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Intra-basaltic sediments 50 m below the top of the Paleogene lava succession at Kap Dalton, East Greenland, contain dinoflagellate cysts of late Ypresian-earliest Lutetian age, while sediments immediately above the lavas contain an assemblage of early Lutetian age. Combined with paleomagnetic results, this constrains the termination of the East Greenland Paleogene Igneous Province to the Early-Middle Eocene transition (nannoplankton chronozones NP13-NP14/earliest NP15). This is 6-8 Ma younger than according to previous biostratigraphic age assignments. The new data show that flood basalt volcanism occurred simultaneously with major intrusions occurring further to the south. This corroborates previous assumptions of an important melting event much younger than the continental break-up.

Intra-basaltic sediments 50 m below the top of the Paleogene lava succession at Kap Dalton, East Greenland, contain dinoflagellate cysts of late Ypresian-earliest Lutetian age, while sediments immediately above the lavas contain an assemblage of early Lutetian age. Combined with paleomagnetic results, this constrains the termination of the East Greenland Paleogene Igneous Province to the Early-Middle Eocene transition (nannoplankton chronozones NP13-NP14/earliest NP15). This is 6-8 Ma younger than according to previous biostratigraphic age assignments. The new data show that flood basalt volcanism occurred simultaneously with major intrusions occurring further to the south. This corroborates previous assumptions of an important melting event much younger than the continental break-up.

Udgivelsesdato: 2007-May-15, Previously we have demonstrated that glucagon receptor mRNA expression in cultured rat hepatocytes and pancreatic islets can be regulated by various factors, including cAMP; however, the regulation of the human glucagon receptor gene has not been well-defined. Here we have characterized the promoter regions of the human glucagon receptor gene. Primer extension studies yielded multiple products in both liver and pancreas, corresponding to transcription start sites situated at -166 and -477 relative to the start of translation, indicating two putative promoters. Both transcription start sites were found to be active, when sequence immediately upstream of the start sites were cloned into luciferase reporter constructs. The transcriptional activity of the proximal promoter, but not the distal promoter, could be inhibited approximately 50% by cAMP, indicating that the previously observed inhibitory effects of cAMP on glucagon receptor mRNA expression is mediated at the level of gene transcription. The cAMP-mediated downregulation of the proximal promoter was examined by deletion analysis in the human hepatoma cell line HepG2 and the cAMP responsiveness was found to be located in a region between 1051 and 1016 base pairs upstream of the transcription start site, which contains several putative cAMP responsive elements. Expression of peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha), known to be upregulated in the liver by fasting, was found to abolish the cAMP-dependent downregulation of glucagon receptor mRNA expression in vitro, whereas overexpression of PGC-1beta had no effect.

Udgivelsesdato: 2007-May-15, Previously we have demonstrated that glucagon receptor mRNA expression in cultured rat hepatocytes and pancreatic islets can be regulated by various factors, including cAMP; however, the regulation of the human glucagon receptor gene has not been well-defined. Here we have characterized the promoter regions of the human glucagon receptor gene. Primer extension studies yielded multiple products in both liver and pancreas, corresponding to transcription start sites situated at -166 and -477 relative to the start of translation, indicating two putative promoters. Both transcription start sites were found to be active, when sequence immediately upstream of the start sites were cloned into luciferase reporter constructs. The transcriptional activity of the proximal promoter, but not the distal promoter, could be inhibited approximately 50% by cAMP, indicating that the previously observed inhibitory effects of cAMP on glucagon receptor mRNA expression is mediated at the level of gene transcription. The cAMP-mediated downregulation of the proximal promoter was examined by deletion analysis in the human hepatoma cell line HepG2 and the cAMP responsiveness was found to be located in a region between 1051 and 1016 base pairs upstream of the transcription start site, which contains several putative cAMP responsive elements. Expression of peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha), known to be upregulated in the liver by fasting, was found to abolish the cAMP-dependent downregulation of glucagon receptor mRNA expression in vitro, whereas overexpression of PGC-1beta had no effect.

&nbsp, Archaeomagnetic dating of a Medieval brick kiln from Tønsberg, Norway Medieval bricks and tile were never commonly used in Norway as they were in Denmark. Thus only 3 Medieval brick kilns have hitherto been found and described in Norway, and their products have not been investigated in greater detail. Dating of the bricks is therefore somewhat uncertain. In the case of the Tønsberg kiln, no tools or written sources providing a date have been found. When the kiln was excavated in 1980-81, magnetic dating was therefore planned (1, 2, 3, 4). The kiln is situated on a small plateau at the northern edge of the Medieval town (fig. 1). Although only partly preserved, the kiln is seen to be of a rectangular shape common in Medieval Scandinavia, the flat floor and the front wall both being constructed in bricks. Five phases of the kiln were found, phase 1 being the oldest and phase 5 the youngest (fig. 2). The remains of the 5 floors are situated one above the other, except for a ca. 20 cm thick layer of sand separating phases 1 and 2. Magnetic measurements The magnetic dating method is a relative method based upon the principle that the direction of the earth's geomagnetic field is stored in the iron oxides of the fired clay during the last cooling, all previous magnetic memory being erased by the last heating above the Curie point of some 580°C (1, 4, 8, 9). As the direction of the geomagnetic field varies slowly with time, the secular variation (5) being typically of the order of 10 per 10 years, the direction of the measured remanent magnetization is diagnostic for the time of the last cooling, provided a mastercurve for the secular variation as a function of time is available. A total of 27 orientated bricks still supposed to be in situ from the oldest and youngest kiln phases were collected (3), with the purpose of possibly establishing the age as well as the duration of the use of the kiln. In the laboratory, 4 to 8 cores were drilled from each brick, and the total nu

history back to c. 7,000 years calBP (6,000 years convBP) in this·extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts- presently restricted to a narrow fringe of land at the shores of the Arctic Ocean-were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5'C, A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice-age mid-latitude environments are not identical.

&nbsp, Archaeomagnetic dating of a Medieval brick kiln from Tønsberg, Norway Medieval bricks and tile were never commonly used in Norway as they were in Denmark. Thus only 3 Medieval brick kilns have hitherto been found and described in Norway, and their products have not been investigated in greater detail. Dating of the bricks is therefore somewhat uncertain. In the case of the Tønsberg kiln, no tools or written sources providing a date have been found. When the kiln was excavated in 1980-81, magnetic dating was therefore planned (1, 2, 3, 4). The kiln is situated on a small plateau at the northern edge of the Medieval town (fig. 1). Although only partly preserved, the kiln is seen to be of a rectangular shape common in Medieval Scandinavia, the flat floor and the front wall both being constructed in bricks. Five phases of the kiln were found, phase 1 being the oldest and phase 5 the youngest (fig. 2). The remains of the 5 floors are situated one above the other, except for a ca. 20 cm thick layer of sand separating phases 1 and 2. Magnetic measurements The magnetic dating method is a relative method based upon the principle that the direction of the earth's geomagnetic field is stored in the iron oxides of the fired clay during the last cooling, all previous magnetic memory being erased by the last heating above the Curie point of some 580°C (1, 4, 8, 9). As the direction of the geomagnetic field varies slowly with time, the secular variation (5) being typically of the order of 10 per 10 years, the direction of the measured remanent magnetization is diagnostic for the time of the last cooling, provided a mastercurve for the secular variation as a function of time is available. A total of 27 orientated bricks still supposed to be in situ from the oldest and youngest kiln phases were collected (3), with the purpose of possibly establishing the age as well as the duration of the use of the kiln. In the laboratory, 4 to 8 cores were drilled from each brick, and the total nu

&nbsp, Archaeomagnetic dating of a Medieval brick kiln from Tønsberg, Norway Medieval bricks and tile were never commonly used in Norway as they were in Denmark. Thus only 3 Medieval brick kilns have hitherto been found and described in Norway, and their products have not been investigated in greater detail. Dating of the bricks is therefore somewhat uncertain. In the case of the Tønsberg kiln, no tools or written sources providing a date have been found. When the kiln was excavated in 1980-81, magnetic dating was therefore planned (1, 2, 3, 4). The kiln is situated on a small plateau at the northern edge of the Medieval town (fig. 1). Although only partly preserved, the kiln is seen to be of a rectangular shape common in Medieval Scandinavia, the flat floor and the front wall both being constructed in bricks. Five phases of the kiln were found, phase 1 being the oldest and phase 5 the youngest (fig. 2). The remains of the 5 floors are situated one above the other, except for a ca. 20 cm thick layer of sand separating phases 1 and 2. Magnetic measurements The magnetic dating method is a relative method based upon the principle that the direction of the earth's geomagnetic field is stored in the iron oxides of the fired clay during the last cooling, all previous magnetic memory being erased by the last heating above the Curie point of some 580°C (1, 4, 8, 9). As the direction of the geomagnetic field varies slowly with time, the secular variation (5) being typically of the order of 10 per 10 years, the direction of the measured remanent magnetization is diagnostic for the time of the last cooling, provided a mastercurve for the secular variation as a function of time is available. A total of 27 orientated bricks still supposed to be in situ from the oldest and youngest kiln phases were collected (3), with the purpose of possibly establishing the age as well as the duration of the use of the kiln. In the laboratory, 4 to 8 cores were drilled from each brick, and the total nu

&nbsp, Archaeomagnetic dating of a Medieval brick kiln from Tønsberg, Norway Medieval bricks and tile were never commonly used in Norway as they were in Denmark. Thus only 3 Medieval brick kilns have hitherto been found and described in Norway, and their products have not been investigated in greater detail. Dating of the bricks is therefore somewhat uncertain. In the case of the Tønsberg kiln, no tools or written sources providing a date have been found. When the kiln was excavated in 1980-81, magnetic dating was therefore planned (1, 2, 3, 4). The kiln is situated on a small plateau at the northern edge of the Medieval town (fig. 1). Although only partly preserved, the kiln is seen to be of a rectangular shape common in Medieval Scandinavia, the flat floor and the front wall both being constructed in bricks. Five phases of the kiln were found, phase 1 being the oldest and phase 5 the youngest (fig. 2). The remains of the 5 floors are situated one above the other, except for a ca. 20 cm thick layer of sand separating phases 1 and 2. Magnetic measurements The magnetic dating method is a relative method based upon the principle that the direction of the earth's geomagnetic field is stored in the iron oxides of the fired clay during the last cooling, all previous magnetic memory being erased by the last heating above the Curie point of some 580°C (1, 4, 8, 9). As the direction of the geomagnetic field varies slowly with time, the secular variation (5) being typically of the order of 10 per 10 years, the direction of the measured remanent magnetization is diagnostic for the time of the last cooling, provided a mastercurve for the secular variation as a function of time is available. A total of 27 orientated bricks still supposed to be in situ from the oldest and youngest kiln phases were collected (3), with the purpose of possibly establishing the age as well as the duration of the use of the kiln. In the laboratory, 4 to 8 cores were drilled from each brick, and the total nu

history back to c. 7,000 years calBP (6,000 years convBP) in this·extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts- presently restricted to a narrow fringe of land at the shores of the Arctic Ocean-were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5'C, A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice-age mid-latitude environments are not identical.

history back to c. 7,000 years calBP (6,000 years convBP) in this·extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts- presently restricted to a narrow fringe of land at the shores of the Arctic Ocean-were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5'C, A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice-age mid-latitude environments are not identical.

Archaeomagnetic Experiments On Reconstructed Kilns Baked clays are known to be somewhat magnetic, and in the archaeological context the magnetic anomaly may be detected by measurements on the surface before excavation is undertaken. The anomaly is caused by the increased values of the two magnetic parameters of the material: the remanent magnetization Jn and the magnetic susceptibility k (Abrahamsen, 1966; Aitken, 1974). In order to investigate a model case (fig. 1) with known geometry and magnetic parameters, a magnetic investigation has been made at Moesgaard Museum of two reconstructions on scale 7:10 of the Medieval Kilns at Bistrup (Hansen and Sørensen, 1980; Abrahamsen et al., 1982). For the reconstruction red, weakly magnetic bricks from a commercial brickworks were used. After the first moderate heating in one of the kilns, the magnetic anomaly was measured over both kilns, and showed only a weak anomaly of about 20 γ (fig. 2). After further heatings in both ovens, an anomaly of ca. 100 γ was found (Fig. 3). This indicates that the all-round temperature now had passed the Curie temperature of magnetite (ca. 578°C), increasing the remanent magnetization significantly. Measurements of the susceptibility and remanent magnetization on the bricks and tiles (Table 1) also show clear correlations between the colour, the degree of reduction, and the heating history of the baked clays involved. This leads to simple rules and estimates of the maximum magnetic anomaly which may be expected over ancient remnants and structures of baked clays. It is concluded, that: groups of unreduced modern bricks will typically cause only minor magnetic anomalies of the order of ± 10 gamma (nannoTesla), the magnetization and hence the magnetic anomaly increase with the degree of reduction of the baked clays and are a strong function of the temperature attained, because of wasters and other scattered fragments, the magnetic background noise will be higher than usual at and around old p,                              &nbsp

Archaeo-Magnetism and Iron-Age Slags In the first three sections a short review is given of magnetic concepts and their use in archaeomagnetic dating and finding, while in the last section an example on their application is given: Slag pits from prehistoric iron-smelting have earlier (Voss, 1962) been excavated at Drengsted in Southwestern Jutland (fig. 6) and some of them C-14-dated on carbonized straw or charcoal to the age of 210 ± 100 A.D. or to the interval between 320 and 410 A.D. while potsherds and a settlement at the same place indicated an age of the 5th century A.D. Hence it is for the moment doubtful whether the settlement and the iron-smelting are of the same age or not. Planning new excavations in the same area it was then decided, as the slag pits are strongly magnetic to make arealmagnetic measurements as well as paleomagnetic determinations; none of these methods have formerly been applied in Danish archaeological work, wherefore collaboration between Forhistorisk Arkæologisk Institut and Geologisk Institut at the University of Aarhus was started.The instrument available at the moment was an Askania-Gfz-vertical-intensity-magnetometer, with which an area of 40 X 80 m2 as shown in red in fig. 7 was measured, and to compare the reliability of the method part of the same area was remeasured with a denser net of measuring-points as shown in fig. 8; the mean-error at a point is ± 4 gamma, while most of the positive anomalies lie between 20 and 100 gramma. Afterwards the northern half of the area was excavated and revealed 47 slag pits (fig. 7) 19 of which were undisturbed (full black dots), while the rest were broken up but still lying in their original places, the slags being between 0.6 and 0.9 m in diameter and with weights up to 450 kg. To determine in detail the magnetic anomaly of typical, unbroken slag pits, two small, isolated anomalies were selected in the undisturbed southern part of the area and remeasured detailed, the anomalies of which turn

Archaeo-Magnetism and Iron-Age Slags In the first three sections a short review is given of magnetic concepts and their use in archaeomagnetic dating and finding, while in the last section an example on their application is given: Slag pits from prehistoric iron-smelting have earlier (Voss, 1962) been excavated at Drengsted in Southwestern Jutland (fig. 6) and some of them C-14-dated on carbonized straw or charcoal to the age of 210 ± 100 A.D. or to the interval between 320 and 410 A.D. while potsherds and a settlement at the same place indicated an age of the 5th century A.D. Hence it is for the moment doubtful whether the settlement and the iron-smelting are of the same age or not. Planning new excavations in the same area it was then decided, as the slag pits are strongly magnetic to make arealmagnetic measurements as well as paleomagnetic determinations; none of these methods have formerly been applied in Danish archaeological work, wherefore collaboration between Forhistorisk Arkæologisk Institut and Geologisk Institut at the University of Aarhus was started.The instrument available at the moment was an Askania-Gfz-vertical-intensity-magnetometer, with which an area of 40 X 80 m2 as shown in red in fig. 7 was measured, and to compare the reliability of the method part of the same area was remeasured with a denser net of measuring-points as shown in fig. 8; the mean-error at a point is ± 4 gamma, while most of the positive anomalies lie between 20 and 100 gramma. Afterwards the northern half of the area was excavated and revealed 47 slag pits (fig. 7) 19 of which were undisturbed (full black dots), while the rest were broken up but still lying in their original places, the slags being between 0.6 and 0.9 m in diameter and with weights up to 450 kg. To determine in detail the magnetic anomaly of typical, unbroken slag pits, two small, isolated anomalies were selected in the undisturbed southern part of the area and remeasured detailed, the anomalies of which turn

Archaeo-Magnetism and Iron-Age Slags In the first three sections a short review is given of magnetic concepts and their use in archaeomagnetic dating and finding, while in the last section an example on their application is given: Slag pits from prehistoric iron-smelting have earlier (Voss, 1962) been excavated at Drengsted in Southwestern Jutland (fig. 6) and some of them C-14-dated on carbonized straw or charcoal to the age of 210 ± 100 A.D. or to the interval between 320 and 410 A.D. while potsherds and a settlement at the same place indicated an age of the 5th century A.D. Hence it is for the moment doubtful whether the settlement and the iron-smelting are of the same age or not. Planning new excavations in the same area it was then decided, as the slag pits are strongly magnetic to make arealmagnetic measurements as well as paleomagnetic determinations; none of these methods have formerly been applied in Danish archaeological work, wherefore collaboration between Forhistorisk Arkæologisk Institut and Geologisk Institut at the University of Aarhus was started.The instrument available at the moment was an Askania-Gfz-vertical-intensity-magnetometer, with which an area of 40 X 80 m2 as shown in red in fig. 7 was measured, and to compare the reliability of the method part of the same area was remeasured with a denser net of measuring-points as shown in fig. 8; the mean-error at a point is ± 4 gamma, while most of the positive anomalies lie between 20 and 100 gramma. Afterwards the northern half of the area was excavated and revealed 47 slag pits (fig. 7) 19 of which were undisturbed (full black dots), while the rest were broken up but still lying in their original places, the slags being between 0.6 and 0.9 m in diameter and with weights up to 450 kg. To determine in detail the magnetic anomaly of typical, unbroken slag pits, two small, isolated anomalies were selected in the undisturbed southern part of the area and remeasured detailed, the anomalies of which turn