Differential scanning calorimetric studies of several compounds showing order-disorder transition

Differential scanning calorimetric measurements have been carried out for Cul, CuBr, Agl, Ag₂S, NaNO₂, NaNO₃ and KSCN. First-order phase transformations occur with the compounds Cul, CuBr, Agl and Ag₂S; NaNO₂, NaNO₃ and KSCN exhibit -type transformations. The enthalpy changes due to phase transitions have been determined. Thermal hysteresis exhibited by these compounds have been examined in the light of their change in unit cell volumes.

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Zusammenfassung Es wurden DSC-Untersuchungen von Cul, CuBr, Agl, Ag₂S, NaNO₂, NaNO₃ und KSCN ausgeführt. Phasenübergänge erster Ordnung verlaufen bei den Verbindungen Cul, CuBr, Agl und Ag₂S, während NaNO₂, NaNO₃ und KSCN Übergänge des -Typs zeigen. Die Phasenübergängen zuzuschreibenden Enthalpieveränderungen wurden bestimmt. Die bei diesen Verbindungen auftretende thermische Hysterese wurde im Zusammenhang mit den Veränderungen des Elementarzellenvolumens untersucht.

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- Cul, CuBr, Agl, Ag₂S, NaNO₂, NaNO₃ KSCN. , Cul, CuBr, Agl Ag₂S -, a NaNO₂, NaNO₃ KSCN- -. . , , .

     

Laser light scattering and isothermal titration calorimetric studies of poly(ethylene oxide) aqueous solution in presence of sodium dodecyl sulfate

The aqueous solution of poly(ethylene oxide) (PEO) in the presence of different concentrations of sodium dodecyl sulfate (SDS) was examined by laser light scattering and isothermal titration calorimetric techniques. A small fraction of PEO aggregates were found to coexist with unimeric PEO chains in dilute solution. The presence of monovalent salt does not alter the hydrodynamic properties of PEO in aqueous solution. Addition of a monovalent anionic surfactant, such as SDS, induces cooperative binding of surfactant monomers to PEO backbones at SDS concentrations ranging from 4.0 mM (critical aggregation concentration) to 16.5 mM (saturation concentration). The hydrodynamic radius of PEO unimers decreases initially and then increases with SDS concentration, resulting from the structural reorganization of the PEO/SDS complex. Beyond the saturation concentration, the hydrodynamic radii of PEO/SDS complex are independent of SDS concentration.     

Differential scanning calorimetric assessment of high purity

The value and limitations of differential scanning calorimetry in the assessment of high-purity substances has been examined. In favorable cases, good agreement has been secured for polycyclic hydrocarbons between DSC purity values and GC assay values. For some halogenated benzoic acids, used as microanalytical reference standards, good agreement has been obtained between DSC purity values and acid—base titration results. DSC studies on cholesterol and urea, which have limited thermal stability, are presented. With the available instrument and technique, the practical upper limit of absolute DSC purity values may be 99.95 mole%, although higher numerical values can be obtained. Because the DSC technique is “blind” to equilibrium solid solution formation, DSC values should not be used as a sole criterion of purity; this recommendation is of special importance for compounds purified by fractional solidification processes.     

Interaction of Stratum Corneum Components With Benzalkonium Chloride. Isothermal titration calorimetric study

The interactions of benzalkonium chloride (BC)with components of stratum corneum, a model system of intercellular lipids in human stratum corneum and homogenized rat stratum corneum were characterized in terms of thermodynamics at pH 7.5 and 37°C. BC was strongly bound to cholesterol and cholesterol sulfate with higher affinities (10⁵~10⁶ M^-1) than to any other components of the stratum corneum by hydrophobic interaction and ionic interaction, respectively. BC binding to the model system of intercellular lipids significantly decreased only in the absence of cholesterol. It is indicated that cholesterol and its derivatives play an important role in the penetration and/or accumulation of BC in stratum corneum. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differential scanning calorimetric analysis of irradiated polytetrafluoroethylene films

Crystalline content of polytetrafluoroethylene (PTFE) can be substantially increased by electron beam irradiation. These changes as a function of radiation dose were examined in PTFE films by differential scanning calorimetry (DSC). Surprisingly small radiation doses (<0.002 Mrad) were found to cause a, fairly substantial increase (25%) in their heat of fusion. Variations in the heat of fusion and the peak melting temperature of PTFE films with radiation dose, in the range of 0.0017 to 16 Mrad, are examined.     

Differential scanning calorimetric examination of ruptured lower limb tendons in human

The tendon ruptures are serious injuries of the lover limb in middle age and physically active population. While the Achilles tendon rupture is common, the patellar ligament and quadriceps ligament ruptures are an absolutely rare injury. Usually there is no correlation between the velocity of the trauma and the supervening of the rupture. The aetiology of the degenerative changes in the collagen structures of the tendons and ligaments which could be disposed for the rupture are still not clear. Our hypothesis was that before the injury there are clear pathological abnormalities in the tissues of the tendons, which are predisposed for the rupture, and could be monitored besides the classical histological methods by differential scanning calorimetry. The thermal denaturation 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. DSC scans clearly demonstrated significant differences between the control and ruptured samples (control: T _m = 59.7 °C, T _1/2 = 1.4 °C and ΔH _cal = 8.54 J/g; ruptured Achilles tendon: T _m = 62.75 °C, T _1/2 = 2.6 °C and ΔH _cal = 1.54 J/g, ruptured Quadriceps tendon: T _m = 64.8 °C, T _1/2 = 1.6 °C and ΔH _cal = 1.53 J/g, ruptured Patellar tendon: T _m = 63.9 °C, T _1/2 = 1.41 °C and ΔH _cal = 0.97 J/g). 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 degenerated human tendons and ligaments. We can prove with this method that the degenerative changes of the tissue elements increase the thermal stability of collagen tissues of the tendons which could be disposed for the rupture.     

Differential scanning calorimetric examination of pathologic scar tissues of human skin

Keloid and hypertrophic scarring is a dermal fibroproliferative disorder characterized by increased fibroblast proliferation and excessive production of collagen. Excess scar formation occurs after dermal injury as a result of abnormal wound healing. Keloid formation has been ascribed to altered growth factor regulation, aberrant collagen turnover, genetics, immune dysfunction, sebum reaction, and altered mechanics. No single hypothesis adequately explains keloid formation. The thermal denaturations of pathologic human skin scar tissues were 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 (intact skin: T _m = 54.8 °C and ΔH _cal = 4.5 J g^?1; normal scar: T _m = 53.8 °C and ΔH _cal = 4.2 J g^?1; hypertrophic scar: T _m = 54.2 °C and ΔH _cal = 2.4 J g^?1; keloid: T _m = 52.9 °C and ΔH _cal = 8.3 J g^?1). The heat capacity change between native and denatured states of 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 keloid and hypertrophic scar tissues. Our results may be of clinical relevance in the future, i.e., in the diagnosis of the two different pathologic scar formations, or in the choice of the optimal therapy of the disease.     

Differential scanning calorimetric examination of transverse carpal ligament in carpal tunnel disease

The objective of this study is to determine the influence of partial substitutions of Ti⁴⁺ by isovalent Hf⁴⁺ in the perovskite-type crystalline structure of PbTiO₃. Different samples over the whole composition range (0 ≤ x≤1) in the PbTi_1-xHf_xO₃ family have been prepared. Phase transitions have been determined by thermal analysis (differential scanning calorimeter: DSC) and complex impedance spectroscopy (IS) over a wide temperature range. As a consequence of the cation replacement the changes that take place in the different phase transition temperature are reported. By both techniques, thermal analysis and electrical characterization, it is shown that for all compositions prepared there is only one phase transition in a temperature range between 230 and 460 °C. With these results and the previously known crystalline structure of pure PbTiO₃ and PbHfO₃ perovskites, the phase diagram of the PbTi_1-xHf_xO₃ family is presented including a morphotropic phase transition at x ~ 0.5.     

Thermodynamics of interaction between sodium bis(2‐ethylhexyl) sulfosuccinae and polymers in aqueous solutions by isothermal titration microcalorimetry

The interactions between sodium bis(2‐ethylhexyl) sulfosuccinae (AOT) and two nonionic water‐soluble polymers, including polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) have been investigated by using isothermal titration microcalorimetry in aqueous solutions at 298.15 K. The results show that the critical aggregation concentration, which corresponding to the first turning point in the curve of experimental interaction heat versus concentration of the surfactant, is lower than the critical micellar concentration (cmc), confirming the existence of polymer‐surfactant interactions. The value of cac is not sensitive to the relative amount of polymer in low concentration range of the polymer. The mono‐layer saturated adsorption concentration, which corresponding to the second turning point, rises as the polymer concentration is increased. The interaction between PVP and AOT is stronger than that between PEG and AOT. The results also indicate that the aggregation of AOT in water and polymers solutions is entropically driven. The observed thermal effects have been interpreted in terms of the interactions of the polymer molecules with AOT monomers or the molecular clusters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 275–283, 2006     

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.     

Differential scanning calorimetric examination of the interfacial membrane in failed hip joint replacements

Aseptic and septic periprosthetic osteolysis following total hip arthroplasty has become increasingly recognized as a major clinical problem. An aggressive granulomatous tissue, the interfacial membrane, develops at the interface between the bone and the prostheses or the bone and the cement. Our hypothesis was that during the septic and aseptic loosening of the total hip arthroplasty, there is a clear pathological abnormality in the tissue elements building up the interfacial membrane, which is responsible for the different aetiologies of the disease and could be monitored besides the classical methods by differential scanning calorimetry. In our study, the interfacial membrane pieces removed during operations of revision hip arthroplasties in the cases of aseptic loosening and during prosthesis removals in the cases of septic implant loosening. We investigated stem parts of cemented hip arthroplasties only. Our measurements were carried out on eight septic and 12 aseptic samples. With our investigations, we could demonstrate that DSC is a useful and well-applicable method for the investigation of the interfacial membrane that develops in septic and aseptic loosening of hip arthroplasty. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (aseptic membrane: T _m ?=?62.2?°C and ??H _cal?=?2.13?J/g, septic membrane: T _m ?=?60.2?°C and ??H _cal?=?3.22?J/g,). These investigations can help us make a correct diagnosis in the problematic cases of loosened total hip arthroplasty. To decide the possible septic feature of a given sample, calorimetry could serve as one of the quickest procedures available.     

Spectrophotometric and calorimetric titration studies on molecular recognition of camphor and borneol by nucleobase-modified beta-cyclodextrins

A series of modified beta-cyclodextrins with nucleobase substituents, that is, mono(6-ade-6-deoxy)-beta-cyclodextrin (2) and mono(6-ura-6-deoxy)-beta-cyclodextrin (3) as well as mono(6-thy-6-deoxy)-beta-cyclodextrin (4), were selected as molecular receptors to investigate their conformation and inclusion complexation behaviors with some chiral molecules, that is, (+)-camphor, (-)-camphor, (+)-borneol, and (-)-borneol, by spectrophotometric and microcalorimetric titrations in aqueous phosphate buffer solution (pH 7.2) at 298.15 K. Circular dichroism and NMR studies demonstrated that these nucleobase-modified beta-cyclodextrins adopted a co-inclusion mode upon complexation with guest molecules; that is, the originally self-included nucleobase substituents of the host did not move out from the beta-cyclodextrin cavity, but coexisted with guest molecule in the beta-cyclodextrin cavity upon inclusion complexation. Significantly, these nucleobase-modified beta-cyclodextrins efficiently enhanced the molecular binding ability and the chiral recognition ability of native beta-cyclodextrin, displaying enantioselectivity up to 3.7 for (+)-camphor/(-)-camphor pair by 2 and 3.5 for (-)-borneol/(+)-borneol pair by 3. The enhanced molecular/chiral recognition abilities of 2-4 toward (+/-)-camphor were mainly attributed to the increased entropic gains due to the extensive desolvation effects, while the favorable enthalpic gains originating from the good size-fit relationship as well as the hydrogen bond interactions between host and guest result in the enhanced molecular/chiral recognition abilities of 2-4 toward (+/-)-borneol.     

Differential scanning calorimetric measurement of cartilage destruction caused by Gram-negative septic arthritis

The treatment of the bacterial arthritis of the joints is still a great challenge for orthopedic surgeons and rheumatologists. Aerobic Gram-negative bacteria are involved only in 20–25 % of cases. The inadequate therapy can cause cartilage destruction and can result in severe osteoarthritis of the affected joint. The aim of this study was to demonstrate and follow the destruction of the joints’ hyaline cartilage by calorimetric method. We induced experimental septic arthritis in knee joints of seven New Zealand rabbits by a single inoculation of Escherichia coli ATCC 25922 culture (0.5 mL cc. 10⁸ ± 5 % c.f.u.). The duration of this experiment was 7 days from the first to the last injection. After euthanizing the first subject, all other animals were given an overdose of anesthetics and samples were isolated from the cartilage of the femurs by surgical intervention for calorimetric measurements. The DSC scans clearly demonstrated the development of infective structural destruction in the cartilage from the first to the tenth day of incubation. In case of healthy control the melting temperatures (T _m) were: 57 and 63.1 °C and the total calorimetric enthalpy change (ΔH) was 0.37 J g^?1. After the third day, the enthalpy increased extremely (3.67 J g^?1), the two transition temperatures shifted toward lower temperature: 47.7 and 62.3 °C. At the fifth day, the effect of infection is culminated with T _m = 62.2 °C and a further elevation in ΔH (3.75 J g^?1). These results can indicate a dramatic change of the structure of rabbit cartilage between the third and fifth days. Therefore, the time elapsed seems to be critical and possesses clinical relevance, since by the sixth day, ΔH decreased to 2.6 J g^?1 with a practically unchanged melting temperature. Between the sixth and tenth days, significantly increased melting temperatures (64.9 °C) were observed with decreased (3.38 J g^?1) calorimetric enthalpy. In conclusion, calorimetric measurements have been proven to be a reliable method in the measurement of cartilage destruction, caused by Gram-negative septic arthritis.     

Differential scanning calorimetric and histological examinations of the long head of the biceps in cadavers

Shoulder pain is a common presentation of the dysfunction of the glenohumeral joint. The long head of the biceps tendon has been proposed as a source of pain in rotator cuff pathologies. The rotator cuff is a dynamic stabilizer of the glenohumeral joint, and its tear can create different shoulder dysfunctions. The long head of the biceps has a special intraarticular localisation, so the arthricular destruction affects its tendon too. In the process of the rotator cuff degeneration and tear the structure of the biceps tendon pathological transforms. With foregoing studies authors have demonstrated the feasibility of DSC in the investigation of the musculoskeletal system. The aim of this study was to establish the curves and the histological properties of the tendon of the long head of the biceps in different magnitudes of the rotator cuff tear on cadavers. The DSC results clearly proved that definitive differences are present between the structural state of the tendons in different magnitudes of the rotator cuff tears, which have also been demonstrated by the histological examination.     

Aggregation behavior of gemini surfactants and their interaction with macromolecules in aqueous solution

Gemini surfactants are constructed by two hydrophobic chains and two polar/ionic head groups covalently connected by a spacer group at the level of the head groups. Gemini surfactants possess unique structural variations and display special aggregate transitions. Their aggregation ability and aggregate structures can be more effectively adjusted through changing their molecular structures compared with the corresponding monomeric surfactants. Moreover, gemini surfactants exhibit special and useful properties while interacting with polymers and biomacromolecules. Their strong self-aggregation ability can be applied to effectively influence the aggregation behavior of both polymers and biomacromolecules. This short review is focused on the performances of gemini surfactants in aqueous solutions investigated in the last few years, and summarizes the effects of molecular structures on aggregation behavior of gemini surfactants in aqueous solution as well as the interaction of gemini surfactants with polymers and biomacromolecules respectively.