[Early results of fenestrated endovascular aortic repair for the treatment of patients with thoracoabdominal pathologies]

Objective: To evaluate the early results of fenestrated endovascular aortic repair (FEVAR) using physician-modified stent grafts (PMSGs) for the treatment of patients with thoracoabdominal pathologies. Methods: Nineteen consecutive patients who underwent FEVAR using PMSGs between April 2012 and September 2017 were retrospectively reviewed. The modality of FEVAR technique was assessed, perioperative clinical data was recorded and the early results were evaluated. Results: Indications were thoracoabdominal aortic pathologies, including juxtarenal abdominal aortic aneurysm (JAAA) (n=12), chronic thoracoabdominal aortic dissection with aneurysmal dilatation (n=3), thoracoabdominal aortic aneurysm (TAAA) (n=1), infrarenal AAA with an accessory renal artery in the segment of the aneurysmal neck (n=2) and type Ⅰ endoleak after EVAR for AAA(n=1). Nineteen fenestrated stent grafts were deployed , including custom-made Cook Zenith fenestrated stent graft(n=1), home-made Cook Zenith TX2 fenestrated stent graft(n=6), home-made Cook Zenith TFFB fenestrated stent graft(n=9), home-made Cook Zenith Cuff fenestrated stent graft(n=2), home-made Gore C3 fenestrated stent graft(n=1). Mean duration for stent graft modification was 110 (90-140) min. Mean operative time was 268.0 (59.0-334.0) min, and fluoroscopy time was 66.0 (15.0-175.0) min. There were a total of 50 target vessels, of which 45 (95%) were stented. Bare metal stents were used in 28 vessels, and covered stents were used in 17 vessels. Technical success rate was 100%. No intraoperative target vessel loss was observed. Perioperative mortality was 5.3% (1/19). Endoleaks were persisted even after ballooning in five patients. A small type Ⅰ proximal endoleak and type Ⅲ endoleak were found in 2 and 1 patients, respectively. Type Ⅲ endoleak combined with type Ⅱ endoleak were observed in 2 patients. All the endoleaks were accepted and needed watching. In two patients, iliofemoral artery problems were resolved after local endarterectomy and stenting. Two patients presented renal deterioration postoperatively and recovered after the conservative therapy. Median length of stay was 6.6 (2.0-12.0)d. No early reintervention (<30 days) was performed. The mean duration of follow-up was 11.2 (2.0-41.0) months. One patient died 6 months after FEVAR due to advanced renal carcinoma. All target vessels remained patent except for one accessory artery occlusion. Conclusion: FEVAR using PMSGs may be a viable alternative for high-risk patients with thoracoabdominal pathologies.

[Wear intensity and surface roughness of microhybrid composite and ceramic occlusal veneers on premolars after the thermocycling and cyclic mechanical loading tests]

OBJECTIVE

To evaluate the wear intensity and surface roughness of occlusal veneers on premolars made of microhybrid composite resin or two kinds of ceramics in vitro after the thermocycling and cyclic mechanical loading tests.

METHODS

In the study,24 fresh extracted human premolars without root canal treatment were prepared (cusps reduction of 1.5 mm in thickness to simulate middle to severe tooth wear, the inclinations of cusps were 20°). The prepared teeth were restored with occlusal veneers made of three different materials: microhybrid composite, heat-pressed lithium disilicate ceramic and computer-aided design/computer-aided manufacturing (CAD/CAM) lithium disilicate ceramic in the thickness of 1.5 mm. The occlusal veneers were cemented with resin cement. The specimens were fatigued using the thermocycling and cyclic mechanical loading tests after being stored in water for 72 h. The wear of specimens was measured using gypsum replicas and 3D laser scanner before and after the thermocycling and cyclic mechanical loading tests and the mean lost distance (mm) was used to indicate the level of wear. The surfaces of occlusal contact area were observed and the surface roughness was recorded using 3D laser scanning confocal microscope before and after the fatigue test. Differences between the groups were compared using ONE-way ANOVA(P<0.05).

RESULTS

All the specimens successfully survived after the thermocycling and cyclic mechanical loading tests. The mean wear of microhybrid composite group, heat-pressed lithium disilicate ceramic group, and CAD/CAM lithium disilicate ceramic group was (-0.13±0.03) mm, (-0.05±0.01) mm and (-0.05±0.01) mm, the wear of microhybrid composite was significantly higher than the two ceramic groups(P<0.001).The mean surface roughness(Ra)before the fatigue test was(1.24±0.20) μm, (0.75±0.09) μm, (0.73±0.14) μm and it became (1.81±0.24) μm, (1.53±0.26) μm and (1.77±0.23) μm after the test . Before the fatigue test, the surface roughness of microhybrid composite was significantly higher than the two ceramic groups(P<0.001) and after the test, the surface roughness of heat-pressed lithium disilicate ceramic was significantly lower than microhybrid composite(P=0.005) and CAD/CAM lithium disilicate ceramic (P=0.010).

CONCLUSION

From the view of wear speed, microhybrid composite was significantly higher than the two kinds of ceramics, but it was similar to enamel when the opposing tooth was natural. The surface roughness before the themocycling and cyclic mechanical loading test of microhybrid composite was significantly higher than that of the two ceramic groups. After the test, the surface roughness of heat-pressed ceramic was significantly lower than that of the other two groups. From the view of surface roughness, heat-pressed ceramic has more advantage.

[Clinical efficacy of clear aligners in treating bimaxillary protrusion]

Objective: To evaluate the efficiency of clear aligners in treating bimaxillary protrusion patients with first premolar extractions. Methods: Eleven patients with bimaxillary protrusion were selected in this study. All of them were treated by using clear aligners with four first premolar extractions and need maximal anchorage. Cephalometric analysis was carried out before and after treatment. Results: Cephalometric analysis results showed that significant changes in teeth and profile could be detected after clear aligner treatment and no change could be found in skeletal pattern. Upper and lower anterior teeth were retracted. The control of anterior torque and posterior anchorage were effective. The soft tissue analysis showed that position of upper and lower lip was significantly changed which improve the profile of patients. After treatment, the distance of U1 to NA and L1 to NB reduced by (5.19±4.12) mm and (4.53±1.20) mm, respectively. The differences were statistically significant (P<0.01). Conclusions: Bimaxillary protrusion patients who needed premolar extractions and maximal anchorage could be treated with clear aligners.

[A cohort study on association between the first trimester phthalates exposure and fasting blood glucose level in the third trimester]

Objective: To examine the association between the phthalate exposure in the first trimester and fasting blood glucose level or gestational diabetes mellitus (GDM) in the third trimester in pregnant women. Methods: A total of 3 474 pregnant women, receiving their prenatal examination in Ma' anshan Maternal and Child Health-Care Hospital of Anhui province, were selected from May 2013 to September 2014. Questionnaires were used to collect the information about their socio-demographic characteristics, clinical characteristics and GDM diagnostic results in the first, second and third trimesters. Urine samples and fasting venous blood samples were collected. Concentrations of 7 kinds of phthalate metabolites in urine samples were detected by solid phase extraction-high performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS/MS), and multiple linear regression model was used for statistical analyses. Logistic regression analysis on the risk of the first trimester phthalate exposure for GDM in the third trimester was conducted. Results: The prevalence of GDM in this study was 12.8%, monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEHHP) exposure levels were positively correlated with the fasting blood glucose level in the third trimester (P<0.05), but mono-(2-ethylhexyl) phthalate (MEHP) and mono-(2-ethyl-5-hydroxylhexyl) phthalate (MEOHP) exposure levels were negatively correlated with the fasting blood glucose level in the third trimester (P<0.05). Stratified analysis showed a positive correlation between MEHHP exposure and the third trimester fasting blood glucose level in both normal group and GDM group. However, MMP, MEP, MBP, MBzP, MEHP and MEOHP exposure levels had influences on the third trimester fasting blood glucose level in normal group but not in GDM group. MMP and MBP exposure might increase the risk of GDM, but MEOHP exposure might reduce the risk of GDM. Conclusion: The phthalate exposure in the first trimester might be associated with the fasting blood glucose level in the third trimester, MMP, MEP, MBP, MBzP and MEHHP concentrations were positively associated with the third trimester blood glucose level, MEHP and MEOHP concentrations were negatively associated with the third trimester blood glucose level. Moreover, the effects of different kinds of phthalates might be different.

Establishment and application of molecular ID in the main inbred lines of Chinese cabbage

Chinese cabbage is an important cruciferous vegetable in China. The differences in the morphology and other characteristics of the different varieties of Chinese cabbage are generally caused by their different genes. Using the simple sequence repeat (SSR) DNA molecular markers is an effective way to identify different genotypes. The identification of a genetic relationship is a key point in the breeding process, and it plays an important role in guiding parent selection and breeding of high-yield varieties. Moreover, the establishment of genomic fingerprints is significant for plant variety protection. Three to five SSR sites were selected from each of the 10 Chinese cabbage chromosomes on the basis of the abundance of SSR loci on them. According to the differences in the SSR polymorphic bands, a genomic fingerprint comprising 36 different loci was established in the 20 main inbred lines of Chinese cabbage, and this fingerprint was converted digitally into a molecular ID with 36 numbers based on the 36 SSR sites. The utility of this core set SSRs was demonstrated in 20 main inbred lines of Chinese cabbage, which could be placed into six clusters that were largely consistent with previous classification based on morphology data. Moreover, the molecular ID of an F1 hybrid can be deduced from its parents molecular IDs, and its purity can be determined by selecting one or two SSR loci from the 36 different loci.

Mechanical properties and failure behavior of phosphorene with grain boundaries

Using the density-functional tight-binding method, we studied the effect of grain boundaries on the mechanical properties and failure behavior of phosphorene. We found that the high-angle tilt boundaries with a higher density of (5∣7) defect pairs (oriented along the armchair direction) are stronger than the low-angle tilt boundaries with a lower defect density, and similarly the high-angle boundaries with a higher density of (4∣8) defect pairs (oriented along the zigzag direction) are stronger than the low-angle boundaries with a lower defect density. The failure is due to the rupture of the most pre-strained bonds in the heptagons of the (5∣7) defect pair or octagons of the (4∣8) pairs. The high-angle grain boundaries are better at accommodating the pre-strained bonds in heptagon and octagon defects, leading to a higher failure stress and strain. The results cannot be described by a Griffith-type fracture mechanics criterion, since this does not take into account the bond pre-stretching. Interestingly, these anomalous mechanical and failure characteristics of tilt grain boundaries in phosphorene are also shared by graphene and hexagonal boron nitride, signifying that they may be universal for 2D materials. The findings revealed here may be useful in tuning the mechanical properties of phosphorene via defect engineering for specific applications.

[Preliminary study of endovascular aneurysm repair using fenestration on table for abdominal aortic aneurysm with short proximal neck]

Objective: To investigate the clinical value of endovascular aneurysm repair(EVAR) using fenestration on table for abdominal aortic aneurysm(AAA) with short proximal neck. Methods: A retrospective analysis of four cases with short proximal neck AAA from Aug. 2015 to May. 2016 of Tianjin Medical University General Hospital treated by EVAR using fenestration on table. Fenestrated stent-grafts were designed according to the preoperative computer tomography angiography(CTA) data. All cases underwent EVAR with the fenestrated stent-grafts on table to revascularize visceral branches. Results: FEVAR was performed in all of the 4 cases successfully. Device deploying success rate was 100%. No type Ⅰ endoleak was found in all of the 4 cases. Transient renal dysfunction occurred in two cases during 7 post-operative days and improved with the medical treatment. Mean follow-up period was 4.7 months(range, 1-9 months). CTA (3 cases) and ultrasonic imaging(1 case) were performed postoperatively. No endoleak was found around fenestrated stent graft and patency of visceral stent grafts were maintained in all of the 4 cases. Conclusion: EVAR using fenestration on table for short proximal neck AAA is safe and feasible, which expand the indication of EVAR for AAA, and the long-term safety and outcomes of this technique need to be assessed in the future.

Fatty acid-binding protein FABP4 mechanistically links obesity with aggressive AML by enhancing aberrant DNA methylation in AML cells

Obesity is becoming more prevalent worldwide and is a major risk factor for cancer development. Acute myeloid leukemia (AML), the most common acute leukemia in adults, remains a frequently fatal disease. Here we investigated the molecular mechanisms by which obesity favors AML growth and uncovered the fatty acid-binding protein 4 (FABP4) and DNA methyltransferase 1 (DNMT1) regulatory axis that mediates aggressive AML in obesity. We showed that leukemia burden was much higher in high-fat diet-induced obese mice, which had higher levels of FABP4 and interleukin (IL)-6 in the sera. Upregulation of environmental and cellular FABP4 accelerated AML cell growth in both a cell-autonomous and cell-non-autonomous manner. Genetic disruption of FABP4 in AML cells or in mice blocked cell proliferation in vitro and induced leukemia regression in vivo. Mechanistic investigations showed that FABP4 upregulation increased IL-6 expression and signal transducer and activator of transcription factor 3 phosphorylation leading to DNMT1 overexpression and further silencing of the p15^INK4B tumor-suppressor gene in AML cells. Conversely, FABP4 ablation reduced DNMT1-dependent DNA methylation and restored p15^INK4B expression, thus conferring substantial protection against AML growth. Our findings reveal the FABP4/DNMT1 axis in the control of AML cell fate in obesity and suggest that interference with the FABP4/DNMT1 axis might be a new strategy to treat leukemia.

An instrument for measuring scintillators efficiently based on silicon photomultipliers

An instrument used for measuring multiple scintillators' light output and energy resolution was developed. The instrument consisted of a light sensor array which was composed of 64 discrete SiPMs (Silicon Photomultipliers), a corresponding individual channel readout electronics system, and a data processing algorithm. A Teflon grid and a large interval between adjacent SiPMs were employed to eliminate the optical cross talk among scintillators. The scintillators' light output was obtained by comparing with a reference sample with known light output. Given the SiPM temperature dependency and the difference among each SiPM, a temperature offset correction algorithm and a non-uniformity correction algorithm were added to the instrument. A positioning algorithm, based on nine points, was designed to evaluate the performance of a scintillator array. Tests were performed to evaluate the instrument's performance. The uniformity of 64 channels for light output measurement was better than 98%, the stability was better than 98% when temperature varied from 15 °C to 40 °C, and the nonlinearity under 511 keV was better than 2%. This instrument was capable of selecting scintillators and evaluating the packaging technology of scintillator arrays with high efficiency and accuracy.

Mechanical properties of phosphorene nanotubes: a density functional tight-binding study

Using the density functional tight-binding method, we studied the elastic properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) under uniaxial tensile strain. We found that the deformation and failure of PNTs are very much anisotropic. For ZZ PNTs, three deformation phases are recognized: the primary linear elastic phase-which is associated with interactions between neighboring puckers, succeeded by the bond rotation phase-where the puckered configuration of phosphorene is smoothed via bond rotation, and lastly the bond elongation phase-where the P-P bonds are directly stretched up to the maximally allowed limit and failure is initiated by the rupture of the most stretched bonds. For AC PNTs, the applied strain stretches the bonds up to the maximally allowed limit, causing their ultimate failure. For both AC and ZZ PNTs, their failure strain and failure stress are sensitive- while the Young's modulus, flexural rigidity, radial Poisson's ratio and thickness Poisson's ratio are relatively insensitive-to the tube diameter. More specifically, for AC PNTs, the failure strain decreases from 0.40 to 0.25 and the failure stress increases from 13 GPa to 21 GPa when the tube diameter increases from 13.3 Å to 32.8 Å; while for ZZ PNTs, the failure strain decreases from 0.66 to 0.55 and the failure stress increases from 4 GPa to 9 GPa when the tube diameter increases from 13.2 Å to 31.1 Å. The Young's modulus, flexural rigidity, radial and thickness Poisson ratios are 114.2 GPa, 0.019 eV · nm(2), 0.47 and 0.11 for AC PNTs, and 49.2 GPa, 0.071 eV · nm(2), 0.07 and 0.21 for ZZ PNTs, respectively. The present findings provide valuable references for the design and application of PNTs as device elements.

[Study on development of rehabilitation therapy for voice problems of hearing impaired children]

The production of voice is related to the coordinated operation of respiratory system,phonation system and resonance system.Sonic wave which is produced by the vibration of vocal fold goes through the resonating cavities to bring the voice out.Hearing and voice are two kinds of functions which are very related.Hearing impaired children have a very strong tendency to be in communication with people by improving the volume of their voice(Lombard's effect).To summarize the reasons,the methods of assessment and therapy of voice problems of hearing impaired children.Review 32 literature related to voice problems of hearing impaired children in the near past 12 years.Hearing intervention and improper way of phonation have great effect on the voice health of hearing impaired children.There are few studies on the therapy efficiency and auditory feedback training of voice problems of hearing impaired children,which are expecting our further study.

Proteomic and gene expression analyses during bolting-related leaf color change in Brassica rapa

Bolting and flowering are key processes during the growth and development of Chinese cabbage (Brassica rapa L. ssp pekinensis). Understanding the molecular mechanisms underlying bolting and flowering is of significance for improving production of the vegetable. A leaf-color change from bright green to gray-green has been observed following differentiation of the flowering stem and before bolting in the vegetable, and is considered to be a signal for bolting. Proteomics in meristem tissues of an inbred line (C30) were analyzed by two-dimensional electrophoresis during the transition period. We found that some proteins were specifically expressed while others were differentially expressed. Among these, 17 proteins were specifically expressed before the color change, 18 were specifically expressed after the color change, 21 were downregulated during the color change, and 29 were upregulated. Mass spectrometric analysis (MALDI-TOF-TOF/MS) was used to analyze 17 protein spots, and four proteins (subunit E1 of vacuolar-type H+ transporter ATPase, the large subunit of Rubicon, S-adenosylmethionine synthetase, and tubulin α-2) were identified. qPCR analysis was conducted to quantify the expression of genes encoding these proteins during the transitional period. The expression of BrVHA-E1, BrSAMS, BrrbcL, and BrTUA6 was significantly different before and after the leaf-color change, suggesting that these genes might be involved in regulating flower differentiation and bolting.

Characterization and parameterization of aerosol cloud condensation nuclei activation under different pollution conditions

To better understand the cloud condensation nuclei (CCN) activation capacity of aerosol particles in different pollution conditions, a long-term field experiment was carried out at a regional GAW (Global Atmosphere Watch) station in the Yangtze River Delta area of China. The homogeneity of aerosol particles was the highest in clean weather, with the highest active fraction of all the weather types. For pollution with the same visibility, the residual aerosol particles in higher relative humidity weather conditions were more externally mixed and heterogeneous, with a lower hygroscopic capacity. The hygroscopic capacity (κ) of organic aerosols can be classified into 0.1 and 0.2 in different weather types. The particles at ~150 nm were easily activated in haze weather conditions. For CCN predictions, the bulk chemical composition method was closer to observations at low supersaturations (≤0.1%), whereas when the supersaturation was ≥0.2%, the size-resolved chemical composition method was more accurate. As for the mixing state of the aerosol particles, in haze, heavy haze, and severe haze weather conditions CCN predictions based on the internal mixing assumption were robust, whereas for other weather conditions, predictions based on the external mixing assumption were more accurate.

Regulation of bolting and identification of the α-tubulin gene family in Brassica rapa L. ssp pekinensis

Microtubules are important components of eukaryotic cells, and they play vital roles in cell morphogenesis, carrying of signaling molecules, transport of materials, and establishing the cell polarity. During bolting of biennial plants, cell division and elongation are involved, and cell elongation inevitably involves the microtubules arrangement and expression of related genes. So we deduce that it is of great significance to figure out the mechanism of bolting and flowering in which TUA genes are involved. In the present study, bioinformatic methods were used to predict and identify the α-tubulin gene family (BrTUAs) in Brassica rapa L. ssp pekinensis (Chinese cabbage) through the alignment of AtTUA gene sequence from Arabidopsis thaliana with the B. rapa genome database (http://brassicadb.org/brad/) using the basic local alignment search tool. The change in the structure and functions of BrTUAs during the process of evolution, cis-acting elements in the promoter sequences of BrTUAs, and the expression of the identified genes was also analyzed. Twelve members of the α-tubulin gene family were identified from Chinese cabbage. The gene length, intron, exon, and promoter regions were determined to have changed significantly during the genome evolution. Only five of the 12 members were encoded completely and were observed to differ in their spatial and temporal expression. The five BrTUA promoter sequences contained different numbers of cis-elements responsive to light and low-temperature response, cis-elements responsive among which hormonal responses were significantly different. We also report that the BrTUAs were involved in the regulation of the bolting in Chinese cabbage, and propose that this process could be controlled by regulating the expression of BrTUAs.

Significant concentration changes of chemical components of PM1 in the Yangtze River Delta area of China and the implications for the formation mechanism of heavy haze-fog pollution

Since the winter season of 2013, a number of persistent haze-fog events have occurred in central-eastern China. Continuous measurements of the chemical and physical properties of PM1 at a regional background station in the Yangtze River Delta area of China from 16 Nov. to 18 Dec., 2013 revealed several haze-fog events, among which a heavy haze-fog event occurred between 6 Dec. and 8 Dec. The mean concentration of PM1 was 212μgm(-3) in the heavy haze-fog period, which was about 10 times higher than on clean days and featured a peak mass concentration that reached 298μgm(-3). Organics were the largest contributor to the dramatic rise of PM1 on heavy haze-fog days (average mass concentration of 86μgm(-3)), followed by nitrate (58μgm(-3)), sulfate (35μgm(-3)), ammonium (29μgm(-3)), and chloride (4.0μgm(-3)). Nitrate exhibited the largest increase (~20 factors), associated with a significant increase in NOx. This was mainly attributable to increased coal combustion emissions, relative to motor vehicle emissions, and was caused by short-distance pollutant transport within surrounding areas. Low-volatility oxidized organic aerosols (OA) (LV-OOA) and biomass-burning OA (BBOA) also increased sharply on heavy haze-fog days, exhibiting an enhanced oxidation capacity of the atmosphere and increased emissions from biomass burning. The strengthening of the oxidation capacity during the heavy pollution episode, along with lower solar radiation, was probably due to increased biomass burning, which were important precursors of O3. The prevailing meteorological conditions, including low wind and high relative humidity, and short distance transported gaseous and particulate matter surrounding of the sampling site, coincided with the increased pollutant concentrations mainly from biomass-burning mentioned above to cause the persistent haze-fog event in the YRD area.

Effect of different fibre sources on performance, carcass characteristics and gastrointestinal tract development of growing Greylag geese

1. The effects of different fibre sources on the growth performance, carcass characteristics and gastrointestinal tract development were studied in growing Greylag geese (Anser anser). 2. Four experimental diets were formulated with corn (maize) straw silage (CSS), steam-exploded corn (maize) straw, steam-exploded wheat straw, and steam-exploded rice straw as fibre sources. A total of 224 male Greylag geese at 28 d of age were randomly assigned to one of the 4 experimental diets. 3. The birds fed on the CSS diets had higher average daily feed intakes than those fed on the steam-exploded straws. However, the 4 treatments had similar average daily gain, which contributed to significant differences in feed conversion ratios. The different fibre sources had no significant effects on the carcass characteristics. 4. The CSS-fed birds had larger gizzards and lower relative length of the caeca than the other three groups. However, the relative weights and lengths of the other gut segments, the relative weights of major organs and the pH values of the gastrointestinal contents were similar between the 4 treatments. It was concluded that straw fibres with different physico-chemical properties exerted an effect on daily feed intake and gastrointestinal development, especially for the gizzard. The pretreatment of straw had a large effect on utilisation efficiency and animal performance. Steam explosion is a promising straw pretreatment for inclusion in diets for geese.

ANALYSIS OF GENOMIC DNA METHYLATION AND GENE EXPRESSION IN CHINESE CABBAGE (Brassica rapa L. ssp. pekinensis) AFTER CONTINUOUS SEEDLING BREEDING

Vernalization plays a key role in the bolting and flowering of Chinese cabbage (Brassica rapa L. ssp. pekinensis). Plants can switch from vegetative to reproductive growth and then bolt and flower under low temperature induction. The economic benefits of Chinese cabbage will decline significantly when the bolting happens before the vegetative body fully grows due to a lack of the edible value. It was found that continuous seedling breeding reduced the heading of Chinese cabbage and led to bolt and flower more easily. In the present study, two inbred lines, termed A161 and A105, were used as experiment materials. These two lines were subjected to vernalization and formed four types: seeds-seedling breeding once, seedling breeding twice, seedling breeding thrice and normal type. Differences in plant phenotype were compared. DNA methylation analysis was performed based on MSAP method. The differential fragments were cloned and analyzed by qPCR. Results showed that plants after seedling breeding thrice had a loosen heading leaves, elongated center axis and were easier to bolt and flower. It is suggested that continuous seedling breeding had a weaker winterness. It was observed that genome methylation level decreased with increasing generation. Four differential genes were identified, short for BraAPC1, BraEMP3, BraUBC26, and BraAL5. Fluorescent qPCR analysis showed that expression of four genes varied at different reproduction modes and different vernalization time. It is indicated that these genes might be involve in the development and regulation of bolting and flowering of plants. Herein, the molecular mechanism that continuous seedling breeding caused weaker winterness was analyzed preliminarily. It plays an important guiding significance for Chinese cabbage breeding.

The structure and elastic properties of phosphorene edges

We investigated the edge atomic structures and elastic properties of defect-free phosphorene nanoribbons (PNRs). Density functional tight binding simulations were used to optimize two main edge configurations: armchair (AC) and zigzag (ZZ). It was found that the energy relaxation of PNRs leads to the noticeable changes in edge atomic configurations. The effective width of the edge region, which includes all the atoms involved in the edge relaxation, was found to contain approximately three atomic rows near the edge for both AC and ZZ PNRs. We further extracted the edge stress and modulus for the ZZ and AC edges. Both the AC and ZZ edge stresses of PNRs are positive, indicating tensile stress at the edges. In addition, both the AC and ZZ edge moduli are positive. However, the edge elastic modulus and edge stress of ZZ PNRs are about three times larger than those of AC PNRs. Furthermore, we showed that the tensile edge stresses along ZZ and AC edges are able to cause distortion in freestanding phosphorene nanoribbons. Our results highlight the importance of accounting for edge stresses in the design and fabrication of PNRs.

Cloning and sequence analysis of sucrose phosphate synthase gene from varieties of Pennisetum species

Sucrose phosphate synthase (SPS) is an enzyme used by higher plants for sucrose synthesis. In this study, three primer sets were designed on the basis of known SPS sequences from maize (GenBank: NM_001112224.1) and sugarcane (GenBank: JN584485.1), and five novel SPS genes were identified by RT-PCR from the genomes of Pennisetum spp (the hybrid P. americanum x P. purpureum, P. purpureum Schum., P. purpureum Schum. cv. Red, P. purpureum Schum. cv. Taiwan, and P. purpureum Schum. cv. Mott). The cloned sequences showed 99.9% identity and 80-88% similarity to the SPS sequences of other plants. The SPS gene of hybrid Pennisetum had one nucleotide and four amino acid polymorphisms compared to the other four germplasms, and cluster analysis was performed to assess genetic diversity in this species. Additional characterization of the SPS gene product can potentially allow Pennisetum to be exploited as a biofuel source.

Isolation of the P5CS gene from reed canary grass and its expression under salt stress

Reed canary grass (RCG) is a perennial grass traditionally cultivated for forage. It is also used as fuel to produce energy in Finland and Sweden, and other countries have expressed interest in the cultivation of RCG. In China, arable land is limited. Salinity is considered to be a major factor limiting plant crop development and productivity. To boost biofuel production of RCG and extend its range in saline soil, we seek to improve its salt tolerance. Proline acts as an osmolyte that accumulates when plants are subjected to abiotic stress. P5CS plays a crucial role in proline biosynthesis. We isolated a P5CS gene from RCG, designated B231P5CS (GenBank accession No. JQ622685). B231P5CS is a fragment (971 bp) that encodes a 323-amino acid polypeptide. We also cloned an actin gene fragment from RCG as a reference gene in expression analysis of B231P5CS gene. Expression analysis revealed that B231P5CS transcripts were upregulated in leaves after treatment with salt (200 mM NaCl) and that transcript levels of B231P5CS reached a maximum 12 h after exposure, which was 14.69 times the level in control plants. The trends of expression were exactly opposite in roots; transcripts were downregulated after salt treatment. Proline concentration increased in leaves after stress. In contrast, proline content of roots decreased up to 3.6-fold relative to controls. Changes in proline concentration after stress were correlated with B231P5CS expression. Our results suggest that B231P5CS is a stress-inducible gene and plays a non-redundant role in plant development. This gene may be used to improve stress tolerance of RGC and other bioenergy feedstock.

Inverse pseudo Hall-Petch relation in polycrystalline graphene

Understanding the grain size-dependent failure behavior of polycrystalline graphene is important for its applications both structurally and functionally. Here we perform molecular dynamics simulations to study the failure behavior of polycrystalline graphene by varying both grain size and distribution. We show that polycrystalline graphene fails in a brittle mode and grain boundary junctions serve as the crack nucleation sites. We also show that its breaking strength and average grain size follow an inverse pseudo Hall-Petch relation, in agreement with experimental measurements. Further, we find that this inverse pseudo Hall-Petch relation can be naturally rationalized by the weakest-link model, which describes the failure behavior of brittle materials. Our present work reveals insights into controlling the mechanical properties of polycrystalline graphene and provides guidelines for the applications of polycrystalline graphene in flexible electronics and nano-electronic-mechanical devices.

Molecular dynamics simulations on the frictional behavior of a perfluoropolyether film sandwiched between diamond-like-carbon coatings

We perform molecular dynamics simulations to investigate the nanoscale frictional behavior of a perfluoropolyether (PFPE) film sandwiched between two diamond-like-carbon (DLC) coatings. We show that the PFPE films behave like a solid and can perform either a motion-station movement or a continuous motion with fluctuating velocities. The former movement is caused by the alternating stick and slip at the two individual interfaces, while the latter is due to the dynamic sliding motions simultaneously occurring at both interfaces. We reveal that these motion characteristics are governed by the competition between the two interfacial adhesion energies, which are strongly affected by the thermal vibrations and interface roughness fluctuations. We also find that the Amonton's law modified by incorporating the adhesion effect can be used to describe the mean friction traction vs normal pressure relation, but large fluctuations are present at low contact pressures. The magnitude of atomic level friction forces at the interface is found to be highly nonuniform. The directions of atomic level friction forces can even be opposite. With increasing the normal pressure, the nonuniformity of atomic level friction forces decreases first and then increases again. This change can be explained by the concurrent effects from the large difference in material stiffness and the changes in surface roughness under normal pressure. The present work reveals interesting insights into the sliding mechanisms in sandwiched structures and provides useful guidelines for the design of nanoscale lubricant systems.

SRAP analysis of genetic diversity of nine native populations of wild sugarcane, Saccharum spontaneum, from Sichuan, China

Saccharum spontaneum is a wild sugarcane species that is native to and widely distributed in China. It has been extensively used in sugarcane breeding programs, and is being tested for the development of bioenergy cultivars. In order to provide basic information for the exploitation of this species, we analyzed genetic variation among and within native S. spontaneum populations collected from Sichuan, China. Eighty plants from nine native populations were sampled. Twenty-one sequence-related amplified polymorphism primer pairs generated 235 clearly scorable bands, of which 185 were polymorphic (78.7%). Nei's genetic diversity was 0.2801 and Shannon's information index was 0.4155 across the populations. Genetic diversity parameters, G(ST) value (0.2088) and N(m) value (1.8944), showed that the genetic variation within populations was greater than that among populations. In the cluster analysis, one major grouping was formed by populations from Ya'an and another one by populations from Sichuan basin; a population from Baoxing formed a single cluster. In order to fully comprehend the genetic diversity of cold-tolerant local germplasm in this species, germplasm should be collected from the heterogeneous environments along the northern regions of this species' distribution. The germplasm that we collected should be a valuable resource for Saccharum breeding.