A series of fresh molecular junctions at a single molecule level were created and the current fluctuations were studied as electrons passed through them. Our results indicate that telegraph-like current fluctuations at room temperature neither originate from electron trapping/detrapping processes nor from molecule re-conformation. Our results will be helpful in better understanding the mechanism of current fluctuations.
Utilizing individual atoms or molecules as functional units in electronic circuits meets the increasing technical demands for the miniaturization of traditional semiconductor devices. To be of technological interest, these functional devices should be high-yield, consume low amounts of energy, and operate at room temperature. In this study, we developed nanodevices called quantized conductance atomic switches (QCAS) that satisfy these requirements. The QCAS operates by applying a feedback-controlled voltage to a nanoconstriction within a stretched nanowire. We demonstrated that individual metal atoms could be removed from the nanoconstriction and that the removed metal atoms could be refilled into the nanoconstriction, thus yielding a reversible quantized conductance switch. We determined the key parameters for the QCAS between the "on" and "off" states at room temperature under a small operating voltage. By controlling the applied bias voltage, the atoms can be further completely removed from the constriction to break the nanowire, generating single-atom nanogaps. These atomic nanogaps are quite stable under a sweeping voltage and can be readjusted with subangstrom accuracy, thus fulfilling the requirement of both reliability and flexibility for the high-yield fabrication of molecular devices.
Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed.
Purpose The purpose of this paper is to study the rent-seeking behavior of stakeholders in construction projects and to provide a reference for further studies on collaboration in China, which could thus improve the collaborative management in construction and reduce the waste of resources. Design/methodology/approach In this paper, the authors discuss and analyze the current situation of rent-seeking behavior in infrastructure construction projects, integrated project delivery (IPD), and the application of a building information model (BIM) in China. The authors analyze the collusive behavior between the supervision department and the contractor via the rent-seeking model on the basis of the game theory and present that BIM and IPD have a positive impact on rent-seeking activities of construction projects. The key factors influencing the rent-seeking activities from the perspective of the owner are studied via a questionnaire survey. Findings The research status of IPD in China includes the application of IPD, IPD collaborative management and the combination of lean construction (LC), IPD and BIM. The enthusiasm of the adoption of BIM and IPD is higher for design institute, construction units, research institutions and universities. The findings indicate that the owner appears to have a significant influence on stakeholders in construction projects, such as supervising efficiency, rewards and punishment. Therefore, the results also demonstrate that the construction project based on BIM and IPD can effectively avoid the rent-seeking activities of the participants. Research limitations/implications The findings are primarily based on questionnaire data originated from Central China; hence there are some limitations that are worth noting. Practical implications First, it provides compelling data evidence for the adoption of BIM and IPD in China. Second, it paves a solid foundation for the behavior of stakeholders in construction projects based on BIM and IPD. Originality/value In this paper, a game model of contractor, supervisor and owner is established, and a preliminary attempt is made to introduce BIM and IPD into the model for the behavioral research of participants.
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