Epidemiologic studies show a dose-response relationship between cigarettes per day and health outcomes such as heart and lung disease, and health outcomes are related to some biomarkers of tobacco exposure. The objective of this study was to examine the relationships between cigarettes per day and levels of selected biomarkers of tobacco toxin exposure: carbon monoxide (CO), metabolites of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and polycyclic aromatic hydrocarbons [total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and 1-hydroxypyrene (1-HOP), respectively], and total cotinine (cotinine plus cotinine-N-glucuronide). We did a cross-sectional analysis of merged data from (a) two clinical trials and (b) two cohorts of light smokers (total n = 400). The mean age of participants was 50.4 years and the range of cigarette consumption was 1 to 100/d; however, few subjects smoked >45 cigarettes/d (n = 12).Results show that levels of the biomarkers CO, total NNAL, and total cotinine increase with an increase in the number of cigarettes smoked per day, but not in a linear fashion. 1-HOP is a less discriminating biomarker as levels are relatively stable regardless of the number of cigarettes smoked per day. There is considerable variability in toxin measurement, especially at high levels of smoking. There was a significant correlation between cigarettes per day and total NNAL, 1-HOP, total cotinine, and CO. Total NNAL was highly significantly correlated with total cotinine and CO and also significantly correlated with 1-HOP. These findings suggest that the number of cigarettes smoked per day is not necessarily a reliable measure of toxin exposure and may underestimate tobacco toxin exposure at low levels of smoking or overestimate exposure at high levels of smoking. (Cancer Epidemiol

A novel flame retardant (FR) DOPO-PEPA, which was synthesized via Atherton–Todd reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]­octane (PEPA), was used as an additive-type FR in epoxy resin (EP). The results of the limiting oxygen index (LOI), vertical burning test, and cone calorimeter test indicated that the flame retardance of FR-EP composites is dependent on the chemical structure of phosphorus-based FRs. EP/DOPO-PEPA shows pretty good mechanical properties and a relatively high degree of cross-linking. Furthermore, the synergy as DOPO-PEPA was more efficient than that of DOPO or PEPA alone to flame retardant EP. When the FR additives were 9.1%, the EP/DOPO-PEPA acquired a LOI value of 35%, UL94 V-0 rating, and the lowest peak of heat release rate (PHRR) of 595 kW/m2. Furthermore, its continuous and firm char residue layer also reinforced this kind of action.

No abstract

With the rapidly increasing development of portable device hardware and flexible electronics, ultrathin electromagnetic interference (EMI) shielding films with a combination of high flexibility and excellent mechanical properties are noticeably required. In addition to minimizing the electromagnetic wave pollution problem, the fire hazards caused by accidental electrical leakage or aging are also a cause of extensive concern. Inspired by nacre and sandwich structure, herein, we fabricated for the first time an electrical insulating sandwich-structured film based on Ca ion cross-linked sodium alginate (SA)–montmorillonite (MMT) and Ti3C2T x MXene through a step-by-step vacuum-assisted filtration process. This novel design strategy not only maintains the inner EMI shielding network but also can act as an excellent fire-resistant barrier to protect the electronic device in case of accidental fire. Compared with the pure Ti3C2T x layer, such kind of sandwich film can effectively maintain the EMI shielding performance (50.01 dB), dramatically enhance the mechanical properties (84.4 MPa), and exhibit excellent fire-resistant performance. Especially, compared with the film composed of mixture, the EMI shielding effectiveness value is only 55% that of sandwich films. Besides, it functions well under long-term heat aging test at 80 °C. Therefore, this unique design provides a novel EMI material strategy to facilitate its future applications in flexible electronics.

In this work, a highly efficient flame retardant and electromagnetic interference (EMI) shielding coating on cotton fabric was fabricated by a simple solution impregnation and dipcoating method, which involved three layers of polyacetimidate (PEI), ammonium polyphosphate (APP), and Ti 3 C 2 T x . When exposed directly to flame, the PEI/APP coating lead to a char layer resulting in self-extinguishing performance. Particularly, the cotton fabric coated by increasing amounts of Ti 3 C 2 T x gradually achieved EMI shielding performance. When the Ti 3 C 2 T x sheets content was 5.2 mg/cm 2 , a high electrical conductivity of 670.3 S•m −1 and a EMI shielding effectiveness of 31.04 dB were achieved in the X-band with an absorption-dominated mechanism. Besides, such modified cotton fabric also has the potential to be used as an electrical heating material. The temperature could even reach up to about 64.3 °C under an applied voltage of just 4 V. Therefore, this work provided a feasible idea for preparing multifunctional fabrics.

A facile and novel approach is provided to improve the dispersion of large-size reduced graphene oxide (LRGO) in a polymer matrix through attachment on the surface of ammonium polyphosphate (APP) in the medium of (3-aminopropyl) triethoxysilane (APTS). Here, a series of LRGO-wrapped APP (named LRAPP) were first prepared and successfully characterized and then blended into thermoplastic polyurethane (TPU). The introduction of LRGO increased the interfacial adhesion between the APP and polymer, thus achieving remarkable enhancement in mechanical and flame retardant properties. Especially TPU/LRAPP1, where APP is encapsulated by 1% LRGO, can obtain a huge increase in tensile strength and elongation at break (189.7% and 24.6%, respectively) compared to those of TPU/APP. In addition, LRAPP0.5 encapsulated by only 0.5% of LRGO could effectively restrain the melt−dripping phenomenon in TPU composites and acquired the lowest peak heat release rate value of 170.6 kW/m 2 . This novel strategy aims to broaden extensive application of large-size graphene.

This study is the first to report that triploids and tetraploids have been successfully produced through embryo sac and zygotic embryo chromosome doubling with high temperatures in P. simonii Carr. and its hybrid. A new synthetic polyploid induced by hybridization with unreduced gametes and heterozygotic embryo chromosome doubling can effectively combine polyploidy and heterosis, which can provide two major breeding advantages. In Populus, successfully creating and cultivating new polyploid varieties have economic and ecological production value. This was the first successful study in which embryo sac and zygotic embryo chromosome doubling was induced using high temperatures to produce triploids and tetraploids in Populus simonii Carr. and its hybrid, P. simonii × P. nigra var. Italica, of Populus sect. Tacamahaca. The relationship between flower bud morphological characteristics (time after pollination) and female meiotic stage (embryo sac and zygotic embryo development) was established to guide the induction treatment period. In the resulting progeny, 37 triploids and 12 tetraploids were obtained and identified using flow cytometry. The optimal temperatures for embryo sac and zygotic embryo chromosome doubling were 38 and 41 °C, respectively. Cytogenetic analysis revealed that 66-72 h after pollination (HAP), a period characterized by a high proportion of one-nucleate and two-nucleate embryo sacs, was the optimal period for embryo sac chromosome doubling. For zygotic embryo chromosome doubling, 168 HAP was the optimal induction period, as there was a high proportion of two-cell and four-cell proembryos. The results indicate that inducing embryo sac and zygotic embryo chromosome doubling is an ideal method for producing polyploids. The methods for inducing polyploids and for evaluating ploidy and offspring with different ploidies and heterozygosity in this study will be useful for genetic research and Populus breeding programmes.

This paper reports experimental results of the transverse impact behaviors of four-step three-dimension carbon/epoxy rectangular braided composite. We employed Split Hopkinson Pressure Bar apparatus to test the transverse impact behaviors. The impact load-displacement curves and impact damages of the braided composite were recorded to analyze the energy absorptions and the impact damage mechanisms. The quasi-static indentation tests and drop-weight impact tests were also performed to compare with those in transverse impact tests. It was found that the failure area and energy absorption is increased as the increase of impact velocity and the failure area is in a saw tooth shape owing to the breakage of the braided fiber tows.