bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rock Typing approach for Reservoir Characterization of Ordovician Sandstones, Fields Case Study, Concessions NC115/NC186, Murzuq Basin, Libya
Authors: Salaheddin K.. , Laksana S.. , Schöbel M.. 
Published: February 2010

AbstractIn order to quantify the high vertical and lateral petrophysical variability of the Late Ordovician sandstones of the Mamuniyat Formation, the GHE methodology (Corbett et al. 2004) has been applied to several fields of the Murzuq Basin in Libya. These reservoirs are characterized by various facies associations and depositional environments as locally interpreted from core.The Mamuniyat Formation is a major oil reservoir in the Murzuq Basin of Libya, made up of massive sandstones, representing a low-stand system track. The formation can be subdivided into Lower (LM), Middle (MM) and Upper Mamuniyat (UM) as recognized in outcrops and correlated to the sub-surface. LM commonly consists of fine- to medium-grained sands, deposited in a shelf-shoreface to tidally influenced estuarine setting, whereas heterolithic ripple laminated, dewatered, and slumped sediments typify the MM. Deposition occurred in a rapidly prograding, unstable braid-delta front system fed by melting ice sheets. UM represents the most prolific reservoir section with typically (very) coarse-grained to pebbly sands of a braided system in an active glacial outwash plain.The complex facies associations entail large internal reservoir variability as reflected by routine core analysis data (poro-perm), log data and the petrophysical interpretation. The Global Hydraulic Element (GHE) approach is tested as a rock typing tool for response and synthesis of all parameters and critical path in the reservoir modeling work flow.In this study ten (10) GHE have been identified for the Mamuniyat Fm. Detailed quality control of the log and core data available have been conducted. The methodology involves the analysis of the routine core porosity and permeability and calculation of the Normalized Porosity (ϕz), Reservoir Quality Index (RQI) and Flow Zone Indicator (FZI). Statistical analysis on GHE and Facies Associations has been performed to better define their relationship.
Temsah Field PLEMS Replacement - Challenges & Technology
Authors: Pomar Alina , Al Sayed Ahmed , D'addario Nico 
Published: February 2010

Abstract
The technology innovation applied and lessons learned acquired in the Temsah field PLEMs change over project further TNW blow out emergency, occurred in August 2004, bring to analyze a real case study for production optimization while operating on in service facilities subsea.
Following the Temsah NW accident, it was of paramount importance to recover the Temsah and Akhen fields' production with a fast track redevelopment project. To match a challenging production restart up (6 months for Akhen) temporary gas and condensate PLEMs were installed in the field. Such PLEMs, procured in 2 months and made of materials (piping and valves) not suitable for subsea applications, allowed operability initially up to one year and extended up to four.
The final Plan of re-Development, as conceived by Petrobel, allowed both PLEMs change over with limited impact on production compared with the original plan.
Smart plugs solutions have been applied in the condensate PLEM replacement while subsea hot tapping and stoppling have been implemented all at once in the gas PLEM replacement.
Due to the water depth of 85 m the offshore activities, in both cases, have been executed in saturation diving mode, operating on different sealines size, from 6″ up to 32″, with the aim to avoid the sealine flooding minimizing the impact in the production facilities.
The reconsideration of the overall Temsah field development with improvements in the subsea facilities allowed not only to recovery the production lost due to the accident but to increase the field production profile which remained almost constant while replacing the PLEM despite sealine were going to be disconnected. Moreover the field operability has been improved thanks to replacement methodology adopted.
The Cabao Fm.: A Transgressive Cretaceous Tidal Dunes Complex Along Djebel Nafusah, North-Eastern Libya
Authors: Rubino Jean-Loup , Lafont Francois , Metais Eddy , Blanpied Christian , Sbeta Ali 
Published: February 2010

Abstract
The Djebel Nafusah Cliff forms very continuous outcrop (300km Long) and can be traced from Libyan Mediterranean coast to southern Tunisia. The cliff is armed by Mid Cretaceous limestone's which prevent underlying Mesozoic series from erosion.
The Mesozoic series starts with Triassic deposits and ends in Maaestrichtian. In the central part of the djebel, a homogeneous sandy series unconformably rests over the pre-existing Mesozoic series and corresponds to the so called Cabao Formation. It is exposed in numerous quarries as well as in natural outcrops. It unconformably overlies the Shekshuk Fm. most likely of Oxfordian age.
In Tunisia, additional stratigraphic units onlap the Austrian unconformity such as the Bouloula and Douiret Formations, Ouaja et al (2002); laterally equivalent units also occurs in western Libya near Wazin.
The Cabao sandstones seems to grade into Chenini sandstones in southern Tunisia, however the relationship is not well constrains and ancient data tends to suggest a north westward pinchout of the lower part of this formation, Bouaziz et al. (1989).
Messinian Salinity Crisis Expression Along North African Margin
Authors: Rubino Jean-Loup , Haddadi Nourredine , Camy-Peyret Jacqueline , Clauzon George , Suc Jean-Pierre , Ferry Serge , Gorini Christian 
Published: February 2010

Abstract
The Mediterranean Messinian Salinity Crisis, Hsu et al. (1973) has two main expressions, 1/ very deep subaerial canyons incision on the the hinterland and along basin margins, 2/ deposition of marginal and abyssal evaporites in the basins. Boths are well known everywhere around Mediterranean Sea, but surprisingly the occurence of canyons is poorly documented along North African margin except in Egypt where the Nile canyon is well known from onshore, to offshore, since a long time, Chumakov (1973), Barber (1981), Dalla et al. (1997). More recently messinian canyons have been reported: –In Algeria with the Algiers complex, Rubino et al. (2005),–Offshore and onshore Tunisia, El Euch-El Koundi et al. (2008)–In offshore Libya, Barr et Walker (1978), Ryan & Cita (1978), or onshore in Sirte and Kufrah basins, Grifin (2002), Rubino et al. (2005), Nicolai (2008), Drake et al. (2008), Paillou et al. (2008).–Evidences have been also reported from Morroco, Loget. (2002).
Application of the Time Series Analysis to the Latest Cenomanian – Early Turonian Sequence Using Foraminifera in the Southern Tethyan Margin
Authors: Soua Mohamed , Smaoui Jalel , Zaghbib-Turki Dalila 
Published: February 2010

Abstract
Time series analysis has been performed for the first time on the Cenomanian-Turonian sequence in Central Tunisia in order to shed light on its Milankovitch-like cyclicity. This analysis was tested and applied on two foraminiferal species: the biserial Heterohelix, an oxygen minimum zone (OMZ) dweller, and the triserial Guembelitria, a eutrophic surface dweller. Average sedimentary rates and the duration of the second Oceanic Anoxic Event OAE-2 in each studied section were estimated. Alternatively, the fluctuations of these two opportunistic species can be related mainly to both precessional (23–19 ka) and eccentricity (414–106 ka) cyclicity suggesting that changes in surface water fertility were linked to the Milankovitch parameters.
North Bardawil Development Project
Authors: Picciani F.. , El Din Ismail N.. , Luce R.. , Guarino M.. 
Published: February 2010

Abstract
The energy demand in Egypt has enjoyed a sustained period of growth over the past decade and this is set to continue in the next years. In order to sustain the demand trend, a remarkable number of subsea gas projects were put on stream during the last years and some more are already under development.
Through its affiliate in Egypt Ieoc, Eni has planned to maintain the role of top foreign hydrocarbon producer in the Country. To achieve this target Eni made investments in cutting edge technology, in particular in the sub-sea production system and for the first time in Egypt, it applied an innovative smart completion system.
On August 2009 Eni begun producing natural gas from the subsea North Bardawil Field. The production rate is 3.0 million standard cubic meters per day, approximately 19,000 boepd, of which about 6,700 boepd is Eni's equity share.
The project consists of two sub-sea wells, Assad and Zaraf, drilled by the semi-submersible Rig Scarabeo-4, the installation of 24 km of sea line, umbilical and subsea equipments in a water depth ranging between 110 and 340 meters, and the tie-back to the existing production platform Barboni.
Assad was developed with well re-entry and intelligent completion in two gas levels in the Pleistocene sequence zones with ICGP sand control, in order to produce through two independent gas flowing intervals. Zaraf re-entry with side-track and completion was executed with single conventional completion and ICGP sand control.
The tie-back to Barboni Platform was performed through simultaneous operations, upgrading the top side facilities on a gas producing platform and minimizing the number of the platform production shutdowns.
Partners on the project include Eni's affiliate in Egypt IEOC with 60% and Kufpec Ltd with 40%. Petrobel is the JV operator. These results were made possible through IEOC and Kufpec with the cooperation of the Ministry of Petroleum and EGPC.
The paper presents the analysis of the challenges, the opportunities, the development strategy and the execution of North Bardawil project in the strategic context of Egypt.
Action Potential: Ionic Mechanisms
Authors: Elmslie Keith S 
Published: February 2010

Abstract

The generation and propagation of the action potential requires sodium influx via voltage‐dependent sodium channels that drives the upstroke of the action potential. This positive feedback cycle is terminated by sodium channel inactivation that shuts down the channel at depolarized membrane potentials. The reduced sodium influx along with increased potassium efflux permits rapid action potential repolarization. The enhanced potassium efflux is mediated by the activity of both voltage‐dependent and voltage‐independent potassium channels. The recovery of sodium channels from inactivation and the slow closing of potassium channels following the action potential determine the refractory period, which is a period of increased action potential threshold. Thus, the kinetics of sodium and potassium channel gating determine not only the action potential shape and duration, but also the threshold for action potential generation.

Key concepts:

Sodium influx via voltage‐dependent sodium channels depolarizes the membrane to activate more sodium channels in a positive feedback mechanism that generates the ballistic rising phase of the action potential.

This positive feedback cycle is terminated by a separate gating process called inactivation, which shuts down sodium flux even though the membrane is still depolarized.

The reduction of sodium influx resulting from inactivation combined with potassium efflux from the cell via both voltage‐dependent and voltage‐independent potassium channels drive the repolarization phase of the action potential.

The voltage‐dependent potassium channels often remain active following the action potential (slow to close) to generate an after‐hyperpolarizing potential (AHP).

The AHP can speed sodium channel recovery from inactivation, which is faster at more hyperpolarized voltages, so that the channels are more rapidly reset to participate in generating the next action potential.

Action potential threshold is determined by the relative activity of sodium versus potassium channels with an action potential being generated if the sodium influx is larger than the potassium efflux.

Insulating the axon with myelin increases the speed of action potential propagation by limiting action potential generation to small unmyelinated gaps called nodes of Ranvier.

High‐density clustering of sodium channels at the nodes of Ranvier ensures sufficient current is generated to exceed threshold at the next node so that the action potential is faithfully propagated along the axon.
Immunology of Fish
Authors: Fletcher Thelma C , Secombes Christopher J 
Published: February 2010

Abstract

Innate immunity provides some form of defence against pathogens in all multicellular organisms but with cartilaginous and bony fish, although the lowest group of jawed vertebrates, the addition of a classic adaptive immune response becomes apparent. This provides the refinements of specificity for antigen recognition and memory. The T‐ and B lymphocytes are the effector leucocytes, acquiring their antigen‐specific receptors (immunoglobulin for B cells and T‐cell receptor for T cells) in the anterior kidney (bone marrow being absent) and thymus. The B cells are responsible for the production of antibodies that function as different immunoglobulin classes, whereas subsets of T lymphocytes are capable of killing target cells or helping with B‐ and other T‐cell functions. Knowledge of these mechanisms is important for the use and design of vaccines, now so essential for the aquaculture industry, whereas studies of fish immunology contribute to the understanding of the evolution of adaptive immunity.

Key concepts:

Fish possess innate and adaptive immune responses, with classical adaptive immunity present only in jawed vertebrates.

Adaptive immunity allows memory of prior exposure to foreign molecules (antigens), so that on subsequent contact protective mechanisms are more rapidly mobilized: the basis of vaccination.

Lymphocytes mediate adaptive immunity and have surface receptors that recognize antigens, initiating the production of circulating antibodies and the activation of cell‐mediated responses.

The functions of the immune system are similar in fish and mammals although there are differences due to the aquatic physiology and ectothermic nature of fish that provide evolutionary interest.

Leucocyte–antigen interactions take place in immune sites, such as the kidneys, spleen, gills and intestine. Bone marrow and lymph nodes are lacking.

Knowledge of fish immunology is proving essential for the development of vaccines for the expanding aquaculture industry.
Vertebrate Central Nervous System: Pattern Formation
Authors: Vermeren Matthieu , Keynes Roger 
Published: February 2010

Abstract

Deciphering the genetic instructions used by the embryo to establish the spatial order of its neuronal populations and their interconnections is the key to understand the wonderfully complex structure of the adult brain and spinal cord. The vertebrate central nervous system develops from a single ‘plate’ of ectoderm cells that fold into the neural tube. Localized signalling centres are placed at defined positions both outside and within the neural plate and tube, and trigger the differentiation of nerve cells. The centres secrete and combine a variety of morphogens that determine, in time and space, the repertoire of genes expressed by neurons in different regions of the nervous system. Gradients and countergradients of morphogens act along the three principal axes – antero‐posterior, dorso‐ventral and left–right – to regulate and coordinate the appearance of diverse neuronal subtypes in their correct anatomical locations.

Key Concepts:

The central nervous system develops from an epithelial ‘plate’ of ectoderm cells, triggered by molecular signals from the early midline mesoderm (‘neural induction’).

Several localized signalling centres, placed both outside and within the neural tube, coordinate patterning and regional differentiation of the nervous system.

The centres establish gradients and countergradients of a variety of morphogens that generate a patterned array of different nerve cell types.

Morphogen gradients generate discrete changes in the populations of transcription factors expressed by individual cells.

Morphogens have different effects according to the differentiation state of the cells they influence.

Diversity in the nervous system arises from the action of a small set of morphogen families expressed in the right place at the right time, such as: SHH, retinoic acid, Wnts, BMPs/TGFβs and FGFs.
Sjögren's Syndrome
Authors: Jonsson Roland , Brun Johan G 
Published: February 2010

AbstractSjögren's syndrome is a lymphoproliferative disease with autoimmune features characterized by mononuclear cell infiltration of exocrine glands, notably the lacrimal and salivary glands (autoimmune exocrinopathy). These lymphoid infiltrations lead to dryness of the eyes (keratoconjunctivitis sicca), dryness of the mouth (xerostomia) and frequently, dryness of the nose, throat, vagina and skin. Sjögren's syndrome is associated with the production of autoantibodies because B‐cell activation is a consistent immunoregulatory abnormality. The spectrum of the disease extends from an organ‐specific autoimmune disorder to a systemic process (musculoskeletal, pulmonary, gastric, haematologic, dermatologic, renal and nervous system involvement). Sjögren's syndrome may occur alone (primary) or in association with almost any of the autoimmune rheumatic diseases (secondary), the most frequent being rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Sjögren's syndrome also is associated with an increased risk of B‐cell lymphoma development. Current treatments are mainly symptomatic.
Vitamin B12: Disorders of Absorption and Metabolism
Authors: Watkins David , Rosenblatt David S 
Published: February 2010

AbstractDerivatives of vitamin B12(cobalamin) are required for activity of two enzymes:methylmalonylCoA mutase, which catalyses conversion ofmethylmalonylCoAtosuccinylCoAandmethionine synthase, which converts homocysteine to methionine. Cobalamin deficiency results in accumulation of methylmalonic acid and homocysteine in blood and urine. Clinically, deficiency results in megaloblastic anaemia, subacute combined degeneration of the spinal cord, loss of sensation, ataxia, dementia and psychosis. Dietary cobalamin deficiency is rare in developed countries, except for individuals consuming a vegan diet. A more common cause of cobalamin deficiency is pernicious anaemia, an autoimmune disease that results in inability to absorb dietary cobalamin from the intestine. A number of rare genetic disorders have been identified that result in inability to absorb dietary cobalamin, inability to transport cobalamin from the intestine to cells that require it for metabolism, or inability to convert intracellular cobalamin to one or both of its coenzyme derivatives, adenosylcobalamin and methylcobalamin.Key Concepts:Cobalamin (vitamin B12) is required for activity of two enzymes, methylmalonylCoA mutase and methionine synthase, in mammalian cells.Cobalamin deficiency results in accumulation of methylmalonic acid and homocysteine in blood and urine.Clinically, deficiency is characterized by megaloblastic anaemia and neurological problems.Uptake of dietary cobalamin requires the binding protein intrinsic factor, secreted by parietal cells of the stomach, and the intestinal receptor cubam.Autoimmune destruction of gastric parietal cells results in pernicious anaemia.Mutations in the genes encoding intrinsic factor or components of cubam result in heritable cobalamin malabsorption.Peripheral cells take up cobalamin bound to the transport protein transcobalamin by carrier‐mediated endocytosis.Cells convert cobalamin to adenosylcobalamin, required by methylmalonylCoA mutase, and methylcobalamin, required by methionine synthase.Rare mutations affecting genes involved in cobalamin metabolism, result in decreased synthesis of either or both cobalamin derivatives.
Infectious Mononucleosis
Authors: Epstein MA , Rickinson AB 
Published: February 2010

Abstract

Infectious mononucleosis is an acute self‐limiting disease caused by an orally transmitted herpesvirus,

Epstein–Barr virus

. The disease typically involves fever, enlarged lymph glands and malaise, with elevated blood lymphocyte counts that reflect an exaggerated cellular immune response to the infection.

Epstein–Barr virus

is widespread in all human populations and is most often acquired asymptomatically in infancy. However, in affluent societies, primary infection can be delayed until the second or third decade, when 25–50% of those involved may develop symptoms. Hence infectious mononucleosis is typically a disease affecting adolescents or young adults in the Western world. Almost all patients recover completely within a few weeks but rare cases with persistent, even fatal, symptoms do occur and involve those with a pre‐existing immune defect or rare individuals where the virus infection spreads into atypical cell types. There is no obvious association between this virus and so‐called chronic fatigue syndrome.

Key concepts:

Infectious mononucleosis is caused by
Epstein–Barr virus
, an orally transmitted human herpesvirus that is common in all human populations.

Most individuals acquire
Epstein–Barr virus
asymptomatically early in life, then carry the virus for life without undue effect.

Only when primary infection has been delayed until adolescence or young adulthood is there a substantial risk of mononucleosis developing; hence, the disease is largely confined to affluent societies where delayed infection is more common.

Infectious mononucleosis is self‐limiting and ‘immunopathological’ in nature: that is, the symptoms (fever and malaise) are caused not by the virus infection per se, but by the patient mounting an exaggerated cellular immune response to that infection.

Most (but not all) cases with the relevant clinical symptoms and large numbers of atypical mononuclear cells in the blood will be
Epstein–Barr virus
‐related; however, definite diagnosis requires serological testing for IgM antibodies to
Epstein–Barr virus
.

Cases where severe disease symptoms persist are extremely rare and involve either patients with a pre‐existing immune defect or individuals where the virus infection has spread into atypical cell types.

A history of proven infectious mononucleosis brings with it an increased risk of subsequently developing another
Epstein–Barr virus
‐associated disease, Hodgkin lymphoma.
RNA
Structure: Tetraloops
Authors: Cheong Chaejoon , Cheong Hae‐Kap 
Published: February 2010

Abstract

Ribonucleic acid
(RNA) hairpins are among the most common RNA secondary structural elements that are frequently capped by tetraloops. An RNA tetraloop structure is composed of a Watson–Crick base‐paired stem and four loop nucleotides. The structure is compact and stable. The first and the fourth nucleotides form a base pair in most of the tetraloops, leaving two unpaired nucleotides in the loop. A sharp turn in the backbone is stabilized by ribose–base, base–phosphate hydrogen bonds and base stacking interactions. Tetraloops help in the folding of RNA by initiating the process. Additionally, they provide sites for RNA tertiary contacts and for protein binding, facilitating the assembly of
ribonucleoprotein
particles. Certain interactions, some of which are sequence‐specific and others structure‐specific, can be involved in the recognition of tetraloops by proteins and RNAs.

Key concepts:

RNA hairpins play important structural and functional roles in RNA.

Tetraloops help the folding of RNA and provide sites for RNA–RNA and RNA–protein interactions.

U turn motif, a sharp backbone turn in tetraloops, is stabilized by ribose–base, base–phosphate hydrogen bonds and base stacking interactions.