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1.
Endocr Connect ; 13(6)2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38688314

RESUMO

Objective: This study aimed to reveal associations between metabolic hormones in cerebral spinal fluid (CSF) and cigarette smoking-induced weight gain and to explore the underlying mechanism. Methods: A total of 156 adult men were included, comprising active smokers and nonsmokers. In addition to demographic information and body mass index (BMI), plasma levels of ApoA1 and ApoB, high-density lipoprotein, low-density lipoprotein, cholesterol, triglyceride, alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase in the participants were measured. Moreover, the metabolic hormones adiponectin, fibroblast growth factor 21 (FGF21), ghrelin, leptin, and orexin A, as well as the trace elements iron and zinc in CSF, were assessed. Results: Compared to nonsmokers, active smokers showed higher BMI, and elevated CSF levels of FGF21, Zn, and Fe, but decreased levels of metabolic hormones adiponectin, ghrelin, leptin, and orexin A. Negative correlations existed between CSF FGF21 and ghrelin, between CSF Zn and ghrelin, as well as between CSF Fe and orexin A in active smokers. Furthermore, elevated CSF FGF21 and Zn predicted ghrelin level decrease in the smokers. Conclusion: These data relate smoking-induced weight gain to its neurotoxic effect on the neurons that synthesize metabolic hormones such as adiponectin, ghrelin, leptin, or orexin A in the brain, by disrupting mitochondrial function and causing oxidative stress in the neurons.

2.
Front Behav Neurosci ; 17: 1288616, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38192488

RESUMO

Introduction: One of the most common mental disorders in the perinatal period is depression, which is associated with impaired emotional functioning due to alterations in different cognitive aspects including thought and facial emotion recognition. These functional impairment may affect emerging maternal sensitivity and have lasting consequences for the dyadic relationship. The current study aimed to investigate the impact of depressive symptoms on the attention bias of infant stimuli during pregnancy. Methods: Eighty-six pregnant women completed the Edinburgh Postnatal Depression Scale and an eye-tracking task comprising infant-related emotion images. All participants showed biased attention to infant-related images. Results: First, compared to healthy pregnant women, pregnant women with depression symptoms initially directed their attention to infant-related stimuli more quickly (F (1, 84) = 6.175, p = 0.015, η2 = 0.068). Second, the two groups of pregnant women paid attention to the positive infant stimuli faster than the neutral infant stimuli, and the first fixation latency bias score was significantly smaller than that of the infant-related negative stimulus (p = 0.007). Third, compared with the neutral stimulus, the non-depression group showed a longer first gaze duration to the negative stimulus of infants (p = 0.019), while the depressive symptoms group did not show this difference. Conclusion: We speculate that structural and functional changes in affective motivation and cognitive-attention brain areas may induce these attentional bias patterns. These results provide suggestions for the implementation of clinical intervention programs to correct the attention bias of antenatal depressed women.

3.
PLoS One ; 17(8): e0273350, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35998192

RESUMO

BACKGROUND: Postoperative pneumonia is a serious complication in elderly patients with hip fracture. It is necessary to identify the influencing factors of postoperative pneumonia in patients with hip fracture. METHODS: Elderly patients with hip fractures admitted to a tertiary hospital in China from January 1, 2020 to August 31, 2021 were included. The characteristics of patients with and without postoperative pneumonia were evaluated and compared. Logistic multivariate regression analyses were conducted to assess the risk factors of postoperative pneumonia. RESULTS: 267 patients with hip fracture were included, the incidence of postoperative pneumonia in patients with hip fracture was 13.11%. There were significant differences in the age, diabetes mellitus, anemia, hypoalbuminemia, anesthesia method and duration of surgery between infection and no infection group, no significant differences in the gender, BMI, hypertension, hyperlipidemia, type of fracture, preoperative oxygen saturation, white blood cell count, platelet count, red blood cell count, creatinine, alanine aminotransferase, aspartate aminotransferase, estimated blood loss during surgery were detected between infection and no infection group. Logistic regression analysis showed that age≥70y (OR2.326, 95%CI1.248~3.129), diabetes mellitus (OR2.123, 95%CI1.021~3.551), anemia (OR3.199,95%CI1.943~5.024), hypoalbuminemia (OR2.377, 95%CI1.211~3.398), general anesthesia (OR1.947, 95%CI1.115~3.038), duration of surgery≥120min (OR1.621, 95%CI1.488~2.534) were the risk factors of postoperative pneumonia in elderly patients with hip fracture (all p<0.05). Escherichia Coli (33.33%), Klebsiella pneumoniae (28.57%), Staphylococcus aureus (21.43%) were the most common bacteria of pulmonary infection. CONCLUSION: There are many risk factors for postoperative pneumonia in elderly patients with hip fractures after surgery. In clinical practice, medical workers should take targeted interventions for those risk factors to reduce postoperative pneumonia.


Assuntos
Fraturas do Quadril , Hipoalbuminemia , Pneumonia , Idoso , Fraturas do Quadril/complicações , Fraturas do Quadril/epidemiologia , Fraturas do Quadril/cirurgia , Humanos , Hipoalbuminemia/complicações , Pneumonia/complicações , Pneumonia/etiologia , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Estudos Retrospectivos , Fatores de Risco
4.
Brain Res ; 1780: 147802, 2022 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-35085574

RESUMO

Cuprizone (CPZ) is a copper-chelator and toxic to mitochondria. Recent studies have shown oligodendrocyte (OL) loss and demyelination along with dopamine (DA) increase and behavioral abnormalities in CPZ-exposed mice, demonstrating its application in schizophrenia research. This study examined effects of CPZ exposure on autonomous behavior and dopaminergic neurotransmission in larval zebra fish. CPZ exposure was found to reduce the swimming velocity of zebra fish thus decreased swimming distance during day and night time. Moreover, the treatment induced a movement response of zebra fish larvae reacting to light-on/off switch featured by swimming velocity increase and decrease during the first and second half of the light-on/off phase, respectively. But, it abolished responses of zebra fish to sound-on/off seen in Control group. HPLC analysis showed elevated DA levels in the zebra fish, no change in NE and 5-HT levels. Transcriptome analysis reported changes in gene expression related to dopaminergic synapse and oxidative phosphorylation in CPZ-exposed larvae relative to Control group. Of the gene expression changes, up-regulation of drd2a, drd2b, drd4a and drd4rs was confirmed by RT-PCR, although no difference existed between Control and CPZ groups in dopaminergic neuron numbers. These results demonstrated dopaminergic hyperactivity and locomotor deficit in CPZ-exposed zebra fish larvae, encouraging further application of this model in exploring neurotoxic effects of CPZ on mitochondria and dopaminergic neurotransmission in zebra fish.


Assuntos
Cuprizona/farmacologia , Dopamina/metabolismo , Neurônios Dopaminérgicos/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Neurônios Dopaminérgicos/metabolismo , Peixe-Zebra
5.
BMC Med ; 19(1): 90, 2021 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-33845843

RESUMO

BACKGROUND: The aim of this study was to quantitatively summarize the available evidence on the association of breastfeeding with the risk of childhood cancer. METHODS: A literature search of PubMed and Embase databases was performed to identify eligible observational studies published from inception to July 17, 2020. The categorical and dose-response meta-analysis was conducted by pooling relative risk (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression and stratification analysis. Sensitivity analysis and publication bias test were also carried out. RESULTS: Forty-five articles involving 475,579 individuals were included in the meta-analysis. Among the thirty-three studies on the association between breastfeeding and risk of childhood leukemia, the pooled risk estimates were 0.77 (95% CI, 0.65-0.91) and 0.77 (95% CI 0.63-0.94) for ever versus non/occasional breastfeeding and longest versus shortest breastfeeding duration group, respectively. There was clear indication for non-linear dose-response relationship between breastfeeding duration and the risk of childhood leukemia (P non-linear < 0.001). The most protective effect (OR, 0.66, 95% CI 0.62-0.70) was observed at a breastfeeding duration of 9.6 months. Four studies examined, the association between breastfeeding and risk of childhood neuroblastoma, and significant inverse associations were consistently observed in both the comparisons of ever breastfeeding versus non/occasional breastfeeding (OR = 0.59, 95% CI 0.44-0.81) and longest versus shortest breastfeeding (OR = 0.61, 95% CI 0.44-0.83). However, no associations of breastfeeding with risk of other cancers were found. CONCLUSIONS: Our study supports a protective role of breastfeeding on the risk of childhood leukemia, also suggesting a non-linear dose-response relationship. Further studies are warranted to confirm the association between breastfeeding and risk of childhood neuroblastoma.


Assuntos
Aleitamento Materno , Neoplasias , Criança , Feminino , Humanos , Neoplasias/epidemiologia , Neoplasias/etiologia , Razão de Chances , Fatores de Risco , Fatores de Tempo
6.
Langmuir ; 36(34): 10110-10119, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32787059

RESUMO

Surfaces that exhibit the reactivity of silica toward surface modification (silanol condensation) were prepared by treating thin films and particles of poly(methylsilsesquioxane) with aqueous potassium persulfate at elevated temperature. Parallel experiments were carried out using a highly cross-linked poly(dimethylsiloxane). Advancing (θA) and receding (θR) water contact angles for all of these oxidized surfaces were θA/θR = ∼10/∼0°, and these low values remain unchanged for months. Reactions of these silica-like surfaces with a range of functional silane reagents indicate that the surface silanol concentration is sufficient to prepare covalently attached monolayers of similar surface density to those prepared using silicon wafers as substrates.

7.
Neurol Res ; 41(12): 1090-1096, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31584351

RESUMO

Background: Serum C-reactive protein (CRP) has been reported to be associated with risk of ischemic vascular disease including ischemic stroke. Genome-wide association studies have revealed several gene variants related to CRP concentration. Methods: We investigated genetic variants in CRP-related genes associated with ischemic stroke in a nested case-control study with 138 ischemic stroke cases and 276 controls. We sequenced the whole coding region of six CPR-related genes and selected eligible SNPs. Three genetic models (additive, dominant and recessive) were calculated by a multivariable conditional logistic regression to estimate the association between SNPs and risk of ischemic stroke. We also calculated gene-environment interactions by using a crossover analysis. Results: Three out of 10 eligible SNPs were shown to be associated with risk of ischemic stroke. rs1800947 in CRP gene (additive model: OR = 2.08, 95% CI: 1.00-4.23) and rs1169288 in HNF1A gene (additive model: OR = 1.45, 95% CI: 1.03-2.06) were associated with an increased risk of ischemic stroke. rs440446 in APOE gene (additive model: OR = 0.63, 95%CI: 0.44-0.88) was associated with a decreased risk of ischemic stroke. Genetic risk scores models including SC-GRS and OR-GRS both showed a significant association with risk of ischemic stroke. These three SNPs interacted with smoking and red meat intake. Conclusions: Our study showed genetic variants of CRP-related genes were associated with risk of ischemic stroke. Our findings could provide useful data for the etiology of ischemic stroke.


Assuntos
Isquemia Encefálica/genética , Proteína C-Reativa/genética , Predisposição Genética para Doença , Acidente Vascular Cerebral/genética , Estudos de Casos e Controles , Feminino , Interação Gene-Ambiente , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Fatores de Risco
8.
Langmuir ; 35(14): 5069-5074, 2019 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-30888172

RESUMO

Difflugia are testate amoebae that use particulate inorganic matter to build a protective shell (generally called a test or theca). Difflugia globulosa were grown both in culture containing only naturally occurring theca-building materials and under conditions where synthetic particles were present also. The presence of monodisperse Stöber silica microspheres of 1, 3, and 6 µm in diameter or 4 µm polystyrene spheres dramatically increased the rate of Difflugia growth, and foreign microspheres became the overwhelmingly dominant construction material. Optical and electron microscopy of the 6 µm particle studies revealed that Difflugia construct spherical vase-shaped thecae with strikingly reproducible composition, morphology, and size. Time-lapse photography revealed construction techniques and masonry skills as Difflugia herded particles together, trapped them using phagocytosis, and applied the particles with biocement from inside the developing theca. The reported observations identify taxonomy complications, biomicrofabrication possibilities, and a discrete environmental impact of synthetic particle pollutants.


Assuntos
Amoeba/metabolismo , Microesferas , Material Particulado/metabolismo , Poliestirenos/metabolismo , Dióxido de Silício/metabolismo , Amoeba/química , Amoeba/crescimento & desenvolvimento , Tamanho da Partícula , Material Particulado/química , Poliestirenos/química , Dióxido de Silício/química , Propriedades de Superfície
9.
Environ Sci Pollut Res Int ; 25(33): 33548-33555, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30269277

RESUMO

Although a growing number of epidemiological studies have been conducted on size-specific health effects of particulate matter in China, results remain inconsistent. In this study, we investigated acute effect of fine and coarse particular matter on cardiovascular hospital visits in Ningbo, China. We used generalized additive models to examine short-term effects of PM2.5 and PM10-2.5 on cardiovascular hospital visits by adjustment for temporal, seasonal, and meteorological effects. Subgroup analyses were conducted by age, sex, and season. We also examined the stability of their effects in multi-pollutant models. We found that PM2.5 were associated with cardiovascular hospital visits (RR = 1.006; 95% CI 1.000, 1.011) and results remained similar after adjustment for PM10-2.5 (RR = 1.005; 95% CI 0.998, 1.013). There was a borderline association between PM10-2.5 and cardiovascular hospital visits (RR = 1.007; 95% CI 0.997, 1.016), which disappeared after controlling for PM2.5 (RR = 1.000; 95% CI 0.988, 1.013). The associations appeared to be stronger in the cold season and among the elderly (≥ 75 years). The findings of this study suggested significant adverse effects of PM2.5, but no independent effects of PM10-2.5 on cardiovascular hospital visits. Additional studies are needed to confirm these findings.


Assuntos
Poluentes Atmosféricos/análise , Doenças Cardiovasculares/epidemiologia , Hospitalização/estatística & dados numéricos , Material Particulado/análise , Idoso , China , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tamanho da Partícula , Estações do Ano , Propriedades de Superfície
10.
J Epidemiol Community Health ; 72(12): 1083-1090, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30077965

RESUMO

BACKGROUND: A J-curve association has been demonstrated for blood pressure (BP) and all-cause mortality, but data on longitudinal change of BP and mortality in Chinese population are limited. METHODS: We performed a retrospective cohort study to examine the association between BP (at baseline and longitudinal change) and risk of mortality in Yinzhou District, Ningbo, China, based on the Yinzhou Health Information System. At baseline, a total of 181 352 subjects aged over 18 years with at least one BP examination record were recruited through the Yinzhou Health Information System. The final analysis was restricted to 168 061 participants after exclusion of outliers of BP. RESULTS: A U-shaped association was observed for BP at baseline and risk of total and cardiovascular mortality. When compared with normotensive participants, patients with hypotension (HRs=1.51, 95% CI 1.21 to 1.88) and stage 3 hypertension (1.28, 95% CI 1.09 to 1.50) had an increased risk of all-cause mortality. Relative to stable BP of normotension, having a rise in BP from normotension to hypertension or from prehypertension to hypertension both conferred an increased risk of total and cardiovascular mortality (total: 1.39 (95% 1.10 to 1.75) and 1.40 (95% 1.15 to 1.69); cardiovascular: 2.22 (95% CI 1.35 to 3.65) and 1.89 (95% CI 1.20 to 2.96), respectively). CONCLUSIONS: Our findings emphasise that hypotension and stage 3 hypertension were associated with an increased risk of all-cause mortality. Longitudinal change from normotensive or prehypertensive levels to 140/90 mm Hg or higher could increase the risk of total and cardiovascular mortality.


Assuntos
Doenças Cardiovasculares/mortalidade , Hipertensão/complicações , Hipotensão/complicações , Adulto , Idoso , Determinação da Pressão Arterial , China/epidemiologia , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco
11.
Environ Sci Pollut Res Int ; 25(16): 16135-16143, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29594907

RESUMO

Few studies were conducted to evaluate health effects of acute exposure to PM2.5 and daily mortality in Asian countries due to lack of large-scale PM2.5 monitoring data. We conducted a time-series study to examine the associations of short-term exposure to four common air pollutants (PM2.5, PM10, NO2, and SO2) and daily mortality in Ningbo, Zhejiang, China. We used generalized addictive model (GAM) to estimate relative risks (RRs) and 95% confidence intervals (CIs) for the association of these four air pollutants with daily mortality. The study included 9365 people in the 2-year study period from 2014 to 2015. SO2 were significantly associated with risk of NAD, RD, and CD mortality with RRs of 1.034 (95% CI 1.004, 1.064), 1.067 (95% CI 1.010, 1.127), and 1.049 (95% CI 1.001, 1.098), respectively.PM2.5 and PM10 were significantly associated with risk of death from NAD mortality in warm season. Similar associations were observed for PM10 (RR = 1.056, 95% CI 1.004, 1.111) and risk of CD mortality. The study provides further evidence that short-term exposure to PM2.5, PM10, NO2, and SO2 are associated with increased risk of daily mortality.


Assuntos
Poluição do Ar/análise , Exposição Ambiental/análise , Material Particulado/química , Ásia , China , Humanos , Material Particulado/análise , Risco , Estações do Ano
12.
Environ Sci Pollut Res Int ; 25(10): 10049-10057, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29380201

RESUMO

Although the effect of air pollution on respiratory health has been identified, few studies can be available to evaluate the association of air pollution with hospital visits for children's pneumonia in China. To explore whether high concentrations of air pollutants (including PM2.5, PM10, NO2, and SO2) are related to hospital visits for pneumonia in children, we conducted a population-based time-series study in Ningbo, China, from January 1st, 2014 to November 1st, 2015. We used a generalized additive Poisson regression model to calculate risk ratios and 95% confidence intervals for the associations of air pollutants and hospital visits for pneumonia in children and found that these four pollutants were associated with the increased hospital visits for pneumonia in children (1.3% for PM2.5, 1.0% for PM10, 2.9% for NO2, 5.0% for SO2 per 10-µg/m3 increase in PM2.5, PM10, NO2, and SO2, respectively). Stronger associations were observed in the cold seasons and among children under 5 years.


Assuntos
Poluentes Atmosféricos/toxicidade , Poluição do Ar , Hospitalização/estatística & dados numéricos , Pneumonia/induzido quimicamente , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Criança , Pré-Escolar , China/epidemiologia , Humanos , Masculino , Material Particulado/análise , Pneumonia/epidemiologia , Estações do Ano
13.
Environ Sci Pollut Res Int ; 24(23): 18860-18869, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28653196

RESUMO

Acute upper and lower respiratory infections are main causes of mortality and morbidity in children. Air pollution has been recognized as an important contributor to development and exacerbation of respiratory infections. However, few studies are available in China. In this study, we investigated the short-term effect of air pollution on hospital visits for acute upper and lower respiratory infections among children under 15 years in Ningbo, China. Poisson generalized models were used to estimate the associations between air pollution and hospital visits for acute upper and lower respiratory infections adjusted for temporal, seasonal, and meteorological effects. We found that four pollutants (PM2.5, PM10, NO2, and SO2) were significantly associated with hospital visits for acute upper and lower respiratory infections. The effect estimates for acute upper respiratory infections tended to be higher (PM2.5 ER = 3.46, 95% CI 2.18, 4.76; PM10 ER = 2.81, 95% CI 1.93, 3.69; NO2 ER = 11.27, 95% CI 8.70, 13.89; SO2 ER = 15.17, 95% CI 11.29, 19.19). Significant associations for gaseous pollutants (NO2 and SO2) were observed after adjustment for particular matter. Stronger associations were observed among older children and in the cold period. Our study suggested that short-term exposure to outdoor air pollution was associated with hospital visits for acute upper and lower respiratory infections in Ningbo.


Assuntos
Poluentes Atmosféricos/análise , Criança Hospitalizada/estatística & dados numéricos , Material Particulado/análise , Infecções Respiratórias/epidemiologia , Criança , Pré-Escolar , China , Feminino , Humanos , Lactente , Projetos de Pesquisa , Infecções Respiratórias/etiologia , Estações do Ano , Fatores de Tempo , Tempo (Meteorologia)
14.
Zhejiang Da Xue Xue Bao Yi Xue Ban ; 45(6): 607-613, 2016 05 25.
Artigo em Chinês | MEDLINE | ID: mdl-28247604

RESUMO

Objective: To explore the association between particulate matter (PM) and daily hospital visits of coronary heart diseases in Ningbo. Methods: Daily data of hospital visits from January 2014 to June 2015 (516 days in total) were obtained from the Yinzhou Health Information System in Ningbo. Daily air pollution data for PM and meteorological data were collected from the database of Ningbo Environmental Monitoring Center and Ningbo Meteorological Bureau. Time-series analysis by quasi-Poisson generalized additive model was used to examine the association between air pollution and hospital visits for coronary heart diseases by adjustment of long-term trends, seasonal patterns and meteorological variables (temperature, humidity), and day of week. Results: An increase of an IQR of PM2.5 accounted for 1.98% (95%CI:-0.59%-4.63%) increase of hospital visits for coronary heart diseases. The associations between PM2.5 and hospital visits for coronary heart diseases among female and the elderly (≥75 years) were stronger (ER=2.70%,95% CI:0.01%-5.47%; ER=3.35%, 95% CI: 0.12%-6.69%). The effects of PM2.5~10 attenuated after adjustment for PM2.5.Conclusion: PM2.5 had short-term effects on daily hospital visits for coronary heart diseases in Ningbo, and such association was stronger among female and the elderly.


Assuntos
Poluentes Atmosféricos/efeitos adversos , Poluição do Ar/efeitos adversos , Poluição do Ar/estatística & dados numéricos , Doença da Artéria Coronariana/epidemiologia , Hospitais/estatística & dados numéricos , Material Particulado/efeitos adversos , Fatores Etários , Idoso , China/epidemiologia , Feminino , Humanos , Umidade/efeitos adversos , Masculino , Pessoa de Meia-Idade , Estações do Ano , Fatores Sexuais , Temperatura , Fatores de Tempo
15.
J Am Chem Soc ; 134(4): 2024-7, 2012 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-22280441

RESUMO

Tetramethylammonium silanolate-initiated ring-opening copolymerization of octamethylcyclotetrasiloxane (D(4)) and bis(heptamethylcyclotetrasiloxanyl)ethane (bis-D(4)) renders cross-linked network polymers that contain ethylene bridges and active silanolate end groups. These "living" reactive anionic species are not neutralized by ambient atmosphere exposure (are stable to water, oxygen, CO(2)) and promote thermally activated equilibration among different network isomers and cyclic oligomers. The cross-link density of these living networks can be controlled by the ratio of D(4):bis-D(4), and the density of active chain ends is determined from the initiator:monomer ratio. We report that samples prepared with particular ratios of initiator:D(4):bis-D(4) can be cut with a sharp knife, even into two pieces, and can heal by siloxane equilibration to restore the original strength of the silicone sample. Fracture toughness measurements were carried out and revealed complete (mechanical) healing. Broken and healed samples generally failed in locations other than the initially cracked region. We call attention to publications and patents from the 1950s that suggest that this self-healing behavior was likely obvious 60 years ago.


Assuntos
Polímeros/síntese química , Siloxanas/química , Estrutura Molecular , Polímeros/química
16.
Langmuir ; 27(13): 7976-9, 2011 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-21627132

RESUMO

Reported are demonstrations that D(4)(H)/D(4)(V) silicone (the product of the platinum-catalyzed hydrosilylation reaction between tetramethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane) is useful and practical as a replica material for both nanoimprint lithography (NIL) and capillary force lithography (CFL). The multiple advantageous properties of this extremely cross-linked material include UV transparency (for photo NIL and photo CFL), thermal stability (for high printing temperatures), high modulus (for high printing pressures), low surface energy (for easy demolding), and low viscosity precursors (for replicating small scale features). The replication performance of this material was tested using Blu-ray discs with sub-25 nm features and anodized aluminum foil with sub-10 nm features. Structures of ∼5 nm length scale on the surface of the anodized Al were replicated using D(4)(H)/D(4)(V) silicone as a mold material for CFL with a photocurable epoxy resin and for NIL with poly(methyl methacrylate) (PMMA). Features (holes in the anodized aluminum) with aspect ratios of greater than 9 were replicated.

17.
Langmuir ; 27(6): 2166-9, 2011 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-21271691

RESUMO

Silicon/silicon dioxide surfaces containing 3 µm (width) × 6 µm (length) × 40 µm (height) staggered rhombus posts were prepared using photolithography and hydrophobized using a perfluoroalkyl-containing monofunctional silane. These surfaces exhibit water contact angles of θ(A)/θ(R) = 169°/156°. Water drops come to rest on a carefully aligned horizontal sample but roll when the surface is tilted slightly. No visible trail or evidence of water "left behind" at the receding edge of the drop is apparent on surfaces that water drops have rolled on or on samples removed from water through the air-water interface. When dimethylbis(ß-hydroxyethyl)ammonium methanesulfonate (N(+)S(-), a nonvolatile ionic liquid) is used as the liquid probe fluid (instead of water), contact angles of θ(A)/θ(R) = 164°/152° are observed and ∼3-µm-diameter sessile drops are visible (by scanning electron microscopy - SEM) on the top of every post of a sample drawn out of this liquid. We interpret the formation of these sessile microdrops as arising from microcapillary bridge failure that occurs during receding events and emphasize that the capillary bridges rupture in primarily a tensile failure mode. Smaller sessile drops could be prepared using mixtures of water and N(+)S(-). Microdroplets of N(+)S(-) were also observed to form selectively at particular features on surfaces containing square holes separated by ridges. This suggests that pinning sites can be identified using microscopy and this ionic liquid probe fluid.

18.
Langmuir ; 26(24): 18585-90, 2010 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-21114260

RESUMO

We demonstrate the preparation of extremely cross-linked poly(dimethylsiloxane) (PDMS)-based materials and report optical, mechanical, and surface properties. Transparent monolithic molded objects are prepared catalytically with no byproducts; parts per million levels of platinum (catalyst) remain in the articles. Essentially the same material was prepared in 1993 and described as a "hard transparent glass." We confirm the thermal stability and chemical structure described in this report. We show that the catalytic reaction used, which was reported in 1999 always to exhibit a "violent exotherm", can be controlled conveniently using a low (parts per million) catalyst concentration. The combination of low surface energy, transparency, hardness, elasticity, and thermal stability makes this an unusual and interesting material. That it can be prepared from commercially available low-viscosity monomers adds to its interest. We comment that the class of materials known as siloxanes or silicones and PDMS in particular is not currently generally well understood (or taught) and review aspects of the structure, properties, and cross-linking chemistry of PDMS.

19.
J Colloid Interface Sci ; 316(1): 53-8, 2007 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-17719596

RESUMO

Amphiphilic colloids of CdS and noble metal nanoparticles, which can be dispersed both in water and organic solvents such as ethanol, N,N-dimethylformamide, chloroform, and toluene, are studied. The amphiphilic colloidal nanoparticles are synthesized by grafting the amphiphilic and thermoresponsive polymer of thiol-terminated poly(N-isopropylacrylamide) to CdS and noble metal nanoparticles. The size and morphology of the PNIPAM-grafted colloidal nanoparticles of CdS@PNIPAM can be tuned by changing the molar ratio of PNIPAM/CdS. The size of CdS@PNIPAM nanoparticles slightly decreases first from 5.5 to 4.4 nm then slightly increases from 4.4 to 6.1 nm with the decrease in the molar ratio from 1/1 to 1/10. Spherical nanoparticles of CdS@PNIPAM are synthesized at a higher molar ratio and worm-like nanoparticles are obtained at a lower molar ratio. The resultant PNIPAM-grafted colloidal nanoparticles of CdS@PNIPAM, Au@PNIPAM, Pd@PNIPAM, and Ag@PNIPAM are thermoresponsive in water and show a cloud-point temperature at about 32.5 degrees C.


Assuntos
Compostos de Cádmio/química , Nanopartículas Metálicas/química , Metais/química , Sulfetos/química , Água/química , Resinas Acrílicas/química , Coloides , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Espectrofotometria , Temperatura , Difração de Raios X
20.
Langmuir ; 22(22): 9393-6, 2006 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-17042559

RESUMO

Template synthesis of various morphological gold colloidal nanoparticles using a thermoresponsive and pH-responsive coordination triblock copolymer of poly(ethylene glycol)-b-poly(4-vinylpyridine)-b-poly(N-isopropylacrylamide) is studied. The template morphology of the thermoresponsive and pH-responsive coordination triblock copolymer, which can be tuned by simply changing the pH or temperature of the triblock copolymer aqueous solution, ranges from single chains to core-corona micelles and further to micellar clusters. Various morphological gold colloidal nanoparticles such as discrete gold nanoparticles, gold@polymer core-shell nanoparticles, and gold nanoparticle clusters are synthesized on the corresponding template of the triblock copolymer by first coordination with gold ions and then reduction by NaBH4. All three resultant gold colloidal nanoparticles are stable in aqueous solution, and their sizes are 2, 10, and 7 nm, respectively. The gold@polymer core-shell nanoparticles are thermoresponsive. The gold nanoparticle cluster has a novel structure, and each one holds about 40 single gold nanoparticles.

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