Unveiling the temperature-dependent thermoelectric properties of the undoped and Na-doped monolayer SnSe allotropes: a comparative study.

Motivated by the excellent thermoelectric (TE) performance of bulk SnSe, extensive attention has been drawn to the TE properties of the monolayer SnSe. To uncover the fundamental mechanism of manipulating the TE performance of the SnSe monolayer, we perform a systematic study on the TE properties of five monolayer SnSe allotropes such asα-,ß-,γ-,δ-, andε-SnSe based on the density functional theory and the non-equilibrium Green's functions. By comparing the TE properties of the Na-doped SnSe allotropes with the undoped ones, the influences of the Na doping and the temperature on the TE properties are deeply investigated. It is shown that the figure of meritZTwill increase as the temperature increases, which is the same for almost all the Na-doped and undoped cases. The Na doping can enhance or suppress theZTin different SnSe allotropes at different temperatures, implying the presence of the anomalous suppression of theZT. The Na doping inducedZTsuppression may be caused basically by the sharp decrease of the power factor and the weak decrease of the electronic thermal conductance, rather than by the decrease of the phononic thermal conductance. We hope this work will be able to enrich the understanding of the manipulation of TE properties by means of dimensions, structurization, doping, and temperature.

Spin-dependent thermoelectric transport properties of Cr-doped blue phosphorene.

We systematically investigate the thermoelectric (TE) properties of the Cr-doped blue phosphorene (blue-P) along the armchair and zigzag directions. First, we find the semiconducting band structure of the blue-P will become spin-polarized due to the Cr-doping, and can be seriously changed by the doping concentration. Then we show the Seebeck coefficient, the electronic conductance, the thermal conductance, and the figures of meritZTs are all dependent on the transport directions and doping concentration. However, two pairs of the peaks of the charge and spinZTs can be always observed with the low-height (high-height) pair on the side of the negative (positive) Fermi energy. In addition, at temperature 300 K the extrema of the charge (spin)ZTs of the blue-P along the two directions are kept to be larger than 22 (90) for the different doping concentrations and will be further enhanced at lower temperature. Therefore, we believe the Cr-doped blue-P should be a versatile high-performance TE material which may be used in the fields of the thermorelectrics and spin caloritronics.

Electronic structures, transport properties, and optical absorption of bilayer blue phosphorene nanoribbons.

Based on first-principles density functional theory and nonequilibrium Green's function, we study the electronic band structures, the electronic transport properties, and the optical absorption of bilayer blue phosphorene nanoribbons (BPNRs). Both bilayer armchair BPNRs (a-BPNRs) and zigzag BPNRs (z-BPNRs) behave as semiconductors in the narrow nanoribbon case and metals in the wide nanoribbon case, sharply different from their monolayer counterparts where the monolayer a-BPNRs (z-BPNRs) are always semiconducting (metallic). This indicates that interlayer couplings or the increasing layer number may induce the switching of the conductivity of the monolayer BPNRs, which is absent in graphene and phosphorene nanoribbons. Furthermore, we explore the edge states of the energy bands near Fermi energy, and find that there are almost no pure edge-state band branches in the bilayer BPNRs, which can be attributed to the interlayer couplings between the edge-states in one layer and the bulk-states in the other. Consequently, the resulting complex band structures cannot be directly analyzed any more in the framework of the two-body coupling picture just according to the simple band structures of the monolayer BPNRs. Finally, we present the current-voltage characteristics and the optical absorption of the bilayer a-BPNRs and z-BPNRs. The influences of the nanoribbon width and the interlayer couplings on the current and the anisotropic optical absorption can be understood based on the complex energy band structures. This research should be an important reference of extending the field of BPNRs from the monolayer to the bilayer case, and deepen the understanding of the difference between the monolayer and bilayer nanoribbons in different materials.

[Pathophysiologic mechanism of CMTM5 low expression in multiple myeloma progression].

Objective: To investigate the mechanism of chemokine-like factor superfamily member (CMTM) 5 on the proliferation of multiple myeloma cells. Methods: RT-qPCR method was used to detect the expression and correlation of CMTM5, caspase3 and caspase9 in U266 after decitabine demethylation treatment; U266 transfected with pcDNA3.1 plasmid overexpressed CMTM5, then cell proliferation activity was detected by CCK-8 assay. Results: Compared with the control group, the low-dose demethylation treatment increased mRNA expression of CMTM5, caspase3, and caspase9 in U266, and showed a time-dependent (P<0.01). The up-trend of CMTM5, caspase3, and caspase9 in the high-demethylation drug treatment group was more significant and also showed time-dependent (P<0.001); There was a significant positive correlation between CMTM5 and caspase3 (r=0.937) and caspase9 (r=0.945) in each group (P<0.001). After transfection of U266 with the pcDNA3.1-CMTM5 plasmid, overexpression of CMTM5 inhibited the cell proliferation activity compared with the control and pcDNA3.1-vector group. Conclusion: Decitabine has a reductive effect on the low level of CMTM5 in U266 cells, and its recovery level is significantly positively correlated with caspase 3 and caspase9. Re-expression of CMTM5 inhibits the proliferative activity of U266.

[Incidence of blood stream infections of 1265 patients with hematopoietic stem cell transplantation and analysis of pathogenic bacteria].

Objective: To analyze the incidence and microbiological features of blood stream infections (BSI) of patients with hematopoietic stem cell transplantation (HSCT) and to provide laboratory data for empirical use of antibiotic for the HSCT patients with BSI. Methods: The incidence of bloodstream infection, the positive rate of blood culture, bacterial spectrum and drug resistance were analyzed in 1 265 HSCT recipients during 2013 and 2015 were retrospectively studied. Results: Of 1265 patients undergoing HSCT, 1 422 cases of suspected BSI occurred in 784 patients (61.98%) , and 464 patients (59.2%) were in the stage of agranulocytosis (ANC<0.5×10(9)/L) . The detection rate of pathogens in 2013-2015 was about 20% and increase year after year. Of the 401 strains detected, 221 were Gram-negative (G(-)) bacteria (55.1%) , 165 Gram-positive (G(+)) bacteria (41.2%) and 15 fungi (3.7%) . Escherichia coli (16.0%) , Staphylococcus epidermidis (15.5%) and Klebsiella pneumoniae (11.2%) were listed the top three. The proportion of multidrug resistant Acinetobacter Bauman and Stenotrophomonas maltophilia was 64.70% and 63.64% respectively, and methicillin resistant Staphylococcus aureus (MRSA) was more than half (57.14%) . The ratio of vancomycin resistant Enterococci (VRE) and carbapenem resistant Enterobacteriaceae (CRE) was 14.29% and 6.78% respectively. More than 40% Enterobacteriaceae bacteria were resistant to three or four generation cephalosporin antibiotics, and less were resistant to the carbapenems (6.4%) . However, many non-fermentating bacteria were highly resistant to these antibiotics and showed diversity among different strains, with a rate of 47.8% resistance to carbapenems. All the Staphylococcus were sensitive to vancomycin, teicoplanin and linezolid. Conclusions: The incidence of BSI in patients with HSCT was high, and the pathogens were mainly G(-) bacteria. In addition to Enterobacteriaceae, the proportion of non-fermentative bacteria was quite high. No Staphylococcus detected were resistant to vancomycin, teicoplanin and linezolid.