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Hurricane Danny resulted in the rapid deposition of 10cm of oxidized, acidic sediment in the Contrary Creek arm of Lake Anna, Virginia. Several biological and geochemical parameters were monitored with time to ascertain how long it took the newly-deposited lake sediments to attain the anaerobic, circumneutral, actively sulfate-reducing state normally observed in this portion of the lake. The sediment platinum-electrode potential dropped from 350 mV to 100 mV within the first week after the storm. The pH of the pore water increased from 4.5 to 5.8 within three weeks, and titratable alkalinity was detected within two weeks and three weeks at 3 cm and 1 cm depths, respectively. Accumulation of reduced products of sulfate reduction (acid volatile sulfide) began by three to four weeks after the storm event. Both methanogens and sulfate reducers were present in high and approximately equal numbers in the freshly deposited material. The rapid neutralization of the acidity in the fresh sediment prior to the onset of sulfate reduction suggests that reactions other than sulfate reduction caused the initial increase in pH and alkalinity in this system. 相似文献
3.
Eighty seven sows, taken from a herd whose mean gestation length was 116 days, were allotted at random on day 114 of gestation to one of five treatment groups as follows: (1) 175 mug prostaglandin analogue (closprostenol I.C.I. Ltd) (2) 1 mg K11941 (alfaprostol VETEM Ltd), (3) 2 mg K11941, (4) 3 mg K11941 (5) 2 ml saline (control). All prostaglandin analogues induced parturition significantly earlier than controls (P < 0.05), but there were no differences between any of the prostaglandin treatments in the interval to birth of the first piglet (P > 0.05). The mean intervals to parturition were 24.6, 22.3, 24.9, 30.7 and 53.0 hours for treatments 1, 2, 3, 4 and 5 respectively. Almost two-thirds of treated sows farrowed during the working period of the day following injection compared with a small proportion of control animals. Induction of parturition had no effect on birth weight, piglet survival to 3 weeks or on subsequent weaning to service interval in treated sows. Results show that this new analogue of prostaglandin (K11941) is effective in inducing farrowing in the sow. 相似文献
4.
Abstract A class of very potent nucleoside transport inhibitors is present in two molecular forms around physiological pH. We investigated whether the monoprotonated or the unionized species of these molecules binds to this camer protein with higher affinity. 相似文献
5.
Christopher I Keeling Macaire MS Yuen Nancy Y Liao T Roderick Docking Simon K Chan Greg A Taylor Diana L Palmquist Shaun D Jackman Anh Nguyen Maria Li Hannah Henderson Jasmine K Janes Yongjun Zhao Pawan Pandoh Richard Moore Felix AH Sperling Dezene P W Huber Inanc Birol Steven JM Jones Joerg Bohlmann 《Genome biology》2013,14(3):R27
6.
A. Daneshjoo AH. Mokhtar N. Rahnama A. Yusof 《Biology of sport / Institute of Sport》2013,30(4):281-288
The study investigates the effects of the 11+ and HarmoKnee injury prevention programmes on knee strength in male soccer players. Under-21-year-old players (n=36) were divided equally into: the 11+, HarmoKnee and control groups. The programmes were performed for 24 sessions (20-25 min each). The hamstrings and quadriceps strength were measured bilaterally at 60°·s-1, 180°·s-1 and 300°·s-1. The concentric quadriceps peak torque (PT) of the 11+ increased by 27.7% at 300°·s-1 in the dominant leg (p<0.05). The concentric quadriceps PT of HarmoKnee increased by 36.6%, 36.2% and 28% in the dominant leg, and by 31.3%, 31.7% and 20.05% at 60°·s-1, 180°·s-1 and 300°·s-1 in the non-dominant leg respectively. In the 11+ group the concentric hamstring PT increased by 22%, 21.4% and 22.1% at 60°·s-1, 180°·s-1 and 300°·s-1, respectively in the dominant leg, and by 22.3%, and 15.7% at 60°·s-1 and 180°·s-1, in the non-dominant leg. In the HarmoKnee group the hamstrings in the dominant leg showed an increase in PT by 32.5%, 31.3% and 14.3% at 60°·s-1, 180°·s-1 and 300°·s-1, and in the non-dominant leg hamstrings PT increased by 21.1% and 19.3% at 60°·s-1 and 180°·s-1 respectively. The concentric hamstrings strength was significantly different between the 11+ and control groups in the dominant (p=0.01) and non-dominant legs (p=0.02). The HarmoKnee programme enhanced the concentric strength of quadriceps. The 11+ and HarmoKnee programmes are useful warm-up protocols for improving concentric hamstring strength in young professional male soccer players. The 11+ programme is more advantageous for its greater concentric hamstring strength improvement compared to the HarmoKnee programme. 相似文献
7.
Egg parasitoids of the exotic invasive brown marmorated stink bug, Halyomorpha halys (Stål), were investigated using lab-reared fresh (live) and frozen (killed) lab-reared sentinel egg masses deployed for 72h on foliage in three habitats—woods, orchard, and soybean field—in Maryland, USA, in summer 2014. Four native hymenopteran species, Telenomus podisi Ashmead (Scelionidae), Trissolcus euschisti (Ashmead) and Tr. brochymenae Ashmead (Scelionidae), and Anastatus reduvii (Howard) (Eupelmidae), developed and emerged from H. halys eggs. One exotic parasitoid, Trissolcus japonicus (Ashmead), emerged, providing the first known occurrence of this species in North America. Native parasitoids emerged from frozen eggs significantly more often than from fresh eggs (89.3% of egg masses and 98.1% of individual eggs), whereas the exotic Tr. japonicus did not show a similar difference, strongly suggesting adaptation to H. halys as a host by Tr. japonicus but not by the native species. Parasitoids were habitat-specific: all three Trissolcus species were significantly more likely to occur in the woods habitat, whereas Te. podisi was found exclusively in the soybean field. Further investigations are required to elucidate evolving host-parasitoid relationships, habitat specificity, and non-target effects of Tr. japonicus over the expanded range of H. halys in North America. 相似文献
8.
The mating system of flowering plant populations evolves through selection on genetically based phenotypic variation in floral traits. The physical separation of anthers and stigmas within flowers (herkogamy) is expected to be an important target of selection to limit self-fertilization. We investigated the pattern of phenotypic and genetic variation in herkogamy and its effect of self-fertilization in a broad sample of natural populations of Aquilegia canadensis, a species that is highly selfing despite strong inbreeding depression. Within natural populations, plants exhibit substantial phenotypic variation in herkogamy caused primarily by variation in pistil length rather than stamen length. Compared to other floral traits, herkogamy is much more variable and a greater proportion of variation is distributed among rather than within individuals. We tested for a genetic component of this marked phenotypic variation by growing naturally pollinated seed families from five populations in a common greenhouse environment. For three populations, we detected a significant variation in herkogamy among families, and a positive regression between parental herkogamy measured in the field and progeny herkogamy in the greenhouse, suggesting that there is often genetic variation in herkogamy within natural populations. We estimated levels of self-fertilization for groups of flowers that differed in herkogamy and show that, as expected, herkogamy was associated with reduced selfing in 13 of 19 populations. In six of these populations, we performed floral emasculations to show that this decrease in selfing is due to decreased autogamy (within-flower selfing), the mode of selfing that herkogamy should most directly influence. Taken together, these results suggest that increased herkogamy should be selected to reduce the production of low-quality selfed seed. The combination of high selfing and substantial genetic variation for herkogamy in A. canadensis is enigmatic, and reconciling this observation will require a more integrated analysis of how herkogamy influences not only self-fertilization, but also patterns of outcross pollen import and export. 相似文献
9.
Reproductive character displacement shapes a spatially structured petal color polymorphism in Leavenworthia stylosa 下载免费PDF全文
Nicholas A. Norton M. Thilina R. Fernando Christopher R. Herlihy Jeremiah W. Busch 《Evolution; international journal of organic evolution》2015,69(5):1191-1207
Character displacement is a potentially important process driving trait evolution and species diversification. Floral traits may experience character displacement in response to pollinator‐mediated competition (ecological character displacement) or the risk of forming hybrids with reduced fitness (reproductive character displacement). We test these and alternative hypotheses to explain a yellow‐white petal color polymorphism in Leavenworthia stylosa, where yellow morphs are spatially associated with a white‐petaled congener (Leavenworthia exigua) that produces hybrids with complete pollen sterility. A reciprocal transplant experiment found limited evidence of local adaptation of yellow color morphs via increased survival and seed set. Pollinator observations revealed that Leavenworthia attract various pollinators that generally favor white petals and exhibit color constancy. Pollen limitation experiments showed that yellow petals do not alleviate competition for pollination. Interspecific pollinator movements were infrequent and low hybridization rates (~0.40–0.85%) were found in each morph, with natural rates likely being lower. Regardless, hybridization rates were significantly higher in white morphs of L. stylosa, yielding a small selection coefficient of s = 0.0042 against this phenotype in sympatry with L. exigua. These results provide support for RCD as a mechanism contributing to the pattern of petal color polymorphism in L. stylosa. 相似文献
10.