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1.
Prog Urol ; 33(12): 572-575, 2023 Nov.
Artigo em Francês | MEDLINE | ID: mdl-38783762

RESUMO

INTRODUCTION: The functional results of radical prostatectomy are a crucial issue for patients to resume fulfilling sexuality. We assessed the feasibility of a care pathway dedicated to sexual rehabilitation in order to improve information, screening of risk situations and the implementation of therapeutic measures. METHODS: From January to May 2023, sexually active patients under 75 years of age undergoing prostatectomy for cancer were offered the opportunity to participate in two sexual rehabilitation sessions (REHAB) led by a nurse-urologist pair. The sessions took place in parallel with the care pathway already in place before and after surgery. The evaluations were carried out by carrying out questionnaires and a clinical examination. A satisfaction questionnaire was given to the patient after the two sessions to assess the format and relevance of the sessions. RESULTS: Fifteen patients were included in the REHAB program. All patients attended both sessions in person and the majority of them (91%) felt they had obtained new information for their rehabilitation. Post-operatively at 6 weeks, 82% of patients were dissatisfied with their sexuality (compared to 64% pre-operatively), Five patients (33%) had regained orgasmic abilities and 20% (n=3) had a penetrative ability. The average IIEF5 score was 19 (6-28) compared to 22.5 pre-operatively (14-30). All patients would recommend these sessions. CONCLUSION: The REHAB sexual rehabilitation program after prostatectomy could be implemented with significant patient adherence and satisfaction.

2.
Prog Urol ; 32(13): 893-898, 2022 Nov.
Artigo em Francês | MEDLINE | ID: mdl-36280377

RESUMO

INTRODUCTION: The purpose of this article is to present the endoscopic papillary abnormalities and stone recognition (EPSR) to state-certified nurses (IDE and IBODE) working in the operating room. METHODS: This article is based on a literature review and the author's experience concerning the endoscopic papillary abnormalities and stone recognition. RESULTS: Since the advent of minimally invasive surgery and the laser, stones are no longer sent as one piece to laboratories, but fragmented. This has made it more difficult for biologists to fully analyze the stones, because they have less morphological data than before. Therefore, endoscopic papillary abnormalities and stone recognition have positioned themselves as tools that can compensate for this loss of information. They play a pivotal role in the identification of the lithogenesis cause, and thus allow a recurrence risk reduction of stones. CONCLUSION: Endoscopic papillary abnormalities and stone recognition are recent tools that require learning. However, the benefit of their uses is proven and is necessary for a complete management of urolithiasis.


Assuntos
Cálculos Renais , Cálculos Urinários , Urolitíase , Humanos , Cálculos Renais/cirurgia , Medula Renal/cirurgia , Endoscopia/efeitos adversos , Cálculos Urinários/diagnóstico , Cálculos Urinários/complicações
3.
Methods Mol Biol ; 1891: 247-255, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30414138

RESUMO

Fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder of progressive extra-skeletal ossification, is the most disabling form of heterotopic ossification (HO) in humans. Most people with FOP carry an activating mutation in a BMP type I receptor gene, ACVR1 R206H, that promotes ectopic chondrogenesis and osteogenesis and in turn HO. Advances in elucidating the cellular and molecular events and mechanisms that lead to the ectopic bone formation are being made through the use of genetically engineered mouse models that recapitulate the human disease. We describe methods for inducing heterotopic ossification in a mouse model that conditionally expresses the Acvr1 R206H allele.


Assuntos
Miosite Ossificante/patologia , Ossificação Heterotópica/patologia , Receptores de Ativinas Tipo I/genética , Alelos , Animais , Biomarcadores , Cardiotoxinas/efeitos adversos , Modelos Animais de Doenças , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , Mutação , Miosite Ossificante/diagnóstico por imagem , Miosite Ossificante/etiologia , Ossificação Heterotópica/diagnóstico por imagem , Ossificação Heterotópica/etiologia , Microtomografia por Raio-X
4.
Int J Mol Sci ; 19(2)2018 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-29439465

RESUMO

Inherited point mutations in collagen II in humans affecting mainly cartilage are broadly classified as chondrodysplasias. Most mutations occur in the glycine (Gly) of the Gly-X-Y repeats leading to destabilization of the triple helix. Arginine to cysteine substitutions that occur at either the X or Y position within the Gly-X-Y cause different phenotypes like Stickler syndrome and congenital spondyloepiphyseal dysplasia (SEDC). We investigated the consequences of arginine to cysteine substitutions (X or Y position within the Gly-X-Y) towards the N and C terminus of the triple helix. Protein expression and its secretion trafficking were analyzed. Substitutions R75C, R134C and R704C did not alter the thermal stability with respect to wild type; R740C and R789C proteins displayed significantly reduced melting temperatures (Tm) affecting thermal stability. Additionally, R740C and R789C were susceptible to proteases; in cell culture, R789C protein was further cleaved by matrix metalloproteinases (MMPs) resulting in expression of only a truncated fragment affecting its secretion and intracellular retention. Retention of misfolded R740C and R789C proteins triggered an ER stress response leading to apoptosis of the expressing cells. Arginine to cysteine mutations towards the C-terminus of the triple helix had a deleterious effect, whereas mutations towards the N-terminus of the triple helix (R75C and R134C) and R704C had less impact.


Assuntos
Substituição de Aminoácidos , Colágeno Tipo II/genética , Osteocondrodisplasias/congênito , Resposta a Proteínas não Dobradas , Linhagem Celular Tumoral , Sobrevivência Celular , Colágeno Tipo II/química , Colágeno Tipo II/metabolismo , Células HEK293 , Humanos , Osteocondrodisplasias/genética , Desnaturação Proteica , Domínios Proteicos , Estabilidade Proteica , Transporte Proteico
6.
J Bone Miner Res ; 33(2): 269-282, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28986986

RESUMO

Heterotopic ossification (HO) is a clinical condition that often reduces mobility and diminishes quality of life for affected individuals. The most severe form of progressive HO occurs in those with fibrodysplasia ossificans progressiva (FOP; OMIM #135100), a genetic disorder caused by a recurrent heterozygous gain-of-function mutation (R206H) in the bone morphogenetic protein (BMP) type I receptor ACVR1/ALK2. In individuals with FOP, episodes of HO frequently follow injury. The first sign of active disease is commonly an inflammatory "flare-up" that precedes connective tissue degradation, progenitor cell recruitment, and endochondral HO. We used a conditional-on global knock-in mouse model expressing Acvr1R206H (referred to as Acvr1cR206H/+ ) to investigate the cellular and molecular inflammatory response in FOP lesions following injury. We found that the Acvr1 R206H mutation caused increased BMP signaling in posttraumatic FOP lesions and early divergence from the normal skeletal muscle repair program with elevated and prolonged immune cell infiltration. The proinflammatory cytokine response of TNFα, IL-1ß, and IL-6 was elevated and prolonged in Acvr1cR206H/+ lesions and in Acvr1cR206H/+ mast cells. Importantly, depletion of mast cells and macrophages significantly impaired injury-induced HO in Acvr1cR206H/+ mice, reducing injury-induced HO volume by ∼50% with depletion of each cell population independently, and ∼75% with combined depletion of both cell populations. Together, our data show that the immune system contributes to the initiation and development of HO in FOP. Further, the expression of Acvr1R206H in immune cells alters cytokine expression and cellular response to injury and unveils novel therapeutic targets for treatment of FOP and nongenetic forms of HO. © 2017 American Society for Bone and Mineral Research.


Assuntos
Receptores de Ativinas Tipo I/genética , Macrófagos/patologia , Mastócitos/patologia , Miosite Ossificante/patologia , Ossificação Heterotópica/patologia , Animais , Proteínas Morfogenéticas Ósseas/metabolismo , Contagem de Células , Citocinas/metabolismo , Modelos Animais de Doenças , Progressão da Doença , Mediadores da Inflamação/metabolismo , Macrófagos/metabolismo , Mastócitos/metabolismo , Camundongos , Músculo Esquelético/patologia , Mutação/genética , Ossificação Heterotópica/metabolismo , Transdução de Sinais
7.
J Bone Miner Res ; 31(9): 1666-75, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26896819

RESUMO

Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable genetic disorder of progressive extraskeletal ossification, is the most disabling form of heterotopic ossification (HO) in humans and causes skeletal deformities, movement impairment, and premature death. Most FOP patients carry an activating mutation in a bone morphogenetic protein (BMP) type I receptor gene, ACVR1(R206H) , that promotes ectopic chondrogenesis and osteogenesis and, in turn, HO. We showed previously that the retinoic acid receptor γ (RARγ) agonist palovarotene effectively inhibited HO in injury-induced and genetic mouse models of the disease. Here we report that the drug additionally prevents spontaneous HO, using a novel conditional-on knock-in mouse line carrying the human ACVR1(R206H) mutation for classic FOP. In addition, palovarotene restored long bone growth, maintained growth plate function, and protected growing mutant neonates when given to lactating mothers. Importantly, palovarotene maintained joint, limb, and body motion, providing clear evidence for its encompassing therapeutic potential as a treatment for FOP. © 2016 American Society for Bone and Mineral Research.


Assuntos
Receptores de Ativinas Tipo I/genética , Extremidades/crescimento & desenvolvimento , Extremidades/fisiopatologia , Mutação/genética , Miosite Ossificante/genética , Ossificação Heterotópica/tratamento farmacológico , Ossificação Heterotópica/fisiopatologia , Pirazóis/uso terapêutico , Estilbenos/uso terapêutico , Animais , Osso e Ossos/anormalidades , Osso e Ossos/patologia , Proliferação de Células/efeitos dos fármacos , Condrócitos/efeitos dos fármacos , Condrócitos/patologia , Modelos Animais de Doenças , Progressão da Doença , Lâmina de Crescimento/efeitos dos fármacos , Lâmina de Crescimento/patologia , Homeostase , Humanos , Camundongos Transgênicos , Movimento , Ossificação Heterotópica/patologia , Osteogênese , Pirazóis/farmacologia , Estilbenos/farmacologia
8.
Stem Cells ; 32(5): 1289-300, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24449086

RESUMO

Bone morphogenetic protein (BMP) signaling is a critical regulator of cartilage differentiation and endochondral ossification. Gain-of-function mutations in ALK2, a type I BMP receptor, cause the debilitating disorder fibrodysplasia ossificans progressiva (FOP) and result in progressive heterotopic (extraskeletal) endochondral ossification within soft connective tissues. Here, we used murine mesenchymal progenitor cells to investigate the contribution of Alk2 during chondrogenic differentiation and heterotopic endochondral ossification (HEO). Alk2(R206H/+) (gain-of-function), Alk2(CKO) (loss-of-function), and wild-type mouse embryonic fibroblasts were evaluated for chondrogenic potential. Chondrogenic differentiation was accelerated in Alk2(R206H/+) cells, due in part to enhanced sensitivity to BMP ligand. In vivo, Alk2(R206H/+) cells initiated robust HEO and recruited wild-type cell contribution. Despite expression of other type I BMP receptors (Alk3 and Alk6), chondrogenesis of Alk2(CKO) cells was severely impaired by absence of Alk2 during early differentiation. Alk2 is therefore a direct regulator of cartilage formation and mediates chondrogenic commitment of progenitor cells. These data establish that at least one effect of ALK2 gain-of-function mutations in FOP patients is enhanced chondrogenic differentiation which supports formation of heterotopic endochondral bone. This establishes ALK2 as a plausible therapeutic target during early chondrogenic stages of lesion formation for preventing heterotopic bone formation in FOP and other conditions.


Assuntos
Receptores de Ativinas Tipo I/genética , Condrogênese/genética , Miosite Ossificante/genética , Ossificação Heterotópica/genética , Receptores de Ativinas Tipo I/metabolismo , Animais , Proteína Morfogenética Óssea 4/farmacologia , Receptores de Proteínas Morfogenéticas Ósseas Tipo I/genética , Receptores de Proteínas Morfogenéticas Ósseas Tipo I/metabolismo , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/genética , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/metabolismo , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Células Cultivadas , Condrócitos/citologia , Condrócitos/metabolismo , Condrogênese/efeitos dos fármacos , Embrião de Mamíferos/citologia , Embrião de Mamíferos/metabolismo , Fibroblastos/citologia , Fibroblastos/metabolismo , Immunoblotting , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Miosite Ossificante/metabolismo , Miosite Ossificante/patologia , Ossificação Heterotópica/metabolismo , Ossificação Heterotópica/patologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Fatores de Tempo
9.
Dis Model Mech ; 5(6): 756-62, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23115204

RESUMO

Fibrodysplasia ossificans progressiva (FOP; MIM #135100) is a debilitating genetic disorder of connective tissue metamorphosis. It is characterized by malformation of the great (big) toes during embryonic skeletal development and by progressive heterotopic endochondral ossification (HEO) postnatally, which leads to the formation of a second skeleton of heterotopic bone. Individuals with these classic clinical features of FOP have the identical heterozygous activating mutation (c.617G>A; R206H) in the gene encoding ACVR1 (also known as ALK2), a bone morphogenetic protein (BMP) type I receptor. Disease activity caused by this ACVR1 mutation also depends on altered cell and tissue physiology that can be best understood in the context of a high-fidelity animal model. Recently, we developed such a knock-in mouse model for FOP (Acvr1(R206H/+)) that recapitulates the human disease, and provides a valuable new tool for testing and developing effective therapies. The FOP knock-in mouse and other models in Drosophila, zebrafish, chickens and mice provide an arsenal of tools for understanding BMP signaling and addressing outstanding questions of disease mechanisms that are relevant not only to FOP but also to a wide variety of disorders associated with regenerative medicine and tissue metamorphosis.


Assuntos
Desenvolvimento Ósseo , Modelos Animais de Doenças , Metamorfose Biológica , Miosite Ossificante/patologia , Miosite Ossificante/fisiopatologia , Receptores de Ativinas/genética , Animais , Humanos , Mutação/genética , Miosite Ossificante/genética , Miosite Ossificante/terapia
10.
J Bone Miner Res ; 27(8): 1746-56, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22508565

RESUMO

Fibrodysplasia ossificans progressiva (FOP; MIM #135100) is a debilitating genetic disorder of dysregulated cellular differentiation characterized by malformation of the great toes during embryonic skeletal development and by progressive heterotopic endochondral ossification postnatally. Patients with these classic clinical features of FOP have the identical heterozygous single nucleotide substitution (c.617G > A; R206H) in the gene encoding ACVR1/ALK2, a bone morphogenetic protein (BMP) type I receptor. Gene targeting was used to develop an Acvr1 knock-in model for FOP (Acvr1(R206H/+)). Radiographic analysis of Acvr1(R206H/+) chimeric mice revealed that this mutation induced malformed first digits in the hind limbs and postnatal extraskeletal bone formation, recapitulating the human disease. Histological analysis of murine lesions showed inflammatory infiltration and apoptosis of skeletal muscle followed by robust formation of heterotopic bone through an endochondral pathway, identical to that seen in patients. Progenitor cells of a Tie2(+) lineage participated in each stage of endochondral osteogenesis. We further determined that both wild-type (WT) and mutant cells are present within the ectopic bone tissue, an unexpected finding that indicates that although the mutation is necessary to induce the bone formation process, the mutation is not required for progenitor cell contribution to bone and cartilage. This unique knock-in mouse model provides novel insight into the genetic regulation of heterotopic ossification and establishes the first direct in vivo evidence that the R206H mutation in ACVR1 causes FOP.


Assuntos
Receptores de Ativinas Tipo I/genética , Substituição de Aminoácidos/genética , Técnicas de Introdução de Genes , Miosite Ossificante/patologia , Receptores de Ativinas Tipo I/metabolismo , Alelos , Animais , Apoptose , Sequência de Bases , Movimento Celular , Condrogênese , Tecido Conjuntivo/patologia , Marcação de Genes , Humanos , Inflamação/complicações , Inflamação/patologia , Linfócitos/patologia , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Músculo Esquelético/lesões , Músculo Esquelético/patologia , Miosite Ossificante/complicações , Miosite Ossificante/diagnóstico por imagem , Miosite Ossificante/fisiopatologia , Ossificação Heterotópica/complicações , Ossificação Heterotópica/patologia , Ossificação Heterotópica/fisiopatologia , Osteogênese , Radiografia , Receptores Proteína Tirosina Quinases/metabolismo , Receptor TIE-2 , Células-Tronco/metabolismo
11.
Prog Urol ; 21(8): 580-2, 2011 Sep.
Artigo em Francês | MEDLINE | ID: mdl-21872163

RESUMO

We report the case of a 66-year-old man, presenting a right kidney mass with an alteration of the clinical status, treated by radical nephrectomy. Pathology reported that it was a pseudotumoral form of a bacterial infection: actinomycosis. This is an uncommon disease in this location. The authors wonder if it is possible to avoid nephrectomy with a preoperative diagnosis, especially with renal biopsy. The patient was well doing after 18 months thanks to long-lasting and effective postoperative antibiotics (Dhanani et al., 2004).


Assuntos
Actinomicose/diagnóstico , Nefropatias/microbiologia , Nefropatias/patologia , Idoso , Humanos , Masculino
12.
Prog Urol ; 21(6): 432-6, 2011 Jun.
Artigo em Francês | MEDLINE | ID: mdl-21620305

RESUMO

Radiofrequency is a minimally invasive therapy allowing tumor destruction by applying physical means to the core of the lesion. There is a particular indication for the hereditary already surgically treated renal carcinomas like Von Hippel-Lindau's disease. We present a case of renal-pleural fistula developed after a percutaneous radiofrequency ablation under computed tomography (CT) guidance of a renal tumor in a VHL female patient with a renal cell carcinoma of the upper pole of the left kidney. The kidney manifestations begin at 20-year-old with the appearance of cystic lesion at the lower pole of the left kidney. At 30-year-old, a computed tomography study revealed a solid lesion arising from a cyst. The patient underwent a partial nephrectomy by flank incision. Follow-up studies discovered three solid lesions of the upper pole of the left kidney. The patient undertook a radiofrequency ablation of these lesions. Follow-up control showed a contrast enhancement of one of the three lesions treated. Under this condition another course of RF was performed, complicated by a renal-pleural fistula. A conservative management of this iatrogenic fistula was attempted combining a water restriction and the insertion of a ureteral catheter. Three weeks were necessary until the fistula completely regress.


Assuntos
Carcinoma de Células Renais/cirurgia , Ablação por Cateter/efeitos adversos , Nefropatias/etiologia , Neoplasias Renais/cirurgia , Doenças Pleurais/etiologia , Fístula do Sistema Respiratório/etiologia , Fístula Urinária/etiologia , Adulto , Carcinoma de Células Renais/etiologia , Feminino , Humanos , Neoplasias Renais/etiologia , Doença de von Hippel-Lindau/complicações
13.
J Visc Surg ; 147(6): e385-8, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21112270

RESUMO

GOAL: Present and analyze the implementation of laparoscopic teaching program at the Surgical School of Paris, introduced in 2008. MATERIAL AND METHODS: Evaluation of the technical capacities of 43 students in six basic tests after four, one and a half hour training sessions with a pelvic-trainer. RESULTS: The time necessary to perform an intracorporeal knot improved significantly by 56% after four sessions. Overall, 89% of students progressed and mastered the basic skills. Asked about their formation, 74% of the students thought their training in laparoscopy was insufficient. CONCLUSION: The pelvic-trainer is an accessible and reliable tool for training of young residents in laparoscopy. Use of the pelvic-trainer must be promoted among young residents during their training.


Assuntos
Laparoscopia/educação , Competência Clínica , Humanos , Laparoscopia/métodos , Paris
14.
Phys Rev Lett ; 100(11): 116102, 2008 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-18517799

RESUMO

We quantitatively evaluate the contribution of electron-hole pair excitations to the reactive dynamics of H2 on Cu(110) and N2 on W(110), including the six dimensionality of the process in the entire calculation. The interaction energy between molecule and surface is represented by an ab initio six-dimensional potential energy surface. Electron friction coefficients are calculated with density functional theory in a local density approximation. Contrary to previous claims, only minor differences between the adiabatic and nonadiabatic results for dissociative adsorption are found. Our calculations demonstrate the validity of the adiabatic approximation to analyze adsorption dynamics in these two representative systems.

15.
J Chem Phys ; 128(15): 154704, 2008 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-18433255

RESUMO

We study the dissociative adsorption of N(2) on W(100) and W(110) by means of density functional theory and classical dynamics. Working with a full six-dimensional adiabatic potential energy surface (PES), we find that the theoretical results of the dynamical problem strongly depend on the choice of approximate exchange-correlation functional for the determination of the PES. We consider the Perdew-Wang-91 [Perdew et al., Phys. Rev. B 46, 6671 (1992)] and Perdew-Burke-Ernzerhof (RPBE) [Hammer et al., Phys. Rev. B 59, 7413 (1999)] functionals and carry out a systematic comparison between the dynamics determined by the respective PESs. Even though it has been shown in earlier works that the RPBE may provide better values for the chemisorption energies, our study brings evidence that it gives rise to a PES with excessive repulsion far from the surface.

16.
J Chem Phys ; 127(16): 164722, 2007 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-17979386

RESUMO

Six-dimensional quantum dynamical and quasiclassical trajectory (QCT) calculations are reported for the reaction and vibrationally inelastic scattering of (v = 0,1,j = 0) H(2) scattering from Cu(110), and for the reaction and rovibrationally elastic and inelastic scattering of (v = 1,j = 1) H(2) scattering from Cu(110). The dynamics results were obtained using a potential energy surface obtained with density functional theory using the PW91 functional. The reaction probabilities computed with quantum dynamics for (v = 0,1,j = 0) were in excellent agreement with the QCT results obtained earlier for these states, thereby validating the QCT approach to sticking of hydrogen on Cu(110). The vibrational de-excitation probability P(v=1,j = 0 --> v = 0) computed with the QCT method is in remarkably good agreement with the quantum dynamical results for normal incidence energies E(n) between 0.2 and 0.6 eV. The QCT result for the vibrational excitation probability P(v = 0,j = 0 --> v = 1) is likewise accurate for E(n) between 0.8 and 1 eV, but the QCT method overestimates vibrational excitation for lower E(n). The QCT method gives probabilities for rovibrationally (in)elastic scattering, P(v = 1,j = 1 --> v('),j(')), which are in remarkably good agreement with quantum dynamical results. The rotationally averaged, initial vibrational state-selective reaction probability obtained with QCT agrees well with the initial vibrational state-selective reaction probability extracted from molecular beam experiments for v = 1, for the range of collision energies for which the v=1 contribution to the measured total sticking probability dominates. The quantum dynamical probabilities for rovibrationally elastic scattering of (v = 1,j = 1) H(2) from Cu(110) are in good agreement with experiment for E(n) between 0.08 and 0.25 eV.

17.
Phys Rev Lett ; 97(5): 056102, 2006 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-17026118

RESUMO

Low-energy N2 molecules easily dissociate on W(100) but not on W(110). In this Letter, the six-dimensional potential energy surface for the dissociation of N2 molecules on W(110) has been determined by density functional calculations. Results are compared to those of N2 dissociation on W(100). The difference in reactivity between the two faces is shown to arise from the characteristics of the potential energy surface far from the surface (>3 A) and not from the properties of a precursor well or those of the final atomic adsorption sites.

18.
J Chem Phys ; 125(14): 144705, 2006 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-17042629

RESUMO

The six-dimensional potential energy surface for the dissociation of N2 molecules on the W(110) surface has been determined by density functional calculations and interpolated using the corrugation reducing procedure. Examination of the resulting six-dimensional potential energy surface shows that nonactivated paths are available for dissociation. In spite of this, the dissociation probability goes to a very small value when the impact energy goes to zero and increases with increasing energy, a behavior usually associated with activated systems. Statistics on the dynamics indicate that this unconventional result is a consequence of the characteristics of the potential energy surface at long distances. Furthermore, two distinct channels are identified in the dissociation process, namely, a direct one and an indirect one. The former is responsible for dissociation at high energies. The latter, which includes long-lasting dynamic trapping in the vicinity of a potential well above the W top position, is the leading mechanism at low and intermediate energies.

19.
J Chem Phys ; 125(5): 051101, 2006 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-16942196

RESUMO

We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.

20.
J Chem Phys ; 124(10): 104704, 2006 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-16542094

RESUMO

We have calculated the six-dimensional (6D) potential energy surface for H2 in front of a frozen Cu(110) surface using density functional theory for 22 H2-surface configurations and the corrugation reducing procedure to interpolate between them. We carry out classical trajectory calculations on the dissociative adsorption process and find excellent agreement with measurements. We find that it is of prominent importance to account for the rovibrational state distribution in the incident H2 beam. A straightforward analysis leads to the conclusion that the motion along the surface does not play an appreciable role in the dynamics whereas the dynamical role of molecular rotation is crucial. The latter fact precludes any interpretation of dissociation in terms of a static concept such as "barrier distributions."

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