Different Types Of Spacers Research Articles

Numerical investigation on boiling crisis in a full-length 5 × 5 fuel assembly under typical pressurized water reactor conditions

Critical heat flux (CHF) presents a research priority in the Pressurized Water Reactor (PWR) safety, as it can lead to the severe accidents and release radioactive materials. In this study, a wall heat flux partition model, proposed by Demarly [1], was employed within the two-fluid model by Computational Fluid Dynamics (CFD) methodology to investigate the characteristics of CHF under typical PWR conditions. A multi-scale interface model was coupled to consider the interfacial transfers in bulk flow during flow regime transition. The models were validated by using experimental data on subcooled flow boiling, boiling crisis in vertical tubes, and rod bundles. The PWR sub-channel and bundle test (PSBT) benchmark, comprising a full-length 5 × 5 fuel assembly with three different types of spacers, was simulated in this study. The CHF value was evaluated, demonstrating an acceptable accuracy compared to the experimental data, with a deviation of less than 10 % in the selected conditions. The CHF location in the cross section was successfully predicted by CFD approach, while the axial location of CHF was underestimated than experimental measurement. Besides, the impacts of mixing vanes with different deflection angles on boiling heat transfer characteristics were analyzed, revealing the crucial role of mixing vanes in the distribution of vapor and dry-patch area fraction in both the circumferential and flow directions.

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene.

A series of β-cyclodextrin dimers selectively permethylated on the primary or secondary rim with two different types of spacers have been synthesized effectively utilizing conventional and newly developed methods. Their structure analyses by 1H NMR and NOESY NMR imply the dependence of molecular symmetry on the type of spacer. The ability of synthesized dimers to increase the solubility of tetracene in DMSO was evaluated and compared to native cyclodextrins and their methylated derivatives. The newly synthesized compounds expressed better effectiveness than other tested supramolecular hosts.

Aromatic Sulfonamides including a Sulfonic Acid Tail: New Membrane Impermeant Carbonic Anhydrase Inhibitors for Targeting Selectively the Cancer-Associated Isoforms.

We report here a new drug design strategy for producing membrane-impermeant carbonic anhydrase (CA; EC 4.2.1.1) inhibitors selectively targeting the tumor-associated, membrane-bound human CAs IX and XII over off-target cytosolic isoforms. To date, this approach has only been pursued by including permanent positively charged pyridinium type or highly hydrophilic glycosidic moieties into the structure of aromatic sulfonamide CA inhibitors (CAIs). Aliphatic (propyl and butyl) sulfonic acid tails, deprotonated at physiological pH, were thus incorporated onto a benzenesulfonamide scaffold by a common 1,2,3-triazole linker and different types of spacers. Twenty such derivatives were synthesized and tested for their inhibition of target (hCAs IV, IX, and XII) and off-target CAs (hCAs I and II). Most sulfonate CAIs induced a potent inhibition of hCAs II, IX, and XII up to a low nanomolar KI range (0.9–459.4 nM) with a limited target/off-target CA selectivity of action. According to the drug design schedule, a subset of representative derivatives was assessed for their cell membrane permeability using Caco-2 cells and a developed FIA-MS/MS method. The complete membrane impermeability of the sulfonate tailed CAIs (≥98%) validated these negatively charged moieties as being suitable for achieving, in vivo, the selective targeting of the tumor-associated CAs over off-target ones.

Accuracy of casts obtained from putty wash impression material using different types of spacers - An Invitro Study

Aim: The aim of this study was to evaluate the accuracy of casts obtained from two stage putty wash impression material employing three different types of spacers. Setting and design: An in vitro comparison of accuracy of two stage putty wash impression using three different spacers Material and method: A master metal die was fabricated to simulate a three unit fixed partial denture and a custom metal tray was made. Two stage putty wash was made using three different spacers-conventional polyethylene sheet, vacuum formed sheet and micropore tape. Fifteen impressions were made using each of the three spacers and casts poured. The resultant casts were assessed for dimensional accuracy using the coordinate measuring machine, with the master metal die as control. The data obtained were statistically analysed using one way ANOVA and Student t test. Statistical analysis used: The data was subjected to statistical analysis using SPSS version 21.0 software. The intergroup comparison was done using sample t-test, and the study models were analyzed using ANOVA statistical analysis. Results: The results obtained showed that casts obtained from two stage putty wash impression technique using the micropore tape spacer produced least dimensional variation of 0.20% at inter-abutment distance and -1.08%,-0.67% at intra-abutment distance 1 and 2 respectively when compared to other two spacers used. Conclusion: Two stage putty wash impression technique using micropore tape spacer yielded casts that have better dimensional accuracy when compared to the conventional polyethylene spacer technique

Organic Spacers in 2D Perovskites: General Trends and Structure‐Property Relationships from Computational Studies

AbstractAddition of large organic molecules to halide perovskites has been shown to provoke dimensionality reduction and formation of two‐dimensional phases that demonstrate improved long‐term stabilities. Optoelectronic properties of the resulting 2D layered perovskites are strongly influenced by the chemical nature of the additive molecules, which opens immense possibilities for preparation of materials with tailored properties. However, given the huge chemical space of possible organic spacers, a systematic and exhaustive search for optimal compounds is impossible and general structure–property relationships that could guide a rational design are still largely absent. Here, we provide an overview of a series of recent computational studies from our group on different types of spacers. We first develop a simplified universal monovalent cation model to map out approximate structural stability maps as a function of the van der Waals radius and the magnitude of dispersion interactions to monitor the possible emergence of 2D phases. We further provide structural and photophysical insights from classical and first‐principles molecular dynamics simulations and density functional theory calculations on 2D hybrid perovskites based on a wide range of spacers with different chemical nature and varying conformational properties. Our computational predictions are validated through comparison with powder diffraction, conductivity and optical measurements. Such comparative study allows for providing some general structure–property correlations, which can serve as design guidelines in the search for optimal 2D and mixed 2D/3D perovskite photovoltaic materials.

Customized intraoperatively molded articulating cement spacers for two-stage revisions TKA with major bone defects.

The use of articulating spacers, molded or prefabricated, becomes difficult in case of severe bone losses. Our idea was to customize the Molded Articulating Cement Spacers with cement stem extensions and if necessary metaphyseal cement augmentations in order to use them also in case of major bone defects. Fifty-four knees in fifty-three patients undergoing 2-stage exchange arthroplasty were divided in 4 groups, treated with 4 different types of spacers (Static, articulating molded, customized molded and metal on Poly) and evaluated in terms of Range of Motion (ROM), Knee Society Score (KSS), patients' related outcome measures (PROMs), rate of complication and ease of the surgical exposure at the time of reimplantation. At final follow-up, no statistical differences in terms of ROM and KSS were found between the articulating groups. Static Spacers showed statistically significant lower results both in terms of ROM and KSS comparing to the other 3 groups (P < 0.05). Considering PROMs, statistically better outcomes for all articulating spacers were found both when spacer was in place and at final follow-up comparing to the static spacers group (P < 0.05). No statistically significant difference was found between the 3 articulating spacers groups. Radiographic analysis did not show signs of loosening, migration or major bone loss. Customized Intraoperatively Molded Articulating Cement Spacers are a safe solution for two-stage revisions TKA with major bone defects and may provide a better quality of life for patients when in place comparing to static ones.

Polyoxyethylene Quaternary Ammonium Gemini Surfactants as a Completion Fluid Additive to Mitigate Formation Damage

Summary During well completion operations, the wells are killed with specific fluids to control the well. These fluids can invade and damage the formation because of fluid/rock interactions. Fluids such as fresh water, brines, and weighted fluids (e.g., barite weighted, calcite weighted, and bentonite weighted) are used to control the formations during completion operations. These fluids can invade and interact with clays and damage the formation. In addition, these fluids may alter the near-wellbore wettability and make them more oil-wet, thereby affecting the production from these formations. In this work, polyoxyethylene quaternary ammonium gemini surfactants with different types of spacers are proposed as clay swelling additives in completion fluids to mitigate the formation damage in unconventional reservoirs. Adding the new surfactants will maintain the in-situ permeability and avoid the formation damage. The novel gemini surfactants are tested on unconventional tight sandstone formation enriched with high clay content to mitigate the formation damage during well completion. The process involved a complete stabilization of clays using gemini surfactants added in deionized water (DW). Coreflooding experiments were carried out on Scioto sandstone rock samples with an average porosity of 15.6% and average absolute permeability of 0.25 md. Several coreflooding experiments were carried out with different fluids, such as potassium chloride (KCl), sodium chloride (NaCl), and different classes of gemini surfactants. Coreflooding experiments were designed in a way that the cores were preflushed with the subjected fluid and then post-flooded with DW. Results showed that the cores saturated with KCl and NaCl solutions lost permeability significantly when flooded with water while gemini surfactant solutions maintained the same permeability even after being treated with DW. Conditioning with the KCl solution resulted in a 38% reduction of permeability and that with NaCl solution resulted in an 80% reduction of permeability when treated with DW. No significant change of permeability was found for the case of gemini surfactants. This indicates that the synthesized surfactants can be used for well completion operation without any side effects.

Influence of Electrode Spacing on a Symmetrical Washer-Type Electrohydrodynamic Conduction Pump

Electrohydrodynamic (EHD) pumping is an attractive method that can be applied to drive a fluid in mass transport and heat transfer enhancement applications, and more particularly for microfluidic applications. EHD pumps are very interesting because they do not require moving parts. The electric energy is directly converted into kinetic energy via the Coulomb force. Three modes can generate this fluid motion: conduction, induction, and injection. This paper presents the experimental results of a parametric investigation on EHD conduction pumps with washer-type electrode geometry. Only symmetrical electrode configuration is investigated in order to highlight the influence of the positive/negative charge mobility ratio. The working fluid is a dielectric liquid (HFE-7100). The pumping mechanism is examined with several washer-type electrode geometries and different types of spacers. For each configuration, pressure and current time variations are recorded and compared.

The First-Stage Treatment Аlgorithm for Deep Infected Total Hip Arthroplasty

Background. Periprosthetic infection after total hip arthroplasty is a relatively common and severe complication. A two-stage revision with the temporary use of a spacer is the gold standard treatment for the deep infected total hip arthroplasty. Some authors report mechanical complications associated with spacers, which can lead to a poor functional outcome. Therefore, the aim of the study was to analyze the effectiveness of the first-stage of treatment of hip PJI with a two-stage method and to develop an spacer application algorithm in order to achieve the optimal functional result.Material and Methods. Between 2015 and 2017, 38 patients with deep periprosthetic infection received an articulation spacer as part of a two-stage protocol in Botkin Moscow City Hospital. The mean age was 60.5 (interquartile range from 5 2 to 69) years. Five different types of spacers were us ed in the study, selected individually according to theW. Paprosky acetabular defects classification. The overall frequency of complications was evaluated.Results. The overall periprosthetic infection treatment effectiveness was 92.1%. There was the recurrent infection in 3 patients (7.9%), in 2 (5.26%) cases microbial associations were founded. Mechanical complications occurred in 8 (21%) patients. Spacer dislocation occurred in 4 (10.4%) cases, spacer fracture in another 2 (5.2%). There were also 2 cases of protrusion into the pelvis (5.2%).Conclusions. The first stage a two-stage revision hip arthroplasty should be carefully plarmed. To choose the appropriate spacer we proposed an algorithm based on our data to achieve a better functional result.

Effect of non-woven net spacer on a direct contact membrane distillation performance: Experimental and theoretical studies

This study provides a comprehensive and systematic overview of the fundamental characteristics of heat and mass transfer in the direct contact membrane distillation (DCMD) process that employs different types of spacers on one or both surfaces of the membrane. Detailed theoretical investigations were carried out to demonstrate the effects of spacers adjacent to the membrane surface on heat and mass transfer enhancement in the DCMD with a PTFE/PP composite membrane, complemented with experimental data for model validation. Thus, this work aimed to propose and demonstrate the heat transfer correlation for spacer-filled channels to reliably predict the heat and mass transfer improvement by non-woven net spacers in the DCMD process. The results showed that the permeate flux enhancement by the spacers ranged between 7% and 19% only for the spacer-filled permeate channels and between 21% and 33% only for the spacer-filled feed channels even at higher flow rates, thus indicating lower flux enhancements in the spacer-filled permeate channels. This was because the influence of spacers on flux improvement became more evident at higher temperatures owing to higher temperature polarization. In this study, the maximum flux enhancement of approximately 43% over the empty channels was achieved using the thinnest and densest spacer with a hydrodynamic angle of 90°, adjacent to both membrane surfaces.

The role of radioprotective spacers in clinical practice: a review.

The delivery of high dose radiotherapy to tumors is often limited by the proximity of the surrounding radiosensitive normal tissues, even using modern techniques such as intensity modulated radiation therapy (IMRT). Previous studies have reported that placement of a spacer can effectively displace normal tissues. So that they are some distance away from the lesion, thus allowing for the safe delivery of high-dose radiation. The application of radioprotective spacers was first reported 30 years ago regarding radiotherapy of tongue and abdominal cancers; more recently, they are increasingly being used in prostate cancer. This review focuses on the published data concerning the features of different types of spacers and their application in various tumor sites. Placement-related complications and the cost-effectiveness of the spacers are also discussed. With the increasing use of high-precision radiotherapy in clinical practice, especially the paradigm-changing stereotactic body radiotherapy (SBRT), more robust studies are warranted to further establish the role of radioprotective spacers through materials development and novel placement techniques.

In vitro/in vivo correlation and modeling of emitted dose and lung deposition of inhaled salbutamol from metered dose inhalers with different types of spacers in noninvasively ventilated patients

Substituting spacer by another in noninvasive ventilation (NIV) involves many variables, e.g. total emitted dose (TED), mass median aerodynamic diameter (MMAD), type of spacer, total lung deposition and total systemic absorption, which must be adjusted to ensure patient optimum therapy. Data mining based on artificial neural networks and genetic algorithms were used to model in vitro inhalation process, predict and optimize bioavailability from inhaled doses delivered by metered dose inhaler (MDI) using different spacers in NIV. Modeling of data indicated that in vitro performance of MDI-spacer systems was dependent mainly on fine particle dose (FPD), fine particle fraction (FPF), MMAD and to lesser extent on spacer type. Ex vivo model indicated that amount of salbutamol collected on facemask filter was directly affected by FPF. In vivo model (24hQ) depended directly on spacer type, FPF and TED. Female patients showed higher 0.5hQ and 24hQ values than males. AeroChamber VC spacer demonstrated higher TED and 24hQ in vivo values. Results indicated suitability of MDI-spacer systems in achieving appropriate in vitro inhalation performance. The possibility of modeling and predicting both ex vivo and in vivo capabilities of MDI-spacer systems from knowledge of in vitro attributes enabled detailed focus on important variables required to deliver safe and accurate doses of salbutamol to ventilated patients.

Results of Mass Production of Internal Tin Nb&lt;sub&gt;3&lt;/sub&gt;Sn Strand for ITER Toroidal Field Coil in Korea

Kiswire Advanced Technology (KAT) has successfully supplied 93 tons of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands produced by the internal tin process for the toroidal field coil to the ITER project, which has been procured by the Korean Domestic Agency for over five years since 2009. There are 19 restacked subelements in a strand. Each has 180 niobium filaments. There are also three different types of spacers that have different component ratios between copper and tin-titanium alloy. The spacers were symmetrically distributed among the modules. During the entire production, statistical process control (SPC) was strictly applied, and a high quality of total fabricated strands was obtained in a highly stable manner. This paper will discuss the design concept of the strand, productivity, and yield ratio in the fabrication procedure, including chromium plating and quality from the perspective of the SPC, and various results of strand performance. The test results of the cable-in-conduit conductor sample for the individual procurement execution phase at SULTAN facility will also be described.

Spacers entre prostate et rectum : optimisation des techniques d’irradiation du cancer de la prostate

In the curative radiotherapy of localized prostate cancer, improvements in biochemical control observed with dose escalation have been counterbalanced by an increase in radiation-induced toxicity. The injection of biodegradable spacers between prostate and rectum represents a new frontier in the optimization of radiotherapy treatments for patients with localized disease. Transperineal injection of different types of spacers under transrectal ultrasound guidance allows creating a 7-to-20mm additional space between the prostate and the anterior rectal wall lasting 3 to 12 months. Dosimetrically, a relative reduction in the rectal volume receiving at least 70Gy (V70) in the order of 43% to 84% is observed with all types of spacers, regardless of the radiotherapy technique used. Preliminary clinical results show for all spacers a good tolerance and a possible reduction in the acute side effects rate. The aim of the present systematic review of the literature is to report on indications as well as dosimetric and clinical advantages of the different types of prostate-rectum spacers commercially available (hydrogel, hyaluronic acid, collagen, biodegradable balloon).

Bis-cationic ionic liquid crystals

A series of bis-cationic imidazolium-based compounds are reported, where two imidazolium head groups are bridged by different types of spacers: a saturated C6 hydrocarbon spacer (type A), an ether bridge (type B), a benzylic spacer (type C) and a 2-butyne spacer (type D). The effect on mesophase formation of (1) the type of spacer, (2) the alkyl side chain length, and (3) the nature of the anion was investigated. The structural flexibility of the spacers seems to be responsible for the temperature range over which mesophases could be observed. Compared to types A, C, and D, the liquid crystalline state in type B is reached at much lower temperature and extends over a broader temperature range. As type B showed the best mesophase properties, we also combined the [B-C12] (bis(n-alkyl)-1,1-(oxydi-2,1-ethane-diyl)bis-imidazolium) cation with other anions such as ClO4−, BF4−, PF6− and the large, weakly coordinating anion bis(trifluoromethanesulfonyl)amide, NTf2−. For compounds [B-C12][BF4]2 and [B-C12][ClO4]2, with an anion of Td symmetry, a rare higher order smectic T phase could be observed, which transited into a smectic A phase during heating. Unexpectedly, mesophase formation was found for compound [B-C12][NTf2]2, which has not previously been observed for compounds with mono-cationic structures paired with this anion. In addition the rheological behavior of the bromide ILCs was investigated. The viscosities of all ILCs depend on the shear rate applied to the sample when the salt is in its mesophase. The viscosity increases drastically following the shear rate decrease, and non-Newtonian viscosity behavior is displayed by the mesophase.

Two-stage revision of septic knee prosthesis with articulating knee spacers yields better infection eradication rate than one-stage or two-stage revision with static spacers

The best method for treating chronic periprosthetic knee infection remains controversial. Randomized, comparative studies on treatment modalities are lacking. This systematic review of the literature compares the infection eradication rate after two-stage versus one-stage revision and static versus articulating spacers in two-stage procedures. We reviewed full-text papers and those with an abstract in English published from 1966 through 2011 that reported the success rate of infection eradication after one-stage or two-stage revision with two different types of spacers. In all, 6 original articles reporting the results after one-stage knee exchange arthoplasty (n = 204) and 38 papers reporting on two-stage revision (n = 1,421) were reviewed. The average success rate in the eradication of infection was 89.8% after a two-stage revision and 81.9% after a one-stage procedure at a mean follow-up of 44.7 and 40.7 months, respectively. The average infection eradication rate after a two-stage procedure was slightly, although significantly, higher when an articulating spacer rather than a static spacer was used (91.2 versus 87%). The methodological limitations of this study and the heterogeneous material in the studies reviewed notwithstanding, this systematic review shows that, on average, a two-stage procedure is associated with a higher rate of eradication of infection than one-stage revision for septic knee prosthesis and that articulating spacers are associated with a lower recurrence of infection than static spacers at a comparable mean duration of follow-up. IV.

Targeted PLGA microparticles as a novel concept for treatment of lactose intolerance

Background Peroral β-galactosidase preparations for the management of lactose intolerance need to be administered in large doses (1500 to 6000 U) immediately before or together with a lactose-containing meal. Aim Therefore, this work aimed at developing an innovative long-acting formulation. For this purpose, biodegradable polymeric microcarriers were functionalized with β-galactosidase and targeted with wheat germ agglutinin (WGA) for bioadhesion and thus prolonged residence time in the small intestine. Methods Spray-dried poly( d, l-lactide-co-glycolide) (PLGA) particles with 2.78 ± 1.05 µm in diameter were functionalized with β-galactosidase from Kluyveromyces lactis and WGA using different types of spacers (polyethyleneimine, hexamethylene diamine, 6-aminocaproic acid) and coupling methods (carbodiimide and glutaraldehyde). The particle-bound enzyme activity was determined, and the bioadhesive characteristics were assessed by interaction with mucin coatings and Caco-2 cell monolayers. Results Up to 1470 U β-galactosidase per gram PLGA were immobilized. The best results were obtained with hexamethylene diamine as a spacer applying the carbodiimide method. Thereby, a nearly 6-fold increase in enzyme activity was obtained as compared to particles without spacer. Upon targeting with WGA, binding to artificial human intestinal epithelium was increased considerably. Conclusions For the delivery of β-galactosidase WGA-targeted PLGA microparticles were prepared, which represent promising candidates for a convenient biomimetic treatment regimen of lactose intolerance.

Two-stage procedure in the treatment of late chronic hip infections - spacer implantation

Infection after total hip arthroplasties (THA) is a devastating complication with significant consequences for both the patients and the healthcare systems. In recent times, a two stage procedure using antibiotic-impregnated interim spacers has become the most popular treatment for late chronic hip joint infections after THA with success rates over 90%. In this review, we discuss the different types of spacers used in the treatment of chronically infected THA and conclude that hip spacers are effective in the treatment of hip joint infections.

Synthesis of Diporphyrins via Palladium-Catalyzed C−O Bond Formation: Effective Access to Chiral Diporphyrins

Diporphyrins can be efficiently synthesized from bromoporphyrin precursors via palladium-catalyzed C-O bond formation. The synthetic methodology is general and can be applied to various diols, forming a series of homo-diporphyrins containing different types of spacers in high to excellent yields. Chiral diporphyrins can be readily constructed through the use of optically active diols. A similar strategy allows access to hetero-diporphyrins and triporphyrins, including free-base and metalloporphyrin hetero dimers.

Phosphonate-linked pyrrolo[2,1- c][1,4]benzodiazepine conjugates: Synthesis, DNA-binding affinity and cytotoxicity

Pyrrolobenzodiazepine-diethylphosphonate conjugates have been designed and synthesized that link through two different types of spacers that are simple alkane chain and also a piperazine moiety side-armed with the alkane chains. These pyrrolobenzodiazepine conjugates have exhibited remarkable DNA-binding affinity and improved solubility in water, a representative compound 7d showing promising in vitro cytotoxicity.