406 research outputs found
A quantum search for zeros of polynomials
A quantum mechanical search procedure to determine the real zeros of a polynomial is introduced. It is based on the construction of a spin observable whose eigenvalues coincide with the zeros of the polynomial. Subsequent quantum mechanical measurements of the observable output directly the numerical values of the zeros. Performing the measurements is the only computational resource involved
Multiplication and Composition in Weighted Modulation Spaces
We study the existence of the product of two weighted modulation spaces. For
this purpose we discuss two different strategies. The more simple one allows
transparent proofs in various situations. However, our second method allows a
closer look onto associated norm inequalities under restrictions in the Fourier
image. This will give us the opportunity to treat the boundedness of
composition operators.Comment: 49 page
Seasonality of aerosol optical properties in the Arctic
Given the sensitivity of the Arctic climate to short-lived climate forcers,
long-term in situ surface measurements of aerosol parameters are useful in
gaining insight into the magnitude and variability of these climate forcings.
Seasonality of aerosol optical properties â including the aerosol
light-scattering coefficient, absorption coefficient, single-scattering
albedo, scattering Ă
ngström exponent, and asymmetry parameter â are
presented for six monitoring sites throughout the Arctic: Alert, Canada;
Barrow, USA; Pallas, Finland; Summit, Greenland; Tiksi, Russia; and Zeppelin
Mountain, Ny-Ă
lesund, Svalbard, Norway. Results show annual variability
in all parameters, though the seasonality of each aerosol optical property
varies from site to site. There is a large diversity in magnitude and
variability of scattering coefficient at all sites, reflecting differences in
aerosol source, transport, and removal at different locations throughout the
Arctic. Of the Arctic sites, the highest annual mean scattering coefficient
is measured at Tiksi (12.47 Mmâ1), and the lowest annual mean
scattering coefficient is measured at Summit (1.74 Mmâ1). At most
sites, aerosol absorption peaks in the winter and spring, and has a minimum
throughout the Arctic in the summer, indicative of the Arctic haze
phenomenon; however, nuanced variations in seasonalities suggest that this
phenomenon is not identically observed in all regions of the Arctic. The
highest annual mean absorption coefficient is measured at Pallas
(0.48 Mmâ1), and Summit has the lowest annual mean absorption
coefficient (0.12 Mmâ1). At the Arctic monitoring stations analyzed
here, mean annual single-scattering albedo ranges from 0.909 (at Pallas) to
0.960 (at Barrow), the mean annual scattering Ă
ngström exponent
ranges from 1.04 (at Barrow) to 1.80 (at Summit), and the mean asymmetry
parameter ranges from 0.57 (at Alert) to 0.75 (at Summit). Systematic
variability of aerosol optical properties in the Arctic supports the notion
that the sites presented here measure a variety of aerosol populations, which
also experience different removal mechanisms. A robust conclusion from the
seasonal cycles presented is that the Arctic cannot be treated as one common
and uniform environment but rather is a region with ample spatiotemporal
variability in aerosols. This notion is important in considering the design
or aerosol monitoring networks in the region and is important for informing
climate models to better represent short-lived aerosol climate forcers in
order to yield more accurate climate predictions for the Arctic.</p
Analysis of the surface state of epi-ready Ge wafers
The surface state of Ge epi-ready wafers (such as those used on III-V multijunction solar cells) supplied by two different vendors has been studied using X-ray photoemission spectroscopy. Our experimental results show that the oxide layer on the wafer surface is formed by GeO and GeO2. This oxide layer thickness differs among wafers coming from different suppliers. Besides, several contaminants appear on the wafer surfaces, carbon and probably chlorine being common to every wafer, irrespective of its origin. Wafers from one of the vendors show the presence of carbonates at their surfaces. On such wafers, traces of potassium seem to be present too
Changes in phosphorus status of 'Cripps' Pink' apple trees after application of mulches
The effect of four different mulches on fruit quality was quantified, either
directly via mineral nutrient contributions or indirectly, by increasing nutrient uptake
efficiency in the soil. We hypothesised that fruit nutrient levels would increase more
when an organic mulch, containing nutrients, was applied to the soil, with smaller/no
increases when an inorganic mulch was applied to the tree row.
In this paper, we concentrate on changes in fruit phosphorus (P) concentrations
after application of five treatments: a clean cultivated control, an inorganic woven
geotextile fabric, and organic mulches â compost, wood chips and a vermi-castings/
wood chips combination. The trial was conducted on a commercial farm, Lourensford
Estate, South Africa, from October 2008 to April 2012 â on an adjacent light, sandy and
heavier, sandy-silt soil.
Mineral nutrient analyses of the soil, leaves, mulches and fruit were performed.
Yield and fruit size were determined. Soil temperatures and soil water status were
recorded hourly during the last two seasons. P concentrations did increase chronologically
from the soil, then into leaves and then into the fruit after application of
mulches that provided additional P to the soil. Sporadic increases in both leaves and
fruit occurred, but could not always be related to treatment effects. The significant
consistent increase of P levels of the vermi-castings treatment in the heavy soil is likely
to be a combination of reduced irrigation volumes, as well as a treatment effect.
All mulches resulted in the well-established buffering of soil temperatures, soil water content and percentage soil carbon. Based on results from this study, it is not
feasible to apply mulches for the sole purpose to increase P levels in the soil, leaves or
fruit of established trees â although increases were noticed from time to time. In
addition to water and temperature modifying effects of mulches that would differ
between soil textures and depend on the mulch source, increases in P concentrations
may result. As yield efficiency is still the primary factor determining income per hectare
for the producer, the decrease in yield that resulted from mulching under these
conditions, will still outweigh any positive contributions of mulches. It is therefore of
utmost importance to first adjust irrigation volumes to a mulch treatment before the
advantageous properties of mulching will be of value.Stellenbosch University and
HortgroScience.http://www.actahort.orgam201
Characterization of chemical bonding in low-k dielectric materialsfor interconnect isolation: a xas and eels study
The use of low dielectric constant materials in the on-chipinterconnect process reduces interconnect delay, power dissipation andcrosstalk noise. To achieve the requirements of the ITRS for 2007-2009minimal sidewall damage from etch, ash or cleans is required. In chemicalvapor deposited (CVD) organo-silicate glass (OSG) which are used asintermetal dielectric (IMD) materials the substitution of oxygen in SiO2by methyl groups (-CH3) reduces the permittivity significantly (from 4.0in SiO2 to 2.6-3.3 in the OSG), since the electronic polarizability islower for Si-C bonds than for Si-O bonds. However, plasma processing forresist stripping, trench etching and post-etch cleaning removes C and Hcontaining molecular groups from the near-surface layer of OSG.Therefore, compositional analysis and chemical bonding characterizationof structured IMD films with nanometer resolution is necessary forprocess optimization. OSG thin films as-deposited and after plasmatreatment are studied using X-ray absorption spectroscopy (XAS) andelectron energy loss spectroscopy (EELS). In both techniques, the finestructure near the C1s absorption or energy loss edge, respectively,allows to identify C-H, C-C, and C-O bonds. This gives the opportunity todifferentiate between individual low-k materials and their modifications.The O1s signal is less selective to individual bonds. XAS spectra havebeen recorded for non-patterned films and EELS spectra for patternedstructures. The chemical bonding is compared for as-deposited andplasma-treated low-k materials. The Fluorescence Yield (FY) and the TotalElectron Yield (TEY) recorded while XAS measurement are compared.Examination of the C 1s near-edge structures reveal a modified bonding ofthe remaining C atoms in the plasma-treated sample regions
The complex TIE between macrophages and angiogenesis
Macrophages are primarily known as phagocytic immune cells, but they also play a role in diverse processes, such as morphogenesis, homeostasis and regeneration. In this review, we discuss the influence of macrophages on angiogenesis, the process of new blood vessel formation from the pre-existing vasculature. Macrophages play crucial roles at each step of the angiogenic cascade, starting from new blood vessel sprouting to the remodelling of the vascular plexus and vessel maturation. Macrophages form promising targets for both pro- and anti-angiogenic treatments. However, to target macrophages, we will first need to understand the mechanisms that control the functional plasticity of macrophages during each of the steps of the angiogenic cascade. Here, we review recent insights in this topic. Special attention will be given to the TIE2-expressing macrophage (TEM), which is a subtype of highly angiogenic macrophages that is able to influence angiogenesis via the angiopoietin-TIE pathway
Tumor-Associated Macrophages (TAMs) Form an Interconnected Cellular Supportive Network in Anaplastic Thyroid Carcinoma
BACKGROUND: A relationship between the increased density of tumor-associated macrophages (TAMs) and decreased survival was recently reported in thyroid cancer patients. Among these tumors, anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors in humans. TAMs (type M2) have been recognized as promoting tumor growth. The purpose of our study was to analyze with immunohistochemistry the presence of TAMs in a series of 27 ATC. METHODOLOGY/PRINCIPAL FINDINGS: Several macrophages markers such as NADPH oxidase complex NOX2-p22phox, CD163 and CD 68 were used. Immunostainings showed that TAMs represent more than 50% of nucleated cells in all ATCs. Moreover, these markers allowed the identification of elongated thin ramified cytoplasmic extensions, bestowing a "microglia-like" appearance on these cells which we termed "Ramified TAMs" (RTAMs). In contrast, cancer cells were totally negative. Cellular stroma was highly simplified since apart from cancer cells and blood vessels, RTAMs were the only other cellular component. RTAMs were evenly distributed and intermingled with cancer cells, and were in direct contact with other RTAMs via their ramifications. Moreover, RTAMs displayed strong immunostaining for connexin Cx43. Long chains of interconnected RTAMs arose from perivascular clusters and were dispersed within the tumor parenchyma. When expressed, the glucose transporter Glut1 was found in RTAMs and blood vessels, but rarely in cancer cells. CONCLUSION: ATCs display a very dense network of interconnected RTAMs in direct contact with intermingled cancer cells. To our knowledge this is the first time that such a network is described in a malignant tumor. This network was found in all our studied cases and appeared specific to ATC, since it was not found in differentiated thyroid cancers specimens. Taken together, these results suggest that RTAMs network is directly related to the aggressiveness of the disease via metabolic and trophic functions which remain to be determined
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