Multicriteria Hydraulic Fracturing Optimization for Reservoir Stimulation

A complete model is presented in this article for design optimization of hydraulic fracturing to enhance reservoir production. The model integrates reservoir properties, various design constraints to avoid induced formation damage, a hydraulically driven fracture geometry model, a hydrocarbon production model, and an economic model in deciding on the optimum values of various treatment parameters. The design constraints are intended to ensure that an optimum design obtained from the model can be executed in the field using the specified surface equipment and without causing uncontrolled fracture growth and/or initiation of multiple secondary fractures. A pseudo-3D fracture model is improved to establish better compatibility relationships between reservoir properties, treatment parameters, and fracture growth. Features of Genetic Algorithm and Evolutionary Operation are combined to develop a robust optimization algorithm that executes complex interactions between the above-mentioned modules to achieve an optimum design. The capability and robustness of the proposed model is demonstrated by applications to a tight-gas reservoir. By trade-off analysis between production/NPV and treatment cost, it is shown that only a 13% sacrifice of the maximum possible production/net present value (NPV) over ten years can save up to 52% of the fracturing treatment cost. Various other design issues are also investigated by sensitivity analyses.     

Enzymic and in sacco methods to estimate rumen degradation of food protein in cattle

BACKGROUND: Two factorial studies compared enzymic and in sacco methods to estimate degradation of ruminant foods. Enzyme degradation (in vitro = enzyme) was determined from the release of leucine‐equivalent amino acid (LA) crude protein (CP) from sunflower meal (SF), maize gluten meal (MG), distillers' dark grain (DG) and field beans (FB) after their separate incubations with Streptomyces griseus enzyme for 0–24 h. In sacco crude protein (CP) degradation of these foods was estimated during washing (0 h) and rumen incubations in fistulated cows for 2–24 h. The LA data were expressed as g LA per either kg of CP (LACP) or acid‐hydrolysable LA (HLA) of each food and compared with in sacco data. RESULTS: These methods showed comparable degradation with time (P < 0.01). The in sacco and HLA were greater than LACP for all foods except MG where in sacco value was either lower or equal to LACP depending upon the incubation time (P > 0.05 or P < 0.05). Conversely, HLA was significantly (P < 0.01) greater than LACP from 2 h onwards. At 0 h, in sacco values were significantly greater than those of enzyme for SF, DG and FB (P < 0.05) but not for MG. The foods differed significantly for degradation constants (a, b, c) in each method (P < 0.05). CONCLUSIONS: Despite variations between in sacco and enzyme estimates for different foods, the relationships between these estimates suggest that the HLA enzyme method has the potential to estimate food degradation. Copyright © 2007 Society of Chemical Industry     

An endo-acting proline-specific oligopeptidase from Treponema denticola ATCC 35405: evidence of hydrolysis of human bioactive peptides

An endo-acting proline-specific oligopeptidase (prolyl oligopeptidase [POPase], EC 3.4.21.26) was purified to homogeneity from the Triton X-100 extracts of cells of Treponema denticola ATCC 35405 (a human oral spirochete) by a procedure that comprised five successive fast protein liquid chromatography steps. The POPase is a cell-associated 75- to 77-kDa protein with an isoelectric point of ca. 6.5. The enzyme hydrolyzed (optimum pH 6.5) the Pro-pNA bond in carbobenzoxy-Gly-Pro-p-nitroanilide (Z-Gly-Pro-pNA) and bonds at the carboxyl side of proline in several human bioactive peptides, such as bradykinin, substance P, neurotensin, angiotensins, oxytocin, vasopressin, and human endothelin fragment 22-38. The minimum hydrolyzable peptide size was tetrapeptide P3P2P1P'1, while the maximum substrate size was ca. 3 kDa. An imino acid residue in position P1 was absolutely necessary. The hydrolysis of Z-Gly-Pro-pNA was potently inhibited by the following, with the Ki(app) (in micromolar) in parentheses: insulin B-chain (0.7), human endothelin-1 (0.5), neuropeptide Y (1.7), substance P (32.0), T-kinin (4.0), neurotensin (5.0), and bradykinin (16.0). Chemical modification and inhibition studies suggest that the POPase is a serine endopeptidase whose activity depends on the catalytic triad of COOH ... Ser ... His but not on a metal. The amino acid sequence around the putative active-site serine is Gly-Gly-Ser-Asn-Pro-Gly. The enzyme is suggested to contain a reactive cysteinyl residue near the active site. Amino acid residues 4 to 24 of the first 24 N-terminal residues showed a homology of 71% with the POPase precursor from Flavobacterium meningosepticum and considerable homology with the Aeromonas hydrophila POPase. The ready hydrolysis of human bioactive peptides at bonds involving an imino acid residue suggests that enzymes like POPase may contribute to the chronicity of periodontal infections by participating in the peptidolytic processing of those peptides.     

Modelling and controller design of an isolated diesel enginepermanent magnet synchronous generator

A method to analyze the steady-state performance of a stand-alone permanent magnet synchronous generator driven by a diesel engine is presented. The proposed method is based on equivalent d-q circuits and the phasor diagram of such a generator under steady-state conditions. A fixed capacitor-thyristor controlled reactor scheme is used to regulate the generator terminal voltage by controlling the thyristor ignition angle. Furthermore the overall system dynamics are modelled in terms of state variables and control inputs. Based on a reduced order linearized model, digital optimal state and output feedback controllers are designed by minimising a quadratic performance index using the dynamic programming technique. The objective of the controller is to maintain the load voltage and frequency constant under varying load conditions. The controller's effectiveness is assessed by examining the closed-loop system response to sudden load changes     

Assembly of hepatic gap junctions. Topography and distribution of connexin 32 in intracellular and plasma membranes determined using sequence-specific antibodies

The subcellular distribution in rat liver and the topography in intracellular and plasma membranes of connexin 32, a major protein component of gap junctions, was studied using sequence-specific anti-peptide antibodies generated to extracellular and intracellular domains of the protein. The distribution of connexin 32 in liver analyzed using SDS-polyacrylamide gel electrophoresis and Western blotting showed the relative protein levels in the subcellular fractions to be: lateral plasma membranes > Golgi membranes > sinusoidal plasma membranes > lysosomes. Low amounts of connexin 32 were detected in microsomes, endosomes, and bile canalicular plasma membranes. Six highly conserved cysteine residues are located in the amino acid sequences comprising the two extracellular loops of all connexins thus far isolated, and these loops are positioned to extend the channel in the lipid bilayers across the intercellular region of the gap junction. In the present work, the intramolecular disulfide bonds linking the extracellular loops in gap junctions were shown to be present in connexins located in plasma membranes, Golgi, and a microsomal fraction, and it was concluded that the disulfide linkages were formed in the endoplasmic reticulum. In addition, immature configurations of connexin 32, probably occurring during membrane insertion, were detected in liver microsomal fractions. The results contribute to charting of the biogenetic routes followed by connexins in hepatocytes and the general mechanisms of gap junction assembly.     

Modeling and control of a finger-like mechanism using bending shape memory alloys

Microsystem Technologies - In this research a biologically inspired finger-like mechanism similar to human musculoskeletal system is developed based on Shape Memory Alloys (SMAs). SMA actuators are...     

Selective chaotic maps Tiki-Taka algorithm for the S-box generation and optimization

Neural Computing and Applications - Cryptography often involves substituting (and converting) the secret information into dummy data so that it could reach the desired destination without leakage....     

A systematic review on emperor penguin optimizer

Neural Computing and Applications - Emperor Penguin Optimizer (EPO) is a recently developed metaheuristic algorithm to solve general optimization problems. The main strength of EPO is twofold....