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Corrosion testing of stents: a novel fixture to hold entire device in deployed form and finish. 支架的腐蚀测试:一种新颖的夹具,以保持整个设备的部署形式和完成。
Pub Date : 1999-01-01 DOI: 10.1002/(sici)1097-4636(1999)48:6<829::aid-jbm10>3.0.co;2-#
R Venugopalan

Stainless steel and nickel-titanium alloy stents for cardiac, biliary, and prostatic clinical applications may be susceptible to loss of mechanical integrity/failure due to their small size and unique geometry. Because their corrosion behavior is a critical aspect of their biocompatibility, it is necessary to test such devices for corrosion behavior using a final deployed form and finish condition. Welding wire leads or holding with metallic clips can result in surface variability or damage to the stents. A novel fixture to hold stents for corrosion testing was designed and evaluated in this study. This fixture design minimally influenced the properties of stents, and also facilitated easy removal post-testing for other types of characterization.

不锈钢和镍钛合金支架用于心脏、胆道和前列腺的临床应用,由于其小尺寸和独特的几何形状,可能容易失去机械完整性/失效。由于它们的腐蚀行为是其生物相容性的一个关键方面,因此有必要使用最终部署形式和完成条件来测试这些设备的腐蚀行为。焊丝引线或金属夹夹会导致支架表面变化或损坏。本研究设计并评估了一种用于支架腐蚀测试的新型夹具。这种夹具设计对支架性能的影响最小,并且便于在其他类型的表征测试后轻松移除。
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引用次数: 31
Fatigue behavior of calcium phosphate coatings with different stability under dry and wet conditions. 干湿条件下不同稳定性磷酸钙涂层的疲劳行为。
Pub Date : 1999-01-01 DOI: 10.1002/(sici)1097-4636(1999)48:5<741::aid-jbm21>3.0.co;2-#
J A Clemens, J G Wolke, C P Klein, K de Groot

To obtain stable plasma sprayed calcium phosphate coatings, coatings with a high crystallinity and low solubility were developed. However, stability of ceramic coatings is also influenced by their fatigue resistance. Recently, fatigue failure was proposed to explain coating detachment from implants under loaded conditions. Therefore, plasma-sprayed calcium phosphate coatings with different crystallinity were investigated in vitro for fatigue failure. An amorphous and a crystalline hydroxylapatite coating (AHA and CHA) and a highly crystalline fluorapatite coating (FA) were subjected to cyclic load tests, both in dry conditions and in simulated body fluid (SBF). The results in SBF revealed that the crystalline CHA and FA coating detached completely at the highest stressed middle section of the bar. The FA coating delaminated earlier than the CHA coating. The amorphous AHA coating showed only partial coating loss at the completion of the test. Tests in dry conditions did not reveal any change in the coatings tested. These results suggest a relation between crystallinity of apatite coatings and their failure due to fatigue: high crystallinity coatings demonstrate earlier and more complete fatigue failure than the amorphous apatite coatings. It can be concluded that coating stability is not determined solely by static dissolution, but by fatigue failure as well.

为了获得稳定的等离子喷涂磷酸钙涂层,开发了高结晶度、低溶解度的涂层。然而,陶瓷涂层的稳定性也受到其抗疲劳性能的影响。最近,疲劳失效被用来解释植入物在载荷条件下涂层脱落的原因。为此,对不同结晶度的等离子喷涂磷酸钙涂层进行了体外疲劳失效研究。非晶和结晶羟基磷灰石涂层(AHA和CHA)和高结晶氟磷灰石涂层(FA)在干燥条件和模拟体液(SBF)中进行了循环载荷试验。SBF结果表明,结晶CHA和FA涂层在棒材的最高应力中部完全分离。FA涂层比CHA涂层更早分层。在测试结束时,非晶AHA涂层仅显示出部分涂层损失。在干燥条件下的测试没有发现涂层有任何变化。这些结果表明了磷灰石涂层的结晶度与其疲劳失效之间的关系:高结晶度涂层比非晶态磷灰石涂层表现出更早和更彻底的疲劳失效。可以得出结论,涂层的稳定性不仅取决于静态溶解,还取决于疲劳破坏。
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引用次数: 27
Real-time dissolution measurement of sized and unsized calcium phosphate glass fibers. 施胶和未施胶磷酸钙玻璃纤维的实时溶解测定。
Pub Date : 1999-01-01 DOI: 10.1002/(sici)1097-4636(1999)48:6<833::aid-jbm11>3.0.co;2-#
J D Rinehart, T D Taylor, Y Tian, R A Latour

The objective of this study was to develop an efficient "real time" measurement system able to directly measure, with microgram resolution, the dissolution rate of absorbable glass fibers, and utilize the system to evaluate the effectiveness of silane-based sizing as a means to delay the fiber dissolution process. The absorbable glass fiber used was calcium phosphate (CaP), with tetramethoxysilane selected as the sizing agent. E-glass fiber was used as a relatively nondegrading control. Both the unsized-CaP and sized-CaP degraded linearly at both the 37 degrees C and 60 degrees C test temperature levels used. No significant decrease in weight-loss rate was recorded when the CaP fiber tows were pretreated, using conventional application methods, with the tetramethoxysilane sizing for either temperature condition. The unsized-CaP and sized-CaP weight loss rates were each significantly higher at 60 than at 37 degrees C (both p < 0.02), as expected from dissolution kinetics. In terms of actual weight loss rate measured using our system for phosphate glass fiber, the unsized-CaP fiber we studied dissolved at a rate of 10.90 x 10(-09) and 41.20 x 10(-09) g/min-cm(2) at 37 degrees C and 60 degrees C, respectively. Considering performance validation of the developed system, the slope of the weight loss vs. time plot for the tested E-glass fiber was not significantly different compared to a slope equal to zero for both test temperatures.

本研究的目的是开发一种高效的“实时”测量系统,能够直接测量可吸收玻璃纤维的溶解速率,以微克分辨率,并利用该系统来评估硅烷基施胶作为延迟纤维溶解过程的手段的有效性。所采用的可吸收玻璃纤维为磷酸钙(CaP),选用四甲基氧基硅烷作为施胶剂。采用e -玻璃纤维作为相对不降解的对照剂。未上浆的cap和上浆的cap在37℃和60℃的测试温度水平下都呈线性退化。采用常规的应用方法对CaP纤维束进行预处理,并在两种温度条件下使用四甲基氧基硅烷施胶,其失重率均未显著降低。未上浆的cap和上浆的cap失重率在60℃时都明显高于37℃(p < 0.02),这与溶解动力学的预期一致。在使用我们的系统测量磷酸盐玻璃纤维的实际失重率方面,我们研究的未上浆的cap纤维在37℃和60℃下分别以10.90 x 10(-09)和41.20 x 10(-09) g/min-cm(2)的速率溶解。考虑到所开发系统的性能验证,与两种测试温度下的斜率等于零相比,被测e -玻璃纤维的失重与时间图的斜率没有显著差异。
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引用次数: 28
In vitro elution of vancomycin from biodegradable beads. 万古霉素在生物可降解微球中的体外洗脱。
Pub Date : 1999-01-01 DOI: 10.1002/(sici)1097-4636(1999)48:5<613::aid-jbm4>3.0.co;2-#
S J Liu, S W Ueng, E C Chan, S S Lin, C H Tsai, F C Wei, C H Shih

The current antibiotics delivery system for orthopedic infection treatment uses polymethylmethacrylate (PMMA) beads as a drug release. However the nonbiodegradable nature of the PMMA necessitates a second operation to remove the beads. This article explores the alternative of using biodegradable polymers as antibiotic beads for a long-term drug release. The effect of different processing factors on the release rate of the beads was investigated. To manufacture an antibiotic bead, polylactide-polyglycolide copolymers were mixed with vancomycin. The mixture was compressed and sintered at 55 degrees C to form beads of different sizes. An elution method was employed to characterize the release rate of antibiotic over a 35-day period at 37 degrees C. Biodegradable beads released high concentrations of antibiotic (well above the breakpoint sensitivity concentration) in vitro for the period of time needed to treat bone infection; i.e., 4-6 weeks. A bacterial inhibition test was carried out to determine the relative activity of the released antibiotics. The diameter of the sample inhibition zone ranged from 6.5-10 mm, which is equivalent to 12.5-100% of relative activity. By changing the processing parameters, we were able to control the release rate of the beads. This provides advantages of meeting the specific antibiotics requirement for patients with various surgical infections.

目前用于骨科感染治疗的抗生素递送系统使用聚甲基丙烯酸甲酯(PMMA)微球作为药物释放。然而,PMMA的不可生物降解性质需要第二次手术来去除珠子。这篇文章探讨了使用生物可降解聚合物作为抗生素珠长期药物释放的替代方案。考察了不同工艺条件对微球释放速度的影响。将聚乳酸-聚乙醇酸共聚物与万古霉素混合制备抗生素微球。将混合物压缩并在55℃下烧结,形成不同大小的珠子。采用洗脱法表征抗生素在37℃下35天内的释放率。可生物降解的微球在体外释放高浓度抗生素(远高于断点敏感浓度),用于治疗骨感染所需的一段时间;即4-6周。进行抑菌试验,测定所释抗生素的相对活性。样品抑制带直径为6.5 ~ 10 mm,相当于相对活性的12.5 ~ 100%。通过改变工艺参数,我们能够控制微球的释放速度。这为满足各种手术感染患者的特定抗生素需求提供了优势。
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引用次数: 47
Adhesion of different bacterial strains to low-temperature plasma-treated sutures. 不同细菌菌株对低温等离子处理缝合线的粘附。
Pub Date : 1998-09-05 DOI: 10.1002/(sici)1097-4636(19980905)41:3<349::aid-jbm2>3.3.co;2-z
A Yousefi Rad, H Ayhan, E Pişkin

In this study, five different bacteria with their different strains were isolated and characterized. Contact angles were measured by a captive-bubble technique. Surface-free energies were calculated from the contact angles. Hydrophobicities also were evaluated by rho-xylene adhesion. The zeta potentials and surface charges of the bacteria were obtained. The contact angles of the gram-positive bacteria and gram-negative bacteria were within the range of 48 degrees-69 degrees and 43.5 degrees-55 degrees, respectively, while corresponding surface-free energies were in the limits of 45.4-51.6 erg/cm-2 and 51.7-61.8 erg/cm-2, respectively. The rho-xylene adhesions were parallel to hydrophobicities defined by contact angles, and 32.2-80.3% and 2.3-36.6% for the gram-positive bacteria and gram-negative bacteria, respectively. The zeta potentials for these bacteria were from -650.2 to +17.5 mV and from -159.6 to -6.0 mV, respectively. Most of the bacteria were negatively charged, except the CNS-2 and CPS-1 strains. In the second part of the study, attachment of these bacteria to Vicryl sutures and their DMAEMA and AAc plasma-treated forms were investigated. Hydrophobic bacteria attached more to hydrophobic Vicryl sutures. Both plasma treatments caused significant drops in bacterial attachment in most cases. Effects of AAc plasma treatment were more pronounced.

在本研究中,分离了5种不同的细菌及其不同的菌株并对其进行了表征。接触角由俘获泡技术测量。根据接触角计算无表面能。疏水性也通过对二甲苯的粘附性进行了评价。得到了细菌的zeta电位和表面电荷。革兰氏阳性菌和革兰氏阴性菌的接触角分别在48°~ 69°和43.5°~ 55°范围内,对应的无表面能分别在45.4 ~ 51.6 erg/cm-2和51.7 ~ 61.8 erg/cm-2范围内。革兰氏阳性菌和革兰氏阴性菌的亲水性分别为32.2 ~ 80.3%和2.3 ~ 36.6%。这些细菌的zeta电位范围分别为-650.2 ~ +17.5 mV和-159.6 ~ -6.0 mV。除CNS-2和CPS-1菌株外,其余菌株均带负电。在研究的第二部分,研究了这些细菌在Vicryl缝合线上的附着以及它们的DMAEMA和AAc等离子体处理形式。疏水性细菌更多地附着在疏水性薇基缝合线上。在大多数情况下,两种血浆治疗都能显著降低细菌附着。AAc血浆治疗效果更明显。
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引用次数: 0
Effect of modification of oxide layer on NiTi stent corrosion resistance. 氧化层改性对NiTi支架耐蚀性的影响。
Pub Date : 1998-01-01 DOI: 10.1002/(sici)1097-4636(199824)43:4<433::aid-jbm11>3.0.co;2-#
C Trépanier, M Tabrizian, L H Yahia, L Bilodeau, D L Piron

Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement.

由于其良好的不透光性、超弹性和形状记忆性能,镍钛(NiTi)是制造支架的潜在材料,因为这些特性可以促进支架的植入和精确定位。然而,镍钛合金的体外研究报告了合金的生物相容性和腐蚀行为取决于表面条件。表面氧化在提高镍钛的耐蚀性和生物相容性方面具有广阔的应用前景。本文研究了电抛光、热处理和硝酸钝化对镍钛支架耐蚀性和表面特性的影响。表征技术,如电位极化测试、扫描电子显微镜、俄歇电子能谱和x射线光电子能谱被用来将腐蚀行为与表面特征和表面处理联系起来。结果表明,所有这些表面处理都提高了合金的耐蚀性。这种改进是由于塑性变形的原生氧化层被去除并被新生长的更均匀的氧化层所取代。氧化层的均匀性,而不是其厚度和成分,似乎是解释耐蚀性提高的主要因素。
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引用次数: 293
Ultrastructural features of the bone response to a plasma-sprayed hydroxyapatite coating in sheep. 羊骨对等离子喷涂羟基磷灰石涂层反应的超微结构特征。
J Hemmerlé, A Onçag, S Ertürk

The intentions of this study were to characterize the macroscopic, microscopic, and structural aspects of a plasma-sprayed implant and to thoroughly investigate bone tissue response after its implantation in sheep. Therefore, we used scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, and energy-dispersive X-ray analyses. Assessment of the biomaterial prior to implantation showed a coating with irregular outlines and varying thickness, mainly consisting of hydroxyapatite (HA) covering a rough metallic implant core. Six months after insertion of the HA-coated Ti-6A1-4V implant, neither mechanical failure of the coating-substrate interface nor a significant loss of coating thickness was evident. However, an occasional lack of HA coating and phagocytosis of HA particles were noted. More generally, the implant was surrounded by well-mineralized bone investing the smallest cavities of the plasma-sprayed layer. Newly formed microcrystals with size, shape, and structure similar to those of bone apatite crystals were growing directly at the coating surface. These results suggest that the bone-bonding behavior of the considered grooved implant should provide satisfactory osseointegration and be suitable for fixed prostheses.

本研究的目的是表征等离子喷涂植入物的宏观、微观和结构方面,并彻底研究其在绵羊体内植入后骨组织的反应。因此,我们使用了扫描电子显微镜、透射电子显微镜、高分辨率电子显微镜、x射线衍射和能量色散x射线分析。植入前对生物材料的评估显示,涂层具有不规则的轮廓和不同的厚度,主要由羟基磷灰石(HA)组成,覆盖在粗糙的金属植入物核心上。在植入ha涂层Ti-6A1-4V种植体6个月后,涂层-基底界面的机械失效和涂层厚度的显著损失都不明显。然而,偶尔缺乏透明质酸涂层和透明质酸颗粒的吞噬被注意到。更普遍的是,种植体被矿化良好的骨包围,覆盖等离子喷涂层的最小空腔。新形成的微晶体在涂层表面直接生长,其大小、形状和结构与骨磷灰石晶体相似。这些结果表明,所考虑的槽状种植体的骨结合行为应提供满意的骨整合,并适用于固定假体。
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引用次数: 0
TiO2-polymer composites for biomedical applications. 生物医学应用的二氧化钛聚合物复合材料。
J Peña, M Vallet-Regí, J San Román

Composite hydrogels of poly(acrylic acid) (PAA) and poly-(methyl metacrylate) (PMMA) reinforced with a bioceramic, TiO2, have been prepared by reactive moulding from a mixture of the bioceramic with PMMA beads and acrylic acid. Cylindrical specimens with various TiO2-polymer compositions, but a constant 3:1 PAA/PMMA ratio were obtained, and their corresponding swelling behavior was followed at pH = 7.0 and pH = 8.0 in buffered solution at 37 degrees C. The composition and structure of the composites prepared was studied by thermogravimetry, 1H-NMR spectroscopy and scanning electron microscopy. The composites prepared present a considerable consistency, even in hydrated media, since their swelling behavior is rather sensitive to the pH of the media. Specific polar interactions of the carboxylic groups of the hydrophilic polymer component PAA with the surface of TiO2 particles, modulate the behavior of the composites against the hydration processes at different pH.

以聚丙烯酸甲酯(PMMA)微珠和丙烯酸为原料,通过反应模塑法制备了生物陶瓷(TiO2)增强的聚丙烯酸(PAA)和聚甲基丙烯酸甲酯(PMMA)复合水凝胶。采用热重法、核磁共振波谱法和扫描电镜对制备的复合材料的组成和结构进行了研究,得到了具有不同tio2 -聚合物组成的圆柱形试样,但PAA/PMMA比例恒定为3:1,在37℃缓冲溶液中pH = 7.0和pH = 8.0时,其相应的膨胀行为。即使在水合介质中,所制备的复合材料也具有相当的一致性,因为它们的膨胀行为对介质的pH相当敏感。亲水聚合物组分PAA的羧基与TiO2颗粒表面的特定极性相互作用调节了复合材料在不同pH下对水化过程的行为。
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引用次数: 0
New radiopaque polyHEMA-based hydrogel particles. 新型不透射线多聚血红蛋白基水凝胶颗粒。
D Horák, M Metalová, F Rypácek

New iodine-containing polymeric hydrogel particles were prepared by suspension radical copolymerization of 2-hydroxyethyl methacrylate (HEMA), 3-(methacryloylamidoacetamido)-2,4,6-triiodobenzoic acid (MABA) and ethylene dimethacrylate (EDMA) in an aqueous medium using azobisisobutyronitrile as an initiator and magnesium hydroxide as a suspension stabilizer. To impart porosity to the product, cyclohexanol and 1-dodecanol were added as inert diluents to the polymerization mixture. Particles containing 27 wt % iodine produced radiopacity sufficient to observe a clearly visible X-ray image. The equilibrium swelling behavior of the particles in water was characterized. Swelling of the particles dramatically increased by converting the acid groups of MABA into their Na+ form. The more MABA the copolymer particle contain, the higher is their swelling in the Na+ form.

以偶氮二异丁腈为引发剂,氢氧化镁为悬浮稳定剂,以2-甲基丙烯酸羟乙酯(HEMA)、3-(甲基丙烯酰胺乙酰胺)-2,4,6-三碘苯甲酸(MABA)和二甲基丙烯酸乙酯(EDMA)为溶剂,在水介质中悬浮自由基共聚制备了新型含碘聚合物水凝胶颗粒。为了使产物具有孔隙度,在聚合混合物中加入了环己醇和1-十二醇作为惰性稀释剂。含有27wt %碘的颗粒产生的射线不透明度足以观察到清晰可见的x射线图像。对颗粒在水中的平衡膨胀行为进行了表征。通过将MABA的酸基团转化为Na+形式,颗粒的膨胀急剧增加。共聚物颗粒中MABA含量越多,其以Na+形式溶胀的程度越高。
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引用次数: 0
In vitro cell response to differences in poly-L-lactide crystallinity. 体外细胞对聚l -丙交酯结晶度差异的响应。
A Park, L G Cima

Many different processing techniques are currently being used to produce tissue regeneration devices from polyesters in the polylactide/polyglycolide family. While it is generally well recognized that processing techniques influence bulk mechanical and degradation properties of these materials, the effects on surface properties are relatively less well studied. We thus investigated the effects of processing conditions that are known to change bulk properties, but not composition, on the surface properties of poly-L-lactide (PLLA). Specifically, we investigated the role of bulk crystallinity of PLLA substrates on several physiochemical aspects of the surface and on the attachment, morphology, and differentiated function of cultured primary hepatocytes and growth of 3T3 fibroblasts. We fabricated smooth, clear PLLA films of 13-37% crystallinity. Glancing angle X-ray diffraction indicated that low crystallinity films lacked order in the first 50 A of the surface while relatively high crystallinity films had detectable order in this range. In other aspects, the surfaces of all PLLA substrates appeared identical with XPS, SEM, and advancing contact angle analysis, but contact angle hysteresis was slightly greater for more crystalline films. Although the physicochemical properties of the surfaces appeared almost identical, we observed differences in cell behavior on less crystalline versus more crystalline films. Hepatocytes formed spheroids on all PLLA substrates, but spheroid formation was faster (24-48 H) on crystalline substrates. quantitative image analysis was used to assess the average cell area as a function of time in culture, and our data confirm previous reports that retention of differentiated function is inversely related to cell spreading where function was assessed by P-450 enzyme activity. In addition, the growth rate of 3T3 fibroblasts was lower on crystalline substrates than on amorphous substrates. An important conclusion from this work is that processing techniques that lead to seemingly inconsequential changes in bulk and surface properties of these polymers may influence biological response.

目前,许多不同的加工技术被用于从聚丙交酯/聚乙二醇酯家族的聚酯中生产组织再生装置。虽然人们普遍认识到加工技术会影响这些材料的整体机械和降解性能,但对其表面性能的影响研究相对较少。因此,我们研究了已知会改变体积性质而不是组成的加工条件对聚l -丙交酯(PLLA)表面性质的影响。具体来说,我们研究了PLLA底物的大块结晶度在表面的几个物理化学方面的作用,以及在培养的原代肝细胞的附着、形态和分化功能以及3T3成纤维细胞的生长方面的作用。我们制备了光滑、透明的PLLA薄膜,结晶度为13-37%。扫角x射线衍射表明,低结晶度的薄膜在表面的前50 A处缺乏秩序,而相对高结晶度的薄膜在这一范围内可以检测到秩序。在其他方面,所有PLLA衬底表面与XPS, SEM和推进接触角分析相同,但接触角滞后略大于更多的晶体膜。虽然表面的物理化学性质几乎相同,但我们观察到在少晶和多晶薄膜上细胞行为的差异。肝细胞在所有PLLA底物上形成球形,但在结晶底物上形成球形更快(24-48 H)。定量图像分析用于评估平均细胞面积作为培养时间的函数,我们的数据证实了先前的报道,即分化功能的保留与细胞扩散呈负相关,其中功能是通过P-450酶活性评估的。此外,3T3成纤维细胞在结晶基质上的生长速率低于在非晶态基质上的生长速率。这项工作的一个重要结论是,导致这些聚合物的体积和表面特性发生看似无关紧要的变化的加工技术可能会影响生物反应。
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引用次数: 0
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Journal of biomedical materials research
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