rheology

流变学
  • 文章类型: Journal Article
    食品增稠剂通常用于制备用于治疗吞咽困难的增稠液体。已知用商业食品增稠剂制备的增稠液体的国家吞咽困难饮食(NDD)厚度水平根据增稠剂类型而变化。增稠剂的推荐量,增稠剂品牌,和准备说明。特别是,制造商必须提供详细的准备说明,以达到正确的厚度水平。然而,制造商提供的产品标签上的流变信息通常不准确。这里,根据制造商的指南,通过混合商业黄原胶(XG)基增稠剂来制备各种布丁粘稠液体,并对其流变特性进行了表征。在韩国销售的四种不同的基于XG的增稠剂(A-D)制备的几种增稠液体不符合基于NDD指南的类似布丁的标准(>1,750mPa·s)。流变参数值的显著差异(ηa,50,n,和G\')也在各种增稠液体中被发现。只有一种在韩国制造的增稠剂(增稠剂A)显示出最佳结果,与其他增稠剂相比,它满足了各种食品液体的布丁稠度粘度范围,并且还显示出较低的粘性和增强的丸剂形成能力,可轻松安全地吞咽(B,C,andD).
    Food thickeners are commonly used to prepare thickened liquids for the management of dysphagia. The National Dysphagia Diet (NDD) thickness levels of thickened liquids prepared with commercial food thickeners are known to vary depending on the thickener type, recommended amount of thickener, thickener brand, and preparation instructions. Particularly, detailed preparation instructions must be provided by the manufacturers to achieve the correct thickness levels. However, the rheological information on product labels provided by manufacturers is typically not accurate. Here, various pudding-thick liquids were prepared by mixing commercial xanthan gum (XG)-based thickeners based on the manufacturers\' guidelines, and their rheological properties were characterized. Several thickened liquids prepared with four different XG-based thickeners (A-D) marketed in Korea did not meet the pudding-like criterion (> 1,750 mPa·s) based on the NDD guidelines. Significant differences in rheological parameter values (ηa,50, n, and G\') were also identified among the various thickened liquids. Only one thickener (thickener A) manufactured in Korea showed optimal results, which satisfied the pudding-thick viscosity range for various food liquids and also showed lower stickiness and enhanced bolus formation ability for easy and safe swallowing when compared to other thickeners (B, C, and D).
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  • 文章类型: Journal Article
    半固体在市场上可获得的局部药物剂型中占很大比例,面霜被认为是释放活性物质进入皮肤的有利可图的系统。这项工作旨在开发一种通用的克霉唑外用乳膏,基于有助于开发此类配方的假设。首先,定义了获得与参比产品尽可能相似的最终制剂的关键参数。然后,棕榈酸十六烷基酯和辛基十二烷醇的百分比被确定为关键变量,并在进一步的研究中选择进行优化。然后使用“设计质量”方法从定性(Q1)和定量(Q2)上确定过程可变性对通用产品的结构和功能相似性(Q3)的影响。应用了双因素中心复合正交设计,开发了11种不同的配方,并进行了物理化学表征和产品性能研究。结果用于估计两个变量在响应变化中的影响,并确定测试因素的最佳点,使用设计空间的方法。最后,获得了优化的配方,并与参考平行进行了分析。获得的结果与化学计量学分析的预测一致,验证开发的多变量模型的可靠性。参考和通用制剂的体外释放和渗透结果相似,支持将微观结构性能与产品性能和稳定性相互作用的重要性。最后,基于质量目标和响应约束,成功实现了最佳工作条件。
    Semisolids constitute a significant proportion of topical pharmaceutical dosage forms available on the market, with creams being considered profitable systems for releasing active substances into the skin. This work aimed at the development of a generic Clotrimazole topical cream, based on the assumptions that assist the development of such formulations. First, the critical parameters to obtain a final formulation as similar as possible to the reference product were defined. Then, the percentages of cetyl palmitate and octyldodecanol were identified as critical variables and chosen for optimization in further studies. A \"quality by design\" approach was then used to identify the effect of process variability on the structural and functional similarity (Q3) of the generic product qualitatively (Q1) and quantitatively (Q2). A two-factor central composite orthogonal design was applied and eleven different formulations were developed and subjected to physicochemical characterization and product performance studies. The results were used to estimate the influence of the two variables in the variation of the responses, and to determine the optimum point of the tested factors, using a design space approach. Finally, an optimized formulation was obtained and analysed in parallel with the reference. The obtained results agreed with the prediction of the chemometric analysis, validating the reliability of the developed multivariate models. The in vitro release and permeation results were similar for the reference and the generic formulations, supporting the importance of interplaying microstructure properties with product performance and stability. Lastly, based on quality targets and response constraints, optimal working conditions were successfully achieved.
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  • 文章类型: Journal Article
    这项研究旨在评估香港一家主要增稠剂制造商提供的现有液体增稠指南,并为实施IDDSI框架提供指导。15名对液体增稠幼稚的参与者被要求从三种饮料基料中制备增稠的液体样品(即,奶茶,中国茶,和凉茶)在两个目标稠度水平(即,轻度和中等/中等厚度)基于两个准则(即,制造商指南和IDDSI驱动指南)。用流变学方法测量样品的粘度以反映液体稠度。制造商指南在两种稠度水平下产生了可区分的粘度(F(1,35.464)=113.764,p<0.001,ηp2=0.802),以及不同饮料基料的不同粘度(F(1.267,35.464=92.951,p<0.001,ηp2=0.769)。制造商和IDDSI驱动的指南之间的比较表明,后者导致所有饮料基料和两种稠度水平的液体样品更粘稠。两种指南之间的差异具有统计学意义(F(1,28)=35.137,p<0.001,ηp2=0.557)。当浓缩非水饮料时,仅遵循制造商的指南可能会导致所得稠度与规定稠度之间的差异。因此,它应该被认为不足以确保吞咽安全。应向患者和护理人员强调饮料基质的作用,并且应该引入服务前测试。尽管在当前的本地框架和IDDSI框架之间使用了类似的分类和术语,应采取措施避免潜在的混淆和吞咽安全的相关威胁。
    This study aimed to evaluate an existing liquid-thickening guideline provided by a major manufacturer of thickener in Hong Kong and to provide directions for the implementation of the IDDSI framework. Fifteen participants who are naïve to liquid thickening were required to prepare thickened liquids samples from three drink bases (i.e., Milk-tea, Chinese tea, and Herbal tea) at two target consistency levels (i.e., mildly and medium/moderately thick) based on two guidelines (i.e., the manufacturer\'s guideline and an IDDSI-driven guideline). Viscosities of the samples were measured rheologically to reflect liquid consistency. The manufacturer\'s guideline resulted in distinguishable viscosities at the two consistency levels (F(1, 35.464) = 113.764, p < 0.001, ηp2 = 0.802), as well as different viscosities in different drink bases (F(1.267, 35.464 = 92.951, p < 0.001, ηp2 = 0.769). Comparison between the manufacturer\'s and the IDDSI-driven guideline showed that the later resulted in more viscous liquid samples in all drink bases and at both consistency levels. The difference between the two guidelines was statistically significant (F(1,28) = 35.137, p < 0.001, ηp2 = 0.557). Following only the manufacturer\'s guideline when thickening non-water beverages may lead to discrepancy between the resultant and prescribed consistencies. Thus, it should be considered inadequate to ensure swallowing safety. The effect of drink base should be emphasized to patients and caregivers, and pre-serving tests should be introduced. Despite similar classifications and terminologies used between the current local framework and the IDDSI framework, measures should be taken to avoid potential confusions and associated threats to swallowing safety.
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  • 文章类型: Journal Article
    技术和仪器的兴起使更多的实验室和诊所能够进行与组织粘弹性特性相关的各种测量。这些仪器包括弹性成像扫描仪,流变剪切粘度计,和各种校准应力应变分析仪。从这些不同的数据来源,分析结果的一个常见步骤是将组织反应的测量值拟合到一些粘弹性模型。在最好的情况下,这将测量结果置于理论框架内,并能够将参数与其他类型的组织进行有意义的比较.然而,建立了大量的流变模型,即使在线性类,因果关系,粘弹性固体模型,Sowhichoftheseshouldbechosen?Isitsimplyamatterofbestfittoaminimummeansquarederrorofthemodeltoseveraldatapoints?Wearguethatthelonghistoryofbiomechanics,包括扩展弛豫谱的概念,以及从粘弹性软组织收集的数据在更大的时间和频率范围内,以及对物理组织的多尺度性质进行建模的多松弛模型的理论框架,所有得出的结论是,分数阶导数模型代表了最简洁和有意义的软组织粘弹性行为模型。提出这些论点的目的是澄清两者之间的一些区别,以及后果,一些最常用的模型,长期目标是在声学的不同子领域之间达成共识,生物力学,和弹性成像在比较组织测量结果方面有共同利益。
    A rising wave of technologies and instruments are enabling more labs and clinics to make a variety of measurements related to tissue viscoelastic properties. These instruments include elastography imaging scanners, rheological shear viscometers, and a variety of calibrated stress-strain analyzers. From these many sources of disparate data, a common step in analyzing results is to fit the measurements of tissue response to some viscoelastic model. In the best scenario, this places the measurements within a theoretical framework and enables meaningful comparisons of the parameters against other types of tissues. However, there is a large set of established rheological models, even within the class of linear, causal, viscoelastic solid models, so which of these should be chosen? Is it simply a matter of best fit to a minimum mean squared error of the model to several data points? We argue that the long history of biomechanics, including the concept of the extended relaxation spectrum, along with data collected from viscoelastic soft tissues over an extended range of times and frequencies, and the theoretical framework of multiple relaxation models which model the multi-scale nature of physical tissues, all lead to the conclusion that fractional derivative models represent the most succinct and meaningful models of soft tissue viscoelastic behavior. These arguments are presented with the goal of clarifying some distinctions between, and consequences of, some of the most commonly used models, and with the longer term goal of reaching a consensus among different sub-fields in acoustics, biomechanics, and elastography that have common interests in comparing tissue measurements.
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  • 文章类型: Journal Article
    Hyaluronic acid (HA) fillers are the most commonly used fillers for soft-tissue augmentation. The face is a dynamic structure. Facial rejuvenation by filler products depends on mechanical forces on the region of the face. The successful use of injectable HA fillers requires an understanding of the options available.
    The purpose of this study is to measure the rheological properties of HA fillers and to clarify how to select these fillers considering their rheological properties.
    Rheological characterization was performed on 41 fillers. Physical parameters directly linked to product performance were measured.
    The properties of the HA fillers varied. These findings provide a basis for selection guideline regarding rheological properties in facial rejuvenation.
    The authors\' report is the largest study to determine the rheological properties of HA fillers to date. Understanding the fillers\' properties can help physicians select the appropriate fillers for more predictable and sustainable results.
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  • 文章类型: Journal Article
    Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.
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  • 文章类型: Comparative Study
    Post-dilution on-line hemodiafiltration (OL-HDF) is the most efficient infusion mode to obtain maximum clearances of uremic toxins, with a recommended manual infusion flow (Qi) of 25% of the blood flow with the main limitation that causes alarms by hemoconcentration throughout the session. Recent technical advances allow automatic prescription of Qi if hematocrit and total protein (TP) values are specified. As these analytical results are not possible to obtain in each dialysis session, a practical way to prescribe Qi is to make an automatic prescription adjusting the hematocrit and total protein values at the beginning of the session to obtain the manual prescription required and we will call it automatic-manual prescription. The aim of this study was to compare manual Qi with automatic-manual Qi in postdilution OL-HDF. 30 patients (16 men and 14 women), 59.9 +/- 15 years old, in hemodialysis program for 50.1 +/- 67 months were included. Every patient underwent four OL-HDF sessions, two with manual Qi (4008-S and 5008 monitors) and two with automatic-manual Qi (A-M), one with the same Qi and one with manual Qi +20 (A-M+20). The same usual dialysis parameters were maintained: helixone dialyzer, dialysis time of 266 +/- 39 minutes, blood flow of 420 +/- 36. Recirculation, Kt and intradialysis alarms were measured at each session. No significant differences in the fistula recirculation or dialysis dose measured using Kt. Total infusion volume was 24.9 +/- 4 (4008 S), 23.4 +/- 4 L (5008) with manual Qi, 23.6 +/- 4 L (A-M) Qi (NS) and 25.8 +/- 5 L (A-M+20). Only 14% of patients had no incidents. The number of alarms was significantly higher with manual prescription 55 alarms with 4008 and 40 with 5008 vs. AM (11) p < 0.01) and A-M+20 (16 alarms) We concluded that automatic-manual Qi is a practical way for post-dilutional OL-HDF prescription where the same efficiency and total reinfusion volume with an important reduction of intradialysis alarms are obtained, allowing to rise Qi by 20% without increasing intradialysis alarms.
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  • 文章类型: Journal Article
    This work aims to facilitate the transition of micro-robotic deposition (microRD) technology from the research bench to a mass manufacturing environment. The bone scaffolding application is targeted; however, the evaluation process developed is applicable to multiple colloidal material systems, length scales, and structure architectures. A design of experiments (DoE) approach is used to develop statistical correlations between three manufacturing treatments (material calcination time, nozzle size, and deposition speed) and defined reliability metrics. All three selected treatments have a significant effect on structure quality. A longer material calcination time improves the deposition of internal features. Logically, a larger nozzle size decreases structural defects. However, an unexpected result is revealed by this study. Higher deposition speeds are shown to either significantly improve or have no effect on structure quality, permitting a decrease in manufacturing time without adverse consequences.
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  • 文章类型: Journal Article
    BACKGROUND: Dysphagia can lead to aspiration of oral feeds, thus causing pneumonia. Dysphagia is diagnosed by assessing the ability to swallow barium test feeds (BTF) of different viscosities. Dysphagia diet foods (DDF) are thickened as recommended by the National Dysphagia Diet (NDD) guidelines. To our knowledge, there are no published data evaluating if the viscosity of BTF or commercial DDF meet NDD guidelines.
    METHODS: A TA1000 rheometer (TA Instruments; New Castle, DE) measured dynamic viscosity of BTF and DDF using creep transformation under controlled stress. Thin DDF studied included Plus Energy Drink (Boost; Novartis/Nestle; Fremont, MI) and Instant Breakfast (Carnation; Wilkes-Barre, PA) and nectar- and honey-thick DDF from Hormel (Hormel Health Labs; Savannah, GA) and Novartis (Novartis/Nestle). The BTF studied were thin, nectar-, and honey-thick Polibar barium suspension or Varibar (E-Z-EM, Inc.; Lake Success, NY). We measured batch-to-batch variability in the viscosity of DDF, with and without shaking, and after 2 h at ambient temperature at a shear rate chosen to match natural swallowing.
    RESULTS: We observed the following: (1) DDF: the viscosity of honey-thick DDF was consistent with NDD guidelines, but other products were not. All products had minimal change in viscosity over 2 h. Boost thin liquid had > 300% increase in viscosity after shaking. (2) BTF: thin barium had a viscosity consistent with NDD guidelines. The nectar- and honey-thick Polibar BTFs were thixotropic and had unacceptably high viscosity. Varibar BTFs were not thixotropic but were more viscous than the NDD guidelines.
    CONCLUSIONS: There was a poor relationship between the viscosity of DDF and BTF. The viscosity of BFTs is much greater than the correspondingly named diet foods and the NDD guidelines. This can place patients at significant risk for oral aspiration.
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  • 文章类型: Journal Article
    Although understanding cells\' responses to mechanical stimuli is seen as increasingly important for understanding cell biology, how to best measure, interpret, and model cells\' mechanical properties remains unclear. We determine the frequency-dependent shear modulus of cultured mammalian cells by using four different methods, both unique and well established. This approach clarifies the effects of cytoskeletal heterogeneity, ATP-dependent processes, and cell regional variations on the interpretation of such measurements. Our results clearly indicate two qualitatively similar, but distinct, mechanical responses, corresponding to the cortical and intracellular networks, each having an unusual, weak power-law form at low frequency. The two frequency-dependent responses we observe are remarkably similar to those reported for a variety of cultured mammalian cells measured with different techniques, suggesting it is a useful consensus description. Finally, we discuss possible physical explanations for the observed mechanical response.
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