Differential scanning calorimetric examination of the degenerated human palmar aponeurosis in dupuytren disease

The Dupuytren contracture - degenerative shortening of the palmar aponeurosis - is a common disease of the hand in Europe. The aetiology of the degenerative changes in the collagen structures is still not clear. To describe the clinical manifestation of the disease we use an international classification according to Iselin. Our hypothesis was that in Dupuytren disease there is a clear pathological abnormality in the tissue elements building up the palmar aponeurosis, which is responsible for the disease, and could be monitored besides the classical histological methods by differential scanning calorimetry. The thermal denaturation of different parts of human samples was monitored by a SETARAM Micro DSC-II calorimeter. All the experiments were performed between 0 and 100°C. The heating rate was 0.3 K min⁻¹. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (control: T _m=63°C and ΔH _cal=4.1 J g⁻¹, stage I.: T _m= 63°C and ΔH _cal=5.1 J g⁻¹, stage II.: T _m=64°C and ΔH _cal=5.2 J g⁻¹, stage III.: T _m=60°C and ΔH _cal=5.2 J g⁻¹, stage IV.: T _m=60.2°C and ΔH _cal=5.3 J g⁻¹). The heat capacity change between native and denatured states of aponeurosis samples increased with the degree of structural alterations indicating significant water loosing. These observations could be explained with the structural alterations caused by the biochemical processes. With our investigations we could demonstrate that DSC is a useful and well applicable method for the investigation of collagen tissue of the human aponeurosis. Our results may be of clinical relevance in the future i.e. in the choice of the optimal time of surgical therapy of different clinical level Dupuytren contractures.     

Thermophysical Investigations of the Polymorphous Phases of Calcium Carbonate

1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T _tr=455±10°C, Δ_tr H=403±8 J mol^–1 at T _tr, V→C: T _tr=320–460°C, depending on the way of preparation,Δ_tr H=–3.2±0.1 kJ mol^–1 at T _tr,Δ_tr H=–3.4±0.9 kJ mol^–1 at 40°C, S _V ^Θ= 93.6±0.5 J (K mol)^–1, A→C: E _A=370±10 kJ mol^–1; XRD only, V→C: E _A=250±10 kJ mol^–1; thermally activated, iso- and non-isothermal, XRD 2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are presented. NCC→C: T _tr=276±10°C,Δ_tr H=–15.0±3 kJ mol^–1 at T _tr, T _tr – transition temperature, Δ_tr H – transition enthalpy, S ^Θ – standard entropy, E _A – activation energy. 3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dissociation Quotients for Citric Acid in Aqueous Sodium Chloride Media to 150°C

The three molal dissociation quotients for citric acid were measured potentiometrically with a hydrogen-electrode concentration cell from 5 to 150°C in NaCl solutions at ionic strengths of 0.1, 0.3, 0.6, and 1 molal. The molal dissociation quotients and available literature data at infinite dilution were fitted by empirical equations in the all-anionic form involving an extended Debye-Hückel term and up to five adjustable parameters involving functions of temperature and ionic strength. This treatment yielded the following thermodynamic quantitites for the first dissociation equilibrium at 25°C: logK _1a=−3.127±0.002, ΔH _1a ^o =4.1±0.2 kJ-mol⁻¹, ΔS _1a ^o =−46.3±0.7 J-K⁻¹-mol⁻¹, and ΔCp _1a ^o =−162±7 J-K⁻¹-mol⁻¹; for the second acid dissociation equilibrium at 25°C: logK _2a =−4.759±0.001, ΔH _2a ^o =2.2±0.1, ΔS _2a ^o =−83.8±0.4, and ΔCp _2a ^o =−192±15, and for the third dissociation equilibrium at 25°C: logK _3a=−6.397±0.002, ΔH _3a ^o =−3.6±0.2, ΔS _3a ^o =−134.5±0.7, and ΔCp _3a ^o =−231±7.     

Catalytic and Thermodynamic Characterization of Endoglucanase (CMCase) from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> cmc-1

Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg⁻¹ protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol⁻¹ at optimum temperature (55 °C), and its temperature quotient (Q ₁₀) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V _max for CMC hydrolysis was 854 U mg⁻¹ protein and K _m was 20 mg CMC ml⁻¹. The turnover (k _cat) was 356 s⁻¹. The pK _a1 and pK _a2 of ionisable groups of active site controlling V _max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol⁻¹, ΔG* = 64.57 kJ mol⁻¹ and ΔS* = −195.05 J mol⁻¹ K⁻¹, respectively. Activation energy for irreversible inactivation ‘E _a(d)’ of the endoglucanase was 378 kJ mol⁻¹, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol⁻¹, 111.36 kJ mol⁻¹ and 833.06 J mol⁻¹ K⁻¹, respectively.     

Phase Diagram of R(+)-S(-) Efaroxan Hydrochloride

The phase diagram of R(+)-S(-) efaroxan hydrochloride (T_fus.(R)=245.1±0.3°C. ΔH_fus.(R)=119.6±3.0 J g^-1) shows a racemic compound. The melting temperature and melting enthalpy of the compound are: T_fus.(RS)=247.8±0.2°C and ΔH_fus. (RS)=124.6±2.4 J g^-1. A solid ↔ solid transformation takes place at T_trs.=180±1°C, ΔH_trs.=15.0±0.4 J g^-1. This transition is observed between 3 and 97% R(+). The stability of the racemic compound already established in a previous study was confirmed by the value of Petterson's coefficient (i=1.19). The two eutectic positions at 20 and 80% R(+) that define the range over which the racemic compound is found, exclude the use of resolution methods by preferential crystallization. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase transitions of K<Subscript>2</Subscript>TaF<Subscript>7</Subscript> within 680–800°C

Three thermal effects on heating/cooling of K₂TaF₇ in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change of the individual processes are: Δ_transIIH_m(K₂TaF₇; 703°C) = 1.7(2) kJ mol⁻¹, Δ_transIH_m(K₂TaF₇; 746°C) = 19(1) kJ mol⁻¹ and Δ_transIIIH_m(K₂TaF₇; 771°C) = 13(1) kJ mol⁻¹. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K₂TaF₇ and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.      

Sulfurization of polymers

Polyethylene exhaustively sulfurized with elemental sulfur shows paramagnetic (spin concentration 2.7–9.7·10¹⁹ sp g⁻¹,g=2.0041–2.0045, ΔH=0.53–0.62 mT) and redox properties, which was demonstrated by both voltammetric and chemical methods (sodium reduction in liquid ammonia). The high concentration of unpaired electrons, the character of the electrochemical activity, and the chemical properties are in agreement with the presence in the polymers of polyconjugated ladder polythiophene and parquet polynaphtho-thienothiophene structures along with polyene-polysulfide blocks. The use of the polymers under consideration as an active cathode material in lithium batteries enables their repeated cycling with a specific charge capacitance of 150–340 mA hg⁻¹.     

Crystallization and melting behaviour of poly(m-xylene adipamide)

The melting and crystallisation behaviour of poly(m-xylene adipamide) (MXD6) are investigated by using the conventional DSC, X-ray diffraction and polarised light microscopy. Triple, double or single melting endotherms are obtained in subsequent heating scan for the samples after isothermal crystallisation from the melt state at different temperatures. The lowest melting peak can be ascribed to the melting of secondary crystals. The melting of primary crystals causes the medium melting peak and the highest melting peak is attributed to the melting of recrystallised species formed during heating. Following the Hoffman–Weeks theory, the equilibrium melting temperature is equal to 250°C and the equilibrium melting enthalpy ΔH _m ⁰ to 175 J g^–1. Then, using the Lauritzen–Hoffmann theory of secondary crystallisation, the analyse of the spherulitic growth shows that the temperature of transition between the growing regimes II and III is equal to 176°C. Finally the Gibbs-Thomson relationship allows the determination of the distribution function of crystalline lamellae.     

Studying Cu2–xSe phase transformation through DSC examination

The thermal effect accompanying the transition of Cu_2–xSe into a superionic conduction state was studied by non-isothermal measurements, at different heating and cooling rates (β=1, 2.5, 5, 10 and 20°C min^–1). During heating the peak temperature (T_p) remains almost stable for all values of β, (136.8±0.4°C for Cu₂Se and 133.0±0.3°C for Cu_1.99Se). A gradual shift of the initiation of the transformation towards lower temperatures is observed, as the heating rate increases. During cooling there is a significant shift in the position of the peak maximum (T_p) towards lower temperatures with the increase of the cooling rate. A small hysteresis is observed, which increases with the increase of the cooling rate, β. The mean value of transformation enthalpy was found to be 30.3±0.8 J g^–1 for Cu₂Se and 28.9±0.9 J g^–1 for Cu_1.99Se. The transformation can be described kinetically by the model f(ǯ)=(1–ǯ)^n(1+kcatX), with activation energy E=175 kJ mol^–1, exponent value n equal to 0.2, logA=20 and log(k_cat)= 0.5.     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _p,m [J K⁻¹ mol⁻¹]=181.43+51.297X −4.7816X ²−1.9734X ³+8.1048X ⁴+11.108X ⁵ [X=(T−135)/55] for the solid phase (80–190 K), C _p,m [J K⁻¹ mol⁻¹]= 349.96+25.106X+9.1320X ²+19.368X ³+2.23X ⁴−8.8201X ⁵ [X=(T−225)/27] for the glass state (198–252 K), and C _p,m[J K⁻¹ mol⁻¹]= 402.40+21.982X−3.0304X ²+3.6514X ³+3.4585X ⁴ [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BPBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BPBF₄ was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH _g=2.157 kJ mol⁻¹ and ΔS _g=11.12 J K⁻¹ mol⁻¹, respectively. The result showed that the melting point of the BPBF₄ is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH _m = 8.453 kJ mol⁻¹ and ΔS _m=30.21 J K⁻¹ mol⁻¹. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF₄ was determined to be Δ_c H _m⁰ = −5451±3 kJ mol⁻¹. The standard molar enthalpy of formation of BPBF₄ was evaluated to be Δ_f H _m⁰ = −1356.3±0.8 kJ mol⁻¹ at T=298.150±0.001 K.     

Kinetics and mechanism of the acid-catalysed hydrolysis of the carbonatotetraimidazolecobalt(III) ion

Summary The kinetics of the acid-catalysed hydrolysis of the [(imidazole)₄Co(CO₃)]⁺ ion was found to follow the rate law -dln[complex]/dt = k ₁ K[H⁺](1 + K[H ⁺]) in the 25–45 °C range, [H⁺] 0.05–1.0 m range and I = 1.0m. The reaction sequence consists of a rapid protonation equilibrium followed by the one-end dissociation of the coordinated carbonato ligand (rate-determining step) and subsequent fast release of the monodentate carbonato ligand. The rate parameter values, k ₁ and ITK, at 25 °C are 6.48 × 10⁻³s⁻¹ and 0.31m ⁻¹, respectively, and activation parameters for k ₁ are ΔH ₁ ^≠ = 86.1 ± 1.2kJ mol⁻¹ and ΔS ₁ ^≠ = 2.1 ± 6.3 J mol⁻¹K⁻¹. The hydrolysis rate increases with increase in ionic strength. The different ways of dealing with the data fit are presented and discussed. The kinetic results are compared with those for the similar cobalt(III) complexes.     

Syntheses, characterization and solid state thermal studies of N-propyl-1,2-diaminoethane (L) and N-isopropyl-1,2-diaminoethane (L′) complexes of nickel(II) nitrite: X-ray single crystal structure of trans-[NiL2(NO2)2]

Linkage isomers trans-bis(N-propyl-1,2-diaminoethane)dinitronickel(II) (brown, 1), trans-bis(N-isopropyl-1,2-diaminoethane)dinitritonickel(II) (blue-violet, 2a) and trans-bis(N-isopropyl-1,2-diaminoethane)dinitronickel(II) (brown, 2b) have been synthesized from solution and X-ray single crystal structure analysis of complex (1) has been performed. Simultaneous TG-DTA analyses reveal that complex (1) exhibits two successive phase transitions before to undergo decomposition (initial temperature of decomposition, Ti = 215 °C). The first one is reversible (82–98 °C; ΔH = 1.75 kJ mol⁻¹ for heating and 93–77 °C; ΔH = −1.65 kJ mol⁻¹ for cooling) and the second one is irreversible endothermic (135–150 °C kJ mol⁻¹; ΔH = 1.80 kJ mol⁻¹) phase transition. No visual color changes are observed in any of the two transitions. The causes related to the first phase transition remain unexplored. However, on the basis of IR spectral studies the second phase transition is supposed to be due to conformational changes of the diamine chelate rings. On the other hand, complexes (2a) and (2b) undergo decomposition without showing any phase transition [Ti = 185 and 195 °C for (2a) and (2b), respectively].     

Polymorphism of paracetamol

The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG _sub²⁹⁸=60.0 kJ mol⁻¹; ΔH _sub²⁹⁸=117.9±0.7 kJ mol⁻¹; ΔS _sub²⁹⁸=190±2 J mol⁻¹ K⁻¹. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition enthalpy at 298 K, ΔH _tr²⁹⁸(I→II)=2.0±0.4 kJ mol⁻¹, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based on ΔH _tr²⁹⁸ (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification II were also estimated (ΔG _sub²⁹⁸=56.1 kJ mol⁻¹; ΔH _sub²⁹⁸=115.9±0.9 kJ mol⁻¹; ΔS _sub²⁹⁸=200±3 J mol⁻¹ K⁻¹). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported found by classical thermochemical methods.     

Thermal behavior of drugs

Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300 and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the heating rate (5, 10, 15, and 20 °C min⁻¹) on the DSC behavior of the both drug samples was verified. The results showed that, as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by various methods, the following order for the thermal stability was noticed: naproxen > celecoxib. Finally, the values of ΔS ^#, ΔH ^#, and ΔG ^# of their decomposition reaction were calculated.     

A study of the adsorption properties of the hypercross-linked polystyrene sorbents Styrosorb by gas chromatography. Effect of the conditioning temperature

The effect of the conditioning temperature of the hypercross-linked polystyrene sorbents Styrosorb on the retention ofn-hexane, benzene. and acetone was studied by gas chromatography. The rigid but mobile structure of 100% cross-linked polymers with a specific surface area of 300–500 m² g⁻¹ prepared in cyclohexane slightly shrinks by conditioning above 200 °C. This results in a significant increase in the specific retention volumes of the adsorbates. The commercial hypercross-linked sorbents MN-100 and MN-200 with specific surface areas of −1000 m² g⁻¹ retain their structure up to 250 °C. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1502–1506, August. 1999.     

Synthesis And Kinetic Analysis of Poly(2,2'-dymethoxy-4,4'-biphenylenevinylene. A novel conducting polymer

The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g^–1) . The activation energy (116±4 kJ mol^–1 ) was determined by Ozawa's method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydroxylamine derivatives in Purex Process

The kinetics of oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and nitrous acid in nitric acid solution have been studied by spectrophotometry at 9.5°C. The rate equation is −d[HNO₂]/dt=K[HNO₂]·[DEHAN][HNO₃] and the rate constantK=12.81 (mol/l)⁻²·min⁻¹. A possible mechanism has been suggested on the basis of chemical analysis and Raman spectra. The activation energyE and the thermodynamic functions ΔH ^#, ΔG ^# and ΔS ^# are also calculated.     

The study of chemical reactions, absorption and extraction, using apparatuses with serpentine pie for pelliclizing-bubbling, XIV. Hydroperoxidation of 1,3-diisopropylbenzene with oxygen

Experimental results obtained by thermal hydroperoxidation of 1,3-diisopropylbenzene in the temperature region of 102–105°C, using a Vodnár-1 type apparatus with discontinuous operation are presented. Based on the results, the activation energy (E=48.5±2 kJ/mol), enthalpy (ΔH⁺=47±2 kJ/mol), entropy (ΔS⁺) and the activation free enthalpy (ΔG⁺) were calculated. XIII. J. Vodnár, A. Chis, A. Biro, S. Békássy and M. Dragan:Studia Univ. Babes-Bolyai, Chemia, Cluj-Napoca, 1997,42, 2.     

Synthesis of silica nanoparticles by modified sol–gel process: the effect of mixing modes of the reactants and drying techniques

A modified preparation of silica nanoparticles via sol–gel process was described. The ability to control the particle size and distribution was found highly dependent on mixing modes of the reactants and drying techniques. The mixture of tetraethoxysilane and ethanol followed by addition of water (Mode-A) produced monodispersed powder with an average particle size of 10.6 ± 1.40 nm with a narrow size distribution. The freeze drying technique (FD) further improved the quality of powder. In addition, the freeze dried samples have shown unique TGA decomposition steps which might be related to the well-defined structure of silica nanoparticles as compared to the heat dried samples. DSC analysis showed that FD preserved the silica surface with low shrinkage and generated remarkably well-order, narrow and bigger pore size and pore volume and also large endothermic enthalpies (ΔH _FD = −688 J g⁻¹ vs. ΔH _HD = −617 J g⁻¹) that lead to easy escape of physically adsorbed water from the pore at lower temperature.     

Preparation and reactivity of metal-containing monomers

The thermal decomposition of iron (III) acrylate, [Fe₃O(CH₂=CHCOO)₆ · 3H₂O]OH (FeAcr), a monomer with a complex cluster cation, has been studied at 200–370 °C. Thermal transformations of FeAcr occur in two temperature regions. The rates of gas evolution in the low temperature region (200–300 °C) and the high temperature region (300–370 °C) are described by first-order equations withk=4.2 · 10²¹exp[−59000/(RT)] s⁻¹ andk=1.3 · 10⁶exp[−30500/(RT)] s⁻¹, respectively. A study of the qualitative and quantitative composition of the products of FeAcr thermolysis was carried out. The thermal transformation of FeAcr is a complex process of dehydration, degradation, and polymerization in the solid phase followed by decarboxylation of the metal-carboxyl groups of the polymer. for part 33 see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1743–1750, October, 1993.