The effect of aromatic side chains on the dilational rheological properties of N-acyltaurate amphiphiles at water-decane interfaces.

To elucidate the effect of aromatic side chains on dilational rheological properties of N-acyltaurate amphiphiles at the decane-water interface, the interfacial rheological properties of sodium N-2-(2-naphthoxy)-tetradecanoyltaurinate (12+N-T) and sodium N-2-(p-butylphenoxy)-tetradecanoyltaurinate (12+4B-T) were investigated utilizing the drop shape analysis method. The effects of adsorption time, interfacial pressure, oscillating frequency, and bulk concentration on the interfacial dilational modulus and phase angle were explored. The results show that the 12+4B-T molecule with a longer hydrophobic chain shows a higher ability for reducing the interfacial tension (IFT). In addition, the interfacial films of both 12+N-T and 12+4B-T are dominated by diffusion exchange at high concentrations. The rigidity of molecules controls the diffusion exchange at low concentrations, while the molecular hydrodynamic radius determines the diffusion exchange at high concentrations. Thus, at low concentrations, the stronger intermolecular interaction between 12+4B-T molecules results in higher dilational modulus values than 12+N-T. When approaching the CMC (critical micelle concentration) value, the rapid diffusion exchange of 12+4B-T between the sublayer micelles and the interface causes a significant decrease in the dilational modulus, while the relatively rigid structure of 12+N-T enables a higher dilational modulus than 12+4B-T. What's more, the longer hydrophobic chain allows 12+4B-T molecules to escape from the interface more easily, resulting in a higher phase angle at low concentrations. However, the diffusion exchange of 12+4B-T is slower than that of 12+N-T, which results in lower phase angles for 12+4B-T than 12+N-T at high concentrations. In general, the introduction of a rigid naphthalene ring in the molecular structure gives the interfacial film greater strength at high concentration. The research results in this paper provide a new technique for the strength regulation of interfacial surfactant adsorption films.

Experimental and Simulation Studies of Imidazolium Chloride Ionic Liquids with Different Alkyl Chain Lengths for Viscosity Reductions in Heavy Crude Oil: The Effect on Asphaltene Dispersion.

Heavy crude oil poses challenges in terms of extraction and transportation due to its high viscosity. In the pursuit of effective methods to reduce viscosity in heavy crude oil, this study investigates the potential of imidazolium chloride ionic liquids with varying alkyl chain lengths as viscosity reducers. The experimental results demonstrate that the addition of 1-dodecyl-3-methylimidazole chloride ([C12-MIM]Cl) leads to a maximum viscosity reduction of 49.87%. Solubility parameters were calculated based on characterization of the average molecular structure of the asphaltenes. The viscosity reduction effect is enhanced when the solubility parameter of the ionic liquid closely matches that of the asphaltene. The initial asphaltene deposition point of heavy crude oil is increased from 63% to 68% with the addition of 150 mg/L [C12-MIM]Cl. Furthermore, the average particle size of asphaltene deposits decreases from 79.35 µm to 48.54 µm. The viscosity of heavy crude oil is influenced by the aggregation of asphaltenes. The ability of ionic liquids, especially those with longer alkyl chains, to disperse asphaltene molecules and reduce viscosity has been confirmed through molecular dynamics and quantum mechanical simulations.

Molecular dynamics simulation on the displacement behaviour of crude oil by CO2/CH4 mixtures on a silica surface.

Produced gas re-injection is an effective and eco-friendly approach for enhancing oil recovery from shale oil reservoirs. However, the interactions between different gas phase components, and the oil phase and rocks are still unclear during the re-injection process. This study aims to investigate the potential of produced gas re-injection, particularly focusing on the effects of methane (CH4) content in the produced gas on shale oil displacement. Molecular dynamics simulations were employed to analyze the interactions between gas, oil, and matrix phases with different CH4 proportions (0%, 25%, 50%, and 100%), alkanes and under various burial depth. Results show that a 25% CH4 content in the produced gas achieves almost the same displacement effect as pure carbon dioxide (CO2) injection. However, when the CH4 content increases to 50% and 100%, the interaction between gas and quartz becomes insufficient to effectively isolate oil from quartz, causing only expansion and slight dispersion. Interestingly, the presence of CH4 has a synergistic effect on CO2, facilitating the diffusion of CO2 into the oil film. During the gas stripping process, CO2 is the main factor separating oil from quartz, while CH4 mainly contributes to oil expansion. In addition, for crude oil containing a large amount of light alkanes, extracting light components through mixed gas may be more effective than pure CO2. This study offers valuable insights for applications of produced gas re-injection to promote shale oil recovery.

Preparation of Amphiphilic Janus-SiO2 Nanoparticles and Evaluation of the Oil Displacement Effect.

In order to meet the requirements of tertiary oil recovery technology in a low-permeability, dense, and high-salt reservoir, gaseous SiO2 nanoparticles were modified with trichloro(octyl)silane and aminopropyl triethoxysilane by interface protection modification, and amphiphilic Janus-SiO2 nanoparticles with hydrophobic carbon chain and hydrophilic amino group were prepared. The basic properties of amphiphilic nanoparticle dispersion were evaluated by surface interfacial tension and wettability tests, and the oil displacement effect of amphiphilic nanoparticle dispersion was investigated. The results show that the size distribution of Janus-SiO2 nanoparticles with n-octyl as the hydrophobic carbon chain and amino group as the hydrophilic headgroup is uniform, and they have good dispersion in mineralized water. The change of salinity has little effect on the interfacial activity. The interfacial tension between the amphiphilic nanoparticle dispersion and crude oil is always on the order of 10-2 mN/m, and the amphiphilic nanoparticle dispersion has good interfacial activity. Amphiphilic nanoparticles adsorbed on the rock surface can enhance the hydrophilicity of the rock surface. Amphiphilic nanoparticle dispersion liquid has a certain effect of improving oil recovery in the environment of high-salt and low-permeability reservoir. Under the condition of 65 °C and salinity of 8000 mg/L, injection of 0.5 PV 0.05% amphiphilic nanoparticle dispersion can enhance oil recovery by 14.6% on the basis of water flooding. The mechanism of amphiphilic nanoparticles to improve the recovery efficiency of low-permeability tight high-salt reservoir mainly includes reducing the oil-water interfacial tension, changing the rock wettability, and enhancing the shear viscosity of oil and water interface and the interfacial film strength, which has excellent potential application prospect in the development of low-permeability tight high-salt reservoir.

Mathematical Model of Imbibition Replacement and Optimization of Soaking Time for Massively Fractured Tight Oil Reservoirs.

Due to the small pore throat characteristics of tight oil reservoirs, their strong capillary pressure makes imbibition replacement an effective development method. Field data has indicated that only a little fracture fluid can flow back and that there is an enhancement in oil recovery with shut-in periods after volume fracturing. A large number of scholars have carried out core-scale experiments on imbibition characteristics, but there has been limited research on the quantitative characterization of the differential pressure and imbibition replacement during counter-current imbibition. At the same time, there was also controversy on the calculation method of the optimal soaking time. In this paper, a mathematical model of oil-water two-phase flow is first established. Then, a mathematical model representing differential pressure and imbibition replacement in tight reservoirs is derived with a diversion function. Based on the saturation equation, Corey relative-permeability curve, and J function, the model is simplified to a mathematical model of spontaneous imbibition in the shut-in periods after volume fracturing. Second, based on the finite difference method, a dynamic solution method for the flow field considering the dynamic capillary force was established, and the variation law of the pressure field and the water saturation field during the soaking time was revealed. The simulation results show that imbibition characteristics are the core of flow field reconstruction, and the differential pressure action can ensure the advancing distance of the fracturing fluid; both of them are not a linear superposition on tight oil development but complement each other and promote each other. Third, according to the growth rate of the imbibition replacement between fractures and the matrix during the soaking time, the calculation method of optimal soaking time was established. Taking the development parameters of the volume fracturing development case in the Ordos Basin into account, a reasonable soaking time was optimized. Finally, we analyzed the optimal soaking time under different conditions, and a chart of optimal soaking time for different initializations was plotted. Such a chart has profound reference significance for engineers, and they can make quick and accurate decisions regarding development and adjustment.

Interfacial rheological behaviors of inclusion complexes of cyclodextrin and alkanes.

The transformation of cyclodextrins (CDs) and alkanes from separated monomers to inclusion complexes at the interface is illustrated by analyzing the evolution of interfacial tension along with the variation of interfacial area for an oscillating drop. Amphiphilic intermediates are formed by threading one CD molecule on one alkane molecule at the oil/aqueous interface. After that, the amphiphilic intermediates transform into non-amphiphilic supramolecules which further assemble through hydrogen bonding at the oil/aqueous interface to generate a rigid network. With the accumulation of supramolecules at the interface, microcrystals are formed at the interface. The supramolecules of dodecane@2α-CD grow into microrods which form an unconsolidated shell and gradually cover the drop. However, the microcrystals of dodecane@2ß-CD are significantly smaller which fabricate into skin-like films at the interface. The amphiphilic intermediates during the transformation increase the feasibility of self-emulsification and the skin-like films enhance the stability of the emulsion. With these unique properties, CDs can be promising for application in hydrophobic drug delivery, food industry and enhanced oil recovery.

Layer-by-layer self-assembled graphene oxide/silica microsphere composites as stationary phase for high performance liquid chromatography.

Graphene oxide (GO) has been layer-by-layer assembled onto silica microspheres to form a GO/SiO(2) composite stationary phase. All the characterizations of GO/SiO(2) by elemental analysis, Raman spectroscopy and Fourier transformed infrared spectrometry confirmed that with the increase of the assembled layer, GO gradually increases on the silica surface. The chromatographic properties of bare SiO(2) and GO/SiO(2) with different GO assembled layers show that the amount of GO plays an important role in the separation of analytes. Only the appropriate amount of GO on SiO(2) can perform a good chromatographic separation. The comparison between chromatographic performances of bare SiO(2) column, GO/SiO(2)-2 column and C18 commercial column clearly show that GO/SiO(2)-2 and C18 columns obtained a better separation; GO/SiO(2)-2 exhibits a large π-electron system and C18 exhibits hydrophobicity. The eluting order, peak width and resolution of analyte on GO/SiO(2)-2 column was highly dependent on the size of its π-electron system, while on the C18 column the decisive factor is its hydrophobic property.

[Application of serum protein fingerprint in diagnosis of pancreatic cancer].

OBJECTIVE: To establish serum protein fingerprint model for early diagnosis of pancreatic cancer with surface enhanced laser desorption/ionization time of flight-mass spectrometry (SELDI-TOF-MS) and bioinformatics techniques. METHODS: A total of 73 samples were analyzed in this study, including 31 cases of pancreatic cancers, 22 cases of pancreatitis and 20 healthy individuals. Samples were first analyzed by SELDI-TOF-MS and two patterns of differentiation model were constructed with support vector machine arithmetic method. RESULTS: The pattern 1 model differentiating pancreatic cancer patients from healthy individuals had a specificity and a sensitivity of both 100.0%. The pattern 2 model differentiating pancreatic cancer from pancreatitis had a specificity of 95.5% and a sensitivity of 93.5%. CONCLUSION: SELDI-TOF-MS technique combined with bioinformatics can facilitate to identify biomarkers for pancreatic cancer.

Laparoscopic splenectomy and azygoportal disconnection with intraoperative splenic blood salvage.

BACKGROUND: Intraoperative blood salvage can reduce or avoid perioperative allogeneic blood transfusion. Salvaging the blood in the portal hypertension-induced enlarged spleen becomes an issue of concern during devascularization surgery because an enlarged spleen accommodates a large red cell pool. We report 20 cases of laparoscopic splenectomy and azygoportal disconnection and present the advantages of the use of intraoperative splenic blood salvage during the procedure. METHODS: A total of 20 cirrhotic patients with esophagogastric variceal bleeding refractory to treatment with ß-blockers and endoscopic therapy were studied. Laparoscopic splenectomy with azygoportal disconnection was performed. During the procedure, an intraoperative autologous blood salvage device recovered the splenic blood. The perioperative data were recorded from various viewpoints. RESULTS: The operative time was 3.1 ± 0.3 h and the blood loss was 70.5 ± 32.5 ml. The weight of the excised and morcellated spleen was 826.0 ± 155.1 g. The volume of autotransfused blood was 541.0 ± 150.4 ml. No patient received a perioperative allogeneic blood transfusion. There were no significant complications either intraoperatively or postoperatively. The hemoglobin value increased from 9.3 ± 0.8 to 11.5 ± 1.1 g/dl at postoperative day 1 (p < 0.01). During a postoperative follow-up period of 18.0 ± 9.0 months for 18 patients, neither esophageal variceal bleeding nor encephalopathy recurred. CONCLUSION: Laparoscopic splenectomy with azygoportal disconnection is a feasible, effective, and safe surgical method for the treatment of bleeding portal hypertension. Intraoperative splenic blood salvage can avoid the risk associated with allogeneic transfusion during the procedure, with an advantage of significantly increased postoperative hemoglobin levels.

Comparative study of laparoscopic sleeve gastrectomy with and without partial enterectomy and omentectomy.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is a novel bariatric surgical procedure that constitutes the first-stage procedure of laparoscopic Roux-en-Y gastric bypass in high-risk patients, the long-term results of which are unknown. Our objective was to establish whether partial enterectomy and omentectomy are necessary in addition to LSG to achieve weight loss in obese patients. The setting was a case series in a provincial hospital. METHODS: A total of 40 obese patients (29 women and 11 men) were separated into 2 equal groups according to patient choice. Group 1 underwent LSG alone, and group 2 underwent LSG plus partial enterectomy and omentectomy. The partial enterectomy left the first 100 cm of the jejunum and the last 200 cm of the ileum. The data were collected during the follow-up examinations, performed at 1, 3, 6, and 12 months postoperatively. RESULTS: The body mass index loss (BMIL) was 3.9 ± .5 kg/m(2) and 9.4 ± 1.3 kg/m(2) at 1 and 12 months in group 1, respectively. The BMIL was 4.5 ± .9 kg/m(2) and 10.4 ± 1.9 kg/m(2) at 1 and 12 months in group 2, respectively. At 1 and 12 months postoperatively, the percentage of excess body weight loss was 32.2% ± 12.6% and 81.5% ± 20.4% in group 1 and 35.5% ± 10.5% and 83.8% ± 24.5% in group 2, respectively. Except for the BMIL at 1 month after surgery, no significant differences were found in the BMIL or percentage of excess body weight loss. CONCLUSION: LSG with and without partial enterectomy and omentectomy in our study was an effective method of bariatric surgery, but they did not differ in their effect on weight loss. However, the long-term effect of weight loss with LSG alone or combined with partial enterectomy and omentectomy needs additional study.

Tribological properties of self-assembled monolayers of catecholic imidazolium and the spin-coated films of ionic liquids.

A novel compound of an imidazolium type of ionic liquid (IL) containing a biomimetic catecholic functional group normally seen in mussel adhesive proteins was synthesized. The IL can be immobilized on a silicon surface and a variety of other engineering material surfaces via the catecholic anchor, allowing the tribological protection of these substrates for engineering applications. The surface wetting and adhesive properties and the tribological property of the synthesized self-assembled monolayers (SAMs) are successfully modulated by altering the counteranions. The chemical composition and wettability of the IL SAMs were characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The adhesive and friction forces were measured with an atomic force microscope (AFM) on the nanometer scale. IL composite films were prepared by spin coating thin IL films on top of the SAMs. The macrotribological properties of these IL composite films were investigated with a pin-on-disk tribometer. The results indicate that the presence of IL SAMs on a surface can improve the wettability of spin-coated ionic liquids and thus the film quality and the tribological properties. These films registered a reduced friction coefficient and a significantly enhanced durability and load-carrying capacity. The tribological properties of the composite films are better than those of pure IL films because the presence of the monolayers improves the adhesion and compatibility of spin-coated IL films with substrates.

Laparoscopic versus open pediatric splenectomy for massive splenomegaly.

Laparoscopic splenectomy (LS) has rapidly evolved into the technique of choice compared with open splenectomy (OS) because of the advantages of the minimally invasive approach. Splenomegaly increases the technical difficulties of LS. LS for massive splenomegaly has generally been found to fail in adults and children. With improvements in laparoscopic technique and accumulation of laparoscopic experience, however, concerns about completing the procedure in pediatric cases with even massive splenomegaly have been lowered. A retrospective review (April 1997-October 2009) of databases at 2 institutions identified 145 children undergoing splenectomy, 79 laparoscopic and 66 open. We defined splenic margin below the umbilicus or anteriorly extending over the midline as massive splenomegaly. By this definition, 22 cases of pediatric laparoscopic and 17 cases of open splenectomies for massive splenomegaly were performed. Perioperative and follow-up data of laparoscopic pediatric splenectomies were compared with those of open splenectomies, including operative time, bleeding, spleen size, complications, and hospital stay. There were no deaths, wound infections, or instances of pancreatitis. No accessory spleen was missed by laparoscopic; accessory spleens were missed in 2 patients in open splenectomies. The complication rate of laparoscopic versus open was 13.6% versus 41.2%. No subsequent surgery was necessary for dealing with complications both in laparoscopic and open series. Laparoscopic pediatric splenectomy for massive splenomegaly is a feasible, effective, and safe procedure and is associated with low morbidity and a short hospital stay.

Laparoscopic splenectomy in portal hypertension: a single-surgeon 13-year experience.

BACKGROUND: Although laparoscopic splenectomy (LS) has become the standard approach for most splenectomy cases, some areas still remain controversial. To date, the indications that preclude LS are not clearly defined. Portal hypertension from liver cirrhosis still is a contraindication to LS in the clinical practice guidelines of the European Association for Endoscopic Surgery published in 2008. This study aimed to evaluate the feasibility of LS for hypersplenism secondary to liver cirrhosis and portal hypertension. METHODS: The study retrospectively analyzed 206 laparoscopic splenectomies performed for a variety of indications over 13 years. According to diagnosis, the patients were divided into group A (hypersplenism secondary to liver cirrhosis and portal hypertension, n = 96) and group B (hematologic and other disorders, n = 110). A detailed review of medical records was conducted. The perioperative data for the two groups were compared including patient characteristics, diagnosis, operative details, complication rates, and postoperative hospital stay. RESULTS: Laparoscopic splenectomy was completed for 201 patients. Conversion from laparoscopic to open surgery was necessary for 5 patients (2.4%) because of hemorrhage, and 26 patients (12.6%) had complications. There were significant differences between groups A and B in terms of mean operation time (2.8 vs. 2.1 h), complication rates (17.7% vs. 8.2%), and postoperative stay (7.1 vs. 4.7 days). However, the two groups showed no significant differences with respect to intraoperative blood loss, blood transfusion, and conversion rate. CONCLUSION: Laparoscopic splenectomy is a feasible, effective, and safe surgical procedure for patients who require splenectomy. Hypersplenism secondary to cirrhosis and portal hypertension should not be considered contraindications for LS.

[Surgical treatment for primary gastrointestinal stromal tumors: a report of 73 cases].

OBJECTIVE: To investigate the effects and prognosis of surgical treatment in primary gastrointestinal stromal tumors (GIST). METHODS: The clinicopathological data of 73 patients with primary GIST underwent operation from April 1997 to December 2007 was retrospectively analyzed, and the prognosis was evaluated too. RESULTS: Among the 73 cases, 68 cases received complete tumor resection, among which 12 cases underwent laparoscopic operation; while palliative resection and biopsy only were carried out in the other 5 cases. There was significant difference in survival rate between the two groups (P = 0.000). The 1-, 3-, 5-year survival rates of the 66 cases had been followed up was 91.0%, 78.2% and 74.1%, respectively. The malignancy risk grades of GIST was related to the survival rates on statistical analysis (P = 0.002). Significant differences were found in the survival rates between the patients with very low grade, low grade and high grade malignancy tumors (P = 0.012, 0.002). CONCLUSIONS: Complete tumor resection should be emphasized in primary GIST, and more attention should be paid to the initial surgical treatment. Extended surgical resection is required for tumors of higher malignancy risk. The indications of laparoscopic surgery in GIST should be selected with caution for tumor complete resection.

Laparoscopic versus open splenectomy for hypersplenism secondary to liver cirrhosis.

BACKGROUND: Since the first laparoscopic splenectomy (LS) in 1991, LS has become the gold standard for the removal of normal-to-moderately enlarged spleens in benign conditions. Compared with open splenectomy (OS), fewer postsurgical complications and better postoperative recovery were observed, but it is contraindicated for hypersplenism secondary to liver cirrhosis owing to technical difficulties associated with splenomegaly, well-developed collateral circulation, and increased risk of bleeding. With the improvements of laparoscopic technique, the concept is changing. METHODS: OS and LS performed for hypersplenism secondary to liver cirrhosis at our institution were analyzed. Relationships between postoperative increases in platelet counts, white blood cell counts, hemoglobin, and liver function were examined. Perioperative data of LSs were compared with those of OSs, including operative time, blood loss, excised spleen weight, complications, and hospital stays. RESULTS: A total of 216 splenectomies (135 OS and 81 LS) were performed from April 1999 to March 2007. Five laparoscopic cases were converted to open surgery owing to operative bleeding or bleeding of splenic fossa. The other 76 patients were performed LSs successfully. No major operative complications occurred. There was no operative death. Excised spleen weight >400 g was present in 56% of cases in this series. At 7 days postoperatively, the platelet counts, white blood cell counts, and hemoglobin significantly increased after open and laparoscopic surgeries, and increase of alanine aminotransferase, aspartate aminotransferase, total bilirubin, and directed bilirubin of LS were significantly different with open cases. Operation times of LS and OS were 2.9+/-0.7 hours and 2.6+/-0.6 hours, respectively. Blood losses were 150.6+/-135.4 mL and 633.8+/-340.3 mL (P<0.01), excised spleen weights were 585.7+/-184.6 g and 591.1+/-153.4 g (P>0.05), and hospital stay were 8.2+/-2.0 days and 11.9+/-3.8 days (P<0.01). Operative associated complications were noted in both LS and OS. Less blood loss, shorter hospital stay, and less impairment of liver function were observed in LS than OS. CONCLUSIONS: LS is feasible, effective, and safe procedures for hypersplenism secondary to liver cirrhosis and contributes to less impairment of liver function, less blood loss, and shorter hospital stay.