Dynamic interfaces for contact-time control of colloidal interactions.

Understanding pairwise interactions between colloidal particles out of equilibrium has a profound impact on dynamical processes such as colloidal self assembly. However, traditional colloidal interactions are effectively quasi-static on colloidal timescales and cannot be modulated out of equilibrium. A mechanism to dynamically tune the interactions during colloidal contacts can provide new avenues for self assembly and material design. In this work, we develop a framework based on polymer-coated colloids and demonstrate that in-plane surface mobility and mechanical relaxation of polymers at colloidal contact interfaces enable an effective, dynamic interaction. Combining analytical theory, simulations, and optical tweezer experiments, we demonstrate precise control of dynamic pair interactions over a range of pico-Newton forces and seconds timescales. Our model helps further the general understanding of out-of-equilibrium colloidal assemblies while providing extensive design freedom via interface modulation and nonequilibrium processing.

Direct measurement of electrostatic interactions between poly(methyl methacrylate) microspheres with optical laser tweezers.

In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br- ions, which could screen electrostatic interactions.

Geometric Effects of Colloidal Particles on Stochastic Interface Adsorption.

The stochastic interface adsorption behaviors of ellipsoid particles were investigated using optical laser tweezers. The particles were brought close to the oil-water interface, attempting to attach forcefully to the interface. Multiple attempts of the particle attachments statistically quantified the dependence of the adsorption probability on the particle aspect ratio. It was found that the adsorption probability proportionally increased with the aspect ratio because of the decrease in electrostatic interactions between the charged particles and the charged interface for higher aspect ratio particles. In addition, the adsorption holding time required for the interface attachments was found to increase as the aspect ratio decreased. Notably, the probabilistic adsorption behaviors of the ellipsoid particles and the holding time dependence revealed that the particle adsorption to the interface occurred stochastically, not deterministically. We also demonstrated that the adsorption behaviors measured on a single-particle scale were consistent with the gravity-induced spontaneous adsorption properties performed on a large scale with regard to the nondeterministic adsorption behaviors and the aspect ratio dependence on the adsorption probability.

Heterogeneous Capillary Interactions of Interface-Trapped Ellipsoid Particles Using the Trap-Release Method.

Heterogeneous capillary interactions between ellipsoid particles at the oil-water interface were measured via optical laser tweezers. Two trapped particles were aligned in either tip-to-tip (tt) or side-to-side (ss) configurations via the double-trap method and were released from the optical traps, leading to particle-particle attractions due to the capillary forces caused by quadrupolar interface deformation. On the basis of image analysis and calculations of the Stokes drag force, the capillary interactions between two ellipsoid particles with the same aspect ratio (E) were found to vary with the particle pairs that were measured, indicating that the interactions were nondeterministic or heterogeneous. Heterogeneous capillary interactions could be attributed to undulation of the interface meniscus due to chemical and/or geometric particle heterogeneity. The power law exponent for the capillary interaction Ucap ≈ r-ß was found to be ß ≈ 4 and was independent of the aspect ratio and particle configuration in long-range separations. Additionally, with regard to the tt configuration, the magnitude of the capillary force proportionally increased with the E value (E > 1) when two ellipsoid particles approached each other in the tt configuration.

Comparison of the effects of acute exercise after overnight fasting and breakfast on energy substrate and hormone levels in obese men.

[Purpose] We compared the effects of acute aerobic exercise following overnight fasting and breakfast on energy substrate and hormone levels in obese male college students. [Subjects and Methods] This crossover study recruited 10 obese male college students with a body mass index >25 kg/m(2) or >20% body fat. One week post-recruitment, the subjects exercised in the morning after an overnight fast. At 2 weeks, they exercised post-breakfast. Energy substrate (glucose, free fatty acid) and metabolic hormone (insulin, growth hormone, and cortisol) levels were measured immediately before and after exercise and at 60 min post-exercise. [Results] We observed interaction effects between the measurement time and exercise treatment for glucose; significant differences between measurement times and between exercise treatments for free fatty acids; interaction effects between the measurement time and exercise treatment for insulin and significant differences in the measurement time; significance differences between measurement times and between exercise treatments for growth hormone; and significant differences between measurement times and between exercise treatments for cortisol. [Conclusion] Morning exercise following an overnight fast can be more effective in reducing body fat than post-prandial exercise. However, increased cortisol levels following exercise after overnight fasting may negatively affect long-term weight loss in obese men.

Surface Topography Induces and Orients Nematic Swarms of Active Filaments: Considerations for Lab-On-A-Chip Devices.

Surface-bound molecular motors can drive the collective motion of cytoskeletal filaments in the form of nematic bands and polar flocks in reconstituted gliding assays. Although these "swarming transitions" are an emergent property of active filament collisions, they can be controlled and guided by tuning the surface chemistry or topography of the substrate. To date, the impact of surface topography on collective motion in active nematics is only partially understood, with most experimental studies focusing on the escape of a single filament from etched channels. Since the late 1990s, significant progress has been made to utilize the nonequilibrium properties of active filaments and create a range of functional nanodevices relevant to biosensing and parallel computation; however, the complexity of these swarming transitions presents a challenge when attempting to increase filament surface concentrations. In this work, we etch shallow, linear trenches into glass substrates to induce the formation of swarming nematic bands and investigate the mechanisms by which surface topography regulates the two-dimensional (2D) collective motion of driven filamentous actin (F-actin). We demonstrate that nematic swarms only appear at intermediate trench spacings and vanish if the trenches are made too narrow, wide, or tortuous. To rationalize these results, we simulate the F-actin as self-propelled, semiflexible chains subject to a soft, spatially modulated potential that encodes the energetic cost of bending a filament along the edge of a trench. In our model, we hypothesize that an individual filament experiences a penalty when its projected end-to-end distance is smaller than the trench spacing ("bending and turning"). However, chains that span the channel width glide above the trenches in a force- and torque-free manner ("crowd-surfing"). Our simulations demonstrate that collections of filaments form nematic bands only at intermediate trench spacings, consistent with our experimental findings.

Quantification of polystyrene microsphere attachment probability at the oil‒water interface using a microfluidic platform.

This study investigates the effects of interparticle interactions and wettability on the particle attachment efficacy to the oil‒water interface. Three types of PS particles with different surface functional groups were examined at varying salt concentrations and the number of particles injected into the interface. Based on the microfluidic method and the surface coverage measurement, we found that the two contributing factors significantly influenced particle attachment efficiency to the interface, while the wettability factor has a major contribution. This research contributes to the understanding of physicochemical aspects of particle assembly at fluid interfaces and can offer strategies for forming tailored structures with desired interfacial properties.

Direct measurements of the colloidal Debye force.

Colloids often behave in a manner similar to their counterparts in molecular space and are used as model systems to understand molecular behavior. Here, we study like-charged colloidal attractions between a permanent dipole on an interfacial particle and its induced dipole on a water-immersed particle caused by diffuse layer polarization. We find that the scaling behavior of the measured dipole-induced dipole (D‒I) interaction via optical laser tweezers is in good agreement with that predicted from the molecular Debye interaction. The dipole character propagates to form aggregate chains. Using coarse-grained molecular dynamic simulations, we identify the separate roles of the D‒I attraction and the van der Waals attraction on aggregate formation. The D‒I attraction should be universal in a broad range of soft matter, such as colloids, polymers, clays, and biological materials, motivating researchers to further conduct in-depth research on these materials.

High impacts of cultivar and home-cooking practice on the content of free myo-inositol, a bioavailable health-promoting cyclitol, in sweet potato.

Free myo-inositol is a bioavailable form of a cyclitol having various health-promoting activities. The impact of cultivar and home-cooking practice on the content of free myo-inositol in sweet potatoes (12 cultivars grown in 2 different locations) was studied. A GC-MS/MS method following in situ trimethylsilylation was established and validated to determine free myo-inositol. The established analytical method was sensitive, precise, and accurate. It was found that free myo-inositol content in sweet potato varied greatly (sevenfolds) with cultivar, ranging from 377.1 to 2628.3 mg/kg dw. A cultivar Poongwon-mi was found to be an exceptionally rich source of free myo-inositol (2628.3 mg/kg dw). Home-cooking practice markedly increased free myo-inositol content (maximum 240%). Baking showed the highest impact on the increase in free myo-inositol, followed by steaming, microwave cooking, and boiling, in decreasing order. This represents the first report of the remarkably high impact of cultivar and home-cooking practice on the free myo-inositol content in sweet potato. PRACTICAL APPLICATION: The free myo-inositol content in sweet potato varied greatly with the cultivars. Poongwon-mi contained a surprisingly high content of free myo-inositol. Home-cooking dramatically increased the free myo-inositol content.

Paroxysmal sympathetic hyperactivity concurrent with hypothalamic injury in a patient with intracerebral hemorrhage: A case report.

BACKGROUND: Paroxysmal sympathetic hyperactivity (PSH) is characterized by exacerbated sympathetic discharge following severe brain injury. Here, we reports a patient diagnosed with PSH after ICH concurrent with hypothalamic injury, as demonstrated by diffusion tensor imaging (DTI). METHODS: A 27-year-old man patient was diagnosed with spontaneous intraventricular hemorrhage and intracerebral hemorrhage in both frontal lobes. Two months after onset, brain magnetic resonance imaging of the brain revealed a leukomalactic lesion in the hypothalamus. Three months after the onset, he presented with intermittent high fever, tachycardia, tachypnea, systolic hypertension, diaphoresis, and aggravated rigidity. Infection was ruled out by a physical examination, laboratory tests, and radiological studies. After administrating morphine and bromocriptine, the clinical manifestations improved dramatically. RESULTS: PSH after intracranial hemorrhage concurrent with the hypothalamic injury. Fractional anisotropy and mean diffusivity values of DTI were obtained in the hypothalamus. No significant difference in fractional anisotropy value was observed between the patient and control group (10 age-matched healthy male subjects) (P > .05). On the other hand, the mean diffusivity value was higher in the patient group than in the control group (P < .05), indicating hypothalamic injury. CONCLUSION: PSH concurrent with hypothalamic injury was observed in a patient with stroke. This study suggests that DTI can be a useful imaging method for evaluating the hypothalamic state of patients presenting with PSH after brain injury.

Effects of atrial fibrillation on motor outcome in patients with cerebral infarction.

BACKGROUND: Atrial fibrillation (AF) has been a leading cause of cerebral infarction, but the association with motor outcome after cerebral infarction remains unreported. In this study, we attempted to identify whether AF affects motor outcomes after cerebral infarction. METHODS: Seventy-six patients with a first-incidence cerebral infarction and who completed 6 months of rehabilitation were recruited to this retrospective study. The patients were divided into two groups based on the presence of AF (AF and non-AF groups). The upper extremity motricity index, lower extremity motricity index (LMI), modified Brunnstrom classification, and functional ambulation category (FAC) were evaluated, and those results were obtained within the first day and after 6 months of onset. Clinical factors that could affect motor outcome after cerebral infarction were also obtained. RESULTS: Compared with the non-AF group, the AF group had an upper extremity motricity index (47.15 ± 20.30 vs 58.66 ± 19.19; P = .032), LMI (53.42 ± 12.27 vs 65.58 ± 13.86; P = .001), and FAC scores (2.39 ± 0.93 vs 3.35 ± 0.93; P < .001) at 6 months after onset. Moreover, the AF group showed a lower FAC score gain than the non-AF group at 6 months after onset (2.33 ± 0.95 vs 3.28 ± 0.94; P < .001). Multivariate linear regression analyses showed that presence of AF had negative correlation with LMI gain (ß = -0.197; P = .010) and FAC gain (ß = -0.254; P = .011). CONCLUSION: We observed that AF had a negative effect on the motor outcome of the affected leg and the recovery of gait function in patients with cerebral infarction.

Retardation of Capillary Force between Janus Particles at the Oil-Water Interface.

Interactions among colloidal particles govern the hierarchical microstructure and its physical properties. Here, optical laser tweezers and Monte Carlo simulations are used to evaluate the effects of azimuthal rotation of Janus particles at the oil-water interface on interparticle interactions. We find that the capillary-induced attractive force between two Janus particles at the interface can be relaxed by azimuthal rotation around the critical separation region, at which the capillary force is ∼0.053 pN. Force relaxation leads to a decrease in capillary force around the critical separation region, resulting in a slight increase in the scaling exponent, compared to the theoretical prediction.

Sex-related differences in bone metabolism in osteoporosis observational study.

ABSTRACT: Although the incidence is lower in men than women, osteoporosis remains a significant health issue in men as it may give rise to severe complications if not managed appropriately. As men and women show different biological and social backgrounds, we retrospectively evaluated the differences in the bone metabolism between men and women using bone biomarkers.Bone mineral density (BMD) was determined in all patients using dual-energy X-ray absorptiometry (DXA) and analyzing various bone biomarkers such as carboxyl-terminal collagen crosslinks (CTX), osteocalcin (OCT), and alkaline phosphatase (ALP). The CTX/OCT ratio was used to estimate the association between bone absorption and formation.OCT, CTX, and ALP levels were elevated in patients with osteoporosis. Women displayed a higher incidence of osteoporosis and greater reduction in BMD than men. The mean OCT level in men was lower than that in women. Moreover, men showed significantly lower OCT levels than women of aged 65 and under 80 years old. Among patients with osteoporosis, men had a higher ratio of bone markers than women.Levels of biomarkers of bone formation and absorption were increased in the osteoporosis group. However, men showed lower increases in bone formation biomarkers than did women, indicating that the rate of bone formation relative to bone absorption did not increase in men compared with that in women. Therefore, we suggest that men and women have different bone metabolism in old age.

Myositis ossificans causing ulnar neuropathy: a case report.

Myositis ossificans (MO) can compress peripheral nerves and cause neuropathy. We herein describe a patient with ulnar neuropathy caused by MO at the medial elbow. A 28-year-old man with a drowsy mentality and multiple organ damage following a traffic accident was admitted to our hospital. After 3 weeks of postoperative care, the patient's mental status recovered. However, he complained of severe sharp pain in his left medial forearm and fourth and fifth fingers. He exhibited weak fifth finger abduction and wrist adduction. Severe elbow joint pain was elicited during range-of-motion testing of his left elbow. Ultrasound also showed an edematous, enlarged, hypoechoic ulnar nerve lying above the MO, and the MO outwardly displaced the ulnar nerve. Elbow radiographic examination, computed tomography, and magnetic resonance imaging revealed MO development and compression of the left ulnar nerve. The patient underwent surgery; the following day, his left medial forearm pain completely disappeared with slight improvement in the motor weakness of fifth finger abduction. Ultrasound is a useful tool to easily evaluate the presence of MO and compression of peripheral nerves caused by MO.

Mid-back pain due to a penetrating atherosclerotic aortic ulcer: do not miss the diagnosis-a case report.

In clinical practice, clinicians often meet patients suffering from mid-back pain. One of the possible causes of mid-back pain is penetrating atherosclerotic aortic ulcer (PAU), but the diagnosis is often delayed owing to its low incidence. Here, we report a patient with mid-back pain due to a PAU, who was diagnosed after receiving several procedures for reducing musculoskeletal pain. A 65-year-old man visited our pain clinic for mid-back pain [numeric rating scale (NRS): 7] experienced for 2 months. The pain was radiated to the lateral chest area and was aggravated when in the supine and standing positions. Trigger point injection, medial branch block, and pulsed radiofrequency were ineffective. The cardiac evaluation and abdominal computed tomography (CT) results showed no abnormalities. On CT aortography at 3 months after pain onset, intraluminal thrombus, multiple ruptured PAUs, and aneurysmal change of the descending thoracic aorta were found. Accordingly, PAU was diagnosed as the origin of the patient's pain. We administered nicardipine with a rate of 1.15 mcg/kg/min and esmolol with a rate of 100 mcg/kg/min for controlling the systolic blood pressure. In addition, an anticoagulant was administered orally. To alleviate the pain, we further administered intravenous opioid. Approximately 6 h after, the systolic blood pressure decreased to 100-120 mmHg, and the pain rating decreased to NRS 1. Two weeks after the discharge, the patient's pain rating was sustained at NRS 1. Clinicians should be aware of the fact that PAU can be a cause of mid-back or chest pain.

Interpretation of interfacial interactions between lenticular particles.

HYPOTHESIS: The geometric features of charged particles at a fluid-fluid interface substantially affect their interfacial configurations and interparticle interactions (electrostatic and capillary forces). Because lenticular particles exhibit both spherical and nonspherical surface characteristics, an investigation of their interfacial phenomena can provide in-depth understanding of the relationship between the configuration and the interactions of these particles at the interface. EXPERIMENTS: Three types of lenticular particles are prepared using a seeded emulsion polymerization method. Pair interactions at the oil-water interface are directly measured with optical laser tweezers. The numerical calculation of the attachment energy of the particle to the interface is used to predict their configuration behaviors at the interface. FINDINGS: The lenticular particles are found to adopt either an upright or inverted configuration that can be determined stochastically. When the interface contacts the truncated boundary or the biconvex boundary, the local interface deformation-induced capillary attraction likely becomes dominant. The contact probability can be estimated on the basis of the attachment energy profile and related to the relative strengths of capillary attraction and electrostatic repulsion between two particles at the interface. Furthermore, possible artifacts in measurements of the pair interactions between nonspherical particles with optical laser tweezers are discussed, depending on their interfacial configurations.

Janus amphiphilic nanoplatelets as smart colloid surfactants with complementary face-to-face interactions.

We introduce amphiphilic nanoplatelets (ANPLs) that not only have a nanoscale Janus platelet geometry, but can also induce complementary face-to-face interactions among Pickering emulsion droplets. We showed that the ANPLs with such high surface activity can be a promising colloid surfactant enabling smart rheology modification of complex emulsion fluids.

Mapping Anisotropic and Heterogeneous Colloidal Interactions via Optical Laser Tweezers.

Heterogeneity among particles is an inherent feature that allows nondeterministic prediction of the properties of assembled structures and materials composed of many particles. Here, we report a promising strategy to quantify the heterogeneous and anisotropic interactions between ellipsoid particles using optical laser tweezers. The configuration and separation between two particles at an oil-water interface were optically controlled, and the capillary interaction behaviors were directly observed and measured. As a result, the optimal particle configurations at energetically favorable states were obtained, and the interaction forces between the particles were identified accurately by determining the trap stiffness in the direction of major and minor axes of the particle. Visualization of the capillary field around individual particles confirmed that the capillary interactions were quadrupolar, anisotropic, and heterogeneous. The measurement method presented here can be widely used to quantify interaction fields for various types of anisotropic particles.

Relationships among Disability, Quality of Life, and Physical Fitness in Lumbar Spinal Stenosis: An Investigation of Elderly Korean Women.

STUDY DESIGN: A cross-sectional, case-control study. PURPOSE: To investigate associations between physical fitness measures and disabilities related to back pain and quality of life (QOL) by the presence of symptomatic lumbar spinal stenosis (LSS) in elderly Korean women. OVERVIEW OF LITERATURE: LSS leads to decreased functioning and reduced QOL. However, correlations among physical fitness, disability, and QOL have not been investigated in elderly women with LSS. METHODS: Participants included women aged 65 years and older (n=192), divided into a study group (n=38) and a control group (n=154) based on the presence/absence of LSS. All participants underwent physical function and fitness tests. Oswestry disability index (ODI) scores and EuroQol five-dimensional questionnaire (EQ-5D-5L) scores were used to assess disability and health-related QOL. RESULTS: The results for the handgrip strength, sit-and-reach, functional reach, and timed up and go (TUG) tests were significantly higher in the control group than the LSS group. ODI scores were significantly higher and EQ-5D-5L scores significantly lower in the LSS group. TUG and functional reach test scores were significantly correlated with ODI scores, and handgrip strength was strongly interrelated with ODI and EQ-5D-5L scores in the LSS group. No other physical fitness measures showed statistically significant relationships with ODI or EQ-5D-5L scores. CONCLUSIONS: In elderly Korean women with LSS, back pain-related disability and QOL are significantly associated with some physical fitness parameters such as handgrip strength. Handgrip strength reflects general muscle strength, which is significantly interrelated with the level of disability and QOL. Our results suggest that enhancing generalized muscle strength helps to reduce disability due to back pain and improve QOL in patients with LSS.