共查询到20条相似文献,搜索用时 15 毫秒
1.
The biodiversity and spatial distribution of macrofauna biomass are studied for 12 sites of stonesand littoral in the Neva
Estuary in 2002–2005. The highest biodiversity has been observed for chironomids and oligochaetes in the Neva Bay (36% and
24% of total species number) and in the eastern Gulf of Finland (33% and 23%). Amphipods (≤89%), molluscs (≤61%), and chironomids
(≤37%) dominate by biomass. The biomass spatial distribution vary dramatically from 9 to 37 g m−2 in the freshwater Neva Bay and from 1 to 68 g m−2 for the other Neva Estuary areas. The bottom fauna biomass in the Neva Bay is significantly lower than in the 1980–1990’s
and constitutes 20–50% of the biomass previously observed. We explain such a significant decrease by a reduction of the insects
and aborigine crustaceans Gammarus lacustris Sars and Asellus aquaticus L. The invasive amphipod species Gmelinoides fasciatus (Stebbing) dominated by biomass for the study period (3.8–15.6 g m−2, or >30% of total macrozoobenthos biomass). 相似文献
2.
Critical levels of selenium in raya (Brassica juncea Czern L.), maize (Zea mays L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were worked out by growing these crops in an alkaline silty loam soil treated with different levels of selenite-Se ranging
from 1 to 25 μg g−1 soil. Significant decrease in dry matter yield was observed above a level of 5 μg Se g−1 soil in raya and maize; 4 μg Se g−1 soil in wheat and 10 μg Se g−1 soil in rice shoots. The critical level of Se in plants above which significant decrease in yield would occur was found to
be 104.8 μg g−1 in raya, 76.9 μg g−1 in maize, 41.5 μg g−1 in rice and 18.9 μg g−1 in wheat shoots. Significant coefficients of correlation were observed between Se content above the critical level and dry
matter yield of raya as well as rice (r = −0.99, P ≤ 0.01), wheat (r = −0.97, P ≤ 0.01) and maize ((r = −0.96, P ≤ 0.01). A synergistic relationship was observed between S and Se content of raya (r = 0.96, P ≤ 0.01), wheat (r = 0.89, P ≤ 0.01), rice (r = 0.85, P ≤ 0.01) and maize (r = 0.84, P ≤ 0.01). Raya, maize and rice absorbed Se in levels toxic for animal consumption (i.e. > 5 mg Se kg−1) when the soil was treated with more than 1.5 μg Se g−1. In case of wheat, application of Se more than 3 μg g−1 soil resulted in production of toxic plants. 相似文献
3.
Two approaches to determine the fraction (μ) of mitochondrial respiration sustained during illumination by measuring CO2 gas exchange are compared. In single leaves, the respiration rate in the light (`day respiration' rate Rd) is determined as the ordinate of the intersection point of A–ci curves at various photon flux densities and compared with the CO2 evolution rate in darkness (`night respiration' rate Rn). Alternatively, using leaves with varying values of CO2 compensation concentration (Γ), intracellular resistance (ri) and Rn, an average number for μ can be derived from the linear regression between Γ and the product riċRn. Both methods also result in a number c* for that intercellular CO2 concentration at which net CO2 uptake rate is equal to –Rd. c* is an approximate value of the photocompensation point Γ* (Γ in the absence of mitochondrial respiration), which is related
to the CO2/O2 specificity factor of Rubisco Sc/o. The presuppositions and limitations for application of both approaches are discussed. In leaves of Nicotiana tabacum, at 22 °C, single leaf measurements resulted in mean values of μ = 0.71 and c* = 34 μmol mol−1. At the photosynthetically active photon flux density of 960 μmol quanta m−2 s−1, nearly the same numbers were derived from the linear relationship between Γ and riċRn. c* and Rd determined by single leaf measurements varied between 31 and 41 μmol mol−1 and between 0.37 and 1.22 μmol m−2 s−1, respectively. A highly significant negative correlation between c* and Rd was found. From the regression equation we obtained estimates for Γ* (39 μmol mol−1), Sc/o (96.5 mol mol−1) and the mesophyll CO2 transfer resistance (7.0 mol−1 m2 s).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
We develop a general mathematical model for a population of cells differentiated by their position within the cell division
cycle. A system of partial differential equations governs the kinetics of cell densities in certain phases of the cell division
cycle dependent on time t (hours) and an age-like variable τ (hours) describing the time since arrival in a particular phase of the cell division cycle.
Transition rate functions control the transfer of cells between phases. We first obtain a theoretical solution on the infinite
domain −∞ < t < ∞. We then assume that age distributions at time t=0 are known and write our solution in terms of these age distributions on t=0. In practice, of course, these age distributions are unknown. All is not lost, however, because a cell line before treatment
usually lies in a state of asynchronous balanced growth where the proportion of cells in each phase of the cell cycle remain
constant. We assume that an unperturbed cell line has four distinct phases and that the rate of transition between phases
is constant within a short period of observation (‘short’ relative to the whole history of the tumour growth) and we show
that under certain conditions, this is equivalent to exponential growth or decline. We can then gain expressions for the age
distributions. So, in short, our approach is to assume that we have an unperturbed cell line on t ≤ 0, and then, at t=0 the cell line is exposed to cancer therapy. This corresponds to a change in the transition rate functions and perhaps incorporation
of additional phases of the cell cycle. We discuss a number of these cancer therapies and applications of the model. 相似文献
5.
Fine root vertical distribution and temporal dynamics in mature stands of two enset (Enset ventricosum Welw Cheesman) clones 总被引:2,自引:0,他引:2
Quantification of the role of fine roots in the biological cycle of nutrients necessitates understanding root distribution,
estimating root biomass, turnover rate and nutrient concentrations, and the dynamics of these parameters in perennial systems.
Temporal dynamics, vertical distribution, annual production and turnover, and nitrogen use of fine roots (≤2 mm in diameter)
were studied in mature (5-year-old) stands of two enset (Ensete ventricosum) clones using the in-growth bag technique. Live fine root mass generally decreased with increasing depth across all seasons
except the dry period. Except for the dry period, more than 70% of the fine root mass was in the above 0-20 cm depth, and
the fine root mass in the upper 0–10 cm depth was significantly higher than in the lowest depth (20–30 cm). Live fine root
mass showed a seasonal peak at the end of the major rainy season but fell to its lowest value during the dry or short rainy
season. The difference between the peak and low periods were significant (p ≤ 0.05). Fine root nitrogen (N) use showed significant seasonal variation where the mean monthly fine root N use was highest
during the major rainy season. There were significant effects on N use due to depths and in-growth periods, but not due to
clones. Enset fine root production and turnover ranged from 2,339 to 2,451 kg ha−1 year−1 and from 1.55 to 1.80 year−1, respectively. Root N return, calculated from fine root turnover, was estimated at 64–65 kg ha−1 year−1. Fine root production, vertical distribution and temporal dynamics may be related to moisture variations and nutrient (N)
fluxes among seasons and along the soil depth. The study showed that fine root production and turnover can contribute considerably
to the carbon and nitrogen economy of mature enset plots. 相似文献
6.
P. O. Vardevanyan A. P. Antonyan G. A. Manukyan A. T. Karapetyan A. K. Shchyolkina O. F. Borisova 《Molecular Biology》2000,34(2):272-276
Isotherms of the EtBr adsorption on native and denatured poly(dA)poly(dT) in the temperature interval 20–70°C were obtained.
The EtBr binding constants and the number of binding sites were determined. The thermodynamic parameters of the EtBr intercalation
complex upon changes of solution temperature 20–48°C were calculated: 1.0·106 M−1≤K≤1.4·106 M−1, free energy ΔG
o=−8.7±0.3 kcal/mol, enthalpy ΔH
o≅0, and entropy ΔS
o=28±0.5 cal/(mol deg). UV melting has shown that the melting temperature (T
m) of EtBr-poly(dA)poly(dT) complexes (μ=0.022,4.16·10−5 M EtBr) increased by 17°C as compared with the ΔT
m of free homopolymer, whereas the half-width of the transition (T
m) is not changed. It was shown for the first time that EtBr forms complexes of two types on single-stranded regions of poly(dA)poly(dT)
denatured at 70°C: strong (K
1=1.7·105 M−1; ΔG
o=−8.10±0.03 kcal/mol) and weak (K
2=2.9·103 M−1; ΔG
o=−6.0±0.3 kcal/mol).The ΔG
o of the strong and weak complexes was independent of the solution ionic strength, 0.0022≤μ≤0.022. A model of EtBr binding
with single-stranded regions of poly(dA)poly(dT) is discussed. 相似文献
7.
8.
The trachymedusa Ptychogastria polaris Allman, 1878 has been identified in seabed photographs from high-Arctic shelves and upper continental slopes off Northeast
Greenland and in the northern Barents Sea. It was found to be a common epifaunal element, being present at 34 of 57 stations
in 40- to 495-m depth and at 7 of 11 stations in 70- to 330-m depth, respectively. All specimens recorded in the photographs
either sat directly at, or hovered very closely (≤ about 1 cm) over, the sea bed, indicating a primarily epibenthic life style
of this hydrozoan species. The small-scale (i.e. within-station) distribution of medusae was rather patchy, with frequencies
along photographic transects – consisting of 35–73 pictures distributed over seabed strips of 150- to 300-m length – varying
from 1 to 58% off Northeast Greenland and from 1 to 34% in the Barents Sea. Absolute maximum density was 6 ind m−2, and station mean abundances ranged from 0.01 to 0.91 ind m−2 and from 0.01 to 0.52 ind m−2, respectively. Values tended to decrease with water depth, albeit significantly only off Northeast Greenland. Otherwise,
no clear relationships to environmental conditions, such as geomorphology or near-bottom water hydrography, were detected.
Circumstantial evidence suggests that seabed granulometry and potential food supply are important distribution determinants.
However, further investigations are required to identify more stringently the key factors controlling the distribution of
P. polaris.
Received: 8 September 1997 / Accepted: 12 September 1997 相似文献
9.
A. S. Karunas B. B. Yunusbaev Yu. Yu. Fedorova G. F. Gimalova N. N. Ramazanova L. L. Gur’eva L. A. Mukhtarova Sh. Z. Zagidullin E. I. Etkina E. K. Khusnutdinova 《Molecular Biology》2011,45(6):911-920
Bronchial asthma is a chronic inflammatory respiratory disease caused by a complex interaction of environmental influences
and genetic susceptibility. The first genome-wide association study of bronchial asthma discovered a significant association
between single nucleotide polymorphisms (SNPs) located within the genomic region 17q12-q21 and childhood bronchial asthma
in individuals of European descent. This result was later replicated in a number of independent population samples of European
and Asian origin. Here we report the results of the first genome-wide association study of bronchial asthma in the Volga-Urals
region of Russia. The study involved 358 unrelated patients with physician-diagnosed bronchial asthma and 369 disease-free
control subjects of different ethnicity (Russians, Tatars, and Bashkirs). DNA specimens were genotyped using an Illumina Human610
quad array as a part of the GABRIEL project (EC contract no. LSHB-CT-2006-018996). After QC filtering procedures, a final
set of 550 915 SNPs genotyped in 330 patients and 348 controls was tested for association with bronchial asthma. Five markers
on chromosome 17q12-21 showed significant association with bronchial asthma (p ≤ 4.79 × 10−7). The rs7216389 SNP located in GSDMB intron 1 showed the strongest evidence for association (p = 1.01 × 10−7). Association with childhood asthma (p = 1.97 × 10−6 for rs7216389) was stronger than with late-onset asthma (p = 1.8 × 10−4 for rs7216389). A replication study of three SNPs located within GSDMB confirmed association only with childhood asthma. In sum, these results suggest that genetic variants of 17q12–q21 play an
important role in susceptibility to bronchial asthma in the Volga-Urals region of Russia. 相似文献
10.
Microbial Succession in a Compost-packed Biofilter Treating
Benzene-contaminated Air 总被引:2,自引:0,他引:2
Borin S Marzorati M Brusetti L Zilli M Cherif H Hassen A Converti A Sorlini C Daffonchio D 《Biodegradation》2006,17(2):79-89
Air artificially contaminated with increasing concentrations of benzene was treated in a laboratory scale compost-packed biofilter
for 240 days with a removal efficiency of 81–100%. The bacterial community in the packing material (PM) at different heights
of the biofilter was analysed every 60 days. Bacterial plate counts and ribosomal intergenic spacer analysis (RISA) of the
isolated strains showed that the number of cultivable aerobic heterotrophic bacteria and the species diversity increased with
benzene availability. Identification of the isolated species and the main bands in denaturing gradient gel electrophoresis
(DGGE) profiles from total compost DNA during the treatment revealed that, at a relatively low volumetric benzene load (1.2≤VBL≤6.4 g m−3
PM h−1), besides low G+C Gram positive bacteria, originally present in the packing compost, bacteroidetes and β- and γ-proteobacteria
became detectable in the colonising population. At the VBL value (24.8 g m−3
PM h−1) ensuring the maximum elimination capacity of the biofilter (20.1 g m−3
PM h−1), strains affiliated to the genus Rhodococcus dominated the microflora, followed by β-proteobacteria comprising the genera Bordetella and Neisseria. Under these conditions, more than 35% of the isolated strains were able to grow on benzene as the sole carbon source. Comparison
of DGGE and automated RISA profiles of the total community and isolated strains showed that a complex bacterial succession
occurred in the reactor in response to the increasing concentrations of the pollutant and that cultivable bacteria played
a major role in benzene degradation under the adopted conditions. 相似文献
11.
Many biochemical reactions consist of the spontaneous fluctuation between two states: A⇌B. For example these two states could
be a ligand bound to an enzyme and the ligand and the enzyme separated from each other. A typical case would be the unbinding
of CO from myoglobin (Mb), namely, MbCO⇌Mb+CO. Another example is the fluctuation in the ion channel protein in the cell membrane
between conformations that are closed to the passage of ions and those that are open to the passage of ions, namely, closed⇌open.
Such chemical reactions can be described as two energy levels corresponding to the two states, separated by a distribution
of activation energy barriers. Since a kinetic rate can be associated with each energy barrier, this is also equivalent to
a distribution of kinetic rate constants. We derive the distribution of the kinetic rates that produces the stretched exponential
probability distribution, exp(−at
b
) where 0<b≤1, which has been observed for such reactions. We also derive the form of the cumulative probability distribution when the
pathways connecting the states have minimum or maximum rate constants. 相似文献
12.
The pulsed EPR inversion recovery sequence has been utilized to monitor the temperature dependence of the electron spin-lattice
relaxation rate of the Mn cluster of the Photosystem II oxygen evolving complex poised in a variety of S
2 state forms giving rise to g = 2 multiline EPR signals. A previous study (Lorigan and Britt (1994) Biochemistry 33: 12072–12076) showed that for PS II
membranes treated with 5% ethanol, the S
2 state Mn cluster relaxes via the Orbach spin-lattice relaxation mechanism, where the relaxation is enhanced via phonon scattering
off an excited state spin manifold, in this case at an energy of Δ = 36.5 cm−1 above the S = 1/2 ground state giving rise to the multiline EPR signal. Parallel experiments are reported for PS II membranes with 5%
methanol, treated with ammonia, and following short and long term dark adaptation. In each case, the temperature dependence
of the electron spin-lattice relaxation rate is consistent with Orbach relaxation, and the range of excited state energies
is relatively narrow (33.8 cm−1 ≤ Δ ≤ 39.7 cm−1). In addition, short term dark adapted (6 min, ‘active state’) PS II membranes show biphasic recovery traces which indicate
that a minority fraction of the oxygen evolving complexes are trapped in a form with greatly slowed spin-lattice relaxation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
The effect of fungal infection on the reproductive potential of two-spotted spider mite, Tetranychus urticae, was evaluated as part of the full biocontrol potential of three entomopathogenic fungi by modeling of fecundity probability.
Female mites (≤2-day-old) on leaves were exposed to the sprays of Beauveria bassiana, Paecilomyces fumosoroseus and Metarhizium anisopliae at the concentrations of 1.13 × 103, 1.55 × 103 and 0.95 × 103 deposited conidia mm−2 and then individually reared at 25°C and 12:12 L:D for oviposition. Mite mortalities 10 days after spraying were 73.1, 75.4
and 67.9% in the fungal treatments versus 15.5% in control. On average, females infected by the three fungal species survived
5.8, 6.2 and 6.3 days, and laid 3.1, 4.0 and 4.0 eggs per capita, respectively. These were 3–4 fold lower than the control
fecundity at 12.3. The cumulative probabilities [P(m ≤ N)] for the counts of infected and non-infected (control) females laying m eggs per capita (m ≤ N) during 10 days fit very well the equation P(m ≤ N) = 1/[1 + exp(a + bm)] (r
2 ≥ 0.98), yielding a solution to the probability for the female mites to achieve a specific fecundity {P(m ≤ N)−P[m ≤ (N − 1)]}. Consequently, the infected mites had 71–78% chance to lay ≤5 eggs per capita but only 5–8% to deposit >10 eggs despite
some variation among the tested fungi. In contrast, the chances for the non-infected mites to achieve the low and high fecundities
were 23 and 55%. The fitted probabilities provide a full coverage of the fecundity potential of infected versus non-infected
mites and are more informative than the mean fecundities. 相似文献
14.
Tolerance of environmental variables differs between corals and their dinoflagellate symbionts (Symbiodinium spp.), controlling the holobiont’s (host and symbiont combined) resilience to environmental stress. However, the ecological
role that environmental variables play in holobiont distribution remains poorly understood. We compared the drivers of symbiont
and coral species distributions at Palmyra Atoll, a location with a range of reef environments from low to high sediment concentrations
(1–52 g dry weight m−2 day−1). We observed uniform holobiont partnerships across the atoll (e.g. Montipora spp. with Symbiodinium type C15 at all sites). Multivariate analysis revealed that field-based estimates of settling sediment predominantly explained
the spatial variation of coral species among sites (P < 0.01). However, none of the environmental variables measured (sedimentation, temperature, chlorophyll concentration, salinity)
affected symbiont distribution. The discord between environmental variables and symbiont distributions suggests that the symbionts
are physiologically tolerant of the variable environmental regime across this location and that the distribution of different
host–symbiont combinations present is largely dependent on coral rather than Symbiodinium physiology. The data highlight the importance of host tolerance to environmental stressors, which should be considered simultaneously
with symbiont sensitivity when considering the impact of variations in environmental conditions on coral communities. 相似文献
15.
A. T. Reid 《Bulletin of mathematical biology》1953,15(3):361-365
A stochastic model of population growth is treated using the Bellman-Harris theory of agedependent stochastic branching processes.
The probability distribution for the population size at any time and the expectation are obtained when it is assumed that
there is probability (1−σ), 0≤σ<1, of the organism dividing into two at the end of its lifetime, and probability σ that division
will not take place. 相似文献
16.
Jing Wang Hua Yang Hong Lu Jiti Zhou Jing Wang Chunli Zheng 《World journal of microbiology & biotechnology》2009,25(5):875-881
An aerobic microbial consortium constructed by the combination of Rhodotorula mucilaginosa Z1, Streptomyces albidoflavus Z2 and Micrococcus luteus Z3 was immobilized in polyurethane foam and its ability to degrade nitrobenzene was investigated. Batch experimental results
showed that polyurethane-foam-immobilized cells (PFIC) more efficiently degrade 200–400 mg l−1 nitrobenzene than freely suspended cells (FSC). Kinetics of nitrobenzene degradation by PFIC was well described by the Andrews
equation. Compared with FSC, PFIC exhibited better reusability (over 100 times) and tolerated higher shock-loadings of nitrobenzene
(1,000 mg l−1). Moreover, In the presence of salinity (≤5% NaCl, w/v), phenol (≤150 mg l−1) and aniline (≤50 mg l−1), respectively, degradation efficiency of nitrobenzene by PFIC reached over 95%. Even in the presence of both 100 mg l−1 phenol and 50 mg l−1 aniline, over 75% nitrobenzene was removed by PFIC in 36 h. Therefore, the immobilization of the defined consortium in polyurethane
foam has application potential for removing nitrobenzene in industrial wastewater treatment system. 相似文献
17.
Recent studies have identified common variants in or near GC, CYP2R1 and NADSYN1/DHCR7 to be associated with 25-hydroxyvitamin D [25(OH)D] levels in European populations. We aimed to examine whether these variants
also influence 25(OH)D levels in Chinese. Seven common variants were successfully genotyped and tested for associations with
plasma 25(OH)D levels in a population-based cohort of 3,210 Chinese Hans from Beijing and Shanghai. Six common variants at
GC (rs4588, rs7041, rs2282679 and rs1155563) and NADSYN1/DHCR7 (rs3829251 and rs1790349) loci were all significantly associated with lower plasma 25(OH)D levels (−0.036 ≤ β ≤ −0.076 per risk-allele, P ≤ 5.7 × 10−5), while CYP2R1-rs2060793 showed a trend toward association with 25(OH)D levels in the Shanghai subpopulation (P = 0.08), but not in the Beijing subpopulation (P = 0.82). Haplotype-based association analyses of the four GC variants showed that only the haplotype that contained all risk-alleles (TACC) was significantly associated with lower plasma
25(OH)D levels (β = −0.085, P = 2.3 × 10−9), while the haplotype containing the risk-alleles of rs4588 and rs2282679 (TATC) was marginally associated with lower 25(OH)D
levels (β = −0.054, P = 0.0562) when compared with GCTA haplotype carrying the four protective alleles. Most notably, conditional analyses showed
that only GC-rs4588 and GC-rs2282679 (r
2 = 0.97) remained significantly associated with 25(OH)D concentrations (P ≤ 1.9 × 10−5) after adjusting for the other two SNPs in GC. In conclusion, GC and NADSYN1/DHCR7 loci individually and collectively contribute to variation in plasma vitamin D levels in Chinese Hans. 相似文献
18.
T. C. Tricas J. G. New 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):89-101
Elasmobranch fishes localize weak electric sources at field intensities of <5 ηV cm−1, but the response dynamics of electrosensory primary afferent neurons to near threshold stimuli in situ are not well characterized.
Electrosensory primary afferents in the round stingray, Urolophus halleri, have a relatively high discharge rate, a regular discharge pattern and entrain to 1-Hz sinusoidal peak electric field gradients
of ≤20 ηV cm−1. Peak neural discharge for units increases as a non-linear function of stimulus intensity, and unit sensitivity (gain) decreases
as stimulus intensity increases. Average peak rate-intensity encoding is commonly lost when peak spike rate approximately
doubles that of resting, and for many units occurs at intensities <1 μV cm−1. Best neural sensitivity for nearly all units is at 1–2 Hz with a low-frequency slope of 8 dB/decade and a high-frequency
slope of −23 dB/decade. The response characteristics of stingray electrosensory primary afferents indicate sensory adaptations
for detection of extremely weak phasic fields near 1–2 Hz. We argue that these properties reflect evolutionary adaptations
in elasmobranch fishes to enhance detection of prey, communication and social interactions, and possibly electric-mediated
geomagnetic orientation.
Accepted: 20 June 1997 相似文献
19.
Gerard Leblondel Yves Mauras Annie Cailleux Pierre Allain 《Biological trace element research》2001,83(3):191-206
The transport and uptake of the most common Se compounds, selenate (SeO
4
2−
), selenite (SeO
3
2−
), selenomethionine, and selenocystine, were investigated using confluent monolayers of Caco-2 cells, a human carcinoma cell
line. Comparative measurements were performed in the absorptive (apical to basolateral side) and exsorptive (basolateral to
apical side) directions. Apparent permeability coefficients (P
app), calculated from transport experiments in the absorptive direction, showed increasing values in the following rank order:
about 1×10−6 cm/s ≤ mannitol ≤ SeO
3
2−
≤ selenocystine < selenomethionine < SeO
4
2−
≤ about 16×10−6 cm/s. The ratios of the P
app measured in the absorptive versus exsorptive directions indicated that only the organic forms presented a net polarized transport
(P
app ratio ≫1), suggesting the presence of a transcellular pathway. No significant excretion was observed. The transport of selenomethionine
was inhibited by its sulfur analog, methionine, suggesting a common transport mechanism. In contrast, an inhibition of the
transport of selenocystine by cysteine was not observed. From the two substrates tested, sulfate and thiosulfate, only thiosulfate
inhibited the transport of SeO
4
2−
. This effect was also observed for SeO
3
2−
(i.e., was unspecific), which questioned the assertion of a common transport for sulfate and SeO
4
2−
and may confirm the paracellular pathway of SeO
4
2−
suggested by the P
app ratio of about 1. The addition of glutathione (GSH) in large excess had no consequence on the passage of SeO
3
2−
but strongly increased the uptake (about fourfold). The liquid chromatography — mass spectrometry (LC-MS) data showed that,
in the ionic condition of incubation medium, GSH promptly reduced SeO
3
2−
(≤2 min) in its elemental form Se0, which cannot ascribe to selenodiglutathione a direct role in the effect of GSH. 相似文献
20.
Microscale photographs were taken of the ice bottom to examine linkages of algal chlorophyll a (chl a) biomass distribution with bottom ice features in thick Arctic first-year sea ice during a spring field program which took
place from May 5 to 21, 2003. The photographic technique developed in this paper has resulted in the first in situ observations
of microscale variability in bottom ice algae distribution in Arctic first-year sea ice in relation to ice morphology. Observations
of brine channel diameter (1.65–2.68 mm) and number density (5.33–10.35 per 100 cm2) showed that the number of these channels at the bottom of thick first-year sea ice may be greater than previously measured
on extracted ice samples. A variogram analysis showed that over areas of low chl a biomass (≤20.7 mg chl a m−2), patchiness in bottom ice chl a biomass was at the scale of brine layer spacing and small brine channels (∼1–3 mm). Over areas of high chl a biomass (≥34.6 mg chl a m−2), patchiness in biomass was related to the spacing of larger brine channels on the ice bottom (∼10–26 mm). Brine layers and
channels are thought to provide microscale maxima of light, nutrient replenishment and space availability which would explain
the small scale patchiness over areas of low algal biomass. However, ice melt and erosion near brine channels may play a more
important role in areas with high algal biomass and low snow cover. 相似文献