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There are few longitudinal studies about South Asians (SAs) and little information about recruitment and retention approaches for this ethnic group.
We followed 906 SAs enrolled in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) cohort for 5 years. Surviving participants were invited for a second clinical exam from 2015 to 2018. A new wave of participants was recruited during 2017–2018. We assessed the yields from different methods of recruitment and retention.
A total of 759 (83%) completed the second clinical exam, and 258 new participants were enrolled. Providing a nearby community hospital location for the study exam, offering cab/shared ride reimbursement, and conducting home visits were the most effective methods for enhancing retention. New participant recruitment targeted women and individuals with lower socioeconomic status, and we found that participant referrals and active community engagement were most effective. Mailing invitational letters to those identified by electronic health records had very low yield.
Recruitment and retention strategies that address transportation barriers and increase community engagement will help increase the representation of SAs in health research.
We present a method for measuring the shear complex modulus of hydrogels by oscillatory nanoindentation, with unprecedented attention to procedure and uncertainty analysis. The method is verified by testing a typical low-molecular-weight gelator formed from the controlled hydrolysis of glucono-δ-lactone. Nanoindentation results are compared with those obtained by rheometry using both vane-in-cup and parallel-plate fixtures. At 10 Hz, the properties measured by oscillatory nanoindentation were G′ = 38.1 ± 2.8 kPa, tan δ = 0.22 ± 0.02. At the same frequency, the properties measured by rheometry were G′ = 15.3 ± 2.9 kPa, tan δ = 0.11 ± 0.016 (vane-in-cup) and G′ = 7.9 ± 1.1 kPa, tan δ = 0.05 ± 0.004 (parallel-plate). The larger shear modulus measured by nanoindentation is due to the scale of testing. Whereas rheometry characterizes the bulk material response, nanoindentation probes the fibrous network of the gel. The procedure and analysis presented here are valuable for nanoindentation testing of other compliant materials such as hydrogels, soft biological tissue, and food products.
It has been established that Coronal Mass Ejections (CMEs) may have significant impact on terrestrial magnetic field and lead to space weather events. In the present study, we selected several CMEs which are associated with filament eruptions on the Sun. We attempt to identify the presence of filament material within ICME at 1AU. We discuss how different ICMEs associated with filaments lead to moderate or major geomagnetic activity on their arrival at the Earth. Our study also highlights the difficulties in identifying the filament material at 1AU within isolated and in interacting CMEs.
Radio-glaciological parameters from the Moore’s Bay region of the Ross Ice Shelf, Antarctica, have been measured. The thickness of the ice shelf in Moore’s Bay was measured from reflection times of radio-frequency pulses propagating vertically through the shelf and reflecting from the ocean, and is found to be 576 ± 8 m. Introducing a baseline of 543 ± 7m between radio transmitter and receiver allowed the computation of the basal reflection coefficient, R, separately from englacial loss. The depth-averaged attenuation length of the ice column, 〈L〉 is shown to depend linearly on frequency. The best fit (95% confidence level) is 〈L(ν)〉= (460±20) − (180±40)ν m (20 dB km−1), for the frequencies ν = [0.100–0.850] GHz, assuming no reflection loss. The mean electric-field reflection coefficient is (1.7 dB reflection loss) across [0.100–0.850] GHz, and is used to correct the attenuation length. Finally, the reflected power rotated into the orthogonal antenna polarization is <5% below 0.400 GHz, compatible with air propagation. The results imply that Moore’s Bay serves as an appropriate medium for the ARIANNA high-energy neutrino detector.
Bacterial infections are commonly found on paper towels and other paper products leading to the potential spread of bacteria and consequent health concerns. The objective of this in vitro study was to introduce antibacterial properties to paper towel surfaces by coating them with selenium nanoparticles. Results showed that the selenium nanoparticle coated paper towels inhibited the growth of S. Aureus and P. aeruginosa by 80%∼90% after 72 hours compared with the uncoated paper towels. Thus, the study showed that nano-selenium coated paper towels may lead to an increased eradication of bacteria to more effectively clean a wide-range of clinical environments, thus, improving health.
We explored the use of galvanostatic electrochemical deposition of Pt for cost-effective fabrication of interconnects in flexible implantable bio-medical devices. Initial studies were done on coupons diced from 200 mm Si wafers coated with PVD TiN. Based on the physical and chemical properties of the electrodeposited Pt films, optimal conditions were chosen for through-mask plating of centimeters long Pt lines on flexible, medical grade, releasable polyimide layers. Possibility for further up-scaling was considered with special emphasis on high throughput manufacturing of Pt interconnects with good adhesion to TiN/flexible substrates, low impurity content and resistivity, and acceptable roughness and uniformity.
With the rise of ageing population, the need to restore the function of degenerative bone greatly drives the market for bone grafts. Hydroxyapatite (HA) is chemically similar to natural bone mineral and has been widely used in bone graft applications. However, its slow osseointegration process and lack of antibacterial property could lead to implant-related infection, resulting in implant failure. Studies on ionic substitution of apatite have gained attention in recent years with greater understanding of the composition of bone mineral being a multi-substituted apatite. An integrated approach is proposed by co-substituting silver (Ag) and silicon (Si) into HA (Ag,Si-HA) to modify its surface for bi-functional properties. Incorporation of Si can enhance the biomineralization of HA and introduction of Ag can create antibacterial property. Ag,Si-HA containing 0.5 wt.% of Ag and 0.8 wt.% of Si was prepared by a wet precipitation method. A phase-pure apatite with a nanorod morphology of dimensions 60 nm in length and 10 nm in width was synthesized. Surface Ag+ ions of Ag,Si-HA were demonstrated to prevent the replication of adherent Staphylococcus aureus bacteria for up to 120 h. Biocompatibility tests revealed that human adipose-derived mesenchymal stem cells (hMSCs) proliferated well on Ag,Si-HA with culturing time. Enhanced cell attachment in turn permitted greater bone differentiation as evidenced in the increase of collagen type I and osteocalcin expressions of hMSCs cultured on Ag,Si-HA as compared to HA from day 14 onwards. Overall, co-substitution of Ag and Si could complement the benefits of each substituent by endowing HA with antibacterial property, and concurrently promoting its biological performance. Their synergistic effects can serve unmet medical needs and solve the problem of implant-related infection. This work also enhances the understanding of substituted apatite with multiple ions for bi-functional properties.
The present investigation involves the synthesis of chitosan based composite sponges in view of their applications in wound dressing, antibacterial and haemostatic. A facile CO2 bubbles template freeze-drying method was developed for the fabrication of macroporous chitosan- poly(vinyl alcohol) (PVA) composite sponges with a typical porosity of 50% and pore size of 100-300 µm. The composite sponges show a high water absorption rate up to 60 times of its weight and a water vapor transmission rate of 30 ∼ 70g/m2 • h. Effects of the content of cross-linking agent and PVA on mechanical properties and moisture permeability were examined. Improved strength and flexibility of the chitosan sponges were observed with the presence of PVA. Further, the antibacterial and haemostatic activities have been demonstrated. The Chitosan/PVA sponges of high liquid absorption, appropriate moisture permeability, excellent antimicrobial and haemostatic activities have a great potential for wound dressing applications.
The aim of this study was to prepare various sized nano-pits on 316 L stainless steel and examine their effects on the attachment and proliferation of fibroblasts. In this study, 316L stainless steel with tunable pit sizes (0, 25, 50, and 60 nm) were fabricated by an anodization procedure in an ethylene glycol electrolyte solution containing 5 vol.% perchloric acid. The surface morphology of 316L stainless steel were characterized by scanning electron microscopy (SEM). The nano-pit arrays on all the 316L stainless steel samples were in a regular arrangement. The surface properties of the 316L stainless steel nano-pit surface showed improved wettability properties as compared to the untreated 316L stainless steel. The nano-pit surfaces with 50 nm and 60 nm diameter were rougher at the nanoscale than other samples. The attachment and proliferation of fibroblasts were investigated for up to 3 days in culture using MTT assays. Compared to unanodized (that is, nano-smooth) and smooth surfaces, 50 and 60 nm diameter nano-pit surfaces dramatically enhanced the initial fibroblast attachment and growth up to 3 days in culture. The results reported in this study showed that the 50 and 60 nm nano-pit surfaces promoted fibroblast adhesion and proliferation by increasing the surface roughness and adsorption of fibronectin. Such nano-pit surfaces can be designed to support fibroblast growth and be important for improving the use of 316L stainless steel for various implant applications (such as for improved skin healing for amputee devices or for percutaneous implants).
A facile technique was developed for a long-term increase in silicone elastomer surface hydrophilicity, eliminating the need for post-cure surface treatment (e.g. oxygen plasma or surface grafting). Well-defined silicones (1-4 kDa) with a central vinyl functionality and discrete PEG2, PEG3 and tetrahydrofurfuryl (THF) pendant endgroups were synthesized, characterized and used as comonomers in addition-cure, platinum catalyzed 2-part silicone elastomer formulations. The modified silicone elastomers were optically clear and maintained the mechanical performance characteristic of this class of material with up to 20 wt.% comonomer in the 2-part formulation. Contact angle measurements of deionized water on the silicone elastomer surface showed improved wettability with comonomer content. The elastomer surface shifted from hydrophobic (contact angle ∼120°C) to hydrophilic (contact angle < 90°C) at ∼5 wt.% comonomer loadings for extended time frames (> 5 months). Coefficient of friction measurements of the modified silicone elastomers revealed an increase in surface lubricity with comonomer loadings.
A hand operated benchtop stamping press was developed to conduct research on microscale hole fabrication in polymer membranes for applications as scaffolds in tissue engineering. A biocompatible and biodegradable polymer, poly(ε-caprolactone), was selected for micropunching. Membranes between 30 μm and 50 μm thick were fabricated by hot melt extrusion, but could not be stamped with a 200 μm circular punch at room temperature, regardless of die clearance due to excessive strain to fracture. This problem was overcome by cooling the membrane and die sets with liquid nitrogen to take advantage of induced brittle behavior below the polymer’s glass transition temperature. While cooled, 203 μm hole patterns were successfully punched in 33 μm thick poly(ε-caprolactone) membranes with 11% die clearance, achieving 71% porosity.
The detection of hydrogen peroxide has been shown to be very important in recent years due to its role in many industrial applications, as well as in biological reactions. Previously, a commercial silver flake-based ink (PF-410, Acheson®), when screen-printed as films to substrate and subsequently coated with surfactant and salt (sodium dodecylbenezene sulphonate (SDBS) and KCl), have been shown to significantly enhance the electrochemical reduction of hydrogen peroxide – up to 80-fold over non-modified films. In this study, an attempt to understand the effect of the silver material within the ink on the catalytic behaviour of the films, as well as the distinct change in behaviour upon modification with surfactant/salt are examined. Factors including Ag morphology, presence of dispersant and Ag material supplier are all investigated to assess their effects on the electrocatalytic breakdown of hydrogen peroxide. To do this, a range of inks were formulated from various Ag materials, e.g., flakes and nanoparticles of various sizes. These inks were then cast as coatings onto conventional glassy carbon (GC) electrodes, and their electrocatalytic behaviours, both as modified and non-modified films were studied.
Hydroxyapatite-chondroitin sulfate (HAp/ChS) composites were synthesized with calcium hydroxide suspension and phosphoric acid solution containing ChS through a precipitation method, and the microparticles were then fabricated by a spray dry method with the suspension of the composites. Bovine serum albumin (BSA) with negative charge or lysozyme (LYZ) with positive charge at pH7.0 was adsorbed onto the HAp/ChS microparticles. However, the HAp/ChS microparticles adsorbed LYZ more than the HAp microparticles compared with BSA due to the electrostatic interaction from negatively-charged sulfate or carboxyl group of ChS in the composites. The release property of BSA from the HAp/ChS microparticles was evaluated in Dulbecco’s phosphate buffered saline (pH7.2). The HAp/ChS microparticles released quickly 100% of the adsorbed BSA, while HAp microparticles released 45% of BSA. These results indicated that incorporation of ChS in the microparticles controls the adsorption and release properties of protein due to the electrostatic interaction. The HAp/ChS microparticles therefore are a candidate of a carrier for drugs like vaccines.
As an emerging manufacturing technique, nanoimprint lithography (NIL) can fabricate micro and nanoscale features of microfluidic devices at very high accuracy and reliability. In high-temperature TNIL process, a polymer melt such as polymethyl-methacrylate (PMMA) is heated beyond the melting temperature so that it behaves predominantly as a fluid during the imprint process. The process parameters such as pressure, temperature, and material properties play critical roles in the NIL process. In this work, the process of thermal nanoimprint lithography (TNIL) is studied computationally with emphasis on the effect of soft-mold deformation on polymer melt flow and finished result by-way-of fluid-structure interaction (FSI) technology. Process is assumed isothermal at 180 °C. Applications of this modeling technique range from micro- and nano-patterns used in micro-channels for biomedical devices to other applications such as biological/particle sensors or super-hydrophobic surfaces. The simulation result is compared to experimental results, and traits observed in TNIL done with soft mold are supported and explained through numerical results.
Nitinol was coated with biocompatible calcium phosphate materials by pulsed electrolytic deposition (ELD) to reduce toxic metal-ions elution. The pulse ELD for the stents was carried out with changing the current off-periods (toff) of the pulse wave. The pulse ELD suppressed the generation of H2 gas due to the electrolysis of water on a calcium phosphate layer and improved the adhesiveness of the coating layer on nitinol compared with a conventional DC-ELD. The coating layers were identified to be octacalcium phosphate (OCP) at lower toff, while they were transformed to dicalcium phosphate anhydraous (DCPA) with an increase of toff. The layers of OCP or DCPA on the nitinol surface were subjected to a NaOH treatment at 60°C for 3days to transform them into hydroxyapatite (HAp). From results of a metal-ions elution test, the deposited calcium phosphates suppressed nickel ions elution at one quarter compared with the bare nitinol stent. These results indicate that the pulse ELD of biocompatible calcium phosphate materials on the nitinol stent was one of the best techniques to create firmly attached coating on it and reduce toxic nickel ions elution.
In hospitals and clinics worldwide, medical device surfaces have become a rapidly growing source of nosocomial infections. Almost immediately after adhering to a device surface, bacteria can begin to form a biofilm, which makes the infection especially difficult to treat and often necessitates device removal. Adding to the severity of this problem is the spread of bacterial genetic tolerance to antibiotics, in part demonstrated by the recent and significant increase in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA).
Nanomaterials are beginning to be used for a wide variety of biomedical applications due to their unique surface properties which have the ability to control initial protein adsorption and subsequent cell behavior. This “nanoroughness” gives nanomaterials a greater functional surface area than conventional materials, which do not have significant features on the nanoscale. In addition, it is theorized that nanoparticles may also have general mechanisms of toxicity towards bacteria that do not cause problems for mammalian cells.
The objective of the present in vitro study was to develop a nanocomposite material by embedding conventional polyvinyl chloride (PVC) with zinc oxide nanoparticles through a simple and inexpensive procedure. The effect of different nanoparticle sizes and %wts were investigated. Results demonstrated that this technique significantly decreased S. aureus density and biofilm formation without the incorporation of antibiotics or other pharmaceuticals, as well as increased the adhesion of human fibroblast cells. Thus, this material could have much promise for use in the manufacture of common implanted medical devices.