bluuebunny/crossref_metadata_2025_split huggingface dataset:
Post-Frac Analysis Based on Flowback Results Using Chemical Frac-Tracers
Authors: Asadi Mahmoud , Woodroof Robert A. , Dumas Jerry Donald 
Published: November 2008

Abstract
Chemical frac tracing is used to evaluate flowback and cleanup efficiencies. The technique utilizes a family of unique, environmentally-friendly, fracturing fluid compatible chemical tracers to quantify segment-by-segment recovery for individual fracturing treatments and stage-by-stage recovery for multi-stage fracturing treatments. These chemical tracers with their unique chemical characteristics are mixed at a known concentration into frac fluid stages as the frac fluid is pumped downhole. Upon flowback, samples are collected and analyzed for tracer concentration. With the use of the mass balance method the flowback efficiency for each stage is calculated. These precise flowback calculations yield a more accurate assessment of cleanup efficiency. This paper presents several case histories in which the technique was implemented. Results and fracture flowback prognoses are presented. The results are also used to assess post-frac performance as a function of flowback efficiency.

Introduction

Chemical Frac Tracers
Chemical frac tracers, CFT's, are used to precisely calculate flowback and hence flowback efficiency and to evaluate fracture cleanup. Various chemical tracers with unique chemical characteristics are mixed at a known concentration and injected according to a pre-determined design throughout the frac fluid stages, such as the pad and the propping laden fluid stages. The characteristics of these tracers are unique. They do not react with each other, the formation or the tubular. They do not degrade with temperature or time, do not self-concentrate, and do not react with frac fluids. These tracers are detectable at low concentrations of 50 ppt (parts per trillion). They are also environmentally safe to handle, pump downhole and dispose. They are soluble in water, and unlike polymers, do not concentrate upon leakoff.
Upon flowback, samples are collected and analyzed for tracer concentration. With the use of the mass balance method, flowback of each frac fluid stage is calculated, and hence flowback efficiency for each stage of frac fluid injected. The precise flowback calculation for each frac fluid stage yields the fracture cleanup efficiency. Chemical frac tracing can also be used as a means to understand vertical communication between zones. Under this scenario, one chemical tracer is injected into each zone. Each zone is flowed back individually after a period of shut-in allowing the flow of fluid within the formation. Samples are collected and analyzed for tracer concentrations. If zones are communicating vertically under static conditions, the tracer from one zone can flow into other zones and hence will be detected accordingly.
Multi-Stage Fracturing Stimulations Improve Well Performance in Tight Oil Reservoirs of the Changqing Oilfield
Authors: Li Xianwen , Wei Hongmei , Chen Baochun , Liu Xinghui , Wang Wangcheng , Zhao Xinzhi 
Published: November 2008

Abstract
The oil reservoirs in the Changqing Oilfield consist of stacked sand/shale deposits, and the majority of the target zones have a permeability of 0.05–0.3mD. All oil wells completed in tight reservoirs from the Changqing Oilfield require fracture stimulation to achieve commercial production and to improve well productivity. Fracture stimulation is also very common for water injection wells to enhance injectivity. Multiple payzones in the region were either stimulated with standalone treatments that were isolated and pumped separately or with single-stage treatments to simultaneously treat several intervals using a kind of limited-entry technique. However, with the continuing development in these fields, larger pay intervals (gross pay thickness up to 75 meters) with poorer reservoir quality were encountered. Post-fracture production results indicated that the above stimulation techniques were not always effective in these tight reservoirs.
As a result, a new staging technique was evolved and employed to stimulate these tighter reservoirs with better economic effectiveness. With this technique, two or three pay intervals were first perforated and dual-stage fracture treatments were then performed: one stage at a time without using any mechanical isolation. The idea was two-fold:using the stress increase around the fracture created by the first injection to divert the subsequent treatment to un-stimulated interval(s), andusing the proppant banks created from the first propped treatment to minimize the proppant settling to the bottom portion of the fracture created by the second propped treatment.
Three-month average post-treatment production data indicated that the dual-stage treatments outperformed conventional single-stage treatments in some reservoir environments. Candidate selection was a key to the success of this technique, and reservoir conditions that favor these types of treatments are as follows: multiple pays, lower permeability, lower net pressure, and less stress contrast between different payzones. Radioactive tracer logging and microseismic fracture mapping were conducted to evaluate fracture height growth. This paper presents a case history of fracture performance evaluations. Reservoir data, fracture modeling and post-fracture production data were compiled and employed to demonstrate the benefits of this fracture treatment technique in some tight oil reservoirs.
Long-term seizure outcome after corpus callosotomy: a retrospective analysis of 95 patients
Authors: Tanriverdi Taner , Olivier André , Poulin Nicole , Andermann Frederick , Dubeau François 
Published: November 2008

Object
The authors report long-term follow-up seizure outcome in patients who underwent corpus callosotomy during the period 1981–2001 at the Montreal Neurological Institute.

Methods
The records of 95 patients with a minimum follow-up of 5 years (mean 17.2 years) were retrospectively evaluated with respect to seizure, medication outcomes, and prognostic factors on seizure outcome.

Results
All patients had more than one type of seizure, most frequently drop attacks and generalized tonicclonic seizures. The most disabling seizure type was drop attacks, followed by generalized tonic-clonic seizures. Improvement was noted in several seizure types and was most likely for generalized tonic-clonic seizures (77.3%) and drop attacks (77.2%). Simple partial, generalized tonic, and myoclonic seizures also benefited from anterior callosotomy. The extent of the callosal section was correlated with favorable seizure outcome. The complications were mild and transient and no death was seen.

Conclusions
This study confirms that anterior callosotomy is an effective treatment in intractable generalized seizures that are not amenable to focal resection. When considering this procedure, the treating physician must thoroughly assess the expected benefits, limitations, likelihood of residual seizures, and the risks, and explain them to the patient, his or her family, and other caregivers.
Molecular markers relating to malignant progression in Grade II astrocytoma
Authors: Yue Wei-Ying , Yu Su-Huan , Zhao Shi-Guang , Chen Zhong-Ping 
Published: November 2008

Object
Astrocytoma may progress rapidly or remain stable for many years. To clarify whether molecular characteristics could be prognostic factors, several cell cycling–associated molecular alterations in the diffuse astrocytoma have been investigated.

Methods
Thirty-three patients in whom WHO Grade II astrocytoma had been initially diagnosed were assigned to 1 of 3 groups. Group 1 consisted of 10 patients with malignant progression; the tumor had recurred within 5 years and histological analysis had confirmed that the tumor progressed to Grade III or IV. Group 2 consisted of 10 patients in whom there was no malignant progression; the tumor recurred within 5 years, but histological analysis confirmed that the tumor remained at Grade II. Group 3 consisted of 13 patients who did not experience recurrence within 5 years. Expression of Ki 67, TP53, p27, and p21 was examined using immunohistochemical analysis for the tumor samples obtained during the first and second (in recurrent cases) surgeries. Exons 5, 7, and 8 of TP53 were scanned by DNA sequencing.

Results
The Ki 67 labeling index expression was significantly higher in Group 1 (even though it was similar between initial and recurrent tumors) than that of Group 3 (p < 0.05). However, there was no difference between Group 2 (both initial and recurrent tumors) and Group 3. The TP53 protein accumulation was also higher in Group 1 than in Group 2 or 3 (p < 0.05); a difference in TP53 expression was not found between Groups 2 and 3. The p27 and p21 was expressed in all cases, but no predictive values were found. The p53 mutation was found only in 6 cases in Group 1.

Conclusions
Overexpression of TP53, TP53 mutation, and Ki 67 labeling index could be molecular markers in astrocytomas predicting malignant progression.
Long-term outcome after temporal lobe epilepsy surgery in 434 consecutive adult patients
Authors: Elsharkawy Alaa Eldin , Alabbasi Abdel Hamid , Pannek Heinz , Oppel Falk , Schulz Reinhard , Hoppe Mathias , Hamad Ana Paula , Nayel Mohamed , Issa Ahmed , Ebner Alois 
Published: November 2008

Object
The aim of this study was to evaluate the long-term efficacy of temporal lobe epilepsy (TLE) surgery and potential risk factors for seizure recurrence after surgery.

Methods
This retrospective study included 434 consecutive adult patients who underwent TLE surgery at Bethel Epilepsy Centre between 1991 and 2002.

Results
Hippocampal sclerosis was found in 62% of patients, gliosis in 17.3%, tumors in 20%, and focal cortical dysplasia (FCD) in 6.9%. Based on a Kaplan-Meier analysis, the probability of Engel Class I outcome for the patients overall was 76.2% (95% CI 71–81%) at 6 months, 72.3% (95% CI 68–76%) at 2 years, 71.1% (95% CI 67–75%) at 5 years, 70.8% (95% CI 65–75%) at 10 years, and 69.4% (95% CI 64–74%) at 16 years postoperatively. The likelihood of remaining seizure free after 2 years of freedom from seizures was 90% (95% CI 82–98%) for 16 years. Seizure relapse occurred in all subgroups. Patients with FCD had the highest risk of recurrence (hazard ratio 2.15, 95% CI 0.849–5.545). Predictors of remission were the presence of hippocampal atrophy on preoperative MR imaging and a family history of epilepsy. Predictors of relapse were the presence of bilateral interictal sharp waves and versive seizures. Six-month follow-up electroencephalography predicted relapse in patients with FCD. Short epilepsy duration was predictive of seizure remission in patients with tumors and gliosis; 28.1% of patients were able to discontinue antiepileptic medications without an increased risk of seizure recurrence (hazard ratio 1.05, 95% CI 0.933–1.20).

Conclusions
These findings highlight the role of etiology in prediction of long-term outcome after TLE surgery.
Implicit dual control based on particle filtering and forward dynamic programming
Authors: Bayard David S. , Schumitzky Alan 
Published: November 2008

AbstractThis paper develops a sampling‐based approach to implicit dual control. Implicit dual control methods synthesize stochastic control policies by systematically approximating the stochastic dynamic programming equations of Bellman, in contrast to explicit dual control methods that artificially induce probing into the control law by modifying the cost function to include a term that rewards learning. The proposed implicit dual control approach is novel in that it combines a particle filter with a policy‐iteration method for forward dynamic programming. The integration of the two methods provides a complete sampling‐based approach to the problem. Implementation of the approach is simplified by making use of a specific architecture denoted as a H‐block. Practical suggestions are given for reducing computational loads within the H‐block for real‐time applications. As an example, the method is applied to the control of a stochastic pendulum model having unknown mass, length, initial position and velocity, and unknown sign of its dc gain. Simulation results indicate that active controllers based on the described method can systematically improve closed‐loop performance with respect to other more common stochastic control approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Iridium‐Catalyzed Enantioselective Allylic Alkylation using Chiral Phosphoramidite Ligand Bearing an Amide Moiety
Authors: Onodera Gen , Watabe Keijiro , Matsubara Masaki , Oda Kazuhiro , Kezuka Satoko , Takeuchi Ryo 
Published: November 2008

AbstractNew chiral phosphoramidites with an amide moiety were used for iridium‐catalyzed asymmetric allylic alkylation reactions. The best results were obtained with a ligand bearing an oxazolidinone moiety. The reaction of cinnamyl acetate with diethyl sodiomalonate without the use of lithium chloride gave the branched product with 94% ee.
Fullerene‐Promoted Singlet‐Oxygen Photochemical Oxygenations in Glass‐Polymer Microstructured Reactors
Authors: Carofiglio Tommaso , Donnola Paola , Maggini Michele , Rossetto Massimiliano , Rossi Emiliano 
Published: November 2008

AbstractIn this paper we report the fabrication of thiolene‐based microstructured reactors (MRs) that have been specifically designed to include solid‐supported reagents within the microchannels network. We propose a convenient solution to realize reversible press‐fit, leak‐proof interconnects that greatly simplify the MR coupling to the external environment such as capillary tubing, sample reservoirs and pumps. The MRs have been used to carry out the oxidation of α‐terpinene and methionine using [60]fullerene, covalently linked to Tentagel® and silica gel matrices, as a singlet oxygen sensitizer. High conversions have been observed for both substrates although, in the case of α‐terpinene, a partial photodegradation of the endo‐peroxide product was detected. Interestingly, in the case of methionine, a quantitative conversion to the corresponding sulfoxides was achieved in about 40 seconds, using low‐power, white LED illumination. The reaction time is considerably shorter when compared to the batch procedure that requires, for the same process, about one hour illumination and the use of a 300‐W tungsten halogen lamp.
Enantioselective Hydrogenation of Enones with a Hydroformylation Catalyst
Authors: Scheuermann née Taylor Caroline J. , Jaekel Christoph 
Published: November 2008

AbstractUse of a typical rhodium precatalyst for hydroformylation results in the enantioselective hydrogenation of cyclic enones with up to 90% ee. Extensive screening of chiral ligands reveals the simple ligand Chiraphos as the best ligand, so far. The hydrogenation shows high chemoselectivity. Exclusive formation of saturated, chiral β‐branched ketones is observed. It is proposed that the catalyst follows a frustrated hydroformylation pathway (“monohydride‐based mechanism”) and differs by that from the classical cationic Schrock–Osborn type rhodium precatalysts (“dihydride‐based mechanism”) for enantioselective hydrogenation. The catalyst operates under neat conditions and is easily recyclable by simply distilling off the reaction mixture and treatment with syn gas prior to hydrogenation.
Are apes inequity averse? New data on the token‐exchange paradigm
Authors: Bräuer Juliane , Call Josep , Tomasello Michael 
Published: November 2008

AbstractRecent studies have produced mixed evidence about inequity aversion in nonhuman primates. Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253–258, 2005] found inequity aversion in chimpanzees and argued that effort is crucial, if subjects are to evaluate how they are rewarded in comparison to a competitor for an identical performance. In this study we investigated inequity aversion with chimpanzees, bonobos and orangutans, using the method of Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253–258, 2005] after introducing some methodological improvements. Subjects always received a less‐preferred food in exchange for a token, whereas the competitor received either the same type of food for their token (equity) or a more favored food for it (inequity). Apes did not refuse more of the less‐preferred food when a competitor had received the more favored food. Thus, with an improved methodology we failed to reproduce the findings of Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253–258, 2005] that apes show inequity aversion. Am. J. Primatol. 71:175–181, 2009. © 2008 Wiley‐Liss, Inc.
The synthesis of PHA‐g‐(PTHF‐b‐PMMA) multiblock/graft copolymers by combination of cationic and radical polymerization
Authors: Macit Hülya , Hazer Baki , Arslan Hülya , Noda Isao 
Published: November 2008

AbstractA new and promising method for the diversification of microbial polyesters based on chemical modifications is introduced. Poly(3‐hydroxy alkanoate)‐g‐(poly(tetrahydrofuran)‐b‐poly(methyl methacrylate)) (PHA‐g‐(PTHF‐b‐PMMA)) multigraft copolymers were synthesized by the combination of cationic and free radical polymerization. PHA‐g‐PTHF graft copolymer was obtained by the cationic polymerization of THF initiated by the carbonium cations generated from the chlorinated PHAs, poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHx) in the presence of AgSbF6. Therefore, PHA‐g‐PTHF graft copolymers with hydroxyl ends were produced. In the presence of Ce+4 salt, these hydroxyl ends of the graft copolymer can initiate the redox polymerization of MMA to obtain PHA‐g‐(PTHF‐b‐PMMA) multigraft copolymer. Polymers obtained were purified by fractional precipitation. In this manner, their γ‐values (volume ratio of nonsolvent to the solvent) were also determined. Their molecular weights were determined by GPC technique. The structures were elucidated using 1H‐NMR and FTIR spectroscopy. Thermal analyses of the products were carried out using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of proccessible polyaniline derivatives for corrosion inhibition
Authors: Bhandari Hema , Sathiyanaranayan S. , Choudhary Veena , Dhawan S. K. 
Published: November 2008

AbstractThis article reports the synthesis and characterization of copolymers based on aniline and substituted anilines by using dodecylbenzene sulfonic acid as a dopant. The copolymers were soluble in organic solvents, such as methanol, ethanol, isopropanol, N‐methylpyrrolidinone, dimethylsulphoxide, and have conductivity of the order of 1.5 to 10−7 S/cm depending upon the monomer ratios and extent of dopant used. The effect of substituents like 2‐methyl, 2‐ethyl, and 2‐isopropyl groups on the electrochemical, conductivity, thermal stability, solubilization, and spectroscopic behavior of the copolymers has been evaluated. The composition of the copolymers was determined by 1H‐NMR spectroscopy. Corrosion inhibition behavior of the copolymers in 1.0N HCl has been evaluated using linear polarization resistance method and Tafel extrapolation method. The corrosion efficiency depends upon the copolymer composition and it increased with increasing amount of 2‐alkyl aniline in the feed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis of Dibenzochalcogenaborins and Systematic Comparisons of Their Optical Properties by Changing a Bridging Chalcogen Atom
Authors: Kobayashi Junji , Kato Keiko , Agou Tomohiro , Kawashima Takayuki 
Published: November 2008

AbstractNovel hetero‐π‐conjugated compounds (dibenzochalcogenaborins) with the same molecular framework, bearing a boron atom as an acceptor and chalcogen atoms as a donor, were synthesized, and systematic comparisons among these molecules were performed. X‐ray crystallographic analysis of these molecules showed similar structures with high planarity. UV/Vis spectroscopy and theoretical calculations revealed that the absorption maxima and the HOMO–LUMO gap changed by systematically changing the bridging chalcogen atom. Dibenzooxaborin and dibenzothiaborin showed fluorescence emission both in solution and in the solid state with a small Stokes shift, indicating the high rigidity of these compounds. On the other hand, dibenzoselenaborin exhibited a very weak fluorescence as a result of the heavy atom effect.
Spatial variability of rainfall regions in West Africa during the 20th century
Authors: Yepdo Djomou Zéphirin , Monkam David , Lenouo André 
Published: November 2008

AbstractFour regions spread in five areas are identified in West Africa for the base period 1901–1940. Trends have a magnitude of up to 1.5 K per century, with a decreasing of the precipitation since the year 1970. The application of a segment of 15 years with overlap going from 1901 to 1940 (P0), and 1961 to 1998 (P4) throughout the periods 1916–1955 (P1), 1931–1970 (P2) and 1946–1985 (P3), shows important spatiotemporal modifications of rainfall regions south of 15°N. From P0 to P4, the surface of semiarid land doubles while wetland is reduced to half. Copyright © 2008 Royal Meteorological Society
Caenorhabditis elegansas an undergraduate educational tool for teaching RNAi
Authors: Andersen Janet , Krichevsky Alexander , Leheste Joerg R. , Moloney Daniel J. 
Published: November 2008

AbstractDiscovery of RNA‐mediated interference (RNAi) is widely recognized as one of the most significant molecular biology breakthroughs in the past 10 years. There is a need for science educators to develop teaching tools and laboratory activities that demonstrate the power of this new technology and help students to better understand the RNAi process.C. elegansis an ideal model organism for the undergraduate laboratory because of the simplicity of worm maintenance, its well‐studied genetic background, and the fact that it can be employed as a model organism in laboratory environments where vertebrate research is restricted. Certain unique features ofC. elegansmake it a very suitable organism for RNAi studies. Specifically, nematode strains highly sensitive to RNAi are readily available from public sources, and RNAi induction by a feeding method is an uncomplicated procedure that lends itself readily as an educational tool. In this article, we provide a detailed depiction of the use ofC. elegansas an RNAi educational tool, describing two separate RNAi‐based experiments. One is a qualitative experiment where students can examine the effects of knocking down theunc‐22gene involved in the regulation of muscle contraction, which results in a “twitching” phenotype. The other experiment is a quantitative RNAi experiment, where students measure the effect of knocking down thelsy‐2gene involved in neuronal development. Although these experiments are designed for a college‐level study, nematode research projects can also be accomplished in secondary school facilities.