649 research outputs found
Topological Background Fields as Quantum Degrees of Freedom of Compactified Strings
It is shown that background fields of a topological character usually
introduced as such in compactified string theories correspond to quantum
degrees of freedom which parametrise the freedom in choosing a representation
of the zero mode quantum algebra in the presence of non-trivial topology. One
consequence would appear to be that the values of such quantum degrees of
freedom, in other words of the associated topological background fields, cannot
be determined by the nonperturbative string dynamics.Comment: 1+10 pages, no figure
In vivo assessment of the mechanical properties of the child cortical bone using quantitative computed tomography
The mechanical properties of the rib cortical bone are extremely rare on children due to difficulties to obtain specimens to perform conventional tests. Some recent studies used cadaveric bones or bone tissues collected during surgery but are limited by the number of samples that could be collected. A non-invasive technique could be extremely valuable to overcome this limitation. It has been shown that a relationship exists between the mechanical properties (apparent Young’s modulus and ultimate strength) and the bone mineral density (assessed using Quantitative Computed Tomography, QCT), for the femur and recently by our group for the adult ribs ex vivo. Thus the aim of this study was to assess the mechanical properties of the child rib cortical bone using both QCT images in vivo and the previous relationship between bone mineral density and mechanical properties of the rib cortical bone. Twenty-eight children were included in this study. Seven age-groups have been considered (1, 1.5, 3, 6, 10, 15, 18 years old). The QCT images were prescribed for various thoracic pathologies at the pediatric hospital in Lyon. A calibration phantom was added to the clinical protocol without any modifications for the patient. The protocol was approved by the ethical committee. A 3D reconstruction of each thorax was performed using the QCT images. A custom software was then used to obtain cross-sections to the rib midline. The mean bone mineral density was then computed by averaging the Hounsfield Units in a specific cross-section and by converting the mean value (Hounsfield Units) in bone mineral density using the calibration phantom. This bone mineral density was assessed for the 6th rib of each subject. Our relationship between the bone mineral density and the mechanical properties of the rib cortical bone was used to derive the mechanical properties of the child ribs in vivo. The results give values for the apparent Young’s modulus and the ultimate strength. The mechanical properties increase along growth. As an example the apparent Young’s modulus in the lateral region ranges from 7 GPa +/-3 at 1 year old up to 13 GPa +/- 2 at 18 years old. These data are in agreement with the few previous values obtained from child tissues. This methodology opens the way to in vivo measurement of the mechanical properties of the child cortical bone based on calibrated QCT images
Random interactions and spin-glass thermodynamic transition in the hole-doped Haldane system YCaBaNiO
Magnetization, DC and AC bulk susceptibility of the =1 Haldane chain
system doped with electronic holes, YCaBaNiO
(0x0.20), have been measured and analyzed. The most striking
results are (i) a sub-Curie power law behavior of the linear susceptibility,
, for temperature lower than the Haldane gap
of the undoped compound (x=0) (ii) the existence of a spin-glass thermodynamic
transition at = 2-3 K. These findings are consistent with (i) random
couplings within the chains between the spin degrees of freedom induced by hole
doping, (ii) the existence of ferromagnetic bonds that induce magnetic
frustration when interchain interactions come into play at low temperature.Comment: 4 pages, 4 figures, to appear in Phys. Rev.
hPG\u3csub\u3e80\u3c/sub\u3e (Circulating Progastrin), a Novel Blood-Based Biomarker for Detection of Poorly Differentiated Neuroendocrine Carcinoma and Well Differentiated Neuroendocrine Tumors
Current blood-based biomarkers for neuroendocrine neoplasms (NENs) lack both sensitivity and specificity. Human circulating progastrin (hPG80) is a novel biomarker that can be easily measured in plasma by ELISA. This study is the first to examine hPG80 in NENs. Plasma hPG80 was quantified from 95 stage IV NEN patients, using DxPG80 technology (ECS Progastrin, Switzerland) and compared with hPG80 concentrations in two cohorts of healthy donor controls aged 50–80 (n = 252) and 18–25 (n = 137). Median hPG80 in NENs patients was 5.54 pM compared to 1.5 pM for the 50–80 controls and 0.29 pM the 18–25 cohort (p \u3c 0.0001). Subgroup analysis revealed median hPG80 levels significantly higher than for either control cohort in neuroendocrine carcinoma (NEC; n = 25) and neuroendocrine tumors (NET; n = 70) including the small-cell lung cancer (SCLC) sub-cohort (n = 13). Diagnostic accuracy, estimated by AUCs, was high for NENs, as well as both sub-groups (NEC/NET) when compared to the younger and older control groups. Plasma hPG80 in NENs may be a diagnostic blood biomarker for both low- and high-grade NENs; further study is warranted. A prospective multi-center trial is ongoing in NET to evaluate hPG80 as a means of monitoring disease (NCT04750954)
The Awesome Power of Yeast Evolutionary Genetics: New Genome Sequences and Strain Resources for the Saccharomyces sensu stricto Genus
High-quality, well-annotated genome sequences and standardized laboratory strains fuel experimental and evolutionary research. We present improved genome sequences of three species of Saccharomyces sensu stricto yeasts: S. bayanus var. uvarum (CBS 7001), S. kudriavzevii (IFO 1802T and ZP 591), and S. mikatae (IFO 1815T), and describe their comparison to the genomes of S. cerevisiae and S. paradoxus. The new sequences, derived by assembling millions of short DNA sequence reads together with previously published Sanger shotgun reads, have vastly greater long-range continuity and far fewer gaps than the previously available genome sequences. New gene predictions defined a set of 5261 protein-coding orthologs across the five most commonly studied Saccharomyces yeasts, enabling a re-examination of the tempo and mode of yeast gene evolution and improved inferences of species-specific gains and losses. To facilitate experimental investigations, we generated genetically marked, stable haploid strains for all three of these Saccharomyces species. These nearly complete genome sequences and the collection of genetically marked strains provide a valuable toolset for comparative studies of gene function, metabolism, and evolution, and render Saccharomyces sensu stricto the most experimentally tractable model genus. These resources are freely available and accessible through www.SaccharomycesSensuStricto.org
The centromeric/nucleolar chromatin protein ZFP-37 may function to specify neuronal nuclear domains
Murine ZFP-37 is a member of the large family of C2H2 type zinc finger
proteins. It is characterized by a truncated NH2-terminal
Kruppel-associated box and is thought to play a role in transcriptional
regulation. During development Zfp-37 mRNA is most abundant in the
developing central nervous system, and in the adult mouse expression is
restricted largely to testis and brain. Here we show that at the protein
level ZFP-37 is detected readily in neurons of the adult central nervous
system but hardly in testis. In brain ZFP-37 is associated with nucleoli
and appears to contact heterochromatin. Mouse and human ZFP-37 have a
basic histone H1-like linker domain, located between KRAB and zinc finger
regions, which binds double-stranded DNA. Thus we suggest that ZFP-37 is a
structural protein of the neuronal nucleus which plays a role in the
maintenance of specialized chromatin domains
Defining freshwater as a natural resource: a framework linking water use to the area of protection natural resources
© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Purpose: While many examples have shown unsustainable use of freshwater resources, existing LCIA methods for water use do not comprehensively address impacts to natural resources for future generations. This framework aims to (1) define freshwater resource as an item to protect within the Area of Protection (AoP) natural resources, (2) identify relevant impact pathways affecting freshwater resources, and (3) outline methodological choices for impact characterization model development. Methods: Considering the current scope of the AoP natural resources, the complex nature of freshwater resources and its important dimensions to safeguard safe future supply, a definition of freshwater resource is proposed, including water quality aspects. In order to clearly define what is to be protected, the freshwater resource is put in perspective through the lens of the three main safeguard subjects defined by Dewulf et al. (2015). In addition, an extensive literature review identifies a wide range of possible impact pathways to freshwater resources, establishing the link between different inventory elementary flows (water consumption, emissions, and land use) and their potential to cause long-term freshwater depletion or degradation. Results and discussion: Freshwater as a resource has a particular status in LCA resource assessment. First, it exists in the form of three types of resources: flow, fund, or stock. Then, in addition to being a resource for human economic activities (e.g., hydropower), it is above all a non-substitutable support for life that can be affected by both consumption (source function) and pollution (sink function). Therefore, both types of elementary flows (water consumption and emissions) should be linked to a damage indicator for freshwater as a resource. Land use is also identified as a potential stressor to freshwater resources by altering runoff, infiltration, and erosion processes as well as evapotranspiration. It is suggested to use the concept of recovery period to operationalize this framework: when the recovery period lasts longer than a given period of time, impacts are considered to be irreversible and fall into the concern of freshwater resources protection (i.e., affecting future generations), while short-term impacts effect the AoP ecosystem quality and human health directly. It is shown that it is relevant to include this concept in the impact assessment stage in order to discriminate the long-term from the short-term impacts, as some dynamic fate models already do. Conclusions: This framework provides a solid basis for the consistent development of future LCIA methods for freshwater resources, thereby capturing the potential long-term impacts that could warn decision makers about potential safe water supply issues in the future
Comparison of S=0 and S=1/2 Impurities in Haldane Chain Compound,
We present the effect of Zn (S=0) and Cu (S=1/2) substitution at the Ni site
of S=1 Haldane chain compound . Y NMR allows us to
measure the local magnetic susceptibility at different distances from the
defects. The Y NMR spectrum consists of one central peak and several
less intense satellite peaks. The shift of the central peak measures the
uniform susceptibility, which displays a Haldane gap 100 K and it
corresponds to an AF coupling J260 K between the near-neighbor Ni spins.
Zn or Cu substitution does not affect the Haldane gap. The satellites, which
are evenly distributed on the two sides of the central peak, probe the
antiferromagnetic staggered magnetization near the substituted site, which
decays exponentially. Its extension is found identical for both impurities and
corresponds accurately to the correlation length (T) determined by Monte
Carlo (QMC) simulations for the pure compound. In the case of non-magnetic Zn,
the temperature dependence of the induced magnetization is consistent with a
Curie law with an "effective" spin S=0.4 on each side of Zn, which is well
accounted by Quantum Monte Carlo computations of the spinless-defect-induced
magnetism. In the case of magnetic Cu, the similarity of the induced magnetism
to the Zn case implies a weak coupling of the Cu spin to the nearest- neighbor
Ni spins. The slight reductionin the induced polarization with respect to Zn is
reproduced by QMC computations by considering an antiferromagnetic coupling of
strength J'=0.1-0.2 J between the S=1/2 Cu-spin and nearest-neighbor Ni-spin.Comment: 15 pages, 18 figures, submitted to Physical Review
Magnetization profiles and NMR spectra of doped Haldane chains at finite temperatures
Open segments of S=1 antiferromagnetic spin chains are studied at finite
temperatures and fields using continuous time Quantum Monte Carlo techniques.
By calculating the resulting magnetization profiles for a large range of chain
lengths with fixed field and temperature we reconstruct the experimentally
measured NMR spectrum of impurity doped YBaNiMgO. For
temperatures above the gap the calculated NMR spectra are in excellent
agreement with the experimental results, confirming the existence of
excitations at the end of open S=1 chain segments. At temperatures below the
gap, neglecting inter chain couplings, we still find well defined peaks in the
calculated NMR spectra corresponding to the chain end excitations. At
low temperatures, inter chain couplings could be important, resulting in a more
complicated phase.Comment: 7 pages, 5 figures, minor correction
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