Relative Mass Change Research Articles

Study of water vapor and surfactant absorption by lipid model systems using the quartz crystal microbalance

Skin is constantly exposed to surfactants which compromise the essential barrier function of normal healthy skin. To model the interactions of surfactants with the barrier lipids of the stratum corneum (SC), it is essential to develop in vitro and in vivo quantitative measurement methods to predict, evaluate, and demonstrate the effect of the different surfactant chemistries and technologies on skin. In the current work, in vitro water vapor uptake and surfactant absorption onto skin lipid model films were quantitatively studied using a technique based on the piezoelectric effect, the quartz crystal microbalance (QCM). This approach is straightforward and reliable in providing subtle surface/interface related mass change information with high resolution and sensitivity. The results show that barrier properties of the lipid model system may be damaged by surfactant absorption, as well as by long-term water exposure due to alterations to the lipid film structure. Surfactant absorption is found to be concentration dependent even beyond its critical micelle concentration (CMC). QCM results for different surfactant systems are consistent with reported clinical data in showing that clinically milder surfactants (SLES) do not perturb the film as much as clinically harsh surfactants (SDS).

Commentaries on Viewpoint: Do oxidative and anaerobic energy production in exercising muscle change throughout growth and maturation?

Commentaries on Viewpoint: Do oxidative and anaerobic energy production in exercising muscle change throughout growth and maturation?

Kinetic study of Argentinean asphaltite gasification using carbon dioxide as gasifying agent

The kinetics of Argentinean asphaltite char gasification using carbon dioxide as gasifying agent was studied between 1048 and 1223 K. The chars were obtained by pyrolysis of an asphaltite in a fixed bed reactor. The relative mass change during the gasification reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of the char with carbon dioxide was determined at about 800 K. The influence of gaseous flow rate, sample mass, carbon dioxide partial pressure and temperature in the reaction rate was analyzed. The experimental condition under which the progress of gasification reaction is chemically controlled was established. In those conditions, an activation energy of 185 kJ mol −1 was obtained with an isoconversional method. Concerning the influence of carbon dioxide partial pressure, it was determined that pressures greater than 50 kPa do not alter the kinetics regime. Finally a reaction order of 0.5 for carbon dioxide partial pressure was determined and a global rate equation that includes these parameters was developed. Rate = d α dt = ( 1 - α ) 2 / 3 · 1.1 × 10 5 exp - 185 kJ mol - 1 R · T · P CO 2 0.5

Electrodeposition of bismuth telluride films from a nonaqueous solvent

The author examines Bi 2Te 3 deposition from a DMSO solution containing TeCl 4 and Bi(NO 3) 3 × 5H 2O by means of cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). Accumulated charges and related mass changes for Bi 2Te 3 deposition on working electrodes are measured in situ. The deposit composition is more dependent on Te 4+ concentrations in DMSO solution than on the potential. In a DMSO solution containing 0.01 M Te 4+ and 0.0075 M Bi 3+, Bi 2Te 3 deposits were obtained in the potential range between −0.2 and −0.8 V vs. Ag/AgCl. In a DMSO solution containing 0.05 M Te 4+ and 0.0375 M Bi 3+, Te-rich deposits were formed from −0.2 to −0.8 V vs. Ag/AgCl.

Effect Of Resistance Training Frequency On Body Composition In Middle-aged Women

The effect of resistance training (RT) frequency on body composition has not been well studied in women, although they are at high risk for loss of lean mass with age. PURPOSE: This study evaluated short-term effects of a 3- versus 4-day a week RT program on changes in absolute (kg) and relative (%) lean and fat mass. METHODS: Nineteen untrained women (age 48 ± 1.2 years; BMI 28.8 ± 1.2) completed 8 weeks of RT. To promote adherence they self-selected assignment to either Group 3, which trained 3 nonconsecutive days of the week using a traditional total body protocol, or Group 4, which trained 4 consecutive days of the week using an alternating split training (upper-lower body) protocol. Group 4 completed 3 sets of 6 upper body exercises (chest press, latissimus pulldown, shoulder press, machine row, triceps pushdown, biceps curl) or 6 sets of 3 lower body exercises (leg press, leg extension, leg curl). Group 3 completed 3 sets of the same 8 exercises (excluding machine row) used for split training. Both groups completed 72 sets of 8-12 repetitions at 50-80% 1RM per week. Body composition was measured using air displacement plethysmography prior to and after completion of the RT program. To control for diet, participants were instructed not to change their intake or restrict calories during the study. RESULTS: Both RT protocols were well-tolerated, had 98% adherence, and resulted in significant increases in upper and lower body strength (p < 0.01). At baseline and after 8 weeks of RT there were no significant between-group differences in age, body mass, BMI, lean or fat mass. However, when both groups were combined there was a significant increase in absolute lean mass (1.1 ± 0.3 kg; p = 0.002) accompanied by increases in body mass (1.04 ± 0.4 kg; p = 0.009) and BMI (0.38 ± 0.1; p = 0.01). A small, non-significant decrease in % body fat (-0.4 ± 0.3 %) was observed. CONCLUSIONS: In untrained, middle-aged women initial, short-term gains in lean mass are not influenced by a training frequency of either 3 or 4 days a week. Consecutive-day split training is as well tolerated as traditional every-other-day total body training, even by novices. Therefore, for convenience and to promote adherence, women beginning a RT program should be taught both training protocols so they may schedule training sessions to fit their normal, weekly routine as closely as possible.

Effects of pre-bloom leaf removal on growth of berry tissues and must composition in two redVitis viniferaL. cultivars

Background and Aims: Little work has been conducted on the effects that summer pruning operations have on the relative growth of grapevine berry parts. Our paper studies whether pre-bloom leaf removal is able to modify the proportions of seed, skin and flesh in ripe grapevines berries and the related effects on must composition. Methods and Results: Pre-bloom defoliation (D) of the first six basal leaves on main shoots was applied to the field-grown cvs Barbera and Lambrusco salamino (Vitis vinifera L.) in Italy's Po Valley and compared with non-defoliated controls. D showed reduced fruitset, hence yield per shoot, and concurrently improved must soluble solids and total anthocyanins in both cultivars as a likely result of increased leaf-to-fruit ratio (+3.4 cm2/g and +5.2 cm2/g for Barbera and Lambrusco, respectively) and improved relative skin mass (from 6.0 to 9.0% in Barbera and from 8.1 to 10.4% in Lambrusco). In both cultivars, skin and seed mass were highly correlated with total berry mass and changes in relative skin mass were generally not related to berry size. Conclusions: These results indicate that berry size per se is not the primary factor in determining final grape composition, which instead seems to depend upon factors differentially affecting the growth of the various berry components. Significance of the Study: Pre-bloom D induced a consistent, site and cultivar-independent increase in relative skin mass suggesting this effect being strongly physiologically regulated.

Identification of AGE-precursors and AGE formation in glycation-induced BSA peptides

The glycation of BSA leads to protein/peptide modifications that result in the formation of AGEs. AGEs react with the amino groups of N-terminal amino acid residues, particularly arginine and lysine residues. Enhanced AGE formation exists in the blood and tissues of diabetics, as well as in aging and other disorders. The Identification of AGEs is of great importance. Mass spectrometry has been applied to identify and structurally elucidate AGEs. Here, we report on the identification of AGE- peptides and AGE-precursors based on relative mass changes as a result of specific AGE formation. HPLC-ESIMS, ESI-MS/MS, and the Mascot database were used. The relative mass changes due to the specific type of AGE formation were added to the identified peptides followed by a manual search of the glycated samples, which resulted in the identification of seven peptides for the formation of five AGEs, namely CML, pyrraline, imidazolone A, imidazolone B, and AFGP. Four glycated peptides (FPK, ECCDKPLLEK, IETMR, and HLVDEPQNLIK) were identified in the formation of AGE-precursors.

Exploring the Mechanism of Selective Noncovalent Adduct Protein Probing Mass Spectrometry Utilizing Site-Directed Mutagenesis To Examine Ubiquitin

Mass spectrometry (MS) is emerging as an additional tool for examining protein structure by way of experiments where structurally related mass changes induced in solution are subsequently detected in the gas phase. Selective noncovalent adduct protein probing (SNAPP) is a recent addition to this type of experiment. SNAPP utilizes noncovalent recognition of lysine residues with 18-crown-6 (18C6) to monitor changes in protein structure. It has been observed that the number of 18C6 adducts that attach to a protein is a function of the structure of the protein. The present work seeks to examine the underlying chemistry which controls the differential attachment of 18C6 to lysine by using ubiquitin as a model system. Ubiquitin is a small protein with a structure that has been well characterized by multiple techniques. Site-directed mutagenesis was used to create a series of ubiquitin mutants where the lysine residues were exchanged for asparagine one at a time. These mutants were then evaluated by SNAPP-MS to determine the relative contribution of each lysine as a binding site for 18C6. It was found that attachment of 18C6 is largely controlled by the strength of intramolecular interactions involving lysine residues. Salt bridges provide the greatest interference, followed by hydrogen bonds. In addition to determining the mechanism for SNAPP, insights are provided about the structure of ubiquitin including confirmation of the existence of two dynamic states for the native structure. These results are discussed in relation to the biological functions of ubiquitin.

SELECTION ON HERITABLE SEASONAL PHENOTYPIC PLASTICITY OF BODY MASS

The ability to cope with environmental change is fundamental to a species' evolution. Organisms can respond to seasonal environmental variation through phenotypic plasticity. The substantial plasticity in body mass of temperate species has often been considered a simple consequence of change in environmental quality, but could also have evolved as an adaptation to seasonality. We investigated the genetic basis of, and selection acting on, seasonal plasticity in body mass for wild bighorn sheep ewes (Ovis canadensis) at Ram Mountain, Alberta, under two contrasting environmental conditions. Heritability of plasticity, estimated as mass-specific summer and winter mass changes, was low but significant. The additive genetic variance component of relative summer mass change was greater under good environmental conditions (characterized by a population increase and high juvenile survival) than under poor conditions (population decrease and low juvenile survival). Additive genetic variance of relative winter mass change appeared independent of environmental conditions. We found evidence of selection on summer (relative) and winter (relative and absolute) mass change. For a given mass, more plastic individuals (with greater seasonal mass changes) achieve greater fitness through reproduction in the following year. However, genetic correlations between mass parameters were positive. Our study supports the hypothesis that seasonal plasticity in body mass in vertebrates is an adaptation that evolved under natural selection to cope with environmental variation but genetic correlations with other traits might limit its evolutionary potential.

Study of electrodeposition of bismuth telluride by voltammetric methods and in-situ electrochemical quartz crystal microbalance method

The authors examine Bi 2Te 3 deposition and stripping mechanisms by means of cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). Accumulated charges and related mass changes for Bi 2Te 3 deposition on working electrodes are measured in-situ. Linear scanning voltammetry and EQCM results are then used to propose a two-stage deposition process. During the initial stage, a thin layer of Bi-rich Bi 2Te 3 forms on the surface of the Au electrode, followed by a bulk deposition of Te-rich Bi 2Te 3. The composition variation is minor. During anodic linear stripping of a thin deposit, Bi 2Te 3 oxidation with a single peak was observed. Two oxidation peaks were detected during anodic stripping of a thick deposit-one corresponding to Bi 2Te 3 oxidation and the other to a combination of Bi 2Te 3 and Te oxidation. The Bi 2Te 3 deposit was synthesized via pulsed plating in order to study the effects of pulse parameters on deposit composition. Results indicate that Bi 2Te 3 film composition is affected by changes in pulse potential from potential pulse plating or by changes in current pulse plating relaxation time.

Age-related changes in thoracic mass: possible reallocation of resources to reproduction in butterflies

In nectar-feeding butterflies, reproductive potential is usually thought to depend on the size of the reproductive reserves in the abdomen, the adult food quality and, for females, the amount of resources received in the spermatophores at mating. Recent findings show that thorax mass and nitrogen content decrease with age in some butterfly species, and that thorax resources may be used for reproduction in the butterfly Pieris napi, just as in some other insects. In order to determine whether this is a general pattern and ascertain how it relates to the investment of resources in reproduction we studied the dynamics of thorax and abdomen mass changes in 11 Swedish butterfly species. By regressing thorax and abdomen mass on age of field-collected specimens, we show that loss of mass from both the thorax and the abdomen is a common phenomenon among nectar-feeding temperate zone butterflies under natural conditions. We argue that our results indicate that resources from flight muscles can be reallocated to reproduction by these butterflies, thus increasing their reproductive potential. Within species, females use proportionately more resources from the thorax than do males, as expected from the difference in investment of resources in reproduction. Among males we expect species with a higher reproductive investment to have a larger decrease in thorax and abdomen mass, and our data indicate that this is the case. Looking at the change in relative thorax mass, our results suggest that the use of resources from the thorax does not affect flight performance negatively, something that could constrain the use of muscle resources.

Sodium Balance And Sweat Loss During The Hawaii IRONMAN Triathlon

PURPOSE To determine the variability in sweating rate and sweat sodium concentration (sweat-Na) and its relationship to changes in serum sodium concentration (serum-Na) in ultra-endurance triathletes competing in the 2003 Ironman Triathlon World Championship. METHODS During the sweat analysis trial, seventy-one heat-acclimatized males and females (22–74y) exercised on a stationary bicycle at 70–75% of HRmax for 30 minutes following an 8 minute warm-up. All trials took place in warm conditions (26.4 ±0.2°CWBGT, 28.5 ± 0.2°C dry bulb, 66.0 ± 0.0% RH) in an outdoor field laboratory in Kailua-Kona, HI, 3–7d prior to the race. Serum-Na and skin-fold thickness were measured prior to exercise. Sweating rate, determined via change in body mass, and sweat-Na were measured during the 30 min exercise bout. Forty-six male and female subjects who participated in the sweating analysis trial were also studied on race-day. Pre- and post-race serum-Na and body mass were measured and race nutritional intake was also recorded. RESULTS The subjects exhibited a large amount of variability in absolute and relative sweating rate (1.39±0.05 L/hr, coefficient of variation (CV) = 30.8%; 19.4 ± 0.7 ml/kg/hr, CV = 28.5%), sweat-Na (43.4±2.1 mEq/L, CV = 40.0%), and absolute and relative sweat-Na loss(61.6±4.1 mEq/hr, CV = 56.0; 0.87 ± 0.06 mEq/kg/hr, CV = 54.2%). In males, the decline in race-day serum-Na was correlated with relative sweat rate, relative rate of sweat-Na loss, and body mass change (r=−0.413, p<0.05; r=−0.457, p<0.05; r=−0.549, p<0.01). Together, the rate of relative sweat-Na loss and body mass change were highly related to changes in serum-Na (r=0.686, p<0.05). In females, body mass changes alone were highly associated with declines in serum-Na (r=0.614, p<0.05). Females had a significant relationship between rate of absolute sweat-Na loss and Na intake (r=0.637, p<0.05), while males did not (r=0.280, p=0.466). CONCLUSIONS Changes in serum-Na during an ultra-endurance triathlon were related to the interactions of sweat-Na loss, sodium ingestion, and fluid balance. Supported by the Gatorade Sports Science Institute.

Sodium Balance And Sweat Loss During The Hawaii IRONMAN Triathlon

PURPOSE To determine the variability in sweating rate and sweat sodium concentration (sweat-Na) and its relationship to changes in serum sodium concentration (serum-Na) in ultra-endurance triathletes competing in the 2003 Ironman Triathlon World Championship. METHODS During the sweat analysis trial, seventy-one heat-acclimatized males and females (22–74y) exercised on a stationary bicycle at 70–75% of HRmax for 30 minutes following an 8 minute warm-up. All trials took place in warm conditions (26.4 ±0.2°CWBGT, 28.5 ± 0.2°C dry bulb, 66.0 ± 0.0% RH) in an outdoor field laboratory in Kailua-Kona, HI, 3–7d prior to the race. Serum-Na and skin-fold thickness were measured prior to exercise. Sweating rate, determined via change in body mass, and sweat-Na were measured during the 30 min exercise bout. Forty-six male and female subjects who participated in the sweating analysis trial were also studied on race-day. Pre- and post-race serum-Na and body mass were measured and race nutritional intake was also recorded. RESULTS The subjects exhibited a large amount of variability in absolute and relative sweating rate (1.39±0.05 L/hr, coefficient of variation (CV) = 30.8%; 19.4 ± 0.7 ml/kg/hr, CV = 28.5%), sweat-Na (43.4±2.1 mEq/L, CV = 40.0%), and absolute and relative sweat-Na loss(61.6±4.1 mEq/hr, CV = 56.0; 0.87 ± 0.06 mEq/kg/hr, CV = 54.2%). In males, the decline in race-day serum-Na was correlated with relative sweat rate, relative rate of sweat-Na loss, and body mass change (r=−0.413, p<0.05; r=−0.457, p<0.05; r=−0.549, p<0.01). Together, the rate of relative sweat-Na loss and body mass change were highly related to changes in serum-Na (r=0.686, p<0.05). In females, body mass changes alone were highly associated with declines in serum-Na (r=0.614, p<0.05). Females had a significant relationship between rate of absolute sweat-Na loss and Na intake (r=0.637, p<0.05), while males did not (r=0.280, p=0.466). CONCLUSIONS Changes in serum-Na during an ultra-endurance triathlon were related to the interactions of sweat-Na loss, sodium ingestion, and fluid balance. Supported by the Gatorade Sports Science Institute.

Ouantitative Analysis of Oxidation Behavior of Free Carbon in S-Ti-C-O Fiber-Bonded Ceramics.

A model for the oxidation kinetics and mechanisms of Si-Ti-C-O fiber-bonded ceramics was newly developed to evaluate the oxidation behavior quantitatively at temperatures ranging between 773 and 1473K in air. The model considers the geometry changes of pores resulting from consumption by oxidation of the free carbon layer, and the oxygen consumption due to oxidation of the pore walls. A differential equation for the oxygen concentration profile along the pore was derived and solved numerically. For materials with very thin carbon layer, the geometry change of the pore has a significant effect on the oxygen concentration profile. The relative mass changes due to oxidation of (1) the external surface, (2) the carbon layer and (3) the pore walls were respectively calculated and thermogravimetric analysis (TGA) curves of the material derived from their sum. The calculated TGA curves well agreed with the experimental data. The length of carbon layer consumed by oxidation was calculated as a function of time and temperature. At low temperatures, the rates of the carbon consumption were low, but pores took place proceeded for long time. At high temperature, in contrast, the oxidation of the carbon layer was inhibited in a short time due to the quick sealing of the pore entrance by silica layer. Thus, the oxidation damage is limited only in the vicinity of the material surface.

Combustion characteristics of WO3/Zn reaction system in SHS process

Tungsten powder was prepared by the Self-Propagating High-Temperature Synthesis (SHS) Process of WO3-Zn mixture. Zn vapor was discovered to affect significantly the combustion parameters such as combustion temperature (Tc), combustion velocity (U), relative mass change (Δm) and relative elongation (Δh) of the sample. These effects could be reduced by decreasing internal Ar pressure and sample density. The ZnO in the product was leached with an HCl solution. The Zinc-thermal reduction mechanism was revealed through a quenching of the sample.

Preparation of tungsten powder by the combustion of CaWC4/Mg

Tungsten powder was prepared by a Self-Propagating High-Temperature Synthesis(SHS) Process of a CaWO4-Mg mixture. Mg vapor was discovered to significantly affect such combustion parameters as the combustion temperature(Tc), the combustion velocity(U), the relative mass change(δm) and the relative elongation(δh) of the sample. These effects could be reduced by decreasing the internal Ar pressure, sample density and reducing agent content. The oxygen content in tungsten was decreased by using 5% excess Mg; the carbon content was diminished when the combustion process occurred under PAr=0.1 MPa. The MgO and CaO in the product was leached with an HC1 solution. Such parameters as combustion temperature(Tc), U, Am, and milling time(τ) were found to affect the tungsten particle size and morphology.

Quantitative determination of oxygen deficiency in PLZT ferroelectric ceramic targets

Oxygen deficiencies in vacuum hot-pressed ferroelectric ceramics were studied using thermogravimetric increase and electrical resistivity. The oxygen increase was found in terms of the relative mass increase of oxygen-deficient sheet samples after being annealed for sufficient times with respect to the oxygen stoichiometric reference samples. It was found that for one PLZT composition the mass increase reaches the same saturation level independent of annealing temperatures. In addition, thinner samples reach to a fully oxidized sate more rapidly than thicker samples. Electrical resistivity measurements on the samples subjected to various heat treatments confirmed that a full oxidized state was achieved. The quantitative calculation of oxygen deficiency was made based on the net increase in the relative mass changes after being fully oxidized. Measurements on two PLZT compositions showed the oxygen deficiency (z) of about 0.095–0.112.

The essential DNA polymerases delta and epsilon are involved in repair of UV-damaged DNA in the yeast Saccharomyces cerevisiae.

We have studied the ability of yeast DNA polymerases to carry out repair of lesions caused by UV irradiation in Saccharomyces cerevisiae. By the analysis of postirradiation relative molecular mass changes in cellular DNA of different DNA polymerases mutant strains, it was established that mutations in DNA polymerases delta and epsilon showed accumulation of single-strand breaks indicating defective repair. Mutations in other DNA polymerase genes exhibited no defects in DNA repair. Thus, the data obtained suggest that DNA polymerases delta and epsilon are both necessary for DNA replication and for repair of lesions caused by UV irradiation. The results are discussed in the light of current concepts concerning the specificity of DNA polymerases in DNA repair.

Bone reactions to titanium screw implants in ovariectomized animals

Objective. The purpose of this study was to investigate the reactions of bone tissue after the placement of implants into the tibiae of osteopenic model rats. Study design. Commercially pure titanium screw implants were placed in the bilateral proximal tibial metaphyses 168 days after ovariectomy had been performed on 12-week-old female Wistar rats. For control purposes, implants were similarly placed in sham-ovariectomy rats. The healing process was examined histologically by means of undecalcified sections at various intervals from 7 to 168 days after implantation. Through use of an automated imaging analytic system, changes in relative bone mass and implant-bone contact were histomorphometrically evaluated. Results. In the cortical bone area, only a slight difference in bone contact was noted with the implant until 28 days after implantation. However, ovariectomy significantly affected bone contact at 56 days after implantation. The rate of bone contact in the cancellous bone area and the relative bone mass around the implant were significantly lower in the test group than in the control group. Conclusions. It is considered that a decrease in bone mass causes a reduction in the contact area between implant and bone and may also cause a reduction in the supporting ability of the implant because of thinning of the surrounding bone tissue. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:411-8)

Digital image ratio: a new radiographic method for quantifying changes in alveolar bone. Part 1: Theory and methodology.

A new world, digital image ratio (DIR), has been developed for directly measuring changes in alveolar bone. The image on the computer monitor represents the relative mass change between two radiographs. Fourier filtering is used to reduce noise artefacts. This method is validated through an experiment with a step wedge. DIR needs only a preliminary calibration of the experimental conditions of operation and avoids tedious calibrations for each measurement as in the case of digital image substraction. Low-voltage X-ray techniques are suggested for long-term quantitative studies of patients to minimize irradiation doses.