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1.
J Subst Use Addict Treat ; 157: 209240, 2024 02.
Artigo em Inglês | MEDLINE | ID: mdl-38061633

RESUMO

BACKGROUND: The current US addiction treatment system does not effectively meet the needs of pregnant and parenting women with substance use disorder (SUD). The aim of this research was to identify barriers and facilitators to engagement and retention in SUD residential treatment for pregnant and parenting women. This research was part of a co-design process to collaboratively create a more patient-centered long-term residential program. DESIGN AND METHODS: The study conducted semi-structured individual interviews with both parenting women with lived experience (WWLE) in residential SUD treatment and SUD treatment providers. Interviews aimed to elicit participants' experiences either receiving or providing care. The study team analyzed data in NVivo-12 using a deductive codebook based on the six principles of trauma informed care (TIC). RESULTS: We conducted a total of 32 interviews (WWLE =13, SUD providers =19). The study identified four major themes: 1) peer relationships provide inspiration and diminish shame; 2) providing individuals safe space to stumble in recovery creates opportunities for growth and builds self-efficacy; 3) reasonable, clear boundaries create a structured, protective environment for early recovery; 4) nonjudgmental connections facilitate engagement and build trust. We identified small pivotal moments along the continuum of care that showed how the elements in the four themes enhanced engagement and retention in treatment. These interactions, along the care continuum, are either structural (workflow process) or relational (interpersonal). CONCLUSION: This research increases understanding of the interplay of the structural and relational barriers and facilitators to engagement and retention in treatment. These seemingly minor positive or negative interactions along the care continuum are pivotal to fully operationalizing TIC and optimizing women's engagement in treatment. Improvement strategies that integrate the voices of WWLE and collaboratively co-design a more patient-centered system are critical steps to improving engagement in SUD treatment and more equitable SUD treatment services.


Assuntos
Comportamento Aditivo , Transtornos Relacionados ao Uso de Substâncias , Gravidez , Humanos , Feminino , Poder Familiar , Continuidade da Assistência ao Paciente , Transtornos Relacionados ao Uso de Substâncias/terapia , Confiança
2.
JPRAS Open ; 33: 155-160, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36046255

RESUMO

Non-melanoma skin cancers (NMSCs) are the most common cancer in fair-skinned individuals with basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) being the most common subtype. While BCC has historically been the most common NMSC, SCC is increasing in incidence relative to BCC. SCC has a very poor prognosis with advanced local infiltration or when it achieves a metastatic state with around 50% of patients with locally advanced disease relapsing with an average overall survival of 10-13 months for patients with recurrent or metastatic disease. The pathogenesis of cutaneous SCC (cSCC) is multifactorial, and many studies have also described in detail the strong link between tumour apoptosis, DNA repair mechanism deficiencies, and developing cSCC. Patients with TP53 mutations are more susceptible to develop cSCC, thus highlighting the importance of cell cycle regulation and also pointing towards the potential therapeutic targets within. This review illustrates the role of the programmed death receptor-1 (PD-1) inhibitor cemiplimab in treating advanced and metastatic cSCC not suitable to surgical excision and describes its development in the context of the translational research paradigm from preclinical studies to its licenced implementation in clinical care and beyond.

3.
Eur J Surg Oncol ; 48(10): 2104-2111, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35725681

RESUMO

BACKGROUND: Although male breast cancer (MBC) is a rare disease, accounting for <1% of all breast cancers, it has significant oncological, survival and psychosocial implications for patients. The aim of this study is to assess the latest literature in the diagnosis, management, oncological outcomes, and psychosocial impact of MBC. METHODS: A systematic literature review was conducted using the PRISMA guidelines (Moher et al., 2009) [1] to explore the management of MBC, with particular focus on investigative imaging, surgical management, oncological outcomes, survival, genetic screening and psychosocial effects. Electronic databases were searched for randomised control trials, cohort studies and case series involving more than 10 patients. Imaging and surgical techniques, local and distant disease recurrence, survival, genetic screening and psychosocial implications in the setting of MBC were assessed. RESULTS: The search criteria identified 199 articles, of which 59 met the inclusion criteria. This included 39,529 patients, with a mean age of 64.5 years (55-71), and a mean follow-up of 66.3 months (26.2-115). Mastectomy remains the most frequently used surgical technique, with an average of 89.6%. Loco-regional and distant recurrence rate was 10.1% and 21.4% respectively. Disease-free survival (DFS) at 5 and 10 years was 66.8% and 54.5% respectively. Disease-specific survival (DSS) at 5 and 10 years was 87.1% and 67.1% respectively. Overall survival (OS) at 5 and 10 years was 72.7% and 50.7% respectively. Genetic screening was conducted in 38.6% of patients of which 4.8% and 15.8% were found to be BRCA1 and BRCA2 carriers respectively. Psychosocial studies were conducted mainly using questionnaire and interview-based methodology focusing primarily on awareness of breast cancer in men, support available and impact on gender identity. CONCLUSIONS: This review demonstrates that men present with later stage disease with subsequent impact on survival outcomes. There remains a paucity of high-level evidence and prospective studies are required. There is a need for increasing awareness amongst the public and health care professionals in order to improve outcomes and reduce stigma associated with MBC.


Assuntos
Neoplasias da Mama Masculina , Neoplasias da Mama , Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Neoplasias da Mama Masculina/terapia , Neoplasias da Mama Masculina/cirurgia , Mastectomia/métodos , Neoplasias da Mama/genética , Neoplasias da Mama/terapia , Recidiva Local de Neoplasia/cirurgia , Identidade de Gênero , Intervalo Livre de Doença
4.
JPRAS Open ; 33: 17-20, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35633992

RESUMO

Raoultella ornithinolytica is a rare encapsulated Gram-negative aerobic and facultative anaerobic rod belonging to the Enterobacteriaceae family. It tends to inhabit water and soil environments and can be found on insects, fish, ticks, and termites, but can also found in the hospital environment.1 , 2 R ornithinolytica has been documented in respiratory, urinary, gastrointestinal, and biliary tract infections as well as bacteraemia and systemic infections but has rarely been documented in soft tissue infections.2 This case study describes a recurrent paronychia infection secondary to R ornithinolytica in a young woman not responding to antibiotics and successfully treated with surgical management.

5.
Matern Child Health J ; 26(5): 985-993, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35029805

RESUMO

INTRODUCTION: Maternal mortality rates have been increasing in the United States for decades. For several years, opioid overdoses have been a leading cause of maternal mortality in several states. New Hampshire (NH) is a particularly severe case, with 50% of all maternal deaths being caused by drug-related overdoses from 2016 to 2017. We report on the implementation of a point-of-care naloxone distribution program for an Ob/Gyn clinic in NH. METHODS: Naloxone distribution was tracked to measure program implementation. Proportion of patients screened for naloxone need was calculated monthly. Proportion of patients with which discussions about naloxone took place was calculated quarterly. Patient and provider perspectives on the program were captured periodically. Statistical process control charts monitored change over time and evaluated for special-cause variation. RESULTS: The clinic has distributed 12 doses of naloxone since program implementation in April 2020. Despite the challenges posed by the COVID-19 pandemic, screening for naloxone need has remained at pre-pandemic rates (moving average: 73%), except for a decrease in April-May 2020. Patient-provider discussions about naloxone have also remained at pre-pandemic rates (moving average: 51%). Qualitative feedback from patients and providers has indicated that the program has been well-received by both groups. DISCUSSION: The purpose of this description is to provide a framework for other Ob/Gyn clinics to use in implementing similar naloxone distribution programs. Although too early to determine whether this intervention will result in a significant decrease in maternal mortality due to opioid overdose in our patients, this measure will continue to be tracked annually. Implementation of a naloxone program in the obstetrical context provides an important way to improve outcomes for a vulnerable perinatal population.


Assuntos
COVID-19 , Overdose de Drogas , Overdose de Opiáceos , Transtornos Relacionados ao Uso de Opioides , Analgésicos Opioides/efeitos adversos , Overdose de Drogas/tratamento farmacológico , Overdose de Drogas/prevenção & controle , Humanos , Mortalidade Materna , Naloxona/uso terapêutico , Antagonistas de Entorpecentes/uso terapêutico , Transtornos Relacionados ao Uso de Opioides/tratamento farmacológico , Pandemias , Estados Unidos
6.
Public Health ; 180: 114-116, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31881465

RESUMO

OBJECTIVES: Pregnancy is a time when optimization of nutrition is critically important, yet pregnant women with substance use disorders face unique nutritional challenges. The aim of this short communication is to summarize existing knowledge about nutritional interventions used in substance use disorders for pregnant and parenting women with opioid use disorder (OUD) and substance use disorders and to inform program development by maternity care and treatment providers. STUDY DESIGN: We conducted a narrative review of nutritional interventions for pregnant women with OUD and performed environmental scanning to explore current practice. METHODS: To gain knowledge about the unique nutritional needs of pregnant women with OUD, we searched the medical literature using Medical Subject Headings terms and key words combining the concepts of nutrition, pregnancy, and substance use. To explore current practice, we interviewed staff of a geographically diverse sample of 35 programs treating women with substance use disorders across the United Stated and Canada on their approach to prenatal nutrition for clients. RESULTS: Literature review identified two studies evaluating the nutritional status of pregnant women with substance use disorders, but neither described nutritional interventions. Lower body mass index and folate, B12, and iron deficiencies were found in women with OUD compared with women without OUD. Two additional studies integrated nutritional interventions in substance use treatment for non-pregnant populations, resulting in significant improvements in dietary habits and psychological well-being for participants. Of 15 substance use treatment programs that responded to our query, only two incorporated longitudinal nutrition curricula for pregnant women. CONCLUSIONS: Pregnancy is a time when a healthy diet is critically important for maternal, fetal, and neonatal health; however, pregnant women with OUD are at significant risk of malnutrition. There is an urgent need to address food insecurity and develop targeted nutrition education programs for pregnant women in early recovery.


Assuntos
Desnutrição/prevenção & controle , Serviços de Saúde Materna/organização & administração , Terapia Nutricional , Transtornos Relacionados ao Uso de Opioides/epidemiologia , Feminino , Humanos , Desnutrição/epidemiologia , Gravidez
7.
Rev Sci Instrum ; 87(5): 055102, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27250465

RESUMO

Simultaneous laser locking of infrared (IR) and ultraviolet lasers to a visible stabilized reference laser is demonstrated via a Fabry-Perot (FP) cavity. LabVIEW is used to analyze the input, and an internal proportional-integral-derivative algorithm converts the FP signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of better than 9 MHz, with a custom-built IR laser undergoing significant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple, computer-controlled, non-temperature-stabilized FP locking scheme for our applications, laser cooling of Ca(+) ions, and its use in other applications with similar modest frequency stabilization requirements.

8.
J Perinatol ; 36(1): 30-4, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26334399

RESUMO

OBJECTIVE: Summarize policies that support maternal and neonatal transport among states and territories. STUDY DESIGN: Systematic review of publicly available, web-based information on maternal and neonatal transport for each state and territory in 2014. Information was abstracted from published rules, statutes, regulations, planning documents and program descriptions. Abstracted information was summarized within two categories: transport and reimbursement. RESULTS: Sixty-eight percent of states and 25% of territories had a policy for neonatal transport; 60% of states and one territory had a policy for maternal transport. Sixty-two percent of states had a reimbursement policy for neonatal transport, whereas 20% reimbursed for maternal transport. Thirty-two percent of states had an infant back-transport policy while 16% included back-transport for both. No territories had reimbursement or back-transport policies. CONCLUSION: The lack of development of maternal transport reimbursement and neonatal back-transport policies negatively impacts the achievements of risk-appropriate care, a strategy focused on improving perinatal outcomes.


Assuntos
Reembolso de Seguro de Saúde/legislação & jurisprudência , Assistência Perinatal/legislação & jurisprudência , Transporte de Pacientes/legislação & jurisprudência , Feminino , Humanos , Recém-Nascido , Gravidez , Estados Unidos
9.
Toxicol Pathol ; 43(5): 730-2, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25530274

RESUMO

The International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice proposal (INHAND) has been operational since 2005. A Global Editorial Steering Committee manages the overall objectives of the project, and the development of harmonized terminology for each organ system is the responsibility of the Organ Working Groups, drawing upon experts from North America, Europe, and Japan. Great progress has been made with 9 systems published to date--respiratory, hepatobiliary, urinary, central/peripheral nervous systems, male reproductive and mammary, zymbals, clitoral, and preputial glands in Toxicologic Pathology and the integument and soft tissue and female reproductive in the Journal of Toxicologic Pathology as supplements and on a Web site--www.goReni.org. INHAND nomenclature guides offer diagnostic criteria and guidelines for recording lesions observed in rodent toxicity and carcinogenicity studies. The guides provide representative photomicrographs of morphologic changes, information regarding pathogenesis, and key references. The purpose of this brief communication is to provide an update on the progress of INHAND.


Assuntos
Pesquisa Biomédica/normas , Guias como Assunto , Patologia/normas , Terminologia como Assunto , Toxicologia/normas , Animais , Camundongos , Ratos , Projetos de Pesquisa
10.
Phys Chem Chem Phys ; 16(8): 3823-9, 2014 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-24435048

RESUMO

It is of great importance to study the catalytic structures under real reaction conditions especially for the bimetallic catalysts, where facile surface restructure or surface segregation can be driven by adsorbate adsorption. Here, we report CO interaction with Cu-Ni/SiO2 bimetallic model catalysts studied by CO temperature programmed desorption (TPD) and in situ CO polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) under CO pressures varying from ultrahigh vacuum (UHV) to near ambient pressure. Under UHV conditions, Cu is enriched on the surface of Cu-Ni/SiO2 bimetallic catalysts. CO spillover from Cu to Ni on Cu-Ni/SiO2 bimetallic catalysts has been observed at about 200 K under UHV conditions. In situ CO PM-IRRAS shows surface segregation of Ni on the Cu-Ni/SiO2 bimetallic catalysts induced by CO adsorption at ambient pressure CO. The behavior of CO induced surface segregation can lead to severe errors in Ni active site measurements by the selective CO chemisorption on Cu-Ni/SiO2 bimetallic catalysts.

11.
Rev Sci Instrum ; 84(11): 113101, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24289382

RESUMO

Linear Paul traps (LPT) are used in many experimental studies such as mass spectrometry, atom-ion collisions, and ion-molecule reactions. Mass selective resonant quenching (MSRQ) is implemented in LPT either to identify a charged particle's mass or to remove unwanted ions from a controlled experimental environment. In the latter case, MSRQ can introduce undesired heating to co-trapped ions of different mass, whose secular motion is off resonance with the quenching ac field, which we call off-resonance energy absorption (OREA). We present simulations and experimental evidence that show that the OREA increases exponentially with the number of ions loaded into the trap and with the amplitude of the off-resonance external ac field.


Assuntos
Espectrometria de Massas/instrumentação , Absorção , Simulação por Computador , Eletrodos , Software
12.
Am J Transplant ; 13(7): 1850-8, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23668890

RESUMO

Whilst initial rates of insulin independence following islet transplantation are encouraging, long-term function using the Edmonton Protocol remains a concern. The aim of this single-arm, multicenter study was to evaluate an immunosuppressive protocol of initial antithymocyte globulin (ATG), tacrolimus and mycophenolate mofetil (MMF) followed by switching to sirolimus and MMF. Islets were cultured for 24 h prior to transplantation. The primary end-point was an HbA1c of <7% and cessation of severe hypoglycemia. Seventeen recipients were followed for ≥ 12 months. Nine islet preparations were transported interstate for transplantation. Similar outcomes were achieved at all three centers. Fourteen of the 17 (82%) recipients achieved the primary end-point. Nine (53%) recipients achieved insulin independence for a median of 26 months (range 7-39 months) and 6 (35%) remain insulin independent. All recipients were C-peptide positive for at least 3 months. All subjects with unstimulated C-peptide >0.2 nmol/L had cessation of severe hypoglycemia. Nine of the 17 recipients tolerated switching from tacrolimus to sirolimus with similar graft outcomes. There was a small but significant reduction in renal function in the first 12 months. The combination of islet culture, ATG, tacrolimus and MMF is a viable alternative for islet transplantation.


Assuntos
Diabetes Mellitus Tipo 1/cirurgia , Rejeição de Enxerto/prevenção & controle , Imunossupressores/uso terapêutico , Transplante das Ilhotas Pancreáticas/métodos , Adolescente , Adulto , Idoso , Austrália/epidemiologia , Glicemia/metabolismo , Células Cultivadas , Diabetes Mellitus Tipo 1/sangue , Feminino , Seguimentos , Rejeição de Enxerto/epidemiologia , Sobrevivência de Enxerto , Humanos , Incidência , Insulina/sangue , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Sirolimo/uso terapêutico , Tacrolimo/uso terapêutico , Resultado do Tratamento , Adulto Jovem
13.
J Fish Biol ; 81(6): 1891-914, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23130690

RESUMO

Phylogenetic structure of four Lampetra species from the Pacific drainage of North America (western brook lamprey Lampetra richardsoni, Pacific brook lamprey Lampetra pacifica, river lamprey Lampetra ayresii and Kern brook lamprey Lampetra hubbsi) and unidentified Lampetra specimens (referred to as Lampetra sp.) from 36 locations was estimated using the mitochondrial cytochrome b gene. Maximum parsimony and Bayesian inferences did not correspond with any taxonomic scheme proposed to date. Rather, although L. richardsoni (from Alaska to California) and L. ayresii (from British Columbia to California) together constituted a well-supported clade distinct from several genetically divergent Lampetra populations in Oregon and California, these two species were not reciprocally monophyletic. The genetically divergent populations included L. pacifica (from the Columbia River basin) and L. hubbsi (from the Kern River basin) and four Lampetra sp. populations in Oregon (Siuslaw River and Fourmile Creek) and California (Kelsey and Mark West Creeks). These four Lampetra sp. populations showed genetic divergence between 2.3 and 5.7% from any known species (and up to 8.0% from each other), and may represent morphologically cryptic and thus previously undescribed species. A fifth population (from Paynes Creek, California) may represent a range extension of L. hubbsi into the Upper Sacramento River.


Assuntos
Variação Genética , Lampreias/classificação , Filogenia , Animais , Teorema de Bayes , Citocromos b/genética , DNA Mitocondrial/genética , Genética Populacional , Lampreias/genética , América do Norte , Análise de Sequência de DNA
14.
Chem Soc Rev ; 41(24): 8009-20, 2012 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-22824870

RESUMO

Pd-Au bimetallic catalysts often display enhanced catalytic activities and selectivities compared with Pd-alone catalysts. This enhancement is often caused by two alloy effects, i.e., ensemble and ligand effects. The ensemble effect is a dilution of surface Pd by Au. With increasing surface Au coverage, contiguous Pd ensembles disappear and isolated Pd ensembles form. For certain reactions, for example vinyl acetate synthesis, this effect is responsible for reaction rate enhancement via the formation of highly active surface sites, e.g., isolated Pd pairs. The disappearance of contiguous Pd ensembles also switches off side reactions catalyzed by these sites. This explains the selectivity increase of certain reactions, for example direct H(2)O(2) synthesis. The ligand effects are electronic perturbation of Pd by Au. Via direct charge transfer or by affecting bond lengths, the ligand effects cause the Pd d band to be more filled, moving the d-band center away from the Fermi level. Both changes make Pd more "atomic like" therefore binding reactants and products more weakly. For certain reactions, this eliminates a so-called "self-poisoning" effect and enhances activity/selectivity.

15.
Phys Chem Chem Phys ; 14(19): 6688-97, 2012 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-22473306

RESUMO

CO oxidation was carried out over Ru(0001) and RuO2(110) thin film grown on Ru(0001) at various O2/CO ratios near atmospheric pressures. Reaction kinetics, coupled with in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and post-reaction Auger electron spectroscopy (AES) measurements, were used to identify the catalytically relevant phases under different reaction conditions. Under stoichiometric and reducing conditions at all reaction temperatures, as well as net-oxidizing reaction conditions below ∼475 K, a reduced metallic phase with chemisorbed oxygen is the thermodynamically stable and catalytically active phase. On this surface CO oxidation occurs at surface defect sites, for example step edges. Only under net-oxidizing reaction conditions and above ∼475 K is the RuO2 thin film grown on metallic Ru stable and active. However, RuO2 is not active itself without the existence of the metal substrate, suggesting the importance of a strong metal-substrate interaction (SMSI).

16.
Annu Rev Phys Chem ; 63: 265-86, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22242729

RESUMO

Surface-science investigations have contributed significantly to heterogeneous catalysis in the past several decades. Fundamental studies of reactive systems on metal single crystals have aided researchers in understanding the effect of surface structure on catalyst reactivity and selectivity for a number of important reactions. Recently, model systems, consisting of metal clusters deposited on planar oxide surfaces, have facilitated the study of metal particle-size and support effects. These model systems not only are useful for carrying out kinetic investigations, but are also amenable to surface spectroscopic techniques, thus enabling investigations under realistic pressures and at working temperatures. By combining surface-science characterization methods with kinetic measurements under realistic working conditions, researchers are continuing to advance the molecular-level understanding of heterogeneous catalysis and are narrowing the pressure and material gap between model and real-world catalysts.

17.
Proc Natl Acad Sci U S A ; 108(3): 931-6, 2011 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-20947802

RESUMO

C(2)H(4)/CO/H(2) reaction is investigated on Rh/SiO(2) model catalyst surfaces. Kinetic reactivity and infrared spectroscopic measurements are investigated as a function of Rh particle size under near atmospheric reaction conditions. Results show that propionaldehyde turnover frequency (TOF) (CO insertion pathway) exhibits a maximum activity near = 2.5 nm. Polarization modulation infrared reflection absorption spectroscopy under CO and reaction (C(2)H(4)/CO/H(2)) conditions indicate the presence of Rh carbonyl species (Rh(CO)(2), Rh(CO)H) on small Rh particles, whereas larger particles appear resistant to dispersion and carbonyl formation. Combined these observations suggest the observed particle size dependence for propionaldehyde production via CO insertion is driven by two factors: (i) an increase in propionaldehyde formation on undercoordinated Rh sites and (ii) creation of carbonyl hydride species (Rh(CO)H)) on smaller Rh particles, whose presence correlates with the lower activity for propionaldehyde formation for < 2.5 nm.


Assuntos
Físico-Química/métodos , Nanopartículas Metálicas/química , Ródio/química , Dióxido de Silício/química , Aldeídos/química , Monóxido de Carbono/química , Catálise , Etilenos/química , Cinética , Tamanho da Partícula , Espectrofotometria Infravermelho , Relação Estrutura-Atividade , Propriedades de Superfície
18.
Faraday Discuss ; 152: 267-76; discussion 293-306, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22455050

RESUMO

Au deposited on Ru(0001)-supported extended, continuous graphene moiré forms large 2-D islands at room temperature that are several nanometers in diameter but only 0.55 nm in height, in the apparent absence of typical binding sites such as defects and adsorbates. These Au islands conform to the corrugation of the underlying graphene and display commensurate moiré patterns. Several extended Au structure models on graphene/Ru(0001) are examined using density functional theory calculations. Close-packed Au overlayers are energetically more stable, but all interact weakly with the support. Preliminary tests found the Au islands/graphene/Ru(0001) surface to be active for CO oxidation at cryogenic temperature, which suggests that the Au itself is the locus of catalytic activity.

19.
Langmuir ; 26(21): 16540-51, 2010 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-20504012

RESUMO

Microscopic and spectroscopic techniques at near-atmospheric pressures have been used in recent years to investigate CO oxidation over Pt-group metals. New insights have been obtained that allow broadening of the understanding of this reaction beyond the ultrahigh vacuum regime where it is well-understood. However, new issues also have arisen that need clarification. In this paper, we review recent work in our laboratory, using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and reaction kinetics measurements from ultrahigh vacuum to near-atmospheric pressures. These studies reveal a continuity of this reaction with respect to pressure over Pt, Pd, and Rh; that is, Langmuir-Hinshelwood kinetics is exhibited over a wide pressure range with no apparent "pressure gap". The difference between Ru(0001) and other noble metals is well-understood with respect to higher oxygen binding energies and reduced CO inhibition. It is concluded that for all Pt-group metals the most active phase is one saturated with chemisorbed oxygen and with low CO coverages. The significance of oxide phases under most industrially relevant catalytic conditions suggested recently in the literature is not consistent with the experimental data.


Assuntos
Monóxido de Carbono/química , Modelos Químicos , Platina/química , Dióxido de Carbono/síntese química , Dióxido de Carbono/química , Catálise , Cinética , Oxirredução , Tamanho da Partícula , Espectrofotometria Infravermelho , Propriedades de Superfície
20.
Chemphyschem ; 11(7): 1468-75, 2010 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-20394098

RESUMO

Pt-Co thin-film electrocatalysts have been characterized using low-energy ion-scattering spectroscopy (LEISS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), temperature-programmed desorption (TPD) and electrochemistry (EC). For comparative purposes, LEISS and EC were also carried out on a bulk Pt(3)Co(111) single crystal. The extensive experimental work resulted in the establishment of the surface phase diagram of the alloy film marked by a substantial divergence between the composition at the interface and that in the interior. When a dual-layer deposit of Pt and Co was annealed at high temperatures, alloy formation transpired in which the outermost layer became single-crystalline and enriched in Pt. The preferential surface segregation of Pt, however, was not sufficient to generate a platinum-only overlayer or "skin". Invariably, Co was found to co-exist with Pt, independent of the substrate [Mo(110) or Ru(0001)] employed; Pt(3)Co was the most favored composition. The same result, the absence of a Pt skin, was likewise indicated at the post-thermally-annealed surface of the bulk Pt(3)Co(111) monocrystal. For alloy-film surfaces more enriched in Pt than Pt(3)Co, the topmost layer was constituted primarily, but not exclusively, of Pt(111) domains. The proclivities of the alloys towards enhanced catalysis of the oxygen-reduction reaction were assessed in terms of their voltage efficiencies, as manifested by the open-circuit potential (OCP) in O(2)-saturated sulfuric acid electrolyte. The Pt(3)Co surface, whether from the thin film or the bulk single crystal, exhibited the highest OCP, a significant improvement over pure Pt but still appreciably lower than the thermodynamic limit. The degradation of the Pt(3)Co thin-film surface was predominantly due to Co corrosion. A minimal amount was spontaneously dissolved upon simple immersion in solution; slightly higher dissolution occurred at potentials above the OCP. The fraction that was not immediately corroded proved to be stable even after prolonged periods at potentials more positive than the OCP.


Assuntos
Cobalto/química , Oxigênio/química , Platina/química , Catálise , Eletroquímica , Membranas Artificiais , Estrutura Molecular , Oxirredução , Propriedades de Superfície
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