Characterisation and comparison of biomass ashes with different thermal histories using TG-DSC

The present research is focused on the characterisation and comparison of biomass ashes from wood pellet with different thermal histories. One of the ashes is obtained in a muffle furnace until its mass stabilization reaching a temperature of 550 °C, low temperature ash (LTA); the other one came from an experimental fixed bed combustor after 4 h of stable combustion in which the temperature reached is above 1,000 °C, high temperature ash (HTA). The samples were studied using Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) techniques, and they were subjected to a heating up to 900 °C under an inert atmosphere with the objective of perceiving the differences in their thermal behaviour. At these temperatures, complex phase transformations occur, related to decomposition of carbonates and formation of silicates. TG and DSC curves are compared and some differences in mass loss, temperature peaks and enthalpy associated to endothermic effects are detected and they are explained based on the different compositions of both samples obtained at different temperatures. Other techniques were applied for the determination of the chemical composition of the ashes; X-ray fluorescence and Scanning electron microscopy with energy dispersive X-ray spectroscopy showed the elements present in the ashes, and X-ray diffraction revealed the crystalline phases and confirms that LTA is mainly composed of carbonates, while HTA mostly consists of silicates.     

Application of the differential scanning calorimeter to purity measurements

This paper presents a new method for the calculation of the purity of organic, non-polymeric samples using the recorder trace from a Differential Scanning Calorimeter (DSC), Perkin-Elmer Corp. The entire DSC recorder trace is employed rather than only the initial portion of the curve. The previous trial and error choice of energy lost by the DSC trace has been replaced by a definite numerical value. Meaningful purity values have been obtained from a single DSC trace on samples of from 95 to 99.9% purity. This new method has been demonstrated to provide more accurate and less ambiguous results than the manufacturer's procedure.     

Characterisation of DM-β-cyclodextrin:prednisolone complexes and their formulation as eye drops

Several ocular treatment options have been developed to overcome a broad range of ocular infections and corneal pathologies. Even though, commonly used ophthalmic formulations are only able to promote a short therapeutic effect, demanding a frequent dosing regimen. This study took advantage of dimethyl-β-cyclodextrin to overcome prednisolone low water solubility through complexes formation. These complexes were characterized by phase-solubility studies (K_s = 732; CE = 0.864), ¹H-NMR, Differential Scanning Calorimetry and Fourier Transform Infrared Spectroscopy. Particle size distribution, prednisolone assay, rheology and osmolality were assessed to evaluate dimethyl-β-cyclodextrin and HPMC influence on the eye formulation main physicochemical properties. ¹H-NMR studies showed a 1:1 molar ratio complexes’ stoichiometry; and the other physical characterisation methods (FTIR spectra and DSC thermograms) proved a successful interaction between prednisolone and dimethyl-β-cyclodextrin. Dimethyl-β-cyclodextrin promoted a statistical significative water solubility increase of drug and the particle size of all suspensions prepared presented a d90 lower than 90 μm. The presence of dimethyl-β-cyclodextrin did not change the pseudoplastic behaviour of this HPMC-based suspension, but a lower viscosity was obtained in the presence of the complexes. As the final formulation was hypotonic its osmolality was adjusted with NaCl. Overall, dimethyl-β-cyclodextrin:prednisolone complexation in the presence of hydrophilic polymer HPMC appears to be an advantageous approach for the ocular administration of this drug.     

Conductivity and dielectric relaxation in various polyvinyl alcohol/ammonium salt composites

We studied electrical conductivity and dielectric relaxation in polyvinyl alcohol/ammonium chloride and polyvinyl alcohol/ammonium acetate composite films. Infrared absorbance showed the presence of H-bonding interaction between the salt and the polymer. X-ray diffraction showed the reduction of the grain size of ordered regions in the polymer matrix after adding salt. Thermo gravimetric analysis (TGA) showed water wt% content between 4.2 and 5.8%. Differential Scanning Calorimetry (DSC) showed the decrease of the glass transition due to retained water indicating its plasticizer effect. The ac conductivity studied in the frequency range from 10^?1 Hz to 1 MHz and the temperature range from 10 to 150°C is described by the universal law of Jonsher characterizing the charge transport in disordered materials. With NH₄Cl inclusion, the dc conductivity showed a higher value in the vicinity of 4% but with NH₄CH₃CO₂ the dc conductivity decreases monotonically by increasing the salt amount. By using the dielectric permittivity and dielectric modulus we detected three relaxation processes which we attributed to electrode/sample polarization, alpha relaxation and conductivity relaxation respectively.     

Study of interaction between nitrogen DBD plasma-treated viscose fibers and divalent ions Ca2+ and Cu2+

Viscose fibers were treated with atmospheric pressure dielectric barrier discharge (DBD) plasma obtained in nitrogen in order to activate the fiber surface prior to sorption of the divalent ions Ca²⁺ and Cu²⁺. Methylene blue sorption was used for estimation of carboxyl group formation on the surface after DBD plasma treatment, through the degree of fabric staining (K/S). Sorption of divalent ions was performed from solutions of each individual ion and from solutions of calcium and copper in succession onto untreated and plasma-treated viscose samples. The quantity of sorbed metal was determined from the neutralization and iodometric titration method. Scanning electron microscopy coupled with energy dispersive X-ray analysis was used for fiber morphology and surface characterization before and after plasma treatment, and after metal ions sorption. Experiments revealed copper microparticles formation on the fiber surface when sorption of copper was performed on samples with bonded calcium. Further analysis confirmed that for growth of copper particles, both calcium ions and nitrogen DBD plasma pretreatments are necessary.     

Study on the optimum ratio and non-isothermal curing kinetics of EP2008/EP2008-S system

This paper systematically reports the optimum ratio and non-isothermal curing kinetics of EPOLAM 2008 RESIN (EP2008)/EPOLAM 2008-S HARDENER (EP2008-S) system studied using Differential Scanning Calorimetry (DSC). In view of the gel time, viscosity, and curing reaction heat, the optimum ratio of m (EP2008)/m (EP2008-S) can be confirmed as 100:20. Subsequently, non-isothermal curing kinetics of the composite system with the optimum ratio of m (EP2008)/m (EP2008-S) is investigated by dynamic DSC. The kinetics mechanism function is analyzed with the nth-order model and two-parameter (m and n) autocatalytic model (?esták–Berggren model). Results indicated that the Málek method discloses the autocatalytic behavior, and that the two-parameter autocatalytic model is able to well simulate the curing reaction. Through the analysis of chemical composition of EP2008/EP2008-S and the value of E _a , the possible curing reaction mechanism can be explained.     

Electrochemical biosensor for simultaneous determination of guanine and adenine based on dopamine-melanin colloidal nanospheres–graphene composites

Dopamine-melanin colloidal nanospheres (Dpa-melanin CNDs)–graphene composites-modified glassy carbon electrode (GCE) was prepared by a simple procedure and then successfully used to simultaneously determine guanine and adenine. Scanning electron microscopy (SEM) images and transmission electron microscopy (TEM) were used to characterize the morphology of the Dpa-melanin CNSs–graphene composite. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode modifying process. Differential pulse voltammetry (DPV) was used to study the electrocatalytic activity toward the electrochemical oxidation of guanine and adenine. The modified electrode exhibited enhanced electrocatalytic behavior and good stability for the simultaneous determination of guanine and adenine compared with bare GCE. The electrochemical biosensor exhibited wide linear range of 0.5 to 150 μM with detection limit of 0.05 and 0.03 μM for guanine and adenine detection (S/N?=?3), respectively. Furthermore, the biosensor showed high sensitivity, good selectivity, good reproducibility, and long-term stability to guanine and adenine detection. At the same time, the fabricated electrode was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfying results. These results demonstrated that Dpa-melanin CNSs–graphene composite was a promising substrate for the development of high-performance electrochemical biosensor.     

The inhibitory effect of bipyridine and its cobalt complex on the corrosion behaviour of carbon steel in acidic medium

The bipyridine (bipy) and its cobalt complex (Co-bipy) were tested as corrosion inhibitors for N80 carbon steel in 0.1 M H₂SO₄ solution by electrochemical polarization and electrochemical impedance spectroscopy (EIS) method. Scanning electron microscopy (SEM) techniques were used to characterize the mild steel surface. The test results showed that the complex and ligand are mixed-type inhibitors and the compounds are adsorbed on the steel surface according to Temkin adsorption isotherm. The inhibition efficiency of the inhibitors follows the trend Co-bipy > bipy. The adsorption of the inhibitors can be classifies as physical adsorption.     

Thermogravimetric studies on aluminium foils for electrolytic capacitors

Thermogravimetry was applied in studies of aluminium foils for electrolytic capacitors. Scanning electron microscopy, X-ray diffraction and surface area determination were also used in the interpretation of the results. Both the specific surface area and the capacity of the foils showed a linear relationship to the height of the oxidation step measured by TG, which was found suitable for following the processes of anodic oxidation and thermal treatment of the foils as well.     

The effect of diameter on the thermal properties of the modeled shape-stabilized phase change nanofibers (PCNs)

The main objective of the present study is to investigate the effect of diameter on thermal properties of phase change fibers at nanoscale in order to develop a shape-stabilized phase change material (PCM). In this regard, polyethylene glycol/cellulose acetate (PEG/CA) electrospun nanofibers as a model of PCM/polymer structure were electrospun. The electrospinning process was optimized using response surface methodology (RSM) to produce phase change nanofibers (PCNs) with achievable minimum and maximum diameter at nanoscale range. Therefore, PCNs with minimum and maximum diameter (223 nm and 545 nm, respectively) were successfully prepared. According to differential scanning calorimetry (DSC) results, the PCNs sample with maximum diameter exhibited higher efficiency of enthalpy (49.41 %) than the PCNs sample with minimum diameter (46.24 %). On the other hand, a test based on the T-history method revealed that PCNs with maximum diameter enjoy higher thermal insulation effect. Scanning electron microscopy (SEM) as well as DSC results showed that the PCNs samples exposed to thermal cycling test not only preserved their structural durability, but also exhibited about twofold increasing in the efficiency of enthalpy than the non-exposed samples. According to thermogravimetric analysis (TG) results, due to successful entrapping, a fraction of PCMs within the structure of polymer matrix, PCNs sample display greater thermal stability comparing to the pure PCM. The present work emphasises that at nanoscale range, higher diameter of PCNs can present more favorable thermal behavior; suggesting a great potential for advanced applications of thermal energy storage and thermal regulating materials fields.     

Cellulosic nanocomposite membranes from hydroxypropyl cellulose reinforced by cellulose nanocrystals

Cellulosic nanocomposite membranes were prepared by incorporation of cellulose nanocrystals (CNCs) into a hydroxypropyl cellulose (HPC) matrix using a mixing/evaporation technique. CNCs were obtained from filter paper using the sulfuric acid hydrolysis method with the aid of ultrasonication. The relationship between the microstructure and mechanical properties of the CNCs/HPC nanocomposite membranes was studied. Scanning electron microscopy showed that the CNCs were well dispersed in the HPC matrix, and the fracture surface demonstrated a fibrous characteristic. With increasing CNCs content, the tensile strength and Young’s modulus of the CNCs/HPC nanocomposite membranes gradually increased. At 5 wt% content of CNCs, the strength was increased by 525 % and the Young’s modulus by 124 % compared with pure HPC membrane. Moreover, the effect of the phase change of HPC on the mechanical properties of the CNCs_5wt%/HPC nanocomposite membranes and the corresponding mechanism were also studied.     

Direct electrochemistry of hemoglobin and its biosensing for hydrogen peroxide on TiO2–polystyrene nanofilms

Nanofilms of titanium dioxide (TiO₂) nanoparticles that mediate the assembly of polystyrene (PS) nanoparticles for immobilizing hemoglobin (Hb) on carbon ionic liquid electrode have been developed. Fourier transform infrared spectroscopy shows that Hb retains its native structure in TiO₂–PS nanofilms. Scanning electron microscopy reveals that the nanofilms possess uniform morphology and Hb is immobilized on the surface of the nanofilms. Electrochemical investigation of the biosensor indicates that the direct electrochemistry of hemoglobin is realized on the nanofilms, and there is a formal potential of ?0.320 V in deaerated buffer solutions; the biosensor shows good electrocatalytic activity toward the reduction of hydrogen peroxide with a linear range from 0.5 to 640 μM, a detection limit of 0.2 μM (S/N = 3) and a sensitivity of 103 μA mM^?1. Thus, the nanofilms will have potential application in the design of novel electrochemical biosensors.     

PHASE TRANSITIONS IN COLLOIDAL SYSTEMS PART II CALOR1METRIC STUDY OF THE PHASE CHANGES IN BINARY OR TERNARY SYSTEM OF WATER,SOS AND PENTANOL

The phase transitions of micellar systems have been studied by Differential Scanning Calorimetry. The binary systems waier+pentanol-1. water+SDS or SDS+pentanol-1 and the ternary system water+SDS+pentanol-1 have been investigated. In the monophasic region of the ternary system, two experimental paths have been chosen: the first one describes the influence of the addition of water and the second one describes the influence of the alcohol.

The analysis of both cooling or heating thermograms has given indications about the structure of these media. It has been particularly shown that the water can be in two states either in a classical macroscopic form melting at 0°C or enclosed in micelles with a so small dimension that melting of the ice occurs at a lower temperature (Ts). So, it has been possible to locate the range of concentration where these two “ices” appear. At the lowest temperature we observe the transformations of pentanol-1.

Generally the undercooling is smaller than for other aqueous solutions [1] suggesting an heterogeneous nudeation. The heating experiments suggest that the phase equilibria concern ice (or crystallized pentanol-1) and the solutions of monomers which rapidly are at the critical micelle concentration (CMC).     

Preparation and characterization of RF aerogel on UV irradiation method

The UV irradiation method provides us a new way of preparing resorcinol–formaldehyde (RF) aerogel. In this paper, water soluble, neutral photo-initiator 659 was used to synthesize RF aerogel by using free radical UV initiator. Incorporation of the UV initiators during the sol–gel stage usually decreases the gel-time. On changing the performed time and initiators quantities in synthesizing RF aerogel, The results will be discussed that gel-time of the RF aerogel definitely depends on the polymerization time and initiators quantities. The paper will also be discussed the RF aerogel developed for UV irradiation method and Sol–gel method by IR spectrum, Scanning electron microscopy, N₂ adsorption/desorption to show that light initiator does not play any role in the formation of the aerogel skeleton; The RF aerogel using UV irradiation method still maintain a high pore structure, shorter gel-time and the three-dimensional size block.     

邻醌式同系物的DSC研究

丹参(Salvia miltirrohiza)和红根草(S.Prionitis)均含有治疗冠心病有效成分—丹参酮Ⅱ-A等二萜醌类化合物,它们的扩冠作用,抑制血小板聚集,抑菌等活性常与该类化合物的结构、晶型、极性、溶解度、熔点有密切的相关性,如前报所述A环为脂环的化合物其熔化热低于芳环的化合物.丹参中的丹参醌Ⅱ-A(1),丹参醌Ⅱ-B(2)和红根草邻醌(3),其抗菌和抗肿瘤活性强度是3>2>1,为探究其晶型结构与药效的内在联系,本文对该类化     

Isotope effects in aqueous systems. VI. partial molal free energies in NaCl−H2O−D2O by freezing-point measurements. The heat of fusion of D2O

The freezing-point depressions of solutions of NaCl in normal and heavy water have been measured between 0.01 and 2m. Extrapolation of the isotope effect data to infinite dilution yields a new value for the heat of fusion of D₂O at its melting point (?1507±3 cal-mole^?1). The freezing-point data were employed to obtain osmotic coefficients at the feezing points of the solutions, which were corrected to rounded temperatures up to 40°C using the enthalpy data reported by Craft and Van Hook (previous paper). The data for H₂O solution are in quantitative agreement with well-established results. Those for the D₂O solvent establish the NaCl?D₂O system as an isopiestic reference. In contrast to the statements of earlier authors, examination of the isotope-effect data reveals a \(\surd \overline m\) dependence within experimental error.     

Synthesis of fragment 8–12 of the natural sequence of ACTH

Two new variants of the synthesis of the pentapeptide 8–12 of the natural sequence of ACTH are presented. In some stages, the trimethylsilyl group was used as temporary protection of the carboxy group of the amino component. The final and intermediate compounds were obtained with good yields, were distinguished by chromatographic homogeneity, and were characterized by their angles of optical rotation, melting points, and electrophoretic behavior. Their purity was checked by TLC and by high-pressure liquid chromatography. Some physicochemical characteristics (angles of optical rotation, melting points, chromatographic mobilities) of the compounds obtained are given.     

Phytase Production by Aspergillus oryzae in Solid-State Fermentation and its Applicability in Dephytinization of Wheat Ban

Aspergillus oryzae SBS50 secreted a high titre of phytase in solid-state fermentation (SSF) using wheat bran at 30 °C after 96 h at the initial substrate to moisture ratio of 1:2 and a water activity of 0.95. The production of phytase increased when wheat bran was supplemented with sucrose and beef extract. Further enhancement in enzyme production was recorded when the substrate was supplemented with the surfactant Triton X-100 (145 U/g of DMB). An overall 29-fold improvement in phytase production was achieved owing to optimization. Under optimized conditions, the mould secreted 9.3-fold higher phytase in SSF as compared to submerged fermentation (SmF). The mesophilic mould also secreted amylase, cellulase (CMCase), pectinase and xylanase along with phytase in SSF. Scanning electron microscopy revealed luxuriant growth of A. oryzae on wheat bran with abundant spores. The enzyme dephytinized wheat bran with concomitant liberation of inorganic phosphate.     

Solvent extraction of hafnium(IV) by TBP and topo from acidic organic-aqueous solutions

Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO₄, 5M HCl, 6M HNO₃ and 8M H₂SO₄ solutions, and by 1·10^?4 M TOPO solution in benzene from 2M HClO₄ and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions.     

Characteristic features of sulphide mineral DTA

Differential thermal analysis and simultaneous electrical conductivity and evolved gas detection measurements were used to determine temperature intervals and in a number of cases the nature of the recorded transformations of 21 sulphides. For example, along with the thermal dissociation of covellite interaction with copper sulphide impurity is also found. The result of polymorphic pentlandite transformation (610–620°) is vaesite; in the incongruent melting of tennantite (710–735°), lautite and sulphur are formed. Dissociation of sulpharsenides is as follows: cobaltite (885–905°) yields cattierite and sulphur; gersdorffite (800–860°) yields niccolite and pentlandite; and arsenopyrite (670–740°) yields loellingite. Endothermic transformation of pyrite (550–580°) results in destruction of its superficial oxidized film. A thermal change typical for each type of iron monosulphide has been established. A method for the quantitative estimation of sulphides is based upon measurement of the gas evolved during interaction of the sulphide with solid oxidants.