Very short-term plasticity in hippocampal synapses

Hippocampal pyramidal neurons often fire in bursts of action potentials with short interspike intervals (2–10 msec). These high-frequency bursts may play a critical role in the functional behavior of hippocampal neurons, but synaptic plasticity at such short times has not been carefully studied. To study synaptic modulation at very short time intervals, we applied pairs of stimuli with interpulse intervals ranging from 7 to 50 msec to CA1 synapses isolated by the method of minimal stimulation in hippocampal slices. We have identified three components of short-term paired-pulse modulation, including (i) a form of synaptic depression manifested after a prior exocytotic event, (ii) a form of synaptic depression that does not depend on a prior exocytotic event and that we postulate is based on inactivation of presynaptic N-type Ca2+ channels, and (iii) a dependence of paired-pulse facilitation on the exocytotic history of the synapse.

Short-term and long-term verbal memory: a positron emission tomography study.

Short-term and long-term retention of experimentally presented words were compared in a sample of 33 healthy normal volunteers by the [15O]H2O method with positron emission tomography (PET). The design included three conditions. For the long-term condition, subjects thoroughly studied 18 words 1 week before the PET study. For the short-term condition, subjects were shown another set of 18 words 60 sec before imaging, with instructions to remember them. For the baseline condition, subtracted from the two memory conditions, subjects read a third set of words that they had not previously seen in the experiment. Similar regions were activated in both short-term and long-term conditions: large right frontal areas, biparietal areas, and the left cerebellum. In addition, the short-term condition also activated a relatively large region in the left prefrontal region. These complex distributed circuits appear to represent the neural substrates for aspects of memory such as encoding, retrieval, and storage. They indicate that circuitry involved in episodic memory has much larger cortical and cerebellar components than has been emphasized in earlier lesion studies.

Short-term Load Forecasting Using Neural Network For Future Smart Grid Application

Short-term load forecasting of power system has been a classic problem for a long time. Not merely it has been researched extensively and intensively, but also a variety of forecasting methods has been raised. This thesis outlines some aspects and functions of smart meter. It also presents different policies and current statuses as well as future projects and objectives of SG development in several countries. Then the thesis compares main aspects about latest products of smart meter from different companies. Lastly, three types of prediction models are established in MATLAB to emulate the functions of smart grid in the short-term load forecasting, and then their results are compared and analyzed in terms of accuracy. For this thesis, more variables such as dew point temperature are used in the Neural Network model to achieve more accuracy for better short-term load forecasting results.

Cardiopulmonary adaptation to short-term high altitude exposure in adult Fontan patients

OBJECTIVE High altitude-related hypoxia induces pulmonary vasoconstriction. In Fontan patients without a contractile subpulmonary ventricle, an increase in pulmonary artery pressure is expected to decrease circulatory output and reduce exercise capacity. This study investigates the direct effects of short-term high altitude exposure on pulmonary blood flow (PBF) and exercise capacity in Fontan patients. METHODS 16 adult Fontan patients (mean age 28±7 years, 56% female) and 14 matched controls underwent cardiopulmonary exercise testing with measurement of PBF with a gas rebreathing system at 540 m (low altitude) and at 3454 m (high altitude) within 12 weeks. RESULTS PBF at rest and at exercise was higher in controls than in Fontan patients, both at low and high altitude. PBF increased twofold in Fontan patients and 2.8-fold in the control group during submaximal exercise, with no significant difference between low and high altitude (p=0.290). A reduction in peak oxygen uptake at high compared with low altitude was observed in Fontan patients (22.8±5.1 and 20.5±3.8 mL/min/kg, p<0.001) and the control group (35.0±7.4 and 29.1±6.5 mL/min/kg, p<0.001). The reduction in exercise capacity was less pronounced in Fontan patients compared with controls (9±12% vs 17±8%, p=0.005). No major adverse clinical event was observed. CONCLUSIONS Short-term high altitude exposure has no negative impact on PBF and exercise capacity in Fontan patients when compared with controls, and was clinically well tolerated. TRIAL REGISTRATION NUMBER NCT02237274: Results.

Long-term Responses of Mountain Ecosystems to Environmental Changes: Resilience, Adjustment, and Vulnerability

The steep environmental gradients of mountain ecosystems over short distances reflect large gradients of several climatic parameters and hence provide excellent possibilities for ecological research on the effects of environmental change. To gain a better understanding of the dynamics of abiotic and biotic parameters of mountain ecosystems, long-term records are required since permanent plots in mountain regions cover in the best case about 50 - 70 years. In order to extend investigations of ecological dynamics beyond these temporal limitations of permanent plots, paleoecological approaches can be used if the sampling resolution can be adapted to ecological research questions, e.g. a sample every 10 years. Paleoecological studies in mountain ecosystems can provide new ecological insights through the combination of different spatial and temporal scales. [f we thus improve our understanding of processes across both steep environmental gradients and different time scales, we may be able to better estimate ecosystem responses to current and future environmental change (Ammann et al. 1993; Lotter et al. 1997). The complexity of ecological interactions in mountain regions forces us to concentrate on a number of sub-systems - without losing sight of the wider context. Here, we summarize a few case studies on the effects of Holocene climate change and disturbance on the vegetation of the Western Alps. To categorize the main response modes of vegetation to climatic change and disturbance in the Alps we use three classes of ecological behaviour: "resilience", "adjustment", and "vulnerability", We assume a resilient (or elastic) behaviour if vegetation is able to recover to its former state, regaining important ecosystem characteristics, such as floristic composition, biodiversity, species abundances, and biomass (e.g. Küttel 1990; Aber and Melillo 199 1). Conversely, vegetation displacements may occur in response to climatic change and/or disturbance. In some cases, this may culminate in irreversible large-scale processes such as species and/or community extinctions. Such drastic developments indicate high ecosystem vulnerability (or inelasticity or instability, for detailed definitions see Küttel 1990; Aber and Melillo 199 1) to climatic change and/or disturbance. In this sense, the "vulnerability" (or instability) of an ecosystem is expressed by the degree of failure to recover to the original state before disturbance and/or climatic change. Between these two extremes (resilience vs. vulnerability), ecosystem adjustments to climatic change and/or disturbance may occur, including the appearance of new and/or the disappearance of old species. The term "adjustment" is hence used to indicate the response of vegetational communities, which adapted to new environmental conditions without losing their main character. For forest ecosystems, we assume vegetational adjustments (rather than vulnerability) if the dominant (or co-dominant) tree species are not outnumbered or replaced by formerly unimportant plant species or new invaders. Adaptation as a genetic process is not discussed here and will require additional pbylogeographical studies (that incorporate the analysis of ancient DNA) in order to fully understand the distributions of ecotypes.

Distribution of grain size and clay minerals in surface sediments of the Kara Sea (Fig 4, 5)

In this paper, we summarize data on terrigenous sediment supply in the Kara Sea and its accumulation and spatial and temporal variability during Holocene times. Sedimentological, organic-geochemical, and micropaleontological proxies determined in surface sediments allow to characterize the modern (riverine) terrigenous sediment input. AMS-14C dated sediment cores from the Ob and Yenisei estuaries and the adjacent inner Kara Sea were investigated to determine the terrigenous sediment fluxes and their relationship to paleoenvironmental changes. The variability of sediment fluxes during Holocene times is related to the post-glacial sea-level rise and changes in river discharge and coastal erosion input. Whereas during the late/middle Holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries, huge amounts of sediments accumulated on the Kara Sea shelf farther north during the early Holocene before about 9 cal kyr BP. The maximum accumulation at that time is related to the lowered sea level, increased coastal erosion, and increased river discharge. Based on sediment thickness charts, echograph profiles and sediment core data, we estimate an average Holocene (0-11 cal kyr BP) annual accumulation of 194,106 t/yr of total sediment for the whole Kara Sea. Based on late Holocene (modern) sediment accumulation in the estuaries, probably 12,106 t/yr of riverine suspended matter (i.e. about 30% of the input) may escape the marginal filter on a geological time scale and is transported onto the open Kara Sea shelf. The high-resolution magnetic susceptibility record of a Yenisei core suggests a short-term variability in Siberian climate and river discharge on a frequency of 300-700 yr. This variability may reflect natural cyclic climate variations to be seen in context with the interannual and interdecadal environmental changes recorded in the High Northern Latitudes over the last decades, such as the NAO/AO pattern. A major decrease in MS values starting near 2.5 cal kyr BP, being more pronounced during the last about 2 cal kyr BP, correlates with a cooling trend over Greenland as indicated in the GISP-2 Ice Core, extended sea-ice cover in the North Atlantic, and advances of glaciers in western Norway. Our still preliminary interpretation of the MS variability has to be proven by further MS records from additional cores as well as other high-resolution multi-proxy Arctic climate records.

Short-term variations in radiolarian faunal dsitribution in the eastern equatorial Pacific

Two short time intervals centered at 2.3 and 4.7 Ma were studied to investigate short-term variations in surface-ocean processes as indicated by changes in the radiolarian microfossil population. These time intervals represent two different settings of late Neogene climate. The older interval represents a time when tropical circulation between the Pacific and Atlantic oceans was not blocked by the Isthmus of Panama, whereas the younger interval represents a time when Northern Hemisphere glaciation was present but did not display the dominance of the 100,000-yr cycle that characterizes the late Pleistocene. The younger time slice at 2.3 Ma was sampled at all Leg 138 sites except Site 844, where significant reworking was evident. All sites except 844, 853, and 854 were sampled for the older time slice. Samples were taken at 10- to 20-cm intervals at each site and spanned a GRAPE density maximum and minimum. Thus, it was possible to investigate whether the changes in carbonate content (as indicated by GRAPE density) were associated with changes in surface-ocean conditions (indicated by radiolarian assemblage variations). For both time slices, the radiolarian data indicate that intervals of decreased carbonate content are periods of cooler water conditions and possibly enhanced biogenic production. Times of increased carbonate content are associated with inferred warmer oceanographic conditions, as indicated by the dominance of tropical assemblages at 2.3 Ma and tropical and western Pacific assemblages during the time slice centered at 4.8 Ma. However, the spatial patterns of change during each time slice show a distinct difference in the mapped patterns of radiolarian assemblage dominance. The older time slice, representing a period before the closing of the Isthmus of Panama, shows more zonal patterns presumably associated with a more zonal character of equatorial circulation. After the closing of the isthmus, the shifts in faunal patterns between times of high and low carbonates are characterized by shifts in the dominance of the tropical and transitional assemblages, respectively, throughout the region.

Executive summaries : apprenticeship 2000 short term research projects.

Cover title.

Common stocks are short term investments.

Reproduced from typewritten copy.

Short-term guidelines to improve crumb rubber modified asphalt concrete pavements. Final report.

Texas Department of Transportation, Austin

Oklahoma City ASAP: short term rehabilitation - analytic study no. V/VI. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Diagnosis, referral and rehabilitation within the Fairfax Alcohol Safety Action Project, 1976: the Fairfax short term rehabilitation study. Analytic study # 5/6. Volume II. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Energy supply and demand in the short term, 1979 and 1980 : analysis report /

"AR/ES/79-28"

Incentive/economic development rates : a short-term marketing option for electric utilities /

"November 1984."