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Results of three years of directional wave measurement at the Eastern Mediterranean coast of Haifa, Israel are presented. The wave-height and energy-flux distributions reveal a moderately high-energy coast with a bimodal annual cycle.The rate of wave-induced longshore sediment transport is estimated from the directional energy flux distributions. It describes an annual cycle with a maximum northward transport of 75 ± 14 × 103 m3/month in midwinter and a southward transport of 26 ± 5 × 103 m3/month in summer. The net annual transport is northward and computed at 110 ± 100 × 103 m3/yr.We show that a wave-induced transport is sufficient in explaining the apparent transport of sediments in the Nile Littoral Cell, from the Nile Delta source to the Haifa Bay sink. 相似文献
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By the use of the model of approaching drops (Arbel and Levin, 1977) the coalescence efficiencies of drops are computed. It is found that for interactions of drops at their terminal velocities the coalescence depends both on the size of the large drop and on the size ratio of the interacting drops in agreement with the experimental results of Whelpdale and List (1971) and Levin and Machnes (1977).The results were found to be sensitive to the assumption of the drops deformation and to the critical separation distance. This distance is defined as the distance at which the drops begin to merge. The variations of the coalescence efficiency with these parameters is discussed.Appendix: List of symbols
D
distance between the deformed surfaces of the drops
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D
o
initial value ofD
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D
s
stop distance, the distance at which the impact velocity vanishes
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D
c
critical coalescence distance
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E
collection efficiency
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E
1
collision efficiency
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E
2
coalescence efficiency
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E
2R
coalescence efficiency for collisions with stationary targets
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F
c
centrifugal force
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p
ratio of the radii of the interacting drops
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r
o
initial distance between drops' centers
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R
L
radius of larger drop
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R
s
radius of smaller drop
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R
D
radius of deformation
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v
approach velocity of two deformed surfaces
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v
o
initial value ofv
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V
i
impact velocity (given negative sign when drops approach each other)
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V
c
critical impact velocity
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W
i
velocity of the smaller drop at infinity for it to reachD
o with velocityv
o
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x
i
impact distance, the distance between the trajectories of the two drops
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x
c
critical impact distance for coalescence
-
average critical impact distance for coalescence
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X
c
critical impact distance for collisions
-
coefficient of deformation given in equation 1
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i
impact angle defined byWhelpdale andList (1971) given also inArbel andLevin (1977)
-
coefficient of deformation given in equation 2
-
viscosity of air
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i
impact angle used inArbel andLevin (1977) and here
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c
critical angle for coalescence
-
average critical angle for coalescence
On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
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主要对以色列野生二粒小麦赫尔蒙种群中分离获得的一个抗条锈病基因进行了分子定位研究 ,将源于赫尔蒙山具抗杀锈病的种系 T.dicoccides H52与普通的栽培种 Langdon进行杂交并创建了 F2 代遗传图。研究发现 H52种系抗条锈病的能力由一种显性基因控制 ,将其暂定名为 Yr H52。从 1 2 0个微卫星标记中 ,已经检测到来自亲本 91 %的多态性 ,而且从其中 56个微卫星分子标记中产生了 79个分离的位点 ,有 9个位点显示出了与 Yr H 52基因连锁 ,其重组率 0 .0 2～ 0 .3 5,遗传距离 2 .0 0～ 4 3 .3 7cm之间 ,L OD值 3 .56～ 54.2 2。由 1 0个微卫星位点和 Yr H52构建的染色体 1 B遗传图 ,其图距全长为 1 0 1 .5cm。Yr H52基因位于 Xgwm2 64 a和 Xgwm2 64 c之间 ,且与 Xgwm2 64 a、Xgwm1 8紧密连锁 ,两侧依次分别与 Xgwm1 3 1 a、Xgwm63 6b、Xgwm2 64 c、Xgwm4 0 3 a、Xgwm1 53、Xgwm550 a和 Xgwm1 2 4连锁。同时 ,Yr H52也与 REL P标记物 N or1紧密连锁 ,图距 1 .4 cm,L OD2 9.62。这显然与野生二粒小麦另一个抗条锈病基因 Yr1 5不同 ,研究证明 Yr1 5与 N or1图距是 1 1 .0 cm。 相似文献
5.
Hartl MG Kilemade M Sheehan D Mothersill C O'Halloran J O'Brien NM van Pelt FN 《Marine environmental research》2007,64(2):191-208
Hatchery-reared turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to sediment collected from polluted sites in Cork Harbour and a reference site at Ballymacoda, Co. Cork, Ireland. The potential of surficial sediment for inducing hepatic biomarkers was assessed at two levels of biological organisation: expression of cytochrome P450 [Western blotting analysis and 7-ethoxy-resorufin O-dealkylase (EROD), 7-benzoxy resorufin O-dealkylase (BROD), 7-methoxy resorufin O-dealkylase (MROD), 7-pentoxy-resorufin O-dealkylase (PROD) activities] and DNA integrity (Comet assay). Positive controls were generated, either by exposing turbot to cadmium chloride-spiked seawater (Comet assay) or to beta-naphthaflavone by intraperitoneal injection (cytochrome P450 induction). The induction of cytochrome P450 activity (EROD, MROD and PROD) in animals following a 7-day exposure to contaminated sediments was significantly higher than those exposed to reference site sediment and remained elevated thereafter; BROD was not induced. DNA single-strand breaks were also significantly higher following exposure to contaminated sediments throughout the experiment. Although no direct correlation between induction of alkoxyresorufin O-dealkylase activities and a particular chemical class was established, the induction of MROD and PROD activities in fish exposed to sediments containing complex contaminant mixtures, appeared to be more sensitive than conventional EROD activity assays. We conclude from the present laboratory study that S. maximus is a suitable sentinel species for the assessment of moderately contaminated sediments and therefore allows for the further development of this model for future, ecologically relevant, field studies. 相似文献
6.
The possibilities of lightning generation on other planets are considered, and the basic conditions that exist in terrestrial clouds during lightning discharges and the various theories of charge separation are reviewed. Recent measurements of cloud structure and whistlers, as well as optical observation of lightning on Jupiter, suggest that charge separation and lightning discharges occur on other planets in ways similar to those in which they occur on Earth. Using these terrestrial ideas, it is concluded that lightning on Venus will probably be found in clouds that are located in regions of convection such as those observed downwind of the subsolar point. It is also possible that if volcanoes on Venus are erupting, they too can produce lightning discharges in their plumes although it seems unlikely that this process can account for the observed rate of discharge. Jovian lightning is most probably generated in the lower water-ice clouds. These clouds are of moderate temperatures and have strong convection and large mass loading, all important ingredients for electrical buildup. Lightning is all but ruled out for Mars, even though some electrification is possible owing to the large dust storms on that planet. 相似文献
7.
Council Approaches to Implementing Sustainability: a case of rearranging deck chairs on the Titanic?
Carmel M. Dunn 《The Australian geographer》2010,41(3):351-366
Local government has a key role to play in implementing sustainability. Yet even councils attempting to address the issue of sustainability are often unacceptably slow and ineffective in their endeavours. This study investigates the approaches that councils currently take in implementing sustainability, as this may shed additional light on the slow progress of councils towards sustainability. The approaches of three New South Wales councils were examined and assessed using a model developed for the study that utilised the Ecological Footprint as the primary assessment tool. The model assessed three key aspects of council approaches to implementing sustainability: (1) the issues councils target for change; (2) the methods councils use to change behaviours; and (3) the clarity and holistic nature of their approaches. All three council approaches scored poorly against the model mainly as a result of the councils' failure to target the behaviours of their residents that are causing the greatest ecological harm. The major implication is that councils need to reconsider, and possibly overhaul, their approaches to implementing sustainability as these approaches are unlikely ever to achieve sustainability. 相似文献
8.
The approach of two water drops in the absence of air flow around them is theoretically investigated. By assuming deformation criteria it is possible to solve the equation of motion of the drops under the influence of a variety of forces. These forces include the viscous force exerted by the air between the two deformed surfaces, the London-Van Der Waals forces and the force of gravity. It is found that the viscous forces dominate over the whole distance of the interaction. The equations have analytical solutions when a head-on approach is considered and when the deformation of the drops is assumed constant during the interaction. The equations were solved numerically for other deformation criteria and for non head-on approaches.The results of the present model are used in the following paper to compute the coalescence efficiencies of water drops. The model is primarily applicable to situations in which the large drop is stationary and the small one approaches it from below. However, it could also be used for interaction between freely falling drops as long as their relative velocities exceed about 13 cm/sec.Appendix: List of symbols
C
constant of the motion
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D
distance between the deformed surfaces of the drops
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D
o
initial value ofD
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D
m
the value at which the viscous force is maximum
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D
N
normalized distance
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D
s
the distance at which the velocity of approach vanishes
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F
c
centrifugal force
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F
g
force due to gravity
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F
N
normalized viscous force
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F
LV
force due to London-Van der Waals effect
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F
R
radial component of the force
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F
V
viscous force
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F
t
tangential component of the force
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g
acceleration due to gravity
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M
L
mass of large drop
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m
s
mass of small drop
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p
ratio of radii of interacting drops
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R
radius of an arbitrary drop
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r
distance between the centers of mass of the two drops
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R
D
radius of deformation
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R
L
radius of larger drop
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R
s
radius of smaller drop
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t
time
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u
defined in equation 20 — has the meaning of kinetic energy
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v
relative velocity of the deformed surfaces
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v
0
initial value ofv
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V
0
initial relative velocity of the centers of the drops
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V
c
critical impact velocity
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V
i
impact velocity
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V
N
,v
n
normalized velocity
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V
t
tangential component of the velocity
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W
i
velocity of the small drop at infinity for it to reach the pointD
0 at velocityV
0
-
x
instantaneous impact distance
-
average critical impact distance for coalescence
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x
0
initial value of the impact distance
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x
c
critical impact distance for coalescence
-
coefficient of deformation
-
i
impact angle according toWhelpdale andList (1971)
-
coefficient of deformation
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viscosity
-
surface tension
- F
s
sum of forces acting on the small drop
- F
L
sum of forces acting on the large drop
-
time constant
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R
Rayleigh's oscillation period
On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
9.
A two-year series of directional wave measurement off the Eastern Mediterranean coast of Israel reveals an abundance of high storm waves. Some of these waves have significant height in excess of 5 meters and periods as long as 15 sec.The evolution of the storm waves is described and related to the growth and paths of the storm fronts in Mid-Mediterranean. Shorter-period waves are found to always lead the arrival of longer-period swell. This characteristic is explained by a short decay distance and/or a high migration velocity of the storm front.The scatter plot of significant wave height vs period for the recorded events of each storm describes an open-loop time sequence. The difference in period between that of the peak height event and the period of a fully arisen sea of the same height is found to be indicative of the true decay distance the waves have travelled. 相似文献
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