Pearl Necklace Research Articles

Designing Novel All-Polymer Nanocomposites with Pearl Necklace Chain Structure with High Strength, High Toughness, and Low Hysteresis

Designing Novel All-Polymer Nanocomposites with Pearl Necklace Chain Structure with High Strength, High Toughness, and Low Hysteresis

Bridging dielectric-magnetic synergistic units with MOFs on fibers structure for high-efficient microwave absorption at low filler loading

Metal-organic framework (MOF) capable of magnetic-dielectric synergy loss mechanisms shine in the field of electromagnetic wave (EMW) absorption, whereas their high filler loading in the matrix remains a challenge and limit their practical application. Here, we mono-disperse bimetallic CoZn-MOF on conductive carbon nanofibers precursor via electrospinning technique and a following heat-treatment was employed to construct a Co–ZnO@NC carbon nanofiber (CNF) composites. The Co–ZnO particles with a size of 2 μm are evenly distributed within the carbon fibers, forming a unique structure resembling a “pearl necklace”. The introduction of one-dimension (1D) CNF can prolong the electron transport path and effectively reduces the percolation threshold of the composites. The composites are endowed with abundant heterogeneous interfaces, excellent magnetic-dielectric synergy and improved impedance matching, benefiting from which the obtained Co–ZnO@NC CNF composites demonstrate a maximum reflection loss (RLmin) of −54.5 dB at a thickness of 2.3 mm and an effective absorption bandwidth (EAB) of 8.12 GHz at a filler loading of merely 10 %. This study provides a feasible strategy for the design of MOF-derived absorbers with enhanced microwave absorption capacity at low filler loading.

A non-resolving bruise and the 'pearl necklace'-Blastic plasmacytoid dendritic cell neoplasm.

A non-resolving bruise and the 'pearl necklace'-Blastic plasmacytoid dendritic cell neoplasm.

Pearl necklace sign and other optical coherence tomography findings in retinal vein occlusion at the first visit

Pearl necklace sign and other optical coherence tomography findings in retinal vein occlusion at the first visit

Polyelectrolytes: From Seminal Works to the Influence of the Charge Sequence.

We propose a selected tour of the physics of polyelectrolytes (PE) following the line initiated by de Gennes and coworkers in their seminal 1976 paper. The early works which used uniform charge distributions along the PE backbone achieved tremendous progress and set most milestones in the field. Recently, the focus has shifted to the role of the charge sequence. Revisited topics include PE complexation and polyampholytes (PA). We develop the example of a random PE in poor solvent forming pearl-necklace structures. It is shown that the pearls typically adopt very asymmetric mass and charge distributions. Individual sequences do not necessarily reflect the ensemble statistics and a rich variety of behaviors emerges (specially for PA). Pearl necklaces are dynamic structures and switch between various types of pearl-necklace structures, as described for both PE and PA.

Comparing polymer-surfactant complexes to polyelectrolytes

HypothesisUnderstanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming ‘pearl necklace’ structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? ExperimentsWe test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N-isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. FindingsAt a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case.

Application of Amoxicillin in the pearl necklace test in the identification of the Anthraxic cause

Identification of the causative agent of anthrax is an integral part of the diagnosis of the disease caused by it, which is registered annually on the territory of our country among animals and people. According to the guidelines for the diagnosis of the causative agent of anthrax, one of the identification tests is to study the sensitivity of the pathogen to penicillin with the registration of the phenomenon of the pearl necklace. Currently, penicillin salts are a hard-to-reach antibacterial drug. Based on this, we used amoxicillin, a penicillin-type antibiotic with a similar mechanism of action, which was the purpose of our study. A nutrient medium with an antibiotic was prepared by analogy with a medium with the addition of penicillin, according to MUC 4.2.2413-08. Amoxicillin in the form of amoxicillin trihydrate produced by Hemofarm (Serbia) was used as an antibacterial drug. To work, amoxicillin, by analogy with penicillin, was diluted 1,000,000 times with sterile Hottinger broth and introduced into a prepared nutrient medium. The loop of the grown daily culture of the strain K-STI-79 B. anthracis was seeded in 3 ml of the prepared medium and incubated for 3 hours at 37 ° C. During the incubation time, smears were prepared from the cells and stained according to the Rebiger. The smears were prepared after 15, 30 minutes and after 1, 2 and 3 hours. As a result of the work carried out, it was found that the use of amoxicillin in the identification of B. anthracis allows us to obtain the necessary results with a characteristic picture of a "pearl necklace". At the same time, the dynamics of changes in the morphology of cells subjected to incubation in a nutrient medium containing amoxicillin was studied. It was found that changes in the cell wall and cell shape can be observed after 15 minutes of incubation. After 1 hour, the cells underwent significant deformation with the appearance of a large number of separate spherical cell forms. After 2 hours of incubation, the chains of B. anthracis began to acquire the characteristic appearance of a pearl necklace, which was traced after 3 hours.

Vermeer’s Jar

Christina An and Menno Fitski write about the jar in Vermeer's painting of Woman with a Pearl Necklace (Gemäldegalerie, Berlin). Whereas it was previously believed to have been painted after a Chinese example, they identify a Japanese prototype and describe the trade relations with Delft.

Generalized eruptive clear cell acanthomas

AbstractIn most cases, clear cell acanthoma (CCA) is an uncommon solitary lesion with distinctive clinicopathological features. We report the case of an 80‐year‐old man with generalized asymptomatic skin lesions predominantly affecting his chest, abdomen and his legs. On dermoscopy, the lesions showed dotted vessels in a linear pearl‐like distribution (“pearl necklace”) surrounded by a slightly whitish halo. Histopathology clearly confirmed the diagnosis of CCA. In conclusion, CCA being an uncommon solitary skin lesion may also appear in very rare cases as a generalized eruptive skin condition.

A rare necklace of pearls

A rare necklace of pearls

On Earth and in My House

On Earth and in My House

Shape Fluctuations of Random Polyampholyte and Intrinsically Disordered Protein Sequences

Charged polymers with quenched charge sequences adopt pearl-necklace structures due to the interplay between charge disorder and thermal fluctuations. Partially globular pearl necklace conformations from random (+/−) sequences are intrinsically heterogeneous and exhibit various structures characterized by different numbers of pearls. On the basis of the molecular dynamics simulations of random model polyampholytes (PAs), we study dynamics of pearls and associated conformational heterogeneity in pearl structures. Fast nucleation/dissolution of small pearls controls the dynamics of the number of pearls, which is well described by first order kinetic equations. Most of the individual sequences we considered have a rather stable number of large pearls. Only a few sequences allow for fast switchings in the number of large pearls following complex processes (trajectories in parameter space) going through states with different numbers of pearls. Processes are most complex in the tail of the switching time distribution. The specific sequences of two intrinsically disordered proteins (IDPs) are studied along the same lines. Our study shows the resemblance in shape fluctuations between the IDP sequences and the fast-switching PA sequences.

Predictive impact of optical coherence tomography biomarkers in anti-vascular endothelial growth factor resistant macular edema treated with dexamethasone implant

PurposeTo perform a longitudinal analysis of the effect of optic coherence tomography (OCT) biomarkers on macular thickness in patients with persistent macular edema secondary to diabetes mellitus and retinal vein occlusion who recieved intravitreal dexamethasone (DEX) implant. MethodsEighty-nine patients were included in the retrospective study. Patients with anti-VEGF-resistant macular edema were included in the study. The effect of the presence or absence of OCT biomarkers before intravitreal DEX implant therapy on central foveal thickness (CFT) was evaluated. In addition, the change in biomarkers from the baseline visit to the final visit was evaluated. The evaluated OCT biomarkers were as follows: ellipsoid zone and external limiting membrane (ELM) integrity, hyperreflective foci (HRF), disorganization of inner retinal layers (DRIL), hard exudates, serous macular detachment (SMD), pearl necklace, posterior vitreous detachment and the epiretinal membrane (ERM). ResultsThe mean age of the overall sample in the study was 64.4 ± 9.6. CFT decreased significantly from 625.3 ± 22.3 μm at baseline to 365.0 ± 21.7 μm in the 1st month but increased significantly to 430.2 ± 22.6 μm in the 3rd month. In the presence of HRF and SMD, recurrence of macular edema was significant in the 3rd month. The percentage of ELM disruption, DRIL, and ERM deteriorated significantly and the percentage of SMD improved significantly at the final visit. ConclusionsDEX implant therapy resulted in a satisfactory reduction in CFT in patients with DME and RVO. The presence of HRF and SMD is a negative predictor of recurrence in CFT in short term. DEX implant therapy resulted in satisfactory improvement in SMD.

Rosary and Pearl Necklace

Question: A 15-year-old girl presented with an 18-month history of intermittent right upper quadrant pain that appeared after meals and was relieved after rest. She denied any nausea, vomiting, chills, diarrhea, or constipation. The patient reported no trauma. At admission, physical examination showed tenderness in the right upper abdomen without rebound or guarding. Murphy’s sign was also present. The laboratory tests were unremarkable.

Fabrication of efficient protein imprinted materials based on pearl necklace-like MOFs bacterial cellulose composites

The acquisition of efficient protein isolation substances is vital for proteomic research, whereas it's still challenging nowadays. Herein, an elaborately designed protein imprinted material based on a bacterial cellulose@ZIF-67 composite carrier (BC@ZIF-67) is proposed for the first time. In particular, due to the ultrafine fiber diameter and abundant hydroxyl functional groups of the bacterial cellulose, BC@ZIF-67 presented a compact arrangement structure similar to a pearl necklace, which greatly promoted template immobilization and mass transfer resistance in protein imprinting technology. Therefore, the protein-imprinted material (BC@ZIF-67@MIPs) fabricated by surface imprinting technology and template immobilization strategy could exhibit ultrahigh adsorption capacity (1017.0 mg g−1), excellent recognition (IF = 5.98) and rapid adsorption equilibrium time (50 min). In addition, based on the experiment outcomes, our team employed BC@ZIF-67@MIPs to enrich template protein in blended protein solutions and biosamples, identifying them as underlying candidates for isolating and purifying proteins.

Complexation in Aqueous Solution of a Hydrophobic Polyanion (PSSNa) Bearing Different Charge Densities with a Hydrophilic Polycation (PDADMAC).

In this work the electrostatic complexation of two strong polyelectrolytes (PEs) was studied, the hydrophilic and positively charged poly (diallyldimethylammonium chloride) (PDADMAC) and the hydrophobic and negatively charged poly (styrene-co-sodium styrene sulfonate) (P(St-co-SSNa)), which was prepared at different sulfonation rates. The latter is known to adopt a pearl necklace conformation in solution for intermediate sulfonation rates, suggesting that a fraction of the P(St-co-SSNa) charges might be trapped in these hydrophobic domains; thus making them unavailable for complexation. The set of complementary techniques (DLS, zetametry, ITC, binding experiment with a cationic and metachromatic dye) used in this work highlighted that this was not the case and that all anionic charges of P(St-co-SSNa) were in fact available for complexation either with the polycationic PDADMAC or the monocationic o-toluidine blue dye. Only minor differences were observed between these techniques, consistently showing a complexation stoichiometry close to 1:1 at the charge equivalence for the different P(St-co-SSNa) compositions. A key result emphasizing that (i) the strength of the electrostatic interaction overcomes the hydrophobic effect responsible for pearl formation, and (ii) the efficiency of complexation does not depend significantly on differences in charge density between PDADMAC and P(St-co-SSNa), highlighting that PE chains can undergo conformational rearrangements favoring the juxtaposition of segments of opposite charge. Finally, these data have shown that the formation of colloidal PECs, such as PDADMAC and P(St-co-SSNa), occurs in two distinct steps with the formation of small primary complex particles (<50 nm) by pairing of opposite charges (exothermic step) followed by their aggregation within finite-size clusters (endothermic step). This observation is in agreement with the previously described mechanism of PEC particle formation from strongly interacting systems containing a hydrophobic PE.

Hyaluronan interactions with cationic surfactants – Insights from fluorescence resonance energy transfer and anisotropy techniques

Interactions of hyaluronan with micelles formed by cationic surfactants were studied by the time-resolved measurement of fluorescence resonance energy transfer (FRET) using perylene and fluorescein as probes. Two surfactants were studied – Cetyltrimethylammonium bromide (CTAB) and Septonex. In pure micellar solutions, the same values of FRET efficiency were found for both surfactants, but values for the binding of the probe pair were lower for Septonex micelles than in the case of CTAB. This was attributed to steric effects of the carbethoxy group in the Septonex polar head. Upon the addition of hyaluronan, decreased FRET efficiency and increased binding were detected in comparison with pure surfactants. To resolve the structure of the formed aggregates, steady state and time-resolved fluorescence anisotropy was employed as an additional technique. All results indicated that cationic micelles bind to hyaluronan forming a pearl necklace structure with micelles of smaller size compared to pure surfactant. Besides theoretical interest, the studied polyelectrolyte-surfactant system may be interesting for the formulation of drug delivery systems.

Association of two polyelectrolytes in salt solutions.

The association of polyelectrolytes (PEs) in solution affects a wealth of structural and dynamic behaviors, and is also fundamentally important for an understanding of protein association and aggregation. Here, we theoretically study the association of two PE chains by addressing the stability and morphology of the non-spherical associates. Our theory predicts that an elongated pearl-necklace (PN) associate can be stable at high salt concentrations due to the screened electrostatic repulsion. This contradicts the implication of scaling theory. In addition, there is no one-to-one correspondence between the morphology of the associate and its constituting unimers, which is demonstrated by the existence of different association modes.

Diffusion of dyes in polyelectrolyte-surfactant hydrogels.

In this work, hydrogels formed by interaction of biopolymeric electrolytes and oppositely charged surfactants are studied from the point of view of their ability to incorporate model hydrophobic dyes in their micelle-like structure. Two types of hydrogels were investigated. The first type was based on cationized dextran cross-linked by sodium dodecylsulphate. The second type was prepared by interactions of hyaluronan with carbethoxypendecinium bromide (septonex). Nile red and Atto488 were used as model dyes for the diffusion experiments. The dyes were dissolved in two different media: surfactant and physiological saline. The diffusion of dyes into hydrogel was monitored over time. Effective diffusion coefficients were determined. It was found that their values are strongly influenced by the hydrogel character, the types of dye used and the solvent. The obtained effective coefficients were higher in comparison with the values determined for the diffusion in the opposite direction (release from the hydrogel). The dyes are presented as free in physiological saline and in the form of micelles or micelle aggregates in surfactants. During diffusion into the hydrogel, they can be gradually incorporated in a “pearl necklace structure” which suppresses their mobility. In contrast, this partial immobilization of dyes can increase the concentration gradient which is a driving force of diffusion. Also, the gradual incorporation of dyes into hydrogel structures influences the values of the effective diffusion coefficients.

A case report of “pearl necklace” in the abdomen: magnetic beads ingestion resulting in an anesthetic emergency

A case report of “pearl necklace” in the abdomen: magnetic beads ingestion resulting in an anesthetic emergency