Low Mechanical Stress Research Articles

Printable Ultrathin Metal Oxide Semiconductor-Based Conformal Biosensors.

Conformal bioelectronics enable wearable, noninvasive, and health-monitoring platforms. We demonstrate a simple and straightforward method for producing thin, sensitive In2O3-based conformal biosensors based on field-effect transistors using facile solution-based processing. One-step coating via aqueous In2O3 solution resulted in ultrathin (3.5 nm), high-density, uniform films over large areas. Conformal In2O3-based biosensors on ultrathin polyimide films displayed good device performance, low mechanical stress, and highly conformal contact determined using polydimethylsiloxane artificial skin having complex curvilinear surfaces or an artificial eye. Immobilized In2O3 field-effect transistors with self-assembled monolayers of NH2-terminated silanes functioned as pH sensors. Functionalization with glucose oxidase enabled d-glucose detection at physiologically relevant levels. The conformal ultrathin field-effect transistor biosensors developed here offer new opportunities for future wearable human technologies.

Stage-frit: A straightforward sub-2 μm nano-liquid chromatography column fabrication for proteomic analysis

In this work we demonstrated a facile method for the fabrication of C18 coordination polymer gel in a capillary, called stage-frit, which was efficiently applied to pack sub-2 μm C18 beads into the capillary by a high pressure bomb for the online separation of proteolytic peptides. The back pressure of the column with 10 cm × 75 μm i.d. is regularly lower than 170 bar at a flow rate of 300 nl/min, which could be operated on a common nanoLC system instead of nanoUPLC system due to the good permeability, low back pressure and high mechanical stress of the frit that will totally reduce the cost for the purchase of instrument. The stage-frit allows long-term continuous flow of the solvent and no significant beads loss or pressure instability was observed during the period. The repeatability of retention time for fifteen BSA tryptic peaks was found to be less than 1.08% (RSD) in six time nanoLC-ESI-MS/MS experiments. The average full width at half maximum (FWHM) of peptide peaks is 5.87 s. The sub-2 μm stage-frit nanoLC column showed better sensitivity than the commercial available for large scale proteomic analysis of total tissue proteins from human spleen. The number of identified peptides is approximately 0.4-fold and 0.2-fold higher than that obtained by utilizing commercial columns packed with 3 μm and 1.8 μm C18 materials, respectively. In the field of analytical chemistry, particularly the use of nanoLC systems, stage-frit nanoLC column offers a great potential for the separation of complex mixtures.

Low power micro-calorimetric sensors for analysis of gaseous samples

This work discusses the design, finite element method modeling (FEM), fabrication and characterization of a silicon-based, catalytic micro calorimetric sensor. The sensing area is comprised of two titanium silicide (TiSi2) – polysilicon (poly-Si) resistive temperature sensors symmetrically positioned relative to a poly-Si heater on which an oxidation promoting catalyst is deposited. The resistive structures are located on a suspended, thereby, thermally isolating, low mechanical stress membrane and integrated into a glass flow channel. The micro-calorimetric sensor is applied for measuring propane and hydrogen concentrations in air.An approach to optimization of thermal and fluidic design of the microsensor is presented based on developed models: (i) a 3D thermo-electric analysis of the suspended heater and (ii) a 2D thermo-chemical analysis of the catalytic oxidation of propane in the flow channel. Influence of the design and material of the membrane on the power consumption and temperature distribution across the sensing area are analyzed. A relationship between the thermal design of the sensor, reaction conditions and its operation as a thermal actuator and sensor of reaction heats are discussed.Various thermo-electrical characterizations (electrical, infrared surface imaging and transient thermal response measurements) in the context of microcalorimetric sensing are performed. Microsensors with a 50μm×50μm sensing area consume ca. 12mW at an operational temperature of 350°C. Thermal imaging with an infrared camera indicates local heating with a temperature gradient across the active area estimated to be 4°Cμm−1 (at ca. 500°C). The heating and cooling times are found to be ca. 1 and 8ms, respectively. Temperature vs. power curves are determined for both stationary and constant flow conditions of various gases. Based on the experimental and modeling results we envision that these microsensors can be successfully used for calorimetric sensing and analysis of gaseous samples.

Influence of Electroacupuncture on the Soft Tissue Healing Process

The aim of this study was to determine the effect of bipolar electroacupuncture (EA) on a soft tissue defect in rabbits. Ten clinically healthy New Zealand white rabbits were divided into two groups: the control group (Group C, n = 5) and the experimental (EA) group (Group T, n = 5). During neuroleptanalgesia, defects of soft tissue (skin and muscle) were made at the dorsum site on the rabbits in both groups, and those defects were stimulated using EA. The biopsy samples were collected on Day 2, Day 4, and Day 6, prepared for histology, and examined microscopically. On the 2nd day, in Group C, the inflammatory degree was higher than it was in Group T; on subsequent days, low or identical degrees of inflammation were observed in both groups. Proliferative fibrous activity was increased on Day 4 for Group T and identical for both groups on Day 6. The dynamics of the epidermal thickness were characterized by a high rate on Day 2, Day 4, and Day 6 for Group T. EA facilitates a low tissue mechanical stress and has a positive effect on the healing of muscular defects. EA enhances the healing process, with no side effects.

Fundamental properties of a-SiNx:H thin films deposited by ICP-PECVD for MEMS applications

In this study, the impact of deposition conditions on the properties of amorphous hydrogenated silicon nitride (a-SiNx:H) films using an inductively coupled plasma enhanced chemical vapor deposition technique (ICP-CVD) is evaluated. Due to the large number of experiments – even when taking only the most important synthesization parameters into account such as the total pressure in the deposition chamber, the substrate temperature, the ICP power and the flow rate ratio of N2/SiH4 – a design of experiments-based approach is chosen. As expected, the deposition rate strongly depends on the ICP power and the N2/SiH4 flow rate ratio, respectively. Films in the field of investigation deposited with a high flow rate of N2 labeled as Type I show relatively low mechanical stress values between −50 and +200MPa, but exhibit a strong drift behavior toward compressive stress. Layers deposited at low nitrogen flow rates (Type II), however, yield large compressive stress and are stable as a function of time. The wet etch rate in hydrofluoric acid shows a gap of over two orders of magnitude when comparing the two a-SiNx:H types, indicating strong differences in the chemical composition. Fourier-transform infrared measurements demonstrate that in Type I films the hydrogen is mainly bonded to nitrogen, in contrast to Type II films, where Si–H bonds dominate. Surface related X-ray photoelectron spectroscopy measurements show that Type II layers have higher relative silicon content, while depth profiles yield that the oxygen content Type I films is above 10at.%. This high oxygen content is proposed to be the result of diffusion of H2O into the layer, causing oxidation, and, as a consequence, the drifting behavior of the intrinsic film stress.

Low temperature deposition of low stress silicon nitride by reactive magnetron sputtering

Silicon nitride thin film is a well-know kind of material in semiconductor industries. These films are used in important applications such as protective layers; insulators for optical devices, as dielectric material for thin film transistors (TFTs), etc. In this work, silicon nitride thin films were deposited at room temperature through of the reaction of sputtered silicon by argon ions and nitrogen gas with relatively high deposition rates in sputtering reactive processes. We have obtained silicon nitride thin films with low stress for MEMS (Micro Electro Mechanical Systems) fabrication and in post-processing of sensors and actuators devices. Silicon nitride thin films obtained in this work showed stoichiometric (Si3N4) and/or rich in silicon with low mechanical stress and good dielectric properties. The films were analyzed by scanning electron microscope, micro-Raman spectroscopy, profilometry, current-voltage (I-V) and capacitance-voltage (C-V) measurements, laser-based measurement for determination the internal stress and Rutherford Backscattering.

Mechanical Stress Reduction of Rotor Core of Interior Permanent Magnet Synchronous Motor

In this paper, the bridge shape of interior permanent magnet synchronous motor (IPMSM) is designed for integrated starter and generator (ISG) which is applied in hybrid electric vehicle (HEV). Mechanical stress of rotor core which is caused by centrifugal force is the main issue when IPMSM is operated at high speed. The bridge is thin area in rotor core where is mechanically weak point and the shape of bridge significantly affects leakage flux and electromagnetic performance. Therefore, bridge should be designed considering both mechanic and electromagnetic characteristics. In the design process, we firstly find a shape of bridge has low leakage flux and mechanical stress. Next, the calculation of mechanical stress and the electromagnetic characteristics are performed by finite element analysis (FEA). The mechanical stress in rotor core is not maximized in steady high speed but dynamical high momentum. Therefore, transient FEA is necessary to consider the dynamic speed changing in real speed profile for durability experiment. Before the verification test, fatigue characteristic is investigated by using S-N curve of rotor core material. Lastly, the burst test of rotor is performed and the deformation of rotor core is compared between prototype and designed model to verify the design method.

Soil compaction effects on growth and root traits of tobacco depend on light, water regime and mechanical stress

Soil compaction can strongly affect plant performance as many other stress factors. In nature, many combinations of different stress factors may be found. We expect that the effects of soil compaction may be different depending of the occurrence of other stress. This has not been fully investigated; most studies have included only one stress factor together with soil compaction. In this study, we combine soil compaction with the interaction of shade, low water availability and mechanical stress. We use as a model system tobacco plants (Nicotiana tabacum), in which the effects of the combination of these factors in a greenhouse experiment were studied on their growth, biomass allocation, root morphology and anatomy. Soil compaction effects on growth and root traits depended strongly on the other factors. In unstressed conditions, plant growth increased with compaction up to 1.4gcm−3 bulk density and then declined. However, at low water and under mechanical stress plant growth declined monotonically with compaction, while under shade, soil compaction had no effect on growth. Soil compaction reduced fine root proportion in all treatments except in shade condition, while it increased root diameter and xylem area only under mechanical stress. These results indicate that analyses of soil compaction effects on plant performance should take the levels of other stress factors into account. More generally, they illustrate the difficulty of interpreting effects of a given stress factor on plants as these effects tend to interact with presence of other stressors.

Solid-state mechanical properties of crystalline drugs and excipients

Abstract Thermal mechanical analysis (TMA) of crystalline drugs and excipients in their pre-melt temperature range performed in this study corroborate their newly found linear dielectric conductivity properties with temperature. TMA of crystalline active pharmacy ingredients (APIs) or excipients shows softening at 30–100 °C below the calorimetric melting phase transition, which is also observed by dielectric analysis (DEA). Acetophenetidin melts at 135 °C as measured calorimetrically by DSC, but softens under a low mechanical stress at 95 °C. At this pre-melting temperature, the crystals collapse under the applied load, and the TMA probe shows rapid displacement. The mechanical properties yield a softening structure and cause a dimensionally slow disintegration resulting in a sharp dimensional change at the melting point. In order to incorporate these findings into a structure–property relationship, several United States Pharmacopeia (USP) melting-point standard drugs were evaluated by TMA, DSC, and DEA, ...

Controversies in selection of block bone grafting and the elevation of the maxillary sinus floor with particulated bone in the reconstruction of posterior–superior alveolar reabsorbed

The process of bone resorption and pneumatization of the maxillary sinus are phenomena related to tooth loss in the posterior–superior area, which at present increase the difficulty mentioned rehabilitation area. However, there are treatment options for this condition as are, among others, the elevation of the maxillary sinus floor with particulated bone indicated for small bone defects exposed to low mechanical stress, and alveolar ridge augmentation with block grafts to reconstruct large areas of bone loss due to its stability.

In this issue

AbstractScaling up production of plasmid DNA vaccinesLara et al., Eng. Life Sci. 2011, 11, 382–386.DNA vaccination is a propitious alternative therapeutic strategy. However, mass production of DNA vaccines for the demanding commercial market has not been fully explored. In this issue, Alvaro Lara and collaborators from the National Autonomous University of Mexico and the AVT Biochemical Engineering Department (Aachen, Germany) set out to develop scale‐up strategies for the production of high‐quality plasmid DNA. Escherichia coli expressing the S region of the hepatitis B virus was cultured at high density in fed‐batch mode at small scale (1 L) using oxygen‐enriched air, and at pilot scale (50 L) using a pressurized bioreactor. Cultivation parameters and DNA topology were similar under high oxygen or elevated pressure conditions, indicating that pressurized bioreactors can be used for scaling up DNA vaccine production……………382.http://dx.doi.org/10.1002/elsc.201000104magnified imageAutomated malaria vaccine productionMartens et al., Eng. Life Sci. 2011, 11, 429–435.Pichia pastoris tirelessly yields high protein production levels, but expression of fusion proteins with multiple units is often achieved at the expense of proteolytic cleavage. In this issue, Reiner Luttmann and his colleagues from the Hamburg University of Applied Sciences (Germany) and the Biomedical Primate Research Center (The Netherlands) describe a self‐engineered fully automated system to efficiently produce anti‐malarial composite vaccines. P. pastoris expressing a fusion of two of the Plasmodium falciparium's membrane proteins were subjected to a sequential integrated bioprocess. This strategy offers stable culturing conditions, as evidenced by constant, elevated expression of high‐quality proteins.……………429http://dx.doi.org/10.1002/elsc.201000163magnified imageA single‐use bioreactor on your benchKaiser et al., Eng. Life Sci. 2011, 11, 359–368.Disposable culture vessels are easy‐to‐handle and cost‐effective systems with no sterilization requirements. However, are these bench‐top bioreactors able to meet the performance of their conventional, reusable counterparts? In this issue, Stephan Kaiser and colleagues from the Institute of Biotechnology (Wädenswil, Switzerland) answer this question by describing the engineering features of the recently marketed Mobius® CellReady 3L. Based on computational modeling, flow patterns, and oxygen mass transfer analyses, the authors show that stirred single‐use bioreactors provide low mechanical stress conditions with adequate oxygen transfer. These findings establish single‐use bioreactors as a valid alternative to conventional bioreactors at bench‐scale.……………359http://dx.doi.org/10.1002/elsc.201000171magnified image

Elongated gas bubble dissolution under a turbulent liquid flow

Mass transfer between an elongated homogeneous gas bubble under a turbulent liquid flow in a duct is investigated experimentally. Elongated gas bubble dissolution is encountered in bioengineering tubular photobioreactors. Such reactors are interesting because they are compact, they have a low contamination risk and a low mechanical stress for a liquid phase containing fragile microalgae cells. It is demonstrated from experimental mass transfer measurements, that the interface of an immobilised elongated bubble can be approximated to a flat plane. Measured mass transfer experimental data, estimated using this simplification, appear to be well fitted by Sh L = 1.76 × 10 −5 × Re 1.506 × Sc 0.5, a correlation from Lamourelle and Sandall [8], given for a turbulent liquid flow in wetted-wall columns. A formula drawn from this hypothesis is proposed for mass transfer prediction in photobioreactors. For different applications, it is suggested that the results obtained for the studied geometry could be used to build mass transfer feedback control systems.

Assessing Low Levels of Mechanical Stress in Aortic Atherosclerotic Lesions From Apolipoprotein E −/− Mice—Brief Report

Despite the fact that mechanical stresses are well recognized as key determinants for atherosclerotic plaque rupture, very little is known about stress amplitude and distribution in atherosclerotic lesions, even in the standard apolipoprotein E (apoE)-/- mouse model of atherosclerosis. Our objectives were to combine immunohistology, atomic force microscopy measurements, and finite element computational analysis for the accurate quantification of stress amplitude and distribution in apoE-/- mouse aortic atherosclerotic lesions. Residual stresses and strains were released by radially cutting aortic arch segments from 7- to 30-week-old pathological apoE-/- (n=25) and healthy control mice (n=20). Immunohistology, atomic force microscopy, and biomechanical modeling taking into account regional residual stresses and strains were performed. Maximum stress values were observed in the normal arterial wall (276±71 kPa), whereas low values (<20 kPa) were observed in all plaque areas. Stress distribution was not correlated to macrophage infiltration. Low mechanical stress amplitude was observed in apoE-/- mouse aortic atherosclerotic lesions. This original study provides a basis for further investigations aimed at determining whether low stress levels are responsible for the apparently higher stability of murine aortic atherosclerotic lesions.

Mechanical skin thinning-to-thickening transition observed in vivo through 2D high frequency elastography

This study was based on two dimensional (2D) high frequency elastography to describe quantitatively the mechanical behavior of the human dermis in vivo. The study was conducted on the forearm skin and elastographic tests were performed using a combination of two devices: an extensiometer developed for the in vivo study of the mechanical behavior of the skin using uniaxial stretching stress, and a 20 MHz real time sonographer (Dermcup 2020™) for ultrasound skin imaging. The staggered strain estimation algorithm (SSE) was used to produce elastograms. A temporal cumulative technique was applied to improve elastogram quality and to monitor variations in skin strain during stretching. The influence of the natural skin tension controlled by arm bending was studied and distinctive mechanical behavior was observed for low and high mechanical stress levels. In a preliminary analysis, the reproducibility of measurements was assessed by means of coefficient of variation (CV) in 5 selected healthy volunteers.Finally, two hypotheses linked to the geometrical and structural properties of the dermis are proposed to account for the new findings described in this study.

Abstract 76: Mitochondrial filamentation

Abstract A number of molecular targets have been scrutinized in cancer research therapeutics. I will call briefly your attention to mitochondrial fillamentation. This is a molecular target important for the development of cancer reversal techniques and the possible use of cancer as a therapeutic agency when all the cancers will be cured for the duration of life. My group signaled recently that when mitochondria are isolated with low thermal, mechanical, and chemical stress many of them appear with short micro filaments, of 25, 10, and 5 nanometers of diameter radially anchored in the mitochondrial external membrane, with or without cones of anchorage or veils of condensation. These probably more physiological mitochondria are partially or almost totally uncoupled from oxidative phosphorylation (1). In darkness, anoxia and in the presence of bicarbonate, fillamented mitochondria are able to produce oxygen at a rate superior to their oxygen uptake. Oscillations of the oxygen concentration are observed when recording these mitochondrial preparations for long periods of time. Also these mitochondria seem to be able to compartmentalize some enzymes of the glycolytic pathway. Fillamented mitochondria are abundant at rest and in young animals. In cancer cells, senility, or high activity their number and extent of fillamentation decrease. My agents for cancer reversal possibly increase mitochondrial fillamentation, while some chemical carcinogens decrease it, even at doses lower than those needed for their mutagenic effects. This is inferred from their effects on oxygen production by fillamented mitochondria (1, 2). These novel aspects of mitochondria, to which I call your attention, deserve further investigation by the cancer and mitochondria research community (1, 2, 3) (1) M Gosálvez Gosálvez. Producción de Oxígeno por Mitocondrias Filamentadas. Importancia para el Cáncer y la Neurodegeración. Anales de la Real Nacional Academia de Medicina, CXV, 3°, 747-756, 1998. Madrid. Spain (2) M Gosálvez Gosálvez. Reversión del Cáncer y Filamentación Mitocondrial. Anales de la Real Nacional Academia de Medicina. CXVII, 4°, 825-834, 2000, Madrid. Spain. (3) Mario Gosálvez y Gosálvez. “The Zipper Mechanism”. Madrid. 1982. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 76.

Highly piezoelectric AlN thin films grown on amorphous, insulating substrates

AlN thin films were grown by reactive sputtering on amorphous SiO2 thin films. Film texture, x-ray rocking curve width, mechanical stress, and the clamped piezoelectric constant d33,f were studied as a function of rf bias power and substrate roughness. A high d33,f of 5.0 pm/V was achieved at low substrate roughness and low mechanical AlN film stress. Increasing substrate roughness and stress leads to a deterioration of d33,f, which is correlated with a higher density of opposite polarity grains detected by piezoresponse force microscopy. Extrapolating to 100% uniform polarity, a d33,f of 6.1 pm/V is derived as highest possible value, probably corresponding to the d33,f=e33/c33E of perfect single crystalline material. Growth mechanisms are proposed and underlined by high resolution transmission electron microscopy to explain the observed phenomena.

Specifications for machining the bovine cortical bone in relation to its microstructure

Until date, many devices have been developed for cutting human bones during orthopedic surgeries. However, bones are anisotropic material, and their machining characteristics depend on the tool feed direction. In this study, microcutting of the bovine cortical bone is performed and its structure observed under a microscope. Furthermore, the formation of cutting chips and measurement of the cutting force during bone machining are dynamically observed while considering the anisotropy of bone tissue. In particular, the fracture of secondary osteons and crack propagation in bones are observed and analyzed. The results indicate that when the cut depth exceeds 20 μm and is greater than the interval of concentric lamellae, cracks are formed together with chips. A new method for bone machining is proposed. This method is based on the characteristics of crack propagation in bones and is expected to produce low mechanical stress and realize highly efficient and precise machining of living tissues such as bones.

Highly dense amorphous Nb2O5 films with closed nanosized pores

This study is focused on tailoring the porosity of Nb2O5 films during reactive pulsed magnetron sputtering. Dense amorphous films containing nanopores only in deeper regions have been grown at a high rate using substrate temperatures below 60 °C. The films exhibit a high refractive index, n400=2.54, a low extinction coefficient, k400∼6×10−4, a low mechanical stress (−90 MPa), and a negligible thermal shift. The specific depth distribution of the nanopores is believed to be the reason for the optimum trade-off between a high refractive index and low mechanical stress.

Optimization of human d-amino acid oxidase expression in Escherichia coli

Human d-amino acid oxidase (hDAAO) is a flavoprotein that plays a key role in the pathophysiology of schizophrenia. So far, the biochemical characterization of this enzyme has been hampered by the difficulty of expressing it in a common heterologous host such as Escherichia coli. Increasing amounts of recombinant hDAAO are indeed required for the investigation of its structure–function relationships and for the screening of new inhibitors to be used in the treatment of schizophrenia. A recombinant hDAAO has been over-expressed in BL21(DE3)Star E. coli cells. By alternating screenings of medium components at flask level and investigating physiological parameters in 2 L controlled batch fermentations, an improved, robust and scalable microbial process was set up giving almost a 40- and 4-fold improvement in volumetric productivity and specific activity, respectively. Under these conditions ∼770 U/L culture hDAAO with a specific activity of ∼0.4 U/mg protein and a specific productivity of 24.9 U/g biomass were produced. Optimization of medium ingredients, of the time and the amount of inducer’s addition, pH control at the moment of induction and harvest, low mechanical shear stress regime during recombinant protein production, represent the factors concurring to achieve the reported expression level. Notably, this expression level is higher than any previously described production of hDAAOs. A yield of 100 mg of pure hDAAO/L culture thus became available in comparison to the 1–10 mg/L previously reported.

Mechanical Tensile Stress Effects on the Expression of Bone Sialoprotein in Bovine Cementoblasts

To develop a new cementoblast culture method and to detect bone sialoprotein (BSP) expression in response to high and low mechanical tensile stress in cementoblast in vitro. Cementoblasts were collected from the roots of newborn bovine teeth and were identified with cementum-derived attachment protein (CAP) antibody 3G9. Cell proliferation was evaluated by MTT [3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, and mineralization was confirmed by von Kossa staining. Mechanical tensile stress was applied in vitro to the cementoblast with the use of a uniaxial four-point bending system with 2000 or 4000 microstrains, at a frequency of 0.5 Hz for 3, 6, 12, 24, or 36 hours. BSP mRNA level was quantified by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). A large amount of cementoblast was observed to be expressing CAP. Cementoblasts had a proliferation tendency similar to that of osteoblasts but different from that of periodontal ligament (PDL) cells. Cementoblasts had the ability to become mineralized between osteoblasts and PDL cells. The mechanical tensile stress significantly up-regulated BSP mRNA expression, which reached a peak at 24 hours in both 2000 and 4000 microstrain groups (P < .01) and was tenfold and sixfold higher than that of controls, respectively. BSP expression dropped toward baseline levels at 36 hours in both groups. Mechanical tensile stress up-regulated the expression of BSP. Low mechanical tensile stress induced earlier and more intensive up-regulation of BSP mRNA; this might represent the optimal stimuli for cementoblast activity.