Calculating embodied carbon for reused structural components with laser scanning

The global warming potential (GWP) of reused building elements can be evaluated based on two variables: structural material quantity (SMQ) and embodied carbon coefficient (ECC). The volume of the SMQ can often be unknown, however, and it is not clear how to best estimate the ECC of a reused element. This paper illustrates a method for extracting the volume of reused metal structural elements to calculate their GWP in buildings that lack documentation. The authors use laser scanning and voxelization to extract the volume and a method based on the Swiss Society of Engineers and Architects (SIA) 2032 norms for calculating the GWP of reused materials. The reality capture method is accurate enough to approximate structural material volume, although it requires exposed structures. The results are important for building managers to understand the relative environmental impact savings from reused versus new building elements

Chiral interface states in p-n graphene junctions

We present a theoretical analysis of unidirectional interface states which form near p−n junctions in a graphene monolayer subject to a homogeneous magnetic field. The semiclassical limit of these states corresponds to trajectories propagating along the p−n interface by a combined skipping-snaking motion. Studying the two-dimensional Dirac equation with a magnetic field and an electrostatic potential step, we provide and discuss the exact and essentially analytical solution of the quantum-mechanical eigenproblem for both a straight and a circularly shaped junction. The spectrum consists of localized Landau-like and unidirectional snaking-skipping interface states, where we always find at least one chiral interface state. For a straight junction and at energies near the Dirac point, when increasing the potential step height, the group velocity of this state interpolates in an oscillatory manner between the classical drift velocity in a crossed electromagnetic field and the semiclassical value expected for a purely snaking motion. Away from the Dirac point, chiral interface states instead resemble the conventional skipping (edge-type) motion found also in the corresponding Schrödinger case. We also investigate the circular geometry, where chiral interface states are predicted to induce sizable equilibrium ring currents

Using a hybrid superconducting-ferromagnetic tip as a magnetic scanning tunneling microscope

Approaching a two-component tip made of a superconductor (S) and a ferromagnet (F) from a magnetic sample allows for two distinct tunneling processes between the ferromagnets, through S: i) Charge and spin are conserved; ii) Charge and spin are reversed, e.g. a Cooper pair flows from S, one electron going into F, the other into the sample. At subgap voltages, this allows two currents to flow from the tip : one is insensitive to the spin polarizations and allows for surface topography, the other directly tracks the relative spin polarizations of F and the sample. The whole device acts as a STM sensitive to the spin polarization at the Fermi level (MSTM). Its sensitivity is studied and optimized with respect to the tip geometry.Comment: 12 pages, 2 figure

Direct Observation of a Fractional Charge

We performed measurements of Quantum Shot Noise in order to determine the quasiparticle charge in the Fractional Quantum Hall regime. The noise is generated by a current flow through a partially transmitting Quantum Point Contact in a 2DEG. The noise is directly proportional to the charge of the quasiparticles, thus allowing direct determination of the charge. We measured Quantum Shot Noise at a filling factor of 1/3 and found that the charge is e/3; as predicted by Laughlin.Comment: 3 pages, PostScript, 4 figures. Submitted to Natur

Spectral flow of non-hermitian Heisenberg spin chain with complex twist

We investigate the spectral flow of the integrable non-hermitian Heisenberg spin chain under boundary conditions with complex twist angle. It is shown that the period of the spectral flow is $4\pi$ up to a certain critical imaginary twist, beyond which the period jumps successively to higher values. We argue that this phenomenon caused by non-hermitian properties of the system is closely related to the metal-insulator transition caused by non-hermitian hoppings for the one-dimensional insulator.Comment: 10 pages, revtex, to appear in NP

Could Intelligent Speed Adaptation make overtaking unsafe?

This driving simulator study investigated how mandatory and voluntary ISA might affect a driver's overtaking decisions on rural roads, by presenting drivers with a variety of overtaking scenarios designed to evaluate both the frequency and safety of the manoeuvres. In half the overtaking scenarios, ISA was active and in the remainder ISA was switched off. A rural road was modelled with a number of 2 + 1 road sections, thus allowing drivers a protected overtaking opportunity. The results indicate that drivers became less inclined to initiate an overtaking manoeuvre when the mandatory ISA was active and this was particularly so when the overtaking opportunity was short. In addition to this, when ISA was activated drivers were more likely to have to abandon an overtaking, presumably due to running out of road. They also spent more time in the critical hatched area - a potentially unsafe behaviour. The quality of the overtaking manoeuvre was also affected when mandatory ISA was active, with drivers pulling out and cutting back in more sharply. In contrast, when driving with a voluntary ISA, overtaking behaviour remained mostly unchanged: drivers disengaged the function in approximately 70% of overtaking scenarios. The results of this study suggest that mandatory ISA could affect the safety of overtaking manoeuvres unless coupled with an adaptation period or other driver support functions that support safe overtaking

Local Electronic Structure of a Single Magnetic Impurity in a Superconductor

The electronic structure near a single classical magnetic impurity in a superconductor is determined using a fully self-consistent Koster-Slater algorithm. Localized excited states are found within the energy gap which are half electron and half hole. Within a jellium model we find the new result that the spatial structure of the positive-frequency (electron-like) spectral weight (or local density of states), can differ strongly from that of the negative frequency (hole-like) spectral weight. The effect of the impurity on the continuum states above the energy gap is calculated with good spectral resolution for the first time. This is also the first three-dimensional self-consistent calculation for a strong magnetic impurity potential.Comment: 13 pages, RevTex, change in heuristic picture, no change in numerical result

Evaluating Impacts of Anthropogenic Disturbance to Wetland Water Quality Functions

Wetland ecosystems play fundamental roles in regulating our freshwater resources, yet they are not comprehensively protected from degradation and loss. West Virginia, USA has wetlands across diverse landscapes and geography that feed into both the Chesapeake Bay and Gulf of Mexico. The state is also comprised of diverse anthropogenic land-use practices. We are assessing 200 wetlands over 2 years to evaluate how anthropogenic disturbance impact wetland water quality functions. Select water quality parameters (20), and relative diversity and abundance of vegetation and macroinvertebrates will be used as bioindicators. They will be compared with GIS assessments of watershed land cover/ land-use practices and climate data to evaluate relationships and determine how they impact a wetland’s ability to carry out select water quality functions. Preliminary results after one year of sampling indicate that wetlands at higher elevation with fewer watershed land-use practices generally had lower E. Coli, heavy metal (Lead and Zinc), and nutrient (Phosphorus and Nitrogen) concentrations relative to wetlands at lower elevations with greater watershed land-use practices. Seasonal conductivity readings increased following precipitation events. Conductivity and salinity readings also decreased along its drainage gradient, indicative of the wetland performing its water quality functions. We also observed that conductivity and nutrient concentrations were highest during the winter and lowest during the summer, coinciding with the bottom and peak periods of primary productivity. The results of this project will be used to develop wetland water quality standards for West Virginia and help advance more comprehensive wetland regulations

Exact non-equilibrium current from the partition function for impurity transport problems

We study the partition functions of quantum impurity problems in the domain of complex applied bias for its relation to the non-equilibrium current suggested by Fendley, Lesage and Saleur (cond-mat/9510055). The problem is reformulated as a certain generalization of the linear response theory that accomodates an additional complex variable. It is shown that the mentioned relation holds in a rather generic case in the linear response limit, or under certain condition out of equilibrium. This condition is trivially satisfied by the quadratic Hamiltonians and is rather restrictive for the interacting models. An example is given when the condition is violated.Comment: 10 pages, RevTex. Final extended versio

Discrimination, Crypticity, and Incipient Taxa in Entamoeba

Persistent difficulties in resolving clear lineages in diverging populations of prokaryotes or unicellular eukaryotes (protistan polyphyletic groups) are challenging the classical species concept. Although multiple integrated approaches would render holistic taxonomies, most phylogenetic studies are still based on single-gene or morphological traits. Such methodologies conceal natural lineages, which are considered “cryptic.” The concept of species is considered artificial and inadequate to define natural populations. Social organisms display differential behaviors toward kin than to nonrelated individuals. In “social” microbes, kin discrimination has been used to help resolve crypticity. Aggregative behavior could be explored in a nonsocial protist to define phylogenetic varieties that are considered “cryptic.” Two Entamoeba invadens strains, IP-1 and VK-1:NS are considered close populations of the same “species.” This study demonstrates that IP-1 and VK-1:NS trophozoites aggregate only with alike members and discriminate members of different strains based on behavioral and chemical signals. Combined morphological, behavioral/chemical, and ecological studies could improve Archamoebae phylogenies and define cryptic varieties. Evolutionary processes in which selection acted continuously and cumulatively on ancestors of Entamoeba populations gave rise to chemical and behavioral signals that allowed individuals to discriminate nonpopulation members and, gradually, to the emergence of new lineages; alternative views that claim a “Designer” or “Creator” as responsible for protistan diversity are unfounded