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1.
The influence of $Ce^{3+}$ ions on the corrosion rate of stainless steel in acidic solutions of different pH-values
Aljana Petek, Sebastijan Kovačič, 2014, izvirni znanstveni članek

Opis: The corrosion resistance of AISI 420 stainless steel in 0.1 mol $L^{−1}$ $H_2SO_4$ + 0.1 mol $L^{−1}$ $Na_2SO_4$ solutions at different pH-values and the inhibiting effect of $Ce^{3+}$ ions was studied using electrochemical polarization methods. The results reveal decreasing of the corrosion rate with an increasing the pH of the solution, which demonstrates the progressive protective character of the inhibitor used. At pH lower than 3.33, the corrosion inhibition was most probably a result of the competitive adsorption of $Ce^{3+}$ with $H^+$ ions on the cathodic sites of the electrode surface, and it was found to be dependent on the relative concentration of $H^+$/$Ce^{3+}$. The peroxide generated from the oxygen reduction reaction at pH 3.33 was found to be capable oxidize trivalent cerium (Ce) to the tetravalent state. As obtained hydroxide precipitates act as diffusion barrier hindering the corrosion processes, whereafter a spontaneous passivity occurs on the steel surface at this pH.
Ključne besede: acid corrosion, green corrosion inhibitor, stainless steel, electrochemical techniques
Objavljeno: 24.07.2017; Ogledov: 10; Prenosov: 0
.pdf Polno besedilo (463,32 KB)

2.
Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment
S. Iwata, Samo Korpar, Peter Križan, Rok Pestotnik, Luka Šantelj, Andrej Seljak, Elvedin Tahirović, 2016, izvirni znanstveni članek

Opis: We have developed a new type of particle identification device, called an aerogel ring imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, hybrid avalanche photo-detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and $\gamma$-ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at $3.5\,{\rm GeV}/c$ is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components.
Ključne besede: H14, elementary particle physics, particle detectors, Belle II detector, ring imaging Cherenkov counters, RICH counters
Objavljeno: 21.07.2017; Ogledov: 37; Prenosov: 0
.pdf Polno besedilo (1,57 MB)

3.
Measurement of branching fractions for $B \to J/\psi \eta K$ decays and search for a narrow resonance in the $J/\psi \eta$ final state
T. Iwashita, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2014, izvirni znanstveni članek

Opis: We report an observation of the $B^{\pm } \to J/\psi \eta K^{\pm }$ and $B^0 \to J/\psi \eta K^0_S$ decays using $772\times 10^{6}B\overline {B}$ pairs collected at the $\Upsilon (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We obtain the branching fractions ${\mathcal B}(B^{\pm }\rightarrow J/\psi \eta K^{\pm })=(1.27\pm 0.11(\hbox {stat.})\pm 0.11(\hbox {syst.}))\times 10^{-4}$ and ${\mathcal B}(B^0\to J/\psi \eta K^0_S)=(5.22 \pm 0.78 (\hbox {stat.}) \pm 0.49 (\hbox {syst.}))\times 10^{-5}$. We search for a new narrow charmonium(-like) state $X$ in the $ J/\psi \eta$ mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, ${\mathcal B}(B^\pm \to XK^\pm){\mathcal B}(X \to J/\psi \eta)$, at $3872\,\hbox {MeV}\,c^{-2}$ where a $C$-odd partner of $X(3872)$ may exist, at $\psi (4040)$ and $\psi (4160)$ assuming their known mass and width, and over a range from 3.8 to $4.8\,\hbox {GeV}\,c^{-2}$. The obtained upper limits at 90% confidence level for $X^{C\hbox {-}{\rm odd}}(3872)$, $\psi (4040)$, and $\psi (4160)$ are $3.8\times 10^{-6}$, $15.5\times 10^{-6}$, and $7.4\times 10^{-6}$, respectively.
Ključne besede: C07, C21, particle properties, lepton collider experiments, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 22; Prenosov: 0
.pdf Polno besedilo (372,20 KB)

4.
High-statistics study of $K^0_S K^0_S$ pair production in two-photon collisions
S. Uehara, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2013, izvirni znanstveni članek

Opis: We report a high-statistics measurement of the differential cross section of the process $\gamma \gamma \to K^0_S K^0_S$ in the range $1.05\,{\mathrm {GeV}} \leq W \leq 4.00$ , where W is the center-of-mass energy of the colliding photons, using 972 $^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider operated at and near the $\Upsilon$-resonance region. The differential cross section is fitted by parameterized S-, $D_0$, $D_2$-, $G_0$-, and $G_2$-wave amplitudes. In the $D_2$ wave, the $f_2$(1270), $a_2$(1320), and $f′_2$(1525) are dominant and a resonance, the $f_2$(2200), is also present. The $f_0$(1710) and possibly the $f_0$(2500) are seen in the S wave. The mass, total width, and product of the two-photon partial decay width and decay branching fraction to the $K \bar {K}$ state $\Gamma _{\gamma \gamma }\mathcal {B}(K \bar {K})$ are extracted for the $f′_2$(1525), $f_0$(1710), $f_2$(2200), and $f_0$(2500). The destructive interference between the $f_2$(1270) and $a_2$(1320) is confirmed by measuring their relative phase. The parameters of the charmonium states $\chi _{c0}$ and $\chi _{c2}$ are updated. Possible contributions from the $\chi _{c0}(2P)$ and $\chi _{c2}(2P)$ states are discussed. A new upper limit for the branching fraction of the P- and CP-violating decay channel $\eta _c \to K^0_S K^0_S$ is reported. The detailed behavior of the cross section is updated and compared with QCD-based calculations.
Ključne besede: C00, C05, C07, C21, quantum chromodynamics, quark model, particle properties, lepton collider experiments, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (2,28 MB)

5.
First model-independent Dalitz analysis of $B^0 \to D^0K^{\ast 0}$, $D\to K_S^0\pi ^+\pi ^-$ decay
K. Negishi, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Marko Starič, Luka Šantelj, Anže Zupanc, 2016, izvirni znanstveni članek

Opis: We report a measurement of the amplitude ratio $r_S$ of $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$ decays with a Dalitz analysis of $D\to K_S^0\pi ^+\pi ^-$ decays, for the first time using a model-independent method. We set an upper limit $r_S < 0.87$ at the 68% confidence level, using the full data sample of $711\,{\rm fb}^{-1}$ corresponding to $772\times 10^6$ $B\bar {B}$ pairs collected at the $\Upsilon (4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. This result is obtained from observables $x_- = +0.4 ^{+1.0 +0.0}_{-0.6 -0.1} \pm 0.0$, $y_- = -0.6 ^{+0.8 +0.1}_{-1.0 -0.0} \pm 0.1$, $x_+ = +0.1 ^{+0.7 +0.0}_{-0.4 -0.1} \pm 0.1$, and $y_+ = +0.3 ^{+0.5 +0.0}_{-0.8 -0.1} \pm 0.1$, where $x_\pm = r_S \cos (\delta _S \pm \phi _3)$, $y_\pm = r_S \sin (\delta _S \pm \phi _3)$, and $\phi _3\ (\delta _S)$ is the weak (strong) phase difference between $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$.
Ključne besede: CO2, CO3, Cabibbo-Kobayashi-Maskawa quark-mixing matrix, CP violation, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (555,01 KB)

6.
The efficiency of a membrane bioreactor in drinking water denitrification
Aleksandra Petrovič, Marjana Simonič, 2015, izvirni znanstveni članek

Opis: The membrane bioreactor (MBR) system was investigated regarding its nitrate removal capacity from drinking water. The performance of a pilot-scale MBR was tested, depending on the operational parameters, using sucrose as a carbon source. Drinking water from the source was introduced into the reactor in order to study the influence of flow-rate on the nitrate removal and denitrification efficiency of drinking water. The content of the nitrate was around 70 mg/L and the C/N ratio was 3:1. Nitrate removal efficiencies above 90% were obtained by flow-rates lower than 4.8 L/h. The specific denitrification rates varied between 0.02 and 0.16 g/L NO3/ (g/L MLSS.d). The efficiencies and nitrate removal were noticeably affected by the flow-rate and hydraulic retention times. At the maximum flow-rate of 10.2 L/h still 68% of the nitrate had been removed, whilst the highest specific denitrification rate was achieved at 0.2738 g/L NO3/ (g/L) MLSS.d). The maximum reactor removal capacity was calculated at 8.75 g NO3/m3.h.
Ključne besede: capacity, denitrification, drinking water, efficiency, membrane bioreactor, sucrose
Objavljeno: 19.07.2017; Ogledov: 18; Prenosov: 0
.pdf Polno besedilo (123,62 KB)

7.
Production of biogas by CSF technology
Maša Knez Hrnčič, Mojca Škerget, Željko Knez, 2016, izvirni znanstveni članek

Opis: Hydrogen is expected to become an important fuel in the long-term since in combination with fuel cells it offers the opportunity of an intrinsically clean energy supply. By application of supercritical water gasification (SCWG) concept, sustainable hydrogen can be produced from biomass and waste. The paper offers an overview of some recently published papers dealing with SCWG of model compounds and a summary of the investigations on SCWG of real agricultural and food processing wastes. In the frame of our work an intense research was performed to support analyses of SCWG of glycerol and was supported by the investigation of phase equilibrium for the systems gas/water and gas mixtures/water. When glycerol/water solutions were directly injected in the reactor operating at supercritical conditions, gases with high C2+ were obtained by the reforming in supercritical water unit. To reduce the hydrocarbon concentrations and to obtain a syngas with higher CO/CO2 ratios from a mixture of gases (H2, CO, CO2 and CH4), catalytic reactions at high pressure and temperature were introduced reflecting in an increase of the content of H2 and CO. Solubility measurements were conducted for the binary systems of gas and water at elevated pressures and temperatures.
Ključne besede: biogas, SCF technology, biotechnology
Objavljeno: 19.07.2017; Ogledov: 17; Prenosov: 0
.pdf Polno besedilo (260,94 KB)

8.
Measurement of D0–D‾0 mixing and search for CP violation in D0 → K+K−,π+π− decays with the full Belle data set
Marko Starič, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Anže Zupanc, 2016, izvirni znanstveni članek

Opis: We report an improved measurement of $D^0–{\overline{D}}^0$ mixing and a search for $CP$ violation in $D^0$ decays to $CP$ -even final states $K^+K^−$ and $\pi^+\pi^-$. The measurement is based on the final Belle data sample of $976 fb^{−1}$. The results are $y_CP=(1.11±0.22±0.09)%$ and $A_Γ=(−0.03±0.20±0.07)%$, where the first uncertainty is statistical and the second is systematic.
Ključne besede: charm mesons, mixing, CP violation
Objavljeno: 17.07.2017; Ogledov: 24; Prenosov: 0
.pdf Polno besedilo (577,27 KB)

9.
Synthesis of nickel and cobalt sulfide nanoparticles using a low cost sonochemical method
Matjaž Kristl, Brina Dojer, Sašo Gyergyek, Janja Kristl, 2017, izvirni znanstveni članek

Opis: Nickel and cobalt sulfides are promising materials in different cutting-edge research areas like solar cells, supercapacitors, catalysts, and electrode materials. Nickel and cobalt sulfides with various stoichiometries have been synthesized sonochemically from $Ni(CH_3COO)_2$ ∙ $4H_2O$, $Co(CH_3COO)_2$ ∙ $2H_2O$ and different sulfur precursors using a direct immersion ultrasonic probe. The products were characterized by X-ray powder diffraction, transmission electron microscopy (TEM) including EDX analysis, IR and UV–Vis spectroscopy and elemental analysis. Following products have been obtained: $NiS$, $Ni_3S_4$, $CoS_{1.097}$ and $Co_9S_8$, with average crystallite sizes in the range 7−30 nm. Effects of different reaction conditions on the size, morphology and optical band-gap energy were evaluated. Optical band-gap energies in the range 3.3 eV−3.8 eV were observed for the obtained nanoparticles.
Ključne besede: material science, inorganic chemistry, nanotechnology
Objavljeno: 14.07.2017; Ogledov: 54; Prenosov: 0
.pdf Polno besedilo (2,41 MB)

10.
Use of non-conventional cell disruption method for extraction of proteins from black yeasts
Maja Čolnik, Mateja Primožič, Željko Knez, Maja Habulin, 2016, izvirni znanstveni članek

Opis: The influence of pressure and treatment time on cells disruption of different black yeasts and on activities of extracted proteins using supercritical carbon dioxide process was studied. The cells of three different black yeasts Phaeotheca triangularis, Trimatostroma salinum, and Wallemia ichthyophaga were exposed to supercritical carbon dioxide (SC $CO_2$) by varying pressure at fixed temperature (35°C). The black yeasts cell walls were disrupted, and the content of the cells was spilled into the liquid medium. The impact of SC $CO_2$ conditions on secretion of enzymes and proteins from black yeast cells suspension was studied. The residual activity of the enzymes cellulase, $beta$-glucosidase, $alpha$-amylase, and protease was studied by enzymatic assay. The viability of black yeast cells was determined by measuring the optical density of the cell suspension at 600 nm. The total protein concentration in the suspension was determined on UV–Vis spectrophotometer at 595 nm. The release of intracellular and extracellular products from black yeast cells was achieved. Also, the observation by an environmental scanning electron microscopy shows major morphological changes with SC $CO_2$-treated cells. The advantages of the proposed method are in a simple use, which is also possible for heat-sensitive materials on one hand and on the other hand integration of the extraction of enzymes and their use in biocatalytical reactions.
Ključne besede: P. triangularis, W. ichtyophaga, T. salinum, supercritical carbon dioxide, enzyme activity, cells
Objavljeno: 10.07.2017; Ogledov: 42; Prenosov: 0
.pdf Polno besedilo (2,13 MB)

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