Transient pressure analysis of a volume fracturing well in fractured tight oil reservoirs

This research was supported by the Ministry of Land and Resources Special Geological Survey: Upper Paleozoic Marine Shale Gas Geological Survey in Yunnan, Guizhou, Guangxi Region (DD20160178), The Key Laboratory of Unconventional Petroleum Geology of Geological Survey of China Open Fund and the Major National R&D Projects: Study on the Test Method for Shale Structure and Composition at Different Scales with project number: 2016ZX05034-003-006.Peer reviewedPostprin

Study on facies-controlled model of a reservoir in Xijiang 24-3 oilfield in the Northern Pearl River Mouth Basin

To better understand the internal structure of the Xijiang 24-3 Oilfield in the Northern Pearl River Mouth Basin, a reasonable and effective three-dimensional quantitative geological model is needed to characterize the distribution characteristics of the reservoir. Xijiang 24-3 Oilfield is a braided river delta deposition, which contains many sedimentary microfacies in three subfacies zones. The reservoir structure is complex and heterogeneous. The reservoir modeling research was conducted on the Xijiang 24-3 oilfield H3A reservoir. Analysis of the oilfield core, the well-logging, and seismic data, establish a regional structural model. The regional sedimentary microfacies model is simulated by multi-point geostatistics. The reservoir property model is established by using facies-controlled modeling technology with sedimentary microfacies as a constraint condition. A facies-controlled property model and a non-facies-controlled property model are established respectively. The facies-controlled model corresponds well with the sedimentary microfacies of the reservoir, and the variation trend of the model shows a higher coincidence rate with the distribution characteristics of the well. The facies-controlled model reflects the spatial distribution characteristics of the physical properties of the underground reservoir and is in accord with the actual geological understanding of the reservoir. This model also provides a reliable basis for the next stage of reservoir description and a basis for further exploration and development work.Cited as: Zheng, L., Chen, C., Lu, C., Cheng, M. Study on facies-controlled model of a reservoir in Xijiang 24-3 oilfield in the Northern Pearl River Mouth Basin. Advances in Geo-Energy Research, 2018, 2(3): 282-291, doi: 10.26804/ager.2018.03.0

An Information Perception-Based Emotion Contagion Model for Fire Evacuation

In fires, people are easier to lose their mind. Panic will lead to irrational behavior and irreparable tragedy. It has great practical significance to make contingency plans for crowd evacuation in fires. However, existing studies about crowd simulation always paid much attention on the crowd density, but little attention on emotional contagion that may cause a panic. Based on settings about information space and information sharing, this paper proposes an emotional contagion model for crowd in panic situations. With the proposed model, a behavior mechanism is constructed for agents in the crowd and a prototype of system is developed for crowd simulation. Experiments are carried out to verify the proposed model. The results showed that the spread of panic not only related to the crowd density and the individual comfort level, but also related to people’s prior knowledge of fire evacuation. The model provides a new way for safety education and evacuation management. It is possible to avoid and reduce unsafe factors in the crowd with the lowest cost

Shear Wave Propagation in Soft Tissue with Ultrasound Vibrometry

Studies have found that shear moduli, having the dynamic range of several orders of magnitude for various biological tissues, are highly correlated with the pathological statues of human tissue such as livers. Shear moduli can be investigated by measuring the attenuation and velocity of the shear wave propagation in a tissue region. Many efforts have been made to measure shear wave propagations induced by different types of force, which include the motion force of human organs, external applied force, and ultrasound radiation force. In the past 15 years, ultrasound radiation force has been successfully used to induce tissue motion for imaging tissue elasticity. Vibroacoustography (VA) uses bifocal beams to remotely induce vibration in a tissue region and detect the vibration using a hydrophone. The vibration center is sequentially moved in the tissue region to form a two-dimensional image. Acoustic Radiation Force Imaging (ARFI) uses focused ultrasound to apply localized radiation force to small volumes of tissue for short durations and the resulting tissue displacements are mapped using ultrasonic correlation based methods. Supersonic shear image remotely vibrates tissue and sequentially moves vibration center along the beam axis to create intense shear plan wave that is imaged at a high frame rate (5000 frames per second). These image methods provide measurements of tissue elasticity, but not the viscosity. Because of the dispersive property of biological tissue, the induced tissue displacement and the shear wave propagation are frequency dependent. Tissue shear property can be modeled by several models including Kelvin-Voigt (Voigt) model, Maxwell model, and Zener model. The Voigt model effectively describes the creep behavior of tissue, The Maxwell model effectively describes the relaxation process, and the Zener model effectively describes both creep and relaxation but it requires one extra parameter. The Voigt model is often used by many researchers because of its simplicity and the effectiveness of modeling soft tissue. The Voigt model consists of a purely viscous damper and a purely elastic spring connected in parallel. For Voigt tissue, the tissue motion at a very low frequency largely depends on the elasticity, while the motion at a very high frequency largely depends on the viscosity. In general, the tissue motion depends on both elasticity and viscosity, and estimates of elasticity by ignoring viscosity are biased or erroneous. In 1951, Dr. Oestreicher published his work to solve the wave equation for the Voigt soft tissue with harmonic motions. With assumptions of isotropic tissue and plane wave, he derived equations that relate the shear wave attenuation and speed to the elasticity and viscosity of soft tissue. However, Oestreicher’s method was not realized for applications until the half century later. In the past ten years, Oestreicher’s method was utilized to quantitatively measure both tissue elasticity and viscosity. Ultrasound vibrometry has been developed to noninvasively and quantitatively measure tissue shear moduli. It induces shear waves using ultrasound radiation force and estimates the shear moduli using shear wave phase velocities at several frequencies by measuring the phase shifts of the propagating shear wave over a short distance using pulse echo ultrasound. Applications of the ultrasound vibrometry were conducted for viscoelasticities of liver, bovine and porcine striated muscles, blood vessels, and hearts. A recent in vivo liver study shows that the ultrasound vibrometry can be implemented on a clinical ultrasound scanner of using an array transducer. One potential application of ultrasound vibrometry is to characterize shear moduli of livers. The shear moduli of liver are highly correlated with liver pathology status. Recently, the shear viscoelasticity of liver tissue has been investigated by several research groups. Most of these studies applied ultrasound radiation force in liver tissue regions, measured the phase velocities of shear wave in a limited frequency range, and inversely solved the Voigt model with an assumption that liver local tissue is isotropic without considering boundary conditions. Because of the boundary conditions, shear wave propagations are impacted by the limited physical dimensions of tissue. Studies shows that considerations of boundary conditions should be taken for characterizing tissue that have limited physical dimensions such as heart, blood vessels, and liver, when ultrasound vibrometry is used

Structural and functional analysis of the pro-domain of human cathelicidin, LL-37

Cathelicidins form a family of small host defense peptides distinct from another class of cationic antimicrobial peptides, the defensins. They are expressed as large precursor molecules with a highly conserved pro-domain known as the cathelin-like domain (CLD). CLDs have high degrees of sequence homology to cathelin, a protein isolated from pig leukocytes and belonging to the cystatin family of cysteine protease inhibitors. In this report, we describe for the first time the X-ray crystal structure of the human CLD (hCLD) of the sole human cathelicidin, LL-37. The structure of hCLD, determined at 1.93 Å resolution, shows the cystatin-like fold and is highly similar to the structure of the CLD of the pig cathelicidin, protegrin-3. We assayed the in vitro antibacterial activities of hCLD, LL-37 and the precursor form, pro-cathelicidin (also known as hCAP18), and we found that the unprocessed protein inhibited the growth of Gramnegative bacteria with efficiencies comparable to the mature peptide, LL-37. In addition, the antibacterial activity of LL-37 was not inhibited by hCLD intermolecularly, since exogenously added hCLD had no effect on the bactericidal activity of the mature peptide. hCLD itself lacked antimicrobial function and did not inhibit the cysteine protease, cathepsin L. Our results contrast with previous reports of hCLD activity. A comparative structural analysis between hCLD and the cysteine protease inhibitor stefin A showed why hCLD is unable to function as an inhibitor of cysteine proteases. In this respect, the cystatin scaffold represents an ancestral structural platform from which proteins evolved divergently, with some losing inhibitory functions

Enhancing Higher Order Question of Student Through Problem Based Learning at Grade X MIA 6 of SMA N 4 Surakarta

The research aims to enhance the Higher Order Question of student through problem based learning in Biology at Grade X MIA 6 of SMA N 4 Surakarta. The research was a four-cycle action research conducted in academic year 2014/2015. All questions were analyzed based on revised Bloom Taxonomy. Data were validated using triangulation method. The result of the research showed that problem based learning effectively enhance student\u27s High Order Question (C4-C6). The percentage of each High Order Question (C4-C6) in pre cycle were 0%. The percentage of C4 type question at first cycle (73,14%), second cycle (52,13%), third cycle (56,05%), and fourth cycle (58,42%). The percentage of each High Order Question (C4-C6) in pre cycle were 0%. The percentage of C5 type question at first cycle (18,37%), second cycle (9,57%), third cycle (10,30%), and fourth cycle (58,42%). The percentage of each High Order Question (C4-C6) in pre cycle were 0%. The percentage of C6 type question at first cycle (8,16%), second cycle (38,30%), third cycle (41,18%) and fourth cycle (25,74%)

Molecular mechanism underlying transport and allosteric inhibition of bicarbonate transporter SbtA

SbtA is a high-affinity, sodium-dependent bicarbonate transporter found in the cyanobacterial CO2-concentrating mechanism (CCM). SbtA forms a complex with SbtB, while SbtB allosterically regulates the transport activity of SbtA by binding with adenyl nucleotides. The underlying mechanism of transport and regulation of SbtA is largely unknown. In this study, we report the three-dimensional structures of the cyanobacterial Synechocystis sp. PCC 6803 SbtA–SbtB complex in both the presence and absence of HCO3− and/or AMP at 2.7 Å and 3.2 Å resolution. An analysis of the inward-facing state of the SbtA structure reveals the HCO3−/Na+ binding site, providing evidence for the functional unit as a trimer. A structural comparison found that SbtA adopts an elevator mechanism for bicarbonate transport. A structure-based analysis revealed that the allosteric inhibition of SbtA by SbtB occurs mainly through the T-loop of SbtB, which binds to both the core domain and the scaffold domain of SbtA and locks it in an inward-facing state. T-loop conformation is stabilized by the AMP molecules binding at the SbtB trimer interfaces and may be adjusted by other adenyl nucleotides. The unique regulatory mechanism of SbtA by SbtB makes it important to study inorganic carbon uptake systems in CCM, which can be used to modify photosynthesis in crops.</jats:p