2,042 research outputs found
InAs nanowire transistors with multiple, independent wrap-gate segments
We report a method for making horizontal wrap-gate nanowire transistors with
up to four independently controllable wrap-gated segments. While the step up to
two independent wrap-gates requires a major change in fabrication methodology,
a key advantage to this new approach, and the horizontal orientation more
generally, is that achieving more than two wrap-gate segments then requires no
extra fabrication steps. This is in contrast to the vertical orientation, where
a significant subset of the fabrication steps needs to be repeated for each
additional gate. We show that cross-talk between adjacent wrap-gate segments is
negligible despite separations less than 200 nm. We also demonstrate the
ability to make multiple wrap-gate transistors on a single nanowire using the
exact same process. The excellent scalability potential of horizontal wrap-gate
nanowire transistors makes them highly favourable for the development of
advanced nanowire devices and possible integration with vertical wrap-gate
nanowire transistors in 3D nanowire network architectures.Comment: 18 pages, 5 figures, In press for Nano Letters (DOI below
CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud
We present the N2H+(J=1-0) map of the Serpens South molecular cloud obtained
as part of the CARMA Large Area Star Formation Survey (CLASSy). The
observations cover 250 square arcminutes and fully sample structures from 3000
AU to 3 pc with a velocity resolution of 0.16 km/s, and they can be used to
constrain the origin and evolution of molecular cloud filaments. The spatial
distribution of the N2H+ emission is characterized by long filaments that
resemble those observed in the dust continuum emission by Herschel. However,
the gas filaments are typically narrower such that, in some cases, two or three
quasi-parallel N2H+ filaments comprise a single observed dust continuum
filament. The difference between the dust and gas filament widths casts doubt
on Herschel ability to resolve the Serpens South filaments. Some molecular
filaments show velocity gradients along their major axis, and two are
characterized by a steep velocity gradient in the direction perpendicular to
the filament axis. The observed velocity gradient along one of these filaments
was previously postulated as evidence for mass infall toward the central
cluster, but these kind of gradients can be interpreted as projection of
large-scale turbulence.Comment: 12 pages, 4 figures, published in ApJL (July 2014
Determining the electronic performance limitations in top-down fabricated Si nanowires with mean widths down to 4 nm
Silicon nanowires have been patterned with mean widths down to 4 nm using top-down lithography and dry etching. Performance-limiting scattering processes have been measured directly which provide new insight into the electronic conduction mechanisms within the nanowires. Results demonstrate a transition from 3-dimensional (3D) to 2D and then 1D as the nanowire mean widths are reduced from 12 to 4 nm. The importance of high quality surface passivation is demonstrated by a lack of significant donor deactivation, resulting in neutral impurity scattering ultimately limiting the electronic performance. The results indicate the important parameters requiring optimization when fabricating nanowires with atomic dimensions
PathOrganic – Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains
PathOrganic assesses risks associated with the consumption of fresh and minimally
processed vegetables due to the prevalence of bacterial human pathogens in plant
produce. The project evaluates whether organic production poses a risk on food safety,
taking into consideration sources of pathogen transmission (e.g. animal manure).
The project also explores whether organic versus conventional production practices
may reduce the risk of pathogen manifestation. In Europe, vegetable-linked outbreaks
are not well investigated. A conceptual model together with novel sampling strategies
and specifically adjusted methods provides the basis for large-scale surveys of organically
grown plant produce in five European countries. Critical control points are
determined and evaluated and factors contributing to a food safety problem are analyzed
in greenhouse and field experiments. The project aims at developing a quantitative
risk assessment model and at formulating recommendations for improving food
safety in organic vegetable production
Pollen-Mediated Gene Flow from Genetically Modified Herbicide Resistant Creeping Bentgrass
Approximately 162 ha of multiple experimental fields of creeping bentgrass (Agrostis stolonifera L.) genetically modified for resistance to Roundup ®herbicide, were planted in central Oregon in 2002. When the fields flowered for the first time in the summer of 2003, a unique opportunity was presented to evaluate methods to monitor potential pollen-mediated gene flow from the experimental GM crop fields to compatible sentinel and resident plants that were located in surrounding, primarily non-agronomic areas
Suicides among Danish cancer patients 1971–1999
Compared to the general population, the suicide risk among Danish cancer patients diagnosed in 1971–1986 was increased by 50% for men and 30% for women. We updated the earlier study to evaluate both long-term and recent trends in the suicide risk. Cancer patients with a first cancer diagnosed between 1971 and 1999 in Denmark were followed-up for completed suicide through 1999. Excluding nonmelanoma skin cancer, 564 508 cancer patients were included and 1241 suicides observed. Both the standardised mortality ratio (SMR) of suicide relative to the general population and the suicide rates were analysed with Poisson regression methods. The overall SMR was increased to 1.7 (95% CI. 1.6–1.9) for men and 1.4 (95% CI: 1.3–1.5) for women. Following the cancer diagnosis, the suicide risk was highest in the first 3 months for men and between months 3 and 12 for women. The risk was higher for nonlocalised cancer and for cancers with perceived poor prognosis. Breast cancer patients had a higher risk than other cancer patients with similar good prognosis. The suicide rates among cancer patients decreased with calendar time, but less so than the rates in the general population. The suicide risk among cancer patients has not decreased as much as in the Danish population and reasons for this should be explored. Breast cancer might be believed by patients to be more life threatening than it is. Assessment and treatment of depression could improve the quality of life for cancer patients who suffer from unrecognised depressions and in turn reduce the risk of suicide in cancer patients
Calibrating the Cepheid Period-Luminosity relation from the infrared surface brightness technique I. The p-factor, the Milky Way relations, and a universal K-band relation
We determine Period-Luminosity relations for Milky Way Cepheids in the
optical and near-IR bands. These relations can be used directly as reference
for extra-galactic distance determination to Cepheid populations with solar
metallicity, and they form the basis for a direct comparison with relations
obtained in exactly the same manner for stars in the Magellanic Clouds,
presented in an accompanying paper. In that paper we show that the metallicity
effect is very small and consistent with a null effect, particularly in the
near-IR bands, and we combine here all 111 Cepheids from the Milky Way, the LMC
and SMC to form a best relation. We employ the near-IR surface brightness
(IRSB) method to determine direct distances to the individual Cepheids after we
have recalibrated the projection factor using the recent parallax measurements
to ten Galactic Cepheids and the constraint that Cepheid distances to the LMC
should be independent of pulsation period. We confirm our earlier finding that
the projection factor for converting radial velocity to pulsational velocity
depends quite steeply on pulsation period, p=1.550-0.186*log(P) in disagrement
with recent theoretical predictions. We delineate the Cepheid PL relation using
111 Cepheids with direct distances from the IRSB analysis. The relations are by
construction in agreement with the recent HST parallax distances to Cepheids
and slopes are in excellent agreement with the slopes of apparent magnitudes
versus period observed in the LMC.Comment: Accepted for publication by Astronomy and Astrophysics. 15 pages, 11
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