A neutronic evaluation of the (Pu–U) and (Am–Pu–U) insertion in a typical fuel of Angra-I

The goal is to evaluate the neutronic behavior when (Pu–U) and (Am–Pu–U) mixed oxide are inserted in a typical cell of a Pressurized Water Reactor (PWR) such as Angra-I. Four types of fuels were studied: (1) MOX fuel enriched at 3.1% and V_m/V_f = 1.15; (2) MOX fuel enriched at 4.5% and V_m/V_f = 1.15; (3) MOX fuel enriched at 4.5% and V_m/V_f = 2.0 and (4) MOX fuel enriched at 4.5%, with 1% of Americium insertion in its composition (62.8% of Am²⁴¹, 0.1% of Am^242m and 37.1% of Am²⁴³) and with V_m/V_f = 2.0. The first case represents the standard state of Angra I, but with Pu. The second case is similar to the first but the enrichment is increased. To evaluate the Americium insertion, a study of the V_m/V_f was made and better results were obtained with V_m/V_f = 2.0 and to compare, this case was too evaluated to (Pu–U) in the third and fourth cases. The idea is to verify the possibility of using these fuels in Angra-I analyzing neutronic parameters such as infinite multiplication factor, hardening spectrum, Boron worth and reactivity temperature coefficients. The results show that it is possible to use all the studied fuels in Angra-I as well as to burn Am inserted in the MOX fuel by a considerable quantity during PWR operation. The WIMS-D5 code was used to perform a simplified neutronic and burnup simulations to evaluate this possibility.     

Cultural variations in virtual spaces design

This paper reports two studies investigating the role of culture on the design and personalisation of virtual spaces. The first study was a systematic analysis of 60 MSN virtual spaces belonging to British and Chinese students. The analysis concentrated on design patterns and communication style. The second study was an on-line survey designed to compare the relative importance of cultural values and personality traits on self-reported behaviour with, and preferences for, virtual space design. Results highlighted the importance of culture on design and communication in virtual spaces. Implications for interaction design are discussed.     

Diamond-like carbon deposited by plasma technique as a function of methane flow rate

Diamond-like carbon (a-C:H) prepared by plasma enhanced chemical vapor deposition (PECVD) as a function of methane gas flow rate is reported. Films deposited at zero flow rate, i.e., without the use of vacuum pumps during the deposition, are also investigated. For that purpose, the reactor chamber was baked and pumped down to about 10^?8 Torr to reduce contamination released from the reactor walls. The films were analyzed by visible, infrared and Raman spectroscopes. It was observed that the deposition rate, hydrogen concentration and optical gap depend on the methane gas flow rate. A maximum for deposition rate found at methane flow was much smaller than the flow usually adopted in conventional procedures.     

A comparison of fitting algorithms for diffusion-weighted MRI data analysis using an intravoxel incoherent motion model

Object

The objective of this study is to propose a modified VARiable PROjection (VARPRO) algorithm specifically tailored for fitting the intravoxel incoherent motion (IVIM) model to diffusion-weighted magnetic resonance imaging (DW-MRI) data from locally advanced rectal cancer (LARC).

Materials and methods

The proposed algorithm is compared with classical non-linear least squares (NLLS) analysis using the Levenberg-Marquardt (LM) algorithm and with two recently proposed algorithms for ‘segmented’ analysis. These latter two comprise two consecutive steps: first, a subset of parameters is estimated using a portion of data; second, the remaining parameters are estimated using the whole data and the previous estimates. The comparison between the algorithms was based on the \(R^2\) goodness-of-fit measure: performance analysis was carried out on real data obtained by DW-MRI on 40 LARC patients.

Results

The performance of the proposed algorithm was higher than that of LM in 64 % of cases; ‘segmented’ methods were poorer than our algorithm in 100 % of cases.

Conclusion

The proposed modified VARPRO algorithm can lead to better fit of the IVIM model to LARC DW-MRI data compared to other techniques.

     

Synthesis and characterization of Y (In,Mn) O3 blue pigment using the complex polymerization method (CPM)

In this paper, a new synthetic pathway is proposed for the system YIn_1-xMn_xO₃, a bright blue inorganic pigment, discovered in 2009. Blue pigment samples with increasing concentration of Mn³⁺ (x?=?0.08, 0.12 and 0.16) were prepared using the complex polymerization method (CPM) and compared with those synthesized via solid state reaction. All powders, the amorphous precursor from CPM and the starting materials for solid state method, were calcined at 1000, 1100, 1200 and 1300?°C for 12?h, and the resulting blue pigments were characterized by X-ray diffraction (XRD), colorimetric system CIE L*a*b* and Near infrared (NIR) reflectance measurements. XRD patterns and Rietveld Refinement show that the lowest temperature at which single hexagonal phase (isostructural to YInO₃) is formed is 1000?°C for CPM method and 1300?°C for conventional solid state method, respectively. The L*a*b* values demonstrate that the coloration of powders prepared by CPM exhibit temperature dependence below 1300?°C, a color shade shift from grayish blue to intense deep blue is observed when heating the samples from 1000 to 1300?°C. Blue pigments obtained by CPM have smaller particle size due to low temperatures and excellent near-infrared reflectance comparable to those by solid state method. Thus, providing advantages for application process and energy efficiency.     

From Spheroids to Organoids: The Next Generation of Model Systems of Human Cardiac Regeneration in a Dish

Organoids are tiny, self-organized, three-dimensional tissue cultures that are derived from the differentiation of stem cells. The growing interest in the use of organoids arises from their ability to mimic the biology and physiology of specific tissue structures in vitro. Organoids indeed represent promising systems for the in vitro modeling of tissue morphogenesis and organogenesis, regenerative medicine and tissue engineering, drug therapy testing, toxicology screening, and disease modeling. Although 2D cell cultures have been used for more than 50 years, even for their simplicity and low-cost maintenance, recent years have witnessed a steep rise in the availability of organoid model systems. Exploiting the ability of cells to re-aggregate and reconstruct the original architecture of an organ makes it possible to overcome many limitations of 2D cell culture systems. In vitro replication of the cellular micro-environment of a specific tissue leads to reproducing the molecular, biochemical, and biomechanical mechanisms that directly influence cell behavior and fate within that specific tissue. Lineage-specific self-organizing organoids have now been generated for many organs. Currently, growing cardiac organoid (cardioids) from pluripotent stem cells and cardiac stem/progenitor cells remains an open challenge due to the complexity of the spreading, differentiation, and migration of cardiac muscle and vascular layers. Here, we summarize the evolution of biological model systems from the generation of 2D spheroids to 3D organoids by focusing on the generation of cardioids based on the currently available laboratory technologies and outline their high potential for cardiovascular research.     

Cyanobacteria,Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons

The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.     

Water soluble trehalose-derived oligoamides

A new family of oligotrehaluronamides was synthesized through the polycondensation of α,α-trehaluronic acid dimethyl ester and different diamines or polyamines. In particular, diamines with different molecular structure (1,n-alkylene diamines, aromatic diamine, and alkyleneoxydiamine) were used in order to modulate the molecular weights and the physical characteristics of the products, such as T_g, hydrophilic or hydrophobic properties, and solubility. α,α-Trehaluronic acid was obtained from a renewable source as α,α-trehalose. The syntheses of oligotrehaluronamides were carried out in different solvents such as ethanol, methanol, THF and DMSO, using triethylamine as catalyst. All the compounds obtained in this study were characterized through FT-IR and NMR spectroscopy. The molecular weights were evaluated by ¹H-NMR and in some cases compared with those obtained from ESI-MS spectrometry. Glass transition temperatures and melting points were detected by differential scanning calorimetry. Low molecular weight oligoamides, containing several hydroxyl groups, are water-soluble and could be used in water-based formulations.     

Computational Studies of Smell and Taste Receptors

Smell and taste are among the basic senses with which we perceive the world around us. In addition to enabling recognition of chemical moieties that provide social or nutritional clues, taste and smell receptors are expressed in many extraoral tissues, including the gastrointestinal, respiratory, and reproductive systems. It is, therefore, likely that taste and smell receptors have additional physiological roles, which are currently under intensive study. Most of the taste modalities, as well as olfaction, are mediated by G-protein coupled receptors (GPCRs). Recent breakthroughs in crystallography and signaling studies of GPCRs (celebrated by the 2012 Nobel Prize in Chemistry to Robert Lefkowitz and Brian Kobilka) provide excellent opportunities for applying this information towards furthering our understanding of taste and smell signaling. No crystal structures of odorant or taste receptors are currently available. However, computational techniques, many of which stem from the pioneering contributions of the 2013 Nobel Prize in Chemistry laureates, Martin Karplus, Michael Levitt, and Arieh Warshel, can shed light on the function of taste and olfactory GPCRs. In this review, we highlight examples of iterative combinations of simulation and experiment that were successfully applied toward delineating binding modes of tastants and odorants and toward predicting additional ligands. Further studies are required in order to answer remaining questions regarding receptor promiscuity versus selectivity, the details of receptor coupling to G-proteins, and the roles of oligomerization and of allosteric modulation in taste and smell transduction.