Correction: In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111).

Correction for 'In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111)' by Daniel Arribas et al., Nanoscale, 2023, https://doi.org/10.1039/d3nr02564k.

In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111).

The catalytic dehydrogenation of alkanes constitutes a key step for the industrial conversion of these inert sp3-bonded carbon chains into other valuable unsaturated chemicals. To this end, platinum-based materials are among the most widely used catalysts. In this work, we characterize the thermal dehydrogenation of n-octane (n-C8H18) on Pt(111) under ultra-high vacuum using synchrotron-radiation X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning tunneling microscopy, combined with ab initio calculations. At low activation temperatures, two different dehydrogenation stages are observed. At 330 K, n-C8H18 effectively undergoes a 100% regioselective single C-H bond cleavage at one methyl end. At 600 K, the chemisorbed molecules undergo a double dehydrogenation, yielding double bonds in their carbon skeletons. Diffusion of the dehydrogenated species leads to the formation of carbon molecular clusters, which represents the first step towards poisoning of the catalyst. Our results reveal the chemical mechanisms behind the first stages of alkane dehydrogenation on a platinum model surface at the atomic scale, paving the way for designing more efficient dehydrogenation catalysts.

Metal-catalyst-free gas-phase synthesis of long-chain hydrocarbons.

Development of sustainable processes for hydrocarbons synthesis is a fundamental challenge in chemistry since these are of unquestionable importance for the production of many essential synthetic chemicals, materials and carbon-based fuels. Current industrial processes rely on non-abundant metal catalysts, temperatures of hundreds of Celsius and pressures of tens of bars. We propose an alternative gas phase process under mild reaction conditions using only atomic carbon, molecular hydrogen and an inert carrier gas. We demonstrate that the presence of CH2 and H radicals leads to efficient C-C chain growth, producing micron-length fibres of unbranched alkanes with an average length distribution between C23-C33. Ab-initio calculations uncover a thermodynamically favourable methylene coupling process on the surface of carbonaceous nanoparticles, which is kinematically facilitated by a trap-and-release mechanism of the reactants and nanoparticles that is confirmed by a steady incompressible flow simulation. This work could lead to future alternative sustainable synthetic routes to critical alkane-based chemicals or fuels.

On-Surface Driven Formal Michael Addition Produces m-Polyaniline Oligomers on Pt(111).

On-surface synthesis is emerging as a highly rational bottom-up methodology for the synthesis of molecular structures that are unattainable or complex to obtain by wet chemistry. Here, oligomers of meta-polyaniline, a known ferromagnetic polymer, were synthesized from para-aminophenol building-blocks via an unexpected and highly specific on-surface formal 1,4 Michael-type addition at the meta position, driven by the reduction of the aminophenol molecule. We rationalize this dehydrogenation and coupling reaction mechanism with a combination of in situ scanning tunneling and non-contact atomic force microscopies, high-resolution synchrotron-based X-ray photoemission spectroscopy and first-principles calculations. This study demonstrates the capability of surfaces to selectively modify local molecular conditions to redirect well-established synthetic routes, such as Michael coupling, towards the rational synthesis of new covalent nanostructures.

Macroscopic Versus Microscopic Schottky Barrier Determination at (Au/Pt)/Ge(100): Interfacial Local Modulation.

Macroscopic current-voltage measurements and nanoscopic ballistic electron emission spectroscopy (BEES) have been used to probe the Schottky barrier height (SBH) at metal/Ge(100) junctions for two metal electrodes (Au and Pt) and different metallization methods, specifically, thermal-vapor and laser-vapor deposition. Analysis of macroscopic current-voltage characteristics indicates that a SBH of 0.61-0.63 eV controls rectification at room temperature. On the other hand, BEES measured at 80 K reveals the coexistence of two distinct barriers at the nanoscale, taking values in the ranges 0.61-0.64 and 0.70-0.74 eV for the cases studied. For each metal-semiconductor junction, the macroscopic measurement agrees well with the lower barrier found with BEES. Ab initio modeling of BEES spectra ascribes the two barriers to two different atomic registries between the metals and the Ge(100) surface, a significant relevant insight for next-generation highly miniaturized Ge-based devices.

Effects of Li Confined Motion on NMR Quadrupolar Interactions: A Combined 7 Li NMR and DFT-MD Study of LiR2 (PO4 )3 (R=Ti or Zr) Phases.

Ab initio molecular dynamics (MD) simulations and NMR GIPAW (gauge including projector augmented wave) calculations have been used to analyze the coordination and mobility of Li ions in LiTi2 (PO4 )3 (rhombohedral), LiZr2 (PO4 )3 (triclinic), and LiZr2 (PO4 )3 (rhombohedral) phases. Significant discrepancies are observed between static calculations of 7 Li quadrupolar parameters and experimental values. The dynamical origin of this disagreement is demonstrated by incorporating in the calculations thermal vibrations and local motion of atoms with MD simulations. For LiTi2 (PO4 )3 , the quadrupolar constant associated with Li ions grows with temperature because the local symmetry of the system decreases, whereas for the Zr phases, the quadrupolar constant decreases because thermal vibrations reduce the anisotropy of the interaction. Finally, for both Zr phases, MD yields Li distributions that compare well with disorder reported from diffraction studies.

The association of parents' behaviors related to salt with 24 h urinary sodium excretion of their children: A Spanish cross-sectional study.

BACKGROUND: Sodium intake is excessive among Spanish children, but the salt use behaviors of parents and children are unknown. This study aims to determine behaviors related to salt intake in both schoolchildren and parents and the relationship between parental behaviors and 24 h urinary sodium excretion (UNa-24h) in children. SUBJECTS AND METHODS: A convenience sample was taken from a cross-sectional analysis. Parents completed a self-reported questionnaire about their behaviors related to salt, and their responses were compared with the UNa-24h of their own children. The median test was used to identify differences in UNa-24h according to behaviors. Logistic regression was used to assess the relationship between the behaviors of parents and high sodium excretion in the children and the risk of children's use of table salt, adjusting for age, sex, and BMI. Multinomial logistic regression models, adjusted by the covariates, were used to study the children's salt preferences. RESULTS: A total of 329 schoolchildren from different Spanish provinces were included in the study (mean age: 9.0 ± 1.2 years, 157 girls). The majority of families (parents mean age: 42.0 ± 5.2 years) reported adding salt to food during cooking (92%), and 59% of them never looked at the sodium content on food labels. However, none of these behaviors were related to UNa-24h (p > 0.05). The use of iodized salt (53%), the presence of a salt shaker on the table (6%), and the use of table salt by fathers (57%), mothers (52%) or children (17%) increased the odds (p < 0.05) of children having a higher UNa-24h. Checking sodium content on food labels and the use of table salt by the children or father was associated with a lower preference for salty foods (p < 0.05). CONCLUSIONS: It is important to make parents aware of the relationship between their behaviors regarding the use of discretionary salt and their children's sodium intake. Our data suggest that salt-specific education programs on how to reduce salt both in-home and outside the home should be implemented to improve behavior skills related to salt consumption in parents and children.

Hydrogen in α-iron: role of phonons in the diffusion of interstitials at high temperature.

Ab-initio Density Functional Theory has been used to compute phonons for interstitial hydrogen in α-iron. In the harmonic approximation, these phonons yield Helmholtz's free energy as a function of temperature, which can be used to obtain diffusion barriers from an Arrhenius plot. By comparing with the experimental database compiled by Kiuchi and McLellan, we show that the role of phonons is crucial to understand the diffusion of interstitial hydrogen at T > 300 K. The computed specific heat for Fe16H and Fe behaves quite differently due to the appearance of optical modes and could be used to calibrate the amount of interstitials in the iron matrix.

On-Surface Hydrogen-Induced Covalent Coupling of Polycyclic Aromatic Hydrocarbons via a Superhydrogenated Intermediate.

The activation, hydrogenation, and covalent coupling of polycyclic aromatic hydrocarbons (PAHs) are processes of great importance in fields like chemistry, energy, biology, or health, among others. So far, they are based on the use of catalysts which drive and increase the efficiency of the thermally- or light-induced reaction. Here, we report on the catalyst-free covalent coupling of nonfunctionalized PAHs adsorbed on a relatively inert surface in the presence of atomic hydrogen. The underlying mechanism has been characterized by high-resolution scanning tunnelling microscopy and rationalized by density functional theory calculations. It is based on the formation of intermediate radical-like species upon hydrogen-induced molecular superhydrogenation which favors the covalent binding of PAHs in a thermally activated process, resulting in large coupled molecular nanostructures. The mechanism proposed in this work opens a door toward the direct formation of covalent, PAH-based, bottom-up synthesized nanoarchitectures on technologically relevant inert surfaces.

How Au Outperforms Pt in the Catalytic Reduction of Methane towards Ethane and Molecular Hydrogen.

Within the context of a "hydrogen economy", it is paramount to guarantee a stable supply of molecular hydrogen to devices such as fuel cells. At the same time, catalytic conversion of the environmentally harmful methane into ethane, with a significantly lower Global Warming Potential, turns into a highly desirable challenge. Herein we propose a first-step novel proof-of-concept mechanism to accomplish both tasks simultaneously. For that purpose we provide transition-state barriers and reaction Helmholtz free energies obtained from first-principles Density Functional Theory by taking account vibrations for 2CH4(g) → C2H6(g) + H2(g) to show that molecular hydrogen can be produced by subnanometer Pt38 and Au38 nanoparticles from natural gas. Interestingly, the active sites for the reaction are located on different planes on the two nanoparticles, effectively differentiating the working principle of the two metals. The analysis shows that the complete cycle to reduce CH4 can be performed on Au and Pt with similar efficiencies, but Au requires only half the working temperature of Pt. This substantial decrease of temperature can be traced back to several intermediate steps, but most crucially to the final one where the catalyst must be cleaned from H(⋆) to be able to restart the catalytic cycle. This simple study case provides useful guidelines to capitalize on finite-size effects in small nanoparticles for the design of new and more efficient catalysts. Interestingly, present results obtained for the intermediate steps of the catalytic cycle show an excellent agreement with previous experimental evidence. Finally, we stress the importance of including the final cleaning steps to start a new fresh catalytic cycle.

On-Surface Bottom-Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior.

On-surface synthesis is an emerging approach to obtain, in a single step, precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. A facile on-surface chemistry route has now been used to synthesize the strong electron-acceptor organic molecule quinoneazine directly on a Cu(110) surface, via thermally activated covalent coupling of para-aminophenol precursors. The mechanism is described using a combination of in situ surface characterization techniques and theoretical methods. Owing to a strong surface-molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings, conferring azo-character at the nitrogen sites.

Irradiación parcial acelerada de mama (apbi) después de cuadrantectomía más biopsia del ganglio centinela axilar: características clínico-patológicas e inmunohistoquímicas / Accelerated partial breast irradiation (apbi) after breast conservative surgery plus sentinel node biopsy: clinical-pathological and immunohistochemical characteristics

Introducción El tratamiento estándar en estadios tempranos del cáncer de mama es la cirugía conservadora (cc) más radioterapia del volumen total mamario (wbi). Dado que la mayoría de las recidivas locales ocurren cercanas al sitio del tumor (85%) y existiendo la posibilidad de acortar tiempos de irradiación ­debido a que esta insume varias semanas­, podría no ser necesario irradiar toda la mama, sino el área donde estaba situado el tumor más margen de seguridad, lo que insume un menor tiempo. Este el fundamento de la Irradiación Parcial Acelerada Mama (apbi). Consensos internacionales proporcionan guías para administrar apbi fuera de ensayos clínicos. Objetivos El objetivo principal de este trabajo es determinar y analizar las características clinico-anatomopatológicas e inmunohistoquímicas de las pacientes que fueron operadas y luego seleccionadas para ser irradiadas con técnica de apbi con radioterapia externa con intensidad modulada guiada por imágenes (imrt). Material y método Se trata de un trabajo prospectivo, no randomizado. La muestra está constituida por las primeras 20 pacientes ingresadas al protocolo apbi. El reclutamiento se realizó entre marzo de 2012 y julio de 2014. Se analizaron las características clínico-patológicas e inmunohistoquímicas de esas pacientes luego de cc más biopsia del ganglio centinela (bgc). Resultados Media de seguimiento en meses: 37,7 (r: 22-51); edad media: 65,7 años. Tamaño tumoral medio por anatomía patológica: 12,03 mm. Media de número de ganglios centinelas extirpados: 1,7. Todos los tumores fueron unifocales. Los márgenes quirúrgicos resultaron negativos en todos los casos. Tumores Luminal A: 19 pacientes; tumores Luminal B: 1 paciente. Hormonoterapia adyuvante en todas las pacientes. Control locorregional: 100%. Conclusiones A pesar del corto tiempo de seguimiento y del escaso número de pacientes, este análisis sugiere que la apbi en el lecho del tumor marcado intraoperatoriamente con fiduciales de titanio es factible para pacientes que reúnen los criterios estrictos clínico-patológicos e inmunohistoquímicos acordes con las guías internacionales.

Introduction The standard conservative treatment for early stage breast carcinomas is the breast conservative surgery plus whole breast irradiation. Because most local recurrences occur close to the site of the primary tumor (80- 90%) and the possibility of shortening the irradiation times ­because it takes several weeks­, it may not be necessary to irradiate the entire breast, but the area where the tumor was located plus a margin of safety in less time. This is the basis of Accelerated Partial Irradiation of the Breast Objectives Determination and analysis of clinical-pathological and immunohistochemical characteristics in patients selected for Accelerated Partial Breast Irradiation (apbi) performed by imrt + igrt technique after breast conservative surgery plus sentinel node biopsy. Materials and method A prospective, non-randomized study of the first 20 patients performed apbi strictly following the recommendations of international consensus. It was initiated in March 2012 until July 2014. Clinical-pathological and immunohistochemical characteristics of these patients were analyzed to be selected for apbi, after breast conservative surgery plus sentinel node biopsy. Results Median follow up: 37.7 months (r: 22-51); average age: 65.7 years. Mean tumor size by pathological analysis: 12.03 mm. Mean number of sentinel nodes removed: 1.7. All tumors were unifocal. Negative surgical margins in all cases. Luminal A tumors: 19 patients; Luminal B tumors: 1 patient. Adjuvant hormone therapy in all patients. Loco-regional control: 100%. Conclusions Despite the short time of follow up and the small numbers of patients, this analysis suggests that apbi performed by imrt + igrt technique added to the placement of fiduciary marks at the time of surgery is feasible for highly selected patients who meet the clinical-pathological and immunohistochemical selection criteria according to international guidelines

Evaluación de la técnica de Biopsia de Ganglio Centinela Axilar a través de la incisión mamaria en la cirugía conservadora / Evaluation of Sentinel Lymph Node Axilar Biopsy through the mammary incision in conservative surgery

Introducción El abordaje del ganglio centinela por incisión mamaria única permite acceder al ganglio evitando la realización de incisión axilar, lo que disminuiría el linfedema, el dolor y las disestesias y mejoraría el resultado estético. Objetivos Describir el abordaje quirúrgico del ganglio centinela a través de la incisión mamaria utilizada para la tumorectomía del carcinoma mamario. Material y método Entre septiembre de 2013 y agosto de 2015, se evaluaron 83 pacientes consecutivas con axila clínicamente negativa, que fueron sometidas a cirugía conservadora más biopsia de ganglio centinela, un grupo mediante abordaje clásico (incisión axilar) y otro por la incisión mamaria. Se estudió: edad; tamaño tumoral y ubicación; tipo histológico; técnica de identificación del ganglio centinela; número de ganglios resecados; ganglios centinelas positivos; y complicaciones perioperatorias. Resultados La detección del ganglio centinela por una única incisión se logró en todas las pacientes (100% de éxito). La realización de una única incisión presentó menores complicaciones en comparación con las pacientes a las que se les realizó diferentes incisiones; además, se encontraron mejores resultados estéticos. Conclusiones El abordaje del ganglio centinela mediante la misma incisión de la cirugía mamaria conservadora presenta una excelente tasa de detección, ofreciendo menos complicaciones y mejores resultados estéticos.

Introduction The sentinel node approach through a single breast incision allows its detection avoiding axillary incision, which could reduce complications and improve aesthetic result. Objectives The aim of this work was to describe the surgical approach of sentinel node via the single incision used for conservative surgery for breast carcinoma. Materials and method Patients (n=83) with clinically negative axilla, who went through conservative surgery and axillary sentinel node biopsy using classical approach (axillary incision) and single breast incision, in early-stage breast cancer, were studied. Clinical, anatomical and pathological variables and perioperative complications were considered. Results Our results showed that the method of detection of sentinel node by a single breast incision was successful in 100 % of the cases. The performance of a single incision presented minor complications compared to patients who underwent different incisions; also better aesthetic results were also found. Conclusions The surgical approach of the sentinel node through the single incision of breast conserving surgery presents an excellent detection rate, fewer complications and better aesthetic results.

ß-Carotene Concentration and Its Association with Inflammatory Biomarkers in Spanish Schoolchildren.

AIM: To examine the correlation between inflammatory biomarkers and plasma ß-carotene levels in children. METHODS: A total of 564 Spanish schoolchildren aged 9-12 were observed and studied. Plasma ß-carotene levels were assessed by HPLC. A ß-carotene level <4.83 µg/dL (0.09 µmol/L) was considered deficient. Plasma tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured by immunoenzyme assays. Serum high-sensitivity C-reactive protein (hs-CRP) was tested by immunonephelometry. RESULTS: Subjects who were ß-carotene-deficient (23.1% of the studied children) had higher IL-6 levels than subjects with normal ß-carotene concentrations. The log-IL-6 and log-hs-CRP concentrations, but not the log-TNF-α level, were strongly and inversely related to the plasma log-ß-carotene level (taking into account log-age, energy intake, log-triglycerides, gender, log-body mass index, log-ß-carotene intake, energy from lipids and cholesterol as covariables). When the 3 inflammatory biomarkers were introduced into the regression model along with the corresponding covariables, only the log-IL-6 level was related to the plasma log-ß-carotene level (ß = -0.505 ± 0.078; p < 0.001). CONCLUSIONS: Inflammatory status, in particular IL-6 levels, appears to be negatively associated with plasma ß-carotene levels in schoolchildren.

Real-time acquisition of complex optical fields by binary amplitude modulation.

We describe, through simulations and experiments, a real-time wavefront acquisition technique using random binary amplitude masks and an iterative phase retrieval algorithm based on the Fresnel propagator. By using a digital micromirror device, it is possible to recover an unknown complex object by illuminating with this set of masks and simultaneously recording the resulting intensity patterns with a high-speed camera, making this technique suitable for dynamic applications.

Antioxidant status in a group of institutionalised elderly people with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is one of the most important and prevalent diseases suffered by the elderly. Evidence exists that its onset and severity might be conditioned by antioxidant status. The aim of the present study was to investigate the relationship between antioxidant status and COPD in institutionalised elderly people. In all, 183 elderly people aged >65 years (twenty-one had COPD and 160 healthy controls) were studied. The subjects' diets were investigated via the use of precise individual weighing for 7 d. Body weight, height, and biceps and triceps skinfold thickness were measured, and body fat (kg) and BMI (kg/m2) were calculated. Serum retinol, α-tocopherol, ß-carotene and vitamin C levels were determined. Subjects with COPD ate less fruits than healthy controls (117 (sd 52) v. 192 (sd 161) g/d), their coverage of the recommended intake of vitamin C was smaller (150 (sd 45) v. 191 (sd 88) %; note that both exceeded 100 %) and their diets had a lower antioxidant capacity (6558 (sd 2381) v. 9328 (sd 5367) mmol trolox equivalent/d). Those with COPD had lower serum vitamin C and α-tocopherol concentrations than healthy controls (32·4 (sd 15·3) v. 41·5 (sd 14·8) µmol/l and 12·1 (sd 3·2) v. 13·9 (sd 2·8) µmol/l, respectively). In addition, subjects with α-tocopherol <14·1µmol/l (50th percentile) were at 6·43 times greater risk of having COPD than those subjects with ≥14·1µmol/l (OR 6·43; 95 % CI 1·17, 35·24; P<0·05), taking sex, age, use of tobacco, body fat and vitamin E intake as covariables. Subjects with COPD had diets of poorer antioxidant quality, especially with respect to vitamins C and E, compared with healthy controls.

Image transmission through dynamic scattering media by single-pixel photodetection.

Smart control of light propagation through highly scattering media is a much desired goal with major technological implications. Since interaction of light with highly scattering media results in partial or complete depletion of ballistic photons, it is in principle impossible to transmit images through distances longer than the extinction length. Nevertheless, different methods for image transmission, focusing, and imaging through scattering media by means of wavefront control have been published over the past few years. In this paper we show that single-pixel optical systems, based on compressive detection, can also overcome the fundamental limitation imposed by multiple scattering to successfully transmit information. But, in contrast with the recently introduced schemes that use the transmission matrix technique, our approach does not require any a-priori calibration process that ultimately makes the present method suitable to use with dynamic scattering media. This represents an advantage over previous methods that rely on optical feedback wavefront control, especially for short speckle decorrelation times.

Etching of graphene in a Hydrogen-rich Atmosphere towards the Formation of Hydrocarbons in Circumstellar Clouds.

We describe a mechanism that explains the formation of hydrocarbons and hydrocarbyls from hydrogenated graphene/graphite; hard C-C bonds are weakened and broken by the synergistic effect of chemisorbed hydrogen and high temperature vibrations. Total energies, optimized structures, and transition states are obtained from Density Functional Theory simulations. These values have been used to determine the Boltzman probability for a thermal fluctuation to overcome the kinetic barriers, yielding the time scale for an event to occur. This mechanism can be used to rationalize the possible routes for the creation of small hydrocarbons and hydrocarbyls from etched graphene/graphite in stellar regions.

Moderate vitamin D deficiency and inflammation related markers in overweight/obese schoolchildren.

OBJECTIVE: Obesity has been associated with vitamin D deficiency and increased oxidative stress, which can lead to the dysregulation of adipokines and inflammation. The aim of the present work was to examine the association of vitamin D status [25(OH)D] on inflammatory related markers in overweight/obese children. SUBJECTS/METHODS: A total of 137 Spanish schoolchildren between 9 and 12 years of age (31.4% with overweight/obesity) were studied. Being overweight was defined as BMI≥85th percentile and obesity as BMI≥97th percentile using the reference tables of Hernández. Serum 25(OH)D concentrations were measured by chemiluminescent assay. Plasma tumor necrosis factor (TNF-α) and interleukin-6 (IL-6) were measured by immunoenzyme assay. Serum adiponectin was determined using an ELISA kit. Serum high-sensitivity C-reactive protein (hs-PCR) was tested by immunonephelometry. RESULTS: IL-6 concentrations were higher in the overweight/obese children with deficient serum 25(OH)D (<20 ng/mL) than in those in this group but whose serum 25(OH)D concentrations were adequate (≥20 ng/mL). Serum 25(OH)D was inversely associated with IL-6 concentrations in the overweight/obese subjects taking into account different covariates; thus, for every 1 ng/mL rise in the former, the latter fell by 0.160 pg/mL (ß=-0.160±0.068; R2=0.131; p=0.023). The obese subjects with concentrations of ≥25 ng/mL had lower hs-CRP values compared to those with concentrations of <25 ng/mL (0.053±0.035 vs. 0.356±0.613 mg/dL; p=0.035). CONCLUSION: Low serum 25(OH)D was significantly associated high serum IL-6 in overweight/obese children, and with increased hs-CRP in obese children.