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1.
BMC Pregnancy Childbirth ; 24(1): 219, 2024 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-38528474

RESUMO

BACKGROUND: At present, individualized interventions can be given to patients with a clear etiology of pregnancy loss to improve the subsequent pregnancy outcomes, but the current reproductive status of the patient cannot be changed. The aim of this study was to investigate the association between female reproductive status and subsequence pregnancy outcome in patients with prior pregnancy loss (PL). METHODS: A prospective, dynamic population cohort study was carried out at the Second Hospital of Lanzhou University. From September 2019 to February 2022, a total of 1955 women with at least one previous PL were enrolled. Maternal reproductive status and subsequent reproductive outcomes were recorded through an electronic medical record system and follow-up. Logistic regression was used to evaluate the association between reproductive status and the risk of subsequent reproductive outcomes. RESULTS: Among all patients, the rates of subsequent infertility, early PL, late PL, and live birth were 20.82%, 24.33%, 1.69% and 50.77% respectively. In logistic regression, we found that age (OR 1.08, 95% CI 1.04-1.13) and previous cesarean delivery history (OR 2.46, 95% CI 1.27-4.76) were risk factors for subsequent infertility in patients with PL. Age (OR 1.06, 95% CI 1.03-1.10), age at first pregnancy (OR 1.06, 95% CI 1.03-1.10), BMI (OR 1.06, 95% CI 1.02-1.11), previous PL numbers (OR 1.18, 95% CI 1.04-1.57) and without pre-pregnancy intervention (OR 1.77, 95% CI 1.35-2.24) were risk factors for non-live birth. Age (OR 1.06, 95% CI 1.03-1.09), age at first pregnancy (OR 1.06, 95% CI 1.02-1.09), BMI (OR 1.07, 95% CI 1.02-1.11), previous PL numbers (OR 1.15, 95% CI 1.02-1.31) and without pre-pregnancy intervention (OR 2.16, 95% CI 1.65-2.84) were risk factors for PL. CONCLUSIONS: The reproductive status of people with PL is strongly correlated with the outcome of subsequent pregnancies. Active pre-pregnancy intervention can improve the subsequent pregnancy outcome. TRIAL REGISTRATION: This study was registered in the Chinese Clinical Trial Registry with the registration number of ChiCTR2000039414 (27/10/2020).


Assuntos
Aborto Espontâneo , Infertilidade , Feminino , Humanos , Gravidez , Aborto Espontâneo/epidemiologia , Estudos de Coortes , Resultado da Gravidez/epidemiologia , Taxa de Gravidez , Estudos Prospectivos , Recém-Nascido
2.
Anim Reprod Sci ; 258: 107359, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37832280

RESUMO

L-proline has been reported to be useful in semen cryopreservation. However, its use has rarely been reported in the freezing of boar semen. The objective of this study was to evaluate the effects of different concentrations of L-proline (0, 10, 30, 50, and 90 mM) on the quality of boar semen after freezing and thawing. Semen samples from boars (n = 6) were frozen using freezing extenders with added concentrations of L-proline. Total sperm motility, progressive motility, survival time at 37 °C, acrosome integrity, mitochondrial activity, DNA integrity, the content of the lipid peroxidation product malondialdehyde (MDA), total antioxidant capacity (T-AOC) and, expression levels of apoptosis protein (cleaved caspase 3 and Bax) were evaluated after thawing. The results showed that total sperm viability (73.96% vs. 63.58%) and progressive motility (56.88% vs. 47.26%) after thawing were significantly higher in the 10 mM L-proline treatment group than in the control group. The survival time at 37 °C and the total motility of sperm in the 10 mM group within one hour after thawing were significantly higher than in the control group. Acrosome integrity and mitochondrial activity of sperm in the 10 mM group were significantly higher than those in the control, 50 mM, and 90 mM groups. The DNA integrity rate in the 10 mM group was significantly higher than in the control group. The L-proline treatment did not affect sperm MDA content or T-AOC. The expression levels of apoptosis protein (cleaved caspase 3 and Bax) in the 10 mM L-proline supplemented group were lower than those in the control group. In conclusion, the freezing extender containing 10 mM L-proline improved semen quality after freezing and thawing and thus would be a useful reagent for boar semen cryopreservation.


Assuntos
Preservação do Sêmen , Sêmen , Masculino , Suínos , Animais , Caspase 3/farmacologia , Análise do Sêmen/veterinária , Proteína X Associada a bcl-2 , Motilidade dos Espermatozoides , Espermatozoides , Criopreservação/veterinária , Criopreservação/métodos , Preservação do Sêmen/veterinária , Preservação do Sêmen/métodos , DNA , Crioprotetores/farmacologia
4.
Reprod Biol Endocrinol ; 20(1): 121, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35971112

RESUMO

BACKGROUND: Intrauterine adhesion (IUA) is a clinical disease characterized by the uterine cavity occlusion caused by the damage of the endometrial basal layer. Bone marrow mesenchymal stem cells (BMSCs) transplantation have the potential to promote endometrial regeneration mainly through paracrine ability. Estrogen is an indispensable and important factor in the repair of endometrial damage, which has been reported as a promising and adjunctive therapeutic application for stem cell transplantation therapy. This study aims to investigate the synergistic effect of BMSCs and estrogen on improving the endometrial regeneration and restoring the endometrium morphology in a dual damage model of IUA in rabbits and the underlying molecular mechanisms. METHODS: BMSCs were isolated and identified by adipogenic and osteogenic differentiation and flow cytometry assays. The rabbit IUA animal model was established by a dual damage method of mechanical curettage and lipopolysaccharide infection. Additionally, we investigated the therapeutic impact of both BMSCs and estrogen either separately or in combination in a rabbit model. The retention of PKH26-labeled BMSCs was observed by vivo fluorescence imaging.The number of endometrial glands and the degree of fibrosis were observed by H&E and Masson staining respectively. Western blotting, Immunohistochemistry and immunofluorescence staining were performed to detect biomarkers related to endometrial epithelium, endometrial fibrosis and EMT. Finally, the protein expression of core molecules of Wnt/ß-catenin pathway was detected by Western blotting. RESULTS: PKH26-labeled fluorescence results revealed that BMSCs appeared and located in the endometrial glands and extracellular matrix area when orthotopic transplanted into the uterine cavity. Histological assays showed that remarkably increasing the number of endometrial glands and decreasing the area of endometrial fibrosis in the BMSCs combined with estrogen treatment group. Moreover, downregulated expression of fibrosis markers (fibronectin, CollagenI, a-SMA) and interstitial markers (ZEB1, Vimentin, N-cadherin), as well as upregulated E-cadherin expression were found in the combined group. Further study of in vivo staining revealed that fluorescence intensity of CK7 was stronger in the combined group than that of direct BMSCs intrauterine transplantation, while vimentin showed the opposite results. Moreover, the protein levels of ß-catenin, Axin2, C-myc, CycinE of Wnt/ß-catenin signaling pathway increased in the BMSCs combined with estrogen group than in the other treatment groups. CONCLUSION: BMSCs combined with estrogen can promote the differentiation of stem cells into endometrial epithelial cells to facilitate the regeneration of damaged endometrium. The potential mechanism of the synergistic effect may inhibit the occurrence of EMT by activating the Wnt/ß-catenin signaling pathway.


Assuntos
Transição Epitelial-Mesenquimal , Células-Tronco Mesenquimais , Doenças Uterinas , Via de Sinalização Wnt , Animais , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Caderinas/metabolismo , Endométrio/metabolismo , Estrogênios/metabolismo , Feminino , Humanos , Osteogênese , Coelhos , Aderências Teciduais , Doenças Uterinas/patologia , Doenças Uterinas/terapia , Vimentina/metabolismo , beta Catenina/metabolismo
5.
Artigo em Inglês | MEDLINE | ID: mdl-34335857

RESUMO

Gastric ulcer is one of the most common gastrointestinal diseases. Anwulignan (AN) is a major active component of Schisandra sphenanthera Rehd. This study was designed to evaluate the protective effect of AN against the acute gastric ulcer induced by HCl/ethanol in mice. The mice were given HCl/ethanol by gavage to establish an acute gastric ulcer model. Then, the serum and gastric tissue samples were taken for biochemical analyses. The results showed that the pretreatment with AN could significantly reduce the gastric ulcer index (GUI) and increase the ulcer inhibition rate, indicating that AN can protect against gastric ulcers. AN showed its antioxidant roles by decreasing the content of reactive oxygen species (ROS), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) and increasing the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and anti-inflammatory roles by decreasing the content of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1ß (IL-1ß), and myeloperoxidase (MPO) and increasing the content of interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-10 (IL-10), prostaglandin E2 (PGE2), and nitric oxide (NO) in both serum and gastric tissue. Furthermore, AN also activated the NRF2/ARE signaling pathway and inhibited the MAPK/NF-κB signaling pathway. AN improves the acute gastric ulcer induced by HCl/ethanol in mice, which may be mainly through its antioxidant capacity and anti-inflammatory effect.

6.
Pathol Oncol Res ; 27: 1609761, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34257616

RESUMO

Intrauterine adhesion (IUA) is one of the most prevalent reproductive system diseases in females. MicroRNAs (miRNAs) are reported to be master regulators in a variety of diseases, including IUA, but the role of microRNA-543 (miR-543) in IUA remains to be elucidated. In this study, we observed that miR-543 was downregulated in transforming growth factor-beta (TGF-ß)-treated endometrial stromal cells (ESCs). Functionally, we observed that miR-543 suppressed the migration, epithelial-to-mesenchymal transition (EMT), and inhibited expression of extracellular matrix (ECM) proteins in TGF-ß-treated ESCs. Mechanistically, MAPK1 is targeted by miR-543 after prediction and screening. A luciferase reporter assay demonstrated that miR-543 complementarily binds with the 3' untranslated region of mitogen-activated protein kinase 1 (MAPK1), and western blot analysis indicated that miR-543 negatively regulates MAPK1 protein levels. In addition, results from rescue assays showed that miR-543 inhibits the migration and EMT of TGF-ß-treated ESCs by targeting MAPK1. In addition, we observed that miR-543 inactivates the Wnt/ß-catenin signaling pathway through inhibiting the phosphorylation of MAPK1 and ß-catenin. Finally, we confirmed that miR-543 represses migration, EMT and inhibits levels of ECM proteins in TGF-ß-treated ESCs by targeting the Wnt/ß-catenin signaling pathway. Our results demonstrated that miR-543 suppresses migration and EMT of TGF-ß-treated ESCs by targeting the MAPK and Wnt/ß-catenin pathways.


Assuntos
Tumores do Estroma Endometrial/patologia , Transição Epitelial-Mesenquimal , MicroRNAs/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Apoptose , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Movimento Celular , Proliferação de Células , Neoplasias do Endométrio/genética , Neoplasias do Endométrio/metabolismo , Neoplasias do Endométrio/patologia , Tumores do Estroma Endometrial/genética , Tumores do Estroma Endometrial/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Proteínas Quinases Ativadas por Mitógeno/genética , Fator de Crescimento Transformador beta/genética , Células Tumorais Cultivadas , Proteínas Wnt/genética , beta Catenina/genética
7.
J Pharmacol Exp Ther ; 378(3): 222-234, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34131018

RESUMO

Anwulignan is one of the monomer compounds in the lignans from Schisandra sphenanthera In this study, we observed the effect of anwulignan on intestinal ischemia/reperfusion (II/R) injury in male Sprague-Dawley rats and explored the underlying mechanisms. The results showed that pretreatment with oral anwulignan could significantly increase the mesenteric blood microcirculatory flow velocity; relieve the congestion and pathologic injury of jejunum; enhance the autonomic tension of jejunum smooth muscle and its reactivity to acetylcholine; increase the activities of superoxide dismutase, catalase, glutathione S-transferase, and choline acetyltransferase; increase the contents of acetylcholine and glutathione in the serum or jejunal tissue; decrease the activities of myeloperoxidase, protein kinase C, and nicotinamide adenine dinucleotide phosphate oxidase; reduce the contents of malondialdehyde, 8-hydroxy-2-deoxyguanosine, nicotinamide adenine, reactive oxygen species, tumor necrosis factor-α, interleukin (IL)-6, and IL-1ß; increase the expression levels of muscarinic receptor 3, PI3K, phosphorylation protein kinase B, p-GSK3ß Ser9, Nrf2, p-Nrf2, heme oxygenase (decycling) 1, and b-cell lymphoma 2 in the jejunal tissue; and decrease the expression levels of p-GSK3ß Tyr216, kelch-like ECH-associated protein 1, Bax, and cleaved caspase-3, suggesting that anwulignan can ameliorate II/R-induced jejunal tissue injury in rats and that the mechanism may be related to its activating the PI3K/protein kinase B pathway and then regulating the Nrf2/Anti-oxidative Response Element signaling pathway and the expression of apoptosis-related proteins to play antioxidant and antiapoptotic roles. SIGNIFICANCE STATEMENT: Anwulignan can significantly reduce jejunal tissue injury and the production of inflammatory factors in rats with intestinal ischemia-reperfusion injury, improve the antioxidant capacity, and reduce the apoptosis of jejunal tissue, and it has the effect of significantly improving intestinal ischemia-reperfusion injury in rats, suggesting that anwulignan may be used as a potential drug for the prevention and treatment of intestinal ischemia-reperfusion injury or a resource for the development of health food.


Assuntos
Traumatismo por Reperfusão , Animais , Microcirculação , Ratos , Ratos Sprague-Dawley
8.
J Phys Condens Matter ; 33(19)2021 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-33691300

RESUMO

Although many schemes have been proposed to obtain full half-metallicity in zigzag silicene nanoribbons with edge monohydrogenation (H-H ZSiNRs) by chemical modification, the resulted negligible energy difference between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations makes the half-metallicity hardly observable practically. In this work, based on density functional calculations, we find that the ZSiNRs with edge dihydrogenation (H2-H2 ZSiNRs) can be tuned to be half-metallic by replacing the central two zigzag Si chains with two zigzag Al-P chains, and more importantly, the FM-AFM energy difference is significantly increased compared with the H-H cases. The obtained half-metallicity originates from the different potential between two edges of the ribbon after doping, which results in the edge states of two spin channels shifting oppositely in energy. This mechanism is so robust that the half-metallicity can always be achieved, irrespective of the ribbon width. Our finding provides a fantastic way for achieving stable half-metallicity in ZSiNRs.

9.
Exp Ther Med ; 21(4): 385, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33680107

RESUMO

Chronic fatigue is frequently accompanied by decreased learning and memory capabilities. Schizantherin A (SCA) is one of the main active monomer components in Schisandra chinensis lignans. In the present study, a chronic fatigue mouse model was established using the exhausted swimming approach to investigate the effects of SCA on learning and memory and its associated mechanism of action. Learning and memory abilities were tested by step through tests and water maze methods. Levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and malondialdehyde (MDA) in hippocampal tissue were measured by corresponding assays. The effect of SCA on the expression of kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Bcl2, Bax and cleaved caspase-3 were determined by western blot. The present results showed that SCA can improve the learning and memory capabilities of chronic fatigue mice. SCA was found to increase the activities of SOD and CAT in addition to increasing the levels of GSH but reduced the levels of MDA in hippocampus tissues. Furthermore, SCA treatment downregulated the protein expression levels of Keap1, Bax and cleaved caspase-3 and upregulated the protein expression levels of Nrf2, HO1 and Bcl2 in the hippocampus. These results suggested that modulations in the Nrf2-Keap1-antioxidant response element pathway, anti-oxidative and anti-apoptosis effects are the causes underlying the improvements from SCA treatment on the learning and memory abilities of chronic fatigue mice.

10.
Braz J Med Biol Res ; 53(8): e9794, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32638833

RESUMO

Although estrogen has crucial functions for endometrium growth, the specific dose and underlying molecular mechanism in intrauterine adhesion (IUA) remain unclear. In this study, we aimed to investigate the effects of estrogen on epithelial-mesenchymal transition (EMT) in normal and fibrotic endometrium, and the role of estrogen and Wnt/ß-catenin signaling in the formation of endometrial fibrosis. CCK-8 and immunofluorescence assay were performed to access the proliferation of different concentrations of estrogen on normal human endometrial epithelial cells (hEECs). qRT-PCR and western blot assay were utilized to explore the effect of estrogen on EMT in normal and fibrotic endometrium, and main components of Wnt/ß-catenin signaling pathway in vitro. Hematoxylin and eosin and Masson staining were used to evaluate the effect of estrogen on endometrial morphology and fibrosis in vivo. Our results indicated that the proliferation of normal hEECs was inhibited by estrogen at a concentration of 30 nM accompanied by upregulation of mesenchymal markers and downregulation of epithelial markers. Interestingly, in the model of transforming growth factor ß1 (TGF-ß1)-induced endometrial fibrosis, the same concentration of estrogen inhibited the process of EMT, which might be partially mediated by regulation of the Wnt/ß-catenin pathway. In addition, relatively high doses of estrogen efficiently increased the number of endometrial glands and reduced the area of fibrosis as determined by the reduction of EMT in IUA animal models. Taken together, our results demonstrated that an appropriate concentration of estrogen may prevent the occurrence and development of IUA by inhibiting the TGF-ß1-induced EMT and activating the Wnt/ß-catenin pathway.


Assuntos
Transição Epitelial-Mesenquimal , Fator de Crescimento Transformador beta1 , Doenças Uterinas , Animais , Estrogênios , Feminino , Humanos , Via de Sinalização Wnt
11.
Braz. j. med. biol. res ; 53(8): e9794, 2020. tab, graf
Artigo em Inglês | LILACS, Coleciona SUS | ID: biblio-1132540

RESUMO

Although estrogen has crucial functions for endometrium growth, the specific dose and underlying molecular mechanism in intrauterine adhesion (IUA) remain unclear. In this study, we aimed to investigate the effects of estrogen on epithelial-mesenchymal transition (EMT) in normal and fibrotic endometrium, and the role of estrogen and Wnt/β-catenin signaling in the formation of endometrial fibrosis. CCK-8 and immunofluorescence assay were performed to access the proliferation of different concentrations of estrogen on normal human endometrial epithelial cells (hEECs). qRT-PCR and western blot assay were utilized to explore the effect of estrogen on EMT in normal and fibrotic endometrium, and main components of Wnt/β-catenin signaling pathway in vitro. Hematoxylin and eosin and Masson staining were used to evaluate the effect of estrogen on endometrial morphology and fibrosis in vivo. Our results indicated that the proliferation of normal hEECs was inhibited by estrogen at a concentration of 30 nM accompanied by upregulation of mesenchymal markers and downregulation of epithelial markers. Interestingly, in the model of transforming growth factor β1 (TGF-β1)-induced endometrial fibrosis, the same concentration of estrogen inhibited the process of EMT, which might be partially mediated by regulation of the Wnt/β-catenin pathway. In addition, relatively high doses of estrogen efficiently increased the number of endometrial glands and reduced the area of fibrosis as determined by the reduction of EMT in IUA animal models. Taken together, our results demonstrated that an appropriate concentration of estrogen may prevent the occurrence and development of IUA by inhibiting the TGF-β1-induced EMT and activating the Wnt/β-catenin pathway.


Assuntos
Humanos , Animais , Feminino , Doenças Uterinas , Fator de Crescimento Transformador beta1 , Transição Epitelial-Mesenquimal , Estrogênios , Via de Sinalização Wnt
12.
Gene ; 707: 65-77, 2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31059736

RESUMO

The genic male sterility (MS) plays a major role in melon hybrids production, it could reduce the cost of pollination and increase the yield and quality. However, the molecular mechanism underlying genetic male sterility is yet poorly understood. The morphological differences of flower buds of melon were observed showed that the flower buds were tetrad when they were 1 mm stage and monocyte microspore when they were 2 mm stage. Electron microscopy showed that there was significant difference between MS lines and MF (male fertility) lines. In order to detect the global expression of the genes during the melon anther development and association with MS, 12 DEGs (differentially expressed genes) libraries were constructed from the anther of MS and MF in the bud stage with 1 and 2 mm diameter, respectively. A total of 765 DEGs expressed in anther during different developmental stage (MS 1 mm vs. MS 2 mm), 148 and 309 DEGs were found to be related to MS as compared to MF (MS 1 mm vs. MF 1 mm, and MS 2 mm vs. MF 2 mm) at a false discovery rate FDR <0.01. Among these, 10 DEGs were expressed in all the three comparisons, including transcription factor bHLH genes. Among the DEGs in RNA-seq analysis, 28 were validated by qRT-PCR. Of these, a number of genes were involved in ABC transfactor B family, cytochrome-related genes, hormone-related genes (auxin transporter, gibberellin-regulated protein), MADS-box protein genes, F-box protein genes, peroxidase-related, and Zinc finger protein genes. These genes are involved in many biological pathways, including starch and sucrose metabolism, signal transduction mechanisms and transcription factors, etc. Compared to the same developmental stage of MS and MF, the different developmental stages of MS indicated diverse gene regulation pathways involved in the anther development in MS. These results would provide novel insight into the global network to male sterility in melon.


Assuntos
Cucumis melo/fisiologia , Perfilação da Expressão Gênica/métodos , Infertilidade das Plantas , Proteínas de Plantas/genética , Quimera/genética , Quimera/fisiologia , Cucumis melo/genética , Cucumis melo/ultraestrutura , Flores/genética , Flores/fisiologia , Flores/ultraestrutura , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Redes Reguladoras de Genes , Microscopia Eletrônica , Análise de Sequência de RNA
13.
Faraday Discuss ; 150: 101-11; discussion 113-60, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22457946

RESUMO

We have developed a high power optical centrifuge for measuring the spectroscopy of molecules in extreme rotational states. The optical centrifuge has a pulse energy that is more than 2 orders of magnitude greater than in earlier instruments. The large pulse energy allows us to drive substantial number densities of molecules to extreme rotational states in order to measure new spectroscopic transitions that are not accessible with traditional methods. Here we demonstrate the use of the optical centrifuge for measuring IR transitions of N2O from states that have been inaccessible until now. In these studies, the optical centrifuge drives N2O molecules into states with J ~ 200 and we use high resolution transient IR probing to measure the appearance of population in states with J = 93-99 that result from collisional cooling of the centrifuged molecules. High resolution Doppler broadened line profile measurements yield information about the rotational and translational energy distributions in the optical centrifuge.

14.
J Phys Chem A ; 112(39): 9396-404, 2008 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-18729434

RESUMO

The outcome of energy transfer due to single collisions between highly vibrationally excited pyrazine (E = 37,900 cm(-1)) and DCl is measured for the appearance of individual low-J rotational states of DCl using high-resolution transient IR absorption. Appearance profiles from double-Gaussian transient lineshapes were measured for a number of DCl states with J = 2-12. These data give information on the recoil velocity distributions, appearance rates, and populations of individual states of the scattered molecules. These data complement previous studies on high-J state DCl scattering (Li, Z.; Korobkova, E.; Werner, K.; Shum, L.; Mullin, A. S. J. Chem. Phys. 2005, 123, 174306), and together, they provide a full description of the V-RT collisions with DCl that quench pyrazine(E). Scattered DCl (v = 0) molecules with J = 2-21 are rotationally hot with T(rot) = 880 +/- 100 K. Center-of-mass translational energy distributions are T(rel) approximately 700 K for J < 15. Broader velocity distributions are observed for the J = 15-20 states. The rate constant for V-RT energy transfer is 4.6 x 10(-10) cm(3) molecule(-1) s(-1). This value is a lower limit to the overall rate constant for energy transfer and corresponds to approximately 85% of the Lennard-Jones collision rate. We estimate scattering into the DCl (v = 1) state occurs in approximately 1% of collisions. The energy transfer probability distribution P(DeltaE) is presented and yields DeltaE = 888 cm(-1).

15.
J Chem Phys ; 129(1): 014303, 2008 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-18624476

RESUMO

We report the energy dependence of strong collisions of CO(2) with highly vibrationally excited azulene for two initial energies, E=20 390 and 38 580 cm(-1). These studies show that both the distribution of transferred energy and the energy transfer rates are sensitive to the azulene energy. Highly excited azulene was prepared in separate studies by absorption of pulsed excitation at lambda=532 or 266 nm, followed by rapid radiationless decay from S(1) or S(4) to vibrationally excited levels of the ground electronic state. The appearance of scattered CO(2) (00(0)0) molecules with E(rot)>1000 cm(-1) was monitored by high-resolution transient IR absorption at lambda=4.3 mum. The average rotational and translational energies of the scattered CO(2) molecules double when the azulene energy is increased by a factor of 2. The rate of energy transfer in strong collisions increases by nearly a factor of 4 when the azulene energy is doubled. The energy transfer probability distribution function for DeltaE>3000 cm(-1) at each initial energy is an exponential decay with curvature that correlates with the energy dependence of the state density, in excellent agreement with predictions from GRETCHEN, a model based on Fermi's golden rule to describe collisional quenching of highly excited molecules.

16.
J Comb Chem ; 8(2): 247-51, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16529520

RESUMO

A catalyst library of 80 samples with different mass ratios of rare earth elements, cobalt (Co), cerium (Ce), and indium (In), was prepared by impregnation of a fresh HZSM-5 zeolite support. A high-throughput detection setup, based on UV absorption spectroscopy, was developed for heterogeneous catalyst selection. The catalytic properties of the library were tested in the selective catalytic reduction of NO by methane at 673 K. Among the Co/Ce series, the catalyst with Co/Ce = 2:1 and Co/H-ZSM5 = 2.5% has shown remarkable efficiency (up to 78%). In the Ce/In series, the reactivity of the catalyst with the support composition of Ce/In = 1:1 and Ce/H-ZSM5 = 2.0% was < or = 88%. Our initial experiments definitely indicated that this simple and inexpensive multichannel setup can be applied for the selection of other heterogeneous catalysts. According to the variation of the UV light intensity, resulting from the absorption of the reactant or product, it was possible to monitor the relative quantity of reactants or products during a catalytic reaction.


Assuntos
Catálise , Técnicas de Química Combinatória/instrumentação , Técnicas de Química Combinatória/métodos , Cinética , Metais Terras Raras , Espectrofotometria Ultravioleta , Zeolitas
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