Differential scanning calorimetric examination of the tracheal cartilage after primary reconstruction with continuos sutures: A preliminary study

Acquired upper airway stenosis is usually associated with a complex of pathological conditions at the high tracheal and the subglottic levels. Reported reconstructive techniques include widening of the airways by incorporation of grafts, segmental resection, and anastomosis or combined procedures. Progress in anaesthesia, surgical techniques, and understanding of the pathophysiology of the trachea has made primary tracheal reconstruction a safe operative procedure, although there are no reports observing its acute effect on the tracheal cartilage. Differential scanning calorimetry (DSC) is a well-established method for the demonstration of thermal consequences of local and global conformational changes in biological systems, including hyaline cartilage, but it has never been applied for the investigation of tracheal cartilage. According to the present study, the thermograms may prove the presence of structural changes of the cartilage after primary reconstruction in the short-term follow up (smaller melting temperature and calorimetric enthalpy in the operated dog). The differences were clearly demonstrated between the intact cartilages and the ones involved in the anastomosis.     

Hydration kinetics of tricalcium silicate by calorimetric methods

The kinetics of the cement hydration reaction is a relevant issue in the cement research field, particularly in the presence of additional inorganic and organic components that consistently increase the complexity of the cement paste. In the present study, the hydration reaction of pure tricalcium silicate has been monitored by different calorimetric approaches: the conventional Isothermal Conduction Calorimetry (IC) and a novel Differential Scanning Calorimetry (DSC) protocol. The measured hydration curves have been modeled by using the Boundary Nucleation and Growth Model (BNGM) to extract thermodynamic parameters of the early stages of the hydration reaction. IC and DSC methods provide similar results in terms of rate constants, linear growth, and nucleation rates even though the IC accesses the total evolved heat while DSC discloses the fraction of unreacted water. The validation of the DSC approach as a reliable analytical method to the study of cement hydration kinetic is of particular importance because it allows following very long hydration processes, such as those of pastes containing organic retarders or superplasticizers. The thermodynamic and kinetic parameters for the tricalcium silicate setting has been also evaluated and discussed as a function of the surface area of the powder.     

DSC examination of the rotator cuff muscles in rabbits

Rotator cuff tear is a common musculoskeletal disorder with pathological changes occurring in the structure of the rotator cuff musculature (fatty infiltration). Severe fatty infiltration, observed on MRI or CT scan, negatively influences the result of rotator cuff reconstruction in human beings. The basic histological and biochemical alterations in fatty infiltration of the rotator cuff muscle with torn tendon are still not clear. Differential scanning calorimetric (DSC) examination is a well-established method for the demonstration of thermal consequences of local and global conformational changes in biological systems. 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 thermograms of the rotator cuff muscles with normal and torn tendons, experimentally induced in rabbits. The DSC results clearly proved that definitive differences are present between the muscles with normal and torn tendons, which have also been demonstrated by MRI and CT scans.     

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.     

DSC examination of intestinal tissue following cold preservation

The fact that small bowel is extremely sensitive to cold preservation had encouraged us to compare the conventional histology and differential scanning calorimetry (DSC) methods in intestinal structural changes following experimental cold storage models. Our histological findings showed that longer cold preservation period caused more severe damage in structure of mucosa and crypts, but there were no changes in the muscular layer. According to our DSC data (transition temperature, calorimetric enthalpy) suggest that the thermal destruction of mucosa, muscular layer and total intestinal wall following preservation injury revealed significant differences compared to normal bowel structure.     

Resolving multiple overlapping calorimetric transitions by use of a microcomputer: studies on erythrocyte membranes

Buffer changes and certain drugs cause temperature shifts, amplitude changes, and transition broadening in the differential scanning calorimetric (DSC) analysis of erythrocyte membranes. However, it has been difficult to interpret and quantitate these shifts and changes because the scans are composed of multiple overlapping transitions and because more than one transition may be simultaneously affected. An empirical approach has been developed by using Gaussian modeling to resolve these calorimetric transitions. Data analysis was carried out on a microcomputer using a nonlinear regression program (PCNONLIN) to fit the data scans. These results show that changes in the calorimetric scans of erythrocyte membranes due to alterations in the buffer environment, such as pH and osmolarity, can be resolved by fitting the data scans with the proposed mathematical model and optimizing the resolution parameters with PCNONLIN. In addition, resolution uncovered hidden characteristics that may not have been readily evident. Under certain conditions, for example, apparent transition shifts were shown to actually be amplitude changes and transition broadening. Determination of the limitations and validity of this method was accomplished with simulation studies. This technique offers a simple means for fitting overlapping DSC transitions by use of a commercially available nonlinear regression program that can be run on a microcomputer.     

DSC examination of intestinal tissue following warm ischemia and reperfusion injury

The fact that small bowel is extremely sensitive to ischemia/reperfusion (I/R) injury had encouraged us to compare the conventional histology and differential scanning calorimetry (DSC) methods in intestinal structural changes following experimental warm I/R models. Our histological findings showed that longer warm I/R period caused more severe damage in structure of mucosa and crypts, but there were no changes in the muscular layer. According to our DSC data (transition temperature, calorimetric enthalpy) suggest that the thermal destruction of mucosa, muscular layer and total intestinal wall following I/R injury revealed significant differences compared to normal bowel structure.     

Adsorption and calorimetric studies of hydrothermally modified carbosils

The article presents the studies of effects of hydrothermal treatment (HTT) (in saturated water vapours or under the liquid water layer) using various sources of thermal energy (classical autoclave or high pressure microwave reactor) on structural and surface properties of initial and modified silica gels and carbon–silica adsorbents. The porous structure of the initial and modified materials was characterised by the low-temperature nitrogen adsorption/desorption method as well as by determining pore volume distribution curves from the calorimetric data (DSC) using the thermal effects of liquid (water) phase transitions previously brought inside the pores of the studied materials. Large compatibility of the characteristics obtained using the above methods was found. The microscopic investigations (SEM, TEM) were also conducted to evaluate the morphology and topography of the samples. It was proved that during HTT, the carbon deposit on the silica surface screens it against the access of water molecules, in this way affecting decrease in intensity of dissolution and condensation of polysilicic acids. At the same time, owing to oxidizing properties of water molecules under hydrothermal conditions, development of porous structure in the carbon deposit is observed. Extent of these changes depends on both the applied system (water vapour/liquid water) and kind of the used energy (classical/microwave).     

Differential scanning calorimetric examination of the human hyaline cartilage of the femoral head after femoral neck fracture

The femoral neck fracture continues to be unsolved fractures and the guidelines for management are still evolving. The primary complications arising from femoral neck fractures are non-union and avascular necrosis. The various methods currently available for predicting the vascularity of the head at the time of fracture are not sufficiently quantitative to be used on a routine clinical basis. The hypothesis was that after the femoral neck fracture there are clear pathological abnormalities in the cartilage of the femoral head, which could be monitored besides the classical 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 different stages avascular samples (control, fresh fractures: T _m  = 68.2 °C, ΔH _cal = 2.87 J/g, avascular necrosis: T _m  = 70.7 °C, ΔH _cal = 3.61 J/g,). These observations could be explained with the structural alterations caused by the biochemical processes during the degeneration of the cartilage due to avascular femoral head necrosis. With the investigations the authors could demonstrate that DSC is a useful and well-applicable method for the investigation of hyaline cartilage of the fractured human femoral head. It was confirmed significances between the changes of calorimetric results and the elapsed time from the primary femoral neck fracture.     

The calorimetric calibration of differential scanning calorimetry cells

In this paper it is shown that in many cases enthalpy determinations can be carried out with a precision <1%. The influences of various sample and instrumental properties are described. The enthalpies of 24 compounds with 30 phase changes (polymorphic transitions or melting points) were redetermined. Twelve of the compounds with 15 transitions in the temperature range 0?670°C are selected and recommended for calorimetric DSC calibration. The linearization of the calibration curve as stated by the manufacturer of the instrument employed was fully confirmed.     

Calorimetric investigation of normal and pathological human meniscus

In this study, human meniscus tissue of normal origin in young adults and in patients with early and late stages of osteoarthritic degeneration were analyzed for their thermoanalytical properties with differential scanning calorimetry. Degenerative changes of knee menisci frequently result from trauma to the joint or are associated with joint diseases. Meniscus damage may play an important role in osteoarthritis pathophysiology. The purpose was to further characterize the altered metabolism in matrix composition during different stages of meniscus degeneration that promotes disease progression. The human knee joint menisectomy specimens were received after surgical removal. The calorimetric properties of samples were determined by DSC method, samples were heated from 0 to 80 °C. The heating rate was 0.3 °C min^?1. Conventional Hastelloy batch vessels were used with 40 μL sample volume. Change in the enthalpy was observed in normal cartilage as 1632.48 J g^?1 (SD = 50.55). In case of early degeneration a greater change at 1707.83 J g^?1 (SD = 112.46), while in the severely degenerated samples at 1677.30 J g^?1 (SD = 182.48) was measured. This method proved to be suitable for compositional thermoanalytical study of normal and degenerative human meniscus samples. All samples that were extracted for this study were obtained during live surgeries. With the rise of temperature an endothermic reaction was observed in all cases. The enthalpy change of the process initiated by the temperature change showed difference between the normal and pathological groups.     

Transformation studies in ALZnMg alloys by calorimetric methods

The possibilities of calorimetric methods like DSC and heat flow microcalorimetry for transformation studies in Aluminium alloys are demonstrated. The influence of pre-existing nuclei upon decomposition rate at various temperatures is described; unassisted nucleation of equilibrium precipitates seems to be confined to a narrow temperature range.Equilibrium precipitates of small size are dissolved simultaneously with metastable phases, thereby complicating the interpretation of DSC-curves.     

Effects of experimental sample mass on the calorimetric study of thermoset resins

It is known that experimental parameters may affect peak characteristics in DSC studies. Kinetic parameters calculated from isothermal and dynamic runs, can also be affected by the choice of experimental conditions.The sample mass can affect the determination of reaction parameters because of the heat transport and the self-insulating properties of large masses.In the curing process of thermoset resins like unsaturated polyester crosslinked by styrene, the exothermal heat results from the reaction advance but it also produces an autocatalytic process that induces an increase in the reaction rate. The sample mass, in this kind of experiments, can influence the determination of reaction parameters not only through the effect of heat transport or thermal lag on the calorimetric results but also through the action that the sample mass exerts on the exothermal heat, and consequently, on the autocatalytic process.In this paper we intend to present the results obtained in the study of the curing kinetics of thermoset resins by DSC technique using different sample masses. We will point out that the reaction heat determined by dynamic measurement was found to be independent of the sample mass. We have obtained differences in the kinetic parameters like the reaction order, activation energy and preexponential factor when the sample mass was changed.The research reported was supported by CICYT under Grant no. MAT89-377-C02-02.     

Human uterus in pregnancy,as it can be monitored by DSC examination

The myometrium is the main component in enlargement of uterus and plays essential role in labour contraction. Its physiologic and elastic state has a decisive role in the labour process. We have made the first attempt to find correlation between the thermal parameters of uterus and progress of gravidity. Significant differences were observed between cyclic, non-pregnant and postmenopausal state (0.69 and 0.98 J g⁻¹ calorimetric enthalpy as well as 60.6 and 63.1°C for T _m), as well as among the different gestational stages and complications. In case of twin pregnancy and dystocia we have found extremities: 0.37 and 1.34 J g⁻¹ calorimetric enthalpies, with 62 and 61.6°C melting temperatures. DSC method seems to be promising tool to follow and understand different molecular changes in the myometrium during pregnancy and its complication of human labour.     

Characterization of Starch Pharmaceuticals by DSC Coupled to a Photovisual System

The present work proposes evaluation of the gelatinization processes of starch by means of DSC coupled with a photovisual system. The use of DSC, TG and DTA for a fast and efficient evaluation of the starch is suggested. The DSC curves of starch gels with water contents of 20, 30, 40 and 50% (mass/v) exhibited different phase transitions, corresponding to the gelatinization processes at the different water contents for the different lots. The DSC-photovisual system confirmed calorimetric behaviour differences between the starch lots studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Application of differential scanning calorimetry to study porous structure of hydrothermally modified silicas

The paper presents the studies on determination of physicochemical and structural properties of hydrothermally treated (HTT) silica gel Si-60, using the differential scanning calorimetry (DSC) and N₂ adsorption methods. Modification was performed in overheated water vapours or under the liquid water layer using various sources of thermal energy (in the classical autoclave or in the high-pressure microwave reactor). The characteristics of porous structure were determined on the basis of low-temperature nitrogen adsorption/desorption isotherms and using the calorimetric data (DSC) of thermal effects of phase transition of water introduced inside pores of the studied materials. Great compatibility of the characteristics obtained by means of the above-mentioned methods was proved. As follows from the SEM analysis, during HTT silica is rebuilt resulting in great changes of surface morphology and porous structure of the materials. The range of these changes depends on both the applied system (water vapour/liquid water) and the kind of used energy (classical/microwave).     

Differential Scanning Calorimetry and Hydrodynamic Study of Bacterial Viruses. About possible heat effects in hermetically closed calorimetric vessels with free volume above the liquid

The phase transitions occurring in aqueous solutions of macromolecules and their complex structures (like order-disorder transitions in proteins or nucleic acids solutions) are usually accompanied by small changes in their specific partial volumes. If the quantity of these substances in the closed calorimetric vessels is relatively large (few mg) and if the phase transition is accompanied by a high change of specific partial volume (like in solution of bacteriophages),it is possible to detect some imaginary heat effects in the DSC calorimeters which have closed (sealed) vessels with free volume above the liquid. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of polymer crystallization from the melt (calorimetric approach)

Crystallization kinetics for 12 polymers including polyolefins, polyesters, polyurethanes, polysiloxanes was measured by the evolution of heat in a modified Calvet-type calorimeter over wide temperature ranges. The results are analyzed in terms of the Avrami equation and a comparison between calorimetric and dilatometric results is carried out. It is concluded that, although in the majority of cases experimental results do not obey the Avrami equation, for some polymers the agreement is rather good. The Avrami parameter obtained, however, depends on the experimental technique. Possible reasons for this disagreement are discussed. Analysis of the calorimetric crystallization rate in the vicinity of the melting point by using the kinetic theory of crystallization shows that the growth is controlled by surface (two-dimentional) nucleation. Energy parameters for the crystallites were determined and it is shown that the surface energy of the crystallites depends on the molecular structure of the polymer. Temperature dependence of the calorimetric crystallization rate of the polymers for which crystallization rates could be determined above and below the maximum rate are analyzed using a kinetic equation with common approximations for the transport term. The influence of melting conditions on the crystallization rate was studied. The results indicate heterogeneous nucleation in the polymer melt. It is concluded that this may be due both to impurities and to high regularity of macromolecules in the polymer melt.     

New principles of calorimetric designs

A brief outline of the historical development of calorimetric instrumentation shows that temperature-measurement- and shielding techniques have been substantially improved and modern electronic methods of data-processing and data-acquisition have been successfully applied to calorimetry during the last decades, but the calorimeter itself has nearly been left unchanged. The limitations of classical calorimetry will be discussed and an information-theoretical approach to calorimetry given. Some of the more important results of a general theory of calorimetry will be stated and used to derive new features of design for a modern calorimeter. Experimental results of thermodynamic measurements with such an instrument disclose large discrepancies between precision calorimetric data in the literature, systematic errors ranging from about 0.1% to as much as 0.4%.