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451.
Better understanding of urban microclimate and bioclimate of any city is imperative today when the world is constrained by both urbanisation and global climate change. Urbanisation generally triggers changes in land cover and hence influencing the urban local climate. Dar es Salaam city in Tanzania is one of the fast growing cities. Assessment of its urban climate and the human biometeorological conditions was done using the easily available synoptic meteorological data covering the period 2001–2011. In particular, the physiologically equivalent temperature (PET) was calculated using the RayMan software and results reveal that the afternoon period from December to February (DJF season) is relatively the most thermal stressful period to human beings in Dar es Salaam where PET values of above 35 °C were found. Additionally, the diurnal cycle of the individual meteorological elements that influence the PET index were analysed and found that air temperature of 30–35 °C dominate the afternoon period from 12:00 to 15:00 hours local standard time at about 60 % of occurrence. The current results, though considered as preliminary to the ongoing urban climate study in the city, provide an insight on how urban climate research is of significant importance in providing useful climatic information for ensuring quality of life and wellbeing of city dwellers. 相似文献
452.
People’s livelihood in several Himalayan regions largely depends on collection, use, and trade of medicinal plants. Traditional
use is generally not a problem, but commercial gathering of selected species to meet increasing national and international
demand can result in over-exploitation. Sustainable management of medicinal plants requires a clear understanding of the respective
roles, responsibilities and viewpoints of the various stakeholders involved. Through personal interviews and group discussions,
this study aimed at investigating the views of two stakeholder groups on use, trade and conservation of medicinal plants in
the Rasuwa district of Nepal. Local people and district and national organizations agreed that medicinal plants are collected
for a combination of commercial and personal uses. Perceptions on market availability differed significantly: 100 % of the
respondents from district and national organizations saw markets as easily available, against only 36 % for local people.
This could explain why medicinal plants were perceived by local people to contribute less to income generation than to livelihood
improvement. Different viewpoints were also expressed concerning the status of medicinal plants in the district: 81 % of the
respondents from district and national organizations considered that medicinal plants were threatened, compared to only 28
% for local people. Despite this disparity, both stakeholder groups agreed upon potential threats to medicinal plants: over-harvesting;
habitat loss due to land-use change and deforestation; and over-grazing by livestock. Several challenges were identified regarding
sustainable management of medicinal plants, such as ambiguous policies; lack of resources, information and infrastructures;
habitat degradation; and over-exploitation. Despite these challenges, respondents agreed that the medicinal plants sector
offers huge opportunities in the Rasuwa district, given resource availability, community awareness and motivation, and the
priority given to the sector by governments and other agencies. Proper collaboration, communication and coordination among
stakeholders are needed to grab these opportunities. 相似文献
453.
Christina L. De La Rocha Pierre Bescont Emmanuel Ponzevera 《Geochimica et cosmochimica acta》2011,75(18):5283-5295
We report here the silicon isotopic composition (δ30Si) of dissolved silicon (DSi) from 42 surface water samples from the Drake Passage, the Weddell Gyre, other areas south of the Southern Boundary of the Antarctic Circumpolar Current (ACC), and the ACC near the Kerguelen Plateau, taken between the beginning of February and the end of March 2007. From the beginning to end of the cruise (ANTXXIII/9), DSi diminished in the Antarctic by 50 μmol L−1 while concentrations of nitrate + nitrite and phosphate showed no net decline, indicating that the high seasonal Si/N removal ratios well known for the Southern Ocean may be more related to the strength of the silicate pump in the Southern Ocean than to the instantaneous Si/N uptake ratio of diatoms. The δ30Si of DSi in samples containing more than 20 μM DSi were strongly negatively correlated to DSi concentrations, supporting the use of δ30Si as a proxy for DSi removal. The “open system” fractionation observed, ε = −1.2 ± 0.11‰, agrees well with results from previous work in other areas, and the estimate of the initial δ30Si of DSi of +1.4‰ is not far off observations of the δ30Si of DSi in Winter Water (WW) in this area. Results were used to model DSi draw down in the past from the δ30Si of sediment cores, although isotopic fractionation during silica dissolution appeared to influence the δ30Si of some surface water samples, inviting further study of this phenomenon. 相似文献
454.
455.
Céline Ducassou Michel Ballèvre Hubert Lardeux Cécile Robin 《International Journal of Earth Sciences》2011,100(7):1451-1475
The Palaeozoic sediments from the Mauges Unit (Armorican Massif, France) are the best-preserved pre-orogenic sequences belonging
to the Upper Allochthon. Two coherent sequences are identified. The southern unit (Chateaupanne Unit) represents the cover
of the Proterozoic basement and consists of Ordovician sediments unconformably overlain by Emsian carbonates followed by Emsian
to earliest Eifelian immature sandstones. The northern unit (Tombeau Leclerc Unit) consists of an Hirnantian to Emsian condensed
sequence, in reverse position, that has been thrust over the southern unit. The Devonian unconformity is interpreted as evidence
for an Early Devonian extension, recorded by normal faults affecting both the Early Devonian limestones and the underlying
Ordovician series. This crustal extension, recorded here for the first time, is possibly related to the opening of a back-arc
basin (Saint-Georges-sur-Loire) associated with the subduction of an ocean located further south (Galicia-Brittany-Massif
Central Ocean). 相似文献
456.
Peloponnesus in the south-western part of the Aegean is formed by a heterogeneous pile of alpine thrust sheets that was reworked
by normal faulting from Upper Miocene to recent times. Upper Miocene–Lower Pliocene extension in Mt Parnon was accommodated
by several mappable brittle detachment faults that exhibit a top-to-the-NE-ENE sense of shear. The hanging wall of the detachments
comprises a number of highly tilted fault blocks containing abundant evidence of intense internal deformation by normal faulting
and layer-parallel shearing contemporaneous with faulting. These fault blocks are remnants of a cohesive extensional block
that slipped to the NE-ENE and broke up along high-angle normal faults that sole into or are cut by the detachments. The largest
part of this block is located at the eastern edge of the metamorphic core forming the hanging wall of East Parnon high-angle
normal fault that excised part of the aforementioned detachments. The lowermost metamorphic Unit of the nappe-pile does not
seem to be affected by the previous extensional episode. Upper plate reconstruction shows that various units of the nappe-pile
were affected by high-angle normal faults that linked to detachment faults in the weaker layers. Since the Middle-Upper Pliocene
further exhumation of the metamorphic rocks has resulted in the formation of high-angle normal faults overprinting Neogene
extensional structures and cut the entire nappe-pile. This new fault system tilted the earlier extensional structures and
produced a NE-SW coaxial deformation of Mt Parnon. 相似文献
457.
Turbiditic levee deposition in response to climate changes: The Var Sedimentary Ridge (Ligurian Sea)
Stéphan J. Jorry Isabelle Jégou Laurent Emmanuel Ricardo Silva Jacinto Bruno Savoye 《Marine Geology》2011,279(1-4):148-161
The Var turbiditic system located in the Ligurian Sea (SE France) is an intermediate mud/sand-rich system. The particularity of the Var deep-sea fan is its single channel with abrupt bends and its asymmetric and hyper-developed levee on the right hand side: the Var Sedimentary Ridge. Long-term sediment accumulation on the Var Sedimentary Ridge makes this an ideal target for studying the link between onshore climate change and deep-sea turbidite stratigraphy. This paper focuses on the establishment of the first detailed stratigraphy of the levee, which is used to analyze the timing of overbank deposition throughout the last deglaciation. Main results indicate that high variability in turbidite frequencies and deposition rates along the Var Sedimentary Ridge are determined by two main parameters: 1) the progressive decrease of the levee height controlling the ability of turbidity currents to spill out from the channel onto the levee, and 2) climatic variations affecting the drainage basin, in particular changes in glacial condition since late Last Glacial Maximum to early Holocene. Compared to other deep-water areas, this study confirms the ability of turbiditic systems to record past climatic events on millennial timescales, and underlines the influence of European deglaciation on the observed decrease in turbidite activity in the Var canyon. The presence of a very narrow continental shelf and a single, large channel-levee system makes the Var Sedimentary Ridge a unique example of climate-controlled turbiditic accumulations. 相似文献
458.
Eric Keto Roger Ball Christopher Skinner John Arens Garrett Jernigan Margaret Meixner James Graham 《Experimental Astronomy》1994,3(1-4):161-162
We present high angular resolution (1.2), narrow band (/=0.1) images of the nucleus of NGC253 at three wavelengths in the mid-IR (8.5, 10.0, and 12.5 m). We find that most of the mid-IR flux in the nucleus of NGC253 derives from a very small region 120 pc in diameter. Within this small region there are three spatially and spectrally distinct IR components: two bright compact sources, and a surrounding envelope of low level, diffuse emission. The mid-IR and 6cm radio are loosely correlated in position but not in brightness. The implication is that the mid-IR - radio correlation may begin to break down on small spatial scales relevant to individual star forming regions and large individual sources. These variations in the mid-IR spectra and in the radio-IR correlation imply that the nuclear emission is excited by more than one mechanism and source type. 相似文献
459.
Edward S. Gilfillan Nicole P. Maher Cecile M. Krejsa Mary E. Lanphear Christopher D. Ball Jeremy B. Meltzer David S. Page 《Marine pollution bulletin》1995,30(12):780-787
Image analysis of historical aerial photographs was used to examine the effects of the Amoco Cadiz oil spill and resulting clean-up on marsh ecology. Two heavily oiled marsh systems were compared. The marsh which received no clean-up recovered to its prior condition. The marshes in the system cleaned by sediment removal were extensively altered as a result of changes in intertidal height of the sediment surface. 相似文献
460.