10 research outputs found
Meltwater controls on ice-marginal sedimentation
This thesis explores the influence that meltwater exerts on styles of ice-marginal sedimentation,
using past and present examples from Iceland. The study glaciers display marked contrasts in
form, size and composition of moraines which are unlikely to reflect differences in rates of
subglacial erosion. This is because the study glaciers occupy a similar climate, show similar
relief, sit above similar bedrock, and are inferred to flow at similar speeds. The observed
variation in moraine properties must reflect some other process which intervenes to modify
sediment transport relationships prior to the arrival of debris at the ice edge. I argue that this
key factor which controls sediment transport - and, as a result, the potential to form moraines -
is the behaviour of subglacial meltwater flows.Studies of the sediment load of its outlet river show that Solheimajokull is a highly erosive
glacier, yet the quantity of debris carried by the ice is extremely small. Consequently, presentday
moraine formation is extremely limited. This can best be explained as the product of an
aggressive subglacial drainage network which captures and evacuates the bulk of debris
generated by subglacial erosion. This state of high efficiency subglacial flushing is likely to
dominate the sediment budget of many temperate glaciers.Whereas the present-day margin of Solheimajokull is debris-poor, the present-day
margins of Gfgjokull and Steinholtsjokull are debris-rich. This debris consists of two major
populations: 1) rounded clasts set in a sorted coarse sand and gravel matrix, derived from a
series of englacial debris bands, and, 2) sub-angular clasts in a poorly-sorted matrix, derived
from unusually thick sequences of basal ice. Overdeepened basins lie beneath the termini of
both Gfgjokull and Steinholtsjokull. It seems that changes in water flow in this zone - rising
water pressures associated with water flow upslope cause drainage to take up an englacial route
- explain both the debris bands and the basal ice. The debris bands form as sediment-laden
englacial channels close-up; simultaneously, the paucity of water at the glacier bed, in
conjunction with strongly compressive ice flow, favours widespread preservation of basal ice. I
extend Hooke's model of the ice-fall/overdeepening as a process system favourable to
subglacial erosion to argue that it also creates conditions favourable to debris retention in ice,
and so rapid accumulation of ice-marginal moraines.The idea that contrasts in the behaviour of drainage account for contrasts in moraine
development adds depth to studies of the glacial geologic record, and its interpretation in termsThis thesis was written with the specific intent of linking process and form in such a way
as to provide a meaningful explanation of moraine development. Different moraine forms are
the emergent product of the multitude of process interactions which make up a complex causal
network dispersed in time and space. The key factor which regulates this is the behaviour of
meltwater. Glacier drainage systems provide the crucial contextual element which links the
basic level of process (reductionist analysis) to the level of surface appearance (observations of
moraine form). Drainage systems carry genuine causal powers which cannot be broken down
into smaller process systems without the loss of explanatory power. This ties in with realist
traditions of science, and recent ideas associated with complexity theory
Class A Orphans in GtoPdb v.2023.1
Table 1 lists a number of putative GPCRs identified by NC-IUPHAR [161], for which preliminary evidence for an endogenous ligand has been published, or for which there exists a potential link to a disease, or disorder. These GPCRs have recently been reviewed in detail [121]. The GPCRs in Table 1 are all Class A, rhodopsin-like GPCRs. Class A orphan GPCRs not listed in Table 1 are putative GPCRs with as-yet unidentified endogenous ligands.Table 1: Class A orphan GPCRs with putative endogenous ligands GPR3GPR4GPR6GPR12GPR15GPR17GPR20 GPR22GPR26GPR31GPR34GPR35GPR37GPR39 GPR50GPR63GPR65GPR68GPR75GPR84GPR87 GPR88GPR132GPR149GPR161GPR183LGR4LGR5 LGR6MAS1MRGPRDMRGPRX1MRGPRX2P2RY10TAAR2 In addition the orphan receptors GPR18, GPR55 and GPR119 which are reported to respond to endogenous agents analogous to the endogenous cannabinoid ligands have been grouped together (GPR18, GPR55 and GPR119)
Class A Orphans in GtoPdb v.2022.3
Table 1 lists a number of putative GPCRs identified by NC-IUPHAR [161], for which preliminary evidence for an endogenous ligand has been published, or for which there exists a potential link to a disease, or disorder. These GPCRs have recently been reviewed in detail [121]. The GPCRs in Table 1 are all Class A, rhodopsin-like GPCRs. Class A orphan GPCRs not listed in Table 1 are putative GPCRs with as-yet unidentified endogenous ligands.Table 1: Class A orphan GPCRs with putative endogenous ligands GPR3GPR4GPR6GPR12GPR15GPR17GPR20 GPR22GPR26GPR31GPR34GPR35GPR37GPR39 GPR50GPR63GPR65GPR68GPR75GPR84GPR87 GPR88GPR132GPR149GPR161GPR183LGR4LGR5 LGR6MAS1MRGPRDMRGPRX1MRGPRX2P2RY10TAAR2 In addition the orphan receptors GPR18, GPR55 and GPR119 which are reported to respond to endogenous agents analogous to the endogenous cannabinoid ligands have been grouped together (GPR18, GPR55 and GPR119)
Class A Orphans (version 2020.5) in the IUPHAR/BPS Guide to Pharmacology Database
Table 1 lists a number of putative GPCRs identified by NC-IUPHAR [194], for which preliminary evidence for an endogenous ligand has been published, or for which there exists a potential link to a disease, or disorder. These GPCRs have recently been reviewed in detail [150]. The GPCRs in Table 1 are all Class A, rhodopsin-like GPCRs. Class A orphan GPCRs not listed in Table 1 are putative GPCRs with as-yet unidentified endogenous ligands.Table 1: Class A orphan GPCRs with putative endogenous ligands
GPR3
GPR4
GPR6
GPR12
GPR15
GPR17
GPR20
GPR22
GPR26
GPR31
GPR34
GPR35
GPR37
GPR39
GPR50
GPR63
GRP65
GPR68
GPR75
GPR84
GPR87
GPR88
GPR132
GPR149
GPR161
GPR183
LGR4
LGR5
LGR6
MAS1
MRGPRD
MRGPRX1
MRGPRX2
P2RY10
TAAR2
In addition the orphan receptors GPR18, GPR55 and GPR119 which are reported to respond to endogenous agents analogous to the endogenous cannabinoid ligands have been grouped together (GPR18, GPR55 and GPR119)
Class A Orphans (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database
Table 1 lists a number of putative GPCRs identified by NC-IUPHAR [191], for which preliminary evidence for an endogenous ligand has been published, or for which there exists a potential link to a disease, or disorder. These GPCRs have recently been reviewed in detail [148]. The GPCRs in Table 1 are all Class A, rhodopsin-like GPCRs. Class A orphan GPCRs not listed in Table 1 are putative GPCRs with as-yet unidentified endogenous ligands.Table 1: Class A orphan GPCRs with putative endogenous ligands GPR3GPR4GPR6GPR12GPR15GPR17GPR20 GPR22GPR26GPR31GPR34GPR35GPR37GPR39 GPR50GPR63GRP65GPR68GPR75GPR84GPR87 GPR88GPR132GPR149GPR161GPR183LGR4LGR5 LGR6MAS1MRGPRDMRGPRX1MRGPRX2P2RY10TAAR2 In addition the orphan receptors GPR18, GPR55 and GPR119 which are reported to respond to endogenous agents analogous to the endogenous cannabinoid ligands have been grouped together (GPR18, GPR55 and GPR119)
Class A Orphans in GtoPdb v.2021.3
Table 1 lists a number of putative GPCRs identified by NC-IUPHAR [161], for which preliminary evidence for an endogenous ligand has been published, or for which there exists a potential link to a disease, or disorder. These GPCRs have recently been reviewed in detail [121]. The GPCRs in Table 1 are all Class A, rhodopsin-like GPCRs. Class A orphan GPCRs not listed in Table 1 are putative GPCRs with as-yet unidentified endogenous ligands.Table 1: Class A orphan GPCRs with putative endogenous ligands GPR3GPR4GPR6GPR12GPR15GPR17GPR20 GPR22GPR26GPR31GPR34GPR35GPR37GPR39 GPR50GPR63GRP65GPR68GPR75GPR84GPR87 GPR88GPR132GPR149GPR161GPR183LGR4LGR5 LGR6MAS1MRGPRDMRGPRX1MRGPRX2P2RY10TAAR2 In addition the orphan receptors GPR18, GPR55 and GPR119 which are reported to respond to endogenous agents analogous to the endogenous cannabinoid ligands have been grouped together (GPR18, GPR55 and GPR119)
Landscape science: a Russian geographical tradition
The Russian geographical tradition of landscape science (landshaftovedenie) is analyzed with particular reference to its initiator, Lev Semenovich Berg (1876-1950). The differences between prevailing Russian and Western concepts of landscape in geography are discussed, and their common origins in German geographical thought in the late nineteenth and early twentieth centuries are delineated. It is argued that the principal differences are accounted for by a number of factors, of which Russia's own distinctive tradition in environmental science deriving from the work of V. V. Dokuchaev (1846-1903), the activities of certain key individuals (such as Berg and C. O. Sauer), and the very different social and political circumstances in different parts of the world appear to be the most significant. At the same time it is noted that neither in Russia nor in the West have geographers succeeded in specifying an agreed and unproblematic understanding of landscape, or more broadly in promoting a common geographical conception of human-environment relationships. In light of such uncertainties, the latter part of the article argues for closer international links between the variant landscape traditions in geography as an important contribution to the quest for sustainability
A review of topographic controls on moraine distribution
Ice-marginal moraines are often used to reconstruct the dimensions of former ice masses, which are then used as proxies for palaeoclimate. This approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability. However, the validity of this assumption is open to question, as a number of additional, nonclimatic factors are known to influence moraine distribution. This review considers the role played by topography in this process, with specific focus on moraine formation, preservation, and ease of identification (topoclimatic controls are not considered). Published literature indicates that the importance of topography in regulating moraine distribution varies spatially, temporally, and as a function of the ice mass type responsible for moraine deposition. In particular, in the case of ice sheets and ice caps ( > 1000km 2 ), one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback, whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles. For the marine-terminating outlets of such ice masses, fjord geometry also exerts a strong control on where moraines are deposited, promoting their deposition in proximity to valley narrowings, bends, bifurcations, where basins are shallow, and/or in the vicinity of topographic bumps. Moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape. In the case of icefields and valley glaciers (10-1000km 2 ), erosional feedback may well play some role in regulating where moraines are deposited, but other factors, including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points, are also likely to be important. This is particularly relevant where land-terminating glaciers extend into piedmont zones (unconfined plains, adjacent to mountain ranges) where large and readily identifiable moraines can be deposited. In the case of cirque glaciers ( < 10km 2 ), erosional feedback is less important, but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris, regulate glacier dimensions and thereby determine where moraines are deposited. In such cases, moraines are likely to be small and particularly susceptible to post-depositional modification, sometimes making them difficult to identify in the modern landscape. Based on this review, we suggest that, despite often being difficult to identify, quantify, and mitigate, topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate (i.e., palaeoclimatic inferences should only be drawn from moraines when topographic controls on moraine distribution are considered insignificant). © 2014 Elsevier B.V
We Are Not Always Tellers of Stories: On Things That Bother Me: Death, Freedom, the Self, Etc., by Galen Strawson
Things That Bother Me: Death, Freedom, the Self, etc., by Galen Strawson. New York Review Books, 2018. ISBN: 978-1-68137-220-4. $17.95/£11.99