229 research outputs found
Evaluation of novel starch-deficient mutants of Chlorella sorokiniana for hyper-accumulation of lipids
When green algae are exposed to physiological stresses such as nutrient deprivation, growth is arrested and the cells channel fixed carbon instead into storage compounds, accumulating first starch granules and then lipid bodies containing triacylglycerides. In recent years there has been significant interest in the commercial exploitation of algal lipids as a sustainable source of biodiesel. Since starch and lipid biosynthesis involves the same C3 precursor pool, it has been proposed that mutations blocking starch accumulation should result in increased lipid yields, and indeed several studies have supported this. The fast-growing, thermotolerant alga Chlorella sorokiniana represents an attractive strain for industrial cultivation. We have therefore generated and characterized starch-deficient mutants of C. sorokiniana and determined whether lipid levels are increased in these strains under stress conditions. One mutant (ST68) is shown to lack isoamylase, whilst two others (ST3 and ST12) are defective in starch phosphorylase. However, we find no significant change in the accumulation or profile of fatty acids in these mutants compared to the wild-type, suggesting that a failure to accumulate starch per se is not sufficient for the hyper-accumulation of lipid, and that more subtle regulatory steps underlie the partitioning of carbon to the two storage products
Modal Extension of the Quantified Argument Calculus
The quantified argument calculus (Quarc) is a novel logic that departs in several ways from mainstream first-order logic. In particular, its quantifiers are not sentential operators attached to variables, but attach to unary predicates to form arguments – quantified arguments – of other predicates. Furthermore, Quarc includes devices to account for anaphora, active-passive-voice distinctions, and sentence- versus predicate-negation. While this base system has already been shown to be sound and complete, modal extensions still lack such results. The present paper fills this lacuna by developing a modal extension of Quarc, including identity. The semantics will invalidate the Quarc-analogues of the Barcan-formula and its converse, as well as treat identity as contingent by default. Furthermore, an unlabelled Gentzen-style natural deduction system will be presented, which includes the full expressive power of Quarc. It will be shown to be strongly sound and complete with respect to relational frames. The paper closes off with considerations on how to extend the system to cover other normal modal logics as well as extensions to suitable three-valued semantics that capture relevant types of presupposition-failure
On the run for water - Root growth of two phreatophytes in the Taklamakan Desert
Desert phreatophytes require extremely fast root growth for a successful establishment We measured the speed of seedling root growth of two phreatophytic plant species, Alhagi sparsifolia and Karelinia caspia, which form dominant or codominant stands around the river oases at the southern fringe of the Taklamakan Desert. As A sparsifolia occurs at sites with deeper groundwater, we expected the roots of this species to reach down more rapidly than those of K caspia. Furthermore, we expected seedlings experiencing no irrigation and low fertilization to have deeper reaching roots than seedlings with irrigation and fertilization. Seeds of both species were sown into 1 and 2 m long tubes in a glasshouse and in a field experiment, respectively. After 16 weeks of growth in the field roots of K. caspia and A. sparsifolia reached down 2 2 m and 1.7 m, respectively. In accordance with a faster growth, K. caspia had a higher water use, which resulted in a faster decrease of water content in the tubes. Species differences in the vertical reach of roots in the glasshouse experiment were comparable to those in the field experiment After 12 weeks without irrigation, A sparsifolia had a higher rooting depth (0.45 m) than with irrigation (0 30 m), while root depths of K caspia showed the opposite pattern with 062 m and 0 72 m, respectively Fertilizing increased total biomass of both species, while low level of fertilization had the tendency to increase the root shoot ratio and the specific root lengths (SRL), most likely a response to acquire nutrients at lower costs. However, plants of K. caspia showed an increase in SLR already after 12 weeks, while it took 16 weeks for A sparsifolia to increase SRL in the low fertilization level. Our results show clearly that both species are able to reach the groundwater table in the river valleys (6 5 m) within a time span of five to six months after germination However, the encountered vegetation pattern is probably not caused by differences in the speed of rooting depth, but might be the result of a higher capability of growing up with sand accumulation of A sparsifolia. As additional irrigation and fertilization did not enhance rooting depth in both species, these factors will have little impact in restoration procedures (C) 2010 Elsevier Ltd All rights reserve
Ab-initio study of the thermopower of biphenyl-based single-molecule junctions
Employing ab-initio electronic structure calculations combined with the
non-equilibrium Green's function technique, we study the dependence of the
thermopower Q on the conformation in biphenyl-based single-molecule junctions.
For the series of experimentally available biphenyl molecules, alkyl side
chains allow us to gradually adjust the torsion angle \phi\ between the two
phenyl rings from 0 to 90{\deg} and to control in this way the degree of
\pi-electron conjugation. Studying different anchoring groups and binding
positions, our theory predicts that the absolute values of the thermopower
decrease slightly towards larger torsion angles, following an a+b*cos^{2}\phi\
dependence. The anchoring group determines the sign of Q and a,b,
simultaneously. Sulfur and amine groups give rise to Q,a,b>0, while for cyano
Q,a,b<0. The different binding positions can lead to substantial variations of
the thermopower mostly due to changes in the alignment of the frontier
molecular orbital levels and the Fermi energy. We explain our ab-initio results
in terms of a \pi-orbital tight-binding model and a minimal two-level model,
which describes the pair of hybridizing frontier orbital states on the two
phenyl rings. The variations of the thermopower with \phi\ seem to be within
experimental resolution.Comment: 8 pages, 4 figues, 3 table
Evaluation of a pilot consultation for maternity protection at work in Switzerland.
Switzerland's Labour Law and its Ordonnance on Maternity Protection aim to protect the health of pregnant employees and their unborn children while enabling them to continue to pursue their professional activities. Some companies encounter difficulties implementing the law's provisions. The Department of Occupational and Environmental Health, part of the Center for Primary Care and Public Health (Unisanté), has provided specialist occupational medicine consultations for pregnant employees since 2015. This study aimed to evaluate how well Swiss' maternity protection legislation is implemented by examining a list of relevant indicators measured during the occupational health consultation. The study also sought to investigate the consultation support provided to the relevant stakeholders and the adjustments made to pregnant employees' working conditions.
Descriptive variables and indicators relative to the application of the Swiss maternity protection legislation for 83 pregnant employees were collected during the consultation's pilot phase (between 2015 and 2016). Descriptive statistics and cross-analyses of these indicators were made.
Most pregnant employees faced multiple exposures to occupational risks. Preventive risk analyses were rare. Few adjustments to workstations were proposed. We found a tendency for employees to leave their workstations early on in their pregnancies due to sick leave certificate prescriptions. Specialist consultation and collaboration with occupational health physicians to recommend interventions for pregnant employees can provide significant benefits and help some pregnant women to continue at their workstations with appropriate adjustments.
A specialised occupational health consultation is a useful instrument for identifying occupational hazards for both the pregnant woman and her unborn child. It is also an opportunity to explain employers' legal responsibilities and obligations to safeguard the health of their pregnant employees and to give specific advice for their company's situation. This consultation also enables employers to maintain their employees' valuable professional competencies in the workplace for as long as possible. Finally, occupational health consultation helps and supports healthcare providers who must, according to the law, make decisions about whether pregnant employees can continue working safely or not
Weak Ferromagnetism and Excitonic Condensates
We investigate a model of excitonic ordering (i.e electron-hole pair
condensation) appropriate for the divalent hexaborides. We show that the
inclusion of imperfectly nested electron hole Fermi surfaces can lead to the
formation of an undoped excitonic metal phase. In addition, we find that weak
ferromagnetism with compensated moments arises as a result of gapless
excitations. We study the effect of the low lying excitations on the density of
states, Fermi surface topology and optical conductivity and compare to
available experimental data.Comment: 10 Pages, 8 Figures, RevTe
The bmi-1 oncoprotein is differentially expressed in non-small cell lung cancer and correlates with INK4A-ARF locus expression
Genes of the polycomb group function by silencing homeotic selector genes that regulate embryogenesis. In mice, downregulation of one of the polycomb genes, bmi-1, leads to neurological alterations and severe proliferative defects in lymphoid cells, whilst bmi-1 overexpression, together with upregulation of myc-1, induces lymphoma. An oncogenic function has been further supported in primary fibroblast studies where bmi-1 overexpression induces immortalization due to repression of p16/p19ARF, and where together with H-ras, it readily transforms MEFs. It was the aim of this study to assess the expression of bmi-1 in resectable non-small cell lung cancer (NSCLC) in association with p16 and p14ARF (=human p19ARF). Tumours (48 resectable NSCLC (32 squamous, 9 adeno-, 2 large cell, 4 undifferentiated carcinomas and 1 carcinoid); stage I, 29, II, 7, III, 12; T1, 18, T2, 30; differentiation: G1 12, G2 19, G3 17) were studied by immunohistochemistry for protein expression and by comparative multiplex PCR for gene amplification analysis. In tumour-free, normal lung tissue from patients, weak – moderate bmi-1 staining was seen in some epithelial cells, lymphocytes, glandular cells and in fibroblasts, whereas blood, endothelial, chondrocytes, muscle cells and adipocytes did not exhibit any bmi-1 expression. In tumours, malignant cells were negative/weakly, moderately and strongly positive in 20, 22 and 6 cases, respectively. As assessed by multiplex PCR, bmi-1 gene amplification was not the reason for high-level bmi-1 expression. Tumours with moderate or strong bmi-1 expression were more likely to have low levels of p16 and p14ARF (P = 0.02). Similarly, tumours negative for both, p16 and p14ARF, exhibit moderate–strong bmi-1 staining. 58% of resectable NSCLC exhibit moderate–high levels of bmi-1 protein. The inverse correlation of bmi-1 and the INK4 locus proteins expression (p16/p14ARF) supports a possible role for bmi-1 misregulation in lung carcinogenesis. © 2001 Cancer Research Campaign www.bjcancer.co
Anomalous NMR Spin-Lattice Relaxation in SrB_{6} and Ca_{1-x}La_{x}B_{6}
We report the results of {11}B nuclear magnetic resonance (NMR) measurements
of SrB_{6} and Ca_{0.995}La_{0.05}B_{6} below room temperature. Although the
electrical resistivities of these two materials differ substantially, their
{11}B-NMR responses exhibit some strikingly common features. Both materials
exhibit ferromagnetic order, but their {11}B-NMR spectra reveal very small
hyperfine fields at the Boron sites. The spin lattice relaxation T_{1}^{-1}
varies considerably with external field but changes with temperature only below
a few K. We discuss these unusual results by considering various different
scenarios for the electronic structure of these materials.Comment: Accepted for publication in Phys. Rev. B Rapid communication, 4
pages, 3 figures. This manuscript replaces an earlier version and includes
some minor changes in the text and in Fig.
Spin-polaron model: transport properties of EuB
To understand anomalous transport properties of EuB, we have studied the
spin-polaron Hamiltonian incorporating the electron-phonon interaction.
Assuming a strong exchange interaction between the carriers and the localized
spins, the electrical conductivity is calculated. The temperature and magnetic
field dependence of the resistivity of EuB are well explained. At low
temperature, magnons dominate the conduction process, whereas the lattice
contribution becomes significant at very high temperature due to the scattering
with the phonons. Large negative magnetoresistance near the ferromagnetic
transition is also reproduced as observed in EuB.Comment: 4 pages, 3 figures, accepted in Phys. Rev.
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