Method: A questionnaire type of survey was conducted among 80 Orthodontic post graduate students (39 male and 41 female). A total of 22 factors were shortlisted for the questionnaire and were grouped under three broad categories as Personal, Curriculum Factors and Clinical Factors which were scored on a four point scale as 0- Not applicable, 1- Mild stress, 2–Moderate stress, 3–Severe stress. Result: The result showed that the majority of the PGs were definitely stressed, with females being more stressed than males, though the difference between two genders was statistically non-significant for most of the perceived sources of stress except for home sickness . In overall stress scores for different variables, the difference was statistically non-significant in all of them. Among the stress busters use of social media, alcohol and smoking were significantly associated with some of the student characteristics. Conclusion: The stress levels in PG curriculum definitely exist and the students should adopt proper stress busters to relieve the stress so as to work efficiently during their course.

Performance Improvement of Membrane Stress Measurement Equipment through Evaluation of Added Mass of Membrane and Error Correction

One of the most important issues in keeping membrane structures in stable condition is to maintain the proper stress distribution over the membrane. However, it is difficult to determine the quantitative real stress level in the membrane after the completion of the structure. The stress relaxation phenomenon of the membrane and the fluttering effect due to strong wind or ponding caused by precipitation may cause severe damage to the membrane structure itself. Therefore, it is very important to know the magnitude of the existing stress in membrane structures for their maintenance. The authors have proposed a new method for separately estimating the membrane stress in two different directions using sound waves instead of directly measuring the membrane stress. The new method utilizes the resonance phenomenon of the membrane, which is induced by sound excitations given through an audio speaker. During such experiment, the effect of the surrounding air on the vibrating membrane cannot be overlooked in order to assure high measurement precision. In this paper, an evaluation scheme for the added mass of membrane with the effect of air on the vibrating membrane and the correction of measurement error is discussed. In addition, three types of membrane materials are used in the experiment in order to verify the expandability and accuracy of the membrane measurement equipment.

Novel kaolinite based coolant for hyperthermal pyrotechnic aerosol cooling

Novel spherical pyrotechnic aerosol cooling granulates which are made of 42.8% kaolinite powder, 38.8% water, 8.1% epoxy A&B glue and 10.2% ethyl cellulose are successfully synthesized and can cool down the temperature of hot pyrotechnic aerosol from 1400 to 400°C below with only a 1:1 mass ratio of coolant to the aerosol forming agent. The cooling system is a packing bed randomly stacked with 5mm diameter cooling granulates. The kaolinite based cooling granulate has proper yield stress to provide the cooling bed a constant porosity in order to avoid any tunneling effect and granulate structural failure during hot aerosol cooling. Moreover, the synthesis process of current novel kaolinite based granulate coolant is simple and economic. Compared to other coolants like irregular granite gravels or ceramic intalox used for pyrotechnic aerosol cooling, the cooling performance of spherical kaolinite based cooling granulates is superior.

Tensile Stress Analyses through Digital Image Correlation of Single Lap Joints of High Strength Steel and Aluminum Alloy Using Adhesive Bonding

Structural adhesives methods for joining multi material sheets have been focus of studies and researches for the last years. The most common and widely known type of test is the tensile test of single lap joints (SLJ). However, there are opportunities for analyzing the mechanical performance of such method in SLJ with materials of different properties, such as ductile structural aluminum alloys and high strength steels. It’s also known that the stress state of SLJ, when stressed longitudinally, generates secondary forces. One of them is known as cleavage force which initially leads to the failure of bonded joints. The aim of this work is to analyze the stress state of similar and dissimilar materials SLJ submitted to tensile stresses and also the influence of some variables, such as overlap length, adhesive film thickness and adherend yield limit, over the stress strength of the samples. As adherend materials it was selected the structural aluminum alloy AA 5083 H111 and the high strength steel DP600. At the end of this work it is expected to understand the proper stress state of the SLJ when using similar and dissimilar materials, identifying stress concentrators that bring the structure to fail, using the Digital Image Correlation (DIC) method. It was discovered that the yield strength associated with the overlap length highly influences the SLJ strength, by leading it to a close to pure adhesive shear stress state.

Phase coexistence in ferroelectric solid solutions: Formation of monoclinic phase with enhanced piezoelectricity

Phase morphology and corresponding piezoelectricity in ferroelectric solid solutions were studied by using a phenomenological theory with the consideration of phase coexistence. Results have shown that phases with similar energy potentials can coexist, thus induce interfacial stresses which lead to the formation of adaptive monoclinic phases. A new tetragonal-like monoclinic to rhombohedral-like monoclinic phase transition was predicted in a shear stress state. Enhanced piezoelectricity can be achieved by manipulating the stress state close to a critical stress field. Phase coexistence is universal in ferroelectric solid solutions and may provide a way to optimize ultra-fine structures and proper stress states to achieve ultrahigh piezoelectricity.

CONSTRUCTIVIST APPROACH: CREATING A MEANING TO LEARNING

The author is wholly concerned with the unstressed learning of the students for which he wants to revolutionize the way of teaching English. A foreign language is learnt specially with the translation method is the practical side of the language learning. The author has experienced the various learning criteria of learning language as he has been working in the Tribal Institution. For the infants the most practical and fruitful method we have gone through is the Direct Method of language learning. The Direct Method refers to the ‘Direct approach in the language application’
 The words, ‘This’, ‘That’, envisage to the appetite of understanding the information of the object. These words are to be regarded as the model words of the ‘Direct Method.’
 In language learning, the presentation of the objects or the things put a sort of stress on the views of the students that is accompanied with the experience. The author is feasibly concerned with the – 1. Actual understanding of the language by the student, 2.Throughout application of the language by the student, 3. The proper information and stress on the words by the students and 4. Beneficence of the learnt language to the student. We look in for the various methodologies in making language learning easy.

Does Prenatal Stress Management Enhance Maternal And Fetal Outcomes?

Background: Antenatal period is a time of rapid change during which fetal organs are vulnerable to various stressors. Studies have suggested that psychosocial stressors during pregnancy could adversely influence physical and behavioral outcomes of the infant. Aim: This paper aimed to discusses the importance of antenatal stress assessment and management on both mothers' and infants' health status. Method: This review aggregated evidence from various studies that examined the impact of maternal stress management and its outcomes on pregnant women and their infants. Results: Maternal stress is generally associated with unpleasant fetal outcomes. The use of stress reduction techniques was approved to reduce psychological stress in pregnant women. Conclusion: Ongoing assessment of antenatal stress using a standardized process promotes proper stress handling strategy.

Magnetic and microstructural properties of Fe3O4-coated Fe powder soft magnetic composites

Soft magnetic composites (SMCs) comprised of ferrite-coated ferrous powder permit isotropic magnetic flux capabilities, lower core losses, and complex designs through the use of traditional powder metallurgy techniques. Current coating materials and methods are vastly limited by the nonmagnetic properties of organic and some inorganic coatings and their inability to withstand high heat treatments for proper stress relief of core powder after compaction. Ferrite-based coatings are ferrimagnetic, highly resistive, and possess high melting temperatures, thus providing adequate electrical barriers between metallic particles. In this work, iron powder was coated with Fe3O4 particles via mechanical milling, then compacted and cured in an inert gas environment. We find density and coercivity to improve with increasing temperatures; however, core loss greatly increases, which is attributed to the formation of a more conductive iron-oxide phase and less resistive Fe volume. Our work begins to exemplify the unique qualities and potential for ferrite-based coatings using traditional powder metallurgy techniques and higher curing temperatures for electromagnetic devices.