Ratios R1 Research Articles

Determination of Physical Properties of some Legume Crops

Physical properties such as principal dimensions, surface area, projected area, volume, mass of 1000 seeds, true and bulk densities and porosity for faba bean and lentil seeds were measured and calculated at different levels of seed moisture contents. The obtained results showed that, the principal dimensions, geometric and arithmetic diameter, surface area, actual and calculated volume, sphericity, mass of 1000 seed and porosity of faba bean (pods and seeds) and lentil seeds generally increased linearly with the increasing of moisture content. For faba bean pods and seeds, shape parameters (flakiness ratio Fr and elongation ratio Er) increased with the increase of moisture content but aspect ratios R1 (W/L), R2 (L/Th) and R3 (W/Th) of faba bean pods and seeds decreased with the increasing of moisture content. The values of projected area for faba bean and lentil seeds were also increased with the increase of moisture content. On the other hand, the results also showed that, both of bulk and true densities decreased by increasing the moisture content. Mathematical relationships were also developed relating the obtained values of all physical properties with the change in seed moisture contents.

Characterization of the hepatosplenic and portal venous findings in patients with Proteus syndrome.

Proteus syndrome (PS) is a rare disorder caused by a mosaic AKT1 variant that comprises patchy overgrowth of tissues derived from all three germinal layers affecting multiple viscera. We sought to delineate the extent of hepatoportal manifestations in patients with PS. We identified patients with PS who had abdominal imaging from 1989 to 2015 in a natural history study. Imaging was characterized for evidence of focal findings in the liver, spleen, and portal vasculature and for organomegaly. Relevant clinical and laboratory data were compared among those with or without organomegaly. Abdominal imaging was available on 38 patients including 20 who had serial studies. Nine patients had focal hepatic lesions including vascular malformations (VMs). Focal splenic abnormalities were noted in seven patients. Patients without cutaneous VMs did not have visceral VMs. Nine patients had splenomegaly, 12 had portal vein dilation, and 4 had hepatomegaly. There was a weak correlation of portal vein dilation to spleen height ratio (r2 = 0.18, p < .05). On laboratory evaluation, hepatic function was normal but there was thrombocytopenia in those with splenomegaly; platelet counts were 179 ± 87K/μL compared to those with normal spleen size at 253 ± 57K/μL (p < .05). Overall, focal hepatosplenic abnormalities occurred in 11 of 38 (29%) patients with PS. Splenomegaly and portal venous dilation were both found in 8 of 38 (21%) patients; however, other than relative thrombocytopenia, there was no evidence of portal hypertension. Although the AKT1-E17K somatic variant is a suspected oncogene, there were no malignant lesions identified in this study.

Caractéristiques de la papille chez les sujets glaucomateux et normaux à l’OCT dans une population Noire Africaine

To determine the correlations between the size of the optic disc and glaucomatous defects in black Africans. Retrospective observational study. The study was conducted over a two-year period from November 2014 to October 2016, based on records of black Togolese patients who had undergone optic nerve head (ONH) OCT or ganglion cell complex OCT for assessment of glaucoma. The population was divided into 3 groups (I, II and III) depending on the size of the ONH. The ONH was considered small (Group I) if its size was less than the mean -1 SD, medium (Group II) if its size was within 1 SD of the mean, and large (Group III) if its size was greater than the mean+1 SD. Glaucomatous lesions were qualitatively identified on RNFL and or GCC. The ONH parameters were compared in the 3 groups. The Chi-square test was used to compare the percentages, and the t test to compare the means with statistical significance of 5%. The Pearson correlation coefficient (r2) was used to measure correlations. A total of 586 eyes of 298 patients were examined, 314 glaucomatous eyes and 272 healthy eyes. The mean age was 41.0±15.7 [6; 86] years. There were 159 men vs. 137 women, with a sex ratio of 1.2. The mean surface area of the ONH was 2.80±0.55mm2. Small ONH's (Group I) were defined as a surface area of less than 2.25mm2, medium-sized ONH's (Group II) as an area between 2.25 and 3.35mm2 and large ONH's (Group III) as an area greater than 3.35mm2. Small ONH's represented 14.7%, (86 eyes), medium-sized 68.6% (408 eyes) and large ONH's 16.8% (98 eyes). The mean surface area of the neuroretinal rim, cup, the cup-disc ratio and the RNFL thickness were statistically significant in the 3 groups. Similarly, all these parameters were significant in groups of glaucomatous or non-glaucomatous eyes, except for the surface area of the cup. The RNFL thickness was weakly correlated with the surface area of the ONH (r2=0.39), moderately correlated with the surface area of the neuroretinal rim (r2=0.57). The surface area of the ONH was strongly correlated with the surface area of the cup (r2=0.7). The neuroretinal rim surface area was strongly correlated with the cup-disc ratio (r2=0.66). The size of the ONH was correlated with the size of the cup, but it was not correlated to the surface area of the neuroretinal rim or the thickness of the nerve fibers. Analysis of the RNFL and GCC is essential for the diagnosis, especially in the case of large ONH's.

Highly Sensitive Diagnosis of Small Hepatocellular Carcinoma Using pH-Responsive Iron Oxide Nanocluster Assemblies.

Iron oxide nanoparticle (IONP)-based magnetic resonance imaging (MRI) contrast agents have been widely used for the diagnosis of hepatic lesions. However, current IONP-based liver-specific MRI contrast agents rely on single-phase contrast enhancement of the normal liver, which is not sensitive enough to detect early stage small hepatocellular carcinomas (HCCs). We herein report i-motif DNA-assisted pH-responsive iron oxide nanocluster assemblies (termed RIAs), which provide an inverse contrast enhancemt effect to improve the distinction between normal liver and target HCC tissues. The acidic pH of the tumor microenvironment triggers the disassembly of the RIAs, which leads to a drastic decrease in their relaxivity ratio ( r2/ r1), thus converting the RIAs from a T2 to T1 contrast agent. This inverse contrast enhancement of normal liver darkening and HCC brightening under T1 imaging mode was validated on an orthotopic HCC model. Our design provides a novel strategy for the exploitation of the next-generation intelligent MRI contrast agents.

Age–age correlations and early selection for growth traits in 40 half-sib families of Larix principis-rupprechtii

Larix principis-rupprechtii Mayr is a dominant species in coniferous forests of North China. However, early selection of L. principis-rupprechtii for growth traits is poorly characterised. To explore the optimal selection age for this species, heights (HT) and diameters at breast (DBH) of 40 half-sib families were measured at ages 3, 12, 22, and 28 years in a progeny test population established in the town of Kangjiahui, Shanxi Province. Age trends in heritability, age–age genetic correlations, and early selection efficiency for height and DBH were analysed. The individual heritability of these growth traits varied over time, and maximized at different ages (0.55 at age 12 for HT and 0.48 at age 28 for DBH). The age–age genetic correlations were always positive, and the majority were high (0.790–0.953) between the juvenile and mature ages for HT and DBH. For the same pairs of measurements, HT demonstrated higher age–age genetic correlations than DBH, and both age–age genetic correlation data sets were described well by the linear relationship with the logarithm of the age ratio (r2 > 0.90). The regression slope for DBH was lower than that for HT. Based on the early selection efficiency estimates, the optimal selection age could be as early as age 6 for DBH and 8–9 years for HT. The results of this study provide information that can be used to assist early selection practices in L. principis-rupprechtii improvement programs in Shanxi Province.

Iron Oxide Nanoparticles with Grafted Polymeric Analogue of Dimethyl Sulfoxide as Potential Magnetic Resonance Imaging Contrast Agents.

Novel water-dispersible hybrid iron oxide nanoparticles grafted with a polymeric analogue of dimethyl sulfoxide (DMSO) were prepared. Superparamagnetic iron oxide nanoparticles with immobilized atom-transfer radical polymerization (ATRP) initiators were prepared via an in situ method using 12-(2-bromoisobutyramido)dodecanoic acid as a surface ligand/initiator. The initiator-functionalized particles were employed in a surface-initiated initiator for continuous activator regeneration ATRP to graft poly(2-(methylsulfinyl)ethyl acrylate) (a polyacrylate analogue of DMSO) from the surface. The resulting hybrid nanoparticles showed a high magnetic relaxivity ratio ( r2/ r1) of 600 at 7 T in fetal bovine serum, and a good biocompatibility up to 1000 mg L-1.

Methacrylate copolymers and their composites with nano-CdS: synthesis, characterization, thermal behavior, and antimicrobial properties

Homo- and copolymers of 2-(N-phthalimido)ethyl methacrylate (NPEMA) and p-chlorophenyl methacrylate (PCPMA) were prepared in N,N-dimethyl formamide (DMF) solution at 70 °C using 2,2-azo-bisisobutyronitrile (AIBN) as initiator. The nano-CdS-doped polymer composite of NPEMA and PCPMA was prepared via in situ technique. The homo- and copolymers of NPEMA and PCPMA were characterized using FT-IR spectroscopy and gel permeation chromatography (GPC). The polymer nano composites were characterized using FT-IR spectroscopy, X-ray diffraction, and transmission electron microscopy. The reactivity ratios (r1 and r2) were obtained from the various linear graphical methods. The values of r1 (NPEMA) = 0.55 and r2 (PCPMA) = 1.30 were found from the same graphical methods. The copolymer microstructures were found from the mean sequence length, run number, and dyad fraction. Thermal behavior of polymers and polymer nano composites under nitrogen atmosphere was studied. The activation energies of neat polymers were varied in the range of 56–85 kJ/mol, while 28–56 kJ/mol energies were found for nano-CdS-doped polymer composites. The thermodynamic parameters of thermal degradation were also obtained. Kinetic and thermodynamic parameters were confirming the stability of the neat polymers than polymer nano composites. The polymers were assessed on different microorganisms for obtaining the antimicrobial properties. Overall, the polymers permit 10–52, 20–58, and 18–56% growth of bacteria, fungi, and yeast, respectively.

Can wetland plant functional groups be spectrally discriminated?

Plant functional traits (PFTs) underpin ecosystem processes and therefore ecosystem service provision. If PFTs are possible to detect and discriminate spectrally, then it may be possible to use remote sensing applications to map ecosystem processes or services within and across landscapes. As a first step towards this application, we explored whether functional groups of 22 dominant South African wetland species were spectrally separable based on their PFTs. We measured 23 biochemical and morphological PFTs in combination with spectra from 350 to 2349 nm using a handheld radiometer. First, we evaluated the possibility of accurately predicting morphological and biochemical PFTs from reflectance spectra using three approaches: spectrum averaging, redundancy analysis (RDA), and partial least squares regression (PLSR). Second, we established whether functional groups and species were spectrally distinguishable. We found seven PFTs to be important in at least two of the three approaches: four morphological and three biochemicals. Morphological traits that were important were leaf area (PLSR: r2 = 0.40, regression: r2 = 0.41), specific leaf area (r2 = 0.67), leaf mass (r2 = 0.43, r2 = 0.38), and leaf length/width ratio (r2 = 0.62). Biochemical traits that play a role in the structural composition of vegetation, like lignin content (r2 = 0.98, r2 = 0.54), concentration (r2 = 0.45) and cellulose content (r2 = 0.57, r2 = 0.49), were found to be important by at least two of the analyses. Three other traits were important in at least one of the analyses: total biomass (r2 = 0.56), leaf C/N ratio (r2 = 0.99), and cellulose concentration (r2 = 0.76). Redundancy analysis suggests that there is a large percentage (52%) of the spectrum not explained by the PFTs measured in this study. However, spectral discrimination of functional groups, and even species, appears promising, mostly in the ultraviolet A part of the spectrum. This has interesting applications for mapping PFTs using remote sensing techniques, and therefore for estimating related ecosystem processes and services.

Synthesis, characterization, microstructure determination, thermal studies of poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate)

ABSTRACTSynthesis of Poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) terpolymer using azobisisobutyronitrile in 1,4-dioxan is described. The polymers with different composition were synthesized and characterized using FTIR, 1HNMR, 13NMR, TGA and DSC techniques. The monomer-monomer interactions were studied using Finemann-Ross and Kelen-Tudos methods by calculating the reactivity ratio. The reactivity ratio r1 and r2 with respect to methyl methacrylate and N-vinylpyrrolidone-maleic anhydride complexomer are found to be 6.05 and 0.06 respectively. The study showed methyl methacrylate have higher reactivity than N-vinyl-2-pyrrolidone-maleic anhydride complex, i.e., the terpolymer contained methyl methacrylate in higher ratio. The thermal stability of poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) was 165°C and the glass transition temperature was found to increase from 153°C to 182°C as MMA concentration increase. The studies indicate the activity of the polymer to inhibit bacterial growth is very poor.

Comparison of the effect of daily versus bolus dose maternal vitamin D3 supplementation on the 24,25-dihydroxyvitamin D3 to 25-hydroxyvitamin D3 ratio.

Supplementing lactating mothers with high doses of vitamin D3 can adequately meet vitamin D requirements of the breastfed infant. We compared the effect of bolus versus daily vitamin D3 dosing in lactating mothers on vitamin D3 catabolism. We hypothesized that catabolism of 25(OH)D3 to 24,25(OH)2D3 would be greater in the bolus than in the daily dose group. Randomized controlled trial (clinicaltrials.govNCT01240265) in 40 lactating women. Subjects were randomized to receive vitamin D3 orally, either a single dose of 150,000IU or 5000IU daily for 28days. Vitamin D metabolites were measured in serum and breast milk at baseline, 1, 3, 7, 14 and 28days. Temporal changes in the serum 24,25(OH)2D3/25(OH)D3 ratio. The concentration of serum 24,25(OH)2D3 was directly related to that of 25(OH)D in both groups (r2=0.63; p<0.001). The mean (±SD) 24,25(OH)2D3/25(OH)D3 ratio remained lower at all time points than baseline values in the daily dose group (0.093±0.024, 0.084±0.025, 0.083±0.024, 0.080±0.020, 0.081±0.023, 0.083±0.018 at baseline, 1, 3, 7, 14, and 28days, respectively). In the single dose group, the increase in 24,25(OH)2D3 lagged behind that of 25(OH)D, but the 24,25(OH)2D3/25(OH)D3 values (0.098±0.032, 0.067±0.019, 0.081±0.017, 0.092±0.024, 0.103±0.020, 0.106±0.024, respectively) exceeded baseline values at 14 and 28days and were greater than the daily dose group at 14 and 28days (p=0.003). The 24,25(OH)2D3/25(OH)D3 ratio remained in the normal range with both dosing regimens. Greater breast milk vitamin D3 values in the single dose group were inversely associated with the 24,25(OH)2D3/25(OH)D3 ratio (r2=0.14, p<0.001), but not with daily dosing. After a 14-day lag, a single high dose of vitamin D led to greater production of 24,25(OH)2D3, presumably via induction of the 24-hydroxylase enzyme (CYP24A1), relative to the 25(OH)D3 value than did daily vitamin D supplementation, and this effect persisted for at least 28days after vitamin D administration. A daily dose of vitamin D may have more lasting effectiveness in increasing 25(OH)D3 with lesser diversion of 25(OH)D3 to 24,25(OH)2D3 than does larger bolus dosing.

Correlation of reactivity ratios, transition-metal salts and ester hydrolysis to radical polymerization of electron-deficient comonomers with 2-(N,N-dimethylamino)ethyl methacrylate as the inimer

The radical copolymerization of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA, M1) as the inimer and electron-deficient monomers (M2, including methyl methacrylate (MMA), acrylamide (AAm) and N,N-dimethylacrylamide (DMAAm)) with transition-metal salts (such as copperII and ironIII) as the oxidizing agent was correlated to their reactivity ratios (r1 and r2), counterions to transition-metal salts and ester hydrolysis of DMAEMA with an objective to obtain high-molecular weight (MW) branched polymers. As r1 ≈ r2 ≈ 1.0, primary chain initiation occurred even at high MMA conversion during CuSO4-DMAEMA redox-initiated radical polymerization of MMA, and thus the polymerization failed to form high-MW branched PMMA free from linear analogues. As r1 > 1.0 > r2, DMAEMA was preferentially converted into -DMAEMA- units during Fe(NO3)3-DMAEMA redox-initiated aqueous radical polymerization of AAm/DMAAm, but N,N-dimethylaminoethanol formed via hydrolysis led to lower-MW chains. Under optimal conditions with minimum hydrolysis, FeCl3-DMAEMA redox-initiated aqueous radical polymerization of DMAAm proceeded via redox-initiated reverse atom transfer radical polymerization (ATRP) generating DMAEMA-terminated chains with a carbon-chloride terminal. FeII-catalyzed self-condensing ATRP led to high-MW branched PDMAAm even under aerobic conditions.

Accurate density functional theory (DFT) protocol for screening and designing chain transfer and branching agents for LDPE systems

This work emphasizes the importance of considering multiple reaction pathways when estimating the rate parameters for free radical polymerization using DFT.

Analytical assessment of some characteristic ratios for s-wave superconductors

We evaluate some thermodynamic quantities and characteristic ratios that describe low- and high-temperature s-wave superconducting systems. Based on a set of fundamental equations derived within the conformal transformation method, a simple model is proposed and studied analytically. After including a one-parameter class of fluctuations in the density of states, the mathematical structure of the s-wave superconducting gap, the free energy difference, and the specific heat difference is found and discussed in an analytic manner. Both the zero-temperature limit T = 0 and the subcritical temperature range T ≲ Tc are discussed using the method of successive approximations. The equation for the ratio R1, relating the zero-temperature energy gap and the critical temperature, is formulated and solved numerically for various values of the model parameter. Other thermodynamic quantities are analyzed, including a characteristic ratio R2, quantifying the dynamics of the specific heat jump at the critical temperature. It is shown that the obtained model results coincide with experimental data for low-Tc superconductors. The prospect of application of the presented model in studies of high-Tc superconductors and other superconducting systems of the new generation is also discussed.

Two-strain epidemic model with two vaccinations

In this paper, we studied an epidemic model consisting of two strains with vaccine for each strain. The model consist of four equilibrium points; disease free equilibrium, endemic with respect to strain 1, endemic with respect to strain 2, and endemic with respect to both strains.The global stability analysis of the equilibrium points was carried out through the use of Lyapunov functions. Two basic reproduction ratios R1 and R2 are found, and we have shown that, if both are less than one, the disease dies out, if one of the ratios is less than one, epidemic occurs with respect to the other. It was also shown that, any strain with highest basic reproduction ratio will automatically outperform the other strain, thereby eliminating it. Condition for the existence of endemic equilibria was also given.Numerical simulations were carried out to support the analytic results and to show the effect of vaccine for strain 1 against strain 2 and the vaccine for strain 2 against strain 1. It is found that the population for infectives to strain 2 increases when vaccine for strain 1 is absent and vice versa.

Clinic-Based Validation of Cerebrospinal Fluid Biomarkers with Florbetapir PET for Diagnosis of Dementia.

Cerebrospinal fluid (CSF) biomarker studies have shown variable accuracy for diagnosis of Alzheimer's disease (AD); therefore, internal validation is recommended. To investigate the correlation between CSF biomarkers and cerebral 18-Florbetapir positron emission tomography (Amyloid-PET) and calculate their sensitivity and specificity to obtain the optimal clinical cut-off points to diagnose the etiology of cognitive impairment. We performed Amyloid-PET scans and CSF biomarker levels analyses in 68 subjects (50 with mild cognitive impairment, 11 with AD dementia, and 7 with non-AD dementia). Visual examination of Amyloid-PET scans was performed. CSF analyses were performed using standard sandwich ELISA. Amyloid-PET was positive in 36 subjects, negative in 26, and inconclusive in 6. Optimal clinical cut-off points for CSF markers were the following: amyloid-β 1-42 (Aβ42) = 629 pg/ml, total tau (t-tau) = 532 pg/ml, phosphorylated tau (p-tau) = 88 pg/ml, and t-tau/Aβ42 ratio = 0.58. T-tau/Aβ42 ratio showed the best sensitivity and specificity (92 and 84%, respectively). T-tau and p-tau CSF levels (r2 = 0.867) followed by the t-tau and t-tau/Aβ42 CSF ratio (r2 = 0.666) showed the strongest inter-marker correlation. Interestingly, subjects with inconclusive Amyloid-PET showed intermediate values for all CSF markers between negative and positive Amyloid-PET groups. CSF t-tau/Aβ42 ratio appears to be the most accurate AD CSF marker. The presence of intermediate values for CSF markers among the subjects with inconclusive Amyloid-PET suggests the presence of other dementias associated with AD pathology or intermediate phenotypes.

The Perception of Breathiness in the Voices of Pediatric Speakers

The perception of pediatric voice quality has been investigated using clinical protocols developed for adult voices and acoustic analyses designed to identify important physical parameters associated with normal and dysphonic pediatric voices. Laboratory investigations of adult dysphonia have included sophisticated methods, including a psychoacoustic approach that involves a single-variable matching task (SVMT), characterized by high inter- and intra-listener reliability, and analyses that include bio-inspired models of auditory perception that have provided valuable information regarding adult voice quality. To establish the utility of a psychoacoustic approach to the investigation of voice quality perception in the context of pediatric voices? Six listeners judged the breathiness of 20 synthetic vowel stimuli using an SVMT. To support comparisons with previous data, stimuli were modeled after four pediatric speakers and synthesized using Klatt with five parameter settings that influence the perception of breathiness. The population average breathiness judgments were modeled with acoustic measures of loudness ratio, pitch strength, and cepstral peak. Listeners reliably judged the perceived breathiness of pediatric voices, as with previous investigations of breathiness in adult dysphonic voices. Breathiness judgments were accurately modeled by loudness ratio (r2 = 0.93), pitch strength (r2 = 0.91), and cepstral peak (r2 = 0.82). Model accuracy was not affected significantly by including stimulus fundamental frequency and was slightly higher for pediatric than for adult voices. The SVMT proved robust for pediatric voices spanning a wide range of breathiness. The data indicate that this is a promising approach for future investigation of pediatric voice quality.

Thermal transistor behavior of a harmonic chain

Thermal transistor behavior of a harmonic chain with three heat reservoirs is explicitly analyzed. Temperature profile and heat currents of the rather general system are formulated and then heat currents for the simplest system are exactly calculated. The matrix connecting the three temperatures of the reservoirs and those of the particles comprises a stochastic matrix. The ratios R 1 and R 2 between heat currents, characterizing thermal signals can be expressed in terms of two external variables and two material parameters. It is shown that the ratios R 1 and R 2 can have wide range of real values. The thermal system shows a thermal transistor behavior such as the amplification of heat current by appropriately controlling the two variables and two parameters. We explicitly demonstrate the characteristics and mechanisms of thermal transistor with the simplest model.

Visualization of Bivariate Sequence Length–Chain Length Distribution in Free Radical Copolymerization

Copolymer properties and processability depend on copolymer microstructure, i.e., copolymer composition and monomer unit arrangements along the copolymer chains. To predict the ultimate properties of copolymers, one needs complete information on the length and position of sequences of each monomer type in every chain. A versatile kinetic Monte Carlo code is developed and applied for the simulation of typical free radical copolymerizations. The code allows explicit monitoring of every growing chain during the course and at the end of polymerization, can account for comonomer systems of any arbitrary reactivity ratios (r1 and r2) over the full range of monomer composition. Meanwhile, it eliminates the need for solving arrays of differential equations arising from deterministic modeling approaches. Since the code virtually synthesizes billions of copolymer molecules and keeps in storage information on each and every copolymer chain in the system, it allows for detailed statistical analysis. The simulator visualizes the bivariate sequence length–chain length distribution for typical copolymerization systems and examples with: r1 &lt; 1 and r2 &lt; 1; r1 &gt; 1 and r2 &lt; 1; (r1 × r2) = 1; and r1 = r2 = 1, and is also applied successfully to an experimental scenario described in the literature.

Raman spectroscopy of weathered shungites

Raman spectroscopy has proven to be a useful tool for the study of carbonaceous material (CM). This method is used to distinguish various types of CM and to study the evolution of Raman spectra characteristics of CM during metamorphic transformations. In the present study, we applied the Raman spectroscopy and electron diffraction methods to investigate the evolution of structural ordering of CM of shungite rocks, Karelia (Russia), during weathering. The studies of the CM structure evolution during weathering are rare and ambiguous. The Raman spectra of weathered shungites are characterized by increase of FWHM‐D1, that is accompanied by the decrease of intensity‐based ratio R1 = ID/IG and the change of the intensity of the bands in second‐order region. The Raman spectral data indicate that weathering results in the alteration of both intralayer and interlayer ordering of shungites, but there are some peculiarities for the shungites subjected to the various types of weathering. The present study establishes that the Raman spectra characteristics of weathered shungites can be used as the indicators of weathering for CM from various carbon‐bearing rocks. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Copolymerization of Partly Incompatible Monomers: An Insight from Computer Simulations

In this work we used dissipative particle dynamics simulations to study the copolymerization process in the presence of spatial heterogeneities caused by incompatibility between polymerizing monomers. The polymer sequence details as well as the resulting system spatial structure in the case if phase segregation occurs during the chain growth can be predicted using the method. We performed the model verification with the available literature data on styrene-acrylic acid copolymerization in the bulk and a very good agreement between experimental and simulated data for both chain average composition and triad fractions was observed. Next, we studied the system properties for a model symmetric reaction process with the reactivity ratios r1 = r2 = 0.5 at different compositions and Flory-Huggins parameters \c{hi}. We found that the system average copolymer "composition-feed" curve does not depend on the \c{hi}-value, but there are significant changes in the copolymer sequences caused by the density fluctuations. Finally, we investigated the formation of gradient copolymers during living styrene-acrylic acid copolymerization at a highly asymmetrical feed composition.