Highly site-specific H2 adsorption on vicinal Si(001) surfaces

Experimental and theoretical results for the dissociative adsorption of H_2 on vicinal Si(001) surfaces are presented. Using optical second-harmonic generation, sticking probabilities at the step sites are found to exceed those on the terraces by up to six orders of magnitude. Density functional theory calculations indicate the presence of direct adsorption pathways for monohydride formation but with a dramatically lowered barrier for step adsorption due to an efficient rehybridization of dangling orbitals.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett. (1998). Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Exploring the perspectives of integrated reporting for future research opportunities

This paper investigates the perspectives of integrated reporting as an emerging field in mainstream academic literature. The current state of research and its development are explored by using the Structured Literature Review (SLR) method on publications indexed in Clarivate Analytics’ Web of Science. An analytical framework is designed for applying the coding procedure. The findings suggest an evolution of integrated reporting research from the phase of spreading awareness regarding the new reporting paradigm towards an impact analysis phase. The accounting and audit journals are noted to have greatly contributed to the shift of IR literature towards studying the integrated reporting as a reporting practice. A further purpose is to examine newly developed research interest in integrated reporting and to establish future paths to be followed. Future research might bring to discussion possible links between integrated reporting, governance and integrated thinking. The complex interrelationships influencing the companies’ ability to create value for the multi-stakeholders need to frame the practice-oriented research

NANOSTRUCTURED TiO2 SENSITIZED WITH PORPHYRINS FOR SOLAR WATER-SPLITTING

Nanostructured TiO2 sensitized with porphyrins for Solar water-splitting.The production of hydrogen from water using solar light is very promising for generations of an ecologically pure carrier contributing to a clean, sustainable and renewable energy system. The selection of specific photocatalyst material for hydrogen production in photoelectrochemical cells (PECs) is based on some important characteristics of semiconductor, such as photo-corrosion and chemical corrosion stability, photocatalytic potential, high sensitivity for UV-visible light. In the present paper, different nanocrystalline TiO2 photoanodes have been prepared via wet-chemical techniques followed by annealing treatment and sensitized with porphyrins and supramolecular complexes of porphyrins. The so obtained photocatalysts were characterized with UV-VIS absorption spectroscopy and spectrofluorimetry. The purpose of these experiments is to show if the prepared materials possess the necessary photocatalytic characteristics and if they can be used with success in H2 production from water decomposition in PECs

Fogazati rendellenességek kezelési szükségletének tárgyilagos felmérése a Dental Aesthetic Index segítségével = Objective evaluation of orthodontic treatment need with Dental Aesthetic Index

Absztrakt: Bevezetés és célkitűzés: Egy marosvásárhelyi felnőtt pácienscsoport fogazati rendellenességeinek, ezek előfordulási arányának és súlyossági fokának életkor és nem szerinti felmérése. Módszer: Hatvannégy, véletlenszerűen kiválasztott pácienst életkor és nem szerint osztályoztunk. A fogazati rendellenességekre jellemző, tíz fogíven belüli elváltozást (hiányzó fogak, hézagok, torlódások stb.) értékeltünk ki minden páciens tanulmányi mintáján. A Dental Aesthetic Index (DAI) szerinti regressziós egyenlettel meghatároztuk minden eset DAI-értékét és a rendellenesség súlyossági fokát. Eredmények: A DAI-érték átlaga 38 volt; 18–79 közötti értékeket találtunk, ami azt mutatja, hogy a vizsgált egyének esetében elengedhetetlen a fogszabályozás. Nem találtunk statisztikailag szignifikáns különbséget a nemek, az életkor és a kezelés szükségszerűsége között. Következtetés: A vizsgált csoport több mint 2/5-ének esetében szükségszerű a fogszabályozás, ha a DAI-értéket használjuk. Orv Hetil. 2018; 159(9): 352–356. | Abstract: Introduction and aim: To evaluate the frequency and severity of the malocclusions and treatment need in a group of adult patients in Târgu-Mureș, dividing them up according to age and gender. Method: Sixty-four, randomly selected patients were divided up according to age and gender. Ten occlusal traits related to dentofacial anomalies according to missing teeth, spacing, crowding and occlusion were used to evaluate the malocclusions on each of their study cast. The Dental Aesthetic Index (DAI) regression equation was used to obtain the DAI score that defines severity. Results: The average DAI score was 38 with a range of 18–79, showing that the majority of patients needed mandatory orthodontic treatment. No statistically significant difference was found between gender, age groups and need for treatment. Conclusion: More than two-fifths of the examined patients have a mandatory need for orthodontic treatment if the DAI scores are the main screening tool. Orv Hetil. 2018; 159(9): 352–356

Density-functional study of hydrogen chemisorption on vicinal Si(001) surfaces

Relaxed atomic geometries and chemisorption energies have been calculated for the dissociative adsorption of molecular hydrogen on vicinal Si(001) surfaces. We employ density-functional theory, together with a pseudopotential for Si, and apply the generalized gradient approximation by Perdew and Wang to the exchange-correlation functional. We find the double-atomic-height rebonded D_B step, which is known to be stable on the clean surface, to remain stable on partially hydrogen-covered surfaces. The H atoms preferentially bind to the Si atoms at the rebonded step edge, with a chemisorption energy difference with respect to the terrace sites of >sim 0.1 eV. A surface with rebonded single atomic height S_A and S_B steps gives very similar results. The interaction between H-Si-Si-H mono-hydride units is shown to be unimportant for the calculation of the step-edge hydrogen-occupation. Our results confirm the interpretation and results of the recent H_2 adsorption experiments on vicinal Si surfaces by Raschke and Hoefer described in the preceding paper.Comment: 13 pages, 8 figures, submitted to Phys. Rev. B. Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO2_2 interfaces

The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO$_2$ interfaces is studied experimentally in planar Si(001)-SiO$_2$-Cr MOS structures by optical second-harmonic generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct two-photon $E_1$ transition of silicon is extracted. A systematic phenomenological model of the EFISH phenomenon, including a detailed description of the space charge region (SCR) at the semiconductor-dielectric interface in accumulation, depletion, and inversion regimes, has been developed. The influence of surface quantization effects, interface states, charge traps in the oxide layer, doping concentration and oxide thickness on nonlocal screening of the DC-electric field and on breaking of inversion symmetry in the SCR is considered. The model describes EFISH generation in the SCR using a Green function formalism which takes into account all retardation and absorption effects of the fundamental and second harmonic (SH) waves, optical interference between field-dependent and field-independent contributions to the SH field and multiple reflection interference in the SiO$_2$ layer. Good agreement between the phenomenological model and our recent and new EFISH spectroscopic results is demonstrated. Finally, low-frequency electromodulated EFISH is demonstrated as a useful differential spectroscopic technique for studies of the Si-SiO$_2$ interface in silicon-based MOS structures.Comment: 31 pages, 14 figures, 1 table, figures are also available at http://kali.ilc.msu.su/articles/50/efish.ht

HEPATORENAL SYNDROME: A REVIEW

Hepatorenal syndrome (HRS) is defined as a functional renal failure in patients with liver disease that features morphologically intact kidneys, where regulatory mechanisms have minimized glomerular filtration and maximized tubular resorption and urine concentration. The syndrome occurs almost exclusively in patients with ascites. Type 1 HRS develops as a consequence of a severe reduction of effective circulating volume due to both an extreme splanchnic arterial vasodilatation and a reduction of cardiac output. Type 2 HRS is characterized by a stable or slowly progressive renal failure so that its main clinical consequence is not acute renal failure, but refractory ascites, and its impact on prognosis is less negative. Liver transplantation is the most appropriate therapeutic method, nevertheless, only a few patients can receive it. The first line treatment includes terlipressin plus albumin. Renal function recovery can be achieved in less than 50% of patients and a considerable decrease in renal function may reoccur even in patients who have been responding to therapy over the short term. Other therapies include transjugular intrahepatic portosystemic shunts (TIPS), dialysis and peritoneovenous shunts which are most commonly done when patients are awaiting a liver transplant or when there is the possibility of improvement in liver function

The role of Bosniak classification in the assessment of renal cystic masses and in the therapeutical protocol

One of the most frequent kidney pathologies encountered in daily practice is represented by the presence of renal cysts. Most of them are asymptomatic and are found accidentally during periodical check-ups because they don’t have clinical signs until they grow and compress the surrounding organs. We have reviewed the current data regarding this pathology, in order to underline the risk of malignant transformation and its impact on the patient’s life. It is estimated that the prevalence rate of renal cysts in the general population is approximately 10% and it increases with age.Imaging investigations, such as contrast tomography or magnetic resonance imaging, are essential for establishing the cysts characteristics, especially when ultrasonography raises the suspicion of a modified renal cyst, as well as in guiding the therapeutical protocol. The Bosniak classification is based on contrast tomography scans and has allowed the standardization of the kidney cysts, considering their characteristics. More attention should be given to Bosniak IIF and III cystic renal masses, which contain thickened walls and more septa, but no enhanced nodules/soft tissue components, because more than half of these cysts can have a malignant component