Potential energy topology and relaxation processes in a model glass

We use computer simulation to investigate the topology of the potential energy $V(\{{\bf R}\})$ and to search for doublewell potential's (DWP) in a model glass . By a sequence of Newtonian and dissipative dynamics we find different minima of $V(\{{\bf R}\})$ and the energy profile along the least action paths joining them. At variance with previous suggestions, we find that the parameters describing the DWP's are correlated among each others. Moreover, the trajectory of the system in the 3$N$-d configurational phase space follows a quasi-1-d manifold. The motion parallel to the path is characterized by jumps between minima, and is nearly uncorrelated from the orthogonal, harmonic, dynamics.Comment: 4 pages, RevTex, 4 PostScript figure

General features of the energy landscape in Lennard-Jones like model liquids

Features of the energy landscape sampled by supercooled liquids are numerically analyzed for several Lennard-Jones like model systems. The properties of quasisaddles (minima of the square gradient of potential energy W=|grad V|^2), are shown to have a direct relationship with the dynamical behavior, confirming that the quasisaddle order extrapolates to zero at the mode-coupling temperature T_MCT. The same result is obtained either analyzing all the minima of W or the saddles (absolute minima of W), supporting the conjectured similarity between quasisaddles and saddles, as far as the temperature dependence of the properties influencing the slow dynamics is concerned. We find evidence of universality in the shape of the landscape: plots for different systems superimpose into master curves, once energies and temperatures are scaled by T_MCT. This allows to establish a quantitative relationship between T_MCT and potential energy barriers for LJ-like systems, and suggests a possible generalization to different model liquids.Comment: 8 pages, 5 figure

Biowaste management in Italy: Challenges and perspectives

The aim of this work is the development of a methodology for the technical and environmental assessment of biowaste valorization in 2G biorefineries. Italy was chosen as case study, considering years 2016–2017. Approach: the Italian context was evaluated through the following key parameters: Gross domestic power, climate, demography, and population density distribution described the Italian framework. The four most abundant biowaste categories were defined through their amounts and geo-localization: wastewater and sewage sludge (WSS, 4.06 Mt/y), organic fraction of municipal solid waste (OFMSW, 1.7 Mt/y), agricultural livestock waste (ALW, 5.7 Mt/y), and waste deriving from the food industry (FIW, 2.6 Mt/y). The geo-localization and quantitative evaluations of the available biowaste amounts were aimed at defining the dimension and localization of the biorefinery plant and at optimizing supply and transport chains, while the qualitative characteristic were aimed to evaluate the most promising process among thermo-valorization (TH) and anaerobic digestion (AD). Results: All considered biowastes were appropriate for biorefinery processes, since carbon content exceeds 40% and the carbon–nitrogen ratio was between 10 and 30. All biowaste categories were evaluated as feedstocks for two biorefinery processes: anaerobic digestion (AD) and thermo-valorization (TH) with energy recovery. Compared to TH, AD achieved in all cases the best performances in terms of produced energy and avoided CO2 emissions. The primary energy production of AD and TH for WSS, OFMSW, ALW, and FIW were respectively: 7.89 vs. 2.4 kWh/kg; 8.7 vs. 2.6 kWh/kg; 10.85 vs. 5.5 kWh/kg; and 12.5 vs. 7.8 kWh/kg. The main findings of this work were: the adoption of AD was technically more suitable than TH; AD increased the avoided CO2 emissions of 10%–89.9% depending on biowaste category

Tetrahedrally bonded ternary amorphous semiconductor alloys

The properties of tetrahedrally bonded ternary amorphous semiconductors a-CSiSn:H and a-CSiGe:H are reviewed with particular emphasis on the temperature dependence of dark conductivity and the coordination in random networks. It is shown here that the dark conductivity as a function of the temperature strongly depends on the carbon content and, more precisely, on the proportion of sp3 and sp2 sites in the carbon. Ternary alloys with different carbon contents are compared to binary alloys using the average coordination number. The ternary alloys have an average coordination number close to the optimal value predicted for amorphous covalent networks

Technical, economic and environmental assessement of bioethanol biorefinery from waste biomass

This study presents a sequential three-steps methodology for the technical, economic and environmental assessment (TEEA) of bioethanol production from waste biomass. In EU the most abundant waste biomasses produced in 2018 could be ascribed to three main categories: lignocellulosic (329.41 Mt), starch (160 Mt) and sugar-based (58.56 Mt). The technical assessment compiled an inventory of the waste biomasses and subsequently designed their biological conversion into ethanol through integrated biorefinery processes by means of material flow analysis (MFA); the economic assessment was aimed at the definition of the cut-off size of the biorefinery plant necessary to achieve profitability; the environmental assessment was based on Life Cycle Analysis (LCA) and energy balance (i.e. energy input consumption). For each of the three waste biomass categories, at least one that was significant as available amount and representative in terms of physico-chemical characteristics, was evaluated: sugarcane for sugar-based, potatoes for starch-based and rice straw, cattle manure and organic fraction of municipal solid waste (OFMSW) for lignocellulosic biomasses. The technical assessment of the biorefinery routes lead to the following yields (kg of bioethanol per kg of biomass): 0.16, 0.17, 0.22, 0.19 and 0.14 respectively. The economic profitability was reached by all biorefineries and Net Present Value (M€) were: 0.85 for sugarcane, 0.11 for potatoes, 0.09 for rice straw, 0.11 for cattle manure and 0.39 for OFMSW. From the environmental perspective, cattle manure reached the highest reduction of climate change and acidification impacts compared to other biomasses, while sugarcane achieved the lowest energy input consumption (around 64%)

Integrated biorefinery strategy for poly(3-hydroxybutyrate) accumulation in Cupriavidus necator DSM 545 using a sugar rich syrup from cereal waste and acetate from gas fermentation

Poly(3-hydroxybutyrate) (PHB) is one of the most well-known biodegradable and biocompatible biopolymers produced by prokaryotic microorganisms. It belongs to the family of polyhydroxyalkanoates (PHAs), and it has gained significant attention in recent years due to its potential as a sustainable alternative to traditional petroleum-based plastics. Cupriavidus necator has been identified as a potential producer of PHB for industrial applications due to its ability to produce high amounts of the polymer under controlled conditions, using a wide range of waste substrates. In this study, the ability of Cupriavidus necator DSM 545 strain to produce PHB was tested in a fed-batch strategy providing two different organic substrates. The first is a sugar-based syrup (SBS), derived from cereal waste. The second is an acetate-rich medium obtained through CO2 -H2 fermentation by the acetogenic bacterium Acetobacterium woodii. The carbon sources were tested to improve the accumulation of PHB in the strain. C. necator DSM 545 proved to be able to grow and to perform high accumulation of biopolymer on waste substrates containing glucose, fructose, and acetate, reaching about 10 g/L of PHB, 83% of biopolymer accumulation in cell dry mass, in 48 h of fed-batch fermentation in 0.6 L working volume in a bioreactor. Moreover, a Life Cycle Assessment analysis was performed to evaluate the environmental impact of the process converting the sugar syrup alone and the integrated one. It demonstrated that the integrated process is more sustainable and that the most impactful step is the PHB production, followed by the polymer extraction

Anhydrous Calcium Oxalate Polymorphism: A Combined Computational and Synchrotron X-ray Diffraction Study

Four possible models for anhydrous calcium oxalate (COA) polymorphs have been investigated through ab initio quantum mechanical methods. Their structural properties, infrared and Raman spectra, and thermodynamic stability in the range of 0–800 K have been analyzed and compared. Along with the known β-COA structure, two models turn out to be possible candidates for the α- and γ-polymorphs that were observed during dehydration of weddellite (calcium oxalate dihydrate, COD) by Walter-Lévy and Laniepce ( C. R. Acad. Sci. Paris 1964, 259, 4685). While the calculated vibrational frequencies show that the four COA models correspond to minimum energy structures, β-COA is the thermodynamically favored phase over the range of temperatures examined in the present study. Despite the fact that computed vibrational spectra and X-ray diffraction (XRD) patterns of these polymorphs exhibit some different features, a definitive assignment of the structures based on computational results is not possible due to the lack of accurate experimental data. In an effort to improve comparative experimental data, the structural evolution of whewellite (calcium oxalate monohydrate, COM) has been probed using time-resolved synchrotron X-ray diffraction, in order to correlate the calculated structures to the observed structures. The evolution has been shown to go through at least four phases identified as COM, α-COA (corresponding to one of the models proposed by computation), β-COA, and CaCO3. The reactions are predominantly two-phase reactions, and at 140 °C evidence of three-phase coexistence has been noted between COM, α-COA, and β-COA. The time-resolved XRD data allow estimation of the kinetics of the reactions; these indicate second-order reactions between COM and α-COA and zeroth-order reactions between α-COA and β-COA

Improving plastic management by means of people awareness

In past decades the usage of plastic has seen a tremendous increment. This raise is mainly caused by industrial development and by the spread of this material in every aspect of people life, from food package to aerospace application. For sure plastic has a key role in society and it is not possible to erase, nevertheless its overuse has a serious impact on the environment as well know. In particular, just a few percentage of the total amount of plastic is recycled, the rest has to be landfilled or burnt causing serious pollution side effect. This poor circularity in plastic value chain is mainly caused by difficulties in sorting processes and expensiveness of recycling. By the way a great part of plastic applications could be avoided without implying a reduction in life quality for the people. In addition, a better education in plastic objects shopping and plastic waste management could decrease the difficulties in sorting and recycling. One of the crucial reason why these applications and incorrect behaviour are still present is that the information on alternatives are not present or very hard to be found. In the present paper a novel platform to enhance a more plastic-free life is presented. First a detailed description of the problem is stated, then the process to achieve the proposed solution is described. Finally the platform prototype is analysed in details among its functionalities

ABEMUS: platform specific and data informed detection of somatic SNVs in cfDNA

MOTIVATION: The use of liquid biopsies for cancer patients enables the non-invasive tracking of treatment response and tumor dynamics through single or serial blood drawn tests. Next generation sequencing assays allow for the simultaneous interrogation of extended sets of somatic single nucleotide variants (SNVs) in circulating cell free DNA (cfDNA), a mixture of DNA molecules originating both from normal and tumor tissue cells. However, low circulating tumor DNA (ctDNA) fractions together with sequencing background noise and potential tumor heterogeneity challenge the ability to confidently call SNVs. RESULTS: We present a computational methodology, called Adaptive Base Error Model in Ultra-deep Sequencing data (ABEMUS), which combines platform-specific genetic knowledge and empirical signal to readily detect and quantify somatic SNVs in cfDNA. We tested the capability of our method to analyze data generated using different platforms with distinct sequencing error properties and we compared ABEMUS performances with other popular SNV callers on both synthetic and real cancer patients sequencing data. Results show that ABEMUS performs better in most of the tested conditions proving its reliability in calling low variant allele frequencies somatic SNVs in low ctDNA levels plasma samples. AVAILABILITY: ABEMUS is cross-platform and can be installed as R package. The source code is maintained on Github at http://github.com/cibiobcg/abemus and it is also available at CRAN official R repository. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online

A model for the generic alpha relaxation of viscous liquids

Dielectric measurements on molecular liquids just above the glass transition indicate that alpha relaxation is characterized by a generic high-frequency loss varying as $\omega^{-1/2}$, whereas deviations from this come from one or more low-lying beta processes [Olsen et al, Phys. Rev. Lett. {\bf 86} (2001) 1271]. Assuming that long-wavelength fluctuations dominate the dynamics, a model for the dielectric alpha relaxation based on the simplest coupling between the density and dipole density fields is proposed here. The model, which is solved in second order perturbation theory in the Gaussian approximation, reproduces the generic features of alpha relaxation