Dynamics of liquids with high viscosity contrast in unevenly rotating Hele-Shaw cell.

The paper is devoted to the experimental study of the dynamics of an interface between two liquids with high viscosity contrast filling a vertical, circular narrow gap rotating about a horizontal axis at a speed modulated by librations. The equilibrium shape and stability of the interphase boundary are considered. In the absence of librations, under the action of the centrifugal force the boundary has an axisymmetric shape. At librations, at certain frequency ratios, the interface loses its axisymmetric position: in the cavity reference frame, it is displaced in the radial direction. It is theoretically shown that the discovered phenomenon is explained by the average action of gravity; the results of experiments and theory are consistent. The experiments reveal that with an increase in the modulation amplitude the circular interface loses stability in a threshold manner: an azimuthally periodic relief, quasi-stationary in the cavity frame, emerges. This is associated with the Kelvin-Helmholtz instability due to tangential oscillations of the less viscous liquid near the interface. A dimensionless parameter that determines the stability of the interface is obtained in the limit of high dimensionless libration frequency. The stability threshold increases with the decrease in the dimensionless frequency. This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'.

Observations of phase changes in monoolein during high viscous injection.

Serial crystallography of membrane proteins often employs high-viscosity injectors (HVIs) to deliver micrometre-sized crystals to the X-ray beam. Typically, the carrier medium is a lipidic cubic phase (LCP) media, which can also be used to nucleate and grow the crystals. However, despite the fact that the LCP is widely used with HVIs, the potential impact of the injection process on the LCP structure has not been reported and hence is not yet well understood. The self-assembled structure of the LCP can be affected by pressure, dehydration and temperature changes, all of which occur during continuous flow injection. These changes to the LCP structure may in turn impact the results of X-ray diffraction measurements from membrane protein crystals. To investigate the influence of HVIs on the structure of the LCP we conducted a study of the phase changes in monoolein/water and monoolein/buffer mixtures during continuous flow injection, at both atmospheric pressure and under vacuum. The reservoir pressure in the HVI was tracked to determine if there is any correlation with the phase behaviour of the LCP. The results indicated that, even though the reservoir pressure underwent (at times) significant variation, this did not appear to correlate with observed phase changes in the sample stream or correspond to shifts in the LCP lattice parameter. During vacuum injection, there was a three-way coexistence of the gyroid cubic phase, diamond cubic phase and lamellar phase. During injection at atmospheric pressure, the coexistence of a cubic phase and lamellar phase in the monoolein/water mixtures was also observed. The degree to which the lamellar phase is formed was found to be strongly dependent on the co-flowing gas conditions used to stabilize the LCP stream. A combination of laboratory-based optical polarization microscopy and simulation studies was used to investigate these observations.

3D printed devices and infrastructure for liquid sample delivery at the European XFEL.

The Sample Environment and Characterization (SEC) group of the European X-ray Free-Electron Laser (EuXFEL) develops sample delivery systems for the various scientific instruments, including systems for the injection of liquid samples that enable serial femtosecond X-ray crystallography (SFX) and single-particle imaging (SPI) experiments, among others. For rapid prototyping of various device types and materials, sub-micrometre precision 3D printers are used to address the specific experimental conditions of SFX and SPI by providing a large number of devices with reliable performance. This work presents the current pool of 3D printed liquid sample delivery devices, based on the two-photon polymerization (2PP) technique. These devices encompass gas dynamic virtual nozzles (GDVNs), mixing-GDVNs, high-viscosity extruders (HVEs) and electrospray conical capillary tips (CCTs) with highly reproducible geometric features that are suitable for time-resolved SFX and SPI experiments at XFEL facilities. Liquid sample injection setups and infrastructure on the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument are described, this being the instrument which is designated for biological structure determination at the EuXFEL.

Simulations and Experimental Analysis of a High Viscosity Inkjet Printing Device Based on Fabry-Pérot Resonator.

The study investigates the effect of changing various input parameters on the pressure responses at acoustic cavities of a droplet-based acoustic printing device consisting of a Fabry-Pérot (FP) resonator and a standing wave-source chamber. The standing wave of the acoustic radiation pressure at the FP resonator is analyzed. The behavior of the standing wave and acoustic radiation force at the FP resonator is presented and compared with the measured results by varying the position of the standing wave-generating plate. The pressure changes inside the standing wave-source chamber are investigated and discussed to determine the reason for the sudden high-pressure drop at the FP resonator. Furthermore, the effects of inserting the nozzle and droplet inside the FP resonator on the standing wave and acoustic radiation force are analyzed. Experimental analysis is performed by collecting acoustic pressure data at the outlet of the FP resonator. The simulated and measured pressure drop behaviors are compared. The presented numerical approach can be used to set optimal design guidelines for obtaining a higher acoustic pressure inside the acoustic cavities of droplet-based acoustic jetting and other acoustofluidic devices.

Effects of high viscosity bone cement percutaneous vertebroplasty on pain, bone specific alkaline phosphatase, Type-I collage cross-linked-telopeptide and Boneglaprotein levels in patients with osteoporotic vertebral compression fractures.

Objectives: To investigate the effects of percutaneous vertebroplasty with high viscosity bone cement on pain and the levels of bone specific alkaline phosphatase (BALP), Type-I collagen cross-linked telopeptide (CTX) and serum osteocalcin (BGP) in patients with osteoporotic vertebral compression fractures. Methods: The medical records of patients with osteoporotic vertebral compression fractures treated in our hospital from February 2020 to February 2021 were selected after retrospective analysis. Patients (43) who received low viscosity bone cement percutaneous vertebroplasty comprised Group-I, and patients (56) who received high viscosity bone cement percutaneous vertebroplasty, comprised Group-II of the study. The occurrence of bone cement leakage, pain (VAS scores), BALP, CTX and BGP were compared and analyzed between the two groups. Results: The incidence of bone cement leakage in Group-II was 16.28%, lower than 3.57% in Group-I (P<0.05). The visual analogue scale (VAS) scores of patients in Group-II were lower than those in Group-I at one and three months after the surgery (P<0.05). The levels of BALP and BGP in Group-II were higher than those in Group-I three months after the surgery (P<0.05), and CTX was lower than those in Group-I (P<0.05). Conclusions: Percutaneous vertebroplasty with high viscosity bone cement in the treatment of osteoporotic vertebral compression fractures can reduce the incidence of bone cement leakage and help to further reduce pain and improve bone metabolism.

Clinical performance of high-viscosity glass ionomer and resin composite on minimally invasive occlusal restorations performed without rubber-dam isolation: a two-year randomised split-mouth study.

OBJECTIVE: The aim of this clinical trial was to evaluate the 2-year clinical performances of high-viscosity glass ionomer and nanohybrid resin composite restorations performed without rubber dam isolation. MATERIALS AND METHODS: Occlusal carious lesions on the right and left mandibular second molars of 56 patients (26 female, 30 male patients) were restored in a split-mouth design. High-viscosity glass ionomer (Hv-GIC) (Equia, GC) and nanohybrid resin composite (GrandioSO, Voco) were used as restorative materials. Clinical evaluations of the restorations were performed according to the Fédération Dentaire Internationale criteria. Data were analysed using the Friedman's analysis of variance and Mann-Whitney U tests (α=0.05). RESULTS: After 2 years, the success rate of Hv-GIC restorations was 96% and that of resin composite restorations was 100%. Hv-GIC showed lower marginal discoloration and greater surface wear and loss of anatomic form (p<0.05). Resin composite showed significantly better surface lustre. CONCLUSION: The 2-year performance of resin composite was similar to that of Hv-GIC for the occlusal restorations of mandibular second molars, in spite of being performed without rubber-dam isolation. CLINICAL RELEVANCE: Saliva contamination can be a clinically significant problem for dental restorations. High-viscosity glass ionomers are a satisfactory alternative to resin composites with the advantage of fast application in such situations. TRIAL REGISTRATION: Clinical Trials Registration number-date: NCT04488380-22/07/2020, retrospectively registered.

Tibial Component Migration After Total Knee Arthroplasty With High-Viscosity Bone Cement.

BACKGROUND: High-viscosity (HV) bone cements have been formulated to offer potentially advantageous handling characteristics. However, alteration in the handling characteristics could influence implant fixation and survival. The primary objective of this study was to use radiostereometric analysis after total knee arthroplasty to assess the migration of the Triathlon tibial component fixed with HV cement (Simplex HV). METHODS: Twenty-three patients were followed for two years with radiostereometric analysis examinations at 6 visits. Migration was compared with published thresholds and with a control group from a previously published study from the same center using the same implants fixed with a medium viscosity cement. Inducible displacement was assessed, and Oxford 12 Knee Scores and satisfaction were recorded. RESULTS: Mean maximum total point motion migration reaching 0.40 mm (SD 0.16) at one year, and 0.41mm (SD 0.17) at two years, demonstrating a pattern of stable fixation, below published thresholds of acceptable migration, and not significantly different from the control group. One implant had continuous migration between 1 and 2 years but was clinically asymptomatic. Mean maximum total point motion inducible displacement measured at least one year postoperatively was 0.3 mm (SD 0.12). Mean Oxford 12 Knee Scores improved from 19 (SD 7) preoperatively to 42 (SD 8) 2 years postoperatively. CONCLUSIONS: The use of HV cement demonstrated an acceptable pattern of migration at 2 years, indicating low risk for aseptic loosening.

Evaluation of low-viscosity bulk-fill composites regarding marginal and internal adaptation.

This study aimed at evaluating the marginal and internal adaptation of low-viscosity bulk-fill composites to enamel and dentin using a self-etch or an etch-and-rinse adhesive without and with artificial ageing. Hundred and twenty-eight MOD cavities in extracted molars were assigned to eight groups (n = 16), restored with the adhesives OptiBond FL (OFL) or Xeno V+ (X) and two low-viscosity bulk-fill composites SDR or x-tra base, covered with Premise. Tetric EvoCeram Bulk Fill and Premise served as a control. n = 8 per group were subjected to prolonged water storage (180 days) and thermocycling (2500×). Scanning electron microscopy was used to determine marginal gaps (MG) and interfacial adhesive defects (IAD). There were no significant differences between composite types in 44 out of 48 (MG) or 43/48 (IAD) comparisons. More MG were observed with X than with OFL (14 out of 16 comparisons, two significant), while in 16 of 16 comparisons with X more IAD were observed (14 significant). After artificial ageing, MG generally increased (9/16 significant), compared to IAD (one significant). The performance of the investigated composite types concerning the integrity of the tooth-composites interface was comparable. Compared to the 1-step self-etch system, the bond with the 3-step etch-and-rinse adhesive was raised.

Two-Year Survival of High-Viscosity Glass Ionomer in Children with Molar Incisor Hypomineralization.

OBJECTIVE: We assessed the clinical survival of a high-viscosity glass ionomer (HVGI) at the 2-year follow-up to restore molar incisors severely affected by hypomineralization after selective carious tissue removal (SCR). The null hypothesis tested was that there are no differences in the overall survival times in the categories of the variables of interest. METHODS: A total of 134 fully erupted first molar incisors with hypomineralization, cavitated and with moderate-to-deep carious lesions without hypersensitivity or pain (MIH treatment need index 2a-c), were included in the study. HVGI (Equia Forte®; GC, Tokyo, Japan) restorations were applied after SCR to soft carious dentin. The follow-up lasted 2 years. The end point was defined as the absence of endodontic and restorative complications. Two-year, and 18-, 12-, and 6-month survival probabilities and standard errors were calculated using the Kaplan-Meier method. Survival probabilities according to patient gender, jaw, and lesion severity groups were compared using the log-rank test. Restorations were evaluated using the modified US Public Health Service criteria. RESULTS: HVGI restorations showed cumulative survival probabilities of 95.5% at 6 months, 94% at 12 months, 87.5% at 18 months, and 87.5% at 24 months. Survival probabilities according to patient gender, jaw, and lesion severity groups were not statistically significantly different (p > 0.05). Therefore, the null hypothesis was accepted. CONCLUSION: Following SCR, HVGI restoration provided moderate survival probabilities, suggesting that the SCR technique is effective.

Sperm-Driven Micromotors Moving in Oviduct Fluid and Viscoelastic Media.

Biohybrid micromotors propelled by motile cells are fascinating entities for autonomous biomedical operations on the microscale. Their operation under physiological conditions, including highly viscous environments, is an essential prerequisite to be translated to in vivo settings. In this work, a sperm-driven microswimmer, referred to as a spermbot, is demonstrated to operate in oviduct fluid in vitro. The viscoelastic properties of bovine oviduct fluid (BOF), one of the fluids that sperm cells encounter on their way to the oocyte, are first characterized using passive microrheology. This allows to design an artificial oviduct fluid to match the rheological properties of oviduct fluid for further experiments. Sperm motion is analyzed and it is confirmed that kinetic parameters match in real and artificial oviduct fluids, respectively. It is demonstrated that sperm cells can efficiently couple to magnetic microtubes and propel them forward in media of different viscosities and in BOF. The flagellar beat pattern of coupled as well as of free sperm cells is investigated, revealing an alteration on the regular flagellar beat, presenting an on-off behavior caused by the additional load of the microtube. Finally, a new microcap design is proposed to improve the overall performance of the spermbot in complex biofluids.

Current status and future opportunities for serial crystallography at MAX IV Laboratory.

Over the last decade, serial crystallography, a method to collect complete diffraction datasets from a large number of microcrystals delivered and exposed to an X-ray beam in random orientations at room temperature, has been successfully implemented at X-ray free-electron lasers and synchrotron radiation facility beamlines. This development relies on a growing variety of sample presentation methods, including different fixed target supports, injection methods using gas-dynamic virtual-nozzle injectors and high-viscosity extrusion injectors, and acoustic levitation of droplets, each with unique requirements. In comparison with X-ray free-electron lasers, increased beam time availability makes synchrotron facilities very attractive to perform serial synchrotron X-ray crystallography (SSX) experiments. Within this work, the possibilities to perform SSX at BioMAX, the first macromolecular crystallography beamline at  MAX IV Laboratory in Lund, Sweden, are described, together with case studies from the SSX user program: an implementation of a high-viscosity extrusion injector to perform room temperature serial crystallography at BioMAX using two solid supports - silicon nitride membranes (Silson, UK) and XtalTool (Jena Bioscience, Germany). Future perspectives for the dedicated serial crystallography beamline MicroMAX at MAX IV Laboratory, which will provide parallel and intense micrometre-sized X-ray beams, are discussed.

How do Caenorhabditis elegans worms survive in highly viscous habitats?

The nematode Caenorhabditis elegans is a filter feeder that lives in various viscous habitats such as soil, the intestines of slugs, and rotting materials such as fruits and stems. Caenorhabditis elegans draws in suspensions of bacteria and separates bacteria from water using the pharyngeal pump. Although these worms often live in highly viscous habitats, it is still unclear how they survive in these environments by eating bacteria. In this study, we investigated the effects of suspension viscosity on the survival rate of malnourished worms by combining live imaging and scaling analyses. We found that survival rate decreased with increases in viscosity because the high viscosity suppressed the amount of food ingested. The same tendency was found in two feeding-defective mutants, eat-6(ad467) and eat-6(ad997). We also found that the high viscosity weakened pump function, but the velocities in the pharynx were not zero, even in the most viscous suspensions. Finally, we estimated the amount of ingested food using scaling analyses, which provided a master curve of the experimental survival rates. These results illustrate that the survival rate of C. elegans worms is strongly dependent on the ingested bacteria per unit time associated with physical environments, such as the viscosity of food suspensions and the cell density of bacteria. The pump function of the C. elegans pharynx is not completely lost even in fluids that have 105 times higher viscosity than water, which may contribute to their ability to survive around the world in highly viscous environments.

Primary Total Knee Arthroplasty Performed Using High-Viscosity Cement is Associated With Higher Odds of Revision for Aseptic Loosening.

BACKGROUND: Aseptic loosening (AL) is the most common reason for revision total knee arthroplasty (TKA). An association between high-viscosity cement (HVC) and AL has been suggested by small, uncontrolled, case series. This study sought to determine whether HVC use during primary TKA is independently associated with AL requiring revision. METHODS: We retrospectively analyzed a prospectively collected institutional knee registry to identify all primary TKAs from January 2007 to December 2016. Patients with less than 2 years of follow-up were excluded. Cement type was divided into 2 groups: HVC and low-viscosity cement. Potential confounders including age, body mass index, preoperative diagnosis, antibiotics in the cement, and implant type were recorded. Multivariable logistic regression analysis was used to determine whether HVC is independently associated with revision for AL. RESULTS: In total, 10,014 patients were included. Revision for AL was significantly higher in the HVC cohort (91/4790; 1.9%) vs the low-viscosity cement cohort (48/5224; 0.92%) (P < .001). Logistic regression demonstrated HVC to be independently associated with higher odds of revision for AL (odds ratio 2.26, 95% confidence interval 1.58-3.22, P < .001). Younger age was also associated with higher odds of revision for AL (odds ratio 0.96, 95% confidence interval 0.94-0.98, P < .001). Body mass index, gender, laterality, preoperative diagnosis, and antibiotics in the cement were not associated with revision for AL. Implant manufacturer, implant design, and cement brand all impacted the odds of undergoing revision for AL. CONCLUSION: Although HVC is an attractive option for use in primary TKA, this appropriately controlled study demonstrates higher odds of revision for AL when using HVC with multiple different implant types.

Three-year clinical evaluation of high-viscosity glass ionomer restorations in non-carious cervical lesions: a randomised controlled split-mouth clinical trial.

OBJECTIVE: To compare the 3-year clinical performance of high-viscosity glass ionomer restorations with that of composite restorations in non-carious cervical lesions (NCCLs). MATERIALS AND METHODS: One hundred thirty-four NCCLs were randomised into two groups according to a split-mouth design. In the experimental group (Hv-GIC), lesions were restored with a high-viscosity glass ionomer (EQUIA Fil, GC), whereas a composite resin (G-aenial, GC) was applied in the control group (E&Ra/comp). All restorative materials were used according to the manufacturers' instructions. Clinical evaluations were performed after 1 week, 6 months, 1 year, 2 years, and 3 years using FDI (World Dental Federation) criteria. Data were analysed using Friedman's ANOVA and Mann-Whitney U tests (α = 0.05). RESULTS: While retention rates of the Hv-GIC group were 98.5%, 96%, 91%, and 87% in respective evaluation periods, no retention loss was observed in the E&Ra/comp group at any time. There was a statistically significant difference between study groups regarding the retention criterion in both the second and third years (p = 0.008 and p = 0.003, respectively). Furthermore, there was a statistically significant difference between the groups in terms of surface lustre at the third-year recall, in favour of the E&Ra/comp group (p = 0.022). CONCLUSIONS: The 3-year clinical performance of E&Ra/comp restorations in NCCLs was better than that of Hv-GIC restorations. The most common problems in Hv-GIC restorations were a loss of retention and reduction in surface lustre. CLINICAL RELEVANCE: Although the 3-year clinical performance of Hv-GIC restorations in non-retentive lesions was acceptable, it was worse than in composites. The operator should consider the benefit/loss ratio of Hv-GIC when he/she decides to use this material in non-retentive cavities, especially those that are shallow.

Split-mouth Randomised Clinical Trial on the Efficacy of GIC Sealant on Occlusal Surfaces of Primary Second Molar.

PURPOSE: To evaluate the clinical performance of high viscosity GIC sealant applied with or without additional light curing in children with early childhood caries (ECC). MATERIALS AND METHODS: A split-mouth clinical trial was conducted in a total of 111 3- to 5-year-old children with ECC. 180 pairs of non-carious primary second molars were selected and divided into two groups: study and control. On the basis of the application technique, selected teeth in the study group were further allotted to group A (sealant application with additional light curing) and group B (sealant application without additional light curing). Caries incidence was observed for 1 year in the anatomical pits and grooves, along with sealant retention and marginal discolouration at various intervals over the 1-year period. RESULTS: Group A (GIC sealant with additional light curing) (44.2%) showed sealant retention similar to that of group B (GIC sealant without additional light curing) (43.0%) (p = 0.885). Caries incidence was significantly higher in the control group (26%) than the sealant groups (1%) (p < 0.001). No marginal discolouration adjacent to the sealant was observed in either anatomical grooves or pits in both sealant groups for the duration of the study. CONCLUSION: Retention and caries prevention by high-viscosity GIC sealant applied with or without additional light curing was found to be similar. At the 12-month assessment, mean dmfs scores and caries incidence in primary second molars were higher in the control than in both study groups.

A Randomized, Controlled, Split-mouth Trial Evaluating the Clinical Performance of High-viscosity Glass-ionomer Restorations in Noncarious Cervical Lesions: Two-year Results.

PURPOSE: To compare the two-year clinical performance of high-viscosity glass ionomer (Hv-GIC) restorations in noncarious cervical lesions with nanohybrid composite restorations applied with a three-step etch-and-rinse adhesive (E&Ra/nanoC). MATERIALS AND METHODS: One hundred thirty-four noncarious cervical lesions were included and assigned to two groups according to the split-mouth design. The cervical lesions in the experimental group were restored with an Hv-GIC (Equia, GC), while a nanohybrid composite (G-aenial, GC) with a three-step etch-and-rinse adhesive (Optibond FL, Kerr) was applied as the control. All tested restorative materials were used according to the manufacturers' instructions. Clinical evaluation was performed after one week, six months, one year, and two years using World Dental Federation criteria. Data were analyzed using Friedman's ANOVA and Mann-Whitney U-tests (α = 0.05). RESULTS: After two years, Hv-GIC restorations had a retention rate of 91% in comparison to 100% for E&Ra/nanoC restorations. Significant differences existed between the two restorative materials solely with respect to the retention parameter after two years (p = 0.008). CONCLUSIONS: The two-year clinical performance of Hv-GIC was clinically acceptable. However, the retention of E&Ra/nanoC restorations was significantly better than that of Hv-GIC restorations after two years.

Trends in the Use of High-Viscosity Cement in Patients Undergoing Primary Total Knee Arthroplasty in the United States.

BACKGROUND: Aseptic loosening remains the most common mode of failure following total knee arthroplasty (TKA). Although the risk of loosening is multifactorial, recent studies reported early failure via debonding at the tibial implant-cement interface and a potential association with high viscosity cement (HVC). The purpose of this study is to determine the type of cement used by surgeons performing elective, primary TKA in the United States. METHODS: A retrospective cohort study was performed using data reported to the American Joint Replacement Registry from 2012 to 2017. The primary variable assessed was the type of cement used in each primary TKA, categorized as HVC, medium viscosity cement, or low viscosity cement based on the manufacturer's specifications. The use of antibiotic-impregnated cement was also assessed. RESULTS: A total of 554,935 primary TKA procedures were reviewed over the 7-year period. The use of HVC steadily increased from 46.0% of TKAs in 2012 to 61.3% of TKAs in 2017. Conversely, the use of low viscosity cement decreased in use from 47.9% of TKAs in 2012 to 30.9% in 2017. The percentage of TKAs performed using antibiotic-impregnated cement also decreased from 44.2% in 2012 to 34.5% in 2017. CONCLUSION: This study demonstrates that the percentage of TKAs performed using HVC has continued to increase over the most recent 7 years for which the American Joint Replacement Registry has data. The risk of aseptic loosening is clearly multifactorial, but close monitoring is necessary to determine whether this change in surgeon preference will affect component survivorship.

Viscosity reduction of isotonic solutions of the photosensitizer TPCS2a by cyclodextrin complexation.

Meso-tetraphenyl chlorin disulphonate (TPCS2a) is a photosensitizer (PS) particularly developed and patented for use in the technology of photochemical internalization (PCI) against cancer. TPCS2a is known to aggregate in aqueous media even at low concentrations (≥0.1 µM) and to form a high-viscosity network at clinically relevant concentrations (mM). The aim of this work was to evaluate the effect of two hydroxypropylated cyclodextrin derivatives of beta and gamma type, respectively i.e. HPßCD and HPγCD, on the aggregation and solubilization of TPCS2a in isotonic solutions. Samples containing micromolar concentrations of TPCS2a were studied spectrophotometrically, while samples containing a clinical relevant concentration (10 mM = 9 mg/ml) of TPCS2a were evaluated by dynamic viscosity measurements. HPßCD was determined to be a more suitable solubilizer of TPCS2a than HPγCD in aqueous media both in the absence and presence of salt. The complexation stoichiometry between TPCS2a/HPßCD at micromolar to millimolar concentrations of TPCS2a was determined to be 1:3 and 1:2 in the absence and presence of isotonic NaCl, respectively. The network of TPCS2a (10 mM) was broken down in the presence of 3% w/v (= 20 mM) HPßCD, i.e. a 1:2 molar ratio between TPCS2a and the cyclodextrin. Formation of the inclusion complex resulted in low viscosity samples both in water and in the presence of isotonic NaCl or phosphate buffered saline (PBS) at 25 °C and 37 °C.

Mixing high-viscosity fluids via acoustically driven bubbles.

We present an acoustofluidic micromixer which can perform rapid and homogeneous mixing of highly viscous fluids in the presence of an acoustic field. In this device, two high-viscosity polyethylene glycol (PEG) solutions were co-injected into a three-inlet PDMS microchannel with the center inlet containing a constant stream of nitrogen flow which forms bubbles in the device. When these bubbles were excited by an acoustic field generated via a piezoelectric transducer, the two solutions mixed homogenously due to the combination of acoustic streaming, droplet ejection, and bubble eruption effects. The mixing efficiency of this acoustofluidic device was evaluated using PEG-700 solutions which are ~106 times more viscous than deionized (DI) water. Our results indicate homogenous mixing of the PEG-700 solutions with a ~0.93 mixing index. The acoustofluidic micromixer is compact, inexpensive, easy to operate, and has the capacity to mix highly viscous fluids within 50 milliseconds.

Low Rates of Aseptic Tibial Loosening in Obese Patients With Use of High-Viscosity Cement and Standard Tibial Tray: 2-Year Minimum Follow-Up.

BACKGROUND: Total knee arthroplasty is overall a very successful surgery, but complications do occur. These complications include aseptic loosening of the tibial component, and obese patients are among the highest risk group. High-viscosity cement (HVC) has been implicated as a possible cause for aseptic loosening of the tibial component. The purpose of this study was to evaluate the incidence of aseptic loosening of the tibial component in obese patients with the use of HVC and standard tibial tray. METHODS: We identified 1366 obese patients (1851 knees) with a body mass index >35 kg/m2 and 2-year minimum follow-up who underwent primary total knee arthroplasty using HVC and a symmetrical, grit-blasted, cobalt-chrome tibial component with 40-mm stem. Preoperative and postoperative range of motion, Knee Society (KS) scores, complications, and reoperations were evaluated. Specifically, we assessed the rate of tibial aseptic loosening. RESULTS: At a mean 5.4 years follow-up, only 1 in 1851 knees had aseptic loosening of the tibial component for an incidence of 0.054%. There was a mean increase of 3.3 degrees of knee range of motion. KS pain level decreased by 38.6 points (50 point scale). KS clinical scores improved by 52.2, Knee Society functional scores improved by 19.5, University of California, Los Angeles, activity score improved by 0.9, and Oxford Knee Score by 15.7. All these improvements were statistically significant with P < .001. CONCLUSION: Standard tibial components and HVC can be used in most patients, including the high-risk obese group, with low rates of tibial aseptic loosening.