An edge $e$ of a $k$-connected graph $G$ is said to be $k$-contractible (or simply contractible) if the graph obtained from $G$ by contracting $e$ (i.e., deleting $e$ and identifying its ends, finally, replacing each of the resulting pairs of double edges by a single edge) is still $k$-connected. In 2002, Kawarabayashi proved that for any odd integer $k\geq 5$, if $G$ is a $k$-connected graph and $G$ contains no subgraph $D=K_{1}+(K_{2}\cup K_{1, 2})$, then $G$ has a $k$-contractible edge. In this paper, by generalizing this result, we prove that for any integer $t\geq 3$ and any odd integer $k \geq 2t+1$, if a $k$-connected graph $G$ contains neither $K_{1}+(K_{2}\cup K_{1, t})$, nor $K_{1}+(2K_{2}\cup K_{1, 2})$, then $G$ has a $k$-contractible edge.
We investigate how one can detect the dualizing property for a chain complex over a commutative local Noetherian ring R. Our focus is on homological properties of contracting endomorphisms of R, e.g., the Frobenius endomorphism when R contains a field of positive characteristic. For instance, in this case, when R is F-finite and C is a semidualizing R-complex, we prove that the following conditions are equivalent: (i) C is a dualizing R-complex; (ii) C\sim RHom_{R}(^{n}R,C) for some n > 0; (iii) G_{C}-dim^{n}R < ∞ and C is derived RHom_{R}(^{n}R,C)-reflexive for some n > 0; and (iv) G_{C}-dim^{n}R < ∞ for infinitely many n > 0., Saeed Nasseh, Sean Sather-Wagstaff., and Obsahuje seznam literatury
Clays (2005) and the Handbook of Clay Science (2006) are new textbooks. Clays, written by Alain Meunier, is for those studying earth sciences. The Handbook of Clay Science, edited by Faїza Bergaya, Benny Theng and Gerhard Lagaly, is concerned particularly with the industrial application of clay mineral science. Both books ar e timely and could fill important gaps in the library of mineral science. Their quality as textbooks is discussed. Critical an alysis of editorial accuracy, indexes and user-friendliness indic ate that both books fall short of the high standards that should be the hallmark of academic publication. Their shortcomings seem to be related to widespread problems that may beset commercial publica tion of scientific books., Christopher V. Jeans., and Obsahuje bibliografické odkazy
We compared the responses of wild type (WT) and three mutants including npq1 (lutein-replete and violaxanthin deepoxidase-deficient), lut2 (lutein-deficient), and lut2-npq1 (double mutant) to high irradiance (HI, 2 000 μmol m-2 s-1) at both low (LT, 5 °C) and room (25 °C) temperature. Xanthophyll-dependent energy dissipation was highest in the WT, followed by the lut2, npq1, and npq1-lut2. At 25 °C the relative stress tolerance expressed by Fv/Fm was consistent with the energy dissipation capacity for the first 2 h of treatment. After 3-4 h, the Fv/Fm levels in lut2 and npq1 converged. Under combined LT and HI the relative tolerance sequence was in contrast to the energy dissipation capacity being WT > npq1> lut2 > lut2-npq1. There were little or no significant change in the contents of xanthophylls and carotenes or the chlorophyll (Chl) a/b ratio in any of the materials. Thus lutein (L) substitution possibly alters the conformation/organisation of L binding proteins to enhance damage susceptibility under HI at LT. The enhanced vulnerability is not compensated for the energy dissipation capacity in the lut2 background at LT. and Chang-Lian Peng, A. M. Gilmore.
Leaves developed at high irradiance (I) often have higher photosynthetic capacity than those developed at low I, while leaves developed at elevated CO2 concentration [CO2] often have reduced photosynthetic capacity compared with leaves developed at lower [CO2]. Because both high I and elevated [CO2] stimulate photosynthesis of developing leaves, their contrasting effects on photosynthetic capacity at maturity suggest that the extra photosynthate may be utilized differently depending on whether I or [CO2] stimulates photosynthesis. These experiments were designed to test whether relationships between photosynthetic income and the net accumulation of soluble protein in developing leaves, or relationships between soluble protein and photosynthetic capacity at full expansion differed depending on whether I or [CO2] was varied during leaf development. Soybean plants were grown initially with a photosynthetic photon flux density (PPFD) of 950 µmol m-2 s-1 and 350 µmol [CO2] mol-1, then exposed to [CO2] ranging from 135 to 1400 µmol mol-1 for the last 3 d of expansion of third trifoliolate leaves. These results were compared with experiments in which I was varied at a constant [CO2] of 350 µmol mol-1 over the same developmental period. Increases in area and dry mass over the 3 d were determined along with daily photosynthesis and respiration. Photosynthetic CO2 exchange characteristics and soluble protein content of leaves were determined at the end of the treatment periods. The increase in leaflet mass was about 28 % of the dry mass income from photosynthesis minus respiration, regardless of whether [CO2] or I was varied, except that very low I or [CO2] increased this percentage. Leaflet soluble protein per unit of area at full expansion had the same positive linear relationship to photosynthetic income whether [CO2] or I was varied. For variation in I, photosynthetic capacity varied directly with soluble protein per unit area. This was not the case for variation in [CO2]. Increasing [CO2] reduced photosynthetic capacity per unit of soluble protein by up to a factor of 2.5, and photosynthetic capacity exhibited an optimum with respect to growth [CO2]. Thus CO2 did not alter the relationship between photosynthetic income and the utilization of photosynthate in the net accumulation of soluble protein, but did alter the relationship between soluble protein content and photosynthetic characteristics in this species.
We compared variation in sun-canopy leaf anatomy, morphology and photosynthetic rates of coexisting woody species (trees and lianas) in an 8-year-old secondary forest (SF) and mature forest (MF) in the wet season in Xishuangbanna, SW China. Variability of leaf traits of 66 species within growth-form groups in each forest was quantified using coefficients of variation (CV). For the mean values, the woody species in the SF had significantly higher leaf thickness and stomatal density, but lower nonmesophyll/mesophyll ratios than those in the MF. The average leaf area and leaf mass area (LMA) in the studied woody species did not change greatly during the successional process, but differed significantly between the growth forms, with trees having higher values than lianas. The light-saturated photosynthetic rate per unit leaf area (Aa) of the woody species in the SF ranged from 11.2 to 34.5 μmol m-2 s-1, similarly to pioneer tree species from literature data in southeast Asia. The Aa and photosynthetic nitrogen-use efficiency (PNUE) were significantly higher than those in the MF; whereas Aa in the MF ranged between 9 to 21 μmol m-2 s-1, with similar values between lianas and trees. For all woody species in both SF and MF, there were no significant differences in the average values of the CV of all measured variables for both lianas and trees. However, considerable variation in leaf anatomy, morphology, and photosynthetic rates within both growth forms and forests existed, as well as substantial variation in leaf size and stomatal density. We concluded that the tropical woody species formed a heterogeneous functional group in terms of leaf morphology and physiology in both secondary and mature forests. and L. Han ... [et al.].
Growth, net photosynthetic rate (PN), chlorophyll fluorescence induction kinetics, and stromal fructose-1,6-bisphosphatase (sFBPase) in annual legumes native to the Mediterranean region, two clovers (Trifolium subterraneum L. ssp. oxaloides Nyman cv. Clare and T. michelianum Savi cv. Giorgia) and two Medicago species (M. polymorpha L. cv. Anglona and M. truncatula Gaertn. cv. Paraggio), shifted from 20 to 10 °C for 1 d or developed at 10 °C were compared with controls kept at 20 °C. Cold development produced a larger stimulation of growth in the clover cv. Giorgia and the Medicago cv. Paraggio. Transferring plants to low temperatures affected PN relatively less in clovers than in Medicago plants. Development at 10 °C relieved the inhibition of photosynthesis in Giorgia and Paraggio, but not in Clare and Anglona, which correlated with increases in the maximum rate of carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO (Vcmax), and the photon-saturated rate of electron transport (Jmax). In Medicago, transfer from high to low temperature inhibited photosynthesis in a lesser extent in Anglona than in Paraggio, which showed severe limitations at level of Vcmax and Jmax. Development at 10 °C in Paraggio produced an efficient photosynthetic cold acclimation, this being associated with a two-fold increase of quantum yield of photosystem 2 electron transport (ΔF/F'm) and with the activity of sFBPase. By contrast, Anglona showed an irreversible inhibition of PN coupled with the reduction of carbon metabolism by impairment of Calvin cycle enzyme activities such as RuBPCO and sFBPase, resulting in a poor cold acclimation of photosynthesis in this cultivar. and M. C. Antolín, M. Hekneby, M. Sánchez-Díaz.
Recent pre-clinical evidence suggests that the active metabolite of tamoxifen, endoxifen, is a substrate for efflux pump P-glycoprotein. The aim of our study was to evaluate, if the polymoprhisms within ABCB1 gene alter tamoxifen adjuvant treatment efficacy in premenopausal women. Totally 71 premenopausal women with estrogen receptor positive breast cancer indicated for tamoxifen adjuvant treatment were followed retrospectively for median period of 56 months. The gentic polymorphisms of CYP2D6 and ABCB1 were analyzed and potential covariates as tumor grading, staging, age at the diagnosis, comedication, quantitative positivity of ER or PR were also evaluated. Cox proportional-hazards regression model indicated that patients carrying at least one variant allele in ABCB1 rs1045642 had significantly longer time to event survival compared to wild type subjects. Non-significant trend was noted for better treatment outcome of patients carrying at least one variant allele in the SNP rs2032582, while for the CYP2D6 polymorphism poor metabolizer phenotype resulted in worse outcome in comparison to extensive metabolizers subjects with HR of 4.04 (95 % CI 0.31-52.19). Similarly, patients using CYP2D6 inhibitors had non-significantly shorter time-to-event as compared to never users resulting in hazard ratio of 2.06 (95 % CI 0.40-10.63). ABCB1 polymorphisms may affect outcome of tamoxifen adjuvant treatment in premenopausal breast cancer patiens. This factor should be taken into account in addition to the CYP2D6 polymorphism or phenotypic inhibition of CYP2D6 activity., S. Argalácsová, O. Slanař, P. Vítek, P. Tesařová, H. Bakhouche, M. Dražďáková, O. Bartošová, T. Zima, L. Pertuželka., and Obsahuje bibliografii
We aimed to compare the effect of angiotensin converting enzyme (ACE) inhibitors captopril (containing thiol group) and enalapril (without thiol group) on the development of spontaneous hypertension and to analyze mechanisms of their actions, particularly effects on oxidative stress and NO production. Six-week-old SHR were divided into three groups: control, group receiving captopril (50 mg/kg/day) or enalapril (50 mg/kg/day) for 6 weeks. At the end of experiment, systolic blood pressure (SBP) increased by 41 % in controls. Both captopril and enalapril prevented blood pressure increase, however, SBP in the captopril group (121±5 mmHg) was significantly lower than that in the enalapril group (140±5 mmHg). Concentration of conjugated dienes in the aorta was significantly lower in the captopril group compared to the enalapril group. Captopril and enalapril increased NO synthase activity in the heart and aorta to the similar level. Neither captopril nor enalapril was, however, able to increase the expression of eNOS. Both ACE inhibitors increased the level of cGMP. However, cGMP level was significantly higher in the aorta of captopril group. We conclude that captopril, beside inhibition of ACE, prevented hypertension by increasing NO synthase activity and by simultaneous decrease of oxidative stress which resulted in increase of cGMP concentration., O. Pecháňová., and Obsahuje bibliografii