Quantum Hall effect in narrow graphene ribbons

The edge states in the integer quantum Hall effect are known to be significantly affected by electrostatic interactions leading to the formation of compressible and incompressible strips at the boundaries of Hall bars. We show here, in a combined experimental and theoretical analysis, that this does not hold for the quantum Hall effect in narrow graphene ribbons. In our graphene Hall bar, which is only 60 nm wide, we observe the quantum Hall effect up to Landau level index k=2 and show within a zero free-parameter model that the spatial extent of the compressible and incompressible strips is of a similar magnitude as the magnetic length. We conclude that in narrow graphene ribbons the single-particle picture is a more appropriate description of the quantum Hall effect and that electrostatic effects are of minor importance.Comment: RevTex, 5 pages, 4 figures (matches published version

Waterbirds of the Chesapeake Bay: Status, Ecological Requirements, and Threats

The Chesapeake Bay is one of the most productive aquatic ecosystems in the world and plays an important role in the life cycle of many bird species. Each year, the rich resources of the Bay attract millions of birds from throughout the western hemisphere. Dependency on the Bay varies from species that stopover for a few days during migration to species that live out their entire life cycle within a single tributary. Many species that depend on the Bay are of high international, national or regional conservation concern. For these species, the Bay is strategically important and may serve a vital role in the recovery of imperiled populations. Because many waterbirds are top consumers and collectively require a broad array of resources, they represent sensitive indicators of overall ecosystem health. Within the mid-Atlantic region, waterbirds also form the basis of a burgeoning ecotourism industry. Effective conservation of waterbirds within the Chesapeake Bay requires that we have a clear understanding of species requirements and the role that the Bay plays in their annual cycle. This document presents a brief overview of the Chesapeake Bay setting and the habitats that are believed to be significant to birds that depend on the Bay’s resources. The document then develops a conceptual model and ecological matrix that within a series of tables presents what is known about species-specific status and trends, phenology of occurrence, resource use and energetics, vital demographic rates, threats, and the importance of the Bay for waterbird species that use the Bay on an annual basis. This information is intended to provide a foundation of what is known and unknown for these species and the basis of a jumping off point for the development of a strategy to prioritize and collect critical information in the future. The Chesapeake Bay provides habitat and resources to 124 species of waterbirds throughout the year. Relationships between these species and the Bay are species-specific and complex. Although it is possible to identify some populations for which the Bay is of critical importance, information is lacking for most species such that definitive assessments cannot be made. Ongoing monitoring programs designed to evaluate population status and trends currently include a relatively small percentage of the overall community. Prominent groups lacking such programs include migratory and wintering seabirds, marshbirds, and migratory shorebirds. Marshbirds in particular stand out as a broad species group with eminent threats but for which we have little baseline data and no effective monitoring program. Information highlights the need for further assessment of monitoring programs and approaches that will result in the development of more comprehensive and coordinated efforts

Gauge Theory for Baryon and Lepton Numbers with Leptoquarks

Models where the baryon (B) and lepton (L) numbers are local gauge symmetries that are spontaneously broken at a low scale are revisited. We find new extensions of the standard model which predict the existence of fermions that carry both baryon and lepton numbers (i.e., leptoquarks). The local baryonic and leptonic symmetries can be broken at a scale close to the electroweak scale and we do not need to postulate the existence of a large desert to satisfy the experimental constraints on baryon number violating processes like proton decay

Stop-over and Migration Ecology of the Whimbrel: Fall 2009 Season Report

The whimbrel (Numenius phaeopus) is a large, Holarctic, highly migratory shorebird. The North American race (N.p. hudsonicus) includes two disjunct breeding populations, both of which winter primarily in Central and South America. The western population breeds in Alaska and the Northwest Territories of Canada (Engelmoer and Roselaar 1998). The eastern population breeds south and west of Hudson Bay in Manitoba and Ontario (Skeel and Mallory 1996, Jehl and Smith 1970). The prevailing thought was that the western population followed a Pacific Coast migration route between breeding and wintering areas in Panama and western South America, and that the Hudson Bay population followed an Atlantic Coast migration route to wintering grounds in Northeast South America (Andres et al. 2009, Skeel and Mallory 1996, Morrison and Ross 1989). Both populations are of high conservation concern due to population declines in recent decades (Bart et al. 2007, Morrison et al. 2006, Watts and Truitt in press). Investigations into the migration routes of whimbrels staging in Virginia have shown a previously unknown link between the eastern and western populations as they stop-over in Virginia (Watts et al. 2008). The primary objective of this project is to examine the stop-over and migration strategies of whimbrels, as they relate to the conservation of the species. A total of four 9.5 gram PTT satellite transmitters were deployed during the fall migration season. Average weight for the whimbrels with transmitters was 527.2 grams, or approximately 200 grams over mean winter (lean) weight. Ten digitally coded glue-on radio transmitters were attached to birds. The cumulative data give us insight into stop-over times for whimbrels as they stage on the Eastern Shore of Virginia before migrating to wintering grounds. Satellite and radio transmittered whimbrels departed the Eastern Shore between 31 August and 20 September 2009. Whimbrels arrived on the Eastern Shore in large numbers as early as early to mid-July due to record low temperatures and winter-like conditions on the breeding grounds. Several unusual migration events were observed during the fall season. Twelve flights greater than 1,000km were documented during the fall. These flights took an average of 95 hours to complete. The average distance traveled during these flights was 2,697km. A total of 5 shorter flights on wintering grounds were also documented, with birds moving from initial locations in Dominica, Venezuela, and Guyana into French Guiana, Suriname, and Brazil, the primary wintering grounds for eastern whimbrels (Morrison and Ross 1989). The mean distance traveled on these flights was 597km with the mean time in flight 47.3 hours

Using Satellite and Radio Telemetry to Examine Stopover and Migration Ecology of the Whimbrel: 2009-2011 Report

The whimbrel (Numenius phaeopus) is a large, Holarctic, highly migratory shorebird. The North American race (N.p. hudsonicus) includes two disjunct breeding populations, both of which winter primarily in Central and South America. The western population breeds in Alaska and the Northwest Territories of Canada (Engelmoer and Roselaar 1998). The eastern population breeds south and west of Hudson Bay in Manitoba and Ontario (Skeel and Mallory 1996, Jehl and Smith 1970). The prevailing idea was that the western population followed a Pacific Coast migration route between breeding and wintering areas in Panama and western South America, and that the Hudson Bay population followed an Atlantic Coast migration route to wintering grounds in Northeast South America (Andres et al. 2009, Skeel and Mallory 1996, Morrison and Ross 1989). Both populations are of high conservation concern due to population declines in recent decades (Bart et al. 2007, Morrison et al. 2006, Watts and Truitt in press). Investigations into the migration routes of whimbrels staging in Virginia have shown a previously unknown link between the eastern and western populations as they stop-over in Virginia (Watts et al. 2008). The primary objective of this project is to examine the stop-over and migration strategies of whimbrels, as they relate to the conservation of the species. A total of 12 9.5 gram PTT satellite transmitters were deployed during the 2009-2010 spring and fall migration seasons. Average weight for the whimbrels with transmitters was 568 ± 53SD grams, or approximately 150-200 grams over mean winter (lean) weight. A total of 67 digitally coded glue-on radio transmitters were attached to birds during these seasons. The cumulative data give us insight into stop-over times for whimbrels as they stage on the Eastern Shore of Virginia before migrating to both breeding and wintering grounds. Satellite and radio transmittered whimbrels departed the Eastern Shore in the spring season between 22 May and 3 June and in the fall season between 11 August and 20 September. Spring birds tend to leave during a short window (CCB/TNC spring whimbrel count unpublished data), whereas fall birds have a much bigger migration window as shown by the wide range of satellite and radio transmitter leave dates. Several unusual migration events were observed during the spring and fall seasons. Twenty flights averaging 2,595 km were documented during the spring seasons. These flights took an average of 81 hours to complete. Twenty-four flights averaging 2,603 km were documented during the fall seasons. These flights took an average of 91hours to complete. A total of 13 shorter flights on breeding grounds were also documented, with birds moving from initial locations in along the Hudson Bay coastline to interior breeding locations. The mean distance traveled on these flights was 435 km with the mean time in flight 44 hours. A total of 17 shorter flights on wintering grounds were documented, with birds moving from initial locations in the Greater and Lesser Antilles, Suriname, and Guyana into French Guiana, Suriname, and Brazil, the primary wintering grounds for the Atlantic population of whimbrels (Morrison and Ross 1989). The mean distance traveled on these flights was 548 km with the mean time in flight 52 hours

An investigation of stopover ecology of the red knot on the Virginia Barrier Island

The Virginia barrier island chain plays a significant role in the life cycle of many of the most vulnerable shorebird species in North America. The large areas of relatively undisturbed beach and marsh habitat available to shorebirds during the migrator

Crystal Structure of an Anti-Ang2 CrossFab Demonstrates Complete Structural and Functional Integrity of the Variable Domain.

Bispecific antibodies are considered as a promising class of future biotherapeutic molecules. They comprise binding specificities for two different antigens, which may provide additive or synergistic modes of action. There is a wide variety of design alternatives for such bispecific antibodies, including the "CrossMab" format. CrossMabs contain a domain crossover in one of the antigen-binding (Fab) parts, together with the "knobs-and-holes" approach, to enforce the correct assembly of four different polypeptide chains into an IgG-like bispecific antibody. We determined the crystal structure of a hAng-2-binding Fab in its crossed and uncrossed form and show that CH1-CL-domain crossover does not induce significant perturbations of the structure and has no detectable influence on target binding

Shot noise in lithographically patterned graphene nanoribbons

We have investigated shot noise and conductance of multiterminal graphene nanoribbon devices at temperatures down to 50 mK. Away from the charge neutrality point, we find a Fano factor F≈0.4, nearly independent of the charge density. Our shot noise results are consistent with theoretical models for disordered graphene ribbons with a dimensionless scattering strength K0 ≈ 10 corresponding to rather strong disorder. Close to charge neutrality, an increase in F up to ∼0.7 is found, which indicates the presence of a dominant Coulomb gap possibly due to a single quantum dot in the transport gap.Peer reviewe

The Injector Layout of BERLinPro

BERLinPro is an Energy Recovery Linac Project running since 2011 at the HZB in Berlin. A conceptual design report has been published in 2012 [1]. One of the key components of the project is the 100 mA superconducting RF photocathode gun under development at the HZB since 2010. Starting in 2016 the injector will go into operation, providing 6.6 MeV electrons with an emittance well below 1mm mrad and bunches shorter than 5 ps. In 2017 the 50 MeV linac will be set up and full recirculation is planned for 2018. The injector design has been finalized and is described in detail in this paper. Emphasis is further laid on beam dynamics aspects and performance simulations of two different gun cavitie