Determination of ionization constants by paper electrophoresis.

PubMed Central

Tate, M E

1981-01-01

Dimensionless apparent ionization constants of charged low-molecular-weight species may be obtained from paper-electrophoretic data at 20-25 degrees C with buffers (I0.1-0.5) of measured pH (1.5-12.5) containing oxalate ions. Relative mobilities rather than absolute mobilities were measured by using glycerol and m-nitrobenzenesulphonate respectively as standards of zero and unit mobility. Application of the procedure to ionizations of adenine, adenosine, 2'-deoxyadenosine, 3'-deoxyadenosine, 3':5'-cyclic AMP, ADP, ADP-glucose-agrocin 84 and ATP is described. PMID:6976169

A Simple Model Predicting Individual Weight Change in Humans

PubMed Central

Thomas, Diana M.; Martin, Corby K.; Heymsfield, Steven; Redman, Leanne M.; Schoeller, Dale A.; Levine, James A.

2010-01-01

Excessive weight in adults is a national concern with over 2/3 of the US population deemed overweight. Because being overweight has been correlated to numerous diseases such as heart disease and type 2 diabetes, there is a need to understand mechanisms and predict outcomes of weight change and weight maintenance. A simple mathematical model that accurately predicts individual weight change offers opportunities to understand how individuals lose and gain weight and can be used to foster patient adherence to diets in clinical settings. For this purpose, we developed a one dimensional differential equation model of weight change based on the energy balance equation is paired to an algebraic relationship between fat free mass and fat mass derived from a large nationally representative sample of recently released data collected by the Centers for Disease Control. We validate the model's ability to predict individual participants’ weight change by comparing model estimates of final weight data from two recent underfeeding studies and one overfeeding study. Mean absolute error and standard deviation between model predictions and observed measurements of final weights are less than 1.8 ± 1.3 kg for the underfeeding studies and 2.5 ± 1.6 kg for the overfeeding study. Comparison of the model predictions to other one dimensional models of weight change shows improvement in mean absolute error, standard deviation of mean absolute error, and group mean predictions. The maximum absolute individual error decreased by approximately 60% substantiating reliability in individual weight change predictions. The model provides a viable method for estimating individual weight change as a result of changes in intake and determining individual dietary adherence during weight change studies. PMID:24707319

New microbial growth factor

NASA Technical Reports Server (NTRS)

Bok, S. H.; Casida, L. E., Jr.

1977-01-01

A screening procedure was used to isolate from soil a Penicillium sp., two bacterial isolates, and a Streptomyces sp. that produced a previously unknown microbial growth factor. This factor was an absolute growth requirement for three soil bacteria. The Penicillium sp. and one of the bacteria requiring the factor, an Arthrobacter sp., were selected for more extensive study concerning the production and characteristics of the growth factor. It did not seem to be related to the siderochromes. It was not present in soil extract, rumen fluid, or any other medium component tested. It appears to be a glycoprotein of high molecular weight and has high specific activity. When added to the diets for a meadow-vole mammalian test system, it caused an increased consumption of diet without a concurrent increase in rate of weight gain.

Statistical Analysis on the Performance of Molecular Mechanics Poisson–Boltzmann Surface Area versus Absolute Binding Free Energy Calculations: Bromodomains as a Case Study

PubMed Central

2017-01-01

Binding free energy calculations that make use of alchemical pathways are becoming increasingly feasible thanks to advances in hardware and algorithms. Although relative binding free energy (RBFE) calculations are starting to find widespread use, absolute binding free energy (ABFE) calculations are still being explored mainly in academic settings due to the high computational requirements and still uncertain predictive value. However, in some drug design scenarios, RBFE calculations are not applicable and ABFE calculations could provide an alternative. Computationally cheaper end-point calculations in implicit solvent, such as molecular mechanics Poisson–Boltzmann surface area (MMPBSA) calculations, could too be used if one is primarily interested in a relative ranking of affinities. Here, we compare MMPBSA calculations to previously performed absolute alchemical free energy calculations in their ability to correlate with experimental binding free energies for three sets of bromodomain–inhibitor pairs. Different MMPBSA approaches have been considered, including a standard single-trajectory protocol, a protocol that includes a binding entropy estimate, and protocols that take into account the ligand hydration shell. Despite the improvements observed with the latter two MMPBSA approaches, ABFE calculations were found to be overall superior in obtaining correlation with experimental affinities for the test cases considered. A difference in weighted average Pearson () and Spearman () correlations of 0.25 and 0.31 was observed when using a standard single-trajectory MMPBSA setup ( = 0.64 and = 0.66 for ABFE; = 0.39 and = 0.35 for MMPBSA). The best performing MMPBSA protocols returned weighted average Pearson and Spearman correlations that were about 0.1 inferior to ABFE calculations: = 0.55 and = 0.56 when including an entropy estimate, and = 0.53 and = 0.55 when including explicit water molecules. Overall, the study suggests that ABFE calculations are indeed the more accurate approach, yet there is also value in MMPBSA calculations considering the lower compute requirements, and if agreement to experimental affinities in absolute terms is not of interest. Moreover, for the specific protein–ligand systems considered in this study, we find that including an explicit ligand hydration shell or a binding entropy estimate in the MMPBSA calculations resulted in significant performance improvements at a negligible computational cost. PMID:28786670

Understanding gas-surface interactions from direct force measurements using a specialized torsion balance

NASA Technical Reports Server (NTRS)

Cook, S. R.; Hoffbauer, M. A.

1996-01-01

The first comprehensive measurements of the magnitude and direction of the forces exerted on surfaces by molecular beams are discussed and used to obtain information about the microscopic properties of the gas-surface interactions. This unique approach is not based on microscopic measurements of the scattered molecules. The reduced force coefficients are introduced as a new set of parameters that completely describe the macroscopic average momentum transfer to a surface by an incident molecular beam. By using a specialized torsion balance and molecular beams of N2, CO, CO2, and H2, the reduced force coefficients are determined from direct measurements of the force components exerted on surface of a solar panel array material, Kapton, SiO2-coated Kapton, and Z-93 as a function of the angle of incidence ranging from 0 degrees to 85 degrees. The absolute flux densities of the molecular beams were measured using a different torsion balance with a beam-stop that nullified the force of the scattered molecules. Standard time-of-flight techniques were used to determine the flux-weighted average velocities of the various molecular beams ranging from 1600 m/s to 4600 m/s. The reduced force coefficients can be used to directly obtain macroscopic average properties of the scattered molecules, such as the flux-weighted average velocity and translational energy, that can then be used to determine microscopic details concerning gas-surface interactions without the complications associated with averaging microscopic measurements.

Absolute molecular sieve separation of ethylene/ethane mixtures with silver zeolite A.

PubMed

Aguado, Sonia; Bergeret, Gérard; Daniel, Cecile; Farrusseng, David

2012-09-12

Absolute ethylene/ethane separation is achieved by ethane exclusion on silver-exchanged zeolite A adsorbent. This molecular sieving type separation is attributed to the pore size of the adsorbent, which falls between ethylene and ethane kinetic diameters.

Placental mitochondrial DNA and CYP1A1 gene methylation as molecular signatures for tobacco smoke exposure in pregnant women and the relevance for birth weight.

PubMed

Janssen, Bram G; Gyselaers, Wilfried; Byun, Hyang-Min; Roels, Harry A; Cuypers, Ann; Baccarelli, Andrea A; Nawrot, Tim S

2017-01-04

Maternal smoking during pregnancy results in an increased risk of low birth weight through perturbations in the utero-placental exchange. Epigenetics and mitochondrial function in fetal tissues might be molecular signatures responsive to in utero tobacco smoke exposure. In the framework of the ENVIRONAGE birth cohort, we investigated the effect of self-reported tobacco smoke exposure during pregnancy on birth weight and the relation with placental tissue markers such as, (1) relative mitochondrial DNA (mtDNA) content as determined by real-time quantitative PCR, (2) DNA methylation of specific loci of mtDNA (D-loop and MT-RNR1), and (3) DNA methylation of the biotransformation gene CYP1A1 (the last two determined by bisulfite-pyrosequencing). The total pregnant mother sample included 255 non-smokers, 65 former-smokers who had quit smoking before pregnancy, and 62 smokers who continued smoking during pregnancy. Smokers delivered newborns with a birth weight on average 208 g lower [95% confidence interval (CI) -318 to -99, p = 0.0002] than mothers who did not smoke during pregnancy. In the smoker group, the relative mtDNA content was lower (-21.6%, 95% CI -35.4 to -4.9%, p = 0.01) than in the non-smoker group; whereas, absolute mtDNA methylation levels of MT-RNR1 were higher (+0.62%, 95% CI 0.21 to 1.02%, p = 0.003). Lower CpG-specific methylation of CYP1A1 in placental tissue (-4.57%, 95% CI -7.15 to -1.98%, p < 0.0001) were observed in smokers compared with non-smokers. Nevertheless, no mediation of CYP1A1 methylation nor any other investigated molecular signature was observed for the association between tobacco smoke exposure and birth weight. mtDNA content, methylation of specific loci of mtDNA, and CYP1A1 methylation in placental tissue may serve as molecular signatures for the association between gestational tobacco smoke exposure and low birth weight.

Theoretical performance of some rocket propellants containing hydrogen, nitrogen, and oxygen

NASA Technical Reports Server (NTRS)

Miller, Riley O; Ordin, Paul M

1948-01-01

Theoretical performance data including nozzle-exit temperature, specific impulse, volume specific impulse and composition, temperature, and mean molecular weight of reaction products based on frozen equilibrium and isentropic expansion are presented for 13 propellant combinations at reaction pressure of 300 pounds per square inch absolute and expansion ratio of 20.4. On basis of maximum specific impulse alone, five fuels had the following order for any given oxidant: liquid hydrogen, hydrazine, liquid ammonia, and either hydrazine hydrate or hydroxylamine. Three oxidants with a given fuel had the following order: liquid ozone, liquid oxygen, and 100-percent hydrogen peroxide.

Ex vivo assessment and validation of water exchange performance of 23 heat and moisture exchangers for laryngectomized patients.

PubMed

van den Boer, Cindy; Muller, Sara H; Vincent, Andrew D; van den Brekel, Michiel W M; Hilgers, Frans J M

2014-08-01

Breathing through a tracheostoma results in insufficient warming and humidification of the inspired air. This loss of air conditioning, especially humidification, can be partially restored with the application of a heat and moisture exchanger (HME) over the tracheostoma. For medical professionals, it is not easy to judge differences in water exchange performance of various HMEs owing to the lack of universal outcome measures. This study has three aims: assessment of the water exchange performance of commercially available HMEs for laryngectomized patients, validation of these results with absolute humidity outcomes, and assessment of the role of hygroscopic salt present in some of the tested HMEs. Measurements of weight and absolute humidity at end inspiration and end expiration at different breathing volumes of a healthy volunteer were performed using a microbalance and humidity sensor. Twenty-three HMEs from 6 different manufacturers were tested. Associations were determined between core weight, weight change, breathing volume, and absolute humidity, using both linear and nonlinear mixed effects models. Water exchange of the 23 HMEs at a breathing volume of 0.5 L varies between 0.5 and 3.6 mg. Both water exchange and wet core weight correlate strongly with the end-inspiratory absolute humidity values (r2 =0.89/0.87). Hygroscopic salt increases core weight. The 23 tested HMEs for laryngectomized patients show wide variation in water exchange performance. Water exchange correlates well with the end-inspiratory absolute humidity outcome, which validates the ex vivo weight change method. Wet core weight is a predictor of HME performance. Hygroscopic salt increases the weight of the core material. The results of this study can help medical professionals to obtain a more founded opinion about the performance of available HMEs for pulmonary rehabilitation in laryngectomized patients, and allow them to make an informed decision about which HME type to use.

Potential energy hypersurface and molecular flexibility

NASA Astrophysics Data System (ADS)

Koča, Jaroslav

1993-02-01

The molecular flexibility phenomenon is discussed from the conformational potential energy(hyper) surface (PES) point of view. Flexibility is considered as a product of three terms: thermodynamic, kinetic and geometrical. Several expressions characterizing absolute and relative molecular flexibility are introduced, depending on a subspace studied of the entire conformational space, energy level E of PES as well as absolute temperature. Results obtained by programs DAISY, CICADA and PANIC in conjunction with molecular mechanics program MMX for flexibility analysis of isopentane, 2,2-dimethylpentane and isohexane molecules are introduced.

Determination of heat capacity of ionic liquid based nanofluids using group method of data handling technique

NASA Astrophysics Data System (ADS)

Sadi, Maryam

2018-01-01

In this study a group method of data handling model has been successfully developed to predict heat capacity of ionic liquid based nanofluids by considering reduced temperature, acentric factor and molecular weight of ionic liquids, and nanoparticle concentration as input parameters. In order to accomplish modeling, 528 experimental data points extracted from the literature have been divided into training and testing subsets. The training set has been used to predict model coefficients and the testing set has been applied for model validation. The ability and accuracy of developed model, has been evaluated by comparison of model predictions with experimental values using different statistical parameters such as coefficient of determination, mean square error and mean absolute percentage error. The mean absolute percentage error of developed model for training and testing sets are 1.38% and 1.66%, respectively, which indicate excellent agreement between model predictions and experimental data. Also, the results estimated by the developed GMDH model exhibit a higher accuracy when compared to the available theoretical correlations.

Major bleeding risks of different low-molecular-weight heparin agents: a cohort study in 12 934 patients treated for acute venous thrombosis.

PubMed

van Rein, N; Biedermann, J S; van der Meer, F J M; Cannegieter, S C; Wiersma, N; Vermaas, H W; Reitsma, P H; Kruip, M J H A; Lijfering, W M

2017-07-01

Essentials Low-molecular-weight-heparins (LMWH) kinetics differ which may result in different bleeding risks. A cohort of 12 934 venous thrombosis patients on LMWH was followed until major bleeding. The absolute major bleeding risk was low among patients registered at the anticoagulation clinic. Once-daily dosing was associated with a lower bleeding risk as compared with twice-daily. Background Low-molecular-weight heparins (LMWHs) are considered members of a class of drugs with similar anticoagulant properties. However, pharmacodynamics and pharmacokinetics between LMWHs differ, which may result in different bleeding risks. As these agents are used by many patients, small differences may lead to a large effect on numbers of major bleeding events. Objectives To determine major bleeding risks for different LMWH agents and dosing schedules. Methods A cohort of acute venous thrombosis patients from four anticoagulation clinics who used an LMWH and a vitamin K antagonist were followed until they ceased LMWH treatment or until major bleeding. Exposures were classified according to different types of LMWHs and for b.i.d. and o.d. use. Cumulative incidences for major bleeding per 1000 patients and risk ratios were calculated and adjusted for study center. Results The study comprised 12 934 patients with a mean age of 59 years; 6218 (48%) were men. The cumulative incidence of major bleeding was 2.5 per 1000 patients (95% confidence interval [CI], 1.7-3.5). Enoxaparin b.i.d. or o.d. was associated with a relative bleeding risk of 1.7 (95% CI, 0.2-17.5) compared with nadroparin o.d. In addition, a nadroparin b.i.d. dosing schedule was associated with a 2.0-fold increased major bleeding risk (95% CI, 0.8-5.1) as compared with a nadroparin o.d. dosing schedule. Conclusions Absolute major bleeding rates were low for all LMWH agents and dosing schedules in a large unselected cohort. Nevertheless, twice-daily dosing with nadroparin appeared to be associated with an increased major bleeding risk as compared with once-daily dosing, as also suggested in a meta-analysis of controlled clinical trials. © 2017 International Society on Thrombosis and Haemostasis.

Magnetic resonance imaging determination of left ventricular mass: junior Olympic weightlifters.

PubMed

Fleck, S J; Pattany, P M; Stone, M H; Kraemer, W J; Thrush, J; Wong, K

1993-04-01

The relationship between left ventricular mass (LVM) and peak VO2 in junior elite Olympic-style weightlifters and sedentary subjects was investigated. Ten male weightlifters (mean +/- SE, age = 17.5 +/- 0.4 yr, wt = 72.9 +/- 3.3 kg) and 15 sedentary males (age = 18.8 +/- 0.4 yr, wt = 69.6 +/- 2.0 kg) served as subjects. Peak VO2 was measured using a continuous, incrementally loaded bicycle ergometry protocol. LVM was measured using magnetic resonance imaging techniques. Absolute peak VO2 was not significantly different (P > or = 0.05) between the weightlifters and the control subjects (3.5 +/- 0.1 vs 3.3 +/- 0.11.min-1). Absolute LVM (g) was significantly (P < or = 0.05) correlated to absolute peak VO2 (1.min-1) in the weightlifters (r = 0.723), but not in the control subjects. No other correlations between LVM in absolute or normalized by body weight, body surface area, or fat free mass terms, and absolute peak or normalized by body weight peak VO2 were significant. The weightlifters absolute LVM was significantly greater (P < or = 0.05) than that of the controls (208.1 +/- 10.0 vs 179.7 +/- 8.4 g). LVM normalized by body weight and body surface area but not by fat free mass, was significantly greater (P < or = 0.05) in the weightlifters than the control subjects. These data indicate that LVM in junior elite weightlifters is greater than that of control subjects and absolute LVM is related to absolute peak VO2 in weightlifters but not control subjects.

The life sciences mass spectrometry research unit.

PubMed

Hopfgartner, Gérard; Varesio, Emmanuel

2012-01-01

The Life Sciences Mass Spectrometry (LSMS) research unit focuses on the development of novel analytical workflows based on innovative mass spectrometric and software tools for the analysis of low molecular weight compounds, peptides and proteins in complex biological matrices. The present article summarizes some of the recent work of the unit: i) the application of matrix-assisted laser desorption/ionization (MALDI) for mass spectrometry imaging (MSI) of drug of abuse in hair, ii) the use of high resolution mass spectrometry for simultaneous qualitative/quantitative analysis in drug metabolism and metabolomics, and iii) the absolute quantitation of proteins by mass spectrometry using the selected reaction monitoring mode.

Theoretical Rocket Performance of Liquid Methane with Several Fluorine-Oxygen Mixtures Assuming Frozen Composition

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Kastner, Michael E

1958-01-01

Theoretical rocket performance for frozen composition during expansion was calculated for liquid methane with several fluorine-oxygen mixtures for a range of pressure ratios and oxidant-fuel ratios. The parameters included are specific impulse, combustion-chamber temperature, nozzle-exit temperature molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, and thermal conductivity. The maximum calculated value of specific impulse for a chamber pressure of 600 pounds per square inch absolute (40.827atm) and an exit pressure of 1 atmosphere is 315.3 for 79.67 percent fluorine in the oxidant.

Trends in Racial and Ethnic Disparities in Infant Mortality Rates in the United States, 1989–2006

PubMed Central

Rossen, Lauren M.; Schoendorf, Kenneth C.

2014-01-01

Objectives. We sought to measure overall disparities in pregnancy outcome, incorporating data from the many race and ethnic groups that compose the US population, to improve understanding of how disparities may have changed over time. Methods. We used Birth Cohort Linked Birth–Infant Death Data Files from US Vital Statistics from 1989–1990 and 2005–2006 to examine multigroup indices of racial and ethnic disparities in the overall infant mortality rate (IMR), preterm birth rate, and gestational age–specific IMRs. We calculated selected absolute and relative multigroup disparity metrics weighting subgroups equally and by population size. Results. Overall IMR decreased on the absolute scale, but increased on the population-weighted relative scale. Disparities in the preterm birth rate decreased on both the absolute and relative scales, and across equally weighted and population-weighted indices. Disparities in preterm IMR increased on both the absolute and relative scales. Conclusions. Infant mortality is a common bellwether of general and maternal and child health. Despite significant decreases in disparities in the preterm birth rate, relative disparities in overall and preterm IMRs increased significantly over the past 20 years. PMID:24028239

Statistical Analysis on the Performance of Molecular Mechanics Poisson-Boltzmann Surface Area versus Absolute Binding Free Energy Calculations: Bromodomains as a Case Study.

PubMed

Aldeghi, Matteo; Bodkin, Michael J; Knapp, Stefan; Biggin, Philip C

2017-09-25

Binding free energy calculations that make use of alchemical pathways are becoming increasingly feasible thanks to advances in hardware and algorithms. Although relative binding free energy (RBFE) calculations are starting to find widespread use, absolute binding free energy (ABFE) calculations are still being explored mainly in academic settings due to the high computational requirements and still uncertain predictive value. However, in some drug design scenarios, RBFE calculations are not applicable and ABFE calculations could provide an alternative. Computationally cheaper end-point calculations in implicit solvent, such as molecular mechanics Poisson-Boltzmann surface area (MMPBSA) calculations, could too be used if one is primarily interested in a relative ranking of affinities. Here, we compare MMPBSA calculations to previously performed absolute alchemical free energy calculations in their ability to correlate with experimental binding free energies for three sets of bromodomain-inhibitor pairs. Different MMPBSA approaches have been considered, including a standard single-trajectory protocol, a protocol that includes a binding entropy estimate, and protocols that take into account the ligand hydration shell. Despite the improvements observed with the latter two MMPBSA approaches, ABFE calculations were found to be overall superior in obtaining correlation with experimental affinities for the test cases considered. A difference in weighted average Pearson ([Formula: see text]) and Spearman ([Formula: see text]) correlations of 0.25 and 0.31 was observed when using a standard single-trajectory MMPBSA setup ([Formula: see text] = 0.64 and [Formula: see text] = 0.66 for ABFE; [Formula: see text] = 0.39 and [Formula: see text] = 0.35 for MMPBSA). The best performing MMPBSA protocols returned weighted average Pearson and Spearman correlations that were about 0.1 inferior to ABFE calculations: [Formula: see text] = 0.55 and [Formula: see text] = 0.56 when including an entropy estimate, and [Formula: see text] = 0.53 and [Formula: see text] = 0.55 when including explicit water molecules. Overall, the study suggests that ABFE calculations are indeed the more accurate approach, yet there is also value in MMPBSA calculations considering the lower compute requirements, and if agreement to experimental affinities in absolute terms is not of interest. Moreover, for the specific protein-ligand systems considered in this study, we find that including an explicit ligand hydration shell or a binding entropy estimate in the MMPBSA calculations resulted in significant performance improvements at a negligible computational cost.

Fragment-based drug discovery using rational design.

PubMed

Jhoti, H

2007-01-01

Fragment-based drug discovery (FBDD) is established as an alternative approach to high-throughput screening for generating novel small molecule drug candidates. In FBDD, relatively small libraries of low molecular weight compounds (or fragments) are screened using sensitive biophysical techniques to detect their binding to the target protein. A lower absolute affinity of binding is expected from fragments, compared to much higher molecular weight hits detected by high-throughput screening, due to their reduced size and complexity. Through the use of iterative cycles of medicinal chemistry, ideally guided by three-dimensional structural data, it is often then relatively straightforward to optimize these weak binding fragment hits into potent and selective lead compounds. As with most other lead discovery methods there are two key components of FBDD; the detection technology and the compound library. In this review I outline the two main approaches used for detecting the binding of low affinity fragments and also some of the key principles that are used to generate a fragment library. In addition, I describe an example of how FBDD has led to the generation of a drug candidate that is now being tested in clinical trials for the treatment of cancer.

Physical fitness and performance. Cardiorespiratory fitness in girls-change from middle to high school.

PubMed

Pfeiffer, Karin A; Dowda, Marsha; Dishman, Rod K; Sirard, John R; Pate, Russell R

2007-12-01

To determine how factors are related to change in cardiorespiratory fitness (CRF) across time in middle school girls followed through high school. Adolescent girls (N = 274, 59% African American, baseline age = 13.6 +/- 0.6 yr) performed a submaximal fitness test (PWC170) in 8th, 9th, and 12th grades. Height, weight, sports participation, and physical activity were also measured. Moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) were determined by the number of blocks reported on the 3-Day Physical Activity Recall (3DPAR). Individual differences and developmental change in CRF were assessed simultaneously by calculating individual growth curves for each participant, using growth curve modeling. Both weight-relative and absolute CRF increased from 8th to 9th grade and decreased from 9th to 12th grade. On average, girls lost 0.16 kg.m.min.kg.yr in weight-relative PWC170 scores (P < 0.01) and gained 10.3 kg.m.min.yr in absolute PWC170 scores. Girls reporting two or more blocks of MVPA or one or more blocks of VPA at baseline showed an average increase in PWC170 scores of 0.40-0.52 kg.m.min.kg.yr (weight relative) and 22-28 kg.m.min.yr (absolute) in CRF. In weight-relative models, girls with higher BMI showed lower CRF (approximately 0.37 g.m.min.kg.yr), but this was not shown in absolute models. In absolute models, white girls (approximately 40 kg.m.min.yr) and sport participants (approximately 28 kg.m.min.yr) showed an increase in CRF over time. Although there were fluctuations in PWC170 scores across time, average scores decreased during 4 yr. Physical activity was related to change in CRF over time; BMI, race, and sport participation were also important factors related to change over time in CRF (depending on expression of CRF-weight-relative vs absolute). Subsequent research should focus on explaining the complex longitudinal interactions between CRF, physical activity, race, BMI, and sports participation.

Ordinary Least Squares and Quantile Regression: An Inquiry-Based Learning Approach to a Comparison of Regression Methods

ERIC Educational Resources Information Center

Helmreich, James E.; Krog, K. Peter

2018-01-01

We present a short, inquiry-based learning course on concepts and methods underlying ordinary least squares (OLS), least absolute deviation (LAD), and quantile regression (QR). Students investigate squared, absolute, and weighted absolute distance functions (metrics) as location measures. Using differential calculus and properties of convex…

Theoretical performance of liquid hydrogen and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid hydrogen and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion-chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ration of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 364.6 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid ammonia and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 311.5 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Does Successful Weight Loss in an Internet-Based Worksite Weight Loss Program Improve Employee Presenteeism and Absenteeism?

PubMed Central

Harden, Samantha M.; You, Wen; Almeida, Fabio A.; Hill, Jennie L.; Linnan, Laura A.; Allen, Kacie C.; Estabrooks, Paul A.

2017-01-01

Certain risk factors associated with overweight and obesity may lead to reduced productivity in the workforce (i.e., increased absenteeism and presenteeism). Participants in a large, Internet-based worksite weight loss intervention, who were present at follow-up (N = 1,030), completed a self-reported productivity measure (World Health Organization’s Health and Work Performance Questionnaire) at baseline and postintervention. Twenty-two percent of the participants lost a clinically meaningful amount of weight (≥5% weight loss). There were no statistically significant (p < .05) relationships between weight change from baseline to 12 months and change scores of absolute or relative absenteeism or for absolute or relative presenteeism. Within a modestly successful Internet-based, worksite weight loss intervention, weight loss did not improve self-reported absenteeism or presenteeism. Further studies are needed to explore the sensitivity of the World Health Organization’s Health and Work Performance Questionnaire and the long-term effects of weight loss on productivity. PMID:25842385

Does Successful Weight Loss in an Internet-Based Worksite Weight Loss Program Improve Employee Presenteeism and Absenteeism?

PubMed

Harden, Samantha M; You, Wen; Almeida, Fabio A; Hill, Jennie L; Linnan, Laura A; Allen, Kacie C; Estabrooks, Paul A

2015-12-01

Certain risk factors associated with overweight and obesity may lead to reduced productivity in the workforce (i.e., increased absenteeism and presenteeism). Participants in a large, Internet-based worksite weight loss intervention, who were present at follow-up (N = 1,030), completed a self-reported productivity measure (World Health Organization's Health and Work Performance Questionnaire) at baseline and postintervention. Twenty-two percent of the participants lost a clinically meaningful amount of weight (≥5% weight loss). There were no statistically significant (p < .05) relationships between weight change from baseline to 12 months and change scores of absolute or relative absenteeism or for absolute or relative presenteeism. Within a modestly successful Internet-based, worksite weight loss intervention, weight loss did not improve self-reported absenteeism or presenteeism. Further studies are needed to explore the sensitivity of the World Health Organization's Health and Work Performance Questionnaire and the long-term effects of weight loss on productivity. © 2015 Society for Public Health Education.

Absolute vs. Weight-Related Maximum Oxygen Uptake in Firefighters: Fitness Evaluation with and without Protective Clothing and Self-Contained Breathing Apparatus among Age Group

PubMed Central

Perroni, Fabrizio; Guidetti, Laura; Cignitti, Lamberto; Baldari, Carlo

2015-01-01

During fire emergencies, firefighters wear personal protective devices (PC) and a self-contained breathing apparatus (S.C.B.A.) to be protected from injuries. The purpose of this study was to investigate the differences of aerobic level in 197 firefighters (age: 34±7 yr; BMI: 24.4±2.3 kg.m-2), evaluated by a Queen’s College Step field Test (QCST), performed with and without fire protective garments, and to analyze the differences among age groups (<25 yr; 26-30 yr, 31-35 yr, 36-40 yr and >40 yr). Variance analysis was applied to assess differences (p < 0.05) between tests and age groups observed in absolute and weight-related values, while a correlation was examined between QCST with and without PC+S.C.B.A. The results have shown that a 13% of firefighters failed to complete the test with PC+S.C.B.A. and significant differences between QCST performed with and without PC+S.C.B.A. in absolute (F(1,169) = 42.6, p < 0.0001) and weight-related (F(1,169) = 339.9, p < 0.0001) terms. A better correlation has been found in L•min-1 (r=0.67) than in ml•kg-1•min-1 (r=0.54). Moreover, we found significant differences among age groups both in absolute and weight-related values. The assessment of maximum oxygen uptake of firefighters in absolute term can be a useful tool to evaluate the firefighters' cardiovascular strain. PMID:25764201

Changes in relative and absolute concentrations of plasma phospholipid fatty acids observed in a randomized trial of Omega-3 fatty acids supplementation in Uganda.

PubMed

Song, Xiaoling; Diep, Pho; Schenk, Jeannette M; Casper, Corey; Orem, Jackson; Makhoul, Zeina; Lampe, Johanna W; Neuhouser, Marian L

2016-11-01

Expressing circulating phospholipid fatty acids (PLFAs) in relative concentrations has some limitations: the total of all fatty acids are summed to 100%; therefore, the values of individual fatty acid are not independent. In this study we examined if both relative and absolute metrics could effectively measure changes in circulating PLFA concentrations in an intervention trial. 66 HIV and HHV8 infected patients in Uganda were randomized to take 3g/d of either long-chain omega-3 fatty acids (1856mg EPA and 1232mg DHA) or high-oleic safflower oil in a 12-week double-blind trial. Plasma samples were collected at baseline and end of trial. Relative weight percentage and absolute concentrations of 41 plasma PLFAs were measured using gas chromatography. Total cholesterol was also measured. Intervention-effect changes in concentrations were calculated as differences between end of 12-week trial and baseline. Pearson correlations of relative and absolute concentration changes in individual PLFAs were high (>0.6) for 37 of the 41 PLFAs analyzed. In the intervention arm, 17 PLFAs changed significantly in relative concentration and 16 in absolute concentration, 15 of which were identical. Absolute concentration of total PLFAs decreased 95.1mg/L (95% CI: 26.0, 164.2; P=0.0085), but total cholesterol did not change significantly in the intervention arm. No significant change was observed in any of the measurements in the placebo arm. Both relative weight percentage and absolute concentrations could effectively measure changes in plasma PLFA concentrations. EPA and DHA supplementation changes the concentrations of multiple plasma PLFAs besides EPA and DHA.Both relative weight percentage and absolute concentrations could effectively measure changes in plasma phospholipid fatty acid (PLFA) concentrations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Resonant acoustic measurement of vapor phase transport phenomenon in porous media

NASA Astrophysics Data System (ADS)

Schuhmann, Richard; Garrett, Steven

2002-05-01

Diffusion of gases through porous media is commonly described using Fick's law and is characterized by a gas diffusion coefficient modified by a media-specific tortuosity parameter. A phase-locked-loop resonance frequency tracker [J. Acoust. Soc. Am. 108, 2520 (2000)] has been upgraded with an insulated copper resonator and a bellows-sealed piston instrumented with an accelerometer. Average system stability (temperature divided by frequency squared) is about 180 ppm. Glass-bead-filled cores of different lengths are fitted into an o-ring sealed opening at the top of the resonator. The rate at which the tracer gas is replaced by air within the resonator is controlled by the core's diffusion constant. Mean molecular weight of the gas mixture in the resonator is determined in real time from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Molecular weight of the gas mixture is determined approximately six times per minute. Changes in the gas mixture concentration are exponential in time (within 0.1%) over nearly two decades in concentration. We will report diffusion constants for two different sizes of glass beads, in samples of five different lengths, using two different tracer gases, to establish the validity of this approach. [Work supported by ONR.

Prediction of frozen food properties during freezing using product composition.

PubMed

Boonsupthip, W; Heldman, D R

2007-06-01

Frozen water fraction (FWF), as a function of temperature, is an important parameter for use in the design of food freezing processes. An FWF-prediction model, based on concentrations and molecular weights of specific product components, has been developed. Published food composition data were used to determine the identity and composition of key components. The model proposed in this investigation had been verified using published experimental FWF data and initial freezing temperature data, and by comparison to outputs from previously published models. It was found that specific food components with significant influence on freezing temperature depression of food products included low molecular weight water-soluble compounds with molality of 50 micromol per 100 g food or higher. Based on an analysis of 200 high-moisture food products, nearly 45% of the experimental initial freezing temperature data were within an absolute difference (AD) of +/- 0.15 degrees C and standard error (SE) of +/- 0.65 degrees C when compared to values predicted by the proposed model. The predicted relationship between temperature and FWF for all analyzed food products provided close agreements with experimental data (+/- 0.06 SE). The proposed model provided similar prediction capability for high- and intermediate-moisture food products. In addition, the proposed model provided statistically better prediction of initial freezing temperature and FWF than previous published models.

12 CFR 324.152 - Simple risk weight approach (SRWA).

Code of Federal Regulations, 2014 CFR

2014-01-01

... (that is, between zero and -1), then E equals the absolute value of RVC. If RVC is negative and less... the lowest applicable risk weight in this section. (1) Zero percent risk weight equity exposures. An....131(d)(2) is assigned a zero percent risk weight. (2) 20 percent risk weight equity exposures. An...

Simultaneous all-optical determination of molecular concentration and extinction coefficient.

PubMed

Cho, Byungmoon; Tiwari, Vivek; Jonas, David M

2013-06-04

Absolute molecular number concentration and extinction coefficient are simultaneously determined from linear and nonlinear spectroscopic measurements. This method is based on measurements of absolute femtosecond pump-probe signals. Accounting for pulse propagation, we present a closed form expression for molecular number concentration in terms of absorbance, fluorescence, absolute pump-probe signal, and laser pulse parameters (pulse energy, spectrum, and spatial intensity profile); all quantities are measured optically. As in gravimetric and coulometric determinations of concentration, no standard samples are needed for calibration. The extinction coefficient can then be determined from the absorbance spectrum and the concentration. For fluorescein in basic methanol, the optically determined molar concentrations and extinction coefficients match gravimetric determinations to within 10% for concentrations from 0.032 to 0.540 mM, corresponding to absorbance from 0.06 to 1. In principle, this photonumeric method is extensible to transient chemical species for which other methods are not available.

Determination of the absolute binding free energies of HIV-1 protease inhibitors using non-equilibrium molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Ngo, Son Tung; Nguyen, Minh Tung; Nguyen, Minh Tho

2017-05-01

The absolute binding free energy of an inhibitor to HIV-1 Protease (PR) was determined throughout evaluation of the non-bonded interaction energy difference between the two bound and unbound states of the inhibitor and surrounding molecules by the fast pulling of ligand (FPL) process using non-equilibrium molecular dynamics (NEMD) simulations. The calculated free energy difference terms help clarifying the nature of the binding. Theoretical binding affinities are in good correlation with experimental data, with R = 0.89. The paradigm used is able to rank two inhibitors having the maximum difference of ∼1.5 kcal/mol in absolute binding free energies.

Predicting the Plate Dent Test Output in Order to Assess the Performance of Condensed High Explosives

NASA Astrophysics Data System (ADS)

Frem, Dany

2017-01-01

In the present study, a relationship is proposed that is capable of predicting the output of the plate dent test. It is shown that the initial density ?; condensed phase heat of formation ?; the number of carbon (C), nitrogen (N), oxygen (O); and the composition molecular weight (MW) are the most important parameters needed in order to accurately predict the absolute dent depth ? produced on 1018 cold-rolled steel by a detonating organic explosive. The estimated ? values can be used to predict the detonation pressure (P) of high explosives; furthermore, we show that a correlation exists between ? and the Gurney velocity ? parameter. The new correlation is used to accurately estimate ? for several C-H-N-O explosive compositions.

Molecular weight analyses and enzymatic degradation profiles of the soft-tissue fillers Belotero Balance, Restylane, and Juvéderm Ultra.

PubMed

Flynn, Timothy Corcoran; Thompson, David H; Hyun, Seok-Hee

2013-10-01

In this study, the authors sought to determine the molecular weight distribution of three hyaluronic acids-Belotero Balance, Restylane, and Juvéderm Ultra-and their rates of degradation following exposure to hyaluronidase. Lot consistency of Belotero Balance also was analyzed. Three lots of Belotero Balance were analyzed using liquid chromatography techniques. The product was found to have high-molecular-weight and low-molecular-weight species. One lot of Belotero Balance was compared to one lot each of Juvéderm Ultra and Restylane. Molecular weights of the species were analyzed. The hyaluronic acids were exposed to ovine testicular hyaluronidase at six time points-baseline and 0.5, 1, 2, 6, and 24 hours-to determine degradation rates. Belotero Balance lots were remarkably consistent. Belotero Balance had the largest high-molecular-weight species, followed by Juvéderm Ultra and Restylane (p < 0.001). Low-molecular-weight differences among all three hyaluronic acids were not statistically significant. Percentages of high-molecular-weight polymer differ among the three materials, with Belotero Balance having the highest fraction of high-molecular-weight polymer. Degradation of the high-molecular-weight species over time showed different molecular weights of the high-molecular-weight fraction. Rates of degradation of the hyaluronic acids following exposure to ovine testicular hyaluronidase were similar. All hyaluronic acids were fully degraded at 24 hours. Fractions of high-molecular-weight polymer differ across the hyaluronic acids tested. The low-molecular-weight differences are not statistically significant. The high-molecular-weight products have different molecular weights at the 0.5- and 2-hour time points when exposed to ovine testicular hyaluronidase and are not statistically different at 24 hours.

The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

2001-01-01

Mechanical testing of the elastic and viscoelastic response of an advanced thermoplastic polyimide (LaRC-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The notched tensile strength was shown to be a strong function of both molecular weight and temperature, whereas stiffness was only a strong function of temperature. A critical molecular weight was observed to occur at a weight average molecular weight of M, approx. 22,000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Low, molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. Furthermore, low molecular weight materials have increased creep compliance and creep compliance rate, and are more sensitive to temperature than the high molecular weight materials. At long timescales (less than 1100 hours) physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested. Low molecular weight materials are less influenced by the effects of physical aging.

Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

1999-01-01

Mechanical Testing of an advanced thermoplastic polyimide (LaRC-TM-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength were all determined as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. A critical molecular weight (Mc) was observed to occur at a weight-average molecular weight (Mw) of approx. 22000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Furthermore, inelastic analysis showed that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microstructural images supported these findings.

76 FR 25240 - Clothianidin; Pesticide Tolerances

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-04

... neurotoxicity were exhibited in both rats (decreased arousal, motor activity and locomotor activity) and mice... (decreased body weight gains and absolute thymus weights in pups, delayed sexual maturation and an increase.../day FQPA SF = 1x day.. based on decreased body weight gains and delayed sexual maturation, decreased...

Thromboprophylaxis after Knee Arthroscopy and Lower-Leg Casting.

PubMed

van Adrichem, Raymond A; Nemeth, Banne; Algra, Ale; le Cessie, Saskia; Rosendaal, Frits R; Schipper, Inger B; Nelissen, Rob G H H; Cannegieter, Suzanne C

2017-02-09

The use of thromboprophylaxis to prevent clinically apparent venous thromboembolism after knee arthroscopy or casting of the lower leg is disputed. We compared the incidence of symptomatic venous thromboembolism after these procedures between patients who received anticoagulant therapy and those who received no anticoagulant therapy. We conducted two parallel, pragmatic, multicenter, randomized, controlled, open-label trials with blinded outcome evaluation: the POT-KAST trial, which included patients undergoing knee arthroscopy, and the POT-CAST trial, which included patients treated with casting of the lower leg. Patients were assigned to receive either a prophylactic dose of low-molecular-weight heparin (for the 8 days after arthroscopy in the POT-KAST trial or during the full period of immobilization due to casting in the POT-CAST trial) or no anticoagulant therapy. The primary outcomes were the cumulative incidences of symptomatic venous thromboembolism and major bleeding within 3 months after the procedure. In the POT-KAST trial, 1543 patients underwent randomization, of whom 1451 were included in the intention-to-treat population. Venous thromboembolism occurred in 5 of the 731 patients (0.7%) in the treatment group and in 3 of the 720 patients (0.4%) in the control group (relative risk, 1.6; 95% confidence interval [CI], 0.4 to 6.8; absolute difference in risk, 0.3 percentage points; 95% CI, -0.6 to 1.2). Major bleeding occurred in 1 patient (0.1%) in the treatment group and in 1 (0.1%) in the control group (absolute difference in risk, 0 percentage points; 95% CI, -0.6 to 0.7). In the POT-CAST trial, 1519 patients underwent randomization, of whom 1435 were included in the intention-to-treat population. Venous thromboembolism occurred in 10 of the 719 patients (1.4%) in the treatment group and in 13 of the 716 patients (1.8%) in the control group (relative risk, 0.8; 95% CI, 0.3 to 1.7; absolute difference in risk, -0.4 percentage points; 95% CI, -1.8 to 1.0). No major bleeding events occurred. In both trials, the most common adverse event was infection. The results of our trials showed that prophylaxis with low-molecular-weight heparin for the 8 days after knee arthroscopy or during the full period of immobilization due to casting was not effective for the prevention of symptomatic venous thromboembolism. (Funded by the Netherlands Organization for Health Research and Development; POT-KAST and POT-CAST ClinicalTrials.gov numbers, NCT01542723 and NCT01542762 , respectively.).

12 CFR 217.52 - Simple risk-weight approach (SRWA).

Code of Federal Regulations, 2014 CFR

2014-01-01

... greater than or equal to −1 (that is, between zero and −1), then E equals the absolute value of RVC. If... this section) by the lowest applicable risk weight in this paragraph (b). (1) Zero percent risk weight... credit exposures receive a zero percent risk weight under § 217.32 may be assigned a zero percent risk...

a Chiral Tagging Strategy for Determining Absolute Configuration and Enantiomeric Excess by Molecular Rotational Spectroscopy

NASA Astrophysics Data System (ADS)

Evangelisti, Luca; Caminati, Walther; Patterson, David; Thomas, Javix; Xu, Yunjie; West, Channing; Pate, Brooks

2017-06-01

The introduction of three wave mixing rotational spectroscopy by Patterson, Schnell, and Doyle [1,2] has expanded applications of molecular rotational spectroscopy into the field of chiral analysis. Chiral analysis of a molecule is the quantitative measurement of the relative abundances of all stereoisomers of the molecule and these include both diastereomers (with distinct molecular rotational spectra) and enantiomers (with equivalent molecular rotational spectra). This work adapts a common strategy in chiral analysis of enantiomers to molecular rotational spectroscopy. A "chiral tag" is attached to the molecule of interest by making a weakly bound complex in a pulsed jet expansion. When this tag molecule is enantiopure, it will create diastereomeric complexes with the two enantiomers of the molecule being analyzed and these can be differentiated by molecule rotational spectroscopy. Identifying the structure of this complex, with knowledge of the absolute configuration of the tag, establishes the absolute configuration of the molecule of interest. Furthermore, the diastereomer complex spectra can be used to determine the enantiomeric excess of the sample. The ability to perform chiral analysis will be illustrated by a study of solketal using propylene oxide as the tag. The possibility of using current methods of quantum chemistry to assign a specific structure to the chiral tag complex will be discussed. Finally, chiral tag rotational spectroscopy offers a "gold standard" method for determining the absolute configuration of the molecule through determination of the substitution structure of the complex. When this measurement is possible, rotational spectroscopy can deliver a quantitative three dimensional structure of the molecule with correct stereochemistry as the analysis output. [1] David Patterson, Melanie Schnell, John M. Doyle, Nature 497, 475 (2013). [2] David Patterson, John M. Doyle, Phys. Rev. Lett. 111, 023008 (2013).

Study on Growth Rhythm of Juveniles Cistolemmys Flavomarginata for One and Two Years Old

NASA Astrophysics Data System (ADS)

Huang, Bin

Growth of one and two year old Cistolemmys flavomarginata is studied. In natural temperature and under artificial feeding condition, juvenile turtles grow for 180 days in Xinyang, one year old turtle average body weight increased from 18.1 g to 54.5 g, the relative growth rate is 204.1%, the absolute growth rate is 0.21. two year old turtle average body weight increased from 46.8 g to 101.1 g, the relative growth rate is 115.98%, the absolute growth rate is 0.30. But two year old turtle growth rate is slower than that of one year old turtle. The body weight, carapace length, carapace width, plastron length, plastron width and carapace high are correlated positively to daily age. The body weight growth equations of one and two year old turtles are deduced. Compared with other reptiles, whole growth cycle is grasped systemically by the growth patterns.

BACKSCAT Lidar Simulation Version 3.0: Technical Documentation and Users Guide

DTIC Science & Technology

1992-12-03

Raman Cross Section of Some Simple Gases, J. Opt. Soc. Am., 63:73. 20 Penny, C.M., St. Peters, R.L., and Lapp, M., (1974) Absolute Rotational Raman...of the molecule, and the remaining columns list the relative normalized cross sections for the respective excitation wavelength. The absolute Raman...cross section is obtained by simply multiplying the relative normalized cross section for a molecular species of interest by the absolute cross section

Improvement of imprinting effect of ionic liquid molecularly imprinted polymers by use of a molecular crowding agent.

PubMed

Jia, Man; Yang, Jian; Sun, Ya Kun; Bai, Xi; Wu, Tao; Liu, Zhao Sheng; Aisa, Haji Akber

2018-01-01

We aimed to improve the imprinting effect of ionic liquid molecularly imprinted polymers (MIPs) by use of a molecular crowding agent. The ionic liquid 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIm][BF 4 ]) was used as the functional monomer and aesculetin was used as the template molecule in a crowding environment, which was made up of a tetrahydrofuran solution of polystyrene. The ionic liquid MIPs that were prepared in the crowding environment displayed an enhanced imprinting effect. NMR peak shifts of active hydrogen of aesculetin suggested that interaction between the functional monomer and the template could be increased by the use of a crowding agent in the self-assembly process. The retention and selectivity of aesculetin were affected greatly by high molecular crowding, the amount of high molecular weight crowding agent, and the ratio of [VEIm][BF 4 ] to aesculetin. The optimal MIPs were used as solid-phase extraction sorbents to extract aesculetin from Cichorium glandulosum. A calibration curve was obtained with aesculetin concentrations from 0.0005 to 0.05 mg mL -1 (correlation coefficient R 2 of 0.9999, y = 1519x + 0.0923). The limit of quantification was 0.12 μg mL -1 , and the limit of detection was 0.05 μg mL -1 . The absolute recovery of aesculetin was (80 ± 2)% (n = 3), and the purity of aesculetin was (92 ± 0.5)% (n = 5). As a conclusion, molecular crowding is an effective approach to obtain ionic liquid MIPs with high selectivity even in a polar solvent environment.

Absolute and relative densities of fast-food versus other restaurants in relation to weight status: Does restaurant mix matter?

PubMed

Polsky, Jane Y; Moineddin, Rahim; Dunn, James R; Glazier, Richard H; Booth, Gillian L

2016-01-01

Given the continuing epidemic of obesity, policymakers are increasingly looking for levers within the local retail food environment as a means of promoting healthy weights. To examine the independent and joint associations of absolute and relative densities of restaurants near home with weight status in a large, urban, population-based sample of adults. We studied 10,199 adults living in one of four cities in southern Ontario, Canada, who participated in the Canadian Community Health Survey (cycles 2005, 2007/08, 2009/10). Multivariate models assessed the association of weight status (obesity and body mass index) with absolute densities (numbers) of fast-food, full-service and other restaurants, and the relative density (proportion) of fast-food restaurants (FFR) relative to all restaurants within ~10-minute walk of residential areas. Higher numbers of restaurants of any type were inversely related to excess weight, even in models adjusting for a range of individual covariates and area deprivation. However, these associations were no longer significant after accounting for higher walkability of areas with high volumes of restaurants. In contrast, there was a direct relationship between the proportion of FFR relative to all restaurants and excess weight, particularly in areas with high volumes of FFR (e.g., odds ratio for obesity=2.55 in areas with 5+ FFR, 95% confidence interval: 1.55-4.17, across the interquartile range). Policies aiming to promote healthy weights that target the volume of certain retail food outlets in residential settings may be more effective if they also consider the relative share of outlets serving more and less healthful foods. Copyright © 2015 Elsevier Inc. All rights reserved.

2,3-diphosphoglycerate in normal and pathologic pregnancy: relationship to neonatal weight.

PubMed

Paparella, P; Francesconi, R; Zullo, M; Giorgino, R; Riccardi, P; Ferrazzani, S; Mancuso, S

1989-03-01

2,3-Diphosphoglycerate levels were assayed in 154 pregnant women in third trimester (61 normal, 52 diabetic, 19 with gestational hypertension, 7 with fetal macrosomia, and 15 with idiopathic fetal underdevelopment). A correlation was found between 2,3-diphosphoglycerate levels and birth weight (absolute and relative birth weight or birth weight expressed as percentile), which was negative in normal patients evaluated in the last 7 days before delivery (r = 0.38; p = 0.04) and positive in diabetic patients (evaluated in the third trimester and in the last 7 days before delivery) and in patients with gestational hypertension (evaluated in the third trimester) (r and p values differ according to whether birth weight is expressed as absolute, relative, or a percentile). No correlation was found between 2,3-diphosphoglycerate levels and birth weight in patients with neonatal underdevelopment or macrosomia of unknown origin. On the basis of these results we hypothesize that in some conditions the fetus can influence maternal 2,3-diphosphoglycerate levels and hence its own oxygen supply and growth in utero.

Molecular Weight Effects on the Viscoelastic Response of a Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

2000-01-01

The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC -SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of each material with different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have increased creep compliance and creep compliance rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of approximately 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly.

Fractionation of Organosolv Lignin Using Acetone:Water and Properties of the Obtained Fractions

DOE PAGES

Sadeghifar, Hasan; Wells, Tyrone; Le, Rosemary Khuu; ...

2016-11-07

In this study, lignin fractions with different molecular weight were prepared using a simple and almost green method from switchgrass and pine organosolv lignin. Different proportions of acetone in water, ranging from 30 to 60%, were used for lignin fractionation. A higher concentration of acetone dissolved higher molecular weight fractions of the lignin. Fractionated organosolv lignin showed different molecular weight and functional groups. Higher molecular weight fractions exhibited more aliphatic and less phenolic OH than lower molecular weight fractions. Lower molecular weight fractions lead to more homogeneous structure compared to samples with a higher molecular weight. In conclusion, all fractionsmore » showed strong antioxidant activity.« less

Degradation mechanisms of bioresorbable polyesters. Part 2. Effects of initial molecular weight and residual monomer.

PubMed

Gleadall, Andrew; Pan, Jingzhe; Kruft, Marc-Anton; Kellomäki, Minna

2014-05-01

This paper presents an understanding of how initial molecular weight and initial monomer fraction affect the degradation of bioresorbable polymers in terms of the underlying hydrolysis mechanisms. A mathematical model was used to analyse the effects of initial molecular weight for various hydrolysis mechanisms including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. Different behaviours were identified to relate initial molecular weight to the molecular weight half-life and to the time until the onset of mass loss. The behaviours were validated by fitting the model to experimental data for molecular weight reduction and mass loss of samples with different initial molecular weights. Several publications that consider initial molecular weight were reviewed. The effect of residual monomer on degradation was also analysed, and shown to accelerate the reduction of molecular weight and mass loss. An inverse square root law relationship was found between molecular weight half-life and initial monomer fraction for autocatalytic hydrolysis. The relationship was tested by fitting the model to experimental data with various residual monomer contents. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Linking Comparisons of Absolute Gravimeters: A Proof of Concept for a new Global Absolute Gravity Reference System.

NASA Astrophysics Data System (ADS)

Wziontek, H.; Palinkas, V.; Falk, R.; Vaľko, M.

2016-12-01

Since decades, absolute gravimeters are compared on a regular basis on an international level, starting at the International Bureau for Weights and Measures (BIPM) in 1981. Usually, these comparisons are based on constant reference values deduced from all accepted measurements acquired during the comparison period. Temporal changes between comparison epochs are usually not considered. Resolution No. 2, adopted by IAG during the IUGG General Assembly in Prague 2015, initiates the establishment of a Global Absolute Gravity Reference System based on key comparisons of absolute gravimeters (AG) under the International Committee for Weights and Measures (CIPM) in order to establish a common level in the microGal range. A stable and unique reference frame can only be achieved, if different AG are taking part in different kind of comparisons. Systematic deviations between the respective comparison reference values can be detected, if the AG can be considered stable over time. The continuous operation of superconducting gravimeters (SG) on selected stations further supports the temporal link of comparison reference values by establishing a reference function over time. By a homogenous reprocessing of different comparison epochs and including AG and SG time series at selected stations, links between several comparisons will be established and temporal comparison reference functions will be derived. By this, comparisons on a regional level can be traced to back to the level of key comparisons, providing a reference for other absolute gravimeters. It will be proved and discussed, how such a concept can be used to support the future absolute gravity reference system.

Efficient parallel algorithms for string editing and related problems

NASA Technical Reports Server (NTRS)

Apostolico, Alberto; Atallah, Mikhail J.; Larmore, Lawrence; Mcfaddin, H. S.

1988-01-01

The string editing problem for input strings x and y consists of transforming x into y by performing a series of weighted edit operations on x of overall minimum cost. An edit operation on x can be the deletion of a symbol from x, the insertion of a symbol in x or the substitution of a symbol x with another symbol. This problem has a well known O((absolute value of x)(absolute value of y)) time sequential solution (25). The efficient Program Requirements Analysis Methods (PRAM) parallel algorithms for the string editing problem are given. If m = ((absolute value of x),(absolute value of y)) and n = max((absolute value of x),(absolute value of y)), then the CREW bound is O (log m log n) time with O (mn/log m) processors. In all algorithms, space is O (mn).

Absolute Molecular Orientation of Isopropanol at Ceria (100) Surfaces: Insight into Catalytic Selectivity from the Interfacial Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doughty, Benjamin; Goverapet Srinivasan, Sriram; Bryantsev, Vyacheslav S.

The initial mechanistic steps underlying heterogeneous chemical catalysis can be described in a framework where the composition, structure, and orientation of molecules adsorbed to reactive interfaces are known. However, extracting this vital information is the limiting step in most cases due in part to challenges in probing the interfacial monolayer with enough chemical specificity to characterize the surface molecular constituents. These challenges are exacerbated at complex or spatially heterogeneous interfaces where competing processes and a distribution of local environments can uniquely drive chemistry. To address these limitations, this work presents a distinctive combination of materials synthesis, surface specific optical experiments,more » and theory to probe and understand molecular structure at catalytic interfaces. Specifically, isopropanol was adsorbed to surfaces of the model CeO 2 catalyst that were synthesized with only the (100) facet exposed. Vibrational sum-frequency generation was used to probe the molecular monolayer, and with the guidance of density functional theory calculations, was used to extract the structure and absolute molecular orientation of isopropanol at the CeO 2 (100) surface. Our results show that isopropanol is readily deprotonated at the surface, and through the measured absolute molecular orientation of isopropanol, we obtain new insight into the selectivity of the (100) surface to form propylene. Our findings reveal key insight into the chemical and physical phenomena taking place at pristine interfaces thereby pointing to intuitive structural arguments to describe catalytic selectivity in more complex systems.« less

Absolute Molecular Orientation of Isopropanol at Ceria (100) Surfaces: Insight into Catalytic Selectivity from the Interfacial Structure

DOE PAGES

Doughty, Benjamin; Goverapet Srinivasan, Sriram; Bryantsev, Vyacheslav S.; ...

2017-06-12

The initial mechanistic steps underlying heterogeneous chemical catalysis can be described in a framework where the composition, structure, and orientation of molecules adsorbed to reactive interfaces are known. However, extracting this vital information is the limiting step in most cases due in part to challenges in probing the interfacial monolayer with enough chemical specificity to characterize the surface molecular constituents. These challenges are exacerbated at complex or spatially heterogeneous interfaces where competing processes and a distribution of local environments can uniquely drive chemistry. To address these limitations, this work presents a distinctive combination of materials synthesis, surface specific optical experiments,more » and theory to probe and understand molecular structure at catalytic interfaces. Specifically, isopropanol was adsorbed to surfaces of the model CeO 2 catalyst that were synthesized with only the (100) facet exposed. Vibrational sum-frequency generation was used to probe the molecular monolayer, and with the guidance of density functional theory calculations, was used to extract the structure and absolute molecular orientation of isopropanol at the CeO 2 (100) surface. Our results show that isopropanol is readily deprotonated at the surface, and through the measured absolute molecular orientation of isopropanol, we obtain new insight into the selectivity of the (100) surface to form propylene. Our findings reveal key insight into the chemical and physical phenomena taking place at pristine interfaces thereby pointing to intuitive structural arguments to describe catalytic selectivity in more complex systems.« less

Ultrahigh molecular weight aromatic siloxane polymers

NASA Technical Reports Server (NTRS)

Ludwick, L. M.

1982-01-01

The condensation of a diol with a silane in toluene yields a silphenylene-siloxane polymer. The reaction of stiochiometric amounts of the diol and silane produced products with molecular weights in the range 2.0 - 6.0 x 10 to the 5th power. The molecular weight of the product was greatly increased by a multistep technique. The methodology for synthesis of high molecular weight polymers using a two step procedure was refined. Polymers with weight average molecular weights in excess of 1.0 x 10 to the 6th power produced by this method. Two more reactive silanes, bis(pyrrolidinyl)dimethylsilane and bis(gamma butyrolactam)dimethylsilane, are compared with the dimethyleminodimethylsilane in ability to advance the molecular weight of the prepolymer. The polymers produced are characterized by intrinsic viscosity in tetrahydrofuran. Weight and number average molecular weights and polydispersity are determined by gel permeation chromatography.

19 CFR 351.224 - Disclosure of calculations and procedures for the correction of ministerial errors.

Code of Federal Regulations, 2012 CFR

2012-04-01

... least five absolute percentage points in, but not less than 25 percent of, the weighted-average dumping... margin or countervailable subsidy rate (whichever is applicable) of zero (or de minimis) and a weighted...

19 CFR 351.224 - Disclosure of calculations and procedures for the correction of ministerial errors.

Code of Federal Regulations, 2010 CFR

2010-04-01

... least five absolute percentage points in, but not less than 25 percent of, the weighted-average dumping... margin or countervailable subsidy rate (whichever is applicable) of zero (or de minimis) and a weighted...

19 CFR 351.224 - Disclosure of calculations and procedures for the correction of ministerial errors.

Code of Federal Regulations, 2014 CFR

2014-04-01

... least five absolute percentage points in, but not less than 25 percent of, the weighted-average dumping... margin or countervailable subsidy rate (whichever is applicable) of zero (or de minimis) and a weighted...

19 CFR 351.224 - Disclosure of calculations and procedures for the correction of ministerial errors.

Code of Federal Regulations, 2013 CFR

2013-04-01

... least five absolute percentage points in, but not less than 25 percent of, the weighted-average dumping... margin or countervailable subsidy rate (whichever is applicable) of zero (or de minimis) and a weighted...

19 CFR 351.224 - Disclosure of calculations and procedures for the correction of ministerial errors.

Code of Federal Regulations, 2011 CFR

2011-04-01

... least five absolute percentage points in, but not less than 25 percent of, the weighted-average dumping... margin or countervailable subsidy rate (whichever is applicable) of zero (or de minimis) and a weighted...

Characterization and analysis of the molecular weight of lignin for biorefining studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tolbert, Allison; Akinosho, Hannah; Khunsupat, Ratayakorn

2014-06-04

The molecular weight of lignin is a fundamental property that infl uences the recalcitrance of biomass and the valorization of lignin. The determination of the molecular weight of lignin in native biomass is dependent on the bioresources used and the isolation and purifi cation procedures employed. The three most commonly employed isolation methods are milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and enzymatic mild acidolysis lignin (EMAL). Common characterization techniques for determining the molecular weight of lignin will be addressed, with an emphasis on gel permeation chromatography (GPC). This review also examines the mechanisms behind several biological, physical, andmore » chemical pre-treatments and their impact on the molecular weight of lignin. The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (D) all vary in magnitude depending on the biomass source, pre-treatment conditions, and isolation method. Additionally, there is a growing body of literature that supports changes in the molecular weight of lignin in response to genetic modifi cations in the lignin biosynthetic pathways. This review summarizes different procedures for obtaining the molecular weight of lignin that have been used in recent years and highlight future opportunities for applications of lignin.« less

Effect of molecular weight on polymer processability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karg, R.F.

1983-01-01

Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers show stress relaxation time and head pressure behavior which correlates with mill processability. As anticipated, compounded stock of EPDM have broad molecular weight distribution has higher stress relaxation time values than EPDM compounds with narrow molecular weight distribution.

12 CFR 324.52 - Simple risk-weight approach (SRWA).

Code of Federal Regulations, 2014 CFR

2014-01-01

... greater than or equal to −1 (that is, between zero and −1), then E equals the absolute value of RVC. If...) Zero percent risk weight equity exposures. An equity exposure to a sovereign, the Bank for..., an MDB, and any other entity whose credit exposures receive a zero percent risk weight under § 324.32...

The Combined Influence of Molecular Weight and Temperature on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

2000-01-01

The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC-SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of five materials of different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have higher creep compliance and creep rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of M (bar) (sub w) 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly. The short-term creep compliance data were used in association with Struik's effective time theory to predict the long-term creep compliance behavior for the different molecular weights. At long timescales, physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested.

Conversion of calibration curves for accurate estimation of molecular weight averages and distributions of polyether polyols by conventional size exclusion chromatography.

PubMed

Xu, Xiuqing; Yang, Xiuhan; Martin, Steven J; Mes, Edwin; Chen, Junlan; Meunier, David M

2018-08-17

Accurate measurement of molecular weight averages (M¯ n, M¯ w, M¯ z ) and molecular weight distributions (MWD) of polyether polyols by conventional SEC (size exclusion chromatography) is not as straightforward as it would appear. Conventional calibration with polystyrene (PS) standards can only provide PS apparent molecular weights which do not provide accurate estimates of polyol molecular weights. Using polyethylene oxide/polyethylene glycol (PEO/PEG) for molecular weight calibration could improve the accuracy, but the retention behavior of PEO/PEG is not stable in THF-based (tetrahydrofuran) SEC systems. In this work, two approaches for calibration curve conversion with narrow PS and polyol molecular weight standards were developed. Equations to convert PS-apparent molecular weight to polyol-apparent molecular weight were developed using both a rigorous mathematical analysis and graphical plot regression method. The conversion equations obtained by the two approaches were in good agreement. Factors influencing the conversion equation were investigated. It was concluded that the separation conditions such as column batch and operating temperature did not have significant impact on the conversion coefficients and a universal conversion equation could be obtained. With this conversion equation, more accurate estimates of molecular weight averages and MWDs for polyether polyols can be achieved from conventional PS-THF SEC calibration. Moreover, no additional experimentation is required to convert historical PS equivalent data to reasonably accurate molecular weight results. Copyright © 2018. Published by Elsevier B.V.

Molecular weight of Escherichia coli β-galactosidase in concentrated solutions of guanidine hydrochloride

PubMed Central

Erickson, Robert P.

1970-01-01

The molecular weight of Escherichia coli β-galactosidase was determined in 6m- and 8m-guanidine hydrochloride by meniscus-depletion sedimentation equilibrium, sedimentation velocity and viscosity. Sedimentation equilibrium revealed heterogeneity with the smallest component having a molecular weight of about 50000. At lower speeds, the apparent weight-average molecular weight is about 80000. By use of a calculation based on an empirical correlation for proteins that are random coils in 6m-guanidine hydrochloride, sedimentation velocity gave a molecular weight of 91000, and the intrinsic viscosity indicated a viscosity-average molecular weight of 84000. Heating in 6m-guanidine hydrochloride lowered the viscosity of β-galactosidase in a variable manner. PMID:4924171

From oligomers to molecular giants of soybean oil in supercritical carbon dioxide medium: 1. Preparation of polymers with lower molecular weight from soybean oil.

PubMed

Liu, Zengshe; Sharma, Brajendra K; Erhan, Sevim Z

2007-01-01

Polymers with a low molecular weight derived from soybean oil have been prepared in a supercritical carbon dioxide medium by cationic polymerization. Boron trifluoride diethyl etherate was used as an initiator. Influences of polymerization temperature, amount of initiator, and carbon dioxide pressure on the molecular weight were investigated. It is shown that the higher polymerization temperature favors polymers with relatively higher molecular weights. Larger amounts of initiator also provide polymers with higher molecular weights. Higher pressure favors polymers with relatively higher molecular weights. The applications of these soy-based materials will be in the lubrication and hydraulic fluid areas.

Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains

NASA Technical Reports Server (NTRS)

Asunmaa, S. K.; Haack, R.

1977-01-01

An attempt is made to report on experiments in which a molecular-weight increase was determined in thin layers of triglyceride-containing glycerides after thin-layer contact for two years with lunar topsoil grains at 25 C without any thermal activation. It is noted that solidification was observed on both dielectric grains and metal-rich areas and that changes in viscosity and molecular weights were first detected by solidification of surface layers. Gel permeation chromatography is described which detected a general shift of the Gaussian distribution of the molecular-weight data toward generally higher molecular weights as well as an increase in mean molecular weight. Reaction mechanisms are considered, and results of spectrographic analysis are cited which support the interpretations of the molecular-weight data.

Effect of molecular weight on polyphenylquinoxaline properties

NASA Technical Reports Server (NTRS)

Jensen, Brian J.

1991-01-01

A series of polyphenyl quinoxalines with different molecular weight and end-groups were prepared by varying monomer stoichiometry. Thus, 4,4'-oxydibenzil and 3,3'-diaminobenzidine were reacted in a 50/50 mixture of m-cresol and xylenes. Reaction concentration, temperature, and stir rate were studied and found to have an effect on polymer properties. Number and weight average molecular weights were determined and correlated well with viscosity data. Glass transition temperatures were determined and found to vary with molecular weight and end-groups. Mechanical properties of films from polymers with different molecular weights were essentially identical at room temperature but showed significant differences at 232 C. Diamine terminated polymers were found to be much less thermooxidatively stable than benzil terminated polymers when aged at 316 C even though dynamic thermogravimetric analysis revealed only slight differences. Lower molecular weight polymers exhibited better processability than higher molecular weight polymers.

77 FR 52246 - Clothianidin; Pesticide Tolerances

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-29

... concern. Clinical signs of neurotoxicity were exhibited in both rats (decreased arousal, motor activity..., delayed sexual maturation and an increase in stillbirths) was observed in the absence of maternal effects... weight gains and FQPA SF = 1X........ day. delayed sexual maturation, decreased absolute thymus weights...

Upper Limit of Weights in TAI Computation

NASA Technical Reports Server (NTRS)

Thomas, Claudine; Azoubib, Jacques

1996-01-01

The international reference time scale International Atomic Time (TAI) computed by the Bureau International des Poids et Mesures (BIPM) relies on a weighted average of data from a large number of atomic clocks. In it, the weight attributed to a given clock depends on its long-term stability. In this paper the TAI algorithm is used as the basis for a discussion of how to implement an upper limit of weight for clocks contributing to the ensemble time. This problem is approached through the comparison of two different techniques. In one case, a maximum relative weight is fixed: no individual clock can contribute more than a given fraction to the resulting time scale. The weight of each clock is then adjusted according to the qualities of the whole set of contributing elements. In the other case, a parameter characteristic of frequency stability is chosen: no individual clock can appear more stable than the stated limit. This is equivalent to choosing an absolute limit of weight and attributing this to to the most stable clocks independently of the other elements of the ensemble. The first technique is more robust than the second and automatically optimizes the stability of the resulting time scale, but leads to a more complicated computatio. The second technique has been used in the TAI algorithm since the very beginning. Careful analysis of tests on real clock data shows that improvement of the stability of the time scale requires revision from time to time of the fixed value chosen for the upper limit of absolute weight. In particular, we present results which confirm the decision of the CCDS Working Group on TAI to increase the absolute upper limit by a factor of 2.5. We also show that the use of an upper relative contribution further helps to improve the stability and may be a useful step towards better use of the massive ensemble of HP 507IA clocks now contributing to TAI.

Global Liver Gene Expression Analysis on a Murine Metabolic Syndrome Model Treated by Low-molecular-weight Lychee Fruit Polyphenol (Oligonol®).

PubMed

Uchiyama, Hironobu; Uehara, Kaori; Nagashima, Takayuki; Nakata, Akifumi; Sato, Keisuke; Mihara, Yoshihiro; Komatsu, Ken-Ich; Takanari, Jun; Shimizu, Shigeomi; Wakame, Koji

2016-07-01

Oligonol® (OLG) is a low-molecular-weight lychee fruit polyphenol mainly containing catechin-type monomers and oligomers of proanthocyanidins. Dietary OLG supplementation reportedly improves lipid metabolism disorder and lowers the visceral fat level in animal and human studies. Thus, we investigated the mechanism behind the protective and beneficial effects of OLG on a Western diet (WD)-induced metabolic syndrome (MetS) of a murine model. Using the C57BL/6J mouse for the MetS model, mice were divided into three groups: control (normal diet: ND), Western diet (WD) and WD + 0.5% OLG (OLG) groups. The WD group was fed a high-calorie (high fructose plus high fat) diet for 12 weeks to develop MetS. At week 12, all mice were sacrificed and the blood and liver were obtained for histological and biological examinations and RNA sequencing (RNA-Seq). Body weight, liver weight, plasma triglycerides (TG), total cholesterol (T-Cho) and alanine aminotransferase (ATS) levels of both OLG groups were significantly lower than those of the WD group. On histological examination of the liver, the area of fatty deposits was shown to be suppressed by OLG administration. Expression gene analysis in the liver of WD- versus OLG-fed mice by RNA-Seq showed that 464/45,706 genes exhibited a significant change of expression (corrected p-value <0.05, absolute value of fold change (FC) ≥2). Gene network analysis showed that genes related to hepatic steatosis, liver inflammation and tumor invasion were inactivated in the OLG group. In particular, the lipid metabolism-related genes Lpin1, Adig and Cidea were regulated by OLG administration. OLG may function to suppress MetS and the progression of geriatric diseases in WD-fed mice by regulating the expression of lipid metabolism, inflammation and tumor-related genes in the liver. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Global analysis of the yeast lipidome by quantitative shotgun mass spectrometry.

PubMed

Ejsing, Christer S; Sampaio, Julio L; Surendranath, Vineeth; Duchoslav, Eva; Ekroos, Kim; Klemm, Robin W; Simons, Kai; Shevchenko, Andrej

2009-02-17

Although the transcriptome, proteome, and interactome of several eukaryotic model organisms have been described in detail, lipidomes remain relatively uncharacterized. Using Saccharomyces cerevisiae as an example, we demonstrate that automated shotgun lipidomics analysis enabled lipidome-wide absolute quantification of individual molecular lipid species by streamlined processing of a single sample of only 2 million yeast cells. By comparative lipidomics, we achieved the absolute quantification of 250 molecular lipid species covering 21 major lipid classes. This analysis provided approximately 95% coverage of the yeast lipidome achieved with 125-fold improvement in sensitivity compared with previous approaches. Comparative lipidomics demonstrated that growth temperature and defects in lipid biosynthesis induce ripple effects throughout the molecular composition of the yeast lipidome. This work serves as a resource for molecular characterization of eukaryotic lipidomes, and establishes shotgun lipidomics as a powerful platform for complementing biochemical studies and other systems-level approaches.

Polymer Molecular Weight Analysis by [Superscript 1]H NMR Spectroscopy

ERIC Educational Resources Information Center

Izunobi, Josephat U.; Higginbotham, Clement L.

2011-01-01

The measurement and analysis of molecular weight and molecular weight distribution remain matters of fundamental importance for the characterization and physical properties of polymers. Gel permeation chromatography (GPC) is the most routinely used method for the molecular weight determination of polymers whereas matrix-assisted laser…

Molecular Weight and Molecular Weight Distributions in Synthetic Polymers.

ERIC Educational Resources Information Center

Ward, Thomas Carl

1981-01-01

Focuses on molecular weight and molecular weight distributions (MWD) and models for predicting MWD in a pedagogical way. In addition, instrumental methods used to characterize MWD are reviewed with emphasis on physical chemistry of each, including end-group determination, osmometry, light scattering, solution viscosity, fractionation, and…

Structure determination of butylone as a new psychoactive substance using chiroptical and vibrational spectroscopies.

PubMed

Spálovská, Dita; Králík, František; Kohout, Michal; Jurásek, Bronislav; Habartová, Lucie; Kuchař, Martin; Setnička, Vladimír

2018-05-01

Recently, there has been a worldwide substantial increase in the consumption of new psychoactive substances (NPS), compounds that mimic the structure of illicit drugs, such as amphetamines or ecstasy. The producers try to avoid the law by a slight modification of illicit structures, thereby developing dozens of temporarily legal NPS every year. The current trends in the detection and monitoring of such substances demand a fast and reliable analysis. Molecular spectroscopy represents a highly effective tool for the identification of NPS and chiroptical methods can provide further information on their 3D structure, which is the key for the determination of their biological activity. We present the first systematic study of NPS, specifically butylone, combining chiroptical and vibrational spectroscopies with ab initio calculations. According to density functional theory calculations, 6 stable lowest energy conformers of butylone were found and their molecular structure was described. For each conformer, the relative abundance based on the Boltzmann distribution was estimated, their population weighted spectra predicted and compared to the experimental results. Very good agreement between the experimental and the simulated spectra was achieved, which allowed not only the assignment of the absolute configuration, but also a precise description of the molecular structure. © 2018 Wiley Periodicals, Inc.

Changes in relative and absolute concentrations of plasma phospholipid fatty acids observed in a randomized trial of Omega-3 fatty acids supplementation in Uganda

PubMed Central

Song, Xiaoling; Diep, Pho; Schenk, Jeannette M; Casper, Corey; Orem, Jackson; Makhoul, Zeina; Lampe, Johanna W; Neuhouser, Marian L.

2016-01-01

Expressing circulating phospholipid fatty acids (PLFAs) in relative concentrations has some limitations: the total of all fatty acids are summed to 100%; therefore, the values of individual fatty acid are not independent. In this study we examined if both relative and absolute metrics could effectively measure changes in circulating PLFA concentrations in an intervention trial. 66 HIV and HHV8 infected patients in Uganda were randomized to take 3g/d of either long-chain omega-3 fatty acids (1,856 mg EPA and 1,232 mg DHA) or high—oleic safflower oil in a 12-week double-blind trial. Plasma samples were collected at baseline and end of trial. Relative weight percentage and absolute concentrations of 41 plasma PLFAs were measured using gas chromatography. Total cholesterol was also measured. Intervention-effect changes in concentrations were calculated as differences between end of 12-week trial and baseline. Pearson correlations of relative and absolute concentration changes in individual PLFAs were high (>0.6) for 37 of the 41 PLFAs analyzed. In the intervention arm, 17 PLFAs changed significantly in relative concentration and 16 in absolute concentration, 15 of which were identical. Absolute concentration of total PLFAs decreased 95.1 mg/L (95% CI: 26.0, 164.2; P = 0.0085), but total cholesterol did not change significantly in the intervention arm. No significant change was observed in any of the measurements in the placebo arm. Both relative weight percentage and absolute concentrations could effectively measure changes in plasma PLFA concentrations. EPA and DHA supplementation changes the concentrations of multiple plasma PLFAs besides EPA and DHA. PMID:27926458

Validating the absolute reliability of a fat free mass estimate equation in hemodialysis patients using near-infrared spectroscopy.

PubMed

Kono, Kenichi; Nishida, Yusuke; Moriyama, Yoshihumi; Taoka, Masahiro; Sato, Takashi

2015-06-01

The assessment of nutritional states using fat free mass (FFM) measured with near-infrared spectroscopy (NIRS) is clinically useful. This measurement should incorporate the patient's post-dialysis weight ("dry weight"), in order to exclude the effects of any change in water mass. We therefore used NIRS to investigate the regression, independent variables, and absolute reliability of FFM in dry weight. The study included 47 outpatients from the hemodialysis unit. Body weight was measured before dialysis, and FFM was measured using NIRS before and after dialysis treatment. Multiple regression analysis was used to estimate the FFM in dry weight as the dependent variable. The measured FFM before dialysis treatment (Mw-FFM), and the difference between measured and dry weight (Mw-Dw) were independent variables. We performed Bland-Altman analysis to detect errors between the statistically estimated FFM and the measured FFM after dialysis treatment. The multiple regression equation to estimate the FFM in dry weight was: Dw-FFM = 0.038 + (0.984 × Mw-FFM) + (-0.571 × [Mw-Dw]); R(2)  = 0.99). There was no systematic bias between the estimated and the measured values of FFM in dry weight. Using NIRS, FFM in dry weight can be calculated by an equation including FFM in measured weight and the difference between the measured weight and the dry weight. © 2015 The Authors. Therapeutic Apheresis and Dialysis © 2015 International Society for Apheresis.

A Note on the Interpretation of Weighted Kappa and its Relations to Other Rater Agreement Statistics for Metric Scales

ERIC Educational Resources Information Center

Schuster, Christof

2004-01-01

This article presents a formula for weighted kappa in terms of rater means, rater variances, and the rater covariance that is particularly helpful in emphasizing that weighted kappa is an absolute agreement measure in the sense that it is sensitive to differences in rater's marginal distributions. Specifically, rater mean differences will decrease…

A Transposon Screen Identifies Genetic Determinants of Vibrio cholerae Resistance to High-Molecular-Weight Antibiotics

PubMed Central

Delgado, Fernanda; Umans, Benjamin D.; Gerding, Matthew A.; Davis, Brigid M.

2016-01-01

Gram-negative bacteria are notoriously resistant to a variety of high-molecular-weight antibiotics due to the limited permeability of their outer membrane (OM). The basis of OM barrier function and the genetic factors required for its maintenance remain incompletely understood. Here, we employed transposon insertion sequencing to identify genes required for Vibrio cholerae resistance to vancomycin and bacitracin, antibiotics that are thought to be too large to efficiently penetrate the OM. The screen yielded several genes whose protein products are predicted to participate in processes important for OM barrier functions and for biofilm formation. In addition, we identified a novel factor, designated vigA (for vancomycin inhibits growth), that has not previously been characterized or linked to outer membrane function. The vigA open reading frame (ORF) codes for an inner membrane protein, and in its absence, cells became highly sensitive to glycopeptide antibiotics (vancomycin and ramoplanin) and bacitracin but not to other large antibiotics or detergents. In contrast to wild-type (WT) cells, the vigA mutant was stained with fluorescent vancomycin. These observations suggest that VigA specifically prevents the periplasmic accumulation of certain large antibiotics without exerting a general role in the maintenance of OM integrity. We also observed marked interspecies variability in the susceptibilities of Gram-negative pathogens to glycopeptides and bacitracin. Collectively, our findings suggest that the OM barrier is not absolute but rather depends on specific OM-antibiotic interactions. PMID:27216069

Development and in vivo evaluation of an oral delivery system for low molecular weight heparin based on thiolated polycarbophil.

PubMed

Kast, Constantia E; Guggi, Davide; Langoth, Nina; Bernkop-Schnürch, Andreas

2003-06-01

It was the purpose of this study to develop a new oral drug delivery system for low molecular weight heparin (LMWH) providing an improved bioavailability and a prolonged therapeutic effect. The permeation enhancing polycarbophil-cysteine conjugate (PCP-Cys) used in this study displayed 111.4 +/- 6.4 microM thiol groups per gram polymer. Permeation studies on freshly excised intestinal mucosa were performed in Ussing chambers demonstrating a 2-fold improved uptake of heparin as a result of the addition of 0.5% (w/v) PCP-Cys and the permeation mediator glutathione (GSH). Tablets containing PCP-Cys, GSH, and 279 IU of LMWH showed a sustained drug release over 4 h. To guarantee the swelling of the polymeric carrier matrix in the small intestine tablets were enteric coated. They were orally given to rats. For tablets being based on the thiomer/GSH system an absolute bioavailability of 19.9 +/- 9.3% (means +/- SD; n = 5) vs. intravenous injection could be achieved. whereas tablets comprising unmodified PCP did not lead to a significant (p < 0.01) heparin concentration in plasma. The permeation enhancing effect and subsequently a therapeutic heparin level was maintained for 24 h after a single dose. Because of the strong and prolonged lasting permeation enhancing effect of the thiomer/GSH system, the oral bioavailability of LMWH could be significantly improved. This new delivery system represents therefore a promising tool for the oral administration of heparin.

Low-molecular-weight heparin to prevent recurrent venous thromboembolism in pregnancy: Rationale and design of the Highlow study, a randomised trial of two doses.

PubMed

Bleker, Suzanne M; Buchmüller, Andrea; Chauleur, Céline; Ní Áinle, Fionnuala; Donnelly, Jennifer; Verhamme, Peter; Jacobsen, Anne Flem; Ganzevoort, Wessel; Prins, Martin; Beyer-Westendorf, Jan; DeSancho, Maria; Konstantinides, Stavros; Pabinger, Ingrid; Rodger, Marc; Decousus, Hervé; Middeldorp, Saskia

2016-08-01

Women with a history of venous thromboembolism (VTE) have a 2% to 10% absolute risk of VTE recurrence during subsequent pregnancies. Therefore, current guidelines recommend that all pregnant women with a history of VTE receive pharmacologic thromboprophylaxis. The optimal dose of low-molecular-weight heparin (LMWH) for thromboprophylaxis is unknown. In the Highlow study (NCT 01828697; www.highlowstudy.org), we compare a fixed low dose of LMWH with an intermediate dose of LMWH for the prevention of pregnancy-associated recurrent VTE. We present the rationale and design features of this study. The Highlow study is an investigator-initiated, multicentre, international, open-label, randomised trial. Pregnant women with a history of VTE and an indication for ante- and postpartum pharmacologic thromboprophylaxis are included before 14weeks of gestation. The primary efficacy outcome is symptomatic recurrent VTE during pregnancy and 6weeks postpartum. The primary safety outcomes are clinically relevant bleeding, blood transfusions before 6weeks postpartum and mortality. Patients are closely monitored to detect cutaneous reactions to LMWH and are followed for 3months after delivery. A central independent adjudication committee adjudicates all suspected outcome events. The Highlow study is the first large randomised controlled trial in pregnancy that will provide high-quality evidence on the optimal dose of LWMH thromboprophylaxis for the prevention of recurrent VTE in pregnant women with a history of VTE. Copyright © 2016 Elsevier Ltd. All rights reserved.

Polymer-induced phase separation and crystallization in immunoglobulin G solutions.

PubMed

Li, Jianguo; Rajagopalan, Raj; Jiang, Jianwen

2008-05-28

We study the effects of the size of polymer additives and ionic strength on the phase behavior of a nonglobular protein-immunoglobulin G (IgG)-by using a simple four-site model to mimic the shape of IgG. The interaction potential between the protein molecules consists of a Derjaguin-Landau-Verwey-Overbeek-type colloidal potential and an Asakura-Oosawa depletion potential arising from the addition of polymer. Liquid-liquid equilibria and fluid-solid equilibria are calculated by using the Gibbs ensemble Monte Carlo technique and the Gibbs-Duhem integration (GDI) method, respectively. Absolute Helmholtz energy is also calculated to get an initial coexisting point as required by GDI. The results reveal a nonmonotonic dependence of the critical polymer concentration rho(PEG) (*) (i.e., the minimum polymer concentration needed to induce liquid-liquid phase separation) on the polymer-to-protein size ratio q (equivalently, the range of the polymer-induced depletion interaction potential). We have developed a simple equation for estimating the minimum amount of polymer needed to induce the liquid-liquid phase separation and show that rho(PEG) (*) approximately [q(1+q)(3)]. The results also show that the liquid-liquid phase separation is metastable for low-molecular weight polymers (q=0.2) but stable at large molecular weights (q=1.0), thereby indicating that small sizes of polymer are required for protein crystallization. The simulation results provide practical guidelines for the selection of polymer size and ionic strength for protein phase separation and crystallization.

Mechanical Properties of LaRC(tm) SI Polymer for a Range of Molecular Weights

NASA Technical Reports Server (NTRS)

Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.; Nicholson, Lee M.

2000-01-01

Mechanical testing of an advanced polyimide resin (LaRC(tm)-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. Elastic and inelastic properties were characterized as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. The combined analysis of calculated yield stress and notched tensile strength indicated that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microphotographs of the failure surfaces also supported these findings.

Interactions between pyrazole derived enantiomers and Chiralcel OJ: Prediction of enantiomer absolute configurations and elution order by molecular dynamics simulations.

PubMed

Hu, Guixiang; Huang, Meilan; Luo, Chengcai; Wang, Qi; Zou, Jian-Wei

2016-05-01

The separation of enantiomers and confirmation of their absolute configurations is significant in the development of chiral drugs. The interactions between the enantiomers of chiral pyrazole derivative and polysaccharide-based chiral stationary phase cellulose tris(4-methylbenzoate) (Chiralcel OJ) in seven solvents and under different temperature were studied using molecular dynamics simulations. The results show that solvent effect has remarkable influence on the interactions. Structure analysis discloses that the different interactions between two isomers and chiral stationary phase are dependent on the nature of solvents, which may invert the elution order. The computational method in the present study can be used to predict the elution order and the absolute configurations of enantiomers in HPLC separations and therefore would be valuable in development of chiral drugs. Copyright © 2016 Elsevier Inc. All rights reserved.

Dual-comb spectroscopy of molecular electronic transitions in condensed phases

NASA Astrophysics Data System (ADS)

Cho, Byungmoon; Yoon, Tai Hyun; Cho, Minhaeng

2018-03-01

Dual-comb spectroscopy (DCS) utilizes two phase-locked optical frequency combs to allow scanless acquisition of spectra using only a single point detector. Although recent DCS measurements demonstrate rapid acquisition of absolutely calibrated spectral lines with unprecedented precision and accuracy, complex phase-locking schemes and multiple coherent averaging present significant challenges for widespread adoption of DCS. Here, we demonstrate Global Positioning System (GPS) disciplined DCS of a molecular electronic transition in solution at around 800 nm, where the absorption spectrum is recovered by using a single time-domain interferogram. We anticipate that this simplified dual-comb technique with absolute time interval measurement and ultrabroad bandwidth will allow adoption of DCS to tackle molecular dynamics investigation through its implementation in time-resolved nonlinear spectroscopic studies and coherent multidimensional spectroscopy of coupled chromophore systems.

Perchlorate-induced combustion of organic matter with variable molecular weights: Implications for Mars missions

NASA Astrophysics Data System (ADS)

Sephton, Mark A.; Lewis, James M. T.; Watson, Jonathan S.; Montgomery, Wren; Garnier, Carole

2014-11-01

Instruments on the Viking landers and Curiosity rover analyzed samples of Mars and detected carbon dioxide and organic compounds of uncertain origin. Mineral-assisted reactions are leading to uncertainty, particularly those involving perchlorate minerals which thermally decompose to produce chlorine and oxygen which can then react with organic matter to generate organochlorine compounds and carbon dioxide. Although generally considered a problem for interpretation, the release profiles of generated gases can indicate the type of organic matter present. We have performed a set of experiments with perchlorate and organic matter of variable molecular weights. Results indicate that organic susceptibility to thermal degradation and mineral-assisted reactions is related to molecular weight. Low molecular weight organic matter reacts at lower temperatures than its high molecular weight counterparts. The natural occurrence and association of organic matter with differing molecular weights helps to discriminate between contamination (usually low molecular weight organic matter only) and indigenous carbon (commonly low and high molecular weight organic matter together). Our results can be used to provide insights into data returning from Mars.

Peptidylation for the determination of low-molecular-weight compounds by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Tang, Feng; Cen, Si-Ying; He, Huan; Liu, Yi; Yuan, Bi-Feng; Feng, Yu-Qi

2016-05-23

Determination of low-molecular-weight compounds by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been a great challenge in the analytical research field. Here we developed a universal peptide-based derivatization (peptidylation) strategy for the sensitive analysis of low-molecular-weight compounds by MALDI-TOF-MS. Upon peptidylation, the molecular weights of target analytes increase, thus avoiding serious matrix ion interference in the low-molecular-weight region in MALDI-TOF-MS. Since peptides typically exhibit good signal response during MALDI-TOF-MS analysis, peptidylation endows high detection sensitivities of low-molecular-weight analytes. As a proof-of-concept, we analyzed low-molecular-weight compounds of aldehydes and thiols by the developed peptidylation strategy. Our results showed that aldehydes and thiols can be readily determined upon peptidylation, thus realizing the sensitive and efficient determination of low-molecular-weight compounds by MALDI-TOF-MS. Moreover, target analytes also can be unambiguously detected in biological samples using the peptidylation strategy. The established peptidylation strategy is a universal strategy and can be extended to the sensitive analysis of various low-molecular-weight compounds by MALDI-TOF-MS, which may be potentially used in areas such as metabolomics.

Isolation of a thermophilic bacterium capable of low-molecular-weight polyethylene degradation.

PubMed

Jeon, Hyun Jeong; Kim, Mal Nam

2013-02-01

A thermophilic bacterium capable of low-molecular-weight polyethylene (LMWPE) degradation was isolated from a compost sample, and was identified as Chelatococcus sp. E1, through sequencing of the 16S rRNA gene. LMWPE was prepared by thermal degradation of commercial PE in a strict nitrogen atmosphere. LMWPE with a weight-average-molecular-weight (Mw) in the range of 1,700-23,700 was noticeably mineralized into CO(2) by the bacterium. The biodegradability of LMWPE decreased as the Mw increased. The low molecular weight fraction of LMWPE decreased significantly as a result of the degradation process, and thereby both the number-average-molecular-weight and Mw increased after biodegradation. The polydispersity of LMWPE was either narrowed or widened, depending on the initial Mw of LMWPE, due to the preferential elimination of the low molecular weight fraction, in comparison to the high molecular weight portion. LMWPE free from an extremely low molecular weight fraction was also mineralized by the strain at a remarkable rate, and FTIR peaks assignable to C-O stretching appeared as a result of microbial action. The FTIR peaks corresponding to alkenes also became more intense, indicating that dehydrogenations occurred concomitantly with microbial induced oxidation.

Molecular weight dependence of LB morphology of poly(n-hexyl isocyanate) (PHIC).

PubMed

Morioka, Takako; Shibata, Osamu; Kawaguchi, Masami

2010-12-07

The morphologies of Langmuir-Blodgett (LB) films of two fractionated poly(n-hexyl isocyanate) (PHIC) and those of their binary mixtures were observed by AFM, together with those of an unfractionated PHIC. The low molecular weight PHIC formed random packing of bundles consisting of rigid rods, while the high molecular weight PHIC formed random packing of bundles consisting of hairy rods. Bundle interpenetration was observed only for the latter in the semidilute regime. In the bilayer region, the area occupied by the PHIC bundles in the upper layer was obviously smaller for the high molecular weight PHIC than for the low molecular weight PHIC, suggesting that the bundles of high molecular weight PHIC more easily interpenetrate than those of low molecular weight PHIC. For the blended films composed of both low and high molecular weight PHICs, the characteristic morphologies of the respective PHIC samples were no longer present. Moreover, the morphologies of the blended films appeared to resemble each other at any molar fraction owing to the ideal miscibility of the low molecular weight and high molecular weight PHICs. The morphologies of the blended films were also similar to that of the unfractionated PHIC film in the dilute regime. In the semidilute regime, the blended films became rounded owing to an increase in bundles interpenetration between PHICs as compared to that in the dilute regime, whereas the morphology of unfractionated PHIC films remained unchanged as compared to that in the dilute regime.

The performance of different propensity score methods for estimating absolute effects of treatments on survival outcomes: A simulation study.

PubMed

Austin, Peter C; Schuster, Tibor

2016-10-01

Observational studies are increasingly being used to estimate the effect of treatments, interventions and exposures on outcomes that can occur over time. Historically, the hazard ratio, which is a relative measure of effect, has been reported. However, medical decision making is best informed when both relative and absolute measures of effect are reported. When outcomes are time-to-event in nature, the effect of treatment can also be quantified as the change in mean or median survival time due to treatment and the absolute reduction in the probability of the occurrence of an event within a specified duration of follow-up. We describe how three different propensity score methods, propensity score matching, stratification on the propensity score and inverse probability of treatment weighting using the propensity score, can be used to estimate absolute measures of treatment effect on survival outcomes. These methods are all based on estimating marginal survival functions under treatment and lack of treatment. We then conducted an extensive series of Monte Carlo simulations to compare the relative performance of these methods for estimating the absolute effects of treatment on survival outcomes. We found that stratification on the propensity score resulted in the greatest bias. Caliper matching on the propensity score and a method based on earlier work by Cole and Hernán tended to have the best performance for estimating absolute effects of treatment on survival outcomes. When the prevalence of treatment was less extreme, then inverse probability of treatment weighting-based methods tended to perform better than matching-based methods. © The Author(s) 2014.

Effect of Sulfation and Molecular Weight on Anticoagulant Activity of Dextran.

PubMed

Drozd, N N; Logvinova, Yu S; Torlopov, M A; Udoratina, E V

2017-02-01

Sulfation (to 2.8) of dextrans with molecular weight of 150 and 20 kDa was followed by the appearance of anticoagulant activity that increased with decreasing their molecular weight and did not depend on antithrombin, plasma inhibitor of serine proteases of the blood coagulation system. Antithrombin activity of dextran sulfate with a molecular weight of 20 kDa reached 12.6-15.3 U/mg. Dextran sulfates with molecular weights of 20 and 150 kDa did not potentiate ADP-induced human platelet aggregation.

Performance of the Cockcroft-Gault, MDRD, and New CKD-EPI Formulas in Relation to GFR, Age, and Body Size

PubMed Central

Grootendorst, Diana Carina; Verduijn, Marion; Elliott, Elise Grace; Dekker, Friedo Wilhelm; Krediet, Raymond Theodorus

2010-01-01

Background and objectives: We compared the estimations of Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations to a gold standard GFR measurement using 125I-iothalamate, within strata of GFR, gender, age, body weight, and body mass index (BMI). Design, setting, participants, & measurements: For people who previously underwent a GFR measurement, bias, precision, and accuracies between measured and estimated kidney functions were calculated within strata of the variables. The relation between the absolute bias and the variables was tested with linear regression analysis. Results: Overall (n = 271, 44% male, mean measured GFR 72.6 ml/min per 1.73 m2 [SD 30.4 ml/min per 1.73 m2]), mean bias was smallest for MDRD (P < 0.01). CKD-EPI had highest accuracy (P < 0.01 compared with Cockcroft-Gault), which did not differ from MDRD (P = 0.14). The absolute bias of all formulas was related to age. For MDRD and CKD-EPI, absolute bias was also related to the GFR; for Cockcroft-Gault, it was related to body weight and BMI as well. In all extreme subgroups, MDRD and CKD-EPI provided highest accuracies. Conclusions: The absolute bias of all formulas is influenced by age; CKD-EPI and MDRD are also influenced by GFR. Cockcroft-Gault is additionally influenced by body weight and BMI. In general, CKD-EPI gives the best estimation of GFR, although its accuracy is close to that of the MDRD. PMID:20299365

Characterizing Low Molecular Weight Organic Matter in Arctic Polygonal Tundra Soils to Identify Biogeochemical Hotspots Using a Dual-Separation, High-Resolution Mass Spectrometry Approach

NASA Astrophysics Data System (ADS)

Ladd, M.; Wullschleger, S. D.; Iversen, C. M.; Hettich, R.

2016-12-01

Reliably modeling biogeochemical processes (e.g. decomposition, plant-microbial competition for nutrients) across spatial or temporal scales requires elucidating the chemical composition of low molecular weight (LMW) dissolved soil organic matter (DOM). Our understanding is limited, however, by the wide-ranging physicochemical properties and high fluxes of these compounds, posing major challenges in detection, isolation, and quantification. Here, we developed and evaluated a sensitive, non-targeted approach to characterize LMW DOM in the Arctic, a unique system that is warming at a rate twice that of the global average and may have significant feedbacks to global C and N cycles. Soil cores were collected from a continuous permafrost, polygonal tundra landscape near Barrow, Alaska (71° 16' N) and sectioned into 5 cm increments. Water and salt extracts from each section were filtered and injected onto C18 reversed-phase or zwitterionic-type hydrophilic interaction chromatography (ZIC-pHILIC) columns for separation. LMW DOM profiles were obtained using high-resolution mass spectrometry (HRMS), and unique features, known and unknown, were characterized by LC retention time, accurate mass (m/z), and molecular fragmentation pattern. Coupling two orthogonal chromatographic separations with HRMS enabled the characterization of hundreds of analytes in a single measurement providing enhanced, high-throughput coverage of LMW DOM from soil extracts. The complexity and relative/absolute intensities of LMW DOM features (e.g. organic acids, amino sugars, peptides) varied across polygon type (high- or low-centered), extract condition, and with depth, providing an information-rich, molecular signal of LMW DOM availability across scales. Comprehensively profiling this complex mixture of small molecules of both biotic and abiotic origin provides a chemical signature of biological function, allowing for more reliable predictions of how discrete, molecular-scale processes may control landscape dynamics. In the Arctic, this platform can be leveraged to identify biogeochemical hotspots to gain insight into to how warming temperatures will impact microbial dynamics and CO2 and CH4 fluxes from these systems.

Phase Behavior of Binary Blends of High Molecular Weight Diblock Copolymers with a Low Molecular Weight Triblock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickiewicz, Rafal A.; Ntoukas, Eleftherios; Avgeropoulos, Apostolos

2009-08-26

Binary blends of four different high molecular weight poly(styrene-b-isoprene) (SI) diblock copolymers with a lower molecular weight poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer were prepared, and their morphology was characterized by transmission electron microscopy and ultra-small-angle X-ray scattering. All the neat block copolymers have nearly symmetric composition and exhibit the lamellar morphology. The SI diblock copolymers had number-average molecular weights, Mn, in the range 4.4 x 10{sup 5}--1.3 x 10{sup 6} g/mol and volume fractions of poly(styrene), {Phi}{sub PS}, in the range 0.43--0.49, and the SIS triblock had a molecular weight of Mn 6.2 x 10{sup 4} g/mol with {Phi}{sub PS} =more » 0.41. The high molecular weight diblock copolymers are very strongly segregating, with interaction parameter values, {chi}N, in the range 470--1410. A morphological phase diagram in the parameter space of molecular weight ratio (R = M{sub n}{sup diblock}/1/2M{sub n}{sup triblock}) and blend composition was constructed, with R values in the range between 14 and 43, which are higher than previously reported. The phase diagram revealed a large miscibility gap for the blends, with macrophase separation into two distinct types of microphase-separated domains for weight fractions of SI, w{sub SI} < 0.9, implying virtually no solubility of the much higher molecular weight diblocks in the lower molecular weight triblock. For certain blend compositions, above R 30, morphological transitions from the lamellar to cylindrical and bicontinuous structures were also observed.« less

Gel filtration applied to the study of lipases and other esterases

PubMed Central

Downey, W. K.; Andrews, P.

1965-01-01

1. Sephadex G-100 and G-200 gel-filtration columns were calibrated for molecular-weight estimation with proteins of known molecular weights, and used to study the composition of several lipase or esterase preparations. 2. Enzymes from cow's milk, rat adipose tissue and pig pancreas were detected in the column effluents by their ability to liberate free acid from emulsified tributyrin at pH 8·5. 3. Four tributyrinases were detected in preparations from individual cow's milks. Molecular weights 62000, 75000 and 112000 were estimated for three of them, but although the fourth may be of unusually low molecular weight an estimate was not possible. 4. Extracts of rat adipose tissue apparently contained six tributyrinases (molecular weights 39000, 47000, 55000, 68000, 75000 and 200000) but the relative amounts of these enzymes varied widely from rat to rat. 5. Tributyrinase activity in juice expressed from pig pancreatic tissue was due mainly to one enzyme (molecular weight 42000). On the other hand, activity in extracts of acetone-dried pancreas was confined to material of molecular weight > 106, which may be an aggregated form of the lower-molecular-weight enzyme. 6. Activity in fractionated wheat-germ extracts was assayed with emulsified triacetin substrate, and was evidently due to one enzyme (molecular weight 51000). 7. Some problems arising in the application of gel filtration to the study of lipase–esterase systems were indicated. PMID:14340054

Ninety-day toxicity evaluation of 1,3,5-trinitrobenzene (Tnb) in Peromyscus leucopus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, T.V.; Torsella, J.; Daniel, F.B.

1995-12-31

The subchronic toxicity of TNB in P. leucopus was evaluated by feeding Certified Rodent Diet 5002 supplemented with TNB (0, 150, 375, and 750 mg of TNB/kg diet), for 90 days. The food and water consumption was not significantly different between dose groups (for either sex). The calculated average daily TNB intake for female and male P. leucopus respectively, was 0, 20, 65, 108 and 0, 23, 67, and 113 mg/kg body weight (BW). There were no differences in the absolute body weights between sexes as well as between dose groups. Similarly, the organ weights (absolute and relative) did notmore » differ significantly between the dose groups (in both sexes) with an exception of male P. leucopus group receiving 750 mg TNB diet. In this group the spleen weights, both absolute and relative (g/100 g bw), were increased significantly. A significant increase in white blood cells and reticulocytes were detected. In addition, histopathological examinations in the aforementioned dose group revealed erythroid cell hyperplasia (spleen) and seminiferous tubular degeneration (testes). Although not significant, an increase in methemoglobin levels with an increased dose was evident. When the TNB concentration in the diet was increased to 1,200 and 1,800 mg/kg (used in the range finding study), the above indicated effects were much more prominent and were seen in both sexes. From this study a NOAEL of 20 mg/day/kg for female and 23 mg/day/kg for male is suggested.« less

Acute physiological responses to different circuit training protocols.

PubMed

Monteiro, A G; Alveno, D A; Prado, M; Monteiro, G A; Ugrinowitsch, C; Aoki, M S; Piçarro, I C

2008-12-01

The purpose of present study was to compare the acute physiological responses to a circuit weight training with the responses to a combined circuit training (weight training and treadmill run). The sample consisted of 25 individuals at an average state of training, 10 men and 15 female, between 18 and 35 year old. There were selected 60 second sets of resistance exercises to the circuit weight training (CWT). Whereas in the combined circuit training (CCT), the subjects spent 30 seconds on the same resistance exercises and 30 seconds running on the treadmill. The rest intervals between the sets lasted 15 seconds. The analysis of variance (ANOVA) with 5% significance level was utilized to the statistical analysis of the results. Comparing circuit training protocols, it was noted that CCT elicits a higher relative and absolute VO2 and energy expenditure values than CWT for both genders (P<0.05). Regarding inter-gender comparison, males showed higher absolute and relative VO2 and absolute energy expenditure values for both CWT and CCT than females (P<0.05). Females showed a significant greater %VO2max value for both CWT and CCT. Due to the experimental conditions used to state both circuit training bouts (CWT and CCT), the VO2 rate found was higher than the values reported by previous studies which used heavier weight lift. CCT seems adequate to produce cardiovascular improvements and greater energy expenditure for both men and women, while CWT group classes are sufficient only for unfit women.

Immunostimulative Activity of Low Molecular Weight Chitosans in RAW264.7 Macrophages

PubMed Central

Wu, Ning; Wen, Zheng-Shun; Xiang, Xing-Wei; Huang, Yan-Na; Gao, Yang; Qu, You-Le

2015-01-01

Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been reported to exert many biological activities, such as antioxidant and antitumor effects. However, complex and molecular weight dependent effects of chitosan remain controversial and the mechanisms that mediate these complex effects are still poorly defined. This study was carried out to investigate the immunostimulative effect of different molecular weight chitosan in RAW264.7 macrophages. Our data suggested that two LMWCs (molecular weight of 3 kDa and 50 kDa) both possessed immunostimulative activity, which was dependent on dose and, at the higher doses, also on the molecular weight. LMWCs could significantly enhance the the pinocytic activity, and induce the production of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interferon-γ (IFN-γ), nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in a molecular weight and concentration-dependent manner. LMWCs were further showed to promote the expression of the genes including iNOS, TNF-α. Taken together, our findings suggested that LMWCs elicited significantly immunomodulatory response through up-regulating mRNA expression of proinflammatory cytokines and activated RAW264.7 macrophage in a molecular weight- and concentration-dependent manner. PMID:26437419

High Pressure Size Exclusion Chromatography (HPSEC) Determination of Dissolved Organic Matter Molecular Weight Revisited: Accounting for Changes in Stationary Phases, Analytical Standards, and Isolation Methods.

PubMed

McAdams, Brandon C; Aiken, George R; McKnight, Diane M; Arnold, William A; Chin, Yu-Ping

2018-01-16

We reassessed the molecular weight of dissolved organic matter (DOM) determined by high pressure size exclusion chromatography (HPSEC) using measurements made with different columns and various generations of polystyrenesulfonate (PSS) molecular weight standards. Molecular weight measurements made with a newer generation HPSEC column and PSS standards from more recent lots are roughly 200 to 400 Da lower than initial measurements made in the early 1990s. These updated numbers match DOM molecular weights measured by colligative methods and fall within a range of values calculated from hydroxyl radical kinetics. These changes suggest improved accuracy of HPSEC molecular weight measurements that we attribute to improved accuracy of PSS standards and changes in the column packing. We also isolated DOM from wetlands in the Prairie Pothole Region (PPR) using XAD-8, a cation exchange resin, and PPL, a styrene-divinylbenzene media, and observed little difference in molecular weight and specific UV absorbance at 280 nm (SUVA 280 ) between the two solid phase extraction resins, suggesting they capture similar DOM moieties. PPR DOM also showed lower SUVA 280 at similar weights compared to DOM isolates from a global range of environments, which we attribute to oxidized sulfur in PPR DOM that would increase molecular weight without affecting SUVA 280 .

Effects of Molecular Weight upon Irradiation-Cross-Linked Poly(vinyl alcohol)/Clay Aerogel Properties.

PubMed

Chen, Hong-Bing; Zhao, Yan; Shen, Peng; Wang, Jun-Sheng; Huang, Wei; Schiraldi, David A

2015-09-16

Facile fabrication of mechanically strong poly(vinyl alcohol) (PVOH)/clay aerogel composites through a combination of increasing polymer molecular weights and gamma irradiation-cross-linking is reported herein. The aerogels produced from high polymer molecular weights exhibit significantly increased compressive moduli, similar to the effect of irradiation-induced cross-linking. The required irradiation dose for fabricating strong PVOH composite aerogels with dense microstructure decreased with increasing polymer molecular weight. Neither thermal stability nor flammability was significantly changed by altering the polymer molecular weight or by modest gamma irradiation, but they were highly dependent upon the polymer/clay ratio in the aerogel. Optimization of the mechanical, thermal, and flammability properties of these composite aerogels could therefore be obtained by using relatively low levels of polymer, with very high polymer molecular weight, or lower molecular weight coupled with moderate gamma irradiation. The facile preparation of strong, low flammability aerogels is an alternative to traditional polymer foams in applications where fire safety is important.

VizieR Online Data Catalog: Yale Trigonometric Parallaxes Preliminary (van Altena+ 1991)

NASA Astrophysics Data System (ADS)

van Altena, W. F.; Lee, J. T.; Hoffleit, D.

1995-10-01

The preliminary edition of the General Catalogue of Trigonometric Stellar Parallaxes, containing 15349 parallaxes for 7879 stars, has been prepared at the Yale University Observatory. In this edition 1480 stars have been added to those contained in the previous edition of the catalog by Jenkins (1952, 1963). This relatively small increase in the number of stars is more than compensated for by the increased accuracy of the newer trigonometric parallaxes. The authors have attempted to include here all trigonometric parallaxes made available to them by March 1991 and will provide for each listed parallax in the final version the reference to its source of publication. For each star it lists the equatorial coordinates for B1900 and the secular variation for 100 years, the proper motion in x and y, the weighted average absolute parallax and its standard error, the number of parallax observations, the quality of interagreement among the different values, the visual magnitude, and various cross identifications with other catalogs. The B1900 equinox has been maintained to avoid assigning yet another star number. Ancillary information, including UBV photometry, MK spectral types, data on the variability and binary nature of the stars, orbits when available, and miscellaneous information to aid in determining the reliability of the data, will be listed in the final version. The relative parallaxes are corrected to absolute parallax using newly computed corrections that are based on an improved model of the galaxy. An analysis of the resulting absolute parallaxes has been made to study the accidental and systematic errors of the parallaxes. The results of that investigation are used to arrive at a weighting system for the catalog, which then yields weighted absolute parallaxes for each star. The weighting system is still under investigation; therefore, the weighted parallaxes may change a bit in the final version. Printed copies of the catalog will be available from the Yale University Observatory when the work has been completed (late 1993?). See the file cdrom.doc which provides the original documentation by W. van Altena. (1 data file).

High resolution mass spectrometry method and system for analysis of whole proteins and other large molecules

DOEpatents

Reilly, Peter T. A. [Knoxville, TN; Harris, William A [Naperville, IL

2010-03-02

A matrix assisted laser desorption/ionization (MALDI) method and related system for analyzing high molecular weight analytes includes the steps of providing at least one matrix-containing particle inside an ion trap, wherein at least one high molecular weight analyte molecule is provided within the matrix-containing particle, and MALDI on the high molecular weight particle while within the ion trap. A laser power used for ionization is sufficient to completely vaporize the particle and form at least one high molecular weight analyte ion, but is low enough to avoid fragmenting the high molecular weight analyte ion. The high molecular weight analyte ion is extracted out from the ion trap, and is then analyzed using a detector. The detector is preferably a pyrolyzing and ionizing detector.

Process for crosslinking and extending conjugated diene-containing polymers

NASA Technical Reports Server (NTRS)

Bell, Vernon L. (Inventor); Havens, Stephen J. (Inventor)

1977-01-01

A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

Production of high molecular weight polylactic acid

DOEpatents

Bonsignore, Patrick V.

1995-01-01

A degradable high molecular weight poly(lactic acid). A poly(lactic acid) has a terminal end group of one of carboxyl or hydroxyl groups with low molecular weight poly(lactic acid) units coupled with linking agents of di-isocyanates, bis-epoxides, bis-oxazolines and bis-ortho esters. The resulting high molecular weight poly(lactic acid) can be used for applications taking advantage of the improved physical properties.

1H MRS Assessment of Hepatic Fat Content: Comparison Between Normal- and Excess-weight Children and Adolescents.

PubMed

Chabanova, Elizaveta; Fonvig, Cilius Esmann; Bøjsøe, Christine; Holm, Jens-Christian; Thomsen, Henrik S

2017-08-01

The purpose of the present study was to obtain a cutoff value of liver fat content for the diagnosis of hepatic steatosis by comparing magnetic resonance (MR) spectroscopy results in children and adolescents with normal and excess weight. The study included 420 children and adolescents (91 normal-weight, 99 overweight, and 230 obese) 8-18 years of age. Proton magnetic resonance spectroscopy was performed with a 3T MR system using point resolved spectroscopy sequence with series echo times. The mean absolute mass concentration of liver fat was obtained: 0.5 ± 0.04% in normal-weight boys; 0.5 ± 0.03% in normal-weight girls; 0.9 ± 0.16% in boys with overweight; 1.1 ± 0.24% in girls with overweight; 1.7 ± 0.24% in boys with obesity; and 1.4 ± 0.21% in girls with obesity. The cutoff value of absolute mass concentration of liver fat for hepatic steatosis was found to be 1.5%. Based on this cutoff value, hepatic steatosis was diagnosed in 16% of boys with overweight, 11% of girls with overweight, 32% of boys with obesity, and 27% of girls with obesity. Proton magnetic resonance spectroscopy was successfully applied to obtain the cutoff value of absolute mass concentration of liver fat for the diagnosis of hepatic steatosis in children and adolescents. Children and adolescents with obesity have higher risk of hepatic steatosis than their peers with overweight. Copyright © 2017 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Non-contact weight measurement of flat-faced pharmaceutical tablets using terahertz transmission pulse delay measurements.

PubMed

Bawuah, Prince; Silfsten, Pertti; Ervasti, Tuomas; Ketolainen, Jarkko; Zeitler, J Axel; Peiponen, Kai-Erik

2014-12-10

By measuring the time delay of a terahertz pulse traversing a tablet, and hence its effective refractive index, it is possible to non-invasively and non-destructively detect the weight of tablets made of microcrystalline cellulose (MCC). Two sets of MCC tablets were used in the study: Set A (training set) consisted of 13 tablets with nominally constant height but varying porosities, whereas Set B (test set) comprised of 21 tablets with nominally constant porosity but different heights. A linear correlation between the estimated absolute weight based on the terahertz measurement and the measured weight of both sets of MCC tablets was found. In addition, it was possible to estimate the height of the tablets by utilizing the estimated absolute weight and calculating the relative change of height of each tablet with respect to an ideal tablet. A good agreement between the experimental and the calculated results was found highlighting the potential of this technique for in-line sensing of the weight, porosity and the relative change in height of the tablets compared to a reference/ideal tablet. In this context, we propose a quantitative quality control method to assess the deviations in porosity of tablets immediately after compaction. Copyright © 2014 Elsevier B.V. All rights reserved.

Physical activity and pregnancy: cardiovascular adaptations, recommendations and pregnancy outcomes.

PubMed

Melzer, Katarina; Schutz, Yves; Boulvain, Michel; Kayser, Bengt

2010-06-01

Regular physical activity is associated with improved physiological, metabolic and psychological parameters, and with reduced risk of morbidity and mortality. Current recommendations aimed at improving the health and well-being of nonpregnant subjects advise that an accumulation of > or =30 minutes of moderate physical activity should occur on most, if not all, days of the week. Regardless of the specific physiological changes induced by pregnancy, which are primarily developed to meet the increased metabolic demands of mother and fetus, pregnant women benefit from regular physical activity the same way as nonpregnant subjects. Changes in submaximal oxygen uptake (VO(2)) during pregnancy depend on the type of exercise performed. During maternal rest or submaximal weight-bearing exercise (e.g. walking, stepping, treadmill exercise), absolute maternal VO(2) is significantly increased compared with the nonpregnant state. The magnitude of change is approximately proportional to maternal weight gain. When pregnant women perform submaximal weight-supported exercise on land (e.g. level cycling), the findings are contradictory. Some studies reported significantly increased absolute VO(2), while many others reported unchanged or only slightly increased absolute VO(2) compared with the nonpregnant state. The latter findings may be explained by the fact that the metabolic demand of cycle exercise is largely independent of the maternal body mass, resulting in no absolute VO(2) alteration. Few studies that directly measured changes in maternal maximal VO(2) (VO(2max)) showed no difference in the absolute VO(2max) between pregnant and nonpregnant subjects in cycling, swimming or weight-bearing exercise. Efficiency of work during exercise appears to be unchanged during pregnancy in non-weight-bearing exercise. During weight-bearing exercise, the work efficiency was shown to be improved in athletic women who continue exercising and those who stop exercising during pregnancy. When adjusted for weight gain, the increased efficiency is maintained throughout the pregnancy, with the improvement being greater in exercising women. Regular physical activity has been proven to result in marked benefits for mother and fetus. Maternal benefits include improved cardiovascular function, limited pregnancy weight gain, decreased musculoskeletal discomfort, reduced incidence of muscle cramps and lower limb oedema, mood stability, attenuation of gestational diabetes mellitus and gestational hypertension. Fetal benefits include decreased fat mass, improved stress tolerance, and advanced neurobehavioural maturation. In addition, few studies that have directly examined the effects of physical activity on labour and delivery indicate that, for women with normal pregnancies, physical activity is accompanied with shorter labour and decreased incidence of operative delivery. However, a substantial proportion of women stop exercising after they discover they are pregnant, and only few begin participating in exercise activities during pregnancy. The adoption or continuation of a sedentary lifestyle during pregnancy may contribute to the development of certain disorders such as hypertension, maternal and childhood obesity, gestational diabetes, dyspnoea, and pre-eclampsia. In view of the global epidemic of sedentary behaviour and obesity-related pathology, prenatal physical activity was shown to be useful for the prevention and treatment of these conditions. Further studies with larger sample sizes are required to confirm the association between physical activity and outcomes of labour and delivery.

Molecular Weight of Deoxyribonucleic Acid Synthesized During Initiation of Chromosome Replication in Escherichia coli

PubMed Central

Kuempel, Peter L.

1972-01-01

Alkaline sucrose gradients were used to study the molecular weight of deoxyribonucleic acid (DNA) synthesized during the initiation of chromosome replication in Escherichia coli 15 TAU-bar. The experiments were conducted to determine whether newly synthesized, replication origin DNA is attached to higher-molecular-weight parental DNA. Little of the DNA synthesized after readdition of required amino acids to cells previously deprived of the amino acids was present in DNA with a molecular weight comparable to that of the parental DNA. The newly synthesized, low-molecular-weight DNA rapidly appeared in higher-molecular-weight material, but there was an upper limit to the size of this intermediate-molecular-weight DNA. This limit was not observed when exponentially growing cells converted newly synthesized DNA to higher-molecular-weight material. The size of the intermediate-molecular-weight DNA was related to the age of the replication forks, and the size increased as the replication forks moved further from the replication origin. The results indicate that the newly synthesized replication origin DNA is not attached to parental DNA, but it is rapidly attached to the growing strands that extend from the replication fork to the replication origin, or to the other replication fork if replication is bidirectional. Experiments are reported which demonstrate that the DNA investigated was from the vicinity of the replication origin and was not plasmid DNA or DNA from random positions on the chromosome. PMID:4562387

Absolute Calibration of Si iRMs used for Si Paleo-nutrient proxies

NASA Astrophysics Data System (ADS)

Vocke, Robert; Rabb, Savelas

2016-04-01

The Avogadro Project is an ongoing international effort, coordinated by the International Bureau of Weights and Measures (BIPM) and the International Avogadro Coordination (IAC) to redefine the SI unit mole in terms of the Avogadro constant and the SI unit kg in terms of the Planck constant. One of the outgrowths of this effort has been the development of a novel, precise and highly accurate method to measure calibrated (absolute) isotopic ratios that are traceable to the SI (Vocke et al., 2014 Metrologia 51, 361, Azuma et al., 2015 Metrologia 52 360). This approach has also been able to produce absolute Si isotope ratio data with lower levels of uncertainty when compared to the traditional "Atomic Weights" method of absolute isotope ratio measurement. Silicon isotope variations (reported as delta(Si30)and delta(Si29)) in silicic acid dissolved in ocean waters, in biogenic silica and in diatoms are extremely informative paleo-nutrient proxies. The utility and comparability of such measurements however depends on calibration with artifact isotopic Reference Materials (iRMs). We will be reporting new measurements on the iRMs NBS-28 (RM 8546 - Silica Sand), Diatomite, Big Batch and SRM 990 using the Avogadro measurement approach, comparing them with prior assessments of these iRMs.

The temperature of large dust grains in molecular clouds

NASA Technical Reports Server (NTRS)

Clark, F. O.; Laureijs, R. J.; Prusti, T.

1991-01-01

The temperature of the large dust grains is calculated from three molecular clouds ranging in visual extinction from 2.5 to 8 mag, by comparing maps of either extinction derived from star counts or gas column density derived from molecular observations to I(100). Both techniques show the dust temperature declining into clouds. The two techniques do not agree in absolute scale.

Estimation of Fetal Weight during Labor: Still a Challenge.

PubMed

Barros, Joana Goulão; Reis, Inês; Pereira, Isabel; Clode, Nuno; Graça, Luís M

2016-01-01

To evaluate the accuracy of fetal weight prediction by ultrasonography labor employing a formula including the linear measurements of femur length (FL) and mid-thigh soft-tissue thickness (STT). We conducted a prospective study involving singleton uncomplicated term pregnancies within 48 hours of delivery. Only pregnancies with a cephalic fetus admitted in the labor ward for elective cesarean section, induction of labor or spontaneous labor were included. We excluded all non-Caucasian women, the ones previously diagnosed with gestational diabetes and the ones with evidence of ruptured membranes. Fetal weight estimates were calculated using a previously proposed formula [estimated fetal weight = 1687.47 + (54.1 x FL) + (76.68 x STT). The relationship between actual birth weight and estimated fetal weight was analyzed using Pearson's correlation. The formula's performance was assessed by calculating the signed and absolute errors. Mean weight difference and signed percentage error were calculated for birth weight divided into three subgroups: < 3000 g; 3000-4000 g; and > 4000 g. We included for analysis 145 cases and found a significant, yet low, linear relationship between birth weight and estimated fetal weight (p < 0.001; R2 = 0.197) with an absolute mean error of 10.6%. The lowest mean percentage error (0.3%) corresponded to the subgroup with birth weight between 3000 g and 4000 g. This study demonstrates a poor correlation between actual birth weight and the estimated fetal weight using a formula based on femur length and mid-thigh soft-tissue thickness, both linear parameters. Although avoidance of circumferential ultrasound measurements might prove to be beneficial, it is still yet to be found a fetal estimation formula that can be both accurate and simple to perform.

High pressure size exclusion chromatography (HPSEC) determination of dissolved organic matter molecular weight revisited: Accounting for changes in stationary phases, analytical standards, and isolation methods

USGS Publications Warehouse

McAdams, Brandon C.; Aiken, George R.; McKnight, Diane M.; Arnold, William A.; Chin, Yu-Ping

2018-01-01

We reassessed the molecular weight of dissolved organic matter (DOM) determined by high pressure size exclusion chromatography (HPSEC) using measurements made with different columns and various generations of polystyrenesulfonate (PSS) molecular weight standards. Molecular weight measurements made with a newer generation HPSEC column and PSS standards from more recent lots are roughly 200 to 400 Da lower than initial measurements made in the early 1990s. These updated numbers match DOM molecular weights measured by colligative methods and fall within a range of values calculated from hydroxyl radical kinetics. These changes suggest improved accuracy of HPSEC molecular weight measurements that we attribute to improved accuracy of PSS standards and changes in the column packing. We also isolated DOM from wetlands in the Prairie Pothole Region (PPR) using XAD-8, a cation exchange resin, and PPL, a styrene-divinylbenzene media, and observed little difference in molecular weight and specific UV absorbance at 280 nm (SUVA280) between the two solid phase extraction resins, suggesting they capture similar DOM moieties. PPR DOM also showed lower SUVA280 at similar weights compared to DOM isolates from a global range of environments, which we attribute to oxidized sulfur in PPR DOM that would increase molecular weight without affecting SUVA280.

Production of high molecular weight polylactic acid

DOEpatents

Bonsignore, P.V.

1995-11-28

A degradable high molecular weight poly(lactic acid) is described. The poly(lactic acid) has a terminal end group of one of carboxyl or hydroxyl groups with low molecular weight poly(lactic acid) units coupled with linking agents of di-isocyanates, bis-epoxides, bis-oxazolines and bis-ortho esters. The resulting high molecular weight poly(lactic acid) can be used for applications taking advantage of the improved physical properties.

Effect of molecular weight profile of sorghum proanthocyanidins on resistant starch formation.

PubMed

Barros, Frederico; Awika, Joseph; Rooney, Lloyd W

2014-04-01

There is a growing interest to increase resistant starch (RS) in foods through natural modification of starch. Sorghum tannins (proanthocyanidins, PAs) were recently reported to interact with starch, increasing RS. However, there is no information about how the molecular weight profile of PAs affects RS formation. This study investigated how different-molecular-weight PAs from sorghum affected RS formation in different starch models. The levels of RS were higher (331-437 mg g(-1)) when high-amylose starch was cooked with phenolic extracts containing mostly high-molecular-weight PAs compared with extracts containing lower-molecular-weight PAs or monomeric catechin (249-285 mg g(-1)). In general, binding capacity of PAs with amylose increased proportionally with molecular weight. For example, the percentage of PAs bound to amylose increased from 45% (PAs with degree of polymerization (DP) = 6) to 94% (polymeric PAs, DP > 10). The results demonstrate that molecular weight of the PAs directly affects their interaction with starch: the higher the molecular weight, the stronger the binding to amylose and the higher the RS formation. Polymeric PAs from sorghum can naturally modify starch by interacting strongly with amylose and are thus most suitable to produce foods with higher RS. © 2013 Society of Chemical Industry.

Chromatographic molecular weight measurements for heparin, its fragments and fractions, and other glycosaminoglycans.

PubMed

Mulloy, Barbara; Hogwood, John

2015-01-01

Glycosaminoglycan samples are usually polydisperse, consisting of molecules with differing length and differing sequence. Methods for measuring the molecular weight of heparin have been developed to assure the quality and consistency of heparin products for medicinal use, and these methods can be applied in other laboratory contexts. In the method described here, high-performance gel permeation chromatography is calibrated using appropriate heparin molecular weight markers or a single broad standard calibrant, and used to characterize the molecular weight distribution of polydisperse samples or the peak molecular weight of monodisperse, or approximately monodisperse, heparin fractions. The same technology can be adapted for use with other glycosaminoglycans.

Synergistic amylomaltase and branching enzyme catalysis to suppress cassava starch digestibility.

PubMed

Sorndech, Waraporn; Meier, Sebastian; Jansson, Anita M; Sagnelli, Domenico; Hindsgaul, Ole; Tongta, Sunanta; Blennow, Andreas

2015-11-05

Starch provides our main dietary caloric intake and over-consumption of starch-containing foods results in escalating life-style disease including diabetes. By increasing the content of α-1,6 branch points in starch, digestibility by human amylolytic enzymes is expected to be retarded. Aiming at generating a soluble and slowly digestible starch by increasing the content and changing the relative positioning of the branch points in the starch molecules, we treated cassava starch with amylomaltase (AM) and branching enzyme (BE). We performed a detailed molecular analysis of the products including amylopectin chain length distribution, content of α-1,6 glucosidic linkages, absolute molecular weight distribution and digestibility. Step-by-step enzyme catalysis was the most efficient treatment, and it generated branch structures even more extreme than those of glycogen. All AM- and BE-treated samples showed increased resistance to degradation by porcine pancreatic α-amylase and glucoamylase as compared to cassava starch. The amylolytic products showed chain lengths and branching patterns similar to the products obtained from glycogen. Our data demonstrate that combinatorial enzyme catalysis provides a strategy to generate potential novel soluble α-glucan ingredients with low dietary digestibility assets. Copyright © 2015 Elsevier Ltd. All rights reserved.

mTOR Regulates Endocytosis and Nutrient Transport in Proximal Tubular Cells.

PubMed

Grahammer, Florian; Ramakrishnan, Suresh K; Rinschen, Markus M; Larionov, Alexey A; Syed, Maryam; Khatib, Hazim; Roerden, Malte; Sass, Jörn Oliver; Helmstaedter, Martin; Osenberg, Dorothea; Kühne, Lucas; Kretz, Oliver; Wanner, Nicola; Jouret, Francois; Benzing, Thomas; Artunc, Ferruh; Huber, Tobias B; Theilig, Franziska

2017-01-01

Renal proximal tubular cells constantly recycle nutrients to ensure minimal loss of vital substrates into the urine. Although most of the transport mechanisms have been discovered at the molecular level, little is known about the factors regulating these processes. Here, we show that mTORC1 and mTORC2 specifically and synergistically regulate PTC endocytosis and transport processes. Using a conditional mouse genetic approach to disable nonredundant subunits of mTORC1, mTORC2, or both, we showed that mice lacking mTORC1 or mTORC1/mTORC2 but not mTORC2 alone develop a Fanconi-like syndrome of glucosuria, phosphaturia, aminoaciduria, low molecular weight proteinuria, and albuminuria. Interestingly, proteomics and phosphoproteomics of freshly isolated kidney cortex identified either reduced expression or loss of phosphorylation at critical residues of different classes of specific transport proteins. Functionally, this resulted in reduced nutrient transport and a profound perturbation of the endocytic machinery, despite preserved absolute expression of the main scavenger receptors, MEGALIN and CUBILIN. Our findings highlight a novel mTOR-dependent regulatory network for nutrient transport in renal proximal tubular cells. Copyright © 2016 by the American Society of Nephrology.

Short-term toxicity study in rats of chlorinated cake flour.

PubMed

Fisher, N; Berry, R; Hardy, J

1983-08-01

Male and female Wistar rats were fed for 28 days on a diet containing either chlorinated (1257 or 2506 ppm chlorine) or unchlorinated flour. No significant differences between groups in body weight were observed in the males. A significant inverse correlation between body weight and treatment level, attributable to a corresponding trend in food intakes, was found for the females only. No significant differences between absolute organ weights were found, but when the weights were adjusted for covariance with body weight, dose-related increases in kidney weight (males) and liver weight (both sexes) were found. Histopathological examination revealed no pathological tissue changes attributable to the chlorination of the flour.

Effect of PEO molecular weight on the miscibility and dynamics in epoxy/PEO blends.

PubMed

Lu, Shoudong; Zhang, Rongchun; Wang, Xiaoliang; Sun, Pingchuan; Lv, Weifeng; Liu, Qingjie; Jia, Ninghong

2015-11-01

In this work, the effect of poly(ethylene oxide) (PEO) molecular weight in blends of epoxy (ER) and PEO on the miscibility, inter-chain weak interactions and local dynamics were systematically investigated by multi-frequency temperature modulation DSC and solid-state NMR techniques. We found that the molecular weight (M(w)) of PEO was a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interactions between PEO and ER. A critical PEO molecular weight (M(crit)) around 4.5k was found. PEO was well miscible with ER when the molecular weight was below M(crit), where the chain motion of PEO was restricted due to strong inter-chain hydrogen bonding interactions. However, for the blends with high molecular weight PEO (M(w) > M(crit)), the miscibility between PEO and ER was poor, and most of PEO chains were considerably mobile. Finally, polarization inversion spin exchange at magic angle (PISEMA) solid-state NMR experiment further revealed the different mobility of the PEO in ER/PEO blends with different molecular weight of PEO at molecular level. Based on the DSC and NMR results, a tentative model was proposed to illustrate the miscibility in ER/PEO blends.

Enzymatic and acidic degradation of high molecular weight dextran into low molecular weight and its characterizations using novel Diffusion-ordered NMR spectroscopy.

PubMed

Iqbal, Samina; Marchetti, Roberta; Aman, Afsheen; Silipo, Alba; Qader, Shah Ali Ul; Molinaro, Antonio

2017-10-01

Low molecular weight fractions were derived from native high molecular weight dextran produced by Leuconostoc mesenteroides KIBGE-IB26. Structural characterization of native and low molecular weight fractions obtained after acidic and enzymatic hydrolysis was done using FTIR and NMR spectroscopy. The molecular weight was estimated using Diffusion Ordered NMR spectroscopy. Native dextran (892kDa) is composed of α-(1→6) glycosidic linkage along with α-(1→3) branching. Major proportion of 528kDa dextran was obtained after prolong enzymatic hydrolysis however, an effective acidic treatment at pH-1.4 up to 02 and 04h of exposure resulted in the formation of 77kDa and 57kDa, respectively. The increment in pH from 1.4 to 1.8 lowered the hydrolysis efficiency and resulted in the formation of 270kDa dextran fraction. The results suggest that derived low molecular weight water soluble fractions can be utilized as a drug delivery carrier along with multiple application relating pharmaceutical industries. Copyright © 2017 Elsevier B.V. All rights reserved.

Functional Comparison for Lipid Metabolism and Intestinal and Fecal Microflora Enzyme Activities between Low Molecular Weight Chitosan and Chitosan Oligosaccharide in High-Fat-Diet-Fed Rats.

PubMed

Chiu, Chen-Yuan; Feng, Shih-An; Liu, Shing-Hwa; Chiang, Meng-Tsan

2017-07-24

The present study investigated and compared the regulatory effects on the lipid-related metabolism and intestinal disaccharidase/fecal bacterial enzyme activities between low molecular weight chitosan and chitosan oligosaccharide in high-fat-diet-fed rats. Diet supplementation of low molecular weight chitosan showed greater efficiency than chitosan oligosaccharide in suppressing the increased weights in body and in liver and adipose tissues of high-fat-diet-fed rats. Supplementation of low molecular weight chitosan also showed a greater improvement than chitosan oligosaccharide in imbalance of plasma, hepatic, and fecal lipid profiles, and intestinal disaccharidase activities in high-fat-diet-fed rats. Moreover, both low molecular weight chitosan and chitosan oligosaccharide significantly decreased the fecal microflora mucinase and β-glucuronidase activities in high-fat-diet-fed rats. These results suggest that low molecular weight chitosan exerts a greater positive improvement than chitosan oligosaccharide in lipid metabolism and intestinal disaccharidase activity in high-fat-diet-induced obese rats.

Development of solvent-free offset ink using vegetable oil esters and high molecular-weight resin.

PubMed

Park, Jung Min; Kim, Young Han; Kim, Sung Bin

2013-01-01

In the development of solvent-free offset ink, the roles of resin molecular weight and used solvent on the ink performance were evaluated by examining the relationship between the various properties of resin and solvent and print quality. To find the best performing resin, the soy-oil fatty acid methyl ester (FAME) was applied to the five modified-phenolic resins having different molecular weights. It is found from the experimental results that the ink made of higher molecular weight and better solubility resin gives better printability and print quality. It is because larger molecular weight resin with better solubility gives higher rate of ink transfer. From the ink application of different esters to high molecular weight resin, the best printing performance was yielded from the soy-oil fatty acid butyl ester (FABE). It is due to its high kinematic viscosity resulting in the smallest change of ink transfer weight upon multiple number of printing, which improves the stability of ink quality.

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2010 CFR

2010-04-01

... ethylene oxide and water with a mean molecular weight of 200 to 9,500. (2) It contains no more than 0.2 percent total by weight of ethylene and diethylene glycols when tested by the analytical methods... the total ethylene and diethylene glycol content of polyethylene glycols having mean molecular weights...

Host-Guest Assembly of a Molecular Reporter with Chiral Cyanohydrins for Assignment of Absolute Stereochemistry.

PubMed

Gholami, Hadi; Anyika, Mercy; Zhang, Jun; Vasileiou, Chrysoula; Borhan, Babak

2016-06-27

The absolute stereochemistry of cyanohydrins, derived from ketones and aldehydes, is obtained routinely, in a microscale and derivatization-free manner, upon their complexation with Zn-MAPOL, a zincated porphyrin host with a binding pocket comprised of a biphenol core. The host-guest complex leads to observable exciton-coupled circular dichroism (ECCD), the sign of which is easily correlated to the absolute stereochemistry of the bound cyanohydrin. A working model, based on the ECCD signal of cyanohydrins with known configuration, is proposed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In vivo anti-radiation activities of the Ulva pertusa polysaccharides and polysaccharide-iron(III) complex.

PubMed

Shi, Jinming; Cheng, Cuilin; Zhao, Haitian; Jing, Jing; Gong, Ning; Lu, Weihong

2013-09-01

Polysaccharides with different molecular weights were extracted from Ulva pertusa and fractionated by ultrafiltration. Iron(III) complex of the low molecular-weight U. pertusa polysaccharides were synthesized. Atomic absorption spectrum showed that the iron content of iron(III)-polysaccharide complex was 27.4%. The comparison between U. pertusa polysaccharides and their iron(III) complex showed that iron chelating altered the structural characteristics of the polysaccharides. The bioactivity analysis showed that polysaccharide with low molecular weight was more effective than polysaccharide with high molecular weight in protecting mice from radiation induced damages on bone marrow cells and immune system. Results also proved that the anti-radiation and anti-oxidative activity of iron(III) complex of low molecular-weight polysaccharides were not less than that of low molecular-weight polysaccharides. Copyright © 2013 Elsevier B.V. All rights reserved.

Factors concerned in the efficient steam sterilization of surgical dressings

PubMed Central

Fallon, R. J.

1961-01-01

Some of the factors affecting the efficient steam sterilization of dressings have been examined. A jacketed sterilizer will process a load more quickly than a sterilizer without a jacket. The level of fore-vacuum is critical and must reach an absolute pressure of 20 mm. Hg (29·2 in.Hg vacuum) or less. This will overcome all conditions of overpacking studied. The level of after-vacuum should be 100 mm. Hg absolute or less, preferably near 50 mm. Hg absolute. Overpacking cannot be defined in terms of weight of a fabric per unit volume of container but occurs when a load is compressed in its container. PMID:13891475

The Local Food Environment and Fruit and Vegetable Intake: A Geographically Weighted Regression Approach in the ORiEL Study.

PubMed

Clary, Christelle; Lewis, Daniel J; Flint, Ellen; Smith, Neil R; Kestens, Yan; Cummins, Steven

2016-12-01

Studies that explore associations between the local food environment and diet routinely use global regression models, which assume that relationships are invariant across space, yet such stationarity assumptions have been little tested. We used global and geographically weighted regression models to explore associations between the residential food environment and fruit and vegetable intake. Analyses were performed in 4 boroughs of London, United Kingdom, using data collected between April 2012 and July 2012 from 969 adults in the Olympic Regeneration in East London Study. Exposures were assessed both as absolute densities of healthy and unhealthy outlets, taken separately, and as a relative measure (proportion of total outlets classified as healthy). Overall, local models performed better than global models (lower Akaike information criterion). Locally estimated coefficients varied across space, regardless of the type of exposure measure, although changes of sign were observed only when absolute measures were used. Despite findings from global models showing significant associations between the relative measure and fruit and vegetable intake (β = 0.022; P < 0.01) only, geographically weighted regression models using absolute measures outperformed models using relative measures. This study suggests that greater attention should be given to nonstationary relationships between the food environment and diet. It further challenges the idea that a single measure of exposure, whether relative or absolute, can reflect the many ways the food environment may shape health behaviors. © The Author 2016. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

[Complex enzyme combined with ultrasound extraction technology, physicochemical properties and antioxidant activity of Hedysarum polysaccharides].

PubMed

Yang, Xiu-Yan; Xue, Zhi-Yuan; Yang, Ya-Fei; Fang, Yao-Yao; Zhou, Xiang-Lin; Zhao, Liang-Gong; Feng, Shi-Lan

2018-06-01

In this study, complex enzymes combined with ultrasonic extraction technology（MC） were used, to select optimal extraction combinations by single factor and orthogonal test, with Hedysarum polysaccharides yield and content as the comprehensive indexes. The components, physicochemical properties and antioxidant activity of Hedysarum polysaccharides from complex enzyme combined with ultrasonic extraction（HPS-MC）and the Hedysarum polysaccharides from hot water extraction（HPS-R）were analyzed. The results showed that：complex enzymes had significant effect on the yield and content of Hedysarum polysaccharides, and the ultrasonic power could significantly improve the content of Hedysarum polysaccharides. The optimum technological parameters were as follows: complex enzyme ratio 1:1, ultrasonic power 105 W, ultrasonic time 60 min, and enzymatic hydrolysis pH 5, achieving （14.01±0.64）% and （92.45±1.47）% respectively for the yield and content of Polysaccharides. As compared with HPS-R, the molecular weight, absolute viscosity and protein content of HPS-MC were decreased, while the content of uronic acid was increased. In the antioxidant system, the concentration of polysaccharide was within the range of 1-7 g·L⁻¹; the antioxidant activity of HPS-MC was higher than that of HPS-R, and HPS-MC (80%) with the lowest molecular weight showed a significant dose effect relationship with the increase of the experimental concentration. In conclusion, MC is a simple, convenient, economical and environmentally friendly extraction technology, and the Hedysarum polysaccharides extracted by this method have obvious antioxidant activity. Copyright© by the Chinese Pharmaceutical Association.

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies

PubMed Central

Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-01-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies. PMID:24658586

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies.

PubMed

Liu, Aiqin; Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-04-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies.

Adsorption of Poly(methyl methacrylate) on Concave Al2O3 Surfaces in Nanoporous Membranes

PubMed Central

Nunnery, Grady; Hershkovits, Eli; Tannenbaum, Allen; Tannenbaum, Rina

2009-01-01

The objective of this study was to determine the influence of polymer molecular weight and surface curvature on the adsorption of polymers onto concave surfaces. Poly(methyl methacrylate) (PMMA) of various molecular weights was adsorbed onto porous aluminum oxide membranes having various pore sizes, ranging from 32 to 220 nm. The surface coverage, expressed as repeat units per unit surface area, was observed to vary linearly with molecular weight for molecular weights below ~120 000 g/mol. The coverage was independent of molecular weight above this critical molar mass, as was previously reported for the adsorption of PMMA on convex surfaces. Furthermore, the coverage varied linearly with pore size. A theoretical model was developed to describe curvature-dependent adsorption by considering the density gradient that exists between the surface and the edge of the adsorption layer. According to this model, the density gradient of the adsorbed polymer segments scales inversely with particle size, while the total coverage scales linearly with particle size, in good agreement with experiment. These results show that the details of the adsorption of polymers onto concave surfaces with cylindrical geometries can be used to calculate molecular weight (below a critical molecular weight) if pore size is known. Conversely, pore size can also be determined with similar adsorption experiments. Most significantly, for polymers above a critical molecular weight, the precise molecular weight need not be known in order to determine pore size. Moreover, the adsorption developed and validated in this work can be used to predict coverage also onto surfaces with different geometries. PMID:19415910

The Molecular Weight Distribution of Polymer Samples

ERIC Educational Resources Information Center

Horta, Arturo; Pastoriza, M. Alejandra

2007-01-01

Various methods for the determination of the molecular weight distribution (MWD) of different polymer samples are presented. The study shows that the molecular weight averages and distribution of a polymerization completely depend on the characteristics of the reaction itself.

Molecular weight dependency of polyrotaxane-cross-linked polymer gel extensibility.

PubMed

Ohmori, Kana; Abu Bin, Imran; Seki, Takahiro; Liu, Chang; Mayumi, Koichi; Ito, Kohzo; Takeoka, Yukikazu

2016-12-11

This work investigates the influence of the molecular weight of polyrotaxane (PR) cross-linkers on the extensibility of polymer gels. The polymer gels, which were prepared using PR cross-linkers of three different molecular weights but the same number of cross-linking points per unit volume of gel, have almost the same Young's modulus. By contrast, the extensibility and rupture strength of the polymer gels are substantially increased with increasing molecular weight of the PR cross-linker.

Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate Pressures

DTIC Science & Technology

2016-07-26

SECURITY CLASSIFICATION OF: The objective of this research is to characterize combustion of high molecular weight hydrocarbon fuels and jet- fuels (in...Unlimited UU UU UU UU 26-07-2016 1-May-2012 30-Apr-2016 Final Report: Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate...Report: Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate Pressures (Research Area 1: Mechanical Sciences) Report Title The

Application of the weibull distribution function to the molecular weight distribution of cellulose

Treesearch

A. Broido; Hsiukang Yow

1977-01-01

The molecular weight distribution of a linear homologous polymer is usually obtained empirically for any particular sample. Sample-to-sample comparisons are made in terms of the weight- or number-average molecular weights and graphic displays of the distribution curves. Such treatment generally precludes data interpretations in which a distribution can be described in...

Synthesis of high molecular weight PEO using non-metal initiators

DOEpatents

Yang, Jin; Sivanandan, Kulandaivelu; Pistorino, Jonathan; Eitouni, Hany Basam

2015-05-19

A new synthetic method to prepare high molecular weight poly(ethylene oxide) with a very narrow molecular weight distribution (PDI<1.5) is described. The method involves a metal free initiator system, thus avoiding dangerous, flammable organometallic compounds.

[Absolute numbers of peripheral blood CD34+ hematopoietic stem cells prior to a leukapheresis procedure as a parameter predicting the efficiency of stem cell collection].

PubMed

Galtseva, I V; Davydova, Yu O; Gaponova, T V; Kapranov, N M; Kuzmina, L A; Troitskaya, V V; Gribanova, E O; Kravchenko, S K; Mangasarova, Ya K; Zvonkov, E E; Parovichnikova, E N; Mendeleeva, L P; Savchenko, V G

To identify a parameter predicting a collection of at least 2·106 CD34+ hematopoietic stem cells (HSC)/kg body weight per leukapheresis (LA) procedure. The investigation included 189 patients with hematological malignancies and 3 HSC donors, who underwent mobilization of stem cells with their subsequent collection by LA. Absolute numbers of peripheral blood leukocytes and CD34+ cells before a LA procedure, as well as a number of CD34+ cells/kg body weight (BW) in the LA product stored on the same day were determined in each patient (donor). There was no correlation between the number of leukocytes and that of stored CD34+ cells/kg BW. There was a close correlation between the count of peripheral blood CD34+ cells prior to LA and that of collected CD34+ cells calculated with reference to kg BW. The optimal absolute blood CD34+ cell count was estimated to 20 per µl, at which a LA procedure makes it possible to collect 2·106 or more CD34+ cells/kg BW.

Determination of the molecular weight of poly(ethylene glycol) in biological samples by reversed-phase LC-MS with in-source fragmentation.

PubMed

Warrack, Bethanne M; Redding, Brian P; Chen, Guodong; Bolgar, Mark S

2013-05-01

PEGylation has been widely used to improve the biopharmaceutical properties of therapeutic proteins and peptides. Previous studies have used multiple analytical techniques to determine the fate of both the therapeutic molecule and unconjugated poly(ethylene glycol) (PEG) after drug administration. A straightforward strategy utilizing liquid chromatography-mass spectrometry (LC-MS) to characterize high-molecular weight PEG in biologic matrices without a need for complex sample preparation is presented. The method is capable of determining whether high-MW PEG is cleaved in vivo to lower-molecular weight PEG species. Reversed-phase chromatographic separation is used to take advantage of the retention principles of polymeric materials whereby elution order correlates with PEG molecular weight. In-source collision-induced dissociation (CID) combined with selected reaction monitoring (SRM) or selected ion monitoring (SIM) mass spectrometry (MS) is then used to monitor characteristic PEG fragment ions in biological samples. MS provides high sensitivity and specificity for PEG and the observed retention times in reversed-phase LC enable estimation of molecular weight. This method was successfully used to characterize PEG molecular weight in mouse serum samples. No change in molecular weight was observed for 48 h after dosing.

Metabolism of AGEs – Bacterial AGEs Are Degraded by Metallo-Proteases

PubMed Central

Cohen-Or, Ifat; Katz, Chen; Ron, Eliora Z.

2013-01-01

Advanced Glycation End Products (AGEs) are the final products of non-enzymatic protein glycation that results in loss of protein structure and function. We have previously shown that in E. coli AGEs are continually formed as high-molecular weight protein complexes. Moreover, we showed that AGEs are removed from the cells by an active, ATP-dependent secretion and that these secreted molecules have low molecular weight. Taken together, these results indicate that E. coli contains a fraction of low molecular weight AGEs, in addition to the high-molecular weight AGEs. Here we show that the low-molecular weight AGEs originate from high-molecular weight AGEs by proteolytic degradation. Results of in-vitro and in vivo experiments indicated that this degradation is carried out not by the major ATP-dependent proteases that are responsible for the main part of bacterial protein quality control but by an alternative metal-dependent proteolysis. This proteolytic reaction is essential for the further secretion of AGEs from the cells. As the biochemical reactions involving AGEs are not yet understood, the implication of a metalloprotease in breakdown of high molecular weight AGEs and their secretion constitutes an important step in the understanding of AGEs metabolism. PMID:24130678

Metabolism of AGEs--bacterial AGEs are degraded by metallo-proteases.

PubMed

Cohen-Or, Ifat; Katz, Chen; Ron, Eliora Z

2013-01-01

Advanced Glycation End Products (AGEs) are the final products of non-enzymatic protein glycation that results in loss of protein structure and function. We have previously shown that in E. coli AGEs are continually formed as high-molecular weight protein complexes. Moreover, we showed that AGEs are removed from the cells by an active, ATP-dependent secretion and that these secreted molecules have low molecular weight. Taken together, these results indicate that E. coli contains a fraction of low molecular weight AGEs, in addition to the high-molecular weight AGEs. Here we show that the low-molecular weight AGEs originate from high-molecular weight AGEs by proteolytic degradation. Results of in-vitro and in vivo experiments indicated that this degradation is carried out not by the major ATP-dependent proteases that are responsible for the main part of bacterial protein quality control but by an alternative metal-dependent proteolysis. This proteolytic reaction is essential for the further secretion of AGEs from the cells. As the biochemical reactions involving AGEs are not yet understood, the implication of a metalloprotease in breakdown of high molecular weight AGEs and their secretion constitutes an important step in the understanding of AGEs metabolism.

Improving the accuracy of hyaluronic acid molecular weight estimation by conventional size exclusion chromatography.

PubMed

Shanmuga Doss, Sreeja; Bhatt, Nirav Pravinbhai; Jayaraman, Guhan

2017-08-15

There is an unreasonably high variation in the literature reports on molecular weight of hyaluronic acid (HA) estimated using conventional size exclusion chromatography (SEC). This variation is most likely due to errors in estimation. Working with commercially available HA molecular weight standards, this work examines the extent of error in molecular weight estimation due to two factors: use of non-HA based calibration and concentration of sample injected into the SEC column. We develop a multivariate regression correlation to correct for concentration effect. Our analysis showed that, SEC calibration based on non-HA standards like polyethylene oxide and pullulan led to approximately 2 and 10 times overestimation, respectively, when compared to HA-based calibration. Further, we found that injected sample concentration has an effect on molecular weight estimation. Even at 1g/l injected sample concentration, HA molecular weight standards of 0.7 and 1.64MDa showed appreciable underestimation of 11-24%. The multivariate correlation developed was found to reduce error in estimations at 1g/l to <4%. The correlation was also successfully applied to accurately estimate the molecular weight of HA produced by a recombinant Lactococcus lactis fermentation. Copyright © 2017 Elsevier B.V. All rights reserved.

How Molecular Structure Affects Mechanical Properties of an Advanced Polymer

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

2000-01-01

density was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength all as a function of molecular weight and test temperature were determined. For the uncrosslinked SI material, it was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. For the crosslinked PETI-SI material, it was shown that the effect of crosslinking significantly enhances the mechanical performance of the low molecular weight material; comparable to that exhibited by the high molecular weight material.

Enhancement of mechanical properties of 3D printed hydroxyapatite by combined low and high molecular weight polycaprolactone sequential infiltration.

PubMed

Suwanprateeb, Jintamai; Thammarakcharoen, Faungchat; Hobang, Nattapat

2016-11-01

A new infiltration technique using a combination of low and high molecular weight polycaprolactone (PCL) in sequence was developed as a mean to improve the mechanical properties of three dimensional printed hydroxyapatite (HA). It was observed that using either high (M n ~80,000) or low (M n ~10,000) molecular weight infiltration could only increase the flexural modulus compared to non-infiltrated HA, but did not affect strength, strain at break and energy at break. In contrast, a combination of low and high molecular infiltration in sequence increased the flexural modulus, strength and energy at break compared to those of non-infiltrated HA or infiltrated by high or low molecular weight PCL alone. This overall enhancement was found to be attributed to the densification of low molecular weight PCL and the reinforcement of high molecular PCL concurrently. The combined low and high molecular weight infiltration in sequence also maintained high osteoblast proliferation and differentiation of the composites at the similar level of the HA. Densification was a dominant mechanism for the change in modulus with porosity and density of the infiltrated HA/PCL composites. However, both densification and the reinforcing performance of the infiltration phase were crucial for strength and toughening enhancement of the composites possibly by the defect healing and stress shielding mechanisms. The sequence of using low molecular weight infiltration and followed by high molecular infiltration was seen to provide the greatest flexural properties and highest cells proliferation and differentiation capabilities.

Origin of change in molecular-weight dependence for polymer surface tension.

PubMed

Thompson, R B; Macdonald, J R; Chen, P

2008-09-01

Self-consistent-field theory is used to reproduce the behavior of polymer surface tension with molecular-weight for both lower and higher molecular-weight polymers. The change in behavior of the surface tension between these two regimes is shown to be due to the almost total exclusion of polymer from the nonpolymer bulk phase. The predicted two regime surface tension behavior with molecular-weight and the exclusion explanation are shown to be valid for a range of different polymer compressibilities.

Rare expression of high-molecular-weight cytokeratin in adenocarcinoma of the prostate gland: a study of 100 cases of metastatic and locally advanced prostate cancer.

PubMed

Yang, X J; Lecksell, K; Gaudin, P; Epstein, J I

1999-02-01

Immunohistochemistry with antibodies for high-molecular-weight cytokeratin labels basal cells and is used as an ancillary study in diagnosing prostate carcinoma, which reportedly lacks expression of high-molecular-weight cytokeratin. A recent report questioned the specificity of this marker, describing immunopositivity for high-molecular-weight cytokeratin in a small series of metastatic prostate cancer. We have also noted rare cases of prostate lesions on biopsy with typical histological features of adenocarcinoma showing immunopositivity for high-molecular-weight cytokeratin, either in tumor cells or in patchy cells with the morphology of basal cells. In some of these cases, it was difficult to distinguish cancer from out-pouching of high-grade prostatic intraepithelial neoplasia. To investigate whether prostate cancer cells express high-molecular-weight cytokeratin, we studied 100 cases of metastatic prostate carcinoma and 10 cases of prostate cancer invading the seminal vesicles from surgical specimens. Metastatic sites included regional lymph nodes (n = 67), bone (n = 19), and miscellaneous (n = 14). Cases with any positivity for high-molecular-weight cytokeratin antibody (34betaE12) were verified as being of prostatic origin with immunohistochemistry for prostate-specific antigen and prostate-specific acid phosphatase. Only four cases were detected positive for high-molecular-weight cytokeratin. In two cases (one metastasis, one seminal vesicle invasion) there was weakly diffuse positivity above background level. Two metastases in lymph nodes showed scattered strong staining of clusters of tumor cells, which represented <0.2% of tumor cells in the metastatic deposits. These positive cells did not have the morphology of basal cells. We conclude that prostate cancer, even high grade, only rarely expresses high-molecular-weight cytokeratin. This marker remains a very useful adjunct in the diagnosis of prostate cancer.

High and low molecular weight hyaluronic acid differentially influence macrophage activation

PubMed Central

Rayahin, Jamie E.; Buhrman, Jason S.; Zhang, Yu; Koh, Timothy J.; Gemeinhart, Richard A.

2015-01-01

Macrophages exhibit phenotypic diversity permitting wide-ranging roles in maintaining physiologic homeostasis. Hyaluronic acid, a major glycosaminoglycan of the extracellular matrix, has been shown to have differential signaling based on its molecular weight. With this in mind, the main objective of this study was to elucidate the role of hyaluronic acid molecular weight on macrophage activation and reprogramming. Changes in macrophage activation were assessed by activation state selective marker measurement, specifically quantitative real time polymerase chain reaction, and cytokine enzyme-linked immunoassays, after macrophage treatment with differing molecular weights of hyaluronic acid under four conditions: the resting state, concurrent with classical activation, and following inflammation involving either classically or alternatively activated macrophages. Regardless of initial polarization state, low molecular weight hyaluronic acid induced a classically activated-like state, confirmed by up-regulation of pro-inflammatory genes, including nos2, tnf, il12b, and cd80, and enhanced secretion of nitric oxide and TNF-α. High molecular weight hyaluronic acid promoted an alternatively activated-like state, confirmed by up regulation of pro-resolving gene transcription, including arg1, il10, and mrc1, and enhanced arginase activity. Overall, our observations suggest that macrophages undergo phenotypic changes dependent on molecular weight of hyaluronan that correspond to either (1) pro-inflammatory response for low molecular weight HA or (2) pro-resolving response for high molecular weight HA. These observations bring significant further understanding of the influence of extracellular matrix polymers, hyaluronic acid in particular, on regulating the inflammatory response of macrophages. This knowledge can be used to guide the design of HA-containing biomaterials to better utilize the natural response to HAs. PMID:26280020

21 CFR 178.3750 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2010 CFR

2010-04-01

... conditions: (a) The additive is an addition polymer of ethylene oxide and water with a mean molecular weight of 200 to 9,500. (b) It contains no more than 0.2 percent total by weight of ethylene and diethylene... ethylene and diethylene glycols if its mean molecular weight is below 350, when tested by the analytical...

Effect of molecular weight of starch on the properties of cassava starch microspheres prepared in aqueous two-phase system.

PubMed

Xia, Huiping; Li, Bing-Zheng; Gao, Qunyu

2017-12-01

Starch microspheres (SMs) were fabricated in an aqueous two-phase system (ATPS). A series of starch samples with different molecular weight were prepared by acid hydrolysis, and the effect of molecular weight of starch on the fabrication of SMs were investigated. Scanning electron microscopy (SEM) showed that the morphologies of SMs varied with starch molecular weight, and spherical SMs with sharp contours were obtained while using starch samples with weight-average molecular weight (M¯w)≤1.057×10 5 g/mol. X-ray diffraction (XRD) results revealed that crystalline structure of SMs were different from that of native cassava starch, and the relative crystallinity of SMs increased with the molecular weight of starch decreasing. Differential scanning calorimetry (DSC) results showed peak gelatinization temperature (T p ) and enthalpy of gelatinization (ΔH) of SMs increased with decreased M¯wof starch. Stability tests indicated that the SMs were stable under acid environment, but not stable under α-amylase hydrolysis. Copyright © 2017. Published by Elsevier Ltd.

A study on the quality control of slow burning polyester

NASA Astrophysics Data System (ADS)

Chen, Bin; Wang, Yinglei; Yan, Zhengfeng; Yu, Tao

2018-04-01

In this paper, the influence of the alcohol/acid mole ratio, reaction temperature, warm-up mode, end-capping, vacuity to the quality of slow burning polyester was studied. The hydroxyl value will increase when the alcohol/acid mole ratio increase, but the acid value and molecular weight will decrease. The molecular weight and molecular weight distribution of the polyester consistent with the designed one can be obtained by stepped heating up. Monobasic alcohol end-capping can be used to control the molecular weight effectively and reduce acid value. Stripping process narrow the molecular weight distribution and reduce the hydroxyl value. Decompression is in favor of the decrease of acid value and increase of the reaction speed to get qualified production.

Highly Conductive Ionic-Liquid Gels Prepared with Orthogonal Double Networks of a Low-Molecular-Weight Gelator and Cross-Linked Polymer.

PubMed

Kataoka, Toshikazu; Ishioka, Yumi; Mizuhata, Minoru; Minami, Hideto; Maruyama, Tatsuo

2015-10-21

We prepared a heterogeneous double-network (DN) ionogel containing a low-molecular-weight gelator network and a polymer network that can exhibit high ionic conductivity and high mechanical strength. An imidazolium-based ionic liquid was first gelated by the molecular self-assembly of a low-molecular-weight gelator (benzenetricarboxamide derivative), and methyl methacrylate was polymerized with a cross-linker to form a cross-linked poly(methyl methacrylate) (PMMA) network within the ionogel. Microscopic observation and calorimetric measurement revealed that the fibrous network of the low-molecular-weight gelator was maintained in the DN ionogel. The PMMA network strengthened the ionogel of the low-molecular-weight gelator and allowed us to handle the ionogel using tweezers. The orthogonal DNs produced ionogels with a broad range of storage elastic moduli. DN ionogels with low PMMA concentrations exhibited high ionic conductivity that was comparable to that of a neat ionic liquid. The present study demonstrates that the ionic conductivities of the DN and single-network, low-molecular-weight gelator or polymer ionogels strongly depended on their storage elastic moduli.

Mapping health outcome measures from a stroke registry to EQ-5D weights.

PubMed

Ghatnekar, Ola; Eriksson, Marie; Glader, Eva-Lotta

2013-03-07

To map health outcome related variables from a national register, not part of any validated instrument, with EQ-5D weights among stroke patients. We used two cross-sectional data sets including patient characteristics, outcome variables and EQ-5D weights from the national Swedish stroke register. Three regression techniques were used on the estimation set (n=272): ordinary least squares (OLS), Tobit, and censored least absolute deviation (CLAD). The regression coefficients for "dressing", "toileting", "mobility", "mood", "general health" and "proxy-responders" were applied to the validation set (n=272), and the performance was analysed with mean absolute error (MAE) and mean square error (MSE). The number of statistically significant coefficients varied by model, but all models generated consistent coefficients in terms of sign. Mean utility was underestimated in all models (least in OLS) and with lower variation (least in OLS) compared to the observed. The maximum attainable EQ-5D weight ranged from 0.90 (OLS) to 1.00 (Tobit and CLAD). Health states with utility weights <0.5 had greater errors than those with weights ≥ 0.5 (P<0.01). This study indicates that it is possible to map non-validated health outcome measures from a stroke register into preference-based utilities to study the development of stroke care over time, and to compare with other conditions in terms of utility.

Absolute instabilities of travelling wave solutions in a Keller-Segel model

NASA Astrophysics Data System (ADS)

Davis, P. N.; van Heijster, P.; Marangell, R.

2017-11-01

We investigate the spectral stability of travelling wave solutions in a Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity function and a constant, sublinear, and linear consumption rate. Linearising around the travelling wave solutions, we locate the essential and absolute spectrum of the associated linear operators and find that all travelling wave solutions have parts of the essential spectrum in the right half plane. However, we show that in the case of constant or sublinear consumption there exists a range of parameters such that the absolute spectrum is contained in the open left half plane and the essential spectrum can thus be weighted into the open left half plane. For the constant and sublinear consumption rate models we also determine critical parameter values for which the absolute spectrum crosses into the right half plane, indicating the onset of an absolute instability of the travelling wave solution. We observe that this crossing always occurs off of the real axis.

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2011 CFR

2011-04-01

... the total ethylene and diethylene glycol content of polyethylene glycols having mean molecular weights... and diethylene glycol content of polyethylene glycols having mean molecular weights below 450. Analytical Method ethylene glycol and diethylene glycol content of polyethylene glycols The analytical method...

Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight

PubMed Central

Zhang, Yanjie; Furyk, Steven; Sagle, Laura B.; Cho, Younhee; Bergbreiter, David E.; Cremer, Paul S.

2008-01-01

The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two step transition was found to be sensitive to the polymer’s molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer’s molecular weight or solution concentration. PMID:18820735

How Does the Preparation of Rye Porridge Affect Molecular Weight Distribution of Extractable Dietary Fibers?

PubMed Central

Rakha, Allah; Åman, Per; Andersson, Roger

2011-01-01

Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance. PMID:21686191

How does the preparation of rye porridge affect molecular weight distribution of extractable dietary fibers?

PubMed

Rakha, Allah; Aman, Per; Andersson, Roger

2011-01-01

Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance.

Molecular Weight Determination by an Improved Temperature-Monitored Vapor-Density Method.

ERIC Educational Resources Information Center

Grider, Douglas J.; And Others

1988-01-01

Recommends determining molecular weights of liquids by use of a thermocouple. Utilizing a mathematical gas equation, the molecular weight can be determined from the measurement of the vapor temperature upon complete evaporation. Lists benefits as reduced time and cost, and improved safety factors. (ML)

Factors that affect molecular weight distribution of Suwannee river fulvic acid as determined by electrospray ionization/mass spectrometry

USGS Publications Warehouse

Rostad, Colleen E.; Leenheer, Jerry A.

2004-01-01

Effects of methylation, molar response, multiple charging, solvents, and positive and negative ionization on molecular weight distributions of aquatic fulvic acid were investigated by electrospray ionization/mass spectrometry. After preliminary analysis by positive and negative modes, samples and mixtures of standards were derivatized by methylation to minimize ionization sites and reanalyzed.Positive ionization was less effective and produced more complex spectra than negative ionization. Ionization in methanol/water produced greater response than in acetonitrile/water. Molar response varied widely for the selected free acid standards when analyzed individually and in a mixture, but after methylation this range decreased. After methylation, the number average molecular weight of the Suwannee River fulvic acid remained the same while the weight average molecular weight decreased. These differences are probably indicative of disaggregation of large aggregated ions during methylation. Since the weight average molecular weight decreased, it is likely that aggregate formation in the fulvic acid was present prior to derivatization, rather than multiple charging in the mass spectra.

Molecular weight kinetics and chain scission models for dextran polymers during ultrasonic degradation.

PubMed

Pu, Yuanyuan; Zou, Qingsong; Hou, Dianzhi; Zhang, Yiping; Chen, Shan

2017-01-20

Ultrasonic degradation of six dextran samples with different initial molecular weights (IMW) has been performed to investigate the degradation behavior and chain scission mechanism of dextrans. The weight-average molecular weight (Mw) and polydispersity index (D value) were monitored by High Performance Gel Permeation Chromatography (HPGPC). Results showed that Mw and D value decreased with increasing ultrasonic time, resulting in a more homologous dextran solution with lower molecular weight. A significant degradation occurred in dextrans with higher IMW, particularly at the initial stage of the ultrasonic treatment. The Malhotra model was found to well describe the molecular weight kinetics for all dextran samples. Experimental data was fitted into two chain scission models to study dextran chain scission mechanism and the model performance was compared. Results indicated that the midpoint scission model agreed well with experimental results, with a linear regression factor of R 2 >0.99. Copyright © 2016 Elsevier Ltd. All rights reserved.

12 CFR 217.152 - Simple risk weight approach (SRWA).

Code of Federal Regulations, 2014 CFR

2014-01-01

... than or equal to -1 (that is, between zero and -1), then E equals the absolute value of RVC. If RVC is... this section. (1) Zero percent risk weight equity exposures. An equity exposure to an entity whose credit exposures are exempt from the 0.03 percent PD floor in § 217.131(d)(2) is assigned a zero percent...

Occurrence of a multimeric high-molecular-weight glyceraldehyde-3-phosphate dehydrogenase in human serum.

PubMed

Kunjithapatham, Rani; Geschwind, Jean-Francois; Devine, Lauren; Boronina, Tatiana N; O'Meally, Robert N; Cole, Robert N; Torbenson, Michael S; Ganapathy-Kanniappan, Shanmugasundaram

2015-04-03

Cellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a phylogenetically conserved, ubiquitous enzyme that plays an indispensable role in energy metabolism. Although a wealth of information is available on cellular GAPDH, there is a clear paucity of data on its extracellular counterpart (i.e., the secreted or extracellular GAPDH). Here, we show that the extracellular GAPDH in human serum is a multimeric, high-molecular-weight, yet glycolytically active enzyme. The high-molecular-weight multimers of serum GAPDH were identified by immunodetection on one- and two-dimensional gel electrophoresis using multiple antibodies specific for various epitopes of GAPDH. Partial purification of serum GAPDH by DEAE Affigel affinity/ion exchange chromatography further established the multimeric composition of serum GAPDH. In vitro data demonstrated that human cell lines secrete a multimeric, high-molecular-weight enzyme similar to that of serum GAPDH. Furthermore, LC-MS/MS analysis of extracellular GAPDH from human cell lines confirmed the presence of unique peptides of GAPDH in the high-molecular-weight subunits. Furthermore, data from pulse-chase experiments established the presence of high-molecular-weight subunits in the secreted, extracellular GAPDH. Taken together, our findings demonstrate the presence of a high-molecular-weight, enzymatically active secretory GAPDH in human serum that may have a hitherto unknown function in humans.

Ultrarapid electrophoretic transfer of high and low molecular weight proteins using heat.

PubMed

Kurien, Biji T; Scofield, R Hal

2009-01-01

An ultrarapid method for the electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate (SDS) polyacrylamide gel is described here. The transfer was performed with heated (70-75 degrees C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight antigens (molecular weight protein standards, a purified protein, and proteins from a human tissue extract) could be carried out in 10 min for a 7% (0.75 mm) SDS polyacrylamide gel. For 10 and 12.5% gels (0.75 mm) the corresponding time was 15 min. A complete transfer could be carried out in 20 min for 7, 10, and 12.5% gels (1.5 mm gels). The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. The heat mediated transfer method was compared with a conventional transfer protocol, under similar conditions. The conventional method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is particularly useful for the transfer of high molecular weight proteins, very rapid, and avoids the use of methanol.

Western blotting of high and low molecular weight proteins using heat.

PubMed

Kurien, Biji T; Scofield, R Hal

2015-01-01

A method for the electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate (SDS) polyacrylamide gel is described here. The transfer was performed with heated (70-75 °C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight antigens (molecular weight protein standards, a purified protein, and proteins from a human tissue extract) could be carried out in 10 min for a 7 % (0.75 mm) SDS polyacrylamide gel. For 10 and 12.5 % gels (0.75 mm) the corresponding time was 15 min. A complete transfer could be carried out in 20 min for 7, 10, and 12.5 % gels (1.5 mm gels). The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. The heat mediated transfer method was compared with a conventional transfer protocol, under similar conditions. The conventional method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is particularly useful for the transfer of high molecular weight proteins, very rapid, and avoids the use of methanol.

Hyaluronic Acid Molecular Weight-Dependent Modulation of Mucin Nanostructure for Potential Mucosal Therapeutic Applications.

PubMed

Hansen, Irene M; Ebbesen, Morten F; Kaspersen, Liselotte; Thomsen, Troels; Bienk, Konrad; Cai, Yunpeng; Malle, Birgitte Mølholm; Howard, Kenneth A

2017-07-03

This study investigates the effects of different molecular weight hyaluronic acids (HAs) on the mucosal nanostructure using a pig stomach mucin hydrogel as a mucosal barrier model. Microparticles (1.0 μm) and nanoparticles (200 nm) were used as probes, and their movement in mucin was studied by a three-dimensional confocal microscopy-based particle tracking technique and by Nanoparticle Tracking Analysis (NTA) after addition of high-molecular weight (900 kDa) and low-molecular weight (33 kDa) HA. This demonstrated a molecular weight-dependent HA modulation of the mucin nanostructure with a 2.5-fold decrease in the mobility of 200 nm nanoparticles. To further investigate these mechanisms and to verify that the natural viscoelastic properties of mucus are not undesirably altered, rheological measurements were performed on mucin hydrogels with or without HA. This suggested the observed particle mobility restriction was not attributed to alterations of the natural mucin cohesive and viscoelastic properties but, instead, indicates that the added high-molecular weight HA primarily modulates the mucin nanostructure and mesh size. This study, hereby, demonstrates how mucus nanostructure can be modulated by the addition of high-molecular weight HA that offers an opportunity to control mucosal pathogenesis and drug delivery.

Correlation of the physicochemical properties of natural organic matter samples from different sources to their effects on gold nanoparticle aggregation in monovalent electrolyte.

PubMed

Louie, Stacey M; Spielman-Sun, Eleanor R; Small, Mitchell J; Tilton, Robert D; Lowry, Gregory V

2015-02-17

Engineered nanoparticles (NPs) released into natural environments will interact with natural organic matter (NOM) or humic substances, which will change their fate and transport behavior. Quantitative predictions of the effects of NOM are difficult because of its heterogeneity and variability. Here, the effects of six types of NOM and molecular weight fractions of each on the aggregation of citrate-stabilized gold NPs are investigated. Correlations of NP aggregation rates with electrophoretic mobility and the molecular weight distribution and chemical attributes of NOM (including UV absorptivity or aromaticity, functional group content, and fluorescence) are assessed. In general, the >100 kg/mol components provide better stability than lower molecular weight components for each type of NOM, and they contribute to the stabilizing effect of the unfractionated NOM even in small proportions. In many cases, unfractionated NOM provided better stability than its separated components, indicating a synergistic effect between the high and low molecular weight fractions for NP stabilization. Weight-averaged molecular weight was the best single explanatory variable for NP aggregation rates across all NOM types and molecular weight fractions. NP aggregation showed poorer correlation with UV absorptivity, but the exponential slope of the UV-vis absorbance spectrum was a better surrogate for molecular weight. Functional group data (including reduced sulfur and total nitrogen content) were explored as possible secondary parameters to explain the strong stabilizing effect of a low molecular weight Pony Lake fulvic acid sample to the gold NPs. These results can inform future correlations and measurement requirements to predict NP attachment in the presence of NOM.

An evaluation of the effects of PEO/PEG molecular weights on extruded alumina rods

NASA Astrophysics Data System (ADS)

Bolger, Nancy Beth

1998-12-01

Alumina rods were piston extruded from bodies containing polyethylene glycols (PEGs) and polyethylene oxides (PEOs) with molecular weights ranging from 1,300 to 3,800,000 g/mol. A blend of aluminas possessing different particle size distributions was evaluated with regard to its extrusion pressure by varying the amount of PEG/PEO addition. Behavior exhibited by the alumina blend was dependent upon the additive that was used. The higher molecular weight binders with average molecular weight of 200,000 g/mol and 3,350,000 g/mol displayed the most severe behaviors of near dilatant and dilatant respectively. Physical properties of the green and fired states, as well as the binder burnout, were investigated with the changing additions. Correlation between the green and fired strengths and the changing molecular weights were examined. The additive present influenced the surface properties of the rods, which affected the green strengths. The highest average molecular weight polyethylene glycols showed higher green strengths, while the lowest green strengths were observed for the high molecular weight polyethylene oxides. Fired strengths generally ranged from approximately 12,000 psi to 16,000 psi for additive batches. Alumina pellets containing twelve separate combinations of polyethylene glycol with polyethylene oxide were dry pressed. Physical properties of the green and fired states were examined. Statistical analysis was performed upon the data and seven combinations of polyethylene glycol with polyethylene oxide were deemed significant. These combinations in conjunction with the same alumina blend were then piston extruded. The addition of polyethylene glycol reduced the near dilatant behavior exhibited by the 200,000 g/mol average molecular weight polyethylene oxide. Dilatant behavior was completely eliminated from the 3,350,000 g/mol average molecular weight polyethylene oxide batches. Physical properties of the green and fired states were again investigated with the changing additions. Polyethylene oxide, in combination with polyethylene glycol, did show an increase in green strength versus the polyethylene oxide alone. Strengths were still lower than those displayed by the polyethylene glycols alone. Reductions or degradations in molecular weight of the polymers due to mixing and extrusion processes may account for lower green strength of bodies, especially those containing polyethylene oxides.

Developmental toxicity study in rats exposed dermally to clarified slurry oil for a limited period of gestation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feuston, M.H.; Mackerer, C.R.

1996-10-11

Clarified slurry oil (CSO, CAS number 64741-62-4), a refinery stream produced by processing crude oil, is a developmental toxicant when administered dermally throughout gestation to pregnant rats. The manifestations of developmental toxicity observed included embryolethlity and growth retardation; evidence of teratogenicity was limited, and not conclusive. The present study was undertaken to further explore the teratogenic potential of CSO. In an attempt to limit emnbryolethality and thereby promote detection of terata, CSO was administered once daily for a limited period of gestation i[gestation days (GD) 9-12], via dermal application, to pregnant Sprague-Dawley rats at doses of 0, 10, 100, andmore » 1000 mg/kg. All animals were sacrificed on GD 20. Detailed examination of the dams was performed. Due to the screening nature of this investigation, fetal evaluations were limited to body weight measurements, external examinations, and evaluation of select visceral endpoints. In the dams exposed to CSO, significant decreases in body weight [absolute and gain (GD 9-13, GD 0-20)] and in the amount of food consumed were observed at 100 and 1000 mg/kg. Additional evidence of maternal toxicity observed at 1000 mg/kg included decreased absolute and relative thymus weights, increased absolute and relative liver weights, and aberrant serum chemistry. Ingestion of the test material was evident at the high dose. Developmental toxicity was observed at 1000 mg/kg and included increased embryolethality, decreased body weight, and anomalous development (cleft palate, brachydactyly, edema). Although a low incidence of abnormal fetal development was observed at 100 mg/kg, it was not conclusive that the alterations were due to CSO exposure. It is likely that three- to seven-ring polycyclic aromatic compounds present in CSO were responsible for the toxic effects observed. 33 refs., 5 tabs.« less

Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss

PubMed Central

Weiss, Edward P.; Racette, Susan B.; Villareal, Dennis T.; Fontana, Luigi; Steger-May, Karen; Schechtman, Kenneth B.; Klein, Samuel; Ehsani, Ali A.; Holloszy, John O.

2015-01-01

Caloric restriction (CR) results in fat loss; however, it may also result in loss of muscle and thereby reduce strength and aerobic capacity (V̇O2 max). These effects may not occur with exercise-induced weight loss (EX) because of the anabolic effects of exercise on heart and skeletal muscle. We tested the hypothesis that CR reduces muscle size and strength and V̇O2 max, whereas EX preserves or improves these parameters. Healthy 50- to 60-yr-old men and women (body mass index of 23.5–29.9 kg/m2) were studied before and after 12 mo of weight loss by CR (n = 18) or EX (n = 16). Lean mass was assessed by dual-energy X-ray absorptiometry, thigh muscle volume by MRI, isometric and isokinetic knee flexor strength by dynamometry, and treadmill V̇O2 max by indirect calorimetry. Both interventions caused significant decreases in body weight (CR: −10.7 ± 1.4%, EX: −9.5 ± 1.5%) and lean mass (CR: −3.5 ± 0.7%, EX: −2.2 ± 0.8%), with no significant differences between groups. Significant decreases in thigh muscle volume (−6.9 ± 0.8%) and composite knee flexion strength (−7.2 ± 3%) occurred in the CR group only. Absolute V̇O2 max decreased significantly in the CR group (−6.8 ± 2.3%), whereas the EX group had significant increases in both absolute (+15.5 ± 2.4%) and relative (+28.3 ± 3.0%) V̇O2 max. These data provide evidence that muscle mass and absolute physical work capacity decrease in response to 12 mo of CR but not in response to a similar weight loss induced by exercise. These findings suggest that, during EX, the body adapts to maintain or even enhance physical performance capacity. PMID:17095635

Branched chain amino acids maintain the molecular weight of poly(γ-glutamic acid) of Bacillus licheniformis ATCC 9945 during the fermentation.

PubMed

Mitsunaga, Hitoshi; Meissner, Lena; Büchs, Jochen; Fukusaki, Eiichiro

2016-10-01

Poly(γ-glutamic acid) mainly produced by Bacillus spp. is an industrially important compound due to several useful features. Among them, molecular weight is an important characteristic affecting on the physical properties such as viscosities and negative charge densities. However, it is difficult to control the molecular size of PGA since it decreases during fermentation. Previous study reported that PGA produced in the media containing different carbon sources such as glucose and glycerol showed differences in molecular weight. Therefore in this study, the effect of carbon source on the PGA molecular weight was examined; with the aim of developing a strategy to maintain the high molecular weight of PGA during fermentation. Our result showed that the weight average molecular weight (Mw) of PGA of Bacillus licheniformis ATCC 9945 cultivated in the media containing PTS-sugars were higher than the medium containing glycerol (non-PTS). The result of metabolome analysis indicated the possibility of CodY (a global regulator protein) activation in the cells cultivated in the media containing PTS-sugars. To mimic this effect, branched-chain amino acids (BCAAs), which are activators of CodY, were added to a medium containing glycerol. As the result, the Mw of PGA in the BCAAs-supplemented media were maintained and high during the early production phase compared to the non BCAAs-supplemented medium. These results indicate that BCAAs can repress the PGA molecular weight reduction during fermentation in B. licheniformis ATCC 9945. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Long-term low-molecular-weight heparin and the post-thrombotic syndrome: a systematic review.

PubMed

Hull, Russell D; Liang, Jane; Townshend, Grace

2011-08-01

Post-thrombotic syndrome causes considerable morbidity. The Home-LITE study showed a lower incidence of post-thrombotic syndrome and venous ulcers after 3 months of treating deep vein thrombosis with the low-molecular-weight heparin tinzaparin versus oral anticoagulation. This systematic review examined whether long-term treatment of deep vein thrombosis using low-molecular-weight heparin, rather than oral anticoagulation, reduces development of post-thrombotic syndrome. We identified 9 articles comparing treatment of deep vein thrombosis using long-term low-molecular-weight heparin with any comparator, which reported outcomes relevant to the post-thrombotic syndrome assessed ≥ 3 months post-deep vein thrombosis. Pooled analysis of 2 studies yielded an 87% risk reduction with low-molecular-weight heparin in the incidence of venous ulcers at ≥ 3 months (P = .019). One study showed an overall odds ratio of 0.77 (P = .001) favoring low-molecular-weight heparin for the presence of 8 patient-reported post-thrombotic syndrome signs and symptoms. Pooled analysis of 5 studies showed a risk ratio for low-molecular-weight heparin versus oral anticoagulation of 0.66 (P < .0001) for complete recanalization of thrombosed veins. These results support the lower incidence of post-thrombotic syndrome and venous ulcers observed in Home-LITE. Long-term treatment with low-molecular-weight heparin rather than oral anticoagulation after a deep vein thrombosis may reduce or prevent development of signs and symptoms associated with post-thrombotic syndrome. Post-thrombotic syndrome and associated acute ulcers may develop more rapidly after deep vein thrombosis than previously recognized. Copyright © 2011 Elsevier Inc. All rights reserved.

Absolute cross sections for electronic excitation of condensed tetrahydrofuran (THF) by 11-16 eV electrons.

PubMed

Lemelin, V; Bass, A D; Cloutier, P; Sanche, L

2016-11-07

Absolute cross section (CS) data on the interaction of low energy electrons with DNA and its molecular constituents are required as input parameters in Monte-Carlo type simulations, for several radiobiological applications. Previously [V. Lemelin et al., J. Chem. Phys. 144, 074701 (2016)], we measured absolute vibrational CSs for low-energy electron scattering from condensed tetrahydrofuran, a convenient surrogate for the deoxyribose. Here we report absolute electronic CSs for energy losses of between 6 and 11.5 eV, by electrons with energies between 11 and 16 eV. The variation of these CSs with incident electron energy shows no evidence of transient anion states, consistent with theoretical and other experimental results, indicating that initial electron capture leading to DNA strand breaks occurs primarily on DNA bases or the phosphate group.

A Simple, Inexpensive Molecular Weight Measurement for Water-Soluble Polymers Using Microemulsions.

ERIC Educational Resources Information Center

Mathias, Lon J.; Moore, D. Roger

1985-01-01

Describes an experiment involving use of a microemulsion and its characteristic thermal phase change to determine molecular weights of polyoxyethylene samples. The experiment provides students with background information on polymers and organized media and with experience in evaluating polymer molecular weight by using a unique property of a…

Determinations of molecular weight and molecular weight distribution of high polymers by the rheological properties

NASA Technical Reports Server (NTRS)

Huang, J. Y.; Hou, T. H.; Tiwari, S. N.

1989-01-01

Several methods are reviewed by which the molecular weight (MW) and the molecular weight distribution (MWD) of polymeric material were determined from the rheological properties. A poly(arylene ether) polymer with six different molecular weights was used in this investigation. Experimentally measured MW and MWD were conducted by GPC/LALLS (gel permeation chromatography/low angle laser light scattering), and the rheological properties of the melts were measured by a Rheometric System Four rheometer. It was found that qualitative information of the MW and MWD of these polymers could be derived from the viscoelastic properties, with the methods proposed by Zeichner and Patel, and by Dormier et al., by shifting the master curves of the dynamic storage modulus, G', and the loss modulus, G'', along the frequency axis. Efforts were also made to calculate quantitative profiles of MW and MWD for these polymers from their rheological properties. The technique recently proposed by Wu was evaluated. It was found that satisfactory results could only be obtained for polymers with single modal distribution in the molecular weight.

Biological and structural analyses of bovine heparin fractions of intermediate and high molecular weight.

PubMed

Nogueira, Alexsandro V; Drehmer, Daiana L; Iacomini, Marcello; Sassaki, Guilherme L; Cipriani, Thales R

2017-02-10

Low molecular weight heparin, which is generally obtained by chemical and enzymatic depolymerization of unfractionated heparin, has high bioavailability and can be subcutaneously injected. The aim of the present investigation was to fractionate bovine heparin using a physical method (ultrafiltration through a 10kDa cut-off membrane), avoiding structural modifications that can be caused by chemical or enzymatic treatments. Two fractions with different molecular weights were obtained: the first had an intermediate molecular weight (B-IMWH; Mn=9587Da) and the other had a high molecular weight (B-HMWH; 22,396Da). B-IMWH and B-HMWH have anticoagulant activity of 103 and 154IU/mg respectively, which could be inhibited by protamine. Both fractions inhibited α-thrombin and factor Xa in vitro and showed antithrombotic effect in vivo. Moreover, ex vivo aPTT assay demonstrated that B-IMWH is absorbed by subcutaneous route. The results showed that ultrafiltration can be used to obtain two bovine heparin fractions, which differ on their molecular weights, structural components, anticoagulant potency, and administration routes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone

NASA Astrophysics Data System (ADS)

Gašparović, Blaženka; Penezić, Abra; Frka, Sanja; Kazazić, Saša; Lampitt, Richard S.; Holguin, F. Omar; Sudasinghe, Nilusha; Schaub, Tanner

2018-04-01

There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed "novel"). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160-300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.

Ultrafiltration for the Determination of Cu Complexed with Dissolved Organic Matters of Different Molecular Weight from a Eutrophic River, China.

PubMed

Li, Anding; Zhang, Yan; Zhou, Beihai; Xin, Kailing; Gu, Yingnan; Xu, Weijie; Tian, Jie

2018-05-21

The molecular weight of dissolved organic matter (DOM) is one of the essential factors controlling the properties of metal complexes. A continuous ultrafiltration experiment was designed to study the properties of Cu complexes with different molecular weights in a river before and after eutrophication. The results showed that the concentration of DOM increased from 26.47 to 38.20 mg/L during the eutrophication process, however, DOM was still dominated by the small molecular weight fraction before and after eutrophication. The amount of Cu-DOM complexes increased with the increasing of molecular weight, however, the amounts of DOM-Cu complexes before eutrophication were higher than those after eutrophication. This is because DOM contained more -COOH and -OH before eutrophication and these functional groups are the active sites complexed with Cu.

Enrichment of low-molecular-weight proteins from biofluids for biomarker discovery.

PubMed

Chertov, Oleg; Simpson, John T; Biragyn, Arya; Conrads, Thomas P; Veenstra, Timothy D; Fisher, Robert J

2005-01-01

The dramatic progress in mass spectrometry-based methods of protein identification has triggered a new quest for disease-associated biomarkers. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and its variant surface-enhanced laser desorption/ionization mass spectrometry, provide effective means to explore the less studied information slice of the human serum proteome -- low-molecular-weight proteins and peptides. These low-molecular-weight proteins and peptides are promising for the detection of important biomarkers. Due to the significant experimental problems imposed by high-abundance and high-molecular-weight proteins, it is important to effectively remove these species prior to mass spectrometry analysis of the low-molecular-weight serum and plasma proteomes. In this review, the advantages afforded by recently introduced methods for prefractionation of serum, as they pertain to the detection and identification of biomarkers, will be discussed.

EPDM polymers with intermolecular asymmetrical molecular weight, crystallinity and diene distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datta, S.; Cheremishinoff, N.P.; Kresge, E.N.

1993-12-31

Rapid extrusion of EPDM elastomers require low viscosity and thus low molecular weights for the polymer. Efficient vulcanization of these elastomers requires network perfection and thus high molecular weights for the polymer. The benefits of these apparently mutually exclusive goals is important in uses of EPDM elastomers which require extrusion of profiles which are later cured. This paper shows that by introducing simultaneously asymmetry in the distribution of molecular weights, crystallinity and vulcanizable sites these apparently contradictory goals can be resolved. While these polymers cannot be made from a single Ziegler polymerization catalyst, the authors show the synthesis of thesemore » model EPDM polymers by blending polymers with very different molecular weights, ethylene and ENB contents. These blends can be rapidly extruded without melt fracture and can be cured to vulcanizates which have excellent tensile properties.« less

Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight

USGS Publications Warehouse

Davis, J.A.; Gloor, R.

1981-01-01

Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (Mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements indicated that alumina particles suspended in the original lake water were highly negatively charged because of adsorbed organic matter. Most of the adsorbed organic compounds were in the Mr range 1000 < Mr < 3000. Adsorption of these compounds during the treatment of drinking water by alum coagulation may be responsible for the preferential removal of trihalomethane precursors. Adsorption may also influence the molecular-weight distribution of dissolved organic material in lakes. surface, the present work will focus on the influence of molecular size and pH on the adsorption behavior of dissolved organic material of a Swiss lake. From a geochemical point of view, it is important to know the molecular-weight distribution of adsorbed organic matter so that we may better assess its reactivity with trace elements. The study also serves as a first step in quantifying the role of adsorption in the geochemical cycle of organic carbon in lacustrine environments. For water-treatment practice, we need to determine whether molecular weight fractionation occurs during adsorption by aluminum oxide. Such a fractionation could be significant in the light of recent reports that chloroform and other organochlorine compounds are preferentially produced by particular molecular-weight fractions (25-27). ?? 1981 American Chemical Society.

Correlation between human maternal-fetal placental transfer and molecular weight of PCB and dioxin congeners/isomers.

PubMed

Mori, Chisato; Nakamura, Noriko; Todaka, Emiko; Fujisaki, Takeyoshi; Matsuno, Yoshiharu; Nakaoka, Hiroko; Hanazato, Masamichi

2014-11-01

Establishing methods for the assessment of fetal exposure to chemicals is important for the prevention or prediction of the child's future disease risk. In the present study, we aimed to determine the influence of molecular weight on the likelihood of chemical transfer from mother to fetus via the placenta. The correlation between molecular weight and placental transfer rates of congeners/isomers of polychlorinated biphenyls (PCBs) and dioxins was examined. Twenty-nine sample sets of maternal blood, umbilical cord, and umbilical cord blood were used to measure PCB concentration, and 41 sample sets were used to analyze dioxins. Placental transfer rates were calculated using the concentrations of PCBs, dioxins, and their congeners/isomers within these sample sets. Transfer rate correlated negatively with molecular weight for PCB congeners, normalized using wet and lipid weights. The transfer rates of PCB or dioxin congeners differed from those of total PCBs or dioxins. The transfer rate for dioxin congeners did not always correlate significantly with molecular weight, perhaps because of the small sample size or other factors. Further improvement of the analytical methods for dioxin congeners is required. The findings of the present study suggested that PCBs, dioxins, or their congeners with lower molecular weights are more likely to be transferred from mother to fetus via the placenta. Consideration of chemical molecular weight and transfer rate could therefore contribute to the assessment of fetal exposure. Copyright © 2014 Elsevier Ltd. All rights reserved.

[The value of low-molecular-weight DNA of blood plasma in the diagnostic of the patological processes of different genesis].

PubMed

Vasil'eva, I N; Zinkin, V N

2013-01-01

The low-molecular-weight DNA appears in blood plasma of irradiated rats, and its content correlates directly with the irradiation dose. Cloning has shown, that enrichment of low-molecular-weight DNA with G+C content and features of its nucleotide sequences point to its ability to form rather stable nucleosomes. DNA obtained after irradiation of rats with principally different doses 8 and 100 Gy differed not only quantitatively, but also by content of the dinucleotides CpG and CpT; this suggests their origin from different sites of genome. For the first time it has been shown that exposure to low-frequency noise results in an increase of the contents of blood plasma low-molecular-weight DNA. In stroke patients blood concentrations of this DNA increased 3 days after the beginning of the acute period, and dynamics of its excretion differs in ischemic and hemorrhagic forms; in the case of ischemia low-molecular-weight DNA appears in cerebrospinal fluid. The chronic obstructive pulmonary disease in the state of remission is characterized by the decline of the level of low-molecular-weight DNA in the blood plasma unlike in the case of the chronic nonobstructive bronchitis. The clear dependence between formation and special features of the low-molecular-weight DNA fraction in blood plasma makes it possible to consider the low-molecular fraction as an universal index of apoptosis, which allows to distinguish basically different conditions of the body.

Fossil fuel combined cycle power system

DOEpatents

Labinov, Solomon Davidovich; Armstrong, Timothy Robert; Judkins, Roddie Reagan

2006-10-10

A system for converting fuel energy to electricity includes a reformer for converting a higher molecular weight gas into at least one lower molecular weight gas, at least one turbine to produce electricity from expansion of at least one of the lower molecular weight gases, and at least one fuel cell. The system can further include at least one separation device for substantially dividing the lower molecular weight gases into at least two gas streams prior to the electrochemical oxidization step. A nuclear reactor can be used to supply at least a portion of the heat the required for the chemical conversion process.

Effect of sterilization irradiation on friction and wear of ultrahigh-molecular-weight polyethylene

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Hady, W. F.; Crugnola, A.

1979-01-01

The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against 316L stainless steel in dry air at 23 C was determined. A pin-on-disk apparatus was used. Experimental conditions included a 1-kilogram load, a 0.061- to 0.27-meter-per-second sliding velocity, and a 32000- to 578000-meter sliding distance. Although sterilization doses of 2.5 and 5.0 megarads greatly altered the average molecular weight and the molecular weight distribution, the friction and wear properties of the polymer were not significantly changed.

Low molecular weight species in humic and fulvic fractions

USGS Publications Warehouse

Wilson, M.A.; Collin, P.J.; Malcolm, R.L.; Perdue, E. Michael; Cresswell, P.

1988-01-01

Fourier transform solution 1H nuclear magnetic resonance (NMR) spectrometry with homogated water peak irradiation is a useful method for detecting low molecular weight substances in humic extracts. Succinate, acetate, methanol, formate, lactate and some aryl methoxyl compounds have been detected in extracts from a wide range of sources. In view of the controversy over whether low molecular weight substances are contaminants in humic extracts introduced by the concentration procedure, we report that some of these materials are not contaminants since 1H-NMR can be used to follow their formation from higher molecular weight species. ?? 1988.

Study of ground state optical transfer for ultracold alkali dimers

NASA Astrophysics Data System (ADS)

Bouloufa-Maafa, Nadia; Londono, Beatriz; Borsalino, Dimitri; Vexiau, Romain; Mahecha, Jorge; Dulieu, Olivier; Luc-Koenig, Eliane

2013-05-01

Control of molecular states by laser pulses offer promising potential applications. The manipulation of molecules by external fields requires precise knowledge of the molecular structure. Our motivation is to perform a detailed analysis of the spectroscopic properties of alkali dimers, with the aim to determine efficient optical paths to form molecules in the absolute ground state and to determine the optimal parameters of the optical lattices where those molecules are manipulated to avoid losses by collisions. To this end, we use state of the art molecular potentials, R-dependent spin-orbit coupling and transition dipole moment to perform our calculations. R-dependent SO coupling are of crucial importance because the transitions occur at internuclear distances where they are affected by this R-dependence. Efficient schemes to transfer RbCs, KRb and KCs to the absolute ground state as well as the optimal parameters of the optical lattices will be presented. This work was supported in part by ``Triangle de la Physique'' under contract 2008-007T-QCCM (Quantum Control of Cold Molecules).

Absolute Intra-Molecular Distance Measurements with Ångström-Resolution using Anomalous Small-Angle X-ray Scattering

DOE PAGES

Zettl, Thomas; Mathew, Rebecca S.; Seifert, Sönke; ...

2016-05-31

Accurate determination of molecular distances is fundamental to understanding the structure, dynamics, and conformational ensembles of biological macromolecules. Here we present a method to determine the full,distance,distribution between small (~7 Å) gold labels attached to macromolecules with very high-precision(≤1 Å) and on an absolute distance scale. Our method uses anomalous small-angle X-ray scattering close to a gold absorption edge to separate the gold-gold interference pattern from other scattering contributions. Results for 10-30 bp DNA constructs achieve excellent signal-to-noise and are in good agreement with previous results obtained by single-energy,SAXS measurements without requiring the preparation and measurement of single labeled andmore » unlabeled samples. Finally, the use of small gold labels in combination with ASAXS read out provides an attractive approach to determining molecular distance distributions that will be applicable to a broad range of macromolecular systems.« less

Factors that affect molecular weight distribution of Suwannee river fulvic acid as determined by electrospray ionization/mass spectrometry

USGS Publications Warehouse

Rostad, C.E.; Leenheer, J.A.

2004-01-01

Effects of methylation, molar response, multiple charging, solvents, and positive and negative ionization on molecular weight distributions of aquatic fulvic acid were investigated by electrospray ionization/mass spectrometry. After preliminary analysis by positive and negative modes, samples and mixtures of standards were derivatized by methylation to minimize ionization sites and reanalyzed.Positive ionization was less effective and produced more complex spectra than negative ionization. Ionization in methanol/water produced greater response than in acetonitrile/water. Molar response varied widely for the selected free acid standards when analyzed individually and in a mixture, but after methylation this range decreased. After methylation, the number average molecular weight of the Suwannee River fulvic acid remained the same while the weight average molecular weight decreased. These differences are probably indicative of disaggregation of large aggregated ions during methylation. Since the weight average molecular weight decreased, it is likely that aggregate formation in the fulvic acid was present prior to derivatization, rather than multiple charging in the mass spectra. ?? 2004 Elsevier B.V. All rights reserved.

Acyclic Cucurbit[n]uril-Type Molecular Container Enables Systemic Delivery of Effective Doses of Albendazole for Treatment of SK-OV-3 Xenograft Tumors.

PubMed

Hettiarachchi, Gaya; Samanta, Soumen K; Falcinelli, Shane; Zhang, Ben; Moncelet, Damien; Isaacs, Lyle; Briken, Volker

2016-03-07

Approximately, 40-70% of active pharmaceutical ingredients (API) are severely limited by their extremely poor aqueous solubility, and consequently, there is a high demand for excipients that can be used to formulate clinically relevant doses of these drug candidates. Here, proof-of-concept studies demonstrate the potential of our recently discovered acyclic cucurbit[n]uril-type molecular container Motor1 (M1) as a solubilizing agent for insoluble drugs. M1 did not induce significant rates of mutations in various Salmonella typhimurium test strains during the Ames test, suggesting low genotoxicity. M1 also has low risk of causing cardiac toxicity in humans since it did not inhibit the human Ether-à-go-go-Related Gene channel as tested on transfected CHO cell lines via patch clamp analysis. Albendazole (ABZ) is a widely used antihelminthic agent but that has also shown promising efficacy against cancerous cells in vitro. However, due to its low aqueous solubility (2.7 μM) and poor pharmacokinetics, ABZ is clinically limited as an anticancer agent. Here we investigated the potential of M1 as a solubilizing excipient for ABZ formulation. A pharmacokinetic study indicated that ABZ escapes the peritoneal cavity resulting in 78% absolute bioavailability, while its active intermediate metabolite, albendazole sulfoxide, achieved 43% absolute bioavailability. The daily dosing of 681 mg/kg M1 complexed with 3.2 mg/kg of ABZ for 14 days did not result in significant weight loss or pathology in Swiss Webster mice. In vivo efficacy studies using this M1·ABZ inclusion complex showed significant decreases in tumor growth rates and increases in survival of mice bearing SK-OV-3 xenograft tumors. In conclusion, we provide substantial new evidence demonstrating that M1 is a safe and efficient excipient that enables in vivo parenteral delivery of poorly water-soluble APIs.

Correlation of transarterial transport of various dextrans with their physicochemical properties.

PubMed

Elmalak, O; Lovich, M A; Edelman, E

2000-11-01

Local vascular drug delivery provides elevated concentrations of drug in the target tissue while minimizing systemic side effects. To better characterize local pharmacokinetics we examined the arterial transport of locally applied dextran and dextran derivatives in vivo. Using a two-compartment pharmacokinetic model to correct the measured transmural flux of these compounds for systemic redistribution and elimination as delivered from a photopolymerizable hydrogel surrounding rat carotid arteries, we found that the diffusivities and the transendothelial permeabilities were strongly dependent on molecular weight and charge. For neutral dextrans, the effective diffusive resistance in the media increased with molecular weight approximately 4.1-fold between the molecular weights of 10 and 282 kDa. Similarly, endothelial resistance increased 28-fold over the same molecular weight range. The effective medial diffusive resistance was unaffected by cationic charge as such molecules moved identically to neutral compounds, but increased approximately 40% when dextrans were negatively charged. Transendothelial resistance was 20-fold lower for the cationic dextrans, and 11-fold higher for the anionic dextrans, when both were compared to neutral counterparts. These results suggest that, while low molecular weight drugs will rapidly traverse the arterial wall with the endothelium posing a minimal barrier, the reverse is true for high molecular weight agents. With these data, the deposition and distribution of locally released vasotherapeutic compounds might be predicted based upon chemical properties, such as molecular weight and charge.

Heat-mediated, ultra-rapid electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes.

PubMed

Kurien, Biji T; Scofield, R Hal

2002-08-01

Here, we report an ultra-rapid method for the transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In this procedure, the electro-transfer was performed with heated (70-75 degrees C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight proteins (a purified protein, molecular weight protein standards and proteins from a human tissue extract) could be carried out in 10 min for a 0.75-mm, 7% SDS-PAGE gel. For 10% and 12.5% gels (0.75 mm), the corresponding time was 15 min. In the case of 1.5-mm gels, a complete transfer could be carried out in 20 min for 7%, 10% and 12.5% gels. The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. When the heat-mediated transfer method was compared with a conventional transfer protocol, under similar conditions, we found that the latter method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is very rapid, avoids the use of methanol and is particularly useful for the transfer of high molecular weight proteins.

Molecular weight dependence of carrier mobility and recombination rate in neat P3HT films

DOE PAGES

Dixon, Alex G.; Visvanathan, Rayshan; Clark, Noel A.; ...

2017-11-02

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3-hexylthyophene (P3HT) were determined for a range of materials of weight-average molecular weights, Mw, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one-phase, paraffinic-like structure comprised of chain-extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of Mw = 48more » kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two-phase structure with increasing Mw, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination.« less

Molecular weight dependence of carrier mobility and recombination rate in neat P3HT films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, Alex G.; Visvanathan, Rayshan; Clark, Noel A.

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3-hexylthyophene (P3HT) were determined for a range of materials of weight-average molecular weights, Mw, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one-phase, paraffinic-like structure comprised of chain-extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of Mw = 48more » kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two-phase structure with increasing Mw, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination.« less

ESIprot: a universal tool for charge state determination and molecular weight calculation of proteins from electrospray ionization mass spectrometry data.

PubMed

Winkler, Robert

2010-02-01

Electrospray ionization (ESI) ion trap mass spectrometers with relatively low resolution are frequently used for the analysis of natural products and peptides. Although ESI spectra of multiply charged protein molecules also can be measured on this type of devices, only average spectra are produced for the majority of naturally occurring proteins. Evaluating such ESI protein spectra would provide valuable information about the native state of investigated proteins. However, no suitable and freely available software could be found which allows the charge state determination and molecular weight calculation of single proteins from average ESI-MS data. Therefore, an algorithm based on standard deviation optimization (scatter minimization) was implemented for the analysis of protein ESI-MS data. The resulting software ESIprot was tested with ESI-MS data of six intact reference proteins between 12.4 and 66.7 kDa. In all cases, the correct charge states could be determined. The obtained absolute mass errors were in a range between -0.2 and 1.2 Da, the relative errors below 30 ppm. The possible mass accuracy allows for valid conclusions about the actual condition of proteins. Moreover, the ESIprot algorithm demonstrates an extraordinary robustness and allows spectral interpretation from as little as two peaks, given sufficient quality of the provided m/z data, without the necessity for peak intensity data. ESIprot is independent from the raw data format and the computer platform, making it a versatile tool for mass spectrometrists. The program code was released under the open-source GPLv3 license to support future developments of mass spectrometry software. Copyright 2010 John Wiley & Sons, Ltd.

Permeation enhancing polymers in oral delivery of hydrophilic macromolecules: thiomer/GSH systems.

PubMed

Bernkop-Schnürch, A; Kast, C E; Guggi, D

2003-12-05

Thiolated polymers (= thiomers) in combination with reduced glutathione (GSH) were shown to improve the uptake of hydrophilic macromolecules from the GI tract. The mechanism responsible for this permeation enhancing effect seems to be based on the thiol groups of the polymer. These groups inhibit protein tyrosine phosphatase, being involved in the closing process of tight junctions, via a GSH-mediated mechanism. The strong permeation enhancing effect of various thiomer/GSH systems such as poly(acrylic acid)-cysteine/GSH or chitosan-4-thio-butylamidine (chitosan-TBA)/GSH could be shown via permeation studies on freshly excised intestinal mucosa in Ussing-type chambers. Furthermore, the efficacy of the system was also shown in vivo. By utilizing poly(acrylic acid)-cysteine/GSH as carrier matrix, an absolute oral bioavailability for low molecular weight heparin of 19.9 +/- 9.3% and a pharmacological efficacy--calculated on the basis of the areas under the reduction in serum glucose levels of the oral formulation versus subcutaneous (s.c.) injection-for orally given insulin of 7% could be achieved. The incorporation of salmon calcitonin in chitosan-TBA/GSH led on the other hand to a pharmacological efficacy based on the areas under the reduction in plasma calcium levels of the oral thiomer formulation versus intravenous (i.v.) injection of 1.3%. Because of this high efficacy (i), the possibility to combine thiomer/GSH systems with additional low molecular weight permeation enhancers acting in other ways (ii) and minimal toxicological risks as these polymers are not absorbed from the GI tract (iii), thiolated polymers represent a promising novel tool for the oral administration of hydrophilic macromolecules.

Variations in organic aerosol optical and hygroscopic properties upon heterogeneous OH oxidation

NASA Astrophysics Data System (ADS)

Cappa, Christopher D.; Che, Daphne L.; Kessler, Sean H.; Kroll, Jesse H.; Wilson, Kevin R.

2011-08-01

Measurements of the evolution of organic aerosol extinction cross sections (σext) and subsaturated hygroscopicity upon heterogeneous OH oxidation are reported for two model compounds, squalane (a C30 saturated hydrocarbon) and azelaic acid (a C9 dicarboxylic acid). For both compounds, the σext values at 532 nm increase substantially as the particles undergo oxidation, exhibiting a logarithmic increase with OH exposure. The increase in σext correlates with both an increase in the particle oxygen to carbon (O:C) atomic ratio and density and a decrease in mean molecular weight. The measurements have been used to calculate the variation with oxidation of the mean polarizability, α, of the molecules comprising the particles. The absolute α values for the two systems are shown to be related through the variation in the particle chemical composition, specifically the relative abundances of C, O, and H atoms and the mean molecular weight. Unlike σext, it was found that the evolution of the particle hygroscopicity upon oxidation is quite different for the two model systems considered. Hygroscopicity was quantified by measuring γext, which is a single-parameter representation of hygroscopicity that describes the increase in extinction upon exposure of the particles to a high-relative humidity environment (here, 75% and 85% RH). For unoxidized squalane, γext was zero and only increased slowly as the particles were oxidized by OH radicals. In contrast, γext for azelaic acid increased rapidly upon exposure to OH, eventually reaching a plateau at high OH exposures. In general, γext appears to vary sigmoidally with O:C, reaching a plateau at high O:C.

In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Atsushi; Nonaka, Hidehiko

2009-09-15

A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicabilitymore » of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes.« less

Weight Outcomes of Latino Adults and Children Participating in the Y Living Program, a Family-Focused Lifestyle Intervention, San Antonio, 2012-2013.

PubMed

Parra-Medina, Deborah; Liang, Yuanyuan; Yin, Zenong; Esparza, Laura; Lopez, Louis

2015-12-10

US Latinos have disproportionately higher rates of obesity and physical inactivity than the general US population, putting them at greater risk for chronic disease. This evaluation aimed to examine the impact of the Y Living Program (Y Living), a 12-week family-focused healthy lifestyle program, on the weight status of adult and child (aged ≥7 years) participants. In this pretest-posttest evaluation, participants attended twice-weekly group education sessions and engaged in physical activity at least 3 times per week. Primary outcome measures were body mass index ([BMI], zBMI and BMI percentile for children), weight, waist circumference, and percentage body fat. Wilcoxon signed-rank tests and mixed effects models were used to evaluate pretest-posttest differences (ie, absolute change and relative change) for adults and children separately. BMI, weight, waist circumference, and percentage body fat improved significantly (both absolutely and relatively) among adults who completed the program (n = 180; all P ≤ .001). Conversely, child participants that completed the program (n = 72) showed no improvements. Intervention effects varied across subgroups. Among adults, women and participants who were obese at baseline had larger improvements than did children who were obese at baseline or who were in families that had an annual household income of $15,000 or more. Significant improvements in weight were observed among adult participants but not children. This family-focused intervention has potential to prevent excess weight gain among high-risk Latino families.

Toxicological assessment of Diplazium esculentum on the reproductive functions of male Swiss albino mouse.

PubMed

Roy, Subhrajyoti; Chaudhuri, Tapas Kumar

2017-04-01

Diplazium esculentum, a commonly consumed seasonal vegetable, has been reported to have some pathological effects in some animals. But, its effect on the male reproductive function has not yet been studied. To investigate the effects of boiled D. esculentum (BDE), the form which human consumes, on male reproductive functions of Swiss albino mice. Male (120 in no.) and female (80 in no.) Swiss albino mice (6-8 weeks of age) were fed orally with 80, 160 and 320 mg/kg bw of BDE within a span of 180 d. After the treatment, body weight, absolute- and relative-testis weight, relative-weight of other organs, their biochemical parameters, hypo-osmotic swelling test (HOST) of spermatozoa, testis histology and fertility and fecundity tests were performed to justify the toxic effects of D. esculentum on male reproductive functions. Significant dose- and time-dependent decreases were observed in body weight, absolute- and relative-testis weight, relative-weights of other organs and their biochemical parameters, percentage of live spermatozoa and percentage of fertility and fecundity in BDE fed mice. Significant decreases were observed in diameter, perimeter and area of the seminiferous tubules of mice treated for 180 d. The percentage of empty seminiferous tubules was increased significantly in BDE treated mice when compared to the controls. These results suggest that the intake of D. esculentum, even after cooking, may induce infertility by altering the male reproductive function, and therefore, should be evaluated further as a potential antifertility agent.

Mapping health outcome measures from a stroke registry to EQ-5D weights

PubMed Central

2013-01-01

Purpose To map health outcome related variables from a national register, not part of any validated instrument, with EQ-5D weights among stroke patients. Methods We used two cross-sectional data sets including patient characteristics, outcome variables and EQ-5D weights from the national Swedish stroke register. Three regression techniques were used on the estimation set (n = 272): ordinary least squares (OLS), Tobit, and censored least absolute deviation (CLAD). The regression coefficients for “dressing“, “toileting“, “mobility”, “mood”, “general health” and “proxy-responders” were applied to the validation set (n = 272), and the performance was analysed with mean absolute error (MAE) and mean square error (MSE). Results The number of statistically significant coefficients varied by model, but all models generated consistent coefficients in terms of sign. Mean utility was underestimated in all models (least in OLS) and with lower variation (least in OLS) compared to the observed. The maximum attainable EQ-5D weight ranged from 0.90 (OLS) to 1.00 (Tobit and CLAD). Health states with utility weights <0.5 had greater errors than those with weights ≥0.5 (P < 0.01). Conclusion This study indicates that it is possible to map non-validated health outcome measures from a stroke register into preference-based utilities to study the development of stroke care over time, and to compare with other conditions in terms of utility. PMID:23496957

Absolute configuration and crystal packing chirality for three conglomerate-forming ortho-halogen substituted phenyl glycerol ethers

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.

2010-06-01

Three conglomerate-forming ortho-Hal (Hal = Cl, Br, I) substituted phenyl glycerol ethers 1- 3 were investigated by single-crystal X-ray analysis, and the absolute configuration for all substances was established. The molecular structures and crystal packing details for halogen derivatives were compared with the same characteristics for ortho-OCH 3 and ortho-CH 3 analogues. Two different types of crystal packing were evaluated for these very much alike compounds. The interplay of the supramolecular crystal organization chirality sense and the single molecule absolute configuration was demonstrated. Some stabilizing and destabilizing interactions involving the ortho-substituents were revealed. The resolution of rac-2 by entrainment procedure was successfully realized.

Toxicity profile of ethanolic extract of Azadirachta indica stem bark in male Wistar rats.

PubMed

Ashafa, Anofi Omotayo Tom; Orekoya, Latifat Olubukola; Yakubu, Musa Toyin

2012-10-01

To investigate the toxic implications of ethanolic stem bark extract of Azadirachta indica (A. indica) at 50, 100, 200 and 300 mg/kg body weight in Wistar rats. Fifty male rats of Wistar strains were randomly grouped into five (A-E) of ten animals each. Animals in Group A (control) were orally administered 1 mL of distilled water on daily basis for 21 days while those in Groups B-E received same volume of the extract corresponding to 50, 100, 200 and 300 mg/kg body weight. The extract did not significantly (P>0.05) alter the levels of albumin, total protein, red blood cells and factors relating to it whereas the white blood cell, platelets, serum triacylglycerol and high-density lipoprotein cholesterol decreased significantly (P<0.05). In contrast, the final body weights, absolute weights of the liver, kidney, lungs and heart as well as their organ-body weight ratios, serum globulins, total and conjugated bilirubin, serum cholesterol, low-density lipoprotein cholesterol and computed atherogenic index increased significantly. The spleen-body weight ratio, alkaline phosphatase, alanine and aspartate transaminases, sodium, potassium, calcium, feed and water intake were altered at specific doses. Overall, the alterations in the biochemical parameters of toxicity have consequential effects on the normal functioning of the organs of the animals. Therefore, the ethanolic extract of A. indica stem bark at the doses of 50, 100, 200 and 300 mg/kg body weight may not be completely safe as an oral remedy and should be taken with caution if absolutely necessary.

Day 6 blastocyst is associated with increased birth weight in full-term singleton newborns after frozen-thawed transfer.

PubMed

Cai, Jiali; Liu, Lanlan; Xu, Yingpei; Liu, Zhenfang; Jiang, Xiaoming; Li, Ping; Sha, Aiguo; Ren, Jianzhi

2018-06-13

The purpose of the study is to compare the newborns weight in singleton term birth following transfer of thawed blastocysts-frozen on either day 5 or day 6 after in vitro fertilization. The retrospective study included 1444 frozen-thawed blastocyst transfer (FBT) cycles resulting in live singleton births between Jan 2013 and Dec 2016. The main outcomes measured were absolute birth weight, z-score adjusted for gestational age and gender, and incidence of large-for-gestational-age (LGA) newborns. Generalized linear model (GLM) and logistic regression were used in multivariate analyses. Both the absolute birth weight (3416.49 ± 404.74 vs 3349.22 ± 416.17) and the z-score (0.6 ± 0.93 vs 0.41 ± 0.93) were significantly higher on day 6 FBT in comparison with day 5 FBT. The incidence of LGA newborns was also increased on day 6 FBT (22.8 vs 14.7%, P = 0.006). Adjusted for maternal age, BMI, PCOS diagnosis, present of vanishing twin, and embryo quality, the odds ratio (95% confidence interval) for LGA on day 6 FBT comparing with day 5 FBT was 1.76 (1.18-2.64). Day 6 FBT is associated with increased birth weight and contributes to the incidence of LGA newborns in FBT.

Genetic parameters for different growth scales in GIFT strain of Nile tilapia (Oreochromis niloticus).

PubMed

He, J; Gao, H; Xu, P; Yang, R

2015-12-01

Body weight, length, width and depth at two growth stages were observed for a total of 5015 individuals of GIFT strain, along with a pedigree including 5588 individuals from 104 sires and 162 dams was collected. Multivariate animal models and a random regression model were used to genetically analyse absolute and relative growth scales of these growth traits. In absolute growth scale, the observed growth traits had moderate heritabilities ranging from 0.321 to 0.576, while pairwise ratios between body length, width and depth were lowly inherited and maximum heritability was only 0.146 for length/depth. All genetic correlations were above 0.5 between pairwise growth traits and genetic correlation between length/width and length/depth varied between both growth stages. Based on those estimates, selection index of multiple traits of interest can be formulated in future breeding program to improve genetically body weight and morphology of the GIFT strain. In relative growth scale, heritabilities in relative growths of body length, width and depth to body weight were 0.257, 0.412 and 0.066, respectively, while genetic correlations among these allometry scalings were above 0.8. Genetic analysis for joint allometries of body weight to body length, width and depth will contribute to genetically regulate the growth rate between body shape and body weight. © 2015 Blackwell Verlag GmbH.

Fluorescence spectroscopy and molecular weight distribution of extracellular polymers from full-scale activated sludge biomass.

PubMed

Esparza-Soto, M; Westerhoff, P K

2001-01-01

Two fractions of extracellular polymer substances (EPSs), soluble and readily extractable (RE), were characterised in terms of their molecular weight distributions (MWD) and 3-D excitation-emission-matrix (EEM) fluorescence spectroscopy signatures. The EPS fractions were different: the soluble EPSs were composed mainly of high molecular weight compounds, while the RE EPSs were composed of small molecular weight compounds. Contrary to previous thought, EPS may not be considered only as macromolecular because most organic matter present in both fractions had low molecular weight. Three different fluorophore peaks were identified in the EEM fluorescence spectra. Two peaks were attributed to protein-like fluorophores, and the third to a humic-like fluorophore. Fluorescence signatures were different from other previously published signatures for marine and riverine environments. EEM spectroscopy proved to be a suitable method that may be used to characterise and trace organic matter of bacterial origin in wastewater treatment operations.

Effect of the different chain transfer agents on molecular weight and optical properties of poly(methyl methacrylate)

NASA Astrophysics Data System (ADS)

Çetinkaya, Onur; Demirci, Gökhan; Mergo, Paweł

2017-08-01

Investigation of molecular weight and optical properties of poly(methyl metacrylate) (PMMA) polymerized in house with different chain transfer agents was studied. Isopropyl alcohol (IPA), n-butyl mercaptan (nBMC) and pentamethyl disilane (PMDS) were used as chain transfer agents. The molecular weight (Mw) of PMMA samples were measured by Ostwald viscometer. Mw of bulk polymer samples were decreased with increase the concentration of chain transfer agents (CTA). Since reactivity of used CTAs is not same, molecular weights of samples which were produced with different type of CTA but same concentration of CTA was varied. Higher concentration of n-BMC showed higher scattering. Transmission of samples could not be correlated with different concentration of CTA. Refractive index of samples was not affected by concentration of CTA nevertheless higher molecular weight of CTA showed higher refractive index.

Low molecular weight salts combined with fluorinated solvents for electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tikhonov, Konstantin; Yip, Ka Ki; Lin, Tzu-Yuan

2015-11-10

Provided are electrochemical cells and electrolytes used to build such cells. An electrolyte includes at least one salt having a molecular weight less than about 250. Such salts allow forming electrolytes with higher salt concentrations and ensure high conductivity and ion transport in these electrolytes. The low molecular weight salt may have a concentration of at least about 0.5M and may be combined with one or more other salts, such as linear and cyclic imide salts and/or methide salts. The concentration of these additional salts may be less than that of the low molecular weight salt, in some embodiments, twicemore » less. The additional salts may have a molecular weight greater than about 250. The electrolyte may also include one or more fluorinated solvents and may be capable of maintaining single phase solutions at between about -30.degree. C. to about 80.degree. C.« less

Manipulation of Molecular Weight Distribution Shape as a New Strategy to Control Processing Parameters.

PubMed

Nadgorny, Milena; Gentekos, Dillon T; Xiao, Zeyun; Singleton, S Parker; Fors, Brett P; Connal, Luke A

2017-10-01

Molecular weight and dispersity (Ð) influence physical and rheological properties of polymers, which are of significant importance in polymer processing technologies. However, these parameters provide only partial information about the precise composition of polymers, which is reflected by the shape and symmetry of molecular weight distribution (MWD). In this work, the effect of MWD symmetry on thermal and rheological properties of polymers with identical molecular weights and Ð is demonstrated. Remarkably, when the MWD is skewed to higher molecular weight, a higher glass transition temperature (T g ), increased stiffness, increased thermal stability, and higher apparent viscosities are observed. These observed differences are attributed to the chain length composition of the polymers, easily controlled by the synthetic strategy. This work demonstrates a versatile approach to engineer the properties of polymers using controlled synthesis to skew the shape of MWD. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Apparatus for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

2001-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, (4) conducting a two-stage separation or (5) any combination of (1), (2), (3) and (4).

Microdialysis unit for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

1999-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, or (4) any combination of (1), (2), and (3).

Development of Bio-impedance Analyzer (BIA) for Body Fat Calculation

NASA Astrophysics Data System (ADS)

Riyadi, Munawar A.; Nugraha, A.; Santoso, M. B.; Septaditya, D.; Prakoso, T.

2017-04-01

Common weight scales cannot assess body composition or determine fat mass and fat-fress mass that make up the body weight. This research propose bio-impedance analysis (BIA) tool capable to body composition assessment. This tool uses four electrodes, two of which are used for 50 kHz sine wave current flow to the body and the rest are used to measure the voltage produced by the body for impedance analysis. Parameters such as height, weight, age, and gender are provided individually. These parameters together with impedance measurements are then in the process to produce a body fat percentage. The experimental result shows impressive repeatability for successive measurements (stdev ≤ 0.25% fat mass). Moreover, result on the hand to hand node scheme reveals average absolute difference of total subjects between two analyzer tools of 0.48% (fat mass) with maximum absolute discrepancy of 1.22% (fat mass). On the other hand, the relative error normalized to Omron’s HBF-306 as comparison tool reveals less than 2% relative error. As a result, the system performance offers good evaluation tool for fat mass in the body.

Management of venous thromboembolism in patients with acute leukemia at high bleeding risk: a multi-center study.

PubMed

Napolitano, Mariasanta; Valore, Luca; Malato, Alessandra; Saccullo, Giorgia; Vetro, Calogero; Mitra, Maria Enza; Fabbiano, Francesco; Mannina, Donato; Casuccio, Alessandra; Lucchesi, Alessandro; Del Principe, Maria Ilaria; Candoni, Anna; Di Raimondo, Francesco; Siragusa, Sergio

2016-01-01

In the last decades, evaluation of clinically relevant thrombotic complications in patients with acute leukemia (AL) has been poorly investigated. The authors performed a multi-center study to evaluate the management of symptomatic venous thromboembolism (VTE) in adult patients with AL. The intention was to find as clinically relevant the following: symptomatic Venous Thrombosis (VT) occurred in typical (lower limbs) and atypical (cerebral, upper limbs, abdominal, etc) sites with or without pulmonary embolism (PE). Over a population of 1461 patients with AL, 22 cases of symptomatic VTE were recorded in hospitalized patients with a mean age of 54.6 years. The absolute incidence of VTE was 1.5%. VTE occurred during chemotherapy in 17/22 (77.2%) cases, mainly (14/17, 82.3%) during the induction phase. Treatment of acute VTE was based on Low Molecular Weight Heparin (LMWH) at full dosage for the first month from diagnosis and reduced dosage (75%) for the following months.

The FPase properties and morphology changes of a cellulolytic bacterium, Sporocytophaga sp. JL-01, on decomposing filter paper cellulose.

PubMed

Wang, Xiuran; Peng, Zhongqi; Sun, Xiaoling; Liu, Dongbo; Chen, Shan; Li, Fan; Xia, Hongmei; Lu, Tiancheng

2012-01-01

Sporocytophaga sp. JL-01 is a sliding cellulose degrading bacterium that can decompose filter paper (FP), carboxymethyl cellulose (CMC) and cellulose CF11. In this paper, the morphological characteristics of S. sp. JL-01 growing in FP liquid medium was studied by Scanning Electron Microscope (SEM), and one of the FPase components of this bacterium was analyzed. The results showed that the cell shapes were variable during the process of filter paper cellulose decomposition and the rod shape might be connected with filter paper decomposing. After incubating for 120 h, the filter paper was decomposed significantly, and it was degraded absolutely within 144 h. An FPase1 was purified from the supernatant and its characteristics were analyzed. The molecular weight of the FPase1 was 55 kDa. The optimum pH was pH 7.2 and optimum temperature was 50°C under experiment conditions. Zn(2+) and Co(2+) enhanced the enzyme activity, but Fe(3+) inhibited it.

Bile Salt Stabilized Vesicles (Bilosomes): A Novel Nano-Pharmaceutical Design for Oral Delivery of Proteins and Peptides.

PubMed

Ahmad, Javed; Singhal, Madhur; Amin, Saima; Rizwanullah, Md; Akhter, Sohail; Kamal, Mohammad Amjad; Haider, Nafis; Midoux, Patrick; Pichon, Chantal

2017-01-01

With the advent of novel vesicular drug delivery systems especially bilosomes, for large molecular weight proteins and peptides, their oral administration seems a viable approach. These nano-vesicles have shown promising results for the effective delivery of insulin and other therapeutics, perhaps due to their structural composition. The present review has elaborated the biopharmaceutical challenges for the oral delivery of therapeutic proteins and peptides as well as presented a novel approach to deliver the essential macromolecules through oral route as bilosomes. The extensive search has been presented related to the formulation, evaluation and in vivo performance of bilosomes. Some of the crucial findings related to bilosomes have corroborated them superior to other colloidal carriers. The successful drug delivery through bilosomes requires significant justifications related to their interaction with the biological membranes. The other aspects such as absolute absorption, safety and toxicity of bilosome drug delivery should also be equally considered. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Evaluation and Applications of the Prediction of Intensity Model Error (PRIME) Model

NASA Astrophysics Data System (ADS)

Bhatia, K. T.; Nolan, D. S.; Demaria, M.; Schumacher, A.

2015-12-01

Forecasters and end users of tropical cyclone (TC) intensity forecasts would greatly benefit from a reliable expectation of model error to counteract the lack of consistency in TC intensity forecast performance. As a first step towards producing error predictions to accompany each TC intensity forecast, Bhatia and Nolan (2013) studied the relationship between synoptic parameters, TC attributes, and forecast errors. In this study, we build on previous results of Bhatia and Nolan (2013) by testing the ability of the Prediction of Intensity Model Error (PRIME) model to forecast the absolute error and bias of four leading intensity models available for guidance in the Atlantic basin. PRIME forecasts are independently evaluated at each 12-hour interval from 12 to 120 hours during the 2007-2014 Atlantic hurricane seasons. The absolute error and bias predictions of PRIME are compared to their respective climatologies to determine their skill. In addition to these results, we will present the performance of the operational version of PRIME run during the 2015 hurricane season. PRIME verification results show that it can reliably anticipate situations where particular models excel, and therefore could lead to a more informed protocol for hurricane evacuations and storm preparations. These positive conclusions suggest that PRIME forecasts also have the potential to lower the error in the original intensity forecasts of each model. As a result, two techniques are proposed to develop a post-processing procedure for a multimodel ensemble based on PRIME. The first approach is to inverse-weight models using PRIME absolute error predictions (higher predicted absolute error corresponds to lower weights). The second multimodel ensemble applies PRIME bias predictions to each model's intensity forecast and the mean of the corrected models is evaluated. The forecasts of both of these experimental ensembles are compared to those of the equal-weight ICON ensemble, which currently provides the most reliable forecasts in the Atlantic basin.

Histidinoalanine, a naturally occurring cross-link derived from phosphoserine and histidine residues in mineral-binding phosphoproteins.

PubMed

Marsh, M E

1986-05-06

Native mineral-containing phosphoprotein particles were isolated from the Heterodont bivalve Macrocallista nimbosa. The native particles are discrete structures about 40 nm in diameter which migrate as a single band during electrophoresis in agarose gels. Removal of the mineral component with ethylenediaminetetraacetic acid dissociates the native protein into nonidentical subunits. The lower molecular weight subunits, representing 8% of the total protein, were obtained by differential centrifugation. The native protein is characterized by a high content of aspartic acid, phosphoserine, phosphothreonine, histidine, and the bifunctional cross-linking residue histidinoalanine. The low molecular weight subunits have the same amino acid composition except for a reduction in histidinoalanine and a corresponding increase in phosphoserine and histidine residues, demonstrating that the alanine portion of the cross-link is derived from phosphoserine residues. Ion-exchange chromatography and molecular sieve chromatography show that the low molecular weight subunits have a similar charge density but differ in molecular weight, and the relative mobilities of the subunits on agarose gels indicate that they are polymers of a single phosphoprotein molecule. The minimum molecular weight of the monomer is about 140 000 on the basis of the amino acid composition. The high molecular weight subunits are rich in histidinoalanine and too large to be resolved by either molecular sieve chromatography or gel electrophoresis. On the basis of the ultrastructural, electrophoretic, chromatographic, and compositional evidence, native phosphoprotein particles are composed of subunits ionically cross-linked via divalent cations. These subunits are variable molecular weight aggregates of a single phosphoprotein molecule covalently cross-linked via histidinoalanine residues. Evidence for a nonenzymatic cross-linking mechanism is discussed.

Development of MRM-based assays for the absolute quantitation of plasma proteins.

PubMed

Kuzyk, Michael A; Parker, Carol E; Domanski, Dominik; Borchers, Christoph H

2013-01-01

Multiple reaction monitoring (MRM), sometimes called selected reaction monitoring (SRM), is a directed tandem mass spectrometric technique performed on to triple quadrupole mass spectrometers. MRM assays can be used to sensitively and specifically quantify proteins based on peptides that are specific to the target protein. Stable-isotope-labeled standard peptide analogues (SIS peptides) of target peptides are added to enzymatic digests of samples, and quantified along with the native peptides during MRM analysis. Monitoring of the intact peptide and a collision-induced fragment of this peptide (an ion pair) can be used to provide information on the absolute peptide concentration of the peptide in the sample and, by inference, the concentration of the intact protein. This technique provides high specificity by selecting for biophysical parameters that are unique to the target peptides: (1) the molecular weight of the peptide, (2) the generation of a specific fragment from the peptide, and (3) the HPLC retention time during LC/MRM-MS analysis. MRM is a highly sensitive technique that has been shown to be capable of detecting attomole levels of target peptides in complex samples such as tryptic digests of human plasma. This chapter provides a detailed description of how to develop and use an MRM protein assay. It includes sections on the critical "first step" of selecting the target peptides, as well as optimization of MRM acquisition parameters for maximum sensitivity of the ion pairs that will be used in the final method, and characterization of the final MRM assay.

Drop-on-demand drop formation of polyethylene oxide solutions

NASA Astrophysics Data System (ADS)

Yan, Xuejia; Carr, Wallace W.; Dong, Hongming

2011-10-01

The dynamics of drop-on-demand (DOD) drop formation for solutions containing polyethylene oxide (PEO) have been studied experimentally. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53 μm, experiments were conducted for a series of PEO aqueous solutions with molecular weights ranging from 14 to 1000 kg/mol, polydispersity from 1.02 to 2.5, and concentrations from 0.005 to 10 wt. %. The addition of a small amount of PEO can have a significant effect on the DOD drop formation process, increasing breakup time, decreasing primary drop speed, and decreasing the number of satellite drops in some cases. The effects depend on both molecular weight and concentration. At lower molecular weights (14 and 35 kg/mol), the effect of PEO over the dilute solution regime is insignificant even at concentrations large enough that the solution does not fall in the dilute regime. As PEO molecular weight increased, the effects became significant. For monodispersed PEO solutions, breakup time and primary drop speed closely correlated with effective relaxation time but not for polydispersed PEO. Effective relaxation time depended greatly on molecular weight distribution. Viscosity-average molecular weight, used in calculating effective relaxation time for polydispersed PEO solutions, did not adequately account for high molecular fractions in the molecular weight distribution of the polydispersed PEOs. A mixture rule was developed to calculate the effective relaxation times for aqueous solutions containing mixtures of monodispersed PEO, and breakup times and primary drop speeds correlated well with effective relaxation times. For our experiments, DOD drop formation was limited to Deborah number ≲ 23.

Overview of the TREC 2009 Chemical IR Track

DTIC Science & Technology

2009-11-01

several classes have been identified. 3 methods for controlling molecular weight of polyhydroxyalkanoate organic, high molecular weight We are a group of...researchers in an university/company. We want to start a project and, before starting, we want more informations about polyhydroxyalkanoate and about...methods for controlling molecular weight of polyhydroxyalkanoate constituted of units containing residue of phenyl-, thienyl-, or cyclohexyl-structure

Temperature and molecular-weight dependences of acoustic behaviors of polystyrene studied using Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Oh, Soo Han; Lee, Byoung Wan; Ko, Jae-Hyeon; Lee, Hyeonju; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

2017-04-01

The acoustic properties of three polystyrene polymers with different molecular weights were investigated as a function of temperature by using Brillouin light scattering. The longitudinal sound velocity showed a change in the slope, which depended on the molecular weight, at the glass transition temperature. The absorption coefficient exhibited a maximum above the glass transition temperature, and the maximum temperature became higher as the molecular weight was increased. Comparison with previous acoustic studies on polystyrene indicate that a substantial frequency dispersion caused by strong coupling between the longitudinal acoustic waves and the segmental motions exists in the high-temperature range.

Isolation and Characterization of a Toxic Moiety of Low Molecular Weight from Clostridium botulinum Type A

PubMed Central

Gerwing, Julia; Dolman, Claude E.; Bains, Hardial S.

1965-01-01

Gerwing, Julia (The University of British Columbia, Vancouver, B.C., Canada), Claude E. Dolman, and Hardial S. Bains. Isolation and characterization of a toxic moiety of low molecular weight from Clostridium botulinum type A. J. Bacteriol. 89:1383–1386. 1965.—A toxic moiety of low molecular weight has been isolated from a type A strain of Clostridium botulinum, by a method involving ammonium sulfate precipitation and elution through diethylaminoethyl cellulose at pH 5.6. By means of electrophoresis and ultracentrifugation, the toxic substance was shown to be homogeneous; a molecular weight of 12,200 was calculated. Images PMID:14293025

Mass spectrometric characterization of membrane integral low molecular weight proteins from photosystem II in barley etioplasts.

PubMed

Plöscher, Matthias; Granvogl, Bernhard; Zoryan, Mikael; Reisinger, Veronika; Eichacker, Lutz Andreas

2009-02-01

In Photosystem II (PSII), a high number of plastid encoded and membrane integral low molecular weight proteins smaller than 10 kDa, the proteins PsbE, F, H, I, J, K, L, M, N, Tc, Z and the nuclear encoded PsbW, X, Y1, Y2 proteins have been described. Here we show that all low molecular weight proteins of PSII already accumulate in the etioplast membrane fraction in darkness, whereas PsaI and PsaJ of photosystem I (PSI) represent the only low molecular weight proteins that do not accumulate in darkness. We found by BN-PAGE separation of membrane protein complexes and selective MS that the accumulation of one-helix proteins from PSII is light independent and occurs in etioplasts. In contrast, in chloroplasts isolated from light-grown plants, low molecular weight proteins were found to specifically accumulate in PSI and II complexes. Our results demonstrate how plants grown in darkness prepare for the induction of chlorophyll dependent photosystem assembly upon light perception. We anticipate that our investigation will provide the essential means for the analysis of protein assembly in any membrane utilizing low molecular weight protein subunits.

The Presence Of Strange Males' Odor Induces Behavioral Responses And Elevated Levels Of Low Molecular Weight Proteins Excreted In The Urine Of Mature Water Vole Males (Arvicola amphibius L).

PubMed

Nazarova, Galina G; Proskurniak, Lyudmila P; Yuzhik, Ekaterina I

2016-03-01

We hypothesized that low molecular weight urinary proteins play a role in male-male chemical communication in the water vole, Arvicola ampibius L. We studied the effect of placing soiled litter from strange males into the cage of another sexually mature male on the intensity of its digging and scattering, urination on the litter, and alteration in the levels of low molecular weight proteins (15-25 kDa) excreted in the urine before and after 4 days of exposure as determined by chip electrophoresis. The intensity of digging and scattering was positively correlated with levels of testosterone in serum of males exposed to strange male odors (r = 0.56; P < 0.01), as well as with the concentration of low molecular weight proteins in the donor's urine (r = 0.52, P < 0.05). At the end of the experiment, the level of low molecular weight protein in excreted urine was elevated in the males exposed to the strange male's litter. These results highlight the importance of quantitative inter-individual variation of low molecular weight urinary proteins in the modulation of the physiology and behavior of conspecifics.

Effects of Molecular Structure in Macroscopic Mechanical Properties of an Advanced Polymer (LARC(sup TM)-SI)

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Hinkley, Jeffrey A.; Whitley, Karen S.; Gates, Thomas S.

2004-01-01

Mechanical testing of an advanced polymer resin with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The elastic properties, inelastic elongation behavior, and notched tensile strength all as a function of molecular weight and test temperature were determined. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature.

Absolute configuration and crystal packing for three chiral drugs prone to spontaneous resolution: Guaifenesin, methocarbamol and mephenesin

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.; Krivolapov, Dmitry B.; Pashagin, Alexander V.; Litvinov, Igor A.

2009-02-01

Popular chiral drugs, guaifenesin, methocarbamol, and mephenesin were investigated by single-crystal X-ray analysis both for enantiopure and racemic samples. The absolute configurations for all substances were established through Flack parameter method. The conglomerate-forming nature for the compounds was confirmed by equivalence of crystal characteristics of enantiopure and racemic samples. The molecular structures and crystal packing details were evaluated and compared with one another for all three investigated substances.

Effects of molecular weight of natural organic matter on cadmium mobility in soil environments and its carbon isotope characteristics.

PubMed

Mahara, Y; Kubota, T; Wakayama, R; Nakano-Ohta, T; Nakamura, T

2007-11-15

We investigated the role of natural organic matter in cadmium mobility in soil environments. We collected the dissolved organic matter from two different types of natural waters: pond surface water, which is oxic, and deep anoxic groundwater. The collected organic matter was fractionated into four groups with molecular weights (unit: Da (Daltons)) of <1 x 10(3), 1-10 x 10(3), 10-100 x 10(3), and >100 x 10(3). The organic matter source was land plants, based on the carbon isotope ratios (delta(13)C/(12)C). The organic matter in surface water originated from presently growing land plants, based on (14)C dating, but the organic matter in deep groundwater originated from land plants that grew approximately 4000 years ago. However, some carbon was supplied by the high-molecular-weight fraction of humic substances in soil or sediments. Cadmium interacted in a system of siliceous sand, fractionated organic matter, and water. The lowest molecular weight fraction of organic matter (<1 x 10(3)) bound more cadmium than did the higher molecular weight fractions. Organic matter in deep groundwater was more strongly bound to cadmium than was organic matter in surface water. The binding behaviours of organic matter with cadmium depended on concentration, age, molecular weight, and degradation conditions of the organic matter in natural waters. Consequently, the dissolved, low-molecular-weight fraction in organic matter strongly influences cadmium migration and mobility in the environment.

Physical characterization of polyethylene glycols by thermal analytical technique and the effect of humidity and molecular weight.

PubMed

Majumdar, R; Alexander, K S; Riga, A T

2010-05-01

Polyethylene glycols (PEGs) are well known as excipients in tablet dosage formulations. PEGs are generally known to be inert and have very few interactions with other components in the solid dosage forms. However, the physical nature of PEGs and how they affect the disintegration of tablets is not very well understood for the different molecular weights of PEGs. The knowledge of the effect of molecular weight of PEGs on their physical properties and the effect of humidity on the physical properties of PEGs are important parameters for the choice of a PEG to be acceptable as an excipient in pharmaceutical formulations. This study was done to determine the precision of the DSC physical properties for a wide range of PEGs with varying molecular weights from 194 to 23000 daltons. Nine different molecular weights of PEGs were examined in a DSC controlled Heat-Cool-Heat-Cool-Heat (HCHCH) cycle and the observed reproducible values of melting temperature, heat of fusion, crystallization temperature and the heat of crystallization were compared with values obtained from the literature and the observed percent crystallinity was again cross-checked by X-ray Diffraction (XRD) studies. The comparison values indicated acceptable precision. This study was also done to check the effect of humidity on the DSC physical properties for the entire range of PEGs. The results indicated that humidity probably has a higher effect on the physical properties of the low molecular weight PEGs as compared to the high molecular weight PEGs.

Effect of polyethylene glycols on the trans-ungual delivery of terbinafine.

PubMed

Nair, Anroop B; Chakraborty, Bireswar; Murthy, S Narasimha

2010-12-01

Topical nail drug delivery could be improved by identifying potent chemical penetration enhancers. The purpose of this study was to assess the effect of polyethylene glycols (PEGs) on the trans-ungual delivery of terbinafine. In vitro permeation studies were carried out by passive and iontophoresis (0.5 mA/cm2) processes for a period of 1 h using gel formulations containing different molecular weight PEGs (30%w/w). The release of drug from the loaded nail plates and the possible mechanisms for the enhanced delivery was studied. Passive delivery using formulation with low molecular weight PEGs (200 and 400 MW) indicated moderate enhancement in the permeation and drug load in the nail plate, compared to the control formulation. However, the effect of low molecular weight PEGs was predominant during iontophoresis process with greater amount of terbinafine being permeated (≈35 µg/cm2) and loaded into the nail plate (≈2.7 µg/mg). However, little or no effect on drug delivery was observed with high molecular weight PEGs (1000- 3350 MW) in passive and iontophoresis processes. Release of drug from the nail plates loaded by iontophoresis using low molecular weight PEG (400 MW) exhibited sustain effect which continued over a period of 72 days. The enhancement in drug permeation by low molecular weight PEGs is likely due to their ability to lead to greater water uptake and swelling of nail. This study concluded that the low molecular weight PEGs are indeed a promising trans-ungual permeation enhancer.

Computer program to perform cost and weight analysis of transport aircraft. Volume 2: Technical volume

NASA Technical Reports Server (NTRS)

1973-01-01

An improved method for estimating aircraft weight and cost using a unique and fundamental approach was developed. The results of this study were integrated into a comprehensive digital computer program, which is intended for use at the preliminary design stage of aircraft development. The program provides a means of computing absolute values for weight and cost, and enables the user to perform trade studies with a sensitivity to detail design and overall structural arrangement. Both batch and interactive graphics modes of program operation are available.

Single machine scheduling with slack due dates assignment

NASA Astrophysics Data System (ADS)

Liu, Weiguo; Hu, Xiangpei; Wang, Xuyin

2017-04-01

This paper considers a single machine scheduling problem in which each job is assigned an individual due date based on a common flow allowance (i.e. all jobs have slack due date). The goal is to find a sequence for jobs, together with a due date assignment, that minimizes a non-regular criterion comprising the total weighted absolute lateness value and common flow allowance cost, where the weight is a position-dependent weight. In order to solve this problem, an ? time algorithm is proposed. Some extensions of the problem are also shown.

Water Quality for Hexachlorethane

DTIC Science & Technology

1988-03-01

50,000 to 100,000 bacterial cells/mL; therefore, the teat organisms wete provided with a food source during testing . Two replicates of five animals ...liver weight was significantly in- creased. Two animals died, one each during weeks 4 and 5. Dermal sensitization tests performed on guinea pigs...absolute body waights starting at week 4 in animals exposed to 260 ppm than in control rats, Relative liver, lung, kidney, and testes weights were increased

Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances

USGS Publications Warehouse

Chin, Y.-P.; Aiken, G.; O'Loughlin, E.

1994-01-01

The number- and weight-averaged molecular weights of a number of aquatic fulvic acids, a commercial humic acid, and unfractionated organic matter from four natural water samples were measured by high-pressure size exclusion chromatography (HPSEC). Molecular weights determined in this manner compared favorably with those values reported in the literature. Both recent literature values and our data indicate that these substances are smaller and less polydisperse than previously believed. Moreover, the molecular weights of the organic matter from three of the four natural water samples compared favorably to the fulvic acid samples extracted from similar environments. Bulk spectroscopic properties of the fulvic substances such as molar absorptivity at 280 nm and the E4/E6 ratio were also measured. A strong correlation was observed between molar absorptivity, total aromaticity, and the weight average molecular weights of all the humic substances. This observation suggests that bulk spectroscopic properties can be used to quickly estimate the size of humic substances and their aromatic contents. Both parameters are important with respect to understanding humic substance mobility and their propensity to react with both organic and inorganic pollutants. ?? 1994 American Chemical Society.

Data and performances of selected aircraft and rotorcraft

NASA Astrophysics Data System (ADS)

Filippone, Antonio

2000-11-01

The purpose of this article is to provide a synthetic and comparative view of selected aircraft and rotorcraft (nearly 300 of them) from past and present. We report geometric characteristics of wings (wing span, areas, aspect-ratios, sweep angles, dihedral/anhedral angles, thickness ratios at root and tips, taper ratios) and rotor blades (type of rotor, diameter, number of blades, solidity, rpm, tip Mach numbers); aerodynamic data (drag coefficients at zero lift, cruise and maximum absolute glide ratio); performances (wing and disk loadings, maximum absolute Mach number, cruise Mach number, service ceiling, rate of climb, centrifugal acceleration limits, maximum take-off weight, maximum payload, thrust-to-weight ratios). There are additional data on wing types, high-lift devices, noise levels at take-off and landing. The data are presented on tables for each aircraft class. A graphic analysis offers a comparative look at all types of data. Accuracy levels are provided wherever available.

40 CFR Table A-7 to Subpart A of... - Data Elements That Are Inputs to Emission Equations and for Which the Reporting Deadline Is March...

Code of Federal Regulations, 2012 CFR

2012-07-01

... mass balance equation. K 98.116(b) Only annual production by product from each EAF (No CEMS). K 98.116... carbon content values, molecular weights for gaseous feedstocks, molecular weights for gaseous products... of gas flared, average molecular weight, carbon content of the flare, and molar volume conversion...

Formation of high molecular weight products from benzene during boundary lubrication

NASA Technical Reports Server (NTRS)

Morales, W.

1985-01-01

High molecular weight products were detected on the wear track of an iron disk at the end of a sliding friction and wear test using benzene as a lubricant. Size exclusion chromagography in conjunction with UV analysis gave evidence that the high molecular weight products are polyphenyl ether type substances. Organic electrochemistry was used to elucidate the possible surface reaction mechanisms.

Antiedematogenic and antioxidant properties of high molecular weight protein sub-fraction of Calotropis procera latex in rat.

PubMed

Chaudhary, Priyanka; de Araújo Viana, Carolina; Ramos, Marcio V; Kumar, Vijay L

2015-03-01

The aim was to evaluate the effect of high molecular weight protein fraction of Calotropis procera latex on edema formation and oxidative stress in carrageenan-induced paw inflammation. A sub-plantar injection of carrageenan was given to induce edema in the hind paw of the rat. The inhibitory effect of high molecular weight protein fraction of C. procera latex was evaluated following intravenous administration (5 and 25 mg/kg body weight) and was compared with that of diclofenac given orally (5 mg/kg). The levels of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS) and myeloperoxidase (MPO) were measured in the inflamed paw tissue at the end of the study. The high molecular weight protein fraction obtained from the latex of C. procera produced a dose-dependent inhibition of edema formation that was accompanied by normalization of levels of oxidative stress markers (GSH and TBARS) and MPO, a marker for neutrophils in the paw tissue. The high molecular weight protein fraction of C. procera latex ameliorates acute inflammation in the paw through its antioxidant effect.

[Crosslinking sodium hyaluronate gel with different ratio of molecular weight for subcutaneous injection: animal experimental study and clinical trials subcutaneous injection].

PubMed

Ran, Weizhi; Wang, Xiaoli; Hu, Yuefei; Gao, Songying; Yang, Yahong; Sun, Jian; Sun, Shuming; Liu, Zhongmei; Wang, Jiangling

2015-05-01

To investigate the biocompatibility and degradation rate of crosslinking sodium hyaluronate gel with different ratio of molecular weight, so as to choose the effective, safe and totally degraded hyaluronate gel for aesthetic injection. (1) Compound colloid was formed by cross-linking the divinyl sulphone and sodium hyaluronate with different molecular weight (4 x 10(5), 8 x 10(5), 10 x 10(5), 12 x 10(5)). (2) Healthy level KM mice was randomly divided into two groups to receive hyaluronic acid gel or liquid injection. Each group was subdivided into three subgroup to receive hyaluronic acid with different molecular weight. The biocompatibility and degradation rate, of hyaluronate were observed at 7, 90, 180 days after injection. At the same time, different molecular weight of sodium hyaluronate gel is sealed or exposed respectively under the low temperature preservation to observe its natural degradation rate. (3) The most stable colloid was selected as aesthetic injector for volunteers to observe the aesthetic effect. The sodium hyaluronate gel with molecular of 4 x 10(5) was completely degraded 90 days later. The sodium hyaluronate gel with molecular of 8 x 10(5) was completely degraded 180 days later. The sodium hyaluronate gel with molecular of 10 x 10(5) was degraded to 90.0% after 180 days. The sodium hyaluronate liquid can be degraded completely within 7 days. The colloid could be kept for at least 12 months when sealed under low temperature, but was totally degraded when exposed for I d. Sodium hyaluronate gel with molecular 10 x 10(5) was confirmed to be kept for at least 6 months in animal experiment and clinical trials. Under the same condition of material ratio, the higher the molecular weight is, the lower the degradation rate is. But the liquidity of gel is not good for injection when molecular weight is too large. It suggests that Sodium hyaluronate gel with molecular 10 x 10(5) maybe the best choice in cosmetic injections.

Correspondence between ion-cluster and bulk thermodynamics: on the validity of the cluster pair approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlcek, Lukas; Chialvo, Ariel; Simonson, J Michael

2013-01-01

Molecular models and experimental estimates based on the cluster pair approximation (CPA) provide inconsistent predictions of absolute single-ion hydration properties. To understand the origin of this discrepancy we used molecular simulations to study the transition between hydration of alkali metal and halide ions in small aqueous clusters and bulk water. The results demonstrate that the assumptions underlying the CPA are not generally valid as a result of a significant shift in the ion hydration free energies (~15 kJ/mol) and enthalpies (~47 kJ/mol) in the intermediate range of cluster sizes. When this effect is accounted for, the systematic differences between modelsmore » and experimental predictions disappear, and the value of absolute proton hydration enthalpy based on the CPA gets in closer agreement with other estimates.« less

Does Use of Low-Molecular-Weight Heparin during Pregnancy Influence the Risk of Prolonged Labor: A Population-Based Cohort Study

PubMed Central

Sandström, Anna; Cnattingius, Sven; Wikström, Anna-Karin

2015-01-01

Background The use of low-molecular-weight heparins (LMWHs) during pregnancy is increasing. In vitro studies and small clinical studies support the hypothesis that LMWH treatment during pregnancy may reduce duration of labor. The aim of this study was to investigate if use of LMWH is associated with a reduced risk of diagnosis of prolonged labor, after taking maternal, fetal and other delivery characteristics into account. Methods and Findings A population-based cohort study from the Swedish Medical Birth Register from April 2006 through December 2011. We identified 514 875 term (≥37 weeks) deliveries of live singleton infants in cephalic presentation with spontaneous or induced onsets of labor. The Birth Register was linked to the Prescribed Drug Register to retrieve information on dispensed LMWH during pregnancy and to the Patient Register for information on underlying diagnosis for use of LMWH. Diagnosis of prolonged labor in the Birth Register was retrieved from diagnosis at discharge from the delivery hospital. The risk of diagnosis of prolonged labor in relation to treatment with LMWH was assessed using logistic regression analysis to estimate unadjusted and adjusted odds ratios. A total of 5 275 (1.0%) of the pregnant women used LMWH. The absolute risk of diagnosis of prolonged labor for nulliparous women was 19.9% among women using LMWH in third trimester, and 21.2% in women without use of LMWH. For parous women the corresponding absolute risks were 4.3% and 4.7%, respectively. Compared to nulliparous women without use of LMWH, nulliparous women with LMWH during third trimester had an odds ratio (OR) of 0.92 (95% CI 0.81–1.05, p-value: 0.051) for diagnosis of prolonged labor in unadjusted analyses and after adjustments for maternal characteristics, gestational age and epidural analgesia the OR was 1.00 (95% CI 0.87–1.15, p-value: 0.673). Parous women treated with LMWH in third trimester presented the same pattern, unadjusted OR for diagnosis of prolonged labor was 0.92 (95% CI 0.76–1.12, p-value: 0.418) and after adjustments OR was 0.99 (95% CI 0.80–1.22, p-value: 0.892). One limitation with the study was that information on prolonged labor was based on discharge diagnoses from the delivery hospital according to the International Classification of Diseases (ICD). Conclusions Treatment with LMWH during pregnancy is not associated with a risk of diagnosis of prolonged labor after adjustments for maternal, fetal and delivery characteristics. PMID:26465918

Integrated Navigation System Design for Micro Planetary Rovers: Comparison of Absolute Heading Estimation Algorithms and Nonlinear Filtering

PubMed Central

Ilyas, Muhammad; Hong, Beomjin; Cho, Kuk; Baeg, Seung-Ho; Park, Sangdeok

2016-01-01

This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional navigation sensors/systems, hence the general methods of terrestrial navigation may not be applicable to these applications. While relative attitude and position can be tracked in a way similar to those for ground robots, absolute navigation information is hard to achieve on a remote celestial body, like Moon or Mars, in contrast to terrestrial applications. In this study, two absolute attitude estimation algorithms were developed and compared for accuracy and robustness. The estimated absolute attitude was fused with the relative attitude sensors in a framework of nonlinear filters. The nonlinear Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) were compared in pursuit of better accuracy and reliability in this nonlinear estimation problem, using only on-board low cost MEMS sensors. Experimental results confirmed the viability of the proposed algorithms and the sensor suite, for low cost and low weight micro planetary rovers. It is demonstrated that integrating the relative and absolute navigation MEMS sensors reduces the navigation errors to the desired level. PMID:27223293

Integrated Navigation System Design for Micro Planetary Rovers: Comparison of Absolute Heading Estimation Algorithms and Nonlinear Filtering.

PubMed

Ilyas, Muhammad; Hong, Beomjin; Cho, Kuk; Baeg, Seung-Ho; Park, Sangdeok

2016-05-23

This paper provides algorithms to fuse relative and absolute microelectromechanical systems (MEMS) navigation sensors, suitable for micro planetary rovers, to provide a more accurate estimation of navigation information, specifically, attitude and position. Planetary rovers have extremely slow speed (~1 cm/s) and lack conventional navigation sensors/systems, hence the general methods of terrestrial navigation may not be applicable to these applications. While relative attitude and position can be tracked in a way similar to those for ground robots, absolute navigation information is hard to achieve on a remote celestial body, like Moon or Mars, in contrast to terrestrial applications. In this study, two absolute attitude estimation algorithms were developed and compared for accuracy and robustness. The estimated absolute attitude was fused with the relative attitude sensors in a framework of nonlinear filters. The nonlinear Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) were compared in pursuit of better accuracy and reliability in this nonlinear estimation problem, using only on-board low cost MEMS sensors. Experimental results confirmed the viability of the proposed algorithms and the sensor suite, for low cost and low weight micro planetary rovers. It is demonstrated that integrating the relative and absolute navigation MEMS sensors reduces the navigation errors to the desired level.

Improved synthesis with high yield and increased molecular weight of poly(alpha,beta-malic acid) by direct polycondensation.

PubMed

Kajiyama, Tetsuto; Kobayashi, Hisatoshi; Taguchi, Tetsushi; Kataoka, Kazunori; Tanaka, Junzo

2004-01-01

The development of synthetic biodegradable polymers, such as poly(alpha-hydroxy acid), is particularly important for constructing medical devices, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing high molecular weight poly(malic acid) (HMW--PMA) as a biodegradable and bioabsorbable water-soluble polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of l-malic acid, including the reaction times, temperatures, and catalysts. The molecular weight of synthesized alpha,beta-PMA is dependent on both the reaction temperature and time. The optimum reaction condition to obtain alpha,beta-PMA by direct polycondensation using tin(II) chloride as a catalyst was thus determined to be 110 degrees C for 45 h with a molecular weight of 5300. The method for alpha,beta-PMA synthesis established here will facilitate production of alpha,beta-PMA of various molecular weights, which may have a potential utility as biomaterials.

Reorganization of low-molecular-weight fraction of plasma proteins in the annual cycle of cyprinidae.

PubMed

Andreeva, A M; Lamas, N E; Serebryakova, M V; Ryabtseva, I P; Bolshakov, V V

2015-02-01

Reorganization of the low-molecular-weight fraction of cyprinid plasma was analyzed using various electrophoretic techniques (disc electrophoresis, electrophoresis in polyacrylamide concentration gradient, in polyacrylamide with urea, and in SDS-polyacrylamide). The study revealed coordinated changes in the low-molecular-weight protein fractions with seasonal dynamics and related reproductive rhythms of fishes. We used cultured species of the Cyprinidae family with sequenced genomes for the detection of these interrelations in fresh-water and anadromous cyprinid species. The common features of organization of fish low-molecular-weight plasma protein fractions made it possible to make reliable identification of their proteins. MALDI mass-spectrometry analysis revealed the presence of the same proteins (hemopexin, apolipoproteins, and serpins) in the low-molecular-weight plasma fraction in wild species and cultured species with sequenced genomes (carp, zebrafish). It is found that the proteins of the first two classes are organized as complexes made of protein oligomers. Stoichiometry of these complexes changes in concordance with the seasonal and reproductive rhythms.

The polysaccharide and low molecular weight components of Opuntia ficus indica cladodes: Structure and skin repairing properties.

PubMed

Di Lorenzo, Flaviana; Silipo, Alba; Molinaro, Antonio; Parrilli, Michelangelo; Schiraldi, Chiara; D'Agostino, Antonella; Izzo, Elisabetta; Rizza, Luisa; Bonina, Andrea; Bonina, Francesco; Lanzetta, Rosa

2017-02-10

The Opuntia ficus-indica multiple properties are reflected in the increasing interest of chemists in the identification of its natural components having pharmaceutical and/or cosmetical applications. Here we report the structural elucidation of Opuntia ficus-indica mucilage that highlighted the presence of components differing for their chemical nature and the molecular weight distribution. The high molecular weight components were identified as a linear galactan polymer and a highly branched xyloarabinan. The low molecular weight components were identified as lactic acid, D-mannitol, piscidic, eucomic and 2-hydroxy-4-(4'-hydroxyphenyl)-butanoic acids. A wound healing assay was performed in order to test the cicatrizing properties of the various components, highlighting the ability of these latter to fasten dermal regeneration using a simplified in vitro cellular model based on a scratched keratinocytes monolayer. The results showed that the whole Opuntia mucilage and the low molecular weight components are active in the wound repair. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-molecular-weight polymers for protein crystallization: poly-γ-glutamic acid-based precipitants

PubMed Central

Hu, Ting-Chou; Korczyńska, Justyna; Smith, David K.; Brzozowski, Andrzej Marek

2008-01-01

Protein crystallization has been revolutionized by the intro­duction of high-throughput technologies, which have led to a speeding up of the process while simultaneously reducing the amount of protein sample necessary. Nonetheless, the chemistry dimension of protein crystallization has remained relatively undeveloped. Most crystallization screens are based on the same set of precipitants. To address this shortcoming, the development of new protein precipitants based on poly-γ-­glutamic acid (PGA) polymers with different molecular-weight ranges is reported here: PGA-LM (low molecular weight) of ∼400 kDa and PGA-HM (high molecular weight) of >1000 kDa. It is also demonstrated that protein precipitants can be expanded further to polymers with much higher molecular weight than those that are currently in use. Furthermore, the modification of PGA-like polymers by covalent attachments of glucosamine substantially improved their solubility without affecting their crystallization properties. Some preliminary PGA-based screens are presented here. PMID:18703844

Effects of the Terminal Structure, Purity, and Molecular Weight of an Amorphous Conjugated Polymer on Its Photovoltaic Characteristics.

PubMed

Kuwabara, Junpei; Yasuda, Takeshi; Takase, Naoto; Kanbara, Takaki

2016-01-27

The photovoltaic characteristics of an amorphous polymer containing EDOT and fluorene units were investigated. In particular, the effects of the terminal structure, residual amount of Pd, and molecular weight were systematically investigated. Direct arylation polycondensation of EDOT followed by an established purification method readily afforded polymers with different terminal structures, Pd contents, and molecular weights. Of these factors, the terminal structure of the polymer was a crucial factor affecting the photovoltaic characteristics. For example, the polymer with a Br terminal had a PCE of 2.9% in bulk-heterojunction organic photovoltaics (BHJ OPVs) with a fullerene derivative, whereas the polymer without a Br terminal had a PCE of 4.6% in the same cell configuration. The decreased Pd residues and high molecular weights of the polymers increased the long-term stability of the devices. Moreover, BHJ OPVs containing the high-molecular-weight polymer could be fabricated with an environmentally friendly nonhalogenated solvent.

Increasing molecular weight parameters of a helical polymer through polymerization in a chiral solvent.

PubMed

Holder, Simon J; Achilleos, Mariliz; Jones, Richard G

2006-09-27

In this communication, we will demonstrate that polymerization in a chiral solvent can affect the molecular weight distribution of the product by perturbing the balance of the P and M helical screw senses of the growing chains. Specifically, for the Wurtz-type synthesis of polymethylphenylsilane (PMPS) in either (R) or (S)-limonene, the weight-average molecular weight of the products (average Mw = 80 000) was twice that of PMPS synthesized in (R/S)-limonene (average Mw = 39 200). Peturbation of the helical segmentation along the polymer chains leads to a reduction in the rate of occurrence of a key termination step. This the first time that a chiral solvent has been demonstrated to have such an effect on a polymerization process in affecting molecular weight parameters in contrast to affecting tacticity.

Production of low-molecular weight soluble yeast β-glucan by an acid degradation method.

PubMed

Ishimoto, Yuina; Ishibashi, Ken-Ichi; Yamanaka, Daisuke; Adachi, Yoshiyuki; Kanzaki, Ken; Iwakura, Yoichiro; Ohno, Naohito

2018-02-01

β-glucan is widely distributed in nature as water soluble and insoluble forms. Both forms of β-glucan are utilized in several fields, especially for functional foods. Yeast β-glucan is a medically important insoluble particle. Solubilization of yeast β-glucan may be valuable for improving functional foods and in medicinal industries. In the present study, we applied an acid degradation method to solubilize yeast β-glucan and found that β-glucan was effectively solubilized to low-molecular weight β-glucans by 45% sulfuric acid treatment at 20°C. The acid-degraded soluble yeast β-glucan (ad-sBBG) was further fractionated into a higher-molecular weight fraction (ad-sBBG-high) and a lower-molecular weight fraction (ad-sBBG-low). Since ad-sBBG-high contained mannan, while ad-sBBG-low contained it only scarcely, it was possible to prepare low-molecular weight soluble β-glucan with higher purity. In addition, ad-sBBG-low bound to dectin-1, which is an innate immunity receptor of β-glucan, and showed antagonistic activity against reactive oxygen production and cytokine synthesis by macrophages. Thus, this acid degradation method is an important procedure for generating immune-modulating, low-molecular weight, soluble yeast β-glucan. Copyright © 2017 Elsevier B.V. All rights reserved.

Retraction Note: Catalytic living ring-opening metathesis polymerization

NASA Astrophysics Data System (ADS)

Nagarkar, Amit A.; Kilbinger, Andreas F. M.

2018-05-01

We the authors are retracting this Article because of our failure to reproduce the molecular weight dispersities (PDI) shown in Fig. 4 using the chain-transfer agent described in the paper (CTA1). While the degenerate chain-transfer mechanism described in Fig. 3 is correct, the best molecular weight dispersities that could be reproduced with the chain-transfer agent shown in the Article are much larger (PDI > 2.0) than reported.We have since studied the kinetics of CTA1 in comparison with several other chain-transfer agents we are currently investigating and we now understand that the reactivity of CTA1 towards propagating ruthenium alkylidene complexes is very low. Very long monomer addition times would therefore have been necessary to gain control over the molecular weight distribution. Such long addition times would exceed the lifetime of the Grubbs catalyst in solution. Faster addition of the monomer has since repeatedly been shown to broaden the molecular weight dispersity.Additionally, the best chain-transfer agents we are currently investigating are orders of magnitude more reactive than CTA1 but give broader molecular weight dispersities than reported in Fig. 4. Molecular weight and dispersity control as shown in Fig. 4 is therefore an inappropriate claim for CTA1.The authors deeply regret these errors and apologize to the community.

Molecular structure of the pyruvate dehydrogenase complex from Escherichia coli K-12.

PubMed

Vogel, O; Hoehn, B; Henning, U

1972-06-01

The pyruvate dehydrogenase core complex from E. coli K-12, defined as the multienzyme complex that can be obtained with a unique polypeptide chain composition, has a molecular weight of 3.75 x 10(6). All results obtained agree with the following numerology. The core complex consists of 48 polypeptide chains. There are 16 chains (molecular weight = 100,000) of the pyruvate dehydrogenase component, 16 chains (molecular weight = 80,000) of the dihydrolipoamide dehydrogenase component, and 16 chains (molecular weight = 56,000) of the dihydrolipoamide dehydrogenase component. Usually, but not always, pyruvate dehydrogenase complex is produced in vivo containing at least 2-3 mol more of dimers of the pyruvate dehydrogenase component than the stoichiometric ratio with respect to the core complex. This "excess" component is bound differently than are the eight dimers in the core complex.

Vapor-pressure osmometric study of the molecular weight and aggregation tendency of a reference-soil fulvic acid

USGS Publications Warehouse

Marinsky, J.A.; Reddy, M.M.

1990-01-01

The molecular weight and aggregation tendency of a reference-soil fulvic acid in Armadale horizon Bh were determined by vapor-pressure osmometry using tetrahydrofuran and water as solvents. With tetrahydrofuran, number-average molecular weight values of 767 ?? 34 and 699 ?? 8 daltons were obtained from two separate sets of measurements. Two sets of measurements with water also yielded values within this range (754 ?? 70 daltons) provided that the fulvic acid concentration in water did not exceed 7 mg ml-1; at higher concentrations (9.1-13.7 mg ml-1) a number-average molecular weight of 956 ?? 25 daltons was resolved, providing evidence of molecular aggregation. Extension of these studies to 80% neutralized fulvic acid showed that a sizeable fraction of the sodium counter ion is not osmotically active.

Post-exercise ingestion of a unique, high molecular weight glucose polymer solution improves performance during a subsequent bout of cycling exercise.

PubMed

Stephens, Francis B; Roig, Marc; Armstrong, Gerald; Greenhaff, Paul L

2008-01-15

The aim of the present study was to determine the effect of post-exercise ingestion of a unique, high molecular weight glucose polymer solution, known to augment gastric emptying and post-exercise muscle glycogen re-synthesis, on performance during a subsequent bout of intense exercise. On three randomized visits, eight healthy men cycled to exhaustion at 73.0% (s = 1.3) maximal oxygen uptake (90 min, s = 15). Immediately after this, participants consumed a one-litre solution containing sugar-free flavoured water (control), 100 g of a low molecular weight glucose polymer or 100 g of a very high molecular weight glucose polymer, and rested on a bed for 2 h. After recovery, a 15-min time-trial was performed on a cycle ergometer, during which work output was determined. Post-exercise ingestion of the very high molecular weight glucose polymer solution resulted in faster and greater increases in blood glucose (P < 0.001) and serum insulin (P < 0.01) concentrations than the low molecular weight glucose polymer solution, and greater work output during the 15-min time-trial (164.1 kJ, s = 21.1) than both the sugar-free flavoured water (137.5 kJ, s = 24.2; P < 0.05) and the low molecular weight glucose polymer (149.4 kJ, s = 21.8; P < 0.05) solutions. These findings could be of practical importance for athletes wishing to optimize performance by facilitating rapid re-synthesis of the muscle glycogen store during recovery following prolonged sub-maximal exercise.

A log-normal distribution model for the molecular weight of aquatic fulvic acids

USGS Publications Warehouse

Cabaniss, S.E.; Zhou, Q.; Maurice, P.A.; Chin, Y.-P.; Aiken, G.R.

2000-01-01

The molecular weight of humic substances influences their proton and metal binding, organic pollutant partitioning, adsorption onto minerals and activated carbon, and behavior during water treatment. We propose a lognormal model for the molecular weight distribution in aquatic fulvic acids to provide a conceptual framework for studying these size effects. The normal curve mean and standard deviation are readily calculated from measured M(n) and M(w) and vary from 2.7 to 3 for the means and from 0.28 to 0.37 for the standard deviations for typical aquatic fulvic acids. The model is consistent with several types of molecular weight data, including the shapes of high- pressure size-exclusion chromatography (HP-SEC) peaks. Applications of the model to electrostatic interactions, pollutant solubilization, and adsorption are explored in illustrative calculations.The molecular weight of humic substances influences their proton and metal binding, organic pollutant partitioning, adsorption onto minerals and activated carbon, and behavior during water treatment. We propose a log-normal model for the molecular weight distribution in aquatic fulvic acids to provide a conceptual framework for studying these size effects. The normal curve mean and standard deviation are readily calculated from measured Mn and Mw and vary from 2.7 to 3 for the means and from 0.28 to 0.37 for the standard deviations for typical aquatic fulvic acids. The model is consistent with several type's of molecular weight data, including the shapes of high-pressure size-exclusion chromatography (HP-SEC) peaks. Applications of the model to electrostatic interactions, pollutant solubilization, and adsorption are explored in illustrative calculations.

A single center retrospective cohort study comparing low-molecular-weight heparins to direct oral anticoagulants for the treatment of venous thromboembolism in patients with cancer - A real world experience.

PubMed

Phelps, Megan K; Wiczer, Tracy E; Erdeljac, H Paige; Van Deusen, Kelsey R; Porter, Kyle; Philips, Gary; Wang, Tzu-Fei

2018-01-01

Introduction Low-molecular-weight heparins are the standard treatment for cancer-associated thrombosis. Recently, direct oral anticoagulants are a new option for thrombosis treatment; however, data supporting the use of direct oral anticoagulants for cancer-associated thrombosis are limited. Objectives The primary objective of this study was to determine the rate of recurrent cancer-associated thrombosis and major bleeding within 6 months of starting either low-molecular-weight heparin or direct oral anticoagulant for treatment of cancer-associated thrombosis. Secondary objectives were to determine the rates of clinically relevant-non-major bleeding and all-cause mortality. Patients/methods This is a retrospective cohort study including adults with cancer-associated thrombosis treated with low-molecular-weight heparin or direct oral anticoagulant between 2010 and 2016 at the Ohio State University. Medical records were reviewed for 6 months after initiation of anticoagulation or until the occurrence of recurrent cancer-associated thrombosis, major bleeding, cessation of anticoagulation of interest, or death, whichever occurred first. Results Four hundred and eighty patients were included (290 low-molecular-weight heparin and 190 direct oral anticoagulant). Patients treated with direct oral anticoagulant were found to carry "lower risk" features including cancer with lower VTE risk and lower rate of metastatic disease. After adjustment for baseline differences, there was no significant difference in the rate of recurrent cancer-associated thrombosis (7.2% low-molecular-weight heparin vs 6.3% direct oral anticoagulant, p = 0.71) or major bleeding (7.6% low-molecular-weight heparin vs 2.6% direct oral anticoagulant, p = 0.08). Conclusions Our study demonstrates that in a select population of cancer patients with VTE, direct oral anticoagulant use can be as effective and safe compared to the standard therapy with low-molecular-weight heparin.

Composite Sandwich Structures for Shock Mitigation and Energy Absorption

DTIC Science & Technology

2016-06-28

analysis of the blast performance of foam -core, composite sandwich panels was that on a per unit areal weight density basis, lighter and more crushable... foam cores offered greater blast resistance and energy absorption than the heavier and stronger foam cores. This was found to be the case even on an...absolute weight basis for cuNed sandwich panels and panels subjected to underwater blast. 15. SUBJECT TERMS composite; foam -core sandwich; blast

Modeling the relationship between body weight and energy intake: A molecular diffusion-based approach

PubMed Central

2012-01-01

Background Body weight is at least partly controlled by the choices made by a human in response to external stimuli. Changes in body weight are mainly caused by energy intake. By analyzing the mechanisms involved in food intake, we considered that molecular diffusion plays an important role in body weight changes. We propose a model based on Fick's second law of diffusion to simulate the relationship between energy intake and body weight. Results This model was applied to food intake and body weight data recorded in humans; the model showed a good fit to the experimental data. This model was also effective in predicting future body weight. Conclusions In conclusion, this model based on molecular diffusion provides a new insight into the body weight mechanisms. Reviewers This article was reviewed by Dr. Cabral Balreira (nominated by Dr. Peter Olofsson), Prof. Yang Kuang and Dr. Chao Chen. PMID:22742862

Hydroxyurea and Growth in Young Children With Sickle Cell Disease

PubMed Central

Houston, Patricia E.; Wang, Winfred C.; Iyer, Rathi V.; Goldsmith, Jonathan; Casella, James F.; Reed, Caroline K.; Rogers, Zora R.; Waclawiw, Myron A.; Thompson, Bruce

2014-01-01

BACKGROUND: Growth impairment is a known complication of sickle cell disease. Effects of hydroxyurea (HU) on growth in very young children are not known. METHODS: Height, weight, BMI, and head circumference (HC) were compared with World Health Organization (WHO) standards in BABY HUG, a multicenter, randomized, double-blinded, placebo-controlled 2-year clinical trial of HU in 193 children 9 to 18 months of age. Anthropometric data were closely monitored and converted to z scores by using WHO standardized algorithms for descriptive analyses. The treatment and placebo groups were compared longitudinally by using a mixed model analysis. RESULTS: At entry, the z scores of BABY HUG children were higher than WHO norms. After 2 years of HU or placebo treatment, there were no significant differences between the groups, except for the mean HC z scores at study exit (HU: +0.8 versus placebo: +1.0, P = .05). Baseline z scores were the best predictors of z scores at study exit. The absolute neutrophil count, absolute reticulocyte count, and total white blood cell count had significant negative correlations with growth measures. CONCLUSIONS: Both groups had normal or near normal anthropometric measures during the study. The HC z scores at study entry and exit were slightly greater than WHO norms. Higher baseline white blood cell count, absolute reticulocyte count, and absolute neutrophil count were associated with poorer growth. The significance of the slightly lower HC in the treatment group at study exit is not clear. Trends toward normalization of weight and height and effects on HC will be monitored in ongoing BABY HUG follow-up studies. PMID:25157002

Source apportionment of soil heavy metals using robust absolute principal component scores-robust geographically weighted regression (RAPCS-RGWR) receptor model.

PubMed

Qu, Mingkai; Wang, Yan; Huang, Biao; Zhao, Yongcun

2018-06-01

The traditional source apportionment models, such as absolute principal component scores-multiple linear regression (APCS-MLR), are usually susceptible to outliers, which may be widely present in the regional geochemical dataset. Furthermore, the models are merely built on variable space instead of geographical space and thus cannot effectively capture the local spatial characteristics of each source contributions. To overcome the limitations, a new receptor model, robust absolute principal component scores-robust geographically weighted regression (RAPCS-RGWR), was proposed based on the traditional APCS-MLR model. Then, the new method was applied to the source apportionment of soil metal elements in a region of Wuhan City, China as a case study. Evaluations revealed that: (i) RAPCS-RGWR model had better performance than APCS-MLR model in the identification of the major sources of soil metal elements, and (ii) source contributions estimated by RAPCS-RGWR model were more close to the true soil metal concentrations than that estimated by APCS-MLR model. It is shown that the proposed RAPCS-RGWR model is a more effective source apportionment method than APCS-MLR (i.e., non-robust and global model) in dealing with the regional geochemical dataset. Copyright © 2018 Elsevier B.V. All rights reserved.

The treatment of adult obesity through direct manipulation of specific eating behaviors.

PubMed

Rodriguez, L; Sandler, J

1981-06-01

The present study investigated the effects of three different conditions on weight loss in adult obese subjects. The three conditions were: (1) Monitoring-Contract (MC) in which subjects were reinforced by the return of a valued possession for changes in eating habits; (2) Monitoring (M); and Attention-Placebo (AP). Subjects in the MC group lost significantly more absolute weight and a significantly greater percentage of weight at the end of treatment than did the subjects in the M and AP groups. These changes were still manifested at a 2 month and a 6 month follow-up. The long-term advantages of a weight reduction program which focuses on a gradual and systematic weight loss through changes in eating habits are discussed.

Characterization of water molecular state in in-vivo thick tissues using diffuse optical spectroscopic imaging

NASA Astrophysics Data System (ADS)

Chung, So Hyun

Structural changes in water molecules are related to physiological, anatomical and pathological properties of tissues. Near infrared (NIR) optical absorption methods are sensitive to water; however, detailed characterization of water in thick tissues is difficult to achieve because subtle spectral shifts can be obscured by multiple light scattering. In the NIR, a water absorption peak is observed around 975 nm. The precise NIR peak's shape and position are highly sensitive to water molecular disposition. A bound water index (BWI) was developed that quantifies the spectral shift and shape changes observed in tissue water absorption spectra measured by broadband diffuse optical spectroscopic imaging (DOSI). DOSI quantitatively measures light absorption and scattering spectra in cm-deep tissues and therefore reveals bound water spectral shifts. BWI as a water state index was validated by comparing broadband DOSI to MRI and a conductivity cell using bound water phantoms. Non-invasive BWI measurements of malignant and normal tissues in 18 subjects showed a significantly higher fraction of free water in malignant tissues (p<0.0001) compared to normal tissues. BWI showed potential as a prognostic index based on high correlations with tumor grade and size. An algorithm for absolute temperature measurements in deep tissues was developed based on resolving opposing effects of water vibrational frequency shifts due to macromolecular binding. DOSI measures absolute temperature with a difference of 1.1+/-0.91°C from a thermistor. Deep tissue temperature measured in forearms during cold-stress was consistent with previously reported invasively-measured deep tissue temperature. Finally, the BWI was compared to Apparent Diffusion Coefficient (ADC) of diffusion weighted MRI in 9 breast cancer patients. The BWI and ADC correlated (R=0.8, p=<0.01) and both parameters decreased with increasing bulk water content in cancer tissues. Although BWI and ADC are positively correlated in vivo, BWI appears to be more sensitive to free water in the extracellular matrix while ADC reflects increased tumor cellularity. The relationship between ADC, BWI and bulk water concentration suggests that both parameters have potential for assessing tumor histopathological grade. My results confirm the importance of water as a critical tissue component that can potentially provide unique insight into the molecular pathophysiology of cancer.

Evaluation of a Viscosity-Molecular Weight Relationship.

ERIC Educational Resources Information Center

Mathias, Lon J.

1983-01-01

Background information, procedures, and results are provided for a series of graduate/undergraduate polymer experiments. These include synthesis of poly(methylmethacrylate), viscosity experiment (indicating large effect even small amounts of a polymer may have on solution properties), and measurement of weight-average molecular weight by light…

Determination of the linear coefficient of thermal expansion in polymer films at the nanoscale: influence of the composition of EVA copolymers and the molecular weight of PMMA.

PubMed

González-Benito, J; Castillo, E; Cruz-Caldito, J F

2015-07-28

Nanothermal-expansion of poly(ethylene-co-vinylacetate), EVA, and poly(methyl methacrylate), PMMA, in the form of films was measured to finally obtain linear coefficients of thermal expansion, CTEs. The simple deflection of a cantilever in an atomic force microscope, AFM, was used to monitor thermal expansions at the nanoscale. The influences of: (a) the structure of EVA in terms of its composition (vinylacetate content) and (b) the size of PMMA chains in terms of the molecular weight were studied. To carry out this, several polymer samples were used, EVA copolymers with different weight percents of the vinylacetate comonomer (12, 18, 25 and 40%) and PMMA polymers with different weight average molecular weights (33.9, 64.8, 75.600 and 360.0 kg mol(-1)). The dependencies of the vinyl acetate weight fraction of EVA and the molecular weight of PMMA on their corresponding CTEs were analyzed to finally explain them using new, intuitive and very simple models based on the rule of mixtures. In the case of EVA copolymers a simple equation considering the weighted contributions of each comonomer was enough to estimate the final CTE above the glass transition temperature. On the other hand, when the molecular weight dependence is considered the free volume concept was used as novelty. The expansion of PMMA, at least at the nanoscale, was well and easily described by the sum of the weighted contributions of the occupied and free volumes, respectively.

Interaction of Mechanical Load with Growth Hormone (GH) and Insulin-Like Growth Factor I (IGF-I) on Slow-Twitch Skeletal Muscle and Bone

NASA Technical Reports Server (NTRS)

Linderman, Jon K.; Gosselink, Kristin L.; Wang, Tommy J.; Mukku, Venkat R.; Grindeland, Richard E.

1994-01-01

Exogenous humoral growth factors, combined with increased mechanical loading, reportedly induce hypertrophy of fast-, but not slow-twitch skeletal muscles, and have little effect in attenuating atrophy of slow-twitch muscle associated with exposure to microgravity in animals with intact neuroendocrine systems. These observations suggest that anabolic adjuvants and muscle tension do not interact to stimulate growth or maintenance of slow-twitch skeletal muscle. The purpose of the present study was to determine whether a chronic increase in mechanical loading (synergistic ablation) or hindlimb unweighting (hindlimb suspension) interact with exogenous GH and IGF-I (Genentech, So San Francisco, CA) in the slow-twitch soleus muscles of female rats (approx. 250 g). Bilateral ablation of the plantaris and gastrocnemius muscles induced 38% and 40% increases in the absolute (mg/pair) and relative (mg/100 g body weight) weights of the soleus, respectively (p less than or = 0.05), in ambulatory rats. GH and IGF-I interacted with chronic loading to increase absolute soleus mass an additional 20% (p less than or = 0.05), and mixed and myofibrillar protein contents an additional 12% and 7%, respectively (NS). In contrast, hindlimb suspension (HLS) resulted in 20% and 18% decreases in the absolute and relative weights of the soleus, respectively (p less than or = 0.05); GH and IGF-I did not spare loss of soleus mass or protein content in HLS rats. HLS decreased tibial plate thickness approx. 11% (p less than or = 0.05), but not weights of the tibia or femus. GH and IGF-I increased tibial plate thickness approx. 30% (p less than or = 0.05), in ambulatory and HLS rats, and increased femur and tibial weights 12% (p less than or = 0.05) and 8% (NS), respectively, in ambulatory rats, but had no effect in HLS rats. Results of the present investigation suggest that GH and IGF-I can stimulate hypertrophy of slow-twitch skeletal muscle when chronically overloaded, but can also stimulate growth of hindlimb bones in the absence of mechanical load.

Gel filtration of sialoglycoproteins.

PubMed Central

Alhadeff, J A

1978-01-01

The role of sialic acid in the gel-filtration behaviour of sialoglycoproteins was investigated by using the separated isoenzymes of purified human liver alpha-L-fucosidase and several other well-known sialic acid-containing glycoproteins (fetuin, alpha1-acid glycoprotein, thyroglobulin and bovine submaxillary mucin). For each glycoprotein studied, gel filtration of its desialylated derivative gave an apparent molecular weights much less than that expected just from removal of sialic acid. For the lower-molecular-weight glycoproteins (fetuin and alpha1-acid glyocprotein), gel filtration of the sialylated molecules led to apparent molecular weights much larger than the known values. The data indicate that gel filtration cannot be used for accurately determining the molecular weights of at least some sialoglycoproteins. Images Fig. 1. PMID:356853

Low Molecular Weight Chitosan–Insulin Polyelectrolyte Complex: Characterization and Stability Studies

PubMed Central

Al-Kurdi, Zakieh I.; Chowdhry, Babur Z.; Leharne, Stephen A.; Al Omari, Mahmoud M. H.; Badwan, Adnan A.

2015-01-01

The aim of the work reported herein was to investigate the effect of various low molecular weight chitosans (LMWCs) on the stability of insulin using USP HPLC methods. Insulin was found to be stable in a polyelectrolyte complex (PEC) consisting of insulin and LMWC in the presence of a Tris-buffer at pH 6.5. In the presence of LMWC, the stability of insulin increased with decreasing molecular weight of LMWC; 13 kDa LMWC was the most efficient molecular weight for enhancing the physical and chemical stability of insulin. Solubilization of insulin-LMWC polyelectrolyte complex (I-LMWC PEC) in a reverse micelle (RM) system, administered to diabetic rats, results in an oral delivery system for insulin with acceptable bioactivity. PMID:25830681

Polyimide molding powder, coating, adhesive, and matrix resin

NASA Technical Reports Server (NTRS)

St.clair, Terry L. (Inventor); Progar, Donald J. (Inventor)

1992-01-01

The invention is a polyimide prepared from 3,4'-oxydianiline (3,4'-ODA) and 4,4'-oxydiphthalic anhydride (ODPA), in 2-methoxyethyl ether (diglyme). The polymer was prepared in ultra high molecular weight and in a controlled molecular weight form which has a 2.5 percent offset in stoichiometry (excess diamine) with a 5.0 percent level of phthalic anhydride as an endcap. This controlled molecular weight form allows for greatly improved processing of the polymer for moldings, adhesive bonding, and composite fabrication. The higher molecular weight version affords tougher films and coatings. The overall polymer structure groups in the dianhydride, the diamine, and a metal linkage in the diamine affords adequate flow properties for making this polymer useful as a molding powder, adhesive, and matrix resin.

A study of physical properties of ODPA-p-PDA polyimide films

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, Abe; St.clair, Terry L.

1990-01-01

Physical properties were investigated of ODPA-p-PDA polyimide films, including their lower molecular weight versions with phthalimide endcaps. Free volume, determined by low energy positron annihilation in the test films, was the major parameter of interest since all other physical properties are ostensibly related to it. It affects the dielectric constant as well as the saturation moisture pickup of the test films. An empirical relation was developed between the free volume and molecular weight of the test films, comparable to the Mark-Houwink relation between the polymer solution viscosity and the molecular weight. Development of such a relation constitutes a unique achievement since it enables researchers to estimate the molecular weight of an intractable polymer in solid state for the first time.

Summary of GPC/DV results for space exposed poly(arylene ether phosphine oxide)s

NASA Technical Reports Server (NTRS)

Siochi, Emilie

1995-01-01

Gel Permeation Chromatography (GPC) was used to analyze poly(arylene ether phosphine oxide)s whose backbones were identical except for the ketone content and placement. These samples were exposed to low Earth orbit environment (predominantly atomic oxygen) on space shuttle flights. The materials and their unexposed controls were then characterized by GPC to investigate the effect of atomic oxygen on the molecular weight distributions. Analysis of the soluble portion of the samples revealed that there was significant loss of high molecular weight species. The presence of insoluble material also suggested that crosslinking was induced by the atomic oxygen exposure and that this very likely occurred at the high molecular weight portion of the molecular weight distribution.

Improvement in Obstructive Sleep Apnea With Weight Loss is Dependent on Body Position During Sleep.

PubMed

Joosten, Simon A; Khoo, Jun K; Edwards, Bradley A; Landry, Shane A; Naughton, Matthew T; Dixon, John B; Hamilton, Garun S

2017-05-01

Weight loss fails to resolve obstructive sleep apnea (OSA) in most patients; however, it is unknown as to whether weight loss differentially affects OSA in the supine compared with nonsupine sleeping positions. We aimed to determine if weight loss in obese patients with OSA results in a greater reduction in the nonsupine apnea/hypopnea index (AHI) compared with the supine AHI, thus converting participants into supine-predominant OSA. Post hoc analysis of data from a randomized controlled trial assessing the effect of weight loss (bariatric surgery vs. medical weight loss) on OSA in 60 participants with obesity (body mass index: >35 and <55) with recently diagnosed (<6 months) OSA and AHI of ≥ 20 events/hour. Patients were randomized to very low calorie diet with regular review (n = 30) or to laproscopic adjustable gastric banding (n = 30) with follow-up sleep study at 2 years. Eight of 37 (22%) patients demonstrated a normal nonsupine AHI (<5 events/hour) on follow-up compared to 0/37 (0%) patients at baseline (p = .003). These patients were younger (40.0 ± 9.6 years vs. 48.4 ± 6.5 years, p = .007) and lost significantly more weight (percentage weight change -23.0 [-21.0 to -31.6]% vs. -6.9 [1.9 to -17.4], p = .001). The percentage change in nonsupine AHI was greater than the percentage change in supine AHI (-54.0 [-15.4 to -87.9]% vs -33.1 [-1.8 to -69.1]%, p = .05). However, the change in absolute nonsupine AHI was not related to change in absolute supine AHI (p = .23). Following weight loss, a significant proportion (22%) of patients with obesity have normalization of the nonsupine AHI. For these patients, supine sleep avoidance may cure their OSA. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

An agarose gel electrophoretic method for analysis of hyaluronan molecular weight distribution.

PubMed

Lee, H G; Cowman, M K

1994-06-01

An electrophoretic method is described for determining the molecular weight distribution of hyaluronan (HA). The method involves separation of HA by electrophoresis on a 0.5% agarose gel, followed by detection of HA using the cationic dye Stains-All (3,3'-dimethyl-9-methyl-4,5,4'5'-dibenzothiacarbocyanine). The recommended sample load is 7 micrograms. Calibration of the method with HA standards of known molecular weight has established a linear relationship between electrophoretic mobility and the logarithm of the weight-average molecular weight over the range of approximately 0.2-6 x 10(6). The separated HA pattern may also be visualized after electrotransfer of HA from the agarose gel to a nylon membrane. The membrane may be stained with the dye alcian blue. Alternatively, specific detection of HA from impure samples can be achieved by probing the nylon membrane with biotin-labeled HA-binding protein and subsequent interaction with a streptavidin-linked gold reagent and silver staining for amplification. The electrophoretic method was used to analyze HA in two different liquid connective tissues. Normal human knee joint synovial fluid showed a narrow HA molecular weight distribution, with a peak at 6-7 x 10(6). Owl monkey vitreous HA also showed a narrow molecular weight distribution, with a peak at 5-6 x 10(6). These results agree well with available published data and indicate the applicability of the method to the analysis of impure HA samples which may be available in limited amounts.

Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.

PubMed

Heffernan, Natalie; Brunton, Nigel P; FitzGerald, Richard J; Smyth, Thomas J

2015-01-16

Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4-12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds.

Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins

PubMed Central

Heffernan, Natalie; Brunton, Nigel P.; FitzGerald, Richard J.; Smyth, Thomas J.

2015-01-01

Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4–12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds. PMID:25603345

Flagellated bacterial motility in polymer solutions

PubMed Central

Martinez, Vincent A.; Schwarz-Linek, Jana; Reufer, Mathias; Wilson, Laurence G.; Morozov, Alexander N.; Poon, Wilson C. K.

2014-01-01

It is widely believed that the swimming speed, v, of many flagellated bacteria is a nonmonotonic function of the concentration, c, of high-molecular-weight linear polymers in aqueous solution, showing peaked v(c) curves. Pores in the polymer solution were suggested as the explanation. Quantifying this picture led to a theory that predicted peaked v(c) curves. Using high-throughput methods for characterizing motility, we measured v and the angular frequency of cell body rotation, Ω, of motile Escherichia coli as a function of polymer concentration in polyvinylpyrrolidone (PVP) and Ficoll solutions of different molecular weights. We find that nonmonotonic v(c) curves are typically due to low-molecular-weight impurities. After purification by dialysis, the measured v(c) and Ω(c) relations for all but the highest-molecular-weight PVP can be described in detail by Newtonian hydrodynamics. There is clear evidence for non-Newtonian effects in the highest-molecular-weight PVP solution. Calculations suggest that this is due to the fast-rotating flagella seeing a lower viscosity than the cell body, so that flagella can be seen as nano-rheometers for probing the non-Newtonian behavior of high polymer solutions on a molecular scale. PMID:25468981

Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

NASA Astrophysics Data System (ADS)

Shimada, Kayori; Kato, Haruhisa; Saito, Takeshi; Matsuyama, Shigetomo; Kinugasa, Shinichi

2005-06-01

Uniform poly(ethylene glycol) (PEG) oligomers, with a degree of polymerization n =1-40, were separated by preparative supercritical fluid chromatography from commercial monodispersed samples. Diffusion coefficients, D, for separated uniform PEG oligomers were measured in dilute solutions of deuterium oxide (D2O) at 30 ° C, using pulsed-field gradient nuclear magnetic resonance. The measured D for each molecular weight was extrapolated to infinite dilution. Diffusion coefficients obtained at infinite dilution follow the scaling behavior of Zimm-type diffusion, even in the lower molecular weight range. Molecular-dynamics simulations for PEG in H2O also showed this scaling behavior, and reproduced close hydrodynamic interactions between PEG and water. These findings suggest that diffusion of PEG in water is dominated by hydrodynamic interaction over a wide molecular weight range, including at low molecular weights around 1000.

Molecular Structure of the Pyruvate Dehydrogenase Complex from Escherichia coli K-12

PubMed Central

Vogel, Otto; Hoehn, Barbara; Henning, Ulf

1972-01-01

The pyruvate dehydrogenase core complex from E. coli K-12, defined as the multienzyme complex that can be obtained with a unique polypeptide chain composition, has a molecular weight of 3.75 × 106. All results obtained agree with the following numerology. The core complex consists of 48 polypeptide chains. There are 16 chains (molecular weight = 100,000) of the pyruvate dehydrogenase component, 16 chains (molecular weight = 80,000) of the dihydrolipoamide dehydrogenase component, and 16 chains (molecular weight = 56,000) of the dihydrolipoamide dehydrogenase component. Usually, but not always, pyruvate dehydrogenase complex is produced in vivo containing at least 2-3 mol more of dimers of the pyruvate dehydrogenase component than the stoichiometric ratio with respect to the core complex. This “excess” component is bound differently than are the eight dimers in the core complex. Images PMID:4556465

Office of the Secretary of Defense Research, Development Test and Evaluation, Development and Test Evaluation, Defense, Director of Operational Test and Evaluation Defense, FY 1994 Budget Estimates, Justification of Estimates Submitted to Congress April 1993

DTIC Science & Technology

1993-04-01

separation capability. o Demonstrate advanced KKVs in the 6-20 KG weight class. o Test planning for SRAM/LEAP and PATRIOT/LEAP integrated technology...packaging techniques to reduce satellite size, weight , power, and total system costs. Further development of these technologies are absolutely 4...1993 o Developed a master plan with a delivery schedule for each light- weight subassembly in the sensor integration payload. o Finalized a contract for

Central effects of ghrelin on the adrenal cortex: a morphological and hormonal study.

PubMed

Milosević, Verica Lj; Stevanović, Darko M; Nesić, Dejan M; Sosić-Jurjević, Branka T; Ajdzanović, Vladimir Z; Starcević, Vesna P; Severs, Walter B

2010-06-01

Ghrelin, a growth hormone secretagogue that exerts an important role in appetite and weight regulation, participates in the activation of the hypothalamo-pituitary-adrenal (HPA) axis. Male Wistar rats (5/group) received daily for 5 days, via an ICV (intracerebroventricular) cannula, 5 microl phosphate buffered saline with or without 1 microg of rat ghrelin. Two hours after the last injection, blood and adrenal glands were collected from decapitated rats for blood hormone analyses and histologic and morphometric processing. Ghrelin treatment resulted in increased (p<0.05) body weight (13%), absolute whole adrenal gland weight (18%) and whole adrenal gland volume (20%). The absolute volumes of the entire adrenal cortex, ZG, ZF, and ZR also increased (p<0.05) after ghrelin by 20%, 21%, 21% and 11%, respectively. Ghrelin-treated rats had elevated (p<0.05) blood concentrations of ACTH, aldosterone and corticosterone (68%, 32% and 67%, respectively). The data clearly provide both morphological and hormonal status that ghrelin acts centrally to exert a global stimulatory effect on the adrenal cortex. Clarifying of the ghrelin precise role in the multiple networks affecting the stress hormone release, besides its well known energy and metabolic unbalance effects, remains a very important research goal.

Model assessment using a multi-metric ranking technique

NASA Astrophysics Data System (ADS)

Fitzpatrick, P. J.; Lau, Y.; Alaka, G.; Marks, F.

2017-12-01

Validation comparisons of multiple models presents challenges when skill levels are similar, especially in regimes dominated by the climatological mean. Assessing skill separation will require advanced validation metrics and identifying adeptness in extreme events, but maintain simplicity for management decisions. Flexibility for operations is also an asset. This work postulates a weighted tally and consolidation technique which ranks results by multiple types of metrics. Variables include absolute error, bias, acceptable absolute error percentages, outlier metrics, model efficiency, Pearson correlation, Kendall's Tau, reliability Index, multiplicative gross error, and root mean squared differences. Other metrics, such as root mean square difference and rank correlation were also explored, but removed when the information was discovered to be generally duplicative to other metrics. While equal weights are applied, weights could be altered depending for preferred metrics. Two examples are shown comparing ocean models' currents and tropical cyclone products, including experimental products. The importance of using magnitude and direction for tropical cyclone track forecasts instead of distance, along-track, and cross-track are discussed. Tropical cyclone intensity and structure prediction are also assessed. Vector correlations are not included in the ranking process, but found useful in an independent context, and will be briefly reported.

In vivo oxidation in remelted highly cross-linked retrievals.

PubMed

Currier, B H; Van Citters, D W; Currier, J H; Collier, J P

2010-10-20

Elimination of free radicals to prevent oxidation has played a major role in the development and product differentiation of the latest generation of highly cross-linked ultra-high molecular weight polyethylene bearing materials. In the current study, we (1) examined oxidation in a series of retrieved remelted highly cross-linked ultra-high molecular weight polyethylene bearings from a number of device manufacturers and (2) compared the retrieval results with findings for shelf-stored control specimens. The hypothesis was that radiation-cross-linked remelted ultra-high molecular weight polyethylene would maintain oxidative stability in vivo comparable with the stability during shelf storage and in published laboratory aging tests. Fifty remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners and nineteen remelted highly cross-linked ultra-high molecular weight polyethylene tibial inserts were received after retrieval from twenty-one surgeons from across the U.S. Thirty-two of the retrievals had been in vivo for two years or more. Each was measured for oxidation with use of Fourier transform infrared spectroscopy. A control series of remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners from three manufacturers was analyzed with electron paramagnetic resonance spectroscopy to measure free radical content and with Fourier transform infrared spectroscopy to measure oxidation initially and after eight to nine years of shelf storage in air. The never-implanted, shelf-aged controls had no measurable free-radical content initially or after eight to nine years of shelf storage. The never-implanted controls showed no increase in oxidation during shelf storage. Oxidation measurements showed measurable oxidation in 22% of the retrieved remelted highly cross-linked liners and inserts after an average of two years in vivo. Because never-implanted remelted highly cross-linked ultra-high molecular weight polyethylene materials had no measurable free-radical concentration and no increase in oxidation during shelf storage, these materials were expected to be oxidation-resistant in vivo. However, some remelted highly cross-linked ultra-high molecular weight polyethylene retrievals showed measurable oxidation after an average of more than two years in vivo. This apparent departure from widely expected behavior requires continued study of the process of in vivo oxidation of ultra-high molecular weight polyethylene materials.

Features of Extrusion Processing of Ultrahigh Molecular Weight Polyethylene. Experiment and Theory

NASA Astrophysics Data System (ADS)

Skul‧skii, O. I.; Slavnov, E. V.

2018-05-01

Experimental studies have been made of the permissible regimes of processing ultrahigh molecular weight polyethylene GUR 2122 with molecular mass of 4.5 million g/moles in a laboratory extruder with an auger diameter 32 mm and a ratio L/D = 20 at temperatures of 155-165oC. On the basis of rotational viscometry, the rheological properties of the melt are described. A mathematical model and a numerical method for calculating the motion of ultrahigh molecular weight polyethylene melt in the auger and in the moulding rigging are proposed. The velocity and stress fields have been determined.

Quantitative [Fe]MRI of PSMA-targeted SPIONs specifically discriminates among prostate tumor cell types based on their PSMA expression levels.

PubMed

Sillerud, Laurel O

2016-01-01

We report the development, experimental verification, and application of a general theory called [Fe]MRI (pronounced fem-ree) for the non-invasive, quantitative molecular magnetic resonance imaging (MRI) of added magnetic nanoparticles or other magnetic contrast agents in biological tissues and other sites. [Fe]MRI can easily be implemented on any MRI instrument, requiring only measurements of the background nuclear magnetic relaxation times (T1, T2) of the tissue of interest, injection of the magnetic particles, and the subsequent acquisition of a pair of T1-weighted and T2-weighted images. These images, converted into contrast images, are subtracted to yield a contrast difference image proportional to the absolute nanoparticle, iron concentration, ([Fe]) image. [Fe]MRI was validated with the samples of superparamagnetic iron oxide nanoparticles (SPIONs) both in agarose gels and bound to human prostate tumor cells. The [Fe]MRI measurement of the binding of anti-prostate specific membrane antigen (PSMA) conjugated SPIONs to PSMA-positive LNCaP and PSMA-negative DU145 cells in vitro allowed a facile discrimination among prostate tumor cell types based on their PSMA expression level. The low [Fe] detection limit of ~2 μM for SPIONs allows sensitive MRI of added iron at concentrations considerably below the US Food and Drug Administration's human iron dosage guidelines (<90 μM, 5 mg/kg).

Characterisation of gunshot residue from three ammunition types using suppressed anion exchange chromatography.

PubMed

Gilchrist, Elizabeth; Jongekrijg, Fleur; Harvey, Laura; Smith, Norman; Barron, Leon

2012-09-10

Gunshot residue (GSR) is commonly analysed in forensic casework using either scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) or gas chromatography-mass spectrometry (GC-MS). Relatively little work has been reported on the post-discharge GSR content of non-metallic inorganic or low molecular weight organic anions to distinguish between different ammunition types. The development of an analytical method using suppressed micro-bore anion exchange chromatography (IC) is presented for the analysis of GSR. A hydroxide gradient was optimised for the separation of 19 forensically relevant organic and inorganic anions in <23min and sensitivities of the order of 0.12-3.52ng of anion detected for all species were achieved. Along with an optimised extraction procedure, this method was applied to the analysis of post-ignition residues from three selected ammunition types. By profiling and comparing the anionic content in each ammunition residue, the possibility to distinguish between each type using their anionic profiles and absolute weight is presented. The potential for interference is also discussed with respect to sample types which are typically problematic in the analysis of GSR using SEM-EDX and GC-MS. To the best of our knowledge this represents the first study on the analysis of inorganic anions in GSR using suppressed ion chromatography. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Tannins from Hamamelis virginiana bark extract: characterization and improvement of the antiviral efficacy against influenza A virus and human papillomavirus.

PubMed

Theisen, Linda L; Erdelmeier, Clemens A J; Spoden, Gilles A; Boukhallouk, Fatima; Sausy, Aurélie; Florin, Luise; Muller, Claude P

2014-01-01

Antiviral activity has been demonstrated for different tannin-rich plant extracts. Since tannins of different classes and molecular weights are often found together in plant extracts and may differ in their antiviral activity, we have compared the effect against influenza A virus (IAV) of Hamamelis virginiana L. bark extract, fractions enriched in tannins of different molecular weights and individual tannins of defined structures, including pseudotannins. We demonstrate antiviral activity of the bark extract against different IAV strains, including the recently emerged H7N9, and show for the first time that a tannin-rich extract inhibits human papillomavirus (HPV) type 16 infection. As the best performing antiviral candidate, we identified a highly potent fraction against both IAV and HPV, enriched in high molecular weight condensed tannins by ultrafiltration, a simple, reproducible and easily upscalable method. This ultrafiltration concentrate and the bark extract inhibited early and, to a minor extent, later steps in the IAV life cycle and tannin-dependently inhibited HPV attachment. We observed interesting mechanistic differences between tannin structures: High molecular weight tannin containing extracts and tannic acid (1702 g/mol) inhibited both IAV receptor binding and neuraminidase activity. In contrast, low molecular weight compounds (<500 g/mol) such as gallic acid, epigallocatechin gallate or hamamelitannin inhibited neuraminidase but not hemagglutination. Average molecular weight of the compounds seemed to positively correlate with receptor binding (but not neuraminidase) inhibition. In general, neuraminidase inhibition seemed to contribute little to the antiviral activity. Importantly, antiviral use of the ultrafiltration fraction enriched in high molecular weight condensed tannins and, to a lesser extent, the unfractionated bark extract was preferable over individual isolated compounds. These results are of interest for developing and improving plant-based antivirals.

The influence of malalignment and ageing following sterilisation by gamma irradiation in an inert atmosphere on the wear of ultra-high-molecular-weight polyethylene in patellofemoral replacements

PubMed Central

Maiti, Raman; Cowie, Raelene M; Fisher, John; Jennings, Louise M

2017-01-01

Complications of patellofemoral arthroplasty often occur soon after implantation and, as well as other factors, can be due to the design of the implant or its surgical positioning. A number of studies have previously considered the wear of ultra-high-molecular-weight polyethylene patellae following suboptimal implantation; however, studies have primarily been carried out under a limited number of degrees of freedom. The aim of this study was to develop a protocol to assess the wear of patellae under a malaligned condition in a six-axis patellofemoral joint simulator. The malalignment protocol hindered the tracking of the patella centrally in the trochlear groove and imparted a constant 5° external rotation (tilt) on the patella button. Following 3 million cycles of wear simulation, this condition had no influence on the wear of ultra-high-molecular-weight polyethylene patellae aged for 4 years compared to well-positioned non-aged implants (p > 0.05). However, under the malaligned condition, ultra-high-molecular-weight polyethylene patellae aged 8–10 years after unpacking (following sterilisation by gamma irradiation in an inert atmosphere) and worn ultra-high-molecular-weight polyethylene components also aged 4 years after unpacking (following the same sterilisation process) exhibited a high rate of wear. Fatigue failure due to elevated contact stress led to delamination of the ultra-high-molecular-weight polyethylene and in some cases complete failure of the patellae. The results suggest that suboptimal tracking of the patella in the trochlear groove and tilt of the patella button could have a significant effect on the wear of ultra-high-molecular-weight polyethylene and could lead to implant failure. PMID:28661229

The influence of malalignment and ageing following sterilisation by gamma irradiation in an inert atmosphere on the wear of ultra-high-molecular-weight polyethylene in patellofemoral replacements.

PubMed

Maiti, Raman; Cowie, Raelene M; Fisher, John; Jennings, Louise M

2017-07-01

Complications of patellofemoral arthroplasty often occur soon after implantation and, as well as other factors, can be due to the design of the implant or its surgical positioning. A number of studies have previously considered the wear of ultra-high-molecular-weight polyethylene patellae following suboptimal implantation; however, studies have primarily been carried out under a limited number of degrees of freedom. The aim of this study was to develop a protocol to assess the wear of patellae under a malaligned condition in a six-axis patellofemoral joint simulator. The malalignment protocol hindered the tracking of the patella centrally in the trochlear groove and imparted a constant 5° external rotation (tilt) on the patella button. Following 3 million cycles of wear simulation, this condition had no influence on the wear of ultra-high-molecular-weight polyethylene patellae aged for 4 years compared to well-positioned non-aged implants (p > 0.05). However, under the malaligned condition, ultra-high-molecular-weight polyethylene patellae aged 8-10 years after unpacking (following sterilisation by gamma irradiation in an inert atmosphere) and worn ultra-high-molecular-weight polyethylene components also aged 4 years after unpacking (following the same sterilisation process) exhibited a high rate of wear. Fatigue failure due to elevated contact stress led to delamination of the ultra-high-molecular-weight polyethylene and in some cases complete failure of the patellae. The results suggest that suboptimal tracking of the patella in the trochlear groove and tilt of the patella button could have a significant effect on the wear of ultra-high-molecular-weight polyethylene and could lead to implant failure.

Effects of different enzymatic hydrolysis methods on the bioactivity of peptidoglycan in Litopenaeus vannamei

NASA Astrophysics Data System (ADS)

Song, Xiaoling; Zhang, Yue; Wei, Song; Huang, Jie

2013-03-01

The effects of different hydrolysis methods on peptidoglycan (PG) were assessed in terms of their impact on the innate immunity and disease resistance of Pacific white shrimp, Litop enaeus vannamei. PG derived from Bifidobacterium thermophilum was prepared in the laboratory and processed with lysozyme and protease under varying conditions to produce several different PG preparations. A standard shrimp feed was mixed with 0.05% PG preparations to produce a number of experimental diets for shrimp. The composition, concentration, and molecular weight ranges of the soluble PG were analyzed. Serum phenoloxidase and acid phosphatase activity in the shrimp were determined on Days 6—31 of the experiment. The protective activity of the PG preparations was evaluated by exposing shrimp to white spot syndrome virus (WSSV). Data on the composition of the PG preparations indicated that preparations hydrolyzed with lysozyme for 72 h had more low-molecular-weight PG than those treated for 24 h, and hydrolysis by protease enhanced efficiency of hydrolysis compared to lysozyme. SDS-PAGE showed changes in the molecular weight of the soluble PG produced by the different hydrolysis methods. Measurements of serum phenoloxidase and acid phosphatase activity levels in the shrimp indicated that the PG preparations processed with enzymes were superior to the preparation which had not undergone hydrolysis in enhancing the activity of the two serum enzymes. In addition, the preparation containing more low-molecular-weight PG enhanced the resistance of the shrimp to WSSV, whereas no increased resistance was observed for preparations containing less low-molecular-weight PG. These findings suggest that the immunity-enhancing activity of PG is related to its molecular weight and that increasing the quantity of low-molecular-weight PG can fortify the effect of immunity enhancement.

Tannins from Hamamelis virginiana Bark Extract: Characterization and Improvement of the Antiviral Efficacy against Influenza A Virus and Human Papillomavirus

PubMed Central

Theisen, Linda L.; Erdelmeier, Clemens A. J.; Spoden, Gilles A.; Boukhallouk, Fatima; Sausy, Aurélie; Florin, Luise; Muller, Claude P.

2014-01-01

Antiviral activity has been demonstrated for different tannin-rich plant extracts. Since tannins of different classes and molecular weights are often found together in plant extracts and may differ in their antiviral activity, we have compared the effect against influenza A virus (IAV) of Hamamelis virginiana L. bark extract, fractions enriched in tannins of different molecular weights and individual tannins of defined structures, including pseudotannins. We demonstrate antiviral activity of the bark extract against different IAV strains, including the recently emerged H7N9, and show for the first time that a tannin-rich extract inhibits human papillomavirus (HPV) type 16 infection. As the best performing antiviral candidate, we identified a highly potent fraction against both IAV and HPV, enriched in high molecular weight condensed tannins by ultrafiltration, a simple, reproducible and easily upscalable method. This ultrafiltration concentrate and the bark extract inhibited early and, to a minor extent, later steps in the IAV life cycle and tannin-dependently inhibited HPV attachment. We observed interesting mechanistic differences between tannin structures: High molecular weight tannin containing extracts and tannic acid (1702 g/mol) inhibited both IAV receptor binding and neuraminidase activity. In contrast, low molecular weight compounds (<500 g/mol) such as gallic acid, epigallocatechin gallate or hamamelitannin inhibited neuraminidase but not hemagglutination. Average molecular weight of the compounds seemed to positively correlate with receptor binding (but not neuraminidase) inhibition. In general, neuraminidase inhibition seemed to contribute little to the antiviral activity. Importantly, antiviral use of the ultrafiltration fraction enriched in high molecular weight condensed tannins and, to a lesser extent, the unfractionated bark extract was preferable over individual isolated compounds. These results are of interest for developing and improving plant-based antivirals. PMID:24498245

Differentiation of parenteral anticoagulants in the prevention and treatment of venous thromboembolism.

PubMed

Fareed, Jawed; Adiguzel, Cafer; Thethi, Indermohan

2011-03-28

The prevention of venous thromboembolism has been identified as a leading priority in hospital safety. Recommended parenteral anticoagulant agents with different indications for the prevention and treatment of venous thromboembolism include unfractionated heparin, low-molecular-weight heparins and fondaparinux. Prescribing decisions in venous thromboembolism management may seem complex due to the large range of clinical indications and patient types, and the range of anticoagulants available. MEDLINE and EMBASE databases were searched to identify relevant original articles. Low-molecular-weight heparins have nearly replaced unfractionated heparin as the gold standard antithrombotic agent. Low-molecular-weight heparins currently available in the US are enoxaparin, dalteparin, and tinzaparin. Each low-molecular-weight heparin is a distinct pharmacological entity with different licensed indications and available clinical evidence. Enoxaparin is the only low-molecular-weight heparin that is licensed for both venous thromboembolism prophylaxis and treatment. Enoxaparin also has the largest body of clinical evidence supporting its use across the spectrum of venous thromboembolism management and has been used as the reference standard comparator anticoagulant in trials of new anticoagulants. As well as novel oral anticoagulant agents, biosimilar and/or generic low-molecular-weight heparins are now commercially available. Despite similar anticoagulant properties, studies report differences between the branded and biosimilar and/or generic agents and further clinical studies are required to support the use of biosimilar low-molecular-weight heparins. The newer parenteral anticoagulant, fondaparinux, is now also licensed for venous thromboembolism prophylaxis in surgical patients and the treatment of acute deep-vein thrombosis; clinical experience with this anticoagulant is expanding. Parenteral anticoagulants should be prescribed in accordance with recommended dose regimens for each clinical indication, based on the available clinical evidence for each agent to assure optimal safety and efficacy.

Establishment of replacement batches for heparin low-molecular-mass for calibration CRS, and the International Standard Low Molecular Weight Heparin for Calibration.

PubMed

Mulloy, B; Heath, A; Behr-Gross, M-E

2007-12-01

An international collaborative study involving fourteen laboratories has taken place, organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM) with National Institute for Biological Standards & Control (NIBSC) (in its capacity as a World Health Organisation (WHO) Laboratory for Biological Standardisation) to provide supporting data for the establishment of replacement batches of Heparin Low-Molecular-Mass (LMM) for Calibration Chemical Reference Substance (CRS), and of the International Reference Reagent (IRR) Low Molecular Weight Heparin for Molecular Weight Calibration. A batch of low-molecular-mass heparin was donated to the organisers and candidate preparations of freeze-dried heparin were produced at NIBSC and EDQM. The establishment study was organised in two phases: a prequalification (phase 1, performed in 3 laboratories in 2005) followed by an international collaborative study (phase 2). In phase 2, started in March 2006, molecular mass parameters were determined for seven different LMM heparin samples using the current CRS batch and two batches of candidate replacement material with a defined number average relative molecular mass (Mn) of 3,700, determined in phase 1. The values calculated using the candidates as standard were systematically different from values calculated using the current batch with its assigned number-average molecular mass (Mna) of 3,700. Using raw data supplied by participants, molecular mass parameters were recalculated using the candidates as standard with values for Mna of 3,800 and 3,900. Values for these parameters agreed more closely with those calculated using the current batch supporting the fact that the candidates, though similar to batch 1 in view of the production processes used, differ slightly in terms of molecular mass distribution. Therefore establishment of the candidates was recommended with an assigned Mna value of 3,800 that is both consistent with phase 1 results and guarantees continuity with the current CRS batch. In phase 2, participants also determined molecular weight parameters for the seven different LMM heparin samples using both the 1st IRR (90/686) and its Broad Standard Table and the candidate World Health Organization (WHO) 2nd International Standard (05/112) (2nd IS) using a Broad Standard Table established in phase 1. Mean molecular weights calculated using 2nd IS were slightly higher than with 1st IRR, and participants in the study indicated that this systematic difference precluded establishment of 2nd IS with the table supplied. A replacement Broad Standard Table has been devised on the basis of the central recalculations of raw data supplied by participants; this table gives improved agreement between values derived using the 1st IRR and the candidate 2nd IS. On the basis of this study a recommendation was made for the establishment of 2nd IS and its proposed Broad Standard Table as a replacement for the 1st International Reference Reagent Low Molecular Weight Heparin for Molecular Weight Calibration. Unlike the 1st IRR however, the candidate material 2nd IS is not suitable for use with the method of Nielsen. The candidate materials were established as heparin low-molecular-mass for calibration batches 2 and 3 by the Ph. Eur. Commission in March 2007 and as 2nd IS low-molecular-weight heparin for molecular weight calibration (05/112) by the Expert Committee on Biological Standardization in November 2007.

Serum cholesterol reduction by feeding a high-cholesterol diet containing a lower-molecular-weight polyphenol fraction from peanut skin.

PubMed

Tamura, Tomoko; Inoue, Naoko; Shimizu-Ibuka, Akiko; Tadaishi, Miki; Takita, Toshichika; Arai, Soichi; Mura, Kiyoshi

2012-01-01

Feeding a high-cholesterol diet with a water-soluble peanut skin polyphenol fraction to rats reduced their plasma cholesterol level, with an increase in fecal cholesterol excretion. The hypocholesterolemic effect was greater with the lower-molecular-weight rather than higher-molecular-weight polyphenol fraction. This effect was possibly due to some oligomeric polyphenols which reduced the solubility of dietary cholesterol in intestinal bile acid-emulsified micelles.

Synthesis and Structural Characterization of New Light Molecular Weight Inorganic Oxidizers and Related Derivatives. Volume: 2

DTIC Science & Technology

1993-02-01

of the strong inductive effect of the five fluorine ligands attached to the tellurium atom. 34 It is prepared under anhydrous conditions according to...MOLECULAR WEIGHT INORGANIC OXIDIZERS AND RELATED DERIVATIVES. VOLUME: II Professor G. J. Schrobilgen McMaster University Department of Chemistry...C: F04611-91-K-0004 Molecular Weight Inorganic Oxidizers and Relative PE: 62302F SDerivatives: Volume II 1PR: 5730 6. AUTHOFR(S) TA: 0*( C

Raman analysis of polyethylene glycols and polyethylene oxides

NASA Astrophysics Data System (ADS)

Sagitova, E. A.; Prokhorov, K. A.; Nikolaeva, G. Yu; Baimova, A. V.; Pashinin, P. P.; Yarysheva, A. Yu; Mendeleev, D. I.

2018-04-01

We present Raman study of commercial liquids and powders of polyethylene glycols and polyethylene oxides with the average molecular weight from 400 Da to 10000 kDa. The most significant spectral changes were observed for the range of the molecular weights, where the liquid/semisolid transition has occurred. For the powders we revealed increase in the content of the molecules in the helical conformation and in the content of the monoclinic crystalline phase with growth of the molecular weight.

Should Low Molecular Weight PSMA Targeted Ligands Get Bigger and Use Albumin Ligands for PSMA Targeting?

PubMed

Huang, Steve S; Heston, Warren D W

2017-01-01

Prostate Specific Membrane Antigen (PSMA) is strongly expressed in prostate cancer. Recently a number of low-molecular-weight inhibitors have demonstrated excellent PSMA targeting activity for both imaging as well as Lutecium-177 radiotherapy in human trials. The paper by Choy et al raises the question of whether we can further increase the effectiveness of PSMA targeted therapy by adding an albumin-binding entity to low-molecular-weight agents.

High-molecular-weight tropomyosins localize to the contractile rings of dividing CNS cells but are absent from malignant pediatric and adult CNS tumors.

PubMed

Hughes, Julie A I; Cooke-Yarborough, Claire M; Chadwick, Nigel C; Schevzov, Galina; Arbuckle, Susan M; Gunning, Peter; Weinberger, Ron P

2003-04-01

Tropomyosin has been implicated in the control of actin filament dynamics during cell migration, morphogenesis, and cytokinesis. In order to gain insight into the role of tropomyosins in cell division, we examined their expression in developing and neoplastic brain tissue. We found that the high-molecular-weight tropomyosins are downregulated at birth, which correlates with glial cell differentiation and withdrawal of most cells from the cell cycle. Expression of these isoforms was restricted to proliferative areas in the embryonic brain and was absent from the adult, where the majority of cells are quiescent. However, they were induced under conditions where glial cells became proliferative in response to injury. During cytokinesis, these tropomyosin isoforms were associated with the contractile ring. We also investigated tropomyosin expression in neoplastic CNS tissues. Low-grade astrocytic tumors expressed high-molecular-weight tropomyosins, while highly malignant CNS tumors of diverse origin did not (P

The binding of sodium dodecyl sulphate to various proteins

PubMed Central

Pitt-Rivers, Rosalind; Impiombato, F. S. Ambesi

1968-01-01

1. The binding of sodium dodecyl sulphate to proteins by equilibrium dialysis was investigated. 2. Most of the proteins studied bound 90–100% of their weight of sodium dodecyl sulphate. 3. The glycoproteins studied bound 70–100% of their weight of sodium dodecyl sulphate, calculated in terms of the polypeptide moiety of the molecule. 4. Proteins not containing S·S groups bound about 140% of their weight of sodium dodecyl sulphate. 5. Reduction of four proteins containing S·S groups caused a rise in sodium dodecyl sulphate binding to 140% of the weight of protein. 6. The apparent micellar molecular weights of the protein–sodium dodecyl sulphate complexes were measured by the dye-solubilization method; they were all found to have approximately the same micellar molecular weight (34000–41000) irrespective of the molecular weight of the protein to which they were attached. PMID:4177067

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) of low molecular weight organic compounds and synthetic polymers using zinc oxide (ZnO) nanoparticles.

PubMed

Watanabe, Takehiro; Kawasaki, Hideya; Yonezawa, Tetsu; Arakawa, Ryuichi

2008-08-01

We have developed surface-assisted laser desorption/ionization mass spectrometry using zinc oxide (ZnO) nanoparticles with anisotropic shapes (ZnO-SALDI-MS). The mass spectra showed low background noises in the low m/z, i.e. less than 500 u region. Thus, we succeeded in SALDI ionization on low molecular weight organic compounds, such as verapamil hydrochloride, testosterone, and polypropylene glycol (PPG) (average molecular weight 400) without using a liquid matrix or buffers such as citric acids. In addition, we found that ZnO-SALDI has advantages in post-source decay (PSD) analysis and produced a simple mass spectrum for phospholipids. The ZnO-SALDI spectra for synthetic polymers of polyethylene glycol (PEG), polystyrene (PS) and polymethylmethacrylate (PMMA) showed the sensitivity and molecular weight distribution to be comparable to matrix-assisted laser desorption/ionization (MALDI) spectra with a 2,5-dihydroxybenzoic acid (DHB) matrix. ZnO-SALDI shows good performance for synthetic polymers as well as low molecular weight organic compounds. Copyright (c) 2008 John Wiley & Sons, Ltd.

Complete Molecular Weight Profiling of Low-Molecular Weight Heparins Using Size Exclusion Chromatography-Ion Suppressor-High-Resolution Mass Spectrometry.

PubMed

Zaia, Joseph; Khatri, Kshitij; Klein, Joshua; Shao, Chun; Sheng, Yuewei; Viner, Rosa

2016-11-01

Low-molecular weight heparins (LMWH) prepared by partial depolymerization of unfractionated heparin are used globally to treat coagulation disorders on an outpatient basis. Patent protection for several LMWH has expired and abbreviated new drug applications have been approved by the Food and Drug Administration. As a result, reverse engineering of LMWH for biosimilar LMWH has become an active global endeavor. Traditionally, the molecular weight distributions of LMWH preparations have been determined using size exclusion chromatography (SEC) with optical detection. Recent advances in liquid chromatography-mass spectrometry methods have enabled exact mass measurements of heparin saccharides roughly up to degree-of-polymerization 20, leaving the high molecular weight half of the LMWH preparation unassigned. We demonstrate a new LC-MS system capable of determining the exact masses of complete LMWH preparations, up to dp30. This system employed an ion suppressor cell to desalt the chromatographic effluent online prior to the electrospray mass spectrometry source. We expect this new capability will impact the ability to define LMWH mixtures favorably.

[The analysis of the low and medium molecular weight substances for differential diagnostics of deaths from acute small-focal myocardial infarction and other forms of cardiac pathology].

PubMed

Edelev, N S; Obuhova, L M; Edelev, I S; Katirkina, A A

The objective of the present study was to analyze the possibilities for the use of the low and medium molecular weight substances for differential diagnostics of deaths from acute small-focal myocardial infarction and other forms of cardiac pathology. We determined the amount of the low and medium molecular weight substances in the urine obtained from the subjects who had died as a result of chronic coronary heart disease, acute myocardial infarction, and alcoholic cardiomyopathy. The levels of the low and medium molecular weight substances in the urine were measured by the method of N.Ya. Malakhov in the modification of T.V. Kopytova [5]. The study has demonstrated the appearance of the products of cardiomyocyte degradation (giving rise to a peak at a wavelength of 278 nm) in the fraction of the low and medium molecular weight substances of the urine from the patients suffering from acute small-focal myocardial infarction and some other forms of cardiac pathology.

Brominated flame retardants in Chinese air before and after the phase out of polybrominated diphenyl ethers

NASA Astrophysics Data System (ADS)

Li, Wen-Long; Qi, Hong; Ma, Wan-Li; Liu, Li-Yan; Zhang, Zhi; Mohammed, Mohammed O. A.; Song, Wei-Wei; Zhang, Zifeng; Li, Yi-Fan

2015-09-01

Brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and novel non-BDE flame retardants (NBFRs), were analyzed in Chinese air during China's POPs Soil and Air Monitoring Program Phase I (SAMP-I) and Phase II (SAMP-II). The levels of Σ12PBDEs and Σ6NBFRs in urban sites were significantly higher than those in rural sites and background sites. The higher detection rate and concentrations of high molecular weight PBDEs and NBFRs in Phase II indicated the changing of the commercial pattern of BFRs after the phase out of PBDEs in China. Temperature was the major factor affecting the seasonal variations of molecular weight BFRs in atmosphere. A significant correlation between BFRs concentration and gross domestic product (GDP) was observed, with the GDP parameter explained 59.4% and 72.7% of the total variability for Octa-BDEs and low molecular weight NBFRs, respectively. Our findings indicated an evolving commercial usage of BFRs from SAMP-I to SAMP-II, i.e. shifting from lower molecular weight to higher molecular weight congeners in China.

MAPLE deposition of PLGA:PEG films for controlled drug delivery: Influence of PEG molecular weight

NASA Astrophysics Data System (ADS)

Paun, Irina Alexandra; Moldovan, Antoniu; Luculescu, Catalin Romeo; Staicu, Angela; Dinescu, Maria

2012-09-01

Implantable devices consisting of indomethacin (INC) cores coated with poly(lactide-co-glycolide):polyethylene glycol films (i.e. PLGA:PEG films) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) were produced. To predict their behavior after implantation inside the body, the implants were studied in vitro, in media similar with those encountered inside the body (phosphate buffered saline (PBS) pH 7.4 and blood). The influence of the molecular weight of PEG (i.e. low (1450 Da) versus high (10 kDa) molecular weights) on the characteristics of the implants was investigated, in terms of morphology, blood compatibility and kinetics of the drug release. The use of PEG of high molecular weight resulted in larger pores on the implants surfaces, enhanced blood compatibility of the implants and higher drug delivery rates. For both molecular weights PEGs, sustained release of INC was maintained over a three weeks interval. Theoretical fitting of the drug release data with Higuchi's model indicated that the INC was released mainly by diffusion, most probably through the pores formed in PLGA:PEG films during PBS immersion.

Derepression of the Azotobacter vinelandii siderophore system, using iron-containing minerals to limit iron repletion.

PubMed Central

Page, W J; Huyer, M

1984-01-01

Azotobacter vinelandii solubilized iron from certain minerals using only dihydroxybenzoic acid, which appeared to be produced constitutively. Solubilization of iron from other minerals required dihydroxybenzoic acid and the siderophore N,N'-bis-(2,3- dihydroxybenzoyl )-L-lysine ( azotochelin ) or these chelators plus the yellow-green fluorescent siderophore azotobactin . In addition to this sequential production of siderophores, cells also demonstrated partial to hyperproduction relative to the iron-limited control. The iron sources which caused partial derepression of the siderophores caused derepression of all the high-molecular-weight iron-repressible outer membrane proteins except a 77,000-molecular-weight protein, which appeared to be coordinated with azotobactin production. Increased siderophore production correlated with increased production of outer membrane proteins with molecular weights of 93,000, 85,000, and 77,000, but an 81,000-molecular-weight iron-repressible protein appeared at a constant level despite the degree of derepression. When iron was readily available, it appeared to complex with a 60,000-molecular-weight protein believed to form a surface layer on the A. vinelandii cell. Images PMID:6233258

Effect of the molecular weight of a neutral polysaccharide on soy protein gelation.

PubMed

Monteiro, Sónia R; Lopes-da-Silva, José A

2017-12-01

The effects of galactomannans with different molecular weights on the heat-induced gelation characteristics of soybean protein were investigated using dynamic small-strain rheometry, under conditions where the proteins carry a net negative charge (pH7). Microstructure of the resulting gels was investigated by confocal laser scanning microscopy. Phase-separated systems were obtained with different morphologies and degree of phase separation, depending on both biopolymer concentrations and polysaccharide molecular weight. In general, a gelling enhancing effect on soy proteins was verified, despite extensive phase-separation processes observed at the higher polysaccharide molecular weight. This effect was demonstrated by an increase of the gelation rate, a decrease in the temperature at the onset of gelation, and an increase of gel stiffness and elastic character, with the length of polysaccharide chains. Overall, the results obtained established that the judicious selection of the galactomannan molecular weight may be used to modify the structure and gelation properties of soy proteins, originating a diversity of rheological characteristics and microstructures that will impact on the design of novel food formulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Polymeric micelles based on poly(methacrylic acid) block-containing copolymers with different membrane destabilizing properties for cellular drug delivery.

PubMed

Mebarek, Naila; Aubert-Pouëssel, Anne; Gérardin, Corine; Vicente, Rita; Devoisselle, Jean-Marie; Bégu, Sylvie

2013-10-01

Poly(methacrylic acid)-b-poly(ethylene oxide) are double hydrophilic block copolymers, which are able to form micelles by complexation with a counter-polycation, such as poly-l-lysine. A study was carried out on the ability of the copolymers to interact with model membranes as a function of their molecular weights and as a function of pH. Different behaviors were observed: high molecular weight copolymers respect the membrane integrity, whereas low molecular weight copolymers with a well-chosen asymmetry degree can induce a membrane alteration. Hence by choosing the appropriate molecular weight, micelles with distinct membrane interaction behaviors can be obtained leading to different intracellular traffics with or without endosomal escape, making them interesting tools for cell engineering. Especially micelles constituted of low molecular weight copolymers could exhibit the endosomal escape property, which opens vast therapeutic applications. Moreover micelles possess a homogeneous nanometric size and show variable properties of disassembly at acidic pH, of stability in physiological conditions, and finally of cyto-tolerance. Copyright © 2013 Elsevier B.V. All rights reserved.

75 FR 20813 - Certain Magnesia Carbon Bricks from the People's Republic of China: Amended Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-21

... other errors, would result in (1) a change of at least five absolute percentage points in, but not less...) preliminary determination, or (2) a difference between a weighted-average dumping margin of zero or de minimis...

Constructing Phylogenies.

ERIC Educational Resources Information Center

Bilardello, Nicholas; Valdes, Linda

1998-01-01

Introduces a method for constructing phylogenies using molecular traits and elementary graph theory. Discusses analyzing molecular data and using weighted graphs, minimum-weight spanning trees, and rooted cube phylogenies to display the data. (DDR)

Influence of excess diamine on properties of PMR polyimide resins and composites

NASA Technical Reports Server (NTRS)

Hurwitz, F. I.

1980-01-01

By varying the stoichiometry of the reactants in the preparation of PMR polyimide resin, changes occur in molecular weight distribution which influence the rheological properties and thus the processability of the resin, as well as the mechanical properties of the composite. The influence of 1-10 percent molar excess MDA on the molecular weight distribution and rheological properties of an imidized PMR system were exposed. Molecular weight distribution is characterized by gel permeation chromatography of the imidized molding compound; shear viscosity is related to changes in average molecular weight. The thermo-oxidative stability at 600 F, glass transition temperature, flexural and interlaminar shear properties of PMR polyimide/Celion 6000 graphite fiber composites are compared as a function of the percent excess MDA in the monomer reactant mixture.

Selenium/Tellurium-Containing Hyperbranched Polymers: Effect of Molecular Weight and Degree of Branching on Glutathione Peroxidase-Like Activity.

PubMed

Thomas, Joice; Dong, Zeyuan; Dehaen, Wim; Smet, Mario

2012-12-21

A series of novel hyperbranched polyselenides and polytellurides with multiple catalytic sites at the branching units has been synthesized via the polycondensation of A2 + B3 monomers. The GPx-like activities of these polymer mimics were assessed and it was found that the polytellurides showed higher GPx-like activities than the corresponding polyselenides. Interestingly, the polymers with higher molecular weights and degree of branching (DB) showed higher GPx-like activities than the analogous lower molecular weight polymer. The enhancement in the catalytical activity of the hyperbranched polymers with increasing molecular weight affirmed the importance of the incorporation of multiple catalytic groups in the macromolecule which increases the local concentration of catalytic sites. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characteristics and bioactivities of different molecular weight polysaccharides from camellia seed cake.

PubMed

Xu, Zhou; Li, Xu; Feng, Shiling; Liu, Jing; Zhou, Lijun; Yuan, Ming; Ding, Chunbang

2016-10-01

Four polysaccharides, namely COP-1, COP-2, COP-3 and COP-4, were ultrafiltrated from crud Camellia oleifera seed cake polysaccharides (COP-c), purified, and characterized, including the determination of antioxidant and antiproliferative activities. Their molecular weights were 7.9, 36, 83 and 225kDa, respectively. All COPs showed the similar FT-IR spectrums, but significant differentials in monosaccharide components. COP-2 exhibited the highest radical scavenging abilities. COP-1 has the strongest metal chelating capabilities. Although with higher molecular weight, COP-4 showed the poorest antioxidant abilities. These results suggested appreciate molecular weight COP possessed a better antioxidant activities. Additionally, all COPs had non-significant antiproliferative abilities in HaLa and HepG2 cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthetic polycations with controlled charge density and molecular weight as building blocks for biomaterials.

PubMed

Kleinberger, Rachelle M; Burke, Nicholas A D; Zhou, Christal; Stöver, Harald D H

2016-01-01

A series of polycations prepared by RAFT copolymerization of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and N-(2-hydroxypropyl)methacrylamide, with molecular weights of 15 and 40 kDa, and APM content of 10-75 mol%, were tested as building blocks for electrostatically assembled hydrogels such as those used for cell encapsulation. Complexation and distribution of these copolymers within anionic calcium alginate gels, as well as cytotoxicity, cell attachment, and cell proliferation on surfaces grafted with the copolymers were found to depend on composition and molecular weight. Copolymers with lower cationic charge density and lower molecular weight showed less cytotoxicity and cell adhesion, and were more mobile within alginate gels. These findings aid in designing improved polyelectrolyte complexes for use as biomaterials.

Quantification of low molecular weight compounds by MALDI imaging mass spectrometry - A tutorial review.

PubMed

Rzagalinski, Ignacy; Volmer, Dietrich A

2017-07-01

Matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry imaging (MSI) permits label-free in situ analysis of chemical compounds directly from the surface of two-dimensional biological tissue slices. It links qualitative molecular information of compounds to their spatial coordinates and distribution within the investigated tissue. MALDI-MSI can also provide the quantitative amounts of target compounds in the tissue, if proper calibration techniques are performed. Obviously, as the target molecules are embedded within the biological tissue environment and analysis must be performed at their precise locations, there is no possibility for extensive sample clean-up routines or chromatographic separations as usually performed with homogenized biological materials; ion suppression phenomena therefore become a critical side effect of MALDI-MSI. Absolute quantification by MALDI-MSI should provide an accurate value of the concentration/amount of the compound of interest in relatively small, well-defined region of interest of the examined tissue, ideally in a single pixel. This goal is extremely challenging and will not only depend on the technical possibilities and limitations of the MSI instrument hardware, but equally on the chosen calibration/standardization strategy. These strategies are the main focus of this article and are discussed and contrasted in detail in this tutorial review. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann. Copyright © 2016 Elsevier B.V. All rights reserved.

Body weight affects ω-3 polyunsaturated fatty acid (PUFA) accumulation in youth following supplementation in post-hoc analyses of a randomized controlled trial.

PubMed

Christian, Lisa M; Young, Andrea S; Mitchell, Amanda M; Belury, Martha A; Gracious, Barbara L; Arnold, L Eugene; Fristad, Mary A

2017-01-01

Guidelines for suggested intake of ω-3 polyunsaturated fatty acids (PUFAs) are limited in youth and rely primarily on age. However, body weight varies considerably within age classifications. The current analyses examined effects of body weight and body mass index (BMI) on fatty acid accumulation in 64 youth (7-14 years) with a diagnosed mood disorder in a double-blind randomized-controlled trial (2000mg ω-3 supplements or a control capsule) across 12 weeks. Weight and height were measured at the first study visit and EPA and DHA levels were determined using fasting blood samples obtained at both the first and end-of-study visits. In the ω-3 supplementation group, higher baseline body weight predicted less plasma accumulation of both EPA [B = -0.047, (95% CI = -0.077; -0.017), β = -0.54, p = 0.003] and DHA [B = -0.02, (95% CI = -0.034; -0.007), β = -0.52, p = 0.004]. Similarly, higher BMI percentile as well as BMI category (underweight, normal weight, overweight/obese) predicted less accumulation of EPA and DHA (ps≤0.01). Adherence to supplementation was negatively correlated with BMI percentile [B = -0.002 (95% CI = -0.004; 0.00), β = -0.44, p = 0.019], but did not meaningfully affect observed associations. As intended, the control supplement exerted no significant effect on plasma levels of relevant fatty acids regardless of youth body parameters. These data show strong linear relationships of both absolute body weight and BMI percentile with ω-3 PUFA accumulation in youth. A dose-response effect was observed across the BMI spectrum. Given increasing variability in weight within BMI percentile ranges as youth age, dosing based on absolute weight should be considered. Moreover, effects of weight should be incorporated into statistical models in studies examining clinical effects of ω-3 PUFAs in youth as well as adults, as weight-related differences in effects may contribute meaningfully to inconsistencies in the current literature. WHO International Clinical Trial Registry Platform NCT01341925 and NCT01507753.

Isomer effects on polyimide properties

NASA Technical Reports Server (NTRS)

Stump, B. L.

1974-01-01

The polymerization of 2,4'-methylene-dianiline with benzophenone tetracarboxylic acid dianhydride yields high molecular weight polyamic acid. Polyimide is formed when films of the polyamic acid are cured between 200 - 300 C. A lower molecular weight polyamic acid is obtained from 2,2'-MDA with BTDA, but it appears that a lowering of the reaction temperature will yield high molecular weight polymer. Evaluation of these polymers is underway. Continued efforts to synthesize 2,3'- MDA and 2,3'-diaminobenzophenone have met with little success.

[Intensive care of children with DIC syndrome based on the use of low molecular weight heparins].

PubMed

Chuprova, A V; Shmakov, A N; Solov'ev, O N; Anokhina, T Iu; Loskutova, S A; Pinegina, Iu S

2002-01-01

The first section of this paper presents data on low-molecular-weight heparins: pharmacokinetics and pharmacodynamics, advantages in comparison with common heparin. The second section presents the results of fraxiparin and clivarin use in 43 children aged 9 months to 14 years with acute/subacute DIC syndrome of infectious origin. Therapeutic and maintenance doses, the mode of injection of low-molecular-weight heparins, and methods for laboratory monitoring of their efficiency and safety are presented.

Toxic effects of chlorinated cake flour in rats.

PubMed

Cunningham, H M; Lawrence, G A; Tryphonas, L

1977-05-01

Four experiments were conducted using weanling Wistar rats to determine whether chlorinated cake flour or its constituents were toxic. Levels of 0.2 and 1.0% chlorine added to unbleached cake flour significantly (p less than 0.01) reduced growth rate by 20.7 and 85.2% and increased liver weight relative to body weight by 16.7 and 25.3%, respectively. Lipids extracted from flour chlorinated at the same levels had similar effects. Rat chow diets containing 0.2 and 0.6% chlorine in the form of chlorinated wheat gluten reduced growth rate and increased liver weight as a percentage of body weight. A rat chow diet containing 0.2% chlorine as chlorinated flour lipids increased absolute liver weight by 40%, kidney by 20%, and heart by 10% compared to pair-fed controls.

A comparison of entropy balance and probability weighting methods to generalize observational cohorts to a population: a simulation and empirical example.

PubMed

Harvey, Raymond A; Hayden, Jennifer D; Kamble, Pravin S; Bouchard, Jonathan R; Huang, Joanna C

2017-04-01

We compared methods to control bias and confounding in observational studies including inverse probability weighting (IPW) and stabilized IPW (sIPW). These methods often require iteration and post-calibration to achieve covariate balance. In comparison, entropy balance (EB) optimizes covariate balance a priori by calibrating weights using the target's moments as constraints. We measured covariate balance empirically and by simulation by using absolute standardized mean difference (ASMD), absolute bias (AB), and root mean square error (RMSE), investigating two scenarios: the size of the observed (exposed) cohort exceeds the target (unexposed) cohort and vice versa. The empirical application weighted a commercial health plan cohort to a nationally representative National Health and Nutrition Examination Survey target on the same covariates and compared average total health care cost estimates across methods. Entropy balance alone achieved balance (ASMD ≤ 0.10) on all covariates in simulation and empirically. In simulation scenario I, EB achieved the lowest AB and RMSE (13.64, 31.19) compared with IPW (263.05, 263.99) and sIPW (319.91, 320.71). In scenario II, EB outperformed IPW and sIPW with smaller AB and RMSE. In scenarios I and II, EB achieved the lowest mean estimate difference from the simulated population outcome ($490.05, $487.62) compared with IPW and sIPW, respectively. Empirically, only EB differed from the unweighted mean cost indicating IPW, and sIPW weighting was ineffective. Entropy balance demonstrated the bias-variance tradeoff achieving higher estimate accuracy, yet lower estimate precision, compared with IPW methods. EB weighting required no post-processing and effectively mitigated observed bias and confounding. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The Vertex Version of Weighted Wiener Number for Bicyclic Molecular Structures

PubMed Central

Gao, Wei

2015-01-01

Graphs are used to model chemical compounds and drugs. In the graphs, each vertex represents an atom of molecule and edges between the corresponding vertices are used to represent covalent bounds between atoms. We call such a graph, which is derived from a chemical compound, a molecular graph. Evidence shows that the vertex-weighted Wiener number, which is defined over this molecular graph, is strongly correlated to both the melting point and boiling point of the compounds. In this paper, we report the extremal vertex-weighted Wiener number of bicyclic molecular graph in terms of molecular structural analysis and graph transformations. The promising prospects of the application for the chemical and pharmacy engineering are illustrated by theoretical results achieved in this paper. PMID:26640513

Middle molecules and small-molecular-weight proteins in ESRD: properties and strategies for their removal.

PubMed

Clark, William R; Winchester, James F

2003-10-01

Molecular weight has traditionally been the parameter most commonly used to classify uremic toxins, with a value of approximately 500 Da frequently used as a demarcation point below which the molecular weights of small nitrogenous waste products fall. This toxin group, the most extensively studied from a clinical perspective, is characterized by a high degree of water solubility and the absence of protein binding. However, uremia is mediated by the retention of a plethora of other compounds having characteristics that differ significantly from those of the previously mentioned group. As opposed to the relative homogeneity of the nitrogenous metabolite class, other uremic toxins collectively are a very heterogeneous group, not only with respect to molecular weight but also other characteristics, such as protein binding and hydrophobicity. A recently proposed classification scheme by the European Uraemic Toxin Work Group subdivides the remainder of molecules into 2 categories: protein-bound solutes and middle molecules. For the latter group, the Work Group proposes a molecular weight range (500-60,000 Da) that incorporates many toxins identified since the original middle molecule hypothesis, for which the upper molecular weight limit was approximately 2,000 Da. In fact, low-molecular-weight peptides and proteins (LMWPs) comprise nearly the entire middle molecule category in the new scheme. The purpose of this article is to provide an overview of the middle molecule class of uremic toxins, with the focus on LMWPs. A brief review of LMWP metabolism under conditions of normal (and in a few cases, abnormal) renal function will be presented. The physical characteristics of several LMWPs will also be presented, including molecular weight, conformation, and charge. Specific LMWPs to be covered will include beta 2-microglobulin, complement proteins (C3a and Factor D), leptin, and proinflammatory cytokines. The article will also include a discussion of the treatment-related factors influencing dialytic removal of middle molecules. Once these factors, which include membrane characteristics, protein-membrane interactions, and solute removal mechanisms, are discussed, an overview of the different therapeutic strategies used to enhance clearance of these compounds is provided.

Surface segregation and surface tension of polydisperse polymer melts.

PubMed

Minnikanti, Venkatachala S; Qian, Zhenyu; Archer, Lynden A

2007-04-14

The effect of polydispersity on surface segregation of a lower molecular weight polymer component in a higher molecular weight linear polymer melt host is investigated theoretically. We show that the integrated surface excess zM of a polymer component of molecular weight M satisfies a simple relation zM=2Ue(M/Mw-1)phiM, where Mw is the weight averaged molecular weight, phiM is the polymer volume fraction, and Ue is the attraction of polymer chain ends to the surface. Ue is principally of entropic origin, but also reflects any energetic preference of chain ends to the surface. We further show that the surface tension gammaM of a polydisperse melt of high molar mass components depends on the number average degree of polymerization Mn as, gammaM=gammainfinity+2UerhobRT/Mn. The parameter gammainfinity is the asymptotic surface tension of an infinitely long polymer of the same chemistry, rhob is the bulk density of the polymer, R is the universal gas constant, and T is the temperature. The predicted gammaM compare favorably with surface tension values obtained from self-consistent field theory simulations that include equation of state effects, which account for changes in polymer density with molecular weight. We also compare the predicted surface tension with available experimental data.

Morphological, spectral and chromatography analysis and forensic comparison of PET fibers.

PubMed

Farah, Shady; Tsach, Tsadok; Bentolila, Alfonso; Domb, Abraham J

2014-06-01

Poly(ethylene terephthalate) (PET) fiber analysis and comparison by spectral and polymer molecular weight determination was investigated. Plain fibers of PET, a common textile fiber and plastic material was chosen for this study. The fibers were analyzed for morphological (SEM and AFM), spectral (IR and NMR), thermal (DSC) and molecular weight (MS and GPC) differences. Molecular analysis of PET fibers by Gel Permeation Chromatography (GPC) allowed the comparison of fibers that could not be otherwise distinguished with high confidence. Plain PET fibers were dissolved in hexafluoroisopropanol (HFIP) and analyzed by GPC using hexafluoroisopropanol:chloroform 2:98 v/v as eluent. 14 PET fiber samples, collected from various commercial producers, were analyzed for polymer molecular weight by GPC. Distinct differences in the molecular weight of the different fiber samples were found which may have potential use in forensic fiber comparison. PET fibers with average molecular weights between about 20,000 and 70,000 g mol(-1) were determined using fiber concentrations in HFIP as low as 1 μg mL(-1). This GPC analytical method can be applied for exclusively distinguish between PET fibers using 1 μg of fiber. This method can be extended to forensic comparison of other synthetic fibers such as polyamides and acrylics. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of computer-assisted molecular modeling (CAMM) for immunoassay of low molecular weight food contaminants: A review

USDA-ARS?s Scientific Manuscript database

Immunoassay for low molecular weight food contaminants, such as pesticides, veterinary drugs, and mycotoxins is now a well-established technique which meets the demands for a rapid, reliable, and cost-effective analytical method. However, due to limited understanding of the fundamental aspects of i...

Melt fracture of linear low-density polyethylenes: Die geometry and molecular weight characteristics

NASA Astrophysics Data System (ADS)

Ebrahimi, Marzieh; Tomkovic, Tanja; Liu, Guochang; Doufas, Antonios A.; Hatzikiriakos, Savvas G.

2018-05-01

The melt fracture phenomena of three linear low-density polyethylenes are investigated as a function of die geometry (capillary, slit, and annular) and molecular weight and its distribution. The onset of melt fracture instabilities is determined by using capillary rheometry, mainly studying the extrudate appearance using optical microscopy. It is found that the onset of flow instabilities (melt fracture phenomena) is significantly affected by die geometry and molecular weight characteristics of the polymers. Use of annular die eliminates the stick-slip transition (oscillating melt fracture) and delays the onset of sharkskin to higher values of shear rate and shear stress. Moreover, it is shown that the molecular weight characteristics of the polymers are well correlated with critical conditions for the onset of flow instabilities based on a criterion proposed in the literature [A. Allal et al., "Relationships between molecular structure and sharkskin defect for linear polymers," J. Non-Newtonian Fluid Mech. 134, 127-135 (2006) and A. Allal and B. Vergnes, "Molecular design to eliminate sharkskin defect for linear polymers," J. Non-Newtonian Fluid Mech. 146, 45-50 (2007)].

[Correlation of molecular weight and nanofiltration mass transfer coefficient of phenolic acid composition from Salvia miltiorrhiza].

PubMed

Li, Cun-Yu; Wu, Xin; Gu, Jia-Mei; Li, Hong-Yang; Peng, Guo-Ping

2018-04-01

Based on the molecular sieving and solution-diffusion effect in nanofiltration separation, the correlation between initial concentration and mass transfer coefficient of three typical phenolic acids from Salvia miltiorrhiza was fitted to analyze the relationship among mass transfer coefficient, molecular weight and concentration. The experiment showed a linear relationship between operation pressure and membrane flux. Meanwhile, the membrane flux was gradually decayed with the increase of solute concentration. On the basis of the molecular sieving and solution-diffusion effect, the mass transfer coefficient and initial concentration of three phenolic acids showed a power function relationship, and the regression coefficients were all greater than 0.9. The mass transfer coefficient and molecular weight of three phenolic acids were negatively correlated with each other, and the order from high to low is protocatechualdehyde >rosmarinic acid> salvianolic acid B. The separation mechanism of nanofiltration for phenolic acids was further clarified through the analysis of the correlation of molecular weight and nanofiltration mass transfer coefficient. The findings provide references for nanofiltration separation, especially for traditional Chinese medicine with phenolic acids. Copyright© by the Chinese Pharmaceutical Association.

The pPSU Plasmids for Generating DNA Molecular Weight Markers.

PubMed

Henrici, Ryan C; Pecen, Turner J; Johnston, James L; Tan, Song

2017-05-26

Visualizing nucleic acids by gel electrophoresis is one of the most common techniques in molecular biology, and reference molecular weight markers or ladders are commonly used for size estimation. We have created the pPSU1 & pPSU2 pair of molecular weight marker plasmids which produce both 100 bp and 1 kb DNA ladders when digested with two common restriction enzymes. The 100 bp ladder fragments have been optimized to migrate appropriately on both agarose and native polyacrylamide, unlike many currently available DNA ladders. Sufficient plasmid DNA can be isolated from 100 ml E. coli cultures for the two plasmids to produce 100 bp or 1 kb ladders for 1000 gels. As such, the pPSU1 and pPSU2 plasmids provide reference fragments from 50 to 10000 bp at a fraction of the cost of commercial DNA ladders. The pPSU1 and pPSU2 plasmids are available without licensing restrictions to nonprofit academic users, affording freely available high-quality, low-cost molecular weight standards for molecular biology applications.

Using molecular recognition of beta-cyclodextrin to determine molecular weights of low-molecular-weight explosives by MALDI-TOF mass spectrometry.

PubMed

Zhang, Min; Shi, Zhen; Bai, Yinjuan; Gao, Yong; Hu, Rongzu; Zhao, Fenqi

2006-02-01

This study presents a novel method for determining the molecular weights of low molecular weight (MW) energetic compounds through their complexes of beta-cyclodextrin (beta-CD) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in a mass range of 500 to 1700 Da, avoiding matrix interference. The MWs of one composite explosive composed of 2,6-DNT, TNT, and RDX, one propellant with unknown components, and 14 single-compound explosives (RDX, HMX, 3,4-DNT, 2,6-DNT, 2,5-DNT, 2,4,6-TNT, TNAZ, DNI, BTTN, NG, TO, NTO, NP, and 662) were measured. The molecular recognition and inclusion behavior of beta-CD to energetic materials (EMs) were investigated. The results show that (1) the established method is sensitive, simple, accurate, and suitable for determining the MWs of low-MW single-compound explosives and energetic components in composite explosives and propellants; and (2) beta-CD has good inclusion and modular recognition abilities to the above EMs.

An NMR (Nuclear Magnetic Resonance) Investigation of the Chemical Association and Molecular Dynamics in Asphalt Ridge Tar Sand Ore and Bitumen

DOE R&D Accomplishments Database

Netzel, D. A.; Coover, P. T.

1987-09-01

Preliminary studies on tar sand bitumen given in this report have shown that the reassociation of tar sand bitumen to its original molecular configuration after thermal stressing is a first-order process requiring nearly a week to establish equilibrium. Studies were also conducted on the dissolution of tar sand bitumen in solvents of varying polarity. At a high-weight fraction of solute to solvent the apparent molecular weight of the bitumen molecules was greater than that of the original bitumen when dissolved in chloroform-d{sub 1} and benzene-d{sub 6}. This increase in the apparent molecular weight may be due to micellar formation or a weak solute-solvent molecular complex. Upon further dilution with any of the solvents studied, the apparent molecular weight of the tar sand bitumen decreased because of reduced van der Waals forces of interaction and/or hydrogen bonding. To define the exact nature of the interactions, it will be necessary to have viscosity measurements of the solutions.

Regional comparison of absolute gravimeters, EURAMET.M.G-K2 key comparison

NASA Astrophysics Data System (ADS)

Pálinkáš, V.; Francis, O.; Val'ko, M.; Kostelecký, J.; Van Camp, M.; Castelein, S.; Bilker-Koivula, M.; Näränen, J.; Lothhammer, A.; Falk, R.; Schilling, M.; Timmen, L.; Iacovone, D.; Baccaro, F.; Germak, A.; Biolcati, E.; Origlia, C.; Greco, F.; Pistorio, A.; De Plaen, R.; Klein, G.; Seil, M.; Radinovic, R.; Reudink, R.; Dykowski, P.; Sȩkowski, M.; Próchniewicz, D.; Szpunar, R.; Mojzeš, M.; Jańk, J.; Papčo, J.; Engfeldt, A.; Olsson, P. A.; Smith, V.; van Westrum, D.; Ellis, B.; Lucero, B.

2017-01-01

In the framework of the regional EURAMET.M.G-K2 comparison of absolute gravimeters, 17 gravimeters were compared in November 2015. Four gravimeters were from different NMIs and DIs, they were used to link the regional comparison to the CCM.G.K2 by means of linking converter. Combined least-squares adjustments with weighted constraint was used to determine KCRV. Several pilot solutions are presented and compared with the official solution to demonstrate influences of different approaches (e.g. definition of weights and the constraint) on results of the adjustment. In case of the official solution, all the gravimeters are in equivalence with declared uncertainties. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Pediatric obesity and depression: a cross-sectional analysis of absolute BMI as it relates to children's depression index scores in obese 7- to 17-year-old children.

PubMed

Benson, Levi P; Williams, Ronald J; Novick, Marsha B

2013-01-01

Depression and obesity are important in children because they affect health in childhood and later life. The exact relationship between obesity and depression, especially in children, remains undefined. Using a cross-sectional chart review design, our study looked at a weight management clinic-based sample of 117 obese children, 7 to 17 years old, to determine the relationship between absolute BMI and depression as measured by the Children's Depression Index (CDI) while accounting for confounders, such as the child's medical problems, physical activity, and family structure. There was no correlation between depression as measured by the CDI and increasing BMI in obese children seeking weight management. However, we did demonstrate a positive correlation between depression and paternal absence and daily television/computer/video game time. Clinicians should encourage decreasing screen time and might consider family therapy for obese children in families that lack paternal involvement.

Discrete distributed strain sensing of intelligent structures

NASA Technical Reports Server (NTRS)

Anderson, Mark S.; Crawley, Edward F.

1992-01-01

Techniques are developed for the design of discrete highly distributed sensor systems for use in intelligent structures. First the functional requirements for such a system are presented. Discrete spatially averaging strain sensors are then identified as satisfying the functional requirements. A variety of spatial weightings for spatially averaging sensors are examined, and their wave number characteristics are determined. Preferable spatial weightings are identified. Several numerical integration rules used to integrate such sensors in order to determine the global deflection of the structure are discussed. A numerical simulation is conducted using point and rectangular sensors mounted on a cantilevered beam under static loading. Gage factor and sensor position uncertainties are incorporated to assess the absolute error and standard deviation of the error in the estimated tip displacement found by numerically integrating the sensor outputs. An experiment is carried out using a statically loaded cantilevered beam with five point sensors. It is found that in most cases the actual experimental error is within one standard deviation of the absolute error as found in the numerical simulation.

Influence of simulated weightlessness on maximal oxygen uptake of untrained rats

NASA Technical Reports Server (NTRS)

Overton, J. Michael; Tipton, Charles M.

1987-01-01

The purpose of this study was to determine the effect of hindlimb suspension on maximal oxygen uptake of rodents. Male Sprague-Dawley rats were assigned to head-down (HD) suspension, horizontal (HOZ) suspension, or cage (C) control for 6-9 days. Rats were tested for maximal oxygen uptake before and after surgical instrumentation (Doppler flow probes, carotid and jugular cannulae), and after suspension. Body weight was significantly decreased after suspension in both HD and HOZ groups, but was significantly increased in the C group. Absolute maximal O2 uptake (ml/min) was not different in the C group. However, because of their increased weight, relative maximal O2 uptake (ml/min per kg) was significantly reduced. In contrast, both relative and absolute maximal O2 uptake were significantly lower, following suspension, for the HD and HOZ groups. These preliminary results support the use of hindlimb suspension as an effective model to study the mechanism(s) of cardiovascular deconditioning.

Targeting Preschool Children to Promote Cardiovascular Health: Cluster Randomized Trial

PubMed Central

Céspedes, Jaime; Briceño, German; Farkouh, Michael E.; Vedanthan, Rajesh; Baxter, Jorge; Leal, Martha; Boffetta, Paolo; Woodward, Mark; Hunn, Marilyn; Dennis, Rodolfo; Fuster, Valentin

2015-01-01

BACKGROUND School programs can be effective in modifying knowledge, attitudes, and habits relevant to long-term risk of chronic diseases associated with sedentary lifestyles. As part of a long-term research strategy, we conducted an educational intervention in preschool facilities to assess changes in preschoolers’ knowledge, attitudes, and habits toward healthy eating and living an active lifestyle. METHODS Using a cluster design, we randomly assigned 14 preschool facilities in Bogotá, Colombia to a 5-month educational and playful intervention (7 preschool facilities) or to usual curriculum (7 preschool facilities). A total of 1216 children aged 3–5 years, 928 parents, and 120 teachers participated. A structured survey was used at baseline, at the end of the study, and 12 months later to evaluate changes in knowledge, attitudes, and habits. RESULTS Children in the intervention group showed a 10.9% increase in weighted score, compared with 5.3% in controls. The absolute adjusted difference was 3.90 units (95% confidence interval [CI], 1.64–6.16; P <.001). Among parents, the equivalent statistics were 8.9% and 3.1%, respectively (absolute difference 4.08 units; 95% CI, 2.03 to 6.12; P <.001), and among teachers, 9.4% and 2.5%, respectively (absolute difference 5.36 units; 95% CI, −0.29–11.01; P = .06). In the intervened cohort 1 year after the intervention, children still showed a significant increase in weighted score (absolute difference of 6.38 units; P <.001). CONCLUSIONS A preschool-based intervention aimed at improving knowledge, attitudes, and habits related to healthy diet and active lifestyle is feasible, efficacious, and sustainable in very young children. PMID:23062403

Weighing up the benefits and harms of a new anti-cancer drug: a survey of Australian oncologists.

PubMed

Chim, L; Salkeld, G; Stockler, M R; Mileshkin, L

2015-08-01

Little is known about the relative importance that oncologists attribute to the benefits and harms of anti-cancer drugs when considering treatment options with their patients. To quantify the trade-offs made between overall survival, progression-free survival and adverse effects. A web-based survey elicited importance weights for the benefits and harms of bevacizumab or everolimus. Combining the importance weights with trial-based probabilities produced a score and ranking for each treatment option. A total of 40 responses was received for the bevacizumab scenario and 32 for the everolimus scenario. All respondents regarded overall survival and progression-free survival as the most important attributes - more important than avoiding the potential harms regardless of drugs. Among the potential harms, respondents allocated the highest mean importance weight to gastrointestinal (GI) perforation and rated absolute improvement in overall survival as 1.6 times and 2.3 times as important as avoiding GI perforation in the two versions of the bevacizumab scenario respectively. For the everolimus scenario, stomatitis and pneumonitis were allocated the highest mean importance weights with absolute improvement in overall survival rated as 2.2 times as important as avoiding stomatitis/pneumonitis. All 40 respondents (100%) favoured treatment option with bevacizumab to no bevacizumab based on respondents' determined weights for treatment attributes. The converse was found for everolimus with 22 (69%) of respondents preferring the 'no everolimus' option. Oncologists' preferences over the benefits and harms of treatment do, when combined with evidence of effect, influence treatment decisions for anti-cancer drugs. © 2015 Royal Australasian College of Physicians.

Effects of gastric acid on euro coins: chemical reaction and radiographic appearance after ingestion by infants and children

PubMed Central

Puig, S; Scharitzer, M; Cengiz, K; Jetzinger, E; Rupprecht, L

2004-01-01

Objectives: This study investigated whether coins of the new European currency (€) corrode when they are exposed to gastric acid, and whether this change can be detected radiographically. Methods: The eight different denominations of € coins were immersed for seven days in 0.15 N hydrochloride acid (HCl), which corresponds to the level of post-prandial gastric acid. A Swedish crown coin and three different Austrian schilling coins were used as controls. The coins were weighed and radiographed daily to evaluate visible corrosions and HCl was analysed daily for possible dissolved substances. Results: All coins lost weight within 24 hours after exposure to HCl. The 1, 2, and 5 € cent coins developed changes that were visible on radiographs. The weights of all coins decreased by 0.43% to 11.30% during one week. The dissolved substances measured in the HCl corresponded to the different metals and alloys of the coins, except for copper, which does not dissolve in HCl. The highest absolute weight loss was observed in the Swedish crown coin (0.67 g), and the highest relative weight loss in the 1 Austrian schilling coin (11.30%). The two € coins that showed the highest absolute and relative weight losses were the 2 € (0.54 g or 6.35%) and the 1 € (0.48 g or 6.39%) coin. Conclusions: A higher rate of toxicity for the new European coins compared with coins of other currencies is not expected, unless a massive coin ingestion occurs. PMID:15333527

Fitness and Activity Assessments among U.S. Army Populations: Implications for NCHS General Population Surveys,

DTIC Science & Technology

1986-01-01

and in some cases -body fat ), are measured twice yearly in the U.S. Army through age 60. Field measures are defined as those conducted by army units...weight and fat standards were originally part of the fitness program and fitness regulations. Because of a considerable increase in emphasis in this...service. Absolute b max is 4/0% less in women but only15% less when adjusted for difference in fat free weight. The relatively small overlap between

Fatigue tests on big structure assemblies of concorde aircraft

NASA Technical Reports Server (NTRS)

Nguyen, V. P.; Perrais, J. P.

1972-01-01

Fatigue tests on structural assemblies of the Concorde supersonic transport aircraft are reported. Two main sections of the aircraft were subjected to pressure, mechanical load, and thermal static tests. The types of fatigue tests conducted and the results obtained are discussed. It was concluded that on a supersonic aircraft whose structural weight is a significant part of the weight analysis, many fatigue and static strength development tests should be made and fatigue and thermal tests of the structures are absolutely necessary.

Effect of molecular weight of polystyrensulfonic acid sodium salt polymers on the precipitation kinetics of sodium bicarbonate

NASA Astrophysics Data System (ADS)

Martínez-Cruz, Nancy; Carrillo-Romo, Felipe; Jaramillo-Vigueras, David

2004-10-01

This paper analyzes the effect of polystyrensulfonic acid sodium salt (NaPSS), obtained by kinetic precipitation from solutions of polymers of molecular weight 245 000 and 38 000 g mol-1 in sodium bicarbonate (NaHCO3) itself precipitated from synthetic brine. Crystal size, shape and the additive adsorbed are reported. X shaped and hexagonal prisms crystals with different aspect ratios were obtained. The results show that with increasing polymer concentration the crystal size decreases, from 0.27 to 0.48 mm. Additionally, the higher molecular weight polymer shows both higher adsorption capacity and higher crystal habit modification. Crystal shape patterns were similar for both polymers; however, the higher molecular weight material induced changes at lower concentration. It was observed that the precipitation rate reached a minimum with increasing additive concentration.

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants.

PubMed

Simal-Gándara, J; Sarria-Vidal, M; Rijk, R

2000-09-01

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.

The development of low-molecular weight hydrogels for applications in cancer therapy

NASA Astrophysics Data System (ADS)

Tian, Ran; Chen, Jin; Niu, Runfang

2014-03-01

To improve the anti-cancer efficacy and to counteract the side effects of chemotherapy, a variety of drug delivery systems have been invented in past decades, but few of these systems have succeeded in clinical trials due to their respective inherent shortcomings. Recently, low-molecular weight hydrogels of peptides that self-assemble via non-covalent interactions have attracted considerable attention due to their good biocompatibility, low toxicity, inherent biodegradability as well as their convenience of design. Low-molecular weight hydrogels have already shown promise in biomedical applications as diverse as 3D-cell culture, enzyme immobilization, controllable MSC differentiation, wound healing, drug delivery etc. Here we review the recent development in the use of low-molecular weight hydrogels for cancer therapy, which may be helpful in the design of soft materials for drug delivery.

Endogenous ethanol affects biopolyester molecular weight in recombinant Escherichia coli.

PubMed

Hiroe, Ayaka; Hyakutake, Manami; Thomson, Nicholas M; Sivaniah, Easan; Tsuge, Takeharu

2013-11-15

In biopolyester synthesis, polyhydroxyalkanoate (PHA) synthase (PhaC) catalyzes the polymerization of PHA in bacterial cells, followed by a chain transfer (CT) reaction in which the PHA polymer chain is transferred from PhaC to a CT agent. Accordingly, the frequency of CT reaction determines PHA molecular weight. Previous studies have shown that exogenous alcohols are effective CT agents. This study aimed to clarify the effect of endogenous ethanol as a CT agent for poly[(R)-3-hydroxybutyrate] [P(3HB)] synthesis in recombinant Escherichia coli, by comparing with that of exogenous ethanol. Ethanol supplementation to the culture medium reduced P(3HB) molecular weights by up to 56% due to ethanol-induced CT reaction. NMR analysis of P(3HB) polymers purified from the culture supplemented with (13)C-labeled ethanol showed the formation of a covalent bond between ethanol and P(3HB) chain at the carboxyl end. Cultivation without ethanol supplementation resulted in the reduction of P(3HB) molecular weight with increasing host-produced ethanol depending on culture aeration. On the other hand, production in recombinant BW25113(ΔadhE), an alcohol dehydrogenase deletion strain, resulted in a 77% increase in molecular weight. Analysis of five E. coli strains revealed that the estimated number of CT reactions was correlated with ethanol production. These results demonstrate that host-produced ethanol acts as an equally effective CT agent as exogenous ethanol, and the control of ethanol production is important to regulate the PHA molecular weight.

Synthesis and Characterisation of Photocrosslinked poly(ethylene glycol) diacrylate Implants for Sustained Ocular Drug Delivery.

PubMed

McAvoy, Kathryn; Jones, David; Thakur, Raghu Raj Singh

2018-01-16

To investigate the sustained ocular delivery of small and large drug molecules from photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) implants with varying pore forming agents. Triamcinolone acetonide and ovalbumin loaded photocrosslinked PEGDA implants, with or without pore-forming agents, were fabricated and characterised for chemical, mechanical, swelling, network parameters, as well as drug release and biocompatibility. HPLC-based analytical methods were employed for analysis of two molecules; ELISA was used to demonstrate bioactivity of ovalbumin. Regardless of PEGDA molecular weight or pore former composition all implants loaded with triamcinolone acetonide released significantly faster than those loaded with ovalbumin. Higher molecular weight PEGDA systems (700 Da) resulted in faster drug release of triamcinolone acetonide than their 250 Da counterpart. All ovalbumin released over the 56-day time period was found to be bioactive. Increasing PEGDA molecular weight resulted in increased system swelling, decreased crosslink density (Ve), increased polymer-water interaction parameter (χ), increased average molecular weight between crosslinks (Mc) and increased mesh size (ε). SEM studies showed the porosity of implants increased with increasing PEGDA molecular weight. Biocompatibility showed both PEGDA molecular weight implants were non-toxic when exposed to retinal epithelial cells over a 7-day period. Photocrosslinked PEGDA implant based systems are capable of controlled drug release of both small and large drug molecules through adaptations in the polymer system network. We are currently continuing evaluation of these systems as potential sustained drug delivery devices.

Gas-film coefficients for streams

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1983-01-01

Equations for predicting the gas-film coefficient for the volatilization of organic solutes from streams are developed. The film coefficient is a function of windspeed and water temperature. The dependence of the coefficient on windspeed is determined from published information on the evaporation of water from a canal. The dependence of the coefficient on temperature is determined from laboratory studies on the evaporation of water. Procedures for adjusting the coefficients for different organic solutes are based on the molecular diffusion coefficient and the molecular weight. The molecular weight procedure is easiest to use because of the availability of molecular weights. However, the theoretical basis of the procedure is questionable. The diffusion coefficient procedure is supported by considerable data. Questions, however, remain regarding the exact dependence of the film coefficint on the diffusion coefficient. It is suggested that the diffusion coefficient procedure with a 0.68-power dependence be used when precise estimate of the gas-film coefficient are needed and that the molecular weight procedure be used when only approximate estimates are needed.

A functional form for injected MRI Gd-chelate contrast agent concentration incorporating recirculation, extravasation and excretion

NASA Astrophysics Data System (ADS)

Horsfield, Mark A.; Thornton, John S.; Gill, Andrew; Jager, H. Rolf; Priest, Andrew N.; Morgan, Bruno

2009-05-01

A functional form for the vascular concentration of MRI contrast agent after intravenous bolus injection was developed that can be used to model the concentration at any vascular site at which contrast concentration can be measured. The form is based on previous models of blood circulation, and is consistent with previously measured data at long post-injection times, when the contrast agent is fully and evenly dispersed in the blood. It allows the first-pass and recirculation peaks of contrast agent to be modelled, and measurement of the absolute concentration of contrast agent at a single time point allows the whole time course to be rescaled to give absolute contrast agent concentration values. This measure of absolute concentration could be performed at a long post-injection time using either MRI or blood-sampling methods. In order to provide a model that is consistent with measured data, it was necessary to include both rapid and slow extravasation, together with excretion via the kidneys. The model was tested on T1-weighted data from the descending aorta and hepatic portal vein, and on T*2-weighted data from the cerebral arteries. Fitting of the model was successful for all datasets, but there was a considerable variation in fit parameters between subjects, which suggests that the formation of a meaningful population-averaged vascular concentration function is precluded.

Absolute Effect of Prostate Cancer Screening: Balance of benefits and harms by center within the European Randomized Study of Prostate Cancer Screening

PubMed Central

Auvinen, Anssi; Moss, Sue M; Tammela, Teuvo L J; Taari, Kimmo; Roobol, Monique J; Schröder, Fritz H; Bangma, Chris H; Carlsson, Sigrid; Aus, Gunnar; Zappa, Marco; Puliti, Donella; Denis, Louis J; Nelen, Vera; Kwiatkowski, Maciej; Randazzo, Marco; Paez, Alvaro; Lujan, Marcos; Hugosson, Jonas

2016-01-01

Purpose The balance of benefits and harms in prostate cancer screening has not been sufficiently characterized. We related indicators of mortality reduction and overdetection by center within the European Randomized Study of Prostate Cancer Screening. Experimental Design We analyzed the absolute mortality reduction expressed as number needed to invite (NNI=1/absolute risk reduction; indicating how many men had to be randomized to screening arm to avert a prostate cancer death) for screening and the absolute excess of prostate cancer detection as number needed for overdetection (NNO=1/absolute excess incidence; indicating the number of men invited per additional prostate cancer case), and compared their relationship across the seven ERSPC centers. Results Both absolute mortality reduction (NNI) and absolute overdetection (NNO) varied widely between the centers: NNI 200-7000 and NNO 16-69. Extent of overdiagnosis and mortality reduction were closely associated (correlation coefficient r=0.76, weighted linear regression coefficient β=33, 95% 5-62, R2=0.72). For an averted prostate cancer death at 13 years of follow-up, 12-36 excess cases had to be detected in various centers. Conclusions The differences between the ERSPC centers likely reflect variations in prostate cancer incidence and mortality, as well as in screening protocol and performance. The strong interrelation between the benefits and harms suggests that efforts to maximize the mortality effect are bound to increase overdiagnosis, and might be improved by focusing on high-risk populations. The optimal balance between screening intensity and risk of overdiagnosis remains unclear. PMID:26289069

Optimizing hidden layer node number of BP network to estimate fetal weight

NASA Astrophysics Data System (ADS)

Su, Juan; Zou, Yuanwen; Lin, Jiangli; Wang, Tianfu; Li, Deyu; Xie, Tao

2007-12-01

The ultrasonic estimation of fetal weigh before delivery is of most significance for obstetrical clinic. Estimating fetal weight more accurately is crucial for prenatal care, obstetrical treatment, choosing appropriate delivery methods, monitoring fetal growth and reducing the risk of newborn complications. In this paper, we introduce a method which combines golden section and artificial neural network (ANN) to estimate the fetal weight. The golden section is employed to optimize the hidden layer node number of the back propagation (BP) neural network. The method greatly improves the accuracy of fetal weight estimation, and simultaneously avoids choosing the hidden layer node number with subjective experience. The estimation coincidence rate achieves 74.19%, and the mean absolute error is 185.83g.

Tailored composite wings with elastically produced chordwise camber

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Chang, Stephen; Zischka, Peter J.; Pickings, Richard D.; Holl, Michael W.

1991-01-01

Four structural concepts were created which produce chordwise camber deformation that results in enhanced lift. A wing box can be tailored to utilize each of these with composites. In attempting to optimize the aerodynamic benefits, researchers found that there are two optimum designs that are of interest. There is a weight optimum which corresponds to the maximum lift per unit structural weight. There is also a lift optimum that corresponds to maximum absolute lift. Experience indicates that a large weight penalty accompanies the transition from weight to lift optimum designs. New structural models, the basic deformation mechanisms that are utilized, and typical analytical results are presented. It appears that lift enhancements of sufficient magnitude can be produced to render this type of wing tailoring of practical interest.

Microgravity vibration isolation: An optimal control law for the one-dimensional case

NASA Technical Reports Server (NTRS)

Hampton, Richard D.; Grodsinsky, Carlos M.; Allaire, Paul E.; Lewis, David W.; Knospe, Carl R.

1991-01-01

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platform. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) exp 4. Low frequency accelerations are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics guaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Microgravity vibration isolation: An optimal control law for the one-dimensional case

NASA Technical Reports Server (NTRS)

Hampton, R. D.; Grodsinsky, C. M.; Allaire, P. E.; Lewis, D. W.; Knospe, C. R.

1991-01-01

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platforms. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward (preview) gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega)(exp 4). Low frequency accelerations (less than 50 Hz) are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics guaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Optimal Weights Mixed Filter for removing mixture of Gaussian and impulse noises

PubMed Central

Grama, Ion; Liu, Quansheng

2017-01-01

In this paper we consider the problem of restoration of a image contaminated by a mixture of Gaussian and impulse noises. We propose a new statistic called ROADGI which improves the well-known Rank-Ordered Absolute Differences (ROAD) statistic for detecting points contaminated with the impulse noise in this context. Combining ROADGI statistic with the method of weights optimization we obtain a new algorithm called Optimal Weights Mixed Filter (OWMF) to deal with the mixed noise. Our simulation results show that the proposed filter is effective for mixed noises, as well as for single impulse noise and for single Gaussian noise. PMID:28692667

Optimal Weights Mixed Filter for removing mixture of Gaussian and impulse noises.

PubMed

Jin, Qiyu; Grama, Ion; Liu, Quansheng

2017-01-01

In this paper we consider the problem of restoration of a image contaminated by a mixture of Gaussian and impulse noises. We propose a new statistic called ROADGI which improves the well-known Rank-Ordered Absolute Differences (ROAD) statistic for detecting points contaminated with the impulse noise in this context. Combining ROADGI statistic with the method of weights optimization we obtain a new algorithm called Optimal Weights Mixed Filter (OWMF) to deal with the mixed noise. Our simulation results show that the proposed filter is effective for mixed noises, as well as for single impulse noise and for single Gaussian noise.

Oligomeric cationic polymethacrylates: a comparison of methods for determining molecular weight.

PubMed

Locock, Katherine E S; Meagher, Laurence; Haeussler, Matthias

2014-02-18

This study compares three common laboratory methods, size-exclusion chromatography (SEC), (1)H nuclear magnetic resonance (NMR), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), to determine the molecular weight of oligomeric cationic copolymers. The potential bias for each method was examined across a series of polymers that varied in molecular weight and cationic character (both choice of cation (amine versus guanidine) and relative proportion present). SEC was found to be the least accurate, overestimating Mn by an average of 140%, owing to the lack of appropriate cationic standards available, and the complexity involved in estimating the hydrodynamic volume of copolymers. MALDI-TOF approximated Mn well for the highly monodisperse (Đ < 1.1), low molecular weight (degree of polymerization (DP) <50) species but appeared unsuitable for the largest polymers in the series due to the mass bias associated with the technique. (1)H NMR was found to most accurately estimate Mn in this study, differing to theoretical values by only 5.2%. (1)H NMR end-group analysis is therefore an inexpensive and facile, primary quantitative method to estimate the molecular weight of oliogomeric cationic polymethacrylates if suitably distinct end-groups signals are present in the spectrum.

Solution pH and oligoamine molecular weight dependence of the transition from monolayer to multilayer adsorption at the air-water interface from sodium dodecyl sulfate/oligoamine mixtures.

PubMed

Halacheva, S S; Penfold, J; Thomas, R K; Webster, J R P

2013-05-14

Neutron reflectivity and surface tension have been used to investigate the solution pH and oligoamine molecular weight dependence of the adsorption of sodium dodecyl sulfate (SDS)/oligoamine mixtures at the air-water interface. For diethylenetriamine, triamine, or triethylenetetramine, tetramine mixed with SDS, there is monolayer adsorption at pH 7 and 10, and multilayer adsorption at pH 3. For the slightly higher molecular weight tetraethylenepentamine, pentamine, and pentaethylenehexamine, hexamine, the adsorption is in the form of a monolayer at pH 3 and multilayers at pH 7 and 10. Hence, there is a pH driven transition from monolayer to multilayer adsorption, which shifts from low pH to higher pH as the oligoamine molecular weight increases from tetramine to pentamine. This results from the relative balance between the electrostatic attraction between the SDS and amine nitrogen group which decreases as the charge density decreases with increasing pH, the ion-dipole interaction between the amine nitrogen and SDS sulfate group which is dominant at higher pH, and the hydrophobic interalkyl chain interaction between bound SDS molecules which changes with oligoamine molecular weight.

Comparison of antimicrobial activities of newly obtained low molecular weight scorpion chitosan and medium molecular weight commercial chitosan.

PubMed

Kaya, Murat; Asan-Ozusaglam, Meltem; Erdogan, Sevil

2016-06-01

In this study the antimicrobial activity of low molecular weight (3.22 kDa) chitosan, obtained for the first time from a species belonging to the Scorpiones, was screened against nine pathogenic microorganisms (seven bacteria and two yeasts) and compared with that of medium molecular weight commercial chitosan (MMWCC). It was observed that the antimicrobial activity of the low molecular weight scorpion chitosan (LMWSC) was specific to bacterial species in general rather than gram-negative or gram-positive bacterial groups. It was also determined that LMWSC had a stronger inhibitory effect than the MMWCC, particularly on the bacterium Listeria monocytogenes and the yeast Candida albicans, which are important pathogens for public health. In addition, it was recorded that the MMWCC had a greater inhibitory effect on Bacillus subtilis than LMWSC. According to the results obtained by the disc diffusion method, the antibacterial activity of both LMWSC and MMWCC against B. subtilis and Salmonella enteritidis was higher than the widely used antibiotic Gentamicin (CN, 10 μg/disc). Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Low-molecular-weight heparin for thromboprophylaxis.

PubMed

Camporese, Giuseppe; Bernardi, Enrico

2009-09-01

Venous thromboembolism represents a potentially threatening complication in surgical and medical patients. Thromboprophylaxis showed a significant reduction of venous thromboembolic events, and low-molecular-weight heparins have been considered the standardized prophylactic regimen for a long time. The purpose of this review is to provide updated evidence on the use of low-molecular-weight heparins for prevention of venous thromboembolism after the publication of the latest American College of Chest Physicians Evidence-Based Clinical Practice Guidelines on antithrombotic and thrombolytic therapy. Low-molecular-weight heparins, used as comparator or investigational drug, have been investigated in several studies not included in the analysis of the latest American College of Chest Physicians Guidelines on Antithrombotic and Thrombolytic Therapy. Data gathered from studies published from December 2007 up to May 2009 dealing with surgical and medical patients have been collected and discussed. Low-molecular-weight heparins are expanding their application, but progressively they will be replaced by other new antithrombotics for the prophylaxis of venous thromboembolism. Surgical patients undergo a more concerted approach to thromboprophylaxis than medical patients. Future research should aim at improving prophylaxis in the latter setting in order to significantly reduce the rate of venous thromboembolic events.

DNA Polymerase in Virions of a Reptilian Type C Virus

PubMed Central

Twardzik, Daniel R.; Papas, Takis S.; Portugal, Frank H.

1974-01-01

A study was made of the DNA polymerase of reptilian type C virus isolated from Russell's viper spleen cells. Simultaneous detection experiments demonstrated the presence of 70S RNA and RNA-dependent DNA polymerase activity in reptilian type C virions. The endogenous activity was dependent on the addition of all four deoxynucleotide triphosphates and demonstrated an absolute requirement for a divalent cation. The reptilian viral DNA polymerase elutes from phosphocellulose at 0.22 M salt. In this respect, it is similar to the avian (avian myeloblastosis virus; AMV) viral enzyme but is different from the mammalian (Rauscher leukemia virus; RLV) viral enzyme which elutes at 0.4 M salt. The molecular weight of the viper DNA polymerase as estimated from glycerol gradient centrifugation is 109,000. It is a smaller enzyme than the AMV DNA polymerase (180,000 daltons) and somewhat larger than the RLV enzyme (70,000 daltons). A comparison of other properties of the type C reptilian DNA polymerase with the enzyme found in other type C oncogenic viruses is made. PMID:4129837

A snapshot of plasma metabolites in first-episode schizophrenia: a capillary electrophoresis time-of-flight mass spectrometry study.

PubMed

Koike, S; Bundo, M; Iwamoto, K; Suga, M; Kuwabara, H; Ohashi, Y; Shinoda, K; Takano, Y; Iwashiro, N; Satomura, Y; Nagai, T; Natsubori, T; Tada, M; Yamasue, H; Kasai, K

2014-04-08

Few biomarkers have been known that can easily measure clinical conditions in mental illnesses such as schizophrenia. Capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) is a new method that can measure ionized and low-molecular-weight metabolites. To explore global metabolomic alterations that characterize the onset of schizophrenia and identify biomarkers, we profiled the relative and absolute concentrations of the plasma metabolites from 30 patients with first-episode schizophrenia (FESZ, four drug-naïve samples), 38 healthy controls and 15 individuals with autism spectrum disorders using CE-TOFMS. Five metabolites had robust changes (increased creatine and decreased betaine, nonanoic acid, benzoic acid and perillic acid) in two independent sample sets. Altered levels of these metabolites are consistent with well-known hypotheses regarding abnormalities of the homocysteine metabolism, creatine kinase-emia and oxidative stress. Although it should be considered that most patients with FESZ received medication, these metabolites are candidate biomarkers to improve the determination of diagnosis, severity and clinical stages, especially for FESZ.

A potential for overestimating the absolute magnitudes of second virial coefficients by small-angle X-ray scattering.

PubMed

Scott, David J; Patel, Trushar R; Winzor, Donald J

2013-04-15

Theoretical consideration is given to the effect of cosolutes (including buffer and electrolyte components) on the determination of second virial coefficients for proteins by small-angle X-ray scattering (SAXS)-a factor overlooked in current analyses in terms of expressions for a two-component system. A potential deficiency of existing practices is illustrated by reassessment of published results on the effect of polyethylene glycol concentration on the second virial coefficient for urate oxidase. This error reflects the substitution of I(0,c3,0), the scattering intensity in the limit of zero scattering angle and solute concentration, for I(0,0,0), the corresponding parameter in the limit of zero cosolute concentration (c3) as well. Published static light scattering results on the dependence of the apparent molecular weight of ovalbumin on buffer concentration are extrapolated to zero concentration to obtain the true value (M2) and thereby establish the feasibility of obtaining the analogous SAXS parameter, I(0,0,0), experimentally. Copyright © 2013 Elsevier Inc. All rights reserved.

Calculation and Comparative Analysis of the IR Spectra of Homobrassinolide and (22S,23S)-Homobrassinolide

NASA Astrophysics Data System (ADS)

Andrianov, V. M.; Korolevich, M. V.

2015-09-01

Normal vibrational frequencies and absolute IR band intensities of the biologically active steroid phytohormones homobrassinolide and (22S,23S)-homobrassinolide were calculated in the framework of an original approach that combined classical analysis of normal modes using molecular mechanics with quantum-chemical estimation of the absolute intensities. IR absorption bands were interpreted based on a comparison of the experimental and theoretical absorption spectra. The impact of structural differences in the side chains of these molecules on the formation of their IR spectra in the region 1500-950 cm -1 was estimated.

Use of Kinematic Viscosity Data for the Evaluation of the Molecular Weight of Petroleum Oils

ERIC Educational Resources Information Center

Maroto, J. A.; Quesada-Perez, M.; Ortiz-Hernandez, A. J.

2010-01-01

A new laboratory procedure for the evaluation of the mean molecular weight (mean relative molecular mass) of petroleum oils with high accuracy is described. The density and dynamic viscosity of three commercial petroleum oils are measured at different temperatures. These experimental data are used to calculate the kinematic viscosity as a function…

Development of haplotype-specific molecular markers for the low-molecular-weight glutenin subunits

USDA-ARS?s Scientific Manuscript database

Low-molecular-weight glutenin subunits (LMW-GSs) are one of the major components of gluten and their allelic variation has been widely associated with numerous wheat end-use quality parameters. These proteins are encoded by multigene families located at the orthologous Glu-3 loci (Glu-A3, Glu-B3 and...

75 FR 29972 - Certain Seamless Carbon and Alloy Steel Standard, Line, and Pressure Pipe from the People's...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-28

... errors, (1) would result in a change of at least five absolute percentage points in, but not less than 25... determination; or (2) would result in a difference between a weighted-average dumping margin of zero or de...

Molecular-Size-Separated Brown Carbon Absorption for Biomass-Burning Aerosol at Multiple Field Sites.

PubMed

Di Lorenzo, Robert A; Washenfelder, Rebecca A; Attwood, Alexis R; Guo, Hongyu; Xu, Lu; Ng, Nga L; Weber, Rodney J; Baumann, Karsten; Edgerton, Eric; Young, Cora J

2017-03-21

Biomass burning is a known source of brown carbon aerosol in the atmosphere. We collected filter samples of biomass-burning emissions at three locations in Canada and the United States with transport times of 10 h to >3 days. We analyzed the samples with size-exclusion chromatography coupled to molecular absorbance spectroscopy to determine absorbance as a function of molecular size. The majority of absorption was due to molecules >500 Da, and these contributed an increasing fraction of absorption as the biomass-burning aerosol aged. This suggests that the smallest molecular weight fraction is more susceptible to processes that lead to reduced light absorption, while larger-molecular-weight species may represent recalcitrant brown carbon. We calculate that these large-molecular-weight species are composed of more than 20 carbons with as few as two oxygens and would be classified as extremely low volatility organic compounds (ELVOCs).

Energy Decomposition Analysis Based on Absolutely Localized Molecular Orbitals for Large-Scale Density Functional Theory Calculations in Drug Design.

PubMed

Phipps, M J S; Fox, T; Tautermann, C S; Skylaris, C-K

2016-07-12

We report the development and implementation of an energy decomposition analysis (EDA) scheme in the ONETEP linear-scaling electronic structure package. Our approach is hybrid as it combines the localized molecular orbital EDA (Su, P.; Li, H. J. Chem. Phys., 2009, 131, 014102) and the absolutely localized molecular orbital EDA (Khaliullin, R. Z.; et al. J. Phys. Chem. A, 2007, 111, 8753-8765) to partition the intermolecular interaction energy into chemically distinct components (electrostatic, exchange, correlation, Pauli repulsion, polarization, and charge transfer). Limitations shared in EDA approaches such as the issue of basis set dependence in polarization and charge transfer are discussed, and a remedy to this problem is proposed that exploits the strictly localized property of the ONETEP orbitals. Our method is validated on a range of complexes with interactions relevant to drug design. We demonstrate the capabilities for large-scale calculations with our approach on complexes of thrombin with an inhibitor comprised of up to 4975 atoms. Given the capability of ONETEP for large-scale calculations, such as on entire proteins, we expect that our EDA scheme can be applied in a large range of biomolecular problems, especially in the context of drug design.

Evaluation of glycodendron and synthetically-modified dextran clearing agents for multi-step targeting of radioisotopes for molecular imaging and radioimmunotherapy

PubMed Central

Cheal, Sarah M.; Yoo, Barney; Boughdad, Sarah; Punzalan, Blesida; Yang, Guangbin; Dilhas, Anna; Torchon, Geralda; Pu, Jun; Axworthy, Don B.; Zanzonico, Pat; Ouerfelli, Ouathek; Larson, Steven M.

2014-01-01

A series of N-acetylgalactosamine-dendrons (NAG-dendrons) and dextrans bearing biotin moieties were compared for their ability to complex with and sequester circulating bispecific anti-tumor antibody (scFv4) streptavidin (SA) fusion protein (scFv4-SA) in vivo, to improve tumor to normal tissue concentration ratios for targeted radioimmunotherapy and diagnosis. Specifically, a total of five NAG-dendrons employing a common synthetic scaffold structure containing 4, 8, 16, or 32 carbohydrate residues and a single biotin moiety were prepared (NAGB), and for comparative purposes, a biotinylated-dextran with average molecular weight (MW) of 500 kD was synthesized from amino-dextran (DEXB). One of the NAGB compounds, CA16, has been investigated in humans; our aim was to determine if other NAGB analogs (e.g. CA8 or CA4) were bioequivalent to CA16 and/or better suited as MST reagents. In vivo studies included dynamic positron-emission tomography (PET) imaging of 124I-labelled-scFv4-SA clearance and dual-label biodistribution studies following multi-step targeting (MST) directed at subcutaneous (s.c.) human colon adenocarcinoma xenografts in mice. The MST protocol consists of three injections: first, a bispecific antibody specific for an anti-tumor associated glycoprotein (TAG-72) single chain genetically-fused with SA (scFv4-SA); second, CA16 or other clearing agent; and third, radiolabeled biotin. We observed using PET imaging of 124I-labelled-scFv4-SA clearance that the spatial arrangement of ligands conjugated to NAG (i.e. biotin) can impact the binding to antibody in circulation and subsequent liver uptake of the NAG-antibody complex. Also, NAGB CA32-LC or CA16-LC can be utilized during MST to achieve comparable tumor- to-blood ratios and absolute tumor uptake seen previously with CA16. Finally, DEXB was equally effective as NAGB CA32-LC at lowering scFv4-SA in circulation, but at the expense of reducing absolute tumor uptake of radiolabeled biotin. PMID:24219178

Chitosan derivatives with antimicrobial, antitumour and antioxidant activities--a review.

PubMed

Jarmila, Vinsová; Vavríková, Eva

2011-01-01

Chitosan is a linear polysaccharide with a good biodegradability, biocompatibility, and no toxicity, which provide it with huge potential for future development. The chitosan molecule appears to be a suitable polymeric complex for many biomedical applications. This review gathers current findings on the antibacterial, antifungal, antitumour and antioxidant activities of chitosan derivatives and concurs with our previous review presenting data collected up to 2008. Antibacterial activity is based on molecular weight, the degree of deacetylation, the type of substitutents, which can be cationic or easily form cations, and the type of bacterium. In general, high molecular weight chitosan cannot pass through cell membranes and forms a film that protects cells against nutrient transport through the microbial cell membrane. Low molecular weight chitosan derivatives are water soluble and can better incorporate the active molecule into the cell. Gram-negative bacteria, often represented by Escherichia coli, have an anionic bacterial surface on which cationic chitosan derivatives interact electrostatically. Thus, many chitosan conjugates have cationic components such as ammonium, pyridinium or piperazinium substituents introduced into their molecules to increase their positive charge. Gram-positive bacteria like Staphylococcus aureus are inhibited by the binding of lower molecular weight chitosan derivatives to DNA or RNA. Chitosan nanoparticles exhibit an increase in loading capacity and efficacy. Antitumour active compounds such as doxorubicin, paclitaxel, docetaxel and norcantharidin are used as drug carriers. It is evident that chitosan, with its low molecular weight, is a useful carrier for molecular drugs requiring targeted delivery. The antioxidant scavenging activity of chitosan has been established by the strong hydrogen-donating ability of chitosan. The low molecular weight and greater degree of quarternization have a positive influence on the antioxidant activity of chitosan. Phenolic and polyphenolic compounds with antioxidant effects are condensed with chitosan to form mutual prodrugs.

Selection of suitable e-learning approach using TOPSIS technique with best ranked criteria weights

NASA Astrophysics Data System (ADS)

Mohammed, Husam Jasim; Kasim, Maznah Mat; Shaharanee, Izwan Nizal Mohd

2017-11-01

This paper compares the performances of four rank-based weighting assessment techniques, Rank Sum (RS), Rank Reciprocal (RR), Rank Exponent (RE), and Rank Order Centroid (ROC) on five identified e-learning criteria to select the best weights method. A total of 35 experts in a public university in Malaysia were asked to rank the criteria and to evaluate five e-learning approaches which include blended learning, flipped classroom, ICT supported face to face learning, synchronous learning, and asynchronous learning. The best ranked criteria weights are defined as weights that have the least total absolute differences with the geometric mean of all weights, were then used to select the most suitable e-learning approach by using TOPSIS method. The results show that RR weights are the best, while flipped classroom approach implementation is the most suitable approach. This paper has developed a decision framework to aid decision makers (DMs) in choosing the most suitable weighting method for solving MCDM problems.

Ring-opening polymerization of 19-electron [2]cobaltocenophanes: a route to high-molecular-weight, water-soluble polycobaltocenium polyelectrolytes.

PubMed

Mayer, Ulrich F J; Gilroy, Joe B; O'Hare, Dermot; Manners, Ian

2009-08-05

Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.

Tribological characteristics of a composite total-surface hip replacement

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Roberts, J. C.; Ling, F. F.

1982-01-01

Continuous fiber, woven E glass composite femoral shells having the same elastic properties as bone were fabricated. The shells were then encrusted with filled epoxy wear resistant coatings and run dry against ultrahigh molecular weight polyethylene acetabular cups in 42,000 and 250,000 cycle wear tests on a total hip simulator. The tribological characteristics of these continuous fiber particulate composite femoral shells articulating with ultrahigh molecular weight polyethylene acetabular cups were comparable to those of a vitallium ball articulating with an ultrahigh molecular weight polyethylene acetabular cup.

Anticancer, antioxidant, and antibacterial activities of low molecular weight bioactive subfractions isolated from cultures of wood degrading fungus Cerrena unicolor

PubMed Central

Jaszek, Magdalena; Stefaniuk, Dawid; Ciszewski, Tomasz; Matuszewski, Łukasz

2018-01-01

The aim of this study is to investigate in vitro the anticancer, antioxidant, and antibacterial activities of three low molecular weight subfractions I, II and III isolated from secondary metabolites produced by the wood degrading fungus Cerrena unicolor. The present study demonstrated that the low molecular weight subfractions III exhibited the strongest inhibitory activity towards breast carcinoma cells MDA-MB-231, prostatic carcinoma cells PC3, and breast cancer cells MCF7 with the half-maximal inhibitory concentration (IC50) value of 52,25 μg/mL, 60,66 μg/mL, and 54,92 μg/mL, respectively. The highest percentage of inhibition was noted at a concentration of 300 μg/mL in all the examined tumor lines. A significant percentage (59.08%) of ex-LMSIII inhibition of the MDA-MB-231 tumor line was reached at a concentration of 15 μg/ml, while the concentration applied did not affect normal human fibroblast cells. The low molecular weight subfraction III was the most effective and additionally showed the highest free radical 1,1-diphenyl-2-picryl-hydrazyl scavenging activity (IC50 20.39 μg/mL) followed by the low molecular weight subfraction I (IC50 64.14 μg/mL) and II (IC50 49.22 μg/mL). The antibacterial activity of the tested preparations was evaluated against three microorganisms: Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. The MIC minimal inhibitory concentration (MIC) values for the low molecular weight subfraction I, II, and III showed a stronger inhibition effect on S. aureus than on B. subtilis and E. coli cells. The MIC values for the low molecular weight subfraction II against S. aureus, B. subtilis, and E. coli were 6.25, 12.5, and 100 mg/mL, respectively. PMID:29874240

Effects of molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase.

PubMed

Kim, Jihoon; Chang, Ji-Youn; Kim, Yoon-Young; Kim, Moon-Jong; Kho, Hong-Seop

2018-05-01

To investigate the effects of the molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase in solution and on the hydroxyapatite surface. Hyaluronic acids of four different molecular weights (10 kDa, 100 kDa, 1 MDa, and 2 MDa), hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used. Viscosity values of hyaluronic acids were measured using a cone-and-plate viscometer at six different concentrations (0.1-5.0 mg/mL). Enzymatic activities of lysozyme and peroxidase were examined by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus and oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein, respectively. In solution assays, only 2 MDa-hyaluronic acid significantly inhibited lysozyme activities in saliva. In surface assays, hyaluronic acids inhibited lysozyme and peroxidase activities; the inhibitory activities were more apparent with high-molecular-weight ones in saliva than in purified enzymes. The 100 kDa-hyaluronic acid at 5.0 mg/mL, 1 MDa-one at 0.5 mg/mL, and 2 MDa-one at 0.2 mg/mL showed viscosity values similar to those of human whole saliva at a shear rate range required for normal oral functions. The differences among the influences of the three conditions on the enzymatic activities were not statistically significant. High-molecular-weight hyaluronic acids at low concentration and low-molecular-weight ones at high concentration showed viscosity values similar to those of human whole saliva. Inhibitory effects of hyaluronic acids on lysozyme and peroxidase activities were more significant with high-molecular-weight ones on the surface and in saliva compared with in solution and on purified enzymes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Improving absolute gravity estimates by the L p -norm approximation of the ballistic trajectory

NASA Astrophysics Data System (ADS)

Nagornyi, V. D.; Svitlov, S.; Araya, A.

2016-04-01

Iteratively re-weighted least squares (IRLS) were used to simulate the L p -norm approximation of the ballistic trajectory in absolute gravimeters. Two iterations of the IRLS delivered sufficient accuracy of the approximation without a significant bias. The simulations were performed on different samplings and perturbations of the trajectory. For the platykurtic distributions of the perturbations, the L p -approximation with 3  <  p  <  4 was found to yield several times more precise gravity estimates compared to the standard least-squares. The simulation results were confirmed by processing real gravity observations performed at the excessive noise conditions.

High Molecular Weight Polymers in the New Chemicals Program

EPA Pesticide Factsheets

There are three categories or types of High Molecular Weight (HMW, 10,000 daltons) polymers typically reviewed by the New Chemicals Program: Soluble, insoluble, and water absorbing. Each of the three types are treated differently.

[Hemapheresis using vesicular plant separation materials].

PubMed

Mavrina, L; Ehwald, R; Matthes, G; Stamminger, G

1990-01-01

The present paper deals with the separation of cells from soluble compounds of blood by means of exclusion chromatography using a recently described vesicular packing material made from the cell wall framework of the small duckweed Wolffia arrhiza. The cells of the periphere blood are hardly retarded in passing through a packing of the vesicular material and eluted as sharp peak at an elution volume which is near to 30% of the column volume. The behavior of cells is similar to that of the excluded high molecular weight plasma proteins (e.g. serumalbumin). Low molecular weight solutes (e.g. salts, glucose, urea, kreatinin), but also substances of considerable molecular weight (e.g. myoglobin and Vitamin B12) which are usually difficult to separate by dialysis from serum, are eluted at nearly 100% of the packing volume and may be separated completely from cells and high molecular weight proteins. In vitro-Tests did not show a reduced vitality of eluted blood cells.

Effect of molecular weight of chitosan on the shelf life and other quality parameters of three different cultivars of Actinidia kolomikta (kiwifruit).

PubMed

Drevinskas, Tomas; Naujokaitytė, Gintarė; Maruška, Audrius; Kaya, Murat; Sargin, Idris; Daubaras, Remigijus; Česonienė, Laima

2017-10-01

The kiwi fruit, Actinidia kolomikta, has valuable properties such as high antioxidant activity, high vitamin C, polyphenols, chlorophylls and organic acids content, but the species are hardly commercialized due to their short shelf life (less than two days). In this study three different cultivars of A. kolomikta (Anykšta, Sentiabrskaya and VIR2) were coated with low, medium and high molecular weight chitosan bio-polymer with the aim to extend the shelf life. The changes in fruit firmness, mass, phenolic compound content, vitamin C content and subjective criteria (withering level, decoloration level and aesthetic appearance) were monitored. It was observed that high molecular weight chitosan had higher positive effect on the shelf life of Sentiabrskaya and Anykšta cultivars than VIR2. Low molecular weight chitosan was found effective on VIR2. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cytotoxicity of polycations: Relationship of molecular weight and the hydrolytic theory of the mechanism of toxicity.

PubMed

Monnery, Bryn D; Wright, Michael; Cavill, Rachel; Hoogenboom, Richard; Shaunak, Sunil; Steinke, Joachim H G; Thanou, Maya

2017-04-15

The mechanism of polycation cytotoxicity and the relationship to polymer molecular weight is poorly understood. To gain an insight into this important phenomenon a range of newly synthesised uniform (near monodisperse) linear polyethylenimines, commercially available poly(l-lysine)s and two commonly used PEI-based transfectants (broad 22kDa linear and 25kDa branched) were tested for their cytotoxicity against the A549 human lung carcinoma cell line. Cell membrane damage assays (LDH release) and cell viability assays (MTT) showed a strong relationship to dose and polymer molecular weight, and increasing incubation times revealed that even supposedly "non-toxic" low molecular weight polymers still damage cell membranes. The newly proposed mechanism of cell membrane damage is acid catalysed hydrolysis of lipidic phosphoester bonds, which was supported by observations of the hydrolysis of DOPC liposomes. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Short communication: possible mechanism for inhibiting the formation of polymers originated from 5-hydroxymethyl-2-furaldehyde by sulfite groups in the dairy thermal process.

PubMed

Guan, Yong-Guang; Zhu, Si-Ming; Yu, Shu-Juan; Xu, Xian-Bing; Zhu, Li-Cai

2013-05-01

5-Hydroxymethyl-2-furaldehyde can undergo polymerization to form high-molecular weight molecules via the Maillard reaction during dairy thermal treatment. In this study, the effect of sulfite group on polymer formation, especially in inhibiting the formation of high-molecular weight polymers has been described. Results showed that the sulfite group significantly inhibited the increase of polymer molecular weight via prevention of the polymerization of 5-hydroxymethyl-2-furaldehyde. The formation of an intermolecular dimer based on the glucose molecule through Schiff base cyclization can lead to a competitive reaction with 1,2-enolization to reduce 5-hydroxymethyl-2-furaldehyde formation, which might be another factor in reducing the formation of high-molecular weight polymers. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Development of thermally stable phosphonitrile elastomers for advanced aerospace structures

NASA Technical Reports Server (NTRS)

Reynard, K. A.; Rose, S. H.

1972-01-01

Attempts to prepare low molecular weight, curable poly-(fluoroalkoxyphosphazenes) have been successful. Derivatization of /Cl2PN/n polymer with alkoxides gave functionally reactive terpolymers. These terpolymers could be crosslinked with polyisocyanates at room temperature. Attempts to control molecular weight have not been as successful. The effects of (Cl2PN)3 monomer purity, use of (Cl2PN)3,4 mixture, and early termination of the bulk polymerization of (Cl2PN)3 were studied briefly. Both low and high molecular weight polymers were obtained. Reaction of NH4Cl with PCl5 with subsequent heating to give chain extension gave either gels of oils with molecular weights of several thousand. The stabilization of poly-(fluoroalkoxyphosphazene) was investigated. The results generally were inconclusive, but acids were found to be deleterious while bases had little discernible effect. Improvements in stability by modification of end groups was inconclusive.

Fossil fuel combined cycle power generation method

DOEpatents

Labinov, Solomon D [Knoxville, TN; Armstrong, Timothy R [Clinton, TN; Judkins, Roddie R [Knoxville, TN

2008-10-21

A method for converting fuel energy to electricity includes the steps of converting a higher molecular weight gas into at least one mixed gas stream of lower average molecular weight including at least a first lower molecular weight gas and a second gas, the first and second gases being different gases, wherein the first lower molecular weight gas comprises H.sub.2 and the second gas comprises CO. The mixed gas is supplied to at least one turbine to produce electricity. The mixed gas stream is divided after the turbine into a first gas stream mainly comprising H.sub.2 and a second gas stream mainly comprising CO. The first and second gas streams are then electrochemically oxidized in separate fuel cells to produce electricity. A nuclear reactor can be used to supply at least a portion of the heat the required for the chemical conversion process.

Predicting RNA Duplex Dimerization Free-Energy Changes upon Mutations Using Molecular Dynamics Simulations.

PubMed

Sakuraba, Shun; Asai, Kiyoshi; Kameda, Tomoshi

2015-11-05

The dimerization free energies of RNA-RNA duplexes are fundamental values that represent the structural stability of RNA complexes. We report a comparative analysis of RNA-RNA duplex dimerization free-energy changes upon mutations, estimated from a molecular dynamics simulation and experiments. A linear regression for nine pairs of double-stranded RNA sequences, six base pairs each, yielded a mean absolute deviation of 0.55 kcal/mol and an R(2) value of 0.97, indicating quantitative agreement between simulations and experimental data. The observed accuracy indicates that the molecular dynamics simulation with the current molecular force field is capable of estimating the thermodynamic properties of RNA molecules.

Influence of molecular size and osmolarity of sugars and dextrans on the synthesis of outer membrane proteins O-8 and O-9 of Escherichia coli K-12.

PubMed Central

Kawaji, H; Mizuno, T; Mizushima, S

1979-01-01

Supplementation of the growth medium with high concentrations of sugars or low-molecular-weight dextrans results in a drastic change in the ratio of outer membrane proteins O-8 and O-9, due to induction of O-8 synthesis and suppression of O-9 synthesis. Sugars and dextrans of molecular weights greater than 600 to 700 switched the synthesis of O-9 to that of O-8 more effectively than those of lower molecular weight, although the effect was almost the same within each of the two groups irrespective of the differences in molecular weight within the group. Proteins O-8 or O-9, or both, are responsible for the formation of pores that allow the passive diffusion of hydrophilic molecules whose molecular weights are smaller than about 600 (T. Nakae, Biochem. Biophys. Res. Commun. 71:877-884, 1976). The results indicate that substances that cannot pass through the outer membrane switch the synthesis of O-9 to that of O-8 more effectively than those that can penetrate this membrane with the aid of O-8, O-9, or both. It is suggested that the osmotic pressure exerted on the outer membrane plays an important role in the regulation of synthesis of the two proteins. PMID:391802

Synthesis of the low molecular weight heat shock proteins in plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mansfield, M.A.; Key, J.L.

1987-08-01

Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation to these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat shock proteins in a broader range of species, two-dimensional electrophoresis was used to resolve total protein from the following species: soybean (Glycine max L. Merr., var Wayne), pea (Pisum sativum L., var Early Alaska), sunflower (Helianthus annuus L.), wheat (Triticummore » asetivum L.), rice (Oryza sativa L., cv IR-36), maize (Zea mays L.), pearl millet (Pennisetum americanum L. Leeke, line 23DB), and Panicum miliaceum L. When identified by both silver staining and incorporation of radiolabel, a diverse array of low molecular weight heat shock proteins was synthesized in each of these species. These proteins accumulated to significant levels after three hours of heat shock but exhibited considerable heterogeneity in isoelectric point, molecular weight, stainability, and radiolabel incorporation. Although most appeared to be synthesized only during heat shock, some were detectable at low levels in control tissue. Compared to the monocots, a higher proportion of low molecular weight heat shock proteins was detectable in control tissues from dicots.« less

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2012 CFR

2012-04-01

... ethylene oxide and water with a mean molecular weight of 200 to 9,500. (2) It contains no more than 0.2..., or equivalent) 12 percent in H2O by weight on 60-80 mesh nonacid washed diatomaceous earth... in cylinder equipped with reducing regulator to provide 50 p.s.i.g. to the gas chromatograph...

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2013 CFR

2013-04-01

... ethylene oxide and water with a mean molecular weight of 200 to 9,500. (2) It contains no more than 0.2..., or equivalent) 12 percent in H2O by weight on 60-80 mesh nonacid washed diatomaceous earth... in cylinder equipped with reducing regulator to provide 50 p.s.i.g. to the gas chromatograph...

Postnatally elevated levels of insulin-like growth factor (IGF)-II fail to rescue the dwarfism of IGF-I-deficient mice except kidney weight.

PubMed

Moerth, Corinna; Schneider, Marlon R; Renner-Mueller, Ingrid; Blutke, Andreas; Elmlinger, Martin W; Erben, Reinhold G; Camacho-Hübner, Cecilia; Hoeflich, Andreas; Wolf, Eckhard

2007-01-01

This study tested whether elevated levels of IGF-II in the postnatal period can rescue the dwarfism in IGF-I-deficient mice. Heterozygous Igf1 mutant mice [I(+/-) II(wt)] were crossed with heterozygous Igf1 mutant, phosphoenolpyruvate carboxykinase promoter IGF-II transgenic mice [I(+/-) II(tg)], and [I(+/+) II(wt)], [I(+/+) II(tg)], [I(-/-) II(wt)], and [I(-/-) II(tg)] offspring were investigated. IGF-II levels were 11- and 6-fold higher in male and female [I(-/-) II(tg)] vs. [I(-/-) II(wt)] animals. Western ligand blot analysis revealed markedly reduced activities of 30- and 32-kDa IGF binding proteins (IGFBPs) (most likely IGFBP-1 and IGFBP-2) and the 39- to 43-kDa IGFBP-3 double band in serum from IGF-I-deficient mice. These binding proteins were partially restored by overexpression of IGF-II. Analysis of weight data from the early postnatal period until d 60 showed that, in the absence of IGF-I, elevated levels of IGF-II have no effect on body weight gain. A detailed analysis of body proportions, bone parameters, and organ weights of 60-d-old mice also failed to show effects of IGF-II with one important exception: in Igf1 mutant and also Igf1 intact male mice, IGF-II overexpression significantly increased absolute (+32.4 and +28.6%; P < 0.01) and relative kidney weights (+29.0 and +22.4%; P < 0.001). These changes in kidney weight were associated with reduced phosphorylation of p38 MAPK. In summary, our genetic model shows that substantial amounts of IGF-II in the circulation do not rescue the postnatal growth deficit of IGF-I-deficient mice but increase absolute and relative kidney weights of normal and IGF-I-deficient male mice, suggesting a gender-specific role of IGF-II for kidney growth.

Automated body weight prediction of dairy cows using 3-dimensional vision.

PubMed

Song, X; Bokkers, E A M; van der Tol, P P J; Groot Koerkamp, P W G; van Mourik, S

2018-05-01

The objectives of this study were to quantify the error of body weight prediction using automatically measured morphological traits in a 3-dimensional (3-D) vision system and to assess the influence of various sources of uncertainty on body weight prediction. In this case study, an image acquisition setup was created in a cow selection box equipped with a top-view 3-D camera. Morphological traits of hip height, hip width, and rump length were automatically extracted from the raw 3-D images taken of the rump area of dairy cows (n = 30). These traits combined with days in milk, age, and parity were used in multiple linear regression models to predict body weight. To find the best prediction model, an exhaustive feature selection algorithm was used to build intermediate models (n = 63). Each model was validated by leave-one-out cross-validation, giving the root mean square error and mean absolute percentage error. The model consisting of hip width (measurement variability of 0.006 m), days in milk, and parity was the best model, with the lowest errors of 41.2 kg of root mean square error and 5.2% mean absolute percentage error. Our integrated system, including the image acquisition setup, image analysis, and the best prediction model, predicted the body weights with a performance similar to that achieved using semi-automated or manual methods. Moreover, the variability of our simplified morphological trait measurement showed a negligible contribution to the uncertainty of body weight prediction. We suggest that dairy cow body weight prediction can be improved by incorporating more predictive morphological traits and by improving the prediction model structure. The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

The Estimation of Gestational Age at Birth in Database Studies.

PubMed

Eberg, Maria; Platt, Robert W; Filion, Kristian B

2017-11-01

Studies on the safety of prenatal medication use require valid estimation of the pregnancy duration. However, gestational age is often incompletely recorded in administrative and clinical databases. Our objective was to compare different approaches to estimating the pregnancy duration. Using data from the Clinical Practice Research Datalink and Hospital Episode Statistics, we examined the following four approaches to estimating missing gestational age: (1) generalized estimating equations for longitudinal data; (2) multiple imputation; (3) estimation based on fetal birth weight and sex; and (4) conventional approaches that assigned a fixed value (39 weeks for all or 39 weeks for full term and 35 weeks for preterm). The gestational age recorded in Hospital Episode Statistics was considered the gold standard. We conducted a simulation study comparing the described approaches in terms of estimated bias and mean square error. A total of 25,929 infants from 22,774 mothers were included in our "gold standard" cohort. The smallest average absolute bias was observed for the generalized estimating equation that included birth weight, while the largest absolute bias occurred when assigning 39-week gestation to all those with missing values. The smallest mean square errors were detected with generalized estimating equations while multiple imputation had the highest mean square errors. The use of generalized estimating equations resulted in the most accurate estimation of missing gestational age when birth weight information was available. In the absence of birth weight, assignment of fixed gestational age based on term/preterm status may be the optimal approach.

Patterns and sources of particle-phase aliphatic and polycyclic aromatic hydrocarbons in urban and rural sites of western Greece

NASA Astrophysics Data System (ADS)

Kalaitzoglou, Maria; Terzi, Eleni; Samara, Constantini

Particle-bound aliphatic and polycyclic aromatic hydrocarbons (AHs and PAHs, respectively) were determined in the ambient air of the Eordea basin, in western Greece, where intensive coal burning for power generation takes place. Thirteen PAHs, n-alkanes (C 14-C 35), hopanes, and isoprenoid hydrocarbons (pristane and phytane) were determined in the total suspended particles collected from the atmosphere of four sites within the basin receiving potential impacts from various sources, such as fly ash, coal mining, automobile traffic, domestic heating, and agricultural or refuse burning. The same organic species were also determined in the fly ash generated in power stations, and in particulate emissions from open burning of biomass (dry corn leaves) and refuse burning. Organic particle sources were resolved using concentration diagnostic ratios and factor analysis (FA). A multivariate statistical receptor model (Absolute Principal Component Analysis, APCA) was finally employed to estimate the contribution of identified sources to the measured concentrations of organic pollutants. Four major sources for ambient PAHs and AHs were identified displaying variable contribution in different sites: (a) fossil fuel combustion, (b) biogenic emissions, (c) refuse burning, and (d) oil residues. Fuel combustion was the major source of ambient PAHs and an important source of n-alkanes in the range C 21-C 28. Oil residues were found to be the major source of low molecular weight n-alkanes (particularly the C 14-C 16), and an important source of pristane, phytane and UCM. Biogenic sources were primarily responsible for the high molecular weight n-alkanes explaining almost the entire concentration levels of homologues >C 32. Biomass burning was particularly important for the C 23-C 26n-alkanes. Despite the vicinity of certain sampling sites to power stations, coal fly ash was not identifiable as a source for ambient PAHs and AHs.

Mathematical modeling of atmospheric fine particle-associated primary organic compound concentrations

NASA Astrophysics Data System (ADS)

Rogge, Wolfgang F.; Hildemann, Lynn M.; Mazurek, Monica A.; Cass, Glen R.; Simoneit, Bernd R. T.

1996-08-01

An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped autos, diesel trucks, paved road dust, tire wear, brake lining dust, meat cooking operations, industrial oil-fired boilers, roofing tar pots, natural gas combustion in residential homes, cigarette smoke, fireplaces burning oak and pine wood, and plant leaf abrasion products. These primary fine particle source emissions were supplied to a computer-based model that simulates atmospheric transport, dispersion, and dry deposition based on the time series of hourly wind observations and mixing depths. Monthly average fine particle organic compound concentrations that would prevail if the primary organic aerosol were transported without chemical reaction were computed for more than 100 organic compounds within an 80 km × 80 km modeling area centered over Los Angeles. The monthly average compound concentrations predicted by the transport model were compared to atmospheric measurements made at monitoring sites within the study area during 1982. The predicted seasonal variation and absolute values of the concentrations of the more stable compounds are found to be in reasonable agreement with the ambient observations. While model predictions for the higher molecular weight polycyclic aromatic hydrocarbons (PAH) are in agreement with ambient observations, lower molecular weight PAH show much higher predicted than measured atmospheric concentrations in the particle phase, indicating atmospheric decay by chemical reactions or evaporation from the particle phase. The atmospheric concentrations of dicarboxylic acids and aromatic polycarboxylic acids greatly exceed the contributions that are due to direct emissions from primary sources, confirming that these compounds are principally formed by atmospheric chemical reactions.

Low molecular weight components in an aquatic humic substance as characterized by membrane dialysis and orbitrap mass spectrometry.

PubMed

Remucal, Christina K; Cory, Rose M; Sander, Michael; McNeill, Kristopher

2012-09-04

Suwannee River fulvic acid (SRFA) was dialyzed through a 100-500 molecular weight cutoff dialysis membrane, and the dialysate and retentate were analyzed by UV-visible absorption and high-resolution Orbitrap mass spectrometry (MS). A significant fraction (36% based on dissolved organic carbon) of SRFA passed through the dialysis membrane. The fraction of SRFA in the dialysate had a different UV-visible absorption spectrum and was enriched in low molecular weight molecules with a more aliphatic composition relative to the initial SRFA solution. Comparison of the SRFA spectra collected by Orbitrap MS and Fourier transform ion cyclotron resonance MS (FT-ICR MS) demonstrated that the mass accuracy of the Orbitrap MS is sufficient for determination of unique molecular formulas of compounds with masses <600 Da in a complex mixture, such as SRFA. The most intense masses detected by Orbitrap MS were found in the 100-200 Da mass range. Many of these low molecular masses corresponded to molecular formulas of previously identified compounds in organic matter, lignin, and plants, and the use of the standard addition method provided an upper concentration estimate of selected target compounds in SRFA. Collectively, these results provide evidence that SRFA contains low molecular weight components that are present individually or in loosely bound assemblies.

Determination of the molecular weight of low-molecular-weight heparins by using high-pressure size exclusion chromatography on line with a triple detector array and conventional methods.

PubMed

Bisio, Antonella; Mantegazza, Alessandra; Vecchietti, Davide; Bensi, Donata; Coppa, Alessia; Torri, Giangiacomo; Bertini, Sabrina

2015-03-19

The evaluation of weight average molecular weight (Mw) and molecular weight distribution represents one of the most controversial aspects concerning the characterization of low molecular weight heparins (LMWHs). As the most commonly used method for the measurement of such parameters is high performance size exclusion chromatography (HP-SEC), the soundness of results mainly depends on the appropriate calibration of the chromatographic columns used. With the aim of meeting the requirement of proper Mw standards for LMWHs, in the present work the determination of molecular weight parameters (Mw and Mn) by HP-SEC combined with a triple detector array (TDA) was performed. The HP-SEC/TDA technique permits the evaluation of polymeric samples by exploiting the combined and simultaneous action of three on-line detectors: light scattering detectors (LALLS/RALLS); refractometer and viscometer. Three commercial LMWH samples, enoxaparin, tinzaparin and dalteparin, a γ-ray depolymerized heparin (γ-Hep) and its chromatographic fractions, and a synthetic pentasaccharide were analysed by HP-SEC/TDA. The same samples were analysed also with a conventional HP-SEC method employing refractive index (RI) and UV detectors and two different chromatographic column set, silica gel and polymeric gel columns. In both chromatographic systems, two different calibration curves were built up by using (i) γ-Hep chromatographic fractions and the corresponding Mw parameters obtained via HP-SEC/TDA; (ii) the whole γ-Hep preparation with broad Mw dispersion and the corresponding cumulative distribution function calculated via HP-SEC/TDA. In addition, also a chromatographic column calibration according to European Pharmacopoeia indication was built up. By comparing all the obtained results, some important differences among Mw and size distribution values of the three LMWHs were found with the five different calibration methods and with HP-SEC/TDA method. In particular, the detection of the lower molecular weight components turned out to be the most critical aspect. Whereas HP-SEC/TDA may underestimate species under 2 KDa when present in low concentration, other methods appeared to emphasize their content.

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

PubMed Central

Rezaee, Mohammad; Cloutier, Pierre; Bass, Andrew D.; Michaud, Marc; Hunting, Darel J.; Sanche, Léon

2013-01-01

Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions. PMID:23030950

MALDI-TOF mass spectrometry analysis of small molecular weight compounds (under 10 KDa) as biomarkers of rat hearts undergoing arecoline challenge.

PubMed

Chen, Tung-Sheng; Chang, Mu-Hsin; Kuo, Wei-Wen; Lin, Yueh-Min; Yeh, Yu-Lan; Day, Cecilia Hsuan; Lin, Chien-Chung; Tsai, Fuu-Jen; Tsai, Chang-Hai; Huang, Chih-Yang

2013-04-01

Statistical and clinical reports indicate that betel nut chewing is strongly associated with progression of oral cancer because some ingredients in betel nuts are potential cancer promoters, especially arecoline. Early diagnosis for cancer biomarkers is the best strategy for prevention of cancer progression. Several methods are suggested for investigating cancer biomarkers. Among these methods, gel-based proteomics approach is the most powerful and recommended tool for investigating biomarkers due to its high-throughput. However, this proteomics approach is not suitable for screening biomarkers with molecular weight under 10 KDa because of the characteristics of gel electrophoresis. This study investigated biomarkers with molecular weight under 10 KDa in rats with arecoline challenge. The centrifuging vials with membrane (10 KDa molecular weight cut-off) played a crucial role in this study. After centrifuging, the filtrate (containing compounds with molecular weight under 10 KDa) was collected and spotted on a sample plate for MALDI-TOF mass spectrometry analysis. Compared to control, three extra peaks (m/z values were 1553.1611, 1668.2097 and 1740.1832, respectively) were found in sera and two extra peaks were found in heart tissue samples (408.9719 and 524.9961, respectively). These small compounds should play important roles and may be potential biomarker candidates in rats with arecoline. This study successfully reports a mass-based method for investigating biomarker candidates with small molecular weight in different types of sample (including serum and tissue). In addition, this reported method is more time-efficient (1 working day) than gel-based proteomics approach (5~7 working days).

NprR-NprX Quorum-Sensing System Regulates the Algicidal Activity of Bacillus sp. Strain S51107 against Bloom-Forming Cyanobacterium Microcystis aeruginosa.

PubMed

Wu, Lishuang; Guo, Xingliang; Liu, Xianglong; Yang, Hong

2017-01-01

Harmful cyanobacterial blooms have severely impaired freshwater quality and threatened human health worldwide. Here, a Gram-positive bacterium, Bacillus sp. strain S51107, which exhibits strong algicidal activity against Microcystis aeruginosa , was isolated from Lake Taihu. We found that the algicidal activity of strain S51107 was regulated primarily by NprR-NprX quorum sensing (QS), in which the mature form of the signaling peptide NprX was identified as the SKPDIVG heptapeptide. Disruption of the nprR-nprX cassette markedly decreased the algicidal activity, and complemented strains showed significantly recovered algicidal activity. Strain S51107 produced low-molecular-weight algicidal compounds [indole-3-carboxaldehyde and cyclo(Pro-Phe)] and high-molecular-weight algicidal substance(s) (>3 kDa). Moreover, the production of high-molecular-weight algicidal substance(s) was regulated by NprR-NprX QS, but the production of low-molecular-weight algicidal compounds was not. High-molecular-weight algicidal substance(s) played a more important role than low-molecular-weight algicidal compounds in the algicidal activity of strain S51107. The results of this study could increase our knowledge about algicidal characteristics of a potential algicidal bacterium, Bacillus sp. strain S51107, and provide the first evidence that the algicidal activity of Gram-positive algicidal bacteria is regulated by QS, which will greatly enhance our understanding of the interactions between algae and indigenous algicidal bacteria, thereby providing aid in the design and optimization of strategies to control harmful algae blooms.

NprR-NprX Quorum-Sensing System Regulates the Algicidal Activity of Bacillus sp. Strain S51107 against Bloom-Forming Cyanobacterium Microcystis aeruginosa

PubMed Central

Wu, Lishuang; Guo, Xingliang; Liu, Xianglong; Yang, Hong

2017-01-01

Harmful cyanobacterial blooms have severely impaired freshwater quality and threatened human health worldwide. Here, a Gram-positive bacterium, Bacillus sp. strain S51107, which exhibits strong algicidal activity against Microcystis aeruginosa, was isolated from Lake Taihu. We found that the algicidal activity of strain S51107 was regulated primarily by NprR-NprX quorum sensing (QS), in which the mature form of the signaling peptide NprX was identified as the SKPDIVG heptapeptide. Disruption of the nprR-nprX cassette markedly decreased the algicidal activity, and complemented strains showed significantly recovered algicidal activity. Strain S51107 produced low-molecular-weight algicidal compounds [indole-3-carboxaldehyde and cyclo(Pro-Phe)] and high-molecular-weight algicidal substance(s) (>3 kDa). Moreover, the production of high-molecular-weight algicidal substance(s) was regulated by NprR-NprX QS, but the production of low-molecular-weight algicidal compounds was not. High-molecular-weight algicidal substance(s) played a more important role than low-molecular-weight algicidal compounds in the algicidal activity of strain S51107. The results of this study could increase our knowledge about algicidal characteristics of a potential algicidal bacterium, Bacillus sp. strain S51107, and provide the first evidence that the algicidal activity of Gram-positive algicidal bacteria is regulated by QS, which will greatly enhance our understanding of the interactions between algae and indigenous algicidal bacteria, thereby providing aid in the design and optimization of strategies to control harmful algae blooms. PMID:29075240

Cleavage of the main carbon chain backbone of high molecular weight polyacrylamide by aerobic and anaerobic biological treatment.

PubMed

Song, Wenzhe; Zhang, Yu; Gao, Yingxin; Chen, Dong; Yang, Min

2017-12-01

High molecular weight partially hydrolyzed polyacrylamide (PAM) can be bio-hydrolyzed on the amide side group, however, solid evidence regarding the biological cleavage of its main carbon chain backbone is limited. In this study, viscometry, flow field-flow fractionation multi-angle light scattering (FFF-MALS), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis were used to investigate the biodegradability of PAM with a nominal molecular weight of 2 × 10 7  Da (Da) in two suspended aerobic (25 and 40 °C) and two upflow anaerobic blanket reactors (35 and 55 °C) operated for 470 d under a hydraulic residence time (HRT) of 2 d. Both anaerobic and aerobic biological treatment reduced the viscosity from 2.02 cp in the influent to 1.45-1.60 cp, and reduced the molecular weight of PAM using FFF-MALS from 2.17 × 10 7  Da to less than one-third its original size. The removals of both the amide group and carbon chain backbone in the PAM molecule were further supported by the FTIR analysis. In comparison with the other conditions, thermophilic anaerobic treatment exhibited higher efficiency for PAM biodegradation. Batch test excluded the influence of temperature on the molecular weight of PAM over the range 25-55 °C, suggesting that cleavage of the main carbon chain backbone was attributed to biological degradation. Our results suggested that high molecular weight PAM was biodegradable, but mineralization did not occur. Copyright © 2017 Elsevier Ltd. All rights reserved.

Novel method for the determination of average molecular weight of natural polymers based on 2D DOSY NMR and chemometrics: Example of heparin.

PubMed

Monakhova, Yulia B; Diehl, Bernd W K; Do, Tung X; Schulze, Margit; Witzleben, Steffen

2018-02-05

Apart from the characterization of impurities, the full characterization of heparin and low molecular weight heparin (LMWH) also requires the determination of average molecular weight, which is closely related to the pharmaceutical properties of anticoagulant drugs. To determine average molecular weight of these animal-derived polymer products, partial least squares regression (PLS) was utilized for modelling of diffused-ordered spectroscopy NMR data (DOSY) of a representative set of heparin (n=32) and LMWH (n=30) samples. The same sets of samples were measured by gel permeation chromatography (GPC) to obtain reference data. The application of PLS to the data led to calibration models with root mean square error of prediction of 498Da and 179Da for heparin and LMWH, respectively. The average coefficients of variation (CVs) did not exceed 2.1% excluding sample preparation (by successive measuring one solution, n=5) and 2.5% including sample preparation (by preparing and analyzing separate samples, n=5). An advantage of the method is that the sample after standard 1D NMR characterization can be used for the molecular weight determination without further manipulation. The accuracy of multivariate models is better than the previous results for other matrices employing internal standards. Therefore, DOSY experiment is recommended to be employed for the calculation of molecular weight of heparin products as a complementary measurement to standard 1D NMR quality control. The method can be easily transferred to other matrices as well. Copyright © 2017 Elsevier B.V. All rights reserved.

Concrete airship sheds at Orly, France. Part I

NASA Technical Reports Server (NTRS)

FREYSSINET

1925-01-01

This report details the contest to design and build concrete airship hangers. The difficulty lies in the magnitude of the absolute dimensions. An airship shed must withstand two principal types of stresses: those resulting from its own weight and those due to the wind. This report discusses both problems in detail.

Molecular resolution and fragmentation of fulvic acid by electrospray ionization/multistage tandem mass spectrometry

USGS Publications Warehouse

Leenheer, J.A.; Rostad, C.E.; Gates, Paul M.; Furlong, E.T.; Ferrer, I.

2001-01-01

Molecular weight distributions of fulvic acid from the Suwannee River, Georgia, were investigated by electrospray ionization/quadrupole mass spectrometry (ESI/QMS), and fragmentation pathways of specific fulvic acid masses were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry (ESI/MST/MS). ESI/QMS studies of the free acid form of low molecular weight poly(carboxylic acid) standards in 75% methanol/25% water mobile phase found that negative ion detection gave the optimum generation of parent ions that can be used for molecular weight determinations. However, experiments with poly(acrylic acid) mixtures and specific high molecular weight standards found multiply charged negative ions that gave a low bias to molecular mass distributions. The number of negative charges on a molecule is dependent on the distance between charges. ESI/MST/MS of model compounds found characteristic water loss from alcohol dehydration and anhydride formation, as well as CO2 loss from decarboxylation, and CO loss from ester structures. Application of these fragmentation pathways to specific masses of fulvic acid isolated and fragmented by ESI/MST/MS is indicative of specific structures that can serve as a basis for future structural confirmation after these hypothesized structures are synthesized.

Analysis of heparin oligosaccharides by capillary electrophoresis-negative-ion electrospray ionization mass spectrometry.

PubMed

Lin, Lei; Liu, Xinyue; Zhang, Fuming; Chi, Lianli; Amster, I Jonathan; Leach, Franklyn E; Xia, Qiangwei; Linhardt, Robert J

2017-01-01

Most hyphenated analytical approaches that rely on liquid chromatography-MS require relatively long separation times, produce incomplete resolution of oligosaccharide mixtures, use eluents that are incompatible with electrospray ionization, or require oligosaccharide derivatization. Here we demonstrate the analysis of heparin oligosaccharides, including disaccharides, ultralow molecular weight heparin, and a low molecular weight heparin, using a novel electrokinetic pump-based CE-MS coupling eletrospray ion source. Reverse polarity CE separation and negative-mode electrospray ionization were optimized using a volatile methanolic ammonium acetate electrolyte and sheath fluid. The online CE hyphenated negative-ion electrospray ionization MS on an LTQ Orbitrap mass spectrometer was useful in disaccharide compositional analysis and bottom-up and top-down analysis of low molecular weight heparin. The application of this CE-MS method to ultralow molecular heparin suggests that a charge state distribution and the low level of sulfate group loss that is achieved make this method useful for online tandem MS analysis of heparins. Graphical abstract Most hyphenated analytical approaches that rely on liquid chromatography-MS require relatively long separation times, produce incomplete resolution of oligosaccharide mixtures, use eluents that are incompatible with electrospray ionization, or require oligosaccharide derivatization. Here we demonstrate the analysis of heparin oligosaccharides, including disaccharides, ultralow molecular weight heparin, and a low molecular weight heparin, using a novel electrokinetic pump-based CE-MS coupling eletrospray ion source. Reverse polarity CE separation and negative-mode electrospray ionization were optimized using a volatile methanolic ammonium acetate electrolyte and sheath fluid. The online CE hyphenated negative-ion electrospray ionization MS on an LTQ Orbitrap mass spectrometer was useful in disaccharide compositional analysis and bottom-up and top-down analysis of low molecular weight heparin. The application of this CE-MS method to ultralow molecular heparin suggests that a charge state distribution and the low level of sulfate group loss that is achieved make this method useful for online tandem MS analysis of heparins.

Effect on the lipid parameters of an intervention to reduce weight in overweight and obese patients.

PubMed

Tárraga Marcos, M Loreto; Panisello Royo, Josefa María; Carbayo Herencia, Julio A; Rosich Domenech, Nuria; Alins Presas, Josep; Tárraga López, Pedro J

To assess the effect on lipid parameters most associated with excess weight (triglycerides [TG], cholesterol, and high density lipoprotein [HDL-C]) of an intervention to reduce weight in overweight and obese patients. A randomised, controlled, double blind clinical trial, with three groups, and a follow-up of 12 months. Patients included in the study were randomised into three intervention groups: Obesity motivational intervention group with previously trained nurse (G1), lower intensity consultation, non-motivational group, with digital platform support (G2), and a third group that received a recommendation to lose weight and usual follow-up (G3). The anthropometric variables measured were height, weight, and abdominal/waist circumference, and laboratory results, total cholesterol, TG and HDL cholesterol). The study include 176 patients, of whom 60 were randomised to G1, 61 to G2, and 59 to G3. All groups significantly decreased body weight at the end of the study, with a decrease in G1 (-5.6kg), followed by G2 (-4.3kg), and G3 (-1.7kg), with an overall mean loss of -3.9kg. There was a also significant decrease (P<.05) in total cholesterol and TG, and an increased HDL-C. These changes were more marked in the G1 group (the group that lost more weight). The clinical relevance indicators that were significant were: in the case of TG: G1/G3: relative risk: 1.42 (95% CI: 1.11-1.80); relative risk reduction: 41.7% (11.4-80.2); absolute risk reduction: 25% (9.2-40.8) and NNT: 5 (3-11). In the case of G1/G2 HDL-C: relative risk: 1.32 (1.07-1.63); relative risk reduction: 32.2% (7.4-62.6); absolute risk reduction: 21.1% (6.4-35.8) and NNT: 5 (3-16). Weight reduction is accompanied by favorable changes in the lipid parameters related to overweight and obesity, being more intense the greater the weight loss. Copyright © 2017 Sociedad Española de Arteriosclerosis. Publicado por Elsevier España, S.L.U. All rights reserved.

Isoleucine epimerization and amino acid composition in molecular-weight separations of Pleistocene Genyornis eggshell

NASA Astrophysics Data System (ADS)

Kaufman, Darrell S.; Miller, Gifford H.

1995-07-01

This study explores the geochronological utility and analytical reproducibility of separating the high-molecular-weight fraction (HMW) from eggshells of the extinct late Pleistocene ratite, Genyornis, using disposable, prepacked gel-filtration columns. The superior integrity of ratite eggshell for the retention of amino acids indicates that this biomineral is better suited for this type of investigation than previously studied molluscan shell. To evaluate the reproducibility of the gel-filtration technique, we analyzed triplicate subsamples of three eggshells of different ages. The reproducibility, based on the average intrashell variation (coefficient of variation; CV) in the extent of isoleucine epimerization (aIle/Ile) in the HMW (enriched in molecules ca. >10,000 MW) is 3%, well within the range appropriate for geochronological purposes. The average intrashell variation in the total amino acid concentration (Σ[aa]) of the HMW is 5%, somewhat better than for the total acid hydrolysate (TOTAL) of the same samples (7%). To evaluate the relation between molecular weight and the rate of isoleucine epimerization, three molecular-weight fractions were separated using gel filtration, plus the naturally hydrolyzed free fraction (FREE), for each of four fossil eggshells. AIle/Ile increases with decreasing molecular weight in all shells, with a ca. sixfold to ninefold difference in ratios between the HMW andFREE, and a ca. fivefold difference between the HMW andTOTAL. Although linear correlations between aIle/Ile measured in each molecular-weight fraction and in theTOTAL are all highly significant (r ⩾ 0.951), the relation between the extent of epimerization in the HMW and in the TOTAL is best expressed as an exponential function (r = 0.951). This relation is consistent with the idea that, as the epimerization reaction approaches equilibrium in theTOTAL (ca. aIle/Ile > 1.1), its rate decreases beyond that of the HMW. The amino acid composition (relative percent of eight amino acids or combinations of amino acids) is more uniform in the HMW of the four samples compared to lower-molecular-weight fractions. The greater "compositional stability" of the HMW indicates that it contains a residuum of macromolecules that have not been affected by the diagenetically driven changes observed in lower-molecular-weight fractions.

Analysis of the major chiral compounds of Artemisia herba-alba essential oils (EOs) using reconstructed vibrational circular dichroism (VCD) spectra: En route to a VCD chiral signature of EOs.

PubMed

Said, Mohammed El-Amin; Vanloot, Pierre; Bombarda, Isabelle; Naubron, Jean-Valère; Dahmane, El Montassir; Aamouche, Ahmed; Jean, Marion; Vanthuyne, Nicolas; Dupuy, Nathalie; Roussel, Christian

2016-01-15

An unprecedented methodology was developed to simultaneously assign the relative percentages of the major chiral compounds and their prevailing enantiomeric form in crude essential oils (EOs). In a first step the infrared (IR) and vibrational circular dichroism (VCD) spectra of the crude essential oils were recorded and in a second step they were modelized as a linear weighted combination of the IR and VCD spectra of the individual spectra of pure enantiomer of the major chiral compounds present in the EOs. The VCD spectra of enantiomer of known enantiomeric excess shall be recorded if they are not yet available in a library of VCD spectra. For IR, the spectra of pure enantiomer or racemic mixture can be used. The full spectra modelizations were performed using a well known and powerful mathematical model (least square estimation: LSE) which resulted in a weighting of each contributing compound. For VCD modelization, the absolute value of each weighting represented the percentage of the associate compound while the attached sign addressed the correctness of the enantiomeric form used to build the model. As an example, a model built with the non-prevailing enantiomer will show a negative sign of the weighting value. For IR spectra modelization, the absolute value of each weighting represented the percentage of the compounds without of course accounting for the chirality of the prevailing enantiomers. Comparison of the weighting values issuing from IR and VCD spectra modelizations is a valuable source of information: if they are identical, the EOs are composed of nearly pure enantiomers, if they are different the chiral compounds of the EOs are not in an optically pure form. The method was applied on four samples of essential oil of Artemisia herba-alba in which the three major compounds namely (-)-α-thujone, (+)-β-thujone and (-)-camphor were found in different proportions as determined by GC-MS and chiral HPLC using polarimetric detector. In order to validate the methodology, the modelization of the VCD spectra was performed on purpose using the individual VCD spectra of (-)-α-thujone, (+)-β-thujone and (+)-camphor instead of (-)-camphor. During this work, the absolute configurations of (-)-α-thujone and (+)-β-thujone were confirmed by comparison of experimental and calculated VCD spectra as being (1S,4R,5R) and (1S,4S,5R) respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Call for papers for special issue of Journal of Molecular Spectroscopy focusing on "Frequency-comb spectroscopy"

NASA Astrophysics Data System (ADS)

Foltynowicz, Aleksandra; Picqué, Nathalie; Ye, Jun

2018-05-01

Frequency combs are becoming enabling tools for many applications in science and technology, beyond the original purpose of frequency metrology of simple atoms. The precisely evenly spaced narrow lines of a laser frequency comb inspire intriguing approaches to molecular spectroscopy, designed and implemented by a growing community of scientists. Frequency-comb spectroscopy advances the frontiers of molecular physics across the entire electro-magnetic spectrum. Used as frequency rulers, frequency combs enable absolute frequency measurements and precise line shape studies of molecular transitions, for e.g. tests of fundamental physics and improved determination of fundamental constants. As light sources interrogating the molecular samples, they dramatically improve the resolution, precision, sensitivity and acquisition time of broad spectral-bandwidth spectroscopy and open up new opportunities and applications at the leading edge of molecular spectroscopy and sensing.

Molecular weight distribution characterization of hydrophobe-modified hydroxyethyl cellulose by size-exclusion chromatography.

PubMed

Li, Yongfu; Meunier, David M; Partain, Emmett M

2014-09-12

Size-exclusion chromatography (SEC) of hydrophobe-modified hydroxyethyl cellulose (HmHEC) is challenging because polymer chains are not isolated in solution due to association of hydrophobic groups and hydrophobic interaction with column packing materials. An approach to neutralize these hydrophobic interactions was developed by adding β-cyclodextrin (β-CD) to the aqueous eluent. SEC mass recovery, especially for the higher molecular weight chains, increased with increasing concentration of β-CD in the eluent. A β-CD concentration of 0.75wt% in the eluent was determined to be optimal for the HmHEC polymers studied. These conditions enabled precise determinations of apparent molecular weight distributions exhibiting less than 2% relative standard deviation in the measured weight-average molecular weight (MW) for five injections on three studied samples and showed no significant differences in MW determined on two different days. The developed technology was shown to be very robust for characterizing HmHEC having MW from 500kg/mol to 2000kg/mol, and it can be potentially applied to other hydrophobe-modified polymers. Copyright © 2014 Elsevier B.V. All rights reserved.

Energy decomposition analysis for exciplexes using absolutely localized molecular orbitals

NASA Astrophysics Data System (ADS)

Ge, Qinghui; Mao, Yuezhi; Head-Gordon, Martin

2018-02-01

An energy decomposition analysis (EDA) scheme is developed for understanding the intermolecular interaction involving molecules in their excited states. The EDA utilizes absolutely localized molecular orbitals to define intermediate states and is compatible with excited state methods based on linear response theory such as configuration interaction singles and time-dependent density functional theory. The shift in excitation energy when an excited molecule interacts with the environment is decomposed into frozen, polarization, and charge transfer contributions, and the frozen term can be further separated into Pauli repulsion and electrostatics. These terms can be added to their counterparts obtained from the ground state EDA to form a decomposition of the total interaction energy. The EDA scheme is applied to study a variety of systems, including some model systems to demonstrate the correct behavior of all the proposed energy components as well as more realistic systems such as hydrogen-bonding complexes (e.g., formamide-water, pyridine/pyrimidine-water) and halide (F-, Cl-)-water clusters that involve charge-transfer-to-solvent excitations.

Determining the linkage of disease-resistance genes to molecular markers: the LOD-SCORE method revisited with regard to necessary sample sizes.

PubMed

Hühn, M

1995-05-01

Some approaches to molecular marker-assisted linkage detection for a dominant disease-resistance trait based on a segregating F2 population are discussed. Analysis of two-point linkage is carried out by the traditional measure of maximum lod score. It depends on (1) the maximum-likelihood estimate of the recombination fraction between the marker and the disease-resistance gene locus, (2) the observed absolute frequencies, and (3) the unknown number of tested individuals. If one replaces the absolute frequencies by expressions depending on the unknown sample size and the maximum-likelihood estimate of recombination value, the conventional rule for significant linkage (maximum lod score exceeds a given linkage threshold) can be resolved for the sample size. For each sub-population used for linkage analysis [susceptible (= recessive) individuals, resistant (= dominant) individuals, complete F2] this approach gives a lower bound for the necessary number of individuals required for the detection of significant two-point linkage by the lod-score method.

Counting numbers of synaptic proteins: absolute quantification and single molecule imaging techniques

PubMed Central

Patrizio, Angela; Specht, Christian G.

2016-01-01

Abstract. The ability to count molecules is essential to elucidating cellular mechanisms, as these often depend on the absolute numbers and concentrations of molecules within specific compartments. Such is the case at chemical synapses, where the transmission of information from presynaptic to postsynaptic terminals requires complex interactions between small sets of molecules. Be it the subunit stoichiometry specifying neurotransmitter receptor properties, the copy numbers of scaffold proteins setting the limit of receptor accumulation at synapses, or protein packing densities shaping the molecular organization and plasticity of the postsynaptic density, all of these depend on exact quantities of components. A variety of proteomic, electrophysiological, and quantitative imaging techniques have yielded insights into the molecular composition of synaptic complexes. In this review, we compare the different quantitative approaches and consider the potential of single molecule imaging techniques for the quantification of synaptic components. We also discuss specific neurobiological data to contextualize the obtained numbers and to explain how they aid our understanding of synaptic structure and function. PMID:27335891

Counting numbers of synaptic proteins: absolute quantification and single molecule imaging techniques.

PubMed

Patrizio, Angela; Specht, Christian G

2016-10-01

The ability to count molecules is essential to elucidating cellular mechanisms, as these often depend on the absolute numbers and concentrations of molecules within specific compartments. Such is the case at chemical synapses, where the transmission of information from presynaptic to postsynaptic terminals requires complex interactions between small sets of molecules. Be it the subunit stoichiometry specifying neurotransmitter receptor properties, the copy numbers of scaffold proteins setting the limit of receptor accumulation at synapses, or protein packing densities shaping the molecular organization and plasticity of the postsynaptic density, all of these depend on exact quantities of components. A variety of proteomic, electrophysiological, and quantitative imaging techniques have yielded insights into the molecular composition of synaptic complexes. In this review, we compare the different quantitative approaches and consider the potential of single molecule imaging techniques for the quantification of synaptic components. We also discuss specific neurobiological data to contextualize the obtained numbers and to explain how they aid our understanding of synaptic structure and function.

Redetermined structure, inter-molecular inter-actions and absolute configuration of royleanone.

PubMed

Fun, Hoong-Kun; Chantrapromma, Suchada; Salae, Abdul Wahab; Razak, Ibrahim Abdul; Karalai, Chatchanok

2011-05-01

The structure of the title diterpenoid, C(20)H(28)O(3), {systematic name: (4bS,8aS)-3-hy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octa-hydro-phenanthrene-1,4-dione} is confirmed [Eugster et al. (1993 ▶). Private communication (refcode HACGUN). CCDC, Union Road, Cambridge] and its packing is now described. Its absolute structure was established by refinement against data collected with Cu radiation: the two stereogenic centres both have S configurations. One cyclo-hexane ring adopts a chair conformation whereas the other cyclo-hexane ring is in a half-chair conformation and the benzoquinone ring is slightly twisted. An intra-molecular O-H⋯O hydrogen bond generates an S(5) ring motif. In the crystal, mol-ecules are linked into chains along [010] by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. The packing also features C⋯O [3.131 (3) Å] short contacts.

Investigation of colloidal graphite as a matrix for matrix-assisted laser desorption/ionisation mass spectrometry of low molecular weight analytes.

PubMed

Warren, Alexander D; Conway, Ulric; Arthur, Christopher J; Gates, Paul J

2016-07-01

The analysis of low molecular weight compounds by matrix-assisted laser desorption/ionisation mass spectrometry is problematic due to the interference and suppression of analyte ionisation by the matrices typically employed - which are themselves low molecular weight compounds. The application of colloidal graphite is demonstrated here as an easy to use matrix that can promote the ionisation of a wide range of analytes including low molecular weight organic compounds, complex natural products and inorganic complexes. Analyte ionisation with colloidal graphite is compared with traditional organic matrices along with various other sources of graphite (e.g. graphite rods and charcoal pencils). Factors such as ease of application, spectra reproducibility, spot longevity, spot-to-spot reproducibility and spot homogeneity (through single spot imaging) are explored. For some analytes, considerable matrix suppression effects are observed resulting in spectra completely devoid of matrix ions. We also report the observation of radical molecular ions [M(-●) ] in the negative ion mode, particularly with some aromatic analytes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Topological analysis of long-chain branching patterns in polyolefins.

PubMed

Bonchev, D; Markel, E; Dekmezian, A

2001-01-01

Patterns in molecular topology and complexity for long-chain branching are quantitatively described. The Wiener number, the topological complexity index, and a new index of 3-starness are used to quantify polymer structure. General formulas for these indices were derived for the cases of 3-arm star, H-shaped, and B-arm comb polymers. The factors affecting complexity in monodisperse polymer systems are ranked as follows: number of arms > arm length > arm central position approximately equal to arm clustering > total molecular weight approximately equal to backbone molecular weight. Topological indices change rapidly and then plateau as the molecular weight of branches on a polyolefin backbone increases from 0 to 5 kD. Complexity calculations relate 2-arm or 3-arm comb structures to the corresponding 3-arm stars of equivalent complexity but much higher molecular weight. In a subsequent paper, we report the application of topological analysis for developing structure/property relationships for monodisperse polymers. While the focus of the present work is on the description of monodisperse, well-defined architectures, the methods may be extended to the description of polydisperse systems.

Effects and mechanism of dual-frequency power ultrasound on the molecular weight distribution of corn gluten meal hydrolysates.

PubMed

Jin, Jian; Ma, Haile; Wang, Bei; Yagoub, Abu El-Gasim A; Wang, Kai; He, Ronghai; Zhou, Cunshan

2016-05-01

The impact of dual-frequency power ultrasound (DPU) on the molecular weight distribution (MWD) of corn gluten meal (CGM) hydrolysates and its mechanism were investigated in the present study. The mechanism was studied from aspects of structural and nano-mechanical characteristics of the major protein fractions of CGM, viz. zein and glutelin. The results of molecular weight distribution indicated that DPU pretreatment of CGM was beneficial to the preparation of peptides with molecular weights of 200-1000Da. Moreover, FTIR spectral analysis and atomic force microscopy characterization showed that the DPU pretreatment changed the contents of secondary structure of proteins, decreased the particle height and surface roughness of glutelin, reduced the Young's modulus and stiffness of zein while increased its adhesion force. In conclusion, DPU pretreatment of proteins before proteolysis is an efficient alternative method to produce short-chain peptides because of its positive effects originating from acoustic cavitation on the molecular conformation, nano-structures and nano-mechanical properties of proteins as well. Copyright © 2015 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.

The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

Success of women in a worksite weight loss program: Does being part of a group help?

PubMed

Rigsby, Andrea; Gropper, Daniel M; Gropper, Sareen S

2009-04-01

This study reports the results of a worksite weight loss program which allowed female hospital and nursing home employees to enroll in a worksite weight loss program as individuals or as part of a group. After 8 weeks, employees (irrespective of group versus individual participation) lost an average of 6.2 lb and 1.5% body fat. The initial weight, body fat, and body mass index reductions were all significantly greater, in absolute and percentage terms, among group participants than individual participants. Weight reduction averaged 7.6+1.1 lb for group participants and 4.2+6.4 lb for individual participants; body fat reduction was 1.7+1.3% for group participants and 0.9+1.3% for individual participants. Exercising more frequently was significantly associated with weight loss in those participating as a group, while following a written diet plan was significantly associated with weight loss in those participating as individuals.

Post-mortem prediction of primal and selected retail cut weights of New Zealand lamb from carcass and animal characteristics.

PubMed

Ngo, L; Ho, H; Hunter, P; Quinn, K; Thomson, A; Pearson, G

2016-02-01

Post-mortem measurements (cold weight, grade and external carcass linear dimensions) as well as live animal data (age, breed, sex) were used to predict ovine primal and retail cut weights for 792 lamb carcases. Significant levels of variance could be explained using these predictors. The predictive power of those measurements on primal and retail cut weights was studied by using the results from principal component analysis and the absolute value of the t-statistics of the linear regression model. High prediction accuracy for primal cut weight was achieved (adjusted R(2) up to 0.95), as well as moderate accuracy for key retail cut weight: tenderloins (adj-R(2)=0.60), loin (adj-R(2)=0.62), French rack (adj-R(2)=0.76) and rump (adj-R(2)=0.75). The carcass cold weight had the best predictive power, with the accuracy increasing by around 10% after including the next three most significant variables. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis of Poly(Propylene Fumarate)

PubMed Central

Kasper, F. Kurtis; Tanahashi, Kazuhiro; Fisher, John P.; Mikos, Antonios G.

2010-01-01

This protocol describes the synthesis of 500 – 4000 Da poly(propylene fumarate) by a two-step reaction of diethyl fumarate and propylene glycol through a bis(hydroxypropyl) fumarate diester intermediate. Purified PPF can be covalently crosslinked to form degradable polymer networks, which have been widely explored for biomedical applications. The properties of crosslinked PPF networks depend upon the molecular properties of the constituent polymer, such as the molecular weight. The purity of the reactants and the exclusion of water from the reaction system are of utmost importance in the generation of high-molecular-weight PPF products. Additionally, the reaction time and temperature influence the molecular weight of the PPF product. The expected time required to complete this protocol is 3 d. PMID:19325548

Step-Growth Polymerization.

ERIC Educational Resources Information Center

Stille, J. K.

1981-01-01

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Low molecular weight thermostable {beta}-D-glucosidase from Acidothermus cellulolyticus

DOEpatents

Himmel, M.E.; Tucker, M.P.; Adney, W.S.; Nieves, R.A.

1995-07-11

A purified low molecular weight {beta}-D-glucosidase is produced from Acidothermus cellulolyticus ATCC 43068. The enzyme is water soluble, possesses activity against pNP-{beta}-D-glucopyranoside, has a high of degree of stability toward heat, exhibits optimal temperature activity at about 65 C at a pH range of from about 2 to about 7, has an inactivation temperature of about 80 C at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5--54.5 kD as determined by SDS-PAGE. 6 figs.

Reduction of diffusional defocusing in hydrodynamically focused flows

DOEpatents

Affleck, Rhett L.; Demas, James N.; Goodwin, Peter M.; Keller, Richard; Wu, Ming

1998-01-01

An analyte fluid stream with first molecules having relatively low molecular weight and a corresponding high coefficient of diffusion has reduced diffusional defocusing out of an analyte fluid stream. The analyte fluid stream of first molecules is associated with second molecules of relatively high molecular weight having a relatively low coefficient of diffusion and a binding constant effective to associate with the first molecules. A focused analyte fluid stream is maintained since the combined molecular weight of the associated first and second molecules is effective to minimize diffusion of the first molecules out of the analyte fluid stream.

Reduction of diffusional defocusing in hydrodynamically focused flows

DOEpatents

Affleck, R.L.; Demas, J.N.; Goodwin, P.M.; Keller, R.; Wu, M.

1998-09-01

An analyte fluid stream with first molecules having relatively low molecular weight and a corresponding high coefficient of diffusion has reduced diffusional defocusing out of an analyte fluid stream. The analyte fluid stream of first molecules is associated with second molecules of relatively high molecular weight having a relatively low coefficient of diffusion and a binding constant effective to associate with the first molecules. A focused analyte fluid stream is maintained since the combined molecular weight of the associated first and second molecules is effective to minimize diffusion of the first molecules out of the analyte fluid stream. 6 figs.

Chemotactic activity from rabbit peritoneal neutrophils. Lack of identity with N-acetyl-DL-phenylalanine beta-napthyl esterase.

PubMed

Tsung, P K; Showell, H J; Kegeles, S W; Becker, E L

1976-08-12

The chemotactic and N-acetyl-DL-phenylalanine beta-naphthyl esterase activities of rabbit peritoneal neutrophils are separable from each other by both DEAE cellulose and Sephadex G-100 column chromatography. Partially purified esterase obtained from DEAE-cellulose chromatography had molecular weight of 70 000. However, the partially purified fraction contained chemotactic activities with major activity in molecular weight of 28000 and minor activities in the molecular weights of 45000, 21900, 14500 and 10500. Esterase activity is inhibited by 10(-7) M p-nitrophenylethyl-5-chloropentylphosphonate but chemotactic activity is not.

Low molecular weight thermostable .beta.-D-glucosidase from acidothermus cellulolyticus

DOEpatents

Himmel, Michael E.; Tucker, Melvin P.; Adney, William S.; Nieves, Rafael A.

1995-01-01

A purified low molecular weight .beta.-D-glucosidase is produced from Acidothermus cellulolyticus ATCC 43068. The enzyme is water soluble, possesses activity against pNP-.beta.-D-glucopyranoside, has a high of degree of stability toward heat, exhibits optimal temperature activity at about 65.degree. C. at a pH range of from about 2 to about 7, has an inactivation temperature of about 80.degree. C. at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5-54.5 kD as determineded by SDS-PAGE.

Preparation of Low Molecular Weight Gelatin Using Microwave Discharge Electrodeless Lamp/TiO2 Photocatalyst Hybrid System.

PubMed

Lee, Do-Jin; Kim, Hangun; Park, Young-Kwon; Kim, Byung Hoon; Lee, Heon; Jungf, Sana-Chul

2016-02-01

In this study, an MDEL/TiO2 photocatalyst hybrid system was applied to the production of low molecular weight gelatin. The molecular weight of produed gelatin decreased with increasing microwave intensity and increasing treatment time. The abscission of the chemical bonds between the con- stituents of gelatin by photocatalytic reaction did not alter the characteristics of gelatin. Formation of any by-products due to side reaction was not observed. It is suggested that gelatin was depolymerized by hydroxyl radicals produced during the MDEL/TiO2 photochemical reaction.

Preparation of Low Molecular Weight Heparin by Microwave Discharge Electrodeless Lamp/TiO2 Photo-Catalytic Reaction.

PubMed

Lee, Do-Jin; Kim, Byung Hoon; Kim, Sun-Jae; Kim, Jung-Sik; Lee, Heon; Jung, Sang-Chul

2015-01-01

An MDEL/TiO2 photo-catalyst hybrid system was applied, for the first time, for the production of low molecular weight heparin. The molecular weight of produed heparin decreased with increasing microwave intensity and treatment time. The abscission of the chemical bonds between the constituents of heparin by photo-catalytic reaction did not alter the characteristics of heparin. Formation of by-products due to side reaction was not observed. It is suggested that heparin was depolymerized by active oxygen radicals produced during the MDEL/TiO2 photo-chemical reaction.

Increase in gap junctional intercellular communication by high molecular weight hyaluronic acid associated with fibroblast growth factor 2 and keratinocyte growth factor production in normal human dermal fibroblasts.

PubMed

Park, Jeong Ung; Tsuchiya, Toshie

2002-07-01

The effects of different molecular weights of hyaluronic acid (HA), a major component of extracellular matrix, on gap junctional intercellular communication (GJIC) in normal human dermal fibroblasts (NHDF cells) were investigated. NHDF cells were cultured for 4 days with different molecular weights of HA and then the extent of GJIC was assessed by the scrape-loading dye transfer method, using Lucifer yellow. The area of dye transfer was greater in the dishes coated with HA than in those to which HA was added. Thus, NHDF cells cultured on surfaces coated with high molecular weight (HMW) HA (MW, 800 kDa) showed greatly enhanced GJIC. Furthermore, another aim of this study was to evaluate the effects of different molecular weights of HA on the production of FGF-2 and KGF, because both are important cytokines produced by NHDF cells. When FGF-2 and KGF cultured levels of cell extracts and media were determined by ELISA, both levels were significantly enhanced when cells were grown on plates coated with HMW HA. This finding indicated that the function of gap junction channels in NHDF cells grown on plates coated with HMW HA may promote the biosynthesis of growth factors such as FGF-2 and KGF.

Effect of frozen storage on molecular weight, size distribution and conformation of gluten by SAXS and SEC-MALLS.

PubMed

Zhao, Lei; Li, Lin; Liu, Guo-Qin; Liu, Xing-Xun; Li, Bing

2012-06-12

In this study, the effects of frozen (-18 °C) storage time on molecular weight, size distribution, conformation, free amino groups and free sulfhydryl groups of gluten were studied by small-angle X-ray scattering (SAXS), multi-angle laser light scattering (MALLS) in conjunction with a size exclusion chromatography (SEC) and spectrophotometrically. The results showed that the gluten dissolved in 50 mM acetic acid appeared to be similar to quasi-spherical of the chain conformation and the slope of the conformation plot decreased during the storage. Both the molecular weight and radius of gyration of the frozen gluten decreased with the storage time showing a depolymerization in the high molecular weight fraction of gluten (10(5) Da ~ 10(9) Da). Therefore, at constant molecular weight the change of the chain conformation did not show a clear correlation with the storage time. The free amino groups content changed little and the free sulfhydryl groups content of the gluten increased from 9.8 μmol/g for the control to 12.87 μmol/g for 120-day-stored gluten, indicating that the water redistribution and ice recrystallization lead to the breakage of the disulphide bonds and may be one of the reasons for the depolymerization of gluten polymer.

Polysaccharides and their depolymerized fragments from Costaria costata: Molecular weight and sulfation-dependent anticoagulant and FGF/FGFR signal activating activities.

PubMed

Hou, Ningning; Zhang, Meng; Xu, Yingjie; Sun, Zhongmin; Wang, Jing; Zhang, Lijuan; Zhang, Quanbin

2017-12-01

Crude polysaccharides from Costaria costata were extracted by hot water and further fractionated by anion exchange chromatography into three polysaccharide fractions. Three low molecular weight fragments were then prepared by degradation of the polysaccharides with hydrogen peroxide and ascorbic acid. The structural features of the polysaccharides and their low molecular weight fragments were elucidated for the first time based on the HGPC, FT-IR, NMR, MS, monosaccharide composition, and other chemical analyses. Their anticoagulant and FGF-1, -2, -7, -8, -9, -10/FGFR1c signaling activation activities in BaF3 cells were also examined. Our studies showed that the polysaccharides were sulfated at different positions of galactose and fucose residues. The APTT-, PT- and TT-based anticoagulant assay results indicated that a high molecular weight and a higher degree of sulfation were essential for their anticoagulant activities. In contrast, not only the polysaccharides but also the depolymerized fragments showed significant FGF/FGFR signal activating activities in a FGF-, molecular weight-, and sulfation-dependent manner. The results presented in current study demonstrated the potential use of the polysaccharides and their fragments as anticoagulants and FGF signal regulators. Copyright © 2017 Elsevier B.V. All rights reserved.

Pectinase hydrolysis of Dendrobium huoshanense polysaccharide and its effect on protein nonenzymatic glycation.

PubMed

Zha, Xue-Qiang; Li, Xiao-Long; Zhang, Hai-Lin; Cui, Shao-Hua; Liu, Jian; Wang, Jun-Hui; Pan, Li-Hua; Luo, Jian-Ping

2013-10-01

The aim of this study was to investigate the inhibitory effects of molecular weight alteration of Dendrobium huoshanense polysaccharide on protein nonenzymatic glycation. For this purpose, one homogeneous active polysaccharide DHPD1 with molecular weight 3.2 kDa was extracted from D. huoshanense. GC analysis showed that DHPD1 was mainly composed of glucose, arabinose, galactose in a molar ratio of 0.023:1.023:0.021 with a trace of mannose and xylose. In order to get DHPD1-derived fragments with different molecular weight, response surface methodology was employed to optimize the enzymatic degradation conditions. The maximum reducing sugar production (0.399 mg/mL) was obtained under an optimal condition including pectinase dosage 126 U/mL, reaction pH 4.46 and reaction temperature 48 °C. By applying this condition, three DHPD1-derived fragments with different molecular weights were obtained through changing the hydrolysis time. Infrared spectroscopy analysis indicated that the backbone structure of DHPD1 was not destroyed by pectinase hydrolysis. Monosaccharide composition analysis showed that pectinase preferred to liberate glucose from DHPD1. The inhibitory action of DHPD1 on protein nonenzymatic glycation reduced with the decrease of molecular weight. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of High Molecular Weight Poly(glycerol monomethacrylate) via RAFT Emulsion Polymerization of Isopropylideneglycerol Methacrylate

PubMed Central

2018-01-01

High molecular weight water-soluble polymers are widely used as flocculants or thickeners. However, synthesis of such polymers via solution polymerization invariably results in highly viscous fluids, which makes subsequent processing somewhat problematic. Alternatively, such polymers can be prepared as colloidal dispersions; in principle, this is advantageous because the particulate nature of the polymer chains ensures a much lower fluid viscosity. Herein we exemplify the latter approach by reporting the convenient one-pot synthesis of high molecular weight poly(glycerol monomethacrylate) (PGMA) via the reversible addition–fragmentation chain transfer (RAFT) aqueous emulsion polymerization of a water-immiscible protected monomer precursor, isopropylideneglycerol methacrylate (IPGMA) at 70 °C, using a water-soluble poly(glycerol monomethacrylate) (PGMA) chain transfer agent as a steric stabilizer. This formulation produces a low-viscosity aqueous dispersion of PGMA–PIPGMA diblock copolymer nanoparticles at 20% solids. Subsequent acid deprotection of the hydrophobic core-forming PIPGMA block leads to particle dissolution and affords a viscous aqueous solution comprising high molecular weight PGMA homopolymer chains with a relatively narrow molecular weight distribution. Moreover, it is shown that this latex precursor route offers an important advantage compared to the RAFT aqueous solution polymerization of glycerol monomethacrylate since it provides a significantly faster rate of polymerization (and hence higher monomer conversion) under comparable conditions. PMID:29805184

Lipid mobilising factors specifically associated with cancer cachexia.

PubMed Central

Beck, S. A.; Tisdale, M. J.

1991-01-01

Both urine and plasma from mice and humans with cancer cachexia have been shown to contain higher levels of lipid mobilising activity than normal controls, even after acute starvation. There was no significant increase in the urinary lipid mobilising activity of either mice or humans after acute starvation, suggesting that the material in the cachectic situation was probably not due to an elevation of hormones normally associated with the catabolic state in starvation. Further characterisation of the lipid mobilising activity in the urine of cachectic mice using Sephadex G50 exclusion chromatography showed four distinct peaks of activity of apparent molecular weights of greater than 20, 3, 1.5 and less than 0.7 kDa. No comparable peaks of activity were found in the urine of a non tumour-bearing mouse. The high molecular weight activity was probably formed by aggregation of low molecular weight material, since treatment with 0.5 M NaCl caused dissociation to material with a broad spectrum of molecular weights between 3 and 0.7 kDa. Lipolytic species of similar molecular weights were also found in the urine of cachectic cancer patients, but not in normal urine even after 24 h starvation. The lipid mobilising species may be responsible for catabolism of host adipose tissue in the cachectic state. PMID:2069843

Oral administration of hyaluronan prevents skin dryness and epidermal thickening in ultraviolet irradiated hairless mice.

PubMed

Kawada, Chinatsu; Kimura, Mamoru; Masuda, Yasunobu; Nomura, Yoshihiro

2015-12-01

Hyaluronan is a component of the extracellular matrix that plays a role in water retention in tissues. In this study, we orally administered hyaluronans of varying molecular weights (300k and less than 10k) repeatedly to hairless mice exposed to ultraviolet (UV) irradiation and examined their effects on the skin of these mice. UV irradiation induces a marked increase in the epidermal thickness of the dorsal skin and a marked decrease in the skin moisture content; however, orally administered hyaluronan, particularly that with a molecular weight of less than 10k, markedly reversed the increase and decrease in the epidermal thickness and skin moisture content, respectively. Furthermore, on analyzing the mice skin, orally administered hyaluronan with a molecular weight of less than 10k increased the levels of the HAS2 gene expression in the skin. Based on these findings, it is assumed that orally administered hyaluronans, with molecular weight of 300k and less than 10k, reversed UV irradiation-induced skin disturbance. In particular, it was considered that the increase in the skin moisture content by orally administered hyaluronan, with a molecular weight of less than 10k, was related to the effect on skin cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of gel-filter method for high enrichment of low-molecular weight proteins from serum.

PubMed

Chen, Lingsheng; Zhai, Linhui; Li, Yanchang; Li, Ning; Zhang, Chengpu; Ping, Lingyan; Chang, Lei; Wu, Junzhu; Li, Xiangping; Shi, Deshun; Xu, Ping

2015-01-01

The human serum proteome has been extensively screened for biomarkers. However, the large dynamic range of protein concentrations in serum and the presence of highly abundant and large molecular weight proteins, make identification and detection changes in the amount of low-molecular weight proteins (LMW, molecular weight ≤ 30kDa) difficult. Here, we developed a gel-filter method including four layers of different concentration of tricine SDS-PAGE-based gels to block high-molecular weight proteins and enrich LMW proteins. By utilizing this method, we identified 1,576 proteins (n = 2) from 10 μL serum. Among them, 559 (n = 2) proteins belonged to LMW proteins. Furthermore, this gel-filter method could identify 67.4% and 39.8% more LMW proteins than that in representative methods of glycine SDS-PAGE and optimized-DS, respectively. By utilizing SILAC-AQUA approach with labeled recombinant protein as internal standard, the recovery rate for GST spiked in serum during the treatment of gel-filter, optimized-DS, and ProteoMiner was 33.1 ± 0.01%, 18.7 ± 0.01% and 9.6 ± 0.03%, respectively. These results demonstrate that the gel-filter method offers a rapid, highly reproducible and efficient approach for screening biomarkers from serum through proteomic analyses.

Vitamin K antagonists or low-molecular-weight heparin for the long term treatment of symptomatic venous thromboembolism.

PubMed

van der Heijden, J F; Hutten, B A; Büller, H R; Prins, M H

2002-01-01

People with venous thromboembolism are generally treated for five days with intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin followed by three months of vitamin K antagonists treatment. Treatment with vitamin K antagonists requires regular laboratory measurements and some patients have contraindications for treatment. To evaluate the efficacy and safety of long-term treatment of venous thromboembolism with low-molecular-weight heparins compared to vitamin K antagonists. Searches of MEDLINE, EMBASE and ISI Web of Science, the Specialised Trials Register of the Cochrane Peripheral Vascular Disease Group and the Cochrane Controlled Trials Register were made and relevant journals were hand-searched. Additional trials were sought through communication with colleagues and pharmaceutical companies. Two reviewers evaluated studies independently for methodological quality. Two reviewers extracted data independently. Primary analysis concerned all trial participants during the period of randomized treatment. Separate analyses were performed for category I and category II studies; i.e. studies using similar treatments initially in both study arms, and those that did not; and the different periods of follow-up. All seven studies fulfilling our criteria combined, a statistically non-significant reduction in the risk of recurrent venous thromboembolism favoring low-molecular-weight heparin treatment (OR 0.70; 95% CI [0.42, 1.16]) was found. Analysis of pooled data for category I studies showed a non-significant reduction in the risk of recurrent venous thromboembolism favoring low-molecular-weight heparin treatment (OR 0.75; 95% CI [0.40, 1.39]). Omitting a potentially-confounded study, a statistically non-significant reduction in the risk of recurrent venous thromboembolism favoring vitamin K antagonist treatment remained (OR 1.95; 95% CI [0.74, 5.19]). All studies combined, the difference in bleeding significantly favored treatment with low-molecular-weight heparin (OR 0.38; 95% CI [0.15, 0.94]), however, considering only category I studies a non-significant trend favoring low-molecular-weight heparin remained (OR 0.80; 95% CI [0.21, 3.00]). No difference was observed in mortality (OR 1.13; 95% CI [0.47, 2.69]). Low-molecular-weight heparins are possibly as effective as vitamin K antagonists in preventing symptomatic venous thromboembolism after an episode of symptomatic deep venous thrombosis, but are much more expensive. Treatment with low-molecular-weight heparin is significantly safer than treatment with vitamin K antagonists and is possibly a safe alternative in some patients; especially those in geographically inaccessible places, reluctant to visit the thrombosis service regularly, or with contraindications to vitamin K antagonists. However, treatment with vitamin K antagonists remains the treatment of choice for the majority of patients.

Echocardiographic left ventricular masses in distance runners and weight lifters

NASA Technical Reports Server (NTRS)

Longhurst, J. C.; Gonyea, W. J.; Mitchell, J. H.; Kelly, A. R.

1980-01-01

The relationships of different forms of exercise training to left ventricular mass and body mass are investigated by echocardiographic studies of weight lifters, long-distance runners, and comparatively sized untrained control subjects. Left ventricular mass determinations by the Penn convention reveal increased absolute left ventricular masses in long-distance runners and competitive weight lifters with respect to controls matched for age, body weight, and body surface area, and a significant correlation between ventricular mass and lean body mass. When normalized to lean body mass, the ventricular masses of distance runners are found to be significantly higher than those of the other groups, suggesting that dynamic training elevates left ventricular mass compared to static training and no training, while static training increases ventricular mass only to the extent that lean body mass is increased.

Cardiac MRI of elite junior Olympic weight lifters.

PubMed

Fleck, S J; Henke, C; Wilson, W

1989-10-01

Cardiac magnetic resonance imaging was performed on 14 junior elite Olympic weight lifters and 14 controls (means +/- Se, age = 18.4 +/- 0.5 and 17.8 +/- 0.4 years, weight = 76.5 +/- 3.6 and 78.8 +/- 3.3 kg, % fat = 6.5% +/- 0.8% and 11.5% +/- 1.7%, respectively). Controls were individually matched to the lifters to within 2 years of age and 2.5 kg of body weight. Systolic (S) and diastolic (D) left posterior wall thickness (LPW), left ventricular short axis (LSA), left ventricular transverse long axis (LLA), spetal wall thickness (SW), right ventricular wall thickness (RWT), and right ventricular short axis (RSA) were determined. Variables were examined in absolute (mm), relative to body surface area (BSA, mm/m2), total body weight (BW, mm/kg), and lean body mass (LBM, mm/kg) terms. In absolute terms S LPW (21.1 +/- 1.7 vs 13.3 +/- 0.5 mm), S SW (15.3 +/- 1.3 vs 11.7 +/- 0.6 mm), and D LLA (75.2 +/- 1.6 vs 69.1 +/- 2.4 mm) were significantly greater and S LSA (23.4 +/- 2.4 vs 36.7 +/- 2.3 mm) and S LLA (46.5 +/- 3.7 vs 58.2 +/- 3.8 mm) were significantly less in the lifters vs the controls. S LPW/BW, S LPW/BSA, S LPW/LBM, S SW/BW, S SW/BSA, S SW/LBM, D LSA/BSA, and D LLA/BSA were significantly greater and S LSA/BW, B LSA/BSA, S LSA/LBM, S LLA/BSA, S LLA/LBM, and D SW/LBM were significantly less in the lifters than the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

A gravimetric method for the measurement of total spontaneous activity in rats.

PubMed

Biesiadecki, B J; Brand, P H; Koch, L G; Britton, S L

1999-10-01

Currently available methods for the measurement of spontaneous activity of laboratory animals require expensive, specialized equipment and may not be suitable for use in low light conditions with nocturnal species. We developed a gravimetric method that uses common laboratory equipment to quantify the total spontaneous activity of rats and is suitable for use in the dark. The rat in its home cage is placed on a top-loading electronic balance interfaced to a computer. Movements are recorded by the balance as changes in weight and transmitted to the computer at 10 Hz. Data are analyzed on-line to derive the absolute value of the difference in weight between consecutive samples, and the one-second average of the absolute values is calculated. The averages are written to file for off-line analysis and summed over the desired observation period to provide a measure of total spontaneous activity. The results of in vitro experiments demonstrated that: 1) recorded weight changes were not influenced by position of the weight on the bottom of the cage, 2) values recorded from a series of weight changes were not significantly different from the calculated values, 3) the constantly decreasing force exerted by a swinging pendulum placed on the balance was accurately recorded, 4) the measurement of activity was not influenced by the evaporation of a fluid such as urine, and 5) the method can detect differences in the activity of sleeping and waking rats over a 10-min period, as well as during 4-hr intervals recorded during active (night-time) and inactive (daytime) periods. These results demonstrate that this method provides an inexpensive, accurate, and noninvasive method to quantitate the spontaneous activity of small animals.

Why to compare absolute numbers of mitochondria.

PubMed

Schmitt, Sabine; Schulz, Sabine; Schropp, Eva-Maria; Eberhagen, Carola; Simmons, Alisha; Beisker, Wolfgang; Aichler, Michaela; Zischka, Hans

2014-11-01

Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility toward inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility toward inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations. Copyright © 2014 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

Free-energy calculations using classical molecular simulation: application to the determination of the melting point and chemical potential of a flexible RDX model.

PubMed

Sellers, Michael S; Lísal, Martin; Brennan, John K

2016-03-21

We present an extension of various free-energy methodologies to determine the chemical potential of the solid and liquid phases of a fully-flexible molecule using classical simulation. The methods are applied to the Smith-Bharadwaj atomistic potential representation of cyclotrimethylene trinitramine (RDX), a well-studied energetic material, to accurately determine the solid and liquid phase Gibbs free energies, and the melting point (Tm). We outline an efficient technique to find the absolute chemical potential and melting point of a fully-flexible molecule using one set of simulations to compute the solid absolute chemical potential and one set of simulations to compute the solid-liquid free energy difference. With this combination, only a handful of simulations are needed, whereby the absolute quantities of the chemical potentials are obtained, for use in other property calculations, such as the characterization of crystal polymorphs or the determination of the entropy. Using the LAMMPS molecular simulator, the Frenkel and Ladd and pseudo-supercritical path techniques are adapted to generate 3rd order fits of the solid and liquid chemical potentials. Results yield the thermodynamic melting point Tm = 488.75 K at 1.0 atm. We also validate these calculations and compare this melting point to one obtained from a typical superheated simulation technique.

Absolute Calibration of Si iRMs used for Measurements of Si Paleo-nutrient proxies

NASA Astrophysics Data System (ADS)

Vocke, R. D., Jr.; Rabb, S. A.

2016-12-01

Silicon isotope variations (reported as δ30Si and δ29Si, relative to NBS28) in silicic acid dissolved in ocean waters, in biogenic silica and in diatoms are extremely informative paleo-nutrient proxies. The resolution and comparability of such measurements depend on the quality of the isotopic Reference Materials (iRMs) defining the delta scale. We report new absolute Si isotopic measurements on the iRMs NBS28 (RM 8546 - Silica Sand), Diatomite, and Big Batch using the Avogadro measurement approach and comparing them with prior assessments of these iRMs. The Avogadro Si measurement technique was developed by the German Physikalish-Technische Bundesanstalt (PTB) to provide a precise and highly accurate method to measure absolute isotopic ratios in highly enriched 28Si (99.996%) material. These measurements are part of an international effort to redefine the kg and mole based on the Planck constant h and the Avogadro constant NA, respectively (Vocke et al., 2014 Metrologia 51, 361, Azuma et al., 2015 Metrologia 52 360). This approach produces absolute Si isotope ratio data with lower levels of uncertainty when compared to the traditional "Atomic Weights" method of absolute isotope ratio measurement calibration. This is illustrated in Fig. 1 where absolute Si isotopic measurements on SRM 990, separated by 40+ years of advances in instrumentation, are compared. The availability of this new technique does not say that absolute Si isotopic ratios are or ever will be better for normal Si isotopic measurements when seeking isotopic variations in nature, because they are not. However, by determining the absolute isotopic ratios of all the Si iRM scale artifacts, such iRMs become traceable to the metric system (SI); thereby automatically conferring on all the artifact-based δ30Si and δ29Si measurements traceability to the base SI unit, the mole. Such traceability should help reduce the potential of bias between different iRMs and facilitate the replacement of delta-scale artefacts when they run out. Fig. 1 Comparison of absolute isotopic measurements of SRM 990 using two radically different approaches to absolute calibration and mass bias corrections.

A Description of Methodologies Used in Estimation of A-Weighted Sound Levels for FAA Advisory Circular AC-36-3B.

DTIC Science & Technology

1982-01-01

second) Dia propeller diameter (expressed in inches) T°F air temperature in degrees Farenheit T°C air temperature in degrees Celsius T:dBA total dBA...eMpiriC31 function to the absolute noise level ordinate. The term 240 log ( MH is the most sensitive and important part of the equation. The constant (240...standard day, zero wind, dry, zero gradient runway, at a sea level airport. 2. All aircraft operate at maximum takeoff gross weight. 3. All aircraft climb

Respiratory weight losses during exercise.

NASA Technical Reports Server (NTRS)

Mitchell, J. W.; Nadel, E. R.; Stolwijk, J. A. J.

1972-01-01

Evaporative water loss from the respiratory tract was determined over a wide range of exercise. The absolute humidity of the expired air was the same at all levels of exercise and equal to that measured at rest. The rate of respiratory water loss during exercise was found to be 0.019 of the oxygen uptake times (44 minus water vapor pressure). The rate of weight loss during exercise due to CO2-O2 exchange was calculated. For exercise at oxygen consumption rates exceeding 1.5 L/min in a dry environment with a water vapor pressure of 10 mm Hg, the total rate of weight loss via the respiratory tract is on the order of 2-5 g/min.

Implementation of GPC characterization of asphalt binders at Louisiana materials laboratory : tech summary.

DOT National Transportation Integrated Search

2013-10-01

Asphalt is a mixture of a wide variety of chemical compounds that include aliphatic hydrocarbons and highly fused : aromatic ring systems. They are classi ed as asphaltenes (medium molecular weight) and maltenes (low molecular : weight). To improv...

Absolute, Extreme-Ultraviolet Solar Spectral Irradiance Monitor (AESSIM)

DTIC Science & Technology

1994-04-01

molecular constituents [Meier 1991]. This radiation is the principal source of energy for producing and maintaining the complex, time-dependent, thermal...158.4 nm emisions for interstellar wind studies. After -2005, there is unlikely to be sufficient power to provide the requisite heating of the scan

Absolute vacuum ultraviolet photoabsorption cross section studies of atomic and molecular species: Techniques and observational data

NASA Technical Reports Server (NTRS)

Judge, D. L.; Wu, C. Y. R.

1990-01-01

Absorption of a high energy photon (greater than 6 eV) by an isolated molecule results in the formation of highly excited quasi-discrete or continuum states which evolve through a wide range of direct and indirect photochemical processes. These are: photoionization and autoionization, photodissociation and predissociation, and fluorescence. The ultimate goal is to understand the dynamics of the excitation and decay processes and to quantitatively measure the absolute partial cross sections for all processes which occur in photoabsorption. Typical experimental techniques and the status of observational results of particular interest to solar system observations are presented.

Absolute Equation-of-State Measurement for Polystyrene from 25 - 60 Mbar Using a Spherically Converging Shock Wave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glenzer, Siegfried

We have developed an experimental platform for the National Ignition Facility (NIF) that uses spherically converging shock waves for absolute equation of state (EOS) measurements along the principal Hugoniot. In this Letter we present radiographic compression measurements for polystyrene that were taken at shock pressures reaching 60 Mbar (6 TPa). This significantly exceeds previously published results obtained on the Nova laser [Cauble et al., Phys. Rev. Lett. 80, 1248 (1998)] at strongly improved precision, allowing to discriminate between different EOS models. We find excellent agreement with Kohn-Sham Density Functional Theory based molecular dynamics simulations.

Development of a Transnasal Delivery System for Recombinant Human Growth Hormone (rhGH): Effects of the Concentration and Molecular Weight of Poly-L-arginine on the Nasal Absorption of rhGH in Rats.

PubMed

Kawashima, Ryo; Uchida, Masaki; Yamaki, Tsutomu; Ohtake, Kazuo; Hatanaka, Tomomi; Uchida, Hiroyuki; Ueda, Hideo; Kobayashi, Jun; Morimoto, Yasunori; Natsume, Hideshi

2016-01-01

A novel system for delivering recombinant human growth hormone (rhGH) that is noninvasive and has a simple method of administration is strongly desired to improve the compliance of children. The aim of this study was to investigate the potential for the intranasal (i.n.) co-administration of rhGH with poly-L-arginine (PLA) as a novel delivery system by evaluating the effects of the concentration and molecular weight of PLA on the nasal absorption of rhGH. The influence of the formation of insoluble aggregates and a soluble complex in the dosage formulation on nasal rhGH absorption was also evaluated by size-exclusion chromatography and ultrafiltration. PLA enhanced the nasal absorption of rhGH at each concentration and molecular weight examined. Nasal rhGH absorption increased dramatically when the PLA concentration was 1.0 % (w/v) due to the improved solubility of rhGH in the formulation. A delay in rhGH absorption was observed when the molecular weight of PLA was increased. This appeared to be because the increase in molecular weight caused the formation of a soluble complex. It seems that the PLA concentration affects the absorption-enhancing effect on rhGH, while the molecular weight of PLA affects the time when the maximum plasma rhGH concentration was reached (Tmax) of rhGH after i.n. administration, mainly because of the interactions among rhGH, PLA, and additives. Therefore, the transnasal rhGH delivery system using PLA is considered to be a promising alternative to subcutaneous (s.c.) injection if these interactions are sufficiently controlled.

Identification of interleukin-6 as an autocrine growth factor for Epstein-Barr virus-immortalized B cells.

PubMed Central

Tosato, G; Tanner, J; Jones, K D; Revel, M; Pike, S E

1990-01-01

Autocrine growth factors are believed to be important for maintenance of an immortalized state by Epstein-Barr virus (EBV), because cell-free supernatants of EBV-immortalized cell lines promote the proliferation of autologous cells and permit their growth at low cell density. In this study, we provide evidence for the existence of two autocrine growth factor activities produced by EBV-immortalized lines distinguished by size and biological activities. Much of the autocrine growth factor activity in lymphoblastoid cell line supernatants resided in a low-molecular-weight (less than 5,000) fraction. However, up to 20 to 30% of the autocrine growth factor activity resided in the high-molecular-weight (greater than 5,000) fraction. While the nature of the low-molecular-weight growth factor activity remains undefined, the high-molecular-weight growth factor activity was identified as interleukin-6 (IL-6). Culture supernatants from six EBV-induced lymphoblastoid cell lines tested contained IL-6 activity, because they promoted proliferation in the IL-6-dependent hybridoma cell line B9. In addition, a rabbit antibody to human IL-6 neutralized the capacity of the high-molecular-weight (greater than 5,000) fraction of a lymphoblastoid cell line supernatant to promote growth both in autologous EBV-immortalized cells and in B9 cells. Similarly, this high-molecular-weight autocrine growth factor activity was neutralized by a monoclonal antibody to human IL-6. Furthermore, characteristic bands, attributable to IL-6, were visualized in supernatants of each of four EBV-induced lymphoblastoid cell lines after immunoprecipitation with a rabbit antiserum to human IL-6. Thus, in addition to its previously reported properties, IL-6 is an autocrine growth factor for EBV-immortalized B cells cultured under serum-free conditions. Images PMID:2159561

Degradation behavior of, and tissue response to photo-crosslinked poly(trimethylene carbonate) networks.

PubMed

Rongen, Jan J; van Bochove, Bas; Hannink, Gerjon; Grijpma, Dirk W; Buma, Pieter

2016-11-01

Photo-crosslinked networks prepared from three-armed methacrylate functionalized PTMC oligomers (PTMC-tMA macromers) are attractive materials for developing an anatomically correct meniscus scaffold. In this study, we evaluated cell specific biocompatibility, in vitro and in vivo degradation behavior of, and tissue response to, such PTMC networks. By evaluating PTMC networks prepared from PTMC-tMA macromers of different molecular weights, we were able to assess the effect of macromer molecular weight on the degradation rate of the PTMC network obtained after photo-crosslinking. Three photo-crosslinked networks with different crosslinking densities were prepared using PTMC-tMA macromers with molecular weights 13.3, 17.8, and 26.7 kg/mol. Good cell biocompatibility was demonstrated in a proliferation assay with synovium derived cells. PTMC networks degraded slowly, but statistically significant, both in vitro as well as subcutaneously in rats. Networks prepared from macromers with higher molecular weights demonstrated increased degradation rates compared to networks prepared from initial macromers of lowest molecular weight. The degradation process took place via surface erosion. The PTMC networks showed good tissue tolerance during subcutaneous implantation, to which the tissue response was characterized by the presence of fibrous tissue and encapsulation of the implants. Concluding, we developed cell and tissue biocompatible, photo-crosslinked PTMC networks using PTMC-tMA macromers with relatively high molecular weights. These photo-crosslinked PTMC networks slowly degrade by a surface erosion process. Increasing the crosslinking density of these networks decreases the rate of surface degradation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2823-2832, 2016. © 2016 Wiley Periodicals, Inc.

Poly(ethylene glycol) analogs grafted with low molecular weight poly(ethylene imine) as non-viral gene vectors.

PubMed

Zhang, Zhenfang; Yang, Cuihong; Duan, Yajun; Wang, Yanming; Liu, Jianfeng; Wang, Lianyong; Kong, Deling

2010-07-01

A novel class of non-viral gene vectors consisting of low molecular weight poly(ethylene imine) (PEI) (molecular weight 800 Da) grafted onto degradable linear poly(ethylene glycol) (PEG) analogs was synthesized. First, a Michael addition reaction between poly(ethylene glycol) diacrylates (PEGDA) (molecular weight 258 Da) and d,l-dithiothreitol (DTT) was carried out to generate a linear polymer (PEG-DTT) having a terminal thiol, methacrylate and pendant hydroxyl functional groups. Five PEG-DTT analogs were synthesized by varying the molar ratio of diacrylates to thiols from 1.2:1 to 1:1.2. Then PEI (800 Da) was grafted onto the main chain of the PEG-DTTs using 1,1'-carbonyldiimidazole as the linker. The above reaction gave rise to a new class of non-viral gene vectors, (PEG-DTT)-g-PEI copolymers, which can effectively complex DNA to form nanoparticles. The molecular weights and structures of the copolymers were characterized by gel permeation chromatography, (1)H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The size of the nanoparticles was<200 nm and the surface charge of the nanoparticles, expressed as the zeta potential, was between+20 and+40 mV. Cytotoxicity assays showed that the copolymers exhibited much lower cytotoxicities than high molecular weight PEI (25 kDa). Transfection was performed in cultured HeLa, HepG2, MCF-7 and COS-7 cells. The copolymers showed higher transfection efficiencies than PEI (25 kDa) tested in four cell lines. The presence of serum (up to 30%) had no inhibitory effect on the transfection efficiency. These results indicate that this new class of non-viral gene vectors may be a promising gene carrier that is worth further investigation. Copyright 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A comparison of the wear of cross-linked polyethylene against itself with the wear of ultra-high molecular weight polyethylene against itself.

PubMed

Joyce, T J; Unsworth, A

1996-01-01

Wear tests were carried out on reciprocating pin-on-plate machines which had pins loaded at 10 N and 40 N. The materials tested were irradiated cross-linked polyethylene sliding against itself, irradiated ultra-high molecular weight polyethylene sliding against itself and non-irradiated ultra-high molecular weight polyethylene sliding against itself. After 153.5 km of sliding, the non-irradiated ultra-high molecular weight polyethylene plates and pins showed mean wear factors under 10 N loads, or a nominal contact stress of 0.51 MPa, of 84.0 x 10(-6) mm3/N m for the plates and 81.3 x 10(-6) mm3/N m for the pins. Under 40 N loads, or a nominal contact stress of 2.04 MPa, the non-irradiated ultra-high molecular weight polyethylene pins sheared at 22.3 km. At the last measurement point prior to this failure, 19.1 km, wear factors of 158 x 10(-6) mm3/N m for the plates and 85.0 x 10(-6) mm3/N m for the pins had been measured. After 152.8 km. the irradiated ultra-high molecular weight polyethylene plates and pins showed mean wear factors under 10 N loads of 59.8 x 10(-6) mm3/N m for the plates and 31.1 x 10(-6) mm3/N m for the pins. In contrast, after 150.2 km, a mean wear factor of 0.72 x 10(-6) mm3/N m was found for the irradiated cross-linked polyethylene plates compared with 0.053 x 10(-6) mm3/N m for the irradiated cross-linked polyethylene pins.

A tunable pH-sensing system based on Ag nanoclusters capped by hyperbranched polyethyleneimine with different molecular weights.

PubMed

Qu, Fei; Zou, Xuan; Kong, Rongmei; You, Jinmao

2016-01-01

In this assay, a tunable pH sensing system was developed based on Ag nanoclusters (Ag NCs) capped by hyperbranched polyethyleneimine (PEI) with different molecular weights (abbreviated as Ag NC-PEIs). For instance, when the molecular weight of PEI was 600 or 1800, the fluorescence intensities of Ag NCs exhibited a linear fashion over the pH range 4.10-7.96; when the molecular weight of PEI was 25,000, the pH linear range was from 4.78 to 7.96; when the molecular weight of PEI was 70,000, the pH linear range was 6.09-8.95. According to the molecular weight of PEI 600/1800, 25,000, and 70,000, the color change point was pH 4.10-4.78, 5.33-6.09, and 6.09-6.80, respectively. Therefore, Ag NC-PEI 600 and 1800 were proper to acid conditions; Ag NC-PEI 25,000 was sensitive to weak acid media; while Ag NC-PEI 70,000 was adapted to neutral solution. The tunable and selective color change points brought an excellent feature of Ag NC-PEIs as visual pH indicators, which was flexible and applicable to a variety of environments. Besides, the ratios of absorbance at 415 nm and 268 nm of Ag NCs also showed linear relationships with pH variations. Therefore, there were three ways of this system for sensing pH values, including fluorescence assay, ultraviolet-visible measurement, and visual detection, suggesting that this tunable pH-sensing platform was more feasible, reliable, and accurate. Copyright © 2015 Elsevier B.V. All rights reserved.

Relationship between molecular weight, monosaccharide composition and immunobiologic activity of Astragalus polysaccharides.

PubMed

Jiang, Yiping; Qi, Xiaohui; Gao, Kai; Liu, Wenjun; Li, Na; Cheng, Ningbo; Ding, Gang; Huang, Wenzhe; Wang, Zhenzhong; Xiao, Wei

2016-10-01

Four Astragalus polysaccharides (APS1-APS4) were isolated from the water extract of Radix Astragali and purified through ethanol precipitation with 20 %, 40 %, 60 % and 80 % ethanol, respectively. The total sugar content was measured by sulfuric acid-phenol method. Their molecular weight was determined using high performance gel permeation chromatography (HPGPC) and their monosaccharide composition was analyzed by reversed-phase high performance liquid chromatography (HPLC) after pre-column derivatization. Then the immunobiologic activity of APS was evaluated by the experiment of spleen lymphocytes proliferation in vitro. The data suggested that precipitation by different concentration of ethanol will obtain different molecular weight APS, the higher concentration of ethanol the smaller molecular weight for APS. The molecular weights of four APS were 257.7 kDa, 40.1 kDa, 15.3 kDa and 3.2 kDa. Monosaccharide composition analysis indicated that APS1 consisted of glucose only, and APS2 all consisted of arabinose. APS3 consisted of rhamnose, glucose, galactose and arabinose and APS4 consisted of galactose and arabinose, in a molar ratio of 1:10.76:6.55:12 and 3.02:1. The result of immunobiologic activity assay showed that both APS2 and APS3 can effectively stimulate normal spleen lymphocyte proliferation in vitro. Apart from this, the effect of APS2 also showed dose dependent tendency from 6.25 μg/mL to 800 μg/mL. The result of this research indicated that Astragalus polysaccharides, which consist of arabinose and their molecular weight between 15.2 kDa to 40.1 kDa, neither too high nor too low, had significant immune activity.

Molecular weight determination and correlation analysis of Dalbergia sissoo polysaccharide with constituent oligosaccharides.

PubMed

Kumar, Vineet; Rana, Vikas; Soni, P L

2013-01-01

Mucilaginous polysaccharide extracted from Dalbergia sissoo Roxb. leaves has a number of medicinal applications. Molecular weight studies and correlation analysis of the structure of polysaccharide with oligosaccharides can be helpful for further utilisation, modification and structure-activity relationship for biological applications. To determine molecular weight of medicinally important polysaccharide. To establish an unequivocal correlation of the polysaccharide monosugars with constituting oligosaccharides and glucuronic acid content based on gas-liquid chromatography (GLC) with the spectrophotometric method. Complete and partial hydrolytic studies of pure polysaccharide yielded constituting monosugars and oligosaccharides. The ratio of sugars in polysaccharide and oligosaccharides was studied by preparation of alditol acetates and analysed using GLC. The uronic acid content was studied by GLC analysis and spectrophotometry. Molecular weight of the polysaccharide was determined using the viscometric method. Dalbergia sissoo leaves yielded 14.0% pure polysaccharide, containing 15.7% of glucuronic acid. Complete hydrolysis and GLC analysis of alditol acetate derivatives of reduced and unreduced monosugars indicated the presence of L-rhamnose, D-glucuronic acid, D-galactose and D-glucose in 1.00:1.00:2.00:2.33 molar ratios. Partial hydrolysis followed by monosugar analysis of oligosaccharides established the monosugar ratio in complete agreement with polysaccharide, thereby corroborating the sugar ratio. Similar uronic acid content was obtained by GLC and spectrophotometry. The polysaccharide had an average molecular weight of 1.5 × 10⁵  Da. The study has established an obvious correlation of the structure of polysaccharide with oligosaccharides, leading to unambiguous identification of monosaccharides, which normally is not studied conclusively while reporting the polysaccharide structure. The molecular weight of the polysaccharide was determined. Copyright © 2012 John Wiley & Sons, Ltd.

I. Dissociation free energies of drug-receptor systems via non-equilibrium alchemical simulations: a theoretical framework.

PubMed

Procacci, Piero

2016-06-01

In this contribution I critically revise the alchemical reversible approach in the context of the statistical mechanics theory of non-covalent bonding in drug-receptor systems. I show that most of the pitfalls and entanglements for the binding free energy evaluation in computer simulations are rooted in the equilibrium assumption that is implicit in the reversible method. These critical issues can be resolved by using a non-equilibrium variant of the alchemical method in molecular dynamics simulations, relying on the production of many independent trajectories with a continuous dynamical evolution of an externally driven alchemical coordinate, completing the decoupling of the ligand in a matter of a few tens of picoseconds rather than nanoseconds. The absolute binding free energy can be recovered from the annihilation work distributions by applying an unbiased unidirectional free energy estimate, on the assumption that any observed work distribution is given by a mixture of normal distributions, whose components are identical in either direction of the non-equilibrium process, with weights regulated by the Crooks theorem. I finally show that the inherent reliability and accuracy of the unidirectional estimate of the decoupling free energies, based on the production of a few hundreds of non-equilibrium independent sub-nanosecond unrestrained alchemical annihilation processes, is a direct consequence of the funnel-like shape of the free energy surface in molecular recognition. An application of the technique to a real drug-receptor system is presented in the companion paper.

Linear rheology and structure of molecular bottlebrushes with short side chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Barrón, Carlos R., E-mail: carlos.r.lopez-barron@exxonmobil.com; Brant, Patrick; Crowther, Donna J.

We investigate the microstructure and linear viscoelasticity of model molecular bottlebrushes (BBs) using rheological and small-angle X-ray and neutron scattering measurements. Our polymers have short atactic polypropylene (aPP) side chains of molecular weight ranging from 119 g/mol to 259 g/mol and narrow molecular weight distribution (M{sub w}/M{sub n} 1.02–1.05). The side chain molecular weights are a small fraction of the entanglement molecular weight of the corresponding linear polymer (M{sub e,aPP}= 7.05 kg/mol), and as such, they are unentangled. The morphology of the aPP BBs is characterized as semiflexible thick chains with small side chain interdigitation. Their dynamic master curves, obtained by time-temperature superposition,more » reveal two sequential relaxation processes corresponding to the segmental relaxation and the relaxation of the BB backbone. Due to the short length of the side chains, their fast relaxation could not be distinguished from the glassy relaxation. The fractional free volume is an increasing function of the side chain length (N{sub SC}). Therefore, the glassy behavior of these polymers as well as their molecular friction and dynamic properties are influenced by their N{sub SC} values. The apparent flow activation energies are a decreasing function of N{sub SC}, and their values explain the differences in zero-shear viscosity measured at different temperatures.« less

Molecular Factors Governing the Liquid and Glassy States Recrystallization of Celecoxib in Binary Mixtures with Excipients of Different Molecular Weights.

PubMed

Grzybowska, K; Chmiel, K; Knapik-Kowalczuk, J; Grzybowski, A; Jurkiewicz, K; Paluch, M

2017-04-03

Transformation of poorly water-soluble crystalline pharmaceuticals to the amorphous form is one of the most promising strategies to improve their oral bioavailability. Unfortunately, the amorphous drugs are usually thermodynamically unstable and may quickly return to their crystalline form. A very promising way to enhance the physical stability of amorphous drugs is to prepare amorphous compositions of APIs with certain excipients which can be characterized by significantly different molecular weights, such as polymers, acetate saccharides, and other APIs. By using different experimental techniques (broadband dielectric spectroscopy, differential scanning calorimetry, X-ray diffraction) we compare the effect of adding the large molecular weight polymer-polyvinylpyrrolidone (PVP K30)-and the small molecular weight excipient-octaacetylmaltose (acMAL)-on molecular dynamics as well as the tendency to recrystallization of the amorphous celecoxib (CEL) in the amorphous solid dispersions: CEL-PVP and CEL-acMAL. The physical stability investigations of the binary systems were performed in both the supercooled liquid and glassy states. We found that acMAL is a better inhibitor of recrystallization of amorphous CEL than PVP K30 deep in the glassy state (T < T g ). In contrast, PVP K30 is a better crystallization inhibitor of CEL than acMAL in the supercooled liquid state (at T > T g ). We discuss molecular factors governing the recrystallization of amorphous CEL in examined solid dispersions.

International Standards and Reference Materials for Quantitative Molecular Infectious Disease Testing

PubMed Central

Madej, Roberta M.; Davis, Jack; Holden, Marcia J.; Kwang, Stan; Labourier, Emmanuel; Schneider, George J.

2010-01-01

The utility of quantitative molecular diagnostics for patient management depends on the ability to relate patient results to prior results or to absolute values in clinical practice guidelines. To do this, those results need to be comparable across time and methods, either by producing the same value across methods and test versions or by using reliable and stable conversions. Universally available standards and reference materials specific to quantitative molecular technologies are critical to this process but are few in number. This review describes recent history in the establishment of international standards for nucleic acid test development, organizations involved in current efforts, and future issues and initiatives. PMID:20075208

A Herschel-SPIRE Survey of the MonR2 Giant Molecular Cloud

NASA Astrophysics Data System (ADS)

Pokhrel, Riwaj; Gutermuth, Robert; Ali, Babar; Megeath, Thomas; Pipher, Judith; Myers, Philip; Fischer, William; Henning, Thomas; Wolk, Scott; Allen, Lori; Tobin, John

2015-08-01

We present a new survey of the MonR2 giant molecular cloud with SPIRE on the Herschel Space Observatory. We cross-calibrated SPIRE data with Planck-HFI and accounted for its absolute offset and zero point correction. We fixed emissivity with the help of flux-error and flux ratio plots. As the best representation of cold dusty molecular clouds, we did greybody fits of the SEDs. We studied the nature of distribution of column densities above and below certain critical limit, followed by the mass and temperature distributions for different regions. We used dendrograms as a technique to study the hierarchical structures in the GMC.

A Herschel-SPIRE Survey of the MonR2 Giant Molecular Cloud

NASA Astrophysics Data System (ADS)

Pokhrel, Riwaj; Gutermuth, Robert A.; Ali, Babar; Megeath, S. Thomas; Pipher, Judith; Myers, Philip C.; Fischer, William J.; Henning, Thomas; Wolk, Scott J.; Allen, Lori; Tobin, John J.

2014-06-01

We present a new survey of the MonR2 giant molecular cloud with SPIRE on the Herschel Space Observatory. We cross-calibrated SPIRE data with Planck-HFI and accounted for its absolute offset and zero point correction. We fixed emissivity with the help of flux-error and flux ratio plots. As the best representation of cold dusty molecular clouds, we did greybody fits of the SEDs. We studied the nature of distribution of column densities above and below certain critical limit, followed by the mass and temperature distributions for different regions. We isolated the filaments and studied radial column density profile in this cloud.

In-Shoe Plantar Pressures and Ground Reaction Forces during Overweight Adults' Overground Walking

ERIC Educational Resources Information Center

de Castro, Marcelo P.; Abreu, Sofia C.; Sousa, Helena; Machado, Leandro; Santos, Rubim; Vilas-Boas, João Paulo

2014-01-01

Purpose: Because walking is highly recommended for prevention and treatment of obesity and some of its biomechanical aspects are not clearly understood for overweight people, we compared the absolute and normalized ground reaction forces (GRF), plantar pressures, and temporal parameters of normal-weight and overweight participants during…

What's in a Grade? Grading Policies and Practices in Principles of Economics

ERIC Educational Resources Information Center

Walstad, William B.; Miller, Laurie A.

2016-01-01

Survey results from a national sample of economics instructors describe the grading policies and practices in principles of economics courses. The survey results provide insights about absolute and relative grading systems used by instructors, the course components and their weights that determine grades, and the type of assessment items used for…

Preclinical Investigation of Lyophilized Platelet Preparations

DTIC Science & Technology

1994-10-31

Western blots of rehydrated platelet preparations. The AMAC antibody reacted strongly with a high molecular weight protein in the fresh platelet lysate , and...to a lesser degree with a protein of identical molecular weight in the rehydrated platelet lysate . The antibody to fibrinogen reacted strongly with

Modification of Alternan by Dextranase

USDA-ARS?s Scientific Manuscript database

Alternan is a unique glucan with a backbone structure of alternating alpha-(1=-6) and alpha-(1=-3) linkages. Previously, we isolated strains of Penicillium sp. that modify native, high molecular weight alternan in a novel bioconversion process to a lower molecular weight form with solution viscosit...

Effect of mahlep on molecular weight distribution of cookie flour gluten proteins

USDA-ARS?s Scientific Manuscript database

Size Exclusion-High performance Chromatography (SE-HPLC) has been extensively used in molecular weight distribution analysis of wheat proteins. In this study the protein analysis was conducted on different cookie dough blends with different percentages of some ingredients. The mean chromatography ...

Products of Chemistry: Alkanes: Abundant, Pervasive, Important, and Essential.

ERIC Educational Resources Information Center

Seymour, Raymond B.

1989-01-01

Discusses the history and commercialization of alkanes. Examines the nomenclature and uses of alkanes. Studies polymerization and several types of polyethylenes: low-density, high-density, low-molecular-weight, cross-linked, linear low-density, and ultrahigh-molecular-weight. Includes a glossary of hydrocarbon terms. (MVL)

TOXICOLOGICAL HIGHLIGHT (REDOX REDUX: A CLOSER LOOK AT CONCEPTAL LOW MOLECULAR WEIGHT THIOLS)

EPA Science Inventory

Glutathione (GSH) is present as the most abundant low molecular weight thiol (LMWT) in virtually all mitochondria-bearing eucaryotic cells, often at millimolar concentrations (Meister, 1988). Functions of GSH include roles in DNA and protein synthesis, maintenance of cell membra...

Intelligent Ensemble Forecasting System of Stock Market Fluctuations Based on Symetric and Asymetric Wavelet Functions

NASA Astrophysics Data System (ADS)

Lahmiri, Salim; Boukadoum, Mounir

2015-08-01

We present a new ensemble system for stock market returns prediction where continuous wavelet transform (CWT) is used to analyze return series and backpropagation neural networks (BPNNs) for processing CWT-based coefficients, determining the optimal ensemble weights, and providing final forecasts. Particle swarm optimization (PSO) is used for finding optimal weights and biases for each BPNN. To capture symmetry/asymmetry in the underlying data, three wavelet functions with different shapes are adopted. The proposed ensemble system was tested on three Asian stock markets: The Hang Seng, KOSPI, and Taiwan stock market data. Three statistical metrics were used to evaluate the forecasting accuracy; including, mean of absolute errors (MAE), root mean of squared errors (RMSE), and mean of absolute deviations (MADs). Experimental results showed that our proposed ensemble system outperformed the individual CWT-ANN models each with different wavelet function. In addition, the proposed ensemble system outperformed the conventional autoregressive moving average process. As a result, the proposed ensemble system is suitable to capture symmetry/asymmetry in financial data fluctuations for better prediction accuracy.

One milliarcsecond precision studies in the regions of Delta Equulei and Chi(sup 1) Orionis

NASA Technical Reports Server (NTRS)

Gatewood, George

1994-01-01

Trigonometric parallaxes for stars in the regions of the binary stars Delta Equulei (HR 8123) and Chi(sup l) Orionis (HR 2047) are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Equ is now +5.42 +/- 0.93 mas, corresponding to absolute magnitudes of 3.87 +/- 0.04 and 3.95 +/- 0.04 mag, respectively, for the primary and secondary. Using the Popper and Dworetsky orbit we find a photocentric semimajor axis of 2.9 +/- 0.8 mas and individual masses of 1.21 +/- 0.090 and 1.19 +/- 0.088 solar masses, respectively, for the primary and secondary components. The weighted mean trigonometric parallax of all studies of the binary star Chi(sup l) Ori is +111.0 +/- 0.92 mas, implying an absolute visual magnitude for the dominant GO V primary of 4.63 +/- 0.018 mag. The photocentric semimajor axis, derived from a fraction of the orbit, is 96.9 +/- 5.4 mas.

The Effect of Molecular Weight on the Composite Properties of Cured Phenylethynyl Terminated Imide Oligomers

NASA Technical Reports Server (NTRS)

Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.

1997-01-01

As part of a program to develop high temperature/high performance structural resins for aeronautical applications, imide oligomers containing terminal phenylethynyl groups with calculated number average molecular weights of 1250, 2500 and 5000 g/mol were prepared, characterized, and evaluated as adhesives and composite matrix resins. The goal of this work was to develop resin systems that are processable using conventional processing equipment into void free composites that exhibit high mechanical properties with long term high temperature durability, and are not affected by exposure to common aircraft fluids. The imide oligomers containing terminal phenylethynyl groups were fabricated into titanium adhesive specimens and IM-7 carbon fiber laminates under 0.1 - 1.4 MPa for 1 hr at 350-371 C. The lower molecular weight oligomers exhibited higher cured Tg, better processability, and better retention of mechanical properties at elevated temperature without significantly sacrificing toughness or damage tolerance than the higher molecular weight oligomer. The neat resin, adhesive and composite properties of the cured polymers will be presented.

Effects of grain development on formation of resistant starch in rice.

PubMed

Shu, Xiaoli; Sun, Jian; Wu, Dianxing

2014-12-01

Three rice mutants with different contents of resistant starch (RS) were selected to investigate the effects of grain filling process on the formation of resistant starch. During grain development, the content of RS was increased with grain maturation and showed negative correlations with the grain weight and the starch molecular weight (Mn, Mw) and a positive correlation with the distribution of molecular mass (polydispersity, Pd). The morphologies of starch granules in high-RS rice were almost uniform in single starch granules and exhibited different proliferation modes from common rice. The lower activities of ADP-glucose pyrophosphorylase and starch branching enzyme and the higher activity of starch synthase and starch de-branching enzyme observed in high-RS rice might be responsible for the formation of small irregular starch granules with large spaces between them. In addition, the lower molecular weight and the broad distribution of molecular weights lead to differences in the physiochemical properties of starch. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low molecular-weight phenols in Tannat wines made by alternative winemaking procedures.

PubMed

Favre, Guzmán; Peña-Neira, Álvaro; Baldi, Cecilia; Hernández, Natalia; Traverso, Sofía; Gil, Graciela; González-Neves, Gustavo

2014-09-01

Low molecular weight phenols of Tannat red wines produced by Traditional Maceration (TM), Prefermentative Cold Maceration (PCM), Maceration Enzyme (ENZ) and grape-Seed Tannins additions (ST), were performed and discussed. Alternatives to TM increased wine phenolic contents but unequally, ST increased mainly smaller flavans-3-ol, PCM anthocyanins and ENZ proanthocyanidins (up to 2250 mg/L). However low molecular weight flavan-3-ols remained below 9 mg/L in all wines, showing that there is not necessarily a correspondence between wine richness in total tannins and flavan-3-ols contents at low molecular weight. PCM wines had particularly high concentrations of tyrosol and tryptophol, yeast metabolism derived compounds. The use of grape-seed enological tannins did not increase grape seed derived phenolic compounds such as gallic acid. Caftaric acid was found in concentrations much higher than those reported in other grape varieties. Wine phenolic content and composition was considerably affected by the winemaking procedures tested. Copyright © 2014 Elsevier Ltd. All rights reserved.

Method for creating an aeronautic sound shield having gas distributors arranged on the engines, wings, and nose of an aircraft

NASA Technical Reports Server (NTRS)

Corda, Stephen (Inventor); Smith, Mark Stephen (Inventor); Myre, David Daniel (Inventor)

2008-01-01

The present invention blocks and/or attenuates the upstream travel of acoustic disturbances or sound waves from a flight vehicle or components of a flight vehicle traveling at subsonic speed using a local injection of a high molecular weight gas. Additional benefit may also be obtained by lowering the temperature of the gas. Preferably, the invention has a means of distributing the high molecular weight gas from the nose, wing, component, or other structure of the flight vehicle into the upstream or surrounding air flow. Two techniques for distribution are direct gas injection and sublimation of the high molecular weight solid material from the vehicle surface. The high molecular weight and low temperature of the gas significantly decreases the local speed of sound such that a localized region of supersonic flow and possibly shock waves are formed, preventing the upstream travel of sound waves from the flight vehicle.

Influence of molecular weight on in vitro immunostimulatory properties of instant coffee.

PubMed

Passos, Cláudia P; Cepeda, Márcio R; Ferreira, Sónia S; Nunes, Fernando M; Evtuguin, Dmitry V; Madureira, Pedro; Vilanova, Manuel; Coimbra, Manuel A

2014-10-15

Instant coffee was prepared and fractionated into higher (>100kDa), medium (5-10, 10-30, 30-100kDa) and lower (1-5, <1kDa) molecular weight fractions. Sugars and linkage composition characteristics of arabinogalactans and galactomannans were recovered in all fractions. Also, amino acid analysis performed after hydrolysis showed similar compositions in all fractions. On the contrary, free chlorogenic acids and caffeine were only detected in the lowest molecular weight fraction (<1kDa). A direct relationship between the melanoidins browning index and the molecular weight was observed. The fractions obtained were incubated in vitro with murine spleen lymphocytes in order to evaluate their possible immunostimulatory abilities. The surface expression of CD69 (early activation marker) on different lymphocyte sub-populations showed that the fraction with 1-5kDa was able to induce activation of B-lymphocytes. This was the only fraction to induce B-lymphocyte activation, since all the other fractions failed, even when higher concentrations were used. Copyright © 2014 Elsevier Ltd. All rights reserved.

Analysis of low molecular weight compounds by MALDI-FTICR-MS.

PubMed

Wang, Hao-Yang; Chu, Xu; Zhao, Zhi-Xiong; He, Xiao-Shuang; Guo, Yin-Long

2011-05-15

This review focuses on recent applications of matrix-assisted laser desorption ionization-Fourier-transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) in qualitative and quantitative analysis of low molecular weight compounds. The scope of the work includes amino acids, small peptides, mono and oligosaccharides, lipids, metabolic compounds, small molecule phytochemicals from medicinal herbs and even the volatile organic compounds from tobacco. We discuss both direct analysis and analysis following derivatization. In addition we review sample preparation strategies to reduce interferences in the low m/z range and to improve sensitivities by derivatization with charge tags. We also present coupling of head space techniques with MALDI-FTICR-MS. Furthermore, omics analyses based on MALDI-FTICR-MS were also discussed, including proteomics, metabolomics and lipidomics, as well as the relative MS imaging for bio-active low molecular weight compounds. Finally, we discussed the investigations on dissociation/rearrangement processes of low molecular weight compounds by MALDI-FTICR-MS. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of alkali lignins with different molecular weights from alkali pretreated rice straw hydrolyzate on enzymatic hydrolysis.

PubMed

Li, Yun; Qi, Benkun; Luo, Jianquan; Wan, Yinhua

2016-01-01

This study investigated the effect of alkali lignins with different molecular weights on enzymatic hydrolysis of lignocellulose. Different alkali lignins fractions, which were obtained from cascade ultrafiltration, were added into the dilute acid pretreated (DAP) and alkali pretreated (AP) rice straws respectively during enzymatic hydrolysis. The results showed that the addition of alkali lignins enhanced the hydrolysis and the enhancement for hydrolysis increased with increasing molecular weights of alkali lignins, with maximum enhancement being 28.69% for DAP and 20.05% for AP, respectively. The enhancement was partly attributed to the improved cellulase activity, and filter paper activity increased by 18.03% when adding lignin with highest molecular weight. It was found that the enhancement of enzymatic hydrolysis was correlated with the adsorption affinity of cellulase on alkali lignins, and the difference in surface charge and hydrophobicity of alkali lignins were responsible for the difference in affinity between cellulase and lignins. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of hyaluronic acid on the thermogelation and biocompatibility of its blends with methyl cellulose.

PubMed

Mayol, Laura; De Stefano, Daniela; De Falco, Francesca; Carnuccio, Rosa; Maiuri, Maria Chiara; De Rosa, Giuseppe

2014-11-04

Aim of this work was to investigate the influence of hyaluronic acid (HA) molecular weight on the thermogelation and biocompatibility of its blends with methyl cellulose in view of a possible application in drug delivery and/or wound healing. We found out that it was possible to obtain MC/HA blends showing a rheological behavior typical of a viscous solution at 20 °C and of a weak gel at 37 °C only when blending MC with low molecular weight HA. Moreover, the blends containing low molecular weight HA did not affect human foreskin fetal fibroblasts viability, proliferation and migration. On the contrary, the cell incubation with high molecular weight HA resulted in a marked and significant reduction of cell viability, compared to control cells. Finally, the optimized blends, in terms of rheological properties and biocompatibility, proved to be able to control and prolong bovine serum albumin release by a combined mechanism of platform dissolution and drug diffusion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Removal of Anabaena spiroides by potassium permanganate pre-oxidation: effect on photosynthetic capacity and molecular weight distribution.

PubMed

Qiao, Junlian; Zhang, Xiaodong; Lv, Liping

2017-11-01

Bench scale tests were conducted to investigate the effect of potassium permanganate pre-oxidation on the photosynthetic activity and molecular weight distribution of Anabaena spiroides. Different concentrations of potassium permanganate were added into the suspension of Anabaena spiroides, one of the dominant algae in water bloom, and after pre-oxidation of permanganate for 1 h, the results show that the removal rate significantly increases by 33.99~36.35% compared to direct coagulation. Then, the algal characteristics, including photosynthetic ability, the changes in extracellular organic matter three-dimensional fluorescence, and the distribution of molecular weight were conducted and the results show that along with increasing concentration of potassium permanganate, the photosynthetic ability of algae decreases, more extracellular organic matter is secreted, and large molecular weight matter (humic-like and fulvic-like substances) are generated. Therefore, this study demonstrates that potassium permanganate could be used in addressing the algae-rich water.

Impact of water extractable arabinoxylan from rye bran on the frozen steamed bread dough quality.

PubMed

Wang, Pei; Tao, Han; Jin, Zhengyu; Xu, Xueming

2016-06-01

Impact of water extractable arabinoxylan from rye bran on frozen steamed bread dough quality was investigated in terms of the bread characteristics, ice crystallization, yeast activity as well as the gluten molecular weight distribution and glutenin macropolymer content in the present study. Results showed that water extractable arabinoxylan significantly improved bread characteristics during the 60-day frozen storage. Less water was crystallized in the water extractable arabinoxylan dough during storage, which could explain the alleviated yeast activity loss. For all the frozen dough samples, more soluble high molecular weight (Mw ≈ 91,000-688,000) and low molecular weight (Mw ≈ 91,000-16,000) proteins were derived from glutenin macropolymer depolymerization. Nevertheless, water extractable arabinoxylan dough developed higher glutenin macropolymer content with lowered level of soluble low molecular weight proteins throughout the storage. This study suggested water extractable arabinoxylan from rye bran had great potential to be served as an effective frozen steamed bread dough improver. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultra-Fast RAFT-HDA Click Conjugation: An Efficient Route to High Molecular Weight Block Copolymers.

PubMed

Inglis, Andrew J; Stenzel, Martina H; Barner-Kowollik, Christopher

2009-11-02

The use of the reversible addition fragmentation chain transfer-hetero Diels-Alder (RAFT-HDA) click reaction for the modular construction of block copolymers is extended to the generation of high molecular weight materials. Cyclopentadienyl end-functionalized polystyrene (PS-Cp) prepared via both atom transfer radical polymerization (ATRP) and the RAFT process are conjugated to poly(isobornyl acrylate) (PiBoA) (also prepared via RAFT polymerization) to achieve well-defined block copolymers with molecular weights ranging from 34 000 to over 100 000 g · mol(-1) and with small polydispersities (PDI < 1.2). The conjugation reactions proceeded in a very rapid fashion (less than 10 min in the majority of cases) under ambient conditions of temperature and atmosphere. The present study demonstrates-for the first time-that RAFT-HDA click chemistry can provide access to high molecular weight block copolymers in a simple and straight-forward fashion. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of an ethanol precipitate from ileal digesta: evaluation of a method to determine mucin.

PubMed

Miner-Williams, Warren M; Moughan, Paul J; Fuller, Malcolm F

2013-11-06

The precipitation of mucin using high concentrations of ethanol has been used by many researchers while others have questioned the validity of the technique. In this study, analysis of an ethanol precipitate, from the soluble fraction of ileal digesta from pigs was undertaken using molecular weight profiling and polyacrylamide gel electrophoresis. The precipitate contained 201 mg·g⁻¹ protein, 87% of which had a molecular weight >20 KDa. Polyacrylamide gel electrophoresis stained with Coomassie blue and periodic acid/Schiff, revealed that most glycoprotein had a molecular weight between 37-100 KDa. The molecular weight of glycoprotein in the precipitate was therefore lower than that of intact mucin. These observations indicated that the glycoprotein in the ethanol precipitate was significantly degraded. The large amount of protein and carbohydrate in the supernatant from ethanol precipitation indicated that the precipitation of glycoprotein was incomplete. As a method for determining the concentration of mucin in digesta, ethanol precipitation is unreliable.

Determination of the presence of hyaluronic acid in preparations containing amino acids: the molecular weight characterization.

PubMed

Bellomaria, A; Nepravishta, R; Mazzanti, U; Marchetti, M; Piccioli, P; Paci, M

2014-10-15

Several pharmaceutical preparations contain hyaluronic acid in the presence of a large variety of low molecular weight charged molecules like amino acids. In these mixtures, it is particularly difficult to determine the concentration and the molecular weight of the hyaluronic acid fragments. In fact zwitterionic compounds in high concentration behave by masking the hyaluronic acid due to the electrostatic interactions between amino acids and hyaluronic acid. In such conditions the common colorimetric test of the hyaluronic acid determination appears ineffective and in the (1)H NMR spectra the peaks of the polymer disappear completely. By a simple separation procedure the presence of hyaluronic acid was revealed by the DMAB test and (1)H NMR while its average molecular weight in the final product was determined by DOSY NMR spectroscopy alone. The latter determination is very important due to the healthy effects of some sizes of this polymer's fragments. Copyright © 2014 Elsevier B.V. All rights reserved.

The Impact of the Polymer Chain Length on the Catalytic Activity of Poly(N-vinyl-2-pyrrolidone)-supported Gold Nanoclusters.

PubMed

Haesuwannakij, Setsiri; Kimura, Tetsunari; Furutani, Yuji; Okumura, Kazu; Kokubo, Ken; Sakata, Takao; Yasuda, Hidehiro; Yakiyama, Yumi; Sakurai, Hidehiro

2017-08-29

Poly(N-vinyl-2-pyrrolidone) (PVP) of varying molecular weight (M w  = 40-360 kDa) were employed to stabilize gold nanoclusters of varying size. The resulting Au:PVP clusters were subsequently used as catalysts for a kinetic study on the sized-dependent aerobic oxidation of 1-indanol, which was monitored by time-resolved in situ infrared spectroscopy. The obtained results suggest that the catalytic behaviour is intimately correlated to the size of the clusters, which in turn depends on the molecular weight of the PVPs. The highest catalytic activity was observed for clusters with a core size of ~7 nm, and the size of the cluster should increase with the molecular weight of the polymer in order to maintain optimal catalytic activity. Studies on the electronic and colloid structure of these clusters revealed that the negative charge density on the cluster surface also strongly depends on the molecular weight of the stabilizing polymers.

A new general method for the assessment of the molecular-weight distribution of polydisperse preparations. Its application to an intestinal epithelial glycoprotein and two dextran samples, and comparison with a monodisperse glycoprotein

PubMed Central

Gibbons, Richard A.; Dixon, Stephen N.; Pocock, David H.

1973-01-01

A specimen of intestinal glycoprotein isolated from the pig and two samples of dextran, all of which are polydisperse (that is, the preparations may be regarded as consisting of a continuous distribution of molecular weights), have been examined in the ultracentrifuge under meniscus-depletion conditions at equilibrium. They are compared with each other and with a glycoprotein from Cysticercus tenuicollis cyst fluid which is almost monodisperse. The quantity c−⅓ (c=concentration) is plotted against ξ (the reduced radius); this plot is linear when the molecular-weight distribution approximates to the `most probable', i.e. when Mn:Mw:Mz: M(z+1)....... is as 1:2:3:4: etc. The use of this plot, and related procedures, to evaluate qualitatively and semi-quantitatively molecular-weight distribution functions where they can be realistically approximated to Schulz distributions is discussed. The theoretical basis is given in an Appendix. PMID:4778265

Complex Forms of Soil Organic Phosphorus-A Major Component of Soil Phosphorus.

PubMed

McLaren, Timothy I; Smernik, Ronald J; McLaughlin, Mike J; McBeath, Therese M; Kirby, Jason K; Simpson, Richard J; Guppy, Christopher N; Doolette, Ashlea L; Richardson, Alan E

2015-11-17

Phosphorus (P) is an essential element for life, an innate constituent of soil organic matter, and a major anthropogenic input to terrestrial ecosystems. The supply of P to living organisms is strongly dependent on the dynamics of soil organic P. However, fluxes of P through soil organic matter remain unclear because only a minority (typically <30%) of soil organic P has been identified as recognizable biomolecules of low molecular weight (e.g., inositol hexakisphosphates). Here, we use (31)P nuclear magnetic resonance spectroscopy to determine the speciation of organic P in soil extracts fractionated into two molecular weight ranges. Speciation of organic P in the high molecular weight fraction (>10 kDa) was markedly different to that of the low molecular weight fraction (<10 kDa). The former was dominated by a broad peak, which is consistent with P bound by phosphomonoester linkages of supra-/macro-molecular structures, whereas the latter contained all of the sharp peaks that were present in unfractionated extracts, along with some broad signal. Overall, phosphomonoesters in supra-/macro-molecular structures were found to account for the majority (61% to 73%) of soil organic P across the five diverse soils. These soil phosphomonoesters will need to be integrated within current models of the inorganic-organic P cycle of soil-plant terrestrial ecosystems.

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

NASA Technical Reports Server (NTRS)

Hundley, N. H.; Patterson, W. J.

1985-01-01

Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.