Microphotoluminescence and microphotoreflectance analyses of CO2 laser rapid-thermal-annealed SiOx surface with buried Si nanocrystals

[[abstract]]The optical properties of a SiOx film rapid-thermal-annealed (RTA) by CO2 laser are primarily investigated. The microphotoluminescence (mu-PL) and high-resolution transmission electron microscopy (HRTEM) analyses indicate that the precipitation of random-oriented Si nanocrystals can be initiated when laser intensity (P-laser) is larger than 4.5 kW/cm(2). At P-laser of 6 kW/cm(2), the Si nanocrystal exhibits a largest diameter of 8 run and a highest density of 4.5 x 10(16) cm(-3), which emits strong PL at 790-825 nm. The microphotoreflectance of the CO2 laser RTA SiOx film reveals a volume density product dependent refractive index increasing from 1.57 to 1.87 as P-laser increases from 1.5 to 7.5 kW/cm(2). Nonetheless, the laser ablation of the SiOx film occurs with a linear ablation slope of 35 nm/kW/cm(2) at beyond 7.5 kW/cm(2), which terminates the enlargement of Si nanocrystals, degrades the near-infrared PL, and slightly reduces the refractive index of the CO2 laser RTA SiOx film.[[fileno]]2020315010031[[department]]材料科學工程學

Surface steps dominate the water formation on Pd(111) surfaces

Water formation is relevant in many technological processes and is also an important model reaction. Although water formation over Pd surfaces is widely studied, questions regarding the active site and the main reaction path (OH* + OH*) or (OH* + H*) are still open. Combining first-principles density functional theory calculations and kinetic Monte Carlo simulations, we find that the reaction rate is dominated by surface steps and point defects over a wide range of conditions. The main reaction path is found to be temperature dependent where the OH* + OH* path dominates at low temperatures, whereas the OH* + H* path is the main path at high temperatures. Steps facilitate the OH* formation, which is the rate limiting step under all conditions. OH* is formed via O* + H* association or OOH* splitting at low temperatures, whereas OH* is exclusively formed via O* + H* association at high temperatures. The results of the first-principles-based kinetic model are in excellent agreement with experimental observations at high and low temperatures as well as different gas-phase compositions

On the Reaction Mechanism of Direct H2O2Formation over Pd Catalysts

Hydrogen peroxide (H2O2) is an effective green oxidant, which is used in many industrial processes. Here, the reaction mechanism for direct formation of H2O2 from H2 and O2 over Pd catalysts is studied using density functional theory calculations and mean-field kinetic modeling. The state of the catalyst as a function of reaction conditions is determined from ab initio thermodynamics. It is found that Pd is in a hydride phase during typical reaction conditions. Reaction landscapes are constructed for the reaction over PdH(111) and PdH(211). Formation of H2O2 instead of H2O requires that O2 adsorbs and that the surface intermediates O2, OOH, and H2O2 do not dissociate. We find that these requirements are fulfilled on the stepped PdH(211) surface. Surface steps are needed for O2 chemisorption as the adsorption on PdH(111) is endothermic. The high H coverage on the surface of the hydride is important to slow down the unwanted scission of the O-O bond and promote the desorption of the products. Comparative calculations for the Pd(111) surface show that this surface is inactive for both H2O2 and H2O formation below room temperature for typical reaction mixtures. Our findings demonstrate the importance of surface steps and high hydrogen coverage for direct synthesis of H2O2 from H2 and O2 over Pd catalysts. The results imply that the selectivity of the reaction toward H2O2 is enhanced by a high partial pressure of H2, which is in agreement with experimental observations

Multiple Roles of Alkanethiolate-Ligands in Direct Formation of H2O2 over Pd Nanoparticles

Coadsorbed organic species including thiolates can promote direct synthesis of hydrogen peroxide from H2 and O2 over Pd particles. Here, density functional theory based kinetic modeling, augmented with activity measurements and vibrational spectroscopy are used to provide atomistic understanding of direct H2O2 formation over alkylthiolate(RS) Pd. We find that the RS species are oxidized during reaction conditions yielding RSO2 as the effective ligand. The RSO2 ligand shows superior ability for proton transfer to the intermediate surface species OOH, which accelerates the formation of H2O2. The ligands promote the selectivity also by blocking sites for unselective water formation and by modifying the electronic structure of Pd. The work rationalizes observations of enhanced selectivity of direct H2O2 formation over ligand-funtionalized Pd nanoparticles and shows that engineering of organic surface modifiers can be used to promote desired hydrogen transfer routes

Delayed diagnosis of Townes‑Brocks syndrome with multicystic kidneys and renal failure caused by a novel SALL1 nonsense mutation: A case report

Townes‑Brocks syndrome (TBS) is a rare autosomal dominant congenital anomaly syndrome characterized by the triad of anorectal, hand and external ear malformations. Kidney involvement is less common and may progress to end‑stage renal failure (ESRF) early in life. The present study reports the case of a male patient presenting with multiple bilateral cortical kidney cysts at the age of 4 years, at which time the kidneys were of normal size and function. A clinical diagnosis of autosomal recessive polycystic kidney disease was made initially as the patient's parents are clinically healthy. However, the consideration of extra‑renal involvements (imperforate anus at birth, preaxial polydactyly and dysplastic right ear) following the progression of the patient to ESRF at the age of 16 years, led to the diagnosis of TBS. This prompted sequencing of the SALL1 gene, which identified a novel heterozygous nonsense mutation in the mutational ‘hotspot’ of exon 2 (c.874C>T, p.Q292X), and this mutation was not detected in healthy controls. The current case highlights that TBS may present with normal sized, cystic kidneys in childhood, while recognition of extra‑renal features of cystic kidney diseases, such as TBS, and genetic testing may facilitate the correct diagnosis and transmission mode. Reaching a correct diagnosis of as TBS is important since this condition has a 50% rate of transmission to offspring and can progress to ESRF early in life

Semi-automatic tool to identify heterogeneity zones in lge-cmr and incorporate the result into a 3d model of the left ventricle

Fatal scar-related arrhythmias are caused by an abnormal electrical wave propagation around non conductive scarred tissue and through viable channels of reduced conductivity. Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is the gold-standard procedure used to differentiate the scarred tissue from the healthy, highlighting the dead cells. The border regions responsible for creating the feeble channels are visible as gray zones. Identifying and monitoring (as they may evolve) these areas may predict the risk of arrhythmias that may lead to cardiac arrest. The main goal of this project is the development of a system able to aid the user in the extraction of geometrical and physiological information from LGE images and the replication of myocardial heterogeneities onto a three-dimensional (3D) structure, built by the methods described by our team in another publication, able to undergo electro-physiologic simulations. The system components were developed in MATLAB R2019b the first is a semi-automatic tool, to identify and segment the myocardial scars and gray zones in every two-dimensional (2D) slice of a LGE CMR dataset. The second component takes these results and assembles different sections while setting different conductivity values for each. At this point, the resulting parts are incorporated into the functional 3D model of the left ventricle, and therefore the chosen values and regions can be validated and redefined until a satisfactory result is obtained. As preliminary results we present the first steps of building one functional Left ventricle (LV) model with scarred zones.authorsversionpublishe

Influence of interleukin-2 on Ca2+ handling in rat ventricular myocytes

In the present study, we examined the effect of interleukin-2 (IL-2) on cardiomyocyte Ca2+ handling. The effects of steady-state and transient changes in stimulation frequency on the intracellular Ca2+ transient were investigated in isolated ventricular myocytes by spectrofluorometry. In the steady state (0.2 Hz) IL-2 (200 U/ml) decreased the amplitude of Ca2+ transients induced by electrical stimulation and caffeine. At 1.25 mM extracellular Ca2+ concentration ([Ca 2+]o), when the stimulation frequency increased from 0.2 to 1.0 Hz, diastolic Ca2+ level and peak intracellular Ca 2+ concentration ([Ca2+]i), as well as the amplitude of the transient, increased. The positive frequency relationships of the peak and amplitude of [Ca2+]i transients were blunted in the IL-2-treated myocytes. The effect of IL-2 on the electrically induced [Ca2+]i transient was not normalized by increasing [Ca2+]o to 2.5 mM. IL-2 inhibited the frequency relationship of caffeine-induced Ca2+ release. Blockade of sarcoplasmic reticulum (SR) Ca2+-ATPase with thapsigargin resulted in a significant reduction of the amplitude-frequency relationship of the transient similar to that induced by IL-2. The restitutions were not different between control and IL-2 groups at 1.25 mM [Ca2+]o, which was slowed in IL-2-treated myocytes when [Ca2+]o was increased to 2.5 mM. There was no difference in the recirculation fraction (RF) between control and IL-2-treated myocytes at both 1.25 and 2.5 mM [Ca 2+]o. The effects of IL-2 on frequency relationship, restitution, and RF may be due to depressed SR functions and an increased Na+-Ca2+ exchange activity, but not to any change in L-type Ca2+ channels. © 2003 Elsevier Ltd. All rights reserved.postprin

Direct measurement of enthalpy and entropy changes in NH3 promoted O2 activation over Cu−CHA at low temperature

Oxygen activation is a key step in the selective catalytic reduction of nitrogen oxides with ammonia (NH -SCR) over Cu-chabazite. We present direct measurements of oxygen adsorption at low temperatures over [NH −Cu−NH ] complexes and framework-bound Cu species in Cu-chabazite with Si/Al=14 using isothermal microcalorimetry combined with mass spectrometry. The enthalpy change for O adsorption over [NH −Cu−NH ] complexes at 200 \ub0C is determined to be −79 kJ/mol. By fitting a Langmuir isotherm, the corresponding entropy change is determined to be −142 J/(mol*K) at 10 % O . The results show that O adsorption at low temperatures over [NH −Cu−NH ] complexes is more facile than on framework-bound Cu species. The experimental results are in agreement with density functional theory calculations showing a lower barrier for O activation over the [NH −Cu−NH ] complexes as compared to the framework-bound Cu species

A comparative test of different density functionals for calculations of NH3-SCR over Cu-Chabazite

A general challenge in density functional theory calculations is to simultaneously account for different types of bonds. One such example is reactions in zeolites where both van der Waals and chemical bonds should be described accurately. Here, we use different exchange-correlation functionals to explore O2 dissociation over pairs of Cu(NH3)2+ complexes in Cu-Chabazite. This is an important part of selective catalytic reduction of NOx using NH3 as a reducing agent. The investigated functionals are PBE, PBE+U, PBE+D, PBE+U+D, PBE-cx, BEEF and HSE06+D. We find that the potential energy landscape for O2 activation and dissociation depends critically on the choice of functional. However, the van der Waals contributions are similarly described by the functionals accounting for this interaction. The discrepancies in the potential energy surface are instead related to different descriptions of the Cu-O chemical bond. By investigating the electronic, structural and energetic properties of reference systems including bulk copper oxides and (Cu2O2)2+ enzymatic crystals, we find that the PBE+U approach together with van der Waals corrections provides a reasonable simultaneous accuracy of the different bonds in the systems

Expression of CD80 and CD86 costimulatory molecules are potential markers for better survival in nasopharyngeal carcinoma

<p>Abstract</p> <p>Background</p> <p>B7 Costimulatory signal is essential to trigger T-cell activation upon the recognition of tumor antigens. This study examined the expression of B7-1 (CD80) and B7-2 (CD86) costimulatory molecules along with HLA-DR and the presence of infiltrating lymphocytes and dendritic cells to assess their significance in patients with nasopharyngeal carcinoma (NPC).</p> <p>Methods</p> <p>Expression of CD80, CD86, HLA-DR, S-100 protein and the presence of infiltrating lymphocytes and follicular dendritic reticulum cells were immunohistochemically examined on the paraffin-embedded tissue blocks from newly diagnosed NPC patients (n = 50). The results were correlated with clinical outcome of patients.</p> <p>Results</p> <p>CD80 and CD86 were each expressed in 10 of 50 cases in which they co-expressed in 9 cases. Univariate analysis revealed that patients with CD80/CD86 expression had significantly better overall survival than those without it (P = 0.017), but after adjustment for stage, nodal status, and treatment, the expression of CD80/CD86 did not significantly correlate with overall survival. Expression of HLA-DR and the presence of infiltrating lymphocytes and dendritic cells did not appear to have impact on the survival of patients.</p> <p>Conclusion</p> <p>Expression of CD80 and CD86 costimulatory molecules appears to be a marker of better survival in patient with NPC.</p