Effect of interfacial oxide thickness on 1/f noise in polysilicon emitter BJTs

The role of the interfacial oxide (IFO) between the polysilicon and monosilicon emitter regions on the noise behavior of n-p-n poly-emitter bipolar transistors was investigated through 1/f noise measurements. Bipolar junction transistors with different IFO thickness, and emitter geometry were utilized. Measurements with variable external base bias resistance (R/sub S/) were used to investigate the relative contribution of each individual noise source from the base current (S/sub IB/), the collector current (S/sub IC/) and, the internal emitter and base series resistances (S/sub Vr/). When the voltage noise power spectral densities S/sub VC/ and S/sub VB/ were measured across resistances in series with the collector and base, respectively, using a relatively large R/sub S/ (/spl sim/1 M/spl Omega/), S/sub IB/ was found to have the dominant noise contribution at lower bias currents. On the other hand, when the voltage noise power spectral densities S/sub VC/ and S/sub VE/ were measured across resistances in series with the collector and emitter, respectively, in a different experimental setup with a low R/sub S/ value, S/sub Vr/ was found to have the dominant noise contribution at higher bias currents. IFO was found to increase S/sub IB/, S/sub IC/, and S/sub Vr/. S/sub IB/ was modeled as a combination of tunneling and diffusion fluctuations of the minority carriers in the emitter; whereas S/sub IC/ was modeled as a combination of number and diffusion fluctuations of the minority carriers in the base. S/sub Vr/ was attributed to the internal emitter resistance noise originating from the fluctuation in the majority carrier flow through the IFO.     

Solar cell efficiency tables (version 46)

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2015 are reviewed. Copyright © 2015 John Wiley & Sons, Ltd.     

Energy stores and mercury concentrations in a common minnow (spottail shiner,Notropis hudsonius) associated with a peaking hydroelectric dam

Peaking hydroelectric facilities release water from dams to match energy production with demand, often on a daily cycle. These fluctuating flows downstream can exert several potential stressors on organisms that may inhibit their growth, indirectly causing higher contaminant concentrations through reduced growth dilution. We collected spottail shiner (Notropis hudsonius) at two sites upstream and two sites downstream of a peaking hydroelectric dam in east‐central Saskatchewan, Canada, and compared their body condition, triglyceride concentrations, and mercury concentrations. Condition decline was observed in one of two downstream sites from August to September, and the lowest triglyceride concentrations were consistently found downstream of the dam where hydropeaking had the most perceptible effects on the shoreline. Mercury concentrations were significantly greater at both downstream sites relative to upstream. Despite these results, inconsistencies in response parameters across sites and time limited our ability to isolate the effects of hydropeaking as a causative agent and suggest indirect effects such as shifts in algal and macroinvertebrate communities may be responsible for our observations. These results suggest that hydroelectric power generation may indirectly increase mercury concentrations in downstream fish, but more research will be required to determine the specific mechanisms by which this occurs. The results and data also provide useful insights into the physiology of wild spottail shiner populations, which can help to inform the development of these fish as a North American sentinel species.     

Differential uptake, partitioning and transfer of Cd and Zn in the soil-pea plant-aphid system

The biomagnification of trace metals during transfer from contaminated soil to higher trophic levels may potentially result in the exposure of predatory arthropods to toxic concentrations of these elements. This study examined the transfer of Cd and Zn in a soil-plant-arthropod system grown in series of field plots that had received two annual applications of municipal biosolids with elevated levels of Cd and Zn. Results showed that biosolids amendmentsignificantly increased the concentration of Cd in the soil and the shoots of pea plants and the concentration of Zn in the soil, pea roots, shoots, and pods. In addition, the ratio of Cd to Zn concentration showed that Zn was preferentially transferred compared to Cd through all parts of the system. As a consequence, Zn was biomagnified by the system whereas Cd was biominimized. Cd and Zn are considered to exhibit similar behaviors in biological systems. However, the Cd/Zn ratios demonstrated that in this system, Cd is much less labile in the root-shoot-pod and shoot-aphid pathways than Zn.     

On the structural topology of wind turbine blades

As wind turbines continue to grow in size, it becomes increasingly important to ensure that they are as structurally efficient as possible to ensure that wind energy can be a cost‐effective source of power generation. A way to achieve this is through weight reductions in the blades of the wind turbine. In this study, topology optimization is used to find alternative structural configurations for a 45 m blade from a 3 MW wind turbine. The result of the topology optimization is a layout that varies along the blade length, transitioning from a structure with trailing edge reinforcement to one with offset spar caps. Sizing optimization was then performed on a section with the trailing edge reinforcement and was shown to offer potential weight savings of 13.8% when compared with a more conventional design. These findings indicate that the conventional structural layout of a wind turbine blade is sub‐optimal under the static load conditions that were applied, suggesting an opportunity to reduce blade weight and cost. Copyright © 2012 John Wiley & Sons, Ltd.     

Measuring the trace elemental composition of size-resolved airborne particles

A new method to measure the trace elemental composition of size-resolved airborne particles that uses acetone extraction followed by ICPMS analysis is compared to three other established methods: copper anode XRF, molybdenum anode XRF, and an ICPMS method that uses HF digestion. The method detection limit (MDL), accuracy, and precision of each method is studied through the analysis of ambient samples collected in California. The MDLs of the new acetone-ICPMS method are similar to MDLs for the established HF-ICPMS method. Both sets of ICPMS MDLs are 1-3 orders of magnitude lower than XRF MDLs for approximately 50 elements other than the light crustal elements such as silicon, sulfur, calcium, and zinc. The accuracy of the acetone-ICPMS method was verified by comparison to measurements made using ion chromatography and the HF-ICPMS method. The acetone-ICPMS analysis method was more precise than the conventional HF-ICPMS method for collocated measurements. Both ICPMS methods were more precise than XRF for most elements. The size distribution of 21 elements contained in ambient particles collected with cascade impactors could be measured with good precision using the new acetone-ICPMS analysis method: lithium, sulfur, potassium, titanium, vanadium, manganese, iron, gallium, germanium, arsenic, selenium, bromine, rubidium, strontium, cadmium, tin, antimony, barium, thallium, lead, and bismuth. It is likely that the size distribution of an additional 9 elements could also be measured when concentrations are sufficiently high: phosphorus, molybdenum, niobium, palladium, cesium, europium, holmium, platinum, and uranium. None of the conventional methods were able to measure the size distribution of these elements with acceptable precision under the conditions studied. The new acetone-ICPMS method should provide useful data for the study of the health effects of airborne particles.     

Structural inhomogeneities in polycrystalline silicon on glass solar cells and their effects on device characteristics

The effects of electrostatic fluctuations due to charged extended defects and strain‐induced bandgap fluctuations are examined in polycrystalline silicon on glass solar cells. The analysis is based on models previously applied to Cu(In,Ga)Se₂ solar cells, but with a new interpretation of the local ideality factor associated with electrostatic fluctuations. It is shown that electrostatic fluctuations become influential to the cell voltage properties as the absorber dopant concentration falls below a certain threshold (a few 10¹⁵ cm⁻³), and the degradations to the open circuit voltage and fill factor are expected to increase with further lowering of dopant density. It is equally plausible that the electrostatic fluctuations originate from charged dislocations or grain boundaries. Bandgap fluctuations on the other hand can be detrimental to the open circuit voltage of cells of any absorber dopant density. However, this voltage degrading effect is seen only in the cells deposited by electron‐beam evaporation, and not amongst those made by plasma enhanced chemical vapour deposition. Copyright © 2011 John Wiley & Sons, Ltd.     

Interactive Narratives: Processes and Outcomes in User‐Directed Stories

Interactive narratives are stories that allow readers to determine the direction of the plot, often at key decision points. Unanswered questions remain about the types of psychological processes evoked by these “Choose Your Own Adventure” style narratives, as well as the relative persuasive influence of interactive narratives compared to traditional narratives. The current paper reviews the existing literature and provides a theoretical framework to guide future research on interactive narratives, particularly as a tool for entertainment‐education efforts. Specifically, we highlight increased user control and looser narrative structure as key elements of interactive narratives, and discuss possible effects of these differences on engagement variables (e.g., transportation, identification, perceived realism), self‐related variables (responsibility), and outcomes (e.g., enjoyment, attitude change, health behaviors).     

Impact of interfacial layer on low-frequency noise of HfSiON dielectric MOSFETs

Low-frequency noise measurements and analysis were performed on n-channel MOSFETs with HfSiON as the gate-dielectric material. The role of SiON interfacial-layer thickness was investigated. It was observed that these fluctuations can be described by the unified flicker-noise model that attributes noise to correlated carrier-number/mobility fluctuations due to trapping states in the gate dielectric. The model was modified to include the effect of different gate stack layers on the observed noise. The carrier-number fluctuations were found to dominate over the correlated mobility fluctuations in the measured bias range and more so at the lower gate overdrives. The noise magnitude showed a decrease with increasing SiON interfacial-layer thickness. Furthermore, an inverse-proportionality relationship was revealed between the effective oxide trap density and SiON thickness.     

On the Mechanism of Cuprate Crystal Growth: The Role of Mixed Metal Carbonates

The mechanism of formation of the superconductor Bi₂Sr₂CaCu₂O_8+x (Bi‐2212) has been an open question since its discovery in 1988. By controlling crystal growth through the use of biopolymers as multivalent cation chelating agents, it is demonstrated through X‐ray diffraction and thermogravimetric analysis, that it is the formation of a mixed metal carbonate eutectic that promotes the formation of the target phase. X‐ray diffraction experiments, supported by infrared spectroscopy, identify this phase as (Sr_1?x Ca _x )CO₃. This knowledge allows to further reduce the eutectic melting point by the incorporation of a biopolymer rich in potassium ions, resulting in the scalable formation of Bi‐2212 at a temperature 50 °C lower than has been achieved previously.