Young's Modulus Change Research Articles

Characterization of Calotropis gigantiea plant leaves biomass-based bioplasticizers for biofilm applications

The present surge in environmental consciousness has pushed for the use of biodegradable plasticizers, which are sustainable and abundant in plant resources. As a result of their biocompatibility and biodegradability, Calotropis gigantiea leaf plasticizers (CLP) serve as viable alternatives to chemical plasticizers. First time, the natural plasticizers from the Calotropis leaves were extracted for this study using a suitable chemical approach that was also environmentally friendly. The XRD results showed a reduced crystallinity index of 20.2 % and a crystalline size of 5.3 nm, respectively. TGA study revealed that the CLP has good thermal stability (244 °C). Through FT-IR study, the existence of organic compounds in CLP can be investigated by key functional groups such as alcohol, amine, amide, hydrocarbon, alkene, aromatic, etc. Further the presence of alcoholic, amino, and carboxyl constituents was confirmed by UV investigation. SEM, EDAX analysis, and AFM are used to examine the surface morphology of the isolated plasticizer. SEM pictures reveal rough surfaces on the CLP surface pores, which makes them suitable for plasticizing new bioplastics with improved mechanical properties. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer matrix, was used to investigate the plasticization impact after the macromolecules were characterised. The biofilm PBAT/CLP had a thickness of 0.8 mm. In addition, the reinforcement interface was examined using scanning electron microscopy. When CLP is loaded differently in PBAT, the tensile strength and young modulus change from 15.30 to 24.60 MPa and from 137 to 168 MPa, respectively. CLP-reinforced films demonstrated better surface compatibility and enhanced flexibility at a loading of 2 % when compared to pure PBAT films. Considering several documented characteristics, CLP may prove to be an excellent plasticizer for resolving environmental issues in the future.

Characterization of the mechanical properties of the cortex region of human hair fibers by multiparametric atomic force microscopy mapping

We show the benefit of the use of atomic force microscopy (AFM) in spectroscopy force mode (FV: force volume) for evaluation of the cosmetic active effectiveness in improving the mechanical properties of human hair fibers cortex region. For this, we characterized human hair fibers without and with chemical damage caused by bleaching process. Fiber and resin (embedding material) data were obtained simultaneously in the mapping in order to have the resin data as a reference to ensure a coherent comparison between data from the different fiber groups. Our AFM results, which were evaluated using statistical tests, demonstrated the degradation of fibers after bleaching, corroborating the findings of transmission electron microscopy analysis and the effectiveness of a cosmetic active ingredient in improving the Young's modulus (elastic modulus) (E) of the damaged fibers. We also found a radial decrease in the natural logarithm of Young's modulus ln(E) along the cross-section of the active group fiber, which is compatible with confocal Raman spectroscopy analysis by other authors, demonstrating variation of the active permeation with depth. We note that Young's modulus was also determined by a tensile tester (macro-scale technique), in which it was not possible to obtain statistically significant differences between the groups, evidencing the advantage of the FV-AFM analysis. We also found an increase in ln(E) accompanied by a decrease in maximum adhesion force between tip and sample (negative Pearson correlation coefficient). This result can be explained by the fact that structures composed of hydrophobic components have a higher Young's modulus than structures composed of hydrophilic components.•Bleaching damage and cosmetic hair treatment assessed by AFM, TEM, and tensile tester.•Young's modulus by AFM nanoindentation of hair fibers monitored by sample standard.•Young's modulus changes radially along the cross-section due to the cosmetic active.•AFM data show statistically significant differences among sample groups.•Tensile tester was not able to show statistically significant differences.

Stabilities of substitutional solutes in α-iron under uniaxial strain

Nonuniform strain fields in ferritic/martensitic steels working in extreme conditions might induce segregation of alloying solutes. We optimized the structures of iron alloy systems under uniaxial tensile strains along [001] direction within density-functional theory. The calculated segregation energies of solutes Ni, Cu, Al, and Si decrease drastically in a linear fashion as the tensile strain increases up to 17.5%, while those of Co and Ti only change slightly. The segregation energies of solutes V, Nb, Ta, Cr, Mo, and W first decrease and then increase. These results might indicate that, for all solutes studied except Co and Ti, segregation behaviors happen in ferritic/martensitic steels under tensile strains. The shape deformation effect plays a major role in the segregation energies of solutes Cu, Al, Si, Ni, Nb, Ta, Cr, and Mo, while the volumetric effect is dominant for solutes V and W. The segregation energy changes owing to the tensile strain increase from 8% to 14% exhibit a linear relation with the Young modulus changes of the alloys relative to α-iron, which indicates a correlation between the stabilities of solutes and their bonding strength with iron neighbors. The linearly decreasing mixing energies of solutes Mg, Zn and Ga in α-iron with increasing uniaxial strain might suggest a new possible way of fabricating supersaturated iron solid solutions.

Interplay between Elastic and Electrochemical Properties during Active Material Transitions and Aging of a Lithium‐Ion Battery

AbstractThe interplay between the internal mechanical properties and external mechanical conditions of a battery cell, e. g., Young's modulus and thickness change, has a crucial impact on the cell performance and lifetime, and thus, needs to be fully understood. In this work, 12 Ah lithium‐ion battery pouch cells were studied during cycling and aging by non‐invasive operando ultrasonic and dilation measurements. The effective Young's modulus increases and the thickness varies the most within a single cycle during the graphite transition from stage 1L to 4, at the beginning of the 2 to 1 stage transition and at the phase transition of the nickel‐rich NCM from H2 to H3. After 1000 cycles of aging, the overall effective Young's modulus of the lithium‐ion battery decreases by ∼11 %–12 % and the cell thickness increases irreversibly by ∼3 %–4 %, which is mostly related to a thicker and possibly softer, more porous solid electrolyte interphase layer.

Mechanical behavior of annealed electrochemically deposited nanocrystalline nickel-iron alloys

Abstract Nanocrystalline nickel-iron layers are produced electrochemically on copper discs by varying the current density and then annealed in a vacuum furnace at a temperature range between 200 and 800 °C. Grain size, iron content, texture and microstrain of the microstructure are primarily characterized by X-ray diffraction (XRD). Instrumented indentation tests and microbending tests for mechanical characterization are carried out. The iron contents of the investigated layers are 5.7, 8.8, 13.5 and 17.7 wt.-%. By varying the annealing temperature, the reduction of the microstrains is initiated at 200 °C and ends at a temperature of about 280 °C. Primary recrystallization starts slightly higher at 220 °C and is completed at 300 °C. With higher iron content, the indicated temperatures shift to slightly higher values. Indentation modulus, Young's modulus, indentation hardness and strength change considerably after the annealing treatment. Fracture strain at the edge, as a measure of ductility, decreases immediately after annealing at 200 °C to 0 %. Low annealing temperatures occurring before the beginning of primary recrystallization lead to an increase in indentation hardness and 0.01-% offset bending yield strength Rp0.01∗ as compared to the electrochemically deposited initial state. After annealing at high temperatures, the mechanical parameters are mostly below the initial values for electrochemical deposition. Hall-Petch (HP) behavior is observed for Rp0.01∗, both for the electrochemically deposited specimens down to almost 6 nm and for the specimens annealed at high temperatures. Specimens annealed at low temperatures deviate from the HP straight line to higher values. In this case, an increase in strength is assumed to be due to the very small nanocrystalline (nc) grain sizes, segregation at the grain boundaries and a decrease in dislocation density. Indentation hardness measurements show almost no dependence on D−0.5 for the electrochemically deposited specimens and also for annealed specimens below 30nm grain size. Above 30nm, the indentation hardness values are considerably higher than for the HP straight line. Overall, the hardness and strength values of the nc specimens, electrochemically deposited or additionally annealed, are significantly higher than those of the microcrystalline (mc) specimens.

Vibrational power flow analysis of cracked functionally graded beams

Abstract In this paper, the vibrational power flow of a cracked beam made of functionally graded materials (FGMs) is investigated. The Young's modulus and mass density change exponentially along the thickness direction of the beam. The cracked FGM beam is divided into two sub-beams at the crack section which are connected by a massless rotational spring. Based on the Timoshenko beam theory, the governing equations of the cracked FGM beam are derived by using the neutral plane as the reference plane. The dynamic response of the FGM beam subjected to a harmonic concentrated transverse force is solved by the wave propagation approach. The input power flow and the transmitted power flow are obtained. The effect of the crack location and depth and the Young's modulus ratio on the input power flow and the transmitted power flow is studied in detail. A new damage index (DI) for the crack identification of FGM beams is proposed by applying continuous wavelet transform (CWT) to the transmitted power flow distribution along the beam longitudinal direction. The peak of DI indicates the crack location in FGM beams with small crack depth.

Multi-parameter ultrasound based on the logistic regression model in the differential diagnosis of hepatocellular adenoma and focal nodular hyperplasia.

BACKGROUNDFocal nodular hyperplasia (FNH) has very low potential risk, and a tendency to spontaneously resolve. Hepatocellular adenoma (HCA) has a certain malignant tendency, and its prognosis is significantly different from FNH. Accurate identification of HCA and FNH is critical for clinical treatment.AIMTo analyze the value of multi-parameter ultrasound index based on logistic regression for the differential diagnosis of HCA and FNH.METHODSThirty-one patients with HCA were included in the HCA group. Fifty patients with FNH were included in the FNH group. The clinical data were collected and recorded in the two groups. Conventional ultrasound, shear wave elastography, and contrast-enhanced ultrasound were performed, and the lesion location, lesion echo, Young’s modulus (YM) value, YM ratio, and changes of time intense curve (TIC) were recorded. Multivariate logistic regression analysis was used to screen the indicators that can be used for the differential diagnosis of HCA and FNH. A ROC curve was established for the potential indicators to analyze the accuracy of the differential diagnosis of HCA and FNH. The value of the combined indicators for distinguishing HCA and FNH were explored.RESULTSMultivariate logistic regression analysis showed that lesion echo (P = 0.000), YM value (P = 0.000) and TIC decreasing slope (P = 0.000) were the potential indicators identifying HCA and FNH. In the ROC curve analysis, the accuracy of the YM value distinguishing HCA and FNH was the highest (AUC = 0.891), which was significantly higher than the AUC of the lesion echo and the TIC decreasing slope (P < 0.05). The accuracy of the combined diagnosis was the highest (AUC = 0.938), which was significantly higher than the AUC of the indicators diagnosing HCA individually (P < 0.05). This sensitivity was 91.23%, and the specificity was 83.33%.CONCLUSIONThe combination of lesion echo, YM value and TIC decreasing slope can accurately differentiate between HCA and FNH.

Atomic force microscopy study revealed velocity-dependence and nonlinearity of nanoscale poroelasticity of eukaryotic cells.

Intracellular network deformation of the cell plays an important role in cellular shape formation. Recent studies suggest that cell reshaping and deformation due to external forces involve cellular volume, pore size, elasticity, and intracellular filaments polymerization degree change. This cell behavior can be described by poroelastic models due to the porous structure of the cytoplasm. In this study, the nanoscale poroelasticity of human mammary basal/claudin low carcinoma cell (MDA-MB-231) was investigated using indentation-based atomic force microscopy. The effects of cell deformation (i.e., indentation) velocity and depth on the poroelasticity of MDA-MB-231 cells were studied. Specifically, the cell poroelastic behavior (i.e., the diffusion coefficient) was quantified at different indenting velocities (0.2, 2, 10, 20, 100, 200 μm/s) and indentation depths (635, 965, and 1313nm) by fitting the force-relaxation curves using a poroelastic model. Cell treated with cytoskeleton inhibitors (latrunculin B, blebbistatin, and nocodazole) were measured to investigate the effect of the cytoskeletal components on the cell poroelasticity. It was found that in general the MDA-MB-231 cells behaved less poroelastic (i.e., with lower diffusion coefficient) at higher indenting velocities due to the local stiffening up and dramatic pore size reduction caused by faster force load, and the cytoplasm is nonlinear in terms of poroelasticity. The poroelastic relaxation was more pronounced when the local cytoplasm porous structure was stretched by higher indentation. Furthermore, inhibition of cytoskeletal components resulted in pronounced poroelastic relaxation when compared with the control, and affected the nonlinearity of cell poroelasticity at different depth range inside of the cell. The comparison between the diffusion coefficient variation and the Young's modulus change under each indentation/treatment condition suggested that the cytoplasm porous geometry is more dominant than the cell Young's modulus in terms of affecting cell poroelasticity.

MRI-based patient-specific human carotid atherosclerotic vessel material property variations in patients, vessel location and long-term follow up.

BackgroundImage-based computational models are widely used to determine atherosclerotic plaque stress/strain conditions and investigate their association with plaque progression and rupture. However, patient-specific vessel material properties are in general lacking in those models, limiting the accuracy of their stress/strain measurements. A noninvasive approach of combining in vivo 3D multi-contrast and Cine magnetic resonance imaging (MRI) and computational modeling was introduced to quantify patient-specific carotid plaque material properties for potential plaque model improvements. Vessel material property variation in patients, along vessel segment, and between baseline and follow up were investigated.MethodsIn vivo 3D multi-contrast and Cine MRI carotid plaque data were acquired from 8 patients with follow-up (18 months) with written informed consent obtained. 3D thin-layer models and an established iterative procedure were used to determine parameter values of the Mooney-Rivlin models for the 81slices from 16 plaque samples. Effective Young’s Modulus (YM) values were calculated for comparison and analysis.ResultsAverage Effective Young’s Modulus (YM) and circumferential shrinkage rate (C-Shrink) value of the 81 slices was 411kPa and 5.62%, respectively. Slice YM value varied from 70 kPa (softest) to 1284 kPa (stiffest), a 1734% difference. Average slice YM values by vessel varied from 109 kPa (softest) to 922 kPa (stiffest), a 746% difference. Location-wise, the maximum slice YM variation rate within a vessel was 311% (149 kPa vs. 613 kPa). The average slice YM variation rate for the 16 vessels was 134%. The average variation of YM values for all patients from baseline to follow up was 61.0%. The range of the variation of YM values was [-28.4%, 215%]. For plaque progression study, YM at follow-up showed negative correlation with plaque progression measured by wall thickness increase (WTI) (r = -0.7764, p = 0.0235). Wall thickness at baseline correlated with WTI negatively, with r = -0.5253 (p = 0.1813). Plaque burden at baseline correlated with YM change between baseline and follow-up, with r = 0.5939 (p = 0.1205).ConclusionIn vivo carotid vessel material properties have large variations from patient to patient, along the diseased segment within a patient, and with time. The use of patient-specific, location specific and time-specific material properties in plaque models could potentially improve the accuracy of model stress/strain calculations.

INFLUENCE OF SPECIFIC THERMAL TREATMENT ON YOUNG'S MODULUS CHANGES IN A NATURAL RUBBER–BASED COMPOUND: STUDY BY AFM NANOINDENTATION

ABSTRACT The determination and study of Young's modulus at the nanometric scale in an efficient and fast way is carried out using atomic force microscopy (AFM) in contact mode. The aim of this study is to evaluate the impact of a specific thermal treatment on Young's modulus changes from the surface toward the bulk of a cured natural rubber (NR)–based compound. The AFM nanoindentation experiments were conducted on a cross-linked NR sample. Following a depth profiling analysis method, AFM deflection distance curves were measured every 40 μm from the oxygen-exposed surface toward the bulk, and then the Hertz's model was applied to force-indentation curves for the calculation of the Young's modulus. Investigations on the thermal-treated samples revealed an overall increase of the Young's modulus along the samples after heating. Moreover, a decrease of Young's modulus values from the surface exposed to oxygen during heating toward the bulk was observed, indicating a stiffening of the sample at the surface.

AFM Imaging of Molecular Spin‐State Changes through Quantitative Thermomechanical Measurements

Quantitative atomic force microscopy is used in conjunction with microwire heaters for high-resolution imaging of the Young's modulus changes across the spin-state transition. When going from the high spin to the low spin state, a significant stiffening is observed.

Free Vibration of Exponential Functionally Graded Beams with Single Delamination

FGMs are regarded as one of the most promising candidates for future advanced composites in many engineering sectors, but they may suffer the problem of delamination. Delaminations in structures may significantly reduce the stiffness and strength of the structure and may affect their vibration characteristics. In the present study, an analytical solution is developed to study the free vibration of exponential functionally graded beams with a single delamination. Kirchhoff-Love hypothesis, the ‘free mode’ and ‘constrained mode’ assumption in delamination vibration are adopted. The shifting of neutral axis due to asymmetrical distribution of material property (in thickness direction) is also taken into consideration. This is the first study on the influences of delamination (its length and location) on the vibration of exponential functionally graded beams. Results show that the natural frequency increases as the Young's modulus ratio increases, but such increase is smaller when the beam suffers a longer delamination. Furthermore, the effect of delamination length and longitudinal location on reducing natural frequency is aggravated when the material property (Young's modulus and density) changes less dramatically from the bottom to the top. The difference of natural frequency between ‘free mode’ and ‘constrained mode’ becomes smaller with a decreasing Young's modulus ratio. The analytical results of this study can serve as the benchmark for FEM and other numerical solutions.

Shear wave elastography in the evaluation of porcine liver treated with radiofrequency ablation: an in vitro experiment

Objective To evaluate the stiffness of porcine liver in vitro treated with the radiofrequency ablation (RFA) using shear wave elastography (SWE).Methods A total number of 24pieces of porcine livers were randomly divided into 4 groups,which were treated with RFA for 6 min or 12 min,and 15 ml ethanol injection combined with RFA for 6 min or 12 min,respectively.The Young modulus were measured before ablation,after ablation immediately and 30 min after ablation when the gas disappeared in ablation zone.Results SWE imaging can clearly delineate the boundary of the stiffness changes in the RFA ablation zone,even that part was difficult to display in baseline ultrasound due to the gas hyperechogenicity reflection.The mean Young modulus before ablation、after ablation immediately and 30 min after ablation without gas reflection were (14.90 ± 4.04) kPa,(94.31 ± 23.03) kPa,(89.32 ± 20.77) kPa,respectively.Both the mean Young modulus of after ablation immediately and 30 min after ablation were significantly different from that of before ablation (P ＜ 0.001,P ＜ 0.001),but there was no significant difference between the mean Young modulus of after ablation immediately and 30 min after ablation (P =0.385).The Young modulus changes of ablation zone of RFA 6 min,12 min,15 ml ethanol injection combined with RFA 6 min or 12 min were (81.29 ± 9.19) kPa,(84.88 ± 9.89)kPa,(97.27 ±16.20)kPa,(103.82 ± 22.04)kPa,respectively.The ethanol injection combined with RFA could make the ablation zone stiffer than only RFA did (P =0.009),whereas prolonging ablation duration would make no change of stiffness in ablation zone (P =0.275).Conclusions SWE can quantitatively monitor the elasticity changes of porcine liver during RFA treatment in vitro,no matter the gas exists in the ablation zone or not.The changes of stiffness in ablation zone were different when ethanol was injected pre-ablation. Key words: Ultrasonography; Catheter ablation; Liver; Elastography

Enhanced dimethyl methylphosphonate (DMMP) detection sensitivity by lead magnesium niobate-lead titanate/copper piezoelectric microcantilever sensors via Young's modulus change

We have examined the detection of dimethyl methylphosphonate (DMMP) using lead magnesium niobate-lead titanate (PMN-PT) piezoelectric microcantilever sensor (PEMS) coated with various planar and particulate receptor coatings. We showed that a two-order-of-magnitude enhancement in the flexural-mode resonance frequency shift, Δf, in DMMP detection that was not accountable for by mass loading alone could be achieved by using a planar Cu2+ adsorbed 11-Mercaptoundecanoic Acid (MUA/Cu2+) or planar 3-mercaptopropyltrimethoxysilane (MPS) coated PEMS. We also showed that the enhancement of Δf of PEMS was a result of the Young's modulus change in the PMN-PT layer induced by the surface stress generated by the binding of DMMP on a continuous receptor coating. Furthermore, the Young's modulus-change enhanced Δf in PEMS with a planar receptor coating was shown to be inversely proportional to the product of the average Young's modulus and thickness of the PEMS and independent of the PEMS lateral dimension. We also showed that with an array of three PEMS, one uncoated, one coated with planar MUA/Cu2+ and the other with planar MPS, the detection Δf pattern for DMMP was distinctively different from those of acetone and ammonia.

Molecular Dynamics Simulations of SOC-Dependent Elasticity of LixMn2O4 Spinels in Li-Ion Batteries

As has been experimentally observed, stresses due to lithium intercalation, phase transition, and thermal loading can cause local fractures in Li-ion battery active materials. These fractures are one of the main degradation mechanisms in Li-ion batteries. Consequently, predicting the stress level inside of the electrode material is of key importance in designing cells and determining their operation conditions. For lithium manganese oxides, however, the values of Young's modulus that have been reported so far differ widely, resulting in commensurately wide gaps between actual and predicted stress levels. Moreover, little is known about how the Young's modulus changes at different states of charge (SOC). In this study, molecular dynamics (MD) simulations were performed to investigate the Young's moduli of LixMn2O4 as a function of SOC (0 < x < 1). MD simulations show that the Young's moduli vary almost 18% depending on SOC. By decomposing interaction forces between atoms, we analyzed how pair interactions influence the variance. The results suggest that the SOC-dependence of Young's modulus may have an effect on both the stress level inside the particle as well as on Li-ion transport as a result of their mutual coupling to Li-ion diffusivity.

Supra- and Nanocrystallinity: Specific Properties Related to Crystal Growth Mechanisms and Nanocrystallinity

The natural arrangement of atoms or nanocrystals either in well-defined assemblies or in a disordered fashion induces changes in their physical properties. For example, diamond and graphite show marked differences in their physical properties though both are composed of carbon atoms. Natural colloidal crystals have existed on earth for billions of years. Very interestingly, these colloidal crystals are made of a fixed number of polyhedral magnetite particles uniform in size. Hence, opals formed of assemblies of silicate particles in the micrometer size range exhibit interesting intrinsic optical properties. A colorless opal is composed of disordered particles, but changes in size segregation within the self-ordered silica particles can lead to distinct color changes and patterning. In this Account, we rationalize two simultaneous supracrystal growth processes that occur under saturated conditions, which form both well-defined 3D superlattices at the air-liquid interface and precipitated 3D assemblies with well-defined shapes. The growth processes of these colloidal crystals, called super- or supracrystals, markedly change the mechanical properties of these assemblies and induce the crystallinity segregation of nanocrystals. Therefore, single domain nanocrystals are the primary basis in the formation of these supracrystals, while multiply twinned particles (MTPs) and polycrystals remain dispersed within the colloidal suspension. Nanoindentation measurements show a drop in the Young's moduli for interfacial supracrystals in comparison with the precipitated supracrystals. In addition, the value of the Young's modulus changes markedly with the supracrystal growth mechanism. Using scanning tunneling microscopy/spectroscopy, we successfully imaged very thick supracrystals (from 200 nm up to a few micrometers) with remarkable conductance homogeneity and showed electronic fingerprints of isolated nanocrystals. This discovery of nanocrystal fingerprints within supracrystals could lead to promising applications in nanotechnology.

Nanoscale characterization of the biomechanical hardening of bovine zona pellucida

The zona pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so-called zona hardening plays a key role in fertilization process, as it blocks polyspermy, which may also be caused by an increase in the mechanical stiffness of the ZP membrane. However, structural reorganization mechanisms leading to ZP's biomechanical hardening are not fully understood yet. Furthermore, a correct estimate of the elastic properties of the ZP is still lacking. Therefore, the aim of the present study was to investigate the biomechanical behaviour of ZP membranes extracted from mature and fertilized bovine oocytes to better understand the mechanisms involved in the structural reorganization of the ZP that may lead to the biomechanical hardening of the ZP. For that purpose, a hybrid procedure is developed by combining atomic force microscopy nanoindentation measurements, nonlinear finite element analysis and nonlinear optimization. The proposed approach allows us to determine the biomechanical properties of the ZP more realistically than the classical analysis based on Hertz's contact theory, as it accounts for the nonlinearity of finite indentation process, hyperelastic behaviour and material heterogeneity. Experimental results show the presence of significant biomechanical hardening induced by the fertilization process. By comparing various hyperelastic constitutive models, it is found that the Arruda-Boyce eight-chain model best describes the biomechanical response of the ZP. Fertilization leads to an increase in the degree of heterogeneity of membrane elastic properties. The Young modulus changes sharply within a superficial layer whose thickness is related to the characteristic distance between cross-links in the ZP filamentous network. These findings support the hypothesis that biomechanical hardening of bovine ZP is caused by an increase in the number of inter-filaments cross-links whose density should be higher in the ZP inner side.

ART-induced biophysical and biochemical alterations of Jurkat cell membrane

Integrity of the cell membrane is a basic requirement for maintaining the biological characteristics of a cell. In this study, cell membrane as the target of drug action was investigated. CCK-8 assay suggested that Artesunate (ART) could significantly suppress the proliferation of Jurkat cells in a dose-dependent manner. Changes in the morphology and mechanics of Jurkat cells were studied by atomic force microscopy (AFM). These changes included decrease of Young's modulus (from 3.18 ± 0.54 to 1.72 ± 0.54 kPa), increase in the fluctuation of surface components, increase in shrinkage, or even the appearance of pores. The Young's modulus change was according to the F-actin protein, not the Tubulin-β or integrin β1 protein. Meanwhile, the activities of plasma membrane Ca 2+–Mg 2+-ATPase and Na +–K +-ATPase were also repressed following ART exposure as well as membrane potential. Western blot was used to detect Caspase 3 and Cyclin D1 protein level. The Cyclin D1 was downregulated and Caspase 3 was activated. Hence, cellular membrane represented a plausible target for ART-induced injury.

Elastic and plastic properties of InxGa1−xAs

The nanoindentation behaviour of In1−xGaxAs heteroepitaxial layers grown onto (0 0 1)-oriented GaAs substrates has been studied. This covers the whole compositional range 0 < x < 1, with emphasis on x < 0.55. A non-linear change in flow stress had been suggested before and was indeed found here with a maximum at x ∼ 0.25. The Young modulus changes approximately linearly between InAs and GaAs.

Mechanism of flexural resonance frequency shift of a piezoelectric microcantilever sensor during humidity detection

We have examined the flexural resonance frequency shift of a piezoelectric microcantilever sensor (PEMS) during humidity detection and have shown that the flexural resonance frequency shift of the PEMS during detection was a result of Young's modulus change of its piezoelectric layer. Because of the piezoelectric layer's Young's modulus change, the PEMS flexural resonance frequency shift was more than 300 times larger than could be accounted for by mass loading.