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1
Pilate, Florence, Rosica Mincheva, Julien De Winter, Pascal Gerbaux, Linbo Wu, Richard Todd, Jean-Marie Raquez und Philippe Dubois. „Design of Multistimuli-Responsive Shape-Memory Polymer Materials by Reactive Extrusion“. Chemistry of Materials 26, Nr. 20 (02.10.2014): 5860–67. http://dx.doi.org/10.1021/cm5020543.
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Wang, Fan, Ling Li, Xiaolong Zhu, Feng Chen und Xiaoxiao Han. „Development of pH-Responsive Polypills via Semi-Solid Extrusion 3D Printing“. Bioengineering 10, Nr. 4 (24.03.2023): 402. http://dx.doi.org/10.3390/bioengineering10040402.
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The low bioavailability of orally administered drugs as a result of the instability in the gastrointestinal tract environment creates significant challenges to developing site-targeted drug delivery systems. This study proposes a novel hydrogel drug carrier using pH-responsive materials assisted with semi-solid extrusion 3D printing technology, enabling site-targeted drug release and customisation of temporal release profiles. The effects of material parameters on the pH-responsive behaviours of printed tablets were analysed thoroughly by investigating the swelling properties under both artificial gastric and intestinal fluids. It has been shown that high swelling rates at either acidic or alkaline conditions can be achieved by adjusting the mass ratio between sodium alginate and carboxymethyl chitosan, enabling site-targeted release. The drug release experiments reveal that gastric drug release can be achieved with a mass ratio of 1:3, whilst a ratio of 3:1 allows for intestinal release. Furthermore, controlled release is realised by tuning the infill density of the printing process. The method proposed in this study can not only significantly improve the bioavailability of oral drugs, but also offer the potential that each component of a compound drug tablet can be released in a controlled manner at a target location.
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Yanagihara, Shin, Yukiya Kitayama, Eiji Yuba und Atsushi Harada. „Preparing Size-Controlled Liposomes Modified with Polysaccharide Derivatives for pH-Responsive Drug Delivery Applications“. Life 13, Nr. 11 (03.11.2023): 2158. http://dx.doi.org/10.3390/life13112158.
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The liposome particle size is an important parameter because it strongly affects content release from liposomes as a result of different bilayer curvatures and lipid packing. Earlier, we developed pH-responsive polysaccharide-derivative-modified liposomes that induced content release from the liposomes under weakly acidic conditions. However, the liposome used in previous studies size was adjusted to 100–200 nm. The liposome size effects on their pH-responsive properties were unclear. For this study, we controlled the polysaccharide-derivative-modified liposome size by extrusion through polycarbonate membranes having different pore sizes. The obtained liposomes exhibited different average diameters, in which the diameters mostly corresponded to the pore sizes of polycarbonate membranes used for extrusion. The amounts of polysaccharide derivatives per lipid were identical irrespective of the liposome size. Introduction of cholesterol within the liposomal lipid components suppressed the size increase in these liposomes for at least three weeks. These liposomes were stable at neutral pH, whereas the content release from liposomes was induced at weakly acidic pH. Smaller liposomes exhibited highly acidic pH-responsive content release compared with those from large liposomes. However, liposomes with 50 mol% cholesterol were not able to induce content release even under acidic conditions. These results suggest that control of the liposome size and cholesterol content is important for preparing stable liposomes at physiological conditions and for preparing highly pH-responsive liposomes for drug delivery applications.
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Sui, Zhijie, und Joseph B. Schlenoff. „Phase Separations in pH-Responsive Polyelectrolyte Multilayers: Charge Extrusion versus Charge Expulsion“. Langmuir 20, Nr. 14 (Juli 2004): 6026–31. http://dx.doi.org/10.1021/la0495985.
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Aliabouzar, Mitra, Adam W. Y. Ley, Sabine Meurs, Andrew J. Putnam, Brendon M. Baker, Oliver D. Kripfgans, J. Brian Fowlkes und Mario L. Fabiilli. „Micropatterning of acoustic droplet vaporization in acoustically-responsive scaffolds using extrusion-based bioprinting“. Bioprinting 25 (März 2022): e00188. http://dx.doi.org/10.1016/j.bprint.2021.e00188.
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Ohsawa, Shizue, John Vaughen und Tatsushi Igaki. „Cell Extrusion: A Stress-Responsive Force for Good or Evil in Epithelial Homeostasis“. Developmental Cell 44, Nr. 3 (Februar 2018): 284–96. http://dx.doi.org/10.1016/j.devcel.2018.01.009.
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Ohsawa, Shizue, John Vaughen und Tatsushi Igaki. „Cell Extrusion: A Stress-Responsive Force for Good or Evil in Epithelial Homeostasis“. Developmental Cell 44, Nr. 4 (Februar 2018): 532. http://dx.doi.org/10.1016/j.devcel.2018.02.007.
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Lee, Chang-Uk, Johanna Vandenbrande, Adam E. Goetz, Mark A. Ganter, Duane W. Storti und Andrew J. Boydston. „Room temperature extrusion 3D printing of polyether ether ketone using a stimuli-responsive binder“. Additive Manufacturing 28 (August 2019): 430–38. http://dx.doi.org/10.1016/j.addma.2019.05.008.
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Hu, Chen, Lukas Hahn, Mengshi Yang, Alexander Altmann, Philipp Stahlhut, Jürgen Groll und Robert Luxenhofer. „Improving printability of a thermoresponsive hydrogel biomaterial ink by nanoclay addition“. Journal of Materials Science 56, Nr. 1 (25.09.2020): 691–705. http://dx.doi.org/10.1007/s10853-020-05190-5.
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Abstract As a promising biofabrication technology, extrusion-based bioprinting has gained significant attention in the last decade and major advances have been made in the development of bioinks. However, suitable synthetic and stimuli-responsive bioinks are underrepresented in this context. In this work, we described a hybrid system of nanoclay Laponite XLG and thermoresponsive block copolymer poly(2-methyl-2-oxazoline)-b-poly(2-n-propyl-2-oxazine) (PMeOx-b-PnPrOzi) as a novel biomaterial ink and discussed its critical properties relevant for extrusion-based bioprinting, including viscoelastic properties and printability. The hybrid hydrogel retains the thermogelling properties but is strengthened by the added clay (over 5 kPa of storage modulus and 240 Pa of yield stress). Importantly, the shear-thinning character is further enhanced, which, in combination with very rapid viscosity recovery (~ 1 s) and structure recovery (~ 10 s), is highly beneficial for extrusion-based 3D printing. Accordingly, various 3D patterns could be printed with markedly enhanced resolution and shape fidelity compared to the biomaterial ink without added clay. Graphic abstract
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Marinho, P. V. T., A. S. Macedo, C. R. A. Ferrigno, I. S. Dal-Bó, A. C. B. C. F. Pinto, C. R. G. R. Ontivero, F. Paes et al. „Pediculectomy and fenestration for spinal cord decompression of the lumbar spine of a bush dog (Speothos venaticus) - case report“. Arquivo Brasileiro de Medicina Veterinária e Zootecnia 72, Nr. 4 (August 2020): 1397–402. http://dx.doi.org/10.1590/1678-4162-11586.
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ABSTRACT A captive adult male bush dog (Speothos venaticus) was referred to our Veterinary Medical Teaching Hospital from a local zoo due to a two-week history of progressive hind limb gait impairment and ataxia, non-responsive to clinical management. Computed tomography revealed decreased disc space at L3 - L4 level, with probable disc extrusion narrowing the right side of the spinal canal, compressing the spinal cord. We opted to surgically remove the disc material using both fenestration and right lateral pediculectomy (mini-hemilaminectomy) techniques. Twelve days after surgery there was mild residual proprioceptive ataxia. Gait was fully regained with remission of the neurological deficits around the 30th postoperative day. This is - to the best of our knowledge - the first successful report of a lumbar intervertebral disc extrusion in a bush dog (Speothos venaticus) surgically treated by pediculectomy and disc fenestration.
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Yang, Yang, Zixun Wang, Yuanyuan Xu, Jingjing Xia, Zhaoxian Xu, Shuai Zhu und Mingjie Jin. „Preparation of Chitosan/Recombinant Human Collagen-Based Photo-Responsive Bioinks for 3D Bioprinting“. Gels 8, Nr. 5 (19.05.2022): 314. http://dx.doi.org/10.3390/gels8050314.
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Collagen and chitosan are frequently used natural biomaterials in tissue engineering. However, most collagen is derived from animal tissue, with inconsistent quality and pathogen transmittance risks. In this context, we aimed to use a reliable Type-III recombinant human collagen (RHC) as an alternative biomaterial together with chitosan to develop novel photo-responsive bioinks for three-dimensional (3D) bioprinting. RHC was modified with methacrylic anhydride to obtain the RHC methacryloyl (RHCMA) and mixed with acidified chitosan (CS) to form composites CS-RHCMA. The characterizations demonstrated that the mechanical properties and the degradation of the bioinks were tunable by introducing the CS. The printabilities improved by adding CS to RHCMA, and various structures were constructed via extrusion-based 3D printing successfully. Moreover, in vitro tests confirmed that these CS-RHCMA bioinks were biocompatible as human umbilical vein endothelial cells (HUVECs) were sustained within the constructs post-printing. The results from the current study illustrated a well-established bioinks system with the potential to construct different tissues through 3D bioprinting.
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Twardowski, Zbylut J., Karl D. Nolph, Ramesh Khanna, Barbara F. Prowant, Leonor P. Ryan und W. Kirt Nichols. „The Need for a “Swan Neck” Permanentl Y Bent, Arcuate Peritoneal Dialysis Catheter“. Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 5, Nr. 4 (Oktober 1985): 219–23. http://dx.doi.org/10.1177/089686088500500404.
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In 1968 to ensure optimal function of a permanent catheter during periodic peritoneal dialysis, Tenckhoff recommended that a double-cuff catheter be inserted so that a slightly arcuate subcutaneous course would give the external and intraperitoneal segment a caudal direction. During the rapid growth of CAPD over the past five years, nephrologists generally have adapted the Tenckhoff's methods of catheter insertion but have encountered numerous complications. This paper describes a retrospective analysis of the complications associated with 83 peritoneal dialysis catheters functioned for 48,325 catheter days (132 catheter years) in 63 patients on continuous ambulatory peritoneal dialysis (CAPD) at our institution. Pericatheter leaks were seen only with midline insertions. Exit-site infections were significantly more resistant to treatment with singlecuff than with double-cuff catheters as assessed by the proportion of time that the exit-site is infected. If the subcutaneous tunnels were directed downward the infections were more responsive to treatment. Significantly more frequent catheter-tip migrations were observed with subcutaneous tunnel directed left and downward. Thus, our study supports Tenckhoff's observation that we can expect the lowest complication rate with double-cuff catheters with an arcuate tunnel, convex upwards. However, frequently this shape of tunnel is associated with external-cuff extrusions due to resilience of the straight catheter. To reconcile these conflicting requirements we recommend a new catheter permanently bent between the cuffs to eliminate one of the forces responsible for cuff extrusion. Such a catheter, named the swan-neck tunnel peritoneal dialysis catheter, should be inserted surgically through the belly of the rectus muscle.
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Hamilton, Charles, Gursel Alici, Geoff Spinks und Marc in het Panhuis. „The Suitability of 3-D Printed Eutectic Gallium-Indium Alloy as a Heating Element for Thermally Active Hydrogels“. MRS Advances 2, Nr. 6 (15.12.2016): 335–40. http://dx.doi.org/10.1557/adv.2016.618.
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ABSTRACTWe report the use of a novel extrusion tip that allows for the omnidirectional printing of eutectic gallium-indium (eGaIn) alloy onto the surface of hydrogel materials into complex 2-dimensional patterns. The use of these printed soft “wires” as an electrothermal heating element for soft robotics purposes was explored. Heating of the eGaIn structures encapsulated in an alginate/acrylamide ionic-covalent entanglement hydrogel was measured by a thermal imaging camera. It was determined that eGaIn is a suitable material for use in future soft robotics applications as an electrothermal heating element to actuate thermally responsive N-isoproylacrylamide hydrogels.
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V, Lotlikar, S. Shidhaye, U. Kedar und V. Kadam. „Formulation and Evaluation of Novel Enteric Coated Extended Release Multiparticulates of Model NSAID Ketoprofen“. International Journal of Pharmaceutical Sciences and Nanotechnology 3, Nr. 2 (31.08.2010): 994–99. http://dx.doi.org/10.37285/ijpsn.2010.3.2.13.
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The aim of this study was to develop a pH responsive enteric coated extended release multiparticulate dosage form containing a model drug ketoprofen, a nonsteroidal anti-inflammatory drug used for rheumatoid arthritis. The drug loaded pellets in matrix form were prepared by using extrusion/spheronization method. The optimized pelletization method revealed that extrusion using 1 mm sieve plate and spheronization friction disc of 2mm carried out at 700 rpm for 5-10 minutes resulted in good spherical pellets and uniformity in size. Evaluated core pellets were coated with polymer Eudragit® RS 30D on Fluid bed coater to achieve a sustainable release for 12 hours. Ketoprofen as like other NSAID have been reported for gastric mucosal irritation so a pH responsive barrier coat of Eudragit L®100-55 was employed on a pan coater for abstaining release in acidic media. The formulated pellets were characterized for shape and size uniformity, friability, surface morphology studies. The particle size of core and polymer coated pellets were found to be in the range of 0.95-1.2 mm and 1.32-1.51 mm respectively. The pellets were spherical in shape with smooth texture and uniformity in size. In-vitro dissolution tests were carried out for pellets in a USP type II dissolution apparatus in media-simulating pH conditions of the gastrointestinal tract. The release of the ketoprofen from formulated pellets was established in pH 1.2 for a period of 2 h, followed by pH 7.5 for rest of the study. The study concluded that the formulated multiparticulate dosage form of ketoprofen was able to relieve symptoms of rheumatoid arthritis.
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Quindoza, Gerardo Martin III, Patrick Aldwin Castillo, Jill Manapat und John Kenneth Cruz. „PREPARATION AND RHEOLOGICAL CHARACTERIZATION OF CELLULOSE-CHITOSAN HYDROGEL FOR EXTRUSION 3D PRINTER“. ASEAN Engineering Journal 12, Nr. 4 (29.11.2022): 157–65. http://dx.doi.org/10.11113/aej.v12.17440.
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The application of three-dimensional (3D) printing in tissue engineering is becoming prominent nowadays. A big obstacle for this technology is the selection of proper ink material. Chitosan hydrogel is an established biocompatible material that can be used as tissue scaffolds, and it has the rheology necessary for processing via extrusion type 3D printer. However, chitosan still has degradation and swelling limitations. Hence, chitosan hydrogel blends were incorporated with cellulose particles and were prepared as ink material. The hydrogels were successfully synthesized via thermo-responsive sol-gel method. Fourier transform infrared spectroscopy (FT-IR) analysis showed that the gelation of hydrogels formed a semi-interpenetrating network of ionically crosslinked chitosan and cellulose particles. Rheological tests have shown that the hydrogels exhibited shear thinning property necessary for printing. However, high cellulose amounts caused clogging during printing, and the presence of water limited the structural rigidity of the printed product. Besides this, it was found that the addition of cellulose was able to increase swelling, decrease degradation rate, and decrease gelation time, but the effect is not significant for any of these three properties.
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Erkoc, Pelin, Yazan Nitham Odeh, Nada Alrifai, Onur Zirhli, Nilay Gunduz Akdogan, Burcin Yildiz, Ibrahim Burc Misirlioglu und Ozan Akdogan. „Photocurable pentaerythritol triacrylate/lithium phenyl‐2,4,6‐trimethylbenzoylphosphinate‐based ink for extrusion‐based 3D printing of magneto‐responsive materials“. Journal of Applied Polymer Science 137, Nr. 35 (04.02.2020): 49043. http://dx.doi.org/10.1002/app.49043.
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Das, Dipankar, Qasim F. M. Alhusaini, Kawaljit Kaur, Mohammad Raoufi und Holger Schönherr. „Enzyme-Responsive Biopolymeric Nanogel Fibers by Extrusion: Engineering of High-Surface-Area Hydrogels and Application in Bacterial Enzyme Detection“. ACS Applied Materials & Interfaces 13, Nr. 11 (12.03.2021): 12928–40. http://dx.doi.org/10.1021/acsami.1c00136.
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Richards, Kerry, und Danish J. Malik. „Bacteriophage Encapsulation in pH-Responsive Core-Shell Capsules as an Animal Feed Additive“. Viruses 13, Nr. 6 (11.06.2021): 1131. http://dx.doi.org/10.3390/v13061131.
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Increasing antibiotic resistance in bacteria that cause zoonotic infections is a major problem for farmers rearing animals for food as well as for consumers who eat the contaminated meat resulting in food-borne infections. Bacteriophages incorporated in animal feed may help reduce carriage and infections in animals including chickens and pigs. There are, however, unmet challenges in protecting phages from processing stresses e.g., during animal feed pelleting operations and during transit of phages through the acidic gastric environment. Core-shell capsules were produced using a concentric nozzle and commercially available encapsulation equipment to fabricate capsules with phages formulated in an oil-in-water microemulsion in the core. pH-responsive capsules released the encapsulated phage cargo within 10–30 min triggered by changes in local environmental pH typically found in the lower gastrointestinal (GI) tract of animals. Acid stability of phages exposed to pH values as low as pH 1 was demonstrated. Encapsulated phages were able to withstand exposure to 95 °C wet heat thermal stress for up to 120 s, conditions typically encountered during feed pellet extrusion processing. Free phages were inactivated within 15 s under these conditions. The present study demonstrates that encapsulation of bacteriophages in core-shell pH-responsive capsules with water-in-oil emulsified phages in the core significantly improves phage viability upon exposure to processing and environmental stresses that require consideration during production of animal feed and application in animals for biocontrol. The results from this study should help guide future development of phage formulations suitable for use in animal feed for animal biocontrol applications.
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Rahim, Muhammad Abdur, Asadullah Madni, Nayab Tahir, Nasrullah Jan, Hassan Shah, Safiullah Khan, Riaz Ullah, Ahmed Bari und Muhammad Sohaib Khan. „Mild Hyperthermia Responsive Liposomes for Enhanced In Vitro and In Vivo Anticancer Efficacy of Doxorubicin against Hepatocellular Carcinoma“. Pharmaceutics 13, Nr. 8 (21.08.2021): 1310. http://dx.doi.org/10.3390/pharmaceutics13081310.
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The current study is aimed to fabricate doxorubicin (Dox) loaded mild temperature responsive liposomes (MTLs) by thin film hydration technique for enhanced in vitro and in vivo anticancer efficacy against hepatocellular carcinoma. The aforementioned Dox loaded MTLs were developed and optimized with extrusion and drug loading techniques. The optimized MTLs were in optimum size range (118.20 ± 2.81–187.13 ± 4.15 nm), colloidal stability (−13.27 ± 0.04 to −32.34 ± 0.15 mV), and enhanced entrapment of Dox (28.71 ± 2.01–79.24 ± 2.16). Furthermore, the optimized formulation (MTL1-E(AL)) embodied improved physicochemical stability deducted by Fourier transform infra-red (FTIR) spectroscopy and mild hyperthermia-based phase transition demonstrated from differential scanning calorimetry (DSC). An in vitro drug release study revealed mild hyperthermia assisted rapid in vitro Dox release from MTLs-E(AL) (T100% ≈ 1 h) by Korsmeyer–Peppas model based Fickian diffusion (n < 0.45). Likewise, an in vitro cytotoxicity study and lower IC50 values also symbolized mild hyperthermia (40.2 °C) based quick and improved cytotoxicity of MTL1-E(AL) in HepG2 and MCF-7 cells than Dox. The fluorescence microscopy also represented enhanced cellular internalization of MTL1-E(AL) at mild hyperthermia compared to the normothermia (37.2 °C). In addition, an in vivo animal study portrayed the safety, improved anticancer efficacy and healing of hepatocellular carcinoma (HCC) through MTL1-E(AL). In brief, the Dox loaded MTLs could be utilized as safe and effective therapeutic strategy against HCC.
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Prathumrat, Peerawat, Mostafa Nikzad, Fareed Tamaddoni Jahromi, Elnaz Hajizadeh und Igor Sbarski. „Three-Dimensional Printing of Shape Memory Liquid Crystalline Thermoplastic Elastomeric Composites Using Fused Filament Fabrication“. Polymers 15, Nr. 19 (30.09.2023): 3961. http://dx.doi.org/10.3390/polym15193961.
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Liquid crystalline elastomers (LCEs) are stimuli-responsive materials utilised in shape memory applications. The processability of these materials via advanced manufacturing is being paid increasing attention to advance their volume production on an industrial scale. Fused filament fabrication (FFF) is an extrusion-based additive manufacturing (AM) technique that offers the potential to address this. The critical challenge, however, is the rheological characteristics of LCEs that need to be tuned to achieve a facile processability through the extrusion-based method. In this work, new filaments of liquid crystalline thermoplastic elastomer (LCTPE) and its composites with lignin were made by the ternary system of LCE, thermoplastic polyurethane (TPU), and lignin. The results showed that TPU improves the melt flow index of the LCTPE system to approximately 10.01 g/10 min, while adding lignin further enhances the value of this index for the composites up to 21.82 g/10 min. The microstructural analysis indicated that the effective distribution of lignin and reduced domain size of the LCEs in the ternary blend contribute to the enhanced flowability of this filament through 3D printing. Samples of 3D-printed LCTPE and LCTPE/lignin composites maintained their shape memory characteristics via thermomechanical activation. Full shape recovery of the new LCTPE matrix and its composites with lignin was achieved in 39 s and 32 s at 130 °C, followed by 28 s and 24 s at 160 °C, respectively. The successful fabrication of LCTPE and LCTPE/lignin composite samples through 3D printing demonstrates a potential procedure for processing these shape memory materials using the FFF technique, and lignin offers a sustainable and cost-effective material solution that enhances the properties of this composite material.
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Garcia Rosales, Carlos Alejandro, Hoejin Kim, Mario F. Garcia Duarte, Luis Chavez, Tzu-Liang Bill Tseng und Yirong Lin. „Toughness-based recovery efficiency of shape memory parts fabricated using material extrusion 3D printing technique“. Rapid Prototyping Journal 25, Nr. 1 (07.01.2019): 30–37. http://dx.doi.org/10.1108/rpj-09-2017-0188.
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Purpose Shape memory polymers (SMPs) are classified as smart materials owing to their inherent stimulus-induced response. SMPs are capable of recovering partially or totally to its original shape after a high degree of deformation by external stimulus. The most used stimuli are thermal, light, magnetic field and electricity. This research aims to characterize the toughness property of thermo-responsive SMP specimens fabricated by the material extrusion (ME) process and to investigate the impact of ME parameters on specimen maximum load and load-displacement curves. Moreover, to investigate the recovery efficiency based on the initial and post toughness generated by the compact tension test. Design/methodology/approach A design of experiments with three parameters (temperature, velocity and layer height) defined the ME settings to fabricate the specimens. The ME raster orientation factor was also evaluated separately. In addition, one more specimen group assisted by a clamp during the recovery process was compared with a specimen control group. After fabrication, specimens were submitted to a thermo-mechanical cycle that encompasses a compact tension test and a thermo-recovery process. Comparison studies of load-displacement, toughness and recovery efficiency of the specimens were carried out to determine the optimized fabrication parameters. Findings It was found that ME parameters and raster orientation impacted the test results. Samples with the clamp support during recovery returned a higher toughness than samples without support. Finally, results showed that the shape memory effect can contribute with up to 43 per cent recovery efficiency in a first recovery and up to 23 per cent in a second recovery of damaged specimens. Originality/value This paper is a reference for toughness and recovery properties of SMP parts produced by the ME fabrication process.
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Ciarleglio, Gianluca, Federica Cinti, Elisa Toto und Maria Gabriella Santonicola. „Synthesis and Characterization of Alginate Gel Beads with Embedded Zeolite Structures as Carriers of Hydrophobic Curcumin“. Gels 9, Nr. 9 (03.09.2023): 714. http://dx.doi.org/10.3390/gels9090714.
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Alginate-based beads containing a porous zeolite filler were developed as carriers of bioactive compounds with a hydrophobic nature, such as curcumin (Cur). Curcumin, a natural pigment extracted from the turmeric (Curcuma longa) plant, exhibits antioxidant, anti-inflammatory, anticarcinogenic, and antiviral properties. To enhance the bioavailability of the drug, curcumin needs to be encapsulated in a suitable carrier that improves its dispersibility and solubility. Commercial A-type zeolites (Z5A) were used as curcumin-binding agents and they were immobilized within the alginate gel beads by cross-linking in calcium chloride solution during an extrusion dripping process. The process parameters (alginate and CaCl2 concentrations, needle gauge, collecting distance) were optimized to fabricate beads with good sphericity factor and 1.5–1.7 mm diameter in their hydrated state. The chemical structure of the gel beads was assessed using FTIR spectroscopy, while their thermal stability was evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Due to the alginate matrix, the composite Alg/ZA5-Cur beads possess pH-responsive properties. In addition, the gel beads were modified by chitosan (CS) to enhance the stability and control the degradation behavior of the gel matrix. The swelling behavior and the degradation of the beads were analyzed in physiological solutions with different pH values. Results demonstrate the stabilizing and protective effect of the chitosan coating, as well as the reinforcing effect of the zeolite filler. This makes the pH-responsive alginate gel beads good candidates for the delivery of lipophilic drugs to specific inflammatory sites.
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Céspedes-Valenzuela, Daniela N., Santiago Sánchez-Rentería, Javier Cifuentes, Mónica Gantiva-Diaz, Julian A. Serna, Luis H. Reyes, Carlos Ostos, Christian Cifuentes-De la Portilla, Carolina Muñoz-Camargo und Juan C. Cruz. „Preparation and Characterization of an Injectable and Photo-Responsive Chitosan Methacrylate/Graphene Oxide Hydrogel: Potential Applications in Bone Tissue Adhesion and Repair“. Polymers 14, Nr. 1 (30.12.2021): 126. http://dx.doi.org/10.3390/polym14010126.
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As life expectancy continues to increase, the inevitable weakening and rupture of bone tissue have grown as concerns in the medical community, thus leading to the need for adhesive materials suitable for bone repair applications. However, current commercially available adhesives face certain drawbacks that prevent proper tissue repair, such as low biocompatibility, poor adhesion to wet surfaces, and the need for high polymerization temperatures. This work aims to develop an injectable and photo-responsive chitosan methacrylate/graphene oxide (ChiMA/GO) adhesive nanocomposite hydrogel of high biocompatibility that is easy to apply by simple extrusion and that offers the possibility for in situ polymer and physiological temperatures. The nanocomposite was thoroughly characterized spectroscopically, microscopically, rheologically, thermally, and through mechanical, textural, and biological assays to fully evaluate its correct synthesis and functionalization and its performance under physiological conditions that mimic those observed in vivo. In addition, a finite element analysis (FEA) simulation was used to evaluate its performance in femur fractures. Results suggest the material’s potential as a bioadhesive, as it can polymerize at room temperature, shows superior stability in physiological media, and is capable of withstanding loads from body weight and movement. Moreover, the material showed remarkable biocompatibility as evidenced by low hemolytic and intermediate platelet aggregation tendencies, and high cytocompatibility when in contact with osteoblasts. The comprehensive studies presented here strongly suggest that the developed hydrogels are promising alternatives to conventional bone adhesives that might be further tested in vivo in the near future.
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Razzaq, Muhammad Yasar, Joamin Gonzalez-Gutierrez, Gregory Mertz, David Ruch, Daniel F. Schmidt und Stephan Westermann. „4D Printing of Multicomponent Shape-Memory Polymer Formulations“. Applied Sciences 12, Nr. 15 (05.08.2022): 7880. http://dx.doi.org/10.3390/app12157880.
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Four-dimensional (4D) printing technology, as a next-generation additive manufacturing method, enables printed objects to further change their shapes, functionalities, or properties upon exposure to external stimuli. The 4D printing of programmable and deformable materials such as thermo-responsive shape-memory polymers (trSMPs), which possess the ability to change shape by exposure to heat, has attracted particular interest in recent years. Three-dimensional objects based on SMPs have been proposed for various potential applications in different fields, including soft robotics, smart actuators, biomedical and electronics. To enable the manufacturing of complex multifunctional 3D objects, SMPs are often coupled with other functional polymers or fillers during or before the 3D printing process. This review highlights the 4D printing of state-of-the-art multi-component SMP formulations. Commonly used 4D printing technologies such as material extrusion techniques including fused filament fabrication (FFF) and direct ink writing (DIW), as well as vat photopolymerization techniques such as stereolithography (SLA), digital light processing (DLP), and multi-photon polymerization (MPP), are discussed. Different multicomponent SMP systems, their actuation methods, and potential applications of the 3D printed objects are reviewed. Finally, current challenges and prospects for 4D printing technology are summarized.
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Gómez-Blanco, J. Carlos, Enrique Mancha-Sánchez, Alfonso C. Marcos, Manuel Matamoros, Antonio Díaz-Parralejo und J. Blas Pagador. „Bioink Temperature Influence on Shear Stress, Pressure and Velocity Using Computational Simulation“. Processes 8, Nr. 7 (17.07.2020): 865. http://dx.doi.org/10.3390/pr8070865.
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Bioinks are usually cell-laden hydrogels widely studied in bioprinting performing experimental tests to tune their rheological properties, thus increasing research time and development costs. Computational Fluids Dynamics (CFD) is a powerful tool that can minimize iterations and costs simulating the material behavior using parametric changes in rheological properties under testing. Additionally, most bioinks have specific functionalities and their properties might widely change with temperature. Therefore, commercial bioinks are an excellent way to standardize bioprinting process, but they are not analyzed in detail. Therefore, the objective of this work is to study how three temperatures of the Cellink Bioink influence shear stress pressure and velocity through computational simulation. A comparison of three conical nozzles (20, 22, and 25G) for each temperature has been performed. The results show that shear stress, pressure, and velocity vary in negligible ranges for all combinations. Although these ranges are small and define a good thermo-responsive bioink, they do not generate a filament on the air and make drops during extrusion. In conclusion, this bioink provides a very stable behavior with low shear stress, but other bioprinting parameters must be set up to get a stable filament width.
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Williams, Baraka S., Raphael D. Isokpehi, Andreas N. Mbah, Antoinesha L. Hollman, Christina O. Bernard, Shaneka S. Simmons, Wellington K. Ayensu und Bianca L. Garner. „Functional Annotation Analytics of Bacillus Genomes Reveals Stress Responsive Acetate Utilization and Sulfate Uptake in the Biotechnologically Relevant Bacillus megaterium“. Bioinformatics and Biology Insights 6 (Januar 2012): BBI.S7977. http://dx.doi.org/10.4137/bbi.s7977.
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Bacillus species form an heterogeneous group of Gram-positive bacteria that include members that are disease-causing, biotechnologically-relevant, and can serve as biological research tools. A common feature of Bacillus species is their ability to survive in harsh environmental conditions by formation of resistant endospores. Genes encoding the universal stress protein (USP) domain confer cellular and organismal survival during unfavorable conditions such as nutrient depletion. As of February 2012, the genome sequences and a variety of functional annotations for at least 123 Bacillus isolates including 45 Bacillus cereus isolates were available in public domain bioinformatics resources. Additionally, the genome sequencing status of 10 of the B. cereus isolates were annotated as finished with each genome encoded 3 USP genes. The conservation of gene neighborhood of the 140 aa universal stress protein in the B. cereus genomes led to the identification of a predicted plasmid-encoded transcriptional unit that includes a USP gene and a sulfate uptake gene in the soil-inhabiting Bacillus megaterium. Gene neighborhood analysis combined with visual analytics of chemical ligand binding sites data provided knowledge-building biological insights on possible cellular functions of B. megaterium universal stress proteins. These functions include sulfate and potassium uptake, acid extrusion, cellular energy-level sensing, survival in high oxygen conditions and acetate utilization. Of particular interest was a two-gene transcriptional unit that consisted of genes for a universal stress protein and a sirtuin Sir2 (deacetylase enzyme for NAD+-dependent acetate utilization). The predicted transcriptional units for stress responsive inorganic sulfate uptake and acetate utilization could explain biological mechanisms for survival of soil-inhabiting Bacillus species in sulfate and acetate limiting conditions. Considering the key role of sirtuins in mammalian physiology additional research on the USP-Sir2 transcriptional unit of B. megaterium could help explain mammalian acetate metabolism in glucose-limiting conditions such as caloric restriction. Finally, the deep-rooted position of B. megaterium in the phylogeny of Bacillus species makes the investigation of the functional coupling acetate utilization and stress response compelling.
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Alghurabi, Hamid, Tatsuaki Tagami, Koki Ogawa und Tetsuya Ozeki. „Preparation, Characterization, and In Vitro Evaluation of Eudragit S100-Coated Bile Salt-Containing Liposomes for Oral Colonic Delivery of Budesonide“. Polymers 14, Nr. 13 (30.06.2022): 2693. http://dx.doi.org/10.3390/polym14132693.
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The aim of this study was to prepare a liposomal formulation of a model drug (budesonide) for colonic delivery by incorporating a bile salt (sodium glycocholate, SGC) into liposomes followed by coating with a pH-responsive polymer (Eudragit S100, ES100). The role of the SGC is to protect the liposome from the emulsifying effect of physiological bile salts, while that of ES100 is to protect the liposomes from regions of high acidity and enzymatic activity in the stomach and small intestine. Vesicles containing SGC were prepared by two preparation methods (sonication and extrusion), and then coated by ES100 (ES100-SGC-Lip). ES100-SGC-Lip showed a high entrapment efficiency (>90%) and a narrow size distribution (particle size = 275 nm, polydispersity index <0.130). The characteristics of liposomes were highly influenced by the concentration of incorporated SGC. The lipid/polymer weight ratio, liposome charge, liposome addition, and mixing rate were critical factors for efficient and uniform coating. In vitro drug release studies in various simulated fluids indicate a pH-dependent dissolution of the coating layer, and the disintegration process of ES100-SGC-Lip was evaluated. In conclusion, the bile salt-containing ES100-coated liposomal formulation has potential for effective oral colonic drug delivery.
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Mea, Hing Jii, Luis Delgadillo und Jiandi Wan. „On-demand modulation of 3D-printed elastomers using programmable droplet inclusions“. Proceedings of the National Academy of Sciences 117, Nr. 26 (15.06.2020): 14790–97. http://dx.doi.org/10.1073/pnas.1917289117.
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One of the key thrusts in three-dimensional (3D) printing and direct writing is to seamlessly vary composition and functional properties in printed constructs. Most inks used for extrusion-based printing, however, are compositionally static and available approaches for dynamic tuning of ink composition remain few. Here, we present an approach to modulate extruded inks at the point of print, using droplet inclusions. Using a glass capillary microfluidic device as the printhead, we dispersed droplets in a polydimethylsiloxane (PDMS) continuous phase and subsequently 3D printed the resulting emulsion into a variety of structures. The mechanical characteristics of the 3D-printed constructs can be tuned in situ by varying the spatial distribution of droplets, including aqueous and liquid metal droplets. In particular, we report the use of poly(ethylene glycol) diacrylate (PEGDA) aqueous droplets for local PDMS chemistry alteration resulting in significant softening (85% reduced elastic modulus) of the 3D-printed constructs. Furthermore, we imparted magnetic functionality in PDMS by dispersing ferrofluid droplets and rationally designed and printed a rudimentary magnetically responsive soft robotic actuator as a functional demonstration of our droplet-based strategy. Our approach represents a continuing trend of adapting microfluidic technology and principles for developing the next generation of additive manufacturing technology.
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Neonaki, M., D. Cunninghame Graham, K. N. White und A. Bomford. „Down-regulation of liver iron-regulatory protein I in haemochromatosis“. Biochemical Society Transactions 30, Nr. 4 (01.08.2002): 726–28. http://dx.doi.org/10.1042/bst0300726.
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Cellular iron homoeostasis is maintained by iron sensor proteins known as iron-regulatory proteins (IRPs), which act post-transcriptionally by binding RNA stem-loop structures, termed iron-responsive elements (IREs), present on the mRNAs of proteins involved in iron storage, utilization and transport. IRP1 is a bifunctional protein that can act either as a cytoplasmic aconitase or as an IRE-binding protein. The RNA-binding activity of IRP1 is regulated post-translationally by the insertion or extrusion of a 4Fe-4S cluster, without changes in the levels of protein. In hereditary haemochromatosis (HH) accumulation of iron in parenchymal tissues, including the liver, occurs, possibly through dysfunctional IRP1. Investigation of IRP1 expression in liver biopsies from HH patients showed that the protein is completely absent or markedly reduced in heavily iron-loaded HH patients. Real-time PCR was then conducted in an attempt to investigate the mRNA levels and establish the underlying mechanism behind the disappearing act of IRP1. The two possibilities are: transcriptional regulation (through the inhibition of transcription) or post-transcriptional regulation (either through increased turnover of protein or inhibition of translation) of IRP1. Preliminary data suggest that transcription of IRP1 is not affected by chronic iron overload, and down-regulation may be attributable instead to degradation of the protein.
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Grapes, Nicholas John, Rowena Mary Anne Packer und Steven De Decker. „Clinical reasoning in canine cervical hyperaesthesia: which presenting features are important?“ Veterinary Record 187, Nr. 11 (11.09.2020): 448. http://dx.doi.org/10.1136/vr.105818.
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BackgroundTo evaluate whether clinical features from the history, presentation, physical and neurological examination of dogs with cervical hyperaesthesia are statistically predictive of the underlying diagnosis.MethodsTwo hundred and ninety-eight dogs presenting with cervical hyperaesthesia between January 2010 and October 2018 were investigated. Only neurologically normal dogs with cervical hyperaesthesia on examination were included, while those with concurrent neurological deficits including gait abnormalities and proprioceptive deficits were excluded. Univariate analysis of clinical variables was performed, and those associated with each diagnosis were retained for multivariable binary logistic regression models.ResultsNinety-five per cent of cervical hyperaesthesia presentations were represented by eight conditions that included steroid-responsive meningitis arteritis (SRMA; n=100), intervertebral disc extrusion (n=78), syringomyelia (SM; n=51), intervertebral disc protrusion (n=30), neoplasia (n=8), cervical spondylomyelopathy (n=7), immune-mediated polyarthritis (n=5) and meningoencephalomyelitis of unknown aetiology (n=5). Younger age (P=0.003), pyrexia (P=0.003) and haematology abnormalities (P=0.03) comprising leucocytosis, neutrophilia or monocytosis were associated with a diagnosis of SRMA.ConclusionsEasy-to-recognise clinical features can be used to identify the most likely differential diagnosis in neurologically normal dogs with cervical hyperaesthesia, which may aid the decision making of veterinary surgeons evaluating dogs with this presentation.
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Farè, Silvia, Luigi de Nardo, S. De Cicco, M. Jovenitti und Maria Cristina Tanzi. „Different Processing Methods to Obtain Porous Structure in Shape Memory Polymers“. Materials Science Forum 539-543 (März 2007): 663–68. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.663.
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In the last few years, clinical procedures undergone huge modifications. Among them, mini-invasive surgery has modified the clinical practice and the quality of life of patients. Shape Memory Polymers (SMPs), a class of stimuli-responsive materials, can be considered ideal candidates for the design of devices for mini-invasive surgical procedures. Such a device can be inserted in a packed in, temporary shape and later can expand at body temperature. A bone defect could be filled by a SMP porous structure, that improves the tissue integration and healing. In this work, two different processing techniques to obtain porous shape memory polymer scaffolds from Calo MER™ and MM-4520, two SMPs, are presented. Porous structures were obtained by micro-extrusion with different chemical foaming agents or with sodium chloride, or by solvent casting/particulate leaching. The morphology, the thermo-mechanical and the shape recovery properties of the SMP porous samples were investigated. Tridimensional porous structures showed a well interconnected morphology, with a pore size in the range aimed for bone interaction applications. The shape memory properties were not significantly affected by the transformation processes: a good ability of recovering the original shape was verified. Therefore, the porous structures, obtained from these SMP materials, appear adequate for an use as bone filler.
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Brar, Sukhdev S., Claude Grigg, Kimberly S. Wilson, Walter D. Holder, Didier Dreau, Catherine Austin, Mareva Foster et al. „Disulfiram inhibits activating transcription factor/cyclic AMP-responsive element binding protein and human melanoma growth in a metal-dependent manner in vitro, in mice and in a patient with metastatic disease“. Molecular Cancer Therapeutics 3, Nr. 9 (01.09.2004): 1049–60. http://dx.doi.org/10.1158/1535-7163.1049.3.9.
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Abstract The thiocarbamate alcoholism drug disulfiram blocks the P-glycoprotein extrusion pump, inhibits the transcription factor nuclear factor-κB, sensitizes tumors to chemotherapy, reduces angiogenesis, and inhibits tumor growth in mice. Thiocarbamates react with critical thiols and also complex metal ions. Using melanoma as the paradigm, we tested whether disulfiram might inhibit growth by forming mixed disulfides with critical thiols in a mechanism facilitated by metal ions. Disulfiram given to melanoma cells in combination with Cu2+ or Zn2+ decreased expression of cyclin A and reduced proliferation in vitro at lower concentrations than disulfiram alone. In electrophoretic mobility shift assays, disulfiram decreased transcription factor binding to the cyclic AMP-responsive element in a manner potentiated by Cu2+ ions and by the presence of glutathione, suggesting that thiocarbamates might disrupt transcription factor binding by inducing S-glutathionylation of the transcription factor DNA binding region. Disulfiram inhibited growth and angiogenesis in melanomas transplanted in severe combined immunodeficient mice, and these effects were potentiated by Zn2+ supplementation. The combination of oral zinc gluconate and disulfiram at currently approved doses for alcoholism also induced >50% reduction in hepatic metastases and produced clinical remission in a patient with stage IV metastatic ocular melanoma, who has continued on oral zinc gluconate and disulfiram therapy for 53 continuous months with negligible side effects. These findings present a novel strategy for treating metastatic melanoma by employing an old drug toward a new therapeutic use.
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Witkowski, J. M., S. P. Li, G. Gorgas und R. A. Miller. „Extrusion of the P glycoprotein substrate rhodamine-123 distinguishes CD4 memory T cell subsets that differ in IL-2-driven IL-4 production.“ Journal of Immunology 153, Nr. 2 (15.07.1994): 658–65. http://dx.doi.org/10.4049/jimmunol.153.2.658.
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Abstract Approximately 25% of T cells in young mice are able to extrude the fluorescent P glycoprotein substrate Rhodamine-123 (R123), and these R123low cells are present within the naive and memory cell populations of both CD4 and CD8 type. The proportion of R123low T cells increases with age to approximately 60% in mice older than 18 mo of age. CD4 memory T cells from young mice secrete more IL-4 compared with cells from old donors when activated by anti-CD3 and further cultured for 7 to 10 days in the presence of IL-2. To determine whether this age-related decline in IL-4 production was related to the parallel accumulation of R123low T cells within the CD4 memory subset, we compared IL-4 production in cell preparations enriched for R123high and R123low cells by electronic cell sorting. IL-2-driven IL-4 production by CD3-activated CD4 memory cells was found to be limited almost entirely to the R123high subset, i.e., the subset that declines with age. Proliferation under these culture conditions also declined with age and was also much more vigorous in R123high than in R123low cells. Not all R123low T cells, however, were resistant to IL-2-dependent proliferation and differentiation: limit dilution analyses showed nearly equal proportions of Con A-responsive proliferative and cytotoxic clones within the R123high and R123low subsets of CD8 naive cells. These data show that P glycoprotein-mediated extrusion of R123 delineates CD4 memory T cell subsets that differ in function.(ABSTRACT TRUNCATED AT 250 WORDS)
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Yokosho, Kengo, Naoki Yamaji und Jian Feng Ma. „Isolation and characterisation of two MATE genes in rye“. Functional Plant Biology 37, Nr. 4 (2010): 296. http://dx.doi.org/10.1071/fp09265.
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Multidrug and toxic compound extrusion (MATE) proteins are widely present in bacteria, fungi, plants and mammals. Recent studies have showed that a group of plant MATE genes encodes citrate transporter, which are involved in the detoxification of aluminium or translocation of iron from the roots to the shoots. In this study, we isolated two homologous genes (ScFRDL1 and ScFRDL2) from this family in rye (Secale cereale L.). ScFRDL1 shared 94.2% identity with HvAACT1, an Al-activated citrate transporter in barley (Hordeum vulgare L.) and ScFRDL2 shared 80.6% identity with OsFRDL2, a putative Al-responsive protein in rice (Oryza sativa L.). Both genes were mainly expressed in the roots, however, they showed different expression patterns. Expression of ScFRDL1 was unaffected by Al treatment, but up-regulated by Fe-deficiency treatment. In contrast, expression of ScFRDL2 was greatly induced by Al but not by Fe deficiency. The Al-induced up-regulation of ScFRDL2 was found in both the root tips and basal roots. Furthermore, the expression pattern of ScFRDL2 was consistent with citrate secretion pattern. Immunostaining showed that ScFRDL1 was localised at all cells in the root tips and central cylinder and endodermis in the basal root. Taken together, our results suggest that ScFRDL1 was involved in efflux of citrate into the xylem for Fe translocation from the roots to the shoots, while ScFRDL2 was involved in Al-activated citrate secretion in rye.
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Li, Jingwen, Feifan Zhang, Yaqi Zhong, Yadong Zhao, Pingping Gao, Fang Tian, Xianhui Zhang, Rusen Zhou und Patrick J. Cullen. „Emerging Food Packaging Applications of Cellulose Nanocomposites: A Review“. Polymers 14, Nr. 19 (26.09.2022): 4025. http://dx.doi.org/10.3390/polym14194025.
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Cellulose is the most abundant biopolymer on Earth, which is synthesized by plants, bacteria, and animals, with source-dependent properties. Cellulose containing β-1,4-linked D-glucoses further assembles into hierarchical structures in microfibrils, which can be processed to nanocellulose with length or width in the nanoscale after a variety of pretreatments including enzymatic hydrolysis, TEMPO-oxidation, and carboxymethylation. Nanocellulose can be mainly categorized into cellulose nanocrystal (CNC) produced by acid hydrolysis, cellulose nanofibrils (CNF) prepared by refining, homogenization, microfluidization, sonification, ball milling, and the aqueous counter collision (ACC) method, and bacterial cellulose (BC) biosynthesized by the Acetobacter species. Due to nontoxicity, good biodegradability and biocompatibility, high aspect ratio, low thermal expansion coefficient, excellent mechanical strength, and unique optical properties, nanocellulose is utilized to develop various cellulose nanocomposites through solution casting, Layer-by-Layer (LBL) assembly, extrusion, coating, gel-forming, spray drying, electrostatic spinning, adsorption, nanoemulsion, and other techniques, and has been widely used as food packaging material with excellent barrier and mechanical properties, antibacterial activity, and stimuli-responsive performance to improve the food quality and shelf life. Under the driving force of the increasing green food packaging market, nanocellulose production has gradually developed from lab-scale to pilot- or even industrial-scale, mainly in Europe, Africa, and Asia, though developing cost-effective preparation techniques and precisely tuning the physicochemical properties are key to the commercialization. We expect this review to summarise the recent literature in the nanocellulose-based food packaging field and provide the readers with the state-of-the-art of this research area.
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Villacres, Jorge, David Nobes und Cagri Ayranci. „Additive manufacturing of shape memory polymers: effects of print orientation and infill percentage on shape memory recovery properties“. Rapid Prototyping Journal 26, Nr. 9 (17.07.2020): 1593–602. http://dx.doi.org/10.1108/rpj-09-2019-0239.
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Purpose The purpose of this paper is to study the shape memory properties of SMP samples produced through a MEAM process. Fused deposition modeling or, as it will be referred to in this paper, material extrusion additive manufacturing (MEAM) is a technique in which polymeric materials are extruded though a nozzle creating parts via accumulation and joining of different layers. These layers are fused together to build three-dimensional objects. Shape memory polymers (SMP) are stimulus responsive materials, which have the ability to recover their pre-programmed form after being exposed to a large strain. To induce its shape memory recovery movement, an external stimulus such as heat needs to be applied. Design/methodology/approach This project investigates and characterizes the influence of print orientation and infill percentage on shape recovery properties. The analyzed shape recovery properties are shape recovery force, shape recovery speed and time elapsed before activation. To determine whether the analyzed factors produce a significant variation on shape recovery properties, t-tests were performed with a 95% confidence factor between each analyzed level. Findings Results proved that print angle and infill percentage do have a significant impact on recovery properties of the manufactured specimens. Originality/value The manufacturing of SMP objects through a MEAM process has a vast potential for different applications; however, the shape recovery properties of these objects need to be analyzed before any practical use can be developed. These have not been studied as a function of print parameters, which is the focus of this study.
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Gordon, Chad R., Gabriel F. Santiago, Judy Huang, Gregory K. Bergey, Shuya Liu, Mehran Armand, Henry Brem und William S. Anderson. „First In-Human Experience With Complete Integration of Neuromodulation Device Within a Customized Cranial Implant“. Operative Neurosurgery 15, Nr. 1 (06.10.2017): 39–45. http://dx.doi.org/10.1093/ons/opx210.
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Abstract BACKGROUND Neuromodulation devices have the potential to transform modern day treatments for patients with medicine-resistant neurological disease. For instance, the NeuroPace System (NeuroPace Inc, Mountain View, California) is a Food and Drug Administration (FDA)-approved device developed for closed-loop direct brain neurostimulation in the setting of drug-resistant focal epilepsy. However, current methods require placement either above or below the skull in nonanatomic locations. This type of positioning has several drawbacks including visible deformities and scalp pressure from underneath leading to eventual wound healing difficulties, micromotion of hardware with infection, and extrusion leading to premature explantation. OBJECTIVE To introduce complete integration of a neuromodulation device within a customized cranial implant for biocompatibility optimization and prevention of visible deformity. METHODS We report a patient with drug-resistant focal epilepsy despite previous seizure surgery and maximized medical therapy. Preoperative imaging demonstrated severe resorption of previous bone flap causing deformity and risk for injury. She underwent successful responsive neurostimulation device implantation via complete integration within a clear customized cranial implant. RESULTS The patient has recovered well without complication and has been followed closely for 180 d. Device interrogation with electrocorticographic data transmission has been successfully performed through the clear implant material for the first time with no evidence of any wireless transmission interference. CONCLUSION Cranial contour irregularities, implant site infection, and bone flap resorption/osteomyelitis are adverse events associated with implantable neurotechnology. This method represents a novel strategy to incorporate all future neuromodulation devices within the confines of a low-profile, computer-designed cranial implant and the newfound potential to eliminate contour irregularities, improve outcomes, and optimize patient satisfaction.
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Qiu, Peikun, Yuanfei Han, Guangfa Huang, Jianwen Le, Lihua Du und Weijie Lu. „Multi-scale reinforcements stimulated dynamic recrystallization and mechanical behavior of as-extruded titanium matrix composites“. MATEC Web of Conferences 321 (2020): 08005. http://dx.doi.org/10.1051/matecconf/202032108005.
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Different volume fraction of TiB, TiC and La2O3 multiple-reinforced Ti6Al4V composites were fabricated by casting and followed by forging and hot extrusion. The microstructural evolution and mechanical behavior of (TiB+TiC+La2O3)/Ti6Al4V composites during hot extrusion were investigated. The microstructural observations showed that the TiBw and TiCp agglomeration disappeared and distributed more homogeneously in the Ti matrix after hot extrusion. Besides, TiBw exhibited highly preferred alignment along the extrusion direction and TiCp distributed along the same direction. Besides, two kinds of microstructure bands with distinctive spatial distributions of reinforcements were formed after hot extrusion: equiaxial bands embedded with fairly substantial reinforcements and finer basket-weave bands containing few reinforcements, in which the micron-scale TiBw, TiCp and submicron-scale La2O3 particle stimulating nucleation occurred and resulting dynamic recrystallization were the main mechanisms responsible for grain refinement. The tensile tests revealed that hot extrusion significantly increased elongation of (TiB+TiC+La2O3)/Ti6Al4V composites from 2.71% to 13.2% accompanied by slightly decreasing ultimate tensile strength from 954MPa to 903MPa, compared with that of the as-forged composites, which due to a complex process of reinforcements/matrix interaction during extrusion and dynamic recrystallization.
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Wang, Zhen Jun, Le Hua Qi und Ji Ming Zhou. „Study on Effect of Extrusion Velocity on Composites Liquid-Solid Extrusion Process Using 3D Thermo-Mechanical Simulation“. Materials Science Forum 575-578 (April 2008): 210–15. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.210.
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On the basis of thermo-mechanical coupled FEM model which characterized the composites liquid-solid extrusion process, the constant-velocity and non-constant-velocity extrusion process were simulated by 3D thermo-mechanical FEM. Their influence on forming temperature, forming quality and deforming force was analyzed and compared. In the constant-velocity extrusion process, the results show the over-high and low forming temperature in earlier and terminal extrusion stage were responsible for the surface annular cracks and inner fibers breakage. In the new non-constant-velocity extrusion process, however, the range of forming temperature can be shortened in a reasonable range and the over-high and low forming temperature were thus eliminated. Therefore the forming quality and its consistency can be improved. In addition, the deforming force can also be reduced. The simulation and the mechanisms analysis coincide with the experiment results reported in previous literatures. The study provides the theoretical gist and a new feasible technical scheme to favor the consistency of the extruded product quality in composites liquid-solid extrusion process.
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Valenzuela-Lagarda, José Luis, Ramón Pacheco-Aguilar, Roberto Gutiérrez-Dorado, Jaime Lizardi Mendoza, Jose Ángel López-Valenzuela, Miguel Ángel Mazorra-Manzano und María Dolores Muy-Rangel. „Interaction of Squid (Dosidicus giga) Mantle Protein with a Mixtures of Potato and Corn Starch in an Extruded Snack, as Characterized by FTIR and DSC“. Molecules 26, Nr. 7 (06.04.2021): 2103. http://dx.doi.org/10.3390/molecules26072103.
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The majority of snacks expanded by extrusion (SEE) are made with vegetable sources, to improve their nutritional content; it has been proposed to incorporate squid (Dosidicus gigas), due to its high protein content, low price and high availability. However, the interaction of proteins of animal origin with starch during extrusion causes negative effects on the sensory properties of SEE, so it is necessary to know the type of protein–carbohydrate interactions and their effect on these properties. The objective of this research was to study the interaction of proteins and carbohydrates of SEE elaborated with squid mantle, potato and corn. The nutritional composition and protein digestibility were evaluated, Fourier transform infrared (FTIR) and Differential Scanning Calorimetry (DSC) were used to study the formation of protein–starch complexes and the possible regions responsible for their interactions. The SEE had a high protein content (40–85%) and biological value (>93%). The melting temperature (Tm) was found between 145 and 225 °C; the Tm values in extruded samples are directly proportional to the squid content. The extrusion process reduced the amine groups I and II responsible for the protein–protein interaction and increased the O-glucosidic bonds, so these bonds could be responsible for the protein–carbohydrate interactions.
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Bakhchevnikov, Oleg, und Sergey Braginets. „Extrusion of Plant Raw Materials in Food Production: A Review“. Food Processing: Techniques and Technology 50, Nr. 4 (30.12.2020): 690–706. http://dx.doi.org/10.21603/2074-9414-2020-4-690-706.
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Introduction. The present review covers the issues of extrusion of plant raw materials in food industry. The authors analyzed foreign publications about various extrusion technologies, their rational parameters, and their effect on the properties of final products. Study objects and methods. The research featured extrusion methods of plant raw materials in food production. The review included scientific articles published in English in 2000–2020.
Results and discussion. Extrusion is an effective processing method for plant raw materials in food industry. The analysis made it possible to define the effect of extrusion parameters on the components of plant raw materials. Extrusion increases digestibility of such plant components as protein and starch. High temperature, speed, and moisture are the optimal parameters for extrusion. High barrel temperature has a negative effect on vitamin and carotene content, while feed rate and screw speed are not important. Extrusion leads to complete mycotoxins reduction at critical temperatures. While high temperature and screw speed are important for process efficiency, they have a negative effect on the nutritional value of the final product.
Conclusion. Optimal parameters of various raw materials and their compounds remain largely understudied, in spite of the fact that they are responsible for the balance between the required extrudate properties and nutritional value. Formation of nutrient complexes and their effect on the process parameters also require further research, especially in regard with protein-carbohydrate and amylaselipid complexes. In general, extrusion of plant raw materials remains a promising but largely neglected research topic in food science.
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Rodak, Kinga, Dariusz Kuc und Tomasz Mikuszewski. „Superplastic Deformation of Al–Cu Alloys after Grain Refinement by Extrusion Combined with Reversible Torsion“. Materials 13, Nr. 24 (18.12.2020): 5803. http://dx.doi.org/10.3390/ma13245803.
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The binary as-cast Al–Cu alloys Al-5%Cu, Al-25%Cu, and Al-33%Cu (in wt %), composed of the intermetallic θ-Al2Cu and α-Al phases, were prepared from pure components and were subsequently severely plastically deformed by extrusion combined with reversible torsion (KoBo) to refinement of α-Al and Al2Cu phases. The extrusion combined with reversible torsion was carried out using extrusion coefficients of λ = 30 and λ = 98. KoBo applied to the Al–Cu alloys with different initial structures (differences in fraction and phase size) allowed us to obtain for alloys (Al-25%Cu and Al-33%Cu), with higher value of intermetallic phase, large elongations in the range of 830–1100% after tensile tests at the temperature of 400 °C with the strain rate of 10−4 s−1. The value of elongation depended on extrusion coefficient and increase, with λ increasing as a result of α-Al and Al2Cu phase refinement to about 200–400 nm. Deformation at the temperature of 300 °C, independently of the extrusion coefficient (λ), did not ensure superplastic properties of the analyzed alloys. A microstructural study showed that the mechanism of grain boundary sliding was responsible for superplastic deformation.
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Akhtar, S. S., Abul Fazal M. Arif und A. K. Sheikh. „Influence of Billet Quality on Hot Extrusion Die Life and its Relationship with Process Parameters“. Advanced Materials Research 83-86 (Dezember 2009): 866–73. http://dx.doi.org/10.4028/www.scientific.net/amr.83-86.866.
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Apart from other factors such as die design and manufacturing, heat treatment, working conditions etc, performance of hot extrusion die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die life based on microstructural and statistical analyses. In microstructural investigation, secondary (remelt) billet cast in-house at local extrusion plant is compared with primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). The statistical study is based on the failure history of some 53 hollow-profile dies in which the effect of billet quality on various measurable process parameters including extrusion ratio, billet temperature, exit temperature and repeated nitriding is analysed and related with useful die service life. Comparatively coarse grain structure, non-homogeneous distribution of secondary phases, and high hardness in the case of secondary billet were found responsible for poor die performance as observed in statistical investigation of failed dies. Two types of regression models are also proposed for prediction of die life in terms of secondary billets’ usage and measurable influencing parameters. Using current results, some suggestions during in-house billet preparation of secondary billets have been devised for improved die life.
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Lomovskaya, O., F. Kawai und A. Matin. „Differential regulation of the mcb and emr operons of Escherichia coli: role of mcb in multidrug resistance.“ Antimicrobial Agents and Chemotherapy 40, Nr. 4 (April 1996): 1050–52. http://dx.doi.org/10.1128/aac.40.4.1050.
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The mcb operon (which is responsible for microcin B17 production) and the emr operon (which encodes a multidrug resistance pump) share a common negative regulator, EmrR. Nevertheless, compounds that induce the emr operon repress the mcb operon. The pump dedicated to microcin B17 extrusion can also protect the calls against sparfloxacin and other toxic compounds.
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Hoffmann, Reinhard W., Wolfgang Barth, Reinhard Schüttler und Bernhard Mayer. „Carbene reactions, XX. Structural Aspects Responsible for the Thermal Extrusion of Carbenes from Norbornadienes“. Chemische Berichte 119, Nr. 11 (November 1986): 3297–315. http://dx.doi.org/10.1002/cber.19861191110.
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Carrasco, Félix, Orlando Santana Pérez, Noel León Albiter und Maria Lluïsa Maspoch. „Improvement of the Thermal Stability of Polymer Bioblends by Means of Reactive Extrusion“. Polymers 15, Nr. 1 (27.12.2022): 105. http://dx.doi.org/10.3390/polym15010105.
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Poly(lactic acid) (PLA) and biosourced polyamide (PA) bioblends, with a variable PA weight content of 10–50%, were manufactured by melt blending in order to improve the behavior of PLA against thermal degradation. The effect of reactive extrusion on the thermal performance of PLA within bioblends was analyzed. The reactive extrusion was made by means of the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE), with the commercial name of Joncryl. Four parameters were considered in order to study the thermal behavior of bioblends against thermal decomposition: the onset decomposition temperature, the shape and temperature interval of the thermal decomposition patterns, the activation energy of the thermal decomposition, and the evidence leading to the most probable mechanism. The latter was determined by means of three evidence: standardized conversion functions, y(α) master plots, and integral mean error. It was shown that reactive extrusion of PLA as well as PA incorporation to the polymer matrix of PLA were responsible for an increase in the onset decomposition temperature of 10.4 °C. The general analytical equation (GAE) was used to evaluate the kinetic parameters of the thermal degradation of PLA within bioblends for various reaction mechanisms. It was shown that the random scission of macromolecular chains is the best mechanism for both untreated and treated PLA by means of reactive extrusion. It was shown that reactive extrusion together with higher content of PA resulted in an increased protective effect against the thermal degradation of PLA as demonstrated by an increase in activation energy of 60 kJ/mol. It was found that there is a relationship between the increase in activation energy and the increase in the onset decomposition temperature when using reactive extrusion. The improvement of the thermal stability of bioblends by means of reactive extrusion was explained by an increase in the complex viscosity from 980 to 2000 Pa·s at 0.06 rad/s and from 250 to 300 Pa·s at 630 rad/s for bioblend containing 30% of PLAREX and by a finer dispersion of PA within the PLAREX matrix. Results from DSC were not conclusive regarding the compatibility between both phases.
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Tanaka, K., M. Akayama, A. Yamamoto, K. Omori und Y. Tashiro. „Quantitative immunoelectron microscopic localization of (Na+,K+)ATPase on rat exocrine pancreatic cells.“ Journal of Histochemistry & Cytochemistry 35, Nr. 6 (Juni 1987): 675–82. http://dx.doi.org/10.1177/35.6.3033064.
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Distribution of (Na+,K+)ATPase in rat exocrine pancreatic cells was investigated quantitatively by immunoelectron microscopy using the post-embedding protein A-gold technique. We found that in acinar and duct cells (Na+,K+)ATPase exists on both the luminal and the basolateral surfaces, with higher particle density on the luminal surface (4.4 times in the acinar cells and 5.6 times in the duct cells). According to Bolender (J Cell Biol 61:269, 1974), the luminal surface represents only 5% of the total cell surface of an average pancreatic acinar cell. It is roughly estimated, therefore, that approximately 80% of the plasma membrane (Na+,K+)ATPase in the acinar cells exists on the basolateral surface. When the acinar and duct cells were compared, more than twice as many particles were found on acinar cells than on duct cells. The enzyme existed on all the cell surfaces, preferentially on the microvilli or on the cell membrane folds, and no clustering was detected. We suggest that the (Na+,K+)ATPase on the basolateral surface is mainly responsible for the extrusion of a large number of sodium ions that are incorporated into the cytoplasm accompanying the secondary active transport of various organic substances and inorganic ions, whereas that on the luminal surface is responsible for active extrusion of sodium ions that are partially responsible for the fluid secretion of the pancreatic cells.
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Wittek, Patrick, Nicole Zeiler, Heike P. Karbstein und M. Azad Emin. „High Moisture Extrusion of Soy Protein: Investigations on the Formation of Anisotropic Product Structure“. Foods 10, Nr. 1 (06.01.2021): 102. http://dx.doi.org/10.3390/foods10010102.
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The high moisture extrusion of plant proteins is well suited for the production of protein-rich products that imitate meat in their structure and texture. The desired anisotropic product structure of these meat analogues is achieved by extrusion at high moisture content (>40%) and elevated temperatures (>100 °C); a cooling die prevents expansion of the matrix and facilitates the formation of the anisotropic structure. Although there are many studies focusing on this process, the mechanisms behind the structure formation still remain largely unknown. Ongoing discussions are based on two very different hypotheses: structure formation due to alignment and stabilization of proteins at the molecular level vs. structure formation due to morphology development in multiphase systems. The aim of this paper is, therefore, to investigate the mechanism responsible for the formation of anisotropic structures during the high moisture extrusion of plant proteins. A model protein, soy protein isolate, is extruded at high moisture content and the changes in protein–protein interactions and microstructure are investigated. Anisotropic structures are achieved under the given conditions and are influenced by the material temperature (between 124 and 135 °C). Extrusion processing has a negligible effect on protein–protein interactions, suggesting that an alignment of protein molecules is not required for the structure formation. Instead, the extrudates show a distinct multiphase system. This system consists of a water-rich, dispersed phase surrounded by a water-poor, i.e., protein-rich, continuous phase. These findings could be helpful in the future process and product design of novel plant-based meat analogues.
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Rodak, Kinga, und Krzysztof Radwański. „Microstructure Formation in Austenitic Steel after Compression with Oscillatory Torsion Test“. Solid State Phenomena 163 (Juni 2010): 110–13. http://dx.doi.org/10.4028/www.scientific.net/ssp.163.110.
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Different techniques have been used to introduce large strains into metals, for example torsion under pressure (HPT), cyclic extrusion compression (CEC), equal channel angular extrusion (ECAE), or accumulative roll bonding (ARB). Recent investigations are focused on analyzing new and alternative techniques for introducing severe plastic deformation (SPD) and to compare SPD techniques in terms of grain refinement and enhancement of properties. Compression with oscillatory torsion was applied to 0H18N9 austenitic steel to achieve a large strains. The microstructure was characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Formation of deformation twins and shear bands are responsible for the structure refinement in materials with low stacking fault energies (SFEs) such as austenitic steel. The investigations revealed, that nano-sized grains of 0H18N9 steel after processing by compression with oscillatory torsion are found in three different types of regions.
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Leiva, Molina, Redondo-Solano, Artavia, Rojas-Bogantes und Granados-Chinchilla. „Pet Food Quality Assurance and Safety and Quality Assurance Survey within the Costa Rican Pet Food Industry“. Animals 9, Nr. 11 (15.11.2019): 980. http://dx.doi.org/10.3390/ani9110980.
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Costa Rican animal feed production is continually growing, with approximately 1,238,243 metric tons produced in 2018. Production-wise, pet cat and dog food are in fifth place (about 41,635 metric tons per year) amongst animal feeds, and it supplies up to 90% of the national market. Pet food production has increased as a response to the increase in the population of dogs and cats in Costa Rica, where 50.5% of households own at least one dog and indicates more responsible ownership in terms of feeding pets. Part of the process of making dry pet food involves a thermal process called extrusion, which is capable of eliminating the microbial load. However, extrusion can compromise nutritional quality to some extent by denaturing proteins, oxidizing lipids, and reducing digestibility. The objective of this study was to evaluate the quality and safety of dry pet food and to assess the effect of the extrusion process on digestibility and the quality of proteins, amino acids, and fatty acids. Pet food samples were collected before and after extrusion and were used to evaluate Good Manufacturing Practices (GMP), based on Central American Technical Regulation (RTCA 65.05.63:11). In general terms, weaknesses in infrastructure, documentary evidence, and post-process practices were observed in two Costa Rican feed manufactories. Feed safety was surveyed through the analysis of Salmonella spp., Escherichia coli, Listeria spp., Staphylococcus aureus, aerobic mesophilic microorganisms, fungi, and yeasts counts. The extrusion process effectively reduced pathogenic microorganisms, and showed no effect on the digestibility of dog food (p = 0.347), however, it could reduce the availability of some nutrients (e.g., amino acids, fatty acids). Furthermore, a retrospective diagnosis was made for puppy food (n = 68), dog food (n = 158), and cat food (n = 25), to evaluate the history of nutritional quality and safety. Finally, it can be confirmed that the correct implementation of GMP allows feed manufacturers to deliver a product of optimum texture, smell, nutritional composition, and safety.