bluuebunny/crossref_metadata_2025_split huggingface dataset:
Borehole images for assessing present day stresses
Authors: Etchecopar Arnaud , Yamada Tetsushi , Cheung Philip 
Published: September 2013

AbstractBorehole images, which are now commonly acquired in the oil industry highlight very precisely damage that affects the borehole wall. Two damage types exist. The first corresponds to drilling operations: corkscrew effect, keyseat, cave etc. The second is related to present day stresses: induced fractures, breakouts or shear on preexisting planes. In addition to the real borehole damage, the acquisition and the processing of the image data may bring confusion in the identification of what is due to stresses. A new processing and filtering method is proposed for identifying the stress induced features and measuring precisely their geometry. Borehole images of two wells drilled in a shaly-sand reservoir particularly tight of the Timimoun basin (Algeria) clearly show that the main parameter that controls the damage geometry is the lithology. The stiffer and tighter is the rock the wider and deeper are the breakouts. To explain this strange behavior it is proposed that long term plasticity redistributes the horizontal tectonic stresses between the layers as a function of their shaliness. Another borehole image from Hassi Messaoud reservoir (Algeria) exhibits strong and progressive variation of the stress state where the well crosses a fault. By analogy to outcrops this perturbation is interpreted as due to a local deviation of the fault plane geometry and not to the average fault orientation itself. Such perturbations are unpredictable apart from images acquired while drilling.Once stress induced features are clearly identified we examine how they can be used for assessing the present day stresses. In a vertical well it is well known that breakouts or induced fractures just provide the azimuth of the principal horizontal stresses as the vertical stress, parallel to the well surface, has no effect on the damage location. In a deviated well the three principal stresses influence breakouts and induced fracture location. Mastin [1988] has clearly demonstrated where breakouts will appear in deviated wells. This location depends on the three following parameters: the horizontal stress azimuth, which stress is vertical and R the shape of the stress tensor. These parameters are exactly the ones that also control the orientation of the shear on a preexisting plane. As a consequence, the observation of a breakout or an induced fracture in a single deviated well does not bring conclusive information on the stress state. But the combination of observations in multiple deviation situations may lead to a clear stress state definition. This is similar to the methods promoted by Jacques Angelier in which slickenside inversion is used for determining the stress tensor. The breakout inversion method applied to 7 wells of a north Ural field drilled with very different azimuth and deviation leads to clear definition of the local stress state. Once the stress tensor parameters are clearly identified, it becomes possible to predict borehole or perforation stability for any well deviations.
Scale effect and impact of discontinuities in the dynamic elastic constants of the Campanian chalk of Bougival (France)
Authors: Porjesz Róbert , Bergerat Françoise 
Published: September 2013

Abstract
Physical properties of in situ rock mass are usually estimated from results obtained through laboratory tests on intact rock samples because the access to in situ rock may be quite challenging. This approach however raises some questions concerning the number of samples needed for reliable result, the validity of the extrapolation of the parameters from centimetre scale to a large rock mass and finally the effect of discontinuities contained in the rock mass.
An underground quarry in Bougival with easy access to metre-scale pillars and the possibility to collect large number of samples has been chosen to analyse the scale effect and the anisotropy of the Campanian chalk. Different experiments have been designed to determine the dynamic elastic properties (Young’s modulus and Poisson’s ratio) based on geophysical approaches: ultrasonic measurements on laboratory samples, and “hammer” seismic measurements in situ. The static Young’s modulus and Poisson’s ratio have been determined through uniaxial compression tests on centimetre core samples.
Pillars with and without visible discontinuities, as well as with various overburden rock thicknesses, have been chosen in order to analyse the possible impact of different heterogeneities on the elastic properties. Core samples of intact chalk, with 40mm to 100mm diameters, have been studied in laboratory. The high dispersion observed on the different results suggests that if only a few tests are analysed, the conclusions may not be representative. A statistical approach is more appropriate to analyse the mechanical properties of the chalk. The dynamic Young’s Modulus and Poisson’s ratio calculated from laboratory samples (centimetres) and in situ rocks (about ten metres) do not reveal any clear impact of size on these elastic properties. The presence of discontinuities has a major impact on both the dynamic Young’s modulus and Poisson’s ratio. Decreasing values of these properties have been observed where discontinuities (fractures, flints) have been detected. Finally, the overburden rock thickness above the underground quarries (from 14m to 50m) seems to have no effect on the mechanical properties; the uncertainty of the measurements, partly due to the heterogeneity of the chalk mass, is likely to be more important than the effect of load on the pillars.
Initiation, geometry and mechanics of brittle faulting in exhuming metamorphic rocks: insights from the northern Cycladic islands (Aegean, Greece)
Authors: Lacombe Olivier , Jolivet Laurent , Le Pourhiet Laetitia , Lecomte Emmanuel , Mehl Caroline 
Published: September 2013

AbstractInitiation, geometry and mechanics of brittle faulting in exhuming metamorphic rocks are discussed on the basis of a synthesis of field observations and tectonic studies carried out over the last decade in the northern Cycladic islands. The investigated rocks have been exhumed in metamorphic domes partly thanks to extensional detachments that can be nicely observed in Andros, Tinos and Mykonos. The ductile to brittle transition of the rocks from the footwall of the detachments during Aegean post-orogenic extension was accompanied by the development of asymmetric sets of meso-scale low-angle normal faults (LANFs) depending on the distance to the detachments and the degree of strain localization, then by conjugate sets of high-angle normal faults. This suggests that rocks became progressively stiffer and isotropic and deformation more and more coaxial during exhumation and localization of regional shearing onto the more brittle detachments. Most low-angle normal faults result from the reactivation of precursory ductile or semi-brittle shear zones; like their precursors, they often initiate between or at the tips of boudins of metabasites or marbles embedded within weaker metapelites, emphasizing the role of boudinage as an efficient localizing factor. Some LANFs are however newly formed, which questions the underlying mechanics, and more generally rupture mechanisms in anisotropic rocks. The kinematics and the mechanics of the brittle detachments are also discussed in the light of recent field and modeling studies, with reference to the significance of paleostress reconstructions in anisotropic metamorphic rocks.
Change of stress magnitudes during the polyphase tectonic history of the Cretaceous Gyeongsang basin, southeast Korea
Authors: Choi Pom-yong , Angelier Jacques , Cadet Jean-Paul , Hwang Jae-Ha , Sunwoo Choon 
Published: September 2013

Abstract
In order to evaluate the change of stress magnitudes in the Gyeongsang basin during its tectonic history, we analyzed multiple faulting episodes in the Barremian-Aptian Hasandong Formation at the Yusu site. As elsewhere in southeast Korea, the recorded sequence consists of a succession of more than fourteen faulting episodes, and the relative chronology shows that a strike-slip faulting episode usually coexisted with a coaxial extensional episode. Likewise, seven couples of synchronous coaxial episodes recognised in the Gyeongsang basin are assigned to seven tectonic events (T_1 to T_7 events). The friction line (in the sense of Byerlee) allows us to determine the ratios between principal stress magnitudes as well as the origin of the dimensionless Mohr diagram. This line can be deduced from tension fractures on fault planes affected by friction and from the lower limit of scattered distribution of the normal stresses vs. shear stresses of faults. Dimensionless failure envelopes drawn for coaxial strike-slip and extensional episodes are adjusted to the experimental Mohr failure envelope derived from rock mechanic tests to determine the complete stress tensors. The maximum principal stress magnitudes of strike-slip episodes show a transition from 169 MPa in the Barremian-Coniacian T_1 Event through 263 MPa and 246 MPa in the T_2 and T_4 events, respectively to 235 MPa in the Quaternary T_7 Event; additional horizontal extension (ΔσT) have changed from −6 MPa in the T_1 Event through −8 MPa in the T_2 Event to −17 MPa in the T_7 Event. Because the studied site is currently exposed, the determined overburden (1.9 km) for the T_7 Event seems to be important, indicating the presumable occurrence of this event during the early Quaternary rather than at the present day.
Physiologic Mechanisms in the Development of Starvation Ketosis in Man
Authors: Grey Neil J , Karl Irene , Kipnis David M 
Published: September 2013

The present study was undertaken to determine whether alterations in ketone body utilization and hepatic production, independent of the FFA load, were also involved in the development of fasting ketosis.
Plasma /β/-OH butyric acid (β-OHB) increased to 2.5-4.5 mM and plasma FFA to 1,000-1,400 μEq/L. in normal weight individuals after five to seven days' starvation and in obese subjects after ten to fourteen days' fasting. Acute elevations of the plasma FFA &gt; 1,500 μEq/L. for sixty minutes in fed normal weight and obese subjects with a fat meal-heparin regimen resulted in peak elevations of plasma β-OHB (0.25-0.45mM), only 10 per cent of that seen during fasting. When plasma FFA were lowered acutely during fasting with the antilipolytic agent Pyrazole to control levels (400-600 μEq/L.), plasma β-OHB decreased 35 ± 5 per cent. Comparable lowering of plasma FFA in normal weight or obese starved subjects given dexamethasone to maintain elevated fasting plasma insulin levels resulted in an 87 ± 3 per cent decrease in plasma β-OHB. Similar studies in obese fasted subjects pretreated with an intravenous infusion of insulin (1.0 U/hr. for eight hours) before receiving Pyrazole resulted in a 65 ± 5 per cent decrease in plasma β-OHB.
Plasma β-OHB half-life, determined after injections of 12 gm. (β-OHB, increased significantly during fasting (110 ± 15 minutes) and was decreased when the fasting subjects were maintained on dexamethasone (65 ± 7 minutes).
These studies indicate that accelerated hepatic ketogenesis during starvation is a result of both enhanced activity of the enzymatic system(s) involved in ketone body production as well as an increased FFA load. The increase in plasma,(β-OHB during fasting reflects not only an accelerated rate of hepatic ketogenesis but also an impairment of peripheral utilization, both processes apparently being sensitive to insulin.
Hormonal Regulation of Glycogen Metabolism in Human Fetal Liver: I. Normal Development and Effects of Dibutyryl Cyclic AMP, Glucagon, and Insulin in Liver Explants
Authors: Schwartz Alan L , Raiha Niels C R , Rall Theodore W 
Published: September 2013

Glycogen accumulates in human fetal liver beginning at the eighth week of gestation. A parallel increase in total glycogen synthase activity is found, although the I-form activity remains low and constant throughout the first two thirds of gestation. Total phosphorylase activity increases slightly during this period, with the proportion in the active form amounting to about one half of the total throughout.
After an initial rapid decline, the glycogen concentration in explants of human fetal liver remained constant for twenty to forty hours at about 20 per cent of the in vivo level. Incubation with glucagon, cyclic AMP (adenosine 3ʹ,5ʹ-monophosphate) or its dibutyryl derivative markedly reduced tissue glycogen concentrations while insulin brought about a small increase. The effect of maximal doses of dibutyryl cyclic AMP and glucagon were the same, and the combination of agents produced no further effect. The response to dibutyryl cyclic AMP was apparent by one hour and maximal by three to six hours, whereas the response to insulin required about six hours to be detected, and it continued for at least eighteen hours. Insulin antagonized the glycogenolytic effect of low doses of glucagon or theophylline but was without significant effect in the presence of high glucagon concentrations. Glucagon stimulated cyclic AMP output from explants, and this effect was further augmented by theophylline.
Insultin had no consistent effect on cyclic AMP output in either the presence or the absence of glucagon or theophylline. Incubation with dibutyryl cyclic AMP resulted in a decrease of glycogen synthase I-form activity, while insulin tended to increase this enzyme activity. In neither circumstance was the proportion of active phosphorylase altered. These results suggest that the regulation of glycogen levels in human fetal liver by cyclic AMP, glucagon, and insulin may entail alterations in the activity of glycogen synthase activity without necessitating alterations in phosphorylase activity.
Cyclic AMP or glucagon was capable of depleting tissue glycogen stores in tissue from fetuses of six weeks’ gestation. Insulin increased tissue glycogen concentrations in tissue from fetuses of seven or more weeks.
Inordinately High Levels of Serum Immunoreactive Insulin in Monoclonal Immunoglobulinemia (On the Problem of “Big, Big Insulin”)
Authors: Sramkova Jarmila , Pav Jaroslav , Engelberth Otto 
Published: September 2013

1. A patient with occasional attacks of hypoglycemia had levels of serum immunoreactive insulin persistently fifty to one-hundred times the normal value. Immunoelectrophoresis revealed presence of monoclonal igG in his serum. The patient's diagnosis was established as paraproteinemic lymphoid and plasmocytic reticulosis proximate to multiple myeloma; insuloma was not found.
2. On gel filtration of native serum, only part of the total immunoreactivity was found in the elution position of crystalline insulin; the major part emerged in the early fractions together with the large proteins. After acidification of the serum, however, practically the entire immunoreactivity was recovered in ethanol extracts and proved to be “little insulin” on gel filtration. Only “little insulin” was also detected after gel filtration of serum incubated with urea.
3. It is suggested that the large component with insulin immunoreactivity obtained in gel filtration of native serum is an insulin-protein complex. The nature of the presumed complex is not clear. It is not a complex of the antigen-antibody type. Insulin “trapping” by monoclonal gamma globulin is considered.
Studies on the Nature and Mode of Action of the Insulin-sensitive Glucoregulator Receptor in the Central Nervous System
Authors: Szabo Olga , Szabo Andrew J 
Published: September 2013

In vivo studies were undertaken in rats to provide evidence for the neural nature, tentative localization and mode of excitation of the insulin-sensitive central nervous system (CNS) glucoregulator center.
In rats under light barbiturate anesthesia minute amounts of insulin injected into the carotid artery resulted in an immediate decrease of the systemic blood sugar. This hypoglycemic action of regional insulinization of the CNS was lost when the animals were subjected to prolonged, deep barbiturate narcosis.
Competitive inhibition of glucose utilization in the CNS region by intracarotid administration of 2-deoxy-D-glucose did not block the systemic hypoglycemic effect of subsequent intracarotid insulin injection. Chronic endogenous hyperinsulinemia produced by daily growth hormone treatment resulted in an insensitivity of the CNS glucoregulator center to exogenous insulin. The ratio of the quantity of the injected insulin and the pre-existent plasma insulin concentration showed direct correlation with the systemic hypoglycemic response that followed intracarotid injection.
Present data support the hypothesis that the insulin-sensitive glucoregulator center located in the area supplied by the carotid artery is neural in nature, because of its inhibition by barbiturate anesthesia. The data are compatible with the working hypothesis that the center is located in the hypothalamus, since light cortical barbiturate anesthesia did not, but deep anesthesia did have an inhibitory effect on it.
Marked interference by chronic hyperinsulinemia suggests that the receptor center estimates the metabolic status of the animal through means related to physicochemical binding of insulin to specific receptors. However, since our attempt to inhibit glucose utilization in the CNS was without effect on the activity of the center, it appears that the signal for the glucoregulatory impulse is not insulin facilitation of glucose utilization in the receptor area, but another parameter of insulin action.
Hyperinsulinemia and Hypoinsulinemia: Insulin Responses to Oral Carbohydrate Over a Wide Spectrum of Glucose Tolerance
Authors: Savage Peter J , Dippe Stephen E , Bennett Peter H , Gorden Phillip , Roth Jesse , Rushforth Norman B , Miller Max 
Published: September 2013

Oral glucose tolerance tests using a 75 gm. carbohydrate load were performed on 396 Pirna Indians. Subjects were divided into groups on the basis of two-hour plasma glucose levels and the patterns of insulin response examined. Two-hour insulin levels were highest in the group with two-hour plasma glucose levels between 140–169 mg./100 ml. and then fell progressively until levels above 400 mg./100 ml. were reached. Half and one-hour insulin levels showed little change in the groups with two-hour glucose levels up to 170 mg./100 ml., but at higher glucose levels these insulin levels also progressively diminished. Fasting insulin levels were relatively unchanged over the entire range of glucose tolerance. Obesity was the most important factor influencing the fasting insulin levels. Glucose level was the major determinant of post-load insulin responses, but these were also significantly influenced by obesity. No effect of age or sex on insulin levels was demonstrated.
Comparison with other published data indicates that different interpretations of insulin response in subjects with “mild diabetes” have resulted from comparisons of groups with different degrees of glucose intolerance.
Plasma and Cerebrospinal Fluid Amino Acid Levels in Diabetic Ketoacidosis Before and After Corrective Therapy
Authors: Aoki Thomas T , Assal Jean Ph , Manzano Francisco M , Kozak George P , Cahill George F 
Published: September 2013

To evaluate the effect of insulin-saline-bicarbonate therapy on amino acid metabolism in diabetic ketoacidosis, arterial and venous blood samples as well as cerebrospinal fluid (CSF) were obtained from six patients before and after initiation of corrective therapy. Levels of CSF glutamine were decreased while alanine, α-amino-n-butyrate, valine, isoleucine and leucine were increased significantly compared to a control group composed of six normal, postabsorptive adults free of any neurologic disease. Following therapy, CSF levels of alanine, α-amino-n-butyrate, valine, isoleucine, and leucine declined while glutamine levels did not change.
Admission arterial plasma levels of the glycogenic amino acids were lower than normal while the branched-chain amino acids were elevated. Plasma alanine and glutamine arterio-venous (A-V) differences across forearm tissue were larger. After four hours of corrective therapy, arterial plasma levels of most of the amino acids had declined sharply and A-V differences for glutamine and alanine were markedly reduced (p &lt;.O25 and p &lt;.O1, paired t, respectively). Coincident with the decrease in A-V amino acid differences, plasma glucagon and free fatty acid levels declined significantly. These data suggest that the effect exerted by insulinsaline-bicarbonate therapy on amino acid metabolism is manifested by diminished A-V plasma alanine and glutamine differences across forearm tissue. Thus, the role played by the splanchnic bed both before and following corrective measures may be secondary to substrate availability.
Influence of Oral Glucose Ingestion on Splanchnic Glucose and Gluconeogenic Substrate Metabolism in Man
Authors: Felig Philip , Wahren John , Hendler Rosa 
Published: September 2013

To evaluate the role of splanchnic and peripheral tissues in the disposal of an oral glucose load, splanchnic exchange of glucose, lactate, pyruvate, glycerol and amino acids was determined in ten healthy subjects in the basal state and for three hours following the oral ingestion of 100 gm. of glucose.
Following glucose ingestion, splanchnic glucose output rose rapidly, reaching values two to three times the basal rate at fifteen minutes and returning to baseline by ninety minutes. A secondary rise in splanchnic glucose output occurred at 150 minutes and coincided with a secondary increment in arterial glucose. Total splanchnic glucose output over three hours was 40 ± 3 gm., representing a total increase of only 15 ± 3 gm. above basal splanchnic glucose output. The peak rise in blood glucose was directly proportional to the increase in splanchnic glucose output.
Arterial concentrations of alanine, lactate and pyruvate rose by 15, 65 and 80 per cent, respectively, following oral glucose. These arterial elevations were preceded by a 75–100 per cent inhibition of splanchnic uptake of alanine and lactate; in the case of pyruvate there was a reversal from a net uptake in the basal state to a significant net splanchnic output after glucose ingestion. Arterial glycerol fell by 50 per cent and was accompanied by a comparable fall in splanchnic uptake.
It is concluded that in normal, postabsorptive man, (a) the major portion of a 100 gm. oral glucose load is retained within the splanchnic bed; (b) only 15 per cent of the ingested glucose is available for disposal by peripheral tissues as increased (abovebasal) glucose utilization; (c) the height and shape of the oral glucose tolerance curve are largely determined by the rate and pattern of splanchnic glucose escape; (d) glucose-induced hyperlactatemia, hyperpyruvicemia and hyperalaninemia are due at least in part, to altered splanchnic exchange of these substrates.