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1.
Chemphyschem ; 2022 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-36401599

RESUMO

The rapidly growing interest for new heterogeneous catalytic systems providing high atomic efficiency along with high stability and reactivity triggered an impressive progress in the field of single-atom catalysis. Nevertheless, unravelling the factors governing the interaction strength between the support and the adsorbed metal atoms remains a major challenge. Based on periodic Density Functional Theory (DFT) calculations, this paper provides insight into the adsorption of single late transition metals on a defect-free anatase surface. Depending on the considered transition metal, we could attribute the strength of this interaction with the support to: i) an electron transfer towards anatase (Ru, Rh, Ni), ii) s-d orbital hybridisation effects (Pt), or iii) a synergistic effect between both factors (Fe, Co, Os, Ir). The driving forces behind the adsorption were also found to be strongly related to Klechkowsky's rule for orbital filling. In contrast, the deviating behaviour of Pd is most likely associated with the lower dissociation enthalpy of the Pd-O bond. Additionally, the reactivity of these systems was evaluated using the Fermi weighted density of states approach. The resulting softness values can be clearly related to the electron configuration of the catalytic systems as well as with the net charge on the transition metal. Finally, these indices were used to construct a model that predicts the adsorption strength of CO on these anatase-supported d-metal atoms.

2.
Clin Nurse Spec ; 36(6): 317-326, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36279493

RESUMO

PURPOSE/AIMS: To explore nurses' perceptions of clinical nurse specialist practice as implemented in a highly specialized university hospital in Spain. DESIGN: A descriptive qualitative study was carried out in 3 inpatient wards, with a clinical nurse specialist within the team, at a high specialized university hospital in Spain. METHOD: Semistructured interviews were conducted by purposive sampling with 17 selected nurses with at least 2 years of professional experience who voluntarily agreed to participate and signed the informed consent form. Analysis of the qualitative data was conducted according to Burnard's method of content analysis. The Consolidated Criteria for Reporting Qualitative Research checklist was used. RESULTS: Four main categories emerged from the analysis of the data: "qualities of the role-holder," "role competencies in practice," "integration with the team," and "impact of the role" on nursing, the patient, and the organization. CONCLUSIONS: The findings of this study have interesting implications for the development and implementation of clinical nurse specialist practice in healthcare organizations. They also provide evidence of the benefit of implementing clinical nurse specialist practice for improving the quality of care, patient outcomes, and healthcare efficiency.


Assuntos
Enfermeiras Clínicas , Humanos , Espanha , Pesquisa Qualitativa , Atenção à Saúde , Hospitais
3.
J Phys Condens Matter ; 34(31)2022 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-35576919

RESUMO

Titanium dioxide is a key material in many fields, including technological, industrial and biomedical applications. Many of these applications are related to the surface reactivity of TiO2and involve its reducibility properties. Recently titania has been banned as a food additive due to its (nano)toxicity, and the release of reactive oxygen species plays a crucial role in many toxicological mechanisms. Determining chemical descriptors that account for the extension of reduction is necessary to understand such processes and necessary for predicting the reactivity of an unknown system. In the present work, we compute a set of chemical descriptors for selected surfaces of anatase and rutile TiO2. The aim is twofold: we want to provide chemically meaningful information on the surface reactivity, and benchmark the descriptors for twoab initioschemes. To do so, we compute the oxygen vacancy formation energy, and the corresponding electronic structure, in four slab models with two different computational schemes (DFT+Uand DFTB). In this way, we characterize the robustness of the dataset, with the purpose of scaling up to more realistic model systems such as nanoparticles or explicit solvent, which are too computationally demanding for state-of-the-art density functional theory approaches.


Assuntos
Nanopartículas , Oxigênio , Oxigênio/química , Solventes
4.
J Nurs Manag ; 30(4): 913-925, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35229386

RESUMO

AIM: This study aims to identify the most effective interventions to facilitate nurses' clinical leadership in the hospital setting. BACKGROUND: There is a gap in the literature on the identification and measurement of effective interventions for leadership skill development among clinical nurses in hospitals. To the best of our knowledge, no systematic review has been performed on this issue. EVALUATION: A systematic review was conducted. The PubMed, CINAHL, PsycINFO and Cochrane databases were reviewed. Data extraction, quality appraisal and narrative synthesis were conducted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. KEY ISSUES: The evidence reveals that interventions designed to promote nurses' clinical leadership are complex, requiring that cognitive, interpersonal and intrinsic competencies as well as psychological empowerment, emotional intelligence and critical reflexivity skills be addressed. CONCLUSIONS: The development of multicomponent, theory-based and mixed-format programmes may be more suitable to facilitate nurses' clinical leadership in the hospital setting. IMPLICATIONS FOR NURSING MANAGEMENT: Strategies to facilitate nurses' clinical leadership in the hospital setting should address simultaneously the knowledge and ability of bedsides nurses to solve the practical problem collaboratively with a sense of control, competency and autonomy. Hence, it would promote high quality care, satisfaction and retention of bedside nurses.


Assuntos
Liderança , Enfermeiras e Enfermeiros , Inteligência Emocional , Hospitais , Humanos , Qualidade da Assistência à Saúde
5.
Nanomaterials (Basel) ; 12(2)2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-35055235

RESUMO

Titanium dioxide nanoparticles have risen concerns about their possible toxicity and the European Food Safety Authority recently banned the use of TiO2 nano-additive in food products. Following the intent of relating nanomaterials atomic structure with their toxicity without having to conduct large-scale experiments on living organisms, we investigate the aggregation of titanium dioxide nanoparticles using a multi-scale technique: starting from ab initio Density Functional Theory to get an accurate determination of the energetics and electronic structure, we switch to classical Molecular Dynamics simulations to calculate the Potential of Mean Force for the connection of two identical nanoparticles in water; the fitting of the latter by a set of mathematical equations is the key for the upscale. Lastly, we perform Brownian Dynamics simulations where each nanoparticle is a spherical bead. This coarsening strategy allows studying the aggregation of a few thousand nanoparticles. Applying this novel procedure, we find three new molecular descriptors, namely, the aggregation free energy and two numerical parameters used to correct the observed deviation from the aggregation kinetics described by the Smoluchowski theory. Ultimately, molecular descriptors can be fed into QSAR models to predict the toxicity of a material knowing its physicochemical properties, enabling safe design strategies.

6.
J Adv Nurs ; 78(2): 363-376, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34363636

RESUMO

AIMS: To identify the most effective interventions to empower cardiorenal patients. DESIGN: A systematic review of the literature has been carried out. DATA SOURCES: The PubMed, CINAHL, PsycINFO and Cochrane databases were reviewed, and journals in the field were manually searched between January and February 2020. REVIEW METHODS: Five randomized clinical trials and quasi-experimental studies that met the selection and CONSORT & TREND methodological quality criteria were selected. RESULTS: The evidence supports that there are no existing interventions aimed at empowering cardiorenal patients. However, the interventions to empower people with chronic kidney disease and heart failure suggest that their integration should address seven domains: patient education, sense of self-management, constructive coping, peer sharing, enablement, self-efficacy and quality of life. CONCLUSION: A gap has been revealed in the literature regarding the empowerment of cardiorenal patients. This review provides relevant information to help design, implement and evaluate interventions to empower these patients by describing the strategies used to empower people experiencing both chronic conditions and the tools used for their assessment. IMPACT: There is a need for further research to design, implement and evaluate a multidimensional intervention that favours the empowerment of cardiorenal patients by using valid and reliable instruments that measure the domains that constitute it in an integrated manner. Interventions aimed at empowering the cardiorenal patient should include seven domains: patient education, sense of self-management, constructive coping, peer sharing, enablement, self-efficacy and quality of life.


Assuntos
Qualidade de Vida , Autogestão , Adaptação Psicológica , Doença Crônica , Humanos , Autoeficácia
7.
Nurs Health Sci ; 24(1): 123-131, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34761512

RESUMO

Understanding the unique experience of nursing students providing frontline support in COVID-19 hospital wards is crucial for the design of strategies to improve crisis management and mitigate future pandemic outbreaks. Limited research concerning this phenomenon has been published. This qualitative study aimed to understand the experience of providing support from COVID-19 frontline nursing students' perspective. Online interviews were conducted with nine nursing students from April to May 2020; interview data were analyzed by content analysis using Burnard's method. Six main categories emerged from the data analysis: "experiencing a rapid transition from student to professional," "fear and uncertainty of the unknown," "resilience throughout the crisis," "sense of belonging to a team," "shared responsibility," and "importance of the profession." Based on these findings, multicomponent strategies that function in parallel with practical contexts should be developed to enable students to diligently adapt their abilities to their new role and cope with health crises.


Assuntos
COVID-19 , Estudantes de Enfermagem , Humanos , Pandemias , Pesquisa Qualitativa , SARS-CoV-2
8.
J Nurs Manag ; 30(1): 79-89, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34592013

RESUMO

AIM: To explore experiences of frontline nurse managers during COVID-19. BACKGROUND: The COVID-19 pandemic has complicated care provision and healthcare management around the world. Nurse managers have had to face the challenge of managing a crisis with precarious resources. Little research has been published about the experiences of nurse managers during the COVID-19 pandemic. METHODS: A qualitative descriptive study of 10 frontline nurse managers at a highly specialized university hospital in Spain was carried out. Semi-structured interviews were conducted between June and September 2020. The Consolidated Criteria for Reporting Qualitative Research checklist was used for reporting. RESULTS: Six themes emerged: constant adaptation to change, participation in decision-making, management of uncertainty, prioritization of the biopsychosocial well-being of the staff, preservation of humanized care and 'one for all'. CONCLUSIONS: This study provides evidence for the experiences of nurse managers during the COVID-19 pandemic. In addition, analysing these experiences has helped identify some of the key competencies that these nurses must have to respond to a crisis and in their dual role as patient and nurse mediators. IMPLICATIONS FOR NURSING MANAGEMENT: Knowing about the experiences of frontline nurse managers during the pandemic can facilitate planning and preparing nurse managers for future health disasters, including subsequent waves of COVID-19.


Assuntos
COVID-19 , Enfermeiras Administradoras , Humanos , Pandemias , Pesquisa Qualitativa , SARS-CoV-2
9.
Index enferm ; 31(2): [77-81], s.f.
Artigo em Espanhol | IBECS | ID: ibc-208875

RESUMO

Objetivo principal: Evaluar el nivel de satisfacción de las enfermeras nóveles con la simulación clínica de alta fidelidad en la formación de RCP, durante la Covid-19. Metodología: Estudio observacional descriptivo transversal. Se utilizó la Escala de Satisfacción en Simulación Clínica de Alta Fidelidad, cuestionario validado de 33 ítems con respuesta tipo Likert. Se utilizó estadística descriptiva, e inferencial no paramétrica (correlación de Spearman) para analizar la correlación entre las variables. Resultados principales: N=35 (100%). La satisfacción global media fue de 4,97±0,17. Los ítems relativos a la adecuación de los casos a los conocimientos de los participantes, la capacidad para proporcionar cuidados a los pacientes, el beneficio de la simulación e impacto en la mejora de sus habilidades técnicas fueron los mejores puntuados (media de 4,97). Se encontró una relación positiva y fuerte entre los ítems: 4-9, y 27-9 (rho= 0,804; p=0,000). Conclusión principal: El nivel de satisfacción de las enfermeras de nueva incorporación con la simulación clínica de alta fidelidad fue elevado, lo que confirma su utilidad en el proceso de aprendizaje en RCP durante la Covid-19 o brotes pandémicos de la misma naturaleza.(AU)


Objective: To assess the satisfaction of novel nurses with high-fidelity clinical simulation in CPR training, during Covid-19. Methods: Cross-sectional descriptive observational study. Satisfaction Scale in High Fidelity Clinical Simulation was used, a validated 33-item questionnaire with a Likert-type response. Descriptive statistics and non-parametric inferential statistics (Spearman's correlation) were used to analyze the correlation between the variables. Results: N = 35 (100%). The mean overal satisfaction was 4.97 ± 0.17. The items related to the adequacy of the cases to the knowledge of the participants, the ability to provide care to patients, the benefit of simulation and the impact on improving their technical skills were the best scored (mean of 4.97). A positive and strong relationship was found between items: 4-9, and 27-9 (rho = 0.804; p = 0.000). Conclusions: Satisfaction level of novel nurses with the high-fidelity clinical simulation was high, confirming its usefulness in the CPR learning process during Covid-19 or pandemic outbreaks of the same nature.(AU)


Assuntos
Humanos , Feminino , Reanimação Cardiopulmonar , Treinamento com Simulação de Alta Fidelidade , Interpretação Estatística de Dados , Estatísticas não Paramétricas , Enfermeiras e Enfermeiros , Pandemias , Betacoronavirus , Vírus da SARS , Infecções por Coronavirus , Epidemiologia Descritiva , Estudos Transversais , Enfermagem , Inquéritos e Questionários
10.
Nurse Educ Pract ; 50: 102963, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33422973

RESUMO

Nurses' continuing professional development (CPD) improves the quality of nursing care, patients' safety, nurses' satisfaction and healthcare costs. However, evidence has shown that nurses do not always participate in their CPD and that CPD does not always address nurses' real needs. To examine this issue, a systematic review of the literature on nurses' experiences regarding their CPD in the clinical context was carried out. The studies selected for this review (n = 9) were analyzed thematically, through which three themes were identified: The relevance of CPD to nurses; the intrinsic and extrinsic motivations of nurses to participate in CPD; and the specific needs of nurses to participate in CPD. The findings of this review highlight that nurses' experiences regarding their CPD is a key issue that has not been deeply studied. For nurses, their CPD continues throughout their professional career, and keeping their knowledge and skills up to date is important. The goals, motivations and needs that nurses may have to lead and participate in their CPD may vary according to their age and position. Organizations should consider nurses' specific professional situation as well as their actual needs to boost their CPD through different approaches and enhance nurses' retention at hospitals.


Assuntos
Educação Continuada em Enfermagem , Motivação , Recursos Humanos de Enfermagem/educação , Recursos Humanos de Enfermagem/psicologia , Hospitais , Humanos , Desenvolvimento de Pessoal
11.
J Clin Nurs ; 29(23-24): 4806-4817, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33007122

RESUMO

AIM: To describe and explain nurses' protocol-based care decision-making. BACKGROUND: Protocol-based care is a strategy to reduce variability in clinical practice. There are no studies looking at protocol-based care decision-making. Understand this process is key to successful implementation. METHOD: A multiple embedded case study was carried out. Nurses' protocol-based care decision-making was studied in three inpatient wards (medical, surgical and medical-surgical) of a university hospital in northern Spain. Data collection was performed between 2015 and 2016 including documentary analysis, non-participant observations, participant observations and interviews. Analysis of quantitative data involved descriptive statistics and qualitative data was submitted to Burnard's method of content analysis (1996). The data integration comprised the integration of the data set of each case separately and the integration of the findings resulting from the comparison of the cases. The following the thread method of data integration was used for this purpose. The SRQR guideline was used for reporting. RESULTS: The multiple embedded case study revealed protocol-based care decision-making as a linear and variable process that depends on the context and consists of multiple interrelated elements, among which the risk perception is foremost. CONCLUSION: This study has allowed progress in protocol-based care decision-making characterisation. This knowledge is crucial to support the design of educational and management strategies aimed at implementing protocol-based care. RELEVANCE TO CLINICAL PRACTICE: Strategies to promote protocol-based care should address the contexts of practice and the ability of professionals' to accurately assess the degree of risk of clinical activity. Hence, it will promote quality of care, patient safety and efficiency in healthcare cost.


Assuntos
Tomada de Decisões , Hospitais , Avaliação em Enfermagem , Humanos , Espanha
12.
Nanomaterials (Basel) ; 9(9)2019 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-31454939

RESUMO

Titanium oxide (TiO2) has been widely used in many fields, such as photocatalysis, photovoltaics, catalysis, and sensors, where its interaction with molecular H2 with TiO2 surface plays an important role. However, the activation of hydrogen over rutile TiO2 surfaces has not been systematically studied regarding the surface termination dependence. In this work, we use density functional theory (PBE+U) to identify the pathways for two processes: the heterolytic dissociation of H2 as a hydride-proton pair, and the subsequent H transfer from Ti to near O accompanied by reduction of the Ti sites. Four stoichiometric surface orientations were considered: (001), (100), (110), and (101). The lowest activation barriers are found for hydrogen dissociation on (001) and (110), with energies of 0.56 eV and 0.50 eV, respectively. The highest activation barriers are found on (100) and (101), with energies of 1.08 eV and 0.79 eV, respectively. For hydrogen transfer from Ti to near O, the activation barriers are higher (from 1.40 to 1.86 eV). Our results indicate that the dissociation step is kinetically more favorable than the H transfer process, although the latter is thermodynamically more favorable. We discuss the implications in the stability of the hydride-proton pair, and provide structures, electronic structure, vibrational analysis, and temperature effects to characterize the reactivity of the four TiO2 orientations.

13.
Chemistry ; 25(46): 10938-10945, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31206860

RESUMO

Valence-shell electron-pair repulsion (VSEPR) theory constitutes one of the pillars of theoretical predictive chemistry. It was proposed even before the advent of the concept of "spin", and it is still a very useful tool in chemistry. In this article we propose an extension of VSEPR theory to understand the core structure and predict core polarization in the main-group elements. We show from first principles (Electron Localization Function analysis) how the inner- and outer-core shells are organized. In particular, electrons in these regions are structured following the shape of the dual polyhedron of the valence shell (3rd period) or the equivalent polyhedron (4th and 5th periods). We interpret these results in terms of "hard" and "soft" core character. All the studied systems follow this trend, providing a framework for predicting electron distribution in the core. We also show that lone pairs behave as "standard ligands" in terms of core polarization. The predictive character of the model was tested by proposing the core polarization in different systems not included in the original set (such as XeF4 and [Fe(CN)6 ]3- ) and checking the hypothesis by means of a posteriori calculations. From the experimental point of view, the extension of VSEPR to the core region has consequences for current crystallography research. In particular, it explains the core polarization revealed by high resolution X-ray experiments.

14.
J Pharm Sci ; 108(10): 3340-3347, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31145922

RESUMO

Polymorphism commonly exists in the preparation of cocrystals and has attracted widespread attention from both the pharmaceutical industry and academia. However, few studies have examined how to discover polymorphic cocrystals and their potential formation mechanism. In this study, we report the novel discovery of salicylic acid: 3-nitrobenzamide (SA-3NBZ) polymorphic cocrystals by thermal methods. The formation mechanism is elucidated based on theoretical calculations. SA-3NBZ polymorphic cocrystals with molar ratio of 1:1 and 2:2 were discovered using the combination of differential scanning calorimetry and hot stage microscopy. Single-crystal X-ray diffraction analysis confirmed this discovery. Density functional theory calculations corrected with dispersion were conducted to illustrate the energetic stabilization of SA polymorphic cocrystals. Compared with the starting materials, formation of the cocrystals at 1:1 and 2:2 present a weak stabilization with overall energy reduction of -0.01 and -0.05 eV/molecule, respectively. The calculated noncovalent interactions index further suggests that intralayer hydrogen bonds and van der Waals forces contribute to these weak interactions. The density functional theory calculations are in good agreement with the X-ray diffraction data. Hence, thermal analysis is a simple and reliable method to discover polymorphic cocrystals.


Assuntos
Cristalização/métodos , Benzamidinas , Varredura Diferencial de Calorimetria/métodos , Cristalografia por Raios X/métodos , Ligação de Hidrogênio , Modelos Moleculares , Difração de Pó/métodos , Ácido Salicílico/química , Solubilidade , Difração de Raios X/métodos
15.
Front Chem ; 7: 37, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30792977

RESUMO

Oxygen vacancies are related to specific optical, conductivity and magnetic properties in macroscopic SiO2 and TiO2 compounds. As such, the ease with which oxygen vacancies form often determines the application potential of these materials in many technological fields. However, little is known about the role of oxygen vacancies in nanosized materials. In this work we compute the energies to create oxygen vacancies in highly stable nanoclusters of (TiO2)N, (SiO2)N, and mixed (TixSi1-xO2)N for sizes between N = 2 and N = 24 units. Contrary to the results for bulk and surfaces, we predict that removing an oxygen atom from global minima silica clusters is energetically more favorable than from the respective titania species. This unexpected chemical behavior is clearly linked to the inherent presence of terminal unsaturated oxygens at these nanoscale systems. In order to fully characterize our findings, we provide an extensive set of descriptors (oxygen vacancy formation energy, electron localization, density of states, relaxation energy, and geometry) that can be used to compare our results with those for other compositions and sizes. Our results will help in the search of novel nanomaterials for technological and scientific applications such as heterogeneous catalysis, electronics, and cluster chemistry.

16.
Nanoscale ; 10(45): 21518-21532, 2018 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-30427364

RESUMO

Nanoscale titania (TiO2) and silica (SiO2) are massively produced technologically important nanomaterials used in a wide range of technological applications where nano-titania is the active component (e.g. water splitting, pollution remediation, self-cleaning coatings). Generally, these applications entail contact with water and a degree of hydration of these nano-oxides. Although the hydration of nano-silica has been fairly well studied, the corresponding level of microscopic understanding for nano-titania is severely lacking. Here, using accurate electronic structure calculations we perform a detailed and comprehensive study of the hydration of titania nanoclusters. Firstly, using global optimisation, we establish the most energetically stable structures of a set of (TiO2)M(H2O)N nanoclusters with sizes ranging through M = 4-16 and with N/M ratios of ≤ 1.0. Using this extensive dataset we investigate how the structures, energy gaps, and thermodynamic stabilities of these species depend on size, temperature and water vapour pressure. To provide a broader chemical context for our study we also provide this full set of data for the respective set of (SiO2)M(H2O)N nanoclusters which we use to compare and contrast their properties with those of nano-titania. Our broad systematic study thus provides a comparative and foundational reference study for a thorough understanding of how hydration affects the structure, energetics and properties of both nano-SiO2 and nano-TiO2.

17.
ACS Omega ; 3(11): 16063-16073, 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31458244

RESUMO

The ability of ceria to break H2 in the absence of noble metals has prompted a number of studies because of its potential applications in many technological fields. Most of the theoretical works reported in the literature are focused on the most stable (111) termination. However, recently, the possibility of stabilizing ceria particles with selected terminations has opened new avenues to explore. In the present paper, we investigate the role of termination in H2 dissociation on stoichiometric ceria. We model (111)-, (110)-, and (100)-terminated slabs together with the stepped (221) and (331) surfaces. Our results support a dissociation mechanism proceeding via the formation of a hydride/hydroxyl CeH/OH intermediate. Both the stability of such an intermediate and the activation energy depend critically on the termination, the (100)-terminated surfaces being the most reactive: the activation energy is 0.16 eV, and the CeH/OH intermediate is stable by -0.64 eV for the (100) slab, whereas the (111) slab presents 0.75 and 0.74 eV, respectively. We provide structural, energetic, electronic, and spectroscopic data, as well as chemical descriptors correlating structure, energy, and reactivity, to guide in the theoretical and experimental characterization of the Ce-H surface intermediate.

18.
Nanoscale ; 10(2): 832-842, 2018 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-29261197

RESUMO

Nanostructured titanosilicate materials based upon interfacing nano-TiO2 with nano-SiO2 have drawn much attention due to their huge potential for applications in a diverse range of important fields including gas sensing, (photo)catalysis, solar cells, photonics/optical components, tailored multi-(bio)functional supports and self-cleaning coatings. In each case it is the specific mixed combination of the two SiO2 and TiO2 nanophases that determines the unique properties of the final nanomaterial. In the bulk, stoichiometric mixing of TiO2 with SiO2 is limited by formation of segregated TiO2 nanoparticles or metastable glassy phases and more controlled disperse crystalline mixings only occur at small fractions of TiO2 (<15 wt%). In order to more fully understand the stability of nano-SiO2 and nano-TiO2 combinations with respect to composition and size, we employ accurate all-electron density functional calculations to evaluate the mixing energy in (TixSi1-xO2)n nanoclusters with a range of sizes (n = 2-24) having different titania molar fractions (x = 0-1). We derive all nanoclusters from a dedicated global optimisation procedure to help ensure that they are the most energetically stable structures for their size and composition. We also consider a selection of representative intimately mixed crystalline solid phase (TixSi1-xO2)bulk systems for comparison. In agreement with experiment, we find that homogeneous mixing of SiO2 and TiO2 in bulk crystalline phases is energetically unfavourable. Conversely, we find that SiO2-TiO2 mixing is energetically favoured in small (TixSi1-xO2)n nanoclusters. Following the evolution of mixing energy with nanocluster size and composition we find that mixing is most favoured in nanoclusters with a diameter of 1 nm with TiO2 molar fractions between 0.3-0.5. Thereafter, mixed nanoclusters with increasing size have progressively less negative mixing energies up to diameters of approximately 1.5 nm. We propose some chemical-structural principles to help rationale this energetically favourable nanoscale mixing. As a guide for experimentalists to observe and characterize these mixed nano-species we also provide two measurable signatures of mixing based on their unique vibrational and structural characteristics.

19.
J Phys Chem A ; 122(4): 1104-1113, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29286673

RESUMO

A detailed density functional theory study is presented to clarify the mechanistic aspects of the methanol (CH3OH) dehydrogenation process to yield hydrogen (H2) and formaldehyde (CH2O). A gas-phase vanadium oxide cluster is used as a model system to represent reduced V(III) oxides supported on TiO2 catalyst. The theoretical results provide a complete scenario, involving several reaction pathways in which different methanol adsorption sites are considered, with presence of hydride and methoxide intermediates. Methanol dissociative adsorption process is both kinetically and thermodynamically feasible on V-O-Ti and V═O sites, and it might lead to form hydride species with interesting catalytic reactivity. The formation of H2 and CH2O on reduced vanadium sites, V(III), is found to be more favorable than for oxidized vanadium species, V(V), taking place along energy barriers of 29.9 and 41.0 kcal/mol, respectively.

20.
Crit Care Med ; 46(2): 181-188, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29023261

RESUMO

OBJECTIVES: The "Pneumonia Zero" project is a nationwide multimodal intervention based on the simultaneous implementation of a comprehensive evidence-based bundle measures to prevent ventilator-associated pneumonia in critically ill patients admitted to the ICU. DESIGN: Prospective, interventional, and multicenter study. SETTING: A total of 181 ICUs throughout Spain. PATIENTS: All patients admitted for more than 24 hours to the participating ICUs between April 1, 2011, and December 31, 2012. INTERVENTION: Ten ventilator-associated pneumonia prevention measures were implemented (seven were mandatory and three highly recommended). The database of the National ICU-Acquired Infections Surveillance Study (Estudio Nacional de Vigilancia de Infecciones Nosocomiales [ENVIN]) was used for data collection. Ventilator-associated pneumonia rate was expressed as incidence density per 1,000 ventilator days. Ventilator-associated pneumonia rates from the incorporation of the ICUs to the project, every 3 months, were compared with data of the ENVIN registry (April-June 2010) as the baseline period. Ventilator-associated pneumonia rates were adjusted by characteristics of the hospital, including size, type (public or private), and teaching (postgraduate) or university-affiliated (undergraduate) status. MEASUREMENTS AND MAIN RESULTS: The 181 participating ICUs accounted for 75% of all ICUs in Spain. In a total of 171,237 ICU admissions, an artificial airway was present on 505,802 days (50.0% of days of stay in the ICU). A total of 3,474 ventilator-associated pneumonia episodes were diagnosed in 3,186 patients. The adjusted ventilator-associated pneumonia incidence density rate decreased from 9.83 (95% CI, 8.42-11.48) per 1,000 ventilator days in the baseline period to 4.34 (95% CI, 3.22-5.84) after 19-21 months of participation. CONCLUSIONS: Implementation of the bundle measures included in the "Pneumonia Zero" project resulted in a significant reduction of more than 50% of the incidence of ventilator-associated pneumonia in Spanish ICUs. This reduction was sustained 21 months after implementation.


Assuntos
Pneumonia Associada à Ventilação Mecânica/prevenção & controle , Cuidados Críticos/métodos , Humanos , Unidades de Terapia Intensiva , Pneumonia Associada à Ventilação Mecânica/epidemiologia , Guias de Prática Clínica como Assunto , Avaliação de Programas e Projetos de Saúde , Estudos Prospectivos , Espanha
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