bluuebunny/crossref_metadata_2025 huggingface dataset:
Productivity Impairment of Openhole Gravel Packs Caused by Drilling-Fluid Filtercake
Authors: Hodge R. , Burton R. , Fischer C. , Constien V.
Published: February 2010

One of the many benefits of installing open-hole completions in high angle or horizontal wells is higher well productivity compared to cased and perforated completions. This is particularly true in applications requiring down-hole sand retention. However, earlier studies have shown that productivity of open-hole completions can be impaired by drilling fluid filtercake or filtercake residue. Unfortunately, to obtain a complete gravel pack in an open-hole section, it is necessary to leave the filtercake intact. Once the gravel is placed, this filtercake becomes trapped between the borehole wall and the gravel pack. The final disposition of this filtercake layer has been the source of much speculation over the past 10 - 15 years. Many proponents of open-hole gravel packing contend the filtercake ultimately disperses into discrete components and passes through the gravel pack and screen without impairing productivity. Others suggest that the filtercake is more tenacious and is breached in random, limited locations along the length of the completion leaving the majority of the filtercake intact. If the filtercake is not effectively removed and inflow area is significantly reduced, areas of concentrated flow commonly referred to as "hot-spots" can be created leading to impaired productivity and/or completion failure.

This paper presents a laboratory investigation of open-hole gravel pack impairment from drilling fluid filtercake conducted under simulated down-hole conditions. A limited number of commonly-used Drill-in Fluid (DIF) formulations were selected for this study along with unconsolidated, formation sand samples obtained from whole core. Gravel sizes used in the study were based on the median grain size of the formation sand and ranged from conservatively sized (D50/d50 ~ 2.0) to aggressively sized (D50/d50 > 8). Results of the tests show the extent of filtercake damage to both the formation sand and the gravel pack as well as the depth of permeability reduction. Finally, the benefit of placing a remedial treatment in the open-hole section following the gravel pack is discussed.
Formation Damage and Impact on Gas Flow Caused by Biofilms Growing Within Proppant Packing Used in Hydraulic Fracturing
Authors: Bottero S. , Picioreanu C. , Enzien M. , van Loosdrecht M. C. , Bruining H. , Heimovaara T.
Published: February 2010

Formation damage as a result of hydraulic fracturing of unconventional gas reservoirs is known to occur by many speculated processes such as: filter cakes on fracture faces, matrix swelling, cleat plugging, gel damage and water blocking. In low permeability matrices, capillary forces can also prevent effective dewatering and result in water blocking of gas flow. Another type of formation damage that may be qualitatively understood but not quantified is the impact of biofilms. This paper combines two micro-scale modeling techniques to evaluate and predict the effects of biofilms on proppant packed fractures in unconventional gas reservoirs. Both a two phase flow model for gas and liquid and a modern cellular automaton biofilm model were combined to simulate the impact on gas flow rates in biofouled propped fractures. Initial simulations of just two phase flow without biofilms but varied proppant surface wettabilities, indicated that hydrophobic proppant surfaces provide better dewatering than hydrophilic surfaces. Gas flow rates dropped in half when biofilms were added to the model at a pore volume of approximately 10%. In addition, further modeling indicated even the same biofilm volume but different distribution within grains and pore-throats can impact gas flow rates as much as 10%. It is hoped that this work will help hydraulic fracturing engineers improve their fracture designs and subsequent treatments to maximize gas flow rates from their assets.
A Flow Simulator for the Design of Extreme-Length Gravel Packs Utilizing Alternate-Path Technology
Authors: Rao B. N. , Amin A. M.
Published: February 2010

A transient flow simulator has been developed for the design of extreme length (5000 ft or longer), horizontal gravel pack operations. The flow simulator incorporates alternate path technology concepts which include shunt tube hydraulics to bypass bridges/barriers in the well/screen annulus.

Alternate path technology has been successfully utilized for sand control in deep water wells and, over the past decade, this technology has been applied in gravel pack intervals up to about 3000 ft. Very recent works (Barry et al. 2007; Yeh et al. 2008) have reviewed the development of alternate path technology and presented the mechanics of slurry diversion in a revised design of the multiple-shunt manifold system for extending gravel pack operations to extreme lengths of 5000 ft or greater.

In this paper, the revised design of the multiple-shunt manifold system (Barry et al. 2007; Yeh et al. 2008) is incorporated in the development of the transient gravel pack flow simulator. The shunt tube hydraulics for various slurry front locations in the well/screen annulus during gravel packing is depicted in example simulations. Results from the simulations are discussed from both steady-state and transient view points. Steady-state results include the variation of pressure and shunt tube flow rates with measured depth. Transient results are presented as variations of pump pressure, crossover tool pressure, and slurry front location with elapsed time. These simulations provide some insight into the shunt tube hydraulics and associated packing mechanism as well as key pressures during gravel packing.

The flow simulator can be utilized to plan and design horizontal gravel pack operations in extremely long intervals in combination with emerging technologies such as openhole gravel packing with zonal isolation or selectively gravel packing targeted intervals using alternate path technology.
Influence of Acid-Fracture Fluid Properties on Acid-Etched Surfaces and Resulting Fracture Conductivity
Authors: Pournik M. , Gomaa A. , Nasr-El-Din H. A.
Published: February 2010

While experimental studies have shown acid type significantly influences resulting fracture conductivity, there has been limited work on how fluid properties relate to etched fracture faces and hence the resulting conductivity. The effects of acid solutions injected into hydraulic fractures created in carbonate formations can be assessed at the laboratory scale in acid fracture conductivity tests that mimic the conditions in an actual acid fracture treatment.

Many different acid systems are currently applied in acid fracturing treatments with various degrees of success. However, there is no clear understanding of the mechanisms that lead to success of a treatment. It is clear that acid properties influence and shape the success of an acid fracturing treatment. In order to develop a better methodology for design of acid fracturing treatments, the effect of acid fluid properties on the resulting conductivity and etching must be determined. A series of acid fracture conductivity tests was conducted using four commonly used acid fracturing fluids—gelled, in-situ gelled, emulsified, surfactant-based acid. Detailed rheological properties were measured in order to explain trends noted with conductivity data.

Acid system influences the degree of etching and the etching pattern due to differences in chemical and physical properties of acid systems. Under our experimental conditions, viscoelastic acid generated the greatest degree of etching and best etching pattern. Majority of experiments showed differences in conductivity among acid systems tested with most optimal acid system depending on the closure stress. While viscoelastic acid generated the highest conductivity at low closure stress, emulsified acid resulted in the largest retained conductivity at higher loads for our experimental conditions. Furthermore, effluent analysis on both the leakoff and fracture flow showed that most of the fracture face etching is the result of leaked acid into the formation with minimal etching from the fracture flow acid.
Modelling Well Inflow Potential in Three Dimensions Using Computational Fluid Dynamics
Authors: Byrne M. T. , Jimenez M. A. , Rojas E. A. , Chavez J. C.
Published: February 2010

Conventional well inflow modeling fails to capture the complexity of flow in to wells from asymmetric near wellbore permeability distribution. In order to simulate flow in to horizontal wells with varying degrees of damage along the well and around the circumference a complex numerical model is required. Computational fluid dynamics enables fluid flow in to the well to be modeled.

Along a horizontal well the magnitude and depth of mud cake, filtrate invasion and formation damage will vary. Longer exposure times at the heel of a well and lower drawdown at the toe will lead to different formation damage, clean-up and inflow patterns along the well. In addition, gravity can have a profound effect on damage distribution at the base, middle and top of the well. Thicker mud cakes will tend to develop at the base of the well and whilst there may be more erosion on the low side, this will only serve to compound the damage by leading to deeper mud invasion. Inevitably, formation damage will have an asymmetric distribution along and around the well. Asymmetric models of fluid flow in to horizontal wells have been created to reflect the damage heterogeneity.

Results of the models have shown that even in homogenous reservoirs, the vast majority of inflow in to the well is derived from the high side of the heel of the well. Modeling shows the potential impact of consistent chemical clean-up and of inflow control along the horizontal well. By fully capturing the magnitude and impact of damage in conventional wells using computational fluid dynamics, the value of well drilling and completion options such as underbalance drilling and hydraulic fracturing can be evaluated.

This paper presents the first use of complex three dimensional computational fluid dynamic models to predict and mitigate against asymmetric formation damage in horizontal wells.
Impact of Organic Acids/Chelating Agents on the Rheological Properties of an Amidoamine Oxide Surfactant
Authors: Li L. , Nasr-El-Din H. A. , Crews J. B. , Cawiezel K. E.
Published: February 2010

Surfactant-based acids have been used for acid diversion because they are less damaging to the formation. Amphoteric viscoelastic surfactant is the main type of surfactants being used today. Low viscosity is observed in the live acid systems, whereas significantly increased viscosity is found when HCl reacts with carbonate and generates divalent salts. The surfactant-acid system can be broken after acid treatments by mixing with reservoir hydrocarbons, or by using an external or internal breaker.

Amidoamine oxide, an amphoteric surfactant, was examined in this work. The prepared surfactant-based live acid system contained 20 wt% HCl, 4 wt% surfactant and 1 wt% corrosion inhibitor. Different organic acids/chelating agents were added to live and spent acids. Calcium carbonate particles were used to neutralize live acids. The objective was to examine how these organic acids/chelating agents affected the rheological properties of spent acid systems. Measurements were made at temperatures from 75 to 200 °F, at a shear rate of 10 s-1 at 300 psi. Several simple organic acids (formic acid, acetic acid, propionic acid, and butyric acid), chelating agents (glycolic acid, lactic acid, gluconic acid, citric acid, tetrasodium EDTA, tetrasodium GLDA and disodium HEIDA) that are used in the field were examined.

Experimental results indicated that the addition of organic acid/chelating agents significantly reduced the viscosity of spent acids. This reduction in viscosity increased with the number of carbon atoms in the acid. The addition of organic acids reduced the temperature range where the surfactant can be used. Chelating agents (α-hydroxyl carboxylic acids and amino acids) also tended to break the surfactant gel if enough acid was used. Based on the results obtained, organic acids can be used to break surfactant gel. TEM tests were first conducted to examine how organic acids/chelating agents interfered with the formation of rod-like micelles in the surfactant-based acid. The results showed that the addition of organic acids to the spent acid generated less elongated micelle structures and resulted in less apparent viscosity. In addition, if chelating agents or simple organic acids are used, then the concentration of the surfactant should be increased to compensate for the loss of viscosity induced by the addition of the organic acids.
New Filtration-Control Polymer for Improved Brine-Based Reservoir Drilling-Fluids Performance at Temperatures in Excess of 400°F and High Pressure
Authors: Ezell R. G. , Ezzat A. M. , Turner J. K. , Wu J. J.
Published: February 2010

Brine-based reservoir drilling fluids are a special class of fluids designed to minimize formation damage, provide the necessary hole cleaning, help reduce wellbore cleanup time and cost, and allow reservoirs to be produced to the maximum of their potential. These fluids should address the wide range of difficulties frequently encountered in horizontal drilling, completion, and workover operations. Filtration control chemicals for currently available drill-in fluid systems exposed to extremely high bottomhole temperatures and pressure conditions are not effective or stable for drilling long horizontal sections of the reservoir. Failure to secure a low filtration rate and thin wallcake causes stuck pipe and loss of expensive downhole tools.

Conventional fluid loss control additives for high performance brine-based drill-in fluids include nonionic water soluble polymers, such as starches, derivatized starches, gums, derivatized gums, and cellulosics. Cross-linked starches are often considered the benchmark of performance for utilization in reservoir fluids, but they do not have the thermal stability required for successful deployment at temperatures exceeding 300°F for extended contact periods.

Conventional linear synthetic polymers are also utilized, but oftentimes they require another additive, such as phyllosilicate particles, to be able to effectively function as fluid loss control additives. The use of clay can be problematic in drill-in fluids, as removing the clay from the formation can be difficult because it infiltrates into pores. Furthermore, the addition of the linear synthetic polymers dramatically increases the viscosity of the fluid, which can result in increased equivalent circulating densities (ECD) and decreased drilling rates.

Through advanced synthetic polymer techniques, a novel polymeric fluid loss control additive has been developed for brine-based reservoir drill-in and completion fluids. The new polymer provides enhanced thermal stability to temperature in excess of 400°F in monovalent and divalent halide brines. This paper presents detailed fluid formulations and discusses the polymer evaluation data under simulated downhole HPHT conditions.
Quantitative Theory for Fines Migration and Formation Damage
Authors: Bedrikovetsky P. , Siqueira F. D. , Furtado C. , de Souza A. L.
Published: February 2010

Particle detachment from the matrix during suspension transport in porous media was widely observed for laboratory corefloods and flows in natural reservoirs. A new mathematical model for detachment of particles is based on mechanical equilibrium of a particle positioned on the internal cake in the pore space. The torque balance of drag, electrostatic, lifting and gravity forces, acting on the particle from the matrix and the moving fluid, is considered. The torque balance determines maximum retention concentration during particle capture. The particle torque equilibrium is determined by dimensionless ratio between the drag and normal forces acting on the particle on cake surface. The maximum retention function of the dislodging number closes system of governing equations for colloid transport with particle release.

One-dimensional problem of coreflooding by suspension accounting for particle release allows for exact solution under the assumptions of constant filtration coefficient and porosity. The explicit formulae permit the calculation of the model parameters (maximum retention concentration, filtration and formation damage coefficients) from the history of the pressure drop across the core during suspension injection. The values for maximum retention concentration, as obtained from two coreflood tests, have been matched by torque balance on the micro scale.
Optimization of Osmotic Dehydration Process of Aonla Fruit in Salt Solution
Authors: Alam Mohammed Shafiq , Singh Amarjeet
Published: February 2010

For optimization of osmotic dehydration process of aonla fruit in salt solution by response surface methodology, the experiments were conducted according to Box and Behnken design. The independent process variables for osmotic dehydration process were osmotic solution concentrations (5-25% w/v salt), osmotic solution temperature (30-60°C), solution to fruit ratio (4-8 v/w), and process time (60-240 minutes). The osmotic drying process was optimized for maximum water loss, overall acceptability and minimum solute gain, colour change, and vitamin-C loss. The optimum conditions were 22% salt concentration, 44.5°C osmotic solution temperature, 6.5 solution to fruit ratio, and 60 minutes process time. An analysis of variance (ANOVA) revealed that, among the process variable, concentration has the most significant effect on water loss, solute gain, and overall acceptability; solution temperature has the most effect on colour change; and process time has the most effect on vitamin-C loss whereas solution-to-fruit ratio observed significantly lower effect on responses.
Antihemolytic and antioxidant activities of Allium paradoxum
Authors: Ebrahimzadeh Mohammad , Nabavi Seyed , Nabavi Seyed , Eslami Bahman
Published: February 2010

Antioxidant activity of the aerial part and bulbs of Allium paradoxum was investigated by eight in vitro assay systems. Extracts showed good antioxidant activity. IC50 for 1,1-diphenyl-2-picryl hydrazyl radical-scavenging activity was 890.9±43.2 and 984.9±33.5 µg/ml for the aerial part and bulbs, respectively. The aerial parts have better reducing power than bulb extracts but not comparable with Vitamin C (P>0.001). Extracts showed weak Fe2+ chelating ability, the IC50 being 959±47 and 530±24 µg/ml for bulbs and aerial parts, respectively. Both tested extracts exhibited good hydrogen peroxide scavenging in a concentration dependent manner. They exhibited good antioxidant activity against the hemoglobin-induced linoleic acid system that was comparable with vitamin C (P>0.01). They showed good activity against cumene hydro peroxide induced hemolysis in RBCs. In addition, they possessed antihemolytic activity. The extract from aerial parts had significantly higher total phenol and flavonoid content than did bulbs. Amounts of eight elements (Cu, Mn, Zn, Fe, Ni, Pb, Cd and Cr) were also determined in the bulb and aerial part using atomic absorption spectroscopy. They contained higher Fe and Mn contents than other elements.
A Simpson Correspondence in Positive Characteristic
Authors: Gros Michel , Le Stum Bernard , Quirós Adolfo
Published: February 2010

Let

p

be a prime number,

k

a perfect ﬁeld of characteristic

p > 0

,

X

a smooth

k

-scheme and

\mathcal D_X^{(m)}

the algebra of (arithmetic) diﬀerential operators of level

m ≥ 0

. We study the Azumaya nature of this algebra and show how to construct, using an additional data, a splitting of a completion (along some ideal contained in its center) of it.
Adams Operations on Higher Arithmetic $K$-theory
Authors: Feliu Elisenda
Published: February 2010

We construct Adams operations on the rational higher arithmetic

K

-groups of a proper arithmetic variety. The deﬁnition applies to the higher arithmetic

K

-groups given by Takeda as well as to the groups suggested by Deligne and Soulé, by means of the homotopy groups of the homotopy ﬁber of the regulator map. They are compatible with the Adams operations on algebraic

K

-theory. The deﬁnition relies on the chain morphism representing Adams operations in higher algebraic

K

-theory given previously by the author. It is shown that this chain morphism commutes strictly with the representative of the Beilinson regulator given by Burgos and Wang.
Magnetic resonance imaging of ligaments and membranes in the craniocervical junction in whiplash-associated injury and in healthy control subjects
Authors: Dullerud Reidar , Gjertsen Øivind , Server Andrés
Published: February 2010

Background: The pathogenesis and imaging findings in whiplash-associated injury (WAD) are poorly understood and remain debatable.

Purpose: To assess the ligaments and membranes in the craniocervical junction with magnetic resonance imaging (MRI) in patients with WAD and to compare them with healthy control subjects.

Material and Methods: Twenty-eight patients with WAD were selected at random from a total number of 180 examined with MRI using 2-mm proton density (PD)-weighted images in three orthogonal planes at 1.5T. The patients were compared with 27 healthy control subjects without neck trauma.

Results: High signal intensity of the alar and transverse ligaments was quite common and was reported at an average of about 50% both among patients and control subjects. The incidence of abnormalities of the tectorial and posterior atlantooccipital membranes was low in both groups. No statistically significant difference between control subjects and patients with WAD was revealed for any of the structures assessed. Additional fat-suppressed images seemed to reduce the number of reported anomalies.

Conclusion: Due to lack of significant differences between patients with WAD and healthy control subjects, it is not recommended that MRI with the current technique and classification system be used in the routine workup of patients with WAD.
Ultrasonography-guided vacuum-assisted biopsy of microcalcifications: Comparison of the diagnostic yield of calcified cores and non-calcified cores on specimen radiographs
Authors: Cho Nariya , Moon Woo Kyung , Chang Jung Min , Park Sang Hee , Lyou Chae Yeon , Park In Ae
Published: February 2010

Background: Microcalcifications found on mammography of asymptomatic women can be sampled by ultrasound (US)-guided percutaneous breast biopsy when stereotactic core biopsy is unavailable or unsuccessful. The role of specimen radiograph needs to be reevaluated after US-guided biopsy.

Purpose: To compare retrospectively the histological diagnoses of calcified cores and non-calcified cores as depicted on specimen radiographs after a US-guided, 11-gauge, vacuum-assisted biopsy using surgical histology as the reference standard.

Material and Methods: A total of 135 consecutive patients underwent a US-guided vacuum-assisted biopsy for calcifications with malignant histological results from 135 lesions. For each lesion, calcification was identified in at least one core on specimen radiographs. Calcified cores and non-calcified cores depicted on specimen radiographs were separately submitted to the pathology department. The pathological diagnoses of calcified cores and non-calcified cores were compared with final diagnoses at surgical excision.

Results: Of a total of 2049 core specimens that were obtained (mean, 15 per lesion; range, 4–35 per lesion), 794 cores (mean, 5.9 per lesion; range, 1–17 per lesion) contained calcifications and 1255 cores (mean, 9.3 cores per lesion; range, 1–34 cores per lesion) did not contain calcifications. Calcified cores were more likely to enable an accurate diagnosis of cancer as compared to non-calcified cores (67%, 91 of 135 versus 52%, 70 of 135; P = 0.009). A diagnosis of cancer was more likely to be missed with non-calcified cores as compared to calcified cores (16%, 21 of 135 versus 4%, 5 of 135; P = 0.002). There was no difference in the underestimation of malignancy between calcified cores (29%, 39 of 135) and non-calcified cores (33%, 44 of 135) ( P = 0.510).

Conclusion: Calcified cores depicted on specimen radiographs are more accurate for a diagnosis of cancer as compared to non-calcified cores obtained during US-guided vacuum-assisted biopsy of microcalcifications.
Infratentorial oligodendrogliomas: Imaging findings in six patients
Authors: Lee In Ho , Kim Sung Tae , Suh Yeon-Lim , Kim Hyung-Jin , Kim Keon Ha , Jeon Pyoung , Byun Hong Sik
Published: February 2010

Background: Oligodendrogliomas are primarily supratentorial tumors. However, infrequently, they can also arise from infratentorial structures. There are only limited numbers of radiological articles on the specific imaging findings of this entity.

Purpose: To investigate the imaging findings of infratentorial oligodendrogliomas.

Material and Methods: We retrospectively reviewed the magnetic resonance imaging (MRI) findings and clinical records of six patients with pathologically proven infratentorial oligodendrogliomas between December 1994 and April 2008. Tumor location, circumscription, signal intensity (SI), enhancement pattern, the presence of restricted diffusion, and the change of the relative cerebral blood volume (rCBV) on MRI were evaluated.

Results: In total, six patients (three male, three female; mean age 65 years, range 51–75 years) were included. The pathology revealed anaplastic oligodendrogliomas in all six patients. The location was cerebellum in four patients, medulla in one patient, and fourth ventricle and tegmentum in one patient. Three of them were of the infiltrative type, and the other three of the mass-forming type. The solid component of the tumors showed high SI ( n=6) on FLAIR and T2-weighted images, and low ( n=5) or iso ( n=1) SI on T1-weighted images. All infiltrative lesions showed multifocal patchy enhancement, and mass-forming lesions showed heterogeneous enhancement ( n=2) and diffuse homogeneous enhancement ( n=1). Three patients had restricted diffusion, and one had leptomeningeal seeding. There was markedly increased rCBV on perfusion-weighted image (PWI) in one patient. Calcification or hemorrhage was not found. Tumor progression after operation, radiation therapy, gamma-knife surgery, or chemotherapy developed in five patients.

Conclusion: Although infratentorial oligodendrogliomas did not show characteristic imaging findings, there was a tendency toward multifocal heterogeneous enhancement and absent or mild mass effect of infiltrative lesions. Infratentorial oligodendrogliomas may be more malignant than supratentorial oligodendrogliomas.
Magnetic resonance sialography using CISS and HASTE sequences in inflammatory salivary gland diseases: Comparison with digital sialography
Authors: Gadodia Ankur , Seith Ashu , Sharma Raju , Thakar Alok , Parshad Rajinder
Published: February 2010

Background: Inflammatory conditions are the most common pathology affecting the salivary glands. Magnetic resonance (MR) sialography has emerged as an alternative to conventional sialography for evaluation of inflammatory salivary gland diseases.

Purpose: To prospectively evaluate the role and diagnostic accuracy of MR sialography in the diagnosis of inflammatory salivary gland disease.

Material and Methods: Thirty-seven glands in 28 patients (19 males and nine females; mean age 31 years, range 3–65 years) presenting with inflammatory salivary gland disorders underwent MR sialography. Conventional sialography was used as the gold standard and was performed in 26 patients (34 glands). Thus, comparative evaluation was done in 26 patients (34 glands). Axial T1-weighted (T1W) and fat-suppressed T2W sequences, a constructive interference in steady state (CISS) sequence in the axial plane with maximum intensity projection (MIP)/multiplanar reformation (MPR) done in the axial and sagittal oblique planes, and a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in the sagittal oblique direction were performed.

Results: Main salivary gland duct was visualized in 32 glands (94.1%) with MR sialography, and in all 34 (100%) glands with conventional sialography. Calculus and strictures were well demonstrated by MR sialography. MR sialography was superior for demonstration of the ductal system proximal to calculus/strictures. Sensitivity and specificity for diagnosis of specific pathology were 87% and 100% with CISS sequence and 90% and 75% with HASTE sequence, respectively. On using a combination of CISS and HASTE sequences, the sensitivity, specificity, and positive and negative predictive values in the diagnosis of specific pathology were 93%, 100%, 100%, and 64%, respectively.

Conclusion: MR sialography using CISS and HASTE sequences is a promising technique and has the potential to replace conventional sialography in patients with inflammatory salivary gland disorders.
Relief of radicular pain in metastatic disease by vertebroplasty
Authors: Mazumdar Avi , Gilula Louis A.
Published: February 2010

Two patients with compression fractures from metastases who had pain with radicular symptoms mainly in upright position that resolved when not upright and were treated with vertebroplasty were retrospectively analyzed. Both patients had symptom relief at treated levels until death. These cases show that patients with radicular signs and symptoms from compression fractures secondary to metastases or myeloma, worse in upright position and relieved when recumbent, may benefit from vertebroplasty.
Role of three-dimensional fluid-attenuated inversion recovery (3D FLAIR) and proton density magnetic resonance imaging for the detection and evaluation of lesion extent of focal cortical dysplasia in patients with refractory epilepsy
Authors: Saini Jitender , Singh Atampreet , Kesavadas Chandrasekharan , Thomas Bejoy , Rathore Chathurbhuj , Bahuleyan Biji , Radhakrishnan Ashalatha , Radhakrishnan Kurupath
Published: February 2010

Background: Focal cortical dysplasia (FCD) is often associated with epilepsy. Identification of FCD can be difficult due to subtle magnetic resonance imaging (MRI) changes. Though fluid-attenuated inversion recovery (FLAIR) sequence detects the majority of these lesions, smaller lesions may go unnoticed while larger lesions may be poorly delineated.

Purpose: To determine the ability of a specialized epilepsy protocol in visualizing and delineating the extent of FCD.

Material and Methods: We compared the imaging findings in nine patients with cortical malformation who underwent routine epilepsy MR imaging as well as a specialized epilepsy protocol. All imaging was done on a 1.5T MR unit. The specialized epilepsy protocol included 3D FLAIR in the sagittal plane as well as proton density (PD) and high-resolution T2-weighted (T2W) images in the transverse plane.

Results: In all nine patients, the specialized protocol identified lesion anatomy better. In three patients in whom routine MRI was normal, the specialized epilepsy protocol including 3D FLAIR helped in identifying the lesions. One of these patients underwent surgery, and histo-pathology revealed a cortical dysplasia. In one patient, lesion characterization was improved, while in the remaining patients the extent of the FCD was more clearly demonstrated in the 3D FLAIR and PD images. Statistical analysis of images for cortical thickness, cortical signal intensity, adjacent white matter abnormalities, and gray–white matter junction showed significant statistical difference in the ability of 3D FLAIR to assess these aspects over conventional images. PD images were also found superior to the routine epilepsy protocol in assessment of cortical signal, adjacent white matter, and gray–white matter junction.

Conclusion: Specialized MRI sequences and techniques should be performed whenever there is a high suspicion of cortical dysplasia, especially when they remain occult on conventional MR protocols. These techniques can also be used to define lesion extent more precisely.
Book Review
Authors: Manninen Hannu
Published: February 2010

Carotid artery stenting: The basics. Edited by J. Saw. Berlin: Springer Verlag, 2009. 276 pages, 129 figures. ISBN: 978-1-60327-313-8. Price (hardback): USD 189.00
Correlation between lactate and neuronal cell damage in the rat brain after focal ischemia: An in vivo 1H magnetic resonance spectroscopic (1H-MRS) study
Authors: Woo Chul-Woong , Lee Byong Sop , Kim Sang Tae , Kim Ki-Soo
Published: February 2010

Background: Increased levels of lactate are observed by 1H magnetic resonance spectroscopy (1H-MRS) in rat brains after stroke. However, it is not known whether the changes in lactate levels are predictive of the degree of neuronal damage.

Purpose: To investigate the correlation between changes in lactate and lipid levels measured by 1H-MRS and neuronal cell damage in the rat brain.

Material and Methods: A middle cerebral artery occlusion (MCAO) model was used to evaluate focal ischemia in rats (n=36). After MCAO for 90 min T2-weighted images (T2WIs), diffusion-weighted images (DWIs), and 1H-MRS data were obtained from brains immediately, 6 hours, 9 hours, 12 hours, 18 hours, 24 hours, 3 days, and 7 days after reperfusion. Infarct volumes were measured in T2WIs obtained 4 weeks after reperfusion. The degree of neuronal damage was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining in three rats from each group at the same time as brain images were collected.

Results: Creatine (Cr)-normalized lactate + lipid levels ([Lac+Lip]/Cr) were negatively correlated with Cr-normalized N-acetyl-L-aspartate levels (NAA/Cr) and positively correlated with TUNEL-positive cell numbers up to 24 hours after reperfusion. (Lac+Lip)/Cr at 6 hours and 9 hours was significantly correlated with NAA/Cr at 7 days, but there was no significant correlation between (Lac+Lip)/Cr during the first 24 hours and infarct volume at 4 weeks.

Conclusion: Up to 24 hours after reperfusion, (Lac+Lip)/Cr was strongly negatively correlated with NAA/Cr, and was a good predictor of neuronal damage at 7 days; however, it was not predictive of final infarct volume at 4 weeks.
Gaze aversion to stuttered speech: a pilot study investigating differential visual attention to stuttered and fluent speech
Authors: Bowers Andrew L. , Crawcour Stephen C. , Saltuklaroglu Tim , Kalinowski Joseph
Published: February 2010

Background: People who stutter are often acutely aware that their speech disruptions, halted communication, and aberrant struggle behaviours evoke reactions in communication partners. Considering that eye gaze behaviours have emotional, cognitive, and pragmatic overtones for communicative interactions and that previous studies have indicated increased physiological arousal in listeners in response to stuttering, it was hypothesized that stuttered speech incurs increased gaze aversion relative to fluent speech. The possible importance in uncovering these visible reactions to stuttering is that they may contribute to the social penalty associated with stuttering.

Aims: To compare the eye gaze responses of college students while observing and listening to fluent and severely stuttered speech samples produced by the same adult male who stutters.

Methods & Procedures: Twelve normally fluent adult college students watched and listened to three 20‐second audio–video clips of the face of an adult male stuttering and three 20‐second clips of the same male producing fluent speech. Their pupillary movements were recorded with an eye‐tracking device and mapped to specific regions of interest (that is, the eyes, the nose and the mouth of the speaker).

Outcomes & Results: Participants spent 39% more time fixating on the speaker's eyes while witnessing fluent speech compared with stuttered speech. In contrast, participants averted their direct eye gaze more often and spent 45% more time fixating on the speaker's nose when witnessing stuttered speech compared with fluent speech. These relative time differences occurred as a function of the number of fixations in each area of interest. Thus, participants averted their gaze from the eyes of the speaker more frequently during the stuttered stimuli than the fluent stimuli.

Conclusions & Implications: This laboratory study provides pilot data suggesting that gaze aversion is a salient response to the breakdown in communication that occurs during stuttering. This response may occur as a result of emotional, cognitive, and pragmatic factors in communication partners. Regardless of the factors contributing to the response, its primary importance may be that gaze aversion is a visible communication partner signal informing the person stuttering that something is amiss in the interaction and hence, may contribute to inducing negative emotions in the persons stuttering, via engagement of the mirror neuron system. We suggest that witnessing and interpreting communication partner responses to stuttering may play a role when a person who stutters engages in future interactions, perhaps contributing to the development of covert strategies to hide stuttering.
Treating children with phonological problems: does an eclectic approach to therapy work?
Authors: Lancaster Gwen , Keusch Susanna , Levin Abigail , Pring Tim , Martin Susanna
Published: February 2010

Background: A survey of clinicians made by Joffe and Pring in 2008 revealed that different approaches exist between researchers and clinicians in the treatment of children with phonological problems. Researchers have examined specific approaches to treatment often giving substantial amounts of therapy and have obtained encouraging results; clinicians, with less time available, often use an eclectic approach mixing different treatment methods. The reasons for this difference are discussed.

Aims: We examined the effectiveness of an eclectic approach giving amounts of therapy more consistent with clinical practice and involving parents in treating their children.

Methods & Procedures: We report two small experiments conducted within Speech and Language Therapy clinics. In the first, a group of treated children are compared with a group of children whose treatment is delayed. Parents attended therapy sessions and were given homework tasks to do with their children. The second compared children treated as in the first experiment with children treated at home by their parents who had attended training sessions and with untreated children.

Outcomes & Results: In the first experiment, a general trend towards improvement was seen in all children. Change during treatment periods was statistically significant. In the second experiment, children treated by therapists showed strongly significant gains. Lesser but significant gains were made by children treated by their parents; no change was found in untreated children.

Conclusions & Implications: The findings offer encouragement to clinicians who use an eclectic approach and who are only able to offer limited amounts of therapy. They also suggest that parental involvement is helpful. However, we find the current incompatibility of research and clinical work worrying and a hindrance to our efforts to understand and treat these children.
Pragmatic language impairment and associated behavioural problems
Authors: Ketelaars Mieke P. , Cuperus Juliane , Jansonius Kino , Verhoeven Ludo
Published: February 2010

Background: Specific language impairment (SLI) is diagnosed when a child shows isolated structural language problems. The diagnosis of pragmatic language impairment (PLI) is given to children who show difficulties with the use of language in context. Unlike children with SLI, these children tend to show relatively intact structural language skills while they do exhibit clear communicative deficits. There is hardly any research on the relationship between pragmatic competence and behavioural problems. Existing research suggests a strong relationship, but has only been executed on clinical SLI samples. Moreover, it is not known whether pragmatic language problems are related to specific types of behavioural problems.

Aims: This study aims to clarify the incidence and nature of behavioural problems in children with PLI using a prognostic design in mainstream education. This design should provide valuable insights into the general relationship between PLI and various behavioural problems.

Methods & Procedures: Teachers completed the Children's Communication Checklist (CCC) and the Strengths and Difficulties Questionnaire (SDQ) and provided additional data for a sample of 1364 children aged 4 years.

Outcomes & Results: Within the community sample, pragmatic competence is highly correlated with behavioural problems. Pragmatic competence is a good predictor of behavioural problems, and once pragmatic competence is accounted for, structural language abilities do not predict behavioural problems. Children with pragmatic language impairment often show behavioural problems, largely of an externalizing nature. The most prominent problems are hyperactivity and the lack of prosocial behaviour, which reach clinical levels for this group. However, all problem levels are elevated compared with normally developing children.

Conclusions & Implications: Young children with PLI show a wide variety of behavioural problems. Early assessment of pragmatic competence may benefit early detection of children at risk of behavioural problems. Furthermore, due to the relationship between pragmatic competence, behavioural problems and possible underlying disorders such as autism and attention‐deficit hyperactivity disorder (ADHD), early assessment of pragmatic competence may also provide an early marker for the detection of autism or ADHD.
Appraisal in student–supervisor conferencing: a linguistic analysis
Authors: Ferguson Alison
Published: February 2010

Background: Student–supervisor conferencing involves a pivotal moment for teaching and learning, involving clinical educators in directing the students' work with clients, promoting the students' learning and self‐evaluation, and in providing feedback to students about their progress. Previous research in the area of student–supervisor conferencing has focused on broad categories of behavioural aspects of this clinical education process, but less is known about how educators and students use their linguistic resources to manage the interpersonal aspects of communication involved in these learning partnerships.

Aims: This paper presents a descriptive study of the way language was used by clinical educators and students in student–supervisor conferences. The main aim of the study was to describe some aspects of the linguistic resources used by clinical educators and students to evaluate their work and learning in routine discussions, outside the framework of a formal assessment of student progress. Within the inherent limits of descriptive research, the study also considered the extent to which selected aspects of language use reflected individual communicative style or varied across partners and over time.

Methods & Procedures: The study was descriptive, using case studies as well as grouped data. Audio recordings of ten authentic student–supervisor interactions were provided voluntarily for the study by four clinical educators and their six speech–language pathology students. After transcription, linguistic analysis described the resources used for Appraisal (Affect, Judgement and Appreciation), from the perspective of Systemic Functional Linguistics.

Outcomes & Results: Educators used proportionally more resources to express Judgement in contrast with students who used proportionally more resources to express evaluation of Affect. Most Judgements were expressed positively and directly, whereas negative Judgements tended to be expressed implicitly. Comparison of clinical educators' language across repeated occasions indicated use of a range of linguistic resources, rather than the use of these interpersonal resources being associated with particular styles for supervision.

Conclusions & Implications: The findings provide directions for clinical educators seeking to reflect on supervisory practice, and also highlight the need for further longitudinal research, and for further research into the interactive learning processes involved in current models of clinical education.
Studies on Polygalacturonase from Aspergllus Flavus
Authors: Gewali Mohan B , Maharjan Jyoti , Thapa Sambhu , Shrestha Jaya Krishna
Published: February 2010

Crude polygalacturonase was obtained from Aspergillus flavus cultured in Glucose Free Medium (GFM) by precipitating cell free broth with 66% cold acetone. Effect of different parameters such as temperature, pH incubation time and enzyme concentration on this polygalacturonase preparation was studied. Furthermore, some inhibition studies on this enzyme preparation were conducted. Key words: Aspergillus flavus; Polygalacturonase. DOI: 10.3126/sw.v5i5.2650 Scientific World, Vol. 5, No. 5, July 2007 19-22
Allelopathic Effects of Aqueous Extract of Leaves of Parthenium Hysterophorus L. on Seed Germination and Seedling Growth of Some Cultivated and Wild Herbaceous Species
Authors: Maharjan Seerjana , Shrestha Bharat Babu , Jha Pramod Kumar
Published: February 2010

Allelopathic effects of aqueous extract of leaves of Parthenium hysterophorus were studied on seed germination and seedling growth of three cereal crops (Oryza sativa L., Zea mays L. and Triticum aestivum L.), three cultivated crucifers (Raphanus sativus L., Brassica campestris L. and Brassica oleracea L.) and two wild species of family Asteraceae (Artemisia dubia Wall ex. Besser and Ageratina adenophora (Spreng) King and HE Robins). Seed germination of all crucifer species was completely inhibited at >2% leaf extract of Parthenium hysterophorus but in other species, except maize, complete failure of seed germination was recorded only at >6% in Triticum aestivum and Ageratina adenophora; at 10% in Oryza sativa and Artemisia dubia. Seed germination of Zea mays was not completely inhibited but it was low at high concentration of the extract. The extract had strong inhibitory effect to root elongation of seedling in cereals and to shoot elongation in crucifers and wild Asteraceae. Leaves of Parthenium hysterophorus may be a source of natural weedicide against Ageratina adenophora which will help to control invasive plants. Key words: Alien invasive; Asteraceae; Cereal crops; Crucifers; Seedling biomass; Weedicide. DOI: 10.3126/sw.v5i5.2653 Scientific World, Vol. 5, No. 5, July 2007 33-39
In Vitro Propagation of Carrot (Daucus Carota) L.
Authors: Pant B , Manandhar S
Published: February 2010

In vitro method for rapid propagation of Daucus carota L. was developed. Root, stem, leaf and nodal explants were cultured on MS medium supplemented with different concentration and combinations of hormones. Multiple shoot were induced from the nodal explant of D. carota by culturing them in MS medium supplemented with 0.5 mg/l of 6-benzylaminopurine (BAP). Differentiation of shoot initiated after one week of culture, and after eight weeks of primary culture, an average of six plantlets were developed from a single shoot. The nodal explant also induced same number of multiple shoot in MS medium supplemented with 2 mg/l of BAP and 1 mg/l of α-nephthalene acetic acid (NAA). The shoots when sub-cultured in the medium supplemented with 1 mg/l NAA produced roots after five weeks of sub-culture. Root and leaf explants induced roots and callus when cultured on MS medium with NAA at the rate of 1 mg/l and 2 mg/ l. Similarly, stem explants also induced roots and callus in the same concentration of hormones whereas few multiple shoot were induced when cultured on MS supplemented with 2 mg/l of BAP and 1 mg/l of NAA. This result suggests that this methodology can be applied for the rapid and mass propagation of this species. Key words: In vitro; Propagation; MS medium; Explant; Culture. DOI: 10.3126/sw.v5i5.2656 Scientific World, Vol. 5, No. 5, July 2007 51-53