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1.
当渔业资源出现衰退时,加强资源增殖放流以养护渔业资源、提高渔业产量对于渔业资源可持续利用具有重要意义;与此同时,增殖放流的实施会对基于资源开发与管理的评估的结果产生影响。基于2001~2015年间东海北部海域三疣梭子蟹(Portunus trituberculatus)渔业数据,采用增殖剩余产量模型,对东海北部海域三疣梭子蟹的最大可持续产量(MSY)及取得MSY时所需捕捞努力量(EMSY)和原存生物量(BMSY)进行了评估,并与传统Schaefer模型评估结果进行了比较。结果表明,当年增殖放流量约在3×106~95×106尾之间时,三疣梭子蟹年产量逐渐增加, MSY在14.2×104 t和14.6×104 t之间, EMSY基本在15×104吨位左右。增殖放流量增加,其对应的MSY也越高,能承受的EMSY也越高(从15×104~15.4×104吨位之间),相反BMSY则减小(从188.4×104 t降至186.6×104 t)。与传统的Schaefer模型评估结果相比,增殖剩余产量模型由于考虑了增殖放流生物量的因素,得到了MSY和EMSY有所增加,而BMSY有所下降的结论。研究结果有望为该研究海域三疣梭子蟹可持续地捕捞、放流与管理提供科学依据。 相似文献
2.
用水热合成法在掺氟氧化锡(SnO2: F, FTO)导电玻璃上合成了ZnO 纳米线并用原子力显微镜(AFM)和扫描电镜(SEM)对其进行了表征。利用LB 膜技术将高等植物菠菜(Spinacia oleracea)和海洋绿藻石莼(Ulva lactuca)的类囊体膜分别固定在纳米ZnO 上组装成光电池, 用太阳能测试系统检测比较了其光电性质。研究表明, 由两种植物的类囊体膜LB 膜组成的光电池都能产生光生电流; 蛋白LB 膜的层数显著影响了光电池的光电转化效率, 随着层数的增加, 光电转化效率大大增加。此外, 石莼类囊体膜组装的光电池光电转化效率明显高于菠菜类囊体膜。 相似文献
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4.
The relationship between seagrass (Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments 总被引：2，自引：0，他引：2
Maria Ll. Calleja Núria Marb Carlos M. Duarte 《Estuarine, Coastal and Shelf Science》2007,73(3-4):583-588
In this study we test the hypothesized negative relationship between seagrass status and porewater hydrogen sulfide (H2S) levels, through a comparative analysis within a range of seven Posidonia oceanica meadows growing over carbonate sediments in the NW Mediterranean Sea around Mallorca Island. The studied meadows range from meadows growing on sediments with very low sulfide porewater concentrations (4.6 μM) to those growing over higher sulfide conditions (33.5 μM). Organic matter content, sulfate reduction rates and sulfide porewater concentrations in the sediments were determined concurrently with the assessment of demographic plant dynamics (specific mortality and net population growth rates). Sulfide porewater concentration increased with increasing organic matter content in the sediment, while net population growth decreased significantly with low increases of sulfide concentrations. Our results confirm the previously suspected vulnerability of seagrass meadows growing on carbonate sediments to increased sulfide levels. An excess of 10 μmols H2S L−1 porewater is identified to already conduce P. oceanica meadows to decline, which this study identifies, particularly, as strongly sensitive to sulfides. The results reported here suggest that even moderate increases in organic carbon inputs may lead to enhancement of dissolved sulfides and may be an important factor for seagrass status in these iron-depleted carbonate sediments from the Mediterranean Sea. 相似文献
5.
The Bonnet Carré Spillway, located 28 miles northwest of New Orleans, was constructed in the early 1930s as part of an integrated
flood-control system for the lower Mississippi River system. From 11 April to 8 May 2008, Mississippi River water was diverted
through the spillway into the 629-square-mile Lake Pontchartrain, which is hydraulically connected to the Gulf of Mexico.
On 8 April, prior to the opening of the spillway, water-quality instruments were deployed and recorded hourly measurements
of water temperature, dissolved oxygen, specific conductance, pH, and nitrate. Discrete water-quality and phytoplankton (algae)
samples were collected in Lake Pontchartrain from 8 April to 3 October 2008 to assess the water-quality nutrient enrichment
effects of the diversion on the lake. The maximum influence of river water in the southern portion of the lake was captured
with continuous (hourly) monitoring of nitrate concentrations, and field measurements such as of specific conductance during
the critical period in late April to early May. By late May, the deployed instruments had recorded the arrival, peak, and
decline of selected constituents associated with the freshwater influx from the Mississippi River/Bonnet Carré Spillway diversion.
The continuous monitoring data showed the short-term interactions of high-nitrate, low-specific conductance river water and
low-nitrate, high-specific conductance lake water. The phytoplankton community composition, as an indicator of water quality,
illustrated an extended response from the river water evident even after the continuous and discrete samples indicated that
the lake had returned to pre-diversion conditions. The initial phytoplankton community response to nutrient increases was
related to accumulations of diatoms. During periods of low nutrient concentrations, accumulations of blue-greens occurred
by July and August. As blue-green algae cell densities and biovolumes increased in the summer, so did the species richness
of blue-green algae, particularly the harmful algae bloom taxa. Cell densities and biovolume of the phytoplankton lake indicator
taxa Skeletonema costatum, Anabaena sp., and Cylindrospermopsis raciborskii were highest and dominated the diatom and blue-green algae communities during the period of most river water influence on
the lake and immediately following the freshwater inflows. The dominance and recession of these indictor taxa reflect the
dramatic changes that occurred in the phytoplankton community in response to an increase in nutrient-rich freshwater from
the diversion into the lake, and not normal seasonal phytoplankton compositional differences. Water-quality data indicated
a gradual reversion to pre-diversion lake conditions by June to July, but shifts in the phytoplankton composition were still
evident through August 2008. Observations from this study were similar to results from previous studies of Mississippi River/Bonnet
Carré Spillway diversion opening in 1997. 相似文献
6.
Experiments are performed on a flat plate with a transverse suction slit in the Reynolds number range 5 × 105 < Re < 1.1 × 106. Mean velocity profiles, RMS values are measured with hot wire anemometry. Friction velocity is numerically calculated. The experiments showed that a classical boundary layer parameter α is related to the suction coefficient Sc with an equation of the form: .The value of A seems to depend strongly on the relative location with respect to suction slit and possibly weakly on Reynolds number. 相似文献
7.
The effect of UV-B radiation enhancement at experimental doses of 0.00,0.24,0.48,0.72,0.96,and 1.20 kJ/m 2 on the population dynamics of the rotifer Brachionus urceus feeding on the alga Chlorella sp.was studied under controlled laboratory conditions using clonal culture and life-table techniques.The results show that UV-B radiation treatment significantly shortened the survival time of the rotifer (P <0.05): The longest survival time (336 h) occurred in the control (0.00 kJ/m 2 ) while the shortest (222 h) occurred when exposed to the highest UV-B radiation treatment (1.20 kJ/m 2 ).The fecundity of the rotifer B.urceus was enhanced by the lower UV-B radiation treatment (0.24 and 0.48 kJ/m 2 ) but inhibited by the higher treatments (0.96 and 1.20 kJ/m 2 ).Life expectancy also was obviously affected by UV-B radiation (P <0.05).The highest life expectancy occurred in the control (0.00 kJ/m 2 ),and it became shorter with increasing doses of UV-B radiation.The resutls in the present study indicate that the life expectancy of the rotifer B.urceus can be used as an indicator for UV-B radiation enhancement. 相似文献
8.
Using density functional theory and quantum transport calculations based on nonequilibum Green's function formalism, we investigate the charge transport properties of endohedral M@C20 (M= Na and K) metallofullerenes. Our results show that the conductance of C20 fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the I-V curves of the Au-M@C20-Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C20 molecule but not in K@C20. 相似文献
9.
In this work, the influence of a small-molecule material, tris(8-hydroxyquinoline) aluminum (Alq3), on bulk heterojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). By doping Alq3 into MEH-PPV:PCBM solution, the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq3 to MEH-PPV, which probably induces the increase of photocurrent generated by excitons dissociation. However, the low carrier mobility of Alq3 is detrimental to the efficient charge transport, thereby blocking the charge collection by the respective electrodes. The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs. For the case of 5 wt.% Alq3 doping, the device performance is deteriorated rather than improved as compared with that of the undoped device. On the other hand, we adopt Alq3 as a buffer layer instead of commonly used LiF. All the photovoltaic parameters are improved, yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer. Even for the 5 wt.% Alq3 doped device, the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq3. The performance deterioration of Alq3-doped devices can be explained by the low solubility of Alq3, which probably deteriorates the bicontinuous D-A network morphology; while the performance improvement of the devices with Alq_3 as a buffer layer is attributed to the increased light harvesting, as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq3 compared with that of MEH-PPV. 相似文献
10.
Mooring forces in horizontal interlaced moored floating pipe breakwater with three layers 总被引：2，自引：0，他引：2
The paper presents the results from model scale experiments on the study of forces in the moorings of horizontally interlaced, multi-layered, moored floating pipe breakwaters. The studies are conducted with breakwater models having three layers subjected to waves of steepness Hi/L (Hi is the incident wave height and L the wavelength) varying from 0.0066 to 0.0464, relative width W/L (W is the width of breakwater) varying from 0.4 to 2.65, and relative spacing S/D (S is the spacing of pipes and D the diameter of pipe) of 2 and 4. The variation of measured normalized mooring forces on the seaward side and leeward side are analyzed by plotting non-dimensional graphs depicting f/γW2 (f is the force in the mooring per unit length of the breakwater, γ the weight density of sea water) as a function W/L for various values of Hi/d (d is the depth of water). It is found that the force in the seaward side mooring increases with an increase in Hi/L for d/W values ranging between 0.081 and 0.276. The experimental results also reveal that the forces in the seaward side mooring decrease as W/L increases, up to a value of W/L=1.3, and then increases with an increase in W/L. It is also observed that the wave attenuation characteristics of breakwater model with relative spacing of 4 is better than that of the model with relative spacing of 2. The maximum force in the seaward side mooring for model with S/D=4 is lower compared to that for the breakwater model with S/D=2. A multivariate non-linear regression analysis has been carried out for the data on mooring forces for the seaside and leeside. 相似文献
11.
急性低氧胁迫对军曹鱼大规格幼鱼血液生化指标的影响 总被引：1，自引：1，他引：0
为了研究军曹鱼在急性低氧应激时体内物质代谢和组织器官机能状态变化,分别测定低氧胁迫前后血液生化指标的含量。结果表明:（1）急性低氧胁迫后,军曹鱼血清电解质含量呈不同程度升高,其中钠、氯和钙离子浓度与胁迫前差异极显著（P<0.01）;钾离子浓度与胁迫前无显著性差异（P>0.05）。（2）急性低氧胁迫后,军曹鱼血清肝功能指标变化情况各异。其中,白蛋白含量与胁迫前略有降低,谷丙转氨酶和谷草转氨酶活性与胁迫前略有上升,但差异均不具有统计学意义（P>0.05）,总蛋白含量显著低于胁迫前（P<0.05）,白蛋白和球蛋白比值则显著高于胁迫前（P<0.05）,碱性磷酸酶极显著低于胁迫前（P<0.01）。（3）急性低氧胁迫后,军曹鱼血清葡萄糖和肌酐浓度均呈升高的变化,且与胁迫前差异极显著（P<0.01）。（4）急性低氧胁迫后,血清肌酸激酶和乳酸脱氢酶活性均呈升高变化,肌酸激酶活性与胁迫前差异显著（P<0.05）,乳酸脱氢酶活性与胁迫前差异极显著（P<0.01）。（5）低氧胁迫后,军曹鱼血脂指标变化情况各异,其中总胆固醇和高密度脂蛋白浓度呈极显著降低的变化（P<0.01）,低密度脂蛋白浓度呈显著升高的变化（P<0.05）,甘油三酯浓度略有升高,但不具有统计学意义（P>0.05）。研究表明,急性低氧胁迫后,军曹鱼大部分血液生化指标发生显著性变化,预示着肝脏、肾脏及心脏组织造成损伤,使其机能出现紊乱。 相似文献
12.
Yoshimi M. Rii Susan L. Brown Francesco Nencioli Victor Kuwahara Tommy Dickey David M. Karl Robert R. Bidigare 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1275
Macronutrients, photosynthetic pigments, and particle export were assessed in two eddies during the E-Flux I and III cruises to investigate linkages between biogeochemical properties and export flux in Hawaiian lee cyclonic eddies. Cyclone Noah (E-Flux I), speculated to be in the ‘decay’ stage, exhibited modest increases in macronutrients and photosynthetic pigments at the eddy center compared to ambient waters. Cyclone Opal (E-Flux III) also exhibited modest increases in macronutrient concentrations, but a 2-fold enhancement in total chlorophyll a (TChl a) concentration within the eddy center. As indicated by fucoxanthin concentrations, the phytoplankton community in the deep chlorophyll maximum (DCM) of Opal was comprised mainly of diatoms. During an 8-day time series in the center of Opal, TChl a concentration and fucoxanthin in the DCM decreased by 50%, which was potentially triggered by silicic acid limitation. Despite the presence of a substantial diatom bloom, Opal did not deliver the expected export of particulate carbon and nitrogen, but rather a large biogenic silica export (4-fold increase relative to export in surrounding waters). Results suggest that controls on the life cycle of a Hawaiian lee cyclone are likely a combination of physical (eddy dynamics), chemical (nutrient limitation), and biological (growth and grazing imbalance) processes. Comparisons between Noah and Opal and previously studied cyclones in the region point to a relationship between the spin-up duration of a cyclone and the resulting biological response. Nonetheless, Hawaiian lee cyclones, which strongly influence the biogeochemistry of areas 100's of km in scale in the subtropical North Pacific Ocean, still remain an enigma. 相似文献
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Structure and seasonal variability of the deep mean circulation of the East Sea (Sea of Japan) 总被引：1，自引：0，他引：1
The horizontal structure of deep mean circulation and its seasonal variability in the Japan/East Sea (JES) were studied using
profiling float and moored current meter data. The deep circulation in the Japan Basin (JB) flows cyclonically, basically
following f/H contours. The correlation between the directions of deep current and f/H contour increases as |▿(f/H)| increases, reaching remarkably high correlation coefficient (>0.8) values in steep slope regions in the JB. In contrast
to the JB, the deep mean circulation in the Ulleung/Tsushima Basin (UTB) is generally weak and cyclonic accompanied by sub-basin-scale
cyclonic and anticyclonic eddies. The UTB shows a poorer correlation between directions of deep current and f/H contours than other basins. The time-space averaged deep mean current is about 2.8 cm/s and the volume transport in the deep
layer (800 m to bottom) in the JB reaches about 10 Sv (10 × 106 m3s−1), which is about four times greater than the inflow transport through the Tsushima Straits. A salient feature is that the
amplitude of deep mean current in the JB reveals a remarkable seasonal variation with a maximum in March and minimum in October.
The annual range of the seasonal variation is about 30% of the mean velocity, whereas that in the southern JES (UTB and Yamato
Basin) is weak. 相似文献
16.
This paper investigates the electronic and optical properties for pure and Ce3+-doped CaS crystals by using the first-principles total energy calculations. The results show that CaS:Ce has a direct band gap of 2.16 eV, and the top of the valence band is determined by S 3p states and the bottom of the conduction band is determined by Ce 4f states, respectively. Our results validate that the yellow emission from CaS:Ce is produced by doped cerium and the green emission quenches at 12.5% cerium concentration. The Ce-S bond shows more covalent character than the Ca-S bond. 相似文献
17.
M. I. Fortus 《Izvestiya Atmospheric and Oceanic Physics》2010,46(5):563-573
In the context of the problem of global warming, the question of how much the observed increase in the mean air temperature
over the last decades is likely due only to natural variability is studied. It is assumed that an observed temperature-data
series of length N is a segment of a stationary random sequence with a spectrum known on an interval that does not include the lowest frequencies.
The variance σ2(N) of the sample mean m* and the standard deviation σ(N), which determines the width of the confidence interval of m*, are calculated for different continuations of the spectrum to the low-frequency region. For a continuation of the spectrum
that boundlessly increases, as does ω−2α (0 < α < 1/2) when the frequency ω tends to zero (red-noise spectrum), it is shown that, the closer the parameter α is to
1/2, the more slowly σ(N) tends to zero at N → ∞. Using an empirical spectrum of a global mean annual temperature series as an example, it is shown that the standard
deviation significantly depends on the form of the spectrum in the lowest frequency region. An attempt has been made to assess
the measure of standard-deviation uncertainty due to a lack of exact information on the spectrum in the low-frequency region.
Important series characteristics—the equivalent number of independent observations N
eq(N) and the time scale of correlation T
1(N) which are determined through the variance σ2(N) of m*—also depend on the form of the spectrum in the low-frequency region. For the red-noise spectrum, N
eq(N) increases with an increase in N proportionally to N
1–2α (but not proportionally to N as in the case of bounded spectrum); the correlation scale T
1(N) is no longer constant (as in the case of bounded spectrum) and increases with an increase in N proportionally to N
2α. 相似文献
18.
Eight microsatellite markers were used to analyze genetic diversity, level of inbreeding, and effective population size of spawner and recaptured populations of Chinese shrimp(Fenneropenaeus chinensis) during stock enhancement in the Bohai Bay in 2013. A total of 254 and 238 alleles were identified in the spawner and recaptured populations, respectively, and the numbers of alleles(N_a) were 8–63 and 6–60, respectively. The numbers of effective alleles(N_e) were 2.52–21.60 and 2.67–20.72, respectively. The polymorphism information content ranged from 0.529 to 0.952. The observed heterozygosity(H_o) values(0.638–0.910 and 0.712–0.927) were lower than the expected heterozygosity(H_e) values(0.603–0.954 and 0.625–0.952), which indicated that the two populations possessed a rich genetic diversity. In 16 tests(2 populations×8 loci), 13 tests deviated from the HardyWeinberg equilibrium. F_(is) values were positive at seven loci and the inbreeding coefficients(F) of the two populations estimated by trio ML were 13.234% and 11.603%, suggesting that there was a relatively high degree of inbreeding. A certain level of inbreeding depression had occurred in the Chinese shrimp population. F_(st) values ranged from 0 to 0.059, with a mean of 0.028, displaying a low level of genetic differentiation in the two populations. Effective population sizes(3 060.2 and 3 842.8) were higher than the minimum number suggested for retaining the evolutionary potential to adapt to new environmental conditions. For enhancement activity in 2014,the ideal number of captured shrimp spawners should have ranged from 7 686 to 19 214 to maintain genetic diversity and effective population size. Further strategies to adjust the balance of economic cost, fishing effort and ideal number of shrimp spawners to maintain a satisfactory effective population size for ensuring the sustainability of Chinese shrimp are proposed. 相似文献
19.
Observation and measurement of the bottom boundary layer flow in the prebreaking zone of shoaling waves 总被引：1，自引：0，他引：1
In this paper, the characteristics of the bottom boundary layer flow induced by nonlinear, asymmetric shoaling waves, propagating over a smooth bed of 1/15 uniform slope, is experimentally investigated. Flow visualization technique with thin-layered fluorescent dye was first used to observe the variation of the flow structure, and a laser Doppler velocimeter was then employed to measure the horizontal velocity, U.The bottom boundary layer flow is found to be laminar except within a small region near the breaking point. The vertical distribution of the phase-averaged velocity U at each phase is non-uniform, which is directly affected by the mean velocity,
. The magnitude of
increases from zero at the bottom to a local positive maximum at about z/δ2.02.5 (where z is the height above the sloping bottom and δ is the Stokes layer thickness), then decreases gradually to zero at z/δ6.07.0 approximately, and finally becomes negative as z/δ increases further. Moreover, as waves propagate towards shallower water, the rate of increase in the maximum onshore oscillating velocity component
is greater than that of the offshore counterpart
except near the breaking point. The free stream velocities in the profiles of the maximum onshore and offshore oscillating velocity components,
and
are found to appear at z/δ≥6.0. This implies that, if the Stokes layer thickness is used as a length scale, the non-dimensionalized boundary layer thickness remains constant in the pre-breaking zone. Although
is greater than
and the asymmetry of the maximum free stream velocities (i.e.
) increases with decrease of water depth, a universal similar profile can be established by plotting z/δ versus (
) or (
). The final non-dimensional profile is symmetric and unique for the distributions of the maximum onshore and offshore oscillating velocity components within the bottom boundary layer, which are induced by nonlinear, asymmetric shoaling waves crossing the pre-breaking zone. 相似文献
20.
High-order ghost imaging with thermal light consisting of N different frequencies is investigated. The high-order intensity correlation and intrinsic correlation functions are derived for such N-colour light. It is found that they are similar in form to those for the monochromatic case, thus most of the conclusions we obtained previously for monochromatic Nth-order ghost imaging are still applicable. However, we find that the visibility of the N-colour ghost image depends strongly on the wavelength used to illuminate the object, and increases as this wavelength increases when the test arm is fixed. On the contrary, changes of wavelength in the reference arms do not lead to any change of the visibility. 相似文献