1,694 research outputs found
Variation and geographical distribution of ploidy levels in Pennisetum section Brevivalvula (Poaceae) in Burkina Faso, Benin and southern Niger
#Pennisetum sect. #Brevivalvula is a species complex characterized by polyploidy and apoximis. Ploidy level was assessed by DAPI-flow cytometry for 304 plants of the section, originating from Burkina Faso, Benin and southern Niger. The results were confirmed for 54 plants based on chromosome counts. The samples show four euploidy levels (with x = 9) distributed among five species : #P. hordeoides (2n = 36, 54), #P. pedicellatum (2n = 36, 45, 54), #P. polystachion (2n = 18, 36, 45, 54), #P. setosum (2n = 54), and #P. subangustum (2n = 18, 36, 54). The geographical distribution of these ploidy levels seems related to major vegetation zones present in Africa. Diploid populations of #P. polystachion and #P. subangustum$ were found in the Banfora area, in Burkina Faso. (Résumé d'auteur
The effect of temporal sampling regime on the characterization of home range for female boreal woodland caribou (Rangifer tarandus caribou) in Labrador, Canada
Our objective was to determine the influence of temporal sampling regime on the characteristics of individual female caribou home ranges and to explore implications of these findings to the conservation of caribou. The study population was 24 adult female caribou monitored for between 4 and 11 consecutive years between 1986 and 2009 from the Red Wine Mountain (RWM) and Lac Joseph (LJ) herds of boreal caribou in Labrador. We evaluated the influence of length of the monitoring period on the size of home ranges and fidelity of caribou to their ranges by measuring the percent overlap of multi-annual ranges on the total time period a caribou was collared and by calculating displacement between centroids of annual and multi-annual ranges for a given caribou. We found that the size of the range increased with each additional year of monitoring—initially at a rate greater than 20% per year, and then more slowly until an asymptote was reached after 7 years. The distance ratio declined with an increase in the monitoring interval until after approximately 6 years of monitoring. Finally, we evaluated trade-offs between monitoring interval and sample size by measuring the proportion of the total herd range captured by multi-annual ranges for given monitoring interval and sample size combinations. Caribou with the longest monitoring interval inevitably captured the greatest portion of the range at each given sample size. Only monitoring intervals of 4 years or greater captured more than 65% of the herd range even when sample size was doubled for shorter monitoring intervals. Our results suggest that long term monitoring is important when defining the extent of caribou ranges
Association between genetic variants in the Coenzyme Q10 metabolism and Coenzyme Q10 status in humans
<p>Abstract</p> <p>Background</p> <p>Coenzyme Q<sub>10 </sub>(CoQ<sub>10</sub>) is essential for mitochondrial energy production and serves as an antioxidants in extra mitochondrial membranes. The genetics of primary CoQ<sub>10 </sub>deficiency has been described in several studies, whereas the influence of common genetic variants on CoQ<sub>10 </sub>status is largely unknown. Here we tested for non-synonymous single-nucleotidepolymorphisms (SNP) in genes involved in the biosynthesis (CoQ3<sup>G272S </sup>, CoQ6<sup>M406V</sup>, CoQ7<sup>M103T</sup>), reduction (NQO1<sup>P187S</sup>, NQO2<sup>L47F</sup>) and metabolism (apoE3/4) of CoQ<sub>10 </sub>and their association with CoQ<sub>10 </sub>status. For this purpose, CoQ<sub>10 </sub>serum levels of 54 healthy male volunteers were determined before (T<sub>0</sub>) and after a 14 days supplementation (T<sub>14</sub>) with 150 mg/d of the reduced form of CoQ<sub>10</sub>.</p> <p>Findings</p> <p>At T<sub>0</sub>, the CoQ<sub>10 </sub>level of heterozygous NQO1<sup>P187S </sup>carriers were significantly lower than homozygous S/S carriers (0.93 ± 0.25 μM versus 1.34 ± 0.42 μM, p = 0.044). For this polymorphism a structure homology-based method (PolyPhen) revealed a possibly damaging effect on NQO1 protein activity. Furthermore, CoQ<sub>10 </sub>plasma levels were significantly increased in apoE4/E4 genotype after supplementation in comparison to apoE2/E3 genotype (5.93 ± 0.151 μM versus 4.38 ± 0.792 μM, p = 0.034). Likewise heterozygous CoQ3<sup>G272S </sup>carriers had higher CoQ<sub>10 </sub>plasma levels at T<sub>14 </sub>compared to G/G carriers but this difference did not reach significance (5.30 ± 0.96 μM versus 4.42 ± 1.67 μM, p = 0.082).</p> <p>Conclusions</p> <p>In conclusion, our pilot study provides evidence that NQO1<sup>P187S </sup>and apoE polymorphisms influence CoQ<sub>10 </sub>status in humans.</p
Asymptotic analysis of the model for distribution of high-tax payers
The z-transform technique is used to investigate the model for distribution
of high-tax payers, which is proposed by two of the authors (K. Y and S. M) and
others. Our analysis shows an asymptotic power-law of this model with the
exponent -5/2 when a total ``mass'' has a certain critical value. Below the
critical value, the system exhibits an ordinary critical behavior, and scaling
relations hold. Above the threshold, numerical simulations show that a
power-law distribution coexists with a huge ``monopolized'' member. It is
argued that these behaviors are observed universally in conserved aggregation
processes, by analizing an extended model.Comment: 5pages, 3figure
Non-equilibrium Thermodynamics: Structural Relaxation, Fictive temperature and Tool-Narayanaswamy phenomenology in Glasses
Starting from the second law of thermodynamics applied to an isolated system
consisting of the system surrounded by an extremely large medium, we formulate
a general non-equilibrium thermodynamic description of the system when it is
out of equilibrium. We then apply it to study the structural relaxation in
glasses and establish the phenomenology behind the concept of the fictive
temperature and of the empirical Tool-Narayanaswamy equation on firmer
theoretical foundation.Comment: 20 pages, 1 figur
The Simplicial Ricci Tensor
The Ricci tensor (Ric) is fundamental to Einstein's geometric theory of
gravitation. The 3-dimensional Ric of a spacelike surface vanishes at the
moment of time symmetry for vacuum spacetimes. The 4-dimensional Ric is the
Einstein tensor for such spacetimes. More recently the Ric was used by Hamilton
to define a non-linear, diffusive Ricci flow (RF) that was fundamental to
Perelman's proof of the Poincare conjecture. Analytic applications of RF can be
found in many fields including general relativity and mathematics. Numerically
it has been applied broadly to communication networks, medical physics,
computer design and more. In this paper, we use Regge calculus (RC) to provide
the first geometric discretization of the Ric. This result is fundamental for
higher-dimensional generalizations of discrete RF. We construct this tensor on
both the simplicial lattice and its dual and prove their equivalence. We show
that the Ric is an edge-based weighted average of deficit divided by an
edge-based weighted average of dual area -- an expression similar to the
vertex-based weighted average of the scalar curvature reported recently. We use
this Ric in a third and independent geometric derivation of the RC Einstein
tensor in arbitrary dimension.Comment: 19 pages, 2 figure
Different Transport Pathways of Individual Precursor Proteins in Mitochondria
Transport of mitochondrial precursor proteins into mitochondria of Neurospora crassa was studied in a cellfree reconstituted system. Precursors were synthesized in a reticulocyte lysate programmed with Neurospora mRNA and transported into isolated mitochondria in the absence of protein synthesis. Uptake of the following precursors was investigated: apocytochrome c, ADP/ATP carrier and subunit 9 of the oligomycin-sensitive ATPase.
Addition of high concentrations of unlabelled chemically prepared apocytochrome c (1–10 μM) inhibited the appearance in the mitochondrial of labelled cytochrome c synthesized in vitro because the unlabelled protein dilutes the labelled one and because the translocation system has a limited capacity [apparent V is 1–3 pmol × min−1× (mg mitochondrial protein)−1]. Concentrations of added apocytochrome c exceeding the concentrations of precursor proteins synthesized in vitro by a factor of about 104 did not inhibit the transfer of ADP/ATP carrier or ATPase subunit 9 into mitochondria. Carbonylcyanide m-chlorophenylhydrazone, an uncoupler of oxidative phosphorylation, inhibited transfer in vitro of ADP/ATP carrier and of ATPase subunit 9, but not of cytochrome c.
These findings suggest that cytochrome c and the other two proteins have different import pathways into mitochondria. It can be inferred from the data presented that different 'receptors' on the mitochondrial surface mediate the specific recognition of precursor proteins by mitochondria as a first step in the transport process
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Forrestal Building Lighting Retrofit Second Live Test Demonstration (LTD)
This report describes and summarizes the Forrestal Building Lighting Retrofit Live Test demonstration (LTD) performed by Pacific Northwest Laboratory (PNL) in Room 5E-080 of the DOE Forrestal Building in Washington, D.C. The purpose of the LTD was to evaluate proposed lighting retrofits for compliance with the requirements laid out in the request for proposal (RFP) for the Shared Energy Savings (SES) Lighting Retrofit Project for the Forrestal Building, Washington, D.C. Testing was conducted from March 9 through March 18, 1992, and again on August 3 through August 6, 1992. Four contractors were initially tested in March. Then, two contractors were retested in August due to changes in the rebate schedule for electronic ballasts being offered by the Potomac Electric Power Company (PEPCO), the utility servicing the Forrestal Building. The two contractors tested in March were retested with different ballasts, tubes, and reflectors. The results from these new tests are reported here and compared with those from the earlier tests
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