bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of the Production Performance of Three Deep Miocene Oil Pools in the Los Angeles Basin
Authors: Doyle C.L.
Published: December 2007

A review is presented of the production performance of the City zone of the Inglewood city pool, Potrero field; the Wardlow pool of the Long Beach field and the Santa Fe zone of the Santa Fe Springs field. Production is from thick sections of Miocene sands with air permeabilities from 10 to 100 md. The pools have produced at near capacity rates from early in their history; oil recovery to date has been primarily from pressure depletion. Maximum gas-oil ratios were reached at recoveries of 46 to 58 per cent of the gas originally in place and 6 to 10.5 per cent of the oil originally in place. Early oil rate vs oil recovery trends indicate 13.5 to 23 per cent ultimate oil recovery. The Wardlow pool is now producing primarily by gravity segregation and considerably higher ultimate oil recovery is foreseen than was indicated front earlier performance. From a depletion standpoint, the substantial oil recovery following maximum gas-oil is largely due to permeability and mobility ratio variation within the thick section.

Introduction

This paper presents a review of the production performance of three deep oil pools in the Los Angeles basin, Calif., which produce from thick sections of Miocene sand in the low permeability range. The pools are the City zone of the Inglewood city pool, Potrero field, the Wardlow pool of the Long Beach field, and the Santa Fe zone of the Santa Fe Springs field. The location of these pools within the basin is shown in Fig. 1. In reference to the central area of the city of Los Angeles, the Inglewood city pool is 8 miles to the southwest, the Wardlow pool 18 miles to the south, and the Santa Fe Springs field 12 miles to the southeast.

This paper is in the nature of a case history of these pools with the purpose of (1)describing the accumulation, (2)reviewing the oil and gas production performance and the indicated oil recovery efficiency, and (3)comparing the behavior and recovery experience of the three accumulations.
Use of a Downhole Mud Motor as a Pump for Drillstem Testing
Authors: Cobbett James S.
Published: December 2007

The increasing expense and complexity of exploration drilling, coupled with rapid advances in computer and microprocessor technology, have led to the development of computer-assisted wellsite logging units. This paper discusses two methods currently in use for the collection and storage of rig and mud data during drilling and tripping operations and application of these methods to improve wellsite safety and drilling efficiency.

Introduction

Mud logging units first were employed in the search for hydrocarbons in the early 1940's. In the following decade, advances in gas chromatography and electromechanical sensors enabled these same units to measure combustible gases and rate of penetration more accurately. In the latter half of the 1960's, an increase in the number of exploration wells being drilled in more dangerous offshore locations and geologically unpredictable environments, such as the North Sea, led to a growing awareness of the need to improve fig safety and to reduce spiraling drilling costs (Fig. 1). As a result of this need, the monitoring and recording of an ever-increasing number of drilling parameters has become the norm.

Development

In the interests of safety and, in particular, in an attempt to reduce the incidence of loss of life and/or property resulting from blowouts, empirical methods were developed in the mid-1960's to identify abnormal pressure regimes with some of the many drilling parameters recorded. Jorden and Shirley (with later refinement by Rehm and McClendon), for example, developed for the Gulf of Mexico the drilling or d exponent to normalize the effects of weight-on-bit (WOB), rotary speed, and bit size on drill rate and to try to make the d exponent accurately reflect changes in pore pressure. The requirement for instantaneous and accurate measurement of these parameters was extremely important. Furthermore, changes in flow-out, mud weight, and pit level remained important factors in preventing a kick from becoming a blowout. Hence the accurate measurement of the drilling and mud parameters was crucial. Drill monitoring systems included kelly height, fig heave, hook load, WOB, rotary speed and torque, and casing and standpipe pressure. Mud monitoring systems included mud weight, temperature, resistivity, and flow in and out, pump strokes, total pit volume, and trip tank volume. Gas monitoring systems included chromatographic analysis and detection of hydrocarbons, H2S gas, CO2, nitrogen, and oxygen.

Centralization of Data Recordings

One serious drawback was that readings were taken at many different locations on the fig. Mud weight was measured in the pits and on the shakers, the driller's weight indicator displayed WOB, and the geolograph recorded standpipe pressure, torque, rotary speed, and hook load. A separate instrument was used to show changes in pit level.

JPT

P. 2899^
A Study of Solubility of Strontium Sulfate
Authors: Jacques Donald F. , Bourland Brent I.
Published: December 2007

This paper describes the results of a solubility study of strontium sulfate in sodium chloride brine. A predictive equation for the solubility of strontium sulfate is presented, which is useful for calculating solubility in water containing 0 to 200 g/L (0 to 200 g/dm3) sodium chloride at temperatures from 100 to 300° F (38 to 149°C), with pressures from 100 to 3,000 psig (689 to 20 684 kPa), and total ionic strengths of 0 to 3.43. This paper also describes the experimental technique employed and the special equipment designed for this study.
Test Results of a Corrosion Logging Technique Using Electromagnetic Thickness and Pipe Analysis Logging Tools
Authors: Iliyan I.S. , Cotton W.J. , Brown G.A.
Published: December 2007

Recent innovations in subsurface corrosion practices of the Arabian American Oil Co. (ARAMCO) have reduced logging and workover costs substantially and have permitted the detection of corrosion in the outer string of two concentric casing strings.

At the request of ARAMCO, Schlumberger conducted test under both simulated and field conditions. Results showed that the data required to evaluate casing corrosion in a 7-in. × 9 5/8 -in. completion can be obtained during a single logging run using a 21.6-in. coil spacing electromagnetic thickness tool (ETT-A TM) sonde (as opposed to two runs with 17.6-in. and 21.6-in. sondes previously used). In addition, corrosion of the outer string of 9 5/8-in. or 13 3/8-in. casing can be detected by using the results of the ETT-A logs and pipe-analysis tool (PAT) logs or caliper logs.

To date, the application of this technique has been very successful in ARAMCO's operations.

Introduction

For several years ARAMCO has used the ETT-A in conjunction with the multifingered caliper (MFC) tool for monitoring casing corrosion in single strings of both 7-in. and 9 5/8-in. casing. The results of these logs were often the basis for workover recommendations in injection wells and to a greater extent, when run in conjunction with workover operations on producing wells, the basis for additional operations to ensure good wellbore integrity.

In the past, two separate logging runs were made to evaluate corrosion in each of the 7-in. and 9 5/8-in. casing strings. The 17.6-in. coil spacing ETT-A sonde was used in 7-in. casing while the 21.6-in. coil spacing ETT-A sonde was employed in 9 5/8-in. casing. The obvious disadvantage of this technique is the additional cost incurred in making two separate logging runs. An additional disadvantage is the added workover rig downtime.

As corrosion in the near-surface outer string of dual casing strings increased, it became imperative to develop a technique by which corrosion in the outer string could be detected and corrected before complete breakdown of the casing resulted in underground communication or surface leaks.

To this end ARAMCO approached Schlumberger to determine whether any of the corrosion monitoring tools (specifically the ETT-A) then in use could be adapted to detect corrosion in the outer string of two strings of pipe and to determine whether an optimal coil spacing existed that could be used in both 7-in. and 9 5/8-in. casing strings.

Tests were undertaken by Schlumberger in their AlKhobar. Saudi Arabia, shops to determine the optimal coil spacing of the ETT-A and to confirm that this spacing could respond to the total metal of dual casing strings. Once this optimal spacing was determined, it would then be possible to use the ETT-A to check the total metal present, and when run in conjunction with the PAT or MFC, it would be possible to differentiate the corrosion affecting the inner and outer strings.

JPT

P. 801^
Effects of Vaporization and Temperature in Gas/Liquid Relative Permeability Experiments
Authors: Counsil John R. , Ramey Henry J.
Published: December 2007

Liquid vaporization can influence the results of unsteady, external gas-drive relative permeability experiments. At elevated temperatures, liquid vaporization may affect (1) displacing gas mixture volume, (2) displacing gas mixture viscosity, and (3) volumetric liquid saturation calculated from a material balance. Approximate methods are presented to correct laboratory displacement data for the effect of liquid vaporization on displacing gas mixture volume and viscosity. An approximate method also is presented to evaluate the magnitude of liquid saturation reduction caused by liquid vaporization. By use of a modified Jones and Roszelle1 calculation procedure, equations are developed to describe the dynamic displacement of liquid water by nitrogen gas at elevated temperatures. A conventional analysis of three displacement experiments demonstrated the apparent temperature dependence of gas relative permeability. Use of the proposed method indicated that corrected gas and water relative permeability curves are not strongly temperature dependent for the artificially consolidated sandstone cores used in this study.
Design and Development of Electric and Hydraulic Cables for Subsea Wellhead Control in the North Sea
Authors: Everett John W. , Jones Idwal L. , Hill David J.
Published: December 2007

This paper presents a development program, from design formulation to field test, for North Sea wellhead-control cables. Typical design considerations, desired performance data, and actual test results are included for both electric and hydraulic cables. Jointing, terminating, and installation techniques also are discussed.

Introduction

Subsea wellheads operating remotely from a tower or manifold center require electric and hydraulic power and control lines. These systems, some for North Sea installation from 1980 onward, require specially developed cables and terminations.

These cables must maintain a stipulated performance and withstand handling and installation performance and withstand handling and installation operations. They must withstand seabed conditions and, in the unfortunate event of damage by trawler or anchor, be capable of recovery and repair.

Cables against one of several contracts have been manufactured and installed in the North Sea during 1980. This paper discusses the general cable design requirements specified and the prototype development program. The values and design parameters given are not specific to any particular system and should be considered as purely typical results from a wide-ranging program.

Typical Cable Specification Requirements

Typical design and performance data, for both hydraulic and electric cables, are given in Tables 1 and 2 (Figs. 1 and 2).

Various hose liners for the hydraulic cables may be specific for compatability with methanol, glycol, synthetic hydraulic fluids, and mineral oils. Cold flexibility and flammability tests also are called for in some specifications.

Cable Environmental and Installation Requirements

The following list summarizes some of the typical requirements.System operational life of up to 25 years.Both minimum and maximum breaking strains for the cables, about 20 and 40 tons (18 and 36 Mg), to give adequate strength but avoid damage to subsea structures if the cable is dragged.Adequate cable modulus for the water depth of installation, typically about 4 naut. miles (7.4 km).Torque-balanced cable due to J-tube and wellhead cable installation.System life resistance to corrosion and abrasion, and adequate weight in water to give stability.The significant but variable trawl and anchor fault hazard to cables in the North Sea calls for monitoring ship control. Suitably maneuverable cable ploughs now exist.

Cable Design and Development Background

The development team was able to draw on many years of worldwide company experience in the design, development, testing, and installation of underwater electromechanical cables.

JPT

P. 413
Pulse Decay Permeability: Analytical Solution and Experimental Test
Authors: Bourbie Thierry , Walls Joel
Published: December 2007

A new analytical solution is presented for the laboratory pulse decay permeability problem. With this solution, permeability of a core sample can be calculated from the decay rate of a pressure pulse applied to one end of the sample. This development permits rapid, accurate measurement of permeability in samples such as tight gas sands, limestones, and shales.
A Continuous Multistage Fracturing Technique
Authors: Webster K.R. , Goins W.C. , Berry S.C.
Published: December 2007

Wells with multiple producing zones can be fractured one zone at a time during continuous pumping with a high degree of probability of treating all zones by [1] perforating with charges designed to produce round, burr-free holes; [21 perforating the same low number of holes [usually eight] into each zone; [3] perforating in acid; and [4] using sealer balls between frac stages exactly matching in number the holes in each zone.

During field trials of the process, recovered fluid-cut sealer balls indicated that quite often jet perforated holes had poor roundness and ragged burrs preventing good seal. It was necessary to have jet charges and guns redesigned to provide consistently round and burr-free entrance holes. Perforating the same number of holes per zone eliminates the guesswork when determining the number of ball sealers to use per stage. Experience has shown that perforating in acid reduces breakdown pressures, allowing the process to be used in areas where previous fracing indicated the method could not be applied. Using sufficient holes per zone to handle the total pumping rate at a low differential pressure prevents breaking down more than one zone at a time. High differential pressure from too few holes consumes energy and adds to the cost of the treatment. A calculation procedure is used to determine the holes required per zone based on flow rates and total cross sectional area of the perforations.

Radioactive frac sand and gamma ray tracer surveys have been used in conjunction with straddle packers to determine the zones treated. Success ratios calculated as the number of zones fractured divided by the number of fractures attempted have been found quite high in 7–8 zone wells and still greater in wells with fewer zones.

The method is less expensive than treating one zone at a time using isolating packers and is much surer of producing multiple fractures than simultaneously fracing generously perforated multiple zones. Continuous multistage fracturing produces maximum fracture area for a given injection rate as compared with simultaneous injection into multiple zones. The multistage technique also allows use of all the steps considered essential to good, single-stage treating.

Results of field trials have consistently indicated vertical fractures. The fracture orientation has been evidenced by low treating pressure gradients and by gamma ray tracer surveys.

Field work with radioactive propping agents provided a means of checking the quality of the cement job after fracturing.
Characterization of Surfactants Using a Scaling Law Interpretation of Coreflood Residual Oil Saturation Profiles
Authors: Davis L. A. , Tyler T. N. , Brost D. F. , Haskin H. K.
Published: December 2007

The characterization of surfactant candidates for a given reservoir can be improved by the use of linear coreflood residual-oil-saturation profiles measured along the core after chemical flooding. A surfactant formulation's functional relation of oil recovery to slug size can be calculated from a single coreflood with the assumption of a relaxed scaling law.

A volumetric linear scaling approach is developed from laboratory coreflood data. Residual-oil-saturation profiles measured in reservoir material with a microwave absorption instrument support this approximate scaling relation. Analysis of 32 linear surfactant-slug corefloods is presented as additional verification. The limits of this scaling law are defined, with emphasis on the role of mixing and dispersion.

The procedure for using saturation profiles to calculate oil recovery as a function of slug size is developed and a test case is presented. A recovery relation derived from a single coreflood saturation profile is compared with that determined by multiple conventional corefloods.
Geological Heterogeneities Important to Future Enhanced Recovery in Carbonate Reservoirs of Upper Ordovician Red River Formation at Cabin Creek Field, Montana
Authors: Ruzyla Kenneth , Friedman Gerald M.
Published: December 2007

Several different pore systems are present in dolomite reservoir rocks of the Red River formation (Upper Ordovician) at Cabin Creek field, MT. Each system is associated with particular depositional environments and diagenetic regimes. Pore geometry is mostly a function of the size and shape of the dolomite crystals composing the rock matrix. Mean pore-throat size, a statistical measure of pore geometry, increases as porosity percent increases, depending on the type of dolomite. This relationship permits prediction of reservoir pore geometry and a better assessment of recovery efficiency once lithofacies distribution, porosity origin, and diagenetic history have been determined for the reservoir by study of cores and rock thin-sections.
Elevated-Temperature Caustic/Sandstone Interaction: Implications for Improving Oil Recovery
Authors: Sydansk Robert D.
Published: December 2007

Caustic in the form of sodium hydroxide solutions is shown to interact strongly with sandstone at elevated temperature (185°F). Such interaction has substantial influence on the success of secondary and tertiary oil-recovery sodium hydroxide floods carried out in sandstone formations of more ordinary temperatures.

Caustic in the form of sodium hydroxide interacts with sandstone at elevated temperature to promote (1) significant dissolution of the more susceptible silicate minerals, predominantly clay and large-surface-area silica minerals; (2) sandstone weight loss; (3) increased porosity; (4) propagation of significant concentrations of water-soluble silicates, including sodium orthosilicate; (5) in-situ formation of new immobile aluminosilicate material; (6) changes in permeability; and (7) hydroxide ion consumption.

Caustic/sandstone interaction resulting from sodium hydroxide dissolution of silicate minerals is limited by kinetics. The interaction increases with increasing temperature, increasing sodium hydroxide concentration, and increasing caustic/sandstone contact time. The rate and the amount of interaction are sensitive to sandstone mineralogy and lithology. Although not studied during this work, the presence of crude oil, along with crude-oil type, may affect the rate and the amount of interaction.

Based on the laboratory study of elevated temperature caustic/sandstone interaction involving silicate-mineral dissolution by sodium hydroxide, it is concluded that, at lower temperatures, the much slower dissolution interaction has implications for field application of sodium hydroxide for improving waterflood sweep efficiency and enhancing oil recovery. Specifically, during field applications, the slow interaction could deplete the active hydroxide ions. More common low-temperature field applications are especially susceptible because of long caustic/sandstone contact times and because, in general, relatively small concentrations of sodium hydroxide have been used historically. This study points out that proper extrapolation of laboratory caustic-flooding results to field conditions should account for slow kinetic phenomena. The study also helps explain detrimental caustic/sandstone interactions and lower-than-expected oil recoveries experienced during a number of long-duration low-temperature enhanced oil recovery (EOR) field tests and floods.

On the positive side, the dissolution interaction, especially at elevated temperatures, generates in-situ significant concentrations of water-soluble silicates, including sodium orthosilicate. Water-soluble silicates have been reported as candidates for improving oil recovery and for use in preflushes to condition formations for other EOR techniques. Other than noting their in-situ formation and propagation, we did not study the alkaline water-soluble silicates in detail, and they are not discussed.
Some Effects of Stress, Friction, and Fluid Flow on Hydraulic Fracturing
Authors: Hanson M. E. , Anderson G. D. , Shaffer R. J. , Thorson L. D.
Published: December 2007

We are conducting a U.S. DOE-funded research program aimed at understanding the hydraulic fracturing process, especially those phenomena and parameters that strongly affect or control fracture geometry. Our theoretical and experimental studies consistently confirm the well-known fact that in-situ stress has a primary effect on fracture geometry, and that fractures propagate perpendicular to the least principal stress. In addition, we find that frictional interfaces in reservoirs can affect fracturing. We also have quantified some effects on fracture geometry caused by frictional slippage along interfaces. We found that variation of friction along an interface can result in abrupt steps in the fracture path. These effects have been seen in the mineback of emplaced fractures and are demonstrated both theoretically and in the laboratory. Further experiments and calculations indicate possible control of fracture height by vertical change in horizontal stresses. Preliminary results from an analysis of fluid flow in small apertures are discussed also.
Laboratory Investigation on the Effect of In-Situ Stresses on Hydraulic Fracture Containment
Authors: Warpinski Norman R. , Clark James A. , Schmidt Richard A. , Huddle Clarence W.
Published: December 2007

Laboratory experiments have been conducted to determine the effect of in-situ stress variations on hydraulic fracture containment. Fractures were initiated in layered rock samples with prescribed stress variations, and fracture growth characteristics were determined as a function of stress levels. Stress contrasts of 300 to 400 psi (2 to 3 MPa) were found sufficient to restrict fracture growth in laboratory samples of Nevada tuff and Tennessee and Nugget sandstones. The required stress level was found not to depend on mechanical rock properties. However, permeability and the resultant pore pressure effects were important. Tests conducted at bimaterial interfaces between Nugget and Tennessee sandstones show that the resultant stresses set up near the interface because of the applied overburden stress affect the fracture behavior in the same way as the applied confining stresses. These results provide a guideline for determining the in-situ stress contrast necessary to contain a fracture in a field treatment.
Automatic Log Computation at Wellsite-Formation Analysis Logs
Authors: Tixier M.P. , Eaton F.M. , Tanguy D.R. , Biggs W.P.
Published: December 2007

New logs and greater flexibility in electrical well logging applications are now provided by truck-mounted computer systems. These special computers digitize and record on tape the data from well surveys. Simultaneously with the recording of a subsequent log, the computers merge taped data and perform continuous log analysis computation. The optical recordings of these computations provide a rapid means of formation evaluation in the field. Two computer systems have been developed. In one the data are recorded digitally on punched paper tape. The second system records the data digitally on magnetic tape using a format compatible with most digital computers. A major application of the truck-mounted computers systems has been the merging of data from an induction-electrical survey with that from either a sonic or a formation density log. The resulting formation analysis log consists of continuous curves of Rwa, Fr/Fs (or Fr/Fd), and apparent porosity. The location of potential pay zones is more easily and quickly accomplished by scanning these computed logs than by manually performing the many computations required for a similar study. Since computations are automatically performed on all zones, it is unlikely that productive zones will be overlooked. Other combinations of log data are also possible.

Introduction

Several years ago a method was proposed by Tixier, et al., in which simple computations of data from resistivity and sonic logs provide more reliable "quick look" interpretations. These techniques, which involve the manual computation of an apparent water resistivity Rwa and of an Fr/Fs ratio, have been widely used by the industry. The methods use the sonic data to normalize formation resistivities for variations in porosity and shaliness. In the application of the techniques, Rwa and Fr/Fs values are computed and tabulated for many levels. Computations are made not only for zones of apparent interest on the resistivity curves, but also for obvious water-saturated intervals and shaly sections. The tabulated results or, even better, semi-continuous plots, as shown in Fig. 1, focus attention on the zones of interest. Oil- or gas-bearing intervals are indicated by Rwa and Fr/Fs values significantly higher than obtained for water-saturated zones. The log analyst may then concentrate his attention on the formations that offer production possibilities. He can selectively use his more complete and more precise methods of interpretation and, thus, perform the necessary evaluations in the shortest time. These quick look methods are particularly beneficial at the wellsite.

JPT

P. 22ˆ
Experimental Determination of Solids Fraction and Minimum Volumetric Requirements in Air and Gas Drilling
Authors: Machado Carlos J. , Ikoku Chi U.
Published: December 2007

There are so many variables involved in air or gas drilling that one general correlation has not been developed to predict appropriate volumetric requirements in the field. The results of previous attempts to calculate minimum volumetric requirements are valid over limited ranges of drilling conditions.

This research has developed new empirical correlations for solids friction factor for sandstone, limestone, and shale. A new and more realistic technique for predicting minimum volumetric requirements is presented. This method includes a complete analysis of pressures throughout the system. It also offers flexibility in the selection of standpipe pressure, air flow rate, and, thus, compressor specification. The method is primarily graphical, so it can be used at the well site without access to a computer.

Our results confirm that existing methods may predict a volumetric flow rate too low or too high.

Introduction

In the late 1940's, air or gas drilling began, which can be defined as a technique that utilizes air or gas as the circulating medium. However, the injection of compressed air as a circulating medium has been in common use since the late 1800's.

Air (gas) is the ultimate low-density drilling fluid. Optimal results and greatest economy from air or gas drilling depend on several factors. Hard formations that are dry or produce relatively few formation liquids provide the best results. In air and gas drilling, the particles transported in the annular flow stream are of various sizes, shapes, and densities; therefore, each particle has a different terminal velocity in a determined medium. The particles are disintegrated during removal by the turbulent flow in the annulus and the grinding action of the drill stream; thus, the distribution of particle sizes varies at different levels in the annulus.

Equations governing the settling of rock particles and volume requirements for air drilling have been given by many researchers. The important relationship between the control of fluid properties and adequate hole cleaning was addressed first by Piggot in 1941. He applied modified forms of Stokes' law for viscous flow and Rittinger's formula for turbulent flow to predict terminal settling velocity.

JPT

P. 2645^
A Proposed Model for Multiphase Flow Through Naturally Fractured Reservoirs
Authors: Evans Ronald D.
Published: December 2007

A general mathematical model is derived that may be used to describe fluid movement through naturally fractured reservoirs. The model treats the reservoir as a double-porosity medium consisting of heterogeneous, isotropic primary rock matrix blocks and an anisotropic, heterogeneous fracture matrix system. The fractures are assumed to have a general distribution in space and orientation called the fracture matrix function to represent their statistical nature. Simplifying assumptions are made concerning flow in individual fractures, and a hemispherical volume integration of microscopic fracture flow equations is performed to arrive at a generalized Darcy-type equation, with a symmetric permeability tensor evolving to describe the flow in the fracture matrix. For flow in the primary rock matrix blocks, Darcy's law for an isotropic medium is assumed.

Time-dependent porosity equations for the primary rock matrix and the fractures are derived and coupled with the conservation of mass principle for each system to arrive at a governing set of continuity equations. Each resulting continuity equation is coupled further by a fluid interaction term that accounts for fluid movement that can take place between rock matrix blocks and fractures. The resulting equations of continuity and the equations of motion are generalized for multiphase flow through the fractured medium with variable rock and fluid properties. To complete the model formulation, a general set of auxiliary equations are specified, which can be simplified to fit a particular application.
An Oscillating Backpressure Regulator for Low Flow Rate, High-Pressure Coreflooding Experiments
Authors: Lease W. O. , Van Egmond C. F.
Published: December 2007

An oscillating back pressure regulator (OBPR) has been developed that is capable of accurately controlling backpressures as high as 6,000 psi at flow rates ranging from approximately 1 to 100 mL/hr. It has been applied successfully in CO2/crude oil coreflooding experiments involving the simultaneous flow of three fluid phases. The device is assembled easily from off-the-shelf components.
Genome size microscale divergence of Cyclamen persicum in Evolution Canyon, Israel
Authors: Pavlíček Tomáš , Bureš Petr , Horová Lucie , Raskina Olga , Nevo Eviatar
Published: December 2007

Using DAPI flow cytometry, we examined genome size divergence of the Persian violet, Cyclamen persicum (Primulaceae) (2n=48) on close opposite slopes of Evolution Canyon (EC), Mt. Carmel, Israel. The range of genome size variation detected among measured cyclamens was 6.41% in relation to the smallest measured DNA content. Our data on C. persicum at EC showed that local variability in the 2C-value exists. Significantly less DNA was recorded in plants growing in one station of the African savannah-like south-facing slope (AS) but not in the remaining two stations of the same slope. We were not able to reject the null hypothesis that there are no significant interslope differences in the genome size between the temperate European garrigue-like north-facing slope (ES) and the drier AS. In spite of the nonsignificant interslope trend for the higher genome size in C. persicum, the data-fusion (meta-analysis) test using correlations between C-values in C. persicum, and earlier studied carob tree (Ceratonia siliqua), trifoil (Lotus peregrinus) and a beetle (Oryzaephilus surinamensis) and their distribution along the aridity gradient indicates a positive relationship between drought and genome size at the microsite.
Coronary angiography and dual-source computed tomography are complementary methods in diagnosis of significant stenosis of the right coronary artery originating from the left aortic sinus
Authors: Veselka Josef , Zemánek David , Duchoňová Radka , Blaško Peter , Adla Theodor , Tesař David , Neuwirth Jiří
Published: December 2007

Anomalous origin of the right coronary artery from the contralateral aortic sinus is a rare but potentially fatal congenital abnormality. We analyzed 8.066 consecutive coronary angiograms and found 4 cases demonstrating this anomaly. In 2 cases the right coronary artery was without significant atherosclerotic lesions and coursed between the aorta and pulmonary trunk. In the 2 other cases the right coronary artery was significantly stenosed. In the last case, diagnosis was based on angiographic and dual-source computed tomographic examinations. Dual-source computed tomography showed precisely the origin and course of the right coronary artery between the ascending aorta and pulmonary artery. Moreover, stenoses of the anomalous coronary artery were depicted. Subsequent coronary interventions required modification of the Amplatz left guiding catheter, which enabled a sufficient support even for coronary artery stenting. Both methods seem to be complementary in the diagnostic and therapeutic process of this coronary anomaly.
Successful discontinuation of insulin treatment after gestational diabetes is shown to be a case of MODY due to a glucokinase mutation
Authors: Talapatra Indrajit , Kalavalapalli Shyam , Robinson Jonathan , Ellard Sian , Tymms David
Published: December 2007

We describe a woman who first presented with gestational diabetes at 26 weeks gestation and was managed with insulin. Following delivery of a healthy baby she had an abnormal OGTT (oral glucose tolerance test) 6 weeks post partum and was managed with diet. In her second pregnancy she was diagnosed with gestational diabetes at 10 weeks and required insulin. Following delivery she was again managed on diet alone. Four years later, during her third pregnancy, she was managed with insulin from the outset. She remained on insulin post partum and for several years. Later her two younger children, aged 11 years and 7 years, were found to have GCK mutation causing MODY (Maturity Onset Diabetes Of the Young) subtype glucokinase. Following this she underwent molecular genetic testing and was also shown to have the GCK mutation. She was gradually taken off insulin and is now managed on diet alone with excellent glycaemic control. Her two children are under regular follow up care and on no medication for diabetes.
Technology and characterisation of GaAsN/GaAs heterostructures for photodetector applications
Authors: Ściana B. , Zborowska-Lindert I. , Pucicki D. , Boratyński B. , Radziewicz D. , Tłaczała M. , Serafińczuk J. , Poloczek P. , Sęk G. , Misiewicz J.
Published: December 2007

The nitrogen-containing conventional AIIIBV semiconductor alloys, so-called diluted nitrides (AIIIBV-N), have been extensively studied recently. Unusual properties of these materials make them very promising for applications in lasers and very efficient multijunction solar cells. This work presents the technology and properties of undoped GaAs1-xNx/GaAs heterostructures used as active regions in the construction of metal-semiconductor-metal (MSM) photodetectors. The atmospheric pressure metal organic vapour phase epitaxy (APMOVPE) was applied for growing MSM test structures. Their structural and optical properties were examined using high resolution X-ray diffraction (HRXRD), photoluminescence (PL), and photoreflectance spectroscopy (PR). Chemical wet etching was applied for forming an active region and a multifinger Schottky metallization was used as MSM contacts. Dark and illuminated current-voltage characteristics were measured. Based on the obtained results, the main detector parameters as responsivity and spectral response were estimated
Temperature dependence of linear electrooptic coefficients r 113 and r 333 in lithium niobate
Authors: Górski P. , Ledzion R. , Bondarczuk K. , Kucharczyk W.
Published: December 2007

A new method of determination of individual linear electrooptic coefficients is proposed. The technique is based on the dynamic polarimetric measurements and takes into consideration the temperature dependences of ordinary and extraordinary refractive indices. Results obtained for the electrooptic coefficients r113 and r333 in LiNbO3 are presented. The coefficients are found to increase significantly within the considered temperature range 25-200°C. The temperature dependences of the intrinsic coefficients m113 and m333, defined in terms of the induced polarisation, are considered as well.
Analysis of quadratic electrooptic response of BaTiO3 crystal in ferroelectric phase
Authors: Izdebski M. , Kucharczyk W.
Published: December 2007

Using the example of BaTiO3 in a ferroelectric phase it is shown that a large difference in magnitudes of individual linear electrooptic coefficients may be a reason of additional indirect quadratic contributions that are independent of real quadratic coefficients. For some directions of the applied field and light, the indirect contributions may be even larger than the real quadratic ones. Independently of nonlinear distortions that can affect applicability of technical devices, a large difference between linear electrooptic coefficients may lead to serious problems in measurements of the real quadratic electrooptic effect. The analysis is based on the extended Jones matrix calculus applied to a Gaussian beam.
Density‐functional Theory of Magnetism
Authors: Bihlmayer Gustav
Published: December 2007

This chapter gives an outline of density‐functional theory (DFT) and its applications in the field of magnetism in the solid state. The basics of non‐spin‐polarized DFT and vector‐spin DFT are presented. Successes and limitations of different approximations to the exchange‐correlation functional, in particular the local‐density approximation (LDA), or the generalized gradient approximation (GGA) are discussed. The main focus in this chapter is on spin magnetism, but orbital magnetism and relativistic effects (magnetocrystalline anisotropy) are briefly introduced. Several methods, that can improve the description of localized states, for example, the self‐interaction correction or the LDA+Umethod are presented, as well as the orbital polarization (OP) technique, which can improve the underestimation of orbital moments in LDA or GGA. The relation to other theoretical methods, that is,GWor the dynamical mean‐field theory (DMFT), is indicated. Special techniques, like adiabatic spin dynamics, constrained local moment calculations and the treatment of incommensurate spiral spin‐density waves are presented. They can be used to determine the magnetic ground state or to extract exchange interaction constants from density‐functional calculations. Applications, for example, the calculation of the spin stiffness or the Curie temperature finally illustrate the predictive power of the theory.
The
K
ondo Effect
Authors: Jones Barbara A.
Published: December 2007

A review is presented of the Kondo effect, with a summary of key experiments and theoretical treatments. Hamiltonians surveyed, in addition to the single‐impurity spin‐1/2 Kondo model, are multichannel Kondo models, the Coqblin–Schrieffer model, two‐impurity problems, including two‐channel, two‐impurity, the Anderson model, and a brief summary of the Kondo lattice. Exact, known results are a focus. Non‐Fermi‐liquid fixed points are a feature of more than one Kondo Hamiltonian, and the phases of these systems can be unusual and quite interesting. Techniques surveyed include scaling, numerical renormalization group, 1/
N
expansion, Bethe ansatz, and conformal field theory. We conclude with a review of the scanning tunneling microscope experiments on Kondo systems, one of the best current realizations of few‐impurity Kondo models, and a source of often surprising new physics.
Magnetic Spectroscopy
Authors: Ebert H.
Published: December 2007

Electron spectroscopic methods are indispensable tools to study magnetic solids, as they can be used to monitor their magnetization in a spatial time‐resolved way and partly in an element‐resolved way, as well as to probe their electronic structure in a most detailed way. This contribution gives an overview on three representative and important techniques widely used for these purposes: magneto‐optics, X‐ray absorption, and photoemission spectroscopy. The theoretical basis for dealing with these spectroscopies is presented putting some emphasis on the consequences of spin‐orbit coupling, as this relativistic effect often plays a central role. After introducing the main concepts for each type of spectroscopy, some illustrative examples are presented.
Dissipative Magnetization Dynamics Close to the Adiabatic Regime
Authors: Fähnle Manfred , Steiauf Daniel
Published: December 2007

The article reviews the theory of dissipative spin dynamics close to the adiabatic regime, which encompasses the timescales from several picoseconds to several nanoseconds typical for long‐wavelength spin waves, for ultrafast magnetization dynamics of the domain walls, or for field‐ and current‐induced switching processes in nanostructures. The emphasis is on single‐phase systems, but links to magnetization dynamics in multilayer systems are also given. After an introduction of the appropriate magnetic dynamical variables for various experiments, the concept of dissipation is discussed. Two situations without damping, that is, the case of infinite electronic scattering time and the case of zero electronic scattering time (‘strictly adiabatic limit’) are considered, and the various physical mechanisms leading to finite scattering times are surveyed qualitatively. Two quantitative models for dissipative spin dynamics are discussed, the s–d model and the breathing Fermi surface model. The latter model is a very powerful tool to describe dissipative spin dynamics in metallic magnets for the limit of small scattering times, and it can be combined with the modern state‐of‐the‐art electronic density‐functional theory. The results of such calculations are reviewed, with special emphasis to the startling properties of damping in systems with reduced dimensionality. The status of the development of parameter‐free,ab initiospin dynamics simulation codes is discussed, and finally concluding remarks and perspectives are given.
Enhanced Magnetoresistance
Authors: Zahn Peter , Mertig Ingrid
Published: December 2007

The phenomenon of giant magnetoresistance (GMR) found in metallic multilayers will be discussed as an example for enhanced magnetoresistance in artificially structured systems. Theoretical formalisms based on ideas of Boltzmann, Landauer, and Kubo are capable of describing the electronic transport in layered structures and have been sketched in this chapter. The microscopic origin of GMR, the coherent band structure of the system, and the scattering at defects and imperfections are discussed by means of
ab initio
calculations based on density‐functional theory (DFT). Trends for the spin asymmetry of scattering will be given in comparison with the resulting resistivities and GMR ratios for the standard systems of magnetoelectronics.
General Micromagnetic Theory
Authors: Kronmüller Helmut
Published: December 2007

The objective of this contribution is a review of the principles of the continuum theory of micromagnetism and to show its applications to the main static and dynamic problems of ferromagnetic materials. Micromagnetism as a continuum theory closes the gap between quantum theory, dealing with atomic scales and the Maxwell theory dealing with macroscopic dimensions. Micromagnetism therefore corresponds to the tool to deal with nano‐ and microscales. Micromagnetism has become an indispensable theory for a fundamental understanding of magnetic domain configurations, magnetization processes and the interaction between magnetization and microstructures. After Landau–Lifshitz's wall calculations in 1935 and Brown's publication of the so‐called Brown's micromagnetic equations in 1940/1941, micromagnetism became the standard method to analyze the basic magnetic properties of ferromagnetic materials in the range of nano‐ and microscales.

The following review gives a brief presentation of the different energy terms involved in the magnetic Gibbs free energy and a derivation of the micromagnetic equilibrium conditions and of the effective field. Some characteristic applications illustrate the effectiveness of micromagnetism in the case of domain walls, nucleation problems, interaction with microstructures, domain patterns, and the dynamics of magnetization processes.

This contribution also gives a definition of the different exchange lengths related to dipolar fields, magnetocrystalline anisotropy energy, magnetostatic energy of external fields and the magnetoelastic coupling energy.

Whereas only a few cases exist where analytical solutions of the highly nonlinear micromagnetic equations are available the progress in computational micromagnetism allowed the numerical solution of many open problems, which will be treated in the following contributions by Miltat
et al.
, Schrefl
et al.
and D. Goll.
The Motion of Domain Walls in Nanocircuits and its Application to Digital Logic
Authors: Cowburn Russell P.
Published: December 2007

Magnetic nanowires form excellent structures for transmitting magnetic domain walls around a network. If the magnetization direction within magnetic domains is taken to represent data values, the nanowires can be used to transport information around an integrated circuit. Furthermore, careful shaping of the nanowires allows Boolean logic functions to be performed on the information, resulting in a nontransistor implementation of digital logic. In this chapter, experimental demonstrations are shown of all of the basic Boolean logic gates, as well as of nanocircuits containing multiple gates. The advantages and limitations of domain‐wall logic are discussed, and the possibilities of ultrahigh‐density three‐dimensional data storage are demonstrated.
Spin Structures and Spin Wave Excitations
Authors: Zaliznyak Igor A.
Published: December 2007

Electronic spin interactions and the resulting spin structures which give rise to various kinds of magnetism existing in many‐electron condensed matter systems are discussed. In most cases, spin structure and excitations in a spin system can be understood in the framework of semiclassical spin‐wave theory. Basic examples observed in magnetic neutron diffraction and inelastic magnetic neutron scattering experiments are presented and discussed with reference to such description. Relationship between the structure of the crystal lattice and spin arrangement and energy dispersion of spin excitations in the crystal are discussed and illustrated by some recent experimental results.