Large Headgroup Research Articles

Molecular structure effects of passivation agents on the performance of perovskite solar cells

The performance of perovskite solar cells (PSCs) is affected by a non-radiative recombination process involving defects in the perovskite films. To tackle this challenge, herein, aryl sulfonates and alkyl sulfates with distinct molecular structures, specifically sodium benzenesulfonate (SBS) and sodium dodecyl sulfate (SDS), as additives to passivate the defects in the methyl ammonium lead iodide (MAPbI3) perovskite films. This study examines the impact of the molecular structure of these additives on both the characteristics of the perovskite films and the performance of the PSCs. The results demonstrate that both SBS and SDS, which contain –S-O- and Na+ ions in their structures, effectively increase the efficiency of PSCs. This improvement is attributed to the ability of these ions to interact with oppositely charged defects, leading to reduced trap densities in the perovskite films. Remarkably, SDS stands out with its long alkyl chain and a larger head group (C-O-S-O-) carrying a higher negative charge, showcasing superior defect passivation compared to SBS. The SBS molecule, on the other hand, features a phenyl group and a smaller head group (C-S-O-) with a reduced negative charge. This is primarily due to the significant role played by the phenyl ring in delocalizing the negative charge. As a result, the SDS-treated PSCs can achieve a remarkable champion power conversion efficiency of 20.70 %. Additionally, the contact angle of water on the SDS-treated perovskite films surpasses that on the SBS-treated film. This highlights an enhanced hydrophobic characteristic, ultimately bolstering the stability of SDS-treated PSCs.

Assessment of Triglyceride Droplet Crystallization Using Mixtures of β-Lactoglobulin and Phospholipids as Emulsifiers

Many applications in the life science and food industries require (semi-)crystalline oil-in-water (O/W) dispersions. Unfortunately, high supercooling and, thus, low temperatures are often needed to induce the crystallization of droplets. As low molecular weight emulsifiers (LMWEs) are able to act as nucleation templates, they might help to decrease the required level of supercooling. Furthermore, proteins and LMWEs are frequently co-formulated to improve the colloidal stability of emulsions and dispersions. Hence, choosing a suitable protein and LMWE mixture would allow for achieving specific product properties for controlling the solid fat content (SFC) and take advantage of the stabilization mechanisms of both emulsifiers. Therefore, this study focuses on the impact of the co-existence of β-lactoglobulin (β-lg) and phospholipids (PLs) LMWEs on the SFC of triglyceride (TAG) droplets at isothermal conditions using a thermo-optical method. When β-lg alone was used as an emulsifier, a maximum SFC of 80% was obtained at a supercooling of 32 K and 42 K for trilaurin and tripalmitin, respectively. The SFC could be increased to 100% using a PL containing saturated fatty acids (FAs) and a small hydrophilic headgroup. At the same supercooling, a PL containing saturated FAs and a large hydrophilic headgroup led to a maximum SFC of 80%. At lower supercooling, the SFC was reduced with this PL by 10% compared to β-lg alone. In addition, when the PLs had more time to adsorb and rearrange with ß-lg at the interface, even lower SFCs were observed compared to cooling directly after emulsification.

QSPR-based prediction of air-water interfacial adsorption coefficients for nonionic PFAS with large headgroups

Air-water interfacial adsorption has been demonstrated to be an important process affecting the retention and distribution of PFAS in soil, surface waters, and the atmosphere, as well as being central to certain remediation methods. Measured or estimated air-water interfacial adsorption coefficients are needed for quantifying and modeling the interfacial adsorption of PFAS. A single-descriptor QSPR model developed in prior work for predicting air-water interfacial adsorption coefficients of PFAS was demonstrated to successfully represent more than 60 different PFAS, comprising all headgroup types and a wide variety of tail structures. However, the model overpredicted values for nonionic PFAS with very large headgroups. A revised QSPR model was developed in the present study to predict air-water interfacial adsorption coefficients for nonionic PFAS with large headgroups. A two-descriptor QSPR model employing molar volume and headgroup-to-tail molar-volume ratio successfully represented measured data for both nonionic PFAS and nonionic hydrocarbon surfactants. This new model provides a means to produce estimates of air-water interfacial adsorption coefficients for nonionic PFAS for which measured values are typically not available.

Revision hip arthroplasty dislocation risk calculator: when to select dual mobility, large heads, constrained liners, or a standard head size? Testing one hundred thousand hip revisions with artificial intelligence.

Preventing dislocation with large head (≥ 36mm), dual mobility, or constrained acetabular liner is another option than a standard (≤ 32mm). Many other dislocations risk factors than size of the femoral head exist after hip arthroplasty revision. Predicting dislocation with a calculator according to the implant, to the indication of revision, and to patient's risks could allow a better surgery decision. Our search method covers the period from 2000 to 2022. A total of 470 relevant citations on hip major revision (cup or stem or both revisions) were identified with artificial intelligence comprising 235 publications of 54,742 standard heads comprising 142 publications of 35,270 large heads, comprising 41 publications of 3945 constrained acetabular components, and 52 publications of 10,424 dual mobility implants. We considered four implant types (standard, large head, dual mobility, or constrained acetabular liner) as the entry layer of the artificial neural network (ANN). Indication for revision THA was the second hidden layer. Demographics, spine surgery, and neurologic disease were the third layer. Implant revision, reconstruction process as next input (hidden layer). Surgery-related factors, and so on. The output was a postoperative dislocation or not. Of the 104,381 hips that underwent a major revision, a second revision for dislocation was performed for 9234 hips. In each implant group, dislocation remained the first cause of revision. The rate of second revision for dislocation as a percentage of first revision procedures was significantly higher in the standard head group (11.8%) than in the constrained acetabular liner group (4.5%), the dual mobility group (4.1%), and the large head group (6.1%). Instability of a previous THA, infection, or periprosthetic fracture as the indication for revision was increased risk factors as compared with aseptic loosening. One hundred variables were used to create the calculator with the best parameter combination of data and ranking the different factors, according to the four implant types (standard, large head, dual mobility, or constrained acetabular liner). The calculator can be used as a tool to identify patients at risk for dislocation after hip arthroplasty revision and individualize recommendations to select another option than a standard head size.

Dual-Mobility versus Large Femoral Heads in Revision Total Hip Arthroplasty: Interim Analysis of a Randomized Controlled Trial

BackgroundThis multicenter randomized controlled trial evaluated if dual-mobility bearings (DM) lower the risk of dislocation compared to large femoral heads (≥36 mm) for patients undergoing revision total hip arthroplasty (THA) via a posterior approach. MethodsA total of 146 patients were randomized to a DM (n = 76; 46 mm median effective head size, range 36 to 59 mm) or a large femoral head (n = 70; twenty-five 36 mm heads [35.7%], forty-one 40 mm heads [58.6%], and four 44 mm heads [5.7%]). There were 71 single-component revisions (48.6%), 39 both-component revisions (26.7%), 24 reimplantations of THA after 2-stage revision (16.4%), seven isolated head and liner exchanges (4.8%), four conversions of hemiarthroplasty (2.7%), and 1 revision of a hip resurfacing (0.7%). Power analysis determined that 161 patients were required in each group to lower the dislocation rate from 8.4 to 2.2% (power = 0.8, alpha = 0.05). ResultsAt a mean of 18.2 months (range, 1.4 to 48.2), there were three dislocations in the large femoral head group compared to two in the DM cohort (4.3 versus 2.6%; P = .67). One patient in the large head group and none in the DM group were successfully treated with closed reduction without subsequent revision. ConclusionInterim analysis of this randomized controlled trial found no difference in the risk of dislocation between DM and large femoral heads in revision THA, although the rate of dislocation was lower than anticipated and continued follow-up is needed.

Effects of surfactant head group modification on vertically oriented mesoporous silica produced by the electrochemically assisted surfactant assembly method.

Production of mesoporous silica films with vertically oriented pores has been a challenge since interest in such systems developed in the 1990s. Vertical orientation can be achieved by the electrochemically assisted surfactant assembly (EASA) method using cationic surfactants such as cetyltrimethylammonium bromide (C16TAB). The synthesis of porous silicas using a series of surfactants with increasing head sizes is described, from octadecyltrimethylammonium bromide (C18TAB) to octadecyltriethylammonium bromide (C18TEAB). These increase pore size, but the degree of hexagonal order in the vertically aligned pores reduces as the number of ethyl groups increases. Pore accessibility is also reduced with the larger head groups.

Revealed Properties of Various Self-Assemblies in Two Catanionic Surfactant Systems in Relation to Their Polarity and Molecular Packing State.

A catanionic surfactant system is an aqueous solution or dispersion of cationic and anionic surfactants that spontaneously self-assemble into structures such as micelles, vesicles, and coacervates. Their structural diversity varies depending on the ratios of cationic and anionic surfactants (compositions), the chemical structure of the constituent molecules, etc. Herein, two types of catanionic surfactant systems were systematically characterized: (i) cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), both typical ionic surfactants; and (ii) dodecylmethylimidazolium ammonium bromide ([C12mim]Br) and SDS, where the former is an ionic liquid. By observing the sample appearance, turbidity, and particle size, the phase state of each system was analyzed according to the total concentration of surfactants and the molar ratio of cationic surfactants to the total concentration. Especially, for specific compositions of catanionic surfactant vesicles (cataniosome), the closed structure of the vesicles was confirmed through calcein entrapment and release detected with a fluorescence assay. The polarities of the interface of the prepared self-assemblies were evaluated using a fluorescence probe, Laurdan. The packing state of the molecules in the formed self-assembly structure was estimated using Raman spectroscopy. The results clearly indicate consistent phase-transition behavior for the CTAB-SDS (i) and [C12mim]Br-SDS (ii) systems, depending on the total surfactant concentration and composition, while the membrane properties of the two systems differed. The cataniosome formed in the CTAB-SDS system was in a tightly packed membrane state and more hydrophobic than that formed in the [C12mim]Br-SDS system owing to the difference in the structure of the constituting molecule: [C12mim]Br has a larger head group and shorter acyl chain than CTAB. The self-assembly properties evaluated in this study were compared with those of typical lipid membranes, liposomes (lipid vesicles), to determine a possible application of the catanionic systems with various self-assembly formulations.

Phase Behavior and Ionic Conductivity of Blended, Ion-Condensed Electrolytes with Ordered Morphologies

In this study, the amphiphilic salt lithium trifluoromethanesulfonylimide octadecane (C18LiTFSI) was used as a basis to investigate the effects of anion density and cation coordination sites within blended electrolytes with strong ionic aggregation. C18LiTFSI was previously reported as a single-component, ion-condensed electrolyte with a wide layered liquid crystalline phase regime. Three additive molecules with varyingly sized polar sulfonyl groups attached to an octodecane-tail were synthesized and mixed with C18LiTFSI. The thermal properties, morphology, and ionic conductivity of the blended electrolytes were characterized. It was found that the blended electrolytes exhibited layered liquid crystalline morphology over a narrower temperature range than the pure salt, and the ionic conductivity of the blended liquid crystalline electrolytes were generally lower than that of the pure salt. Surprising, the additives were found to have the greatest effect on the bulk ionic conductivity of the semicrystalline phase of the electrolytes. Addition of minor fractions of methylsulfonyloctadecane to C18LiTFSI resulted in increases in conductivity of over two orders of magnitude at room temperature, while addition of ethylsulfonyloctadecane or isopropylsulfonyloctadecane with the larger head group resulted in decreased ionic conductivity over the entire composition space and temperature range investigated.

Cloud point, auto-coacervation, and nematic ordering of micelles formed by ethylene oxide containing carboxylate surfactants

HypothesisIn a recent paper, we determined the phase behavior of an aqueous solution of octyl ether octaethylene oxide carboxylic acid ([H+][C8E8c−], Akypo™ LF2) and with partial replacement of H+ by Na+ and Ca2+. It was found that even the neat surfactants are liquid at room temperature and that they form only direct micelles for any aqueous content and over large temperature ranges. The aim of the present work was to find an explanation for the clouding in these systems as well as for the coacervation observed at very low surfactant content. We expected that very similar phase diagrams would be found for a full replacement of H+ by the mentioned ions. ExperimentsWe established the respective phase diagrams of the above-mentioned salts in water and determined the structures of the occurring phases in detail with small-and wide-angle X-ray scattering, small-angle neutron scattering, dynamic light scattering, heat flux differential scanning calorimetry, as well as surface tension, ESI-MS, and NMR experiments. FindingsTo our surprise, we discovered a new type of nematic phase between an isotropic and a hexagonal phase. Based on the complete description of all occurring phases both in the acidic and the charged surfactant systems, we were able to design a coherent and unified picture of all these phases, including the auto-coacervation at low surfactant concentration, the non-conventional clouding at high temperatures, the unusual liquid crystalline phases in a small domain at high surfactant concentrations, and the Lβ phase at low temperatures and at very low water content. It turned out that all phenomena are a consequence of the subtle interplay between a) the packing constraint due to the very large head-group, b) the relatively small hydrocarbon chain and c) the tunable electrostatic interactions versus entropy.

In Revision THA, Is the Re-revision Risk for Dislocation and Aseptic Causes Greater in Dual-mobility Constructs or Large Femoral Head Bearings? A Study from the Australian Orthopaedic Association National Joint Replacement Registry.

Dislocation is one of the most common causes of a re-revision after a revision THA. Dual-mobility constructs and large femoral head bearings (≥ 36 mm) are known options for mitigating this risk. However, it is unknown which of these choices is better for reducing the risk of dislocation and all-cause re-revision surgery. It is also unknown whether there is a difference between dual-mobility constructs and large femoral head bearings according to the size of the acetabular component. We used data from a large national registry to ask: In patients undergoing revision THA for aseptic causes after a primary THA performed for osteoarthritis, (1) Does the proportion of re-revision surgery for prosthesis dislocation differ between revision THAs performed with dual-mobility constructs and those performed with large femoral head bearings? (2) Does the proportion of re-revision surgery for all aseptic causes differ between revision THAs performed with dual-mobility constructs and those performed with large femoral head bearings? (3) Is there a difference when the results are stratified by acetabular component size? Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) were analyzed for 1295 first-revision THAs for aseptic causes after a primary THA performed for osteoarthritis. The study period was from January 2008-when the first dual-mobility prosthesis was recorded-to December 2019. There were 502 dual-mobility constructs and 793 large femoral head bearings. There was a larger percentage of women in the dual-mobility construct group (67% [334 of 502]) compared with the large femoral head bearing group (51% [402 of 793]), but this was adjusted for in the statistical analysis. Patient ages were similar for the dual-mobility construct group (67 ± 11 years) and the large femoral head group (65 ± 12 years). American Society of Anesthesiologists (ASA) class and BMI distributions were similar. The mean follow-up was shorter for dual-mobility constructs at 2 ± 1.8 years compared with 4 ± 2.9 years for large femoral head bearings. The cumulative percent revision (CPR) was determined for a diagnosis of prosthesis dislocation as well as for all aseptic causes (excluding infection). Procedures using metal-on-metal bearings were excluded. The time to the re-revision was described using Kaplan-Meier estimates of survivorship, with right censoring for death or database closure at the time of analysis. The unadjusted CPR was estimated each year of the first 5 years for dual-mobility constructs and for each of the first 9 years for large femoral head bearings, with 95% confidence intervals using unadjusted pointwise Greenwood estimates. The apparent shorter follow-up of the dual-mobility construct group relates to the more recent increase in dual-mobility numbers recorded in the registry. The results were adjusted for age, gender, and femoral fixation. Results were subanalyzed for acetabular component sizes < 58 mm and ≥ 58 mm, set a priori on the basis of biomechanical and other registry data. There was no difference in the proportion of re-revision for prosthesis dislocation between dual-mobility constructs and large femoral head bearings (hazard ratio 1.22 [95% CI 0.70 to 2.12]; p = 0.49). At 5 years, the CPR of the re-revision for prosthesis dislocation was 4.0% for dual mobility constructs (95% CI 2.3% to 6.8%) and 4.1% for large femoral head bearings (95% CI 2.7% to 6.1%). There was no difference in the proportion of all aseptic-cause second revisions between dual-mobility constructs and large femoral head bearings (HR 1.02 [95% CI 0.76 to 1.37]; p = 0.89). At 5 years, the CPR of dual-mobility constructs was 17.6% for all aseptic-cause second revision (95% CI 12.6% to 24.3%) and 17.8% for large femoral head bearings (95% CI 14.9% to 21.2%). When stratified by acetabular component sizes less than 58 mm and at least 58 mm, there was no difference in the re-revision CPR for dislocation or for all aseptic causes between dual-mobility constructs and large femoral head bearings. Either dual-mobility constructs or large femoral head bearings can be used in revision THA, regardless of acetabular component size, as they did not differ in terms of re-revision rates for dislocation and all aseptic causes in this registry study. Longer term follow-up is required to assess whether complications develop with either implant or whether a difference in revision rates becomes apparent. Ongoing follow-up and comparison in a registry format would seem the best way to compare long-term complications and revision rates. Future studies should also compare surgeon factors and whether they influence decision-making between prosthesis options and second revision rates. Nested randomized controlled trials in national registries would seem a viable option for future research. Level III, therapeutic study.

The impact of the glycan headgroup on the nanoscopic segregation of gangliosides

Gangliosides form an important class of receptor lipids containing a large oligosaccharide headgroup whose ability to self-organize within lipid membranes results in the formation of nanoscopic platforms. Despite their biological importance, the molecular basis for the nanoscopic segregation of gangliosides is not clear. In this work, we investigated the role of the ganglioside headgroup on the nanoscale organization of gangliosides. We studied the effect of the reduction in the number of sugar units of the ganglioside oligosaccharide chain on the ability of gangliosides GM1, GM2, and GM3 to spontaneously self-organize into lipid nanodomains. To reach nanoscopic resolution and to identify molecular forces that drive ganglioside segregation, we combined an experimental technique, Förster resonance energy transfer analyzed by Monte-Carlo simulations offering high lateral and trans-bilayer resolution with molecular dynamics simulations. We show that the ganglioside headgroup plays a key role in ganglioside self-assembly despite the negative charge of the sialic acid group. The nanodomains range from 7 to 120 nm in radius and are mostly composed of the surrounding bulk lipids, with gangliosides being a minor component of the nanodomains. The interactions between gangliosides are dominated by the hydrogen bonding network between the headgroups, which facilitates ganglioside clustering. The N-acetylgalactosamine sugar moiety of GM2, however, seems to impair the stability of these clusters by disrupting hydrogen bonding of neighboring sugars, which is in agreement with a broad size distribution of GM2 nanodomains. The simulations suggest that the formation of nanodomains is likely accompanied by several conformational changes in the gangliosides, which, however, have little impact on the solvent exposure of these receptor groups. Overall, this work identifies the key physicochemical factors that drive nanoscopic segregation of gangliosides.

Effects of cationic counterions and surfactant on viscosity of an amino acid-based surfactant system

Many sulfate-free and amino acid-based surfactant systems for personal care formulations do not respond to thickening with salt and/or amphoteric cosurfactants as readily as traditional sulfate-based formulations. Although this phenomenon is generally understood to be associated with large headgroups, the mechanistic basis for the difference is poorly understood. To address this question we have combined an empirical approach involving traditional determination of low shear viscoelasticity with a state-of-the-art mesoscopic analysis of micelle dynamics enabled by high frequency rheological measurements obtained optically (Zou and Larson, Journal of Rheology 2014, 58 (3), 681-721) We studied the impact of various organic and inorganic counterions as well as a cationic surfactant as alternative thickening agents for a model formulation of sodium lauroyl sarcosinate (SLSar) and cocamidopropyl hydroxysultaine (CAHS). These additives include lithium chloride (LiCl), sodium chloride (NaCl), L-arginine (Arg), triethanolamine (TEA), trimethylphenylammonium chloride (TMPAC), and cetyltrimethylammonium chloride (CTAC). The zero-shear viscosity for all systems studied was obtained using steady-state rheology at varying concentration and pH. The viscoelastic properties of systems containing an effective thickener (CTAC 1%) and an ineffective one (LiCl 1%) were obtained over a frequency range of 1–105 rad/s and subjected to the Zou and Larson analysis. The analysis showed that the high viscosity in the CTAC 1% system was associated with the combination of a high plateau modulus and a long relaxation time. The low viscosity in LiCl 1% system was attributable to the fast breakage time and high breakage rate constant. The latter result was consistent with findings from a previous study comparing the SLSar/CAHS system to a sodium lauryl ether sulfate/cocamidopropyl betaine (SLES/CAPB) formulation.

Impact of PIP2 Lipids, Force Field Parameters, and Mutational Analysis on the Binding of the Osh4's α6-α7 Domain.

All-atom molecular dynamics simulations are used with the highly mobile membrane mimetic method to study the α6-α7 peptide of the critical yeast Osh4 peripheral membrane protein. This research focuses on the impact of 1-palmitoyl-2-oleoyl-sn-glycero-phosphatidylinoside 4,5-bisphosphate (PIP2) lipids and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine on the protein's ability to bind to the membrane. Details of the binding mechanism are described qualitatively and quantitatively by measuring the position of the deepest residues, angle of the peptide during binding, root mean square deviation of the atomic positions within the peptide, and interaction energy, while changing variables, such as the force field used and the presence of the PIP2 lipids. The negatively charged PIP2 has a large head group that is a few Ångstroms above the main membrane phosphates enabling the PIP2 lipids to interact with the peptide before it binds deeper into the membrane. The PIP2 lipids can alter the position of the peptide during binding by recruiting charged residues on the α7 helix, such as R344 and R347. Residues R347 and R344 are unusual because they are slightly out of the reach of the main membrane phosphates but optimally positioned to interact with the PIP2 lipids. The salt-bridge interactions can also typically occur between cationic peptide residues such as R314, K325, and K336. The force field interaction effect on peptide binding was also investigated by changing the standard CHARMM36m to an improved description between some amino acids and lipid moieties (Phys. Chem. Chem. Phys. 20, 8432-8449). This resulted in the total number of salt bridges and hydrogen bonds being drastically reduced, the interaction energy was also reduced, and there was more balance between electrostatic and nonpolar interactions, but the general bound structure is maintained. This work is an important initial step to understand the effect of the Osh4 protein on the membrane binding and to quantify the effect of PIP2 lipids on this domain.

Salinity‐ and Heat‐Tolerant VES (Viscoelastic Surfactant) Clean Fracturing Fluids Strengthened by a Hydrophobic Copolymer with Extremely Low Damage

AbstractAs good thickeners for clean fracturing fluids, high salt‐tolerant surfactants have received increasing attention. Based on previous studies, we have further studied the performances of four surfactants, EDAS (JS‐SO), EHSB (JS‐OH‐SO), ETAC (JN) and EDHB (JS‐OH), in monovalent (NaCl) and divalent (CaCl2) salts. This is of great significance for the application of high‐salinity formation water to directly prepare fracturing fluids. The results showed that in high‐salinity aqueous solutions, both zwitterionic surfactants and cationic surfactants can exhibit extremely strong salt tolerance. The addition of the counter ion salt can destroy the internal salt, thus increasing water solubility of zwitterionic surfactants. Cationic surfactants have strong water solubility, and the counter ion Cl− will weaken the electrostatic shielding effect between the head groups. Surfactants can still maintain excellent network structures under high‐salinity conditions. This is mainly owing to the extreme insensitivity of zwitterionic surfactants to salts and the large initial head group area of cationic surfactants. In actual applications, the formation water from the Tahe Oilfield was used directly to prepare the fracturing fluids. Testing the rheological properties of fracturing fluid systems found that adding a small amount of hydrophobic associating polymers can increase the temperature resistance from 100 °C to 140 °C, and the final viscosity can be maintained above 30 mPa S. At the same time, they all showed excellent proppant suspension properties and extremely low core damage rates. The results indicated that even in high‐salinity formation water and high‐temperature formation, these fracturing fluid systems still have good performances, extremely low damage and meet fracturing fluid industry standards.

Catastrophic failure of femoral stem modular junction when combined with metal-on-metal bearing in comparison to ceramic-on-ceramic: A retrospective cohort study

BackgroundMetal ion release from total hip arthroplasty's (THA) metal-on-metal (MoM) bearing surfaces or head-neck modular junction (trunnionosis) has been identified as a major cause of adverse reaction to metal debris (ARMD). No study has compared the effects of these bearing couples when combined with modular neck femoral stems (MNFS) (i.e. did a modular CoCr have a higher effect than large MoM bearings on whole blood ion concentrations and ARMD). Therefore we did a retrospective comparative analysis of prospectively collected data aiming to: (1) assess the difference in metal ion release between a group of MoM and CoC bearings implanted with a non-cemented MNFS; (2) compare the ARMD and the related revision rates between the two bearing types; (3) compare the patients’ HOOS and Harris Hip scores. HypothesisMetal ion levels and complications rate will be higher in MoM group. MethodsThirty hips received the same short MNFS with modular CoCr. Seventeen had CoC bearing (16=36mm) and 13 large diameter head (LDH) MoM bearing (mean=50mm, 44-54mm) Both groups had whole blood Cobalt (Co) and Chromium (Cr) concentrations measurements at last follow up or before revision surgery (if any) and were compared to 41 control individuals without implants. ARMD, revision rates and other complications were censed. Functional outcome differences between operative groups were assessed with HOOS and Harris Hip scores. ResultsMean whole blood Co and Cr were 1.9μg/L (0.1–10.6 min–max) and 1.2μg/L (0.2–4.6 min–max) in the CoC group and 12.7μg/L (2.5–40.7 min–max) and 8.2μg/L (2.8–40.6 min–max) for MoM group. Controls presented whole blood Co and Cr levels of 0.2μg/L (0.04–0.2 min–max) and 0.6μg/L (0.1–0.7 min–max) respectively. CoC had significantly higher whole blood metal ion concentrations than controls, while MoM had significantly higher concentrations than both (p<0.001). MoM had a 9/13 (69%) revision rate due to ARMD (with stem-neck junction corrosion and wear were present in all cases) while the CoC had none. Functional scores at last follow up did not statistically differ between groups (Harris: CoC=94.1±8.4 vs MoM 91.8±14.8 (p=0.22) and CoC HOOS 90.2±10.7 vs 75.6±21.7 (p=0.08)). ConclusionIn our study, MNFS with CoCr modular neck released metal ion systemically, as shown in CoC THAs, but when combined with MoM LDH bearings, that elevation was significantly higher. In MNFS MoM, these high metal ion levels translated into a dramatic ARMD related revision rate where stem-neck junction corrosion and wear were present in all cases. More research is required to understand the effects of MoM bearing on neck-stem junctions, and its mechanisms of corrosion. Level of evidenceIII; retrospective comparative study.

Factors Affecting the Penetration of Niosome into the Skin, Their Laboratory Measurements and Dependency to the Niosome Composition: A Review.

Skin, the most significant protective organ in the body, may face serious problems, including cancer, infectious diseases, etc., requiring different drugs for the treatment. However, most of these drugs have poor chemical and physical stability, and insufficient penetration through the skin layers. In recent years, with the development of nanotechnology, it has been possible to load a variety of drugs into nanocarriers, to effectively targeted drug delivery. The unique structure of niosome presents an effective novel drug delivery system with the ability to load both hydrophilic and lipophilic drugs, having many potential therapeutic applications including skin treatment. However, surveying and discussing these recent, rapidly growing reported studies, along with their theoretical principals, are required for the full understanding and exploring the great potential of this approach in skin diseases and cosmetic treatments. To this aim, an emphasis has been given to the factors affecting the penetration of niosome into the skin and their laboratory measurements and dependency on the niosome composition. In sum, longer tail surfactants for storing hydrophobic drugs and intracellular passing and surfactants with a large head group for penetrating hydrophilic drugs are more suitable. Cholesterol and oleic acid are commonly used lipids to gain more stability and permeability, respectively. The ionic component in the niosome interrupts cellular connectivity, thus making it more permeable, but it may cause relative cell toxicity. Herbal oils have been used in the structure to make the nanoparticles elastic and allow them to pass through pores without changing the size of the particles.

A Quantitatively Accurate Theory to Predict Adsorbed Configurations of Asymmetric Surfactant Molecules on Polar Surfaces.

We introduce a theoretical model that predicts adsorbed configurations of asymmetric surfactant molecules on polar surfaces. This model extends the ideas developed in our previous work for predicting adsorbed configurations of linear surfactant molecules on polar surfaces. The surfactant molecules have a large polar headgroup and a linear alkyl tail. These asymmetric molecules form cylindrical/spherical morphologies in the adsorbed state. Our model predicts that the molecules adsorb either with their molecular axis parallel to the surface (lying-down configuration) or perpendicular to the surface (standing-up configuration). The standing-up and lying-down configurations result in significantly different adsorbed morphologies. In the standing-up configuration, the adsorbed morphology is like that of full cylinders, while, in the lying-down configuration, the adsorbed morphology resembles partial spheres. The standing-up configuration is obtained when the strength of interaction of the polar headgroup with the surface dominates over the interactions of the alkyl tail with the surface. When interactions of the alkyl tail are dominant, the molecules attain the lying-down configuration. Predictions from the theoretical model quantitatively match the results obtained from Langevin dynamics simulations. The theoretical model also explains the different kinetic pathways that have been reported in the experimental studies on the organization of adsorbed surfactants on polar surfaces.

MHC Restriction: Where Are We Now?

MHC Restriction: Where Are We Now?

Study of Structural stability and formation mechanisms in DSPC and DPSM liposomes: A coarse-grained molecular dynamics simulation

Liposomes or biological vesicles can be created from cholesterol, phospholipid, and water. Their stability is affected by their phospholipid composition which can influence disease treatment and drug delivery efficacy. In this study, the effect of phospholipid type on the formation and stability of liposomes using coarse-grained molecular dynamics simulations is investigated. For this purpose, the simulation study of the DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine) and DPSM (Egg sphingomyelin) lipids were considered. All simulations were carried out using the Gromacs software and Martini force field 2.2. Energy minimization (3000 steps) model, equilibrium at constant volume to adjust the temperature at 400 Kelvin and equilibrium at constant pressure to adjust the pressure, at atmospheric pressure (1 bar) have been validated. Microsecond simulations, as well as formation analysis including density, radial distribution function, and solvent accessible surface area, demonstrated spherical nanodisc structures for the DPSM and DSPC liposomes. The results revealed that due to the cylindrical geometric structure and small-size head group, the DSPC lipid maintained its perfectly spherical structure. However, the DPSM lipid showed a conical geometric structure with larger head group than other lipids, which allows the liposome to form a micelle structure. Although the DSPC and DPSM lipids used in the laboratory tests exhibit liposome and micelle behaviors, the simulation results revealed their nanodisc structures. Energy analysis including overall energy, Van der Waals interaction energy, and electrostatic interaction energy showed that DPSM liposome is more stable than DSPC liposome.

Dislocation after total hip arthroplasty: does head size really matter?

Recent advances in polyethylene and ceramic technologies has allowed us to use larger sized heads without compromising the wear properties of a total hip arthroplasty (THA). 1 benefit of this change has been proposed to be a lower incidence of dislocation. We retrospectively evaluated the dislocation rate in 913 THAs performed using the same standardised surgical technique employed by a single team of surgeons at our institution between 1995 and 2015. Patients were assigned to 2 groups: small (⩽28 mm), large diameter heads (⩾36 mm and larger). The cup position was measured and plotted to determine its status according to the Lewinnek's safe zone (15° ± 10° for anteversion, 40° ± 10° for inclination). 16 of the 472 small heads dislocated (3.4%) while 5 of the 441 in large head group (1.1%) (p = 0.04). In all of the large head patients that dislocated the cup position was in the safe range of Lewinnek. However, in the large head group only 64.5% of the cups were in the safe zone. By changing the head size to 36 mm, we were able to decrease the dislocation rate significantly. Errors of cup positioning according to Lewinnek became oblivious when using large heads. In our opinion, using large heads in THA makes a difference in terms of dislocation.