Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 31
Filter
Add more filters










Publication year range
1.
ACS Appl Mater Interfaces ; 16(20): 26004-26014, 2024 May 22.
Article in English | MEDLINE | ID: mdl-38728621

ABSTRACT

Two-dimensional (2D) transition metal carbides, known as MXenes, have captured much attention for their excellent electrical conductivity and electrochemical capability. However, the susceptibility of MXenes to oxidation, particularly Ti3C2Tx transforming into titanium dioxide upon exposure to ambient air, hinders their utilization for extended operational life cycles. This work introduces a simple and straightforward method for producing ultrathin MXene electrode films tailored for energy storage applications, employing centrifugal-gravity force. Our approach significantly suppresses the oxidation phenomenon that arises in MXene materials and also effectively prevents the recrystallization of potentially residual LiF during the film formation. Additionally, the utilization of this MXene electrode in an all-solid-state microsupercapacitor (MSC) with an interdigitated pattern demonstrates an exceptionally improved and stable electrochemical performance. This includes a high volumetric capacitance of approximately 467 F cm-3, an energy density of around 65 mWh cm-3, and impressive long-term cycle stability, retaining about 94% capacity after 10 000 cycles. Moreover, a downsized MSC device exhibits remarkable mechanical durability, retaining over 98% capacity even when folded and sustaining stability over extended periods. Therefore, we believe that this study provides valuable insights for advancing highly integrated energy storage devices, ensuring exceptional electrochemical efficiency and prolonged functionality in diverse environments, whether ambient or humid.

2.
West J Nurs Res ; 46(4): 315-326, 2024 04.
Article in English | MEDLINE | ID: mdl-38420931

ABSTRACT

BACKGROUND: Paid caregivers are needed to support older adults, but caregiver burden contributes to high turnover rates. Assistive technologies help perform activities of daily living (ADLs) and can reduce caregiver burden, but little is known about how they impact paid caregivers. OBJECTIVE: This scoping review provides an overview of evidence on using assistive technology to reduce burdens on paid caregivers working with older adults. DESIGN: The review was conducted from May to August 2022. The eligibility criteria included: (1) publication within 5 years in peer-reviewed journals, (2) investigation of assistive technology, (3) main participants include paid caregivers supporting older adults, and (4) describing impacts on caregiver burden. Searches were conducted in 6 databases, generating 702 articles. The charted data included (1) country of study, (2) participant care roles, (3) study design, (4) main outcomes, and (5) types of assistive technology. Numerical description and qualitative content analysis of themes were used. RESULTS: Fifteen articles reporting on studies in 9 countries were retained for analysis. Studies used a variety of quantitative (8/15), qualitative (5/15), and mixed (2/15) methods. Technologies studied included grab bars and handrails, bidet seats, bed transfer devices, sensor and monitoring systems, social communication systems, and companion robots. Articles identified benefits for reducing stress and workload, while paid caregivers described both positive and negative impacts. CONCLUSIONS: Literature describing the impact of assistive technology on paid caregivers who work with older adults is limited and uses varied methodologies. Additional research is needed to enable rigorous evaluation of specific technologies and impacts on worker turnover.


Subject(s)
Caregivers , Self-Help Devices , Humans , Aged , Activities of Daily Living , Research Design
3.
Small ; 20(28): e2308821, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38308357

ABSTRACT

The branched network-driven ion solvating quasi-solid polymer electrolytes (QSPEs) are prepared via one-step photochemical reaction. A poly(ethylene glycol diacrylate) (PEGDA) is combined with an ion-conducting solvate ionic liquid (SIL), where tetraglyme (TEGDME), which acts like interneuron in the human brain and creates branching network points, is mixed with EMIM-NTf2 and Li-NTf2. The QSPE exhibits a unique gyrified morphology, inspired by the cortical surface of human brain, and features well-refined nano-scale ion channels. This human-mimicking method offers excellent ion transport capabilities through a synaptic branched network with high ionic conductivity (σDC ≈ 1.8 mS cm-1 at 298 K), high dielectric constant (εs ≈ 125 at 298 K), and strong ion solvation ability, in addition to superior mechanical flexibility. Furthermore, the interdigitated microsupercapacitors (MSCs) based on the QSPE present excellent electrochemical performance of high energy (E  =  5.37 µWh cm-2) and power density (P  =  2.2 mW cm-2), long-term cycle stability (≈94% retention after 48 000 cycles), and mechanical stability (>94% retention after continuous bending and compressing deformation). Moreover, these MSC devices have flame-retarding properties and operate effectively in air and water across a wide temperature range (275 to 370 K), offering a promising foundation for high-performance, stable next-generation all-solid-state energy storage devices.

4.
J Allergy Clin Immunol Pract ; 12(2): 290-299, 2024 02.
Article in English | MEDLINE | ID: mdl-38013155

ABSTRACT

Disparities in environmental and social determinants of health (DOH) are associated with morbidity in atopic dermatitis (AD). The socioecological model (SEM) is a framework that can be applied to better understand how such DOH impacts patients with AD. We include a case scenario of a remote Indigenous patient reflective of real-world situations of living with AD and examine relevant impact, gaps in knowledge, and further research needs. This review highlights a variety of social and environmental exposures as important DOH which must be addressed to achieve optimal management in AD. The "rainbow model" is a modified framework to help illustrate how complex environmental and social forces impact both AD presentation and therapeutic success. However, practical applications and outcome metrics for health promotion are limited. An inter- and transdisciplinary approach is paramount to address the complex challenges associated with AD care, as well as multistakeholder approach integrating culturally-competent equitable health frameworks. This review underscores the importance of expanding the focus of AD management beyond basic science and clinical trials to recognize and address health disparities and to promote optimal health and well-being in patients with AD, and contributes a working approach to mapping the complex interventions and patient-oriented research needed using a focus on remote North American Indigenous patients affected by AD.


Subject(s)
Dermatitis, Atopic , Humans , Dermatitis, Atopic/epidemiology , Dermatitis, Atopic/therapy , Health Promotion , Racial Groups , Rural Population , North America
5.
Adv Sci (Weinh) ; 10(32): e2303838, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37792271

ABSTRACT

Soft robotics systems are currently under development using ionic electroactive polymers (i-EAP) as soft actuators for the human-machine interface. However, this endeavor has been impeded by the dilemma of reconciling the competing demands of force and strain in i-EAP actuators. Here, the authors present a novel design called "ions-silica percolated ionic dielectric elastomer (i-SPIDER)", which exhibits ionic liquid-confined silica microstructures that effectively resolve the chronic issue of conventional i-EAP actuators. The i-SPIDER actuator demonstrates remarkable electromechanical conversion capacity at low voltage, thanks to improved ion accumulation facilitated by interpreting electrode polarization at the electrolyte-electrode interface. This approach concurrently enhances both strain (by approximately 1.52%) and force (by roughly 1.06 mN) even at low Young's modulus (merely 5.9 MPa). Additionally, by demonstrating arachnid-inspired soft robots endowed with user-desired tasks through control of various form factors, the development of soft robots using the i-SPIDER that can concomitantly enhance strain and force holds promise as a compelling avenue for ushering in the next generation of miniaturized, low-powered soft robotics.

6.
ACS Appl Mater Interfaces ; 15(2): 3054-3068, 2023 Jan 18.
Article in English | MEDLINE | ID: mdl-36621929

ABSTRACT

Due to the lower cost and greater natural abundance of the sodium element on the earth than those of the lithium element, sodium-based ionic gel polymer electrolytes (IGPEs) are becoming a more cost-effective and popular material choice for portable and stationary energy solutions. The sodium-based IGPEs, however, appeared relatively inferior to their lithium-based counterparts for use in high-performance microsupercapacitors in terms of ionic conductivity and electrochemical stability. To tackle these issues, poly(ethylene glycol) diacrylate (PEGDA) with fast polymerization to build a polymer matrix and sodium perchlorate (NaClO4) with high chemical stability and high thermal stability are employed to generate free ions for an ionic conducting phase with the support of tetramethylene glycol ether (G4) and 1-ethyl-3-methylimidazolium bis(triflouromethylsulfonyl)imide (EMIM-TFSI). It was found that the ionic conductivity (σdc) of this sodium-based IGPE reaches up to 0.54 mS/cm at room temperature. To manifest a high-conductivity sodium-based IGPE (SIGPE), a microsupercapacitor (MSC) with an area of 5 mm2 is designed and fabricated on an interdigital reduced graphene oxide electrode. This MSC demonstrates prominent performance with a high power density of ∼2500 W/kg and a maximum energy density of ∼0.7 Wh/kg. Furthermore, after 20,000 cycles at an operating potential window from 0.0 to 1.0 V, it retains approximately 98.9% capacitance. An MSC array in 3 series × 3 parallels (3S × 3P) was successfully designed as a power source for a basic circuit with an LED. Therefore, we believe that our sodium-based IGPE microsupercapacitor holds its promising role as a solid-state energy source for high-performance and high-stability energy solutions.

7.
Nat Commun ; 13(1): 3769, 2022 Jun 30.
Article in English | MEDLINE | ID: mdl-35773254

ABSTRACT

Implementing self-healing capabilities in a deformable platform is one of the critical challenges for achieving future wearable electronics with high durability and reliability. Conventional systems are mostly based on polymeric materials, so their self-healing usually proceeds at elevated temperatures to promote chain flexibility and reduce healing time. Here, we propose an ion-cluster-driven self-healable ionoconductor composed of rationally designed copolymers and ionic liquids. After complete cleavage, the ionoconductor can be repaired with high efficiency (∼90.3%) within 1 min even at 25 °C, which is mainly attributed to the dynamic formation of ion clusters between the charged moieties in copolymers and ionic liquids. By taking advantages of the superior self-healing performance, stretchability (∼1130%), non-volatility (over 6 months), and ability to be easily shaped as desired through cutting and re-assembly protocol, reconfigurable, deformable light-emitting electroluminescent displays are successfully demonstrated as promising electronic platforms for future applications.

8.
RSC Adv ; 10(36): 21309-21317, 2020 Jun 02.
Article in English | MEDLINE | ID: mdl-35518755

ABSTRACT

Taking advantage of the triboelectrification effect and electrostatic induction, triboelectric nanogenerators (TENGs) provide a simple and efficient path to convert environmental mechanical energy into electric energy. Since the generation of surface charges and their density on triboelectric materials are the key factors in determining TENG performance, many efforts have been undertaken to engineer the structures and chemistry of triboelectric materials. Among others, dielectric control of triboelectric materials is an emerging approach because the dielectric constant is intimately correlated with the capacitance of materials. In this regard, we prepared porous polydimethylsiloxane (PDMS) composites decorated with Au nanoparticles (NPs), which was designed to engineer the compressibility and dielectric constant of PDMS elastomer. To this end, a polydopamine layer was synthesized on the PDMS surface to facilitate the homogeneous deposition of Au NPs. Unlike untreated PDMS sponges, Au NPs were efficiently coated onto polydopamine-treated PDMS sponges to increase the dielectric constant. When the resulting porous NP-PDMS composites were assembled into TENG devices, the electrical output of the TENGs initially improved but decreased with the amount of Au NPs. This trade-off relationship has been discussed in terms of charge generation on the air surface and pores of NP-PDMS composites based on a recent experimental model.

9.
ACS Appl Mater Interfaces ; 11(45): 42221-42232, 2019 Nov 13.
Article in English | MEDLINE | ID: mdl-31613585

ABSTRACT

To achieve both high structural integrity and excellent ion transport, designing ion gel polymer electrolytes (IGPEs) composed of an ionic conducting phase and a mechanical supporting polymer matrix is one of the promising material strategies for the development of next-generation all-solid-state energy storage systems. Herein, we prepared an IGPE thin film, in which an ion-diffusing phase containing ionic liquids and lithium salts was bicontinuously intertwined with a cross-linked epoxy phase, using a silicon elastomer-based stamping method, thus producing a homogeneous IGPE-based thin film with low surface roughness (Rrms = 0.5 nm). Following the optimization of the IGPE thin film in terms of the concentrations of ionic constituents, the film thickness, and various process parameters, the IGPE itself showed a high ionic conductivity of 0.23 mS/cm with a low activation energy for lithium-ion transport, as well as the high capacitance of approximately 10 µF/cm2 based on the metal-insulator-metal configuration. Furthermore, an all-solid-state supercapacitor containing two IGPE coating-activated carbon electrodes produced using our poly(dimethylsiloxane) (PDMS) stamping method exhibited high energy and power densities (44 W h/kg at 875 W/kg and 28 kW/kg at 3 W h/kg). It was also found that this supercapacitor showed a dramatic reduction (more than 50%) of the current-resistance (IR) drop, which is an indicator of low interface resistance, while maintaining the initial electrochemical performance even after severe mechanical deformation such as bending or rolling. Therefore, all these results support the fact that our developed PDMS stamping method enables the rendering of a high-performance ion gel polymer thin-film-based electrolyte with acceptable stability and mechanical flexibility for all-solid-state wearable energy storage devices.

10.
Sci Rep ; 9(1): 2463, 2019 02 21.
Article in English | MEDLINE | ID: mdl-30792420

ABSTRACT

Hydrogels have been developed and applied to various biomedical applications due to their biocompatibility. However, understanding of modulation between cells to hydrogel interface is still unclear, and parameters to explain the interaction are not sophisticated enough. In this report, we studied the effect of polymer chain flexibility on cell adhesion to various hydrogel constructs of collagen and fibrin gels. Specifically, novel method of semi-flexible model-based analysis confirmed that chain flexibility mediated microstructure of the hydrogels is a critical factor for cell adhesion on their surfaces. The proposed analysis showed possibility of more accurate prediction of biocompatibility of hydrogels, and it should be considered as one of the important criteria for polymer design and selections for enhancing both biocompatibility and biofunctionality.


Subject(s)
Biocompatible Materials/chemistry , Human Umbilical Vein Endothelial Cells/cytology , Hydrogels/chemistry , Animals , Cell Adhesion , Collagen/chemistry , Elastic Modulus , Fibrin/chemistry , Humans
11.
RSC Adv ; 9(7): 3972-3978, 2019 Jan 25.
Article in English | MEDLINE | ID: mdl-35518086

ABSTRACT

A series of dicationic imidazolium bis(tetrafluoroborate) salts were newly synthesized, and their phase transition behaviors were correlated with thermal, scattering, optical and conductivity results. The bis-imidazolium salts having side-chain lengths of C6-C10 showed plastic crystal mesophases, while a liquid crystal mesophase was formed in the bis-imidazolium salts with long side-chains (C11 and C12). Soft plastic and liquid crystalline phases were also confirmed by wide-angle X-ray diffraction. For the bis-imidazolium salts exhibiting a plastic crystal mesophase, the ionic conductivity suddenly increased at the melting temperature. However, the bis-imidazolium salts with long side-chains showed a slope increase during the liquid crystal-liquid crystal transition.

12.
Nat Commun ; 9(1): 5029, 2018 11 28.
Article in English | MEDLINE | ID: mdl-30487526

ABSTRACT

The synthesis of high-conductivity solid-state electrolyte materials with eliminated polarization loss is a great challenge. Here we show a promising potential of single-ion block copolymers with crystalline protogenic channels as efficient proton conductors. Through the self-organization of zwitterion, imidazole, and polystyrene sulfonate with controlled dipolar interactions therein, the distance between neighboring proton donors and acceptors in ionic crystals, as well as the dipolar orientation in nanoscale ionic phases was precisely tuned. This allowed a markedly high static dielectric constant comparable to water and fast structural diffusion of protons with a low potential barrier for single-ion polymers. The optimized sample exhibited a high proton diffusion coefficient of 2.4 × 10-6 cm2 s-1 under anhydrous conditions at 90 °C.

13.
ACS Appl Mater Interfaces ; 10(41): 35108-35117, 2018 Oct 17.
Article in English | MEDLINE | ID: mdl-30230315

ABSTRACT

Solid polymer electrolytes (SPEs) have drawn attention for promising multifunctional electrolytes requiring very good mechanical properties and ionic conductivity. To develop a safe SPE for energy storage applications, mechanically robust cross-linked epoxy matrix is combined with fast ion-diffusing ionic liquid/lithium salt electrolyte (ILE) via a simple one-pot curing process. The epoxy-rich SPEs show higher Young's modulus ( E), with higher glass transition temperature ( Tg) but lower ionic conductivity (σdc) with a higher activation energy, compared to the ILE-rich SPEs. The incorporation of inorganic robust Al2O3 nanowire simultaneously provides excellent mechanical robustness ( E ≈ 1 GPa at 25 °C) and good conductivity (σdc ≈ 2.9 × 10-4 S/cm at 25 °C) to the SPE. This suggests that the SPE has a bicontinuous microphase separation into ILE-rich and epoxy-rich microdomain, where ILE continuous conducting phases are intertwined with a sturdy cross-linked amorphous epoxy framework, supported by the observation of the two Tgs and low tortuosity as well as the microstructural investigation. After assembling the SPE with activated carbon electrodes, we successfully demonstrate the supercapacitor performance, exhibiting high energy and power density (75 W h/kg at 382 W/kg and 9.3 kW/kg at 44 W h/kg). This facile strategy holds tremendous potential to advance multifunctional energy storage technology for next-generation electric vehicles.

14.
Nanomaterials (Basel) ; 8(7)2018 Jun 21.
Article in English | MEDLINE | ID: mdl-29933616

ABSTRACT

Directed-assembly of nanowires on the dielectrics-covered parallel electrode structure is capable of producing uniformly-spaced nanowire array at the electrode gap due to dielectrophoretic nanowire attraction and electrostatic nanowire repulsion. Beyond uniformly-spaced nanowire array formation, the control of spacing in the array is beneficial in that it should be the experimental basis of the precise positioning of functional nanowires on a circuit. Here, we investigate the material parameters and bias conditions to modulate the nanowire spacing in the ordered array, where the nanowire array formation is readily attained due to the electrostatic nanowire interaction. A theoretical model for the force calculation and the simulation of the induced charge in the assembled nanowire verifies that the longer nanowires on thicker dielectric layer tend to be assembled with a larger pitch due to the stronger nanowire-nanowire electrostatic repulsion, which is consistent with the experimental results. It was claimed that the stronger dielectrophoretic force is likely to attract more nanowires that are suspended in solution at the electrode gap, causing them to be less-spaced. Thus, we propose a generic mechanism, competition of dielectrophoretic and electrostatic force, to determine the nanowire pitch in an ordered array. Furthermore, this spacing-controlled nanowire array offers a way to fabricate the high-density nanodevice array without nanowire registration.

15.
Nanomaterials (Basel) ; 7(10)2017 Oct 19.
Article in English | MEDLINE | ID: mdl-29048363

ABSTRACT

Placing nanowires at the predetermined locations on a substrate represents one of the significant hurdles to be tackled for realization of heterogeneous nanowire systems. Here, we demonstrate spatially-controlled assembly of a single nanowire at the photolithographically recessed region at the electrode gap with high integration yield (~90%). Two popular routes, such as protruding electrode tips and recessed wells, for spatially-controlled nanowire alignment, are compared to investigate long-range dielectrophoretic nanowire attraction and short-range nanowire-nanowire electrostatic interaction for determining the final alignment of attracted nanowires. Furthermore, the post-assembly process has been developed and tested to make a robust electrical contact to the assembled nanowires, which removes any misaligned ones and connects the nanowires to the underlying electrodes of circuit.

16.
J Neuroinflammation ; 14(1): 183, 2017 Sep 08.
Article in English | MEDLINE | ID: mdl-28886715

ABSTRACT

BACKGROUND: Despite the use of combination antiretroviral therapy for the treatment of HIV-1 infection, cognitive impairments remain prevalent due to persistent viral replication and associated brain inflammation. Primary cellular targets of HIV-1 in the brain are macrophages, microglia, and to a certain extent astrocytes which in response to infection release inflammatory markers, viral proteins [i.e., glycoprotein 120 (gp120)] and exhibit impaired glutamate uptake. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily of ligand-activated transcription factors. Compelling evidence suggests that PPARγ exerts anti-inflammatory properties in neurological disorders. The goal of this study was to examine the role of PPARγ in the context of HIV-1ADA gp120-induced inflammation in vitro, in primary cultures of rat astrocytes and microglia, and in vivo, in a rodent model of HIV-1ADA gp120-associated brain inflammation. METHODS: Primary mixed cultures of rat astrocytes and microglia were treated with PPARγ agonists (rosiglitazone or pioglitazone) and exposed to HIV-1ADA gp120. Inflammatory cytokines and indicator of oxidative stress response (TNFα, IL-1ß, iNOS) were measured using qPCR, and glutamate transporter (GLT-1) was quantified by immunoblotting. In vivo, rats were administered an intracerebroventricular injection of HIV-1ADA gp120 and an intraperitoneal injection of PPARγ agonist (rosiglitazone) or co-administration with PPARγ antagonist (GW9662). qPCR and immunoblotting analyses were applied to measure inflammatory markers, GLT-1 and PPARγ. RESULTS: In primary mixed cultures of rat astrocytes and microglia, HIV-1ADA gp120 exposure resulted in a significant elevation of inflammatory markers and a decrease in GLT-1 expression which were significantly attenuated with rosiglitazone or pioglitazone treatment. Similarly, in vivo, treatment with rosiglitazone reversed the gp120-mediated inflammatory response and downregulation of GLT-1. Furthermore, we demonstrated that the anti-inflammatory effects of PPARγ agonist rosiglitazone were mediated through inhibition of NF-κB. CONCLUSION: Our data demonstrate that gp120 can induce an inflammatory response and decrease expression of GLT-1 in the brain in vitro and in vivo. We have also successfully shown that these effects can be reversed by treatment with PPARγ agonists, rosiglitazone or pioglitazone. Together our data suggest that targeting PPARγ signaling may provide an option for preventing/treating HIV-associated brain inflammation.


Subject(s)
AIDS Dementia Complex/metabolism , PPAR gamma/metabolism , Animals , Encephalitis/metabolism , HIV-1 , Male , Pioglitazone , Rats , Rats, Wistar , Rosiglitazone , Thiazolidinediones/pharmacology
17.
Vet Comp Oncol ; 15(4): 1585-1589, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28185388

ABSTRACT

OBJECTIVE: Early and proper diagnosis of cancer is the most critical factor for the survival and treatment of veterinary cancer patients. In this study, we evaluated extracellular cyclic AMP-dependent protein kinase A (ECPKA) level in serum as a useful cancer biomarker in dogs. METHODS: ECPKA levels were detected in sera from dogs with cancers (n = 48), benign tumours (n = 18), and non-tumour diseases (n = 102) as well as healthy control dogs (n = 54) utilizing enzyme-linked immunosorbent assay (ELISA). RESULTS: Sera from dogs bearing various types of cancer exhibited markedly increased levels of ECPKA by up to 7.1-, 8.8-, and 10.9-fold compared with those from dogs harbouring benign tumours, dogs with non-tumour diseases, and healthy control dogs, respectively (P < .0001). In addition, serum ECPKA level did not show statistically significant correlation with gender, breed, or age of dogs or their non-cancerous disease conditions. CONCLUSION: Our data strongly propose that detection of serum ECPKA level is a potential and specific diagnostic tool for cancer in dogs.


Subject(s)
Cyclic AMP-Dependent Protein Kinases/blood , Dog Diseases/blood , Neoplasms/veterinary , Animals , Biomarkers, Tumor/blood , Case-Control Studies , Dog Diseases/diagnosis , Dogs , Enzyme-Linked Immunosorbent Assay/veterinary , Female , Male , Neoplasms/blood , Neoplasms/diagnosis
18.
Nat Commun ; 7: 13576, 2016 11 18.
Article in English | MEDLINE | ID: mdl-27857067

ABSTRACT

The key challenges in the advancement of actuator technologies related to artificial muscles include fast-response time, low operation voltages and durability. Although several researchers have tackled these challenges over the last few decades, no breakthrough has been made. Here we describe a platform for the development of soft actuators that moves a few millimetres under 1 V in air, with a superfast response time of tens of milliseconds. An essential component of this actuator is the single-ion-conducting polymers that contain well-defined ionic domains through the introduction of zwitterions; this achieved an exceptionally high dielectric constant of 76 and a 300-fold enhancement in ionic conductivity. Moreover, the actuator demonstrated long-term durability, with negligible changes in the actuator stroke over 20,000 cycles in air. Owing to its low-power consumption (only 4 mW), we believe that this actuator could pave the way for cutting-edge biomimetic technologies in the future.

19.
ACS Appl Mater Interfaces ; 8(5): 3215-25, 2016 Feb 10.
Article in English | MEDLINE | ID: mdl-26735584

ABSTRACT

Dielectric relaxation spectroscopy was used to investigate the segmental dynamics of a series of siloxane-based polar copolymers combining pendant cyclic carbonates and short poly(ethylene oxide) (PEO) chains. The homopolymer with cyclic carbonate as the only side chain exhibits higher glass transition temperature T(g) and dielectric constant ε(s) than the one with only PEO side chains. For their copolymers the observed T(g) (agreeing well with the predicted values from the Fox equation) and ε(s) decrease with increasing PEO side chain content. These polar polymers exhibit a glassy ß relaxation with Arrhenius character, attributed to local chain motions of side groups attached to the main chain, and a segmental α relaxation, associated with the glass transition with a Vogel temperature dependence. As PEO side chain content increases, narrowing of the local glassy ß relaxation was observed in the copolymers. The segmental α dynamics were observed to be faster, with an increase in breadth and decrease in strength with increasing PEO side chain content. Owing to the trade-off between T(g) and ε(s), copolymers of intermediate composition result in the highest ionic conductivity when these copolymers are used to plasticize Li single-ion conducting ionomers.

20.
Lett Appl Microbiol ; 57(1): 69-76, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23565693

ABSTRACT

UNLABELLED: Korean kimchi is known for its myriad of lactic acid bacteria (LAB) with diverse bioactive compounds. This study was undertaken to isolate an efficient antifungal LAB strain among the isolated kimchi LABs. One thousand and four hundred LABs isolated from different kimchi samples were initially screened against Aspergillus niger. The strain exhibiting the highest antifungal activity was identified as Lactobacillus plantarum YML007 by 16S rRNA sequencing and biochemical assays using API 50 CHL kit. Lact. plantarum YML007 was further screened against Aspergillus oryzae, Aspergillus flavus, Fusarium oxysporum and other pathogenic bacteria. The morphological changes during the inhibition were assessed by scanning electron microscopy. Preliminary studies on the antifungal compound demonstrated its proteinaceous nature with a molecular weight of 1256·617 Da, analysed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF). The biopreservative activity of Lact. plantarum YML007 was evaluated using dried soybeans. Spores of A. niger were observed in the negative control after 15 days of incubation. However, fungal growth was not observed in the soybeans treated with fivefold concentrated cell-free supernatant of Lact. plantarum YML007. The broad activity of Lact. plantarum YML007 against various food spoilage moulds and bacteria suggests its scope as a food preservative. SIGNIFICANCE AND IMPACT OF THE STUDY: After screening 1400 kimchi bacterial isolates, strain Lactobacillus plantarum YML007 was selected with strong antifungal activity against various foodborne pathogens. From the preliminary studies, it was found that the bioactive compound is a low molecular weight novel protein of 1256·617 Da. Biopreservative potential of Lact. plantarum YML007 was demonstrated on soybean grains, and the results point out YML007 as a potent biopreservative having broad antimicrobial activity against various foodborne pathogens.


Subject(s)
Antifungal Agents/isolation & purification , Antifungal Agents/pharmacology , Aspergillus/drug effects , Food Microbiology , Food Preservatives/isolation & purification , Food Preservatives/pharmacology , Lactobacillus plantarum/chemistry , Antifungal Agents/chemistry , Food Preservatives/chemistry , Fusarium/drug effects , Lactobacillaceae/chemistry , Lactobacillaceae/isolation & purification , Lactobacillus plantarum/genetics , Lactobacillus plantarum/isolation & purification , Lactobacillus plantarum/metabolism , Glycine max/microbiology
SELECTION OF CITATIONS
SEARCH DETAIL
...