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1.
Sensors (Basel) ; 21(18)2021 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-34577386

RESUMEN

Pyroelectric Infrared (PIR) sensors are low-cost, low-power, and highly reliable sensors that have been widely used in smart environments. Indoor localization systems can be categorized as wearable and non-wearable systems, where the latter are also known as device-free localization systems. Since the binary PIR sensor detects only the presence of a human motion in its field of view (FOV) without any other information about the actual location, utilizing the information of overlapping FOV of multiple sensors can be useful for localization. In this study, a PIR detector and sensing signal processing algorithms were designed based on the characteristics of the PIR sensor. We applied the designed PIR detector as a sensor node to create a non-wearable cooperative indoor human localization system. To improve the system performance, signal processing algorithms and refinement schemes (i.e., the Kalman filter, a Transferable Belief Model, and a TBM-based hybrid approach (TBM + Kalman filter)) were applied and compared. Experimental results indicated system stability and improved positioning accuracy, thus providing an indoor cooperative localization framework for PIR sensor networks.


Asunto(s)
Algoritmos , Procesamiento de Señales Asistido por Computador , Humanos , Movimiento (Física)
2.
Genes (Basel) ; 12(1)2020 12 24.
Artículo en Inglés | MEDLINE | ID: mdl-33374471

RESUMEN

Adiponectin (APN) is suggested to be a potential biomarker for predicting diabetic retinopathy (DR) risk, but the association between APN and DR has been inconsistent in observational studies. We used a Mendelian randomization (MR) analysis to evaluate if circulating APN levels result in DR. We applied three different genetic risk scores (GRS): GRSAll combined all 47 single nucleotide polymorphisms (SNPs), which from a genome-wide association study (GWAS) database-catalog reach significance level; GRSLimited comprised 16 GRSAll-SNPs with a rigorous threshold (p < 5.0 × 10-8 for GWAS), and GRSAPN combined 5 SNPs significantly associated with APN level. The MR-inverse-variance weighted method analysis showed that for each 1-SD increase in genetically induced increase in plasma APN, the OR of having DR was ß = 0.20 (95% CI: -0.46-0.85, p = 0.553) for GRSAPN, 0.61 (95% CI: 0.10-1.13, p = 0.020) for GRSAll, and 0.57 (95% CI: -0.06 to 1.20, p = 0.078) for GRSLimited. Sensitivity analysis, including MR-egger regression and the weighted-median approach, did not provide evidence of the pleiotropic effect of IVs. Limited evidence for the causal role of APN in DR risk among Taiwanese diabetic patients was shown based on MR analysis in the present study.


Asunto(s)
Adiponectina/sangre , Diabetes Mellitus Tipo 2/complicaciones , Retinopatía Diabética/epidemiología , Adiponectina/genética , Anciano , Pueblo Asiatico/genética , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/genética , Retinopatía Diabética/sangre , Retinopatía Diabética/genética , Femenino , Pleiotropía Genética , Estudio de Asociación del Genoma Completo , Humanos , Masculino , Análisis de la Aleatorización Mendeliana , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Medición de Riesgo/métodos , Taiwán/epidemiología
3.
Artículo en Inglés | MEDLINE | ID: mdl-31958309

RESUMEN

OBJECTIVE: Diabetic nephropathy (DN) and diabetic retinopathy (DR) comprise major microvascular complications of diabetes that occur with a high concordance rate in patients and are considered to potentially share pathogeneses. In this case-control study, we sought to investigate whether DR-related single nucleotide polymorphisms (SNPs) exert pleiotropic effects on renal function outcomes among patients with diabetes. RESEARCH DESIGN AND METHODS: A total of 33 DR-related SNPs were identified by replicating published SNPs and via a genome-wide association study. Furthermore, we assessed the cumulative effects by creating a weighted genetic risk score and evaluated the discriminatory and prediction ability of these genetic variants using DN cases according to estimated glomerular filtration rate (eGFR) status along with a cohort with early renal functional decline (ERFD). RESULTS: Multivariate logistic regression models revealed that the DR-related SNPs afforded no individual or cumulative genetic effect on the nephropathy risk, eGFR status or ERFD outcome among patients with type two diabetes in Taiwan. CONCLUSION: Our findings indicate that larger studies would be necessary to clearly ascertain the effects of individual genetic variants and further investigation is also required to identify other genetic pathways underlying DN.


Asunto(s)
Diabetes Mellitus Tipo 2/complicaciones , Nefropatías Diabéticas/genética , Retinopatía Diabética/genética , Marcadores Genéticos , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Polimorfismo de Nucleótido Simple , Anciano , Estudios de Casos y Controles , Estudios de Cohortes , Nefropatías Diabéticas/etiología , Nefropatías Diabéticas/patología , Retinopatía Diabética/etiología , Retinopatía Diabética/patología , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Factores de Riesgo , Taiwán
4.
In Vivo ; 33(5): 1685-1690, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31471424

RESUMEN

BACKGROUND/AIM: C-Reactive protein (CRP) is a common marker of inflammation. Elevated CRP levels have been associated with increased risk of development of type 2 diabetes mellitus (T2DM). This study aimed to evaluate the association of CRP gene polymorphisms with early-onset T2DM and the effect of genetic variants on CRP level. MATERIALS AND METHODS: In total, 948 individuals with early-onset (n=271) or late-onset (n=677) T2DM were enrolled in the study. Five single-nucleotide polymorphisms (SNPs) in the CRP gene, namely rs3093077, rs2808630, rs1800947, rs11265263, and rs11265265, were selected for genotyping, and CRP levels were measured. RESULTS: Genotypic, allelic, and haplotype frequencies of these five SNPs were not significantly different between patients with early- and those with late-onset. T2DM Higher serum CRP levels were independently associated with the C-allele of rs3093077 and T-allele of rs11265265 (p<0.001). Furthermore, the C-allele of rs3093077 was associated with higher CRP level in both early- (p=0.016) and late-onset (p<0.001) T2DM. CONCLUSION: CRP gene variants may contribute to the risk of early-onset T2DM by affecting the serum CRP level.


Asunto(s)
Proteína C-Reactiva/genética , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/genética , Variación Genética , Adulto , Edad de Inicio , Alelos , Biomarcadores , Diabetes Mellitus Tipo 2/diagnóstico , Femenino , Frecuencia de los Genes , Genotipo , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple
5.
Medicine (Baltimore) ; 98(11): e14878, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-30882695

RESUMEN

Adiponectin (APN) and its receptors have been reported to be associated with metabolic phenotypes. To better understand the effects of APN levels and its receptors on diabetic retinopathy (DR), we investigated the association of the plasma APN level and variations in APN-related genes with DR, individually and in combination.Patients with type 2 diabetes (T2D; N = 1604), above 20 years of age from the Taiwanese population participated in the study. Demographic information, blood pressure, and serological markers were recorded at enrollment. Genomic DNA was isolated and genotyped. The plasma APN levels were measured by enzyme-linked immunosorbent assay.T2D patients with DR (N = 632) had diabetes for a longer duration, and had higher HbA1c, and systolic and diastolic blood pressure compared to those without DR (N = 972) (P < .001, for all the parameters). Overall, 10 single nucleotide polymorphisms (SNPs) in ADIPOQ and CDH13 susceptibility loci were associated with DR. Gene risk score (GRS) was calculated based on 10 SNPs for each subject and the cumulative effect of genes was observed. Among the subjects with plasma APN level (N = 518), natural logarithm (LN) of APN (LN [APN]; odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.19-2.25) and GRS (OR = 1.90, 95% CI = 1.11-3.26 for middle range of GRS, and OR = 2.61, 95% CI = 1.48-4.59 for high range of GRS) were independent risk factors for DR after adjustment for other parameters.In conclusion, the plasma APN level and the genetic variations in adiponectin receptors were associated with DR.


Asunto(s)
Adiponectina/análisis , Retinopatía Diabética/genética , Valor Predictivo de las Pruebas , Adiponectina/sangre , Adiponectina/genética , Anciano , Análisis de Varianza , Cadherinas/genética , Estudios de Casos y Controles , Complicaciones de la Diabetes , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/epidemiología , Retinopatía Diabética/epidemiología , Femenino , Genotipo , Hemoglobina Glucada/análisis , Humanos , Masculino , Persona de Mediana Edad , Factores de Riesgo , Estadísticas no Paramétricas , Taiwán/epidemiología
6.
J Clin Med ; 7(12)2018 Nov 26.
Artículo en Inglés | MEDLINE | ID: mdl-30486327

RESUMEN

Diabetic nephropathy (DN) is a major complication in diabetic patients. Microalbuminuria testing is used to identify renal disease; however, its predictive value is questionable. We aimed to identify urinary biomarkers to early diagnosis nephropathy before identifiable alternations in kidney function or urine albumin excretion occurs. Proteomic approaches were used to identify potential urinary biomarkers and enzyme-linked immunosorbent assay was performed to verify the results. The data identified haptoglobin (HPT) and α-1-microglobulin/bikunin precursor (AMBP) as two biomarkers with the highest ability to distinguish between healthy individuals and patients with nephropathy, and between diabetic patients with and without DN. Further, the HPT-to-creatinine ratio (HCR) was evaluated as an independent predictor of early renal functional decline (ERFD) in a cohort with an average follow-up of 4.2 years. The area under the curve (AUC) value for ERFD prediction was significantly improved when the HCR biomarker was included in the model with albumin to creatinine ratio (ACR) and baseline characteristics (AUC values were 0.803 and 0.759 for HCR and ACR, respectively; p value was 0.0423 for difference between models). In conclusion, our results suggest that HCR represents an early indicator of nephropathy, and a marker related to ERFD among diabetic patients in Taiwan.

7.
Sci Rep ; 8(1): 14535, 2018 09 28.
Artículo en Inglés | MEDLINE | ID: mdl-30266984

RESUMEN

The aim of this study is to explore the effect of genetic variation on diabetic retinopathy (DR) risk in a Taiwanese population. The logistic regression model was used to evaluate the relationship between DR status and risk factors, including the conventional parameters and genetic risk score (GRS). Candidate single nucleotide polymorphisms (SNPs) in GRS were selected based on previous reports with a combined P < 10-4 (genome-wide association) and P < 0.05 (meta-analysis). In total, 58 SNPs in 44 susceptibility loci were selected, and four were used to calculate GRS. After adjustment for age, systolic blood pressure, diabetes duration, and HbA1c, the DR risk was 4.95 times higher for patients in the top GRS third tile than for those in the bottom third tile (95% CI = 2.99-8.18; P < 0.001). The addition of genetic information improved DR prediction, increasing the area under the curve (AUC) from 0.72 to 0.77 (P = 0.0024) and improving the sensitivity of the model such that 40 more subjects were reclassified into DR status. The developed multivariate logistic regression model combining conventional risk factors and the multilocus GRS can predict DR, thus enabling timely treatment to reduce blindness in T2D patients.


Asunto(s)
Retinopatía Diabética/genética , Anciano , Pueblo Asiatico/genética , Retinopatía Diabética/epidemiología , Femenino , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Factores de Riesgo , Taiwán/epidemiología
8.
Sensors (Basel) ; 18(7)2018 Jun 25.
Artículo en Inglés | MEDLINE | ID: mdl-29941793

RESUMEN

In many Internet of Things (IoT) applications, large numbers of small sensor data are delivered in the network, which may cause heavy traffics. To reduce the number of messages delivered from the sensor devices to the IoT server, a promising approach is to aggregate several small IoT messages into a large packet before they are delivered through the network. When the packets arrive at the destination, they are disaggregated into the original IoT messages. In the existing solutions, packet aggregation/disaggregation is performed by software at the server, which results in long delays and low throughputs. To resolve the above issue, this paper utilizes the programmable Software Defined Networking (SDN) switch to program quick packet aggregation and disaggregation. Specifically, we consider the Programming Protocol-Independent Packet Processor (P4) technology. We design and develop novel P4 programs for aggregation and disaggregation in commercial P4 switches. Our study indicates that packet aggregation can be achieved in a P4 switch with its line rate (without extra packet processing cost). On the other hand, to disaggregate a packet that combines N IoT messages, the processing time is about the same as processing N individual IoT messages. Our implementation conducts IoT message aggregation at the highest bit rate (100 Gbps) that has not been found in the literature. We further propose to provide a small buffer in the P4 switch to significantly reduce the processing power for disaggregating a packet.

9.
Front Neurosci ; 11: 608, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-29163012

RESUMEN

Targeting neuropeptide systems is important for future advancements in treatment of neurological and psychiatric illnesses. However, many of the peptides and their analogs do not cross the blood-brain barrier (BBB) efficiently. Nanoparticles such as iron oxide can cross the BBB, and here we describe a novel method for the conjugation of a peptide antisauvagine-30 (ASV-30) to iron oxide nanoparticles. Previous research has shown that direct infusion of ASV-30 into the brain reduces anxiety-like behavior in animal models via actions on corticotropin releasing factor type 2 (CRF2) receptors. Therefore, we tested whether iron oxide+ASV-30 complexes cross the BBB of rats and then determined whether iron oxide+ASV-30 nanoparticles are localized with CRF2-expressing neurons. Finally we tested the hypothesis that systemic infusion of iron oxide+ASV-30 can reduce anxiety-like behavior. First we describe the synthesis and demonstrate the stability of iron oxide-peptide nanoparticle complexes. Next, nanoparticles (87.7 µg/kg Fe2O3) with or without ASV-30 (200 µg/kg, ip) were injected into male rats 30 min prior to transcardial perfusion and brain fixation for immunohistochemical analysis, or before testing on the elevated plus maze (EPM) in an amphetamine withdrawal model of anxiety. Systemically administered iron oxide+ASV-30 particles were present in the brain and associated with neurons, including those that express CRF2 receptors, but did not localize with the iron storage protein ferritin. Furthermore, systemic administration of ironoxide+ASV-30 reduced amphetamine withdrawal-induced anxiety without affecting locomotion, suggesting that the anxiolytic effects of ASV-30 were preserved and the bioavailability of ASV-30 was sufficient. The findings demonstrate a novel approach to peptide delivery across the BBB and provide insight as to the neural distribution and efficacy of this nanotechnology.

10.
Sci Rep ; 7(1): 6372, 2017 07 25.
Artículo en Inglés | MEDLINE | ID: mdl-28744006

RESUMEN

Human height can be described as a classical and inherited trait model. Genome-wide association studies (GWAS) have revealed susceptible loci and provided insights into the polygenic nature of human height. Familial short stature (FSS) represents a suitable trait for investigating short stature genetics because disease associations with short stature have been ruled out in this case. In addition, FSS is caused only by genetically inherited factors. In this study, we explored the correlations of FSS risk with the genetic loci associated with human height in previous GWAS, alone and cumulatively. We systematically evaluated 34 known human height single nucleotide polymorphisms (SNPs) in relation to FSS in the additive model (p < 0.00005). A cumulative effect was observed: the odds ratios gradually increased with increasing genetic risk score quartiles (p < 0.001; Cochran-Armitage trend test). Six affected genes-ZBTB38, ZNF638, LCORL, CABLES1, CDK10, and TSEN15-are located in the nucleus and have been implicated in embryonic, organismal, and tissue development. In conclusion, our study suggests that 13 human height GWAS-identified SNPs are associated with FSS risk both alone and cumulatively.


Asunto(s)
Pueblo Asiatico/genética , Estatura/genética , Predisposición Genética a la Enfermedad/genética , Polimorfismo de Nucleótido Simple , Pueblo Asiatico/etnología , Proteínas Portadoras/genética , Quinasas Ciclina-Dependientes/genética , Ciclinas/genética , Proteínas de Unión al ADN/genética , Endonucleasas/genética , Estudio de Asociación del Genoma Completo , Humanos , Herencia Multifactorial , Proteínas Nucleares/genética , Fosfoproteínas/genética , Proyectos Piloto , Proteínas de Unión al ARN , Proteínas Represoras/genética , Taiwán/etnología , Factores de Transcripción
11.
Molecules ; 20(12): 21881-95, 2015 Dec 08.
Artículo en Inglés | MEDLINE | ID: mdl-26670222

RESUMEN

Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO2(B). The mesoporous TiO2 materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO2(B) exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy.


Asunto(s)
Nanotecnología/métodos , Dióxido de Silicio/química , Titanio/química , Catálisis , Hidrógeno/metabolismo , Luz , Tamaño de la Partícula , Fármacos Fotosensibilizantes/química , Porosidad , Propiedades de Superficie , Agua/química
12.
ACS Appl Mater Interfaces ; 7(7): 4368-80, 2015 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-25633643

RESUMEN

Mesoporous TiO2 photocatalysts were prepared in ethanol media by using relatively green, template free sol-gel technique. A mild hydrothermal treatment procedure was employed to tune the pore sizes of the materials. Comprehensive techniques that include powder X-ray diffraction, diffuse reflectance spectroscopy, specific surface area analysis, electron microscopy, FT-IR, TGA, and ζ-potential measurements were used to characterize the titania materials. Porosity (pore size and pore volume) of the materials were found to be key factors for the variation in the rate of photocatalytic degradation of rhodamine B; in addition to specific surface area, and surface hydroxyl groups. An increase in porosity permits effective transport of the dye molecules resulting in an increase in the rate of the degradation in materials having larger pores. A detailed electrospray ionization-mass spectrometric (ESI-MS) study was carried out for selected materials to identify photodegraded intermediates and products formed during the degradation of rhodamine B. In addition, experiments were also carried out to understand the role of reactive oxygen species (ROS). In summary, this work provides a simple way to tune pore sizes without the use of any template and an insight into the influence of pore size for the photocatalytic degradation of rhodamine B.

13.
Environ Geochem Health ; 37(2): 233-49, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25185928

RESUMEN

The purpose of this study is to characterize metallic elements associated with atmospheric particulate matter in the dry deposition plate, total suspended particulate, fine particles, and coarse particles at Taichung Harbor and Gong Ming Junior High School (airport) in central Taiwan at a sampling site from June 2013 to August 2013. The results indicated that: (1) the average concentrations of the metallic elements Cr and Cd were highest at the Gong Ming Junior High School (airport), and the average concentrations of the metallic elements Ni, Cu, and Pb were highest at the Taichung Harbor sampling site. (2) The high smelting industry density and export/import rate of heavily loaded cargos were the main reasons leading to these findings. (3) The average metallic element dry deposition and metallic element PM(2.5-10) all followed the order of Pb > Cr > Cu > Ni > Cd at the two sampling sites. However, the average metallic elements Cu and Pb were found to have the highest dry deposition velocities and concentrations in PM(2.5) for the two sampling sites in this study. (4) The correlation coefficients of ambient air particle dry deposition and concentration with wind speed at the airport were higher than those from the harbor sampling site. The wind and broad open spaces at Taichung Airport were the possible reasons for the increasing correlation coefficients for ambient air particle concentration and dry deposition with wind speed at the Taichung Airport sampling site.


Asunto(s)
Metales Pesados/análisis , Material Particulado/análisis , Contaminación del Aire/análisis , Monitoreo del Ambiente , Metalurgia , Tamaño de la Partícula , Estaciones del Año , Taiwán , Viento
14.
Environ Sci Nano ; 1(2): 123-132, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25221673

RESUMEN

Given the increased use of iron-containing nanoparticles in a number of applications, it is important to understand any effects that iron-containing nanoparticles can have on the environment and human health. Since iron concentrations are extremely low in body fluids, there is potential that iron-containing nanoparticles may influence the ability of bacteria to scavenge iron for growth, affect virulence and inhibit antimicrobial peptide (AMP) function. In this study, Pseudomonas aeruginosa (PA01) and AMPs were exposed to iron oxide nanoparticles, hematite (α-Fe2O3), of different sizes ranging from 2 to 540 nm (2 ± 1, 43 ± 6, 85 ± 25 and 540 ± 90 nm) in diameter. Here we show that the greatest effect on bacterial growth, biofilm formation, and AMP function impairment is found when exposed to the smallest particles. These results are attributed in large part to enhanced dissolution observed for the smallest particles and an increase in the amount of bioavailable iron. Furthermore, AMP function can be additionally impaired by adsorption onto nanoparticle surfaces. In particular, lysozyme readily adsorbs onto the nanoparticle surface which can lead to loss of peptide activity. Thus, this current study shows that co-exposure of nanoparticles and known pathogens can impact host innate immunity. Therefore, it is important that future studies be designed to further understand these types of impacts.

15.
Phys Chem Chem Phys ; 16(5): 2048-61, 2014 Feb 07.
Artículo en Inglés | MEDLINE | ID: mdl-24343278

RESUMEN

CdS incorporated Si-MCM-48 and Ti-MCM-48 cubic phased mesoporous photocatalysts were prepared by a two-step modification synthetic approach under relatively mild conditions. A highly efficient (24.8%, apparent quantum yield (AQY)) photocatalyst for visible light (λ > 400 nm) enabled solar hydrogen evolution can be realized by assembling CdS with Ti-MCM-48 cubic mesoporous materials in the absence of a noble metal co-catalyst. The photocatalytic mechanism was thoroughly investigated and demonstrated by conducting a wealth of characterization techniques such as powder X-ray diffraction (XRD), nitrogen adsorption isotherm, transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UVPS), atomic absorption spectroscopy (AAS), photoluminescence (PL) spectroscopy, time-resolved fluorescence emission decay, and electron paramagnetic resonance (EPR) spectroscopy studies. This work is the first to unambiguously identify the band positions of both CdS and TiO2 encapsulated in porous materials. The photocatalytic activity of the CdS incorporated Ti-MCM-48 mesoporous photocatalysts was found to be dependent on the content of both CdS and TiO2. A correlation between the electron injection efficiency and the photocatalytic activity was established as well in the CdS incorporated Ti-MCM-48 mesoporous photocatalysts.

16.
Chem Commun (Camb) ; 49(31): 3221-3, 2013 Apr 21.
Artículo en Inglés | MEDLINE | ID: mdl-23482963

RESUMEN

A RuO2-CdS-Ti-MCM-48 mesoporous material has been prepared. This composite material generates hydrogen and oxygen in the absence of a Pt co-catalyst and most importantly photocorrosion of CdS is completely eliminated.

17.
Chem Commun (Camb) ; 49(12): 1223-5, 2013 Feb 11.
Artículo en Inglés | MEDLINE | ID: mdl-23282532

RESUMEN

A MOF-5 [Zn(4)O(BDC)(3); BDC = 1,4-benzenedicarboxylate]@SBA-15 hybrid material has been prepared by using SBA-15 as a matrix. This hybrid material exhibits improved hydrostability under ambient conditions and unique gas adsorption behavior compared with pristine MOF-5.

18.
Langmuir ; 28(1): 396-403, 2012 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-22122742

RESUMEN

Understanding size-dependent processes, including dissolution, of engineered nanoparticles is essential in addressing the potential environmental and health impacts of these materials as well as their long-term stability. In this study, experimental measurements of size-dependent dissolution of well-characterized zinc oxide (ZnO) nanoparticles with particle diameters in the range of 4 to 130 nm have been measured at circumneutral pH (pH 7.5) and compared. Dissolution was found to be enhanced with smaller ZnO nanoparticles compared to larger-sized particles, even though the nanoparticles were present in solution as aggregates with hydrodynamic diameters on the order of 1-3 µm in size. The presence of citric acid significantly enhanced the extent of ZnO dissolution for all sizes, and the greatest enhancement was observed for the 4 nm particles. Although these results are found to be in qualitative agreement with theoretical predictions, a linearized form of the Kelvin equation to calculate a surface free energy yielded quantities inconsistent with expected values from the literature. Reasons for this inconsistency are discussed and include potential deviations of solubility behavior from classical thermodynamics as a result of a lack of detailed knowledge of surface structure and surface properties, including the presence of different surface crystal facets, and the aggregation state.

19.
Biochemistry ; 50(43): 9248-54, 2011 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-21942297

RESUMEN

NH(3) is a structural analogue of substrate H(2)O and an inhibitor to the water oxidation reaction in photosystem II. To test whether or not NH(3) is able to replace substrate water molecules on the oxygen-evolving complex in photosystem II, we studied the effects of NH(3) on the high-frequency region (3750-3550 cm(-1)) of the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectra (pH 7.5 at 250 K), where OH stretch modes of weak hydrogen-bonded active water molecules occur. Our results showed that NH(3) did not replace the active water molecule on the oxygen-evolving complex that gave rise to the S(1) mode at ~3586 cm(-1) and the S(2) mode at ~3613 cm(-1) in the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectrum of PSII. In addition, our mid-frequency FTIR results showed a clear difference between pH 6.5 and 7.5 on the concentration dependence of the NH(4)Cl-induced upshift of the S(2) state carboxylate mode at 1365 cm(-1) in the S(2)Q(A)(-)/S(1)Q(A) spectra of NH(4)Cl-treated PSII samples. Our results provided strong evidence that NH(3) induced this upshift in the spectra of NH(4)Cl-treated PSII samples at 250 K. Moreover, our low-frequency FTIR results showed that the Mn-O-Mn cluster vibrational mode at 606 cm(-1) in the S(2)Q(A)(-)/S(1)Q(A) spectrum of the NaCl control PSII sample was diminished in those samples treated with NH(4)Cl. Our results suggest that NH(3) induced a significant alteration on the core structure of the Mn(4)CaO(5) cluster in PSII. The implication of our findings on the structure of the NH(3)-binding site on the OEC in PSII will be discussed.


Asunto(s)
Amoníaco/metabolismo , Complejo de Proteína del Fotosistema II/química , Complejo de Proteína del Fotosistema II/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier/métodos , Spinacia oleracea/metabolismo , Luz , Modelos Moleculares , Oxidación-Reducción , Oxígeno/metabolismo , Spinacia oleracea/química , Agua/metabolismo
20.
J Nanosci Nanotechnol ; 10(9): 5715-22, 2010 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21133096

RESUMEN

Preparation of platinum nanoparticles from two beta-diketonate complexes of platinum, Pt(hfac)2 and Pt(acac)2 (hfac: hexafluoroacetylacetonate, acac: acetylacetonate) in organic media will be presented in the contribution. Nearly spherical, well-dispersed platinum nanoparticles were fabricated by thermally-induced reduction of Pt(hfac)2 in the presence of teraalkylammonium salts as the stabilizing agents in several organic solvents. Particle sizes ranging from 9 to 15 nm can be controlled by variation of the surfactant, the concentrations of precursor and surfactant, as well as reaction temperature. Heating the solution of Pt(acac)2 complex in 1-octanol at appropriate temperatures provided the platinum nanocubes and the influence of reaction temperature on the particle shape was investigated.

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