Changes in mid-troposphere snow accumulation on Mt. Logan, Yukon, over the last three centuries

EXTRACT (SEE PDF FOR FULL ABSTRACT): A net snow accumulation time series is presented. It is derived from a 102.5 m ice core retrieved from Mt. Logan at an altitude of 5340 m a.s.l. Annual increments are identified using stable isotopes, trace chemistry, and beta activity. ... The resulting time series of nearly 300 years seems to indicate a lower mean accumulation from AD 1700 to the mid-19th century than after that time. The last 100 years of the series correlates significantly with certain instrumental station records at mid-northern latitudes.

Snow accumulation time series and their climatic interpretation

EXTRACT (SEE PDF FOR FULL ABSTRACT): Several snow accumulation time series derived from ice cores and extending over 3 to 5 centuries are examined for spatial and temporal climatic information. ... A significant observation is the widespread depression of net snow accumulation during the latter part of the "Little Ice Age". This initially suggests sea surface temperatures were significantly depressed during the same period. However, prior to this, the available core records indicate generally higher than average precipitation rates. This also implies that influences such as shifted storm tracks or a dustier atmosphere may have been involved. Without additional spatial data coverage, these observations should properly be studied using a coupled (global) ocean/atmosphere GCM.

Growth, osmoregulation and ion accumulation in the coastal halophyte Arthrocnemum indicum under field conditions

Life cycle and population biology of a perennial halophyte Arthrocnemum indicum Willd, was studied from February 1992 to January 1993. During the 12 months, the population was exposed to great variations in soil salinity from 35 to 58 ms/cm2 and soil moisture ranging from flood to drought levels. Seasonal changes in dry weight are directly related to soil salinity stress. When salinity levels become low, the dry matter production increases. A little increase in dry weight from April to July indicates that more negative soil water potentials were limiting plant growth. Proline content increased considerably during the dry season with a corresponding increase in salinity. Water soluble oxalate did not vary much with changes in salinity.

Status of the shore area from Tiengiang to Camau: causes of accumulation and erosion

The paper presents some results of the research programs which had been performed during 1996-1999 (“Studying of river-sea interaction in the mouth of Tien river” and KHCN.06.08). Based on these results the morphological schemes of the shore areas from Tiengiang to Camau were compiled; causes and mechanics of accumulation and erosion were also determined. These results may be used as scientific basis for forecasting the development of the shoreline, it will contribute to the management, protection and reasonable exploitation the shore areas.

Chronic Morphine Treatment Impaired Hippocampal Long-Term Potentiation and Spatial Memory via Accumulation of Extracellular Adenosine Acting on Adenosine A(1) Receptors

Chronic exposure to opiates impairs hippocampal long-term potentiation (LTP) and spatial memory, but the underlying mechanisms remain to be elucidated. Given the well known effects of adenosine, an important neuromodulator, on hippocampal neuronal excitability and synaptic plasticity, we investigated the potential effect of changes in adenosine concentrations on chronic morphine treatment-induced impairment of hippocampal CA1 LTP and spatial memory. We found that chronic treatment in mice with either increasing doses (20-100 mg/kg) of morphine for 7 d or equal daily dose (20 mg/kg) of morphine for 12 d led to a significant increase of hippocampal extracellular adenosine concentrations. Importantly, we found that accumulated adenosine contributed to the inhibition of the hippocampal CA1 LTP and impairment of spatial memory retrieval measured in the Morris water maze. Adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine significantly reversed chronic morphine-induced impairment of hippocampal CA1 LTP and spatial memory. Likewise, adenosine deaminase, which converts adenosine into the inactive metabolite inosine, restored impaired hippocampal CA1 LTP. We further found that adenosine accumulation was attributable to the alteration of adenosine uptake but not adenosine metabolisms. Bidirectional nucleoside transporters (ENT2) appeared to play a key role in the reduction of adenosine uptake. Changes in PKC-alpha/beta activity were correlated with the attenuation of the ENT2 function in the short-term (2 h) but not in the long-term (7 d) period after the termination of morphine treatment. This study reveals a potential mechanism by which chronic exposure to morphine leads to impairment of both hippocampal LTP and spatial memory.