bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk evaluation in cutaneous melanoma patients undergoing lymph node dissection: impact of POSSUM
Authors: Egberts F , Hartje C , Schafmayer C , Kaehler KC , von Schönfels W , Hauschild A , Becker T , Egberts JH
Published: October 2011

INTRODUCTION

When lymphatic metastasis occurs, surgery is the primary treatment modality in melanoma patients. Depending on the tumour stage, patients receive a completion lymph node dissection (CLND) when a positive sentinel node is detected. Patients with clinically evident disease of the regional lymph nodes are recommended to undergo a therapeutic lymph node dissection (TLND). The aim of this study was to assess the morbidity of CLND and TLND and to evaluate the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) for preoperative risk adjustment of postoperative morbidity.

METHODS

The hospital files of 143 patients who underwent CLND and TLND for malignant melanoma were analysed. The POSSUM score was used to predict morbidity rates after surgery for the total patient group as well as separated for CLND and TLND patients.

RESULTS

The overall complication rate was 28.0% and the mortality rate was 0%. The morbidity rate predicted by POSSUM was 32.9%, the mortality 8.3%. Morbidity in patients undergoing CLND was significantly higher with regard to overall wound complications compared with patients with TLND. In these subgroups, POSSUM failed to predict the rates precisely.

CONCLUSIONS

The POSSUM score predicted the morbidity of the total patient group accurately but failed to predict the rates in the TLND and CLND subgroups. Patients receiving CLND showed the highest morbidity rates. Preoperative sentinel lymph node biopsy therefore has more influence on postoperative morbidity than the physiological parameters represented in the POSSUM physiological score.
Trends in presentation of bone and soft tissue sarcomas over 25 years: little evidence of earlier diagnosis
Authors: Smith GM , Johnson GD , Grimer RJ , Wilson S
Published: October 2011

Earlier diagnosis is a key aim in achieving improved outcomes for patients with cancer. Bone and soft tissue sarcomas represent approximately 1% of all malignant tumours. Delays in diagnosis are frequent both because of their rarity and because the clinical features are easily confused with other conditions. In 2000 advice on earlier diagnosis was widely publicised. This study investigates how two factors that may act as a proxy for delay in diagnosis have varied over a 25-year period and whether there is evidence of improvement. Data on symptom duration and tumour size were collected prospectively on all new sarcoma patients referred to an orthopaedic oncology unit over 25 years.

Data were available for 2,568 patients with primary bone sarcomas and 2,366 with soft tissue sarcomas. The mean sarcoma size at diagnosis was 10.7cm and 9.9cm respectively. The size of bone sarcomas had not changed over time but there had been a slight decrease in the size of soft tissue sarcomas (10.3cm before 2000 vs 9.6cm after 2000, p=0.03). The duration of symptoms reported by patients varied widely with a median of 16 weeks for bone sarcomas and 26 weeks for soft tissue sarcomas. The median duration of symptoms for bone sarcomas had actually increased since 2000 (16 weeks before vs 20 weeks after 2000, p<0.01). It remained unchanged for soft tissue sarcomas. These data show there is huge room for improvement in diagnosing bone and soft tissue sarcomas. New strategies are needed urgently.
Technical approaches to single port/incision laparoscopic appendicectomy: a literature review
Authors: Rehman H , Ahmed I
Published: October 2011

INTRODUCTION

Single port/incision laparoscopic surgery (SPILS) is a modern advancement toward stealth surgery. Despite the paucity of high-quality scientific studies assessing its effectiveness, this procedure is being used increasingly. This review aims to describe commonly used techniques for SPILS appendicectomies (SPILA), to summarise complication rates in the literature and to provide discussion on indications and implementation.

METHODS

All available databases including the Cochrane Central Register of Controlled Trials, MEDLINE® and Embase™ were searched in February 2011 and cross-referenced for available English literature describing SPILA in patients of any age.

RESULTS

Three broad technical approaches are described: procedures using laparoscopic instruments through a single skin incision in the abdominal wall, regardless of the number of fascial incisions, with or without the additional use of percutaneous sutures or wires to ‘assist’ the operation, and hybrid procedures, in which the appendix is exteriorised using a single incision laparoscopically assisted operation but subsequently divided using a conventional ‘open’ appendicectomy technique. Complication rates seem to be highest in SPILA procedures unassisted by sutures or wires.

CONCLUSIONS

Future research assessing the efficacy of single incision laparoscopic procedures should consider variation in technique as a possible factor affecting outcome.
The role of carbohydrate drinks in preoperative nutrition for elective colorectal surgery
Authors: Jones C , Badger SA , Hannon R
Published: October 2011

INTRODUCTION

Traditionally, patients have been fasted from midnight on the night before elective surgery. With the advent of the enhanced recovery programme for elective colorectal surgery, there has been a major change in established practice with patients able to continue with clear fluids up to two hours prior to surgery and solids up to six hours prior to surgery. It has been suggested that nutritional supplements in the immediate pre-operative period enhance post-operative recovery. The aim of this review was therefore critically to appraise the evidence available regarding the use of pre-operative carbohydrate (CHO) supplements for elective colorectal surgery.

METHODS

A literature search was performed using: PubMed, MEDLINE®, Athens and Google Scholar. The following keywords were used: ‘pre-operative’, ‘carbohydrate supplements’, ‘enhanced recovery’ and ‘colorectal surgery’, singly or in combination. To ensure an up-to-date literature search, the search was restricted to the last ten years. To maximise the search, backward chaining of reference lists from retrieved papers was also undertaken. Only English language articles were included.

CONCLUSIONS

The use of CHO drinks pre-operatively in colorectal surgery is both safe and effective. There is no increased risk of aspiration and it results in a shorter hospital stay, a quicker return of bowel function and less loss of muscle mass. On the basis of this evidence, the use of pre-operative CHO drinks should be standard in elective colorectal patients. Further research is nevertheless required for those with diabetes mellitus.
Colorectal cancer presenting with dysarthria and ataxia: a case of isolated leptomeningeal metastasis
Authors: Lahiri RP , Burnand KM , Bandi A , Farooq N , Sathesh-Kumar T
Published: October 2011

We report the case of a 72-year-old man who presented with weight loss, anorexia and a change in bowel habit. Computed tomography (CT) of the chest, abdomen and pelvis demonstrated widespread thoracic and abdominal lymphadenopathy and a lesion within the splenic flexure. This was confirmed as an adenocarcinoma after a colonoscopic biopsy. A CT guided biopsy of the abdominal lymph node confirmed the adenocarcinoma. Within three days of admission, the patient developed worsening, progressive cerebellar symptoms that left the patient aphasic and bed bound. CT of the head was reported as normal. Magnetic resonance imaging of the head demonstrated widespread leptomeningeal metastases. We describe a case of isolated leptomeningeal metastasis from a colorectal primary tumour.
An atypical presentation of aortic rupture: intuition and investigation can avoid disaster
Authors: Shah TT , Herbert P , Beresford T
Published: October 2011

Introduction

Patients with an acute abdomen are a common presentation for those participating in emergency surgery cover. The aetiology of this presentation incorporates the spectrum of organ systems and is often not identified satisfactorily. Nevertheless, certain diagnoses will always be difficult to make and some presentations can be deceptive. Radiological investigations increasingly play a role in establishing an accurate diagnosis and frequently allow prompt management to be instituted. Patients with an acute abdomen are a common presentation for those participating in emergency surgery cover. The aetiology of this presentation incorporates the spectrum of organ systems and is often not identified satisfactorily. Nevertheless, certain diagnoses will always be difficult to make and some presentations can be deceptive. Radiological investigations increasingly play a role in establishing an accurate diagnosis and frequently allow prompt management to be instituted. Ruptured AAA should be considered as a differential diagnosis in all elderly patients presenting with acute severe abdominal pain who may be haemodynamically stable. Atypical history and examination with inconsistent or equivocal clinical signs should raise the suspicion of aneurysm, particularly in elderly men with known arterial disease. There should be a low threshold for both requesting and justifying definitive imaging (ie CT) in such cases if a catastrophic outcome through misdiagnosis is to be avoided.
Postcoital vaginal rupture after hysterectomy presenting as generalised peritonitis
Authors: Eid-Arimoku L , Trompetas V
Published: October 2011

Postcoital vaginal rupture is a rare but well documented complication of hysterectomy. Evisceration of the small intestine, vaginal bleeding and pelvic pain are common presenting features. We report the unusual case of vaginal rupture presenting with generalised peritonitis without vaginal evisceration.
A rare case of primary bone lymphoma mimicking a pelvic abscess
Authors: Singh R , Al Wattar BH , Mohanty K
Published: October 2011

Primary bone lymphoma (PBL) is a rare, malignant, neoplastic disorder of the skeleton that accounts for less than 5% of all primary bone tumours. We present an extremely rare case of PBL mimicking a pelvic abscess around the sacroiliac joint, which has never been reported in the medical literature, and discuss learning points highlighted from this case.
Peritonitis from an abdominal wall biloma: a unique reason to avoid prophylactic surgical drainage
Authors: Thrumurthy SG , Shetty VD , Ward JB , Pursnani KG , Mughal MM
Published: October 2011

Prophylactic drainage of the peritoneal space after major surgery is widely practised despite evidence against its efficacy. We describe the case of a 56-year-old woman who underwent a converted cholecystectomy and whose correctly sited abdominal drain resulted in the formation of a biloma between the external and internal oblique musculature. Subsequent leakage from the biloma into the abdominal cavity presented as peritonitis days after surgery, necessitating an emergency laparotomy. This case represents the first reported description of an abdominal wall biloma as a complication of post-cholecystectomy abdominal drainage. The evidence surrounding prophylactic drainage is discussed.
A painful perineal lump: an unusual case of ectopic breast tissue
Authors: Hanief MR , Yongue G , Leff D , Lamb BW , Karim S , Aref F , Vashisht R
Published: October 2011

We report the case of a 40-year-old lady who presented with an episodically painful perineal lump. Clinical and radiological investigations were inconclusive. Excision biopsy confirmed an ectopic breast mass. Ectopic breast tissue is difficult to diagnose but close attention to clinical findings can help to guide further investigation and diagnosis.
Combined ventriculoperitoneal shunt blockage, viscus perforation and migration into urethra, presenting with repeated urinary tract infection
Authors: Chen TH , Lin MS , Kung WM , Hung KS , Chiang YH , Chen CH
Published: October 2011

We present an extremely rare case of delayed and combined ventriculoperitoneal shunt blockage, viscus perforation and migration into the urethra manifested by a repeated urinary tract infection. This was discovered six months after the shunt was inserted. Although there were various other transient symptoms, the patient did not show obvious peritoneal signs. This complication could have been lethal if the discovery had been delayed. One of the best ways of preventing such migration is possibly the use of a softer catheter. However, making sure of appropriate redundancy for the abdominal part of the catheter may be of equal importance.
Alginate Ion Adsorption on a TiO2Particle Film and Interactions of Adsorbed Alginate with Calcium Ions Investigated by Attenuated Total Reflection Infrared (ATR-IR) Spectroscopy
Authors: Petrone Luigi , McQuillan A. James
Published: October 2011

The adsorption of alginic acid on a TiO2particle film from aqueous solution was investigated by attenuated total reflection infrared (ATR-IR) spectroscopy. ATR-IR spectra recorded at different pHs confirmed that alginate adsorption to TiO2is favored at pH 3.0 and no significant adsorption occurs above pH 5.0. Upon adsorption the carboxylic acid groups of alginic acid are converted to the carboxylate form and bind to surface Ti(IV) ions via bridging bidentate structures. Spectral analyses of the carboxylic acid and carboxylate stretching vibrations indicated that about three in four –COOH groups are converted to –COO−groups as they bind coordinately to TiO2. Additionally, the spectral data at pH 8.0 showed specific interactions of Ca2+ions with the free COO−groups of the polysaccharide backbone of adsorbed alginic acid.
Optical Properties of Suspensions of Organic and Inorganic Red Pigments
Authors: Heuer Jana , Niskanen Ilpo , Klein Susanne , Peiponen Kai-Erik
Published: October 2011

Optical characterization of three red pigments, two organic and one inorganic, was studied in order to provide important and reliable parameters for research and applications. The pigments were C.I. Pigment Red 176, C.I. Pigment Red 57:1, and C.I. Pigment Red 101. All three pigments were used in their transparent form, that is, their radius of gyration was smaller than 250 nm. The particles were suspended in an apolar solvent and absorption, reflection, and scattering of the suspensions were measured by means of a single spectrophotometer and the effective complex refractive index was determined.
Determination of Lithium in Mineral Water Samples by X-Ray Fluorescence Spectrometry
Authors: Zawisza Beata , Sitko Rafał
Published: October 2011

A method is shown for the determination of trace amounts of lithium by X-ray fluorescence spectrometry (XRF) in natural mineral waters with various therapeutic effects originating in Poland. The method is an expansion of X-ray fluorescence spectrometry applications to the determination of a very light element. The direct determination of lithium by XRF is practically impossible due to the extremely low fluorescence yield and long-wavelength characteristic radiation of such a light element. The lithium is determined via iron after precipitation with stoichiometric potassium lithium periodatoferrate(III) complex. The solution obtained after dissolving the complex was pipetted onto Mylar foil for XRF analysis. As little as 1 μg Li may be determined with this method. Accurate lithium determinations can be obtained using simple calibration samples requiring only pipetting Fe solution in the range 8.0–28.0 μg onto the Mylar foil. The prepared samples are thin, which allows the errors resulting from self-absorption or matrix effects to be neglected. Our studies give essential information about the quality of the analyzed waters.
Spectroscopic Characterization of the Oligomeric Surface Structures on Polyamide Materials Formed during Accelerated Aging
Authors: Chernev Boril S. , Eder Gabriele C.
Published: October 2011

Crystalline surface species were observed at the surface of polyamide 12 materials upon accelerated aging. After detection of the depositions with scanning electron microscopy (SEM), the crystalline surface precipitations were analyzed with Fourier transform infrared (FT-IR) and Raman imaging microscopy. These surface species were supposed to be cyclic oligomers (dimer and trimer) of the PA12 monomer laurolactam, which are usually present in polyamide materials and tend to migrate to the surface when the material is subjected to accelerated aging. The evidence for the chemical identity of the crystalline surface structures to be mainly the cyclic dimer and trimer of laurolactam was given by melting-point identification and mass spectroscopic analysis of the methanol eluate of the surface. The Raman and FT-IR spectra of the mixture were extracted from the recorded images.
The Calculation of the Optical Depths of Homogeneous Plasmas: Analytical, Experimental, and Numerical Considerations
Authors: Di Rocco Héctor O. , Bredice Fausto , Palleschi Vincenzo
Published: October 2011

Starting from the general expressions describing the line emission by a homogeneous plasma in local thermal equilibrium (LTE), in the approximation of Lorentzian shape of the line profile, a universal expression can be obtained relating the optical depth of the line to measurable quantities such as integrated line intensity, peak value, and full width at half-maximum (FWHM). This universal curve could be used for calculating the optical depth from experimental spectra without knowledge of the spectroscopic parameters of the emission line. Examples are given using experimental and computer-generated synthetic spectra.
Spatial Differentiation of Sub-Micrometer Domains in a Poly(Hydroxyalkanoate) Copolymer Using Instrumentation That Combines Atomic Force Microscopy (AFM) and Infrared (IR) Spectroscopy
Authors: Marcott Curtis , Lo Michael , Kjoller Kevin , Prater Craig , Noda Isao
Published: October 2011

Atomic force microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument (AFM-IR) capable of producing sub-micrometer spatial resolution IR spectra and absorption images. This new capability enables the spectroscopic characterization of micro-domain-forming polymers at levels not previously possible. Films of poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) were solution cast on ZnSe prisms, followed by melting and annealing to generate crystalline microdomains of different sizes. A tunable IR laser generating pulses of the order of 10 ns was used for excitation of the sample films. Short duration thermomechanical waves, due to infrared absorption and resulting thermal expansion, were studied by monitoring the resulting excitation of the contact resonance modes of the AFM cantilever. Dramatic differences in the room-temperature IR spectra are observed in the 1200–1300 cm−1 range as a function of position on a spatial scale of less than one micrometer. This spectral region is particularly sensitive to the polymer backbone conformation. Such dramatic spectral differences have also been observed previously in bulk IR measurements, but only by comparing room-temperature spectra with ones collected at higher temperatures. Less dramatic, but significant, AFM-IR spectral differences are observed in the carbonyl stretching region around 1720 cm−1 as a function of location on the sample. Two overlapping, but relatively sharp, carbonyl bands are observed near 1720 cm−1 in more crystalline regions of the polymer, while a broader carbonyl stretching band appears centered at 1740 cm−1 in the more amorphous regions. Using this spectral region, it is possible to monitor the development of polymer crystalline structures at varying distances from a nucleation site, where the site was generated by bringing a heated AFM tip close to a specific location to locally anneal the sample.
Broadband Absorbance in a Liquid-Core Optical Ring Resonator
Authors: Oates Thomas C. , Burgess Lloyd W.
Published: October 2011

We have demonstrated the application of broadband absorption spectroscopy in a liquid-core optical ring resonator. An initial proof of concept of the broadband liquid-core optical ring resonator (BLCORR) was constructed using a thinned-wall, 250-μm-inner-diameter fused silica capillary, tapered multimode optical fibers for input and output coupling, and a light-emitting diode (LED) source. When compared with standard cuvette measurements, an apparent path length as high as 5 cm was observed for methylene blue (MB). MB is a cationic dye that exhibits strong surface interaction with bare silica. Bromothymol blue (BTB), on the other hand, has a similar absorbance spectrum but does not share this same surface activity. On comparing these two dyes, the apparent path length for MB was found to reach more than 50 times that of BTB, confirming the expectation that the sensing region being probed is largely within the evanescent field at the inner surface of the capillary. The BLCORR may also inherit, from attenuated total reflection (ATR) spectroscopy, the ability to analyze highly concentrated chromophores. Concentrations of BTB as high as 10−2and 10−3M were easily distinguished from each other at the λmaxin the BLCORR, whereas this was not the case in a 4-mm cuvette cell. Our presented device employs commercially available materials and could incorporate well into micro-fluidic systems. These benefits, along with the demonstrated ability to take enhanced surface absorbance measurements in a capillary, give the BLCORR potential in a variety of applications.
Using Laser-Induced Breakdown Spectroscopy to Assess Preservation Quality of Archaeological Bones by Measurement of Calcium-to-Fluorine Ratios
Authors: Rusak David Alexander , Marsico Ryan Matthew , Taroli Brett Louis
Published: October 2011

We determined calcium-to-fluorine (Ca/F) signal ratios at the surface and in the depth dimension in approximately 6000-year-old sheep and cattle bones using Ca I 671.8 and F I 685.6 emission lines. Because the bones had been previously analyzed for collagen preservation quality by measurement of C/N ratios at the Oxford Radiocarbon Accelerator Unit, we were able to examine the correlation between our ratios and quality of preservation. In the bones analyzed in this experiment, the Ca I 671.8/F I 685.6 ratio was generally lower and decreased with successive laser pulses into poorly preserved bones while the ratio was generally higher and increased with successive laser pulses into well-preserved bones. After 210 successive pulses, a discriminator value for this ratio (5.70) could be used to distinguish well-preserved and poorly preserved bones regardless of species.
How Do Multinational Suppliers Formulate Mechanisms of Global Account Coordination? An Integrative Framework and Empirical Study
Authors: Gao Tao (Tony) , Shi Linda Hui
Published: October 2011

Existing global account management (GAM) studies mostly focus on multinational suppliers’ decision on which customers to serve with GAM programs, while paying limited attention to how to formulate mechanisms of global account coordination to best serve a chosen account. The issue of making optimal choices on specific coordination modes is pressing to global account managers because GAM programs are both costly and consequential. First, building on prior research that suggests the existence of two modes of global account coordination—namely, interorganizational coordination (IOC) and intercountry coordination (ICC)—the authors propose a formal framework that delineates their similarities and differences along the domain (internal vs. external), level (horizontal vs. vertical), and foci (strategic execution vs. relationship maintenance). Second, following the resource-based view and power-dependency theory, the authors propose an integrative framework on how various supplier, interorganizational, and customer factors influence global marketing managers’ coordination mechanism choices. They further advance several hypotheses on the curvi-linear nature of influences of several antecedents on coordination mode choices and examine the impacts of forms of global account coordination modes on suppliers’ market and relational performance. They test the conceptual model using data collected from a cross-national sample of more than 200 global account managers. The findings show that the two coordination modes have different sets of antecedents and exert independent, different influences on supplier performance. Therefore, they should be treated separately in research as well as practice.
Competitive Action in the Diffusion of Internet Technology Products in Emerging Markets: Implications for Global Marketing Managers
Authors: Zhang Cheng , Song Peijian , Qu Zhe
Published: October 2011

This research explores the extent to which competitive actions of multinational corporations (MNCs) and local vendors of Internet technology products shape the diffusion of their respective products in emerging markets. Drawing on competitive technology diffusion, the Austrian perspective on firms’ market processes, and resource advantage theory, the authors develop a set of hypotheses regarding the characteristics of the competitive actions of MNCs and local vendors. They validate the hypotheses with longitudinal field data from two pairs of competing Internet technology products in search engine and consumer-to-consumer electronic markets. The findings indicate that specific market-oriented actions of local vendors and MNCs influence the diffusion of technology products. In particular, global marketing managers should concentrate on a few key actions and take new actions that differ from those of local vendors in emerging markets. This study provides a wealth of knowledge in high-technology product diffusion and demonstrates how competition between local vendors and MNCs in emerging markets differs from typical within-industry competition. In addition, this study conveys important implications to the theory of international business.
Inpatriate Marketing Managers: Issues Associated with Staffing Global Marketing Positions
Authors: Moeller Miriam , Harvey Michael
Published: October 2011

This article addresses the strategic role of an inpatriate marketing staffing approach in the development of a global marketing mind-set within global organizations. The premise lies in addressing the liability-of-foreignness concept, which, the authors suggest, impedes the inpatriate marketing manager's integration process, from the individual level of analysis. Drawing from reference point theory, the article highlights potential hardships manages face with an analysis of the managerial and contextual liability of foreignness that inpatriate marketing managers may perceive in their transition from home countries to headquarter locations. Implications of identifying and attending to such hardships are important in light of the significance attributed to these semipermanent to permanent assignments across different cultural contexts.
The Double-Edged Sword of Signaling Effectiveness: When Salient Cues Curb Postpurchase Consumption
Authors: Zhu Meng , Billeter Darron M. , Inman J. Jeffrey
Published: October 2011

In juxtaposition to the common belief that marketing cues highlighting product effectiveness will generate positive influences on consumer demand, the authors argue that signaling effectiveness is a double-edged sword. While effectiveness cues may increase initial purchase, they can curb postpurchase consumption and potentially decrease long-term product sales. Four studies demonstrate that salient cues in advertising or packaging (e.g., pictures, brand names) can increase perceived product efficacy and lead to a lower usage amount on a single occasion. The authors show that the impact of effectiveness cues on product usage is driven by inference making and is moderated by cue salience and people's need for cognition. Furthermore, the authors find that promoting effectiveness with certain cues does not increase product choice yet reduces product usage. These results stress the importance of seeking salient cues that work to stimulate both choice and usage.
The Bergman property for endomorphism monoids of some Fraïssé limits
Authors: Dolinka Igor
Published: October 2011

Based on an idea of Y. Péresse and some results of Maltcev, Mitchell and Ruškuc, we present sufficient conditions
under which the endomorphism monoid of a countably infinite ultrahomogeneous first-order structure has the Bergman
property. This property has played a prominent role both in the theory of infinite permutation groups and, more
recently, in semigroup theory. As a byproduct of our considerations, we establish a criterion for a countably infinite
ultrahomogeneous structure to be homomorphism-homogeneous.
Transport Properties and Microstructure of Indium and Cerium added Cobalt-Antimony based Skutterudites
Authors: Sesselmann A. , Dasgupta T. , Stiewe C. , Müller E.
Published: October 2011

Indium and cerium added cobalt-antimony based skutterudites with different filling fractions were synthesized using different annealing synthesis parameters. Phase homogeneity and microstructure of the resulting as-cast material were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The skutterudite material was further compacted using a current-assisted short-term sintering device. Temperature dependent measurements of the Seebeck coefficient, electrical and thermal conductivity were carried out on the compacted specimens in the temperature range of 350 K-700 K. Results indicate significant differences in the transport properties between the slowly cooled and quenched as‑cast materials and also with different filling fractions. Based on the measured transport properties the dimensionless figure of merit ZT was calculated for different filling fractions of indium and cerium. Among these compositions a ZTmax of 1.1 at 700 K was obtained.
Is catchment productivity a useful predictor of taxa richness in lake plankton communities?
Authors: Soininen Janne , Luoto Miska
Published: October 2011

The influence of catchment variables on lake organisms is understudied. The terrestrial zone in the vicinity of lakes is, however, probably highly important for biota due to the effects on water chemistry and to various processes operating across ecosystem boundaries. We examined the relative importance of lake and catchment variables, as well as large‐scale geographical factors, on the taxa richness of phyto‐ and zooplankton in 100 small lakes in Finland. In variation partitioning, the variability of phytoplankton richness was most strongly related to the effects of lake variables, the joint effects of lake and catchment variables, and the joint effects of all three groups of variables. Zooplankton richness, in turn, was most strongly related to the effects of lake and catchment variables and the joint effect of lake and catchment variables. The exact results of the variation partitioning depended on the catchment sizes considered in the regression models. Among lake variables, planktonic richness was strongly related to variables indicating productivity. Among catchment variables, the normalized difference vegetation index (NDVI), indicating catchment productivity, showed a relatively strong association with planktonic richness. These results provide evidence that catchment variables such as the NDVI may be efficient predictors of planktonic richness in small lakes. It is possible that individual lakes embedded in a highly productive landscape have higher taxa richness than solitary, potentially productive lakes because of the high influx of dispersing propagules from the regional pool. We also suggest that catchment variables may respond to environmental changes at different scales than the lake variables, and explicit consideration of catchment productivity would therefore be useful when planning research and monitoring programs for freshwater organisms.
Hydraulic Fracture Simulation of Two-Phase Flow: Discrete Fracture Modelling/Mixed Finite Element Approach
Authors: Belhaj Hadi , Dhabi Abu , Mnejja Mokhles
Published: October 2011

Hydraulic fracturing is a technique commonly used to mitigate formation damage and improve well productivity. This stimulation technique is frequently used to improve oil and gas recoveries from tight reservoirs by virtue of squeezing fracturing fluid under high pressure exceeding formation fracture and propagation pressures. However, the prediction of the production performance of hydraulically-fractured wells, an essential step during hydraulic fracture design, uses analytical solutions that cannot reproduce the complexities associated with flow from the near-wellbore area into the well with both matrix and fracture flow contributions.

A sophisticated numerical model, which is based on Computational Fluid Dynamics (CFD), has been used to simulate the fluid flow near the wellbore with the presence of an induced fracture perpendicular to the well trajectory at the pay zone. We used the DFM (Discrete Fracture Model) where the hydraulic fracture is explicitly represented in the model.

In this modeling proposal, the fracture is presented as an interface through the rock matrix domain with nonlocal transmission conditions. This allows for communication between flow through the fracture and flow into the matrix systems. Therefore, it will not be necessary to use mesh refinement around the fracture. This is considered a big advantage over most currently used modeling techniques. It is emphasized in this modeling scheme that the fracture is discretized as a 1-D entity to account for fracture aperture by an integral form of the flow equations. Following this, the discrete fracture model is implemented using the MFEM (Mixed Finite Element Method). A case study is presented to support the field application of this unique modeling approach.
Experimental Design for Resource Estimation: A Comparison with the Probabilistic Method
Authors: Cebastiant A. , Osbon R. A.
Published: October 2011

This paper presents a comparison between the increasingly popular experimental design method and the simpler and quicker Monte-Carlo probabilistic technique used to manage subsurface uncertainty, and provide estimates of hydrocarbons in place and ultimate recovery. The experimental design method is based on simulated reservoir models which describe the key static and dynamic uncertainties.

Experimental design can be an expensive tool to adopt, especially when dealing with large numbers of static uncertainties, as it involves significant investment in time and human and computing resources to construct the required reservoir models. A case study is presented whereby Monte-Carlo probabilistic volume estimations were calculated prior to the experimental design method to obtain a quick estimate of the hydrocarbon in place and ultimate recovery. An experimental design was then undertaken and the results compared with the probabilistic outcomes.

The analysis provides interesting insights into the benefits and some of the limitations of the two methods when used for estimation of hydrocarbon in place and ultimate recovery. Fields examples are used to illustrate the different methodologies.
Impact of Miscibility on Gas-Oil Gravity Drainage in Fractured Reservoirs
Authors: Suicmez V. Sander , Karpan Volodymyr , Dindoruk Birol
Published: October 2011

A significant proportion of the world remaining oil reserves is residing in fractured reservoirs. Conventional recovery mechanisms may result in low oil recovery efficiencies in such reservoirs. Gas injection may be one of the few techniques, which can boost production from these resources. However, higher capillary pressures associated with the matrix blocks coupled with the extreme hydraulic contrast between the matrix and the fractures may result in ultimate recovery factors significantly lower than the equivalent non-fractured systems. Miscible or near-miscible gas injection may substantially boost the ultimate oil recovery as the interfacial tension and hence the capillary pressure vanishes or diminishes. Furthermore, the viscosity of the oil can be significantly reduced by mixing and interacting with the injectant, leading to further increase in oil drainage rate.

Due to the nature of the problem that originates from the extreme contrast between matrix and fracture, numerically it is considered to be a difficult problem. Therefore, it is important to design an appropriate grid system for this class of reservoir systems. We first validate our model by conducting black oil simulations to match the previously performed gas-oil gravity drainage (GOGD) experiments. We then generate a three-component synthetic oil to perform compositional simulations of gas injection at different enrichment conditions; immiscible, near-miscible and first-contact miscible. We show that ultimate recovery and oil drainage rate significantly increase once the miscibility is developed. In addition, we study the effect of various block boundary conditions that are aligned with various geological artifacts, like horizontally-oriented impermeable shale layers on recovery efficiency. We show that impermeable layers significantly reduce the performance of the gas-oil gravity drainage process for immiscible gas injection, while increasing the recoveries substantially for multiple- and first-contact miscible gas injection cases.
Three-Phase Pore-Network Modelling for Mixed-Wet Carbonate Reservoirs
Authors: Al-Dhahli Adnan R. , Geiger Sebastian , van Dijke Marinus I.
Published: October 2011

Carbonate reservoirs have structural heterogeneities (triple porosity: pore-vug-fracture) and are mixed-to oil-wet. The interplay of structural and wettability heterogeneities impacts the sweep efficiency and oil recovery. The choice of an IOR or EOR process and the prediction of oil recovery requires a sound understanding of the fundamental controls on fluid flow in mixed-to oil-wet carbonate rocks and physically robust flow functions, i.e. relative permeability and capillary pressure functions. Obtaining these flow functions is a challenging task, especially when three fluid phases coexist. In this work we use pore-network modelling, a reliable and physically-based simulation tool, to predict three-phase flow functions. We have developed a new pore-scale network model for rocks with variable wettability. Unlike other models, this model comprises a novel thermodynamic criterion for formation and collapse of oil layers. The new model hence captures film/layer flow of oil adequately which impacts the oil relative permeability at low oil saturation and hence the accurate prediction of residual oil. Pore-networks extracted from pore-space reconstruction methods and CT images have been used as input for our simulations and the model comprises a constrained set of parameters that can be tuned to mimic the wetting state of a given reservoir. We have validated our model with available experimental data for a range of wettabilities. A sensitivity analysis has been carried out to investigate the dependency of relative permeabilities on layer collapse and film/layer flow under various wetting conditions. Additionally, WAG injection has been simulated with different lengths of so-called multi-displacement chains and different flood end-points. The flow functions generated by our model can be passed to the next scales (upscaling) to predict the oil recovery at the reservoir scale and we demonstrate this using a proof-of-concept study.
Optimizing Development Well Placements Within Geological Uncertainty Utilizing Sector Models
Authors: Yuen Bevan , Rashid Omar , Al-Shammari Methgal , Al-Ajmi Fahad , Pham Tony , Rabah Mesdour , Moreno Juan Carlos
Published: October 2011

Uncertainties, particularly in geological parameters are always present and are significant in field and reservoir development. These uncertainties could be those perceived by geologists and engineers or exist in the available data. Industry has been using uncertainty analysis to identify, address and mitigate risk. Field development strategies and well placement depend significantly on reservoir geological characterization, maturity of the depletion stage, technological factors, drive mechanism and other parameters. Well placement optimization is normally performed using a deterministic (most likely) model. The optimum placement of wells within geologic uncertainty is the issue addressed in this paper.

This paper discusses an application of the workflow performing uncertainty analysis on a sector model of a conceptual reservoir and its optimization technique of development wells under geological uncertainty. Tornado plots are used to identify the highest critical parameters among the list of uncertainties of the reservoir. Experimental Design, Proxy Model, and Monte Carlo simulation are then used to generate a density probabilistic distribution of cumulative production to identify the 10%, 50% and 90% probability (P10, P50 and P90) cases. The best field operation strategy is identified by the lowest risk (highest probability) among strategies considered. Optimum injector-producer spacing, producer-producer spacing, horizontal completion, well length and orientation are obtained at pre-defined risk level under geologic uncertainties. Results show that the optimized development plan has reduced the associated risk substantially compared to the pre-optimized case with this process.
Fracture Modeling in a Weakly Fractured Carbonate Reservoir, Offshore UAE
Authors: Williams M. P. , Nivarthi S. S. , Al-Shehhi B. H. , Edwards E.
Published: October 2011

This paper describes the workflow used to assess modeling the impact of fractures (and faults) on the dynamic performance of a Lower Cretaceous reservoir located offshore Abu Dhabi. The reservoir is not highly fractured and the modeling challenge is to identify a practical method to incorporate their impact in a geologic and simulation model. The work plans developed to address these issues consist of four elements of a conceptual fault and fracture model - these are: two groups of diffuse fractures in specified layers; seismic scale faults; and fracture corridors. This paper focuses on learnings from the study of the first two elements of the developed work plans - i.e., modeling the impact of diffuse fractures on water movement.

The workflow began by modelling diffuse fractures at mini-sector scale (single geo-model grid-cell with layers and properties). Fracture parameters have been defined for low-side, most likely and high-side cases based on core data from 80 wells. By preparation of discrete fracture network (DFN) models for these cases and calibration to well test permeability, we are able to define a permissible range of fracture parameter values; and also to define the sensitivity of each fracture parameter. Dual media mini-sector simulation models are then used to compare water breakthrough time and evolution for different DFN models. The mini-sector models are also used to estimate the range of possible behaviours given the uncertainty in fracture data and other key factors like matrix-fracture transfer.

The results of this modeling work were used to formulate plans and recommendations for full-field modeling. A key conclusion derived from this study was that an effective single medium model would be adequate for full-field modeling of the subject reservoir. Work on the effective single medium full-field model is currently underway and the results-to-date are promising in terms of modeling reservoir behavior.
A New Simulation Grid Type is Demonstrated for the Giant Troll Oil and Gas Field
Authors: Vinje Jo , Nybø Roger , Grinestaff George
Published: October 2011

A new type of grid used in the dynamic simulation model of the giant Troll Field is presented. The grid consists of a stratigraphic and a horizontal layered part. Hence, it is named hybrid grid. The horizontal part encompasses the thin oil zone and a small distance into the gas cap and water zone, the rest of the grid follows the stratigraphy. The reason for choosing such a grid for the Troll Field is the dipping stratigraphic layering, a thin oil column, and the large area that the field covers. Another factor is the long horizontal wells that drain the oil. The horizontal grid has a high vertical resolution of 2 m to accurately capture the thin oil column, and for satisfactorily representing horizontal wells close to the fluid contacts. Above and below the horizontal grid the layers follow the stratigraphy to represent the geology with a minimum number of grid blocks. The paper shows why the hybrid grid is superior compared to other grid types for a gas field with a thin oil column, and covering a large area. The paper also describes how to build a hybrid grid, and the work processes for up-scaling and history matching the model. The new Troll model has currently replaced the 15 simulation models that previously were used to represent dynamically the Troll Field.
Reservoir Characterization, Fracture Mapping, and Well Placement Using a Suite of Logging-While-Drilling Images with Multiple Resolutions in a Marginal, Middle East Carbonate Reservoir
Authors: Al Daghar Khadija , Ihab Tarek , Sayed Raza , Abdelaal Atef , Ramos Luis , Chemali Roland , Aki Ahmet , Azzam Samer , Razek Omar Abdel
Published: October 2011

In a low-permeability Middle East carbonate reservoir, geologists, petrophysicists, and reservoir and drilling engineers had multiple requirements to optimally place the well, characterize and model fractures and faults, and evaluate the petrophysical attributes and cutoffs of the formation. A suite of logging-while-drilling (LWD) sensors was combined into a single bottomhole assembly (BHA) with the objective of acquiring the information needed to update the static model.

An integrated study was then performed using production logs, which led to an improved dynamic model within this sector of the reservoir. An additional objective was to evaluate the contribution from each sensor for future applications in this field, or in similar fields. Based on this assessment, a workflow was agreed upon for optimizing the petrophysical data acquisition program and conveyance methods. From a scientific point of view, the comparison of the various logs and images helped to better understand the response of the various sensor measurements for this particular field.
Improving Reservoir Characterisation and Simulation with Near Wellbore Modeling
Authors: Chandra V. , Hamdi H. , Corbett P. W. , Geiger S.
Published: October 2011

New reservoir characterisation methods are needed to integrate multi-scale exploration and development data, particularly at the interface between well and field models. In this paper we illustrate a novel workflow involving high resolution Near Wellbore Modeling (NWM), which allows us to accurately include seismic, wire-line data, FMI, and well core logs from multi-porosity reservoirs in field-scale reservoir simulations. We demonstrate that NWM improves reservoir characterization and production management. The workflow was applied to a realistic clastic reservoir with high variance at small scale and can also be extended for carbonate reservoirs. We have performed a number of sensitivities comparing conventional local grid refinement in the near wellbore region with that involving NWM and obtained a significant increase in the accuracy of reservoir characterization and the calibration of dynamic models. Centimetre-scale models, containing several million cells, representing the fine geological details of the near-wellbore region were constructed using available data from seismic, core, open-hole and production well-log suits. Sensitivities were performed using these high-resolution models to obtain regular grids with the best possible up-scaling. The resulting well models were imported into a field-scale simulation model to evaluate the dynamic behavior of the reservoir employing numerical well testing. Our results show that using NWM tools for reservoir modeling yields more precise flow calculations and improves our fundamental understanding of the interactions between the reservoir and the wellbore.