The use of mesenchymal stem cells adhered to the suture filament in the closure of rat aponeurosis.

AimTo estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with riboflavin.MethodsExcimer laser ablation studies were performed ex vivo (32 eyes of 16 rabbits) by phototherapeutic keratectomy (PTK) and in vivo (24 eyes of 12 rabbits) by transepithelial photorefractive keratectomy (TransPRK), with and without riboflavin saturation of the stroma. Then, we performed corneal optical coherence tomography on 36 eyes of 18 patients with varying degrees of myopia at different times after the TransPRK was performed with riboflavin saturation of the stroma.ResultsBiomechanical testing of corneal samples saturated with riboflavin revealed cross-linking effect accompanied by the increase in tensile strength and maximum strength. PTK showed increase in tensile strength from 5.1±1.4 to 7.2±1.6 MPa (P=0.001), while Trans-PRK showed increase in tensile strength from 8.8±0.9 to 12.8±1.3 MPa (P=0.0004). Maximum strength increased from 8.7±2.5 to 12.0±2.8 N (P=0.005) in PTK and from 12.8±1.6 to 18.3±1.2 N (P=0.0004) in TransPRK. Clinical optical coherence tomography studies of the biomicroscopic transparent cornea at different times after TransPRK showed increased density in the surface layers of the stroma and membrane-like structure beneath the epithelium.ConclusionPhotorefractive ablation of the preliminary corneal stroma saturation with riboflavin causes the effect of laser-induced cross-linking, which is attended with an increase in corneal tensile strength, maximum strength, increased density in the surface layers of the stroma, and formation of a membrane-like structure beneath the epithelium after TransPRK.

The tensile strength of skin wounds has been studied in rats at different times after operation. Cortisol acetate (5 or 50 mg/kg) or prednisolone acetate (1 or 10 mg/kg) were injected daily subcutaneously. According to the dose and potency of the corticosteroid given, the wound tensile strength was found to be decreased between the 3rd and 9th day. This effect was most pronounced on the 6th day. On the 12th day and even more distinctly on the 20th day after operation, a reversal of this effect could be observed. Low doses of glucocorticoids resulted in an increase in wound tensile strength, whereas high doses, already toxic after prolonged administration, still caused a decrease. If treatment was started at the end of the collagen phase (11th day), only an increase in wound tensile strength was seen, regardless of the dose of glucocorticoid administered. Short-term treatment during the scar phase (day 19 to 20) resulted in an increase in wound tensile strength which correlated with the dose and potency of the glucocorticoid given. It is therefore concluded that scar tissue of wounded skin reacts like normal connective tissue as far as the increase in tensile strength induced by glucocorticoids is concerned.

Chemically modified cellulose micro- and nanofibrils were successfully used as paper strength additives. Three different kinds of cellulose nanofibrils (CNFs) were studied: carboxymethylated CNFs, periodate-oxidised carboxymethylated CNFs and dopamine-grafted carboxymethylated CNFs, all prepared from bleached chemical fibres of dissolving grade, and one microfibrillated cellulose from unbleached kraft fibres. In addition to mechanical characterization of the final paper sheets the fibril retention, sheet density and sheet morphology were also studied as a function of addition of the four different cellulose fibrils. In general, the cellulose fibrils, when used as additives, significantly increased the tensile strength, Young’s modulus and strain-at-break of the paper sheets. The effects of the different fibrils on these properties were compared and evaluated and used to analyse the underlying mechanisms behind the strengthening effect. The strength-enhancing effect was most pronounced for the periodate-oxidised CNFs when they were added together with polyvinyl amine (PVAm) or poly(dimethyldiallylammonium chloride) (pDADMAC). The addition of periodate-oxidised CNFs, with pDADMAC as retention aid, resulted in a 37% increase in tensile strength at a 2 wt% addition and an 89% increase at a 15 wt% addition (from 67 to 92 and 125 kNm/kg, respectively) compared to a reference with only pDADMAC. Wet-strong sheets with a wet tensile index of 30 kNm/kg were also obtained when periodate-oxidised CNFs and PVAm were combined. This significant increase in wet strength is suggested to be the result of a formation of cross-links between the aldehyde groups, introduced by the periodate oxidation, and hydroxyl groups on the lignocellulosic fibres and the primary amines of PVAm. Even though less significant, there was also an increase in wet tensile strength when pDADMAC was used together with periodate-oxidised fibrils which shows that the aldehyde groups are able to increase the wet strength without the presence of the primary amines of the PVAm. As an alternative method to strengthen the fibre network, carboxymethylated CNFs grafted with dopamine, by an ethyl dimethylaminopropyl carbodiimide coupling, were used as a strength additive. When used as an additive, these CNFs showed a strong propensity to form films on and around the fibres and significantly increased the mechanical properties of the sheets. Their addition resulted in an increase in the Young´s modulus by 41%, from 5.1 to 7.2 GPa, and an increase in the tensile strength index of 98% (from 53 to 105 kNm/kg) with 5 wt% retained dopamine-grafted CNFs.

This study is planned to evaluate the efficacy of two biological matrices represented by autologous platelet rich fibrin matrix, as well as a cross linked decellularized caprine pericardial extracellular matrix on enhancing healing of the experimentally severed superficial digital flexor tendon in a goat model. It was carried out on 48 adult apparently healthy bucks, which were divided randomly into three equal groups. Under the effect of sedative and local ring block anesthesia, superficial digital flexor tendon was severed at the mid metacarpal region of the right forelimb. In the first control group, tenorrhaphy was performed and left without additives. While in the second group the tenorrhaphy site was wrapped with a previously prepared autologous platelet rich fibrin strips, as well as in the third group the tenorrhaphy site was wrapped with a cross linked decellularized pericardial extracellular matrix strip which was prepared from the whole fresh caprine pericardium obtained from the slaughter house. Both matrices were fixed in their position at the tenorrhaphy site by few interrupted stitches. The biomechanical evaluation of the operated tendon indicated an increase in tensile strength with time in all groups, but the comparisons among groups showed a significant (P≤0.05) increase at day 15 in both treated as compared to control animals. On day 45 the pericardial extracellular matrix group showed a significant increase in tensile strength as compared to platelet rich fibrin matrix and control groups, but at day 75 there were no differences among groups, at day 180 the pericardial extracellular matrix group showed a significant increase in the tensile strength as compared to platelet rich fibrin matrix and control groups. In conclusion, both biological matrices led to improvement in the biomechanical properties of the operated tendons with time.

CD45 regulates homing and engraftment of immature normal and leukemic human cells in transplanted immunodeficient mice

The wound healing properties of Channa striatus-cetrimide cream — tensile strength measurement

Non-metallic composite fittings are increasingly used in modern construction due to their high mechanical characteristics, corrosion resistance, durability in concrete and aggressive external environments, and other properties. At the sametime, usually, non-metallic composite reinforcement is used in the form of rods with the main supporting element in the form of basalt, glass, aramid or roving made of other materials, which is thin fibers with a diameter of 7...20 mm.The specified roving, as an element of reinforcement of concrete structures, will be used in the form of fiber to a much lesser extent, although it is a real alternative to traditional steel fiber with all the advantages of fiber reinforcement, to which corrosion resistance is also added. The limited number of experimental explains the current situation andtheoretical studies of non-metallic fiber reinforcement, in particular, tensile strength, which is one of the main advantages of fiber reinforcement of concrete.This article presents the results of experimental studies of the tensile strength of concrete reinforced with fiber from basalt roving with a diameter of 16 μm and a length of 24 mm, which included bending tensile tests of three series of concrete samples with a strength class of compression, respectively, C20/25, C25/30, C30/35 and percentage of fiber reinforcement within 2.0...8%.As a result of the conducted research, it was established that the fiber reinforcement from the baseboard roving leads to an increase in the axial tensile strength of concrete. At the same time, the most intensive increase in tensile strength took place when the percentage of reinforcement was increased in the range of 2.0...4.0%. With a further increase in the percentage of reinforcement in the range of 6.0...8.0%, this growth stopped, which indicates that fiber reinforcement in the range of 2.0...4.0% is the most effective, regardless of the class of concrete in terms of compressive strength.Other things being equal, the increase in axial tensile strength of concrete with an increase in the percentage of fiber reinforcement within the limits of 2.0...8.0% is 15...20% compared to concrete without reinforcement.

The Hewlett-Packard (HP) Multi Jet Fusion (MJF) process is a recently emerged polymer powder bed fusion (PBF) additive manufacturing (AM) process that utilizes a combination of powder bed and inkjet printing to fabricate functional parts with voxel resolution. While the MJF technology offer several advantages over other PBF processes such as Selective Laser Sintering (SLS), MJF applications are limited to its small material palette of engineering polymers, which do not cater to applications where high performance is required. As research of MJF is still in its infancy, literature on the MJF materials and MJF printing mechanisms are scarce and do not provide sufficient depth to aid in the development of new MJF materials. Therefore, this Ph.D. research aims to provide an in-depth analysis of the existing MJF materials, provide some insight on the MJF printing mechanisms, and develop new high-performance composites using existing MJF materials as the polymer matrix. A thorough understanding of the physical, chemical, and mechanical properties of the MJF materials is essential for the selection of a suitable polymer matrix for MJF polymeric composite development. Three commercial MJF materials, namely polyamide 12 (PA12), polyamide 11 (PA11), and thermoplastic polyurethane (TPU) were characterized to determine the most suitable material candidate to serve as the polymer matrix for composite development based on their printability and print quality. With a powder morphology consisting of near-spherical particles with smooth surfaces and the highest sintering window (32°C) among all three material candidates, PA12 possessed the best powder flowability and the largest printing temperature range. Although the mechanical strength of PA12 (49.6 MPa) was slightly lower than that of PA11 (50.9 MPa), PA12 was deemed to be a more suitable candidate for composite development due to a higher sintering window which allows for less precise control over the printing temperature. HP PA12 GB powder is a commercially available MJF glass bead-reinforced PA12 (GB/PA12) composite powder that possesses enhanced tensile modulus at the cost of a drastic reduction in tensile strength. To alleviate the significant reduction in tensile strength, alternative compositions of GB/PA12 composites were designed and fabricated using an MJF testbed printer (Dalmata printer). An alternative high-temperature annealing method, which can be used to replace the existing post-print annealing process in commercial MJF printers, was performed on the GB/PA12 specimens to further improve their mechanical performance. Printing optimization of the GB/PA12 specimens revealed that the powder bed temperature must be set above the onset crystallization temperature of the GB/PA12 powder (160°C) to avoid printing defects such as the “staircase” effect or layer shifting. In comparison to the commercial PA12 GB parts, the fabricated 10% GB/PA12 specimens achieved a 92% increase in tensile strength while maintaining a similar tensile modulus of 3.37 GPa. The fabricated GB/PA12 specimens also achieved a 19% increase in tensile strength and a 113% increase in tensile modulus when compared to MJF-printed PA12 parts. Through the use of the Dalmata printer, several fiber-reinforced PA12 composites with anisotropic directional properties have been developed. To reduce the effect of anisotropy, a novel composition of high-strength glass bead/glass fiber/polyamide 12 (GB/GF/PA12) hybrid composite was developed and fabricated using the Dalmata printer. Compared to the previously fabricated glass fiber-reinforced PA12 (GF/PA12), the degree of anisotropy in observed in the 5GB/20GF/PA12 specimens was notably reduced as it exhibited a 14.1% and 10.7% increase in tensile strength when printed along the X (powder recoating direction) and Z (layer building direction) orientations, respectively. Overall, the GB/GF/PA12 composite specimens achieved a 45% increase in tensile strength and 253% increase in tensile modulus when compared to commercial PA12 parts. The GB/GF/PA12 fabricated in this thesis attained the highest tensile strength and modulus among all reported glass-reinforced PA12 composites printed using PBF processes. The compatibility of the GB/GF/PA12 powder with commercial MJF printing was later showcased on a commercial MJF printer. The GB/GF/PA12 specimens fabricated using the MJF 5200 printer possessed similar mechanical properties to their Dalmata-printed counterparts, demonstrating that the GB/GF/PA12 is a viable high-strength polymer composite candidate for commercial MJF printing. This Ph.D. thesis provides an in-depth analysis of the existing MJF materials, the development and optimization of a new composition of GB/PA12 composites with enhanced mechanical performance using an alternative high-temperature annealing method, the development of a novel composition of high-strength GB/GF/PA12 glass hybrid composites using the Dalmata printer, and a demonstration print of the GB/GF/PA12 composite powder using a commercial MJF printer to showcase its compatibility with the MJF print mode. This thesis serves as an effective guideline for the printing optimization of MJF-printed PA12 composites and can be used as a foundation for future composite development in MJF.

In the present study, the effect of water-dispersed powder Graphene Oxide (GO) nanoparticles on cement mortar and its mechanical Strength after 3, 7 and 28 days of Curing is analysed. These properties were studied by adding 0.00 w/w% ,0.03 w/w%,0.05 w/w%,0.07 w/w% of cement to Obtain Compressive strength and tensile strength of cement mortar. It observed that for 0.03% w/w of cement addition increase in compressive strength is 23.07%, for 0.05% w/w of cement addition increase in compressive strength is 35.59%, and for 0.07% w/w of cement addition increase in compressive strength is 31.52% after 28 Days of curing. Tensile strength analysis for 0.03% w/w of cement addition increase in Tensile strength is 4.46%, for 0.05% w/w of cement addition increase in Tensile strength is 34.70%, that for 0.07% w/w of cement addition increase in Tensile strength is 37.45% after 28 Days of curing. By the addition of different proportions of graphene oxide, the compressive strength increases till the addition of 0.05 % w/w of cement slightly decreases. For tensile strength with addition of graphene oxide the tensile strength is increased.

Epoxy resin matrix based on diglycidyl ether of bisphenol A (DGEBA) was modified with addition of epoxidized soybean oil (ESBO). Structural jute composites prepared with ESBO modified DGEBA resin showed a decrease in tensile strengths, owing to reduced cross linking density. Percentage elongation of the samples increased with addition of ESBO. An optimized composition was identified, at which the composite showed increase in tensile strength, modulus and elongation. Interestingly, impact strengths increased initially with incorporation of ESBO, but with further increase in ESBO, impact strengths decreased. Structural Jute composites were also prepared by incorporating polyvinyl (chloride) (PVC) plastisol into the modified matrix which showed an increase in both tensile and impact strengths. Fourier transform infrared spectroscopy (FT‐IR) analysis indicated the curing state of the composites. The spectrum peaks became increasingly stronger in the OH band with increasing ESBO quantities. This could be attributed to the hydrophilic nature of ESBO, a result that was well supported by the moisture absorption test. Although, water uptake capacity of ESBO/DGEBA modified matrix composites recorded increasing trend with increased ESBO content, with inclusion of plastisol, the water uptake values dropped. Composite with DGEBA/ESBO/plastisol modified matrix actually recorded water uptake capacity comparable to composite with neat DGEBA, possibly owing to improved interfacial adhesion and hydrophobic nature of PVC plastisol. POLYM. COMPOS., 37:391–397, 2016. © 2014 Society of Plastics Engineers

A novel highly functional plant oil-based polyols, Methoxylated Sucrose Soyate Polyols (MSSP), were cross-linked with isocyanate to formulate MSSP-based polyurethane (PU) thermosets. The degree of cure or conversion was studied using differential scanning calorimetry (DSC). Compression molding process was used to make composite panels out of MSSP-based polyurethane and flax fiber reinforcement of about 50 vol %. The MSSP-based PU resin reinforced with 50 vol % unidirectional E-glass fiber mats was tested as a reference. The composites were cured at 150°C for 60 minutes. Properties of the MSSP-based PU thermosets and its corresponding flax/glass-fiber reinforced thermoset composites were assessed by tensile strength and modulus, flexural strength and modulus, interlaminar shear strength (ILSS), nanoindentation test, and impact strength. Specific tensile modulus and strength of the flax fiber composites were found to compare with those of glass/MSSP-based PU. The glass/MSSP-based PU composite exhibited superior mechanical properties compared to both bio-based and petroleum-based composites used in previous studies. Compared to soybean oil based composites used in previous studies, bio-based composites based on MSSP showed 70 % and 101 % increase in flexural strength and modulus respectively, 102 % and 93 % increase in tensile strength and modulus respectively, and 56 % increase in ILSS. Compared to petroleum-based PU/glass composites used in previous studies, bio-based composites based on MSSP showed 60 % and 40 % increase in flexural strength and modulus respectively, 102 % and 78 % increase in tensile strength and modulus respectively, 50 % increase in ILSS. Higher mechanical properties in MSSP-based PU composites can be attributed to high functionality, rigid and compact chemical structures of MSSP oligomers in polyol resin.

In recent years, the speed of modernization construction in China has been exponentially growing. The trend of high parameters, large capacity, and large-scale development of the welding structure has been promoted. It needs higher requirements on the type and quality of the welding materials. Most of the welding materials are imported to China. The main reason is that China still follows the traditional design method. The quality of the welding materials is also low. The design of metal welding materials involves many factors and properties. There is no fixed-function relationship between the properties and components of the welding materials. This makes it difficult to design metal welding materials. The emergence of neural network algorithms provides a new way to analyze the weldability of metal materials. In this paper, BP (backpropagation) network is used to analyze the welding performance of metals. The tensile test of welded joints is carried out through training test samples. The results show that the tensile strength and yield strength of metal materials are about 500 MPa (megapascals) and 400 MPa, respectively. For further analysis of the influence of welding current, electrode pressure, and power-on time on the tensile and shear strength of metal materials, a shear test and tension test were used. With the increase of welding current, the shear strength of spot welding continuously increased. When the welding current was 10,000A (Ampere), the shear strength decreased rapidly from 24.25 MPa to 18.84 MPa. After prolonging the welding time, at first, both tensile strength and shear strength increase and then decrease. When the welding pressure increases from 32psi to 48psi, the tensile strength increases from 16.47 MPa to 24.52 MPa and then decreases continuously to 17.26 MPa, whereas the shear strength decreases first and then increases.

A simple dip test was devised using 1 wt % HF solution to establish an accelerated test which gives similar information on increase and decrease in tensile strength to that displayed in the exposures in the dynamic test system. Herty Sample Nos. 53, 54, and 56 contained only asbestos and L-134 fibers; their unexposed tensile strength ranged from 60 to 70 g. Herty Sample No. 58 contained asbestos and Johns-Manville L-134 fibers plus 3m's Kel-F binder, and DuPont's fluorinated water-repellant Zepel. This sample had a tensile strength of about 700 g. The tenfold increase in tensile strength due to the additives in Sample No. 58 disguised the tensile strength change by the fibers during both types of test, since most of the strength is due to the additives. (LK)

Evaluation of electrospinning parameters on the tensile strength and suture retention strength of polycaprolactone nanofibrous scaffolds through surface response methodology

A wealth of evidence attests that the organs of developing embryos, particularly the developing brain, are acutely sensitive to chemical perturbations. However, scientists know very little about how exposures to specific endogenous chemicals actually impact human development or children’s ability to learn. And there are almost no data on how the vast majority of the 84,000 chemicals currently listed in the Toxic Substances Control Act (TSCA) Inventory1—including most of the 201 compounds known to be neurotoxic to adults and the 1,000 chemicals shown to be neurotoxic to animals2—may affect developing infants. It is also unclear whether testing with animals always provides accurate insights into human developmental susceptibility. A new line of research based on human stem cells is providing important insights into how chemicals may affect neonatal development. Stem cells are the master cells capable of producing some or all of the 200-plus different types of cells in the human body. In time, some researchers believe stem cells may enable scientists to amass far more data on how exposure to environmental chemicals affects human development, particularly the development of the brain. Now is a “critical time to be talking about stem cell research in the environmental health context,” says Tracey Woodruff, director of the Program on Reproductive Health and the Environment at the University of California, San Francisco (UCSF) Medical School.