Thermal analysis on phase behavior of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) interacting with aliphatic polyesters

Abstract  

Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LM_w-PLLA) or high-molecular-weight PLLA (HM_w-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH₂/CO) ratio in main chains. The blends of LM_w-PLLA/PEA and LM_w-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LM_w-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LM_w-PLLA/PTA and LM_w-PLLA/PEA blends, HM_w-PLLA with polyesters are mostly immiscible; and HM_w-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LM_w-PLLA/PEA and LM_w-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LM_w-PLLA and PTA or PEA.     

Heat capacity of methacetin in a temperature range of 6 to 300 K

Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C _p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal to 243.1 J K⁻¹ mol⁻¹ and 36360 J mol⁻¹, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C _p = AT ³. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of paracetamol.     

Energy level alignment at interfaces between 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butyl phenyl)-1, 2, 4-triazole (TAZ) and metals (Ca,Mg, Ag,and Au): experiment and theory

We have performed ultraviolet photoelectron spectroscopy measurements and density functional theory calculations to study the electronic structure at the interface between organic semiconductor (3-(4-biphenylyl)-4-phenyl-5-(4-tert-butyl phenyl)-1,2,4-triazole (TAZ)) and metals (Ca, Mg, Ag, and Au). The basic mechanism of interface states at organic–metal interfaces can be understood by controlling the injection of charge carriers at these interfaces. The position of highest occupied molecular orbital relative to the Fermi level and the magnitude of the interface dipole are measured for each organic–metal interface. For TAZ on Ca, Mg, and Ag, interface states are observed near the Fermi level. However, no interface state is observed for TAZ on Au. It is analyzed qualitatively that the interface state is formed due to interaction of TAZ lowest unoccupied molecular orbital composed of C2p and metal s levels. It is suggested that the interface state plays an important role in charge transport at the interface. The mechanism of formation of interface states and electrical properties are discussed.     

Synthesis and characterization of SmAlO<Subscript>3</Subscript> dielectric material by citrate precursor method

SmAlO₃ nanopowder synthesized by a citrate precursor method using citric acid as a chelating agent and ethylene glycol as an esterifying agent was reported in this paper. The phase purity of the as-prepared powder was examined using thermogravimetry (TG) analysis and differential scanning calorimetry (DSC) analysis, Fourier transform infrared spectroscopy (FTIR). The X-ray diffraction (XRD) studies showed that pure SmAlO₃ phase with orthorhombic perovskite structure could be synthesized at 800 °C for 2 h without any detectable intermediate phase. The average particle size calculated from transmission electron microscopy (TEM) investigation for the powder synthesized at 900 °C was as low as 45 nm. The nanopowder was sintered to a density of 97% of the theoretical density at 1,550 °C for 2 h and the bulk ceramics exhibited excellent microwave dielectric properties as follows: a dielectric constant of 20.54, a quality factor of 75,380 GHz and a temperature coefficient of resonate frequency of −69.2 ppm/K.     

Ethanol production in a bioreactor with an integrated membrane distillation module

Ethanol production in a bioreactor with integrated membrane distillation (MD) module has been investigated. A hydrophobic capillary polypropylene membrane (Accurel PP V8/2 HF), with an external/internal diameter ratio, d _out/d _in = 8.6 mm/5.5 mm and pore size 0.2 μm, was used in these studies. The products (mainly ethanol and acetic acid) formed during the fermentation of sugar with Saccharomyces cerevisiae inhibited the process. These products were selectively removed from the fermentation broth by the MD process, which increased the efficiency of the conversion of sugar to alcohol from 0.45 g to 0.5 g EtOH per g of fermented sucrose. The bioreactor efficiency also increased by almost 30 %. Separation of alcohol by the MD generates a higher yield of ethanol in the permeate than in the broth. The enrichment coefficient amounted to 4-8, and depended on the ethanol concentration in the broth. The separated solutions did not wet the membrane in use for 2500 h of the MD experiments and the retention of inorganic solutes was close to 100 %.     

Molecular fragment shape variation index for functional groups and the holographic properties of electron density

For a specific functional group, considered as a molecular fragment, the rest of the molecule produces a range of interactions which influence various properties of the functional group. Considering a family of molecules with the “same” functional group, the range of variations in properties determines the range of chemical reactivity of the functional group, and a similar conclusion is valid for more general molecular fragments. By the application of conventional as well as more advanced indices of fragment properties, including local electron density shape characterization, various shape variation indices can be introduced for fragments, and their relations to the holographic properties of electron densities can be examined.     

Rare earth elements,thorium and uranium in ores of the North-Latium (Italy)

In geochemistry, the distribution of the Rare Earth Elements (REEs) in earth crust and mantle allows to understand geochemical cycles and origin and age of igneous rocks. In this article REEs (Ce, Dy, Eu, La, Nd, Sm, Tb, and Yb), Th and U in ores of the North-Latium (Bracciano area, Ceriti Mt., Fate Mt., Sabatini Mt., Vulsini Mt., Acqua Rossa basin), have been investigated for evaluating the extraction feasibility for industrial applications. 107 samples were irradiated in the rotating rack of the TRIGA Mark II reactor of the R.C. Casaccia (ENEA) at neutron flux of 2.6 × 10¹² n × cm⁻² × s⁻¹ for 12 h together with primary and secondary standards. The gamma spectrometry measurements were performed after 8 h, 3 and 30 days of decay by means of HPGe detector (FWHM 1.75 keV at 1332.5 keV, peak/Compton ratio 55.1, relative efficiency of 22%) connected to a multi-channel analyzer. The total REE mean content is 105 μg g⁻¹, ranging widely between 2.23 and 410.5 μg g⁻¹ (average coefficient of variation 112%). A similar behavior is found for Th and U: their average levels are 13.5 and 6.0 μg g⁻¹, respectively. A quite good correlation between REEs and Th (and U) is found for Ceriti Mt. (r ² > 0.8) whereas for the other areas the correlation is <0.7. The results obtained evidence the low U content in the investigated locations.     

Cloning of Thermostable Cellulase Genes of <Emphasis Type="Italic">Clostridium thermocellum</Emphasis> and Their Secretive Expression in <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

Screening for the powerful cellulase genes with improved activities remains a challenge for the biorefinery research. In this study, five cellobiohydrolase genes and one endoglucanase gene sourced from Clostridium thermocellum DSM 1237, cbhA, celK, celO, cel48Y, cel48S, and celA were cloned into a newly established tool vector pP43JM2 and expressed in two Bacillus subtilis strains, B. subtilis WB600 and B. subtilis WB800, respectively. Most of the cellulases produced in the B. subtilis recombinants were efficiently secreted into the culture medium. These secreted soluble proteins showed distinct cellulase activities using phosphoric acid swollen cellulose (PASC) as the substrate and they also demonstrated strong synergistic effects for PASC, Avicel cellulose, and the dilute acid pretreated corn stover. The current work provided a quick secretive cloning method for screening cellulase genes and may provide a host strain for constructing a consolidated bioprocessing platform with the capacity of secretive expression of multiple cellulases.     

Thermophysical Properties of High-Temperature Reacting Mixtures of Carbon and Water in the Range 400–30,000 K and 0.1–10 atm. Part 1: Equilibrium Composition and Thermodynamic Properties

This paper is devoted to the calculation of the chemical equilibrium composition and thermodynamic properties of reacting mixtures of carbon and water at high temperature. Equilibrium particle concentrations and thermodynamic properties including mass density, molar weight, entropy, enthalpy and specific heat at constant pressure, sonic velocity, and heat capacity ratio are determined by the method of Gibbs free energy minimization, using species data from standard thermodynamic tables. The calculations, which assume local thermodynamic equilibrium, are performed in the temperature range from 400 to 30,000 K for pressures of 0.10, 1.0, 3.0, 5.0 and 10.0 atm. The properties of the reacting mixture are affected by the possible occurrence of solid carbon formation at low temperature, and therefore attention is paid to the influence of the carbon phase transition by comparing the results obtained with and without considering solid carbon formation. The results presented here clarify some basic chemical process and are reliable reference data for use in the simulation of plasmas in reacting carbon and water mixtures together with the need of transport coefficients computation.     

Detection of protein-RNA crosslinks by nanoLC-ESI-MS/MS using precursor ion scanning and multiple reaction monitoring (MRM) experiments

Protein-RNA interactions within ribonucleoprotein particles (RNPs) can be investigated by UV-induced crosslinking of proteins to their cognate RNAs and subsequent isolation and mass-spectrometric analysis of crosslinked peptide-RNA oligonucleotides. Because of the low crosslinking yield, a major challenge in protein-RNA UV crosslinking is the detection of the crosslinked species over the excess of non-crosslinked material, especially when complex systems (native RNPs) are investigated. Here, we applied a novel approach that uses on-line nanoLC-ESI-MS/MS to detect and subsequently sequence peptide-RNA oligonucleotide crosslinks from crude mixtures. To detect the crosslinks we made use of features shared by crosslinks and phosphopeptides, that is, the phosphate groups that both carry. A precursor ion scan for m/z 79 (negative-ion mode, -ve) is applied to selectively detect analytes bearing the phosphate-containing species (i.e., residual non-crosslinked RNA and peptide-RNA crosslinks) from crude mixtures and to determine their exact m/z values. On this basis, a multiple reaction monitoring (MRM) experiment monitors the expected decomposition from the different precursor charge states of the putative crosslinks to one of the four possible RNA nucleobases [m/z 112, 113, 136, 152 (positive-ion mode, +ve)]. On detection, a high-quality MS/MS is triggered to establish the structure of the crosslink. In a feasibility study, we detected and subsequently sequenced peptide-RNA crosslinks obtained by UV-irradiation of (1) native U1 snRNPs and (2) [15.5K-61K-U4atac] snRNPs prepared by reconstitution in vitro. MRM-triggered collision-induced dissociation (CID) MS/MS enabled us to obtain sequence information about the crosslinked peptide and RNA moiety.