A discussion on the affecting factors of the fitting procedures' reliability in isothermal titration calorimetry analysis.

The standard isothermal titration calorimetry (ITC) curve, characterized as a typical sigmoid is strictly confined by the so-called c value, which is a ratio of titrand concentration to KD. The proper c value with a range from 5 to 500 is commonly recommended as a standard protocol in routine detection process for acquiring the reliable fitting results in 1:1 binding mode. However, if the c value is less than "1" due to the weak binding or low concentration of analyte, fitting precision gets unstable and susceptible to the data noise. Herein, we first got a deep discussion into the reliability of the fitting procedure for 1:1 binding mode by data simulation, then quantized the effect of several affecting factors on the precision of parameters estimation through mathematical analysis. Finally, we proposed the value of 2~4 times KD for final ligand concentration is optimal for the ITC titration in low c system (c < 1). All the theoretical derivations were further verified by a practical experiment of Magnesium-EDTA binding test.

Fast and Robust Quantification of Detergent Micellization Thermodynamics from Isothermal Titration Calorimetry.

Detergents are widely used in modern in vitro biochemistry and biophysics, in particular to aid the characterization of integral membrane proteins. An important characteristic of these chemicals in aqueous solutions is the concentration above which their molecular monomers self-associate to form micelles, termed the critical micellar concentration (CMC). Micelles are supramolecular assemblies arranged with the hydrophobic portions oriented inward and the hydrophilic head groups positioned outward to interact with the aqueous solvent. Knowledge of the CMC is not only of practical relevance but also of theoretical interest because it provides thermodynamic insights. Isothermal titration calorimetry (ITC) is a powerful method to determine CMCs, as it furnishes additional information on the enthalpy and entropy of micellization. Here we describe our extension of previous methods to determine CMCs and other thermodynamic parameters from ITC demicellization curves. The new algorithm, incorporated into the stand-alone software package D/STAIN, analyzes ITC demicellization curves by taking advantage of state-of-the-art thermogram-integration techniques and automatically providing rigorous confidence intervals on the refined parameters. As a demonstration of the software's capabilities, we undertook ITC experiments to determine the respective CMCs of n-octyl ß-d-glucopyranoside (OG), n-dodecyl ß-d-maltopyranoside (DDM), and lauryldimethylamine N-oxide (LDAO). Motivated by the fact that in vitro membrane protein studies often require additives such as precipitants (e.g., polyethylene glycol (PEG)), we also carried out ITC demicellization studies in the presence of PEG3350, finding in all cases that PEG had significant effects on the thermodynamics of detergent micellization.

Hábitos nutricionales y de actividad física en escolares de educación primaria: datos del estudio longitudinal "OBIN" 2011-2017 / Nutritional habits and physical activity in primary school children: data from the longitudinal study "OBIN" 2011-2017 / Hábitos nutricionais e atividade física em escolas primárias de educação: dados do estudo longitudinal "OBIN" 2011-2017

Objetivo: Determinar los hábitos de alimentación y actividad física de forma comparada entre niños y niñas, en un estudio longitudinal a seis años y empleando técnicas de calorimetría para valorar el nivel de actividad física y poderlo contrastar con la información proporcionada por los cuestionarios clásicos. Método: A lo largo de seis cursos de primaria 155 sujetos (86 niñas y 69 niños) cumplimentaron un cuestionario de actividad física y otro de dieta mediterránea. A 41 sujetos (25 niñas y 16 niños) se les midió anualmente el gasto energético total (GET) y en actividad (GEA) durante 48 horas con un medidor ArmBand(R). Resultados: Se registraron GEA de 600 kcal/dia en niñas y 900 kcal/dia en niños (40 y 50 % del GET respectivamente). Dado que ArmBand considera GEA todo el gasto por encima de 2.5 METs, las niñas y niños del estudio tuvieron gastos energéticos por encima de 2.5 METs durante el 40 y 50 % del tiempo respectivamente. Los niños realizan 18000 pasos diarios y las niñas 14.000. Todo ello representa un nivel medio de actividad que podemos calificar del moderado-alto. Conclusiones: La actividad física medida por calorimetría muestra mejor información que los cuestionarios. El nivel de actividad es claramente mayor en niños que en niñas y se mantiene estable durante los 6 años. La adherencia a la dieta mediterránea puede calificarse de media, necesitando mejoras

Objective: To determine the habits of nutrition and physical activity in a comparative way between boys and girls, in a longitudinal study to six years and using calorimetry techniques to assess the level of physical activity and to be able to contrast with the information by the classic questionnaires. Method: Throughout six primary courses, 155 children (86 girls and 69 boys) completed a physical activity questionnaire and a Mediterranean diet questionnaire. Total energy expenditure (GET) and activity (GEA) were measured annually for 48 hours with an ArmBand(R) device in 41 subjects (25 girls and 16 boys). Results: GEA of 600 kcal / day in girls and 900 kcal / day in boys were recorded (40 and 50% of GET respectively). Since ArmBand considers GEA to be all expenses above 2.5 METs, the children in the study had energy costs above 2.5 METs during 40 and 50% of the time respectively. The children perform 18000 daily steps and the girls 14000. All this represents a level of activity that we can qualify as moderate-high. Conclusions: Physical activity measured by calorimetry shows better information than questionnaires. The level of activity is clearly higher in boys than in girls and it remains stable during the 6 years. The adherence to the Mediterranean diet can be described as medium, needing improvements

Objetivo: Determinar os hábitos de alimentação e atividade física de forma comparativa entre meninos e meninas, em um estudo longitudinal de seis anos com utilização técnicas de calorimetria para avaliar o nível de atividade física e contrastá-la com as informações fornecidas pelos questionários clássicos. Método: Ao longo de seis anos primários, 155 indivíduos (86 meninas e 69 meninos) responderam um questionário de atividade física e um questionário sobre dieta mediterrânea. Desses, 41 indivíduos (25 meninas e 16 meninos) foram avaliados anualmente quanto ao gasto energético total (GET) e de atividade (GEA) por 48 horas com um medidor ArmBand(R). Resultados: GEA de 600 kcal/dia em meninas e 900 kcal/dia em meninos foram registrados (40 e 50% do GET, respectivamente). Como a ArmBand considera a GEA todas as despesas acima de 2,5 METs, as crianças do estudo tiveram gastos de energia acima de 2,5 METs durante 40 e 50% do tempo, respectivamente. Os meninos do estudo realizaram 18.000 passos diários e as meninas 14.000. Tudo isso representa um nível médio de atividade que podemos qualificar como moderado-alto. Conclusões: A atividade física medida pela calorimetria mostra melhor informação do que os questionários. O nível de atividade é claramente maior em meninos do que em meninas e permanece estável durante os 6 anos. A adesão à dieta mediterrânea pode ser descrita como moderada, necessitando de melhorias

Integration and global analysis of isothermal titration calorimetry data for studying macromolecular interactions.

Isothermal titration calorimetry (ITC) is a powerful and widely used method to measure the energetics of macromolecular interactions by recording a thermogram of differential heating power during a titration. However, traditional ITC analysis is limited by stochastic thermogram noise and by the limited information content of a single titration experiment. Here we present a protocol for bias-free thermogram integration based on automated shape analysis of the injection peaks, followed by combination of isotherms from different calorimetric titration experiments into a global analysis, statistical analysis of binding parameters and graphical presentation of the results. This is performed using the integrated public-domain software packages NITPIC, SEDPHAT and GUSSI. The recently developed low-noise thermogram integration approach and global analysis allow for more precise parameter estimates and more reliable quantification of multisite and multicomponent cooperative and competitive interactions. Titration experiments typically take 1-2.5 h each, and global analysis usually takes 10-20 min.

MIRG Survey 2011: snapshot of rapidly evolving label-free technologies used for characterizing molecular interactions.

The field of label-free biophysical technologies used to quantitatively characterize macromolecular interactions with each other and with small molecules has grown enormously in the last 10 years. The most widely used analytical technologies for characterizing biomolecular interactions are surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), biolayer interferometry (BLI), and analytical ultracentrifugation (AUC). Measuring interaction parameters accurately and quantitatively is challenging, as it requires specialized expertise, training, and instrumentation. The Molecular Interaction Research Group (MIRG) conducted an online survey designed to capture the current profile of label-free technologies, including ITC, SPR, and other biosensors used in academia and the pharmaceutical industry sector. The main goal of the survey was to take a snapshot of laboratory, instrumentation, applications for measuring various biophysical parameters, confidence in data interpretation, data validation and acceptability, and limitations of using various technologies. Through this survey, we anticipate that the participating laboratories will be able to gauge their own capabilities and gain insights into the relative success of the different technologies that they use for characterizing molecular interactions.

Calorimetry as a tool for understanding biomolecular interactions and an aid to drug design.

The binding of two biomolecules viewed from the atomic level is highly complex. It involves the formation or removal of many individual non-covalent bonds both between the interacting molecules as well as with solvent. Currently, our understanding of the thermodynamic quantification of biomolecular interactions is somewhat naïve. ITC (isothermal titration calorimetry) provides a rapid route to a full thermodynamic characterization of a biomolecular interaction. Armed with these data, what are we really able to understand about complex formation and can any of this information provide a useful tool to aid drug development? Correlations between thermodynamic data and structural detail have been investigated, allowing insight into ways in which these can be used to understand protein-ligand interactions and provide input into the decision-making process in drug development.

Increased energy expenditure and glucose oxidation during acute nontraumatic skin pain in humans.

BACKGROUND AND OBJECTIVE: Tissue injury is accompanied by pain and results in increased energy expenditure, which may promote catabolism. The extent to which pain contributes to this sequence of events is not known. METHODS: In a cross-over design, 10 healthy volunteers were examined on three occasions; first, during self-controlled nontraumatic electrical painful stimulus to the abdominal skin, maintaining an intensity of 8 on the visual analogue scale (0-10). Next, the electrical stimulus was reproduced during local analgesia and, finally, there was a control session without stimulus. Indirect calorimetry and blood and urine sampling was done in order to calculate energy expenditure and substrate utilization. RESULTS: During pain stimulus, energy expenditure increased acutely and reversibly by 62% (95% confidence interval, 43-83), which was abolished by local analgesia. Energy expenditure paralleled both heart rate and blood catecholamine levels. The energy expenditure increase was fuelled by all energy sources, with the largest increase in glucose utilization. CONCLUSION: The pain-related increase in energy expenditure was possibly mediated by adrenergic activity and was probably to a large extent due to increased muscle tone. These effects may be enhanced by cortical events related to the pain. The increase in glucose consumption favours catabolism. Our findings emphasize the clinical importance of pain management.

Studying multisite binary and ternary protein interactions by global analysis of isothermal titration calorimetry data in SEDPHAT: application to adaptor protein complexes in cell signaling.

Multisite interactions and the formation of ternary or higher-order protein complexes are ubiquitous features of protein interactions. Cooperativity between different ligands is a hallmark for information transfer, and is frequently critical for the biological function. We describe a new computational platform for the global analysis of isothermal titration calorimetry (ITC) data for the study of binary and ternary multisite interactions, implemented as part of the public domain multimethod analysis software SEDPHAT. The global analysis of titrations performed in different orientations was explored, and the potential for unraveling cooperativity parameters in multisite interactions was assessed in theory and experiment. To demonstrate the practical potential and limitations of global analyses of ITC titrations for the study of cooperative multiprotein interactions, we have examined the interactions of three proteins that are critical for signal transduction after T-cell activation, LAT, Grb2, and Sos1. We have shown previously that multivalent interactions between these three molecules promote the assembly of large multiprotein complexes important for T-cell receptor activation. By global analysis of the heats of binding observed in sets of ITC injections in different orientations, which allowed us to follow the formation of binary and ternary complexes, we observed negative and positive cooperativity that may be important to control the pathway of assembly and disassembly of adaptor protein particles.

Ritmo de sudoración como mejor indicador de aclimatación al calor / Sweat rate as best indicator of heat aclimation

Objetivo: Determinar cual de los tres índices de aclimatación comúnmente utilizados (temperatura timpánica, ritmo de sudoración, o frecuencia cardiaca) es el más sensible y reproducible. Material y métodos: Siete jóvenes estudiantes universitarios (28+/- asños y 4,2+/-0,6 L/min VO2max) pedalearon a una intensidad del 60% del VO2max durante 60 minutos por 7 días (2 días de descanso máximo) en una cámara climática a 34,4+/-0,3ºC y 27,7+/-0,1% de humedad relativa, con 0,2 m/s de velocidad de viento. Este proceso de aclimatación se repitió 3 veces (A1, A2 y A3) espacidas por 3 meses para estudiar la reproducibilidad de las respuestas. Resultados: Tras 3 días de aclimatación el ritmo de sudoración (RS) subió por encima del ritmo del día 1 en todas las aclimataciones (p<0.05) pero no alcanzó un estado estable tras 7 días. La reproducibilidad entre aclimataciones fue alta para el ritmo de sudoración (R1=0.90), y frecuencia cardiaca final (R1=0.71). Conclusiones: El ritmo de sudoración es el índice más sensible y reproducible de aclimatación y recomendamos su uso en vez de frecuencia cardíaca o temperatura timpánica. Aunque los efectos de una semana de aclimatación al calor se pierden en 3 mese (día 1 de A1, A2 y A3 son similares) las respuestas son altamente reproducibles. Por último, confirmamos datos anteriores que más de 7 días son necesarios para alcanzar la máxima adaptación en ritmo de sudoración y frecuencia cardíaca

Purpose: to determine which of three commonly used indexed to evaluate acclimation (tympanic temperature, sweat rate, or heart rat is the most sensitive and reliable). Material and methods: seven young University students (28+/-8 years and 4.2+/-0.6 L/min VO2max) pedalled at 60% del VO2max for 60 minutes during 7 days (maximum of 2 rest days in between) in a climatic chamber set at 34.4+/-0.3ºC and 27.7+/-0.1% of relative humidity with 0.2 m/s of wind speed. This acclimation protocol was repeated in 3 occasions () A1, A2 y A3) separated by 3 months to study reliability. Results: After 3 days of acclimation sweat rate was higher than on day 1 in all (p<0.05) although a steady-state was not achieved at day 7. Tympanic temperature at the end of exercise was unchanged with no effect of days of acclimation. Heart rate at the end of exercise was lower than the day 1 after 5-6 days in all acclimations (p<0.05) without reaching a steady-state. There were a high reliability in sweat rate (R1=0.90) and heart rate (R1=0.84) but moderate for tympanic temperature (R1=0.71). Conclusions: Sweat rate is the most sensitive indication of acclimatation and we recommended its use over heart rate or tympanic temperature. Although the effects 1 week acclimation are lost within 3 months (day 1 of A1, A2, and A3 are similar) the responses are highly reliable. Finally, we confirm previous reports that indicates that indicate that over 7 days are needed to reach a steady-state response in sweat rate and heart rate

Recent developments for the analysis of data obtained from isothermal calorimetry.

Isothermal calorimetry is rapidly becoming an indispensable tool for the quantitative determination of a variety of kinetic and thermodynamic parameters for a wide range of systems. In particular calorimetry is finding increased application to the investigation of stability and incompatibility of pharmaceutical materials. In order to draw meaningful conclusions and to predict behaviour in related systems it is necessary to have the means to calculate accurately parameters such as the rate constant and enthalpy. To this end several groups have been developing equations which describe calorimetric output in these terms. This paper will briefly outline some of these equations and discuss some of the limitations that currently exist in their application. A particular emphasis is placed on the recent developments relating to the application of these equations to flow calorimetric data. The main application of these equations is usually found in the pharmaceutical industry. Pharmaceutical formulations are usually extremely complex mixtures consisting of many different excipients as well as the active drug. Because of these large numbers of ingredients it is often observed that multiple chemical and physical process occur over the lifetime of the study. This complexity is then reflected in the calorimetric data rendering the application of the simple equations useless. Dealing with this complexity is a major issue amongst the calorimetric community and some of the recent advances in this field are also discussed.

Isothermal titration calorimetry.

Isothermal titration calorimetry is an ideal technique for measuring biological binding interactions. It does not rely on the presence of chromophores or fluorophores, nor does it require an enzymatic assay. Because the technique relies only on the detection of a heat effect upon binding, it can be used to measure the binding constant, K, the enthalpy of binding, DeltaH degrees and the stoichiometry, or number of binding sites, n. This chapter describes instrumentation, experimental design, and the theoretical underpinnings necessary to run and analyze a calorimetric binding experiment.

Why zinc fingers prefer zinc: ligand-field symmetry and the hidden thermodynamics of metal ion selectivity.

The zinc finger, a motif of protein-nucleic acid recognition broadly conserved among eukaryotes, is a globular minidomain containing a tetrahedral metal-binding site. Preferential coordination of Zn(2+) (relative to Co(2+)) is proposed to reflect differences in ligand-field stabilization energies (LFSEs) due to complete or incomplete occupancy of d orbitals. LFSE predicts that the preference for Zn(2+) should be purely enthalpic in accord with calorimetric studies of a high-affinity consensus peptide (CP-1; Blasie, C. A., and Berg, J. (2002) Biochemistry 41, 15068-73). Despite its elegance, the general predominance of LFSE is unclear as (i) the magnitude by which CP-1 prefers Zn(2+) is greater than that expected and (ii) the analogous metal ion selectivity of a zinc metalloenzyme (carbonic anhydrase) is driven by changes in entropy rather than enthalpy. Because CP-1 was designed to optimize zinc binding, we have investigated the NMR structure and metal ion selectivity of a natural finger of lower stability derived from human tumor-suppressor protein WT1. Raman spectroscopy suggests that the structure of the WT1 domain is unaffected by interchange of Zn(2+) and Co(2+). As in CP-1, preferential binding of Zn(2+) (relative to Co(2+)) is driven predominantly by differences in enthalpy, but in this case the enthalpic advantage is less than that predicted by LFSE. A theoretical framework is presented to define the relationship between LFSE and other thermodynamic factors, such as metal ion electroaffinities, enthalpies of hydration, and the topography of the underlying folding landscape. The contribution of environmental coupling to entropy-enthalpy compensation is delineated in a formal thermodynamic cycle. Together, these considerations indicate that LFSE provides an important but incomplete description of the stringency and thermodynamic origin of metal-ion selectivity.

Thermodynamic mechanism and consequences of the polyproline II (PII) structural bias in the denatured states of proteins.

A quantitative characterization of the structure and energy of the denatured states of proteins represents the cornerstone to a molecular-level understanding of both protein stability and fold specificity. Recent studies have revealed a significant bias in unstructured peptides toward the polyproline II (P(II)) conformation, even when no prolines are present in the sequence. This indicates that the P(II) conformation is a dominant component of the denatured states of proteins, although a quantitative description of the component enthalpy and entropy functions associated with this conformation (i.e., the thermodynamic mechanism) has thus far proven elusive. An experimental system has been designed that, when analyzed with high-precision isothermal titration calorimetry, provides direct access to the residue-specific thermodynamics of the P(II) structure formation in disordered proteins and peptides. Here, it is shown that the P(II) bias is driven by a favorable and significant enthalpy (Deltah) of -1.7 kcal mol(-1) residue(-1), which is partially offset by an unfavorable entropy (TDeltas) of -0.7 kcal mol(-1) residue(-1), relative to the ensemble of disordered conformations of the molecule. In addition to impacting dramatically the interpretation of thermal denaturation experiments, these experimental values form the framework of a quantitative energetic description of the denatured states of proteins.

Evaluation of a scanner-assisted colorimetric MIC method for susceptibility testing of gram-negative fermentative bacteria.

We describe the ScanMIC method, a colorimetric MIC method for susceptibility testing of gram-negative fermentative bacteria. The method is a slight modification of the National Committee for Clinical Laboratory Standards (NCCLS) recommended broth microdilution method that uses a redox indicator 2,3,5-triphenyltetrazolium chloride (TTC) to enhance the estimate of bacterial growth inhibition in a microplate and a flatbed scanner to capture the microplate image. In-house software was developed to transform the microplate image into numerical values based on the amount of bacterial growth and to generate the MICs automatically. The choice of indicator was based on its low toxicity and ease of reading by scanner. We compared the ScanMIC method to the NCCLS recommended broth microdilution method with 197 coliform strains against seven antibacterial agents. The interpretative categorical agreement was obtained in 92.4% of the assays, and the agreement for MIC differences (within +/-1 log(2) dilution) was obtained in 96% for ScanMIC versus broth microdilution and 97% for a two-step incubation colorimetric broth microdilution versus the broth microdilution method. The method was found to be labor-saving, not to require any initial investment, and to show reliable results. Thus, the ScanMIC method could be useful for epidemiological surveys that include susceptibility testing of bacteria.

Eco-efficiency analysis of an agricultural research complex.

The Model Sustainable Agricultural Complex (MSAC) is a 600-acre experimental farm in south-central Louisiana, in the very southern reaches of the United States, approximately 40 km north of the Gulf of Mexico. The MSAC consists of many land uses and facilities, including a dairy, crawfish center, beef herd, sugarcane crop, and equestrian center, as well as numerous features and programs for research, education, and residence. The mission of the MSAC, which is operated by the Department of Renewable Resources at the University of Louisiana at Lafayette, has been to accommodate research and education in production agriculture, while generating revenues through the delivery of food products into the local economy. In recent years, environmental conservation has been increasingly important at the MSAC. Best management practices (BMPs) were implemented to reduce soil loss and mitigate nonpoint source pollution. Research was initiated to quantify the effectiveness of these BMPs, and workshops were conducted to explain preliminary results to local farmers. However, environmental improvements at the MSAC had until 2000 been piecemeal, which may be said as well for agriculture overall. What is needed is a comprehensive integrated approach to analyzing and improving environmental performance, as is possible when implementing an environmental management system (EMS). This manuscript describes our efforts to integrate piecemeal environmental improvements into a farm-wide program of systematic improvement. This process began with a qualitative ranking of the MSAC's inputs and outputs, followed by a quantification of certain key parameters related to the consumption of resources and provision of services at the Complex. Certain measures related to the Complex's eco-efficiency were combined into a ratio that provides a useful target for management and continuous improvement. Eco-efficiency, which is defined as 'the efficiency with which receivables are converted into deliverables', is a good way to apply the lessons of industry to the agricultural sector, for instance, by monitoring and managing resource efficiency as an aspect in an EMS such as prescribed by ISO 14000. This will require disciplined recordkeeping and managed conservation, and will promote long-term environmental improvement.

Entropic nature of the interaction between promoter bound CRP mutants and RNA polymerase.

The interaction between CRP, T127L, S128A, and CRP and RNA polymerase bound to a 104 bp synthetic promoter were determined by ITC at 298 K and ranges from a deltaG(b) degrees = 1.4 +/- 0.8 kJ mol(-)(1) (cAMP-ligated S128A) to 4.5 +/- 0.3 kJ mol(-)(1) (cAMP-ligated double mutant CRP) with endothermicities that range from 4 +/- 3 kJ mol(-)(1) (cAMP-ligated CRP) to 47 +/- 8 kJ mol(-)(1) (cGMP-ligated T127L). The interaction is, thus, entropically driven, exhibits enthalpy-entropy compensation, and increases the binding affinity of the RNA polymerase to the promoter by factors ranging from 1.7 +/- 0.1 (cAMP-ligated S128A) to 6.1 +/- 0.1 (cAMP-ligated CRP). Although the binding affinities to the promoter alone, except for cAMP-ligated S128A, are the same as to a shorter 40 bp duplex containing the same CRP consensus binding site sequence (conDNA), the binding enthalpies of CRP/mutant to the promoter are lower by factors of 2-3 x than the corresponding binding enthalpies to conDNA. Small angle neutron scattering measurements on the DNA-CRP/mutant complexes in D(2)O/H(2)O solutions exhibit an increase in the Rg of the CRP/mutant component from 22 to 27-31 A that can be attributed to a conformational change in the N-terminal domain of CRP. The Rg = 27 A for the bound conDNA can be attributed to a slight unwinding of the DNA in solution that would also enhance the activation of transcription. The Rg = 53 +/- 3 A for the bound promoter is attributed to bending of the promoter in solution that can be responsible for the lower CRP/mutant-promoter binding endothermicities.

Interrelation between thermochemical and structural data of polymorphs exemplified by diflunisal.

Three known and one new unsolvated polymorphic phase A, B, C, and D of diflunisal were grown and studied by X-ray diffraction, IR-spectroscopy, solution calorimetry, and DSC methods. Their structures are compared to another previously described modification E.1 Relationships were studied between O-H and C=O stretching frequencies and between C=O stretching frequency and the molecular volume of diflunisal in the respective crystal lattice. According to regularities found it was proposed that the existence of polymorphic forms is determined by conformational flexibility of the molecule, ability to create inter- and intramolecular hydrogen bonds and the competition between nonspecific van der Waals and specific hydrogen bond interactions. The volume per molecule in the crystal lattice are: A < B < C < E < D (XRD Ito method). Forms A and C are enantiotropic with a difference in crystal lattice energies of 1.9 +/- 0.5 kJ.mol( - 1). Modifications B, C, D, and A, B, D are monotropic. Based on solution enthalpies, absolute values of the lattice showed only small differences ("isoenergetic" polymorphs), and can be arranged in increasing order: B approximately A < C < D.

A taxa metabólica basal é superestimada pelas equaçoes preditivas em universitárias do Río de Janeiro, Brasil / Basal metabolic rate is overestimated by predictive equations in college aged women of Rio de Janeiro, Brazil

Alguns estudos têm demostrado que a taxa metabólica basal (TMB) é superestimada ao se usar equaçoes preditivas (EP) em populaçoes viviendo nos trópicos. O presente trabalho teve por objetivo comparar os valores da TMB medidos e os estimados por EP em 50 universitárias do curso de graduaçao em Nutriçao da Universidade Federal Fluminense. Foram realizadas medidas antropométricas (estatura e massa corporal) e de composiçao corporal (bio-impedância). A mensuraçao da TMB foi feita através de calorimetra indireta e as EP usadas foram as publicadas em: FAO/WHO/ONU (1985), Haris & Benedict (1919) e Henry & Rees (1991). As TMB estimadas pelas equaçoes foram significativamente maiores que a TMB medida, sendo a Harris & Benedict a que mais superestimou (18,9 por ciento), seguida pela da FAO/WHO/ONU (12,5 por ciento) e Henry & Rees (7,2 por ciento). Nao houve relaçao entre superestimava da TMB e a composiçao corporal das universitárias. Esses resultados reforçam a necessidade de mais estudos na populaçao brasileira para elaboraçao de EP edequedas as características da populaçao

The calibration of therapy level electron beam ionization chambers in terms of absorbed dose to water.

During 1998, NPL plans to introduce the world's first absorbed dose calibration service for electron beam radiotherapy. The service will be based on the primary standard graphite calorimeter, and will enable the direct calibration of electron ionization chambers, without reference to air kerma standards. This calibration is a two-step process. Firstly, a set of NACP-designed parallel-plate reference chambers have been calibrated against the calorimeter over the last few years. These chambers are then used to calibrate user chambers by direct comparison in a water phantom under standard conditions. This paper describes the calibration of the reference chambers against the calorimeter and the derivation of absorbed dose to water calibration factors (with an estimated uncertainty in this calibration of +/-1.50% at the 95% confidence level).