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1.
Am J Dent ; 33(5): 235-238, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33017524

RESUMO

PURPOSE: To evaluate the in vitro antimicrobial effect of low- and high-viscosity experimental mouthrinses containing cetylpyridinium chloride (CPC) and 4-isopropyl-3-methylphenol (IPMP) on Streptococcus pneumoniae, Klebsiella pneumoniae, Porphyromonas gingivalis, Streptococcus mutans, and Candida albicans. METHODS: Low- and high-viscosity experimental mouthrinses containing 0.05% CPC and 0.1% IPMP were fabricated. Non-viscous mouthrinses containing either CPC- or IPMP were used as controls. The antimicrobial activity (sterilization or exposure time) of mouthrinses was evaluated based on the bactericidal criterion of <10¹ viable cells in 0.1 mL of culture medium. RESULTS: The sterilization time of the low-viscosity experimental mouthrinse was shorter than that of the high-viscosity mouthrinse. However, whereas a 10-minute exposure to the low-viscosity mouthrinse resulted in no viable cells of C. albicans, neither the CPC- or IPMP mouthrinses had an antimicrobial effect for the same exposure time. These findings show that the low-viscosity experimental mouthrinse containing anodal CPC and neutral IPMP exhibited superior antimicrobial effects against pneumonia- and oral infection-related bacteria compared with the control mouthrinses. CLINICAL SIGNIFICANCE: In Japan, the oral care with the low-viscosity experimental mouthrinse containing CPC and IPMP as alternatives to those based on chlorhexidine are available for preventing the development of pneumonia- and oral infection-related bacteria.


Assuntos
Anti-Infecciosos Locais/farmacologia , Cetilpiridínio/farmacologia , Cresóis , Antissépticos Bucais/farmacologia , Viscosidade
2.
Acta Odontol Latinoam ; 33(2): 59-68, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32920607

RESUMO

The aim of this in vitro study was to evaluate the effect of bleaching protocols on the surface roughness (Ra), color change and surface micromorphology of a low-viscosity bulk-fill composite (Filtek Bulk Fill Flow, 3M ESPE), a highviscosity bulk-fill composite (Filtek Bulk Fill, 3M ESPE) and a conventional nanoparticulate composite resin (control) (Filtek Z350 XT, 3M ESPE). Forty samples of each composite (disks 5 mm in diameter and 2 mm thick) were randomly divided into four groups (n=10), according to bleaching protocol: a) 10% carbamide peroxide gel (Opalescence, Ultradent Products) (2 h/ day, for 14 days); b) 40% hydrogen peroxide gel (Opalescence Boost, Ultradent Products) (three bleaching sessions, once a week, 45 min/session); c) whitening rinse (Listerine Whitening Extreme, Johnson & Johnson) (2 min/day, for 14 days); and d) distilled water (control). The samples were submitted to triplicate readings (Ra and color [CIELAB parameters]) before and after contact with bleaching protocols. Micromorphology was analyzed in a scanning electron microscope (SEM). Ra and color parameters (ΔL, Δa, Δb and ΔE) were analyzed by generalized linear models (α=0.05). The Ra of the high-viscosity bulk-fill was significantly higher than that of the other composites (p<0.05). Ra increased significantly (p<0.05) and surface became more irregular (SEM analysis) in all the composite resins, regardless of the bleaching protocol (p<0.05). The high-viscosity bulk-fill composite resin group had significantly lower ΔE (p<0.05) than the nanoparticulate composite resin group immersed in distilled water. It was concluded that the characteristics of each resin significantly influenced the Ra more than the bleaching protocol. The high-viscosity bulk-fill resin presented minor color change.


Assuntos
Resinas Compostas/química , Peróxido de Hidrogênio/química , Clareadores Dentários/química , Clareamento Dental/métodos , Descoloração de Dente/tratamento farmacológico , Viscosidade/efeitos dos fármacos , Cor , Humanos , Teste de Materiais
3.
Z Gastroenterol ; 58(9): 847-854, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32947630

RESUMO

BACKGROUND: The aim of our study is to analyze viscosity characteristics of focal liver lesions (FLLs) and the diagnostic performance of shear wave dispersion (SWD) in differentiating benign and malignant FLLs. METHODS: Between January 2018 and April 2018, 58 consecutive patients (median age 57, age range 21-74 years, 37 males) with 58 FLLs located on the right lobe of liver were prospectively studied. The Aplio i900 series diagnostic ultrasound system (Canon Medical systems) equipped with a curvilinear PV1-475BX transducer (1-8 MHz) was used. SWD slope and viscosity measurements were expressed as mean ± standard deviation for both liver tumors and background liver parenchyma. Histopathological results after surgery were regarded as the gold standard for diagnosis. RESULTS: Final diagnosis included 40 cases of malignant and 18 cases of benign FLLs. The mean viscosity value were 14.78 ±â€Š1.86 m/s/kHz for hepatocellular carcinoma (n = 30), 14.81 ±â€Š2.35 m/s/kHz for liver metastasis lesions (n = 10), 13.23 ±â€Š1.31 m/s/kHz for hemangioma (n = 13), and 13.67 ± 2.72 m/s/kHz for focal nodular hyperplasia (n = 5). Malignant FLLs showed higher mean viscosity values (14.79 ±â€Š3.15 m/s/KHz) than benign FLLs (13.36 ±â€Š2.76 m/s/KHz) (p < 0.05). The best performing cut-off value of lesion viscosity was 13.15 m/s/kHz (sensitivity 83.3 %; specificity 56.5 %; area under the curve (AUC) 0.71) for malignancy) (p < 0.05). CONCLUSIONS: The analysis of SWD slope and liver viscosity parameters provide additional viscoelastic information about FLLs before operation.


Assuntos
Técnicas de Imagem por Elasticidade/métodos , Neoplasias Hepáticas/diagnóstico por imagem , Fígado/diagnóstico por imagem , Adulto , Idoso , Meios de Contraste , Diagnóstico Diferencial , Humanos , Fígado/patologia , Neoplasias Hepáticas/patologia , Masculino , Pessoa de Meia-Idade , Sensibilidade e Especificidade , Ultrassonografia , Viscosidade , Adulto Jovem
4.
J Oral Sci ; 62(4): 444-448, 2020 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-32879159

RESUMO

PURPOSE: High-viscosity glass ionomer cements (HV-GICs) are reinforced with ultrafine, highly reactive glass particles, as well as a higher-molecular-weight polyalkenoic acid component. Silver diammine fluoride (SDF) is an agent with promising activity against active caries. The present study aimed to evaluate the shear bond strength (SBS) and interfacial morphology of a new HV-GIC bonded to dentin after treatment with various adhesive protocols including SDF. METHODS: HV-GIC cylinders were bonded to dentin after various surface treatments (6 groups, n = 22): water; polyalkenoic acid; SDF; SDF + potassium iodide (KI); SDF + KI + polyalkenoic acid; SDF + KI + two weeks of storage in water + polyalkenoic acid. For each group, 20 samples were tested for SBS after 48 h, and 2 samples were cut and subjected to environmental scanning electron microscopy (E-SEM) and energy-dispersive X-ray (EDX) analysis. RESULTS: No significant differences in SBS were found between any of the protocols tested. However, E-SEM and EDX images showed different interfaces when SDF was applied. CONCLUSION: SDF has no influence on the adhesion of HV-GIC to sound dentin and could potentially improve the cario-resistance of the dentin/HV-GIC interface.


Assuntos
Colagem Dentária , Cimentos de Ionômeros de Vidro , Amônia , Dentina , Fluoretos , Teste de Materiais , Resistência ao Cisalhamento , Compostos de Prata , Viscosidade
5.
Nat Commun ; 11(1): 4628, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934220

RESUMO

Liquid phase separation into two or more coexisting phases has emerged as a new paradigm for understanding subcellular organization, prebiotic life, and the origins of disease. The design principles underlying biomolecular phase separation have the potential to drive the development of novel liquid-based organelles and therapeutics, however, an understanding of how individual molecules contribute to emergent material properties, and approaches to directly manipulate phase dynamics are lacking. Here, using microrheology, we demonstrate that droplets of poly-arginine coassembled with mono/polynucleotides have approximately 100 fold greater viscosity than comparable lysine droplets, both of which can be finer tuned by polymer length. We find that these amino acid-level differences can drive the formation of coexisting immiscible phases with tunable formation kinetics and can be further exploited to trigger the controlled release of droplet components. Together, this work provides a novel mechanism for leveraging sequence-level components in order to regulate droplet dynamics and multiphase coexistence.


Assuntos
Arginina/química , Lisina/química , Cinética , Transição de Fase , Polinucleotídeos/química , Viscosidade
6.
Wiad Lek ; 73(4): 696-699, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32731699

RESUMO

OBJECTIVE: The aim of the present research was to investigate the rheological properties of the medicinal syrup for oral administration with glucosamine hydrochloride and levocarnitine. PATIENTS AND METHODS: Matherials and methods: Coefficient of the dynamic flow (at shear rates of 3,49 and 10,3 s -1, as well as at shear rates of 27.2 and 149.0 s-1), mechanical stability, the index of destruction and restoration were studied. The rheological (structural-mechanical) properties of the samples were determined using a Rheolab QC rotary viscometer (AntonPaar, Austria) with coaxial cylinders CC27 / S-SN29766. The rheological parameters were studied at the temperature 20±0,5 °Ð¡. RESULTS: Results: It is established that the syrup has weakly expressed plastic viscous and thixotropic properties (the hysteresis area for the syrupis 1710.19 Pas/s). Such results characterize the system as a reopex. CONCLUSION: Conclusions: The results of the study enables classification of the research object as system with a low degree of fluidity. Such dependence is typical for systems of the Newtonian type of flow and characterizes the syrup under investigation as a weakly structured disperse system.


Assuntos
Reologia , Administração Oral , Viscosidade
7.
Phys Rev Lett ; 125(6): 068101, 2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32845697

RESUMO

Shape, dynamics, and viscoelastic properties of eukaryotic cells are primarily governed by a thin, reversibly cross-linked actomyosin cortex located directly beneath the plasma membrane. We obtain time-dependent rheological responses of fibroblasts and MDCK II cells from deformation-relaxation curves using an atomic force microscope to access the dependence of cortex fluidity on prestress. We introduce a viscoelastic model that treats the cell as a composite shell and assumes that relaxation of the cortex follows a power law giving access to cortical prestress, area-compressibility modulus, and the power law exponent (fluidity). Cortex fluidity is modulated by interfering with myosin activity. We find that the power law exponent of the cell cortex decreases with increasing intrinsic prestress and area-compressibility modulus, in accordance with previous finding for isolated actin networks subject to external stress. Extrapolation to zero tension returns the theoretically predicted power law exponent for transiently cross-linked polymer networks. In contrast to the widely used Hertzian mechanics, our model provides viscoelastic parameters independent of indenter geometry and compression velocity.


Assuntos
Actinas/química , Fibroblastos/química , Fibroblastos/citologia , Modelos Biológicos , Actinas/fisiologia , Animais , Fenômenos Biomecânicos , Linhagem Celular , Membrana Celular/química , Membrana Celular/fisiologia , Força Compressiva , Cães , Elasticidade , Microscopia de Força Atômica , Miosinas/química , Miosinas/fisiologia , Reologia/métodos , Viscosidade
8.
Am J Dent ; 33(4): 213-217, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32794397

RESUMO

PURPOSE: To perform a clinical and radiographic evaluation comparing Filtek Bulk Fill high viscosity bulk-fill resins with Filtek Z350 XT nanoparticulate for 1 year. METHODS: 58 restorations were performed for each material (bulk-fill and nanoparticulate), for a total of 116 restorations. Among these, 42 Class I and 16 Class II restorations were performed for each group, in molars and premolars. Clinical evaluation was performed 7 days (baseline), 6 months and 1 year after restorations, using the World Dental Federation (FDI) criteria. Radiographs were obtained at 7 days and 1 year after the restoration was placed and the radiopacity was measured using Image J software at the same time interval. RESULTS: Of the 70 restorations available for evaluation at 1 year, the Mann-Whitney and Friedman tests showed no statistically significant difference for the FDI criteria analyzed. Greater radiopacity was observed for bulk-fill resin compared to nanoparticulate (two-way ANOVA, P= 0.022). This same test showed no difference in radiopacity between the groups in the two evaluation periods (P= 0.062). The high viscosity bulk-fill resin composite presented similar clinical performance to nanoparticulate resin in this evaluation period and higher radiopacity was observed for this material when compared to nanoparticulate resin, in both time periods. CLINICAL SIGNIFICANCE: The high viscosity bulk-fill resin composite showed similar performance to the nanoparticulate resin during the evaluation period of 1 year. Radiopacity showed high values for the bulk-fill resin when compared to nanoparticulate resin. The bulk-fill resin has potential to be used in posterior teeth.


Assuntos
Materiais Dentários , Restauração Dentária Permanente , Dente Pré-Molar , Resinas Compostas , Dente Molar , Viscosidade
9.
Braz Oral Res ; 34: e099, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785474

RESUMO

The composition of infiltrants can influence their physical properties, viscosity and depth of penetration (DP). Strategies are used to increase the DP, such as the addition of diluents or the use of heat. This study aimed to evaluate the effect of preheating and composition on physical properties and DP of infiltrants in demineralized enamel. The groups were assigned, and the following experimental formulations were made: 25%BisEMA +75%TEGDMA; 25%BisEMA +65%TEGDMA +10%ethanol; 25%BisEMA +65%TEGDMA +10%HEMA; 100%TEGDMA; 90%TEGDMA +10%ethanol; 90%TEGDMA +10%HEMA. The samples were photoactivated at two temperatures (25°C and 55°C). Degree of conversion (DC) was performed using an infrared spectrophotometer. Elastic modulus (E), flexural strength (FS) and contact angle (CA) tests were also performed. The DP of an infiltrant in demineralized enamel was determined by confocal laser scanning microscopy (CLSM) using an indirect labeling technique. The data were analyzed by two-way ANOVA and Tukey's test. DC increased after preheating in all the groups; however, 90%TEGDMA+10%ethanol showed the lowest DC for both temperatures, and the lowest E. Preheating did not influence E or FS. The CA increased at 55°C for most groups, but decreased for groups containing HEMA. Temperature did not seem to influence DP, and Icon showed the lowest DP values. The 100%TEGDMA composition showed more homogeneous penetration, whereas Icon showed heterogeneous and superficial penetration. The preheating technique does not improve all properties in all the material compositions. The composition of a material can influence and improve its properties.


Assuntos
Esmalte Dentário , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Módulo de Elasticidade , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Ácidos Polimetacrílicos , Viscosidade
10.
Water Res ; 182: 116031, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32810736

RESUMO

Recent reports and experimental data closely indicate that bed-sediment entrainment by debris flows strongly impacts the evolution of the topographic signature of a valley. However, it is difficult to constrain the physics of the entrainment process in numerical models. The challenge is deeply embedded in the shape of the velocity profile, whose knowledge is fundamental for estimating debris-flow basal shear stress exerting on bed sediment. Most two-dimensional models are restricted because the depth-integrated shallow water assumption is problematic in this aspect. One alternative is to combine a three-dimensional, particle-based numerical model with a progressive entrainment law. In this paper, we propose a three-dimensional, surface cell (SC)-based smooth particle hydrodynamics (SPH) model for simulating bed-sediment entrainment by viscous debris flows. The dynamic behavior of a debris flow is simulated by the open-source DualSPHysics scheme, into which the Herschel-Bulkley-Papanastasiou (HBP) rheology model is incorporated. Subsequently, the bed surface is meshed, over which the particles belonging to a certain cell at each time step are identified to represent the basal velocity and flow depth using a novel SC-based algorithm. With the extracted velocities of these basal particles, the sediment entrainment rate of each cell can be estimated using the optimized progressive entrainment law. The proposed SC-HBP-SPH method is tested by means of a full-scale flume experiment carried out in a previous study. The results show that the proposed model can adequately describe and reproduce the complex dynamic process of bed-sediment entrainment by overriding debris flows.


Assuntos
Hidrodinâmica , Movimentos da Água , Sedimentos Geológicos , Reologia , Viscosidade
11.
PLoS One ; 15(8): e0236063, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32756567

RESUMO

The primary objective of this research was to extract the essential information needed for setting atomization break up models, specifically, the Linear Instability Sheet Atomization (LISA) breakup model, and alternative hollow cone models. A secondary objective was to gain visualization and insight into the atomization break up mechanism caused by the effects of viscosity and surface tension on primary break-up, sheet disintegration, ligament and droplet formation. High speed imaging was used to capture the near-nozzle characteristics for water and drug formulations. This demonstrated more rapid atomization for lower viscosities. Image processing was used to analyze the near-nozzle spray characteristics during the primary break-up of the liquid sheet into ligament formation. Edges of the liquid sheet, spray break-up length, break-up radius, cone angle and dispersion angle were obtained. Spray characteristics pertinent for primary breakup modelling were determined from high speed imaging of multiple spray actuations. The results have established input data for computational modelling involving parametrical analysis of nasal drug delivery.


Assuntos
Sprays Nasais , Nebulizadores e Vaporizadores , Administração Intranasal , Aerossóis/química , Composição de Medicamentos , Sistemas de Liberação de Medicamentos/instrumentação , Desenho de Equipamento , Humanos , Tamanho da Partícula , Tensão Superficial , Viscosidade , Água/química
12.
Int J Nanomedicine ; 15: 5405-5416, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32801696

RESUMO

Purpose: Although the effective and safe medical defoamers, dimethicone (DM) and simethicone (SM) are widely used in electronic gastroscope examination (EGE), their preparations are presented in the form of suspensions or emulsions, these are untransparent or milk-like in appearance and can easily cause misdiagnosis as a result of an unclear field of vision if the doctor does not master the amount of defoamer or operates incorrectly. At the same time, it is also difficult to wash out the camera and pipeline, due to the large oil droplets of preparations. The purpose of this study was to develop a new clear and transparent oil in water (O/W) DM nanoemulsions (DMNs) and observe the effect of application in EGE. Methods: The oil phase was chosen for its antifoaming activity and viscosity. The emulsifier and co-emulsifier were selected according to the solubility of the oil phase in them. The water titration method was used to make the pseudoternary phase diagrams of nanoemulsions and optimize the prescription composition. DM-in-water nanoemulsion was prepared by the low energy method and evaluated for appearance, antifoaming ability, droplet size, and stability. The effect of DMNs utilized in EGEs was also observed. Results: The optimal formulation of DMNs contained CRH-40 as an emulsifier, PEG-400 as a co-emulsifier, DM as oil phase with the viscosity of 10 mPa.s, and their proportion was 4.5:4.5:1, respectively. DMNs obtained the average particle size of 67.98 nm with the polydispersity index (PDI) of 0.332, and 57.14% defoaming rate. The result of using an EGE showed that DMNs were superior in comparison to the emulsions with regard to the defoaming effect, visual clarity, and easy cleanup. Conclusion: DMNs were found to provide excellent visual clarity to its other preparations. The novel DMNs is a promising substitute for DM emulsions or suspensions in EGEs.


Assuntos
Antiespumantes/química , Dimetilpolisiloxanos/química , Emulsões/química , Gastroscopia/métodos , Antiespumantes/efeitos adversos , Antiespumantes/uso terapêutico , Óleo de Rícino/química , Dimetilpolisiloxanos/efeitos adversos , Dimetilpolisiloxanos/uso terapêutico , Emulsificantes/química , Feminino , Gastroscopia/efeitos adversos , Humanos , Masculino , Nanoestruturas/química , Tamanho da Partícula , Polietilenoglicóis/química , Solubilidade , Viscosidade
13.
PLoS One ; 15(8): e0237517, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804974

RESUMO

Climate change, limited water resources and expected population increases would require crops which contribute toward more resilient, more productive, more sustainable and climate-smart food systems. The cactus pear is a drought-resistant and sustainable food source to humans and livestock alike. Cactus mucilage has multiple applications in the food and packaging industry. It is eco-friendly, economical, functional and has multiple health benefits. However, the researchers observed umpteen variations in extracted mucilage yield and viscosity every time the cladodes were harvested, making the standardisation of formulations troublesome. We aimed to examine the effect of weather conditions on the physicochemical characteristics of cactus pear cladodes and mucilage extracted over two seasons to understand these observed variations in mucilage characteristics. Forty cladodes, ten from each of Opuntia ficus-indica Algerian, Morado and Gymno-Carpo and Opuntia robusta Robusta were harvested every month from February to August in Bloemfontein, South Africa. Daily weather data were obtained, weight and moisture contents determined on cladodes and yield, viscosity, pH, conductivity and malic acid content determined on extracted mucilage. Pearson correlation coefficients were calculated between the weather conditions, cladode properties, and mucilage properties. Contrary to common belief, neither increasing cladode weight as they grow, nor rainfall were the leading causes of mucilage inconsistencies. However, the correlations showed a relationship between environmental temperatures, cladode pH and conductivity, and mucilage viscosity and yields. In hot summer weather, the pH was lower, which led to an abundance of positive ions in cladodes. The H+ ions neutralise the negative charges along the outstretched mucilage molecule, causing it to coil up, reducing the viscosity of the mucilage. Thus, environmental temperatures rather than rainfall or cladode maturity influenced the physicochemical characteristics of mucilage. The findings should make an essential contribution in predicting the physicochemical characteristics of mucilage for specific food-related functions by observing the weather conditions.


Assuntos
Opuntia/crescimento & desenvolvimento , Mucilagem Vegetal/química , Brotos de Planta/química , Mudança Climática , Malatos/química , Opuntia/química , Opuntia/classificação , Estações do Ano , África do Sul , Viscosidade
14.
PLoS Comput Biol ; 16(8): e1008018, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32813688

RESUMO

Visually inferring material properties is crucial for many tasks, yet poses significant computational challenges for biological vision. Liquids and gels are particularly challenging due to their extreme variability and complex behaviour. We reasoned that measuring and modelling viscosity perception is a useful case study for identifying general principles of complex visual inferences. In recent years, artificial Deep Neural Networks (DNNs) have yielded breakthroughs in challenging real-world vision tasks. However, to model human vision, the emphasis lies not on best possible performance, but on mimicking the specific pattern of successes and errors humans make. We trained a DNN to estimate the viscosity of liquids using 100.000 simulations depicting liquids with sixteen different viscosities interacting in ten different scenes (stirring, pouring, splashing, etc). We find that a shallow feedforward network trained for only 30 epochs predicts mean observer performance better than most individual observers. This is the first successful image-computable model of human viscosity perception. Further training improved accuracy, but predicted human perception less well. We analysed the network's features using representational similarity analysis (RSA) and a range of image descriptors (e.g. optic flow, colour saturation, GIST). This revealed clusters of units sensitive to specific classes of feature. We also find a distinct population of units that are poorly explained by hand-engineered features, but which are particularly important both for physical viscosity estimation, and for the specific pattern of human responses. The final layers represent many distinct stimulus characteristics-not just viscosity, which the network was trained on. Retraining the fully-connected layer with a reduced number of units achieves practically identical performance, but results in representations focused on viscosity, suggesting that network capacity is a crucial parameter determining whether artificial or biological neural networks use distributed vs. localized representations.


Assuntos
Modelos Neurológicos , Redes Neurais de Computação , Viscosidade , Percepção Visual/fisiologia , Adulto , Biologia Computacional , Feminino , Humanos , Masculino , Adulto Jovem
15.
PLoS One ; 15(7): e0235822, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32658896

RESUMO

Studies concerning the mechanical properties of the human periodontal ligament under dynamic compression are rare. This study aimed to determine the viscoelastic properties of the human periodontal ligament under dynamic compressive loading. Ten human incisor specimens containing 5 maxillary central incisors and 5 maxillary lateral incisors were used in a dynamic mechanical analysis. Frequency sweep tests were performed under the selected frequencies between 0.05 Hz and 5 Hz with a compression amplitude that was 2% of the PDL's initial width. The compressive strain varied over a range of 4%-8% of the PDL's initial width. The storage modulus, ranging from 28.61 MPa to 250.21 MPa, increased with the increase in frequency. The loss modulus (from 6.00 MPa to 49.28 MPa) also increased with frequency from 0.05 Hz- 0.5 Hz but remained constant when the frequency was higher than 0.5 Hz. The tanδ showed a negative logarithmic correlation with frequency. The dynamic moduli and the loss tangent of the central incisor were higher than those of the lateral incisor. This study concluded that the human PDL exhibits viscoelastic behavior under compressive loadings within the range of the used frequency, 0.05 Hz- 5 Hz. The tooth position and testing frequency may have effects on the viscoelastic properties of PDL.


Assuntos
Incisivo/fisiologia , Ligamento Periodontal/fisiologia , Adulto , Fenômenos Biomecânicos , Força Compressiva , Elasticidade , Humanos , Masculino , Pessoa de Meia-Idade , Estresse Mecânico , Viscosidade
16.
Proc Biol Sci ; 287(1931): 20201031, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32673555

RESUMO

In species with internal fertilization, the female genital tract appears challenging to sperm, possibly resulting from selection on for example ovarian fluid to control sperm behaviour and, ultimately, fertilization. Few studies, however, have examined the effects of swimming media viscosities on sperm performance. We quantified effects of media viscosities on sperm velocity in promiscuous willow warblers Phylloscopus trochilus. We used both a reaction norm and a character-state approach to model phenotypic plasticity of sperm behaviour across three experimental media of different viscosities. Compared with a standard medium (Dulbecco's Modified Eagle Medium, DMEM), media enriched with 1% or 2% w/v methyl cellulose decreased sperm velocity by up to about 50%. Spermatozoa from experimental ejaculates of different males responded similarly to different viscosities, and a lack of covariance between elevations and slopes of individual velocity-by-viscosity reaction norms indicated that spermatozoa from high- and low-velocity ejaculates were slowed down by a similar degree when confronted with high-viscosity environments. Positive cross-environment (1% versus 2% cellulose) covariances of sperm velocity under the character-state approach suggested that sperm performance represents a transitive trait, with rank order of individual ejaculates maintained when expressed against different environmental backgrounds. Importantly, however, a lack of significant covariances in sperm velocity involving a cellulose concentration of 0% indicated that pure DMEM represented a qualitatively different environment, questioning the validity of this widely used standard medium for assaying sperm performance. Enriching sperm environments along ecologically relevant gradients prior to assessing sperm performance will strengthen explanatory power of in vitro studies of sperm behaviour.


Assuntos
Aves/fisiologia , Motilidade Espermática , Espermatozoides/fisiologia , Animais , Masculino , Comportamento Sexual Animal , Viscosidade
17.
J Chromatogr A ; 1625: 461117, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709364

RESUMO

To obtain consistent chromatographic behavior, it is important to develop resin packing methods in accordance with the characteristics of each resin. Resins, particularly those with a significant level of compressibility, require proper knowledge of the packing methodology to ensure scalable performance. The study demonstrates the applicability of pressure-flow modeling based on the Blake-Kozeny equation for cellulose based resins, using the MEP HyperCel (Pall) resin as a case study. This approach enabled the understanding of the appropriate bed compressibility and the determination of the minimum column diameter that can predict bed integrity during commercial manufacturing scale operation. Studies suggested that scale-dependent wall effects become negligible for column diameters exceeding 20 cm. Pressure-flow modeling produced a minimum compression recommendation of 0.206 for the MEP HyperCel resin. Columns with diameters up to 80 cm packed with this bed compression yielded incompressible beds with pressure-flow curves consistent with model predictions. Model parameter (particle diameter, viscosity, porosity) values were then varied to demonstrate how changing operating conditions influence model predictions. This analysis supported the successful troubleshooting of unexpected high pressures at the commercial manufacturing scale using MEP HyperCel resin, further supporting the applicability of this approach.


Assuntos
Produtos Biológicos/isolamento & purificação , Cromatografia Líquida/métodos , Anticorpos Monoclonais/isolamento & purificação , Géis/química , Porosidade , Pressão , Viscosidade
18.
Food Chem ; 332: 127327, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32615380

RESUMO

The effect of variation in acid gel pH during cream cheese production was investigated. The gel microstructure was denser and cheese texture firmer, as the pH decreased from pH 5.0 to pH 4.3, despite the viscoelasticity of these gels remaining similar during heating. Protein hydration and secondary structure appeared to be key factors affecting both cheese microstructure and properties. Proteins within the matrix appeared to swell at pH 5.0, leading to a larger corpuscular structure; greater ß-turn structure was also observed by synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy and the cheese was softer. A decrease in pH led to a denser microstructure with increased aggregated ß-sheet structure and a firmer cheese. The higher whey protein loss at low pH likely contributed to increased cheese hardness. In summary, controlling the pH of acid gel is important, as this parameter affects proteins in the cheese, their secondary structure and the resulting cream cheese.


Assuntos
Queijo/análise , Gorduras/química , Manipulação de Alimentos , Proteínas/química , Reologia , Concentração de Íons de Hidrogênio , Viscosidade
19.
Proc Natl Acad Sci U S A ; 117(30): 18110-18118, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32669427

RESUMO

Mechanical patterns control a variety of biological processes in plants. The microviscosity of cellular structures effects the diffusion rate of molecules and organelles, thereby affecting processes such as metabolism and signaling. Spatial variations in local viscosity are also generated during fundamental events in the cell life cycle. While crucial to a complete understanding of plant mechanobiology, resolving subcellular microviscosity patterns in plants has remained an unsolved challenge. We present an imaging microviscosimetry toolbox of molecular rotors that yield complete microviscosity maps of cells and tissues, specifically targeting the cytosol, vacuole, plasma membrane, and wall of plant cells. These boron-dipyrromethene (BODIPY)-based molecular rotors are rigidochromic by means of coupling the rate of an intramolecular rotation, which depends on the mechanics of their direct surroundings, with their fluorescence lifetime. This enables the optical mapping of fluidity and porosity patterns in targeted cellular compartments. We show how apparent viscosity relates to cell function in the root, how the growth of cellular protrusions induces local tension, and how the cell wall is adapted to perform actuation surrounding leaf pores. These results pave the way to the noninvasive micromechanical mapping of complex tissues.


Assuntos
Modelos Biológicos , Células Vegetais , Fenômenos Fisiológicos Vegetais , Viscosidade , Corantes Fluorescentes/química , Proteínas Motores Moleculares/metabolismo , Sondas Moleculares/química , Especificidade de Órgãos , Organelas/metabolismo
20.
Food Chem ; 332: 127391, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32603920

RESUMO

The objectives of the present work were to investigate the influence of Gum Arabic (GA) on the physicochemical properties and ultra-high temperature (UHT) processability of ß-lactoglobulin(ß-lg)-stabilized d-limonene emulsions. Moreover, we also wanted to evaluate the antimicrobial efficiency and mechanism of ß-lg-GA bilayer d-limonene emulsions. Physicochemically stable bilayer emulsions could be formed with an optimal concentration of GA (1.00 wt%), which showed a higher tolerance to both flocculation and coalescence, as well as better protective effects on d-limonene against UHT-treatment that up to 94.32% of d-limonene was retained in emulsions. Likewise, it is also noteworthy that no obvious difference in the minimal inhibitory concentration could be found between bilayer emulsions with or without UHT processing. Moreover, the antimicrobial effects of the bilayer emulsions with UHT treatment were shown to be dose-dependent, which was evidenced from the results of scanning electron microscopy and the determination of released cell constituents. Keywords: ß-lactoglobulin; gum arabic; d-limonene emulsion; physicochemical stability; UHT processability, antimicrobial efficiency.


Assuntos
Antibacterianos/química , Emulsões/química , Manipulação de Alimentos/métodos , Limoneno/química , Bicamadas Lipídicas/química , Antibacterianos/farmacologia , Elasticidade , Emulsões/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Goma Arábica/química , Temperatura Alta , Lactoglobulinas/química , Testes de Sensibilidade Microbiana , Viscosidade
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