irina popescu - Academia.edu (original) (raw)

Papers by irina popescu

Research paper thumbnail of Field strength prediction in indoor environment with a neural model

This paper presents the results of our studies concerning the application of the neural networks ... more This paper presents the results of our studies concerning the application of the neural networks to the field strength prediction in an indoor environment. The proposed model consists of a multilayer perceptron trained with measurements. The results of the prediction show good agreement with the measurements

Research paper thumbnail of Romania trying to be an European brand

Building a coherent country branding program at international level requires a strong coordinatio... more Building a coherent country branding program at international level requires a strong coordination between the government, the business sector, the decision makers from educational and cultural sector, the civil society and, the mass media representatives in any country. The paper presents the main efforts Romania has done to build a country image with a significant impact at international level. It focuses on the main policies and programs applied by Romania in the specific field of the national branding, offering a good analysis on the institutional framework and experience in promoting the country's image internationally.

Research paper thumbnail of Romania trying to be an European brand

Building a coherent country branding program at international level requires a strong coordinatio... more Building a coherent country branding program at international level requires a strong coordination between the government, the business sector, the decision makers from educational and cultural sector, the civil society and, the mass media representatives in any country. The paper presents the main efforts Romania has done to build a country image with a significant impact at international level. It focuses on the main policies and programs applied by Romania in the specific field of the national branding, offering a good analysis on the institutional framework and experience in promoting the country's image internationally.

Research paper thumbnail of The Danube submarine canyon (Black Sea): morphology and sedimentary processes

Marine Geology, 2004

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleist... more The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath bathymetry in the canyon area combined with different types of seismic data.

Research paper thumbnail of The Danube submarine canyon (Black Sea): morphology and sedimentary processes

Marine Geology, 2004

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleist... more The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath bathymetry in the canyon area combined with different types of seismic data.

Research paper thumbnail of A post Younger Dryas Black Sea regression identified from sequence stratigraphy correlated to core analysis and dating

Quaternary International, 2010

The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Dan... more The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Danube delta/prodelta system includes important records on the Black Sea water level fluctuations. This study integrates newly acquired high-resolution single channel seismic reflection profiles and Calypso piston cores recovered along a transect extending from the Danube delta deep into its deep sea fan. The correlated results provide information on the Late Quaternary architecture of the Danube Black Sea shelf and on the role of global glacio-eustatic fluctuations on the building of the Danube delta/prodelta. The sedimentary sequences in the Black Sea are strongly affected by water level changes. For the whole duration of Late Glacial-Holocene period, the level of the Black Sea was controlled by the regional climate modifications rather than the global eustatic changes. The seismic sequences recognized on a very high-resolution seismic profile were dated by two Calypso piston cores. Based on the obtained data, during the Last Glacial Maximum the Black Sea was a land locked lake with the level below −120 m. In the course of the deglaciation the lake level rose up to −40 m, which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water. Following the Younger Dryas, 11 000-8500 14 C BP, there occurred a new level lowering to the level of −100 m, identified by the forced regression deposits recorded on the Romanian shelf. This last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at −100 m depth. All these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 14 C BP.

Research paper thumbnail of A post Younger Dryas Black Sea regression identified from sequence stratigraphy correlated to core analysis and dating

Quaternary International, 2010

The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Dan... more The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Danube delta/prodelta system includes important records on the Black Sea water level fluctuations. This study integrates newly acquired high-resolution single channel seismic reflection profiles and Calypso piston cores recovered along a transect extending from the Danube delta deep into its deep sea fan. The correlated results provide information on the Late Quaternary architecture of the Danube Black Sea shelf and on the role of global glacio-eustatic fluctuations on the building of the Danube delta/prodelta. The sedimentary sequences in the Black Sea are strongly affected by water level changes. For the whole duration of Late Glacial-Holocene period, the level of the Black Sea was controlled by the regional climate modifications rather than the global eustatic changes. The seismic sequences recognized on a very high-resolution seismic profile were dated by two Calypso piston cores. Based on the obtained data, during the Last Glacial Maximum the Black Sea was a land locked lake with the level below −120 m. In the course of the deglaciation the lake level rose up to −40 m, which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water. Following the Younger Dryas, 11 000-8500 14 C BP, there occurred a new level lowering to the level of −100 m, identified by the forced regression deposits recorded on the Romanian shelf. This last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at −100 m depth. All these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 14 C BP.

Research paper thumbnail of Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions

Marine Geology, 2006

A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-reso... more A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-resolution reflection seismic data in the Danube deep-sea fan, associated with acoustic features indicating free gas. Our study provides evidence that this pattern is developed in relation with the architecture of distinct channel-levee systems of the Danube fan. Channel-levee systems hosting multiple BSRs act as relatively sealed gas-bearing systems whose top is situated above the base of the gas hydrate stability zone (BGHSZ). Inside these systems, free gas accumulates below the BGHSZ under a combined lithological, structural and stratigraphical control.

Research paper thumbnail of Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions

Marine Geology, 2006

A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-reso... more A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-resolution reflection seismic data in the Danube deep-sea fan, associated with acoustic features indicating free gas. Our study provides evidence that this pattern is developed in relation with the architecture of distinct channel-levee systems of the Danube fan. Channel-levee systems hosting multiple BSRs act as relatively sealed gas-bearing systems whose top is situated above the base of the gas hydrate stability zone (BGHSZ). Inside these systems, free gas accumulates below the BGHSZ under a combined lithological, structural and stratigraphical control.

Research paper thumbnail of Late Quaternary channel avulsions on the Danube deep-sea fan, Black Sea

Marine Geology, 2001

Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously publis... more Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously published sidescan data, together with piston cores on the Danube Fan provide new insight into the recent sedimentation processes in the deep northwestern Black Sea.

Research paper thumbnail of Late Quaternary channel avulsions on the Danube deep-sea fan, Black Sea

Marine Geology, 2001

Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously publis... more Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously published sidescan data, together with piston cores on the Danube Fan provide new insight into the recent sedimentation processes in the deep northwestern Black Sea.

Research paper thumbnail of Water-level fluctuations in the Black Sea since the Last Glacial Maximum

Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 comp... more Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 complement previous seabed mapping and subsurface sampling by various international expeditions. They show that the lake level rose on the continental shelf to at least the -40 to -30 m isobath based on the landward limit of a Dreissena layer representative of very low salinity conditions (<5‰). The Black Sea then shows clear evidence for an onset of marine conditions at 7150 BP. From these observations, concluded that the Black Sea could have filled abruptly with saltwater cascading in from the Mediterranean. Despite critical discussions of this interpretation, recent IFREMER discoveries of well preserved drowned beaches, sand dunes, and soils appear to lend support to the flood hypothesis. This new evidence includes (1) multibeam echo-sounding and seismic reflection profiles that reveal wave-cut terraces at about -100 m, (2) Romanian shelf cores that show an erosion surface indicating subaerial exposure well below the sill of the modern Bosphorus, (3) 14C ages documenting a colonization of the former terrestrial shelf surface by marine molluscs at 7150BP, (4) evidence of sea water penetration into the Black Sea in the form of recent canyon heads at the Bosphorus outlet, and (5) palynological analysis and dinocyst studies that pinpoint the arrival of freshwater during the Younger Dryas and, later, the rapid replacement of Black Sea dinocysts by a 2 Mediterranean population.

Research paper thumbnail of Water-level fluctuations in the Black Sea since the Last Glacial Maximum

Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 comp... more Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 complement previous seabed mapping and subsurface sampling by various international expeditions. They show that the lake level rose on the continental shelf to at least the -40 to -30 m isobath based on the landward limit of a Dreissena layer representative of very low salinity conditions (<5‰). The Black Sea then shows clear evidence for an onset of marine conditions at 7150 BP. From these observations, concluded that the Black Sea could have filled abruptly with saltwater cascading in from the Mediterranean. Despite critical discussions of this interpretation, recent IFREMER discoveries of well preserved drowned beaches, sand dunes, and soils appear to lend support to the flood hypothesis. This new evidence includes (1) multibeam echo-sounding and seismic reflection profiles that reveal wave-cut terraces at about -100 m, (2) Romanian shelf cores that show an erosion surface indicating subaerial exposure well below the sill of the modern Bosphorus, (3) 14C ages documenting a colonization of the former terrestrial shelf surface by marine molluscs at 7150BP, (4) evidence of sea water penetration into the Black Sea in the form of recent canyon heads at the Bosphorus outlet, and (5) palynological analysis and dinocyst studies that pinpoint the arrival of freshwater during the Younger Dryas and, later, the rapid replacement of Black Sea dinocysts by a 2 Mediterranean population.

Research paper thumbnail of Seismic expression of gas and gas hydrates across the western Black Sea

Geo-marine Letters, 2007

This study is a synthesis of gas-related features in recent sediments across the western Black Se... more This study is a synthesis of gas-related features in recent sediments across the western Black Sea basin. The investigation is based on an extensive seismic dataset, and integrates published information from previous local studies. Our data reveal widespread occurrences of seismic facies indicating free gas in sediments and gas escape in the water column. The presence of gas hydrates is inferred from bottom-simulating reflections (BSRs). The distribution of the gas facies shows (1) major gas accumulations close to the seafloor in the coastal area and along the shelfbreak, (2) ubiquitous gas migration from the deeper subsurface on the shelf and (3) gas hydrate occurrences on the lower slope (below 750 m water depth). The coastal and shelfbreak shallow gas areas correspond to the highstand and lowstand depocentres, respectively. Gas in these areas most likely results from in situ degradation of biogenic methane, probably with a contribution of deep gas in the shelfbreak accumulation. On the western shelf, vertical gas migration appears to originate from a source of Eocene age or older and, in some cases, it is clearly related to known deep oil and gas fields. Gas release at the seafloor is abundant at water depths shallower than 725 m, which corresponds to the minimum theoretical depth for methane hydrate stability, but occurs only exceptionally at water depths where hydrates can form. As such, gas entering the hydrate stability field appears to form hydrates, acting as a buffer for gas migration towards the seafloor and subsequent escape.

Research paper thumbnail of Seismic expression of gas and gas hydrates across the western Black Sea

Geo-marine Letters, 2007

This study is a synthesis of gas-related features in recent sediments across the western Black Se... more This study is a synthesis of gas-related features in recent sediments across the western Black Sea basin. The investigation is based on an extensive seismic dataset, and integrates published information from previous local studies. Our data reveal widespread occurrences of seismic facies indicating free gas in sediments and gas escape in the water column. The presence of gas hydrates is inferred from bottom-simulating reflections (BSRs). The distribution of the gas facies shows (1) major gas accumulations close to the seafloor in the coastal area and along the shelfbreak, (2) ubiquitous gas migration from the deeper subsurface on the shelf and (3) gas hydrate occurrences on the lower slope (below 750 m water depth). The coastal and shelfbreak shallow gas areas correspond to the highstand and lowstand depocentres, respectively. Gas in these areas most likely results from in situ degradation of biogenic methane, probably with a contribution of deep gas in the shelfbreak accumulation. On the western shelf, vertical gas migration appears to originate from a source of Eocene age or older and, in some cases, it is clearly related to known deep oil and gas fields. Gas release at the seafloor is abundant at water depths shallower than 725 m, which corresponds to the minimum theoretical depth for methane hydrate stability, but occurs only exceptionally at water depths where hydrates can form. As such, gas entering the hydrate stability field appears to form hydrates, acting as a buffer for gas migration towards the seafloor and subsequent escape.

Research paper thumbnail of Structural properties of some transition metal highly doped carbon aerogels

Journal of Alloys and Compounds, 2007

Structural characterization of transition metal highly doped carbon aerogels obtained through the... more Structural characterization of transition metal highly doped carbon aerogels obtained through the sol-gel polymerization process of the formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO 2 and carbonization at 1050 • C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were used and it was found that the metal-containing phase is more homogeneously distributed in Cu-doped carbon aerogels. The presence of the metal species determines both the growth of graphitic nanoribbons and the change of framework of the interconnected carbon particles.

Research paper thumbnail of Synthesis and structural characteristics of nitrogen doped TiO 2 aerogels

Microporous and Mesoporous Materials, 2010

Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying w... more Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying with liquid CO 2 . Urea and NH 3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450°C to 550°C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO 2 lattice were observed. The immersion of the TiO 2 aerogels in NH 3 solution induced a decreasing by 48.86% and by 80% of the S BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO 2 was found to depend mainly on the nitrogen incorporation in the TiO 2 lattice.

Research paper thumbnail of Synthesis and structural characteristics of carbon aerogels with a high content of Fe, Co, Ni, Cu, and Pd

Journal of Non-crystalline Solids, 2006

High content metal carbon aerogels have been prepared by sol-gel polymerization of formaldehyde w... more High content metal carbon aerogels have been prepared by sol-gel polymerization of formaldehyde with potassium salt of 2,4-dihydroxybenzoic acid, followed by K + -exchange with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Pd(II) ions from an aqueous or acetoneous solution and subsequent supercritical drying with CO 2 . Carbonization at 1050°C, under an inert atmosphere, transforms the metal ion doped organic aerogels into metal and/or metal oxide nanoparticles-doped carbon aerogels. The resulting materials were characterized by means of elemental analysis, nitrogen adsorption, transmission electron microscopy and X-ray diffraction. The structural properties and metal concentration of the doped carbon aerogel depend on the type and valence of the precursor metal salt. The presence of some graphitic nano-ribbons was evidenced in the case of Fe-, Co-, and Ni-doped carbon aerogels.

Research paper thumbnail of Structural properties of some transition metal highly doped carbon aerogels

Journal of Alloys and Compounds, 2007

Structural characterization of transition metal highly doped carbon aerogels obtained through the... more Structural characterization of transition metal highly doped carbon aerogels obtained through the sol-gel polymerization process of the formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO 2 and carbonization at 1050 • C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were used and it was found that the metal-containing phase is more homogeneously distributed in Cu-doped carbon aerogels. The presence of the metal species determines both the growth of graphitic nanoribbons and the change of framework of the interconnected carbon particles.

Research paper thumbnail of Synthesis and structural characteristics of nitrogen doped TiO 2 aerogels

Microporous and Mesoporous Materials, 2010

Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying w... more Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying with liquid CO 2 . Urea and NH 3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450°C to 550°C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO 2 lattice were observed. The immersion of the TiO 2 aerogels in NH 3 solution induced a decreasing by 48.86% and by 80% of the S BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO 2 was found to depend mainly on the nitrogen incorporation in the TiO 2 lattice.

Research paper thumbnail of Field strength prediction in indoor environment with a neural model

This paper presents the results of our studies concerning the application of the neural networks ... more This paper presents the results of our studies concerning the application of the neural networks to the field strength prediction in an indoor environment. The proposed model consists of a multilayer perceptron trained with measurements. The results of the prediction show good agreement with the measurements

Research paper thumbnail of Romania trying to be an European brand

Building a coherent country branding program at international level requires a strong coordinatio... more Building a coherent country branding program at international level requires a strong coordination between the government, the business sector, the decision makers from educational and cultural sector, the civil society and, the mass media representatives in any country. The paper presents the main efforts Romania has done to build a country image with a significant impact at international level. It focuses on the main policies and programs applied by Romania in the specific field of the national branding, offering a good analysis on the institutional framework and experience in promoting the country's image internationally.

Research paper thumbnail of Romania trying to be an European brand

Building a coherent country branding program at international level requires a strong coordinatio... more Building a coherent country branding program at international level requires a strong coordination between the government, the business sector, the decision makers from educational and cultural sector, the civil society and, the mass media representatives in any country. The paper presents the main efforts Romania has done to build a country image with a significant impact at international level. It focuses on the main policies and programs applied by Romania in the specific field of the national branding, offering a good analysis on the institutional framework and experience in promoting the country's image internationally.

Research paper thumbnail of The Danube submarine canyon (Black Sea): morphology and sedimentary processes

Marine Geology, 2004

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleist... more The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath bathymetry in the canyon area combined with different types of seismic data.

Research paper thumbnail of The Danube submarine canyon (Black Sea): morphology and sedimentary processes

Marine Geology, 2004

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleist... more The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath bathymetry in the canyon area combined with different types of seismic data.

Research paper thumbnail of A post Younger Dryas Black Sea regression identified from sequence stratigraphy correlated to core analysis and dating

Quaternary International, 2010

The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Dan... more The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Danube delta/prodelta system includes important records on the Black Sea water level fluctuations. This study integrates newly acquired high-resolution single channel seismic reflection profiles and Calypso piston cores recovered along a transect extending from the Danube delta deep into its deep sea fan. The correlated results provide information on the Late Quaternary architecture of the Danube Black Sea shelf and on the role of global glacio-eustatic fluctuations on the building of the Danube delta/prodelta. The sedimentary sequences in the Black Sea are strongly affected by water level changes. For the whole duration of Late Glacial-Holocene period, the level of the Black Sea was controlled by the regional climate modifications rather than the global eustatic changes. The seismic sequences recognized on a very high-resolution seismic profile were dated by two Calypso piston cores. Based on the obtained data, during the Last Glacial Maximum the Black Sea was a land locked lake with the level below −120 m. In the course of the deglaciation the lake level rose up to −40 m, which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water. Following the Younger Dryas, 11 000-8500 14 C BP, there occurred a new level lowering to the level of −100 m, identified by the forced regression deposits recorded on the Romanian shelf. This last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at −100 m depth. All these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 14 C BP.

Research paper thumbnail of A post Younger Dryas Black Sea regression identified from sequence stratigraphy correlated to core analysis and dating

Quaternary International, 2010

The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Dan... more The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Danube delta/prodelta system includes important records on the Black Sea water level fluctuations. This study integrates newly acquired high-resolution single channel seismic reflection profiles and Calypso piston cores recovered along a transect extending from the Danube delta deep into its deep sea fan. The correlated results provide information on the Late Quaternary architecture of the Danube Black Sea shelf and on the role of global glacio-eustatic fluctuations on the building of the Danube delta/prodelta. The sedimentary sequences in the Black Sea are strongly affected by water level changes. For the whole duration of Late Glacial-Holocene period, the level of the Black Sea was controlled by the regional climate modifications rather than the global eustatic changes. The seismic sequences recognized on a very high-resolution seismic profile were dated by two Calypso piston cores. Based on the obtained data, during the Last Glacial Maximum the Black Sea was a land locked lake with the level below −120 m. In the course of the deglaciation the lake level rose up to −40 m, which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water. Following the Younger Dryas, 11 000-8500 14 C BP, there occurred a new level lowering to the level of −100 m, identified by the forced regression deposits recorded on the Romanian shelf. This last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at −100 m depth. All these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 14 C BP.

Research paper thumbnail of Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions

Marine Geology, 2006

A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-reso... more A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-resolution reflection seismic data in the Danube deep-sea fan, associated with acoustic features indicating free gas. Our study provides evidence that this pattern is developed in relation with the architecture of distinct channel-levee systems of the Danube fan. Channel-levee systems hosting multiple BSRs act as relatively sealed gas-bearing systems whose top is situated above the base of the gas hydrate stability zone (BGHSZ). Inside these systems, free gas accumulates below the BGHSZ under a combined lithological, structural and stratigraphical control.

Research paper thumbnail of Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions

Marine Geology, 2006

A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-reso... more A previously unknown pattern of multiple bottom-simulating reflections (BSRs) occurs on high-resolution reflection seismic data in the Danube deep-sea fan, associated with acoustic features indicating free gas. Our study provides evidence that this pattern is developed in relation with the architecture of distinct channel-levee systems of the Danube fan. Channel-levee systems hosting multiple BSRs act as relatively sealed gas-bearing systems whose top is situated above the base of the gas hydrate stability zone (BGHSZ). Inside these systems, free gas accumulates below the BGHSZ under a combined lithological, structural and stratigraphical control.

Research paper thumbnail of Late Quaternary channel avulsions on the Danube deep-sea fan, Black Sea

Marine Geology, 2001

Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously publis... more Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously published sidescan data, together with piston cores on the Danube Fan provide new insight into the recent sedimentation processes in the deep northwestern Black Sea.

Research paper thumbnail of Late Quaternary channel avulsions on the Danube deep-sea fan, Black Sea

Marine Geology, 2001

Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously publis... more Analysis of new high-resolution seismic-reflection profiles, chirp profiles and previously published sidescan data, together with piston cores on the Danube Fan provide new insight into the recent sedimentation processes in the deep northwestern Black Sea.

Research paper thumbnail of Water-level fluctuations in the Black Sea since the Last Glacial Maximum

Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 comp... more Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 complement previous seabed mapping and subsurface sampling by various international expeditions. They show that the lake level rose on the continental shelf to at least the -40 to -30 m isobath based on the landward limit of a Dreissena layer representative of very low salinity conditions (<5‰). The Black Sea then shows clear evidence for an onset of marine conditions at 7150 BP. From these observations, concluded that the Black Sea could have filled abruptly with saltwater cascading in from the Mediterranean. Despite critical discussions of this interpretation, recent IFREMER discoveries of well preserved drowned beaches, sand dunes, and soils appear to lend support to the flood hypothesis. This new evidence includes (1) multibeam echo-sounding and seismic reflection profiles that reveal wave-cut terraces at about -100 m, (2) Romanian shelf cores that show an erosion surface indicating subaerial exposure well below the sill of the modern Bosphorus, (3) 14C ages documenting a colonization of the former terrestrial shelf surface by marine molluscs at 7150BP, (4) evidence of sea water penetration into the Black Sea in the form of recent canyon heads at the Bosphorus outlet, and (5) palynological analysis and dinocyst studies that pinpoint the arrival of freshwater during the Younger Dryas and, later, the rapid replacement of Black Sea dinocysts by a 2 Mediterranean population.

Research paper thumbnail of Water-level fluctuations in the Black Sea since the Last Glacial Maximum

Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 comp... more Two IFREMER oceanographic surveys carried out in the northwestern Black Sea in 1998 and 2002 complement previous seabed mapping and subsurface sampling by various international expeditions. They show that the lake level rose on the continental shelf to at least the -40 to -30 m isobath based on the landward limit of a Dreissena layer representative of very low salinity conditions (<5‰). The Black Sea then shows clear evidence for an onset of marine conditions at 7150 BP. From these observations, concluded that the Black Sea could have filled abruptly with saltwater cascading in from the Mediterranean. Despite critical discussions of this interpretation, recent IFREMER discoveries of well preserved drowned beaches, sand dunes, and soils appear to lend support to the flood hypothesis. This new evidence includes (1) multibeam echo-sounding and seismic reflection profiles that reveal wave-cut terraces at about -100 m, (2) Romanian shelf cores that show an erosion surface indicating subaerial exposure well below the sill of the modern Bosphorus, (3) 14C ages documenting a colonization of the former terrestrial shelf surface by marine molluscs at 7150BP, (4) evidence of sea water penetration into the Black Sea in the form of recent canyon heads at the Bosphorus outlet, and (5) palynological analysis and dinocyst studies that pinpoint the arrival of freshwater during the Younger Dryas and, later, the rapid replacement of Black Sea dinocysts by a 2 Mediterranean population.

Research paper thumbnail of Seismic expression of gas and gas hydrates across the western Black Sea

Geo-marine Letters, 2007

This study is a synthesis of gas-related features in recent sediments across the western Black Se... more This study is a synthesis of gas-related features in recent sediments across the western Black Sea basin. The investigation is based on an extensive seismic dataset, and integrates published information from previous local studies. Our data reveal widespread occurrences of seismic facies indicating free gas in sediments and gas escape in the water column. The presence of gas hydrates is inferred from bottom-simulating reflections (BSRs). The distribution of the gas facies shows (1) major gas accumulations close to the seafloor in the coastal area and along the shelfbreak, (2) ubiquitous gas migration from the deeper subsurface on the shelf and (3) gas hydrate occurrences on the lower slope (below 750 m water depth). The coastal and shelfbreak shallow gas areas correspond to the highstand and lowstand depocentres, respectively. Gas in these areas most likely results from in situ degradation of biogenic methane, probably with a contribution of deep gas in the shelfbreak accumulation. On the western shelf, vertical gas migration appears to originate from a source of Eocene age or older and, in some cases, it is clearly related to known deep oil and gas fields. Gas release at the seafloor is abundant at water depths shallower than 725 m, which corresponds to the minimum theoretical depth for methane hydrate stability, but occurs only exceptionally at water depths where hydrates can form. As such, gas entering the hydrate stability field appears to form hydrates, acting as a buffer for gas migration towards the seafloor and subsequent escape.

Research paper thumbnail of Seismic expression of gas and gas hydrates across the western Black Sea

Geo-marine Letters, 2007

This study is a synthesis of gas-related features in recent sediments across the western Black Se... more This study is a synthesis of gas-related features in recent sediments across the western Black Sea basin. The investigation is based on an extensive seismic dataset, and integrates published information from previous local studies. Our data reveal widespread occurrences of seismic facies indicating free gas in sediments and gas escape in the water column. The presence of gas hydrates is inferred from bottom-simulating reflections (BSRs). The distribution of the gas facies shows (1) major gas accumulations close to the seafloor in the coastal area and along the shelfbreak, (2) ubiquitous gas migration from the deeper subsurface on the shelf and (3) gas hydrate occurrences on the lower slope (below 750 m water depth). The coastal and shelfbreak shallow gas areas correspond to the highstand and lowstand depocentres, respectively. Gas in these areas most likely results from in situ degradation of biogenic methane, probably with a contribution of deep gas in the shelfbreak accumulation. On the western shelf, vertical gas migration appears to originate from a source of Eocene age or older and, in some cases, it is clearly related to known deep oil and gas fields. Gas release at the seafloor is abundant at water depths shallower than 725 m, which corresponds to the minimum theoretical depth for methane hydrate stability, but occurs only exceptionally at water depths where hydrates can form. As such, gas entering the hydrate stability field appears to form hydrates, acting as a buffer for gas migration towards the seafloor and subsequent escape.

Research paper thumbnail of Structural properties of some transition metal highly doped carbon aerogels

Journal of Alloys and Compounds, 2007

Structural characterization of transition metal highly doped carbon aerogels obtained through the... more Structural characterization of transition metal highly doped carbon aerogels obtained through the sol-gel polymerization process of the formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO 2 and carbonization at 1050 • C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were used and it was found that the metal-containing phase is more homogeneously distributed in Cu-doped carbon aerogels. The presence of the metal species determines both the growth of graphitic nanoribbons and the change of framework of the interconnected carbon particles.

Research paper thumbnail of Synthesis and structural characteristics of nitrogen doped TiO 2 aerogels

Microporous and Mesoporous Materials, 2010

Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying w... more Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying with liquid CO 2 . Urea and NH 3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450°C to 550°C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO 2 lattice were observed. The immersion of the TiO 2 aerogels in NH 3 solution induced a decreasing by 48.86% and by 80% of the S BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO 2 was found to depend mainly on the nitrogen incorporation in the TiO 2 lattice.

Research paper thumbnail of Synthesis and structural characteristics of carbon aerogels with a high content of Fe, Co, Ni, Cu, and Pd

Journal of Non-crystalline Solids, 2006

High content metal carbon aerogels have been prepared by sol-gel polymerization of formaldehyde w... more High content metal carbon aerogels have been prepared by sol-gel polymerization of formaldehyde with potassium salt of 2,4-dihydroxybenzoic acid, followed by K + -exchange with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Pd(II) ions from an aqueous or acetoneous solution and subsequent supercritical drying with CO 2 . Carbonization at 1050°C, under an inert atmosphere, transforms the metal ion doped organic aerogels into metal and/or metal oxide nanoparticles-doped carbon aerogels. The resulting materials were characterized by means of elemental analysis, nitrogen adsorption, transmission electron microscopy and X-ray diffraction. The structural properties and metal concentration of the doped carbon aerogel depend on the type and valence of the precursor metal salt. The presence of some graphitic nano-ribbons was evidenced in the case of Fe-, Co-, and Ni-doped carbon aerogels.

Research paper thumbnail of Structural properties of some transition metal highly doped carbon aerogels

Journal of Alloys and Compounds, 2007

Structural characterization of transition metal highly doped carbon aerogels obtained through the... more Structural characterization of transition metal highly doped carbon aerogels obtained through the sol-gel polymerization process of the formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO 2 and carbonization at 1050 • C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were used and it was found that the metal-containing phase is more homogeneously distributed in Cu-doped carbon aerogels. The presence of the metal species determines both the growth of graphitic nanoribbons and the change of framework of the interconnected carbon particles.

Research paper thumbnail of Synthesis and structural characteristics of nitrogen doped TiO 2 aerogels

Microporous and Mesoporous Materials, 2010

Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying w... more Nitrogen doped TiO 2 aerogels were obtained by sol-gel process followed by supercritical drying with liquid CO 2 . Urea and NH 3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450°C to 550°C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO 2 lattice were observed. The immersion of the TiO 2 aerogels in NH 3 solution induced a decreasing by 48.86% and by 80% of the S BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO 2 was found to depend mainly on the nitrogen incorporation in the TiO 2 lattice.