Yiyi Chen

This report describes the analytical models Lawrence Berkeley National Laboratory developed to estimate impacts of the U.S. Environmental Protection Agency’s WaterSense® labeling program. The models assess national impacts for WaterSense labeled toilets, faucets, faucet aerators, showerheads, flushing urinals, commercial pre-rinse spray valves, and weather or soil moisture sensor-based irrigation controllers by analyzing national inputs for water use in residential and commercial/institutional markets. For irrigation controllers, LBNL’s methodology also incorporates a scenario that evaluates impacts in three key large states that are considered to be the principal market for “smart” irrigation controllers: California, Florida, and Texas. The models estimate impacts for the water savings attributable to the program and the net present value of the lifetime water savings from more efficient products.

© 2016 American Chemical Society.Hydrostatic pressure applied using diamond anvil cells has been widely explored to modulate physical properties of materials by tuning their lattice degree of freedom. Independently, electrical field is able to tune the electronic degree of freedom of functional materials via, for example, the field-effect transistor configuration. Combining these two orthogonal approaches would allow discovery of new physical properties and phases going beyond the known phase space. Such experiments are, however, technically challenging and have not been demonstrated. Herein, we report a feasible strategy to prepare and measure FETs in a DAC by lithographically patterning the nanodevices onto the diamond culet. Multiple-terminal FETs were fabricated in the DAC using few-layer MoS2 and BN as the channel semiconductor and dielectric layer, respectively. It is found that the mobility, conductance, carrier concentration, and contact conductance of MoS2 can all be significantly enhanced with pressure. We expect that the approach could enable unprecedented ways to explore new phases and properties of materials under coupled mechano-electrostatic modulation.

© 2016 American Physical Society.An extreme magnetoresistance has recently been observed in several nonmagnetic semimetals. Increasing experimental and theoretical evidence indicates that the XMR can be driven by either topological protection or electron-hole compensation. Here, by investigating the electronic structure of a XMR material, YSb, we present spectroscopic evidence for a special case which lacks topological protection and perfect electron-hole compensation. Further investigations reveal that a cooperative action of a substantial difference between electron and hole mobility and a moderate carrier compensation might contribute to the XMR in YSb.

© 2016 American Chemical Society.Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution, we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimSuperconductivity in monolayer niobium diselenide on bilayer graphene is studied by electrical transport. Monolayer NbSe2 is grown on bilayer graphene by molecular beam epitaxy and capped with a selenium film to avoid degradation in air. The selenium capped samples have TC = 1.9 K. In situ measurements down to 4 K in ultrahigh vacuum show that the effect of the selenium layer on the transport is negligible. The superconducting transition and upper critical fields in air exposed and selenium capped samples are compared. Schematic of monolayer NbSe2/bilayer graphene with selenium capping layer and electrical contacts.

© 2016 American Chemical Society.High quality WSe2 films have been grown on bilayer graphene with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

© 2016 Macmillan Publishers Limited.Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge density wave order and superconductivity. In bulk NbSe 2 a CDW sets in at T CDW = 33 K and superconductivity sets in at T c = 7.2 K. Below T c these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional layer of NbSe 2 by means of low-temperature scanning tunnelling microscopy/spectroscopy, angle-resolved photoemission spectroscopy, and electrical transport measurements. We demonstrate that 3 × 3 CDW order in NbSe 2 remains intact in two dimensions. Superconductivity also still remains in the 2D limit, but its onset temperature is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of= 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified electronic structure of single-layer NbSe 2, thus providing insight into CDW formation and superconductivity in this model strongly correlated system.

Background: Although ethics consultation has been introduced to clinical practice for many years, the results of empirical studies to evaluate the effectiveness of ethics consultation are still controversial. The design of randomised controlled trials is considered the best research design to evaluate the effect of a clinical practice on the outcomes of interests. In order to understand the effects of ethics consultation, we conducted this search for studies with the design of randomised controlled trials to evaluate ethics consultation.Objective: To provide an integrated review of studies with the design of randomised controlled trials to evaluate the effectiveness of ethics consultation.Methods: PubMed was used to search for studies using the randomised controlled trial design to evaluate the effectiveness of ethics consultation. The search term used was “ethics consultation”. The selection criterion was limited to “randomised controlled trial”.Results: Four articles that met both search criteria were retrieved. One of these articles reported a study that did not actually use the design of a randomised controlled trial and is excluded from the following discussion.Conclusions: To apply randomised controlled trials to evaluate the effectiveness of ethics consultation is extremely difficult as long as two issues are not resolved: the standardisation of ethics consultation and a placebo for ethics consultation to eliminate the placebo effect. Thus, the results generated by the design of randomised controlled trials are always problematic. Furthermore, as long as the two issues exist, the results generated by the design of quantitative research methods always pose problems

There is currently an evidentiary gap in the scholarship concerning medical tourism's impact on low- and middle-income destination countries (LMICs). This article reviews relevant evidence that exists and concludes that there are signs of correlation between medical tourism and the expansion of private, technology- intensive health care in LMICs, which has largely remained out of reach for the majority of the local patients. In light of this health care inequity between local residents and medical tourists in LMICs, we argue that the presumption should not be in favor of medical tourism and that governments have a legitimate interest in seeking to regulate this industry to ensure that the net effects for their citizens is positive. Moreover, sending countries, particularly those in the developed world, have the responsibility to adopt public policies to diminish demand on the part of their citizens for medical tourism and to work with LMICs to ensure that the growth of medical tourism does not occur at the expense of the poorest of the poor

Travelling internationally to acquire medical treatments otherwise unavailable or inaccessible in one’s home country is not a novel concept. Conventionally, such medical travel largely entailed patients from developed countries or wealthy patients from the developing world seeking care in Western facilities like the Mayo Clinic in the U.S. and myriad private clinics along Harley Street in London, England. What is different about the topical phenomenon known as “medical tourism” is the growing trend of health services export in the opposite direction. The number of patients travelling from the developed world to low- and middle-income countries for treatments has ballooned in recent years, primarily driven by difficulties with accessing affordable care at home. According to a liberal estimate by the Deloitte Center for Health Solutions, the number of Americans travelling abroad for care rose from 750,000 in 2007 to 1.6 million in 2012. On the flip side, Thailand reportedly treated a total of 1.3 million foreign nationals in 2007, which represented a 16% leap from 2001.

Venneman and colleagues argue that “do not resuscitate” (DNR) is problematic and should be replaced by “allow natural death” (AND). Their argument is flawed. First, while end-of-life discussions should be as positive as possible, they cannot and should not sidestep painful but necessary confrontations with morality. Second, while DNR can indeed be nonspecific and confusing, AND merely replaces one problematic term with another. Finally, the study’s results are not generalisable to the populations of physicians and working nurses and certainly do not support the authors’ claim that there is a movement to replace DNR with AND

The structure of Au layers deposited by sputtering on oxidized p-type Si substrates is investigated by a combination of scanning electron microscopy and scanning probe microscopy. The effect of the temperature on the grain structure of the layers has been determined, revealing that an annealing temperature of 300° C results in a larger grain size and smoother surfaces but generates some cracks in the film surface. At an annealing temperature of 500° C, further grain growth is observed, but a high density of cracks and voids also results while there is little enhancement regarding the smoothness of the grain surfaces

© 2015 American Physical Society.The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To gauge the correlation strength, we performed a systematic angle-resolved photoemission spectroscopy study on the iron chalcogenide series Fe1+ySexTe1-x, a model system with the simplest structure. Our measurement reveals an incoherent-to-coherent crossover in the electronic structure as the selenium ratio increases and the system evolves from a weakly localized to a more itinerant state. Furthermore, we found that the effective mass of bands dominated by the dxy orbital character significantly decreases with increasing selenium ratio, as compared to the dxz/dyz orbital-dominated bands. The orbital-dependent change in the correlation level agrees with theoretical calculations on the band structure renormalization, and may help to understand the onset of superconductivity in Fe1+ySexTe1-x.

Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models, which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.