Tuning SMSI Kinetics on Pt-loaded TiO2_2(110) by Choosing the Pressure: A Combined UHV / Near-Ambient Pressure XPS Study

Pt catalyst particles on reducible oxide supports often change their activity significantly at elevated temperatures due to the strong metal-support interaction (SMSI), which induces the formation of an encapsulation layer around the noble metal particles. However, the impact of oxidizing and reducing treatments at elevated pressures on this encapsulation layer remains controversial, partly due to the 'pressure gap' between surface science studies and applied catalysis. In the present work, we employ synchrotron-based near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to study the effect of O$_2$ and H$_2$ on the SMSI-state of well-defined Pt/TiO$_2$(110) catalysts at pressures of up to 0.1 Torr. By tuning the O$_2$ pressure, we can either selectively oxidize the TiO$_2$ support or both the support and the Pt particles. Catalyzed by metallic Pt, the encapsulating oxide overlayer grows rapidly in 1x10$^{-5}$ Torr O$_2$, but orders of magnitudes less effective at higher O$_2$ pressures, where Pt is in an oxidic state. While the oxidation/reduction of Pt particles is reversible, they remain embedded in the support once encapsulation has occurred

Communication: In search of four-atom chiral metal clusters

A combined study utilizing anion photoelectron spectroscopy and density functional theory was conducted to search for four-atom, chiral, metal, and mostly metal clusters. The clusters considered were AuCoMnBi−/0, AlAuMnO−/0, AgMnOAl−/0, and AuAlPtAg−/0, where the superscripts, −/0, refer to anionic and neutral cluster species, respectively. Based on the agreement of experimentally and theoretically determined values of both electron affinities and vertical detachment energies, the calculated cluster geometries were validated and examined for chirality. Among both anionic and neutral clusters, five structures were identified as beingchiral

Wpływ treningu i biegu półmaratońskiego na prawą komorę u biegaczy amatorów

Introduction. Endurance running may lead to heart remodelling. There are little data on the right ventricular (RV) changes in amateur athletes running shorter than marathon distances. The study aimed to investigate whether training and running a half marathon affect the anatomy and function of the RV in amateur runners and whether these changes affect the athlete's competitive performance. Material and methods. The study included 45 recreational runners with a mean age of 32.96 (5.12) years, 27 men. Echocardiography was performed before the ten-weeks training period and before and after the half marathon run. The morphological and functional parameters of the RV were analysed, including two-dimensional, Doppler and speckle-tracking echocardiography. Results. In training period, the RV outflow tract (27.98 [5.46] vs. 30.07 [4.90]; p = 0.003) and the RV index of myocardial performance (0.36 [0.29; 0.45] vs. 0.39 [0.33; 0.52]; p = 0.017) increased significantly and no changes were found for E/e’. After the half marathon run, the absolute value of the RV free wall global longitudinal strain increased significantly (–25.89 [3.08] vs. –27.20 [3.42]; p = 0.008). Athletes who trained more intensively during the training period achieved significantly better half marathon results (r = –0.4; p ≤ 0.05). Conclusions. More enhanced physiological RV remodelling under exercise in amateur athletes results in better half marathon finishing times. The preparation period and 21.0975 kilometres run do not affect the diastolic function of the RV in recreational runners. The RV systolic function improves immediately after the half marathon performance.Wstęp. Biegi długodystansowe mogą prowadzić do przebudowy serca. Niewiele jest danych na temat zmian w prawej komorze u sportowców amatorów biegających na dystansach krótszych niż maratoński. Celem pracy było wykazanie, czy trening i ukończenie półmaratonu wpływają na anatomię i funkcję prawej komory u biegaczy amatorów oraz czy zmiany te wpływają na osiągany przez sportowca wynik. Materiał i metody. Badaniem objęto 45 biegaczy amatorów w średnim wieku 32,96 (5,12) lat, w tym 27 mężczyzn. Echokardiografię wykonano przed 10-tygodniowym okresem treningowym oraz przed i po biegu półmaratońskim. Analizie poddano parametry morfologiczne i czynnościowe prawej komory. Wykonano echokardiografię dwuwymiarową, dopplerowską i stosowano technikę śledzenia plamki akustycznej. Wyniki. W okresie treningowym droga odpływu prawej komory (27,98 [5,46] vs. 30,07 [4,90]; p = 0,003) oraz wskaźnik sprawności prawej komory (0,36 [0,29; 0,45] vs. 0,39 [0,33; 0,52]; p = 0,017) wzrosły znacząco i nie stwierdzono zmian dla E/e’. Po półmaratonie wartość bezwzględna globalnego podłużnego odkształcenia wolnej ściany prawej komory istotnie wzrosła (–25,89 [3,08] vs. –27,20 [3,42]; p = 0,008). Sportowcy, którzy w okresie treningowym trenowali intensywniej, osiągnęli istotnie lepsze wyniki w półmaratonie (r = –0,4; p ≤ 0,05). Wnioski. Silniejsza fizjologiczna przebudowa prawej komory serca pod wpływem ćwiczeń u sportowców amatorów skutkuje lepszym czasem ukończenia półmaratonu. Okres przygotowań i przebiegnięcie 21,0975 km nie wpływa na funkcję rozkurczową prawej komory u biegaczy rekreacyjnych. Funkcja skurczowa prawej komory poprawia się natychmiast po ukończeniu półmaratonu

Electron transfer and hydride transfer pathways in the Stoltz-Grubbs reducing system (KOtBu-Et3SiH)

Recent studies by Stoltz, Grubbs et al. have shown that triethylsilane and potassium tert-butoxide react to form a highly attractive and versatile system that shows (reversible) silylation of arenes and heteroarenes as well as reductive cleavage of C-O bonds in aryl ethers and C-S bonds in aryl thioethers. Their extensive mechanistic studies indicate a complex network of reactions with a number of possible intermediates and mechanisms, but their reactions likely feature silyl radicals undergoing addition reactions and SH2 reactions. This paper focuses on the same system, but through computational and experimental studies, reports complementary facets of its chemistry based on (a) single electron transfer (SET), and (b) hydride delivery reactions to arenes

Electronic and optical properties of families of polycyclic aromatic hydrocarbons: a systematic (time-dependent) density functional theory study

Homologous classes of Polycyclic Aromatic Hydrocarbons (PAHs) in their crystalline state are among the most promising materials for organic opto-electronics. Following previous works on oligoacenes we present a systematic comparative study of the electronic, optical, and transport properties of oligoacenes, phenacenes, circumacenes, and oligorylenes. Using density functional theory (DFT) and time-dependent DFT we computed: (i) electron affinities and first ionization energies; (ii) quasiparticle correction to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap; (iii) molecular reorganization energies; (iv) electronic absorption spectra of neutral and $\pm1$ charged systems. The excitonic effects are estimated by comparing the optical gap and the quasiparticle corrected HOMO-LUMO energy gap. For each molecular property computed, general trends as a function of molecular size and charge state are discussed. Overall, we find that circumacenes have the best transport properties, displaying a steeper decrease of the molecular reorganization energy at increasing sizes, while oligorylenes are much more efficient in absorbing low-energy photons in comparison to the other classes.Comment: 26 pages, 9 figures, 4 tables, accepted for pubblication in Chemical Physics (14/04/2011

Hip Joint Stability during and after Femoral Lengthening in Congenital Femoral Deficiency

Background: Hip stability remains a major preoccupation during femoral lengthening in Congenital Femoral Deficiency (CFD). We aimed to review hip stability in Paley type 1a CFD patients undergoing femoral lengthening. Methods: A total of 33 patients with unilateral CFD, who were treated between 2014 and 2023, were retrospectively reviewed. In 20/33 cases (60.6%) the SUPERhip preparatory surgery was performed at a mean age of 4.3 years (range 2.7–8.1). The femoral lengthening using an external fixator was performed at a mean age of 7.8 years (range 4.3–14.3). Results: All patients presented with a stable hip joint after preparatory surgery and during femoral lengthening. Six cases of hip instability at a mean of 637 days after the external fixator removal were observed (range 127 to 1447 days). No significant differences between stable and unstable hips were noted for (1) Center-Edge Angle: 23.7 vs. 26.1 deg; (2) Acetabular Inclination: 12.8 vs. 11.7 deg; and (3) Ex-Fix Index: 35.6 days/cm vs. 42.4 days/cm; p > 0.05. Late hip instability was related to Coxa Vara and decreased femoral antetorsion before lengthening. Conclusions: Late hip joint instability in Paley type 1a CFD patients may occur long after femoral lengthening despite hip morphology appearing to be normal on radiograms before and at the end of femoral lengthening. Coxa Vara, femoral torsional deformity, and posterior acetabular deficiency might be risk factors for hip instability

Preparation and Spectroscopic Properties of Monolayer-Protected Silver Nanoclusters

Silver nanoclusters protected by 2-phenylethanethiol (1), 4-fluorothiophenol (2), and l-glutathione (3) ligands were successfully synthesized. The optical properties of the prepared silver nanoclusters were studied. The absorption signal of Ag@SCH2CH2Ph in toluene can be found at 469 nm, and Ag@SPhF in THF shows two absorption bands at 395 and 462 nm. Ag@SG in water absorbs at 478 nm. Mie theory in combination with the Drude model clearly indicates the peaks in the spectra originate from plasmonic transitions. In addition, the damping constant as well as the dielectric constant of the surrounding medium was determined. In addition, the CD spectra of silver nanoclusters protected by the three ligands (1–3) were also studied. As expected, only the clusters of type 3 gave rise to chiroptical activity across the visible and near-ultraviolet regions. The location and strength of the optical activity suggest an electronic structure of the metal that is highly sensitive to the chiral environment imposed by the glutathione ligand. The morphology and size of the prepared nanoclusters were analyzed by using transmission electron microscopy (TEM). TEM analysis showed that the particles of all three types of silver clusters were small than 5 nm, with an average size of around 2 nm. The analysis of the FTIR spectra elucidated the structural properties of the ligands binding to the nanoclusters. By comparing the IR absorption spectra of pure ligands with those of the protected silver nanoclusters, the disappearance of the S–H vibrational band (2535–2564 cm–1) in the protected silver nanoclusters confirmed the anchoring of ligands to the cluster surface through the sulfur atom. By elemental analysis and thermogravimetric analysis, the Ag/S ratio and, hence, the number of ligands surrounding a Ag atom could be determined

CO₂-Activation by size-selected tantalum cluster cations (Ta_1–16⁺): thermalization governing reaction selectivity

The reactions of tantalum cluster cations of different sizes toward carbon dioxide are studied in an ion trap under multi-collisional conditions. For all sizes studied, consecutive reactions with several CO2 molecules are observed. This reveals two different pathways, namely oxide formation and the pickup of an entire molecule. Supported by calculations of the thermochemistry of TanO+ formation upon reaction with CO2, changes in the branching ratios at a particular cluster size are related to heat effects due to the vibrational heat capacity of the clusters and the exothermicity of the reaction

Chiral Gold and Silver Nanoclusters: Preparation, Size Selection, and Chiroptical Properties

In this work we studied different properties of gold and silver nanoclusters (AuNCs and AgNCs) protected by the chiral ligands l-glutathione (L-GSH), and <i>N</i>-acetyl-l-cysteine (NALC), and we present a thorough characterization of the synthesized clusters. The synthesis was performed by reduction of the corresponding metal salt with NaBH₄. Fractions of gold nanoclusters with different sizes were isolated by methanol-induced precipitation. The ellipticity of the clusters was obtained by circular dichroism (CD) spectroscopy, showing that the chirality of the ligands is transferred to the metal core either in its structure or at least in its electronic states via perturbation of the electronic field of the ligands. The optical properties of gold and silver nanoclusters in water were studied by UV–vis spectroscopy. The absorption signal of the clusters shows characteristic bands, which can be assigned to plasmonic transitions of the metal core. In addition, UV–vis spectroscopy has served as a tool for studying the stability of these clusters in air. In general, gold nanoclusters are highly stable in air, and it was found that the stability of Au_<i>n</i>(NALC)_<i>m</i> clusters even exceeds that of Au_<i>n</i>(SG)_<i>m</i> clusters. In contrast to gold clusters, silver nanoclusters very often tend to decompose upon exposure to air. We found, however, that Ag_<i>n</i>(NALC)_<i>m</i> are surprisingly stable at atmospheric pressures. The average molecular formula of the nanoclusters was determined by thermogravimetric analysis (TGA). The particle sizes of AuNCs and AgNCs were assessed by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) analysis. For studying the fluorescent properties of the metal nanoparticles, photoluminescence spectroscopy (PL) was performed. In summary, we succeeded to synthesize ligand-protected silver clusters (Ag_<i>n</i>(NALC)_<i>m</i>) with very high stability and rather narrow size distribution; furthermore, we could show the controlled precipitation to be applicable to other systems, such as that Au_<i>n</i>(NALC)_<i>m</i>, yielding two fraction of very narrow size distribution

Ocena dojrzałości kostnej metodą Sandersa u pacjentek ze skoliozą idiopatyczną

Introduction. Skeletal maturity assessment in Idiopathic Scoliosis (IS) is used for the evaluation of deformation progression risk, as well as selecting a method of treatment. The Sanders Maturity Scale (SMS) is based on the ossification of phalanges, metacarpal bones and radius rated on AP radiograms of the left hand. Aim. This retrospective study aimed to compare SMS to other skeletal maturity assessment methods used in daily practice. Materials and methods. We included 39 female patients with IS (50 series of radiograms) with a mean age of 13.4, ranging from 10.3 to 17.3. Each series of radiograms was evaluated by three observers with different experience. Skeletal maturity was assessed using the Sanders Maturity Scale (SMS), Risser sign, Greulich and Pyle (GP) atlas, as well as the closure of the triradiate cartilage. Results. The majority of patients, 17 out of 50 (34 %) were classified as type 3 (adolescent rapid – early). Intra-observer and inter-observer reliability for the SMS was very good (Krippendorff’s alpha >0.95). The GP and Risser method showed good reliability, whereas the triradiate cartilage closure assessment showed lower reliability. The Risser 0 grade corresponded with as many as four Sanders stages, 16 out of 20 (80 %) were rated Sanders 3. All radiograms with open triradiate cartilage (7/50, 14 %) were rated Sanders 2 or 3; they all received a Risser 0 grading. Conclusions. The SMS proved to have a very good intra-observer and inter-observer reliability, it is easy to be used by physicians and does not require an atlas. The SMS enhances the assessment of skeletal maturity of IS patients by providing additional stages in the early phase of growth (Risser 0).Wstęp. Ocena wieku kostnego pacjentów leczonych z powodu skoliozy idiopatycznej (SI) służy określeniu ryzyka progresji deformacji oraz decyzji o wyborze sposobu leczenia. Metoda Sandersa opiera się na ocenie kostnienia paliczków i kości promieniowej na radiogramach AP ręki lewej. Cel. Celem pracy było porównanie metody Sandersa oraz innych stosowanych w codziennej praktyce metod oceny wieku kostnego. Materiał i metody. Do badania włączonych zostało 39 pacjentek (50 serii radiogramów) z rozpoznaniem SI, w wieku 13,4 lat (od 10,3 do 17,3). Każda seria radiogramów została oceniona przez trzech obserwatorów o różnym doświadczeniu. Dojrzałość kostna została oceniona przy użyciu skali Sandersa, testu Rissera, atlasu Greulicha i Pyle (GP) oraz obecność chrząstki Y. Wyniki. Najwięcej pacjentek, 17 z 50 (34%) zostało ocenionych jako stopień 3 w skali Sandersa (adolescent rapid – early). Skala Sandersa cechowała się bardzo dobrą zgodnością wewnątrz oraz między obserwatorami (Krippendroff’s alpha>0,95). Test Rissera i metoda GP cechowały się dobrą zgodnością, a ocena chrząstki Y słabą. Pacjentkom ze stopniem Risser 0 odpowiadały aż 4 różne stopnie w skali Sandersa, 16 z 20 (80%) pacjentek została oceniona jako Sanders 3. Pacjentki z otwartą chrząstką Y (7/50, 14 %) były oceniane jako Sanders 2 i Sanders 3; wszystkie zostały ocenione jako Risser 0. Wnioski. Metoda Sandersa cechuje się bardzo dobrą zgodnością i powtarzalnością, jest łatwa w stosowaniu i nie wymaga używania atlasu. Początkowym etapom szybkiego wzrastania (Risser 0) odpowiadają aż 4 stadia Sandersa, co zwiększa precyzję oceny wieku kostnego u pacjentek ze skoliozą idiopatyczną