A computational study of the effect of structures of nanocomposites on their elastic properties is presented. The special program code for the automatic generation of 3D multiparticle unit cells ...with/without overlapping, effective interface layers around particles is developed for nanocomposite modeling. The generalized effective interface model, with two layers of different stiffnesses and the option of overlapping layers is developed here. The effects of the effective interface properties, particle sizes, particle shapes (spherical, cylindrical, ellipsoidal and disc-shaped) and volume fraction of nanoreinforcement on the mechanical properties of nanocomposites are studied in numerical experiments. The higher degree of particle clustering leads to lower Young’s modules of the nanocomposites. The shape of nanoparticles has a strong effect on the elastic properties of the nanocomposites. The most effective reinforcement is cylindrical one, followed by ellipsoids, discs, and last, spheres. Ideally random oriented and correlated microstructures lead to the same average Young moduli, yet, the standard deviation of Young modulus for correlated microstructure is nearly 4 times of that for fully random orientation case.
Time-series analyses have shown that ozone is associated with increased risk of premature mortality, but little is known about how O3 affects health at low concentrations. A critical scientific and ...policy question is whether a threshold level exists below which O3 does not adversely affect mortality. We developed and applied several statistical models to data on air pollution, weather, and mortality for 98 U.S. urban communities for the period 1987-2000 to estimate the exposure-response curve for tropospheric O3 and risk of mortality and to evaluate whether a "safe" threshold level exists. Methods included a linear approach and subset, threshold, and spline models. All results indicate that any threshold would exist at very low concentrations, far below current U.S. and international regulations and nearing background levels. For example, under a scenario in which the U.S. Environmental Protection Agency's 8-hr regulation is met every day in each community, there was still a 0.30% increase in mortality per 10-ppb increase in the average of the same and previous days' O3 levels (95% posterior interval, 0.15-0.45%). Our findings indicate that even low levels of tropospheric O3 are associated with increased risk of premature mortality. Interventions to further reduce O3 pollution would benefit public health, even in regions that meet current regulatory standards and guidelines.
► We developed an algorithm in ABAQUS to generate multiparticle unit cell models of nanocomposites. ► We studied the influence of microstructural parameters on elastic properties of nanocomposites. ► ...The effective interface model is improved by introducing a parameter of clustering effects. ► The nanoparticles with higher aspect ratios ensure higher stiffness than the round nanoparticles.
A computational numerical-analytical model of nano-reinforced polymer composites is developed taking into account the interface and particle clustering effects. The model was employed to analyze the interrelationships between microstructures and mechanical properties of nanocomposites. An improved effective interface model which is based on Mori–Tanaka approach and includes the nanoparticle geometry and clustering effects was developed. A program code for the automatic generation of two-dimensional multiparticle unit cell models of nanocomposites and finite element meshes on the basis of “grid method” algorithm was developed in the ABAQUS Scripting Interface. In the computational studies, it was observed that the elastic modulus increases with the increasing the aspect ratio of nanoparticles. The thickness and properties of effective interface layers and the shape and degree of particles clustering have strong influence on the mechanical properties of nanocomposite.
Background
Season of birth has been reported as a risk factor for food allergy, but the mechanisms by which it acts are unknown.
Methods
Two populations were studied: 5862 children from the National ...Health and Nutrition Examination Survey (NHANES) III and 1514 well‐characterized food allergic children from the Johns Hopkins Pediatric Allergy Clinic (JHPAC). Food allergy was defined as self‐report of an acute reaction to a food (NHANES), or as milk, egg, and peanut allergy. Logistic regression compared fall or nonfall birth between (i) food allergic and nonallergic subjects in NHANES, adjusted for ethnicity, age, income, and sex, and (ii) JHPAC subjects and the general Maryland population. For NHANES, stratification by ethnicity and for JHPAC, eczema were examined.
Results
Fall birth was more common among food allergic subjects in both NHANES (OR, 1.91; 95% CI, 1.31–2.77) and JHPAC/Maryland (OR, 1.31; 95% CI, 1.18–1.47). Ethnicity interacted with season (OR, 2.34; 95% CI, 1.43–3.82 for Caucasians; OR, 1.19; 95% CI, 0.77–1.86 for non‐Caucasians; P = 0.04 for interaction), as did eczema (OR, 1.47; 95% CI, 1.29–1.67 with eczema; OR, 1.00; 95% CI, 0.80–1.23 without eczema; P = 0.002 for interaction).
Conclusions
Fall birth is associated with increased risk of food allergy, and this risk is greatest among those most likely to have seasonal variation in vitamin D during infancy (Caucasians) and those at risk for skin barrier dysfunction (subjects with a history of eczema), suggesting that vitamin D and the skin barrier may be implicated in seasonal associations with food allergy.
Multicity time series studies of particulate matter and mortality and morbidity have provided evidence that daily variation in air pollution levels is associated with daily variation in mortality ...counts. These findings served as key epidemiological evidence for the recent review of the US national ambient air quality standards for particulate matter. As a result, methodological issues concerning time series analysis of the relationship between air pollution and health have attracted the attention of the scientific community and critics have raised concerns about the adequacy of current model formulations. Time series data on pollution and mortality are generally analysed by using log-linear, Poisson regression models for overdispersed counts with the daily number of deaths as outcome, the (possibly lagged) daily level of pollution as a linear predictor and smooth functions of weather variables and calendar time used to adjust for time-varying confounders. Investigators around the world have used different approaches to adjust for confounding, making it difficult to compare results across studies. To date, the statistical properties of these different approaches have not been comprehensively compared. To address these issues, we quantify and characterize model uncertainty and model choice in adjusting for seasonal and long-term trends in time series models of air pollution and mortality. First, we conduct a simulation study to compare and describe the properties of statistical methods that are commonly used for confounding adjustment. We generate data under several confounding scenarios and systematically compare the performance of the various methods with respect to the mean-squared error of the estimated air pollution coefficient. We find that the bias in the estimates generally decreases with more aggressive smoothing and that model selection methods which optimize prediction may not be suitable for obtaining an estimate with small bias. Second, we apply and compare the modelling approaches with the National Morbidity, Mortality, and Air Pollution Study database which comprises daily time series of several pollutants, weather variables and mortality counts covering the period 1987-2000 for the largest 100 cities in the USA. When applying these approaches to adjusting for seasonal and long-term trends we find that the Study's estimates for the national average effect of PM10at lag 1 on mortality vary over approximately a twofold range, with 95% posterior intervals always excluding zero risk.
The optimal strategy of maintenance therapy for patients with mCRC is controversial. This study was to evaluate the efficacy and safety of maintenance therapy with capecitabine versus observation ...following inductive chemotherapy in patients with metastatic colorectal cancer.
In this randomized, open-label, multicenter, phase III trial, patients who received 18–24 weeks of induction chemotherapy with XELOX or FOLFOX and achieved disease control were randomly assigned centrally (1:1) to receive maintenance therapy of capecitabine or only observation until disease progression. The primary end point was progression-free survival (PFS) from randomization; the secondary end points included overall survival (OS), PFS from induction treatment (PFS2) and safety. Analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT02027363.
Between 30 July 2010 and 15 September 2013, 274 patients were enrolled in the study from 11 sites in China and randomly assigned to maintenance group (n = 136) or observation group (n = 138). Clinicopathological characteristics were balanced in two groups. The median follow-up time from randomization was 29.0 months interquartile range (IQR) 21–36 months. The primary end point of PFS was statistically significantly longer in capecitabine maintenance group than in observation group {6.43 95% confidence interval (CI) 5.26–7.71 versus 3.43 (2.83–4.16) months, HR 0.54 (0.42–0.70), P < 0.001}. The median OS of capecitabine maintenance group was longer than that of observation group, but not statistically significant 25.63 (22.46–27.80) versus 23.30 (19.68–26.92) months; HR 0.85 (0.64–1.11), P = 0.2247. Similar safety profiles were observed in both arms. The most common grade 3 or 4 toxicities in capecitabine maintenance group versus observation group were neutropenia, hand–foot syndrome, and mucositis.
Maintenance therapy with a single agent of capecitabine can be considered an appropriate option following the induction of XELOX or FOLFOX in mCRC patients with acceptable toxicities.
NCT02027363.
To balance the utilization of rare earth (RE) resource and develop Ce-based permanent magnets with high performance/cost ratio, the role of La substitution in the melt-spun (Ce
1−
x
La
x
)
y
Fe
14
B ...(
x
= 0–0.4, and 0.5;
y
= 2–4) alloys has been investigated. It has been confirmed that the hard magnetic properties of Ce-based magnets can be effectively enhanced by partial substitution of La. The maximum (
BH
)
max
of (Ce,La)–Fe–B alloys can be obtained at a Ce:La atomic ratio of 7:3. The lattice parameters and Curie temperature of the hard magnetic (Ce/La)
2
Fe
14
B phase increase linearly with increasing La content. Three different alloy systems with
y
= 2, 2.5 and 3 show similar behavior of magnetic properties dependences on La. In the RE-rich compositions, La substitution for Ce can effectively inhibit the precipitation of the CeFe
2
phase. A solid solution, Ce(La) phase with a space group of Fm-3m, appears in the (Ce
0.7
La
0.3
)
y
Fe
14
B alloys with
y
≥ 3.5. A good combination of magnetic properties with
H
cj
= 345 kA/m,
J
5T
= 1.03 T,
J
r
= 0.60 T, and (
BH
)
max
= 6.3 MGOe is obtained in (Ce
0.7
La
0.3
)
2.5
Fe
14
B alloy. In addition, 30 at.% La substitution for Ce can significantly refine the grains, resulting in the enhancement of exchange coupling interaction. The present finding is beneficial for designing new and low-cost magnetic materials.
The aberrant activation of tyrosine kinases represents an important oncogenic mechanism, and yet the majority of such events remain undiscovered. Here we describe a bead-based method for detecting ...phosphorylation of both wild-type and mutant tyrosine kinases in a multiplexed, high-throughput and low-cost manner. With the aim of establishing a tyrosine kinase-activation catalog, we used this method to profile 130 human cancer lines. Follow-up experiments on the finding that SRC is frequently phosphorylated in glioblastoma cell lines showed that SRC is also activated in primary glioblastoma patient samples and that the SRC inhibitor dasatinib (Sprycel) inhibits viability and cell migration in vitro and tumor growth in vivo. Testing of dasatinib-resistant tyrosine kinase alleles confirmed that SRC is indeed the relevant target of dasatinib, which inhibits many tyrosine kinases. These studies establish the feasibility of tyrosine kinome-wide phosphorylation profiling and point to SRC as a possible therapeutic target in glioblastoma.
The influence of the pre-annealing on Mn partitioning behavior was investigated for hot-rolled Fe–0.095C–6.93Mn–1Al–1.07Si medium-Mn-TRIP steel. Unlike the fully martensitic microstructure before ...one-step intercritical annealing, a mixed microstructure of preexisting ferrite, austenite and martensite was obtained prior to the final annealing in two-step annealed steels. The microstructure observation showed that lath-type austenite existed in the martensitic matrix, blocky and granular austenite occurred at the boundaries of primary austenite/preexisting ferrite or martensite/preexisting ferrite after two-step annealing. Based on the numerical simulations of the second annealing process, the preexisting austenite further grew rapidly without nucleation, while some secondary austenite nucleated at the martensitic lath boundaries and then grew into martensite at a relatively sluggish rate. Moreover, significant Mn partitioning with a special “bimodal distribution” feature was detected in the preexisting austenite, resulting in the formation of martensite/austenite constituents. Compared with the case of one-step heat treatment, an excellent combination of strength (1145 MPa) and ductility (39%) was obtained in the steel with pre-annealing, which was ascribed to the occurrence of martensite/austenite islands and positive TRIP effect over a wide strain range.
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