GaAs/GaP Superlattice Nanowires for Tailoring Phononic Properties at the Nanoscale: Implications for Thermal Engineering.

The possibility to tune the functional properties of nanomaterials is key to their technological applications. Superlattices, i.e., periodic repetitions of two or more materials in one or more dimensions, are being explored for their potential as materials with tailor-made properties. Meanwhile, nanowires offer a myriad of possibilities to engineer systems at the nanoscale, as well as to combine materials that cannot be put together in conventional heterostructures due to the lattice mismatch. In this work, we investigate GaAs/GaP superlattices embedded in GaP nanowires and demonstrate the tunability of their phononic and optoelectronic properties by inelastic light scattering experiments corroborated by ab initio calculations. We observe clear modifications in the dispersion relation for both acoustic and optical phonons in the superlattices nanowires. We find that by controlling the superlattice periodicity, we can achieve tunability of the phonon frequencies. We also performed wavelength-dependent Raman microscopy on GaAs/GaP superlattice nanowires, and our results indicate a reduction in the electronic bandgap in the superlattice compared to the bulk counterpart. All of our experimental results are rationalized with the help of ab initio density functional perturbation theory (DFPT) calculations. This work sheds fresh insights into how material engineering at the nanoscale can tailor phonon dispersion and open pathways for thermal engineering.

Origin of the Critical Thickness in Improper Ferroelectric Thin Films.

Improper ferroelectrics are expected to be more robust than conventional ferroelectrics against depolarizing field effects and to exhibit a much-desired absence of critical thickness. Recent studies, however, revealed the loss of ferroelectric response in epitaxial improper ferroelectric thin films. Here, we investigate improper ferroelectric hexagonal YMnO3 thin films and find that the polarization suppression, and hence functionality, in the thinner films is due to oxygen off-stoichiometry. We demonstrate that oxygen vacancies form on the film surfaces to provide the necessary charge to screen the large internal electric field resulting from the positively charged YMnO3 surface layers. Additionally, we show that by modifying the oxygen concentration of the films, the phase transition temperatures can be substantially tuned. We anticipate that our findings are also valid for other ferroelectric oxide films and emphasize the importance of controlling the oxygen content and cation oxidation states in ferroelectrics for their successful integration in nanoscale applications.

Applications of a novel electron energy filter combined with a hybrid-pixel direct electron detector for the analysis of functional oxides by STEM/EELS and energy-filtered imaging.

The performance and suitability of a new electron energy filter in combination with a hybrid pixel, direct electron detector for analytical (scanning) transmission electron microscopy are demonstrated using four examples. The STEM-EELS capabilities of the CEOS Energy Filtering and Imaging Device (CEFID) were tested with focus on weak signals and high spatio-temporal resolution. A multiferroic, multilayer structure of REMnO3 (RE = Yb, Er, Tb, Y), grown on yttria-stabilized zirconia (YSZ), is used to exemplify that this new instrumental setup produces valuable electron energy-loss spectroscopy (EELS) data at high energy losses even when using short acquisition times, providing detailed chemical information about the interfaces in this complex multilayer sample. Another functional oxide, namely a ferromagnetic La2NiMnO6 thin film grown on SrTiO3, demonstrates that atomically resolved spectrum images can be recorded, using short dwell times and moderate beam currents in order to warrant the integrity of the sample. In a third example, inhomogeneously Er-doped YSZ shows by EELS spectrum imaging that elements at low concentrations can be detected semi-quantitatively, uncovering the expected layered Er distribution but revealing substantial interdiffusion. In a final example, we simply demonstrate that the hybrid pixel detector in combination with the energy filter can also be used for energy-filtered imaging and thus for elemental mapping complementary to EELS in scanning transmission mode.

Solid wetting-layers in inorganic nano-reactors: the water in imogolite nanotube case.

By combined use of wide-angle X-ray scattering, thermo-gravimetric analysis, inelastic neutron scattering, density functional theory and density functional theory molecular dynamics simulations, we investigate the structure, dynamics and stability of the water wetting-layer in single-walled aluminogermanate imogolite nanotubes (SW Ge-INTs): an archetypal system for synthetically controllable and monodisperse nano-reactors. We demonstrate that the water wetting-layer is strongly bound and solid-like up to 300 K under atmospheric pressure, with dynamics markedly different from that of bulk water. Atomic-scale characterisation of the wetting-layer reveals organisation of the H2O molecules in a curved triangular sublattice stabilised by the formation of three H-bonds to the nanotube's inner surface, with covalent interactions sufficiently strong to promote energetically favourable decoupling of the H2O molecules in the adlayer. The evidenced changes in the local composition, structure, electrostatics and dynamics of the Ge-INT's inner surface upon the formation of the solid wetting-layer demonstrate solvent-mediated functionalisation of the nanotube's cavity at room temperature and pressure, suggesting new strategies for the design of nano-rectors towards potential control of chemical reactivity in nano-confined volumes.

Engineering Transport in Manganites by Tuning Local Nonstoichiometry in Grain Boundaries.

Interface-dominated materials such as nanocrystalline thin films have emerged as an enthralling class of materials able to engineer functional properties of transition metal oxides widely used in energy and information technologies. In particular, it has been proven that strain-induced defects in grain boundaries of manganites deeply impact their functional properties by boosting their oxygen mass transport while abating their electronic and magnetic order. In this work, the origin of these dramatic changes is correlated for the first time with strong modifications of the anionic and cationic composition in the vicinity of strained grain boundary regions. We are also able to alter the grain boundary composition by tuning the overall cationic content in the films, which represents a new and powerful tool, beyond the classical space charge layer effect, for engineering electronic and mass transport properties of metal oxide thin films useful for a collection of relevant solid-state devices.

Atomic-Scale Determination of Cation Inversion in Spinel-Based Oxide Nanoparticles.

The atomic structure of nanoparticles can be easily determined by transmission electron microscopy. However, obtaining atomic-resolution chemical information about the individual atomic columns is a rather challenging endeavor. Here, crystalline monodispersed spinel Fe3O4/Mn3O4 core-shell nanoparticles have been thoroughly characterized in a high-resolution scanning transmission electron microscope. Electron energy-loss spectroscopy (EELS) measurements performed with atomic resolution allow the direct mapping of the Mn2+/Mn3+ ions in the shell and the Fe2+/Fe3+ in the core structure. This enables a precise understanding of the core-shell interface and of the cation distribution in the crystalline lattice of the nanoparticles. Considering how the different oxidation states of transition metals are reflected in EELS, two methods of performing a local evaluation of the cation inversion in spinel lattices are introduced. Both methods allow the determination of the inversion parameter in the iron oxide core and manganese oxide shell, as well as detecting spatial variations in this parameter, with atomic resolution. X-ray absorption measurements on the whole sample confirm the presence of cation inversion. These results present a significant advance toward a better correlation of the structural and functional properties of nanostructured spinel oxides.

Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial.

PURPOSE: Stenosis is the main cause of arteriovenous fistula (AVF) failure. It is still unclear whether surveillance based on vascular access blood flow (QA) enhances AVF function and longevity. METHODS: We conducted a three-year follow-up randomized, controlled, multicenter, open-label trial to compare QA-based surveillance and pre-emptive repair of subclinical stenosis with standard monitoring/surveillance techniques in prevalent mature AVFs. AVFs were randomized to either the control group (surveillance based on classic alarm criteria; n = 104) or to the QA group (QA measured quarterly using Doppler ultrasound [M-Turbo®] and ultrasound dilution [Transonic®] added to classic surveillance; n = 103).The criteria for intervention in the QA group were: 25% reduction in QA, QA<500 mL/min or significant stenosis with hemodynamic repercussion (peak systolic velocity [PSV] more than 400 cm/sc or PSV pre-stenosis/stenosis higher than 3). RESULTS: At the end of follow-up we observed a significant reduction in the thrombosis rate in the QA group (0.025 thrombosis/patient/year in the QA group vs. 0.086 thrombosis/patient/year in the control group [p = 0.007]). There was a significant improvement in the thrombosis-free patency rate (HR, 0.30; 95% CI, 0.11-0.82; p = 0.011) and in the secondary patency rate in the QA group (HR, 0.49; 95% CI, 0.26-0.93; p = 0.030), with no differences in the primary patency rate between the groups (HR, 0.98; 95% CI, 0.57-1.61; p = 0.935).There was greater need for a central venous catheter and more hospitalizations associated with vascular access in the control group (p = 0.034/p = 0.029).Total vascular access-related costs were higher in the control group (€227.194 vs. €133.807; p = 0.029). CONCLUSIONS: QA-based surveillance combining Doppler ultrasound and ultrasound dilution reduces the frequency of thrombosis, is cost effective, and improves thrombosis free and secondary patency in autologous AVF.

Hipertensión pulmonar en pacientes en hemodiálisis: prevalencia y factores asociados / Pulmonary hypertension in hemodialysis patients: Prevalence and associated factors

Introducción y objetivo: La hipertensión pulmonar (HTP) es un trastorno progresivo que puede deberse a enfermedades subyacentes o a una alteración intrínseca de la vascularización pulmonar. El aumento crónico de la presión en el árbol vascular pulmonar lleva a cambios en la arquitectura de los vasos que perpetúan la propia HTP y producen disfunción ventricular derecha; todo esto podría disminuir la supervivencia y calidad de vida de los pacientes. El objetivo de este estudio es establecer la prevalencia de HTP en los pacientes en hemodiálisis y su asociación con factores propios de este grupo de pacientes. Material y métodos: Incluimos a un total de 202 pacientes prevalentes en hemodiálisis durante al menos 6 meses y estables clínicamente, se recogieron datos demográficos, parámetros analíticos de rutina y los datos de un ecocardiograma doppler-2D. Definimos HTP como una presión sistólica de arteria pulmonar (PSAP) estimada mediante ecografía doppler por encima de 35 mmHg. El estado de hidratación se valoró mediante la determinación de los niveles de fragmento N terminal del péptido natriurético cerebral (Nt-proBNP). Resultados: La prevalencia de HTP fue del 37,1% (75 pacientes). La media de PSAP en toda la población estudiada fue de 32 ± 12 mmHg y en el grupo con HTP de 45 ± 11 mmHg. Encontramos una correlación directa estadísticamente significativa entre la presencia de HTP y la edad (p = 0,001), el tiempo en tratamiento renal sustitutivo (p = 0,04), la presencia de disfunción sistólica (p = 0,007), disfunción diastólica (p = 0,01), valvulopatía mitral (p = 0,01) y doble lesión mitral y aórtica (p = 0,007). La sobrecarga de volumen se asocia estrechamente con HTP como se demuestra por la correlación entre la PSAP y los niveles de Nt-ProBNP (p = 0,001). Conclusión: Concluimos que la prevalencia de HTP en los pacientes en hemodiálisis es alta y uno de los factores asociados más importante es la hipervolemia. Son necesarios más estudios para establecer el impacto de la HTP sobre la morbimortalidad de los pacientes y valorar si un mejor control de la volemia lleva a mejoría de la HTP (AU)

Background and objective: Pulmonary hypertension (PH) is a progressive disorder that can be caused by several underlying conditions or an intrinsic alteration of the pulmonary vasculature. Chronic increased pressure in the pulmonary vasculature leads to changes in the architecture of the vessels that can perpetuate PH and produce right ventricular dysfunction. These structural and functional alterations can decrease survival and quality of life of patients on hemodialysis; however, there is a lack of evidence about this problem in this population. The aim of this study is to establish the prevalence of PH in patients on hemodialysis and its association with specific factors related to this patient population. Material and methods: We included 202 prevalent patients on hemodialysis for at least 6 months and who were clinically stable. We collected demographic data, routine laboratory parameters and data of 2D Doppler-echocardiography. PH was defined as a systolic pulmonary artery pressure (SPAP) estimated by Doppler ultrasound above 35 mmHg. Hydration status was assessed by determining the plasma concentration of N-terminal pro brain natriuretic peptide (Nt-proBNP). Results: PH prevalence was 37.1% (75 patients). The average SPAP in the entire study population was 32 ± 12 mmHg and in the group with PH it was 45 ± 11 mmHg. We found a direct and statistically significant correlation between the presence of PH and age (P = .001), time on renal replacement therapy (P = .04), the presence of systolic dysfunction (P = .007), diastolic dysfunction (P = 01), mitral valve disease (P = .01) and double mitral and aortic disease (P = .007). Volume overload was closely associated with PH, as demonstrated by the correlation between the SPAP and Nt-proBNP levels (P = .001). Conclusion: We conclude that prevalence of PH in hemodialysis patients is high. And one of the most important associated factors is volume overload. More studies are needed to establish the impact of PH on morbidity and mortality of patients and to assess whether a better volume control improves PH (AU)

Pulmonary hypertension is an independent predictor of cardiovascular events and mortality in haemodialysis patients.

AIM: The evidence about prevalence, associated factors of pulmonary hypertension (PH) and its impact on patient's outcomes is limited. METHODS: We included 211 haemodialysis patients, we estimated the systolic pulmonary artery pressure (SPAP) by 2D Doppler echocardiography defining PH as a SPAP above 35 mmHg, the median follow-up was 39 (19-56) moths, and the primary endpoints were all cause mortality and cardiovascular events. RESULTS: We found PH in 91 patients (43.9%). Independent determinants of PH were age, previous cardiovascular disease, the Nt-pro-BNP level hs-TnT, the systolic dysfunction, diastolic dysfunction and left ventricular hypertrophy. Over the follow-up 94 cardiovascular events occurred, variables associated were: PH, age, history cardiovascular disease, dyslipidaemia, elevated concentration of Nt-pro-BNP and hs-TnT, systolic and diastolic dysfunction, in a multivariate model, the PH maintained its independent association. Mortality data: 88 patients died (41.7%); 35 (29.5%) in the no PH group and 53 (58.5%) in the PH group (P < 0.001). In the Cox survival analysis, we found an association between mortality and age, previous cardiovascular disease, history of peripheral vascular disease, Nt-pro-BNP levels. In a multivariate model the PH remains as independent predictor of mortality. CONCLUSIONS: Pulmonary hypertension is a common finding in HD patients and a valuable predictor of mortality and cardiovascular events. Prospective studies are needed to assess the effect of intervention on risk factors in improving patient's outcomes.

The impact of access blood flow surveillance on reduction of thrombosis in native arteriovenous fistula: a randomized clinical trial.

PURPOSE: The usefulness of access blood flow (QA) measurement is an ongoing controversy. Although all vascular access (VA) clinical guidelines recommend monitoring and surveillance protocols to prevent VA thrombosis, randomized clinical trials (RCTs) have failed to consistently show the benefits of QA-based surveillance protocols. We present a 3-year follow-up multicenter, prospective, open-label, controlled RCT, to evaluate the usefulness of QA measurement using Doppler ultrasound (DU) and ultrasound dilution method (UDM), in a prevalent hemodialysis population with native arteriovenous fistula (AVF). METHODS: Classical monitoring and surveillance methods are applied in all patients, the control group (n = 98) and the QA group (n = 98). Besides this, DU and UDM are performed in the QA group every three months. When QA is under 500 ml/min or there is a >25% decrease in QA the patient goes for fistulography, surgery or close clinical/surveillance observation. Thrombosis rate, assisted primary patency rate, primary patency rate and secondary patency rate are measured. RESULTS: After one-year follow-up we found a significant reduction in thrombosis rate (0.022 thrombosis/patient/year at risk in the QA group compared to 0.099 thrombosis/patient/year at risk in the control group [p = 0.030]). Assisted primary patency rate was significantly higher in the QA group than in control AVF (hazard ratio [HR] 0.23, 95% confidence interval [CI] 0.05-0.99; p = 0.030). In the QA group, the numbers unddergoing angioplasty and surgery were higher but with no significant difference in non-assisted primary patency rate (HR 1.41, 95% CI 0.72-2.84; p = 0.293). There was a non-significant improvement in secondary patency rate in the QA group (HR 0.510, 95% CI 0.17-1.50; p = 0.207). CONCLUSIONS: The measurement of QA combining DU and UDM shows a reduction in thrombosis rate and an increased assisted primary patency rate in AVF after one-year follow-up. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02111655.

[Pulmonary hypertension in hemodialysis patients: Prevalence and associated factors]. / Hipertensión pulmonar en pacientes en hemodiálisis: prevalencia y factores asociados.

BACKGROUND AND OBJECTIVE: Pulmonary hypertension (PH) is a progressive disorder that can be caused by several underlying conditions or an intrinsic alteration of the pulmonary vasculature. Chronic increased pressure in the pulmonary vasculature leads to changes in the architecture of the vessels that can perpetuate PH and produce right ventricular dysfunction. These structural and functional alterations can decrease survival and quality of life of patients on hemodialysis; however, there is a lack of evidence about this problem in this population. The aim of this study is to establish the prevalence of PH in patients on hemodialysis and its association with specific factors related to this patient population. MATERIAL AND METHODS: We included 202 prevalent patients on hemodialysis for at least 6 months and who were clinically stable. We collected demographic data, routine laboratory parameters and data of 2D Doppler-echocardiography. PH was defined as a systolic pulmonary artery pressure (SPAP) estimated by Doppler ultrasound above 35mmHg. Hydration status was assessed by determining the plasma concentration of N-terminal pro brain natriuretic peptide (Nt-proBNP). RESULTS: PH prevalence was 37.1% (75 patients). The average SPAP in the entire study population was 32±12mmHg and in the group with PH it was 45±11mmHg. We found a direct and statistically significant correlation between the presence of PH and age (P=.001), time on renal replacement therapy (P=.04), the presence of systolic dysfunction (P=.007), diastolic dysfunction (P= 01), mitral valve disease (P=.01) and double mitral and aortic disease (P=.007). Volume overload was closely associated with PH, as demonstrated by the correlation between the SPAP and Nt-proBNP levels (P=.001). CONCLUSION: We conclude that prevalence of PH in hemodialysis patients is high. And one of the most important associated factors is volume overload. More studies are needed to establish the impact of PH on morbidity and mortality of patients and to assess whether a better volume control improves PH.

Body Composition Affects Urea Distribution Volume Estimated by Watson's Formula.

OBJECTIVE: Dialysis machines use the Watson formula (Vwatson) to estimate the urea distribution volume (UDV) to calculate the online Kt/V for each dialysis session. However, the equation could give rise to inaccuracies. The present study analyzes whether body composition affects UDV estimated by Vwatson in comparison to bioimpedance spectroscopy (Vbis) as the reference method. DESIGN: This is a transversal study performed in the setting of a hemodialysis unit. SUBJECTS: Prevalent hemodialysis patients. INTERVENTION: The same day, UDV was measured using Vwatson and Vbis. We compared their results. MAIN OUTCOME MEASURE: Differences between UDV using Watson equation and Vbis. RESULTS: We included 144 prevalent patients. Vwatson overestimated the volume with regard to Vbis (Vwatson - Vbis) by 2.5 L (1.8 L; P = .001). We found an excellent correlation between the 2 methods. A higher mean Vwatson - Vbis value was correlated to older age (P = .03), body mass index (P = .01), fat tissue index (P = .001), lower lean tissue index (P = .001), lower extracellular water (P = .01), and intracellular water (P = .001). CONCLUSION: Body composition affects UDV estimated by Vwatson, thus modifying the result of Kt/V. In young patients who present more lean tissue and less fat tissue, Kt/V is underestimated with Vwatson.

Amorphous sub-nanometre Tb-doped SiO(x)N(y)/SiO2 superlattices for optoelectronics.

Amorphous sub-nanometre Tb-doped SiOxNy/SiO2 superlattices were fabricated by means of alternating deposition of 0.7 nm thick Tb-doped SiOxNy layers and of 0.9 nm thick SiO2 barrier layers in an electron-cyclotron-resonance plasma enhanced chemical vapour deposition system with in situ Tb-doping capability. High resolution transmission electron microscopy images showed a well-preserved superlattice morphology after annealing at a high temperature of 1000 °C. In addition, transparent indium tin oxide (ITO) electrodes were deposited by electron beam evaporation using a shadow mask approach to allow for the optoelectronic characterization of superlattices. Tb(3+) luminescent spectral features were obtained using three different excitation sources: UV laser excitation (photoluminescence (PL)), under a bias voltage (electroluminescence (EL)) and under a highly energetic electron beam (cathodoluminescence (CL)). All techniques displayed Tb(3+) inner transitions belonging to (5)D4 levels except for the CL spectrum, in which (5)D3 transition levels were also observed. Two competing mechanisms were proposed to explain the spectral differences observed between PL (or EL) and CL excitation: the population rate of the (5)D3 state and the non-radiative relaxation rate of the (5)D3-(5)D4 transition due to a resonant OH-mode. Moreover, the large number of interfaces (trapping sites) that electrons have to get through was identified as the main reason for observing a bulk-limited charge transport mechanism governed by Poole-Frenkel conduction in the J-V characteristic. Finally, a linear EL-J dependence was measured, with independent spectral shape and an EL onset voltage as low as 6.7 V. These amorphous sub-nanometre superlattices are meant to provide low-cost solutions in different areas including sensing, photovoltaics or photonics.

Estudio de sobrehidratación en los pacientes en diálisis y su relación con la inflamación / Study on overhydration in dialysis patients and its association with inflammation

Antecedentes: Los pacientes con enfermedad renal crónica en tratamiento en hemodiálisis (HD) están sometidos a variaciones constantes en su estado de hidratación que pueden repercutir en su supervivencia. Objetivos: Analizar el estado de hidratación y composición corporal en los pacientes en HD y su asociación con parámetros de inflamación. Métodos: Se incluyeron 128 pacientes prevalentes en HD en situación de estabilidad. Se analizó la composición corporal mediante bioimpedancia espectroscópica y el estado inflamatorio mediante parámetros analíticos. Resultados: Los pacientes con mayor tejido magro presentaron mayor agua intracelular (p = 0,02) y extracelular (p = 0,001). No hubo asociación entre el tejido graso y la hidratación. La sobrehidratación media fue de 7,5 %. Encontramos una asociación entre sobrehidratación ajustada al agua extracelular (OH/AEC) mayor del 15 % similar a 10 %. Ambas se asociaron con niveles bajos de prealbúmina (p = 0,001 y p = 0,05, respectivamente) y a niveles bajos de tejido graso (p = 0,001 y p = 0,05, respectivamente).Conclusiones: La hiperhidratación definida como OH/AEC mayor de 10 % y mayor de 15 % se asocia a disminución de prealbúmina y de tejido graso. Proponemos disminuir el límite de hiperhidratación medido por bioimpedancia a OH/AEC mayor de 10 % (AU)

Background: Patients with chronic kidney disease receiving haemodialysis (HD) have permanent variations in hydration status that may affect their survival. Objectives: To analyse hydration status and body composition in patients on haemodialysis and its relation to inflammation. Methods: We included 128 prevalent clinically stable patients on haemodialysis. We analysed body composition using spectroscopic bioimpedance and inflammation using blood parameters. Results: Patients with higher lean tissue had less intracellular (p=0.02) and extracellular water (p = 0.001). We did not find association with fat tissue and hydration. Mean overhydration was 7.5 %. We found an association between overhydration adjusted to extracellular water (OH/ECW) higher than 15 % similar to 10 %. They were both associated with low prealbumin levels (p = 0.001 and p = 0.05 respectively) and low levels of fat tissue (p = 0.001 and p = 0.05 respectively). Conclusions: Overhydration defined as OH/ECW higher than 10 % and 15 % are related to low prealbumin levels and low fat tissue. We suggest decreasing the overhydration limit measured by bioimpedance to OH/ECW higher than 10 % (AU)

Study on overhydration in dialysis patients and its association with inflammation.

BACKGROUND:  Patients with chronic kidney disease receiving haemodialysis (HD) have permanent variations in hydration status that may affect their survival.  OBJECTIVES:  To analyse hydration status and body composition in patients on haemodialysis and its relation to inflammation.  METHODS:  We included 128 prevalent clinically stable patients on haemodialysis. We analysed body composition using spectroscopic bioimpedance and inflammation using blood parameters.  RESULTS:  Patients with higher lean tissue had less intracellular (p=0.02) and extracellular water (p = 0.001). We did not find association with fat tissue and hydration. Mean overhydration was 7.5 %. We found an association between overhydration adjusted to extracellular water (OH/ECW) higher than 15 % similar to 10 %. They were both associated with low prealbumin levels (p = 0.001 and p = 0.05 respectively) and low levels of fat tissue (p = 0.001 and p = 0.05 respectively).  CONCLUSIONS:  Overhydration defined as OH/ECW higher than 10 % and 15 % are related to low prealbumin levels and low fat tissue. We suggest decreasing the overhydration limit measured by bioimpedance to OH/ECW higher than 10 %.

Body composition affects the response to erythropoiesis-stimulating agents in patients with chronic kidney disease in dialysis.

BACKGROUND: The response to erythropoiesis-stimulating agents (ESA) in patients with chronic kidney disease (CKD) is variable. The body mass index (BMI) variations can modify the response to ESA. The objective was to assess the effect of body composition on the response to ESA in dialysis patients. METHODS: This is an observational cross-sectional study. Prevalent hemodialysis and peritoneal dialysis (PD) patients were selected. In the same day, a single blood test, a body composition analysis using bioimpedance spectroscopy and anthropometric measurements were performed. We collected ESA doses. We analyzed erythropoietin resistance index (ERI). The ERI was calculated dividing the weekly weight-adjusted (kg) dose of ESA (IU) by the hemoglobin level (g/dL). RESULTS: The study was comprised of 218 patients (58% men; age 65 (16) years old; 80% hemodialysis, 20% PD). There was an inverse correlation between ERI and BMI (p=0.01), fat tissue index (FTI) (p=0.01) and prealbumin (p=0.04). We found an independent association between higher ERI levels and lower FTI and prealbumin values. CONCLUSION: Response to ESA is influenced by body composition. Fat tissue favors the body's response to ESA.

Cyclic enolates of Ni and Pd: equilibrium between C- and O-bound tautomers and reactivity studies.

2-acylaryl complexes of Ni and Pd containing chelating diphosphines react with KtBuO to give metallacyclic enolate complexes. While coordination through the carbon atom is preferred in the case of Pd, the nickel O-enolate compounds are formed as the corresponding O-tautomers. Slow equilibration between O- and C-enolate tautomers is observed for the nickel complex with an unsubstituted enolate function (M-O-C=CH(2)). Theoretical DFT calculations suggest that the barrier for the tautomer exchange has its origin in the rigidity of the metallacycle. Whilst the C-enolate tautomer is unreactive towards aldehydes, the corresponding O-enolate adds to MeCHO and PhCHO, giving rise to products that retain the enolate functionality. The carbonylation of these products cleanly leads to the formation of enol lactones in a highly selective manner.

Synthesis, solid-state structure, and bonding analysis of the beryllocenes [Be(C5Me4H)2], [Be(C5Me5)2], and [Be(C5Me5)(C5Me4H)].

The beryllocenes [Be(C(5)Me(4)H)(2)] (1), [Be(C(5)Me(5))(2)] (2), and [Be(C(5)Me(5))(C(5)Me(4)H)] (3) have been prepared from BeCl(2) and the appropriate KCp' reagent in toluene/diethyl ether solvent mixtures. The synthesis of 1 is facile (20 degrees C, overnight), but generation of decamethylberyllocene 2 demands high temperatures (ca. 115 degrees C) and extended reaction times (3-4 days). The mixed-ring beryllocene 3 is obtained when the known [(eta(5)-C(5)Me(5))BeCl] is allowed to react with K[C(5)Me(4)H], once more under somewhat forcing conditions (115 degrees C, 36 h). The structures of the three metallocenes have been determined by low-temperature X-ray studies. Both 1 and 3 present eta5/eta1 geometries of the slip-sandwich type, whereas 2 exhibits an almost regular, ferrocene-like, sandwich structure. In the mixed-ring compound 3, C(5)Me(5) is centrally bound to beryllium and the eta(1)-C(5)Me(4)H ring bonds to the metal through the unique CH carbon atom. This is also the binding mode of the eta(1)-ring of 1. To analyze the nature of the bonding in these molecules, theoretical calculations at different levels of theory have been performed on compounds 2 and 3, and a comparison with the bonding in [Be(C(5)H(5))(2)] has been made. As for the latter molecule, energy differences between the eta5/eta5 and the eta5/eta1 structures of 2 are very small, being of the order of a few kcal mol(-1). Constrained space orbital variations (CSOV) calculations show that the covalent character in the bonding is larger for [Be(C(5)Me(5))(2)] than for [Be(C(5)H(5))(2)] due to larger charge delocalization and to increased polarizability of the C(5)Me(5) fragment.

Coupling of internal alkynes in tp(me2)ir derivatives: selective oxidation of a noncoordinated double bond of the resulting iridacycloheptatrienes.

The reaction of different Tp(Me2)Ir derivatives and dimethylacetylene dicarboxylate (DMAD) allows the preparation of three different metallacycloheptatriene complexes and an unusual allyl-terminated metallacycle. The C atoms of distant C=C bonds in the metallacycles, including aromatic ones, can be converted selectively to the corresponding keto functionality under mild conditions.

Synthesis and aldol reactivity of o- and C-enolate complexes of nickel.

The often facile C-/O-tautomerization of transition metal enolates is severely hindered in the cyclic Ni complexes 1 and 2, allowing the study of their individual reactivities. At room temperature only the O-bound tautomer, 2, reacts with aldehydes, giving rise to the corresponding addition products.