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1.
Proc Natl Acad Sci U S A ; 120(18): e2218380120, 2023 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-37094114

RESUMO

The nature of mass transport in plants has recently inspired the development of low-cost and sustainable wood-based electronics. Herein, we report a wood electrochemical transistor (WECT) where all three electrodes are fully made of conductive wood (CW). The CW is prepared using a two-step strategy of wood delignification followed by wood amalgamation with a mixed electron-ion conducting polymer, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS). The modified wood has an electrical conductivity of up to 69 Sm-1 induced by the formation of PEDOT:PSS microstructures inside the wood 3D scaffold. CW is then used to fabricate the WECT, which is capable of modulating an electrical current in a porous and thick transistor channel (1 mm) with an on/off ratio of 50. The device shows a good response to gate voltage modulation and exhibits dynamic switching properties similar to those of an organic electrochemical transistor. This wood-based device and the proposed working principle demonstrate the possibility to incorporate active electronic functionality into the wood, suggesting different types of bio-based electronic devices.

2.
J Lipid Res ; : 100588, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38969065

RESUMO

Lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease. A size polymorphism in the apolipoprotein(a) [apo(a)] gene, determined by the number of Kringle (K) repeats, inversely regulates Lp(a) levels. Non-genetic factors including dietary saturated fat influence Lp(a) levels. However, less is known about the effects of carbohydrates including dietary sugars. In this double-blind, parallel-arm study among 32 overweight/obese adults, we investigated the effect of consuming glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks on Lp(a) level and assessed the role of the apo(a) size polymorphism. The mean (± SD) age of participants was 54 ± 8 years, 50% were women, and 75% were of European descent. At the end of the 10-week intervention, Lp(a) level was reduced by an average (± SEM) of -13.2% ± 4.3% in all participants (p=0.005); by -15.3% ± 7.8% in the 15 participants who consumed glucose (p=0.07); and by -11.3% ± 4.5% in the 17 participants who consumed fructose (p=0.02), without any significant difference in the effect between the two sugar groups. The relative changes in Lp(a) levels were similar across subgroups of lower vs higher baseline Lp(a) level or carrier vs non-carrier of an atherogenic small (≤22K) apo(a) size. In contrast, LDL-C increased. In conclusion, in older, overweight/obese adults, consuming sugar-sweetened beverages reduced Lp(a) levels by ∼13% independently of apo(a) size variability and the type of sugar consumed. The Lp(a) response was opposite to that of LDL-C and triglyceride concentrations. These findings suggest that metabolic pathways might impact Lp(a) levels.

3.
Biomacromolecules ; 25(6): 3731-3740, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38712827

RESUMO

Interface engineering is essential for cellulosic fiber-reinforced polymer composites to achieve high strength and toughness. In this study, carboxymethyl cellulose (CMC) functionalized with hydrophobic quaternary ammonium ions (QAs) were utilized to modify the interface between holocellulose fibers (HF) and acrylic resin. The wet HF/CMC papers were prepared by vacuum filtration, akin to papermaking, followed by cationic ion exchange with different hydrophobic QAs. Subsequently, the modified papers were dried, impregnated with an acrylic resin monomer, and cured to produce transparent composite films. The effect of the hydrophobic QA moieties on the structure and optical and mechanical properties of the HF/CMC/acrylic resin composites were investigated. The composite film with cetyltrimethylammonium (CTA)-functionalized CMC showed high optical transmittance (87%) with low haze (43%), while the composite film with phenyltrimethylammonium (PTMA)-functionalized CMC demonstrated high Young's modulus of 7.6 GPa and high tensile strength of 180 MPa. These properties are higher than those of the composites prepared through covalent interfacial modification strategies. The results highlighted the crucial role of hydrophobic functionalized CMCs in facilitating homogeneous resin impregnation in the HF fiber network, producing a composite with enhanced interfacial adhesion strength, increased optical transparency, and mechanical strength. This facile use of hydrophobic CMCs as interfacial compatibilizers provides an energy-efficient route for preparing transparent, thin, and flexible composite films favorable in optoelectronic applications.


Assuntos
Resinas Acrílicas , Carboximetilcelulose Sódica , Interações Hidrofóbicas e Hidrofílicas , Resistência à Tração , Carboximetilcelulose Sódica/química , Resinas Acrílicas/química , Compostos de Amônio Quaternário/química , Celulose/química , Módulo de Elasticidade
4.
J Lipid Res ; 64(9): 100420, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37482217

RESUMO

Reducing dietary saturated fatty acids (SFA) intake results in a clinically significant lowering of low-density lipoprotein cholesterol (LDL-C) across ethnicities. In contrast, dietary SFA's role in modulating emerging cardiovascular risk factors in different ethnicities remains poorly understood. Elevated levels of lipoprotein(a) [Lp(a)], an independent cardiovascular risk factor, disproportionally affect individuals of African descent. Here, we assessed the responses in Lp(a) levels to dietary SFA reduction in 166 African Americans enrolled in GET-READI (The Gene-Environment Trial on Response in African Americans to Dietary Intervention), a randomized controlled feeding trial. Participants were fed two diets in random order for 5 weeks each: 1) an average American diet (AAD) (37% total fat: 16% SFA), and 2) a diet similar to the Dietary Approaches to Stop Hypertension (DASH) diet (25% total fat: 6% SFA). The participants' mean age was 35 years, 70% were women, the mean BMI was 28 kg/m2, and the mean LDL-C was 116 mg/dl. Compared to the AAD diet, LDL-C was reduced by the DASH-type diet (mean change: -12 mg/dl) as were total cholesterol (-16 mg/dl), HDL-C (-5 mg/dl), apoA-1 (-9 mg/dl) and apoB-100 (-5 mg/dl) (all P < 0.0001). In contrast, Lp(a) levels increased following the DASH-type diet compared with AAD (median: 58 vs. 44 mg/dl, P < 0.0001). In conclusion, in a large cohort of African Americans, reductions in SFA intake significantly increased Lp(a) levels while reducing LDL-C. Future studies are warranted to elucidate the mechanism(s) underlying the SFA reduction-induced increase in Lp(a) levels and its role in cardiovascular risk across populations.


Assuntos
Negro ou Afro-Americano , Dieta , Gorduras na Dieta , Adulto , Feminino , Humanos , Masculino , LDL-Colesterol/sangue , Gorduras na Dieta/administração & dosagem , Lipoproteína(a)/sangue
5.
Small ; 19(17): e2205056, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36703510

RESUMO

Nature has evolved elegant ways to alter the wood cell wall structure through carbohydrate-active enzymes, offering environmentally friendly solutions to tailor the microstructure of wood for high-performance materials. In this work, the cell wall structure of delignified wood is modified under mild reaction conditions using an oxidative enzyme, lytic polysaccharide monooxygenase (LPMO). LPMO oxidation results in nanofibrillation of cellulose microfibril bundles inside the wood cell wall, allowing densification of delignified wood under ambient conditions and low pressure into transparent anisotropic films. The enzymatic nanofibrillation facilitates microfibril fusion and enhances the adhesion between the adjacent wood fiber cells during densification process, thereby significantly improving the mechanical performance of the films in both longitudinal and transverse directions. These results improve the understanding of LPMO-induced microstructural changes in wood and offer an environmentally friendly alternative for harsh chemical treatments and energy-intensive densification processes thus representing a significant advance in sustainable production of high-performance wood-derived materials.


Assuntos
Celulose , Madeira , Celulose/química , Madeira/química , Polissacarídeos , Oxirredução , Oxigenases de Função Mista/metabolismo , Estresse Oxidativo
6.
Small ; 19(28): e2301262, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36970834

RESUMO

The sustainable development of functional energy-saving building materials is important for reducing thermal energy consumption and promoting natural indoor lighting. Phase-change materials embedded in wood-based materials are candidates for thermal energy storage. However, the renewable resource content is usually insufficient, the energy storage and mechanical properties are poor, and the sustainability aspect is unexplored. Here a novel fully bio-based transparent wood (TW) biocomposite for thermal energy storage, combining excellent heat storage properties, tunable optical transmittance, and mechanical performance is introduced. A bio-based matrix based on a synthesized limonene acrylate monomer and renewable 1-dodecanol is impregnated and in situ polymerized within mesoporous wood substrates. The TW demonstrates high latent heat (89 J g-1 ) exceeding commercial gypsum panels, combined with thermo-responsive optical transmittance (up to 86%) and mechanical strength up to 86 MPa. The life cycle assessment shows that the bio-based TW has a 39% lower environmental impact than transparent polycarbonate panels. The bio-based TW holds great potential as scalable and sustainable transparent heat storage solution.

7.
Arterioscler Thromb Vasc Biol ; 42(1): e48-e60, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34647487

RESUMO

High levels of lipoprotein(a) [Lp(a)], an apoB100-containing lipoprotein, are an independent and causal risk factor for atherosclerotic cardiovascular diseases through mechanisms associated with increased atherogenesis, inflammation, and thrombosis. Lp(a) is predominantly a monogenic cardiovascular risk determinant, with ≈70% to ≥90% of interindividual heterogeneity in levels being genetically determined. The 2 major protein components of Lp(a) particles are apoB100 and apolipoprotein(a). Lp(a) remains a risk factor for cardiovascular disease development even in the setting of effective reduction of plasma low-density lipoprotein cholesterol and apoB100. Despite its demonstrated contribution to atherosclerotic cardiovascular disease burden, we presently lack standardization and harmonization of assays, universal guidelines for diagnosing and providing risk assessment, and targeted treatments to lower Lp(a). There is a clinical need to understand the genetic and biological basis for variation in Lp(a) levels and its relationship to disease in different ancestry groups. This scientific statement capitalizes on the expertise of a diverse basic science and clinical workgroup to highlight the history, biology, pathophysiology, and emerging clinical evidence in the Lp(a) field. Herein, we address key knowledge gaps and future directions required to mitigate the atherosclerotic cardiovascular disease risk attributable to elevated Lp(a) levels.


Assuntos
Aterosclerose/genética , Lipoproteína(a)/genética , American Heart Association , Aterosclerose/sangue , Aterosclerose/tratamento farmacológico , Aterosclerose/epidemiologia , Biomarcadores/sangue , Consenso , Medicina Baseada em Evidências , Predisposição Genética para Doença , Fatores de Risco de Doenças Cardíacas , Humanos , Hipolipemiantes/uso terapêutico , Lipoproteína(a)/sangue , Prevalência , Prognóstico , Medição de Risco , Estados Unidos
8.
BMC Geriatr ; 23(1): 535, 2023 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-37660032

RESUMO

BACKGROUND: While assessment tools can increase the detection of cognitive impairment, there is currently insufficient evidence regarding clinical outcomes based on screening for cognitive impairment in older adults. METHODS: The study purpose was to investigate whether Timed Up and Go dual-task test (TUGdt) results, based on TUG combined with two different verbal tasks (name different animals, TUGdt-NA, and recite months in reverse order, TUGdt-MB), predicted dementia incidence over a period of five years among patients (N = 186, mean = 70.7 years; 45.7% female) diagnosed with Subjective Cognitive Impairment (SCI) and Mild Cognitive Impairment (MCI) following assessment at two memory clinics. Associations between TUG parameters and dementia incidence were examined in Cox regression models. RESULTS: During follow-up time (median (range) 3.7 (0.1-6.1) years) 98 participants converted to dementia. Novel findings indicated that the TUGdt parameter words/time, after adjustment for age, gender, and education, can be used for the prediction of conversion to dementia in participants with SCI or MCI over a period of five years. Among the TUG-related parameters investigated, words/time showed the best predictive capacity, while time scores of TUG and TUGdt as well as TUGdt cost did not produce significant predictive results. Results further showed that the step parameter step length during TUGdt predicts conversion to dementia before adjustment for age, gender, and education. Optimal TUGdt cutoffs for predicting dementia at 2- and 4-year follow-up based on words/time were calculated. The sensitivity of the TUGdt cutoffs was high at 2-year follow-up: TUGdt-NA words/time, 0.79; TUGdt-MB words/time, 0.71; reducing respectively to 0.64 and 0.65 at 4-year follow-up. CONCLUSIONS: TUGdt words/time parameters have potential as cost-efficient tools for conversion-to-dementia risk assessment, useful for research and clinical purposes. These parameters may be able to bridge the gap of insufficient evidence for such clinical outcomes. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05893524: https://www. CLINICALTRIALS: gov/study/NCT05893524?id=NCT05893524&rank=1 .


Assuntos
Disfunção Cognitiva , Demência , Memória Episódica , Feminino , Humanos , Animais , Masculino , Escolaridade , Instituições de Assistência Ambulatorial , Disfunção Cognitiva/diagnóstico , Disfunção Cognitiva/epidemiologia , Demência/diagnóstico , Demência/epidemiologia
9.
Eur Heart J ; 43(39): 3925-3946, 2022 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-36036785

RESUMO

This 2022 European Atherosclerosis Society lipoprotein(a) [Lp(a)] consensus statement updates evidence for the role of Lp(a) in atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis, provides clinical guidance for testing and treating elevated Lp(a) levels, and considers its inclusion in global risk estimation. Epidemiologic and genetic studies involving hundreds of thousands of individuals strongly support a causal and continuous association between Lp(a) concentration and cardiovascular outcomes in different ethnicities; elevated Lp(a) is a risk factor even at very low levels of low-density lipoprotein cholesterol. High Lp(a) is associated with both microcalcification and macrocalcification of the aortic valve. Current findings do not support Lp(a) as a risk factor for venous thrombotic events and impaired fibrinolysis. Very low Lp(a) levels may associate with increased risk of diabetes mellitus meriting further study. Lp(a) has pro-inflammatory and pro-atherosclerotic properties, which may partly relate to the oxidized phospholipids carried by Lp(a). This panel recommends testing Lp(a) concentration at least once in adults; cascade testing has potential value in familial hypercholesterolaemia, or with family or personal history of (very) high Lp(a) or premature ASCVD. Without specific Lp(a)-lowering therapies, early intensive risk factor management is recommended, targeted according to global cardiovascular risk and Lp(a) level. Lipoprotein apheresis is an option for very high Lp(a) with progressive cardiovascular disease despite optimal management of risk factors. In conclusion, this statement reinforces evidence for Lp(a) as a causal risk factor for cardiovascular outcomes. Trials of specific Lp(a)-lowering treatments are critical to confirm clinical benefit for cardiovascular disease and aortic valve stenosis.


Assuntos
Estenose da Valva Aórtica , Aterosclerose , Calcinose , Doenças Cardiovasculares , Adulto , Estenose da Valva Aórtica/complicações , Aterosclerose/etiologia , Calcinose/complicações , Doenças Cardiovasculares/complicações , LDL-Colesterol , Humanos , Lipoproteína(a)/genética , Fatores de Risco
10.
J Aging Phys Act ; 31(5): 823-832, 2023 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-37019438

RESUMO

The Timed Up-and-Go (TUG) test has been combined with different verbal/cognitive tasks (i.e., TUG dual task [TUGdt]) as a form of motor-cognitive testing. However, it is still unclear how different TUGdt conditions affect gait among older adults. Thirty community-dwelling older adults, with mean age of 73 years, participated in the study. Data were collected using marker-free video recordings. Gait parameters were extracted using a semiautomatic deep learning system. Comparisons of execution time and gait parameter outcomes were made under TUG and three types of TUGdt test conditions: TUGdt-naming animals, TUGdt-months backwards, and TUGdt-serial 7s. Statistical analyses were based on mean values of the gait parameters for each participant and TUG condition, including TUGdt gait cost, that is, the relative difference between TUGdt and TUG. All the investigated TUGdt conditions resulted in varying degrees of gait parameter changes. Under TUGdt conditions, participants took shorter and slower steps, with TUGdt-serial 7s causing the largest interference.


Assuntos
Marcha , Vida Independente , Humanos
11.
Environ Res ; 208: 112626, 2022 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-34973191

RESUMO

Persistent organic pollutants (POPs) are industrial chemicals resistant to degradation and have been shown to have adverse effects on reproductive health in wildlife and humans. Although regulations have reduced their levels, they are still ubiquitously present and pose a global concern. Here, we studied a cohort of 185 women aged 21-43 years with a median of 2 years of infertility who were seeking assisted reproductive technology (ART) treatment at the Carl von Linné Clinic in Uppsala, Sweden. We analyzed the levels of 9 organochlorine pesticides (OCPs), 10 polychlorinated biphenyls (PCBs), 3 polybrominated diphenyl ethers (PBDEs), and 8 perfluoroalkyl substances (PFASs) in the blood and follicular fluid (FF) samples collected during ovum pick-up. Impact of age on chemical transfer from blood to FF was analyzed. Associations of chemicals, both individually and as a mixture, to 10 ART endpoints were investigated using linear, logistic, and weighted quantile sum regression, adjusted for age, body mass index, parity, fatty fish intake and cause of infertility. Out of the 30 chemicals, 20 were detected in more than half of the blood samples and 15 in FF. Chemical transfer from blood to FF increased with age. Chemical groups in blood crossed the blood-follicle barrier at different rates: OCPs > PCBs > PFASs. Hexachlorobenzene, an OCP, was associated with lower anti-Müllerian hormone, clinical pregnancy, and live birth. PCBs and PFASs were associated with higher antral follicle count and ovarian response as measured by ovarian sensitivity index, but also with lower embryo quality. As a mixture, similar findings were seen for the sum of PCBs and PFASs. Our results suggest that age plays a role in the chemical transfer from blood to FF and that exposure to POPs significantly associates with ART outcomes. We strongly encourage further studies to elucidate the underlying mechanisms of reproductive effects of POPs in humans.


Assuntos
Poluentes Ambientais , Hidrocarbonetos Clorados , Praguicidas , Bifenilos Policlorados , Animais , Feminino , Líquido Folicular/química , Éteres Difenil Halogenados , Humanos , Poluentes Orgânicos Persistentes , Gravidez , Técnicas de Reprodução Assistida
12.
Nano Lett ; 21(7): 2883-2890, 2021 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-33734720

RESUMO

Transparent wood biocomposites based on PMMA combine high optical transmittance with excellent mechanical properties. One hypothesis is that despite poor miscibility the polymer is distributed at the nanoscale inside the cell wall. Small-angle neutron scattering (SANS) experiments are performed to test this hypothesis, using biocomposites based on deuterated PMMA and "contrast-matched" PMMA. The wood cell wall nanostructure soaked in heavy water is quantified in terms of the correlation distance d between the center of elementary cellulose fibrils. For wood/deuterated PMMA, this distance d is very similar as for wood/heavy water (correlation peaks at q ≈ 0.1 Å-1). The peak disappears when contrast-matched PMMA is used, indeed proving nanoscale polymer distribution in the cell wall. The specific processing method used for transparent wood explains the nanocomposite nature of the wood cell wall and can serve as a nanotechnology for cell wall impregnation of polymers in large wood biocomposite structures.


Assuntos
Polimetil Metacrilato , Madeira , Celulose , Polímeros , Espalhamento a Baixo Ângulo
13.
J Nutr ; 150(8): 2089-2100, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32492148

RESUMO

BACKGROUND: Factor VIIc, fibrinogen, and plasminogen activator inhibitor 1 (PAI-1) are cardiovascular disease (CVD) risk factors and are modulated, in part, by fat type and amount. OBJECTIVE: We evaluated fat type and amount on the primary outcomes: factor VIIc, fibrinogen, and PAI-1. METHODS: In the Dietary Effects on Lipoproteins and Thrombogenic Activity (DELTA) Trial, 2 controlled crossover feeding studies evaluated substituting carbohydrate or MUFAs for SFAs. Study 1: healthy participants (n = 103) were provided with (8 wk) an average American diet [AAD; designed to provide 37% of energy (%E) as fat, 16% SFA], a Step 1 diet (30%E fat, 9% SFA), and a diet low in SFA (Low-Sat; 26%E fat, 5% SFA). Study 2: participants (n = 85) at risk for CVD and metabolic syndrome (MetSyn) were provided with (7 wk) an AAD, a step 1 diet, and a high-MUFA diet (designed to provide 37%E fat, 8% SFA, 22% MUFA). RESULTS: Study 1: compared with AAD, the Step 1 and Low-Sat diets decreased mean factor VIIc by 1.8% and 2.6% (overall P = 0.0001), increased mean fibrinogen by 1.2% and 2.8% (P = 0.0141), and increased mean square root PAI-1 by 0.0% and 6.0% (P = 0.0037), respectively. Study 2: compared with AAD, the Step 1 and high-MUFA diets decreased mean factor VIIc by 4.1% and 3.2% (overall P < 0.0001), increased mean fibrinogen by 3.9% and 1.5% (P = 0.0083), and increased mean square-root PAI-1 by 2.0% and 5.8% (P = 0.1319), respectively. CONCLUSIONS: Replacing SFA with carbohydrate decreased factor VIIc and increased fibrinogen in healthy and metabolically unhealthy individuals and also increased PAI-1 in healthy subjects. Replacing SFA with MUFA decreased factor VIIc and increased fibrinogen but less than carbohydrate. Our results indicate an uncertain effect of replacing SFA with carbohydrate or MUFA on cardiometabolic risk because of small changes in hemostatic factors and directionally different responses to decreasing SFA. This trial was registered at https://clinicaltrials.gov/ct2/show/NCT00000538?term=NCT00000538&rank=1 as NCT00000538.


Assuntos
Doenças Cardiovasculares/metabolismo , Gorduras na Dieta/administração & dosagem , Gorduras na Dieta/farmacologia , Fator VII/metabolismo , Fibrinogênio/metabolismo , Inibidor 1 de Ativador de Plasminogênio/metabolismo , Adulto , Idoso , Dieta , Gorduras na Dieta/classificação , Fator VII/genética , Feminino , Fibrinogênio/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Hemostasia , Humanos , Masculino , Pessoa de Meia-Idade , Inibidor 1 de Ativador de Plasminogênio/genética , Fatores de Risco , Adulto Jovem
14.
Biomacromolecules ; 21(5): 1795-1801, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-31958232

RESUMO

Recyclable biocomposites based on degradable polymer systems and cellulosic plant fibers are attractive in a sustainable society, because of enhanced polymer properties and also from an end-of-life perspective. Improved understanding is required for how the degradable polymer matrix is affected during compounding in addition to effects from the cellulosic fiber structure and its chemical nature. This work reveals that a poly(ε-caprolactone) matrix undergoes localized, heterogeneous polymer degradation in the fiber-matrix interphase region during melt-compounding. The extent of localized degradation correlates with the initial moisture content in the wood cellulose fiber, where moisture content is controlled by different fiber modification methods by PCL-grafting. As an effect, high moisture content results in a destabilized and degraded fiber-matrix interphase. This was found through careful analysis of how the polymer population changed after compounding, using two different methods: molar mass distribution from SEC and end-group concentration from NMR. The results are important not only with regard to fiber/matrix interface compatibility but also to understand fiber modification for improved biocomposites recycling.


Assuntos
Celulose , Polímeros , Interfase , Peso Molecular , Madeira
15.
Biomacromolecules ; 21(2): 597-603, 2020 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-31769663

RESUMO

Chemical modification of wood cellulose fibers is important for tailored wood-polymer interfaces, reduced moisture sorption, and novel grades of chemical wood pulp. The present study shows how the reaction solvent system influences hydroxyl accessibility during chemical fiber modification. Surface initiated ring-opening polymerization of ε-caprolactone from wood cellulose fibers was investigated in a wide range of solvent systems. The hydrogen bond donor strength of the solvent increased graft density and the amount of grafted polycaprolactone (PCL) on the fiber surface, and on nanoscale fibrils inside the fiber. Specifically, the reaction system with acetic acid as a new, green solvent for cellulose grafting increased graft density 24 times compared to bulk polymerization conditions. The results show relationships between solvent properties, hydroxyl accessibility, and grafting results in cellulosic plant fibers. The study clarifies the opportunities provided by controlling the interior of the cellulosic plant fiber cell wall during chemical modification so that the fiber becomes a swollen cellulose nanofibril gel.


Assuntos
Celulose/química , Poliésteres/química , Madeira/química , Varredura Diferencial de Calorimetria , Hidróxidos/química , Espectroscopia de Ressonância Magnética , Polimerização , Solventes/química , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
16.
Biomacromolecules ; 21(2): 604-612, 2020 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-31742385

RESUMO

The α-chitin nanofibril is an alternative to nanocellulose as a building-block for strong films and other nanomaterials. The hypothesis of high film strength for films based on mildly treated insect cuticles was tested. Fibrils from the cuticle of Ruspolia differens (a long-horned bush cricket grasshopper locally known as senene) are disintegrated by a mild process, subsequently characterized by transmission electron microscopy, NMR, Fourier transform infrared spectroscopy, and XRD, and used to prepare strong and transparent films. A mild process (with 20% NaOH treatment for 2 weeks and at room temperature) was used to largely remove the strongly bound protein associated with chitin. The purpose was to reduce chitin degradation. The native structure of chitin was indeed well preserved and close to the native state, as is supported by data for degree of acetylation, molar mass, crystallinity, and crystallite dimensions. The diameter of the smallest chitin fibrils was as small as 3-7 nm (average 6 nm) with lengths larger than or around 1 µm. A stable and well-dispersed colloidal chitin fibril suspension in water was achieved. A nanostructured chitin film prepared by filtration showed high optical transmittance (∼90%) and very high tensile strength (220 MPa). The high tensile strength was attributed to the well-preserved chitin structure, high intrinsic fibril strength, and high colloidal stability of the fibril suspension. Strong, transparent insect chitin films offer interesting alternatives to nanocellulose films because of different resource origins, surface chemistries, and potential antimicrobial properties.


Assuntos
Quitina/química , Gafanhotos/química , Nanoestruturas/química , Animais , Gafanhotos/anatomia & histologia , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Água/química , Difração de Raios X
17.
Biomacromolecules ; 21(5): 1920-1928, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32160463

RESUMO

Here we investigate the relationship between thermomechanical properties and chemical structure of well-characterized lignin-based epoxy resins. For this purpose, technical lignins from eucalyptus and spruce, obtained from the Kraft process, were used. The choice of lignins was based on the expected differences in molecular structure. The lignins were then refined by solvent fractionation, and three fractions with comparable molecular weights were selected to reduce effects of molar mass on the properties of the final thermoset resins. Consequently, any differences in thermomechanical properties are expected to correlate with molecular structure differences between the lignins. Oxirane moieties were selectively introduced to the refined fractions, and the resulting lignin epoxides were subsequently cross-linked with two commercially available polyether diamines (Mn = 2000 and 400) to obtain lignin-based epoxy resins. Molecular-scale characterization of the refined lignins and their derivatives were performed by 31P NMR, 2D-NMR, and DSC methods to obtain the detailed chemical structure of original and derivatized lignins. The thermosets were studied by DSC, DMA, and tensile tests and demonstrated diverse thermomechanical properties attributed to structural components in lignin and selected amine cross-linker. An epoxy resin with a lignin content of 66% showed a Tg of 79 °C from DMA, Young's modulus of 1.7 GPa, tensile strength of 66 MPa, and strain to failure of 8%. The effect of molecular lignin structure on thermomechanical properties was analyzed, finding significant differences between the rigid guaiacyl units in spruce lignin compared with sinapyl units in eucalyptus lignin. The methodology points toward rational design of molecularly tailored lignin-based thermosets.


Assuntos
Eucalyptus , Lignina , Fracionamento Químico , Resinas Epóxi , Peso Molecular
18.
Biomacromolecules ; 21(6): 2536-2540, 2020 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-32233473

RESUMO

Nanocellulose-based materials and nanocomposites show extraordinary mechanical properties with high stiffness, strength, and toughness. Although the last decade has witnessed great progress in understanding the mechanical properties of these materials, a crucial challenge is to identify pathways to introduce high wet strength, which is a critical parameter for commercial applications. Because of the waterborne fabrication methods, nanocellulose-based materials are prone to swelling by both adsorption of moist air or liquid water. Unfortunately, there is currently no best practice on how to take the swelling into account when reporting mechanical properties at different relative humidity or when measuring the mechanical properties of fully hydrated materials. This limits and in parts fully prevents comparisons between different studies. We review current approaches and propose a best practice for measuring and reporting mechanical properties of wet nanocellulose-based materials, highlighting the importance of swelling and the correlation between mechanical properties and volume expansion.


Assuntos
Celulose , Nanocompostos , Água
19.
BMC Geriatr ; 20(1): 258, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32727472

RESUMO

BACKGROUND: Discrimination between early-stage dementia and other cognitive impairment diagnoses is central to enable appropriate interventions. Previous studies indicate that dual-task testing may be useful in such differentiation. The objective of this study was to investigate whether dual-task test outcomes discriminate between groups of individuals with dementia disorder, mild cognitive impairment, subjective cognitive impairment, and healthy controls. METHODS: A total of 464 individuals (mean age 71 years, 47% women) were included in the study, of which 298 were patients undergoing memory assessment and 166 were cognitively healthy controls. Patients were grouped according to the diagnosis received: dementia disorder, mild cognitive impairment, or subjective cognitive impairment. Data collection included participants' demographic characteristics. The patients' cognitive test results and diagnoses were collected from their medical records. Healthy controls underwent the same cognitive tests as the patients. The mobility test Timed Up-and-Go (TUG single-task) and two dual-task tests including TUG (TUGdt) were carried out: TUGdt naming animals and TUGdt months backwards. The outcomes registered were: time scores for TUG single-task and both TUGdt tests, TUGdt costs (relative time difference between TUG single-task and TUGdt), number of different animals named, number of months recited in correct order, number of animals per 10 s, and number of months per 10 s. Logistic regression models examined associations between TUG outcomes pairwise between groups. RESULTS: The TUGdt outcomes "animals/10 s" and "months/10 s" discriminated significantly (p < 0.001) between individuals with an early-stage dementia diagnosis, mild cognitive impairment, subjective cognitive impairment, and healthy controls. The TUGdt outcome "animals/10 s" showed an odds ratio of 3.3 (95% confidence interval 2.0-5.4) for the groups dementia disorders vs. mild cognitive impairment. TUGdt cost outcomes, however, did not discriminate between any of the groups. CONCLUSIONS: The novel TUGdt outcomes "words per time unit", i.e. "animals/10 s" and "months/10 s", demonstrate high levels of discrimination between all investigated groups. Thus, the TUGdt tests in the current study could be useful as complementary tools in diagnostic assessments. Future studies will be focused on the predictive value of TUGdt outcomes concerning dementia risk for individuals with mild cognitive impairment or subjective cognitive impairment.


Assuntos
Disfunção Cognitiva , Demência , Idoso , Cognição , Disfunção Cognitiva/diagnóstico , Estudos de Coortes , Estudos Transversais , Demência/diagnóstico , Feminino , Humanos , Masculino
20.
J Strength Cond Res ; 34(9): 2528-2536, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30199449

RESUMO

Sjöberg, H, Aasa, U, Rosengren, M, and Berglund, L. Content validity index and reliability of a new protocol for evaluation of lifting technique in the powerlifting squat and deadlift. J Strength Cond Res 34(9): 2528-2536, 2020-The aim of the study was to create a protocol to cover aspects of technique considered to be associated with risk of injury in the powerlifting squat and deadlift and to examine the content validity and reliability of the aspects included in the protocols. For the content validity investigation, a consensus group of 3 powerlifting physiotherapists identified the domains of content (risk of injury) for 2 protocols (1 for squat and 1 for deadlift) of essential aspects of lifting technique through discussions and a review of the literature. Eight selected powerlifting experts rated the relevance of each aspect in relation to risk of injury (acute or by overuse), and a quantitative estimate of the content validity of each aspect was measured through calculations of a Content Validity Index (CVI). Aspects of low content validity were discarded, and the remainders were evaluated for their inter-rater and intra-rater reliability among 4 experienced powerlifters used to coaching and evaluating powerlifting technique. The reliability was calculated and analyzed with kappa and percentage of agreement. The final protocols included 17 aspects of squat technique and 10 aspects of deadlift technique that showed good to excellent CVI and percentage of agreement between 64 and 100%. The protocols, formed in this study, will provide evidence-based recommendations on safe lifting technique for coaches and strength practitioners' to use to make relevant assessments and instructions.


Assuntos
Modalidades de Fisioterapia/normas , Levantamento de Peso/fisiologia , Fenômenos Biomecânicos , Humanos , Masculino , Postura , Reprodutibilidade dos Testes
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