Single-Probe-Based Colorimetric and Photothermal Dual-Mode Identification of Multiple Bacteria.

Effective identification of multiple pathogenic bacteria in unknown samples is important for disease prevention and control but remains a challenge yet. A single-mode array-based sensing approach is simple and sensitive, but it usually relies on the use of multiple cross-reactive receptors to construct sensor arrays, which is cumbersome and insufficiently accurate. Here, we developed a sensor array with colorimetric and photothermal dual mode of differentiating multiple pathogenic bacteria. The sensor array was based on boronic acid-functionalized Au-Fe3O4 nanoparticles (BA-GMNPs), which not only possess localized surface plasmon resonance properties, showing a burgundy color similar to that of AuNPs, but also exhibit mild superparamagnetism, allowing for the differentiation of bacteria before and after binding to the nanoparticles. Immobilization of BA-GMNPs on the bacterial cell surface by covalent bonding would diminish NaCl-induced assembly of BA-GMNPs. Different BA-GMNPs@bacterial complexes differed in their ability to resist assembly and produced different colorimetric and photothermal response signals. A unique molecular fingerprint of each bacterium was obtained by linear discriminant analysis of the response patterns, demonstrating an effective differentiation among the six species studied. Compared with single-mode sensing arrays based on multiple receptors, this method only requires the preparation of a single nanomaterial, which produces two signal outputs for the identification of multiple bacteria with better differentiation. It can distinguish not only multiple pathogenic bacteria but also Gram-negative and Gram-positive bacteria, and, more importantly, it can perform preliminary discrimination of unknown samples.

Topological and Stacked Flat Bands in Bilayer Graphene with a Superlattice Potential.

We show that bilayer graphene in the presence of a 2D superlattice potential provides a highly tunable setup that can realize a variety of flat band phenomena. We focus on two regimes: (i) topological flat bands with nonzero Chern numbers, C, including bands with higher Chern numbers |C|>1 and (ii) an unprecedented phase consisting of a stack of nearly perfect flat bands with C=0. For realistic values of the potential and superlattice periodicity, this stack can span nearly 100 meV, encompassing nearly all of the low-energy spectrum. We further show that in the topological regime, the topological flat band has a favorable band geometry for realizing a fractional Chern insulator (FCI) and use exact diagonalization to show that the FCI is in fact the ground state at 1/3 filling. Our results provide a realistic guide for future experiments to realize a new platform for flat band phenomena.

Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS_{2}.

Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS_{2}. We observe strong intravalley coupling between the B_{1s} exciton and A_{n>1} states. Our measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum. While this conservation is consistent with Coulomb exchange-driven valley depolarization, we do not observe a momentum or energy dependence to the depolarization rate as would be expected for the exchange-based mechanism.

Mitigating challenges in aberration-corrected electron-beam lithography on electron-opaque substrates.

Aberration-corrected electron-beam lithography (AC-EBL) using ultra-thin electron transparent membranes has achieved single-digit nanometer resolution in two widely used electron-beam resists: poly (methyl methacrylate) (PMMA) and hydrogen silsesquioxane. On the other hand, AC-EBL implementation on thick, electron-opaque substrates is appealing for conventional top-down fabrication of quantum devices with nanometer-scale features. To investigate the performance of AC-EBL on thick substrates, we measured the lithographic point spread function of a 200 keV aberration-corrected scanning transmission electron microscope by defining both positive and negative patterns in PMMA thin films, spin-cast on thick SiO2/Si substrates. We present the problems encountered during pre-exposure beam focusing and discuss methods to overcome them. In addition, applying some of these methods using commercial 50 nm thick SiNXmembranes with thick Si support frames, we printed arrays of holes in PMMA with pitches around 26 nm on SiNX/Si substrates with increasing Si thickness. Our results show that proximity effects from even 50 nm thick SiNXmembranes limit hole arrays to 20 nm pitch; however, down to this limit, the effect of the substrate thickness on the pattern quality is minimal. These results highlight the need for novel resists less susceptible to proximity effects, or resists which can be used directly, after development, as the dielectric material in periodic gates in 2D quantum devices.

Uncovering Topological Edge States in Twisted Bilayer Graphene.

Twisted bilayer graphene (t-BLG) has recently been introduced as a rich physical platform displaying flat electronic bands, strongly correlated states, and unconventional superconductivity. Studies have hinted at an unusual Z2 topology of the moiré Dirac bands of t-BLG. However, direct experimental evidence of this moiré band topology and associated edge states is still lacking. Herein, using superconducting quantum interferometry, we reconstructed the spatial supercurrent distribution in t-BLG Josephson junctions and revealed the presence of edge states located in the superlattice band gaps. The absence of edge conduction in high resistance regions just outside the superlattice band gap confirms that the edge transport originates from the filling of electronic states located inside the band gap and further allows us to exclude several other edge conduction mechanisms. These results confirm the unusual moiré band topology of twisted bilayer graphene and will stimulate further research to explore its consequences.

Advances and applications of genetically modified pig models in biomedical and agricultural field.

Compared with rodents, pigs are closer to humans in terms of anatomy, metabolism and physiology, so they are ideal animal models of human diseases and xenotransplantation donors. In addition, as one of the most important livestock in China, pigs are closely related to our lives in terms of breeding improvement, disease prevention and animal welfare. In this review, we mainly summarize the research progress and future application of genetically modified pig models in the fields of xenotransplantation, molecular breeding and human disease models. We wish to take this opportunity to raise the awareness of researchers in related fields on cutting-edge technologies such as gene editing and understand the significance of genetically modified pig models in life science research.

Helic[6]arene-Based Chiral Pseudo[1]rotaxanes and [1]Rotaxanes.

Chiral pseudo[1]rotaxanes and [1]rotaxanes constructed from macrocyclic arenes still remain a big challenge mainly owing to the lack of such chiral macrocycles. In this work, a new system of chiral pseudo[1]rotaxanes formed by self-inclusion of helic[6]arene containing amide linked with the terminal tertiary amines was first discovered. Based on an atom-economic stopping strategy, a pair of chiral [1]rotaxanes were conveniently obtained in almost quantitative yields by blocking the pseudo[1]rotaxanes with monobenzyl bromide of tetraphenylethene. The structures of pseudo[1]rotaxanes and [1]rotaxanes were characterized by 2D NMR spectra in solution, combined with DFT calculations. The photophysical properties further revealed the efficient chirality transfer of helic[6]arene to the tetraphenylethene moiety, compared to their unthreaded chiral isomers. The discovery of the chiral pseudo[1]rotaxanes allows for a wide and available synthesis of chiral [1]rotaxanes, and also opening a new avenue to the design of chiral supramolecular materials.

Reading struggle stories of role models can improve the perseverance of undergraduates with low perseverance.

Perseverance refers to the ability that individuals show in the process of overcoming failure repeatedly and achieving success. The present study aimed to investigate how many stories about struggling role models undergraduates with a low level of perseverance need to read to effectively improve their perseverance after experiencing failure. Undergraduates with high and low levels of perseverance who had experienced failure were randomly assigned to read 5 struggle stories or 5 achievement stories of role models. They were asked to report their confidence in success, their emotional experience, and their persistent intentions after experiencing failure (i.e., their initial report after reading 0 stories) and then again after reading each story. The results showed that the participants' initially reported level of confidence in success improved after reading 1 struggle story of a role model and further improved after reading 5 struggle stories of role models. Furthermore, the participants' initially reported level of positive emotions increased after reading 1 struggle story or 1 achievement story of a role model, and the positive effects began to level off after reading 4 struggle stories or 4 achievement stories of role models. The participants' initially reported persistent intentions improved after reading 5 struggle stories of role models. These findings reveal that undergraduates can benefit from reading struggle stories of role models regardless of their perseverance levels. Undergraduates' confidence in success and their emotional experience can be improved more quickly than their persistent intentions after experiencing failure.

Moiré Band Topology in Twisted Bilayer Graphene.

Recently twisted bilayer graphene (t-BLG) has emerged as a strongly correlated physical platform. Besides the apparent significance of band flatness, band topology may be another critical element in t-BLG and yet receives much less attention. Here we report the compelling evidence for nontrivial noninteracting Moiré band topology in t-BLG through a systematic nonlocal transport study and a K-theory examination. The nontrivial topology manifests itself as two pronounced nonlocal responses in the electron and hole superlattice gaps. We show that the nonlocal responses are robust to the twist angle and edge termination, exhibiting a universal scaling law. We elucidate that, although Berry curvature is symmetry-trivialized, two nontrivial Z2 invariants characterize the Moiré Dirac bands, validating the topological origin of the observed nonlocal responses. Our findings not only provide a new perspective for understanding the strongly correlated t-BLG but also suggest a potential strategy to achieve topological metamaterials from trivial vdW materials.

Towards the Highly Efficient Synthesis and Selective Methylation of C(sp3 )-Bridged [6]Cycloparaphenylenes from Fluoren[3]arenes.

An approach to the highly efficient synthesis of C(sp3)-bridged [6]cycloparaphenylenes (C[6]CPPs) from fluoren[3]arenes (F[3]As) was developed. Consequently, F[3]As as a new kind of macrocyclic arenes were synthesized. Followed by the demethylation, triflation and intramolecular aryl-aryl coupling reactions, C[6]CPPs were then conveniently obtained. Interestingly, C[6]CPPs could be selectively methylated to produce their fully outer-methyl-substituted derivatives. The crystal structures showed the hydroxyl-substituted F[3]As had bowl-shaped conformations, and the C[6]CPPs exhibited rigid belt-shaped structures with deep cavities. Moreover, C[6]CPPs exhibited high HOMO energies and narrow energy gaps. An unclosed belt was further obtained, and it not only showed a similar narrow energy gap to those of the aromatic belts, but also displayed strong fluorescence property, which can play a vital role in the design and synthesis of new aromatic belts.

A Green Fluorescent Nitrogen-Doped Aromatic Belt Containing a [6]Cycloparaphenylene Skeleton.

The design and synthesis of nitrogen-doped aromatic belts with conjugated structures still remain a challenge. Here, we report the first nitrogen-doped aromatic belt with a [6]cycloparaphenylene skeleton, which is conveniently synthesized from the easily available calix[3]carbazole. The aromatic belt has a rigid conjugated structure and deep cavity, and it can encapsulate one dichloromethane both in solution and in the solid state. Interestingly, the aromatic belt shows strong green fluorescence with a quantum yield of 0.39 and exhibits a narrow HOMO-LUMO energy gap of 2.02 eV. The belt-shaped conjugated structure composed of three carbazole subunits has specific optoelectronic properties that will promote wide applications in supramolecular chemistry and materials science.

Enhanced production of L-methionine in engineered Escherichia coli with efficient supply of one carbon unit.

OBJECTIVE: L-methionine is an important sulfur-containing amino acid essential for humans and animals. Its biosynthesis pathway is complex and highly regulated. This study aims to explore the bottleneck limiting the improvement of L-methionine productivity and apply efficient strategies to increase L-methionine production in engineered E. coli. RESULTS: The enzyme O-succinylhomoserine sulfhydrylase involved in thiolation of OSH to form homocysteine was overexpressed in the engineered strain E. coli W3110 IJAHFEBC/PAm, resulting in L-methionine production increased from 2.8 to 3.22 g/L in shake flask cultivation. By exogenous addition of L-glycine as the precursor of one carbon unit, the titer of L-methionine was increased to 3.68 g/L. The glycine cleavage system was further strengthened for the efficient one carbon unit supply and a L-methionine titer of 3.96 g/L was obtained, which was increased by 42% compared with that of the original strain. CONCLUSIONS: Insufficient supply of one carbon unit was found to be the issue limiting the improvement of L-methionine productivity and its up-regulation significantly promoted the L-methionine production in the engineered E. coli.

miR164c and miR168a regulate seed vigor in rice.

MicroRNAs (miRNAs) are key regulators of gene expression in many important biological processes of plants. However, few miRNAs have been shown to regulate seed vigor. Here, we conducted microarray assays to analyze miRNA expression levels in seeds of the rice (Oryza sativa L.) cultivar ZR02. Results showed significant differences in the expression of 11 miRNAs between artificially aged and untreated control seeds. Among these, osa-miR164c was transcriptionally upregulated, while osa-miR168a was downregulated in artificially aged seeds; this was verified by quantitative real-time PCR analysis. Under the same aging condition, osa-miR164c overexpression in OE164c transgenic seeds and osa-miR168a silencing in MIM168a transgenic seeds of the rice cultivar Kasalath led to lower germination rates, whereas osa-miR164c silencing in MIM164c and osa-miR168a overexpression in OE168a resulted in higher seed germination rates compared with wild-type seeds. Meanwhile, changes in cytomembrane permeability of seeds and in the expression level of osa-miR164c target genes (OsPM27 and OsPSK5) and osa-miR168a target genes (OsAGO1 and OsPTR2) under aging conditions coincided with changes in seed vigor induced by osa-miR164c and osa-miR168a. Thus, genetic manipulation of miRNAs has important implications in the development of crop cultivars with high vigor and extended life span of seeds.

Photo-induced terahertz near-field dynamics of graphene/InAs heterostructures.

In this letter, we report optical pump terahertz (THz) near-field probe (n-OPTP) and optical pump THz near-field emission (n-OPTE) experiments of graphene/InAs heterostructures. Near-field imaging contrasts between graphene and InAs using these newly developed techniques as well as spectrally integrated THz nano-imaging (THz s-SNOM) are systematically studied. We demonstrate that in the near-field regime (λ/6000), a single layer of graphene is transparent to near-IR (800 nm) optical excitation and completely "screens" the photo-induced far-infrared (THz) dynamics in its substrate (InAs). Our work reveals unique frequency-selective ultrafast dynamics probed at the near field. It also provides strong evidence that n-OPTE nanoscopy yields contrast that distinguishes single-layer graphene from its substrate.

Moral stories emphasizing actors' negative emotions toward their nonhelping behavior promote preschoolers' helping behavior.

Specific emotions, especially guilt, are considered to facilitate children's prosocial behavior. The current study differentiated moral stories with a helping theme in terms of the valence and source of emotions and aimed to clarify the effect of these stories on preschoolers' helping intentions and behavior. A total of 322 preschoolers between 4 and 6 years old were randomly assigned to four experimental groups and one control group. A specific type of moral story was presented to each of the experimental groups, whereas a nonmoral story was presented to the control group. The preschoolers were also asked to answer relevant questions to examine their story comprehension. The preschoolers' donating intentions and behavior were then measured. The results showed that all the experimental groups expressed more donating intentions than the control group. However, only the group that read the moral story emphasizing the actor's negative emotions toward his nonhelping behavior displayed more donating behavior than the control group. Therefore, the current study reveals that various moral stories dealing with a helping theme can facilitate helping intentions among preschoolers and that only certain stories can promote their helping behavior. Thus, it indicates the specificity of moral stories that facilitate prosocial behavior in terms of the valence and source of emotions in those stories.

Random Gauge Field Scattering in Monolayer Graphene.

Strain-induced lattice deformation affects electron hopping between the atoms. This effectively gives rise to a gauge field which impacts on the charge transport. In graphene, such gauge field is associated with a vector potential which mimics that of a magnetic field. Understanding the impact of the gauge field on charge transport is of essential importance for emerging topics including straintronics and valleytronics in two-dimensional materials. While extensive theoretical works have been carried out over the past decade, experimental progress has been largely limited to local probe and optical studies. Experimental charge transport study has been baffled by the challenge in creating an effective and independent tuning knob of strain without compromising the quality of graphene. Here we studied high quality suspended graphene field effect transistors fabricated on flexible Polyimide substrates. Applying uniaxial strain by bending the substrate, we observed a strain-induced resistivity with power-law carrier density dependence. The power factor is found to be correlated with the surface fractal dimension of the rippled graphene, in good agreement with the random gauge field scattering theory. Both phase coherent transport and magnetotransport properties are found to be strain-dependent, which can be understood in terms of a strain-tunable disorder.

[Relative Survival of Patients with Ischemic Stroke].

OBJECTIVE: To estimate the relative survival ratio of patients with ischemic stroke and its risk factors. METHODS: Lifetable and Ederer Ⅱ methods were used to estimate the relative survival ratio of patients with ischemic stroke. The Poission error structure model was adopted to determine the risk factors associated with survival. RESULTS: The patients had 99%, 98%, 98% and 99% relative survival ratio 1 year, 3 years, 5 years and 7 years after stroke, respectively. The relative excess risk of death increased with age [53-62 yr. vs. <53 yr., relative excess risk (RER=26.975, 95%CI: 1.668-410.90, P=0.020 1], higher mRS scores (≥3 vs. <3 points, RER=14.700, 95%CI: 1.05-206.45, P=0.047 3), and under body mass (vs. normal body mass, RER=10.082, 95%CI: 2.076-48.958, P=0.004 2). CONCLUSION: Ischemic stroke patients have a good prognosis, with slightly lower survival rates than the matched general populations. Those who are older, under body mass, and have a higher mRS score have lower survival rates.

[Health Utility of Patients with Stroke Measured by EQ-5D and SF-6D].

OBJECTIVE: To compare EQ-5D and SF-6D for measuring health utility of stroke patients in health economic evaluation studies. METHODS: A prospective cohort study was conducted on 596 stroke patients in the West China Hospital of Sichuan University from 2010 to 2016. Data were collected at baseline through face to face interviews and at the follow-up stages through telephone interviews with a three-month interval. EQ-5D and SF-6D were used for measuring health utility scores of the participants. The consistency of the two instruments was assessed using Bland-Altman plot and Intraclass correlation coefficient (ICC) . Logistic regression models were established to identify predictors of health utility. RESULTS: The participants had a mean utility score of 0.78 (95% confidence interval:0.76, 0.80) in EQ-5D,compared with 0.74 (95% confidence interval: 0.73, 0.76) in SF-6D,and a median (interquartile range) of 0.86 (0.68, 1.00) in EQ-5D and 0.73 (0.62, 0.86) in SF-6D. The 95% limits of agreement between the two instruments ranged from -0.28 to 0.35,with an ICC of 0.67 (95% confidence interval: 0.62,0.71). EQ-5D had a higher ceiling effect. The health utility score of stroke patients changed there rapidly in acute phase (less than 3 months) but barely changed there after.Severity of stroke was a major predictor of health utility scores. CONCLUSION: The two instruments generate inconsistent results in health utility. SF-6D is better for measuring health utility in patients with stroke in China.

[Sample Size Calculation using SAS for Phaseâ ¡in Two-stage Clinical Trials of Anti-tumor Drugs].

OBJECTIVE: To compare Gehan two-stage design and Simon two-stage design in sample size calculations for phase Ⅱ clinical trials of anti-tumor drugs. METHODS: We explained the sample size calculation methods with a single-stage design, Gehan two-stage design, and Simon optimal two-stage and minimax two-stage designs in line with the principle of exact binomial probability. By setting up different parameters in SAS macro program, the advantages and disadvantages of these designs were compared. RESULTS: The minimax two-stage design does not increase the maximum sample size compared with the single-stage design. Compared with the Gehan two-stage design, the Simon two-stage design has the advantage of being able to determine an early termination of trials when no or low anti-tumor activities are evident. CONCLUSION: Simon two-stage design is better than single-stage design and Gehan two-stage design. The minimax design is more popular than the optimal design.

[Application of Competing Risks Model in Predicting Smoking Relapse Following Ischemic Stroke].

OBJECTIVE: To determine factors associated with smoking relapse in men who survived from their first stroke. METHODS: Data were collected through face to face interviews with stroke patients in the hospital, and then repeated every three months via telephone over the period from 2010 to 2014. Kaplan-Meier method and competing risk model were adopted to estimate and predict smoking relapse rates. RESULTS: The Kaplan-Meier method estimated a higher relapse rate than the competing risk model. The four-year relapse rate was 43.1% after adjustment of competing risk. Exposure to environmental tobacco smoking outside of home and workplace (such as bars and restaurants) (P=0.01), single (P<0.01), and prior history of smoking at least 20 cigarettes per day (P=0.02) were significant predictors of smoking relapse. CONCLUSION: When competing risks exist, competing risks model should be used in data analyses. Smoking interventions should give priorities to those without a spouse and those with a heavy smoking history. Smoking ban in public settings can reduce smoking relapse in stroke patients.