Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 14 de 14
Filtrar
Más filtros

Banco de datos
País/Región como asunto
Tipo del documento
País de afiliación
Intervalo de año de publicación
1.
Zhonghua Yu Fang Yi Xue Za Zhi ; 58(2): 208-212, 2024 Feb 06.
Artículo en Zh | MEDLINE | ID: mdl-38387952

RESUMEN

Objective: To understand the prevalence of occasional hypertension in preschool children in three provinces in the middle and lower reaches of the Yangtze River in China, and analyze the relationship between their sleep status and occasional hypertension. Methods: From October to November 2017, a total of 24 842 preschool children from 109 kindergartens in 11 cities in Hubei, Anhui and Jiangsu provinces were selected by intentional sampling method. A self-made questionnaire was used to collect basic information about the subjects, and the sleep status data was collected by the Children's Sleep Habits Questionnaire. Physical examinations were performed on the subjects, and height, weight and blood pressure were measured on-site. The difference in occasional hypertension detection rate among preschool children with different characteristics was compared, and the correlation between sleep status and occasional hypertension detection rate was analyzed by the multivariate logistic regression model. Results: The age of the subjects was (4.4±1.0) years, including 12 729 boys (51.2%). The prevalence of occasional hypertension was 31.8% (7 907/24 842). The prevalence of occasional hypertension among preschool children in three provinces of the middle and lower reaches of the Yangtze River was 31.8%. There were statistically significant differences in the detection rate of occasional hypertension among preschool children of different genders, age groups, family residence, family economic status and parents' education level (all P values<0.05). The detection rate of occasional hypertension in children with less than 10 hours of sleep was higher than those with sufficient sleep, and the difference was statistically significant (P<0.05). The results of multivariate logistic regression analysis showed that after adjusting for factors such as gender, age, family residence, family economic status, parental education level, parental smoking history, and physical constitution, the ORs (95%CI) for less than 10 hours of sleep, turning on the lights while sleeping, and poor sleep quality were 1.09 (1.03-1.15), 1.17 (1.07-1.28) and 1.04 (0.91-1.18), respectively, compared with the corresponding reference group. Conclusion: The detection rate of occasional hypertension is high in preschool children in the middle and lower reaches of the Yangtze River and there is a positive correlation between insufficient sleep and turning on the light when sleeping and occasional hypertension in preschool children.


Asunto(s)
Hipertensión , Ríos , Humanos , Masculino , Preescolar , Femenino , Sueño , Hipertensión/epidemiología , Presión Sanguínea , China/epidemiología
2.
Zhonghua Nei Ke Za Zhi ; 55(4): 289-92, 2016 Apr 01.
Artículo en Zh | MEDLINE | ID: mdl-27030617

RESUMEN

OBJECTIVE: To estimate the prevalence of anemia in urban community dwelling elderly population. METHODS: This study was a cross-sectional survey of prevalence of anemia in randomly selected community dwelling residents aged over 65 years in Beijing. Anemia was defined as hemoglobin concentration less than 130 g/L in men and 120 g/L in women. RESULTS: The hemoglobin concentration was (135.65±14.48) g/L in total of 1 947 eligible participants and was much higher in men than in women [(142.56±15.56) g/L vs (130.95±11.53) g/L, P<0.001]. There were 288 (14.8%) patients with anemia, including 16.3%(129/789) in men and 13.7%(159/1 158) in women. The prevalence of anemia increased significantly with age, which was 7.6% in 65-69 years, 10.8% in 70-74 years, 18.8% in 75-79 years and 24.1% over 80 years (P<0.001). Two hundred and seventy-nine (96.9%) subjects were mild anemia, 8 (2.8%) moderate, only 1 subject (0.3%) severe. Unexplained anemia was predominant, which accounted for 63.2%. Only 16.7% people were diagnosed as nutritional anemia, renal anemia 5.2%, anemia of chronic disease (ACD) 12.2%. There were 2.4% people with overlapped renal anemia and ACD. Compared with non-anemic subjects, more subjects with unexplained anemia represented macrocytosis (7.1% vs 3.2%, P=0.007). CONCLUSIONS: Anemia is a common health problem in urban community dwelling elderly population. Most subjects have anemia with unknown origin. Further investigation is needed to explore the mechanism and related factors of elderly anemia.


Asunto(s)
Anemia/epidemiología , Anemia/etiología , Vida Independiente , Población Urbana , Distribución por Edad , Anciano , Anciano de 80 o más Años , Beijing/epidemiología , Estudios de Casos y Controles , Enfermedad Crónica , Estudios Transversales , Femenino , Humanos , Masculino , Prevalencia , Distribución Aleatoria , Índice de Severidad de la Enfermedad , Distribución por Sexo
3.
Eur Rev Med Pharmacol Sci ; 27(18): 8428-8437, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37782160

RESUMEN

OBJECTIVE: To explore the lumbar spine biomechanics of graded ventral facetectomy and determine the appropriate extent of resection for foraminoplasty. PATIENTS AND METHODS: We retrospectively measured several radiological parameters of superior articular process (SAP) and bony intervertebral foramen in computed tomography scans of 170 lumbar vertebral discs. The intact finite element (FE) spine of L2-sacrum was modified to simulate foraminoplasty with two typical graded ventral facetectomy methods (Method Ⅰ: basal part resection of SAP; Method Ⅱ: apical part resection of SAP) to explore the biomechanical effects under different physiological motions. RESULTS: Examination of the radiological parameters of the bony intervertebral foramen indicated that they were generally narrower than the diameters of commercially available working cannulas. Some of these parameters showed gender differences. The biomechanical evaluation indicated that the range of motion increased gradually with the expansion of the resection extent, and the differences compared to the intact spine at the same level were greater in Method I than in Method Ⅱ. CONCLUSIONS: The appropriate ventral resection extent of the basal part of the SAP (Method I) was 4 mm, 3 mm, and 3 mm on the lateral view at L3-L4, L4-L5, and L5-S1, respectively. The appropriate ventral resection extent of the apical part of the SAP (Method II) were 10 mm, 6 mm and 6 mm on the lateral view at L3-L4, L4-L5, and L5-S1, respectively. Extensive resection of foraminoplasty may destabilize lumbar motion segments.


Asunto(s)
Discectomía Percutánea , Desplazamiento del Disco Intervertebral , Humanos , Vértebras Lumbares/diagnóstico por imagen , Vértebras Lumbares/cirugía , Desplazamiento del Disco Intervertebral/diagnóstico por imagen , Desplazamiento del Disco Intervertebral/cirugía , Estudios Retrospectivos , Discectomía , Fenómenos Biomecánicos , Rango del Movimiento Articular/fisiología
4.
Cell Mol Life Sci ; 67(1): 123-33, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19898775

RESUMEN

Brain iron homeostasis is maintained by a balance of both iron uptake and release, and accumulating evidence has revealed that brain iron concentrations increase with aging. Hepcidin, an iron regulatory hormone produced by hepatocytes in response to inflammatory stimuli, iron, and hypoxia, has been shown to be the long-sought hormone responsible for the regulation of body iron balance and recycling in mammals. In this study, we report that hepcidin is widely expressed in the murine brain. In cerebral cortex, hippocampus and striatum, hepcidin mRNA levels increased with aging. Injection of hepcidin into the lateral cerebral ventricle resulted in decreased Fpn1 protein levels in cerebral cortex, hippocampus, and striatum. Additionally, treatment of primary cultured neurons with hepcidin caused decreased neuronal iron release and Fpn1 protein levels. Together, our data provide further evidence that hepcidin may be involved in the regulation of brain iron metabolism.


Asunto(s)
Péptidos Catiónicos Antimicrobianos/fisiología , Encéfalo/metabolismo , Hierro/metabolismo , Envejecimiento , Animales , Péptidos Catiónicos Antimicrobianos/metabolismo , Proteínas de Transporte de Catión/metabolismo , Células Cultivadas , Corteza Cerebral/metabolismo , Hepcidinas , Hipocampo/metabolismo , Ratones , Ratones Endogámicos BALB C , Neuronas/metabolismo , Ratas
5.
Zhonghua Xue Ye Xue Za Zhi ; 40(8): 667-672, 2019 Aug 14.
Artículo en Zh | MEDLINE | ID: mdl-31495134

RESUMEN

Objective: To analyze the efficacy of HLA-haploidentical peripheral hematopoietic stem cell transplantation (haplo-PBSCT) following reduced intensity conditioning (RIC) regimen to treat the patients with hematological malignancies who were older than 50 years old. Methods: Eighteen patients with hematological malignancies over 50 years were enrolled, including 8 male and 10 female patients. The median age of all patients was 52 (range: 50-66) years. Of them, 8 patients had acute myeloid leukemia (AML) , 2 chronic myelocytic leukemia (CML) , 5 myelodysplastic syndrome (MDS) , 2 acute lymphoblastic leukemia (ALL) , and 1 aggressive natural killer cell leukemia (ANKL) . All patients received fludarabine, cytarabine and melphalan with rabbit anti-human thymocyte globulin (FAB+rATG regimen) and transplanted with high dose non-T cell-depleted peripheral hematopoietic stem cells from donors. Enhanced graft versus host disease (GVHD) prophylaxis and infection prevention were administered. Results: Fifteen days after transplantation, 16 patients achieved complete donor chimerism. One of them rejected the donor graft completely at thirty days after transplantation, and the other 2 patients had mixed chimerism 15 days after transplantation and converted to complete recipient chimerism at 30 days after transplantation. The cumulative incidence of acute GVHD (aGVHD) was 61.1% (95%CI49.6%-72.6%) . The incidence of grade Ⅱ-Ⅳ aGVHD was 35.4% (95%CI 21.1%-49.7%) , whereas grade III-IV was 13.8% (95%CI 4.7%-22.9%) . The 2-year cumulative incidence of chronic GVHD (cGVHD) rate was estimated at 38.2% (95%CI 25.5%-50.9%) . Patients were followed-up for a median of 14.5 months (range, 3-44 months) . The Kaplan Meier estimates of 2-year overall survival (OS) and disease-free survival (DFS) was 72.6% (95%CI 60.1%-85.1%) and 63.7% (95%CI 49.2%-78.2%) , respectively. The 2-year cumulative incidence of relapse and non-relapse-mortality (NRM) was 31.2% (95%CI 16.5%-45.9%) and 12.5% (95%CI 4.2%-20.8%) , respectively. Conclusion: RIC-haplo-PBSCT protocol can achieve better results in patients with hematologic malignancies over 50 years old.


Asunto(s)
Enfermedad Injerto contra Huésped , Neoplasias Hematológicas , Trasplante de Células Madre Hematopoyéticas , Síndromes Mielodisplásicos , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Acondicionamiento Pretrasplante
6.
Zhonghua Liu Xing Bing Xue Za Zhi ; 39(6): 786-791, 2018 Jun 10.
Artículo en Zh | MEDLINE | ID: mdl-29936748

RESUMEN

Objective: To investigate the prevalence and influencing factors on respiratory disease related symptoms (coughing, expectoration, persistent coughing and persistent expectoration) in Chinese people ≥40 years old. Methods: Data was collected from 162 surveillance points in the China Non-communicable and Chronic Disease Surveillance Project in 2010. A total number of 56 066 people, aged ≥40 years, were selected by multi-stage cluster random sampling method in this study. The prevalence rates of coughing, expectoration, persistent coughing and persistent expectoration were calculated according to gender by χ(2) test. Multivariate logistic regression model was used to analyze the related influencing factors. Results: The prevalence rates of coughing, persistent coughing, expectoration and persistent expectoration in men were significantly higher than that in women (P<0.01). The prevalence rate of respiratory symptoms was positively correlated with age and duration and amount of cigarette smoking (P<0.01), while negatively correlated with participants'education level (P<0.01). Results from multivariate logistic regression analysis showed that gender, age, education level, smoking-related parameters, areas of residency (in urban or rural areas), etc. were appeared as influencing factors on the prevalence of respiratory symptoms. Conclusion: The symptoms of chronic respiratory diseases appeared prevalent in Chinese population aged ≥40 years. Factors as older age, living in the central/western regions and smoking-related parameters were identified as of higher risks.


Asunto(s)
Pueblo Asiatico/estadística & datos numéricos , Enfermedad Crónica/epidemiología , Tos/epidemiología , Enfermedades no Transmisibles/epidemiología , Adulto , Anciano , Anciano de 80 o más Años , China/epidemiología , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Prevalencia , Factores de Riesgo , Población Rural , Fumar
7.
Zhonghua Xue Ye Xue Za Zhi ; 37(6): 458-63, 2016 Jun 14.
Artículo en Zh | MEDLINE | ID: mdl-27431067

RESUMEN

OBJECTIVE: To compare occurrence and curative effect of interstitial pneumonia (IP) of patients with malignant hematologic disease after related HLA-haploidentical peripheral blood stem cell transplantation without T-cell depletion (RHNT-PBSCT) and non T cell-depleted HLA-matched sibling peripheral blood stem cell transplantation (MSNT-PBSCT). METHODS: 109 patients with malignant hematologic disease as the research cases received RHNT-PBSCT from January 2006 to December 2014, which were compared with 125 patients treated with MSNT-PBSCT during the same period to determine the occurrence of IP and curative effect produced by ganciclovir and joint adrenal glucocorticoids. RESULTS: The incidences of IP in RHNT-PBSCT and MSNT-PBSCT groups were 15.60%(17/109) and 13.60%(17/125) (P=0.150), respectively; both the effective rates were 76.47%(13/17) (P=0.536), the difference was not statistically significant. Single factor analysis showed that acute graft versus host disease was a risk factor for the occurrence of IP after RHNT-PBSCT (P=0.001). CONCLUSION: The incidence of IP in patients with malignant hematologic disease after RHNT-PBSCT didn' t increase when compared with patients after MSNT-PBSCT. The curative effects of the two groups were equivalent after priority to ganciclovir and joint adrenal glucocorticoids.


Asunto(s)
Enfermedades Hematológicas/complicaciones , Enfermedades Hematológicas/terapia , Enfermedades Pulmonares Intersticiales/complicaciones , Trasplante de Células Madre de Sangre Periférica/métodos , Ganciclovir/uso terapéutico , Glucocorticoides/uso terapéutico , Enfermedad Injerto contra Huésped/complicaciones , Humanos , Incidencia , Factores de Riesgo , Hermanos
8.
Zhonghua Xue Ye Xue Za Zhi ; 37(3): 177-82, 2016 Mar.
Artículo en Zh | MEDLINE | ID: mdl-27033752

RESUMEN

OBJECTIVE: To investigate the incidence, clinical and microbiological features of febrile, and risk factors during neutropenia periods in patients with hematological diseases. METHODS: From October 20, 2014 to March 20, 2015, consecutive patients who had hematological diseases and developed neutropenia during hospitalization were enrolled in the prospective, multicenter and observational study. RESULTS: A total of 784 episodes of febrile occurred in 1 139 neutropenic patients with hematological diseases. The cumulative incidence of febrile was 81.9% at 21 days after neutropenia. Multivariate analysis suggested that central venous catheterization (P<0.001, HR=3.407, 95% CI 2.276-4.496), gastrointestinal mucositis (P<0.001, HR=10.548, 95% CI 3.245-28.576), previous exposure to broad-spectrum antibiotics within 90 days (P<0.001, HR=3.582, 95% CI 2.387-5.770) and duration of neutropenia >7 days (P<0.001,HR=4.194, 95% CI 2.572-5.618) were correlated with higher incidence of febrile during neutropenia. With the increase of the risk factors, the incidence of febrile increased gradually (35.4%, 69.2%, 86.1%, 95.6%, P<0.001). Of 784 febrile cases, 253 (32.3%) were unknown origin, 429 (54.7% )of clinical documented infections and 102(13.0%) of microbiological documented infections. The most common sites of infection were pulmonary (49.5%), upper respiratory (16.0%), crissum (9.8%), blood stream (7.7%). The most common pathogens were gram-negative bacteria (44.54%), followed by gram-positive bacteria (37.99% ) and fungi (17.47% ). There was no significant difference in mortality rates between cases with febrile and cases without febrile (9.2% vs 4.8%, P=0.099). Multivariate analysis also suggested that >40 years old (P=0.047, HR=5.000, 95% CI 0.853-28.013), hemodynamic instability (P=0.001, HR=13.185, 95% CI 2.983-54.915), prior colonization or infection by resistant pathogens (P=0.005, HR=28.734, 95% CI 2.921-313.744), blood stream infection (P=0.038, HR=9.715, 95% CI 1.110-81.969) and pulmonary infection (P=0.031, HR=25.905, 95% CI 1.381-507.006) were correlated with higher mortality rate in cases with febrile. CONCLUSIONS: Febrile was the common complication during neutropenia periods in patients with hematological disease. There was different distribution of organisms in different sites of infection. Moreove, the duration of neutropenia >7 days, central venous catheterization, gastrointestinal mucositis and previous exposure to broad-spectrum antibiotics within 90 days were the risk factors for the higher incidence of febrile.


Asunto(s)
Neutropenia Febril/epidemiología , Fiebre/epidemiología , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Cateterismo Venoso Central/efectos adversos , China/epidemiología , Neutropenia Febril/microbiología , Bacterias Gramnegativas/aislamiento & purificación , Bacterias Grampositivas/aislamiento & purificación , Humanos , Mucositis/epidemiología , Estudios Prospectivos , Factores de Riesgo , Encuestas y Cuestionarios , Factores de Tiempo
10.
Neuroscience ; 284: 234-246, 2015 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-25301748

RESUMEN

Brain iron levels are significantly increased in Parkinson's disease (PD) and iron deposition is observed in the substantia nigra (SN) of PD patients. It is unclear whether iron overload is an initial cause of dopaminergic neuronal death or merely a byproduct that occurs in the SN of PD patients. In this study, ceruloplasmin knockout (CP-/-) mice and mice receiving an intracerebroventricular injection of ferric ammonium citrate (FAC) were selected as mouse models with high levels of brain iron. These mice were administered with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by intraperitoneal injection. Their behavior and the dopaminergic neuron damage to their substantia nigra pars compacta (SNpc) were assessed. These findings suggest that the injection of FAC or the absence of the CP gene may exacerbate both the observed apoptosis of TH-positive neurons and the behavioral symptoms of the MPTP-treated mice. The intracerebroventricular injection of deferoxamine (DFO) significantly alleviated the neuronal damage caused by MPTP in CP-/- mice. Furthermore, our findings suggest that the increased nigral iron content exacerbates the oxidative stress levels, promoting apoptosis through the Bcl-2/Bax pathway and the activated caspase-3 pathway in the brain. Therefore, iron overload in the brain exacerbates dopaminergic neuronal death in SNpc and leads to the onset of PD.


Asunto(s)
Encéfalo/fisiopatología , Hierro/metabolismo , Intoxicación por MPTP/fisiopatología , Animales , Antiparkinsonianos/farmacología , Apoptosis/efectos de los fármacos , Apoptosis/fisiología , Encéfalo/efectos de los fármacos , Caspasa 3/metabolismo , Ceruloplasmina/deficiencia , Ceruloplasmina/genética , Deferoxamina/farmacología , Neuronas Dopaminérgicas/efectos de los fármacos , Neuronas Dopaminérgicas/fisiología , Compuestos Férricos , Intoxicación por MPTP/tratamiento farmacológico , Masculino , Ratones Endogámicos BALB C , Ratones Noqueados , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/fisiología , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Compuestos de Amonio Cuaternario , Tirosina 3-Monooxigenasa/metabolismo , Proteína X Asociada a bcl-2/metabolismo
11.
Free Radic Res ; 49(9): 1069-80, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-25968939

RESUMEN

Disruption of neuronal iron homeostasis and oxidative stress are closely related to the pathogenesis of Parkinson's disease (PD). Ginkgetin, a natural biflavonoid isolated from leaves of Ginkgo biloba L, has many known effects, including anti-inflammatory, anti-influenza virus, and anti-fungal activities, but its underlying mechanism of the neuroprotective effects in PD remains unclear. The present study utilized PD models induced by 1-methyl-4-phenylpyridinium (MPP(+)) and 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) to explore the neuroprotective ability of ginkgetin in vivo and in vitro. Our results showed that ginkgetin could provide significant protection from MPP(+)-induced cell damage in vitro by decreasing the levels of intracellular reactive oxygen species and maintaining mitochondrial membrane potential. Meanwhile, ginkgetin dramatically inhibited cell apoptosis induced by MPP+ through the caspase-3 and Bcl2/Bax pathway. Moreover, ginkgetin significantly improved sensorimotor coordination in a mouse PD model induced by MPTP by dramatically inhibiting the decrease of tyrosine hydroxylase expression in the substantia nigra and superoxide dismutase activity in the striatum. Interestingly, ginkgetin could strongly chelate ferrous ion and thereby inhibit the increase of the intracellular labile iron pool through downregulating L-ferritin and upregulating transferrin receptor 1. These results indicate that the neuroprotective mechanism of ginkgetin against neurological injury induced by MPTP occurs via regulating iron homeostasis. Therefore, ginkgetin may provide neuroprotective therapy for PD and iron metabolism disorder related diseases.


Asunto(s)
Biflavonoides/química , Hierro/química , Fármacos Neuroprotectores/química , Enfermedad de Parkinson/tratamiento farmacológico , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/efectos adversos , 1-Metil-4-fenilpiridinio/efectos adversos , Animales , Antígenos CD/metabolismo , Apoferritinas/metabolismo , Apoptosis , Caspasa 3/metabolismo , Línea Celular Tumoral , Supervivencia Celular , Modelos Animales de Enfermedad , Regulación Enzimológica de la Expresión Génica , Ginkgo biloba , Homeostasis , Humanos , Quelantes del Hierro/efectos adversos , Masculino , Potencial de la Membrana Mitocondrial , Ratones , Ratones Endogámicos C57BL , Neuronas/metabolismo , Estrés Oxidativo , Especies Reactivas de Oxígeno/metabolismo , Receptores de Transferrina/metabolismo , Superóxido Dismutasa/metabolismo , Tirosina 3-Monooxigenasa/metabolismo
12.
Brain Res ; 861(1): 181-5, 2000 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-10751581

RESUMEN

The extracellular signal-regulated protein kinase-1 and -2 (ERK1 and ERK2), also referred to as the p44/42 mitogen-activated protein kinase (p44/42 MAP kinase), plays an essential role in neuronal signal transduction, but its function involved in nociceptive response has not been deeply studied yet. Here we report immunohistochemical evidence that p44/42 MAPK might be critical in nociceptive response. We found that after formalin was injected into the perioral skin of the upper lip of mice, the number of activated p44/42 MAPK-like immunoreactive neurons was significantly increased in the laminae I and II of the caudal subnucleus of the trigeminal spinal nucleus (Sp5C). The positive neurons and fibers were mostly concentrated in the middle portion of Sp5C dorsoventrally, where the afferent fibers innervating the skin of the upper lip are terminated. The reactive products were localized in perikarya, dendrites, nuclei, and diffusely in the neuropil. The present result suggests that p44/42 MAPK may be important in the transmission and modulation of noxious information in Sp5C.


Asunto(s)
Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Dolor/metabolismo , Núcleo Caudal del Trigémino/metabolismo , Animales , Fijadores , Formaldehído , Masculino , Ratones , Ratones Endogámicos BALB C , Proteína Quinasa 3 Activada por Mitógenos , Dolor/inducido químicamente
13.
Environ Pollut ; 181: 115-21, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23845769

RESUMEN

A steady state Level III fate model was established and applied to quantify source-receptor relationship in a coking industry city in Northern China. The local emission inventory of PAHs, as the model input, was acquired based on energy consumption and emission factors. The model estimations were validated by measured data and indicated remarkable variations in the paired isomeric ratios. When a rectification factor, based on the receptor-to-source ratio, was calculated by the fate model, the quantitatively verified molecular diagnostic ratios provided reasonable results of local PAH emission sources. Due to the local ban and measures on small scale coking activities implemented from the beginning of 2004, the model calculations indicated that the local emission amount of PAHs in 2009 decreased considerably compared to that in 2003.


Asunto(s)
Monitoreo del Ambiente/métodos , Contaminantes Ambientales/análisis , Hidrocarburos Policíclicos Aromáticos/análisis , China , Ciudades , Coque , Contaminación Ambiental/estadística & datos numéricos , Industrias , Modelos Químicos , Multimedia
14.
Nanotechnology ; 19(4): 045705, 2008 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-21817522

RESUMEN

The effects of Dy(3+) doping concentration and calcinations on the fluorescence properties of La(3)Ga(5.5)Nb(0.5)O(14) (Dy:LGN) nanocrystals were examined for the first time. High quality Dy:LGN nanocrystals were synthesized by the sol-gel method. The room temperature fluorescence spectra were measured; they showed a yellow emission, which can be attributed to the (4)F(9/2)-(6)H(13/2) transition. The relationship between the relative emission intensity and the doping concentration of the specimens, sintered at different temperatures, is consistent with a Gaussian distribution according a fitted and modified formula. The optimum value of the Dy(3+) doping concentration in LGN nanocrystals is in the range 2.0-2.5%. Moreover, in LGN bulk crystal for laser use, the optimum value, calculated through the obtained formula, is presumed in the range 1.5-2.0%. The fluorescent lifetime of a 2.0% Dy:LGN nanocrystal is quite short, only about 8.5 ns.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA