雪藻高密度连续培养中生物量和花生四烯酸的高产率

以 1 .4cm和 2 .8cm光径的平板光生物反应器 ,恒定高光强 [2 4 0 0 μE/(m2 ·s) ],通气、无菌高密度连续培养雪地绿藻 (简称雪藻 )。连续采收并补充等量新鲜培养液 ,当藻体生物量(以去灰分干重表示 ,AFDW)达恒态时 ,研究雪藻比生长速率 (SGR)、藻体的生物产量、总脂肪酸 (TFA)和花生四烯酸 (AA)产率。结果表明 ,尽管随着比生长速率增加 ,雪藻高密度连续培养体系的AA/TFA、TFA/AFDW和AA/AFDW三个指标有不同程度的降低 ,但生物产量、总脂肪酸及其花生四烯酸产出都相当高。 2 .8cm光径的平板光生物反应器中 ,雪藻SGR为0 .2d- 1 时 ,每平方米光照面积日获 35 .3gAFDW的高产量 ;SGR 0 .1 35d- 1 时 ,TFA产率最大 ,为7.0g/(m2 ·d) ,此时AA产率也最高 ,达 2 .6g/(m2 ·d)。尽管 1 .4cm光径的反应器的培养体积比前者下降了 5 0 % ,但细胞浓度明显提高 ,单位光照面积的AFDW和TFA最大日产率只下降了37.3%和 1 0 % ,分别为 2 2 .1和 6.3g/(m2 ·d) ,而AA的最大日产率也是 2 .6g/(m2 ·d)。结果还表明 ,氮或磷营养亏缺能明显提高雪藻AA含量的各项指标 ,同时高光强也有利于雪藻累积AA。     

Acoustic reflectivity and shallow sedimentary structure in the Sea of Galilee, Jordan Valley

Mapping the floor of the Sea of Galilee (Lake Kinneret) with a shallow seismic system of 3.5 kHz resulted in interesting data that were not obtained previously with standard single-channel seismic systems. Over most of the lake acoustic penetration is not possible, probably because of the high gas content in the top sedimentary sequence. However, in a few areas, excellent penetration of about 20 m was achieved. One area is a terrace in the southern part of the lake, south of a small bathymetric escarpment at depths of 13–21 m along Israel latitudinal Grid 238. It is unclear whether the existence of gas in the sediment or other parameters are responsible for the marked difference in acoustic penetration on both sides of the scarp.Another area with acoustic penetration is in the vicinity of hot and salty submarine springs. Although there is no difference in the composition of the upper sedimentary layers between these areas and neighbouring areas, there is a marked difference in the acoustic penetration. The contact between areas with acoustic penetration to areas without acoustic penetration is very sharp. The craters of the submarine springs are usually located on the borders of the areas with acoustic penetration or even at some distance away from them. It is possible that the activity of the hot and salty submarine springs controls the acoustic penetration. However, determination of the exact mechanism for the existence of the zones of acoustic penetration must await further studies of the sediments, especially for measurements of various parameters that control the seismic response of the rock.Another discovery made with the shallow seismic profiles is the existence of some bathymetric irregularities on the floor of the Sea of Galilee. In view of the high sedimentation rate in the lake, which tends to smooth the floor, a bathymetric irregularity such as a linear bathymetric step could be a surface expression of an active fault.     

Experimental Global Forecasts of Atmospheric Parameters Based on Experimental Technology that Takes into Account Ozone Photochemistry (FOROZ Model)

Geomagnetism and Aeronomy - The results of numerical seasonal forecasts of temperature calculated with two interactive global numerical models, the CHARM photochemical model (0–90 km) of the...     

Reappraised list of historical earthquakes that affected Israel and its close surroundings

Numerous historical reports of damaging earthquakes in the Levant have accumulated over the last 3000 years. Here, we screen that information and focus on the damaging earthquakes that affected Israel from the second millennia BCE to the 1927 CE Jericho earthquake and list the earthquakes by date, of major damage, type of sequence, and degree of size. The compilation results in three different lists: (i) 71 reliable earthquakes that in our opinion were most probably associated with the Dead Sea Transform (DST) and affected Israel and its close surroundings; (ii) 41 questionable earthquakes that should be re-evaluated or ignored; and (iii) 46 earthquakes that probably occurred but were erroneously associated with damage in Israel. What emerges from the list of the reliable earthquakes is that (i) Israel and its close surroundings suffered damage about 32 times during the last two millennia, that is, once in about 60 years, although not regularly; (ii) 21 of the earthquakes occurred during the last millennia, i.e., an event every ～45 years; and (iii) three intervals of increased reporting are noticed: between the fourth and the mid-eighth century, from the beginning of the eleventh to the end of the thirteenth century, and from the end of the eighteenth century up to the last entry in 1927, though this period may be extended until today. In-depth evaluation of the changing regimes over time within the study area, the historical reports of earthquake damage outside of Israel, and comparison with physical paleo- and archaeo-seismology evidence, such as the “137–206” and “165–236” paleoseismic earthquakes for which there is no historical match, indicates that the historical list is far from being complete. Thus, we argue that the apparent cycles of historical reporting do not necessarily reflect the actual rate of seismic activity and further investigation is needed to establish a compiled, multi-sourced list to decipher the true nature of cycles of strong earthquakes in this region during historical times.     

Inland notches: lithological characteristics and climatic implications of subaerial cavernous landforms in Israel

Inland notches, are elongated concave‐shape indentations that develop on the carbonate rocky cliffs of mountainous zones, down to the desert fringe. These rock shelters form as a result of the interaction between specific petrologic characteristics and climatic controls, emphasizing the importance of environment upon rock decay. Inland notches are shaped due to slight differences (1–15%) in the porosity of the visor and cavity bed: the cavity bed is more porous, so more likely to erode by exfoliation and dissolution. Thus, the cavity bed retreats at a faster rate compared to the slower subaerial dissolution of the visor bed, until a critical point is reached where the visor collapses. In Israel, inland notches inhabit the same lithostratigraphic units as do large caves. The vast majority (71%) of inland notches are formed in hard, dense, and crystalline limestone deposited throughout the Turonian age. Another 27% are cut into the dolomitic sequence of the upper Albian and lower Cenomanian. The rest (2%) are dispersed in the various formations of the Cenomanian and Eocene eras. Notches are most common in semi‐arid and in Mediterranean climates but mainly in areas with annual rainfall of between 400 mm and 850 mm. In more humid areas (> 900 mm/yr) notches are negligible or completely absent, due to the rapid rate of chemical dissolution of carbonate rocks. In the desert fringe (200–300 mm/yr), mechanical decay is accelerated and notches exhibit disintegration processes, visor collapse, and rock falls. In the desert area (< 200 mm/yr), salt decay replaces the chemical decay characteristic of inland notches, encouraging tafoni formation. In addition, notches form through fluvial activity or on account of greater petrophysical differences between consecutive beds; i.e. elongated cavities may form in soft rocks, shaded by harder visors or crusts. Copyright © 2017 John Wiley & Sons, Ltd.     

The influence of bend amplitude and planform morphology on flow and sedimentation in submarine channels

We present a series of experiments that investigate the morphology of sediment deposits within sinuous submarine channels of different sinuosity (S = 1.14–1.94) and planform (symmetric and asymmetric bends), generated by bedload-dominated turbidity current flows. Flows were generated by releasing dense saline gravity currents over a mobile sediment bed through pre-formed sinuous channels. Flows had a basal-outwards helicity and produced a characteristic bed morphology with point bars downstream of the bend apex at the inside of bends and scour at the outside of bends. An increasing loss of fluid through overspill with increasing channel sinuosity results in a decreasing magnitude of cross-stream velocity downstream, a decreasing amount of erosion and deposition, and decreasing transverse slopes of in-channel deposits. Basal fluid from within the channel is transported over the outer-levee at bends, implying that proximal outer-bend levee deposits will have similar sediment composition to that within the channel. More deposition of coarse material might be expected on levees and in overbank regions close to higher amplitude bends. No simple relationship was observed between superelevation and sinuosity, probably due to changes in the relative influences of downstream velocity and bend curvature on centrifugal force and inertial run-up. In the channel with the tightest initial bend curvature, overspill fluid from Bend 1 re-entered the channel at Bend 2, dominating flow characteristics and disrupting the basal-outwards helicity observed in the other channels. Higher sinuosity channels and those with shallow regional and levee slopes are thus more likely to have a higher proportion of anomalous flow and sedimentation patterns due to the influence of overspill fluid re-entry into the channel. The results of this investigation are combined with published observations to enable the synthesis of a new model for sedimentation in sinuous submarine channels.     

Field investigation of ridge–runnel dynamics on an intertidal mudflat

Flow-parallel linear ridge–runnel (R–R) bedforms composed of mainly cohesive sediments have been investigated at an intertidal site located at Hills Flats in the Severn Estuary, UK. It is argued that the sequences of sand–mud laminae in the ridge sediments indicate strongly that R–R are depositional bedforms. Faint R–R topography scoured in the underlying soft bedrock and parallel rows of coarser particle now found at the base of ridges are evidence of secondary vortices that may have provided a catalyst for mud ridge growth. Bed shear stress remains below the erosion threshold for all but the most recent and weak surficial mud deposits which are removed by evorsion [mechanical erosion by turbulent flows that may also carry sand and/or gravel] during Spring tidal flow ca. 60 cm/s. Differences in flow characteristics between ridges and runnel are minor. Corrasion [to erode or be eroded by abrasion] by sparse coarse sediment largely prevents net deposition in the runnels. Over time a slight imbalance between mud deposition and erosion rates allows slow growth of the ridges suggesting that these mudflats may be especially sensitive to slight changes in the local hydrodynamic regime and/or sediment supply.     

Stable isotopes of a subfossil Tamarix tree from the Dead Sea region, Israel, and their implications for the Intermediate Bronze Age environmental crisis

Trees growing on the Mt. Sedom salt diapir, at the southern Dead Sea shore, were swept by runoff into salt caves and subsequently deposited therein, sheltered from surface weathering. A subfossil Tamarix tree trunk, found in a remote section of Sedom Cave is radiocarbon dated to between  2265 and 1930 BCE. It was sampled in 109 points across the tree rings for carbon and nitrogen isotopes. The Sedom Tamarix demonstrates a few hundred years of ¹³C and ¹⁵N isotopic enrichment, culminating in extremely high δ¹³C and δ¹⁵N values. Calibration using modern Tamarix stable isotopes in various climatic settings in Israel shows direct relationship between isotopic enrichment and climate deterioration, particularly rainfall decrease. The subfossil Tamarix probably reflects an environmental crisis during the Intermediate Bronze Age, which subsequently killed the tree  1930 BCE. This period coincides with the largest historic fall of the Dead Sea level, as well as the demise of the large regional urban center of the 3rd millennium BCE. The environmental crisis may thus explain the archaeological evidence of a shift from urban to pastoral culture during the Intermediate Bronze Age. This was apparently the most severe long-term historical drought that affected the region in the mid-late Holocene.