Expandable endoprostheses in skeletally immature patients:Where we are

Approximately 45 percent of malignant bone tumors are seen under the age of 16 and one of the important results of growth plate sacrification in patients with immature skeletons is limb inequality.Until the early 1990s,the treatment options for these patients were rotationplasty or amputation.Multimodal approaches that combine imaging,chemotherapy,and surgical techniques have enabled the development of limb-preserving methods with satisfactory results.In order to overcome inequality problems,expandable prostheses have been developed in the 1980s.Extendable endoprosthesis replacements have been improved over the years and are now an established and safe alternative.Noninvasive prostheses appear to be advantageous compared to minimally invasive expandable prostheses that require multiple surgical procedures,but the complication rate remains high.Therefore,although expandable prostheses are not the definitive answer to the treatment of bone sarcomas in skeletally immature children,they are still a suitable interim choice until full adulthood is achieved.Due to reported high complication rates,the procedures require significant experience and are recommended for use only in specialized cancer centers.

Covered self expandable metallic stent with flared plastic one inside for pancreatic pseudocyst avoiding stent dislodgement

Endoscopic ultrasound-guided drainage has recently been recommended for increasing the drainage rate of endoscopically managed pancreatic fluid collections and decreasing the morbidity associated with conventional endoscopic trans-mural drainage. The type of stent used for endoscopic drainage is currently a major area of interest. A covered self expandable metallic stent (CSEMS) is an alternative to conventional drainage with plastic stents because it offers the option of providing a larger-diameter access fi stula for drainage, and may increase the fi nal success rate. One problem with CSEMS is dislodgement, so a metallic stent with flared or looped ends at both extremities may be the best option. An 85-year-old woman with severe comorbidity was treated with percutaneous approach for a large (20 cm) pancreatic pseudocyst with corpuscolated material inside. This approach failed. The patient was transferred to our institute for EUS-guided transmural drainage. EUS confi rmed a large, anechoic cyst with hyperechoic material inside. Because the cyst was large and contained mixed and corpusculated fluid, we used a metallic stent for drainage. To avoid migration of the stent and potential mucosal growth above the stent, a plastic prosthesis (7 cm, 10 Fr) with flaps at the tips was inserted inside the CSEMS. Two months later an esophagogastroduodenoscopy was done, and showed patency of the SEMS and plastic stents, which were then removed with a polypectomy snare. The patient experienced no further problems.

Corrosion behavior of the expandable tubular in formation water

The corrosion behavior of expandable tubular materials was investigated in simulated downhole formation water environments using a series of electrochemical techniques. The corrosion morphologies in the real downhole environment after three months of application were also observed by stereology microscopy and scanning electron microscopy （SEM）. The results show that, compared with the unex- panded sample, the area of ferfite increases dramatically after a 7.09% expansion. The expanded material shows a higher corrosion current in the polarization curve and a lower corrosion resistance in the electrochemical impedance spectroscopy （EIS） plot at every studied tempera- ture. The determined critical pitting temperatures （CPT） before and after expansion are 87.5℃and 79.2℃, respectively. SEM observations demonstrate stress corrosion cracks, and CO2 corrosion and H2S corrosion also occur in the downhole environment. Due to additional defects generated during the plastic deformation, the corrosion performance of the expanded tubing deteriorates.

One-step palliative treatment method for obstructive jaundice caused by unresectable malignancies by percutaneous transhepatic insertion of an expandable metallic stent

AIM： To describe a simple one-step method involving percutaneous transhepatic insertion of an expandable metal stent （EMS） used in the treatment of obstructive jaundice caused by unresectable malignancies. METHODS： Fourteen patients diagnosed with obstructive jaundice due to unresectable malignancies were included in the study. The malignancies in these patients were a result of very advanced carcinoma or old age. Percutaneous transhepatic cholangiography was performed under ultrasonographic guidance. After a catheter with an inner metallic guide was advanced into the duodenum, an EMS was placed in the common bile duct, between a point 1 cm beyond the papilla of Vater and the entrance to the hepatic hilum. In cases where it was difficult to span the distance using just a single EMS, an additional stent was positioned. A drainage catheter was left in place to act as a hemostat. The catheter was removed after resolution of cholestasis and stent patency was confirmed 2 or 3 d post-procedure. RESULTS： One-step insertion of the EMS was achieved in all patients with a procedure mean time of 24.4 min. Out of the patients who required 2 EMS, 4 needed a procedure time exceeding 30 min. The mean time for removal of the catheter post-procedure was 2.3 d. All patients died of malignancy with a mean follow-up time of 7.8 mo. No stent-related complication or stent obstruction was encountered. CONCLUSIONS： One-step percutaneous transhepaticinsertion of EMS is a simple procedure for resolving biliary obstruction and can effectively improve the patient＇s quality of life.

Treatment of gastric outlet and duodenal obstructions with uncovered expandable metal stents

AIM:To investigate and evaluate the technical feasibility and clinical effectiveness of fluoroscopically guided peroral uncovered expandable metal stent placement to treat gastric outlet and duodenal obstructions. METHODS:Fifteen consecutive patients underwent peroral placement of Wallstent^(TM)Enteral Endoprosthesis to treat gastric outlet and duodenal obstructions(14 malignant,1 benign).All procedures were completed under fluoroscopic guidance without endoscopic assistance.Follow-up was completed until the patients died or were lost,and the clinical outcomes were analyzed. RESULTS:The technique success rate was 100%,and the oral intake was maintained in 12 of 14 patients varying from 7 d to 270 d.Two patients remained unable to resume oral intake,although their stents were proven to be patent with the barium study.One patient with acute necrotizing pancreatitis underwent enteral stenting to treat intestinal obstruction,and nausea and vomiting disappeared.Ten patients died during the follow- up period,and their mean oral intake time was 50 d. No procedure-related complications occurred.Stent migration to the gastric antrum occurred in one patient 1 year after the procedure,a tumor grew at the proximal end of the stent in another patient 38 d post-stent insertion. CONCLUSION:Fluoroscopically guided peroral metal stent implantation is a safe and effective method to treat malignant gastrointestinal obstructions,and complications can be ignored based on our short-term study.Indications for this procedure should be discreetly considered because a few patients may not benefit from gastrointestinal insertion,but some benign gastrointestinal obstructions can be treated using this procedure.

Nanostructured N-doped carbon materials derived from expandable biomass with superior electrocatalytic performance towards V^(2+)/V^(3+) redox reaction for vanadium redox flow battery

Vanadium redox flow battery(VRFB)is one of the most promising large-scale energy storage systems,which ranges from kilowatt to megawatt.Nevertheless,poor electrochemical activity of electrode for two redox couples still restricts the extensive applications of VRFB.Compared with V^(2+)/V^(3+)redox reaction,V^(2+)/V^(3+)reaction plays a more significant role in voltage loss of VRFB owing to slow heterogeneous electron transfer rate.Herein,N-doped carbon materials derived from scaphium scaphigerum have been developed as negative electrocatalyst by hydrothermal carbonization and high-temperature nitridation treatments.The undoped carbon material hardly has electrocatalytic ability for V^(2+)/V^(3+)reaction.Based on this,N-doped carbon materials with urea as nitrogen source exhibit excellent electrocatalytic properties.And the material nitrided at 850°C(SSC/N-850)exhibits the best performance among those from700 to 1000℃.SSC/N-850 can accelerate the electrode process including V^(2+)/V^(3+)reaction and mass transfer of active ions due to the large reaction place,more active sites,and good hydrophilicity.The effect of catalyst on comprehensive performance of cell was evaluated.SSC/N-850 can improve the charge-discharge performance greatly.Utilization of SSC/N-850 can lessen the electrochemical polarization of cell,further resulting in increased discharge capacity and energy efficiency.Discharge capacity and energy efficiency increase by 81.5%and 9.8%by using SSC/N-850 as negative catalyst at 150 m A cm^(-2),respectively.Our study reveals that the developed biomass-derived carbon materials are the low-cost and efficient negative electrocatalyst for VRFB system.

Determination of the load bearing capacity of pre-stressed expandable props for ground support in underground mines

This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation.It is deduced that the expandable device could have much higher strength(>89 MPa)by laboratory tests,and the load bearing capacity of the expandable prop may depend on the stability of the supporting steel pipe structure.A good agreement was found between the laboratory test and numerical results in terms of the load bearing capacity and the final macro-bending failure pattern for expandable props with heights of 1.5 and 2.7 m,and the theoretical calculation for the strength of traditional steel structures is not directly suitable for the expandable props.Moreover,additional numerical simulations were performed for the expandable props with different normalized slenderness ratiosλ_(n)and loading eccentric distances e.The variation of stability coefficient of the expandable prop is in line with the Perry-Robertson equation and its correlation coefficients are fitted as a of 0.979 and b of 0.314.For estimating the load bearing capacity of the expandable props,the strength equation for traditional steel structures is improved by introducing a bending magnification factor and by modifying the normalized slenderness ratio to a converted slenderness ratio.Based on the underground field monitoring for the strength of expandable props with different heights,the empirical eccentric distances were back calculated,and a safety factor is introduced to obtain the designed strength of the expandable prop.In addition,a four-step design procedure is proposed for the expandable prop.

Synergistic effects of expandable graphite and dimethyl methyl phosphonate on the mechanical properties, fire behavior, and thermal stability of a polyisocyanurate-polyurethane foam

In this study, a series of flame-retardant polyisocyanurate-polyurethane (PIR-PUR) foams were prepared using various concentrations (0-25% by weight) of expandable graphite (EG) and dimethyl methyl phosphonate (DMMP) (0-7% by weight). The effect of these additives on the properties of the PIR-PUR foams, including physico-mechanical, morphological, flame retardancy, and thermal stability, was studied. Increasing amounts of EG in the PIR-PUR foam caused a significant drop in the compression strength. However, DMMP caused the mechanical properties of PIR-PUR foam to improve compared to foam filled with EG alone. The flame retardancy of PIR-PUR foams containing both EG and DMMP was enhanced significantly compared to EG filled foams. Thermogravimetric analysis (TGA) indicated that EG enhances the thermal stability of PIR-PUR foams but that DMMP decreased it. The morphology of the residual char provided conclusive evidence for the weak thermal stability of foams filled with DMMP.

Application of Thermally Expandable Microspheres in Adhesives: Review

Adhesives are used to bond various substrates such as metals, polymers, ceramics, rubber, wood and wood-based products. The use of adhesive as bonding agent rather than mechanical fasteners like nails results in the potential for reduced cost and weight of assemblies. However, adhesives are unprotected to a wide range of conditions, such as thermo-mechanical cycling in the environment, creep and fatigue imposed by structural joint configurations, and residual stress due to mismatch of thermal expansion between adhesives and objects. Thus, there will be a need for development of new chemistries and processes for easy repair and reprocessing of bonded structures are becoming of current great interest for the industries. In some cases, to improve the protection of various items/objects during handling and transportation, currently used protective products such as padded wraps, envelopes, packages and containers need to be modified. One technology which can solve the problem is the adhesives modified with thermally expandable particles (TEPs) which can be dismounted by heating the joint in a few seconds. The expandable composition is providing the necessary protective insulation and cushioning required in packages and containers. This paper reviews the application of unexpanded microspheres in the adhesive segment.

EXPANDABLE PARALLEL FINITE ELEMENT METHODS FOR LINEAR ELLIPTIC PROBLEMS

In this article,two kinds of expandable parallel finite element methods,based on two-grid discretizations,are given to solve the linear elliptic problems.Compared with the classical local and parallel finite element methods,there are two attractive features of the methods shown in this article:1)a partition of unity is used to generate a series of local and independent subproblems to guarantee the final approximation globally continuous;2)the computational domain of each local subproblem is contained in a ball with radius of O(H)(H is the coarse mesh parameter),which means methods in this article are more suitable for parallel computing in a large parallel computer system.Some a priori error estimation are obtained and optimal error bounds in both H^1-normal and L^2-normal are derived.Finally,numerical results are reported to test and verify the feasibility and validity of our methods.

An Effective Green Porous Structural Adhesive for Thermal Insulating,Flame-Retardant,and Smoke-Suppressant Expandable Polystyrene Foam

To develop an efficient way to overcome the contradiction among flame retardancy,smoke suppression,and thermal insulation in expanded polystyrene(EPS)foams,which are widely used insulation materials in buildings,a novel"green"porous bio-based flame-retard ant starch(FRS)coating was designed from starch modified with phytic acid(PA)that simultaneously acts as both a flame retardant and an adhesive.This porous FRS coating has open pores,which,in combination with the closed cells formed by EPS beads,create a hierarchically porous structure in FRS-EPS that results in superior thermal insulation with a lower thermal conductivity of 27.0 mW·(m·K)^(-1).The resultant FRS-EPS foam showed extremely low heat-release rates and smoke-production release,indicating excellent fire retardancy and smoke suppression.The specific optical density was as low as 121,which was 80.6%lower than that of neat EPS,at 624.The FRS-EPS also exhibited self-extinguishing behavior in vertical burning tests and had a high limiting oxygen index(LOI)value of 35.5%.More interestingly,after being burnt with an alcohol lamp for 30 min,the top side temperature of the FRS-EPS remained at only 140℃with ignition,thereby exhibiting excellent fire resistance.Mechanism analysis confirmed the intumescent action of FRS,which forms a compact phosphorus-rich hybrid barrier,and the phosphorus-containing compounds that formed in the gas phase contributed to the excellent flame retardancy and smoke suppression of FRS-EPS.This novel porous biomass-based FRS system provides a promising strategy for fabricating polymer foams with excellent flame retardancy,smoke suppression,and thermal insulation.

Multi-scale elastoplastic mechanical model and microstructure damage analysis of solid expandable tubular

We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcracks are found on the inner surface of SET. Their morphology and parameters such as length and depth are investigated by use of metallographic microscope and scanning electron microscope (SEM). In addition, the Voronoi cell technique is adopted to characterize the multi-phase material microstructure of the SET. By using the anisotropic elastoplastic material constitutive model and macro/microscopic multi-dimensional cross-scale coupled boundary conditions, a sophisticated and multi-scale finite element model (FEM) of the SET is built successfully to simulate the material microstructure damage for different expansion ratios. The microcrack initiation and growth is simulated, and the structural integrity of the SET is discussed. It is concluded that this multi-scale finite element modeling method could effectively predict the elastoplastic deformation and the microscopic damage initiation and evolution of the SET. It is of great significance as a theoretical analysis tool to optimize the selection of appropriate tubular materials and it could be also used to substantially reduce costly failures of expandable tubulars in the field. This numerical analysis is not only beneficial for understanding the damage process of tubular materials but also effectively guides the engineering application of the SET technology.

Poly(lactic acid)-starch/Expandable Graphite (PLA-starch/EG) Flame Retardant Composites

This work reports on the effect of commercial expandable graphite(EG)on the flammability and thermal decomposition properties of PLA-starch blend.The PLA-starch/EG composites were prepared by melt-mixing and their thermal stability,volatile pyrolysis products and flammability characteristics were investigated.The char residues of the composites,after combustion in a cone calorimeter,were analyzed with environmental scanning electron microscopy(ESEM).The thermal decomposition stability of the composites improved in the presence of EG.However,the char content was less than expected as per the combination of the wt%EG added into PLA-starch and the%residue of PLA-starch.The flammability performance of the PLA-starch/EG composites improved,especially at 15 wt%EG content,due to a thick and strong worm-like char structure.The peak heat release rate(PHRR)improved by 74%,the total smoke production(TSP)by 40%and the specific extinction area(SEA)by 55%.The improvements are attributed to the ability of EG to exfoliate at increased temperatures during which time three effects occurred:(i)cooling due to an endothermic exfoliation process,(ii)dilution due to release of H2O,SO2 and CO2 gases,and (iii)formation of a protective intumescent char layer.However,the CO and CO2 yields were found to be unfavorably high due to the presence of EG.

Self-expandable metallic stent placement plus laparoscopy for acute malignant colorectal obstruction

AIM:To investigate the clinical advantages of the stent-laparoscopy approach to treat colorectal cancer(CRC)patients with acute colorectal obstruction(ACO).METHODS:From April 2008 to April 2012,surgeryrelated parameters,complications,overall survival(OS),and disease-free survival(DFS)of 74 consecutive patients with left-sided CRC presented with ACO who underwent self-expandable metallic stent(SEMS)placement followed by one-stage open(n=58)or laparoscopic resection(n=16)were evaluated retrospectively.The stent-laparoscopy group was also compared with a control group of 96 CRC patients who underwent regular laparoscopy without ACO between January 2010 and December 2011 to explore whether SEMS placement influenced the laparoscopic procedure or reduced long-term survival by influencing CRC oncological characteristics.RESULTS:The characteristics of patients among these groups were comparable.The rate of conversion to open surgery was 12.5%in the stent-laparoscopy group.Bowel function recovery and postoperative hospital stay were significantly shorter(3.3±0.9 d vs 4.2±1.5 d and 6.7±1.1 d vs 9.5±6.7 d,P=0.016 and P=0.005),and surgical time was significantly longer(152.1±44.4 min vs 127.4±38.4 min,P=0.045)in the stent-laparoscopy group than in the stent-open group.Surgery-related complications and the rate of admission to the intensive care unit were lower in the stent-laparoscopy group.There were no significant differences in the interval between stenting and surgery,intraoperative blood loss,OS,and DFS between the two stent groups.Compared with those in the stentlaparoscopy group,all surgery-related parameters,complications,OS,and DFS in the control group were comparable.CONCLUSION:The stent-laparoscopy approach is a feasible,rapid,and minimally invasive option for patients with ACO caused by left-sided CRC and can achieve a favorable long-term prognosis.

Effect of dosage of expandable graphite,dimethyl methylphosphonate,triethanolamine,and isocyanate on fluidity,mechanical,and flame retardant properties of polyurethane materials in coal reinforcement

In this study,orthogonal experiments were conducted to investigate the influence of expandable graphite(EG),dimethyl methylphosphonate(DMMP),triethanolamine(TEA),and isocyanate content on the compressive and bonding strengths,oxygen index,and fluidity of rigid polyurethane foam(RPUF).The results revealed that EG significantly increased the oxygen index of RPUF,enlarged the diameter of foam cells,and decreased the cell-closed content in foam;thus,leading to a pressure drop in RPUF.However,excessive EG was capable of reducing the fluidity of polyurethane slurry.TEA exhibited significant influence on the compressive strength of RPUF,which dropped initially,and then increased.DMMP had a remarkable effect on the flame retardant property and compressive strength of RPUF.Compressive strength of RPUF initially displayed an increase followed by a decrease with increasing dosage of DMMP,and achieved the maximum value at DMMP dosage of 4%.DMMP could effectively reduce the diameter of RPUF cells leading to an increase in the percentage of close area in foam.DMMP displayed the flame-retardation effects mainly in the gas phase leading to a significant enhancement in the oxygen index of RPUF.Moreover,the compressive strength and bonding strength of RPUF decrease significantly with the increase of isocyanate content due to the increased blowing efficiency by the CO_2.The oxygen index and flowing length of foam increased with the increase in isocyanate dosage.

Role of self expandable stents in management of colorectal cancers

Acute malignant colorectal obstruction is a complication of colorectal cancer that can occur in 7%-29% of patients. Self-expanding metallic stent placement for malignant colorectal obstruction has gained popularity as a safe and effective procedure for relieving obstruction. This technique can be used in the palliation of malignant colorectal obstruction, as a bridge to elective surgery for resectable colorectal cancers, palliation of extracolonic malignant obstruction, and for nonmalignant etiologies such as anastomotic strictures, Crohn's disease, radiation therapy, and diverticular diseases. Self-expanding metallic stent has its own advantages and disadvantages over the surgery in these indications. During the insertion of the self-expanding metallic stent, and in the followup, short term and long term morbidities should be kept in mind. The most important complications of the stents are perforation, stent obstruction, stent migration, and bleeding. Additionally, given the high risk of perforation, if a patient is treated or being considered fortreatmentwith antiangiogenic agents such as bevacizumab, it is not recommended to use self-expanding metallic stent as a palliative treatment for obstruction. Therefore, there is a need for careful clinical evaluation for each patient who is a candidate for this procedure. The purpose of this review was to evaluate self-expanding metallic stent in the management of the obstruction of the colon due to the colorectal and extracolonic obstruction.

Fully covered self-expandable metal stents for treatment of malignant and benign biliary strictures

AIM:To present a series of covered self-expandable metal stents(CSEMS) placed for different indications and to evaluate the effectiveness,complications and extractability of these devices.METHODS:We therefore retrospectively reviewed the courses of patients who received CSEMS due to malignant as well as benign biliary strictures and postsphincterotomy bleeding in our endoscopic unit between January 2010 and October 2011.RESULTS:Twenty-six patients received 28 stents due to different indications(20 stents due to malignant biliary strictures,six stents due to benign biliary strictures and two stents due to post-sphincterotomy bleeding).Biliary obstruction was relieved in all cases,regardless of the underlying cause.Hemostasis could be achieved in the two patients who received the stents for this purpose.Complications occurred in five patients(18%).Two patients(7%) developed cholecystitis,stents dislocated/migrated in other two patients(7%),and in one patient(3.6%) stent occlusion was documented during the study period.Seven stents were extracted endoscopically.Removal of stents was easily possible in all cases in which it was desired using standard forceps.Twelve patients underwent surgery with pylorus preserving duodenopancreatectomy.In all patients stents could be removed during the operation without difficulties.CONCLUSION:Despite the higher costs of these devices,fully covered self-expanding metal stents may be suitable to relief biliary obstruction due to bile duct stenosis,regardless of the underlying cause.CSEMS may also represent an effective treatment strategy of severe post-sphincterotomy bleeding,not controlled by other measures.

A Novel Method for the Synthesis of Carboxylic Esters Catalyzed by Expandable Graphite

Esterification reaction of carboxylic acid and alcohol has been carried out in excellent yield with expandable graphite as a catalyst.

A NEW METHOD TO SYNTHESIZE EXPANDABLE GRAPHITE WITH LESS POLLUTION

The paper deals with a new method to synthesize expand-able graphite with H2O2 as oxidizer. This method causes less environ ——mental pollution than the tradi——tional method using HNO3. Some, opti-mum technical conditions have been given here. It is shorvn that traditional method for manufacturing expandable graphite with HNO3 as oxidizer can be replaced completely with H2O2 as an oxidizer. Expandable graphite made, in this way has the same characteristics as that made in traditional way, but the pollution of NO2 to air decreases greatly.

Self-expandable metal stents in patients with postoperative delayed gastric emptying after distal gastrectomy

AIM To investigate the efficacy and safety of endoscopic stent insertion in patients with delayed gastric emptying after gastrectomy.METHODS In this study, we prospectively collected data from patients who underwent stent placement for delayed gastric emptying(DGE) after distal gastrectomy between June 2010 and April 2017, at a tertiary referral academic center. Clinical improvement, complications, and consequences after stent insertion were analyzed.RESULTS Technical success was achieved in all patients(100%). Early symptom improvement was observed in 15 of 20 patients(75%) and clinical success was achieved in all patients. Mean follow-up period was 1178.3 ± 844.1 d and median stent maintenance period was 51 d(range 6-2114 d). During the follow-up period, inserted stents were passed spontaneously per rectum without any complications in 14 of 20 patients(70%). Symptom improvement was maintained after stent placement without the requirement of any additional intervention in 19 of 20 patients(95%).CONCLUSION Endoscopic stent placement provides prompt relief of obstructive symptoms. Thus, it can be considered an effective and safe salvage technique for post-operative DGE.