Center Of Core Research Articles

Sustainability obstacles of free bike-sharing model

Cycling is one of the options for sustainable urban mobility. Although this transport mode is not so widely used in Slovak cities, the bike-sharing project in Žilina with 80 thousand inhabitants has been remarkably successful. The system comprises of 120 shared bikes and 20 bike stations located mainly in the city core and wider centre to cover important transport destinations. During the first-year usage, a great interest of citizens has been recorded also thanks to the one-hour-free-of-charge service. That leads to an average rental number of 35 thousand bicycles per month (with a maximum of 47 thousand) and a high usage rate of the system (on average, 9.5 rides per bike per day). A more detailed analysis, including the Covid-19 pandemic’s impact on reducing bicycle rental, is presented in the article. In addition to the positive experience with the bike-sharing system, the disadvantages of the one-hour-free service model are discussed. In addition to the reduced service availability for citizens with real transport needs or higher users’ disrespect to the system, the technical operation costs are about 40 % higher due to an excessive wear system, poorer technical condition, and shorter lifespan of bicycles, or increase in a certain form of vandalism due to the bicycle joyriding. Ultimately, the overall loss is much higher because of no income, which threatens the sustainability of this system.

Local and high distance neutron and gamma measurements of fuel rods oscillation experiments

We report in the present article on the successful observation using noise analysis of the lateral oscillation of one fuel rod by ±2.5 mm around nominal at 0.1 Hz frequency, using an mm3miniature neutron scintillatorat the rod level, and a BGO gamma detectorseven meters away from the reactor core center. The experiment was conducted as part of the COLIBRI program in the CROCUS reactor, which is dedicated to the investigation of reactor noise induced by fuel vibrations. It consists in experiments on rod lateral displacement (static) and oscillation (dynamic) with different rods’ numbers at various relevant amplitudes and frequencies. Its main motivation is the increased amplitudes in the neutron noise distributions recorded in ex- and in-core detectors that have been observed in recent years in Siemens pre-Konvoi type of PWR reactors. The obtained experimental data are used for the purpose of code validation, especially within the framework of the European project CORTEX on reactor noise applications. During the first phase of COLIBRI, the observation of a spatial dependence of the perturbation noise, also called neutron modulation, was demonstrated. In the second phase of COLIBRI starting 2021, it is planned to use a core mapping array of neutron detectors to record its propagation. It consists in about 150 miniature scintillators coupled to optical fibers and SiPM readouts, to be distributed in the reactor core. As a feasibility test, experiments were performed using a miniature scintillator prototype placed on a fuel rod, and oscillating the instrumented rod or the one directly adjacent to the detector. In addition, it is theoretically possible to measure branching or perturbation reactor noise using gamma radiation. Following recent developments on gamma measurements in CROCUS, the fuel oscillation was simultaneously recorded with a gamma detection array, LEAF. Its large BGO detectors were used by placing them at the maximum distance to the core, i.e. seven meters away with a clear line of sight using an experimental channel through the shielding of the reactor cavity.

Analysis of lutetium-177 production at the WWR-K research reactor

Production of lutetium-177 using direct nuclear reaction 176Lu(n,γ)177Lu by WWR-K reactor neutrons on enriched LuCl3 (up to 82% of 176Lu) is described. Calculations were performed by MCNP6 transport code. Two different irradiation positions of the WWR-K research reactor were considered. Estimates of the maximum specific activity of the luthetium-177 are obtained for the reactor irradiation positions located: (a) in the reactor core centre, (b) in the core periphery. In these positions, thermal neutron flux is two times different.Experimental data was shown that k-factor is 1.5 for considered irradiation positions. The study shows that for the position located in the core center, the estimated maximum specific activity of lutetium-177 is 819 GBq/mg, is to be achieved after 15 days of irradiation. For the position located in the core periphery, specific activity of lutetium-177 is 561 GBq/mg, is to be achieved after 20 days of irradiation. Ratio of Lu-177m to Lu-177 specific activity is not more than 0.025 for both irradiation positions.

Numerical Investigation of Tip Vortex Cavitation Inception and Noise of Underwater Propellers of Submarine Using Sequential Eulerian–Lagrangian Approaches

In this study, the high-fidelity numerical methods are developed to investigate the tip vortex cavitation (TVC) inception and noise of underwater propellers, namely, Model-A and Model-B, which are designed to investigate the effects of sweep angle on cavitation inception and noise. In addition, the entire body of the DARPA Suboff submarine is included to consider the effects of the inflow distortion originating from the boundary layer flow of the submarine body on the cavitating flow of the propellers. The Eulerian approach consisting of Reynolds-averaged Navier–Stokes (RANS) solver and the vortex model is coupled with the Lagrangian approach using the bubble dynamics equations and the acoustic analogy for nuclei initially distributed in inlet flow. First, three-dimensional incompressible unsteady RANS simulations are performed to predict the hydrodynamic flow field driven by underwater propellers installed on a DARPA Suboff submarine body. The Scully vortex model and dissipation vortex model (DVM) are used to regenerate the tip vortex dissipated by artificial numerical damping and low grid resolution around the vortex core center, which is identified by using minimum λ2-criterion in the swirling flow field originating from the propeller blade tip. Then, tip vortex cavitation inception is simulated by applying the bubble dynamics equations to nuclei initially distributed in the inflow region. The volume and location of each nucleus are obtained by solving the bubble dynamics equations on the flow field obtained using the Eulerian method. Finally, the cavitation noise is predicted by modeling each bubble with a point monopole source whose strength is proportional to its volume acceleration. The validity of the present numerical methods is confirmed by comparing the predicted acoustic pressure spectrum with the measured ones.

High Frequency Characteristics of the Near Wake and Vortex Past a Triangular Cylinder

Abstract The flow past a triangular cylinder is one of the fundamental flows and widely utilized in flame stabilization and heat transfer. In this study, the near wake and vortex characteristics of the flow past an equilateral triangular cylinder are experimentally measured by a high frequency particle image velocimetry (PIV) system at 3 kHz. The triangular cylinder is installed in a wind tunnel with Reynolds numbers ranging from 10,700 to 17,700. The Reynolds-averaged and phase-averaged methods are utilized to analyze the flow field. Based on the flow fields, the length of the vortex formation region is about 1.5 times of the length of the equilateral triangle side. The residence time of a vortex in the vortex formation region is equal to a vortex shedding period. The stream wise velocity of the vortex core center downstream the vortex formation is about 0.8 times of the freestream velocity, which is slightly larger than the value about 0.7 for the flow past a circular cylinder at the same Reynolds number. The maximum tangential velocity at the periphery of the vortex core maybe occurs slightly in advance of the vortex reaching the boundary of the vortex formation region. The normalized lengths of the recirculation zone of the triangular cylinder keep nearly unchanged and are about 1.55 to 1.9 times of those of the circular cylinder at the same Reynolds number. The normalized normal wise instead of stream wise turbulence intensity has stronger effects on the distribution of the normalized turbulent kinetic energy.

Statistical data analysis in the DANSS experiment

DANSS is a one cubic meter highly segmented solid scintillator detector. DANSS is placed under a 3.1 GW industrial reactor at the Kalininskaya NPP (Russia) on a movable platform. The distance from the reactor core center is varied from 10.9 m to 12.9 m on-line. The inverse beta decay (IBD) process is used to detect antineutrinos. DANSS detects about 5000 IBD events per day with the background from cosmic muons at the level of 2%. Sterile neutrinos are searched for assuming a 4 neutrino model (3 active and 1 sterile neutrino). The exclusion area in the sterile neutrino parameter plane is obtained using a ratio of positron energy spectra collected at different distances. New analysis that uses information about relative counting rates as well as changes in positron energy spectra shapes is described. We present recent results based on 3.5 million IBD events collected at 3 distances from detector to reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to sin2 2θ ee < 0.008 in the most sensitive region. The significance of the best-fit point in the parameters space is 1.5σ.

Intensity-modulated refractometer based on mode-mismatch in surface waveguides inscribed by femtosecond laser direct writing

Optical waveguides were fabricated at the surface of Eagle2000 glass substrates, using femtosecond laser direct writing and wet etching, and their potential as intensity-modulated refractometers was assessed. Through the analysis of their broadband spectral response to different refractive index oils, we observed that mode mismatch is present when the guided mode reaches the surface of the substrate and interacts with the external medium, thus enabling the use of such optical waveguides in refractive index sensing. Refractive indices equal to or greater than that of the substrate also induced a coupling mechanism that was shown not to be suitable in these devices. The device’s wavelength of operation was found to be tunable by controlling the distance between the surface and the center of the optical waveguide. However, the sensitivity was seen to diminish by increasing the latter, being nonexistent for distances greater than 5.5 µm. In this study, the maximum sensitivity values were found for a surface to core center distance between 1 and 2 µm, in the biological range, and 2.5 to 3 µm, for a refractive index nearing that of the substrate. Accordingly, maximum sensitivities of ≈25 dB/RIU and ≈1200 dB/RIU were found between 1.300 <nD25ºC< 1.400 and 1.490 <nD25ºC< 1.500, respectively.

Standardization and harmonization in hematology: Instrument alignment, quality control materials, and commutability issue.

In the hub and spoke laboratory network, the number of hematology analyzers (HAs) within each core center has increased, and the control of HAs alignment is becoming necessary requirement to ensure analytical quality. In this scenario, HA alignment can be assessed by analyzing the same control material used for internal quality control on multiple HAs, assuming its commutability. The aim of the study was to verify the applicability of a protocol for the alignment of HAs based on control material rather than on fresh whole-blood samples. The alignment of five HAs was evaluated for red (RBC, Hb, MCV, RET), white (WBC, NE, LY, MO, EO, BA, IG), and platelet (PLT) series parameters, following a protocol by SIBioC, using human sample (HS) and quality control material (QC), after the verification of commutability, according to the IFCC protocol. Maximum bias was derived from biological variation data. A complete alignment between instruments was confirmed for the majority of the parameters investigated both for HS and QC material. Partial misalignments or inconcludent results were instead evident for MCV, MO, EO, BA, and IG. Interestingly, QC material was found to be not commutable for LY, MO, and BA. The alignment of hematologic analyzers for main cell population parameters may be verified with both QC and HS, displaying consistent results and interpretation. The evaluation for some white series parameters (EO, BA, and IG) is critical, and particular attention must be paid to the values of the material used for the alignment.

Approaches to simulate destruction of a fuel rod with different fuel types

Due to the revival of interest to the development of fast reactors cooled by liquid metals, the theoretical research for improving their safety is actual. A detailed calculation of all stages of an accident from the beginning to the end requires knowledge of the laws for modelling physical processes occurring in the reactor in case of emergency. The most serious are accidents with core destruction. Simulation of a severe accident in a nuclear reactor is the key element in safety analysis of nuclear power plants. Destruction of fuel rods is one of the most important processes during core degradation that should be calculated. For different types of fuels the mechanisms of the degradation are different too. For example, oxide and metallic fuels usually melt congruently at high temperature, but nitride fuel dissociates. The main objective of the proposed research is to develop models and numerical algorithms for calculation of the destruction of fuel rods with oxide, metallic and nitride fuels. The models of destruction and some calculation results are presented in the paper. The processes are investigated for the first phase of severe accidents, covering the period from the onset of fuel-rod melting to the melt escape from the core center.

Testing Oxygen Nuclear Data Libraries in Research Center Rez

Abstract Oxygen belongs to the group of the most important isotopes in the nuclear data field. The aim of this paper is validate various oxygen nuclear data libraries in different scenarios with high content of oxygen. For this purpose, fast neutron spectra were measured by a stilbene scintillation detector in the region of 1–10 MeV in the three model cases involving 252Cf neutron source and light water reactor. The cases include measurements of leakage spectra using 252Cf neutron source placed in the centers of the light water and heavy water spheres of 0.30 m diameter. Following measurements were carried out inside the concrete biological shielding of the VVER-1000 mock-up simulator in the LR-0 reactor and in the dry channel located in the center of the special core placed in the LR-0 reactor. In the case of the special core, symmetric active core consisted of six standard fuel assemblies which surround the experimental dry module, where the fast neutron spectrum was measured. The measured neutron spectra were compared with MCNP6 transport code calculations in ENDF/B-VII.1, ENDF/B-VIII.0, JENDL-4.0, and IRSN 16O nuclear data evaluations. Experimental results for all cases follow similar trend. All considered libraries underestimate experimental measurement in the region of 3–4 MeV in all cases.

Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ): A Chloride-Centered Ag-Au Bimetallic Cluster for Optics.

We report the single-crystal synthesis of a chlorine-centered bimetallic cluster, Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ), which bears a quatrefoil-structured Cl@Ag22 (SR)16 core studded by six Au(SR)2 staples showing a quasi Td symmetry. This cluster bears 28 metal atoms and 28 ligands, with a chlorine atom hosted in the center of the metallic Ag22 Au6 core. Single-crystal analysis shows that this cluster possesses essentially a different bonding nature compared with other monolayer-protected metal clusters (MPCs) or traditional metal-sulfur complexes. We fully dissect the structure evolution in forming such a chlorine-centered cluster. Interestingly, this cluster, Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ), displays a fluorescence emission at 570 nm and supports the solid emission with a minor red shift at 574 nm. On the other hand, we have tested the nonlinear optical property and observed unambiguous nonlinear optical property with a normal valley-shaped transmittance curve corresponding to reverse saturated absorption (RSA) of the cluster.

Dynamics of Pd Dopant Atoms inside Au Nanoclusters during Catalytic CO Oxidation.

Doping gold nanoclusters with palladium has been reported to increase their catalytic activity and stability. PdAu24 nanoclusters, with the Pd dopant atom located at the center of the Au cluster core, were supported on titania and applied in catalytic CO oxidation, showing significantly higher activity than supported monometallic Au25 nanoclusters. After pretreatment, operando DRIFTS spectroscopy detected CO adsorbed on Pd during CO oxidation, indicating migration of the Pd dopant atom from the Au cluster core to the cluster surface. Increasing the number of Pd dopant atoms in the Au structure led to incorporation of Pd mostly in the S–(M–S)n protecting staples, as evidenced by in situ XAFS. A combination of oxidative and reductive thermal pretreatment resulted in the formation of isolated Pd surface sites within the Au surface. The combined analysis of in situ XAFS, operando DRIFTS, and ex situ XPS thus revealed the structural evolution of bimetallic PdAu nanoclusters, yielding a Pd single-site catalyst of 2.7 nm average particle size with improved CO oxidation activity.

Reduction of differential modal gain in a two-mode amplifier using a void-inscribed EDF.

We propose a technique for reducing the differential modal gain (DMG) that occurs in a two-mode erbium-doped fiber (2M-EDF) by inscribing voids in the core center of a 2M-EDF with a femtosecond laser. We show that an empty void inscribed at the core center can attenuate the linearly polarized (LP01) mode selectively while suppressing excess loss for the LP11 mode. We also reveal that DMG can be controlled by means of void diameter. The longitudinal position dependence of the void in a 2M-EDF was also investigated considering its influence on gain and noise figure (NF) characteristics. Finally, we realize a sufficiently low DMG of less than 0.5 dB in the full C-band as well as a sufficient gain and NF by using the proposed technique.

Identification of Protein Complexes Based on Core-Attachment Structure and Combination of Centrality Measures and Biological Properties in PPI Weighted Networks.

In protein interaction networks, a complex is a group of proteins that causes a biological process to take place. The correct identification of complexes can help to better understand function of cells used for therapeutic purposes, such as drug discoveries. This paper uses core-attachment structure, centrality measures, and biological properties of proteins to identify protein complex with the aim of enhancing prediction accuracy compared to related work. We used the inherent organization of complex to the identification in this article, while most methods have not considered such properties. On the other hand, clustering methods, as the common method for identifying complexes in protein interaction networks have been applied. However, we want to propose a method for more accurate identification of complexes in this article. Using this method, we determined the core center of each complex and its attachment proteins using the centrality measures, biological properties and weight density, whereby the weight of each interaction was calculated using the protein information in the gene ontology. In the proposed approach to weighting the network and measuring the importance of proteins, we used our previous work. To compare with other methods, we used datasets DIP, Collins, Krogan, and Human. The results show that the performance of our method was significantly improved, compared to other methods, in terms of detecting the protein complex. Using the p-value concept, we show the biological significance of our predicted complexes. The proposed method could identify an acceptable number of protein complexes, with the highest proportion of biological significance in collaborating on the functional annotation of proteins.

Rapid elimination of small dust grains in molecular clouds

We argue that impact velocities between dust grains with sizes of less than ∼0.1 μm in molecular cloud cores are dominated by drift arising from ambipolar diffusion. This effect is due to the size dependence of the dust coupling to the magnetic field and the neutral gas. Assuming perfect sticking in collisions up to ≈50 m s−1, we show that this effect causes rapid depletion of small grains, consistent with starlight extinction and IR and microwave emission measurements, both in the core center (n ∼ 106 cm−3) and envelope (n ∼ 104 cm−3). The upper end of the size distribution does not change significantly if only velocities arising from this effect are considered. We consider the impact of an evolved grain-size distribution on the gas temperature, and argue that if the depletion of small dust grains occurs as expected from our model, then the cosmic ray ionization rate must be well below 10−16 s−1 at a number density of 105 cm−3.

Phosphorylation remodels amyloid

Structural Biology Abnormal aggregation of the protein α-synuclein (α-syn) is a hallmark of Parkinson's disease (PD) and several other neurodegenerative disorders. Disease-associated α-syn amyloid fibrils accumulate in Lewy bodies and are often phosphorylated. Phosphorylation at tyrosine 39 (Y39) increased neuropathology in a PD mouse model. Zhao et al. combined chemical synthesis and bacterial expression to prepare α-syn that could be site-specifically phosphorylated at Y39 (pY39). A structure determined by cryo–electron microscopy showed that in the pY39 fibril, the fibril core extends to include the entire N-terminal domain (the core ordinarily starts at around residue 40). Charged residues at the N terminus, including pY39, form a network of interactions in the center of the fibril core. This extended core may explain why pY39 fibrils are resistant to proteolysis, and the structure highlights how posttranslational modifications can affect the structure of fibrils, which in turn mediates their pathology. Proc. Natl. Acad. Sci. U.S.A. 117 , 20305 (2020).

Core and blanket thermal–hydraulic analysis of a molten salt fast reactor based on coupling of OpenMC and OpenFOAM

In the core of a molten salt fast reactor (MSFR), heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant. Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation. Therefore, the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics. Moreover, recirculation flow occurs, and nuclear heat is accumulated near the fertile blanket, which significantly affects both the flow and the temperature fields in the core. In this work, to further optimize the conceptual geometric design of the MSFR, three geometries of the core and fertile blanket are proposed, and the thermal–hydraulic characteristics, including the three-dimensional flow and temperature fields of the fuel and fertile salts, are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM. The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core. Moreover, eight cooling loops with a total flow rate of 0.0555 m3 s−1 ensure an acceptable temperature distribution in the fertile blanket.

Impurity states in InGaAsP/InP core–shell quantum dot under external electric field

In the framework of effective mass envelope function approximation, the impurity states are calculated in InGaAsP/InP core–shell quantum dots by plane wave expansion method, and the effect of electric field is considered. The impurity binding energies in 1s and 2p ± states, and the impurity transition energy between 1s state and 2p ± state are calculated and analyzed in detail with the change of shell thickness, core radius, impurity position, and electric field strength. The results show that the impurity states in the core are stable when the shell thickness is more than 0.4a * . The binding energies and transition energies decrease with the increase of core radius. The applied electric field destroys the symmetrical distribution of binding energy and transition energy about the core center. The increase or decrease of the binding energy and transition energy depend upon the position of impurity and the direction of electric field.

Attitudes of pain and opioids prescription practices in U.S. cystic fibrosis centers

BackgroundThe high incidence and prevalence of chronic pain in patients with cystic fibrosis (CF) is well documented. However, there is limited data on chronic pain management in this population. MethodsWe designed a questionnaire examining care team members’ views on the prevalence and characteristics of pain, pain management, and opioid use. The questionnaire was distributed to accredited programs throughout the US via a CF Foundation (CFF) email list-serve. ResultsResponses came from 52 adult core or affiliated centers (Adult Responders – AR), 36 pediatric core or affiliated centers (Pediatric Responders – PR), and 9 were from combined programs. AR perceive more patients having chronic pain compared to PR. Furthermore, 40% of the AR said that > 50% of those with chronic pain also have comorbid depression or anxiety. 61% of PR ranked sinus/headache symptoms as the most common while AR ranked chest wall as the most frequent site (58%). While most centers (83%) report that pain management in patients with CF is a very important or important issue, 50% of AR feel uncomfortable or only slightly comfortable in prescribing opioids. 44% report that CF providers are currently responsible for this task. ConclusionsChronic pain is common in adult patients with CF and management presents a formidable challenge to providers. The development of guidelines and/or collaboration with pain specialists will likely benefit both patients and providers.

Electro-Absorption Optical Modulator Based on Graphene-Buried Polymer Waveguides

By exploiting the electro-absorption characteristic of graphene, we proposed and theoretically demonstrated an electro-absorption optical modulator (EOM) based on the graphene-buried polymer waveguides. By burying the graphene layers inside the polymer waveguide, acquiring a strong graphene-light interaction when the graphene layers buried in the center of core, which bring about an important change of the optical mode and effective mode index in the waveguide. The width of the graphene capacitor was also optimized to enhance the bandwidth of the device. Calculations show that the proposed EOM can realize 29 dB extinction ratio, 7 dB modulation depth and 42 GHz bandwidth with an 800 μm-long active region. The required switching voltage form its minimum to maximum absorption state is 1.6 V and 1.55 pJ/bit energy consumption can be achieved. The proposed modulator can remedy the lack of high-speed optical modulator on the passive polymer waveguide and have a potential application for polymer-based photonic integrated circuits.